US2385763A

US2385763A - Photographic developers

Info

Publication number: US2385763A
Application number: US443559A
Authority: US
Inventors: Verne H Reckmeyer
Original assignee: General Aniline and Film Corp
Current assignee: GAF Chemicals Corp
Priority date: 1942-05-19
Filing date: 1942-05-19
Publication date: 1945-09-25
Anticipated expiration: 1962-09-25

Description

surface.

Patented Sept. 25, 1945 PHOTOGRAPH! DEVELOPERS Verne ll. Reckmeyer, Bin ghamton, N. Y., assignor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application May 19, 1942.

Serial No. 443,559

4C'iaims.

This invention pertains to a photographic de-" veloper, and more particularly to a. developer which has greatly improved characteristics of speed and fineness of grain.

Many so-called flne grain developers have been proposed from time to time in thepast, but none of these prior developers is entirely satisfactory. In all of these previous proposals, improved fineness of grain is achieved only at the cost of a considerable loss in effective threshold speed. Attempts have been made to avoid this speed loss by the use of various alkalies in the developer. The use of the customary alkalies, such as borax, sodium metaborate, trisodium phosphate, triethanol amine and the like, however, has always resulted in a considerable coarsening of the grain. Thus the desirable line grain characteristics were lost.

With these defects of the prior art in view, it is accordingly one object of the present invention to provide a new and improved fine grain developer.

A further object is to provide a line grain developer which will retain threshold speed without impairment of the line grain characteristics.

Still another object is to provide a dee working fine grain developer which will maintain maximum speed with a minimum of graininess.

Other objects and advantages will be apparent from the following description.

It is known that in the use of ordinary developers in connection with photographic gelatino silver halide emulsions, the main development takes place nearest to the surface of the exposed layer. In other words, the chief density is due to the presence of developed silver particles near this These silver particles form grain clusters, and it is apparent that the presence of these grain clusters in a relatively thin layer near the surface of the emulsion will give rise to a graininess effect due to passage of light between the grains. I

To avoid the above dimculties, certain developers have been used which achieve the same given density by a more uniform distribution of silver throughout the light sensitive layer. These are the so-called deepworking developers, of which They show oped silver particles are more evenly distributed by reason of the characteristic solvent action of the developing compound. Thus. even though the graininess characteristics are improved, the developer is unsatisfactory from a practical standpoint due to the effective loss in speed, which may correspond to diilerences of from 1 to 1% lens stops in a particular case.

We have now found that the above stated objects canbe accomplished by the use of 9. developing agent to give uniform distribution of the developed silver particles energised with an easily oxldizable organic compound, which, when oxidized, tends to set free a limited amount of alkali. Preferably easily oxidizable alkali metal salts of organic compounds of the phenolic type are employed for this purpose. Thus, the phenolates are particularly useful as energizers. If the developing agent employed were energized by ordinary alkalies the increased clustering or coarseness of grain typical of prior art developers would result.

Typical examples of the easilyoxidizable compounds according to the present invention are the alkali metal salts of compounds of the N-substituted o-amino phenols such as the alkali metal salts or 2[di(hydroxyethyl) l-amino-i-hydroxy benzenes disclosed in U. 8. Patent 1,712,716 of Gustav Reddelien and Werner Mueller. These salts are characterized by their sensitivity to oxidation and by the fact that, when so oxidized,

they set free a limited amount of alkali. These compounds have a weak developing action by themselves but such developing action must be weaker than that of the developing a ent which the easily oxidizable compound energizes. Thus,

5 when mono'N-methyl o-amino phenol is the de- 40 suits in an increase in speed without any appreciable increase in grain, It should be noted that the improved results of the present invention as to fineness of grain with increased threshold speed, which are not achieved by the use of custl tomary sources of alkali, can be determined by measuring the iineness 0! grain on a graininess meter.

As the developing agent itself. we use mono N-alkyl o-amino phenols. Especially good resuits are obtained by the use of monomethyl ortho amino phenol. As a matter of fact. the addition of a substantial amount of hydroquinone to the ortho-methyl amino phenol is dssirablein order to obtain greatly improved contrast characteristics. Whilethcuseofhydroquinonehalblofl proposed previously in combination with orthomethyl amino-phenols. it has not been proposed in the threefold combination or a mono-N-aikyl ortho amino phenol. hydroquinone, and an energizer oi the type described above. The new developers which include these three ingredients are particularly important because the extreme fineness of grain which is characteristic of the resulting developed image. This fineness of grain is achieved without loss in threshold speed. In fact, the threshold speed can even be increased by the use of larger amounts or the energizing compounds.

The following examples will serve to illustrate the invention. The parts are by weight unless otherwise indicated.

Examples Grams 1. Sodium suliite 100.0 o-Methyl aminophenol 5.0

2[Di(hydroxyethyl)] amino-l-hydroxy benzene sodium salt Hydroqulnone 7.5 Water is added to make the solution up to 1000 cc. This solution will develop 35 mm. film of the type sold by the General Aniline & Film Co. under the trade name Supreme, in from 12-18 minutes at 68 F.

' Grams II. Sodium sulfite 100.0 o-Methyl amino phenol 5.0

zlDithydroxyethyhl amino 1 hydroxy benzene sodium salt Water is added to make the solution up to 1000 cc. This solution will develop mm. film of the type mentioned in Example I, in from 20-30 minutes at 68 F.

Having now fully set forth and described my invention, and having illustrated the best manner in which to perform it by specific examples. what I claim as new and desire to have secured by Letters Patent is:

l. A photographic developer comprising in combination an N-mono alkyl o-amino phenol, and an alkali metal salt of a 2[di(hydroxyethyl) l-l-amino-l-hydroxy benzene which upon oxidation sets free limited amounts of alkali said developer being initially free of alkali.

2. A photographic developer comprising in combination hydroquinone an N-mono alkyl 0- amino phenol, and an alkali metal salt of a 2 [di (hydroxyethyl) l -amino-1-hydron benzene which upon oxidation sets free limited amounts of alkali said developer being initially free of alkali.

3. A. photographic developer comprising in combination hydroquinone, o-methyl aminophenol, and the sodium salt oi 2[di(hydroxyethyl) l-amino-l-hydroxy benzene which upon oxidation sets free limited amounts of alkali said developer being initially tree 0! alkali.

4. A photographic developer comprising in combination o-methyl amino-phenol and the sodium salt of 2[di(hydroxyethylll-amino-1- hydroxy benzene which upon oxidation sets free limited amounts of alkali said developer being initially free of alkali.

vnannxnncmmrna.

CERTIFICATE OF COHRECTI ON.

parent No. 2,585,765.

September 25, 1915.

V'ERNE H RECIQ'EEYER.

It is hereby certified that error appears in patent requiring correctionas follows: Page 2, secof the above numbered the printed spec lfication 0nd column, line 12., claim 1, for "-1-amino-1-" read -amino1- and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 26th day of February, A. D. 19li6.

iSeal) Leslie Frazer First Assistant Commissioner of Patents.

proposed previously in combination with orthomethyl amino-phenols. it has not been proposed in the threefold combination or a mono-N-aikyl ortho amino phenol. hydroquinone, and an energizer oi the type described above. The new developers which include these three ingredients are particularly important because the extreme fineness of grain which is characteristic of the resulting developed image. This fineness of grain is achieved without loss in threshold speed. In fact, the threshold speed can even be increased by the use of larger amounts or the energizing compounds.