DK149306B - PROCEDURE FOR CREATING A LIGHT-TRANSMITTING METAL OXIDE COATING ON A SUBSTRATE AT LEAST A PART OF GLASS - Google Patents

Description

in 149306

The present invention relates to a process for producing a light transmitting metal oxide coating on a substrate at least partially made of glass, in which a solution of a metal acetylacetonate or a mixture of metal acetylacetonates is applied to the substrate and the ethyl acetate or acetyl acetates are converted. in situ by heating to form a coating of at least one metal oxide.

It is known to produce oxide coatings, e.g. cobalt oxide coatings, by spraying a solution of a hydrated metal salt in water, e.g. an aqueous solution of CoCl2.6H2O or FeCl2, 6H2O on a substrate surface heated to a sufficiently high temperature to effect conversion of the metal salt in situ. When this treatment is carried out, the coating is usually of poor quality, especially when assessed for degree of uniformity of thickness and composition. For example, when is applied to an aqueous cobalt salt solution, the coatings consist of a grainy deposit of uniform thickness, and the coating generally has very little adhesion to the substrate. Coatings made in this way can often be removed in the form of particles simply by rubbing a finger over the coating, or by applying a piece of adhesive tape to the coating and then pulling off the tape.

It is also known to apply metal oxide coatings to substrates, such as glass, using solutions of metal acetylacetonates which, under the influence of heat, are converted to the corresponding metal oxides. In this known process, methanol, benzene or toluene are used as solvents. The use of such solvents presents the disadvantage that explosion or fire hazards may occur under the heating conditions required to convert said metal acetylacetonates to the corresponding metal oxides.

In another known method, metal acetylacetonates dissolved in halogenated solvents such as methylene chloride are used. These solvents are not combustible but present the disadvantage that they are very volatile and therefore more difficult to use, especially in hot atmospheres and that acidic and / or toxic degradation products can be formed.

French Patent No. 1,528,973 also discloses a process which produces a coating of indium oxide on a glass substrate by spraying a solution of indium acetylacetonate in butyl acetate on the glass substrate while at a temperature of 500 ° C. However, as a solvent for metal acetylacetonates, butyl acetate is generally not well suited for use in processes of the kind indicated, in part because it is relatively volatile (vapor pressure: 12.3 mm Hg at 2J ° C) and has a low ignition point (38 ° C). and therefore easily give rise to fire and explosion hazards, and partly because it has a dielectric constant of only 5.01 and is therefore generally a poor solvent for metal acetylacetonates.

The object of the present invention is to provide light transmitting metal oxide coatings of good mechanical and optical quality on substrates, which are at least partially made of glass, by a method of the kind initially described but which do not suffer from the above-mentioned drawbacks.

This is achieved by the process according to the invention, which comprises the characteristics stated at the outset and which is characterized in that the solvent consists of an aprotic solvent with a dielectric constant of more than 15 and a dipole moment of more than 3D and is selected from a group of solvents consisting of dimethylformamide. , dimethylacetamide, tetramethylurea, dimethylsulfoxide, acetonitrile, nitrobenzene, ethylene carbonate, tetramethylene sulfone, hexamethylphosphoramide or mixtures of two or more of the aforementioned solvents.

From the description to Danish Pat. 1441/73, which corresponds to Danish Patent Publication No. 139-513 and which has priority from 17 March 1972, it is known to carry out the process referred to in the preamble of the claim with acetylacetone as the solvent. (Acetylacetone has a dielectric constant of 25.7 and a dipole moment of 3.05 D). However, the method in question constitutes only PL § 2.2.2 technique in relation to the present invention.

Using the method of the invention, it is possible to provide metal oxide coatings having substantially uniform thickness and composition, such as e.g. is necessary in the case of very thin coatings with a substantial light transparency. Therefore, the method is suitable for use in providing optical coatings on glass bodies or articles to modify their light transmitting and / or light reflecting properties, e.g. to impart a toned appearance to the bodies or objects when viewed in transmitted or reflected light.

