Electrochromic device and method for manufacturing the same

There is provided an electrochromic device comprising a pair of transparent substrates facing each other, a pair of transparent electrodes facing each other between the pair of transparent substrates, and an electrochromic layer and a transparent ion conductive layer sandwiched by the pair of transparent electrodes, wherein at least the electrochromic layer and the transparent ion conductive layer are coated with a resin in a state that carrier precursor in the electrochromic layer and in the transparent ion conductive layer is ionized. As a result, film breakage of the electrochromic device and peeling off of the sealing resin and the sealing substrate are prevented, thus improving the durability of the electrochromic device.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an electrochromic device and a method for 
manufacturing the same, which device is used for a display device, a 
transmittance-variable filter, etc. 
2. Related Background Art 
Application of an electrochromic device (hereinafter referred to simply as 
"EC device"), colored or colorless (approximately transparent), 
corresponding to an applied electrical field to a display device, a 
transmittance-variable filter, etc. has been investigated, because the EC 
device, compared with ordinary liquid crystal devices and the like, has 
high optical transmittance in a colorless state, is unaffected by 
polarization, and exhibits a memory effect. 
As an EC device of entirely solid type, there is known by, for example, 
U.S. Pat. No. 3,521,941 a four-layered structure device in which an 
a-WO.sub.3 film, an insulating layer such as SiO.sub.2 or CaF.sub.2, and 
an Au electrode are successively stacked on Nesa glass (SnO.sub.2 : 
transparent electrode). Also, Japanese Patent Publication No. 60-31355 and 
U.S. Pat. No. 4,350,414, etc. disclose a five-layered structure EC device 
in which an In.sub.2 O.sub.3 transparent electrode, an oxidative coloring 
EC layer consisting of Ir(OH).sub.x, a transparent ion conductive layer 
(solid electrolyte layer) consisting of Ta.sub.2 O.sub.5, a reductive 
coloring EC layer consisting of WO.sub.3, and an In.sub.2 O.sub.3 
transparent electrode are successively formed on a transparent substrate 
such as glass, to thereby improve speed of response and repeated 
durability (i.e. durability under driving condition). 
It is known that these EC devices are apt to be affected by ambient 
humidity and show no coloring/bleaching at all particularly in a vacuum, 
as described in S.K. Deb: Phil. Mag. 27 (1973) 801., Matsuhisa and Masuda: 
Shinku (Vacuum), vol. 11 (1980), pp. 503-514, and Japanese Patent 
Publication No. 4-35735. 
To improve the durability of the EC device by preventing it from being 
affected by ambient humidity, there is disclosed a technique of sealing an 
EC device using a sealing substrate such as a glass substrate and a 
sealing resin such as epoxy resin in Japanese Patent Publication No. 
4-35735, Japanese Patent Application Laid-Open No. 63-294536, etc. 
The above-described Japanese Patent Publication No. 4-35735 also discloses 
that an EC device is sealed after confirming that the EC material contains 
10-30 vol. % of water to prevent generation of irregular coloring after 
sealing and lowering of performance after weathering resistance test. 
However, the above-described devices have a problem that repeated coloring 
and loss of color generates gas in the EC device, whereby volume expansion 
of the EC device is caused to induce film breakage of the EC device and 
peeling off of the sealing resin or the sealing substrate, followed by 
deterioration of external appearance (scattering of light). 
The coloring and loss of color reactions in the above-described 
four-layered structure EC device comprising a WO.sub.3 layer and an 
insulating layer are presumably expressed by the following formulae: 
(1) Coloring reactions 
EQU 2nH.sub.2 O .fwdarw.2nH.sup.+ +2nOH.sup.- 
EQU 2WO.sub.3 +2nH.sup.+ +2ne.sup.- .fwdarw.2H.sub.n WO.sub.3 
EQU 2nOH.sup.31 .fwdarw.nH.sub.2 O +(1/2)nO.sub.2 .uparw.+2ne.sup.31 
(2) Loss of color reactions 
EQU 2H.sub.n WO.sub.3 .fwdarw.2WO.sub.3 +2nH.sup.+ +2ne.sup.- 
EQU 2nH.sup.+ +2ne.sup.- .uparw.nH.sub.2 .uparw. 
Further, the coloring and loss of color reactions in the above-described 
five-layered structure EC device comprising an Ir(OH).sub.x layer further 
added to the WO.sub.3 layer and the insulating layer are presumably 
expressed by the following formulae: 
(3) Coloring reactions 
EQU nH.sub.2 O .fwdarw.nH.sup.+ +nOH.sup.- 
EQU WO.sub.3 +nH.sup.+ +ne.sup.- .fwdarw.H.sub.n WO.sub.3 
EQU nOH.sup.- +Ir(OH).sub.x Ir(OH).sub.n+x +ne.sup.- 
(4) Loss of color reactions 
EQU H.sub.n WO.sub.3 .fwdarw.WO.sub.3 +nH.sup.+ +ne.sup.- 
EQU Ir(OH).sub.n+x +ne.sup.- .fwdarw.nOH.sup.- +Ir(OH).sub.x 
EQU nH.sup.+ +nOH.sup.- .fwdarw.nH.sub.2 O.uparw. 
