US3620738A

US3620738A - Dye transfer color photography

Info

Publication number: US3620738A
Application number: US712931A
Authority: US
Inventors: Hans K Wong
Original assignee: Itek Corp
Current assignee: Northrop Grumman Guidance and Electronics Co Inc
Priority date: 1968-03-14
Filing date: 1968-03-14
Publication date: 1971-11-16
Anticipated expiration: 1988-11-16

Abstract

Method of making a dye transfer print by directly applying dye to an imaging medium in which a photographic image is defined by selectively softened portions of a supported photosensitive layer comprising a finely divided photoconductor and a binder therefor, and then transferring applied dye therefrom to a receptor surface, without prior removal of said selectively softened portions of said supported layer to create a photographic relief image.

Description

United States Patent [72] Inventor Hans K. Wong Arlington, Mass. [211 Appl. No. 712,931 [22] Filed Mar. 14, 1968 [45] Patented Nov. 16, 1971 [73] Assignee lick Corporation Lexington, Ma.

[54] DYE TRANSFER COLOR PHOTOGRAPHY 9 Claims, No Drawings [52] US. 96/48, 96/28 [51] Int. Pl G03c 5/24 [50] Field olSeai-eh 96/28, 88, 48; 101/464 [56] References Cled UNITED STATES PATENTS 2,713,305 7/1955 Yutzy etal 96/30 X 2,834,676 5/ 1958 Stanley et al. 96/28 3,146,104 8/1964 Yackel eta] 96/33 3,159,485 12/1964 Van Hoot et 211.... 96/33 X 2,013,116 9/1935 Troland 101/464 2,381,704 8/1945 Terry 101/464 Primary Examiner-Norman G. Torchin Assistant Examiner-John L. Goodrow Anomeys-Horner 0. Blair, Robert L. Nathans and W. Gary Goodson DYE TRANSFER COLOR PHOTOGRAPHY BACKGROUND OF THE INVENTION 1 Field of the Invention This invention relates to improved methods for making dye transfer prints by transfer of dye to a receptor sheet from an imaging medium of a type suitable for the preparation of photographic relief images, and relates in particular to the use of such a medium, in which a photographic image is defined by selectively softened portions of a photosensitive layer, for dye transfer prior to removal of selectively softened portions thereof to form a relief image.

2. Description of the Prior Art Commonly owned copending US. Pat. application Ser. No. 713,022, filed Mar. 14, 1968, of Robert H. Sprague for Direct Positive Photographic Relief Image," filed on even date herewith, discloses methods for making direct positive photographic relief images and dye transfer prints therefrom employing an imaging medium having a supported photosensitive layer comprising a finely divided photoconductor dispersed in a binder therefor. Exposure of such an imaging medium to actinic radiation such as visible or ultraviolet light activates the photoconductor, rendering it capable of effecting chemical reactions which are utilized to develop a visible image in the medium. Specifically, the exposed medium is developed with a developing agent comprising reducible metal ions, whereby free metal is deposited in said radiation-exposed portions. The deposited free metal is next oxidized to metal ions in the presence of a metal ion-activated softening agent for said binder, whereby the binder is softened in radiation-exposed areas. According to the invention disclosed in this copending application, softened binder is next removed from radiationexposed areas to produce a positive relief image defined therein by removed and unremoved binder portions. A dye suitable for dye transfer processes is next taken up into unremoved portions of the binder and then transferred therefrom to a receptor surface, such as a mordanted paper or transparent film base.

SUMMARY OF THE INVENTION According to the present invention it has been found that photographic imaging media exposed, developed, bleached, and softened according to the process of the prior art as described above can be used directly to prepare dye transfer prints by direct application of dye to the photographic imaging medium in which an image is defined by selectively softened portions of binder, i.e., without prior removal of softened binder to form a relief image. It has been found that these softened portions of binder do not significantly take up dye ap plied thereto and do not transfer significant quantities of dye therefrom to the receptor sheet in the making of a dye transfer print.