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The coating uniformity made possible by the present invention is due not only to the use of a solution of a metal acetylacetonate but, in particular, to the selection of a solvent from the listed groups. Generally, such solvents are very good solvents for the metal acetylacetonates best suited for use in the production of metal oxide surface coatings, especially optical coatings. The said compounds can therefore be applied in relatively highly concentrated solution. Another important factor is the safety with which these solvents can be used under conditions which expose them to very high temperatures. It is therefore possible to provide very rapid heating and evaporation of the solvent from the applied coating and rapid conversion of the metal compound or compounds, and this is also an important factor in promoting the formation of uniform density coatings.

Preferably, the substrate is preheated to a temperature sufficiently high to provide the heat necessary to effect the conversion of the metal acetylacetonate or metal acetylacetonates. Thus, by preheating the substrate, it is possible to provide evaporation of the solvent and conversion of the metal compound (s) largely by the immediate contact of the solution at the substrate. As already stated, this rapid transformation promotes the uniformity of the coating. For purposes primarily aimed at, the optimum temperature of the substrate at the time of coating is usually in the range of 300 to 700 ° C. The temperature should generally be chosen as high as possible, provided that deterioration of the substrate is avoided. For coating glass substrates, the recommended temperature range is 450 to 650 ° C. By using this range, very uniform coatings can be produced and, in addition, a very strong adhesion of the coating to the glass substrate can be obtained, this adhesion being also affected by the temperature of the substrate upon coating.

The solution of metal acetylacetonate or "acetonates is preferably applied in the form of small droplets. The necessary results can most easily be obtained by applying the solution in this form. For example, a spray gun can be used with internal mixture fed separately with compressed air and solution of metal acetylacetonate or acetonates, both at the same pressure, which may be, for example, of the order of 1.5 kg / cm above atmospheric pressure.The acetylacetonate solution as such may be at room temperature or any higher temperature, provided that no is any excessive premature evaporation of the solvent or decomposition and oxidation of the acetylaeetonate or "aeetonates, and provided that the substrate is not subjected to a harmful thermal shock.

Suitable aprotic solvents are the following: dimethylformamide, dimethylacetamide, tetramethylurea, dimethylsulfoxide, acetonitrile, nitrobenzene, ethylene carbonate, tetramethylene sulfone and hexamethylphosphoramide.

Dimethylformamide is particularly preferred. This solvent is a particularly good solvent for most of the acetylacetonates of interest in the preparation of optical coatings so that the acetylacetonate or acetonates can be applied at relatively high concentrations, which means the volume application rate of the solution for a given substrate surface area may be relatively small to achieve a given coating thickness. Dimethylformamide can also be used to coat substrates at very high temperatures without causing a fire hazard.

In selecting the aprotic solvent for use in the practice of the present invention, one having a dielectric constant above 15 and a dipole moment greater than 3D is selected. It has been found that these properties are necessary for a satisfactory aprotic solvent. All of the above-mentioned special aprotic solvents possess these properties. (D denotes Debye device).

In portions, the solution applied to the substrate is a solution of an acetyl acetate of a metal selected from Fe, Ni,

Co, Zn, V, Mn, Cu, In, Al, Ti, Zr, Th and Cr or a mixture of acyl tylaetonates of two or more of these metals. When such solutions are used, very high quality thin metal oxide coatings can be made to modify the light-reflecting or light transmitting properties of a substrate, and the oxide coatings are very well adhered to ceramic substrates or substrates made of glass or a partially glassy material, f. eg. glass ceramics or vitro-crystalline materials, which are the most important materials required to provide optical coating. (The term "vitrocrystalline material" means a material formed from glass by a treatment which induces the formation of one or more crystalline phases therein while leaving one or more vitreous phases on the surface of the material).

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Other important acetylacetonate solutions for application to the substrate are solutions of an acetylacetonate of a metal selected from Mg, Bi, Y, W and Ce.

As already stated, the present invention is of particular importance for use in the manufacture of metal oxide coatings on glass and partially glassy substrates, e.g. substrates of glass ceramics or vitrocrystalline material. This is due to the ability of the method to provide thin metal oxide coatings with a high degree of uniformity as far as thickness and density are concerned, which are particularly sought after for optical coatings to color or tone or otherwise modify optical properties of the bodies. or objects on which they are produced. In the following further description, the invention will be mainly described in connection with the optical coating of glass and partially glassy substrates, for which purpose the coatings consisting of one or more oxides of one or more of the metals listed above are the primary not the only ones suitable.

