DE2154075A1 - Direct positive silver halide photographic emulsion - Google Patents

Description

Direct positive silver halide photographic emulsion

The invention relates to a direct-positive photographic silver halide emulsion, which produces latent images for the most part inside the silver halide grains and forms a nucleation Contains compound (masking agent).

It is known that so-called direct-positive photographic silver halide emulsions are used to produce positive photographic emulsions Can use images directly, i.e. without making a photographic negative.

These direct positive photographic emulsions or inverse emulsions produce latent images on exposure for the most part in the interior of the silver halide grains. The production Direct-positive photographic images are caused by the fact that the unexposed areas of a direct-positive photographic emulsion layer are selectively fogged and that corresponding to the unexposed, fogged areas a normal silver photographic image is developed. The concealment agent can be used in a so-called "concealment bath" applied to treat the imagewise exposed silver halide emulsion layer prior to image development will. On the other hand, the fogging agent can also be used in the developer solution or in the Reverse emulsion can be incorporated before it is applied to a substrate.

The known nucleating compounds or fogging agents usually consist of hydrazine compounds. This is how it is, for example from US patent specification 2,563,785, in particular column 1, lines 18 to 34 and column 3, line 28 to column 5, Line 23, known, hydrazine compounds as nucleating compounds or to use fogging agents in surface-type silver halide developing solutions. Furthermore it is for example from U.S. Patent 2,588,982, particularly column

WHEEL

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1, lines 21 to 34 and column 4, line 1 to column 5, line 52 known hydrazine compounds as nucleating compounds or Fogging agents in silver halide developer solutions from Surface type or to use in the reverse emulsion itself.

The disadvantage of using the known hydrazine compounds as Nucleating agents are that they, especially when they are incorporated into the silver halide emulsion itself, to achieve a Adequate nucleation in relatively high concentrations must be, for example in concentrations of about 2 g per mole of silver, as is shown, for example, in U.S. Patent No. 2,588,982. When using such high concentrations it is difficult to obtain consistent sensitometric results because because larger amounts of the nucleating agent compounds get into the developing solution, where they discolour the photographic material in the non-image background districts.

Presumably, the necessity of using high concentrations of the known nucleating agent compounds is based on the fact that these compounds are not adsorbed or only weakly adsorbed by the silver halide grains. The migration of the nucleator compound in the developer solution is not only the high concentration, in which the compounds are present in the emulsion, promoted, rather rather also due to the high pH value required when using these compounds, which is usually above 12, as a rule at 12 to 13 and above and which is required to have a To achieve nucleation within an acceptable period of time.

The object of the invention is to provide a direct-positive photographic Silver halide emulsion that generates latent images predominantly in the interior of the silver halide grains and nucleates one

BATH ORIGINAL

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Compound contains, to indicate which such a nucleating compound or such a masking agent contains, which can be used in photographic direct-positive silver halide emulsions or reversal emulsions in low concentrations and discoloration when they are used the non-image background areas are avoided.

It has been found that quaternary heterocyclic salts with a heterocyclic ring with 5 to 6 ring atoms including the quaternary nitrogen atom in which the quaternary nitrogen

ti

where R is a hydrogen

-CH ₂ CH ₂ CR substituted alkyl-

atom by a remainder of the formula atom or one if applicable or aryl radical is substituted, excellently effective Represent nucleating compounds or obscurants. Characteristic of these quaternary heterocyclic salts is further that the heterocyclic ring has a core carbon atom adjacent to the quaternary nitrogen atom, the is substituted by an optionally substituted short-chain alkyl radical.

The invention thus provides a direct-positive photographic silver halide emulsion which produces latent images predominantly in the interior of the silver halide grains, and contains a nucleating compound (masking agent), which is characterized in that, as the nucleating compound, it is a quaternary heterocyclic salt represented by the following formula contains:

c

• CH,

Il

CH ₂ CH ₂ CR

BATH ORIGINAL

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where mean:

Z to complete a heterocyclic ring atoms required with 5 to 6 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, aryloxy or Ethylene residue;

η * 1 or if R represents an ethylene radical ■ 2 and

ο
X is an anion.

