KR20000067118A - High aperture ratio and high transmittance LCD improved response time - Google Patents

Abstract

PURPOSE: A high aperture rate and high transmissibility LCD having improved response speed is provided to form pixel electrodes and counter electrodes with transparent material and enhance the mobile characteristics of the molecules. CONSTITUTION: A high aperture rate and high transmissibility LCD having improved response speed comprises a bottom substrate(20), gate/data bus lines(21,23), TFTs(25), counter electrodes(27) and pixel electrodes(29). The bottom substrate(20) is a transparent insulation substrate, on which the gate/data bus lines(21,23) are arrayed to be crossed to define unit pixels. The TFTs(25) are formed on the cross points of the gate/data bus lines(21,23). The counter electrodes(27) and the pixel electrodes(29) for driving LC molecules are formed within the unit pixels

Description

High aperture ratio and high transmittance LCD improved response time

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high aperture ratio and high transmittance liquid crystal display, and more particularly, to a high aperture ratio and a high transmittance liquid crystal display in which a response speed is improved to enable moving images.

In general, a high aperture ratio and a high transmittance liquid crystal display have been proposed to improve a low aperture ratio and a transmittance of a general IPS mode liquid crystal display, and this technology has been filed in Korean Patent Application No. 98-9243.

Such a high aperture ratio and high transmittance liquid crystal display device forms a counter electrode and a pixel electrode with a transparent conductor, and forms a gap between the counter electrode and the pixel electrode to be smaller than a gap between the upper and lower substrates, thereby forming a fringe field on the counter electrode and the pixel electrode. (fringe filed) is formed.

Here, a conventional high aperture ratio and high transmittance liquid crystal display is shown in FIG. 1. As shown in the figure, the lower substrate 1 and the upper substrate 10 are opposed to each other at a predetermined distance. Here, the distance between the lower substrate 1 and the upper substrate 10 is referred to as a cell gap d hereinafter. The liquid crystal layer 15 is interposed between the lower substrate 1 and the upper substrate 10. On the lower substrate 1, the counter electrodes 3 are spaced apart at regular intervals with a predetermined width. In addition, the counter electrode 3 may be formed in a plate shape. Here, the counter electrode 3 is formed of a transparent conductor, for example, indium tin oxide (ITO). The gate insulating film 5 is formed on the lower substrate 1 on which the counter electrode 3 is formed, and the pixel electrode 7 is formed between the counter electrodes 3 on the gate insulating film 5. In this case, the pixel electrode 7 is also formed of a transparent conductor, and the distance l between the pixel electrode 5 and the counter electrode 3 is smaller than the cell gap d.

Alignment films 8 and 11 are formed on the uppermost opposing surface of the lower substrate 1 and on the opposing surface of the upper substrate 10 to uniformly arrange liquid crystal molecules in the liquid crystal layer 15 before an electric field is formed. have. In this case, the alignment layers 8 and 11 have a low pretilt angle (about 2 ° or less), and are non-parallel to achieve a predetermined angle, for example, maximum transmittance, with the direction in which the electric field is formed. -parallel) is rubbing.

The high aperture ratio and high transmittance liquid crystal display having such a configuration is such that, before the electric field is formed between the counter electrode 3 and the pixel electrode 7, the substrate is almost horizontal to the substrate under the influence of the alignment films 8 and 11. Are arranged.

On the other hand, when an electric field is formed between the counter electrode 3 and the pixel electrode 7, a fringe field is formed in which the shape of the electric field includes a vertical component, and the liquid crystal molecules have their optical axis perpendicular or horizontal to the electric field direction. It turns out and leaks light.

However, the above-described high aperture and high transmittance liquid crystal display device is formed such that the pixel electrode and the counter electrode are made of a transparent material, and the liquid crystal molecules are easily operated on the pixel electrode and the counter electrode, so that the liquid crystal of the conventional inflation switching mode can be used. It is much better in terms of aperture ratio and transmittance than display devices.

However, the response time is very slow compared to the conventional twist nematic mode, which makes it difficult to use a moving picture.

1 is a cross-sectional view of a conventional high opening ratio and high transmittance liquid crystal display device.

2 is a plan view of a lower substrate of the high aperture ratio and high transmittance liquid crystal display according to the present invention;

3 is a plan view showing the operation of the liquid crystal of the high aperture and high transmittance liquid crystal display according to the present invention.

