Title of Invention

MULTILAYER PIGMENTS BASED ON GLASS FLAKES

Abstract Multilayer pigments based on glass flakes characterized in that the glass flakes are coated with alternaTing layers with a high and a low refracTive index and that the glass flakes are coated with at least three layers, wherein the thickness of the flakes is < 1&#956;m and that the aspect raTio of the glass flakes is in the range of 10-300.
Full Text Multilayer pigments based on glass flakes
The present invention relates to multilayer pigments based on glass flakes,
to a method for the production of such pigments and their use in plastics,
paints, coatings, powder coatings, inks, printing inks, glasses, ceramic
products, agriculture foils, for laser-marking of papers and plastics and in
cosmetic formulations.
Lustre pigments or special-effect pigments are employed in numerous
fields in industry, especially in the sector of automotive finishes, in
decorative coatings, in plastics, in paints, in printing inks and in cosmetic
formulations.
Multilayer interference pigments with alternating layers of high and low
refractive index are known. They differ in respect of the carrier material and
of the material of the individual layers, and in the preparation process. The
layers are prepared either by precipitation in a wet process or by vapor
deposition or sputtering under vacuum. The layers applied to the carrier or
to a release layer are all optically active and contribute to the development
of the interference colors.
U.S.P. 4,434,010 discloses a multilayer interference pigment consisting of
a central layer of a reflective metal, such as aluminum, and alternating
layers of two transparent dielectric materials of high and low refractive
index respectively, such as titanium dioxide and silicon dioxide, for
example. This multilayer pigment is used preferably for counterfeit-
protected products like securities or banknotes.
JP H7-759 discloses a multilayer interference pigment with metallic lustre,
for which a substrate is coated with alternate layers of titanium dioxide and
silicon dioxide. The substrate comprises flakes of aluminum, gold or silver,
or of mica or glass, with a coating of metals. The depth effect which is
characteristic of and desired for interference pigments, however, cannot be
generated. This is because of the total reflection of the light at the metal
layer which forms the core. Consequently, the interference effect remains
limited to the layers which are located on top of the metal layer.
Furthermore, the lack of transparency of the substrate greatly restricts
options for combinations with further pigments in applications-related
formulations.
U.S.P. 3,438,796 and U.S.P. 5,135,812 describe, for example, metal lustre
pigments having a central essentially non-transparent aluminum film
coated on both sides in alternation with dielectric films of low refractive
index, such as silicon dioxide or magnesium fluoride, and with partially
transparent metal films, such as films of chromium or aluminum, for
example. Owing to the preparation process, the central metal film of these
pigments is coated only on the top and bottom sides of the platelets, while
the side areas constitute broken edges and lie open towards the medium.
DE 44 05 494, DE 44 37 753, DE 195 16 181 and DE 195 15 988 disclose
lustre pigments prepared by coating metal platelets, especially aluminum
flakes, with metal oxide layers of low refractive index, such as with a silicon
dioxide layer, and with non-selectively absorbing metal oxide layers or
metal layers of high refractive index, using CVD or wet chemical
techniques.
Lustre pigments based on metal substrates frequently have good
properties, including good hiding , but the result on application, such as in
the paint, for example, is a "hard" metallic lustre, which is frequently
undesired.
Lustre pigments based on transparent platelet-shaped substrates which
do not have this "hard" metallic lustre are the subject of WO 93/12182.
Mica flakes are covered with a metal oxide layer of high refractive index,
such as TiO2, and with a nonselectively absorbing layer. Depending on the
thickness of the TiO2 layer, when viewed straight on these pigments exhibit
a particular interference colour which becomes increasingly weaker as the
viewing angle becomes more oblique and which finally flips to gray or
black. The interference color does not change, but a decrease is found in
the color saturation.
JP 1992/93206 claims lustre pigments on the basis of glass flakes or mica
particles which are covered with a reflecting metal layer and with
alternating layers of SiO2 and TiO2.
EP 0 753 545 A2 discloses lustre pigments based on multiply coated, non-
metallic, platelet-shaped substrates which are of high refractive index and
which are at least partially transparent to visible light and have at least one
layer assembly comprising a colorless coating of low refractive index and a
reflective coating which absorbs selectively or nonselectively.
Disadvantages of this invention are the technically very complex and costly
preparation process and the frequent difficulty in reproducing the pigments
in the desired product quality.
U.S.P. 3,331,699 discloses that glass flakes may be coated with a
translucent layer of particles of metal oxide having a high index of
refraction, such as titanium dioxide, provided there is first deposited on the
glass flakes a nucleating substance which is insoluble in the acidic solution
from which the translucent layer of metal oxide is deposited. The patent
does not mention that smooth transparent films, not particles, are
necessary for quality interference pigments to be developed. The patent
teaches that the nature of the glass is not critical, but that the presence of
the nucleated surface is critical. It is further stated that there are only a
small number of metal oxide compounds which are insoluble in the acidic
solution and capable of forming a nucleated surface on the glass flakes; tin
oxide and a fibrous boehmite form of alumina monohydrate are the only
two such materials disclosed. As demonstrated in the examples below,
products prepared according to the teachings of this patent are poor in
quality.
U.S. Patent 5,436,077 teaches a glass flake substrate which has a metal
covering layer on which is formed a dense protective covering layer of a
metal oxide such as titanium dioxide. In this patent, the nature of the glass
is unimportant, the metallic coating provides the desired appearance and
the overcoating of the metal oxide is present to protect the metallic layer
from corrosive environments.
For the preparation of pearlescent pigments the transparency and the
thickness of the platy substrate are very important. For the first time
EP 0 289 240 B1 discloses the manufacturing of extremely thin glass
flakes at reasonable costs. According to the claimed process the glass
flakes can be made in any desired composition, e. g., from pure SiO2 and
also in any thickness tailored for the intended application down to below
1.0 µm.
It is an object of the present invention to overcome the problems of the
prior art and to provide novel multilayer pigments which have
advantageous application properties.
Surprisingly, an interference pigment has now been found which is based
on multiply coated glass flakes and comprises a particular arrangement of
optically functional layers by means of which particular optical effects are
achieved.
The invention therefore provides interference pigments on the basis of
multiply coated glass flakes which contain at least three alternating layers
with a high and a low refractive index.
Preferably the layer structure is as of follows:
(A) a coating having a refractive index n > 1.8,
(B) a coating having a refractive index n = 1.8, and
(C) a coating having a high refractive index n > 1.8
and, if desired,
(D) an outer protective layer.
The invention also provides the pigments of the invention for the use in
paints, lacquers, printing inks, plastics, agricultural foils, ceramic materials,
glasses and cosmetic formulations and for the use in laser-marking of
papers and plastics.
Preferred glass flakes have a thickness of less than 1 µm, preferably µm. Especially preferred are glass flakes with a thickness of Glass can be classified for example as A glass, C glass, E glass, ECR
glass. For the present invention quartz glass is preferred but this glass is
very expensive.
Suitable glass flakes preferably prepared according to EP 0 289 240 B1
are characterized in that they contain an average particle size in the range
of 5 -1000 µm, preferably in the range of 5 - 150 µm. Preferred glass
flakes have an average particle size in the range of 5 -150 µm and a
thickness of 0.1 - 0.8 µm, preferably of 0.2 - 0.5 µm. The aspect ratio of
glass flakes is in the range of 10 - 300, preferably in the range of 50 - 200.
The glass flakes can be coated in the same way as conventional pearl
lustre pigments. Coatings with a metal oxide may be accomplished by any
known methods, such as hydrolysis of a metal salt by heating or under
alkaline conditions, which deposits hydrated metal oxide, followed by
calcination. In general, the procedure involves the dispersing of the thin
glass flake particles and combining that dispersion with a precursor which
forms a hydrous metal oxide film coating on the flakes.
The thickness of the individual layers of high and low refractive index on
the base substrate is essential for the optical properties of the pigment. For
a pigment with intensive interference colors, the thickness of the individual
layers must be adjusted precisely with respect to one another.
If n is the refractive index of a thin layer and d its thickness, the
interference colour of this layer is defined by the product n d (n d =
optical thickness). The colors which result from such a film under
perpendicular light incidence in reflected light result from an intensification
of the fight of wavelength

