GB1531240A - Diffusion-transfer photographic method and film unit - Google Patents

Abstract

1531240 Photographic diffusion transfer silver halide film unit FUJI PHOTO FILM CO Ltd 7 Nov 1975 [12 Nov 1974] 46272/75 Headings G2C and G2X A photographic film unit comprises (1) a transparent support bearing on one side an opaque sheet which is bonded by a first bonding means to the support so that after processing it is readily detachable from the support at least all over its area apart from one edge, and bearing on the other side of the support, in order, an image-receiving layer, at least one photo-sensitive silver halide emulsion layer capable of releasing diffusible image-formation material transferable to the image-receiving layer under the influence of the aqueous alkaline processing composition (3), which silver halide layer is detachably bonded to the image-receiving layer by a second bonding means, (2) a transparent sheet which covers the side of the film unit intended to be imagewise exposed and is adapted to retain processing composition during processing and (3) the aqueous alkaline processing composition provided in one or more rupturable containers attached to be spreadable between (2) and (1), a developing agent being present in the composition or elsewhere in the film unit from which it is diffusible in the presence of (3), (3) also containing a substance which provides protection to one side of the silver halide layer from light during development. In Example 1 the film unit is used in a silver salt diffusion transfer process and in Examples 2 and 3 in a colour diffusion transfer process. The first and second bonding means may comprise pressure-sensitive tape. The first bonding means may comprise a double layer bonding strongly to the support and more weakly to the opaque sheet, e.g. layers of zein and ethyl cellulose or layers of polyvinyl alcohol and ethyl cellulose. The surface of the transparent support nearer the opaque sheet may be coated with a silicone resin or other release agent. When the opaque sheet is placed over the silver halide layer, after spreading (3) and removing the transparent support bearing the image-receiving layer, the opaque sheet and the silver halide layer are preferably bonded mechanically by a corrugated portion formed in the surface of the first bonding means near one edge and a corresponding portion formed in the surface of the silver halide layer see Fig. 5(d) (not shown). A positive print is obtained as well as a negative for producing further copies without the need of special optical means for image reversal in an associated camera.