US2228762A - Process for the production of photographs of luminous images and particularly of X-ray cinematographic images and developing solutions therefor - Google Patents

Description

Patented Jan. 14, 1941 UNITED a STATES PROCESS FOR THE PRODUCTION OF PHO- TOGRAPHS' OF LUMINOUS IMAGES AND PARTICULARLY OF X-RAY CINEMATO- GRAPHIG MAGES AND DEVELOPING SO- IUTION S THEREFOR Franz Hafstein, Bostock, Helmut Borst, Berlin-- Kopenick, and -Walther Forstmann, Berlin- Tempelhof, Germany No-Drawing. Application July 9. 1938. Serial No.

In Germany July 10, 1937 12 Claims. (01. 95-88) This invention relates producing photographic images .of pictures on luminous screens and especially to produce X-ray cinematographic images from luminous screens and developing 5 methods and baths for making the same.

Previously X-ray cinematographic photographs were made with apparatus which were very large and costly and which moreover required particularly experienced operators. Moreover, for this purpose supersensitised exposure material was employed whose high sensitivity could not be used since this material in photographic baths inclined extraordinarily readily to fogging which was particularly favoured by the low stability.

To sum up it is to be noted that attempts have been. made to improve X-ray cinematography merely from the aspect of the apparatus, luminous screens and films employed.

According to the invention, on the contrary, screen images free from defects as, e. g. X-ray cinematographic images are prepared without costly apparatus by subjecting the exposure material .used to an intensive development. This is the more astonishing as the view was previously.

firstly too much fogging was obtained particularly withthe use of supersensitised exposure material, and secondly too coarse a grain which has a disturbing efiect in the projection.

As intensive developer according to the invention, advantageously a developer containing a caustic alkali may be added. In general it is,

true the customary rapid developers often pro- 0 duce such coarse grain that the projection, particularly of small films developed in this way, is impossible, since the detail is lost in luminous screen images or X-ray photographs. This disadvantage is avoided with the developers according. to the invention in that to'the developer are added considerable quantities of sodium sulphite or another agent which dissolves silver, i. e. up to about 100 grams per litre. It was not to be expected that in caustic alkali developers which contain large quantities of reducing agents and maintained that by the intensive development,

other salts, such quantities of a silver solvent would be able to dissolve.

A developer rich in sulphite is prepared somewhat as follows:

and after solution 32 grams of caustic potash are added. With this developer for example on hard,

fog-free acting exposure material as is generally used in practice at present, a relatively small fogging with high gamma values is obtained, e. g.

a gamma value of 1.6-2.0and a fogging of 0.15 to 0.25 and, moreover, the weakest lightimpression is developed as well as possible since, furthermore, in this developer a developing time of 10-20 minutes may be employed.

A higher gamma value can also be obtained by addition of substances increasing the gradation oi the developer. preferably such substances as are not attacked in the strongly alkaline developer. As substances increasing the gradation ni-troor chloro-benzimidarole and chloro-benzotriazole may be particularly mentioned.

With such developers, for. the attainment ofscreen images free from defects, several methods may be used. Firstly, a negative development may be carried out with films of average sensitivity (up to about 17/ 10 Din.) which preferably are suited to the luminous screen in their spectral sensitivity, and which yield fine-grained images without fogging.

It is preferable to use a film material with a thin layered, preferably single layered, emulsion. In this it is not unconditionally necessary to use a particularly highly sensitive film; in fact less sensitive films produce the same effects. By the present process thus a completely new method is adopted. I

A hard acting film material has been shown to be particularly eifective. By hard acting exposure material, a material is understood which shows a harder gradation than the normal cinematographic film. The film material can preferably be hardened either in or after its manufacture or after the exposure or even during the development.

In general forv the purpose according to the J invention an exposure material is suitable in which by intensive development the lower part of the blackening curve rises steeply with simultaneous displacement of the curve to the left.

