US3493376A - Dry working black image compositions - Google Patents

Description

United States Patent 3,493,376 DRY WORKING BLACK IMAGE COMPOSITIONS Harry L. Fichter, Jr., Lakewood, Ohio, assignor to Horizons Incorporated, a Division of Horizons Research Incorporated, a corporation of Ohio No Drawing. Filed Oct. 18, 1966, Ser. No. 587,429 Int. Cl. G03c 1/52 US. Cl. 96-90 6 Claims ABSTRACT OF THE DISCLOSURE A photosensitive composition comprising an organic halogen compound, a triphenylmethane leuco compound, a substituted skatole, and a substituted indole.

This invention relates to photosensitive compositions from which a black or near neutral image is obtained as a direct printout or as the result of the application of heat to said composition after it has been photographically exposed. More particularly, it relates to photosensitive compositions having improved photographic speed as compared with prior art compositions and which have totally dry working characteristics.

Photosensitive compositions which are believed to be based on free radicals are described in a large number of patents and patent applications and in technical articles published by Horizons Incorporated and a list of issued United States patents is appended below for the purpose of incorporating their disclosures herein, by reference.

Some of the listed patents and publications describe free radical photographic systems which are dry fixing, i.e. in which the image obtained after exposure is fixed and rendered insensitive to light by totally dry means. Others of the listed patents and publications describe free radical photographic systems which yield a black image or near neutral image.

A specific object of this invention is to provide a dry working photographic composition yielding a black or near neutral image as a direct printout or as the result of the application of heat to said composition after it has been photographically exposed and particularly to compositions having a greatly improved photographic speed as compared with prior art compositions having totally dry working characteristics.

With the exception of color photographic printing or where as specific colored image is desired for display purposes, virtually every practical application of the above noted free radical photographic systems prefer a black or near black image color. Such contemplated uses include: office photocopy; microfilm retrieval systems; photographic printing, e.g. portraiture proofing; and even such military uses as the multigeneration aerial reconnaisance printing described in PS&E, vol. IX, No. 2, pp. 133-137, 1965; and all such uses demand a suitable black image produced without recourse to wet processing.

UNITED STATES PATENTS Photographic Science and Engineering, volume 5, Number 2, March-April 1961, pages 98-103.

Photographic Science and Engineering, volume 8, Number 2, March-April 1964, pages 91-95.

3,493,376 Patented Feb. 3, 1970 Photographic Science and Engineering, volume 8, Number 2, March-April 1964, pages -103.

Photographic Science and Engineering, volume 9, Number 2, March-April 1965, pages 133-137.

The neutral image dry working characteristics of the compositions herein described are particularly important in certain of the above uses since the use of a wet working system in high speed aircraft or space vehicles is almost inconceivable. One such use whose feasibility has been established is the preparation of multigeneration printing of aerial reconnaissance negatives as described in the above noted publication. When a military reconnaissance aircraft photographs a target, the negative resulting from that photograph is developed and reproduced through as many as four generations for determination of the intelligence revealed in the photograph. The original negative is printed only once and then is stored in the archives. All subsequent prints are made from the second generation prepared from the orginal negative. Conventional silver halide systems are not completely suitable for this multigeneration printing purpose, since the image is granular (particulate) and consequently each subsequent generation loses information which may be valuable in strategic decisions made from the use of these photographs. Free radical photo-systems being molecular rather than granular have almost unlimited resolution particularly when coated in thin layers, (about 4 to 5 microns thick), to take advantage of the geometry of present printer processors and their light sources. Free radical photographic systems have been established to be an excellent medium for these multigeneration aerial reconnaissance printing, especially photosensitive free radical compositions based on the teachings of United States Patent 3,109,736 and described in Photographic Science and Engineering, vol. IX, No. 2, pp. 133-137, for March and April 1965 under the title of New Photographic Processes, No. 4, the Cyanine Base Free Radical PhotosystemA Panchromatic Black Image High Resolution Printout Film. The compositions described yield excellent jet black images and retain high latitude multigeneration printing through four generations, with the minimum loss of intelligence. However, the compositions are not dry working, but require a solvent rinse after exposure to render the image fixed and stable to ambient light.

