Liquid crystal cells – elements and systems – Nominal manufacturing methods or post manufacturing... – Injecting liquid crystal
Reexamination Certificate
1998-02-20
2001-09-04
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Nominal manufacturing methods or post manufacturing...
Injecting liquid crystal
C349S073000, C349S153000, C349S176000
Reexamination Certificate
active
06285434
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention is directed, in general, to liquid crystal displays (“LCD”s) and, more specifically, to a cell wall structure for an LCD that allows for a multi-color, or multi-liquid crystal, display and a method of manufacture of the cell wall structure.
BACKGROUND OF THE INVENTION
The development of improved liquid crystal (“LC”) flat-panel displays is an area of very active research, driven in large part by the proliferation of and demand for portable electronic appliances, including computers and wireless telecommunications devices. Moreover, as the quality of LC displays improves, and the cost of manufacturing declines, it is projected that LC displays (“LCD”s) may eventually displace conventional display technologies, such as cathode-ray-tubes.
One aspect of LCDs, to which significant research has been directed in recent years, is the demand for such displays to provide full-color images. It is quite possible that LCDs capable of displaying full-color images, at full-motion video rates, will eventually displace conventional cathode-ray tubes in television and computer display applications. Several characteristics of conventional LCD materials and methods of manufacturing such displays, however, present barriers to an efficient method of manufacturing full-color displays.
LCDs are constructed by trapping a thin film of LC between two substrates of glass or transparent plastic. The conventional method of trapping the LC between the substrates is to first join the substrates and then introduce a LC into the interstitial region(s) formed therebetween. The substrates are usually manufactured with transparent electrodes, typically made of indium tin oxide (“ITO”), to which electrical “driving” signals are coupled. The driving signals induce an electric field which can cause a phase, or state, change in the LC material; the LC exhibits different electro-optical characteristics according to its phase and/or state.
One practical difficulty of manufacturing full-color displays, using conventional techniques, is controlling the wavelength maxima for each individual microscopic pixel (or sub-pixel). Conventional manufacturing techniques introduce a LC and a predetermined amount of twist agent, as a homogenous solution, into the region between the display substrates, which results in a LCD capable of displaying only one color, or black and white, that is dependent on the relative ratio of twist agent to LC, and/or the arrangement of polarizers. To realize a full-color display, a color filter having, for example, red, green and blue (“RGB”) regions (corresponding to individual sub-pixels) can be mated to the LCD; the use of a color filter, however, reduces the overall brightness, and contrast ratio, of the display.
Therefore, what is needed in the art is a LCD, and one or more methods of manufacture thereof, that is optimized for mass production and adaptable to allow multi-color LCDs to be produced without the need for a separate color filter.
SUMMARY OF THE INVENTION
To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to improve the manufacturability of multi-color liquid crystal displays (“LCD”s).
In the attainment of the above-described primary object, the present invention provides a substrate for a multi-color liquid crystal display (LCD), an LCD having the substrate, and methods of manufacturing the substrate and the LCD. In one embodiment, the substrate includes: (1) a substantially planar base and (2) a cell wall structure, located on a surface of the base, that defines at least first and second sets of independent cells having corresponding independent fluid fill ports when the cell wall structure is bonded to an opposing substrate.
The present invention therefore introduces a substrate having a cell wall structure that enhances manufacturability by isolating the fluid fill ports corresponding to each set of independent cells, whereby each set of independent cells can be selectively-filled with a liquid crystal having desired properties. By isolating the fluid fill ports, the likelihood that liquid crystal fill fluids for the sets of independent cells can be inadvertently mixed during manufacture is reduced substantially.
In one embodiment of the present invention, fluid fill ports corresponding to a first set of independent cells are on an opposite end of the substrate from fluid fill ports corresponding to a second set of independent cells. In an alternate embodiment, the fluid fill ports are all located along a common edge of the substrate, but are selectively sealed or unsealed to allow each set of independent cells to be filled separately from the other set(s) of independent cells.
In one embodiment of the present invention, the cell wall structure comprises recesses that form at least first and second sets of independent cells bounded by said cell wall structure and the first and second substrates, the first and second sets of independent cells having corresponding independent fluid fill ports adapted to be opened and filled independently; in an embodiment to be illustrated and described, three sets of independent cells are provided.
The sets of independent cells may be filled with LC fill fluids having different intrinsic wavelengths to yield a multi-color, or full-color, LCD; for example, LC fill fluids having intrinsic wavelengths corresponding to the colors red, green and blue may be independently introduced into the three sets of independent cells. As used herein, “intrinsic color” means the liquid crystal molecules have the characteristic of reflecting a certain wave band of incoming light with a center wavelength of &lgr;=np, where n is the average refractive index of the liquid crystal. The color tint depends on the relative concentration of the twisting, or chiral, liquid crystal material, which determines the pitch of the liquid crystal. “Extrinsic color,” as used herein, means that the liquid crystal itself cannot generate color, but an extrinsic material can be doped into the nematic liquid crystal solution as an additive, such as a dichroic dye or dichroic dye polymer mixture, or dichroic polymer dispersed liquid crystal (PDLC); the color tint depends on the different dye molecules. A full color display can also be achieved by filling different extrinsic colors into different columns of the liquid crystal cells.
In one embodiment of the present invention, the independent cells are parallel to one another. In a related embodiment, the independent cells form columns of the LCD; alternatively, the independent cells may form rows of the LCD or other desirable configurations.
In one embodiment of the present invention, the substrate further comprises an opposing substrate mated to the cell wall structure, the fluid fill ports adapted to receive a seal to selectively trap liquid crystal fill fluids within the independent cells. In an embodiment to be illustrated and described, seals are formed after an appropriate LC fill fluid is introduced into the independent cells. In alternate embodiments, seals may be broken to allow a set of independent cells to be filled with an LC fill fluid; subsequent to filling, the set of independent cells may be resealed.
In one embodiment of the present invention, an LCD employing the substrate comprises fill fluids having different intrinsic, or extrinsic, wavelengths, located in different sets of independent cells, to form a multicolor LCD.
In one embodiment of the present invention, the cell wall structure consists of a single serpentine wall; the cell wall structure may alternatively be formed of multiple independent and/or interleaved walls.
In one embodiment of the present invention, the cells are sufficiently narrow to be filled by means of capillary action; a vacuum may be employed to enhance capillary action. Those skilled in the art are familiar with various conventional techniques for introducing fill fluid into the cells of an LCD.
The foregoing has outlined rather broadly the features and technical advantages of t
Gao Jianmi
Hou Jianan
Ma Yao Dong
Wang Yong-Jing
Wu Bao-Gang
Advanced Display Systems, Inc.
Chowdhury Tarifur R.
Jackson Walker L.L.P.
Sikes William L.
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