Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-01-17
2002-12-10
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S143000
Reexamination Certificate
active
06493049
ABSTRACT:
The disclosures of the Japanese Applications Nos. 2000-008572, 2000-010963, 2000-175774 and 2000-387282, are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid-crystal display device making use of a polymer-dispersed liquid crystal.
2. Related Background Art
In liquid-crystal display devices which make use of polymer-dispersed liquid crystal to perform efficient action, usually the display is made utilizing two states that the liquid crystal is brought into a non-transparent state (made to stand non-transparent: light scattering state) by non-electrification and is brought into a transparent state (made to stand transparent: light non-scattering state) by electrification. Stated specifically, in the liquid-crystal display devices of such a type, a polymer-dispersed liquid crystal is so disposed as to be held between opposing transparent electrodes. Upon application of in-phase alternating-current signals to both the transparent electrodes, the liquid crystal comes into a light scattering state where no voltage is applied, and, upon application of out-of-phase alternating-current signals to both the transparent electrodes, it comes into a transparent state where a voltage is applied. The driving of liquid crystal in this way brings patterns into the transparent state and their surroundings into the light scattering state, whereby transparent regions can be displayed on a white background similar to ground glass; or brings patterns into the light scattering state and their surroundings into the transparent state, whereby white regions can be displayed on a transparent background.
Where transparent regions are displayed on a white background, any particular problem does not arise even in apparatus constructed as described above. However, where it is attempted to display white regions on a transparent background, the following problems may arise.
Think about display regions set like islands in a transparent background. In such a case, even when the background region which surrounds display regions is kept into a transparent background by applying a voltage thereto, wiring areas extending to the display regions come into question. More specifically, where the island-like display regions stand non-electrified, i.e., the voltages applied to the both electrodes are in phase, the wiring areas extending to those regions have of course the same phase as the opposing transparent electrodes. This means that, when the island-like display regions are displayed in the light scattering state, the wiring areas extending there to the display regions also come into the light scattering state and are inevitably simultaneously displayed.
In liquid-crystal display devices, the fact that the island-like display regions are displayed in the background standing transparent means that, when a liquid-crystal display panel is incorporated in an optical system, display marks are so displayed as to come up to the surface as white regions in a state what is called “superimposed” to image formed by light beam transmitted through a transparent region. In such a case, to the display mark, wiring through which a voltage is supplied thereto is connected, and hence the voltage is applied to the liquid crystal via the wiring, so that all the segments that constitute the display mark look like as if strings are attached corresponding to the wiring areas extending from the margin of a picture, to spoil the light beam image transmitted through the transparent region.
In addition, at the boundary between a background area and a display mark, there is a boundary between the segments that constitute the transparent electrodes corresponding to the both, and this boundary remains inevitably as a blank area where no electrode pattern is present. In this blank area, no electric field comes up to the liquid-crystal region present opposingly to this blank area, and hence the light scattering state is always maintained. Namely, what is to be displayed when the background area is made transparent and the display mark is also made transparent is displayed as a white region as if the blank area is an edging of the display mark. When the display mark area is made white, a display mark is formed in which both the blank area and the display mark area are painted out as a white region.
Thus, in conventional liquid-crystal display devices, the display mark can not completely be made to disappear even when it is unnecessary, and there comes to be a disadvantage on display that the wiring area goes on and off concurrently every time the display mark goes on and off. Such a disadvantage provides a great obstacle when any desired display is optically superimposed on a background image. That is, the display to be superimposed is desired not only to be simply displayed, but also to disappear completely when it is unnecessary.
As for the polymer-dispersed liquid crystal, it responds more slowly as temperature is lower, and hence may cause a problem that the brightening of display segments does not agree with the timing of illumination as long as the illumination is merely performed.
For example, at a normal temperature of 25° C., the polymer-dispersed liquid crystal takes about 10 msec as a time taken to change from the light scattering state to the transparent state and about 60 msec as a time taken to change from the transparent state to the light scattering state, changing almost instantaneously. However, at a low temperature of −10° C., it takes about 300 msec as a time taken to change from the light scattering state to the transparent state and about 1,400 msec as a time taken to change from the transparent state to the light scattering state, showing a very slow response.
Hence, where one of a plurality of segments is selected by a selector, the liquid crystal responds so slowly at low temperature that the illumination may end before the selected segment changes into the light scattering state, and further that a segment having been selected before that is illuminated. Thus, there is a problem that any selected segment is not accurately illuminated. This problem has not been solved under existing circumstances.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide, as first invention of the present application, a liquid-crystal display device that enables any desired display to be superimposed on the background image while preventing the difficulty that the wiring area extending to a display mark is displayed or only the edging of the display mark is displayed.
To achieve the above object, the liquid-crystal display device of the first invention comprises a polymer-dispersed liquid-crystal layer capable of coming into a light scattering state when no voltage is applied, and first and second transparent electrodes capable of forming an electric field in the polymer-dispersed liquid-crystal layer;
the first transparent electrode having a first electrode pattern and a second electrode pattern disposed adjoiningly to the first electrode pattern via a boundary area between them;
the boundary area having a width adequate to make transparent the polymer-dispersed liquid-crystal layer at its area corresponding to the boundary area, by the action of an electric field formed by the second electrode pattern and second transparent electrode.
According to the first invention, when in the above device the first electrode pattern and the second electrode pattern come into the transparent state upon application of a voltage to the both, the surrounding electric field strays into the polymer-dispersed liquid-crystal layer lying in a region opposing to the boundary area of the both patterns, so that the boundary area of the both patterns is not displayed and not seen.
In the liquid-crystal display device of the first invention, preferably the first electrode pattern may be a display pattern, the second electrode pattern may be a background pattern, and boundary area may have a width substantially equal to the layer thickness of the polym
Chowdhury Tarifur R.
Miles & Stockbridge P.C.
Sikes William L.
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