Roll-to-roll fabricated light sheet and encapsulated semiconductor circuit devices
A method of making a light active sheet. A bottom substrate having an electrically conductive surface is provided. A hotmelt adhesive sheet is provided. Light active semiconductor elements, such as LED die, are embedded in the hotmelt adhesive sheet. The LED die each have a top electrode and a bottom electrode. A top transparent substrate is provided having a transparent conductive layer. The hotmelt adhesive sheet with the embedded LED die is inserted between the electrically conductive surface and the transparent conductive layer to form a lamination. The lamination is run through a heated pressure roller system to melt the hotmelt adhesive sheet and electrically insulate and bind the top substrate to the bottom substrate. As the hotmelt sheet is softened, the LED die breakthrough so that the top electrode comes into electrical contact with the transparent conductive layer of the top substrate and the bottom electrode comes into electrical contact with the electrically conductive surface of the bottom substrate. Thus, the p and n sides of each LED die are automatically connected to the top conductive layer and the bottom conductive surface. Each LED die is encapsulated and secured between the substrates in the flexible, hotmelt adhesive sheet layer. The bottom substrate, the hotmelt adhesive (with the embedded LED die) and the top substrate can be provided as rolls of material. The rolls are brought together in a continuous roll fabrication process, resulting in a flexible sheet of lighting material.
1. A light active sheet comprising:
a bottom substrate flexible sheet having an electrically conductive surface;
a top transparent substrate flexible sheet having a transparent conductive layer disposed thereon;
an electrically insulative adhesive flexible sheet;
light active semiconductor elements fixed to the electrically insulative adhesive sheet, said light active semiconductor elements each having an n-side and a p-side, the electrically insulative adhesive sheet having the light active semiconductor elements fixed thereon being inserted between the electrically conductive surface and the transparent conductive layer to form a lamination and activated so that the electrically insulative adhesive electrically insulates and binds the top substrate sheet to the bottom substrate sheet so that one of said n-side or said p-side of the light active semiconductor elements is in electrical communication with the transparent conductive layer of the top substrate sheet and so that the other of said n-side or said p-side of each said light active semiconductor element is in electrical communication with the electrically conductive surface of the bottom substrate sheet to form a light active device,
wherein the bottom substrate, the electrically insulative adhesive and the top substrate are provided as respective rolls of material; and the step of inserting comprising bringing the bottom substrate, the electrically insulative adhesive and the top substrate together in a continuous roll fabrication process.
2. A light active sheet according to claim 1 ; wherein the electrically insulative adhesive comprises a hotmelt material activatable by applying heat and pressure to the lamination to soften the hotmelt material.
3. A light active sheet according to claim 1 ; wherein the adhesive is activatable by at least one of solvent action, evaporation, catalytic reaction and radiation curing.
4. A light active sheet according to claim 1 ; wherein the light active semiconductor elements are light emitting diode die.
5. A light active sheet according to claim 1 ; wherein the light active semiconductor elements are light-to-energy devices.
6. A light active sheet according to claim 1 ; wherein a first portion of the light active semiconductor elements emit a first wavelength of radiation and a second portion of the light active semiconductor elements emit a second wavelength of radiation.
7. A light active sheet according to claim 1 ; wherein the electrically insulative adhesive comprises a hotmelt sheet; and the light active semiconductor elements are embedded into the hotmelt sheet before forming the lamination.
8. A light active sheet according to claim 1 ; wherein the light active semiconductor elements are formed into a predetermined pattern.
9. A light active sheet according to claim 8 ; wherein the light active semiconductor elements are formed into the predetermined pattern by electrostatically attracting a plurality of said light active semiconductor elements on a transfer member and transferring the predetermined pattern onto the insulative adhesive.
10. A method of making a light active sheet according to claim 8 ; wherein the light active semiconductor elements are formed into the predetermined pattern by magnetically attracting a plurality of said light active semiconductor elements on a transfer member and transferring the predetermined pattern onto the insulative adhesive.
11. A light active sheet according to claim 1 ; wherein the transparent conductive layer comprises a transparent conductive material formed as conductive light transmissive connecting lands, each said land for connecting with a respective light active semiconductor.
12. A light active sheet according to claim 11 ; further comprising a relatively higher conducting line pattern formed on at least one of the top substrate and the bottom substrate for providing a relatively lower path of resistance from a power supply source to each said light active semiconductor element.
13. A light active sheet according to claim 1 ; wherein the electrically conductive surface and the electrically conductive pattern comprise a respective x and y wiring grid for selectively addressing individual said light active semiconductor elements for forming a display.
14. A light active sheet according to claim 1 ; further comprising a phosphor provided in the lamination, said phosphor being optically stimulated by a radiation emission of a first wavelength from the light active semiconductor element to emit light of a second wavelength.