and by an attenuation of the light of wavelength

where N is a positive integer.
The variation in color which results with increasing film thickness is a
consequence of the intensification or attenuation of certain light
wavelengths through interference. If two or more layers in a multilayer
pigment possess the same optical thickness, the color of the reflected light
becomes more intense as the number of layers increases. In addition,
it is possible through an appropriate choice of layer thickness to achieve a
particularly strong variation of color as a function of the viewing angle. A
pronounced, so-called color flop is developed. The thickness of the
individual layers, preferably metal oxide layers, irrespective of their
refractive index, depends on the field of use and is generally from 10 to
1000 nm, preferably from 15 to 800 nm and, in particular, 20 to 600 nm.
The multilayer pigments of the invention preferably feature a coating (A) of
high refractive index in combination with a colorless coating (B) of low
refractive index and located thereon a coating of high refractive index. The
pigments can comprise two or more, identical or different combinations of
layer assemblies, although preference is given to covering the substrate
with only one layer assembly (A) + (B) + (C). In order to make the color flop
more intense the pigment of the invention may comprise up to 4 layer
assemblies, although the thickness of the combined layers on the substrate
should not exceed 3 µm.
The glass particles can be coated with three or more layers, preferably with
3,4, 5, 6 or 7 layers from the group consisting of metal oxides, metal
suboxides, metal fluorides, metal oxyhalides, metal sulfides, metal
chalcogenides, metal nitrides, metal oxynitrides, metal carbides, or
mixtures thereof. Especially preferred are glass flakes coated with 3, 5 or 7
layers. The layer packet (A) and (B) may be present in the standard layer
assembly (A) + (B) + (C) up to four times.
The layer (A) of high refractive index has a refractive index n > 1.8,
preferably n > 2.1. Materials suitable as the layer material (A) are all
materials known to the skilled worker which are of high refractive index, are
filmlike and can be applied homogeneously to the substrate particles.
Particularly suitable materials are metal oxides, metal sulfides or metal
oxide mixtures, such as TiO2, Fe2O3, TiFe2O5, Fe3O4, BiOCI, CoO, Co3O4,
Cr2O3, VO2, V2O3, Sn(Sb)O2l ZrO2, ZnO or SnO2, iron titanates, iron oxide
hydrates, titanium suboxides (reduced titanium species having oxidation
states from mixtures or mixed phases of these compounds with one another or with
other metal oxides.
Metal sulfide coatings are preferably selected from sulfides of tin, silver,
lanthanum, rare earth metals, preferably cerium, chromium, molybdenum,
tungsten, iron, cobalt and/or nickel.
The thickness of the layer (A) is 10 - 550 nm, preferably 15 - 400 nm and,
in particular, 20 - 350 nm.
Colorless materials of low refractive index suitable for the coating (B) are
preferably metal oxides or the corresponding oxide hydrates, such as SiO2,
MgF2, AI2O3, AIO(OH), B2O3 or a mixture of these metal oxides, The
thickness of the layer (B) is 10 - 1000 nm, preferably 20 - 800 nm and, in
particular 30 - 600 nm.
Materials particularly suitable for the coating (C) of high refractive index are
colorless or colored metal oxides such as TiO2, Fe2O3, TiFe2O5, Fe3O4,
BiOCI, CoO, CO3O4, Cr2O3, VO2, V2O3, Sn(Sb)O2, ZrO2, ZnO or SnO2, iron
titanates, iron oxide hydrates, titanium suboxides, bismuth vanadate, cobalt
aluminate, and also mixtures or mixed phases of these compounds with
one another or with other metal oxides. The TiO2 layers additionally can
contain absorbing material, e.g. carbon, or coated therewith. Also of
particular interest are multiply coated glass flakes whose TiO2 coating (C)
is partially reduced and which as well as unchanged TiO2 contains reduced
titanium species having oxidation states from Ti3O5, Ti2O3 through TiO, titanium oxynitrides and also titanium nitride). It is
also possible to use colorless high refractive materials, for example metal
oxides such as zirconium dioxide, in particular titanium dioxide, which have
been colored with selectively absorbing colorants, by incorporation of
colorants in the metal oxide layer, by doping thereof with selecTively
absorbing metal caTions or by coaTing the metal oxide layer with a colorant
like for example prussian blue or carmine. The thickness of the layer (C) is
10 - 550 nm, preferably 15-400 nm and, in parTicular, 20 - 350 nm.
In addiTion to the standard layer packet (A) + (B) + (C), in which the layer
packet of (A) + (B) may be present up to four Times in the pigment of the
invenTion, there are other preferred embodiments. For instance, between
the substrate (S) and the layer (A), between the layer (A) and (B), between
layer (B) and (C) and/or between layer (C) and the top layer (D) the
pigment of the invenTion may have a further absorbing or nonabsorbing
layer [(S1), (A1), (B1), (C1)]. The thickness of the interlayers is 1 - 50 nm,