Advantageously, in the stated form, Z stands for that to complete an indole, azole or quinoline ring required atoms. Typical azole rings are, for example, imidazole, oxazole, thiazole and selenazole rings.

Typical rings that Z can stand for are, for example: Indolenine rings; Imidar oil rings, e.g. Benzimidazole rings, e.g. 5-chlorobenzimidazole rings or naphthimi-

dazole rings;

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

Benzothiazole rings, e.g. benzathiazole, 4-chlorobenzothiazole, 5-chlorobenzothiazole, 6-chlorobenzothiazole, 7-chlorobenzothiazole, 4-methylbenzothiazole, 5-methylbenzothiazole, 6-methylbenzothiazole, 5-bromobenzothiazole, 6-bromobenzothiazole , 4-phenylbenzo-

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thiazole, 5-phenylbenzothiazole, 4-methoxybenzothiazole, 5-methoxybenzothiazole, 6-methoxybenzothiazole, 5-iodobenzothiazole, 6-iodobenzothiazole, 4-ethoxybenzothiazole, 5-ethoxybenzothiazole, Tetrahydrobenzothiazole, 5,6-dimethoxybenzothiazole, 5-hydroxybenzothiazole, and 6-hydroxybenzothiazole rings;

Naphthothiazole rings e.g.

Thionaphtheno-7 ¹ 6 ·, 4,5-thiazole, for example, 4'-Methoxythi * naphtheno-7 ^f, 6 ', 4,5-thiazole;

Oxazole rings, e.g. 4-methyloxazole, 5-methyloxazole, 4-phenyloxazole, 4,5-diphenyloxazole, 4-ethyloxazole, 4,5-dimethyloxazole, and 5-phenyloxazole rings;

Benzoxazole rings, for example benzoxazole, 5-chlorobenzojcazole, 5-methylbehzoxazole, 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., α-naphthoxazole rings; Selenazole rings such as 4-methylselenazole or 4-phenylselenazole rings;

Benzoselenazole rings, e.g. benzoselenazole, 5-chlorobenzoselentzole, 5-methoxybenzoselenazole, 5-hydroxybenxoselenazole, or tetrahydrobenzoselenazole rings;

Naphthoselenazole rings, e.g., α-naphthoselenazole rings or Quinoline rings »-

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Z can furthermore represent other heterocyclic rings with 5 or There are 6 ring atoms which, in addition to the quaternary nitrogen atom, consist of carbon, nitrogen, oxygen, sulfur and selenium atoms can exist. This means that Z, for example, also for such heterocyclic! Can stand rings that contain a chromophoric nitrogen atom and 4 to 5 other atoms, of which 3 to 4 Atoms are carbon atoms and the remaining atoms are carbon, nitrogen, oxygen, sulfur or selenium atoms.

The short-chain alkyl radicals represented by R and R have preferably 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 represent alkyl radicals having 1 or 2 carbon atoms. If R and R are substituted alkyl radicals, then these, for example, consist of aralkyl radicals, e.g. benzyl, phenylethyl or phenoxymethyl radicals.

If R and R 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 has the meaning of an aryloxy radical, then this exists preferably from an aryloxy radical of the phenoxy or naphthoxy series with 6 to 10 carbon atoms. A preferred aryloxy radical is the phenoxy radical.

X can be, for example, a halide anion, e.g. a bromide, Chloride or iodide anion or, for example, a sulfate or hydrosulfate anion or a short-chain alkyl sulfate anion, for example a methyl sulfate or ethyl sulfate anion or an aromatic one Sulfonate anion, for example a toluenesulfonate or benzenesulfonate anion or an anion derived from a carboxylic acid, for example tin acetate, trifluoroacetate? or propionate anion

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or, for example, a perchlorate, cyanate, thiocyanate, sulfamate or benzoate anion.

These have proven to be particularly advantageous concealment agents proven whose anions consist of halide anions.

