Horology: time measuring systems or devices – Power supply details – Electrical
Reexamination Certificate
1998-07-30
2001-05-08
Roskoski, Bernard (Department: 2859)
Horology: time measuring systems or devices
Power supply details
Electrical
C368S242000, C368S083000, C368S234000
Reexamination Certificate
active
06229767
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a display device for displaying letters, numbers, patterns, and the like. The present invention also relates to an electronic watch for measuring and displaying time, such as a wristwatch or a stopwatch.
2. Description of Related Art
Hitherto, a display device, which displays numbers, letters, and other types of information by utilizing a flat display such as a liquid crystal display, has been widely known. As such a display device, for example, a display device shown in
FIG. 20
is well known, in which a pair of polarizers
52
and
53
are located on both sides of a liquid crystal panel
51
and a reflector
54
is located on the back side of one of the polarizers
53
. The pair of polarizers
52
and
53
are placed, for example, so that their polarization axes form a right angle.
In this conventional display device, information, such as numbers, are displayed by applying a predetermined on-state voltage between electrodes of the liquid crystal panel
51
, and a background of white or the like is displayed by not applying a voltage. In the figure, a region where an on-state voltage is applied is indicated by “ON”, and a region where a voltage is not applied is indicated by “OFF”.
In this display device, when a voltage is not applied to the liquid crystal panel
51
, as shown by arrow P, linearly polarized light of the external light, that is, natural light that is polarized parallel to the plane of the page passes through the polarizer
52
, and is turned into linearly polarized light polarized perpendicular to the plane of the page with its polarization direction twisted through an angle of 90° by the liquid crystal panel
51
in the off state. After passing through the polarizer
53
, this linearly polarized light is irregularly reflected by the surface of the reflector
54
. A part of the irregularly reflected light sequentially passes through the polarizer
53
, the liquid crystal panel
51
, and the polarizer
52
, and is visible to an outside viewer. This part is thereby perceived as a reflection image from the reflector
54
, normally, as a uniform white background.
Next, when an on-state voltage is applied to the liquid crystal panel
51
, as shown by arrow Q, linearly polarized light that is parallel to the plane of the page is separated from the external light by the polarizer
52
, and passes through the liquid crystal panel
51
. Since the liquid crystal panel
51
is in an on state at this time, the polarization direction of the linearly polarized light is kept parallel to the plane of the page without being twisted, and therefore, this linearly polarized light is absorbed by the polarizer
53
. As a result, this part is perceived as a dark color, such as black, from outside.
As mentioned above, in this conventional display device, information, such as numbers, is displayed in a dark color of black or the like on a reflection image from the reflector
54
, normally, on a uniform white background.
Furthermore, for example, Japanese Unexamined Patent Publication No. 52-55565 discloses the technique of forming the reflector
54
, which constitutes a display section of an electronic watch, of a solar battery. According to this electronic watch, a power supply for watch driving is charged with an electromotive force of the solar battery, and the liquid crystal panel and the like are driven by the charged watch-driving power supply.
As mentioned above, while it has been already known that the reflector
54
in the display device is formed of a solar battery, since the surface of the solar battery usually has a dark color, such as black or dark blue, when a background is displayed by reflecting external light by the reflector
54
, as shown by arrow P in
FIG. 20
, it is displayed in a dark color of black or the like. On the other hand, information, such as numbers, is displayed in a dark color of black or the like by using a light absorption property of the polarizer
53
, as shown by the arrow Q.
In short, when the reflector is formed of a solar battery in the conventional display device, information, such as numbers, is displayed in a dark color of black or the like on a background of a similar dark color such as black. Therefore, the information, such as numbers, cannot be clearly distinguished. Consequently, the technique of placing a solar battery within a display plane of a watch or the like has not yet been put into actual use. When the solar battery is used, it cannot help being located outside the display plane of the watch or the like.
SUMMARY OF THE INVENTION
The present invention has been made in view of the problems mentioned above, and a first object of the present invention is to permit information, such as numbers, to be clearly distinguished from a background when a solar battery is placed within a display plane of a watch or the like.
A second object of the present invention is to produce a display on a watch or the like using light emitted from a light emitting device in a dark place where external light does not enter when a solar battery is placed within a display plane of the watch or the like.
(1) In order to achieve the above first object, a display device of the present invention includes (a) a first polarization separator that transmits linearly polarized light polarized in a first direction and does not transmit linearly polarized light polarized in a direction perpendicular to the first direction, (b) a polarization changing element positioned to receive linearly polarized light emerging from the first polarization separator and that selects between a state of changing the polarization direction of polarized light transmitted therethrough and a state of not changing the polarization direction, (c) a second polarization separator disposed opposite to the first polarization separator with the polarization changing element interposed therebetween, the second polarization separator transmitting linearly polarized light polarized in a second direction and reflecting linearly polarized light polarized in a direction perpendicular to the second direction, and (d) a solar battery disposed opposite to the polarization changing element with the second polarization separator disposed therebetween, the solar battery receiving external light and converting the external light into electric energy.
In the above structure and structures that will be described below, the first polarization separator has the polarization separating function of transmitting linearly polarized light of light incident from the side of a viewer that is polarized in a first predetermined direction and not transmitting other polarized light, and furthermore, of transmitting linearly polarized light of light incident from an opposite side to the viewer that is polarized in the first direction and not transmitting other polarized light.
Furthermore, the second polarization separator has the polarization separating function of transmitting linearly polarized light of light incident from the side of the polarization changing element that is polarized in a second direction, reflecting other polarized light, and furthermore, of transmitting linearly polarized light of light incident from an opposite side to the polarization changing element that is polarized in the second direction.
The first polarization separator may be formed of a conventional polarizer. A conventional polarizer is a polarized light separation element having a property of transmitting linearly polarized light of incident light that is polarized in one direction and not transmitting other linearly polarized light. For example, it may be formed by sandwiching a polarizing layer between protective layers of TAC (Triacetyl Cellulose).
The polarization changing element may be formed of, for example, liquid crystal. As the liquid crystal, various kinds of liquid crystals may be used, such as TN (Twisted Nematic) liquid crystal, STN (Super-Twisted Nematic) liquid crystal, and ECB (Electrically Controlled Birefringence) liquid crystal. The
Arikawa Yasuo
Miyazawa Eiichi
Oliff & Berridg,e PLC
Roskoski Bernard
Seiko Epson Corporation
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