US3485627A - Process and material for the preparation of masks for the reproduction of color images - Google Patents

Description

Dec. 23, 1969 E. HELLMIG PROCESS AND MATERIAL FOR THE PREPARATION OF MASKS FOR THE REPRODUCTION OF COLOR IMAGES Filed Feb. 15, 1965 INVENTOR.

. z .41: HELLMIG Int. Cl. G030 7/04, J/78 US. Cl. 96-9 6 Claims ABSTRACT OF THE DISCLOSURE Very effective masking of multicolor images to correct color distortion, is obtained with a mask made by exposing to the image by means of red and green light, a pair of silver halide emulsions on a support, each emulsion having a gamma between 0.1 and 0.4 and essentially the same speed as the other, one emulsion being sensitized to green light and the other to red, and the emulsion combination having a combined gamma not over 0.6. The exposed emulsions are processed to either silver images, or orange-to-red dye images, or to both silver and dye images. A modified mask can be prepared as by giving the red-sensitive emulsion a little exposure to blue or giving the green-sensitive emulsion a little sensitivity to red.

This invention relates to a process of making masking images for improving the colors of colorphotographic reproductions, as well as to a photographic element for performing the said process.

It is known that dyes used for subtractive color photographic images do not transmit all of the light which theoretrical considerations demand. The cyan dye for example, which should absorb red light and transmit green and blue light usually absorbs a small amount of green and 'blue light as well as the major portion of red light. The magenta dye which should absorb green light and transmit blue and red light usually absorbs a considerable amount of blue light and a small amount of red light, too. The yellow dye which should absorb blue light and transmit green and red light, is usually satisfactory although sometimes it absorbs a small amount of red light. The result of printing a multi-colored image formed of such dyes is to introduce unequal parts of all three records in each image which is made regardless of the color of light used in printing or the sensitivity of the printing material employed. Correction of the colors of printing is therefore desirable and this is usually done by masking.

A large number of masking processess exist and differ from one another with respect to the nature of the masks which are used eg. polychrome masks in multilayer color materials with different association of spectral sensitivity of the individual layer and image colour; monochrome masks, and black-and-white masks which are different because of the color of the light with which they are produced. One of these processes which uses a single blackand-white mask for masking all or at least two color separation records, has acquired great importance on acnited States Patent ice count of its simplicity, rapidity and reliability. For the production of such masks a panchromatically sensitized silver halide layer is used.

The mask leads to a good color correction, taking into account the simplicity, rapidity and reliability of its preparation and use. However, certain defects in the colorcorrecting eifect still exist, and these cannot be eliminated by suitable choice of the color of the light used in the exposure of the masking film. For example, a mask prepared with wellow-orange light leads to a satifactory color correction of the magenta separation record but the yellow separation record remains insufiiciently corrected (insufficient masking of magenta); conversely, exposure with the yellow-green light leads to a satisfactorily corrected yellow separation record, but the magenta separation record (in the green and cyan colors) is undercorrected.

It is among the objects of the present invention to overcome these disadvantages and to provide a process'of making improved masking images as well as a light-sensitive photographic element for performing the said process.

We now have found that an outstanding masking effect is obtained by utilizing a light-sensiive material which consists of a substantially red-sensitive layer and a substantially green-sensitive layer. The maximum of the green-sensitivity is at 500 to 600 preferably at about 530 me, and that of the red sensitivity at 600 to 700 preferably at about 640 The light-sensitive layers are arranged on a suitable support, either with one layer on each of the different sides of the support or with both layers on the same side of the support. The two layers are exposed with green light and with red light from the original to be reproduced, which exposure can take place successively with filters of suitable spectral transmissivity (e.g. with so-called reproduction separation filters), or simultaneously with a yellow filter. In both cases, whether the light-sensitive layers are on one or on both sides of the support, either the red-sensitive or the green-sensitive layer can face the light source. The yellow filter preferably is arranged in the form of a yellow-colored gelatin layer which can be bleached out in the photographic baths and which is applied onto the uppermost lightsensitive layer or also on the layer-free side of the support. In order to adjust the relative sensitivity of the redsensitive and green-sensitive layers, the yellow filter may contain a certain quantity of green, cyan or also red or magenta dye. According to another preferred embodiment of the invention at least one of the light-sensitive layers is dyed with a dye that is removable in the processing baths e.g. tartrazine, azilanorange (Color Index 16230) or pangelb, so that the dyed light-sensitive layer itself acts as a yellow filter.

