US 3178284 A
Description (OCR text may contain errors)
United States Patent 3,178,284 PHQTOGRAPHIC DEVELOPER CQMPQSITEUNS David Hugh Gakley John, Sheniield, Brentwood, and George Terence James Field, Chadweil Heath, England, assigaors to May & Baker Limited, Dagenham, England, a British company No Drawing. Filed Apr. 3, 1961., Ser. No. 1%,013 Claims priority, application Great Britain, Apr. 14, 1969, 13,532/ 6% 2 Ciaims. (Cl. 9:1-66) This invention relates to developer compositions for photographic silver halide emulsions, especially concentrated solutions which before use merely require to be diluted with water.
The use of the developing agent l-phenyl-S-pyrazolidone is known. This agent is, however, unstable in alkaline solution and compositions containing it have tended to suffer from considerable loss in activity on storage. This loss of activity is very marked at high temperatures (for example 40-60" C.) and this causes considerable difficulty when the developer is required for use in a tropical climate. This instability is discussed in a paper by Alletag, Phot. Sci. Engng, 1959, 2, 213.
It is an object of the present invention to provide developer compositions of enhanced stability, which are.
suitable for use in tropical countries.
According to one aspect of the present invention, there is provided a developer composition in the form of a solution comprising at least one alkali metal normal sulphite as a preservative, at least one alkali and, as develop- 7 ing agents, l-phenyl-3-pyrazolidone and both hydroquinone and chlorohydroquinone, said composition being capable of being prepared for use by mere dilution with water to yield a solution having a pH of 11.0 to 11.8. These compositions which are prepared for use merely by dilution with water are referred to hereinafter as developer concentrates.
Although the compositions of the invention are preferably in the form of the developer concentrate because this form is more economical to transport and store, they may, if desired, be sold as solutions which are sufliciently dilute to be ready for use and need not be diluted with water, and such solutions are included within the scope of the invention.
The developer compositions ready for use preferably have a pH of 11.0 to 11.5; a particularly convenient pH is 11.3. These pH values and the others in thisspecification are measured on a pH meter using a standard calomel electrode as a reference electrode and a glass electrode.
The compositions may with advantage contain in solution one or more of the following additional ingredients:
a fog restraining agent, e.g. benzotriazole; a bulfering agent, e.g. lactic acid or boric acid; and a silver halide solvent (i.e. a compound which converts the silver halide to a soluble complex ion), e.g. a thiocyanate or thiosulphate. Solutions containing such silver halide solvents and commonly known as monobathsperform a dual function, that is to say they develop and fix the photographic images. It is also advantageous that potassium compounds constitute the main source of alkali metal ions in a the composition.
The alkali metal normal sulphite, which may be added as such or formed in situ by reaction of a-bisulphite with 3,178,284 Patented Apr. 13, 1965 concentration of each of the ingredients must not exceed 7 the solubility thereof in the composition Within the temperature range of conditions of storage and use. The minimum concentration is, of course, dependent on the extent to which the composition is to be diluted before use, which in turn depends on the solubility of the ingredients and the purpose for which the developer is intended. a
In a preferred embodiment of the invention, the developer composition comprises, besides l-phenyl-3-pyrazolidone, chlorohydroquinone and hydroquinone as developing agents, caustic potash as the sole source of alkali, and potassium sulphite as preservative, the composition preferably including a bufiering agent, e.g. lactic or boric acid. a
Preferably, the developer concentrate .contains as developing agents, l-phenyl-3-pyrazolidonein an amount at least equal to 1 gram per litre, cblorohydroquinone in an amount at least equal to 25 grams perv litre, hydroquinone in an amount at least equal to 25 grams per litre and potassium sulphite in amount at least equal to 200 grams per litre, the maximum concentration of all these ingredients not exceeding the solubility thereof in the concentrate within the temperature range of conditions of storage and use. Where, as is preferred, the composition comprises lactic acid, the amount of the additive in the formulation is preferably at least 10 grams per litre.
The invention is illustrated in the following examples.
Example I A developer concentrate is formulated as follows:
Trisodium salt of N-hydroxyethylenediaminetriacetic acid (in the form or" a 34% W./W. aqueous.
Water to make 1000 cc.
On dilution of 1 part by volume of the developer concentrate with 9 parts by volume of water, solutions of pH 11.3 suitable for developing photographic silver halide emulsions are obtained.
Four different batches tested at random over a period of about seven months confirmed the high degree of stability of the concentrate. The photographic activity of these batches was measured both before and after storage at 40 C. for six Weeks. The loss of activity found was ap-.
proximately forty times less than that occurring in one a 7 commercial brand of developer concentrate which pos-l sessed similar photographic properties, and which was known to contain l-phenyl-S-pyragolidone.
Concentration Example No. of potassium pH of diluted hydroxide, composition g./litre The following data compare the stability of the diluted compositions of Examples I to VII against control composition which are identical with them except that they contain lesser quanties of potassium hydroxide giving solutions of pH below 11.0. The fall on storage in the value of the contrast (determined as gamma by conventional means) and speed (determined as Rel log E by conventional means) is an indication of the stability of the developer.
Gamma Rel log E Composition After After 'pH Prestorage Prestorage storage for 12 storage for 12 weeks weeks 3.3 1.2 2.0 1. 32 10. 02 3.3 1.62 2.0 '1. 42 10. 3 3. 3 1. 96 2.0 1. 53 10. 5 3. 3 2. 4 2.0 1. 63 10. 7 3.3 2.7 2.0 1. 75 11.0 3. 3 2. 74 2. O 1. 78 11.1 3. 3 2. 8 2.0 1. 80 11. 2 3. 3 2. 9 2. 0 1. 83 11.3 3.3 3.0 2.0 1.87 11.4 3. 3 3. 12 2.0 1. 91 11. 5 Example VII 3. 3 3. 26 2. 0 1.97 11. 6
' We claim:
1. A developer concentrate comprising an aqueous solution of at least 1 gram per litre of 1-phenyl-3-pyrazolidone, at least 25 grams per litre of hydroquinone, at least 25 grams per litre of chlorohydroquinone, at least 200 grams per litre of an alkali metal sulphite of the formula M (where M represents an alkali metal atom), at least 10 grams per litre of lactic acid and 86 to 108.5 grams per litre of potassium hydroxide.
2. A developer concentrate having the following composition for each 1000 cc.
A 34% by weight aqueous solution of the trisodium salt of N-hydroxyethylenediaminetriacetic acid ml 20 Potassium sulphite g 400 Chlorohydroquinone g 51 Hydroquinone g 51 1-phenyl-3-pyrazolidone g 2.44 Benzotriazole g 3.45 Potassium hydroxide g 94.5 Lactic acid g 23.3 Water to make 1000 cc.
References Cited by the Examiner UNITED STATES PATENTS 2,136,968 11/58 Doran 9666 2,901,350 8/59 Goldhammer.
3,022,168 2/62 Stjarnkvist 96-66 3,088,824 5/63 Jacobs 9666 FOREIGN PATENTS 542,502 1/42 Great Britain.
OTHER REFERENCES Gauvin: Academic des Sciences, Comptes rendus, vol. T236, pp. 807-9 (1953).
Mees: The Theory of The Photographic Process, page 391, The Macmillan Co., New York (1942).
NORMAN G. TORCHIN, Primary Examiner. PHILIP E. MANGAN, Examiner.