IL39867A - Process for forming a metal oxide coating on a substrate - Google Patents

Abstract

1397742 Metal oxide coatings GLAVERBEL 22 June 1972 [8 July 1971] 29383/72 Heading C1A [Also in Division C2] An acetyl acetonate coprecipitate of two or more metals is applied to a substrate and is simultaneously or subsequently heated to produce a metal oxide coating which is at least partly composed of an oxidic compound containing two or more metals. The necessary heat may be supplied by pre-heating the substrate and the coprecipitate may be applied in a solution, preferably in droplet form. The solution may contain as solvent an aprotic solvent (e.g. having a dielectric constant greater than 15 and a dipolar moment greater than 3 Debye units), a substituted or unsubstituted monocarboxylic acid solvent, an amine or diamine solvent, or a mixture of two or more solvents selected from solvents of the above classes. The coating may be applied to glass which is being manufactured as a continuous ribbon and to other vitreous and partly vitreous articles. The coatings may be compounds of the type AB 2 O 4 where A is a bivalent metal and B is a trivalent metal, e.g. zinc cobaltite, Cd, Ni, Zn, Mn and Fe, chromites and Mn, Co, Cu, Cd, Ni and Zn ferrites; ABO 3 , A being bivalent, e.g. Ni, Zn, Fe Cu or Co zirconates; A 2 B 2 O 7 , e.g. yttrium zirconate or nickel vanadate; ABO 4 , e.g. iron or chromium vanadate or nickel tungstate. The acetyl acetonate coprecipitate can be prepared by bringing, e.g. the hydroxides, halides, carbonates or nitrates into contact with a solution of acetyl acetone. Examples describe the preparation of coatings from acetyl acetonate coprecipitates of (1) Fe and Cu; (2) V and Fe; (3) Zn and Co; (4) Zn and Cr. In Example 5 the coatings are of Ni 2 V 2 O 7 , NiCr 2 O 4 , MnFe 2 O 4 , CoCr 2 O 4 , CrVO 4 , CuCr 2 O 4 , NiZrO 3 , Y 2 Zr 2 O 7 , NiWO 4 , InVO 4 , BiVO 4 , the solvents used being variously acrylic acid, dimethylformamide, formic acid, ethylene diamine, propylamine, nitrobenzene, propylene diamine and thioglycolic acid. [GB1397742A]

Description

A Process f or forming a Metal flxlde Coating on 8 Substrate neuron ΊΏ rano raionn "70 ^TM Π3«·7 ΠΒ*·© This invention relates to a process for forming a metal oxide coating on a substrate wherein a composition comprising at least one metal compound is applied to a substrate and the applied composition is converted to leave a metal oxide coating. /'The invention also relates to coating compositions for use in carrying out this process and to substrates which have been coated by that process.

It is known to form coatings of an oxide, for instance cobalt oxide, or a mixture of oxides, for instance cobalt and iron oxides, on a surface of vitreous material by spraying an aqueous salt solution, e.g., an aqueous solution of cobalt chloride or of cobalt chloride and iron chloride, onto such surface while this surface is at an adequate temperature to cause conversion of the metal salts (s) in situ. It is also possible to form on the glass coatings of oxides obtained by pyrolysis of metallic acetylacetonates or mixtures of such acetylacetonates which are dissolved in an alcohol, benzene or toluene. It is not possible by this process to form a coating with properties fulfilling any specification which may from time to time be required for a given purpose because the factors influencing the properties of the coating are not infinitely variable, one of these factors being the choice of metal compounds used in forming the coating.

It is possible to form on certain refractory substrates coatings which comprise oxidized compositions o(f several metals of spinellE type, by thermic decomposition of metallic acetyl acetylacetonates and subsequent thermic treatment of the formed coating ( at highly elevated temperatures) . Such a treatment could never be applied for obtaining oxide coatings of good optical qualities on a substrate like glass.

It is an object of the invention to provide a process whereby metal oxide coatings with optical and other specifications whic are not attainable by using the said known method can be produced.

A process according to the invention of forming a film on tw' surface of antf at least partially vitreous material, such finlm comprising at least two metallic oxides by contacting said surface with a coprecititate of at least two acetylacetonates of such metals, said surface being at, or being brought to, a temperature at which said compounds are converted to metallic oxides thus forming -said film which consists at least partially of mixed oxides of said metals.

By means of the process according to the invention it is possible to form metal oxide coatings with specifications which cannot be obtained by the prior process hereinbefore referred to. In particular it is possible by a process according to the present invention to form light-transmitting coatings with light-transmitting and/or light-reflecting properties different from those possessed by metal oxide coatings obtainable by the said known process.

The metal oxide coatings formed by a process according to the invention are in fact of novel structure. The process can be used for coating a variety of different substrates. Particular mention is made of the use of the process for forming metal oxide coatings on vitreous substrates, e.g., glazing sheets and vehicle windscreens, to which substrates the new coatings in many cases show much better adherance than coatings formed ' . y the previously known process. This and other further advantages of the invention will be referred to in more detail hereinafter.

