GB2082340A - Production of Photographic Masked Colour Images - Google Patents

Abstract

Masks for photographic dye images have been described which improve colour quality or correct tone reproduction. They are of opposite sign to the image being reproduced or printed, and preferably deliberately made unsharp. According to the invention there is provided a method of producing a photographic dye image masked by an unsharp masking dye image in a mask layer characterised in that the unsharpness of the masking dye image is obtained by causing the masking dye to diffuse over a distance into the mask layer from another layer. The photographic dye image and the masking dye image are preferably produced concomitantly. In an example, a redox dye releaser associated with an imagewise exposed negative working silver halide emulsion on development releases a diffusible dye in the light-struck areas which diffuses over a distance into the mask layer forming a masking dye image for the retained dye image. A masked positive transparency can be produced in this way.

Description

SPECIFICATION Production of Photographic Masked Colour Images This invention relates to the production of photographic masked dye images.

Using masks to improve the quality of photographic reproductions or prints from original photographs or negatives is well known in the art. One early variety of 'Kodacolor' film incorporated a mask layer which developed to form a low contrast, black and white, positive image to provide a correction to tone reproduction of prints made from that material.

Some methods for preparing separate masks to correct for some of the inaccuracies which occur when reproducing photographs or making prints from negatives, are described in "Principles of Colour Reproduction" by John C. Yule and also in "The Reproduction of Colour" by R. W. G. Hunt.

Masks are described which can be used to improve the colour quality and others which are used to correct tone reproduction. These masks are of opposite sign to the image being reproduced or printed, e.g. a negative mask is used together with a transparency original in order to improve the quality of a reproduction or print.

Both the above authors point out that additional further benefits can be obtained if the masks are deliberately made unsharp. In particular an improvement in sharpness is apparent in the print or reproduction if the mask is unsharp. The technique, which is commonly used in the Graphic Arts Industry is described as unsharp masking.

According to the present invention there is provided a method of producing a photographic dye image masked by an unsharp masking dye image in a mask layer characterised in that the unsharpness of the masking dye image is obtained by causing the masking dye to diffuse over a distance into the mask layer from another layer.

Preferably said diffusible dye is produced by the same imagewise exposure and development as said photographic dye image.

The unsharpness of a dye diffusion image arises partly from the distance the dyes have to diffuse from the donor to the mordant layer. The further the dyes have to diffuse the more they spread.

In the present invention the distance over which the masking dye diffuses can be regulated by a spacer layer.

Preferably the masking dye is mordanted in the mask layer. The density of the mask can be adjusted by limiting the amount of mordant used. Useful amounts of mordant are in the range t).2 to 1 gram/m2.

One example of a photographic colour image transfer process to which this present invention can be applied is described by W. T. Hanson in Photographic Science and Engineering, 20, 155 (1976).

According to one embodiment of the present invention said photographic dye image is obtained by developing an imagewise exposed silver halide emulsion layer with which is associated a compound which forms a diffusible dye as a function (direct or inverse) of development, allowing the diffusible dye to diffuse through a spacer layer to the masking layer to form said masking dye image and removing the developed silver from said emulsion layer.

In the above embodiment the silver halide emulsion may be negative working and said compound may be a redox dye releaser, e.g. as described in UK specification 1405662.

In the above embodiment only a portion of the diffusible dye may be retained in the mask layer, the remainder being allowed to diffuse through the mask layer into a separable image-receiving layer to form a colour transfer image.

In the description which follows the light-sensitive film described in the reference articles will be described as the 'donor' film.

One embodiment of the invention is a method of producing an integral unsharp mask in a colour image transfer photographic material in order to improve the sharpness of the photographic dye image retained in the donor film.

The integral unsharp mask is obtained by incorporating a mordant-containing layer and a spacer layer in the donor multilayer film. The dye image formed in the mordanted masking layer is unsharp because the dye has diffused away from its point of origin in the donor layers, through the spacer layer to finish on the mordanted mask layer. In this way an unsharp mask is formed concomitantly with the primary photographic image during the photographic processing step. No additional process is required to form the mask.

The degree of unsharpness of the mask can be controlled during film manufacture by adjusting the dye diffusion path length between its point of origin and the mordant, for example by adjusting the thickness of the spacer layer.

The density of the mask can be controlled during film manufacture by limiting the amount of mordant used.

Because the mask is of opposite sign to the donor image it adds substantial density to the minimum density areas of the donor photographic image. For this reason the preferred use of the invention is in negative or positive colour image transfer films from which prints or reproductions are to be made and the invention is less useful in films for direct display.

It is particularly suitable for photographic colour image transfer (C.l.T.) films which are used to prepare original photographs from which further prints or reproductions are required. The improved sharpness is achieved by means of an integral unsharp mask which is produced coincidentally with the primary photographic image during the transfer process. This is an advantage over the prior art in which unsharp masks usually have to be prepared by separate exposure and processing steps using additional photographic materials.

