Note: Descriptions are shown in the official language in which they were submitted.
-
, ~ 218~66g
Goniochromatic luster pigments based on transparent, nonmetallic,
platelet-shaped substrates
5 The present invention relates to novel goniochromatic luster pig-
ments based on multiply coated, high refractive, nonmetallic,
platelet-shaped substrates which are at least partially transpar-
ent to visible light, _ _~; n~ at least one layer packet of
10 A) a colorless coating having a refractive index n < 1. 8 and
B) a reflecting, selectively or nonselectively absorbing coatin~
which i3 at least partially transparent to visible light,
15 and also, if desired, additionally
C) an outer protective layer,
and to tlleir use for coloring paints, inks, ;nr~ ;ng printing
20 inks, plastics, glasses, ceramic products and decorative cosmetic
preparations .
Luster effect pigments are used in many sectors of industry, for
example in automotlve coatings, decorative coating, plastics pig-
25 mentation, paints, printing inks, ~spe~ lly security printinginks, and cosmetics.
Their optical effect i8 based on the directed reflection of light
_~ at ~L~::.' ' nAntly sheetlike, mutually parallel-oriented, metallic
30 or strongly refractive pigment particles. ~Qr~n<i;nq on the com-
po3ition of the pigment platelets, interference, reflection and
absorption rh~- -- create angle de~lldelll color and lightness
ef f ects .
35 Owing to their uncopyable optical effect3, these pigments are be-
coming increasingly important for the production of counterfeit-
proof security documents, such as banknotes, checks, check cards,
credit cards, tax stamps, postage stamps, rail and air tickets,
t.~l~rh.~n~ card8, lottery ticketg, gift vouchers, pas3es and iden-
40 tity cards.
~arkings prepared with luster effect pigments and the absence of
these markings or their alteration, f or example in a color copy
rpe~rance of color flops and luster effects) ~ are reliably
45 discernible by the unaided, naked eye and 80 make it easy to dis-
tinguish the copy from the original.
2180669
Goniochromatic luster pigments, which exhibit an angle-dependent
color change between a piurality of intensive interference cOlorc
and are of particular interest because of their color play, have
hitherto only been known on the basis of multiply coated, plate-
5 let-shaped metallic substrates.
US-A-3 438 796 and 5 135 812 describe for example metallic luster
pigments . ~;n~ a central opaque aluminum film coated on both
sides alternatingly with dielectric low refractive films (silicon
10 dioxide, magnesium fluoride) and transparent metal films
(aluminum, chromium). Owing to their additionally very compli-
cated manufacture (alternate vapor deposition of the various film
materials on a substrate foil in a high vacuum, removing the foil
from the vapvl d~osited multilayered film and its comminution to
15 pigment particle size), the central metal film of these pigments
is coated only on the platelet top and bottom surfaces.
DE-A-44 05 IL92 and DE-A-44 37 753, which were llnrllhli~h,~ at the
priority date of the prese~t invention, and German Patent
20 Applications 19516181.5 and 19515988.8 disclo~e goniochromatic
luster pigments produced by coating metal platelets (in
particular aluminum platelets) by CVD (chemical vapor deposition)
~LV~s~es or wet- rh~;c~lly with low refractive metal oxide
layers (in particular SiO2) and nonselectively absorbing metal,
25 metal oxide and/or metal 3ulfide layers or selectively absorbing,
high refractive metal oxide layers.
It is true that metal--based lu~ter pigments have good application
properties, ;nrlll~;nq good hiding power, but the use in a var-
30 nish, for example, results in a "har8h~ metallic luster which maynot always be desired.
Luster pigments based on transparent, platelet-shaped substL-ates
that do not exhibit this harsh metallic luster are described for
35 example in WO-A-93/12182, which concerns mica platelets coated
with a high refractive metal oxide layer (in particular titanium
dioxide) and a nonselectively ~h~rrh; n5 layer. These pigments
exhibit in plan view, ~l~r~n~; n~ on the Tio2 layer thickness, a
certain interference color which becomes increasingly weaker with
40 an increasingly flat viewing angle and finally turn3 gray or
black . This is in f act not the result of a change in the hue of
the interference color, but only the result of a decrease in the
intensity (saturation~ of the color.
45 Silicon dioxide platelet luster pigments expensively produced by
apelying a waterglass solution to a 3ubstrate tape, gelling, dry-
ing, detaching, washing out of the salts and comminuting the ~sio2
_ . . , .. _ _ .. . , .. . _ ___ __ _ _ _ ~ ,
~, ,, 21810669
filmN are known from WO-A-93/8237. Coloring the SiO2 film with
organic or inorganic pigments and coating the added--colorant sio2
platelets with SnO2-containing titanium diox~ de gives pigments
which, A~r-~s~7; ns on the angle, exhibit either the interference
5 color or the body color of the pigment.
Finally, JP-A-93206~1992 ~1~5rr; h~ luster pigments based on glass
flakes coated with an opaque metal layer and alternating SiO2 and
Tio2 layers, which luster pigments resemble metallic luster
10 pigments.
It is an object of the present invention to provide further
goniochromatic luster pigments which shall have advantageous ap-
plication properties and be preparable in an ~e ~ rnl manner.
We have found that this object is achieved by the goniochromatic
luster pigments defined at the b~inn;n~, which are useful for
coloring coatings, inks, ; nr~ ; n~ printing ink8, plastics,
glasses, ceramic products and decorative co8metic preparations.
The goniochromatic luster pigments of the present invention are
notable for high refractive, nonmetallic, platelet-shaped sub-
strates which are at least partially transparent to visible
light .
For the purpo3es of the present invention, "at least partially
transparent to visible light~V means that the substrate generally
transmits at lea3t 10 %, preferably at least 30 96, of the inci-
dent light.
