KR100768196B1 - Method for transient driving of optically compensated birefringence liquid crystal display and apparatus thereof - Google Patents

Abstract

The present invention relates to a transition driving method of an OCB liquid crystal display panel and an apparatus for effectively enabling initial bend alignment of liquid crystals in a liquid crystal display having an OCB (Optically Compensated Birefringence) mode. In the transition driving method of the OCB liquid crystal display panel according to the present invention, the pixel is formed in the region where the scan lines and the data lines intersect, and at the initial startup of the OCB liquid crystal display panel in which the common lines pass through each pixel. The bend alignment transition of the liquid crystal molecules is performed by the transition voltages applied to the scan lines, the data lines, and the common lines, respectively, and the transition voltages applied to the adjacent data lines have different polarities.

Description

Method for transient driving of optically compensated birefringence liquid crystal display and apparatus

1 is a view for explaining the operation of the general OCB mode.

2 is a circuit diagram schematically showing the configuration of a thin film transistor liquid crystal display device to which a transition driving method of an OCB liquid crystal display panel of the present invention is applied.

3 is a waveform diagram schematically illustrating a transition driving method of an OCB liquid crystal display panel according to another exemplary embodiment of the present invention.

4 is a waveform diagram schematically illustrating a transition driving method of an OCB liquid crystal display panel according to another exemplary embodiment of the present invention.

5 is a diagram schematically illustrating the polarity of a transition voltage applied to each pixel in a thin film transistor substrate.

6A is a diagram schematically illustrating an alignment direction of liquid crystals in some pixels of a thin film transistor substrate.

6B is a diagram schematically illustrating an alignment direction of liquid crystals in some pixels of a common electrode substrate.

6C is a diagram schematically illustrating an alignment direction of liquid crystal in some pixels.

7 is a block diagram schematically showing a transition driving apparatus of an OCB liquid crystal display panel as a preferred embodiment according to the present invention.

<Explanation of symbols for main parts of the drawings>

10: OCB liquid crystal display panel, 720: data driver,

730: scan driver, 740: common driver.

The present invention relates to a transition driving method and an apparatus of an OCB liquid crystal display panel, and more particularly, to an OCB liquid crystal display panel that enables an initial bend orientation of a liquid crystal in an LCD having an OCB (Optically Compensated Birefringence) mode. The present invention relates to a transition driving method and an apparatus thereof.

In general, liquid crystal displays (LCDs) are thin, light, emit less electromagnetic waves, and consume less power. Therefore, it is widely used as a screen display element of a portable information device such as a mobile phone or a notebook computer. In addition, the recent increase in the size of the screen has attracted attention as a home appliances such as TV.

Such a liquid crystal display device has a large disadvantage in view angle characteristics and response speeds in which contrast and color are changed according to the viewing direction of the screen. Various methods have been proposed to overcome these disadvantages.

For example, in order to improve the viewing angle of an LCD (Liquid Crystal Display), a method of attaching a prism plate to the surface of the light guide plate to improve the linearity of incident light from the backlight and improving the luminance in the vertical direction by 30% or more has been put into practical use. A method of increasing the viewing angle by attaching a plate is being applied.

In addition, many attempts have been made to improve the viewing angle and response speed by driving liquid crystals such as OCB, Polymer Dispersed Liquid Crystal (PDLC), and Deformed Helix Ferroelectric (DHF) using TFT (Thin Film Transistor). In particular, in the case of the OCB mode, the response speed of the liquid crystal is fast, and because of the advantages of having a wide viewing angle characteristics, research and development is actively underway.

Next, the operation of the OCB mode described above will be briefly described with reference to FIG. 1.

1 is a view for explaining the operation of the general OCB mode.

Referring to the drawings, the initial alignment state of the liquid crystal positioned between the upper electrode and the lower electrode is a homogenous state (H), and when a predetermined voltage is applied to the upper and lower electrodes, a transient splay; It is converted into a bend state (hereinafter referred to as B) through T) and Asymmetric splay (A), and then operates in OCB mode.

