Lamp coated with an iron-oxide pigment, organic coloring material and silicon-oxygen compound layers

#The invention relates to a colored luminaire, in particular a colored signal luminaire for motorcars, which includes a lamp and a cover, wherein the lamp comprises a bulb provided with a coating including a layer containing an iron-oxide pigment.

#Colored luminaires are used at different locations in motorcars, where they are used, for example, for brake lights, turn signal lamps and fog lamps. In conventional, colored luminaires the bulb of the lamp is made of clear glass and the lamp is arranged under a colored, generally red or yellow, luminaire cover. More recently, there is a tendency to use, for the colored luminaires, colored lamps under a cover that is either colorless or of a uniform neutral color. This enables signal lamps of different colors to be mounted as a lamp ensemble under a uniform cover.

#Luminaires comprising colored lamps under a cover that is either colorless or of a uniform neutral color have the advantage that they enable a flexible, optically attractive design for integrated front and rear luminaires. In addition, they are cheaper than luminaires having a multicolor housing or multicolor covers. In addition, these luminaires contribute to a higher traffic safety because the difference between the “on” and the “off”-state of the lighting at daylight can be more readily distinguished with lights comprising colored lamps situated under a cover which is either colorless or of a neutral color.

#To manufacture the bulb coating, first a dispersion of 15.0 wt. % transparent iron-oxide pigment PR 101, 0.75 wt. % sodium polyacrylate as the dispersing agent, 0.075 wt. % (?) polyethylene propylene oxide as the anti-foaming agent are wet grounded with water in an agitated grinder until the agglomerated pigment is dispersed. The purified and baked lamp bulbs are immersed in this dispersion and subsequently burned in at 480° C. A quantity of 180 g tetraethylorthosilicate is mixed with 2077 g ethanol, 146 g 1 n hydrochloric acid and 27 ml of an anionic surface-active agent. The precoated lamp bulbs are immersed in this mixture and baked at a temperature of at least 450° C. so as to convert tetraethylorthosilicate into a silicon dioxide layer. Subsequently, the lamp bulbs thus pretreated are immersed in a 25% solution of SY 82 in xylene containing cellulose nitrate, alkyd resin and trkesyl phosphate in a ratio of 1:0.5:0.6, and subsequently dried.

#The coated lamp is exposed to an accelerated thermal load test, where the lamp is permanently exposed to a temperature of 250° C. Within a period of 500 hours, the color location changed only to a very small degree within the color specification range determined by the E.C.E. and S.A.E.