DE1547779B - Direct positive photographic silver halide emulsion containing a spectral sensitizing dye and an electron acceptor - Google Patents

Description

CH - CY = C

χβ

wherein R ₁ , R ₂ , R ₃ , R ₆ , Rs, &9> Rio »R-ii» Ri2> Y ^unc ^ X® have the meaning given.

4. Direct positive silver halide emulsion according to claim 1, characterized in that it has a Contains spectral sensitizing dye of the following formula:

R.

■ 7 (k)

C = CH - CH = CH - C

X ^e

wherein R ₇ , R ₉ , R ₁₀ , R ₁₁ , k and X® have the meanings already given.

5. Direct-positive silver halide emulsion according to claim 1, characterized in that it has a Contains spectral sensitizing dye of the following formula:

CH = CH-C

wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , k and X® have the meaning given.

The invention relates to a direct positive dye, a spectral sensitizing dye and an electron acceptor containing, photographic silver halide emulsion, the silver halide of which is at least 50 mole percent consists of silver bromide, the silver halide grains of which have a reducing effect Compound and a gold, rhodium, platinum, palladium or iridium compound has been veiled are.

It is known e.g. B. from German Patent 1008 118, to sensitize color formers containing direct-positive silver halide emulsions bis (1 - alkyl - 2 - phenylindole - 3) - trimethine cyanine dyes to use. In the silver halide emulsions described in the German patent they are direct-positive emulsions of the so-called solarization type.

It is also known e.g. From British Patent 723 019, direct positive photographic To prepare silver halide emulsions, the silver halide grains thereof by treatment with a gold compound or a compound of another metal more electropositive than silver and one reducing compound have been veiled. From British Patent 723 019 it is also known, the direct-positive emulsions as so-called electron traps or To add desensitizers that act as electron acceptors and that are composed of organic dyes, z. B. Pinacryptolgelb, can exist.

The disadvantage of the direct-positive photographic silver halide emulsions known from British patent 723 019 is that the electron acceptors added to the emulsions do not bring about an effective spectral sensitization of the emulsions, that is, the emulsions known from British patent 723 019 are useful for the longer wavelengths of light insensitive.
The object of the invention is to provide direct-positive photo-

silver halide graphic emulsions of the type containing an electron acceptor, the silver halide grains thereof with a reducing compound and a gold, rhodium, platinum, palladium or indium compound have been obscured from wavelengths above 480 πΐμ intensively sensitize, so that the same not as those known from British patent specification 723 019 Emulsions need to be exposed to blue light.

The subject matter of the invention is based on a direct positive, a spectrally sensitizing one A dye and an electron acceptor-containing photographic silver halide emulsion, the silver halide of which consists of at least 50 mol percent silver bromide and the silver halide grains thereof with a reducing compound and a gold, rhodium, platinum, palladium or Iridium compound have been obscured from and is characterized by being spectral sensitizing dye a dye one in its use in direct positive emulsions known dye type of the formulas:

R.

■ 7 (t)

or

CH = CH-CY = Q-X ©

C-CH = CH-Q ₁ Χ ^θ

contains, wherein R ₁ denotes an optionally substituted alkyl radical, R ₂ and R ₃ individually hydrogen or halogen atoms or optionally substituted alkyl radicals or together the atoms required to complete a fused aromatic ring with 6 carbon atoms, R ₆ a hydrogen or halogen atom or an alkyl radical or together with R ₁ an alkylene radical, R ₇ a hydrogen or halogen atom or a nitro group, R ₈ an aryl radical or heterocyclic radical with 5 or 6 ring atoms whose hetero atom consists of a nitrogen, sulfur or oxygen atom, R ₉ , R ₁₀ and R ₁₁ each represents an optionally substituted alkyl or aryl radical, k = 1, 2 or 3, Q which forms a dimethine cyanine or trimethine cyanine dye to complete a desensitizing indole, imidazo [4,5-b] quinoxaline, 6-nitrobenzthiazole, 5-nitroindolenine or pyrrolo- [2,3-b] -pyridoringes required atoms, Q _{1 is} a radical of the formula - CH = Q, where Q has the meaning already given, Y is a water atom, an alkyl, alkoxy or aryl radical or a heterocyclic radical and X® is an acid anion, the emulsion containing selected dyes which

a) the emulsion to radiation of wavelengths of more than 480 πΐμ spectrally in

sensitize the way that the ratio - Q - X ^e of relative minus blue sensitivity to

Blue sensitivity is at least 7,

b) which are at the same time electron acceptors and where

c) the sum of the anodic and cathodic polarographic half-wave potentials results in a positive value.

