Electrochromic device manufacturing process

The present invention is directed to method for manufacturing electrochromic devices using laser ablation techniques. More specifically, the present invention uses laser ablation to provide a simple, noncontact method of patterning electrochromic devices to a controlled depth, to form an electrochromically active area. Furthermore, laser patterning is conducive to the formation of multiple electrochromic devices on a single substrate.

BACKGROUND OF THE INVENTION 
1. The Field of the Invention 
The present invention is directed to the manufacture of electrochromic 
devices. More specifically, the present invention is directed to a process 
for manufacturing electrochromic devices having precisely patterned 
electrochromically active areas. 
2. The Relevant Technology 
Electrochromic materials exhibit a transition, or change in color, in 
response to an applied voltage. In use, electrochromic materials are 
typically deposited as a thin film with an electrolyte and an electrical 
conducting material to form an electrically switchable optical device. A 
voltage is applied to the electrochromically active materials through the 
electrical conducting layers creating an electrical field across the 
electrochromic materials, thereby varying the light transmittance or 
reflectance through the device. Reversal of the electrical field causes 
the electrochromic device to return to its original state. 
As illustrated in FIG. 1, a typical electrochromic device comprises a 
supportive substrate 12, having an first electrical conducting layer 14 
formed thereon. Layer 16 formed on the electrical conducting layer is 
either an ion storage layer or an electrochromic layer. An ion conducting 
layer 18, such as a polymeric electrolyte or an ion conductive thin film, 
is formed on layer 16. Layer 20, formed on the ion conducting layer, is 
either an ion storage layer or an electrochromic layer depending on layer 
16. For example, if layer 16 is an electrochromic layer, layer 20 is 
either an ion storage layer or an electrochromic layer. If layer 16 is an 
ion storage layer, however, layer 20 is an electrochromic layer. A second 
electrical conducting layer 22 is formed on layer 20. An additional 
protective barrier may be located on layer 22. 
In the manufacture of multi-layer thin film electrochromic devices, 
provisions must be made for electrical conductivity. It is also important 
to avoid shorting the electrical conducting layers during fabrication of 
the electrochromic structure. These objectives are typically met by 
patterning the electrochromic device during the manufacture of the device. 
Patterning of electrochromic devices entails the formation of regions of 
electrical and/or ionic isolation in the layers of an electrochromic 
device. Currently, these regions of electrochromic isolation are formed 
using masking, chemical etching and photolithography techniques during the 
manufacture of the electrochromic device. For example, U.S. Pat. No. 
4,488,781, issued to Giglia, discloses the use of these techniques to form 
electrochromic display devices. In this process, a glass substrate having 
a conductive layer thereon is photoetched to form a pattern in the 
conductive material. An electrochromic material is then deposited through 
a mask onto the photoetched conductive layer. The electrochromic material 
is coated with a photoresist material, a mask is placed over the 
photoresist, and the photoresist is exposed to ultraviolet light to form a 
pattern. Once developed, this process is repeated for the each of the 
following layers that are patterned. 
Although photolithography, masking, and etching techniques are effective 
patterning processes, these methods have many drawbacks. For instance, 
harsh chemicals used in photolithography and chemical etching processes 
often contaminate and adversely affect the electrochromic device being 
formed. In addition, photolithography processes are extremely time 
consuming and tedious. This problem is often compounded when a variety of 
different geometries are used, such as with sunglasses, where new sets of 
masks must be fabricated and registered for each different lens geometry. 
Still further, physical manipulation and contact inherent in the use of 
conventional patterning techniques often damages or destroys the 
electrochromic device being manufactured. Electrochromic devices are 
inherently fragile, delicate structures. Mechanical contact on the 
electrochromic device, or chemical contamination of the electrochromic 
device during standard patterning techniques greatly increases the 
probability of damaging or destroying the integrity of the device. 
Other methods of patterning electrochromically active devices are known, 
such as laser scribing, laser cutting, sand blasting, punching, and 
stamping. These processes have, however, been subject to some of the same 
high labor and contact intensive drawbacks as the processes described 
above. 
