DE1769383B - Direct positive fogged silver halide photographic emulsion - Google Patents

Description

20th

contains, in which means

m = 1 or 2,

/ i = 1 or 2,

L a something group,
R _{1 is} an alkyl, alkenyl or aryl group,

Z to complete a desensitizing acting nitrobenzoxazole, nitrobenzothiazole, nitrobenzoselenazole, imidazo [4.5 - b] quinoxaline-. 3,3 - dialkyl - 3 H - pyrrolo [2,3 - b] pyridine, 3,3 - dialkyl - 3 H - nitroindole, Thiazolo [4,5-b] quinoxaline or nitroquinol rings required atoms and

Q to complete a fused heterocyclic ring with 5 or 6 ring atoms required atoms.

2. Direct positive fogged silver halide photographic emulsion according to claim 1 characterized characterized in that it contains a merocyanine dye of the formula indicated in which n, L and R, have the meaning given, and Q is used to complete a condensed Thiazole, oxazole, selenazole, thiazoline, pyridine, quinoline, 3,3-dialkylindolenine, imidazole or oxazole ring represents required atoms.

3. Direct positive fogged silver halide photographic emulsion according to claim 1 characterized characterized in that it contains as merocyanine dye:

50

55

60

⁶ 5

QyCJ oxalinyliden) ethylidene] -2H-pyrimido- [2.1 -b] benzothiazole-2,4- (3 H) -dione;

3 - [(1,3-Diethyl-2- (l H) -imidazo [4,5-b] quinoxalinylidene) ethylidene] -2H-pyrimido [ 1,2-a] benzimidazole-2,4- (3 H) -dione;

3 - [(1,3-Diethyl-2- (1 H) -imidazo [4,5-b] quinoxalinylidene) ethyIides] -2H-pyrido- [1,2-a] pyrimidine-2,4- (3 H) -dione;

3 - [(6-Chloro-1,3-diphenyl-2- (1H) -imidazo [4,5-b] quinoxalinylidene) ethylidene] ~

2 H-pyrido [1,2-a] pyrimidine-2,4- (3 H) -dione; 3 - [(3-EthyI-6-nitro-2-benzothiazolinylidene) ethylidene] -2H-pyrido [1,2-a] pyrimidine-

2,4- (3H) -dione;
3 - [(6,7-dichloro-1,3-diphenyl-2- (1H) -imide-

azo [4,5-b] quinoxalinylidene) ethylidene] -2H-pyrido [1,2-a] pyrimidine-2,4- (3H) -dione

or
3 - [(3-Methyl-6-nitro-2-benzoselenazolinylidene) ethylidene] -2H-pyrido [1,2-a] pyrimidine-2,4- (3 H) -dione.

Il

C-N

C-N

Ii - ■■

C-.

4. Direct positive fogged photographic silver halide emulsion according to claims 1 to 3, characterized in that at least 95 percent by weight of the veiled silver halide grains have a diameter that is not greater than flour than 40% of the mined K.onidurchmes:> er deviates.

The invention relates to a direct positive photographic silver halide emulsion made with the aid of of a reducing and gold haze is veiled and one that acts as an electron acceptor Connection contains.

It is known e.g. From British Patent 723 019 for the production of direct positive images Recording materials having a photosensitive layer of a direct positive photographic Silver halide emulsion containing a desensitizing agent acting as an electron acceptor and their silver halide grains by treatment with a reducing compound and a compound of a metal that is more electropositive than silver, namely a gold compound, have been veiled. Advantageous in the known direct positive photographic silver halide emulsions is that the areas of high lights of the images obtained therewith are practically free of veils are. A disadvantage of the known direct positive silver halide emulsions, however, is that they are a Have insufficient sensitivity for many photographic applications, in particular to radiation from the green to red areas of the spectrum.

It is also known e.g. B. from German patent specification 1008 Π8, for panchromatic sensitization direct positive silver halide emulsions containing color couplers, certain cyanine dyes to use. For orthochromatic sensitization of direct positive emulsions without The dyes known in German Patent No. 1,008,118 practically do not contain any color couplers usable, as can be seen, for example, from column 1, lines 31 to 34, of the German patent specification 1 153 246 results, from which dimethine cyanine dyes also contain certain indole nuclei for the orthochromatic sensitization of direct positive photographic silver halide emulsions are known that the direct production of positive images according to the so-called solarization effect allow.

There are also known direct positive photographic silver halide emulsions containing on merocyanine dyes of the most varied of types, although they are used as spectral sensitizers, not however, act as electron acceptors. Direct positive silver halide emulsions are of this type not with the help of reducing agents and gold haze obscured, and direct positive images are produced in a variety of ways.

So z. B. a negative emulsion according to the method known from US Pat. No. 2,497,876 of the inner grain type exposed imagewise and then developed in an air fogging developer, wherein the emulsion incorporates sensitizing merocyanine dyes of certain types to increase their sensitivity to air fogging by the developer. In this known method, the image is reversed due to an internal grain image desensitization effect through the first exposure to the cores that can be developed above the surface, which are caused by the veiling Surface developers are generated. The added dyes cause an increase the maximum density or a lowering of the minimum density (please refer to Mees. "The Theory of the Photographic Process". 3rd Edition. P. 161).

"In the method known from US Pat. No. 2,828,203, a direct positive image is obtained produced according to the so-called Clayden effect. A merocyanine dye is used to carry out this process containing negative silver halide emulsion initially briefly imagewise a light source exposed to high intensity, whereupon uniformly for a long time with a light source of low intensity exposed and then developed in a surface developer. The short-term Initial exposure produces an internal grain latent image which desensitizes the silver halide grains to form of a surface latent image in the second exposure. The existing dyes effect also in this case either an increase in the maximum density or a decrease in the minimum Density.

The German Auslegeschrift 1 190 331 specifies the use of merocyanine dyes Type in direct positive, coarse-grained silver halide emulsions of the solarization type known to Purposes of reducing the contrast of the images obtained. These well-known silver halide modules

Sions are pre-obfuscated by exposure or, with the help of chemical reducing agents, their obfuscation however, it does not take place with the help of reducing agents and gold haze.

These from US Patents 2,497,876 and 2,828,203 and the German Auslegeschrift 1,190,331 known silver halide emulsions incorporated merocyanine dyes are for image reversal in direct positive silver halide emulsions obscured with the aid of reducing agents and gold haze not capable due to the lack of an electron accepting effect, and its addition to such Emulsions would become completely blackened images upon imagewise exposure and development to lead.

It is the object of the invention. direct positive veiled silver halide emulsions of the British patent 723 019 known type, the silver halide grains with the help of reducing and gold veils are veiled to improve their sensitivity, in particular compared to radiation in the green to red region of the spectrum, is increased.

