US3893862A

US3893862A - Reduced pyridine compounds

Info

Publication number: US3893862A
Application number: US400276A
Authority: US
Inventors: Jal F Munshi; Richard L White
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1973-09-24
Filing date: 1973-09-24
Publication date: 1975-07-08
Anticipated expiration: 1992-07-08

Abstract

Reduced pyridine compounds, including 1,4-dihydropyridine compounds and 1,2-dihydropyridine compounds, are useful as latent image amplifiers. They can be incorporated in a silver halide emulsion or incorporated in a layer adjacent to a silver halide emulsion layer in a photographic element. The reduced pyridine compound may be used in a silver halide developer solution or in an activator solution for use in a silver halide photographic element containing an incorporated developer. Silver halide emulsions when developed in the presence of the reduced pyridine compounds are found to have increased effective speed.

Description

Jnited States Patent lunshi et al.

REDUCED PYRIDINE COMPOUNDS Inventors: Jal F. Munshi; Richard L. White,

both of Rochester, NY.

Appl. No.: 400,276

52] US. Cl 96/66.3; 96/50 R; 96/66 R; 96/76 R; 96/95 31] Int. Cl. G03c 5/30; G03c 1/48 i8] Field of Search 96/50, 66 R, 66.3, 76 R, 96/95 i6] References Cited UNITED STATES PATENTS 288,226 6/1942 Carroll et a1 ..96/107 288,586 6/1942 Dersch et a1 96/665 648,604 8/1963 Welliver et a1 96/663 340,851 6/1960 Beavers et a1 ..96/66.3 520,689 7/1970 Nagne et a1 ..96/66.3 39,048 10/1974 Pool ..96/5O R July 8, 1975 FOREIGN PATENTS OR APPLICATION Primary ExaminerMary F. Kelley Attorney, Agent, or Firm-H. E. Byers [57} ABSTRACT Reduced pyridine compounds, including 1,4- dihydropyridine compounds and 1,2-dihyclropyridine compounds, are useful as latent image amplifiers. They can be incorporated in a silver halide emulsion or incorporated in a layer adjacent to a silver halide emulsion layer in a photographic element. The re duced pyridine compound may be used in a silver halide developer solution or in an activator solution for use in a silver halide photographic element containing an incorporated developer. Silver halide emulsions when developed in the presence of the reduced pyridine compounds are found to have increased effective speed.

24 Claims, No Drawings 1 REDUCED PYRIDINE COMPOUNDS BACKGROUND OF THE INVENTION This invention concerns silver halide emulsions containing reduced pyridine compounds as latent image amplifiers and photographic elements containing a reduced pyridine compound in at least one layer adjacent to a silver halide layer. It also concerns silver halide developer solutions and activator solutions containing reduced pyridine compounds as latent image amplifiers and silver halide photographic elements containing the reduced pyridine compounds. The invention also concerns the process of using the reduced pyridine compounds as latent image amplifiers by developing a silver halide emulsion in the presence of the reduced pyridine compounds.

In the development of photographic materials, it is often desired to increase effective photographic speed of the photographic materials. To obtain this, however, many compounds known in the art as development accelerators increase not only effective emulsion speed but also change the contrast of the developed emulsion. Changes in contrast may not be desirable for normal photographic purposes. For example, increased contrast affects the appearance of the picture to the extent that the pleasing middle tones and details in the shadow and highlight areas are frequently lost. Moreover, many of the known development accelerators increase the fog appreciably of the silver halide emulsion, a feature which is always undesirable. In addition, some of the known development accelerators are not compatible with silver halide emulsions and can only be incorporated in a developing solution or activator solution.

US. Pat, No. 2,648,604, issued Aug. 11, 1953 to Welliver et al., discloses a photographic developer containing a pyridinium salt and process of development. However, when a compound of the type disclosed in this patent is added to a silver halide emulsion, as illustrated in Example 6, below, it is found to have little effect on the relative speed of the emulsion.

US. Pat. No. 3,062,645, issued Nov. 6, 1962 to Carroll, also describes development accelerators but when used in an emulsion as described in Example 7, below, did not appear to effectively increase the relative speed as compared to the compounds of the invention.

Accordingly, it has been desirable to obtain com pounds (latent image amplifiers) which can be used either in a developer solution or in a silver halide element which will increase the effective speed without having a significant increase in fog or contrast and when used in a photographic element also act as chemical sensitizers.

