Patent Application
20160010236
1. Field of Invention
The present invention generally relates to forming a transparent metal oxide layer on a conductive surface of a dielectric substrate material such as glass, ceramic or polymer material, for example. The transparent metal oxide layer may be conductive, semi-conductive, or non-conductive.
2. Description of Related Art
Materials used to form conductive coatings generally fall into four categories: metals, metal oxides, conductive polymers, and nanomaterial. Metallic coatings exhibit the highest conductivity, particularly in nanomaterial form, however only ultra-thin continuous layers of about 5-10 nm thickness, for example, can be practically considered to be transparent. Metal oxides are generally orders of magnitude less conductive than metals but provide better transparency. Conductive plastics are also far less conductive than metals but offer greater flexibility, and sufficient transparency at lower cost. Nanomaterial coatings include metals and metal oxides, and at present are still at the lab scale of development. Transparent metal oxide layers are currently needed for industrial applications to provide transparent conductors in electronics such as in flat panel displays (FPDs), for example.
Transparent conductive oxides (TCO) are doped metal oxide films that have a poly- or micro-crystalline, or amorphous microstructure. These materials provide greater than 80% transmittance of incident light in the visible spectrum and have a resistivity of about 10−3-10−4 Ω·cm. A combination of two TCO layers each of about 30-50 nm thickness separated by an intermediate metallic layer of about 10-20 nm in thickness provides a composite structure having a tenfold reduction in resistivity and an increased light transmittance of up to 95%. Recently, industrial applications of TCOs have expanded greatly. Rigid liquid crystal displays and other FPDs are the largest market for TCO coatings, but a variety of new market applications including touch screen displays, flexible displays, transparent displays, organic light emitting diode (OLED) displays, smart windows and solid state lighting are utilizing TCO coating as well. Although all of these technologies use TCO coatings to enable product functionality, technical requirements for TCOs in new applications are often different from those typical for a conventional LCD display.
Historically, the TCO market has been dominated by demands for Indium Tin Oxide (ITO). At the same time, sputtering has emerged as a dominant deposition technology for TCOs in general and for ITO coatings, in particular. While sputtering ITO has proven to be sufficient to satisfy industry needs up until now, both sputtering and ITO have a number of important drawbacks that are becoming increasingly apparent.
One such drawback is manufacturing costs. Indium is a scarce and expensive material and sputtering typically results in utilization of only approximately 30% of the indium with the remaining 70% of it being deposited on the walls of the sputtering chamber. Additionally, long down times are typically associated with vacuum based sputtering and this further contributes to the high overall cost of the ITO TCO process. Vacuum equipment such as magnetron sputtering is complex to operate and maintain. As a result, manufacturing lines utilizing this type of equipment generally require highly skilled labor and engineering staff in order to ensure stable line operation. In addition, magnetron sputtering technology requires pretreatment of the substrate surface by ion bombardment to provide adhesion of sputtered material. Finally, high temperatures are typically associated with the sputtering process or post-annealing treatment and this greatly restricts the application of ITO coating to substrates capable of withstanding such temperatures. As a result, the use of ITO based TCO coatings on temperature sensitive substrates such as plastics is challenging.
Another issue is that there are currently no viable alternatives that will provide the electrical and optical characteristics of ITO coatings yet a growing number of market applications require greater conductivity and optical transparency.
The net result is that, at this time, there is a broad market opportunity for new, lower cost ITO deposition processes capable of replacing capital intensive and material wasteful sputtering for a number of existing market applications. There is also a market for a new “indium-free” TCO coating process that is capable of providing the market with a both lower cost and a better performance alternative to ITO in the mid-to long-term. For this reason, new TCO materials such as doped binary compounds, for example, aluminum doped zinc oxide (AZO), indium doped zinc oxide, yttrium doped zinc oxide, and cadmium doped zinc oxide, have been tested in several laboratories and have been proposed as alternative materials.
Alternative TCO deposition methods recently explored by industry and research communities include wet-process methods such as electrochemical methods. Electrochemical methods are based on electric current-driven deposition of metal or metal oxides primarily on the surfaces of substrates with sufficient bulk conductivity. However, there is a principle limitation in the use of such methods for coating dielectric substrates such as glass, ceramic and polymers, used in the production of consumable products. Conductive surfaces are needed to facilitate the use of electrochemical processes on these dielectric materials.
Thin layers of conductive metal oxides, for example FZnO fluoride doped zinc oxide FZnO, AZO or ITO can be deposited on glass and other dielectric substrates through various deposition methods, including for example metal organic chemical vapor deposition (MOCVD), metal organic molecular beam deposition (MOMBD), and sputtering, thus making them potentially accessible to electrochemical processes.
U.S. Pat. No. 5,316,697 “CONDUCTIVE, PARTICULATE, FLUORINE-DOPED ZINC OXIDE” 1994 to Palmer et al. describes a method for making a conductive, particulate, fluorine-doped, zinc oxide product using chemical vapour deposition. The process involves reacting vapour phase reactants in a vapour phase oxidation system at a temperature sufficient to form the conductive, particulate, fluorine-doped, zinc oxide product. Vapour phase reactants are used in the process and include elemental zinc vapour, at least one fluorine source, and at least one water source.
Glass sheets and polyester films coated with conductive metal oxides are commercially available, for example from Zhuhai Kaivo Electronic Components Co. Limited, No. 110, Yuanlinroad, Jida, Zhuhai, Guangdong-519015, China.
Another possibility for producing conductive layers on surfaces of dielectric substrates involves electroless deposition technology, also known as auto-catalytic plating, which is capable of making conductive surfaces on non-conductive substrates. This is a non-galvanic plating method that involves several sequential electroless chemical reactions at an interface between aqueous electrolytes and non-conductive substrate surfaces which occur without the use of external electrical power. See, for example, U.S. Pat. No. 6,464,762 BI “Aqueous solution for the formation of indium oxide film by electroless deposition”, to Ara; U.S. Pat. No. 6,387,542 BI “ELECTROLESS SILVER PLATING” to Kozlov et al; U.S. Pat. No. 6,806,189 B2 “Method of silver (Ag) electroless plating on ITO electrode” to Kim et al.; U.S. Pat. No. 6,527,840 B1 “Silver alloy plating bath and method of forming a silver alloy film by means of the same” to Igarashi et al.; JP59143059 “Electroless plating apparatus” to ITSUPEI et al.; JP11152578A “ELECTROLESS INDIUM OXIDE PLATING AQUEOUS SOLUTION AND ELECTROLESS PLATING METHOD” to KOZO; and JP 2057336 “Electroless plating for plastic”, to YOSHIHIRO.