The invention is based on the knowledge that certain merocyanine dyes, consisting of two 5- or 6-link. heterocyclic rings containing at least 1 nitrogen atom, which are connected to each other connected via a double bond or a dimethine bridge, one of which is a desensitizing agent acting ring, which via one of its carbon atoms to the dimethine bridge or to the double bond is bound. both excellent electron acceptors and spectral sensitizers for direct positive fogged photographic silver halide emulsions of the specified type, when the other ring is a complex fused pyrimidonedione ring. the one about his 3-carbon atom is bound to the dimethine bridge or to the double bond and to its 1- and 6-atoms another heterocyclic ring or further heterocyclic rings are fused on.

The object of the invention is based on a direct positive photographic. Silver halide emulsion, which is veiled with the help of a reducing agent and a gold haze and one as an electron acceptor containing active compound, and is characterized in that it acts as both an electron acceptor as well as a spectral sensitizer acting merocyanine dye of the following structural formula :

R ₁ -Nl-CH = CH) ^ ₁ -Cf = LL) ^ f = C O
CN

C-N

Il ■ · ο

contains, where means:
m - 1 or 2,
»Ι = 1 or 2,
L a something group,
R _{1 is} an alkyl, alkenyl or aryl group,
Z the completion of a desensitizing nitrobenzoxazole, nitrobenzothiazole, nitrobenzoselenazole. Imidazo [4.5-b] quinoxaline, 3.3 - dialkyl - 3 H - pyrrolo [2.3 - b] pyridine-. 3,3 - dialkyl - 3 H - nitroindole-. Thiazolor4,5 - b] quinoxaline or nitroquinine rings required atoms and

Q to complete a fused-on heterocyclic ring with 5 or 6 ring atoms required atoms.

The invention achieves excellent image reversal as well as the Sensitivity of direct positive fogged silver halide emulsions of the specified type, in particular with respect to radiation of the green to red regions of the spectrum, is increased. Furthermore, achieves that the additional use of a spectral sensitizer in addition to an electron acceptor of the type known from British patent specification 723 019 is unnecessary, since the invention Usable merocyanine dyes not only spectrally sensitizing, but at the same time also as Electron acceptors work.

In the structural formula given, L can be, for example have the meaning of one of the following form- ij my:

-CH = -CfCH.,) = And -CfC ₆ H ₅ ) =

R ₁ can be a simple or substituted alkyl group, preferably a short-chain alkyl group having 1 to 4 carbon atoms, for example a methyl group. Ethyl, propyk isopropyl, butyl. Hexyl-. Cyclohexyl, decyl or dodecyl group. or in the case of a substituted alkyl group. which is also preferably short chain, a hydroxyalkyl group, e.g. B. a, / - Hydroxyäthyl-, or n-Hydroxybutylgruppe or an alkoxyalkyl group. z. B. a, / - methoxyethyl or ez-butoxybutyl group. or a carboxyalkyl group. z. B. a / »'- carboxyethyl or o-carboxybutyl group. or a sulfoalkyl group. z. B. a, i'-sulfoethyl or «i-sulfobutyl group. or a sulfatoalkyl group. z. B. a // - SuI-fatoäthyl- or o-sulfatobutyl group. or an acyloxyalkyl group. z. B. a / i'-Acetoxyäthyl-,; -Acetoxypropyl- or fi-Butyryloxybutylgruppe. or an alkoxycarbonylalkyl group, e.g. B. a // '- Methoxycarbonyläthyl- or o-Äthoxycarbonylbutylgruppe. or an aralkyl group. z. B. a benzyl or phenyl group. If R _{1 has} the meaning of an alkenyl group, this can for example consist of an allyl group. 1-propenyl or 2-butenyl group. If R _{1 has} the meaning of an aryl group, this can for example consist of a phenyl group. ToIyI-. Naphthyl, methoxyphenyl or chlorophenyl group.

Z can, for example, be used to complete one of the following desensitizing rings The required atoms are present, the desensitizing effect obviously being accompanied by an electron accepting effect is coupled (see, for example, Mcc s. "The Theory of the Photographic Process". 3rd Edition. P. 259):

a 5-nitrobenzothiazole-. 6-nitrobenzolhiazole-. or S-chloro-o-nitrobenzothiazole ring:

of a 5-nitrobenzoxazole, 6-nitrobenzoxazole or 5-chloro-6-nitrobenzoxazole ring:

a 5-nitrobenzoselenazole, 6-nitrobenzoselenazole or S-chloro-o-nitrobenzoselenazole ring; ^ _{0 of} a 1,3-dialkylimidazo [4,5-b] quinoxaline ring. ζ. B. a 1,3-diethylimidazo [4,5-b] quinoxaline or 6-chloro-1,3-diethylimidazo [4,5-b] quinoxaline ring. or a 1,3-dialkenylimidazo [4.5-b] quinoxaline ring. z. B. a ', 3-diallylimidazo & 5 [4,5-b] quinoxaline or o-chloro-1,4-diallylimidazo [4,5-b] quinoxaline ring. or a 1,3-diarylimidazo [4,5-b] quinoxaline ring, e.g. B. a 1,3-diphenylimidazo [4,5-b] quinoxaline or a 6 - chloro -1,3 - diphenylimidazo [4,5 - b] quinoxaline ring;

a 3,3-dimethyl-3 H-pyrrolo [2,3-b] pyridine or a 3,3-diethyl-3 H-pynOlo [2,3-b] pyridine ring;

one 3,3 - dimethyl - 5 - nitro - 3 H - indole, one 3,3-diethyl-5-nitro-3 H-indole- or a 3,3-dimethyl-6-nitro-3 H-indole rings or

a 5-nitroquinoline or a 6-nitroquinoline ring.

Further desensitizing rings, which are indicated in the Structural formula that can be completed by Z are, for example, substituted nitrobenzoxazole, Nitrobenzselenazole or nitrobenzthiazole rings. such as B. nitronaphthothiazole, nitronaphthxazole, or nitronaphthoselenazole rings.

Rings that have a desensitizing effect are those that are symmetrical after conversion Carbocyanine dye and addition of the carbocyanine dye to a gelatin-silver chlorobromide emulsion with 40 mole percent chloride and 60 mole percent Bromide at a concentration of 0.01 to 0.2 g of dye per mole of silver by trapping of electrons lead to a loss of at least about 80% in the emulsion's blue sensitivity, when this is exposed sensitometrically and for 3 minutes at room temperature in a developer A the following composition is developed:

Developer A

N-methyl-p-aminophenylene sulfate .... 2.0 g

Sodium sulfite (anhydrous) 90.0 g

Hydroquinone 8.0 g

Sodium carbonate (monohydrate) .... 52.5 g

Potassium bromide 5.0 g

Made up to 1.0 1 with water

Particularly advantageous, such desensitizing rings are those that are after transfer or conversion to a symmetrical carbocyanine dye and testing in that described Way to an almost or almost complete desensitization of the test emulsion to blue Lead light, d. H. a greater than about 90 to 95% loss in sensitivity to blue radiation bring about.

