Formulation for an LED encapsulation material

1. A formulation comprising:

a polymer comprising a first repeating unit U 1 and a second repeating unit U 2 ,

wherein the first repeating unit U 1 is represented by formula (I) and the second repeating unit U 2 is represented by formula (II):

—[—SiR 1 R 2 —NR 5 —]—  (I)

—[—SiR 3 R 4 —[O—SiR 3 R 4 —] a —NR 5 —]—  (II)

wherein R 1 , R 2 , R 3 , R 4 and R 5 are at each occurrence independently from each other selected from the group consisting of hydrogen, organyl and organoheteryl groups, and a is an integer from 1 to 60,

wherein the polymer comprises at least one further repeating unit U 1 which is represented by formula (I), wherein the at least one further repeating unit U 1 is different from the first repeating unit U 1 ; and

surface-modified nanoparticles, wherein the surface-modified nanoparticles do not contain any zirconium dioxide.

2. The formulation according to claim 1 , wherein the surface-modified nanoparticles are surface-modified nanoparticles containing one or more inorganic nanoparticle materials selected from M 2 O, M 3 2 O 3 , M 4a O 2 , M 2 M 4b O 3 , M 2 S, M 2 SO 3 , M 2 SO 4 , M 2 2 SiO 4 , M 3 N, M 4b C, M 4b SiO 4 and diamond,

wherein M 2 is a divalent metal element, M 3 is a trivalent metal element, M 4a is a tetravalent metal element excluding Zr and M 4b is a tetravalent metal element.

3. The formulation according to claim 2 , wherein M 2 is a divalent metal element selected from the list consisting of Mg, Ca, Sr, Ba, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Hg, Sn and Pb;

M 3 is a trivalent metal element selected from the list consisting of Sc, Y, Lu, Cr, Mn, Fe, B, Al and Ga;

M 4a is a tetravalent metal element excluding Zr selected from the list consisting of Ti, Hf, Si, Ge and Sn; and

M 4b is a tetravalent metal element selected from the list consisting of Ti, Zr, Hf, Si, Ge and Sn.

4. The formulation according to claim 1 , wherein the surface of the nanoparticles is modified with surface modifying agents selected from alkyl-alkoxysilanes, alkenyl-alkoxysilanes or aryl-alkoxysilanes.

5. The formulation according to claim 1 , wherein R 1 and R 2 are at each occurrence independently from each other hydrogen or alkyl having 1 to 20 carbon atoms or phenyl.

6. The formulation according to claim 1 , wherein R 3 and R 4 are independently from each other hydrogen or alkyl having 1 to 40 carbon atoms or phenyl.

7. The formulation according to claim 1 , wherein R 5 is at each occurrence independently hydrogen or alkyl having 1 to 20 carbon atoms or phenyl.

8. The formulation according to claim 1 , wherein said formulation comprises one or more solvent(s) selected from the group consisting of ethers, cyclic ethers, ketones, esters, mixed ether/ester solvents, hydrocarbons, aromatic solvents, wherein one or more hydrogen atoms in the solvent(s) may be optionally substituted by chlorine or fluorine atoms.

9. A method for preparing a formulation according to claim 1 , wherein a polymer containing a first repeating unit U 1 and a second repeating unit U 2 is mixed with a dispersion of surface-modified nanoparticles, wherein the surface-modified nanoparticles do not contain any zirconium dioxide.

10. An encapsulation material for an LED, obtainable by

(a) providing a formulation according to claim 1 ; and

(b) curing said formulation at a temperature of 70 to 300° C. for a period of 1 to 24 h.

11. An LED comprising an encapsulation material according to claim 10 .

12. The LED according to claim 11 , wherein the encapsulation material is comprised in a converter layer.

13. The LED according to claim 11 , wherein the encapsulation material is comprised in a converter layer which comprises one or more converters selected from phosphors and/or quantum materials.

14. A method for producing an LED comprising the steps of

(a) applying a formulation according to claim 1 to an LED precursor; and

(b) curing the formulation at a temperature of 70 to 300° C. for a period of 1 to 24 h.

15. A method for producing an LED according to claim 14 , wherein the formulation is applied in step (a) by dispensing, screen printing, stencile printing, spray coating, slot coating, spin coating or ink-jet printing.

16. A method for producing an LED according to claim 14 , wherein the formulation which is applied in step (a) to an LED precursor forms part of a converter layer comprising one or more converters selected from phosphors and/or quantum materials.