US2193023A - Photographic reversal process - Google Patents

Description

Patented Mar. 12, 1

UN l1" S Com, New do u No z.

a one.

producing positive images by reversal.

Photographic reversal images are produced in two general ways. in each of these the sensitive layer is exposed to light and the original latent image is developed to a negative. The negative silver image produced in way is then re- ,inoved without destroying the sensitivity of the unexposed silver halide. 'fiiis is usually done by means of a bath of potassium permanganate and sulfuric acid. After removal of the negative silver image in this way, the sensitive layer may be either exposed to light or checally logged without exposure to light, to produce a latent image which may then he developed in the usual way to produce a positive reversal image.

It is an object-oi the present invention to simplify this reversal process by provig a means for omitting one of the customary steps. A further object is to provide a method for producing a black and white reversal image in a silver halide layer without removal of the negative silver image prior to the final fimng step. Other objects will appear from the folio description of our invention.

'These objects are accomplished by w-r out the reversal development in a coupler developer which produces both a silver image and also a dye image which protects the silver image so i that it is not removed in later -1 such as ferricyanide and hypo.

in care out our process the sensitive layer is first exposed, either to an object or under a transparency of an image, and is developed to a negative silver image in an ordinary developer, such as a customary metal-hydroquinone developer. The layer is then thoroughly washed in water and is exposed to the desired extent without removal of the negative silver image. This exposure may he made either from the emulsion side or through the support in the case of a film or plate. The layer is then developed to the required density in a coupler developer which forms a positive silver image and a dye image simultaneously in the layer. The coupler compound must be one which produces a dye of substantially neutral grey density or which protects the positive silver image in such a way that it is not removed in subsequent baths of the process. The layer is then fixed in a solution, such as potassium ferricyanide and hypo, which removes either the negative silver image or both the negative and positive silver images without afiecting the positive dye image. The positive ng baths.

arcane v nsvansm. rnooass Weslcy T. Hanson, Ira,

Rochester, N. E, asslgnors to Eastman heater, N.

FPF T Application dell-lull No.

1'1 FFICE Y., a corporation of April 6, was. 200,501

dye or dye and silver image rem duce substantial neutral grey dye images may also he used.

Thefollowing eaamples, which are illustrative only, indicate developing solutions which may he used'ior the reversal development, accord to our invention:

Example I Diethyl p-phenylene dla g Sodium carbonate do 30 Sodium subtitle". do 6 p-Benzyl phenol do 3 Sodium hydroxide do 5 ater to er" 1 ltaumple H 2-amino-5-diethyl won: toluene chloride "er Sodium sulflte do Sodium carbonate dot Potassium bromide do Potassium thio'cyanate ..do p-Benzyl phenol -do Sodium hydroxide do- Water to -Jiter-..

It is to be understood that we may use a of the usual p-phenylene diamine coupler developers other than those referred to above, such as dlmethyl psphenylene diamlne, or any other p-phenylene diamine developer conta a primery amino group. The developing solution may also contain other well known ingredients and the proportions of the various developer oonstituents may be varied over wide ranges.

Other well known expedients of photographic reversal processes may be used in conjunction with our reversal development. For exple,

the light exposure prior to the reversal deve opment may be controlled to produce the desired density in the final image. ,If the originalex-.

posure is too great, a longer second exposure can be given and vice versa so that a constant developing time will aflord equally good results. The

process of controlling the second exposure in our process is somewhat diflerent from that used in the customary reversal processes in which the silver is removed before the second exposure so that an over-exposed film has a high transmission and an unexposed film has a lower transmission. In the present process an overexposed negative will have a very low transmission and an unexposed negative will have a high transmission, and a suitable exposure control method must be used. This method of controlling the density of the final image in a color development reversal process is described in Seymour U. 5. Patent No. 1,939,231, granted December 12, 1933.

The action of p-benzyl phenol in a coupler developer is somewhat difierent than that of the majority of coupler compounds in that it prevents the removal of the metallic silver by treatment in the usual oxidizing baths. 'Ilie final image is, therefore, a combined silver and dye image which is substantially neutral grey in color and which is highly satisfactory for the production of black and white photographic images. Although we do not wish to be limited to any particular explanation of the reason for this action, we believe that the dye formed by union of the p-benzyl phenol with the oxidation prodvuct of p-phenylene diamine developing agent protects the metallic silver image in some manner such as by formation of a protective coating of the dye around the silver image, so that the oxidizing baths are not able to attack the silver. It is to be understood that numerous other modifications and equivalents are possible in our process and that our invention is to be limited only by the scope of the appended claims.

, What we claim is: 1. The method of forming a photographic reversal image having a substantially neutral grey color which comprises exposing a gelatino-silver halide layer to a light image to form a negative latent image therein and developing said latent image to metallic silver, exposing the layer to a uniform light source, without removing the negative silver image from,the layer, developing the layer in a developing solution containing a p-phenylene diamine developing agent and a p-benzyl phenol coupler compound to form a positive image in the. layer and removing the metallic silver negative ie from the layer.

2. The method of forming a photographic reversal image having a substantially neutral gray color which comprises exposing a gelatino-silver halide layer to a light image to form a negative latent image therein and developing said latent image to metallic silver, exposing the layer to a uniform light source, without removing the negative silver image from the layer, developing the layer in a developing solution containing a p-phenylene diamine developing agent and a p-benzyl phenol coupler compound to form a positive image in the layer ahd fixing the layer in a ferricyanide and hypo bath.

3. In the method of producing a black and white photographic image by reversal, the step which comprises developing the reversal image in a coupler developer containing a p-phenylene diamine developing agent and a p-benzyl phenol coupler compound. g

4. In. the method of producing a black and White photographic image by reversal, the steps which comprise developing a negative metallic silver image in the layer and without removal of the metallic silver image, developing a reversal image in the layer in a coupler developer containing a p-phenylene diamine developing agent and a p-benzyl phenol coupler compound.

5. In the method of producing a black and white photographic image by reversal, the steps which comprise developing a metallic silver, negative image in the layer and without removal of the negative image, developing in the layer a reversal image in a coupler developer comprising a diethyl p-phenylene diamine developer and a p-benzyl phenol in substantially equal amounts.

6. In the method of producing a black and white photographic image by reversal, the steps which comprise developing a metallic silver neg-= ative in the layer and without removal of the negative image, developing in the layer a reversal image in a coupler developer comprising a diethyl