1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a multi-domain vertical alignment liquid crystal display device.
2. Description of Related Art
A conventional liquid crystal display device generally has polarizers 1, 2 to enhance the contrast ratio of a displayed image, in addition to a top substrate 10 and a bottom substrate 20 both of which sandwich liquid crystals 7 (as shown in
However, when such a conventional construction is applied to a multi-domain vertical alignment liquid crystal display device, as shown in
The present invention provides a multi-domain vertical alignment liquid crystal display device so as to reduce light-leaking generated in the vicinity of protrusions of pixel electrodes and improve the image quality of the liquid crystal display devices.
A multi-domain vertical alignment liquid crystal display device according to the present invention comprises a first polarizer having a polarizer axis; a second polarizer having a polarizer axis which intersects the polarizer axis of the first polarizer; a first substrate having a plurality of protrusions disposed on a surface of the first substrate with an angle ranging from 0 to 10 degrees or from 80 to 90 degrees with respect to the polarizer axis of the first substrate and the polarizer axis of the second substrate; a second substrate interposed between the first polarizer and the second polarizer, having a plurality of pixel electrodes disposed on a surface of the second substrate; and a liquid crystal layer interposed between the first substrate and the second substrate. Also, the protrusions of the first substrate are disposed between the first substrate and the second substrate.
The surfaces of the pixel electrodes of the liquid crystal display device according to the present invention may selectively further comprise a plurality of slits to improve the uniformity of brightness. The slits are disposed on the edge of the pixel electrodes and extend in a direction to intersect the projections of the protrusions on the second substrate. The intersection angle between the extension from the slits and the projections of the protrusions is not specifically defined to be different from a known angle. Preferably, the angle between the extension from the slits and the projections of the protrusions is in the range of 80 degrees and 110 degrees. The length distribution of the slits is not specifically defined. Preferably, at least two of the slits are different in length, and more preferably, the length of the slits is arranged to be gradually decreased or increased from both ends of the same edge of the pixel electrodes toward the middle of the pixel electrodes. The width distribution of the space or the interval between the slits is not specifically defined. Preferably, the slits have at least two different spaces, and more preferably, the width of the intervals between the slits is arranged to be gradually decreased or increased from both ends of the same edge of the pixel electrodes toward the middle of the pixel electrodes. The intersection angle between the polarizer axis of the second polarizer and the polarizer axis of the first polarizer is not specifically defined to be different from a known angle. Preferably, the polarizer axis of the second polarizer is perpendicular to the polarizer axis of the first polarizer. The angle between the protrusions and the polarizer axis of the first polarizer and the polarizer axis of the second polarizer according to the present invention is not specifically defined to be different from a known angle in the range of 0 degree and 10 degrees or 80 degrees and 90 degrees. Preferably, they are perpendicular to or parallel with each other. The first substrate and the second substrate according to the present invention can be conventional transparent substrate, preferably, glass substrates. The pixel electrodes of the present invention can be a conventional transparent electrode, preferably an indium tin oxide (ITO) or an indium zinc oxide (IZO). The shape of the protrusions distributed on the first substrate is not specifically defined, preferably zigzag. The liquid crystals suitable for the present invention are not specifically defined. Preferably, the liquid crystal molecules are those having negative dielectric anisotropy.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
a is a side view of a conventional multi-domain vertical alignment liquid crystal display device.
b is a top view of a conventional multi-domain vertical alignment liquid crystal display device.
a is a side view of a preferred embodiment of the present invention.
b is a top view of a preferred embodiment of the present invention.
a is a top view of a preferred embodiment of the present invention in a black state.
b is a top view of a preferred embodiment of the present invention in a bright state.
At first, reference is made to both
In the present embodiment, multiple protrusions are formed or laid on the top substrate 10 for directing the longitudinal axis direction 71 of the liquid crystal molecules to tilt toward the protrusions 3 by utilizing the change of the space. Generally, the longitudinal axis direction 71 of the liquid crystal molecules is perpendicular to the protrusion 3 as viewed from the top. In the present embodiment, the protrusions 3 are shaped as zigzag. The projections of the zigzag protrusions 3 on the surface of the bottom substrate 20 are parallel with or perpendicular to the polarizer axis 11 of the first polarizer 1 or the polarizer axis 22 of the second polarizer 2. With such an arrangement of the protrusions 3, the longitudinal axis direction 71 of the liquid crystal molecules is perpendicular to the protrusions 3. Thus, the longitudinal axis direction 71 of the liquid crystal molecules is parallel with or perpendicular to the polarizer axis 11 of the first polarizer 1 or the polarizer axis 22 of the second polarizer 2. In other words, the longitudinal axis direction 71 of the liquid crystal molecules and the transmission axis 31 of the first polarizer 1 or the transmission axis 32 of the second polarizer 2 form an angle of about 45 degrees. The light-leaking resulted from the interaction of the liquid crystal molecules 7 and the protrusions 3 can be greatly reduced through the arrangement of the present embodiment. Since the transmission axes 31, 32 are not parallel with the longitudinal axis direction 71 of the liquid crystal molecules in the present embodiment, the light-leaking between the liquid crystal molecules 7 and the protrusions 3 owing to the refraction of the liquid crystal molecules can be significantly reduced.
