Title of Invention

SILVER PIGMENTS

Abstract The invention relates to a silver pigment, consisting of a transparent, platelet-shaped substrate, which is an SiO2 platelet, AI2O3 platelet, a polymer platelet, asingle crystal or a glass platelet, having a refractive index ≤1.9, and an average thickness of individual platelets within a standard deviation of ≤20%, and on said substrate a coating of TiO2 and optionally an outer protective layer, said pigment having a silver interference color, whereby said pigment exhibits color travel.
Full Text Silver pigments
The present invention relates to silver interference pigments based on
flake-form, transparent, low-refractive-index substrates and to the use
thereof in paints, coatings, printing inks, plastics, as dopants for the laser
marking of plastics and papers, as additives in the foods and pharmaceutic
cals sectors and in cosmetic formulations.
Lustre or effect pigments are employed in many areas of industry, in par-
ticular in the area of automotive finishes, decorative coatings, plastics,
paints, printing inks and in cosmetic formulations.
Owing to their colour play, lustre pigments, which exhibit an angle-
dependent colour change between a plurality of interference colours, are
of particular interest for automotive finishes and in forgery-proof docu- _
ments of value.
Mineral-based pearlescent pigments are of particular importance. Pearles-
cent pigments are prepared by coating an inorganic, flake-form support
with a high-refractive-index, usually oxidic layer. The colour of these pig-
ments is caused by wavelength-selective partial reflection and interference
of the reflected or transmitted light at the medium/oxide or oxide/substrate
interfaces.
The interference colour of these pigments is determined by the thickness
of the oxide layer. The hue of a silver pigment is generated by a (in the
optical sense) single high-refractive-index layer whose optical thickness
causes a reflection maximum (1st order) in the visible wavelength range at
about 500 nm. This wavelength is perceived by the human eye as the
colour green. However, the intensity curve of this maximum on its wave-
length axis is so broad that so much light is reflected throughout the region
of visible light that the human eye perceives a very bright, but colourless
impression.
According to the known rules - in particular from the coating of optical
components - of the optics of thin layers, the intensity of the reflected light
in an arrangement of a plurality of layers with alternating high and low
refractive indexes increases greatly compared with a single layer. Thus,
the application of a TiO2-SiO2-TiO2 layer system to mica particles,
increases the intensity of the reflected light by about 60% compared with a
TiO2 single-layer system. Accordingly, the profile of the light reflected by
interference is significantly more pronounced, so that an intense and bright
reflection colour must be expected for a multilayered system of this type.
Pigments of this type are described in DE 196 18 569 A1.
The prior art discloses silver pigments based on mica flakes which have a
very broad scattering of the layer thickness and therefore have a neutral
behaviour with respect to the interference colour. Pearlescent pigments
that have a single high-refractive-index coating of mica therefore represent
single-layer optical systems, i.e. the interference colour is determined
exclusively by the layer thickness of the high-refractive-index metal-oxide
layer. The colouristic design latitude of a mica/metal oxide silver pigment is
therefore very restricted.
In addition, mica particles, owing to their layer structure, have irregularities
on the surface which cause scattering and thus reduce the transparency
and colouristic quality of the product. Furthermore, mica exhibits a more or
less highly pronounced grey-brown body colour. This property reduces the
transparency further and influences the absorption colour of the application
media in an undesired manner.
Furthermore, multilayered pigments which cause a silver colour impres-
sion, as described, for example, in EP 1213330 A1, are known. In the case
of these pigments, an intense colour can be suppressed by the SiO2 layer
of the TiO2-SiO2-TiO2 layer sequence having been applied very thinly
about 50 nm). These pigments, like the single-layered mica-based silver
pigments, offer only a very small latitude in the design of the colouristic
properties and have the above-mentioned disadvantages of mica as sub-
strate.
The object of the present invention is therefore to provide a silver-coloured
interference pigment which is distinguished, in particular, by high trans-
parency, a pure-white body colour and colouristic design possibilities which
go beyond an exclusively silver effect.
Surprisingly, it has now been found that a specific transparent, low-refrac-
