US2794741A - Accelerator for color developer solutions - Google Patents

Description

Unit States Patehto ACCELERATOR FOR COLOR DEVELOPER SOLUTIONS Application November 30, 1953, Serial No. 395,258

Claims. (Cl. 96-66) I No Drawing.

The present invention relates to color photography and more particularly relates to a composition for improving the first developers in the reversal color processing of multi-layer emulsions.

The primary object of the invention is to provide a composition which may be added to any of the known first developers used in reversal color processing, for example, the first developing formulas published by Ansco, Kodak, Schwerin and others, which composition creates a strong increase in the developing activity of these developers without any noticeable increase of their fog tendency.

In accordance with the primary object, the invention consists in providing an accelerating composition for use with a first developer that will accelerate the developing speed of these developers from three to five times their normal activity and therefore speed up the whole developing process, this speed-up being accomplished without increasing the usual unavoidable tendency of increasing the general fog level.

Another object of the invention is to provide a novel first developer for short procedure utilizing the acceleratingcomposition.

A further object of the invention is to apply the accelerating composition of the present invention to emulsion coated color print material to make direct color prints of the photographed object without the employment of intermediate negative or positive color transparencies which will greatly shorten the exposure time necessary for the emulsion coated print material. This object has particular advantages for use in booth cameras which will take color pictures directly on the emulsion coated print material, the prints being finished within a few minutes.

In general, the present invention has for its object the introduction of a new compound composed of well known chemicals, which chemicals under given critical concentration, speed up the activity of the first developers without increase of the general fog level, which phenomenon occurs generally when a speeding up of the developing solution is tried.

The accelerating composition of the present invention consists primarily of two chemicals:

1. Thiourea 2. Beuzotriazole Thiourea is sometimes used as a constituent of photographic developing solutions. It introduces under certain conditions a reversal of the negative image and produces a certain coloration of the gelatine. However, in the present invention, these two properties would be harmful in the case of color processing, as mentioned in the objects of the invention. The concentration of diluted thiourea in accordance with the invention, produces solely a speeding up of the developing solution used in color processes Without the appearance of reversal of the negative image and gelatine coloration.

But, as a consequence of the introduction of thiourea into the developing solution, the general fog level in- Patented June 4, 1957 creases strongly. The development of this intense color fog has been a great stumbling block in the building up of a short first developer.

To eliminate the increase in fog caused by the above accelerator, the second chemical, benzotriazole, is introduced into the composition in a concentration which does not influence the speed gain produced by the presence of thiourea in the composition, and which does not decrease the sensitivity of the developer.

Other anti-fog substances, such as para-nitrobenzimidazole, quinone, etc., may be utilized in suitable concentration in the composition in place of benzotriazole.

The accelerating composition is formed in the following manner:

1. Thiourea gr 2.25-3.25 2. Sodium carbonate (monohyd-r.) gr 10.00-20.00 3. Beuzotriazole gr 2.002.5 4. Water cc 500 an increase in the amount of thiourea over the maximum amount given above will cause reversal of the negative image and produce coloration of the gelatine. Should the benzatriazole be varied beyond the maximum and minimum amounts given above, it would either fail to decrease the fog tendency created by the thriourea or would decrease the sensitivity of the developer.

The first developer used in the developing process of reversal multi-layer color films produces in a general manner a negative image in the different layers of the film, the density of this negative image depending mainly on three 'diflerent factors: (1) exposure time, (2) speed (sensitivity) of emulsion, and (3) activity of the developing solution. Certain photographic three-layer emulsions, particularly those coated on an opaque base and exposed for a fixed exposure time, show a rather low density of the negative image when processed in a first developer of known composition. The composition comprising the invention when added to a first developer stimulates an increase in the activity of the first developer, increasing the speed of emulsion and when utilized on the emulsions applied on an opaque base for direct color reproduction, decreases the exposure time necessary.

Below is given an example of a suitable first developer and the use of the accelerating composition constituting the present invention with this developer.

The following example is to a novel first develo er for short procedure utilizing the accelerating composition.

exam; "LE 2 When utilized with any of the above first developers,

and many other first developers-not mentioned, the ac celera-tin'g' composition constituting the present hivention produces high quality 7 color prints in s considerably shorter time than wires using the existing first deverepers; per so, while at thessme' time st'to'iigly reducing the unavoidable fog produced by the customary first developer's; particularly if the processing time is a long one.

