US2599518A

US2599518A - High contrast photographic developers

Info

Publication number: US2599518A
Application number: US222940A
Authority: US
Inventors: Schwarcz Morton
Original assignee: EDWAL LAB Inc
Current assignee: EDWAL LAB Inc; EDWAL LABORATORIES Inc
Priority date: 1951-04-25
Filing date: 1951-04-25
Publication date: 1952-06-03
Anticipated expiration: 1969-06-03

Description

Patented june 3, 1952 HIGH CONTRAST PHOTOGRAPHIC DEVELOPERS Morton Schwarcz, Highland Park, 111., assignor to The Edwal Laboratories, Inc., Ringwood, 111.,

a corporation of Illinois No Drawing. Application April 25, 1951,

12 Claims.

This invention relates to photographic developers. More particularly, this invention relates to high contrast photographic developers. Still more particularly, this invention relates to high contrast photographic developers having a markedly longer working life than hitherto known developers of this type.

As is well known to those skilled in the art, photographic developing solutions usually contain at least one component selected from each of four different types of materials, namely, developing agents, preservatives, alkalies and restrainers. Most developing agents in pure form are slightly acid or neutral in reaction and exhibit feeble reducing action or even no reducing action with respect to the silver halide latent image. For this reason, an alkali is usually incorporated in the developing solution to accelerate the reducing action. Developing agents in alkaline solution react with and are more or less rapidly destroyed by atmospheric oxygen. To retard or prevent this oxidation of the developing agent by atmospheric oxygen a preservative, such as an alkali metal sulfite, is added to stabilize the developer solution. A restrainer, such as an alkali metal bromide or benzotriazole, is usually incorporated in developer solutions to reduce or eliminate reduction of the unexposed portions of the negative or print being developed.

. In most instances it is desired to develop a negative to a state of intermediate contrast and many photographic developing formulations are available that accomplish this end in an eminently satisfactory fashion. However, in certain specific fields, high contrast negatives are essential. For example, in the graphic arts, high contrast negatives are essential for the preparation of satisfactory off-set plates and similar reproduction media.

I-Iydroquinone is characterized by its inherent ability to produce high contrast negatives. However, due to the low reduction potential of this developing agent, a very strong alkali, for example, an alkali metal hydroxide, is necessary to obtain reasonable developing speed when hydroquinone is the sole developing agent present. Under conditions of high alkalinity, the activity of this developing agent .is at such a high level that the density of exposed portions of the film is built up very rapidly and a strong contrast negative results.

Unfortunately, hydroquinone in strongly alkaline solution is extremely susceptible to air oxidation so that even in the presence of preservatives Serial No. 222,940

such solutions have a working life of onlya few minutes. In addition, such strongly alkaline solutions have a deleterious action on the hands of technicians using such solutions in the processing of negatives.

In orderto overcome these disadvantages of. highly alkaline high contrast developing solu-' tions it has been the practice in the prior art to prepare high contrast developing solutions at a lower pH value than required for the activity necessary to produce high contrast negatives, at.

the same time incorporating in such solutionsa material that results in the continuous .production of a strong alkali over a considerable period of time. Among such auxiliary agents employed in formulations of the prior art may be men-' aldehyde in turn reacts with the alkali metal;

sulfite present (as a preservative) with the production of alkali metal hydroxide in accordance,

with the reaction:

CH20+Na2SO3+H20=CH2(OI-I SOsNa+NaOH The sodium hydroxide formed as above indicated activates the developer to such a degree that high contrast negatives are produced. It is to be understood that this explanation represents theory only and I do not wish to be bound by the explanation offered.

High contrast developing solutions of the prior' art containing formaldehyde releasing compounds of the above nature represent a considerable advance over hydroquinone-sodium hydroxide solutions but even these improved formulations are far from perfect. For example, the prior art high contrast developing solutions containing formaldehyde releasing compounds have a working life of four hours or less. In the lithographic shop this means that freshdeveloper solution must be prepared twice each shift.

I have discovered that if the formaldehyde. releasing compound found in prior art formula-f tions is replaced with a methylol derivative, for

example, a hydantoin carrying at least i one methylol group, a high contrast developer results.

whichhas a working life of 24 hours or more; One object of my invention is to provide an improved high contrast photographic developer solution. I I

Another object of my invention is to provide' high contrast photographic developer solutions having a markedly longer working life than hitherto known developers of this type.

Additional objects of my invention will become apparent as the description thereof proceeds.

For the better understanding of my invention, it will be described in connection with illustrative but non-limiting examples thereof. In accordance with conventional practice, in the formulas of the examples the several components are listed in the order in which they are added to the water.

Example 1 Water quarts 3 Sodium sulfite g- 120 Hydroquinone g 90 Borlc acid g Sodium bromide g 5.6 Sodium bisulfite g 10.5 Monomethylol 5,5-dimethyl hydantoin g 30 Water to .gallon 1 It will be noted that the above formulation contains hydroquinone which, because of its low reduction potential, requires the presence of a strong alkali for activation to. the degree necessary for the production of high contrast negatives. However, this formulation contains no strong alkali. Nevertheless, this formulation (after. dilution with additional water if desired) produces, by virtue of the methylol derivative contained therein, an excellent high contrast developing solution having a working life of 24 hours. or longer in distinct contrast to formulations of the prior art for the same purpose which have a working life of four hours or less.

It is believed that the formaldehyde releasing compounds of prior art high contrast developer formulations decompose with the release of formaldehyde at too rapid a rate. As a result, the developing agent is converted to the active 'form more rapidly than is required by the developing process itself and as a result a large part of the highly active developing agent reacts.

with and is destroyed by atmospheric oxygen resulting in a short working life. On the other hand, the improved formaldehyde releasing compounds of my invention are more stable and decompose at sucha rate that activated developing agent becomes available at approximately the rate necessary to give the desired developing action. As a result, most if not all of the developing agent of the formulations of my-invention is employed in the reduction of the latent image while little if any is destroyed byreaction with atmospheric oxygen. Again it is to'be understood that this explanation represents theory only and I am in no way to be bound thereby.

