US3658536A

US3658536A - Multilayered color film of increased sharpness

Info

Publication number: US3658536A
Application number: US54539A
Authority: US
Inventors: Wilfred L Wolf
Original assignee: WILFRED L WOLF
Current assignee: WILFRED L WOLF
Priority date: 1970-07-13
Filing date: 1970-07-13
Publication date: 1972-04-25
Anticipated expiration: 1989-04-25
Also published as: GB1350249A; BE769966A; FR2101627A5; CA944999A

Abstract

In a multilayered color film having a double-coated bluesensitive emulsion a layer of the blue-sensitive emulsion is placed below the green- or red-sensitized emulsion to yield images with increased sharpness.

Description

United States Patent Wolf [451 Apr. 25, 1972 [54] MULTILAYERED COLOR FILM OF INCREASED SHARPNESS 21 Appl. No.: 54,539

52 us. Cl ..96/69, 96/74 [51] lnt.Cl ..G03c1/76 [58] FieldoISearch ..96/69, 74

[56] References Cited UNITED STATES PATENTS 2,258,187 10/1941 Mannes ..96/69 2,316,803 4/1943 Michaelis. .....96/69 2,376,217 5/1945 Wilder ..96/74 3,016,306 1/1962 Mader ..96/69 FOREIGN PATENTS OR APPLICATIONS 659,733 3/1963 Canada.... ..96/74 726,137 1/1966 Canada ..96/74 923,045 4/1963 Great Britain ..96/74 OTHER PUBLICATIONS Defensive Publication, March, 1969, Graham, 580,216.

Primary ExaminerNorman G. Torchin Assistant Examiner-J. R. Hightower Attorney-William H. J. Kline, James R. Frederick and Ogden H. Webster ABSTRACT In a multilayered color film having a double-coated blue-sensitive emulsion a layer of the blue-sensitive emulsion is placed below the greenor red-sensitized emulsion to yield images with increased sharpness.

5 Claims, 6 Drawing Figures BL UE- SENS/T/VE LA YER YELLOW F/LTER LAYER aREE/v-sE/vs/r/zEo LAYER RED- SENS/T/ZED LAYER LOWER BLUE-$ENSITIVE LAYER SUPPORT Patented A ril 25, 1972 P v R 3,658,536

2 Shuts-Shoot l F G. P-BL UE- SENSITIVE LAYER /6 z "YELLOWF/LTER LAYER GREE/V- SENS/T/ZED LAYER A21:

r-REO- SENS/T/ZED LA YER wk sup/mm BLUE-SENS/T/VE LAYER YELLOW F/LTER LAYER GREEIV-$EIVSITIZED LAYER RED- SENS/T/ZED LAYER l7 LOWER BLUE-SENSITIVE LAYER SUPPORT 30 F IG. 3

' BLUE-SENSITIVE LAYER v SLOW BLUE-SE/VS/T/VE LAYER YELLOW FILTER LAYER GREEN5E/V$/T/ZEO LAYER SLOW GREE/V- SE/VS/T/ZED LAYER REDSE/V$/T/ZED LAYER SLOW RED-SENS/T/ZED LAYER SUPPORT W/LFRED L. WOLF INVENTOR.

ATTORNEY Patented A ril 25, 1972 3,658,536

2 Shoots-Shoot 2 BLUE-SENSITIVE LAYER LLOW FILTER LAYER GREEN-SENSITIZED LAYER LOWER GREEN-SEIVS/T/ZED LAYER RED-SENSITIZED LAYER LOWER RED-SENS/T/ZEO LAYER LOWER BLUE-SENSITIVE LAYER SUPPORT BLUE-SENSITIVE LAYER YELLOW FILTER LAYER GREEN-SENSIT/ZED LAYER LOWER GREEN-SENS/T/ZED LAYER LOWER BLUE-SENSITIVE LAYER RED-SENSIT/ZED LAYER LOWER REDSE/VS/T/ZED LAYER BLUE-SENSITIVE LAYER YELLOW FILTER LAYER GREEN-SENSIT/ZED LAYER LOWER GREEN-SEIVS/T/ZED LAYER RED-SENS/T/ZED LAYER LOWER RED-$EN5ITIZED LAYER SUPPOR T W/LFRED L; wou

IN'VENTOR.

g a-w' A TTORIVE Y MULTILAYERED COLOR FILM OF INCREASED SHARPNESS This invention relates to photography and more particularly to a multilayer color film of improved sharpness.

