KR100687322B1 - LCD having high aperture ratio and high transmittance ratio - Google Patents

Abstract

The present invention discloses a high opening ratio and a high transmittance liquid crystal display device. The present invention discloses an upper substrate and a lower substrate spaced apart from each other; A liquid crystal layer comprising a plurality of liquid crystal molecules interposed between the upper and lower substrates; Gate bus lines and data bus lines arranged on the lower substrate to define unit pixels; Thin film transistors formed around intersection points of the gate bus lines and the data bus lines, respectively; A counter electrode formed in each unit pixel and formed of a transparent conductor having a rectangular plate shape spaced apart from the data bus line; And a pixel electrode formed in the unit pixel to overlap the counter electrode and having a plurality of comb teeth arranged at equal intervals and a transparent conductor including one end of the comb portions electrically connected to the thin film transistor. And the plurality of comb portions of the pixel electrode are arranged to be inclined at an angle with a data bus line in the selected unit pixel, and the comb portions of other unit pixels adjacent to the selected unit pixel with the data bus line interposed therebetween are included. The comb portion of the selected unit pixel is arranged symmetrically with respect to the data bus line, and the comb portion of another unit pixel adjacent to the selected unit pixel with the gate bus line interposed therebetween is a comb portion of the selected unit pixel and the gate bus line. It is arranged symmetrically with reference.

Description

High aperture ratio and high transmittance liquid crystal display {LCD having high aperture ratio and high transmittance ratio}

1 is a plan view of a typical high opening ratio and high transmittance liquid crystal display;

2 is a plan view of a high aperture ratio and high transmittance liquid crystal display for improving a conventional color shift.

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

4 is a view schematically showing an electric field formed in the liquid crystal display device of the present invention and the arrangement of the liquid crystal molecules according thereto.

Explanation of symbols on main parts of drawing

10: lower substrate 11: gate bus line
13: data bus line 15: counter electrode

15a: common electrode line 17: pixel electrode

17a: comb teeth 17b: bar

The present invention relates to a high aperture ratio and a high transmittance liquid crystal display device, and more particularly, to a high aperture ratio and a high transmittance liquid crystal display device capable of improving image quality characteristics.

The high aperture ratio and high transmittance liquid crystal display is proposed to improve the low aperture ratio and transmittance of a general In Plain Switching (IPS) mode liquid crystal display, and has been filed by the present applicant 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.

Such a high aperture and high transmittance liquid crystal display is shown in FIG. 1.

Referring to the drawings, the gate bus line 2 and the data bus line 4 are arranged on the lower substrate 1 to define a unit pixel, and the intersection point of the gate bus line 2 and the data bus line 4 is defined. In the vicinity, a thin film transistor TFT is disposed.

The counter electrode 5 is a transparent conductor and is formed for each unit pixel. The counter electrode 5 includes a plurality of branches 5a arranged at equal intervals and a body portion 5b connected to one end of the branches 5a and interconnected with the counter electrodes 5 of adjacent pixels. . At this time, the counter electrode 5 receives a common signal continuously.

The pixel electrode 7 is formed in each unit pixel space so as to overlap with the counter electrode 5. The pixel electrode 7 connects one end of the plurality of comb portions 7a and the comb portions 7a, which are parallel to the data bus line 4 and are respectively inserted between the branches 5a of the counter electrode 5. And a bar 7b contacting the drain electrode of the thin film transistor TFT. In this case, the pixel electrode 7 is also formed of a transparent conductor. The pixel electrode 7 is insulated from the counter electrode 5 with the gate insulating film interposed therebetween.

On the other hand, although not shown in the drawing, the upper substrate (not shown) facing the lower substrate 1 is less than the distance between the comb portion 7a of the pixel electrode 7 and the branch 5a of the counter electrode 5. They are arranged at large distances. In addition, a liquid crystal layer having a plurality of liquid crystal molecules is interposed between the lower substrate 1 and the upper substrate.

The high aperture ratio and high transmittance liquid crystal display device having such a configuration operates as follows.