(Explanation of symbols for the main parts of the drawing)

21-Gate Bus Lines 23-Data Bus Lines

25-Thin Film Transistor 27-Counter Electrode

29-pixel electrode 31-common electrode line

In order to achieve the above object of the present invention, according to an embodiment of the present invention, a gate bus line, a data bus line intersected with the gate bus line to define a unit pixel, and formed of a transparent material in the unit pixel A lower substrate including a counter electrode and a pixel electrode formed in the unit pixel and formed of a transparent material and forming a fringe field together with the counter electrode; An upper substrate facing the lower substrate at a predetermined distance; A ferroelectric liquid crystal layer interposed between the upper and lower substrates; An alignment layer disposed between the liquid crystal layer and the lower substrate and between the liquid crystal layer and the upper substrate, respectively; And a polarizing plate disposed on a rear surface of the lower substrate and a rear surface of the upper substrate, wherein the alignment layer is a horizontal alignment layer, and the alignment layers have a long axis of 45 when the electric field is formed between the counter electrode and the pixel electrode. Rubbed to form °, wherein the polarization axis of the lower polarizing plate is disposed to be parallel to the long axis direction of the liquid crystal molecules before the electric field is formed, the polarization axis of the upper polarizing plate is characterized in that arranged to be orthogonal to the polarization axis of the lower polarizing plate.

Here, the rubbing axis of the lower alignment layer is rubbed to form about 10 to 25 ° with the data bus line, more preferably about 22.5 ° with the data bus line. The polarization axis of the polarizer of the lower substrate is parallel to the data bus line.

In addition, the ferroelectric liquid crystal layer is arranged in a twistless state, the pitch is larger than the cell gap.

According to the present invention, the response time can be greatly improved by using the ferroelectric liquid crystal as the liquid crystal in the high opening ratio and the high transmittance liquid crystal display device.

Accordingly, moving images can be implemented.

(Example)

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

2 is a plan view of a lower substrate of the high aperture ratio and high transmittance liquid crystal display according to the present invention, and FIG. 3 is a plan view illustrating the operation of the liquid crystal of the high aperture ratio and high transmittance liquid crystal display according to the present invention.

First, as shown in FIG. 2, the high aperture ratio and high transmittance liquid crystal display according to the present invention intersects the gate bus line 21 and the data bus line 23 on a lower substrate 20, for example, on a transparent insulation substrate. Arranged to define unit pixels. The thin film transistor 25 is provided at the intersection of the gate bus line 21 and the data bus line 23.

In the unit pixel space, a counter electrode 27 for driving liquid crystal molecules (not shown) is formed in a comb shape.

In addition, the pixel electrode 29 is formed in the unit pixel space so as to drive the liquid crystal molecules by forming a fringe field together with the counter electrode 27. Here, the pixel electrode 29 is also formed of an ITO material, which is a transparent conductor, is formed in a comb form like the counter electrode 27, and is arranged to form a tooth structure with the counter electrode 27.

The common electrode line 31 is disposed in parallel with the gate bus line 21 to be in contact with the counter electrode 27.

An upper substrate (not shown) is disposed on the lower substrate 20 at predetermined intervals. This upper substrate is also a transparent insulating substrate.

A liquid crystal layer (not shown) is interposed between the lower substrate 20 and the upper substrate. The liquid crystal layer of the present invention uses a ferroelectric liquid crystal to improve the response characteristics of the liquid crystal display device. In general, ferroelectric liquid crystal is a material that spontaneously polarized as is known, and the response speed is much faster than that of a general nematic liquid crystal. Here, the ferroelectric liquid crystals of the present invention are arranged without twisting, and are formed so that their pitch is longer than the cell gap.

In order to control the initial arrangement of the ferroelectric liquid crystal molecules between the lower substrate and the liquid crystal layer and between the upper substrate and the liquid crystal layer, an alignment layer, for example, a horizontal alignment layer (not shown) having a pretilt angle of 10 ° or less is interposed. . Among the horizontal alignment layers, the lower horizontal alignment layer has the optical axis of the electric field and the liquid crystal molecules at ± 45 ° when the electric field is applied, so that the maximum transmittance can be satisfied. For example, the data bus line 23 and the rubbing axis may be 10 to 45 °. Preferably rubbed to achieve about 22.5 °. In addition, the upper horizontal alignment layer (not shown) is rubbed in parallel with the lower horizontal alignment layer.