In multilayer photographic films and papers for color photography, and particularly for camera films, a conventional order of the individual layers, from the outer surface to the support, is: (a) a blue-sensitive emulsion layer which records the yellow image, (b) a yellow filter layer which absorbs any blue light that has passed through the blue-sensitive emulsion layer, (c) a green-sensitized emulsion layer which records the magenta image and (d) a red-sensitized emulsion layer which records'the cyan image. In the so-called doublycoated multilayer photographic elements, each of the emulsions is coated as two'layers, the uppermost of which serves as the normal speed emulsion and the other as the slower speed emulsion for the particular color sensitivity.

With the described order of emulsion layers and for exposure from the emulsion side it is generally agreed that resolution is best in the top layer and diminishes progressively in the lower layers. Thus the layer which records the sharpest image is the top or blue-sensitive emulsion. However this yellow image-producing emulsion contributes little to the visual image because of its high luminosity. The magenta image layer (green-sensitized) contributes the most to the sharpness of the image because the peak sensitivity of the human eye is in the green region of the spectrum which is absorbed by this layer. Accordingly, the described order of emulsion layers in which the light reaches the magenta layer after diffusion by the turbid blue-sensitive emulsion is not the most favorable for optimum resolution of fine detail.

Hanson, in The Journal of the Society of Motion Picture and Television Engineers 58, 273 (1952), discloses placing the green-sensitized, magenta'image-producing emulsion on top and the blue-sensitive, yellow image-producing emulsion on the bottom of the layer order. A problem with this arrangement is that it is difficult to keep the blue light, which is needed to expose the blue-sensitive bottom layer, from affecting the other two layers which are inherently blue-sensitive.

U.S. Pat. No. 2,258,187 to Mannes et al discloses a doublycoated multilayer element having a layer order in whichthe blue-sensitive emulsion is divided into a fast and slow segment and in which the slow blue segment is placed between the yellow filter layer and the first green component. This layer and segment order permits the slow blue segment to be used as a color correction mask. There is no reference to improved sharpness.

In general it can be said that the prior attempts to alter the described layer arrangements in multilayercolor films and papers have either not improved sharpness significantly or have done so only with the introduction of serious defects, such as excessive loss in blue speed or defects in color reproduction.

l have discovered, in accordance with the present-invention, that a multilayer, multicolor photographic element will yield color images of improved sharpness and of suitable speed and colorquality when one portion of the blue-sensitive emulsion is positioned as an upper blue-sensitive layer above the yellow filter layer and the rest of the blue-sensitive emulsion is positioned as a lower blue-sensitive layer beneath the greenor red-sensitized layers.

It is accordingly an object of this invention to provide a multilayer, multicolor element of novel layer arrangement which results in improved sharpness without excessive loss incolor quality or photographic speed.

A further object is to provide a multilayer,-multicolor element wherein the red-sensitized emulsion or both the red-' and green-sensitized emulsions are between two blue-sensitive emulsion layers.

The invention will be described in more detail-by reference to the drawings in which:

FIG. 1 is a diagrammatic cross section of a known type of multilayered, multicolored photographic element.

FIG. 2 is a diagrammatic cross section showing the layer arrangements of a photographic element in accordance with one embodiment of the present invention.

FIG. 3 is a diagrammatic cross section of a known type of multilayered, multicolored photographic element in which each emulsion layer is doubly coated.

FIG. 4 is a diagrammatic cross section showing the layer arrangements in accordance with another embodiment of the present invention.

FIG. 5 is a diagrammatic cross section showing the layer arrangements of still another embodiment of the present invention.

FIG. 6 is a diagrammatic cross section of an element similar to that of FIG. 3 but with the lower blue-sensitive emulsion having been omitted.

Referring to the drawings in more detail, each figure schematically represents a multilayered, multicolored photographic element for a subtractive color system. The element can be, for example, a photographic color film, a photographic paper for color printing or other type of such photographic element. The lowermost component in each instance is a support 11 which can be any of the sheet-like materials used for photographic supports such as cellulose acetate,

polyethylene terephthalate, glass, paper or the like. Normally the support will be coated on its lower side with an anti-halation coating and on its upper side with a subbing layer which improves the adhesion of the lowermost photographic emulsion layer -to the support. However, these conventional layers or coatings are omitted from the drawings for the sake of simplicity. Also omitted for the same reason are various possible interlayers.

Therefore, disregarding any such subbing or interlayers or the like, in FIG. 1 the photographic element 10 is a known type of reversal color film for cameras in which a red-sensitized emulsion 12 is positioned above the support 11. When incorporated color coupler emulsions are used this emulsion cancontain, for example, a phenolic cyan-forming coupler such as described in U.'S. Pat. No. 2,423,730.