Unfortunately, the quality of the conductive layers produced on dielectric substrates by the above presented methods is not sufficient for consumer electronic products due to low conductivity of the layers produced by electroless deposition, low thickness uniformity and low light transmittance from CVD and sputtering technologies. This has resulted in consideration of the use of a pre-coated surface on the dielectric substrate prior to forming a transparent conductive metal oxide layer using electrochemical processes.
Several research institutions have demonstrated the possibility of producing Cd-doped and Y-doped ZnO on conductive surfaces pre-formed on glass substrates but these results have only been demonstrated on small samples and were produced in conventional electrochemical chambers that are impractical to employ in mass production industrial processes.
PCT patent application No. CA2011/001013 “Electroplating Metal Oxides on Flat Conductive Surfaces” to Rubin et al. describes a method and apparatus for electrochemically forming an oxide layer on the flat conductive surface of semiconductor devices and photovoltaic (PV) cells. The method involves positioning a working electrode bearing the flat conductive surface in opposed parallel spaced apart relation to a flat conductive surface of a counter electrode. A volume of organic electrolyte solution containing chemicals for forming the oxide layer on the flat conductive surface of the working electrode is arranged to flood and to occupy the space defined between the flat conductive surface of the working electrode and the counter electrode. An electric current flows between substantially only the flat conductive surface of the counter electrode and substantially only the flat conductive surface of the working electrode, in the organic electrolyte solution, for a period of time and at a magnitude sufficient to cause the chemicals to form the oxide layer on the flat conductive surface of the working electrode. The apparatus is specially designed so that the working and counter electrodes receive electrical power at their rear sides to protect their power input terminals from immediate contact with electrolyte which would damage them. Therefore, the use of this apparatus is well suited to use with substrates and counter electrodes that have bulk conductivity but the apparatus is not suitable for forming metal oxide layers on dielectric materials, even if their surfaces are pre-coated with a conductive layer.
Therefore there remains a challenge for forming high uniformity conductive metal oxide layers with high conductivity and high transparency over a large substrate area while keeping both electric terminals of the electrochemical apparatus protected from interaction with the electrolyte.
In accordance with one aspect of the invention, there is provided a method of forming a transparent metal oxide layer on a conductive surface of a dielectric substrate. The method involves exposing first and second conductive surface portions of the conductive surface of the dielectric substrate to first and second electrolytes respectively, and forming a first electrochemical cell comprised of the first conductive surface portion in contact with the first electrolyte and a first electrode in contact with the first electrolyte and spaced apart from the first conductive surface portion. The method further involves forming a second electrochemical cell comprised of the second conductive surface portion in contact with the second electrolyte and a second electrode in contact with the second electrolyte and spaced apart from the second conductive surface portion. The first and second electrochemical cells are electrically connected together in series by the conductive surface. The first electrolyte has first chemicals that facilitate conduction of electric current through the first electrolyte without facilitating significant electrochemical reaction at the first electrode or at the first conductive surface portion. The second electrolyte has second chemicals that facilitate conduction of electric current through the second electrolyte, the second chemicals including a non-aqueous solvent, metal ions in a metal ion concentration at least sufficient to facilitate formation of the transparent metal oxide layer to a desired thickness and a source of oxygen suitable to facilitate formation of the transparent metal-oxide surface of the second conductive surface portion. The method further involves applying an electric potential between the first and second electrodes such that the second electrode has a positive polarity relative to the first electrode to cause an electric current to flow between the second electrode and the first electrode in series through the second electrolyte, the second conductive surface portion, the first conductive surface portion and the first electrolyte. The second electrode is at a sufficiently more positive potential than the second conductive surface portion to cause an electrochemical reaction to occur at the second conductive surface portion to form the transparent metal oxide layer on the second conductive surface portion.
The non-aqueous solvent may be protic or aprotic.
The method may involve releasing metal ions capable of forming the transparent metal oxide layer to be optically transparent in the visible region of the electromagnetic spectrum, from salts soluble the in non-aqueous solvent.
The method may involve causing the second electrolyte to include a dopant electrochemically embeddable into the transparent metal oxide layer to produce a conductive transparent metal oxide layer.
The method may involve admitting a chemical supplement into at least one of the first and second electrolytes.
The method may involve counting coulombs of charges in the electric current and ceasing the application of the electric potential when a coulomb charge count meets a charge count criterion associated with a desired thickness of the transparent metal oxide layer.
The method may involve interrupting the current when the metal ion concentration in the second electrolyte meets a metal ion concentration criterion, replacing the second electrolyte, and re-establishing the electric current.
The method may involve moving the substrate relative to the first and second electrolytes in a direction from the first electrolyte to the second electrolyte while the electric current is flowing, to cause the transparent metal oxide layer to be formed in a lengthwise direction along the conductive surface of the substrate.
Forming the first and second electrochemical cells may involve holding the first electrolyte in a first open-faced container and holding the second electrolyte in a second open-faced container.
The method may involve defining the first and second open-faced containers by an entrance wall, an interior wall, an exit wall, first end wall portions and a first bottom wall portion, such that the first open-faced container is defined between the entrance wall, the interior wall, the first end wall portions and the first bottom wall portion and such that the second open-faced container is defined between the interior wall, the exit wall, second end wall portions and a second bottom wall portion.
The method may involve causing the first electrode to extend through the entrance wall, a first end wall portion or the first bottom wall portion, at a first position in parallel spaced apart relation to the substrate and causing the second electrode to extend through the exit wall, a second end wall portion or the second bottom wall portion, at a second position in parallel spaced apart relation to the substrate.
The method may involve admitting the dielectric substrate having the conductive surface through an entrance opening in the entrance wall and causing the substrate to extend over the first and second open-faced containers such that the conductive surface faces the first and second open-faced containers. The first conductive surface portion is a portion of the conductive surface that extends over the first container and the second conductive surface portion is a portion of the conductive surface that extends over the second open-faced container and the method may further involve causing a portion of the substrate to extend through an exit opening in an exit wall of the second open-faced container.
The method may involve causing the entrance opening and the exit opening to be sealed against the conductive surface of the dielectric substrate to prevent leakage of the first and second electrolytes respectively from the entrance and exit openings respectively.
The method may involve causing the interior wall to be sealed against the conductive surface of the dielectric substrate to prevent exchange of the first and second electrolytes at the interior wall.
The method may involve moving the substrate relative to the first and second electrolytes in a direction from the first electrolyte to the second electrolyte while the electric current is flowing, to cause the transparent metal oxide layer to be formed in a lengthwise direction along the conductive surface of the substrate.
Moving may involve moving the substrate while holding the first and second open-faced containers stationary.
The method may involve causing the first and second open-faced containers to be placed open-face down on the conductive surface of the dielectric substrate such that the substrate extends under the entrance wall, the interior wall, the exit wall, and the first and second end wall portions such that the first and second conductive surfaces of the dielectric substrate face the first and second open-faced containers. The first conductive surface portion is a portion of the conductive surface that extends under the first open-faced container and the second conductive surface portion is a portion of the conductive surface that extends under the second open-faced container and the method may further involve causing a portion of the conductive surface of the dielectric substrate to extend under the exit wall of the second open-faced container.
