KR101897745B1 - liquid crystal display device - Google Patents

Abstract

The present invention provides a liquid crystal display comprising: a pixel; A common electrode formed on the front surface of the pixel in a plate shape; A plurality of first pixel electrodes bent on the common electrode and having at least one bending point formed therein and having a curved rod shape and a plurality of pixel electrodes formed by alternately forming a plurality of second pixel electrodes having a straight rod shape, Device.

Description

[0001] The present invention relates to a liquid crystal display device,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device that efficiently disperses static electricity generated during a liquid crystal panel manufacturing process.

2. Description of the Related Art [0002] As an information-oriented society develops, demands for a display device for displaying an image have increased in various forms. Recently, a liquid crystal display (LCD), a plasma display panel (PDP) Various flat display devices such as organic light emitting diode (OLED) devices have been utilized.

Here, the liquid crystal display device can be downsized, and is widely used in portable information devices and computers. In such a liquid crystal display device, a data voltage is applied to the pixel electrode, a common voltage is applied to the common electrode, and the liquid crystal is driven by the voltage difference.

In recent years, an in-plane switching liquid crystal display device has been widely used in which a common electrode and a pixel electrode are formed on the same substrate to improve the viewing angle. In addition, in order to improve the color shift phenomenon and the gray inversion phenomenon, a multi-domain (for example, 2-domain) for driving a liquid crystal by dividing a pixel into a plurality of regions is widely used .

Hereinafter, a pixel structure of a general transverse electric field type liquid crystal display device driven by a 2-domain will be described with reference to FIG.

1 is a plan view showing a pixel structure of a general transverse electric field type liquid crystal display device.

First, a common electrode CE is formed on the entire surface of the pixel PX.

A pixel electrode PE is formed on an upper portion of the common electrode CE with an insulating layer (not shown) therebetween. In this case, the pixel electrode PE has a plurality of elongated bar shapes, .

Accordingly, the liquid crystal constituting the pixel PX varies in the direction of rotation according to the electric field generated corresponding to the voltage applied to the pixel electrode PE and the common electrode CE.

For example, as the electric field is generated, the liquid crystal located in the upper region of the pixel PX rotates counterclockwise, and the liquid crystal located in the lower region of the pixel PX rotates in the clockwise direction.

That is, the liquid crystal of one pixel PX rotates in different directions to form a multi-domain.

In addition, since the common electrode CE is formed on the entire surface of the pixel PX and the pixel electrode PE is formed in a slit shape with the insulating layer interposed therebetween, the liquid crystal is driven not only by the horizontal electric field but also by the vertical electric field. That is, the pixel PX is driven by a fringe field.

A method of driving the liquid crystal by forming such a fringe field electric field can be referred to as a FFS (fringe field switching) type liquid crystal display device.

The FFS type liquid crystal display device has a problem that a large driving voltage is required and power consumption is also increased due to the necessity of a large driving voltage.

In order to improve this, a high-k liquid crystal has been generally developed and used. However, the use of such a high-k liquid crystal has a limitation in reducing driving voltage and power consumption.

Will be described with reference to FIG.

2 is a graph showing the driving voltage according to the dielectric constant of the liquid crystal.

First, in the first period, the driving voltage is efficiently reduced as the dielectric constant of the liquid crystal increases, but the driving voltage is not decreased even if the dielectric constant of the liquid crystal is increased in the second period.

That is, even if the dielectric constant of the liquid crystal is increased, there is a limit to decrease the driving voltage.

Further, as the dielectric constant of the liquid crystal is increased, the viscosity of the liquid crystal is also increased, which not only lengthens the response speed of the liquid crystal, but also takes a long time to return to the liquid crystal state.

That is, in the FFS type liquid crystal display, the high-k liquid crystal is used to reduce the driving voltage and the power consumption. In addition to the limitation of the driving voltage reduction due to the increase of the dielectric constant of the liquid crystal, There arises a problem such as a delay in response speed and an increase in afterimage.

There is a problem in providing a transverse electric field type liquid crystal display device capable of reducing a driving voltage and power consumption and improving a quick response speed and a residual image problem of a liquid crystal.

In order to achieve the above-described object, the present invention provides a liquid crystal display comprising: a pixel; A common electrode formed on the front surface of the pixel in a plate shape; A plurality of first pixel electrodes bent on the common electrode and having at least one bending point formed therein and having a curved rod shape and a plurality of pixel electrodes formed by alternately forming a plurality of second pixel electrodes having a straight rod shape, Device.

A first width between an end of the plurality of first pixel electrodes and an end of a second pixel electrode located at one side of the plurality of first pixel electrodes among the plurality of second pixel electrodes, And a second width between the bending point and a second pixel electrode located on the other side of the plurality of first pixel electrodes.

