Glass manufacturing – Processes – With coating
Reexamination Certificate
1998-11-20
2001-04-24
Jones, Deborah (Department: 1775)
Glass manufacturing
Processes
With coating
C065S060500, C065S060510, C065S060800, C427S553000, C427S557000, C427S559000, C427S397700, C427S314000
Reexamination Certificate
active
06220055
ABSTRACT:
BACKGROUND OF THE INVENTION
Efforts have long been made to strengthen glass articles, including flat glass, glass containers formed of ordinary soda lime glass, and borosilicate low expansion articles. These efforts have been directed primarily towards tempering of the glass by a variety of processes including chemical tempering and air tempering which involves rapid cooling of the surfaces of a heated article to place the surfaces in compression. Additionally, it has long been known to apply coatings to glass articles, tempered as well as non-tempered, for a variety of purposes. These processes are exemplified in the following prior art patents: U.S. Pat. Nos. 5,108,479; 5,089,039; 5,085,805; 5,043,002; 4,728,353; 4,615,916; 4,530,857; 4,457,957; 3,996,035: and 3,850,679.
DISCLOSURE OF THE INVENTION
Under the present invention, the glass article is treated while in a heated condition at or above its annealing temperature (typically 500° C. for soda lime and borosilicate glasses) and below the softening point temperature (typically 725° C. for soda lime and 800° C. for borosilicate glasses) with chemicals selected from certain groups of chemicals depending upon the formulation of the glass substrate. Thus, the groups of chemicals used and the way in which they are combined, will vary depending on whether the substrate is (1) ordinary silica-soda-lime glass such as that used for windows or glass containers or (2) low expansion borosilicate glass such as that used for scientific laboratory glassware. The present invention may be used for strengthening a wide variety of glass articles including, but not limited to, flat glass, bent glass, glass containers, glass drinking tumblers, scientific glass, and solar collectors.
Under the present invention, the glass, while in a heated condition at a temperature above its annealing point (typically 500° C.) and below its softening point (typically 725° C. for soda lime and 800° C. for borosilicate glasses) is exposed to an atmosphere containing metalorganic compounds from a specific group. The atmosphere may be gaseous or may include liquids in a fine mist obtained by spraying. The heat from the glass maintained in the above mentioned proper temperature range causes the metalorganic compounds to decompose leaving a chemically modified ceramic surface. The group of metalorganics for use with a specific type of glass will vary depending on the coefficient of thermal expansion of the glass and is selected such that the chemically modified ceramic surface has a coefficient of thermal expansion lower than that of the unmodified glass substrate. In contrast to prior art coatings in which there is a sharp demarcation between the metallic oxide coating and the glass, under the present invention, there is formed a chemically modified ceramic surface created by chemical reaction of the decomposing metalorganics with the surface of the unmodified substrate. If desired, the glass article, concurrent with the application or immediately after the application of the metalorganic compounds, may be subjected to an infrared radiation treatment to enhance the chemical reaction. As a result of the fact that the chemically modified ceramic surface has a lower coefficient of thermal expansion than the substrate, the chemically modified ceramic surface will, upon cooling of the composite glass article (i.e., the glass substrate with the chemically modified ceramic surface), be placed in compression thus providing greater strength for such composite glass article as compared to a similar article formed solely from a similar type of glass without the benefit of the prescribed treatment with the metalorganic compounds.
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Glass Engineering Handbook, pp. 17-18, McGraw-Hill.
Duck Charles P.
Francel Josef
Emch, Schaffer, Schaub & Porcello & Co., L.P.A.
Jones Deborah
Stein Stephen
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