US3887378A

US3887378A - Image recording and receiving materials

Info

Publication number: US3887378A
Application number: US460534A
Authority: US
Inventors: Alfons Klein; Anita Von Konig; Albert Lucien Poot; Karlfried Wedemeyer
Original assignee: Agfa Gevaert AG
Current assignee: Agfa Gevaert NV; Agfa Gevaert AG
Priority date: 1973-04-16
Filing date: 1974-04-12
Publication date: 1975-06-03
Anticipated expiration: 1992-06-03
Also published as: BE813733A; FR2225771B1; DE2319080A1; FR2225771A1; DE2319080B2; JPS5014334A; GB1460355A; JPS5710419B2; CA1029233A; IT1014593B

Abstract

An image reproduction material for producing copies in a dry way comprising a layer which contains a substantially lightinsensitive silver salt, a reducing agent and a toner, characterized in that it contains a hydroxyindane as reducing agent.

Description

United States Patent [191 Klein et al. V

[ June 3,1975

[ IMAGE RECORDING AND RECEIVING MATERIALS [75] Inventors: Alfons Klein, Dusseldorf; Anita Von .Konig, Leverkusen, both of Germany; Albert Lucien Poot, Kontich, Belgium; Karlfried Wedemeyer, Cologne-Stammheim, Germany [73] Assignee: Agfa-Gevaert, Mortsel, Belgium [22] Filed: Apr. 12, 1974 [21] Appl. No.: 460,534

[30] Foreign Application Priority Data Apr. 16, 1973 Germany 2319080 [52] U.S. Cl. 96/114.l; 96/67; 96/1 14.6 [51] Int. Cl G03c 1/02 [58] Field of Search 96/114.1, 67, 114.6

[56] References Cited UNITED STATES PATENTS 3,773,512 ll/l973 Poot et al 96/48 HD Primary Examiner-Norman G. Torchin Assistant Examiner-Alfonso T. SuroPico Attorney, Agent, or F irm-William J. Daniel [57] ABSTRACT An image reproduction material for producing copies in a dry way comprising a layer which contains a substantially light-insensitive silver salt, a reducing agent and a toner, characterized in that it contains a hydroxyindane as reducing agent.

18 Claims, No Drawings IMAGE RECORDING AND RECEIVING MATERIALS This invention relates to materials including recording materials and image receiving materials for dry processes of producing copies and the use of such materials in thermal recording processes and photographic processes.

Dry thermal recording and photographic processes for producing copies of an original are already known. The materials used for these processes contain lightsensitive or heat-sensitive layers. When these layers are exposed to light or heat in accordance with the image, a colour producing reaction is initiated which results in the formation of an image.

Heat sensitive copying foils which change colour imagewise by a thermally initiated reduction reaction have been disclosed in British Pat. Specification No. 318,203 filed Aug. 16, 1929 by Marconis Wireless Telegraph Co., German Pat. Specification No. 888,045 filed June 29, 1943 by Agfa AG and U.S. Pat. No. 2,129,242 of Samuel E. Sheppard and Waldemar Vanselow issued Sept. 6, 1938; U.S. Pat. No. 2,504,593 of Andr Schoen issued Apr. 18, 1950; U.S. Pat. No. 2,663,654 of Carl S. Miller and Bryce L. Clark issued Dec. 22, 1953; U.S. Pat. No. 2,663,657 of Carl S. Miller and Bryce L. Clark issued Dec. 22, 1953 and U.S. Pat. No. 2,910,377 of Richard Owen issued Oct. 27, 1959.

The recording materials used for the copying process described in German Pat. No. 1,300,014 filed Apr. 23, 1964 by Minnesota Mining and Manufacturing Co. contain an oxidizing agent, a reducing agent and a minor quantity of a light-sensitive compound. After exposure to light followed by heating, a redox reaction takes place in the light struck areas to form a coloured image. The oxidizing agents used are organic silver salts and the reducing agents aminophenols, hydroxylamines, pyrazolidones or phenols, phenylene diamine or etherified naphthols, e.g. 4-methoxy-l-naphthol. Suitable light-sensitive compounds are heavy metal salts which form traces of the free metal on exposure to light; these are in particular light-sensitive silver salts, e.g. silver halides which form silver by a photolytic reaction on exposure to light. These photolytically formed heavy metal nuclei initiate the redox reaction.

1f these materials are to be suitable for use in practice, it is essential to use light-insensitive silver salts as oxidizing agents, e.g. silver saccharide or silver salts of long chain fatty acids. Exceptionally high sensitivity to light is obtained if the required silver halide is produced on the surface of the light-sensitive silver salt by a reaction with halide ions or with a compound which forms halide ions, e.g. by the process described in U.S. Pat. No. 3,457,075 of David A. Morgan and Benjamin L. Shely, issued July 22, 1969. These materials have a sensitivity in the shortwave part of the spectrum corresponding to the intrinsic sensitivity of the silver halides used and they can also be sensitized to longer wave light by the addition of spectral sensitizing dyes.

Another photographic dry copying process is known in which a photographic material which contains a sil ver salt and a reducing agent for this silver salt is exposed imagewise and the exposed material is heated to a temperature at which the reducing agent reduces the silver compound in the light-struck areas to form a visible silver image. The photographic material used for this process comprises a layer which contains a silver compound which is substantially insensitive to light under the conditions of the process, a reducing agent and a polymethine sensitizer to spectrally sensitize the light-insensitive silver compound.

Other methods of producing copies by image-wise exposure of a light-sensitive layer are known in which the layer contains a light-sensitive compound and an image producing compound which is transferrable to an image receiving layer. In these processes, the image producing compound is converted in the light-struck areas into a non-transferrable compound, the exposed layer is brought into contact with an image receiving layer which contains compounds capable of reacting with the image producing compound to form coloured compounds, and the two layers are heated in contact with each other to a temperature at which the image producing compound is transferred from those areas of the light-sensitive layer which have not been struck by light to the image receiving layer.

This type of copying process includes the process described in German Pat. No. 1,234,243 filed Jan. 2, 1962 by Minnesota Mining and Manufacturing Co. in which the light-sensitive layers used contain a volatile compound and a dye. Exposure to light converts the volatile compound, e.g. 4-methoxy-1-naphthol, into a non-volatile product. By subsequently heating the layer, this compound can be transferred from the areas which have not been struck by light to a receiving material where it reacts with a silver salt to produce a coloured positive image.

