Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-01-25
2001-04-10
Dudek, James A. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S113000
Reexamination Certificate
active
06215538
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device for use in office automation (OA) equipment (e.g., word processors and personal computers), portable information equipment (e.g., electronic books), video cassette recorders (VCRs) incorporating a liquid crystal monitor, and the like.
2. Description of the Related Art
Recently, liquid crystal display devices have been widely used in OA equipment (e.g., word processors and personal computers), portable information equipment (e.g., electronic books), video cassette recorders (VCRs) incorporating a liquid crystal monitor and the like, utilizing the features of a thin display thickness and low power consumption.
Such liquid crystal display devices include a transmission-type liquid crystal display device using a thin, transparent, electrically conductive film such as ITO (Indium Tin Oxide) as pixel electrodes, and a reflection-type liquid crystal display device using reflective electrodes of, for example, a metal as pixel electrodes.
Unlike CRTs (cathode ray tubes) and EL (electroluminescence), liquid crystal display devices are not self-light-emitting display devices. Therefore, in the case of the transmission-type liquid crystal display device, an illumination device such as a fluorescent tube, which is a so-called backlight, is placed behind the liquid crystal display device, whereby a display is provided using incident light of the backlight. On the other hand, in the case of the reflection-type liquid crystal display device, a display is provided by reflecting incident light from the outside by the reflective electrodes.
Since the transmission-type liquid crystal display device uses the backlight to provide a display, the transmission-type liquid crystal display device has an advantage of providing a bright, high-contrast display without being significantly affected by the brightness around the liquid crystal display device. However, the backlight consumes about 50% or more of the overall power consumption of the liquid crystal display device, whereby power consumption is disadvantageously increased.
On the other hand, since the reflection-type liquid crystal display device does not use such a backlight, the reflection-type liquid crystal display device has an advantage of significantly reducing power consumption. However, brightness and contrast of the display are affected by environmental factors such as brightness around the liquid crystal display device and/or the conditions under which the liquid crystal display device is used.
In the case of the reflection-type liquid crystal display device, visual recognition of the display is affected by environmental factors such as brightness around the liquid crystal display device, and is extremely deteriorated particularly when ambient light is dark. On the other hand, in the case of the transmission-type liquid crystal display device, visual recognition of the display is reduced when ambient light is extremely bright such as in good weather.
As means for solving such problems, liquid crystal display devices having functions of both reflection- and transmission-type liquid crystal display devices (hereinafter, referred to as “transmission/reflection-type liquid crystal display devices”) are disclosed in copending U.S. application Ser. No. 09/122,756 filed on Jul. 27, 1998 and U.S. application Ser. No. 09/220,792 (not yet assigned; first named inventor Masumi KUBO et al.; assigned to Sharp Kabushiki Kaisha; Sharp internal reference No. 98435/US/PB; Attorney Docket No. 829-493) filed on Dec. 28, 1998, which is a continuation-in-part of U.S. application Ser. No. 09/122,756. These U.S. applications are incorporated herein by reference.
In the transmission/reflection-type liquid crystal display devices proposed by the above-mentioned U.S. applications, each pixel region includes a reflective electrode region for reflecting ambient light and a transmissive electrode region for transmitting light from a backlight, the transmissive electrode region being formed from a film having a relatively high light-reflectance. As a result, the transmission/reflection-type liquid crystal display device (i) serves, in a pitch-dark environment, as a transmission-type liquid crystal display device which provides a display by using light from the backlight transmitted through the transmissive electrode regions, (ii) serves, in a dark environment, as a transmission/reflection-type liquid crystal display device which provides a display by using both light from the backlight transmitted through the transmissive electrode regions and ambient light reflected by the reflective electrode regions, and (iii) serves, in a bright environment, as a reflection-type liquid crystal display device which provides a display by using light reflected from the reflective electrode regions.
Hereinafter, the terms “reflective electrode region”, “transmissive electrode region”, “reflective region” and “transmissive region” as used herein will be defined.
A reflection-type liquid crystal display device which provides a display in a reflection mode by using ambient light has reflective electrode regions for reflecting ambient light transmitted through a liquid crystal layer, the reflective electrode regions being provided on one of a pair of substrates. The reflective electrode region may be formed from a reflective electrode, or may be formed from a combination of a transparent electrode and a reflective layer (reflective plate). In other words, an electrode for applying a voltage to the liquid crystal layer may be formed from the transparent electrode, and the reflective layer for reflecting incident light does not have to function as an electrode.
Like the reflection-type liquid crystal display device, the transmission/reflection-type liquid crystal display device also has reflective electrode regions, in addition to transparent electrode regions. Each reflective electrode region may be formed from a reflective electrode, or may be formed from a combination of a transparent electrode and a reflective layer (reflective plate). Each transparent electrode region is typically formed from a transparent electrode.
In the transmission/reflection-type liquid crystal display device according to the present invention, a region for providing a display in a transmission mode is referred to as a transmissive region, whereas a region for providing a display in a reflection mode is referred to as a reflective region. The transmissive region includes a transmissive electrode region and a liquid crystal region defined by the transmissive electrode region, and the reflective region includes a reflective electrode region and a liquid crystal region defined by the reflective electrode region. Although a semi-transmission/reflection-type liquid crystal display device using a semi-transmissive/reflective film (i.e., a porous, reflective film) has reflective electrode regions and transmissive electrode regions, light passing through respective liquid crystal regions defined by the reflective electrode regions and transmissive electrode regions is mixed and overlaps each other. Therefore, a region for providing a display in a transmission mode (i.e., a transmissive region) and a region for providing a display in a reflection mode (i.e., a reflective region) cannot be defined independently. In other words, among the liquid crystal display devices wherein each pixel region has a transmissive electrode region and a reflective electrode region, a liquid crystal device in which a region for providing a display in a transmission mode and a region for providing a display in a reflection mode cannot be defined independently (that is, they substantially overlap each other) is referred to as a semi-transmission/reflection type liquid crystal display device.
The term “pixel region” as used herein will now be described. The liquid crystal display device of the present invention includes a plurality of pixel regions for providing a display. A single pixel region indicates a portion (component)
Fujioka Shogo
Ishii Yutaka
Katayama Mikio
Kubo Masumi
Narutaki Yozo
Dudek James A.
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
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