A liquid composition, curable by exposure to light irradiation ranging from λ=200-900 nm, containing: (a) at least one polymerisable component selected from the group consisting of: (i) an ethylenically unsaturated monomer, the polymerization of which may be effected by free radical polymerization; and/or (ii) an ethylenically unsaturated monomer or an epoxy-containing monomer; the polymerization of which may be effected by cationic polymerization; (b) a photoinitiator complex of formula I or II: wherein Q 1 represents a conjugated polyaromatic system containing two nitrogen atoms whose lone pair of electrons forms a bond with the copper atom; Q 2 and Q 3 independently represent a conjugated polyaromatic system containing one nitrogen atom whose lone pair of electrons forms a bond with the copper atom; W represents a phosphorus or nitrogen atom; R 1, R 2, R 3, R 4, R 5 and R 6 each independently represents a C 6-20 alkyl or C 6-10 aryl moiety; wherein the alkyl and/or the aryl moieties may be, individually, further substituted with one or more linear or branched C 1-6 alkyl or C 6-10 aryl moieties; and wherein R 3 and R 4, together with the P, Cu and W atoms, may form a 6- to 8-membered ring; X represents a suitable counterion; preferably BF 4 -, PF 6, SbF 6 - or Cl -; (c) an iodonium salt of formula (R A) 2 I +; wherein each occurrence of R A independently represents a C 6-10 aryl moiety; wherein the aryl moiety may be, individually, further substituted with one or more linear or branched C 1-6 alkyl or C 6-10 aryl moieties; and provided that, when at least one polymerisable component (a) is an ethylenically unsaturated monomer or an epoxy-containing monomer polymerisable by cationic polymerization, the liquid composition further comprises (b) a vinyl cation initiator having the structure III or IV: wherein R 7 represents a linear or branched C 1-6 alkyl or C 1-10 heteroalkenyl moiety or a C 6-10 aryl moiety; and R 8 and R 9 independently represent a linear or branched C 1-6 alkyl moiety or a C 6-10 aryl moiety; where R 8 and R 9 together may form a cyclic heteroaryl moiety. (a) at least one polymerisable component selected from the group consisting of: (i) an ethylenically unsaturated monomer, the polymerization of which may be effected by free radical polymerization; and/or (ii) an ethylenically unsaturated monomer or an epoxy-containing monomer; the polymerization of which may be effected by cationic polymerization; (i) an ethylenically unsaturated monomer, the polymerization of which may be effected by free radical polymerization; and/or (ii) an ethylenically unsaturated monomer or an epoxy-containing monomer; (b) a photoinitiator complex of formula I or II: wherein Q 1 represents a conjugated polyaromatic system containing two nitrogen atoms whose lone pair of electrons forms a bond with the copper atom; Q 2 and Q 3 independently represent a conjugated polyaromatic system containing one nitrogen atom whose lone pair of electrons forms a bond with the copper atom; W represents a phosphorus or nitrogen atom; R 1, R 2, R 3, R 4, R 5 and R 6 each independently represents a C 6-20 alkyl or C 6-10 aryl moiety; wherein the alkyl and/or the aryl moieties may be, individually, further substituted with one or more linear or branched C 1-6 alkyl or C 6-10 aryl moieties; and wherein R 3 and R 4, together with the P, Cu and W atoms, may form a 6- to 8-membered ring; X represents a suitable counterion; preferably BF 4 -, PF 6, SbF 6 - or Cl -; Q 1 represents a conjugated polyaromatic system containing two nitrogen atoms whose lone pair of electrons forms a bond with the copper atom; Q 2 and Q 3 independently represent a conjugated polyaromatic system containing one nitrogen atom whose lone pair of electrons forms a bond with the copper atom; W represents a phosphorus or nitrogen atom; R 1, R 2, R 3, R 4, R 5 and R 6 each independently represents a C 6-20 alkyl or C 6-10 aryl moiety; wherein the alkyl and/or the aryl moieties may be, individually, further substituted with one or more linear or branched C 1-6 alkyl or C 6-10 aryl moieties; and wherein R 3 and R 4, together with the P, Cu and W atoms, may form a 6- to 8-membered ring; X represents a suitable counterion; preferably BF 4 -, PF 6, SbF 6 - or Cl -; (c) an iodonium salt of formula (R A) 2 I +; wherein each occurrence of R A independently represents a C 6-10 aryl moiety; wherein the aryl moiety may be, individually, further substituted with one or more linear or branched C 1-6 alkyl or C 6-10 aryl moieties; and provided that, when at least one polymerisable component (a) is an ethylenically unsaturated monomer or an epoxy-containing monomer polymerisable by cationic polymerization, the liquid composition further comprises (b) a vinyl cation initiator having the structure III or IV: wherein R 7 represents a linear or branched C 1-6 alkyl or C 1-10 heteroalkenyl moiety or a C 6-10 aryl moiety; and R 8 and R 9 independently represent a linear or branched C 1-6 alkyl moiety or a C 6-10 aryl moiety; where R 8 and R 9 together may form a cyclic heteroaryl moiety. wherein R 7 represents a linear or branched C 1-6 alkyl or C 1-10 heteroalkenyl moiety or a C 6-10 aryl moiety; and R 8 and R 9 independently represent a linear or branched C 1-6 alkyl moiety or a C 6-10 aryl moiety; where R 8 and R 9 together may form a cyclic heteroaryl moiety.