When a voltage is applied between the counter electrode 5 and the pixel electrode 7, the distance between the upper and lower substrates is greater than the distance between the counter electrode 5 and the pixel electrode 7, so that a vertical component is included between the two electrodes. Fringe field E is formed. This fringe field extends over the counter electrode 5 and the pixel electrode 7 so that all of the liquid crystal molecules on the electrode are operated. Thereby, a high opening rate and a high transmittance can be realized.

In the above-described high aperture ratio and high transmittance liquid crystal display, most of the liquid crystal molecules in the pixel space are all operated to achieve high aperture ratio and high transmittance. However, when an electric field is formed between the counter electrode and the pixel electrode, liquid crystal molecules having refractive index anisotropy operate simultaneously in the same direction, so that the polar angle is near 0 ° and the azimuth is near 0 °, 90 °, 180 °, and 270 °. In spite of the condition, a certain color appears. This phenomenon is called color shift, and the color shift is explained in more detail by the following equation (1).

T ≒ T ₀ sin2 (2χ) · sin2 (π · Δnd / λ) .............. (Equation 1)

T: transmittance

T ₀ : Transmittance for reference light

χ: angle formed between the optical axis of the liquid crystal molecules and the polarization axis of the polarizer

Δn: refractive index anisotropy

d: distance or gap between the upper and lower substrates (thickness of the liquid crystal layer)

λ: incident light wavelength

According to Equation 1, in order to obtain the maximum transmittance T, χ should be π / 4 or Δnd / λ should be π / 2. At this time, when Δnd is changed (because the refractive index anisotropy value of the liquid crystal molecules changes depending on the viewing direction), the λ value is changed to satisfy π / 2. Accordingly, the color corresponding to the changed light wavelength [lambda] is displayed on the screen.

Thus, as shown in FIG. 1, in the direction α of looking at the short axis of the liquid crystal molecules 9, the wavelength of incident light for reaching the maximum transmittance is relatively shortened as Δn is relatively reduced. Accordingly, the user sees blue having a wavelength shorter than that of white.

On the other hand, in the direction β looking at the long axis of the liquid crystal molecules 9, the wavelength of the incident light becomes relatively long as Δn is relatively increased. Accordingly, the user sees yellow with a wavelength longer than that of white.

For this reason, the image quality characteristic of a high opening ratio and a high transmittance liquid crystal display falls.

In order to prevent such color shift, as shown in FIG. 2, as shown in FIG. 2, both the branch 5a of the counter electrode 5 and the comb portion 7a of the pixel electrode 7 are "<". A method of bending in form has been proposed. In this case, two electric fields symmetrical are formed in one unit pixel to compensate for refractive anisotropy of the liquid crystal molecules.

However, in the case of this technique, the branch 5a and the comb portion 7a are bent in the form of " <&quot; to form a portion X where no electric field is formed, that is, the branch 5a of the counter electrode 5 and the data bus. The spacing of the line 4 is increased, and accordingly, liquid crystal molecules are not operated in this portion, and the aperture ratio is reduced. As a result, the inherent purpose of achieving high opening rate and high transmittance cannot be achieved.

Accordingly, it is an object of the present invention to provide a high aperture ratio and high transmittance liquid crystal display device capable of improving color shift in a range that does not reduce the aperture ratio.

In order to achieve the above object, the present invention, the upper substrate and the lower substrate spaced apart from each other; A liquid crystal layer comprising a plurality of liquid crystal molecules interposed between the upper and lower substrates; Gate bus lines and data bus lines arranged on the lower substrate to define unit pixels; Thin film transistors formed around intersection points of the gate bus lines and the data bus lines, respectively; A counter electrode formed in each of the unit pixels and formed of a transparent conductor having a rectangular plate shape which maintains a predetermined distance from the data bus line; And a pixel electrode formed in the unit pixel to overlap the counter electrode and having a plurality of comb teeth arranged at equal intervals and a transparent conductor including one end of the comb portions electrically connected to the thin film transistor. And the plurality of comb portions of the pixel electrode are arranged to be inclined at an angle with a data bus line in the selected unit pixel, and the comb portions of other unit pixels adjacent to the selected unit pixel with the data bus line interposed therebetween. The comb portion of the selected unit pixel is arranged symmetrically with respect to the data bus line, and the comb portion of another unit pixel adjacent to the selected unit pixel with the gate bus line interposed therebetween is formed with the comb portion of the selected unit pixel. Symmetric about the gate bus line Provides a high aperture ratio, characterized in that the arrangement place and high transmissivity liquid crystal display device.