SUMMARY OF THE INVENTION A developer or activator solution is prepared having a reduced pyridine compound as a latent image amplifier. Latent image amplifier" is a term used to define a compound which, in addition to acting as a development accelerator, also acts as a chemical sensitizer when incorporated in a photographic element. The amplifier can be added to the black-and-white developer or to an alkaline color-forming developer in which a primary aromatic amine is used as a developing agent. In a preferred embodiment, reduced pyridine compounds are added to a developer solution containing hydroquinone and N-methyl-p-aminophenol sulfate having a pH of about 1 l. In another embodiment, the reduced pyridine compounds are added to a silver halide emulsion or to a layer adjacent to a silver halide emulsion.

DETAILED DESCRIPTION OF THE INVENTION A wide range of described reduced pyridine compounds can be employed according to the invention. Suitable l,4-dihydropyridine compounds include, for example, compounds of the formula:

in which R is carbamoyl, carboxyalkyl, alkoxycarbonyl, acyl, all having l-S carbon atoms, cyano or halogen; R' is aryl, aralkyl or alkyl, substituted or unsubstituted, having l-12 carbon atoms; R is hydrogen or halogen: and 1,2-dihydropyridine compounds having the formula in which R' and R"" are each selected from the class consisting of an aliphatic radical of not more than five carbon atoms, said radical selected from the group consisting of alkyl, chloroalkyl, bromoalkyl, hydroxyalkyl. carboxymethyl, carbalkoxymethyl and alkoxyalkyl, and R' and R"", when taken together are atoms forming a 5-6 member heterocyclic ring containing an O. N, or S atom. Particularly useful compounds are disclosed in the following Compound Identification Table. When used in a developer solution, the concentration is typically within the range of about 0.020 to about 0.300 grams per liter, preferably 0.025 to 0.150 grams per liter. When used in a silver halide emulsion, the concentration is about 2.0 to about 300.0 milligrams per mole of silver, preferably about 6.0 to about 100.0 milligrams per mole of silver. This is also the concentration typically used when the latent image amplifier is incorporated in a layer adjacent to the silver halide emulsion layer.

Compound R R R" Name I -CONH CH H l-Benzyll ,4-dihydronicotanamide ll -COOCH; -CH H Methyl-l-benzyI-l ,4-dihvdronicotinate lll -COCH;, -CH H 3-Acetyll -benzyll ,4-dihydropyritline lb CONH -CH;, H S-Carhumoyl- ,4-dihydro l -methyI-pyridine VI CN -CH;, H 3-Cyano-l ,4-dihydrol -methylpyridine VI --COCH; -CH-,CH; H 3-Acelyll ,4-dihydro- 1 -ethylpyridine V": CI -CH-,C,,H;, Cl l-Benzyl-3.5-dichloro-l .4dihydro-pyridine IX ErON -CH-,C,,H H l-Benzyl-3-bromol ,4-dihydropyridine H H 2(3-Carbamoyl-l .4-dihydro-1-pyridyll-hydroquinone 1,2-Dihydropyridine Compounds X 8-Chloro-3-methyl-l-phenyll H-pyrido-l 2,1-h lbenzothiazole Photographic silver halide emulsions, preparations, addenda, processing and systems are disclosed in Product Licensing Index, Volume 92, December 197], Publication 9232, pages 107-110, Paragraphs l-XXV.

The reduced pyridine compounds of the invention can be added to developer solutions, including those referred to in the Product Licensing lndex referred to above, a. any time during the preparation of the developing solution.

In addition. the reduced pyridine compounds may be used in activator solutions at the same concentrations as used in a developer solution when the developer is incorporated in the photographic element.

Alkaline activators which can be employed in developing a latent image in a photographic element as described include any of those which provide the desired activation of the described silver halide developing agent precursor. These include, for instance, aqueous alkaline activator solutions commonly employed in rapid access processing of photographic elements, such as those employed in so-called reader-printers. Alkaline activators which are suitable include inorganic alkali such as alkali metal hydroxides, especially sodium hydroxide, potassium hydroxide and/or lithium hydroxide, alkali metal carbonates, such as sodium carbonate and potassium carbonate, sodium or potassium phosphates, and organic alkaline development activators such as quaternary ammonium bases and salts and alkanolamines such as ethanol amine, and similar alkaline materials and/or alkali releasing materials. Such development activators can be applied to the photographic element employed in the practice of the invention in any suitable manner, including for example, dipping, spraying and/or surface application such as with rollers, as described in U.S. Pat. No. 3,025,779 of Russell et al issued Mar. 20, 1962 or by surface application processing as described in U.S. Pat. No. 3,418,132 of Kitze issued Dec. 24, 1968.

