Method of producing transparent heat reflecting layers of tin oxide on glass

The invention relates to a process for the production of transparent thermally reflective layers of tin oxide on a glass substrate.

One of the ways to reduce energy consumption for heating buildings in winter is to reduce heat leakage from the rooms through the windows to the exterior by means of thermally reflective transparent thin layers on the glass. These layers reflect the long-wave heat radiation back into the room and thereby improve the thermal insulation properties of the windows. Very advantageous and recently intensively developed types of heat reflective layers are semiconductor layers based on tin oxides Sn or indium In, doped to increase reflectivity by suitable electrically active impurities, most often fluorine F or antimony Sb.

There are a number of methods of applying these layers. The most preferred and also most commonly used are thermal decomposition of a suitable compound which is brought into contact with the surface of the heated glass either in liquid (aerosol spraying, dipping and soaking, pouring, etc.) or in the gas phase (scrubbing the surface with gas mixtures). The principle of this method has been known for a long time, according to U.S. Patent No. 2,564,708, a variety of combinations of heat reflective oxide layers can be formed by hydrolyzing metal salts. Further improvements of this process, including improved methods of construction of the necessary equipment, are disclosed, for example, in German Patent No. 2,716,183, France No. 2,348,167, United Kingdom No. 1,506,668, Australia No. 482,853 and USSR No. 269,226 .

The most important requirement for the properties of the thermal reflective layers is to achieve the highest possible value of infrared reflectance with a reduced visible transmission. The known methods solve the problem of maximum reflectance in the infrared range by selecting the appropriate concentration of electrically active impurities, which is determined experimentally. It is known that the fluorine F or antimony Sb content must be kept within certain limits, lower or higher concentrations lead to a decrease in reflectance or a sharp decrease in visible transmission.

However, as has now been determined by a series of experimental tests, the optimum concentration of electrically active impurities is not a constant but depends on the deposition temperature. At different application temperatures, maximum infrared reflectivity and visible »transmittance for» different admixture concentration values ​​are achieved. If the fluorine F or antimony Sb content is determined irrespective of the deposition temperature, as shown in the prior art methods, there is no guarantee that maximum infrared reflectivity and visible transmittance are achieved in all cases.

The disadvantages of the present invention are eliminated by the process for producing transparent thermal reflective layers of Sn tin oxide according to the invention, which comprises contacting a heated glass surface with a medium comprising at least one decomposable organic or inorganic tin Sn compound and at least one decomposable electrically active additive compound. fluorine F and antimony Sb, for a time sufficient to form a layer of Sn, wherein the exact value of the dopant concentration is chosen in the range of 0.5 to 5% by weight depending on the glass heating temperature. The deposition temperature is not fixed in advance; In addition to the type of starting compounds, it is also governed by the deposition technology, the composition of the base glass, its viscosity and other parameters. The combination of these effects results in a certain temperature value at which the glass will be heated when the layers are applied. And only on the basis of this temperature, the exact concentration of impurities - fluorine F or antimony Sb - is determined experimentally (by measuring the reflectivity of a series of samples with variable content of electrically active ingredient) so that the layers have the highest infrared reflectivity.

The thermally reflective glass according to the invention is suitable for use in thermally insulating glazing of buildings, thereby reducing heat loss from the room to the environment in winter. Energy savings can be achieved in the case of double glazing units with reflective layers up to about 50 ° / o.

More detailed features of the invention are best elucidated by several examples of the preparation of a heat reflective sheet on a flat glass.

He did

Float glass with a thickness of 3 mmi is heated to a temperature of 640 ° C and for 10 seconds a solution is sprayed onto the surface with the aid of an air spray gun resulting from the mixing of 100 grams of tin (II) dichloride (100 ml of distilled water H2O and 3.9 g). ml of HF. On the glass, a tertiary tin oxide layer is formed »SnO2 with a mass content of 2.5 ° / o of fluorine F with a uniform light green color in reflection, with a transmission in the visible part of the spectrum in the range of 70-87%. 70 - - 80

Example 2

Float glass of 3 mm thickness is heated to 650 ° C and a solution formed by mixing 100 grams of stannous dimethyl chloride (CH3) 2SnCl2, 100 ml of distilled H2O and 5.2 ml is sprayed onto the surface for 8 seconds with an air spray gun. HF. A homogeneous layer of tin (II) SnO2 with a mass of 3,5% fluorine F with a uniform light green color in reflection, with a transmission in the visible part of the spectrum ranging between 70 and 85%, is reflected on the glass and reflects220175 - 80%.

Example 3

Float glass with a thickness of 5 mm is heated to a temperature of 580 ° C and a mixture of tin tetrachloride vapor and antimony trichloride is fed to the surface for 6 s.

SbCl 3 in a weight ratio of 1: 0.8. A homogeneous layer of tin (II) SnO2 with a content of about 1% antimony Sb with a uniform light green color in reflection, with a transmission in the visible part of the spectrum in the range of 70-80% and with a reflectance in the 5-12 µm range .