electrochromic display device manufacture method wherein electrochromic material is deposited in a single layer on a single film of conductive material over the whole area of glass substrate and then the electrochromic material and conductive material are successively etched through a single mask which defines a display segment pattern and remains in position throughout the whole etching process, whereby etched edge portions of the different materials are in excellent alignment and there is therefore small plate area for a reverse emf cell and good display device performance is achieved. The electrochromic material may be etched by the solution employed for developing the photoresist, whereby an etching process step is eliminated.
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1. An electrochromic display device manufacture manufacturing method comprising the steps of:
preparing a first substrate and a second substrate, at least one of said substrates being transparent; applying a first electrode on said first substrate and a second electrode on said second substrate, at least one of said electrodes being transparent and being applied on a transparent said substrate and said second electrode serving as a counter electrode;, and applying a layer of transition metal oxide material on said first electrode;, wherein initially applying said first electrode and said transition metal oxide layer are successively applied on said first substrate over an area greater than that necessary to define a required display segment and external circuit connection pattern thereon; forming a mask defining said required pattern on said transition metal oxide layer; applying at least one layer of insulatory material which covers those portions of said transition metal oxide layer which are unrequired for display purposes; successively etching said transition metal oxide layer and said first electrode through said mask in discrete steps and with respectively discrete etchants peculiar thereto, thereby producing said required pattern in said transition metal oxide layer and said first electrode; positioning said first substrate assembly and said second substrate assembly in an electrode facing relationship and joining said assemblies by spacer means; and introducing electrolyte into the space defined between said assemblies and said spacer means, said elecrolyte being retained in said space.
2. electrochromic The electrochromic display device manufactured manufacturing method as claimed in
3. The method of
4. The method of
5. The method of
stripping said mask from said etched transition metal oxide layer and first electrode; applying a negative photoresist material layer over said etched transition metal oxide layer and first electrode; exposing said negative photoresist material to a light pattern corresponding to said required pattern; and developing said exposed negative photoresist material to form said layer of insulatory material.
6. The method of
7. The method of
8. The method of
9. The method of
depositing a layer of external connector material over said first electrode prior to forming said mask and outside the boundaries of said required pattern, said external connector material being etchable by the same discrete etchant as said first electrode; wherein said mask includes a predetermined pattern for said external connector material; and etching said layer of external connector material in said predetermined pattern through said mask, simultaneously with the etching of said first electrode.
10. The method of
depositing a layer of external connector material over said first electrode prior to forming said work and outside the boundaries of said required pattern, said external connector material being etchable by the same discrete etchant as said transition metal oxide layer; wherein said mask includes a predetermined pattern for said external connector material; and etching said layer of external connector material in said predetermined pattern through said mask, simultaneously with the etching of said transition metal oxide layer.
11. The method of
12. The method of
deposting a layer of external connector material over said first electrode prior to forming said mask and outside the boundaries of said required pattern, said external connector material being etchable by the same discrete etchant as said first electrode; wherein said mask includes a predetermined pattern for said external connector material; and etching said layer of external connector material in said predetermined pattern through said mask, simultaneously with the etching of said first electrode; and further, wherein subsequent to forming said required pattern in said transition metal oxide layer and prior to forming said required pattern in said first electrode, said etchant discrete to said transition metal oxide layer is
removed and post baking is effected. 13. The method of
depositing a layer of external connector material over said first electrode prior to forming said work and outside the boundaries of said required pattern, said external connector material being etchable by the same discrete etchant as said transition metal oxide layer; wherein said mask includes a predetermined pattern for said external connector material; and etching said layer of external connector material in said predetermined pattern through said mask, simultaneously with the etching of said transition metal oxide layer; and further, wherein subsequent to forming said required pattern in said transition metal oxide layer and prior to forming said required pattern in said first electrode, said etchant discrete to said transition metal oxide layer is removed and post baking is effected.
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The present invention relates to a method for .: There were employed two glass substrates constituting a first substrate 1 and a second substrate 8. A layer of indium oxide, In2 O3, was deposited onto one side of the second substrate 8 by an evaporation process thereby to form a second electrode 7, which was subsequently divided into separate portions by a conventional photoengraving process to constitute a counter electrode and a reference electrode.