Particularly advantageous nucleating compounds or masking agents are, for example, those given below quaternary heterocyclic salts:

a) 3- (Z-Formyläthyl-Z-methylbenzothiazolium-,

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

c) 3- (2-Foniylithyl) -2-propylbenzothiazolium- _l

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

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

f) 3- (2-acetylethyl) -2-propylbenzothiazolium-, ⁱ

g) 3- (2-formylethyl) -2-methylnaphtho ^ ~ 2, S- ^ thiazolium-, h) 3- (2-acetylethyl) -2phenoxymethylbenzothiazolium-,

i) 2,2'-Ethylene bis ^ -3- (2-acetylethyl) benzothiazolium7-,

j) 2-benzyl-3- (2-propionylethyl) benzothiazolium,

k) 3- (2-acetylethyl) -2-ethylbenzothiazlium-,

1) 3- (2-acetylethyl) -2-benzylbenzoselenazolium-,

m) 3- (2-acetylethyl) -2-benzyl-5-phenylbenzoxazolium and

n) 3- (2-Benzoylethyl) -2-ethylbenzothiazolium salts.

The quaternaries used to prepare a direct positive silver halide photographic emulsion according to the invention Heterocyclic salts can be according to customary methods by reacting a cyclammonium hydro salt with a compound an active double bond system, e.g., an ethylenic double bond between the first and second carbon atoms of a aliphatic molecules or radicals.

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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 may also be carried out at temperatures of from about 2O ° C to about 30 ⁰ C in an advantageous manner, although higher and lower temperatures can be used, remain in solution as long as the reaction · W components and they are not heated to temperatures above their decomposition temperature will. The reaction products precipitate out of the solution and can be purified by washing with solvents or repeated recrystallization by customary known methods.

The preparation of a heterocyclic which can be used according to the invention Salt can be represented, for example, by the following reaction scheme:

¹ CR ³ Il

* 9 ^ T ^K + CHrZ = TCH-CR

¹ θ

ΗΧ ^Η

CH ₂ - 9 a-

C-O

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where R is a radical of the formula -CH ₂ -R ¹ and R ¹ and R, Z and X have the meanings given.

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

f CH 3 N '
I. > ■ β CH -C —Η -CH ₂ -

Br ⁹

can be made, for example, as follows:

100 g of 2-methylbenzothiazolium hydrobromide and 48.7 g of acrolein were mixed with one another with stirring at room temperature in 150 ml of dimethylacetamide for 24 hours. A pale yellow crystalline precipitate separated out and was filtered off, washed thoroughly with acetonitrile and dried. The yield was 100 g, corresponding to 31.3% of theory. The melting point of the compound was 233 to 236 ^° C.

The direct positive photographic silver halide emulsions of the present invention incidentally have those known for direct-positive photographic silver halide emulsions or reversal emulsions Composition, i.e. they can consist, for example, of the usual gelatin-silver halide emulsions, their silver halide consists for example of silver bromide, silver bromide iodide or silver chloride bromide. The use of sensitizing dyes is not required, although it may be advantageous to use the emulsions to increase their spectral sensitivity

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to add such dyes. Sensitizing dyes that can be used advantageously for the spectral sensitization of the emulsions "are known, for example, from US Pat. No. 2,497,876, in particular column 2, line 15 to column 4, line 20. The direct positives according to the invention photographic silver halide emulsions can consist of undigested or digested silver halide emulsions, wherein the digestion occurs without the addition of a chemical surface sensitizer.

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An emulsion of this type is known, for example, as "Burton's" emulsion (see, for example, the book by Wall »7Verlag: The American Photo Publishers, Boston, USA, pages 52 and 53). Another type of reverse emulsion that is latent Most of the images are inside the silver halide grains producing emulsion is known, for example, from US Pat. No. 2,592,250.

Direct-positive photographic silver halide emulsions, which produce latent images for the most part in the interior of the silver halide grains, i.e. so-called inner grain emulsions, can thereby be used produce that first in one or more process stages Silver salt grains are generated which at least partially consist of a silver salt that is more soluble in water than silver bromide. At least some of the grains are then converted into silver bromide or silver bromide iodide, which is followed by ripening, preferably followed in the absence of ammonia, whereupon part of the total amount of soluble salts present which was used for the preparation of the emulsion, usually sodium nitrate and / or Potassium nitrate and sodium chloride and / or potassium chloride is washed out. This is followed by the preparation of the final emulsion the addition of soluble salts, e.g. a soluble chloride, bromide or iodide. In this way, a "built up" silver chlorobromide, bromide iodide, or chlorobromide iodide reverse emulsion is formed obtain.

