KR100303442B1 - Wide viewing angle liquid crystal display device - Google Patents

Abstract

The common electrode of the color filter substrate is divided into a plurality of pieces by a rectangular annular opening pattern formed by crossing an opening in a horizontal direction and an opening in a vertical direction, and the pixel electrode of the thin film transistor substrate is located in the center of the rectangular annular opening pattern. A cross-shaped opening is formed in the corresponding portion so that when a voltage is applied to the two electrodes, the liquid crystal layer between the two substrates is divided into four regions having different arrangement directions of the liquid crystal molecules. A black matrix corresponds along the edge of the pixel electrode, which is electrically connected to the pieces of the common electrode, respectively, so that the pieces of the common electrode are not electrically isolated.

Description

Wide viewing angle liquid crystal display device

The present invention relates to a wide viewing angle liquid crystal display device.

In general, a liquid crystal display device has a structure in which a liquid crystal is injected between two substrates, and the amount of light transmitted is controlled by adjusting the intensity of the electric field applied thereto.

A vertically aligned twisted nematic (VATN) type liquid crystal display includes a pair of transparent substrates having transparent electrodes formed on an inner surface thereof, a liquid crystal material between two transparent substrates, and an outer surface of each transparent substrate. It consists of two polarizers attached to and polarizing light. In the state in which no electric field is applied, the liquid crystal molecules are vertically oriented with respect to the two substrates, and when the electric field is applied, the liquid crystal molecules filled between the two substrates are parallel to the substrate and twist in a spiral with a constant pitch.

In the case of the VATN liquid crystal display, the liquid crystal molecules are vertically aligned with respect to the substrate in the state in which no electric field is applied, and thus, when the polarizing plate is perpendicular to each other, light may be completely blocked in the state in which the electric field is not applied. That is, since the luminance of the off state is very low in the normally black mode, a high contrast ratio may be obtained as compared with a conventional twisted nematic liquid crystal display. However, in a state where an electric field is applied, particularly in a state where a gradation voltage is applied, as in the normal twisted nematic mode, there is a problem in that the viewing angle is narrow due to a large difference in retardation of light depending on the viewing direction of the liquid crystal display. .

In order to solve this problem, a method of forming an opening in a transparent electrode of a thin film transistor substrate or a color filter substrate is used. By using the fringe field, which is a phenomenon in which the electric field is symmetrically bent on the basis of the opening, a plurality of regions having different alignment directions of the liquid crystal are formed.

Next, a vertical alignment liquid crystal display according to the related art will be described with reference to the accompanying drawings.

1 and 2 illustrate an arrangement of liquid crystal molecules divided into a state in which an electric field is not applied and a state in which an electric field is sufficiently applied in the vertically aligned liquid crystal display according to the related art, and FIG. 3 is an embodiment of the present invention. FIG. 7 is a cross-sectional view illustrating an arrangement of liquid crystal molecules when a multi-domain is formed by patterning an ITO electrode in a vertical alignment liquid crystal display.

1 and 2, two substrates 1 and 2 made of glass or quartz face each other, and a transparent conductive material such as indium tin oxide (ITO) is formed on the inner surface of the two substrates 1 and 2. Transparent electrodes 12 and 120 and alignment films 14 and 140 are formed in this order. Between the two substrates 1 and 2 is a liquid crystal layer 100 made of a liquid crystal material having negative dielectric anisotropy. On the outer surface of each of the substrates 1 and 2, polarizing plates 13 and 130 for polarizing the light incident to the liquid crystal layer 100 and the light passing through the liquid crystal layer 100 are attached to the lower substrate 1. The polarization axis of the polarizing plate 13 attached to) is formed at an angle of 90 ° with respect to the polarization axis of the polarizing plate 130 attached to the upper substrate 2. The alignment film 14 may or may not be subjected to a rubbing treatment.

1 illustrates a case in which no electric field is applied, and the liquid crystal molecules 3 of the liquid crystal layer 100 are arranged in a direction perpendicular to the surfaces of the two substrates 1 and 2 by the alignment force of the alignment layer 14. have.

At this time, the light passing through the polarizing plate 13 attached to the lower substrate 1 passes through the liquid crystal layer 100 without changing the polarization direction. This light is then blocked by the polarizing plate attached to the upper substrate 2 to show the black state.

