Horology: time measuring systems or devices – Displays or display device details – Optical
Reexamination Certificate
2001-09-24
2003-04-29
Miska, Vit (Department: 2841)
Horology: time measuring systems or devices
Displays or display device details
Optical
C345S050000, C345S053000, C349S138000, C349S142000
Reexamination Certificate
active
06556515
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a timepiece (electronic timepiece) with a liquid crystal display panel for displaying either time information or calendar information or both. This timepiece includes a digital display type wristwatch, table clock and wall clock each for displaying by characters or numerals only time, or a year, a month, a date, and days of the week (calendar information) in addition to time, various combination types of timepieces each for performing analog display of time by hands and digital display of calendar information, and a calendar timepiece for performing digital display of only calendar information, and the like.
BACKGROUND TECHNOLOGY
There are display methods in an electronic timepiece: a digital display mode of displaying time information and/or calendar information by characters or numerals using a liquid crystal display panel; and an analog display mode of displaying time by rotating hands (second hand, minute hand, hour hand) by a stepping motor.
Further, there are segment-type and matrix-type liquid crystal display panels for digital display, each for displaying information by characters and numerals. The segment type is positively used as a display portion for time and the like of an electronic timepiece because of ease for use and low manufacturing cost though it has low flexibility of display (display capacity) as compared to the matrix type.
A conventional segment-type liquid crystal display panel is structured such that two glass substrates has a liquid crystal layer sandwiched therebetween, one of the substrates has thereon a plurality of segment electrodes of segment-type electrodes forming a pattern of numeral or the like, and the other substrate has thereon an opposite electrode which is disposed to face the segment electrodes to perform a display by a pattern of combination of the segment electrodes through use of optical change in the liquid crystal layer caused by selectively applying voltage to the liquid crystal layer by means of the segment electrodes and the opposite electrode.
Hence, in such a conventional segment-type liquid crystal display panel, only a portion where the segment electrode and the opposite electrode overlap each other operates as a pixel area (display area), but a display state in the other area (background area) can not be controlled.
Accordingly, specifically in the case in which a mixed liquid crystal layer composed of a liquid crystal and a transparent solid substance is used as the liquid crystal layer, and when the liquid crystal layer has a scattering property where no voltage is applied thereto or when it has a transmission property where no voltage is applied thereto, it is impossible to easily reverse brightness and darkness of the display as in the liquid crystal display panel using a twisted nematic liquid crystal layer or the like and a polarizer.
Similarly, also when a mixed liquid crystal layer composed of a liquid crystal and a dichroic dye is used as the liquid crystal layer, it is impossible to easily reverse a transmission area and a colored area in the liquid crystal layer.
In the case of the liquid crystal display panel using a twisted nematic (TN) liquid crystal layer or a super twisted nematic (STN) liquid crystal layer and a polarizer, brightness and darkness of display can be reversed by an attaching angle of the polarizer but it is impossible to perform a display by optionally controlling brightness and darkness of the display area and the background area.
One example of the conventional segment-type liquid crystal display panel used as a time display portion of a timepiece is now explained with reference to the drawings.
FIG. 36
is a plane view showing an enlarged arrangement example of segment electrodes and an opposite electrode in the conventional segment-type liquid crystal display panel, and
FIG. 37
is a partially enlarged cross-sectional view of the liquid crystal display panel taken along a line XXXVII—XXXVII in FIG.
36
.
In this liquid crystal display panel, as shown in
FIG. 37
, a first substrate
1
that is a transparent glass substrate disposed at the upper side (visible side) and a second substrate
2
that is a transparent glass substrate disposed at the lower side (the opposite side to the visible side) are coupled together with a predetermined gap intervening therebetween with spacers and a sealing material which are not shown, and a liquid crystal layer
3
is sealed in the gap, which is composed of a mixed liquid crystal of a liquid crystal and a transparent solid substance.
On the first substrate
1
(inner surface), as clearly shown in
FIG. 36
, a plurality of segment electrodes
5
a
to
5
g
(referred to as “segment electrodes 5” when they are collectively called) are provided, which are made of a transparent conductive film. On the other hand, on the second substrate
2
(inner surface), an opposite electrode
6
made of a transparent conductive film is provided to face the entire region including the segment electrodes
5
a
to
5
g.
In this example, seven segment electrodes
5
a
to
5
g
take a pattern arrangement of the form of “8”, and gaps are provided between the segment electrodes
5
a
to
5
g
respectively. This is a so-called seven-segment type arrangement. Further, the segment electrodes
5
a
to
5
g
have respective wiring electrodes
12
which are respectively connected to segment electrode terminals (not shown) for individually applying external signals thereto.
Overlaps between the segment electrodes
5
a
to
5
g
and the opposite electrode
6
form a pixel area (display area)
32
, and the other portion forms a background area
33
.
The transparent solid substance in the liquid crystal layer
3
is formed in such a manner that a liquid crystal, in which an organic monomer is dissolved in advance, is injected into the gap between the first substrate
1
and the second substrate
2
and then applied with ultraviolet light.
A display by this liquid crystal display panel is performed utilizing anisotropy of optical refractive index of the mixed liquid crystal forming the liquid crystal layer
3
. More specifically, when optical refractive indices of the liquid crystal and the transparent solid substance which constitute the mixed liquid crystal are substantially the same, the display becomes transparent, and as both optical refractive indices become different, its scattering degree increases.
Actually, a predetermined signal (voltage) is selectively applied to the liquid crystal layer
3
by the segment electrodes
5
and the opposite electrode
6
which are in contact with both upper and lower surfaces of the liquid crystal layer
3
respectively to control the optical refractive index of the mixed liquid crystal, thereby performing a desired display.
For example, when numeral “1” is displayed, voltage is applied between the segment electrodes
5
c
and
5
g
, and the opposite electrode
6
, and not applied between the other segment electrodes
5
a
,
5
b
,
5
d
,
5
e
and
5
f
, and the opposite electrode
6
, whereby only portions of the pixel area
32
where the liquid crystal layer
3
is sandwiched between the segment electrodes
5
c
and
5
g
, and the opposite electrode
6
reduce in scattering degree (increase in transmittance) to have a scattering degree different from that of the other portion of the pixel area
32
and background area
33
, thereby enabling recognition of “1”.
In such a conventional liquid crystal display panel, however, scattering and transmission of the liquid crystal layer
3
at the pixel area
32
provided with the segment electrodes
5
can be controlled by applying voltage between the segment electrodes
5
and the opposite electrode
6
, but they at the background area
33
around the pixel area
32
can not be controlled, allowing the liquid crystal layer
3
at the background area
33
to always maintain the scattering state.
Accordingly, in order to bring the background area
33
into the transmission state, it is necessary to improve the material of the mixed liquid crystal or man
Citizen Watch Co. Ltd.
Miska Vit
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