The next layer is a green-sensitized silver halide emulsion 14 containing, for example, a pyrazolone magenta-forming coupler of the type described in U. S. Pat. No. 2,600,788.

The next layer shown in FIG. I is the yellow filter layer 16. This type of layer which is normally present in multilayer photographic elementsfor subtractive color systems can be of any material which will transmit red and green light and absorb blue light. However, since it is desirable to render this layer invisible in the subsequent processing steps after exposure, the yellow filter is advantageously composed of a gelatin layer containing yellow colloidal silver. This is commonly called a Carey Lea silver or CLS layer. Instead of colloidal silver theiyellow filter layer may contain a yellow dye. There are many known ways of preparing such layers and they can be given any desired thickness or concentration of colloidal silver or yellow dye to provide the desired degree of filtering of blue light while transmitting red and green light. As explained hereinafter, in certain embodiments of my invention, I employ a yellow filter layer which transmits more blue light than would be transmitted by a yellow filter layer for a conventional photographic element as in FIG. 1.

Above the yellow filter layer 16 in FIG. 1 is blue-sensitive emulsion 17. When incorporated coupler emulsions are used this emulsion would contain, for example, an aryl acetanilide yellow-forming coupler of the type described in U. S. Pat. No. 2,875,057.

The manner in which a multilayer color film functions, with particular'reference to the element of FIG. 1, is as follows:

The blue-sensitive layer 17 has the inherent sensitivity of silver halides to blue light, whereas the other two emulsions are madesensitive to'green and red, respectively, by spectral sensitizing dyes. Sincethe green-sensitized and the red=sensitized emulsions retain their intrinsic blue sensitivity, the yellow filter layer 16 isused to absorb blue light. When a picture is taken of a subject having blue, greenand red areas, the blue light that the subject reflects will affect only the blue-sensitive emulsion 17, since substantially no blue light passes the yellow filter layer 16. Light reflected from the green areas will not affect the spectrally unsensitized blue-sensitive emulsion 17 but will form a latent image in the green-sensitized emulsion 14. Light reflected from the red area will not affect the upper emulsions but will form a latent image in the red-sensitized emulsion 12.

FIG. 2 illustrates a photographic element 20 of the invention. An important difference between it and known photographic elements such as element of FIG. 1 is that there are two blue-sensitive emulsion layers 17 and 17 and the bluesensitive emulsion layer 17' is coated below the green and/or redsensitized layers. Specifically in FIG. 2 it is coated below both the greenand red-sensitized

layers

14 and 12. Other layers can be substantially as described for FIG. 1.

The expression blue-sensitive emulsion layer is used herein to refer to layers such as layers 17 and 17' that are primarily sensitive to blue or shorter wavelengths and are no spectrally sensitized to longer wavelengths, i.e., longer than about 540 nm. The other emulsion layers, although intrinsically blue-sensitive, are referred to by the color to which they are spectrally sensitized, i.e., as the green-sensitized emulsion layer or the red-sensitized emulsion layer.

Emulsion layer 17 is referred to herein as the lower bluesensitive emulsion layer. Likewise in reference to other emulsion layers of a particular color sensitivity, the layer closest to the support will be called the lower layer of that particular sensitivity and the other layer will be called, for example, simply the blue-sensitive layer or the upper blue-sensitive layer. It should be understood, however, that these designations are used merely to distinguish between the two layers of the same color and that with some films an exposure may be made through the transparent base or support, e.g., as in exposing a reversal color film to red light during processing. In any event, the layers on the emulsion side which are closest to the support are called lower layers.

The lowermost of conventional doubly coated layers of the same color sensitivity is sometimes referred to as the slow or slower emulsion layer. This terminology is avoided in referring to the photographic elements of the present invention, however, because it is possible and even highly advantageous for the lower blue-sensitive layer to be an emulsion that, if singly coated and identically exposed, would be much faster than the normal speed blue-sensitive emulsion which provides the uppermost emulsion layer. Because of their lower positions the lower layers of any particular color sensitivity receive less light than the corresponding upper layers. This is especially true of the lower blue-sensitive layer which, in accordance with the present invention, is positioned below the yellow filter layer and re receives a much lower blue light exposure than the upper blue-sensitive layer. Therefore, although because of its lower position the lower layer may become, in effect, a slower speed layer, the emulsion itself can be considerably faster than the emulsion of the upper layer of the same color sensitivity, so to avoid confusion it is called the lower layer rather than the slower layer.

Normally, with doubly coated layers, the speeds of the emulsions are selected so that in combination with the positioning of the layers, the resulting speed of the upper layer will be from about 0.2 to about 1.4 log exposure faster than the lower layer of the same color sensitivity.