The invention achieves that direct-positive silver halide emulsions of the one electron acceptor containing type, their silver halide grains with a reducing compound and a gold, rhodium, platinum, palladium or iridium compound has been veiled are obtained with high sensitivity to wavelengths above 480 πΐμ, where it applies that the spectral sensitization of the silver halide emulsions is at least the same, preferably is greater than the sensitivity of the emulsions to blue radiation, i. H. a radiation from 400 to about 480 ηΐμ. Spectral awareness is achieved by using dyes, which are also effective electron acceptors and are therefore referred to as spectral sensitizing electron acceptors be able.

Dyes of the type used in the present invention are known, e.g. B. from the German patent 1008 118.

As particularly advantageous direct-positive silver halide emulsions According to the invention, those have been found to have a dye of one of the specified Contain formulas that sensitizes the emulsion in such a way that the ratio of minus blue sensitivity for blue sensitivity is greater than 10.

Those dimethine and trimethine dyes of those specified have proven to be particularly advantageous dyes Proven formulas in which the desensitizing ring represented by Q is in the form of a symmetrical carbocyanine dye after addition to a silver chlorobromide emulsion with 40 mol-

C = CH-CH-Q-X®

percent chloride and 60 mole percent bromide at a concentration of 0.01-0.2 grams of dye per mole Silver that desensitizes emulsion to blue radiation, d. H. of at least 80% Reduction of the blue sensitivity of the emulsion results when it is exposed sensitometrically and For 3 minutes in a developer of the following composition:

Water, about 50 ^° C. 500 cm ³

N-methyl-p-aminophenol sulfate 2.0 g

Sodium sulfite, dehydrated 90.0 g

Hydroquinone 8.0 g

Sodium carbonate, monohydrate 52.5 g

Potassium bromide 5.0 g

Filled up with cold water to ... 1.0 1

is developed at room temperature.

Dyes of the formulas given have proven particularly suitable with such a desensitizing agent Proven core, which is converted into a symmetrical carbocyanine dye and described in the Way tested to a practically complete desensitization of the test emulsion to bluer Radiation leads, d. H. of at least 90%, preferably more than 95%, loss the sensitivity to blue radiation.

Particularly advantageous dyes are those of the formulas given in which Q is for the formation of an imidazo- [4,5-b] -quinoxaline ring is required, which through its 2-carbon atom to the Methine chain is bound.

In an advantageous manner, Q can furthermore, for example, be a ring of the following structural formula being:

wherein R ₁₅ , R ₁₆ and R _{17 are} each optionally substituted alkyl or aryl radicals.

Q ₁ can, for example, represent the atoms required to complete a pyrazolone nucleus or an indole nucleus which is substituted in the 2-position by an aromatic radical and which is bonded to the methine chain through the 3-carbon atom, ie Q ₁ can, for example, represent a Remainder of the following structural formula:

—C

(VI)

wherein R ₁ , R ₂ , R ₃ , R ₆ and R _{8 have} the meanings already given.

According to a particularly advantageous embodiment of the invention, the direct positive contains photographic The silver halide emulsion of the invention comprises a dye of the following formula:

CH = CH-C2

■ 7 (A)

(VII).

wherein R ₁ , R ₂ , R ₃ , R ₇ , R ₈ , k and X® have the meaning given and R ₄ . and R _{5 are} each optionally substituted alkyl or aryl radicals or allyl, alkenyl, alkynyl, cycloalkyl or dialkylaminoalkyl radicals.

In the formula given, R _{8 can,} for example, be an optionally substituted phenyl or naphthyl ring, the rings, for example, by alkyl radicals having preferably 1 to 8 carbon atoms, e.g. B. by methyl, ethyl, propyl or butyl radicals, or by alkoxy radicals with preferably 1 to 8 carbon atoms, z. B. methoxy, ethoxy, propoxy or butoxy radicals, or by halogen atoms, e.g. B. bromine, chlorine or iodine atoms, or aryl radicals, e.g. B. phenyl radicals can be substituted.

