Pigmented and scattering particles in side coating materials for LED applications
Phosphor-converted LED side reflectors disclosed herein comprise pigments that are photochemically stable under illumination by light from the pcLED. The pigments absorb light in at least a portion of the spectrum of light emitted by the first phosphor converted LED. The side reflector may also comprise light scattering particles or air voids. The pigments, light scattering particles, or air voids may be homogeneously distributed in the reflector. Alternatively the side reflector may be layered, with the pigments, light scattering particles, or air voids inhomogeneously distributed in the reflector. The side reflector can include phosphor particles.
1. A light emitting device comprising:
a substrate;
a first phosphor converted LED comprising a first semiconductor LED disposed on the substrate, a first wavelength converting structure disposed on a surface of the first semiconductor LED opposite from the substrate, a light emitting external surface located opposite from the substrate, and side walls extending from the substrate to the light emitting surface;
a second phosphor converted LED comprising a second semiconductor LED disposed on the substrate, a second wavelength converting structure disposed on a surface of the second semiconductor LED opposite from the substrate, a light emitting external surface opposite from the substrate, and side walls extending from the substrate to the light emitting surface, the second phosphor converted LED being spaced apart from the first phosphor converted LED by a street defined by the substrate, a side wall of the first phosphor converted LED, and an adjacent side wall of the second phosphor converted LED, the street being less than about 0.10 millimeters wide; and
a side reflector disposed in the street on a side wall of the first phosphor converted LED and including one or more pigments that absorb light in at least a portion of the spectrum of light emitted by the first phosphor converted LED.
2. The light emitting device of claim 1 wherein the first and second phosphor converted LEDs are monolithically integrated on the substrate and have transverse dimensions less than about 1.0 millimeters.
3. The light emitting device of claim 2 , wherein the first and second phosphor converted LEDs have transverse dimensions less than about 0.10 millimeters, and the street is less than about 0.050 millimeters wide.
4. The light emitting device of claim 1 , wherein one or more of the pigments absorb blue light, absorb green light and transmit or reflect red light, or absorb red light and transmit or reflect green light.
5. The light emitting device of claim 1 , wherein the one or more pigments reflect or transmit blue light and absorb green light, red light, or both.
6. The light emitting device of claim 1 , wherein the one or more pigments are dispersed in a transparent binder material.
7. The light emitting device of claim 6 , wherein the transparent binder material includes air voids.
8. The light emitting device of claim 1 , wherein the side reflector includes light scattering particles.
9. The light emitting device of claim 8 , wherein the one or more pigments and the light scattering particles are distributed homogenously in a transparent binder material.
10. The light emitting device of claim 9 , wherein the transparent binder material is in contact with the adjacent side wall of the second phosphor converted LED and fills the street.
11. The light emitting device of claim 9 , comprising phosphor particles distributed homogeneously in the transparent binder material.
12. The light emitting device of claim 11 , wherein the transparent binder material is in contact with the adjacent side wall of the second phosphor converted LED and fills the street.
13. The light emitting device of claim 8 , wherein:
the light scattering particles are dispersed in a first layer of transparent binder material disposed on the side of the first phosphor converted LED; and
the pigments are dispersed in a second layer of transparent binder material disposed on the first layer opposite from the side wall of the first phosphor converted LED.
14. The light emitting device of claim 13 , comprising additional pigments disposed in the first layer.
15. The light emitting device of claim 8 , wherein:
a first plurality of the light scattering particles is dispersed in a first layer of transparent binder material disposed on the side of the first phosphor converted LED;
a second plurality of the light scattering particles is dispersed in a second layer of transparent binder material disposed on the adjacent side of the second phosphor converted LED;
the pigments are disposed in a third layer of transparent binder material disposed between the first layer and the second layer; and
the side reflector fills the street.
16. The light emitting device of claim 15 , comprising a first plurality of phosphor particles dispersed in the transparent binder material of the first layer and a second plurality of phosphor particles dispersed in the transparent binder material of the second layer.
17. A method for making a light emitting device, the method comprising:
depositing on or applying to a side wall of a first phosphor converted LED a side reflector that includes one or more pigments that absorb light in at least a portion of a spectrum of light emitted by the first phosphor converted LED,
the first phosphor converted LED comprising a first semiconductor LED disposed on a substrate, a first wavelength converting structure disposed on a surface of the first semiconductor LED opposite from the substrate, a light emitting external surface located opposite from the substrate, and side walls extending from the substrate to the light emitting surface,
a second phosphor converted LED being disposed on the substrate, the second phosphor converted LED comprising a second semiconductor LED disposed on the substrate, a second wavelength converting structure disposed on a surface of the second semiconductor LED opposite from the substrate, a light emitting external surface opposite from the substrate, and side walls extending from the substrate to the light emitting surface,
the first and second phosphor converted LEDs being monolithically integrated on the substrate and having transverse dimensions less than about 1.0 millimeters, the second phosphor converted LED being spaced apart from the first phosphor converted LED by a street defined by the substrate, the side wall of the first phosphor converted LED, and an adjacent side wall of the second phosphor converted LED, the street being less than about 0.10 millimeters wide.
18. The method of claim 17 wherein depositing or applying the side reflector comprises substantially filling the street with a transparent binder material that includes dispersed therein light scattering particles and the one or more pigments.
19. The method of claim 17 wherein depositing or applying the side reflector comprises:
depositing on or applying to the side wall of the first phosphor converted LED a transparent binder material that includes light scattering particles dispersed therein;
depositing on or applying to the side wall of the second phosphor converted LED a transparent binder material that includes light scattering particles dispersed therein; and
filling a space remaining between the binder materials on the respective side walls a transparent binder material that includes the one or more pigments dispersed therein.
20. The method of claim 17 wherein depositing or applying the side reflector comprises:
filling the street with a transparent binder material that includes light scattering particles dispersed therein;
cutting or etching a groove or trench in the transparent binder material so as to leave binder material on both side walls of the street; and
filling the groove or trench with a transparent binder material that includes the one or more pigments dispersed therein.