Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
1999-05-05
2001-03-27
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C428S428000, C428S701000, C501S014000, C501S016000, C501S017000, C501S020000, C501S021000, C427S508000, C427S510000, C065S060530, C065S106000
Reexamination Certificate
active
06207285
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to ceramic enamels, particularly for use with automotive glass.
BACKGROUND OF THE INVENTION
Ceramic enamel paint compositions are well known in the art. They can be used for a variety of applications as, for example, decorative coatings for glassware, chinaware, and the like. They are especially useful in forming colored borders around glass sheets used for automotive windshields, sidelights and backlights. The colored borders enhance appearance as well as prevent UV degradation of underlying adhesives.
In general, these enamel compositions consist mainly of a glass frit, a colorant and an organic vehicle. They are applied to a substrate and subsequently fired to burn off the organic vehicle and fuse the frit thus bonding the enamel coating to the substrate.
Glass sheets for automotive use are generally coated with the ceramic enamel composition and then subjected to a forming process at elevated temperatures. During this treatment the enamel melts and fuses to the glass substrate and the glass is formed into a desired final shape. However, many prior art coatings exhibit a tendency to adhere to the materials covering the forming die, such as a fiberglass or metal fiber covered die, because these conventional enamels have a low viscosity after melting and stick to other materials at high temperature. Accordingly, these materials are not suitable for use in glass forming processes in which the heated glass coated with enamel contacts a material-covered forming die.
Various approaches have been suggested in order to facilitate the forming of glass sheets with a ceramic enamel coated thereon, withstanding of the elevated bending or forming temperatures, and repeated contact of the glass sheet and the covered forming die without the enamel adhering to the forming die. For example, U.S. Pat. Nos. 4,596,590 and 4,770,685 (issued to Boaz) and EP 201241 propose the addition of a low valent metal oxide powder, e.g., cuprous oxide, to the paint composition to provide a non-stick barrier between the coating and the fiberglass-covered forming die. U.S. Pat. Nos. 4,684,389; 4,857,096 and 5,037,783 (issued to Boaz), propose adding finely divided zinc metal powder for a similar effect. The use of an iron metal powder is proposed in U.S. Pat. No. 4,983,196 (issued to Stotka).
The use of other metal oxide powders, including bismuth oxide-containing formulations have been proposed in U.S. Pat. No. U.S. Pat. No. 4,029,605 (issued to Kosiorek); U.S. Pat. No. 4,098,949 (issued to Kosiorek); U.S. Pat. No. 4,892,847 (issued to Reinherz); U.S. Pat. No. 4,959,090 (issued to Reinherz); U.S. Pat. No. 4,970,178 (issued to Klimas et al.); U.S. Pat. No. 5,093,285 (issued to Murkens); U.S. Pat. No. 5,203,902 (issued to Murkens) and EP 370,693.
However, certain of the bismuth containing systems produce a weak glass, such as when lithium is present, and have poor silver bleed-through properties, as well as inadequate anti-stick properties.
U.S. Pat. No. 4,828,596 proposes introducing copper sulfide or copper sulfate into the ceramic enamel composition as an anti-stick agent. Sulfides or sulfates of other metals have been proposed as anti-stick agents in U.S. Pat. No. 4,822,396 (issued to Reinherz et al.).
A purportedly improved anti-stick ceramic enamel composition is proposed by U.S. Pat. Nos. 5,153,150 and 5,208,191 (issued to Ruderer et al.) wherein a seed powder containing Zn
2
SiO
4
is introduced into an oxide composition with or without the presence of bismuth oxide.
As a further problem, a number of previous ceramic enamel systems employ a lead-containing glass frit. For environmental considerations it is desirable to avoid the use of any lead-containing system.
Also, while some of the above-mentioned enamel systems may perform fairly well in conventional glass forming processes, some are not satisfactory for use in the newly-developed “deep bend” processes for forming automotive glass.
It is essential that the enamel compositions also possess adequate resistance to certain chemical agents, which they may contact, and many of the prior art compositions fail in this respect.
Each of the previously known enamel compositions suffers from one or more of the deficiencies noted above, making it desirable to provide a composition which avoids these shortcomings. The present invention provides such ceramic enamel compositions, a method for employing the compositions, and substrates coated therewith.
SUMMARY OF THE INVENTION
The present invention is for a ceramic enamel composition that forms an at least partially crystalline bismuth silicate material on a glass substrate upon fusing at high temperature.
A ceramic enamel composition of the invention comprises 20-80% by weight of an oxide frit, 0.5-60% by weight of a bismuth silicate seed material, 10-40% by weight of a pigment, and 10-40% by weight of a vehicle. The bismuth silicate seed material is preferably provided as seed crystals in the composition and may be further generated from bismuth oxide and silicon dioxide in the composition, e.g., as provided by the oxide frit, upon firing the composition, particularly when the seed material provides nuclei for further crystal growth.
A method of preparing an instant ceramic enamel composition comprises combining in no particular order the aforementioned components in the desired amounts.
The invention is also for a method of using the aforesaid ceramic enamel with automotive glass, so as to form a colored border and/or UV resistant border around the periphery of the automotive glass. Thus, a glass substrate is provided with a ceramic enamel coating by applying an aforementioned ceramic enamel composition to the glass substrate, and firing the coated glass substrate to fuse components of the ceramic enamel composition to the glass substrate.
Accordingly, a glass substrate having a ceramic enamel coating adherent thereto is contemplated, in which the ceramic enamel coating is composed at least in part of a crystalline bismuth silicate material. Preferably, the coating is provided on at least a portion of the periphery of the glass substrate.
Furthermore, a method of forming a glass substrate provided with an instant coating is described, which comprises (a) applying an aforementioned ceramic enamel composition to a glass substrate; (b) heating the coated glass to an elevated temperature, preferably at least 1200° F.; (c) subjecting the heated glass to a conventional forming pressure, e.g., in the range of 1 to 3 psi, typically about 2 psi, with a forming die; and (d) separating the formed glass from the die.
Among the advantages of the present invention are its excellent anti-stick properties, good consistency, chemical durability, broad temperature firing range, and low stress.
The invention will now be described in more detail and with reference to examples.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a ceramic enamel composition that contains at least one bismuth silicate seed material as a component. An instant bismuth silicate seed material is described more fully hereinbelow.
A composition of the invention contains the following components: (1) at least one conventional oxide glass frit; (2) a bismuth silicate seed material; (3) a colorant (pigment); and (4) a vehicle for components (1)-(3). The bismuth silicate seed material is believed to assist in nucleating and growing microcrystalline structures, e.g., crystalline bismuth silicate compounds, in the composition upon firing.
Typically, an instant ceramic enamel composition comprises 20-80% by weight of an oxide frit, 0.5-60% by weight of a bismuth silicate seed material, 10-40% by weight of a pigment, and 10-40% by weight of a vehicle. More preferably, a bismuth silicate seed material is provided in an amount of 2-40% by weight, and an oxide frit is provided in an amount of 40-80% by weight.
As referred to herein, the terms crystal, crystalline, microcrystalline, and the like, mean that the subject material is sufficiently crystalline (ordered) to reveal one or more discrete
Ryan Joseph W.
Sakoske George E.
Cerdec Corporation
Jones Deborah
McNeil Jennifer
Wenderoth Lind & Ponack, LLP.
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