Objects or bodies of any form, consisting of glass or partially glass, may be coated by the method of the invention to impart a predetermined color or tint to them, but especially to impart these particular, light-reflecting properties. The method is very suitable for use in the manufacture of coatings extended over the entire surface of transparent glass bodies and articles, e.g. car windscreens or glass plates, as metal oxide coatings can be produced which impart a predetermined color to the object or body, considered both by transmitted and reflected light. The method is not only suitable for producing a metal oxide coating directly on a glass surface or a partially glassy surface, but also for making such a metal oxide coating on an already manufactured coating film which adheres strongly to the glass substrate, and especially on an existing metal oxide film, e.g. a membrane of titanium or copper oxide.

An interesting application of the method is its use for coating a heat absorbing glass with a highly reflective layer without substantially increasing the energy absorption.

The light or energy transmission of a coating of a given thickness can be increased without significantly altering the light or energy reflection coefficient by using appropriately selected metal ethyl acetate, e.g. one or more acetylacetonates of a metal or metals within the group: aluminum, zinc, thorium, cerium, yttrium and magnesium.

For preparing an optical coating on flat glass, the process can be performed particularly economically by spraying a solution of a metal acetylacetonate or a mixture of methyl acetylacetonates on a continuous glass band during its preparation, e.g. at a coating station disposed in the drawing chamber of a glass extractor or in an annealing refrigerator. The solution is preferably applied where the glass is at temperatures within the temperature range of 300 to 700 ° C, preferably from 450 to 650 ° C as discussed above. It is very convenient to direct the spray solution spraying at right angles to the glass band and pass the syringe member back and forth across the direction of movement of the tape past the coating station.

For the purposes primarily intended, the thickness of the metal oxide coating formed is preferably in the range of 200 to · 1000 Å. The thickness chosen in any given case will depend on the intended function of the coating. A coating of a given thickness can be constructed, if necessary or desired, by applying two or more layers in succession. The thickness of a coating can best be measured using interference measurements, but it is also possible to dissolve the coating and determine the weight of the coating per unit. unit surface area by analytical means, then the thickness is calculated taking into account the known density of the oxide and its degree of compression in the coating.

By using a mixture of two or more metal acetylacetonates, it is possible to adjust the coating color seen in transmitted and / or reflected light by adjusting the ratio of the various compounds. For example, mixtures of nickel acetylacetonate and cobalt acetylacetonate, vanadium acetylacetonate and zirconium acetylacetonate, manganese acetylacetonate and chromacetylacetonate, copper acetylacetonate and titanyl acetylacetonate, and cobalt acetylacetonate and iron acetate When using iron acetylacetonate, the amount of weight in the mixture of oxides should preferably not exceed $ 50 to make the coating sufficiently resistant to chemical change by atmospheric humidity. Such mixtures of methyl acetylacetonates are dissolved in the aprotic solvent of claim 1, e.g. dimethylformamide or a mixture of two or more of such solvents.

It is often desirable to use the metal acetylacetonate (s) in perfectly crystallized form so that these compounds can be completely dissolved in the solvent. By way of example, it is possible to prepare the following compounds in perfectly crystallized state: cobalt acetylacetonate crystallized with two molecules of water, anhydrous nickel acetylacetonate and copper acetylacetonate crystallized with one molecule of water.

In preparing the solution of metal acetylacetonate or acetates, the total amount of the compound (s) to be used is preferably dissolved very gradually. In preparing a solution of two different ethyl acetate, the total amount of one acetyl acetate is preferably dissolved first, the other acetyl acetone being gradually added to the solution thus prepared. Thus, when a solution of iron and cobalt acetyl acetates is prepared, the iron acetylacetonate is preferably dissolved first, with the cobalt acetylacetonate then gradually added and dissolved in the already formed solution of the iron compound.

The preparation of the solution in the manner discussed above favors the formation of solutions which are stable for long periods of time and as they remain free of precipitation, do not need to be filtered prior to use.

