GB2027920A - Photographic silver halide developer composition - Google Patents

Abstract

High contrast photographic silver halide developer compositions with increased solution stability (dish or machine life) comprise a superadditive development agent combination, sulphite ions and an amount of a contrast-increasing substituted indazole which provides a concentration of at least 65 mg/litre of the indazole in the working solution. The composition may additionally contain up to 60 g/litre sodium sulphite and/or 25-75 g/litre of sodium chloride and/or an amine, e.g. an alkanolamine.

Description

SPECIFICATION Photographic high contrast developer compositions This invention relates to photographic high contrast developer compositions for use in making halftone photographic intermediates for use in printing processes.

The obtaining of very high contrast using the so-called lith effect or infectious development was described by J. A. C. Yule in the Journal of the Franklin Institute, 239 (1945) 221-230.

Such developers rely on the use of hydroquinone as sole developing agent and a controlled supply of sulphite ions.

British Specification 1,376,600 describes developer compositions for obtaining very high contrast images which contain a pdihydroxybenzene developing agent, sulphite ions, alkali and a nitroindazole or nitrobenzimidazole with the proviso that the composition should contain no more than 0.5g/l of an auxiliary developing agent showing a superadditive effect. The specification at p.4 1.34 warns that larger amounts of auxiliary superadditive developing agent will destroy the lith effect.

We have now found that lith developers can be formulated using a superadditive developing agent combination in the presence of a group of compounds which include 5-nitroindazole.

According to the present invention there is provided a high contrast silver halide developing composition which comprises a superadditive developing agent combination, sulphite ions and an amount of a contrast-increasing substituted indazole which provides a concentration of at least 65 mg/litre of the indazole in the working solution.

The contrast-increasing substituted indazole produces an increase in contrast in the silver halide emulsion layer which is developed and may, for example, be 5-nitroindazole, 6nitroindazole, 5-chloroindazole or 5-cyanoindazole. Its concentration in the working solution is preferably from 65 mg/l to 1 g/l, particularly from 150 mg/l to 500 mg/I.

The superadditive developing agent combination preferably comprises hydroquinone and p methylaminophenol sulphate. The working solution may, for example, contain 20-50 g/litre of hydroquinone and a superadditive quantity of pmethyl-aminophenol sulphate, e.g. 2-7g/litre.

However, other superadditive combinations may be employed, for example, 20-50g/l of ascorbic acid with 0.3-1.0g/l of l-phenyl-3-pyrazolidone.

The use of a superadditive developing agent combination can lead to an increase in speed of the developed silver halide material and to increased developer solution stability (dish or machine life) while retaining the high contrast performance of previously known developers containing hydroquinone only. As suggested above the present developer compositions may be employed in both machine and dish processing with good results.

The present developer compositions may contain free sulphite ions corresponding to a concentration of sodium sulphite of up to 60g/l of the working solution. The compositions may also contain an alkali metal chloride corresponding to a concentration of sodium chloride of 25-75g/l of the working solution.

The present developer compositions may also contain an amine, for example an alkanolamine, e.g. 2-methylaminoethanol. They may also contain development accelerators e.g. non ionic development accelerators, antifoggants and restrainers. When potassium bromide is used its concentration should be no more than 1 gm/I. Nucleating agents as described in British Specification 1,061,294 may also be used to obtain even higher contrast.

The present developer compositions may be in the form of a working solution, a liquid concentrate, a powder or a kit including liquid and/or powder constituents.

The silver halide emulsion to be developed may be a 100% silver chloride emulsion or a predominantly silver chloride emulsion which may contain up to 5% silver bromide and/or 1 % silver iodide (mole percentages). The preferred emulsions have a mean grain size of 0.5 to 0.5 jum and may be monodisperse, especially cubic regular. The emulsions may be made and may contain addenda as described in PLI December 1971 pp.107-110 published by Industrial Opportunities Limited, Havant, Hampshire.

The present invention further provides a method of processing a high contrast silver halide emulsion comprising 94-100 mole % chloride, 0-5 mole % bromide and 0-1 mole % iodide which comprises the step of developing it in a developer composition of the present invention.

The development process may take place at a temperature of from 15 to 45 C. It is preferred to use a high rate of agitation to obtain optimum dot quality.

The following Examples are included for a better understanding of the invention. Anhydrous reagents are used unless otherwise stated.

