Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-03-11
2001-08-07
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S098000, C349S061000, C349S106000, C349S064000
Reexamination Certificate
active
06271901
ABSTRACT:
TECHNICAL FIELD
The invention relates to a liquid crystal display device for use as a display panel in various electronic equipment such as a timepiece (watch and clock), portable information equipment, and so forth.
BACKGROUND TECHNOLOGY
A timepiece for indicating digital display of time information such as the hour, minute, and second, and calendar information such as the date, days of the week, the month, and the year, by use of a liquid crystal display panel, has been in widespread use for wrist watches and clocks, provided with a crystal oscillation circuit.
There has also been in use a combination watch wherein an analog display indicating time information by the hands of the watch is used in combination with digital display indicating time information and calendar information in numbers and letters.
Further, there has been proposed an analog watch for selectively displaying markers in various patterns, or for displaying simulated hands for an hour hand, a minute hand, and a second hand, by providing the dial thereof based on a liquid crystal display panel (refer to, for example, Japanese Patent Laid-open S 54-153066).
A reflective-type liquid crystal display device, small in size and consuming very little electric power, has been in widespread use as a display panel for displaying necessary information (character information and graphic information) in various electronic equipment other than a timepiece, such as cellular phones, desktop electronic computers, game players, and so forth.
As such a liquid crystal display device as described above, in a conventional liquid crystal display panel, a liquid crystal cell filled with liquid crystals is sandwiched between two transparent substrates having an electrode on respective inner surfaces thereof, facing each other, and an upper polarizing film and a lower polarizing film are disposed, respectively, on the external surface of the transparent substrates, on the opposite sides. If an electric field is applied to the liquid crystals by applying a voltage to a pair of electrodes on the transparent substrates holding the liquid crystal cell therebetween, the optical property of the liquid crystals is changed, thereby locally controlling transmission and absorption of light falling on the liquid crystal display panel such that a predetermined display is effected.
Either of the upper polarizing film or the lower polarizing film is a polarizing film absorbing the light linearly polarized in the direction orthogonal to the transmission axis thereof.
In the case of a watch using the conventional liquid crystal display panel described above, time information and calendar information are displayed in black against a white background in a normally white mode that is common.
However, by simply displaying time information and calendar information in black against the white background as described in the foregoing, neither variation in design nor interest can be offered, with a resulting tendency to lose soon popularity with consumers. Probably, as a result, consumption of digital watches has recently been on the decline, and neither combination watches nor analog watches with a liquid crystal display panel have since received market acceptance.
Similarly, with the conventional liquid crystal display panel used in electronic equipment other than a timepiece, various information expressed in characters and graphics is generally displayed in black against the white background, and although there are some wherein information can be displayed in white against the black background in an inverse mode, the conventional liquid crystal display panel has still been found lacking in design variation and aesthetic qualities.
In light of the present situation as described, the present invention has been developed, and an object of the invention is to provide a liquid crystal display device for use in various electronic equipment such as a timepiece (watch and clock), and so forth, capable of offering attractive variation in design and displaying information clearly so that a viewer can see the display with greater ease.
DISCLOSURE OF THE INVENTION
To this end, a liquid crystal display device according to the invention comprises a liquid crystal cell with liquid crystals sealed therein, sandwiched between two transparent substrates having an electrode on each of the inner surfaces thereof facing each other, a first reflective polarizing film disposed on the visible side of the liquid crystal cell, a second reflective polarizing film disposed on the side of the liquid crystal cell, opposite from the visible side thereof, and a light absorption film disposed on the side of the second reflective polarizing film, opposite from the liquid crystal cell, and is characterized in that the first reflective polarizing film as well as the second reflective polarizing film is a polarizing sheet reflecting the light linearly polarized in the direction orthogonal to the transmission axis thereof.
Further, a backlight may be substituted for the light absorption film. In such a case, a translucent absorbing film is preferably installed between the backlight and the second reflective polarizing film.
Otherwise, first reflective polarizing film of the liquid crystal display device according to the invention may be disposed on the visible side of the liquid crystal cell, the second reflective polarizing film on the side of the liquid crystal cell, opposite from the visible side thereof, and an absorption-type polarizing film on the visible side of the first reflective polarizing film, such that the absorption-type polarizing film is a polarizing sheet absorbing the light linearly polarized in the direction orthogonal to the transmission axis thereof, and the transmission axis of the absorption-type polarizing film is oriented substantially in the direction of the transmission axis of the first reflective polarizing film.
In this case, the absorption-type polarizing film is preferably a color polarizing film mainly absorbing a light component at a specific wavelength, out of the light linearly polarized in the direction orthogonal to the transmission axis thereof.
Further, a light diffusion layer (light diffusion film) may be installed in place of the absorption-type polarizing film.
In the liquid crystal display devices described in the foregoing, a light absorption film or a backlight may preferably be disposed on the side of the second reflective polarizing film, opposite from the liquid crystal cell.
In the case where the backlight is installed, a translucent absorbing film is preferably installed between the backlight and the second reflective polarizing film.
It is desirable that in the liquid crystal display devices described above, the first reflective polarizing film and the second reflective polarizing film be disposed such that the transmission axes thereof cross each other at right angles or run parallel with each other.
Further, liquid crystals causing linearly polarized light passing therethrough to undergo phase modulation or intensity modulation are sealed in the liquid crystal cell. The liquid crystals causing phase modulation to occur are twisted nematic liquid crystals or supertwisted nematic liquid crystals, while the liquid crystals causing intensity modulation to occur are guest host liquid crystals.
It is desirable that the first reflective polarizing film is disposed such that the transmission axis thereof is oriented in the direction parallel with or orthogonal to the long axes of liquid crystal molecules located on the visible side of the liquid crystal cell.
With the liquid crystal display device according to the invention, constructed as above, half of the light falling thereon from the visible side thereof is reflected by the first reflective polarizing film, but the other half of light is transmitted therethrough, falling on the liquid crystal cell. The other half of the light is caused to undergo a change in optical property locally when transmitted through the liquid crystal cell, forming portions thereof where light is fully reflected by
Akiba Yuichi
Akiyama Takashi
Ide Masafumi
Kikuchi Masami
Nakagawa Koji
Armstrong Westerman Hattori McLeland & Naughton LLP
Chowdhury Tarifur R.
Citizen Watch Co. Ltd.
Sikes William L.
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