Direct-positive emulsion containing internally fogged, silver halide grains free of surface fog and a desensitizing compound

Claim 2

The direct positive photosensitive silver halide emulsion of claim 1 wherein said internally fogged silver halide contains on the surface of said silver halide about 209 to about 800 mg. of said desensitizing compound per silver mole in said silver halide.

Claim 3

The direct positive photosensitive silver halide emulsion of claim 1 wherein said desensitizing compound is an imidazoquinolxaline sensitizing dye.

Claim 4

The direct positive photosensitive silver halide emulsion of claim 1 which also contains a sensitizing dye having a polarographic reduction potential more negative than -1.00 V. and an oxidation potential more positive than +0.76 V.

Claim 5

A photographic element comprising a support having thereon a photosensitive silver halide emulsion which provides a maximum density of at least 0.5 upon no sensitometric exposure and processing for 12 minutes at 20*C. in an internal silver halide developer having the composition: water 500 cc. N-methyl-p-aminophenol sulfate 2.0 g. sodium sulfite 90.0 g. hydroquinone 8.0 g sodium carbonate, monohydrated 52.5 g. potassium bromide 5.0 g. potassium iodide 0.5 g. water to make 1 liter; said emulsion comprising internally fogged photosensitive silver halide grains which are free of surface fog and which have on the surface thereof from about 10 to about 800 milligrams per mole of silver of a a cyanine or merocyanine dye selected from the group consisting of (A) cyanine dyes containing desensitizing basic nuclei and merocyanine dyes containing desensitizing basic nuclei or acid nuclei, said cyanine or merocyanine dyes having a polarographic reduction potential less negative than -1.00 V and a polarographic oxidation potential more positive than +0.76 V or (B) cyanine or merocyanine dyes having a polaroprapic reduction potential more negative than -1.00 V and a polarographic oxidation potential more positive then +0.76 V with an auxiliary electron trapping agent having a polarographic reduction potentiAl less negative than -1.00 V and a polarographic oxidation potential more positive than +0.76 V.

Claim 6

The photographic element of claim 6 wherein said photosensitive silver halide consists essentially of a fogged photosensitive silver halide core having thereon a shell of photosensitive silver halide free of surface fog.

Claim 7

The photographic element of claim 6 wherein said internally fogged silver halide contains on the surface of said silver halide about 200 to about 800 mg. of said desensitizing compound per silver mole in said silver halide.

Claim 8

The photographic element of claim 6 wherein said desensitizing compound is an imidazoquinoxaline sensitizing dye.

Claim 9

In a method of preparing an internally fogged photosensitive silver halide emulsion comprising silver halide grains free of surface fog comprising mixing a silver salt solution with a halide solution in a liquid reaction medium wherein the silver salt solution contains about 0.5 to about 7.0 mole percent iodide per mole of silver and wherein the mixing is carried out in the presence of at least 0.5 gram of a thioether silver halide solvent per mole of silver in the liquid reaction medium the improvement comprising adding to the surface of said internally fogged photosensitive silver halide grains about 200 to about 800 mg. of a a cyanine or merocyanine dye selected from the group consisting of (A) cyanine dyes containing desensitizing basic nuclei and merocyanine dyes containing desensitizing basic nuclei or acid nuclei, said cyanine or merocyanine dyes having a polarographic reduction potential less negative than -1.00 V and a polarographic oxidation potential more positive than +0.76 V or (B) cyanine or merocyanine dyes having a polarographic reduction potential more negative than -1.00 V and a polarographic oxidation potential more positive than +0.76 V with an auxiliary electron trapping agent having a polarographic reduction potential less negative than -1.00 V and a polarographic oxidation potential more positive than +0.76 V.

Claim 10

The emulsion of claim 1 wherein the desensitizing compound is a cyanine or merocyanine dye containing at least one desensitizing basic nucleus selected from the group consisting of 1H-imidazo (4,5-b) quinozaline, 3H-pyrido (2,3-b) pyridine, nitro-substituted benzoxazole, nitro-substituted quinoline, nitro-substituted 3H-indole, carbozole, pyrazole, 2-amino-5-thiazole, imidazo (1,2-a) pyridine, 2-pyrrole, pyrrolo (2,3-b) quinoxaline, pyrylium and 2-arylindole.

Claim 11

The emulsion of claim 1 wherein the desensitizing compound is a merocyanine dye containing at least one desensitizing acidic necleus selected from the group consisting of pyrido (1,2-a) pyrimidinedione, tetrazolo (1,5-a) pyrimidin-7-one, quaternated pyrazolones and isoxazolones.

Claim 12

The element of claim 6 wherein the desensitizing compound is a cyanine or merocyanine dye containing at least one desensitizing basic nucleus selected from the group consisting of 1H-imidazo (4,5-b) quinoxaline, 3H-pyrido (2,3-b) pyridine, nitro-substituted benzothiazole, nitro-substituted benzoxazole, nitro-substituted quinoline, nitro-substituted 3H-indole, carbazole, pyrazole, 2-amino-5-thiazole, imidazo (1,2-a) pyridine, 2-pyrrole, pyrrolo (2,3-b) quinoxaline, pyrylium and 2-arylindole.

Claim 13

The element of claim 6 wherein the desensitizing compound is a merocyanine dye containing at least one desensitizing acidic nucleus selected from the group consisting of pyrido (1,2-a) pyrimidinedione, tetrazolo (1,5-a) pyrimidin-7-one, quaternated pyrazolones and isoxazolones.

Claim 14

The method of claim 10 wherein the desensitizing compound is a cyanine or merocyanine dye containing at least one desensitizing basic nucleus selectEd from the group consisting of 1H-imidazo (4,5-b) quinoxaline, 3H-pyrido (2,3-b) pyridine, nitro-substituted benzothiazole, nitro-substituted benzoxazole, nitro-substituted quinoline, nitro-substituted 3H-indole, carbazole, pyrazole, 2-amino-5-thiazole, imidazo (1,2-a) pyridine, 2-pyrrole, pyrrolo (2,3-b) quinoxaline, pyrylium and 2-arylindole.

Claim 15

The method of claim 10 wherein the desensitizing compound is a merocyanine dye containing at least one desensitizing acidic nucleus selected from the group consisting of pyrido (1,2-a) pyrimidinedione, tetrazolo (1,5-a) pyrimidin-7-one, quaternated pyrazolones and isoxazolones.

Claim 16

The emulsion of claim 1 wherein the desensitizing compound is 1,1''-di-n-butyl-4,4''-dipyridinium dibromide.

Claim 17

The emulsion of claim 1 wherein the desensitizing compound is

Claim 18

The emulsion of claim 1 wherein the desensitizing compound is

Claim 19

The emulsion of claim 1 wherein the desensitizing compound is

Claim 20

The element of claim 6 wherein the desensitizing compound is 1,1''-di-n-butyl-4,4''-dipyridinium dibromide.

Claim 21

The element of claim 6 wherein the desensitizing compound is

Claim 22

The element of claim 6 wherein the desensitizing compound is

Claim 23

The element of claim 6 wherein the desensitizing compound is

Claim 24

The method of claim 10 wherein the desensitizing compound is 1,1''-di-n-butyl-4,4''-dipyridinium dibromide.

Claim 25

The method of claim 10 wherein the desensitizing compound is

Claim 26

The method of claim 10 wherein the desensitizing compound is

Claim 27

The method of claim 10 wherein the desensitizing compound is