Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-11-24
2004-01-20
Dudek, James (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S113000, C349S114000
Reexamination Certificate
active
06680765
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a liquid crystal device and, in particular, to a structure of a liquid crystal device capable of switching between reflection type display and transmission type display and to an electronic apparatus using this liquid crystal device.
BACKGROUND ART
Conventionally, a reflection type liquid crystal device, which consumes little power, has been widely used as a display section attached to a portable device or apparatus. It has a problem in that it makes the display visible by utilizing external light, so that it is impossible to read the display in a dark place. In view of this, a liquid crystal device has been proposed which, in a light place, utilizes external light as a usual reflective type liquid crystal device but which, in a dark place, enables the display to be seen by means of an inner light source. As disclosed in Japanese Utility Model Laid-Open No. 57-049271, in this proposed device, a polarizing plate, a transflective plate, and a backlight are arranged in this order on the outer surface of the liquid crystal panel, which is the side opposite to the observation side. In this liquid crystal device, when it is light surroundings, external light is taken in and the light reflected by the transflective plate is utilized to effect reflection type display. When it becomes dark, the backlight illuminates and the display is made visible by the light transmitted through the transflective plate, thus effecting transmission type display.
Japanese Patent Laid-Open No. 8-292413 discloses another liquid crystal device in which the brightness of the reflection type display is improved. In this liquid crystal device, a transflective plate, a polarizing plate, and a backlight are arranged in this order on the outer surface of the liquid crystal panel on the side opposite to the observation side. Under the light surroundings, external light is taken in and the light reflected by the transflective plate is utilized to effect reflection type display, and under the dark surroundings, the back light illuminates and the display is made visible by the light transmitted through the polarizing plate and the transflective plate, thus effecting transmission type display. In this construction, there is no polarizing plate between the liquid crystal cell and the transflective plate, so that it is possible to achieve a reflection type display brighter than that of the above-described liquid crystal device.
DISCLOSURE OF INVENTION
However, in the liquid crystal device disclosed in Japanese Patent Laid-Open No. 8-292413, a transparent substrate exists between the liquid crystal layer and the transflective plate, resulting in a double image, a smeared image, etc.
Further, nowadays, as portable apparatus, OA apparatus, etc. are developed, a colored display is required of liquid crystal devices, and in many apparatuses using reflection type liquid crystal devices, a colored display is required. However, in the system as disclosed in the above-mentioned publication, in which a liquid crystal device is combined with a color filter, the transflective plate is arranged behind the liquid crystal panel, so that a thick transparent liquid crystal panel exists between the liquid crystal layer or the color filter and the transflective plate, with the result that a double image, a smeared image, etc. are generated by parallax, making it impossible to achieve a satisfactory color development.
To solve the above problem, Japanese Patent Laid-Open No. 7-318929 proposes a transflective type color liquid crystal device in which a reflecting plate is arranged so as to be in contact with the liquid crystal layer. However, in this liquid crystal device, it is impossible to recognize the display in the dark surroundings.
On the other hand, a transflective type liquid crystal device has been proposed in Japanese Patent Laid-Open No. 7-318929 in which a pixel electrode also serving as the transflective layer is formed on the inner surface of the liquid crystal cell. Further, disclosed is a construction in which a pixel electrode consisting of an ITO (indium tin oxide) layer is superimposed on a transflective layer consisting of a metal layer through the intermediation of an insulating layer. Further, in this liquid crystal device, on the back side of the liquid crystal cell, there is no optical element which varies the polarization of the incident light from the backlight between the transflective plate and the polarizing plate, so that the incident light from the backlight always impinges upon the liquid crystal cell as linearly polarized light passing through the polarizing plate. As a result, when the optical characteristics of the polarizing plate and the phase plate on the front side of the liquid crystal cell, and the liquid crystal cell, etc. are set so as to enhance the contrast characteristic at the time of reflection type display, it is impossible to achieve a satisfactory contrast characteristic at the time of transmission type display. Conversely, when the optical characateristics of these components are set so as to enhance the contrast characteristic at the time of transmission type display, it is impossible to achieve a satisfactory contrast characteristic at the time of reflection type display. Similarly, when the optical characteristic of these components are set so that the color compensation for the color due to wavelength dispersion of light may be effected in a satisfactory manner at the time of reflection type display, such color compensation cannot be effected in a satisfactory manner at the time of transmission type display. Conversely, when the optical characteristics of these components are set so that such color compensation may be effected in a satisfactory manner at the time of reflection type display, such color compensation cannot be effected in a satisfactory manner at the time of transmission type display. That is, generally speaking, it is very difficult to achieve high contrast or effect color compensation in a satisfactory manner at the time of both reflection type display and transmission type display, making it impossible to effect high quality image display.
The present invention has been made in view of the above problem. It is accordingly an object of the present invention to provide a transflective type liquid crystal device of type which is capable of switching between reflection type display and transmission type display, wherein a double image or smeared image due to parallax is not generated, making it possible to effect high quality image display at the time of both reflection type display and transmission type display and an electronic apparatus using such a liquid crystal device.
To achieve the above object, there is provided, in accordance with the present invention, a liquid crystal device comprising a pair of first and second transparent substrates, a liquid crystal layer held between the first and second substrates, a laminate which is formed on the liquid crystal layer side surface of the second substrate and in which at least a transflective layer and a transparent electrode layer are stacked together, an illuminating device arranged on the side of the second substrate which is opposite to the liquid crystal layer, a first polarizing plate arranged on the side of the first susbstrate which is opposite to the liquid crystal layer, a first phase plate arranged between the first substrate and the first polarizing plate, a second polarizing plate arranged between the second substrate and the illuminating device, and a second phase plate arranged between the second substrate and the second polarizing plate.
In the liquid crystal device of the present invention, at the time of reflection type display, the laminate reflects external light coming from the first substrate side to the liquid crystal layer side by the transflective layer included therein. Since the laminate is arranged on the liquid crystal layer side of the second substrate, there is scarcely any gap between the laminate and the liquid crystal layer, so that a do
Maeda Tsuyoshi
Okamoto Eiji
Okumura Osamu
Seki Takumi
Dudek James
Harness & Dickey & Pierce P.L.C.
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