The resulting elimination of the step of removing softened portions of the binder prior to the first application of dye thereto involves a considerable saving of time in the preparation of dye transfer prints and decreases the chance of image damage during this binder removal step. Also, elimination of the step of removing softened binder portions in the preparation of a relief image significantly simplifies the structure of apparatus for performing the steps necessary for preparing dye transfer prints of an image to be copied.

In the process of this invention, softened portions of binder from the photosensitive layer of the imaging medium are usually transferred to receptor surfaces by adhesion thereto during the making of the first or the first few dye transfer prints. Hence, a relief image is soon formed in the photographic imaging medium, which relief image can then be used in conventional fashion to make further dye transfer prints. The first dye transfer print made from an imaging medium to which dye has been applied according to this invention, i.e., before formation of a true relief image in the medium, bears both dye transferred from unsoftened portions of the binder and deposits of softened binder which tend to become adhered to the receptor sheet and are in this manner physically removed from the imaging medium. The softened binder transferred to the dye transfer print is substantially uncolored, i.e., the softened material has not significantly taken up the dye applied to the imaging medium prior to contact with the transfer sheet. This softened binder adhering to the print can be readily removed by washing of the print without harming its quality.

Most of the softened binder from the imaging medium is generally transferred when the first contact print is made, but small amounts of softened binder may be transferred in the preparation of subsequent prints. Substantially all of the softened binder is removed from the imaging medium after two or three prints have been made. The relief image so formed may now be used, as known in the prior art, for the subsequent manufacture of multiple dye transfer images.

Details of the preparation of imaging media suitable for forming relief images and making dye transfer prints therefrom, and comprising softened binder portions defining an image therein, are to be found in the aforesaid copending application, incorporated herein by reference. The imaging media described in this copending application comprise a finely divided photoconductor suitably dispersed in a binder therefor to form a photosensitive layer on a support such as paper, metal foil, plastic, glass, or the like. The photoconductors of greatest utility for use in such imaging media are compounds formed between metals and elements of Group VIA of the Periodic Table, for example metal oxides, sulfides, selenides, and tellurides. Preferred materials from the point of view of color, light sensitivity, ease of development and the like are titanium dioxide and zinc oxide.

A radiation-exposed imaging medium, in which radiation struck areas of the photosensitive layer comprise activated photoconductor, is suitably developed by contacting the exposed medium with a developing agent comprising metal ions which are reduced by the activated photoconductor to form a deposit of free metal. Next, the free metal deposited in radiation-exposed areas in reoxidized (bleached) to form metal ions dispersed throughout the binder in radiation-struck portions. The reoxidation is effected in the presence of a metal ion-activated softening agent for said binder so that those portions of the binder surrounding the metal ions formed in the exposed medium by reoxidation become softened.

According to the present invention, the medium comprising selectively softened binder portions may now be treated with a dye of the type conventionally used in the photographic arts for making dye transfer prints. Monochrome prints may be made, or full color dye transfer prints proceeding as described in detail in the copending application mentioned earlier herein.

DESCRIPTION OF PREFERRED EMBODIMENT The methods and materials of the present invention are particularly useful in systems employing hardened gelatin as a binder for a photoconductor in an imaging medium.

In such a preferred embodiment, a photographic imaging medium comprising a support layer such as of paper having a finely divided photoconductor, such as finely divided titanium dioxide, dispersed throughout a hardened gelatin layer on said support is exposed to imaging radiation as described. Lightstruclt areas of the imaging medium are then developed by contact of the exposed medium with a developing agent comprising a dissolved metal salt, suitably a dissolved silver salt, resulting in the deposition of metal in the light-struck areas. The image so formed may be intensified by techniques analogous to physical development. The metal image, e.g., a silver image, is next bleached (reoxidized) in the presence of a softening agent for the gelatin, which becomes softened in light-struck areas and leaves hardened gelatin in unexposed areas.

Development with silver ion is conveniently done by contacting the exposed imaging medium with aqueous silver nitrate to form a metallic silver image in the medium. This image can be intensified by contact with a redox system, preferably an organic redox system such as hydroquinone, metol (p-methylamino phenol sulfate) or the like, which promotes further deposition of metal where metal is already present. The metal ion and redox system may be applied separately or in admixture.