Example 1 A developing solution was prepared as follows: pmethylaminophenol sulphate 5g Hydroquinone 40g Sodium sulphite 50g Sodium chloride 50g Sodium carbonate 43g 2 methylaminoethanol 42ml 5-nitroindazole 1% solution 16ml in a 50:50 by volume mixture of acetic acid and methanol Water to 1 litre An ortho-dye-sensitized 100% silver-chloride emulsion with 0.25 micrometre cubic grains coated on poly(ethyleneterephthalate) film base was exposed for 10 seconds under a continu ous-tone step wedge to the light from a 48 watt, 6 volt 'point-source' tungsten lamp at 1 metre distance, the light being modified by a Corning OB8 filter.Strips of the exposed film were dish processed in 150 ml of the developer for 45, 60 and 90 seconds at 30 C. Development, in this and the following examples, was stopped by bathing in a 2% acetic acid bath for 10 seconds followed by conventional fix, wash and drying stages. The results are given in Table I below.

Example 2 A developing solution was prepared as follows: Ascorbic acid 20g 1-phenyl-3-pyrazolidone 0.5g Sodium sulphite 50g Sodium carbonate 43g Sodium chloride 50g 2-methylaminoethanol 50ml 5-nitroindazole 1 % solution 30ml (as used in Example 1) Water to make 1 litre Exposed film strips, as in Example 1, were processed in this developer for 60, 90 and 120 seconds at 30 C. The results are given in Table I below: 'Table I Log Dev. Time Relative Base + Fog Example No. Seconds Speed Gamma Density 1 45 0.61 16 0.06 1 60 0.64 31 0.06 1 90 0.64 31 0.06 2 60 0.50 16 0.03 2 90 0.50 18 0.04 2 120 0.50 18 0.04 Example 3 The silver chloride emulsion coating of Example 1 was exposed in vacuum contact with a Kodak Gray Contact Screen (Negative) Elliptical dot with a ruling of 133 lines/inch. Exposed strips were developed in 150 ml of the developer described in Example 1 and halftone dots of high quality were obtained.

Claims (15)

1. A high contrast silver halide developing composition which comprises a superadditive developing agent combination, sulphite ions and an amount of a contrast-increasing substituted indazole which provides a concentration of at least 65 mg/litre of the indazole in the working solution.

2. A developing composition as claimed in Claim 1 in which the substituted indazole is 5 nitroindazole, 6-nitroindazole, 5-chloroindazole or 5-cyanoindazole.

3. A developing composition as claimed in Claim 1 or 2 in which the amount of the indazole is such that it provides a concentration of from 65 mg/litre to 1 g/litre, particularly from 150 mg/litre to 500 mg/litre in the working solution.

4. A developing composition as claimed in any of Claims 1-3 in which the superadditive developing agent combination comprises hydroquinone and pmethylaminophenol sulphate.

5. A developing composition as claimed in Claim 4 in which the amount of the developing agents is such that there is provided 20-50 g/litre of hydroquinone and 2-7 g/litre of p methylaminophenol sulphate in the working solution.

6. A developing composition as claimed in any of Claims 1-3 in which superadditive developing agent combination comprises ascorbic acid and 1-phenyl-3-pyrazolidone.

7. A developing composition as claimed in Claim 6 in which the amount of the developing agents is such that there is provided 20-50 g/litre of ascorbic acid and 0.3-1.0 g/litre of 1phenyl-3-pyrazolidone in the working solution.

8. A developing composition as claimed in any of Claims 1-7 which contains an amount of sodium sulphite which provides a concentration of up to 60 g/litre in the working solution.

9. A developing composition as claimed in any of Claims 1-8 which contains an alkali metal chloride in an amount which provides an equivalent of 25-75 g/litre of sodium chloride in the working solution.

10. A developing composition as claimed in any of Claims 1-9 which contains an amine, particularly an alkanolamine.

11. A high contrast silver halide developing composition substantially as described herein and with reference to the Examples.

12. A method of processing a high contrast silver halide emulsion comprising 94-100 mole % chloride, 0-5 mole % bromide and 0-1 mole % iodide which comprises the step of developing it in a developer composition according to any preceding claim.

13. A method as claimed in Claim 12 in which the developing step is effected at a temperature of 15-45 C.

14. A method as claimed in Claim 12 or 13 in which a high rate of agitation is employed during the developing step.

15. A method according to Claim 12 substantially as described herein and with reference to the Examples.