Generally, coatings made in accordance with the present invention and using the preferred coating ingredients are very hard. Panels bearing such coatings can be used with the coating exposed, being normally resistant to mechanical damage, but of course, a coating made according to the present invention can be protected with a protective layer, e.g. with a layer of Sn02 ·

A metal acetylacetonate for use in preparing a coating solution for use in a process of the present invention can be prepared by contacting a metal compound such as a metal halide, if necessary in hydrated form, with acetylacetone in the presence of an alkali metal acetate, so that the acetylacetonate is crystallized. completely. Eg. a cobalt acetylacetonate can be prepared by dissolving cobalt II chloride crystallized with 6 molecules of water in distilled water, which may also contain a small amount of ethyl alcohol to improve the production yield provided there is no risk of fire or explosion, and preferably mixing this solution in a stoichiometric ratio with an aqueous solution of sodium acetate in acetylacetone. The obtained metal acetylacetonate precipitate is filtered off, washed if necessary with the demineralized water filter and dried.

Two or more acetylacetonates can be prepared in the manner described and then mixed in predetermined ratios to obtain a required optimal composition of the finished metal oxide coating.

When a solution of cobalt acetylacetonate is prepared, it is not necessary to crystallize the cobalt acetylacetonate prior to dissolution thereof. However, for some acetylacetonates, such as for iron acetylacetonate, it may be necessary to recrystallize it in alcohol if complete solubility is to be obtained.

In the aforementioned method of preparing the metal acetylacetonates, it is often convenient to use the solution of sodium acetate in acetylacetone in a greater amount than the exact stoichiometric ratio to the chloride used. For example, to obtain iron acetylacetonate, 1 mole of iron chloride, 3 moles of acetate and 3 moles of acetylacetone can be used, obtaining a reaction yield of $ 80. It is more convenient to use 1 mole of iron chloride, 6 moles of acetate and 6 moles of acetylacetone, thereby obtaining a reaction yield of $ 97. Acetylacetonates correspond to the general formula where x corresponds to the valence of the metal M.

Of course, there are other methods for preparing metal acetylacetonates. Thus, a complex compound, such as the acetylacetonate of indium, can be prepared by starting from the nitrate and acetylacetone in the presence of ammonia. In preparing the acetylacetonate of titanium, it is preferable to assume an organometallic compound such as titanium isopropylate.

The wetting of a glass carrier with the applied solution may be enhanced by suitable additives to promote uniformity of the coating.

For examining the hardness and adhesion of the coatings obtained by the method of the present invention, a reciprocating rubbing member having a surface area of 1 cm and made of rubber containing corundum grains may be used. a diameter of 75-125 microns. The rubbing member is arranged in a weight-loaded tube (weight of assembly: 100 g), sliding vertically in a support member. This ensures constant contact between the rubbing member and the sample. The assembled unit constituted by the rubbing means and the supporting means is moved back and forth by means of a crank system. The amplitude of the motion is 3 cm, ° S its frequency is one reciprocating motion per second. second. After a certain amount of time, a wear pattern is formed from scratches which are very close together with unbroken coating between them. In various experiments it was found that after 5 minutes 5% of the surface area that had been subjected to rubbing was destroyed by scratching. It took at least 1 hour for 95% of the surface to be scratched.

The present invention will be further elucidated and the advantages obtained will become more apparent from the following discussion of a number of non-limiting examples.

Example 1.

Various filmogenic solutions were prepared for use in the preparation of glass substrate coatings containing chromium oxide and cobalt, respectively. The solutions were prepared by dissolving the acetylacetonate of the corresponding metal in the solvents listed in the table below.

The concentration in each metal acetate layer ethanate solution was 40 g of the corresponding metal oxide per ml. liter of solution.

The solutions were sprayed onto pieces of flat glass with a thickness of 4 mm and preheated to a temperature of the order of 580 ° C.

The radiation transmitting, reflecting and absorbing properties of the metal oxide layers produced are given in the table below, in which the term "energy" means the total radiant energy over the entire spectrum comprising infrared and ultraviolet light.

149306 ίο

Co ^ G ^

Solvent Dime-Dimethylethylformamide sulfoxide ___

Thickness of 920 A 600 A

coating

Color by trans- brown greyish green light

Energy Trans 35.5 68.2 Mission (%)

Energy reflection 38.2 19.8 on coated side (%)

Energy absorption 26.3 12.0 on coated side (%)

Light transmission (.%) 2638 64.9

Light reflection of 39.9 24.8% coated side in%)

Example 2 150 g of cobalt acetylacetonate and 150 g of iron acetylacetonate were dissolved in 1 liter of dimethylformamide, and the resulting solution was sprayed onto 7 flat glass test pieces preheated to a temperature of the order of 580 ° C.