Advantageous silver chlorobromide inner grain emulsions or inner core emulsions can also be used in an advantageous manner produce by adding an aqueous silver nitrate solution and an aqueous solution at the same time to an aqueous gelatin solution in motion of potassium chloride and potassium bromide can be added, as is known, for example, from Example 4 of US Pat. No. 2,996,382 is.

7 "Photographic Emulsions"

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A photographic silver halide emulsion which produces latent images predominantly in the interior of the silver halide grains, i.e. a so-called internal latent image emulsion (internal latent image emulsions) is such an emulsion that typically behaves as follows:

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10 G 100 G 1 liter

If a test portion of the emulsion is exposed for a certain time up to about 1 second through a light intensity scale and developed for 4 minutes at 2O ⁰ C in a conventional surface developer, ie a developer that develops an image only on the surface of the grains of an internal image emulsion and the for example has the following composition:

p-hydroxyphenylglycine
Sodium carbonate (crystals) made up with water

so a maximum density is obtained, which is not greater than ■ ix 1/5 of the maximum density obtained when the same emulsion exposed in the same way and 3 minutes is developed at 2O ⁰ C in a so-called. interior grain developer long, which sucked in a picture inside the grains. Developed inner grain emulsion, the developer may, for example, have the following composition.

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

made up to 1 liter with water.

It is preferable that the maximum density obtained by development with the surface type developer should not be greater than 1/10 of the maximum density obtained when the same emulsion is developed in the internal grain developer. Expressed the other way around an internal grain emulsion, when developed in an internal grain developer, leads to a maximum density, the minimum 5 times, preferably at least 10 times the maximum

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Density corresponds to that obtained when the emulsion in the same Way exposed and in a surface type developer is being developed.

The compounds or obscurants which form nuclei according to the invention (Nucleating agents or fogging agents) used quaternary heterocyclic salts are particularly suitable as Fogging agents or nucleating compounds for silver halide reversal emulsions of the type known, for example, from U.S. Patents 2,566,180 and 2,592,250. The quaternary Heterocyclic salts are used in such amounts that are necessary to achieve sufficient concealment in To generate the form of tiny surface development centers, which favor the generation of direct-positive / ß by development or support financially. The quaternary heterocyclic salts used according to the invention are apparently more solid on the surfaces of the Silver halide grains adsorb than the hitherto known fogging agents, particularly the known hydrazine compounds which are known from US Pat. No. 2,588,982, since when using the quaternary used according to the invention heterocyclic salts lower concentrations of the same are required. By having lower concentrations of fogging agents sufficient to produce the desired concealment, constantly advantageous sensitometric results can be achieved in particular because less fogging agent gets into the developer solutions.

For the preparation of direct-positive photographic silver halide emulsions According to the invention, concentrations of about 100 to about 1500 mg per mole of silver of the silver halide emulsion have been found Proven to be useful. The use of about 200 to about 1400 mg of masking agent has proven to be particularly advantageous per mole of silver. These concentrations are for common direct positive photographic silver halide emulsions

/" Pictures

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typical"

The direct positive photographic silver halide emulsions of the present invention can further include those for direct positive photographic emulsions photographic silver halide emulsions contain typical additives, e.g. spectral sensitizing dyes, coating aids, optical brighteners, hardeners, developer compounds and the like. To build up the emulsions, the customary known binders, in particular the known hydrophilic, water-permeable binders are used, for example gelatin, colloidal albumin, polyvinyl compounds, cellulose derivatives, acrylamide polymers and the like., and either alone or in combination with one another. If appropriate, the binders can be used to prepare the emulsions 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. Too dreary Polymers include, for example, the water-insoluble polymers and latex copolymers of alkyl acrylates and alkyl methacrylates, acrylic acid, sulfoalkyl acrylates, or sulfoalkyl methacrylates.