Bleaching solutions having a softening effect on hardened gelatin layers are known in the photographic arts and are taught, for example, in Glafkides, Photographic Chemistry," Vol. 2, Fountain Press, London (1960), page 668.

Because the present invention involves processing of a layered photographic imaging medium involving selective softening and the ultimate removal of portions of a photosensitive binder layer from a support layer, the medium is conventionally exposed to imaging radiation from its light-sensitive side to insure that softening and removal of the binder layer will occur in proportion to the amount of radiation received thereby, i.e., that a complete removal of the binder layer from the support layer will only occur in those portions of the medium in which the light intensity is strongest, penetrating to the interface between the binder layer and support layer. As is also known in the art of preparing relief images by radiationinduced sofiening of a binder layer, a light-attenuating agent is suitably dispersed in the binder layer of the imaging medium to control the depth of light penetration on exposure. For example, in panchromatic silver halide films used for the production of relief images, finely divided carbon is generally dispersed through the imaging medium as a moderator or attenuator. Alternatively, a yellow dye is often dispersed through silver halide layers for the same reason.

In the present invention, a moderator or attenuator is also suitably employed to control the depth of radiation penetration on exposure. In the preparation of positive relief images ancillary to producing full color dye transfer prints, the photoconductor in the imaging medium may be dye sensitized with known dye sensitizers to be receptive to red, green, or blue light, all as taught in said aforesaid copending patent application. The dyes used for this sensitization are generally present in the binder layer in amounts sufficient for the dye to not also as a moderator or attenuator, so that the need for carbon or an additional dye as a light moderator is obviated.

A better understanding of the present invention and of its many advantages will be had by referring to the following specific examples, given by way of illustration.

EXAMPLE 1 Preparation of a Photographic Imaging Medium Adaptable to the Manufacture of Direct Positive Photographic Relief Images 50 grams of an aqueous slurry containing 25 percent of finely divided titanium dioxide (about 0.3-0.4 micron) were diluted with 42.6 ml. of distilled water and 3.4 ml. of a percent solution of a commercial wetting agent (Tiwet"). The resulting mixture was heated to about 100 F. and then combined with 100 grams of a 10 percent aqueous solution of gelatin swelled and heated to 100 F. 2.6 ml. of a 50 percent aqueous solution of glycerin were added to the resulting slurry as a humectant and antifoaming agent, and 2 ml. of a 4 percent aqueous solution of formaldehyde were added to the slurry as a hardening agent for the gelatin The resulting slurry was then uniformly poured onto a fiat piece of subbed triacetate film and drawn down with a hot wire rod. The resulting hardened gelatin coating was dried for minutes at room temperature and for another 20 minutes at about 50 C. in a circulating hot air oven.

EXAMPLE 2 Dye Sensitization of a Photographic Imaging Medium A sheet of the film prepared as in example 1 was dip dyed for 2 minutes in an aqueous solution containing 100 mg. per liter of Z-(p-dimethylamino styryl)-4-methyl thiazolium methochloride,

which sensitizes the film to green light. The sensitizing dye here used acts also as a light moderator to control the depth of light penetration into the gelatin binder on exposure.

EXAMPLE 3 Exposure and Processing A 5-second exposure to a photographic image to be copied was made using a watt lightbulb at a distance of 12 inches. A green filter was used in view of the dye sensitization of the film to green light.

The exposed printing medium was next developed by contacting with 3 N aqueous silver nitrate solution, briefly draining, and the contacting with an aqueous solution of 2 percent metol and 0.5'percent citric acid for l0 seconds to intensify the silver image and render it visible. The print was fixed in a standard acid hypo fixing bath and washed.

The film containing a silver image was next bleached for 2 minutes with a sottening bleach of a type known in the art, prepared, for example, by combining one part by volume of a 3 percent aqueous solution of hydrogen peroxide with three parts by volume of an aqueous solution containing 75 grams of CuSO '5l-L0, 2 grams of KBr, 25 ml. of concentrated 14,80 and water to make 1,500 ml. (cf. Glafkides, op. cit., p. 668). The bleach softens the gelatin in the silver image areas of the imaging medium but leaves intact those portions of the gelatin binder where no silver ion is present. The gelatin matrix so prepared was merely rinsed in lukewarm or cold water after removal from the softening bath to rinse off any film of adhering softening bath. No significant removal of softened gelatin is involved, for example either by brushing or the like or by extended washing to remove softened gelatin.