If desired, a stock solution may be prepared in accordance with the above formula with the exception that the methylol derivative is omitted. Such a stock solution is very stable. Then, just before use, the methylol derivativemay be added to give a high contrast developing solution. By operating in this manner, a stable stock solution may be prepared by a manufacturer of photographic chemicals under carefully controlled conditions with respect to purity and volume of water, the composition, purity and weight of chemicals employed, et cetera. When a high contrast developing solution is-needed in the lithographic shop it is only necessary to add the required amount of the methylol derivative to this stock solution.

Example 2 Water cc 750 Sodium sulfite g 100 Sodium metasilicate g 24 Hydroquinone g Boric acid g 12 Sodium bromide g 9 Benzotriazole g 3 Sodium hydroxide g 21 Monomethylol 5,5-dimethyl hydantoin g 10 Water to quart" 1 In the formula of this example, a considerable portion of the developing agent is converted to the sodium salt by the sodium hydroxide present. Because of this it is possible to achieve a much higher concentration of developing agent than was possible in the formulation of Example 1. This permits the preparation of a very concentrated stock solution which may be considerably diluted to produce the working solution actually used. Again, the formulation of this example results in the production of high contrast negatives but at the same time the working life of the developer is 24 hours or more.

Many compounds, other than the monomethylol 5,5-dimethyl hydantoin specifically mentioned in the above examples may be employed to accomplish the objects of my invention. Among these may be mentioned monomethylol l-alkyl hydantoins, monomethylol 3-alkyl hydantoins, monomethylol and dimethylol 5-alkyl hydantoins, monomethylol 1,5-dialkyl hydantoins, dimethylol 5,5-dialkyl hydantoins, monomethylol and dimethylol hydantoins, monomethylol and dimethylol ethyleneurea (monomethylol and dimethylol 2-imidazolidone), monomethylol and dimethylol urea and the like.

While my invention has been described in connection with the use of hydroquinone as the developing agent, other developing agents, especially those of low reduction potential, may be used.

Be it remembered, that while my invention has been described by'means of numerous examples thereof, these are illustrative and non-limiting and it is to be understood that my invention covers all changes and modifications of the examples thereof, herein chosen for purposes or disclosure, that do not constitute departures from the spirit and scope of my invention.

I claim: I

1. An aqueous photographic developing solution comprising a silver halide developing agent, an alkali metal sulfite and a methylol hydantion.

2. An aqueous photographic developing solution comprising hydroquinone, an alkali metal sulfite and a methylol hydantoin.

3. An aqueous photographic developing solutioncomprising a silver halide developing agent, an alkali metal sulfite and a material selected from the group consisting of a monomethylol hydantoin, dimethylol hydantoin, a monomethylol l-alkyl hydantoin, a monomethylol S-alkyl hydantoin, a monomethylol 5-alkyl hydantoin, a dimethylol 5-alkyl hydantoin, a monomethylol 1,5-dialkyl hydantoin, a monomethylol 3,5-dialkyl hydantoin, a monomethylol 5,5-dialkyl hy-' dantoin, a dimethylol 5,5-dialkyl hydantoin, a monomethylol 1,5,5-trialkyl hydantoin and a monomethylol 3,5,5-trialkyl hydantoin.

4. The composition of claim 3, further characterized by the fact that said developing agent is hydroquinone.

5. An aqueous photographic developing solution comprising a silver halide developing agent, an alkali metal sulflte and monomethylol 5,5- dimethyl hydantoin.

6. An aqueous photographic developing solution comprising hydroquinone, an alkali metal sulfite and 3-methylol 5,5-dimethyl hydantoin.

'7. In preparing photographic images, developing a latent silver halide image by an aqueous solution containing a silver halide developing agent, an alkali metal sulfite and a methylol hydantoin.

8. In preparing photographic images, developing a latent silver halide image by an aqueous solution containing hydroquinone, an alkali metal sulfite and a methylol hydantoin.

9. In preparing photographic images, developing a latent silver halide image by an aqueous solution containing a silver halide developing agent, an alkali metal sulfite and a material selected from the group consisting of a monomethylol hydantoin, dimethylol hydantoin, a monomethylol l-alkyl hydantoin, a monomethylol 3-alkyl hydantoin, a monomethylol B-alkyl hydantoin, a dimethylol 5-alky1 hydantoin, a monomethylol 1,5-dialkyl hydantoin, a monomethylol 3,5-dialkyl hydantoin, a monomethylol 5,5-dialkyl hydantoin, a dimethylol 5,5-dialkyl hydantoin, a monomethylol 1,5,5-trialkyl hydantoin and a monomethylol 3,5,5-trialkyl hydantoin.

10. The process of claim 9, further characterized by the fact that said silver halide developing agent is hydroquinone.

11. In preparing photographic images, developing a latent silver halide image by an aqueous solution containing a silver halide developing agent, an alkali metal sulfite and monomethylol 5,5-dimethyl hydantoin.

12. In preparing photographic images, developing a latent silver halide image by an aqueous solution containing hydroquinone, an alkali metal sulfite and monomethylol 5,5-dimethyl hydantoin.

MORTON SCHWARCZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

Claims

1. AN AQUEOUS PHOTOGRAPHIC DEVELOPING SOLUTION COMPRISING A SILVER HALIDE DEVELOPING AGENT, AN ALKAKI METAL SULFITE AND A METHYLOL HYDANTION.