The sensitivity of the two layers on exposure with white (unfiltered) light must be substantially the same. Since the 'y-value of the individual layers is very low, a tolerance of 50% in the mutual sensitivity (about half a diaphragm stop) does not detract from the masking efiect.

With the process according to the invention, the v-values of the two separate masks of the two-layer material are adapted to the value of the secondary densities of those dyes of the original which are to be masked or to the printing colors which are similarly masked and in addition to the required degree of correction. The 'y-values of the light-sensitive layers are between 0.1 and 0.4 and the sum of the 'y-values of both layers should not exceed 0.6. It is preferred to use a material with a total 'y-value of about 0.4, the individual -values each being about 0.2. The most suitable 'y-values for any given original will be apparent to those skilled in the art upon making the ordinary tests and observations customarily used in the masking technique. One preferred embodiment of the light-sensitive photographic material of the invention is illustrated in the accompanying drawing.

The illustrated material consists of a transparent sup- I port 1, the red-sensitive silver halide emulsion 2 and the green-sensitive silver halide emulsion layer 3 on one side of the support and a yellow-colored gelatin filter layer 4 on the other side, the yellow color of which can be bleached out in the photographic processing baths, and which simultaneously acts as non-curling layer.

The film, with the image to be masked below it, is exposed to light through the gelatin filter layer 4. It is obvious that the filter layer can also be arranged above the uppermost light-sensitive layer. In addition, it is also expedient for one or both light-sensitive layers to be similarly dyed with a suitable dye. Tartrazine or acilanorange are, for example, suitable for this purpose.

After exposure the photographic element is developed to yield a pair of masking images with a -y-value between 0.1 and 0.4 and opposite in sign to the gamma derived from the undesirable absorption of the image dye as well as opposite in sign to that of the original image.

The photographic material can be processed to form a masking image consisting of silver or an orange or red dye which absorbs substantially light of the blue and green region of the spectrum, or silver and the orange or red dye. This can be accomplished by methods known per se. If a silver image is to be produced the material need not to contain any color coupler and is developed with an ordinary black-and-white developer. A silver masking image might in some cases cause a slight overmasking of the cyan separation record. In order to prevent or reduce this undesired eflect, an orange or red colored masking image or a combined silver and orange or red dye image can be produced instead of the silver image. Suitable materials for these embodiments include silver halide layers which contain color couplers capable of reacting with the oxidation products of color-forming primary aromatic amino developer to form an orange or red dye. It is possible either to apply an orange or red color coupler or a mixture of a yellow and a magenta color coupler. The materials are processed in accordance with common practice by developing with a color-forming developer particularly of the phenylendiamin type.

If a pure orange or red dye image is desired, the material is treated with an ordinary bleaching or bleachfixing bath to remove the silver image. Where a combined silver-dye image is necessary, the material is fixed in the usual manner after development. The masking effect can be still further improved by the following additional steps:

The so-called over-masking of partial colors of the original which sometimes occurs with the use of singlestage masking processes and which is known to be shown by this color in the separation record negative having a higher density than white can be obviated in simple manner by giving one of the two light-sensitive layers of the masking film of the invention an additional but substantially smaller sensitivity in another third of the spectrum. It is in the order of magnitude of -30% of the main sensitivity of the layer concerned and is dependent on the extent of the established over-masking. The spectral position (the third of the spectrum) of this additional sensitivity and the decision as to which layer is to be given the additional sensitivity is determined in the following simple manner. The additional sensitivity lies in the same third of the spectrum as the transmissivity range of the separation record filter with which the separation record with the oVer-masked colour was produced. The layer which must be given the additional sensitivity is determined according to the main density of the over-masked color. For example, if cyan is over-masked in the blue filter separation record, the additional sensitivity must be arranged in the blue third of the spectrum of the red-sensitive Separate layer (cyan has its main density in the red). correspondingly, with the overmasking of magenta in the red filter separation record, the green-sensitive layer must be given an additional red sensitivity.

In this modification, the case can also arise where one of the light-sensitive layers must be given an additional sensitivity not only in one third of the spectrum. but also in the third third of the spectrum (if for example cyan in the yellow separation record and simultaneously green in the magenta separation record, are over-masked, but green less strongly than cyan).

The underlying feature of the invention is not limited to the embodiments which have been discussed, but other developments and variations are also possible. The same applies as regards the use. Thus, the process according to the invention is not restricted to use in the reproduction art, but the masks prepared according to the invention rather can be used with advantage, for example, also in the color negative-positive printing process or also for the production of duplicates in the color reversal process or color-direct positive process.

