US3708297A

US3708297A - Stabilizing with iodide an imagewise exposed photosensitive composition containing a halogenated photoactivator and an organic amine color former

Info

Publication number: US3708297A
Application number: US00079283A
Authority: US
Inventors: A Poot; E Hazenbosch
Original assignee: Agfa Gevaert AG
Current assignee: Agfa Gevaert NV; Agfa Gevaert AG
Priority date: 1969-10-09
Filing date: 1970-10-08
Publication date: 1973-01-02
Anticipated expiration: 1990-01-02
Also published as: JPS504147B1; BE757145A; DE2049700A1; CA955448A; GB1323060A; CH549821A; FR2065925A5

Abstract

A PHOTOGRAPHIC PRINT-OUT IMAGE OBTAINED BY EXPOSING TO ACTIVATING ELECTROMAGNETIC RADIATION A RECORDING ELEMENT COMPRISING A PHOTOSENSITIVE ORGANIC POLYHALOGEN COMPOUND RELEASING ON SUCH EXPOSURE A HALOGEN-CONTAINING FREE RADICAL INTO WORKING RELATIONSHIP WITH AN AMINE HAVING AN AROMATIC CHARACTER AND REACTIVE WITH THE PHOTOLYTICALLY PRODUCED FREE RADICAL TO FORM A DYE IS STABILIZED AGAINST DISCOLORATION BY TREATING THE REMAINING UNEXPOSED POLYHALOGEN COMPOUND WITH A COMPOUND CONTAINING IONICALLY BOUND IODINE.

Description

United States Patent 3,708,297 STABILIZING WITH IODIDE AN lNlAGEWISE EXPOSED PHOTOSENSITIVE COMPOSITION CONTAINING A HALOGENATED PHOTO- ACTIVATOR AND AN ORGANIC AMINE COLOR FORMER Albert Lucien Poot, Koutich, and Edwin Hendrik Hazenbosch, Mechelen, Belgium, assignors to Agfa-Gevaert, Mortsel, Belgium No Drawing. Filed Oct. 8, 1970, Ser. No. 79,283 Claims priority, application Great Britain, Oct. 9, 1969, 49,685/69 Int. Cl. G03c 5/24 US. Cl. 9648 11 Claims ABSTRACT OF THE DISCLOSURE A photographic print-out image obtained by exposing to activating electromagnetic radiation a recording element comprising a photosensitive organic polyhalogen compound releasing on such exposure a halogen-containing free radical into working relationship with'an amine having an aromatic character and reactive with the photolytically produced free radical to form a dye isstabilized against discoloration by treating the remaining unexposed polyhalogen compound with a compound containing ionically bound iodine.

A preferred photosensitive polyhalogen compound corresponds to the following general formula:

wherein: Z represents the necessary atoms to close a benzene nucleus, and a preferred ionic iodine compound is an alkali metal iodide, alkaline earth metal iodide, or onium iodide.

The present invention relates to non-silver print-out photographic recording and recording materials suited therefor.

It is well known that polyhalogen compounds, such as carbon tetrabromide, are split into free-radical fragments on irradiation with ultra-violet light.

A print-out photographic process based on a colour reaction produced by an exposure to ultraviolet light of a mixture of carbon tetrabromide and diphenylamine and other secondary and tertiary arylamines has been described in Phot. Sc. and Eng. 5, March-April 1961, pp. 98l03. By the fact that carbon tetrabromide is relatively volatile it is possible to obtain a fixed or stabilized image by heating the exposed recording element. The high volatility of the carbon tetrabromide impairs, however, the shelf life of the recording material so that it can already be useless a few days after its manufacture.

Therefore it has been proposed to apply polyhalogenated aromatic hydrocarbon or particular polyhalogenated heterocyclic compounds that have a sufliciently high photosensitivity and by means of which recording layers with an improved shelf life are produced.