The spraying conditions were regulated so as to obtain coatings which increased in thickness from one sample to the next, however, the various coatings contained cobalt and iron oxides in similar proportions. The optical properties and energy properties of the coatings are summarized in the table below, where the samples designated 1 to 7 are arranged in sequence corresponding to increasing thickness of their coatings.

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Sample No. 12 3 4 5 6 7 '

Color in ref play - Gray Light Yellow Light - Purple Blue Blue tart light yellow red to purple _purpur_

Color i- trans- Bronze Bronze --- deep bronze ----------- Brown sparkling light

Light transmission ($) 38.1 34.4 33.6 32 30.4 24.7 20

Light Reflection ($) 36.8 38.6 30.4 25. 21.4 17.9 25.7

Energy transmission 46.6 41.6 40.7 39 37.9 34.8 35.2 (%)

Energy reflection (%) 29.3 33 31.7 29.9 28.1 25.9 24

Energy absorption ($) 24.1 25.4 27.6 31.1 34 39.3 40.2 - 0.82 0.82 0.82 0.82 0.80 0.71 0.57

Energy Transmission * 3 1 3 3 31 3J '

Example 3

A coating consisting of 80% by weight of cobalt oxide and 20 $ iron oxide was formed on a heat-absorbing flat glass having a thickness of 5 mm and of ordinary composition.

Cobalt acetylacetonate was first prepared in the following steps; 1) 122 g of CoCl2.6H2 O was dissolved in 300 ml of demineralized water and 100 ml of ethyl alcohol, 2) 120 g of acetylacetone was dissolved in 400 ml of an aqueous solution of 150 g of anhydrous sodium acetate. 10 g of alcohol diacetone were added to give the acetylacetone satisfactory solubility, 3) the two solutions thus prepared were heated to a temperature of 55 ° C, 4) the second solution was slowly poured into the first. A cobalt acetylacetonate precipitate product was obtained which was filtered off and, if necessary, washed several times on the filter with demineralized water. The precipitate product was pure and very crystallized, so that no recrystallization was needed.

The amount of recovered cobalt acetylacetonate Co (C 1 H 2 O 2) 2,2 O was 153 g.

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Iron acetate layer acetate was then prepared in a similar manner, starting from 40.5 g of FeCl 3, 6H 2 O, dissolved exclusively in demineralized water. The other reagents listed in step 2 above were used relative to the iron chloride molarity.

The amount of recovered iron acetate lacetonate was 53 g ·

The filmogenic solution was then prepared by first dissolving 53 g of iron acetate lacetonate in 1 liter of dimethylformamide at 40 ° C over a period of about 15 minutes and then slowly dissolve 153 g of cobalt acetylacetonate over a period of approx. 45 minutes in the already prepared solution of iron acetate layer etonate. The result was a solution that did not need to be filtered and suitable for spraying on preheated substrate (in the present example preheated to 58 ° C).

The above method resulted in a solution that was stable for a number of days.

The solution was heated to 70 ° C and sprayed onto a glass band which was prepared continuously in known manner by drawing it up from a source of molten glass and into an annealing refrigerator, the solution being sprayed onto the glass band at a location where the band had a temperature of 580 ° C. An internal mixing atomizing spray gun was used, which applied to the coating solution and compressed air, both at a pressure of 1.5 kg / cm above atmospheric pressure. The gun nozzle was placed at a distance of 25 cm from the glass band. The spray gun was continuously moved back and forth across the direction of movement of the belt, the speed of this movement being 1.5 meters per second. minute. The spray gun was moved back and forth with a frequency of one reciprocating motion every 6 seconds (width of glass band 3 meters). The spray gun delivered 15 liters of solution per hour, corresponding to a release of 0.04 liters per m glass band and an actual application of 0.03 liters per m2 when taking into account losses.

The thickness of the coating formed was 400 Å. The table below lists the optical properties and energy properties of a heat-resistant glass of the type indicated before and after coating.

Before Coating After Coating Light Transmission 77 »8 $ 33.7%

Energy transmission 51 * 4 29

Energy reflection 6.1 25

Energy absorption 42.5 46

Light reflection 7.6 31 13 149306

The ratio of light transmission to energy transmission for a common non-coated glass was only 1.03: 1 »the corresponding ratio for non-coated heat-resistant glass used in this example was 1.51: 1, while the corresponding ratio for the coated heat-resistant glass was 1.16: 1.