Example 1 A demonstration of the improved sharpness which can be obtained by this embodiment of the method of this invention was made by first preparing the three donor films and an activator as follows: Coating weights in g/m2 Film A Film B Layer Layer 8. Mordant Gelatine 0.60 Mask Layer Mordant 4 0.50 7. Protective Gelatin 0.60 7. Spacer Gelatin 5.0 Overcoat Layer 6. Blue Sensitive Gelatin 1.20 6. As coating A Yellow dye- Emulsion 1 0.38 releasing Layer RDR 1 0.45 5. Interlayer Gelatin 1.08 5. As coating A Yellow coloured colloidal silver 0.18 4. Green Sensitive Gelatin 1.20 4. As coating A Emulsion layer Emulsion 0.53 3. Magenta dye- Gelatin 1.20 3. As coating A releasing RDR 2 0.55 layer 2. Interlayer Gelatin 1.08 2. As coating A 1. Red Sensitive Gelatin 1.20 1. As coating A Cyan dye Emulsion 3 0.20 releasing layer RDR 3 0.37 Film Support Support As coating A BVSME hardener in each layer at 1% by weight of dry gelatin BVSME is bis(vinyl sulphonyl methyl)ether RDR=redox dye releasing compound.

Receiver C Coating weights in g/m2 Gelatin 2.15 Mordant 4 2.1 5 ETA 0.27 R. C. Paper Hardened at 2% of dry gelatin with BVSME.

ETA is 1 -phenyl-4-hydroxymethyl-4-methyl-pyrazolidone.

Emulsions 1, 2 and 3 are all the same basic negative, high speed, silver chlorobromide emulsion but each is sensitized to different regions of the spectrum. Emulsion 1 is blue, Emulsion 2 is green and Emulsion 3 red sensitive.

Activator Potassium Hydroxide 28 g Benzyl alcohol 8 ml 1 1 -aminoundecanoic acid 2g Potassium bromide 4g 5-Methylbenzotriazole lg Distilled water to 1000 ml Film A, the control, colour image transfer, multilayer coating consists of seven layers. Film B has identical emulsion and dye-forming layers to Film A, but in place of the protective overcoat, layer 7, it has a gelatin-containing, spacer, layer coated on top of the light-sensitive layers and a mordantcontaining layer (which forms the unsharp mask) coated on top of that.

The Receiver C, has a layer of mordant mixed with gelatin coated on a paper support. In this Example, the ETA is also coated in the receiver layer to enable an activator process to be used.

However it is not necessary to coat the developing agent in the receiver, it can alternatively be added to the processing solution or the donor.

The donor films A and B were exposed and processed, together with the receiver C, to produce a retained transparency dye image in the donor and a transferred negative reflection print image in the receiver.

Process Cycle The exposed donor was first soaked in activator at 82.50F for 14 seconds, then laminated to the receiver coating C.

After 3 minutes the laminate was peeled apart to give a retained dye+silver image in the donor and a transferred dye image in the receiver C.

In order to remove the silver the donor was then treated in the following way:~ Washed for 2 minutes in water.

Bleach fixed for 2 minutes in 'Ektaprint' 3 bleach-fix solution.

Washed for 1 minute in water.

Rinsed for 15 seconds in a solution of 28 g/l of KOH.

Rinsed for 5 seconds in distilled water.

The sensitometric results obtained for~ 1. the retained transparency dye image in the donor.

2. the transferred, reflection print image in the receiver.

are given in Figures 1, 2 and 3 for both films A and B, laminated individually with receiver C. Figure 1, gives the red density records, Figure 2 the green and Figure 3 the blue densities.

The superior sharpness of the donor image formed in film B with the integral mask is illustrated in Figure 4. This shows microdensitometer traces taken from the processed images of fine line exposures on the two films A and B.

The trace from the image on film B shows a considerable edge effect. This gives increased visibility to this image of the fine line exposure and hence increased sharpness.

Although the above Example is a positive transparency material, this invention is equally applicable to a negative, retained image, C.I.T. material. In either case, the primary image is formed from retained dye-releaser and the mask is formed from released dye which has the opposite sign.

The optimum positioning of the mask forming layer and the optimum amount of mordant needed may be experimentally determined for any particular system by those skilled in the art.

The invention can be applied to any photographic imaging system in which a dye is rendered mobile imagewise as a function of development. Thus, the invention can be used in photographic systems in which the main imaging occurs by the formation of non-diffusible dye if additional positive imaging compounds, which release mobile dyes with the opposite sign to the main image-forming compounds, are incorporated into the system together with the main image-forming compounds and the mordant layer.

Thus there is also provided another embodiment of the method of the present invention wherein said photographic dye image and the masking dye image are obtained by developing two oppositely working, imagewise exposed, silver halide emulsion layers with one of which is associated a compound which forms an immobile dye as a function (direct or inverse) of development and with the other of which is associated a compound which forms a diffusible dye of the same hue but of opposite sign to said immobile dye and allowing said diffusible dye to diffuse over a distance into a mask layer.

