US2367936A - Photographic printing method - Google Patents

Description

Jim. 23, 11945. B GASPAR 2,367,936

PHOTOGRAPHIC PRINTING METHOD' Filed June 12, 1941 2 Sheets-Sheet 1 151.05 SENSITIVE -1 n=0 YELLOW ji/ 5- RED SENSITIVE DYED BLUE 1x w z 300 40o 500, 600 mm x 4 xx c xxxxxxxxw XX X amen 1M Em GAS'PAR;

Jan. 23, 345. B. GASPAR 2,367,936

PHOTOGRAPHIC PRINTING METHOD I Filed June 12, 1941 2 Sheets-She et 2 9300 40 500 (:00 700 III/13 .0 WA ViMNTH r Patented Jan. 23, i945 ornca rno'rodnarmo ransrnso METHOD Bela Gaspar, HollywoocL' calm, assignor to Chromogen, Incorporated, a corporation of Nevada Application June 12, I941, Serial No. 397,781

- I 2' Claims.

This inventionrelates to color photography and more particularly to a method and means for producing color prints to be viewed by re-.

ducing full color prints to be viewed by reflection. In the most common form of such prints, a, plurality of image layers are mounted on a paper support, although other types ofsupporting materials have been suggested and may be used. In the type of print with which the pres ent invention is primarily concerned, the image layers are formed. from photographic lightsensitive emulsion layers in each of which a color separation image hasbeen recorded and developed. Probably the most successful of these types of materials include emulsion layers comprising means within the emulsion layer for producing the desired color. Various c'oloring means are known, such as color coupling components, color formers including leuco com-' pounds, or dyes of the desired color or capable of being converted into the desired color." Following exposure, these coloring means have been transformed into colored color-separation ages of the desired color to form a multi-color print a r i I While these materials have many advantages over the processes which employ subsequent dying or toning, or the registration of individmatrices as by inhibition, there have been certain defects in the use of these preferred materials. The use of color formers or couplersv produces an oxidation product in the form of a residue which is dispersed through the emulsion layers and this residue may be suilicient to reduce the true color rendition and brilliance of the colors; Furthermore, although the emulsion layers comprfsingthese color formers are selec: tively sensitive to diiferent spectral ranges there is usually an overlapping of these spectral sensitivities so that undesirable false images may be produced in succeeding layers by exposure of an outer layer to light for which it is predominantly sensitive.

To overcome this overlapping of the spectralsensitivity, it often has been the practice to incorporate filter dyes in the photographic material so as to absorb the light within the undesired spectral ranges before it can effect a succeeding emulsion layer. Even when predyed emulsion layers have been used, wherein the age forming dyehas been evenly distributed throughout the emulsion; it has been found necessary in certain cases, to include filter dyes to help absorb the light within the overlapping sensitivity ranges oi' the various emulsion layers; Although these filter dyes are soluble and their color readily removable, their use complicates the production of the material and they usually leave a residue within the layer which is sometimes suillcient to aflect the brilliance of the colors. I

In order to overcome the hereinbeiore described difiiculties and many others incumbent thereto, it is desirable to eliminate the'source of trouble. It readily follows that the use of a predyed emulsion layer which comprises an image-forming dye evenly distributed throughout the emulsion will eliminate the oxidation product and other residue produced by the use of color formers and coupling components. In the case of colored prints to be viewed by reflection, it has been found that the best color renditions are produced by the use of weakly dyed layers due to the fact that the visiblelight beam travelsthrough the dyed layers to the support and is reflected by the support back through the same layers so that light isabsorbed by each passage through the emulsion. In such a case, a concentration of the dye which is proper for the formation of an image may sometimes be insufllcient to perform the added function of also acting as a filter, in which event a considerable amount 01 lightwithin the overlapping sensitivity ranges of the emulsion layers penetrates the layer for which it is intended and aflfects the succeeding layers thereby producing undesirable false images.

While this difficulty could be overcome by the use of filter dyes, in addition to the imageiorming dyes, these filter dyes, as above stated, present somewhat of a problem and consequently it may be desirable to avoid their use. It has nowbeen found' that the weakly dyed selectively sensitive layers may be properly exposed by means of a new printing method and without recourse to the use of filter dyes. In using this method additional filter dyes may be eliminated provided the emulsion layers are exposed to light of a predetermined spectral range that lies within the region of maximum absorption of the image-forming'dyes used to color the. weakly dyed emulsion layers. In other words, the layers are exposed with colored light of, a predetermined wave length which approximately coincides with the regions near the peal: oi the spectral absorption curves of the various dyes used" for coloring the emulsions. The

with a yellow dye. The natural blue printing light'has a narrow spectral composition which will be within the region of maximum absorption of the dye withwhich the emulsion layer is colored. By exposing the emulsions in this manner the printing light is sufllciently absorbed by the colored emulsion so that false images in the overlapping regions of sensitivity of succeeding layers are substantially eliminated.