Suitable 3ubstrate materials are (semi)transparent materials
which are intr;n~icAlly high refractive, ie. have a refractive
index of generally > 2, preferably > 2.4, or are intrinsically
only low ref ractive and have been provided with a high
35 refractive, light-transmitting coating.
Examples of particularly suitable intrinsically high re~rac tive
materials are in particular platelet-shaped iron oxide~, prefer-
ably platelet-shaped iron(III) oxide a-Fe2O3 doped with silicon
40 (EP-A-14 382), aluminum (EP-A-68 311) or aluminum and manganese
(EP-A-265 820), and also platelet-shaped bismuth oxychloride
3iOCl (EP-A-315 849). In principle, it is also possible to use
platelet-shaped titanium dioxide and zirconium dioxide, but these
materials are costly to produce (US-A-4 168 986).
,, 2180~69
Examples of particularly suitable, intr;n--;rAlly low refractive
materials coated with high refractive material are in particular
silicatic platelets coated with a high refractive metal oxide
layer. Silicatic platelets are in particular light-colored or
5 white micas, and flakes of prefera~ly wet--ground muscovite are
particularly preferred. Of course, it is also possible to use
other natural micas such as phlogopite and biotite, artificial
micas, talc and glass flakes.
10 The metal oxide coating of the silicatic platelets can be
constructed from ~ rl ~A88 high refractive metal oxides such as
titanium, zirconium, zinc and tin oxides and bismuth oxychloride
and absorbing high refractive metal oxides such as iron and chro-
miu~ oxides, ilmenite or else mixtures of these oxides. Aluminum
15 oxide and silicon oxide may likewise be presQnt, albeit in a
minor amount.
Particularly pref erred substrate materials are mica platelets
comprising an oxide coating which consists essentially of tita-
20 nium dioxide and contains only small amounts ( generally 5 ~ byweight~ of further, preferably colorless, metal oxides. Such pig-
ments are generally known and commercially available under the
names Iriodinl9 (Merck, Darmstadt~, Flonac D (}~emira Oy, Porit or
Mearlin'9 (Mearl Corporation, ~ew York~.
ThQ thickness of the Tio2 layer (geometric layer th;~kn/~55~ is
customarily from 10 to 300 nm, preferably from 20 to 200 nm. With
particular advantage it is also possible to use mica pigments
having only thin Tio2 coatings (from about 20 to 40 nm~ as sub-
30 strates.
Also of particular lnterest for use as substrate material are ti-
tania-coatQd mica pigments whose Tio2 coating is partially reduced
and which as well a8 unchanged Tio2 contains reduced titanium spQ-
35 cies having oxidation states from 4 to 2 (lower oxides such asTi30s, Ti203 through Tio, titanium oxynitridQs and also titanium
nitride~. The reduced pigments are more color--intensive than the
unreduced, TiO2-coated pigments, and as the degree of reduction
increases their body color shifts in the direction of the
40 absorption color of the reduction products of titanium, ie. into
the blue to violet hue range. Their preparation can be effected,
as is known, by reduction with ammonia, hydrogen and also
hydrocarbons and hydrocarbon/ammonia mixtures (cf. EP-A-332 071
and German Patent Applications 1951696.8 and 19511697.6 and the
45 reference cited therein~, in which case the pigments reduced in
the presence of hydrocarbons generally also contain carbon.
-
~ . ~ 2~8~6~
The size of the substrate particles in the luster pigments of the
pre~ient invention is not critical per se and can be adapted to
the particular application. Generally, the platelet-shaped par-
ticles have average largest diameters of from about 1 to 200 llm,
5 in particular of from about ~ to 100 llm, and thi~kn~cseS of from
about 0.1 to 1 llm, in particular about 0.3 llm. Their specific free
surface area (BET) is customarily within the range from 1 to
15 m2tg, in particular within the range from 1 to 12 m2/g.
10 The luster pigments of this invention have a colorless, low re-
fractive coating (A) in combination with a reflective coating (B)
which c2n be selectively ;~hs-~rh; nS or nonselectively absorbing
but in any case shall be at least partially transparent to vis-
ible light. They may contain a plurality of identical or differ-
15 ent combinations (layer packets) of (A) + (3), but preference isgiven to coating with only one layer packet (A) + (B). Addition-
ally, to protect the underlying layer (B), an outer layer (c) may
be applied.
20 The low refractive coating (A) generally has a refractive index
n < 1.8, preferably < 1.6.
Suitable for use as the layer material (A) is any low refractive
colorless substance which can be applied as a durable film to the
25 :i uL,~ ~L CIS~ particles .
Particularly suitable examples besides magnesium fluoride and
aluminum phosphate are in particular metal oxides such as silicon
oxide, silicon oxide hydrate, aluminum oxide, aluminum oxide hy-
30 drate and mixtures thereof, of which silicon oxide ( hydrate ~ ispref erred .
The th; rkn,.cs of the coatings (A) is generally from 20 to 800 nm,
preferably from 50 to 600 nm. Since the layer (A) essentially de-
35 termines the interference colors of the pigments of this inven-
tion, it has a minimum thi~kn~s~q of about 100 nm in luster pig-
ments which have only one layer packet (A) + ( 3) and exhibit a
particularly pronounced color play and hence are also preferred.
If a plurality (eg. 2, 3 or 4) of layer packets (A) + (B) are
40 present, the thiekn~cs of (A) is preferably within the range from
50 to 300 nm.
Suitable substances for the reflecting coating (B) include not
only high refractive, selectively or nonselectively absorbing
45 substances but also low refractive, nonselectively absorbing sub-
2180669.,
stances having a high absorption constant, which must of cou~ se
also be depositable as a durable film.