If R ₂ and R ₃ are halogen atoms, they can consist of chlorine, bromine or iodine atoms, for example. If R ₂ and R ₃ are alkyl radicals, they preferably have 1 to 8 carbon atoms, that is, R ₂ and R ₃ can be, for example, methyl, ethyl, propyl, butyl, methoxy, propoxy or hydroxyethyl radicals .
The optionally substituted alkyl radical represented by R _{1 preferably has.} to 8 carbon atoms and consists, for example, of a methyl, ethyl, propyl, butyl or octyl radical, or a sulfoalkyl radical, e.g. B. a sulfopropyl or sulfobutyl radical, or a sulfatoalkyl radical, e.g. B. a sulfatopropyl or sulfatobutyl radical, or a carboxyalkyl radical, e.g. B. a carboxyethyl or carboxybutyl radical.

If R ₄ and R ₅ are optionally substituted alkyl radicals, these preferably have 1 to 18 carbon atoms and consist, for example, of methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, hexyl, dodecyl -, Octadecyl, benzyl, or ß-phenylethyl or sulfoalkyl, z. B. sulfopropyl or sulfobutyl radicals; Sulfoatoalkyl radicals, e.g. B. sulfatopropyl or sulfatobutyl radicals; Carboxyalkyl radicals, e.g. B. carboxyethyl or carboxybutyl radicals; Hydroxyalkyl radicals, e.g. B. hydroxyethyl, hydroxypropyl or hydroxybutyl

209 531/476

ίο

leftovers; Allyl residues; Alkenyl residues, e.g. B. propenyl or butenyl radicals; Alkynyl radicals, such as. B. propargyl residues; Cycloalkyl radicals, e.g. B. cyclobutyl or cyclohexyl radicals, or dialkylaminoalkyl radicals, e.g. B. Dimethylaminoäthylresten. If R ₄ and R _{5 have} the meaning of aryl radicals, these can consist, for example, of phenyl, p-tolyl, o-tolyl or 3,4-dichlorophenyl radicals.

If R ₆ forms an alkylene radical together with R ₁ , this can for example consist of a trimethylene or dimethylene radical.

X can be, for example, a chloride, bromide, iodide, p-toluenesulfonate, thiocyanate, sulfonate, Methyl sulfate, ethyl sulfate or perchlorate anion.

According to a further particularly advantageous embodiment of the invention, the direct-positive one contains silver halide photographic emulsion contains a dye of the following structural formula:

= CH - CY = C

(VIII)

11th

wherein R ₁ , R ₂ , R ₃ , R ₆ , R ₈ , Rg,
substituted alkyl radical.

n, Y and X® have the meaning given and R ₁₂ optionally

In addition to a hydrogen atom, Y can be, for example, a methyl, ethyl, propyl or butyl radical or a methoxy, ethoxy or propoxy radical i l i

According to a further particularly advantageous embodiment of the invention, the direct-positive one contains photographic silver halide emulsion according to k

y py g

or an optionally substituted phenyl radical or 25 of the invention as electron-accepting color

a thiophene residue.

R ₉

R.

■ 7 (ic)

CH - CH = CH - C

substance has the following structural formula:

(IX)

wherein R ₇ , R ₉ , R ₁₀ , R ₁₁ , k and X® have the meaning already given.

According to a further particularly advantageous embodiment, the direct positive contains photographic The silver halide emulsion of the invention comprises an electron-accepting dye of the following structural formula : η

K ₄

CH = CH-C

(X)

wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , k and X® have the meanings already given.

Dyes of the formulas I and II in which R ₁ and R ₆ together form an alkylene radical are, for. B.

2,2'-diphenyl-1,7;
rV-Ditrimethylene-S ^ '- indolocarbocyanine-

bromide;
S'-Ethyl-o'-nitro ^ -phenyl-l ^ -trimethylene-

3-indolothiacarbocyanine p-toluenesulfonate;
l, 3-diethyl-2'-phenyl-l ', 7'-trimethylene

imidazo- [4,5-b] -quinoxalino-3'-indolo-

carbocyanine iodide;
l ', 3', 3'-trimethyl-2-phenyl-l, 7-trimethylene

3-indolopyrrolo- [2,3-b] -pyridocarbocyanine-

iodide and
l'-methyl-2,2 ', 10-triphenyl-l, 7-trimethylene

S ^ '- indolocarbocyanine perchlorate.

The direct-positive silver halide emulsions preferably contain of the invention a spectral sensitizing electron acceptor in concentrations from 50 to 2000, especially 400 to 800 mg

55 per mole of silver.