In general, the OCB liquid crystal cell has a pretilt angle of about 5 to 15 °, a thickness of the liquid crystal cell of 3 to 7 μm, and rubbing the alignment film in the same direction. Since the arrangement of the liquid crystal molecules in the center of the liquid crystal layer is symmetrical, the inclination angle is 0 ° below a certain voltage, and the inclination angle is 90 ° above a specific voltage, so that a large voltage is initially applied to the liquid crystal layer. The inclination angle of the liquid crystal molecules is set to 90 °, and the applied voltage is changed to modulate the polarization of light passing through the liquid crystal layer by changing the tilt of the remaining liquid crystal molecules except for the liquid crystal molecules in the middle of the alignment layer and the liquid crystal layer.

The inclination angle of the liquid crystal molecules in the middle is usually several seconds to arrange from 0 ° to 90 °, the cell thickness is thin, the liquid crystal has a backflow (backflow) shape is small, the reaction time is characterized by very fast as about 10㎳.

However, there is a problem that it takes a certain time before the liquid crystal to obtain the bend orientation for driving in the OCB mode. In particular, a high voltage is applied for a short time after the PC monitor or the TV switch is turned on, so that it is possible to use it only when a bend alignment transition is induced in the entire LCD panel.

The present invention is to solve the above problems, by applying a transition voltage of different polarity to the odd and even lines of the data line, the liquid crystal of the boundary region of the odd and even lines to the twisting effect It is an object of the present invention to provide a transition driving method and an apparatus for an OCB liquid crystal display panel which can become a transition nucleus and enable effective transition.

In the transition driving method of the OCB liquid crystal display panel according to the present invention for achieving the above object, the pixel is formed in the region where the scan line and the data line intersect, the OCB is formed so that the common line passes through each pixel During initial startup of the liquid crystal display panel, a bend alignment transition of liquid crystal molecules is performed by a transition voltage applied to each of the scan lines, the data lines, and the common lines, and a transition applied to the adjacent data lines. Voltages are different in polarity from each other.

It is preferable that a positive transition voltage is applied to odd-numbered data lines and a negative transition voltage is applied to even-numbered data lines.

During the period in which the transition voltage is applied, it is preferable that the voltage applied to the common lines maintain the ground level.

The OCB liquid crystal display panel includes a thin film transistor substrate on which a thin film transistor is formed, a common electrode substrate on which a common electrode is formed, and a liquid crystal layer formed between the thin film transistor substrate and the common electrode substrate. A pixel electrode connected to the liquid crystal layer, a gate electrode connected to the scan line, a source electrode connected to the data line, and a drain electrode connected to the pixel electrode, wherein the common electrode is connected to the common line It is desirable to be.

While a bipolar transition voltage is applied to the odd-numbered data lines, a voltage for turning on the gate electrode is applied to the scan lines.

In the transition driving method of an OCB LCD panel according to another aspect of the present invention, a pixel is formed in a region where scan lines and data lines intersect, and an initial stage of an OCB LCD panel is formed such that common lines pass through each pixel. At start-up, the liquid crystal molecules are bend aligned by a transition voltage applied to each of the scan lines, the data lines, and the common lines, and a negative transition voltage is applied to odd-numbered data lines. Bipolar transition voltages are applied to even-numbered data lines.

In the transition driving apparatus of the OCB liquid crystal display panel according to another aspect of the present invention, a pixel is formed in an area where scan lines and data lines intersect, and an initial stage of an OCB liquid crystal display panel is formed such that common lines pass through each pixel. At start-up, the liquid crystal molecules are bend-oriented transitioned by transition voltages applied to each of the scan lines, the data lines, and the common lines, and the transition voltages applied to the adjacent data lines are polarized with each other. different.

A timing controller for generating a data driving signal, a scan driving signal, and a common driving signal corresponding to an image signal to be displayed on the OCB liquid crystal display panel, and data applying a data driving voltage according to the data driving signal to the data lines. The driving unit may include a scan driver for applying a scan driving voltage according to the scan driving signal to the scan lines, and a common driver for applying a common driving voltage according to the common driving signal to the common lines.

According to the present invention, by applying transition voltages of different polarities to odd-numbered and even-numbered lines of the data line, the liquid crystals at the boundary regions of odd-numbered and even-numbered lines become transition nuclei due to the twisting effect, and thus effective transition. Is possible.

