KR20070100036A - Wide viewing angle vertical align mode liquid crystal display - Google Patents

Abstract

A wide viewing angle vertical alignment mode liquid crystal display apparatus is provided to use a spacer in which alignment agent is coated as a deflecting unit of a liquid crystal for widening viewing angle of the liquid crystal display apparatus, thereby implementing a vertical alignment mode liquid crystal display apparatus with a wide viewing angle by simple processes. A wide viewing angle vertical alignment mode liquid crystal display apparatus comprises the following parts: a lower and upper substrate; a gate line(GL) and a data line(DL); a thin film transistor(TFT) which is formed in a cross unit of the gate line and the data line; a pixel electrode(52) which is separated to a plurality of unit areas; a spacer(53) in which an alignment agent(54) is coated in a surface; a liquid crystal layer having negative dielectric constants; a counterelectrode which is formed inside surface of the upper substrate; a vertical alignment film which is installed between a liquid crystal layer and a pixel electrode or the counterelectrode and the liquid crystal layer; and a polarized plate which is mounted in the outside of the lower substrate and upper substrate.

Description

Wide viewing angle vertical alignment mode liquid crystal display

1 is a cross-sectional view showing a conventional multidomain vertical alignment (MVA) mode liquid crystal display device.

2 is a cross-sectional view showing a conventional patterned vertical alignment (PVA) mode liquid crystal display device.

3A and 3B are plan views illustrating the spacer coated with the alignment agent of the present invention.

4 is a schematic view showing a spacer forming method by an inkjet printing technique of the present invention.

5 is a plan view illustrating a wide viewing angle vertical alignment mode liquid crystal display according to an exemplary embodiment of the present invention.

6A and 6B are plan views illustrating liquid crystal alignment aspects of the wide viewing angle vertical alignment mode liquid crystal display device according to the present invention;

Explanation of symbols on the main parts of the drawings

GL: Gate Line DL: Data Line

TFT: thin film transistor 52: pixel electrode

53, 53a, 53b: spacer 54: aligning agent

54a: horizontal alignment agent 54b: vertical alignment agent

LC: Liquid Crystal

The present invention relates to a vertical alignment mode liquid crystal display device, and more particularly, to a vertical alignment mode liquid crystal display device having a wide viewing angle.

As is well known, a vertical alignment (VA) mode liquid crystal display is proposed to improve the low viewing angle and response speed characteristics of a twist nematic liquid crystal display which is a horizontal alignment mode. It became. Although not shown, the VA mode liquid crystal display device includes a liquid crystal layer composed of liquid crystals having negative dielectric anisotropy between upper and lower substrates provided with liquid crystal driving electrodes, with spacers for maintaining gaps, and facing surfaces of the upper and lower substrates. Each of them has a vertical alignment film, and each of the back surfaces of the upper and lower substrates has a structure in which a polarizing plate is attached so that polarization axes cross each other.

In the VA mode liquid crystal display, before the electric field is formed, the liquid crystal molecules are vertically arranged on the substrate under the influence of the vertical alignment layer, and in this case, a dark screen is realized in relation to the vertical polarizers crossing vertically. . Subsequently, when an electric field is formed between the liquid crystal driving electrodes of the upper and lower substrates, the liquid crystal molecules are twisted so that their major axis is perpendicular to the electric field direction, and thus light is leaked through the misaligned liquid crystal molecules, thereby producing a white screen. Implement

However, in the VA mode liquid crystal display device, the screens are different from each other depending on the viewing angle because the liquid crystal has refractive index anisotropy. For example, when an electric field is applied to the liquid crystal, when the liquid crystal molecules lie only in a specific direction, the phase difference of the liquid crystal varies depending on the viewing position, thereby causing problems such as a viewing angle deterioration and color shift. Therefore, there is a need for a technique for controlling the direction in which the liquid crystal molecules lie in various directions to form a multidomain, thereby compensating for the change in the phase difference according to the viewing direction.

Therefore, as a technique for solving the structural disadvantages of the typical VA mode, MVA (Multidomain Vertical Align) mode using projection (Fujitsu; US Pat. No. 6,288,762) and PVA (Patterned Vertical Align) mode using slits (Samsung) and ASV (Advanced Super View) mode (Sharp) have been proposed.

