CH653780A5 - PRODUCT FOR IMAGE TRANSFER PHOTOGRAPHY. - Google Patents

Description

The present invention relates to a product for image transfer photography, comprising a support with at least one emulsion layer containing a dispersion medium and photosensitive silver halide grains, and an image-receiving layer.

The most commonly used photographic products contain one or more layers of photosensitive silver halide emulsions. Their wide use is due to their ability to provide excellent quality images and their high sensitivity which allows them to be used for shooting with portable devices in very different lighting conditions.

However, silver halide photographic products are significantly limited in terms of access to the visible photographic image. Photographic exposure of an emulsion layer to silver halides does not produce an immediately visible photographic image; it produces in the emulsion an invisible latent image which it is necessary to develop to produce a visible image. This means removing the photographic product from the camera and processing it in aqueous solutions to obtain a visible image. In most cases, the first image obtained is negative, and it is necessary to proceed to a second exposure of another photographic product through the negative image, and to the treatment of this product, to obtain a positive image visible from the subject initially. photography. It is also possible to directly obtain a positive image in a photographic product exposed according to an image, by modifications of the products or processes.

Image transfer photography has reduced the time between exposure and obtaining a visible image. The photosensitive silver halide emulsion layer (s) are brought into contact with a treatment solution immediately after exposure. While the development of silver halides takes place, there is a transfer of a silver image (black and white) or a dye image into a receiving layer where this image is visible. In this way, one can have access to a visible photographic image in a few minutes, and even in a few seconds.

However, although measured in seconds, the image access time remains an important limitation of silver halide photography by image transfer. The opportunities to photograph a subject can be fleeting, and the photographer needs to visually verify as instantly as possible whether the photographic image is acceptable.

Although image transfer methods have reduced the image access time of silver halide photographic products, this advantage has not been achieved without further sacrifice. An important long-term problem with image transfer photography is the consumption of money. Color photographic products, whether conventionally processed or dye image transfer products, require relatively high silver titers to provide maximum photographic speed. Usually it takes about 1000 mg of silver per square meter in each of the blue, green and red recording elements. In a conventionally processed color product, the final image does not contain silver, which is, in principle, fully recoverable. On the contrary, in image transfer photography, silver is seldom recovered and, in composite products with an inseparable structure, all the money remains in the product containing the visible image.

Another drawback inherent in image transfer photography is the reduction in image clarity due to scattering.

When the image-forming substances diffuse from the silver halide emulsion layers or from adjacent layers, this diffusion occurs both towards the receiving layer and laterally, which causes the image to spread and a loss of sharpness. Sharpness can be improved by shortening the diffusion path to the receiving layer. This can be done by adjusting the number and thickness of the layers to be crossed. Unfortunately, the minimum thickness of the silver halide emulsion layers is limited by the size of the grains of silver halides and by the ratio of the mass of gelatin to that of the silver halides. In addition, in composite products operating by image transfer, which contain three superimposed dye-forming elements, the dyes diffusing towards the receiving layer must pass through the intermediate dye-forming elements and the separating interlayers.

Another problem with image transfer photography is the variability of image density as a function of temperature. Since the opportunities for taking photographs arise under a wide variety of temperature conditions, and the main advantage of image transfer photography being easy access to the image, it follows that the ability to give acceptable images under various temperature conditions is also an important factor for image transfer products. In this respect, image transfer photography is very different from conventional photography because, in the latter, processing is rarely carried out without temperature regulation.

There are a number of limitations in the production of images transferred with dyes. For example, high silver titers, as noted above, and also greater amounts of dye-forming substances than is required by stoichiometry, are required to obtain maximum acceptable densities of the transferred images. . As the dye transfer efficiency deviates from that resulting from stoichiometry, more dye-forming substances must be incorporated into the photographic materials, and the thickness of the layers must be increased to introduce these increased amounts of substances. In addition, the speed of release of the dyes to be transferred can have an effect on the time of access to the visible image. When the development reaction product serves to prevent transfer of the dye, as with many conventional positive-effect dye imaging compounds, the rate of development of silver halides also limits the maximum rate to which the dye may become available for transfer, since too rapid release of the dye relative to the rate of development of the silver halides results in the loss of discrimination. Improving one or more of these factors can therefore significantly improve the transfer of the dye image.

Different grain forms, regular and irregular, have been observed in photographic silver halide emulsions. The regular grains are often cubic or oc-taedric in shape. The grain edges can be rounded due to ripening effects and, in the presence of strong ripening agents such as ammonia, the grains can even be spherical or have the form of thick, almost spherical tablets, as is described for example in United States patent No. 3894871 and by Zelikman and Levi in "Making and Coating Photography Emulsions", Focal Press, 1964, pp. 221-223. Stick-shaped or tabular-shaped grains have frequently been observed in varying proportions associated with grains of other shapes, particularly when pAg (i.e., the negative logarithm of the silver ion concentration) emulsions were modified during precipitation, as is the case, for example, in single-jet precipitation processes.

6S Tabular grains (i.e. grains which developed essentially along two dimensions and, by comparison, weakly according to the third) have given rise to numerous studies, but the grains thus studied were often grains of

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large size without photographic utility. What, in the present description, is understood by tabular grain is a grain delimited by two parallel or practically parallel crystalline faces which each have a significantly larger surface than any other face of the crystal constituting the grain. The question of tabular grains of silver bromo-iodide is discussed by Duffin, "Photography Emulsion Chemistry", Focal Press, 1966, pp. 66-72, and by Trivelli and Smith, in "The Effect of Silver Iodide Upon The Structure of Bromo-Iodide Precipitation Sériés", in "The Photography Journal", vol. LXXX, July 1940, pp. 285-288. According to Trivelli and Smith, a marked decrease in grain size and shape index is observed as iodide is introduced.

Tabular-grain silver bromide emulsions of high shape index have been described by De Cugnac and Chateau in "Evolution of the Morphology of Silver Bromide Crystals Düring Physical Ripening", in "Photographic Science and Industry", vol. 33, N ° 2 (1962), pp. 121-125.

Silver bromide emulsions with tabular grains sensitized to sulfur having an average shape index of about 5 to 7: 1,

in which tabular grains represented more than 50% of the projected surface of the total grain population, were incorporated into a radiographic product directly sensitive to X-rays, sold by the firm Eastman Kodak Cy., from 1937 until the 1950s, under the reference Sereen X. Ray Code 5133. Gutoff, in “Nucleation and Growth Rates Düring the Precipitation of Silver Halide Photography Emulsions”, in “Photography Sciences and Engineering”, vol. 14, N ° 4, July-August 1970, pp. 248-257, describes the preparation of silver bromide and bromo-iodide emulsions by a single jet process using a continuous precipitation apparatus.

Methods for preparing emulsions consisting mainly of silver halides in the form of tabular grains have recently been described in publications. U.S. Patent No. 4063951 describes the formation of tabular-shaped silver halide crystals bounded by cubic faces [100] and whose shape index (calculated relative to the length of edge) is between 1.5 and 7: 1. The tabular grains have a square and rectangular shape characteristic of the crystal faces [100]. U.S. Patent No. 4,067,739 describes the preparation of silver halide emulsions consisting mainly of twin crystals of the octahedral type; these crystals are formed by first preparing crystalline seed seeds which are then grown by Ostwald maturation in the presence of a silver halide solvent and the growth of the grains is completed without renucleation or maturation of Ostwald by controlling pBr (negative logarithm of bromide ion concentration). United States patents Nos. 4150994, "4184877 and 4184878, as well as English patent No. 1570581 and German patent application publications No. 5 2905655 and 2921077 relate to the formation of silver halide grains octahedral tabular twins from seed crystals with an iodide content of at least 90 mole% (Unless otherwise indicated, all references to halide percentages are calculated based on the silver contained in the emulsion, the grain or the region of the grain concerned; for example, a grain of silver bromo-iodide containing 40 mol% of iodide also contains 60 mol% of bromide.)

In several of these references, the increase in covering power is mentioned and it is indicated that the emulsions obtained are useful for black and white and color filming. According to United States Patent No. 4063951, the upper limit of the shape index of these tabular grains is 7: 1;

but, according to the very low shape indices obtained in the examples (2: 1), this upper limit of 7: 1 appears to be overestimated. It is clear, as the reproduction of the examples and the examination of the published photomicrographs show, that the grain shape indices obtained according to the above references are also less than 7: 1.

The subject of the invention is a product for image transfer photography, comprising a support, at least one emulsion layer containing a dispersion medium and photosensitive silver halide grains, and a receptor layer for picture; this product has a photographic speed / silver titer ratio (quantity of silver halides per unit area), and a contrast as a function of development times which are higher.

The photographic product according to the invention is characterized in that at least 50% of the projected surface of the photosensitive silver halide grains io of at least one emulsion layer is formed of silver halide grains tabular with a thickness less than 0.5 µm, with a diameter of at least 0.6 µm (the grain diameter is defined as the diameter of a circle having an area equal to the projected area of the grain), and an average shape index greater than 15 to 8: 1 (the shape index is the ratio of the diameter of the grain to its thickness).

The products according to the invention have a number of advantages. They can provide visible images more quickly after the start of treatment. The intermediate contrasts obtained are higher in relation to the duration of development. Image clarity is improved. These products are particularly advantageous in that they allow the reduction of the silver titer, a more efficient use of the dye-forming substances, a more advantageous arrangement of the layers, the elimination or reduction of the yellow filter substances and a less temperature on image formation. Other photographic advantages can also be obtained with various particular structures of the product according to the invention, structures which will be described below.

The use of chemically and spectrally sensitized tabular grain index emulsions with high shape index provides additional important advantages with regard to the speed / granularity relationship, the sharpness and the differences in sensitivity in blue and in blue minus. Tabular grain emulsions with a high shape index improve the clarity of the underlying emulsions when they are placed so as to receive a non-scattered light. These emulsions are particularly effective in this regard when they form the emulsion layers closest to the source of the exposure radiation. When they are spectrally sensitized outside the blue part of the spectrum, the silver bromide and bromo-iodide emulsions with tabular grains of high shape index exhibit a great separation of the velocities in the blue part of the spectrum and in the part of the spectrum where they are spectrally sensitized. These emulsions sensitized to blue minus are much less sensitive to blue light than to light from blue minus, and do not require a protective filter to give acceptable recordings of blue minus when exposed to neutral light. such as daylight at 5500 ° K. Tabular grain emulsions of high shape index have improved speed / granularity-50 relationships when compared to those of previously known tabular grain emulsions, and those of emulsions of the same halide composition which have so far given the best speed / granularity relationships. If spectral blue sensitizers are used, tabular-grain silver bromo-iodide emulsions of high form index with 55 bromide emulsions produce significant increases in blue sensitivity compared to natural sensitivity of these emulsions for blue.

Fig. 1 is a graph representing the relative sensitivity as a function of the silver titer; A is the curve of a control point and B 60 that of a product according to the invention.

Silver halide emulsions

To obtain the advantages of the invention, at least one emulsion layer of the product for image transfer photography 65 consists of an emulsion of silver halides with tabular grains of high shape index. The expression “high shape index” means, according to the invention, that the silver halide grains having a thickness of less than 0.5 μm, and preferably in

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smaller than 0.3 pm, and a diameter of at least 0.6 (im, have an average shape index greater than 8: 1, and represent at least 50% of the total projected area of the halide grains of silver.

The preferred emulsions used in the products according to the invention contain silver halide grains having a thickness of less than 0.5 µm (preferably less than 0.3 µm, and optimally less than 0.2 µm). tm), a diameter of at least 0.6 µm and an average shape index of at least 12: 1, and optimally at least 20: 1. These silver halide grains have a diameter medium less than 30 (im (preferably less than 15 (im, and optimally less than 10 jim). Preferably, these silver halide grains represent at least 70% and, optimally, at least 90 % of the total projected area of the silver halide grains.

The thinner the tabular grains represent a given percentage of the projected surface, the higher is the average shape index of the emulsion. In general, the average thickness of the tabular grains is at least 0.03 µm although in principle even thinner tabular grains can be used, for example grains of 0.01 µm thick depending on the composition of the halide.

The grain characteristics of the silver halide emulsions indicated above can be readily demonstrated by methods well known in the art. As indicated, the expression shape index designates the ratio of the diameter of the grain to its thickness. The term diameter itself is defined as the diameter of a circle having an area equal to the projected area of the grain as it appears on a photomicrograph or on an electron micrograph of the emulsion sample. From the shadows cast by an electron micrograph of an emulsion, it is possible to determine the thickness and the diameter of each grain and to identify those of the tabular grains whose thickness is less than 0.5 [ im (or 0.3 (im) and whose diameter is at least 0.6 jim. From these data, the shape index of each of these tabular grains can be calculated and the shape indices of all the tabular grains of the sample which satisfy the conditions of thickness and diameter can be used to make an average which constitutes the average shape index.

According to this definition, the average shape index is the average of the shape indices of each grain. In practice, it is generally simpler to obtain an average thickness and an average diameter of the tabular grains having a thickness of less than 0.5 μm or 0.3 Jim and a diameter of at least 0.6 μm and to calculate the average form index which is then the ratio of these two means. Whatever the evaluation method chosen, and taking into account the tolerances of the particle size measurements, the values obtained for the average shape index do not differ significantly.

One can add up the projected surfaces of the tabular grains of silver halide which satisfy the conditions of thickness and diameter and then, separately, one can add up the surfaces of the other grains of silver halide from the photomicrography. ; from these two respective sums, one can obtain the percentage of the total projected surface occupied by the tabular grains of silver halides whose thickness and diameter satisfy the conditions expressed above.

For the above assessments, a reference tabular grain was chosen; this grain has a thickness of less than 0.5 μm and preferably less than 0.3 μm. The purpose of this choice is to distinguish tabular grains of small thickness from thicker tabular grains whose photographic characteristics are lower. A grain diameter of 0.6 μm was chosen as a reference, since for smaller diameters it is not always possible to distinguish, on micrographs, the tabular grains from those which are not.

The term projected area is used in the same sense as the terms projective area or projection area, commonly used in the art (see, for example, James and Higgins, "Fundamentals of Photography Theory", Morgan and Morgan, New York, p . 15).

The silver halide crystals constituting the tabular grains can have any composition known to be useful for photography. In a preferred form which offers numerous advantages, silver bromo-iodide emulsions with a high form index are used in the products according to the invention.

