US2293406A - Photographic process - Google Patents

Description

i This application has to do with the Patented Aug. 1942 UNITEDSTATES PATENT OFFICE Y rno'roeaarnrc raoonss Henrik Sartov and Alfred Llndstedt, Beverly Hills, Calii'., assignors to Omnicolor Pictures Corporafornia tion, Los Angelcs, Califl, a

corporation of Cali- No Drawing. Application June is, 1940, Serial No. 341,141

4 Claims.

production of prints on gelatin coated papers, and is particularly useful in processes in which pictures are produced on gelatin coated papers by dye-transfer. A particular field of usefulness is in the pro- (4) Papers .of a coarse or grained surface must j be elastic enough to permit perfect contact of the matrix.

It has been the practice to first place the pa per in a water bath until the gelatin was rentent, such that it is impossible to produce proper contact for effective dye transfer when using papers of coarse texture, and operations are thereby limited to. relatively smooth surface papers.-

The main object of this invention is to eliminate the foregoing defects of prior-known methods of manipulating gelatin coated paper print stock and to thereby greatly facilitate the production of prints on such stock by dyetransfer methods. 1

In accordance with the invention,-we accomplish this'object by employing as the wetting bath for the conditioning of gelatin coated print stock, a solution containing water and glycerin as its essential ingredients, and later washing the completed prints in water to remove the absorbed glycerin. l

Although it is not essential to use any exact proportions of glycerlnand water, we have found it very satisfactory in practice to use substantially equal amounts, by volume, of the two.

Considering the advantages of the use of our wetting bath as compared to the aforelisted disdered sufiiciently soft and receptive. Thereafter the paper was removed from the bath and squeegeed onto a slab, attempt being made to wipe all free water off of the gelatin surface. Thereafter the desired dye transfer matrix'was pressed against the paper on the slab for the necessary length of time to effect transfer of the dye. In making natural color photographs, several different matrices made from color separation negatives and carrying dyes of different colors, were successively pressed against the print stockwhile,

it was on the slab.

This prior method of preparing the paper stock has the following serious disadvantages:

1) Some papers require longer soaking than others. Hence it is difficult to know when a maximum expansion is reached;

(2) When the paper has been wetted in a water bath it expands further under pressure, such as is employed in making a transfer, and therefore, expansion may go on during transfer, resulting in loss of registration;

(3) The stock eventually begins to dry out after being placed on the slab. This, drying is very objectionable because it is accompanied by: (a) shrinkage of the stock, rendering perfect registration with successive matrices impossible; (b) changes in the dye-receiving properties of the stock for successive impressions from different matrices, in color work;

(4) The gelatin coating on the stock is softened and rendered elastic to only a limited exadvantages of the prior-known bath:

Whereas paper print stock cannot be left in an ordinary water bath for more than a few days, without serious detrimental effects on the gelatin coating, such stock can be left in our glycerin bath substantially indefinitely. Thus it is found that paper stock continuously immersed in our glycerin bath for periods of time measured in years has remained in perfect condition for use,

if, indeed, it is not actually improved by the long immersion. Because of this fact, operations are greatly facilitated, since a large quantity of stock can be maintained in the glycerin bath ready for immediate use at any time, with the knowledge that it will be in the best possible condition.

The defects incident to expansion of the stock under the pressure of the transfer operation are eliminated by the present invention because stock taken from the glycerin bath has reached its'fllll expansion and does not expand further under the pressure of the transfer operation.

The defects incident-to progressive drying of the stock on the slab are completely eliminated. when the stock has been first treated with glycerin in accordance with the invention. The stock can be left on the slab for hours, if necessary,

during special types of process work, without any apparent drying or shrinkage, or any h n e in the gelatin coating rendering it less receptive to the dyes to be transferred thereto. The absence of shrinkage eliminates defects in multicolor work which have previously resultedfrom imperfect registration of different matrices applied successively to the prints.

Whereas with prior-known processes the gelatin of the print was so lacking in elasticity that it was impracticable to attempt dye transfer printing with coarse textured papers, our glycerin treatmeht appears to so markedly improve the elasticity of the gelatin as to enable the use of relatively coarse textured papers, which are often desired to produce particular artistic effects.

Despite the fact that the glycerin renders the gelatin physically more elastic, it appears when properly hardened or mordanted to substantially reduce the tendency of dye to spread through the gelatin coating. Instead, the dye is largely retained on the surface and there is a minimum of spreading laterally. so that the detail is not destroyed, and more nearly perfect color values are obtained in three-color work. As a result of the improved elasticity of the coating and the reduction of spreading of the dye, our process makes it possible to obtain clean transfers on papers of coarse textures which it would be impossible to produce by the prior-known processes.

It is desirable, in most instances, to remove the glycerin after a print has been completed, in order that the print may be dried. Such removal is easily produced by washing the print in distilled water for five minutes. A rather remarkable characteristic of the process is that this final washing in distilled water to remove the glycerin has no noticeable effect on the dye.

The invention is applicable to any photographic process employing contact transfer to a gelatin surface.

It has previously been indicated that the paper can be left in the glycerin bath indefinitely.

0n the other hand, a long immersion is not essential, and most papers are in condition to be used after an immersion of approximately twenty-four hours.

to remove the glycerin therefrom.

2. The method of producing prints on gelatin coated print stock, which includes the steps of first soaking the stock in a water solution of glycerin, then cleaning the surface of the gelatin on the stock, then transferring dye to the stock by pressing it into intimate contact .with the matrix containing the dye, and thereafter washing the stock to remove the g y er n t erefrom.

3. The method of treating gelatin coated print stock used in dye transfer printing, which comprises soaking the stock in a water solution of glycerin prior to transferring the dye thereto, transferring dye to the stock, and washing the print in water to remove the glycerin therefrom after dye-transfer thereto has been completed.

4. The method of conditioning gelatin coated photographic print stock for contact transfer of color, which consists in soaking the stock in a water solution of glycerin, removing all f ee glycerin from the surface of the gelatin, while leaving absorbed glycerin in the body of the stock, and subsequently washing the print in water after completion of color transfer thereto for the removal of the absorbed glycerin.

HENRIK SARTOV.

ALFRED LINDSTEDT.