KR20030073225A - Fringe field switching vertical align mode liquid crystal display - Google Patents

Abstract

PURPOSE: A fringe field switching vertical align mode liquid crystal display is provided to reduce response time of liquid crystal using vertical alignment and remove a disclination line to improve transmissivity. CONSTITUTION: A fringe field switching vertical align mode liquid crystal display includes upper and lower substrates combined with each other, having a liquid crystal layer interposed between them, a vertical alignment film for vertically aligning liquid crystal molecules of the liquid crystal layer, a counter electrode(130) and a pixel electrode(140) for generating fringe field for driving the liquid crystal molecules. The pixel electrode and counter electrode are formed of a transparent material on the lower substrate, having an insulating layer formed between them. A pixel electrode is partially superposed on the counter electrode. Each of the counter electrode and pixel electrode has an open region and a non-open region. The insulating layer covers the non-open region of the counter electrode but does not cover the open region of the counter electrode.

Description

Fringe field switching vertical alignment mode liquid crystal display {FRINGE FIELD SWITCHING VERTICAL ALIGN MODE LIQUID CRYSTAL DISPLAY}

The present invention relates to a fringe field switching vertical alignment mode liquid crystal display device, and more particularly, to a fringe field switching vertical alignment mode liquid crystal display device which drives a vertically aligned liquid crystal using a fringe field to improve screen quality. It is about.

Twist nematic (TN) mode, which has been recently attracting attention as a flat panel display technology, has been proposed for vertical alignment (VA) mode and in-plane switching (IPS) mode due to characteristics such as narrow viewing angle. there was. However, the VA mode can shorten the response time of the liquid crystal, but has disadvantages such as a decrease in transmittance due to the multi-domain configuration. there was.

In order to solve this problem, a fringe field switching vertical alignment (hereinafter, referred to as fringe field switching) can improve transmittance by forming the electrode as a transparent body and reducing the gap between the counter electrode and the pixel electrode smaller than zero or cell gap while taking advantage of the VA mode. , FFS VA) mode has been proposed.

In the conventional FFS VA mode liquid crystal display, as shown in FIG. 1, a box shape is formed on an upper surface of a lower substrate 1 on which gate lines 3 and data lines 5 are arranged in a matrix form. The counter electrode 7 and the slit pixel electrode 9 are arranged. Here, the counter electrode 7 is connected to the common electrode line 6, the pixel electrode 9 is connected to the thin film transistor 4, and the counter electrode 7 and the pixel electrode 9 are insulating films. (Not shown) overlapping with each other up and down, the gap is smaller than the gap between the lower substrate 1 and the upper substrate (not shown) to form a parabolic electric field (fringe field).

The FFS VA mode liquid crystal display device has an advantage that the screen quality is improved by the response time of the liquid crystal, optical reagent angle, and high transmittance than the conventional liquid crystal display device.

However, the FFS VA mode liquid crystal display according to the prior art has the following problems.

In the prior art, as shown in FIG. 2, a region in which the vertically aligned liquid crystal 10 does not move in the center of the region where the counter electrode 7 and the pixel electrode 9 overlapping the insulating film 8 are overlapped. This will occur. There is a problem that the screen quality is deteriorated because of the disclination line due to this area.

Accordingly, the present invention has been made to solve the problems of the prior art, an object of the present invention is to form a slit in the counter electrode but to remove or reduce the disclination line to form a 90 degrees to the slit direction of the pixel electrode An FFS VA mode liquid crystal display device is provided.

1 is a plan view showing a conventional FFS VA mode liquid crystal display device.

2 is a cross-sectional view for explaining the driving of liquid crystal molecules in a conventional FFS VA mode liquid crystal display device.

3 is a plan view showing a FFS VA mode liquid crystal display device according to the present invention.

4 is a perspective view for explaining the arrangement of liquid crystal molecules when no voltage is applied in the FFS VA mode liquid crystal display device according to the present invention;

5 is a cross-sectional view for explaining driving of liquid crystal molecules when voltage is applied in the FFS VA mode liquid crystal display device according to the present invention;

Fig. 6 is a plan view for explaining driving of liquid crystal molecules when voltage is applied in the FFS VA mode liquid crystal display device according to the present invention.

-Explanation of symbols for the main parts of the drawings-

100; Lower substrate 110; Gate line

120; Data line 130; Counter electrode

135; Insulating film 140; Pixel electrode

150; Common line 200; Liquid crystal molecules

In order to achieve the above object, a fringe field switching vertical alignment mode liquid crystal display device includes: an upper substrate and a lower substrate bonded to each other at regular intervals with a liquid crystal layer interposed therebetween and having a polarizing plate attached to an outer surface thereof; ; A vertical alignment layer for vertically aligning the liquid crystal molecules in the liquid crystal layer; In a fringe field switching vertical alignment mode liquid crystal display device including a counter electrode and a pixel electrode for generating a fringe field capable of driving the liquid crystal molecules, the pixel electrode and the counter electrode may have an insulating film formed on an upper surface of the lower substrate. The pixel electrode is a slit type extending in a longitudinal direction where the non-opening area and the opening area are alternately continuous, and the counter electrode is the non-opening area and the opening area. The alternating continuous slit-shaped slit type is characterized in that the insulating film covers the non-opening region of the counter electrode but not the opening region of the counter electrode.

