US3852070A

US3852070A - Photo-imaging utilizing uranyl compounds

Info

Publication number: US3852070A
Application number: US00283465A
Authority: US
Inventors: S Levinos
Original assignee: Keuffel and Esser Co
Current assignee: Keuffel and Esser Co
Priority date: 1972-08-24
Filing date: 1972-08-24
Publication date: 1974-12-03
Anticipated expiration: 1991-12-03

Abstract

Imagewise light exposure of a layer of a composition comprising a uranyl compound and an hydroxyl-containing compound results in photolytic reduction of uranyl ions which, upon subsequent contact with a developer fluid containing ferricyanide ions, form an imagewise deposition of a distinct uranyl ferrocyanide color body. Application of a toning fluid containing ferric ions may subsequently be employed to achieve neutral image tones.

Description

nite States Levinos Dec. 3, 1974 I PHOTO-IMAGING UTILIZING URANYL COMPOUNDS [75] Inventor: Steven Levinos, Chatham, NJ.

[73] Assignee: Keuffel & Esser Company,

Morristown, NJ.

22 Filed: Aug. 24, 1972 21 Appl. No.: 283,465

[52] US. Cl. 96/48 R, 96/88 v [51] Int. Cl G03c 5/24, G03c 1/00 {58] Field 0fSear1:h..... 96/88, 48 R, 48 PD [56] References Cited UNITED STATES PATENTS 7/1986 Ravich 96/90 R 3/1960 Jonker et al 96/48 PD OTHER PUBLICATIONS British Journal of Photography, Vol. LXXXVI, Mar. 24, 1939, page 186.

Primary Exunu'm'rRonald H. Smith Assistant Examiner-Won H. Louie, Jr.

Attorney, Agent, or Firm-Lionel N. White, Esq.

[ 5 7] ABSTRACT color body. Application of a toning'fluid containing ferric ions may subsequently be employed to achieve neutral image tones.

4 Claims, No Drawings PHOTO-IMAGING UTILIZING URANYL COMPOUNDS SUMMARY The present invention provides a photoimaging material which comprises a supporting sheet member selected from any of a host of common web materials such as paper, plastic film and the like, a coating of a photo-sensitive composition comprising a uranyl compound, and a source of hydroxyl groups. Upon imagewise exposure to actinic radiation, preferably in the region of ultraviolet light, there'occurs in the material a photolytic redox reaction wherein the uranyl ions in the exposed areas are reduced to the uranous form by abstraction of electrons from available hydroxyl groups. The source of such groups may be conveniently included in a coating composition in the form of filmforming binder materials such as polyvinyl alcohol, hydroxyethyl cellulose and the like, and thus serve a dual function in the procedureof the present invention. A useful alternative to binders for this purpose is the employment of surface saponification of film supports such as cellulose acetate- Subsequent to imagewise light exposure, the material of the present invention is contacted with a developing fluid containing ferricyanide ions, for example by the application of an aqueous solution of an alkali metal ferricyanide. The resulting oxidation of the photolytically generated uranous ions to the uranyl state and concurrent reduction of the ferricyanide ions to ferrocyanide yield, in light exposed areas, substantially insoluble distinctly colored uranyl ferrocyanide. A water rinse thereafter removes the excess developer solution and the vestiges of the original water-soluble uranyl compound from the unexposed areas of the imaging material. Thus, there remains on the carrier sheet the imagewise deposit of the distinctly colored uranyl ferrocyanide color body.

In further application of thepresent invention, the image may be provided in a more neutral blue-black tone by the application of a solution comprising ferric ions, for example an aqueous solution of ferric nitrate.

The resulting metathetic formation of ferric ferrocya nide in the image areas not only provides the more pleasing tone but also yields an image which is less moisture sensitive and thus more permanent.

In addition to the more simple material thus far noted, the present invention provides a means for sig nificantly sensitizing the composition by the incorporation of formic acid salts which contribute to the photolytic reduction of the uranyl ions of thecomposition. In this manner, a composition of a uranyl compound in a binder material comprising hydroxyl groups may be greatly increased in light sensitivity by the addition of sodium, potassium, or ammonium formate which, apparently upon the photolytic decomposition of formic acid, further promotes the reduction of the uranyl ions to the uranous form, thereby substantially increasing the density of photoformed reducing centers.