If desired an alkaline solution can be employed containing conventional silver halide developing agents, such as those described. So-called web processing can be employed as described, for example, in U.S. Pat. No. 3,179,517 ofTregillus et a1. issued Apr. 20, 1965 or socalled stabilization processing as describes in Russell et al., PSA Journal, vol. 161), Aug, 1950.

The time for processing a photographic element in the practice of the invention, that is developing and sta bilizing a desired latent image, can vary over a wide range, typically between about 1 second to several minutes depending on the desired image, processing conditions and the like.

The conditions for processing can also vary. but usually ambient pressures and temperatures of about 20C. to about 30C. are employed. lfdesired, higher temperatures can be used such as temperatures up to about 50C.

It can be useful in some cases to wash the resulting photographic element after processing with water, such as a water rinse, for about 1 second to about 5 seconds to remove water-soluble compounds. This can improve post-processing stability and reduce any strain.

The photographic silver halide developer solutions can comprise a silver halide solvent. Typical silver halide solvents include, for example, alkali metal or ammonium thiosulfates and thiocyanates, such as sodium thiosulfatc, sodium thiocyanate or ammonium thiocyanulc.

The developer solution, as described, can be a monobath. Typical compounds of monobaths are described, for example, in the Monobath Manual," by Grant M. Haist, published by London Press, 1966.

The following examples are included for a further understanding of the invention:

EXAMPLE l A developing solution having the following formulation is prepared.

Formula Hydroquinone 40.0 grams Sodium sulfite 60.0 grams Elon (N-methyl-p-aminophenol sulfate) 10.0 grams Potassium bromide 5.0 grams Distilled water to 1.0 liter Potassium hydroxide to pH 1 1.2

To portions of this developing solution are added the latent image amplifiers (reduced pyridine compounds) of the present invention at the concentrations indicated below. Samples of a coarse grain, medium speed, silver bromoiodide gelatin emulsion (Type A) are exposed (1/50" Neg.)** and the samples are then processed in a roller transport processor (28 sec. development at 32C) with the following photographic results. 500 watt exposure on an Eastman Model 18 Sensitometer at a color temperature distribution of 2650 to 5400 Kelvin. Trademark Samples of a fine grain silver bromoiodine gelatin emulsion (Type B) are exposed and processed as in Example l, except a 14 sec. development time is used.

Relative Compound g/l. Speed Contrast Fog Control 1.79 .06 l .025 159 1.50 .08 l .050 263 1.33 .16

EXA MPLE 3 The photographic elements of Examples 1 and 2 are processed for 56 sec. and 40 sec. respectively, in a developer as described in Example 1 plus 0.06 g/l. S-methyl-benzotriazole plus 0.25 g/l. S-nitroindazole containing a compound of the present invention.

Relative Emulsion C om g/ l. Speed Contrast Fog pound Type A Control 100 2.23 .08 Type A l .10 I35 2.42 .08 Type A l .20 148 2.99 .08 Type A 1 .30 200 3.65 .03 Type B Control I 2.03 .06 Type B 1 .10 ns 2.16 .06 Type B l .20 126 2.43 .06 Type B I .30 166 2.50 .06

EXAMPLE 4 A monodispersed fine grain silver bromoiodide emulsion (Type B) is given a finishing treatment with sodium thiosulfate. potassium chloroaurate and sodium thiocyanate. The reduced pyridine compounds are added to this emulsion. coated on a support, exposed (1/5" Pos)* and processed in Kodack Developer D-l9 a high contrast developer having the formula pmethylaminophenol sulfate 8.8 g.; sodium sulfite. dessicated, 384.0 g.; hydroquinone 35.2 g.; sodium carbonate. dessicated, 192.0 g.; potassium bromide 20.0 g.; cold water to make 4.0 liters. The results are shown below:

"500 watt exposure on an Eastman Model lB Sensitometer at a color temperature of 3000"Kelvin.

