Process for preparing luminescent materials

Claim 1

A PROCESS FOR PREPARING SUBMICRON PARTICLES OF A LUMINESCENT SILICATE COMPRISING: (1) MECHANICALLY MIXING PARTICLES OF A BULKY FORM OF SILICA AND PARTICLES OF AT LEST ONE OTHER REACTANT IN PROPORTIONS WHICH REACTOT PRODUCE SAID LUMINESCENT MATERIAL, SAID SILICA HAVING AN APPARENT DENSITY SUBSTANTIALLY LESS THAN THE REAL DENSITY THEREOF, SAID MIXING BEING CONDUCTED IN A DRY MEDIUM BY TUMBLING SAID REACTANTS IWTH OBJECTS OF A RESILIENT MATERIAL, (2) HEATING SAID MIXTURE FOR A TIME AND AT TEMPERATURES SUFFICIENT TO FORM SINTERED AGGREGATES OF CRYSTALS OF SAID LUMINESCENT MATERIAL, SAID HEATING BEING CONDUCTED TO PRODUCE A MINIMUM OF SINTERING BETWEEN THE CRYSTALS OF SAID LUMINESCENT MATERIAL, AND THEN (3) IMMERSING SAID AGGREGATES IN A LIQUID MEDIUM, IMMERSING A DISC OF A RESILIENT MATERIAL IN SAID MEDIUM, AND THEN ROTATING SAID DISC ABOUT ITS AXIS IN SAID MEDIUM AT A SPEED WHEREBY SAID AGGREGATES ARE BROKEN APART SUBSTANTIALLY ENTIRELY AT THE AREAS OF CONTACT BETWEEN ADJACENT CRYSTALS.