KR20110049264A - Driving method for ocb mode liquid crystal display device - Google Patents

Abstract

PURPOSE: A driving method for an OCB mode liquid crystal display device is provided to reduce power consumption by reducing a driving voltage required for transiting a spray alignment to a band alignment. CONSTITUTION: In a driving method for an OCB mode liquid crystal display device, a color filter array substrate has a common electrode(33) and a first alignment layer(35) which are successively laminated thereon. The array substrate of a thin film transistor has a thin film transistor array, a pixel electrode, and a second alignment layer which are successively laminated thereon. A liquid crystal layer(40) has OCB mode liquid crystal molecules between the color filter array substrate and the thin film transistor. The gate line is formed in a lower substrate in one direction. A gate insulating layer is formed on the front side of the lower substrate including the gate electrode.

Description

Driving method for OCB mode liquid crystal display device

The present invention relates to a method of driving a liquid crystal display, and more particularly, to a method of driving an OCB mode liquid crystal display.

Twisted nematic (TN) mode liquid crystal displays have been widely used in displays such as notebook computers, despite their narrow viewing angles. However, improving the viewing angle is an essential prerequisite for liquid crystal displays to replace cathode ray tube (CRT) displays in the monitor and television markets.

Accordingly, recently, an optically compensated band (hereinafter referred to as OCB) mode liquid crystal display device that compensates refractive index anisotropy of liquid crystal molecules to improve response speed while obtaining even viewing angle characteristics in all directions is proposed. It became.

The OCB liquid crystal display device includes an electrode for driving liquid crystal molecules of the liquid crystal layer on each inner surface of the upper and lower substrates, and an alignment layer for the alignment of liquid crystal molecules, respectively, between the upper and lower substrates disposed opposite to each other. And a polarizing plate having a predetermined polarization axis on each of the outer surfaces of these substrates, and continuously applying a predetermined high voltage to the initial splay oriented liquid crystal molecules to bend the array of liquid crystal molecules. After the transition to the orientation, by changing the magnitude of the voltage to adjust the degree of bending of the band by controlling the transmittance of light to display an image.

However, since the OCB liquid crystal display has a structure in which the liquid crystal molecules must be shifted from the splay orientation to the band orientation as described above, a high driving voltage of 20 V or more is required to achieve this, so that the increase in power consumption accordingly It is a problem.

An object of the present invention for solving the above problems is to provide a driving method of the OCB mode liquid crystal display device to reduce the power consumption by lowering the driving voltage required to transition from the splay orientation to the band orientation.

In order to achieve the above object, a method of driving an OCB mode liquid crystal display device includes a color filter array substrate in which a color filter array, a common electrode, and a first alignment layer are sequentially formed, a thin film transistor array, a pixel electrode, and a second alignment layer are sequentially formed. A driving method of an OCB mode liquid crystal display device comprising a thin film transistor array substrate and a liquid crystal layer in which OCB mode liquid crystal molecules are formed between the color filter array substrate and the thin film transistor array substrate. The initial voltage for transitioning from the splay state to the band I state is repeatedly performed in the on state and the off state.

In the on state of the initial voltage, the voltage difference between the pixel electrode and the common electrode is 10V, and in the off state of the initial voltage, the voltage difference between the pixel electrode and the common electrode is 0V.

One of the pixel electrode and the common electrode in the on state is 0V, and the pixel electrode and the common electrode in the off state are 0V.

The first on state of the initial voltage generates transition nuclei in one region of the liquid crystal layer, and the second on state generates transition nuclei in one region and the other region of the liquid crystal layer.

The off state of the initial voltage maintains the transition nucleus generated in the on state.

The off state of the initial voltage is driven for a time of 10 to 50ms.

The driving method of the OCB mode liquid crystal display according to the present invention requires a driving voltage of about 10V, which is lower than when the initial voltage applied is 20V or more in order to transition from the conventional splay state to the band I state. It has the effect of decreasing.

In addition, if the on state and the off state are repeatedly applied than the initial voltage is continuously applied in the high voltage state, the generation speed of the transition nucleus is increased, thereby reducing the down time during the initial driving of the OCB mode liquid crystal display. There is an effect that can be reduced.

Hereinafter, an OCB mode liquid crystal display according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view of an OCB mode liquid crystal display device according to an exemplary embodiment of the present invention.