From the foregoing, it is readily apparent that there is a need for a 
simple process for manufacturing electrochromic devices that avoids the 
use of harsh chemicals. Furthermore, it is clear that there is a need for 
a noncontact, precise process of patterning electrochromic devices that is 
conducive to the continuous production of electrochromic devices. 
SUMMARY AND OBJECTS OF THE INVENTION 
It is, therefore, an object of the present invention to provide improved 
methods of manufacturing electrochromic devices. 
It is another object of the present invention to provide methods for 
manufacturing electrochromic devices that are not labor intensive. 
It is also an object of the present invention to provide improved processes 
for patterning electrochromic devices. 
It is a further object of the present invention to provide simple 
noncontact processes for patterning electrochromic devices. 
Still further, it is an object of the present invention to provide methods 
for patterning electrochromic devices so as to avoid the use of harsh 
chemical reagents. 
Moreover, it is an object of the present invention to provide high 
precision depth control and resolution to allow layer specific patterning 
of the electrochromic device. 
To achieve the foregoing objects, and in accordance with the invention as 
embodied and broadly described herein, the present invention is directed 
to methods for manufacturing electrochromic devices using laser patterning 
techniques. 
In a preferred embodiment of the present invention, a first electrical 
conducting layer is formed on a substrate. A region of electrical 
isolation is formed in the first electrical conducting layer partitioning 
the electrical conducting layer into at least two electrically separate 
areas. Once a pattern has been formed in the first electrical conducting 
layer, an electrochromic layer, an ion conducting layer, an ion storage 
layer and a second electrical conducting layer are deposited on the first 
electrical conducting layer in one vacuum using physical vapor deposition. 
A second region of isolation is then formed in the electrochromic device 
by laser ablation, separating the electrical conducting layer, the ion 
storage layer, the ion conducting layer, and the electrochromic layer into 
at least two electrically and ionically separate areas. The electrochromic 
device is patterned in such a manner that the first region of electrical 
separation and the second region of isolation intersect to define at least 
one electrochromically active area. The precise nature of laser patterning 
allows the second region of isolation to be formed to a specific, 
predetermined depth without extending into the first electrical conducting 
layer. 
An advantage of the present invention is that the precision control 
provided by laser patterning techniques allows each of the layers above 
the first electrical conducting layer to be formed by physical vapor 
deposition in one vacuum without breaking the vacuum and thereafter 
patterned to form a second region of isolation. 
Furthermore, in accord with the present invention, and contrary to 
conventional knowledge, it has been discovered that by using laser 
patterning techniques, multiple electrochromic devices can be formed on a 
single substrate and thereafter separated into individual electrochromic 
devices. 
These and other objects and features of the present invention will become 
more fully apparent from the following description and appended claims, or 
may be learned by the practice of the invention as set forth hereinafter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention is directed to the manufacture of electrochromic 
devices using laser ablation techniques to precisely pattern an 
electrochromically active area. Electrochromically active areas as used 
herein are defined as the area of an electrochromic device that changes 
transmittance or reflectance in response to an applied voltage. 
Traditionally, electrochromic devices have been patterned using 
photolithography, chemical etching and masking techniques. These methods, 
however, are labor intensive typically requiring a masking, photoresist 
and photoresist removal for each layer to be patterned. In addition to 
being tedious and time consuming, these steps involve the use of harsh 
chemicals that can contaminate or destroy the layers of the electrochromic 
device. Furthermore, traditional patterning techniques are contact 
intensive, often damaging or destroying the inherently fragile 
electrochromic devices. 
Although other methods of patterning electrochromic devices, such as sand 
blasting, laser scribing, laser cutting, punching or stamping are known, 
these methods have heretofore exhibited the same labor and contact 
intensive drawbacks as photolithography, etching and masking techniques. 
It is a feature the present invention to provide a simple, noncontact 
process for patterning electrochromic devices that does not use harmful 
chemicals. More specifically, it is a feature of the present invention to 
provide a precise process for patterning electrochromic devices using 
laser patterning techniques. 