As a general principle, both with the widely separated blue layers which characterize the photographic elements of the invention, and with the redand green-sensitized layers when they are doubly coated, it is advantageous to have the speed relationship such that the sensitometric curve (curve relating to developed image density vs the log exposure) of the upper and lower emulsion layers that are sensitive to the same color, together produce a smooth composite curve having the desired characteristics. The methods used to determine the optimum speed relationship between the two emulsions are well known in the art. The color-forming layers and/or color forming units in a given photographic element are advantageously made so that their sensitometric curves have the relationship required to reproduce a neutral scale as well as the color scales from the minimum density to the maximum density as disclosed in British Pat. No. 923,045. Although photographic speeds of our color-forming layers may vary over a wide range, it is usually advantageous to make their speeds as high as possible, especially for camera films.

Advantageously, in accordance with my invention, adjustments are made in the blue light absorbing ability of the yellow filter layer 16 in relation to the blue light absorbing ability of the upper blue sensitive emulsion layer and/or the blue light sensitivity of the greenand red-sensitized

layers

14 and 12 in order to control the amount of blue light reaching the lower blue-sensitive layer 17'. For example, the amount of colloidal silver per unit area in the CLS layer is reduced to increase blue light transmission. In preferred embodiments, the yellow filter layer has a blue light transmission sufficient to expose the lower blue-sensitive layer to about 10 to 50 percent of the blue light received by the upper blue sensitive layer.

The photographic element of FIG. 2 offers at least two important advantages which also characterize other embodiments of the invention. One is that the turbid slower blue-sensitive layer is removed from the top of the element and this reduces the scatter of the red and green light components of the image. The other is that since the normal speed blue-sensitive layer of low turbidity is above the yellow filter layer which absorbs blue light the maximum exposure and speed in this blue-sensitive layer and good color reproduction are achieved. These advantages received by positioning the upper blue-sensitive emulsion above the yellow filter layer and the lower blue-sensitive emulsion below the yellow filter layer and below the red and/or green-sensitized emulsions are highly useful in films utilizing a turbid lower blue-sensitive emulsion where maximum sharpness is needed as in aerial films, microfilms and 8mm. movie films. The principle would also be beneficial in color negative films, positive print films and in color-sensitized papers.

The remaining figures of the drawings illustrate photographic elements in which each of the silver halide emulsions ofa particular color sensitivity is doubly coated.

FIG. 3 illustrates a doubly coated, multilayer photographic element 30 of known type. Each of the doubly coated emulsions of a particular color sensitivity retains the same layer order as in FIG. 1. Thus above the support 11 the red-sensitized emulsion consists of a slower red-sensitized emulsion layer 12 and a fast or normal speed red-sensitized emulsion 12. Likewise there is a slower green-sensitized emulsion l4 and a normal speed emulsion I4. Overlying these layers is the yellow filter layer 16. Both blue-sensitive layers, Le, a slower blue-sensitive emulsion layer 17 and a normal speed blue-sensitive emulsion layer 17, are coated above the yellow filter layer.

FIG. 4 represents a photographic element of the invention in which each emulsion of a particular color sensitivity is doubly coated but in which the blue-sensitive emulsion layer 17' is placed below the red-sensitized layers 12 and I2 and the green-sensitized

layers

14 and 14, while the normal speed blue-sensitive emulsion remains above the yellow filter layer 16.

FIG. 5 illustrates another embodiment of the invention in which the lower blue-sensitive emulsion is coated between the red-sensitized emulsion 12 and the slower green-sensitizecl emulsion 14. Other layers are substantially as indicated with respect to FIG. 4 except that the yellow filter layer 16 can be adjusted to provide somewhat lower transmission of blue light than would be desirable in the embodiments of FIGS. 2 and 4 where the blue light must pass through both the greenand red-sensitized layers before reaching the lowermost blue-sensitive layer.

FIG. 6 illustrates a photographic element similar to the known type of element of FIG. 3 but in which the blue-sensitive emulsion has been singly coated. There is no separate lower blue-sensitive layer. This type of photographic element is compared hereinafter with photographic elements of the invention as depicted in FIGS. 4 and 5.