The heterocyclic ring with 5 or 6 ring atoms formed by Q can contain, in addition to the nitrogen atom have a further heteroatom in the specified position 1, for example an oxygen. Sulfur, selenium or nitrogen atom. For example, Q can represent the atoms that are required to complete one of the following rings, namely

a thiazole ring, e.g. B. a thiazole, 4-methylthiazole, 4-phenylthiazole, 5-methylthiazole. 5-phenylthiazoI-. 4.5-dimethylthiazole, 4.5-diphenylthiazole, 4 - (2 - thienyl) · ■ thiazole, benzothiazole 4-chlorobenzothiazole, 5-chlorobenzothiazole, 6-chlorobenzothiazole, 7-chlorobenzo-

thiazole-. 4-methylbenzothiazole, 5-methylbenzothiazole, 6-methylbenzothiazole, 5-bromobenzothiazole, 6-bromobenzothiazole, 6-phenylbenzothiazole. 5-phenylbenzothiazole, 4-methoxybenzothiazole, 5-methoxybenzothiazole, 6-methoxybenzothiazole. 5-iodobenzothiazole, 6-iodobenzothiazole, 4-ethoxybenzothiazole, 5-ethoxybenzothiazole, tetrahydrobenzothiazole, 5,6-dimethoxyberizothiazole, 5,6-dioxymethylene benzothiazole, 5-hydroxybenzothiazole, 6-hydroxybenzothiazole, 6-hydroxybenzothiazole, 6-hydroxybenzothiazole -, /, '- naphthothiazole-. 5-methoxy-fi, / i-naphthothiazol-, 5-ethoxy- fi - naphthothiazol-, 8 - methoxy - a - naphthothiazole 7-methoxy-d-naphthothiazole- or a 4'-methoxythianaphtheno-7 ', 6'. 4,5-thiazole ring: '5 of an oxazole ring, e.g. B. a 4-methyloxazole. 5-methyioxazoi. 4-phenyloxazole, 4,5-diphenyloxazole. 4-Athyloxazole-, 4,5 - Dimethyloxazole-, 5 - Phenyloxazole-, Benzoxazole-. 5 - chlorobenzoxazole, 5-methylbenzoxazole-. 5-phenylbenzoxazole-, 6-methylbenzoxazole-, 5,6-dimethylbenzoxazole-, 4,6-dimethylbenzoxazole- j 5-methoxybenzoxazole-, 5-ethoxybenzoxazole-. 5-chloronaphthoxazole, 6-methoxybenzoxazole, 5-hydroxybenzoxazole. 6-hydroxybenzoxazole-. «-Naphthoxazole or one - / - naphthoxazole ring;

of a selenazole ring, ζ. B. a 4-methylselenazole, 4-phenylselenazole, benzoselenazole, S-chlorobenzoselenazole, 5-methoxybenzoselenazole, 5-hydroxybenzoselenazole, tetrahydrobenzoselenazole, "-Naphthoselenazole or fi-naphthoselenazole rings;

a thiazole ring, e.g. B. a thiazoline or a 4-methylthiazoline ring; a pyridine ring, e.g. B. a pyridine, 3-methylpyridine or a 4-methylpyridine ring;

a quinoline ring, e.g. B. a quinoline, 3-methylquinoline, 5-ethylquinoline, 6-chloroquinoline. e-chloroquinoline or 6-methoxyquinoline ring;

a 3,3-dialkylindolenin ring, e.g. B. one 3,3-dimethylindolenine or a 3,3-diethylindolenine ring;

an imidazole ring. z. B. an imidazole, 1-A1-kylimidazole, 1 - alkyl - 4,5 - dimethylimidazole, benzimidazole, 1-alkylbenzimidazole. 1-aryl-5,6-dichlorobenzimidazole, 1-alkylnaphthimidazole-, l-aryl-zJ-naphthimidazole- or one 1-alkyl-5-methoxy-naphthimidazole ring.

Dyestuffs of the formula I given, in which Q is used to complete a fused-on pyridine ring represents required atoms, have proven to be particularly advantageous.

The use in this invention are excellent merocyanine effective electron acceptors for direct positive silver halide photographic emulsions of the specified type and STEL <*> len also z. B. are extremely effective desensitizers in emulsions which can be used in the context of the process described, for example, in US Pat. No. 3,250,618.

The merocyanine dyes which can be used according to the invention are easy to prepare. A suitable method for the production of such merocyanine dyes z. B. consisting of a mixture from 1. a heterocyclic compound of the following structural formula:

where n, R ₁ and Z have the meanings already given and X is an acid anion and R _{2 is} an alkyl, arylkyl or aryl group, for example a methyl, ethyl or benzyl group, and 2. a complex condensed pyrimidinedione compound of the following structural formula :

N-C

.CC = L-NH-R ₂ III

N-C

- · ■ 'II ο

0.

wherein L and Q have the meaning already given and R _{2 is} an aryl group, for example a phenyl or tolyl group in preferably approximately equimolar amounts in the presence of a condensing compound, for example in the presence of a trialkylamine, e.g. B. triethylamine, or piperidine or N-methylpiperidine, to be heated in an inert solvent such as acetic anhydride.

The crude dyes formed in the reaction can be easily removed from the reaction mixture separate and by one or more recrystallization from suitable solvents, for example clean with hot ethanol, m-cresol or pyrimidine.

The pyrimidine compounds of the formula used to prepare the new merocyanine dyes III can be easily prepared, for example by heating a mixture of approximately equimolar Sets of

(1) a compound of the following structural formula:

N-C

_CHl

6 ^N ~ ^C

^Q v_ ··· ii

and (2) ethyl isoformanilide in an inert solvent such as m-cresol or 1-methylpyrrolidinone, whereupon the reaction product separated and from a suitable solvent such as for example pyridine, can be recrystallized. For making direct positive photographic Silver halide emulsions of the invention can be appropriately fogged silver halide emulsions one or more of the new merocyanine dyes are incorporated.

The concentration of merocyanine dye in the emulsion can vary widely. Preferably about 50 to 2000 mg, in particular about 400 to 800 mg, of merocyanine dye per mole of silver halide the direct positive emulsion is used.

