Light emitting device with high near-field contrast ratio
A light emitting device includes an LED having a light emitting top surface and sidewalls. A phosphor structure is attached to the light emitting surface of the LED. The phosphor structure has a light emitting top surface facing away from the LED light emitting surface, and sidewalls. A light reflective material is arranged to cover the sidewalls of the LED and the phosphor structure. A light absorptive region is defined in the light reflective material around a perimeter of the light emitting surface of the phosphor structure. The light absorptive region may be spaced apart from the perimeter of the phosphor structure by a gap. The light absorptive region may be formed by ultraviolet laser illumination of the light reflecting material.
1. A light emitting device comprising:
a semiconductor light-emitting diode having a light emitting first surface, an oppositely positioned second surface, and sidewalls connecting the first and second surfaces;
a phosphor structure having a light emitting first surface, an oppositely positioned second surface, and sidewalls connecting the first and second surfaces, the second surface of the phosphor structure attached to the first surface of the semiconductor light-emitting diode;
a light reflective material disposed on the sidewalls of the light-emitting diode and the sidewalls of the phosphor structure; and
a light absorptive region in the light reflective material around a perimeter of the light emitting first surface of the phosphor structure, the light absorptive region having a flat surface coplanar with the light emitting first surface of the phosphor structure, the light absorptive region spaced apart from the perimeter of the light emitting first surface of the phosphor structure in a plane of the light emitting first surface of the phosphor structure, the light absorptive region is a thin region penetrating into the light reflective material to a depth of about 40 to about 80 microns from the flat surface of the light absorptive region.
2. The light emitting device of claim 1 , wherein the light absorptive region surrounds the perimeter of the light emitting first surface of the phosphor structure.
3. The light emitting device of claim 1 , wherein the light absorptive region is spaced apart from the perimeter of the light emitting first surface of the phosphor structure in a plane of the light emitting first surface of the phosphor structure by at least thirty microns.
4. The light emitting device of claim 3 , wherein the light absorptive region is spaced apart from the perimeter of the light emitting first surface of the phosphor structure in a plane of the light emitting first surface of the phosphor structure by no more than 80 microns.
5. The light emitting device of claim 1 , wherein the light absorptive region has a width in a plane of the light emitting first surface of the phosphor structure of between about 100 microns and about 200 microns.
6. The light emitting device of claim 1 , wherein the light reflective material comprises light scattering or reflective metal oxide particles dispersed in a binder material, and the light absorptive region comprises light absorbing metallic material and is depleted of binder material compared to the light reflective material.
7. The light emitting device of claim 1 , wherein the light reflective material comprises TiO 2 dispersed in a binder.
8. The light emitting device of claim 7 , wherein the light reflective material comprises 70% or more SiO 2 and TiO 2 in a binder.
9. The light emitting device of claim 8 , wherein the TiO 2 coats SiO 2 particles.
10. The light emitting device of claim 8 , wherein the light reflective material comprises less than 30% TiO 2 .
11. The light emitting device of claim 1 , wherein the light reflective material includes SiO 2 , TiO 2 , and Al 2 O 3 in a binder.
12. The light emitting device of claim 1 , wherein the light absorptive region:
surrounds the perimeter of the light emitting first surface of the phosphor structure and is spaced apart from the perimeter of the light emitting first surface of the phosphor structure in a plane of the light emitting first surface of the phosphor structure by at least thirty microns;
has a width in a plane of the phosphor structure of between about 100 microns and about 200 microns; and
comprises 70% or more SiO 2 and TiO 2 in a binder.
13. The light emitting device of claim 12 , wherein the light absorptive region comprises light absorbing metallic material and is depleted of binder material compared to the light reflective material.