The gamma value should lie with development times of up to minutes'preferably above 1.5 in

' order to reproduce the feeble screen image in the a change 60-130 per second) as well as exposures with normal image change numbers (16-24) without necessitating expensive apparatus and films which are not storable for some time.

So that usable darkenings are obtained with such a rapid succession of images and consequent short exposure time, according to the invention preferably emulsions are used with a so-called tail in the gradation curve between the threshold and the beginning of the part of the curve used in photography. Such emulsions may have with normal exposures in certain circumstances a smaller sensitivity than other sorts; nevertheless these tail emulsionsin contrast to the general rules of photography-are preferred for the process according to the invention.

11, however, it is desired to develop exposed highly sensitive and in particular super-sensitised emulsions in the intensive developers care must be taken of the fact that these emulsions are more readily inclined to fogging than hard and less sensitive fine grained emulsions. If, therefore, they are to be developed in intensive developers so that their higher sensitivity compared with the less sensitive fine grained film is fully used, the fogging formed particularly with longer posure cinematographic film exposures of the X- ray luminous screen. In this first development fogging can not be avoided. In order to obtain a. clear image, therefore, the fogging is dissolved.

out in a reversal bath and the second development which gives a positive image is carried out in a fine grain developer like, e. g. with paraor ortho-phenylenediamine to which for improvement of the gradation, nitrobenzimidazole or similar materials are preferably added raising the gradation. When using this method of developing it is not necessary to over expose the light sensitive material up to six times as is necessary when using a fine grain developer without reversing the image.

A third possibility of producing photographic reproductions of pictures of feebly lighted objects on fluorescent screen consists in using any film material, especially such of high sensitivity,

provided a developer is employed. for instance, a developer containing carbonate to which com-I pounds are added capable of increasing gradation and power of developing especially at the lower part of the curve of gradation, i. e. a developer capable of developing even the faintest traces of a picture in a manner being relatively rich in contrast.

For the purpose of increasing gradation organic nitrogen compounds such as amines or their salts are suitable that, in the developersolutions used, split oil ammonia only in traces or not at all and that at the same time increase gradation. In many cases the addition of alkali iodides, especially of potassium iodide has proved of value. The following developer solution may be given as an example for this type of developer:

In 1 litre of water are dissolved Grams Hydroquinone 6 Monomethyl p-amido phenol sulfate 2 Sodium meta phosphate 0.5 Anhydrous sodium sulfite 25 Anhydrous sodium carbonate 40 Potassium bromide s 2 Ethylamine hydrochloride 0.1 Sodium iodide 0.25

In the place of the last named two compounds ethyl amine hydroiodide may be used likewise. When employing hexamethylene tetramine as compound increasing gradation even alkalihydroxide may be added to the developer solution in order to increase its developing power; for, the splitting off of ammonia in such a developer takes place only very slowly.

In general, the amount and the kind of alkali and/or carbonate added to the developer depends on the compounds used for increasing gradation.

Further it is preferable that the spectral sensitivity, i. e. the colour sensitivity of the photographic emulsion is similar to the emission spectrum of the luminous screen or that the spectral sensitisation of the emulsion is substantially uniform in the range between violet and orange.

It is advantageous particularly with exposures with a high image change uxgEr, to take a strongly illuminating light scree which, in proportion to its power of illumination, shows practically no after-lighting effect. There may be used for example a suitable zinc-cadmium sulphide screen which is on the market under the name Super-Sirius.

The use of X-ray screens is advantageous whose screen brightness rises with increase of X-ray energy. Such screens are those which with smaller energies, e. g. in diagnosis give a greater brightness which, however, with increasing energy does not increase considerably.

By the advance of the luminous screen technique, which is now capable of producing fluorescent screens which are able to emit intensive fiuorescent light even from the short wave part 'of the photographically eifective spectrum, the working up of films can be rendered essentially more easy. In consequence of this in accordance withthe invention a screen may be used which radiates, e. g. blue-violet light and an emulsion with a particularly high individual sensitivity for these wavelengths, which thus does not need to be specially optically sensitised. The working up or development of this'emulsion may then take place with orange light in a convenient manner which renders the working process particularly easy.

This process can also be used if cinematographic images are not to be made but individual images, or small images from the luminous screen,

particularly with very short exposure times.

Likewise, in this way also exposures of oscillating graphs or the like may be made.

Of course many changes and variations may be made in the exposure material use, in the developing method and so forth in accordance with the principles set forth herein and in the claims annexed hereto. What we claim is:

1. A process for the preparation of photographic and cinematographic pictures which comprises providing a film having highly light sensitive exposure material thereon, exposing the same to an image on a luminous fluorescent screen and subjecting the film toan intensive alkaline developing operation, characterised in that'devel-v opers containing a high proportion of caustic alkali are used witha considerable content, approximately to the limit. of solubility, of reducing agents. f

2. A process for the preparation of photographic and cinematographic pictures which comprises providing a film having highly light sensitive exposure material thereon, exposing the same to an image on a luminous fluorescent screen and subjecting the film' to an intensive alkaline developing operation, characterised in that strongly alkaline developers are used with an addition of materials raising the gradation.

3. Process for the preparation of photographic and cinematographic pictures which comprises providing a film having highly light sensitive exposure material thereon, exposing the same to an image on a luminous fluorescent screen, and subjecting the film to an intensive alkaline developing operation, the exposure material being flrst subjected to an intensive development and after reversal to a development capable of producing fine grained images. r

4. Process according to claim 3, characterised in that as a fine grain developer at phenylene-diamine taken from the class consisting of the ortho and para compounds is used.

5. Process for the preparation of photographic and cinematographic pictures which comprises providing a film having highly light sensitive exposure material thereon, exposing the same to an image on a luminous fluorescent screen, and subjecting the fllm to an intensive alkaline developing operation, such developers being used which contain alkali carbonate and an. organic nitrogen compound capable of increasing gradation.

6. Process according to claim 5, characterised in that as'organic nitrogen compounds organic amines or their salts are used.

7. Process according to claim 5, characterised in that alkali iodide is used besides the organic nitrogen compound capable o'fincreasing gradation.

8. A developer for the preparation of photographs obtained by exposure of a film to a luminous fluorescent screen comprising a material of high sensitivity and having a high proportion of caustic alkali, the solution being substantially saturated with the developer.

9. A developer for the preparation of photographs obtained by exposure of a film to a luminous fluorescent screen comprising a material of solution containing hydroquinone to a p int of I substantial saturation, a substance taken from the class of amines and amine salts, a relatively high concentration of a soluble sulphite and of caustic alkali. j

11. Process for the preparation of photographic 'and cinematigraphic .pictures which comprises preparing "a film which has a highly sensitive emulsion, exposing the same without overexposixig, placing the same in an intensive developing solution containing hydroquinone to a point of substantial saturation, a substance taken from the class of amines and amine salts, a relatively high concentration of a soluble sulphite and of caustic alkali, said solution containing also a substance capable of increasing gradation taken from the class of nitroand chloro-be'nzimidazole and chloro-benzotriazole.

preparing a film which has a highly sensitive emulsion, exposing the same without overexposing, placing the same in an intensive developing solution containing hydroquinone to a. point of substantial saturation,. a substance taken from the class' of amines and amine salts, a relatively high concentration of a soluble sulphite and of caustic alkali, said solution containing also a substance capable of increasing gradation taken from the class of nitroand chloro-benzimidazole and chloro-benzotriazole,- and-then treating the film vin a reversal bath to dissolve out fogging, said bath containing phenylenediamine.

FRANZ HAFSTEIN. HELMU'I' BORST. WAL'IHER FORSTMANN.