A similar process has been described in U.S. Pat. No. 3,619,237 ofAlbert W. Leclair issued Nov. 9, 1971 and in French Pat. No. 2,037,847 filed Mar. 9, 1970 by Nashua Corporation, in which acetoacetonitrile derivatives or pyrazolin-S-one derivatives which can be inactivated by light and transferred by heat and react with a silver salt are used.

In the layers which contain a silver salt, the quantity of reducing agent must be kept to a minimum in order to prevent unwanted darkening of the casting solution or of the layer, i.e., reduction of the organic silver salts during preparation and storage of the material. The materials for the above mentioned processes preferably contain weak reducing agents such as o-alkylsubstituted phenols or hydroxy coumarans or hydroxychromans such as those described e.g. in German Offenlegungsschrift No. 1,908,761 filed Feb. 18, 1969 by Minnesota Mining and Manufacturing Co. and German Offenlegungsschrift No. 2,031,748 filed June 26, 1970 by Agfa-Gevaert AG or in German Pat. No. 1,250,842 filed Nov. 21, 1963 by Minnesota Mining and Manufacturing Co.

Apart from the fact that some of the known materials have insufficient stability during preparation and storage, there is the further disadvantage that discoloration is found to take place in the background of the image, i.e., in the image whites, due to oxidation of the reducing agents which remain in the layer after its preparation. In some of the known reducing agents this discoloration is so severe that a yellow or brown patchy background is formed after only a short time in storage.

It is an object of this invention to find reducing agents for the photographic processes described above which will not reduce the stability of the material during preparation or storage and will have not deleterious effect on the whites of the finished photographic image.

in which R, hydrogen, alkyl preferably containing up to 12 carbon atoms such as methyl, ethyl or butyl, cycloalkyl such as cyclopentyl or cyclohexyl, aralkyl such as benzyl or another hydroxyindane group of the above formula which is attached via a thioether bridge or a straight chain or branched chain alkylene bridge, in particular an alkylene bridge of the following formula:

P no- R or R hydrogen, halogen, in particular chlorine,

alkyl with preferably up to 12 carbon atoms, cycloalkyl such as cyclopentyl or cyclohexyl, aralkyl such as benzyl or phenyl, including the groups alkyl, cycloalkyl, aralkyl and phenyl in substituted form,

R or R hydrogen, alkyl preferably containing up to six carbon atoms, cycloalkyl such as cyclopentyl or cyclohexyl, or phenyl or R and R together may represent the ring members for a cycloaliphatic,

' preferably S-membered or 6-membered ring;

R or R hydrogen or alkyl including substituted alkyl preferably alkyl containing up to six carbon atoms, cycloalkyl including substituted cycloalkyl e.g. cyclopentyl or cyclohexyl, or aralkyl including substituted aralkyl e.g. benzyl or phenyl, or R and R may also represent the ring members for a cycloaliphatic ring containing preferably five or six ring members;

R or R hydrogen or alkyl preferably containing up to nine carbon atoms and R and R may also together represent the ring members for a cycloaliphatic ring with preferably five or six ring members.

Those hydroxyindanes of the above formula in which the hydroxyl group is in the 5-position and R in the 6- position represents hydrogen, alkyl, in particular tert.- butyl or isopropyl, cycloalkyl or another hydroxyindane group attached by a bridge member are particularly suitable.

This invention covers both light-sensitive materials and light-insensitive recording materials, e.g. photographic heat-sensitive materials and image receiving materials for producing photographic copies by a dry transfer process, the image receiving material containing mainly light-insensitive, reducible silver salts, a hydroxyindane as reducing agent and toner.

The materials according to the invention can be prepared without difficulty. Both the casting solutions for the layers and the finished material have excellent stability in storage. The special advantage lies in the quality of the finished images. Excellent whites without any yellowing are obtained.

Hydroxyindanes of the following formulae are particularly suitable:

CH CH Cl 2 CH OH CH CH 4 CH CH 5 CH cn The hydroxyindanes for use according to the invention are prepared in known manner by reacting alkylphenols with olefines in which at least one carbon atom carrying a double bond has exclusively carbon-carbon bonds, the reaction being carried out in the presence of acid catalysts at temperatures of between 100 and 350 C. The desired substituents may already be present in the alkyl' phenol or they may be introduced into the hydroxyindane at a later stage. For their preparation reference may be had to German Patent Applications P 23 04 588 filed Jan. 31, 1973 by Bayer Aktiengesellschaft and P 23 19 079 filed Apr. 16, 1973 by Bayer Aktiengesellschaft.

The preparation of some of the compounds is described in detail below.

COMPOUND l l 12 g (2 mol) of isobutylene are pumped for 1 hour at 150 C into an autoclave containing 136 g (1 mol) of 4-isopropyl-phenol in 100 ml of toluene and 30 g of an acid activated Fullers earth with stirring. Stirring is then continued for a further 6 hours at 150 C. After removal of the catalyst by filtration, 120 g of pure 1,1,- 3,3-tetramethyl--hydroxyindane are obtained by fractional distillation.

BP mm 144 C; Mp 119 C.

COMPOUND 2 75 g (1.33 mol) of gaseous isobutylene are introduced at 150 C with stirring into 1 14 g (0.06 mol) of 2-chloro-4-isopropyl-phenol and 20 g of an acid activated Fullers earth in a glass flask. Stirring is then continued for 1 hour at 150 C. After removal of the catalyst by suction filtration, the product is isolated by fractional distillation. 41 g of l,l,3,3-tetramethyl-5- hydroxy--chloroindane are obtained.

Bp mm Hg 79 C; Mp 52 C.

COMPOUND 12 22 g of isobutyraldehyde are slowly added at 120 C to l 14 g of l,1,3,3-tetramethyl-5-hydroxyindane and 3 g of cone. H 50 The temperature is lowered to 80 C while the isobutyraldehyde is added. The reaction mixture is then heated to 90 C for 2 hours and is then boiled up with 400 ml of benzene, 300 ml of water and 15 g of sodium acetate. Crystals precipitate from the separated benzene layer on cooling. The crystals are suction filtered, dried and recrystallised from dioxane. Yield 91.2 g; Mp 220- 221 C.

COMPOUND 13 38 g of l,l,3,3-tetramethyI-S-hydroxyindane and 6.4 ml of sulphur dichloride are stirred together in 150 ml of benzene at 50 C for 3 hours. After cooling, the precipitated crystals are suction filtered, dried and recrystallised from chloroform.

Yield 21 g; Mp 228 230 C.

The other compounds shown in the above table of formulae may be prepared in analogous manner.

The recording and image receiving materials according to the inventionwhich contain hydroxyindanes are used for the dry processes described above for producing silver images.

