Egress and/or flicker-free lighting device with persistent luminescence

1. A lighting device, comprising:

a substrate;

two or more light-emitting elements formed over the substrate;

an affixing layer fixing the two or more light-emitting elements in place;

a transparent conductive layer in electrical contact with the light-emitting elements;

the substrate and the transparent conductive layer sandwich the affixing layer with the light-emitting elements in place;

the affixing layer is an electrically insulating material;

the affixing layer is doped with a photo active or photochromic material,

in a first mode when the light-emitting elements are energized, the photo active or photochromic material of the affixing layer is excited by the light-emitting elements, and

in a second mode when the light-emitting elements are de-energized, the affixing layer produces a persistent luminescence.

2. The lighting device of claim 1 , further comprising,

in the first mode, while using AC voltage to drive the light-emitting elements, during any one off-cycle of the AC, the light-emitting elements are off and the affixing layer surrounding the light-emitting elements produces the persistent luminescence for at least a duration of the one off-cycle of the AC, to avoid flickering during the one off-cycle.

3. The lighting device of claim 1 , wherein the transparent conductive layer is semi-transparent and bounces at least some of the light from the light-emitting elements back into the affixing layer to further excite the affixing layer to produce additional persistent luminescence.

4. The lighting device of claim 1 , further comprising a semi-transparent layer sandwiching the transparent conductive layer, the semi-transparent layer bounces at least some of the light from the light-emitting layer back into the affixing layer to further excite the affixing layer to produce additional persistent luminescence.

5. The lighting device of claim 1 , wherein the light-emitting elements can be oriented any direction in the affixing layer, to emit the persistent luminescence when the lighting device is powered down.

6. The lighting device of claim 1 , wherein the wave length of the light-emitting elements is UV or blue.

7. The lighting device of claim 1 , the affixing layer includes non-doped areas to comprise a pattern of a pre-determined non-persistent-luminescent area.

8. An emergency light comprising:

the lighting device of claim 1 , driven by DC voltage,

in a power-on mode the DC voltage drives the light emitting elements,

in a power-off mode, the DC voltage does not drive the light emitting elements, and the affixing layer acts as a persistent luminescent marker.

9. A lighting device, comprising:

a substrate;

two or more light-emitting elements formed over the substrate;

a protective surrounding layer fixing the two or more light-emitting elements in place;

the protective surrounding layer is doped with a photo active or photochromic material,

in a first mode when the light-emitting elements are energized, the photo active or photochromic material of the affixing layer is excited by the light-emitting elements, and

in a second mode when the light-emitting elements are de-energized, the affixing layer produces a persistent luminescence.

10. The lighting device of claim 9 , further comprising,

in the first mode, while using AC voltage to drive the light-emitting elements, during any one off-cycle of the AC, the light-emitting elements are off and the affixing layer surrounding the light-emitting elements produces the persistent luminescence for at least a duration of the one off-cycle of the AC, to avoid flickering during the one off-cycle.

11. The lighting device of claim 9 , further comprising a semi-transparent layer sandwiching the protective surrounding layer, the semi-transparent layer bounces at least some of the light from the light-emitting layer back into the protective surrounding layer to further excite the protective surrounding layer to produce additional persistent luminescence.

12. The lighting device of claim 9 , wherein the light-emitting elements can be oriented any direction in the protective surrounding layer, to emit the persistent luminescence when the lighting device is powered down.

13. The lighting device of claim 9 , wherein the wave length of the light-emitting elements is UV and/or blue.

14. An emergency light comprising:

the lighting device of claim 9 , driven by DC voltage,

in a power-on mode the DC voltage drives the light emitting elements,

in a power-off mode, the DC voltage does not drive the light emitting elements, and the protective surrounding layer acts as a persistent luminescent marker.

15. A method of forming a lighting device, comprising:

providing a substrate;

forming two or more light-emitting elements over the substrate;

forming an affixing layer on the substrate fixing the two or more light-emitting elements in place; and

forming a transparent conductive layer over the affixing layer;

wherein the substrate and the transparent conductive layer sandwich the affixing layer with the light-emitting elements in place;

wherein the affixing layer is an electrically insulating material;

wherein the affixing layer is doped with a photo active or photochromic material,

in a first mode when the light-emitting elements are energized, the photo active or photochromic material of the affixing layer is excited by the light-emitting elements,

in a second mode when the light-emitting elements are de-energized, the affixing layer produces a persistent luminescence when energized.

16. The method of claim 15 , wherein the transparent conductive layer is semi-transparent and bounces at least some of the light from the light-emitting elements back into the affixing layer to further excite the affixing layer to produce additional persistent luminescence.

17. The method of claim 15 , further comprising

forming a semi-transparent layer on the transparent conductive layer, the semi-transparent layer bounces at least some of the light from the light-emitting layer back into the affixing layer to further excite the affixing layer to produce additional persistent luminescence.

18. The method of claim 15 , wherein the wave length of the light-emitting elements is UV or blue.

19. The method of claim 15 , further comprising

pre-forming the affixing layer to include non-doped areas to comprise a pattern of a pre-determined non-persistent-luminescent area.

20. A method of forming a lighting device, comprising:

providing a substrate;

forming two or more light-emitting elements over the substrate; and

forming a protective surrounding layer on the substrate with the two or more light-emitting elements, the protective surrounding layer fixes the two or more light-emitting elements in place;

wherein the protective surrounding layer is doped with a photo active or photochromic material,

in a first mode when the light-emitting elements are energized, the photo active or photochromic material of the protective surrounding layer is excited by the light-emitting elements, and

in a second mode when the light-emitting elements are de-energized, the protective surrounding layer produces a persistent luminescence.

21. The method of claim 20 , further comprising

forming a semi-transparent layer on the protective surrounding layer, the semi-transparent layer bounces at least some of the light from the light-emitting layer back into the protective surrounding layer to further excite the protective surrounding layer to produce additional persistent luminescence.

22. The method of claim 20 , wherein the wave length of the light-emitting elements is UV and/or blue.