preferably 1-40 nm and, in parTicular, 1-30 nm. The invenTive pigments
may contain a plurality of idenTical or different combinaTions (layer packets)
of(A) + (B).
The mulTilayer coated glass flakes obtained in this way are characterised in
that at least three homogeneous layers are surrounding the uniform thin
glass flakes.
Preferred effect pigments of the present invenTion are given in the
following:
glass flakes + TiO2 + SiO2 + TiO2
glass flakes + TiO2 + SiO2 + Fe2O3
glass flakes + TiO2 + SiO2 + TiO2/Fe2O3
glass flakes + TiO2 + SiO2 + (Sn,Sb)O2
glass flakes + (Sn,Sb)O2 + SiO2 + TiO2
glass flakes + Fe2O3 + SiO2 + (Sn,Sb)O2
glass flakes + TiO2/Fe2O3 + SiO2 + TiO2/Fe2O3
glass flakes + TiO2 + SiO2 + MoS2
glass flakes + TiO2 + SiO2 + Cr2O3
glass flakes + Cr2O3 + SiO2 + TiO2
glass flakes + Fe2O3 + SiO2 + TiO2
glass flakes + TiO2 + AI2O3 + TiO2
glass flakes + Fe2TiO5 + SiO2 + TiO2
glass flakes + TiO2 + SiO2 + Fe2Ti05/TiO2
glass flakes + TiO suboxides. + SiO2 + TiO2 suboxides
glass flakes + TiO2 + SiO2 + TiO2+SiO2+TiO2+ Prussian Blue
glass flakes + TiO2 + SiO2 + TiO2 + SiO2 + TiO2
glass flakes + TiO2+SiO2+TiO2 + SiO2 + TiO2 + SiO2 + TiO2
and if desired,
(D) an outer protecTive layer.
A parTicularly preferred embodiment is the coaTing of the glass flakes with
the following layer assembly:
(S1) opTional, SnO2
(A) TiO2 or Fe2O3
(B) SiO2
(B1) opTional, SnO2
(C) TiO2
(D) final coaTing related to applicaTion
CoaTing the substrates with layers (A) and (C) with a high refracTive index
and, if desired, further colored or colorless coaTings produces pigments
whose color, gloss, hiding power and angular dependence of perceived
color can be varied within wide limits.
The pigments of the invenTion are easy to produce by virtue of the
generaTion of three or more interference layers of high and low refracTive
index, precisely defined thickness and smooth surface on the thin glass
flakes. In case of layers with different metal oxides or metal oxide mixtures
the sequences of high refracTive index layers in the mulTilayer stack can be
arranged arbitrary as long as a low refracTive index layer is present in
between.
The metal oxide layers are preferably applied by wet-chemical means, it
being possible to use the wet-chemical coaTing techniques developed for
the producTion of pearl lustre pigments; techniques of this kind 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, DE 38 42 330 or else in further patent
documents and other publicaTions.
Layers of TiO2 can be in the ruTile or anatase modificaTion. Preferred are
TiO2 (ruTile) layers. Titanium dioxide layers can be also reduced by known
means, e.g. ammonia, hydrogen, hydrocarbon vapor and mixtures thereof
or metal powders, as described in EP 0 735 114, DE 34 33 657, DE 41 25
134, EP 0 332 071, EP 0 707 050 or WO 93/19131. Mixed iron oxide/
Titanium dioxide layers can be made either by subsequent precipitaTion or
by co-precipitaTion of the individual metal oxides. In the case of wet
coaTing, the substrate parTicles are suspended in water, and hydrolysable
metal salts are added at a pH which is appropriate for hydrolysis and is
chosen such that the metal oxides or metal oxide hydrates are precipitated
directly onto the platelets without any instances of side precipitaTion. The
pH is kept constant usually by simultaneous metered addiTion of a base
and/or acid. Subsequently, the pigments are filtered off, washed and dried
and, if desired, calcined, with the opTion to adjust the calcinaTion
temperature in respect of the parTicular coaTing present. In general, the
calcinaTion temperatures are between 250 and 1000 °C, preferably
between 350 and 900 °C. If desired, the pigments may be calcined before
being resuspended for the applicaTion of further layers by precipitaTion.
CoaTing can also take place in a fluidized-bed reactor by means of gas-
phase coaTing, in which case it is possible, for example, to make
appropriate use of the techniques proposed in EP 0 045 851 and
EP 0 106 235 for preparing pearl lustre pigments.
The metal oxide of high refracTive index used is preferably Titanium dioxide
and/or iron oxide, and the metal oxide of low refracTive index preferably
used is silicon dioxide.
For the applicaTion of the Titanium dioxide layers, preference is given to the
technique described in US 3,553,001.
An aqueous Titanium salt soluTion is added slowly to a suspension of the
substrate to be coated, heated to about 50-100 °C, and a substanTially
constant pH of about 0.5 - 5 is maintained by simultaneous metered
addiTion of a base, for example aqueous ammonia soluTion or aqueous
alkali metal hydroxide soluTion. As soon as the desired layer thickness of
the TiO2 precipitate has been reached, the addiTion of both Titanium salt
soluTion and base is terminated.
This technique, also referred to as the TitraTion process, is notable for the
fact that it avoids an excess of Titanium salt. This is achieved by supplying
to the hydrolysis only that quanTity per unit Time which is necessary for
uniform coaTing with the hydrated TiO2 and which can be received per unit
