CA1070185A - Forming a film of snox on a glass surface by spraying an anhydrous solution containing snc12 - Google Patents
Forming a film of snox on a glass surface by spraying an anhydrous solution containing snc12Info
- Publication number
- CA1070185A CA1070185A CA248,168A CA248168A CA1070185A CA 1070185 A CA1070185 A CA 1070185A CA 248168 A CA248168 A CA 248168A CA 1070185 A CA1070185 A CA 1070185A
- Authority
- CA
- Canada
- Prior art keywords
- glass
- snox
- spraying
- film
- anhydrous
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Surface Treatment Of Glass (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A sheet of glass coated with SnOx by intermittent spraying of a mixture of materials in non-aqueous solution and in an oxidizing atmosphere, while maintaining the glass at a fixed temperature by supporting the glass in molten liquid at a controlled temperature, the spraying being conducted in suc-cessive passes involving small amounts of spray per pass, and the sheet of glass moving continuously along a pool of the molten liquid during the spraying process.
A sheet of glass coated with SnOx by intermittent spraying of a mixture of materials in non-aqueous solution and in an oxidizing atmosphere, while maintaining the glass at a fixed temperature by supporting the glass in molten liquid at a controlled temperature, the spraying being conducted in suc-cessive passes involving small amounts of spray per pass, and the sheet of glass moving continuously along a pool of the molten liquid during the spraying process.
Description
r~3 B~CKGROUND OF THE INVENTION
In our United States Patent No. 3,880,633, there is a method of coating a glass sheet with a thin film of SnO , in a continuous process, the glass moving continuously in a bath of molten material, and a spray containing a tin compound being applied in successive transverse passes of the glass.
The glass moves in a bath of molten material which may be tin, but may also be a salt, capable of sustaining the glass or partially sustaining the glass. In the latter case further support is supplied for the glass, so that its upper surface remains exposed, while at least its under surface is immersed.
It is known to coat glass with SnO , and it is also known that if glass is coated with SnO , the SnO being trans-parent and electrically conducting, the coating will serve to reflect infra-red energy while passing visible light, so that heating energy applied internally of a heated enclosure, employing one or more panes of such coated glass, is conserved internally of the enclosure since readiation of infra-red energy outwardly of the structure through the glass is reduced.
It is an object of the present invention to improve such coatings in such manner as to increase infra-red reflectivity of the SnO coating, while maintaining good transmission in the visible spectrum. The increase is a function of the reduced resistivity of the film, which is about 8-17 ohms per square, transmissibility of visible light being about 80%.
Conventional coating have resistivities of about 50-90 ohms per square and transmissibilities of about 70-78%. ~sJQ~ /sq.
is reduced transmissibility of visible light is not radically reduced but a large increase of infra-red reflectivity occurs.
30 ~ - 2 -SUMMARY OF THE INVENTION
According to the present invention, glass coated with SnO has a resistivity of about 8-17 ohms per square, trans-mlssivi-ty of visible light of substantially 80% and a reflect-ivity to infra-red energy of about 82%. Therefore, even though the improved coating of the present invention has a much lower resistivity than the prior art, its infra-red reflectivity has been substantially increased without affecting its good trans-mission in the visible spectrum.
The method of providing the coated glass of the pre-sent invention comprises heating the glass to substantially eliminate temperature gradients from at least one of its sur-faces, spraying a portion of the surface with an anhydrous tin containing solution in the presence of oxygen and maintaining the surface being sprayed, substantially free of temperature gradients and at a temperature sufficient to form the SnO
coating.
DETAILED DISCLOSURE OF SPECIFIC EMBODIMENT :
A molten bath is preheated to 600F. A glass plate is heated to 500 and moves along the bath. The bath is heated so that the exposed surface of the glass is at about 950 F. Spraying is accomplished by means of an air atomizing nozzle of an air spray, at 40 PSI for about 1 1/2 minutes, at 50 cc per minute. The following solution is employed:
250 ml methanol 0.7 gm phenyl hydrazine hydrochloride 3.0 gm ammonium bifluoride (NH4FHF) 70 gm SnC12 (anhydrous) The solution should be stirred for about five minutes before spraying, to clear the solution.
1 The solvent must not contain water, but methanol is employed as a solvent only because it is the most economical solvent available. Other non-aqueous solvents may be employed.
