Photopolymerizable composition and element

Claim 1

A PHOTOPOLYMERIZABLE COMPOSITION CAPABLE OF FORMING RELATIVELY HIGH-CONTRAST IMAGES WHEN SUBJECTED TO RELATIVELY LOW-CONTRAST IMAGEWISE IRRADIATION, WHICH COMPOSITION COMPRISES: (1) AN ADDITION POLYMERIZABLE, NON-GASEOUS, ETHYLENICALLY UNSATURATED COMPOUND CONTAINING AT LEAST ONE TERMINAL ETHYLENIC GROUP, HAVING A BOILING POINT ABOVE 100*C. AT NORMAL ATMOSPHERIC PRESSURE AND BEING CAPABLE OF FORMING A HIGH POLYMER BY FREERADICAL INITIATED, CHAIN-PROPAGATING ADDITION POLYMERIZATION, (2) AT LEAST ONE IMINE OXIDE SENSITOMETRIC MODIFIER SELECTED FROM THE GROUP CONSISTING OF: (A) 1-(A-N(=O)=),4-(O=)-CYCLOHEXA-2,5-DIENE (B) 1,4-DI(A-N(=O)=)-CYCLOHEA-2,5-DIENE (C) 1,4-DI(O=),2-(A-N(=O)=),3-(A''-N(=O)=)-CYCLOHEX-5-ENE (D) 5,10-DI(O=)-PHENAZINE (E) A-N(=O)=(CYCLOHEXA-2,5-DIEN-1,4-YLIDENE)=(CYCLOHEXA2,5-DIEN-1,4 -YLIDENE)=N(=O)-A'' (F) A-N(=O)=CH-Z WHEREIN: A AND A'' ARE SUBSTITUTED AND UNSUBSTITUTED HYDROCARBON RADICALS SELECTED FROM THE GROUP CONSISTING OF TERTIARY ALKYL RADICALS OF 1 TO 6 CARBON ATOMS AND ARYL RADICALS OF 6 TO 10 CYCLIC CARBON ATOMS; AND, Z IS AN AORMATIC RING SYSTEM; SAID SENSITOMETRIC MODIFIER BEING PRESENT IN AN AMOUNT FROM 0.001 TO 3 PARTS BY WEIGHT PER 100 PARTS BY WEIGHT OF CONSTITUENT (1), AND (3) A FREE-RADICAL GENERATING ADDITION POLYMERIZATION PHOTOINITIATOR ACTIVATABLE BY ACTINIC RADIATION.