It has been found that there are important differences between an acetyl acetonate coprecipitate of two metals on the one hand and a mixture of an acetyl acetonate of one metal with an acetyl acetonate of another metal on the other hand, even though the molar concentrations are identical in the two cases. For instance, the properties of an acetyl acetonate coprecipitate of vanadium and iron (containing equimolar amounts of vanadium and iron) differ from the properties of an equimolar mixture of an acetyl acetonate of vanadium and an acetyl acetonate of iron. The substances differ, e.g., in tint. Vanadium and iron are here taken only by way of example. Comparison of other acetyl acetonate coprecipitates with mixtures of acetyl acetonates of the corresponding metals likewise show differences.

If a mixture of acetyl acetonates is sprayed and decomposed on a hot glass surface, the result is a coating comprising a mixture of two oxides forming what is known as a solid solution. In a solid solution of this kind, the relative concentrations of the two oxides can vary between 0 and 100 . The properties of the coating are predictable from the known properties of coatings formed of the individual oxides, the law of additivity being applicable, e.g., as regards the tint of the coating. Thus, by spraying and converting mixtures of vanadium acetyl acetonate and iron acetyl acetonate, it is possible to obtain coatings the tints of which, viewed by transmitted light, are in the range yellow to green, depending on the relative concentrations of the different acetyl acetonates. However, by spraying and pyrolysis of an acetyl acetonate coprecipitate of vanadium and iron, coatings which are of greenish-grey tint as viewed by transmitted light are obtained. The law of additivity therefore does not apply in the latter case. The acetyl acetonate coprecipitate of vanadium and iron is itself bright red,while an equimolar mixture of the acetyl acetonates of such metals is brownish red.

Thus it is that by.using a process according to the invention coatings with tints different from those obtained by the known process can be formed.

It is moreover to be noted that by performing a process according to the invention, the formed coating., always comprises an oxidic compound containing the two or more metals, i.e., there is present a mixed metal oxide in which the elements are in stoichiometric proportions forming a true molecule of definite composition. If the acetyl acetonate coprecipitate contains two metals in other relative proportions, then the oxide coating will contain a certain amount of oxide of the metal present in excess, in addition to a true oxidic compound containing the two metals.

A further indication of the difference between an acetyl acetonate coprecipitate as used according to the invention, and a mixture of acetyl acetonates of the different metals is the fact that the solubility of the coprecipitate in a given solvent, e.g., acetic acid or dimethylformamide , is often higher than that of l:.e corresponding mixture of two simple acetyl acetonates. In some cases, when preparing a mixture of an acetyl acetonate of one metal with an acetyl acetonate of another metal, one of the acetyl acetonate has to be recrystallised in alcohol. This is the case for example when preparing a mixture of cobalt acetyl acetonate and iron acetyl acetonate. By way of contrast, when an acetyl acetonate coprecipitate of cobalt and iron is formed, it is directly formed in perfectly crystallised state.

Another noteworthy fact is that usually a light-transmitting coating comprising an oxidic compound containing two or more metals and formed according to the invention usually has a rather high light-transmission/total energy transmission ratio as compared with a coating containing the same elements but in the form of a mixture of oxides.

In most cases the oxide coatings formed according to the invention are very hard. Moreover, when applying the coating compositions by the preferred techniques hereinafter referred to, the coatings are strongly adherent to vitreous surfaces. This is in marked contrast to coatings formed by the previously known process, which can often be removed in the form of particles simply by rubbing a finger along the coating or by applying a piece of adhesive tape onto the coating and then peeling the tape away. In general, coa.tiigsforiaed according to the invention have a high refractive index and optical coatings can therefore be produced which have very good radiation-reflecting properties .

The acetyl acetonate coprecipitate selected for applying to the substrate can be applied by vapouri:sing the coprecipitate at relatively low temperature and if necessary at reduced pressure, to form on the substrate a deposit which is then converted by thermal treatment and further oxidation into the metal oxide coating.

Although this procedure gives acceptable results in certain cases and for certain purposes, it is not ideal. Usually, it is difficult to ensure complete oxidation of all of the metal and the presence of unoxidised metal particules impairs the quality of the coating and its adherence to the substrate. Coating by evaporation can be achieved by vapourising the coprecipitate in the presence of an inert gas and bringing the vapour into contact with the substrate while this is at elevated temperature, in the presence of oxygen. However, this special procedure is technically rather complicated and even then the results are not of the highest quality.

An alternative procedure is to apply the coprecipitate in dispersed state in a liquid medium, but while this procedure also is not excluded it is not the most recommended one. By applying the coprecipitate as a dispersion in a liquid medium and converging the coprecipitate in situ on the substrate it is possible to produce oxide coatings of the new structure and therefore possessing concomitant advantages, but it is difficult to produce coating which have over their entire area predetermined optical properties as is usually required in the case of optical coatings intended to impart modified radiation-transmitting and/or radiation-reflecting properties to bodies or articles of vitreous or partly vitreous composition.

The preferred coating technique is to apply the coprecipitate in dissolved state. Accordingly, in the most preferred embodiments of the present invention, the acetyl acetonate coprecipitate is applied to the substrate in solution in a liquid solvent. By adopting this technique, coatings which are of very good qualit can be readily obtained.