The method may involve holding the substrate with the conductive surface face-up in a container holding an initial electrolyte and causing the first and second open-faced containers to be placed open-face down on the conductive surface of the dielectric substrate. This may involve causing the first and second open-faced containers to be substantially submerged in the initial electrolyte and causing the entrance wall, the exit wall, and the first and second end wall portions to be sealed against the substrate to contain a first volume of the initial electrolyte in the first open-faced container and to contain a second volume of the initial electrolyte in the second open-faced container.
The method may involve causing the interior wall to be sealed against the conductive surface of the dielectric substrate to prevent leakage of the first and second electrolytes respectively under the interior wall.
The method may involve moving the substrate relative to the first and second electrolytes in a direction from the first electrolyte to the second electrolyte while the electric current is flowing, to cause the transparent metal oxide layer to be formed in a lengthwise direction along the conductive surface of the substrate.
Moving may involve moving the first and second open-faced containers while holding the substrate stationary.
In accordance with another aspect of the invention, there is provided a method of forming a transparent metal oxide layer on a first conductive surface of a first dielectric substrate. The method involves pressing the first conductive surface of a first dielectric substrate against a space-defining frame gasket on a second conductive surface of a second dielectric substrate such that the frame defines a sealed space between the first conductive surface and the second conductive surface. The method further involves admitting an electrolyte having chemicals that facilitate conduction of electric current through the electrolyte into the sealed space through an opening in the frame gasket, the chemicals including a non-aqueous solvent, metal ions in a metal ion concentration at least sufficient to facilitate formation of the transparent metal oxide layer to a desired thickness and a source of oxygen suitable to facilitate formation of the transparent metal-oxide surface of the second conductive surface. The method further involves applying an electric potential between the first and second conductive surfaces such that the second conductive surface has a negative polarity relative to the first conductive surface to cause an electric current to flow between the first conductive surface and the second conductive surface through the electrolyte to cause an electrochemical reaction to occur at the first conductive surface to form the transparent metal oxide layer on the first conductive surface.
The non-aqueous solvent may be protic or aprotic.
The method may involve releasing metal ions capable of forming the transparent metal oxide layer to be optically transparent in the visible region of the electromagnetic spectrum, from salts soluble in the non-aqueous solvent.
The method may involve causing the second electrolyte to include a dopant electrochemically embeddable into the transparent metal oxide layer to produce a conductive transparent metal oxide layer.
The method may involve admitting a chemical supplement into the electrolyte.
The method may involve counting coulombs of charges in the electric current and ceasing the application of the electric potential when a coulomb charge count meets a coulomb charge count criterion associated with a desired thickness of the transparent metal oxide layer.
The method may involve interrupting the current when a metal ion concentration in the electrolyte meets a metal ion concentration criterion, replacing the electrolyte, and re-establishing the electric current.
The pressing may involve pressing sufficiently to compress the space-defining frame gasket to sufficiently seal the sealed space to prevent leakage of the electrolyte from the sealed space.
Applying an electric potential may involve fastening first and second conductive clamps on first and second opposite edges respectively of the first substrate to make electrical contact with the first conductive surface at opposite edges of the first substrate and fastening third and fourth of conductive clamps on third and fourth edges of the dielectric substrate to make electrical contact with the second conductive surface on the dielectric substrate and connecting the first and second clamps to a positive terminal of a current source and connecting the third and fourth clamps to a negative terminal of the current source.
In accordance with another aspect of the invention, there is provided an apparatus for forming a transparent metal oxide layer on a conductive surface of a dielectric substrate. The apparatus includes provisions for holding a first electrolyte and a first electrode in contact with the first electrolyte, and provisions for holding a second electrolyte and a second electrode in contact with the second electrolyte. The apparatus further includes provisions for simultaneously exposing first and second conductive surface portions of the conductive surface of the dielectric substrate to the first and second electrolytes respectively, such that the first and second conductive surface portions are spaced apart from the first and second electrodes respectively to form first and second electrochemical cells respectively and whereby the first and second electrochemical cells are electrically connected together in series by the conductive surface of the dielectric substrate. The first electrolyte has first chemicals that facilitate conduction of electric current through the first electrolyte without facilitating significant electrochemical reaction at the first electrode or at the first conductive surface portion. The second electrolyte has second chemicals that facilitate conduction of electric current through the second electrolyte, the second chemicals including a non-aqueous solvent, metal ions in a metal ion concentration at least sufficient to facilitate formation of the transparent metal oxide layer to a desired thickness and a source of oxygen suitable to facilitate formation of the transparent metal-oxide layer on the second conductive surface portion. The apparatus further includes provisions for applying an electric potential between the first and second electrodes such that the second electrode has a positive polarity relative to the first electrode to cause an electric current to flow between the second electrode and the first electrode in series through the second electrolyte, the second conductive surface portion, the first conductive surface portion and the first electrolyte. The second electrode is at a sufficiently more positive potential than the second conductive surface portion to cause an electrochemical reaction to occur at the second conductive surface portion to form the transparent metal oxide layer on the second conductive surface portion.
The non-aqueous solvent may be protic or aprotic solvent.
The apparatus may include releasing metal ions capable of forming the transparent metal oxide layer to be optically transparent in the visible region of the electromagnetic spectrum, from salts soluble the in non-aqueous solvent.
The apparatus may include causing the second electrolyte to include a dopant electrochemically embeddable into the transparent metal oxide layer to produce a conductive transparent metal oxide layer.
The apparatus may include provisions for counting coulombs of charges in the electric current and means, in communication with the means for counting coulombs, for ceasing the application of the electric potential when a coulomb charge count indicated by the means for counting coulombs meets a coulombs count criterion associated with a desired thickness of the transparent metal oxide layer.
The apparatus may include provisions for interrupting the current when a metal ion concentration in the second electrolyte meets a metal ion concentration criterion, means for replacing the second electrolyte, and means for re-establishing the electric current after second electrolyte has been replaced.
The apparatus may include provisions for moving the substrate relative to the first and second electrolytes in a direction from the first electrolyte to the second electrolyte while the electric current is flowing, to cause the transparent metal oxide layer to be formed in a lengthwise direction along the conductive surface of the substrate.
The means for holding the first electrolyte and the first electrode may include a first open-faced container and the means for holding the second electrolyte and the second electrode may include a second open-faced container.
The first open-faced container may include an entrance wall and an interior wall, a pair of first end walls and a first bottom wall portion and the second open-faced container may comprise the interior wall and an exit wall and a pair of second end walls and a second bottom wall portion the first and second open-faced containers have first and second end wall portions.