Alternatively the invention can be used in materials in which the main imaging occurs by the formation of non-diffusible dye if additional negative imaging dye-releasing compounds or couplers which form mobile dyes are incorporated into an additional layer (or layers) together with a direct positive emulsion (or emulsions). The mordant-containing mask layer is also needed. In this case the sole purpose of extra imaging layer or layers is to form the unsharp mask.

Thus there is also provided another embodiment of the method of the present invention wherein said photographic dye image and said masking dye image are obtained by development of an imagewise exposed silver halide emulsion layer with which is associated a compound which forms an immobile dye as a function of development (direct or inverse) and with which is also associated a compound which forms a diffusible dye of the same hue but of opposite sign and allowing said diffusible dye to diffuse over a distance into a mask layer.

Also a system based on dye developers can be used. In such a system the opaque base for the silver halide and dye developer layers should be capable of being made transparent by removing an opaque cover, or by bleaching, and the mordanted mask layer may be placed in front of or behind those layers as viewed from the base. The image-receiving layer together with its support and polymeric acid and timing layers can be stripped off, leaving a retained dye image and mask from which the silver may be removed by normal bleaching treatment.

It should be noted that in the systems in which the main image is formed by coupling to form non-diffusible dyes, the mask density can be controlled by emulsion characteristics and the coating weights of the extra layers e.g. of the couplers used to form the diffusible dyes, while the mordant in the mask layer may be of any thickness above that required to mordant the diffusible dye formed. Since no dye has to pass right through, it could thus be coated on a separate mordant receiving layer, and the sandwich processed by a soak and laminate process. However, this would necessitate re-registering the mask after processing but before printing.

The present invention also provides photographic materials described above for carrying out the method of the present invention in its several embodiments.

Kodak, Kodacolor, Extraprint and Estar are registered trade marks.

Claims (11)

Claims

1. A method of producing a photographic dye image masked by an unsharp masking dye image in a mask layer characterised in that the unsharpness of the masking dye image is obtained by causing the masking dye to diffuse over a distance into the mask layer from another layer.

2. A method according to claim 1 wherein said photographic dye image is obtained by developing an imagewise exposed silver halide emulsion layer with which is associated a compound which forms a diffusible dye as a function (direct or inverse) of development, allowing the diffusible dye to diffuse through a spacer layer to the mask layer to form said masking dye image and removing the developed silver from said emulsion layer.

3. A method according to claim 2 wherein said silver halide emulsion is negative-working and said compound is a redox dye releaser.

4. A method according to claim 2 or 3 wherein only a portion of the diffusible dye is retained in said mask layer, the remainder being allowed to diffuse through said mask layer into a separable image-receiving layer to form a colour transfer image.

5. A method according to claim 4 substantially as described in Example 1 using Film B.

6. A method according to claim 1 wherein said photographic dye image and the masking dye images are obtained by developing two oppositely working, imagewise exposed, silver halide emulsion layers with one of which is associated a compound which forms an immobile dye as a function (direct or inverse) of development and with the other of which is associated a compound which forms a diffusible dye of the same hue but of opposite sign to said immobile dye and allowing said diffusible dye to diffuse over a distance into a mask layer,

7.A method according to claim 1 wherein said photographic dye image and said masking dye image are obtained by development of an imagewise exposed silver halide emulsion layer with which is associated a compound which forms an immobile dye as a function of development (direct or inverse) and with which is also associated a compound which forms a diffusible dye of the same hue but of opposite sign and allowing said diffusible dye to diffuse over a distance into a mask layer.

8. A photographic material useful in a method according to claim 2 or 3 comprising a support bearing at least one light-sensitive silver halide emulsion layer having associated therewith a dye image-providing compound such that an imagewise distribution of diffusible dye is produced on imagewise exposure and development of the silver halide emulsion layer and also bearing a mordant layer comprising an amount of mordant for said diffusible dye sufficient to improve the sharpness of the dye image provided by said compound when said diffusible dye has diffused therefrom into said mordant layer but insufficient to form an image of density equal to that of said dye image, said mordant layer being separated from said dye image-providing compound by a spacer layer.

9. A photographic material useful in the method according to claim 6 which comprises a support and two oppositely working silver halide emulsion layers having associated therewith, respectively, the compounds defined in claim 6 and which also comprises a mordant layer as defined in claim 8 which is separated from the compound which forms a diffusible dye by a spacer layer.

10. A photographic material useful in the method according to claim 7 comprising a support and a silver halide emulsion layer having associated therewith the compounds defined in claim 7 and comprising a mordant layer as defined in claim 8 which is separated from the compound which forms a diffusible dye by a spacer layer.

11. A photographic material according to claim 8 substantially as described in Example 1 with reference to Film B.