Ultraviolet light curable compositions for producing coatings of low gloss

An ultraviolet light curable coating composition comprising:

• a. at least one photoinitiator which generates a radical pair by way of unimolecular homolysis resulting from photoexcitation, at least one member of said radical pair being capable of initiating addition polymerization of acrylyloxy groups;
• b. at least one photosensitizer which
• (1) has a triplet energy in the range of from 54 to 72 kilocalories per mole, and
• (2) promotes photopolymerization through bimolecular photochemical reactions;
• c. at least one quencher
• (1) having at least one quenching moiety which quenches said photosensitizer to an extent greater than the extent to which said photosensitizer is quenched by acrylyloxy groups,
• (2) which is not itself either an effective initiator or an effective inhibitor of free radical polymerization of acrylyloxy groups,
• (3) which does not produce products during quenching of said photosensitizer which are either effective initiators or effective inhibitors of free radical polymerization of acrylyloxy groups,
• (4) which either does not quench said photoinitiator or quenches said photoinitiator at a rate much less than the rate at which said photoinitiator induces polymerization of acrylyloxy groups so as not to significantly interfere with the initiation of free radical polymerization of acrylyloxy groups by said member of said radical pair, and
• (5) which has at least one of the following characteristics:
• (i) a triplet energy in the range of from 35 to 68 kilocalories per mole, but lower than the triplet energy of said photosensitizer,
• (ii) an ionization potential in the range of from about 61/2 to 9 electron volts,
• (iii) an ionization potential in the range of from 101/2 to about 12 electron volts;
• and
• d. at least one compound having a plurality of acrylyloxy groups and capable of being free radically addition polymerized by interaction with said photoinitiator and said photosensitizer;
• wherein upon exposure to ultraviolet light, a coating of said coating composition is cured to a crosslinked film having a lower gloss than if said quencher were absent.