is further subjected to mixing and then firing baking for 3 to 7 hours in a reducing atmosphere consisting of a mixed gas of n 2 h 2 at a temperature ranging from 1000 to 1600 u00b0 c a first fired product thus obtained is pulverized and again placed into a vessel with respect to the degree of pulverization there is not any particular limitation namely the pulverization can be performed by mortar to such an extent that agglomerates that have been generated due to the firing can be pulverized to increase the surface area of the fired powder the pulverized powder is again placed in a furnace which is then purged with nitrogen gas in vacuum the vacuum on this occasion should preferably be 1000 pa or less if the degree of vacuum is higher than 1000 pa the water adhered onto the raw material cannot be removed then the aforementioned first fired product is further subjected to firing for 2 to 6 hours in a reducing atmosphere consisting of n 2 h 2 and having a hydrogen concentration of 5 to 100 at a temperature ranging from 1000 to 1600 u00b0 c the fired product thus obtained is pulverized by mortar and sieved using a sieve of suitable mesh size thereby obtaining a fluorescent particle consisting of an alkaline earth ortho silicate represented by the aforementioned general formula 2 the fluorescent particle according to.