In the above, the angle between the comb portion of the pixel electrode and the data bus line is 5 to 15 °, and the pixel electrode bar extends in parallel with the gate bus line.

According to the present invention, the electric fields formed in the selected unit pixel space are symmetrical with respect to the electric fields formed in the left and right pixel spaces of the pixel and the data bus lines, and the electric fields formed in the upper and lower pixel spaces of the pixels and They are symmetrical with respect to the gate bus line. As a result, a symmetrical electric field is formed for each of the adjacent pixels, and thus multiple domains are formed in the liquid crystal display. As a result, the refractive index anisotropy of the liquid crystal molecules is compensated for, thereby preventing color shift. Image quality characteristics are improved.

(Example)

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

FIG. 3 is a plan view of a high aperture ratio and high transmittance liquid crystal display device according to the present invention, and FIG. 4 is a view schematically showing an arrangement of an electric field and subsequent liquid crystal molecules formed in the liquid crystal display device of the present invention.

Referring to FIG. 3, a plurality of gate bus lines 11 are arranged in the x-axis direction on the lower substrate 10, and a plurality of data bus lines 13 are arranged in the y-axis direction substantially perpendicular to the x-axis direction. Arranged, each unit pixel space p1, p2, p3, p4 is defined.

A gate insulating film (not shown) is interposed between the gate bus line 11 and the data bus line 13 to insulate these two lines. The gate bus line 11 and the data bus line 13 are formed of an opaque metal film having excellent conductivity, for example, one metal film selected from among MoW, Al, Ta, and Ti.

A thin film transistor (TFT) serving as a switching role is provided near the intersection point of the gate bus line 11 and the data bus line 13.

Counter electrodes 15 are formed in the unit pixel spaces p1, p2, p3, and p4. The counter electrode 15 is formed of a transparent conductor, and also formed in the form of a square plate. At this time, the counter electrode 15 is in contact with the common electrode line 15a made of an opaque metal film and electrically connected to another adjacent counter electrode 15. The counter electrode 15 is spaced apart from the data bus line 13 by a predetermined distance.

In addition, pixel electrodes 17 are formed in the unit pixel spaces p1, p2, p3, and p4 so as to overlap the counter electrode 15. The pixel electrode 17 includes a plurality of comb portions 17a arranged parallel to each other at equal intervals, and a bar 17b electrically connected to the thin film transistor TFT while connecting one end of the comb portions 17a. Include. At this time, the comb portion 17a of the pixel electrode 17 forms an angle with the direction of the data bus line 15, that is, the y-axis direction, preferably about 5 to 15 degrees. On the other hand, the angle formed by the comb portion 17a and the data bus line 13 in the selected unit pixel (for example, p3) is adjacent to the left and right of the pixel (adjacent in the x-axis direction). For example, the angle between the comb portion 17a of the p4 and the data bus line 13 is symmetrical with respect to the data bus line 13. In addition, the angle formed by the comb portion 17a of the selected unit pixel (for example, p3) and the data bus line 13 is equal to the unit pixel (for example, adjacent to the y-axis direction) above and below the pixel. The angle between the comb portion 17a of the p1 and the data bus line 13 is symmetrical with respect to the gate bus line 11.
The comb portion 17a of the pixel electrode 17 is formed to overlap the counter electrode 15 and is formed so as not to protrude outside the counter electrode 15. In addition, the bar 17b of the pixel electrode 17 extends in parallel with the gate bus line 11.

