US3794496A - Photographic processes and imaging media therefor - Google Patents

Abstract

AN IMAGING MEDIUM COMPRISES A PHOTOSENSITIVE LAYER COMPRISING A RADIATION-SENSITIVE SILVER HALIDE SALT WHICH UPON EXPOSURE TO AN IMAGE PATTERN OF ACTIVATING RADIATION PRODUCES A CATALYST CAPABLE OF ACCELERATING THE DECOMPOSITION OF A DECOMPOSABLE METAL COMPOUND AND AN IMAGE-FORMING MATERIAL COMPRISING THE DECOMPOSABLE METAL COMPOUND. THE EXPOSED PHOTOSENSITIVE LAYER MAY BE DEVELOPED BY HEATING, BY EXPOSURE TO ELECTROMAGNETIC RADIATION OR BY MERELY PROLONGING THE INITIAL EXPOSURE TO AN IMAGE PATTERN OF ACTIVATING RADIATION. EXAMPLES OF SUITABLE IMAGE FORMING MATERIALS ARE METAL COMPLEXES SUCH AS SILVER EDTA.

Description

United States Patent 3,794,496 PHOTOGRAPHIC PROCESSES AND IMAGING MEDIA THEREFOR John R. Manhardt, Nashua, NH, assignor to Itek Corporation, Lexington, Mass.

No Drawing. Continuation-impart of application Ser. No. 45,909, June 12, 1970. This application May 26, 1972, Ser. No. 257,103

Int. Cl. G03c 1/02, 1/72 US. Cl. 96-1141 12 Claims ABSTRACT OF THE DISCLOSURE An imaging medium comprises a photosensitive layer comprising a radiation-sensitive silver halide salt which upon exposure to an image pattern of activating radiation produces a catalyst capable of accelerating the decomposition of a decomposable metal compound and an image-forming material comprising the decomposable metal compound. The exposed photosensitive layer may be developed by heating, by exposure to electromagnetic radiation or by merely prolonging the initial exposure to an image pattern of activating radiation. Examples of suitable image forming materials are metal complexes such as silver EDTA.

This application is a continuation-in-part application of US. Ser. No. 45,909, filed June 12, 1970.

BACKGROUND OF THE INVENTION There is a great need for simplified photographic materials, methods and apparatus for a myriad of uses and applications in which it is desired to produce a transparency or a paper copy of printed, written or stored information. Numerous methods exist and each, of course, has its individual uses and advantages. There remains, however, a continuing need for improvement in the art of making permanent copies by rapid and convenient means which do not involve liquid or semi-liquid chemical solutions and which do not involve complicated, expensive or cumbersome equipment.

One such simplified system employs heat or radiant energy as an image-producing means. It has been found, for example, that controlled originals may be employed to produce copies according to methods and apparatus in which radiant heat is involved in the production of a visible image. Numerous other methods employ materials which are caused to react by heat, shock, electric field, light or the like. In one such method, it has been found that in a photographic system known as photothermography, it is possible to produce a developable latent image by exposure to light or similar activating radiation and to develop this image by means of external energy supplied as heat.

The present invention is an improvement in the art of photography whereby high-quality, continuous tone or line-copy images can be produced with a minimum of complication and difficulty.

GENERAL STATEMENT OF THE INVENTION A new and improved imaging medium comprises a photosensitive layer comprising (1) a radiation-sensitive silver halide salt which upon exposure to activating radiation produces a catalyst capable of accelerating the decomposition of a decomposable metal compound, and (2) an image-forming component comprising the decomposable metal compound, which is substantially stable under normal ambient conditions and which can be decomposed by (a) heating to moderately elevated temperatures of the order of 65 C. to 200 C. or (b) by exposure to developing radiation. The developing radiation can be, for example, by prolonging theexposure to activating radiation or by uniformly exposing to developing radiation. If re- Patented Feb. 26, 1974 quired, the print formed by one of these above mentioned processes may be fixed or stabilized by contacting with a conventional fixing or stabilizing bath or by removal of unreacted composition.

PREFERRED EMBODIMENTS The radiation-sensitive heavy metal salt preferably comprises silver halide such as silver chloride, silver bromide, silver iodide, or mixtures thereof, such as silver chloroiodide, silver bromoiodide, silver chlorobromide or silver chlorobromoiodide. Preferably the radiation-sensitive heavy metal salt is present in the photosensitive layer in an amount, based on the total atomic amount of silver present in the layer, between about 5% and and preferably in an amount between about 40% and 70%.

