Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Patent
1998-10-26
2000-10-17
Harrison, Robert H.
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
106415, 106417, 106453, 106454, 106472, 427216, 427217, 42725515, C09C 162
Patent
active
06132504&
DESCRIPTION:
BRIEF SUMMARY
The invention relates to multilayer interference pigments consisting of alternating layers of a material of low refractive index and of a metal or of a material of high refractive index, the central layer being formed from an absorbing material.
Multilayer pigments having alternating layers of a material of high refractive index and a material of low refracting index are known. They comprise predominantly metal oxides. However, the material of high refractive index can also be replaced by a semitransparent metal layer. The metal oxide layers are produced either by a wet method, by precipitating the metal oxide hydrates from a metal salt solution onto a substrate material, or by vapor deposition or sputtering in a vacuum. For instance, U.S. Pat. No. 4,434,010 describes a multilayer interference pigment consisting of a central layer of a reflective material (aluminium) and alternating layers of two transparent, dielectric materials of high and low refractive index, for example titanium dioxide and silicon dioxide, either side of the central aluminium layer. In a further embodiment of the pigment the layers following the central aluminium layer are formed by magnesium fluoride and chromium. This pigment is employed for the printing of securities.
JP H7-759 (A) describes a multilayer interference pigment with a metallic luster. It consists of a substrate which is coated with alternating layers of titanium dioxide and silicon dioxide. The substrate is formed from platelets of aluminium, gold or silver, or from platelets of mica and glass which are coated with metals.
All types of pigment having a metal layer as the central layer have the disadvantage that every wavelength is reflected from this reflection layer, with the effect that, although a high luster is obtained, the actual interference color is at the same time masked.
The object of the invention is to provide an interference pigment having strong interference colors, a close angular dependency of the interference colors, and a high hiding power.
This object is achieved according to the invention by a multilayer interference pigment consisting of a central layer of an absorbing material and alternating layers of a material of low refractive index and of a metal or of a material of high refractive index either side of the central layer.
This object is also achieved, according to the invention, by a process for preparing the novel pigment by a substrate, low refractive index and of a metal or of a material of high refractive index onto the release layer, the central layer applied being a layer of an absorbing material, release layer, and washing and drying the resulting platelet-shaped interference pigment, 300.degree. C., and
The invention also provides for the use of the novel pigments for pigmenting paints, printing inks, plastics and cosmetics and for producing films.
The material of high refractive index is a metal oxide or mixtures of metal oxides with or without absorbing properties, for example TiO.sub.2, ZrO.sub.2, Fe.sub.2 O.sub.3, Fe.sub.3 O.sub.4, Cr.sub.2 O.sub.3 or ZnO, or a compound of high refractive index, for example iron titanates, iron oxide hydrates or titanium suboxides or mixtures and/or mixed phases of these compounds with one another or with other metal oxides.
The metal is preferably aluminum, chromium, nickel, a chromium-nickel alloy or silver. Chromium and aluminum are preferred in this context, since they are easy to deposit. Furthermore, the layers here have a reflectivity which is easy to control and high corrosion resistance. Metal layers are preferred over layers of a material of high refractive index.
The material of low refractive index is MgF.sub.2 or a metal oxide such as SiO.sub.2, Al.sub.2 O.sub.3 or a mixture thereof, and can likewise have absorbing or nonabsorbing properties. If desired, the material of low refractive index can include alkali metal oxides and alkaline earth metal oxides as constituents.
As the material of low refractive index, however, it is preferred to employ polymers, for example acrylates. The m
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English Abstract of WO 9308237.
Bauer Gerd
Kuntz Matthias
Pfaff Gerhard
Schank Christina
Harrison Robert H.
Merck Patent Gesellschaft mit Berschrankter Haftung
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