Tungsten Oxide Coating for Solar Control Glass

Solar control glass is the glass that transmits the total incident radiation energy (total solar heat) through a high percentage of incident light and a low percentage of total incident radiation energy. One way to produce such glass is to deposit coatings containing one or more layers of various materials, especially metal oxides, such as tungsten oxide, on the glass, which are usually of sub-micron thickness.

For the coating process, the growth rate of high coating is expected. In order to obtain this high growth rate in the chemical vapor deposition of tungsten oxide layer, it is necessary for tungsten compounds to have high volatility (which helps to obtain a good shift of tungsten compounds to the glass surface) and good thermal stability (which reduces thermal decomposition before reaching the glass surface). Therefore, the researchers introduced the air flow of tungsten halide or tungsten chloride and oxygen source to the surface of glass substrates, and deposited tungsten oxide coatings on the surface of glass substrates.

1.In the glass production process, the moving float glass strip is coated by the laminar flow chemical vapor deposition process in the tank. The width of the coated glass strip is 10 cm, and then the silica bottom layer is deposited on the glass by the water-cooled graphite head coater at 0.

2.Deposition of tungsten oxide coatings: the precursor gas mixture is formed by mixing WOCl₄ with the precursor gas mixture, supplementing 5.5 liters/minute nitrogen, and adding oxygen to dilute the precursor gas mixture. The diluted precursor gas mixture is transported to the reactor through the equipment pipeline, which maintains the temperature at 200 ℃. The diluted precursor gas mixture is introduced into the heated glass substrate in the reactor, resulting in the deposition of tungsten oxide coating.

The deposition process lasts for 10 or 30 seconds. At the end of the deposition process, the coated glass is cooled to room temperature in nitrogen. The thickness of tungsten oxide coating was measured by standard optical and/or contact tip method. Tungsten oxide layer can be covered by other coatings, which can be metal oxide layer, preferably fluorine doped tin oxide. Because tin oxide can prevent degradation of tungsten oxide, and if the other layer is fluorine doped tin oxide, it has additional advantages of providing solar control coatings, with low emissivity (high infrared reflection), and whether tungsten oxide layer can be used from halogen tungsten oxide or tungsten chloride or other substances.

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