An indium oxide film was evaporated onto one side of the first substrate 1 also thereby to form a first electrode 2. Layers 9 of ferro-chrome, Fe-Cr, intended to permit soldered connection of external activation circuit leads in the completed electrochromic device were evaporated onto outer edge portions of the exposed surface of the first electrode 2. At this stage of the electrochromic device manufacture there is no need for precise control over dimensions of the ferro-chrome layers 9, since the layers 9 may be subsequently etched to form connection studs simultaneously with etching of the first electrode 2, as described below. This is an advantage in mass-manufacture processes since the layers 9 may be initially applied in approximately-sized strips along opposite edge portions or along a plurality of peripheral portions of the first electrode 2.
The remainder of the exposed surface of the first electrode 2 was then covered by a layer 3 of tungsten trioxide, WO3, deposited by an evaporation process. The tungsten trioxide layer 3 and the ferro-chrome layers 9 were coated with the positive-type resist material which is known under the trade name of AZ-119A and is manufactured by the Shipley Corporation, this coat of resist material being applied by spinner. After being dried, the resist material was exposed to a mask pattern defining display segment portions to be formed by the tungsten trioxide layer 3 and first electrode 2 and external lead connection studs to be formed by the ferro-chrome layers 9.
After exposure the resist material was developed by the developer solution known under the trade name of AZ-303A and manufactured by the Shipley Corporation. By maintaining the developer solution in contact with the resist material longer than usual it was made possible to etch the required pattern in the tungsten trioxide layer 3 in a single process step. Ferro-chrome being resistant to the developer solution employed, the layers 9 were not etched at this stage. Needless to say, however, the manufacturing process is basically the same if the material of the layers 9 is conductive and may also be etched by the developer solution employed.
After a time sufficient to complete etching of the tungsten trioxide layer 3, the developer solution was removed, post-baking was effected, and then the ferro-chrome layers 9 and the first electrode 2 were etched through the same mask by a liquid mixture of ferric chloride, FeCl3, and hydrogen chloride, HCl. As noted above, outer edge portions of the tungsten trioxide layer 3 and of the first electrode 2 are not etched to define boundaries of display segments since these outer edge portions are required to constitute, constructional elements in assembly of the electrochromic device. Therefore, after stripping of the above-described mask, layers 4 of negative type resist material were applied on outer edge portions of the tungsten trioxide layer 3, the negative resist material employed being the commercially available product known under the trade name of KMER and manufactured by the Kodak Corporation of U.S.A., and, in order to facilitate the application process, also being applied on the unetched portions of the ferro-chrome layers 9. The layers 4 of negative resist material were then exposed to light projected through a mask defining the requisite display segment configurations and external connection studs, after which the layers 4 were developed, with the result that those portions of the tungsten trioxide layer 3 required for display purposes were exposed and hence contactable by electrolyte, and other portions thereof remained covered and protected by the negative resist material of the layers 4, the external connection studs also being uncovered. Finally, the first and second substrate assemblies were joined by spacers 5, which also defined side walls and which with respect to the electrochromic device were located inwardly of the external connection layers 9 and first electrode portions supporting the layers 9, electrolyte 6 was introduced into the space defined between the first and second substrate assemblies and the spacers 5 and the electrochromic device, now having the construction shown in FIG. 4 was sealed. The electrolyte 6 employed in this example was a 10 M solution of lithium perchlorate LiClO4, in methyl ethyl ketone, in which solution was mixed a 1:1 by weight addition of barium sulfate, BaSO4, to provide a white background for viewal of the electrochromic display.
In an electrochromic display device constructed according to the method of the invention, electrochromic material other than tungsten trioxide may be employed, examples being molybdenum trioxide, MoO3, and titanium dioxide, TiO2. The electrolyte is suitably constituted by an electrolytic substance such as lithium perchlorate dissolved to a concentration of 1.0 m or to saturation in a solvent such as acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, or similar ketone, ethyl acetate, isopropyl acetate, n-propyl acetate, or similar alkyl acetate, or 2-ethoxy ethyl acetate, for example the product known under the trade name of Cellosolve acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, for example the product known under the trade name of Carbitole acetate, diethylene glycol monobutyl ether acetate, for example the product known under the trade name of butyl carbitole acetate, or similar alkoxy ethyl acetate. If the electrochromic device is employed in a single-side display unit, suitable pigments which are further included in the electrolyte to provide an improved background for viewal of a display include barium sulfate, BaSO4, alumina, Al2 O3, titanium dioxide, TiO2, and Zirconium dioxide, ZrO2.
