US2590857A - Photographic carbon tissue - Google Patents

Description

April 1, 1952 J. F. HANSMAN ET AL 2,590,857

PHOTOGRAPHIQ CARBON TISSUE Filed Sept. 10, 1945 reduces the sharpness.

Patented Apr. 1, 1952 UN ITED PHOTOGRAPHIC CARBON TISSUE John F..Hansman and Melvin J. Jurisch, Chicago, 111.; said Hansman assignor to said Juriscli Application September 10,1945, Serial No. 615,507

(01. Nib-128.2)

11' Claims. 1

This invention relates to photographic carbon tissue and more particularly to a method of employing the same in the manufacture of photographic silkscreen.

Photographic carbon tissue comprises a fibrous backing material which is provided with a photosensitive or photosensitizable surface of gelatin or other, colloid adhering to the backing. Normally the paper is sensitized with a bichromate and on account of the effect of the bichromate on thegelatin, the sheets are normally sensitized shortly before use. For thatreason the paper is normally sold in an unsensitized form.

In employing the carbon tissue in silk screen work,v the carbon tissue is first sensitized in a bichromate solution and exposed to animage while in contact with a photographic negative or positive; Light acting upon the sensitized gelatin renders those portions insoluble which are exposed to it, while the protected areas remain soluble in warm water. The exposed sheet is thenapplied to a silk screen.

There were two general methods in use for supporting the tissue duringexposure to an image. Invthem the carbon tissue, is supported, as, for; example, on a thin sheet of Celluloid or a varnished negative. The wet sensitized carbon tissue is squeegeed to the wax surface of the Celluloid or varnished surface of the negative and it may be exposed to the light while so supported. After exposure, it is placed in warm water and the paper backing stripped away. Thereafter the soluble areas were washed away. Because of. thewet swollen condition ofthe gelatinand. thelack of close and intimate contact between the sensitized surface and the. negative or: the Celluloid, there was a. loss of sharpness. If asupportwas used a thickness of the support Likewise light does not penetrate as well into the swollen gelatin. Exposure must be greatly increased because of the diminished sensitiveness of the wet film. There is also a tendency of a gelatin film to frill and reticulate during the warm water development owing to lack of adhesion to the wet film and the wax surface.

An embodiment of a photographic carbon tissue made in accordance with this invention is illustrated in the accompanying drawing, in which:

Fig; 1 is a plan view of a photographic carbon tissue illustrating the various layers composing the. tissue; and

Fig. 2 is a vertical cross section of the tissue shown in Fig. 1.

As contrasted with the wet processes heretofore employed, the present invention makes it possible to employ either a. dry or damp process in which the-sensitized gelatin is either dry or only slightly moist. This is accomplished by applying to the surface of the gelatin I l on the carbon tissue a thin transparent coating or film l2, preferably of a wax adherent material. Themeferred film is produced by the application of a weak solution of collodion. Such a film I2 is porous or permeable to liquid solutions and particularly to liquid solutions incorporating a bichromate. During storage the film l2 protects the gelatin l I from mechanical and possibly from chemical deterioration, and it does not materially interfere with sensitization. For example, the use of the film hereinafter described permits sensitization of the underlying gelatin by immersion for 3 minutes in a 4% solution of bichromate in water at a temperature of F. After sensitization the sensitized tissue may be dried and then applied directly to the negative or to a wax support if desired. The film has great adherence and, therefore, avoids the dificulties due to lack of adherence of the gelatin. At the same time it is not necessary to have the gelatin in wet form during the exposure, and the difficulties due to wetting of the gelatin may be avoided.

The followingis an example of the preferred film. A carbon tissue m of usual form comprising an. opaque fibrous backing of paper, having asurface coated withnon-sensitized-gelatin I I, is treated with asolutionby weight of:

1O9.4 parts-a1cohol 109.4 parts ether 1.2 parts gun cotton 1 part glycerine Thisv solution is spread over. the surface of the gelatin in any suitable manner, drained, and then permitted to dry thereon, thus producing a very thin nitrocellulose film. The glycerine is employed to render the film porous or permeable to liquid. Diethylene glycol will also serve the same purpose. While the chemical action of the glycerine is not thoroughly understood, it is believed to act as a hydrophilic material within the normally hydrophobic nitrocellulose whereby permeability to water is produced.