Photointerpreters who evaluate these aerial reconnaissance photographs traditionally have been schooled in the use of black image materials and are reluctant to use other colors; hence the need for a dry working black image system to be used for aerial reconnaissance multigeneration printing.

One preferred composition in accordance with the present invention is as follows:

Pliolite-S-SA 15% in methylene chloride cc 300 The composition is prepared by bringing the several constituents together in a suitable solvent system under a safelight or in total darkness and, after thoroughly mixing the composition, applying it to a solid substrate such as baryta paper or a film of polyester, glass or other suitable support.

After the composition has been laid down as a thin film, it is permitted to dry in air, in the dark or under a safelight, and then it is photographically exposed to the equivalent of 1.4 watt seconds/cm? and heat fixed for minutes at 135 C.150 C. in moving air, whereby a very stable dense black image was observed in the exposed areas. With this amount of exposure, maximum density of about 1.0 is achieved and the heated film is completely fixed, i.e. the image and background do not change upon further exposure to light.

While not Wishing to be bound by any specific explanation as to the function of each of the several constituents, it is believed that three constituents contribute to the formation of a black or near neutral image when acted on by the products which result when the iodoform is exposed to a suitable dose of radiant energy, namely the triphenyl methane compound, the S-methoxyskatole, and the 2,5-dimethylindole, even though the 4,4,4"-tri(p-toluidino)-triphenylmethane when photolyzed alone in the presence of a halogen activator gives brilliant blue images, S-methoxyskatole when photolyzed with a halogen activator gives a brownish-black image, and dirnethylindole when photolyzed with a halogen activator gives a pink image.

The function of the 4-picoline-N-oxide in the composition appears to be that of an organic oxidizing agent which acts as a speed promoter in these systems containing leuco compounds.

The triphenylstibine and 2,6-di-t-butyl-p-cresol appear to act as stabilizers and prevent oxidation or degradation of the color formers during the exposure and the subsequent heating of the composition when in the form of a photosensitive film. The use of these compounds is described in other issued patents and/or co-pending patent applications filed on behalf of the applicants assignee.

The thioacetamide in the composition is for the purpose of providing a darker color when the triphenylmethane component is converted to its colored form.

The indole-3-carboxaldehyde appears to hasten the formation of the colored product when the indole compounds, in this case, 5-methoxyskatole and 2,5-dimethylindole, are photolyzed in the presence of the activator, as described in United States Patent 3,164,467 noted above.

Binders for these compositions can be chosen from any one of a number of binders described in the patents already issued on free radical photographic compositions. Polystyrene, polyvinyl chloride, styrene-acrylonitrile copolymers, ethyl cellulose, both G type and N type, cellulose acetate butyrate, polyvinyltoluene, butadiene-styrene copolymers, the copolymer of polyvinyl chloride and vinyl isobutyl ether, have all been used successfully in the practice of this invention. The choice of binder, however, produces considerable variation in photographic speed and image color. All of the foregoing binders give a neutral to black image.

Various substitutions may be made in the above formulation without departing from the intended scope of the invention.

For instance, instead of polystyrene in benzene, other film forming binders can be used. Particularly preferred are polystyrene with molecular Weights above 100,000 (e.g. about 223,000) and a butadiene-styrene copolymer sold as Pliolite-S5A (Goodyear Chemical Co.).

Further, instead of triphenylstibine, other triaryl compounds may be used, such as triphenylarsine, phosphine or bismuthine, as described in United States Patent 3,275,443 issued Sept. 27, 1966, to Eugene Wainer.

Similarly, it is possible to use other organic halogen compounds as described in U.S. Patent 3,042,515 issued July 3, 1962, to Eugene Wainer, instead of the preferred iodoform.