Concentration Relative Compound (mg/mole of Ag) Speed Contrast Fog Control 100 2. l .04 I 5 209 l .7 .06 X 2 5 l 3 2 .0 .04 X 6 603 l .9 .24

Quaternary pyridinium compounds which speed up the early part of a development process are commonly referred to as development accelerators. The oxidized form of l which is l-benzyl-3-carbamoylpyridinium chloride (Xl) is inactive in the developer solutions under the test conditions outlined above. Further tests with this compound incorporated in silver halide emulsions clearly exclude it as the active component.

EXAMPLE 5 Solutions of compounds I, XI and 2-methyl-lphenethyl pyridinium iodide (Xll) are added to an emulsion of Type B and digested for 10 minutes at 40C. These are coated on a support, exposed (l" Pos)* and processed in an Elon-hydroquinone developerv 500 watt exposure on an Eastman Model H; Sensitometer at a color temperature of 3000 Kelvin.

EXAMPLE 6 Tetradecamethylenebis( l l -pyridinium )perchlorate (Xlll) is described in US. Pat. No. 3,062,645 as a de velopment accelerator. lt is comparatively tested in emulsion of Type B, exposed (1/5" Pos)* and processed in Kodak Developer Dl9, as shown below:

Concentration Relative Compound (mg/mole of Ag) Speed Contrast Fog Control 3.0 .04

This illustrates the improved results obtained by the compounds of the invention.

EXAMPLE 7 A medium speed bromoiodide emulsion (Type C) is given a finishing treatment with sodium thiosulfate, potassium aurochlorate and sodium thiocyanate. Compound X is added to it, digested for 5 minutes and coated, exposed (1/50" Neg) and processed in Kodak Developer D-l9 (3 minutes).

500 watt exposure on an Eastman Model lB Sensitometer at a color temperature of 3000" Kelvin.

Concentration Relative Compound (mg/mole of Ag) Speed Contrast Fog Control 100 1.8 .18 X 0.5 182 1.9 .36

EXAMPLE 8 Reduced pyridines are also incorporated in a gelatin overcoat spread over the emulsion layer. A conventional antifoggant is added to emulsion of Type C and coated, Compound I is added to a gelatin solution which is spread at a uniform concentration over the emulsion layer, exposed (1/50" Neg)" and processed in Kodak Developer D-l9.

"500 watt exposure on an Eastman Model [B Sensitometer at a color temperature distribution of 2650 to 5400 Kelvin.

Concentration Relative Com pound (mg/m"') Speed Contrast Fog Control I00 2.00 .08 l I08 l5 1 1.94 .13

EX AMPL E 9 Compound I is added to a gelatin solution which is spread uniformly over a coarse grain, medium speed. silver bromoiodide gelatin emulsion (Type A) at a concentration of 6.5 mg/m exposed (1/50" Neg)** and processed in Kodak Developer Dl9.

"500 watt exposure on an Eastman Model 18 Sensitometer at a color temperature distribution of 2650 to 5400 Kelvin.

Relative Compound Speed Contrast Fog Control l00 196 .05

l l48 L94 l 0 The invention has been described with particular reference to preferred embodiments thereof but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

We claim:

1. An alkaline photographic developer composition for silver halide comprising an aromatic silver halide developing agent and a reduced pyridine compound selected from the class consisting of l,4-dihydropyridine compounds having the formula:

I RYI'I wherein R' and R"", taken separately. are each an aliphatic radical of not more than five carbon atoms that is selected from the group consisting of an alkyl radical. a chloroalkyl radical, a bromoalkyl radical, a hydroxyalkyl radical, a carboxymethyl radical, a carbalkoxymethyl radical and an alkoxy alkyl radical and R' and R"", taken together, are the atoms necessary to form a -6 member heterocyclic ring containing an O, N or S atom.

2. An alkaline photographic developer composition of claim 1 containing l-benzyl-1,4- dihydronicotinamide.

3. An alkaline photographic developer composition of claim 1 containing methyl-l-benzyl-l ,4- dihydronicotinate.

4. An alkaline photographic developer composition of claim 1 containing 3-acetyl-l-benzyl-l ,4- dihydropyridine.

5. An alkaline photographic developer composition of claim 1 containing B-carbamoyl-l,4-dihydro-lmethyl-pyridine.

6. An alkaline photograhie developer composition of claim 1 containing 3-cyanol ,4-dihydrol methylpyridine.

7. An alkaline photographic developer composition of claim 1 containing 3-acetyl-l,4-dihydro-lethylpyridine.

8. An alkaline photographic developer composition of claim 1 containing l-benzyl-3,5-dichloro-l,4 dihydropyridine.

9. An alkaline photographic developer composition of claim 1 containing l-benzyl-3-bromo-l ,4- dihydropyridine.

10. An alkaline photographic developer composition of claim 1 containing 2(3-carbamoyl-l ,4-dihydro-1- pyridyl)-hydroquinone.

