CA2180669A1

CA2180669A1 - Goniochromatic luster pigments based on transparent, nonmetallic, platelet-shaped substrates

Info

Publication number: CA2180669A1
Application number: CA002180669A
Authority: CA
Inventors: Raimund Schmid; Norbert Mronga
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1995-07-13
Filing date: 1996-07-05
Publication date: 1997-01-14
Also published as: JP3691910B2; EP0753545A3; EP0753545A2; JPH0931355A; DE59609738D1; EP0753545B1; DE19525503A1; EP0753545B2

Abstract

Goniochromatic luster pigments based on multiply coated, high re-fractive, nonmetallic, platelet-shaped substrates which are at least partially transparent to visible light, comprising at least one layer packet of A) a colorless coating having a refractive index n 1.8 and B) a reflecting, selectively or nonselectively absorbing coating which is at least partially transparent to visible light, and also, if desired, additionally C ) an outer protective layer, and their use for coloring paints, inks, including printing inks, plastics, glasses, ceramic products and decorative cosmetic prep-arations.

Description

-, ~ 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.

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 .

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~

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~

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~

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 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 .

Claims

1. Goniochromatic luster pigments based on multiply coated, high refractive, nonmetallic, platelet-shaped substrates which are at least partially transparent to visible light, comprising at least one layer packet of A) a colorless coating having a refractive index n 1.8 and B) a reflecting, selectively or nonselectively absorbing coating which is at least partially transparent to vis-ible light, and also, if desired, additionally C) an outer protective layer.

2. Luster pigments as claimed in claim 1 wherein the platelet-shaped substrate has a refractive index n 2Ø

3. Luster pigments as claimed in claim 1 wherein the platelet-shaped substrate consists essentially of silicatic platelets coated with a high refractive layer which is at least par-tially transparent to visible light, or of platelet-shaped iron oxides.

4. Luster pigments as claimed in claim 1 wherein the platelet-shaped substrate consists essentially of mica platelets coated with high refractive metal oxides.

5. Luster pigments as claimed in claim 1 wherein said coating (A) consists essentially of low refractive metal oxides and/
or magnesium fluoride.

6. Luster pigments as claimed in claim 1 wherein said coating (A) consists essentially of silicon oxide, silicon oxide hy-drate, aluminum oxide and/or aluminum oxide hydrate.

7. Luster pigments as claimed in claim 1 wherein said coating (B) consists essentially of metals, metal oxides, metal sul-fides and/or metal nitrides

8. Luster pigments as claimed in claim 1 wherein said protective layer (C) consists essentially of colorless or selectively absorbing metal oxides and/or is phosphate-, chromate- and/or vanadate-containing.

9. Luster pigments as claimed in claim 1 comprising only one layer packet (A) + (B).

10. A method for coloring paints, inks, including printing inks, plastics, glasses, ceramic products and decorative cosmetic preparations which comprises using the luster pigments as claimed in claim 1.