The dried film is normally marketed with the gelatin unsensitized. When it comes time to use the tissue, it is immersed in a sensitizing solution such as a 4% solution of bichromate in water. Three minutes at 65 F. will serve to sensitize gelatin beneath the film here described. Thereafter the surplus sensitizer is drained off and the tissue may be hung up to dry or it may be squeegeed to a highly polished plate. When hung up to dry it should not be used until the film surface is dry to the touch. When dried on a polished plate it should not be stripped until a small corner has been lifted and found dry to the touch. When the surface is dry the sheet will remove easily from the plate.

' If" desired, to reduce any overmoistness of the gelatin a small quantity of talcum powder may be dusted over'the entire film surface with a soft brush.

' The dried tissue is then placed in contact with a. photographic negative. or positive, the emulsicns: of each. facing each. other. The time of.

exposure depends upon the type of equipment and is no part of this invention. A reasonable example would be 7 to 10 minutes at 5 feet with a 35-ampere arc light. After exposure the film is dipped for several seconds in a cool water bath and is then squeegeed to a temporary developing support which has been polished with a tacky wax. It is allowed to stand for a few minutes and is then placed in hot water at about 100 F. until the paper back has softened sufficiently to permit the paper back to be peeled off. This usually takes about or minutes.

The soluble gelatin is then washed out until the image alone remains, after which the plate is rinsed in cold water and drained and placed under a black silk screen, with the screen in contact with the residual gelatin. The gelatin is then dried while in contact with the silk and becomes adherent thereto. The silk with the gelatin is then stripped from the support and any residual porous film may be removed with a suitable solvent, such as ether or a combination of alcohol and ether.

The foregoing detailed description has been given for clearness of understanding only, and no unnecesary limitations should be understood therefrom.

What we claim as new, and desire to secure by Letters Patent, is:

1. The method which comprises providing a carbon tissue with a facial film of a water-insoluble transparent material containing a minor proportion of a hydrophilic material and an intermediate layer of a water-soluble colloid, sensitizing the tissue in an aqueous bath containing a sensitizing agent through the film, drying the tissue, exposing the tissue to an image, placing the film side of the tissue in adherent contact with a rigid support, removing the backing and surplus colloid from the tissue While on said support and while held by said film, then bringing a silk screen into adherent contact with the colloid while the material is still on the support, and finally stripping off the film.

2. The method as set forth in claim 1, in which the film is cellulose nitrate.

3. The method as set forth in claim 1, in which the film contains a small proportion of a polyhydric alcohol.

4. The method as set forth in claim 1, in which the colloid is gelatin and the sensitizer is a bichromate.

5. The method which comprises providing a carbon tissue comprising a backing of an opaque fibrous material and a thin layer of an unsensitized soluble colloid thereon capable of being sensitized with a light-sensitizing agent, covering the face of the colloid with a thin adherent film of a wax-adherent material permeable to the light-sensitizing agent, sensitizing the colloid through the film, exposing the sensitized colloid to an image through the film, applying the film side of the colloid and backing to a waxed surface, and stripping off the backing while the film is adhered to the waxed surface and the colloid is adhered to the film.

6. The method which comprises providing a carbon tissue comprising a backing of an opaque fibrous material and a thin layer of an unsensitized soluble colloid thereon capable of being sensitized with a light-sensitizing agent, covering the face of the colloid with a thin adherent -film of a wax-adherent material permeable to the light-sensitizing agent,.sensitizing the colloid through the film by applying a solution of a light-sensitizing agent, substantially drying the carbon tissue and film, exposing the sensitized colloid to an image through the film, applying the film side of the colloid and backing to a waxed surface, and stripping off the backing while the film is adhered to the waxed surface and the colloid is adhered to the film.

