Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
1999-07-06
2001-04-17
Epps, Georgia (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S270000, C359S273000, C359S275000, C427S125000
Reexamination Certificate
active
06219173
ABSTRACT:
TECHNICAL FIELD
BACKGROUND OF THE INVENTION
The present invention relates to an optical apparatus, and a manufacturing method therefor, for use in, for example, a reflection type display unit which uses deposition/dissolution of metal and which is employed in place of an electrochromic display unit to display characters or numerics or an X-Y matrix display or the like and in an optical filter which is capable of controlling light transmittance in a visible light region (wavelength 1=400 nm to 700 nm).
Hitherto, an electrochromic device (hereinafter called an “ECD”) which has been employed in a digital clock or the like is a non-luminous display unit using reflected light or transmitted light. Therefore, an advantage can be obtained in that fatigue can be prevented even if observation is performed for a long time. Moreover, advantages can be obtained in that a relatively low operating voltage is required and power consumption can be reduced. For example, a liquid ECD disclosed in Japanese Patent Laid-Open No. 59-24879 has been known, the foregoing liquid ECD being composed of an EC material which is an organic viologen molecule derivative which reversibly realizes a coloring/decoloring state.
However, the ECD composed of the viologen molecule derivative has a problem of unsatisfactorily low response speed and an insufficient shielding characteristic.
Therefore, a reflection type dimmer using deposition/dissolution of metal salts has attracted attention in place of the ECD. Thus, an electrochemical dimmer using deposition/dissolution of silver has been researched and developed.
FIGS. 13A
,
13
B and
14
show the structure of a cell of the foregoing conventional electrochemical dimmer.
As shown in
FIGS. 13A and 14
, a pair of transparent glass substrates
24
and
25
serving as display windows are disposed apart from each other for a predetermined distance. As shown in
FIG. 13A
, opposite working electrodes
22
and
23
made of ITO (Indium Tin Oxide prepared by doping tin into indium oxide) are disposed on the inner surfaces of the substrates
24
and
25
. Silver-salt solution
21
is placed between the opposite working electrodes
22
and
23
. Reference numeral
26
represents a counter electrode in the form of a silver plate disposed between the outer peripheries of the substrates
24
and
25
and also serving as a spacer.
The silver-salt solution
21
is prepared by dissolving silver bromide in dimethyl sulfoxide (DMSO). As shown in the drawing, the counter electrode
26
is disposed as an anode and the working electrodes
22
and
23
are disposed as a cathode. When a DC operating voltage is applied between the cathode and anode for a predetermined time, the following oxidation-reduction reactions occur on the cathode:
Ag
+
+e
−
→Ag
The obtained deposits of Ag cause the working electrodes
22
and
23
serving as the cathode to be converted from a transparent state to a coloring state.
FIG. 13B
is a diagram showing the principle of the above-mentioned phenomenon.
Since Ag is deposited on the working electrodes
22
and
23
as described above, specific color (for example, reflected light) caused from the deposited Ag can be observed through the display window. The filtering effect caused from coloring, that is, the transmittance of visible light (the depth of color) is changed in accordance with the level of the voltage or time for which the voltage is applied. Therefore, control of the voltage or the time enables the foregoing cells to act as the transmittance-variable display devices or optical filters.
When a DC voltage is applied between the counter electrode
26
and the working electrodes
22
and
23
in a direction opposite to the above-mentioned process, the working electrodes
22
and
23
, on which Ag has been deposited, serve as an anode. Thus, the following reactions occur:
Ag→Ag
+
+e
−
As a result, Ag deposited on the working electrodes
22
and
23
is dissolved in the silver-salt solution
21
. Thus, the state of the colored working electrodes
22
and
23
is changed from the colored state to a transparent state.
FIGS. 15 and 16
show another electrochemical dimming device. In this example, a pair of transparent glass substrates
4
and
5
forming a cell are disposed apart from each other by a predetermined distance as shown in
FIG. 15
which is a cross sectional view. Pairs of working electrode
2
a
,
2
b
,
2
c
,
2
d
and
2
e
and
3
a
,
3
b
,
3
c
,
3
d
and
3
e
each of which is made of ITO and which are disposed opposite to one another are formed on the inner surfaces of the substrates
4
and
5
. Counter electrodes
7
a
and
7
b
in the form of silver plates are disposed on the outer peripheries of the working electrodes
2
a
to
2
e
and
3
a
to
3
e
. The substrates
4
and
5
are disposed apart from each other by a predetermined distance by a spacer
6
. Silver-salt solution
1
is enclosed between the substrates
4
and
5
.
As shown in
FIG. 16
which is a plan view, the working electrodes
2
a
to
2
e
and
3
a
to
3
e
and the counter electrodes
7
a
and
7
b
are formed into a concentric pattern. The electrodes
2
a
and
3
a
,
2
b
and
3
b
,
2
c
and
3
c
,
2
d
and
3
d
,
2
e
and
3
e
and
7
a
and
7
b
are connected to operating power sources
8
a
,
8
b
,
8
c
,
8
d
,
8
e
and
8
f
through electric lines
9
a
,
9
b
,
9
c
,
9
d
,
9
e
and
9
f
in the form of thin chrome wires.
When predetermined potentials (V
1
, V
2
, V
3
, V
4
and V
5
, while V
6
is a referential potential at the counter electrodes
7
a
and
7
b
) are applied between opposite working electrodes
2
a
and
3
a
,
2
b
and
3
b
,
2
c
and
3
c
,
2
d
and
3
d
and
2
e
and
3
e
, silver can be deposited from the silver-salt solution
1
on each electrode which is the cathode. Thus, color can be developed. The transmittance of visible light (or the density of color) is changed in accordance with the level of the voltage or time for which the voltage is applied.
When the voltages are made such that V
1
=V
2
=V
3
=V
4
=V
5
, color can be developed in the overall region of the cell. Moreover, the density can uniformly be changed in accordance with the voltage or the time for which the voltage is applied. When the voltages are made such that, for example, |V
1
|<|V
2
|<|V
3
|<|V
4
|<|V
5
|, the density of the color is raised from the center to the periphery (that is, the transmittance is reduced). When the voltages are made such that |V
1
|>|V
2
|>|V
3
|>|V
4
|>|V
5
|, the transmittance is enlarged from the center to the periphery. The above-mentioned structure is effective to serve as an optical diaphragm for a CCD (Charge Coupled Device) for a TV camera or the like. The structure is able to sufficiently raise the density of integration of the CCD.
The above-mentioned electrochemical dimming device has a problem that the cost cannot be reduced because raw metal plates, such as the raw silver plates, are employed as it is to serve as the counter electrodes,
7
a
,
7
b
and
26
. Since the lifetime of the device has been enlarged, there arises another problem in that silver particles inactivated and deposited on the counter electrode float in the silver-salt solution. Thus, the inside portion of the device is contaminated, causing the transmittance, which is realized when the device is in the transparent state, to deteriorate. Moreover, the electrodes are short-circuited.
When decoloring of the working electrodes of the device shown in
FIGS. 15 and 16
is performed, silver is deposited on the counter electrodes
7
a
and
7
b
which are the cathode. At this time, electric lines of force of the electric field are concentrated to sharp portions of the electrodes, as shown in
FIG. 17
(for example,
7
b
is shown). It leads to a fact that silver is enlarged into grains each having a relatively lar
Imoto Hiroshi
Kawabata Masaru
Miyagaki Hideharu
Udaka Tooru
Yamada Shinichiro
Epps Georgia
Sonnenschein Nath & Rosenthal
Sony Corporation
Thompson Tim
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