KR19990017976A - Transverse electric field liquid crystal display device - Google Patents

Abstract

In the transverse electric field type liquid crystal display device of the present invention, the protective film and the gate insulating film are made of BenzoCycloButene. An inorganic insulating film is laminated on the BCB gate insulating film in order to improve the insulating property. The protective film is applied only on the semiconductor layer of the thin film transistor and the gate insulating layer of the pixel region, and is rarely applied on the data electrode.

Description

Transverse electric field liquid crystal display device

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 image quality 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 semiconductor layer 15 formed on the gate insulating film 12, and the source electrode 6 formed on the semiconductor layer 15 and connected to the data wiring 2 and the data electrode 8, respectively. And a drain 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 15 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 substrates 10 and 11 is generated between the data electrode 8 and the common electrode 9. . Accordingly, the liquid crystal molecules oriented 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 drawing, when the protective film 20 is formed only on the thin film transistor to protect the semiconductor layer 15, the strength of the transverse electric field between the electrodes 8 and 9 does not decrease, thereby lowering the driving voltage. 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, a step | step will generate | occur | produce in the orientation film 23a. When the alignment layer 23a is oriented by rubbing and a mechanical method, such a step may cause a region in which the alignment direction is not determined in the alignment layer 23a, resulting in a 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.

In addition, in order to open the pad when the protective film 20 is opened, the gate insulating film 12 must be overetched, but the etching of the gate insulating film 12 causes a defect in the gate insulating film itself. Moreover, the above defects of the gate insulating film affect the gate metal. For example, when Cr is used as the gate electrode, moisture penetrates into the gate electrode due to the defect of the gate insulating film described above, and disconnection occurs in the gate electrode (or gate wiring).

Furthermore, since the gate insulating film formed on the first substrate with a thickness of about 4000 kV is also stacked on the common electrode, the strength of the electric field between the electrodes 8 and 9 is weakened, thereby increasing the driving voltage.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and an object of the present invention is to provide a transverse electric field type liquid crystal display device having a simple manufacturing process and improving image quality by forming a protective film with benzocyclobutene, which is an organic insulating film.

It is another object of the present invention to provide a transverse electric field type liquid crystal display device which can reduce driving power by forming a protective film and a gate insulating film of BCB to increase the strength of the transverse electric field between electrodes.

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, the gate wiring and A thin film transistor disposed at an intersection of the data wiring lines, a data electrode and a common electrode arranged in parallel with the gator wirings, a protective film made of BCB coated on the thin film transistors, and the entire first substrate. The first alignment film, the black matrix formed on the second substrate, the color filter layer formed over the entire second substrate, the second alignment film coated on the color filter layer, and the first substrate and the second substrate. It consists of a liquid crystal layer formed in.

The thin film transistor includes a gate electrode formed on the first substrate, at least one gate insulating film formed on the gate electrode, a semiconductor layer formed on the gate insulating film, and a source electrode and a drain electrode formed on the semiconductor layer.

In the gate insulating film composed of the first gate insulating film made of BCB and the second gate insulating film made of inorganic materials such as SiOx and SiNx, the BCB film is evenly coated, so that the surface of the entire gate insulating film is flat and the thickness on the common electrode is first. It becomes smaller than the thickness on the substrate.

Since the protective film made of BCB is applied by spin coating, it is formed to have almost the same thickness as the data electrode. Therefore, the above protective film is applied only on the thin film transistor and the gate insulating film, but not on the data electrode. Therefore, the strength of the transverse electric field between the electrodes is increased to reduce the driving voltage.

As described above, both the protective film and the gate insulating film may be formed of BCB, and either the protective film or the gate insulating film may be coated with BCB, and the other may be formed of the inorganic film.

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 cross-sectional view of a transverse electric field type liquid crystal display device according to a first embodiment of the present invention.

Explanation of symbols for main parts of the drawings

105: gate electrode 106: source electrode

107: drain electrode 108: data electrode

109: common electrode 110: first substrate

111: second substrate 112, 113: gate insulating film

115: semiconductor layer 120: protective film

123: alignment layer 128: black matrix

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 cross-sectional view of a transverse electric field type liquid crystal display device according to a first embodiment of the present invention. Since the plan view of the transverse electric field type liquid crystal display device of the present invention is the same as that of FIG. 1, the description of the plan view will be omitted and the present invention will be described with reference to FIG. 2.

As shown in the drawing, the gate electrode 105 and the common electrode 109 are formed on the first substrate 110, and the first gate insulating film 113 and the second gate insulating film 112 are formed thereon. . The gate electrode 105 and the common electrode 109 are formed by etching a metal thin film of about 3000 kV, such as Al, Mo, Ta, or Al alloy, which are stacked by a sputtering method, and the first gate insulating film 113 is formed of benzocyclobutene. (BenzoCycloButene) is formed by applying a spin coating method (spin coating). In addition, the second gate insulating layer 112 is formed by stacking an inorganic material such as SiNx, SiOx, or the like by a CVD (Chemical Vapor Deposition) method. Since BCB, which is an organic material, is thicker than the gate electrode 105 and the common electrode 109 with a thickness of about 2500 kV by spin coating, the surface is flat despite the step difference between the gate electrode 105 and the common electrode 109. Is formed. Therefore, when the second gate insulating film 112 made of an inorganic material having good insulation is formed thereon, the surface of the second gate insulating film 112 is also formed flat. As shown in the drawing, the gate insulating films 112 and 113 are formed flat, so that the gate insulating films 112 and 113 on the common electrode 109 are thinner than the insulating films 112 and 113 on the first substrate 110. It means that it is formed. Therefore, the weakness of the electric field is prevented by the insulating films 112 and 113 described above when voltage is applied.

The semiconductor layer 115 is formed on the second 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 source electrode 106, the drain electrode 107, and the data electrode 108 are formed on the ohmic contact layer and the second gate insulating layer 112. The source electrode 106, the drain electrode 107, and the data electrode 108 are formed by etching a metal thin film of about 1000 mW, such as Al, Cr, Ti, and Al alloy, which are stacked by a sputtering method. Although not shown in the figure, data wirings are formed simultaneously with the formation of the source electrode 106, the drain electrode 107, and the data electrode 108.

The passivation layer 120 is coated on the semiconductor layer 115 and the second gate insulating layer 112. The passivation layer 120 is coated by BCB by spin coating, and is formed to a thickness of about 1000 mW, which is almost the same as that of the source electrode 106, the drain electrode 107, and the data electrode 108. Therefore, the passivation layer 120 is formed only on the semiconductor layer 115 and the second gate insulating layer 112, but not on the data electrode 108. As a result, when a voltage is applied to the data electrode 108, an electric field having a stronger intensity is applied as compared with the conventional liquid crystal display in which a protective film is stacked on the data electrode 108. Therefore, the liquid crystal molecules can improve the driving speed, thereby reducing the driving voltage. Also in the manufacturing process, it is not necessary to etch the protective film of the pixel region, so that the process is simpler compared to the etching of the protective film of the pixel region in order to reduce the driving voltage conventionally, and the manufacturing cost is greatly reduced. In addition, since a portion of the gate insulating film 112 is conventionally etched when the protective film 120 is etched to prevent staining on the screen, it is possible to implement good image quality. At this time, the protective film 120 can be made thinner than 1000 kPa, and can be applied only on the semiconductor layer 115.

Although not shown in the drawing, the pad region is opened by etching the first gate insulating film 113, the second gate insulating film 112, and the protective film 120 at the same time after the protective film 120 is applied. In the pad opening process, the manufacturing process is reduced compared to opening the protective layer after etching the gate insulating layer in the conventional transverse type liquid crystal display, and thus the manufacturing cost is greatly reduced and the yield is improved.

The first alignment layer 123a is applied over the entire first substrate 110. As the alignment layer, a photoreactive material such as polyimide or polyvinylcinnamate (PVCN) -based material or polysiloxane-based material is generally used. 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. .

In the case where a photoreactive material is used as the alignment layer 123a, the alignment layer is determined by irradiating light such as ultraviolet rays onto 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.

A black matrix 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 black matrix 128 is formed by etching a Cr thin film or a CrOx thin film deposited by a 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.

As described above, in the transverse electric field type liquid crystal display device of the present invention, since the protective film 120 is applied only on the semiconductor layer 115 and the second gate insulating film 112 in the pixel region, the surface is almost flat throughout the liquid crystal panel. Will be achieved. In addition, since the passivation layer 120 is not coated on the data electrode 108, the driving voltage can be significantly reduced.

In the above description, the protective film 120 is coated on the semiconductor layer 115 and the second gate insulating film 112 in the pixel region, but it is also possible to apply the protective film 120 only on the semiconductor layer 115. In addition, although the gate insulating films 112 and 113 are formed of a double layer of BCB and an inorganic insulating film and the protective film 120 is formed by applying BCB, the gate insulating film is formed of a single layer made of an inorganic insulating film and the protective film 120 is formed. May be formed of BCB, and of course, the gate insulating film may be formed of a single layer made of BCB, and the protective film may be formed of an inorganic insulating film.

In the transverse electric field liquid crystal display device of the present invention, since the first gate insulating film is made of BCB and the first gate insulating film made of inorganic material is stacked thereon, the surface of the gate insulating film is flat. Therefore, the thickness of the gate insulating film on the common electrode is much smaller than in the prior art. Therefore, the driving voltage can be reduced because the intensity of the electric field is not reduced by the insulating film. In addition, since the protective film is not coated on the data electrodes, the driving voltage is further reduced.

The protective film is applied to a thickness substantially the same as that of the data electrode, so that its surface is flat in the pixel area, so that unaligned areas do not occur when rubbing the alignment film, thereby improving image quality.

Also in the manufacturing process, the pad and the gate insulating film are etched at the same time to open the pad, thereby simplifying the manufacturing process. In addition, since it is not necessary to etch the protective film of the pixel region, the gate insulating film is not etched when the protective film is etched, so that the image quality is further improved.

Claims (28)

A substrate; A first electrode formed on the substrate; At least one flat first insulating layer stacked over the substrate; A second electrode formed on the first insulating layer; An electrode structure of a transverse electric field type liquid crystal display device comprising a flat second insulating layer formed on the first insulating layer. 2. The electrode structure of a transverse electric field liquid crystal display device according to claim 1, wherein the first electrode is a common electrode and the second electrode is a data electrode. The electrode structure according to claim 1, wherein the first insulating layer is a gate insulating film and the second insulating layer is a protective film. The electrode structure of a transverse electric field type liquid crystal display device according to claim 1, wherein the second insulating layer is made of an organic material. 5. The electrode structure of a transverse electric field liquid crystal display device according to claim 4, wherein the organic material is benzocyclobutene. The electrode structure of a transverse electric field type liquid crystal display device according to claim 1, wherein the first insulating layer is formed of a double layer. 7. The electrode structure of a transverse electric field liquid crystal display device according to claim 6, wherein the first insulating layer comprises an organic insulating layer and an inorganic insulating layer. A first substrate and a first substrate; Gate wiring and data wiring arranged vertically and horizontally on the first substrate to define a pixel region; A thin film transistor disposed at an intersection of the gate line and the data line; At least a pair of electrodes arranged in said pixel region for applying a transverse electric field; A transverse electric field liquid crystal display device comprising a protective film made of an organic material coated on the thin film transistor. The transverse electric field liquid crystal display device according to claim 8, wherein the organic material is benzocyclobutene. The transverse electric field liquid crystal display device according to claim 8, wherein the electrodes are a data electrode and a common electrode. The thin film transistor of claim 8, wherein the thin film transistor comprises: a gate electrode; A gate insulating film formed on the gate electrode; A semiconductor layer formed on the gate insulating film; And a source electrode and a drain electrode formed on the semiconductor layer. 12. The transverse electric field liquid crystal display device according to claim 11, wherein a protective film is coated on the gate insulating film. The transverse electric field liquid crystal display device according to claim 12, wherein the thickness of the passivation layer is the same as that of the data electrode. 10. The method of claim 8, further comprising: a first alignment film coated over the entire first substrate; A black matrix formed on the second substrate; A color filter layer formed on the second substrate and the black matrix; A second alignment film applied over the entire second substrate; A transverse electric field type liquid crystal display device further comprising a liquid crystal layer formed between the first substrate and the second substrate. A first substrate and a first substrate; Gate wiring and data wiring arranged vertically and horizontally on the first substrate to define a pixel region; And a gate insulating film made of a gate electrode formed on the first substrate, an organic material applied over the entire first substrate, a semiconductor layer formed on the gate insulating film, and a source electrode and a drain electrode formed on the semiconductor layer. A thin film transistor disposed at an intersection of one gate wiring and a data wiring; A transverse electric field liquid crystal display device comprising at least one pair of electrodes arranged in the pixel area to apply a transverse electric field. The transverse electric field liquid crystal display device according to claim 15, wherein the organic material is benzocyclobutene. The transverse electric field liquid crystal display device according to claim 15, wherein the electrodes are a data electrode and a common electrode. The transverse electric field liquid crystal display device according to claim 15, further comprising an insulating film stacked on the gate insulating film. The transverse electric field liquid crystal display device according to claim 18, wherein the insulating film is an inorganic insulating film. The semiconductor device of claim 15, further comprising: a protective film formed over the entire first substrate; A first alignment film coated on the protective film; A black matrix formed on the second substrate; A color filter layer formed on the second substrate and the black matrix; A second alignment film applied over the entire second substrate; A transverse electric field type liquid crystal display device further comprising a liquid crystal layer formed between the first substrate and the second substrate. A first substrate and a first substrate; Gate wiring and data wiring arranged vertically and horizontally on the first substrate to define a pixel region; And a gate insulating film made of a gate electrode formed on the first substrate, an organic material applied over the entire first substrate, a semiconductor layer formed on the gate insulating film, and a source electrode and a drain electrode formed on the semiconductor layer. A thin film transistor disposed at an intersection of one gate wiring and a data wiring; At least a pair of electrodes arranged in said pixel region for applying a transverse electric field; A transverse electric field liquid crystal display device comprising a protective film made of an organic material coated on the thin film transistor. 22. The liquid crystal display device according to claim 21, wherein the organic material is BenzoCycloButene. The transverse electric field liquid crystal display device according to claim 21, wherein the electrodes are a data electrode and a common electrode. 22. The transverse electric field liquid crystal display device according to claim 21, further comprising an insulating film stacked on the gate insulating film. A transverse electric field liquid crystal display device according to claim 24, wherein said insulating film is an inorganic insulating film. A transverse electric field liquid crystal display device according to claim 25, wherein a protective film is coated on the gate insulating film. 27. The transverse electric field liquid crystal display device according to claim 26, wherein the thickness of the protective film is the same as the thickness of the data electrode. 22. The method of claim 21, further comprising: a first alignment film coated on the protective film; A black matrix formed on the second substrate; A color filter layer formed on the second substrate and the black matrix; a second alignment layer applied over the entire second substrate; A transverse electric field type liquid crystal display device further comprising a liquid crystal layer formed between the first substrate and the second substrate.