The materials according to the invention may be used, in a first process which is a thermographic process requiring a material with a layer which contains a light-insensitive silver salt and a hydroxyindane as reducing agent to reduce the silver salt in the heated areas. A process of this kind and materials for carrying it out have been described in U.S. Pat. No. 2,910,377 of Richard Owen issued Oct. 27, 1959.

The materials according to the invention may be used in a second process which is a photographic process employing photographic materials with a layer which contains a light-insensitive silver salt and generally small quantities of a light-sensitive heavy metal salt, in particular silver salt, as well as a hydroxyindane as reducing agent for reducing the silver salts in the light struck areas. Processes of this kind have been described in U.S. Pat. No. 3,589,903 of Stephen P. Birkeland issued June 29, 1971.

[n a third process for which the materials according to the invention may be used, the photographic material used comprises a layer which contains a lightinsensitive silver salt, the hydroxyindane compound as reducing agent and a polymethine sensitizer for the spectral sensitization of the light-insensitive silver compound. A process of this kind has been described in published German Pat. Application P 21 40 462 filed Aug. 12, 1971 by Agfa-Gevaert AG.

The sensitizers are generally dissolved in organic solvents before they are added to the casting solution described below although they may also be added in solid form to the silver salt before grinding or only shortly before application of the casting to a support. The concentration of sensitizer in the layer may vary within wide limits and depends on the effect desired and the nature of the sensitizer in combination with the silver salt. Concentrations of 0.01 to 2.0 g of sensitizing dye, preferably 0.2 to 0.6 g per mol of silver salt have generally been found to be sufficient. in individual cases, the sensitizers may also be used in quantities outside these limits.

The reducing agents used according to the invention may be added to the light-sensitive layer or either partly or completely to an adjacent layer.

In a fourth process, the photographic materials according to the invention are used for the transfer process described above for obtaining positive copies by a dry process. The materials used in this process for producing positive copies are light-sensitive materials comprising a layer which contains a photo-oxidizable reducing agent which is transferrable at temperatures of between and 200 C and a light-sensitive substance which activates the oxygen (to the triplet state) in the light-struck areas and converts the reducing agent into a non-transferrable form by oxidation.

The exposed layer is then brought into contact with the image receiving layer of a photographic material which contains a light-insensitive silver compound, a toner and the reducing agents according to the invention. The two layers are then heated in contact so that the reducing agent from those areas of the lightsensitive layer which have not been struck by light is transferred to the image receiving layer where it acts as additional reducing agent which together with the hydroxyindane reduces the light-insensitive silver salt in accordance with the image. A positive image of the original is obtained.

The hydroxyindanes to be used according to the invention may be added to the layers in various quantities. The optimum quantity depends on the effect desired and the composition of the layer. The optimum quantity for any given case can be determined by a few simple tests well known to the average expert. The hydroxyindanes may be used in concentration of 0.1 to 4 mol, preferably 0.5 to 3 mol of reducing agent per mol of oxidizing agent, i.e., per mol of light-insensitive organic silver salt. 1f the hydroxyindane is added to the light-insensitive image receiving layer, it is preferably used in quantities of 0.3 to 1.5 mol.

The reducing agents to be used according to the invention may also be used as mixtures with known reducing agents. The concentration of the additional reducing agents may vary within wide limits; see, for example, the o-alkyl-substituted monophenols or bisphenols described in German Offenlegungsschrift No. 1,908,761 filed Feb. 18, 1969 by Minnesota Mining and Manufacturing Co. and German Offenlegungsschrift No. 2,031,748 filed June 26, 1970 by Agfa- Gevaert AG or in German Pat. No. 1,250,842 filed Nov. 21, 1963 by Minnesota Mining and Manufacturing Co.

The bishydroxyindanes may, for example, be used as mixtures with sterically hindered 2,6- dialkylmonophenols such as 2,6-ditert.-buty1 monophenols and/or with 2,6dicycloalkylmonophenols such as 2,6-dicyclohexylmonophenols in an image receptor material. Examples of suitable sterically hindered monophenols have been described in U.S. Pat. No. 3,218,166 of John L. Reitter issued Nov. 16, 1965 and U.S. Pat. No. 3,653,907 of Charles H. Benbrook and Albert W. Leclair issued Apr. 4, 1972, e.g. 2,6-di-tert.- butyl-4-methylphenol or 2,6-dicyclohexyl-p-cresol.

The reducing agents for use according to the invention may be employed in the materials conventionally used for the given thermal development process, e.g. in a light-sensitive copying material which contains a silver salt or in a heat-sensitive material which is insensitive to light, e.g. an image receiving material. They may also be used in combination with the compounds normally used in these materials, e.g. reducing agents, binders, silver salts and other heavy metal salts, toners, white pigments and stabilizers. Materials of this kind are known per se and have been described in, for example, the following Patents: German Pat. No. 1,234,243 filed Jan. 2, 1962 by Minnesota Mining and Manufacturing Co., German Pat. No. 1,250,842 filed Nov. 21, 1963 by Minnesota Mining and Manufacturing Co. and German Pat. No. 1,300,014 filed Apr. 23, 1964 by Minnesota Mining and Manufacturing Co.; U.S. Pat. No. 3,074,809 of Richard Owen issued Jan. 22, 1963; U.S. Pat. No. 3,107,174 ofThomas G. Wartman issued Oct. 15, 1963; U.S. Pat. No. 3,457,075 of David A. Morgan and Benjamin L. Shely issued July 22, 1969, U.S. Pat. No. 3,460,946 of Gerhard W. R. Puerckhauer, Burt K. Sagawa and Bruce W. Wittnebel issued Aug. 12, 1969, U.S. Pat. No. 3,589,901 of Thomas D. Lyons issued June 29, 1971; U.S. Pat. No. 3,589,903 of Stephen P. Birkeland issued June 29, 1971; U.S. Pat.

No. 3,619,237 of Albert W. Leclair issued Nov. 9,.

June 6, 1967 by Fuji Shashin Film Kabushiki Kaishaand German Offenlegungsschrift Nos. 2,020,939 filed Apr. 29, 1970 by Agfa-Gevaert AG; 2,023,629 filed May 14, 1970 by Agfa-Gevaert AG; 2,031,748 filed June 26, 1970 by Agfa-Gevaert AG; Aug. 25, 1970 by Agfa-Gevaert AG; Aug. 27, 1970 by Agfa-Gevaert AG; 2,042,663 filed Aug. 28, 1970 by Agfa-Gevaert AG; 2,106,577 filed Feb. 11, 1971 by Agfa-Gevaert AG; 2,140,462 filed Aug. 12, 1971 by Agfa-Gevaert AG; 2,220,597 filed Apr. 27, 1972 by Agfa-Gevaert AG; 2,220,618 filed Apr. 27, 1972 by Agfa-Gevaert AG and 2,261,739 filed Dec. 16, 1972 by Agfa-Gevaert AG.

