LED-based illumination modules with thin color converting layers
An illumination module includes a plurality of Light Emitting Diodes (LEDs). The illumination module may include a reflective color converting element with a PTFE layer and a color converting layer fixed to the PTFE layer. The color converting layer includes phosphor particles embedded in a polymer matrix and has a thickness that is less than five times an average diameter of the phosphor particles. The illumination module may include a transmissive color converting element. The color converting elements may be produced by mixing a polymer binder with a solvent and phosphor particles to form a homogeneous suspension of the phosphor particles. The homogeneous suspension is applied to a surface to form an uncured color converting layer, which is heated to vaporize the solvent. The cured color converting layer includes the phosphor particles suspended in the polymer binder.
1. A method comprising:
mixing a polymer binder with a solvent and a plurality of phosphor particles to form a homogeneous suspension of the phosphor particles;
applying the homogeneous suspension to a surface of a transparent substrate to form an uncured color converting layer; and
heating the uncured color converting layer to vaporize the solvent to form a cured color converting layer, wherein the cured color converting layer includes the phosphor particles suspended in the polymer binder, and wherein a thickness of the cured color converting layer on the transparent substrate is less than five times an average diameter of the phosphor particles.
2. The method of claim 1 , further comprising:
enclosing the color converting layer between the first transmissive element and a second transmissive element with a seal that fixedly couples the first and second transmissive elements.
3. The method of claim 1 , further comprising:
encapsulating the color converting layer on the first transmissive element with a sealing element.
4. The method of claim 1 , wherein the heating involves heating the uncured color converting layer to no more than three hundred degrees Centigrade.
5. The method of claim 1 , wherein the polymer binder is taken from the group consisting of: an ethyl cellulose and a polyvinyl butyral.
6. The method of claim 1 , wherein the solvent is taken from the group consisting of: a butyl carbolite acetate and a terpineol.
7. The method of claim 1 , wherein the thickness of the cured color converting layer is a monolayer of the phosphor particles.
8. The method of claim 7 , wherein a packing density of the cured color converting layer is less than 0.95.
9. The method of claim 8 , wherein at least ten percent of a light incident to the optically transparent substrate is transmitted without color conversion.
10. A method comprising:
mixing a polymer binder with a solvent and a plurality of phosphor particles to form a homogeneous suspension of the phosphor particles;
applying the homogeneous suspension to a surface of a polytetrafluoroethylene (PTFE) material to form an uncured color converting layer; and
heating the uncured color converting layer to vaporize the solvent to form a cured color converting layer, wherein the cured color converting layer includes the phosphor particles suspended in the polymer binder, and wherein a thickness of the cured color converting layer on the PTFE material is less than five times an average diameter of the phosphor particles.
11. The method of claim 10 , wherein the heating involves heating the uncured color converting layer to no more than three hundred degrees Centigrade.
12. The method of claim 10 , wherein a packing density of the cured color converting material is greater than 0.5.
13. The method of claim 10 , wherein an average diameter of the phosphor particles is between five and twenty microns.
14. The method of claim 10 , wherein the surface is an interior surface of an LED based illumination module.
15. An apparatus comprising:
a light source sub-assembly having a plurality of Light Emitting Diodes (LEDs); and
a transmissive color converting element comprising an optically transparent layer and a first color converting layer fixed to the optically transparent layer, wherein the first color converting layer includes a plurality of phosphor particles of a first type embedded in a polymer matrix, wherein the thickness of the first color converting layer is less than three times an average diameter of the phosphor particles.
16. The apparatus of claim 15 , further comprising:
a reflective color converting element comprising a polytetrafluoroethylene (PTFE) layer and a second color converting layer fixed to the PTFE layer, wherein the second color converting layer includes a plurality of phosphor particles of a second type embedded in a polymer matrix, and wherein a thickness of the second color converting layer is less than five times an average diameter of the phosphor particles of the second type.
17. The apparatus of claim 15 , wherein the phosphor particles of the first type have a peak emission wavelength of no more than 600 nanometers.
18. The apparatus of claim 15 , wherein a light transmitted through the first color converting layer has a correlated color temperature less than 3,100 degrees Kelvin.
19. The apparatus of claim 15 , wherein a packing density of the first color converting layer is less than 0.95.
20. The apparatus of claim 16 , wherein a packing density of the second color converting layer is greater than 0.5.