Wavelength converting element

A wavelength converting element comprising a polymeric material having a polymeric backbone, said polymeric material comprising a wavelength converting moiety, wherein said wavelength converting moiety is adapted to convert light of a first wavelength to light of a second wavelength, and wherein said wavelength converting moiety is covalently attached to said polymer backbone, wherein said polymeric material having a polymeric backbone comprises a random polyester copolymer comprising said wavelength converting moiety, said random polyester copolymer comprising at least three different repeating units of the following general formula n1, n2, n3, n4:

• wherein said repeating units are randomly distributed along the length of said polymeric backbone,
• wherein AA is selected from the following first group of aromatic moieties:
• wherein BB is selected from the following:
• —(CH2)2—, —(CH2)4— or
• wherein CC and DD are said wavelength converting moieties having one of the following general formula I, II, or III:
• in which
• G1 is a linear or branched alkyl group or oxygen-containing alkyl group
• CnH2n+1Om, n being an integer from to 44 and m<n/2, or Y, or a linking group;
• each of A and C independently is hydrogen, isopropyl, t-butyl,
• fluorine, methoxy, or unsubstituted saturated alkyl CnH2n+1, n being an integer from 1 to 16;
• each of B, J and Q independently is hydrogen, isopropyl, t-butyl, fluorine, methoxy, or unsubstituted saturated alkyl CnH2n+1, n being an integer from 1 to 16, or a linking group;
• each of G2, G3, G4 and G5 independently is hydrogen, fluorine, methoxy, or
• unsubstituted saturated alkyl group CnH2n+1, n being an integer from 1 to 16, or X, or OX, wherein D, M, E, L and I are hydrogen, or a linking group;
• each of G2 and G3 may independently be C1 to C12, preferably C1 to C6, linear, branched or cyclic alkoxy group, optionally bonded via the oxygen;
• each of D and M independently is hydrogen, fluorine, methoxy, or unsubstituted saturated alkyl group CnH2n+1, n being an integer from 1 to 16;
• each of E, I and L independently is hydrogen, fluorine, methoxy, or unsubstituted saturated alkyl group CnH2n+1, n being an integer from 1 to 16, or a linking group;
• and each of T, T′, R, R′ independently is hydrogen, isopropyl, t-butyl, fluorine, alkyloxy, aryloxy, cyano CO2RxOCORx or unsubstituted saturated alkyl CnH2n+1, n being an integer from 1 to 16 and Rx being aryl or saturated alkyl CnH2n+1, n being an integer from 1 to 16, or a linking group;
• and wherein each wavelength converting moiety comprises two linking groups at any two of the positions:
• G1, G2, G3, G4, G5, E, L, B, J, Q, T, T′, R, R′, said linking groups providing covalent attachment of said wavelength converting moiety to the ester and/or alcohol functionalities of said polymer backbone;
• and wherein said random polyester copolymer comprises either a mixture of said repeating units n1, n2, n3 and n4 or a mixture of said repeating units n1, n2 and n4, said repeating units are randomly distributed along the length of said polymeric backbone, and the total number of the repeating units of the general formula n1 and n2 is larger than the total number of repeating units of the general formula n2 and n4.