In more detail, as shown in FIG. 3, ferroelectric liquid crystal molecules generally operate in a conical spiral with respect to a rubbing axis (R). Accordingly, when the electric field is formed, the rubbing axis R is taken in the 22.5 ° direction, which is 1/2 of 45 ° with the data bus line, so that the long axis (or short axis) and the electric field of the liquid crystal molecules are 45 degrees. It is desirable to.

That is, when the rubbing axis R is rubbed to form 22.5 ° with the data bus line 23, the long axis of the liquid crystal molecules before the electric field is formed is in the direction of the data bus line 23 forming the rubbing axis at −22.5 ° (as shown in the drawing). Direction).

On the other hand, when the electric field is formed, the liquid crystal molecules are rearranged in a conical spiral, and arranged in a direction (direction ②) of the drawing to form a rubbing axis with + 22.5 °.

Therefore, when the electric field is applied, the electric field direction F and the major axes of the liquid crystal molecules form 45 ° to each other, and the maximum transmittance is satisfied by 45 degrees with the major axis of the liquid crystal molecules and the absorption axes of the upper and lower polarizers, respectively.

In addition, a polarizing plate is disposed on the back surface of the lower substrate 20 and the upper substrate (not shown). The polarization axis of the polarizing plate (not shown) of the lower substrate 20 is dark when no electric field is formed in the liquid crystal display. In order to be in a state, it is disposed parallel to the data bus line, and the polarization axis of the polarizing plate of the upper substrate is arranged to be orthogonal to the polarization axis of the lower polarizing plate.

The high aperture ratio and high transmittance liquid crystal display device of the present invention improves the response speed by several ms by using a ferroelectric liquid crystal having a very fast response speed by spontaneous polarization instead of nematic liquid crystal.

Further, in consideration of the conical helical operation of the ferroelectric liquid crystal molecules with respect to the rubbing axis R, the rubbing axis R of the alignment layer is rubbed to achieve 22.5 ° with respect to the data bus line 23. Accordingly, when the electric field is applied, the liquid crystal molecules and the electric field form 45 degrees, and the maximum transmittance is satisfied by forming 45 degrees with the long axis of the liquid crystal molecules and the absorption axes of the upper and lower polarizers, respectively. Maximum transmittance can be achieved.

As described in detail above, according to the present invention, by using the ferroelectric liquid crystal as the liquid crystal in the high opening ratio and high transmittance liquid crystal display device, the response time can be greatly improved.

Accordingly, moving images can be implemented.

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

Claims (6)

A gate bus line, a data bus line intersecting with the gate bus line to define a unit pixel, a counter electrode formed in the unit pixel and formed of a transparent material, and formed of a transparent material in the unit pixel and having a fringe field together with the counter electrode. A lower substrate including a pixel electrode to be formed; An upper substrate facing the lower substrate at a predetermined distance; A ferroelectric liquid crystal layer interposed between the upper and lower substrates; An alignment layer disposed between the liquid crystal layer and the lower substrate and between the liquid crystal layer and the upper substrate, respectively; And It includes a polarizing plate disposed on the lower substrate back and the upper substrate back, respectively, The alignment layer is a horizontal alignment layer, and the alignment layers are rubbed to form a 45 ° long axis between the electric field and the liquid crystal molecules formed when an electric field is formed between the counter electrode and the pixel electrode. The polarization axis of the lower polarizing plate is arranged to be parallel to the long axis direction of the liquid crystal molecules before the electric field is formed, the polarization axis of the upper polarizing plate is arranged to be orthogonal to the polarization axis of the lower polarizing plate, the high aperture ratio and high transmittance is improved Liquid crystal display. The liquid crystal display of claim 1, wherein the rubbing axis of the lower alignment layer is rubbed to form about 10 to 25 ° with the data bus line. The liquid crystal display of claim 1, wherein the rubbing axis of the lower alignment layer is rubbed to form about 22.5 ° with the data bus line. The liquid crystal display of claim 3, wherein the polarization axis of the polarizer of the lower substrate is parallel to the data bus line. The liquid crystal display of claim 1, wherein the ferroelectric liquid crystal layers are arranged without twisting. The liquid crystal display of claim 1, wherein the ferroelectric liquid crystal layer has a pitch larger than that of a cell gap.