Preferably the substrate is preheated to a sufficiently high temperature to provide the heat required to effect the conversion of the coating composition to form the metal oxide coating. By thus preheating the substrate it is possible to bring about evaporation of the solvent and conversion of the coprecipxtate substantially immediately on contact of the solution with the substrate. This rapid conversion promotes coating uniformity. In general, for the purposes primarily in view, the optimum temperature of the substrate at the time that it is coated is in the range 300 to 700°C. The temperature should in general preferably be chosen as high as possible consistent with avoiding impairment of the substrate. For coating vitreous substrates , the recommended temperature range is 50 to 650°C. By working within this range, very uniform coatings can be formed and moreover very strong adherence of the coating to the vitreous substrate can be achieved, this adherence also being influenced by the temperature of the substrate on coating.

The solution of the coprecipxtate is preferably applied in the form of droplets. The required results can be most easily achieved by applying the solution in that form. Use for example can be made of an inside-mixing atomising gun fed separately with compressed air and the coating solution, both at the same pressure, which may e.g., be of the order of 2. 0 kg/cm above atmospheric pressure. The solution itself can be at ambient temperature or any higher temperature provided that there is no undue premature evaporation of the solvent or decomposition and oxidation of the coprecipitate and provided that the substrate is not subjected to a harmful thermal shock.

When using the preferred coating technique wherein the coprecipitate is applied as a solution to the substrate, the choice of solvent is a material factor influencing the quality of the final coating. When it is important to form coatings of a very high standard of uniformity insofar as their optical and other properties are concerned, it is recommended to select a solvent which is a very good solvent for the coprecipitate so that the latter can be applied in fairly concentrated solution. Another factor which has often to be taken into account in selecting the solvent is the risk of fire or explosion when working under high temperature conditions.

In the most preferred embodiments of the invention, the acetyl acetonate coprecipitate is applied in solution in an aprotonic solvent, a substituted or unsubstituted monocarboxylic acid solvent, an amine or diamine solvent, or a mixture of two or more solvents selected from solvents of those classes. In general, such solvents are very good solvents for acetyl acetonate coprecipitates most suitable for use in forming metal oxide surface coatings, in particular optical coatings. The said coprecipitate can therefore be applied in relatively highly concentrated solution. Such solvents can moreover be used in conditions in which they are exposed to very high temperatures. It is therefore possible to bring about very rapid heating and evaporation of the solvent from the applied coating, and rapid conversion of the coprecipitate , and these are also important factors for promoting the formation of coatings of uniform density. By using such solvents it is possible to form high quality optical coatings which adhere quite strongly to vitreous and partly vitreous substrates, e.g., optical coatings for tinting or otherwise modifying the optical properties of glazing sheets, windscreens, sheets of patterned rolled glass, lenses for sunglasses, and other vitreous articles .

As examples of suitable aprotonic solvents, the following are cited s dimethyl ormamide , dimethylace-tamide , tetramethylurea, dimethylsulphoxide , acetonitrile , nitrobenzene, ethylene carbonate , tetramethylene sulphonef •i hexamethylphosphoramide .

Particular preference is given to dimethylformamide. This solvent is a particularly good solvent for most of the acetyl acetonate coprecipitates which are of interest for forming optical coatings so that such coprecipitates. can be applied in high concentrations, which means that the volume rate of application of the solution to a given area of substrate surface can be low for achieving a given coating thickness.

Dimethylforraamide oan also be used for coating substrates at very high temperatures without creating a fire hazard.

When selecting an aprotonic solvent for use in carrying out the invention, preference is given to those having a dielectric constant greater than 15 and a dipolar nonent greater than 3D. It has been found that these are properties of the most satisfactory of the aprotonic solvents. Such properties are possessed by all of the specific aprotonic solvents hereinbefore identified.

The preferred classes of solvents for use in carrying out the invention also include substituted and unsubstituted: r:onocar cary1ic acids. Preference is given to aliphatic substituted and unsubstituted ffionocarboxylic acids, particularly good examples being acetic acid (CH^COOH), butyric acid (CH CHgCOOH) , acrylic acid (CH CHCOOH), thioglycolic acid (HSCI^COOH) , and formic acid (HCOOH) .

The third of the specified preferred classes of solvents which can be used in carrying out the invention comprises amine and diamine solvents. Preference is given to alkyl and alkylene amino and diamino solvents in which the amino group( c ) are unsubstituted, particularly good examples beings ethylene diamine, propylene diamine, butyl amine, propyl amine.

While stress has been laid on the use of a solvent or solvents selected from the special classes hereinbefore identified, it is to be understood that other solvents can be used, particularly in circumstances where the formed oxidic coating does not have to satisfy very stringent optical specifications. Thus it is in certain cases suitable to use an alcohol or a hydrocarbon solvent, e.g., an aromatic solvent such as benzene, toluene or xylene.

Tlhen using certain of the solvents belonging to the specified preferred classes, and particularly when using a substituted or unsubstxtuted monocarboxylic acid, advantages are sometimes to be gained by the addition of a small amount of inorganic acid, e.g.,HC1, H 03, or H2S0 .

P Preference is given to embodiments of the invention in which the coprecipitate applied to the substrate is an acetyl acetonate coprecipitate of two or more metals selected from the group sFe, Ni, Co, Zn, V,Cu,Cr, Zr, n.