The following example will provide a further understanding of this invention. It compares photographic elements of the invention as illustrated in FIGS. 4 and 5 with other photographic elements as illustrated in FIGS. 3 and 6. In measuring sharpness l have employed the procedure of Crane (J. Soc. Mot. Pict. Telev. Engrs., 73, 643 (1964) who has described a quantity for predicting the sharpness of a photograph based on Modulation Transfer Functions of the elements which he calls "System Modulation Transfer (SMT) acutance. The experimental data required are the areas A, under the Modulation Transfer curves of each element (camera, film, observer, etc.) in the system and the magnification M, between each element and the retina of the observers eye. Then SMT acutance is defined as observer magnificationy] -25 log =ca mera TG area,

EXAMPLE lmage sharpness measurements are made for photographic elements as illustrated in FIGS. 3, 4, 5 and 6. The results of these measurements are tabulated as follows:

SMY Acutance Layer Order of 16 mm. Super 8 8 mm.

Photographic Movie Movie Movie Rating Element Film Film Film Area Fig. 3 92.56 85.30 82.06 60.866 Fig. 4 94.73 88.60 85.66 79.903 Fig.5 93.38 86.50 83.36 66.838 Fig. 6 94.39 88.05 85.06 76.118

These data show marked superiority in image sharpness, in terms of SMT acutance rating area, for the layer arrangement in accordance with the invention (FIGS. 4 and 5) as compared with that of FIG. 3 which is a widely used conventional arrangement.

The SMT acutance for the element of FIG. 6, which is a modification of FIG. 3 in which the lower blue layer is omitted, is higher than that of the element of FIG. 5. However, the element of FIG. 6 has a serious drawback which is not shown by these data. The maximum density obtainable in its blue layer is very low. For good color quality the maximum densities obtainable in each color layer should be about equal. When an element of FIG. 6 is exposed with a sensitometer, then processed conventionally and measured through complimentary filters with a transmission densitometer it is found that the maximum density of the blue-sensitive layer is much lower than the maximum densities of the greenand red-sensitized layers. Attempts to correct this defect by increasing the coverage of the blue-sensitive layer above the yellow filter would increase the turbidity above the green-sensitized emulsion and reduce the image sharpness as in the element of FIG. 3. In comparison the elements of FIGS. 4 and 5 provide a desirable combination of image sharpness and color quality and any lack of color quality by low density in the blue-sensitive layers can be corrected by increasing the coverage of the lower blue-sensitive layer without substantial loss in image sharpness, since the increase in turbidity caused by the additional blue-sensitive emulsion is below the green-sensitized layer.

Although I have described the emulsion layer arrangement of my invention with reference in the drawings to one type of multilayer, multicolor photographic element, namely, a color reversal, coupler-incorporated photographic film, it should be understood that the novel arrangement can be employed with all types of such multilayer, multicolor photographic elements employed in subtractive color photography. The term photographic elements is used in its usual broad sense to include negative and positive film, paper and the like, and includes not only such elements that render true visible color reproductions but also those that record as visible colors radiation which is outside the visible spectrum, e.g., infrared radiation.

In elements having incorporated color couplers, the color forming couplers are dispersed in a suitable medium such as one of those described in U. S. Pat. Nos. 2,322,027; 2,304,940; 2,801,171 or 2,852,382. Representative useful color formers which may be used in such processes are well known in the literature, and are described for example in Fierke et al. U. S. Pat. No. 2,801,171; Weissberger et al. L. S. Pat. No. 2,474,293; Glass et al. U. S. Pat. No. 2,521,908; and McCrossen et al. U. S. Pat. No. 2,857,057; or, color-forming compounds of the fat-tail" variety (see F.I.A.T. Final Report, No. 721, for examples thereof). Such elements can be developed by one of the processes described and referred to in Graham et a1 U. S. Pat. No. 3,046,129. General classes of the most useful color formers include phenolic, 5-pyrazolone, heterocyclic and open-chain ketomethylene compounds.

Usually the couplers used to advantage in our materials are ballasted to make then non-diffusible in the silver halide emulsions in which they are incorporated. The couplers utilized in the photographic elements of our invention can be dispersed in a high-boiling, crystalloidal compound which can be used as a vehicle for incorporating the coupler in the photographic emulsion according to method well-known in the art. Various other known methods of incorporating the color-forming couplers in our element may also be utilized. For example, the low solvent dispersion described in Fierke U. S. Pat. No. 2,801,107 is used to advantage; or the couplers may be dispersed in natural resin-type solvents as described in Materinz U. S. Pat. No. 2,284,879; or the couplers may be dissolved in a monomeric solution which is then polymerized in the presence of gelatin to produce dispersions of the coupler in the polymer as described in U. S. Pat. No. 2,825,382. Alternatively, the color-forming couplers can be of the "fat-tail" variety, that is, the Fischer-type which have solubilizing groups on them which render them soluble in alkaline solution.

