KR100675928B1 - Fringe Field Drive Mode Liquid Crystal Display - Google Patents

Abstract

The present invention discloses a fringe field driving liquid crystal display device capable of preventing rubbing defects. According to the present invention, a plurality of gate bus lines, data bus lines, and upper and lower substrates are formed on upper and lower substrates disposed at a predetermined distance and formed on the lower substrate, and are arranged in a matrix form to define unit pixels. A liquid crystal layer including liquid crystal molecules having positive dielectric anisotropy, a counter electrode formed on each unit pixel of the lower substrate, and a fringe field are formed together with the counter electrode, the body portion having a frame shape overlapping the edge of the counter electrode. And a pixel electrode including a comb tooth formed at a predetermined angle with the gate bus line, a first horizontal alignment layer formed on an inner surface of the lower substrate, and an inner surface of the upper substrate. And a second horizontal alignment layer having a rubbing axis that is non-parallel to the rubbing axis of the first horizontal alignment layer. , Comb teeth of the pixel electrode is said to prevent rubbing failure to minimize the area that forms the gate bus line and from 45 to 85 ° or from 5 to 45 °, that the gate bus lines and the data bus line and the rubbing roller contact The first horizontal alignment layer is characterized in that it has a rubbing axis which is 45 degrees with respect to the gate bus line .

Description

Fringe field drive mode liquid crystal display device {FRINGE FIELD SWICHING MODE LCD}

1 is a plan view showing a conventional fringe field drive mode liquid crystal display device.

2 is a schematic representation of the gate bus line and data bus line and rubbing roll of the FFS-LCD;

3 is a plan view of an FFS-LCD in accordance with an embodiment of the present invention.

4 is a plan view of an FFS-LCD according to another embodiment of the present invention;

Explanation of symbols on main parts of drawing

21- Gate Bus Lines 23-Data Bus Lines

25-counter electrode 27,270-pixel electrode

27b, 270b-comb teeth

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a fringe field switching liquid crystal display (FFS-LCD), and more particularly, to an FFS-LCD capable of minimizing rubbing unevenness.

In general, the FFS-LCD has been proposed to improve the low opening ratio and transmittance of a general in-plane switching (IPS) mode LCD, and has been filed in Korean Patent Application No. 98-9243.

1 is a plan view showing a lower substrate structure of an FFS-LCD.

Referring to FIG. 1, the gate bus line 3 and the data bus line 7 are cross-arranged on the lower substrate 1 to define a unit pixel Pix. The thin film transistor TFT is disposed near the intersection point of the gate bus line 3 and the data bus line 7. The counter electrode 2 is formed of a transparent conductor and is formed for each unit pixel pix. In this case, the counter electrode 2 may be formed in the shape of a square plate or in the form of a comb. The common signal line 30 is disposed in contact with the counter electrode 2 in order to continuously supply the common signal to the counter electrode 2. In this case, the common signal line 30 is formed of a metal film having excellent signal transmission characteristics, and is generally formed of a metal film for a gate bus line. In addition, the common signal line 30 includes a first portion 30a parallel to the gate bus line 3 and in contact with a predetermined portion of the counter electrode 2, and the data bus line 7 from the first portion 30a. And a second portion 30b extending in parallel with each other and disposed between the counter electrode 2 and the data bus line 7, respectively. The pixel electrode 9 is formed in the unit pixel pix so as to overlap with the counter electrode 2. At this time, the pixel electrode 9 and the counter electrode 2 are electrically insulated. The pixel electrode 9 is formed in a comb shape, and connects a plurality of comb portions 9a formed at equal intervals in parallel with the data bus line 7 and one end of the comb portion 9a of the thin film transistor TFT. And a bar 9b in contact with the predetermined portion. On the other hand, although not shown in the figure, the upper substrate facing the lower substrate 1 is opposed and replaced with a width larger than the distance between the pixel electrode 9 and the counter electrode 5, the lower substrate 1 and the upper substrate In between, a liquid crystal layer containing several liquid crystal molecules is interposed. In addition, a horizontal alignment layer is disposed on the inner surface of the lower substrate 1 and the inner surface of the upper substrate (not shown). Among them, the horizontal alignment layer of the lower substrate has a rubbing axis that forms 60 to 90 ° with the projection line (i.e., gate bus line) of the fringe field in order to obtain the maximum transmittance when using liquid crystal molecules having a positive dielectric anisotropy, The horizontal alignment layer of the upper substrate has a rubbing axis that is not parallel to the rubbing axis of the horizontal alignment layer of the lower substrate.