Hereinafter, a fringe field switching vertical alignment (hereinafter referred to as FFS VA) mode liquid crystal display according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 is a plan view showing an FFS VA mode liquid crystal display device according to the present invention. FIG. 4 is a perspective view for explaining an arrangement of liquid crystal molecules when no voltage is applied in the FFS VA mode liquid crystal display device according to the present invention. 5 is a cross-sectional view for explaining driving of liquid crystal molecules when voltage is applied in the FFS VA mode liquid crystal display according to the present invention, and FIG. It is a top view for demonstrating the drive of a liquid crystal molecule.

In the FFS VA mode liquid crystal display according to the present invention, as shown in FIG. 3, a counter transparent material is formed on an upper surface of the lower substrate 100 on which the gate lines 110 and the data lines 120 are arranged in a matrix form. The electrode 130 and the pixel electrode 140 overlap vertically.

In this case, the counter electrode 130 is connected to the common line 150 to receive a common signal, and the pixel electrode 140 is connected to the thin film transistor 160 to be applied to the data line 120. Receive a signal. Thus, an electric field is formed between the counter electrode 130 and the pixel electrode 140.

In addition, the pixel electrode 140 is a slit type extending in the longitudinal direction in which the non-opening region and the opening region are alternately continuous, and the counter electrode 130 has a horizontal side in which the non-opening region and the opening region are alternately continuous. Direction slit-shaped, the width w1 of the opening region of the counter electrode 130 is about 4 to 30 μm which is equal to or slightly larger than the width of the opening region of the pixel electrode 140, and the counter electrode ( The distance w2 between the opening area and the closest opening area of 130 is about 10 to 100 mu m.

Although the lower substrate 100 is not shown in the drawing, the upper substrate including the color filter and the liquid crystal layer are bonded to each other, but the gap between the upper and lower substrates is between the counter electrode 130 and the pixel electrode 140. It is formed about 2-10 micrometers larger than the space | interval between a). Here, the liquid crystal layer is composed of negative liquid crystal molecules having refractive index anisotropy of 0.02 to 1.5, dielectric anisotropy of -15 to -3, or positive liquid crystal molecules having dielectric constant anisotropy of 3 to 15. In addition, a vertical alignment layer may be formed between the liquid crystal layer and the lower substrate to vertically align liquid crystal molecules.

As shown in FIG. 4, an insulating film 135 is interposed between the counter electrode 130 and the pixel electrode 140, and the insulating film 135 includes the counter electrode 130 and the pixel electrode ( 140) is formed to a thickness such that a short circuit problem does not occur in the manufacturing process, for example, a thickness of about 2,500 kPa to 15,000 kPa. In addition, the insulating layer 135 covers the non-opening region of the counter electrode 130, but does not cover the opening area of the counter electrode 130.

Therefore, an initial pretilt angle of the liquid crystal may be affected between the region where the insulating layer 135 is formed and the region where the insulating layer 135 is not formed, with a step of about 2,500 kV to 15,000 kV. As a result, the liquid crystal molecules 200a on the opened region are different from the liquid crystal molecules 200b on the pixel electrode 140 in a direction in which an initial pretilt angle is parallel to the slit of the pixel electrode 140. To have a value between approximately 80 and 89 degrees.

Polarizers (not shown) are attached to outer surfaces of the lower substrate 100 and the upper substrate, respectively, and the transmission axes between the polarizers are perpendicular to each other, and the transmission axes of any one polarizer are the pixel electrode 140 and the counter electrode. 30-60 degrees, Preferably it is 45 degree with the electric field direction formed between 130.

The FFS VA mode liquid crystal display device having the above structure operates as follows.

When no voltage is initially applied and a voltage is applied while a dark state is applied, as shown in FIG. 5, for example, the negative liquid crystal molecules 200 are twisted in the electric field direction to each other. They are arranged in a symmetrical direction.

In particular, as shown in FIG. 6, in the case of the liquid crystal molecules 200b at the center of the electrode surface of the pixel electrode 140 and the liquid crystal molecules 200a on the opened region of the counter electrode 130, the pretilt angle is different. As described above, the liquid crystal molecules 200c on the edge portion of the pixel electrode 140 have a value of about 80 to 89 degrees in a direction parallel to the slit of the pixel electrode 140, and lie symmetrically with each other. As a result, it is impossible to lie down in the electric field direction, and as a result, it lie down in the slit direction of the pixel electrode 140. Therefore, the area where the conventional disclination line is generated can be utilized as the transmittance, and the response time is shortened because the initial direction of the liquid crystal molecules 200 is set in advance.

In addition, in the FFS VA mode liquid crystal display according to the present invention, one or more phase compensation films may be attached between the substrate and the polarizing plate to make the dark state in which the initial liquid crystal is vertically aligned uniformly, thereby further expanding the viewing angle. have. Here, in order to compensate for the phase difference of the liquid crystal when the liquid crystal panel is inclined from the side without showing a phase difference when viewed from the front, a disc type phase compensation film is required.

The phase compensation film is a film in which disc-shaped (Nx = Ny> Nz) liquid crystal molecules are cured in order to isotropicize refractive index anisotropy characteristics of rod-shaped (Nx = Ny <Nz) liquid crystal molecules. By compensating for it, it provides a function to visually make liquid crystal molecules look like isotropic liquid crystal molecules having the same radius and height. Meanwhile, a phase compensation film made of biaxially crystalline liquid crystal molecules having different refractive indices in three directions may be used.

At this time, for complete isotropy of the liquid crystal molecules, the retardation of the phase compensation film is the same as the retardation of the liquid crystal molecules used. The retardation of the liquid crystal molecules is determined from a value that can obtain the maximum transmittance, and the approximate retardation of the liquid crystal molecules is between 0.25 and 0.6.

In addition, in the FFS VA mode liquid crystal display according to the present invention, a box-shaped auxiliary counter electrode to which the same voltage as that of the counter electrode of the bottom substrate is applied may be further disposed on the upper substrate. In this structure, a vertical electric field component is increased to obtain a stronger electric field than driving liquid crystal molecules by a fringe field existing only on the lower substrate. Therefore, the twisting degree of the liquid crystal molecules can be facilitated by such a strong electric field.

Various embodiments can be easily implemented as well as self-explanatory to those skilled in the art without departing from the principles and spirit of the present invention. Accordingly, the claims appended hereto are not limited to those already described above, and the following claims are intended to cover all of the novel and patented matters inherent in the invention, and are also common in the art to which the invention pertains. Includes all features that are processed evenly by the knowledgeable.

As described above, the FFS VA mode liquid crystal display according to the present invention has the following effects.

In the present invention, it is possible to shorten the response time of the liquid crystal by using the vertical alignment, to increase the transmittance by removing the disclination line, it is possible to implement a wide viewing angle.

Claims (8)

An upper substrate and a lower substrate bonded to each other at regular intervals with a liquid crystal layer interposed therebetween, and having a polarizing plate attached to an outer surface thereof; A vertical alignment layer for vertically aligning the liquid crystal molecules in the liquid crystal layer; In the fringe field switching vertical alignment mode liquid crystal display device comprising a counter electrode and a pixel electrode for generating a fringe field capable of driving the liquid crystal molecules, The pixel electrode and the counter electrode are made of a transparent body so as to overlap a predetermined portion up and down with an insulating film interposed therebetween on the upper surface of the lower substrate, wherein the pixel electrode extends in the longitudinal direction where the non-opening area and the opening area are alternately continuous. Slit type, the counter electrode is a slit type extending in the transverse direction in which the non-opening region and the opening region alternately continuous, the insulating film covers the non-opening region of the counter electrode, but covers the opening region of the counter electrode Fringe field switching vertical alignment mode liquid crystal display, characterized in that the opening is not present. The method of claim 1, The opening region of the counter electrode has a width of 4 ~ 30㎛, the width between the opening region and the closest opening region is 10 ~ 100㎛ fringe field switching butterlin alignment mode liquid crystal display device. The method of claim 1, Fringe field switching vertical alignment mode liquid crystal display, characterized in that the insulating film is 2,500 ~ 15,000Å thickness. The method of claim 1, The liquid crystal molecule has a refractive index anisotropy of 0.02 to 1.5, and a dielectric constant anisotropy of -15 to -3 or 3 to 15. The method of claim 1, Fringe field switching vertical alignment mode liquid crystal display, characterized in that the interval between the upper substrate and the lower substrate is 2 ~ 10㎛. The method of claim 1, A fringe field switching vertical alignment mode liquid crystal display device further comprising a box-shaped auxiliary counter electrode to which the same voltage as that of the counter electrode on the bottom substrate is further formed on the inner surface of the upper substrate. The method of claim 1, And a phase compensation film is further attached between each of the upper and lower substrates and the polarizing plate. The method of claim 7, wherein The retardation value of the phase compensation film is the same as the retardation value of the liquid crystal molecules fringe field switching vertical alignment mode liquid crystal display device.