The phenyl hydrazine hydrochloride may be ommitted, but its presence has been found to reduce haze in the film. The pro-portions specified are selected on an ecomonomic and not a chemical basis, i.e., the smallest amount is employed which is satisfactory in producing a clear film. NH4FHF is a dopant, which can decrease film resistivity by a large factor, as much as 300%. The quantity of NH4FHF employed is selected on an economic basis, i.e., as little is used as is consistent with desired resistivity values.
The coating formed is about .3-.6 microns thicko The coated glass has reflectivity for infra-red of about 82%. The best prior art SnO coated glass with high transmission of the visible spectrum has an infra-red reflectivity of about 50%.
It is as mentioned above, crucial, in the process of of the invention, in order to achieve the desired characteris-tics of low resistivity, high reflectivity to infra-red radiation, and high transmissivity of the visible spectrum in a thin film coating, to supply heat to the glass continuously and uniformly and at uniform temperature. This cannot be accomplished by placing the glass on a heated surface, nor in an oven, but can be done by means of a heated liquid bath in which the glass is supported and which constitutes a large capacity heat resevoir to which the bottom surface of the glass is exposedO
It is required that spraying which is done in the presence of oxygen be accomplished intermittently, and very slowly, so that the temperature of the exposed surface of the glass can recover between sprays, and so that the glass is not cooled ....~
.. ~,~
., . : , ~ : ... , . :
1 appreciably by the sprays. It is important that the sprayed mixture be anhydrous, and that the environmental water be avoided, and that all supply lines, spray heads and the like be carefully flushed with methanol before spraying commences.
Presence of water increases resist.ivity and produces spots in the film.
- After the coating process is completed the glass sheet is slowly cooled, to anneal the glass, according to con-ventional techniques.
The present system lends itself to coating a sheet of glass with SnOx, as the glass is produced by a continuous process glass making machine, as in United States Patent No.
3,880,633. Glass is produced, in such a continuous process, in long sheets about ten feet wide. Since the glass is hot when produced, its heat is employed to maintain hot the float tanks in which the coating process is carried out. The process of coating may, accordingly, be carried out as part of a continuous glass making process. The process may, however, also be carried out on a pre-fabricated glass. In the latter case, the glass may be pre-heated to 950F in a conveyor furnace, and transferred to a molten liquid tank, the liquid being heated to a temperature which maintains the exposed surface of the glass at about 950F. In the first method the waste heat of the glass making process is employed to heat the glass, . 25 which represents an ecomonic advantage.
: Glass coated in accordance with the present method has particular advantage as window glass, for vehicles, dwellings, '.'' ~ 5 -~. , ...,.~
~L~ 97~L85 large buildings, hot houses, and the like. It also has applicatlon to ovens having viewing windows, and to solar heating systems, where it is desirable to avoid heat loss via infra-red radiation.
While the preferred fluoride is NH4FHF, it is feasible S to employ SnF2, i.e., a fluoride containing only F and Sn. The function of the NH~FHF is to provide fluorine plus a volatile remainder.
The material in the float tanks may be liquid tin or a molten salt capable of being mainLained at the required temperature.
In our United States Patent No. 3,880,633, there is a method of coating a glass sheet with a thin film of SnO , in a continuous process, the glass moving continuously in a bath of molten material, and a spray containing a tin compound being applied in successive transverse passes of the glass.
The glass moves in a bath of molten material which may be tin, but may also be a salt, capable of sustaining the glass or partially sustaining the glass. In the latter case further support is supplied for the glass, so that its upper surface remains exposed, while at least its under surface is immersed.
It is known to coat glass with SnO , and it is also known that if glass is coated with SnO , the SnO being trans-parent and electrically conducting, the coating will serve to reflect infra-red energy while passing visible light, so that heating energy applied internally of a heated enclosure, employing one or more panes of such coated glass, is conserved internally of the enclosure since readiation of infra-red energy outwardly of the structure through the glass is reduced.
It is an object of the present invention to improve such coatings in such manner as to increase infra-red reflectivity of the SnO coating, while maintaining good transmission in the visible spectrum. The increase is a function of the reduced resistivity of the film, which is about 8-17 ohms per square, transmissibility of visible light being about 80%.
Conventional coating have resistivities of about 50-90 ohms per square and transmissibilities of about 70-78%. ~sJQ~ /sq.
is reduced transmissibility of visible light is not radically reduced but a large increase of infra-red reflectivity occurs.