2,042,054 filed 2,042,531 filed Silver compounds which are substantially insensitive to light under the conditions of the process have proved to be particularly suitable, e.g. the silver salts of aliphatic carboxylic acids containing a thioether group which have been described in BritishPatent Specification No. 1,111,492 filed Aug. 13, 1965 by Agfa AG or silver salts of long chain fatty acids such as silver behenate, silver palmitate, silver stearate, silver oleate, silver laurate, silver hydroxystearate, silver caprate, or silver myristate. The following are also examples of typical silver salts which are suitable for use as oxidizing agents: silver benzoate, silver phthalazinone, silver benzotriazole, silver saccharide, silver-4'-n-octadecyloxydiphenyl-4-carboxylic acid, silver o-aminobenzoate, silver acetate, amidobenzoate, silver furoate, silver camphorate, silver p-pheny'lbenzoate, silver phenylacetate, silver salicylate, silver butyrate, silver terephthalate, silver phthalate, silver acetate and silver hydrogenphthalate.

The reducing agents for use according to the invention may be employed in combination with known organic reducing agents which contain active hydrogen atoms attached to O, N or C, e.g. o-alkylor cycloalkylsubstituted phenols, diand trihydroxyaryl, aminophenol, aminonaphthol, p-phenylenediamine and hydroxylamine derivatives, gallates, acetoacetonitriles, pyrazolidin-3-one, pyrazolin-S-one, and indane-1,3-dione derivatives, hydroxy tetronic acids, hydroxy tetronimides, reductones, e.g. anhydrodihydropyrrolidinohexose reductone, ascorbic acid derivatives and hydroxychroman and hydroxycoumaran derivatives, e.g. according to German Offenlegungsschrift No. 2,031,748 filed June 26, 1970 by Agfa AG; preferred reducing agents are, for example, o-alkyl-substituted phenols, acetoacetonitrile and methoxynaphthol derivatives.

In those materials according to the invention which contain light-sensitive heavy metal salts and in particular silver salts as light-sensitive compounds the layers may be optically sensitized by the addition of dyes. The

most suitable sensitizers are those compounds which are also commonly used for optically sensitizing conventional silver halide emulsion layers, i.e., cyanine dyes, merocyanines, oxonoles or rhodacyanines of various kinds, e.g. those described in the book by F. M. Hamer The Cyanine Dyes and Related compounds (1964).

To prepare a material according to the invention, the components for the redox reaction and the lightsensitive heavy metal are used together with a suitable binder. The binders used may be any of the usual natural or synthetic film-forming polymers, e.g. proteins such as gelatine, alginic acid and its derivatives, starch ethers or gallactomannane. The preferred substances used as binders are organic polymers such as copolymers of vinyl chloride and vinyl acetate or of butadiene and styrene, polyethylene, polyamides, polyisobutylene, polyvinyl chloride, polyvinyl alcohol/polyvinyl acalkoxynaphthols,-

etate or partly or completely saponified polyvinyl acetate, polyvinylidene chloride, polyvinyl pyrrolidone, polystyrene, chlorinated rubber, polyvinyl butyral, polymers of acrylic or methacrylic acid esters, acrylamide or copolyrners of derivatives of acrylic and methacrylic acid, cellulose derivatives, particularly cellulose ethers, cellulose esters such as carboxymethyl cellulose, nitrocellulose, cellulose acetates, cellulose propionates or mixtures thereof such as cellulose acetobutyrates, etc.

The light-sensitive layer which contains silver salts may be used as a self-supporting layer but is preferably applied to a suitable support. The support must be stable at the operating temperatures of between 80 and 200 C. Suitable supports are for example sheets or foils of paper, cellulose acetates, polyethyleneterephthalate, textile fabrics, metal foils and glass. In the case of paper supports, the paper may contain the usual auxiliary layers such as baryta layers, polyethylene layers,

etc.

Light-sensitive heavy metal salts which are suitable for the second of the processes mentioned and which react to light to form metal nuclei which are capable of initiating the image producing redox reaction are, for example, inorganic or organic salts of silver, mercury or gold. Heavy metals of sub-group lb of the Periodic System of Elements are preferred, particularly silver salts and among these again the silver halidies are preferred. The most suitable light-sensitive heavy metal salt for any given redox system can be determined by a few laboratory tests, for example the metal salt in the form of its aqueous suspension may be mixed with components of the redox reaction and the mixture must not undergo any change in the dark but should discolour relatively rapidly on exposure to UV light. If these conditions apply then the heavy metal salt is suitable for the redox system.

The light-sensitive heavy metal salt is used in relatively small quantities of about 0.1 to by weight, preferably 0.2 to l by weight, based on the weight of oxidizing agent. This proportion of light-sensitive salt is sufficient for most systems although in exceptional cases percentages above or below these limits may, of course, be used.

The light-sensitive heavy metal salt, e.g. the silver halide, should be present in sufficient quantities to enable the photolytically formed heavy metal nuclei to initiate the redox reaction but at the same time the concentration of silver halide should be low enough to that the metal nuclei formed will cause little or no discoloration of the copying material.

Silver halide may be added to the casting solution for the layer which contains the components for the redox reaction or it may be prepared in the casting solution in situ, i.e., by precipitation of the silver halide in the mixture. The silver ions for the precipitated silver halide may in that case be derived mainly from that silver salt which is not sensitive to light. 0

Preparation of the silver halides from the silver salts which are insensitive to light may be carried out by various methods, for example the surface of the lightinsensitive silver salts may be treated with vapours of hydrohalic acids, e.g. hydrochloric acid, hydrobromic acid or hydroiodic acid. The quantities of silver halide produced on the surface by this method can be kept within the desired limits by the concentration of the hydrogen halide in the vapour phase and the treatment time. I

The light-insensitive silver salts of organic acids may, of course, also be treated with a solution which contains halogen ions such as chlorine, bromine or iodine ions. These halogen ions may be derived from the hydrohalic acids or from their salts, in particular ammonium or alkali metal salts.

The light-insensitive silver salts which are reacted with the compounds which give off halogen ions are preferably used in the form of suspensions in a volatile, non-aqueous liquid although the reaction may also be carried out with dry salts, e.g. vapours of hydrogen halide.

Apart from the hydrohalic acids and their salts, e.g. the alkali metal and ammonium salts already mentioned above, alkaline earth metal salts or other metal salts such as Zinc or mercury salts and ionisable organic halogen compounds, e.g. triphenylmethyl chloride, triphenylmethyl bromide, 2-bromo-2-methylpropane, 2- bromobutyric acid, 2-bromoethanol or benzophenone dichloride may also be used.

In this embodiment it is preferred to form the lightsensitive silver halides from the light-insensitive silver salts of the organic acids. This enhances the capacity of the silver halides to form photolytic silver nuclei which are particularly efficient for initiating the redox reaction. Although suitable materials can also be obtained by preparing the silver halides separately and then mixing them with the light-insensitive silver salts, the photolytic heavy metal nuclei formed from such mixtures are generally not so effective.

Some of the silver salts which can be used in the present invention e.g. in the thermographic materials of the first process and the image receiving materials of the fourth process and which are in themselves insensitive to light manifest a certain even if slight characteristic sensitivity when, as is customary for the preparation of conventional silver halide gelatine emulsions, they are precipitated in the presence of a protective colloid such as protein and in particular gelatine. Precipitation of the silver salts for preparing the material according to the invention must therefore be carried out in such a way that the resulting silver salts are insensitive to light. This is generally achieved simply by precipitating without the presence of a protective colloid.

The dried silver salts are then added to solutions or dispersions of the desired layer binder. The concentration of silver salts in the dispersions of binder may vary within wide limits depending on the quantity of silver which is desired in the photographic layers. Quantities of 0.01 to 0.1 mol of silver salt per kilogram of casting solution are generally sufficient. The quantities used are preferably 0.02 to 0.05 mol of silver salt per kilogram of solution or dispersion. The same applies to the application of silver in the finished photographic layer. Here also the concentration may be varied within wide limits according to the effect desired and the purpose for which the material is to be used. Silver applications of 0.1 to 1.5 g of silver in the form of the silver salt per sq.m. and preferably 0.2 to l g per sq.m. are generally employed. One may, of course, also use mixtures of various light-insensitive silver compounds for the material according to the invention.

Other light-insensitive heavy metal compounds may also be added to improve the photographic properties of the material according to the invention; they are preferably added to the layer which contains the lightinsensitive silver salt. These additional substances may be used, for example, to reduce fogging, increase the density or shift the image tone towards a particular col our, e.g. towards neutral black.

Substances which are suitable for this purpose are e.g. salts or other compounds of mercury, cadmium, lead, uranium, gold, platinum, palladium or rhodium. These heavy metal compounds may be added at the stage of precipitation of the silver salt, in which case solutions of the heavy metal salts and of the silver salts are preferably added to the given precipitation component by the double jet method and so precipitated simultaneously. Although simultaneous precipitation of the silver salt and heavy metal salt is particularly advantageous and provides particularly suitable effects according to the nature of the heavy metal salt, the heavy metal salts may also be added as solids or in solution to casting solutions for the photographic layer which already contain silver salt. Alternatively, the heavy metal salts may be mixed with the dried silver salts by grinding or added shortly before the solution for the photographic layer is cast. Combinations of several metal salts may, of course, also be used.

The quantity of heavy metal salts or heavy metal compounds added may vary within wide limits. Here again the concentration depends on the nature of the heavy metal salt and of the silver salt and on the effect desired. The optimum quantity can easily be determined by a few simple tests which can be carried out with anyone with average knowledge of the art. The effect of the heavy metal salts is often more marked if they are prepared by the process of simultaneous pre cipitation. If this method is employed, concentrations of 0.001 to 10 mols percent and particularly 0.01 to moles percent are generally sufficient to achieve the effect desired. If the heavy metal salts are added at a later stage of preparation of the photographic material before it is cast, then concentrations of 0.001 to 0.2 mol of heavy metal salt, e.g. mercury(ll) acetate and preferably 0.005 to 0.07 mol per mol of silver salt are sufficient.

The image tone and image density of the image receiving material can be improved by certain metal salts, e.g. lead(ll)stearate. Such metal ion image intensifiers and their use have been described in US. Pat. No. 3,460,946 of Gerhard W. R. Puerckhauer, Burt K. Sagawa and Bruce W. Wittnebel issued Aug. 12, 1969.

So-called toners which shift the image tone from brown to black may be added to the recording and image receiving layers of the present invention to obtain images with sufficient optical density which result in sufficient contrast in the finished copy. 2H- phthalazinone-(l), barbituric acid, saccharin, 2-mercaptobenzoxazole, phthalimides and 2-acyl-2H- phthalazinones-( 1) are examples of such compounds.

The 2-carbamoyl-phthalazinone toners described in German Offenlegungsschrift Nos. 2,220,597 filed Apr. 27, 1972 by Agfa-Gevaert AG and 2,220,618 filed Apr. 27, 1972 by Agfa-Gevaert AG and the benzoxazine dione and quinazoline dione toners described in German Patent Application P 22 61 739 filed Dec. 16, 1972 by Agfa-Gevaert AG and corresponding to the following general formula:

wherein:

X represents oxygen or =N-alkyl, each of R R R and R represents hydrogen, halogen, hydroxy, an alkyl group, a cycloalkyl group, an alkoxy group, an alkylthio group, or a dialkylamino group, or R, and R R and R or R and R together represent the ring members necessary to complete a fused-on aromatic ring, are also suitable. The toners are generally used in quantities of 0.2 to 6 mol, preferably 0.3 to 5 mol per mol of light-sensitive silver salt. The layers may also contain white pigments such as zinc oxide, silicon dioxide or titanium dioxide as fillers, to improve the whites and to influence the tendency of the layers to stickiness and they may contain terpene resins and organic acids to improve the stability in storage. Layers of this kind have been described in US Pat. Nos. 3,074,809 of Richard Owen issued Jan. 22, 1963 and 3,107,174 of Thomas G. Wartman issued Oct. 15, 1963.

When choosing binders for the recording layer and image receiving layer, care should be taken to ensure that the layers will not stick when heated. These difficulties, however, are well known from other processes such as the silver salt diffusion process or heat development process and can easily be solved by making use of the experience gained in these known fields.

The usual sources of light used for reproduction work such as halogen lamps, iodine quartz lamps or incandescent lamps may be used for exposing the lightsensitive layers which contain silver salts or for use in the fourth process are free from silver salts and contain a combination of dye and reducing agent. Which particular source of light is used depends on the spectral sensitivity of the heavy metal salt or sensitizing dye used. The exposure time amounts to a few seconds.

Development of the light-sensitive copying materials which contain silver salts is carried out in the heat at temperatures of between and 200 C. The apparatus used for development may include heatable presses, drying drums, rollers or the apparatus described in Belgian Pat. No. 628,174 filed Feb. 8, 1963 by Agfa AG or in French Pat. Nos. 1,419,101 filed Dec. 4, 1964 by Agfa AG; 1,416,752 filed Dec. 4, 1964 by Agfa AG and 1,512,332 filed Sept. 18, 1964 by Agfa AG, as well as the usual apparatus available on the market.

Development of the light-sensitive silver saltcontaining material by heat may be carried out in contact with a foil such as a polyester foil in order to protect the layer and produce an image with a high gloss. The most suitable temperature and heating time depend, of course, on the composition of the lightsensitive silver salt-containing material. The development time varies from 3 to 80 seconds according to the temperature, which varies from 80 to 200 C, and the apparatus employed.

Transfer of the image-producing compounds from those areas of the light-sensitive layer which have not been struck by light to the image receiving layer takes place in the heat at temperatures of between 80 and 200 C. Heating may be carried out e.g. by passing the exposed light-sensitive layer in contact with the image receiving layer over hot plates or rollers or by irradiation with infra-red light. The most suitable temperature and heating time depend, of course, on the nature of the image producing compound and composition of the light-insensitive silver salt-containing copying material. They can be determined by a few simple tests.

unexposed test strips which had been developed at the same temperatures and for the same lengths of time as the step wedge.

The development by heat is carried out with the layer side of the material in contact with a polyester foil in order to protect the layer.

The images obtained after development are brown, brownish black or grey to neutral black on white grounds, depending on the developer and toner combinations used and the operating conditions.

Table Experi- Com g/quan- Toner g/quant Development Sensitivity Maxi- Grey lmage tone pound mum ment tity of ity of Temp. Time density fog No. reaction reaction C sec. steps V 2 mixture mixture 1 1 1.7 I 0.7 137 80 20 0.88 0.15 dark grey 2 2 1.3 l 0.7 137 40 22 0.98 0.16 black 3 8 1.8 l 0.7 137 60 22 0.96 017 black 4 10 1.8 1 0.7 137 60 21 0.71 0.15 black 5 1 1 1.9 11 0.3 127 40 21 1.07 0.1 1 black 6 1 1 1.9 111 1 1 20 1.15 0.13 black 7 12 1.3 IV 0.7 137 80 22 1.17 0.12 black 8 13 1.2 IV 0.7 137 80 21 1.04 0.1 l blackish brown 9 14 1.2 IV 0.7 137 80 21 1.01 0.12 blackish brown 10 1 1.7 111 1 122 40 22 1.08 0.18 blackish brown 1 l 2 1.3 111 1 122 20 22 1.12 0.20 blackish brown 12 8 1.8 111 1 126 20 21 1.05 0.20 blackish brown 13 12 1.3 111 l 110 20 21 1.18 0.19 black 14 14 1.2 111 1 110 20 21 1.02 011 black EXAMPLE 1 The following toners were used:

Light-sensitive material:

An equimolar mixture of silver behenate and behenic acid is prepared by precipitating silver nitrate with a solution of sodium behenate and behenic acid in alcohol and water. The precipitate is carefully washed and dried.

The suspension for preparing the layer is prepared by stirring the following mixture for 6 hours with a magnetic stirrer in the presence of glass beads:

1.8 g of silver behante/behenic acid (molar ratio 1:1 a toner in the quantity given in the following table,

5 mg of l,1'-bis-(benzothiazolyl)-mercury(ll),

1.5 g of cellulose acetobutyrate,

0.75 g of a copolymer of vinyl chloride and vinyl acetate (ratio by weight 60:40),

40 g of butanone.

0.5 mg of the sensitizer 5-[(3-ethylthiazilidin-2- ylidine)-ethylidene]-3-allyl-2-thio-oxazolidin-2,4- dione dissolved in 0.5 ml of butanone and a developer in the quantity given in the following table are added to this suspension with stirring before it is cast.

The casting solution is applied to a paper support and dried. The quantity of silver applied is 0.6 to 0.8 g of silver in the form of the silver compound per sq.m.

The above mixture is divided into several portions and the developers and toners shown in the following table are added to the individual samples in the quantities indicated in the tables.

The material according to the invention is exposed for seconds in a conventional copying apparatus equipped with tungsten filament lamps, behind a step wedge with an increment of 2 and it is then developed by heat. Brown, grey or black copies of the wedge are obtained. The maximum density and grey fog were determined by means of a densitometer on exposed and l 5,8-dimethyl-1,3-benzoxazine-2,4-dione I1 7-methyl-1,3-benzoxazine-2,4-dione 111 2H-phthalazinones-( 1 IV 6,8-dimethyl-l ,3-benzoxazine-2,4-dione.

EXAMPLE 2 The following layers are applied to a baryta paper support:

1. Light-sensitive layer from the following casting solution'.

1.8 g of silver behenate/behenic acid (molar ratio 3.0 g of cellulose acetate,

4.5 ml ofa 1% solution of calcium bromide in methanol,

5.7 m1 ofa 1% methanolic solution of mercury-ll acetate which has been acidified by the addition of glacial acetic acid,

3.0 m1 of a 0.01% solution of l-methyl-3-allyl-5-[2- (3-ethylbenzoxazolylidene-(2))-ethylidene]-2- thiohydantoin in chloroform,

0.15 g of silicon dioxide,

55.0 g of acetone,

1.0 g of a copolymer of vinyl chloride and vinyl acetate (ratio by weight 88:12) dissolved in 25 g of butanone and a toner in the quantity indicated in the following table.

2. Covering layer from the following casting solution:

10.0 g of polyvinylbutyral,

g of acetone and a toner and a developer in the quantities indicated in the following table.

The casting solution for the light-sensitive layer is ground in a ball mill for 16 hours before application. The light-sensitive layer contains 0.06 to 0.8 g of silver per sq.m. in the form of the given silver salts.

The covering layer is applied to the dried lightmogenization is stopped when the particle size in the sensitive layer. The quantity of reducing agent in the dispersion is less than ,um. covering layer is 0.5 to 1.5 g per sq.m. The solids content of the resulting mixture is then de- Several portions are prepared from the above mixtermined. In the case of a dispersion which has a solids ture and the casting solution for the covering layer and 5 content of 26 g per 100 ml (Dispersion A) the followthe developers and toners shown in the following table ing ingredients are added per 100 g of Dispersion A: are added in the given quantities to the individual samples. The light-sensitive material is exposed and devel- 36-Dlcyclohexyl'4'melhylpheml g d d .b d E l 1 Th bt d Ethyl acetate 120.00 g OpC 8S SCT1 6 1n xamp 6 e lll'llgCS 0 8.1116 Methy] ethyl ketone 20000 g after development are brown, brownish black, olive 10 black or grey to neutral black on a white to yellow The solids content of the mixture is then 13 gper 100 ground, depending on the developer and toner combiml. This mixture is applied to a paper support in a nations used and the operating conditions. thickness corresponding to 120 ml per sq.m. and dried.

Table Comp Top Toner Light- Top Development Sensitivity Maxi- Grey Image tone mum ound layer sensilayer Temp. Time density to No. g tive g C secv steps V 2 g layer 2 10 111 3 g l 110 20 0.82 0.20 brown 2 10 l 1.4 g 0.7 1 10 20 21 0 92 0.19 greyish black 11 12 Ill 3 g 1 104 10 20 0.82 0.20 brown 12 10 111 3 g l l 16 40 20 1.05 0.21 black l2 l0 1 1.4 g 0.7 127 40 21 1.03 0.19 black l3 10 111 3 g l 127 60 21 0.98 0.20 black EXAMPLE 3 The resulting image receiving material 1 is compared in An image receiving material I is prepared as follows: its prtggelrties with analogous image receiving materials 0.7 kg of stearic acid are dissolved in 8 kg of ethyl ac- H to I l H f etate by stirring and heating to 32 C in a water bath. Image l i l g g i 1 g i i The following ingredients are added to the resulting somg matena m t at 0 exy y p eno has been replaced by an equimolar quantity of 1,1 ,3,3- tetramethyl-6-hydroxyindane.

35 Image receiving material 111 contains a mixture of 0.945 g of 2,6-dicyclohexyl-4methylphenol and 0.074

lution with stirring and in the sequence indicated, care being taken to ensure that each fresh ingredient is added only when the previous one has been dissolved:

difi d phenol resin g g of 1,1 ,3,3-tetramethyl-6-hydroxyindane instead of 2,- (acid number 18 28, melting point 6-d1cyc1ohexyl-4-methylphenol. 3 35 6 33 67: 150 dame dens'ty Image receiving material 1V differs from image re- Polyvinyl acta te 4 g 40 ceiving material 1 in that 2,6-dicyclohexyl-4- e vpggg gp y methylphenol has been replaced by an equimolar quanreezing p01 I i POWeFhYl-meihacwla-te 220 g tlty of 1,1,3,3 tetramethyl-5-chloro-6hydroxy ndane.

(intr nsi Viscosity of a 05 7 by wei ht lmage receiving material V contains a mixture of gggggg ggggggg 3 80 g 0.945 g of 2,6-dicyclohexyl-4-methylphenol and 0.019

The following ingredients are added to the resulting g of l ,1,3,3-tetramethyl-5-chloro-6-hydroxyindane inz gg g mm'nued 1650 g stead of 2,6-dicyclohexyl-4-methylphenol alone.

finely divided silica 100 g Materials V1 and V11 are the same as materials 111 and Rhthalazmone g V except that 2,6-dicyclohexyl-4-methylphenol is resilver stearate 360 g.

placed by 0.77 g of 2,6-di-tert.-butyl-p-creso1.

Materials V111 to X111 are the same as materials 11 to V11 except that phthalazinone used as toner has been replaced by an equal quantity of a phthalazinone deriv- The following ingredients are added to the resulting solution with continued stirring:

zinc oxide 1 g ative of the following structural formula (described in gai y f Silica 15 German Offenlegungsschrift No. 2,220,618 filed Apr.

a azlnone silver stearate 360 27v 1972 y Agfa'GeVaert AG)- 0 u CH CH c x 2 2 N C NH CH CH I l ca ca Stirring is continued in a mixing apparatus and the The image receiving materials are processed identitemperature is raised to 40 C at the same time. cally with a light-sensitive material in which an organic reducing compound is rendered ineffective and diffusion resistant by exposure to light, e.g. according to German Offenlegungsschrift No. 2,010,837 filed Mar. 7, 1970 by Nashua Corporation.

A light-sensitive material of this kind is prepared as follows:

A transparent paper is coated with the following mixture in a thickness corresponding to 25 g/sq.m.:

(p Chlorophenyl)-acetoacetonitrile as 1.0 g

reducing agent Erythrosine 0.440 g Ethyl cellulose 50.0 g

Methyl ethyl ketone 500.0 g

The resulting layer is dried and exposed imagewise to a 1,500 Watt tungsten lamp for 30 seconds from a distance of cm.

Each of the image receiving materials described above was brought into contact with one of these exposed light-sensitive layers for 5 seconds at 125 C. Materials I to XIII were subjected to a stability test (8 days storage at 60 C and 8% relative humidity) before being used as described above. It was found that in the image receiving materials II to XIII which contained the given indane derivative, the image density had reduced much less than in the comparison material I which only contained 2,6-dicyclohexy1-3-methylphenol as auxiliary reducing agent. The image receiving material V had ex cellent stability and showed no loss of density after the given storage time.

EXAMPLE 4 An imagereceiving material I was prepared as in Example 3. The material obtained in this way was compared in its properties with analogous image receiving materials XIV to XVIII.

Image receiving material XIV differs from image receiving material I in that it contains 0.1 g of hydroxyindane 12 in addition to 2,6-dicyclohexyl-4- methylphenol.

Image receiving material XV differs from image receiving material I in that it contains 0.1 g of hydroxyindane 13 in addition to 2,6-dicyclohexyl-4- methylphenol.

Image receiving material XVI differs from image receiving material I in that it contains 0.1 g of hydroxyindane 14 in addition to 2,6-dicyclohexyl-4- methylphenol.

Image receiving material XVII differs from image receiving material I in that instead of 2,6-dicyclohexyl-4- methylphenol it contains an equivalent quantity of hydroxyindane 11.

Image receiving material XVIII differs from image receiving material I in that it contains 0.130 g of hydroxyindane 11 per 1.05 g of 2,6-dicyclohexyl-4- methylphenol.

The image receiving materials obtained are processed in identical manner together with the lightsensitive material from Example 3.

