Single exposure positive-working photopolymer element

Claim 2

A photopolymer element comprising a support and a layer of photopolymerizable material, characterised in that a positive-working photopolymer element consists essentially of a support, on one side of which is coated, in order, (1) a nonphotosensitive layer comprising a mixture of a hardenable binder and a releasable hardening agent, and (2) a permeable photopolymerizable layer.

Claim 3

An element according to claim 1 wherein the nonphotosensitive layer 1) comprises a gelatin binder, a colorant selected from pigments and dyes, and a sodium bisulfite adduct of a gelatin hardening agent selected from glutaraldehyde, glyoxal, formaldehyde and starch dialdehyde.

Claim 4

An element according to claim 1 or 2 wherein the nonphotosensitive layer 1) is opaque and the colorant is carbon black.

Claim 5

An element according to claim 1, 2 or 3 wherein the support is a polyethylene terephthalate film.

Claim 6

An element according to any one of the preceding claims wherein the photopolymerizable layer 2) comprises a photoinitiator, an actinic radiation absorber, a photopolymerizable monomer, and a polymeric binder.

Claim 7

An element according to claim 5'wherein.the photopolymerizable monomer is selected from a copolymer of styrene and maleic anhydride (SMA), triethyleneglycol dimethacrylate (TDMA), and polyoxyethylated trimethylolpropane triacrylate (TEOTA).

Claim 8

A process for preparing a direct-positive image in a photopolymer element as claimed in any one of the preceding claims which process comprises the steps of (a) imagewise exposing the photopolymerizable layer (2), (b) contacting the exposed layer (2) with an aqueous developer solution which preferentially diffuses through the unexposed areas of the photopolymerizable layer (2) and into the corresponding underlying areas of the nonphotosensitive layer (1) where it releases the hardening agent, whereupon the hardenable binder is hardened in the areas of the nonphotosensitive layer (1) underlying the unexposed areas of the photopolymerizable layer (2), and (c) washing off the photopolymerizable layer (2) together with the unhardened areas of the nonphotosensitive layer (1), leaving a direct-positive image comprising the hardened areas of the nonphotosensitive layer (1) on the support.

Claim 9

A process according to claim 7 wherein the developer is an aqueous solution of K 2 CO 3 /KHCO 3 .

Claim 10

A process according to claim 7 or 8 wherein the wash-off solvent employed in step c) is warm water.