KR100494676B1 - Liquid crystal display device - Google Patents

Abstract

The present invention discloses a liquid crystal display device capable of forming an electric field parallel to the lower substrate when a voltage is applied.

The disclosed invention includes a plurality of gate bus lines and data bus lines arranged in a lattice form on a lower substrate to define a unit cell, a thin film transistor formed near an intersection of the gate bus line and a data bus line, and the unit Disposed in the cell space to drive the liquid crystal, the wiring unit being arranged in parallel while being spaced apart by a predetermined distance from the gate bus line for selecting the unit cell, toward the gate bus line for selecting the unit cell from the wiring unit, etc. A counter electrode including a plurality of branches spaced apart from each other, a first electrode connected to the thin film transistor and driving the liquid crystal together with the counter electrode, and arranged in parallel with the data bus line between the branches; A third region connecting the second region, one end of the first region and the second region, and a second region A pixel electrode including a fourth region connecting the other end of the region and a gate insulating layer insulating the gate bus line from the data bus line, and insulating the counter electrode from the pixel electrode; Are all formed on the lower substrate surface.

Description

Liquid crystal display device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display (LCD), and more particularly, to an in plane switching (IPS) -LCD in which electrodes for driving liquid crystal are formed on a lower substrate.

In general, the IPS-LCD is a structure proposed to improve the narrow viewing angle characteristic of the twist nemetic (TN) -LCD. The IPS-LCD has a structure in which the counter electrode formed on the upper plate is disposed on the lower plate on which the pixel electrode is formed.

That is, in the conventional TN-LCD, an electric field perpendicular to the substrate is formed between the counter electrode formed on the upper plate and the pixel electrode formed on the lower plate, whereas the IPS-LCD is disposed on the substrate because the counter electrode and the pixel electrode are disposed on the lower plate. Parallel electric fields are formed.

This conventional IPS-LCD is shown in FIG. 1, which will be described with reference to this.

The plurality of gate bus lines 2 are arranged in parallel on the lower insulating substrate 1 at regular equal intervals, and the data bus lines 3 are similarly spaced at regular intervals, but are perpendicular to the gate bus lines 2. Disposed so as to intersect with each other to define a unit cell space in a lattice form. At each intersection of the gate bus line 2 and the data bus line 3, the channel layer 4 of the thin film transistor is provided. In this case, the data bus line 3 overlaps one side of the channel layer 4, and preferably, the data bus line 3 is placed on the channel layer 4, and the gate bus line 2 is formed of the channel layer ( 4) Pass the lower part.

In each of the LCD unit cell spaces, counter electrodes 5 for driving molecules in the liquid crystal are disposed. The counter electrode 5 is directed toward the wiring portion 5a arranged in parallel with the gate bus line 2 and toward the gate bus line 2 for selecting the unit cell from the wiring portion 5a. At least one, for example, three branches 5b extending parallel to 3). The branches 5b are spaced apart at regular equal intervals. At this time, the wiring portion 5a of the counter electrode 5 is connected to the wiring portions of the left and right cells, so that each counter electrode receives the same common signal voltage.

The pixel electrode 6 which drives the liquid crystal together with the counter electrode 5 is arranged so as to overlap with the counter electrode 5 in the unit cell. At this time, a gate insulating film (not shown) is interposed between the gate bus line 2 and the data bus line 3 and between the counter electrode 5 and the pixel electrode 6 to insulate each other. Here, the pixel electrode 6 is disposed parallel to the branch 5b between the first region 6a which is disposed to pass a part of the channel layer 4 and serves as a drain, and the branch 5b of the counter electrode 5. 4th which connects the other end of the 2nd area | region 6b arrange | positioned respectively, and the 3rd area | region 6c which connects the one end of the 1st area | region 6a and the 2nd area | region 6b, and the other end of the 2nd area | region 6b, respectively. Area 6d. At this time, since the second region 6b of the pixel electrode 6 is inserted between the branches 5b of the counter electrode 5, the pixel electrode 6 and the counter electrode 5 are alternately arranged. . In addition, the 4th area | region 6d is arrange | positioned so that it may overlap with the wiring part 5a, and a storage capacitor is formed in this part.

FIG. 2 is a cross-sectional view taken along the line II-II 'of FIG. 1, and the branches 5b of the counter electrodes are spaced at equal intervals on the upper surface of the lower substrate 1. The gate insulating layer 7 is covered on the lower substrate 1 on which the branch 5b is formed. The second region 6b of the pixel electrode is disposed at equal intervals above the gate insulating film 7 corresponding to the space between the branches 5b of the counter electrode. In addition, a data line 3 is formed on the gate insulating layer 7 on the edge of the branch formed in the edge of the branch formed in the unit pixel.

