US2352014A - Photomechanical printing process and printing material for carrying out the same - Google Patents

Description

Patented June 20, 1.944

PHOTOMECHANIOAL PRINTING PROCESS" AND PRINTING MATERIAL FOR GARRY- ING OUT THE SAME Andr Rott, Berchem-Antwerp, Belgium; vested in the Alien Property, Custodian No Drawing. Application July 21, 1941,

. Serial No. 403,392-

8 Claims.

The present invention relates to a photo-meand the print is produced by exposing such lightsensitive printing materials through a masterimage and thereafter developing and fixing the print in the usual manner.

It has now been found that a photographic image produced in a silver halide layer can be made to produce a reversed imag on an inert material, i. e. a material which is not sensitive to light, provided thesilver halide layer, after being exposed to light for the production of a master image and then being impregnated with a developer to develop this image, is pressed or squeezed, in the presence of a fogging agent and. x

a silver halide solvent, onto an inert printing material (reception material) while the layer is still imbibed with the developing liquid. If this is done, that part of the silver halide in the layer which was not reduced during the exposure to light and which in the ordinary photographic process would be fixed out in the fixing bath, will adhere to and, if the reception material is porous, will enter this material by diffusion and will produce thereon a reversed image. In order to render this image freely visible, the light sensitive layer containing the master image will normally be removed from the reception material.

Fogging agents are known to be substances capable of promoting the reduction of silver halides without requiring for this the action of light. Of these substances there may be mentioned by way of example: colloidal silver, colloidal forms of sulfur, silver sulfites, hypophosphites, stannous chloride and organic sulfur compounds, which are capable of splitting off sulfur in the form of a bivalent ion. One of these latter compounds is thiosinamine.

Ithas been found that the presence of substances 'suchas referred to in the foregoing will improve and acceleratethe transfer process. To be noted is the fact thatthese substances may belong to the class of products whichact as reduction nuclei or crystallization nuclei for silver halides, as for example colloidal silver, silver sul phide, colloidal sulphur, phosphorous, or to the class of substances which are not such nuclei themselves but may form such nuclei by interaction with the diffusing silver halides, either by reduction as in the instance of stannous chloride or by the formation with the silver halides of diflicultly soluble compounds such as sulphides or organic substances which easily split off sulphur as for instance thiosinamine.

The silver halide solvents contained in the usual photographic developers such as sodium sulphite, suffice, but also special solvents may be added. Sodium thiosulfate, which is a silver halide solvent, acts also as a fogging agent by promoting the reduction of the halides without requiring the action of light.

The fogging agent is preferably incorporated in the reception material either during the manufacture of the latter or by impregnation of the finished material. I v

The expression reception material as used throughout this specification and in the appended claims is to be understood as the material on which the image is finally deposited according to this invention.

Furthermore, it has proved to be useful to fix the active substances in the reception material by means of precipitants (for instance sodium thiosulphate may be precipitated by barium chloride) As reception materials there may b used coated and uncoated paper, multilayered or stripping supports, textiles, wood, Celluloid and other plastics, metal, glass, porcelain and many other materials which may not be suited for the normal photographic process.

The process according to the present invention is particularly useful in the transfer of images onto both sides of a sheet formed carrier, which is of great importanc in the reproduction of documents and books; wherein it offers the advantage of avoiding the risk incurred with a material coated with light sensitive layers on both sides, but being not sufficiently impervious to light to prevent the light rays used for printing from affecting the opposite sensitive layer.

The photographic images obtained by transfer according to this process consist of very finely divided silver and silver compounds. They are accessible to any of th subsequent treatments employed in photography, such as intensification, reduction, toning, colouring by dye mordanting processes or colour development and may also be used in contact-tanning reactions like ordinary photographic images. They may be used for building up colour images by the silver bleaching process.

any subsequent treatment the developed image'is pressed onto a textile support and kept in/contact with it for 10 minutes. After stripping the" photographic paper, a positive image remains on the textile support.

For the purpose of obtaining the same design in colour, it is bleached in a bath containing 5 g. potassium ferricyanide and 5 g. potassium bromide per liter, then washed and developed in a known colour developer, containing as a colour coupler trichloro-a1pha-naphthene. A'blue image is obtained by this treatment.

