Patent ID: 7635438

Claim:
A europium-activated alkaline earth orthosilicate luminescent material comprising: a compound having a composition represented by a following formula 1 and showing an emission band having a peak wavelength of 600 nm or more when the compound is excited by ultraviolet radiation having a wavelength of 254 nm: (Sr x Ba y Ca z Eu w ) 2 SiO 4 formula 1 wherein, x, y, z and w satisfy following relational expressions 2, and 4 to 7, and are values satisfying the expression 3 when a, b, c and d are assumed to be 573, 467, 623 and 736, respectively: x+y+z+w= 1 expression 2 600≦ ax+by+cz+dw expression 3 0≦ x /(1− w )≦0.95 expression 4 0≦ y /(1− w )≦0.4 expression 5 0< z /(1− w )≦0.95 expression 6 0.02≦w≦0.2 expression 7.