Examples of high refractive materials suitable for coating (B)
5 are nonselectively ~hsrrhi nrJ materials such as metals, metal ox-
ides, metal sulfides and mixtures thereof, which may also contain
selectively ~hsrrh; ng metal oxides in a minor amount, and selec-
tively Ahsrrhin~ materials such as, in partLcular, metal oxides,
which generally each have a refractive index n > 2.0, preferably
10 n > 2.4.
Specific examples of nonselectively ~h~nrhi n~ high refractive ma-
terials suitable for coating (B) are:
15 -- metals which can be applied by gas phase A~ ; tion of
volatile metal: _ '-, such as particularly preferably
molybdenum, preferably iron, tungsten and chromium, also co-
balt and nickel, and also mixtures thereof; metals which can
be deposited wet-rhnrirnlly by reduction of metal salt solu-
tions, such as silver, copper, gold, palladium and platinum
and also cobalt and nickel and alloys such as NiP, NiB, NiCo,
NiWP, CoP and AgAu;
- metal oxides such as preferably magnetite Fe304, cobalt oxide
(CoO~ Co304) and vanadium oxide (V02, V203) and also mixtures
of these oxides with the metals, such as in particular
magnetite and iron;
-- metal sulfides such as particularly preferably molybdenum
. 30 sulfide, preferably iron sulfide, tungsten sulfide and chro-
mium sulfide, also cobalt sulfide and nickel sulfide and also
mixtures of these sulfides such as MoS2/WS2 and in particular
mixtures of these sulfides with the respective metal, such as
in particular ~052 and molybdenum, and mixtures with oxides
of the respective metal, such as MoS2 and molybdenum oxides.
Also suitable for use as nrn~,nl~rtively absorbing high refractive
coating (B) are for example layers of colorless high refractive
materials such as zirconium dioxide and in particular titanium
40 dioxide incoreorating nonselectively ~hs~lrh; n~ (black) material
(eg. carbon) or coated therewith (EP-A-499 864).
Examples o~ selectively absorbing high refractive layer materials
(B) are in particular colored oxides such as preferably iron(III)
45 oxide (~- and y-Fe203, red), chromium(III) oxide (green),
titanium(III) oxide (Ti2o3, blue) and also vanadium pentoxide
(orange) as well as colored nitrides such as preferably titanium
218~6~9
oxynitrides and titanium nitride (~ioxNyr TiN~ blue), the lower
titanium oxides and nitrides generally being present in a mixture
with titanium dioxide.
S E~ere it is of course also possible to use colorless high refrac-
tive materials, for example metal oxides such as zirconium diox-
ide, in particular titanium dioxide, which have been colored with
selectively Ahgnrhi n~ colorants, by incorporation of colorants in
the metal oxide layer, by doping thereof with selectively absorb-
10 ing metal cations or by coating the metal oxide layer with a filmcontaining a colorant (cf . DE-A-44 37 753, llnr-lhl ~ ~hD-I at the
priority date of the present invention ) .
Finally, suitable low refractive, nonselectively Ah~ rh;ns mate-
15 rials having a high absorption constant for u3e as coating (B)
are in particular metalg guch as Al ' _
The coating (B) should of course not be opaque, but be at least
partially transparent (semitransparent) to visible light and its
20 thicknD~s therefore differs as a function of the optical proper-
ties of the chosen layer materials.
The layer thirkno~s of coating (B) in the case of nonselectively
Ah5~rh;ns high refractive materials such ag metals, black metal
25 oxides and sulfides is generally within the range from 1 to 100
nm, preferably within the range from about 1 to 25 nm for strong-
ly Ahs~rhins metals such as molybdenum and chromium, within the
range from about 10 to 50 nm for less strongly Ah~rhin~ materi-
als such as magnetite, and preferably within the range from 5 to
- 30 20 nm in the case of metal-sulfide-containing materials such as
MoS2--containing layers.
In the case of colored high refractive metal oxide coatings (B)
the layer thi ~-knD~s is customarily within the range from 1 to
35 500 nm, preferably from 10 to 150 nm.
Low refractive, but strongly Ah5~rh;n~ aluminum layers (3) are
finally generally from 1 to 25 nm, preferably from 5 to 20 nm,
thick .
If a plurality of layer packets (A) + (3) are present, the layer
thil-kn~s of coating (3) is customarily reduced by from about 50
to 75 ~.
~ 8 2180669
The coating of the high refractive, (semi)tran3parent substrates
with the low refractive layer ~A) produces a pigment which exhib-
its a series of interference colors which are determined by the
optical properties of the substrate (Ahsrlrhing/n~nAh5~rhing)
~nAhc~rhin~ (colorlegg) high refractive substrates may, if of
appropriate layer thi~kn~c5 (from about 40 to 160 nm), have in-
terference colors lntrinc;~Ally. A coating with (A) continues the
interference series at the point determined by the starting mate-
10 rial, and the interference color becomes more angle l~e~ t atthe same time.
If, for example, silvery ~iO2-coated mica platelets or silvery
BiOCl platelets are coated with silicon dioxide, the interference
15 colors blue, green, gold and red become repeatedly observable in
8-lr- ~csi~n with increasing sio2 layer th;~kn~c5 in a plan view of
the dry pigment eowder. A pigment which reflects blue in plan
view exhibits for example a red color at a flatter viewing angle.
20 However, the interference colors of the n~nAhc~7rh;n~ substrates
coated with (A) are visible only in the dry state, ie. in the
pigment powder, and completely 7; cArpc~Ar in the moist state or in
a varnish.
25 Additional coating with a nonselectively Ah5r~rh~n~ layer (B), for
example with molybdenum, causes the interference colors to be
equally enhanced for each hue and to remain visible even in a
varnish .
