Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Patent
1998-10-13
2000-05-16
Koslow, C. Melissa
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
106437, 106446, 106481, 106482, 427585, 427215, 427255, 4272557, 427377, C09C 128
Patent
active
060631791
DESCRIPTION:
BRIEF SUMMARY
SPECIFICATION
The present invention relates to novel goniochromatic luster pigments based on silicon dioxide platelets, CVD coated with
A) a nonselectively absorbing filmlike layer at least partially transparent to visible light, and
B) if desired an outer layer which consists essentially of colorless or selectively absorbing metal oxide and/or comprises phosphate, chromate and/or vanadate.
This invention further relates to the production of these luster pigments and to their use for coloring paints, inks, including printing inks, plastics, glasses, ceramic products and decorative cosmetic preparations.
Luster effect pigments are used in many sectors of industry, for example in automotive coatings, decorative coating, plastics pigmentation, 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.
Owing to their uncopyable optical effects, these pigments are becoming increasingly important for the production of forgeryproof security documents, such as banknotes, checks, checkcards, credit cards, tax stamps, postage stamps, rail and air tickets, telephone cards, lottery tickets, gift vouchers, passes and identity cards.
Markings prepared using luster effect pigments and the absence of these markings or their alteration, for example in a color copy (disappearance of color flops and luster effects), are reliably discernible by the unaided, naked eye and so make it easy to distinguish the copy from the original.
WO-A-93/08237 discloses luster pigments based on platelet-shaped substrate particles composed of a silicon dioxide matrix, wet-chemically coated with metal oxides by hydrolysis of metal salts or with metals by reduction of aqueous metal salts. The substrate SiO.sub.2 platelets are produced by brushing a waterglass solution on a circulating belt in a thickness of about 10 .mu.m, drying and then washing the waterglass film initially with acid and then with water, detaching the resulting gellike SiO.sub.2 film and washing and also grinding the resulting fragments. The SiO.sub.2 platelets can also be colored by incorporating colorants in the waterglass film.
However, the metal-coated SiO.sub.2 platelet luster pigments described in WO-A-93/08237 are not satisfactory, since the wet-chemical metalization fails to produce an unbroken metal film, but deposits the metal in a more coarsely crystalline, island like state. Hence the exemplified coating of the SiO.sub.2 platelets with silver produces only silvery gray platelets which do not exhibit any interference colors.
Similarly, the physical vapor deposition (PVD) process mentioned therein fails to produce metalized SiO.sub.2 platelets in satisfactory quality. To obtain SiO.sub.2 platelets that are metalized on both sides, the circulating belt would initially have to have a metal film vapor-deposited onto it in a vacuum chamber. The thus-coated belt would then have to be passed through the waterglass solution. In the course of this step and in the course of the subsequent acidic wash of the silicate film, the metal film would be attacked. Also, the SiO.sub.2 film will crumble off the belt during the wash, making it difficult to vapor-deposit the second metal layer.
It is an object of the present invention to provide goniochromatic luster pigments having good coloristic and application properties.
We have found that this object is achieved by the luster pigments defined at the beginning.
The present invention further provides a process for producing these luster pigments, which comprises coating silicon dioxide platelets with said layer (A) and if desired said layer (B) by chemical gas phase decomposition of vaporizable metal compounds.
This invention also provides for the use of these luster pigments for coloring paints,
REFERENCES:
patent: 5763086 (1998-06-01), Schmid et al.
Chemical Abstract citation 123:259,909: abstract for DE 4,441,223, Jun. 1, 1995.
Chemical Abstract citation 120:10,430: abstract for WO 93/8237, Apr. 29, 1993.
Proceedings of the XIVTH International Conference in Organic Coatings Science and Technology, vol. 12, Angelos V. Patsis, Jul. 11-15, 1998, Technomic Publishing Co., Inc.
Mronga Norbert
Schmid Raimund
BASF - Aktiengesellschaft
Koslow C. Melissa
LandOfFree
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