30 ~ - 2 -SUMMARY OF THE INVENTION
According to the present invention, glass coated with SnO has a resistivity of about 8-17 ohms per square, trans-mlssivi-ty of visible light of substantially 80% and a reflect-ivity to infra-red energy of about 82%. Therefore, even though the improved coating of the present invention has a much lower resistivity than the prior art, its infra-red reflectivity has been substantially increased without affecting its good trans-mission in the visible spectrum.
The method of providing the coated glass of the pre-sent invention comprises heating the glass to substantially eliminate temperature gradients from at least one of its sur-faces, spraying a portion of the surface with an anhydrous tin containing solution in the presence of oxygen and maintaining the surface being sprayed, substantially free of temperature gradients and at a temperature sufficient to form the SnO
coating.
DETAILED DISCLOSURE OF SPECIFIC EMBODIMENT :
A molten bath is preheated to 600F. A glass plate is heated to 500 and moves along the bath. The bath is heated so that the exposed surface of the glass is at about 950 F. Spraying is accomplished by means of an air atomizing nozzle of an air spray, at 40 PSI for about 1 1/2 minutes, at 50 cc per minute. The following solution is employed:
250 ml methanol 0.7 gm phenyl hydrazine hydrochloride 3.0 gm ammonium bifluoride (NH4FHF) 70 gm SnC12 (anhydrous) The solution should be stirred for about five minutes before spraying, to clear the solution.
1 The solvent must not contain water, but methanol is employed as a solvent only because it is the most economical solvent available. Other non-aqueous solvents may be employed.
The phenyl hydrazine hydrochloride may be ommitted, but its presence has been found to reduce haze in the film. The pro-portions specified are selected on an ecomonomic and not a chemical basis, i.e., the smallest amount is employed which is satisfactory in producing a clear film. NH4FHF is a dopant, which can decrease film resistivity by a large factor, as much as 300%. The quantity of NH4FHF employed is selected on an economic basis, i.e., as little is used as is consistent with desired resistivity values.
The coating formed is about .3-.6 microns thicko The coated glass has reflectivity for infra-red of about 82%. The best prior art SnO coated glass with high transmission of the visible spectrum has an infra-red reflectivity of about 50%.
It is as mentioned above, crucial, in the process of of the invention, in order to achieve the desired characteris-tics of low resistivity, high reflectivity to infra-red radiation, and high transmissivity of the visible spectrum in a thin film coating, to supply heat to the glass continuously and uniformly and at uniform temperature. This cannot be accomplished by placing the glass on a heated surface, nor in an oven, but can be done by means of a heated liquid bath in which the glass is supported and which constitutes a large capacity heat resevoir to which the bottom surface of the glass is exposedO
It is required that spraying which is done in the presence of oxygen be accomplished intermittently, and very slowly, so that the temperature of the exposed surface of the glass can recover between sprays, and so that the glass is not cooled ....~
.. ~,~
., . : , ~ : ... , . :
1 appreciably by the sprays. It is important that the sprayed mixture be anhydrous, and that the environmental water be avoided, and that all supply lines, spray heads and the like be carefully flushed with methanol before spraying commences.
Presence of water increases resist.ivity and produces spots in the film.
- After the coating process is completed the glass sheet is slowly cooled, to anneal the glass, according to con-ventional techniques.
The present system lends itself to coating a sheet of glass with SnOx, as the glass is produced by a continuous process glass making machine, as in United States Patent No.
3,880,633. Glass is produced, in such a continuous process, in long sheets about ten feet wide. Since the glass is hot when produced, its heat is employed to maintain hot the float tanks in which the coating process is carried out. The process of coating may, accordingly, be carried out as part of a continuous glass making process. The process may, however, also be carried out on a pre-fabricated glass. In the latter case, the glass may be pre-heated to 950F in a conveyor furnace, and transferred to a molten liquid tank, the liquid being heated to a temperature which maintains the exposed surface of the glass at about 950F. In the first method the waste heat of the glass making process is employed to heat the glass, . 25 which represents an ecomonic advantage.
: Glass coated in accordance with the present method has particular advantage as window glass, for vehicles, dwellings, '.'' ~ 5 -~. , ...,.~
~L~ 97~L85 large buildings, hot houses, and the like. It also has applicatlon to ovens having viewing windows, and to solar heating systems, where it is desirable to avoid heat loss via infra-red radiation.