Other important embodiments are embodiments in which the coprecipitate applied to the substrate is an acetyl acetonate coprecipitate of two or more metals selected from the group comprising the metals hereinbefore specified and also comprising Bi,Y,IJ and In.

By making such a selection,metal oxide coatings can be formed which are hard and very adherent to the substrate and which have well defined optical properties. ■ijr As already indicated, the invention is of special importance for forming metal oxide coatings on vitreous and partly vitreous substrates, e.g., substrates of vitrocrystalline or vitroceramic material. This is because of the ability of the process in its pre erred embodiments to produce thin metal oxide coatings of a high degree of uniformity in thickness and density which are properties particularly looked for in optical coatings for the purpose of tinting or otherwise modifying the optical properties of the bodies or articles in which they are formed. In the following further description the invention will be considered mainly in the context of the optical coating of vitreous and partly vitreous substrates, for which purpose coatings which are at least partly composed of an oxide compound containing fryo or more of the metals hereinbefore listed are the ones which are maiily but no means exclusively useful.

Vitreous and partly vitreous articles or bodies of any shape can be coated by the process to impart a predetermined tint thereto, but more particularly in order to impart special light-reflecting properties. The process is very advantageous for forming all-over coatings on transparent vitreous bodies and articles, e.g., on vehicle windscreens or glazing sheets because metal oxide coatings can be formed which give the article or body a predetermined tint as viewed both by transmitted and reflected light . The process is not only useful for forming- a metal oxide coating directly on a glass or partly vitreous surface but also for forming such a metal 03d.de coating on an already formed coating fiia whic is strongly adherent to the vitreous substrates and part cularly on an existing metal oxide film, e.g., a film of titanium or copper oxide,, One interesting application of the process is its use for coating a heat-absorbing glass with a highly reflecting layer„ without substantially increasing the energy absorption.

The light or energy transmission of a coating of a given thickness can be. increased without substantially altering the light or energy reflectance j by adding to the solution an acetyl ?xetonats such as that of alumium, zinc , thori ir^ cerium or yttrium.

For forming an optical coating on flat glass, the process can be particularly economically performed by spraying a solution of an acetyl acetonate coprecipitate of two or more metals onto a continuous glass ribbon in course of its production, e„g. „ at a coating station located at the drawing chamber of a glass drawing machine or in an annealing lehr„ The solution is preferably applied where the glass is at temperatures within the temperature range 300° to 700° , most preferably . 50°C to 650°C, as hereinbe ore referred to. It is very suitable to direct the spray of coating solution normally to the glass ribbon and to reciprocate the spraying device transversely of the direction of moveinent of the ribbon past the coating station. In such a process it is of course desirable to use a non-inflammable and non-explosive solvent, such as a solvent of one of the preferred classes hereinbefore referred to, unless special safety precautions are taken. It is preferred to use an aprotonic solvent, a substituted or unsubstituted monocarboxylic acid solvent or an amine or diamine solvent.

For the purposes mainly in view the thickness of the metal oxide coating which is formed preferably lies in the range 200 to 1, 2002. The thickness chosen in any given case will depend on the intended function of the coating. A coating of a given thickness can if necessary or desired be built up by applying two or more layers in succession. The thickness of a coating can best be measured by interferometry, but it is also possible to dissolve the coatin and to determine the weight of the coating per unit surface area analytically, the thickness then being calculated taking into account the known density of the oxides and their degree of compaction in the coating.

By performing the invention under the most favourable conditions as herein directed , high quality opticr.l coatings can be formed. In other cases, the formed coating may occasionally be marred by small darlc stains often referred to as "pittings" . It is to be noted however,, that the appearance of exxc defects to any material degree depends in part on various other factors, and more particularly on the composition and geometry of the coated surface and the coating thickness ·. For example, when forming a coating on patterned glass having a fairly close pattern or on wired or pro iled glass , e.g., glass bodies of U-shape, the defects are much less apparent than when forming a coating on plane-faced flat glass. Even when the coating is formed on a plane glass face,, the presence of defects tends to be less apparent according as the thickness of the coating is greater . On the other hand the greater' the thickness of the coating the less is the light- transmissivity of the coating and where this factor is of importance, the optimum coating thickness represents a compromise betwee the competing objectives of freedom from defects and a high degree of light- transparenc .

Coa.tings formed, according to the invention and using the preferred cor^ting ingredients are e }r hard. Glazings beaxing such coatings can be used, with the coating exposed because^ it is for normal purposes sufficiently resistant to mechanical damage.

The wettability of a vitreous support by a solution of the acetyl acetonate coprecipitate can be improved, in order to promote uniformity of coating, by means of suitable additives. For example, up to 10 by weight of acetyl acetone cr iron acetyl acetonate or even zinco acetate may be added to the solvent.

A very considerable range of mixed oxide coat" ings c n be formed by a process according to the invention.

For example, compounds of the type A3„0i can be formed, in which A is a bivalent metal such as Zn,Fe, Viiii Co, Ni, and B is a trivalent metal such as In, Fo, Cr, Co. Examples of compounds of this structure are sine cobaltito (ZnCc^O^), the chromite of ca.dmium, nickel zinc, manganese and iron,, manganese ferrite ( nFe?0^) and similarly the ferrites of cobalt, copper., cadmi ra, manganese, nickel, zinc etc.

