Wavelength conversion member and light-emitting device
Provided is a wavelength conversion member in which the following are dispersed in a thermoplastic resin: a LuYAG fluorescent material that is represented by (Y 1-α-β Lu α Ce β ) 3 Al 5 O 12 (in which α is a positive number between 0.3-0.8 inclusive and β is a positive number between 0.01-0.05 inclusive), that emits yellow-green light as a result of excitation by blue light, and that has a diffraction peak within a range in which the diffraction angle 2θ in X-ray diffraction by the K α1 line of Cu is 52.9° to 53.2° inclusive; and a KSF fluorescent material that is represented by K 2 (Si 1-x Mn x )F 6 (in which x is a positive number between 0.001 and 0.3 inclusive) and that emits red light as a result of excitation by blue light. The content of the KSF fluorescent material in the wavelength conversion member is 1 to 5 times the content of the LuYAG fluorescent material by mass ratio. The wavelength conversion member makes it possible to provide a light-emitting device that has small color deviation, that is suitable as a lighting device, that emits white light, and that has good color rendering properties in a color temperature range of 4,000-6,500K, i.e., the color temperature range from white to daylight color.
1. A wavelength conversion member comprising a phosphor dispersed in a thermoplastic resin, the phosphor comprising
(A) a cerium-activated lutetium-yttrium-aluminum garnet phosphor represented by the compositional formula (1):
(Y 1-α-β Lu α Ce β ) 3 Al 5 O 12 (1)
wherein α is a positive number of from 0.3 to 0.8 and β is a positive number of from 0.01 to 0.05, capable of emitting yellow-green light upon excitation with blue light, and having a diffraction peak within a diffraction angle 2θ range of from 52.9° to 53.2° in X-ray diffraction by the K α1 line of Cu, and
(B) a manganese-activated silicon complex fluoride phosphor represented by the compositional formula (2):
K 2 (Si 1-x Mn x )F 6 (2)
wherein x is a positive number of from 0.001 to 0.3, and capable of emitting red light upon excitation with blue light,
in a weight ratio of the phosphor as component (B) to the phosphor as component (A) of from 1/1 to 5/1.
2. The wavelength conversion member of claim 1 wherein the phosphor as component (A) has an outer appearance color having an a* value of from −23.0 to −21.0 and a b* value of from 87.0 to 97 as chromaticity coordinates in the CIE L*a*b* colorimetric system.
3. The wavelength conversion member of claim 1 wherein the thermoplastic resin comprises at least one resin selected from the group consisting of a polyolefin, polystyrene, styrene copolymer, fluoro-resin, acrylic resin, nylon, polyester, polyethylene terephthalate, polycarbonate, vinyl chloride resin and polyether resin.
4. A light-emitting device comprising a blue LED light source capable of emitting light containing a blue light component having a peak wavelength of 440 to 470 nm and having an optical axis and a wavelength conversion member disposed on the optical axis of the blue LED light source, the wavelength conversion member being of claim 1 .
5. The light-emitting device of claim 4 which emits light of color having an x value of from 0.3100 to 0.3850 and a y value of from 0.3190 to 0.3790 as chromaticity coordinates in the xy chromaticity diagram (CIE 1931).
6. The light-emitting device of claim 4 which is of remote phosphor type.