Silver bromo-iodide emulsions with tabular grains of high shape index can be prepared as follows. A dispersion medium is introduced into a conventional reactor for the precipitation of silver halides, equipped with an appropriate stirring device. In general, the dispersion medium thus initially introduced into the reactor represents at least approximately 10% and preferably from 20 to 80% of the total mass of the dispersion medium which will be present in the emulsion of silver bromo-iodide to the end of the precipitation. The dispersion medium can be removed from the reactor by ultrafiltration during the precipitation of the silver bromo-iodide grains, according to the indications of Belgian patent No. 886645 and French patent No. 2471620; the volume of dispersion medium present at the start in the reactor can therefore be equal to or even slightly greater than the volume of the silver bromo-iodide emulsion which will be in the reactor at the end of the precipitation of the grains. Preferably, the dispersion medium introduced at the start consists of water or of a dispersion of peptizer in water possibly containing other substances, for example one or more agents for maturing silver halides and / or metal dopants, described in more detail below. When a peptizing agent is present at the start, its concentration represents at least 10% and preferably at least 20% of the total peptizing silver present at the end of the precipitation of silver bromo-iodide. An additional quantity of the dispersion medium is added to the reactor with the silver salt and the halides and optionally by means of a separate jet. Usually, the proportion of dispersing medium is adjusted, in particular in order to increase the proportion of peptizing agent, once the addition of the salts is complete.

A small part, generally less than 10% by mass of bromide used to form grains of silver bromo-iodide, is present at the start in the reactor to adjust the concentration of bromide ions at the beginning of the precipitation of bromo-iodide silver. In addition, at the start of precipitation, the dispersion medium contained in the reactor should in principle not contain iodide ions; in fact, the presence of iodide ions before the introduction of silver salt and bromide promotes the formation of thick grains which are not tabular. When, in the present description, it is indicated that the reactor does not in principle contain iodide ions,

this means, with regard to the ingredients present in the reactor, that if the iodide ions are present in the reactor, their concentration relative to the bromide ions is insufficient to cause the precipitation of a distinct phase of silver iodide. This is why, in practice, it is preferred to maintain the iodide concentration in the reactor below 0.5 mol% relative to the total amount of halides present in the reactor before the introduction of the silver salt. If the pBr of the dispersion medium is initially too high, the tabular grains of silver bromo-iodide that are produced will be comparatively thick and therefore have a low shape index. Care is therefore taken to maintain the initial pBr of the reactor at a value equal to or less than 1.6 and preferably less than 1.5. On the other hand, if the pBr is too low, this promotes the formation of silver bromo-iodide grains which are not tabular; this is why it is necessary to maintain the pBr equal to or greater than 0.6 and preferably greater than 1.1. It will be recalled that pBr is the negative logarithm of the concentration of bromide ions and that pH and pAg are respectively defined in the same way for the concentrations of hydrogen and silver ions.

During precipitation, the silver salts, bromide and iodide are added to the reactor according to well known techniques. In general, a solution of a silver salt is introduced into the reactor.

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soluble, for example a silver nitrate solution, together with bromide and iodide solutions. Bromide and iodide are also introduced in the form of an aqueous solution of one or more ammonium or alkali metal salts, for example sodium or potassium, or alkaline earth metal salts, for example salts magnesium or calcium. The silver salt, at least initially, is introduced into the reactor by a separate jet from that of the iodide. The iodide and bromide can be added to the reactor separately or as a mixture.

When a silver salt is introduced into the reactor, the nucleation phase of the grain formation process is started. A population of germs capable of constituting precipitation sites for silver bromide and silver iodide is formed as the addition of the silver salt, bromide and iodide continues. The precipitation of bromide and silver iodide on existing germs constitutes the growth phase of grain formation. The shape index of the tabular grains formed according to the present invention is less influenced by the concentration of iodide and bromide during the growth phase than during the nucleation phase. This is why, during the growth phase, it is possible to increase the latitude for fixing the pBr so as to have, during the introduction of the salts, a pBr greater than 0.6, preferably between approximately 0.6 and 2.2, and preferably between 0.8 and 1.6. It is of course possible and, in fact, advantageous, to maintain the pBr throughout the introduction of the salts into the reactor within the limits indicated above in the initial stage, before the introduction of the silver salt. This latter interval is particularly preferred when the rate of germ formation continues appreciably during the introduction of the salts, as is the case in the preparation of emulsions with high polydispersity. If the pBr rises above 2.2 during the growth of the tabular grains, this leads to the formation of thicker grains, but there is in many cases a tolerance which makes it possible to still obtain shape indices greater than 8: 1.

A variant for the introduction of the silver salts, bromide and iodide consists in introducing these salts at the start or in the growth phase, in the form of fine grains of silver halides in suspension in a dispersion. The diameter of the grains is such that their maturation of Ostwald on larger seeds is possible as soon as they are introduced into the reactor, if such seeds are present. The maximum useful grain diameter depends on the specific conditions prevailing in the reactor, for example the temperature and the presence of solubilization or maturation silver. It is thus possible to introduce grains of silver bromide, silver iodide and / or silver bromo-iodide; since bromide and / or iodide preferentially precipitate over chloride, it is also possible to use grains of silver chlorobromide and silver chlorobromo-iodide; these silver halide grains are preferably very small, that is to say that their average diameter is less than 0.1 p.m.

Subject to the conditions relating to pBr set out above, the concentration and the flow rate of the jets of bromide silver salts and of iodide can be produced in suitable conventional forms. The silver salts and the halides are preferably introduced at a concentration of between 0.1 and 5 mol / l, although wider intervals can be envisaged ranging from 0.01 mol / l to saturation. The preferred precipitation techniques are those which allow the shortest precipitation times to be obtained by increasing the quantities of silver salts and halides introduced during precipitation. This increase can be obtained by increasing either the flow rate or the concentration of the salt jets. We prefer to increase the flow rate of the jets, but by keeping it below a threshold from which the formation of new germs would be favored, that is to say from which there would be a renucleation, according to the indications given to U.S. Patents Nos. 3672900, 3650757, 4242445, as well as the publication of German Patent Application No. 2107118, European Patent Application No. 80102242 and by Wey, in "Photography Science and Engineering ", flight. 21, N ° 1, January-February 1977, pp. 14 et seq. By avoiding the formation of additional germs in the growth step, relatively monodispersed populations of tabular grains of silver halide can be obtained. Emulsions with coefficients of variation of less than about 30% can be prepared. Remember that the coefficient of variation is the standard deviation of the grain diameter multiplied by 100 and divided by the average grain diameter. If the renucleation is deliberately favored during the growth phase, it is of course possible to form polydispersed emulsions whose coefficient of variation is significantly higher.

The iodide concentration in the silver bromo-iodide emulsions according to the present invention can be controlled by acting on the introduction of the iodide. Any conventional concentration of iodide may be used. Even very low concentrations, for example as low as 0.5 mol-%, can be, as is known, advantageous. Preferably, the emulsions according to the invention contain approximately at least 0.1 mol% of iodide. Silver iodide can be incorporated into tabular grain emulsions of silver bromo-20 iodide until the solubility limit of silver iodide in silver bromide is reached at the formation temperature. grains. Thus, for precipitation temperatures of 90 ° C., the concentration of silver iodide can reach 40 mol% in the tabular grains of silver bromo-iodide. In practice, the precipitation temperature can be lowered almost to room temperature, i.e. up to 30 ° C, but in general it is preferred to carry out precipitation at temperatures between 40 and 80 ° C. For most photographic applications, the maximum iodide concentration is limited to about 20% and preferably does not exceed about 15%.

The respective amounts of iodide and bromide introduced into the reactor during precipitation can be maintained in a fixed ratio, so as to obtain tabular grains of silver bromo-iodide whose iodide concentration has a uniform profile, but this profile can be varied to obtain various photographic effects. Particular advantages can be obtained by increasing the proportion of iodide in an annular or eccentric region of the silver bromo-iodide grains of high shape index; this means that in these regions of the tabular grain, the iodide concentration is greater than it is in the center of the grain. The iodide concentration in the center of the grain can be between 0 and 5 mol% and, at least in a peripheral annular region, the iodide concentration can go up to the solubility limit of silver iodide in silver bromide; preferably, the iodide concentration can reach up to 20 mol%, and optimally up to about 15 mol%.

A variant consists in stopping the addition of iodide or the addition of bromide and iodide before stopping the addition of silver salt, so that the excess of hologides reacts with the salt of silver. As a result, a silver bromide shell is formed on the tabular grains of silver bromo-iodide. It is therefore clear that the tabular grains of silver bromo-iodide according to the invention can have uniform or variable iodide concentration profiles and that this variation can be controlled, if desired, to promote a concentration of iodide higher either inside, near, or on the surface of the tabular grains of silver bromo-iodide.

The preparation of silver tabular grain bromo-iodide emulsions of high shape index has been described with reference to a process providing emulsions which are neutral or non-ammoniacal; but the present invention is not limited to this particular process. Another process constitutes an improvement on that described in the patent of the United States of America No. 4150994, as well as in the publications of German applications No. 2985655 and 65 2921077. In a preferred form, the iodide concentration is lowered silver in the reactor below 0.05 mol / l and the maximum diameter of the silver iodide grains initially present in the reactor below 0.05 µm.

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Tabular-grain silver bromide emulsions of high form index without iodide can be prepared by the method described in detail above modified so as not to use iodide.

High bromide tabular grain silver bromide emulsions can also be prepared according to a process based on the indications given by De Cugnac and Chateau in the publication cited above.

High shape index silver bromide emulsions consisting of square and rectangular grains can be prepared by a method of using cubic shaped seed grains with an edge less than 0.15 µm. By keeping the pAg of the seed grain emulsion between 5.0 and 8.0, the emulsion is matured in the absence of silver complexing silver ion other than the hologenides, so forming tabular silver bromide grains with an average shape index of at least 8: 1. The examples below provide other methods of preparing high-index-index tabular-grain silver bromide emulsions without iodide.

The variety of emulsions which can be used according to the invention can be illustrated by the fact that tabular grains of silver chloride can be prepared, the interior of which contains practically neither silver iodide nor silver bromide. To this end, a double jet precipitation process is implemented according to which chloride and a silver salt are introduced at the same time into a reactor containing a dispersion medium in the presence of ammonia. During the introduction of the chloride, the pAg in the dispersion medium is maintained between 6.5 and 10 and the pH between 8 and 10. At high temperature, the presence of ammonia tends to cause the formation of thick grains. This is why the precipitation temperature does not exceed 60 "C to obtain silver chloride emulsions with tabular grains of high shape index.

It is also possible to prepare tabular grains containing at least 50 mol% of chloride and, of which two opposite crystal faces are in crystal planes [111], at least one peripheral edge, according to a preferred embodiment, being parallel to a crystallographic vector <211> in the plane of one of the main faces. Such tabular grain emulsions can be prepared by reacting aqueous solutions of silver salt and halides containing chloride, in the presence of an amount capable of modifying the crystalline form of an aminoaza-indene and a peptizing agent containing a thioether bridge.

It is also possible to prepare tabular grain emulsions in which the grains contain chloride and bromide at least in one annular region of the grain and preferably throughout the grain. The regions of the tabular grains containing silver, chloride and bromide are formed by maintaining the molar ratio of chloride to bromide between 1.6: 1 and 260: 1 and maintaining the total concentration of halide ions in the reactor between 0.10 and 0.90N during the introduction of the silver salt, chloride and bromide and optionally iodide, into the reactor. The molar ratio of silver bromide to silver chloride in tabular grains is between 1:99 and 2: 3.

The tabular grain emulsions according to the present invention can have extremely high shape indices. These shape indices can be increased by increasing the grain diameter. Advantages can therefore be obtained with regard to sharpness, but the maximum grain diameter is generally limited by granularity considerations for a given photographic application. Shape indices can also be increased by decreasing the average grain thickness. When the silver title is kept constant, the reduction in the thickness of the tabular grains generally leads to an improvement in the granularity in direct proportion to the increase in the shape index. Consequently, the maximum average shape index of the tabular grain emulsions according to the invention depends on the maximum average diameter acceptable for the photographic application considered and on the minimum grain thickness that can be obtained. The maximum shape indices that have been observed are variable depending on the precipitation techniques used and the halide composition of the grains. The highest shape indices that have been observed are 500: 1 for the tabular grains still having grain diameters useful from a photographic point of view; these grains were obtained by Ostwald ripening of silver bromide grains; we obtained indices of 100: 1. 200: 1 or more with double jet precipitation techniques. The presence of iodide generally leads to a reduction in the maximum average shape indices that can be obtained, but it is still possible to prepare emulsions with tabular grains of silver bromo-iodide whose shape indices reach 100: 1, and even 200: 1 or more. Tabular silver chloride grains may be prepared, possibly containing bromide and / or iodide, the shape indices of which reach 50: 1 or even 100: 1. The maximum average grain diameters are in all cases less than 30 µm, preferably 15 µm and, optimally, do not exceed 10 µm.

Modifying agents may be present during the precipitation of the tabular grains, ie initially in the reactor,

be added together with one or more of the salts, according to conventional methods. These modifiers may be compounds of copper, thallium, lead, bismuth, cadmium, zinc, medium chalcogen (i.e., sulfur, selenium and tellurium), gold and noble metals of group VIII, according to the indications given to the patents of the United States of America 25 Nos 1195432, 1951933, 2448060, 2628167, 2950972, 3488709,

3737313, 3772031,4269927 and in the journal "Research Dischlo-sure", vol. 134, June 1975, publication 13452. The journal "Research Disclosure" and the title that preceded it, "Product Licensing Index", are published by Industriai Opportunities Limited; Homewell, 30 Havant; Hampshire, P09; 1EF; United Kingdom. Tabular grain emulsions can be sensitized by reduction inside the grains during precipitation, as described by Moisar et al., "Journal of Photography Science", vol. 25, 1977, pp. 19 to 27.

The silver salts and the halides can be added to the reactor by means of surface or sub-surface supply tubes, by gravity feed or by means of devices which allow the regulation of the speed of addition as well as pH, pBr and / or pAg of the contents of the reactor, according to the indications given to the 40 patents of the United States of America N05 3821002 and 3031304 and by Claes in "Photographische Korrespondenz", vol. 102, No. 10, 1967, p. 162. To obtain a rapid distribution of the reactants in the reactor, specially adapted mixing devices such as those described in United States patents 45 Nos 2996287, 3342605, 3415650, 3785777, 4147551 and 4171224 can be used. British patent application no. 2022431 A, German patent application Nos. 2555364 and 2556885 and in "Research Disclosure", vol. 166, February 1978, publication 16662.

To precipitate emulsions with tabular grains, one can use a concentration of peptizer of between 0.2 and about 10% by mass relative to the total mass of the constituents of the emulsion in the reactor. It is common to keep the peptizing concentration in the reactor below about 6% of the total mass, before and during the formation of the silver halide, and to adjust later to higher values the vehicle concentration of the emulsion (the vehicle term including the binder and the peptizer), by additional vehicle additions, to obtain the optimal coating characteristics. The emulsion initially formed may contain approximately 5 to 50 g of peptizer / mol of silver halide, preferably approximately 10 to 30 g / mol of silver halide. A vehicle may be added later additional to bring the concentration up to 1000 g / mol of silver halide. Advantageously, in the finished emulsion, there is more than 50 g of vehicle, mol of silver halide. Once coated and dried 65 in a photographic product, the vehicle forms approximately 30 to 70% by mass of the emulsion layer.

