High speed lithographic film element

High speed litho film in which short-life development accelerators such as cysteine methyl ester and its analogues are incorporated into the silver halide emulsion layer.

We claim:

1. A lithographic film element comprising a film support having one or more light-sensitive gelatino-silver halide emulsion layers coated thereon, each of which contains a development accelerator of the general formula: ##STR2## or a salt thereof, wherein each of R.sub.1 ; and R.sub.2 =H or C.sub.1 -C.sub.5 alkyl, each of R.sub.3 and R.sub.4 =H or -COOR, where R, R.sub.5, and R.sub.6 =C.sub.1 -C.sub.5 alkyl.

2. The lithographic film element of claim 1 wherein the development accelerator is 2-dimethylamino-ethanethiol-1 [cystein methyl ester, and their salts] or a salt thereof.

3. The lithographic film element of claims 1 or 2, wherein said element contains the development accelerator in combination with a dot sharpening agent selected from the group consisting of a polyalkylene oxide and a poly-N-vinyl lactam.

4. The lithographic film element of claim 2 in which the polyalkylene oxide is a polyethylene oxide having a molecular weight between 1,000 and 40,000.

5. The lithographic film element of claims 3 or 4, wherein the light-sensitive emulsion is coated in the form of a double coating with a thickness ratio between 1:1 and 1:9, and the dot sharpening agent is added to the thinnest of the emulsion layers.

6. The lithographic film element of one of the claims 1-5, wherein said element contains in the light-sensitive layer 50 to 500 mg hydroquinone per mole silver halide.

7. The lithographic film element of anyone of claims 3-6, wherein the development accelerator is in the light-sensitive layer and the polyalkylene oxide or poly-N-vinyl lactam is in an intermediate layer between the film base and the light-sensitive layer.

8. A lithographic film element consisting essentially of (a) a polyethylene terephthalate film support, (b) a light-sensitive gelatino-silver chlorobromide emulsion on said support, (c) an auxiliary underlayer between the film support and the emulsion, characterized in that the emulsion layer contains a development accelerator consisting of 2-dimethylamino-ethanethiol-1- or a salt thereof; and wherein the auxiliary underlayer contains a polyethylene oxide of M.W. circa 20,000, in an amount of sufficient to serve as a dot sharpening agent.