2 illustrates a case where an electric field is sufficiently applied, and the liquid crystal molecules 3 are twisted in a spiral so as to form an angle of 90 ° from the lower substrate 1 to the upper substrate 2 so that the liquid crystal molecules 3 are separated. It has a twisted structure in which the direction of the major axis changes continuously. Here, since the alignment force of the alignment layer 14 is stronger than the force due to the applied electric field in the portions adjacent to the two substrates 1 and 2, the liquid crystal molecules 3 maintain their original state of being vertically aligned.

At this time, the light polarized through the polarizing plate 13 attached to the lower substrate 1 passes through the liquid crystal layer 100 and its polarization axis is rotated by 90 ° along the twist in the long axis direction of the liquid crystal molecules 3, Thereby, it passes through the polarizing plate 13 adhering to the board | substrate 2 of the opposite side, and becomes white state.

FIG. 3 illustrates a proposed structure and principle for compensating a viewing angle in a vertically aligned liquid crystal display according to the related art.

Referring to FIG. 3, a part of the ITO electrode 12 formed on the lower substrate 1 is removed and opened. In the state in which no electric field is applied, as shown in FIG. 1, the liquid crystal molecules 3 are arranged perpendicular to the two substrates 1 and 2, and thus exhibit the same black state as when the electrodes are not opened. . When an electric field is applied, an electric field perpendicular to the substrates 1 and 2 is formed at most points, but the electric field near the portion where the ITO electrode 12 is removed is not completely perpendicular to the two substrates 1 and 2. Do not. The curved electric field formed near this open portion is called the fringe field.

Since the liquid crystal has negative dielectric anisotropy, the alignment direction of the liquid crystal molecules 3 is to be perpendicular to the direction of the electric field. Thus, the long axis of the liquid crystal molecules 3 near the portion opened by the fringe field is twisted while being inclined with respect to the surfaces of the two substrates 1 and 2. In this case, two regions in which the inclination directions of the liquid crystal molecules are reversed on both sides of the center line of the portion where the ITO electrode is opened, and optical properties of the two regions are compensated with each other, thereby widening the viewing angle.

Although not shown in the drawing, similarly to the lower ITO pixel electrode 12, an opening in which a part of the ITO common electrode 120 of the upper color filter substrate 2 is removed may be formed.

As shown in FIG. 3, when an opening is formed by removing a part of the ITO electrode, not only the divisional alignment can be formed by a simple process compared to the rubbing or the like, but also the fine adjustment of the region where the arrangement of the liquid crystal molecules differs is very fine. The advantage is that it can be made into many different shapes.

Usually, the best viewing angle characteristic can be obtained when the quadrant oriented area is contained in one pixel.

4 is a plan view illustrating one pixel area as an example of an opening pattern for quadrature alignment of a liquid crystal display according to the related art.

4, the linear openings 10 and 21 for the split orientation are alternately formed in the thin film transistor substrate 1 and the color filter substrate 2 in the horizontal direction, and also in the vertical direction. ) And the color filter substrate 2 are alternately formed. In such a structure, four regions in which liquid crystal molecules are arranged in different directions are formed by an almost closed rectangular opening 21 of the color filter substrate 2 and an opening 10 of the thin film transistor substrate 2 positioned therein. Is formed.

However, the ends of the openings 10 and 21 are formed to be open so that a signal is transmitted to the entire electrode, so that the discoloration or irregular tissue (the arrangement of the liquid crystal molecules at the ends of the openings 10 and 21) is disturbed. texture), it is difficult to obtain stable split orientation.

In the disorientated region, not only light leaks in the off state but also appears darker in the on state than other parts of the surrounding state, and when the arrangement of the liquid crystal molecules is changed, the distorted portion is moved to cause afterimages. .

SUMMARY OF THE INVENTION An object of the present invention is to widen the viewing angle of a liquid crystal display by forming an opening pattern for quadrilateral alignment on a transparent electrode.

Another object of the present invention is to close the end of the opening pattern for the split orientation to reduce the brightness degradation and light leakage caused by the foreground or irregular tissue.

1 and 2 are conceptual views illustrating alignment of liquid crystal molecules in a vertical alignment liquid crystal display device according to a black mode and a white mode,

3 is a cross-sectional view illustrating the principle of divided alignment of a vertically aligned liquid crystal display device;

4 is a plan view illustrating an opening pattern for split alignment of a vertically aligned liquid crystal display according to a related art;

FIG. 5 is a plan view illustrating an opening pattern for split alignment of a vertically aligned liquid crystal display according to an exemplary embodiment of the present invention; FIG.

6 is a plan view illustrating an opening pattern in the color filter substrate of FIG. 5;

FIG. 7 is a cross-sectional view taken along the line VII-VII ′ of FIG. 6.