EXAMPLE 1 On a transparent polyester support based on polyethylene terephthalate and having a thickness of 0.15 mm. there is applied in a thickness of 3.5;; a layer of a fine grained silver halide gelatin emulsion such as described, for example, in BIOS Final Report No. 1355, page 35. diluted by adding a 3% aqueous gelatin solution in the ratio 1:1. The usual additives such as an aqueous formaldehyde solution as hardener and an aqueous saponin solution as wetting agent, 40 mg. of the red sensitizer of the following formula CzHa l and 4 g. of Acilanorange GX (Color Index No. 16230) in aqueous solution, per kg. of the original emulsion, are added to the emulsion before casting.

Applied above this emulsion layer is a second layer. likewise 3.5 thick, of the above diluted finegrained emulsion, to which the green sensitizer of the following formula and the same quantity of Acilanorange GX (Color Index 16230) are added prior to the dilution. The quantity of sensitizer is such that both emulsions have the same sensitivity when they are exposed through the antihalation layer (see below) and then developed for 2 /2 minutes in the developer indicated below. In the above layers the Acilanorange can be replaced by another dye such as Tartrazin (Color Index 1940) or Pangelb which is described in Example 4 of US. Patent 2,036,546.

A hardened gelatin layer with a thickness of Lu, is then applied to the uppermost emulsion for protection against mechanical damage.

A colored, clear and hardened antihalation layer of gelatin and having a thickness of 3a is applied to the other side of the support, the said layer having added thereto one of each of the known dyes with a yellow, red and green color capable of being bleached out in the photographic baths. The color density of this layer is equal to 1.5 behind a blue filter (Agfa reproduction separation record filter 352L), 0.6 behind a green filter (Agfa reproduction separation record filter 54L) and 0.3 behind a red filter (Agfa reproduction separation record filter 45L).

The material is brought, with the colored antihalation layer, into contact with the transparent multicolor original to be masked and is exposed with unfiltered light through this layer. It is treated for 2 /2 minutes in the following developer:

G. Monomethyl-p-aminophenol sulfate 7.5 Sodium sulfite 40.0 Hydroquinone 3.5 Anhydrous sodium carbonate 30.0 Potassium bromide 3.0

Made up with water to 1 liter.

EXAMPLE 2 A light-sensitive photographic material as described in Example 1 is fixed with the emulsion layer downwards on the suction wall of a reproduction camera, the antihalation layer of the material facing the camera objective. From the multicolor non-transparent original which is to be reproduced, the material is exposed in the camera with unfiltered light, developed as indicated above, fixed, rinsed and dried to form a masking image.

Meanwhile, the red filter separation record is prepared in the camera in known manner without using a mask and is likewise developed, fixed, rinsed and dried.

Thereupon, the dried masking image is again fixed on the suction plane by means of register eyes and in registry with the path of rays and through this mask, by means of a green separation record filter, the magenta separation record is produced by exposure of the original photographic element. The said photographic element is arranged between the mask and suction plane. In similar manner, the yellow separation record is produced through a blue separation record filter. The green and yellow separation records are thereafter developed, fixed, rinsed and dried. The three color separation records are then further processed in known manner.

EXAMPLE 3 Onto a transparent support of polyethylene terephthalate which contains a subbing layer and which has a thickness of 0.175 mm. are applied the following layers:

(1) The subbing layer of'the support is coated with a red-sensitive silver halide gelatin emulsion layer. The silver halide consists essentially of silver bromide and contains the additives customarily applied such as the stabilizer l,3,3a,7-tetraaza 4 hydroxy-6-methyl indene, saponin as Wetting agent and formaldehyde as hardening agent. The layer is sensitized with a red sensitizer as, for instance, described in Example 1. The layer contains a yellow and a magenta color coupler of the following formulae:

coon

i H NH-CCHz-CNH-CO-Cul a5 boon SOaH The concentration and the proportions of the color couplers are so adjusted that upon color-forming development an orange image of a gamma of 0.25 is obtained.

The layer contains silver halide in an amount of about 0.5-1 g. per square meter based on silver. The thickness of the layer is about 2-3 microns.

(2) Onto the red-sensitive layer is applied a greensensitive silver halide emulsion layer containing the same silver halide emulsion as layer 1. The red-sensitizer is replaced by the green-sensitizer described in Example 1. The concentration of the color couplers is adjusted to obtain an orange image having a gamma of 0.35. The layer contains per square meter 0.8l.2 g. silver as silver halide. The layer thickness is about 3 to 4 microns.