The image-forming material in the imaging medium of this invention is a decomposable metal compound, which decomposition is catalyzed by the product formed by exposure of the silver halide which is in contact with the decomposable metal compound to thereby accelerate the decomposition of such compound when being heated or exposed to developing radiation as described above. The decomposition products of the decomposable metal compound may also act as a catalyst for further decomposition. Such decomposition of the decomposable metal com pound is caused to proceed by heating above ambient conditions and preferably at elevated temperatures of the order of 65 to 200 C., by prolonged exposure to an image pattern of activating radiation, or by substantially flooding exposure to developing radiation. The preferred decomposable metal compound comprises the reaction product of a metal ion and a complexing agent. Preferably the complexing agent is a chelating agent such as a complexing organic acid containing (1) at least two carboxyl groups, (2) at least one carboxyl group and at least one mercapto group, or (3) at least one basic nitrogen group and at least two carboxyl groups, or the readily soluble salt of such acids such as the ammonium salts or salts of Group I-A or II-A of the Periodic Table.

Preferred decomposable metal compounds suitable for use in this invention are represented by the following structural formulas:

R1I N/ wherein:

R is H, alkyl, aryl, aralkyl, or

R2 'R l IRuwherein R and R are H, alkyl, aryl, aralkyl;

R and R are '(CH ),,COOH or -(OH ),,O0OAg, but at least one of R and R is --(CH ),,COOAg, where n is zero or a whole number and preferably 20 or less;

In is a whole number greater than zero and preferably 20 or less.

Examples of these Class I compounds are:

disilver ethylenediamine tetraacetate;

tetrasilver ethylenediamine tetraacetate;

tetrasilver cyclohexanediamine tetraacetate;

pentasilver diethylenetriamine pentaacetate;

disilver 1,Z-diaminopropane-N,N,N',N'-tetraacetate;

tetrasilver l,2-diaminopropane-N,N,N',N'-tetraacetate;

disilver 1,3-diamino-2-hydroxypropane-N,N,N',N'-

tetraacetate;

disilver ethylenediamine tetrapropionate;

disilver N-(Z-hydroxyethyl)-iminodiacetate;

Periodic Table from Langes Handbook of Chemistry, 9th edition, pp. 56-57.

disilver ethylenediamine-N,N'-diacetate;

disilver iminodiacetate;

di silver [ethylenebis (oxyethylenenitrilo) tetraacetate;

and

tetrasilver [ethylenebis (oxethylenenitrilo) 1 tetraacetate.

(II) R --[COOM],,

wherein:

M is a metal atom, preferably of Group I-B of the Periodic Table of the Elements. Silver and copper are preferred.

R3 is wherein m is a whole number, n is 1, and R and R are H, alkyl, aryl, etc. (examples: silver-l l-aminoundecanoate, silver aminovalerate) or R0 is R wherein R is alkoxy and n is 1 (example: silvertrimethoxybenzoate) or MP1 Lid.

where R and R are H, OH, SH, COOH, n is 2, and m is 0, 1, 2, or 3. Examples of these Class II compounds are disilver oxalate, disilver mercaptosuccinate, silver citrate, silver malonate.

(HI) M 80 wherein M is a metal atom, preferably of Group I-B of the Periodic Table of the Elements. Silver and copper are preferred. Examples of these Class III compounds are Cu CO and Ag SO Suitable metal ions useful in preparing the decomposable metal compound are silver ion, copper ion, mercury ion, tin ion, nickel ion, gold ion and the like. Presently silver ion is preferred due to the improved results with this ion.

Other suitable decomposable metal compounds for this invention are silver and other metal salts of chloroacetates, benzoates and nitrochloro and amino benzoates, phthalates, maleates, nitrides, acetylides, azides, formates, cyanamides and the like.

The image-forming material is preferably included in the photosensitive layer of the imaging medium from about to 95% based upon the total atomic amount of metal in the photosensitive layer including a radiation sensitive silver halide salt and image-forming material. More specifically, hte most preferred percentages in a heat developed system are 25 to 95 in a printout system where the image is formed by prolonging the initial exposure5 to 40%; and in an optically developed system where the image is amplified by uniform exposure to developing radiationl0 to 60%.

When the imaging medium of this invention is developed thermally, especially desirable results are obtained. It has been found that the thermal decomposition can be controlled within an exposed image area to produce clear, high resolution, stable images of improved photographic speed as compared with other photothermographic systems.

In one embodiment of the invention the imaging medium comprises a mixture of a radiation-sensitive silver halide, and an image-forming material comprising a decomposable metal salt such as the silver salt of a carboxylic acid such as silver oxalate or a silver salt of ethylenediaminetetraacetic acid or the like. In another embodiment of the invention an additional decomposable metal salt such as silver azide or the like may be included in the composition.

