Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
1998-07-06
2001-08-21
Dixon, Merrick (Department: 1774)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C428S429000, C428S432000, C428S442000, C428S335000, C428S357000
Reexamination Certificate
active
06277492
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to glass sheets having painted exterior surfaces. More particularly, the invention is directed to a method for painting the exterior surfaces of glass sheets with successive layers of paints which provides an aesthetically appealing yet durable product useful for automotive and architectural glazings.
BACKGROUND OF THE INVENTION
It would be desirable for automotive styling opportunities to be able to apply a band of colored organic paint around the periphery of an automotive vehicle glass to match the paint color of the vehicle. Presently, organic paints would not be sufficiently adherent to the glass surface to allow their use directly on glass in most commercial applications. The present inventor, in U.S. Pat. No. 5,328,753, disclosed the use of a metal-containing ceramic paint as an interlayer between the glass and organic paint to provide adherence therebetween. The paint was disclosed to have ceramic frit, pigment, an organic vehicle like pine oil, and metal powder. The metal powder was taught to keep the ceramic paint from adhering to the mold during glass shaping operations and hence prevent the formation of surface defects. One drawback with that invention is that the ceramic paint uses organic solvents which are less than environmentally desirable. Further, the ceramic paint, until it is cured at high temperatures, is prone to scratching during handling. Therefore, the use of the ceramic paint to provide adhesion between the glass and the organic paint has drawbacks which make such use less than optimal.
In another U.S. Pat. No. 5,698,026, the present inventor discloses a water based silicate paint useful on automotive glass, such as around the periphery for “black out” of the glass areas. I have now unexpectedly found that the water-based paint can be used to adhere the organic paint to glass but only if the water-based paint is contacted with a silane sensitizer material prior to the application of the organic paint. Use of only the water-based paint on the glass, without sensitizer, was found by the inventor to not provide good adhesion of the organic paint to the glass. The use of the water-based paint to adhere the organic paint to the glass has advantages as compared to using the ceramic paint for that function as in U.S. Pat. No. '753 noted above. That is, the water-based paint can be cured at lower temperatures to avoid distorting the glass and avoids the used of organic solvents which provides commercial and environmental benefits. In addition, I have unexpectedly found that the water-based paint, after it is cured, has a rougher surface than the ceramic paint of the '753 patent which is advantageous to adhering the organic paint thereto. I believe this roughness results from the evaporation of the water during curing. Hence, this improves the adhesion of the organic paint to the sensitized water based paint as compared to only glass treated with a sensitizer.
SUMMARY OF THE INVENTION
The present invention is a method for providing a coating of organic paint on a glass sheet, the process comprises the steps of:
A) applying a layer of a water-based silicate paint to a surface of the glass sheet and curing the paint at a temperature below the plastic set temperature of the glass sheet;
B) heating the glass sheet to its plastic set temperature and shaping the glass sheet;
C) coating the water-based silicate paint with a layer of a silane material useful to sensitize the paint; and
D) applying a layer of an organic paint over the layer of sensitized water-based silicate paint and curing the organic paint.
The water-based paint comprises water-soluble silicate, water, water-soluble base, finely divided metal oxide powder, soda-lime-silica glass powder, and, optionally, at least one of zinc oxide and low-melting frit. More particularly, this water-based paint comprises:
(i) water-soluble sodium silicate forming 20 to 45 weight percent of said composition;
(ii) water forming 5 to 25 weight percent of said composition;
(iii) water-soluble base in an amount sufficient to provide said composition with a pH of at least 10.5;
(iv) finely divided metal oxide powder selected from the group consisting of oxides of copper, iron, nickel, cobalt and mixtures thereof forming 20 to 45 weight percent of said composition and having a particle size, on average, less than 7 microns; and
(v) particles of soda-lime-silica glass forming 3 to 55 weight percent of the composition and having a diameter, on average, less than 20 microns and having a melting point of at least about 1700° F.
The paint further comprises at least one material selected from the group consisting of:
(vi) low-melting glass frit powder melting below 1300° F. forming up to 20 weight percent of said composition and having a particle size, on average, less than 10 microns; and
(vii) zinc oxide forming up to 10 weight percent of said composition. In addition, preferably the composition comprises small amounts of aluminum hydroxide.
The painted glass sheets of the present invention are particularly well suited for preparing automotive or architectural glazings having concealment bands on the exterior (i.e., facing the outer environment) surfaces thereof.
Advantageously, the invention provides excellent adherence of an organic paint to glass in an environmentally desirable way through the use of water-based paint and silane sensitizer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention is directed to a process for painting the surface of a glass sheet, by applying consecutive layers of a water-based silicate paint, a silane sensitizer for the paint, and thereafter an organic paint. The surface to be painted may be the exterior surface of the glass sheet since the invention product has been found to be of excellent durability. By the term “exterior” as it is used herein is meant that surface of the glass sheet which is intended to be exposed to the corrosive and erosive effects of the atmosphere exterior of the vehicle or building enclosed by the glass sheet. As would be appreciated, the paint may be applied to other than exterior glass surfaces, for example, in a laminated windshield it may be applied to one of the surfaces which contact the interlayer between the glass sheets. By the term “surface of the glass sheet” as it is used herein is meant the entire area of either major surface of the glass sheet, or any portion thereof.
According to the present invention, the glass sheet is provided first with a coating of a water-based silicate paint in an area on which it is intended that the organic paint is to be located. Two embodiments of useful water based silicate paints are disclosed in U.S. Pat. No. 5,698,026 and its CIP U.S. patent application Ser. No. 08/972832 filed Nov. 18, 1997, the teachings of both of these documents being expressly incorporated by reference herein. As disclosed above, the water-based silicate paint broadly includes water-soluble silicate, water, water-soluble base, finely divided metal oxide powder, soda-lime-silica glass powder, and at least one of zinc oxide and low-melting frit.
Water-soluble sodium silicates form between about 20 and 45 weight percent of the composition of this invention, more preferably, between about 30 and 38 weight percent of the composition, i.e., as used herein “weight percent of the composition” meaning a fraction of the total weight of the composition. They may comprise a single sodium silicate or a mixture of silicates. In addition to the water-soluble sodium silicate, water-soluble potassium silicates of similar formula may also be included in the composition.
Yet another required component of the composition is water which is included in an amount between about 5 and 25 weight percent of the total composition weight, preferably in an amount between about 10 and 25 weight percent. The composition also includes a water-soluble base which is employed to provide the paint composition with a pH of at least about 10.5, preferably being above 12.5, more preferably about 13.5. The pH
Brinks Hofer Gilson & Lione
Dixon Merrick
Oberholtzer Steven L.
Visteon Global Technologies Inc.
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