Formulae (1) and (2) show that the EC device of four-layered structure 
generates oxygen gas and hydrogen gas in the coloring and loss of color 
reactions. Formulae (3) and (4) represent that in the EC device of 
five-layered structure, the decomposition and re-composition of water 
occur in a reversible fashion, and that coloring and loss of color are 
repeated while no oxygen gas nor hydrogen gas generates. The H.sub.2 O in 
the above formulae exists mainly in the transparent ion conductive layer 
and dissociates into H.sup.+ and OH.sup.31 by application of an electric 
field. These H.sup.+ and OH.sup.- are substances which conduct charge 
transfer through the transparent ion conductive layer, i.e., carrier. 
Accordingly, the above mentioned H.sub.2 O can be regarded as a carrier 
precursor. To sustain such reversible reactions, a balance is necessary to 
be kept between the amount of substance (mainly, reductive coloring EC 
substance, e.g., WO.sub.3) in the reductive coloring EC layer capable of 
reacting with H.sup.+ ions and the amount of substances (mainly, oxidative 
coloring EC substance, e.g., Ir(OH).sub.x) in the oxidative coloring EC 
layer capable of reacting with OH.sup.- ions. 
However, even in the above-described five-layered EC device, when coloring 
and loss of color are repeated, the balance between the reacted amount of 
substance in the reductive coloring EC layer and the reacted amount of 
substance in the oxidative coloring EC layer will be lost, thereby 
generating oxygen gas and/or hydrogen gas. 
Further, when a plurality of EC devices are manufactured using the method 
described in Japanese Patent Publication No. 4-35735 in which sealing is 
carried out after incorporating water into the EC material, there arises a 
problem that a slight difference in the manufacturing conditions (such as 
manufacturing atmosphere) for the respective EC devices causes differences 
in the coloring speed and speed of loss of color, and in the amount of 
change in coloring concentration. 
SUMMARY OF THE INVENTION 
The present invention has been accomplished in view of the above described 
circumstances, and an object of the present invention is to provide an EC 
device that is free from problems such as film breakage of EC device, 
peeling off of a sealing resin or a sealing substrate, and deterioration 
of external appearance, resulting from repeated coloring and loss of 
color, irrespective of the layer-structure of the EC device. 
Further, another object of the present invention is to provide an EC device 
that exhibits a good repeatability of specified coloring speed and speed 
of loss of color and amount of change in coloring concentration (or 
contrast) after sealing. 
In addition, still another object of the present invention is to provide an 
EC device that has excellent repeated durability and exhibits stable 
coloring speed and speed of loss of color, and stable amount of change in 
coloring concentration. 
To attain the above-described objects, according to the present invention, 
there is provided an electrochromic device comprising a pair of 
transparent substrates facing each other, a pair of transparent electrodes 
facing each other between the pair of transparent substrates, and an 
electrochromic layer and a transparent ion conductive layer sandwiched by 
the pair of transparent electrodes, wherein at least the electrochromic 
layer and the transparent ion conductive layer are coated with a resin 
having a Young's modulus of 8-60 Kgf/cm.sup.2. 
Further, according to the present invention, there is provided an 
electrochromic device comprising a pair of transparent substrates facing 
each other, a pair of transparent electrodes facing each other between the 
pair of transparent substrates, and an electrochromic layer and a 
transparent ion conductive layer sandwiched by the pair of transparent 
electrodes, wherein at least the electrochromic layer and the transparent 
ion conductive layer are coated with a resin in a state that a carrier 
precursor in the electrochromic layer and in the transparent ion 
conductive layer is ionized. 
Furthermore, according to the present invention, there is provided a method 
for manufacturing an electrochromic device comprising a pair of 
transparent substrates facing each other, a pair of transparent electrodes 
facing each other between the pair of transparent substrates, and an 
electrochromic layer and a transparent ion conductive layer sandwiched by 
the pair of transparent electrodes, the method comprising coating at least 
the electrochromic layer and the transparent ion conductive layer with a 
resin having a Young's modulus of 8-60 Kgf/cm.sup.2. 
Still further, according to the present invention, there is provided a 
method for manufacturing an electrochromic device comprising a pair of 
transparent substrates facing each other, a pair of transparent electrodes 
facing each other between the pair of transparent substrates, and an 
electrochromic layer and a transparent ion conductive layer sandwiched by 
the pair of transparent electrodes, the method comprising coating at least 
the electrochromic layer and the transparent ion conductive layer with a 
resin in a state that a carrier precursor in the electrochromic layer and 
in the transparent ion conductive layer is ionized.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Now the description is made of the preferred embodiments of the EC device 
according to the present invention with reference to the drawings. 
