KR19990046345A - Development of dhan-lcd by using fringe field effect - Google Patents

Abstract

According to the present invention, the fringe field effect (field effect) caused by the ITO slit electrode pattern structure makes it possible to realize a video even at a wide viewing angle and a large screen, which cannot be realized in a conventional HAN (liquid aligned nematic) -liquid crystal display (LCD). The present invention relates to a dual domain hybrid aligned nematic (DHAN) -LCD using a field effect capable of realizing a response speed. The DHAN liquid crystal display using the electric field effect is displayed on the second road.

Field effect DHAN-LCD of the present invention has a dual domain formed by only one rubbing treatment using a fringe field effect when a pattern is formed on an ITO slit electrode to apply an electric field, compared to a general dual domain mode using an orientation treatment. The manufacturing process is simple and the response speed and viewing angle characteristics are superior to the conventional TN (twisted nematic) mode. In addition, instead of rubbing treatment on the horizontal alignment surface substrate on one side with vertical orientation and the other side with horizontal orientation, the optical orientation method using the photopolymerization method can easily realize 0 ° of pretilt angle. There is an advantage that non-rubbing treatment is possible. Therefore, DHAN-LCD has a much better response characteristic than other modes known as the wide viewing angle mode (about 15ms), and it is a breakthrough liquid crystal display device that can obtain wide viewing angle characteristics by using electric field effect. The manufacturing process is very simple and has the advantage of being very reliable.

Description

DEVELOPMENT OF DHAN-LCD BY USING FRINGE FIELD EFFECT}

The present invention relates to a DHAN mode in which a slit structure is formed on an ITO electrode and a dual domain is formed using a fringe field effect, thereby realizing a wide viewing angle characteristic and a high speed response speed.

A liquid crystal display is a display having excellent characteristics such as small size, light weight, low power consumption, and the like, and is a screen display device using a difference in light transmittance caused by a change in liquid crystal array.

With thin-film-transister technology and improved driving, TFT-driven liquid crystal displays using TN (twisted nematic) mode have been commercialized by being applied to high-performance displays such as large screen, high resolution, and full color. Because of its thin and long shape, the optical characteristics become asymmetrical in the vertical direction, so that the viewing angle is narrow and the brightness is reversed between grayscales, and the response speed is slow to realize a perfect moving image.

Modes currently being studied to compensate for the shortcomings of the TN mode include IPS (in plane switch) mode, OCB (optically compensated bend) mode, VA (vertically aligned) mode. However, the development of high-speed response LCD for the next generation as well as the implementation of such a wide viewing angle is very important. Therefore, in this development, we propose a new DHAN-LCD capable of wide viewing angle and high speed response.

Conventional HAN LCD is manufactured by injecting a positive liquid crystal by using a vertical alignment film on one substrate and a horizontal alignment film oriented (rubbing) in a predetermined direction on the other substrate. When a voltage greater than the threshold is applied to the liquid crystal layer, the liquid crystal molecules are perpendicular to the electric field, and the liquid crystal cell has a phase difference, and the transmittance is changed according to the polarization state of light passing through the liquid crystal layer.

In the HAN-LCD, a multi domain is formed by two alignment processes such that a pretilt angle of opposite direction is generated when a liquid crystal is injected by dividing a liquid crystal array in two regions. The method is shown in FIG. This method has a disadvantage in that the fabrication process is complicated, such as an alignment treatment, a photoresist applied thereon, etching a portion again, and the alignment treatment in the opposite direction. In addition, the method of using the optical alignment method is known, but in order to use this method, the pretilt angle must be able to be kept stable at least 3 ° to prevent defects. In addition, the alignment film using the photopolymerization method, which is already published, is difficult and unstable to control the pretilt, so it is difficult to realize the dual domain hybrid tunable birefringence (HTB) mode. Therefore, the characteristics of the present development is that stable dual domain alignment is possible by using an alignment process with a pretilt angle of 0 ° in the initial orientation and controlling the liquid crystal molecules bidirectionally by using an electric field effect, and an alignment method using a photopolymerization method. When used, the orientation in which the pretilt angle is 0 ° can be easily obtained by vertical irradiation of only one UV light (ultraviolet ray). That is, by using the electric field effect than the dual domain HTB-LCD using the conventional alignment treatment, the DHAN-LCD can be easily manufactured by one rubbing treatment when using the rubbing treatment and one UV light irradiation when using the optical alignment method. have. This DHAN-LCD is an excellent mode with advantages such as high speed response speed (about 15ms), wide viewing angle characteristics, normally black mode and simple manufacturing process. It can be seen that the above characteristics are in accordance with the characteristics required for the large-area moving picture described below.

