KR19990026637A - Transverse electric field liquid crystal display device - Google Patents

Abstract

In the transverse electric field liquid crystal display device of the present invention, the protective film is made of BenzoCycloButene. The data electrode is formed on the gate insulating layer, and the common electrode is formed to overlap a portion of the data line on the passivation layer to block an electric field due to the data line and to prevent light leakage into the data line area. The thin film transistor is formed on the gate wiring so that the gate wiring serves as a gate electrode of the thin film transistor.

Description

Transverse electric field liquid crystal display device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a transverse electric field type liquid crystal display device having improved aperture ratio and reduced manufacturing cost.

Recently, a large area has been strongly demanded in thin film transistor liquid crystal displays (TFT LCDs), which are widely used in portable televisions and notebook computers. However, the above-described TFT LCDs have a problem in that contrast ratio is changed depending on the viewing angle. In order to solve this problem, various liquid crystal display devices such as a twisted nematic liquid crystal display device equipped with an optical compensation plate and a multi-domain liquid crystal display device have been proposed. It is difficult to solve the problem that the contrast ratio decreases and the color changes depending on the viewing angle.

Another type of liquid crystal display device that is proposed to realize a wide viewing angle is a liquid crystal display device of the in plane switching mode (JAPAN DISPLAY 92 P547, Japanese Patent Laid-Open No. 7-36058, Japanese Patent Laid-Open No. 7-225538, It is proposed to ASIA DISPALY 95 P107.

1 is a view showing a conventional transverse electric field type liquid crystal display device. In the conventional transverse electric field type liquid crystal display device, as shown in FIG. 1A, the gate line 1 and the data line 2 are arranged on the first substrate 10 to define a pixel area. The common wiring 3 arranged in the pixel in parallel with the gate wiring 1, the thin film transistor arranged at the intersection of the gate wiring 1 and the data wiring 2, and the data wiring 2 in the pixel. And a data electrode 8 and a common electrode 9 arranged in substantially parallel with each other. As shown in FIG. 1B, the TFT may include a gate electrode 5 formed on the first substrate 10 and connected to the gate wiring 1, and a gate insulating layer stacked on the gate electrode 5. 12, the active layer 15 formed on the gate insulating film 12, the source electrode 6 and the drain formed on the active layer 15 and connected to the data wiring 2 and the data electrode 8, respectively. It consists of an electrode 7. The common electrode 9 in the pixel is formed on the first substrate 10 and connected to the common wiring 3, and the data electrode 8 is formed on the gate insulating film 12 and connected to the drain electrode 7 of the thin film transistor. . The passivation layer 20 is formed only on the semiconductor layer 20 of the thin film transistor, and the first alignment layer 23a is coated over the entire first substrate 10.

The second substrate 11 is formed with a light blocking layer 28 that prevents light leakage near the thin film transistor, the gate wiring 1, the data wiring 2, and the common wiring 3. 29) and the second alignment film 23b are formed. In addition, a liquid crystal layer 30 is formed between the first substrate 10 and the second substrate 11.

In the transverse electric field type liquid crystal display device configured as described above, when a voltage is applied from an external driving circuit, a transverse electric field parallel to the surfaces of the substrates 10 and 11 is formed between the data electrode 8 and the common electrode 9. Occurs. Accordingly, the liquid crystal molecules in the liquid crystal layer 30 rotate along the above-described transverse electric field, thereby controlling the amount of light passing through the liquid crystal layer 30.

In a typical transverse electric field type liquid crystal display device, since the passivation layer 20 is stacked over the first substrate 10, the passivation layer 20 acts as a capacitor to form a gap between the data electrode 8 and the common electrode 9. The strength of the transverse electric field is reduced. Therefore, as shown in the figure, when the protective film 20 is formed only on the thin film transistor to protect the semiconductor layer 150, the driving voltage is lowered because the strength of the transverse electric field between the electrodes 8 and 9 does not decrease. It becomes possible. However, since the thickness of the said protective film 20 is about 3000 micrometers, when the 1st orientation film 23a is apply | coated, the level | step difference will arise in the orientation film 123a. Such a step causes an unoriented region to be generated in the alignment layer 23a when the alignment layer 23a is oriented by rubbing and a mechanical method, thereby causing disclination.

The passivation layer 20 and the gate insulating layer 12 are generally made of an inorganic material such as SiOx or SiNx. Therefore, since the protective film 20 and the gate insulating film 12 have the same or similar etching selectivity, the gate insulating film 12 is also often etched when the protective film 20 in the region excluding the thin film transistor is etched. This will stain your screen.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and an object thereof is to provide a transverse electric field type liquid crystal display device having a uniform cell gap by forming a protective film with benzocyclobutene.

It is another object of the present invention to reduce the influence of liquid crystal molecules by the electric field of the data wiring by overlapping the common electrode with the data wiring, and at the same time the manufacturing process is simple and the manufacturing cost by the common electrode serves as a light shielding layer It is to provide a greatly reduced transverse electric field type liquid crystal display device.

It is still another object of the present invention to provide a transverse electric field type liquid crystal display device having a greatly improved aperture ratio by forming a thin film transistor on a gate wiring.

In order to achieve the above object, a transverse electric field type liquid crystal display device according to the present invention comprises a first substrate and a second substrate, a gate wiring and a data wiring arranged vertically and horizontally on the first substrate, and on the gate wiring. A thin film transistor, a data electrode arranged in parallel with the gator wiring, a BCB coated over the first substrate, and a protective film formed on the passivation layer in parallel with the data electrode. The common electrode overlapping the data wiring, the first alignment layer coated on the common electrode and the passivation layer, the light shielding layer formed on the second substrate, the color filter layer formed on the entire second substrate, and the color filter layer. And a coated second alignment film and a liquid crystal layer formed between the first substrate and the second substrate.

The thin film transistor is formed on the gate wiring described above. That is, the thin film transistor includes a gate wiring, a gate insulating film formed on the gate wiring, a semiconductor layer formed on the gate insulating film, and a source electrode and a drain electrode formed on the semiconductor layer.

Since the protective film is made of BCB, which is an organic material, not only a uniform cell gap can be maintained but also an unoriented region due to the step of the alignment film is not generated during the alignment treatment by rubbing.

The common electrode overlapping the data line on the passivation layer blocks an electric field due to the data line and prevents light leakage near the data line. The common wiring and the data electrode form a storage capacitor with a protective film interposed therebetween.

1A is a plan view of a conventional transverse electric field type liquid crystal display device.

(B) is sectional drawing A-A 'of FIG. 1 (a).

2 is a plan view of a transverse electric field type liquid crystal display device according to the present invention;

FIG. 3A is a cross-sectional view taken along the line BB ′ of FIG. 2.

FIG. 3B is a cross-sectional view taken along the line CC 'of FIG. 2.

* Explanation of symbols for main parts of the drawings

101: gate wiring 102: data wiring

103: common wiring 106: source electrode

107: drain electrode 108: data electrode

109: common electrode 110: first substrate

111: second substrate 112: gate insulating film

115: semiconductor layer 120: protective film

123: alignment layer 128: light shielding layer

129: color filter layer 130: liquid crystal layer

Hereinafter, a transverse electric field type liquid crystal display device according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a plan view of a transverse electric field type liquid crystal display device according to the present invention. As shown in the figure, in the present invention, a thin film transistor is formed on the gate wiring 101. The gate wiring 101 and the data wiring 102 intersecting with each other are arranged on the substrate. Although only one pixel is shown in the figure, n x m pixels are formed by the n gate wirings 101 and the m data wirings 102 in the actual liquid crystal display device. In the pixel, the data electrode 108 and the common electrode 109 are arranged in parallel with the data wiring 102 described above, and the common electrode 109 is electrically connected to the common wiring 103. The thin film transistor including the semiconductor layer 115, the source electrode 106, and the data electrode 108 is formed on the gate wiring 101. In this case, the gate wiring 101 serves as a gate electrode of the thin film transistor. As shown in the figure, the biggest feature of the present invention is that a part of the common electrode 109 overlaps the data wiring 102.

3 (a) and 3 (b) are cross-sectional views taken along lines B-B 'and C-C' of FIG. 2, respectively, to clearly show the features of the present invention. As shown in the figure, a gate wiring 101 is formed on the first substrate 110, and a gate insulating film 112 is stacked thereon. The gate wiring 101 of the present invention serves as a gate electrode of a thin film transistor, and is formed by etching a metal thin film of about 3000 kV such as Al, Mo, Ta, or Al alloy deposited by a sputtering method, and the gate insulating film 112. Silver is formed by laminating inorganic materials such as SiNx or SiOx by CVD (Chemical Vapor Deposition) method.

The semiconductor layer 115 is formed on the gate insulating layer 112. The semiconductor layer 115 is a channel layer, and is formed by laminating and etching amorphous silicon (a-Si) by a CVD method. Although not shown, an ohmic contact layer made of n ⁺ a-Si is formed on the semiconductor layer 115. The data wiring 102, the source electrode 106, the drain electrode 107, and the data electrode 108 are formed on the ohmic contact layer and the gate insulating layer 112. The data wiring 102, the source electrode 106, the drain electrode 107, and the data electrode 108 are etched by a metal thin film of about 1000 mm, such as Al, Cr, Ti, and Al alloy, which are deposited by a sputtering method. Form.

The passivation layer 120 is coated on the thin film transistor, the data wiring 102, the data electrode 108, and the gate insulating layer 112. Since the passivation layer 120 is stacked with an organic material such as benzocyclobutene by spin coating, the surface of the passivation layer 120 is flat.

The common electrode 109 and the common wiring 103 are formed on the passivation layer 120. As shown in FIG. 2 and FIG. 3B, a part of the common electrode 109 overlaps with the data wiring 102. Accordingly, the common electrode 109 shields an electric field generated by the data wiring 102, thereby preventing the liquid crystal molecules from being affected by the electric field generated from the data wiring 102. In addition, since the common electrode 109 blocks light leaking near the data wiring 102, the light blocking layer 128 can be formed only along the gate wiring 101 as shown in FIG. This simplifies the manufacturing process and significantly reduces the manufacturing cost.

On the passivation layer 120 and the common electrode 109, a first alignment layer 123a made of a photoreactive material such as polyimide, polyvinylcinnamate (PVCN), or polysiloxane (polysiloxane) material is coated. When polyimide is used as the alignment film, a mechanical rubbing method is used to determine the orientation direction on the alignment film. When the BCB is used as the protective film 120 as in the present invention, no step occurs in the alignment film, and thus, even when the orientation direction is determined by the rubbing process, the unoriented area is not generated, thereby preventing the foreground from appearing on the screen. .

When the photoreactive material is used as the first alignment layer 123a, the alignment direction is determined by irradiating light such as ultraviolet rays to the alignment layer. Since the orientation direction determined by the alignment film varies depending on the intrinsic properties of the light, such as the polarization direction of the irradiated light, it is possible to solve the problem of dust or static electricity generated in the alignment film when mechanical rubbing is used.

The common wiring 103 and the data electrode 108 are formed with the passivation layer 120 interposed therebetween to form a storage capacitor as shown in FIG. 2.

Although not shown in the drawing, in addition to forming the common wiring 3 on the passivation layer 120, it is also possible to simultaneously form the gate wiring 101 on the first substrate 110. In this case, the common electrode 109 is connected to the common wiring 103 through a contact hole formed in the passivation layer 120.

A light blocking layer 128 is formed on the second substrate 111 to prevent light leakage near the gate wiring, the data wiring, the common wiring, and the thin film transistor, and the color filter layer 129 is formed thereon. The light shielding layer 128 is formed by etching the Cr thin film or CrOx thin film laminated by the sputtering method. In the color filter layer 129, R, G, and B layers are repeatedly formed for each pixel. After the second alignment layer 123b made of polyimide or a photoreactive material is coated on the color filter layer 129, the orientation direction is determined by rubbing or irradiation of light. In addition, a liquid crystal is injected in a vacuum state between the first substrate 110 and the second substrate 111 to form the liquid crystal layer 130.

In the transverse electric field liquid crystal display device of the present invention, since the organic material BCB is used as the protective film, the cell gap between the first substrate and the second substrate can be maintained uniformly. In addition, since the common electrode is formed on the passivation layer and a part thereof overlaps with the data wiring, there is no need to form a light shielding layer in the data wiring region, thereby simplifying the manufacturing process and significantly reducing the manufacturing cost. . Furthermore, since the thin film transistor is formed on the gate wiring, the aperture ratio is greatly improved.

Claims (13)

A first substrate and a second substrate; A plurality of gate wirings and data wirings formed on the first substrate to define pixel regions; A plurality of thin film transistors formed at intersections of the gate lines and data lines; A first electrode formed in the pixel region; A protective film made of an organic material coated on the first substrate; A second electrode arranged in parallel with the first electrode on the passivation layer and partially overlapping the data line; A transverse electric field liquid crystal display device comprising a liquid crystal layer formed between the first substrate and the second substrate. The transverse electric field liquid crystal display device according to claim 1, wherein the first electrode is a data electrode and the second electrode is a common electrode. The transverse electric field liquid crystal display device according to claim 1, wherein the thin film transistor is formed on a gate wiring. According to claim 3, wherein the thin film transistor, Gate wiring; A gate insulating film stacked on the gate wiring; A semiconductor layer formed on the gate wiring; A transverse electric field liquid crystal display device comprising a source electrode and a drain electrode formed on the semiconductor layer. The transverse electric field liquid crystal display device according to claim 1, wherein the protective film is made of BenzoCycloButene. The method of claim 1, A common wiring formed in the pixel region of the first substrate and connected to the common electrode; And a light shielding layer formed along the gate wiring on the second substrate. The transverse electric field liquid crystal display device according to claim 6, wherein the common wiring is formed on the first substrate simultaneously with the gate wiring. The transverse electric field liquid crystal display device according to claim 6, wherein the common wiring is formed on the passivation layer. The transverse electric field liquid crystal display device according to claim 8, wherein the common wiring and the data electrode form a storage capacitor. The method of claim 1, A first alignment layer coated on the first substrate; A color filter layer formed on the second substrate; And a second alignment layer coated on the second substrate and the color filter layer. The transverse electric field liquid crystal display device according to claim 10, wherein the first alignment layer or the second alignment layer is made of polyimide. The transverse electric field liquid crystal display device according to claim 10, wherein the first alignment layer or the second alignment layer is made of a photoreactive material. The transverse electric field liquid crystal display device according to claim 12, wherein the photoreactive material is selected from the group consisting of polyvinylcinnamate (PVCN) material and polysiloxane material.