The first electrode may extend through the entrance wall, at least one of the first end wall portions or the first bottom wall portion, at a first position in parallel spaced apart relation to the substrate and the second electrode may extend through the exit wall, at least one of the second end wall portions or the second bottom wall portion, at a second position in parallel spaced apart relation to the conductive surface of the dielectric substrate.
The means for simultaneously exposing the first and second surface portions of the conductive surface of the substrate may include an entrance opening in the entrance wall and an exit opening in the exit wall, for receiving and positioning the dielectric substrate to cause the dielectric substrate to extend over the first and second open-faced containers such that the first conductive surface portion faces the first open-faced container and such that the second conductive surface portion faces the second open-faced container.
The apparatus may include entrance and exit seals operably configured to seal the entrance opening and the exit opening against the conductive surface of the dielectric substrate to prevent leakage of the first and second electrolytes respectively from the entrance and exit openings respectively.
The apparatus may include an interior wall seal operably configured to seal the interior wall against the conductive surface of the dielectric substrate to prevent exchange of the first and second electrolytes at the interior wall.
The apparatus may include provisions for moving the substrate relative to the first and second electrolytes in a direction from the first electrolyte to the second electrolyte while the electric current is flowing, to cause the transparent metal oxide layer to be formed in a lengthwise direction along the conductive surface of the substrate.
The provisions for moving may include provisions for moving the substrate and provisions for holding the first and second open-faced containers stationary while the substrate is being moved.
The apparatus may further include provisions for positioning the first and second open-faced containers face down on the conductive surface of the dielectric substrate such that the substrate extends under the entrance wall, the interior wall, the exit wall, and the first and second pairs of end walls such that the first and second conductive surfaces of the dielectric substrate face the first and second open-faced containers.
The apparatus may include provisions for holding a volume of an initial electrolyte, provisions for holding the dielectric substrate with the conductive surface face-up in the initial electrolyte, and the provisions for positioning the first and second open-faced containers face down on the conductive surface of the dielectric substrate may comprise provisions for causing the first and second open-faced containers to be substantially submerged in the initial electrolyte. The apparatus may further include provisions for sealing the entrance wall, the exit wall, and the first and second end wall portions against the substrate to contain a first volume of the initial electrolyte in the first open-faced container and to contain a second volume of the initial electrolyte in the second open-faced container.
The apparatus may include provisions for sealing the interior wall against the conductive surface of the dielectric substrate to prevent leakage of the first and second electrolytes respectively at the interior wall.
The apparatus may include provisions for moving the substrate relative to the first and second electrolytes in a direction from the first electrolyte to the second electrolyte while the electric current is flowing, to cause the transparent metal oxide layer to be formed in a lengthwise direction along the conductive surface of the substrate.
The provisions for moving may include provisions for moving the first and second open-faced containers and provisions for holding the substrate stationary while the first and second open-faced containers are being moved.
In accordance with another aspect of the invention, there is provided an apparatus for forming a transparent metal oxide layer on a first conductive surface of a first dielectric substrate. The apparatus includes a space-defining frame gasket positioned on the conductive surface of the dielectric substrate. The gasket has an inner wall defining a space bounded by the inner wall and a portion of the conductive surface of the dielectric substrate. The apparatus further includes provisions for pressing a second conductive surface of a second dielectric substrate against the space-defining frame gasket to cause the space to be a sealed space, and an opening in the frame gasket for admitting into the sealed space an electrolyte having chemicals that facilitate conduction of electric current through the electrolyte. The chemicals include non-aqueous solvent, metal ions and a source of oxygen suitable to facilitate formation of the transparent metal-oxide layer on the conductive surface of the first dielectric substrate. The apparatus further includes provisions for applying an electric potential between the second conductive surface of the second dielectric substrate and the first conductive surface of the first substrate such that the first conductive surface of the first substrate has a negative polarity relative to the second conductive surface of the second dielectric substrate to cause an electric current to flow between the second conductive surface and the first conductive surface, through the electrolyte to cause an electrochemical reaction to occur at the first conductive surface to form the transparent metal oxide layer on the first conductive surface.
The non-aqueous solvent may be protic or aprotic solvent.
The apparatus may include releasing metal ions capable of forming the transparent metal oxide layer to be optically transparent in the visible region of the electromagnetic spectrum, from salts soluble the in non-aqueous solvent.
The apparatus may include causing the second electrolyte to include a dopant electrochemically embeddable into the transparent metal oxide layer to produce a conductive transparent metal oxide layer.
The apparatus may include provisions for counting coulombs of charges in the electric current and means in communication with the means for counting coulombs for ceasing the application of the electric potential when a coulomb charge count indicated by the means for counting coulombs meets a coulomb count criterion associated with a desired thickness of the transparent metal oxide layer.
The apparatus may include provisions for interrupting the current when a metal ion concentration in the electrolyte meets a metal ion concentration criterion, provisions for replacing the electrolyte, and provisions for re-establishing the electric current after the electrolyte has been replaced.
The provisions for pressing may be operably configured to press sufficiently to compress the space-defining frame gasket to sufficiently seal the sealed space to prevent leakage of the electrolyte from the sealed space.
The provisions for applying an electric potential may include first and second conductive clamps on first and second opposite edges respectively of the first substrate in electrical contact with the first conductive coating at opposite side edges of the first substrate and third and fourth conductive clamps on third and fourth opposite edges of the dielectric substrate in electrical contact with the second conductive surface of opposite side edges of the dielectric substrate. The first and second clamps are operably configured to be connected to a negative terminal of a current source and the third and fourth clamps are operably configured to be connected to a positive terminal of the current source.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.
In drawings which illustrate embodiments of the invention,
Referring to
In this embodiment, the apparatus includes provisions shown generally at 12 for holding a first electrolyte 14 and a first electrode 16 in contact with the first electrolyte 14. The apparatus 10 further includes provisions shown generally at 18 for holding a second electrolyte 20 and a second electrode 22 in contact with the second electrolyte. The apparatus 10 also includes provisions shown generally at 24 and 26 for simultaneously exposing first and second conductive surface portions 28 and 30 of the conductive surface 32 of the dielectric substrate 34 to the first and second electrolytes 14 and 20 respectively. The first and second conductive surface portions 28 and 30 are spaced apart from the first and second electrodes 16 and 22 respectively to form first and second electrochemical cells 36 and 38 respectively such that the first and second electrochemical cells 36 and 38 are electrochemically connected together in series by the conductive surface 32 of the dielectric substrate 30.