The second width is 0.5 mu m.

The internal angle of the bending point of the plurality of first pixel electrodes is 140 to 174 degrees.

At least one end of the plurality of first pixel electrodes and both ends of the plurality of second pixel electrodes are connected to each other.

And an insulating layer is further formed between the common electrode and the pixel electrode.

In the present invention, not only the driving voltage and the power consumption can be reduced, but also the color shift phenomenon and the gray scale inversion can be improved by implementing the multi-domain.

1 is a plan view showing a pixel structure of a general transverse electric field type liquid crystal display device.
2 is a graph showing a driving voltage according to a dielectric constant of a liquid crystal.
3 is a view schematically showing a liquid crystal display device according to an embodiment of the present invention.
4 schematically shows a pixel structure according to an embodiment of the present invention;
5 is a simulation showing liquid crystal driving of an entire pixel designed according to an embodiment of the present invention.
6 is a graph showing the transmittance of a pixel structure according to an embodiment of the present invention and a drive voltage of a general pixel structure.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

3 is a view schematically showing a liquid crystal display device according to an embodiment of the present invention.

3, the liquid crystal display device 100 according to the embodiment of the present invention includes a liquid crystal panel 200, a driving circuit unit 900, and a backlight 800. As shown in FIG.

First, in the liquid crystal panel 200, a plurality of gate lines GL extend in the first direction, for example, in the row direction. A plurality of data lines DL extend in a second direction that crosses the first direction, for example, in the column direction. The plurality of gate lines GL and the plurality of data lines DL intersecting each other define a plurality of pixels P arranged in a matrix form.

Each pixel P includes a thin film transistor T, a liquid crystal capacitor Clc, and a storage capacitor Cst.

The thin film transistor T is formed at an intersection of a plurality of gate lines GL and a plurality of data lines DL, respectively. A pixel electrode (not shown) is connected to the thin film transistor T. On the other hand, a common electrode (not shown) is formed corresponding to the pixel electrode.

The pixel electrode and the common electrode are formed on the same substrate to form in-plane switching, thereby driving the liquid crystal located therebetween. More specifically, when a data voltage is applied to the pixel electrode and a common voltage is applied to the common electrode, an electric field is formed between them to drive the liquid crystal.

The pixel electrode, the common electrode, and the liquid crystal located between these electrodes constitute a liquid crystal capacitor Clc. Each pixel P further includes a storage capacitor Cst, which serves to store the data voltage applied to the pixel electrode until the next frame.

Each pixel P may be composed of R, G, and B subpixels displaying red, green, and blue, for example. That is, neighboring R, G, and B sub-pixels constitute a pixel P which is a unit of image display.

The backlight 800 functions to supply light to the liquid crystal panel 200. A cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), a light emitting diode (LED), or the like may be used as the light source of the backlight 800. [

The driving circuit unit 900 may include a timing control unit 300, a gate driving unit 400, a data driving unit 500, a gamma voltage supplying unit 600, and a power generating unit 700.

Here, the timing controller 300 receives image data RGB, a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a main clock signal MCLK, and a data enable signal from an external system such as a TV system or a video card And receives a control signal TCS such as a signal DE. Although not shown, these signals may be input through the interface configured in the timing controller 300. [

The timing control unit 300 uses the input control signal TCS to control the gate control signal GCS for controlling the gate driving unit 400 and the data control signal DCS for controlling the data driving unit 500, .

The timing controller 300 receives image data RGB from an external system, aligns the image data, and transmits the image data to the data driver 500.

The gate driver 400 sequentially applies scan pulses to the plurality of gate lines GL in response to the gate control signal GCS supplied from the timing controller 300. [

For example, a plurality of gate lines GL are sequentially selected for every frame and a gate high voltage Vgh, for example, which turns on the thin film transistor T with respect to the selected gate line GL, . By the gate high voltage (Vgh), the thin film transistor T positioned on the corresponding row line is turned on. For example, a gate low voltage Vgl is output to turn off the thin film transistor T to the gate line GL until the next frame scan, and the thin film transistor T is turned off State.

The data driver 500 supplies the data voltages to the plurality of data lines DL in response to the data control signal DCS and the video data RGB supplied from the timing controller 300. That is, the data voltage corresponding to the image data RGB is generated using the gamma voltage Vgamma, and the generated data voltage is supplied to the corresponding data line DL.

The gamma voltage supplier 600 divides the high and low potential voltages generated from the power generator 700 to generate a gamma voltage Vgamma and supplies the gamma voltage Vgamma to the data driver 500.

The power generating unit 700 generates various driving voltages necessary for driving the liquid crystal display device 100. For example, the power supply voltage supplied to the timing controller 300, the data driver 500 and the gate driver 400 and the gate high voltage Vgh and the gate low voltage Vgl supplied to the gate driver 400 .