An object of the present invention is to implement a wide viewing angle and high-speed response characteristics in DHAN-LCD by the fringe field effect orientation control method that can satisfy the above conditions.

First degree orientation division HAN mode

FIG. 2 Field Effect HAN Mode Structure

3A also shows no voltage effect of the field effect DHAN-LCD of the present invention.

3B also shows the voltage applied to the field effect DHAN-LCD of the present invention.

4th field HAN mode electric field distribution

Fig. 5 ITO slit electrode pattern shape

6th Slit Electrode Structure Fabrication

In order to achieve the above object, the present invention proposes a basic DHAN-LCD of FIG. 3A shows an alignment state of the liquid crystal when no voltage is applied, and FIG. 3B shows a liquid crystal alignment state when the voltage is applied.

The DHAN-LCD of the present invention can control the liquid crystal molecules by forming a slit electrode structure on the ITO electrode to form a dual domain using a fringe field effect.

4 shows the electric field distribution of the DHAN-LCD of the present invention. The dual domain can be formed by this slit electrode pattern, for the following reasons.

If the pattern is not formed on the upper and lower substrates, and the ITO electrode is on the front side, the electric field is formed in the vertical direction up and down, but the electric field is alternately formed in the upper and lower substrates in a parabolic shape by patterning the horizontal orientation. As a result, the liquid crystal molecules can be controlled in both directions, and the DHAN-LCD can be realized only when the horizontal alignment film is rubbed once and the pretilt angle is about 0 °. Instead of the rubbing treatment, an easy way to implement the photopolymerization (a kind of photo-alignment method) is to achieve an orientation with 0 ° of pretilt. This is implemented.

The manufacturing method of the DHAN-LCD using the fringe field effect by forming a slit electrode pattern on the ITO electrode according to the present invention will be described.

5 shows the shape of the slit electrode pattern formed on the ITO electrode.

6 shows a photoresist process for forming the slit pattern of FIG.

The production order is as follows:

First, apply photo resist on ITO glass.

Second, run the photo lithography process.

Third, run development.

Fourth, etch by ITO etchant.

Fifth, the removal of photoresist

The following is a DHAN mode fabrication method in which a slit electrode pattern is formed on an ITO electrode to form a dual domain using a fringe field effect.

The production sequence is as follows.

First, a slit electrode pattern is formed on ITO glass.

Second, a vertical alignment film is coated on the ITO substrate on which the slit electrode pattern is formed, and this is determined as the upper substrate.

Third, the horizontal alignment layer is coated on the ITO substrate on which the slit electrode pattern is formed, and this is designated as the lower substrate.

Fourth, the liquid crystal molecules are horizontally aligned by rubbing the substrate coated with the horizontal alignment layer (or vertically irradiating the polarized UV light using the optical alignment).

Fifth, the top and bottom substrates are combined to keep the cell gab at 4㎛ so that the electrodes alternate with each other and inject a positive liquid crystal. However, since the cell thickness is determined by Δnd, it is produced by combining well with the properties of the liquid crystal and the retardation film.

As described above, according to the present invention, the DHAN-LCD using the field effect can easily form a dual domain by using a fringe field effect by forming a slit pattern on the ITO electrode, thereby realizing a wide viewing angle and achieving a HAN mode. Characteristics such as high-speed response, which are advantages, can be realized. In addition, the manufacturing process can be simplified and stable liquid crystal molecular control is possible than the conventional DHTB mode using the orientation split method.

Those skilled in the art will be able to easily make various modifications without departing from the scope and spirit of the invention. Accordingly, the claims appended to this description should not be limited to the description of the present description but should be construed broadly.

Claims (3)

Wide viewing angle HAN-LCD using fringe field effect by forming slit pattern on ITO electrode. The DHAN-LCD according to claim 1, wherein the DHAN-LCD has two or more slit electrode structures in which one pixel is alternated between upper and lower substrates. The HAN-LCD according to claim 1, wherein an orientation characteristic of a pretilt angle of 3 degrees or less in a horizontal orientation is used.