The main function of the first electrolyte 14 is to conduct electric current between the first conductive surface portion 28 and the first electrode 16. The chemical composition of the first electrode can be quite simple and may include merely only a solvent and dissolved potassium chloride salt, for example. With this simple chemical composition there will be no significant chemical reaction at the first electrode or at the first conductive surface portion that will significantly degrade either of these entities. The second electrolyte 20 has a chemical composition that is much more complex. The chemical composition of the second electrolyte 20 is configured to facilitate conducting electric current between the second electrode 22 and the second conductive portion 30 and to facilitate electrochemical formation of the desired transparent metal oxide layer on the second conductive surface portion 30 of the dielectric substrate 34. The chemicals in the second electrolyte 20 include a non aqueous solvent, metal ions in a concentration at least sufficient to facilitate formation of the transparent metal oxide layer to a desired thickness on the second conductive surface portion 30 and a source of oxygen suitable to facilitate formation of the transparent metal oxide layer on the second conductive surface portion 30. The apparatus 10 further includes provisions for applying an electric potential between the first and second electrodes 16 and 22 such that the second electrode 22 has a positive polarity relative to the first electrode 16 to cause an electric current to flow between the second electrode 22 and the first electrode 16, in series, through the second electrolyte 20, the second conductive surface portion 30, the first conductive surface portion 28 and the first electrolyte 14. This creates an electric circuit wherein the second electrode 22 is at a sufficiently more positive potential than the second conductive surface portion 30 to cause an electrochemical reaction to occur at the second conductive surface portion 30, to form the transparent metal oxide layer on the second conductive surface portion 30.
Referring to
The body 53 may be produced from Teflon® reflowed anodized aluminium, Teflon®, organic glass or other chemically and mechanically stable materials. The length of the body 53 may be defined between outer surfaces of the entrance and exit walls 54 and 62 and may be from about 10 cm to about 200 cm. The width of the body 53 may be defined between outer surfaces of the respective pairs of side walls 58 and 59 and may be about 10 cm to about 200 cm. The width may be determined, based on the width of the dielectric substrate 34 on which the transparent metal oxide layer is to be formed. The height of the body 53 may be between about 4 cm to about 50 cm. The height, of course, defines the depth of the first and second open-faced containers 50 and 52 respectively and may be set within the above indicated range to provide for a suitable spacing of the first and second electrodes from the first conductive surface portion 28 and the second conductive surface portion 30 respectively and to provide for a sufficient volume of first and second electrolytes 14 and 20 to provide a suitable supply of chemicals for forming the transparent metal oxide to a desired thickness. For example, the first and second open-faced containers 50 and 52 may have depths from about 3 cm to about 47 cm and widths from about 20 cm to about 190 cm but their lengths may be different. For example, the first open-faced container 50 may have a length of about 10 cm to about 50 cm and the second open-faced container 52 may have a length of about 2 cm to about 150 cm.
Still referring to
The first electrode 16 is a planar electrode comprising a dielectric substrate 80 such as glass having a thickness of about 0.3-4 mm for example, having a conductive surface 82 disposed on one broad face thereof. The conductive surface 82 may be produced from chemically stable materials, for example, fluoride doped zinc oxide having a thickness of about 300 nm to about 1500 nm and a sheet resistance from about 20 Ω/sq to about 0.1 Ω/sq. This conductive layer may be produced on the dielectric substrate 80 by CVD or sputtering techniques, for example. The first electrode 16 is inserted through the entrance opening 70 such that an end portion 84 of the first electrode rests adjacent a first surface 86 of the interior wall 56. A support (not shown) may be provided to position the end portion 84 such that the first electrode will be parallel with the first conductive surface portion 27. The first upper and lower elastomeric seals 76 and 78 bear upon the conductive surface 82 and a non-conductive surface 88 of the first electrode 16 to prevent the first electrolyte 14 from leaking out through the entrance opening 70. The first electrode 16 further has an outer edge 90 that extends outside of the first open-faced container 50 and to which is secured a first conductive clamp 92 comprising a contact element 94 and a C-shaped channel 96 having first and second opposite legs 98 and 100. The contact element 94 is received between the first leg 98 and the conductive surface 82 of the first electrode 16 so as to make contact therewith. The contact element 94 is made from soft sufficiently conductive metal such as silver or indium, for example. Screws such as shown at 102 are provided to press the contact element 94 solidly against the conductive surface 82 to make good electrical contact therewith. The clamp 92 is connected to a wire 104 which in turn is connected to a negative terminal 106 of a power supply 108.
Similarly, the exit wall 62 is provided with an elongated opening 110 having upper and lower wall portions 112 and 114 to which are secured second upper and lower elastomeric seals 116 and 118 respectively. The second electrode 22 is the same as the first electrode 16 and has a substrate 120 having a lower non-conductive surface 122 and an upper conductive surface 124. The second electrode 22 is inserted into the opening 110 until an end portion 126 thereof is adjacent a second surface 128 of the interior wall 56. A support (not shown) may be provided to position the end portion 126 such that the second electrode will be parallel with the second conductive surface portion 30. The second upper and lower elastomeric seals 116 and 118 are the same as those described in connection with the first electrode (76 and 78) and bear against the conductive and non-conductive surfaces 124 and 122 respectively to seal the opening 110 to prevent leakage of the second electrolyte 20 through the opening 110. The second electrode is provided with a second conductive clamp 130 the same as the conductive clamp 92 used on the first electrode 16 and a wire 132 is connected to the second conductive clamp 130 to connect it to a positive terminal 134 of the power supply 108.
The first electrode 16 and the first conductive surface portion 28 may be spaced apart by about 1 mm to about 50 mm. The second electrode 22 and the second conductive surface portion 30 may be spaced apart by the same distance.
The provisions for simultaneously exposing the first and second conductive surface portions 28 and 30 of the conductive surface 32 on the substrate 34 to the first and second electrolytes respectively include an entrance opening 150 in the entrance wall 54 and an exit opening 152 in the exit wall 62, for receiving and positioning the dielectric substrate 34 to cause the dielectric substrate to extend over the first and second open faced containers 50 and 52 such that the first conductive surface portion 28 faces the first open-faced container 50 and such that the second conductive surface portion 30 faces the second open-faced container 52. The entrance opening 150 has respective upper and lower entrance walls 154 and 156 to which are attached upper and lower entrance seals 158 and 160 respectively. The upper and lower entrance seals 158 and 160 are the same as the elastomeric seals 76 and 78. The upper entrance seal 58 bears upon the uncoated surface of the dielectric substrate 34 while the lower entrance seal 160 bears upon the conductive surface 32 of the substrate and thus seals the entrance opening to prevent leakage of the first electrolyte 14 from the entrance opening 150.
