US1812981A - Process for transferring gelatine silver bromide pictures - Google Patents

Description

Patented July 7, 1931 MI [CHEL raooounnm-qoasn, OFPARIS, FRANCE, ASSIGNOB '10 SOCIETE iDE PHOTO- CHIMIE ELKA, OF NICE, FRANCE PROCESS FOR TRANSFERRING GELATINE SILVER fiROHIDE PICTURES Application filed January 31, 1927, Serial No. 165,038, and in France February 8, 1826.

It is known that an image on gelatine silver bromide layer developed with certain developers which tan the gelatine in the presence of nascent silver (especially pyrogallic acid slightly sulphited can be transerred to an surface, either at or cylindrical, and a erw ards developed with hot water to produce a gelatine relief corresponding to the white parts of the picture photo- I 10 graphed.

The application of this principle to photomechanical processes has been made known by Koppmann but up to the present time gelatine-silver-bromide paper has not been used practically in the photomech'anical industry except perhaps by direct inking of the paper more orless according to the Bromoil process, and by transferring the ink upon the plate.

Numerous difficulties are met when trying to utilize the tanning properties of pyro-' gallic acid or like developers when transporting and developing with the hot water the pictures themselves as pigmentary pictures.

The main difficulty consists in the fact that it is usually impossible, even in the most simple line pictures, to obtain in the spaces between the portions or reserves of gelatine, a metal or the like (according to the nature of the support used) which is quite bare and capable of firmly retaining the ink.

If the action of the tanning developer is pushed sufliciently far to obtain a picture sufficiently tanned to withstand hot water, even in the small isolated points of the reserve, then the transparent parts are equally slightly hardened, and especially in very narrow spaces it is impossible to remove completely the gelatine. Otherwise stated it is impossible to make use of the transfer of a picture having both fine black and fine white details.

In the most favourable cases as when the picture is quite black and white, and when the emulsion diffuses very little while giving very contrasty pictures which are free from fog, the metal or the other support is not perfectly bare, even though it is not possibleto detect, even by dyeing, any trace of gelatine in the parts from which the gelatine was washed out. Experiments show that the metal or the like retains in its pores a little 'gelatinized water which prepares it in the sulp uric acid for the removal of gelatine,

the ink first becomes removed from those parts where it would be thought that the bare metal would be capable of retaining it.

According to the present invention, in order to remedy this defect, a well defined differentiation of the two gelatines is obtained (tanned gelatine and tender or non-hardened gelatine) whereby the tender gelatine is as far as possible removed, while almost perfect bare portions can thus be formed on the support in the spaces of the reserves.

For this purpose development is carried out in two stages, i. e. a first partial development with a tanning developer, completed by a development with an ordinary develo er.

hen a picture, suitably taken on gelatine bromide aper, has been developed up to about hal intensity with a tanning developer (pyrogallic acid slightly sulphited for example) then if development is brought to completion with a second strong developer not possessing tanning properties (diamido-phen01, mono ethyl-p-amino-m-cresol sulphate (metol), hydroquinone or the'like, and even pyrogallic acid normally .sul hited) the silver reduced by this second eveloper in the presence of the pyrogallic acid remaining in the layer, accelerates the tanning of the picture which takes place much more rapidly without hardening the transparent parts of the picture. The picture can then be transv ferred on to metal, for example, exactly as a carbon picture, and bare metal in the spaces of the resist can be obtained much more easily.

If however necessary, it is very easy to clean off the metal or other sup ort in the transparent parts of thefilm (w en for example the gelatine of these trans arent parts has been very slightly harden in spite of the two stage development), by rubbing the surface of the plate with a pad of cotton wool impregnated with a slightly abrasive mixture (a cream of Spanish white in alcohol or the like), this cleaning can be effected very easily and rapidly.

This cleaning, which is however not absolutel necessary with the aforesaid twostage evelopment, may alone sufiice in certain cases, as for example with lines of mediuni fineness, to render the metal bare in the spaces of the substance so that the process will then become a simple ordinary tanning development.

When fine drawings are in question however, it is necessary to develop in two stages as indicated above, with or without subsequent cleaning.