EXAMPLE 4 OaNu IIzN H O H O The cyan dye image was then transferred by 5 seconds contact with a piece of preconditioned commercial (Kodak) transfer paper.

On removal of the imaging medium from the mordanted transfer paper, softened gelatin adhered to the paper, from which it was easily removed by gently swabbing the pring with a wet tissue, without harmful efiect to the transferred dye image therein.

After the making of the first print, the photographic image in the imaging medium was defined therein in relief because of removal of the softened gelatin therefrom by transfer to the receptor sheet on making the first dye transfer print.

Subsequent dye transfer receptor sheets did not show further significant portions of softened gelatin being transferred from the imaging medium.

What is claimed is:

1. In the method of making dye transfer prints by transferring dye to a receptor surface from a relief image formed from a photographic imaging medium comprising a supported photosensitive layer of a finely divided photoconductor which is reversibly activatable by actinic radiation dispersed in a gelatin binder therefor, said imaging medium bearing a photographic image defined in said supported layer by portions of said gelatin binder which have been selectively softened, the improvement wherein dye to be transferred is directly applied to said imaging medium and then transferred to said receptor surface without prior removal of said selectively softened portions of the gelatin binder, said softened portions neither significantly taking up nor transferring dye applied thereto.

2. A process as in claim 1 wherein said supported layer comprises finely divided titanium dioxide dispersed in a gelatin binder.

3. The method of making a dye transfer print from a direct positive photographic image which comprises exposing a photosensitive imaging medium to imaging radiation, said imaging medium comprising a finely divided photoconductor which is reversibly activatable by actinic radiation dispersed in a gelatin binder therefor; developing radiation-exposed portions of said imaging medium with a developing agent comprising reducible metal ions, whereby free metal is deposited in said radiation-exposed portions; and reoxidizing said free metal to metal ions in the presence of a metal ion-activated softening agent for said gelatin binder to soften said binder in radiation-exposed areas to produce a photographic image of unsoftened gelatin binder; and transferring dye from said positive photographic image to a receptor sheet without prior removal of softened portions therefrom to thereby form a dye transfer print.

4. The method of making a full color dye transfer positive print which comprises respectively exposing three photosensitive imaging media to imaging radiation from a set of red, green, and blue color separation positives, said imaging media each comprising a finely divided photoconductor which is reversibly activatable by actinic radiation dispersed in a supported layer of a gelatin binder therefor, said photoconductor being dye sensitized to said imaging radiation; developing radiation-exposed portions of said imaging media with a developing agent comprising reducible metal ions, whereby free metal is deposited in said radiation-exposed portions; reoxidizing said free metal to metal ions in the presence of a metal ion-activated softening agent for said gelatin binder to soften said binder in radiation-exposed areas to produce a photographic image of unsoftened gelatin; and subsequently,

without prior removal of softened portions therefrom, respectively taking up cyan, magenta, and yellow dye in unsoftened portions of the binder of the images respectively prepared by exposure to said red, green, and blue color separation positives; and transferring dye from said images to a receptor sheet in register to produce a full color positive dye transfer print.

5. The method of making a full color dye transfer positive print which comprises respectively exposing three photosensitive imaging media to imaging radiation from a positive color image through a red, green, and blue filter; said imaging media each comprising a finely divided photoconductor which is reversibly activatable by actinic radiation dispersed in a supported layer of a gelatin binder therefor, said photoconductor being dye sensitized to said imaging radiation; developing radiation-exposed portions of said imaging media with a developing agent comprising reducible metal ions, whereby free metal is deposited in said radiation-exposed portions; reoxidizing said free metal to metal ions in the presence of a metal ion-activated sofiening agent for said gelatin binder to soften said binder in radiation-exposed areas to produce a photographic image of unsoftened gelatin; and subsequently, without prior removal of softened portions therefrom, respectively taking up cyan, magenta and yellow dye in unsoftened portions of the gelatin binder of the images respectively prepared by exposure through said red, green, and blue filter; and transferring dye from said images to a receptor sheet in register to produce a full color positive dye transfer print.