As already mentioned, the emulsions are concealed with the aid of reducing agents and gold haze.

Typical reducing fogging agents suitable for masking are e.g. B. stannous salts, e.g. B. stannous chloride, Hydrazine, sulfur-containing compounds, e.g. B. thiourea dioxide and phosphonium salts, e.g. B. Tetra (hydroxymethyl) phosphonium chloride. Typical suitable gold veils are e.g. B. potassium chloroaurate and aurichloride.

The concentrations of reducing agents and gold haze can vary widely. As beneficial has proven to be the use of about 0.05 to 40 mg reducing compound per mole Silver halide and from 0.5 to 15.0 mg gold compound per mole of silver halide. All Particularly advantageous results are both more reducing at low concentrations Connection as well as gold connection achieved.

As is obscured here and hereinafter an emulsion containing silver halide grains, that produce a density of at least 0.5, when processed for 5 minutes at 2O ⁰ C in a developer of the following composition B without exposure, the testing of Emulsion takes place in the form of an emulsion layer, which was obtained by applying the emulsion to a layer support in a thickness corresponding ^{to 50 to 500 mg of silver per 0.0929 m 2.}

Developer B

N-methyl-p-aminophenol sulfate 2.5 g

Sodium sulfate (anhydrous) 30.0 g

Hydroquinone 2.5 g

Sodium metaborate 10.0 g

Potassium bromide 0.5 g

Made up to 1.0 1 with water

The new merocyanine dyes can advantageously be incorporated into direct-positive emulsions, the silver halide grains thereof have a water-insoluble silver salt core and an outer shell from a veiled, water-insoluble silver salt, which can be developed into silver without exposure is. In this case, the new merocyanine dyes are preferably the outer shell incorporated into the silver halide grains of such emulsions.

The shell of such grains can be produced, for example, by precipitating a light-sensitive, Silver salt which is insoluble in water and which can be concealed, but whose haze is produced by a bleaching process can be removed on the nuclei of the silver halide grains. The shell should be of sufficient strength have to prevent the developer from penetrating to the core during the development of the emulsion to avoid. The silver salt shell becomes a surface covering subjected, so that it can be developed into metallic silver using conventional surface developers

It has proven to be expedient to veil the silver salt of the shell so strongly that a density of at least about 0.5 is produced when the emulsion is developed for 6 minutes at 20 ^° C. in a developer C of the composition described below, after the emulsion has been applied to a layer support in a layer thickness corresponding to 100 mg silver per 0.0929 m ^2. Such concealment can be achieved by chemical sensitization to haze with the indicated sensitizing compounds. While the cores of the silver halide grains of the emulsion need not be sensitized to fog, the shell is fogged. The concealment of the shell of the silver

ij halide grains can optionally also after application the emulsion are carried out on a layer support.

Developer C

N-methyl-p-aminophenol sulfate 2.5 g

Ascorbic acid 10.0 g

Potassium metaborate 35.0 g

Potassium bromide 1.0 g

Made up to 1.0 1 with water

pH adjusted to 9.6

Before the shell of water-insoluble silver salt is produced on the silver salt cores, the Core emulsion initially chemically or physically pretreated to create centers, which cause the precipitation of photolytic silver, d. H. core centers producing latent images,

favor. The centers can be different known methods are generated. Chemical processes have proven to be particularly advantageous Proven awareness, for example in the journal "Science et Industries Photographiques", Vol. XXVIII, January 1957, pp. 1 to 23, and January 1957, pp. 57 to 65. The chemical sensitization processes described can be divided into three main classes, namely the sensitization by means of gold or other

ren noble metal compounds, the sensitization means Sulfur, for example compounds with labile sulfur atoms, and the so-called reduction sensitization, d. H. the treatment of the silver halide with a strongly reducing compound,

which creates tiny spots or specks of metallic silver in the silver salt crystals or grains. The new merocyanine dyes of the invention are particularly advantageous electron acceptors for highly sensitive direct positive silver halide

emulsions with fogged silver halide grains, such as those in the Belgian U.S. Patent 695,366. The fogged silver halide grains of such emulsions are characterized by the fact that they are after

Application in the form of a photographic silver halide emulsion to a support to produce a maximum density of at least about 1 after 6 minutes of development at 20 ^° C. in a developer B lead to a maximum density which

is at least about 30% greater than the maximum density of an identical test specimen which was developed for 6 minutes at about 20 ^° C. in the same developer B after it was developed for about 10 minutes

11 ^f 12

at 20 ° C in a bleaching bath of the following composition. Such silver-

composition: halide emulsions proven, whose silver halide

",. . _{,, n} grains of at least 50 mole percent of bromide

Potassium cyanide 50 mg ^ consist. Particularly advantageous silver halide

tis vinegar. j, 4 / cm _{5 gene} emulsions according to the invention are silver

mtnumacetat u, 4y g bromoiodide emulsions, especially those

Potassium bromide. ... 119 mg _{h less than rt 10 mol percent iodide} .

Aufgerullt with water to 1.0 _{1 p} ^ p _{otogra Hischen} silver halide emulsions

has been bleached. the invention can advantageously be used in

The grains of such emulsions lose at least such strength on conventional photographic media

at least about 25%, generally at least about about, of the carrier that is applied to a carrier surface

40% of their veil if they contain about 50 to about 500 mg of silver ^{for 10 minutes at 0.0929 m 2}

20 ⁰ C in a potassium cyanide bleach bath of the accrued.

given composition can be bleached. This in the production of photographic silver fog loss can be illustrated by halide emulsions, the dyes are preferred the silver halide grains in the form of a washed, finished silver halide mulphotographic Silver halide emulsion incorporated on a sion in which it is thoroughly dispersed Carrier to achieve a maximum density of be.

at least 1.0 after 6 minutes of development method of incorporating dyes and

at about 20 ° C in developer B and comparison 20 other additives in photographic silver halide

the density of the test specimen with an identical test emulsion are known and can easily be carried out. So

ling, which for 6 minutes at 20 ° C in the ent, it has proven to be advantageous, for example, the

winder B was developed after the test specimen dyes in the form of solutions in suitable

to incorporate in the potassium cyanide solvents of the emulsion for about 10 minutes at 20 ^{° C., wherein}

Bleaching bath of the composition described, of course, only use such solvents

had been bleached. can be det that the light-sensitive emul-

As stated earlier, the maximum density of the sion does not adversely affect it. As a suitable solution

unbleached test specimen at least 30% larger, solvents have, for example, methanol. Iso-

generally at least 60% greater than propanol, pyridine and water, either alone or

maximum density of the bleached test specimen. 30 proved to be mixed with each other.