The MVA, PVA, and ASV have a structure in which the liquid crystal is oriented in four directions by distorting the electric field, thereby improving the viewing angle of the VA mode liquid crystal display. Hereinafter, an MVA mode liquid crystal display and a PVA mode liquid crystal display will be described in more detail with reference to FIGS. 1 and 2.

As shown in FIG. 1, the MVA mode liquid crystal display using the protrusions has a structure in which protrusions 13 are formed on each of the lower substrate 11 and the upper substrate 12. When the electric field is formed, the protrusions 13 Distortion of the electric field occurs in the vicinity of (), the liquid crystals LC are oriented in a direction symmetrical with each other, so that a multi domain of the liquid crystal is formed to compensate for the deterioration in image quality due to the refractive anisotropy of the liquid crystal.

Meanwhile, in the PVA mode liquid crystal display using the slit, as shown in FIG. 2, the liquid crystal driving electrodes of the upper substrate 21 and the lower substrates 21 and 22, that is, the pixel electrode 23 and the counter electrode. Each of the structures 24 is provided with a slit S, and the driving principle of the PVA mode liquid crystal display device is the same as that of the MVA mode liquid crystal display device shown in FIG.

However, the MVA mode liquid crystal display device and the PVA mode liquid crystal display device have an advantage in that the image quality can be prevented through distortion of the electric field, but a separate mask process and an etching process must be performed to form protrusions and slit structures. , Undesirable in terms of manufacturing process and cost.

In addition, although not shown, the ASV mode liquid crystal display device implements a multi-domain by varying the liquid crystal alignment direction by using projections similar to the MVA mode liquid crystal display device, which is also a process similar to the MVA and PVA mode liquid crystal display devices. The disadvantage is that the number is increased.

Accordingly, the present invention has been made to solve the above-described conventional problems, and improves the viewing angle of the vertical alignment mode liquid crystal display without the problem of increasing the number of processes by controlling the alignment direction of the liquid crystal by a new means instead of protrusions and slits. It is an object of the present invention to provide a wide viewing angle vertical alignment mode liquid crystal display device.

In order to achieve the above object, the present invention, the lower substrate and the upper substrate spaced apart from each other; Gate lines and data lines arranged vertically on the inner side of the lower substrate so as to partition sub-pixel regions; A thin film transistor formed at an intersection of the gate line and the data line; A pixel electrode formed in the subpixel area to be connected to the thin film transistor and divided into a plurality of unit areas connected to each other; A spacer disposed on the center portion of each unit region of the pixel electrode to maintain a gap with an upper substrate, and having an alignment agent coated on a surface thereof; A liquid crystal layer interposed in a region between the lower substrate and the upper substrate and having negative dielectric anisotropy; A counter electrode formed on an inner surface of the upper substrate; A vertical alignment layer interposed between the counter electrode and the liquid crystal layer and between the pixel electrode and the liquid crystal layer; And a polarizing plate attached to each of the outer side surfaces of the lower substrate and the upper substrate, wherein the spacer coated with the alignment agent serves to widen the viewing angle by deflecting the alignment direction of the liquid crystal. Provide a display device.

Here, the alignment agent is a horizontal alignment agent or a vertical alignment agent.

The spacer coated with the alignment agent on the surface is formed to be disposed on the central portion of each unit region of the pixel electrode by an inkjet printing technique.

Chiral dopant is added to the liquid crystal layer.

The chiral dopant is added such that a pitch corresponding to one rotation distance of the liquid crystal is 16 to 100 µm.

(Example)

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

First, the technical principle of the present invention will be briefly described as follows.

In the present invention, a spacer coated with an alignment agent is used in place of a conventional protrusion or slit as a means for causing distortion of an electric field. That is, the present invention implements a vertical alignment mode liquid crystal display having a wide viewing angle by forming a multi-domain by varying the alignment direction of the liquid crystal using only the spacer coated with the alignment agent.

