Patent ID: 7129629

Claim:
A light source comprising: a fluorescent lamp that contains a phosphor layer emitting light whose peak emissions are in four wavelength ranges of 440 nm to 470 nm, 505 nm to 530 nm, 540 nm to 570 nm, and 600 nm to 620 nm; and wherein at least 70 wt % of the phosphor layer is a combination of: a phosphor containing bivalent europium as an emission center and having a peak emission in a wavelength range of 440 nm to 470 nm; a phosphor containing bivalent manganese as an emission center and having a peak emission in a wavelength range of 505 nm to 530 nm; a phosphor containing trivalent terbium as an emission center and having a peak emission in a wavelength range of 540 nm to 570 nm; and a phosphor containing trivalent europium as an emission center and having a peak emission in a wavelength range of 600 nm to 620 nm, and the light source emitting light whose whiteness W is no smaller than 65 obtained when the light emitted by the light source is reflected from a blank surface of a newspaper, the whiteness W being calculated using an equation (7), W =−3.3 C +100 (7) wherein C is chroma of the light emitted by the light source, calculated with a method defined by the CIE 1997 Interim Color Appearance Model (Simple Version); emitting light whose chromaticity is, on the CIE 1931 chromaticity diagram, in a range expressed by two equations (8) and (9); and emitting light whose visual clarity index is no smaller than 110: y ≧−2.63 x 2 +2 63 x −0.263 (8) y ≧−3.09 x +1.22 (9), wherein the light emitted by the light source has a correlated color temperature T[K] satisfying an inequality (4) related to a ratio of a radiant energy Qv in a wavelength range of 380 nm to 780 nm to radiant energy Qg in a wavelength range of 505 nm to 530 nm, Qg/Qv ≧−0.11×10 4 /T +0.30 (4).