KR100303349B1 - High Opening and High Transmittance Liquid Crystal Display - Google Patents

Abstract

The present invention discloses a high aperture ratio and high transmittance liquid crystal display device in which a spacing between the counter electrode and the pixel electrode can be reduced while maintaining a constant gap between the counter electrode and the pixel electrode, while reducing parasitic capacitance generated between the counter electrode and the pixel electrode. The disclosed invention is spaced apart from each other by a predetermined distance between the upper and lower substrates facing each other with a liquid crystal interposed therebetween, a transparent counter electrode formed on an inner surface of the lower substrate, and having a narrower distance than the distance between the counter electrode and the upper and lower substrates. And a transparent pixel electrode which forms a fringe field for driving molecules in the liquid crystal together with a counter electrode, and a gate insulating film which insulates the counter electrode from the pixel electrode. The counter electrode and the pixel electrode are formed in the form of a comb including several strips, and the strips of the pixel electrodes are inserted between the counter electrode strips, with both ends overlapping the ends of the strips of the counter electrode by a misalignment maximum. It is characterized by.

Description

High Opening and High Transmittance Liquid Crystal Display

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly, to a high opening ratio and a high transmittance liquid crystal display for fringe field switching having a small change in transmittance.

In general, a high aperture ratio and a high transmittance liquid crystal display have been proposed to improve the low aperture ratio and transmittance of a general IPS mode liquid crystal display, and have 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. (frin ge filed) is formed.

Such a high aperture 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. At this time, the alignment layers 8 and 11 have a low pretilt angle (about 2 ° or less) and are rubbed in an anti-parallel state to form a predetermined angle with the direction in which the electric field is formed.

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 high aperture ratio and high transmittance liquid crystal display devices have the following problems.

First, in a liquid crystal display having a high aperture ratio and a high transmittance, transmittance is largely changed according to a space between the counter electrode and the pixel electrode. That is, when manufacturing the counter electrode and the pixel electrode, if the electrode forming mask is shifted due to slight misalignment, the transmittance is greatly changed. For this reason, there is a problem in that accurate alignment is required in manufacturing the counter electrode and the pixel electrode.

Secondly, in the method of forming the counter electrode in the shape of a plate so that there is no problem in alignment, a constant distance can be maintained between the counter electrode and the pixel electrode, but excessive capacitors are formed, which affects the driving of the liquid crystal display. do.

Accordingly, the present invention is to solve the above-described problems, the high aperture ratio which can reduce the parasitic capacitance generated between the counter electrode and the pixel electrode while reducing the variation in transmittance by maintaining a constant interval between the counter electrode and the pixel electrode And a high transmittance liquid crystal display device.

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

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

3A is a view illustrating a state in which a pixel electrode is shifted to the right in a high opening ratio and high transmittance liquid crystal display according to an exemplary embodiment of the present invention.

3B is a view illustrating a state in which a pixel electrode is shifted to the left in the high aperture ratio and high transmittance liquid crystal display according to the present invention.

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

20-lower substrate 22-counter electrode

22a, 22b, 22c-strips of counter electrodes

24-gate insulating film 26-pixel electrode

26a, 26b-pixel electrode strip

In order to achieve the above object of the present invention, according to an embodiment of the present invention, a transparent counter electrode formed on the inner surface of the lower substrate and the upper and lower substrates opposed to each other by a predetermined distance with the liquid crystal interposed therebetween. And a transparent pixel electrode spaced apart from each other by a distance smaller than the distance between the counter electrode and the upper and lower substrates to form a fringe field for driving molecules in the liquid crystal together with the counter electrode, and a gate insulating the counter electrode from the pixel electrode. In a high aperture and high transmittance liquid crystal display including an insulating film, the counter electrode and the pixel electrode are formed in a comb form including several strips, and the strips of the pixel electrode are inserted between the counter electrode strips and both ends thereof. And overlaps an end portion of the strip of the counter electrode by a misalignment maximum value. The.

The maximum misalignment value may be a sum of a CD bias width of the counter electrode, a CD bias width of the pixel electrode, and an overlay value of the counter electrode and the pixel electrode.

According to the present invention, both the counter electrode and the pixel electrode are formed in a comb shape, and the strips of the pixel electrode are formed to be disposed between the strips of the counter electrode, so that both ends of the strips of the pixel electrode overlap with the counter electrode. In this case, the overlapping degree is a maximum value at which misalignment can be generated, so that the end of the pixel electrode strip and the end of the counter electrode strip coincide with each other even if the misalignment is shifted to the left or right direction at the maximum value. .

Accordingly, even when a misalignment occurs when viewed from the front surface of the substrate, a uniform transmittance can be obtained because the distance between the counter electrode and the pixel electrode does not change.

In addition, even if a misalignment occurs, the overlapping area does not change, and thus the capacitance does not change.

(Example)

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

2 is a cross-sectional view of a lower substrate of a high aperture and high transmittance liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 3a illustrates a state in which a pixel electrode is shifted to the right in the high aperture and high transmittance liquid crystal display according to the present invention. 3B is a view showing a state in which the pixel electrode is shifted to the left in the high aperture ratio and high transmittance liquid crystal display according to the present invention.

