| abstract |
A white light source comprises an insulating substrate, a light emitting diode chip arranged on the insulating substrate and emitting ultraviolet light having a wavelength of 330-410 nm, and a phosphor layer formed to cover the light emitting diode chip and containing a red light emitting phosphor, a green light emitting phosphor and a blue light emitting phosphor dispersed into a transparent cured resin as a phosphor, wherein t and L satisfy a relation 3.2≤t/L, assuming the shortest distance between the surface of the phosphor layer and the outer circumference of the light emitting diode chip is t (mm), and an average free path defined by the following expression (1) is L (mm);nL=1/(n·σ) (1)n(n: number of phosphors per unit volume (pcs/mm 3 ), σ: average cross-section area of phosphors in the phosphor layer (mm 2 )). The white light source has good distribution properties of luminous intensity. |