White light emitting device with red and green-yellow phosphor

摘要

A white light emitting device includes a light emitting element having a peak wavelength at from 430 nm to 460 nm; and a fluorescent layer on the light emitting element containing a red fluorescent material and a green-yellow fluorescent material. The white light emitting device achieves high color rendering properties, a high average color rendering index Ra and a high luminescent efficiency, or a high white efficiency.

主权项

1. A white light emitting device, comprising:
a light emitting element having a peak wavelength in a wavelength range of 430 nm or more and 460 nm or less; and a fluorescent layer formed above the light emitting element and contains a red fluorescent material and a green-yellow fluorescent material, wherein when a peak wavelength of a fluorescent material, a full width at half maximum of light emitted from a fluorescent material, an effective wavelength width of a spectrum for light emitted from a fluorescent material, and an external quantum efficiency of a fluorescent material are respectively denoted by λp, FWHM, EWW, and η, the red fluorescent material has the characteristics of:
625 nm≦λp≦635 nm; 15 nm≦EWW≦45 nm; and 40%≦η≦η≦75%, the green-yellow fluorescent material has the characteristics of:
545 nm≦λp≦565 nm; 95 nm≦FWHM≦110 nm; and 75%≦η≦90%, the red fluorescent material has a composition of formula (1):
Aa(M1-s,Mns)Fb  (1) wherein, in formula (1), A is at least one element selected from K (potassium) and Cs (cesium), M is at least one element selected from Si (silicon) and titanium (Ti), and a, b, and s are numerical values which respectively satisfy 1.7≦a≦2.1, 5.3≦b≦6.3, and 0(Y1-u-v,Gdu,Cev)c(Al1-w,Gaw)5Od  (2) wherein, in formula (2), c, d, u, v, and w represent numerical values which respectively satisfy 2.8≦c≦3.2, 11.5≦d≦12.5, 0≦u≦0.2, 0.02≦v≦0.15, and 0≦w≦0.3,
(Bax,Sr1-z,Cay,Euz)eSiOf  (3) wherein, in formula (3), e, f, x, y, and z represent numerical values which respectively satisfy 1.9≦e≦2.1, 3.6≦f≦4.1, 0.15≦x≦0.4, 0≦y≦0.1, and 0