It is also possible to form compounds of the type AB0„ in which the sum of the degrees of oxida -ion of the elements A and B is 6, A being a bivalent or trivalent metal and B being a tetravalent or trivalent metal respectively. Examples of compounds of such a structure are nickel zirconate (NiZrO^) and even the zirconates of zinc, iron, copper, cobalt It is also possible to form compounds of the type in w ich A is a trivalent cation and B is a tetravalent cation, for example yttrium zirconate Y^ r^Q^ or even where A is a bivalent cation and B is a pentavalent cation, for example nickel vanadate (lii V 0„) ; compounds of the type ABOj^ where A is a trivalent cation and B a pentavalent cation, for example iron vanadate (FeYO^) or chromium vanadate (CrVO^).; and compounds of the type BO^ where A is a bivalent and B a hexavalent cation, for example nickel tungstate The potential range of optico.l and other specifications which can be fulfilled by oxide coatings formed in accordance with the invention is particularly large( in view of the fact that for obtaining coatings of a particular tint, viewed by transmitted and/or reflected light, it is possibl to use a. coating composition comprising an acetyl acetonate coprecipitate of more than two metals , e.. g of three metals. A particular example is an acetyl acetonate coprecipitate of vanadium, iron and iiic el It is also within the scope of the invention to use a coating composition comprising a mixture of different acetyl acetonate coprecipitates of two or more metals. Thus, merely by way of example, a composition may be used comprising an acetyl acetonate coprecipitate of iron and copper, mi ed with an acetyl acetonate coprecipitate of chrotsiuta and manganese; or a mixture of an acetyl acetonate coprecipitate of vanadium and zinc, with an acetyl acetonate coprecipitate of iron and nickel.

To test the hardness and adherence of coatings obtained by the process according to the invention, use can be made of a reciprocating rubbing element having a surface area of 1 cm" and formed by rubber incorporating corundum grains 75-125 microns in diameter. The rubbing member is set in a weighted tube (weight of assembl s 100 gr) sliding vertically in a support . Constant contact in therefore ensured between the rubbing member and the sample. The assembly formed by the rubbing member and the support is reciprocated by a crank system. The amplitude of the movement is 3 cm, its frequency being 1 reciprocation per second. After a certain time, a pattern of wear is obta.ined formed by scratches very close together with undestroyded coating left therebetween. In general, coatings formed according to the invention are hard and firmly adherent to vitreous substrates.- For example, the abrasion test has to be continued for an hour and a half to spoil 95$ of the surface area sujected to rubbing.

The invention includes a coating composition comprising an acetyl acetonate coprecipitate of two or more netals represented in the group; Fc, Hi Co, 2n, V, Cu, Zr, Cr, Mn, Bi , Y„ TJ, In.

The invention also includes a method of preparing an acetyl acetonate coprecipitate of two or core metals, e.g. „ metals selected frotn the said group, characterised in that a solution of compound of at least two different metals, such compounds being represented in the grou s hydroxides, halides carbonate, nitrates, is brought into contact with a solution of acetyl .acetone Advantageously, a solution of freshly precipito-ted hydroxides is brought into contact with a solution of acetyl acetone. This procedure is particularly suitable in the casr of metals selected from the group Fe, Co and N .

Advcoitageousl , an aquecus solution of two or more halides is brought into contact with an aqueous solution of alkali motal acetate ( anhydrous or not) and acetyl acetone. This procedure is suit able more particularly in the case that the netals are selected from the groups Co, Cr, Cu, Fe, Mn, Ni, V, Zn, U, Bi and In.

In certain embodd reacts , an aqueous solution of nitrates of two metals is brought into contact with an aqueous solution of alkali metal carbonate cjxd acetyl acetone. This procedure is suitable more particularly in the case that the metals are selected from the groups Co., Cr, Cu,, Fe, Μη> Hi, Zrij. Zn, Zr,, Th and Y.

According to another procedure, an aqueous solution of the nitrates of two or core netals is brought into contact -with an aqueous solution of NHi OH and acetyl acetone. This procedure is a iit— able more particularly in the case of metals such as Mi j. In, and Fe, In a further embodiment of the process of preparing a coprecipitate, an alcoholic solution of the nitrates of two or more netals is brought into contact with a.cetyl acetone. This procedure is suitable more particularly for the metals Co, Cr, Cu.

In order to give the acetyl acetonate coprecipitate satisfactory solubility, it is preferably in the perfectly crystallised state. If necessary the precipitate obtained is recryotalliced in alcohol.

Advantageously , the amount of acetyl acetone theoretically required from the stoichiometric point of view is doubled cr trebled to obtain a high yield of acetyl acetonate coprecipitate. In this way a yield very close to can be reached.

The invention also includes a solution, of an acetyl acetonate coprocipitate as above defined or as prepared by a process above defined.

Preferably 5 the solvent used in the solution of the acetyl acetonate coprecipitate comprises an aprotonic soli vent, a substituted or uncubstituted monocarooxylic a.cid solvent, an amine or diamine solvent or a mixture of two or nore solvents selected from solvents of those classes. Advantageously one or more of the solvents, belonging to tho classes which, have been hereinbefore specifically identified is used.