The photosensitive layer preferably comprises a binder material such as is conventional in the photographic arts. Also the photosensitive layer is preferably deposited on a suitable support base such as glass, transparent film base such as polyethylene terephthalate, and cellulose triacetate, paper, metal or the like. U.S. Reissue Pat. 26,719 and U.S. Pat. 3,457,075 disclose a print-out process and imaging medium comprising a radiation-sensitive heavy metal salt and an image-forming composition comprising (1) an organic silver salt, and (2) an organic reducing agent. The subject invention is believed to be an improvement over these U.S. patents, inasmuch as a separate reducing agent is not necessary. The aforementioned U.S. patents are incorporated herein by reference.

It is believed that exposure of a silver halide to activating radiation forms a latent image of free silver and halogen or other byproducts, which singly or together are capable of acting as a catalyst for the decomposable metal compound of this invention. This catalyst in combination with heat or the proper electromagnetic radiation exposure or combination of exposures will accelerate the decomposition of the decomposable metal salt to produce decomposition products which in turn catalyze further decomposition of the decomposable metal salt.

When heat development is utilized, the decomposable metal salt is preferably disilver EDTA or a mixture of disilver EDTA and tetrasilver EDTA. When prolonged exposure or a uniform exposure to developing radiation is used to develop the final visible image, the tetra silver EDTA is the preferred decomposable metal salt.

In order to obtain good shelf stability, it has been found that it is preferable to maintain a pH in the photosensitive layer below about five (5).

Developing radiation as used in this invention is defined to mean red and near infrared radiation and/ or activating radiation for the imaging medium of the invention. The preferred band of wavelengths lies between about 600 and 800 nanometers, most preferably between 660 and 720 nanometers.

DETAILED DESCRIPTION OF THE INVENTION Example I A base solution was prepared containing 10% by weight of an acrylic acid-acrylamide binder commercially available under the name Cyanamer P-26 (available from American Cyanamid Company). To 25 ml. of this binder solution was added one millimole sodium chloride. A silver nitrate solution was separately prepared, containing 10 millimoles silver nitrate in 25 ml. water. Next, 2 /2 ml. of this silver nitrate solution (equivalent to one millimole silver nitrate) was added to the sodium chloride-binder solution. Nine millimoles of sodium azide solid was added to the mix, and stirred, and the remainder of the silver nitrate solution was added. Finally, 10 millimoles of solid oxalic acid was added with mixing.

The product is a 5% binder solution containing silver in an amount equivalent to 10 millimoles in 5 O mls. of solution, one millimole chloride, 9 millimoles azide and 10 millimoles oxalate. The final pH was 1.3.

This mixture was coated on a paper base and dried to produce a photothermographic layer. The photothermographic paper as thus prepared was exposed to an image to be recorded by contact exposure methods. An ll-step Wedge (AOD-0.3 per step) is placed on the surface of the photothermographic paper, and the paper is exposed about 0.001 sec. to a xenon flash. Development was achieved by heating to 330 F. for 10 seconds. A blackbrown image showed at least 9 visible steps. The maximum density was 1.27, and the base and fog density was 0.10. Repeating the exposure and development with a document in place of a step wedge produced a good quality easily readable document having a pleasant tonal appearance.

Example II The procedure of Example I was repeated except that the proportions of chloride and azide were changed so that the chloride was present in an amount equivalent to 40% of the total atomic amount of silver and the azide was present in an amount equivalent to 60% of the total atomic amount of silver. D was about 1.6 compared to 1.27 in Example I. The photographic speed was substantially higher. Density in the base or background areas and fog were slightly higher, remaining well below 0.2.

Example III The procedure of Example I was repeated as a control for purposes of comparison. In another sample, the procedure was repeated except that varying relative proportions of oxalic acid were replaced with potassium oxalate while keeping the total oxalate constant to 1 mole per mole of silver. Both photographic speed and discrimination between image and background areas decreased with the substitution. At 75% oxalic acid and 25% potassium oxalate, the number of steps visible on the step wedge image had decreased to 7, and the tone of the image had changed from black-brown to brown. Below 50% oxalic acid, there was further decrease in quality, together with fog.

Example IV The procedure of Example I was repeated as a control for comparison purposes, and in a separate sample the procedure was repeated with a mixture of silver azide and oxalic acid without silver chloride. D of the sample with silver chlordie was about 1.25, and D of the sample without silver chloride was about 0.59. The relative photographic speeds, as determined by the least visible step in the step wedge image, were about 16 to 1, with the sample containing silver chloride being about 16 times as fast as the sample without silver chloride.

Example V The procedure of Example II was repeated using 1.5 millimoles of trisodium EDTA instead of sodium azide and the resulting photothermographic paper was tested in comparison with a concurrently-produced photothermographic product according to Example II. The products had nearly equal photographic speed. Both developed well at temperatures of about 330 F. in about to about seconds. Where low background density was sought, the product containing EDTA was developed for 20 seconds at 310 F. to produce a very light background in combination with a black-brown image.