Because of the rather low vapour pressure of said compounds the complete stabilization of the obtained image is often difficult to realize or requires relatively high temperatures and a rather long heat treatment.

It is the main object of the present invention to provide a stabilization technique that is not based on the volatility of the photosensitive organic polyhalogen compounds and that offers the possibility to produce photosensitive printout recording materials having an improved shelf life, high photosensitivtiy and good image stabilization properties.

3,708,297 Patented Jan. 2, 1973 A method has now been found of recording and stabilizing a photographic print-out image containing the steps of:

(1) Exposing a recording material to activating electromagnetic radiation, said recording material containing a recording element comprising a photosensitive organic polyhalogen compound generating on exposure to active electormagnetic radiation a halogen-containing free radical, said polyhalogen organic compound during exposure being in working relationship with an amine having an aromatic character, and being capable of forming a dye by reaction with a photolytically produced free radical generated by the photographically exposed organic polyhalogen compound; and

(2) Treating the remaining unexposed organic polyhalogen compound with a compound that contains ionical- 1y bound iodine, and preferably simultaneously applying heat to accelerate the stabilization reaction preventing thereby darkening of the image background on a subsequent overall ultraviolet light exposure.

By the term in working relationship has to be understood, that the halogen-containing free radicals produced on exposure can come in effective contact with a properly selected aromatic amine. The ionic iodine compound(s), however, when present in the recording material has (have) to be kept (at room temperature (20 C.)) away from direct chemically reactive contact (i.e., to be kept in nonworking relationship) with respect to said organic polyhalogen compound before and preferably also during exposure, for it has been experienced that otherwise a reduction in photosensitivity takes place especially when aromatic amines being free from a N-vinyl group are used.

Preferred organic polyhalogen compounds are within the scope of the following general formula:

R-CX wherein R is hydrogen, chlorine, bromine or iodine, an aliphatic radical including a substtiuted aliphatic radical, e.g. a substituted or unsubstituted alkyl radical, or an aromatic hydrocarbon radical including a substituted aromatic hydrocarbon radical e.g. a phenyl radical, a heterocyclic radical, a substituted heterocyclic radical, an acyl group, including a car'boxylic acid acyl group, a sulphonic acid acyl group and a sulphinic acid acyl group, a carboxyl group, a carboxylic acid ester group, an amide group or an aldehyde group, and

each of X is chlorine, bromine or iodine.

Particularly suited organic polyhalogen compounds are:

carbon tetrabromide, bromoform, iodoform, chloroform, fl-tribromoethanol, trichlorobromomethane, hexabromoethane, bromodichloromethane, pentachloroethane, methyl trichloroacetate, ethyl tribromoacetate,

tribromoaceta-mide, tribromoacetaldehyde, tribromomethylbenzene, p-nitrotribromomethylbenzene, hexachloroethane, pentabromoethane, tetrabromobutane, hexachlorobenzene, tetrachlorotetrahydronaphthalene, a,a,a-tribromoacetophenone, 4-bromo-u,-m,a-tribromoacetophenone, 3-nitro-a,a,a-tribromoacetophenone, 4-nitro-m,a,u-tribromoacetophenone, 2-tribromomethylquinoline, 2-tribromomethyl-8-nitro-quinoline, 2-tribromomethylquinoxaline,

2,3hexabromodimethylquinoxaline, chloro-2-tribromomethylquinoxaline Each of these compounds is a halogenated organic compound in which the carbon atom substituted with more than one halogen atom carries no more than one hydrogen atom.

Organic polyhalogen compounds preferred for their property to yield a recording material with particularly high shelf life and good photosensitivity and stabilizability correspond to the following general formula:

Z represents the necessary atoms to close a benzene nucleus or substituted benzene nucleus e.g. carrying one or more substituents of the group of alkyl, alkoxy, halogen and nitro.