While the preferred fluoride is NH4FHF, it is feasible S to employ SnF2, i.e., a fluoride containing only F and Sn. The function of the NH~FHF is to provide fluorine plus a volatile remainder.
The material in the float tanks may be liquid tin or a molten salt capable of being mainLained at the required temperature.
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of forming a transparent conductive film of SnOx having a resistivity of about 8-17 ohms per square, a transmissivity of visible light of substantially 80% and a reflectivity to infra-red of about 82%, on a glass surface comprising: heating a sheet of glass to substantially elimin-ate temperature gradients from at least one surface thereof;
spraying a portion of said surface with an anhydrous tin-containing solution in the presence of an atmosphere containing sufficient oxygen for formation of said film of SnOx while maintaining the surface being sprayed substantially free of temperature gradients and at a temperature sufficient to form said film of SnOx, said solution containing a quantity of SnCL2.
spraying a portion of said surface with an anhydrous tin-containing solution in the presence of an atmosphere containing sufficient oxygen for formation of said film of SnOx while maintaining the surface being sprayed substantially free of temperature gradients and at a temperature sufficient to form said film of SnOx, said solution containing a quantity of SnCL2.
2. A method according to Claim 1, wherein said glass is substantially uniformly heated to maintain said surface substantially free of temperature gradients during the spraying of said surface with said tin-containing solution.
3. A method according to Claim 2, wherein said surface is intermittently sprayed with said tin-containing solution to progressively form said film of SnOx.
4. A method according to Claim 1 or 2 or 3, wherein the solution sprayed comprises an anhydrous solvent, and a fluo-ride which provides a fluoride ion and a volatile remainder.
5. A method according to Claim 1 or 2 or 3, wherein the solution sprayed comprises an anhydrous solvent, and a fluoride which provides a fluoride ion and a volatile re-mainder and wherein said anhydrous solvent is methanol.
6. A method according to Claim 1 or 2 or 3, wherein the solution sprayed comprises anhydrous solvent, and a fluoride which provide a fluoride ion and a volatile remainder and wherein the spray is carried out to form a film of SnOx having a sheet resistivity of 8-15 ohms per square and a transmissivity of incident visible light of about 80%.
7. A method of forming a transparent conductive film of SnOx having a resistivity of about 8-17 ohms per square, a transmissivity of visible light of substantially 80% and a reflectivity to infra-red of about 82%, on a window glass surface comprising: maintaining the temperature of said surface constant at a temperature of about 950°F by floating said glass in a heated liquid bath; and spraying onto said glass surface an anhydrous solution containing anhydrous SnCL2; said spraying being conducted in an atmospher containing sufficient oxygen for formation of said film of SnOx and in successive, intermittent passes over said surface, each of said passes spraying only a portion of said glass surface at any instant of time, and at a rate of spray such that said temperature remains substantially constant; said spray-ing further being conducted for a total time sufficient to form a film of SnOx of substantially 0.4 microns in thickness.
8. A method according to Claim 7, wherein said solu-tion includes a non-aqueous solvent, and a fluoride which provides a fluoride ion and a volatile remainder.
9. A method according to Claim 7, wherein said anhydrous solution includes methanol, ammonium bifluoride and anhydrous SnCL2.
10. A method according to Claim 8, wherein said fluoride is ammonium bifluoride.
11. A method according to Claim 8 or 9 or 10, wherein said solution also contains phenylhydrazine hydrochloride.
12. A method according to Claim 1, 2 or 7, wherein during the spraying the glass is conveyed along a tank of hot molten material on which it floats.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA248,168A CA1070185A (en) | 1976-03-18 | 1976-03-18 | Forming a film of snox on a glass surface by spraying an anhydrous solution containing snc12 |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA248,168A CA1070185A (en) | 1976-03-18 | 1976-03-18 | Forming a film of snox on a glass surface by spraying an anhydrous solution containing snc12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1070185A true CA1070185A (en) | 1980-01-22 |
Family
ID=4105487
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA248,168A Expired CA1070185A (en) | 1976-03-18 | 1976-03-18 | Forming a film of snox on a glass surface by spraying an anhydrous solution containing snc12 |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1070185A (en) |
-
1976
- 1976-03-18 CA CA248,168A patent/CA1070185A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |