US 3628960 A
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United States Patent  Inventors Herman Adclbert Philippaerts Mortsel; Hans Josephus Corluy, Berehem, both of Belgium; Herbert Gernert, Munich; Guenther E. W. Schulz, llolzkircheu, both of Germany  Appl. No. 712,646  Filed Mar. 13, 1968  Patented Dec. 21, 1971  Assignee Gevaert-AGFA N.V.
Mortsel, Belgium  Priority Apr. 21, 1967 [3 3] Great Britain [31 18,542/67  LIGHT SENSITIVE IIALIDE MATERIAL WITH VARIABLE CONTRAST 21 Claims, 5 Drawing Figs.
 US. Cl 96/124,
/27, lL Ll lQ  Int. Cl G03c 1/12  Field of Search 96/27, 103
 References Cited UNITED STATES PATENTS 2,202,026 5/1940 Renwick 96/103 X 2,331,660 10/1943 Davey 96/103 2,388,859 11/1945 Mannes et al.. 96/103 2,703,282 3/1955 Carroll 96/103 3,450,536 6/1969 Wyckoff 96/27 X Primary ExaminerGeorge F. Lesmes Assistant ExaminerR. E. Martin Arr0rneyWilliam J. Daniel ABSTRACT: A composite light-sensitive photographic silver halide emulsion layer having the characteristic of gamma wavelength variability is obtained by means of a mixture of a plurality of differently constituted light-sensitive silver halide emulsion; each of said emulsions having a spectral region to which it is inherently sensitive; said light-sensitive emulsions containing at least one sensitizing dye. each such dye being incorporated in all of the emulsions, to spectrally sensitize the same to a further spectral region outside the inherent region; the emulsions having in the presence of such sensitizing dye spectral responses in the spectral region of inherent sensitivity which vary from one another and also spectral responses in the further spectral region which vary from one another and also spectral responses in the further spectral region which vary from one another, the extent of the variations in the two spectral regions being sufficiently different as to produce a gradation difference of at least 20 percent in the contrast of photographic images obtained by exposing identical samples of the material in the respective spectral regions and developing under identical conditions; the proportions of emulsions in the mixture being so selected in relation to the extent of said differences in sensitivity that gray wedge prints produced by exposure in each of the inherent and further spectral regions and development under identical conditions show different gradations; and the amount of such sensitizing dye being so selected that minor variations in such amount produces no significant change in the ratio of the gradations in the gray wedge prints.
Preferred emulsions are a silver bromoidide emulsion wherein the silver halide grains contain about 1-9 mol percent iodide and the other being a silver chloride-bromide emulsion wherein the silver halide grains contain about 15-85 mol percent bromide and up to about 5 mol percent iodide, and preferred sensitizing dyes are diffusible methine dyes.
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INVENTORS ATTORNEYS in Q/ mvvb LIGHT SENSITIVE HALIDE MATERIAL WITH VARIABLE CONTRAST This invention relates to photographic materials and a method of manufacturing them, more particularly to a lightsensitive material containing a silver halide emulsion layer wherein the gradation depends upon the wavelength of the light to which the emulsion layer is exposed.
According to a technique described in the British Pat. specification No. 494,088 filed Mar. 18, 1937 by Renwick F. F., a light-sensitive material with wavelength-variable-gamma is produced by combining two or more silver halide emulsions of which each emulsion has its own gamma value and is sensitive to a particular wavelength region of the light spectrum to which an other emulsion is substantially not sensitive.
In practice this technique utilizes a combination of two emulsions, one of which, normally a silver chloride gelatin emulsion of high contrast, is sensitized to the blue-green region of the visible spectrum to such an extent that its normal violet sensitivity is negligible, and the other, is a noncolor sensitized silver bromide gelatin emulsion or silver bromideiodide gelatin emulsion of soft contrast sensitive to the blueviolet region of the spectrum. The said emulsions can be coated into separate layers or mixed in order to form a layer. So, the combination of emulsions is chosen in such a way that a gradation depending on the spectral composition of the copying light is obtained.
For example, if such a light-sensitive material is exposed to light passing through a blue-green filter, the emulsion works normally and is suitable for negatives of normal gradation. If, however, it is desired to print from a negative with strong contrast, the light which acts upon the emulsion which works hard is cut off by means of a filter permeable only to blue, and a normal picture is obtained by means of the emulsion which works soft. If, on the other hand, it is desired to print from a negative with but little contrast, the light which acts upon the emulsion which works soft is cut off by means of a filter permeable only to green, and a normal picture is obtained by means of the emulsion which works hard.
According to the said British Pat. Specification, in the case the two emulsions are mixed in one and the same layer it is absolutely necessary that the applied spectral sensitizing agent(s) have a negligible tendency to diffuse. In practice to inhibit diffusion as far as possible the sensitizing dye is used in diffusion resistant state in one emulsion layer and the unsensitized layer applied thereon.
According to another technique described in the U.S. Pat. specification No. 2,280,300 of Rowland S. Potter, Brightford Heights and Ray Seward Hagaman issued Apr. 21, 1942, a silver halide emulsion with wavelength-variable gradation (gamma-lambda variability) is prepared by the use of sensitizing dyes which have a preferential action on some of the silver halide particles and wherein such sensitizing dyes are used in a considerably less quantity than required to produce maximum sensitivity. The selected dye or dyes act on the different silver halide particles in such a way that they confer to the emulsion a gradation, which varies in the sensitized region with the amount of dye used, more particularly impart to the emulsion a substantially softer gradation when exposed to light within the spectral region for which the silver halide is made sensitive than when exposed to light in the region of wavelengths to which the emulsion is naturally sensitive.
It is admitted that the difference in gamma obtained by exposure in the spectral region for which the emulsion is made sensitive and in the region of inherent sensitivity is due to preferential action of the sensitizing dye on the silver halide grains depending on their size, apparently, the larger the particles, the more rapid and complete that they can be sensitized. Therefore, it is necessary to restrict the action of the dye either by the time wherein they are allowed to adsorb or quantity of sensitizer incorporated in the emulsion bulk.
The advantage of the said technique is to be seen in the fact that only one type of emulsion is to be used with the disadvantage however, that a sensitization depending from the quantity of the sensitizing agent is critical and difficult to reproduce, more particularly, when a coarse grain high-sensitive emulsion is to be prepared requiring only very small amounts of sensitizing dye and the adsorption of small amounts of dyes easily can be changed by the adsorption of other emulsion ingredients.
According to the present invention a light-sensitive material is provided wherein:
a. there is a support bearing a light-sensitive layer containing two independently prepared silver halide emulsions;
b. there is a dye or dyes which spectrally sensitize(s) both emulsions to light in a spectral region outside the region in which the emulsions are inherently sensitive;
c. in the presence of said dye or dyes, the difference in sensitivity" of the said emulsions to light of a wavelength range in the region of inherent sensitivity differs from the difference in sensitivityof the said emulsions to light in the spectral region to which the emulsion layer is made sensitive, the latter region being called furtheron the spectral sensitization region;
d. the proportion of said emulsions in said emulsion layer is such, and the differences between said sensitivities are different in such a degree that the gradation of a grey wedge print produced in said emulsion layer by an exposure in the inherent sensitivity region and development differs from the gradation of a grey wedge print produced on said emulsion layer by an exposure in the spectral sensitization region and development under the same development conditions;
e. the quantity of sensitizing dye or dyes is such that the presence of a little more or less of such dye or dyes would not have a substantial effect on the ratio of said gradations.
In the foregoing definition sensitivity is here expressed in terms of inertia which is defined as the log E value corresponding with the intersection point between the straightline portion of a Density log E curve and the log E axis.
In regard to the feature (0) it will be clear from the subsequent description herein that the difference in sensitivity of the emulsions to light in one of the spectral regions referred to may, if desired, be zero.
Saying that a little more or less of the spectrally sensitizing dye or dyes has no substantia effect on the values of the gradation of the twin emulsion layer it is meant that little variations in the quantity of the sensitizing dye or dyes used brings on a variation of no more than 10 percent in the ratio of the gradations obtained by exposure in the inherent sensitivity region respectively obtained by exposure in the spectral sensitization region.
The said two emulsions having the characteristics as defined can be built up by silver halide grains originating from different preparations, so that said grains to a minor or major extent can differ in size and halide composition.
Preferably the combination of said two emulsions and their sensitivities in the different spectral regions is such that by exposure of the layer through a neutral grey wedge to light in spectral sensitization region and development, a wedge image is obtainable having a gradation which differs by at least 20 percent from the gradation of the image obtainable by corresponding exposure of an identical layer through a same wedge to light in the region of inherent sensitivity and development under the same development conditions. The percentage difference is here calculated on the basis of the lower gradation value.
By means of said emulsion layeran image can be obtained with a gradation or contrast varying (keeping the development time and conditions constant) with the spectral composition of the exposing light, i.e. varying with the proportion of the light with wavelengths situated in the region of the inherent sensitivity of the emulsion layer and the light with wavelengths in the spectral sensitization region.
In order that the material will have a gradation or gamma continuously varying with the spectral composition of the exposing light it is preferable for the log exposure values corresponding to a density about 0.1 above fog density to be substantially the same for the two spectral regions of exposure (inherent sensitivity region and spectral sensitization region).
The principle underlying the present invention can be explained by reference to FIGS. 1a and lb of the accompanying drawings.
Referring firstly to FIG. la this FIGURE shows two sensitometric curves A and B Curve A relates to an image formed by exposing a light-sensitive layer comprising a single light-sensitive emulsion A and a sensitizing dye, through a neutral grey wedge, to blue light, i.e. to light in the spectral region to which the emulsion A is inherently sensitive, and development of the latent image under certain conditions. Curve B relates to an image formed by exposing a light-sensitive layer comprising a single light-sensitive emulsion B and a sensitizing dye to a corresponding quantity of blue light, to which the emulsion B is also inherently sensitive, and development under the same conditions. It will be seen that emulsion A is appreciably more sensitive to blue light than emulsion B. If now the two emulsions, together with the sensitizing dye, are incorporated in one light-sensitive layer and this twin-emulsion layer is correspondingly exposed to blue light, the image resulting from this exposure followed by development under the conditions which yielded the individual curves A and B, will have a gradation corresponding with the characteristic curve R. In effect the increments of density attributable to emulsion B become added to the image density for which emulsion A is responsible, the lower or toe part of curve R derives from emulsion A whereas the upper or shoulder part of curve R is a reproduction of curve 8 higher in the density scale and this is indicated by the vertical broken lines and arrows extending upwardly from curve B.
FIG. lb shows a sensitometric curve resulting from corresponding exposure of each of the two single-emulsion layers (one containing emulsion A plus the dye and the other containing emulsion B plus the dye) to light in the spectral sensitization region, i.e. to minus blue light, and development under the same development conditions used in obtaining the results represented in FIG. la. The sensitometric curve is the same for the two cases, and the curve is denoted A and B" in FIG. lb. If now a twin-emulsion layer comprising the two emulsions A and B and the dye is correspondingly exposed to minus blue light, the image resulting from this exposure followed by development under the same conditions will have a gradation corresponding with characteristic curve R the ordinate of each point on which curve is twice the ordinate of the coinciding curves A and B at the corresponding log expo-- sure value.
It will be apparent that the occurrence of a difference between the gradations or gamma values of curves R and R is due to the fact that the difference between the sensitivities of emulsions A and B to light in the inherent sensitivity region is different from the distance between the sensitivities of such emulsions to light in the spectral sensitization region. Thus whereas the curves appertaining to emulsions A and B in FIG. la (exposure to blue light) are well spaced apart, the curves appertaining to the same emulsions in FIG. lb (exposure to minus blue light) coincide (difference is zero).
To ensure that separation negatives or positives with a rather strongly different contrast can be printed in such way that prints with the same gradation (a balanced gradation) can be obtained, it is preferred that curve R is at least percent higher than the gradation of curve R. Tests have shown that by appropriate selection of emulsions and dye the gradations appertaining to exposures in the two spectral regions may be in a ratio as high as 2: I. This ratio can be called the gamma-lambda-variability of the light-sensitive layer and may be expressed as a percentage, a ratio of 2:1 corresponding with a variability of I00 percent.
It is to be noted that even if the curves A and B in FIG. lb did not coincide, the gamma value of the curve appertaining to exposure of the twin-emulsion layer in the spectral sensitization region would still be higher than that of the curve appertaining to exposure of this layer in the region of inherent sensitivity provided the horizontal spacing of the curves A and B in the graph relating to exposure in the spectral sensitization region were less than the corresponding spacing of the curves A and B in the other graph. Provided that the gradations under the two exposure conditions differ by at least 20 percent that is sufficient for the purpose in view.
The difference between the differences in sensitivities of the two emulsions when comparing exposure in the region of inherent sensitivity with exposure in the spectral sensitization region is not necessarily dependent only on the efiect of the dye on the sensitivities of the emulsions to light in the spectral sensitization region. Referring to the particular case represented by FIG. la and FIG. lb said difference obviously depends in part on the sensitivities of the emulsions A and B to light in the region of inherent sensitivity (a factor which is reflected in the horizontal spacing of curves A and B in FIG. la) and such sensitivities in the inherent sensitivity region can also be influenced by the dye. Thus, the dye may have the effect of desensitizring one of the emulsions to light in the region of inherent sensitivity, or of desensitizing one of the emulsions and sensitizing the other to light in that region, or of sensitizing both emulsions to such light to different extents.
In the example represented by FIGS, la and lb the emulsions A and B have substantially different sensitivities in the spectral region of inherent sensitivity. However, the emulsions may have the same or substantially the same sensitivity in the region of inherent sensitivity provided that their sensitivities in the spectral sensitization region are sufficiently different. This is apparent from FIGS. 2a and 2b. FIG. 2a is a graph showing a sensitometric curve designated C and D which applies to each of two emulsions C and D considered separately but in the presence ofa sensitizing dye in each case, the curve appertaining to exposure in the region of inherent sensitivity (blue light). A light-sensitive layer incorporating both emulsions C and D together with the dye will yield a sensitometric curve R assuming exposure of the layer to light in the region of inherent sensitivity. FIG. 2b shows the sensitometric curves of the single-emulsion layers C and D appertaining to exposure in the spectral sensitization region (minus blue light). The sensitivity of emulsion C is appreciably higher than emulsion D to this light. When a twin-emulsion layer incorporating both emulsions and the dye is exposed to minus blue light, a sensitometric curve R is obtained which has a lower gamma than curve R the gamma difference .for practical purposes being at least 20 percent. The characteristic curves in FIGS. 2a and 2b relate of course to the gradation of images obtained by exposure end development steps which are the same for all cases save for the composition ofthe exposure light.
In the embodiments represented by the drawings, the two combined or mixed emulsions provide a twinemulsion layer yielding images with a sensitomctric curve having only one straight line part between toe and shoulder thus, having the density (D) constantly directly proportional to log exposure (log E) which is necessary for correct printing (deformationless printing).
In any given embodiment of the invention, the required dif ference between the differences of the sensitivities of the said two emulsions when comparing exposures in the different spectral regions may be due to any one of a number of different effects or combinations of effects; e.g. it may be due to the fact that the sensitizing dye is differently adsorbed by the silver halide grains of the two emulsions and/or to a different light-energy transfer (the relative quantum yield of the sensitizing agent) and/or to a different desensitizing action of the dye on the different silver haiides in the inherent sensitivity region depending on the type and the ratio of the halide ions in the silver halide grains and the size of the grains.
In carrying out the invention it is preferred to use emulsions which are inherently sensitive even above 400 nm; in other words preference is given to emulsions which are not of the pure silver chloride type.
Materials wherein the light-sensitive layer has a gammalambda-variability from to 1 l0 percent are very suitable for use in an intermediate step of a photomechanical reproduction (graphic art) process for producing the necessary interthe technique described in the US. Pat. specification No.
2,280,300 of Rowland S. Potter, Brightford Heights and Ray Seward Hagaman issued Apr. 21, 1942 (ref. page 1, column 2, lines -22).
When using two emulsions which are both sensitive above 400 nm, in other words sensitive to blue, and in addition are sensitized in a spectral region outside the inherent sensitivity region as described in the present invention it is possible to manufacture a gamma-lambda variable photographic material having for the same sensitivity a lower silver halide content than is the case for a material built up according to the 20 technique described in the British Pat. specification No. 494,088 filed Mar. 18, 1937 by Renwick F. F., wherein one of the emulsions is selected and spectrally sensitized in such a way that it is sensitive to a spectral region to which the other is substantially insensitive.
A further specific advantage in respect of an embodiment of said British Pat. specification lies in the fact that there is no need to use a sensitizing dye which is resistant to diffusion. So, a-gamma-lambda-variable material can be obtained with only one light-sensitive layer.
Having stated the general concept of this invention, a detailed description will now be made of particularly interesting photographic compositions, their manufacture, the composition and structure of the silver halide grains, suitable sensitizing agents for the preparation of said coatings and selection technique for determining whether or not a particular sensitizing agent is suitable for the purpose of the present invention.
For preparing a silver halide emulsion layer with wavelength dependent gamma preferably a mixture of silver halide grains having a qualitatively different halide ion composition is used. Thus, e.g. silver halide grains used of the bromide-iodide type, with preferably from 1 to 9 mole percent of iodide (emulsion A), in combination with silver halide grains of the silver chloride-bromide type preferably containing from 15 to percent bromide and which contain a minor amount of iodide (maximum 5 mole percent (emulsion B).
As spectral sensitizing agents preferably dyes e.g. methine dyes are used which have a spectral sensitizing action, which is sufficiently different with respect to the halide grains of the two part emulsions, which emulsions when mixed on coating the mixture yield an emulsion layer having a gamma-lambdavariability of at least 20 percent calculated on the lowest gamma value obtainable under the same developing conditions.
The determination of the spectral sensitizing action can proceed according to the procedure described in l. Spence and EH. Carrol, Journal of Physical Chemistry, Vol. 52, page 1,090 (1948), wherein also the light-energy transfer yield on silver halide and the decrease of the inherent sensitivity of a light-sensitive silver halide emulsion by a spectrally sensitizing dye are discussed.
Suitable spectrally sensitizing agents with low spectral sensitizing action in respect of silver halide grains of the bromideiodide type and high spectral sensitizing action in respect of silver halide grains of the chloride or chloridebromide type can be found in the class of the methine dyes more particularly in the class of the carbocyanines.
Suitable representatives of these methine dyes are listed in the following table.
f 0 m m Wn mm 5 mm s m T m e i a m w c N c mm s .m mm a h H 0 W 0 m mm H S C .n mw m M O N O m rm 8 m Wm. C 8 I I 8V. H H Tm m m. U 0 5 5 5 P. m g m a C H H 0 C 0 3 H w m o N nw H "W H 0 H l c 5 2m N C 0 U a 1 m 0 c O CzHa to be reproduced as positive prints with the same contrast.
The sensitizing dye or dyes used according to the present invention can be added to the light-sensitive silver halide emulsion during different preparation steps of the light-sensitive material. For example the dye or dyes can be incorporated therein by a separate addition or can be added as a mixture with one or more ingredients used in the formation of the different silver halide grains, during the physical or chemical ripening or during another step preceding the coating of the emulsion. The sensitizing dye or dyes can also be incorporated in a water-permeable layer adjacent to the silver halide emulsion layer, but have then to come by diffusion in working contact with the light-sensitive silver halide grains.
For the purpose of increasing the gradation, the sensitizing compounds are preferably used in combination with development accelerating compounds e.g. water-soluble alkylene oxide condensation products or polymers e.g. as described in the U.S. Pat. specifications No. 1,970,578 of Conrad Schoeller and Max Wittwer, issue Aug. 21, 1934, 2,240,472 of Donald R. Swan, issued Apr. 29, 1941, 2,423,549 of Ralph Kingsley Blake, William Alexander Stanton and Ferdinand Schulze, issued July 8, 1947, 2,441,389 of Ralph Kingsley Blake, issued May 1 l, 1948, 2,531,832 of William Alexander Stanton, issued Nov. 28, 1950, 2,533,990 of Ralph Kingsley Blake, issued Dec. 12, 1950 and the British Pat. specification Nos. 991,608 filed June 14, 1961 by Kodak Limited, 920,637 filed May 7, 1959, 945,340 filed Oct. 23, 1961, 940,051 filed Jan. 1, 1961, and 1,015,023 filed Dec. 24, 1962 all by Gevaert Photo-Producten N.V. For suitable development accelerating polymeric products of another type reference is made to our published Dutch Pat. applications 6,614,230 filed Oct. 10,
1966 and 6,614,291 filed Oct. 11, 1966. Other compounds 1 which sensitize the photographic emulsion by development acceleration, and which can be used together with the spectral sensitizing compounds are organic onium compounds and polyonium compounds, preferably of the ammonium or sulfonium type, e.g. quaternary tetra alkylammonium salts, alkyl pyridinium salts, bis-alkylene pyridinium salts, alkyl-quinolinium salts, and trialkylsulphonium salts.
The spectral sensitizing compounds can further be combined with chemical sensitizers known in the art e.g. sulfurcontaining compounds such as allyl isothiocyanate, allyl thioutea, or sodium thiosulfate reducing compounds such as the tin compounds described in the Belgian Pat. specifications Nos. 493,464 filed Jan. 24, 1950 and 568,687 filed June 18, 1958 both by Gevaert Photo-Producten N.V., the imino-aminomethane sulfinic acid compounds described in the British Pat. specification No. 798,823 filed Dec. 11, 1956 by Mullard, Ltd., or noble metal compounds such as gold, platinum, palladium, iridium, ruthenium, and rhodium compounds.
The sensitizing compounds used according to the present invention can also be applied in combination with known emulsion ingredients e.g. color couplers, filter or screening dyes, wetting agents, protein hardening agents, and stabilizing agents for silver halide emulsion, e.g. mercury compounds, sulfur compounds such as 1-phenyl-2-tetrazoline-5-thion, the compounds described in the Belgian Pat. specifications Nos. 571,916 and 571,917 both filed Oct. 10, 1958 by Gevaert Photo-Producten N.V., either or not in combination with chemically sensitizing and stabilizing cadmium salts.
Together with one or more of the above mentioned ingredients, derivatives of tetra-azaindenes e.g. having the following general formula can be used as fog-inhibiting compounds in the light-sensitive material:
each of R and R, represents a hydrogen atom, an alkyl, an aralkyl, or an aryl radical, and
R; represents a hydrogen atom, an alkyl, a carboxy, or an alkoxy carbonyl group.
The sensitized silver halide can be incorporated in common hydrophilic photographic colloids as e.g. carboxy-methylcellulose, poly-N-vinylpyrrolidon, polyvinylalcohol, alginic acid and salts thereof or casein but preferably in gelatin or in a mixture of gelatin with the above colloids.
The silver halide emulsion composition can be coated as a part of a monolayer or multilayer photographic material e.g. containing more than one light-sensitive layer with gradationwavelength dependency. Any type of support known in silver halide photography may be coated by said composition according to usual coating techniques, e.g. a paper, cellulose triacetate or polyester resin support. Before coating the silver halide emulsion, the usual coating aids and additives for hardening are incorporated therein e.g.: a wetting agent e.g. saponine and hardening agents e.g. chromium and alum salts or aldehydes such as formaldehyde, glyoxal, and mucochloric acid.
The silver halide materials with wavelength-variable-gamma can be used for making a photographic print with desired contrast without depending on the gradation of the original. A particular advantage of such material lies in the fact that starting from originals or internegatives with widely varying contrast the processing conditions such as developing time and the temperature of the developing bath which are both known features for regulating the gradation can be kept constant and only a properly chosen composition of the exposure-light will produce a copy with the desired contrast. This is particularly important when carrying out the processing in processing machines wherein the development for practical reasons is standardized and automated.
In order to illustrate the possible techniques which can be applied for exposing the silver halide materials with wavelength-variable-gamma the following examples are given:
1. According to one exposure technique the light-sensitive material can be exposed in subsequent steps at or through the same internegative in such a way that one of the exposures is mainly situated in the wavelength range corresponding with the inherent light-sensitivity of the emulsions and another exposure is situated in the wavelength range outside the inherent sensitivity range wherein the sensitizing dye is active, the exposures being dosed in such a way that with a particular development the desired gradation or contrast in the print is obtained.
2. According to another technique there is a single exposure to light, the composition and quantity of this exposure light being such, that with a particular development the desired gradation or contrast in the print is obtained.
The following examples illustrate the present invention without, however, limiting it thereto.
EXAMPLE 1 An acid silver chloride-bromide emulsion prepared by simultaneous addition from separate jets of a silver nitrate solution and a solution of the water-soluble halide mole percent bromide and 15 mole percent chloride containing traces of iodide 0.15 mole percent, average grain size 0.25 11.) into a gelatin solution (emulsion B), was after optimal chemical ripening mixed with a highly sensitive ammoniacal silver bromideiodide emulsion (emulsion A, having an average grain size 0.8 p.) containing 6.5 mole percent of iodide prepared by a slow addition of ammoniacal silver nitrate in an aqueous solution containing an excess of dissolved halide.
The sensitivity of the emulsion A in the inherent sensitivity region was found to be about 10 times the inherent sensitivity of emulsion B.
The emulsions A and B were mixed in a molar ratio of 2.66:1.
The emulsion mixture was spectrally sensitized with 20 mg. of the sensitizing dye No. 1 of the table per 0.34 mole of silver halide and was coated at a rate of 0.059 of silver halide per sq.
m. after incorporation of the necessary emulsion ingredients such as stabilizing, hardening and wetting agents. Two strips of the light-sensitive material were respectively exposed through the filter U 449 and L 519 the density-versus--wavelength curves of which are given in FIG. 3.
Both strips were developed under the same circumstances and the gradation ('y-values) calculated from the slope of the straight line which was drawn between density 0.3 and density 1.4 of the sensitometric curve.
The following values were obtained:
-y 0.62 after exposure through the filter U 440 (exposure in the inherent sensitivity region) EXAMPLE 7 1.08 after exposure through the filter L 519 (exposure in the spectral sensitization region).
EXAMPLE 2 The same emulsion grain composition and coating conditions as described in example 1 were applied but the total amount of sensitizing agent was added to the part emulsion B before mixing with the part emulsion A. Before coating the sensitizing agent, was allowed to diffuse to the emulsion grains of emulsion part A by keeping the whole mixture for 30 min. at 36 C.
The following y-values obtained by an exposure and processing as applied in example 1 were noted:
y 0.58 after exposure through the filter U 449. 7 1.02 after exposure through the filter L 519.
EXAMPLE 3 ln order to prove that the gamma-lambda-variability of the invention is obtained with an amount of sensitizing agent within the range of amounts which have no substantial influence on the gamma-lambda-variability the following experiment was carried out.
The same emulsion combination and coating conditions were applied as described in example 1 with the proviso, however, that one emulsion portion K was sensitized with 13 mg. of the mentioned sensitizing agent and an other emulsion portion L having the same silver halide content sensitized with 26 mg. of the same sensitizing agent.
After exposure through the indicated filters, the following -y-values were obtained:
Filler U 449 Filter L 5 I) Emulsion portion K -y=0.fi2 y=1.l5 Emulsion portion L 7 063 7 115 EXAMPLE 4 Light-sensitive materials were prepared in the same conditions as described in example 2 but using the sensitizing agents mentioned hereinafter in an amount of 26 mg. The following results were obtained.
No. of the sensitizing dye Filter U 449 Filter L 519 4 =0.52 004 5 y=0.50 7 077 6 y=0.57 y=0.84
EXAMPLE 5 ill.
After exposure through the filter U 449 and L 519 the following y-values were respectively obtained: y 0.84 and y 1.90.
EXAMPLE 6 A bromide-iodide emulsion prepared as described in example 5 was mixed in a ratio of 3 to l with a silver chloride bromide emulsion prepared by double jet precipitation containing 60 mole percent of chloride and 40 mole percent of bromide.
The emulsion mixture was spectrally sensitized with 12 mg. of the sensitizing dye No. 2 per 0.24 mole of silver halide and coated at a rate of 0.047 mole of silver halide per sq. m.
After exposure through the filters U 449 and L 519 the following y-Values were respectively obtained: y 0.84 and y 1.78.
1. A light-sensitive material comprising 1. a support and 2. a light-sensitive layer on said support and containing a mixture of a plurality of differently constituted light-sensitive silver halide emulsions,
a. each of said emulsions having a spectral region to which it is inherently sensitive b. said light-sensitive emulsions containing at least one sensitizing dye, each such dye being incorporated in all of said emulsions, to spectrally sensitize the same to a further spectral region outside said inherent region c. the emulsions having in the presence of such sensitizing dye spectral responses in the spectral region of inherent sensitivity which vary from one another and also spectral responses in the further spectral region which vary from one another, the extent of the variations in the two spectral regions being sufficiently different as to produce a gradation difference of at least 20 percent in the contrast of photographic images obtained by exposing identical samples of the material in the respective spectral regions and developing under identical conditions.
d. the proportions of emulsions in said mixture being so selected in relation to the extent of said differences in sensitivity that gray wedge prints produced by exposure in each of the inherent and further spectral regions and development under identical conditions show different gradations, and
e. the amount of such sensitizing dye being so selected that minor variations in such amount produces no significant change in the ratio of the gradations in said gray wedge prints.
2. A light-sensitive material according to claim 1, wherein each such dye is present in the light-sensitive layer in a nondiffusion resistant state.
3. A light-sensitive material according to claim 1 wherein the silver halide emulsions are inherently sensitive even above 400 nm.
4. A light-sensitive material according to claim 1, wherein there are two silver halide emulsions in the light-sensitive layer.
5. A light'sensitive material according to claim 1, wherein the log exposure value corresponding to a density of 0.1 above fog density is substantially the same in the inherent sensitivity region as in the spectrally sensitized region.
6. A light-sensitive material according to claim 1, wherein the gamma factor difference of the light-sensitive layer is from 110 to percent.
7. A light-sensitive material according to claim 1, wherein the sensitivities of said spectrally sensitized silver halide emulsions in the region of inherent sensitivity are so different that the lower toe portion of the characteristic curve of an image resulting from exposure of the layer to light in that region, and subsequent development, derives from one of the emulsions, while the upper shoulder part of such curve derives from the other emulsion.
8. A light-sensitive material according to claim 1, wherein the sensitivities of said spectrally sensitized silver halide emul- L sions in the region of inherent sensitivity are substantially the same but the sensitivities of one of said emulsions in the spectrally sensitized region is substantially higher or lower than the sensitivity of the other emulsion in that region.
9. A light-sensitive material according to claim 1, wherein said emulsion layer is a twin-emulsion layer containing a mixture of a silver chlorobromide emulsion and a silver bromoiodide emulsion.
10. A light-sensitive materialaccording to claim 9, wherein the silver chloro-bromide emulsion contains a small proportion of silver iodide.
11. A light-sensitive material according to claim 9, wherein the silver bromoiodide emulsion contains from 1 to 9 mole percent of iodide and the silver chlorobromide emulsion contains from to 85 mole percent of bromide and a maximum of 5 mole percent of iodide.
12. A light-sensitive material according to claim 1, wherein CzHs 5 sensitizing effect upon the silver halide grains of the other emulsion.
18. The material of claim '1 wherein the difference in the gradation of said gray wedge prints is at least percent.
19. The material of claim 1 wherein said light-sensitive layer 10 contains two light-sensitive emulsions, one of which has grains of silver bromide-iodide and the other has grains of silver chloride, silver chloride-bromide or mixtures thereof with not more than a minor amount of silver iodide.
20. The material of claim 1 wherein each such sensitizing dye is a methine dye.
21. A gamma-wavelength variable light-sensitive silver halide material comprising a light-sensitive composite silver halide emulsion layer formed of a mixture of two independently 13. A light-sensitive material according to claim 1 wherein the emulsions are spectrally sensitized in the wavelength range of 500 to 620 nm.
14. A light-sensitive material according to claim 1, wherein the emulsions are spectrally sensitized in the wavelength range 500 to 560 nm.
15. A light-sensitive material according to claim 1, wherein the spectrally sensitizing dye is present in an amount which imparts maximum spectral sensitivity to the silver halide emulsion layer.
16. A method of manufacturing a light-sensitive layer with gamma-lambda-variability wherein, a plurality of differently constituted silver halide emulsions are spectrally sensitized with at least one sensitizing dye to light in a region outside the the layer is at least 20 percent and the amount of dye(s) being such that the presence of a little more or less of such dye or dyes would have substantially no effect on the said variability.
bHr -NH-sorom tim-p-Kusm-on.
prepared silver halide emulsions, one of said emulsions being a silver bromoiodide emulsion wherein the silver halide grains contain about l-9 mol percent of iodide and the other being a silver chloride-bromide emulsion wherein the silver halide grains contain about 15-85 mol percent bromide and up to about 5 mol percent iodide; said two independent emulsions having spectral responses in the region to which they are inherently responsive which vary from one another to a sufficient extent that the characteristic curve of a photographic image produced in the composite layer exhibits a lower toe portion derived essentially from one emulsion and an upper shoulder region derived essentially from the other emulsion; the silver halide grains of said two emulsions being spectrally sensitized in a spectral region other than said region of inherent sensitivity by means of at least one diffusible methine dye, the degree of said spectral sensitization varying for the respective grains of the two emulsions, the extent of the variations in spectral responses of the different silver halide grains in the two spectral regions being sufficiently different as to produce a gamma-wavelength variability of at least 20 percent.
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