Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
1998-09-28
2001-01-16
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S451000, C106S452000, C501S018000, C501S032000, C065S024000, C065S060200
Reexamination Certificate
active
06174359
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to ceramic decorating substances with increased color saturation (chroma value C* according to DIN 5033), substantially comprising a zirconium pigment of the host lattice or inclusion type and a glass flux of one or more glass frits, wherein the pigment volume concentration (PVC) is at least 30%. The invention further is directed toward a process for the production of the decoration coloring substances as well as their use, in particular for production of ceramic decorations which are burned above 1000° C., more particularly from 1100 to 1250° C.
Decoration coloring substances for the production of ceramic decorations are known. Conventionally they comprise substantially one or several pigments and a glass flux of one or several glass frits. The decoration coloring substance is formed by intimately grinding the components together (see Ullmann's Enzyklopadie der technischen Chemie, Fourth Edition (1977), Volume 14, pp. 9-10).
The market demands brilliant decorations with the strongest possible coloring power, and decorations burned in high-temperature burning processes are gaining importance. Strict requirements exist for the thermal stability of decoration coloring substances suitable for this purpose. A thermally stable pigment class comprises the so-called zirconium pigments, these being host lattice pigments such as zirconium praseodymium yellow, zirconium vanadium blue and zirconium iron pink, and zirconium inclusion pigments in which coloring crystals, such as in particular cadmium sulfide or cadmium sulfoselenides are included in zirconium silicate (=zircon) (loc. cit. pp. 2-3). The strong coloring power of a decoration coloring substance, thus its color saturation, is specified in the CIE laboratory system (DIN 5033, Part 3) as chroma value C*, wherein C*=(a
2
+b
2
)
0.5
and, at the correct color shade, should have a maximum value. The C* value can be increased by increasing the pigment volume concentration (pigment in percent by volume in the fused decoration coloring substance), however, there exists interest in increasing the c* value further at a given PVC.
The object of the present invention is to provide a path by which, in a simple manner, the C* value at a PVC of at least 30% can be increased.
SUMMARY OF THE INVENTION
It has been found that by using a glass flux with et very high PbO content, surprisingly higher C* values of the decoration coloring substances burned above 1000° C. are obtained, than with a glass flux with low or average PbO content.
Accordingly, the present invention provides a ceramic decoration coloring substance with increased color saturation C*, comprising a zirconium pigment of the host lattice or inclusion type and a glass flux of one or more glass frits, wherein the pigment volume concentration (PVC) is at least 30%, which is characterized in that the glass flux comprises at least 71 wt. % of lead oxide (PbO).
DETAILED DESCRIPTION OF THE INVENTION
The preferred flux comprises 75 to 85 wt. % lead oxide. Preferred zirconium pigments are the pigments listed above in the discussion of the background of the invention.
The glass flux is one comprised of glass compositions known per se, but with the specified high PbO content. The compositions of the glass are based most frequently on lead borosilicates, but they can also be SiO
2
-free glasses based on lead borates. Up to a PbO content of the glass flux of approximately 70 wt. %, the C* value does not increase at all with increasing PbO content, increases or only by a slight amount—minor fluctuations can result from other glass components or a special combination of the same. However, at a content of approximately 70 wt. % PbO the C* value of the decoration increases suddenly. By using such a glass flux in the form of a glass frit, it is consequently possible to obtain color-intensive decorations.
The composition preferably substantially comprises the zirconium pigment and one or several glass frits.
The pigment volume concentration is at least 30%, preferably 40 to 70%, and the pigment is preferably selected from zirconium vanadium blue, zirconium praseodymium yellow and the yellow to red zirconium inclusion pigments, such as cadmium sulfide, cadmium sulfoselenide and cadmium selenide.
The process for producing the composition of the present invention comprises grinding the zirconium pigment together with the glass flux, and optionally auxiliary substances (for example a liquid milling medium, e.g. water and/or alcohol, wetting agents, e.g. terpineol, and sedimentation agents, e.g. magnesium acetate), in a manner known per se, wherein, however, a glass flux with at least 71 wt. % PbO, preferably 75 to 85 wt. % PbO, is used.
The decoration coloring substances according to the invention can be used generally for decorating glass, porcelain and ceramics, however, they are especially well suited for the production of decorations, such as in-glaze decorations, on porcelain and other dense glazed ceramic materials, which are burned at temperatures above 1000° C., most frequently at 1100 to 1250° C.
Thus, the present invention also provides a process for production of ceramic decorations, which comprises placing the composition of the invention on a substrate to be decorated, and burning the composition in a temperature range of from 1000 to 1250 ° C., preferably 1100 to 1250° C.
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Huber Adalbert
Jarnicki Holger
Speer Dietrich
Bell Mark L.
Cerdec Aktiengesellschaft Keramische Farben
DiVerdi Michael J.
Wenderoth , Lind & Ponack, L.L.P.
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