tiye-index flake, such as, for example, an SiO2 flake, coated, with a thin
TiO2 layer causes a silver colour impression. This is achieved through the
coating of the flake with a TiO2 layer whose thickness is matched precisely
to the thickness of the flake.
Compared with single-coated mica-based silver pigments and the interfer-
ence pigments from EP 1213330 A1, the pigments according to the inven-
tion exhibit the following properties:
excellent transparency in the application medium
pure-white body colour
very bright silver interference colour.
In addition to these properties, the pigments according to the invention are
distinguished over the known interference pigments by the following fea-
tures:
strong sparkle effect
adjustable hue
angle-dependence of the hue
The said hue can be varied over a broad range by adjusting the TiO2 layer
thickness and through the choice of transparent flakes, such as, for exam-
ple, SiO2 flakes, of various thickness without losing the impression of an
interference pigment.
The invention therefore relates to silver interference pigments based on
flake-form, transparent, low-refractive-index substrates which have a high-
refractive-index coating consisting of TiO2 having a layer thickness of 5 -
300 nm and optionally an outer protective layer.
The invention furthermore relates to the use of the silver pigments
according to the invention in paints, coatings, printing inks, plastics, button
pastes, ceramic materials, glasses, for seed coating, as dopants in the
laser marking of plastics and papers, as additives for colouring in the foods
and pharmaceuticals sectors and in particular in cosmetic formulations.
The pigments according to the invention are furthermore also suitable for
the preparation of pigment compositions 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 and for
cosmetic formulations.
Suitable base substrates for the interference pigments according to the
invention are substrates having a refractive index of flake-form SiO2 flakes, as described, for example, in WO 93/08237. Fur-
thermore, besides the said SiO2 flakes, any flake-form, transparent sub-
strate known to the person skilled in the art, such as, for example, AI2O3
flakes, glass flakes and flake-form plastic particles, is suitable. Very par-
ticularly preferred substrates are SiO2 flakes. The particular properties,
such as the tuneable hue and in particular the angle dependence thereof,
are particularly supported by a defined average density with a narrow
thickness distribution.
The standard deviation of the thickness of the substrate flakes should
therefore be based on the average layer thickness thereof.
The size of the base substrate is not crucial per se and can be matched to
the particular application. In general, the flake-form transparent substrates
have an average thickness of between 0.02 and 10 urn, preferably
between 0.03 and 5 urn, in particular between 0.05 and 3 urn. The size in
the two other dimensions is usually between 1 and 450 urn, preferably
between 2 and 200 urn and in particular between 5 and 100 urn.
In order to achieve a pure silver effect with superimposed, angle-depend-
ent hue, it is important that the average thickness of the individual flakes is
within a standard deviation of The aspect ratio (diameter/thickness ratio) of the substrate is preferably 1
- 1000, in particular 3 - 500 and very particularly preferably 5 - 200.
The thickness of the TiO2 layer and of the substrate, for example SiO2
substrate, is essential for the optical properties of the pigment. The thick-
ness ofthe layer must be set precisely and matched to the average thick
ness of the substrate flakes. Preference is given to TiO2 layer thicknesses
of 5 -300nm, preferably 10 - 200nm,in particular 30 - 1.50. nm,
The pigments according to the invention can be prepared relatively easily
by forming a high-refractive-index TiO2 interference layer having precisely
defined thickness and a smooth surface on the finely divided, flake-form
substrates. The TiO2 can be eithenn the form of rutile or in the form of
anatase. The TiO2 is preferably in the rutile modification) Particular prefer-
ence is given to SiO2 flakes coated with a rutile layer.
Suitable substrates are all inorganic and organic transparent materials
which can be produced in the form of finely divided flakes having a narrow
thickness distribution. Suitable organic substrates are, inter alia, polymers,
such as, for example, polyesters (for example PET), polycarbonates,
polyimides and polymethacrylates.
Particular preference is given to interference pigments based on SiO2,
AI2O3, all single crystals with a flaky appearance and glass flakes coated
with a thin titanium dioxide layer.
The metal-oxide layer is preferably applied by wet-chemical methods, it
being possible to use the wet-chemical coating methods developed for the
