Multi-domain vertical alignment liquid crystal display panel

A multi-domain vertical alignment liquid crystal display panel comprising a first substrate, a second substrate, a liquid crystal layer and a plurality of phase-compensating protrusions is provided. The second substrate is configured above the first substrate. The liquid crystal layer is formed between first substrate and the second substrate. The phase-compensating domain regulating protrusions are formed on at least one of the first substrate and the second substrate. The phase-compensating domain regulating protrusions have a plurality of anisotropic birefringence molecules. The slow-axes of the anisotropic birefringence molecules are in a different direction from the slow-axes of the liquid crystal molecules near the phase-compensating protrusions. Therefore, the plurality of anisotropic birefringence molecules can compensate for the phase retardation here, thereby improving the light leakage in the dark state.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 93135546, filed on Nov. 19, 2004. All disclosure of the Taiwan application is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device. More particularly, the present invention relates to a multi-domain vertical alignment (MVA) liquid crystal display panel.

2. Description of the Related Art

With the concept of environmental protection on the rise in recent years, display devices having high picture quality, high spatial utilization, low power consumption and radiation-free operation are in great demand. Hence, thin film transistor liquid crystal displays (TFT LCD), which have all the aforementioned advantages, have become one of the mainstream products in the market.

At present, some of the additional features for a liquid crystal display include high contrast ratio, no gray scale inversion, little color shift, high luminance, rich colors, high color saturation level, rapid response and wide viewing angle. Currently, the displays capable of meeting the demand for a wide viewing angle include a twisted nematic (TN) liquid crystal display added with a wide viewing film, an in-plane switching (IPS) liquid crystal display, a fringe field switching liquid crystal display and a multi-domain vertical alignment (MVA) liquid crystal display. Here, a conventional multi-domain vertical alignment liquid crystal display is used as an illustration.

FIG. 1is a schematic cross-sectional view of a conventional multi-domain vertical alignment (MVA) liquid crystal display panel. As shown inFIG. 1, the MVA liquid crystal display panel mainly comprises a color filter substrate102, a thin film transistor array substrate100, a liquid crystal layer104and a domain regulating protrusion106. The domain regulating protrusion106activates the liquid crystal molecules105to align in multiple directions. The domain regulating protrusion106can be disposed on the color filter substrate102or the thin film transistor array100or disposed on both.

In the conventional multi-domain vertical alignment (MVA) liquid crystal display, the slow-axes direction (the long axes direction of the liquid crystal molecules105) of the liquid crystal molecules105are perpendicular to the thin film transistor array substrate100and the color filter substrate102when the display screen is in a dark state as shown inFIG. 1. Furthermore, in the presence of a polarizing plates (not shown), the picture on the display can have an optimal dark state to produce high contrast effect. However, the liquid crystal molecules105near the domain regulating protrusion106are in a tilted state corresponding to the surface contour of the domain regulating protrusion106. This often leads to light leakage in an area (the area108inFIG. 1) close to the domain regulating protrusion106and results in a drop of contrast in the display panel.

SUMMARY OF THE INVENTION

Accordingly, at least one objective of the present invention is to provide a multi-domain vertical alignment liquid crystal display panel capable of reducing light leakage in a dark state and improving contrast on a display panel.

To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a multi-domain vertical alignment (MVA) liquid crystal display panel. The MVA liquid crystal display panel mainly comprises a first substrate, a second substrate, a liquid crystal layer and a plurality of phase-compensating domain regulating protrusions. The second substrate is configured above the first substrate. The liquid crystal layer is disposed between the first substrate and the second substrate. The liquid crystal layer comprises a plurality of liquid crystal molecules. Each phase-compensating domain regulating protrusion comprises a plurality of anisotropic birefringence molecules. The phase-compensation domain regulating protrusions are disposed on at least one of the first substrate and the second substrate.

In one embodiment of the present invention, the slow-axes direction of the liquid crystal molecules near the phase-compensating domain regulating protrusions are different from the corresponding slow-axes direction of the anisotropic birefringence molecules. In one embodiment, the slow-axes of the liquid crystal molecules near the phase-compensating domain regulating protrusions are substantially perpendicular to the slow-axes of the anisotropic birefringence molecules.

The present invention also provides an alternative multi-domain vertical alignment (MVA) liquid crystal display panel. The MVA liquid crystal display panel mainly comprises a first substrate, a second substrate, a liquid crystal layer, a plurality of domain regulating protrusions and a phase-compensating film. The second substrate is configured above the first substrate. The liquid crystal layer is disposed between the first substrate and the second substrate. The liquid crystal layer comprises a plurality of liquid crystal molecules. The domain regulating protrusions are disposed on at least one of the first substrate and the second substrate. The phase-compensating film is disposed on each domain regulating protrusion. The phase-compensating film comprises a plurality of anisotropic birefringence molecules.