Referring now to the drawings, FIGS. 2 and 3b illustrate an electrochromic 
device 40, having a pattern formed therein defining an electrochromically 
active area 42. Electrochromic device 40 comprises a first electrical 
conductive layer 46 on substrate 44 and second electrical conducting layer 
48 at the opposite end of the electrochromic device. The two electrical 
conducting layers allow a voltage to be applied across the electrochromic 
materials. 
Sandwiched between the electrical conducting layers are an electrochromic 
layer, an ion conducting layer and an ion storage layer (hereinafter also 
referred to collectively as an electrochromic stack). Layers 50 and 54 of 
the electrochromic stack, being interchangeable, are selected from the 
group consisting of an electrochromic layer and an ion storage layer. In 
one embodiment of the present invention, one of layers 50 and 54 is an ion 
storage layer while the other layer is an electrochromic layer. In another 
embodiment, rather than using an electrochromic layer and an ion storage 
layer, two electrochromic layers can be used, one of which colors upon 
reduction and one of which colors upon oxidation. This configuration of 
the two electrochromic layers will cause both electrodes to become clear 
or colored simultaneously in response to an appropriate voltage. Hence, 
layers 50 and 54 can both be electrochromic layers, however, if either 
layer 50 or 54 is an ion storage layer, the other layer is an 
electrochromic layer. U.S. Pat. No. 5,080,471, issued to Cogan et al., 
herein incorporated by reference, discloses the use of two electrochromic 
layers in an electrochromic device. To complete the electrochromic stack, 
ion conducting layer 52 is located between layers 50 and 54. 
As shown in FIGS. 2 and 3b, in a preferred embodiment of the present 
invention, the order of the layers comprising the electrochromic device 
are as follows: substrate 44, first electrical conducting layer 46, ion 
storage layer 50, ion conducting layer 52, electrochromic layer 54, and 
second electrical conducting layer 48. 
To complete the electrochromic device, regions of electrical isolation 56 
and 58 are formed in the electrical conducting layers 46 and 48 using 
laser ablation to form an electrochromically active area 42. A voltage is 
applied across the electrochromic device by voltage means 30 and 32. 
Voltage means 30 and 32 can be any means of applying voltage across the 
electrochromic device, such as voltage contacts which include, but are not 
limited to conductive tape, solder, silver paint or carbon paint. In a 
preferred embodiment as shown in FIG. 2, contact pad 30 is formed to 
provide an electrical contact through layers 50, 52 and 54 to the lower 
conducting layer 46a. Electrical contact through numerous layers such as 
shown in FIG. 2, can be accomplished by direct soldering of the pad to the 
thin film layers. In addition, FIGS. 4d-4g illustrates the use of 
conductive tape 34 such as foil with an edge mask so that voltage may be 
applied to layer 46a 
Now referring to FIGS. 3a-3b and 4a-4g, an electrochromic device in 
accordance with the present invention is manufactured by forming a first 
electrical conducting layer 46 on a support substrate 44. Electrical 
conducting layer 46 can be formed onto the substrate by any suitable means 
known in the art and is preferably a glass substrate precoated with an 
electrical conducting layer material such as indium tin oxide. It is 
readily apparent to one of ordinary skill that the substrate can be any 
suitable material, such as glass or plastic. 
Although the first electrical conducting layer can be patterned by any 
method known in the art, a laser is preferably used to pattern a first 
region of electrical isolation 56 partitioning the electrical conducting 
layer into at least two electrically separate regions 46a and 46b. In one 
embodiment of the present invention, the first electrical conducting layer 
46 can be patterned in vacuo using laser patterning techniques. Using this 
method allows the deposition of the entire electrochromic device in a 
single vacuum cycle. 
Layers 50, 52 and 54, are formed on the first electrical conducting layer 
46. As discussed above, layer 50 is either an electrochromic layer or an 
ion storage layer, layer 52 is an ion conducting layer and layer 54 is 
either an electrochromic layer or an ion storage layer. Layers 50 and 54 
can both be electrochromic layers where they act in concert as described 
above. 