At this time, between the comb portion 17a and the counter electrode 15 so that a fringe field can be formed between the comb portion 17a of the pixel electrode 17 and the counter electrode 15 exposed by the comb portion 17a. The gap is formed to be smaller than the distance between the upper and lower substrates, and the width of the comb portion 17a and the exposed counter electrode 15 is designed so that an electric field can extend across the upper portions of the electrodes.

Although not shown in FIG. 3, the upper substrate is disposed to face the upper portion of the lower substrate at a predetermined distance, and a liquid crystal layer including a plurality of liquid crystal molecules is interposed between the lower substrate and the upper substrate.

In the case of the liquid crystal display having such a configuration, when voltage is applied to the counter electrode 15 and the pixel electrode 17, a fringe field E is formed between the counter electrode 15 and the pixel electrode 17 of each pixel. do. In this case, since the comb portions 17a of the pixel electrodes 17 are arranged symmetrically in each of the unit pixel spaces p1, p2, p3, and p4, the fringe field E is also formed in other pixels adjacent to the top, bottom, left, and right sides. The fringe field E is symmetrical with respect to the gate bus line 11 and the data bus line 13, respectively.

Accordingly, as shown in FIG. 4, the liquid crystal molecules 20 are also arranged parallel to each other in the same pixel space, but are arranged symmetrically with respect to the data bus line and the gate bus line with respect to the upper, lower, left, and right pixel spaces. .

Accordingly, in the unit pixel side, the liquid crystal molecules 20 are arranged in one direction to form a single domain, whereas in the unit pixel side, the liquid crystal molecules 20 between adjacent pixels are arranged to be symmetrical. Domains are formed. Accordingly, since both the short axis and the long axis of the liquid crystal molecules are seen in any direction of the screen, the refractive index anisotropy of the liquid crystal molecules is compensated, and the color shift phenomenon is prevented.

As described above in detail, according to the present invention, the electric fields formed in the selected unit pixel spaces are symmetrical with respect to the electric fields and data bus lines formed in the pixel spaces adjacent to the left and right of the pixels, and the upper and lower sides of the pixels They are symmetrical with respect to the electric field formed in the pixel space adjacent to the gate bus line. Accordingly, a symmetrical electric field is formed between adjacent pixels, thereby forming multiple domains in the liquid crystal display. Therefore, the high aperture ratio and high transmittance liquid crystal display device of the present invention can compensate for the refractive index anisotropy of the liquid crystal molecules, thereby preventing color shift, thereby improving the image quality characteristics.

In addition, in the high aperture ratio and high transmittance liquid crystal display of the present invention, since the distance between the counter electrode and the data bus line is kept constant, the opening area is not reduced, and thus the opening ratio can be prevented from being reduced.

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

Claims (3)

An upper substrate and a lower substrate spaced apart from each other; A liquid crystal layer comprising a plurality of liquid crystal molecules interposed between the upper and lower substrates; Gate bus lines and data bus lines arranged on the lower substrate to define unit pixels; Thin film transistors formed around intersection points of the gate bus lines and the data bus lines, respectively; A counter electrode formed in each of the unit pixels and formed of a transparent conductor having a rectangular plate shape which maintains a predetermined distance from the data bus line; And A pixel electrode formed in the unit pixel to overlap with the counter electrode, the pixel electrode including a plurality of comb teeth arranged at equal intervals and a transparent conductor including one bar of the comb teeth electrically connected to the thin film transistor; Include, The plurality of comb portions of the pixel electrode are arranged to be inclined at an angle with a data bus line in the selected unit pixel, and the comb portions of other unit pixels adjacent to the selected unit pixel with the data bus line therebetween are selected from the selected unit. The comb portion of the pixel is arranged symmetrically with respect to the data bus line, and the comb portion of another unit pixel adjacent to the selected unit pixel with the gate bus line therebetween is a comb portion of the selected unit pixel and the gate bus line. A high aperture ratio and high transmittance liquid crystal display, characterized in that arranged in a symmetric with respect to. The liquid crystal display of claim 1, wherein an angle formed by the comb portion of the pixel electrode and the data bus line is 5 to 15 degrees. The liquid crystal display of claim 1, wherein the pixel electrode bar extends in parallel with the gate bus line.

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