Example VI A base solution was prepared containing 10% by weight of an acrylic acid-acrylamide binder commercially available under the name Cyanamer P-26 (available from American Cyanamid Company). To mls. of this binder solution was added one millimole sodium chloride. A silver nitrate solution was separately prepared containing 10 millimoles silver nitrate and 25 ml. water. Next, 2% ml. of this silver nitrate solution was added to the sodium chloride binder solution. Next, 2.5 millimoles of the tetrasodium salt of diaminocyclohexanetetraacetic acid (DCTA) was added with mixing and the remainder of silver nitrate solution was added. The product is a 5% binder solution mix containing silver in an amount equivalent to 10 millimoles in 50 milliliters of solution and containing the equivalent of 2.5 millimoles of DCTA.

This mixture was coated on a baryta paper base and dried to produce a photothermographic layer. The photothermographic layer, as thus prepared, was exposed to an image to be recorded by contact exposure methods. An II-step wedge (AOD-0.3 per step) was placed on the surface of the photothermographic paper, and the paper was exposed to a xenon flash. Development was achieved by heating to 330 F. for 10 seconds. A black-brown image showed at least nine visible steps. The maximum density was about 1.2 and the base and fog density was less than 0.10. Repeating the exposure and development with a document in place of a step wedge produced a good quality, easily readable document having a pleasant tonal appearance.

The procedure was repeated with the tetrasodium salt of ethylenediaminetetraacetic acid (EDTA) in place of the DCTA. This product has excellent photographic speed, developed well at temperatures of about 330 F. to produce an image having high density and low background.

Examples VII to XVI Several comparative tests were run with procedures which evaluated the quantitative relationship between silver bromide concentrations and silver EDTA concentrations with four different forms of subsequent permanent image formation. In one of these, named printout in Table I, the paper was exposed to an image pattern with a xenon flash until a permanent image appeared on the paper (approximately 0.001 sec.). In the next, named optically developed in Table I, the paper was exposed as in Example I and was developed to form a permanent visible image by flooding with light, preferably of wavelength greater than 660 millimicrons, which is provided by light from a 100 watt tungsten lamp filtered through Wratten 29 and 36 filters. In the third method of permanent image formation, the paper waes exposed and thermally developed as in Example I. In the fourth method of development, the paper was first optically developed and then thermally developed.

In preparing the paper for this series of examples, the base solution of Example VI was employed. To this binder solution was added 5 ml. of 1.0 M sodium bromide (5 millimoles) and the indicated quantities of EDTA and silver ion. As illustrated by the examples, operable results are achieved and good photographic images are formed over a Wide-spread range of conditions and compositions. Although a relatively broad range is operable, there are certain guides, varying with the development method.

Generally speaking, the amount of silver present as silver halide (all percentages being expressed as a percentage of total silver) is preferably between about 10 and about 95%. Operability is achieved at 5% or less silver halide, but at least 10% is desirable. When thermal development is employed, between about 15% and 75 silver halide is desired and between about 30% and 60% is presently preferred. When optical development is employed, a higher ratio of silver halide is preferred, generally between about 40% and about 90%, preferably between about 60% and about Optical development with red or infra-red radiation is achieved, as distinguished from ultra-violet radiation which might have seemed more appropriate.

In addition to forming visible images, the reaction products in the exposed areas may promote crosslinking or hardening of binders. Images made with either natural gelatins or some synthetic binders are selectively hardened in the exposed areas and can be selectively dyed or can be selectively washed to form relief images.

In addition to the specific examples illustrated, it has also been found that the photosensitive layer may be improved in its photographic speed and in its response in certain spectral ranges by the addition of photographic sensitization dyes. Similarly, it has been found that silver bromide can be substituted for silver chloride with substantial increase in photographic speed. Other halides such as silver bromide-iodide and a silver chloride-iodide also can be used with specific improvements.