Vehicles can be chosen from the substances usually used in silver halide emulsions for this purpose. The

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preferred peptizers are hydrophilic colloids which can be used alone or in combination with hydrophobic substances. Suitable hydrophilic vehicles include substances such as proteins, protein derivatives, cellulose derivatives, for example cellulose esters, gelatin, for example gelatin treated with an alkaline agent (skin or bone gelatin ) or gelatin treated with an acid agent (pigskin gelatin), gelatin derivatives, for example acetylated gelatin and phthalylated gelatin. These and other vehicles are described in "Research Disclosure", Vol. 176, December 1978, publication 17643, section IX.

The vehicle, in particular hydrophilic colloids, as well as useful hydrophobic substances combined with them, can be used not only in the emulsion layers of the photographic products of the invention, but also in other layers, such as overlays , interlayers and layers placed below the emulsion layers.

The preparation of the silver halide emulsions according to the invention may comprise a stage of maturation of the grains and the preferred way consists in carrying out the maturation of the grains in the reactor during at least the formation of the silver halide grains. Solvents of known silver halides are used to promote maturation, such as, for example, an excess of bromide ions in the reactor. It is known, for example, that the bromide solution introduced into the reactor can itself promote maturation. It is also possible to use other maturing agents which can be entirely incorporated into the dispersing medium in the reactor before the addition of silver salt and halides or which can be introduced into the reactor at the same time as one or more several of the silver salts, halides or peptizer. According to another embodiment, the curing agent can be introduced independently during the addition of the halide and the silver salt. Although ammonia is a known curing agent, it does not constitute a preferred curing medium for the emulsions according to the invention, the relationship of speed / granularity is the highest. Preferably, the emulsions according to the invention are not ammoniacal, or are neutral.

Advantageous ripening agents are those which contain sulfur. Thiocyanates can be used in the form of alkali metal salts, usually sodium and potassium, and ammonium thiocyanates. Conventional amounts of thiocyanate can be used, but the advantageous concentrations are generally between about 0.1 and 20 g of thiocyanate / mol of silver halide. The use of thiocyanate as a ripening agent is described in United States patents Nos. 2222264, 2448534 and 3320069. Thioethers, such as those described in United States patents, can also be used conventionally. Nos 3271157, 3574628 and 3737313.

The tabular grain emulsions with a high shape index are preferably washed, to remove the soluble salts, by known techniques such as decantation, filtration and / or by jelly and filtration, as described in "Research Disclosure ”, vol. 176, December 1978, publication 17643, section II. It is particularly advantageous according to the present invention to complete the maturation of the tabular grains by washing after the end of precipitation, to avoid increasing their thickness, reducing their shape index and / or excessive increase in their diameter. Emulsions with or without a sensitizer can be dried and stored before use.

The methods for preparing tabular grains described above make it possible to obtain emulsions in which the tabular grains meeting the criteria of thickness and diameter necessary to obtain a high shape index represent at least 50% of the total projected surface of the total population of silver halide grains; but additional benefits can be obtained by increasing the proportion of tabular grains. It is advantageous that at least 70% (and optimally at least 90%) of the total projected surface is represented by tabular silver halide grains meeting the criteria of thickness and diameter. Although the presence of small amounts of non-tabular grains is fully compatible with most photographic applications, the proportion of tabular grains can be increased to obtain the full benefits of flat grains. The larger tabular silver halide grains can be mechanically separated from the smaller, non-tabular grains in a mixed grain population using conventional separation means, such as a centrifuge or a hydrocyte. clone. Separation by hydrocyclone is illustrated in US Patent No. 3,326,641.

According to current practice, it is possible to mix the tabular grain emulsions with a high shape index either between themselves or with conventional emulsions, in order to obtain emulsions having particular characteristics. For example, it is known to mix emulsions to adjust the characteristic curve of a photographic product for a specific purpose. The mixture can be used to increase or decrease the maximum densities obtained by exposure and treatment, to decrease or increase the minimum densities, and to adjust the shape of the characteristic curve between the foot and the shoulder. Conventional silver halide emulsions which can be used as a mixture are described in the journal "Research Disclosure", vol. 176, December 1978, publication 17643, paragraph I.

The silver tabular grain halide emulsions of high form index, according to the present invention, are chemically sensitized. They can be chemically sensitized with active gelatin, as indicated by T.H. James, "The Theory of the Photography Process", 4th ed., Macmillan, 1977, 30 pp. 67-76; chemical sensitization can also be carried out with sulfur, selenium, tellurium, gold, platinum, palladium, iridium, osmium, rhodium, rhenium or phosphorus sensitizers, or with combinations of these different sensitizers, and with a pAg of, for example, between 5 and 10, 35 at a pH between 5 and 8, and at a temperature between 30 and 80 ° C., as indicated in "Research Disclosure" , flight. 120, April 1974, paragraph 12008, "Research Disclosure", vol. 134, June 1975, paragraph 13452, to U.S. Patents Nos. 1623499, 1673522, 2399083, 2642361, 3297447, 40 3297446; English Patent No. 1,315,755; to United States patents Nos. 3772031, 3761267, 3857711, 3565633, 3901714 and 3904415 and to English patent No. 1396696; chemical sensitization is optionally carried out in the presence of thiocyanates, as described in the patent of the United States of America No. 2642361, in the presence of compounds containing sulfur such as those described in the patents of the United States of America Nos 2521926, 3021215 and 4054457. Emulsions can be chemically sensitized in the presence of chemical sensitization modifiers, that is to say compounds known for their ability to suppress haze and increase speed under these conditions; such compounds are, for example, aza-indenes, azapyridazines, azapyrimidines, benzothiazolium salts and sensitizers having one or more heterocyclic rings. Examples of modifiers are given in United States patents Nos. 2131038, 55 3411914, 3554757, 3565631, 3901714 as well as in Canadian patent No. 778723 and by Duffin in "Photographie Emulsion Chemistry", Focal Press (1966 ), New York, pp. 138-143. In addition to the various chemical sensitizations defined above, or as an alternative to these sensitizations, the emulsions can be further sensitized by reduction, for example with hydrogen, as described in the patents of the United States. from America Nos 3891446 and 3984249, or by subjecting them to conditions combining a low pAg, for example less than 5, and / or a high pH, for example greater than 8, or by means of various reducing agents such as 65 stannous chloride, thiourea dioxide, polyamines and borane amines, as described in US Patents Nos. 2983609, 2518698, 2739060, 2743182, 2743183, 3026203, 3361564, as well as in " Research Disclosure ”, vol. 136,

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August 1975, paragraph 13654. Surface chemical sensitization or chemical sensitization can be carried out in an area immediately below the surface, as described in United States Patent Nos. 3917485 and 3966476.

The high form index tabular grain emulsions of the present invention are also spectrally sensitized. It is planned to use spectral sensitizing dyes which exhibit maximum absorption in blue and minus blue, that is to say in the red and in the green of the visible spectrum. In addition, for certain specific uses, spectral sensitizing dyes can be used which improve the spectral response in the region of the spectrum situated beyond the visible part. One can for example use absorbent spectral sensitizers in the infrared region.

Silver halide emulsions can be spectrally sensitized with dyes belonging to various classes, in particular cyanines and merocyanines, complex cyanines and mero-cyanines (tri-, tetra- or polynuclear), oxonols, hemioxonols, styrylic, merostyrylic and strep-tocyanin dyes.

Spectral sensitizing dyes of the cyanine type comprise two heterocyclic rings of basic character linked by a methine bond; these heterocyclic rings are derived for example from quaternary salts of quinolinium, pyridinium, iso-quinolinium, 3H-indolium, benz [e] indolium, oxazolium, oxazoli-nium, thiazolinium, thiazolium, selenazolium, selenazolinium, imidazolium, imidazolinium, benzazol benzoseleazolium, benzimidazolium, naphtoxazolium, naphthothiazolium, naphtoselenazolium, dihydronaphtothiazolium, pyrylium and imidazopyrazinium.

The spectral sensitizing dyes of the merocyanine type comprise, linked by a methine bond, a nucleus of basic character of the type found in the formula of cyanines and an acid nucleus derived for example from barbituric acid, acid 2 -thiobarbitaric, rhodanin, hydantoin, 2-thiohy-dantoin, 4-thiohydantoin, 2-pyrazoline-5-one, 2-isoxazoli-ne-5-one, indan-I, 3- dione, cyclohexane-1,3-dione, 1,3-dioxan-ne-4,6-dione, pyrazolin-3,5-dione, pentane-2,4-dione, alkylsul-fonylacetonitrile, malononitrile, isoquinolin-4-one and chro-man-2,4-dione.

One or more spectral sensitizing dyes can be used. Dyes are known with sensitization maximums for wavelengths distributed over the entire extent of the visible spectrum and providing spectral sensitivity curves of very different shape. The choice and the relative proportions of dyes depend on the region of the spectrum to which the grains are to be sensitized and on the shape of the spectral sensitivity curve which it is desired to obtain. Dyes with partially overlapping spectral sensitivity curves often provide, when used in combination, a curve such that the sensitivity at each wavelength in the overlap region is approximately the sum of the sensitivities of each dyes. Thus, it is possible to use combinations of dyes having different maximums, in order to obtain a spectral sensitivity curve having a maximum situated between the sensitization maximums of each of the dyes.

Certain combinations of spectral sensitizing dyes produce an oversensitizing effect, that is to say, provide, in one region of the spectrum, a spectral sensitization greater than that resulting from the use of one of the dyes alone at any point. it concentration, or resulting from the addition of several dyes. Oversensitization can be achieved with selected combinations of spectral sensitizing dyes and other additives such as stabilizers, anti-stars, development accelerators or inhibitors, coating aids, optical brighteners and antistatics. Mechanisms to explain over-sensitization and compounds to achieve it are described by Gilman in "Review of the Mechanisms of

Supersensitization ”, in“ Photography Science and Engineering ”, vol. 18, 1974, pp. 418-430.

Spectral sensitizing dyes can also exert other actions on emulsions. These dyes can also play the role of anti-veil, stabilizers, development accelerators or inhibitors, halide acceptors or electron acceptors, as described in the United States patents. America Nos. 2131038 and 3930860.

In order to record the exposure to blue light in the emulsion layers, it is generally sufficient to use the natural sensitivity in the blue of bromide or silver bromo-iodide; but according to a specific aspect of the present invention, appreciable advantages can be obtained by using spectral sensitizers, even with sensitizers whose main absorption is located in the region of the spectrum where these emulsions have their natural sensitivity. For example, the present invention particularly relates to obtaining specific advantages linked to the use of spectral sensitizing dyes for blue. Even when the emulsions of the present invention consist of grains of high form index of bromide and silver bromide iodide, significant increases in speed can be achieved by using spectral blue dyes. When it is intended to exhibit the emulsions of the present invention in the region of their natural sensitivity, gains in sensitivity can be obtained by increasing the thickness of the tabular grains.

To sensitize spectrally in blue the emulsions of silver bromide and bromo-iodide with tabular grains of high shape index, one can choose dyes in all the known classes of spectral sensitizing dyes. The spectral sensitizers for blue, which are preferred, belong to the class of polymethine dyes, such as cyanines, merocyanines, hemicyanins, hemioxonols, merostyryls. In general, we can choose useful spectral blue sensitizers,

in these classes of dyes, according to the absorption characteristics, that is to say according to the shade. Correlations have been established, however, with the structural characteristics which can serve as a guide for an advantageous selection of blue sensitizers. In principle, the shorter the methine chain, the shorter the wavelength of the maximum sensitization. The nuclei also have an influence on absorption. The addition of cycles attached to the nucleus tends to favor absorption towards the longer wavelengths. The substituents can also modify the absorption characteristics.

Among the spectral sensitizing dyes useful for sensitizing emulsions to silver halides, mention may be made of those described in "Research Disclosure", vol. 176, December 1978, publication 17643, section III.

For the spectral sensitization of non-tabular silver halide grains, conventional amounts of dyes can be used. To take full advantage of the advantages offered by the present invention, it is preferable to adsorb an optimal quantity of sensitizing dyes on the surface of the tabular grains of high shape index. By optimum quantity is meant the quantity sufficient to reach at least 60% of the maximum photographic speed which it is possible to achieve with these grains under the conditions provided for the exposure. The amount of dye to be used depends on the nature of the dye or the combination of dyes chosen, or on the size and shape index of the grains. It is known in the photographic technique that optimal spectral sensitization can be obtained with organic dyes when these dyes are used in an amount which makes it possible to produce a monolayer on approximately 25% or more of the total available surface of the grain. silver halide with surface sensitivity, as described for example by West in "The Adsorption of Sensitizing Dyes in Photographie Emulsions", in "Journal of Phys. Chem. ”, Vol. 56, p. 1065, 1952; by Spence et al., in "Desensitization of Sensitizing Dyes", in "Journal of Physi-cal and Colloid Chemistry", vol. 56, N ° 6, June 1948, pp. 1090-1103,

s

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20

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30

35

40

45

50

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65

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and by Gilman et al., in US Patent No. 3,979,213. The optimal amounts and concentrations of dyes can be determined by the methods indicated by Mees, in "Theory of the Photography Process", pp. 1967-1069, already cited.

Spectral sensitization can be carried out at any stage of the preparation of the emulsion which has been recognized to be useful for this purpose. Usually, spectral sensitization is carried out after the end of chemical sensitization. However, spectral sensitization can be carried out, either at the same time as chemical sensitization, or entirely with chemical sensitization, and even it can be started before the precipitation of the silver halide grains, according to the indications given to the patents of the United States of America Nos 3628960 and 4225666. The patent of the United States of America No. 4225666 specifically provides for introducing the spectral sensitizing dye into the emulsion in stages, so that a portion of this dye is present before chemical sensitization, while another part is introduced after chemical sensitization. Unlike what is shown in U.S. Patent No. 4,225,666, it is possible according to the present invention to add the spectral sensitizer after 80% of the silver halide has been precipitate. Sensitization can be improved by adjusting the pAg, including through cyclic variations, during chemical sensitization and / or spectral sensitization. A specific example of pAg setting is given in "Research Disclosure", vol. 181, May 1979, publication 18155.

Silver halide emulsions with tabular grains of high shape index, chemically and spectrally sensitized, have a better speed / granularity relationship than that obtained hitherto with emulsions with tabular grains and with emulsions which provide the best speed / granularity relationships. The best results are obtained by using spectral sensitizing dyes for the blue minus.

According to an advantageous embodiment, the spectral sensitizers are incorporated into the emulsions of the invention before chemical sensitization. Similar results have also been obtained in some cases by introducing other adsorbable substances, such as curing modifiers into emulsions with chemical sensitization.

Another means which can be used, alone or in combination with only one or two of the means indicated above, consists in adjusting the concentration of silver and / or halide present immediately before or during the chemical sensitization. Soluble silver salts can be introduced, such as silver acetate, silver trifluoroacetate and silver nitrate, as well as salts which can precipitate on the surface of the grains, such as silver thiocyanate. , silver phosphate, silver carbonate, etc. Fine silver halide grains (i.e. bromide, iodide and / or silver chloride) capable of undergoing Ostwald ripening can be introduced onto the surfaces of the tabular grains . For example, a Lippmann emulsion can be introduced during chemical sensitization. Chemical sensitization of spectrally sensitized high index tabular grain emulsion can be carried out at one or more sites distinct from the tabular grains. It is believed that the preferential adsorption of spectral sensitizing dyes on the crystallographic surfaces forming the main faces of the tabular grains allows chemical sensitization to occur selectively on surfaces of these grains other than crystallographic.

Advantageous chemical sensitizations for obtaining the best speed / granularity relationships are sensitization to gold and sulfur, sensitization to gold and selenium, and sensitization to gold, sulfur and selenium. In an advantageous embodiment of the invention, the emulsions of silver bromo-iodide with tabular grains of high shape index contain a chalcogen, such as sulfur and / or selenium, which may not be detectable, and gold that is detectable. Emulsions also usually contain detectable amounts of thiocyanate, although the concentration of thiocyanate in the final emulsion can be greatly reduced by known washing techniques. In the various embodiments indicated above, the surface of the tabular grains of silver bromo-iodide may comprise another silver salt such as a silver thiocyanate, or another different silver halide ( for example silver chloride or silver bromide),

although this other silver salt may be present in undetectable amounts.

Although it is not necessary to obtain all of their advantages, the emulsions defined according to the invention are preferably chemically and spectrally sensitized in an optimal manner, in accordance with current manufacturing practices. This means that their speed represents at least 60% of the maximum of the logarithm of the speed that can be expected from the grains in the spectral region I5 of sensitization and under expected conditions of use and treatment. The logarithm of speed is defined as 100 (1 - log E), where E is measured in lux • second at a density of 0.1 above the veil. Once the silver halide grains of a product have been characterized, it is possible to estimate, from other analyzes made on the product and from the evaluation of its performance, whether a layer emulsion of this product was sensitized chemically and spectrally in an optimal way, by comparison with other comparable commercial products.

^ Analog image transfer

In the probably simplest application of the invention, a layer of silver halide emulsion of a conventional product for photography by silver image transfer is replaced by a layer of halide emulsion of silver with 30 tabular grains of high shape index. In addition to a conventional photographic support on which "is placed the tabular silver halide emulsion layer, the product advantageously contains a silver receiving layer comprising seeds of physical development of silver halides or agents to precipitate silver. To produce a transferred silver image, the silver receiving layer and the emulsion layer are juxtaposed and, after photographic exposure of the tabular grain emulsion layer, a solution is released. treatment containing a silver halide solvent in contact with the emulsion layer and the receiving layer.

A wide variety of seeds or silver precipitants can be used in the receiving layers for the transfer of silver image. These seeds are incorporated into layers of conventional photographic organic hydrophilic colloid, such as 45 layers of gelatin or polyvinyl alcohol, and include seeds of physical development or chemical precipitating agents such as: a) heavy metals, particularly in colloidal form, and their salts; b) salts whose anions form less soluble silver salts than the silver halides of the emulsion to be treated, and c) non-diffusible polymeric substances having groups capable of combining with the silver ions and thus to insolubilize them.

Commonly used silver precipitators include sulfides, selenides, poylsulfides, polyselenites, thiourea and its derivatives, mercaptans, stannous halides, silver, gold , platinum, palladium, mercury, colloidal silver, aminoguanidine sulfate, aminoguanidine carbonate, arsenious oxide, sodium stannite, substituted hydrazines, xanthates, etc. Polyvinyl mercaptoacetate is a 6o example of a suitable indifusible polymer precipitation agent. Heavy metal sulfides, such as lead, silver, zinc, aluminum, cadmium and bismuth sulfides are useful, and in particular lead and zinc sulfides alone or as a mixture, or their salts complexes with thioacetamide, dithiooxamide or dithio-65 biuret. Heavy metals and noble metals, especially in colloidal form, are especially effective. Other silver precipitating agents are known in the photographic art.

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The processing solution can be any conventional developer containing a silver halide solvent. Such processing solutions useful for providing an image of silver transferred into a photographic product are described in US Pat. Nos. 2352014, 2543181, 2861885, 3020155 and 3769014.

In products operating by silver image transfer, the emulsion layer (s) and the receptor layer may be arranged relative to each other in any suitable conventional manner. They can be placed on the same support or on different supports. When the receiving layer is applied on a separate support, the layer and the support, as well as possibly other additional layers, are called together receiving element. In a conventional structure of products with separable elements, the support carrying the emulsion layer is opaque, and the receiving support is reflective (for example, white) or is provided with a reflective layer placed under the receiving layer. The product is exposed before juxtaposing the receiving element and the emulsion layer for treatment. In a unitary structure (with non-separable elements) the receiving support and the support of the emulsion layer are both transparent, and a reflective background is produced for the observation of the silver image, by applying to the receiving layer. a layer of reflective pigment, or by introducing such a pigment into the treatment solution. An advantageous receiving element also usually comprises a neutralization layer (also called acid layer, or layer lowering the pH), to stop the development, and at least one retarding layer (also sometimes called spacer layer, or inert spacer layer ). Alternatively, the neutralizing and retarding layers may be located on the support carrying the emulsion. The supports carrying the receiving element and the emulsion preferably form a unitary structure, that is to say are united during the exposure, the processing and the observation of the image but, in other structures, they can be separated during exposure, observation, and / or part of the treatment. Examples of substances which can be used in the neutralizing and retarding layers are given in "Research Disclosure", vol. 123, July 1974, publication 13331, et'vol. 135, publication 13525, July 1975. Details on the reflective layers and the substances constituting the supports, as well as ultraviolet absorbing agents and incorporated optical brightening agents, are given in "Research Disclosure", vol. 151, November 1976, publication 15162. Particularly advantageous substances for forming transparent supports are polyethylene terephthalate and cellulose esters. Preferred reflective supports are resin coated paper supports.

In a preferred embodiment, the products according to the invention contain an alkaline treatment composition, and means for containing and releasing it. An advantageous means consists of a frangible container (for example, a capsule), placed in the product so that compression applied by means of pressing devices, such as those of instantaneous cameras, has the effect of the discharge of the contents of the capsule into the product. However, other methods can be used to introduce the alkaline treatment composition. Other treatments are also described in "Research Disclosure", publication 17643, already cited, paragraph XXIII, C and G.

Dye image transfer

The products for image transfer photography according to the invention can also provide a transferred dye image. Except as indicated, the characteristics of the dye image transfer products may be identical to those of the silver image transfer products described above.

A silver image transfer product can be converted to a dye image transfer product by simply replacing the silver-receiving layer with a dye-receiving layer, and incorporating a dye-forming substance into the emulsion layer. with silver halides, or in an adjacent layer. In this case, the silver halide is not normally transferred to the receiving layer and the presence of a silver halide solvent in the alkaline treatment solution is therefore not essential.

A monochrome image-forming product by diffusion-transfer according to the invention may comprise a support, with a single dye image-forming element which contains a layer of tabular silver halide emulsion, as described above. above, and at least one dye imaging compound located either in the emulsion layer itself, or in a layer adjacent thereto. In addition, the product includes a dye receiving layer capable of etching or immobilizing in any way after migration, the dye image is formed. To obtain the transferred dye image, the tabular grain emulsion layer is exposed in an image, then it is treated with a basic treatment composition, juxtaposing the emulsion layers with the dye receiving layer. In a particularly advantageous embodiment, where a monochrome transferred dye image is formed, a combination of dye image forming compounds is used to obtain a neutral transferred dye image. This image can be used to reinforce a transferred silver image, or to completely replace it, in order to obtain a visible image in black and white. One can, however, form a monochrome transferred dye image having any desired hue.

The diffusion-transfer color image-forming products according to the invention comprise: three dye-forming elements, namely: 1) a blue-green dye-forming element which comprises a red-sensitive silver halide emulsion with which is associated a blue-green dye-forming compound, 2) a magenta dye-forming element which comprises a green-sensitive silver halide emulsion with which is associated a magenta dye-forming compound, and 3) an element yellow dye former which comprises a blue sensitive silver halide emulsion with which a yellow dye former is associated. Each dye-forming element contains one, two, three, or more layers of separate silver halide emulsions, and the dye-forming compound 40 may be disposed in one or more of these layers. Any one or more emulsion layers may contain high form index tabular grain silver halide emulsions as described above. According to an advantageous embodiment of the invention, at least the fastest emulsion layers of the blue-green and magenta dye-forming elements are silver halide emulsions with tabular grains of high shape index, as described above. The yellow dye-forming element can also advantageously comprise, at least in the fastest emulsion layer, a silver halide emulsion with tabular grains of high shape index, as described above, but it is also possible to use in the yellow dye-forming element conventional silver halide emulsions and, in the blue-green and magenta dye-forming elements, silver halide emulsions with 55 tabular grains d 'high form index.

Depending on the nature of the dye-forming compound used, it can be incorporated in the silver halide emulsion layer or in a separate layer, associated with the emulsion layer. The dye-forming compounds can be conventional compounds, such as dye-forming couplers, developing dyes, dye-releasing compounds, and the dye-forming compound used will depend on the nature of the forming element. dye or product and the desired image quality. Useful colo-65 forming compounds contain a dye group and a group that controls the release of the dye. This latter group, in the presence of the basic treatment composition, and depending on the development of the silver halides, ensures a modification of the mobility of the

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coloring group. These dye-forming compounds can be initially mobile and can be made immobile depending on the development of the silver halides, as described in US Pat. No. 2,983,606. According to other embodiments, these forming compounds colorants can be initially immobile and can be made mobile in the presence of a basic treatment composition, depending on the development of the silver halides. This latter class of compounds includes compounds which release dyes by redox. In these compounds, the control group which controls the release of the dye is a carrier group from which the dye is released in direct function or in inverse function to the development of the silver halides. The compounds which release dyes as a direct function of the development of silver halides are called negative effect compounds, while the compounds which release dyes as a function of reverse development of silver halides are called positive effect compounds .

An advantageous class of compounds with a positive effect comprises the nitrobenzenes and the quinones described in US Pat. , in the ortho position of the nitro group or of the quinone oxygen atom, and it is released by the reduction of the compound by an electron donor compound contained in the product or in the treatment composition. In areas where the electron donor compound is consumed by the development of the silver halides, the coloring group is not released.

Other useful compounds with a positive effect are the hydroquinones described in United States patent No. 3,980,479, and the ben-zisoxazolones described in United States patent

No. 4199354.

Advantageous compounds with a negative effect are the ortho- or parasulfonamidophenols and -sulfonamidonaphthols as described in US Pat. Nos. 4054312, 4055428 and 4076529. In these compounds, the coloring group is attached to a sulfonamido group which is itself located ortho or para relative to the hydroxyphenolic group and it is released by hydrolysis, after oxidation of the sulfonamido groups during development.

Another useful class of negative effect compounds are ballast dye-forming couplers or couplers, which include a mobile dye attached to a site separating at coupling. By coupling with an oxidized chromogenic developing agent, such as paraphenylenediamine, the mobile dye is moved and can be transferred to an image receiving element. The use of such dye-forming compounds with a negative effect is described, for example, in United States patents Nos. 3227550 and 3227552 and in British patent No. 1445797.

Since the silver halide emulsions used in the diffusion transfer composite imaging films according to the invention are negative emulsions, the use of 50 dye forming compounds with negative effect will provide dye images transferred negative. To obtain positive transferred images with dye-releasing compounds with negative effect, a known photographic product can be used which reverses the image, and processing modifications, as described in the 55 patents of the United States of America Nos. 3998637 and 4258117.

The dye image-receiving layer of the products according to the invention can contain any substance, insofar as this can etch or fix the dye which diffuses towards it. The choice of the best substance will obviously depend on the nature of the dye (s) to be etched. The dye-receiving layer may further contain ultraviolet absorbing compounds, to protect the dye image from weakening due to ultraviolet light, optical brighteners, and the like to protect or strengthen the dye image. The "5

image receiving layer, or a layer adjacent thereto, may further contain a polyvalent metal, advantageously immobilized by association with a polymer, to form a complex with the transferred dye image, as described, for example , to United States Patent Nos. 4239849 and 4241163. Useful dye image receptor layers and substances useful in their preparation are described in "Research Disclosure", Vol. 151, publication 15162 (November 1976) and to U.S. Patent No. 4,258,117.

The basic treatment composition used in the products according to the invention may be an aqueous solution of a basic compound, such as a hydroxide or a carbonate of an alkali metal (for example sodium hydroxide or sodium carbonate ), or an amine (for example diethylamine). This basic composition advantageously has a pH value greater than 11. The substances useful for preparing these compositions are described in "Research Disclosure", publication 15162 cited above.

A developing agent is advantageously present in the basic treatment composition, but it can also be present in a solution distinct from the basic treatment solution, or in the treatment sheet, or it can be present in any layer of the product which can be crossed by the treatment composition. When the developing agent is not present in the basic treatment composition, the latter serves to activate the developing agent and allows the latter to come into contact with the silver halides and to develop them.

Various silver halide developing agents can be used to treat the products according to the invention. Choosing the best developer depends on the type of product it is used with and the particular dye-forming compound used. Suitable developing agents can be chosen from compounds such as hydroquinone, aminophenols, for example N-methylaminophenol, 1-phenyl-3-pyrazolidinone, 1-phenyl-4,4-dimethyl-3-pyrazolidinone, 1-phenyl-4-methyl-4-hydroxymé-thyl-3-pyrazolidinone and N, N, N ', N'-tetramethyl-p-phenylenedia-mine. It is advantageous to use the non-chromogenic developers from the above list in the products according to the invention, since their tendency to form parasitic colorations in the dye image receiving layers is reduced. All of these developing agents are also useful in products for silver image transfer photography.

Influence of tabular grains on processing speeds

One of the surprising advantages of the products according to the invention lies in the fact that the transferred dye image quickly becomes visible. This rapid access to the visible transferred image is directly linked to the presence of one or more silver halide emulsions with tabular grains of high shape index as defined above. Without limiting the invention by any particular theory, it is assumed that the geometric configuration of the tabular silver halide grains allows rapid access to the transferred images. The geometry of the tabular grains provides a very large surface area for the silver halide grains in relation to their volume, and it is believed that this characteristic influences the speed of their development. In diffusion-transfer color image formation processes, it is the development of silver halide grains, modulated according to an image according to the exposure, which in turn modulates the transferred image. In certain processes, for example in those which use dye-releasing compounds with negative effect, as described above, the development of the silver halides is directly linked to the image-forming substances transferred. It follows that the substances which form the image are made visible all the more quickly as the silver halides develop more quickly.

In other processes, such as those using silver image transfer and those using positive dye-releasing compounds described above, the development of silver halides is a concurrent reaction, or acts on a competing reaction, which delays the transfer of the compounds forming the image, and has an effect on the minimum density of the visible image. If the development of silver halides is accelerated, we can accelerate

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rer also the mechanisms responsible for the transfer of image-forming compounds, mechanisms which compete with the development of silver halides and have an effect on modulation.

