Photopolymerizable composition and element

Claim 1

A PHOTOPOLYMERIZABLE ELEMENT CAPABLE OF FORMING RELATIVELY HIGH-CONTRAST IMAGES WHEN SUBJECTED TO RELATIVELY LOW-CONTRAST IMAGEWISE IRRADIATION, WHICH ELEMENT COMPRISES A SUPPORT BEARING A PHOTOPOLYMERIZABLE LAYER OF 0.00005 TO 0.010 INCH THICKNESS OF A PHOTOPOLYMERIZABLE COMPOSITION COMPRISING: (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 FROMING A HIGH POLYMER BY FREE-RADICAL INITIATED, CHAIN-PROPAGATING ADDITION POLYMERIZATION, (2) AT LEAST ONE N-SUBSTITUTED P-NITROSOANILINE SENSITOMETRIC MODIFIER REPRESENTED BY THE FORMULA: R-N(-R1)-(1,4-PHENYLENE)-N=O WHEREIN R IS A MEMBER SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, ALKYL OF 1 TO 5 CARBON ATOMS, HYDROALKYL WHEREIN THE ALKYL GROUP IS OF 1 TO 5 CARBON TOMS, PHENYL, TOLUYL, XYLYL AND ETHYLPHENYL; AND R1 IS A MEMBER SELECTED FROM THE GROUP CONSISTING OF ALKYL OF 1 TO 5 CARBON ATOMS, HYDROXYALKYL WHEREIN THE ALKYL GROUP IS OF 1 TO 5 CARBON ATOMS, PHENYL, TOLUYL, XYLYL AND ETHYLPHENYL, ACETAMIDO, N''ALKLY, AND N'',N''-DIALKYL SUBSTITUTED ACETAMIDO AND PSULFOPHENOXYBUTYL, SAID SENSITOMETRIC MODIFIER BEING PRESENT IN AN AMOUNT FROM 0.001 TO 3.0% BY WEIGHT OF CONSTITUTENT (1), (3) A FREE-RADICAL GENERATING ADDITION POLYMERIZATION PHOTOINITIATOR ACTIVATBLE BY ACTINIC RADIATION, AND (4) A VISCOSITY MODIFYING AGENT CONSISTING OF A THERMOPLASTIC COMPOUND SOLID AT 50*C.