The silver and the color coupler content is preferably adjusted so that the total density of the resulting dye does not exceed 1.2.

To the opposite side of the support is applied a colored hardened antihalation layer of gelatin containing tartrazine as yellow dye and small amounts of a red and a green dye. All the dyes are removable in the photographic processing baths. The antihalation layer has the following densities:

Behind a blue filter (Agfa 350L) About 1.5 Behind a green filter (Agfa 450L) About 0.15 Behind a red filter (Agfa 45L) About 0.15

The above photographic element is processed according to common practice which includes exposure, development with a color-forming developer, such as N,N-diethyl phenylen diamine and bleach-fixing in an ordinary bleachfixing bath.

The resulting masking image is used as described in Example 2.

If a masking image is desired which consists of a silver and a dye image the bleach-fixing of the material has to be omitted and the developed material is only fixed according to common practice. In this case the silver con tent and the color coupler content of the material has to be adjusted to yield a masking image the total density (silver and dye density) of which does not exceed 1.2.

The mixture of the yellow and magenta coupler in the above material can be replaced by a red color coupler.

I claim:

1. A process for the production of a color-correcting mask from an original multicolor image which comprises (a) exposing with red and green light a light-sensitive photographic material to the original multicolor image, which light-sensitive photographic material consists essentially of the following elements:

(i) a supporting layer, (ii) a silver halide emulsion layer substantially sensitive to the green region of the visible spectrum, having a gamma of between 0.1 and 0.4, and

(iii) a silver halide emulsion layer substantially sensitive to the red region of the visible spectrum, having a gamma of between 0.1 and 0.4, having essentially the same speed as layer (ii), the total gamma of the layers (ii) and (iii) not exceeding 0.6,

(b) color developing the exposed light-sensitive photographic material with a color-forming primary aromatic amino developer to form in each emulsion an orange to red dye masking image which absorbs light of the blue and green regions of the spectrum and having a gamma opposite in sign to that of the original image, and

(c) subsequently bleach-fixing the thus developed photographic material.

2. A process as defined in claim 1, wherein the silver halide emulsion layer (ii) has a gamma of about 0.25 and the silver halide emulsion layer (iii) has a gamma of about 0.35.

3. The process according to claim 1 wherein the lightsensitive photographic material additionally contains a yellow colored filter dye that is removed during photographic processing and absorbs light of the blue region of the visible spectrum to effectively keep the unprocessed emulsions from being exposed to blue light.

4. A process for the production of a color-correcting mask from an original multicolor image which comprises (a) exposing with red and green light a light-sensitive photographic material to the original multicolor image, which light-sensitive photographic material consists essentially of the following elements:

(i) a supporting layer,

(ii) a silver halide emulsion layer substantially sensitive to the green region of the visible spectrum, having a gamma of between 0.1 and 0.4, and

(iii) a silver halide emulsion layer substantially sensitive to the red region of the visible spectrum,

having a gamma of between 0.1 and 0.4 having essentially the same speed as layer (ii), and the total gamma of layers (ii) and (iii) not exceeding 0.6,

(b) color developing the exposed light-sensitive photographic material with a color-forming primary aromatic amino developer to form in each emulsion a masking image of silver with orange to red dye which absorbs light of the blue and green regions of the spectrum, each masking image having a gamma opposite in sign to that of the original image, and

(c) subsequently fixing the thus developed photographic material.

5. A process as defined in claim 4, wherein the silver halide emulsion layer (ii) has a gamma of about 0.25 and the silver halide emulsion layer (iii) has a gamma of about 0.35.

6. The process according to claim 4 wherein the lightsensitive photographic material additionally contains a yellow colored filter dye that is removed during processing and absorbs light of the blue region of the visible spectrum to eifectively keep the unprocessed emulsions from being exposed to blue light.

References Cited UNITED STATES PATENTS 2,375,344 5/1945 Bruylants et al. 96-100 3,362,820 1/1968 Hellmig 969 2,382,690 8/1945 Yule 96ti 3,251,689 5/1966 Hellmig 969 3,291,602 12/1966 Hellmig 96-5 FOREIGN PATENTS 562,854 7/1944 Great Britain. 755,458 8/1956 Great Britain.

J. TRAVIS BROWN, Primary Examiner U.S. Cl. X.R. 9674

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