As shown in FIG. 1, the liquid crystal panel employing the OCB mode liquid crystal includes an upper substrate 31 in which a color filter array (not shown), a common electrode 33, and a first alignment layer 35 are sequentially formed. ), The lower substrate 21 on which the TFT array, the pixel electrode 23 and the second alignment layer 25 are formed, and the upper substrate 31 and the lower substrate 21 are defined by spacers (not shown). A liquid crystal layer 40 in which the first and second liquid crystal molecules 40a and 40b of the OCB mode injected into the predetermined space have a gap of and the upper and lower parts disposed outside the upper and lower substrates 31 and 21. And polarizing plates 39 and 29.

In this case, although not shown in the drawings, the TFT array includes a gate line formed in one direction on the lower substrate 21, a gate electrode protruding from the gate line, and a gate insulating film formed on the entire lower substrate 21 including the gate electrode. And a semiconductor layer formed on the gate insulating film above the gate electrode, source / drain electrodes and data lines formed on both sides of the semiconductor layer via an ohmic contact layer, and contact holes on the drain electrode. And a pixel electrode 23 formed on the passivation layer to be electrically connected to the drain electrode through the contact hole. In this case, the gate electrode, the gate insulating film, the semiconductor layer, and the source / drain electrodes form a thin film transistor (TFT).

In addition, although not shown in the drawings, the color filter array includes a black matrix on the upper substrate 31 facing the lower substrate 21 to prevent light leakage to the gate line, the data line, and the thin film transistor TFT; It includes a color filter for implementing the RGB color on the black matrix, and a common electrode formed on the color filter.

The alignment layers of the upper substrate 31 and the lower substrate 21 are aligned in the same direction. The first and second liquid crystal molecules 40a and 40b of the OCB mode, which are injected between the upper substrate 31 and the lower substrate 21, have a specific voltage depending on the voltage difference formed in the upper substrate 31 and the lower substrate 21. A splay state, which is an initial alignment state, is maintained below Vth, and a band I state and a band II state are maintained above a specific voltage Vth.

2A to 2C are schematic cross-sectional views illustrating an arrangement state of liquid crystal molecules according to driving of an OCB mode liquid crystal display device according to the present invention. FIG. 2A shows a splay state, FIG. 2B shows a band I state, and FIG. 2C shows a band II state.

Referring to FIG. 2A, which shows a splay state, the first liquid crystal molecules 40a adjacent to the first and second alignment layers 35 and 25 in a state where no voltage is applied are formed. The first pretilt angle θ1 of the first liquid crystal molecules 40a may be arranged in the symmetrical state with respect to 40b), and the first and second alignment layers 35 and 25 or the upper and lower substrates 31 may be formed. 1 to 3 ° with respect to the surface, and the second liquid crystal molecules 40b in the center are formed on the surfaces of the first and second alignment layers 35 and 25 or the first and second substrates 31 and 21. It will have a horizontal state.

When a voltage is applied in this splay state, the voltage reaches the band I state of FIG. 2B, and the voltage at this time is referred to as an initial voltage VI. In the OCB mode liquid crystal display, an initial voltage is applied to the electrodes formed on each of the upper substrate 31 and the lower substrate 21, thereby turning on and displaying a white image. In this state, the first liquid crystal molecules 40a adjacent to the first and second alignment layers 35 and 25 have a second pretilt angle θ2 greater than the first pretilt angle θ1 in the splay state. The second liquid crystal molecules 40b in the center have a state perpendicular to the surfaces of the first and second alignment layers 35 and 25 or the first and second substrates 31 and 21.

When a voltage equal to or greater than a driving voltage greater than the initial voltage is applied, a band II state is obtained as shown in FIG. 2C, and the OCB mode LCD is formed on each of the upper substrate 31 and the lower substrate 21. The electrodes are turned off to display a black image. In this case, the first liquid crystal molecules 40a adjacent to the first and second alignment layers 35 and 25 have a third pretilt angle θ3 greater than the second pretilt angle θ2 in the band I state.

As described above, the liquid crystal display of the OCB mode has a band I state when the initial voltage is applied in the splay state and a band II state when the driving voltage is applied in the band I state.

On the other hand, when the initial voltage is applied in the splay state, a transition nucleus is generated in one region of the pixel region, that is, one region of the liquid crystal to which the voltage is applied, such as a portion in which the thin film transistor is formed (FIG. 3A), and the application time of the initial voltage is increased. As the transition nucleus grows to another part of the liquid crystal (FIG. 3b), the entire region of the liquid crystal can transition to the band I state.

At this time, when the initial voltage is repeatedly performed in an on state and an off state, the transition nucleus formed in one region of the liquid crystal grows to another part of the liquid crystal and the entire region of the liquid crystal is transferred to the band I state. Can be.

4 is a waveform diagram illustrating a method of applying an initial voltage, which will be described in more detail with reference to the drawing. At this time, the initial voltage on state is the common electrode (33, Vcom of FIG. 1) formed on the upper substrate (31 in FIG. 1) and the pixel electrode (23, FIG. Although the voltage difference between the data) is 10V and the initial voltage is off, the voltage difference between the common electrode and the pixel electrode is 0V, but the voltage difference and the applied electrode are not limited thereto.

First, when the first on state of the initial voltage, that is, 0V is applied to the pixel electrode and 10V is applied to the common electrode, a transition nucleus is generated in one region of the liquid crystal, and the first off state. That is, when 0V is applied to the pixel electrode and 0V is applied to the common electrode, the generated transition nucleus does not disappear, but the second on state of the voltage, that is, 0V is applied to the pixel electrode, and the common electrode In the state where -10V is applied, transition nuclei are generated not only in one region but also in other regions, and when the second off state is applied, that is, 0V is applied to the pixel electrode and 0V is applied to the common electrode. The transition nucleus formed in the cell will not disappear.

At this time, the off state of the voltage must be performed for a time of 10 to 50 ms, so that the generated transition nucleus is maintained without disappearing.

As described above, since the transition nucleus is generated in the on state of the initial voltage, the transition nucleus is formed in the entire region of the liquid crystal by repeatedly performing the on state of the initial voltage and preventing the generated transition nucleus from disappearing in the off state. This region can transition to the band I state.

Therefore, in the present invention, since the voltage applied to generate the on state and the off state is about 10V as the initial voltage applied to transition from the splay state to the band I state, the transition from the existing splay state to the band I state In order to reduce the power consumption, a lower driving voltage is required than when the initial voltage applied is greater than 20V.

In addition, if the on state and the off state are repeatedly applied than the initial voltage is continuously applied in the high voltage state, the generation speed of the transition nucleus is increased, thereby reducing the down time during the initial driving of the OCB mode liquid crystal display. Can be reduced.

1 is a cross-sectional view of an OCB mode liquid crystal display device according to an embodiment of the present invention.

2A to 2C are schematic cross-sectional views illustrating arrangement states of liquid crystal molecules according to driving of an OCB mode liquid crystal display according to the present invention.

3A and 3B show transition nuclei generated when and after an initial voltage is applied;

4 is a waveform diagram illustrating an initial voltage applying method of an OCB mode liquid crystal display according to an exemplary embodiment of the present invention.

Claims (7)

A color filter array substrate on which a color filter array, a common electrode and a first alignment layer are sequentially formed, a thin film transistor array substrate on which a thin film transistor array, a pixel electrode and a second alignment layer are sequentially formed, and between the color filter array substrate and a thin film transistor array substrate In the driving method of an OCB mode liquid crystal display device comprising a liquid crystal layer formed on the liquid crystal molecules of the OCB mode, And an initial voltage applied to each of the pixel electrode and the common electrode to repeatedly transition from a splay state to a band I state in an on state and an off state. According to claim 1, In the on state of the initial voltage, the voltage difference between the pixel electrode and the common electrode is 10V, and in the off state of the initial voltage, the voltage difference between the pixel electrode and the common electrode is 0V. Way. The method of claim 2, And one of the pixel electrode and the common electrode in the on state is 0V. The method of claim 2, And the pixel electrode and the common electrode in the off state are 0V. The method of claim 1, wherein the first on state of the initial voltage is A transition nucleus is generated in one region of the liquid crystal layer, and the second on state generates transition nuclei in one region and the other region of the liquid crystal layer. The method of claim 1, wherein the off state of the initial voltage is And driving the transition nucleus generated in the on state. The method of claim 1, wherein the off state of the initial voltage is A method of driving an OCB mode liquid crystal display, characterized in that for driving for a time of 10 ~ 50ms.

Images