LAMINATION OF A LIGHT SOURCE HAVING A LOW-DENSITY SET OF LIGHT-EMITTING ELEMENTS

1 . A method comprising:

providing a set of multiple light-emitting elements disposed on a flexible polymer layer, each light-emitting element comprising one or more inorganic microLEDs that are arranged to generate and emit output light to propagate out-of-plane relative to a corresponding localized area of the polymer layer surrounding that light-emitting element; and

attaching a rigid layer to the polymer layer with the set of light-emitting elements therebetween, the rigid layer and the polymer layer forming a laminated structure that is transparent for visible light, each light-emitting element of the set being sufficiently small in at least one transverse dimension, and the light-emitting elements occupying a sufficiently small fraction of an areal extent of the set, so as to enable visual observation of a scene through the laminated structure along a sight line that passes through the set of light-emitting elements.

2 . The method of claim 1 wherein providing the set of light-emitting elements includes transferring individually each light-emitting element from a carrier onto the polymer layer.

3 . The method of claim 1 wherein providing the set of light-emitting elements includes transferring simultaneously groups of multiple light-emitting elements from a carrier onto the polymer layer.

4 . The method of claim 1 , each light-emitting element comprising one or more direct-emitting or phosphor-converted inorganic semiconductor microLEDs, the microLEDs including one or more UV-, visible-, or infrared-emitting microLEDs, each microLED including one or more materials among III-V, II-VI, or Group IV semiconductor materials.

5 . The method of claim 1 , one or more of the light-emitting elements including corresponding wavelength-converting structures.

6 . The method of claim 1 further comprising forming on the polymer layer multiple electrically conductive traces that are arranged and connected for providing electrical drive current to the light-emitting elements of the set, the traces being sufficiently transparent, sufficiently narrow, or spaced sufficiently far apart so as to enable visual observation of the scene through the laminated structure along the sight line that passes through the set of light-emitting elements.

7 . The method of claim 1 , each light-emitting element having a largest transverse dimension that is less than 200 μm.

8 . The method of claim 1 , the light-emitting elements occupying less than 25% of the areal extent of the set.

9 . The method of claim 1 , the set of light-emitting elements occupying an area of the laminated structure having a smallest transverse dimension that is greater than 5 mm.

10 . The method of claim 1 further comprising applying an adhesive layer between the rigid layer and the polymer layer, the adhesive layer adhering together the rigid layer and the polymer layer and at least partly encapsulating the set of light-emitting elements, the adhesive layer being transparent for visible light.

11 . The method of claim 1 , the entire rigid layer being planar.

12 . The method of claim 1 , the rigid layer including one or more areal regions that are curved, or two or more planar areal regions that are not coplanar with respect to one another, wherein attaching the rigid layer to the polymer layer includes deforming or molding the polymer layer to conform to the rigid layer.

13 . The method of claim 1 wherein attaching the rigid layer to the polymer layer includes preventing, avoiding, or eliminating bubbles or voids between the rigid layer and the polymer layer.

14 . The method of claim 1 , the polymer layer remaining flexible after attachment to the rigid layer.

15 . The method of claim 1 wherein attaching the rigid layer to the polymer layer includes curing or cross-linking the polymer layer.

16 . The method of claim 15 , the polymer layer being rigid after curing or cross-linking.

17 . The method of claim 1 , (i) the polymer layer including one or more polymeric materials among clear polyimide (PI), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), or other flexible or curable transparent polymer, or (ii) the rigid layer including one or more materials among silica, optical glasses, polycarbonate, polymethylmethacrylate (PMMA), or other rigid transparent polymers.

18 . The method of claim 1 , each light-emitting element being sufficiently small in at least one transverse dimension, and the light-emitting elements of the set being spaced sufficiently far apart, so that, with the light-emitting elements in an off state or emitting only non-visible light, the set does not substantially interfere with visual observation of the scene through or reflected by the substrate by a naked eye of a human observer along the sight line that passes through the set.

19 . The method of claim 1 , each light-emitting element being sufficiently small in at least one transverse dimension, and the light-emitting elements of the set being spaced sufficiently far apart, so that to a naked eye of a human observer the set is only negligibly visible when in an off state or when emitting only non-visible light.

20 . The method of claim 1 , each light-emitting element being sufficiently small in at least one transverse dimension, and the light-emitting elements of the set being spaced sufficiently far apart, so that to a naked eye of a human observer the set resembles dust on the laminated structure when in an off state or when emitting only non-visible light.