30 Applying a selectively Ahsnrh;n~ (colored) layer (B) enhances in
particular the interference colors which come close to the ab-
sorption color of (B), while deviating interference colors are
;nich~d For instance, a very guitable choice is iron(III) ox-
ide for red to golden interference colors, chromium(III) oxide
35 for green interference colors, and reduced titanium dioxide,
especially ammonia-reduced titanium dioxide, for blue interfer-
ence colors.
In the case of absorbing ( semi ) transparent substrates, a distinc-
40 tion has to be made between nonselectively Ahs~rh; ng and selec-
tively absorbing materials.
Nonselectively absorbing substrates appear dark away from the
specular angle. Elere suitable substrates are for example silvery
45 ~iO2--coated micas which have been reduced with hydrogen at 800 C
and which, owing to formation of reduced titanium oxides, exhibit
reduced light transmissivity coupled with a virtually unchanged
21806~3
silvery luster, and mica3 coated with Tio2 doped with carbon
black .
Nonselectively absorbing substrates exhibit more intensive inter-
5 ference colors in air than n-~nAhc~nrh; ng substrates when coated
with layer ( A) .
As with the transparent substrates, interference colors of non-
selectively Ah~^rh; nS substrates become visible in a varnish on
10 coating with layer (B), and selectively absorbing layers (B) can
be reconformed to the interference colors of the substrate coated
with (A) .
In the case of selectively Ah~rhin~ (colored) substrates such as
15 platelet-shaped iron oxides, mica platelets coated with iron(III~
oxide, and ammonia-reduced (blue) TiO2-co~ted mica platelets, the
absorption color of the substrate mixes with the interference
system produced when coating with layer (A).
20 For instance, (A)-coated hematite platelets (-Fe203, red) and
Fez03-containing micas show a series of strongly angle dc ~ dt llt~
high-hr~ 11; An~ e interference colors in the greenish golden to
bluish red hue range, whereas green and blue hues are d;m;n~h-~d
by the substrate Ah~nrb; n~ in this range. Conversely, blue re-
25 duced TiO2-coated mica platelets give rise to particularly bril-
liant interf erence colors in the blue to green hue range .
An c~nhAr t of the interference colors can in turn be effected
by coating with layer (B), in which case preference among the se-
30 lectively Ah~3nrh; n~ subgtrateg is given to gelectively slh~nrh; nqlayers (B) which, as described above, can be conformed to the in-
terference colors of the pigment (hence to the absorption color
of the substrate ) .
35 Finally, the luster pigments of this invention may additionally
include an outer layer (C), in particular for protecting essen-
tially metallic layers (B), or layers (B) containing reduced (low
valence ) metal oxides, underneath .
40 Said layer (C) can be constructed from low refractive or high re-
fractive metal oxides which can be not only ~nl c~rl ~ s but also
selectively Ahqnrh; ng. Examples of suitable metal oxides include
silicon oxide, silicon oxide hydrate, aluminum oxide, alumil~um
oxide hydrate, tin oxide, titanium dioxide, zirconium oxide,
45 iron(III) oxide and chromium(III) oxide, pre~erence being given
to silicon oxide and aluminum oxide.
218~669
Layer (C) can also be a phosphate-, chromate- and/or vanadate-
containing or 0190 phosphate-- and SiOz-containing layer obtained
by gas phase passivation (EP-A-595 131 and l)E-A-44 14 079, which
was ~lnrllhl i ~hr~tl at the priority date of the present invention~,
5 which also makes it possible in particular to use the luster
pigments of the present invention comprising a substantially
metallic layer (B) in waterborne coatings or other aqueous
systems .
10 The thirkn~s of the layer ~c) is generally from about 1 to
400 nm, preferably from 5 to 250 nm.
Of course, layer (C3 may likewise contribute to the interferellce
of the pigment and continue the interference series at the point
15 determined by the substrate coated with (A) and (B). This is the
case, for example, when zirconium oxide or titanium oxide is ap-
plied as layer (C). If, in contrast, layer (C) consists essen-
tially of silicon oxide, this layer will be hardly coloristically
noticeable in the application medium ( eg . paints or inks ) which
20 has a similar refractive indeY.
Finally, colored metal oxides such as iron oxide and chromium ox-
ide will with their absorption color modify, and with increasing
th;~ l~n~5 ultimately obscure, the interference color of the
25 multilayer system.
The luster pigments of this invention are noticeable for the uni-
form, h~ , and filmlike construction of their interfer-
ence-capable coating, which covers the substrate platelet on all
30 sides, and not only on the upper and lower surfaces.
They exhibit very intensive and extremely angle-dependent inter-
ference colors which, given the transparency of the substrate
particles, could not have been e~cpected.
Unlike the known strongly reflecting goniochromatic luster pig-
ments with a metallic base, the luster pigments of this invention
remain transparent to visible light, ie. they have different ~
tary) interference colors in reflected and transmitted
40 light, but are noticeable for high hiding powder, despite their
transparency .
In addition, in a varnish, they do not exhibit the "harsh" metal-
lic luster typical of metallic luster pigments, but a softer lus-
45 ter seemingly from deep within the viewed object, which is whythey also create the illusion of spatial depth when applied.
-
11 21~û669
The luster pigments of this invention are preferably produced by
multiple coating of the substrate platelet3 via gas phase decom-
position of volatile metal, ' (CVD) or wet-rh~ir~lly via
hydrolytic d~ - 5 i tion of organic metal ~ ' e, in particu-
5 lar.
The wet-chemical and the CVD route are equally suitable for pro-
ducing the silicon oxide and/or aluminum oxide layers ~B).