A second electrical conducting layer 48 is formed on layer 54 so that a 
voltage can be applied across the electrochromic stack. Although layers 
50, 52, 54 and 48 can be formed by any suitable technique known in the 
art, including but not limited to sputtering, sintering, evaporation, 
spreading, or other similar techniques, the electrochromic stack and the 
second electrical conducting layer are preferably formed using physical or 
chemical vapor deposition techniques. 
Once all layers of the electrochromic device have been deposited, a second 
region of electrical isolation 58 is formed using laser ablation. As 
illustrated in FIG. 4d, the second region of isolation 58 formed by laser 
ablation extends at least through electrical conducting layer 48. In a 
preferred embodiment of the present invention, the second region of 
isolation extends into layers 54 through 50, but not through first 
electrical conducting layer 46 as shown in FIG. 4g. Nevertheless, in 
accordance with the present invention, the second region of isolation can 
extend to any point down to first electrical conducting layer 46. 
It is readily understood by one of skill in the art in view of the 
teachings herein, that when the second region of isolation extends only 
through second electrical conducting layer 48, a region of electrical 
isolation is formed. Likewise, when second region 58 of isolation is 
formed by laser ablation extends through the electrical conducting layer 
48 and into the electrochromic layer, ion conducting layer, or ion storage 
layer, the pattern also acts as a region of ionic isolation. Hence, when 
second region of isolation 58 extends into the electrochromic stack a 
region of electrical and ionic separation is formed. 
In a preferred embodiment of the present invention, the second region of 
isolation extends through second electrical conducting layer 48 into the 
electrochromic stack, i.e. layers 54, 52, and 50, to form a region of 
electrical and ionic separation as illustrated in FIGS. 4d through 4g. By 
extending the second region of isolation into the electrochromic stack, 
them is no migration of ions into the electrochromically active area that 
can cause blurring or contamination of the electrochromically active area. 
Thus, extending the second region of isolation into the electrochromic 
stack ensures the distinctiveness of the boundary of the 
electrochromically active area. 
As illustrated in FIG. 3b, the first region of electrical isolation and the 
second region of isolation intersect to form a pattern that defines at 
least one electrochromically active area 42. Depending on the patterning 
of the first and second regions of isolation, the electrochromically 
active area can be any shape or geometry desired. 
Laser patterning provides a noncontact, intrinsically fast method of 
delineating regions of isolation in electrochromic devices. Laser 
patterning techniques further provide a clean, precise method of forming 
distinct areas of electrochromic activity. In accordance with the present 
invention, laser delineations in electrochromic devices are prepared by 
irradiating specific areas of the electrochromic device with laser pulses 
(also hereinafter referred to as "shots"). 
A significant advantage of laser ablation patterning is its ability to 
delineate areas of the electrochromic device to a precisely controlled 
depth. The lack of control associated with traditional patterning 
techniques has heretofore prohibited delineation of the electrochromic 
device to specific depths. The precise nature of laser ablation, however, 
allows the second region of isolation to be formed to any desired depth 
after all layers of the electrochromic device have been deposited, without 
cutting into, or through, first electrical conducting layer 46. It is, 
therefore, a novel feature of the present invention to deposit the 
electrochromic stack and the second electrical conducting layer in one 
vacuum chamber, without breaking the vacuum, and subsequently form a 
second region of electrical isolation using laser ablation techniques. 
The wavelength of the laser pulse used depends on the materials to be 
delineated and the depth of delineation desired. The laser typically used 
has a wavelength in the range between 100 nm and 400 nm, and, in use, is 
focused to a desired energy density. It is noted that the size of the 
delineation is controlled by varying the size of the laser beam. It is 
readily understood that the laser used in the ablation patterning process 
can be programmed to strike a specific area of the electrochromic device 
so as to delineate any desired pattern. 
The radiation used in the laser ablation process can be produced by any 
suitable laser which is strongly absorbed by the layers to be patterned 
and which allows for cutting to a controlled depth. Typically, the energy 
density of in the laser beam should be greater than 1 millijoule/cm.sup.2. 
In a preferred embodiment of the present invention, the laser is an 
ultraviolet eximer laser, such as XeCl (308 nm), KrF (248 nm) or ArF (193 
nm). Other suitable lasers that may be used include, but are not limited 
to: gas, chemical, and solid state lasers. 