As described above, the common electrode and the pixel electrode according to the embodiment of the present invention are formed on the same substrate.

At this time, the common electrode is formed on the entire surface of the pixel P, and the pixel electrode is formed by alternating a long rod shape and a long rod shape bent in a slit shape above the common electrode with an insulating layer interposed therebetween.

Accordingly, the pixel electrode and the common electrode form a fringe field to drive the liquid crystal, and the pixel P is driven according to the fringe field switching (FFS) method.

By constituting the pixel P as described above, the pixel P is driven by being divided into the first and second regions (D1 and D2 in FIG. 7), and is driven into a multi domain, for example, do.

Hereinafter, the structure of the pixel P according to the embodiment of the present invention will be described in detail with reference to FIG.

4 is a schematic diagram illustrating a pixel structure according to an embodiment of the present invention.

A gate wiring GL extending in a row direction (horizontal direction) and a data wiring DL extending in a second direction (for example, column direction) are formed in a first direction, Intersect each other to define the pixel P.

A thin film transistor T, a pixel electrode 110, and a common electrode 120 are formed in the pixel P.

The thin film transistor T is formed at the intersection of the gate line GL and the data line DL.

Specifically, the thin film transistor T includes a gate electrode 101, a semiconductor layer 102, an ohmic contact layer (not shown), a source electrode 103 and a drain electrode 104.

Here, the gate electrode 101 is formed in connection with the gate line GL, and a semiconductor layer 102 and an ohmic contact layer (not shown) are sequentially formed on the gate electrode 101.

A source electrode 103 and a drain electrode 104 are formed on the ohmic contact layer (not shown). The source electrode 103 is connected to the data line DL and the drain electrode 104 is formed to correspond to the source electrode 103 with the gate electrode 101 interposed therebetween. At this time, the source electrode 103 and the drain electrode 104 are formed to overlap with both sides of the semiconductor layer 102 through the ohmic contact layer (not shown).

The pixel electrode 110 is formed by applying a data voltage from the data line DL through the thin film transistor T to the drain electrode of the thin film transistor T through the contact hole 105 formed in the protective layer 104, respectively.

The common electrode 120 is connected to a common wiring (not shown) and is formed corresponding to the pixel electrode 110. When a data voltage is applied to the pixel electrode 110 and a common voltage is applied to the common electrode 120 from a common wiring (not shown), an electric field is formed therebetween to drive the liquid crystal. The pixel electrode 110 and the common electrode 120, and the liquid crystal located between the pixel electrode 110 and the common electrode 120 constitute a liquid crystal capacitor.

Here, the common electrode 120 and the pixel electrode 110 will be described in more detail.

First, the common electrode 120 is formed in a plate shape on the entire surface of the pixel P.

An insulating layer is formed on the common electrode 120, though not shown. This is to prevent an electrical short between the common electrode 120 and the pixel electrode 110 formed in a plurality of slits.

The pixel electrode 110 is formed on the common electrode 120 with an insulating layer interposed therebetween.

In addition, the pixel electrode 110 is formed in a slit shape, and the first pixel electrode 111 having a curved long rod shape and the second pixel electrode 112 having a long rod shape are alternately formed.

First, the first pixel electrode 111 has a curved long bar shape, so that the first pixel electrode 111 has a curved shape as a whole.

On the other hand, the second pixel electrode 112 extends in parallel with the y-axis in a straight long rod shape.

At least one of the ends of the first and second pixel electrodes 111 and 112 may be connected to each other.

The first width w1 between the first pixel electrode 111 and one end of the first pixel electrode 111, for example, the second pixel electrode 112 located on the right side, 111 may be equal to or greater than the second width w2 between the second pixel electrode 112 located on the left side of the first pixel electrode 111 and the bending point BP of the first pixel electrode 111. [ At this time, the second width w2 may be, for example, 0.5 mu m.

Also, the first pixel electrode 111 is preferably bent to be symmetrical with respect to each other in the first and second regions D1 and D2.

It is preferable that the internal angle A of the bending point BP of the first pixel electrode 111 is, for example, 140 to 174 degrees. This is because the transmittance may be lowered when the internal angle A is less than 140 degrees and the color shift phenomenon may be intensified when the internal angle A is greater than 174 degrees.

In this case, the number of bending points BP of the first pixel electrode 111 is one, but two or more bending points BP may be used.

By forming the common electrode 120 on the entire surface of the pixel P and the slit-shaped pixel electrode 120 including the first and second pixel electrodes 111 and 112 on the common electrode 110, Field can be formed.

