US2493838A

US2493838A - Photoprinting processes

Info

Publication number: US2493838A
Application number: US606036A
Authority: US
Inventors: Bennett F Terry
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-07-19
Filing date: 1945-07-19
Publication date: 1950-01-10
Anticipated expiration: 1967-01-10

Description

Patented Jan. 10, 1950 UNITED STATES PATENT OFFICE l 2, 38. PHOTOPRINTING PROCESSES Bennett F. Terry, Stamford, Conn.

N Drawing. Application July 19, 1945, Serial No. 606,036

2 Claims. (01. 95-54? This invention relates to improvements in photoprintin processes and is directed more particularly to aging the gelatine in freshly prepared gelatine emulsions. It is well known that aged gelatine, after wetting, is tougher than a green or freshly prepared gelatine similarly wetted. In the formation of photographic films, plates and other emulsions, the process of aging requires a number of months, and in my process apparently results in a more complex gelatine molecule. For ordinary photographic work it is of minor importance except in warm climates, whether the gelatine is hard or soft, since such plates or films are used dry after they have been developed and fixed.

However, in my photographic processes, of which co-pending application Serial No. 391,101, filed April 30, 1941, now Patent No. 2,38 l,857 of September 18, 1945, is typical, the plate, must be kept wet while in use. According to this photoprinting process I have a plate carrying an emulsion the outer surface of which is toothed, roughened or grained. This plate is placed n a camera and the matter to be printed is photographed thereon. The plate is then developed and fixed in the usual way; then the plate is placed in an image tanning bath. All portions of the emulsion are tanned or hardened in proportion as to the relative content of the metal forming the image.

The plate may then be washed and then it may be mounted on the printing mechanism ready for the application of a suitable aqueous repellent and greasy ink. The unhardened portions of the plate remain relatively soft and absorb and adsorb the aqueous repellent. The hardened portions of the plate do not take up the repellent and, therefore, readily receive the greasy ink.

In this specification the term plate or printing plate may be taken to mean any carrier of a photographic emulsion, regardless of whether the carrier is glass, a film, a metallic sheet or a non-metallic sheet.

If the gelatine in the emulsion is not properly aged it is too soft to mechanically withstand the action in the process and it will disintegrate.

Due to the fact that the user has no way of determining whether the gelatine in the plates has been aged at all, or just how long it has been aged, I prefer to artifically age the gelatine in all plates before using them.

Now, in order to artificially age or toughen the gelatine to make it satisfactory for use in 2 p n n w h u a g-i d s r te when subjected t the action of the press, I have evolved the following method of treating the plates, which may be effected before they are exposed, after they are. exposed, developed and fixed, or after they are exposed, developed, fixed, and tanned. I find that best results are ob.- tained by treating the plates after they are exposed, developed, fixed, and washed, but before they are tanned. In other words, after the plates are fixed they are treated in accordance with any one of the methods hereinafter described and then they are placed-in the tanning solution.

It is known that formaldehyde is a good hardening agent for gelatine. I have found that a plate may be satisfactorily toughenedby immersing it in a formaldehyde bath employing from to 16. ounces of 37% form-aldehyde pergallon of solution for from three to five minutes. A plate treated in this manner and then tanned in the bichromate bath results in spottyink pick-up and poor reproduction is obtained in printing. Excess formalin in the gelatine adversely affects the ink pick-up qualities of the plate,'therefore the object isto use a compound which c'om; bines with any excess of formalin to form inert compounds (compounds which do not interfere with the ink pick-up qualities of the plate).

After treating the plate in the formaldehyde bath I tried placing it in a second solution containing ammonia to neutralize the formaldehyde effect. This worked out very well, but the alkalinity of the ammonia tended to soften the gelatine. By adding methyl alcohol the softening action due to the alkalinity of the ammonia was decreased and good results were obtained.

I have found that urea forms an even better neutralizer than ammonia with none of the disadvantages of the ammonia.

Thiourea produces still better results and the neutralization is such that excellent reproductions are obtained.

Both urea and thiourea have minor disadvantages in their tendency to form insoluble compounds with formaldehyde which gradually cause the neutralizing solution to become cloudy after prolonged use. Due to the fact that they tend to form insoluble compounds with formaldehyde, the emulsion must first be treated in the formaldehyde bath and then placed in a separate bath containin the urea or thiourea.

The ink retention of the image is also weak, although very good printing results, even when continuous tone plates, instead of screened plates,

I find further that this neutralizing agent may be introduced into the formaldehyde bath thus eliminating one step in the process withf eq'ually,"

good results. Plates removed from this bath are given a short rinse in clear water' and then treated in the bichromate bath and again; f

washed. The plate is then ready to be used a'ndE can be used in a printing press to produce. thousands of prints without loss of detail.