Similarly, the exit opening 152 has upper and lower walls 162 and 164 to which are connected upper and lower exit seals 166 and 168 respectively, the same as the elastomeric seals 116 and 118. The upper exit seal 166 bears upon the uncoated surface of the substrate 34 while the lower exit seal 168 bears upon the second conductive surface portion 30 of the dielectric substrate 34 to seal the exit opening 152 to prevent leakage of the second electrolyte 20 from the exit opening 152. The entrance and exit openings 150 and 152 are disposed in a common substrate plane which is parallel to and spaced apart from an electrode plane in which the first and second electrodes 16 and 22 lie. The substrate plane and the electrode plane are disposed so that the first and second electrolytes 14 and 20 contact the entire first and second conductive surface portions 28 and 30 of the conductive surface 32 respectively. In the embodiment shown, the interior wall 56 is disposed mid-way between the entrance and exit walls 54 and 62 and has an upper portion 170 that is disposed slightly below the substrate plane. An interior wall seal 172 is disposed on the upper portion 170 so as to contact the conductive surface 32 of the dielectric substrate 34. The interior wall seal 172 has a thickness about the same thickness of the lower entrance seal 160. This sufficiently prevents ion exchange between the first electrolyte 14 and the second electrolyte 20. If the thickness of the interior seal 172 is lower than the thickness of the entrance seal 160, a space between the conductive surface 32 of the substrate 34 and the entrance seal 172 is formed, resulting in an ion exchange path between the first electrolyte 14 and the second electrolyte 20 (not shown). The creation of such an ion exchange path between the first and second electrodes 16 and 22 through the first and the second electrolytes 14 and 20 may result in undesirable metal oxide plating on the first electrode 16.
Each of the entrance wall 54 and the interior wall 56 and the exit wall 62 have elongated openings 180, 182 and 184 respectively in which are received respective heater elements 186, 188, and 190 respectively, seen best in
Still referring to
Ideally, the first and second electrodes 16 and 22 and dielectric substrate 34 are positioned as shown in
The first and second electrolytes 14 and 20 have chemicals that facilitate conduction of electric current therethrough and may include protic non-aqueous solvents that include at least one of methanol, ethanol, propanol, isopropanol, ethylene glycol, glycerol and tetrahydrofurfuryl alcohol.
Alternatively, they may include aprotic non-aqueous solvents that include at least one of N-Methylacetamide, dimethylformamide, acetonitrile, dimethylsulfoxide (DMSO) and propylene carbonate.
As described above, the first electrolyte 14 may, for example, be very simple and include merely a non-aqueous solvent and at least one salt, for example potassium chloride, to provide for conductivity.
At least the second electrolyte 20 has a chemical composition that includes a source of oxygen sufficient to permit the transparent metal oxide layer to be formed to a desired thickness. The source of oxygen may include dissolved oxygen or at least one oxygen precursor such as at least one of dissolved nitrate, nitrite, peroxo compounds, ozone, and traces of water. The concentration of dissolved oxygen ready for use in the electrochemical process of forming the transparent metal oxide layer should be selected such that at least enough source oxygen is provided in the volume of second electrolyte 20 dispensed into the second open-faced container 52 to facilitate formation of a metal oxide layer of a desired thickness.
The chemical composition of the second electrolyte 20 also includes an ionic source of metal sufficiently soluble in the selected solvent and that will facilitate formation of the metal transparent oxide layer to a desired thickness and such that the transparent metal oxide layer has an optical transparency from about 85% to about 95% in a spectral region having wavelengths from about 380 nm to about 750 nm.
Using the apparatus described, where a transparent zinc oxide layer is to be formed, the chemicals in the second electrolyte will include an ionic source of metal such as at least one dissolved zinc salt or at least one zincate or a combination of the at least one dissolved zinc salt and the at least one zincate. The at least one dissolved zinc salt may be nitrate, chloride, perchlorate or sulphate, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L (gram equivalent/litre) to 0.1 Eq/L of zinc or from 0.0001 Eq/L of zinc to a saturation concentration to produce a zinc oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where a transparent non-conductive aluminum oxide layer is intended to be formed, the ionic source of metal may include at least one dissolved aluminum salt or at least one aluminate or a combination of the at least one dissolved aluminum salt or at least one aluminate. The dissolved aluminium salt may be nitrate, chloride, perchlorate or sulphate, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L (gram equivalent/litre) to 0.1 Eq/L of aluminum or from 0.0001 Eq/L of aluminum to a saturation concentration to produce an aluminum oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where a transparent non-conductive indium oxide layer is to be formed, the ionic source of metal may include at least one dissolved indium salt. The at least one dissolved indium salt may be nitrate, chloride or sulphate, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L to 0.1 Eq/L of indium or from 0.0001 Eq/L of indium to a saturation concentration to produce an indium oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where a transparent non-conductive cadmium oxide layer is to be formed, the ionic source of metal may include at least one dissolved cadmium salt. The at least one dissolved cadmium salt may be nitrate, chloride, perchlorate or sulphate, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L to 0.1 Eq/L of cadmium or from 0.0001 Eq/L of cadmium to a saturation concentration to produce a cadmium oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where a transparent non-conductive magnesium oxide layer is to be formed, the ionic source of metal may include at least one dissolved magnesium salt. The at least one dissolved magnesium salt may be nitrate, chloride or perchlorate, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L to 0.1 Eq/L of magnesium or from 0.0001 Eq/L of magnesium to a saturation concentration to produce a magnesium oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where a transparent non-conductive silver oxide layer is to be formed, the ionic source of metal may include at least one dissolved silver salt. The at least one dissolved silver salt may be nitrate or perchlorate, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L to 0.1 Eq/L of silver or from 0.0001 Eq/L of silver to a saturation concentration to produce a silver oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where a transparent non-conductive yttrium oxide layer is to be formed, the ionic source of metal may include at least one dissolved yttrium salt. The at least one dissolved yttrium salt may be nitrate, chloride, perchlorate or sulphate, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L (gram equivalent/litre) to 0.1 Eq/L of yttrium or from 0.0001 Eq/L of yttrium to a saturation concentration to produce an yttrium oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where a transparent non-conductive scandium oxide layer is to be formed, the ionic source of metal may include at least one dissolved scandium salt. The at least one dissolved scandium salt may be nitrate, chloride, perchlorate or sulphate, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L (gram equivalent/litre) to 0.1 Eq/L of scandium or from 0.0001 Eq/L of scandium to a saturation concentration to produce a scandium oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where a transparent non-conductive oxide layer of a lanthanide is to be formed, the ionic source of lanthanide may include at least one dissolved lanthanide salt. The at least one dissolved lanthanide salt may be nitrate, chloride, perchlorate or sulphate, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L to 0.1 Eq/L of lanthanide or from 0.0001 Eq/L of lanthanide to a saturation concentration to produce a lanthanide oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where a transparent non-conductive gallium oxide layer is to be formed, the ionic source of metal may include at least one dissolved