The silver halide of the direct positive silver halide emulsions of the invention can consist of any of the conventional for the production of direct-positive photographic Emulsions used consist of silver halides, for example of silver chloride or Silver bromide or silver bromoiodide, silver chlorobromide or silver chlorobromoiodide.

Suitable reducing compounds to mask the emulsions are, for example, stannous salts, z. B. stannous chloride, hydrazine, sulfur compounds, e.g. B. thiourea dioxide and phosphonium salts, z. B. Tetra (hydroxymethyl) phosphonium chloride. Connections suitable for concealment

11 12

of gold, rhodium, platinum, palladium and iri- It has also proven to be particularly advantageous, diums, which are preferably used in the form of soluble salts when the emulsion veiled silver halide, are, for example, aurichloride grains, of which at least 95 weight and (NH ₄ ) ₂ PdCl ₆ . Percent have a diameter that is no longer

It has also proven to be advantageous 5 to deviate by ± 40% from the mean grain diameter.

when the silver halide emulsions according to the invention give way.

Finally, it has proven to be particularly advantageous

Compound per mole of silver halide and 0.5 to proven when the silver halide grains have an average

15.0 mg of the noble metal compound are obscured. Larger particle diameters from 0.01 to 2 microns

Particularly good results are then obtained if you have 10.

when the silver halide grains are very low The determination of the anodic and cathodic

Concentrations of reducing compounds - polarographic half-wave potentials, d. H. the

dung, d. H. Reduction fogging agents and precious metal oxidation-reduction potentials, of dyes

Connection are veiled. According to one particular, known methods can be used. Catho-

Advantageous embodiment of the invention are 15 dical measurements can be performed with 1 χ 10 ~ ⁴ molar solu

the silver halide grains of the emulsion with 0.0005 solutions of a dye in a solvent,

up to 0.06 milliequivalents of reducing fogging agent e.g. B. methanol, which

and 0.001 to 0.01 millimoles of the noble metal compound is 0.05 molar with respect to lithium chloride. This will be

dung veiled. a dripping mercury electrode is used, where

Preferably, the silver halide grains of FIG. 20 are the half-wave polarographic potential for the

Emulsion with a compound of one of the most positive cathodic stages is designated as E _c ,

benen metals and a reducing agent anodic measurements can be performed with 1 χ 10 ~ ⁴ molar

veiled in a ratio of 1: 3 to 20: 1. aqueous solutions, for example methanolic

As a particularly advantageous combination of compounds solutions, the dye can be carried out, wel-

for the concealment, the combination of 25 before 0.05 molar with respect to sodium acetate and

Thiourea dioxide and potassium chloroaurate proved. Are 0.005 molar with respect to acetic acid. This will be

The silver halide grains of a direct-positive uses a graphite electrode, the voltome-

photographic silver halide emulsion of the invention. Irish half-wave potential for the most negative

application are obscured in such a way that the emul-anodic reproduction is referred to as E _a . at

sion after application to a layer support in a 30 two measurements, the reference electrode can be made

Strength, corresponding to 50 to 500 mg of silver per 0.09 m ^{2 of} an aqueous silver-silver chloride (saturated potassium

Layer support surface after a 5 minute long entlium chloride) electrode exist, whereby at 20 ⁰ C

development at 20 ° C in a developer of the following works. Electrochemical measurement methods this

Composition, without prior exposure, type are for example in the book »New

a density of at least 0.5 results in: 35 Instrumental Methods in Electrochemistry «by

Water 52 ° C 500cm ³ Delahay, Interscience Publishers, New York,

ν-Wpjn ^^ bÄ ::::: 2,5,

Sodium Sulphate (dehydrated) 30.0 g _Interscience Publishers, New York, New York, 1952J

NafrilmTabörät '.'. ". '.'. '.'. '. ". '.W [V. 10.0 g " ^the journal" Analytical Chemistry "36.2426 (1964), _v ru -A nc as well as in the journal" Analytical Chemistry ", 30,

STa ^b _s up _g eranta "r ::::::::::?; f «« «" * ■ ■., ..,

° The direct positive silver halide emulsions

According to a particularly advantageous embodiment of the invention, conventional photographic

In the form of the invention, the silver halide grains are coated on 45 phical supports, ζ. Β. such

only so veiled that one on a layer of glass, foils, z. B. made of cellulose acetate, cellulose