In one embodiment of the present invention, the slow-axes direction of the liquid crystal molecules near the domain regulating protrusions are different from the corresponding slow-axes direction of the anisotropic birefringence molecules in the phase-compensating film on the domain regulating protrusions. In one embodiment, the slow-axes of the liquid crystal molecules near the domain regulating protrusions are substantially perpendicular to the slow-axes of the anisotropic birefringence molecules in the phase-compensating film on the domain regulating protrusions.

According to the embodiment of the present invention, the first substrate is a thin film transistor array substrate and the second substrate is a color filter array substrate, for example. In another embodiment, the first substrate is a color filter on array (COA) substrate and the second substrate comprises a substrate and a common electrode thereon, for example.

According to the embodiment of the present invention, the phase-compensating domain regulating protrusions and the phase-compensating film are fabricated using a high polymer, preferably mesogen.

According to the embodiment of the present invention, the phase-compensating protrusions and the phase-compensating film are fabricated using cylindrical anisotropic birefringence molecules. The slow-axes of these cylindrical anisotropic birefringence molecules are parallel to the extending direction of the domain regulating protrusions.

According to the embodiment of the present invention, the phase-compensating domain regulating protrusion and the phase-compensating film are fabricated using disc-shaped anisotropic birefringence molecules, for example. In the present embodiment, the slow-axes of a portion of the anisotropic birefringence molecules on the surface of the protrusions are parallel to the surface of the corresponding protrusions.

In the present invention, an anisotropic material film with birefringence property is disposed on the domain regulating protrusions of a conventional multi-domain vertical alignment (MVA) liquid crystal display panel or an anisotropic material with birefringence property is directly used to fabricate the domain regulating protrusions. Furthermore, the slow-axes of the material are set in a direction different from the slow-axes of the liquid crystal molecules near the material so that the domain regulating protrusions can perform optical compensation on the liquid crystal molecules close to the domain regulating protrusions to reduce light leakage. Ultimately, the contrast of the picture displayed on the MVA liquid crystal display panel is increased.

DESCRIPTION OF THE EMBODIMENTS

The present invention mainly utilizes a material having an anisotropic birefringence property to provide optical compensation of liquid crystal molecules near the domain regulating protrusions, thereby reducing the phase retardation after the passage of light through the liquid crystal molecules so that light leakage in a display panel can be minimized. In the following, embodiments are used to describe various aspects of the invention. However, they should by no means limit the scope of the present invention as such because anyone familiar with the art could easily modify any one of the following embodiments within the spirit of the present invention.

FIG. 2is a schematic cross-sectional view of a single pixel structure of a multi-domain vertical alignment (MVA) liquid crystal display panel according to one embodiment of the present invention.FIG. 3is a top view of the first substrate220inFIG. 2. As shown inFIGS. 2 and 3, the multi-domain vertical alignment (MVA) liquid crystal display panel200mainly comprises a first substrate220, a second substrate210, a liquid crystal layer230and a plurality of phase-compensating domain regulating protrusions240(only one is shown inFIG. 2). The first substrate220is a thin film transistor array substrate comprising a plurality of scan lines222, a plurality of data lines224, a plurality of thin film transistors226and a plurality of pixel electrodes228, for example. As shown inFIG. 3, the areas enclosed by the scan lines222and the data lines224on the substrate221are the pixel areas227. The thin film transistors226are disposed in the pixel areas227, and are driven by the signals transmitted from a corresponding scan lines222and data lines224. The pixel electrodes228are disposed within the respective pixel areas227and electrically connected to corresponding thin film transistors226.

The second substrate210is configured above the first substrate220. The second substrate210is a color filter array substrate comprising a substrate material216, a plurality of color-filtering films212(only one color-filtering film212is shown inFIG. 2) and a common electrode214covering the color-filtering film212. Furthermore, each color-filtering film212corresponds to a pixel electrode228on the first substrate220. The liquid crystal layer230is disposed between the first substrate220and the second substrate210and comprises a plurality of liquid crystal molecules232.

It should be noted that the first substrate220could be a color filter on array (COA) substrate in another embodiment of the present invention. In other words, the first substrate220is a substrate comprising a color-filtering film212and a thin film transistor array. In addition, the second substrate210is a substrate comprising a substrate material216and a common electrode214thereon as shown inFIG. 4, for example. In other words, the location of the color-filtering film212in the MVA liquid crystal display panel is not restricted in the present invention.

