US2251965A

US2251965A - Color photography and color photograph

Info

Publication number: US2251965A
Application number: US195386A
Authority: US
Inventors: Verkinderen Honore
Original assignee: Gevaert Photo Producten NV
Current assignee: Gevaert Photo Producten NV
Priority date: 1937-03-30
Filing date: 1938-03-11
Publication date: 1941-08-12
Anticipated expiration: 1958-08-12
Also published as: BE427106A; GB511535A; FR835567A

Description

Aug. 12, 1941. H. VERKINDEREN 2,251,965

COLOR PHOTOGRAPHY AND COLOR PHOTOGRAPH l Fi1ed March 11, 1938 f/'X /uc Componen f ase from, 1 7 f/gif Z0 l/mdalwf g'gglgnage Zig/zi and Develop of rea/2 bmw/:m fo Yellow /ae-67ee/z /ma e uppar Yellow /magfe 35x 05e /rrau haai p g Wiege/zia /mage Patented Aug. 12, 1941 COLOR PHOTOGRAPHY AND COLOR PHOTOGRAPH Honor verhinderen, Mortsel, near Antwerp, Belgium, assignor to Gevaert Photo-Producten, N. V., Dude-God, near Antwerp, Belgium Application March 11, 1938, Serial No. 195,386 In Austria March 30, 1937 2 Claims.

This invention relates to color photography.

The invention has for its object an improvement in color photography and consists in a method which through color development enables a dilTerently colored image to be produced in each of the separate emulsion layers of a multilayer photographic material.

Different methods of producing differently colored images by color development in the different emulsion layers of a multilayer photographic material have already been proposed.

One of these methods consists in this, that to each emulsion layer -a dierent dye component is added, which for each individual layer produces with the oxidation products of one and the same developer the ldesired color. This method has on the one hand the advantage, that with a single development the different color images are produced in all emulsion layers, and on the other hand very great disadvantages, namely:20

thechoice of the dyes is limited, owing to the fact that the diierent colors have to be produced with the oxidation products of one and the same developer: the dyestuii components added to the emulsion have a detrimental effect on the durability of the emulsion; iinally the fixing of the dyestu components in the different emulsion layers so that they will not wander from one layer into the other is a problem which is diicult to solve.

Another known method consists in this, that each layer is developed separately by means of a suit-able developer, to which a suitable dye component is added. For carrying this into effeet the so-called controlled penetration Ol the baths into lthe superposed emulsion layers is employed. According to this method, certain chemicals, which greatly retard the penetration of the Abaths in the emulsion layers, are added to the baths, the penetration of which it is desired to control. As soon as the bath has penetrated to the bottom of the layer to be treated, the action of the bath is checked, so that it is thus possible 'to operate separately on each layer. The practical application of the controlled penetration of the baths is however very complicated and requires a very exact and difficult control. Moreover, the treatment of a lm by this method takes much time, as before each treatment, in which the penetration of the bath is to be controlled, the film has to be dried.

According to the invention eachlemulsion layer of a multilayer material is also developed with the desired developer, to which a suitable dye component is added. For enabling each indi- 50 sharp one.

., after exposure, is developed to the desired color,

this being done before the exposure and development of another layer. The separate exposure of each l-ayer is carried out by a method which might be called the controlled penetration of light.

The method is based on the phenomena now to be described:

If an emulsion layer be exposed to ordinary light and then developed and if a microscopic cross-section be thereupon made through the ayer thus developed, it wm be found, that the boundary in depth between the zone without developed silver and the Zone with developed silver is not sharp, but that there is a transitory transition, namely from the zone where the density of the emulsion has reached its maximum towards the zone where no silver is present. If ithis experiment be carried out with a multilayer material, the emulsion layers of which possess approximately the same sensitivity and the same sensitiveness to color, the undermost l-ayers will,

with increasing exposure, exhibit a rather high degree density long before the uppermost layer has reached its maximum density. In this case a micro cross-section will show that the uppermost silver grains of the lower emulsion layers are already capable of being developed long before the lowermost silver grains of the upper emulsion layer become capable of being developed. This is to be explained by the fact that the uppel'most silver grains of an emulsion layer are always more sensitive than the undermost silver grains of the same emulsion layer.

The result is entirely different, however, when the emulsion layer, ihstead of being exposed to ordinary light, is exposed to a light which is strongly absorbed by the emulsion l-ayer. If a gelatine emulsion layer be exposed for instance to short wave ultra-Violet light, a light which, as is Well known, is strongly absorbed by the gelatine, it will be found, on a microscopic crosssection of the developed material, being made, that the boundary in depth between the zone Where all the silver grains and the zone where no silver grains have been developed is a very This boundary is all the sharper, the more thoroughly the light used is absorbed by the emulsion layer. Thus, when the exposure is made to short Wave ultra-violet light, the boundary between the zone showing the maximum density and the zone showing no blackening the emulsion a dyestufr which strongly absorbs the light with the wave-length employed. The same effect may be obtained, if the exposure be made for instance to blue light, and the emulsion be dyed yellow before the exposure.