Supported photographic silver halide loose acetate butyrate, polyesters, for example polyethylene

emulsion, if it is used for 6 minutes on a template terephthalate, from paper, as well as on paper layer

temperature of 2O ⁰ C in a developer of the applied carriers, which are coated with a baryta layer,

benen composition to a maximum density 50 also on a layer support made of paper, which has a poly

of at least about 1 is developed, have a maximum olefin layer, ζ. B. a layer of poly-

Male density by at least about 30% ethylene or polypropylene, the substrate

is greater than the maximum density of a comparative - if necessary, can be irradiated with electrons -

sample developed under the same conditions to increase the adhesion of the emulsion,

after it has been stored for 10 minutes at 20 ° C in 55 The silver halide grains can thereby be in the

a bleaching bath of the following composition: conventional photographic hydrophilic colloids

ν γ · λ en be dispersed, as for example in column 13

EisessT 3 47 ⁸ cm ^{3 of the} USA.-Patent 3 039 873 are described

Natnumacetat 11.49 g _6q G _egebenenfal i _s k _{ann the} emulsion usual supply

:::::: "! Γ ⁸ ££; ™ l ^ S:" ^{Hardeners and plastic}

has been bleached. The dyes used according to the invention read

Particularly advantageous emulsions are also sen by known processes, in particular those in which at least 80% by weight or 65% by refluxing a carboxyaldehyde-80% the number of silver halide grains of the emulsion of a compound with one of the specified sion a regular, preferably a cubic-regular desensitizing rings and an alkyl structure own. substituted quaternary salt with a second

desensitizing ring in a suitable solvent produce.

Compounds of the formula VII can be prepared, for example, by refluxing an indole-3-carboxyaldehyde which is substituted in the 2-position by an aromatic radical, with a compound with a 2-alkylimidazo [4,5-b] quinoxalium ring in a suitable solvent, for example Acetic anhydride.

Dyes of the formula IV can be prepared in a corresponding manner, using a 2-alkylenepyrrolo- [2,3-b] pyridine compound goes out.

Dyes of the formula VIII given can be prepared by processes such as those for example in U.S. Patent 2,930,694.

Dyes of the formula IX given can be prepared, for example, by processes as described in the Belgian patent 660 253 are described.

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

example 1
(Comparative example)

It was a gelatin-silver bromoiodide emulsion with 2.5 mole percent iodide as the halide and one average grain size of about 0.2 microns made by adding an aqueous potassium bromide solution and an aqueous potassium iodide solution and further an aqueous silver nitrate solution at the same time vigorous stirring to an aqueous gelatin solution at a temperature of 70 ° C within a period of time of 35 minutes were added. The resulting emulsion was then quenched, noodled and washed out with cold water. The emulsion was then fogged by adding 0.2 mg of thiourea dioxide per mole of silver halide added, the emulsion heated to 65 ° C for 60 minutes, 4.0 mg of potassium chloroaurate per mole of silver was added and the emulsion was applied again for 60 minutes 65 ° C was heated. The fogged emulsion was then divided into several portions, followed by the various Portions of 0.87 millimoles each of the dyes listed in the following table per mole Silver halide were added. The dyes 1 to 4 are according to the status electron acceptors previously used in technology. Dyes 5 to 17 are used in the present invention Dyes.

50

Dye No.

Designation:

Phenosafranine
Pinacryptol yellow

S ^ '- diethyl-o ^' - dinitrothiacarbocyanine chloride

Crystal violet

Dye no.

Designation:

1,1-dimethyl-2,2'-diphenyl-3,3'-indolocarbocyanine bromide

U'-Dimethyl- ^ S-triphenyl-S ^ '- indolocarbocyanine perchlorate

2,2'-di-p-methoxyphenyl-1,1'-dimethyl-3,3'-indolocarbocyanine bromide

l, r, 3,3'-tetraethylimidazo- [4,5-b] -quinoxalinocarbocyanine chloride

6,6'-DiChIOrO-I ₅ I ', 3,3' -tetraphenylimidazo-t ^ S-bJ-quinoxalinocarbocyanine p-toluenesulfonate

1,1'-3,3,3 ', 3'-hexamethyl-5,5'-dinitroinocarbocyanine-p-toluenesulfonate

y
thiacarbocyanine iodide

1,3-piallyl-3- [2- (9-methyl-3-carbzolyl) -vinyl] -imidazo- [4,5-b] -quinoxalinium- p-toluenesulfonate