Time by the available surface area of the parTicles to be coated. Hereby, the
formaTion of hydrated Titanium dioxide parTicles not precipitated onto the
surface to be coated can be minimized.
The applicaTion of the silicon dioxide layers can be performed, for example,
as follows: A potassium or sodium silicate soluTion is metered into a heated
(50-100 °C) suspension of the substrate that is to be coated. The pH is
held constant at about 6 - 9 by simultaneous addiTion of a dilute mineral
acid, such as HCI, HNO3 or H2SO4. As soon as the desired layer thickness
of SiO2 has been reached, the addiTion of the silicate soluTion is terminated.
The suspension is subsequently sTirred for about 0.5 h.
To enhance the light and weather stability it is frequently advisable,
depending on the field of applicaTion, to subject the mulTilayer coated glass
flakes to a surface treatment. Useful surface treatments and
aftertreatments include for example the processes described in DE-C 22
15 191, DE-A 31 51 354, DE-A 32 35 017 or DE-A 33 34 598, DE 40 30
727 A1, EP 0 649 886 A2, WO 97/29059, WO 99/57204, US 5,759,255.
This surface treatment further enhances the chemical stability of the
pigments and/or facilitates the handling of the pigment, especially its
incorporaTion into various applicaTion media.
MulTilayer pigments generated in this way yield opTically highly improved
effect pigments at comparaTively low costs with
- superior brilliance
- clear and intense colors
- intense color travel
- alternaTively high performance opTical filter properTies
- very good transparency (important in mixed formulaTions)
and therefore suited for pracTically all applicaTions known in the field of
pigments. At the same Time their shape and parTicle size can be freely
tailored for an opTimum performance.
Especially the last menTioned aspect is of high importance as for many
applicaTions it is absolutely necessary to adjust the parTicle shape. For
cosmeTic use, it is necessary to reduce the size and the thickness to achieve
a smooth and silky appearance. For automoTive paints or prinTing inks it is a
must to reduce the parTicle sizes down to below 40 urn or even 20 urn in
diameter. This of course means that the thicknesses must follow this trend to
maintain an aspect raTio needed for attracTive effects. For these examples
therefore thicknesses of the substrate of The glass flakes made by the above menTioned process fulfill these
requirements. Furthermore they show a superior planarity and smoothness
(surface microstructure) which can be expressed by the raTio BET (specific
surface area) to WCA (water covering area) as described for aluminum
pigments in U.S.P. 4,936,913 and U.S.P. 5,127,951. The values are around 3
which indicate the opTimum suitability of the material. The high quality of
these flakes also explains the observed high transparency of pigments made
therefrom.
The preferred designs for the invenTive mulTilayer pigments are:
> 3 - 10-35 µm, and
> 0.2 - > 3 - > 0.2 - The effect pigments of the present invenTion are advantageously useful for
many purposes, such as the coloring of plasTics, glasses, ceramic
products, agricultural foils, decoraTive cosmeTic formulaTions and in
parTicular coaTings, especially automoTive coaTings, and inks, including
prinTing inks. All customary prinTing processes can be employed, for
example offset prinTing, intaglio prinTing, bronzing, flexographic prinTing.
The effect pigments of the present invenTion are also advantageously
useful for these purposes in admixture with filler pigments or transparent
and hiding white, colored and black organic and anorganic pigments and
also with convenTional transparent, colored and black luster pigments
based on metal oxide coated mica, TiO2 flakes, SiO2 flakes or AI2O3 flakes
and coated or uncoated metal pigments, BiOCI pigments, platelet shaped
iron oxides, or graphite flakes. The invenTive pigments can be further
coated with organic or inorganic layers to yield combinaTion pigments.
AddiTionally, the invenTive pigment mixture can contain organic or inorganic
colorants, thixotropic agents, wetTing agents, dispersing agents, water,
organic solvent or solvent mixtures, etc.
The pigment mixture of the invenTion is simple and easy to handle. The
pigment mixture can be incorporated into the system in which it is used by
simple sTirring. Laborious milling and dispersing of the pigments is not
necessary.
The coated glass flakes of the invenTion can be used for pigmenTing and/or
coaTing materials, prinTing inks, plasTics, agricultural films, button pastes,
for the coaTing of seed, for the coloring of food, coaTings of medicaments or
cosmeTic formulaTions. The concentraTion of the pigments in the system in
which it is to be used is generally between 0.01 and 50 % by weight,
preferably between 0.1 and 5 % by weight, based on the overall solids
content of the system. This concentraTion is generally dependent on the
specific applicaTion.
PlasTics comprising the pigment mixture of the invenTion in amounts of 0.1