In the drawings, only the lower substrate structure is shown, and the upper substrate structure is not shown, and the upper substrate structure and the lower substrate structure are spaced apart by a predetermined distance.

First, as shown in FIG. 2, in the high opening ratio and high transmittance liquid crystal display device according to the present invention, the counter substrate 22 made of a transparent conductor of the lower substrate 20, for example, ITO, has a comb shape. Is formed. At this time, only a cross section of several strips 22a, 22b and 22c constituting the comb is shown, and these strips 22a, 22b and 22c have a constant width W1 and are spaced at equal intervals. .

The gate insulating layer 24 is formed on the lower substrate 20 on which the counter electrode 22 is formed. In this case, as the gate insulating layer 24, a material having excellent adhesion to the substrate 20 and having a relatively low dielectric constant is used.

A pixel electrode 26 made of a transparent conductor is formed on the gate insulating film 24. In this case, the pixel electrode 26 is also formed in a comb shape including several strips 26a and 26b, and cross-sections of the strip portions 26a and 26b of the pixel electrode 26 are illustrated in the drawing. Here, the strip portions 26a and 26b of the pixel electrode 26 are disposed in the space between the strip portions 22a, 22b and 22c of the counter electrode 22, and the strip portions 26a and 26b of the pixel electrode 26 are disposed. Both ends of 26b are arranged to overlap the ends of the strip portions 22a, 22b, 22c of the counter electrode 22 by a predetermined width, preferably a misalignment maximum, respectively.

At this time, in forming the pixel electrode 26, overlapping widths OL of both sides of the strip portions 26a and 26b are equal to each other. In addition, in the present exemplary embodiment, the maximum misalignment of the overlapping width OL is the CD (critical dimension) bias width of the counter electrode 22 and the CD bias width of the pixel electrode 26 and the counter electrode 22 and the pixel. The overlay value of the electrode 26 is shown as the sum total. At this time, the CD bias value is the area that is reduced than the design value at the completion of the process, the overlay value represents the misalignment value of the counter electrode 22 and the pixel electrode 26, these values are calculated in advance by the test pattern to be.

For example, the CD bias value of the counter electrode 22 calculated in advance is 0.5 µm, the CD bias value of the pixel electrode 26 is 0.5 µm, and the overlay value of the counter electrode 22 and the pixel electrode 26 is In the case of 1 μm, the width OL at which one end of the strips 26a, 26b, 26c of the pixel electrode 26 overlaps with the counter electrode 22 is 2 μm, and both sides of the pixel electrode 26 are viewed. 2 micrometers overlap.

When the electrodes are arranged in this manner, even when the left or right side is shifted in the process as shown in FIG. 3A or 3B, even if the shifted width does not exceed the overlay margin, the CD bias is generated and the counter end and the counter of the strip of the pixel electrode 26. The ends of the strips of electrode 22 coincide. Therefore, when viewed from the front of the substrate 20, the distance between the counter electrode 22 and the pixel electrode 26 does not change, and thus the transmittance does not change even when the mask is shifted.

In addition, when formed as described above, even if the overlapping area of the counter electrode 22 and the pixel electrode 26 is shifted left or right, the overlapping area is not changed. Therefore, there is no change in capacitance.

As described in detail above, according to the present invention, both the counter electrode and the pixel electrode are formed in a comb shape, and the strips of the pixel electrode are formed so that the strips of the pixel electrode are disposed between the strips of the counter electrode, Make it overlap. In this case, the overlapping degree is a maximum value at which misalignment can be generated, so that the end of the pixel electrode strip and the end of the counter electrode strip coincide with each other even if the misalignment is shifted to the left or right direction at the maximum value. .

Accordingly, even when a misalignment occurs when viewed from the front surface of the substrate, a uniform transmittance can be obtained because the distance between the counter electrode and the pixel electrode does not change.

In addition, even if a misalignment occurs, the overlapping area does not change, and thus the capacitance does not change.

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 opposed to each other by a predetermined distance with the liquid crystal interposed therebetween; A transparent counter electrode formed on an inner side surface of the lower substrate; A transparent pixel electrode spaced apart from each other by a distance smaller than the distance between the counter electrode and the upper and lower substrates to form a fringe field for driving molecules in the liquid crystal together with the counter electrode; A high aperture and high transmittance liquid crystal display comprising a gate insulating film insulated between the counter electrode and a pixel electrode, The counter electrode and the pixel electrode are formed in a comb form including several strips The strip of the pixel electrode is inserted between the counter electrode strip, both ends overlap the end of the strip of the counter electrode by a misalignment maximum, high opening ratio and high transmittance liquid crystal display device. The liquid crystal display of claim 1, wherein the maximum misalignment is a sum of a CD bias width of a counter electrode, a CD bias width of a pixel electrode, and an overlay value of the counter electrode and the pixel electrode. .