As described above, in the IPS-LCD, the branch 5b of the counter electrode and the second region 6 of the pixel electrode are alternately spaced by a predetermined interval on the lower substrate 1. Since the branch 5b and the second region 6 are both formed on the lower substrate 1, an electric field parallel to the substrate 1 is formed. As a result, the liquid crystal molecules lie parallel to the electric field (when the dielectric anisotropy of the liquid crystal is positive), so that the liquid crystal molecules are shortened on either side. Thus, the viewing angle is improved. At this time, the counter electrode 5 and the pixel electrode 6 are alternately arranged in one unit cell in order to reduce the response speed by making the length of the electric field relatively short.

However, the IPS-LCD as described above has the following problems.

That is, the counter electrode 5b and the pixel electrode 6b are formed on the same substrate surface in order to form parallel electric fields, but the counter electrode 5b and the pixel electrode 6b sandwich the gate insulating film 7 therebetween. It is placed up and down.

As a result, rather than forming a parallel electric field, an electric field of oblique or elliptical shape is formed as shown in FIG. 2, and thus it is difficult to form an electric field perfectly parallel to the substrate 1.

Accordingly, the present invention has been made to solve the above-mentioned problems, and to provide a liquid crystal display device capable of forming a parallel electric field by placing a counter electrode and a pixel electrode which actually drive a liquid crystal on the same plane. The purpose.

In order to achieve the above object of the present invention, the present invention, a plurality of gate bus lines and data bus lines arranged in a lattice form on the lower substrate to define a unit cell, the intersection of the gate bus line and the data bus line A thin film transistor formed in the vicinity, a wiring unit disposed in the unit cell space to drive a liquid crystal, the wiring unit being arranged in parallel with a predetermined distance from the gate bus line selecting the unit cell, and the unit from the wiring unit A counter electrode including a plurality of branches spaced apart at equal intervals toward the gate bus line for selecting a cell, a first region for driving a liquid crystal together with the counter electrode, and connected to the thin film transistor, and between the branches A second region disposed in parallel with the data bus line, and a first region and a second region A pixel electrode including a third region connecting the stages and a fourth region connecting the other end of the second region, and insulating the gate bus line from the data bus line, and insulating the counter electrode from the pixel electrode. And a gate insulating layer, wherein both of the branch and the second region are formed on the lower substrate surface.

In addition, the present invention is a liquid crystal display device in which a counter electrode and a pixel electrode for driving a liquid crystal are insulated from each other, and both are formed on a lower substrate and have an electric field parallel to the lower substrate. The actual liquid crystal drive parts of the electrodes are each provided on the lower substrate surface, and are arranged on the same plane with each other.

According to the present invention, by forming both the counter electrode portion and the pixel electrode portion which actually drive the liquid crystal in the IPS-LCD on the lower substrate surface, an electric field parallel to the substrate can be obtained.

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

Figure 3 is a plan view of the IPS-LCD according to the present invention, Figure 4 is a cross-sectional view taken along the line IV-IV 'of FIG.

In this embodiment, in order to form an electric field formed between the common electrode and the pixel electrode in a form parallel to the substrate, the common electrode portion and the pixel electrode portion for driving the liquid crystal are formed on the same plane, that is, the lower substrate surface.

More specifically, as shown in FIG. 3, a plurality of gate bus lines 12 are arranged in parallel on the lower insulating substrate 11 at equal intervals, and the data bus lines 14 are similarly disposed as gate bus lines ( 12, spaced at regular equal intervals so as to intersect perpendicularly with 12), to define a unit cell space in the form of a grid. A gate insulating film (not shown) is interposed between the gate bus line 12 and the data bus line 14 to insulate and separate these two lines 12 and 14. The thin film transistor TFT as a switching element is provided near the intersection point of the gate bus line 12 and the data bus line 14. The thin film transistor TFT includes a gate bus line 12, a channel layer 15 thereon, and a data bus line 14 passing through one side of the channel layer 15.

In each of the LCD unit cell spaces, counter electrodes 16 for driving molecules in the liquid crystal are disposed. The counter electrode 16 is connected to the wiring portion 16a arranged in parallel with the gate bus line 12 and the data bus line 14 toward the gate bus line 12 which selects the unit cell from the wiring portion 16a. And at least one, for example, three branches 16b extending in parallel to). The branches 16b are spaced apart at regular equal intervals. At this time, the wiring portion 16a of the counter electrode 16 is connected to the wiring portions of the left and right cells, so that each counter electrode receives the same common signal voltage. Here, the counter electrode 16 is formed on the surface of the lower substrate 11 together with the gate line 12.

