IL26863A - Glazing for attenuating ultraviolet radiation - Google Patents

Description

C O H E N Z E D E K & S P I S B A C H R E O D. PAT E NT A T TO R N EYS 24, LEVONTIN STR., P. O. B. 1169 15955 66 T E L - A V I V P A T E N T S & D E S I G N S O R D I N A N C E SPECIFICATION GLAVEHBEL , a Belgian Societe Anonyme , of 166, chaussee de la Hulpe , ^atermael-Boitsfort , Belgium, (formerly 79, Avenue Louise, Bruxelles 5, Belgium.), HEREBY DECLARE the nature ot this invention and in what manner the same is to be performed to be particularly described and ascertained in and by the following statement: This invention relates to light-transmitting-materials and articles.

An object of the invention is to facilitate the mass-production manufacture of light-transmitting materials whic show significant light-absorption in the ultraviolet region but differ inter se in the extent to which ultraviolet light is absorbed and/or in one or more other optical properties such as the transparency to visible light or to light in a particular part or parts of the visible light spectrum.

It is known to incorporate ultraviolet-absorbing compounds into glass during its manufacture but if that is done, a very precise control of the conditions in the glass-melting furnace must be exercised and it is not possible to switch quickly from one glass composition to another;, e.g., to satisfy demands for glasses with different characteristics;, e.g., different colours.

According to the present invention, a material or article comprises at least one piece of glass or other light-transmitting material bearing a light-transmitting dielectric coating layer with a refractive index higher than that of said material, which coating layer incorporates at least one substance which absorbs ultraviolet light and at least one substance which does not absorb ultraviolet light or not to any significant extent.

It is sufficient for the main purposes in view to form the dielectric coating layer from two ingredients only, viz. one substance which appreciably absorbs ultraviolet light and one substance showing subs antially no ultraviolet absorbing property and in the interest of simplifying the following descriptions, the use of only two ingredients will be assumed save where specific reference is made to the alternative.

When mass-producing material according to the invention, the ultraviolet-absorbing characteristic imparted to the material can easily be varied by changing the proportion of ultraviolet-absorbing substance in the applied coating mixture. The other ingredient can be selected with a view to influencing some other characteristic affecting the visible light and/or infra-red transmitting property of the material.

The invention is primarily concerned with the production of coated glass, and particularly glass in sheet form. Consequently sheet glass will be more particularly referred to as the coated material in the further description of the invention. However it should be kept in mind that other light-transmitting materials may be employed;, e.g. various plastic materials.

By means of the invention, glass products with a range of different optical properties can be produced on the basis of ordinary glass; the different optical properties required can be imparted by applying coating-layers of various compositions.

The dielectric coating layer comprising the ultraviolet-absorbing substance and having a refractive index higher than that of the glass, influences the surface reflectance of the product, and the invention is particularly suitable for use in the manufacture of products with anti-reflection and semi-reflection coatings In choosing the coating composition;, a selection can be made from various ultraviolet absorbing substances which have refractive indices higher than the refractive index of glass. By using in conjunction with a said ultraviolet-absorbing substance, a substance which has a refractive index higher than -that of glass and not very different from that of the ultraviolet-absorbing substance, the advantage can be realised that the optical thickness of the coating layer, which determines the light-reflectance, does not change very markedly with change in the proportion of ultraviolet-absorbing substance in the coating, even if such proportion is substantial. The dependency of one factor on the other is of course influenced by the extent of difference between the refractive indices of the different constituents · of the coating layer.

Preferably the refractive indices of the different constituents are equal or differ only to a small extent (say by not more than 0.5) so that the refractive index of the coating layer as a whole is not dependent or not dependent to any significant extent on the proportion of ultraviolet-absorbing substance in such layer. In such-cases, changes can easily be made in the course of mass-production manufacture so as to vary the ultraviolet-absorbing power (determined by the proportion of ultraviolet-absorbing substance in the coating) and/or the visible light and/or infra-red transmitting power (v;hich can be influenced by the other ingredient of the coating) while retaining a given reflectance characteristic.

In order to achieve this advantage in the case that the coating layer comprises two or more ultraviolet absorbing substances and/or two or more substances influencing the visible light and/or infra-red transmitting property of the material , it is of course necessary for the different ingredients in the same category, i.e., in the ultra-violet absorbing category or in the other category, to have the same or substantially the same refractive index.

In assigning a refractive index to a coating substance, it is the refractive index of a notional thin transparent coating layer formed from such substance, which is in question.

The ingredient used in conjunction with the ultraviolet-absorbing substance can be selected to influence any of a variety of optical properties of the material, e.g., its light-transmitting or reflecting power expressed as a percentage of incident light or its colour viewed by reflected or transmitted light. If the refractive index of said ingredient is similar to the refractive index of the selected ultraviolet-absorbing substance as above referred to, or if the proportion of ultraviolet-absorbing substance in the coating layer is to be very small, the thickness of a coating of the said ingredient required for achieving a given modification of the optical property in question, can be predetermined as if this ingredient were to be the sole ingredient of the coating layer, since the presence of the ultraviolet-absorbing substance will not significantly affect the refractive index of the layer.

The invention has been defined as including materials and articles. By way of example , sheet materials capable of being cut to required sizes , and articles such as single, double , or multiple glazing units incorporating one or more sheets of such material are envisaged.

Such materials and articles can be used in various situations where an ultraviolet screen is required, e.g., for protecting textiles from discolouration and fading or for protecting foodstuffs and pharmaceutical preparation from degradation.

The dielectric coating layer can be formed by deposition of the ingredients by methods knovm. per se, e.g., evaporation in vacuo ov by applying solutions of substances which can be converted to the required ingredients in situ, e.g., by heating. In mass-production manufacture the composition of a coating layer can be changed very quickly by bringing different electrodes into use, in the case that the evaporation technique is used, or by employing different coating solutions in the case that the wet process is used.

The ultraviolet absorbing substance is preferably an oxide. The following oxides are very suitable: manganese oxide, nickel oxide, iron oxide, cerium oxide, vanadium oxide, tungsten oxide, tellurium oxide, chromium oxide, cobalt oxide, cadmium oxide.

The foregoing ultraviolet-absorbing oxides have refractive indices which are between 1.8 and 2.3 an thus substantially higher than the refractive index of glass.

The ingredient used in conjunction with such ultraviolet-absorbing oxides may, e.g. be a sulphur compound. However, it is preferable for such ingredient also to be an oxide. Oxides with hig refractive indices which are very suitable for use in conjunction with the ultraviolet-absorbing oxides are: thorium oxide , aluminium oxide , zirconium oxide, antimony oxide, indium oxide, silicon oxide, tin oxide, tantalum oxide. These oxides have refractive indices between 1.7 and 2.-4. Another oxide which can be used in conjunction with an ultraviolet-absorbing oxide is titanium oxide. Titanium oxide is in fact the preferred oxide. It has a refractive index of between 2.1 and 2.3 according to the nature of the deposition of the thin coating. Titanium oxide has the advantage that it is capable of forming thin layers which are resistant to abrasion and do not require to be protected.

According to preferred embodiments of "the invention, the dielectric coating layer incorporating the ultraviolet-absorbing substance forms one of two or more coating layers constituting an interference assembly which reflects a portion of incident radiation. Thus the invention may be applied in the production of semi-mirrors with desirable properties in both the visible and infra-red regions of the spectrum. By a careful selection of the thicknesses of the layers, glazings which screen off ultraviolet light and also have anti-heat properties can be produced, such glazings having any of a variety of colours in transmission and 3?eflection according to choice. The optical thickness of each coating layer of a said interference assembly is preferably equal to a quarter of the wave-length of the radiation which it is desired to reflect to the maximum extent, or to an integral multiple of a quarter of such wave-length.

By way of example of the use of the invention in a sheet material with a plural layer coating, such material may bear a first coating layer of titanium oxide incorporating an oxide which absorbs ultraviolet radiation, a second coating layer of silicon dioxide and a third coating layer of titanium oxide. Alternatively, the titanium oxide layer containing the oxide which absorbs ultraviolet radiation may be the outermost of the three layers, in γ/hich case different optical characteristics are obtained.

The invention can also be utilised in the preparation of coated sheet materials with plural layer anti-reflection coatings. Such a material may, e.g., comprise a sheet of glass bearing a first coating layer of silicon dioxide and titanium oxide, a second coating layer comprising titanium oxide and an oxide which absorbs ultraviolet radiation and a third coating layer of silicon dioxide, the refractive indices of the first and third layers and the glass being related according to the equation: nexternal layer.nglaefl = n2 first layer, where n in each case represents the refractive index of the glass or of the indicated layer as the case may be. When this condition is observed, surface reflectance is reduced to a low value and there is little or no sensible effect on the colour of the transmitted light.

The invention can also be employed in the manufacture of sheet materials with double-layer anti-reflection coatings. For example such a material may comprise a first coating layer of titanium oxide and an oxide which absorbs ultraviolet radiation and a second coating layer of silicon dioxide.

Certain examples of the invention will now be given. These examples have reference to the accompanying drawings , wherein: Fig. 1 is a cross-sectional view of part of a glazing material, Fig. 2 is a cross-sectional viev of part of another glazing material;, Fig. 3 is a cross-sectional view of a double glazing units, ancL Fig. k. is a cross-sectional view of a triple glazing unit .

ExampleJl This example relates to a material as shown in Fig. 1 comprising a sheet of glass 1 bearing a single coating-layer 2. The thin coating layer is formed by a mixture of titanium oxide and iron oxide. The iron oxide is the ultraviolet-absorbing component. To form the coating , a solution is prepared by adding 200 cc of titanium isopropyl and 20 cc of water to one litre of ethyl alcohol. To the solution thus obtained, 1 litre of an alcoholic solution containing 80 grammes of FeCl^.6 E^O is added. One face of the sheet of glass is coated with the solution and then dried in a furnace at a temperature of about 150°C for five minutes and fired at a temperature of about --00oC. The refractive index of the continuous film thus deposited is 2.2, i.e., between the values of 2.1 and 2.3? obtained when using titanium oxide on its own.

A coating having an optical thickness of 180 nu can be deposited in this way. The resulting anti-ultraviolet glazing has an energy transmission of.30 .in the ultraviolet and the near visible region, for a light transmission of 57$. The colour of the glass in transmission is light yellow, while it has a brilliant reflection.

For a coating having an optical thickness of 270 ι 9 the energy transmission in the ultraviolet and the near visible region drops to 13%. The colour of the glazing in transmission is deep yellow; the reflection has a slightly bluish-purple tint.

E aij)le,..

This example relates to an alternative way of forming a material as shown in Fig. 1. The sheet of glass is introduced into an evacuated enclosure containing filaments for the simultaneous deposition of silicon monoxide and vanadium oxide. A thin transparent coating of silicon monoxide has a refractive index of 1.97 j while a thin transparent coating of vanadium oxide has a refractive index of 2. By depositing the two oxides together, a coating is formed having a refractive index rather higher than 1.97. The resulting product has a yellowish colour. ¾mjDle,. Jl This example relates to the production of a material as shown in Fig. 2 comprising a sheet of glass 3 bearing three coating layers 1+, 5 and 6 which form an interference assembly. The first coating layer is produced by treating the sheet 3 with the solution described in Example 1 to deposit a continuous coating comprising titanium oxide and iron oxide. The second coating-layer 5 is a coating of silicon oxide formed by applying a solution containing 125 cc of methyl orthosilicate and 110 cc of distilled water per litre of ethyl alcohol.

The drying and firing times are similar to those used in Example 1 for the layer of titanium oxide and iron oxide. The third coating layer 6 is a layer of pure titanium oxide formed by applying a solution containing 200 cc of titanium isopropyl and 20 cc of distilled water per litre of ethyl alcohol used as a solvent, and drying and firing.

An anti-ultraviolet glazing having outstanding anti-heat properties is obtained for optical thicknesses of the layers 2+—6 of 190, 225 and 230 mu respectively.

The infra-red reflection is 5%9 while the energy transmission in the ultraviolet and the near-visible region is 17%. In transmission the glazing has a yellowish-green colou J the reflection varies from light purple to light green over the range from perpendicular reflection to oblique reflection.

Ej¾amp_le. l By reversing the order used in Example 3 of the different coating layers, an anti-ultraviolet glazing is produced which also has anti-heat properties, but has different colours viewed in reflection.

A first titanium oxide layer having an optical thickness of 230 m^u is deposited on a sheet of glass and thereafter a silicon dioxide layer of 215 mu and a layer of titanium oxide and iron oxide of 225 m i in. optical thickness are applied in succession. The resulting glazing has an energy transmission in the ultra-violet of l % and the reflection in the infra-red is 1+6%. The colour of the glass in transmission is yellowish-brown; the colour in reflection has a brilliant blue tint.

E ample ^ By depositing thin coating layers as in Example , but with different optical thicknesses , an anti-ultraviolet glazing is produced showing simply an attenuated light transmission. Thus, when the optical thicknesses are 210 nyu for the first layer of titanium oxide, Hj mu for the layer of silicon oxide and 120 nyu for the layer of iron oxide and titanium oxide, the energy transmission of light is 1+0%, while that of ultraviolet radiation is 25 . The glazing is green in transmission and yellowish-purple in reflection, An anti-ultraviolet glazing having non-reflecting properties is produced by depositing on a sheet of glass a first coating layer formed by a mixture of titanium oxide and silicon dioxide, a second coating layer of titanium oxide and iron oxide, and a third coating layer of silicon dioxide. Titanium oxide is incorporated with the silicon dioxide in the first layer so that the folloviriung refractive index relationship applies: 2 nexternal ,layer,nglanss = n first layrfer,' where n is the refractive index of the glass or of the indicated layer as the case may be. When the three layers have optical thicknesses of 11+0, 270 and 170 n i respectively, the light reflection is 0.6%.

An anti-ultraviolet glazing which has low reflecting properties is produced by applying only two thin coating layers. The resulting glazing is less satisfactory than v/hen applying three layers but the product is less expensive. Thus, the light reflection can be reduced to 2% by applying a layer of titanium oxide and iron oxide of 275 n u optical thickness, and then a layer of silicon dioxide with an optical thickness of 11+0 mu . If the iron oxide content of the first layer is increased so that the iron oxide is preponderant, the light reflection reaches 3%.

The foregoing examples show that it is possible to produce a variety of glazings having anti-ultraviolet properties by incorporating an ultreaviolet-absorbing substance in a thin transparent dielectric coating layer. Depending on the composition of the coatings , different optical effects are obtained, such as an increase or reduction in reflection, variations of colour in transmission and reflection, and attenuation of light transmission. The examples refer to materials with one or more coating layor(s) applied to only one face of the glass. It will be clear that both faces can be coated, in which case, when a solution is used for forming the coatings, it is preferable to immerse the sheet into the solution. Sheets of glass coeited with one or more transparent layers, either on one face or both, can be used as single glazings, or form one or more elements of double or multiple glazings, e.g. as shown in Figs. 3 and k» Fig. 3 shows an anti-ultraviolet double-glazing unit comprising a first sheet of glass 7 according to the invention, one face of which bears a layer 8 which absorbs ultraviolet radiation. The layer can be the only layer applied to the sheet or it can constitute one layer of an interference assembly. The coated glass sheet 7 is connected to a sheet of glass 9 by means of a fluid tight joint 10 to form the double glazing unit.

The ultraviolet-absorbing layer is disposed on the inside, between the two sheets of glass. Fig. 1+ shows a triple-glazing unit according to the invention comprising a glass sheet 11 bearing coatings 12 and 13 on its opposite faces, and two uncoated sheets ΙΙ+, 15» The sheet 11 is used as the middle one of the three sheets so that both coatings are protected. The sheets are connected by fluid-tight joints 16. A sheet of glass 11 according to the invention and coated on only one face can likewise be used as the middle sheet of a triple glazing unit.

While the invention has been described with particular reference to glazings, other materials and articles are included. For example the invention includes lenses of sunglasses comprising pieces of glass or other light-transmitting material bearing an ultraviolet-absorbing coating as herein defined.

Another potential field of application of the invention is the treatment of glass containers for products which have to be protected from ultraviolet radiation, such as some foodstuffs and chemical or pharmaceutical products.

Claims (3)

1. HAVING HOW particularly describes and ascertained the nature of our said invention and in what manner ae same is to be performed, we declare that what we claim isi 1. A material or article comprising at least one piece, of glass or other light-transmitting material bearing a light-transmitting dielectric coating layer with a refractive index higher than that of said material, which coating layer incorporates at least one substance which absorbs ultraviolet light and at least one substance which does not absorb ultraviolet light or not to any significant extent.

2. A material or article according to claim 1 wherein said dielectric coating layer is composed of two substances, one of which appreciably absorbs ultraviolet light and the other of which substantially influences the visible light and/or infra-red transmitting property of the material or article and has a refractive index the same as or close to that of said ultraviolet-absorbing substance so that the refractive index of the coating as a whole is not dependent or not dependent to any significant extent on the proportion of ultraviolet-absorbing oxide in the coating.

3. A material or article according to claim 2, but modified in that the said coating layer comprises two or more substances which appreciably absorb ultraviolet light and have the same or substantially the same refractive index, and/or in that the said coating comprises two or more substances which substantially influence the visible light and/or infra-red transm tting property of the material or article and which have the same or substantially the same index of refraction as each other. l A material or article according to claim 2 or 3 wherein the refractive indices of the ultraviolet-absorbing and substantially non-ultraviolet-absorbing substances differ by not more than 0.5. 5. material or article according to any preceding claim wherein said dielectric coating layer incorporates an ultraviolet-absorbing oxide. 6. A material or article according to claim 5 wherein said dielectric coating layer incorporates an ultraviolet-absorbing oxide of manganese, nickel, iron, cerium, vanadium, tungsten, tellurium, chromium, cobalt or cadmium. 7. A material or article according to any preceding claim wherein said dielectric coating layer incorporates a substantially non-ultraviolet-absorbing oxide. 8. A material or article according to claim 7 wherein said dielectric coating layer incorporates titanium oxide. 9. A material or article according to claim 7 wherein said dielectric coating layer incorporates an oxide of thorium, aluminium, zirconium, antimony, indium, silicon, tin or tantalum. 10. A material or article according to any preceding claim wherein said dielectric coating layer is . one of two or more coating layers borne by said light-transmitting material and constituting an interference assembly which reflects a portion of incident radiation. 11. A material or article according to claim 10 wherein said piece of light-transmitting material bears a coating layer incorporating titanium oxide and an ultraviolet-absorbing oxide, a coating layer of silicon dioxide and a coating layer of titanium oxide. 12. A material or article according to claim 11 wherein the coating layer incorporating titanium oxide and an ultraviolet-absorbing oxide is in contact with said piece of material. 13. A material or article according to claim 11 wherein the coating layer incorporating titanium oxide and an ultraviolet-absorbing oxide is the outermost coating-laye . Ik, A material or article according to any of claims 1 to 9 wherein said dielectric coating layer is one of two or more layers of a plural-layer anti-reflection coating borne by said piece of material. 15. A material or article according to claim Ik wherein said piece of material is glass and bears a first coating layer incorporating silicon dioxide and titanium oxide, a second coating layer incorporating titanium oxide and an ultraviolet-absorbing oxide, and a third coating layer of silicon dioxide, the refractive indices of the first and third coating layers and the glass being related according to the equation: ne∑teEriQl layer.nglaes = n2 first layer, where n in each case represents the refractive index of the glass or the indicated layer as the case may be. 16. A material or article according to claim Ik wherein said piece of material bears a first coating layer incorporating titanium dioxide and an ultra-violet-absorbing oxide and a second coating layer of silicon dioxide. 17. A material or article according to any preceding claim wherein said piece of light-transmitting material is sheet glass. 18, An article according to any preceding claim, being a single, double or multiple glazing unit. 19. A material or article substantially as herein described with reference to the accompanying drawings. DADIB 2H2S 1 h day of November, 19S6. P.O.BOX 1169» SBWVIV Attorneys for Applicants light and have the same or substantially, the same · refractive index, and/or in that the said coating comprises two or more substances which substantially influence the visible light and or infra-red transmitting property of the material or article arid which have the same or substantially the same index of refraction as · each other.