Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2002-09-05
2004-02-17
Koslow, C. Melissa (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S417000, C106S418000, C106S430000, C106S436000, C106S439000, C106S456000
Reexamination Certificate
active
06692561
ABSTRACT:
The present invention relates to intensely coloured interference pigments based on multicoated platelet-shaped substrates.
Lustre or effect pigments are employed in many areas of industry, in particular in the area of automotive paints, decorative coating, in plastic, in surface coatings, printing inks and in cosmetic formulations.
Owing to their colour play, lustre pigments which exhibit an angle-dependent colour change between a number of interference colours are of particular interest for automotive paints and in counterfeiting-proof securities. Pigments of this type based on multicoated platelet-shaped substrates are disclosed in U.S. Pat. No. 4,434,010, JP H7-759, U.S. Pat. No. 3,438,796, U.S. Pat. No. 5,135,812, DE 44 05 494, DE 44 37 753, DE 195 16 181 and DE 195 15 988.
Lustre pigments based on transparent platelet-shaped substrates which do not have a “hard” metallic lustre are the subject-matter of WO 93/12182. Mica platelets are covered with a high-refractive-index metal-oxide layer, such as, for example, TiO
2
, and a non-selectively absorbing layer. Depending on the TiO
2
layer thickness, these pigments exhibit a certain interference colour when viewed perpendicularly which becomes weaker and weaker with increasingly oblique viewing angle and finally drops off to grey or black. The interference colour does not change, but a decrease in colour saturation is observed.
JP 1992/93206 claims lustre pigments based on glass flakes or mica particles which are covered with an opaque metal layer and alternating SiO
2
and TiO
2
layers.
EP 0 753 545 A2 discloses goniochromatic lustre pigments based on multi-coated, high-refractive-index, non-metallic, platelet-shaped substrates which are at least partially transparent to visible light, which pigments have at least one layer pack comprising a colourless, low-refractive-index coating and a reflective coating which absorbs selectively or non-selectively. The preparation process described in EP 0 753 545 A2 involves coating the pigment substrate by CVD (chemical vapour deposition) in a fluidised-bed reactor (“fluidised bed process”). Here, the substrate, for example finely divided mica, is fluidised in a stream of an inert carrier gas and kept in motion. The reagents necessary for the formation of the oxide layers are supplied via the stream of inert gas or further inert-gas inlets. However, owing to the high density difference between the mica/pigment and the carrier gas, a significant problem in this process is uniform distribution of the solid particles and thus uniform coating. Accordingly, disadvantages of this invention are the technically very complex and expensive preparation process and the often difficult reproducibility of the pigments in the desired product quality.
Goniochromatic lustre pigments having a silicon-containing coating based on multicoated platelet-shaped metallic substrates are disclosed in EP 0 768 343 A2.
A common feature of the multilayered pigments known from the prior art is that they have inadequate tinting strength and comparatively low hiding power. Furthermore, the pigments are in some cases very difficult to prepare or reproduce.
The object of the present invention is to provide gold- and orange-red interference pigments having high tinting strength and high hiding power which are distinguished by their advantageous applicational properties and at the same time can be prepared in a simple manner.
Surprisingly, gold- and orange-red pigments based on multicoated platelet-shaped substrates which have a certain arrangement of optically functional layers, giving particular optical effects, have now been found.
The intensely coloured interference pigments according to the invention are distinguished by their extraordinarily high chroma C (“tinting strength”), their very high hiding power and very strong lustre with glitter effect. In contrast to gold-coloured pearlescent pigments as disclosed, for example, in EP 0 211 351 B1, the gold-coloured interference pigments according to the invention exhibit significantly higher tinting strength and higher hiding power. The gold pigments according to the invention are an equivalent—and with respect to lustre and tinting strength—superior alternative to the known metal bronzes, in particular in gravure printing on textiles.
In contrast to the goniochromatic pigments, the pigments according to the invention have only a slight angle-dependent colour effect, or none at all.
The invention thus relates to intensely coloured interference pigments based on multicoated platelet-shaped substrates which comprise at least two layer sequences comprising
(A) a colourless coating having a refractive index n of ≦1.8,
(B) a high-refractive-index coating consisting of a mixture of TiO
2
and Fe
2
O
3
in a ratio of from 1:0.1 to 1:5, and optionally one or more metal oxides in amounts of ≦20% by weight, based on layer (B),
and optionally
(C) an outer protective layer.
The invention furthermore relates to the use of the pigments according to the invention in paints, coatings, plastics, printing inks, security printing inks, ceramic materials, glasses and cosmetic formulations and in particular in printing inks. The pigments according to the invention are furthermore also suitable for the preparation of pigment preparations and for the preparation of dry preparations, such as, for example, granules, chips, pellets, briquettes, etc. The dry preparations are particularly suitable for printing inks.
Suitable base substrates for the multilayered pigments according to the invention are on the one hand opaque platelet-shaped substrates and on the other hand transparent platelet-shaped substrates. Preferred substrates are phyllosilicates and metal oxide-coated platelet-shaped materials. Particularly suitable substrates are natural and/or synthetic mica, talc, kaolin, platelet-shaped iron oxides or aluminium oxides, glass flakes, SiO
2
flakes, TiO
2
flakes or synthetic ceramic flakes, synthetic support-free platelets, liquid crystal polymers (LCPs), holographic pigments, BiOCl, metal platelets, such as, for example, aluminium platelets, platelets of aluminium bronzes, brass bronzes, zinc bronzes, titanium bronzes, or of other comparable materials.
The size of the base substrates is not crucial per se and can be matched to the respective application. In general, the platelet-shaped substrates have a thickness of between 0.05 and 5 &mgr;m, in particular between 0.1 and 4.5 &mgr;m. The extension in the two other ranges is usually between 1 and 250 &mgr;m, preferably between 2 and 200 &mgr;m, and in particular between 5 and 60 &mgr;m.
The thickness of the individual layers of high (for example pseudobrookite) and low refractive index on the base substrate is essential for the optical properties of the pigment. For a pigment having intense interference colours, the thickness of the individual layers must be set precisely with respect to one another.
If n is the refractive index of a thin layer and d is its thickness, the interference colour of this layer is determined by the product n·d (n·d=optical thickness).
The colours arising in a film of this type in reflected light in the case of perpendicular light incidence arise from an amplification of the light having the wavelength
λ
=
4
2
N
-
1
·
n
·
d
and by attenuation of the light having the wavelength
λ
=
2
N
·
n
·
d
where N is a positive integer.
The variation in the colour resulting in the case of increasing film thickness arises from the amplification or attenuation of certain wavelengths of the light by interference. If a plurality of layers in a multilayered pigment have the same optical thickness, the colour of the reflected light becomes more intense with increasing number of layers. Given a suitable choice of the layer thicknesses, however, it is also possible to obtain very attractive interference pigments with layers of different optical thickness. The thickness of the individual metal-oxide layers, independently of their refractive index, i
Bernhardt Klaus
Schmidt Christoph
Schoen Sabine
Koslow C. Melissa
Manlove Shalie
Merck Patent Gesellschaft mit beschränkter Haftung
Millen White Zelano & Branigan P.C.
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