6. A method of claim 3 wherein said photoconductor comprises titanium dioxide.

7. A method of claim 6 wherein said titanium dioxide is dye sensitized.

8. A method of claim 7 wherein said imaging medium comprising dye-sensitized titanium dioxide is exposed to imaging radiation from a positive color image through a filter passing red, green, or blue light to which said titanium dioxide is sensitized.

9. A method of claim 7 wherein said imaging medium comprising dye-sensitized titanium dioxide is exposed through a color separation positive to imaging radiation to which said titanium dioxide is sensi tize d. a 2,

Claims

2. A process as in claim 1 wherein said supported layer comprises finely divided titanium dioxide dispersed in a gelatin binder.
3. The method of making a dye transfer print from a direct positive photographic image which comprises exposing a photosensitive imaging medium to imaging radiation, said imaging medium comprising a finely divided photoconductor which is reversibly activatable by actinic radiation dispersed in a gelatin binder therefor; developing radiation-exposed portions of said imaging medium with a developing agent comprising reducible metal ions, whereby free metal is deposited in said radiation-exposed portions; and reoxidizing said free metal to metal ions in the presence of a metal ion-activated softening agent for said gelatin binder to soften said binder in radiation-exposed areas to produce a photographic image of unsoftened gelatin binder; and transferring dye from said positive photographic image to a receptor sheet without prior removal of softened portions therefrom to thereby form a dye transfer print.
4. The method of making a full color dye transfer positive print which comprises respectively exposing three photosensitive imaging media to imaging radiation from a set of red, green, and blue color separation positives, said imaging media each comprising a finely divided photoconductor which is reversibly activatable by actinic radiation dispersed in a supported layer of a gelatin binder therefor, said photoconductor being dye sensitized to said imaging radiation; developing radiation-exposed portions of said imaging media with a developing agent comprising reducible metal ions, whereby free metal is deposited in said radiation-exposed portions; reoxidizing said free metal to metal ions in the presence of a metal ion-activated softening agent for said gelatin binder to soften said binder in radiation-exposed areas to produce a photographic image of unsoftened gelatin; and subsequently, without prior removal of softened portions therefrom, respectively taking up cyan, magenta, and yellow dye in unsoftened portions of the binder of the images respectively prepared by exposure to said red, green, and blue color separation positives; and transferring dye from said images to a receptor sheet in register to produce a full color positive dye transfer print.
5. The method of making a full color dye transfer positive print which comprises respectively exposing three photosensitive imaging media to imaging radiation from a positive color image through a red, green, and blue filter; said imaging media each comprising a finely divided photoconductor which is reversibly activatable by actinic radiation dispersed in a supported layer of a gelatin binder therefor, said photoconductor being dye sensitized to said imaging radiation; developing radiation-exposed portions of said imaging media with a developing agent comprising reducible metal ions, whereby free metal is deposited in said radiation-exposed portions; reoxidizing said free metal to metal ions in the presence of a metal ion-activated softening agent for said gelatin binder to soften said binder in radiation-exposed areas to produce a photographic image of unsoftened gelatin; and subsequently, without prior removal of softened portions therefrom, respectively taking up cyan, magenta and yellow dye in unsoftened portions of the gelatin binder of the images respectively prepared by exposure through said red, green, and blue filter; and transferring dye from said images to a receptor sheet in register to produce a full color positive dye transfer print.
6. A method of claim 3 wherein said photoconductor comprises titanium dioxide.
7. A method of claim 6 wherein said titanium dioxide is dye sensitized.
8. A method of claim 7 wherein said imaging medium comprising dye-sensitized titanium dioxide is exposed to imaging radiation from a positive color image through a filter passing red, green, or blue light to which said titanium dioxide is sensitized.
9. A method of claim 7 wherein said imaging medium comprising dye-sensitized titanium dioxide is exposed through a color separation positive to imaging radiation to which said titanium dioxide is sensitized.