Photographic colloid transfer facilitated by enzyme treatment

Feb. 23, 1971 _c. m. mar£chal 3,565,618

PHOTOGRAPHIC COLLOID TRANSFER FACILITATED BY ENZYME TREATMENT

Filed July 5, 1966

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FIXED, WASHED AND DRIED PHOTOGRAPHIC ELEMENT

UNHARDENED EMULSION LAYER

FIG· I

<img file="US3565618A_D0002.tif" />

UNIFORM AREA BY ENZYME

AFFECTED

FIG· 2

<img file="US3565618A_D0003.tif" />

FIG-3

<img file="US3565618A_D0004.tif" />

TRANSFERRED EMULSION STRATUM

FIG' 4

CLAUDE M- MARECHAL

INVENTOR.

<img file="US3565618A_D0005.tif" />

3,565,61$

Patented Feb. 23, 1971

United States Patent Office

3,565,618

PHOTOGRAPHIC COLLOID TRANSFER FACILITATED BY ENZYME TREATMENT

Claude M. Marechai, Vincennes, France, assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey

Filed July 5,1966, Ser. No. 562,863

Claims priority, application France, Mar. 2, 1966, 51,627

Int. Cl. G03c 11/12

U.S. Cl. 96—28 20 Claims

ABSTRACT OF THE DISCLOSURE

Colloid transfer of a photographic image from an image bearing photographic element having a proteinaceous binder is accomplished by treating the protein binder with an enzyme such as a proteinase to soften a thin layer which is then transferred by contacting against a receiving support. Subsequent transfers can be made by repeating the treatment.

This invention relates to photography and particularly to a transfer process of printing a photographic image.

Various methods of forming an image in an unsensitized sheet by transfer have been described in the literature. In U.S. Pat. 2,596,754, E. C. Yackel has described a procedure according to which a photographic image formed in an unhardened gelatin layer by conventional processing is transferred to a dry absorbent receiving sheet by squeegeeing the print, after processing, into contact with the dry absorbent surface, then stripping the two apart after a short interval of contact. In this process, a stratum of gelatin layer adheres to the receiving surface and is transferred leaving behind the remainder of the gelatin layer containing a part of the image. Upon rewetting the gelatin layer, successive transfers can be made.

Although the above described process has, for the most part, met with a good deal of success, there have been drawbacks associated with the transfer step. One of the problems in this respect is the lack of uniformity in the thickness of the transferred colloid. This results in prints having distorted image intensities and generally reduced image quality. Also, the process has heretofore been applicable to a rather limited number of readily available photographic elements.

It shall be one object of this invention to provide an improved method and materials for reproducing photographic images. Another object shall be to provide improved methods and materials for colloid transfer processes. Still another object shall be to provide transferred images of improved quality. A further object shall be to provide a bath which substantially improves colloid transfer. Another object of the invention shall be to provide a method for colloid transfer applicable to a wide variety of available photographic elements. A still further object is to provide a colloid transfer method useful on relatively dry colloid layers.

These and other objects which shall be apparent in light of the detailed disclosure are accomplished by the employment of enzymes to facilitate colloid transfer. This invention, in its broader sense, is applicable to photographic elements wherein the pigment, dye, sliver, etc., forming the photographic image are suspended in a binder or emulsion vehicle which is a substantially unhardened, proteinaceous colloid. This invention will be better understood by reference to accompanying drawings where:

FIG. 1 illustrates, in enlarged cross-sectional view, a processed photographic element carrying an unhardened emulsion layer containing a silver image.

FIG. 2 shows an enlarged cross-sectional view emphasizing the sharply defined area affected by the enzyme treatment.

FIG. 3 shows in enlarged cross-sectional view the method of transferring a stratum of the processed emulsion layer to a receiving support.

FIG. 4 shows in enlarged cross-sectional view the appearance of the transferred emulsion stratum on the receiving support.

This invention will now be described in greater detail with reference to the drawings. According to a particularly useful embodiment of the invention, a substantially unhardened, dried processed gelatin emulsion layer is wetted with a proteinase solution. When the emulsion is dipped into the proteinase solution, the emulsion is superficially degraded and the hydrolysis front progresses in depth with a remarkable and surprising regularity. The emulsion is then brought (by rolling, squeegeeing, etc.) into intimate contact with a suitable receiving support, such as paper, cloth, wood or similar absorptive material. After stripping the receiving support from the emulsion layer, a thin stratum of degraded emulsion is found transferred to the receiving support. The process can be repeated for successive transfers. The appearance of the processed photographic element is simulated in enlarged cross-sectional view in FIG. 1 wherein layer 10 is the emulsion support of a proper base (paper, film or other material) carrying an unhardened emulsion layer 11 containing the image (silver, dye, etc.) 12. The effect of the proteinase treatment on the emulsion is emphasized in FIG. 2 wherein the support 10 is now carrying essentially unaffected emulsion layer 13 containing the image area 14. The layer affected by the proteinase is layer 15 containing image area 16. The method of transferring stratum 15 containing image area 16 to a receiving support is shown in FIG. 3 wherein layer 10 is the emulsion support carrying the residual unhardened emulsion layer 13 and residual image 14 which are left on support 10 after stripping off the stratum of emulsion 15 containing the image 16, 15 and 16 adhering to the receiving support 17. The appearance of the transferred emulsion stratum on the receiving support is shown in enlarged cross-sectional view in FIG. 4 wherein layer 17 is the receiving support carrying emulsion stratum 15 containing the image 16.

According to one embodiment of the invention, several prints are obtained simultaneously by accomplishing transfer onto a stack of several sheets of very thin porous paper. Advantageously, the sandwich formed by the receiving sheets and the matrix sheet is kept at a higher temperature than room temperature, e.g., 40° C. in order to increase the hydrolysis speed. As the hydrolysis progresses, the hydrolysis materials migrate through the paper sheets and carry along the silver grains or the dyes of the matrix. A single operation is sufficient for obtaining multiple prints.

The following examples are illustrative of this invention but are in no way intended to limit the scope of the invention.

EXAMPLE 1

A daylight incorporated coupler type reversal color film was exposed and processed, except that the emulsion was not hardened. The completely processed and dried element was treated for 15 seconds in a solution containing 4 g. of trypsin per liter. Several successive strata (four or five) of each of the emulsion layers which constitute the color film could be transferred to successive unsized 88 g. paper sheets to obtain as many prints of each of the three separation images. Between two successive transfer operations, the matrix was dipped in the enzyme solution.

Multiple transfers were obtained as follows: The image carrying matrix was placed on a rotating drum whose

3,565,618 lower portion was dipped into a tank containing the enzyme solution. The receiving paper was passed at the upper part of the drum between the drum and a counterroller rotating in the opposite direction. At each rotation of the drum, the matrix first went through the enzyme soluion, then came into contact with the receiving paper and a thin stratum of said matrix was transferred to the receiving paper.

EXAMPLE 2

The procedure of Example 1 was repeated, but the trypsin solution was replaced, respectively, by:

a solution of 4 g. per liter of takamin, a solution of 5 g. per liter of papaine, a solution of 10 g. per liter of pepsin, a solution of a saccharifying enzyme sold as Rhozyme PH (by Rohm &amp; Haas).

In each case, prints similar to those of Example 1 were obtained.

EXAMPLE 3

A film with a high contrast silver halide emulsion coated on a thin base, was exposed and developed in a nonhardening developer of the following composition:

G.

N-methyl-para-aminophenol sulfate 1

Sodium sulfite (desiccated) 75

Hydroquinone 9

Sodium carbonate (desiccated)25

Potassium bromide______: 5

Water to make 1 liter.

After developing the emulsion layer, it was fixed-out in a nonhardening fixing bath of the following composition:

G.

Sodium thiosulfate (desiccated) 150

Sodium sulfite (desiccated) 10

Sodium metabisulfite 25

Water to make 1 liter.

After fixing and washing, the emulsion was subjected to gelatin softening treatment by a solution of 10 g. urea in 1 liter of water. It was dried and then dipped for 5 seconds in the following enzyme solution:

Trypsin (40,000 units)—4 g.

Water to make—1 liter.

It was then possible to transfer several times a thin stratum of the emulsion layer to paper receiving sheets, the matrix being wetted by the enzyme bath between two successive transfers.

EXAMPLE 4

The procedure of Example 3 was repeated, except that enzyme solutions containing a softening agent and having one of the following compositions (A) to (D) were used:

Solution A

G

Takamin 4

Urea 4

Distilled water to make 1000 ml.

Solution B

Papaine 5

Urea 4

Distilled water to make 1000 ml.

Solution C

Pepsin 15

Urea_________________________________10

Distilled water to make 1000 ml.

Solution D

Rhozyme Pll 10

Urea 10

Distilled water to make 1000 ml.

Results similar to those of Example 3 were obtained.

Baths (A) to (D) contain urea as a softening agent. This softening agent may be used also in a distinct bath as in Example 3; in this case, treatment is first carried out with the softening bath and then with the enzyme bath which itself may contain a softening agent. Softening baths used as a pretreatment are made up of solutions containing 10 g. of urea per liter or 20 g. of potassium thiocyanate per liter. Of course, the bath or baths to be used will depend on the hardening of the emulsion employed and is a matter of choice. With substantially unhardened emulsions such as those of Examples 1 and 2, enzyme baths without any softening agent are used, whereas with more hardened emulsions, the baths of Example 4 are used or the baths of Examples 1 and 2 with a softening pretreatment as mentioned in Example 3; and finally, with still more hardened emulsions, a softening bath is used jointly with an enzyme bath, containing a softening agent such as those of Example 4.

In this specification, “substantially unhardened emulsion” means an emulsion having a melting point of about 40° C. in hot water. These gelatin emulsions may also be defined as emulsions which are not harder than would be the case with gelatin containing 0.25 ounce of formaldehyde (40%, diluted 1 to 3 with water) per pound of gelatin when freshly coated, or 0.1 ounce of the formaldehyde solution per pound of gelatin for a sample aged 3 to 6 months.

By using softening agents, as explained above, it is possible to transfer strata of more hardened emulsions having a melting point of up to 96° C. in hot water. The process of the aforementioned U.S. Pat. 2,596,754 can only use “substantially unhardened” emulsions. When emulsions hardened with chromium alum are used, the enzyme treatment may be preceded by treating for two minutes at about 25° C. with a solution containing 25 g. of citric acid per liter.

EXAMPLE 5

It is possible to carry out development in a hardening developer containing an enzyme; for example an emulsion of the type described in Example 4 can be processed in a developer of the following composition:

G.

Hydroquinone 10

Sodium sulfite (desiccated) 2

Sodium carbonate (desiccated)20

Trypsin (20,000 units) 5

Distilled water 1000 ml.

During this processing, the developed areas are hardened and resist the enzyme hydrolysis. Only the undeveloped areas are transferred.

Examples 6 and 7 give compositions of developers that may be used in place of the one described in Examples 3 and 4.

EXAMPLE 6

G.

N-methyl-para-aminophenol sulfate2.5

Sodium sulfite (desiccated) 50

Hydroquinone2.5

Sodium metaborate 20

Potassium bromide0.5

Water to make 1 liter.

EXAMPLE 7

G.

N-methyl-para-aminophenol sulfate0.3

Sodium sulfite 38

Hydroquinone 6

Sodium carbonate (desiccated) 19

Potassium bromide0.9

Citric acid0.7

Water to make 1 liter.

3,565,618

EXAMPLE 8

A print was prepared which contained a color image in a mordanted gelatin layer, by the imbibition printing process. The print was soaked with a ¹/looo solution of trypsin, at 25° C., then the emulsion side was applied into contact with a stack of sheets of 12 g./m.² paper, intended for the making of tea bags, also soaked with enzyme. The sandwich was drained between two rubber rollers and kept at 40° C. on a heating plate. Two minutes later, four prints were obtained.

This process provides multiple prints from any of a variety of known gelatin and gelatin derivative emulsions which are used in standard, commercial, X-ray, graphic arts black and white negative, color, negative, black and white positive, and color positive film. The number of transfers possible is dependent upon the time the enzyme acts on the colloid, the particuler enzyme chosen, as well as the hardening characteristics, temperature, thickness, etc., of the emulsion. While in the preferred embodiment, the system is utilized for a stratum transfer, i.e., a thin layer of the total surface of the photographic element is carried off into a receiving support, the system works well with emulsions which have portions of the surface area hardened and portions unhardened. The hardened areas are substantially unaffected while the unhardened areas are transferred readily to a receiving support.

The major function of the enzyme is to break down the proteinacious colloid structure to a sufficient degree to facilitate transfer to a receiving support. Therefore, any enzymes which hydrolyze the interior peptide bonds of proteins are applicable with varying success to the present invention. Proteinases which are very effective in the invention are pepsine, trypsin, papaine, in solution in relatively pure state or admixed with other enzymes, etc. as in pancreatine, which is a mixture of lipase, amylase and trypsin and also in commercially available proteinase compositions, e.g. Rhozyme (registered trademark of Rohm and Haas Co.) which is known as a saccharifying enzyme. Enzymes of this type are also useful in my invention. Other enzymes which hydrolyze proteins include: peptidase, erepsin, arginase, carbamase, nuclease, etc. The selection of the specific enzymes in each case is mainly dependent upon the pH at which the operation is to be conducted. For example, pepsin is active in low pH medium whereas trypsin acts optimally at slightly alkaline pH values. The bath is generally kept at 22° C. although for the specific enzymes mentioned, the hydrolysis may start at about 18°. At about 55° C. the enzymes are most active but the activity drops off sharply at 70° C. The concentration of the enzyme can vary from only a few milligrams to several grams per liter of bath.

The enzyme solution can contain any of a number of conventional photographic addenda and can serve as a simultaneous processing bath and enzyme bath, providing the pH, etc., of the processing bath do not inhibit enzyme action. If the pH does inhibit the enzyme action, an after bath adjusting the enzyme soaked film to the proper pH can be effective. The enzyme solution can also be applied to the film in various ways, for example dipping the film in a bath as mentioned above, spraying the solution on the film, applying the solution from a processing pod wherein the enzyme is normally associated in a thickened (e.g., with carboxymethylcellulose) aqueous solution. The enzyme solution has to be in contact with the colloid only for a short time, for example, when employing an enzyme bath, usually only a 2-10 second period (preferably 4-5 seconds) is required. Most effective transfers can be accomplished in 10-20 seconds later.

The process and materials of the present invention have a host of apparent uses in experimental photography such as in determining the penetration of light, in determining the penetration of various processing baths, study of hardening diffusion of the sensitizing dyes, position of coating defects, study of interimage effects, etc. Commercial applications are just as numerous, e.g., illustrating punch cards, black and white and color copying processes, coating extra thin layers, personalizing conventional household and business items, etc. In particular, it is possible to transfer images by the process of the invention to a suitable porous paper, then to coat this paper with thermosetting resin and to prepare advertising items in a known manner, etc. This invention finds particular advantage in the solvent transfer system wherein previously no practical, inexpensive method existed for making multiple prints. Utilizing the present invention, multiple copies of a diffusion transfer print could be readily prepared.

This invention has been described in considerable detail with particular reference to certain preferred embodiments thereor, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.