The pixel electrode 17 which drives the liquid crystal together with the counter electrode 16 is disposed so as to overlap with the counter electrode 16 in the unit cell. The pixel electrode 17 passes through a portion of the channel layer 15, that is, the branch 16b is connected between the first region 17a which is connected to the thin film transistor and serves as a drain, and the branch 16b of the counter electrode 16. ) And the other ends of the second region 17b and the third region 17c and the second region 17b that connect one end of the first region 17a and the second region 17b, respectively. And a fourth region 17d for connecting. Here, the fourth region 17d overlaps the wiring portion 16a of the counter electrode 16 to form the storage capacitor. The second regions 17b are respectively inserted between the branches 16b, so the number is two. In this case, the counter electrode 16 and the pixel electrode 17 may be formed of an opaque metal film having excellent conductivity.

Here, the portions that actually drive the molecules in the liquid crystal (not shown) are the branch 16b of the counter electrode 16 and the second region 17b of the pixel electrode 17 which are alternately arranged. In this case, the gate insulating film corresponding to the region indicated by X in the drawing so that the branch 16b and the second region 17b are formed on the same plane, that is, on the surface of the substrate 11 so that an electric field parallel to the substrate can be formed. Remove it. At this time, since the branch 16b and the second region 17b do not overlap in the X portion, even if the gate insulating film is removed, no short is generated.

Referring to FIG. 4, the gate bus line 12 (see FIG. 3) and the counter electrode 16 are formed on the lower substrate 11. Subsequently, the gate insulating layer 13 is coated on the lower substrate 11 on which the gate bus line 12 and the counter electrode 16 are formed. Thereafter, a portion of the gate insulating film 13 corresponding to the portion where the branch 16b of the counter electrode 16 is formed is partially removed. Then, a metal film is deposited on the lower substrate 11, and a predetermined portion is etched to form the data bus line 14 and the pixel electrode 17. At this time, since the gate insulating layer 13 is not formed in the portion where the second region 17b of the pixel electrode 17 is formed, the branch of the pixel electrode 17, the second region 17b, and the counter electrode 17 is formed. 17b is formed on the same plane, that is, on the lower substrate 11 surface.

Accordingly, the gate insulating film 13 does not exist between the pixel electrode 17b and the counter electrode 16b which actually drive the liquid crystal, and no electric field in the form of a diagonal line is formed, and an electric field parallel to the substrate 11 is generated. Is formed.

The present invention is not limited only to the above embodiment.

For example, in the present invention, a counter electrode having three branches has been described as an example, but the same applies to other IPS-LCD structures.

As described in detail above, according to the present invention, an electric field parallel to the substrate can be obtained by forming both the counter electrode portion and the pixel electrode portion which actually drive the liquid crystal in the IPS-LCD on the lower substrate surface.

Thus, the viewing angle is improved.

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

1 is a cross-sectional view of a conventional IPS liquid crystal display device.

FIG. 2 is a cross-sectional view taken along the line II-II ′ of FIG. 1. FIG.

3 is a plan view of an IPS-LCD according to the present invention;

4 is a cross-sectional view taken along the line IV-IV 'of FIG.

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

11: lower substrate 12: gate bus line

13 gate insulating film 14 data bus line

15 channel layer 16 counter electrode

17: pixel electrode

Claims (2)

A plurality of gate bus lines and data bus lines arranged in a lattice form on a lower substrate to define a unit cell, and thin film transistors formed in the vicinity of an intersection of the gate bus line and the data bus line. A liquid crystal display device comprising a counter electrode for driving, a pixel electrode for driving a liquid crystal together with the counter electrode on the same plane as the counter electrode, and a gate insulating film for insulating between the gate bus line and the data bus line; The counter electrode includes a wiring part arranged in parallel while being spaced apart by a predetermined distance from the gate bus line for selecting the unit cell, and a plurality of branches extending at equal intervals from the wiring part toward the gate bus line for selecting the unit cell. Is provided, The pixel electrode may include a first region connected to the thin film transistor, a second region disposed in parallel with the data bus line between the branch, a third region connecting one end of the first region and the second region; A fourth region connecting the other end of the second region is provided, And the gate insulating layer is patterned to expose the branches of the counter electrode and the second region of the pixel electrode, respectively. The liquid crystal display of claim 1, wherein the counter electrode and the pixel electrode are formed of an opaque metal film.

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