10 In the wet-chemical variant, ~l~acrrihed in DE-A-44 05 492,
llnrl-hl; qh~tl at the priority date of the present invention,
organic silicon and/or aluminum, in which the organic
radical3 are bonded to the metals via oxygen atoms are hydrolyzed
in the presence of the substrate particles and of an organic
15 solvent in which the metal are 301uble and which is
miscible with water.
The preferred ';- L is the hydrolysis of the metal ~lkrs;~ g
(especially tetraethoxysilane and aluminum triisopropoxide) in
20 the presence of an alcohol (~-cper;:~lly isopropanol) and of
aqueous ammonia as catalyst.
A preferred ~L~Jc:duL_ comprises charging substrate particles,
isopropanol, water and ammonia initially, heating this mixture to
25 from 40 C to 80 C, in particular to from about 60 C to 70 C, with
stirring, and continuou~ly metering in a solution of the metal
alkoxide in isopropanol. Following a ~uL.~e~u~ stirring time of
usually from about 1 to 15 h, the mixture is coolQd down to room
temperature and the coated pigment is isolated by filtration,
30 washing and drying.
In the CVD variant, ~crrihed in DE-A-44 37 752, lnp~hl;ch~ at
the priority date of the present invention, silanes which contain
at least one alkanoyloxy radical are ~ ?d in the gas phase
35 with water vapor and, if the silanes also contain alkyl or phenyl
radicals, oxygen in the presence of agitated substrate particles.
Preferred silanes have alkoxy and alkanoyloxy radicals, particu-
lar preference being given to di--tert-butoxydiacetoxysilane
To carry out the CVD variant, it is advisable, as is generally
the case with CVD processes, to use a fluidized bed reactor as
described for example in ~P--A 45 851. The substrate particles are
heated in the reactor to the desired reaction temperature (gener-
45 ally from lO0 to 600 C, preferably from 150 to 300 C) under flui-
dization with an inert gas such as nitrogen, and silane and water
vapor (and also, if appropriate, oxygen) are then introduced with
_ _ _ _ _ _ _ _ _ _ ,
12 2i8066~
the aid of inert carrier gas streams ( advantageously part-streams
of the fluidizing gas~ from upstream vaporizer vessels via sepa-
rate nozzles, advantageously maintaining the concentration of the
silane at < 5 & by volume, preferably < 2 % by volume, based on
5 the total amount of gas in the reactor. The amount of water vapor
should correspond at least to the amount 8t~irh;~ ~Lically
required for hydrolysis of the silane, but preference is given to
an amount of from 10 to 100 times that amount.
10 Layers (B) are preferably produced by the CVD process, under
reaction conditions which differ with the desired layer material.
As is known from WO-A-93/12182, metallic layers (B) are
preferably applied by ,1 _-~ition of metal carbonyls such as
15 iron pentacarbonyl, chromium h~yslr~rh~nyl~ molybdenum hexa-
carbonyl, tungsten hexacarbonyl, nickel tetracarbonyl and/or
dicobalt octacarbonyl at from 70 to 350 C under inert conditions.
The particularly preferred ~lo(CO)6 is ideally ds -' at tem-
~LCI~UL~a from 200 to 250 C.
Aluminum layers (B), as described in German Patent Application
19516181.5, can be deposited by inert gas phase ~ ition of
or~ ~n-~1 , especially aluminum alkyls or alkylamine adducts
of aluminum hydrides.
Suitable alumlnum alkyls besides monoalkyl 1l hydrides and
halides are preferably dialkyl ~1 nllm hydrides and halides and
in particular aluminum trialkyls, ~pe~ ~lly for example tri-
ethyl~l,.m~ and trimethyl~l
Aluminum layers ( B ) are advantageously applied by charging the
aluminum alkyl to a vaporizer vessel which i8 disposed upstream
of the coating reactor and which has been heated stepwise to
about 100-150-C, in the form of a solution in a low volatile hy-
35 drocarbon such as petroleum, transferring the aluminum alkyl bymeans of an inert gas stream ( eg . argon or in particular nitro-
gen) passed through this solution into the reactor, via a prefer-
ably tempera~uL~ h~Lulled nozzle, and thermally decomposing it
in the reactor, generally at from 100 to 500 C, preferably at from
40 150 to 400 C, for which the gas guantity of the volatile aluminum
compound should generally not exceed 2 % by volume, pref erably
1 % by volume, of the total amount of gas in the reactor.
The preferred reactor is in particular the abovementioned fluid-
45 ized bed reactor, but it is also possible to use a single-neck,
round-bottom flask made of quartz glass which is rotated by a mo-
tor, provided with gas inlet and outlet lines in the axis of
21~U669
.
13
rotation, and heated by a rl :~mch~l 1 oven, the gross assembly
amounting to a rotary sphere furnace. In principle, the reactor
used can be any heatable mixer which agitates the substrate par-
ticles gently by means of appropriate internal f itments and per-
s mits the supply and removal of gas. For a continuous process on
an industrial scale it is also possible to use, for example, a
rotary tube ~urnace to which the substrate particles and the alu-
minum alkyl~inert gas mixture are fed continuously.
lO Metallic layers (B) can finally also be applied wet-chemically by
reduction of suitable metal salt solutions. In this way it i8
possible to deposit in particular nobler metals such as in par-
ticular silver, but also copper, gold, cobalt, nickel, p~11 At~; ~lr
and platinum. A8 rl~crr~ h-~l in EP-A-353 544, a number o~ reduc-
15 tants are suitable for this purpose, especially mild organic re-
ductants, for example sugar3 such as glucose and dextrose, but
also f~)rr-l ~hyde
Generally, however, the metal layers applied from the gas phase
20 will be pre~erable to the ~r_t- l~ , rs~l l y applied ones because of
their higher quality ~more finely crystalline, ~ilmlike), since
they usually produce more brilliant and stronger luster pigments.
