DE2154075B2 - Direct positive silver halide photographic emulsion - Google Patents

Description

C-CH ₁ -R '

I.
(CH ₂ ),

CO

3- (2-acetylethyl) -2-phenoxymethylbenzo-

thiazolium bromide;
2,2-ethylene bis [3- (2-acetylethyl) benzo-

thiazolium bromide];
2-benzyl-3- (2-propionyiäthyl) benzo-

thiazolium bromide;
3- (2-acetylethyl) -2-ethylbenzothiazolium-

bromide;
3- (2-acetylethyl) -2-benzylbenzoselen-

azolium bromide;
3- (2-acetylethyl) -2-benzyl-5-phenyl-

benzoxazolium bromide or
3- (2-Benzoylethyl) -2-äthylbenzothiazoliuiii-

bromide;
3- (2-formylethyl) -2-methylbenzothiazolium-

bromide;
3- (2-acetylethyl) -2-benzylbenzothiazolium-

bromide;
3- (2-formylethyl) -2-propylbenzothiazolium-

bromide.

C- (CH ₂ ), -C

• N

\, J

(CH ₂ ), 2X
CO
R.

(CH ₂ ),
CO
R.

where mean:

Z those required to complete an imidazole, oxazole, thiazole or selenazole ring Atoms;

R is a hydrogen atom or an optionally substituted short-chain alkyl or aryl radical;

R 'is a hydrogen atom or an optionally substituted short-chain alkyl, aryl or Aryloxy radical and

Χ ^Θ an anion.

2. Silver halide emulsion according to claim 1, characterized in that it is 0.2 to 1.4 g Contains fogging agents per mole of silver halide.

3. Silver halide emulsion according to claim 1 and 2, characterized in that it is a color coupler contains.

4. Silver halide emulsion according to Claims 1 to 3, characterized in that it consists of a gelatin-silver bromide iodide emulsion consists.

5. Silver halide emulsion according to Claims 1 to 4, characterized in that it is used as a fogging agent contains:

5-chloro-3- (2-formylethyl) -2-methylbenzo-

thiazolium bromide;
3- (2-formylethyl) -5-methoxy-2-methylbenzo-

thiazolium bromide;
3- (2-acetylethyl) -2-propylbenzothiazolium-

bromide; .
3- (2-formylethyl) -2-methyl-naphtho-

[2,3-d] thiazolium bromide;

The invention relates to a direct positive silver halide photographic emulsion which produces latent images for generated predominantly in the interior of the silver halide grains and contains a fogging agent.

It is known that so-called direct positive photographic silver halide emulsions for Herjo direct positive photographic images, d. H. without making a photographic negative, can use.

These direct positive photographic emulsions produce latent images on exposure to the r> predominantly in the interior of the silver halide grains. The production of direct positive photographic images is thereby caused that the not exposed areas of a direct positive photographic emulsion layer can be selectively fogged and that corresponding to the unexposed, fogged areas a normal photographic silver image is being developed. The concealment agent can be used in a so-called "concealment bath" are brought, with which the imagewise exposed silver halide emulsion layer before Image development is dealt with. On the other hand, the fogging agent can also be used in the developer solution Applied or incorporated into the reverse emulsion before applying this to a Layer support is applied.

The known nucleating compounds or masking agents usually consist of Hydrazine compounds. It is for example from US-PS 25 63 785, in particular column 1, lines 18 to 34 and column 3, line 28 to column 5, line 23, known hydrazine compounds as fogging agents in Surface-type silver halide developing solutions to use. Furthermore, it is, for example, from US Pat. No. 25 88 982, in particular column 1, lines 21 to 34 and column 4, line 1 to column 5, line 52, hydrazine compounds are known as fogging agents in Surface-type silver halide developing solutions or in the emulsion itself.

The disadvantage of using the known hydrazine compounds as fogging agents is that they, especially when they are incorporated into the silver halide emulsion itself, for Achieving sufficient fogging in relative

high concentrations must be applied, e.g. B. in concentrations of 2 g per mole of silver halide, as can be seen, for example, from US Pat. No. 2,588,982. When using such high concentrations it is difficult to obtain uniform sensitometric results because of the larger size Quantities of the fogging agent get into the developing solution, where they discolor the photographic Material in the non-image background districts.