The image density was higher in materials XIV to XVIII than in material I. In contrast to material I, the materials according to the invention were not found to have any unwanted yellow in the background after they had been processed as described above. The image tone obtained with material XVII was greenish black and in the other cases it was brownish black.

EXAMPLE 5 A mixture of the following composition is ground in a ball mill for 12 hours:

Ethyl acetate 40.00 g

Stearic acid 7.00 g;

Polymethylmethacrylate 0.6 g

GV.688PCT (the viscosity of a 5 solution in chloroform at 20C is 0.91 0]?) Cellulose acetobutyrate 0.2 g;

(degree of substitution of acetate and butyrate 0.5 to 2.5, and the viscosity of a 20 solution in acetone is '15 P) II C\ I (toner) 0.25 g c Zinc oxide 4- g (average'particle size '10 microns) Silver stearate -9 g Methyl ethyl ketone 20.0 g l, l ,3,3-tetramethyl-6-hydroxyindane The final mixture is applied to a substrated polyethylene terephthalate support in a thickness corresponding to 150 g per sq.m. After application, the layer is brought into thermally conductive contact with a paper carrying a text which has been printed with printing ink containing carbon black, and it is then exposed to infrared radiation by contact exposure in a Thermofax copying apparatus.

The thermofax copying apparatus, Model 47-3M, is a thermographic copying apparatus of Minnesota Mining and Manufacturing Company, St. Paul, Minn., U.S.A.

A neutral black, positive copy with high density is obtained.

Similar results are obtained with hydroxyindane compounds 2 and 3.

We claim:

1. An image reproduction material selected from the group consisting of a recording material and an imagereceiving material comprising a layer which contains a substantially light-insensitive silver salt, a reducing agent and a toner, characterized in that it contains a hydroxyindane as reducing agent.

2. A material according to claim 1, characterized in that it contains a hydroxyindane of the following formula:

in which R, hydrogen, alkyl, cycloalkyl, aralkyl or another hydroxyindane group of the above formula attached by a thioether bridge or a straight chain or branched chain alkylene bridge;

R or R hydrogen, halogen, an alkyl group, a cycloalkyl group, an aralkyl group or a phenyl group;

R or R hydrogen, alkyl, cycloalkyl or phenyl, or

R and R represent the ring members for a cycloaliphatic five-membered or six-membered ring;

R or R hydrogen, an alkyl group, a cycloalkyl group, an aralkyl group or a phenyl group, or R and R represent the ring members for a 5- or 6- membered cycloaliphatic ring;

3. A photographic recording material according to claim 1, characterized in that it contains in addition a light-sensitive heavy metal compound and/or a polymethine sensitizer for sensitizing the light-insensitive silver salt.

4. A material according to claim 2, characterized in that it contains a silver salt of a long chain fatty acid as light-insensitive silver salt.

5. A material according to claim 4, characterized in that it contains silver behenate or silver stearate.

6. A photographic recording material according to claim 3, characterized in that the light-sensitive heavy metal compound contained in it is a silver halide.

7. A photographic recording material according to claim 3, characterized in that the light-sensitive heavy metal compound is contained in it in quantities of 0.05 to 0.2% by weight, based on the weight of lightinsensitive silver salt.

8. A material according to claim 2, characterized in that the reducing agent is contained in it in quantities of O.l to 4 moles per mol of light-insensitive silver salt.

9. A photographic recording material according to claim 3, characterized in that the layer which contains the light-insensitive silver salt contains a polymethine sensitizer for sensitizing the light-insensitive silver salt and that a reducing agent is contained in this layer or in an adjacent layer.

10. A material according to claim 2, characterized in that the light-insensitive silver salt is a silver salt of a long chain aliphatic carboxylic acid which is substituted with a thioether group.

11. A photographic recording material according to claim 3, characterized in that it contains a mercury(ll) compound.

12. A material according to claim 2, characterized in that the hydroxyl group is in the 5-position.

13. A material according to claim 2, characterized in that R represents an additional hydroxyindane group attached by a thioether bridge or a bridge member of the following formula:

in which:

R or R hydrogen or alkyl or R and R together represent the ring members for a cycloaliphatic five-membered or six-membered ring.

14. A material according to claim 2, characterized in that R and/or R represents a cycloalkyl group.

15. A material according to claim 2, characterized in that R.,, R R and R represent methyl.

16. A material according to claim 12, characterized in that R in the 6-position represents hydrogen, alkyl, cycloalkyl or another hydroxyindane group attached by said bridge member.

17. A material according to claim 2, characterized in that it contains as additional reducing agent an o-alkylsubstituted or cycloalkylsubstituted monophenol or bisphenol.

18. A material according to claim 2, characterized in that it contains as toner a 2H-phthalazinone-(l), a 2- carbamoyl-2H-phthalazinone-( l) or a benzoxazine- 2,4dione.

Claims

1. AN IMAGE REPORUDCTION MATERIAL SELECTED FROM THE GROUP CONSISTING OF A RECORDING MATERIAL AND AN IMAGE-RECEIVING MATERIAL COMPRISING A LAYER WHICH CONTAINS A SUBSTANTIALLY LIGHT-INSENSTIVE SILVER SALT, A RREDUCING AGENT AND A TONER, CHARACTERIZED IN THAT IT CONTAINS A HYDROXYINDANE AS REDUCING AGENT.

1. An image reproduction material selected from the group consisting of a recording material and an image-receiving material comprising a layer which contains a substantially light-insensitive silver salt, a reducing agent and a toner, characterized in that it contains a hydroxyindane as reducing agent.

7. A photographic recording material according to claim 3, characterized in that the light-sensitive heavy metal compound is contained in it in quantities of 0.05 to o.2% by weight, based on the weight of light-insensitive silver salt.

8. A material according to claim 2, characterized in that the reducing agent is contained in it in quantities of 0.1 to 4 moles per mol of light-insensitive silver salt.

11. A photographic recording material according to claim 3, characterized in that it contains a mercury(II) compound.

13. A material according to claim 2, characterized in that R1 represents an additional hydroxyindane group attached by a thioether bridge or a bridge member of the following formula:

14. A material according to claim 2, characterized in that R2 and/or R3 represents a cycloalkyl group.

15. A material according to claim 2, characterized in that R4, R5, R8 and R9 represent methyl.

16. A material according to claim 12, characterized in that R1 in the 6-position represents hydrogen, alkyl, cycloalkyl or another hydroxyindane group attached by said bridge member.

17. A material according to claim 2, characterized in that it contains as additional reducing agent an o-alkyl-substituted or cycloalkyl-substituted monophenol or bisphenol.