Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2000-02-09
2003-01-21
Koslow, C. Melissa (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S419000, C106S425000, C106S436000, C106S450000, C106S456000, C106S472000, C106S480000, C106S479000
Reexamination Certificate
active
06508876
ABSTRACT:
The present invention relates to a colored interference pigment comprising absorption pigments in the carrier material and in the coating.
BACKGROUND OF THE INVENTION
Interference pigments which comprise absorption pigments either in the substrate or in the coating are known.
EP 0 608 388 describes SiO
2
flakes comprising soluble or insoluble colorants and produced on a continuous belt. Insoluble colorants used are pigments having a particle size of less than 1 &mgr;m, pigments meaning white, black, colored or fluorescent pigments. The pigments are dispersed in the precursor of the SiO
2
matrix, for example in a sodium waterglass solution, and the dispersion is applied to the continuous belt. Soluble colorants which may be present in the SiO
2
matrix are chromophoric metal oxides or soluble organic pigments. In this case, solutions of these colorants are added to the precursor prior to application to the continuous belt. The SiO
2
flakes produced in this way are used as substrates for interference pigments.
Interference pigments comprising carbon black as an absorption pigment in the metal oxide coating are known from EP 0 499 864. They are prepared by mixing a substrate dispersion and a carbon black dispersion, metering in the aqueous solution of a metal salt, and precipitating a metal oxide layer on the substrate, in the course of which the carbon black is entrained and becomes embedded in the metal oxide layer. The pigment is subsequently calcined at from 700 to 900° C. in the absence of oxygen.
Interference pigments enveloped by a thin layer of an organic dye are known from U.S. Pat. No. 5,156,678. They are prepared by preparing a suspension of the pigment in a solution of the dye and mixing the resultant suspension with a solvent in which the dye is insoluble.
With platelet-shaped pigments, it is often difficult to achieve hiding power and luster simultaneously to a satisfactory extent.
For instance, SiO
2
flakes or mica platelets coated, for example, with one or more thin metal oxide layers are distinguished by interference colors and a high luster but also at the same time, as a result of the transparent substrate, by a high transparency and hence a comparatively low hiding power. The need therefore exists to improve the hiding power.
In the case of pigments which, besides the metal oxide layer which is responsible for generating the interference color, comprise only an absorption pigment, optical effects such as color flops, for example, are limited. The need therefore exists to expand the optical effects of these pigments.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an interference pigment which possesses not only a high hiding power but also comparatively more optical effects.
Upon further study of the specification and appended claims, further objects and advantages of this invention will become apparent to those skilled in the art.
Such objects are achieved, for example, by means of an interference pigment having a platelet-shaped layer as substrate, at least one coating of at least one metal oxide layer and, optionally, a further layer, at least two layers comprising or consisting of colorants.
Such objects are additionally achieved by a process for preparing the pigment of the invention, in which
a colorant is dispersed or dissolved in a precursor of the substrate material,
the dispersion is applied as a thin film to a continuous belt,
the liquid film is solidified by drying, the resultant layer is separated from the belt and, if desired, is treated with an acid,
the resultant substrate particles are washed and then coated with one or more layers of metal oxides, the precipitation of the metal oxides taking place from a dispersion or solution of a colorant.
The invention additionally provides for the use of the pigments of the invention for pigmenting paints, printing inks, plastics, cosmetics and glazes for ceramics and glasses. For this purpose they can also be employed as mixtures with commercially customary pigments, examples being organic and inorganic absorption pigments, metal effect pigments and LCP pigments.
In a first embodiment, the pigment of the invention consists of a platelet-shaped substrate (
1
) and of a coating (
2
) of at least one metal oxide layer, the pigment in the substrate (
1
) and in the coating (
2
) comprising at least one colorant (
3
). The structure of this pigment is shown in FIG.
1
.
In a second embodiment, the pigment of the invention consists of a platelet-shaped substrate (
1
), of a coating (
2
) of at least one metal oxide layer, and of a colorant layer (
4
), the pigment in the substrate (
1
) and in the coating (
2
) comprising at least one colorant (
3
). The structure of this pigment is shown in FIG.
2
.
In a third embodiment, the pigment of the invention consists of a platelet-shaped substrate (
1
), of a coating (
2
) of at least one metal oxide layer, and of a colorant layer (
4
) on the coating (
2
), the substrate comprising at least one colorant (
3
) The structure of this pigment is shown in FIG.
3
.
In a fourth embodiment, the pigment of the invention consists of a platelet-shaped substrate (
1
), of a coating (
2
) of at least one metal oxide layer, and of a colorant layer (
4
) on the coating (
2
), the pigment in the coating (
2
) comprising at least one colorant (
3
). The structure of this pigment is shown in FIG.
4
.
In case of the embodiments
2
to
4
of the pigment according to the invention the substrate can be repeatedly laminated with the two-layer system consisting of the coating (
2
) and the colorant layer (
4
). However, a laminating from one coating (
2
) and one colorant layer (
4
) is preferred.
The pigments of the invention are based on platelet-shaped substrates. These substrates may consist, for example, of silica, silicates, boron oxide, borates, alumina or other transparent, stable materials capable of accommodating the soluble or insoluble colorants.
Precursors used for preparing the substrates are solutions of organic or inorganic compounds of the metals aluminum, silicon, potassium or sodium with borates, aluminates, polyphosphates, metaphosphates, silicates and mixtures thereof. A preferred precursor is waterglass.
In the case of the embodiment 4 of the pigment of the invention, the substrate may also consist of mica, synthetic mica, other phyllosilicates or glass flakes.
The platelet-shaped substrate particles preferably have a thickness of from 0.05 to 5 &mgr;m and, in particular, from 0.2 to 2 &mgr;m. The extent in the two other dimensions is preferably from 1 to 250 &mgr;m and, in particular, from 2 to 100 &mgr;m.
In accordance with the embodiments 1 to 3 of the pigment of the invention, pigment particles whose dimensions are markedly smaller than the thickness of the substrate are incorporated as insoluble colorants into the substrate. The particle size of the commercially customary pigments must therefore be adapted to the desired layer thickness of the substrate. The term pigment particles as the colorants here is to be interpreted broadly and embraces white, black, colored and fluorescent pigments.
Suitable inorganic pigments are white pigments such as titanium dioxide, barium sulphate or zinc oxide, examples being titanium dioxide 2310 (manufacturer: Kronos), titanium dioxide R-D (manufacturer: Bayer), and titanium dioxide R-506 (manufacturer: Sachtleben).
Suitable black pigments are magnetite or pigment-grade carbon black, an example being Farbru&bgr; FW 200 (Degussa).
Suitable colored pigments are iron oxide or chromium oxide, mixed-phase oxides such as (Ti, Cr, Sb)O
2
, CoAl
2
O
4
(Thenard's Blue), ZnAl
2
O
4
(Rinman's Green), (Fe, Cr)
2
O
3
and also sulphides, for example CdS.
Also, suitable are inorganic fluorescent pigments, such as fluorescent silver-doped zinc oxide, phosphorescent copper-doped zinc sulphide, or ultramarine pigments.
Suitable organic pigments are azo pigments, anthraquinone pigments, indigo or thioindigo derivatives, diketopyrrolopyrrole pigments, perylene pigments and phthalocyanine pigments. P
Bernhardt Klaus
Brückner Hans-Dieter
Osterried Karl
Vogt Reiner
Koslow C. Melissa
Merck Patent Gesellschaft mit beschrankter Haftung
Millen White Zelano & Branigan P.C.
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