to 50 % by weight, in parTicular from 0.5 to 7 % by weight, are frequently
notable for a parTicular brilliance.
In the coaTing sector, especially in automoTive finishing, the pigments
according to the invenTion are employed in amounts of 0.5 to 10 % by
weight.
In the pigmentaTion of binder systems, for example for paints and prinTing
inks for intaglio, offset or screen prinTing, the pigment is incorporated into
the prinTing ink in amounts of 2 - 50 % by weight, preferably 5-30 % by
weight and in parTicular 8 -15 % by weight.
The invenTion likewise provides pigment preparaTions comprising mulTilayer
coated glass flakes, opTionally effect pigments, binders and, if desired,
addiTives, said preparaTions being in the form of substanTially solvent-free,
free-flowing powders or granules. Such granules contain up to 95 % by
weight of the invenTive pigments. A pigment preparaTion in which the
mulTilayer coated glass flakes of the invenTion are pasted up with a binder
and with water and/or an organic solvent, with or without addiTives, and in
which the paste is subsequently dried and brought into a compact
parTiculate form, e.g. granules, pellets, briquettes, a masterbatch or tablets,
is parTicularly suitable as a precursor for prinTing inks.
The present invenTion therefore also provides formulaTions containing the
pigments of the invenTion.
In order to further illustrate the invenTion, various non-limiTing examples are
set forth below. In these, as well as throughout the balance of this
specificaTion and claims, all parts and percentages are by weight and all
temperatures are in degrees cenTigrade unless otherwise indicated.
Examples
Example 1
100 g glass flakes with a maximum diameter of 40 µm (average 22 urn)
and an average thickness of 0.5 µm (refracTive index 1.5) are suspended in
21 deionized water. Under vigorous sTirring the slurry is heated to 75 °C
and the coaTing is started by feeding an aqueous soluTion of SnCl4
represenTing an amount of 3 % of SnO2 relaTive to the glass flakes within
0.5 h. As soon as pH 2,0 is reached 32 % NaOH soluTion is simultaneously
fed in to keep the pH at this value.
The slurry is kept sTirring for 15 min before the feeding of aqueous TiCl4
soluTion (400 g TiCM H2O) is started. The pH is kept constant at 2.0 with
NaOH. It is conTinued unTil the desired colour is achieved. The slurry is kept
sTirring for again 15 min.
By slowly adding NaOH the pH is raised to 8.0 before the feeding of 1,35
ml/min of 10% sodium silicate soluTion (from 74 ml of sodium silicate
soluTion with 8 % Na and 27 % SiO2 diluted with 170 ml of deionized water)
is started. The amount necessary for a proper layer thickness has to be
exactly calculated because it is not opTically visible during the coaTing
process. After again sTirring for 15 min the pH is lowered with 10 % HCI to
2.0 and the second coaTing of TiO2 is carried out like the first one unTil the
desired end point is reached. The slurry is kept sTirring for one more hour,
then filtered off, washed free from salts, dried, calcined at 800 °C (for 30
minutes) and sieved.
From the pigment yielded a draw down is made to measure the colorisTic
properTies. It shows a highly brilliant clear color effect combined with a
superior transparency. Especially in the shallow observaTion angle of the
black background it nearly "disappears".
Example 2 (comparaTive example)
This is carried out in the same way like Example 1. Instead of glass flakes
mica of the same parTicle size distribuTion is used.
The effect on the draw down of the finished pigment is brilliant and color
intense but it does not exhibit the unique clearness and parTicularly the
transparency in the shallow angle shown by the glass flakes based
mulTilayer pigments.
Example 3
100 g glass flakes with a maximum diameter of 40 |jm (average 22 urn)
and an average thickness of 0.8 urn (refracTive index 1.5) are suspended in
2 I of deionized water. The suspension is heated to 75 °C, adjusted to a pH
of 1.8 with dilute hydrochloric acid, first of all coated with SnO2 by adding
3.3 ml/min of SnCI4 soluTion (from 2.2 g of SnCI4 and 7.5 ml of cone,
hydrochloric acid in 100 ml of deionized water). The pH is held constant
using 32 % sodium hydroxide soluTion.
STirring is conTinued for 15 minutes and then coaTing with TiO2 is carried
out under the same pH/temperature condiTions by adding 1.5 ml/min of
TiCI4 soluTion (400 g of TiCl4l) and keeping the pH constant with 32 %
sodium hydroxide soluTion. CoaTing is interrupted after the second-order
green end point is reached, sTirring is conTinued for 15 minutes, the pH is
adjusted to 8.0 with diluted sodium hydroxide soluTion (over the course of
about 15 minutes), and then sTirring is conTinued for 10 minutes more.
CoaTing with SiO2 is then carried out by adding 3 ml/min of dilute sodium
silicate soluTion (from 7.3 g of sodium silicate soluTion with 8 % Na and
27 % SiO2 and 80 ml of deionized water) without pH compensaTion.
Afterwards, sTirring is conTinued for 15 minutes, the pH is readjusted to 1.8
with dilute hydrochloric acid (over the course of about 10 minutes) and a