As can be seen by the specific examples, excellent results can be achieved With a layer including a binder and dispersed in the binder, active ingredients including a silver halide, thermally decomposable silver salt and, optionally, an azide. According to the presently preferred embodiments of the invention, exellent results can be achieved with the two active components, namely, a silver halide and a thermally decomposable silver salt in the absence of the azide, and, accordingly, this simplified embodiment of the invention is preferred. It is to be recognized, of course, that silver ion and halide ion are both present. X-ray diifraction analysis of such coatings has confirmed the presence of silver halide. The term silver halide, therefore, is used herein to denote the presence of silver ion and halide ion, probably in the form If an azide or similar material is employed, desirable results are achieved with about 10 molecular partsof oxalate for each 10 atomic parts of silver, but it has been found that good results are achieved with as little as 6 molecular parts of oxalate per 10 atomic parts of silver, and with as much as 16 molecular parts of oxalate per Cuprous azide has been employed as the thermally decomposable metal salt. It has been found that the product prepared from cuprous azide produces images which discriminate between light and dark, and which discriminate between image and non image areas which operate at photographic speeds, but that the images are characteristic of having somewhat lower density and somewhat A wide variety of thermally decomposable materials has been successfully employed in conjunction with a silver halide. The silver salts of both oxalic acid and ethylenediaminetraacetic acid (EDTA) have been used with silver halide, both without an additional active ingredient and in mixture with each other. Further, each of these thermally decomposable materials has been used successfully with an azide, such as silver, copper, mercury, or other azides in addition to silver halide and with others of the thermally decomposable materials which have been used alone or in admixture, always together with a radiation sensitive heavy metal salt such as silver halide. Silver salts of diaminocyclohexanetetraacetic acid (DCTA) have been found to be one of the preferred species. Other compounds of nonsilver metals such as copper and mercury in the form of phosphate, pyrophosphate, bisulfite and other salts have been employed suc- Example XVII An aqueous emulsion is prepared by first preparing Ethylenediamine tetraacetic acid, tetrasodium salt,

Ethylenediamine tetraacetic acid, disodium salt, di-

All subsequent operations are performed in the absence To 50 ml. of solution I, add 30 ml. of solution II and 8 ml. of solution III. Stir continuously and adjust pH to 4.0 by addition of a 1.0 molar solution of oxalic acid. Add 10 m1. of solution IV over a period of 30 seconds with rapid, continuous stirring. After 4% minutes of additional stirring, 0.8 ml. of a 0.025 molar solution of phenylmercuric acetate, dissolved in a mixture of by volume ethanol and 10% by volume water, is 75 added. After 10 minutes of additional stirring, the emula. 0 m 1 c w w a a m 4 8 d m w a k L n a B 8 O C O S 9 3 3 m m m m a m 2 a r o 6 S n cu h 4 e B N n m u m w o m m a g n a S m 0 w .w 1 N A h .n o s l m m r r .m a C g y w d a .w I h m g a P n .m .Zm k v. .m o o H ..v. .m w .1 w w w .m ym m m c .S m :1 1V. .m H m a n d h a n 0 n 0 e 0 r w .mPW.m W.m h-w t h a m r f m m m u 2 m t S g S e l 1 1 l 0 .1 O m 1 h w m m s s m m 5 o 0 5 0 r0 0 2 4 A: 5 5 6 S 2 2 a 2 Ed o +2 s 2 8 8- s 3 mo a +2 2 g. S 8- m mm .5 5 1: e 2 a BS 2 a as EH ma 3% 2 2 S a 2 5 5 +2 22 2 S 2 m S we 2 2 8---+2 a 3 E 8 w 2 8 a 2 a 23 2 2 28 a we as 2 2 S a 2 new 2 +2 a; S 3 2 :8... S 2 2 2 3 +2 fi S aw 8 w 3 8 a 2 a 28 ES 2 2 as E am BM 2 2 2 a S 3 5 +2 5 2 2 $2 :8... S 2 2 2 $2 -+2 E S a 8-- w mm a 2 E a 28 2 3 2 www 25 22M 2 2 2 2 Z 22 +2 2 2 2 8 2 e 2 a 8 8 2 +2 2 2 5 a w e 5 2 as 22 2 2 2 a 2 o 22 +2 2 2 3 82 2 2 8 2 2 2 2 -%---+2 we 2 E 8-- w a: 2 2 ES 3; 3; I 8 2B 3 2M 2 2 2 a 2 3 7 2 +2 2 2 mm N: 3--- S 2 2 2 a: -8- +2 E 2 mm 8 w s so 8 2 n w 23 2 2 25 a N 2 2 2 2 E o +2 3 mm 2 2 2 mm 2 8 2 ww---+2 mm 2 3 %w a a 8 8 a: a 2 a 2 a m 2 e2 25 8 v2 a B 2 E n :2 3 2 +2 8 2 an $2 2 m 2 2 E 2 2 :2 +2 E S 2 m a an S a 2: a 2 8 2 2 2a 2895 2803 59% 2922 SE 3 SE n 2E n n +2 8 2 an $2. n 2 a 2 2 3 2 2 2 +2 am 2 a 6 a 8 me no a a 25 a 2 2H 2 2 ma 2 @9222 33m Q4 .EEQ m ems: 33w D e .259 3 32 5 39% Q4 fl .SEQ mums: 32w G4 EEQ .259 2025. maz 2 FHQHSZ $232. .NH d 30 2 a ee z a so 2 8 6o 2 20s 23 22. See 22: Sec .20 UQQBEEQ 32:52; ueno eu 228 20 335.5

sion is coated onto single-weight baryta photographic base paper at a coverage of 2.8 grams of elemental silver per square meter and dried at room temperature.

A sample of the coated paper is exposed behind a photographic step tablet, having a 0.15 optical density pitch, to a bank of incandescent lamps for 2 seconds. It is then thermally developed between the jaws of a Sentinel heat sealer at a temperature of 275 F. and a jaw pressure of 7 p.s.i.g. for 11 seconds. The sample, which now contains a dense negative image of the step wedge, is then stabilized in a solution comprised of Sodium thiosulfate, 158 g. Sodium bisulfite, 15.8 g. Water to, 1 liter.

for one minute and dried. The D and fog optical densities are 1.75 and 0.02, respectively. The coated paper exhibits panchromatic spectral response.

Example XVIII A nonaqueous emulsion is prepared by first preparing disilver EDTA powder as follows:

Solution I:

Ethylenediamine tetraacetic acid, disodium salt, di-

hydrate, 22.32 g. Water to 600 ml. Concentrated HNO sufiicient to adjust pH to 4.0. Solution II:

AgNO (0.1 molar aqueous solution), 1200 ml.

All subsequent operations are performed in the absence of actinic light.

Add solution II to continuously and rapidly stirred solution I over a period of 30 seconds. Continue stirring for 15 minutes, then allow the precipitate to settle for 15 minutes without stirring. Decant the supernate; suction filter the precipitate wash the precipitate several times with cold distilled water and finally once with cold acetone. Dry in a vacuum desiccator and refrigerate. Yield: 27 g.

The emulsion was then prepared by ball milling the following mixture for one week:

Polyvinylbutyral (Butvar B-76), 15 g. Acetone, 138 ml. Disilver EDTA powder, 8.1 g.

To 92 ml. of the ball milled mixture was added 8 ml. of a 1.0 molar solution of ammonium bromide dissolved in 80% by volume ethanol and by volume water. The total volume was 100 ml. This emulsion was stirred for 8 minutes and then coated on single weight baryta photographic base paper at a silver coverage of 3.0 grams elemental silver per square meter and dried at room temperature.

A sample of the dried paper was exposed as in Example XVII and heat developed under the same conditions for 9 seconds. The sample, which now contained a dense negative image of the step tablet, was stabilized by immersion for one minute in a solution of:

Ammonium thiocyanate, 90 g. Hexamethylene tetramine, 90 g. Water, 36 ml.

Anhydrous ethanol, 684 ml.

and then dried. The D and fog optical densities were 1.28 and 0.02, respectively. The coated paper exhibited panchromatic spectral response.

Example XIX Three samples of the photosensitive coated paper prepared as in Example XVII were exposed as described in Example XVII. Two of the samples were then photodeveloped by uniform overall exposure for 66 hours and 168 hours, respectively, to a watt incandescent lamp covered by a Wratten 1A safelight filter placed at a dis- Photodeveloping time: Relative speed Undeveloped control 1 66 hours 700 '168 hours 1,600

Similar results were obtained with photosensitive coated paper samples prepared as in Example XVIII.

Example XX The inherent panchromatic response of the coating of Example XVIII is shown in this example. The step tablet was divided longitudinall into thirds by partially covering it with strips of Wratten 29 and 58 color separation filters. The center third of the step tablet remained bare. A sample of the coated paper prepared in Example XVIII was exposed behind the filtered step tablet for one minute to a bank of incandescent lamps and then stabilized as described in Example XVIII. Another sample of the same coated paper was identically exposed, heat developed and stabilized as described in Example XVIII. Characteristic curves of optical density as a function of the logarithm of the relative exposure were constructed for the unfiltered, green-filtered, and red-filtered exposures on each sample. The relative paper speeds, measured at 0.60 net optical density, were as follows:

Undeveloped Developed Unfiltered..- 1. 0 21 Green-filtered 0. 6 4. 8 Red-filtered 1. 1 3. 8

green and red light can be raised further by incorporation of spectral sensitizing dyes. The sensitization by these dyes is additive to the inherent response of the composition.

The use of by-products of the heat developing reaction, e.g. formaldehyde, is illustrated in the following three examples:

Example XXI Light-insensitive receiving sheets were prepared by coating an aqueous 5% w./v. solution of Cyanamer P-26, colored by the addition of india ink, onto single-weight baryta photographic base paper and subbed polyester photographic film base.

