Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-08-28
2003-11-18
Lee, Eddie (Department: 2815)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S067000, C349S113000, C349S160000
Reexamination Certificate
active
06650395
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a liquid crystal device, an electronic device and a method of manufacturing the liquid crystal device, and more specifically, the present invention relates to the structure of a liquid crystal device comprising a reflecting layer provided on one of two substrates which constitute the liquid crystal device.
2. Description of the Related Art
A reflective liquid crystal display device is conventionally widely used, in which a display can be visualized by using external light. This reflective liquid crystal display device eliminates the need for a light source such as a back light or the like, and thus has the advantage that the power consumption can be decreased, and the size and weight can easily be decreased, as compared with a transmissive liquid crystal display device. Therefore, the reflective liquid crystal display device is widely used for portable devices, etc. Also, a transflective liquid crystal display device which can be used as a reflective liquid crystal display device with external light, and which can visualize a display by using light of a back light in the dark, and a liquid crystal display device with a front light which can visualize a display by using light from the front light have been developed.
The reflective or transflective liquid crystal display device or the liquid crystal display device with a front light comprises a reflecting layer provided under a liquid crystal layer, for reflecting light incident from the observation side. In this case, the reflecting layer having a mirror plane as a reflecting plane causes reflection of a background, and room illumination, etc., thereby causing the problem of making a display image hard to see. In order to solve this problem, a method is conventionally used, in which a surface of the reflecting layer is roughened to appropriately scatter reflected light.
As a conventionally used method for roughening the surface of the reflecting layer, for example, a roughening method for roughening a surface of the reflecting layer is known, in which the substrate surface is polished and roughened by an abrasive and a metal film is formed on the roughened surface.
However, in a liquid crystal device comprising a reflecting layer having the conventional roughened surface, a surface of a substrate is totally roughened, and alignment marks, switching elements, a sealing material, etc., which should be formed on a flat surface of a substrate, are inevitably formed on the roughened surface of the substrate, thereby causing the problem of deteriorating mark visibility, or causing a defect in the operation of the switching elements, a defect in sealing, or the like.
Also, the surface of the reflecting layer is regularly roughened to produce interference in reflected light, thereby causing the problem of coloring an image. Ideally, the surface of the reflecting layer is irregularly roughened to form an irregularly roughened surface. However, it is very difficult to finely control the state of surface roughness in order to form the irregularly roughened surface.
A possible method for solving the above problem comprises etching or chemically polishing a portion of the surface of a substrate to form an irregularly roughened surface. However, in such partial chemical processing of the surface of the substrate, the roughened surface area (referred to as a “roughened surface area” hereinafter) is recessed, as compared with a flat surface area (referred to as a “flat surface area” hereinafter). Therefore, in dispersing a spacer for regulating a cell gap between two substrate, the spacer extends to the flat surface area or mixes with a sealing material to increase the cell gap in the periphery of a liquid crystal display area. This possibly causes a variation in display contrast, or the like due to nonuniformity in the cell gap.
Accordingly, the present invention has been achieved for solving the above problem, and an object of the present invention is to provide a liquid crystal device comprising a reflecting layer having a conventional roughened reflecting plane, and a novel cell structure capable of decreasing an optical defect and a defect in the cell structure due to the roughened reflecting plane.
SUMMARY OF THE INVENTION
A liquid crystal device of the present invention comprises a liquid crystal sandwiched between two substrates, a roughened surface area and a flat surface area which are formed on a surface of one of the substrates opposite to the other substrate, and a reflecting layer formed on the roughened surface area, wherein the reference plane of the roughened surface area is lower than the surface of the flat surface area.
Particularly, in the present invention, the total thickness of a surface structure selectively formed on the roughened surface area of one of the substrates and a surface structure selectively formed on the area of the other substrate opposite the roughened surface area is equivalent to or larger than the step difference between the reference plane height of the roughened surface area and the surface height of the flat surface area.
The terms “selectively formed on the roughened surface area” mean substantially no formation on the flat surface area, and the terms “selectively formed on the area of the substrate opposite to the roughened surface area” mean substantially no formation on the region opposite to the flat surface region.
In the present invention, the reference plane of the roughened surface area is lower than the surface of the flat surface area, but the total of the thickness of the surface structure selectively formed on the roughened surface area of one of the substrates and the thickness of the surface structure selectively formed on the area of the other substrate opposite the roughened surface area is equivalent to or larger than the step difference between the roughened surface area and the flat surface area. Therefore, the distance between the substrates in the roughened surface area comprising the reflecting layer can be made equivalent to or smaller than that in the flat surface area.
Therefore, in regulating the space between both substrates by control means such as a spacer or the like, the distance between the substrates in the roughened surface area can be accurately regulated by the control means, and thus an optical function portion comprising the reflecting layer having a roughened surface can be precisely formed. In this case, the step difference between the reference plane height of the roughened surface area and the surface height of the flat surface area can be freely set to some extent, thereby permitting the preferred roughness state of the roughened surface area to be easily formed without great restriction.
In the present invention, the total of the thickness of the surface structure selectively formed on the roughened surface area of one of the substrates and the thickness of the surface structure selectively formed on the area of the other substrate opposite the roughened surface area is preferably larger than the step difference between the roughened surface area and the flat surface area.
As another aspect of the present invention, a liquid crystal device comprises a predetermined surface structure formed on one of two substrates, wherein the surface height of the substrate including the surface structure in the roughened surface area is equivalent to or larger than that in the flat surface area. In this case, the surface of the substrate including the surface structure in the roughened surface area is preferably higher than that in the flat surface area.
As a further aspect of the present invention, a liquid crystal device comprises a colored layer and a protecting layer laminated in turn on a reflecting layer, or an insulating layer formed on the reflecting layer, wherein the total thickness of the reflecting layer, the colored layer and the protecting layer, or the total thickness of the reflecting layer and the insulating layer is equivalent to or larger than the step
Harness & Dickey & Pierce P.L.C.
Lee Eddie
Richards N. Drew
Seiko Epson Corporation
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