US1962348A - Photographic reversal process - Google Patents

Description

Patented June 12,1934

. rnorrooimrmo nEvEasAIi ra'oonss Edwin Ernest Jelley, Weald stone, England, assigner toEastman Kodak Company, Rochester;

N. Y., a corporation of New York l This invention relates to the production of positivephotographic images upon the same support inthe same sensitive layer as that which is exposed" in the camera by a reversalprocess of the kind i-n which no exposure to actinic light is made after the first development. In such processessodium sulphide or a compound of formaldehydeand sodium hydrosulphite has hitherto been used to "fog or darken the image after the plate or filmhas" been treated in the reversal bath but with the substances hitherto used it has not been possible'fsubsequently to employ the'usual photographic developers and as a result'the'control image has been considerably restricted.

'Ihe object'of the present invention is to providea process by which these disadvantages can be overcome.

. l 'Accordin g t'o-this invention the him after it has been submitted t" the reversal bath is treated with ance or a selected dye-stufi, in itself well known,

' prior to redevelopment with any suitable known "photographic developer or in conjunction with As a result the colour and opacity such'develope'r. of the final image can be controlledwithinwide limits during'the'final developing operation even the case "of v ry thin emulsions.

-. m' b tances found suitable for use as nucleus forming or iogging agents prior-to or in con"unction with (well-known photographic developers, are sodium hydrosulphite, methylene blue, hydrazine and; hydrogen peroxide.

Theuse of'hydraz'ine tends to cause the'ernul sion' to separate from its support during the redevelopment of the film owing to the gas which is then evolved and to counteract this it is therefore necessary for the developer to contain an aldehyde or ketone such for example as formaldehyde acetone or acetaldehyde which combines chemically with the excess of hydrazine and yields an inert compound.

The following are specific examples of 'how the invention can be carried out.

Example I .-The sensitive plate, film or paper (hereafter referred to as a film) is first exposed in the usual way in the photographic apparatus and fully developed in any known suitable developer such for example as one made up of equal parts of the following solutions:---

Solution A Ounces Hydroquinone 2 sodium bisulphite 3 Formalin (Commercial) 2 Water to make fluid ounces of the op'acityand colour of the final positive "a nucleus forming agent such as a reducing subin a caustic hydroquinone developer as above deafter bein'g treated in a 10% aqueous solution of N0 Drawing. Application April, 2, 19 30,[Serial In Great Britain November 13,

Waterto make 80 fluid ounces Afterbeing washed for about a minute the film is bleached in a solution which may be as follows:-.-

1 Potassium bichromate. ounce- Sulphuric acid -4 1 fiuid ounces Waterto make80 fluid ounces 70 The filmis then again washedand immersed in a clearing hath made up as follows:--

. 7 Parts Sodium sulphite 10 Sodium hydro'sulphite 2 Water L' 87 /2 After being rinsed, the mm is then developed scribed and subsequently given such washing or other treatment as would be necessary or'customary,and is dried in the usual manner.

Example II. The film is exposed, developed and bleached'inthe manner above described and 85 sodium sulphite is immersed in a separate bath containing an aqueous solution of 0.01% methylene blue prior to being redeveloped and treated in the'm'anner already described.

' Example 1II.-'-Instead'of the'film being submittedto the action of a'fogging or nucleusforming agent prior to redevelopment, this agent is incorporated in the redeveloping bath. The film after beingdeveloped andclea'red' in a 20% aqueous solution of sodium sulphite is washed and immersed in a caustic hydroquinone developing bath (made up as already described) containing in addition one part of methylene blue to every 1000 parts of developing solution. The addition of this dye-stuff to the developing bath enables the opacity and colour of the image to be controlled within wide limits and eliminates the separate step of treating the film in a bath containing afogging or nucleus-forming agent prior to redevelopment.

It will be appreciated that the particular solutions stated above are given by way of example; only and that considerable modifications may be made in the process within the limits of the invention.

What I claim as my invention and desire to secure by Letters Patent is:--

1. In a process of making positive photographic images by reversal from negative photographic images in a light-sensitive element which process comprises rendering the negative image inert and transparent, treating the light-sensitive element by chemical means to render it developable and then developing the sensitive element, the improved step of submitting said element, before development begins, to the action of a solution containing methylene blue as a nucleus-forming agent for the sensitive element.

2. In a process of making positive photographic images by reversal from negative photographic images in a light-sensitive element which process comprises rendering the negative image inert and transparent, treating the light-sensitive element by chemical means to render it developable and then developing the sensitive element, the improved step of submitting said element, before development begins, to the action of a solution containing hydrazine as a nucleus-forming agent Ior 4 the sensitive element.

3. A process of making positive photographic images by reversal from negative photographic images in a light-sensitive element which comprises bleaching in an aqueous solution of potassium bichromate and sulphuric acid, treating the light-sensitive element with an aqueous solution of sodium sulphite and sodium hydrosul phite and developing the sensitive element in a caustic hydroquinone developer.

4. A process of making positive photographic images by reversal from negative photographic images in a light-sensitive element which comprises bleaching in an aqueous solution of potassium bichromate and sulphuric acid, clearing and treating the light-sensitive element by immersion respectively in a 10% aqueous solution of sodium sulphite and then in an aqueous solution of 0.01% methylene blue and developing the sensitive element in a caustic hydroquinone developer.

5. A process of making positive photographic images by reversal from negative photographic images in a light-sensitive element which comprises bleaching in an aqueous solution of potassium bichromate and sulphuric acid, immersing the light-sensitive element in an aqueous clearing solution of 20% sodium sulphite and developing in a solution of a caustic hydroquinone developer containing one part of methylene blue to every 1000 parts of developing solution.

6. In a process of making positive photographic images by reversal from negative photographic images in a light-sensitive element which process comprises rendering the negative image inert and transparent, treating the light-sensitive ele- .ment by chemical means to render it developable and then developing the sensitive element, the

improved step of submitting said element, before development begins, to the action of a solution containing hydrazine as a nucleus-forming agent for the sensitive element and adding an aldehyde to the solution used in the subsequent developing.

7. In a process of making positive photographic images by reversal from negative photographic images in a light-sensitive element which process comprises rendering the negative image inert and transparent, treating the light-sensitive element by chemical means to render it developable and then developing the sensitive element, the improved step of submitting said element, before development begins, to the action of a solution containing hydrazine as a nucleus-forming agent for the sensitive element and adding a ketone to the solution used in the subsequent developing.

. 8. In a process for making positive photographic images by reversal from negative photographic images in a light-sensitive element, which process comprises rendering the negative image inert and transparent and then redeveloping the sensitive element, the improved step of rendering the element redevelopable, without reexposure, in developers having ordinary developing properties that comprises submitting the element to a bath including hydrazine.

9. In a process for making positive photographic images by reversal from negative photographic images in a light-sensitive element, which process comprises rendering the negative image inert and transparent and then redeveloping the sensitive element, the improved step of rendering the element redevelopable without reexposure, in developers having ordinary developing properties that comprises submitting the element to a bath including methylene blue.

10. A photographic reversal process comprising the formation of a silver image in a light sensitive, silver halide, emulsion layer, rendering the silver image inert and transparent, treating the remaining silver salts with a bath including a nucleus forming agent and redeveloping the salts with an agent other than the nucleus forming agent.

11. A photographic reversal process comprising the formation of a silver image in a light sensitive, silver halide, emulsion layer, rendering the silver image inert and transparent, treating the remaining silver salts withsodium hydrosulfite to an extent insuflicient to reduce the remaining silver salts but suflicient to render them developable, and redeveloping the salts with an agent other than the sodium hydrosulflte.

EDWIN ERNEST J ELLEY.