Method for producing zinc sulfide based phosphor

A method for producing a zinc sulfide based phosphor, comprising:

• firing a mixture comprising a zinc sulfide based phosphor precursor, sulfur, and a chlorine-containing flux to obtain a fired product;
• and
• firing the fired product,
• wherein the firing of the mixture comprises:
• heating the mixture in an atmosphere into which oxygen is introduced such that a temperature of the mixture is increased from normal temperature to a first temperature in a range of 800° C. to 850° C., inclusive, at which a transformation of a crystal system of the phosphor precursor is initiated;
• when a temperature of the mixture is increased above the first temperature, switching the atmosphere to a nitrogen atmosphere and continuing the heating of the mixture;
• and when the temperature of the mixture reaches a temperature in a range of 1000° C. to 1200° C., inclusive, maintaining the temperature of the mixture at a constant level and thereafter rapidly quenching the mixture and washing the mixture to obtain a fired product;
• and
• wherein the firing of the fired product comprises:
• heating the fired product in the nitrogen atmosphere such that a temperature of the fired product is increased from normal temperature to a temperature in a range of 650° C. to 1000° C., inclusive;
• and when a temperature of the fired product reaches the temperature in the range of 650° C. to 1000° C., inclusive, introducing oxygen while maintaining the temperature of the fired product and thereafter rapidly quenching the fired product and washing the fired product to obtain a zinc sulfide based phosphor.