By bending the first pixel electrode 111, the liquid crystal constituting the pixel P is divided into the first and second regions D1 and D2 and driven.

Referring to FIG. 5, the liquid crystal driving of the pixel P designed according to the embodiment of the present invention will be described.

5 is a simulation showing the liquid crystal driving of the entire pixel designed according to the embodiment of the present invention.

First, the common electrode (120 in FIG. 4) is formed on the front surface of the pixel P and the first and second pixel electrodes 111 and 112 are formed in a slit shape on the common electrode (120 in FIG. 4).

At this time, the first pixel electrode 111 is in the shape of a long bar bent and the second pixel electrode 112 is in the shape of a long bar parallel to the y axis.

Here, when a voltage is applied to generate an electric field, the liquid crystal rotates counterclockwise in the first region D1 and the liquid crystal rotates clockwise in the second region D2.

Specifically, the rotation angle of the liquid crystals LC1 and LC3 adjacent to the second pixel electrode 112 is close to 90 deg., And the first and second pixel electrodes 111 , And 112 is 45 degrees.

In other words, in the pixel P structure according to the embodiment of the present invention, the liquid crystal is divided into the first and second regions D1 and D2 so that the directions of rotation are different from each other and correspond to the positions of the liquid crystal rotation angle liquid crystal And are different from each other.

Accordingly, the liquid crystal in one pixel P rotates in different directions to form multi domains. The compensation effect of the liquid crystal panel improves the color shift phenomenon of the liquid crystal panel, You can spread it.

Further, due to the nonuniform rotation of the liquid crystal, the driving voltage of the liquid crystal panel can be reduced, thereby reducing power consumption.

The effect of the pixel structure according to the embodiment of the present invention will be described with reference to FIG.

FIG. 6 is a graph illustrating the transmittance of a pixel structure and a pixel structure according to an embodiment of the present invention. Referring to FIG.

Ref in FIG. 6 is a graph of transmittance versus drive voltage in the general pixel structure of FIG. 1, and FIG. 6 is a graph of transmittance versus drive voltage of a pixel structure according to an embodiment of the present invention.

As shown in Fig. 6, the driving voltage necessary for realizing the same transmittance is smaller than Ref in the embodiment of the present invention.

Specifically, for example, in order to realize the maximum transmittance, about 6.5 V is required for Ref, but about 5.8 V is required in the embodiment of the present invention. Thus, the required driving voltage is reduced by about 11%.

This not only drives the pixel to the 2-domain, but also decreases the driving voltage as the rotation angle is different corresponding to the position of the liquid crystal with respect to the first and second electrodes, as described above.

Therefore, the present invention can improve the color shift phenomenon and the gradation reversal shape of the liquid crystal panel, thereby providing a clearer image quality.

The embodiment of the present invention described above is an example of the present invention, and variations are possible within the spirit of the present invention. Accordingly, the invention includes modifications of the invention within the scope of the appended claims and equivalents thereof.

100: liquid crystal display device 200: liquid crystal panel 110: pixel electrode
111: center pixel electrode 112: branching pixel electrode 120: common electrode
121: center common electrode 122: branch common electrode LC: liquid crystal
D1: first region D2: second region

Claims (7)

A pixel including first and second regions;
A common electrode formed on the front surface of the pixel in a plate shape;
A plurality of first pixel electrodes having a curved rod shape bent to be symmetrical with respect to each other in the first and second regions with respect to one bending point, and a plurality of second pixel electrodes A pixel electrode formed alternately;
A liquid crystal layer formed on the pixel electrode,
/ RTI >
Wherein an internal angle of the bending point of the plurality of first pixel electrodes is 140 to 174 deg.
An electric field is generated between the lower common electrode and the upper pixel electrode by voltage application,
The liquid crystal is rotated in the counterclockwise direction in the first region and clockwise in the second region by the electric field,
Wherein a rotation angle of the liquid crystal adjacent to the plurality of second pixel electrodes is 90 degrees and a rotation angle of the liquid crystal between the plurality of first pixel electrodes and the plurality of second pixel electrodes is 45 degrees.
The method according to claim 1,
A first width between an end of the plurality of first pixel electrodes and an end of a second pixel electrode located at one side of the plurality of first pixel electrodes among the plurality of second pixel electrodes, And a second width between the bending point and a second pixel electrode located on the other side of the plurality of first pixel electrodes,
Liquid crystal display device.
3. The method of claim 2,
The second width is 0.5 [micro] m
Liquid crystal display device.
delete The method according to claim 1,
At least one end of the plurality of first pixel electrodes and both ends of the plurality of second pixel electrodes are connected to each other
Liquid crystal display device.
The method according to claim 1,
An insulating layer is further formed between the common electrode and the pixel electrode
Liquid crystal display device. delete

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