Furthermore, it is a surprising feature of the present invention to be able 
to form a manufacturing construct having a plurality of electrochromically 
active areas arranged on a single substrate. The plurality of 
electrochromically active areas can then separated into a plurality of 
individual electrochromic devices. Alternatively, the plurality of 
electrochromically active areas can be individually addressed by voltage 
means, yet remain on their common substrate. 
Now referring to FIGS. 5 and 6, a manufacturing construct 200, similar to 
the plurality of electrochromic devices discussed above, comprises a first 
electrical conducting layer 46 on the substrate 44 and the second 
electrical conducting layer 48 at the opposite end of the manufacturing 
construct. An electrochromic stack (layers 50, 52, 54), is sandwiched 
between the electrical conducting layers. A first pattern of electrical 
isolation 210 separating the first electrical conducting layer into a 
plurality of electrically partitioned regions is formed, and a second 
pattern of isolation 220, separating at least the second electrical 
conducting layer 48 into a plurality of separate regions of isolation, is 
formed using laser ablation following stack deposition. As with individual 
electrochromic devices, depending on the depth of the delineation, the 
second region of isolation can be a region of electrical or electrical and 
ionic isolation. In the manufacturing construct, the first pattern of 
isolation and the second pattern of isolation intersect to form a 
plurality of electrochromically active areas which are thereafter 
separated into a plurality of individual electrochromic devices 230. 
Voltage means 250 and 252 provide a means for providing voltage across 
each individual electrochromic device. The electrochromic devices can be 
separated into individual electrochromic devices by any suitable means, 
such as scribing and breaking or sawing. 
It will be understood that a substrate used to form a manufacturing 
construct is typically larger than the substrates used for the individual 
electrochromic devices. In addition, as with the laser patterning of the 
individual electrochromic devices, the geometry of the electrochromically 
active area can be tailored to the specific uses of the electrochromic 
device. 
Here again, as with the process for forming individual electrochromic 
devices discussed above, layers 46, 48, 50, 52, and 54 can be formed using 
any suitable method, including, but not limited to spreading, sintering, 
evaporating, sputtering, or other similar techniques, but are preferably 
formed using vapor disposition techniques. As with individual 
electrochromic devices, all of the layers above the first electrical 
conducting layer can be formed using vacuum deposition without breaking 
the vacuum, thus providing an efficient method of mass-producing 
electrochromic devices. Additionally, with in vacuo laser patterning of 
the first electrical inductive layer, the entire electrochromic device can 
be deposited in a single vacuum cycle, thereby providing an even more 
efficient method of mass production. 
In another embodiment of the current invention, as illustrated in FIG. 7, 
the electrochromic device can be formed as two half cells and joined 
together to form an electrochromic device having a polymer electrolyte ion 
conducting layer. Accordingly, an electrochromic device having a polymer 
electrolyte ion conducting layer 340, is prepared by forming a first 
electrical conducting layer 320 on a substrate 310 and laser patterning a 
first region of electrical isolation 380 partitioning the first electrical 
conducting layer into at least two electrically separate areas. A second 
layer 330 being either a ion storage layer or an electrochromic layer is 
formed on the first electrical conducting layer 320, to form a first 
substrate assembly 400. 
A second electrical conducting layer 360 is then formed on a second 
substrate 420 and is laser patterned to form a second region of isolation 
390 separating the second electrical conducting layer into at least two 
electrically separate areas. A layer 350 being either an electrochromic 
layer or an ion storage layer is then formed on the second electrical 
layer 360 to form a second substrate assembly. Here again, whether an 
electrochromic layer or an ion storage layer is formed is dependent upon 
whether the first substrate assembly comprises an electrochromic layer or 
an ion storage layer. If the first substrate assembly comprises an 
electrochromic layer, layer 350 can be either an electrochromic layer or 
an ion storage layer, whereas if layer 330 is an ion storage layer, layer 
350 is an electrochromic layer. 