Other color formers have been used in place of the three compounds as preferred. For example, leuco opal blue is a suitable replacement for 4,4',4-tri(p-toluidino)- triphenylmethane in these compositions, however, less background stain is observed after heat fixing with 4,4',4"- tri(p-toluidino)-triphenylmethane than is normally observed with leuco opal blue. Other leuco compounds taken from the triphenylmethane class of dyestuffs such as leuco crystal violet, leuco malachite green work equally well in these compositions, except that the resulting color is not black.

Finally, it should be noted that although the proportions given in the preceding example are believed to give optimum results for the specified constituents, the percentage of the individual constituents can be varied over a considerable range, depending in some instances on the solubility of the specific ingredient and in others on the nature and amount of the other compounds present in the formulation and on the results desired.

With the formulation given above, proportions which have been found suitable are as follows:

4,4,4-tri (p-toluidino -triphenylmethane grams- 2 to 10 4-picoline-N-oxide mg 50 to 1000 Triphenylstibine g 0.1 to 10 2,6-di-t-butyl-p-cresol g 1 to 5 Idoform g 10 to 50 5 -methoxyskatole g 2 to 10 Thioacetamide mg to 500 2,5 -dimethylindole g 2 to 10 Indole-3-carboxaldehyde g 0.1 to 10 With formulations within the above percentages, a range of exposure of from 0.05 to 5.0 Watt seconds/ per square centimeter have been found to be quite adequate. Exposures of more than 5 watt seconds/per square centimeter appear to amount to overexposure and to give some fog build-up.

With other ingredients substituted in the above, or with other relative proportions, the range of exposure may be readily determined from a sensitivity curve made with calibrated monochromatic exposures in a manner known in the art.

Having now described a preferred embodiment of this invention, it is not intended that it be limited except as may be required by the appended claims.

I claim:

1. A photosensitive composition comprising: an organic halogen compound having at least three halogen atoms attached to a terminal carbon atom; a mixture of colorless light sensitive color forming constituents in proportions which yield a near neutral or black image when reacted with the products resulting from the photolytic exposure of said organic halogen compound, wherein the light sensitive constituents in said mixture are a triphenyl methane leuco compound, a substituted skatole, and a substituted indole; and a support for said composition.

2. The composition of claim 1 wherein the light sensitive color forming constituents are 4,4,4"-tri(p-toluidino)- triphenylmethane, S-methoxyskatole and 2,5-dimethylindole.

3. The composition of claim 1 including in addition at least one additional compound which enhances the formation of the resulting image, and is selected from the group consisting of: 4-picoline-N-oxide; triphenylstibine; di-tbutyl-p-cresol; thioacetamide; and indole 3-carboxaldehyde.

4. The composition of claim 1 wherein the constituents are 4, 4,4' '-t1'i p-toluidino -triphenylmethane grams 2 to 10 4-picoline-N-oxide mg 50 to 1000 Triphenylstibine g 0.1 to 10 2,6-dit-butyl-p-cresol g l to 5 Iodoform g 10 to 50 S-methoxyskatole g 2 to 10 Thioacetamide mg 100 to 500 2,5-dimethylindole g 2 to 10 Indole-3-cat'boxaldehyde g 0.1 to 10 5. The composition of claim 1 wherein the constituents are 4,4',4"-tri (p-toluidino -triphenylmethane gm 5 4-picoline-N-oxide rng 5 00 Triphenylstibine gm 1 2,6-di-t-butyl-p-cres0l gm 2.5 Iodoform gm 20 S-methoxyskatole "gm 5 Thioacetamide mg 300 2,5 -dimethylindole gm 5 Indole-3-carboxaldehyde -gm- 1 Acetone cc 100 Benzene cc 100 P1ioliteS-5A 15% in methylene chloride cc 300 6. A dry working photographic process which comprises preparing composition of claim 1 in a thin film; exposing said composition to a pattern of radiant energy,

3,164,467 1/1965 Sprague et al 969O 3,275,443 9/1966 Wainer 96-90 FOREIGN PATENTS 723,124 12/1965 Canada.

NORMAN G. TORCHIN, Primary Examiner I. R. HIGHTOWER, Assistant Examiner US. Cl. X.R. 9665, 88