1,3-Diethyl-1'-methyl-2'-phenyl-imidazo [4,5-b] -quinoxalino-3'-indolocarbocyanine iodide

o-chloro-l'-methyl-l ^ '^ - triphenylimide-

azo- ^ jS-bJ-quinoxalinocarbocyanine-

p-toluenesulfonate
1,1 ', 3,3-tetramethyl-5-nitro-2' -phenyl-

indo-3 '-indolocarbocyanineiodide S'-ethyl-l-methyW-phenyl-o'-nitro-

3-indolothiacarbocyanine iodide 5'-chloro-1,3'-dimethyl-2-phenyl-6'-nitro-

3-indolothiacarbocyanine-p-toluenesulfonate

55

60 The individual emulsions were coated on cellulose acetate support in such a way that accounted for a substrate surface of 0.09 m ² 100 mg of silver and 400 mg gelatin. The recording materials obtained were then exposed in a sensitometer with a tungsten lamp with the inclusion of Wratten filters No. 35 and 38A with blue light and with the inclusion of a Wratten filter No. 16 with minus blue light.

The exposed specimens were then for 6 minutes at room temperature in a developer the following composition:

Water, about 50 ^° C. 500 cm ³

N-methyl-p-aminophenol sulfate 2.0 g

Sodium sulfite, dehydrated 90.0 g

Hydroquinone 8.0 g

Sodium carbonate, monohydrate 52.5 g

Potassium bromide 5.0 g

Filled up with cold water to ... 1.01

The test specimens were then fixed, washed and dried. It became the following Get results:

dye
No. Sensitivity
maximum Relative blue
sensitivity (B) Relative minus
Blue sensitivity
(MB) ratio of
Minus blue too
Blue sensitivity E _a + E _c 1*)
2 *) 550
440 8.9
19.0 21.0
1.8 2.36
0.095 > 0.58
0.40

According to the state of the art.

Continued 16

dye
No. Sensitivity
maximum Relative blue
sensitivity (B) Relative minus
Blue sensitivity
(MB) ratio of
Minus blue too
Blue sensitivity Ea + E ₁ 3 *) 640 10.7 26.5 2.48 0.32 4 *) 610 5.9 34.0 5.76 > 0.23 5 625 27.5 347.0 12.6 > 0.80 6th 660 18.5 490.0 26.5 > 0.65 7th 590 14.5 141.0 9.75 > o, io 8th 690 17.5 501.0 28.7 > 0.28 9 660 23.0 1260.0 55.0 > 0.28 10 620 19.5 417.0 21.3 > 0.10 11th 645 19.0 174.0 9.18 0.65 12th 570 19.5 468.0 24.0 > 0.10 13th 550 21.0 276.0 13.1 0.23 14th 580 18.0 501.0 Z /, O > 0.10 15th 560 18.5 257.0 13.9 > 0.10 16 575 21.0 302.0 14.4 > 0.48 17th 570 20.5 363.0 17.7 > 0.10

*) According to the state of the art.

The results obtained show that the direct-positive photographic emulsions according to the invention have a considerably improved spectral sensitivity compared to previously known direct-positive emulsions if (1) the emulsions contain a spectrally sensitizing electron acceptor which has an anodic polarographic potential (E. ₀ ) and has a cathodic polarographic potential (E _c ) , the sum of which gives a positive number, and if (2) the spectrally sensitizing electron acceptor spectrally sensitizes the emulsion in such a way that the ratio of relative minus blue sensitivity to blue sensitivity is at least 7.

Example 2

A silver halide emulsion as described in Example 1 was prepared again. The emulsion was divided into different proportions, whereupon the following dyes Nos. 18 to 26 with the required half-wave potentials were added:

Dye no

20th

21

22nd

23

24

25th

26th

Dye no.