preparation of peariescent pigments. Methods of this type are described,
for example, in DE 14 67 468, DE 19 59 988, DE 20 09 566, DE
22 14 545, DE 22 15 191, DE 22 44 298, DE 23 13 331, DE 25 22 572, DE
31 37 808, DE 31 37 809, DE 31 51 343, DE 31 51 354, DE 31 51 355, DE
32 11 602, DE 32 35 017, and also in further patent documents and other
publications known to the person skilled in the art.
In the case of wet coating, the substrate particles are suspended in water,
and one or more hydrolysable titanium salts are added at a pH which is
suitable for hydrolysis, the latter being selected in such a way that the
metal oxides or metal oxide hydrates are precipitated directly onto the
flakes without significant secondary precipitations occurring. The pH is
usually kept constant by simultaneous metering-in of a base and/or acid.
The pigments are subsequently separated off, washed and dried at 50-
150°C and, if desired, calcined for 0.5-3 hours, where the calcination tem-
perature can be optimised with respect to the coating present in each
case. In general, the calcination temperatures are between 250 and
1000°C, preferably between 350 and 950°C.
The coating can furthermore also be carried out in a fluidised-bed reactor
by gas-phase coating, it being possible, for example, correspondingly to
use the processes proposed in EP 0 045 851 A1 and EP 0 106 235 A1 for
the preparation of pearlescent pigments.
The hue of the pigments can be varied within very broad limits while
retaining the silver effect by choosing different covering amounts or layer
thicknesses resulting therefrom. The fine tuning for a certain hue can be
achieved beyond the pure choice of amount by approaching the desired
colour under visual or measurement technology control.
In order to increase the light, water and weather stability, it is frequently
advisable, depending on the area of application, to subject the finished
pigment to post-coating or post-treatment. Suitable post-coatings or post-
treatments are the processes described, for example, in German Patent
22 15 191, DE-A 31 51 354, DE-A 32 35 017 and DE-A 33 34 598. This
post-coating further increases the chemical stability or simplifies handling
of the pigment, in particular incorporation into various media. In order to
improve the wettability, dispersibility and/or compatibility with the applica-
tion media, functional coatings of AI2O3 or Zr02 or mixtures or mixed
phases thereof may be applied to the pigment surface, furthermore,
organic or combined organic/inorganic post-coatings are possible, for
example with silanes, as described, for example, in EP 0090259, EP 0 634
459, WO 99/57204, WO 96/32446, WO 99/57204, U.S. 5,759,255, U.S.
5,571,851, WO 01/92425 or in J.J. Ponjee, Philips Technical Review, Vol.
44, No. 3, 81 ff., and P.H. Harding J.C. Berg, J. Adhesion Sci. Technol.
Vol. 11 No. 4, pp. 471-493.
The silver pigments according to the invention are simple and easy to
handle. The pigments can be incorporated into the application system by
simple stirring-in. Complex grinding and dispersal of the pigments is not
necessary.
Since the silver pigments according to the invention combine high gloss
with high transparency and a pure-white body colour, they enable particu-
larly effective effects to be achieved in the various application media with-
out the absorption colour being significantly affected.
It goes without saying that, for the various applications, the interference
pigments can also advantageously be used in the form of a mixture with
organic dyes, organic pigments or other pigments, such as, for example,
transparent and opaque white, coloured and black pigments, and with
flake-form iron oxides, organic pigments, holographic pigments, LCPs
(liquid crystal polymers) and conventional transparent, coloured and black
lustre pigments based on metal oxide-coated mica and SiO2 flakes, etc.
The interference pigments can be mixed in any ratio with commercially
available pigments and fillers.
In the various applications, the pigment according to the invention can also
be combined with further colorants of any type, for example organic and/or
inorganic absorption pigments and dyes, multilayered interference pig-
ments, such as, for example, Timiron® , Sicopearl® (BASF AG), Chroma-
Flair® (Flex Products Inc.), BiOCI pigments, pearl essence or metal
pigments, for example from Eckart. There are no limits to the mixing ratios
and concentration.
The pigments according to the invention are compatible with a multiplicity
of colour systems, preferably from the area of paints, coatings and printing
inks. For the production of printing inks for, for example, gravure printing,
flexographic printing, offset printing or offset overprinting, a multiplicity of
binders, in particular water-soluble grades, as marketed, for example, by
BASF, Marabu, Proll, Sericol, Hartmann, Gebr. Schmidt, Sicpa, Aarberg,
Siegberg, GSB-Wahl, Follmann, Ruco or Coates Screen INKS GmbH, are
suitable. The printing inks may be water-based or solvent-based. The pig-
ments are furthermore also suitable for the laser marking of paper and
plastics and for applications in the agricultural sector, for example for
greenhouse sheeting, and, for example, for the colouring of tent awnings.
The silver pigment according to the invention can be used for the pig-
menting of surface coatings, printing inks, plastics, agricultural sheeting,
seed coatings, food colourings, button pastes, medicament coatings or
cosmetic formulations, such as lipsticks, nail varnishes, compact powders,
shampoos, loose powders and gels. The concentration of the pigment
mixture in the application system to be pigmented is generally between 0.1
and 70% by weight, preferably between 0.1 and 50% by weight and in
particular between 0.5 and 10% by weight, based on the total solids con-
tent of the system. It is generally dependent on the specific application.
Plastics comprising the silver pigment according to the invention in
amounts of from 0.01 to 50% by weight, in particular from 0.1 to 7% by
weight, are frequently distinguished by a particularly pronounced sparkle
effect.
In the surface coatings sector, in particular in automotive paints, the silver
pigment is also employed for three-coat systems in amounts of 0.1-10% by
weight, preferably from 1 to 3% by weight.
In surface coatings, the pigment according to the invention has the
advantage that the target gloss is achieved by a one-coat finish (one-coat
system or base coat in two-coat systems). Compared with finishes com-
prising a mica-based multilayered pigment instead of the silver pigment
according to the invention, finishes comprising the pigment according to
the invention exhibit a clearer depth effect and a more highly pronounced
gloss effect.
The silver pigment according to the invention can also advantageously be
employed in decorative and care cosmetics. The use concentration
extends from 0.01% by weight in shampoos to 100% by weight in the case
of loose powders. In the case of a mixture of the silver pigments with
spherical fillers, for example SiO2, the concentration can be 0.01-70% by
weight in the formulation. The cosmetic products, such as, for example,
nail varnishes, lipsticks, compact powders, shampoos, loose powders and
gels, are distinguished by particularly interesting gloss effects. The sparkle
effect in nail varnish can be significantly increased compared with conven-
tional nail varnishes with the aid of the pigments according to the invention.
Furthermore, the pigment according to the invention can be employed in
bath additives, toothpastes and for the finishing of foods, for example
mass colouring and/or coatings of boiled sweets, wine gums, such as, for
example, jelly babies, pralines, liquorice, confectionery, sticks of rock, fizzy
drinks, sodas, etc., or as a coating, for example, in standard and coated
tablets in the pharmaceuticals sector.
The pigment according to the invention can furthermore be mixed with
commercially available fillers. Fillers which may be mentioned are, for
example, natural and synthetic mica, nylon powder, pure or filled melamine
resins, talc, glasses, kaolin, oxides or hydroxides of aluminium, magne-
sium, calcium, zinc, BiOCI, barium sulfate, calcium sulfate, calcium car-
bonate, magnesium carbonate, carbon, and physical or chemical combi-
nations of these substances. There are no restrictions regarding the parti-
cle shape of the filler. It can be, for example, flake-shaped, spherical or
needle-shaped in accordance with requirements.
It is of course also possible for the pigments according to the invention to
be combined in the formulations with cosmetic raw materials and assis-
tants of any type. These include, inter alia, oils, fats, waxes, film formers,
preservatives and assistants which generally determine the technical
properties, such as, for example, thickeners and rheological additives,
such as, for example, bentonites, hectorites, silicon dioxides, Ca silicates,
gelatines, high-molecular-weight carbohydrates and/or surface-active
assistants, etc.
The formulations comprising the pigments according to the invention can
belong to the lipophilic, hydrophilic or hydrophobic type. In the case of
heterogeneous formulations having discrete aqueous and non-aqueous
phases, the pigments according to the invention may in each case be pre-
sent in only one of the two phases or alternatively distributed over both
phases.
The pH values of the formulations can be between 1 and 14, preferably
between 2 and 11 and particularly preferably between 5 and 8.
No limits are set for the concentrations of the pigments according to the
invention in the formulation. They can be - depending on the application -
between 0.001 (rinse-off products, for example shower gels) and 100%
(for example gloss-effect articles for particular applications).
The pigments according to the invention may furthermore also be com-
bined with cosmetic active ingredients. Suitable active ingredients are, for
example, insect repellents, UV A/BC protective filters (for example OMC,
B3 and MBC), anti-ageing active ingredients, vitamins and derivatives
thereof (for example vitamin A, C, E, etc.), self-tanning agents (for exam-
ple DHA, erythrulose, inter alia), and further cosmetic active ingredients,
such as, for example, bisabolol, LPO, ectoin, emblica, allantoin, bioflavon-
oids and derivatives thereof.
In the pigmenting of binder systems, for example for surface coatings and
printing inks for gravure printing, offset printing or screen printing, or as
precursors for printing inks, the use of the interference pigments according
to the invention in the form of highly pigmented pastes, granules, pellets,
etc., has proven particularly suitable. The pigment is generally incorpor-
ated into the printing ink in amounts of 2-35% by weight, preferably 5-25%
by weight and in particular 8-20% by weight. Offset printing inks can com-
prise the pigments in amounts of up to 40% by weight or more. The pre-
cursors for printing inks, for example in the form of granules, as pellets,
briquettes, etc., comprise up to 98% by weight of the pigment according to
the invention in addition to the binder and additives. Printing inks compris-
ing the pigment according to the invention exhibit purer silver hues than
with conventional effect pigments. The particle thicknesses of the pigments
according to the invention are relatively small and therefore effect
particularly good printability.
The interference pigments according to the invention are furthermore suit-
able for the preparation of flowable pigment compositions and dry prepa-
rations, in particular for printing inks, comprising one or more silver pig-
ments according to the invention, binders and optionally one or more addi-
tives.
The invention thus also relates to formulations comprising the silver pig-
ment according to the invention.
The following examples are intended to explain the invention, but without
limiting it.
Examples
Example 1: Silver pigment with colour travel from green via red-violet to
gold-green
100 g of SiO2 flakes (particle size 5-50 urn, average thickness 450 nm,
standard deviation of the thickness: 5%) are suspended in 2 I of deionised
water and heated to 80°C with vigorous stirring. A solution of 12 g of SnCI4
x 5 H2O and 40 ml of hydrochloric acid (37%) in 360 ml of deionised water
is metered into this mixture at pH 1.6 at a rate of 4 ml/min. 370 ml of TiCl4
solution (400 g of TiCl4/l) are subsequently metered in at a pH of 1.6 at a
rate of 2 ml/min. The pH is kept constant during the addition of both the
SnCl4 x 5 H2O solution and TiCI4 solutions using NaOH solution (32%).
The pH is subsequently adjusted to 5.0 using sodium hydroxide solution
(32%), and the mixture is stirred for a further 15 minutes.
For work-up, the pigment is filtered off, washed with 201 of deionised
water, dried at 110°C and calcined at 850°C for 30 minutes. The product is
a silver interference pigment having a slight green tint which shifts via red-
violet to gold-green when viewed at an angle.
Example 2: Silver pigment with colour travel from neutral silver via red-
violet to gold-yellow
100 g of SiO2 flakes (particle size 5-50 urn, average thickness 450 nm,
standard deviation of the thickness: 5%) are suspended in 2 I of deionised
water and heated to 80°C with vigorous stirring. A solution of 12 g of SnCl4
x 5 H2O and 40 ml of hydrochloric acid (37%) in 360 ml of deionised water
is metered into this mixture at pH 1.6 at a rate of 4 ml/min. 350 ml of TiCI4
solution (400 g of TiCI4/I) are subsequently metered in at a pH of 1.6 at a
rate of 2 ml/min. The pH is kept constant during the addition of both the
SnCI4 x 5 H2O solution and TiCI4 solutions using NaOH solution (32%).
The pH is subsequently adjusted to 5.0 using sodium hydroxide solution
(32%), and the mixture is stirred for a further 15 minutes.
For work-up, the pigment is filtered off, washed with 20 I of deionised
water, dried at 110°C and calcined at 850°C for 30 minutes. The product is
a silver interference pigment whose colour shifts via red-violet to gold-
yellow when viewed at an angle.
Example 3: Silver pigment with colour travel from slightly bluish silver via
red to gold-green
100 g of SiO2 flakes (particle size 5-50 urn, average thickness 450 nm,
standard deviation of the thickness: 5%) are suspended in 2 I of deionised
water and heated to 80°C with vigorous stirring. A solution of 12 g of SnCI4
x 5 H2O and 40 ml of hydrochloric acid (37%) in 360 ml of deionised water
is metered into this mixture at pH 1.6 at a rate of 4 ml/min. 340 ml of TiCl4
solution (400 g of TiCl4/l) are subsequently metered in at a pH of 1.6 at a
rate of 2 ml/min. The pH is kept constant during the addition of both the
SnCl4 x 5 H2O solution and TiCI4 solutions using NaOH solution (32%).
The pH is subsequently adjusted to 5.0 using sodium hydroxide solution
(32%), and the mixture is stirred for a further 15 minutes.
For work-up, the pigment is filtered off, washed with 20 I of deionised
water, dried at 110°C and calcined at 850°C for 30 minutes. The product is
a silver interference pigment whose colour shifts via red to gold-green
when viewed at an angle.
Preparation:
Melt and stir all constituents of phase C at about 75°C until everything has
melted. Initially introduce the water of phase B cold, homogenise in the
Blanose using the Turrax, scatter in the Veegum, and re-homogenise.
Warm to 75°C and dissolve the other constituents therein with stirring. Stir
in the constituents of phase A. Add phase C at 75°C with stirring and
homogenise for 2 minutes. Cool the mixture to 40°C with stirring, add
phase D. Cool further to room temperature with stirring and adjust to pH
6.0 - 6.5 (for example using citric acid solution).
Example B: Shower gel
Preparation:
For phase A, stir the pigment into the water. Slowly scatter in the Keltril T
with stirring and stir until it has dissolved. Add phases B and C succes-
sively while stirring slowly until everything is homogeneously distributed.
Adjust the pH to from 6.0 to 6.4.
Example C: Eyeliner gel
Preparation:
Disperse the effect pigments and Ronasphere® in the water of phase A.
Acidify using a few drops of citric acid in order to reduce the viscosity,
scatter in the Carbopol with stirring. After complete dissolution, slowly stir
in the pre-dissolved phase B and adjust the pH to from 7.0 to 7.5.
Example D: Eve shadow
Preparation:
Combine and pre-mix the constituents of phase A. Subsequently add the
molten phase B dropwise to the powder mixture with stirring. The powders
are pressed at from 40 to 50 bar.
Preparation:
Disperse the effect pigments and Ronasphere® in the water of phase A.
Acidify using a few drops of citric acid in order to reduce the viscosity,
scatter in the Carbopol with stirring. After complete dissolution, slowly stir
in the pre-dissolved phase B.
Preparation:
Combine and pre-mix the constituents of phase A. Subsequently add the
molten phase B dropwise to the powder mixture with stirring. The powders
are pressed at from 40 to 50 bar.
Preparation:
The pigment is weighed out together with the varnish base, mixed well by
hand using a spatula and subsequently stirred at 1000 rpm for 10 minutes.
Example H: Lip lacquer
Preparation:
Warm all constituents (apart from the Foral 85-E) of phase B to 80°C and
slowly add the Foral 85-E with stirring. Add phase A and phase C to the
molten phase B. Pour the homogeneous melt into the mould at 50°C.
WE CLAIM
1. A silver pigment, consisting of a transparent, platelet-shaped substrate, which
is an SiO2 platelet, AI2O3 platelet, a polymer platelet, a single crystal or a glass
platelet, having a refractive index =1.9, and an average thickness of individual
platelets within a standard deviation of =20%, and on said substrate a coating of
TiO2 and optionally an outer protective layer, said pigment having a silver
interference color, whereby said pigment exhibits color travel.
2. A silver pigment as claimed in claim 1, wherein the TiO2 coating has a layer
thickness of 5-300 nm.
3. A silver pigment as claimed in claim 2, wherein the transparent platelet is an
SiO2 platelet.
4. A silver pigment as claimed in claim 1, wherein the average thickness of
individual platelets is within a standard deviation of =10%.
5. A silver pigment as claimed in claim 1, wherein the TiO2 is in the rutile
modification.
6. A process for the preparation of a silver pigment as claimed in claim 1,
comprising a coating of the substrate by wet-chemical methods, by hydrolytic
decomposition of metal salts in aqueous medium or by thermal decomposition by
a CVD or PVD process.
7. A process as claimed in claim 6, wherein the TiO2 coating is matched to the
substrate as to produce a silver interference color.
8. In a paint, coating, printing ink, security printing ink, plastic, button paste,
ceramic material, glass, seed coating, dopant for laser marking of plastics or
papers, an additive for coloring of foods or pharmaceuticals or, cosmetic
formulation comprising a pigment the improvement wherein the pigment is one
as claimed in claim 1.
9. A pigment composition comprising at least one binder, at least one silver
pigment as claimed in claim 1, and optionally conventional additives.
10. A dry preparation comprising pellets, granules, chips or briquettes of a silver
pigment as claimed in claim 1.

The invention relates to a silver pigment, consisting of a transparent, platelet-
shaped substrate, which is an SiO2 platelet, AI2O3 platelet, a polymer platelet, a
single crystal or a glass platelet, having a refractive index ≤1.9, and an average
thickness of individual platelets within a standard deviation of ≤20%, and on
said substrate a coating of TiO2 and optionally an outer protective layer, said
pigment having a silver interference color, whereby said pigment exhibits color
travel.

Documents:

110-kol-2004-abstract.pdf

110-kol-2004-claims.pdf

110-kol-2004-correspondence.pdf

110-kol-2004-description (complete).pdf

110-kol-2004-examination report.pdf

110-kol-2004-form 1.pdf

110-kol-2004-form 18.pdf

110-kol-2004-form 2.pdf

110-kol-2004-form 3.pdf

110-kol-2004-form 5.pdf

110-kol-2004-gpa.pdf

110-kol-2004-granted-abstract.pdf

110-kol-2004-granted-claims.pdf

110-kol-2004-granted-correspondence.pdf

110-kol-2004-granted-description (complete).pdf

110-kol-2004-granted-examination report.pdf

110-kol-2004-granted-form 1.pdf

110-kol-2004-granted-form 18.pdf

110-kol-2004-granted-form 2.pdf

110-kol-2004-granted-form 3.pdf

110-kol-2004-granted-form 5.pdf

110-kol-2004-granted-gpa.pdf

110-kol-2004-granted-priority document.pdf

110-kol-2004-granted-reply to examination report.pdf

110-kol-2004-granted-specification.pdf

110-kol-2004-granted-translated copy of priority document.pdf

110-kol-2004-priority document.pdf

110-kol-2004-reply to examination report.pdf

110-kol-2004-specification.pdf

110-kol-2004-translated copy of priority document.pdf


Patent Number 235906
Indian Patent Application Number 110/KOL/2004
PG Journal Number 36/2009
Publication Date 04-Sep-2009
Grant Date 03-Sep-2009
Date of Filing 16-Mar-2004
Name of Patentee MERCK PATENT GMBH
Applicant Address FRANKFURTER STRASSE 250, 64293 DARMSTADT
Inventors:
# Inventor's Name Inventor's Address
1 DR. CHRISTOPH SCHMIDT BEETHOVENSTRASSE 3, 65830 KRIFTEL
2 MRS. TANJA DELP MARTIN-BUBER-STRASSE 69, 64287 DARMSTADT
3 DR. JOHANN DIETZ AM BIEBERBACH 20, 63218 DIETZENBACH
PCT International Classification Number C04B 2/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10313978.8 2003-03-27 Germany