US2179790A - Photographic developer - Google Patents

Description

Nov. 14, 1939.

PHOTOGRAPHIC DEVELOPER Filed June 14, 193,9 2 Sheets-Sheet l FIG. l.

DK-SO TYPE DEVELOPER Nov. 14, 1939.

L. c. JoNEs Er AL. 2,179.790

PHOTOGRAPHI C DEVELO PER Filed June 14, 1939 .2. Sheets-Sheet 2 FIG. 2.

DK-SO TYPE DEVELOPER LIGHTI 2 3 4 5 6 7 B 9 DARK mixture ci alkaline substances. notably borates. l

Patented? Nev. Mt. i939 PATENT Frio p aliarse rno'rocnic n'cvmvoren tion of Maine Application .inne ld, 1039, Serial No. 279,094

M Claims.

This invention relates to photographic deu velopers, and more particularly to developers for photographic negatives which are vcapable of variation of contrast This application is a continuation in part of our application Sert No. 218,972, filedI July 13,

193, and HOW Pat. Nol 2,165,797, July 11, 1939.

The ordinary type of photographic developer of which the metol-hydroquinone types are the most common normally contain at least three types of ingredients; the actual developers vsuchl as metol, hydrocuinone and thev like, protective agents against oxidation such as sodium sulte, and a suitable alkali to produce a pH suited 4for the particular developer. In addition, other ingredients such as restrainers, for example alkali metal bromides and in the case of tropical de velopers, sodium sulfate, may be present. Normally, a developer formula is balanced-with regard to the three main ingredients in order to give results and produce a, satisfactory iidelity in reproducing the various gradations of light and shadow of the object photographed. When a curve is constructed having ordinates proportional to the density of the final developed negative, that is to say, the negative logarithm of transmission and with abscissae proportional to the logarithm of exposure, there should be a long, reasonably straight portion of the curve in order to reproduce with reasonable fidelity various exposures within a certain range. With most modern developers, satisfactory delity is obtained7 but a relatively large numberv of formulae are in use because it is d ilcult to change the characteristics of a. particular formula without upsetting its balance.

A fenT years ago, a new alkali consisting of a was introduced by the Eastman Kodak Company under'the name Kodallr and is covered by U. Sn Patent No. 1,990,800. Four dilerent formulae oi the lilastman Kodak Company, namely 13K-15,`

Dill-50,V DKT-60 and Dld-76, have been formulated using the new alkali and claims have been made.

(ci. ss-ssy While Kodalk possesses the properties l represents a distinct advance over the use of standard alkalies such as sodiumcarbonate, in some formulae it leaves much tolloe desired. Its change in contrast is sometimes accompanied by a loss of iidelity. According to the present invention, it has been found that a new class of bases which can be used to supply the alkaline reaction necessary for most photographic developers possesses the advantages of variation in contrast with variation in amount of the base, and in some formulae the best of them are superior in this respect to Kodalk, The compounds of the present invention are quaternary ammonium hydroxides which are strong organic bases. Among the most effective compounds of the present. invention are trimethylbenzylammonium hydroxide, known to the trade as Tetrone B, and tetramethylammonium hy droxide.

. The invention willv be described in detail in conjunction with specic examples illustrating the use of the compounds of the present invention in typical metol-hydroquinone developer formulae. The compounds are also useful in other types of developers such as those using p-phenylene diamine and Glycine, but are of less importance with this class of developers which are normally used at low contrast to produce extreme fine grain.Y` vThe invention will also'be described in conjunction `with"curves showing the results of densitometric measurements on exposed negatives which are illustrated on the drawings in which Fig. 1 represents a series of curves with a. DK-50 Wpc developer; and

Fig. 2 is a series of curves with a DK-60 type developer.

Example 1 Water cc-- 500 Metol grams 1.25 Sodium sulte, des do 15.00 Hydroquinone do 1.25 Kodalk d0 5.00 Potassium bromide do 0.25

This formula DK-150 is one used for the development of normal films of both orthochromatic and panchromatic type.

