Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
2002-10-24
2004-04-13
Koslow, C. Melissa (Department: 1755)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C106S415000, C106S436000, C106S439000, C106S440000, C106S479000, C106S481000
Reexamination Certificate
active
06719838
ABSTRACT:
The present invention relates to 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 coatings, plastics, surface coatings, printing inks and cosmetic formulations.
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.
EP 0 753 545 A2 discloses goniochromatic lustre pigments based on multicoated, 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 multilayer pigments known from the prior art are in some cases built up from layer materials which have little or no transparency to light and can therefore only be combined with absorption pigments in a very restricted manner in use. In addition, the interference colour of these pigments is highly dependent on the viewing angle, which is undesired in the majority of applications. Furthermore, these pigments are in some cases very difficult to prepare or reproduce.
An object of the present invention is to provide coloured multilayer pigments of high tinting strength which do not have pronounced goniochromaticity, are distinguished by their advantageous applicational properties and at the same time can be prepared in a simple manner.
Upon further study of the specification and appended claims, further objects and advantages of this invention will become apparent to those skilled in the art.
Surprisingly, coloured interference pigments based on multicoated, platelet-shaped substrates have now been found on which firstly a defined absorption is produced and subsequently an interference system is defined. This combination of absorption and interference on a platelet-shaped substrate results in a coloured pigment having high colour purity of the interference colour and intense lustre.
The pigments according to the invention are distinguished over the pigments from the prior art through their extraordinarily high chroma C, their high hiding power, their high colour purity of the interference colour and high brightness. In contrast to the goniochromatic pigments from the prior art, they do not exhibit any angle dependence of the interference colour.
The invention thus relates to coloured interference pigments based on multicoated, platelet-shaped substrates, characterised in that they comprise
(A) a coloured coating having a refractive index of n>1.8,
(B) a colourless coating having a refractive index of n>1.8,
(C) a colourless coating having a refractive index of n≦1.8,
(D) a colourless coating having a refractive index of n>1.8, and optionally
(E) an outer protective layer.
The invention furthermore relates to the use of the interference pigments according to the invention in paints, coatings, printing inks, plastics, ceramic materials, glasses and for laser marking. Owing to the high colour strength, the pigments according to the invention are particularly suitable for decorative cosmetics. Furthermore, the pigments according to the invention are also suitable for the production of pigment preparations and for the production of dry preparations, such as, for example, granules, chips, pellets, briquettes, etc. The dry preparations are particularly suitable for printing inks, coatings and cosmetic formulations.
Suitable base substrates for the coloured pigments according to the invention are transparent platelet-shaped substrates. Preferred substrates are phyllosilicates. Particularly suitable substrates are natural or synthetic mica, talc, kaolin, platelet-shaped iron oxides or aluminium oxides, BiOCl, glass platelets, SiO
2
platelets, TiO
2
platelets, graphite platelets, synthetic support-free platelets, or other comparable materials. It is also possible to employ mixtures of different substrates. Particularly preferred substrate mixtures are
mica platelets+SiO
2
platelets
mica platelets+Al
2
O
3
platelets
mica platelets+glass platelets
mica platelets+TiO
2
platelets
mica platelets+oxynitride platelets
mica platelets+nitride platelets
mica platelets+pearl essence
mica platelets+graphite platelets
mica platelets+BiOCl
SiO
2
platelets+Al
2
O
3
platelets
glass platelets+SiO
2
platelets
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 1.5 &mgr;m, in particular between 0.1 and 1 &mgr;m. The extension in the two other regions is usually between 1 and 250 &mgr;m, preferably between 2 and 200 &mgr;m, and in particular between 5 and 60 &mgr;m. It is also possible to employ substrates having different particle sizes. Particular preference is given to a mixture of mica fractions of N mica (10-60 &mgr;m) and F mica (5-20 &mgr;m). Preference is furthermore given to N and S fractions (10-130 &mgr;m) and F and S fractions (5-130 &mgr;m).
The thickness of the individual layers on the base substrate is essential for the optical properties of the pigment. Layer (A) in particular has a significant effect on the colour properties
The interference pigments according to the invention have an absorption layer (A) and an interference system (B, C, D), the latter consisting of alternating high-refractive-index layers (B, D) and low-refractive-index layer (C). The high-refractive-index layers (B) and (D) have a refractive index of n>1.8, preferably n≧2.0.
Layer (A) preferably consists of coloured oxides, sulfides, tellurides, selenides or mixed systems of these anions and of the elements from main groups 2-5 and subgroups 1, 2 and 4-8, furthermore the lanthanides and actinides. Layer (A) particularly preferably consists of Fe
2
O
3
, Fe
3
O
4
, Ce
2
O
3
, Cr
2
O
3
, Ti suboxides (TiO
2
partially reduced with oxidation states of from <4 to 2 and lower oxides, such as Ti
3
O
5
, Ti
2
O
3
up to TiO), titanium oxynitrides and titanium nitride, molybdenum oxides, CoO, Co
3
O
4
, VO
2
, V
2
O
3
, NiO, MoS
2
, WS
2
, V
2
O
5
, CuO, Cu
2
O, Ag
2
O, CeO
2
, MnO
2
, Mn
2
O
3
, Mn
2
O
5
or mixtures or combinations (mixed oxides) thereof. Layer (A) particularly preferably consists of Fe
2
O
3
, Fe
3
O
4
, furthermore of Cr
2
O
3
, CoO, Co
3
O
4
, VO
2
, V
2
O
3
, NiO, MoS
2
, WS
2
, V
2
O
5
, CuO, CeO
2
, Ce
2
O
3
, MnO
2
, Mn
2
O
3
and/or Ag
2
O.
Layers (B) and (D) preferably consist of TiO
2
, ZrO
2
, SnO
2
, ZnO or BiOCl. Layers (B) and (D) are particularly preferably a TiO
2
layer. The TiO
2
here can be in the rutile or anatase modification, preferably rutile.
Materials which are suitable as colourless, low-refractive-index materials for coating (C) are preferably metal oxides or the corresponding oxide hydrates, such as, for example, SiO
2
, Al
2
O
3
, AlO(OH), B
2
O
3
, MgF
2
, MgSiO
3
, or a mixture of the said metal oxides. Layer (C) preferably consists of SiO
2
, MgF
2
, Al
2
O
3
or mixtures thereof.
It is advantageous for the optical properties of the pigments according to the invention if layer (A) is very thin. The thickness of layer (A) is preferably from 1 to 100 nm, in particular from 1 to 50 nm and particularly preferably from 5 to 20 nm.
The thickness of layers (B) and (D) is preferably from 20 to 250 nm, in particular from 25 to 180 nm and particularly preferably from 40 to 150 nm. The layer thick
Heider Lilia
Kniess Helge
Loch Manuela
Schupp Nicole
Koslow C. Melissa
Manlove Shalie A.
Merck Patent GmbH
Millen White Zelano & Branigan P.C.
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