Designation designation

5-chloro-3-methyl-2- / 5- (9-methylcarbazolyl) vinyl-6-nitrobenzothiazolium p-toluenesulfonate

l, l'-dimethyl-2,2'-di- (3-pyridyl) -3-indolo-

carbocyanine bromide dihydrobromide 3'-ethyl-l-methyl-6'-nitro-2- (3-pyridyl) -

S-indolothiacarbocyanine-p-toluenesulfonate-

hydro-p-toluenesulfonate 1,3-diethyl-1'-methyl-2 '- (3-pyridyl) -imide-

azo- [4,5-b] -quinoxalino-3'-indolocarbo-

cyanine dihydroiodide

1,1'-Dimethyl-2,2'-diphenyl-3-benz- [gj-indolocarbocyanine bromide

1,3-Dimethyl-6'-nitro-2-phenyl-3-benz- [g] -indolothiacarbocyanine-p-toluene- sulfonate

l ', 3'-Diethyl-l-methyl-2-phenyl-3-benz- [g] -indoloimidazo- [4,5-b] -quinoxalino- carbocyanine iodide

1,3-diethyl-2- / 9- (9-methyl-3-carbazolyl) vinylimidazo [4,5-b] quinoxalinium iodide

3-methyl-2 - /? - (9-methyl-3-carbazolyl) -vinyl-6-nitrobenzothiazolium-p-toluenesulfonate The emulsions obtained were then, as described in Example 1, applied to the substrate, exposed and developed. The following results were obtained:

dye Concentration of Density in uncoated D "" "in exposed ocna, IVi α λ. OClIo. DCl ClLIl No. Dye in g / mol cleared districts Districts Πΐμ ΙΏμ Ag 575 up to 650 18th 0.176 2.02 0.05 550 to 630 19th 0.214 1.93 0.04 no def. to 620 20th 0.90 2.08 0.08 maximum 635 to 680 21 0.269 1.74 0.1 560 to 610 22nd 0.258 1.84 0.07 550 up to 600 23 0.244 1.81 0.04

209 531/476

continuation

dye Concentration of Density in uncoated D _mm in exposed \ αηρ \ rtoγ OClIb. JJCl CICit No. Dye in g / mol cleared districts Districts OCHj. IVIdA. ΙΏμ Ag Πΐμ to 685 24 0.20 1.98 0.06 640 up to 600 25th 0.243 1.99 0.06 565. up to 590 26th 0.20 1.96 0.05 535 exposure without - 2.05 Density at the Increase in

From the results obtained, it is found that all the dyes used are excellent can achieve spectral sensitizations.

Example 3

This example shows that the dyes used according to the invention can also be used together with color coupler dispersions whereas known unsymmetrical two aromatically substituted indole dyes cannot be used as sensitizers can be used in the presence of color coupler dispersions.

A silver halide emulsion as described in Example 1 was prepared again. Different The proportions of the emulsion before it was applied to the substrate were those in the following table specified dyes and color coupler dispersions incorporated. The test items were then as in the example 1 described tested.

dye concentration Dispersion Density in uncoated
cleared districts />"""In illuminated
Districts Sens. Max. Sens. Area g / mole Γϋμ ΓΠμ A *) 0.187 1.66 0.05 630 to 685 A *) 0.187 | *** \ 1.66 Density at the exposure 24 0.60 1.62 630 24 0.60 1***) 1.62 640 C **) 0.675 1.58 Increase in 550 C **) 0.675 2 **** \ 1.57 0.08 Density at to 710 26th 0.735 1.38 0.06 550 up to 700 26th 0.735 2 ****) 1.52 0.06 535 up to 650 the exposure Increase in to 610 0.06 to 580 0.38

*) = l, r-dimethyl-2,2'-diphenyl-3,3'-indolocarbocyanine bromide.

**) = 1,3-Diethyl-r-raethyl-2'-phenylimidazo- [4,5-b] -quinoxolino-3-indolocarbocyanine iodide. ***) = a dispersion of a phenolic cyan coupler of the type described in U.S. Patent 2,474,293

in di-n-butyl phthalate.

****) = a dispersion of a pyrazolone purple coupler of the type described in U.S. Patent 2,600,788 in tri-o-cresyl phosphate.

Example 4

(Comparative example)

There were three typical dyes of the German patent 1 008 118, namely:

Dye 1:

1,1'- dimethyl - 2,2 '- diphenyl - 3,3' - indolocarbo-

cyanine bromide;
Dye 2:

2,2 '- di - ρ - methoxyphenyl - 1,1' - dimethyl-

3,3'-indolocarbocyanine bromide and
Dye 3:

1,1 '- dimethyl - 2,2', 8 - triphenyl - 3,3 '- indolocarbocyanine perchlorate

on their effectiveness, namely in a direct positive emulsion A according to the invention and in a solarizing Direct positive emulsion B tested.

