Electronic timepiece

Details Electronic timepiece Electronic timepiece

1998-07-08

2001-03-13

Miska, Vit (Department: 2859)

Horology: time measuring systems or devices

Chronological

With electro-optical display

C368S242000, C349S096000, C349S097000

Reexamination Certificate

active

06201770

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an electronic timepiece for measuring and displaying time, such as a wristwatch or a stopwatch.
2. Description of Related Art
Conventionally, there are widely known electronic timepieces which utilize flat displays, such as liquid crystal displays, for displaying numbers, characters, or other information. For example, as shown in
FIG. 10
, in an electronic timepiece utilizing a liquid crystal display device, a pair of polarizers
52
and
53
are placed on both sides of a liquid crystal panel
51
, and a light-emitting element
54
is disposed at the back side of the polarizer
53
. The pair of polarizers
52
and
53
are disposed such that, for example, their azimuthal angles are set to form a right angle.
During daytime, conventional electronic timepieces display numerical information or the like using external light, whereas during the night they display numerical information or the like using light emitted from the light-emitting element
54
, when necessary. Numerical information or the like is displayed by applying a predetermined voltage between the electrodes of the liquid crystal panel
51
, with the area to which voltage is not applied appearing as a white background or the like. In the figure, the area to which a voltage is applied to display information is represented as ON, whereas the background color area to which a voltage is not applied is represented as OFF.
As indicated by arrow P, when external light is used to produce background color of a display (liquid crystal panel is turned off), the linearly polarized light component of the external light or natural light, which is oriented parallel to the plane of the figure, passes through the polarizer
52
. Then, the polarization direction thereof is twisted 90 degrees by the liquid crystal panel
51
in an off state, causing the linearly polarized light to be oriented perpendicular to the plane of the figure. The linearly polarized light, which has passed through the polarizer
53
, is irregularly reflected by a surface of the light-emitting element
54
, and part of the irregularly reflected light is transmitted successively back through the polarizer
53
, the liquid crystal panel
51
, and the polarizer
52
to produce a white background which is perceived by any viewer.
As indicated by arrow Q, when numerical information or the like is to be displayed using external light (the liquid crystal panel
51
is turned on), linearly polarized light, which is oriented parallel to the plane of the figure, 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, the polarization direction of the linearly polarized light is maintained parallel to the plane of the figure, so that it is absorbed by the polarizer
53
. The portion that has absorbed the light appears black to any viewer.
As can be understood from the foregoing description, when external light is used, numbers or the like are displayed on a background having a color corresponding to that reflected from the light-emitting element
54
in order to display the time or other information.
On the other hand, as indicated by arrow C, when a background color is to be produced using light emitted from the light-emitting element
54
(the liquid crystal panel
51
is turned off), the linearly polarized light which is oriented perpendicular to the plane of the figure is separated from randomly polarized light emitted from the light-emitting element
54
by the polarizer
53
. Since the liquid crystal panel
51
is in an off state, the polarization direction of the linearly polarized light is twisted 90 degrees by the liquid crystal panel
51
, causing the linearly polarized light to be oriented parallel to the plane of the figure. Then, the polarized light passes through the polarizer
52
and is perceived by an outside viewer. The perceived color is the color emitted from the light emitting element
54
, which is ordinarily white.
As indicated by arrow D, when numerical information or the like is to be displayed using light emitted from the light emitting element
54
(the liquid crystal panel
51
is turned on), the linearly polarized light, which is oriented perpendicular to the plane of the figure, is separated from the light emitted from the light emitting element
54
by the polarizer
53
, passes through the liquid crystal panel
51
in an on state, and reaches the polarizer
52
. Here, the polarization direction of the linearly polarized light does not match the polarization direction of the polarizer
52
, so that the linearly polarized light is absorbed by the polarizer
52
. The portion of the polarizer which has absorbed the light, appears black to an outside viewer.
As can be understood from the foregoing description, when light from the light-emitting element
54
is used, numbers or the like are displayed in black or the like on a background having a color corresponding to the color emitted from the light emitting element
54
.
In the above-described conventional electronic timepiece, two polarizers
52
and
53
are disposed on both sides of the liquid crystal panel
51
. These polarizers are capable of absorbing linearly polarized light other than that having a predetermined polarization direction. Therefore, the intensity of the light, emitted to the outside for producing a background color or displaying numerical information or the like, may be greatly reduced, causing numerical information or the like to appear dark, and thus difficult to read.
In addition, in the above-described conventional electronic timepiece, only one color is reflected by or emitted from the light emitting element
54
within a plane, so that the background color and the displayed information, such as numerical information, have a single tone, which is not capable of sufficiently attracting the attention of any viewer.
SUMMARY OF THE INVENTION
In view of the above-described problems, an object of the present invention is to provide an electronic timepiece which is bright and easy to see. Another object of the present invention is to provide an electronic timepiece which provides a greater variety of display forms of numerical information or the like, and background colors, in order to easily attract the attention of any viewer.
To these end, according to the present invention, there is provided an electronic timepiece that may include
(1) a first polarization separator that transmits linearly polarized light polarized in a first direction while not transmitting therethrough light linearly polarized in a direction perpendicular to said one direction;
(2) a polarization changing element disposed at a position to receive the linearly polarized light from the first polarization separator, that selects either one of a state in which a polarization direction of the polarized light being transmitted is changed and a state in which the polarization direction of the polarized light being transmitted is not changed; and
(3) a second polarization separator that transmits the linearly polarized light polarized in a second direction and reflects light linearly polarized in a direction perpendicular to said second direction, the second polarization separator disposed opposite the first polarization separator with the polarization changing element interposed therebetween, the second polarization separator has, within a plane, a plurality of polarization separating portions reflecting light of different wavelengths.
In both of the above-described structures, an ordinary polarizer may be used for the first polarization separator. An ordinary polarizer may be composed of a film-like element capable of allowing linearly polarized light, polarized in a certain direction, of the incident natural light to leave the display device. It is formed by, for example, placing a polarization layer in a cellulose triacetate (TAC) protective layer.
A liquid crystal panel, for example, may be used for the aforementione

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