Timepiece

Details Timepiece Timepiece

2000-02-09

2001-01-02

Miska, Vit (Department: 2859)

Horology: time measuring systems or devices

Chronological

With electro-optical display

C349S086000, C349S096000, C349S098000, C349S115000

Utility Patent

active

06169708

ABSTRACT:

TECHNICAL FIELD
The invention relates to a timepiece (watch and clock) for displaying at least time information such as hour, minute, and second, or calendar information such as date, days of the week, month, and year by use of a liquid crystal display panel.
BACKGROUND TECHNOLOGY
A timepiece for indicating digital display of time information such as hour, minute, and second, and calendar information such as date, days of the week, month, and 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 timepiece 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, minute hand, and a second hand, by making up the dial thereof based on a liquid crystal display panel.
In a conventional liquid crystal display panel for displaying time information and calendar information, as in a watch or clock, a liquid crystal cell filled with liquid crystals is sandwiched between two transparent substrates each having an electrode on an inner facing surface thereof, and an upper polarizing film and a lower polarizing film are disposed, respectively, on the external opposite surface of each transparent substrate. If an electric field is applied to the liquid crystals by applying a voltage to the 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.
Each of the upper polarizing film and 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 dark against a white background in the normally white mode that is common.
However, by simply displaying time information and calendar information in dark against the white background as described in the foregoing, neither variation in design nor fun of use can be offered, leading to rapid decline in product popularity among consumers. Probably as a result, consumption of digital watches has recently been on the decline, and neither combination timepieces nor analog watches with liquid crystal display panels have received market acceptance.
Therefore, by use of the monochromatic color liquid crystal display panel in which a background portion of a display and a display portion are colored, attempts have been made to improve digital watches and so forth capable of providing variation in design and colored display.
In reference to the monochromatic color liquid crystal display panel like this, several types have been proposed in the past.
A first type is a monochromatic color liquid crystal display panel made up by providing a color polarizing film on the outer side of a liquid crystal cell thereof. This type has generally been in widespread use due to its simple constitution.
A second type is a monochromatic color liquid crystal display panel wherein a dichroic pigment is mixed in nematic liquid crystals sealed in a liquid crystal cell thereof, and the dichroic pigment is caused to move together with the nematic liquid crystals by the action of nematic liquid crystal molecules, and this type is called a guest-host LCD.
However, with any of these conventional-type monochromatic color liquid crystal display panels, colored characters and colored graphics produced by a dye or the dichroic pigment are displayed against a background in white, or white characters and white graphics are displayed against a background color produced by the dye or the dichroic pigment. Consequently, contrast declines. Furthermore, since the numbers of available dyes and dichroic pigments are limited, there is also a problem that the number of colors in which such liquid crystal display panels as described above can indicate display.
Accordingly, there has been proposed a third type of monochromatic color liquid crystal display panel comprising a polarizing film, a 90° twisted nematic (TN) liquid crystal cell, a retardation film for circularly polarizing film (a quarter-wavelength plate, ¼&lgr; plate), a cholestric liquid crystal polymer sheet, and a light absorbing member.
Referring to
FIG. 15
, the display principle of the monochromatic color liquid crystal display panel of this type is described hereinafter.
Shown in
FIG. 15
, the monochromatic color liquid crystal display panel is made up of a polarizing film
8
, a twist-aligned 90° TN liquid crystal cell which is not shown, a retardation film
9
for circularly polarized light, a cholestric liquid crystal polymer sheet
10
, and a light absorbing member
11
.
In the left-hand part of the figure, an OFF-state indicating colored display is shown, wherein the polarizing film
8
and the retardation film
9
for circularly polarized light are disposed such that the transmission axis
8
b
of the polarizing film
8
is inclined 45° clockwise toward the phase delay axis
9
a
of the retardation film
9
for circularly polarized light. As a result, linearly polarized light transmitted through the polarizing film
8
is turned into right-handed circularly polarized light after passing through the retardation film
9
for circularly polarized light.
In the cholestric liquid crystal polymer sheet
10
, a twist direction
10
a
is right handed, and a twist pitch is close to a natural light wavelength, and accordingly, upon the right-handed circularly polarized light falling on the cholestric liquid crystal polymer sheet
10
, light components in a scattering band width &Dgr;&lgr; around a scattering center wavelength &lgr;c are reflected due to the selective scattering phenomenon. Transmitted light composed of light components in wavelength regions, other than the scattering band width &Dgr;&lgr;, is absorbed by the light absorbing member
11
made of a black paper or a black plastic sheet, whereupon a bright reflected color can be obtained.
If one defines n as the refractive index of a cholestric liquid crystal polymer, and P as the twist pitch of the cholestric liquid crystal polymer, the scattering center wavelength &lgr;c is given by the following formula:
&lgr;c=n×P
Hence, the cholestric liquid crystal polymer sheet
10
having various reflected colors can be obtained by adjusting the twist pitch P of the cholestric liquid crystal polymer.
Meanwhile, in the right-hand part of
FIG. 15
, an ON-state indicating black display is shown, wherein the polarizing film
8
and the retardation film
9
for circularly polarized light are disposed such that the transmission axis
8
a
of the polarizing film
8
is inclined 45° counterclockwise toward the phase delay axis
9
a
of the retardation film
9
for circularly polarized light by rotating the transmission axis
8
a
of the polarizing film
8
through 90°, so that linearly polarized light after passing through the retardation film
9
for circularly polarized light is turned into left-handed circularly polarized light.
Accordingly, even if the left-handed circularly polarized light falls on the cholestric liquid crystal polymer sheet
10
having the twist direction
10
a
which is right handed, the selective scattering phenomenon does not occur. As a result, all components of the left-handed circularly polarized light are transmitted through the cholestric liquid crystal polymer sheet
10
, and absorbed by the light absorbing member
11
, thus indicating black display.
If a 90° TN liquid crystal cell is installed between the polarizing film
8
and the ret

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