In the liquid crystal display device, the spacer is interposed between the lower substrate and the upper substrate together with the liquid crystal to maintain a gap between the lower substrate and the upper substrate, that is, a cell gap. The cell gap is closely related to the characteristics such as the response speed, contrast ratio, viewing angle, brightness uniformity, etc. of the liquid crystal display device, so that the cell gap is maintained uniformly. However, in the present invention, the alignment direction of the liquid crystal is controlled by coating a horizontal or vertical alignment agent on the surface of the spacer and placing the spacer coated with the horizontal or vertical alignment agent on the central portion of each unit region of the pixel electrode.

That is, the present invention implements a vertically aligned liquid crystal display having a wide viewing angle by forming a multi-domain by using a spacer for maintaining a cell gap as a liquid crystal tilting means.

To this end, in the present invention, a spacer coated with a silane coupling agent including an alkyl group of a polymer, that is, a spacer coated with an alignment agent is formed at a specific position of the pixel electrode by an inkjet printing technique.

3A and 3B are plan views illustrating a liquid crystal alignment pattern around a spacer coated with a silane coupling agent including an alkyl group of a polymer and surroundings thereof, and FIG. 3A is a coating of a silane coupling agent exhibiting horizontal alignment characteristics. 3B is a case where a silane coupling agent exhibiting vertical alignment characteristics is coated. As shown, in the case of the spacer 30a coated with the horizontal alignment agent 31a, the liquid crystal LC is arranged in parallel with the surface of the spacer 30a, and the spacer 30b coated with the vertical alignment agent 31b. ), The liquid crystal LC is arranged perpendicular to the surface of the spacer 30b.

On the other hand, Figure 4 is a schematic diagram showing a spacer forming method using the inkjet printing method of the present invention, referring to this, in the present invention, after mixing the spacer 30 coated with the alignment agent 31 in the ink 32, Ink 32 including the spacer 30 is formed at a specific position of the pixel electrode 34 using an inkjet printer. Since the ejected ink 32 is volatilized and removed, only the spacer 30 coated with the alignment agent 31 remains on the pixel electrode 34. Here, as the inkjet printer, both a bubble jet or a piezoelectric printer may be used. Unexplained reference numeral 33 denotes a lower substrate, and 35 denotes an inkjet nozzle.

Hereinafter, the wide viewing angle vertical alignment mode liquid crystal display device of the present invention will be described with reference to FIG. 5.

5 is a plan view illustrating a wide viewing angle vertical alignment mode liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 5, each of the wide-view vertical alignment mode liquid crystal displays using the spacers coated with the horizontal alignment agent of the present invention includes a lower substrate and an upper substrate (not shown) spaced apart from each other, and the inside of the lower substrate. A gate line GL and a data line DL vertically arranged to partition the subpixel area on the side surface, and a thin film transistor TFT formed at an intersection of the gate line GL and the data line DL; And a pixel electrode 52 formed in the subpixel area so as to be connected to a thin film transistor TFT, and divided into a plurality of unit areas connected to each other, and disposed at the center of each unit area of the pixel electrode 52, and having a surface. A liquid crystal layer having a negative dielectric anisotropy interposed in a region between the spacer 53 coated with the alignment agent 54 and a lower substrate other than the spacer 53 and an upper substrate (not shown). It includes.

In addition, although not shown, the wide viewing angle vertical alignment mode liquid crystal display device of the present invention includes a counter electrode formed on an inner surface of the upper substrate, interposed between the counter electrode and the liquid crystal layer, and between the pixel electrode and the liquid crystal layer. And a polarizing plate attached to each of the vertical alignment layer and outer surfaces of the lower substrate and the upper substrate.

Here, dividing the pixel electrode 52 into a plurality of unit regions connected to each other allows an electric field (fringe field) to be formed at each edge of each unit region so that the movement of liquid crystal molecules is more easily performed by the electric field. To control.

In the wide viewing angle vertical alignment mode liquid crystal display of the present invention having such a structure, the spacer 53 coated with the alignment agent 54 is formed at the center of each unit region of the pixel electrode 52 by the inkjet printing technique described above. It is formed to function to widen the viewing angle by deflecting the liquid crystal alignment direction.

6A and 6B are plan views illustrating alignment patterns of liquid crystals in a unit region of a pixel electrode according to types of alignment agents coated on a spacer, and FIG. 6A illustrates a spacer 53a coated with a horizontal alignment agent 54a. 6B illustrates a case in which the spacer 53a coated with the vertical alignment agent 54b is used.