second TiO2 layer is applied as described above by adding TiCl4 soluTion.
CoaTing is interrupted after the third-order green comparison end point has
been reached, sTirring is conTinued for 15 minutes, and then the pigment is
filtered off, washed, dried and calcined at 850 °C for 30 minutes.
The pigment obtained has an intense green interference color. The division
of the TiO2 layers is as follows:
1st layer: about 170 nm
2nd layer: about 85 nm
Total layer: about 260 nm.
The thickness of the SiO2 interlayer is about 5 nm.
Example 4
100 g glass flakes with a maximµm diameter of 40 µm (average 22 µm)
and an average thickness of 0.5 µm (refracTive index 1.5) are suspended in
2 I of deionized water. The suspension is heated to 75 °C, adjusted to a pH
of 1.8 with dilute hydrochloric acid, first of all coated with SnO2 by adding
3.3 ml/min of SnCI4 soluTion (from 2.2 g of SnCI4 and 7.5 ml of conc,
hydrochloric acid in 100 ml of deionized water). The pH is held constant
using 32 % sodiµm hydroxide soluTion.
STirring is conTinued for 15 min.f the pH is adjusted to 2.6 with 32 % sodiµm
hydroxide soluTion and an Al2O3/Fe2O3/FiO2 layer is applied by adding 1
ml/min TiCl4/FeCl3/AICI3 soluTion (394 ml from 165 g 30 % TiCl4 soluTion,
274 g, 34 % FeCI3 soluTion, 6.2 g AICI3 x 6 H2O and 63 ml deionized
water).
STirring is conTinued for 15 min., the pH is adjusted to 7.5 with 1.3 ml/min
32 % sodiµm hydroxide and then sTirring is conTinued for 15 min. more.
Coating with SiO2 is carried out by adding 2 ml/min sodiµm silicate soluTion
with 13.5 % SiO2 (from 196 g sodiµm silicate soluTion with 27 % SiO2 and
196 ml deionized water). The pH is held constant using 15 % hydrochloric
acid.
STirring is conTinued for 30 min., the pH is adjusted to 1.8 by adding 1
ml/min of SnCI4 soluTion (from 3 g of SnCI4, 10 ml of cone, hydrochloric
acid and 90 ml deionized water).
STirring is conTinued for 15 min., pH is adjusted to 2.6 with 32 % sodiµm
hydroxide soluTion and a second TiO2/Fe2O3/Al2O3 layer is applied by
adding 1 ml/min TiCl4/FeCl3/AICI3 soluTion (394 ml of the same composiTion
as first layer). The sTirring is conTinued for another 15 min and then the
pigment is filtered off, washed, dried and calcined at 850 °C for 30 min.
The pigment obtained shows a brilliant and intense gold interference color.
Example 5
100 g glass flakes with a maximµm diameter of 40 urn (average 22 urn)
and an average thickness of 0.5 µm (refracTive index 1.5) are suspended in
2 I of deionized water. The suspension is heated to 75 °C, adjusted to a pH
of 1.8 with dilute hydrochloric acid, first of all coated with SnO2 by adding
3.3 ml/min of SnCI4 soluTion (from 2.2 g of SnCl4 and 7.5 ml of conc,
hydrochloric acid in 100 ml of deionized water). The pH is held constant
using 32 % sodiµm hydroxide soluTion.
STirring is conTinued for 15 min and then coaTing with TiO2 is carried out
under the same pH/temperature condiTions by adding 1 ml/min TiCI4
soluTion (15 ml with 400 g TiCl4/l) and keeping the pH constant with 32 %
sodiµm chloride soluTion.
STirring is conTinued for 15 min., the pH is adjusted to 2.6 with 32 % sodiµm
hydroxide soluTion and an Al2O3/Fe2O3/TiO2 layer is applied by adding
1 ml/min TiCl4/FeCI3/AICI3 soluTion 376 ml from 157.5 g 30 % TiCl4
soluTion, 236 g 34 % FeCI3 soluTion, 5.9 g AICI3 x 6 H2O and 60 ml
deionized water).
STirring is conTinued for 15 min., the pH is adjusted to 7.5 with 1.3 ml/min
32 % sodiµm hydroxide and then sTirring is conTinued for 15 min more.
CoaTing with SiO2 is carried out by adding 2 ml/min sodiµm silicate soluTion
with 13.5 % SiO2 (from 196 g sodiµm silicate soluTion with 27 % SiO2 and
196 ml deionized water). The pH is held constant using 15 % hydrochloric
acid.
STirring is conTinued for 30 min., the pH is adjusted to 1.8 by adding 1
ml/min of SnCl4 soluTion (from 3 g of SnCl4, 10 ml of conc, hydrochloric
acid and 90 ml deionized water).
STirring is conTinued for 15 min and then the second coaTing with TiO2 is
carried out under the same pH/temperature condiTions by adding 2 ml/min
TiCl4 soluTion (280 ml with 400 g TiCl4/l) and keeping the pH constant with
32 % sodiµm hydroxide soluTion.
STirring is conTinued for 15 min., pH is adjusted to 2.6 with 32 % sodiµm
hydroxide soluTion and a final TiO2/Fe2O3/Al2O3 layer is applied by adding
0.8 ml/min TiCl4/FeCl3/AICl3 soluTion (72 ml of the same composiTion as the
first layer). The sTirring is conTinued for another 15 min. and then the
pigment is filtered off, washed, dried and calcined at 850 °C for 30 min.
The pigment obtained shows an even more brilliant and intense gold
interference color than the pigment according to example 4.
Use Examples
Use Example 1: Shimmering FoundaTion
Phase A
Extender W Mica, Cl 77891 (Titaniµm Dioxide) 9,00% (1)
Microna® Matte Yellow Mica, cl 77492 (iron oxides) 4,00 % (1)
Microna® Matte Red ci 77491 (iron oxides), Mica 0,40% (1)
Procedure:
Heat all ingredients of phase C to 75 °C while sTirring unTil everything is
melted. Add Blanose and Veegµm separately to cold water of phase B
