U.S. patent number 3,668,861 [Application Number 05/197,378] was granted by the patent office on 1972-06-13 for solid state electronic watch.
This patent grant is currently assigned to Kabushiki Kaisha Suwa Seikosha. Invention is credited to Hiromitsu Mitsui.
United States Patent |
3,668,861 |
Mitsui |
June 13, 1972 |
SOLID STATE ELECTRONIC WATCH
Abstract
A watch is provided with a liquid crystal display system
operable at high levels of ambient illumination and a solid state
display system operable at low levels of ambient illumination. A
photo-transistor selects the display system appropriate to the
ambient light level.
Inventors: |
Mitsui; Hiromitsu (Nagano,
JA) |
Assignee: |
Kabushiki Kaisha Suwa Seikosha
(Tokyo, JA)
|
Family
ID: |
14281192 |
Appl.
No.: |
05/197,378 |
Filed: |
November 10, 1971 |
Foreign Application Priority Data
|
|
|
|
|
Nov 17, 1970 [JA] |
|
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45/100709 |
|
Current U.S.
Class: |
368/82;
252/299.01; 968/956; 368/239; 968/932 |
Current CPC
Class: |
G04G
9/0041 (20130101); G04G 9/085 (20130101) |
Current International
Class: |
G04G
9/00 (20060101); G04G 9/08 (20060101); G04b
019/30 (); H03k 019/14 () |
Field of
Search: |
;58/23,50 ;350/160 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Tomsky; Stephen J.
Assistant Examiner: Jackmon; Edith C. Simmons
Claims
What is claimed is:
1. A solid state electronic watch comprising a passive display
element for time display in regions of relatively high incident
light intensity, an active display element for time display in
regions of relatively low light intensity and means for activating
said passive and active display elements.
2. A solid state electronic watch as defined in claim 1, wherein
said passive display element includes a sealed cell having a
transparent outer face and liquid crystal material within said cell
and said activating means includes means for imposing a voltage
transverse to said cell sufficient to cause said liquid crystal
material to disperse light.
3. A solid state electronic watch as defined in claim 2, wherein
said outer face has thereon segments in an array such that any
digit from 0 to 9 may be shown by suitable activation by said
activation means.
4. A solid state electronic watch as defined in claim 1, wherein
said active display element includes an electroluminescent material
activatable by said activation means to emit radiation, said
activation resulting from passage of current through said
electroluminescent material.
5. A solid state electronic watch as defined in claim 3, wherein
said active display element has thereon segments in an array such
that any digit from 0 to 9 may be shown by suitable activation by
said activation means.
6. A solid state electronic watch as defined in claim 1, wherein
said activation means comprises a photo-transistor positioned in
said watch to sense the level of said incident light and generate a
signal characteristic of said incident light level, and circuit
means to activate said passive display element at high incident
light levels and to activate said active display element at low
incident light levels.
7. A solid state electronic watch as defined in claim 1, wherein
said active display element is disposed behind said passive display
element so that said active display element, when activated, may be
viewed through said passive display element.
8. A solid state electronic watch as defined in claim 6, wherein a
portion of said active display element overlies a portion of said
passive display element.
9. A solid state electronic watch as defined in claim 1, wherein
said watch includes a semi-conductor base plate and said display
elements and said activating means are mounted monolithically on
said base plate.
10. A solid state electronic watch as defined in claim 3, wherein
said electroluminescent material is gallium arsenide.
Description
BACKGROUND OF THE INVENTION
Liquid crystal display devices depend upon the fact that the
imposition of a sufficient electric field on a liquid crystal
material causes the liquid crystal material to disperse light and
thus to appear to be luminous. However, the light to be dispersed
must be provided from outside the device. Consequently, even though
the amount of electrical energy required is very small, such a
device is unsuitable for use where the level of ambient
illumination is low.
In contrast, electroluminescent, i.e., self-luminous devices such
as those based on gallium-arsenide require substantially greater
amounts of energy since the temperature of the display element must
be increased. Also the heat produced must be rejected to the
exterior of the device. When an attempt is made to use such a
device in regions of high ambient illumination, a high level of
luminescence is required for the light produced to be perceptible,
resulting in a considerable energy drain from the energy
source.
SUMMARY OF THE INVENTION
Incorporated in a watch are a liquid crystal display device and a
self-luminous display device. The former is a passive device and is
suitable for use at high ambient light levels. The latter is an
active device and utilizes an electrically powered self-luminous
solid state material such as gallium-arsenide; it is suitable for
use at low ambient light levels or in complete darkness. In this
device, a photo-transistor senses the ambient light level, and, in
accordance with the light level, either imposes an electric field
on the liquid crystal material or powers the self-luminous solid
state material. In order to decrease the total energy consumed, the
photo-transistor, its associated circuitry and the selected display
device are energized only when the user wishes to note the
time.
Accordingly, an object of the present invention is to provide an
improved watch having an electrically powered display system
suitable for use at all levels of illumination, including total
darkness.
Another object of the invention is to provide an improved
electrically powered display system comprising a liquid crystal
material for use at high levels of illumination and a solid state
self-luminous material for low levels of illumination.
A further object of the invention is to provide an improved
electrically powered display system incorporating a device for
determining the level of illumination and selecting an appropriate
display means.
Yet another object of the invention is to provide an improved
electrically powered display system which functions only when
energized by an exterior signal.
Still other objects and advantages of the invention will in part be
obvious and will in part be apparent from the specification.