11. An alkaline photographic developer composition of claim 1 containing 8-chloro-3-methyl-4-phenyl-lH- pyridobenzothiazole.

[2. A process for the development of a photographic image, comprising treating an exposed silver halide emulsion with an alkaline photographic developer composition comprising an aromatic silver halide developing agent, said treatment being in the presence of a latent image amplifier which is selected from the class consisting of 1,4-dihydropyridine compounds having the formula:

wherein R is a carbamoyl radical, a carboxyalkyl radical having from 1 to 8 carbon atoms, an alkoxycarbonyl radical having from l to 8 carbon atoms, an acyl radical having from 1 to 8 carbon atoms, a cyano radical or a halogen atom; R is an aryl radical or an alkyl radical, each being substituted or unsubstituted and having from 1 to l2 carbon atoms; and R" is a hydrogen atom or a halogen atom, and l,2-dihydropyridine compounds having the formula:

wherein R' and R"", taken separately, are each an aliphatic radical of not more than five carbon atoms that is selected from the group consisting of an alkyl radical, a chloroalkyl radical, a bromoalkyl radical, a hydroxyalkyl radical. a carboxymethyl radical, a carbalkoxymethyl radical and an alkoxy alkyl radical and R' and R"". taken together, are the atoms necessary to form a 5-6 member heterocyclic ring containing an O, N or S atom.

13. A photographic image forming composition comprising silver halide and a reduced pyridine compound selected from the class consisting of L4- dihydropyridine compounds having the formula:

wherein R is a carbamoyl radical, a carboxyalkyl radical having from 1 to 8 carbon atoms, an alkoxycarbonyl radical having from l to 8 carbon atoms, an acyl radical having from 1 to 8 carbon atoms, a cyano radical or a halogen atom; R is an aryl radical or an alkyl radical, each being substituted or unsubstituted and having from 1 to 12 carbon atoms; and R" is a hydrogen atom or a halogen atom, and l,2-dihydropyridine compounds having the formula:

p I t, ,r

l ii 't/ i wherein R' and R", taken separately, are each an wherein R is a carbamoyl radical, a carboxyalkyl radical having from l to 8 carbon atoms, an alkoxycarbonyl radical having from I to 8 carbon atoms, an acyl radical having from 1 to 8 carbon atoms, a cyano radical or a halogen atom, R is an aryl radical or an alkyl radical, each being substituted or unsubstituted and having from 1 to 12 carbon atoms; and R" is a hydrogen atom or a halogen atom, and l,2-dihydropyridine compounds having the formula:

wherein R' and R"", taken separately, are each an aliphatic radical of not more than five carbon atoms that is selected from the group consisting of an alkyl radical, a chioroalkyl radical, a bromoalkyl radical, a hydroxyalkyl radical, a carboxymethyl radical, a carbalkoxymethyl radical and an alkoxy alkyl radical and R' and R"", taken together, are the atoms necessary to form a 5-6 member heterocyclic ring containing an O, N or S atom.

15. A photographic element of claim 14 containing l-benzyl-1,4-dihydronicotinamide 16. A photographic element of claim 14 containing methyl-l-benzyl-1,4-dihydronicotinate.

17. A photographic element of claim 14 containing S-acetyll -benzyll ,4-dihydropyridine.

18. A photographic element of claim 14 containing 3-carbamoyl-l ,4-dihydrol-methyl-pyridine.

19. A photographic element of claim 14 containing 3-cyano-l ,4'dihydrol-methylpyridine.

20. A photographic element of claim 14 containing S-acetyll ,4-dihydrol -ethylpyridine.

21. A photographic element of claim 14 containing l-benzyl-3,5-dichlorol ,4-dihydropyridine,

22. A photographic element of claim 14 containing l-benzyl-3-bromo-l ,4-dihydropyridine.

23. A photographic element of claim 14 containing 2(3-carbamoyll ,4-dihydrol-pyridyl)-hydroquinone.

24. An alkaline photographic element of claim 14 containing S-chloro-3-methyl-4phenyll H-pyridobenzothiazole.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT N0. 3,893,862

DATED July 8, 1975 INVENTOR(S) Jal F. Munshi and Richard L. White I! is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 7, line 59, photograhid' should read ---photographic--.

