1. Field of the Invention
The present invention relates generally to a liquid crystal display and, more particularly, to driving the sub-pixels in the liquid crystal display.
2. Description of the Prior Art
As known in the art, a color liquid crystal display (LCD) panel 1 has a two-dimensional array of pixels 10, as shown in
In a transflective liquid crystal display panel, as shown in
As known in the art, there are many more layers in each pixel for controlling the optical behavior of the liquid crystal layer. These layers may include one or more passivation layers disposed on the lower substrate. Various components such as storage capacitors are also disposed on the lower substrate. As it is known in the art, an LCD panel also has quarter-wave plates and polarizers. Moreover, the device layer 70 may contain a number of metal lines or areas used as gate lines, data lines, capacitors and so forth. These metal lines and areas are covered with one or more dielectric layers. The lower electrodes are usually deposited on top of the dielectric layers.
In order to achieve a liquid crystal layer of a certain thickness, spacers are generally used to control the gap between the lower and upper substrates. If the spacers are not located properly in the liquid crystal display panel, line defects may occur.
It is desirable and advantageous to provide a method for disposing the spacers in a liquid crystal display panel so as to improve the viewing quality of the display.
The present invention uses a plurality of spacers to control the gap in a liquid crystal display panel. In particular, when a spacer is associated with an electrode in the lower substrate, it is located substantially at the center of the electrode. The lower substrate is where the TFTs, gate lines and data lines are disposed. In a transflective LCD sub-pixel, a spacer may be disposed at the center of one of the transmissive and reflective electrodes. Alternatively, a spacer is disposed at the center of each of the transmissive and reflective electrodes. When the electrode in a sub-pixel comprises different sections to affect the alignment of the liquid crystal layer associated with the electrode, the spacer is located at the intersection of the sections, if possible, so that the spacer is located at the intersections of different domains of the liquid crystal layer. Those intersections are defined as the centers of domain symmetry. As such, line defects, known as disclination, arising from singularities in the orientation order in a director field associated with the liquid crystal layer can be minimized or eliminated.
Thus, the first aspect of the present invention provides a liquid crystal display panel wherein a plurality of spacers are used to control the gap and the spacers are positioned substantially at one of the centers of domain symmetry in the sub-pixels. The second aspect of the present invention provides a method of placing and positioning the spacers in such a manner in a liquid crystal display panel.
The present invention will become apparent upon reading the description taken in conjunction with
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
a is a schematic representation of a sub-pixel in a transflective LCD, showing the preferred location of the spacer, according to one embodiment of the present invention.
b is a schematic representation of a sub-pixel in a transflective LCD, showing the location of the spacer, according to another embodiment of the present invention.
c is a schematic representation of a sub-pixel in a transflective LCD having two spacers, according to the present invention.
a is a schematic representation of a pixel with three color sub-pixels wherein one spacer is disposed in each color sub-pixel.
b is a schematic representation of a pixel with three color sub-pixels wherein a spacer is disposed in one of the sub-pixels.
c is a schematic representation of a pixel with three color sub-pixels wherein spacers are disposed in two of the sub-pixels.
a shows the preferred location of a spacer in a sub-pixel wherein the liquid crystal layer in the sub-pixel is aligned differently in four domains.
b shows the preferred location of a spacer in a sub-pixel wherein the liquid crystal layer in the sub-pixel is aligned differently in three domains.
c shows the preferred location of a spacer in a sub-pixel wherein the liquid crystal layer in the sub-pixel is aligned differently in two domains.
a is a cross sectional view of a sub-pixel in a transflective LCD, showing the preferred location of the spacer, according to one embodiment of the present invention.
b is a cross sectional view of a sub-pixel in a transflective LCD, showing the location of the spacer, according to another embodiment of the present invention.
Line defects, known as disclination, may occur in a liquid crystal display. These defects arise from singularities in the orientation order in a director field associated with the liquid crystal layer. The orientation order is associated with a domain in the liquid crystal layer in a pixel or sub-pixel. The location of a spacer in the pixel or sub-pixel may enhance the line defects. In particular, when the spacers are fabricated in a photo-lithographic or photo-etching process, the location of these photo-spacers may affect the alignment of the liquid crystal molecules around the photo-spacers. Certain misalignment produces disclination lines and affects the view quality of the LCD panel. For example, the disclination lines may give rise to a defect known as image retention.
The present invention provides a way of placing the photo-spacers in an LCD panel so that that the occurrence of disclination lines can be reduced or eliminated. It should be noted that, in an LCD panel having a 2-dimentional array of pixels, it may not be necessary that each of the pixels will have a spacer disposed therein. However, when a pixel has one or more spacers disposed therein, each spacer is located at a center of symmetry of the electrode associated with that spacer.
In a sub-pixel that has only one lower electrode to control the alignment of the liquid crystal layer in that sub-pixel, the spacer is located substantially at the center of the electrode. As shown in
In a sub-pixel having two lower electrodes to separately control the alignment of the liquid crystal layer in that sub-pixel, one or two spacers may be used.
In a pixel 10 with a plurality of color sub-pixels 12, as shown in
In a pixel or sub-pixel where a strip-like electrode is used to affect the alignment of the liquid crystal layer above the electrode, as shown in
It should be noted that, although only one strip-like electrode is used to control the liquid crystal layer in a sub-pixel or pixel, the spacer is not necessarily located at the center of electrode such as that shown in
When the liquid crystal layer in a sub-pixel or pixel has more than one joining domain, it is preferred that a spacer is placed at the center of symmetry of the domains. For example, in a sub-pixel having four domains D1, D2, D3 and D4 as shown in
In
Preferably, the spacer 90 is made of a photo-resist material and produced in a photo etching process. It is possible to dispose a black masking material in the color filter layer 42 above the spacer 90.
Thus, although the present invention has been described with respect to one or more embodiments thereof, it will be understood by those skilled in the art that the foregoing and various other changes, omissions and deviations in the form and detail thereof may be made without departing from the scope of this invention.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
This application is a continuation of U.S. application Ser. No. 11/453,189, filed on Jun. 13, 2006.
Number | Date | Country | |
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Parent | 11453189 | Jun 2006 | US |
Child | 12829393 | US |