In order to illustrate the preparation of such photosensitive compounds reference is made to the preparation receipt of 2-tribromomethylquinoxaline (J. Chem. :Soc. 1928, 1974). The bromination is preferably carried out according to the following procedure:

A mixture of 330 g. of sodium acetate, 660 g. of acetic acid and 0.64 mole of a Z-methylquinoxaline, is heated till the temperature reaches 70 C. Whilst thoroughly stirring at that temperature 315 g. (1.9 mole) of bromine dissolved in 600 ml. of acetic acid are added in a period of time of 75 min. Thereupon the reaction mixture is boiled for 5 hr., subsequently cooled down on a waterbath, and finally poured into water. The formed precipitate is filtered by suction and washed with water.

2-tribromomethylquinoxaline can be easily recrystallized from ethanol and melts at 112 C.

Suitable amines having an aromatic character and that are used in working relationship with the photosensitive organic polyhalogen compound include primary, secondary and tertiary aromatic amines, e.g. the amines corresponding to the following general formula:

wherein:

R represents an alkyl group, e.g. a C -C alkyl group, an aralkyl group, e.g. a benzyl group, a hydroxyalkyl group, e.g. a hydroxyethyl group, or a sulphoalkyl group, e.g. a C -C sulphoalkyl group,

Z represents the necessary atoms to close a ring or ring system having an aromatic character including such ring or ring system in substituted form, e.g. a benzene ring or a naphthalene ring and such rings substituted e.g. with halogen, an alkyl group, an amino group or substituted amino group,

L represents a bivalent organic radical capable to link two amino groups together e.g. an alkylene or substituted alkylene radical, or organic radical containing alkylene groups, e.g. methylene groups interrupted by an aromatic radical, e.g. by a phenylene group or by hetero atoms, e.g. oxygen, or a bivalent amino group or substituted bivalent amino group, e.g. a

' group, a CH -O-CH group or 3.

.il l.

group wherein R represents hydrogen, an alkyl group,

a substituted alkyl group or an aralkyl group.

4 A particularly suited amine falling within the scope of said general formula is N,'N-dipheny1-N,N-diethylethylenediamine.

Other particularly suited aromatic amines are:

arylamines e.g. diphenylamine, dibenzylamine, triphenylamine, N,N-diethylam'1ine, N,N-dimethylaniline, N-hydroxyethyl-N-ethylaniline, o-amino-diphenylamine, p-hydroxydiphenylamine, a-naphthylamine, p-amino N-diethylaniline, p-aminodiphenyl, Z-aminodiphenyl, p-aminodiphenylamine, N-benzylaniline, lN-butylaniline, N-sec.butylaniline, 2,4-dia-mino diphenylamine, N,N-dibenzylethylenediamine, 2,6-di-tert.butylamine, a-dimethylamino-p-cresol, 3,4-dichloroaniline, m-N-diethylaminophenol, N-diethylaminotoluene, 'N,N-diphenylethylenediamine, diphenyl-p-phenylenediamine, p-dimethylaminobenzaldehyde, o- (dimethylaminomethyl -phenol, m-dimethylaminophenol, N,N'-dimethyl-a-naphthylamino, di-B-naphthylamine, di-fi-naphthyl-p-phenylenediamine, di-n-propylaniline, N-ethylaniline, N,N-benzylethylaniline, N-ethyl-N-phenylethanolamine, N-(2-ethylhexyl)-aniline, N-ethyl-o-toluidine, N-ethyl-m-toluidine, 2-phenylaminoethanol, N-phenyl-cyclohexylarnine, phenyl-u-naphthyla-mine, phenyl-fi-naphthylamine, 3-hydroxy-diphenylamine, N-methylaniline, IN-(a-methylbenzyl)-diethanolamine, N- a-methylbenzyl) -ethanolamine, N-methyl-o-toluidine, p-tolyl-u-naphthylamine, N-butyl-N-w-amino acetic acid propylaniline, N-ethylN-w-sulphonic acid butylaniline, 3,S-diethyl-N-n-hexadecylaniline, 3,S-di-tert.butyl-N, N-dimethylaniline, 3,5-dimethyl-N,nhexadecylaniline, N-n-hexadecylaniline, -N,N-ethyl-octylaniline, N,N-ethyl-n-hexadecylaniline, N,N-ethyl-p-toluene-sulphonylaniline, N,N-ethyl-dodecylaniline, [t- (N -ethyl-anilino)ethyl carbanilate and heterocyclic amino compounds such as indoline, 1,2,3- trimethylindole, Z-aminobenzimidazole, 3-phenylindole, a-diethylaminopyridine, N-ethylcarbazole or 1,2-dihydro- 2,2,4-trimethylquinoline.

Aromatic amines containing a N-vinyl group yield much fog and therefore are of no particular practical value for use in the process of the present invention. Suitable ionic iodine compounds are water-soluble iodides. Image stabilization is preferably carried out by means of alkali metal iodides, alkaline earth metal iodides and onium iodides, e.g. sodium iodide, potassium iodide, organic and inorganic ammonium iodides and barium iodide. Organic onium iodides are described more particularly in the published United Kingdom patent application 1,151,363 filed Apr. 30, 1965, by Gevaert-Agfa N.V. which for that part has to be read in conjunction herewith.

In order to prevent a premature reduction of the photosensitivity of the photosensitive colour-producing system consisting of a photolytically free radical-producing organic polyhalogen compound (photoactivator) and an aromatic amine (dye modificator) the ionic iodine compound is incorporated according to a first embodiment into the recording material in such a way that direct chemically reactive contact with the photosensitive polyhalogenated organic compound is prevented at room temperature (20 C.).

According to a secorid embodiment the ionic iodine compound is incorporated into the recording material in a stage following the information-wise exposure to activating electromagnetic radiation.

According to a preferred embodiment the ionic iodine compound is applied from a liquid (solvent, solvent mixture or dispersing medium), wherein the photosensitive organic polyhalogen compound is not soluble, whereas the latter is applied from a liquid wherein the ionic iodine compound is not soluble.

When producing the recording material by starting from an aqueous phase and a hydrophobic phase, the ionic iodine compound is preferably applied from the aqueous phase and the photosensitive organic polyhalogen compound together with the aromatic amine compound from the hydrophobic or lipophilic phase.

When using binding agents for one or both of said compounds preferably a more hydrophobic binding agent is used for the photoactivator and dye modificator than is used for the ionic iodine compound.

According to a special embodiment the photo-sensitive organic polyhalogen compound is present in a thermoplastic hydrophobic binder layer, whereas the ionic iodine compound is present in a hydrophilic binder layer, the binder of the hydrophobic layer being selected in such a way that on melting it can penetrate in the hydrophilic binder layer. For thermosensitive materials containing such binders in separate layers reference is made to the French patent specification 1,531,440 filed Apr. 3, 1967 by Gevaert-Agfa N.V.

According to another special embodiment the photosensitive organic polyhalogen compound and the ionic iodine compound are applied in a mixture of two binding agents one of which contains the organic polyhalogen compound and the other the ionic iodine compound. Said binding agents are selected in such a way that they are not compatible at room temperature, so that one of them at this temperature is present in the form of dispersed particles in the continuous phase of the other binding agent, which forms a homogeneous mixture with the dispersed binding agent by melting.

For such type of binding agents reference is made to the United States pjatent specification 3,223,838 of Shoishiro Hoshino and Akira Kato, issued Dec. 14, 1965.

According to still another embodiment one or both of said compounds are encapsulated or separated from each other by means of a meltable layer, e.g. a hydrophobic thermoplastic polymer layer or wax layer. Suitable encapsulating techniques for aqueous media are described in the United Kingdom patent specifications 1,048,696 and 1,048,697 both filed July 10, 1963, by Gevaert-Photo- Producten N.V.

Further, the ionic iodine compound can be applied in a porous hydrophilic support, e.g. paper, by imbibition and the photosensitive compound applied thereto in a meltable hydrophobic binding agent. The contact of the ionic iodine compound with the organic photosensitive compound may be improved by hygroscopic compounds, e.g. glycerol, that come at the disposal of both compounds at the right moment after the photographic exposure. Glycerol and the ionic iodine compound can be encapsulated according to the technique described in the Belgian patent specification 741,954 filed Apr. 3, 1967, by Gevaert-Agfa N.V. (corresponding with United Kingdom patent applications 55,080/68 filed Nov. 20, 1968 and 2,229/69 filed Dec. 31, 1968, both by Gevaert- Agfa N.V.). The capsules can release their contents by rupture (pressure treatment) or melting of the capsule wall (heat treatment). Although a completely dry stabilization is preferred the present invention does not exclude the use of ionic iodide-producing compounds present in a treating liquid applied after the photographic exposure. A semi-wet stabilization may be carried out by means of a stabilizing liquid comprised in a container or pod that can be ruptured and releases its contents upon advancing the photosensitive element and sheetlike container material between a pair of pressure rollers.

Suitable binding agents for the photosensitive organic polyhalogen compounds are hydrophobic hermoplastic binding agents e.g. acetylcellulose, having an acylation degree of preferably at least 2, cellulose acetate-butyrate, ethylcellulose (DS ethoxy preferably at least 2), hydrophobic vinyl polymer and copolymers, e.g. polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, alkyl polyacrylates, alkyl polymethacrylates, and polystyrene.

Optionally a plasticizer is used in admixture with the binder. Suitable plasticizers include tricresyl phosphate, tri(2-ethylhexyl) phosphate, dioctyl phthalate, di(2-ethylhexyl) tetrahydrophthalate, di(2-ehtylhexyl) maleate and polyethylene glycol.

The spectral sensitivity of the photosensitive print-out system containing a normally, only U.V.-sensitive organic polyhalogen compound and an aromatic amine can be extended. So, the inherent photosensitivity of Z-tribromomethyl-quinoxaline being in the spectral range of 300 to 450 nm. can be extended to include a part of the visible spectrum by means of azocompounds as described in the United States patent specification 3,042,516 of Eugene Wainer, issued July 3, 1962.

Particularly suited for that purpose are, e.g., the yellow N,N-dimethylphenylazoaniline and 4-phenylazodiphenylamine. These azocompounds are used in rather small amounts so that a heavy background colouration is excluded.

Other suitable spectral sensitizing agents are found in the class of spectral sensitizing agents for light-sensitive silver halide and photoconductive zinc oxide, e.g. in the class of the acridine dyes, cyanine dyes and styryl dyes, e.g. cyanine dyes and styryl dyes described in the United Kingdom patent specification 1,000,195 filed Apr. 2, 1962 by Horizons Inc., thiazine dyes and xanthene dyes, e.g. phthaleine dyes. In that respect have to be mentioned par ticularly acridine orange, acridine red, rose bengale, methylene blue, pinacyanol and pinacryptol yellow.

In order to give an idea of the proportion of the different ingredients in preferred photosensitive coating compositions the following list of ingredients expressed in parts by weight is presented:

Parts Solvent 1000 Film forming binding agent 10-50 Photosensitive organic polyhalogen compound 5-30 Aromatic amine 20-50 Spectral sensitizing agent 1-5 Said compositions may be coated onto a suitable support, e.g. a paper or resin support, according to any coating technique known in the art.

As already mentioned the stabilization of the obtained image preferably proceeds in dry state and with the aid of heat. Heat can be supplied to the photographically exposed recording material by an infrared lamp or by contact with a hot body, e.g. by conveying it between a pair of hot rollers having a surface temperature of C.

In order to obtain a particularly clean image background the ionic iodine compounds are preferably combined with a hydrogen sulphite or hydrogen sulphitegenerating compound that can produce sulphur dioxide in acid medium.

Especially good results are obtained by means of a mixture of sodium hydrogen sulphite or sodium disulphite (Na S O and sodium iodide.

Ionic iodine compound Solvent To a baryta-coated paper support a solution of the following stabilizing composition was applied in a ratio of 40 ml. per sq. rn.:

Sodium iodide g 1 Sodium hydrogen sulphite g 1 Propanol ml 20 Water ml 80 After drying, a photosensitive coating composition containing the following ingredients was coated theeron in a ratio of 40 ml. per sq. rn.:

2-tribromomethylquinoxaline g 5 Diphenylamine g Polystyrene g 2 Chloroform ml 100 The recording material was dried and contact-exposed for 10 sec. through a line transparency in a diazocopying apparatus Actina S (trade name of Regrna N.V., Brussels, Belgium). The exposure source was a 1000 w. mercury vapour bulb arranged at a distance of 5 cm. from the photosensitive material. An intense green negative image of the original was obtained on a light yellow background. The exposed recording material was conveyed between a pair of hot rollers having a surface temperature of 150 C. Thereby the image colour turned to intense grey-violet and the image background colour remained unchanged even after an intense exposure to ultraviolet light.

EXAMPLE 2 To a glassine type paper support having been precoated with a stabilizing composition as described in Example 1, a photosensitive coating composition containing the following ingredients was applied in a ratio of 40 ml. per

sq. rn.:

2-tribromomethylquinoxaline g 2 N,N-ethyl-fl-hydroxyethylaniline g 2 Cellulose acetate-butyrate (type half second butyrate of Eastman, Kingsport, Tenn., U.S.A.DS Butyryl 1.7-DS acetyl 1.0-viscosity of a by weight solution in acetone at C.:48 cp.) g 2 Acetone l 100 The recording material was dried and contact-exposed for 6 see. through a line transparency in an Actina S (trade name) diazocopying apparatus. The exposure source was a 1000 W. mercury vapour bulb arranged at a distance of 5 cm. from the photosensitive material. An intense green negative image of the original on a light yellow background was obtained. A stabilized image was obtained in the exposed recording material by conveying it between a pair of hot rollers having a surface temperature of 125 C. The stabilized image had an intense violet colour and the slightly yellow image background did not darken even by a strong exposure to ultraviolet rays.

EXAMPLE 3 To a baryta-coated paper precoated With a stabilizing composition as described in Example 1 a photosensitive coating composition containing the following ingredients was applied at a rate of 40 ml. per sq. 111.:

2-tribromomethylquinoxaline g 2 fl-(N-ethylanilino)-ethyl carbanilate g 3 Cellulose acetate-butyrate (as in Example 2) g 3 Acetone ml 100 The recording material was dried and contact-exposed for 6 see. through a line transparency in an Actina S (trade name) diazo copying apparatus. The exposure source was a 1000 w. mercury vapour bulb arranged at a distance of 5 cm. from the recording material. An intense green image was obtained. An intense purplish black stabilized image was obtained in the exposed recording material by leading it between a pair of hot rollers having a surface temperature of 125 C.

EXAMPLE 4 To a baryta-coated paper precoated with a stabilizing composition as described in Example 1, a photosensitive coating composition containing the following ingredients was applied in a ratio of 40 ml. per sq. m.:

2-tribromomethylquinoxaline g 5 N-vinylcarbazole g 5 Cellulose acetate-butyrate (see Example 2) g 5 Acetone ml 100 The recording material was dried and contact-exposed for 10 see. through a line transparency in an Actina S (trade name) diazo'copying apparatus. The exposure source 'was a 1000 w. mercury vapour bulb arranged at a distance of 5 cm. from the recording material. A yellowish-brown negative image of the original was obtained. A stabilized image was obtained by leading the recording material between a pair of hot rollers the surface temperature of which was 125 C. The stabilized image had an intense brown colour.

EXAMPLE 5 On a polyethylene terephthalate film support a photosensitive layer was coated in a ratio of 40 ml. per sq. m. from the following composition:

2-tribromomethylquinoxaline g 8 N-ethyl-N-fi-hydroxyethylaniline g 8 Cellulose acetate-butyrate (see Example 2) g 2 Acetone ml 100 After drying of the photosensitive layer, a top-coat for image-stabilizing purposes was applied thereto in a ratio of 40 ml. per sq. m. from a solution having the following composition:

Sodium iodide g 0.6 Sodium hydrogen sulphite g 1 Water ml Propanol ml 20 After drying, the recording material was contact-exposed for 20 sec. through a line transparency in an Actina S (trade name) diazo copying apparatus. The exposure source was a 1000 w. mercury vapour bulb arranged at a distance of 5 cm. from the recording material. An intense green negative image of the original was obtained. A stabilized image was obtained by conveying the exposed recording material between a pair of hot rollers the surface temperature of which was 110 C. The stabilized image had an intense greyish violet colour and the image background remained clear even after a strong exposure to ultraviolet rays or an exposure to daylight for several days. If said stabilizing treatment was not carried out the image background turned green to grey after a few minutes exposure to daylight.

EXAMPLE 6 To a baryta-coated paper support a solution of the following stabilizing composition was applied in a ratio of 40 ml. per sq. rn.:

Sodium iodide mg 600 Sodium disulphite mg 600 Water ml Propyl alcohol N-ethyl-N-B-hydroxyethylaniline mg 100 Exposure and heating for initiating and accelerating the stabilization were efiected as described in Example 1. A stable negative green print of the original was obtained.

EXAMPLE 7 To a baryta-coated paper support a stabilizing composition as described in Example 6 was applied.

On the dry stabilizing coating a photosensitive coating composition containing the following ingredients was coated in a ratio of 40 ml. per sq. m.:

N-ethyl-N-B-hydroxyethylaniline mg 100 2-tribromomethylquinoline mg 100 Cellulose acetatebutyrate (see Example 2) mg 50 Acetone ml 5 The exposure and heating for initiating and accelerating the stabilization were carried out as described in Example l. A stable violet-gray negative print-out image of the original was obtained.

EXAMPLE 8 To a bartya-coated paper support a stabilizing composition as described in Example 6 was applied.

On the dry stabilizing coating a photosensitive coating composition containing the following ingredients was Exposure and heating for initiating and accelerating the stabilization were carried out as described in Example 1. A stable blue negative print-out image of the original was obtained.

EXAMPLE 9 To a baryta-coated paper support a solution of the following stabilizing composition was applied in a ratio of 40 ml. per sq. m.:

Sodium iodide g-.. 1 Sodium hydrogen sulphite g 2 Propanol ml 20 Water ml 80 After drying, a photosensitive coating composition containing the following ingredients was coated thereon in a ratio of 40 ml. per sq. m.:

2 tribromomethylquinoxaline g 5 l,2-dihydro-2,2,4-trimethylquinoline g..- 10 Cellulose acetate-butyrate (see Example 2) g 2 Methyl ethyl ketone ml 100 The recording material was dried and contact-exposed for 5 sec. through a line transparency in a diazocopying apparatus Actina S (trade name). The exposure source was a 1000 w. mercury vapour bulb arranged at a distance of 5 cm. from the photosensitive material. An intense brown negative image of the original was obtained on a light yellow background. The exposed recording material was conveyed between a pair of hot rollers having a surface temperature of 150 C. Thereby the image colour turned to intense greyish black and the image background colour remained almost unchanged even after an intense exposure to ultraviolet light.

EXAMPLE 10 To a glassine type paper support having been precoated with a stabilizing composition as described in Example 2, a photosensitive coating composition containing the following ingredients was applied in a ratio of 40 ml. per sq. m.:

10 2-tribromomethylquinoxaline g 5 N,N'-diphenyl-N,N'-diethylethylenediamine g 5 Cellulose acetate-butyrate (see Example 2) g 2 Acetone l The recording material was dried and contact-exposed for 6 sec. through a line transparency in an Actina S (trade name) diazocopying apparatus. The exposure source was a 1000 w. mercury vapour bulb arranged at a distance of 5 cm. from the photosensitive material. An intense green negative image of the original on a light yellow background was obtained. A stabilized image was obtained in the exposed recording material by conveying it between a pair of hot rollers having a surface temperature of C. The stabilized image had an intense brown colour and the slightly yellow image background did not darken even by a strong exposure to ultraviolet rays.

We claim:

1. A method of forming and stabilizing a photographic print-out image containing the steps of:

(1) imagewise exposing to activating electromagnetic radiation, a recording material containing a recording element comprising a photosensitive organic polyhalogen compound generating on exposure to activating electromagnetic radiation a halogen-containing free radical and in working relation with said polyhalogen compound during exposure an amine free of N-vinyl groups having an aromatic character capable of forming a dye image in the exposed areas by reaction with a photolytically produced free radical generated by the photographically exposed organic polyhalogen compound, and

(2) after said exposure contacting the remaining unexposed polyhalogen compound with a water-soluble inorganic or organic iodide to stabilize the unexposed areas of said material against color change upon exposure to light.

2. A method according to claim 1, wherein the iodide is present in the recording material in isolated relation preventing direct chemically reactive contact with the photosensitive organic polyhalogen compound at room temperature and is brought into contact with said polyhalogen compound by heating the recording material after the exposure.

3. A method according to claim 1, wherein the iodide and photosensitive polyhalogen compound are present in the recording material in two separate and distinct coatmgs.

4. A method according to claim 3, wherein the iodide and photosensitive organic polyhalogen compound are coated from different liquids that are not miscible with each other.

5. A method according to claim 1, wherein the recording material after its image-wise exposure is treated with a liquid containing a water-soluble iodide.

6. A method according to claim 1, wherein the photosensitive organic polyhalogen compound is a compound of the following general formula:

R--CX wherein:

R is hydrogen, chlorine, bromine or iodine, an aliphatic group, an aromatic hydrocarbon group, a heterocyclic group, an acyl group, a carboxylic acid ester group, an amide group or an aldehyde group, and each of X is chlorine, bromine or iodine. 7. A method according to claim 1, wherein the photosensitive polyhalogen compound corresponds to the following general formula:

vNs

wherein:

R represents an alkyl group, or an aralkyl group,

Z represents the necessary atoms to close a ring or ring system having aromatic character, and

L represents a bivalent organic radical linking two amino groups.

9. A method according to claim 1, wherein the iodide is an alkali metal iodide, alkaline earth metal iodide or onium iodide.

10. A recording material according to claim 2, wherein the iodide in said isolated relation is in admixture with hydrogen sulphite or with a hydrogen sulphite-generating compound.

11. A recording material according to claim 1, wherein the recording material contains a spectrally sensitizing agent selected from the class of azo dyes, acridine dyes,

12 cyanine dyes, styryl dyes, xanthene dyes, phthaleine dyes, and thiazine dyes.

References Cited UNITED STATES PATENTS 3,565,628 2/1971 Garland 96-90 3,512,976 5/1970 Yamada et al. 96-90 X 3,042,516 7/ 1962 Wainer 96-48 3,527,639 9/1970 Moraw 96-90 3,042,518 7/1962 Wainer 96-90 X FOREIGN PATENTS 916,779 1/1963 Great Britain 96-90 957,192 5/1964 Great Britain 96-90 OTHER REFERENCES J. Chem. Soc. 1928, p. 1974.

NORMAN G. TORCHIN, Primary Examiner W. H. LOUIE, JR., Assistant Examiner US. Cl. X.R. 96-90