The two assemblies are then positioned so that said first substrate 
assembly and the second substrate assembly are in an electrode-facing 
relationship. The two assemblies are then joined by a spacer means 370 so 
that a space is formed between the assemblies. An electrolyte 340 is 
introduced into the space defined between the two assemblies and the 
spacer means, so that electrolyte 340 is retained in the space. The first 
region of electrical isolation 380 and the second region of isolation 390 
intersect to define at least one electrochromically active area. 
Several types of electrochromic materials are known, including metal oxides 
and electrically conductive polymers. Exemplary of the metal oxides are 
niobium oxide Nb.sub.2 O.sub.5 ; nickel oxide NiO; iridium oxide IrO.sub.2 
; vanadium pentoxide V.sub.2 O.sub.5 ; rhodium oxide Rh.sub.2 O.sub.3 ; 
and molybdenum trioxide MoO.sub.3 ; and preferably tungsten oxide 
WO.sub.3. Conductive polymers include polyaniline, polyacetylene, 
polypyrrole, polythiophene, polyphenylene, polyphenylene vinylene, 
polyphenylene sulfide, polypheryl diamene, poly (N,N.sup.1 
dipherylbenzidine) and derivatives, copolymers and bilayers. 
Suitable solid state ion conductor materials include Ta.sub.2 O.sub.5, 
ZrO.sub.2, MgF.sub.2, LiNbO.sub.3 and suitable polymer ion conductor 
materials include proton conducting polymers such as polyAMPS 
(2-acrylamido-2-methylpropanesulfonic acid) and Li.sup.+ conducting 
polymer such as PMMA (poly methyl methacrylate) inferences doped with 
LiClO.sub.4. 
Suitable ion storage materials include, but are not limited to NiO, 
IrO.sub.2 and V.sub.2 O.sub.5. In a preferred embodiment the ion storage 
material is NiO. 
Suitable electrical conducting layers include, but are not limited to ITO, 
SnO.sub.2 :F, ZnO, Al, Mo, Ni and Au. When the electrochromic device is 
transparent, the electrical conducting layer is preferably an ITO layer. 
Furthermore, when the electrochromic materials form a reflective device, 
the electrical conducting layer is preferably a reflecting metal such as 
Al, Au, Mo and Ni. 
The substrate can be any suitable material such as plastic or glass. In 
addition, depending on its use, the substrate can be either transmissive 
if used in windows or glasses, or the substrate can be reflective if used 
in mirrors. 
In a preferred embodiment of the invention, the electrochromic device uses 
a glass substrate; an indium tin oxide electrical conducting layer; a 
nickel oxide ion storage layer; a tantalum pentoxide ion conducting layer; 
and a tungsten oxide electrochromic layer. 
EXAMPLE 
Laser ablation processes within the scope of the present invention are 
further clarified by consideration of the following example, which is 
intended to be purely exemplary of the present invention and should not be 
viewed as a limitation on any claimed embodiment. 
An electrochromic device such as that shown in FIG. 4c can be delineated to 
controlled depths using laser ablation techniques. The number of pulses 
necessary to cut to a specific depth is dependent on a number of variables 
including, the wavelength of the laser used and the materials being 
delineated. 
At an energy density of 2 J/cm.sup.2 at a wavelength of 248 nm, a single 
shot was found to form a second region of isolation sufficiently deep in 
the electrochromic device to obtain isolated performance between 
individual electrochromically active areas with no evidence of cross-talk 
or bleeding between the areas. In order to ablate the electrochromic 
devices sufficiently for contact with the bottom first electrical 
conducting layer, approximately five pulses (also hereinafter referred to 
as shots) of the laser are necessary, at a 2 J/cm.sup.2 laser energy 
density (as illustrated in FIG. 8). 
It is readily understood by one of skill in the art that the shot energies 
and shot number can be varied without altering the layer systems ability 
to delineate the device to a controlled depth. 
The present invention may be embodied in other specific forms without 
departing from its spirit or essential characteristics. The described 
embodiments are to be considered in all respects only as illustrated and 
not restrictive. The scope of the invention is, therefore, indicated by 
the appended claims rather than by the foregoing description. All changes 
which come within the meaning and range of equivalency of the claims are 
to be embraced within their scope.