Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-03-27
2003-07-29
Ngo, Julie (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S112000, C349S113000, C349S119000, C349S178000, C430S007000
Reexamination Certificate
active
06600536
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a display apparatus. More particularly, the invention relates to a reflection type liquid crystal display apparatus for producing a color display having a high brightness, a high contrast and a high color purity without employing a back-light, by using external light, such as natural light, indoor light or the like.
As disclosed in Japanese Patent Application Laid-Open No. Heisei 9 (1997)-258219, Japanese Patent Application Laid-open No. Heisei 10 (1998)-161110, for example, the conventional reflection type liquid crystal display apparatus employing a single polarizing plate has a structure in which a pair of substrates formed with electrodes and orientation films, respectively, are arranged in opposition to each other and a liquid crystal layer is disposed between the substrates. One of the electrode is a reflecting electrode which serves as a reflection plate.
On the other hand, as disclosed in Japanese Patent Application Laid-Open No. Heisei 8 (1996)-166585, an electrode substrate on the side of the reflection plate is formed by providing a color filter and a flattening layer on a metal reflection plate, with a transparent electrode being formed thereover.
In the foregoing publications, both the reflection electrode and the reflection plate are formed with a thin metal film. Since the thin metal film has a low chemical strength and a low mechanical strength, it is easily oxidized or vulcanized, resulting in a lower reflectivity, and it is easily scratched. Accordingly, in the reflection electrode structure formed of an aluminum thin film, in which the electrode serves as a reflection plate, the surface of the aluminum thin film (reflection surface) inherently contacts the photosensitive resin, developer fluid, photosensitive resin peeling liquid, washing liquid (purified water) and the like during manufacture, to cause lowering of the reflectivity due to oxidization or corrosion of the surface in a process of patterning the aluminum thin film into the shape required for each electrode by way of a photolithographic process.
Furthermore, in the construction where the electrode serves as a reflection plate, the surface of the aluminum thin film which provides the reflection surface is exposed until the orientation film is formed. Therefore, the reflection surface inherently contacts the air to cause oxidization which will lower the reflectivity. Also, it is possible to scratch the reflection surface during the fabrication process, thereby lowering the process yield.
An aluminum terminal of the reflection electrode extended outside of a liquid crystal cell and exposed therefrom has a low mechanical strength and is easily oxidized or corroded, causing a difficulty in connecting with a tape carrier package (hereinafter referred to as TCP) mounting a liquid crystal driving IC or in peeling off the TCP for correction. Furthermore, it is also possible to cause an increase in the connection resistance or to cause a connection failure or display failure due to fluctuation.
In a construction where the transparent electrode is formed on the metallic reflection plate via the color filter and the flattening layer, since the color filter and the flattening layer are dielectric substances, viewed as an electric circuit, they form a capacitor structure. In this construction, since the reflection electrode is formed over the entire surface of the substrate, a structure is provided in which respective transparent electrodes are connected by capacitors. Therefore, the predetermined liquid crystal driving voltage applied to each transparent electrode may fluctuate due to capacitive coupling, thereby to cause degradation of the display quality.
On the other hand, since the color filter is directly formed on the metallic reflection plate, the surface of the metallic reflection plate (reflection surface) contacts the developer fluid, the washing liquid (pure water or the like) and so on to lower reflectivity due to oxidization or corrosion of the surface in the process for forming the color filter by way of photolithographic processing.
Furthermore, in case of a reflection type liquid crystal display apparatus employing a diffuse reflection electrode which is formed with an irregularity on the surface of the reflection electrode, since large number of irregularities will be present on the surface of the electrode within one pixel, the thickness of the liquid crystal layer (thickness of the liquid crystal layer between the substrates arranged in opposition) becomes non-uniform so as to cause a non-uniformity of the threshold voltage of the liquid crystal within the pixel, resulting in disturbance of the orientation of the liquid crystal molecule and a lowering of the contrast of the display.
In the reflection type liquid crystal display apparatus employing a diffuse reflection electrode, a gap between the substrates arranged in opposition across the liquid crystal layer is restricted by spacer beads. However, due to the irregularity on the reflection electrode, a difficulty is encountered in restricting the gap between the substrates with high precision, resulting in a non-uniformity of display or a lowering of the contrast.
In the reflection type liquid crystal display apparatus for color display employing a color filter, a multi-color display by tone control becomes possible. However, since an optical compensation by the liquid crystal and a phase difference film is not optimized, a monochrome display with good achromatic color cannot be obtained, and, thus, a color display with high color purity becomes difficult.
Furthermore, in the construction of the reflection electrode, where a display electrode serves as the reflection plate, when the color filter is provided on the substrate on the side of the reflection plate, the color filter is provided on the reflection electrode. Then, the voltage applied between the electrode arranged in opposition across the liquid crystal layer it, divided by the liquid crystal layer, the color filter and the orientation control layer so as to cause an elevating of the drive voltage.
SUMMARY OF THE INVENTION
The present invention has been developed in view of the problems set forth above. Therefore, it is an object of the present invention to provide a reflection type liquid crystal display apparatus which does not cause degradation of a reflection surface or an electrode terminal, provides a multiple color display with a high color purity, and reduces fluctuation of the voltage caused by loss of a drive voltage or capacitive coupling even when a color filter is provided on the substrate on the side of the reflection plate, thereby to realize a bright display having a high contrast.
According to one aspect of the present invention, a reflection type liquid crystal display apparatus comprises: a pair of substrates; a pair of orientation films disposed between the pair of substrates; a liquid crystal layer disposed between the pair of orientation films; a plurality of electrodes disposed respectively opposing the substrates and the orientation films; a reflection layer disposed between a plurality of the electrodes and the substrates within a space defined between one of the substrates and one of the orientation films; and at least one or more thin films having an insulating property arranged between the plurality of the electrodes and the reflection layer.
In the construction set forth above, a plurality of signal electrodes may be arranged on at least one substrate at an end portion thereof.
The reflection surface of the reflection layer may be a mirror surface.
The reflection layer may be a diffuse reflection surface having an irregularity on the surface thereof, the thin film having an insulating property serving as a flattening layer.
The reflection type liquid crystal display apparatus may further comprise a color filter disposed between the substrate and the orientation film.
The thin film having an insulating property may be formed with at least one of a reflection enhancing film consisti
Funahata Katsuyuki
Itou Osamu
Komura Shinichi
Kuwabara Kazuhiro
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Ngo Julie
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