For the spectral sensitization of the direct-positive photographic silver halide emulsion according to the invention, for example, those described in U.S. Patents 2,526,632 and 2,503,776 known spectral sensitizing dyes can be used. The dyes which can be used for spectral sensitization can for example of cyanine, merocyanine, complex trinuclear cyanine, complex trinuclear merocyanine, styryl and hemicyanine dyes.

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The direct positive photographic silver halide emulsions of the present invention can also use the customary known non-ionogenic, anionic and / or amphoteric coating auxiliaries contain, for example saponin, aryloxyalkylene ethylsulfonates substituted by alkyl radicals, for example that from the USA patent 2,600,831 known type, maleopimarates, e.g. of the type known from US Pat. No. 2,823,123, furthermore taurine derivatives, for example of the type known from U.S. Patent 2,739,891 and alkylaminopropionates such as that disclosed in U.S. Patent Specification 3,133,816 known type. Other known ones that can be used advantageously Coating auxiliaries and surface-active Verbin-P fertilize for the production of the photographic invention Silver halide emulsions that can be used are, for example, alkylphenoxypoly (hydroxyalkylene oxides), e.g., alkylphenoxypoly (glycidols) with from about 5 to about 12 glycidol units, for example those as described in British Patent 1,022,878 are known.

For the preparation of the direct positive photographic silver halide emulsions Optical brighteners which are advantageously suitable according to the invention are, for example, those having at least a heterocyclic 5- or 6-membered ring, for example Derivatives of stilbene, stilbene triazofe, triazine stilbene, coumarin,. Triazinylaminocoumarins, Oxazoles, Benzidens, Benzimidazoles, Benzo- ™ thiazole, benzoxazole, pyrazoline or naphthalenimide. Typical for making a direct positive silver halide photographic emulsion Optical brighteners which can be used according to the invention are, for example, from US Pat. Nos. 2,933,390 and 3 406 070 known.

The direct positive photographic silver halide emulsions of the present invention can be hardened with the usual known hardeners or combinations of hardeners, e.g. with aldehyde hardeners

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agents, for example formaldehyde, glutaraldehyde and maleic acid dialdehyde, also mucochloric acid, with aziridine hardeners, hardeners consisting of derivatives of dioxane, vinyl sulfones, Oxypolysaccharides, e.g. oxy starch, oxidized vegetable gums, as well as inorganic hardening agents e.g. chromium salts and the like

For the production of direct-positive photographic recording materials, which can be developed by the reverse process can be the silver halide photographic emulsions of the present invention on conventionally known supports, such as those used for the production of direct-positive photographic recording materials are known to be applied. Typical such layer supports consist, for example, of films made of cellulose esters, for example Cellulose acetate, cellulose triacetate, cellulose acetate butyrate and the like., Poly-α-olefins, e.g. polyethylene and polypropylene, polycarbonates, polyesters, e.g. polyethylene terephthalate, as well as metal substrates, e.g. Zinc and aluminum or paper, which may optionally have a layer of a poly-α-olefin, e.g. a polyethylene or Polypropylene coating.

The direct positive photographic silver halide emulsions of the present invention can consist of reversal color photographic emulsions as well as black-and-white silver halide emulsions. The direct-positive color reversal silver halide emulsions according to the invention are particularly suitable for preparation such color reversal recording materials made using of cyan, magenta and yellow dye-producing color couplers, which are those listed Color couplers in contact with various silver halide emulsion layers that record light of a color that is practically complementary to the color of the generated with the help of the color coupler

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Dye is. Color photographic recording materials of this type are, for example, from the USA patents 3,227,550 and 3,227,552 are known. To sensitize the silver halide Spectral sensitizing dyes can be used in the usual way. In the case of a usual multilayer color photographic recording material can, for example, the red-recording emulsion layer a color coupler, such as 5- (p-amylphenoxybenzenesulfonamido) -1-naphthol contain the green recording layer a coupler, such as, for example, 2-cyanoacetyl-5- (p-sec.-amylbenzoylamino) -coumarone and the blue-recording emulsion layer has a coupling

ler w, such as N-amyl-p-benzoylacetaminobenzolsulfonat.

Optionally, color couplers can also be added to the developer solution, as is known, for example, from US Patents 2,252,718 and 2,507,154. In this case, multiple exposures and color development stages are required. After imagewise exposure, the photographic recording materials with direct-positive photographic silver halide emulsion layers according to the invention can be developed in a conventional manner with the aid of a conventional surface developing solution having a relatively low solvent action on the silver halide, positive photographic images being produced. The surface developers used for developing the recording materials can advantageously contain image-intensifying compounds which increase the maximum image density and lead to a reduction in D _min . Such compounds can consist, for example, of benzotriazoles such as are known, for example, from US Pat. No. 2,497,917.

In the case of color photographic recording materials can common developer solutions with p-phenylenediamine color developing agents are used, for example 4-amino-N-dialkylanilines, as it is, for example, from the book by Mees, "The Theory of the Photographic Process "3rd Edition (1966), pages 294 bis

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295 is known. Using a color developer compound, you can one or more dye images can be produced, depending on the structure of the particular color photographic recording material. In the case of polychromatic color recording materials, blue-green, magenta and yellow dye images are usually formed in the red-sensitive, green-sensitive and blue-sensitive layers, respectively generated. The remaining silver is first converted into a soluble silver salt and then processed in the usual way Treatment with a fixative such as sodium thiosulphate removed.

The following examples are intended to illustrate the invention in more detail. example 1

For comparison purposes, a recording material / (Comparative material) produced by placing a gelatin silver bromide iodide reversal emulsion on a conventional cellulose acetate layer support of the type known from U.S. Patent 2,592,250. After applying and drying the The recording material obtained became emulsion in a sensitometer of the Eastman 1B type exposed. The recording material was then immersed in a developer solution at 38 ° C. for about 1 minute with the following composition:

p-methylaminophenol sulfate 2 g

Sodium sulfite (dehydrated) 90 g

Hydroquinone 8 g

Sodium carbonate (monohydrate) 52.5g

Potassium bromide 5 g made up to one liter with water.

The developed ifXi & iXAWt image was then stabilized in that it reasonable for 3 minutes in a fixing solution of 20 ⁰ C in the following

/ without masking agents or nucleating agents

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given composition was brought:

Sodium thiosulfate 240 g

Sodium sulfite (dehydrated) 15 g

Acetic acid (281) 48 ml boric acid, crystals 7.5 g

Potassium aluminum sulphate 15 g made up to 1 liter with water

A second recording material (recording material no. 2) was produced, exposed and developed in a corresponding manner, with the exception, however, that for the preparation of the recording material a silver halide emulsion was used which per mole Silver as a fogging agent 200 mg of 3- (2-formylethyl) -2-methylbenzothiazolium bromide contained.

A reverse image was obtained.

The results obtained are summarized in the following table:

Relative Relative

^D _{m £} , v " ^value Ci" value gamma

Iu ti Λ.

Comparative material 1 1 0.05

Recording mate- _K r <? r ι nn

rial Mi · 7 ^ »^ *» ·> I, UU

rial No. 2

From the results obtained, the quaternary salt used was found to be an effective fogging agent or effective Nucleating compound can be used to make reverse emulsions.

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--re - 2154Q75

ti

Example 2

First, an inside picture silver halide emulsion of the type used to make Layer 1 described in Example 15 of U.S. Patent 3,227,552 was prepared. However, the i-formyl-2-phenylhydrazide used in Example 15 of US Pat. No. 3,227,552, which was used in a concentration of 7 mg per 0.0929 m, was replaced by 0.14 mg of 3- (2-formylethyl) -2-methylbenzothiazolium bromide replaced ^{per 0.0929 m 2 of substrate surface.} The resulting red-sensitized photographic recording material was then exposed in an Eastman 1B sensitometer using the method described in Example 15 of US Pat. No. 3,227,552. After exposure, the recording material was developed as follows:

A) 4 minutes development at. 37.8 ⁰ C in a developer solution of the following composition:

Benzyl alcohol 12 ml

Sodium sulfite 1.5 g

Potassium bromide 1.0 g

4-Amino-N-ethyl-3-methyl-N-ß-methylsulfonamidoethyl-7.0 g aniline

Potassium carbonate (anhydrous) 55.0 g 5-nitrobenzimidazole 5.0 ml

Made up to 1000 ml with water, pH adjusted to 11.15 with sodium hydroxide.

B) from 15 seconds Water Wash 37.8 ⁰ C.

C) 2 minute bleach-fixing at 37.8 ⁰ C in a bleach-fixing solution of the composition indicated below to remove

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of developed silver metal and remaining silver salts:

Potassium ferricyanide 35 g

Sodium acetate 20 g

1.8 dihydroxy-3,6-

dithiooctane 25 g

Glacial acetic acid 3 ml

made up to 1 liter with water

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 of 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

After the development process and drying of the developed recording material, a positive cyan dye image was obtained with a maximum image density (D) of 1.94 and a minimum image density (Dj _n ^ _n ) of 0.25. The image quality differed advantageously from the quality of those images which can be produced using previously known direct-positive recording materials, although the concentration of fogging agent has been greatly reduced compared with the known recording materials. Furthermore, a developer with a reduced pH value could be used to develop the recording material, ie a developer with a pH value which is below the pH value of the developer, which when using a developer

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hydrazine type fogging agent must be used (See, for example, the pH of the developer in Example 15 of U.S. Patent 3,227,552 of 12.0).

Example 5

There were six pairs of direct positive photographic materials produced, exposed and developed like recording material no. 2 of Example 1, with the exception, however, that in each case one recording material of a pair of recording materials was developed at a pH of 12.15, the obtained by adding sodium hydroxide to the developing solution. The remaining recording material of the recording pairs was developed at a pH of 10.5.

The recording materials are produced using various fogging agents. The type of fogging agent used, the coating thickness and the sensitometric results obtained, such as maximum _{image density (D mav} ) »minimum image density (D ._) and image contrast (γ) are summarized in the following table:

Couple quaternary salt coating pH »10.5

strength in mg / _D i

ρΗ «12.15

g _DD

Mole of silver max min 'max min ¹

1 3- (2-formylethyl) -2-methylbenzothiazo-450 lium bromide

2 3- (2-AceAethyl) -2-benzylbenzothiazo-450 lium bromide

3 3- (2-formylethyl) -2-propylbenzothia-1200 zolium bromide

0.55 0.10 1.0 1.22 0.09 1.3 0.94 0.18 1.4 3.27 0.20 2.7 1.85 0.08 4.0 2.10 0, 07 2.9

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3 *

5-chloro-3- (2-formylethyl) -2- _4QQ methylbenzothiazolium bromide

3- (2-Formylethyl) -5-methoxy-2-methyl-400 benzothiazole bomide

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

0.88 0.08 2.0 1.45 0.10 1.8 0.40 0.10 0.7 1.30 0.11 1.1 0.38 0.08 0.7 1.80 0. 06 2.3

From the sensitometric results compiled in the table gives the nucleating activity of the quaternary heterocyclic salts used according to the invention.

gaxkäeaxxiäÄKxiaxxixueaigäeffiri ^

edxiecxkid3dx ^ iec] Q! U6 <} edxiecKxHsd (Qac9d ^

Example 4

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

The results obtained are also summarized in the table below.

2 0 9820/0933

Germinating compound

Solvent with which the nucleating compound was added to the emulsion pH of the
Developer

^D max ^D min

3- (2-acetylethyl) -2-benzothiazolium bromide

Acetonitrile

3- (2-acetylethyl) -2-benzylbenzozolium bromide methanol

3- (2-acetylethyl) -2-benzylbenzoselenazolium bromide methanol

3- (2-acetylethyl) -2-benzylbenzoselenazolium bromide methanol

3- (acetylethyl) -2-benzyl-5-phenyl-benzoxazolium bromide methanol

3- (acetylethyl> 2-benzyl-5-phenylbenzoxazolium bromide methanol

3- (2-acetylethyl) -2-phenoxymethylbenzothiazolium bromide

Acetonitrile

3- (2-propionyl-

benzothiazolium _{acid solution (1; 1)}

3- (2-acetylethyl) -2-ethylbenzo thiazolium bromide Methanol 10.5

12.1

10.5

12.1

10.5

12.1

12.1

12.1

12.1

1, 35

3.28

0.60

2.71

0.23

2.42

0.85

2.33

0.24

0.21

0.15

0.18

0.05

0.09

0.13

0.35

1.59 0.09

209820/0933

-U-

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

Acetonitrile

12.1

2.52

0.07

The advantageous effectiveness results from the results obtained of the nucleating compounds used according to the invention.

- 25 -

20 9 8 20/0933

Claims (8)

215-075 PATENT CLAIMS Ciy direct positive photographic silver halide emulsion, the latent images for the most part in the interior of the silver halide grains and contains a nucleating compound (concealment agent), characterized in that that it contains a quaternary heterocyclic salt of the following formula as the nucleating compound: CH ₂ CH ₂ CR C - CH ₂ -f] ti where mean: the atoms required to complete a heterocyclic ring having 5 to 6 ring atoms; a hydrogen atom or an optionally substituted one short-chain alkyl or aryl radical; a hydrogen atom or an optionally substituted short-chain alkyl, aryl, aryloxy or Ethylene residue; = 1 or if R represents an ethylene radical = 2 and an anion. 209820/0933 ψ- .215 * 075 ft 2. Direct positive photographic silver halide emulsion after Claim 1, characterized in that it is a quaternary contains heterocyclic salt of the formula given in which X is a halide anion. 3. Direct positive photographic silver halide emulsion after Claims 1 and 2, characterized in that it contains a quaternary heterocyclic salt of the formula given} in which: ^p R is an alkyl radical having 1 to 2 carbon atoms or an optionally substituted phenyl radical and R ^{1 is} an alkyl radical having 1 to 2 carbon atoms or an optionally substituted phenyl radical or an optionally substituted phenoxy radical * 4. Direct positive photographic silver halide emulsion Claims 1 to 3, characterized in that it is a contains quaternary heterocyclic salt of the formula given, in which Z contains the necessary to complete a tndole, Azole or quinoline ring represents the required atoms. 5. Direct-positive silver halide photographic emulsion Claims 1 to 4, characterized in that it contains 100 mg to 1400 mg of the quaternary heterocyclic salt per mole of silver halide. 6. Direct-positive photographic silver halide emulsion according to Claims 1 to 5, characterized in that it contains a color coupler. 7. Direct positive photographic silver halide emulsion after Claims 1 to 6, characterized in that it consists of one BATH ORIGINAL 209820/0933 Gelatin silver bromide iodide emulsion. 8. Direct-positive photographic silver halide emulsion according to claims 1 to 7, characterized in that it is as quaternary heterocyclic salt contains: 5-chloro-3- (2-ormylethyl) -2-methylbenzothiazoliurabromide; 3- (2-formylethyl) -5-methoxy-2-methylbenzothiazolium bromide; 3- (2-acetylethyl) -2-propylbenzothiazolium bromide; 3- (2-formylethyl) -2-methyl ~ naphtho / ~ 2,3-d7thiazolium bromide; 3- (2-acetylethyl) -2-phenoxymethylbenzothiazolium bromide; 2,2-ethylene-bis / 3- (2-acetylethyl) benzothiazolium bromide7; 2-benzyl-3- (2-propionylethyl) benzothiazolium bromide; 3- (2-acetylethyl) -2-ethylbenzothiazolium bromide; 3- (2-acetylethyl) -2-benzylbenzoselenazolium bromide; 3- (2-Acetylethyl) -2-benzyl-5-phenyl-benzoxazolium bromide or 3- (2-benzoylethyl) -2-ethylbenzothiazolium bromide, 3- (2-methylethyl) -2-methylbenzothiazolium bromide; 3- (2-acetylethyl) -2-benzylbenzothiazolium bromide; 3- (2-Forraylethyl) -2-propylbenzothiazolium bromide. 209920/0933