KR101055202B1 - Transverse electric field liquid crystal display device - Google Patents

Abstract

The present invention relates to a transverse electric field liquid crystal display device in which an organic insulating film is formed at an edge of a pixel to overlap a pixel electrode and a data line, and an organic insulating film in the pixel opening is removed to easily form a transverse electric field. The transverse electric field liquid crystal display device includes a substrate; A gate wiring, a common wiring and a common electrode formed on the substrate; An interlayer insulating film formed on the entire surface including the gate wiring; A data line defining a unit pixel on the interlayer insulating layer by perpendicularly crossing the gate line; A thin film transistor formed at an intersection point of the gate line and the data line; An organic insulating layer formed on the data line and opened in an opening of a unit pixel; And a pixel electrode formed on the interlayer insulating film inside the pixel, parallel to the common electrode, connected to the thin film transistor, and overlapping an edge of the data line on the organic insulating film.

High opening ratio, polysilicon, transverse electric field

Description

Transverse electric field type liquid crystal display device {In-Plane Switching Mode Liquid Crystal Display Device}

1 is a plan view of a transverse electric field type liquid crystal display device according to the prior art.

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

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

4 is a cross-sectional view taken along line II-II ′ of FIG. 3.

* Explanation of symbols on the main parts of the drawings

110 substrate 111 buffer layer

112: gate wiring 113: gate insulating film

115: data wiring 117: pixel electrode

116: interlayer insulating film 118: organic insulating film

118a: open area 124: common electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a liquid crystal display device (LCD), and more particularly, to a transverse electric field type liquid crystal display device for improving the aperture ratio of the device and easily forming a transverse electric field.

Recently, a liquid crystal display device, which is one of the flat panel display devices that are attracting attention, is an element that changes the optical anisotropy by applying an electric field to a liquid crystal having both liquidity and optical properties of crystals. Compared with the low power consumption, small volume, large size, and high definition, it is widely used.

The liquid crystal display device has a variety of different modes depending on the nature of the liquid crystal and the structure of the pattern.

Specifically, the TN mode (Twisted Nematic Mode) for arranging the liquid crystal directors to be twisted by 90 ° and then applying a voltage to the liquid crystal directors, and dividing one pixel into several domains to change the viewing angle of each domain to change the wide viewing angle. Multi-domain mode to implement, OCB mode (Optically Compensated Birefringence Mode) to compensate the phase change of light according to the direction of light by attaching a compensation film to the substrate, and two electrodes on one substrate In-plane switching mode in which the directors of the liquid crystal are twisted in parallel planes of the alignment layer, and VA mode in which the long axes of the liquid crystal molecules are vertically aligned with the alignment layer plane by using a negative liquid crystal and a vertical alignment layer. Vertical Alignment Mode).

Among them, the transverse electric field type liquid crystal display device is usually composed of a color filter array substrate and a thin film transistor array substrate disposed opposite to each other and having a liquid crystal layer therebetween.

That is, a black matrix for preventing light leakage and a color filter layer of R, G, and B for implementing color on the black matrix are formed on the color filter array substrate.

The thin film transistor array substrate includes gate wirings and data wirings defining unit pixels, switching elements formed at intersections of the gate wirings and data wirings, and a common electrode and a pixel electrode alternately crossing each other to generate a transverse electric field. Is formed.

In this case, a thin film transistor (TFT) is mainly used as the switching element, and the thin film transistor uses an active layer made of amorphous silicon (amorphous silicon: a-Si) according to which silicon is used as the active layer. It can be classified into using and using an active layer made of polycrystalline silicon having a crystalline phase. As polycrystalline silicon, polysilicon (poly-Si) or microcrystalline silicon (μc-Si) is mainly known.

The active layer made of polycrystalline silicon has a feature that carrier mobility is about 10 to 100 times larger than the active layer made of amorphous silicon, and has a very excellent characteristic as a constituent material of a switching element.

On the other hand, in the case of using polycrystalline silicon, a low temperature process is possible because a high temperature crystallization process is not performed.

Liquid crystal display devices employing low temperature polycrystalline silicon (LTPS) technology using polycrystalline silicon generate storage capacitance by opposing active layers and gate patterns and thin gate insulating films formed therebetween, thereby reducing the area of the storage electrode. It can be reduced, and the opening ratio by the area of the reduced storage electrode is improved.

Hereinafter, a transverse electric field type liquid crystal display device according to the related art will be described with reference to the accompanying drawings. Hereinafter, the thin film transistor array substrate of the transverse electric field type liquid crystal display device will be mainly described.

1 is a plan view of a transverse electric field type liquid crystal display device according to the prior art, and FIG. 2 is a cross-sectional view taken along line II ′ of FIG. 1.

On the thin film transistor array substrate 10, as shown in FIGS. 1 and 2, a buffer layer 11 formed on the front surface of the substrate to prevent foreign substances from contaminating the upper pattern, and on the buffer layer 11. A gate line 12 vertically intersecting the formed active layer (not shown), the gate insulating layer 13 formed on the entire surface including the active layer, and the interlayer insulating layer 16 therebetween to define a unit pixel. And an organic insulating film 18 formed on the entire surface including the data wiring 15, the common electrode 24 formed in the unit pixel, the data wiring 15, and the common electrode on the organic insulating film 18. A pixel electrode 17 is formed parallel to the 24 to form a transverse electric field E for driving the liquid crystal.

At this time, a thin film transistor (not shown) including the active layer is formed at an intersection of the gate line 12 and the data line 15 to turn on / off the data signal by a signal flowing through the gate line. Is determined to display an image. In this case, the active layer is formed of a polysilicon layer, and becomes a top-gate thin film transistor.                         

On the other hand, the pixel electrode 17 and the common electrode 24 are each integrally connected inside the unit pixel, and in particular, the common electrode 24 is a common wiring formed in parallel to the gate wiring 12 (not shown). The common voltage signal is applied from the outside of the active region. The common electrode 24 and the common wiring are formed simultaneously with the gate wiring.

Such a transverse electric field type liquid crystal display device rotates the liquid crystal molecules in a horizontal direction by a transverse electric field, thereby greatly improving the viewing angle. However, since the reduction of the aperture ratio is the biggest problem in the transverse electric field type liquid crystal display device, it is absolutely necessary to study the improvement of the aperture ratio.

Recently, the organic insulating film 18 is formed between the pixel electrode 17 and the data wiring 15 for a high opening ratio. When the organic insulating film is used, the dielectric constant is low and the step is thick, so that the pixel electrode 17 and the data wiring ( The parasitic capacitance Cdp between the layers 15) is not large, and the pixel electrode and the data wiring may overlap. At this time, when the pixel electrode 17 overlaps the data line 15, the opening of the pixel is widened, thereby improving the aperture ratio of the device.

For reference, the inorganic insulating film has a dielectric constant of about 6.5 and is formed to a thickness of 5000 to 7000 ,, and the organic insulating film has a dielectric constant of about 2.65 and a thickness of 1.3 to 1.5 mu m. The gate insulating film 13 and the interlayer insulating film 16 are formed of an inorganic insulating film.

However, in the case where the low dielectric constant organic insulating film is used as described above, the transverse electric field for driving the liquid crystal cannot be effectively formed by the organic insulating film between the common electrode 24 and the pixel electrode 17.

Specifically, as shown in FIG. 2, the parasitic capacitance applied to the interlayer insulating film 16 is called C1, the parasitic capacitance applied to the organic insulating film 18 is referred to as C2, and the parasitic capacitance applied to the liquid crystal layer is referred to as C3. In this case, since the interlayer insulating film 16 is formed of an inorganic insulating film having a high dielectric constant, C1 becomes larger than C2.

On the other hand, when C3 is larger than C2, V = V2 becomes larger than V3 due to Q = CV, which means that the voltage applied to the interlayer insulating film becomes larger than the voltage applied to the liquid crystal layer by parasitic capacitance. When almost no voltage is applied to the liquid crystal, it becomes difficult to form a transverse electric field.

Therefore, in the above structure, in order to apply a constant voltage to the liquid crystal, a very large voltage must be applied. In this case, power consumption increases.

The present invention has been made to solve the above problems, and an organic insulating film is formed at the edge of the pixel to overlap the pixel electrode and the data wiring, and the organic insulating film is removed from the opening of the pixel so that sufficient voltage can be applied to the liquid crystal. It is an object of the present invention to provide a transverse electric field type liquid crystal display device in which a high electric field ratio is realized and a transverse electric field is easily formed.

In accordance with one aspect of the present invention, a transverse electric field type liquid crystal display device includes a gate wiring, a common wiring and a common electrode formed on a substrate, an interlayer insulating film formed on the entire surface including the gate wiring, and the gate on the interlayer insulating film. A data wiring defining a pixel perpendicular to the wiring, a thin film transistor formed at an intersection of the gate wiring and the data wiring, an organic insulating film formed on the data wiring and opened in an opening of a unit pixel, and the pixel. And a pixel electrode formed on an interlayer insulating film therein and parallel to the common electrode and connected to the thin film transistor.

That is, a low dielectric constant organic insulating film is formed between the data wiring and the pixel electrode overlapping the data wiring to reduce the parasitic capacitance, and the voltage applied to the liquid crystal by removing the organic insulating film between the common electrode and the pixel electrode generating the transverse electric field. It is characterized by maintaining enough.

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

3 is a plan view of a transverse electric field type liquid crystal display device according to the present invention, and FIG. 4 is a cross-sectional view taken along line II-II 'of FIG. 3.

In the thin film array substrate 110 of the transverse electric field type liquid crystal display device according to the present invention, as shown in FIGS. 3 and 4, a plurality of gate lines 112 arranged in a line and the gate lines 112 are provided. An interlayer insulating film 116 formed on the entire surface thereof, a data line 115 perpendicular to the gate line 112 to define a unit pixel, an organic insulating film 118 formed on the data line 115, and A plurality of common electrodes 124 integrally connected inside the unit pixel and to which a common voltage signal is applied from an outside of the active region, and formed in parallel between the common electrodes 124 to generate a transverse electric field together with the common electrodes; The pixel electrode 117 is provided.

The gate wiring 112, the gate electrode, and the common electrode 124 may be provided on the same layer, and a buffer layer 111 of SiO ₂ may be further provided on the upper surface of the substrate 110.

In this case, the thin film transistor is formed at the intersection of the gate wiring 112 and the data wiring 115 and includes a gate electrode, an active layer, and a source / drain electrode. Specifically, when polysilicon which can be processed at low temperature is used as the active layer, a top-gate composed of an active layer, a gate insulating layer 113, a gate electrode, an interlayer insulating layer 116, and a stacked layer of a source / drain electrode When a top-gate type thin film transistor is used and amorphous silicon is used as the active layer, a bottom-gate composed of a laminated film of a gate electrode, an interlayer insulating film 116, an active layer, and a source / drain electrode is used. -gate) thin film transistor.

Here, the source / drain electrodes provided on the same layer as the data line 115 are also covered by the organic insulating layer 118 and insulated from the upper layer. However, a predetermined portion of the drain electrode is exposed to the outside to be in contact with the pixel electrode 117.

That is, the organic insulating film 118 is formed on the data line 115 and the thin film transistor. The organic insulating layer 118 may be formed on the gate line 112, and may be formed on all of the remaining regions except for the opening of the pixel.

As such, by covering the data line 115 with the organic insulating film 118 having a low dielectric constant, the pixel electrode 117 can overlap a part of the data line 115. By overlapping the data line 115 and the pixel electrode 117, the opening of the pixel becomes large, and the dielectric constant of the organic insulating layer 118 is low, so that the parasitic capacitance is small, thereby achieving a high opening ratio.

The organic insulating layer 118 is formed by applying BCB (Benzocyclobutene) or photo acryl resin having a dielectric constant of about 2.65 to a thickness of 1.3 to 1.5 μm.

At this time, in the case of using the BCB, after the BCB and the photoresist are applied to the entire surface including the data wiring, the photoresist is exposed and developed, the BCB is etched to contact the drain electrode and the pixel electrode and at the same time, the pixel openings. BCB is also etched to pattern the organic insulating film.

In the case of using an acrylic resin, the photoacrylic resin is applied to the entire surface including the data wiring, and then the photoacrylic resin is exposed and developed to contact the drain electrode and the pixel electrode, and the open area of the pixel opening. 118a) are formed simultaneously.

On the other hand, the organic insulating layer 118 is not formed inside the unit pixel in which the common electrode 124 and the pixel electrode 117 are formed, but the strength of the transverse electric field formed between the common electrode 124 and the pixel electrode 117. To increase the That is, since only the high dielectric constant interlayer insulating film 116 is formed between the common electrode 124 and the pixel electrode 117, more voltage is applied to the liquid crystal layer than before.

At this time, the interlayer insulating film 116 is formed by depositing silicon nitride (SiNx) or silicon oxide (SiOx) with a dielectric constant of about 6.5 to 7000 Å.                     

Therefore, since the strength of the transverse electric field is increased, the driving of the liquid crystal is easy, and the power consumption of the device can be reduced since the intensity of the voltage does not have to be increased to drive the liquid crystal as desired. Accordingly, the present invention is characterized in that the formation of the transverse electric field is efficiently improved while achieving a high opening ratio.

Hereinafter, a method of manufacturing a transverse electric field type liquid crystal display device according to an embodiment of the present invention will be described.

First, SiO ₂ is deposited on the entire surface of the substrate 110 to form a buffer layer 111, an amorphous silicon layer is formed thereon, and an annealing process using an excimer laser is performed to crystallize into a polysilicon layer. After that, the crystallized polysilicon layer is patterned to form an active layer.

Next, an inorganic insulating film such as silicon nitride (SiNx) or silicon oxide (SiOx) is deposited on the entire surface including the active layer to form a gate insulating film 113.

In addition, copper (Cu), aluminum (Al), aluminum alloy (AlNd: Aluminum Neodymium), molybdenum (Mo), and molybdenum-tungsten (MoW) having low specific resistance to prevent signal delay on the gate insulating layer 113. After depositing a metal such as a pattern, a plurality of gate wirings 112, gate electrodes, and common electrodes 124 are formed.

The gate electrode is formed to branch from the gate line, and the common electrode 125 is formed to be separated from the gate line.

Next, an impurity ion is implanted into the active layer using the gate electrode as a mask to form a source / drain region, and then an inorganic material such as silicon nitride (SiNx) or silicon oxide (SiOx) is formed on the entire surface including the gate wiring 112. An insulating material is deposited by PECVD to form an interlayer insulating film 116.

Further, a plurality of metals such as copper (Cu), aluminum (Al), aluminum alloy (AlNd: Aluminum Neodymium), molybdenum (Mo), and molybdenum-tungsten (MoW) are deposited on the interlayer insulating layer 116 and then patterned to form a plurality of metals. Data wirings 115 and source / drain electrodes are formed.

In this case, the data line 115 crosses the gate line 112 to define a unit pixel, and the source / drain electrode is formed through a contact hole formed by removing the gate insulating layer 113 and the interlayer insulating layer 116. The active layer is contacted.

Next, an organic insulating film 118 and a photoresist are sequentially formed on the entire surface including the data line 115, and the photoresist is exposed and developed to pattern the photoresist. Subsequently, the organic insulating layer 118 exposed between the patterned photoresist is etched to form a contact hole through which the drain electrode is exposed, and at the same time, an open region 118a is formed in the opening of the unit pixel. At this time, the organic insulating film 118 is not removed from the edge of the pixel including the data line 115.

Next, a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO) is deposited and patterned on the entire surface including the organic insulating layer to be connected to the drain electrode, and the pixel electrode parallel to the common electrode 124. 117 is formed. In this case, the pixel electrode 117 is formed to overlap the edge of the data line 115 on the organic insulating layer 118.

As a result, a transverse electric field type liquid crystal display device having high aperture ratio and easily forming a transverse electric field is completed.

In this case, the transverse electric field type liquid crystal display device is described as including an example of a top-gate type polysilicon thin film transistor, but is not limited thereto and may be applied to a liquid crystal display device having a bottom-gate type thin film transistor. Do.

On the other hand, the present invention described above is not limited to the above-described embodiment and the accompanying drawings, it is possible that various substitutions, modifications and changes within the scope without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill in Esau.

The transverse electric field type liquid crystal display device of the present invention as described above has the following effects.

An organic insulating film is formed at the edge of the pixel to overlap the pixel electrode and the data wiring to improve the aperture ratio, and the organic insulating film is removed from the opening of the pixel so that a sufficient voltage can be applied to the liquid crystal, thereby easily forming a transverse electric field.

In addition, since the strength of the transverse electric field increases, driving of the liquid crystal becomes easy, and the power consumption of the device is reduced because the intensity of the voltage does not need to be increased to drive the liquid crystal as desired.

Claims (8)

Board; A gate wiring, a common wiring and a common electrode formed on the substrate; An interlayer insulating film formed on the entire surface including the gate wiring; A data line defining a unit pixel on the interlayer insulating layer by perpendicularly crossing the gate line; A thin film transistor formed at an intersection point of the gate line and the data line; An organic insulating layer formed on the data line and opened in an opening of a unit pixel; And And a pixel electrode formed on the interlayer insulating film inside the pixel, parallel to the common electrode, connected to the thin film transistor, and overlapping an edge of the data line on the organic insulating film. Liquid crystal display device. The method of claim 1, The thin film transistor includes a polysilicon layer, a gate insulating film, a gate electrode, an interlayer insulating film, and a stacked film of a source / drain electrode. The method of claim 2, A buffer layer is further provided on the lower surface of the polysilicon layer, And a gate insulating film is further provided between the polysilicon layer and the gate wiring. The method of claim 1, And the thin film transistor includes a laminated film of a gate electrode, an interlayer insulating film, an active layer, and a source / drain electrode. delete The method of claim 1, The organic insulating film is a transverse electric field liquid crystal display device, characterized in that formed of BCB or photoacrylic resin. The method of claim 1, The opening of the unit pixel is a transverse electric field type liquid crystal display device, characterized in that only the interlayer insulating film is provided between the pixel electrode and the common electrode. The method of claim 1, And the organic insulating layer is formed on the thin film transistor or the gate wiring.

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