In the first developer-for short-procedure-,-- the developer is applied directly to the color printmaterial and the photograph is developed-directly on this emulsion coated print material.- Thisprint material canbe put up in' film packs or rolls for amateur photographers and for use in contemplated color booth cameras in direct. color picture taking with the omission of films.

From the foregoing description, the method of formulating and utilizing the accelerating composition of the present invention is believed to be readily apparent to those skilled in the art, and it is desired to limit the invention only withinthe scope of the appended claims.

What is claimed as new is as follows:

1. An acceleratorto be added to a first developer solution of multi-layer color films and print material, said first developer comprising hydroquinone, sodium sulphate, sodium thiocyana'te, potassiurn bromide and water, said accelerator consisting ofan alkaline solution containing thiourea and benzotriaz'ole inthe approximate proportion of 2.25-3.25 g. of thi'o'ure'a and 2-2. g. of benzotriazole per 500 cc. of alkaline solution, adapted to be combined with the first developer solution inthe proportion of l0-30 cc. of the accelerator to approximately 1000 cc. of the first developer.

2. The composition of claim 1 wherein the alkaline solution consists of from -20 gr. of sodium carbonate dissolved in 500 cc. of water.

3. An accelerating composition to be added to a first y qll flne Len;- -=.=g -1 developer for color photographs for accelerating the Sodiumisu-lp'hite g 5 5 activity of the developer Without increasing the general Sodium yanate ug 2.5 fog level, said first developer comprising hydroquinone, Potassium bromide grsodium sulphate, sodium thiocyanate, potassium bromide Caustic Soda ---'--'---'-'--g Pi and water said accelerating composition consisting of Accelerating compfisition" 1 2.25-3.25 grams thiourea and 2-2.5 grams of henzotria- Water, to 1000 cc. 1O zole dissolvedin 500 cc. of an aqueous solution of sodium carbonate. v

4. In combination with a developing solution consist- 'ing of approximately 5 grams n-methyLp -amino phenol of sodiumthiocyanate, 2.8 grams of an alkali metal halide, 15 grams of sodium hydroxide, 20 cc. of an accelerating composition consisting of 2.25-3.25 gramsgof thiourea, 1.0-20 grams of sodium carbonate, 2-2.5 grams of benzotriazole and 500 cc. of wa'te'nandv suficient water ito make 1000 cc.

References Citedin the file of this patent UNITED STATES PATENTS 2447,441 en Feb. 14, 1939' 2,371,740 nearing Mar. 20', 1945 2,404,774 De'r'ts'ch 1111 30, 1946 2,626,215 schw'erin Ian. 20, 1953' OTHER REFERENCES British Journal of Photography,- Nov. 1, 1912, pp. 840-842 and Nov. 8r, 19l2; pp. 860-864.

Henney et al.: Handbook of Photography, Whittlesey House, New York, N; Y.',- 1939, pp; 341-343.

Mes: The Theory of the Photographic Process, MacMillan Co.-, New York, N. Y.,- 1942', pp. 459-461.

Claims (1)

1. AN ACCELERATE TO BE ADDED T A FIRST DEVELOPER SOLUTION OF MULTI-LAYER COLOR FILMS AND PRINT MATERIAL, SAID FIRST DEVELOPER COMPRISING HYDROQUINONE, SODIUM SULPHATE, SODIUM THIOCYANATE, POTASSIUM BROMIDE AND WATER, SAID ACCELERATOR CONSISTING OF AN ALKALINE SOLUTION CONTAINING THIOUREA AND BENZOTRIAZOLE IN THE APPROXIMATE PROPORTION OF 2.25-3.25 G. OF THIOUREA AND 2-2.5 G. OF BENZOTRIAZOLE PER 500 CC. OF ALKALINE SOLUTION, ADAPTED TO BE COMBINED WITH THE FIRST DEVELOPER SOLUTION IN THE PROPORTION OF 10-30 CC. OF THE ACCELATOR TO APPROXIMATELY 1000CC. OF THE FIRST DEVELOPER.