Stock material or miscellaneous articles – Composite – Of quartz or glass
Patent
1998-02-03
1999-08-17
Lusignan, Michael
Stock material or miscellaneous articles
Composite
Of quartz or glass
65 602, 65 605, 65 608, 359839, 359900, 427165, 427166, 427167, 4272557, 4274192, 4274193, 428702, B32B 1500, B32B 1706
Patent
active
059392010
DESCRIPTION:
BRIEF SUMMARY
The invention relates to the process of depositing a reflective layer, more particularly a metallic layer, on glass.
Depending on its thickness, a metallic layer may in fact impart various properties to a glass substrate intended to become a glazing panel: at relatively low thickness, this metallic layer acts as a coating for protection against solar radiation and/or as a low-emissivity coating. With a greater thickness, it enables a true mirror, having a very high light reflectance, to be obtained.
The most widespread example is silver: it is known to deposit it as a thin film, especially having an interferential thickness, using vacuum techniques of the sputtering type, or as a thicker layer in order to make mirrors, for example using the conventional wet technique of a silvering line. However, silver is a material of limited durability as a thin film when it is exposed to a chemically aggressive medium, and the deposition techniques mentioned above can only be carried out in a subsequent step, discontinuously, on glass plates once they have been cut from the glass ribbon of a float production line.
It is therefore worthwhile considering other metals, which have properties similar to silver but which could possibly be deposited, continuously and less expensively, directly on the glass ribbon of a float line, and which have superior durability, for example aluminium.
It is thus known from Patent FR-2,011,563 to deposit an aluminium layer on a glass ribbon, when it is in the very chamber of the float bath, using a mass of molten metal emitting aluminium vapour towards the glass, the vapour condensing on the surface of the glass ribbon in order to leave a continuous coating. However, this type of technique has drawbacks--it is tricky to implement, it is not easy to ensure a deposition of uniform thickness and, above all, the deposition rate is low, the limiting factor being the very low partial vapour pressure of metallic aluminium.
It is also known, from Patent GB-A-2,248,853, to deposit aluminium layers on a ribbon of float glass at a temperature of at least 100.degree. C. Here, the technique used is one of pyrolysis in the liquid phase, in which organometallic compounds in a solvent are sprayed towards the glass and decompose into elemental metal on coming into contact therewith. This type of pyrolysis is not devoid of drawbacks either--in particular, it requires the discharging and treatment of large quantities of solvents.
The aim of the invention is then to develop a novel process for continuously manufacturing a metallic reflective layer on a ribbon of float glass which palliates the aforementioned drawbacks and which especially makes it possible to obtain layers of high quality compatible with the requirements of the industrial production of glazing panels.
The subject of the invention is a process for depositing, especially continuously, on a glass ribbon of a float line, a reflective layer based on a metal whose melting point is less than or equal to the temperature at which the glass ribbon acquires dimensional stability. It consists in carrying out the deposition in a controlled atmosphere, this being inert or reducing, when the glass ribbon has already acquired this dimensional stability, by bringing the surface of the ribbon into contact with the metal in question in pulverulent form or in molten form, the temperature of the ribbon during contacting being chosen so that the powder melts and coalesces, or so that the molten metal forms a sheet, at the surface of the ribbon, leaving a solid continuous layer when the temperature of the ribbon decreases during the flat-glass forming process down to a temperature of less than or equal to the melting point of the metal.
Within the context of the invention, "metal" is understood to mean a material having an electrical behaviour which is essentially of the conductive type. It is an essentially metallic material, either based on at least two metals, for example in the form of an intermetallic compound, an alloy or a eutectic compound.
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REFERENCES:
patent: 4056650 (1977-09-01), Dates et al.
patent: 5580364 (1996-12-01), Goodman et al.
Patent Abstracts of Japan, JP 60 215762, Oct. 29, 1985.
Silikattechnik, vol. 32, No. 10, Oct. 1981, "Plasmaspritzen auf Glass".
Boire Philippe
Joret Laurent
Lusignan Michael
Saint-Gobain Vitrage
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