FIG. 8 is a cross-sectional view taken along line VIII-VIII ′ of FIG. 6.

9 is a plan view illustrating another opening pattern in the color filter substrate of FIG. 5;

FIG. 10 is a cross-sectional view taken along line X-X 'of FIG. 9;

FIG. 11 is a cross-sectional view taken along line XI-XI ′ of FIG. 9.

In order to solve the above problems, in the liquid crystal display according to the present invention, an opening for splitting alignment is formed in the pixel electrode and the common electrode, and a rectangular annular opening is formed by crossing the openings in the horizontal and vertical directions on the common electrode. A pattern is formed, and an opening is formed in the pixel electrode in a region corresponding to two opposite sides of a rectangular ring shape.

As such, the rectangular annular opening pattern is completely closed so the foreground is minimized.

A light blocking film is formed along the edge of the pixel electrode. It is preferable to prevent the pieces of the common electrode from being electrically isolated by allowing the pieces of the common electrode to be electrically connected to the light blocking films, respectively.

An insulating film is formed between the light blocking film and the common electrode, and the insulating film has a plurality of contact holes through which the light blocking film is partially exposed, through which the pieces of the common electrode may be in contact with the light blocking film.

A transparent conductive film formed entirely over the light blocking film and an insulating film covering the transparent conductive film may be further formed, and the insulating film has a plurality of contact holes through which the transparent conductive film is partially exposed. It may be in contact with the transparent conductive film.

The openings formed in the pixel electrode may have a cross shape.

As such, when the ITO electrode is patterned, four regions having different alignment directions of the liquid crystal molecules can be obtained, thereby widening the viewing angle of the liquid crystal display, and reducing the foreground because the common electrode has a rectangular shape in which the opening is completely closed. In addition, by electrically connecting the common electrode fragmented by the opening with the light blocking film, it is possible to prevent the signal from being applied to a portion of the common electrode.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

5 is a plan view illustrating an opening pattern for split alignment of the vertical alignment liquid crystal display according to the first and second embodiments of the present invention. Here, only one pixel region is shown, and only the opening pattern for the divisional orientation is illustrated without any other components such as the thin film transistor and the wiring.

As shown in FIG. 5, similar to the structure of FIG. 4, linear openings 10 and 22 for splitting alignment are alternately formed in the thin film transistor substrate 1 and the color filter substrate 2 in the horizontal direction. Also in the longitudinal direction, they are alternately formed on the thin film transistor substrate 1 and the color filter substrate 2. The portion indicated by the thick solid line indicates the opening portion 10 formed in the thin film transistor substrate 1, and the portion indicated by the hatched rod shape indicates the opening portion 22 formed in the color filter substrate 2. In the case of the liquid crystal display device having such openings 10 and 22, the liquid crystal molecules are formed on one of the square substrates forming each micro area defined by the openings 10 and 22 formed in the two substrates 1 and 2. The pattern formed on the other substrate is arranged in a diagonal direction from the bent portion to the bent portion, and the alignment direction of the liquid crystal molecules in the adjacent region is 90 degrees. Therefore, four regions having different arrangements of liquid crystal molecules are formed in one pixel of the liquid crystal display.

In addition, since the openings 22 of the color filter substrate 2 are removed in a completely closed square shape, when the openings 10 and 22 patterns of the two substrates 1 and 2 correspond to each other, the entire opening patterns are uneven. By being completely closed, the irregular structure or the foreground at the end of the opening 10 of the thin film transistor substrate 1 having the open end can be prevented.

In the embodiment of the present invention, since the transparent common electrode is divided into a plurality of parts isolated by the opening 22 of the color filter substrate 2, it is necessary to make a signal transmission path so that the common voltage signal is transmitted to the entire common electrode. .

6 to 8 illustrate a structure in which a common electrode is connected to a black matrix so that a signal is applied to an isolated common electrode.

FIG. 6 is a plan view illustrating an opening pattern according to a first embodiment of the present invention, and illustrates an opening pattern of a thin film transistor substrate, which corresponds only to the opening pattern formed on the color filter substrate of FIG. 5. Is not shown. 7 is a cross-sectional view taken along the line VII-VII 'of FIG. 6, and FIG. 8 is a cross-sectional view taken along the line VIII-VIII' of FIG. 6.

6 to 8, a black matrix 30 is formed on an edge of a portion of the color filter substrate 1 that is to be a pixel region made of metal such as chromium (Cr), and the black matrix 30 is formed in the pixel region. The color filter 40 is formed so as to partially overlap with the edge of the). The passivation layer 4 covers the color filter 40 and the black matrix 30, and the passivation layer 4 includes at least two contact holes C1 and C2 exposing the black matrix 30 in one pixel area. It is open.

The common electrode 20 is formed on the passivation layer 4 using a material such as indium-tin-oxide (ITO). As described above with reference to FIG. 5, when referring to one pixel area, the electrode is removed along the edge of the pixel area and the electrode is removed in a form crossing the center of the pixel area. The opening 22 is formed. At this time, the common electrode 20 is sculpted in the shape of a rectangular ring formed by crossing the pattern of the opening 22 extending in the horizontal direction and the pattern of the opening 22 extending in the vertical direction, and the pieces are drilled in the protective film 4. Each contact with the black matrix 30 through the contact holes C1 and C2 is such that the pieces of the common electrode 20 are connected without being electrically isolated.

However, in such a structure, since the black matrix 30 must overlap the common electrode 20 at both sides with respect to the opening 22 of the common electrode 20, the opening ratio may be reduced as a whole.

9 to 11 show a second embodiment of the present invention for improving this.

9 is a plan view illustrating the opening pattern formed on the color filter substrate, and the opening pattern of the thin film transistor substrate corresponding to the opening pattern of the color filter substrate is not shown. FIG. 10 is a cross-sectional view taken along line X-X 'of FIG. 9 and FIG. 11 is a cross-sectional view taken along line XI-XI' of FIG.

9 to 11, similarly to the first embodiment, the black matrix 31 is formed on the transparent insulating substrate 2 so as to surround the edge of the portion to be the pixel region, and the black matrix 31 is formed. The color filter 40 is formed in the pixel area so as to partially overlap the edge of the pixel area.

At this time, the width of the black matrix 31 is formed narrower than the width of the black matrix 30 in the first embodiment.

On the black matrix 31 and the color filter 40, a transparent conductive film 50 made of a material such as ITO is formed on the entire surface. A protective film 4 is covered on the transparent conductive film 50, and the protective film 4 Two or more contact holes C3 and C4 exposing the transparent conductive film 50 are drilled.

On the protective film 4, the common electrode 20 is formed of ITO in the same form as in the first embodiment described above. However, pieces of the common electrode 20 are in contact with the ITO transparent conductive film 50 instead of the black matrix 31 through the contact holes C3 and C4 bored through the protective film 4.

In this structure, since the common electrode 20 divided into several pieces by the opening 31 pattern is electrically connected by the transparent conductive film 50 disposed below, the signal is transmitted to the entire common electrode 20. It is not necessary to form the matrix 31 widely, so that the reduction of the aperture ratio can be prevented.

As mentioned above, in the vertically aligned liquid crystal display according to the exemplary embodiment of the present invention, the viewing angle may be widened by dividing the alignment direction of the liquid crystal molecules by using the opening pattern formed in the transparent electrode.

By forming the end of the opening pattern to be completely closed, the transparent electrode isolated by the opening pattern is electrically connected through the lower black matrix or the transparent conductive film, thereby preventing the generation of the foreground and the increase of the brightness, as well as transmitting the signal throughout the electrode. To be possible.

Thus, stable split orientation is possible.

Claims (8)

A first substrate having a plurality of pixel electrodes having a first opening formed therein; Along the edge of the common electrode and the pixel electrode having a second opening in the horizontal direction and a third opening in the vertical direction and divided into a plurality of pieces by a rectangular annular opening pattern made by crossing the second and third openings. A second substrate having a corresponding light blocking film, The first opening of the first substrate is formed in a region corresponding to two opposite sides of the rectangular annular opening pattern. In claim 1, And a plurality of pieces of the common electrode are in contact with the light blocking layer and electrically connected to each other. In claim 2, The light blocking layer overlaps the common electrode on both sides of the second and third openings. In claim 3, An insulating film formed between the light blocking film and the common electrode and having a plurality of contact holes partially exposing the light blocking film, wherein the plurality of pieces of the common electrode are in contact with the light blocking film through the contact hole; Liquid crystal display. In claim 2, The insulating film may further include a transparent conductive film formed entirely on the light blocking film, and an insulating film covering the transparent conductive film and having a plurality of contact holes through which the transparent conductive film is partially exposed. And a liquid crystal display in contact with the transparent conductive film. In claim 1, The first opening is a cross-shaped liquid crystal display device. In claim 1, And at least two second openings are formed in one pixel. In claim 7, And the third opening is formed to correspond to an edge of the pixel.