Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Patent
1996-12-02
1997-12-02
Marcheschi, Michael
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
106415, 106436, 101491, 162140, 1621814, C04B 1420, C09C 162
Patent
active
056931352
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of International Application No. PCT/EP 95/01871, filed May 17, 1995, published as WO/95/33009 Dec. 7, 1995.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the use of specific interference pigments based on titanium dioxide-coated silicatic platelets which have been heated in a reducing atmosphere, in combination with scattering color pigments or scattering white pigments, for preparing forgeryproof documents and packaging.
2. Discussion of the Background
The forgeryproofing of documents such as paper money, postage stamps, checks, tax stamps, checkcards, rail or air tickets, credit cards, telephone cards, lottery tickets, share certificates, gift vouchers, passes or identity cards is becoming more and more important in view of the introduction of evermore powerful color copiers and the attendant scope for forgery. The same is true of valuable packaging.
Forgeryproofness has in the past been pursued in various ways. For instance, the originals were marked using magnetic pigments, or fluorescent dyes. However, these markings have the disadvantage that their presence is not immediately recognizable visually; they can only be detected using appropriate, more or less complex, reading apparatus. The same is true of marking with IR or UV dyes or pigments.
Greater interest therefore pertains to marks which are sufficiently reliably recognizable with the unaided, naked eye and make it easy to distinguish the copy from the original. In practice this kind of mark has taken the form of water marks--silvery bright metal strips which show up black in the copy owing to the total reflection of the light--or holograms. However, the disadvantage of these marks is that they are easy to imitate or, in the case of holograms, costly and prone to damage.
The most recent addition to the ways of marking authenticity is the use of simple interference pigments. However, applied atop a light-colored ground, interference pigments are virtually invisible, the exact field of the identifying mark is difficult to make out, and the markings are consequently easily overlooked.
Interference pigments in the conventional sense (described for example in U.S. Pat. No. 3.087,827 are plateletlike luster pigments consisting predominantly of a mica substrate coated with a layer of highly refractive material, eg. rutile, zirconium dioxide or tin dioxide, in a certain thickness (generally >50 nm) to form thin platelet colors. Interference pigments have to be applied in an oriented state. However, the intensity of the color of interference color pigments is low compared with that of scattering color pigments. They have an angle-dependent reflection maximum. Interference pigments of this type have for many years been used in cosmetics and plastics.
There have also been disclosed multi-layer pigments which exhibit a distinct angle-dependent color change and are produced by pulverizing thin film security devices--thin multi-layer films detached from the substrate (U.S. Pat. Nos. 4,434,010, 5,059,245). The optical principle underlying such pigments is that of the transmission filter. The sequence of layers making up such pigments typically includes 5 layers: a dielectric layer of low refractive index, eg. silicon dioxide, a semitransparent reflecting metal layer, eg. titanium, aluminum or chromium, a dielectric layer of low refractive index, eg. silicon dioxide, a highly reflecting opaque metal layer, eg. aluminum or titanium, a dielectric layer of low refractive index, eg. silicon dioxide, a semitransparent reflecting metal layer, eg. aluminum, chromium or titanium, and a dielectric layer of low refractive index., eg. silicon dioxide.
Pigments of this type have the disadvantage that they are costly, impossible to produce in large amounts, not stable to alkali and, what is more, usually do not have the desired acid fastness.
DE-A-42 41 753, an earlier patent document which was unpublished at the priority date of the present invention, describes interference pigments for forgeryproof d
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patent: 5059245 (1991-10-01), Phillips et al.
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patent: 5573584 (1996-11-01), Ostertag et al.
Kirk-Othmer, "Encyclopedia of Chemical Technology", Third edition, vol. 17, John Wiley & Sons, N.Y., p. 807 1982 (no month).
Kaliba Claus
Mronga Norbert
Ostertag Werner
Schmid Raimund
Schmidt Helmut
BASF - Aktiengesellschaft
Marcheschi Michael
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