The novel features that are considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both in its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein like reference characters indicate like parts throughout and in which:

Figure 1 is a diagrammatic view in cross section of a multi-layer light-sensitive photographic material;

Figures 2, 3 and 4 are spectograms that define the absorption characteristics of the dyes used for coloring light-sensitive emulsion layers of Figure 1; and

Figure 5 is a diagrammatic cross sectional view of the material showing the sensitivity and absorption of the layers and the range of light for exposing each of them.

The new photographic printing material is best illustrated by Figure 1 of the drawings. It will be seen by this figure that the material may comprise a support A which will probably be paper, but which may be any other suitable material. On this support A may be coated a ligh t-sensitive silver halide emulsion B which has been sensitized for the red range of the spectrum and has been colored with a blue dye. A second silver halide emulsion layer C may be superposed over the emulsion layer B and this second layer C may be sensitized for the green range of the spectrum and colored with a magenta dye. A third silver halide emulsion layer D may be superposed over the first-mentioned emulsions B and C, this layer 1) being blue sensitive and colored sensitivity of the emulsion D may be employed solely or the emulsion may be additionally sensitized to increase its sensitivity in the blue range. -Whereas the photographic printing material shown and described comprises three emulsion layers, it will be understood that two or more emulsions may be employed. Furthermore, different arrangements of the emulsions with respect to their sensitivity and color may be used as long as the precepts of the invention are adhered to.

The first mentioned emulsion layer B may preierably be made red sensitive by a red sensitizer; such as Pinacyanol. This emulsion then hasa blue-green dye uniformly dispersed therethrough such as Diamine Pure Blue Edition, No. 511). The emulsion may contain approximately 0.3-0.4 g. per square meter ofv the dye to provide the emulsion with a color density of less than 2. The character of this dye-will best be understood from the spectogram forming Figure 2, wherein it may be seen that the dye has a maximum absorption at approximately 625m and is used in a quantity to provide a color density of approximately 1.5 for the emulsion.

The second emulsion'layer C may preferably be sensitized to the green range as by the use of benzothio-pseudo cyanine. This emulsion may then be colored magenta by the use of approxstantially absorbed by imately 0.4-0.5 g. per square meter of Sirius- Rubin B (Ullmann-Enzyklopadie der Technischen Chemie, vol. 9, page 524), the dye being uniformly distributed through the emulsion. The character of this dye will best be understood from the spectrogram forming Figure 3, wherein it may be seen that the dye has a maximum absorption at approximately 530m and may be employed to provide a color density of approximately 1.25 for the emulsion.

The top layer D employs the regular blue sensitivity of a silver bromide emulsion and may be colored yellow by the use of approximately 0.5 g. per square meter of Xylenwalkgelb G (Schultz, 7th Edition, vol. 11, page 232), the dye being uniformly distributed throughout the emulsion. The character of this dye will best be understood from the spectrogram forming Figure 4, wherein it may be seen that the dye hasa maximum absorption at approximately 380m; and is employed so as to provide a color'density of approximately 2.2 for the emulsion. It is preferable that the top layer be employed as a blue sensitive layer and also, that the layer have a higher density whereby the blue rays may be substantially absorbed by this top layer and not permitted to pass through to the succeeding layers which, of course, may also have a natural blue sensitivity.

As this photographic printing material is to be used for producing colored pictures to be viewed by reflection, it is preferable that the emulsion layers be dyed weakly so that the colors will not appear too strong. In other words, due to the fact that the light rays must pass through the emulsion layers to the support and be refiected back through the same emulsions to the observer, the color of the emulsions must have a lower density than the ordinary transparency as each-of the dyes and emulsions act to filter the light rays twice. It has been found that it is best to color the emulsions so that by reflection they will have an over-all color density of approximately 2 or below. By this provision, the dyes will transmit from 6.5to 17% of the light rays in their absorption maxima. It will be noted that in the above described example, the bluegreen and magenta dyes are arranged to have an absorption maximum below 2, whereas, the yellow dye in the top layer is provided with an absorption maximum of slightly above 2.

In printing this material the images for the various layers are printed by light of a restricted spectral range which will fall approximately within the absorption maximum or the dye which is used to color the particular emulsion to be exposed. The selected printing light is provided with suflicient intensity to properly expose the particular layer being printed but will be subthe dye in said layer. Whereas the dye will substantially absorb the proper intensity of printing light and prevent its passing through to other layers, this dye is so low in its density that it does not materially hinder the light from aflecting the particular emulsion being exposed. Furthermore, the main overlapping sensitivity of the emulsions will be within the blue range; the blue sensitive emulsion is so located to be the first exposed and the yellow dye coloring the emulsion is provided with suiilcient density to substantially absorb the blue light in its absorption maximum. In the sensitize layer B to it is known that a certain amount of imparted. However, by

case of Pinacyan'ol used tored light green sensitivity is also tion negatives and restricting the green printing light to the absorption maximum of the magenta dye in layer C the green light will be substantially absorbed before it can penetrate the layer B.

As diagrammatically illustrated, in Figure .5, monochromatic or filtered light may be selected for individually exposing each of the emulsions. As an example, the top emulsion layer D may be exposed with violet light having a wave length of approximately 404.6m l, as indicated by the arrow X. A suitable printing light may be produced by using potassium light which is filtered with Wratten filter Nos. 2 and 36. The middle layer C may be printed with light of approximately 530m l, as indicated by the arrow Y, which may be obtained by the use of a Wratten filter No. 62, or by a green filter in combination with a mercury vapor lamp. In lieu of the mercury vapor lamp, thallium light having a wave length of 535mg. may be used. The bottom emulsion layer B may be exposed with red lithium light having a wave length of 610.4 mi as indicated by the arrow Z. and preferably in combination with Wratten filter No. 29. It might be pointed out that the restricted range of printing light produced in the above manner is absolutely necessary only when there is another layer below the layer being printed. In the above example for instance, the red sensitive layer, having no other emulsion below it, may be printed by exposure to any red light.

The layers-are exposed through color separathe silver images developed in each of the layers. The dyes contained in the emulsion layers B, C and D are unaffected by the development of the silver images but are susceptible'to local destruction in the presence of the silver images with the aid of suitable solutions. Accordingly, after the development of the silver images, the material is then subjected to a dye destroying treatment such as with a thiocarbamide solution disclosed in my United States Patent No. 2,020,775. Such a treatment locally bleaches the dye in each layer in the presence of the metallic silver image so that each oi the emulsion layers thereafter contains both silver and dye images. The remaining silver may be removed by a bleaching treatment in a suitable bath, such as a 10% cupric chloride solution, in accordance with the teaching of my United States Patent No. 2,042,253. After the silver has been bleached, the emulsions may then be fixed, whereupon they will contain only pure dye images. The dyes in the photographic layers may be present in a non-diflusing salt form as disclosed in my United States Patents Nos. 2,046,067; 2,075,190 and 2,107,605.

Although certain specific embodiments of the present invention have been showmand described, many modifications thereof are possible, and the present disclosure should be construed only in illustrative sense. The present invention is not to be restricted except insofar as is necessitated by the prior art and the spirit of the appended claims.

I claim:

1. In a method of printing a color separation image into a layer'of a multilayer photographic material having'at least two light sensitive silver halide emulsion layers, one being a layer which is predominantly sensitive to a predetermined spectral range and the other being a layer arranged behind said first mentioned layer and being predominantly sensitive to a different predetermined spectral range but also sensitive to a portion of said first predetermined spectral range, said first mentioned layer being colored with an image forming dyestuff in weak concentration requisite for reflection viewing, which dyestuii is fast to ordinary photographic treating baths and capable of being bleached in the presence of a metallic silver image to form a-dye image and absorbs substantially in the region of its absorption maximum light rays for only a portion of said first predetermined spectral range and transmits to a substantial extent light rays other than those in the region of said absorption maximum said other light rays including those for which said second mentioned layer is also sensitive, said light sensitive silver halide layers being devoid of any other filtering substance therein and therebetween which substantially absorbs light of said first predetermined spectral range to which'said second mentioned layer is sensitive, the step which comprises printing said color separation image into said first mentioned layer with a printing light in said first predetermined spectral range and restricting said light to a narrow spectral composition within said region of said absorption maximum.

2. In a method of printing color separation images into the different layers of a multilayer photographic material having at least three light sensitive silver halide emulsion layers, one being a layer which is predominantly sensitive to a predetermined spectral range and the second being a layer arranged behind said first mentioned layer and being predominantly sensitive to a second and different predetermined spectral range but also sensitive to a portion of said first predetermined spectral range, and the third being a layer arranged behind said second mentioned layer and being predominantly sensitive to a third and still different predetermined spectral range but also sensitive to a portion of one of said first mentioned predetermined spectral ranges, at least the first two of said layers.

being colored with image forming dyestufi's in weak concentration requisite for reflection viewing, which dyestufls are fast to ordinary photographic treating baths and capable of being bleached in the presence 01 a metallic silverimage the region of their absorption maxima light rays for only a portion of the predetermined spectral range to which the. emulsion comprising the dyestufl is predominantly sensitive and transmit to a substantial extent light rays other. than those in the region of their respective absorption maxima said transmitted light rays including those for which a succeeding layer is sensitive, said light sensitive silver halide layers being devoid of any other filtering substance therein and therebetween which substantially absorbs light of one of said predetermined spectral ranges to which a succeeding layer is sensitive, which comprises the steps of printing the diflerent color separation images into each of said first and second layers with printing lights in the predetermined spectral ranges to which the respective layers are sensitive and restricting said lights each to a narrow spectral composition within the region of the absorption maximum of the dyennm GASPAR stufl used to color the layer.

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