The invention accordingly comprises an article of manufacture
possessing the features, properties, and the relation of elements
which will be exemplified in the article hereinafter described, and
the scope of the invention will be indicated in the claims.
BRIEF DESCRIPTION OF THE DRAWING
For a fuller understanding of the invention, reference is had to
the following description taken in connection with the accompanying
drawing, in which:
FIG. 1 is a plan view of an electrically powered digital display
system constructed in accordance with a preferred embodiment of the
present invention;
FIG. 2 is a cross-sectional elevational view of the device of FIG.
1;
FIG. 3 is a sectional view at an enlarged scale, taken along line
3--3 of FIG. 1; and
FIG. 4 shows schematically the arrangement of the components of the
display device.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A solid state electronic watch in accordance with the present
invention is generally indicated by the reference numeral 10. The
watch has a transparent base plate 11. The display portion of the
watch is made up of segments 12; in the embodiment shown in FIG. 1
each of the indicia has seven segments. Photo-transistor 13 which
is responsive to incident light controls a divider, oscillation and
driving circuit and crystal vibrator portion 14, using an MOS
(metal oxide-semiconductor) transistor. Day and date display
elements 15 and 16 are preferably mechanically activated. In a
preferred form, the day and the date are printed on planar,
ring-shaped disks which are advanced once a day by means of
electric plungers, for instance; it is not uneconomical of
electrical energy to advance these disks in this way because the
electro-mechanical activation elements need be energized only for a
short time.
While the advancement of the day and date disks 15 and 16 occurs
automatically, the time display consisting of the segments 12 is
activated only on pressing a switch 17. The selection of the
display mode is, of course, controlled by the photo-transistor 13,
but the level of incident light at which the choice changes can be
set manually. This adjustment is not shown. Similarly, the current
fed to self-luminous element 18 (FIG. 2) may also be adjusted by
means not shown.
A cell for holding liquid crystal material is formed by spacers 21
between cover 22 and transparent base plate 11. Liquid crystal
material 19 normally is transparent, but when a sufficiently high
voltage transverse to the cell is impressed between appropriate
segments 12 and transparent base plate 11, a desired numeral
becomes visible by reason of dispersion of incident light from the
surroundings. It should be noted that the brighter the incident
light, the more light is dispersed, and consequently the brighter
the indicia appear. Consequently, indication of the time by this
method is eminently satisfactory where the level of illumination is
high.
Where the level of illumination is low, or where illumination is
completely absent, photo-transistor 13 passes current through
appropriate display elements of gallium-arsenide crystal 18. As is
evident, the lower the level of the ambient illumination, the more
strongly will the self-luminous display elements appear.
Another embodiment is shown in FIG. 3 wherein a gallium-arsenide
display element, an MOS transistor and a liquid crystal cell are
mounted monolithically on one semi-conductor base plate 23. Base
plate 23 consisting of a sapphire or a spinel is separated from
cover 22 by sealing layer 24. Electrode 25 is provided for driving
liquid crystal 19 into the dispersion state. Self-luminous element
26 of gallium-arsenide is mounted on semi-conductor base plate 23.
Display cell 27 is so arranged that each desired segment is
illuminated from the rear by infra-red radiation emitted by
electroluminescent element 26. By using the liquid crystal material
in combination with the infra-red radiating self-luminous material,
visible light is produced and the power requirement is very low.
Where the available space is small as is the case with a watch, it
is desirable that the self-luminous display element and the liquid
crystal element be combined, but if desired, they may be arranged
separately, or one may overlie the other in part only.
The arrangement of the electrical components of the system is shown
in the electrical block diagram of FIG. 4 wherein the signal of
crystal oscillator 29 which constitutes the time standard for the
system is divided by divider 31 which employs an MOS transistor.
The output from divider circuit 31 is supplied to driving circuit
32 from which energy is then transferred either to liquid crystal
system 33 or self-luminous system 34. The selection is made by the
photo-transistor circuit 28. Since the energy expended in operating
liquid crystal display system 33 is in the range of microwatts,
this display system is termed "passive." The self-luminous display
system 34 consumes energy in the range of milliwatts and is
therefore termed "active." Where the base plate 23 is of
semi-conductor material as shown in FIG. 3, then the
photo-transistor 13 may be mounted in the base plate.
Although the day and the date displays are more conveniently
mounted on separate wheels, they are shown as one wheel 35 in FIG.
3. If desired, however, the day and the date may also be presented
by means of display elements similar to those used for indicating
time. Such an arrangement is shown diagrammatically in FIG. 4 by
boxes 36 and 37.
It will thus be seen that a novel solid state electronic watch of
high reliability is provided in which the time can be shown with an
extremely small expenditure of energy. Consequently, such a watch
will operate for extended periods of time between replacements of a
driving battery. By means of the system described, time is
displayed where the level of illumination is high with virtually no
expenditure of energy, and where the level of illumination is low,
at very low expenditure of energy. Operation by these alternate
means is made possible by the use of a photo-transistor with
associated circuitry, so adjusted that the method of display is
changed at a selected level of illumination.
It will thus be seen that the objects set forth above, among those
made apparent from the preceding description, are efficiently
attained and, since certain changes may be made in the above
article without departing from the spirit and scope of the
invention, it is intended that all matter contained in the above
description and shown in the accompanying drawing shall be
interpreted as illustrative and not in a limiting sense.
It is also to be understood that the following claims are intended
to cover all of the generic and specific features of the invention
herein described, and all statements of the scope of the invention
which, as a matter of language, might be said to fall
therebetween.
* * * * *