Column 8, line 9, should read pyrido-[2,l-b] benzothiazole Column 9, lines 33-42 the formula should read as follows Column 9, lines 10-18 the formula should read as follows H H rr R Column 10, line 5, before the word "hehzothiazole insert [2,1-b]

glgncd and Scaled this [SEAL] thirtieth D3) 0f September1975 Arrest:

RUTH C. MASON ummrssrnrrcr u] Pan-ms and Trademarks

Claims

1. AN ALKALINE PHOTOGRAPHIC DEVELOPER COMPOSITION FOR SILVER HALIDE COMPRISING AN AROMATIC SILVER HALIDE DEVELOPING AGENT AND A REDUCED PYRIDINE COMPOUND SELECTED FROM THE CLASS CONSISTING OF 1,4-DIHYDROPYRIDINE COMPOUNDS HAVING THE FORMULA:

2. An alkaline photographic developer composition of claim 1 containing 1-benzyl-1,4-dihydronicotinamide.

3. An alkaline photographic developer composition of claim 1 containing methyl-1-benzyl-1,4-dihydronicotinate.

4. An alkaline photographic developer composition of claim 1 containing 3-acetyl-1-benzyl-1,4-dihydropyridine.

5. An alkaline photographic developer composition of claim 1 containing 3-carbamoyl-1,4-dihydro-1-methyl-pyridine.

6. An alkaline photograhic developer composition of claim 1 containing 3-cyano-1,4-dihydro-1-methylpyridine.

7. An alkaline photographic developer composition of claim 1 containing 3-acetyl-1,4-dihydro-1-ethylpyridine.

8. An alkaline photographic developer composition of claim 1 containing 1-benzyl-3,5-dichloro-1,4-dihydropyridine.

9. An alkaline photographic developer composition of claim 1 containing 1-benzyl-3-bromo-1,4-dihydropyridine.

10. An alkaline photographic developer composition of claim 1 containing 2(3-carbamoyl-1,4-dihydro-1-pyridyl)-hydroquinone.

11. An alkaline photographic developer composition of claim 1 containing 8-chloro-3-methyl-4-phenyl-1H-pyrido- benzothiazole.

12. A process for the development of a photographic image, comprising treating an exposed silver halide emulsion with an alkaline photographic developer composition comprising an aromatic silver halide developing agent, said treatment being in the presence of a latent image amplifier which is selected from the class consisting of 1,4-dihydropyridine compounds having the formula:

13. A PHOTOGRAPHIC IMAGE FORMING COMPOSITION COMPRISING SILVER HALIDE AND A REDUCED PYRIDINE COMPOUND SELECTED FROM THE CLASS CONSISTING OF 1,4-DIHYDROPYRIDINE COMPOUNDS HAVING THE FORMULA:

14. A photographic element comprising a support having thereon at least one silver halide layer and a reduced pyridine compound selected from the class consisting of 1,4-dihydropyridine compounds having the formula:

15. A photographic element of claim 14 containing 1-benzyl-1,4-dihydronicotinamide.

16. A photographic element of claim 14 containing methyl-1-benzyl-1,4-dihydronicotinate.

17. A photographic element of claim 14 containing 3-acetyl-1-benzyl-1,4-dihydropyridine.

18. A photographic element of claim 14 containing 3-carbamoyl-1, 4-dihydro-1-methyl-pyridine.

19. A photographic element of claim 14 containing 3-cyano-1,4-dihydro-1-methylpyridine.

20. A photographic element of claim 14 containing 3-acetyl-1,4-dihydro-1-ethylpyridine.

21. A photographic element of claim 14 containing 1-benzyl-3,5-dichloro-1,4-dihydropyridine.

22. A photographic element of claim 14 containing 1-benzyl-3-bromo-1,4-dihydropyridine.

23. A photographic element of claim 14 containing 2(3-carbamoyl-1,4-dihydro-1-pyridyl)-hydroquinone.

24. An alkaline photographic element of claim 14 containing 8-chloro-3-methyl-4-phenyl-1H-pyrido- benzothiazole.