US2262986A - Photographic backing paper - Google Patents

Description

Nov. 18, 1941- E. L. BAXTER PHOTOGRAPHIC BACKING PAPER Filed Nov.- 2, '1940 wank? IN V EN TOR W A TTORNEYS Patented Nov. 18, 1941 PHOTOGRAPHIC BACKING PAPER Ernest L. Baxter, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application November 2, 1940, Serial No. 364,061

4 Claims.

This invention relatesto photographic backing paper, and more particularly to the ink with which photographic backing paper is marked.

As is well known in the art, it is customary to roll up photographic roll film with a strip of backing paper, which is usually black on one side and colored on the other. This backing paper carries, on the colored side, markings or indicia which can be seen through the small window in the back of the camera, and indicate to the user the points at which winding should be stopped, and the serial numbers of the exposures. The markings are usually covered by a transparent overcoating on the paper. When the film is rolled up with the backing paper, the printed side of the paper is in contact with the emulsion side of the film.

The accompanying drawing shows a section of two convolutions of film with an interposed layer of backing paper, as it occurs in a roll film cartridge. I, I represents the film base, carrying the emulsion 2, 2. 3 represents the backing paper, carrying indicia 4.

The inks which have been most used for mark-- ing photographic backing paper usually consist of a dye, a binder and a solvent, and are such as to have no effect on unexposed photographic emulsions with which they are in contact. However, if a considerable period of time fel'apses between the exposure of a portion of the film and its development, so that the backing paper remains in contact with an emulsion containing a latent image, the markings on the backing paper may reproduce themselves as an intensification of the latent image on the film. When the film is developed, the markings thus appear in the pictures.

I have discovered that intensification of the latent image on a photographic film by the markings on the backing paper may be prevented byv incorporating certain reducing agents in the ink used for marking the backing paper. I have tested a very considerable number of reducing agents for this purpose, I have found only a few which are operative. These are: sodium sulfite, ferrous sulfate, sodium formaldehyde sulfoxylate, and sodium hydrosulfite. I prefer to use sodium sulfite because it oxidizes to sodium sulfate, which is normally found as a loading agent in all dyes and hence does not introduce a foreign substance into the ink.

While I have found that an amount of sodium sulfite equal to about 1% of the total solids in the ink is effective for preventing intensification of the latent image by the ink. 0.5% has been found to be ineffective, and 2% has been found to destroy the latent image. 1% of sodium sulfite, based on the total solids in the ink, has been found to have no action on unexposed film even under tropical storage conditions.

By way of illustration, by which I am not to be limited, I give the following example of an ink for marking photographic backing paper according to my invention.

2% of Nigrosine 2011 Gone. is dissolved in a 4% aqueous gelatin solution to form an ink. To 25 /2 lbs. of this ink is added 7 grams of sodium sulfite dissolved in 100 cc. of hot water.

What I claim as'my invention and desire to be secured by Letters Patent of the United States is:

1. Photographic backing paper bearing indicia printed with an ink comprising a dye and approximately l%, calculated on the total solids in the ink, of a reducing agent selected from the group consisting of sodium sulfite, ferrous sulfate, sodium formaldehyde sulfoxylate and sodium hydrosulfite.

2. Photographic backing paper bearing indicia printed with an ink comprising a dye and approximately 1%, calculated on the total solids in the ink, of sodium sulfite.

3. A roll film cartridge comprising inter-rolled strips of film carrying a photographic emulsion and of backing paper, that surface of the backing paper which is in contact with the photographic emulsion carrying indicia printed with an ink comprising a dye and approximately 1%. calculated on the total solids in the ink, of a reducing agent selected from the group consisting of sodium sulfite, ferrous sulfate, sodium formalde hyde sulfoxylate and sodium hydrosulfite.

4. A roll film cartridge comprising inter-rolled strips of film carrying a photographic emulsion and of backing paper, that surface of the backing lated on the total solids in the ink, of sodium ERNEST L. BAIXTER.

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