The FFS-LCD having such a configuration operates as follows.

When an electric field is formed between the counter electrode 5 and the pixel electrode 9, the distance between the counter electrode 5 and the pixel electrode 9, that is, the distance between the upper and lower substrates is larger than the thickness of the gate insulating film, so that the two electrodes are larger. Fringe fields are formed between and over the electrodes. This fringe field extends over the counter electrode 5 and the pixel electrode 9 so that all of the liquid crystal molecules on the electrode are operated. Thereby, a high opening rate and a high transmittance can be realized.

In the above-described FFS-LCD, most liquid crystal molecules in the unit pixel were operated to achieve a high opening ratio and a high transmittance.

However, in the conventional FFS-LCD, the following problem occurs during the rubbing treatment of the first horizontal alignment layer to obtain the maximum transmittance.                         

That is, FIG. 2 schematically illustrates the gate bus line 3, the data bus line 7, and the rubbing roll 100 of the FFS-LCD. According to FIG. 2, a predetermined height is provided below the first horizontal alignment layer. The gate bus line 3 and the data bus line 7 are disposed, and the first horizontal alignment film is rubbed by the rubbing roll 100 so as to form 60 to 90 degrees with the projection line of the fringe field. At this time, when the rubbing axis rubs with the fringe field to form 60 to 90 °, an area in contact with the rubbing roll 100, the gate bus line 3, and the data bus line 7 increases, resulting in rubbing defects. Easy to be

Accordingly, an object of the present invention is to provide a fringe field driving liquid crystal display device capable of preventing rubbing defects.

In order to achieve the above object of the present invention, the present invention, the upper and lower substrates disposed at a predetermined distance, formed on the lower substrate, the gate bus line and data bus formed in a matrix form to define the unit pixels A liquid crystal layer including liquid crystal molecules having positive dielectric anisotropy interposed between the line and the upper and lower substrates, a counter electrode formed at each unit pixel of the lower substrate, and a fringe field together with the counter electrode, A pixel electrode including a body portion overlapping an edge and having a frame shape, a space surrounded by the body portion, a comb teeth forming an angle with the gate bus line, a first horizontal alignment layer formed on an inner surface of the lower substrate, A rubbing axis that is formed on an inner surface of the upper substrate and is in parallel with a rubbing axis of the first horizontal alignment layer. And a second horizontal alignment layer having a shape, wherein the comb teeth of the pixel electrode form a 45 to 85 ° or 5 to 45 ° angle with the gate bus line, and a contact area between the gate bus line and the data bus line and the rubbing roller. In order to minimize rubbing defects, the first horizontal alignment layer has a rubbing axis of 45 ° with respect to the gate bus line .

In addition, the present invention, the upper and lower substrates disposed at a predetermined distance, the number formed on the lower substrate, interposed between the gate bus line, data bus line, upper and lower substrates arranged in a matrix form to define unit pixels A liquid crystal layer including liquid crystal molecules having negative dielectric anisotropy, a counter electrode formed on each unit pixel of the lower substrate, and a fringe field together with the counter electrode, the body having a frame shape overlapping the edge of the counter electrode A pixel electrode including a portion and a space surrounded by the body portion, the comb teeth forming a predetermined angle with the gate bus line, and a first horizontal alignment layer formed on an inner surface of the lower substrate; And a second horizontal alignment layer formed on an inner surface of the upper substrate, the second horizontal alignment layer having a rubbing axis that is non-parallel to the rubbing axis of the first horizontal alignment layer, wherein the comb teeth of the pixel electrode are 90 + α ° with the gate bus line. Here, α is 45 to 85 ° or 5 to 45 °), and the first horizontal alignment layer is the gate to prevent rubbing failure by minimizing the area where the gate bus line, the data bus line and the rubbing roller contact It is characterized by having a rubbing axis which makes 45 degrees with respect to a bus line .

(Example)

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

3 is a plan view of an FFS-LCD according to an embodiment of the present invention, and FIG. 4 is a plan view of an FFS-LCD according to another embodiment of the present invention.

Referring to FIG. 3, the lower substrate 20 and the upper substrate (not shown) face each other at a predetermined distance, and a liquid crystal layer (not shown) including several liquid crystal molecules between the lower substrate 20 and the upper substrate. Not included). At this time, the liquid crystal molecules in this embodiment have a positive dielectric anisotropy.

The gate bus line 21 and the data bus line 23 are alternately arranged on the inner side surface of the lower substrate 20 to define a unit pixel in a matrix form. The thin film transistor TFT as a switching element is disposed near the intersection of the gate bus line 21 and the data bus line 23.

The counter electrode 25 is disposed in the form of a plate in the unit pixel of each lower substrate 20. In this case, the counter electrode 25 is formed of a transparent conductive material, for example, an indium tin oxide (ITO) material, and is spaced apart from the gate bus line 21 and the data bus line 23 defining a unit pixel by a predetermined distance. . At this time, although not shown in the drawing, the counter electrode 25 is in contact with the common signal line and continuously receives the common signal.

The pixel electrode 27 is formed to overlap the counter electrode 25 in each unit pixel. Like the counter electrode 25, the pixel electrode 27 is formed of a transparent conductive material, and a predetermined portion of the pixel electrode 27 is in contact with the thin film transistor TFT. The pixel electrode 27 has a rectangular frame-shaped body portion 27a overlapping the edge of the counter electrode 25 and a plurality of comb teeth 27b partitioning a space surrounded by the body portion 27a into several spaces. At this time, the comb teeth 27b extend in parallel at equal intervals, respectively, and form a predetermined angle α, preferably 45 to 85 degrees or 5 to 45 degrees, with the gate bus line 21. In addition, the pixel electrode 27 is partially contacted with the thin film transistor TFT.

The first horizontal alignment layer (not shown) is covered on the result of the lower substrate 20. This first horizontal alignment film has a pretilt angle of 10 ° or less and has a predetermined rubbing axis R. As shown in FIG. Here, the rubbing axis R of the first horizontal alignment layer is 45 ° with respect to the gate bus line 21. This is because when the rubbing axis R forms 45 ° with the gate bus line 21, the area passing through the gate bus line 21 and the data bus line 23 is minimized, thereby reducing rubbing defects.

On the other hand, a color filter (not shown) for realizing colorization is disposed on the inner surface of the upper substrate (not shown), and a second horizontal alignment film (not shown) is formed on the surface of the color filter. Here, the second horizontal alignment layer has a rubbing axis that is not parallel to the rubbing axis R of the first horizontal alignment layer.

The polarizer (not shown) is disposed on the outer side of the lower substrate 20 and has a polarization axis coincident with the rubbing axis R to be driven in the normally black mode. On the other hand, an optically related decomposer (not shown) is disposed on the outer side of the upper substrate and has an absorption axis orthogonal to the polarization axis.

This FFS-LCD of the present invention operates as follows.

First, if no voltage difference is generated between the counter electrode 25 and the pixel electrode 27, the liquid crystal molecules (not shown) are arranged such that their long axes coincide with the rubbing axis R. FIG.

Thereafter, when a voltage difference is generated between the counter electrode 25 and the second pixel electrode 27, a fringe field is formed in each unit pixel. At this time, in the unit pixel, the fringe field E1 having a normal shape is formed on the comb teeth 27b by the comb teeth 27b and the counter electrode 25. Accordingly, the liquid crystal molecules in which the rubbing axis and the long axis are arranged in parallel are twisted to coincide with the long axis and the field, thereby generating a maximum transmittance. That is, even if the rubbing axis R of the first horizontal alignment layer is formed to be 45 degrees with respect to the gate bus line, the maximum transmittance is achieved by changing the shape of the pixel electrode 27.

On the other hand, in the case of using liquid crystal molecules having negative dielectric anisotropy, the shape of the pixel electrode is changed as shown in FIG. 4 while the rubbing axis forms 45 ° with the gate bus line 21. That is, as shown in FIG. 4, the pixel electrode 270 is 90 ° symmetric with the body portion having a rectangular frame shape and the comb teeth 27b when the above-mentioned amount of liquid crystal molecules are used. Arrange so that it may make (alpha) ((alpha == 45-85 degree or 5-45 degree). Even in this configuration, rubbing defects are minimized while achieving maximum transmittance.

As described in detail above, according to the present invention, in the FFS-LCD, the rubbing axis forms 45 ° with the gate bus line, and the shape of the pixel electrode is changed so that the fringe field forms a predetermined angle with the rubbing axis.

Accordingly, the area in which the rubbing roll and the gate bus line and the data bus line contact each other during rubbing is minimized, thereby reducing rubbing defects.

Thus, the image quality characteristic of the FFS-LCD is improved.

In addition, this invention can be implemented in various changes within the range which does not deviate from the summary.

Claims (2)

Upper and lower substrates disposed at a predetermined distance; A gate bus line and a data bus line formed on the lower substrate and disposed in a matrix to define unit pixels; A liquid crystal layer comprising liquid crystal molecules having positive dielectric anisotropy interposed between the upper and lower substrates; A counter electrode formed on each unit pixel of the lower substrate; A pixel electrode including a fringe field formed together with the counter electrode, a body portion overlapping an edge of the counter electrode and having a frame shape, and a space surrounded by the body portion, and comb teeth having an angle with the gate bus line; ; A first horizontal alignment layer formed on an inner surface of the lower substrate; A second horizontal alignment layer formed on an inner surface of the upper substrate and having a rubbing axis that is non-parallel to the rubbing axis of the first horizontal alignment layer; The comb teeth of the pixel electrode form 45 to 85 ° or 5 to 45 ° with the gate bus line, and minimize the area where the gate bus line and the data bus line come into contact with the rubbing roller to prevent rubbing failure. 1. The FFS-LCD, wherein the horizontal alignment layer has a rubbing axis at 45 ° with respect to the gate bus line . Upper and lower substrates disposed at a predetermined distance; A gate bus line and a data bus line formed on the lower substrate and disposed in a matrix to define unit pixels; A liquid crystal layer comprising liquid crystal molecules having negative dielectric anisotropy interposed between the upper and lower substrates; A counter electrode formed on each unit pixel of the lower substrate; A pixel electrode including a fringe field formed together with the counter electrode, a body portion overlapping an edge of the counter electrode and having a frame shape, and a space surrounded by the body portion, and comb teeth having an angle with the gate bus line; ; A first horizontal alignment layer formed on an inner surface of the lower substrate; And A second horizontal alignment layer formed on an inner surface of the upper substrate and having a rubbing axis that is non-parallel to the rubbing axis of the first horizontal alignment layer; The comb teeth of the pixel electrode form 90 + α ° with the gate bus line (where α is 45 to 85 ° or 5 to 45 °), and the area where the gate bus line and the data bus line are in contact with the rubbing roller. And the first horizontal alignment layer has a rubbing axis of 45 [deg.] With respect to the gate bus line to minimize rubbing failure .

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