Two developers were prepared according to the Eastman Kodak DK-50 formula as follows, the first having ve times the normal amount of Kodalk and the second having an amount of trimethylbenzylammonium hydroxide to give the same pH as the iirst:

A photographic wedge made by the Eastman Kodak Company and having nine steps between light and dark arranged.logarithmically, each step from dark to light representing a transmission 150% that of the preceding step, was used to make exposures on 35 mm. Eastman Kodak Supersensitive panchromatic iilm. This iilm was chosen as being representative of a medium fast, long latitude panchromatic film which would show up lack of fidelity or excessive fogglng rapidly and which is a type f iilm Where variations in contrast produced by the developer are normally most necessary. All exposures were carefullycalibrated using'a Leitz enlarger with a watt bulb and lens stopped down to F125 as a source of illumination. All conditions of development including time, temperature, agitation, iixing, washing and the like were kept uniform and the only difference between the tests was the developer used. Densitometric measurements were made in a photoelectric densitometer calibrated against the wedge used for the exposures. The densitometric readings are plotted in the curves shown in Fig. 1. It will be noted that trimethylbenzylammonium hydroxide gave results similar to the Kodalk with slightly less contrast but greater delity as evidenced by the longer more perfectly straight portion of the curve.

Example 2 A developer was prepared according to the Eastman Kodak DK-50 formula having an amount of tetramethylammonium hydroxide to give a pH of the same value as the developer of Example 1 containing five times normal Kodalk, A photographic wedge was prepared as in Example 1 and a curve of the densitometer readings is also shown in Fig. 1. Examination of the curve indicates better iidelity and only slightly less contrast than the Kodalk curve.

Example 3l A surprising result is obtained when mixtures of trimethylbenzylammonium hydroxide and sodium carbonate are used. The mixtures appear to have substantially the desirable characteristics of the quaternary ammonium hydroxide alone.

The formula DK-50 type was prepared substituting a mixture of 3.82 cc. of trimethylbenzylammonium hydroxide and 5.10 grams of sodium carbonate to produce a iive times concentrated developer. The pH was-approximately 10.65. A photographic wedge was prepared as in Example l and a curve of the densitometer is shown in Fig. 1. It will be noted as shown by the curves of Fig. 1 that this mixture produced a curve having better contrast and equivalent fidelity to the Kodalk. The possibility of substituting sodium carbonate for a considerable part of the quaternary ammonium compound represents a real commercial advantage because of the lower price oi the sodium carbonate.

Example 4 Water cc-- 500 Metol; grams-- 1.25 Sodium suliite; des do 15.00 Hydroquinon do 1.25 Kodalk do 10.00

, Potassium bromide do 0.25

This type developer DK-60 is also intended for general development of iilms of both the orthochromatic and panchromatic type where a somewhat higher contrast is desired.

Two developers were prepared according to the Eastman Kodak formula DK-SO as follows, the first containing five times the amount of Kodalk and the other an amount of trimethylbenzylammonium hydroxide to give an equivalent pH. Photographic wedges were prepared as in Example 1 and densitometer readings were taken and plotted into curves as shown in Fig. 2.

It will be noted that the contrast and the iidelity are somewhat better than that of Koda1k.

What we claim is:

l. A photographic developer for silver halides containing as an alkalinity producing agent a quaternary ammonium hydroxide in eilective amount.

2. A photographic developer for silver halide containing as the sole alkalinity producing agent a quaternary ammonium hydroxide.

3. A metol-hydroquinone photographic developer containing as an alkalinity producing agent a quaternary ammonium hydroxide in effective amount.

4. A metol-hydroquinone photographic developer containing as the sole alkalinity producing agent a quaternary ammonium hydroxide.

5. A photographic developer for silver halides containing as its alkalinity producing agent a -mixture of sodium carbonate and a quaternary mixture of sodium carbonate and tetramethyl-l ammonium hydroxide in effective amounts.

10. A metol-hydroquinone photographic developer containing as its alkalinity producing agent a mixture of sodium carbonate and tetramethylammonium hydroxide in eiective amounts.

1l. A photographic developer for silver halides containing as its alkalinity producing agent trimethylbenzylammonium hydroxide in effective amount.

12. A metol-hydroquinone photographic developer containing as its alkalinity producing agent trimethylbenzylammonium hydroxide in eiective amount. Y

13. A photographic developer for silver halides containing as its alkalinity producing agent a mixture of sodium carbonate and trimethylbenzylammonium hydroxide in effective amounts.

14. A metol-hydroquinone photographic developer containing as its alkalinity producing agent a mixture of sodium carbonate and trimethylbenzylammonium hydroxide in elective amounts. A

LOUIS C. JONES. ROBERT BOWLING BARNES. GARNET PHILIP HAM.

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