In other embodiments, the solution of the acetyl acetonate coprecipitate comprises an alcohol or hydrocarbon as solvent. Prudent use will be made of alcohols, e.g., methyl alcohol, ethyl alcohol and propylic alcohol, and hydrocarbons, which latter class of solvents includes, inter alia, aromatic hydrocarbons such as benzene toluene, and xylene.

A solvent which is very suitable in many cases is glacial acetic acid, even if the acetyl acetonate coprecipitate crystallises in hydrated form. Dimethyl formamxde is also very suitable.

The dissolving of the coprecipitate in the selected solvent or solvents should preferably be carried out gradually.

The invention will be better understood and its advantages better appreciated from the following description of a number of non-limitative Examples thereof.

In the following Examples, it should be noted in practice that if a start is made from two metal salts in equimolar proportions, the result will not necessarily be an acetyl acetonate coprecipitate in which the two metals are in equimolar concentrat ions, this being explained by the difference in reactivity (CM*yield) of the different metals. For instance, if an acetyl acetonate coprecipitate equimolar in two raetals is to be obtained, a start will be made, for instance, from an equimolar mixture of salts of two metals, and an analysis will be made of the acetyl coprecipitate obtE-ined; this will enable a correctional factor to be established by calculation. If the correction proves to be inadequate, a second correction will be ma.de by calculation.

Example 1.

This Example relates to the formation of copper ferrites (CuFo 0. ) in tli"eo tests -J-...B.C. 2 4 For these tests the salts specified in Table 1 , were dissolved in the st.ated amounts, in one litre of demineralised water.

TABLE 1 B FcC1 ,6H 0 0.2 mole 0.35 mole = 95 gr Ο.65 mole CuC1?2H20 0.8 mole Ο.65 mole = 110 gr 0.35 mole For each of the mixtures A, B and C, 638 gr of sodium acetate crystallising with 3*1,-, 0 (^·7 moles )vas dissolved in two litres of demineralised water and 482 cc of acetyl acetone (4.7 moles).

The solutions of chorides and acetate were heated to 55°C. One- of the a.cetate solutions was poured into each of the chloride solutions at a rate of 3 litres per hour.

The precipitate obtained was filtered, washed with water, dried and recrystallxsed in ethyl alcohol. The three acetyl acetonate coprecipitates of copper and iron were recovered. The character-istics of these coprecipitates are set out in Table 2.

TABLE 2 , A B Weight of acetyl 29 gr 30 gr gr actetonate recovered eight of copper 51 gr 22 . 3 gr 1 9 . 1 gr Weight of iron 1 1 . 2 gr 36 · 3 g 33 » 5 gr Tint blue red bright red Ea.ch of the three acetyl acetonate1? coprecipitate was then dissolved in glacial acetic acid i an amount of 285 gr per 0 . 8 litre.

The solutions A, B,C were separately applied by a spraying gun to three glass ribbons 3 metres in width during movement thereof past the coating station at a speed of 1 . 5 metres per minute. In these coating operations, use was made of an internal mixing gun fed with compressed air and coating solution, both at a pressure of 2. 5 to 3 . 0 kg/cm above atmospheric pressure. The nozzle of the gun was at a distance of 20 cm from the glass. The glass was at a tempera.ture of 580°C, while the solutions, A o B . C were at ambient temperature. The gun was reciprocated perpendicularly to the direction of forward movement of the glass ribbon, the gun reciprocating at a frequency of 1 reciprocation every six seconds.

Allowing for losses of the coating solution, the amounts of mixed oxide effectively deposited per square metre of surface were 0.035 r; 0.231 gr; 0.2 5 gr for the tests A,B,C. Coatings containing copper ferrite, on its own or with the addition of CuO and/or Fe^O^ were obtained having the 5 characteristics set out in the following table 3» TABLE 3.

A B C o Thickness in A 0 45Ο 45Ο p Weight of CuO per m 0.248g 0.017g 0 g Tint in Transparency bronz grey-brownish grey Tint in Reflection grey-yellowish grey grey Light transmisson (°/o) 43.6 1.2 54.3 Energy transmisson (°/o) 53.5 56.2 4.Ο Light reflection (fa) 34.2 29.8 29.1 Energy reflection (°/o) 27.8 21.1 23.2 Energy absorption (">) 18.7 22.7 22.8 Light transmission 0.81 0.91 1.01 Energy transmisson ~ Example 2. 7.85 gr of VC13 and 13.5 gr of FeCl^. 6Η 0 were quickly dissolved simultaneously in 100 cc of distilled water. A second solution was formed by dissolving 60 cc of acetyl acetone in a solution of 200 cc of water containing 81 gr of sodium acetate, The two solution were heated to 60°CS whereafter the second solution was slowly poured into the first one, over a period of half an hour. A well-crystallised reel precipitate was formed which was filtered, washed with demineralised water and dried. 35· 2 gr of acetyl acetonate coprecipitate of trivalent vanadium and trivalent iron were obtained. Examination under an optical microscope revealed the difference between crystals of this coprecipitate and a mixture, having the same molarity, of crystals of vanadium acetyl acetonat© and iron acetyl acetonate.

The coprecipitate obtained as above described was rapidly dissolved in 200 cc of dimethylformamide at ambient temperature.

The resulting solution was sprayed onto a substrate under the same conditions as those of Exa pl 1. A film containing iron vanadate (FeVO^) was obtained having a greenish-grey tint in transmission and a grey tint in reflection.

Other energy properties of the coating were as ollows : Light transmission ( °/o ) s 52.0 Energy transmission ( °/o ) % k7.7 Light reflection ( ) % 30.9 Energy reflection ( °/o ) s 24.8 Energy absorption ( °/o ) s 27.5 Light transmission Energy transmission 1.09 A similar film can be obtained by replacing the dimethylformamide by acetonxtrxle , tetramethylure , ethylene carbonate, tetramethylenesulphone , nitrobenzene diraethylsulphoxide s diinethylacetaniidc , hexamethylphosphoramide toluene, benzene or xylene Example 3 ·.

An acetyl acetonate coprecipitate of Zn and Co was prepared as follows s 1 mole of Co (NO^ ) , 6H20 ( ?-91 g ) and 1 mole cf Zn(NO^)2. βΗ^Ο ( 297 g) were dissolved in two litres of deinineralised water; 2 moles of N ^CO^ ( 21 2 g) were dissolved in four litres of demineralised water and 600 cc of acetyl acetones The two solutions were heated to 0°Cj the carbonate solution was poured into the nitrate solution accompanied by strong agitation, the reaction taking place during one hour; the pink coprecipitate was washed, dried and recrystallised in alcohol, 5 0 gr of acetyl acetonate coprecipitate of Zn and Co were recovered The coprecipitate was dissolved in three litre of a mixture containing 50$ by volume of methanol and 0$ of n-butyla.niine „ . The solution h s obtained was sprayed under the same conditions as those of Example 1 , at a rate of 10 litres per hour.

The result was a coating containing sine cobaltitc (Z Co20^ ) having the following properties? Thickness; 575 S Tint in trcmsEiisoion grey-greenish Tint in reflection; grey Light transmission (°/) s 48. 7 Light reflection (°/o) % 7 .

Energy transmission (°/o) s 46. 3 Energy reflection (°/o) s 2k.2 Energy absorption (°/o) ; 29 . 5 Light trcnstnisson _ ^ Q _ Energy transmission" A second test was made in which only 300 cc of acetyl acetone was used instead of 600 cc. Only 23 gr of acetyl acetonate coprecxpitate were recovered. The hardness and adherence of the coating formed were tested by the hardness test hereinbefore described. It took at least an hour and a half to scratch away 95% of the coating.

An identical result was obtained when methanol was replaced by ethanol or propanol.

Example 4 .

An acetyl acetonate coprecxpitate of Zn and Cr of violet tint was prepared in a manner similar to the preceding Examples - i.e., by reacting one mole of zinc chlox- de (ZnCl ) ( 1 36 g) and one mole of chromium chloride (CrCl^.611^0) ( 266 g) with ten mole of acetyl acetone (1000 cc) in the presence of ten moles of anhydrous sodium acetate (820 g).

After dissolving the acetyl acetonate coprecip tate in dimethylformamide , a coating containing zinc chrornite (ZnCr^O^) was formed by the same technique as that set forth in Example 1.

The thin coating film had the folloxtfing properties Thickness; 620 ° Tint in transmission; grey greenish Tint in reflections grey Light transmission (0) s 55· 3 Light reflection ( °/o ) s 26.2 Energy transmission ( c/o ) 5 56.1 Energy reflection { °/v ) % 2k .3 Light transmission _ 0 98 Energy transmission ~ In a second test, the coprecipitate was dissolved in dimethylformamide to which 10% HCl. had been added. It was found that the solubility of the acetyl acetonate coprecipitate was greater by } " °/ο than when using dimethylformami.de alone as solvent.

The coo.ting film containing zinc chrornite obtained by applying this solution of the coprecipitate i dimethylfor amide and hydrochloric acid, which coating was formed by the same technique as that set out in Example 1 y was clearly more grey in transparency than the zinc chrornite film of the first test, and the film had the following properties;.

Light transmission ( c/o ) s 48,0 Light reflection ( ) s 2 .3 Energy transmission ( °/o ) s ^5.2 Energy roflection(^) j 28.9 Energy absorption (°/o ) s 25.9 Light transmission _ ^ ^ Energy tra.nsrnd.ssion ~ Example rj.

Using the techniques set forth in the preceding description concerning the formation of the acetyl acetonates of various metals, a number of acetyle acetonate coprecipitates were prepared which were then dissolved in different solvents and applied by spraying as in the method described in Example 1. Coating films were obtained, constituted at least in part of the following oxidic compounds and having the specified tints in transparency and reflections Solvent Tint in transparency Tint in reflection Acrylic acid yellow grey-greenish Ni2V2°7 NiCr2° Dimethylformamide rose blue MnFe20^ Formic acid brown-grey grey CoCr20 Dimethylformaraide grey grey CrVO^ Ethylene diamine yellow green CuCr20 Dimethylformamide blue-grey grey NiZr^O Propylamine Grey grey Nitrobenzene blue-grey yellow Y2Zr2°7 NiWo^ Dimethylformamide yellowish yellow InV0 Propylene diamine yellowish-grey grey B±V0 Thioglycolic acid yellowish- rey grey Examination of the coatings by an electron microscope showed the difference in structure between the structure of the oxidic compounds formed by conversion of the acetyl acetonate coprecipitates and that structure of oxides formed from a mixture of two simple metal acetyl acetonates of the same molarity.

Of course, the invention is not limited to the foregoing Examples, and modifications could be made thereto without departing from the scope of the invention.

Claims (28)

39867/2 WHAT IS CLAIMED IS:

1. A process of forming a film on the surface of an at least partially vitreous material which film contains at least two metallic oxides, which compr ses contacting said surface with a coprecltltate of at least two acetyl ace ton ates of such metals, said surface being at, or being brought to, a temperature at which said compounds ate converted to metallic oxides thus forming said film which consists at least partially of mixed oxides of said metals.

2. A process according to claim 1, characterised in that said acetyl ace ton ate copreclpHate Is applied 1n solution to said substrate.

3. A process according to claim 2, characterised in that the substrate Is pre-heated to a sufficiently high temperature to provide the heat required to effect said conversion of the copreclnltate.

4. A process accordnng to claim 3, characterised In that the substrate Is pre-heated to bring the temperature of the surface to be coated to a value within the range 300° to 700° C.

5. A process according to any of claims 2 to 4, characterised In that the said solution 1s applied 1n droplet form.

6. , A process according to any of claims 2 to 5» characterised in that said acetyl acetonate coprecipitate is applied in solution in an aprotonic solvent, a substituted or unsubstituted raonocarboxylic acid solvent, an amine or diamine solvent, or a mixture of two or more solvents selected from solvents of those classes.

7. , process according to claim 6, characterised in that the solvent used comprises an aprotonic solvent having a dielectric constant greater than 15 and a dipolar moment greater than 3D,

8. , A process according to claim 7» characterised in that dimethylformaraide is used as a solvent.

9. , A process according to claim 7» characterised in that an aprotonic solvent specifically identified herein as such, other than dimethylform'amide , is used,

10. , A process according to any of claims 2 to 9 characterised in that a substituted or unsubstituted monocarboxylic acid solvent specifically identified herein as such, is used.

11. , A process according to any of claims 2 to 10 characterised in that the solvent used comprises an alkyl or alkylene amine or diamine in which the amino group or groups is or are unsubstituted. '1> 1 2.

12. A process according to claim 1 1 , characterised in that an alkyl^ or alkylene amine or diamine solvent specifically identified herein as such, is used. 1 3.

13. A process according to any preceding claim, characterised in that the said coprecipitate is an acetyl acetonate coprecipitate of two or more metals represented in the groups Fe ,Ni ,Co , Zn,V, Cu, Cr, Zr , n. 1 .

14. A process according to any of claims 1 to 1 2 characterised in that the said coprecipitate is an acetyl acetonate coprecipitate of two or more metals represented in the groups Fe ,Ni , Co , Zn,V, Cu, Zr , Cr, Mn,Bi,Y,I7,In.

15. 1 5. A process according to any preceding claim, characterised in that the said corapostion is applied to a substrate w2iich is at least partly vitreous.

16. A process according to claim 1 5 » characterised in that said composition is selected and applied so that the formed metal oxide coating is a light-transmitting coating.

17. 1 7. A process according to claim 1 6 , characterised in that the formed metal oxide coating has a thickness in the range 200 to 1 200 S.

18. A process according to any preceding claim, characterised in that said substrate is flat glass which is in course of being manufactured as a continuous ribbon.

19. A process according to claim 18, characterised in that said solution is applied to the glass ribbon at a zone where its temperature is in the range o , o 5Ο to 65Ο C.

20. An acetyl acetonate coprecipitate of two or more metals represented in the groups Fe ,Ni , Co , Zn, V , Cu , Zr Cr ,Mn , Bi , Y , ¥ , In.

21. A method of preparing an acetyl acetonate coprecipitate of two or more metals, characterised in that a solution of compounds of at least two different metals, such compounds being represented in the group; hydroxides, halides, carbonates, nitrates, is brought into contact with a solution of acetyl acetone .

22. A method according to claim 21, characterised in that the different metals are represented in the groups Fe, Ni , Co, Zn, V, Cu, Zr, Cr, Mn, Bi , Y, ¾r, In. r

23. Δ solution of an acetyl acetonate coprecipitate as claimed in claim 20 or prepared according to claim 21 or 22 „ 2h.

24. A solution according to claim 23 , characterised in that the solvent in which the acetyl acetonate coprecipitate is dissolved comprises an aprotonic solvent, a substituted or unsubstituted monocarboxylic acid solvent, an amine or diamine solvent or a mixture of two or more solvents selected from solvents of those classes .

25. solution according to claim 23 or 2 , characterised in that the solvent in which the acetyl acetonate coprecipitate is dissolved, comprises an alcohol or hydrocarbon.

26. Δ process according to claim 1 and substantially according to any of the Examples herein.

27. A vitreous or partly vitreous substrate bearing a metal oxide coating formed by a process according to any of claims 1 to 19 and 26.

28. A non-vitreous substrate bearing a metal oxide coating formed by a process according to any of claims 1 to Ik. P.0. Box 331 16 , T e l - A v i v Attorneys for A p p l i c a n t