In the other type of color reversal photographic process, couplers of the type referred to above are incorporated in a color developer solution. These processes are described in the literature, such as Marines et al. U. S. Pat. No. 2,252,718 issued Aug. 19, 1941.

Couplers that form diffusible dyes may also be used in our elements wherein interest is indicated in the transfer of the color image to a contiguous receiver sheet as is described in Whitmore et al U. S. Pat. No. 3,227,550.

The elements described herein are also useful in color transfer processes wherein a dye, a developer, a dye-developer or a coupler is transferred to a receiver layer or sheet. Such processes are described in Rogers U. S. Pat. No. 2,983,606.

Our photographic elements are advantageously color processed after exposure by conventional color processing techniques. In the reversal processes, the film is first developed with a black-and-white negative developer solution, then following exposure to white light or treatment in a nucleating bath is given color development in an aqueous alkali solution containing a primary aromatic amine color developing agent. After color development, the photographic material is treated with a ferricyanide bleach solution followed by a thiosulfate fixing bath to remove the silver image and residual silver halide, thus leaving the dye images.

Especially useful color developing agents are primary phenylene diamines and their derivatives, such as N,N-dimethyl-p-phenylenediamine N,N-diethylp-phenylenediamine N-carbamidomethyl-N-methyl-p-phenylenediamine N-carbamidomethyl-N-tetrahydrofurfuryl-Z-methyI-pphenylenediamine N-ethyl-N-carboxymethyl-2-methyl-p-phenylenediamine N-carbamidomethyl-N-ethyl-2-methyl-p-phenylenediamine N-ethyl-N-tetrahydrofurfuryl-Z-methyl-p-aminophenol 3-acetylamino-4-aminodimethylaniline N-ethyl-N-B-methanesulfonamidoethyl-4-aminoaniline N-ethy1-N-B-methanesulfonamidoethyl-3-methyl-4- aminoaniline Sodium salt ylenediamine and the like.

The emulsions used in the photographic elements of our invention can be chemically sensitized by any of the accepted procedures. The emulsions can be digested with naturally active gelatin, or sulfur compounds can be added, such as those described in Sheppard U. 5. Pat. No. 1,574,944, issued Mar. 2, 1926; Sheppard et al. U. S. Pat. No. 1,623,499, issued Apr. 5, 1927; and Waller et al. U. S. Pat. No. 2,399,083; McVeigh U. 5. Pat. No. 3,297,447 and Dunn U. 5. Pat. No. 3,297,446.

The emulsions can also be treated with salts of the noble metals, such as ruthenium, rhodium, palladium, iridium and platinum, as described in Smith et al U. S. Pat. No. 2,448,060, issued Aug. 31, 1948 and as described in Trivelli et al. U. S. Pat. Nos. 2,566,245 and 2,566,263 both issued Aug. 28, 1951.

Spectral sensitizing dyes can be used conveniently to confer additional sensitivity to the light-sensitive silver halide emulsion of the multilayer photographic elements of the invention. For instance, additional spectral sensitization can be obtained by treating the emulsion with a solution of a sensitizing dye in an organic solvent or the dye may be added in the form of a dispersion as described in Owens et al. British Pat. No. 1,154,781. For optimum results, the dye may either be added to the emulsion as a final step or at some earlier stage.

Sensitizing dyes useful in sensitizing such emulsions are described, for example, in Brooker et a1 U. S. Pat. No. 2,526,632, issued Oct. 24, 1950; Sprague U. S. Pat. No. 2,503,776, issued Apr. 11, 1950; Brooker et a1. U. S. Pat. No. 2,493,748; and Taber et al. U. S. Pat. No. 3,384,486. Spectral sensitizers which can be used include the cyanines, merocyanines, complex (tri or tetranuclear) merocyanines, complex (tri or tetranuclear) cyanines, holopolar cyanines, styryls, hemicyanines (e.g. enamine hemicyanines), oxonols and hemioxonols.

Dyes of the cyanine classes may contain such basic nuclei as the thiazolines, oxazolines, pyrrolines, pyridines, oxazoles, thiazoles, selenazoles and imidazoles. Such nuclei may contain alkyl, alkylene, hydroxyalkyl, sulfoalkyl, carboxyalkyl, aminoalkyl and enamine groups and may be fused to carbocyclic or heterocyclic ring systems either unstubstituted or substituted with halogen, phenyl, alkyl, haloalkyl, cyano or alkoxy groups. The dyes may be symmetrical or unsymmetrical and may contain alkyl, phenyl, enamine or heterocyclic substituents on the methine or polymethine chain.

The merocyanine dyes may contain the basic nuclei mentioned above as well as acid nuclei such as thiohydantoins, rhodanines, oxazolidenediones, thiazolidenediones, barbituric acids, thiazolineones and malononitrile. These acid nuclei may be substituted with alkyl, alkylene, phenyl, carboxyalkyl, suloalkyl, hydroxyalkyl, alkoxyalkyl, alkylamino groups or heterocyclic nuclei. Combinations of these dyes may be used, if desired. In addition, supersensitizing addenda which do not absorb visible light may be included, for instance, ascorbic acid derivatives, azaindenes, cadmium salts, and organic sulfonic acids as described in McFall et al. U. S. Pat. No. 2,933,390 and Jones et a1 U. S. Pat. No. 2,937,089.

The emulsion may also contain speed-increasing compounds of the quaternary ammonium type of Carroll U. S. Pat. No. 2,271,623, issued Feb. 3, 1942; Carroll et al. U. S. Pat. No. 2,288,226, issued June 30, 1942; and Carroll et al. U. S. Pat. No. 2,334,864, issued Nov. 23, 1943; and the polyalkylene glycol type of Carroll et a1. U. S. Pat. No. 2,708,162, issued May 10, 1955; and the thioether type of Dann and Chechak U. S. Pat. No. 3,046,134.

The photographic layers and other layers of a photographic element employed as described herein can be coated on a of N-methyl-N-B-sulfoethyl-p-phenwide variety of supports. Typical supports include cellulose nitrate film, cellulose ester film, poly(vinyl acetal) film, polystyrene film, poly(ethylene terephthalate) film, polycarbonate film and related films or resinous materials, as well as glass, paper, metal and the like. Typically, a flexible support is employed, especially a paper support, which can be partially acetylated or coated with baryta and/or an alpha-olefin polymer, particularly a polymer of an alpha-olefin containing two to 10 carbon atoms such as polyethylene, polypropylene, ethylenebutene copolymers and the like.

The emulsions of our invention may employ various binders therefor. Among such materials are natural and/or synthetic binding materials, for example, gelatin, colloidal albumin, water-soluble vinyl polymers, cellulose derivatives, proteins, water-soluble polyacrylamides, polyvinyl pyrrolidone and the like. These binders may be utilized alone or mixtures thereof may be utilized. In addition to the hydrophilic colloids, the binders may contain dispersed polymerized vinyl compounds, e.g. synthetic polymers of alkyl acrylates and methacrylates and acrylic acid, sulfoalkyl acrylates or methacrylates and the like.

The photographic and other hardenable layers used in the practice of this invention can be hardened by various organic or inorganic hardeners, alone or in combination, such as the aldehydes, and blocked aldehydes, ketones, carboxylic and carbonic acid derivatives, sulfonate esters sulfonyl halides and vinyl sulfonyl ethers, active halogen compounds, epoxy compounds, aziridines, active olefins, isocyanates, carbodiimides, mixed function hardeners and polymeric hardeners such as oxidized polysaccharides like dialdehyde starch, oxyguargum and the like.

The silver halide emulsions used in the practice of this invention can be protected against the production of fog and can be stabilized against loss of sensitivity during keeping. Suitable antifoggants and stabilizers each used alone or in combination include thiazolium salts described in Brooker et a1 U. S. Pat. No. 2,131,038 and Allen et a1. U. S. Pat. No. 2,694,716; the azaindenes described in Piper U. S. Pat. No. 2,886,437 and Heimbach et al. U. S. Pat. No. 2,444,605; the mercury salts as described in Allen et a1. U. S. Pat. No. 2,728,663; the urazoles described in Anderson et al. U. 5. Pat. No. 3,287,135; the sulfocatechols described in Kennard et al. U. S. Pat. No. 3,236,652; the oximes described in Carroll et al. British Pat. No. 623,448; nitron; nitroindazoles; the mercaptotetrazoles described in Kendall et al U. S. Pat. No. 2,403,927; Kennard et al. U. S. Pat. No. 3,266,897 and Luckey et al. U. S. Pat. No. 3,397,987; the polyvalent metal salts described in Jones U. S. Pat. No. 2,839,405; the thiuronium salts described in Herz et a1 U. S. Pat. No. 3,220,839; the palladium, platinum and gold salts described in Trivelli et al U. S. Pat. No. 2,566,263 and Yutzy et al. U. S. Pat. No. 2,597,915.

The silver halide emulsions used with this invention can comprise silver chloride, silver bromide, silver bromoiodide, silver chlorobromoiodide or mixtures thereof. The emulsions may be coarse or fine grain and can be prepared by any of the wellknown procedures, e.g., single jet emulsions, double jet emulsions, such as Lippmann emulsions, ammoniacal emulsions, thiocyanate or thioether ripened emulsions such as those described in Nietz et al. U. S. Pat. No. 2,222,264; lllingsworth U. S. Pat. No. 3,320,069; and McBride U. S. Pat. No. 3,271,157. Surface image emulsions may be used or internal image emulsions such as those described in Davey et a] U. S. Pat. No. 2,592,250; Porter et a1 U. S. Pat. No. 3,206,313; Berriman U. 5. Pat. No. 3,367,778 and Bacon et al. U. S. Pat. No. 3,447,927. If desired, mixtures of surface and internal image emulsions may be used as described in Luckey et al. U. S. Pat. No. 2,996,382. Negative type emulsions may be used or directed positive emulsions such as those described in Leermakers U. S. Pat. No. 2,184,013; Kendall et al U. S. Pat. No. 2,541,472; Berriman U. S. Pat. No. 3,367,778; Schouwenaars British Pat. No. 723,019; Illingsworth et al. French Pat. No. 1,520,821; Ives U. S. Pat. No. 2,563,785; Knott et al. U. S.

Pat. No. 2,456,953 and Land U. S. Pat. No. 2,861,885. The emulsions may be regular grain emulsions such as the type described in Klein and Moisar, J. Phot. Sci., Vol. 12, No. 5, Sept/Oct., 1964, pp. 242-251.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

[claim 1. In a multilayer, multicolor photographic element comprising a support and a plurality of silver halide emulsion layers and a yellow filter layer disposed above said support, the improvement which comprises employing the following sequence of layers in the direction from the outer surface of the element to the support:

a. an upper blue-sensitive silver halide emulsion layer,

b. a yellow filter layer which transmits at least some blue light,

c, at least one silver halide emulsion layer sensitized to light of longer wavelength than blue, and a lower blue-sensitive silver halide emulsion layer which is not spectrally sensitized to wavelengths longer than about 540 nm. and which, if singly coated and identically exposed, would be faster than said upper blue-sensitive silver halide emulsion layer.

2. An element according to claim 1 in which the blue light transmission of the yellow filter layer is sufficient to expose the lower blue-sensitive layer to about 10 to 50 percent of the blue light received by the upper blue-sensitive layer.

3. A photographic element according to claim 1 in which an upper and lower emulsion layer is provided for each color sensitivity.

4. An element according to claim 3 comprising layers in the following sequence from the outer surface to the support:

a. a blue-sensitive emulsion layer,

b. a yellow filter layer,

c. a green-sensitized emulsion layer,

(1. a lower green-sensitized emulsion layer,

e. a red-sensitized emulsion layer,

f. a lower red-sensitized emulsion layer, and

g. a lower blue-sensitive emulsion layer.

5. An element according to claim 3 comprising layers in the following sequence from the outer surface to the support:

a. a blue-sensitive emulsion layer,

b. a yellow filter layer,

c. a green-sensitized emulsion layer,

d. a lower green-sensitized emulsion layer,

e. a lower blue-sensitive emulsion layer,

f. a red-sensitized emulsion layer, and

g. a lower red-sensitized emulsion layer.

{g gs UNITED STATES PATENT OFFICE v CERTIFICATE OFCORRECTION I Patent No. 3,658,536 Dated April 25, 1972 InventOfl UJiILired Li Wolf It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

ra v Wilfred L. Wolf is the assignor to Eastman Kodak Company, Rochester, N. Y.

Signed and sealed this 25th day of July 1972.

(SEAL) Attest:

EDWARD M.FLETOHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents

Claims

2. An element according to claim 1 in which the blue light transmission of the yellow filter layer is sufficient to expose the lower blue-sensitive layer to about 10 to 50 percent of the blue light received by the upper blue-sensitive layer.
3. A photographic element according to claim 1 in which an upper and lower emulsion layer is provided for each color sensitivity.
4. An element according to claim 3 comprising layers in the following sequence from the outer surface to the support: a. a blue-sensitive emulsion layer, b. a yellow filter layer, c. a green-sensitized emulsion layer, d. a lower green-sensitized emulsion layer, e. a red-sensitized emulsion layer, f. a lower red-sensitized emulsion layer, and g. a lower blue-sensitive emulsion layer.
5. An element according to claim 3 comprising layers in the following sequence from the outer surface to the support: a. a blue-sensitive emulsion layer, b. a yellow filter layer, c. a green-sensitized emulsion layer, d. a lower green-sensitized emulsion layer, e. a lower blue-sensitive emulsion layer, f. a red-sensitized emulsion layer, and g. a lower red-sensitized emulsion layer.