Referring to FIG. 6A, when the spacer 53a coated with the horizontal alignment agent 54a is used, when an electric field is applied between the pixel electrode 52 and the counter electrode (not shown), the liquid crystal LC is in a state of lying down. It is arranged in the form of a pinwheel rotating in the right or left direction about 53a. As described above, when the spacer 53a coated with the horizontal alignment agent 54a is used in the present invention, the liquid crystal LC is in the form of a pinwheel, that is, the alignment direction continuously in a predetermined direction in one unit region. This slightly different form has a wider viewing angle characteristic than the prior art having a four domain structure.

In this case, a chiral dopant may be further included in the liquid crystal layer to determine the rotation direction of the spacer 53a in a specific direction (right or left), and the chiral dopant may be disposed at one rotation distance of the liquid crystal. It adds so that the applicable pitch may be 16-100 micrometers.

Meanwhile, referring to FIG. 6B, when the spacer 53b coated with the vertical alignment agent 54b is used, the liquid crystal LC is in a lying state when an electric field is applied between the pixel electrode 52 and the counter electrode (not shown). In this case, the liquid crystal LC has a 4-domain structure in one unit region, which is arranged perpendicular to the surface of the spacer 53b. In this case, the viewing angle is somewhat narrower than when the horizontal alignment agent 54a is coated, but there is an advantage that the chiral dopant does not need to be used.

As described above, the present invention uses a spacer coated with an alignment agent as a deflecting means of liquid crystal for widening the viewing angle of the vertical alignment mode LCD.

Therefore, in the present invention, an additional mask process and an etching process for forming protrusions and slits are not required, and thus, the manufacturing process is simpler than the conventional MVA, PVA, and ASV modes.

In addition, since the liquid crystal can be aligned in the form of a pinwheel by using a spacer coated with a horizontal alignment agent, the viewing angle can be wider than that of a conventional four-domain structure. Can be implemented.

As mentioned above, although the present invention has been illustrated and described with reference to specific embodiments, the present invention is not limited thereto, and the scope of the following claims is not limited to the scope of the present invention. It can be easily understood by those skilled in the art that can be modified and modified.

As described above, the present invention provides a wider viewing angle in a simpler process by using a spacer coated with an alignment agent instead of conventional protrusions and slits as a deflection means for liquid crystals to widen the viewing angle of the vertical alignment mode liquid crystal display device. The vertical alignment mode liquid crystal display device may be implemented.

In addition, the present invention can align the liquid crystal in the form of a continuous pinwheel (pinwheel) when using a spacer coated with a horizontal alignment agent, it is possible to widen the viewing angle than the conventional four-domain structure, excellent wide viewing angle characteristics A liquid crystal display device can be implemented.

Claims (5)

A lower substrate and an upper substrate spaced apart from each other; Gate lines and data lines arranged vertically on the inner side of the lower substrate so as to partition sub-pixel regions; A thin film transistor formed at an intersection of the gate line and the data line; A pixel electrode formed in the subpixel area to be connected to the thin film transistor and divided into a plurality of unit areas connected to each other; A spacer disposed on the center portion of each unit region of the pixel electrode to maintain a gap with an upper substrate, and having an alignment agent coated on a surface thereof; A liquid crystal layer interposed in a region between the lower substrate and the upper substrate and having negative dielectric anisotropy; A counter electrode formed on an inner surface of the upper substrate; A vertical alignment layer interposed between the counter electrode and the liquid crystal layer and between the pixel electrode and the liquid crystal layer; And And a polarizing plate attached to each of the outer side surfaces of the lower substrate and the upper substrate. The liquid crystal display of claim 1, wherein the alignment agent is a horizontal alignment agent or a vertical alignment agent. The liquid crystal display of claim 1, wherein the spacer coated with the alignment agent on the surface is formed to be disposed at the center of each unit region of the pixel electrode by an inkjet printing technique. The liquid crystal display of claim 1, wherein the liquid crystal layer is a chiral dopant. The liquid crystal display of claim 4, wherein the chiral dopant is added such that a pitch corresponding to one rotation distance of the liquid crystal is 16 to 100 µm.

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