Presumably, the need to use high concentrations is based on the known ones Fogging agents ensure that these compounds are not or only weakly from the silver halide grains are adsorbed. The migration of the fogging agents into the developing solution is not only caused by the high concentration in which the compounds are present in the emulsion, promoted, but rather also due to the high pH value required when using these compounds, which is normally above 12, usually 12 to 13, and the is required to achieve obfuscation within an acceptable amount of time.

The object of the invention is to provide a direct positive photographic silver halide emulsion, the latent Images generated predominantly inside the silver halide grains indicate which one contains such a fogging agent which is used in photographic direct positive silver halide emulsions in lower concentrations than before can be used and discoloration when it is used the non-image background areas are avoided.

It has been found that certain quaternary heterocyclic salts with a hnidazole, oxazole, Thiazole or selenazole ring are outstandingly effective concealing agents.

The invention thus provides a photographic direct positive silver halide emulsion which latent images generated predominantly in the interior of the silver halide grains and contains a fogging agent which is characterized by being Fogging agent contains 0.1 to 1.5 g per mole of silver halide of a compound of the following formulas:

O-

-N

(CH ₂ ), X
CO
R.
or

Z \ / Z

! C- (CH ₂ ), -C j

^V NN - ''

I I

(CH ₂ ), (CH ₂ ) ₂ 2X

CO CO

R R

where mean:

Z the atoms required to complete an imidazole, oxazole, thiazole or selenazole ring;

R is a hydrogen atom or an optionally substituted short-chain alkyl or aryl radical;

R 'is a hydrogen atom or an optionally substituted short-chain alkyl, aryl or Aryloxy radical and

X ^{8 is} an anion.

Typical rings that Z can stand for are, for example:

Benzimidazole rings, e.g. B. 5-chlorobenzimidazole rings or

Naphthimidazole rings; Oxazole rings, e.g. B.

4-methyloxazole, 5-methyloxazole, 4-phenyloxazole, 4,5-diphenyloxazole, 4-Ethyloxazole, 4,5-Dimethyloxazole and

5-phenyloxazole rings; Benzoxazole rings, for example Benzoxazole, 5-chlorobenzoxazole, 5-methylbenzoxazole, 5-phenylbenzoxazole, . 6-methylbenzoxazole, 5,6-dimethylbenzoxazole, 4,6-dimethylbenzoxazole, 5-methoxybenzoxazole, 5-ethoxybenzoxazole, 5-chlorobenzoxazole, 6-methoxybenzoxazole, 5-hydroxybenzoxazole or

6-hydroxybenzoxazole rings; Naphthoxazole rings, e.g. B.

Λ-naphthoxazole rings; j5 thiazole rings, e.g. B.

Thiazole, 4-methylthiazole, 4-phenylthiazole, 5-methylthiazole, 5-phenylthiazole, 4,5-dimethylthiazole, 4,5-diphenylthiazole and 4- (2-thienyl) thiazole rings; Benzothiazole rings, e.g. B.

Benzothiazoles 4-chlorobenzothiazole, 5-chlorobenzothiazole, 6-chlorobenzothiazole, 7-chlorobenzothiazole, 4-methylbenzothiazole, 5-methylbenzothiazole, 6-methylbenzothiazole, 5-bromobenzothiazole, 6-bromobenzothiazole, 4-phenylbenzothiazole, 5-phenylbenzothiazole, 4-methoxybenzothiazole, 5-methoxybenzothiazole, 6-methoxybenzothiazole, 5-iodobenzothiazole,

6-iodobenzothiazole, 4-ethoxybenzothiazole,

5-ethoxybenzothiazole, bo tetrahydrobenzothiazole,

5,6-dimethoxybenzothiazole, 5-hydroxybenzothiazole and

6-hydroxybenzothiazole rings; Naphthothiazole rings, e.g. B. b5 a-naphthothiazole,

8-methoxy - «- naphthothiazole, 7-methoxy -« - naphthothiazole and Naphtho [2, l -d] thiazole rings;

Thionaphlheno-7 ', 6', 4,5-thiazole rings, e.g. B.

4'-methoxythionaphtheno-7 ', 6', 4,5-thiazole rings;
Selenazole rings, ζ. Β.
4-methylselenazoI- or
4-phenylselenazole rings;
Benzoselenazole rings, e.g. B.
Benzoseienazole, 5-chlorobenzoselenazole,
5-methoxybenzoselenazole,
5-hydroxybenzoselenazole or
Tetrahydrobenzoselenazole rings or
Na |) liihoselenazole rings, e.g. B.
a.- Naphthoselenazole rings.

The short-chain alkyl radicals represented by R and R ¹ preferably have 1 to 4 carbon atoms and thus consist, for example, of methyl, ethyl, propyl or butyl radicals. Of particular importance are compounds of the structural formula given in which R and R ^{1 represent} alkyl radicals having 1 or 2 carbon atoms. If R and R ^{1 represent} substituted alkyl radicals, these can for example consist of aralkyl radicals, e.g. B. benzyl, phenethyl or phenoxymethyl radicals.

If R and R ^{1 represent} optionally substituted aryl radicals, these preferably consist of aryl radicals of the phenyl or naphthyl series with 6 to 10 carbon atoms in the aryl group. A preferred aryl radical is the phenyl radical.

If R ^{1 has} the meaning of an aryloxy radical, this preferably consists of an aryloxy radical of the phenoxy or naphthoxy series with 6 to 10 carbon atoms. A preferred aryloxy group is the phenoxy group.

For example, Χ ^θ can be a halide anion, e.g. B. a bromide, chloride or iodide anion, a sulfate, hydrogen sulfate or a short-chain alkyl sulfate anion, for example a methyl sulfate or ethyl sulfate anion, an aromatic sulfonate anion, for example a toluenesulfonate or benzenesulfonate anion, an anion derived from a carboxylic acid for example an acetate, trifluoroacetate or propionate anion or, for example, a perchlorate cyanate, thiocyanate, sulfamate or benzoate anion.

Those whose anions have proven to be particularly advantageous fogging agents Halide anions exist.

Particularly advantageous masking agents are, for example, the quaternary ones indicated below heterocyclic salts:

a) 3- (2-formylethyl) -2-methylbenzothiazolium-,

b) 3- (2-acetylethyl) -2-benzylbenzothiazolium-,

c) 3- (2-formylethyl) -2-propylbenzothiazolium-,

d) 5-chloro-3- (2-formylälhyl) -2-methylbenzothiazolium-,

e) 3- (2-formylethyl) -5-methoxy-2-methylbenzothiazolium-,

f) 3- (2-Acetyläthy!) -2-propylbenzothiazolium-,

g) 3- (2-formylethyl) -2-methylnaphlho- [2,3-d] thiazolium-,

h) 3- (2-acetylethyl) -2-phenoxymethylbenzo-

thiazolium,
i) 2,2'-Ethylene bis [-3- (2-acetylethyl) benzo-

thiazolium] -,

j) 2-benzyl-3- (2-propionylethyl) benzothiazolium,
k) 3- (2-acetylethyl) -2-ethylbenzothiazolium-,
I) S - ^ - AcetyläthyO ^ -benzylbcnzoselenazolium-,
m) 3- (2-acetylethyl) -2-benzyl-5-phenylbenz-

oxazolium and
n) 3- (2-BenzoylälhyI) -2-ethylbenzothiazolium salts.

The fogging agents according to the invention can be according to customary methods by reacting a Cyclammonium hydro salt with a compound with an active double bond system, e.g. B. one Ethiopian double bond between the first and second carbon atoms of an aliphatic molecule or radicals.

The reaction can be carried out in an inert organic solvent as the reaction medium, in particular in an inert organic solvent of moderate polarity which dissolves both reaction components but is not a solvent for the quaternary salt formed during the reaction. Typical advantageous solvents for carrying out the reaction with moderate polarity are, for example, acetonitrile and dimethylacetamide. The reaction normally takes place without the addition of catalysts. It can be carried out at temperatures from 20 ⁰ C to 30 ° C further advantageously, although higher and lower temperatures can be used, so long as the reactants remain in solution and are not heated to temperatures above their decomposition temperature. The reaction products precipitate out of the solution and can be purified by washing with solvents or repeated recrystallization according to customary known methods.

The preparation of a heterocyclic salt which can be used according to the invention can be carried out, for. B. by reproduce the following reaction scheme:

ί CR ³ + CH, - = CH —C — R

HX

CR ¹ + X

(CH ₂ ),
CO

wherein R ^{3 is} a radical of the formula -CH ₂ -R ¹ and R ¹ and R, Z and X ^{e have} the meaning given.

A typical heterocyclic salt which can be used according to the invention, namely 3- (2-formylethyl) -2-methylbenzothiazolium bromide the formula:

CH ₃

S.
N

(CH ₂ ), Br
CO

H

can be made, for example, as follows:
100 g of 2-methylbenzothiazolium hydrogen bromide and

48.7 g of acrolein were added with stirring at room temperature mixed together in 150 ml of dimethylacetamide for 24 hours. A pale yellow crystalline precipitate separated out, which is filtered off, washed thoroughly with acetonitrile and dried. The yield was 100 g, corresponding to 31.3% the theory. The melting point of the compound was 233 to 236 ° C.

Incidentally, the direct positive silver halide photographic emulsions of the present invention have the composition known for direct positive photographic silver halide emulsions, d. H. she can for example consist of the usual gelatin silver halide emulsions, their silver halide consists for example of silver bromide, silver bromide iodide or silver chloride bromide. The usage of Sensitizing dye is not required, although it may be advantageous to add the emulsions to Add such dyes to extend their spectral sensitivity. Sensitizing dyes. Those in Can advantageously be used for the spectral sensitization of the emulsions are, for example from US-PS 24 97 876, in particular column 2, line 15, to column 4, line 20, known. the Direct positive photographic silver halide emulsions of the present invention can be prepared from undigested or digested silver halide emulsions, the digestion without the addition of a chemical Surface sensitizer takes place.

An emulsion of this type is known, for example, as "Burton's" emulsion (see for example that Book by Wall, "Photographic Emulsions", Publisher: The American Photo Publishers, Boston, USA, Seilen 52 and 53). Another type of direct positive emulsion that is predominantly latent images Part inside the silver halide grain-forming emulsion is disclosed, for example, in U.S. Patent 25 92 250 known.

Direct positive photographic silver halide emulsions containing latent images for the most part can be produced in the interior of the silver halide grains in that first in one or several process steps produce silver halide grains which are at least in part made of silver chloride exist. Then at least some of the grains are converted into silver bromide or silver bromide iodide, followed by ripening, preferably in the absence of ammonia, followed by part up to the total amount of soluble salts present, usually sodium nitrate and / or potassium nitrate and Sodium chloride and / or potassium chloride, is washed out. After that it closes to prepare the final Emulsion the addition of soluble salts, ζ. Β. of a soluble chloride, bromide or iodide. To this Thus, a "built up" silver chlorobromide, bromide iodide or chloride bromide iodide direct positive emulsion obtain.

Advantageous silver chloride bromide emulsions, the latent images predominantly inside the Produce silver halide grains can also be produced in an advantageous manner that to a moving aqueous gelatin solution at the same time an aqueous silver nitrate solution and an aqueous one Solution of potassium chloride and potassium bromide are added, as is, for example, from Example 4 of the US-PS 29 96 382 is known.

A typical photographic silver halide emulsion containing latent images for the most part in the

Generated inside the silver halide grains is one such emulsion, which behaves as follows:

If a proportion of the coated emulsion to 1 second exposed through a light intensity scale, and developed at 20 ⁰ C in a conventional surface developers for 4 minutes, that is, a developer containing a UIID only on the surface of the grains of an emulsion that form latent images predominantly generated and developed inside the silver halide grains and which has, for example, the following composition:

p-hydroxyphenylglycine 10 g

Sodium carbonate (crystals) 100 g

made up to 1 liter with water

so a maximum density is obtained, which is not larger than ¹ A of the maximum density obtained when the same emulsion exposed in the same way and 3 minutes is developed at 20 ⁰ C in a so-called inside-grain developer long, which an image in the interior of the grains of an emulsion which produces latent images predominantly in the interior of the silver halide grains, where the developer can have the following composition, for example:

Hydroquinone 15 g
Monomethyl-p-aminophenol-

sulfate 15 g

Sodium sulfite (anhydrous) 50 g

Potassium bromide 10 g

Sodium hydroxide 25 g

Sodium thiosulphate (crystals) 20 g

topped up with water to 1 liter

Preferably, the maximum density obtained by development with the surface-type developer will not be greater than '/ to the maximum density obtained when the same emulsion is in the inner grain developer is developed. Conversely, an emulsion leads to the latent images predominantly generated inside the silver halide grains when placed in an internal grain developer is developed to a maximum density which is at least the Sfachcn, preferably at least the corresponds to 10 times the maximum density obtained when the emulsion is exposed in the same way and is developed in a surface-type developer.

The compounds to be used according to the invention are particularly suitable for direct positive emulsions of the type known, for example, from US Pat. Nos. 25 66 180 and 25 92 250. You become obvious adsorbed more firmly on the surfaces of the silver halide grains than those known from US Pat. No. 2,588,982 Hydrazine compounds, and therefore when using the inventive compounds lower concentrations of the same are required. As a result of the fact that low concentrations of emulsifier are sufficient to achieve the desired concealment, constant advantageous sensitometric results can be achieved, in particular by the fact that less abrasive means gets into the developer solution.

The use of 0.2 to 1.4 g of compound mill per mole has proven to be particularly advantageous Proven silver halide.

The directly positive photograph according to the invention!

silver halide emulsions can also be seen contain the additives typical for direct positive photographic silver halide emulsions, e.g. B. spectral sensitizing dyes, coating aids, optical brighteners, hardeners and developing agents. To build up the emulsions, the customary known binders, in particular the known hydrophilic binders permeable to water are used, for example gelatin, colloidal albumin, polyvinyl compounds, cellulose derivatives and acrylamide polymers, on their own or in combination with each other. Optionally, the binders that are used to prepare the Emulsions used also contain dispersed polymerized polyvinyl compounds, for example those known from U.S. Patents 3,142,568, 3,193,386, 3,062,672 and 3,220,844. to Such polymers include, for example, the water-insoluble polymers and latex copolymers of alkyl acrylates, alkyl methacrylates, acrylic acid, sulfoalkyl acrylates or sulfoalkyl methacrylates.

For the spectral sensitization of the direct positive silver halide photographic emulsion of the present invention can, for example, the spectral sensitizing known from US-PS 25 26 632 and 25 03 776 Dyes are used. The dyes which can be used for spectral sensitization can for example from cyanine, merocyanine, complex trinuclear cyanine, complex trinuclear merocyanine, Styryl and hemicyanine dyes exist.

The direct positive silver halide photographic emulsions of the present invention can also be used contain the usual known nonionic, anionic and / or amphoteric coating auxiliaries, for example saponin, substituted by alkyl radicals aryloxylalkylene ethylsulfonate, z. B. from the US-PS 26 00 831 known type, Maleopimarate, e.g. B. of the type known from US-PS 28 23 123, furthermore Taurine derivatives, e.g. of the type known from US Pat. No. 2,739,891, and alkylaminopropionates, e.g. B. des of the type known from US-PS 3133 816. Further known, advantageously usable coating auxiliaries are for example alkylphenoxypoly (hydroxyalkylene oxides), e.g. B. alkylphenoxypoly (glycidols) with 5 to 12 glycidol units, for example those known from GB-PS 10 22 878.

For the preparation of the direct positive photographic silver halide emulsions according to the invention in advantageously suitable optical brighteners are, for example, those with at least one heterocyclic 5- or 6-membered ring, for example derivatives of stilbene, stilbene triazole, triazine stilbene, coumarin, Triazinylaminocoumarins, oxazoles, benzidines, benzimidazoles, benzothiazoles, benzoxazoles, pyrazolines or Naphthalenimide. Typical for making a direct positive silver halide photographic emulsion according to the invention usable optical brighteners are for example from US-PS 29 33 390 and 34 06 070 known.

The direct positive photographic Silver halide emulsions can be prepared with customary known hardeners or hardener combinations harden, e.g. B. with Aldehydhärtungsmittcln, such as formaldehyde, glutaraldehyde and Maleic acid dialdehyde, also mucochloric acid, with aziridinhürtern, hardeners made from derivatives of Dioxane, vinyl sulfone, oxyl polysaccharide,

z. B. Oxystärke, oxidized vegetable gums, also inorganic hardeners, z. B. Chromium Salts.

For the production of direct positive photographic recording materials according to the invention photographic silver halide emulsions can be coated on conventionally known supports. Typical substrates of this type consist, for example, of cellulose esters, for example cellulose acetate, Cellulose triacetate and cellulose acetate butyrate, poly-n-colefins, for example polyethylene and polypropylene, polycarbonates, polyesters, e.g. B. polyethylene terephthalate, as well as of metals, e.g. B. zinc and aluminum or paper, which optionally has a layer of one Poly-ß £ -olefin may have, for. B. one made of polyethylene or polypropylene.

The direct positive photographic silver halide emulsions of the present invention can be prepared from color photographic as well as black and white silver halide emulsions. The direct positives according to the invention Color emulsions are particularly suitable for the production of such direct-positive color recording materials, those generating using cyan, magenta and yellow dyes Color couplers are produced, the listed color couplers in contact with various Silver halide emulsion layers are located that record light of a color that is practically complementary is the color of the dye produced with the aid of the color coupler. Color photographic recording materials of this type are known, for example, from US Pat. No. 3,227,550 and 3,227,552. To raise awareness of the silver halide, spectral sensitizing dyes can be used in the usual way will. In the case of a conventional multilayer color photographic recording material, the red recording emulsion layer, for example 5- (p-amylphenoxybenzenesulfonamido) -1 -naphthol, the green-recording emulsion layer, for example, 2-cyanoacetyl-5- (p-sec.-amylbenzoylamino) -coumaron and the blue-recording emulsion layer, for example, N-amyl-p-benzoylacetaminobenzene sulfonate. Possibly the color couplers can also be added to the developer solution, for example from U.S. Patents 2252718 and 2507 154 is known. In in this case several exposures and color development steps are required. According to the pictorial The photographic recording materials can be exposed to direct positive photographic Silver halide emulsion layers according to the invention in a conventional manner with the aid of a conventional surface developing solution can be developed with relatively little solvent action on the silver halide, wherein positive photographic images are produced. Those used to develop the recording materials Surface developers can advantageously contain image-intensifying compounds which Increase the maximum density and lead to a decrease in D "" ". Such connections can for example consist of benzotriazoles, as known for example from US Pat. No. 2,497,917 are.

In the case of color photographic recording materials Usual developer solutions with p-phenylenediamine color developer compounds can be used can be used, for example, 4-amino-N-dialkylanilines such as for example from the book by M e s, "The Theory of the Photographic Process", 3rd edition (1966), pages 294 to 295 is known. By means of a color developer

Il

bond, one or more dye images can be generated, depending on the makeup of the particular color photographic recording material. In the case of polychromatic color recording materials normally turn blue-green, magenta and yellow in the red, green and blue sensitive layers, respectively Dye images generated. The remaining silver is first converted into a soluble silver salt and then removed in the usual way by treatment with a fixing agent, for example sodium thiosulphate.

The following examples are intended to illustrate the invention in more detail.

example 1

For comparison purposes, a recording material without fogging agent (comparison material) was initially used. produced by a gelatin silver bromide iodide direct positive emulsion on a conventional cellulose acetate support of the type known from US-PS 25 92 250 was applied. After applying and drying the emulsion layer the recording material obtained was exposed in an Eastman 1 B sensitometer. Thereupon the recording material became the following in a developing solution at 38 ° C. for 1 minute specified composition:

p-methylaminophenol sulfate 2 g

Sodium sulfite (dehydrated) 90 g
Hydroquinone 8 g

Sodium carbonate (monohydrate) 52.5 g
Potassium bromide 5 g

made up to 1 liter with water

The developed image was then stabilized by placing it in a fixing bath of 20 ^° C. of the following composition for 3 minutes:

Example 2

First, a silver halide emulsion, the latent images for the most part in the interior of the

"ι silver halide grains produced, of the type used for Preparation of the layer 1 described in Example 15 of US Pat. No. 3,227,552 was used. However, the l-formyl-2-phenylhydrazide used in Example 15 of US Pat. No. 27,552, the

in was used in a concentration of 7 mg per 0.0929 m ² , replaced by 0.14 mg of 3- (2-formylethyl) -2-methylbenzothiazolium bromide per 0.0929 m ^{2 of} substrate surface. The resulting red-sensitized photographic material was then used in

π exposed to an Eastman I B sensitometer, namely according to the method described in Example 15 of US Pat. No. 3,227,552. After the exposure it was the recording material is developed as follows:

A) 4 minutes of development at 37.8 ° C in a developer solution of the following composition:

Benzyl alcohol 12 ml

Sodium sulfite 1.5 g

2Ί potassium bromide 1.0 g
C) 2 minutes N-0-methylsulfone

amidoethylanaline 7.0 g

Potassium carbonate (anhydrous) 55.0 g

5-nitrobenzimidazole 5.0 ml

jo made up to 1000 ml with water

pH adjusted to 11.15 with sodium hydroxide.

B) Wash with water at 37.8 ° C for 15 seconds.
j-, C) 2 minutes bleach-fix at 37.8 ° C in a bleach-fix solution of the following composition to remove developed silver metal and remaining silver salts:

Sodium thiosulfate 240 g ■ to Potassium ferricyanide 35 g Sodium sulfite (dehydrated) 15g Sodium acetate 20 g Acetic acid (28%) 48 ml 1.8 dihydroxy-3,6-dithiooctane 25 g Boric acid, crystals 7.5 g Glacial acetic acid 3 ml Potassium aluminum sulfate 15g topped up with water 1 liter topped up with water 1 liter -I)

A second recording material (recording material No. 2) was made in a similar manner produced, exposed and developed, with the exception, however, that for the production of the recording material a silver halide emulsion containing 200 mg per mole of silver halide as a fogging agent was used 3- (2-Formylethyl) -2-methylbenzothiazolium bromide contained.

A direct positive image was obtained.

The results obtained are summarized in the following table:

Relative Relative Gamma «" "" value

pH adjusted to 5.0 with acetic acid.

D) Wash for 2 minutes with water at 37.8 ° C.

E) Stabilize for 2 minutes at 37.8 ° C in a stabilizer bath with the following composition:

Citric acid 20.0 g

Sodium tetraborate 14.0 g
Sodium hydroxide 0.22 g

Formaldehyde (37% aqueous
Solution) 1.0 ml

made up to 1 liter with water

Comparative material 1 1 0.05 Recording 5.5 2.5 1.00 material no. 2

From the results obtained, it can be seen that the sealing agent used is suitable for manufacture of direct positive emulsions.

After the development process and drying of the developed recording material, a positive blue-green dye image with a maximum density (Dunn) of 1.94 and a minimum density (Dmii) of 0.25 was obtained. The Bildqualitül differed favorably on the quality of such images under h ^r> using known previously dircktposiliver Aiifzeichnungsmuterialicn can be produced, although compared with the known Aufzeichnungsmalerialieii the concentration of strong Verschleierungsmiltel

had been diminished. Furthermore, the Development of the recording material a developer be used with reduced pH, d. Ii. a developer with a pH that is below pH of the developer applied when a hydrazine type mistressing agent was used had to be (see, for example, the pH of the developer in Example 15 of US Pat. No. 3,227,552 of 12.0).

Example 3

Six pairs of direct positive photographic materials were prepared, exposed and as in Recording Material No. 2 of Example I, with the exception, however, that each one wraps Recording material of a pair of recording materials was developed at a pH of 12.15, which thereby obtained wunJc, JaB sodium hydroxide for Developing solution was given. The remaining recording material of the recording pair was developed at a pH of 10.5.

The recording materials were produced using various fogging agents. The type of concealment agent used, the coating thickness and the sensitometric results obtained, such as maximum density (D _mai ), minimum density (D _n ,,,,) and contrast (γ) are summarized in the following table:

Pair Concealers Coating pH = 10.5 "mm ) ' pH = 12.15 A ™ ] ' strength 0.10 1.0 0.09 1.3 in mg / mol silver 0.18 1.4 0.20 2.7 halide Α ,,,, ν "ma *: 1 3- (2-formylethyl) -2-methyl- 450 0.55 0.08 4.0 1.22 0.07 2.9 bcnzothiazolium bromide 2 3- (2-acctylethyl) -2-benzyl 450 0.94 (1.08 2.0 3.27 0.10 1.8 benzothiazolium bromide 3 3- (2-formylethyl) -2-propyl- 1200 1.85 0.10 0.7 2.10 0.11 U benzothiazolium bromide 4th 5-chloro-3- (2-formylethyl) -2- 400 0.88 0.08 0.7 1.45 0.06 2.3 methylbenzothiazolium bromide 5 3- (2-formylethyl) -5-methoxy-2- 400 0.40 1.30 methylbenzothiazolium bromicl 6th 3- (2-Acctylethyl) -2-nronvl- 400 0.38 1.80

benzothiazolium bromide

From the sensitometric data compiled in the table Results show the advantageous effect of the fogging agents according to the invention.

Example 4

There were other direct positive photographic recording materials as described in Example 3, produced, exposed and developed, with the exception, however, that those in the following table listed fogging agents were used in concentrations of 425 mg per mole of silver halide became.

The results obtained are also summarized in the table below.

Compressants

Solvent for the
Disguising means

pH value of the

Developer

O _m

3- (2-Acelylethyl) -2-benzothiazolium bromide
3- (2-Acctylethyl) -2-benzylbenzozolium bromide
3- (2-Acctyliithyl) -2-benzylbenzoselcnazolium bromide
3- (2-Acetylethyl) -2-benzylbenzosclenazolium bromide

3- (Acclylethyl) -2-benzyl-5-phenyl-benzoxazolium bromide

3- (Aectyla'thyl) -2-bcnzyl-5-phenylbcnzoxa-

zolium bromide

3- (2-Acctylethyl) -2-plicnoxymethylbenzothiazolium-

brum id

3- (2-I ^> ropionylülliyl) -2-bcnzylbcnzothiazolium-

b ro mi ti

3- (2-Acclyliithyl) -2-ethy I benzothiazolium bromide

3- (2-Accly lathy l) -2-üthylbonzothinznl iu mbromiil

Acetonitrile 10.5 1.35 0.24 Methanol 12.1 3.28 0.21 Methanol 10.5 0.60 0.15 Methanol 12.1 2.71 0.18 Methanol 10.5 0.23 0.05 Methanol 12.1 2.42 0.09 Acetonitrile 12.1 0.85 0.13 Ethanol / 1% vinegar 12.1 2.33 0.35 acid solution (1: 1) Methanol 12.1 1.59 0.09 Acetonitrile 12.1 2.52 0.07

The results obtained show the advantageous effectiveness of the invention

Claims (1)

Patent claims: 1. Direct positive silver halide photographic emulsion predominantly containing latent images Part generated inside the silver halide grains and containing a fogging agent thereby characterized in that they contain 0.1 to 1.5 g per mole of silver halide as a fogging agent Compound of the following formulas contains: