White light emitting device with red and green-yellow phosphor

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):

A a (M 1-s ,Mn s )F b   (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<s≦0.05,

the green-yellow fluorescent material has a composition of formula (2) or (3):

(Y 1-u-v ,Gd u ,Ce v ) c (Al 1-w ,Ga w ) 5 O d   (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,

(Ba x ,Sr 1-z ,Ca y ,Eu z ) e SiO f   (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<z≦0.15, and

wherein the white light emitting device has an Ra value from 86 to 90 and a white efficiency from 196 to 218 lm/excitation light W.

2. The device according to claim 1 , wherein the red fluorescent material has an internal quantum efficiency η′ of 60% or more.

3. The device according to claim 1 , wherein the green-yellow fluorescent material has an internal quantum efficiency η′ of 85% or more.

4. The device according to claim 1 , wherein the fluorescent layer is formed by dispersing the red fluorescent material and the green-yellow fluorescent material in a resin.

5. The device according to claim 4 , wherein the red fluorescent material and the green-yellow fluorescent material are dispersed at a ratio of 5 wt % or more and 50 wt % or less in the resin.

6. The device according to claim 1 , wherein a surface coating process is applied to the red fluorescent material and the green-yellow fluorescent material.

7. The device according to claim 1 , wherein a color temperature of the white light emitting device is a bulb color.

8. The device of claim 1 , wherein the green-yellow fluorescent material has a composition of formula (2).

9. The device of claim 1 , wherein the green-yellow fluorescent material has a composition of formula (3).