KR19990042090A - Liquid crystal display element - Google Patents

Abstract

The present invention provides a liquid crystal display device having planarized surface characteristics.

According to the present invention, a liquid crystal display device having a structure in which a predetermined portion of a gate line and a data line overlaps a pixel electrode, and has a structure in which a first organic insulating film is interposed between the gate line and data line and the pixel electrode. A second organic insulating film is formed on the electrode and the first organic insulating film and its surface is flat. Here, the first organic insulating film and the second organic insulating film are resin films. In addition, the thickness of the second organic insulating film is about 1 μm.

Description

LCD

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having a structure in which a pixel electrode overlaps with a gate line and a data line.

As the capacity of the liquid crystal display device increases, the efficiency of the battery is gradually slowed. As a method for solving such a decrease in battery efficiency, there is a method of improving the transmittance of the liquid crystal panel. In order to improve the transmittance of such a liquid crystal panel, the aperture ratio of the liquid crystal panel is improved or the development of a high-permeability polarizing plate and a high-permeability color filter are used.

Here, a method for improving the aperture ratio of the liquid crystal panel will be described with reference to FIGS. 1 and 2.

1 is a plan view of a liquid crystal display device having a high opening ratio.

Referring to FIG. 1, a gate line 10 and a data line 20 are formed to cross on a transparent insulating substrate 1 (see FIG. 2) such as a glass substrate, and the gate line 10 and the data line 20 are formed. The thin film transistor 100 connected to the gate line 10 and the data line 20 is arranged at the intersection. In addition, the pixel electrode 30 overlaps with the gate line 10 and the data line 20 in a space formed by the gate line 10 and the data line 20, and is connected to the thin film transistor. In addition, the storage electrode 10a, which is a lower electrode of the storage capacitor 200, is arranged in parallel with the gate line 10, and the conductive layer pattern 20a, which is an upper electrode thereof, is arranged on the storage electrode 10a. The pixel electrode 30 is in contact with the source 22 of the thin film transistor 100 and is in contact with the conductive layer pattern 20a, which is an upper electrode of the storage capacitor.

FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. 1, and the cross-sectional structure of the TFT-LCD described above will be described with reference to FIG. 2.

As shown in FIG. 2, a storage node that is a lower electrode of the storage capacitor 200 arranged in parallel with the gate line 10 and the gate 10b extending from the gate line 10 on the insulating substrate 1. The electrode 10a is formed. A gate insulating film 2 is formed on the substrate on which the gate 10b and the storage node electrode 10a are formed. In addition, a semiconductor layer 11 made of amorphous silicon is formed on the gate insulating film 2 corresponding to the gate 10b, and an etch stopper 12 is formed on the semiconductor layer 11 corresponding to the gate 10b. The source / drains 21 and 22 are formed on the semiconductor layer 11 through the ohmic layer 3 made of amorphous silicon or the like doped with impurities so that the top surface of the etch stopper 12 is exposed. In addition, a conductive layer pattern 20a that is an upper electrode of the storage capacitor 200 is formed on the gate insulating layer 2 corresponding to the storage node electrode 10a. In addition, a data line 20 is formed on a predetermined portion on the gate insulating film 2. An organic insulating film 4 having a contact hole exposing the source 21 and the conductive film pattern 20a is formed on the entire surface of the substrate, and the source 21 and the contact hole are formed on the organic insulating film 4 through the contact hole. The pixel electrode 30 in contact with the conductive film pattern 20a is formed. Here, the organic insulating film 4 is a resin film having a low dielectric constant (? Exclude.

That is, as the pixel electrode 30 overlaps the gate line 10 and the data line 20 without being spaced apart, the aperture ratio is improved.

However, in the above-described conventional TFT-LCD having a high opening ratio, the substrate surface after the formation of the organic insulating film 4 is only flattened by about 90% by the thin film transistor 100 and the conductive film pattern 20a. . In addition, when the contact hole for contact between the source 21 and the conductive layer pattern 20a and the pixel electrode 30 is formed, the contact hole side surface is generally formed in a tapered shape to reduce the step difference caused by the contact hole formation. The taper angle between the surface and the contact hole side was 30 to 45 degrees, but the surface of the substrate was not completely flattened. Such unplanarization of the lower substrate prevents obtaining an alignment process for the operation of a desired liquid crystal molecule when forming an alignment film (not shown) that determines the initial driving state of the liquid crystal molecules. In addition, when the electric field is applied through the thin film transistor, an abnormal electric field is applied to the curved portion of the substrate surface, so that the electric field is concentrated, which may cause light leakage. As a result, the reliability of the liquid crystal display device is lowered.

Accordingly, an object of the present invention is to provide a liquid crystal display device having a flattened surface characteristic by reducing a taper angle.

1 is a plan view of a general liquid crystal display device.

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

3 is a cross-sectional view of a liquid crystal display device according to an embodiment of the present invention.

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

1 Insulation Substrate 2 Gate Insulation

3: ohmic layers 4a and 4b: first and second organic insulating films

10: gate line 10a: storage electrode

10b: gate 11: semiconductor layer

12: etch stopper 20: data line

20a: conductive film pattern 21, 22: source and drain

100: thin film transistor 200: storage capacitor

30: pixel electrode

In order to achieve the above object, a liquid crystal display device having a structure in which a predetermined portion of a gate line and a data line overlaps with a pixel electrode, and a first organic insulating film is interposed between the gate line and data line and the pixel electrode. And a second organic insulating film formed on the pixel electrode and the first organic insulating film and having a flat surface.

Here, the first organic insulating film and the second organic insulating film are resin films. In addition, the thickness of the second organic insulating film is about 1 μm.

According to the present invention, by forming the second organic insulating film after the formation of the pixel electrode, the taper angle by the first organic insulating film is reduced and the surface of the substrate is planarized, thereby applying an electric field when the electric field is applied through the thin film transistor. Concentration is prevented and light leakage phenomenon is suppressed, whereby the reliability of the liquid crystal display device is improved.

(Example)

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention.

3 is a cross-sectional view of a liquid crystal display device according to an exemplary embodiment of the present invention, and is a cross-sectional view taken along line AA ′ of FIG. 1, similar to FIG. 2.

In the present invention, after forming the pixel electrode, an organic insulating layer is further formed on the substrate to reduce the taper angle of the contact hole while planarizing the surface of the substrate. Referring to FIG. 3, the liquid crystal display device according to the present invention will be described. Here, the same reference numerals are assigned to the same components as those in FIG.

As shown in FIG. 3, a gate capacitor 10b extending from a gate line 10 (see FIG. 1) on a transparent insulating substrate 1, such as a glass substrate, and a storage capacitor arranged side by side with the gate line 10. The storage node electrode 10a, which is a lower electrode of 200, is formed. A gate insulating film 2 is formed on the substrate on which the gate 10b and the storage node electrode 10a are formed, and a semiconductor layer 11 made of amorphous silicon is formed on the gate insulating film 2 corresponding to the gate 10b. The etch stopper 12 is formed on the semiconductor layer 11 corresponding to the gate 10b. The source / drain 21 and 22 are formed on the semiconductor layer 11 under the ohmic layer 3 made of amorphous silicon doped with impurities so that the top surface of the etch stopper 12 is exposed. In addition, a conductive layer pattern 20a that is an upper electrode of the storage capacitor 200 is formed on the gate insulating layer 2 corresponding to the storage node electrode 10a. In addition, a data line 20 is formed on a predetermined portion on the gate insulating film 2.

A first organic insulating film 4a having a contact hole exposing the source 21 and the conductive film pattern 20a is formed on the entire surface of the substrate, and a source 21 is formed on the organic insulating film 4a through the contact hole. ) And the pixel electrode 30 in contact with the conductive film pattern 20a are formed. Here, the first organic insulating film 4a is a resin film having a low dielectric constant (ε = 2 to 4), formed to a thickness of about 3 μm, thereby eliminating the formation of parasitic capacitors. In addition, a second organic insulating film 4b is formed on the substrate on which the pixel electrode 30 is formed. Here, the second organic insulating film 4b is formed of the same film as the first organic insulating film 4a and has a thickness of about 1 μm. At this time, the second organic insulating film 4b is formed by the spin coating method and is evenly coated on the substrate, so that the taper angle of the contact hole of the first organic insulating film 4a is reduced by 10 to 5 degrees, thereby making the surface of the substrate flat. It's about 99%.

According to the present invention described above, by forming the second organic insulating film after the formation of the pixel electrode, the taper angle at the time of forming the contact hole through the first organic insulating film is reduced, thereby making the surface of the substrate flat. As a result, a desired alignment process is enabled, and when the electric field is applied through the thin film transistor, electric field concentration is prevented and light leakage is suppressed, thereby improving reliability of the liquid crystal display device.

In addition, this invention is not limited to the said Example, It can variously deform and implement within the range which does not deviate from the technical summary of this invention.

Claims (3)

A liquid crystal display device having a structure in which a predetermined portion of a gate line and a data line overlaps a pixel electrode, and a first organic insulating film is interposed between the gate line and the data line and the pixel electrode. And a second organic insulating film formed on the pixel electrode and the first organic insulating film and having a flat surface. The liquid crystal display device according to claim 1, wherein the first and second organic insulating films are resin films. The liquid crystal display device according to claim 1, wherein the thickness of the second organic insulating film is about 1 mu m.