So basically the uv light is kicking the electrons up multiple levels in the "photoinitiators", the "photoinitiators" stabilize by dropping levels and giving off photons. These photons excite the "Monomers" and "Oligomers" between which electrons can freely flow (radicals) making it possible to form new bonds, creating longer chains of atoms (a polymer) /amateurexplenation
Not sure about the exact chemistry but I think there are actually two exposures, one to harden the shape after which the unused material is removed, and then another higher one to make it less sticky or "detackify" it.
So the molecules that it's made of up combine into new molecules that are solid? Do you know what the chemical reaction is?