Whatever the procedures adopted, the plate may then be treated by any known process of inversion. It may for example be inked up, the gelatine then removed with a soft brush in a very weak bath of sulphuric acid for example, leaving a transfer with the greasy inks which is inverse to the first image and is therefore black and white as in the picture which was photographed. These transfers can be used for lithographic printings or be engraved as typographic plates by all known processes.

It is to be noted further that the two-stage development process, which is the subject of this invention, allows further advantages to be obtained by overcoming the secondary phenomena of silvering frequently occurring eretofore.

Experiment shows that when the usual fixing following a tanning development is not pushed much be ond the moment in which the white image as disappeared, the soluble silver salts remaining in the layer will give silver stains on zinc, beneath the black ortions as well as in the transparent parts 0 the picture. Now nascent silver also possesses tanning properties under these conditions, and the soluble gelatine will become insoluble at the places where such stains exist.

These defects are easily avoided when the ordinary fixing process is replaced by a nontannin develo ment in day-light or white light, t us pro onging the two-stage development described whereby the bromide picture is masked by a thorough blackening.

One may, for example, after com letely de veloping the picture in the secon ordinary developer, continue development with white light, u to complete blackenin of the material. Washing will then su cc to avoid secondar tanning phenomena due to the silvering o the metal.

As the gelatine which has remained soluble is now strongly coloured, its removal with hot water is more easily effected.

In order to make the steps of my process clearer, reference is made to the accompanythe emulsion layer 6, a portion of which,

within the bracketed zone 0, is represented as having been treated according to the process. (1 are the grains of silver bromide which are more or less enlarged and condensed according to the stage of development, and the crosses e are the oxydizing products which remain after the action of the developer. The hatching f shows the tanned parts of the layer. I

Fig. 1 shows the plate as it appears after the first (tanning) development has been partially carried out. The grains of silver (Z are small and spaced and the oxydizing products e are present in the zone but their action is notsuflicient to render the gelatine insoluble. v

Fig. 2 shows the same part of the plate after the second development with ordinary developer has been carried out to a certain degree. This second development has considerably increased the mass of the reduced silver and the amount of the oxydizing roducts ofthe tanning development is su cient to insolubilize the gelatine.

Fig. 3 shows the same portion of the plate after the second development has been com pleted. It will be seen that the reduced silver is dispersed and is present everywhere. The paper is black everywhere but the gelatine is tanned only where the first development left oxidated residues. Elsewhere the gelatine remains soluble in hot water.

In a process according to the invention it may be desired to color the sensitive layer more or less with colours which do not act on the bromide (Congo red or the like) in order to limit the phenomena of the diffusion of the light in gelatine which hinders the production of fine details in the picture, and thus to increase the resolving power of the emulsion.

In the preceding, where metallic or like supporting plates have been spoken of, it is understood that there may also be used metallic plates already covered with a reserve varnish on which the gelatine transfer allows of local action by dissolving.

Naturally also the reserves of gelatine obtained can be strengthened by producing ozobrome pictures at their surfaces.

Finally, it is also evident that all gelatine silver bromide papers can be used for carrying out this invention.

Among the application of this invention, may be mentioned, among others, the reissue of texts and music scores, as also transfers on metal of texts and of music composed with the aid of machines using photography.

What I claim is:

1. In a process for transferring gelatine silver-bromide pictures, the steps which comprise first partly develo ing the picture with a tanning develo er an then continuing the development wit an ordinary non-tanning developer.

2. A process for transferring gelatine silver bromide pictures as claimed in claim 1,

m in which the operation of double developing of the picture is prolonged by a. non-tanning developing in white light, to obviate secondary tanning efiects caused by silvering of the metal.

3. Process as claimed in claim 1 in which a sensitive layer of gelatine bromide tinted with a colour having no action on the bromide is employed, whereby difiusion of light in gelatine is eliminated and its resolving power increased.

4. In a process for transferring gelatine silver bromide ictures the steps which comprise first partlally developing with a tanning developer, then with an ordinary developer, continuin the second development in white light, inking the plate and after removing the gelatine as for an inversion, resining and heating the ink and treating with acid to obtain a first relief.

5. In a process for transferring gelatine silver bromide pictures, the steps which comprise partiall developmg the picture with a tanning deve oper and then continuing and completing the development with a non-tanning developer.

I In testimony whereof I have afiixed'my signature.

MICHEL PROCOUDINE-GORSKY.

Images