FIG. 1 is a schematic cross sectional view showing an example of the EC 
device of the present invention. The EC device according to a preferred 
embodiment of the invention is constituted of a five-layered structure in 
which, on a transparent substrate 1, a transparent electrode (transparent 
electroconductive layer) 2a, an oxidative coloring EC layer 3, a 
transparent ion conductive layer (solid electrolyte layer) 4, a reductive 
coloring EC layer 5, and a transparent electrode (transparent 
electroconductive layer) 2b are successively stacked. A transparent 
substrate (sealing substrate) 7 is provided so as to face the transparent 
electrode 2b. Between the sealing substrate 7 and the transparent 
electrode 2b, and at the periphery of the respective layers positioned 
between the transparent electrode 2a and the transparent electrode 2b, a 
transparent resin (sealing resin) 6 is provided. That is, the EC device 10 
is sealed with the resin. The sealing resin 6 plays not only a role of 
bonding the transparent electrode 2b and the transparent substrate 7 but 
also a role of coating the respective layers of the oxidative coloring EC 
layer 3, the transparent ion conductive layer 4, and the reductive 
coloring EC layer 5 to thereby prevent these layers from being exposed to 
outside air. In this state, the externally connecting portions of the 
transparent electrodes 2a and 2b may be exposed to outside air. The 
externally connecting portions may be wired in a desired pattern. Also, 
the transparent substrates 1 and 7 play not only a role of physically 
protecting the EC device 10 but also a role of further reducing the affect 
of outside air to the EC device. 
Of the above-described layers, the oxidative coloring EC layer 3 may be a 
layer consisting of a mixture of an oxidative coloring EC substance and a 
metal oxide, (hereinafter referred to simply as "mixture layer"). 
Alternatively, a mixture layer may be arranged between the oxidative 
coloring EC layer 3 and the transparent ion conductive layer 4, apart from 
the oxidation coloring EC layer 3, to thereby form an EC device having a 
six-layered structure. 
As the transparent substrate 1 and the sealing substrate 7, a glass 
substrate is preferably used. Nevertheless, substrates of various kinds of 
transparent materials such as plastic may be used depending on the use of 
the EC device. It is preferable that the surface of the transparent 
substrate 1 at the side opposite to the transparent electrode 2a and a 
back surface of the substrate 7 facing to the transparent substrate 2b are 
provided with a single layer film consisting of a dielectric such as 
Al.sub.2 O.sub.3, TiO.sub.2, MgF.sub.2, etc. or with a plurality of the 
single layer films as built up, thereby effecting the anti-reflection 
coating (ARC). 
As the transparent electrodes 2a and 2b, there may be used In.sub.2 
O.sub.3, SnO.sub.2, ITO (Indium Tin Oxide). However, from the point of 
optical characteristics (light-transmittance) and a resistance value, ITO 
is preferable, and an ITO consisting of In.sub.2 O.sub.3 and SnO.sub.2 at 
a rate of approximately 95:5 is more preferable. 
The oxidative coloring EC layer 3 preferably contains at least one selected 
from the group consisting of Co, Ni, Fe, Ir, Cu, Ru, Rh, Pd, Pt, Cr, Dy, 
and Er. These elements exist therein as a metallic simple substance (M), 
its oxide (MO.sub.x), its hydroxide (M(OH).sub.x), its oxyhydroxide 
(MO.sub.x (OH).sub.y), or a mixture thereof. Further the oxidative 
coloring EC layer 3 is more preferable to be made of a substance or a 
mixture of two or more substances selected from the group consisting of 
iridium, iridium oxide, iridium hydroxide, iridium oxyhydroxide cobalt, 
cobalt oxide, cobalt hydroxide, cobalt oxyhydroxide, nickel, nickel oxide, 
nickel hydroxide, nickel oxyhydroxide, from the viewpoint of optical 
characteristics and repeated durability. 
A preferable thickness of the oxidative coloring EC layer 3 is from 1-50 
nm. When the thickness of the layer is smaller than 1 nm, the repeated 
durability degrades, and when the thickness is larger than 50 nm, the 
absorbance increases. 
When a mixture layer is formed, the oxidative coloring EC substance used in 
the mixed layer preferably contains at least one selected from the group 
consisting of Co, Ni, Fe, Ir, Cu, Ru, Rh, Pd, Pt, Cr, Dy, and Er. These 
elements exist therein as a metallic simple substance (M), its oxide 
(MO.sub.x), its hydroxide (M(OH).sub.x), its oxyhydroxide (MO.sub.x 
(OH).sub.y), or a mixture thereof. The oxidative coloring EC substance is 
further preferable to be consisting of a substance or a mixture of two or 
more substances selected from the group consisting of iridium, iridium 
oxide, iridium hydroxide, iridium oxyhydroxide, cobalt, cobalt oxide, 
cobalt hydroxide, cobalt oxyhydroxide, nickel, nickel oxide, nickel 
hydroxide, nickel oxyhydroxide, from the viewpoint of optical 
characteristics and repeated durability. 
The metal oxide used in the mixture layer is preferably the one that has a 
high light transmittance. The metal oxide is preferably a substance which 
does not exhibit reductive coloring electrochromism under application of a 
practical voltage. A preferred metal oxide is one of or a mixture of two 
or more selected from the group consisting of TiO.sub.2, Ta.sub.2 O.sub.5, 
ZrO.sub.2, HfO.sub.2, Y.sub.2 O.sub.3, Al.sub.2 O.sub.3, SiO.sub.2, and 
SnO.sub.2. 
