US1976299A - Photographic developer - Google Patents

Description

1,976,299 PATENT OFFICE PHOTOGRAPHIC DEVELOPER Harold D. Russell, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New York No Drawing. Application January 26, 1934, Serial No. 708,478

4 Claims.

This invention relates to photographic developers and more particularly to photographic developers in dry form, such as in the form where the necessary dry components of the developers are packaged in quantities sufiicient to make up a selected quantity of liquid developer.

In my application Serial No. 626,203, filed July 29, 1932, I describe and claim photographic developers containing as their principal alkaline component a substance resulting from the interaction with a strong alkali of a substance con taining tetraboric acid (HZB407). In that application it is stated that the substances interacting may predominate in borax or in strong alkali, so that by including this range of compounds it is apparent that an alkali metaborate, such for instance as sodium or potassium metaborate, would be included in that description.

I have found, however, that the alkali metaborates have unusual properties in their dry and relatively pure form as the principal alkaline component for dry developers, since these metaborates are far less deliquescent than sodium hydroxide, for instance, and therefore do not cake up the packaged developer. Furthermore, their combination with CO2 of the air is relatively slight, so that decomposition of the developer is negligible. Furthermore, there is not the difiiculty and hazard in handling and packaging the metaborates which is connected with theuse of sodium hydroxide.

Very important in the use of these alkaline metaborates in developers is the fact that blistering of the negative or positive being developed is avoided, for the reason that COzis not generated by the acid in thefixing bath as is the case where sodium carbonate isnemployed, as the alkaline agent of the developer, it being impossible, of course, to completely free the photographic film from all traces of developer by the time it reaches the fixing bath.

It is, therefore, an object of my invention to provide a photographic developer in dry form in which an alkali metaborate is employed as the alkaline component. Other objects will appear hereinafter.

As examples of various developer formulm in dry form, containing an alkali metaborate, such for instance as sodium metaborate, I would give the following:

The proportions may, of course, be in'grams or any other suitable unit of weight.

proportion of borax are so reacted, one normally obtains sodium metaborate with eight molecules of water of crystallization (Na2B-2O4.8H2O).

A simpler method and much more efiicient one for preparing the alkali metal metaborates is to merely mix together a powdered alkali metal hydroxide and an alkali metal salt of tetraboric acid; preferably, the two alkali metals are the same. Assuming that sodium metaborate is being prepared, one mixes borax and caustic soda in molecular proportions. During the process, the caustic removes the water from the borax and goes into solution, generating considerable heat. Borax, being soluble in the caustic solution, also dissolves and the whole mixture becomes liquid. Sodium metaborate is thus formed and the whole liquid will solidify on cooling. If the mixture is stirred throughout the process, the metaborate will crystallize from the solution in a fine powder. Otherwise it will set to a solid which is difiicult to grind.

The reaction by which sodium metaborate is formed may be represented as follows:

uazisiomi'omo+suaon zNazszol-mzomnzo This latter method of preparation was developed by Mr. Arthur W. M. Dickins.

The other alkali metal metaborates may be prepared either by the dry method or from solutions by interaction of the proper metal hydroxide and the oxygen acids of boron or those of their corresponding salts which are less alkaline than the metaborates.

The packages of dry developer may, of course, be prepared in any suitable way from the above or any other developer formulae which may be worked out. The above formula, if ingrams, require the addition of one liter of water to make a proper developing solution. Hence, for one liter of developer the above formulae should be compounded in grams. If a smaller or larger volume of developing solution than one liter is required, one prepares the developer in correspondingly smaller or larger proportions.

It will be seen from the above formula that they all have common thereto a developing agent, sodium sulfite and an alkali metaborate. I do not claim any particular novelty to the proportions in the formulm or to the ingredients therein, other than the alkali metaborate, as it will be apparent that various developing agents known to those skilled hi the art may be employed, and that the potassium bromide may or may not be present according to the use to which the developer is to be put. Other preserving agents than sodium sulfite may, according to experience, be employed if desired.

It will be noted that I do not substitute my alkali metaborate in equal proportions for sodium carbonate ordinarily employed in corresponding developer formula. If the same amount of developing agent is to be retained in the developer formula, I generally employ about twice as much alkali metaborate as sodium carbonate ordinarily employed. However, I may employ less alkali metaborate by adjusting the developing agent accordingly. For instance, if a lesser ratio of metaborate to carbonate is substituted than 2 to 1, this reduction may be compensated for in the above formula by changing the ratio of elon to hydroquinone, namely by increasing the elon content.

As an alkali metaborate, I may employ sodium metaborate, potassium metaborate or ammonium metaborate. Others within this class will, of

course, be apparent to those skilled in the art irom the above description.

I have found one very interesting fact in connection with the use of these alkali metaboratcs. namely, that with developing agents which contain two hydroxyl groups in ortho positions of the benzene nucleus (such as pyro and pyrocatccncl) the developing power is relatively much less than with other common developing agents.

What I claim as my invention and desire to be secured by Letters Patent of the United States is:

1. A photographic developer in dry form comprising an alkali metaborate and a developing agent.

2. A photographic developer in dry form comprising an alkali metal metaborate and :1 developingagent.

3. A photographic developer in dry form comprising sodium metaborate and a developing agent.

4. A photographic developer in dry form comprising potassium metaborate and a developing agent.

HAROLD D. RUSSELL.