DESCRIPTION hydroxyl-containing substantially water-dispersible binder materials are available and, in addition to those previously noted, include hyd'roxypropyl cellulose and sodium carboxymethyl cellulose.

In order to take advantage of the aqueous medium employed in the sensitizing compositions and to effectively insure an intimate combination of the cationic uranium with the source of hydroxyl groups, any of the numerous water-soluble uranyl compounds are employed. These include the acetate, nitrate, chloride, sulfate, formate, propionate, succinate, glutarate and phenyl acetate. The simple combination of the uranyl salt in aqueous solution with a selected binder provides a coatable composition useful in the preparation of the instant imaging materials.

It is to be noted that the cellulosic character of paper fibers and the saponified surfaces of cellulose ester film base materials to a significant extent provide the hydroxyl-containing component of the present imaging materials. Additional useful sources of this component are represented in humectant adjuncts such as glycerin and ethylene glycols, which materials also provide for the maintenance of substantial moisture in the imaging sheet. It has been observed that such moisture effectively assists in the image-forming process.

The earlier-noted chemical sensitization achieved through the addition of water soluble formate salts takes advantage of the aqueous nature of the sensitizing composition. It should be pointed out, however, that an acidic pH is preferably maintained in the coating composition in order to prevent the formation of insoluble basic uranyl compounds.

In use, the imaging material of the present invention is exposed image-wise to light, preferably of the ultraviolet region, in the manner of utilizing sources common to normal photoimaging procedures. In areas of the imaging material thus exposed to photolytic radiation, the uranyl ions are reduced to a lower valence form, for example the uranous form, by acquisition of electrons from the hydroxyl groups of the base, the binder material, or the humectant adjuncts. It has been found that the uranous form of the compounds included in the imaging material are less water soluble than the uranyl form and on this basis an improvement in the background areas of the final image may be attained through the use of a short water rinse immediately following the light exposure step. Thus, a substantial amount of the original uranyl compound is removed from the material and is not available for vagrant formation of the color body during the development step.

In order to form a distinct color body which will define the light exposure image, the exposed material is contacted with a solution containing ferricyanide ions, for example an aqueous solution of an alkali metal fer ricyanide. From the concurrent oxidation of the uranous ions and reduction of the ferricyanide ions, there results the formation of an imagewise disposition of the distinctly colored insoluble uranyl ferrocyanide in the following manner: j

The developed image sheet is again subsequently rinsed with water to remove the unused development solution as well as any uranyl ferricyanide which forms in the unexposed areas of the imaged material. It

sure. That is not to say that some time span may not occur between the exposure and development step, since the noted degradation of the uranous ion, i.e., its reversion to the uranyl form by aerial oxidation, requires a few hours to be of any consequence.

The developed uranyl ferrocyanide image is of a brown tone which may not be as preferred in ultimate use as the more neutral blue-black tones obtained with many conventional imaging processes. For this reason the imaged material may be subjected to an additional toning step which comprises application of an aqueous solution of a ferric salt. By metathesis the ferric ions replace the uranyl ions and the composition of the image acquires a significant proportion of the blue ferric ferrocyanide color body. The final image tone is, of course, regulated simply by the extent of time allowed for the toning step. A final water wash and drying complete the processing and yield a permanent, well-toned image.

PREFERRED EMBODIMENTS Example 1 v A solution was prepared of the following composition:

Uranyl nitrate 6H,O Deionized water 4 Glycerin A sheet of filter paper was immersed in the solution and allowed to dry at normal room conditions under yellow safe light. In the meantime, a similar composition was prepared and one gram of sodium formate was added. The solution remained clear and thus was evidently sufficiently acid that no basic uranyl salt was present. Using filter paper, imaging material was likewise prepared with this solution. The sheets were individually exposed through an opaque stencil to the light from a bank of black light" lamps (GE F8T5 BLB) at a distance of about 2 cm. After exposure, the sheets were rinsed in clear water for about 15 seconds and'then immersed in a aqueous solution of potassium ferricyanide for about seconds. A red-brown image was formed in the light exposed areas and a final water rinse of about 15 seconds completed the imaging process. In order to achieve image densities of substantial equivalence, the material of this example devoid of the formate salt was exposed for about 2 minutes while that including the formate accelerator was exposed for only 1 minute. Example 2 A sheet of porous paper (filter paper) was saturated with the following solution and dried under subdued light at normal room conditions:

