Metal halogen vapor lamp provided with a heat reflecting layer

Abstract

The invention relates to a metal halogen vapor lamp with a discharge tube coated on surfaces adjacent to its electrodes with a heat reflecting layer. The discharge space comprising a discharge tube is made of a material which is permeable to light, preferrably quartz. The discharge space is between electrodes having a high melting point. An arc discharge takes place in the discharge space between the electrodes. The discharge space contains a metal of high vapor pressure at operational temperatures, a noble gas and, as additives, at least one metal and a halogen which forms a halogen compound with said metal. There is a heat reflecting layer with advantageous properties at one or both ends of the discharge tube of a material of high melting point, preferably quartz. The characteristics of said layer differ in many respects from the properties of previously known heat reflecting layers since it is bound to the surface of the quartz discharge tube by an inorganic binding material. The heat reflecting layer prepared in accordance with our invention comprises as heat reflecting materials, zirconium oxide, cobalt aluminate, quartz wool or combinations thereof which are fixed or bound onto the discharge tube by means of magnesium oxychloride, known as Sorel-Cement. The binder remains on the discharge tube even after the tube is burnt.