For the preparation of the silver halide emulsions The new merocyanine dyes can be used

can be the usual known photographic the usual known and various types

Silver halides are used; d. H. example of photographic silver halide emulsions sensitive

silver bromide, silver iodide, silver chloride, silver bilize.

chlorobromide, silver bromoiodide and silver chloro- 35 Such emulsions can be used in known

bromide. Way using a wide variety of hydro-

Silver halophilic colloids have been found to be particularly advantageous, for example genide emulsions containing silver halide grains of less than about medium average grain size using naturally occurring binding, such as gelatin, albumin, agar-agar, gum-1 Microns, especially less than about 0.5 "microns, 40 arabic. Alginic acid and the like, or using proven. The silver halide grains can be hydrophilic synthetic resins such as have a regular structure or any other polyvinyl alcohol, polyvinyl pyrrolidone. Cellulose leather known structures, for example a cubic ether, partially hydrolyzed (cellulose acetates and the like. or octahedral structure, as for example in The binders of the emulsions can des weider Belgian patent 695 366 describes 45 teren dispersed. polymerized vinyl compounds will. contained, for example, in the USA.

Preferably, the grains also have an identical font 3,142,568, 3,193,386, 3,062,674 and 3,220,844

moderate diameter distribution, as they are also described in. To such polymerized

of the Belgian patent 695 366 described vinyl compounds include, for example, those in

will. For example, at least 95% water-insoluble polymers of alkyl acrylates can be used

weight percent of the silver halide grains and alkyl methacrylates, acrylic acid, sulfoalkylacrylic

Have a diameter of no more than about latates or sulfoalkyl methacrylates.

40%, preferably by no more than about 30%. If necessary, the silver halide emulsions can

differs from the mean grain diameter ions to which the new merocyanine dyes are added

Mean grain diameter, i.e. H. average 55 sets, also so-called color formers, for example

Grain sizes, can easily be determined according to procedures so-called color couplers contain,

Materials described, for example, in The Silver Halide Emulsions with a Content

"The Photographic Journal", Vol. LXXIX, on one or more of the new merocyanine color

1949, pp. 330 to 338. substances can be applied to the usual photographic

Apply the veiled silver halide grains of these 60 film supports, for example on film direct-positive photographic emulsions produced from glass, foils, e. B. films made of cellulose have a density of at least 0.5, if they, without acetate, cellulose acetate butyrate, polyesters, z. B. Polyexposed to be developed for 5 minutes at 20 ° C in the ethylene terephthalate or on the support made of paper developer B after the basket-based papers, coated with polyolefins in the form of the silver halide emulsion in a 65 paper, for example paper that is coated with polyethylene layer thickness of 50 to about 500 mg of silver per or polypropylene, and which is ^{applied to a carrier at 0.0929 m 2} to improve the adhesion of the emulsion with electrolytes. tronen was irradiated.

2673

Are photographic recording materials using a silver halide emulsion according to the invention prepared, the silver halide emulsion layer as well as others Layers of the photographic material in a conventionally known manner with the aid of conventional Hardening agents are hardened, e.g. B. with aldehyde curing agents, e.g. B. formaldehyde and Mucochloric acid, aziridine hardeners, hardeners made from derivatives of dioxane or from Oxypolysaccharides such as oxidized starch or oxidized vegetable gums exist.

The emulsion layers can also contain additives, as are normally the case with Production of photographic recording materials can be used, e.g. B. lubricants, stabilizers, sensitizers, light absorbing dyes and / or plasticizers. Furthermore, the silver halide photographic emulsions optionally contain additional spectral sensitizing dyes. Further The silver halide emulsions according to the invention can contain color couplers or optionally developed in solutions containing color couplers or other color-forming compounds. Typical suitable color couplers are e.g. B. monomeric and polymeric color formers, for example pyrazolone color couplers. as well as phenolic, heterocyclic and open-chain color couplers with a reactive methylene group.

The dye-forming couplers can be direct positive photographic silver halide emulsions are incorporated according to the invention by customary known methods, such as, for example are described in U.S. Patents 2,322,027, 2,811,171 and 1,055,155 as well as 1 102 028 and 2 186 849. The silver halide emulsions according to the invention can also be used, for. B. by means of incorporated developers are developed, for example by means of polyhydroxybenzenes, aminophenols and 3-pyrazol'donen.

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

example 1

3 - [(1,3-Diethyl-2- (1H) -imidazo [4,5-b] -

quinoxalinylidene) ethylidene] -2 H-pyrimido [2,1 -b] -

benzothiazoI-2,4- (3 H) -dione

A mixture consisting of 0.8 g of 3-anilinomethylene-2H-pyrimido [2, l-b] benzothiazole-2,4- (3H) -dione, 0.7 g of 1,3 - diethyl - 2 - methylimidazoquinoxalinium p-toluenesulfonate and 0.2 g of triethylamine. was refluxed in 20 ml of acetic anhydride for 15 minutes. The reaction mixture was then allowed to dry using a concentrated rotating evaporator. The residue was taken up in methanol and filtered would. The solid was then dissolved in hot pyridine, the solution filtered and methanol added would. After cooling the solution, the obtained crystals were filtered off and washed with methanol washed. The crude dye was then dissolved in chloroform and the solution passed through a column.

ίο which was filled with aluminum oxide (activity II). was given. The dye was then made by concentrating the chlorofoim solution using a rotating evaporator isolated. The yield of red crystals was 16%. The crystals had a melting point of above 310 ° C.

The dye produced, the core having a desensitizing action, a 1,3-diethylimidazo [~ 4,5-b] quinoxaline core contained, was examined for its usefulness as an elecronic accepioi and s> pectr ^! e & sensitizers for fogged direct positive photographic silver halide emulsions according to the following Procedure tested:

A gelatin silver bromoiodide emulsion with 2.5 mole percent iodide as halide and an average grain size of about 0.2 microns was prepared by adding an aqueous solution of potassium bromide and potassium iodide and an aqueous solution of silver nitrate simultaneously with vigorous stirring to an aqueous gelatin solution at a temperature of 70 ^G C was added over a period of about 35 minutes. The emulsion obtained, after solidification by cooling, was then noodled and washed in cold water in the usual manner.

The emulsion was then veiled by adding 0.2 mg of thiourea dioxide per mole of silver added and the emulsion was heated to 65 C for 60 minutes, whereupon you continue to 4.0 mg Incorporated potassium chloroaurate per mole of silver and the emulsion again at 65 ° C. for 60 minutes was heated.

Then as much 3- [1.3-ethyl - 2 - (1 H) - imidazo [4,5 - b] quinoxalinylidene) ethylidene] - 2 H - pyrimido [2, l - b] benzothiazole-2,4- (3 H) -dione added so that the dye was present in a concentration of 0.08 g per mole of silver.

The emulsion obtained was then applied to a conventional cellulose acetate layer support in such a way that 100 mg of silver were ^{deposited on a support area of 0.0929 m 2}

and 400 mg of gelatin were omitted.

A sample of the recording material obtained was then in a conventional sensitometer with a Tungsten lamp exposed, whereupon the exposed material for 6 minutes at room temperature in the

winder A was developed.

The material was then fixed, washed and dried. The results obtained are summarized in Table 1 below.
When using this dye, a maximum density in the unexposed areas of 2.44 and a minimum density in the exposed areas of 0.08 were achieved. The maximum sensitivity of the emulsion was 530 πΐμ with a relative sensitivity of 295.

From the results obtained, it is found that dei new merocyanine dye as both an electron acceptor and a spectral sensitizer works.

769 383

Using the in the manner described produced photographic material, direct positive images of excellent quality were obtained.

Excellent magenta dye images were obtained when the emulsion was al? Color formers 1- (2,4,6-Trichlorophenyl) -3,3 '- (2 ", 4" -di-t.-amylphenoxyacetamido) benzime idazo - 5 - pyrazolone incorporated and the emulsion applied to a conventional carrier, was exposed by means of a tungsten light source through filters (Wratten filters No. 61 and 16) and in usually by the reverse process, for example, as described in U.S. Patent 3,046,129 is described, with the exception that the black and white development omitted, was developed. The color development could be shortened to a period of one minute. the Development takes place in total darkness until after fixation. The procedure was as follows:

(1) Color development 1 minute

(2) Clarify 5 minutes

(3) Silver bleaching for 8 minutes

(4) Fix 3 minutes

It was then washed and dried. The color developer used had the following composition:

Water, 21 to 27 ° C 1.01

Benzyl alcohol 6.0 cm ³

Sodium hexametaphosphate 2.0 g

Sodium sulfite, dehydrated, 5.0 g

Trisodium phosphate 40.0 g

Potassium bromide 0.25 g

0.1% solution of potassium iodide ... 10.0 cm ³

Sodium hydroxide 6.5 g

4-Amino-N - (/ f-methanesulfonamidoethyl) -m-toluidensquisulfate-

Monohydrate 11.33 g

Ethylene diamine sulfate 7.8 g

Citrazinic acid (2,6-dihydroxyisonicotinic acid) 1.5 g

The clarification bath had the following composition:

Water 1.01

Sodium bisulfite 10.0 g

Hydroquinone 0.5 g

The silver bleach bath had the following composition:

Sodium ferricyanide 60.0 g

Sodium hypophosphate H ₂ O 17.6 g

Sodium bromide 15.0 g

Sodium hydroxide 3.5 g

Sodium thiocyanate 5.0 g

Made up to 1.01 with water

The fixer used had the following composition:

Water (27 ^° C) 1.01

Sodium thiosulfate 95.6 g

Sodium bisulfite 20.0 g

Example 2

3 - [(1,3-Diethyl-2- (1 H) -imidazo [4,5-b] -

quinoxalinylidene) ethylidene] -2 H-pyrimido [l, 2-a] -

benzimidazole-2,4- {3 H) -dione

A mixture of 3.06 g of 3-anilinomethylene-2 H-pyrimido [1,2-a] benzimidazo] -2,4- (3 H) -dione, 0.2ml acetic anhydride and 30 ml 1-methylpyrrolidinone

was heated to the boiling point of the mixture. Thereupon 2.76 g of 1,3-diethyl-2-methylimidazo [4,5-b] quinolxalinium chloride were added and 2 g of triethylamine were added, whereupon the mixture was heated to the re-nut temperature for 1 minute and then to room temperature has been cooled. The deposited precipitate was filtered off and washed with methanol. After extraction of the solid precipitate with boiling pyridine, the precipitate was in hot Dissolved m-cresol, whereupon the solution is filtered and

Methanol was added. After cooling, the precipitated dye was filtered off. After repeated recrystallization in the manner described, orange-red crystals having a melting point of above 31o C ^0. The dye yield was 8%.

The dye obtained, the ring having a desensitizing effect, a 1,3-diethyiimidazo [4,5-b] quinolxaline ring was tested according to the procedure described in Example 1. The received The results are compiled in Table 1 below. From the results obtained it is found that the dye is an extremely effective electron acceptor for obscured, direct-positive, represents silver halide photographic emulsions.

Example 3

3 - [(1,3-Diethyl-2- (1 H) -imidazo [4,5-b] -quinoxalinylidene) ethylidene] -2H-pyrido [1,2-a] -

pyrimidine-2,4- (3 H) -dione
O

C = CH-CH =

A mixture of 1.3 g of 3-anilinomethylene-2 H-pyrido [1,2-a] pyrimidine-2,4- (3 H) -dione, 1.8g 1,3-diethyl - 2 - methylimidazo [4,5 - b] quinoxalinium iodide and 0.6 g of triethylamine was refluxed in 25 ml of acetic anhydride for 5 minutes heated. The reaction mixture was then allowed to cool and for 2 hours at room temperature

(O

^κ 18

kept. The solid precipitate was then filtered off and washed with acetic anhydride.

The crude dye was then dissolved in hot m-cresol and the resulting solution filtered and methanol was added to the filtrate. After cooling and filtering, the filtered precipitate became treated again in the manner described. There were orange-red crystals with a Melting point of 281 to 283 ° C (dec.) Obtained. The dye yield was 27%.

The dye obtained, which has a desensitizing ring, a 1,3-diethyl-imidazo [4,5-b] quinoxaline ring was tested according to the procedure described in Example 1. The results obtained are compiled in Table 1 below. From the results obtained It is found that the dye is an excellent electron acceptor and an excellent spectral Is a sensitizer for fogged direct positive photographic silver halide emulsions. When using the dye described, the densities were for the unexposed and exposed areas of 2.38 and 0.04, respectively. The maximum sensitivity of the dye was around 550 ηΐμ, while the relative sensitivity of the emulsion was 1000.

Example 4

3 - [(6-chloro-1,3-diphenyl-2- (1H) -imidazo [4,5-b] -

quinoxalinylidene) ethylidene] -2H-pyrido [l, 2-a] -

pyrimidine-2,4- (3 H) -dione

is an excellent electron acceptor and spectral sensitizer for fogged direct positive photographic emulsions.
Example 5

3 - [(3-Ethyl-6-nitro-2-benzothiazolinylidene) ethylidene] -2 H-pyrido [1,2-a] pyrimidine-2,4- (3 H) -dione

NO-

C _n H,

C = CH-CH = C

C ₆ H ₅

A mixture of 2.6 g of 3-anilinomethylene-2 H-pyrido [1,2 - a] pyrimidine - 2,4 - (3 H) - dione, 5.4 g 6 - chloro - 2 - methyl -1,3 - diphenylimidazo [4,5 - b] quinoxalinium p-toluenesulfonate and 1.1 g of triethylamine was refluxed in 25 ml of acetic anhydride for 5 minutes. The reaction mixture was then allowed to cool, whereupon the deposited precipitate was filtered off and washed with acetic anhydride was washed. The crude dye was then dissolved in 400 ml of hot ethanol, whereupon the solution was filtered and 5 ml of triethylamine were added to the filtrate. After the filtrate has cooled the precipitated dye was filtered off, washed with ethanol and dried. They turned deep red Crystals with a melting point of 282 to 286 ° C (dec.) Were obtained. The dye yield was 30%.

The dye obtained was tested according to the method described in Example 1. The received The results are compiled in Table 1 below. From the results obtained it is found that densities in the unexposed and exposed areas of 2.04 and 0.04, respectively, were obtained. The maximum sensitivity was 550 ηΐμ, at a relative sensitivity of 501. From the results obtained, it was found that the dye

A mixture of 2.6 g of 3-anilinomethylene-2 H-pyndoU, 2-ajpynmidin-2,4- (3 H) -dione, 3.9 g 3-ethyl-

2 - methyl - 6 - nitrobenzthiazolium - ρ - toluenesulfonate and 1.1g of triethylamine were for 5 minutes in 25 ml Acetic anhydride heated to reflux temperature.

The reaction mixture was then cooled, whereupon the deposited precipitate was filtered off and washed with Methanol was washed. The crude dye was then dissolved in hot m-cresol, whereupon the The solution was filtered and methanol and 5 ml of triethylamine were added to the filtrate. After The solution was cooled and the dyestuff which had precipitated out was filtered off and washed with methanol. There were dark, shiny crystals with a melting point of 277 to 279 ° C (dec.) are obtained. The yield at Dye was 64%.

The dye obtained has a 3-ethyl-6-nitro-2-benzthiazole ring was then tested according to the procedure described in Example 1. The results obtained are compiled in Table 1 below. From the results obtained found the dye to maximum densities of 1.82 and 0.04 in the unexposed and exposed, respectively Districts, with a maximum sensitivity of 550 πΐμ and a relative sensitivity of 436 were obtained. From the results obtained, the dye was found to be an excellent electron acceptor and an excellent spectral sensitizer for veiled, represents reversal photographic emulsions.

Equally favorable results were obtained when in the preparation of the dye instead of

3-ethyl - 2 - methyl - 6 - nitrobenzothiazolium - p-toluenesulfonate equivalent amounts of another quaternary 3-alkyl-2-methyl-6-nitrobenzoxazolium salt were used, for example the corresponding methyl, ethyl, propyl, isopropyl, butyl, hexyl, Decyl or dodecyl derivatives or, accordingly, the chlorides, bromides, iodides, perchlorates or others p-toluenesulfonates.

Correspondingly favorable results were also obtained when instead of 3-ethyl-2-methyl-6-nitrobenzothiazolium p-toluenesulfonate other quaternary 3-alkyl-2-methyl-6-nitrobenzoselenazolium salts were used, for example the corresponding ones Methyl, ethyl, propyl, isopropyl, butyl, hexyl, decyl or dodecyl derivatives and / or the corresponding Chlorides, bromides, iodides, perchlorates or p-toluenesulfonates.

ί \ X

In this way, for example, the following electron acceptors and spectral sensitizers will be obtained:

3 - [(3-ethyl-6-nitro-2-benzoxazolinylidene) ethy-

liden] -2H-pyrido [1,2-a] -pyrimidine-2,4-

(3H) -dione;
3 - [(3-Ethyl-6-nitro-2-benzoselenazolinylidene) ethylidene] -2 H-pyrido [1,2-a] pyrimide in 2,4- (3H) -dione.

The 3-aninomethylene-2 used as the starting component H-pyrido [1,2-a] pyrimidine-2,4- (3 H) -dione can also be obtained by equimolar amounts of the most varied other compounds falling under the formula III are replaced, for example by 3 - anilinomethylene - 2 H - pyrimido [2, l - b] benzothiazole-2,4- (3H) -dione or 3-anilinomethylene-2 H-pyrimido- [1,2-a] benzimidazole-2,4- (3 H) -dione. In all cases, merocyanine dyes which were excellent were obtained were effective electron acceptors and spectral sensitizers.

Example 6

3 - [(6,7-dichloro-1,3-diphenyl-2- (1H) -imidazo [4,5-b] -quinoxalinylidene) ethylidene] -2 H-pyrido [1,2-a] -

pyrimidine-2,4- (3 H) -dione

C ₆ H ₅

A mixture of 2.2 g of 3-anilinomethylene-2 H-pyrido [1,2-a] pyrimidine-2,4- (3H) -dione and 5.3 g of 6.7 dichloro - 2 - methyl -1,3 - diphenylimidazo [4,5 - bjquinoxalinium iodide was heated to reflux temperature in 50 ml of acetic anhydride for 1 minute. the The reaction mixture was then filtered hot, whereupon the solid mass obtained was dissolved in 300 ml of ethanol containing 1.2 g of diazobicyclo-octane was stirred for 2 hours. The raw dye was then used filtered off and washed with ethanol. The dye was then purified by pouring it into 25 ml m-cresol dissolved by filtering the solution and the resulting filtrate containing 350 ml of methanol added to 2 g of diazobicyclo-octane, the solution was placed in the cold for 4 hours and the deposited Crystals were filtered off. There were shiny green crystals with a melting point of 298 to 299 ° C (dec.) Obtained. The dye yield was 17%.

The dye obtained, which has a 6,7-dichloro-1,3-diphenyl-2- (1 H) -imidazo [4,5-b] quinoxaline ring as the desensitizing ring was tested according to the procedure described in Example 1. The received The results are compiled in Table 1 below. From the results obtained It is found that the dye is an excellent electron acceptor as well as an excellent one represents a spectral sensitizer for fogged direct positive photographic emulsions. As can be seen from Table 1, a relative sensitivity of 1380 was measured for this dye. The densities in the unexposed and exposed areas of the images obtained were 1.84 and 0.03. The maximum sensitivity was 565 πΐμ.

Example 7

3 - [(3-methyl-6-nitro-2-benzoselenazolinylidene) -

ethylidene] -2H-pyrido [1,2-a>

pyrimidine-2,4n (3 H) -dione

NO ₂

C = CH-CH = C

CH ₃

2.13 g of 2,3 - dimethyl - 6 - nitrobenzoselenazolium p-toluene sulfonate and 1.27 g of 2,3-dimethylaminomethylene - 2 H - pyrido [1,2 - a] pyrimidine - 2,4 - (3 H) - dione hydrochloride were mixed together in 20 ml of acetic anhydride, whereupon the mixture for 2 minutes was heated for a long time at the reflux temperature. The reaction mixture obtained was then placed in the cold, whereupon the dye obtained is filtered off in the form of the hydrochloride salt, washed with acetone and was dried. After two recrystallization by dissolving the dye in m-cresol, pouring the solution in methyl alcohol and converting the dye into the free base by adding Diazabicyclo-octane, the pure dye was obtained in a yield of 38%. The dye had one Melting point from 301 to 302 ° C (dec).

The dyestuff contained was a nitrobenzselenazole ring containing a desensitizing ring then tested according to the procedure described in Example 1. The results obtained are as follows Table 1 compiled. From the results, it was found that the dye was excellent Electron acceptor and an excellent spectral sensitizer for obscured, represents direct positive photographic emulsions. The results in Table 1 show that that the dye leads to a relative speed of 795 and that the images obtained have densities in the unexposed and exposed areas of 1.82 and 0.17, respectively. The maximum measured Sensitivity was 570 ηΐμ.

Example 8

3 - [(5-chloro-3-methyl-6-nitro-2-benzoxazolinylidene) ethylidene] -2 H-pyrido [1,2-a] pyrimidine-2,4- (3 H) -dione

Cl

The production was carried out according to the method described in Example 5. The dye was, in 88% yield was obtained and had a melting point of 161 ° C. (decomp.). The testing took place

as described in example 1. The results obtained are shown in Table 1 below.

The results obtained when testing the merocyanine dyes described in Examples 1 to 8 are listed in Table 1 below.

Table 1

FarbiiofT- Relative Maximum Minimal Marimal Example! focus
tration Sensation
opportunity Density un-
exposed Density be
clearer Sensation
opportunity (g / Mo! Ag) Districts Districts (Πΐμ) 1 0.080 295 2.44 0.08 530 2 0.460 91 2.26 0.30 - 3 0.450 1000 2.38 0.04 550 4th 0.650 501 2.04 0.04 550 5 0.650 436 1.82 0.04 550 6th 0.650 1380 1.84 0.03 565 7th 0.750 795 1.82 0.17 570 8th 0.800 912 1.56 0.04 520

Example 9

To 4.08 kg of a gelatin-silver chloride emulsion with an equivalent of 100 g of silver nitrate was added 0.017g 3 - [(1,3-diethyl-2- (lH) -imidazo [4,5-b] cbinoxalinyidene) ethylidene] - 2 H - pyrido [l, 2 - a] pyrimidine-2.4- (3 H) -dione (dye according to Example 3) was added.

The resulting emulsion was applied to a non-glossy paper support, whereupon the obtained emulsion layer was flash-exposed with white light so that after development in a Developer of the composition given below after dilution with 2 parts of water per 1 part of stock developer solution a density of 1.2 was obtained.

N-methyl-p-aminophenol sulfate 3.1 g

Sodium sulfite, dehydrated 45 g

Hydroquinone 12 g

Sodium carbonate, dehydrated, 67.5 g

Potassium bromide 1.9 g

Made up to 1.01 with water

The recording material obscured by exposure was then exposed imagewise, namely with light modulated by a No. 15 Wratten filter. A direct positive image was obtained.

Correspondingly advantageous results were obtained when, instead of the dye of Example 3, the Dye of Example 6 was used.

Example 10

3.175 kg of a gelatin-silver chloride emulsion with an equivalent of 100 g of silver nitrate were ^{heated to 40 °} C., whereupon the pH of the emulsion was adjusted to 7.8. Then, a 40% formalin solution were added to 8 ml and the emulsion 10 minutes, heated to 4O ⁰ C long. The pH of the emulsion was then adjusted to 6.0, whereupon 0.125 g of 3 - [(3-ethyl-6-nitro-2-benzothiazolinylidene) ethylidene] - 2 H - pyrido [1,2 - a] pyrimidine-2 , 4- (3 H) -dione (dye corresponding to the

game 5) were added. The emulsion then became applied to a support, whereupon the material obtained was exposed in the manner described. Direct positive images of excellent quality were obtained. Correspondingly beneficial results were obtained when, instead of the dye of Example 5, the dye of Example? used would.

The following describes the preparation of some condensed compounds used as starting compounds Pyrimidinediones described.

A. 3-Anilinomethylene-2 H-pyrido [1,2-a] -pyrimidine-2,4- (3 H) -dione

Ii

N-C

C = CH-NH-C ₆ H,

N-C

Il ο

A mixture of 8.1 g of 2H-pyrido [1,2-a] pyrimidine-2,4- (3 H) -dk> n and 100 ml of m-cresol was heated to reflux temperature, whereupon 8.3 g of ethyl isoformanilide were admitted. The reaction mixture was then cooled, followed by the reaction product was precipitated by adding methanol. After recrystallization from pyridine (50 ml / g) turned light yellow Crystals of the reaction product were obtained in a yield of 40%.

B. In the manner described under A. 3 - anilinomethylene - 2 H - pyrimido [2, l - b] benzothiazole - 2,4 - (3H) - dione from 3.6 g of 2H-pyrimido- [2, l-b] benzothiazole-2,4- (3H) -dione and 2,8g ethyl isoformanilide. It turned pale yellow Crystals obtained. Tj> the yield of reaction product was 61%.

C. 3-Anilinomethylene-2H-pyrimido [1,2-a] -benzimidazole-2,4- (3 H) -dione

A mixture of 10g of 2H-pyrimido [l, 2-a] benz- <«> Imidazole-2,4- (3 H) -dione and 100 ml 1-methylpyrrolidinone was heated until completely dissolved, whereupon 8.3 g of ethyl isoformanilide were added. The reaction mixture was then cooled and methanol was added. The whole thing was then placed in the cold, whereupon the precipitated reaction product is filtered off and washed with methanol would. The yield of cream colored crystals was 64%.

Claims (1)

Patent claims: 1. Direct positive photographic silver halo holds, characterized in that si genide emulsion, which with the help of a reduction one both as an electron acceptor and al and gold fogging agent and a spectral sensitizer acting merocyanine Compound acting as an electron acceptor decolorant of the following structural formula R ₁ -Nf-CH = CH) - Q = LL) = T = C