A sample of the coating prepared in Example XVII was exposed as described in Example XVII, placed in emulsion-to-emulsion contact with the film receiving sheet, and the sandwich was heat developed as described in Example XVII. After heating, the sandwich was separated. A developed negative image of the step tablet was visible in the photosensitive sample, but the receiving sheet appeared uniformly black. The receiving sheet was then briefly rinsed in warm tap water which washed away portions of the coating to leave behind a negative image of the step tablet. The formaldehyde formed imagewise by heat development did not react with the polyvinyl alcohol binder in the photosensitive layer. Instead it diffused out of that layer to crosslink the Cyanamer P-26 on the receiving sheet. The tanned image on the receiving sheet was then developed with warm water. The same result was obtained when the paper receiving sheet was used.

Example XXII A coating was prepared as described in Example XVII except that Cyanamer P-26 was used instead of Lemol 42-88. The emulsion was coated onto single-weight baryta photographic paper base and subbed polyester photographic film base and dried. A sample of the film coating was exposed behind a high-contrast lithographic line negative of a road map to a bank of incandescent lamps for 2 seconds and heat developed as described in Example XVII. It was then fixed by rinsing in tap water for 30 seconds which removed the untanned emulsion in the background area of the image. The result was a positive image of the road map consisting of a deep brown image on a clear, transparent background. Equivalent results were obtained with the paper coating.

The film image was imbibed with Kodak dye transfer cyan dye, rinsed in dilute acetic acid, and rolled into contact with mordauted Kodak dye transfers receiving paper. After separation, a cyan image of the map remained on the paper receiving sheet.

Example XXIII This illustrates use as a direct positive lithographic printing plate.

An emulsion prepared as described in Example XVII, except that photographic gelatin was used instead of Lemol 42-88, was coated onto a brush-grained aluminum sheet and dried. It was exposed behind a high-contrast lithographic line positive of a road map to a bank of incandescent lamps for 2 seconds and heat developed as described in Example XVII. The untanned portions of the coating were removed by rinsing briefly in warm tap water, resulting in a negative relief image of the road map on a bare aluminum surface. Excess moisture was removed by passing the image bearing aluminum plate between a pair of rotating squeegee rollers. A lithographic plate lacquer was then applied before the plate had completely dried. The lacquer adhered only to the bare aluminum and was repelled by the tanned coating remaining on the plate. Thus the lacquer formed a positive image of the road map. The plate was rinsed with water, squeegeed, and placed on an offset lithographic printing press. The ink was repelled by the tanned coating and was accepted by the lacquer resulting in printed copies which were positive with respect to the original lithographic line positive image; ink was deposited in areas that were opaque on the original and no ink was deposited in areas that were transparent on the original.

A combination of AgBr and disilver EDTA in the pro portion of 4 moles AgBr per 3 moles Ag H EDTA is preferred.

I claim:

1. An imaging medium comprising (1) a radiationsensitive silver halide which upon exposure to activating radiation produces a catalyst capable of accelerating the decomposition of a decomposable metal compound, and (2) an image-forming component comprising a decomposable metal compound which is diflerent than the silver halide and which is substantially stable under normal ambient conditions and which can be decomposed by contact with said catalyst when exposed to heat or developing radiation to thereby produce a visible change in color corresponding to the portions of the medium exposed to activating radiation, the image-forming component comprising a decomposable metal compound being represented by the following structural formulas:

ill- N 1 2 wherein:

R is H, alkyl, aryl, aralkyl, or

R2 -R|I IRs wherein R and R are H, alkyl, aryl, aralkyl;

R and [R are -(CH ),,COOH or -(CH C0OAg, but at least one of R and R is (CH COOAg, wherein n is zero or a whole number; and

m is a whole number greater than zero;

(II) Rs-[COOM1 wherein:

M is a metal atom; and R3 is N(CH )mwherein m is a whole number, n is 1, and R and R are H, alkyl or aryl; or R3 IS wherein R is alkoxy and n is 1 or R5 is Fiq LILLL wherein R and R are H, OH, SH, COOH, n is 2, and m is 0, 1, 2, or 3; and

(III) M 50 wherein M is a metal atom.

2. An imaging medium as in claim 1 wherein the decomposable metal compound is at least one member selected from the group consisting of disilver ethylenediamine tetraacetate;

tetrasilver ethylenediamine tetraacetate;

tetrasilver cyclohexanediamine tetraacetate;

pentasiliver diethylenetriamine pentaacetate;

disilver 1,Z-diaminopropane-N,N,N',N'-tetraacetate;

tetrasilver 1,Z-diaminopropane-N,N,N',N-tetraacetate;

disilver 1,3-diamino-Z-hydroxypropane-N,N,N,N'-

tetraacetate;

disilver ethylenediamine tetrapropionate;

disilver N-(2-hydroxyethyl)-iminodiacetate;

disilver ethylenediamine-N,N'-diacetate;

disilver iminodiacetate;

disilver [ethylenebis (oxyethylenenitrilo) Jtetraacetate;

tetrasilver[ethylenebis(oxyethylenenitroilo) tetraacetate;

silver-l l-aminoudecanoate;

silver aminovalerate;

silvertrimethoxybenzoate;

disilver oxalate;

disilver mercaptosuccinate;

silver citrate;

silver malonate;

Cu- SO and Ag SO 3. An imaging medium comprising (1) a radiationsensitive silver halide which upon exposure to a pattern of activating radiation produces a catalyst capable of accelerating the decomposition of a decomposable metal compound, and (2) an image forming material comprising said decomposable metal compound different than the silver halide, which is stable under normal ambient conditions and which can be decomposed by (a) heating to moderately elevated temperatures of the order of 65 C.

to 200 C. or by (b) exposing to developing radiation, but which decomposition is accelerated when said catalyst is in contact with the decomposable metal compound during the heating or exposing steps in order to produce an image of the original pattern of activating radiation which can readily be read out of the imaging medium, and wherein the metal in the image-forming material is present in an atomic amount of between about and 95% based upon the total atomic amount of metal in the imaging medium and wherein said decomposable metal compound comprises the reaction product of a metal ion and a chelating agent.

4. An imaging medium as in claim 3 wherein the chelating agent comprises a complexing organic acid or the soluble metal salts of such acid.

5. An imaging medium as in claim 4 wherein the complexing organic acid contains (1) at least two carboxyl groups, (2) at least one carboxyl group and at least one mercapto group, or at least one basic nitrogen group and at least two carboxyl groups.

6. An imaging medium as in claim 5 wherein the metal ion is silver ion.

7. An imaging medium as in claim 5 wherein the complexing organic acid comprises ethylenediaminetetraacetic acid or its soluble metal salts.

8. An imaging medium as in claim 7 wherein the metal ion is silver ion.-

9. An imaging medium comprising a substrate having thereon a photosensitive material in a binder, said photosensitive material comprising (1) a radiation-sensitive silver halide which upon exposure to activating radiation produces a catalyst for accelerating the decomposition of an image forming component and (2) said image forming component comprising silver ethylenediaminetetraacetate which image forming' component is substantially stable under normal ambient conditions, but which isdecom posed by heating at elevated temperatures of the order of C. to 200 C., and wherein under these conditions decomposition is accelerated in contact with said catalyst, said image forming component in an amount eifective t0 produce a visible image and wherein at least one mole of image forming component is present for every four moles of silver halide.

10. An imaging medium as in claim 9 wherein the" silver halide comprises silver bromide andthe image forming component comprises disilver ethylenediamine tetraacetate. u

11. An imaging medium as in claim 10 wherein one" mole of silver ethylenediaminetetraacetate is present for every 1-4 moles of silver bromide.

12. An imaging medium as in claim 10 wherein the photosensitive heavy metal salt and image forming component form an emulsion having a pH below about five (5).

References Cited UNITED STATES PATENTS Re. 26,719 11/1969 Sorensen et al 96-'63 3,457,075 7/1969 Morgan et al. 96-67 3,549,379 12/1970 'Hellings et al. 96-1l4.1

RONALD H. SMITH, Primary Examiner ALFONSO T. SURO PICO, Assistant Examiner US. Cl. XJR. 96-94 R, 114.6

v UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION -Patenl: No; 3,79%496 Dated February 26, 1974 Inv eficoflsyJohn'R. Manhardt 1 It is eert i'fied that error appears in the ebove-idefitified patefit and that said Letters Patent are hereby corrected as shbwn below:

Column 3, line 41 delete "Cu C0 and insert in its place-- a I v 2 3 2 3 Column 3, line 57, delete "hte" and insert in its place--the--.

C ol'um n 5', Line 33, delete "chlord'le" and insert in its place-- chloride". I

Column 6', line 29, delete "wa-es"'-a nd insert in its place-- H W -a v v R9 Column l2, line 25, delete the chemical structure "R v l and insert .in its place the chemical structure" v R R 7 "Columnl2, l' ine 47, please delete "pentasil'iv-er and insert in 1' 125- pl ace--pentasilver-- Column l2, line 57, please delete "(oxyethylenenitroilo)" and insert in its pl-ace--(ox yethylenenitrilo--.

Column l-2, line 59, please delete "aminoudecanoate" and insert in its place--aminoundecano ate--.

Signed and sealed this 20th day of August 1974.

' KC E v Acjtes't:

"f'Mc'co Y M. GIBSON; JR. v c. MARSHALL DANN" I Attesting-Officer Commissioner of Patents ='ORM PO-105O 10-69 v l USCOMM-DC 603164 69 u. 5. GOVERNMENT nmmue ornc: Isa o-s'u-au