Electrochromic display device

An electrochromic display device for use in automobiles, etc. comprises a plurality of mutually parallel strip-shaped display electrodes, a plurality of mutually parallel strip-shaped opposite electrodes, electrochemically-color-developing solid layers, solid electrolyte layers as intermediate layers, and an electrically insulating layer. The display electrodes and the opposite electrodes are arranged so as to three-dimensionally intersect each other. The electrochemically-color-developing solid layers and the solid electrolyte layers are present only at the spaces formed by the intersection between the display electrodes and the opposite electrodes. The electrically insulating layer occupies all portions other than the electrodes, electrochemically-color-developing solid layers and solid electrolyte layers within the device.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an electrochromic display device. More 
particularly, it relates to an electrochromic display device used, for 
example, in dashboards of automobiles, etc., which contains a matrix of 
coincident selection display elements capable of selectively coloring when 
electrified, thereby providing various pattern displays. 
2. Description of the Prior Art 
In conventional electrochromic display devices, display electrodes are 
provided on a substrate in the form of dots so as to form a pattern and a 
lead electrode is connected to each of these dot electrodes, while, as 
opposite electrodes, there can be used either a sheet-like electrode 
common to all dot electrodes, or electrodes provided in the form of dots 
corresponding to respective dots of display electrodes. In the latter 
case, a lead electrode must be connected to each dot, as in the case of 
display electrodes. 
In the structures of some of said conventionl electrochromic display 
devices, both the display electrodes and opposite electrodes are provided 
in the form of dots so as to form a pattern and lead electrodes need to be 
connected to all of these dots. Therefore, the structure becomes complex 
and the lead electrodes are increased in number and inevitably become 
thinner. As a result, the electrical resistance of each lead electrode is 
increased and the quantity of the electric current flowing through the 
lead electrodes becomes reduced, which affects both the response time and 
contrast of pattern. 
SUMMARY OF THE INVENTION 
The object of this invention is to provide an electrochromic display device 
free from the drawbacks of the conventional devices, giving a good 
response and a sharp contrast with no color unevenness and causing no 
cross-talk phenomenon. 
According to this invention, there is provided an electrochromic display 
device which comprises (a) a plurality of mutually parallel strip-shaped 
display electrodes, (b) a plurality of mutually parallel strip-shaped 
opposite electrodes, said display electrodes and said opposite electrodes 
being arranged so as to three-dimensionally intersect each other; (c) 
electrochemically-color-developing layers; (d) electrolyte layers as 
intermediate layers, said layers (of (c) and of (d)) existing between said 
electrodes (of (a) and of (b)) only at the spaces formed by the 
intersection of the electrodes of (a) and (b); and (e) an electrically 
insulating layer occupying all portions inside the device, other than (a), 
(b), (c) and (d). 
In this invention, it is not necessary to use electrodes provided in the 
form of dots so as to form a pattern and, moreover, the number of lead 
electrodes can be decreased considerably, compared with that in the 
conventional devices. Accordingly, providing a desired pattern becomes 
easier and the production efficiency of the devices can be enhanced. 
Furthermore, because of fewer lead electrodes, the use of thin lead 
electrodes, which was necessary in the conventional electrochromic display 
devices, becomes unnecessary, whereby both the response and contrast of 
pattern can be improved. Furthermore, as an important feature of the 
present device, no cross-talk occurs. 
The electrochromic display panel obtained according to this invention can 
be used for various applications such as meters to be mounted on 
automobiles, graphic displays, etc. It is possible to simultaneously 
exhibit plural information on one display panel.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
This invention will be illustrated hereinunder in detail referring to the 
drawing. 
The drawing shows a partially enlarged sectional perspective view of an 
example of an electrochromic display device of a transparent type 
according to this invention. The display device according to this 
invention comprises a plurality of mutually parallel strip-shaped display 
electrodes 3 and 4, a plurality of mutually parallel strip-shaped opposite 
electrodes 2, said display electrodes 3 and 4 and said opposite electrodes 
2 being arranged so as to three-dimensionally intersect each other, 
electrochemically-color-developing layers 5 and 6 and electrolyte layers 7 
and 8 as intermediate layers, said layers 5, 6, 7 and 8 existing between 
said display electrodes 3 and 4 and said opposite electrodes 2 only at the 
spaces formed by the intersection between these two kinds of electrodes 3 
and 4 and electrodes 2, and an electrically insulating material 1 
occupying all portions other than the elements 2, 3, 4, 5, 6, 7 and 8 
within the device. The device may be covered by upper and lower substrates 
9 and, since the display device shown in the drawing attached is of a 
transparent type, both the substrates are must therefore be transparent. 
Materials constituting portions 1 to 9 are already known and can be 
optionally selected. For example, the strip-shaped display electrodes and 
strip-shaped opposite electrodes may be composed of electroconductive 
inorganic oxides such as indium oxide (In.sub.2 O.sub.3) and/or tin oxide 
(SnO.sub.2). These electrodes may further contain, if necessary, antimony 
(Sb), cadmium (Cd) or lead (Pb). The electrochemically-color-developing 
layers may be produced from a substance such as tungsten trioxide, 
molybdenum trioxide or indium trioxide. The electrolyte layers as 
intermediate layers may be produced from a highly dielectric material such 
as lithium iodide (LiI), lithium nitride (Li.sub.3 N), magnesium fluoride 
(MgF.sub.2) or calcium fluoride (CaF.sub.2); a solid electrolyte such as 
sodium .beta.-alumina (Na--.beta.--Al.sub.2 O.sub.3); or a paste-like 
mixture such as urea, p-toluenesulfonic acid and glycerol. These two kinds 
of layers are produced by a process such as an electron beam process, 
vapor deposition process or a sputtering or spraying process. The 
transparent weight substrates 9 may be produced from glass or a high 
molecular substance film. Two substrates (upper and lower) may be used as 
shown in the drawing, however, either of them may be eliminated as 
necessary. 
An electrically insulating material constituting the electrically 
insulating layer 1 may be an inorganic material such as silica (SiO.sub.2) 
or yttria (Y.sub.2 O.sub.3) or may be an organic material such as an epoxy 
or a silicone. A silica insulating layer can be formed of the vapor 
deposition process or the sputtering process and an epoxy or silicone 
resin insulating layer can be formed by a screen printing process. 
The thickness of each layer may be optionally selected within the thickness 
ranges of respective conventional techniques. 
A specific example of this invention will be illustrated referring again to 
the drawing. 
On a transparent glass substrate 9 having a thickness of 1.1 mm, there was 
vapor-deposited a transparent electroconductive film having a thickness of 
400 .ANG. composed of 5% of SnO.sub.2 and 95% of In.sub.2 O.sub.3. On this 
film, there was formed a pattern of parallel strips by photoetching. After 
etching the film, the photoresist mask was removed. Thus, the parallel 
strip-shaped electrodes 3 and 4 were formed on the substrate 9. Then, on 
the substrate 9 and the strip-shaped electrodes 3 and 4, there was formed 
an insulating layer of SiO.sub.2 by the vacuum deposition process, and 
subsequently a photoresist film was produced on the whole area of the 
insulating layer, and a plurality of dots positioned on the strip-shaped 
electrodes 3 and 4 were etched to remove the insulating layer at the dots 
and subsequently the photoresist mask was removed. Then, a WO.sub.3 film 
having a thickness of 3000 .ANG. was vapor-deposited on the insulating 
layer and the exposed part of the electrodes corresponding to the above 
dots. A photoresist film was formed on the part of the WO.sub.3 film 
positioned at the above dots of the electrodes. Etching was conducted to 
remove the WO.sub.3 film on the insulating layer and subsequently the 
photoresist mask was removed, whereby electrochemically-color-developing 
layers 5 and 6 were formed in the form of dots on the strip-shaped 
electrodes 3 and 4. Then, an electrolyte layer of MgF.sub.2 having a 
thickness of 3000 .ANG. was formed on the insulating layer and the 
electrochemically-color-developing layers 5 and 6. A photoresist film was 
formed on the part of the electrolyte layer on the 
electrochemically-color-developing layers 5 and 6. Etching was conducted 
to remove the electrolyte layer on the insulating layer and the 
photoresist mask was removed, whereby electrolyte layers 7 and 8 as 
intermediate layers were formed on the color-developing layers 5 and 6, 
respectively. Thus, on each strip-shaped electrode were formed a 
color-developing layer and an electrolyte layer as intermediate layers. On 
the insulating layer and the electrolyte layers, there was vapor-deposited 
a transparent electroconductive film. Using the photoetching process, the 
electroconductive film was converted to parallel strip-shaped opposite 
electrodes 2 which contact with the electrolyte layers and 
three-dimensionally intersect the strip-saped electrodes 3 and 4 at an 
angle of 90.degree.. Finally, the insulating layer and the opposite 
electrodes 2 were covered with a transparent substrate 9. The insulating 
layer 1 occupied all spaces between the upper and lower substrates and had 
a thickness of 6800 .ANG.. 
In the display device obtained as above, when a voltage was applied between 
the electrodes 2 and 3, the electrochemically-color-developing layers 5 
displayed a blue color. 
When the polarity was changed between the electrodes 2 and 3, the color 
disappeared. In this display device, there was no cross-talk. That is, the 
electric current flowed normally (2.fwdarw.7.fwdarw.5.fwdarw.3) and there 
was no abnormal current flow due to leakage (e.g. 
2.fwdarw.8.fwdarw.6.fwdarw.4) and accordingly no color-developing of 
unintended dots.