Example 2.-In the production of a reception material 100 ccms. of a gelatine solution of 1% are mixed with com. silver nitrate, 10% and 1 com. hydroquinone 1% are added. ccms. of the colloidal silver'sol formed are mixed with a solution of 60 g. gelatine and l g. sodium thiosulfate in one liter water. This mixture is cast on a paper support.

From a photographic diapositive an enlargement is made on silver bromide paper and developed in a paramethylamido hydroxybenzene hydroquinone developer and to which 1 g. sodium thiosulphate is added per litre. After development, the image, without having been Washed, is squeezed onto the reception material, which during development in order to promote the reaction has already been treated with the developer together with the silver bromide paper. After 10 minutes the two layers are separated. An enlarged positive image remains on the reception material and it may be treated subsequently in a selenium toning bath so as to enhance the toning.

Example 3.In the production of another reception material 1 liter of a 10% gelatine solution is mixed with 100 ccms. of a 0.1% sodium sulfide solution and 200 ccms. of a 0.1% silver nitrate solution. The mixture is heated one hour at 40-45 C. and after solidification is shredded, washed and after melting, cast onto a paper support and dried. This material may be used in ously in the same bath so as to promote the proceeding. After th exposure and development of the refiectographic paper sheets are pressed onsided positive copy and after washing no further the transfer of images as described with reference to Example 2.

Example 4.In order to produce a. reception material two mixtures are prepared viz. a solution A, containing, 100 g. gelatine and 150 g. bariumchloride in 1 liter water and a solution B, containing 100 g. gelatine and 150 g. sodium thiosulfate in 1 liter water. The solutions are mixed at a temperature of C. and the solidified mixture is shredded, washed again and after remelting mixed with an equa1 quantity of 0.1% sodium sulfide solution. The mixture is cast onto a paper support and dried. A similar mixture is cast on the backside of the support and dried.

On two sheets of silver halide paper a print is made refiectographically of each side of a doublesided printed document. The two sheets are developed for one minute in a usual paramethylamido hydroxybenzene hydroquinone developer, the reception material being treated simultanetreatmefitis" required.-

7 Example 5.In the manufacture of a reception material a solution comprising 1 liter gelatine 6%, 30 com, of a 0.2% thiosinamine solution and 20 com. of a 10% sodium thiosulphate solution are cast on a multilayered support of medium thickness which includes a stripping layer and a thin paperlayer.

A sheet of silver halide is exposed reflectographically and developed one minute in a hydroquinone development. At the same time the reception material is treated in the same bath. After development both layers are pressed upon one another and after ten minutes are separated. The positive thus obtained may be stripped after washing and drying. This method of transfer is particularly suitable for use in air mail correspondence.

Example 6.On a paper support, provided with a stripping gelatine layer, a mixture consisting of 50 g. gelatine, 3 g. sodium thiosulphate and 0.3 g. stannous chloride are cast and dried.

The treatment of this material for image transfer is the same as described with reference to Example 5. After washing and drying, the thick gelatine layer may be stripped. There remains a diapositive of the text which may be used further according to known photomechanical processes. Various changes may be made in the details disclosed in the foregoing specification without departing from the invention or sacrificing the advantages thereof.

I claim:

1. The process of photographic image transfer which comprises contacting a photographic silver halide layer containing a developing solution and a developed photographic image in the presence of a silver halide solvent and a fogging agent with a reception material which is insensitive to light.

2. The process of claim 1, in which the fogging agent is a colloidal precious metal compound,

3. The process of claim 1, in which the fogging agent is a sulfur containing substance capable of splitting off sulfur in the form of bivalent ions.

4. The process of claim 1, in which the fogging agent is a tin compound capable of splitting off in an alkaline medium stannous ions.

5. The process of claim 1, in which sodium thiosulfate is present to act both as a silver halide solvent and a fogging agent.

6. A reception material adapted for use in the process of claim 1 consisting of a material insensitive to light and which contains stannous chloride as a fogging agent.

7. A reception material adapted for use in the process of claim 1 consisting of a material insensitive to light and which contains thiosinamine as a fog ing agent.

ANDRE. Borr-