I have found that anthranilic acid forms a good neutralizer, b'ut'it nema be placed in -a separate bath because it forms insoluble compounds with formaldehyde. Sul fanilic acid, in soluble salt form (sodium or ammonium) is an excellent neutralizer and it, like glycine, may be mixed in and combined with the formaldehyde one bath. The' herein described process of artificially aging and neutralizing gelatine has been found to be of substantial advantage not" only for makingplates for greasy ink printing as herein described, but also for general photographic pur poses, particularly in the tropics; .iSince even in normal times one does not know how long the gelatine emulsions in plates and films have been aged it would, therefore; be apparent that with plates of difierent ages consistent results would not be obtained.

I, therefore, by the herein described process, artificially age or harden the gelatine and new tralize the hardener on all emulsions. used in my 1 processes and, thereby, obtain uniform and 0011-,

sistent results, regardless of their age, inacc'or'de ance with the herein disclosed process. iii

Although] have described herein; by. way ofexample, several embodiments oftheiinve'ntion'. I do not wish to be limited to the exact chemicals 4 employed in said examples as many changes may be made by those skilled in the art without departing from the spirit of the invention as set forth in the following claims.

What is claimed is:

1. The herein described method of treating the gelatine in photographic emulsions which consists of immersing a medium carrying a gelatine emulsion for several minutes in a solution containing formaldehyde and aminoacetic acid,

whereby said formaldehyde acts as an agent for artificially aging or hardening said gelatine, and

said acid acts to neutralize the residual formaldehyde remaining in said emulsion.

2. The method of treating a plate or film carrying a photographic emulsion which consists of immersing the exposed plate, after it has been developed and fixed, for several minutes in a solution containing .-formalin and an amino compound, whereby said formalin artificially ages said gelatine, and said amino compound combines with excess formalin in the gelatine to form inert compounds whichdo not interfere with ink pick-up, and the final step of tanning said plate in a solution containing a bichromate for making'the portions of said plate containing metallic silver greasy ink selective.

BENNETT F. TERRY.

REFERENCES CITED The following references are of record in the file of this patent: I

UNITED STATES PATENTS 7 Number Name Date 1,482,612 vJohn Feb. 5, 1924 1,746,162 Nickowitz Feb. 4, 1930 1,933,789 Crabtree et al, Nov. '7, 1933 2,139,774 Sheppard et a1. Dec. 13, 1938 2,165,421 Sheppard et al. July 11, 1939 2,247,569 Brunken et al July 1, 1941 2,251,295 Sheesley Aug. 5, 1941 2,279,411 Peterson Apr. 14, 1942 2,327,540 McQuiston Aug. 24, 1943 2,354,662 Bryce Aug; 1, 1944 2,367,511 Loweet a1. Jan. 16, 1945

Claims

1. THE HEREIN DESCRIBED METHOD OF TREATING THE GELATINE IN PHOTOGRAPHIC EMULSIONS WHICH CONSISTS OF IMMERSING A MEDIUM CARRYING A GELATINE EMULSION FOR SEVERAL MINUTES IN A SOLUTION CONTAINING FORMALDEHYDE AND AMINOACETIC ACID, WHEREBY SAID FORMALDEHYDE ACTS AS AN AGENT FOR ARTIFICIALLY AGING OR HERDENING SAID GELATINE, AND SAID ACID ACTS TO NEUTRALIZE THE RESIDUAL FORMALDEHYDE REMAINING IN SAID EMULSION.

2. THE METHOD OF TREATING A PLATE OR FILM CARRYING A PHOTOGRAPHIC EMULSION WHICH CONSISTS OF IMMERSING THE EXPOSED PLATE, AFTER IT HAS BEEN DEVELOPED AND FIXED, FOR SEVERAL MINUTES IN A SOLUTION CONTAINING FORMALIN AND AN AMINO COMPOUND, WHEREBY SAID FORMALIN ARTIFICIALLY AGES SAID GELATINE, AND SAID AMINO COMPOUND COMBINES WITH EXCESS FORMALIN IN THE GELATINE TO FORM INERT COMPOUNDS WHICH DO NOT INTERFERE WITH INK PICK-UP, AND THE FINAL STEP OF TANNING SAID PLATE IN A SOLUTION CONTAINING A BICHROMATE FOR MAKING THE PORTIONS OF SAID PLATE CONTAINING METALLIC SILVER GREASY INK SELECTIVE.