The emulsion A was prepared as follows: First, a gelatin-silver bromoiodide emulsion was prepared with 2.5 mole percent iodide prepared by the method described in Example 1, but with the Sensitizers were added as follows: First, the emulsion per mole of silver 0.25 mg of thiourea dioxide was added, whereupon the emulsion was heated to 65 ° C. for 60 minutes.

Then 2.5 mg of potassium chloroaurate per mole of silver were added to the emulsion, whereupon the emulsion was heated again to 65 ° C for 60 minutes.

Emulsion B was prepared according to the process known in Example 1 of US Pat. No. 2,005,837. (The USA patent specification 2005 837 corresponds to the German patent specification 606 392, which is expressly referred to in the German patent specification 1 008 118 in column 10, line 13.) The pAg value of the emulsion was determined by adding a 3% aqueous Potassium bromide solution adjusted to 8.2.
The following results were obtained:

attempt
No. emulsion dye Relative blue sensitivity
opportunity Relative minus blue
sensitivity D _n ^ - £>"" ■ "
(Minus blue) 1
2 A.
A. 1 1
16 186 1.02

continuation

attempt emulsion dye Relative blue sensitivity Relative minus blue D - D No. opportunity sensitivity (Minus blue) 3 A. 2 15th 229 1.11 4th A. 3 13th 162 Ui 5 B. ■ - 0.27 no reversal 6th B. 1 0.068 0.18 0.64 7th B. 2 slight inversion 0.25 8th B. 3 0.13 0.19 0.55

The measurement results obtained clearly show the particular effectiveness of the dyes in the type of emulsion according to the invention.

Claims (3)

Patent claims: 1. Direct positive, containing a spectral sensitizing dye and an electron acceptor silver halide photographic emulsion of which the silver halide is at least 50 mole percent consists of silver bromide, the silver halide grains of which with a reducing effect Compound and a gold, rhodium, platinum, palladium or iridium compound veiled have been characterized in that they are used as a spectral sensitizing dye a dye of one known per se in its use in direct positive emulsions Dye type of the formulas -Ο-Χ ^θ (I) CH = CH-CY = QX ^e (Π) ■ 7 (W (III)
C = CH-CH-QX © R ₉ R ₁₀ C (IV) C-CH = CH-Q ₁ Χ® contains, wherein R ₁ denotes an optionally substituted alkyl radical, R ₂ and R ₃ individually hydrogen or halogen atoms or optionally substituted alkyl radicals or together the atoms required to complete a fused aromatic ring with 6 carbon atoms, R ₆ a hydrogen or halogen atom or an alkyl radical or together with R ₁ an alkylene radical, R ₇ a hydrogen or halogen atom or a nitro group, R ₈ an aryl radical or heterocyclic radical with 5 or 6 ring atoms, the hetero atom of which consists of a nitrogen, sulfur or oxygen atom, R ₉ , R ₁₀ and R ₁₁ each represent an optionally substituted alkyl or aryl radical, k = 1, 2 or 3, Q which forms a dimethine cyanine or trimethine cyanine dye to complete a desensitizing indole, imidazo - [4,5 - b] - quinoxaline -, 6 - nitrobenzthiazole, 5-nitroindolenine or pyrrolo [2,3-b] pyridoringes required atoms, Q ₁ a radical of the form el - CH = Q, where Q has the meaning already given, Y is a hydrogen atom, an alkyl, alkoxy or aryl radical or a heterocyclic radical and Χ ^{θ is} an acid anion, the emulsion containing selected dyes which a) the emulsion with respect to radiation of wavelengths of more than 480 ηΐμ spectrally sensitize in such a way that the ratio of relative minus blue sensitivity for blue sensitivity is at least 7, b) which are at the same time electron acceptors and where c) the sum of the anodic and cathodic polarographic half-wave potentials results in a positive value. 2. Direct-positive silver halide emulsion according to claim 1, characterized in that it has a Contains spectral sensitizing dye of the following formula: CH = CH-C wherein R ₁ , R ₂ , R ₃ , R ₆ , R7, Rs , k and X® have the meaning given and R ₄ and R ₅ each optionally substituted alkyl or aryl radicals or allyl, alkenyl, alkynyl, cycloalkyl or dialkylaminoalkyl radicals. 3. Direct positive silver halide emulsion according to claim 1, characterized in that it has a Contains spectral sensitizing dye of the following formula: