Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2002-02-28
2003-03-18
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S417000, C106S418000, C106S431000, C106S436000, C106S439000, C106S440000, C106S441000, C106S450000, C106S453000, C106S456000
Reexamination Certificate
active
06533857
ABSTRACT:
The present invention relates to novel luster pigments based on multiply coated reflecting platelet-shaped substrates and comprising at least one layer packet comprising
A) a low refractive coating which selectively absorbs visible light and
B) a reflective coating which is at least partially transparent to visible light and also, if desired,
C) an outer protective layer.
The invention further relates to the use of these luster pigments for coloring paints, inks, including printing inks, plastics, glasses, ceramic products and decorative cosmetic preparations.
Luster or effect pigments are used in many sectors of industry, for example in automotive coatings, decorative coating, plastics coloration, paints, printing inks, especially security printing inks, and cosmetics.
Their optical effect is based on the directed reflection of light at predominantly sheetlike, mutually parallel-oriented, metallic or strongly refractive pigment particles. Depending on the composition of the pigment platelets, interference, reflection and absorption phenomena create angle-dependent color and lightness effects.
Particular interest pertains to goniochromatic luster pigments which exhibit an angle-dependent color change between two or more intensive interference colors and hence an attractive color play. These pigments typically have a light-reflecting platelet-shaped core which is coated with alternating low and high refractive layers.
An overview of goniochromatic luster pigments is given in European Coatings Journal 7-8, page 702-705 (1997). Details relating to the goniochromatic luster pigments described therein and others are described in U.S. Pat. No. 3,438,796, U.S. Pat. No. 4,434,010, EP-A-668 329, WO-A-96/34917, EP-A-708 154, EP-A-753 545 and DE-A-197 46 067 and prior German Patent Applications 198 08 657.1 and 198 22 046.4.
A common feature of all known goniochromatic luster pigments is a colorless low refractive layer, which is frequently referred to as a dielectric layer, which is responsible for the angle-dependent color of the pigments and whose delicate interference colors are enhanced by the combination with high refractive and optionally absorbing layers. In use, the color play of these pigments is customarily modified by blending with other colorants to match the particular coloristic requirements and the personal taste of the user. Since color sensation and personal taste are very individual, however, there is still a need for new effects which cannot always be satisfied by combining known colorants.
It is an object of the present invention to provide further goniochromatic luster pigments which exhibit new coloristic effects and have advantageous application properties.
We have found that this object is achieved by the goniochromatic luster pigments defined at the beginning.
The invention further provides for the use of the luster pigments according to the invention for coloring paints, inks, including printing inks, plastics, glasses, ceramic products and decorative cosmetic preparations.
The luster pigments of the invention are based on multiply coated reflecting platelet-shaped substrates comprising a low refractive coating (A) which selectively absorbs visible light, in combination with a reflective coating (B) which is at least partially transparent to visible light.
Useful substrate materials for the luster pigments of the invention include all platelet-shaped materials which reflect perpendicularly incident light completely or partially (typically at not less than 10%). These materials are generally high refractive and customarily have a refractive index of generally ≧2, preferably ≧2.4; they can be opaque, semiopaque or transparent and also colored in reflected or transmitted light.
One group of useful substrate materials are metal platelets. Any metallic effect pigment metals and alloys may be used, for example steel, copper and its alloys such as brass and bronzes and especially aluminum and its alloys such as aluminum bronze. Preference is given to aluminum flakes, which are simple to produce by stamping out of aluminum foil or according to common atomizing and grinding techniques, and it is possible to use commercially available products whose surface, however, should be substantially free of greases or similar coatings and may be passivated, ie stablilized with regard to water in particular.
The metallic substrate particles may if desired already be coated with high refractive metal compounds such as-high refractive metal oxide, metal nitride or metal sulfide, especially for example iron oxide or titanium oxide, and therefore already possess a (weak) self-color due to interference effects with or without absorption (Paliocrom®, BASF). However, this coating should not be too thick (from about 5 to 150 nm) in order that the substrate particles may retain their metallic coloristics. Furthermore, the metallic substrate particles may also be coated with magnetic materials such as iron, cobalt, nickel or &ggr;-iron(III) oxide and hence be magnetizable.
A further group of suitable substrate materials are nonmetallic platelets which are inherently high refractive or inherently only low refractive and therefore provided with a high refractive coating.
Examples of particularly suitable inherently high refractive materials are selectively or nonselectively absorbing materials, for example platelet-shaped metal oxides, sulfides and nitrides such as in particular platelet-shaped (semiopaque) &agr;-iron(III) oxide (&agr;-Fe
2
O
3
, hematite), which may be doped with silicon (EP-A-14 382), aluminum (EP-A-68 311) or aluminum and manganese (EP-A-265 820) (eg Paliocrom® Kupfer L3000, BASF; AM200, Titan Kogyo), platelet-shaped (opaque) iron(II/III) oxide (Fe
3
O
4
, magnetite), molybdenum sulfide, boron nitride and graphite platelets. Also suitable are nonabsorbing (colorless) transparent materials such as platelet-shaped bismuth oxychloride, titanium dioxide and zirconium dioxide platelets.
Examples of particularly suitable inherently only low refractive materials are in particular silicatic platelets such as especially light-colored or white micas, preferably wet-ground muscovite, but also other natural micas, for example phlogopite and biotite, artificial micas, talc and glass flakes and silicon dioxide platelets.
The high refractive coating for these low refractive materials may be in particular high refractive metal oxides, metal nitrides and metal sulfides such as titanium oxide, zirconium oxide, zinc oxide and tin oxide, bismuth oxychloride, iron oxides, chromium oxide and ilmenite and also reduced titanium compounds containing titanium having oxidation states of <4 to 2, such as Ti
3
O
5
, Ti
2
O
3
, TiO, titanium oxynitrides and TiN, which are formed on reducing titania-coated substrates with ammonia, hydrogen and/or hydrocarbons. Preference is given not only to ilmenite but in particular to titanium dioxide and its reduction products and also to iron(III) oxide.
Thusly coated mica pigments are likewise commercially available (Paliocrom, BASF; Iriodin®, Merck; Mearlin®, Mearl).
Customary geometric layer thicknesses for these high refractive coatings lie in the range from about 10 to 300 nm, especially in the range from 20 to 200 nm.
The size of the substrate particles may be adapted to the particular application. Generally the platelets have average largest diameters of from about 1 to 200 &mgr;m, especially from 5 to 100 &mgr;m, and thicknesses from about 0.1 to 1 &mgr;m, especially round about 0.5 &mgr;m, in the case of metallic substrates and around about 0.3 &mgr;m in the case of nonmetallic substrates. Their specific free surface area (BET) is typically in the range from 1 to 15 m
2
/g, especially from 0.1 to 5 m
2
/g in the case of metallic and from 1 to 12 m
2
/g in the case of nonmetallic substrates.
The luster pigments of the invention comprise a low refractive coating (A) which absorbs visible light selectively in combination with a reflective coating (B) which is at least partially transparent to visible light. They may include a plurality of identical
Böhm Arno
Clemens Thorsten
Mronga Norbert
Schmid Raimund
Seeger Oliver
Bell Mark L.
Manlove Shalie
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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