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

2 is a circuit diagram schematically showing the configuration of a thin film transistor liquid crystal display.

Referring to the drawings, a thin film transistor (TFT) liquid crystal display (LCD) may include a thin film transistor liquid crystal display panel 10 and a driving device for driving the thin film transistor liquid crystal display panel. The thin film transistor liquid crystal display panel 10 is active by a thin film transistor, and includes a thin film transistor substrate, a common electrode substrate, and a liquid crystal layer injected between the two substrates. The thin film transistor liquid crystal display panel 10 is preferably an OCB liquid crystal display panel having the OCB mode as shown in FIG. 1.

The liquid crystal display including the OCB liquid crystal display panel 10 may further include a back light unit (not shown). The present invention can be applied not only to the case where the liquid crystal display panel is active but also to the case of the passive type.

In the OCB liquid crystal display panel 10, pixels are formed in regions where the scan lines LS and the data lines LD intersect, and the common lines COM pass through each pixel. That is, each pixel of the OCB liquid crystal display panel 10 includes an OCB type liquid crystal L, a thin film transistor, and a common electrode connected to the common line COM. The thin film transistor is connected to the pixel electrode E connected to the liquid crystal L, the gate G connected to the scan line LS, the source S connected to the data line LD, and the pixel electrode E. A drain D is provided.

During the initial startup of the OCB liquid crystal display panel, the liquid crystal molecules are bent aligned by a transition voltage applied to each of the scan lines LS, the data lines LD, and the common lines OCM.

The source electrode S protrudes from the data line LD line toward the scan line LS. The drain electrode D may protrude from the source electrode S toward the scan line LS. The drain electrode D is a counter electrode of the source electrode S, and extends to the pixel electrode E inside the pixel region. In this case, the data line LD may be formed in a double layer or more structure. In this case, at least one layer may be formed of a metal material having low resistance.

In addition, the scan line LS extends to intersect the data line LD, and the gate electrode G may protrude from the scan line LS toward the data line LD. In the thin film transistor substrate having the top gate structure, the gate electrode G is formed on the upper layer of the source electrode S and the drain electrode D. FIG. In this case, the scan line LS includes a gate line extending in the horizontal direction and a gate electrode G protruding from the gate line.

The liquid crystal layer is formed by filling liquid crystal molecules between the alignment layers. It is preferable that a liquid crystal layer becomes an OCB liquid crystal cell driven in an OCB mode. The OCB liquid crystal cell has a pretilt angle of about 5 to 15 °, a thickness of the liquid crystal cell of 3 to 7 μm, and a rubbing of the alignment film in the same direction. Since the arrangement of the liquid crystal molecules in the center of the liquid crystal layer is symmetrical, the inclination angle is 0 ° below the specific voltage, and the inclination angle is 90 ° above the specific voltage. Therefore, the inclination angle of the liquid crystal molecules in the center of the liquid crystal layer is initially set at 90 ° by applying a large voltage at an initial stage, and the change in the tilt of the remaining liquid crystal molecules except for the liquid crystal molecules in the center of the alignment layer and the liquid crystal layer by changing the applied voltage. This modulates the polarization of light passing through the liquid crystal layer.

The inclination angle of the liquid crystal molecules in the middle is usually several seconds to arrange from 0 ° to 90 °, the cell thickness is thin, and the liquid crystal has little backflow, so the reaction time is very fast at about 10 ms. However, after the switch of the display device is turned on, that is, before driving the liquid crystal display of the liquid crystal display panel, the bend alignment transition is applied to the entire panel through the respective electrode lines LS, LD, and COM according to the present invention. It is necessary to induce.

3 is a waveform diagram schematically illustrating a transition driving method of an OCB liquid crystal display panel according to another exemplary embodiment of the present invention.

5 is a diagram schematically illustrating the polarity of a transition voltage applied to each pixel in a thin film transistor substrate. 6A is a diagram schematically illustrating an alignment direction of liquid crystals in some pixels of a thin film transistor substrate. 6B is a diagram schematically illustrating an alignment direction of liquid crystals in some pixels of a common electrode substrate. FIG. 6C is a diagram schematically illustrating an alignment direction of liquid crystals in some pixels in an OCB LCD panel having a liquid crystal layer formed between a thin film transistor substrate and a common electrode substrate.