7. The method which comprises providing a carbon tissue comprising a backing of an opaque fibrous material and a thin layer of unsensitized gelatin, covering the face of the gelatin with a thin layer comprising essentially nitrocellulose, sensitizing the colloid through the film by applying an aqueous solution of a water-soluble bichromate, substantially drying the carbon tissue and film, exposing the gelatin to an image through the film, applying the film side of the carbon tissue to a waxed surface, immersing the composite structure in water, removing the fibrous backing and washing out the soluble gelatin in the water, transferring the gelatin side to a silk screen, and stripping off the film.

8. A photographic carbon tissue comprising superposed layers consisting of an opaque fibrous backing, an unsensitized water soluble colloidal coating on the backing, and a thin porous film containing approximately equal amounts of nitrocellulose and glycerine on the surface of the colloid, said backing and film being adherent to the colloid but capable of being stirpped therefrom.

9. A photographic carbon tissue comprising an opaque fibrous backing, an unsensitized water soluble colloidal coating superposed on the backing, and a thin porous film containing approximately equal amounts of nitrocellulose and a material of the class consisting of glycerine and diethylene glycol on the surface of the colloid.

10. A photographic carbon tissue comprising an opaque fibrous backing, an unsensitized water soluble colloidal coating on the backing, and a thin porous film containing approximately equal amounts of nitrocellulose and a polyhydroxy a1- cohol on the surface of the colloid.

11. A photographic carbon tissue comprising superposed layers consisting of a fibrous backing, an unsensitized coating comprising gelatin on the backing, and a thin porous film containing approximately equal amounts of nitrocellulose and a material of the class consisting of glycerine and diethylene glycol on the surface of the coating.

JOHN F. HANSMAN. MELVIN J. JURISCH.

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

UNITED STATES PATENTS Number Name Date 1,327,931 Waters Jan. 13, 1920 1,640,815 Eggiman et al Aug. 23, 1927 1,804,555 Gentile May 12, 1931 1,915,873 Spencer June 27, 1933 1,942,872 Murray Jan. 9, 1934 2,030,731 Young Feb. 11, 1936 2,121,205 Lippert June 21, 1938 2,326,058 'Nadeau Aug. 3, 1943 2,337,012 Bjeig et al Dec. 14', 1943 2,367,420 Mullen Jan. 16, 1945 FOREIGN PATENTS Number Country Date 201,241 Great Britain Aug. 2, 1923

Claims (2)

1. THE METHOD WHICH COMPRISES PROVIDING A CARBON TISSUE WITH A FACIAL FILM OF A WATER-INSOLUBLE TRANSPARENT MATERIAL CONTAINING A MINOR PROPORTION OF A HYDROPHILIC MATERIAL AND AN INTERMEDIATE LAYER OF A WATER-SOLUBLE COLLOID, SENSITIZING, THE TISSUE IN AN AQUEOUS BATH CONTAINING A SENSITIZING AGENT THROUGH THE FILM, DRYING THE TISSUE, EXPOSING THE TISSUE TO AN IMAGE, PLACING THE FILM SIDE OF THE TISSUE IN ADHERENT CONTACT WITH A RIGID SUPPORT, REMOVING THE BACKING AND SURPLUS COLLOID FROM THE TISSUE WHILE ON SAID SUPPORT AND WHILE HELD BY SAID FILM, THEN BRINGING A SILK SCREEN INTO ADHERENT CONTACT WITH THE COLLOID WHILE THE MATERIAL IS STILL ON THE SUPPORT, AND FINALLY STRIPPING OFF THE FILM.

11. A PHOTOGRAPHIC CARBON TISSUE COMPRISING SUPERPOSED LAYERS CONSISTING OF A FIBROUS BACKING, AN UNSENSITIZED COATING COMPRISING GELATIN ON THE BACKING, AND A THIN POROUS FILM CONTAINING APPROXIMATELY EQUAL AMOUNTS OF NITROCELLULOSE AND A MATERIAL OF THE CLASS CONSISTING OF GLYCERINE AND DIETHYLENE GLYCOL ON THE SURFACE OF THE COATING.

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