U.S. Philips Corporation

Johannes H Schmitz

Gustaaf H Van Der Hoorn

Caspert G Van Der Staak

Piet Wiedijk

Franciscus J Swinkels

Rudolfus J Bannenberg

Antonius Henricus Van Der Stap

Joseph J Lamberts

The projection screen has a transparent substrate having a front surface which is provided with mutually parallel ribs. Light-absorbing particles 7 whose size is 20 to 75% of the width of the grooves measured halfway the depth of these grooves, are disposed at the bottom of the grooves 4 between the ribs 2. The particles are fixed by means of a glue layer 6.

Transmission projection screen and method of manufacturing same

In a method of preparing a luminescent aluminate comprising aluminium and one or more of the metals yttrium and elements of the lanthanum series the component metals of the aluminate are co-precipitated from aqueous solutions of salts of these metals by combining these salts with a precipitation agent comprising carbon dioxide and ammonia in a quantity from 1 to 3 mole per mole of carbon dioxide. Such a quantity of the precipitation agent is used that the molar ratio of the carbon in the precipitation agent to the sum of the metals in the salts has a value from 1 to 10, a higher value in that range being chosen for this ratio according as the desired average grain size of the precipitate is larger. Finally, the precipitate obtained is heated at an elevated temperature.

Method of preparing a luminescent aluminate

A high-pressure gas discharge lamp having a discharge vessel of aluminium oxide or yttrium oxide. Disposed within the discharge vessel is an electrode which is connected to a vacuum tight led-out current supply conductor which consists mainly of borides from the group consisting of titanium boride and zirconium boride.

High-pressure gas discharge lamp

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Eindhoven, Netherlands

Johannes H Schmitz