As a specific example, if the resist material employed is AZ-119A, it is suitably applied by roller coater, using Gyrex 9, to a thickness of 3μ, pre-baked at a temperature of 80°C for 10 minutes and then exposed for 10 seconds, using light emitted by a 3 KW mercury lamp. The developer solution employed for this material is suitably AZ-303A and using this solution a 2-minute developing process at 25°C permits etching of the tungsten trioxide layer also. Development is followed by post-baking for 20 minutes at 110°, after which the supporting electrode material is etched. If the electrode material is indium oxide the etchant employed is suitably a solution having a specific gravity of 42° Be' ferric chloride, FeCl3 and concentrated hydrochloric acid, HCl, in a 1:1 ratio by volume. After this the resist material is stripped by means of acetone.
The material of the insulatory layers 4 applied on the electrochromic material 3 may be a material which is applied by spraying or similar process, for example the abovenoted negative-type resist material manufactured by the Kodak Corporation and known under the trade name of KMER, or a resin such as an epoxy resin, for example the product known under the trade designation of Epiform R-2401/H160 and manufactured by Somal Industries Incorporated of Japan, a cellulose resin, for example the product known under the trade designation of WS-120 and manufactured by the Soken Chemical Corporation of Japan, or a polyvinyl alcohol resin, or a material which is applied by evaporation process, for example silicon oxide, SiO, silicon dioxide, SiO2, alumina, Al2 O3, or magnesium fluoride, MgF2.
The positive type resist applied on the electrochromic material layer 3 and external connection layer or layers 9 and employed for production of a mask defining display segments and external connection studs may be for example any of the products manufactured by the Shipley Corporation and known under the trade designations AZ-111, AZ-119A, AZ-1350, AZ-2400, AZ-2415, and AZ-2430, the product known under the trade designation of OFPR and manufactured by Tokyo Oka Co., Ltd., or either of the products known under the trade designations of ISOFINE SR-30 and ISOFINE PR-36 manufactured by the Micro Image Technology Corporation of Japan. For each of these resist materials there is available a special developer solution which may be suitably employed in association therewith.
Evaporation conditions for deposition of a tungsten trioxide film are suitably as follows. The evaporation source is a resistance-heated tungsten crucible, the process chamber is evacuated to a pressure of 5×10-4 torr, substrate temperature is 350°C, and the tungsten film is deposited at a rate of 10 A per second to a thickness of 5000 A.
Other examples of electrochromic display devices manufactured according to the method of the invention are as follows.
An electrochromic device was manufactured employing a 1.0 m solution of lithium perchlorate, LiClO4, in propionitrile as the electrolyte, procedure and materials being otherwise the same as for Example 1.
An electrochromic display device was manufactured employing a 1.0 m solution of lithium perchlorate, LiClO4, in propylene carbonate as the electrolyte, procedure and materials being otherwise the same as for Example 1.
An electrochromic display device was manufactured employing molybdenum trioxide, MoO3, as the electrode material, instead of tungsten trioxide WO3, procedure and materials being otherwise the same as for Example 1.
An electrochromic display device was manufactured employing silicon oxide, SiO, evaporated through a mask as the material of the layers 4, instead of KMER, procedure and materials being otherwise the same as for Example 1.
An electrochromic display device was manufactured following the procedure of Example 5 except that silicon dioxide, SiO2, was employed in place of silicon oxide, SiO.
An electrochromic display device was manufactured following the procedure of Example 5 except that alumina, Al2 O3, was employed in place of silicon oxide, SiO.
An electrochromic display device was manufactured following the procedure of Example 5 except that magnesium fluoride was employed in place of silicon oxide, SiO.
Although the present invention has been fully described by way of example, it should be noted that various changes and modifications are apparent to those skilled in the art, it being understood that such changes and modifications should be construed as included therein unless they depart therefrom.
Uede, Hisashi, Hamada, Hiroshi, Inami, Yasuhiko, Yano, Kozo
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