Photopolymerizable composition containing a sensitized aromatic sulfonium compound and a cationacally polymerizable monomer

A photopolymerizable composition comprising:

• a. a cationically polymerizable monomer;
• b. an aromatic sulfonium compound of the following forumula:
• ##STR12## wherein R.sub.1, R.sub.2 and R.sub.3 are selected from the group consisting of aryl groups having 4 to 20 carbon atoms and alkyl radicals having 1 to 20 carbon atoms;
• wherein at least one of R.sub.1, R.sub.2 and R.sub.3 is aryl;
• wherein Z is selected from the group consisting of oxygen;
• sulfur;
• ##STR13## where R is aryl or acyl;
• a carbon-to-carbon bond;
• or ##STR14## where R.sub.4 and R.sub.5 are selected from the group consisting of hydrogen, an alkyl radical having 1 to 4 carbon atoms, and an alkenyl radical having 2 to 4 carbon atoms;
• and n is zero or 1;
• and X- is a halogen-containing complex anion selected from tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate, and hexafluoroantimonate;
• and
• c. a sensitizing compound selected from the group consisting of:
• i. aromatic tertiary amines having the formula ##STR15## where Ar.sup.1, Ar.sup.2 and Ar.sup.3 are groups having 6-20 carbon atoms;
• Z is selected from oxygen;
• sulfur;
• ##STR16## a carbon-to-carbon bond;
• or ##STR17## where R.sub.4 and R.sub.5 are selected from hydrogen, alkyl radicals of 1-4 carbons, and alkenyl radicals of 2-4 carbons, and wherein n is zero or 1;
• ii. aromatic tertiary diamines having the formula ##STR18## where Y is a divalent radical selected from arylene and Ar.sup.8 --Z--Ar.sup.9, where Z is as described above;
• Ar.sup.4, Ar.sup.5, Ar.sup.6, Ar.sup.7, Ar.sup.8 and Ar.sup.9 are aryl groups having 6-20 carbon atoms;
• and wherein n and m are zero or 1;
• and
• iii. aryl polycyclic compounds having at least three fused benzene rings and further having an ionization energy less than about 7.5 ev.