In the present embodiment, the bottom substrate (second substrate) 20 has a plurality of arrayed pixel electrodes 4. The pixel electrodes 4 are made of ITO in the present embodiment. The pixel electrodes 4 in the vicinity of the bottom substrate (second substrate) 20 are spaced apart, a plurality of slits 5 being formed on the edge of the pixel electrodes 4 spaced apart. In the present embodiment, the slits 5 extend in a direction having a 45-degree angle with respect to the polarizer axes 11, 22 of the polarizers. The slits are different in length.
The slits 5 are disposed on the edge of the pixel electrodes 4, extending in a direction having an intersection angle of about 45 degrees with respect to the projections of the protrusions 3 on the bottom substrate (second substrate) 20. Furthermore, the lengths (L) of the slits 5 are arranged to be gradually decreased or increased from both ends of the same edge of the pixel electrodes 4 to the middle of the pixel electrodes 4. When a voltage is applied to the liquid crystal display device, the negative liquid crystal molecules 7 in a grayscale generally tilt in various tilted angles since the lengths of the slits affect the electric field. In other words, the liquid crystal molecules 7 have various tilted angles in the vicinity of one of the protrusions 3 in a pixel electrode 4. Even so, the tilted angles of the liquid crystal molecules 7 are distributed in a regular manner because the slits are distributed in a regular manner. It has been known that the transmissivity of the liquid crystal display relates to the total average refractive index caused by the tilted angle of the liquid crystal molecules 7. With the arrangement of the slits as disclosed in the present invention, the total average tilted angle of the liquid crystal molecules 7 in the vicinity of the protrusions 3 are about the same. Thus, the total average refractive index caused by the tilted angle of the liquid crystal molecules 7 is almost the same. Hence, the transmittance of the area neighboring to the protrusions 3 is almost the same, too. In this connection, the brightness distribution of the various pixel electrodes 4 in the liquid crystal display device can be improved, resulting in a uniform brightness of the liquid crystal display device. Through the arrangement of the device illustrated above, a stable average angle of the various angles between the sight line of a viewer and the longitudinal axis direction 71 of the liquid crystals in a grayscale can be obtained. When the liquid crystal display device is viewed from different angles, the angle between the sight line and the longitudinal axis direction 71 of the liquid crystals remains as the average value. Therefore, the angle between the sight line and the longitudinal axis direction 71 of the liquid crystals does not vary with a change of the viewing angle. Hence, the liquid crystal display device has a uniform brightness regardless of the viewing angle.
Reference is made to both
That is to say, non-uniform brightness caused by light-leaking of the liquid crystal molecules 7 can be improved by arranging the directions of the polarizer axes 11, 22 of the polarizers and the tilted angle of the protrusions 3. In addition, the difference between variant total average refractive indexes resulted from the tilted angles of the homogeneously arranged liquid crystal molecules around the two neighboring areas of the protrusions 3 can be improved. Therefore, the light-leakage and the brightness distribution of conventional multi-domain vertical alignment liquid crystal display devices can be effectively improved. Moreover, the contrast ratio of the displayed image of conventional multi-domain vertical alignment liquid crystal display devices can be increased, and the display quality thereof can be improved.
This embodiment has the same effects as the aforesaid embodiment. Non-uniform brightness caused by light-leakage of the liquid crystal molecules 7 can be improved by arranging the direction of the polarizer axes 11, 22 of the polarizers and the tilted angle of the protrusions 3. In addition, the difference between variant total average refractive indexes resulted from the tilted angles of the homogeneously arranged liquid crystal molecules around the two neighboring areas of the protrusions 3 can be improved. Therefore, the light-leakage and the brightness distribution of conventional multi-domain vertical alignment liquid crystal display devices can be effectively improved. Moreover, the contrast ratio of the displayed image of conventional multi-domain vertical alignment liquid crystal display devices can be increased, and the display quality thereof can be improved.
This embodiment has the same effects as the aforesaid embodiment. Non-uniform brightness caused by light-leaking of the liquid crystal molecules 7 can be ameliorated by arranging the direction of the polarizer axes 11, 22 of the polarizers and the tilted angle of the protrusions 3. In addition, the difference between variant total average refractive indexes resulted from the tilted angles of the homogeneously arranged liquid crystal molecules around the two neighboring areas of the protrusions 3 can be improved. Therefore, the light-leakage and the brightness distribution of conventional multi-domain vertical alignment liquid crystal display devices can be effectively improved. Moreover, the contrast ratio of the displayed image of conventional multi-domain vertical alignment liquid crystal display devices can be increased, and the display quality thereof can be improved.
Although the present invention has been explained in relation to its preferred embodiments, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.
Number | Date | Country | Kind |
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093132414 | Oct 2004 | TW | national |