The radiation reflective properties were greatly improved.

Example 4

A solution of titanyl acetylacetonate (prepared by reacting titanium isopropylate with acetylacetone and removing the resulting isopropyl alcohol by evaporation in dimethylacetamide was sprayed onto a gray glass plate having a thickness of 6.5 mm preheated to a temperature of 550 ° C.

The energy properties of the gray glass before and after coating were as follows:

Uncoated Gray glass gray glass coated with TiO2

Light transmission (%) 38.0 25.9

Reflection of light (%) 5.3 27.6

Energy transmission (50 39.2 31.7

Energy reflection (%) 5.0 20.0

Energy absorption (%) 55.8 48.3

It is noteworthy that the presence of the metal oxide layer diminished the energy absorption. Such coating therefore reduces the risk of breakage of the glass due to heating by absorbed radiation, which is an important advantage for glass panes made from this type of glass.

Example 5

In a first experiment, a filmogenic solution containing iron acetylacetonate Fe (C CH₂O₂), vanadium acetylacetonate V (C ^H₂O₂) kob and cobalt acetylacetonate C0 (C ^H₂O₂) 2

These acetylacetonates were dissolved in dimethylformamide to a total concentration corresponding to 60 g / liter oxide (more specifically 5 g / liter Fe-OO 2, 5 g / liter V 2 O 2 and 50 g / liter Co 2 O 2).

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In another experiment, a filmogenic solution was prepared containing only iron acetylacetonate and cobalt acetylacetonate, these compounds being dissolved in the same solvent, i.e. dimethylformamide. The solution contained amounts of the acetylacetonate corresponding to a concentration of ca. 55 wt.% Co 2 O 2 and 45 wt.% Fe 2 O 2.

The two solutions were sprayed onto two samples of glass of the same thickness preheated to the same temperature.

The properties of the coatings turned out to be the following: First try Second try coating: coating:

Fe20 ^ + Co ^ Ojj + VgO ^ Fe20j + Co ^ O ^

Light transmission (%) 36.1 36.1

Reflection of light (%) 35.8 37.7

Energy Transmission (%) 42.7 46.1

Energy reflection (50 31.8 29.7

Energy absorption (50 25.5 24.2

It is noted that coatings can be obtained with the same light transmission but with different energy transmission by simply varying the composition of the layer. Thus, the coating obtained in the first experiment had a smaller energy transmission than the coating obtained in the second experiment, where the same treatment conditions were observed but where the coating composition contained only 2 metal acetylacetonates.

Example 6

Two groups of filmogenic solutions were prepared containing in one case iron acetate acetone together with thorium or yttrium or cerium acetylacetonate, and in the other case iron acetyl acetone together with aluminum or magnesium acetate acetate.

Each mixture of acetylacetonates was dissolved in dimethyl sulfoxide at concentrations such that the metal oxide coating prepared by spraying the solution on heated glass contained 23 wt% Fe 2 O 2 and 77 wt% of the other metal oxide.

The optical properties and energy properties of the oxide coatings thus obtained were as follows:

Fe2O3 + (ThO2, Y2O3 Fe2O3 + (A1203 or CeO2) or MgO)

Energy Transmission (%) 69.5 7 ^, 0

Energy reflection on coating 18.8 18.2 ket side (#)

Energy reflection at non-21.0 18.6 coated side {%)

Energy absorption at over 11.9 7 »8 drawn side (#)

Non-9.7 7.4 coated side energy absorption (%)

Light transmission 70.3 75> 8

Light reflection at coated 22.5 22.8 side

Light reflection at non-23.8 23.1 coated side

Light transmission 1 01 1 00

Energy Transmission * *

Example 7 ♦

Solutions of tungsten acetate acetone in dimethylformamide were prepared and bismuth or indium acetylacetonate was added thereto.

The concentrations of the various acetylacetonates were chosen such that by spraying the solution on heated glass a layer was obtained whose calculated weight was 7055 WO3 and 30 # Bi2 O3 or ln2 O3.

The coatings obtained by spraying a solution onto a piece of glass heated to a temperature of the order of 600 ° C had a greenish-yellow color when viewed in transmitted light.