Referring to the drawings, according to the transition driving method of the OCB liquid crystal display panel of the present invention, transition voltages having different polarities are applied to adjacent data lines (LD of FIG. 2). In the embodiment shown in FIG. 3, the bipolar transition voltage V _source (2n + 1) is applied to the odd-numbered data lines s1, s3, and s5, and the even-numbered data lines s2, s4, and s6. The negative transition voltage (V _source (2n)) is applied.

In the transition period T _t for transitioning the OCB liquid crystal to the bend state, the transition voltage V _source (2n + 1) applied to the odd-numbered data lines s1, s3, and s5 has a bipolar V ₁ level. And the transition voltage V _source (2n) applied to the even-numbered data lines s2, s4, and s6 is a negative V _G level. In addition, during the transition period T _t , the common lines (COM of FIG. 2) maintain the ground level V _G , and the scan lines g1 to g6 are applied through the data lines s1 to s6. A voltage V ₂ is applied to turn on the gate electrode to which power is applied through the scan lines g1 to g6 so that a voltage can be applied to the liquid crystal from the source to the drain.

As such, voltages having different polarities are applied to the odd-numbered and even-numbered lines of the data lines s1 to s6 of the thin film transistor substrate, thereby twisting the liquid crystal in the boundary region between the odd-numbered and even-numbered lines by 90 degrees. Will have an effect. In addition, the transition to the bend state may occur more effectively during the initial activation of the OCB liquid crystal through this.

That is, as shown in FIGS. 5 and 6A to 6C, the alignment direction LCp of the liquid crystal in each pixel near the thin film transistor substrate is directed upward in the drawing. In addition, since the positive voltage is applied to the odd data lines and the negative voltage is applied to the even data lines, a lateral field is formed from the odd data lines toward the even data lines. The alignment direction LCb of the liquid crystal in the boundary area between the odd-numbered and even-numbered lines is directed from the odd-numbered lines to the even-numbered lines in the drawing. As described above, the alignment of the liquid crystal in the boundary region by the 90-degree effect of the transition nucleus functions as a transition nucleus, and the transition state grows around the liquid crystal in the pixel centered on the transition nucleus.

In this case, no voltage is applied to the common electrode to which the transition voltage is applied through the common line of the common electrode substrate, and the alignment direction LCu of the liquid crystal in the entire region of the panel near the common electrode substrate is upward as shown in FIGS. 6B and 6C. However, the alignment direction LCb of the liquid crystal in the boundary area between the odd-numbered and even-numbered lines near the thin film transistor substrate is directed toward the side, so that the liquid crystal is 90 degrees toward the common electrode substrate in the thin film transistor substrate at the boundary area. It has a kink effect.

4 is a waveform diagram schematically illustrating a transition driving method of an OCB liquid crystal display panel according to another exemplary embodiment of the present invention.

Referring to the drawings, according to the transition driving method of the OCB liquid crystal display panel of the present invention, transition voltages having different polarities are applied to adjacent data lines (LD of FIG. 2). In the embodiment shown in FIG. 4, the negative transition voltage V _source (2n + 1) is applied to the odd-numbered data lines s1, s3, and s5, and the even-numbered data lines s2, s4, and s6. The bipolar transition voltage V _source (2n) is applied to it.

In the transition period T _t for transitioning the OCB liquid crystal to the bend state, the transition voltage V _source (2n + 1) applied to the odd-numbered data lines s1, s3, s5 is the negative V _G level. The transition voltage V _source (2n) applied to the even-numbered data lines s2, s4, and s6 is a bipolar V ₁₁ level. In addition, during the transition period T _t , the common lines (COM of FIG. 2) maintain the ground level V _G , and the scan lines g1 to g6 are applied through the data lines s1 to s6. A voltage V ₂ is applied to turn on the gate electrode to which power is applied through the scan lines g1 to g6 so that a voltage can be applied to the liquid crystal from the source to the drain.

In this case, since the negative voltage is applied to the odd-numbered data lines and the positive voltage is applied to the even-numbered data lines, the lateral field is moved from the even-numbered data lines near the thin film transistor substrate toward the odd-numbered data lines. ) Is formed so that the alignment direction of the liquid crystal in the boundary region of the odd-numbered and even-numbered lines is directed from the even-numbered lines to the odd-numbered lines.

The alignment direction LCu of the liquid crystal in the entire region of the panel near the common electrode substrate is upward, but the alignment direction LCb of the liquid crystal in the boundary region between the odd-numbered and even-numbered lines near the thin film transistor substrate is even-numbered. From the lines to the side in the direction of the odd-numbered lines, the liquid crystal is twisted 90 degrees toward the common electrode substrate in the thin film transistor substrate in the boundary region.

As described above, the alignment caused by the 90-degree twisting effect of the liquid crystal in the boundary region functions as a transition nucleus, and the transition state grows around the liquid crystal in the pixel around the transition nucleus. Therefore, the transition to the bend state may occur more effectively at the initial startup of the OCB liquid crystal.

FIG. 7 is a block diagram schematically illustrating a transition driving device of an OCB liquid crystal display panel as a preferred embodiment of the present invention.

Referring to the drawings, the transition driving apparatus 700 of the OCB LCD panel includes a timing controller 710, a data driver 720, a scan driver 730, a common driver 740, a gray voltage generator 750, And a light source controller 760. The transition driving apparatus 700 of the OCB liquid crystal display panel according to the present embodiment is a driving device to which the transition driving method of the OCB liquid crystal display panel of FIGS. 3 and 4 is applied. Accordingly, the descriptions of FIGS. 3 and 4 also apply to the transition driving apparatus 700 of the OCB liquid crystal display panel according to the present embodiment.

The timing controller 710 receives a gray scale data signal (R, G, B DATA), a horizontal sync signal (Hsync), a vertical sync signal (Vsync) from an external or graphic controller (not shown), OCB liquid crystal display panel Gray level data (R, G, B DATA), data driving signal (Sd), scan driving signal (Sg), common driving signal (Sc), and light source control signal (Sb) corresponding to the video signal to be displayed are generated. .

The data driver 720 applies a data transition voltage V _source corresponding to the data driving signal Sd to the data lines LD. The scan driver 730 applies a scan transition voltage V _gate according to the scan driving signal Sg to the scan lines LS. The common driver 740 applies the common transition voltage V _com according to the common driving signal Sc to the common lines COM.

In the transition period for transitioning the OCB liquid crystal to the bend state, transition voltages having different polarities are applied to adjacent data lines (LD of FIG. 2). That is, the positive transition voltage V _source (2n + 1) is applied to odd-numbered data lines s1, s3, and s5, and the negative transition voltage is applied to even-numbered data lines s2, s4, and s6. (V _source (2n)) is applied. In this embodiment, the negative transition voltage V _source (2n + 1) is applied to the odd-numbered data lines s1, s3, and s5, and the bipolarity is applied to the even-numbered data lines s2, s4, and s6. A transition voltage of V _source (2n) may be applied.

The manufacturing voltage generator 750 outputs a gray level signal corresponding to the gray level data R, G, and B data to the data driver 720. The light source controller 760 controls the backlight 400 according to the light source control signal Sb.

According to the transition driving method and apparatus for an OCB liquid crystal display panel according to the present invention, by applying transition voltages having different polarities to odd-numbered and even-numbered lines of a data line, the boundary region between odd-numbered and even-numbered lines is applied. The liquid crystal becomes a transition nucleus due to the twisting effect, and thus an effective transition is possible.

Although the present invention has been described with reference to one embodiment shown in the accompanying drawings, it is merely an example, and those skilled in the art may realize various modifications and equivalent other embodiments therefrom. I can understand. Accordingly, the true scope of protection of the invention should be defined only by the appended claims.

Claims (16)

At the initial startup of an OCB liquid crystal display panel in which pixels are formed in regions where scan lines and data lines intersect, and common lines pass through each pixel, the scan lines, the data lines, and the common line. Bend orientation transition of the liquid crystal molecules by the transition voltage applied to each of the lines, The transition voltages applied to the adjacent data lines have different polarities, During the period in which the transition voltage is applied, the voltage applied to the common lines maintains the ground level, A transition driving method of an OCB liquid crystal display panel in which an odd transition voltage is applied to odd-numbered data lines and a negative transition voltage is applied to even-numbered data lines. delete delete The method of claim 1, The OCB liquid crystal display panel includes a thin film transistor substrate on which a thin film transistor is formed, a common electrode substrate on which a common electrode is formed, and a liquid crystal layer formed between the thin film transistor substrate and the common electrode substrate. The thin film transistor substrate includes a pixel electrode connected to the liquid crystal layer, a gate electrode connected to the scan line, a source electrode connected to the data line, and a drain electrode connected to the pixel electrode, The OCB liquid crystal display panel of claim 1, wherein the common electrode is connected to the common line. The method of claim 4, wherein And a voltage for turning on the gate electrode is applied to the scan lines while a bipolar transition voltage is applied to the odd-numbered data lines. At the initial startup of an OCB liquid crystal display panel in which pixels are formed in regions where scan lines and data lines intersect, and common lines pass through each pixel, the scan lines, the data lines, and the common line. Bend orientation transition of the liquid crystal molecules by the transition voltage applied to each of the lines, A negative transition voltage is applied to odd-numbered data lines, and a bipolar transition voltage is applied to even-numbered data lines. And a voltage applied to the common lines maintains a ground level while the transition voltage is applied. delete The method of claim 6, The OCB liquid crystal display panel includes a thin film transistor substrate on which a thin film transistor is formed, a common electrode substrate on which a common electrode is formed, and a liquid crystal layer formed between the thin film transistor substrate and the common electrode substrate. The thin film transistor substrate includes a pixel electrode connected to the liquid crystal layer, a gate electrode connected to the scan line, a source electrode connected to the data line, and a drain electrode connected to the pixel electrode, The OCB liquid crystal display panel of claim 1, wherein the common electrode is connected to the common line. The method of claim 8, And a voltage for turning on the gate electrode is applied to the scan lines while a bipolar transition voltage is applied to the odd-numbered data lines. At the initial startup of an OCB liquid crystal display panel in which pixels are formed in regions where scan lines and data lines intersect, and common lines pass through each pixel, the scan lines, the data lines, and the common line. Bend orientation transition of the liquid crystal molecules by the transition voltage applied to each of the lines, The transition voltages applied to the adjacent data lines have different polarities, During the period in which the transition voltage is applied, the voltage applied to the common lines maintains the ground level, A transition driving device of an OCB liquid crystal display panel in which an odd transition voltage is applied to odd-numbered data lines and a negative transition voltage is applied to even-numbered data lines. The method of claim 10, A timing controller for generating a data driving signal, a scan driving signal, and a common driving signal corresponding to an image signal to be displayed on the OCB liquid crystal display panel, and data applying a data driving voltage according to the data driving signal to the data lines. An OCB liquid crystal display panel includes a scan driver which applies a scan driving voltage according to the scan driving signal to the scan lines, and a common driver which applies a common driving voltage according to the common driving signal to the common lines. Transition drive. delete At the initial startup of an OCB liquid crystal display panel in which pixels are formed in regions where scan lines and data lines intersect, and common lines pass through each pixel, the scan lines, the data lines, and the common line. Bend orientation transition of the liquid crystal molecules by the transition voltage applied to each of the lines, The transition voltages applied to the adjacent data lines have different polarities, During the period in which the transition voltage is applied, the voltage applied to the common lines maintains the ground level, A transition driving device of an OCB liquid crystal display panel, wherein a negative transition voltage is applied to odd-numbered data lines and a positive transition voltage is applied to even-numbered data lines. delete The method according to claim 10 or 13, The OCB liquid crystal display panel includes a thin film transistor substrate on which a thin film transistor is formed, a common electrode substrate on which a common electrode is formed, and a liquid crystal layer formed between the thin film transistor substrate and the common electrode substrate.  The thin film transistor substrate includes a pixel electrode connected to the liquid crystal layer, a gate electrode connected to the scan line, a source electrode connected to the data line, and a drain electrode connected to the pixel electrode. And an OCB liquid crystal display panel connected to the common line. The method of claim 15, And a voltage for turning on the gate electrode is applied to the scan lines while an anode or cathode transition voltage is applied to the odd-numbered data lines.

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