under high agitaTion (Turrax). Heat to 75 °C and add the remaining
ingredients of phase B and mix unTil the mixture is smooth and uniform.
Add ingredients of phase A. At 75 °C incorporate phase C into phase A/B
and homogenize for 2 min. Add phase D at 40 °C. Cool down to room
temperature while sTirring and adjust pH to 6,0 - 6,5 einstellen (e.g. citric
acid soluTion).
Supplier:
(1) Merck KGaA/Rona®
(2) Aqualon GmbH
(3) Vanderbilt
(4) Cognis GmbH
(5) Croda GmbH
(6) Fragrance Resources
(7) SchuIke & Mayr GmbH
Disperse the pigment in the water of phase A. Incorporate Keltrol T while
sTirring and mix unTil thoroughly dispersed. Add phase B and phase C
successively to phase A while sTirring and sTir slowly unTil the gel is
homogeneous.
Supplier:
(1) Merck KGaA/Rona®
(2) Kelco
(3) Cognis GmbH
(4) Haarmann & Reimer GmbH
(5) BASFAG
Use Example 3: Intaglio prinTing ink
Intaglio prinTing ink consisTing of
70 g Nitrocellulose-based binder from Gebruder Schmidt 95 MB 011
with a solid content of 20 %
15 g Minatec® 31 CM (conducTive pigment from Merck KGaA,
Darmstadt, Germany
15 g Coated glass flakes according to Example 1
Use Example 4: PlasTic
1 kg of polyethylene (PE-HD) granules are uniformly wetted in a tµmble
mixer with 2 g of adhesion agent. Then 10 g coated glass flakes according
to Example 4 and 2 g of Iriodin LS 825 (conducTive pigment from Merck
KGaA, Darmstadt, Germany with a parTicle size components are mixed for 2 minutes.
These granules are processed under convenTional condiTions on an
injecTion moulding machine to give small stepped plates measuring 4 x 3 x
0.5 cm. The small stepped plates are notable for their lustre and their laser
markability.
Use Example 5: CoaTing
30 g Coated glass flakes according to Example 5
10 g Minatec® 40 CM (conducTive pigment from Merck KGaA,
Darmstadt, Germany
42 g Paint base (AU-MF system, solids = 19 %)
18 g Diluent mixture
WE CLAIM:
1. Multilayer pigments based on glass flakes characterized in that
the glass flakes are coated with alternaTing layers with a high
and a low refracTive index and that the glass flakes are coated
with at least three layers, wherein the thickness of the flakes is
range of 10-300.
2. MulTilayer pigments as claimed in claim 1, wherein the pigments
comprise at least one layer sequence comprising
(A) a coaTing having a refracTive index n > 1.8
(B) a coaTing having a refracTive index n (C) a coaTing having a refracTive index n > 1.8, and if desired,
(D) an outer protecTive layer
with the proviso that the layer packet (A) + (B) may be present in
the standard layer assembly (A) + (B) + (C) up to four Times.
3. MulTilayer pigments as claimed in claim 1, wherein the layers
consist of metal oxides, metal suboxides, metal fluorides, metal
oxyhalides, metal chalcogenides, metal sulfides, metal nitrides,
metal oxynitrides, metal carbides, or mixture thereof.
4. MulTilayer pigments as claimed in any of the claims 1 to 3,
wherein the layer with a high refracTive index consist of TiO2,
Fe2O3, TiFe2O5, Fe3O4l BiOCI, Cr2O3, ZrO2, ZnO, SnO2, CoO,
CO3O4, VO2, V2O3, iron Titanates, iron oxide hydrates, Titaniµm
chalogenides, metal nitrides, metal oxynitrides, metal carbides,
or mixtures thereof.
5. MulTilayer pigments as claimed in any of claims 1 to 4, wherein
the layer with a low refracTive index consists of SiO2, AI2O3,
AIO(OH), B2O3, MgF2 or mixtures thereof.
6. MulTilayer pigments as claimed in claim 2, wherein they have
the following layer structure:
glass flakes + TiO2 + SiO2 + TiO2
glass flakes + TiO2 + SiO2 + Fe2O3
glass flakes + TiO2 + SiO2 + TiO2/Fe2O3
glass flakes + TiO2 + SiO2 + (Sn,Sb)O2
glass flakes + (Sn,Sb)O2 + SiO2 + TiO2
glass flakes + Fe2O3 + SiO2 + (Sn, Sb)O2
glass flakes + TiO2/Fe2O3 + SiO2 + TiO2/Fe2O3
glass flakes + TiO2 + SiO2 + MoS2
glass flakes + TiO2 + SiO2 + Cr2O3
glass flakes + Cr2O3 + SiO2 + TiO2
glass flakes + Fe2O3 + SiO2 + TiO2
glass flakes + TiO2 + AI2O3+ TiO2
glass flakes + Fe2TiO5 + SiO2 + TiO2
glass flakes + TiO2 + SiO2 + Fe2Ti05/Ti02
glass flakes + TiO suboxides + SiO2 + TiO2 suboxides
glass flakes + TiO2 + SiO2 + TiO2+SiO2+TiO2+
Prussian Blue
glass flakes + TiO2 + SiO2 + TiO2+SiO2+TiO2
glass flakes + TiO2+SiO2+TiO2 + SiO2 + TiO2+SiO2+TiO2
and if desired,
(D) an outer protecTive layer.
7. MulTilayer pigments as claimed in any of the claims 1 to 6,
wherein the glass flakes are coated with three layers.
8. A method of preparing a mulTilayer pigment as claimed in
claim 1 to 7 comprising:
CoaTing of the glass flakes by wet chemical coaTing, or by
chemical or physical vapor deposiTion and calcining the coated
glass flakes.
9. FormulaTions containing the mulTilayer pigments as claimed in
claim 1.
10. Non-dusTing powders, pastes and granules containing
mulTilayer pigments as claimed in claim 1.
Multilayer pigments based on glass flakes characterized in that the
glass flakes are coated with alternaTing layers with a high and a low
refracTive index and that the glass flakes are coated with at least
three layers, wherein the thickness of the flakes is aspect raTio of the glass flakes is in the range of 10-300.