In the mixture layer, the weight ratio of the oxidative coloring EC 
substance to the metal oxide is preferably 0.02.ltoreq.(oxidative coloring 
EC substance/metal oxide) .ltoreq.1. When the ratio is greater than 1, the 
absorbance increases, and when the ratio is smaller than 0.02, the 
coloring speed (speed of response) reduces and the durability degrades. 
A preferable thickness of the mixture layer is 10-5000 nm from the point of 
speed of response and light transmittance. When the layer thickness is 
greater than 5000 nm, the absorbance increases, and when the thickness is 
smaller than 10 nm, the coloring speed (speed of response) decreases and 
the durability degrades. 
The transparent ion conductive layer (solid electrolyte layer) 4 preferably 
consists of one or a mixture of Ta.sub.2 O.sub.5, ZrO.sub.2, SiO.sub.2, or 
MgF.sub.2, and Ta.sub.2 O.sub.5 is particularly preferable from the 
viewpoint of optical characteristics and repeated durability. 
The reductive coloring EC layer 5 preferably consists of one or a mixture 
of WO.sub.3, MoO.sub.3, Nb.sub.2 O.sub.5, and WO.sub.3 is particularly 
preferable from the viewpoint of coloring speed. Further, forming the 
reduction coloring EC layer 5 using a mixture of WO.sub.3 and MoO.sub.3 
can provide an EC device which becomes black on coloring. 
A preferable thickness of the respective layers except for the oxidative 
coloring EC layer 3 and for the mixture layer is 1-5000 nm. The thickness 
is determined based on the required optical characteristics, repeated 
durability, and the like. 
According to a first aspect of the present invention, the sealing resin 6 
is a resin having an elasticity in terms of a Young's modulus within a 
range of 8-60 Kgf/cm.sup.2. The Young's modulus was determined by tensile 
test carried out at a stress rate of 10 mm/min. A preferable sealing resin 
6 is a silicone resin, an urethane resin, a modified acrylate resin, and 
an epoxy resin. These resins preferably have the Young's modulus in the 
range described above. The preferred range of Young's modulus for 
respective specified resins is determined by the adhesion strength of the 
resin and other characteristics. The preferable range of Young's modulus 
is 10-60 Kgf/cm.sup.2 for a silicone resin, 8-34 Kgf/cm.sup.2 for an 
urethane resin, 8-35 Kgf/cm.sup.2 for a modified acrylate resin, and 10-40 
Kgf/cm.sup.2 for an epoxy resin. 
According to the first aspect of the present invention, the above-described 
structure allows the sealing resin to absorb the deformation of the EC 
device due to volume expansion caused by gas generation induced from 
repeated coloring and loss of color, thereby preventing substantial damage 
and deterioration of external appearance. The effect is obtained by using 
a resin having Young's modulus within a range given above. Thus, the 
deterioration of characteristics of the EC device caused by sealing can be 
prevented. 
The EC device according to the second aspect of the present invention is 
featured by that the carrier precursor existing in the EC device is 
ionized before conducting the sealing with a resin, and that the sealing 
with a resin is conducted in a state that the carrier precursor is ionized 
(i.e., in a state that the carrier precursor is converted into carriers). 
The term "carrier precursor" as used in the specification and claims 
refers to those substances which easily dissociate into cations and anions 
by application of an electric field and contribute to charge transfer in 
the transparent ion conductive layer. Taking into account the charge 
transfer rate, it is preferred that the carrier precursor is a substance 
which dissociates into small ions, such as a hydride, a Li compound and 
the like. As the carrier precursor, there can be specifically included 
H.sub.2 O, LiI, Li.sub.3 N, Li.sub.2 WO.sub.4 and the like, with H.sub.2 O 
being preferred in view of charge transfer rate and of no need of any 
special injecting equipment. 
The carrier precursor existing in the transparent ion conductive layer 4 is 
ionized to form carriers, which migrate to the reduction coloring EC layer 
or the like. This facilitates the incorporation of the ionized substances 
into the transparent ion conductive layer. 
Further, application of a voltage induces coloring of the respective EC 
layers. By monitoring the coloring density and performing the 
resin-sealing when a desired coloring density has been attained, it is 
possible to reduce the dispersion of the coloring speed and speed of loss 
of color and of the amount of change in coloring density (contrast) after 
sealing as conventionally caused by a slight difference in EC device 
manufacturing conditions (manufacturing atmosphere, etc.). 
The EC device of the embodiment is structured by successively stacking the 
transparent electrode 2a, the oxidative coloring EC layer 3, the 
transparent ion conductive layer 4, the reductive coloring EC layer 5, and 
the transparent electrode 2b, on the transparent substrate 1. On the 
contrary, the EC device may be structured by successively stacking in the 
inverse order, the transparent electrode, the reductive coloring EC layer, 
the transparent ion conductive layer, the oxidative coloring EC layer, and 
the transparent electrode, on the transparent substrate. 
Next, the description is made of a manufacturing method of the EC device 10 
according to an embodiment of the present invention. 
First, the transparent electrode (transparent electroconductive layer) 2a 
is formed on the transparent substrate 1 by a known film-forming method 
such as vacuum deposition, sputtering, ion plating, CVD, etc. 
Next, the oxidative coloring EC layer 3 is formed on the transparent 
electrode 2a by a known film-forming method such as vacuum deposition, 
sputtering, ion plating, CVD, etc. 
Next, the transparent ion conductive layer 4 is formed by a known 
film-forming method described above. 
Then, the reductive coloring EC layer 5 and the transparent electrode 
(transparent electroconductive layer) 2b are successively formed by a 
known film-forming method described above. 
Finally, the EC device 10 is resin-sealed using the sealing resin 6 and the 
sealing substrate 7. 
Here, the description is made of the resin-sealing method according to the 
second aspect of the present invention by referring to FIG. 2. 
FIG. 2 is a schematic cross sectional view showing an example of an EC 
device immediately before the sealing in the manufacturing process of the 
EC device according to the second aspect of the present invention. The 
same component as in FIG. 1 has the same reference numeral in FIG. 1, and 
the description thereof is omitted. The EC device 20 shown in FIG. 2 is a 
four-layered EC device having no oxidative coloring EC layer. Hereinafter, 
the four layers are collectively referred to as a single four-layered 
structure member 8. The reference numeral 9 denotes a constant voltage 
power source that is connected to the transparent electrodes 2a and 2b to 
apply a voltage between these electrodes. 
In the resin-sealing method according to the second aspect of the present 
invention, the carrier precursor electrolyte in the four-layered structure 
body is ionized by applying a voltage, using the constant voltage power 
source 9, between the transparent electrodes 2a and 2b before conducting 
the resin-sealing, and, the resin-sealing is carried out under the 
application of voltage to form a shape similar to one as shown in FIG. 1. 
Specifically, by ionizing the carrier precursor while controlling the 
voltage applied between the electrodes so as to attain a range of color 
concentration within which the coloring and loss of color of the EC device 
20 is reversible, and more preferably so as to further obtain a specified 
coloring speed (for example, a speed to give an optical density change 
.DELTA.OD=1.0 within 2 sec. when a voltage of 3V is applied), it is 
possible to stabilize the characteristics such as coloring speed and speed 
of loss of color after sealing and amount of change in color 
concentration. 
Further, when water is used as the carrier precursor and ionized into 
H.sup.+ and OH.sup.- by application of a voltage, controlling the ionizing 
amount and monitoring the coloring density as described above makes it 
possible to incorporate a necessary amount of water from the atmosphere 
into the EC device, especially into the transparent ion conductive layer 
with a good reproducibility, regardless of humidity change in the 
atmosphere. Thus, any special control of the sealing environment is not 
necessary, and an injection equipment conventionally needed when a Li 
compound or the like is used as the carrier precursor becomes unnecessary. 
Hereinafter, the present invention will be described in more detail by 
employing the following Examples and Comparative Examples. 
EXAMPLE 1 
A glass substrate having an anti-reflection film provided on one surface 
was subjected to vacuum deposition of ITO on the other surface thereof 
under the conditions of a substrate temperature=300.degree. C. and an 
O.sub.2 partial pressure=5.times.10.sup.-2 Pa to form a transparent 
electrode (transparent electroconductive layer) having a 150 nm-thickness 
layer as a first layer. 
Next, the transparent electrode was subjected to film formation by high 
frequency sputtering using a target of metallic iridium under the 
conditions of a substrate temperature=room temperature, a mixed gas 
pressure of water vapor and argon=5 Pa, and a flow rate ratio of water 
vapor to argon=3, thus forming an oxidative coloring EC layer having a 
thickness of 5 nm as a second layer. The input power applied to the 
metallic iridium target was 130 W. The oxidative coloring EC layer 
contains iridium oxide and iridium hydroxide as main components. 
Next, the oxidative coloring EC layer was subjected to vacuum deposition of 
tantalum pentoxide under the conditions of a substrate 
temperature=300.degree. C. and an O.sub.2 partial 
pressure=3.times.10.sup.-2 Pa to form a transparent ion conductive layer 
having a thickness of 300 nm as a third layer. 
Next, the transparent ion conductive layer was treated by vacuum deposition 
of tungsten trioxide under the conditions of a substrate 
temperature=300.degree. C. and an O.sub.2 partial 
pressure=5.times.10.sup.-2 Pa to form a reductive coloring EC layer having 
a thickness of1000 nm as a fourth layer. 
Subsequently, the reductive coloring EC layer was subjected to deposition 
of ITO by high frequency ion plating under the conditions of a substrate 
temperature=300.degree. C., an O.sub.2 partial pressure=5.times.10.sup.-2 
Pa, and a high frequency power of 150 W to form a transparent electrode 
(transparent conductive layer) having a thickness of 450 nm as a fifth 
layer. 
Finally, the resin-sealing was conducted using a sealing substrate and a 
modified acrylate resin having 10 Kgf/cm.sup.2 of Young's modulus. 
Following the above-described procedure, an EC device having a five-layered 
structure as shown in FIG. 1 was obtained. 
When a voltage was applied to the transparent electrodes 2a and 2b of the 
device with the transparent electrode 2b being used as a negative 
electrode, an oxidation-reduction reaction occurred to effect coloring. 
When a voltage was applied to the electrodes with the transparent 
electrode 2b being used as a positive electrode, a reverse 
oxidation-reduction reaction occurred to effect loss of color. 
In the EC device of this Example, repeating coloring and loss of color 
results in expansion of the film of the EC device due to generation of a 
gas. However, the sealing resin having elasticity absorbs the film 
expansion to suppress the breakage of the film and the peeling off of the 
sealing resin and the sealing substrate. In addition, the sealing resin 
reduces the effect of atmospheric humidity on the oxidation coloring EC 
layer, the transparent ion conductive layer, and the reduction coloring EC 
layer. The sealing substrate also plays a role of protecting the sealing 
resin. 
When a voltage of 3 V was applied between the electrodes of the EC devices 
of this Example, and when the coloring and loss of color were repeated 
such that the optical density change .DELTA.OD is 1.0, none of the film 
breakage of EC device, the peeling off of the sealing resin and the 
sealing substrate, and the deterioration of external appearance was 
observed after 500 thousand repetition. The optical density change 
.DELTA.OD was determined after the repeated coloring and loss of color to 
obtain 1.0, which was the same as the initial value, and no deterioration 
in the device characteristics was observed. The optical density change 
.DELTA.OD as referred to in the specification is determined by the 
equation of .DELTA.OD=log.sub.10 (T.sub.O /T), where T.sub.o is a 
transmittance when colorless, and T is a transmittance when colored. 
EXAMPLE 2 
An EC device was prepared by the same procedure as in Example 1 except that 
a silicone resin having 60 Kgf/cm.sup.2 of Young's modulus was used in 
place of the sealing resin of Example 1. Similar to Example 1, a voltage 
of 3 V was applied between the transparent electrodes, and 500 thousand 
cycles of coloring and loss of color were repeated so as to obtain an 
optical density change .DELTA.OD of 1.0. As a result, the film breakage of 
the EC device, the peeling off of the sealing resin and the sealing 
substrate did not occur, and the deterioration of external appearance, and 
the variation in optical density change .DELTA.OD were not observed. 
EXAMPLE 3 
An EC device was prepared by the same procedure as in Example 1 except that 
an epoxy resin having 17 Kgf/cm.sup.2 of Young's modulus was used in place 
of the sealing resin of Example 1. Similar to Examples 1 and 2, 3 V of a 
voltage was applied between the transparent electrodes, and 500 thousand 
cycles of coloring and loss of color were repeated so as to obtain 1.0 of 
an optical density change .DELTA.OD. As a result, the film breakage of the 
EC device, the peeling off of the sealing resin and the sealing substrate 
did not occur, and the deterioration of external appearance, and the 
variation in optical density change .DELTA.OD were not observed. 
EXAMPLE 4 
An EC device was prepared by the same procedure as in Example 1 except that 
the structure was four-layered one having no oxidative coloring EC layer. 
Similar to Examples 1 through 3, 3 V of a voltage was applied between the 
transparent electrodes, and 200 thousand cycles of coloring and loss of 
color were repeated so as to obtain 1.0 of an optical density change 
.DELTA.OD. As a result, the film breakage of the EC device, the peeling 
off of the sealing resin and the sealing substrate did not occur, and the 
deterioration in external appearance, and the variation in optical density 
change .DELTA.OD were not observed. 
COMATIVE EXAMPLE 1 
An EC device was prepared by the same procedure as in Example 1 except that 
the sealing resin of Example 1 was changed into an epoxy resin having 2000 
to 3000 Kgf/cm.sup.2 of Young's modulus, having poor elasticity, and being 
usually used for adhesion of optical parts having dimensional precision. 
Similar to Examples 1 through 4, 3 V of a voltage was applied between the 
transparent electrodes, and repeated cycles of coloring and loss of color 
were carried out so as to obtain 1.0 of an optical density change 
.DELTA.OD. Then, after 20 to 50 cycles of coloring and loss of color, lots 
of bubbles appeared within the EC device, and the film breakage of the EC 
device and the peeling off of the sealing substrate occurred, 
deterioration in external appearance was observed, and the optical density 
change .DELTA.OD was determined to be lowered to 0.1-0.4. 
COMATIVE EXAMPLE 2 
An EC device was prepared by the same procedure as in Example 1 except that 
the sealing resin of Example 1 was changed into a modified acrylate resin 
having 70 to 100 Kgf/cm.sup.2 of Young's modulus. Similar to Examples 1 
through 4, 3 V of a voltage was applied between the transparent 
electrodes, and repeated cycles of coloring and loss of color were carried 
out so as to obtain 1.0 of an optical density change .DELTA.OD. Then, 
similar to Comparative Example 1, after 20 to 50 cycles of coloring and 
loss of color, bubbles appeared within the EC device, and deterioration in 
external appearance was observed, and optical density change .DELTA.OD was 
determined to be lowered to 0.5-0.6. 
COMATIVE EXAMPLE 3 
An EC device was prepared by the same procedure as in Example 1 except that 
the sealing resin of Example 1 was changed into a silicone resin having 3 
to 6 Kgf/cm.sup.2 of Young's modulus. Similar to Examples 1 through 4, 3 V 
of a voltage was applied between the transparent electrodes, and repeated 
cycles of coloring and loss of color were carried out so as to obtain 1.0 
of an optical density change .DELTA.OD. The EC device was significantly 
deformed, and the functioning of the device for mounting in an optical 
path was impaired. 
COMATIVE EXAMPLE 4 
An EC device was prepared by the same procedure as in Example 4 except that 
the sealing resin of Example 4 was changed into a modified acrylate resin 
having 70 to 100 Kgf/cm.sup.2 of Young's modulus. Similar to Examples 1 
through 4, 3 V of a voltage was applied between the transparent 
electrodes, and repeated cycles of coloring and loss of color were given 
so as to obtain 1.0 of an optical density change .DELTA.OD. Then, after 12 
to 16 cycles of coloring and loss of color, lots of bubbles appeared 
within the EC device, and deterioration in external appearance (light 
scattering) was observed. When the optical density change .DELTA.OD was 
measured, it was lowered to 0.5-0.6. 
EXAMPLE 5 
A glass substrate having an anti-reflection film provided on one surface 
was subjected to vacuum deposition of ITO on the other surface thereof 
under the conditions of a substrate temperature=300.degree. C. and an 
O.sub.2 partial pressure=5.times.10.sup.2 Pa to form a transparent 
electrode (transparent electroconductive layer) having a layer thickness 
of 150 nm as a first layer. 
Next, the transparent electrode was subjected to vacuum deposition of 
tantalum pentoxide under the conditions of a substrate 
temperature=300.degree. C. and an O.sub.2 partial 
pressure=3.times.10.sup.-2 Pa to form a transparent ion conductive layer 
having a thickness of 300 nm as a second layer. 
Next, the transparent ion conductive layer was treated by vacuum deposition 
of tungsten trioxide under the conditions of a substrate 
temperature=300.degree. C. and an O.sub.2 partial 
pressure=5.times.10.sup.-2 Pa to form a reductive coloring EC layer having 
a thickness of 1000 nm as a third layer. 
Subsequently, the reductive coloring EC layer was to deposition of ITO by 
high frequency ion plating under the conditions of a substrate 
temperature=300.degree. C., an O.sub.2 partial pressure=5.times.10.sup.-2 
Pa, and a high frequency power=150 W to form a transparent electrode 
(transparent conductive layer) having a layer thickness of 450 nm as a 
fourth layer. Thus, a four-layered structure EC device (before sealing) as 
shown in FIG. 2 were prepared. 
Then, the reductive coloring EC layer was colored by applying a voltage 
between the transparent electrodes 2a and 2b of the four-layered structure 
EC device (before sealing) using the power source 9 with the transparent 
electrode 2b being used as a negative electrode. The voltage application 
was controlled such that a change in optical density within a range 
capable of reversible coloring and loss of color occurred (in this 
Example, the optical density change .DELTA.OD, which is the amount of 
change in coloring concentration, was 1.6 or less). Specifically, the 
voltage application was controlled such that the coloring progressed at a 
constant speed (in this Example, 10 sec.) up to 1.2 of the optical density 
change .DELTA.OD. As a result, water as the carrier precursor in the 
four-layered structure member 8 was ionized into H.sup.30 and OH.sup.31. 
Under the above mentioned colored state, the resin-sealing was conducted 
using a sealing substrate applied with a sealing resin. The sealing resin 
used was a modified acrylate resin having 60 Kgf/cm.sup.2 of Young's 
modulus. 
In a plurality of EC devices of this Example prepared in the 
above-described manner, a voltage was applied between the transparent 
electrodes 2a and 2b with the transparent electrode 2b being used as a 
positive electrode to induce an oxidation-reduction reaction to effect 
loss of color. Then, 3 V of a voltage was applied between the transparent 
electrodes to determine the coloring speed and speed of loss of color and 
the optical density change .DELTA.OD. The result was that all the EC 
devices gave 6 sec. of coloring speed and speed of loss of color and 1.0 
of an optical density change .DELTA.OD, and that there was observed no 
difference in the coloring speed and speed of loss of color and the 
optical density change .DELTA.OD after the sealing. 
After repeating the coloring and loss of color cycles 200 thousand times, 
the EC devices of this Example showed no deterioration of characteristics, 
giving 6 sec. of the coloring speed and speed of loss of color and 
1.0.+-.0.1 of the optical density change .DELTA.OD. 
As a result, also in this Example, a plurality of EC devices could be 
obtained having uniform characteristics and having high durability and 
stable characteristics. 
EXAMPLE 6 
EC devices were prepared in the same procedure as in Example 5 except that 
the ionization of water as the carrier precursor in the four-layer 
structure member 8 into H.sup.30 and OH.sup.- was conducted under a 
control of voltage application between the transparent electrodes such 
that the optical density change .DELTA.OD became 1.2 at a constant speed 
(15 sec.) smaller than that in Example 5. 
Thus prepared plural number of EC devices were evaluated as in the case of 
Example 5, and the result showed 6 sec. of coloring speed and speed of 
loss of color and 1.0 of an optical density change .DELTA.OD for all the 
EC devices tested. There was observed no difference in the coloring speed 
and speed of loss of color and in the optical density change .DELTA.OD 
after the sealing. 
After repeating the coloring and loss of color cycles 200 thousand times, 
the EC devices of this Example showed no deterioration of characteristics 
giving 6 sec. of the coloring speed and speed of loss of color and 
1.0.+-.0.1 of the optical density change .DELTA.OD. 
As a result, also in this Example, a plurality of EC devices could be 
obtained having uniform characteristics and having high durability and 
stable characteristics as in the case of Example 5. 
It should be noted that Examples 5 and 6 dealt with the EC devices of 
four-layered structure. Nevertheless, the procedure described in Examples 
5 and 6 is effective for EC devices having other structure, and gives 
similar effect with regard to, e.g., an EC device with five-layered 
structure described in Example 1. The following is an example of that type 
of EC device. 
EXAMPLE 7 
A plurality of EC devices having five-layered structure were prepared in 
the same procedure as in Example 1, except that the same procedure as 
shown in Example 5 was adopted to ionize water as the carrier precursor in 
the five-layered structure member 8 into H.sup.30 and OH.sup.31 before the 
sealing. 
The plurality of EC devices thus prepared in this Example were evaluated as 
in the case of Example 5, and the result showed 6 sec. of the coloring 
speed and speed of loss of color and 1.0 of the optical density change 
.DELTA.OD for all the EC devices tested. There was observed no difference 
in the coloring speed and speed of loss of color and in the optical 
density change .DELTA.OD after the sealing. 
After repeating the coloring and loss of color cycles 500 thousand times, 
the EC devices of this Example showed no deterioration of characteristics 
giving 6 sec. of the coloring speed and speed of loss of color and 
1.0.+-.0.05 of the optical density change .DELTA.OD. Furthermore, it was 
found that the repeated durability of these EC devices having five-layered 
structure was superior to the EC devices having four-layered structure. 
As a result, also in this Example, like Example 5, a plurality of EC 
devices could be obtained having uniform characteristics and having high 
durability and stable characteristics. 
Examples 5 through 7 proved that by ionizing an electrolyte while 
controlling the voltage applied between the transparent electrodes of the 
EC device in such a manner that the coloring speed and speed of loss of 
color and the optical density change show specified values before the 
sealing of the EC device, it is possible to control the characteristics 
such as coloring speed and speed of loss of color and optical density 
change .DELTA.OD after the sealing. 
COMATIVE EXAMPLE 5 
EC devices were prepared by similar procedure with Example 5 except that 
water as the carrier precursor in the four-layered structure member 8 was 
not ionized to H.sup.30 and OH.sup.31 but the four-layered structure 
member was impregnated with water to about 30 vol. %, followed by 
resin-sealing. 
The plurality of EC devices thus prepared in this Example were subjected to 
3 V of a voltage application between the transparent electrodes 2a and 2b 
to determine the coloring speed and speed of loss of color and the optical 
density change .DELTA.OD. As a result, the coloring speed that gave 1.0 of 
the optical density change .DELTA.OD were different for each device, 
giving a dispersion ranging from 4 to 12 sec. 
Repeat of coloring and loss of color cycles revealed that some devices 
showed less than 0.5 of the optical density change .DELTA.OD after 600 
cycles. Thus the devices were concluded not applicable to practical use. 
As described above, according to the first aspect of the present invention, 
the film-expansion on an EC device induced by repeated coloring and 
discoloring is absorbed by a sealing resin so that the film breakage of EC 
device and the peeling off of the sealing resin and the sealing substrate 
are prevented, whereby the durability of EC device is significantly 
improved. In an EC device with five-layer structure, in order to allow the 
desired reactions to progress, the oxidative coloring EC layer, the 
transparent ion conductive layer, the reductive coloring EC layer and the 
like are necessary to be formed with good precision and reproducibility of 
properties and thickness of the respective layers. However, the first 
aspect of the present invention allows some latitude in the film-forming 
conditions, thereby increasing the productivity of EC devices. 
According to the second aspect of the present invention, the difference in 
coloring speed and speed of loss of color and of optical density change 
for every EC device induced from a slight change in EC device 
manufacturing conditions can be eliminated, thus providing EC devices 
having uniform characteristics and having high durability and stable 
characteristics. In addition, by ionizing the carrier precursor while 
controling a voltage applied between the electrodes of the EC device such 
that the coloring speed and speed of loss of color and the optical density 
change show specified values before sealing the EC device, the 
characteristics such as coloring speed and speed of loss of color and 
optical density change after the sealing can be controlled. Particularly 
when water is used as the carrier precursor in the EC device, specific 
control of the sealing environment is not needed and any special equipment 
for injecting carrier precursor is not needed because a necessary amount 
of water can be supplied from outside air into the EC device independently 
of the humidity change in outside air and stored in an ionized state. Thus 
the productivity of EC devices can significantly be increased. 
When the first aspect and the second aspect of the invention are 
simultaneously applied, more excellent EC devices can be obtained. 
The invention may be embodied in other specific forms without departing 
from the spirit or essential characteristics thereof. The present 
embodiments and examples are therefore to be considered in all respects as 
illustrative and not restrictive, the scope of the invention being 
indicated by the appended claims rather than by foregoing description and 
all changes which come within the meaning and range of equivalency of the 
claims are therefore intended to be embraced therein.