gallium salt. The at least one dissolved gallium salt may be nitrate, chloride, perchlorate or sulphate, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L to 0.1 Eq/L of gallium or from 0.0001 Eq/L of gallium to a saturation concentration to produce a gallium oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where it is desired to form a transparent non-conductive oxide layer comprised of a transition metal of Sub-Group IVA of the periodic table, such as titanium, zirconium or hafnium, the ionic source of such transition metal may include at least one dissolved metal salt. The at least one dissolved metal salt may be chloride or sulphate, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L to 0.1 Eq/L of the transition metal or from 0.0001 Eq/L of the transition metal to a saturation concentration to produce a transparent metal oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where it is desired to form a transparent non-conductive oxide layer comprised of a metal of Sub-Group IVB of the periodic table, such as germanium, tin or lead, the ionic source of the appropriate metal may include at least one dissolved metal salt. The at least one dissolved metal salt may be chloride or sulphate, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L to 0.1 Eq/L of metal or from 0.0001 Eq/L of metal to a saturation concentration to produce a metal oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where it is desired to form a transparent non-conductive oxide layer comprised of a transition metal of Sub-Group VA of the periodic table, such as vanadium, niobium or tantalum, the ionic source of such transition metal may include at least one dissolved transition metal salt. The at least one dissolved transition metal salt may be nitrate or chloride, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L to 0.1 Eq/L of metal or from 0.0001 Eq/L of metal to a saturation concentration to produce a metal oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where it is desired to form a transparent non-conductive oxide layer comprised of a transition metal of Sub-Group VIA of the periodic table such as chromium, molybdenum, or tungsten, the ionic source of such transition metal may include at least one dissolved transition metal salt. The at least one dissolved transition metal salt may be chloride or sulphate, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L to 0.1 Eq/L of metal or from 0.0001 Eq/L of metal to a saturation concentration to produce a metal oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where it is desired to form a transparent non-conductive oxide layer of a transition metal of Sub-Group VIIA of the periodic table such as manganese or rhenium, the ionic source of such transition metal may include at least one dissolved transition metal salt. The at least one dissolved transition metal salt may be chloride or sulphate, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L to 0.1 Eq/L of metal or from 0.0001 Eq/L of metal to a saturation concentration to produce a metal oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where it is desired to form a transparent non-conductive oxide layer of metals of Group VIII of the period table, such as iron, cobalt, nickel or ruthenium, the ionic source of the appropriate metal may include at least one dissolved metal salt. The at least one dissolved metal salt may be chloride or sulphate, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L to 0.1 Eq/L of metal or from 0.0001 Eq/L of metal to a saturation concentration to produce a metal oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where it is desired to form a transparent non-conductive oxide layer of a metal of Sub-Group VB of the periodic table, such as antimony or bismuth, the ionic source of the appropriate metal may include at least one dissolved metal salt. The at least one dissolved metal salt may be nitrate, chloride or sulphate, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L to 0.1 Eq/L of metal or from 0.0001 Eq/L of metal to a saturation concentration to produce a metal oxide film having a thickness of about 10 nm to about 500 nm, for example.
The second electrolyte 20 may include a dopant at a concentration that causes the transparent metal oxide layer to be conductive. The dopant and a concentration of its precursor in the second electrolyte 20 is selected such that a doped transparent conductive metal oxide is formed on the second conductive surface 30, to have a sheet resistance in the range of 1000-1.0 Ω/sq, and a transmittance in the visible wavelength range in the range from 60% to 100%. Dopants may include at least one element from the group comprising halogens, zinc, cadmium, magnesium, copper, silver, gold, boron, aluminum, gallium, indium, scandium, yttrium, germanium, tin, lead, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, rhenium, iron, cobalt, nickel, ruthenium, arsenic, antimony, bismuth, Pt-group of metals, and lanthanides, for example.
Where a transparent conductive aluminum-doped zinc oxide layer is to be formed, the ionic source of metal may include at least one dissolved zinc salt and at least one dissolved aluminum salt. The dissolved zinc salt may be nitrate, chloride, perchlorate or sulphate, for example. The dissolved aluminum salt may be selected from nitrate, chloride, perchlorate or sulphate for example. The organic solvent electrolyte solution may contain gram equivalents of zinc and aluminum in the ratio of between about 10000:1 to 5:1 to produce an aluminum-doped zinc oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where an yttrium-doped zinc oxide layer is to be formed, the ionic source of metal may include at least one dissolved zinc salt and at least one dissolved yttrium salt. The dissolved zinc salt may be selected from nitrate, chloride, perchlorate or sulphate for example. The dissolved yttrium salt may be selected from nitrate, chloride, perchlorate or sulphate, for example. The organic solvent electrolyte solution may contain gram equivalents of zinc and yttrium in the ratio of between about 10000:1 to 5:1 to produce an yttrium-doped zinc oxide film having a thickness of about 10 nm to about 500 nm.
Where a transparent conductive indium-doped zinc oxide layer is to be formed, the ionic source of metal may include at least one dissolved zinc salt and at least one dissolved indium salt. The dissolved zinc salt may be nitrate, chloride, perchlorate or sulphate for example, and the at least one dissolved indium salt, may be nitrate, chloride, perchlorate or sulphate, for example. The organic solvent electrolyte solution may contain gram equivalents of zinc and indium in the ratio of between about 10000:1 to 5:1 to produce an indium-doped zinc oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where a transparent conductive cadmium-doped zinc oxide layer is to be formed, the ionic source of metal may include at least one dissolved zinc salt and at least one dissolved cadmium salt. The dissolved zinc salt may be nitrate, chloride, perchlorate or sulphate for example, and the at least one dissolved cadmium salt, may be nitrate, chloride, perchlorate or sulphate, for example. The organic solvent electrolyte solution may contain gram equivalents of zinc and cadmium in the ratio of between about 10:1 to 1:10 to produce a cadmium-doped zinc oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where a transparent conductive chlorine-doped zinc oxide layer is to be formed, the ionic source of metal may include at least one dissolved zinc salt and at least one dissolved chloride. The at least one zinc salt may be nitrate, chloride, perchlorate or sulphate, for example. The organic solvent electrolyte solution may contain from 0.0001 Eq/L (gram equivalent/litre) to 0.1 Eq/L of zinc or from 0.0001 Eq/L of zinc to concentration of saturated solution and from 0.0001 Eq/L to 0.1 Eq/L of chloride or from 0.0001 Eq/L of chloride to concentration of saturated solution to produce a chlorine-doped zinc oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where a transparent conductive tin-doped indium oxide layer is to be formed, the ionic source of metal may include at least one dissolved indium salt and at least one dissolved tin salt. The dissolved indium salt may be nitrate, chloride, perchlorate or sulphate for example, and the at least one dissolved tin salt may be selected from nitrate, chloride, or sulphate, for example. The organic solvent electrolyte solution may contain gram equivalents of indium and tin in the ratio of between about 200:1 to 1:1 to produce an tin-doped indium oxide film having a thickness of about 10 nm to about 500 nm, for example.