Uranyl acetate 2H,O(8% aq. sol.) 2 Sodium formate Glycerin Dilute formic acid to clear solution (pH 4.2)

Portions of the resulting sheet were individually exposed through an opaque stencil for about one minute as in Example 1 and for about one minute to a source of substantial visible actinic radiation (500-watt photoflood lamp) at a distance of about 15 cm. After a short water rinse, the exposed sheets were immersed in a 5% solution of potassium ferricyanide for about 15 seconds and were then rinsed with water to yield equally dense red-brown images in the light-exposed areas. The sheets were then immersed for about 15 seconds in a 5% aqueous solution of ferric nitrate 9H O, followed by a water rinse to yield similar neutral blue-black tone images.

Example 3 The following coating composition was prepared:

Deionized water 95.0 ml. Hydroxypropyl cellulose 5.0 g. Uranyl nitrate 6H O 2.5 g. Glycerin 1.0 g. Sodium formate l.0 g.

The resulting solution was coated on a baryta-surfaced sheet commonly employed in the preparation of photographic materials to a wet thickness of about 130 microns. After drying at normal room conditions under yellow safe lights, the sheet was exposed for seconds through an opaque metal stencil to light from the black light arrangement of Example 1. Development treatment with 5% aqueous potassium ferricyanide and toning with 5% aqueous potassium ferricyanide and toning with 5% aqueous ferric nitrate provided a dense, neutral-toned image.

What is claimed is:

1. Imaging material comprising a support and a coating thereon of a light-sensitive composition consisting essentially of a water-soluble uranyl compound and a water-soluble formate salt in intimate admixture with a substantially water-dispersible film-forming binder selected from the group consisting of polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxymethyl cellulose, sodium carboxymethyl cellulose, and saponified cellulose esters.

2. The method of forming a visible image comprising:

a. exposing imagewise to light sheet material according to claim 1; and

b. contacting at least the light exposed areas of said material with a developing fluid comprising ferricyanide ions, thereby forming a distinct imagedefining color body in said light-exposed areas.

3. A method according to claim 2 which further comprises contacting at least said image-defining color body with a toning fluid comprising ferric ions, thereby to provide a neutral-toned image in said light-exposed areas.

4. A method according to claim 3 wherein said developing fluid comprises an aqueous solution of a ferricyanide salt, and said toning fluid comprises an aqueous solution of a ferric salt, which method further comprises the steps of rinsing said sheet material with water immediately subsequent to each of the light exposing,

developing, and toning steps.

Claims

1. IMAGING MATERIAL COMPRISING A SUPPORT AND A COATING THEREON OF A LIGHT-SENSITIVE COMPOSITION CONSISTING ESSENTIALLY OF A WATER-SOLUBLE URANYL COMPOUND AND A WATER-SOLUBLE FORMATE SALT IN INTIMATE ADMIXTURE WITH A SUBSTANTIALLY WATERDISPERSIBLE FILM-FORMING BINDER SELECTED FROM THE GROUP CONSISTING OF POLYVINYL ALCOHOL, HYDROXYETHYL CELLULOSE, HYDROXYPROPYL CELLULOSE, HYDROXYMETHYL CELLULOSE, SODIUM CARBOXYMETHYL CELLULOSE, AND SAPONIFIED CELLULOSE ESTERS.

2. The method of forming a visible image comprising: a. exposing imagewise to light sheet material according to claim 1; and b. contacting at least the light exposed areas of said material with a developing fluid comprising ferricyanide ions, thereby forming a distinct image-defining color body in said light-exposed areas.

4. A method according to claim 3 wherein said developing fluid comprises an aqueous solution of a ferricyanide salt, and said toning fluid comprises an aqueous solution of a ferric salt, which method further comprises the steps of rinsing said sheet material with water immediately subsequent to each of the light exposing, developing, and toning steps.