Documents:

171-kolnp-2004-granted-abstract.pdf

171-kolnp-2004-granted-claims.pdf

171-kolnp-2004-granted-correspondence.pdf

171-kolnp-2004-granted-description (complete).pdf

171-kolnp-2004-granted-examination report.pdf

171-kolnp-2004-granted-form 1.pdf

171-kolnp-2004-granted-form 18.pdf

171-kolnp-2004-granted-form 2.pdf

171-kolnp-2004-granted-form 3.pdf

171-kolnp-2004-granted-form 5.pdf

171-kolnp-2004-granted-gpa.pdf

171-kolnp-2004-granted-reply to examination report.pdf

171-kolnp-2004-granted-specification.pdf


Patent Number 234246
Indian Patent Application Number 171/KOLNP/2004
PG Journal Number 20/2009
Publication Date 15-May-2009
Grant Date 12-May-2009
Date of Filing 09-Feb-2004
Name of Patentee MERCK PATENT GMBH
Applicant Address FRANKFURTER STRASSE 250, 64293 DARMSTADT
Inventors:
# Inventor's Name Inventor's Address
1 AMBROSIUS, KLAUS AM SCHLOSS STOCKAU 13, 64807 DIEBURG
2 SCHOEN, SABINE GUNDOLFSTRASSE 25, 64287 DARMSTADT
3 ANSELMANN, RALF MUHLSTRASSE 11, 67305 RAMSAU
4 ANSELMANN, RALF MUHLSTRASSE 11, 67305 RAMSAU
5 AMBROSIUS, KLAUS AM SCHLOSS STOCKAU 13, 64807 DIEBURG
6 SCHOEN, SABINE GUNDOLFSTRASSE 25, 64287 DARMSTADT
PCT International Classification Number C09C 1/00
PCT International Application Number PCT/EP2002/07219
PCT International Filing date 2002-07-01
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 01 117 004.0 2001-07-12 EPO