Where a transparent conductive indium-doped cadmium oxide layer is to be formed, the ionic source of metal may include at least one dissolved cadmium salt and at least one dissolved indium salt. The dissolved cadmium salt may be nitrate, chloride, perchlorate or sulphate for example, and the at least one dissolved indium salt may be nitrate, chloride, perchlorate or sulphate for example. The organic solvent electrolyte solution may contain gram equivalents of cadmium and indium in the ratio of between about 1000:1 to 10:1 to produce an indium-doped cadmium oxide film having a thickness of about 10 nm to about 500 nm, for example.
The apparatus may be used as shown in
Referring to
In effect, resistances 203, 205, 207, 209, 211 and 213 are connected in series across the positive and negative terminals of the power supply 108 such that the second electrode 22 is at a higher positive potential than the first electrode 16. This causes a voltage drop to occur across each of the resistances which sets the potential at an interface 215 between the second electrode 22 and the interface 217 between the second electrolyte and the second conductive surface portion 30 to be at a higher potential which facilitates a cathodic chemical reaction at the interface 217 that forms the transparent metal oxide layer. The second conductive surface portion 30 has a relatively low conductivity and therefore the negative cathodic potential is relatively uniform along the second conductive surface portion 30 and facilitates the formation of a corresponding uniform transparent metal oxide layer on the second conductive surface portion 30.
It will be appreciated that if an ion exchange path between the first electrolyte 14 and the second electrolyte 20 is present, a resistive current flow path as represented by resistance R7 in
Referring back to
While the apparatus 10 shown in
Referring to
To facilitate this relative movement of the substrate relative to the first and second electrolytes the apparatus 10 is provided with a first entrance capstan 220 and entrance pinch roller 222 and with an exit capstan 224 and exit pinch roller 226. The entrance and exit capstans 220 and 224 and the pinch rollers 222 and 226 have resiliently deformable outer surfaces that gently grip the dielectric substrate 34 and its conductive surface 32 to direct the dielectric substrate through the apparatus 10. The entrance capstan 220 is rotated in a clockwise direction and bears upon the conductive surface 32 of the dielectric substrate 34 while the entrance pinch roller 222 bears upon the uncoated surface of the dielectric substrate 34. The dielectric substrate 34 is thus pinched between the entrance capstan 220 and the entrance pinch roller 222 such that when the entrance capstan 220 rotates, the dielectric substrate 34 is pushed into the entrance opening 70 in a direction shown by arrow 228.
At the same time, the exit capstan 224 also rotates in a clockwise direction and bears upon the conductive surface 32 of the dielectric substrate 34 that has just been coated due to exposure to the second electrolyte 20, while the exit pinch roller 226 bears upon the uncoated surface of the dielectric substrate 34 such that the substrate is pinched between the exit capstan 224 and the exit pinch roller 226, which further assists linear movement of the dielectric substrate 34 by drawing the substrate out of the exit opening 152. This allows a dielectric substrate having a conductive surface, of any length to be coated with a transparent metal oxide layer. The speed of rotation of the entrance and exit capstans 220 and 224 is such that the time that a given second surface portion 30 of the conductive surface 32 on the dielectric substrate 34 is exposed to the second electrolyte 20 is sufficient to cause a transparent metal oxide layer of a desired thickness to be formed thereon. As the concentration of metal ions in the second electrolyte 20 decreases the speed of rotation of the entrance and exit capstans 220 and 224 should be decreased accordingly, to maintain a uniform thickness in the layer being formed until the concentration of metal ions in the second electrolyte 20 reaches a predefined metal ion concentration at which point the sequence of ceasing the application of current, replacing the second electrolyte, and then reapplying the electric current, as described above, is initiated. A succession of sequences i.e. replenishments of the second electrolyte, may be required and the number of replenishments will depend upon the length of the dielectric substrate on which the transparent metal oxide layer is to be formed. In the embodiment shown, the entrance and exit capstans 220 and 224 may be rotated so as to produce a linear motion of the substrate 34 relative to the apparatus 10, on the order of between about 0.1 cm per minute and about 10 cm per minute, for example.
The lengths of the first or second open-faced containers and the speed of the dielectric substrate motion are independently optimised for high uniformity in conductive metal oxide thickness, optical transparency and conductivity on a large length of dielectric substrate.
Referring to
Referring to
Referring back to
As seen by the depiction of the apparatus 350 in broken outline, the apparatus is lowered into the deep tray 302 by the vertical retractable and extendable stand 432. The deep tray 302 and the apparatus 350 are dimensioned such that the first and second pairs of end walls 358, 359 abut inside surfaces of the side walls 308 and 310.
Referring to
The air gaps enable electrolyte adjustment chemicals to be added to the first and/or second volumes through the openings 400 and 402. For example, it may be desirable to add acid or alkali to the first volume to adjust the pH of the first volume of electrolyte to a desired value to protect the first electrode from metal oxide formation on its surface.
Still referring to
If the apparatus 350 is kept stationary in the tray 302, only the second conductive surface portion 424 in contact with the electrolyte in the second open faced container 382 will be coated. To coat a larger surface area however, the horizontally extendable and retractable arm 430 may be moved, in a direction shown by arrow 433 while holding the tray 302 and the dielectric substrate 318 stationary, to move the apparatus 350 into the position shown in broken outline in
Referring to
Referring to
The electrochemical cell assembly 502 further includes a second electrode 505 comprising a second substrate 550 having a second conductive surface 552 and third and fourth clamps 554 and 556 disposed along first and second edges 558 and 560 respectively of the second substrate 550 and in contact with the second conductive surface 552. The clamps 554 and 556 are the same as the clamps shown at 512 and 514 and hence the same as the clamp shown at 92 in
Referring back to
Referring back to
In each of the embodiments described above, there is provided a process and apparatus for electrochemically forming a transparent metal oxide on a conductive surface of a dielectric substrate such as glass, polymer or ceramic material. The above described apparatus and processes they perform provide a metal oxide layer having a high uniformity of thickness and a high degree of uniformity of electrical conductivity and optical transparency. This high degree of uniformity can be achieved over a relatively large conductive surface of the dielectric substrate by using above-described the methods of moving the substrate while holding the electrolytes stationary as described in connection with the first, second, third and fourth embodiments above or by moving the electrolytes while holding the substrate stationary as in the fourth embodiment. In the case of the first, second, third and fourth embodiments, the conductive layer on the substrate is coated with the transparent metal oxide layer with little or no degradation of the counter electrodes used in the respective first and second electrochemical cells employed.
While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CA2013/000208 | 3/6/2013 | WO | 00 |