By exposing the film to a light which is sufflclently absorbed by the emulsion it is therefore possible, by correctly adjusting the exposure, selectivelyto regulate the depth of penetration of the light into the emulsion layer. It has been found, that for a definite intensity of illumination and for a denitely strong absorption capacity of' the emulsion for the light used for expesare the possibility of penetration of the emulsion layer by the light is limited and, with suf= ficiently long periods of exposure, becomes independent of the duration of exposure.

If exposure to a light which is suilciently strongly absorbed by the emulsion layers be employed with a multilayer film, it is possible, with a correctly adjusted exposure, to limit the developability of the light-sensitive layers to one or to several layers. This can be best effected if the exposure be made from the rear side, for the very reason that, as already stated above, the uppermost silver grains of an emulsion layer are always more sensitive than the lowermost silver grains.

The process according to the invention is based on the phenomenon just described and consists furthermore in this, that in the first place one of the outer emulsion layers of a multilayer material, either the top or the bottom emulsion layer, is separately exposed to a light which is strongly absorbed by the emulsion, that the emulsion layer thus exposed is thereupon de veloped with a color developer which produces a colored image in the desired color and that finally the emulsion layer which follows the developed layer or the other outer emulsion layer is in the same way separately exposed and developed with a suitable color developer and the further layers are treated successively in the same way. The remaining last layer may of course be exposed to ordinary light which is not absorbed by the emulsion.

In order to explain the process a description is given below of the mode of operation with reference to the accompanying drawing, showing a flow diagram of the operations, according to which an image in natural colors is obtained on a three-layer material. It is of course to be understood that the invention is not limited to this mode of operation, but that the invention comprises all modes of operation in which one or more light-sensitive layers of a multi-layer material are exposed separately to a light which is strongly absorbed by the emulsion layers.

The three-layer material for instance, which is used for the production of images in natural colors, is of the known type. On a support the following layers are coated, one over the other: an emulsion layer sensitised for red; a gelatine layer which may contain a red filtering dyestuf; an emulsion layer sensitised for green; a gelatine layer which may contain a yellow filtering dyestui; finally an emulsion layer which is not sensitised and is therefore only sensitive to blue. The yellow filtering dyestuf may alternatively be added to the uppermost emulsion layer instead of to the underlaying Gelatine layer. Although the gelatine layers Vbetween the various emulsions are not indispensable, their presence is of advantage, They offer great advantages for the reason that they make it possible, when the individual light-sentitive layers are separately exposed, to employ a more thorough exposure and thus make allowance for the differences in thickness of the layers.

The three-layer material is exposed in an ordinary photographic or cinematographic camera; through the exposure a latent image is formed, viz. by the blue rays in the upper, the green rays in the intermediate and the red rays in the lower light-sensitive layer. After exposure in the camera the three-layer material is developed in an ordinary developer and thoroughly fixed. In this way three images are produced, one in each emulsion layer. 'I'he silver developed in the three layers is then reconverted by one of the known methods into light-sensitive halogen silver, whereupon each' halogen silver image is separately developed to a color image of deinite color. The procedure is for instance such that the lower emulsion layer is exposed from the back of the film to short wave ultra-Violet light, this exposure being so adjusted according to intensity and duration that the layer is rendered developable through and through, whereas the other two layers remain undevelopable. The material exposed in this manner is thereupon developed with a color developer which develops the halogen silver image in the lower layer and gives a blue-green color image. A suitable developer is, for instance:

Formula 1 Dimethyl-p-phenylendiamine g-- 0.70 Sodiumsulphite, cryst g-- 10.00 Sodiunicarbonate, anhydr g-- 20.00 Water e ccm-- 1000.00 a-Naphthol g 0.80 Methylalcohol ccm 100.00

When the film has been washed after development, it is treated for two minutes in a bath of tartrazine solution, The upper emulsion layer is then exposed from above to short wave ultraviolet light. The intensity of' exposure and the concentration of the tartrazine solution are regulated in such a manner that the penetration of the light remains limited to the upper emulsion layer which is itself rendered developable through and through. After this exposure the material is developed in a color developer which develops the halogen silver image in the upper layer and gives a yellow color image. A suitable developer is, for instance:

Formula 2 Dimethyl-p-phenylendiamine g-- 0.80 Sodiumsulphlte, cryst g 10.00 Sodiumcarbonate, anhydr g-- 20.00 Water ccm-- 1000.00 Acetoacetanilide g-- 0.80 Isopropylalcohol ccm 100.00

After development the film is exposed to white light and exposed through and through, whereby the halogen silver image in the middle layer as well is rendered developable; after this exposure the material is developed in a color developer which develops the halogen silver image in the middle layer and gives a magenta color image. A suitable developer is, for instance:

Formula 3 Dimethyl-p-phenylendiamine g 0.70 Sodiumsulphite, cryst g 10.0.0 Sodiumcarbonate, anhydr g 20.00 Water com 1000.00 'p-Nitrobenzylcyanide g-- 0.80 Acetone com 30.00 Isopropylalcohol ,ccm 70.00

After in this way the desired color image has been formed in each emulsion layer, the metallic silver is removed from the material, for instance by Farmers reducer. A negative color image is obtained, in which the images consist exclusively of color gelatine. If such a negative lm be printed on a similar three-layer material and this material be treated by the process described above, a positive color image in natural colors is finally obtained. p

The process described above may of course be modified in many ways. Thus, for instance, after exposing and developing the lower layer, the reduced silver may be removed from this layer and thereupon the three-layer material be dyed a diffused yellow by immersion in a 5% solution of tartrazine. The so-treated threelayer material may then be exposed again from the reverse side, for instance with `dark blue light which is not absorbed by the color image in the lower layer, but is absorbed by yellow dyestuff which enters the material, owing to its treatment in the bath of tartrazine solution. The length of exposure may be so regulated that the light illuminates the middle layer through and through and renders it developable, without the upper layer being rendered developable. The halogen silver image in the middle layer may then be developed with the developer already given under Formula 3 to a magenta color image, whereupon the material may be exposed to white light and the halogen silver image in the upper layer developed to a yellow color image by means of the developer according to Formula 2.

Instead of the material which is exposed in a camera being developed to a negative image, the material may be developedl directly to a positive image, namely by the known reversal method. For this purpose the material, after being exposed in the camera, is first developed, whereupon the reduced silver is removed from the material, for instance by means of an acid solution of sodium permanganate. A positive halogen silver image will thus remain in each layer. Each of these halogen silver images may be developed by the processes already described to a color image .of the desired color, so that, aft-er remova1 of the silver reduced during the color development, a positive image in natural colors is left.

I claim:

1. A method of producing a composite threecolor image on a photographic material consisting of a support coated with three superposed,

differentially color-sensitive emulsion layers having a latent image of a color component of said color image in each of said layers which comprises converting the latent image in each of said layers into a corresponding light-sensitive silver salt image, said layers being otherwise undifferentiated, exposing one side of said material to short-wave, ultra-violet light which is strongly absorbed by the gelatin of said emulsion layers independently of the presence of any other light absorbent and selected as to intensity to be substantially wholly absorbed by said gelatin of the outer emulsion layer on the exposed side of the material whereby the silver salt image in said layer is converted into a corresponding latent image without substantially affeecting the silver salt image in the layer below it, developing the latent image formed by said exposure to a corresponding color image, thereafter exposing the other side of said material to short-wave, ultraviolet light which is strongly absorbed by the gelatin of said emulsion layers independently of the presence of any other light absorbent and selected as to intensity to be substantially wholly absorbed by said gelatin of the outer emulsion layer on the second exposed side of the material whereby the silver salt image in said layer is converted into a corresponding latent image without substantially affecting the silver salt image in the layer below it, developing the latent image formed by said second exposure to a corresponding color image, and thereafter exposing the intermediate emulsion layer to light which will penetrate said imtermediate layer through one of said outer layers and developing the latent image thereby formed to a corresponding color image.

2. A method of producing a composite threecolor image on a photographic material consisting of a support coated with three superposed emulsion layers containing in each of said layers a light-sensitive silver salt image corresponding to a dilerent color component of said color image, said layers being otherwise undifferentiated, which comprises exposing one side of said material to short-wave, ultra-violet light which is strongly absorbed by the gelatin of said emulsion layers independently of the presence of any other light absorbent and selected as to intensity to be substantially Wholly absorbed by the gelatin of the outer emulsion layer on the exposed side of the material whereby the silver salt image in said layer is converted into a corresponding latent image without substantially affecting the silver salt image in the layer below it, treating the material with a color developing solution adapted to convert the latent image formed in said outer layer by said exposure to a corresponding color image, thereafter exposing the other side of said material to short-wave, ultra-l violet light Which is strongly absorbed by the gelatin of said emulsion layers independently of the presence of any other light absorbent and selected as to intensity to be substantially wholly absorbed by the gelatin of the outer emulsion layer on the second exposed side of the material whereby the silver salt image in said layer is converted into a corresponding latent image without substantially affecting the silver salt image in the layer below it, treating the material with a second color developing solution adapted to convert the latent image formed in said second outer layer by said second exposure to a corresponding color image differing in color from said first color image, and thereafter exposing the intermediate emulsion layer to light which will penetrate said intermediate layer through one of said outer layers and treating the material with a third color developing solution adapted to convert the latent image formed in said intermediate layer by said third exposure to a corresponding color image diiering in color from both said rst and said second color images.

HoNoR VERKINDEREN.