The phase-compensating domain regulating protrusions240comprise a plurality of anisotropic birefringence molecules242, for example. The anisotropic birefringence molecules242are high polymers, preferably mesogen. In the present embodiment, the phase-compensating domain regulating protrusions240are disposed on the second substrate210, for example.

In addition, the phase-compensating domain regulating protrusions240can be in the shape of linear stripes disposed on the second substrate210. Moreover, the linear phase-compensating domain regulating protrusions240can have a curved surface or a surface comprising two slant surfaces. In other words, the phase-compensating domain regulating protrusions240can have a triangular (as shown inFIG. 5), a semi-circular or a semi-elliptical cross-sectional profile.

FIG. 5is a transparent perspective view of a phase-compensating domain regulating protrusion240inFIG. 4. Using a triangular phase-compensating domain regulating protrusion as shown inFIG. 5as an example, the phase-compensating domain regulating protrusion240has a surface comprising a first slant surface244and a second slant surface246. The second slant surface246is connected to the first slant surface244. Furthermore, the second slant surface246has a slant direction different from the first slant surface244. In particular, the anisotropic birefringence molecules242inside the phase-compensating domain regulating protrusions240have a cylindrical shape. Moreover, the slow-axes of the anisotropic birefringence molecules242are parallel to the extending direction of the linear phase-compensating domain regulating protrusions240as shown inFIG. 5, for example.

In finer detail, the extending direction of the phase-compensating domain regulating protrusions240is parallel to the x-axis as shown inFIG. 2. Therefore, the slow-axes of the anisotropic birefringence molecules242are parallel to the x-axis and the slow-axes of the liquid crystal molecules232near the phase-compensating protrusions alignment240are parallel to the y-z plane. In other words, the slow-axes of the liquid crystal molecules232(the long axes of the liquid crystal molecules232) in the vicinity of the phase-compensating domain regulating protrusions240are in different direction from the slow-axes of the anisotropic birefringence molecules242. Preferably, they are perpendicular to each other. Hence, in the dark state, when the liquid crystal molecules232in the vicinity of the phase-compensating domain regulating protrusions240tilt in a particular direction to cause some retardation to the passing light, the anisotropic birefringence molecules242inside the phase-compensating domain regulating protrusions240can compensate (or offset) a portion of the phase retardation. Ultimately, light leakage in the dark state from the MVA liquid crystal display panel200will be significantly improved and the contrast of the display screen will be increased.

It should be noted that there is no particular restriction to the shape of the phase-compensating protrusions in the present invention. In other embodiments, the protrusions are in different shapes. In the following, a hemispherical phase-compensating protrusion is used as an example.

FIG. 6is a schematic cross-sectional view of a multi-domain vertical alignment (MVA) liquid crystal display panel according to another embodiment of the present invention. As shown inFIG. 6, the MVA liquid crystal display panel300has a structure similar to that of the aforementioned MVA liquid crystal display panel200in the aforementioned embodiment. Since the major difference is in the phase-compensating protrusions, detailed description of other components is not repeated herein.

In the present embodiment, the phase-compensating domain regulating protrusions340are of a hemispherical shape and the anisotropic birefringence molecules342inside the phase-compensating domain regulating protrusions340are of a disc shape.FIG. 7is a perspective view showing the structure of an anisotropic birefringence molecule342inside the phase-compensating domain regulating protrusion340inFIG. 6. It should be noted that the refractive index along the optical axes of the anisotropic birefringence molecules342are ne(the extraordinary refractive index), the refractive index perpendicular to the optical axes are no(the ordinary refractive index) and ne<no. In other words, the slow-axes of the disc-shape anisotropic birefringence molecules342are perpendicular to its optical axes.

As shown inFIG. 6, the slow-axes of the anisotropic birefringence molecules342on the surface of the phase-compensating protrusions340are parallel to the surface of the corresponding phase-compensating domain regulating protrusions340. Hence, in the dark state, a portion of the phase retardation due to the passage of light through the liquid crystal molecules232in the vicinity of the phase-compensating domain regulating protrusions340will be offset by the anisotropic birefringence molecules342. In other words, the phase-compensating protrusions340constructed using anisotropic birefringence molecules342are quite effective in reducing the light leakage in the dark state and increasing the contrast in a display panel.

In addition, anyone familiar with the skill of fabricating a MVA liquid crystal display panel may notice that the phase-compensating domain regulating protrusions in the two aforementioned embodiments can be disposed on the second substrate210(as shown inFIGS. 2 and 6), or disposed on the first substrate220(on the pixel electrode228as shown inFIGS. 8 and 9), or simultaneously disposed on the second substrate210and the first substrate220(as shown inFIGS. 10 and 11). Furthermore, if phase-compensating domain regulating protrusions are disposed on the second substrate210and the first substrate220simultaneously, the shape of the phase-compensating domain regulating protrusions on the second substrate210and those on the first substrate220can be identical or can be different. In the present invention, the shape and location of the phase-compensating domain regulating protrusions are not limited. Yet, no matter the phase-compensating domain regulating protrusions are disposed on the first substrate220, the second substrate210or both, the phase-compensating domain regulating protrusions are generally disposed inside a corresponding pixel area. Thus, anyone familiar with the art may select suitable locations to dispose the phase-compensating domain regulating protrusions according to the actual manufacturing process.

In another embodiment of the present invention, a layer of phase-compensating film can be disposed over a conventional MVA liquid crystal display panel to achieve an effect identical to the aforementioned embodiments. In the following, embodiments are given in detail.

FIG. 12is a schematic cross-sectional view of multi-domain vertical alignment (MVA) liquid crystal display panel according to yet another embodiment of the present invention. It should be noted that the main difference between the MVA liquid crystal display panel400inFIG. 12and the MVA liquid crystal display panel200inFIG. 2is in the domain regulating protrusions. Hence, in the following, detailed description of other components of the MVA liquid crystal display panel400is omitted.

As shown inFIG. 12, the MVA liquid crystal display panel400mainly comprises a second substrate210, a first substrate220, a liquid crystal layer230, a domain regulating protrusion440and a phase-compensating film441. The second substrate210is configured above the first substrate220. The liquid crystal layer230is disposed between the first substrate220and the second substrate210. The liquid crystal layer230comprises a plurality of liquid crystal molecules232. It should be noted that the domain regulating protrusions440could be disposed on the second substrate210, the first substrate220or on the second substrate210and the first substrate220simultaneously. InFIG. 12, the domain regulating protrusion440disposed on the second substrate210is described in the following as an example.

The phase-compensating film441is disposed on the domain regulating protrusion440. The phase-compensating film441is fabricated using a high polymer, preferably mesogen. The phase-compensating film441comprises a plurality of anisotropic birefringence molecules424. In the present embodiment, the domain regulating protrusion440is a linear stripe of protruding material having a first slant surface444and a second slant surface446, for example. Furthermore, the phase-compensating film441is disposed on the first slant surface444and the second slant surface446of the domain regulating protrusion440. Similar to the aforementioned embodiments, the domain regulating protrusions440in the present embodiment can be linear protrusions having a curved surface. In addition, the anisotropic birefringence molecules424constituting the phase-compensating film441can be cylindrical anisotropic birefringence molecules as shown inFIG. 5. In other words, the slow-axes of the anisotropic birefringence molecules424in the present embodiment are parallel to the x-axis direction so that a portion of the phase retardation of light passing near the domain regulating protrusion440is compensated and the amount of light leakage in this area is improved.

As shown inFIG. 13, according to another embodiment, the phase-compensating film541can be disposed on the hemispherical domain regulating protrusion540. In the present embodiment, the anisotropic birefringence molecules542within the phase-compensating film541are disc-shaped anisotropic birefringence molecules shown inFIG. 7. In other words, the slow-axes of the anisotropic birefringence molecules542are parallel to the corresponding surface544of the domain regulating protrusion540so that the phase retardation of light passing in the vicinity of the domain regulating protrusion540can be compensated. Similarly, the domain regulating protrusion540covered with the phase-compensating film541can be disposed on the first substrate220or simultaneously disposed on the first substrate220and the second substrate210. Since anyone skilled in the art can easily reproduce the aforementioned structures, additional drawings and explanations for the structures are omitted.

In summary, the present invention provides an anisotropic material film with birefringence property disposed on the domain regulating protrusions of a conventional multi-domain vertical alignment (MVA) liquid crystal display panel, or an anisotropic material with birefringence property is directly used to fabricate the domain regulating protrusions. Furthermore, the slow-axes of the anisotropic birefringence molecules are set in a direction different from the slow-axes of the liquid crystal molecules near the anisotropic birefringence material so that the domain regulating protrusions can perform optical compensation on the liquid crystal molecules and reduce the light leakage therein. Ultimately, the contrast of the picture displayed on the MVA liquid crystal display panel is enhanced.