The CVD deposition of nonselectively ~hsrrhinrJ layers (B) COII-
25 sisting essentially of lower metal oxidQs ~eg. Fe304, V02, V2~3)
is likewise known ~rom WO-A-g3/12182. EiQre the metal carbonyls
such as iron pentacarbonyl or oxyrh1 or~ ~c-c such as vanadium
oxychloride are ds - . with water vapor. I~ the gas phase
~' _ ; tion initially gives rise to higher metal oxides such as
30 V20s, these have to be ~,uLse~u~ l~tly reduced, for example with
hydrogen or ammonia, to the desired oxide.
As described in EP-A-579 091 and German Patent Application
19515988.8, nonselectively absorbing metal-sulfide-containing
35 layers (B) can be applied to the (A)-coated substrate particles
by initially depositing a metal or metal oxide layer, pre~erably
by gas phase ~e~ ition of volatile metal ~ _ '- in the
presence of an inert gas or of oxygen and/or water vapor, and
then converting this metal or metal oxide layer by reaction with
40 a volatile sul~ur-containing compound or with sulfur vapor into
the desired metal-sul~ide-containing layer (B), or depositing the
layer (B) directly by gas phase ~ ltion of volatile metal
ds in a sul~ur-containing atmosphere.
-
2I8066~
14
As well as the sulfur-containing organic, _ c mentioned in
EP--A--579 091, preferred sulfur donors include in particular hy-
drogen sulfide and especially sulfur itself.
5 If elementary sulfur is used, an advantageous procedure comprises
charging finely ground sulfur powder together with the substrate
material to the reactor, inertizing for from about 1 to 4 hr and
then heating to the reaction t, rLLuL~ (in general from 200 to
500 C, preferably from 300 to 500 C, particularly preferably from
lO 400 to 450 C) in the absence of oxygen.
Suitable reactors include the reactors mentioned f or the coating
with r~ n~lm_
15 Any residual sulfur present is easily removed by sublimatio~ in
an inert gas stream. Generally, however, this will not be neces-
sary, since the sulfur is converted guantitatively (up to the
amount st~ h;~ ILically required to form the metal sulfide) and
therefore can easily be added in the amount cuLL~u~.ding to the
20 sulfide content desired for layer (3). Preference is given to U8-
ing sufficient sulfur for the preferred metallic or else oxidic
starting layer to be at least covered by an uninterrupted densQ
sulfide layer which renders further passivation llnn ~r r ~E~ry. The
region of layer (B) on the inside ~closer to the substrate) can
25 be virtually free of sulfide and consist essentially only of the
respective metal or metal oxide.
Similarly, selectively Ahc(~rh;nq layers (B) consisting essential-
ly of colored metal oxides and/or metal nitrides are suitably
30 producible using in particular CVD ~Luce83a3 already rl~c~-r;h~d
For instance, the deposition of -iron(III) oxide, chromium(III)
oxide and titanium(III) oxide by oxidative 'IQ , -;tion of iron
pentacarbonyl and chromium hexacarbonyl or hydrolytic
35 ~ ition of titanium tetraisuyLu~ ide or titanium
tetrachloride and the subsequent reduction of the resulting
titanium dioxide with hydrogen or with ammonia and also
ammonia-propane mixtures, at which point Ti2O3 (beside Tio2) is
present in a mixture with titanium oxynitrides and nitrides ( and
40 also possibly carbon), are well known (EP-A-33 457, EP-A-338 428,
German Patent Applications 19511696.8 and 19511697.6).
Wet-r h~m; ~-Al 1 y, -Fe2û3 and Cr203 layers could be applied by
hydrolytic ~ ition of iron(III) salts such as iron(III)
45 chloride and sulfate and chromium( III ) chloride and subse~uent
conversion of the resulting hydroxide-containing layers into the
oxide layers by tempering. Similarly, Ti2o3 coating could l~e
_ _ _ _ _ _ _ _ _ _ .
218~669
.
achieved by hydrolysis of TiCl4 and auL:Se~u~ht reduction of ~he
resulting Tio2 with hydrogen or ammonia.
The coating with selectively absorbing y-Fe2O3 (B) can be carried
5 out by the CVD process variants ~ c~-r;h rl in DE-A-43 40 141 by
first de~, _ inq Fe(CO)s in the presence of water vapor to depos-
it a magnetite film, which is subsequently oxidized with air to
y-Fe2O3, or first oxidatively r3r-, in~ Fe(CO)s to deposit an
c~-Fe2O3 film, which is subseguently reduced with hydrogen to
10 iron(II)-containing products and ~uLseuu~ ly oxidi2ed with air
to y-Fe2o3-
Vanadium~V) oxide layers (B) can finally be deposited by ga3phase ~ j tion of vanadium oxychloride with water vapor.
For the production of added-colorant Tio2 layers (B), reference is
made to DE--A-44 37 753, which was llnruhl; Rh d at the priority
date of the prQsent invention.
20 Outer protective layers (C) consisting essentially of r~lorl~ss
or selectLvely ~hcrlrb; n~ metal oxides can be produced according
to the already .1 c.-ri h d ~Lv~ess~s by oxidative or hydrolytic gas
phase ~lr- -~ition of the metal carbonyls or metal ~lk-~Y;~ c or
wet--h mi~lly by hydrolysis of organic metal ,lc (silicon,
25 aluminum) or inorganic metal salts.
Phosphate-, chromate- and/or vanadate-containing and also pllos-
phate- and SiO2-containing outer layers (C) can be applied by the
passivating ~L~,cesse~ described in EP-A-S9S 131 and
30 DE-A-44 14 079, which was llnrllhl; Rh 1 at the priority date of the
present invention by hydrolytic or oxidative gas phase
d-- ~~ition of oxide halides of the metals (eg. CrO2Cl2, VOCl3),
in particular of phosphorus oxyhalides (eg. POCl3), rhrsrhr~r~r and
phosphorous esters (eg. di- and trimethyl and -ethyl pho3phite)
35 and of a_ino--containing or~noa; 1; r~rmc (eg. 3--aminopropyltrieth-
oxy- and --trimethoxy-silane).
Luster pigments which are particularly stable in aqueous sys~ems
are obtained from a combined ~ ition of the phosphorus and
40 silicon ,ic.
The luster pigments of this invention are advantageously useful
for many purposes, such as the coloring of plastics, glasses, ce-
ramic products, decorative cosmetic preparations and in particu-
45 lar coatings, especially automotive coatings, and inks, espe-
cially security pri ~ting inks . All customary printing processes
... , .. . ~
218~66~
16
can be employed, for example screen printing, intaglio printing,
bronze printing, flexographic printing and of ~set printing.
The pigments of this invention are also advantageously useful for
S these purposes in admixture with transparent and hiding white,
colored and black pigments and also conventional transparent,
colored and black luster pigments based on metal-oxide--coated
mica and metal pigments, platelet-shaped iron oxides, graphite,
molybdenum sulfide and platelet-shaped organic pigments.
Examples
Preparation and application of luster pigments according to l~his
invention
~o incorporate the pigments into a paint, O . 4 g of each pigment
was stirred into 3. 6 g of a mixed-polyester varnish having a 501-
ids content of 21 9~ by weight and the mixture was dispersed in a
Red Devil for 2 min. Drawdowns of the pigmented varnishes were
20 knife-coated onto black and white cardboard at a wet film thick-
ness of 160 !Im.
Example 1
25 100 g of a silvery TiO2--coated mica pigment (Iriodin(~ 103 Rutile
Sterling Silver; Merck) were inertized in a rotary sphere furnace
by passing 50 l~h nitrogen thereover for 1 h. After heating to
600 C, 20 l/h of hydrogen were in~L~--lu~ d for 2 h. On completion
of the reduction, the contents were cooled down to room tempera-
- 30 ture under renewed flushing with nitrogen.
After the reduction, the originally white pigment exhibited a
silvery body color and better hiding power.
35 In a L~ul-d b.,l.~om flask equipped with reflux n~nrl~n~ r and stir-
rer, the reduced mica pigment was ~u_yended in 800 ml of isopro-
panol. After addition of 300 ml of water and 30 ml of 25 ~
strength by weight aqueous a~monia solution, the s~lepnn~inn was
heated to 60 C with vigorous stirring. At the same time the me-
~0 tered addition was ~ -ed of a mixture of 200 ml of isopro-
panol and 400 g of tetraethoxysilane (rate of addition 100 ~l/h,
6 h ) . ~ollowing a subsequent stirring time of 2 h and cooling of
the suspension, the product was filtered off, thoroughly washed
with isopropanol and dried at 80 C.
218066~
17
In air the dried SiO2--coated pigment exhibited a pale blue inter-
ference color in plan view, which flopped into a pale red at
f latter viewing angles .
5 210 g of the SiO2-coated mica pigment were then heated in a fluid-
ized bed reactor at 220 C under fluidlzation with a total of
600 l/h of nitrogen. From a hot upstream vessel at 60 C, 32.3 g of
molybdenum hexacarbonyl were additionally carried during 8 h, by
a nitrogen stream of 400 l/h, into the reactor and ~
lO therein into molybdenum and carbon monoxide. On completion of the
molybdenum deposition, the fl~ ;7;ng gases were admixed with
some air in the course of the cooling to passivate the molybdenum
surf ace .
15 In varnish the molyb~ ~ oated pigment exhibited an intensive,
greenish blue interference color in plan view, which flopped via
pure blue toward violet at f latter viewing angles .
100 g of the Mo-coated pigment were then mixed with 2.5 g of
20 finely ground ~ulfur powder, initially inertized in a rotary
sphere furnace with 30 l/h of nitrogen for 1 hour, and then
he~ted to 500 C in the course of about 30 min under a nitrogen
stream of 5 l/h. After 2 h the contents were cooled down to room
t. _ dtUL~ undQr nitrogen.
~he pigment obtained had a titanium content of 7 . 5 96 by weight, a
silicon content of 30.5 '6 by weight, a molybdenum content of
3.6 ~ by weight and a sulfur content of 0.96 % by weight. On ap-
plication, it exhibited an intensive, bluish green interference
30 color in plan view, which flopped via violet toward red Wit~l in-
creasing flatness of the viewing angle.
Example 2
35 Example 1 wa~ repeated except that the 100 g of the silvery
'riO2-coated mica pigment were reduced with hydrogen at 800 C.
After reduction, the pigment likewise exhibited a silvery body
color and improved hiding power compared with the pigment of Ex-
40 ample 1.
100 g of the reduced pigment were coated with sio2 similarly toExample 1 by suspending in 100 ml of isopropanol and admixing
initially with 400 ml of water and 40 ml of 25 96 strength by
45 weight ammonia and then over 9 h with a mixture of 300 ml of iso-
218~669
18
propanol and 600 g of tQtraethoxysilane. The subsequent stirring
time was 14 h.
In air the dried sio2--coated pigment (268 g) exhibited a bluish
5 violet shimmer in plan view, which became a red shimmer at flat-
ter viewing angles.
185 g of the SiO2-coated pigment were then coated with molybd~enum
using 27.5 g of Mo(CO)6 over 6 h analogously to Example 1.
In varnish the Mo--coated pigment exhibited an intensive, blue in-
terference color in plan view, which flopped toward violet at
f latter viewing angles .
15 100 g of the Mo-coated pigment were then reacted with 4.5 g of
sulfur powder similarly to Example 1.
The pigment obtained had a Ti content of 6 . 0 % by weight, an Si
content of 31 & by weight, an Mo content of 3.3 % by weight and
20 an S content of 1. 7 % by weight. On applicatlon it exhibited an
intensive, rQddish blue interference color in plan view, which
flopped via red toward gold with an increasingly flat viewing
angle .
25 Example 3
150 g of the silvery TiOz-coated mica pigment were coated with
sio2 similarly to Example 1 by suspending in 150 ml of isopropanol
and admixing initially with 500 ml of water and 50 ml of 25 %
30 strength by weight ammonia and then over 7 h with a mixture of
375 ml of isopropanol and 750 g o~ tetraethoxysilane (rate of
addition 160 ml/h). The subsequent stirring time was 1 h.
The dried SiO2-coated pigment (352 g) retained its white body
35 color and exhibitQd in air a pale, red interference color at flat
viewing angles only against a black background.
310 g of the SiO2-coated pigment were then coated with molybdenum
using 49.8 g of Mo(CO)6 over 15 h similarly to Example 1.
In varnish the Mo-coated pigment exhibited an intensive, red in-
tQrference color in plan view, which flopped via reddish gold to-
ward greenish gold with increasing flatness of the viewing angle.
45 100 g of the Mo-coated pigment were then reacted with sulfur pow-
der analogously to Example 1.
218~663
! . .
1'~
The pigment obtained had a Ti content of 8.4 % by weight, an si
content of 27 . 4 % by weight, an ~o content of 4 . 6 % by weight and
an s content of 1. 2 % by weight. On Arrl; rAt; nn it exhibited an
intenaive, bluish red interference color in plan view, which
5 flopped via red toward gold with increasing flatness of the view-
ing angle.
Example 4
10 150 g of a bluish silvery, ammonia-reduced, TiO2-coated mica pig-
ment (Paliocrom~19 Blue Silver L 6000; BASF) were coated with SiO2
analogously to Example 1 by suspending in 1500 ~nl of isopropanol
and admixing initially with 500 ml of water and 50 ml of 25 ~
strength by weight a~monia and then over 7 h with a mixture of
15 300 ml of isopropanol and 600 g of tetraethoxysilane. The
subsequent stirring time was 14 h.
In air the dried SiO2-coated pigment (312 g) exhibited an inten-
sively blue interference color in plan view, which flopped toward
20 violet at flatter viewing angles.
300 g of the SiO2-coated pigment were then coated with !~Lolybdenum
using 30 g of Mo(CO) 6 over 7 h similarly to Example 1.
25 The pigment obtained had a Ti content of 7.7 % by weight, an Si
content of 2g . 6 % by weight and an rqO content of 2 . 6 % by weight.
On application it exhibited an intensive, blue interference color
in plan view, which flopped toward violet at flatter viewing
angles .
Example 5
2 g of the SiO2-coated pigment of Example 2 were ~u~y~ ~d in
100 ml of water. Following addition of 1 g of dextrose, the pH of
35 the suspension was adjusted to 9 with 2 % ~trength by weight am-
monia. Following addition of a solution of 0 . 2 g of silver ni-
trate in 50 ml of water, the suspension wa~ heatQd to 40 C and
stirred at that temperature for 2 h and at room temperature for a
further 15 h. The product was filtQred off, washed first with wa-
40 ter and then with acetone and dried at room tempQrature.
The pigment obtained had a Ti content of 7 . 4 ~ by weight, an sicontent of 34 . 4 % by weight and a silver content of 6 . 6 % by
weight. On application in varnish it exhibited a grayish blue
g5 color in plan view, which shifted via red toward green with in-
creasing flatness of the viewing angle.
_ _ _ _ . . ..... _
218066g
Example 6
150 g of a coppery, aluminum- and manganese-doped, platelet-
shaped -iron(III) oxide pigment (2.2 % by weight of aluminum,
5 0.3 a by weight of manganese, each ba~ed on the total pigment;
average particle diameter 18 llm; prepared similarly to Example 1
of EP-A-265 280, but with 10 times the batch in a 3.5 1 auto-
clave ) were coated with sio2 similarly to Example 1 by suspending
in 1200 ml of isopropanol and admixing initially with 500 ml of
10 water and 50 ml of 25 % strength by weight ammonia and then over
5 h with 500 g of tetraethoxysilane. The ~iub3e~ue--~ stirring time
was 2 h.
In air the dried SiO2--coated pigment (280 g) exhibited a red in-
15 terference color in plan view, which flopped toward greenish gold
at f latter viewing angles .
120 g of the SiO2-coated pigment were then heated to 190 C in a
fluidized bed reactor under fluidization with 400 l/h of nitro-
20 gen. In addition, 300 l/h of nitrogen, loaded with water vapor bypassing it through a water reservoir t~ e~ uLe ~ ~".LLvlled to
40 C, and also 200 l/h of air were i-l~L~-lu~ e d via two further
nozzles on the side. From a room temperature reservoir, 120 g of
iron pentacarbonyl were carried during 12 h into the reactor with
25 a further 300 l/h of nitrogen and d- ~ A therein to -Fe2O3.
~he pigment obtained had an si content of 18.4 % by weight and a
total iron content of 37 . 5 % by weight. On application it exhib-
ited a greeni~h interference color in plan view, which flopped
30 via blue toward red with increasing flatness of the viewing
angle .