The fact of using tabular grains to reduce the time which separates the start of the treatment from the moment when the transferred image becomes visible, that is to say to reduce the access time, does not in any way prevent the use of conventional means known to reduce this access time. When implementing the present invention in combination with usual means to reduce the access time, one can normally expect to obtain at least additive results. In addition, the products according to the invention have specific additional characteristics which contribute to reducing the access time.

A second advantage of the products according to the invention, containing at least one emulsion layer with silver halogen-iodides (preferably silver bromo-iodide) with flat grains of high shape index, lies in the fact that the characteristics of the transferred image vary little depending on the temperature. These slight variations in the characteristics of the transferred image result directly from the use of one or more layers of tabular silver halide emulsions, as described above in which the tabular grains contain at least 2% moles of iodide. Without limiting the invention by any particular theory, it is assumed that the tabular silver halide halide grains exhibit rates of development which vary little as a function of temperature. In diffusion-transfer imaging processes in which the development of silver halo-iodides is directly related to the transfer of image-forming substances, this reduced dependence on the development of ha-logeno-iodide grains silver tabular with respect to temperature has the direct result of obtaining visible images whose variations in characteristics are also reduced. In processes that employ competition mechanisms to form visible images, the small variation in the development of silver halo-iodides as a function of temperature can reduce the variation in the transferred image to the extent that this variation is attributable to the variation in the development of silver halides, and to the extent that this variation is added to the variations due to temperature in the competition mechanisms used in the formation of images.

Influence of tabular grains on silver titles

It has been noticed, surprisingly, that the products according to the invention have, for a lower silver titer, photographic sensitivities significantly higher than conventional products for color photography by transfer of a comparable titer. It is well known that when the silver titer is lowered below a certain threshold, a reduction in the photographic sensitivity is obtained, which can be observed on the transferred dye image. Although the photographic sensitivity decreases when the silver titers of silver halide emulsions decrease, this reduction in sensitivity is much more gradual when using tabular grain emulsions of high shape index; these emulsions therefore make it possible to use weaker silver titles.

Acceptable photographic sensitivities are usually obtained in the usual products for color photography by image transfer by using dye-forming elements respectively yellow, magenta and blue-green, the silver halide layers of which contain equal silver titles. or greater than about 1000 mg / m2. The implementation of the present invention makes it possible to use, in the photographic products according to the invention, significantly lower silver titers. When the silver halide grains of the emulsions of the dye-forming elements yellow, magenta and blue-green respectively are tabular, as described above, these emulsions can be effectively used in a silver titer of between about 150 and

750 mg / m-, advantageously between around 200 and 700 mg / m2 and very particularly between 300 and 650 mg / m2. With lower or higher film titles, lower or higher photographic sensitivities are obtained, but the above-mentioned film title intervals provide an effective compromise between photographic performance and film titles, for the most part. applications. When the product contains a single dye-forming element containing grains of tabular silver halides, the silver titles indicated above are applicable to this single element. When the three dye-forming elements contain tabular silver halide emulsions, silver savings can be obtained which are at least additive.

Structures

The products according to the invention can have any of the layer arrangements used in conventional products with one or more layers of silver halide photosensitive emulsions. In addition, the special properties of tabular silver halide emulsions make it possible to lay out layers which are particularly advantageous and hitherto unknown. The specific arrangements of the layers described below are given simply by way of example, but other arrangements are also possible.

To avoid unnecessary repetitions, the characteristics and advantages of the arrangement of the layers are described below in detail for the first structure. If a characteristic or an advantage does not appear in the arrangement of the layers of a following structure, this difference is noted.

Structure I

Silver image forming product by diffusion transfer after lamination and separation

Reflective support Argentic image receiving layer Exposure i

Tabular silver halide emulsion layer Support

Structure I is an example of a usual product forming a silver image by diffusion-transfer after lamination and separation. After exposure, a developable latent image is obtained in the tabular silver halide negative emulsion layer. Next, a silver image-receiving layer containing seeds of precipitation is laminated on the exposed photosensitive element, and a basic treatment composition, not shown, is released between the silver image-receiving layer and the emulsion layer. Upon contact with the basic processing composition, the tabular silver halide grains which contain latent image sites develop. The silver halide solvent contained in the treatment composition dissolves the undeveloped silver halide grains. These dissolved silver halides migrate to the receptor layer where they are physically developed. We obtain a positive silver image transferred to the image receiving layer. The treatment is stopped by separating the reflecting support which carries the silver image receiving layer from the residual photosensitive element.

Although this layer arrangement is usual and these layers contain the usual compounds, apart from the tabular silver halide emulsion, significantly better results can be obtained. The access time required to obtain a visible silver image in the receiving layer is significantly reduced. This result can be attributed to the special advantages ap5

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carried by the tabular silver halide grains. First, tabular silver halide grains, as defined above, grow faster than comparable non-tabular silver halide grains. Next, and this is at least of equal importance, the tabular silver halide grains dissolve at a significantly higher rate than comparable non-tabular grains.

Although these two processing mechanisms (development and solubilization) may be sufficient to reduce the access time obtained with structure I, it is also possible to use a third characteristic of tabular grain emulsions to obtain a further reduction in access time. Although tabular grain emulsions with a high shape index can be applied in thicknesses similar to those of the usual emulsions, it is however advantageous to reduce their thickness. In conventional image transfer products, the thickness of the emulsion layers is significantly greater than the average diameter of the silver halide grains, calculated from the projected surfaces of the grains. In addition, the thickness of the layers is large enough to adapt not only to the average grain size, but also to the larger grains. Thus, if the largest non-tabular silver halide grains have an average diameter of 1 to 2 µm, the emulsion layer will be at least 1 to 2 µm thick, and usually significantly larger . On the other hand, it is possible to use tabular silver halide grains, as defined above, having diameters, measured according to the average projected surfaces, from 1 to 2 μm and often more, while the thickness of these tabular grains is less than 0.5 µm or even less than 0.3 µm. Thus, for example, with tabular grains whose average thickness is equal to 0.1 | im and the average diameter equal to 1 to 2 | im, it is easy to reduce the thickness of the emulsion layer to a value significantly less than 1 | im. The layers of tabular grain emulsions with a high shape index,

as described above, advantageously have an average thickness equal to less than four times the average thickness of the tabular grains and very particularly equal to less than twice. Significantly reducing the thickness of the silver halide emulsion layers with tabular grains of high shape index can help reduce access times by reducing the length of diffusion paths. In addition, by reducing the length of the diffusion paths, it is also possible to improve the sharpness of the images.

Structure II

Unit image transfer product

Observation

1

Transparent support Neutralization layer

Retardant layer Silver receiving layer Reflective layer Opaque layer Silver halide emulsion with tabular grains Alkaline + opacifying treatment composition Transparent support

î

Exposure

Structure II is a classic structure of a unitary product forming a silver image by diffusion-transfer. It differs from the prior art only by the incorporation of an emulsion layer with tabular silver halides. This structure combines all the advantages of the tabular grains exposed above for structure I, with the known advantages provided by a unitary structure. Due to the presence of an opacifier in the alkaline treatment solution, it is necessary to introduce it in the indicated place after exposure. Once in place, the opacifier prevents further exposure of the emulsion layer, which could occur, for example, when the film is removed from the camera. The end of the treatment is determined by the joint action of the retarding and neutralizing layers.

Structure III

Unit product forming a monochromatic image by diffusion-transfer Observation l

Transparent support Dye image receiving layer Reflective layer Opaque layer

Tabular silver halide emulsion layer with dye-forming compound

Basic treatment composition + opacifying agent Delaying layer Neutralization layer Transparent support t

Exhibition following a picture

The basic treatment composition which contains the opacifying agent is not originally placed in the location mentioned above. As a result, image exposure reaches the tabular silver halide emulsion layer. A latent image is thus obtained corresponding to the exposed areas of the emulsion layer. To initiate treatment, the basic treatment composition is applied in the location indicated above. Although it is not essential, it is customary to remove the film from the camera after exposure, immediately after the application of the basic treatment composition and the opacifying agent. The opacifying agent and the opaque layer prevent further exposure of the emulsion layer. By development, a mobile dye or dye precursor is released from the emulsion layer. When the dye-forming compound is a compound with a positive effect, it releases the dye in the initially unexposed areas of the emulsion layer; when this compound has a negative effect, it is the opposite. The mobile dye or dye precursor passes through the opaque layer and the reflective layer and is etched or immobilized in the dye image receiving layer in the form of an image which can be observed through the upper transparent support. The treatment is stopped by the retarding layer and by the neutralization layer.

It is possible to transform structures I and II into a product forming monochromatic images, by incorporating a dye-forming compound into the emulsion layers by replacing the silver-receiving layer with a dye-receiving layer, and using a composition basic treatment suitable for dye transfer. It is therefore easy to obtain transferred color images by modifying structures I and II.

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Once these modifications have been made, the structure III still differs from the structure II by the location of the retarding layer and of the neutralization layer. The locations of these layers are interchangeable in structures II and III. It is also possible to combine the transfer of silver and the transfer of dye in a single product, the two methods being compatible. A useful example of such a combination is a product where the density of the silver image is enhanced by a dye, which allows the use of weak silver titles. Except in the case of a process combining silver transfer and dye transfer, the dissolution of undeveloped silver halides is normally not provided for in structure III, and is not necessary to obtain the reduction the access time to the image. The presence of dye-forming substance in the silver halide emulsion with tabular grains of high shape index can significantly increase the thickness of this layer. As already indicated, it is possible to significantly reduce the silver titles in the emulsion layers described according to the invention, while maintaining acceptable photographic speed values. Structure III is capable of providing this advantage.

Structure IV

Unit product for color photography by image transfer Exhibition

I

Transparent support Neutralization layer Retarding layer

Basic treatment composition + opacifying agent Transparent overcoat

Tabular silver halide emulsion layer, sensitive to blue

Layer containing a yellow dye-forming compound

Interlayer with immobilizer for oxidized developers

Tabular silver halide emulsion layer, sensitive to green

Layer containing a magenta dye-forming compound

Interlayer with immobilizer for oxidized developers

Tabular silver halide emulsion layer, sensitive to red

Layer containing a blue-green dye-forming compound Opaque layer Reflective layer Dye image-receiving layer Transparent support t

Observation

Structure IV is similar to Structure III, except that it comprises three separate dye-forming elements, each consisting of a layer of tabular silver halide emulsion of high shape index and a layer containing a dye-forming compound. The dye-forming compound can be arranged either in the emulsion layer itself or in an adjacent layer, as is carried out, respectively, in structures III and IV, as desired.

To avoid color contamination in adjacent dye-forming elements, an interlayer containing an oxidizing developer immobilizer is disposed between two dye-forming elements. The use of these agents in interlayers is described in United States patent No. 2336327 and in the dye-forming elements themselves in United States patent No. 2937086. These can be used agents in either of these locations.

According to a variant of structure IV, the interlayers are eliminated. Since the silver halide emulsion layers with tabular grains of high shape index can be very thin, compared to the silver halide emulsion layers commonly used in image transfer products, It is possible to arrange each layer of silver halide emulsion with tabular grains of high shape index between two layers of dye-forming compounds. Preferably, these two layers do not contain an agent immobilizing the oxidized developer, but, if desired, they can contain such an agent, according to the sensitivity of each dye-forming element to color contamination and according to the nature of the selected dye-forming compounds. By having a layer containing a dye-forming compound adjacent to each side of the silver halide emulsion layer with tabular grains of high shape index, a close association is provided between the dye-forming compounds and the halide d 'silver. This arrangement of the layers is particularly advantageous when the dye-forming compounds of each element are originally colorless or at least have an offset maximum absorption, so that the dye-forming compound does not absorb in the region of the spectrum to which silver halides are sensitive.

When the yellow dye-forming compound is originally yellow, it acts, in association with the silver halide emulsion layer with tabular grains of high index of index, sensitive to blue, so as to intercept light blue which could otherwise reach the silver halide emulsion layers with tabular grains of high shape index respectively sensitive to green and red. When the silver halide emulsion layers sensitive to green and sensitive to red contain grains of silver bromide or silver bromo-iodide in a common product of the same type, it is necessary to intercept the light blue which could contaminate the dye images formed in the layers of emulsions sensitive to green and sensitive to red. However, when the green-sensitive and red-sensitive emulsions are tabular grain emulsions of high shape index, as described above, it is not necessary to filter the blue light so that it is attenuated before reaching these layers of emulsions sensitive to green and sensitive to red. Thus, when the yellow dye-forming compound is originally colorless or at least does not absorb in the blue region of the spectrum, it is however possible to obtain correct color reproduction in the image forming layers of dye respectively magenta and blue-green, without interposing a layer of yellow filter dye. Furthermore, as described in more detail below, the dye-forming elements can be located in any desired order.

(Table at the top of the next column)

During the exposure of this product, the basic treatment composition which contains the reflective substance and the indicator dye is not in the position indicated above, but is released in this position after the exposure, so as to allow

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Structure V

Product for color image transfer photography with unitary structure

Opaque support

Layer containing a yellow dye-forming compound

Silver halide emulsion layer with tabular grains, sensitive to blue

Interlayer with oxidizing developer immobilizer

Layer containing a blue-green dye-forming compound

Silver halide emulsion layer with tabular grains, sensitive to red

Interlayer with oxidizing developer immobilizer

Layer containing a magenta dye-forming compound

Silver halide emulsion layer with tabular grains, sensitive to green

Transparent overlay

Basic treatment composition with reflective substance and indicator dye

Dye image receiving layer

Retardant layer

Neutralization layer

Transparent support t

Exposure following an image and observation of the treatment. The indicator dye has a high density at the high pH value where the treatment takes place. It thus protects the silver halide emulsion layers from further exposure if the product is removed from the camera during processing. When the neutralization layer decreases the pH value to stop the treatment, the indicator dye becomes a practically colorless compound. The basic treatment composition further contains an opaque reflective substance which provides a white background for observing the dye image transferred after treatment.

This structure is an example of a product with a unitary structure, in which the exposure following an image and the observation are done through the same support. This product of structure V differs from the products of the prior art, not only by the use of silver halide emulsions with tabular grains of high shape index, but also by the arrangement of the various dye-forming elements. The silver halide emulsion layer with tabular grains of high index sensitive to green is the closest to the source of exposure, while the silver halide emulsion layer with tabular grains of green high form index, sensitive to blue, is the furthest from the source of exposure. This arrangement of the layers is possible without contamination of the colors, because of the relatively large separation of the responses to blue and to blue minus that allow silver halide emulsions with tabular grains of high shape index spectrally sensitized to blue minus. By placing the magenta dye-forming element closest to the source of exposure and closest to the dye image-receiving layer, the image of the magenta dye is improved in clarity and the time taken is reduced. access. The magenta dye image is the single most important contributor to the visual impression of a color image. The blue-green dye image is second in order of importance for this visual contribution and is also closer to the source of exposure and the dye image receiving layer than in a conventional product. Thus, the product of structure V provides significant advantages with regard to the reduction of the access time and the improvement of the sharpness of the image, in addition to the improvements attributable to the tabular silver halide grains of high form index, discussed above for other structures. Although the product of structure V can contain any silver halide with tabular grains of high shape index, it is particularly advantageous to use tabular grains of silver bromide or silver bromo-iodide .

Structure VI

Unit structure product for color photography by image transfer, with image inversion Exposition i

Transparent support Neutralization layer Retarding layer

Alkaline treatment composition + opacifying agent

Tabular silver halide emulsion layer sensitive to green

Interlayer with oxidizing developer immobilizer

Compound forming magenta dye and developmental germs

Interlayer with oxidizing developer immobilizer and developmental germs

Tabular silver halide emulsion layer sensitive to red

Interlayer with oxidizing developer immobilizer

Blue-green dye-forming compound and developmental germs

Interlayer with oxidizing developer immobilizer and developmental germs

Blue sensitive tabular silver halide emulsion layer

Interlayer with immobilizing agent of the oxidized developer Compound forming yellow dye and development germs Opaque layer Reflective layer Dye receiving layer Transparent support

î

Observation

During the exposure of the product, the alkaline treatment composition containing the opacifying agent is not in the place indicated above; she is placed there to begin treatment. Initially each of the emulsion layers develops within the exposed ranges. Each emulsion layer contains an immobilizing agent

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of the oxidized developer to avoid any interaction between the oxidized developer produced by the development of the exposed silver halides and the dye-forming compounds. Interlayers containing an oxidizing developer immobilizing agent are also placed, for the same purpose, between each emulsion layer and its corresponding layer containing the dye-forming compound.

In the unexposed areas, the silver halides, which have not developed, are dissolved by a solvent for the silver halides contained in the treatment composition. These dissolved silver halides migrate through the adjacent interlayer containing the oxidizing developer immobilizer, and are converted to silver on the developing seeds present in the layer containing the dye-forming compound. Developmental seeds are those used for physical development in silver image transfer processes. The oxidized developer produced by physical development is free to react with the dye-forming compound to release a dye or a mobile dye precursor. The contamination of the colors between adjacent elements is avoided by interposing between them a layer containing an immobilizing agent for the oxidized developer, which prevents the passage of the latter, and of development germs, which prevent the passage of the halide from solubilized silver.

Structure VI is an example of a product which provides a positive transferred dye image with negative silver halide emulsions and dye releasing compounds with negative effect. Although the basic principle of this structure has been described previously, for example in British Patent No. 904364, unexpected advantages are obtained by the use of tabular silver halide emulsions of high shape index as described here. It should be noted that the development and solubilization of the silver halides are both necessary to ensure the transfer of the dye image. Due to the increase in development rates and possible solubilization with emulsions defined according to the invention, it is possible to reduce the time of access to the image to values lower than those obtained hitherto with products of this type. The products of structure VI also have the advantages due to the arrangement of the layers, similar to those already described for structure V.

Although the photographic products according to the invention have been described with reference to certain particularly advantageous structures, it will be noted that it is not always necessary for the silver halide emulsions with tabular grains of high shape index to be present as flat, continuous layers. These layers can be subdivided into discrete fractions moved laterally. In color products, the layers are not necessarily superimposed on each other, but may be present in the form of interleaved layer segments. It is possible to use silver halide emulsions with tabular grains of high shape index, as described above, in microcellular products, such as those described in PCT patent application No. W080 / 01614. , published August 7, 1980, as well as those described in British Patent No. 2091433 and United States Patent No. 4307165, which are improvements thereof.

Although all the advantages attributed to silver tabular grain halide emulsions with high shape index can be obtained in microcellular products for diffusion-transfer photography, the important separations of speed in blue and in blue minus which can be obtained with these spectrally sensitized emulsions, more particularly with silver bromide and bromo-iodide emulsions, are particularly advantageous in microcellular image transfer products intended for obtaining color images . Since the groups of microcells intended to respond to blue, green and red light respectively are arranged so as to receive the same incident light, yellow filter layers are usually interposed when using conventional silver bromide emulsions and silver bromo-iodide, to improve the separation of speed in blue and in blue minus. This may require a coating step or an additional cell filling step and may reduce photographic sensitivity. High-index-index tabular-grain silver halide emulsions, as described above, are useful for preparing microcellular products for image transfer photography, without the use of a yellow filter, which simplifies significantly the preparation of these products and improves their performance.

It is clear that the products according to the invention can contain various conventional adjuvants which have not been specifically mentioned above. For example, they may contain optical brightening agents, anti-stars, stabilizers, diffusing or absorbing substances, tanning agents, coating aids, plasticizers, lubricants, and matting agents.

These adjuvants are described in "Research Disclosure", vol. 176, December 1978, publication 17643, paragraphs V, VI, Vili, X, XI, XII and XVI. The addition, coating and drying processes described in paragraphs XIV and XV may be used. The conventional photographic supports described in paragraph XVII can be used. Other usual compatible characteristics, not specifically described, will be readily apparent to technicians.

Examples:

The following examples illustrate the invention.

Unless otherwise indicated, in each example, the term percent denotes the percentage by mass, the letter M denotes the molar concentration, all the solutions are aqueous solutions. In the emulsions of the examples, a certain number of tabular grains with a diameter of less than 0.6 (im are included in the calculation of the average diameter of the tabular grains and of the percentage of projected surface (unless their exclusion is specifically indicated), but their number is insufficient to significantly change the numbers shown.

Example 1:

Control emulsion A-l

A conventional control emulsion of silver bromo-iodide of low shape index, having an average grain diameter of 1.1 μm and containing 9 mol% of iodide, is prepared, as described in US Pat. America No. 3320069. The emulsion is sensitized to sulfur and gold optimally in the presence of thiocyanate and spectrally sensitized to green light with a sensitizing association of carbocyanine dye.

Tabular grain emulsion B

A silver tabular grain bromide emulsion of high shape index is prepared containing tabular silver bromide grains having an average diameter of 4 µm, an average thickness of 0.13 (im, and a shape index average of about 30: 1. The tabular silver bromide grains represent approximately 90% of the total projected surface of the grains. The emulsion is chemically sensitized to sulfur and gold in the optimal presence of thiocyanate and sensitizes it spectrally with the same association of sensitizing dyes as that used for the control emulsion A1.

Monochrome products for image transfer photography

A series of products with decreasing silver titers (1.38, 0.69, 0.53 and 0.36 g / m2) is prepared by applying the control emulsion A1 to a support provided with an antihalo layer. as well as the compounds indicated below:

Headline

RDR 1 compound

0.69 g / m2

Incorporating reducing agent 2

0.42 g / m2

Inhibitor incorporated 3

0.009 g / m2

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Headline

4-Hydroxy-6-methyl-l, 3.3a,

7-tetraaza-indene Gelatin

1.2 g / mol silver 1.1 g / m2

In addition to the gelatin indicated above, a mass of gelatin equal to the mass of silver is added to the coating composition.

Another series of products with decreasing silver titers (1.35, 0.67 and 0.40 g / m2) is prepared by applying the tabular grain emulsion B and the tabulations to a transparent cellulose acetate support. compounds listed below:

Headline

Compound RDR 1 Reducing agent incorporated 2 Inhibitor incorporated 3 4-Hydroxy-6-methyl-l, 3.3a,

7-tetraaza-indene Gelatin

0.80 g / m2 0.37 g / m2 0.01 g / m2 3.6 g / mol silver 1.2 g / m2

In addition to the gelatin indicated above, a mass of gelatin equal to the mass of silver is added to the coating composition.

Compound RDR 1, releasing a dye by redox, with positive effect o

2

0

CH

ch

-CH

ch

CH

çh

(12

= -ch, n-coo ocon-ch ch.rc-cocF,

Dispersed in diethyllauramide Solid / solvent ratio: 1/1

KHSO

Incorporating reducing agent 2 (IRA-2)

OH

-CONHI CH, i .0

CH

-t

NHCOCHCO-C-CH

3

h3ccoo ch3

Dispersed in diethyllauramide Solid / solvent ratio: 2/1

Anti-blind incorporated 3 or inhibitor 3

ch n -

n-C.

12 25

NOT -

sconch ch

Dispersed in diethyllauramide.

Solid / solvent ratio: 2/1

Image receiving element

The image receptor element with the following structure (the titles indicated in parentheses- are in grams per square meter): 6. layer of hydroxyethylcellulose (Natrosol 250 L, sold by the company Hercules "Inc.) (0.97 );

5. layer of gelatin (1.1);

4. opaque layer: carbon (1.9), gelatin (1.1);

3. reflective layer: titanium dioxide (19), gelatin (3.0); 2. mordant layer: poly- (4-vinylpyridine) (2,2), gelatin (2,2); 1. layer containing a metal: nickel sulfate hexahydrate (0.58), gelatin (1.1).

The layers are applied on a transparent polyester support in the order of numbering.

Exposure and treatment.

The products described above are exposed to a tungsten light source of 2850 ° K and 600 W, for 1/100 s, on a sensitometric scale, a neutral filter of density 1.0 and a Kodak Wratten filter No. 16.

To treat the products, a treatment composition is released at the interface of the receiving element and the emulsion layer, from a capsule, by passing the products between the rolls of stainless steel adjusted so as to such that the thickness of the developer layer is 75 µm. The treatment composition for the control emulsion A1 (capsule L) is indicated below in Example 2. The treatment composition for the emulsion with tabular grains B is identical to that of the capsule L, except that contains 16 g / l of 3-pyrazolidinone (electron transfer agent) instead of

B g / 1.

In both cases, transfers are carried out in 10 min, at room temperature. We separate the receiving elements and we read the density in green (status A). The characteristic curves are plotted, and the velocities relative to 0.2 density unit below the maximum density are determined.

The sensitometric results are shown below. The relative speed thresholds for decreasing silver securities for the two types of emulsions are particularly interesting. If we compare the emulsions with tabular grains and the conventional emulsions with three-dimensional grains, we see that, significantly, the relative velocities of the emulsions with tabular grains are maintained at a higher value when the silver title decreases.

(Table at the top of the next column)

The effect is also shown graphically in fig. 1.

Example 2:

Control emulsion A-2

A conventional polydispersed emulsion of silver bromo-iodide of low shape index, of which some large grains reach about 2 μm, and containing 6.2 mol% of iodide, is prepared, as described in the United States patent. 'America N ° 3320069. We

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Silver title

Dmax

Dmin

Contrast

Relative speed *

Control emulsion A-l

1.38 g / m2 0.69 g / m2 0.53 g / m2 0.36 g / m2

1.74 2.04 2.11 2.16

0.16 0.17 0.13 0.17

1.7

2.2 2.4

2.3

100 59 51. 24

Tabular grain emulsion B

1.35 g / m2 0.67 g / m2 0.40 g / m2

1.04 1.44 1.77

0.12 0.12 0.10

1.2 1.8 2.1

100 90 88

* 30 = 0.3 log E

chemically sensitizes the emulsion to sulfur and gold, optimally, in the presence of thiocyanate, and it is spectrally sensitized to green light with the same sensitizers as those used for the emulsion with tabular grains C described below .

Tabular grain emulsion C

A silver bromo-iodide emulsion with tabular grains of high shape index, having an average grain diameter of 4.7 μm, an average grain thickness of 0.16 μm, and an average shape index is prepared. 29: 1. Tabular grains of silver bromo-iodide occupy more than 95% of the total projected grain area. The emulsion is chemically sensitized to sulfur and to gold, optimally, in the presence of thiocyanate, and it is spectrally sensitized to green light with a supersensitizing association of carbocyanine dyes.

Monochrome products for image transfer photography

Products having a unitary structure are prepared both receptors and image formers, using the above emulsions. The products have the following structure (unless otherwise indicated, the titles are given in grams per square meter);

7. hydroxyethylcellulose overlay (Natrosol 250 L, sold by Hercules, Inc.) (0.54);

6. magenta image-forming layer: negative C green tabular grain emulsion (0.74 silver), RDR-1 compound (0.67), reducing agent 2 (0.36), inhibitor 3 (0.009) , 4-hy-droxy-6-methyl-1,3,3a, 7-tetraaza-indene (3.5 g / mol silver), gelatin (1.7);

5. gelatin interlayer (1,2);

4. opaque layer: carbon (1.9), gelatin (1.2);

3. reflective layer: titanium dioxide (16.0), gelatin (2.6); 2. mordant layer: poly- (4-vinylpyridine) (2,2), gelatin (2,2);

1. layer containing a metal: nickel sulfate hexahydrate (0.58), gelatin (1.1).

The layers are applied on a transparent polyester support in the order of numbering.

A similar control product is prepared, except that the tabular grain emulsion C is replaced by the control emulsion A-2, at a rate of 1.48 g Ag / m2. The two products are hardened with 1.1% bis (vinyl-sulfonyl) methane relative to the mass of gelatin.

Additional sheets of the following structure are prepared:

2. Retardant layer: physical mixture 1/1 of the following two polymers applied at a rate of 4.8 g / m2:

- copolymer of acrylonitrile, vinylidene chloride and acrylic acid (14/79/1 by mass);

- carboxyesterlactone formed by cyclization of a copolymer of vinyl acetate and maleic anhydride in the presence of 1-butanol to produce a partial butyl ester of acid / ester 15/85 proportion.

1. Acid layer: copolymer of n-butyl acrylate and acrylic acid (30/70 by mass), at a rate of 140 mEq of acid / m2.

The layers are applied on a transparent polyester support in the order of numbering.

Treatment capsules are prepared having the following two compositions:

Capsule L

Capsule M

Potassium hydroxide

60 g / 1

60 g / 1

4-Hydroxymethyl-4-methyI-

1-phenyl-3-pyrazolidinone

8 g / 1

6 g / 1

Potassium bromide

5 g / 1

10 g / 1

Sodium sulfite

2 g / 1

2 g / 1

Carboxymethylcellulose

57 g / 1

57 g / 1

15

Exposure and treatment

Each unit product is exposed in a sensitometer to obtain a complete densitogram, from Dmin to Dmax, after treatment with a viscous treatment composition in a capsule. The treatment composition is spread between the unit product and the complementary sheet, using a pair of rollers which provide a space of 100 µm. After 12 to 24 h, the density is read in the green (status A) on the receiving side of the unit product, to obtain the sensitometric layers. The sensitometric parameters - 25 Dmax, Dmin, contrast and relative speed (at D = 0.3 below the Dmax) are obtained from the curves.

As shown in the table of results below, the tabular grain emulsion C, whether with the L capsule or with the less active M capsule, has a higher relative speed of 0.2 log E than 30 l control emulsion treated with the same capsule, despite its much lower silver content (0.74 g / m2 against 1.40 g / m2). The difference in speed is even higher, 0.4 log E, if we compare the speed of the two emulsions with a density closer to the Dm ”. Under direct observation conditions, by visual examination (1/1 of magnification), normally used for products of this type, there is no difference in apparent granulation.

Dmax

Dmin

Contrast

Relative speed in the green

40

Emulsion

Capsule in in in

green green green

Witness A-2

L

1.3

0.13

1.4

100

45

Tabular grain emulsion C

L

1.8

0.13

2.0

119

Witness A-2

M

1.6

0.13

1.6

77

Tabular grain emulsion C

M

1.9

0.13

1.8

99

50

Example 3:

A unitary product forming and receiving a color image is prepared, with the following structure:

55 11. overlay;

10. yellow imaging layer;

9. interlayer;

8. magenta image-forming layer: negative emulsion of silver bromo-iodide with tabular grains, sensitized to green D so (identical to emulsion C) (silver title 0.65 g / m2), compound RDR -1 positive (0.53), reducing agent-2 (0.32), inhibitor-3 (0.010), 4-hydroxy-6-methyl-1, 3,3a, 7-tetraaza-indene (3.6 g / mol of silver), gelatin (1,3);

7. interlayer;

65 6. blue-green imaging layer;

5. gelatin interlayer;

4. opaque layer;

3. reflective layer;

21

653,780

2. mordant layer: poly- (4-vinylpyridine) (2,2), gelatin (2,2);

1. layer containing a metal: nickel sulfate hexahydrate (0.58),

gelatin (1.1).

The layers are applied on a transparent polyester support, in the order of numbering.

A similar control product is prepared, but containing in the magenta imaging layer 8 an emulsion of silver bromo-iodide of low shape index, A-3.

The two products are hardened (example and control), with 0.9% of bis (vinylsulfonyl) methane relative to the mass of gelatin.

The same additional sheet is used as in Example 2.

Treatment capsules of the following composition are prepared:

similar to those of Example 2, except that the tabular grain emulsion C is replaced by emulsion F.

The complementary sheet and the capsules L and N are the same as those of Examples 2 and 3.

The products are used as described in Example 2.

The unit product above containing the emulsion E gives a complete densitogram, from Dmin to Dmax, when it is exposed in an Estman IB sensitometer for 1/100 s on a sensito-metric scale. This indicates that the emulsion E has a photographic speed that is sufficient to be considered as usable in an instant camera, with image transfer compositions. The sensitometric parameters are collated in the table below.

15

20

Capsule N

(l / R

Potassium hydroxide

60.0

4-Hydroxymethyl-4-methyl-1 -p-

tolyl-3-pyrazolidinone

12.0

Potassium bromide

5.0

Disodium acid salt

ethylenediaminetetraacetic

10.0

Caboxymethylcellulose

57.0

Dmax

Dmin

Contrast

Emulsion

Capsule in in in

green green green

E

L

1.6

0.3

1.1

E

NOT

1.0

0.31

0.7

The products thus prepared are used in the following manner:

The unit product is exposed in color in a sensitometer to obtain a neutral image at a density of 1.0 (status A), after treatment with a viscous capsule composition. The contents of a capsule are spread between the unit product and the complementary sheet, using a pair of rollers which provides a space of 100 µm. Within 12 to 24 hours, we read the density in the green (status A), on the receiver side of the unit product, to obtain the sensi-tomometric curve. The sensitometric parameters in the green - Dmax, Dmin, contrast and relative speed (at D = 0.2 below the Dmax) - are obtained from the curve.

The table of results below shows that the tabular grain emulsion D has a relative sensitivity almost 0.3 log E higher than the control emulsion, although it contains only 2 hours of the amount of silver. In direct observation conditions (1/1 magnification), used for products of this type, there is also no significant difference in visible granulation here when looking at the products under a green filter.

Dmax

Dmin

Contrast

Relative speed in the green

Emulsion

Capsule in in in

green green green

Witness A-3

NOT

1.9

0.12

1.5

100

Tabular grain emulsion D

NOT

2.0

0.23

1.4

127

Example 4:

Tabular grain emulsion E

A silver tabular grain emulsion of high form index, having an average grain diameter of 6.0 (xm, an average grain thickness of 0.28 µm and an average form index of 22: 1. The tabular grains of silver chloride represent more than 80% of the total projected surface of the grains. The emulsion is chemically sensitized to sulfur and gold in the presence of thiocyanate, and is sensitized spectrally in green light with an oxacarbocyanine dye in the presence of 3 mol-% of bromide.

Products for image transfer photography

We use unitary image forming and receiving products

Example 5:

M Tabular grain emulsion F

A silver bromo-iodide emulsion is prepared, the tabular grains of high shape index being used as carrier grains for an epitaxial deposition of silver chloride used to sensitize; these tabular grains have an average diameter of 3.0 µm, an average thickness of 0.09 µm and an average shape index of 33: 1, and they represent more than 85% of the total projected surface area of the grains.

A unitary image-forming and receptor product similar to that of Example 2 is prepared, except that layer 6 contains the tabular grain emulsion F (silver title 0.67 g / m2) and that layer 5 is deleted.

The complementary sheet and the capsule N are the same as in Examples 2 and 3. The above products are used in the same manner as in Example 2.

The above unit product containing the emulsion F gives a complete densitogram, from Dmin to Dmax, when it is exposed in an Eastman IB sensitometer for 1/100 s on a sensometric scale. This indicates that the emulsion F has a photographic rapidity sufficient to be considered as usable in a similar camera for instantaneous shots, with image transfer compositions. The sensitometric parameters are collated in the table below.

Emulsion

Capsule

Dmax in the green

Dmin in the green

Contrast in the green

F

NOT

2.0

=? 0.15

2.1

Example 6:

A silver bromo-iodide emulsion (molar proportion bromide / iodide: 97/3), with tabular grains having an average diameter 6o of 1.6 | im, an average thickness of 0.10 | im, a shape index means of 16: 1, and representing more than 80% of the total projected surface of the grains, is indicated under the name of emulsion G.

This emulsion is chemically sensitized in an optimal manner with 100 mg / mol of silver of sodium thiocyanate, 9.0 mg / mol 65 of silver of sodium thiosulfate pentahydrate, and 3.0 mg / mol Ag of potassium tetrachloroaurate, and it is spectrally sensitized optimally in the green with an absorbent carbocyanine in the green.

653780

22

A control emulsion of silver bromo-iodide (bromide / iodide molar ratio: 97/3}, of the type described in United States Patent No. 3320059; the grains of which have an average diameter of

0.81 µm, an average thickness of about 1.55 µm, and an average shape index of 1.5: 1, is referred to as the C-6 control emulsion.

This control emulsion C-6 is chemically sensitized in an optimal manner, with 1.2 mg / mol of silver of sodium thiosulfate pen-tahydrate and 0.4 mg / mol of silver of potassium tetrachloroaurate, and it is spectrally sensitized optimally in the green region of the spectrum with the same absorbent carbocyanin in the green as above.

Monochrome image forming and receptor unit products, having the following structure, are prepared with the control emulsion C-6, described above. Titles are given in parentheses, in grams per square meter.

7. Overlay: bis (sulfonyl) methane (0.071), gelatin (0.54). 6. Silver halide layer: silver bromo-iodide emulsion (3 mol% iodide) with tabular grains, sensitized to green, G (0.81 silver), RDR-1 with positive effect (0.67), incorporated reducing agent-2 (0.32), inhibitor-3 (0.043), gelatin (1.6). 5. Gelatin layer (4.8).

4. Opaque layer: carbon (1.9), gelatin (1.3).

3. Reflective layer: titanium dioxide (17), gelatin (2.6). 2. Mordant layer: poly (vinylpyridine) (2.2), gelatin (2.2).

1. Layer containing a metal: nickel sulfate hexahydrate (0.58), gelatin (1.1).

The layers are applied on a transparent polyester support in the order of numbering.

A monochrome control product of identical structure is prepared, except that layer 6 contains the control emulsion C-6 with silver bromo-iodide (3 mol% of iodide) sensitized to green (0.81 in silver).

Capsules having the following composition are prepared:

Potassium hydroxide

55.0 g / 1

Electron transfer agent (ETA):

4-hydroxymethyl-4-methyl-1 -p-tolyl-3-

pyrazolidinone

15.0 g / 1

Potassium bromide

4.0 g / 1

Ethylenediaminetetraacetic acid

7.8 g / 1

Sodium sulfite

2.0 g / 1

Carboxymethylcellulose

56.0 g / 1

Carbon

165.0 g / 1

Anionic surfactant (Tamol SNR)

(sodium salt of a formaldehyde condensate

and naphthalenesulfonic acid)

2.0 g / 1

Lead oxide

0.4 g / 1

Additional sheets are prepared as in Example 2.

The products are exposed in a sensitometer through a sensitometric scale, for 1/200 s, with a neutral filter of sufficient density to produce a complete densitogram, of D max EUX Dmin, after treatment with a viscous composition in capsule. The contents of the capsule are spread, at room temperature (233 ° C.), between the product and the complementary sheet, using a part of juxtaposed rollers leaving between them a space of 100 Jim. Before 24 hours have elapsed, the density (status A) is read from the receiver side of the product and the inverted D / log E curve integrated by computer is obtained. The sensitometric parameters obtained from this curve are collated in the table below.

(Table at the top of the next column)

These results show that the tabular grain emulsion of high shape index of the example has a significantly higher contrast than a three-dimensional emulsion of equivalent speed. The values of Dmin are the same; the emulsion of the example has a Dmax

POOR QUALITY

Emulsion

Contrast*

Relative speed **

Dmax

Dmm

Example G Witnesses C-6

3.2 2.0

100 99

0.22 0.22

1.8 1.6

* We measure the contrast between a density of 0.2 above the Dmin and a density of 0.2 below the Dmax.

** We measure the relative speed at a density of 0.5, 30 units of relative speed = 0.3 log E.

slightly higher, which is an added benefit. The foot and the shoulder of the curves are equivalent. High contrast, for a given silver title, is a very desirable characteristic for products of this type allowing direct observation of the image.

Example 7:

Two series of monochrome image forming and receptor unit products having the same structure as those of Example 6 are prepared, except for the modifications to layer 6 indicated below. The optimally sensitized tabular grain emulsion G and the control emulsion C-6 are used, as described in Example 6.

Silver halide layer 6: tabular grain emulsion of silver bromo-iodide (3 mol% iodide) sensitized to green. G, or silver bromo-iodide control emulsion (3 mol% iodide) sensitized to green, C-6, and dispersions of image-forming reagents indicated in the table below.

Emulsion

Emulsion G (example) (g / m2)

Emulsion C-6 (control) (g / m2)

Silver title (see table below) RDR-1 positive Reducing agent-2 Inhibitor-3 Gelatin

0.08 to 0.97 0.67 0.11 0.086 1.6

0.08 to 0.97 0.67 0.15 0.17 1.6

Capsules are prepared as in Example 6, except that they contain 20.0 g / l of the electron transfer agent, and 2.0 g / l of potassium bromide. The same additional sheets are used as in Example 2, and the products are exposed and treated as in Example 6, except that the exposure time is 1/50 s.

Dye density

Threshold

Silver title in green speed

Fast

Dmax

Relative Dmin *

Tabular grain emulsion G

0.97 g / m2

1.55

0.16

198

0.65 g / m2

1.70

0.17

187

0.32 g / m2

1.87

0.18

163

48

0.16 g / m2

1.93

0.24

139

Control emulsion C-6

0.97 g / m2

0.63

0.16

_

0.65 g, m2

1.63

0.16

180

0.32 g / m2

1.98

0.17

130

89

0.16 g / m2

2.03

0.41

91

* 30 units = 0.3 log E, measured approximately 0.3 density unit above the D. ™ x.

** Speed difference between the title of 0.16 g / m2 and the title of 0.65 g / m2.

5

10

15

20

25

30

35

40

45

50

55

60

65

23

653,780

The haze of the emulsion is highlighted by lower Dmax of transferred dye. A high Dmin reflects a degree of oxidation of the incorporated reducing agent (IRA) by the development of silver halides insufficient to prevent the reduction of the positive RDR compound by the incorporated reducing agent. For a silver grade of 0.65 g / m2, the two emulsions have an almost equivalent speed threshold.

For a silver grade of 0.97 g / m2, the control emulsion was far too veiled to have a significant speed value. Between 0.65 and 0.16 g / m2 of silver, the two emulsions give good discrimination, but the speed of the control emulsion decreases by 89 units, while the speed of the tabular emulsion decreases only by 48 units.

In these two series of products, the titles of incorporated reducing agent and of inhibitor (released according to the image in the unexposed areas, thus removing the haze) are notably different.

To achieve comparable results, on any silver grade, much less incorporated reducing agent and inhibitor is required for tabular grain emulsions. Fewer photographic reagents are therefore required. If the control emulsion is applied with the same reducing agent and inhibitor titles as the tabular grain emulsion, the products having the three highest silver titles are completely veiled (Dmax = 0.17 to 0.22) .

APPENDIX

The following details relate to the precipitation of emulsions. Emulsion B:

To an aqueous solution of bone gelatin (1.5% gelatin) containing 0.17 M potassium bromide (solution A) at pBr 0.77 and 55 ° C., is added by double-jet addition, with stirring, and at constant flow rate, in 0.5 min, aqueous solutions of 1.51 M potassium bromide (solution B1) and 1.0M silver nitrate (solution C-1); 0.06% of the total money is consumed. (In all emulsion preparations, the contents of the reactor are vigorously stirred during the addition of the silver salt.) The addition of the solutions B1 and Cl is stopped and the emulsion is maintained at pBr 0.77 and at 55 ° C for 5 min.

The solution C-1 is then added at a constant flow rate until the pBr reaches 1.14 at 55 ° C .; 3.49% of the total money is consumed; then the addition of solution C-1 is stopped.

An aqueous solution of 4.52M potassium bromide (solution B-2) and 2.0M silver nitrate (solution C-2) is then added in double jet, at an accelerated rate (6.5 times from start to end), at pBr 1.14 and at 55 ° C, until the solution C-2 is used up (approximately 64 min; 93.0% of the total silver is consumed). The addition of solution B-2 is stopped.

A 2M aqueous silver nitrate solution (solution C-3) is then added until the pBr reaches 1.51 at 55 ° C; we consume 3.42% of the total money. A total of 6.45 mol of silver is used to prepare this emulsion.

Finally, the emulsion is cooled to 35 ° C, and washed by coagulation, as described in U.S. Patent No. 2,614,929.

Emulsion C:

7 1 of an aqueous solution of gelatin of bone (17.1% in gelatin, solution A), containing 0.17 M sodium bromide at pH 2.0 and at 70 ° C. are prepared. adjusted to pBr 0.77 at pH 2.0 and at 70 ° C., is added by double jet addition, at constant flow rate,

for 4 min, aqueous solutions of 0.45M sodium bromide (solution B-1) and 0.1M silver nitrate (solution C-1). The addition of solutions B-1 and C-1 is stopped and the reaction vessel is kept at 70 ° C. for 2 min.

Solutions B1 and Cl are then added to solution A, keeping the pBr at 0.77, at constant flow rate, by simultaneously adding, at twice the flow rate, aqueous solutions of 3.78 M sodium bromide (solution B- 2) and silver nitrate

2.72M (solution C-2) respectively to solutions B-1 and C-1.

When solutions B-1 and B-2 are exhausted (after approximately 29 min, 81.8% of the total silver is consumed), solution C-1 is continued to be added until the pBr reaches 1.15. The addition of solutions C-1 and C-2 is stopped. *

An aqueous 0.13M sodium iodide solution (solution D) is then added, at constant flow rate, for approximately 2.5 min. After keeping solution A at 70 ° C and pBri, 02 for 2 min, the addition of solutions C-1 and C-2 is resumed until exhaustion (17.6% of the total silver is consumed). The total duration of addition of solution C is approximately 43 min. The final pBr in the reactor is approximately 1.83. 6.0 mol of silver is used to prepare this emulsion.

The emulsion is cooled to 40 ° C. and washed by coagulation,

as described for emulsion B.

Emulsion D:

This emulsion is prepared in the same way as emulsion C. Emulsion E:

21 is prepared of an aqueous solution of the copolymer of 3-thiopentyl metha-crylate, acrylic acid and sodium salt of 2-methacryloyloxyethyl-1-sulfonic acid (molar ratio: 1/2/7) at 0 , 63% (solution A) containing 0.5M dihy-drated calcium chloride, adenine (0.35%) and 0.013M sodium bromide at pH 2.6 and at 55 ° C. To this solution A, maintained at the initial concentration of chloride ions throughout the preparation, aqueous solutions of 2.0M calcium chloride (solution B) and nitrate d are added by double jet, at constant rate, over 1 min. '2.0M silver (solution C); 0.7% of the total money is consumed.

After the first constant flow minute, solutions B and C are added, in double jet, at accelerated flow (2, 3 times from start to finish), in 15 min (18.8% of the total money is consumed ).

After this addition period of 15 min at accelerated flow, solutions B and C are added, in double jet, at constant flow, for approximately 46 min (80.5% of the total silver is consumed).

To maintain the pH at 2.6 at 55 ° C., an aqueous 0.2M sodium hydroxide solution (solution D) is used. 4.0 mol of silver is used to precipitate this emulsion.

Emulsion F:

To 6.0 1 of a 1.5% gelatin solution containing 0.12 M potassium bromide at 55 ° C., potassium bromide solution 2 is added, with stirring and in a double jet, over 8 min. , 0M containing 0.12M potassium iodide and 2.0M silver nitrate solution, maintaining the pBr at 0.92 (5.3% of the total silver is consumed). We then continue to add the bromide and silver salt solutions in a double jet, always maintaining the pBr at 0.92, but at an accelerated speed (6 times from start to finish), for 41 min (we consume 94 , 7% of the total money). A total of about 3.0 mol of silver is used. The emulsion is cooled to 35 ° C, washed by the coagulation process described in US Patent No. 2,614,929 and stored at pAg 7.6 measured at 40 ° C. The emulsion silver bromo-iodide (6 mol-% iodide) with tabular grains obtained at an average grain diameter of 3 (xm, an average grain thickness of 0.09 µm, a shape index of 33: 1 The tabular grains represent 85% of the total projected surface of the grains.

120 g (0.12 mol) of the silver bromo-iodide emulsion, prepared above, are adjusted to pAg 7.2 at 40 ° C., simultaneously adding a solution of silver nitrate 0.1 M and a 0.006M potassium iodide solution. Then 3.0 ml of a 0.74M sodium chloride solution is added. The emulsion is spectrally sensitized with 1.5 mmol of the triethylamine salt of anhydro-5-chloro-9-ethyl-5'-phenyl-3,3'-di- (3-sulfopropyl) oxacarbocyanine hydroxide / mol of silver and kept at 40 ° C for 30 min. The spectrally sensitized emulsion is then centrifuged and again suspended twice in a solution of NaCl 1.85 × s

10

15

20

25

30

35

40

45

50

55

60

65

24

653,780

10 "2M. In 40.0 g (0.04 mol) of this emulsion, 1.25 mol-% of silver chloride is precipitated by double-jet addition, over 2.1 min, of chloride chloride solution. 0.55M sodium and 0.5M silver nitrate, maintaining the pAg at 7.5 at 40 ° C. 15 s after the start of precipitation of the silver chloride, the following is added to the precipitation vessel 0, 5 mg of Na2S203, 5H20 and 0.5 mg of KAuCl4 / mol of silver.

During the preparation of each of these emulsions, the contents of the reaction vessel are vigorously stirred during the introduction of the silver salt and the halides.

R

1 drawing sheet

Claims (4)

653,780 1. Product for image transfer photography comprising a support, at least one emulsion layer, containing a dispersing medium and photosensitive silver halide grains, and an image-receiving layer, characterized in that '' at least 50% of the total projected surface of the photosensitive silver halide grains of at least one emulsion layer is formed of tabular silver halide grains of thickness less than 0.5 µm, of diameter equal to or greater than 0.6 µm, the grain diameter being defined as the diameter of a circle having an area equal to the projected area of the grains, and with an average shape index greater than 8: 1, the shape index being the ratio of the diameter of the grain to its thickness. 2. Product according to claim 1, characterized in that the receiving layer is adjacent to a second support. 2 3 653,780 at least 20: 1 occupy at least 70% of the total projected area of the photosensitive silver halide grains of each of the green-sensitive and red-sensitive emulsion layers. 24. Product according to one of claims 20 to 23, characterized in that at least one emulsion containing the tabular grains and an emulsion with silver bromide or silver bromo-iodide sensitive to red or sensitive to green , and is placed to receive the exposure radiation before the other layers of silver halide emulsions in the product. 25. Product according to claim 1, for color photography by image transfer, comprising: - a support, - dye-forming elements, each comprising at least one dye-forming compound and at least one silver halide emulsion consisting of a dispersing medium and of photosensitive silver halide grains, said elements comprising an element containing a red-sensitive emulsion and a blue-green dye-forming compound, an element containing a green-sensitive emulsion and a magenta dye-forming compound, and an element containing a blue-sensitive emulsion and a yellow dye-forming compound, - a transparent additional sheet, - an image-receiving layer placed on the support or on the complementary sheet, - an alkaline treatment composition, Means for releasing the treatment composition in contact with the dye-forming elements, Means for stopping the development of silver halides placed adjacent to the support or to the complementary sheet, characterized in that at least 70% of the total projected surface of the photosensitive silver halide grains present in at least one emulsion layer is formed of tabular silver halide grains having a thickness of less than 0, 5 jim, a diameter of at least 0.6 ^ m, and a shape index of at least 12: 1, said emulsion layer having a silver titer between 150 and 750 mg / m2. 26. Product according to claim 1, for color photography by image transfer, comprising: - a support, - dye-forming elements, each comprising a compound releasing a dye by oxidation-reduction with a positive effect, and at least one negative emulsion containing a dispersing medium and grains of photosensitive bromide or bromo-iodide of silver, said elements comprising an element containing a red-sensitive emulsion and a compound releasing a blue-green dye, an element containing a green-sensitive emulsion and a compound releasing a magenta dye, and an element containing a blue-sensitive emulsion and a compound releasing a yellow dye, - a transparent complementary sheet, a dye-receiving layer placed on the support or on the complementary sheet, - an alkaline treatment composition, Means for releasing this composition in contact with the dye-forming elements, and Means for stopping the development of silver halides placed adjacent to the support or to the complementary sheet, characterized in that at least 70% of the total projected surface of the photosensitive silver halide grains present is formed of tabular grains of silver bromide or bromo-iodide having a thickness of less than 0.3 | im, a diameter of at least 0.6 µm, and an average shape index of at least 12: 1, each of said emulsions having a silver titer of between 200 and 700 mg / m2. 27. Product according to claim 26, characterized in that each of said emulsions has a silver titer between 300 and 650 mg / m2. 28. Product according to claim 1, for color photography by image transfer, comprising: - a support, A yellow dye-forming element, comprising a yellow dye-forming compound and a negative emulsion sensitive to blue, A first transparent interlayer containing an agent for im-5 mobilizing the oxidized developer, A blue-green dye-forming element placed on the first interlayer, comprising a blue-green dye-forming compound and a negative emulsion, sensitive to red, A second transparent interlayer containing an im-I0 mobilizing agent for the oxidized developer, - a magenta dye-forming element placed on the second interlayer, formed of a magenta dye-forming compound and a negative emulsion sensitive to green, Each of the emulsions containing a dispersion medium and grains of photosensitive silver bromide or silver bromo-iodide, and - a receiving layer giving a transferred color image visible after the photographic exposure and the treatment, characterized in that at least 70% of the total projected area of 20 photosensitive silver halide grains present in at least said green and red sensitive emulsions is formed of tabular grains of silver bromide or silver bromo-iodide having a thickness of less than 0.3 (im, a diameter of at least 0.6 (im, and an average shape index of at least 12: 1, the silver titer of each of said green-sensitive and red-sensitive emulsions being between 200 and 700 mg / m2, and the receiving layer being located closer to the blue-green dye-forming element or the magenta dye-forming element than other dye-forming elements, during processing. 29. Product according to claim 28, characterized in that the dye-forming compounds are dyes-developers. 30. Product according to claim 1, for color photography by image transfer, comprising: 35 - an opaque support, A yellow dye-forming element placed on the support, comprising a compound with a positive effect releasing a yellow dye by oxidation-reduction and a negative emulsion sensitive to blue, A first transparent interlayer containing an agent for im-40 mobilizing the oxidized developer, - a blue-green dye-forming element placed on the first interlayer, formed of a compound with a positive effect releasing a beueu-green dye by oxidation-reduction and a negative emulsion sensitive to red, 45 - a second transparent interlayer containing an agent for immobilizing oxidized development, A magenta dye-forming element placed on the second interlayer, comprising a compound with a positive effect releasing a magenta dye by oxidation-reduction and a negative emulsion sensitive so to green, Each of the emulsions containing a dispersing medium and grains of silver bromide or photosensitive silver bromo-iodide, - a transparent additional sheet, 55 - a dye receiving layer placed on the complementary sheet, An alkaline treatment composition containing a reflecting substance and an indicator dye colored at alkaline pH and practically colorless at acid pH, 60 - means for releasing the treatment composition between the receiving layer and the dye-forming elements, Means for stopping the development of silver halides placed adjacent to the support or to the complementary sheet, 65 characterized in that at least 70% of the total projected surface of the photosensitive grains present in the emulsions sensitive to green and red is formed of tabular grains having a thickness of less than 0.3 µm, a diameter of at least minus 0.6 µm, and an index of 653,780 3. Product according to claim 2, characterized in that the second support is reflective. 4. Product according to claim 2, characterized in that the second support is transparent. 5. Product according to one of claims 2 to 4, characterized in that it further comprises an alkaline treatment composition and means for releasing this composition between the supports. 6. Product according to claim 5, characterized in that the alkaline treatment composition comprises a solvent for silver halides, and the receiving layer comprises seeds of physical development, to produce the physical development of the halide d solubilized money. 7. Product according to one of claims 1 to 6, characterized in that a dye-forming compound is present in the layer or layers of emulsions or in an adjacent layer. 8. Product according to one of claims 1 to 7, characterized in that the tabular grains of silver halides represent at least 70% of the total projected surface of the photosensitive grains present in the emulsion layer or layers. 9. Product according to one of claims 1 to 8, characterized in that the silver halide grains are bromide or bromo-iodide silver grains. 10. Product according to one of claims 1 to 9, characterized in that the tabular grains of silver halides have an average shape index of at least 12: 1. 11. Product according to claim 1, for silver image transfer photography, comprising: - a transparent support, - at least one emulsion layer containing a dispersing medium and photosensitive silver halide grains sensitized chemically and spectrally, - a transparent additional sheet, and A silver receiving layer located on the complementary sheet and receiving the silver transferred from the emulsion layer through an alkaline treatment composition containing a solvent for silver halides, a composition located between the receiving layer and the emulsion layer, characterized in that the tabular grains of silver halide having a thickness of less than 0.5 µm, a diameter of at least 0.6 µm, and an average shape index of at least 12: 1 occupy at minus 70% of the total projected area of the photosensitive silver halide grains. 12. Product according to claim 11, characterized in that it further comprises means for initially containing the alkaline treatment composition and, after photographic exposure, for releasing it between the emulsion layer and the receiving layer, and means for stopping the development of the silver halides, means placed adjacent either to the support or to the complementary sheet. 13. Product according to one of claims 11 or 12, characterized in that it further comprises a reflective layer adjacent to the receiving layer, placed between the receiving layer and the emulsion layer or layers. 14. Product according to one of claims 11 to 13, characterized in that the tabular grains of silver halides have an average shape index of at least 20: 1. 15. Product according to claim 1, for color photography by image transfer, comprising: - a transparent support, - at least one layer of emulsion placed on the support containing a dispersion medium and photosensitive silver halide grains chemically and spectrally sensitized, a dye-forming compound placed in the layer or layers of emulsions or in a layer adjacent, - a transparent additional sheet, A dye image receiving layer placed on the complementary sheet, receiving the dye image transferred through an alkaline treatment composition placed between the receiving layer and the emulsion layer, characterized in that the tabular silver halide grains having a thickness of less than 0.5 µm, a diameter of at least 0.6 µm, and an average shape index of at least 12: 1 occupy at minus 70% of the total projected area of the photosensitive silver halide grains. 16. Product according to claim 15, characterized in that it further comprises means for initially containing the alkaline treatment composition and, after photographic exposure, for releasing it between the emulsion layer and the receiving layer, and means for stopping the development of the silver halides, means placed adjacent either to the support or to the complementary sheet. 17. Product according to one of claims 15 or 16, characterized in that it further comprises a reflective layer adjacent to the receiving layer, placed between the receiving layer and the emulsion layer or layers. 18. Product according to one of claims 15 to 17, characterized in that the tabular grains of silver halides have an average shape index of at least 20: 1. 19. Product according to one of claims 15 to 18, characterized in that the emulsion layer has a silver content of less than 750 mg / m2. 20. Product according to claim 1, for color photography by image transfer, comprising: - a support, - dye-forming elements placed on the support, each comprising at least one dye-forming compound and at least one layer of silver halide emulsion consisting of a dispersion medium and of photosensitive silver halide grains , said elements comprising an element containing a red-sensitive emulsion and a blue-green dye-forming compound, an element containing a green-sensitive emulsion and a magenta dye-forming compound, and an element containing a blue-sensitive emulsion and a compound yellow dye trainer, and - an image receiving layer, characterized in that the tabular silver halide grains having a thickness of less than 0.5 µm, a diameter of at least 0.6 µm, and an average shape index of at least 12: 1 occupy at least 70% of the total projected surface of the photosensitive silver halide grains of at least one of the emulsion layers. 21. Product according to claim 20, characterized in that the tabular grains of silver halides occupy at least 90% of the total projected surface of the grains of said emulsion layer. 22. Product according to one of claims 20 or 21, characterized in that said emulsion has a silver count between 150 and 750 mg / m2. 23. Product according to one of claims 20 or 22, characterized in that the tabular grains having a thickness of less than 0.3 (im, a diameter of at least 0.6 (im and an average shape index) 5 10 15 20 25 30 35 40 45 50 55 60 65 4 average form of at least 12: 1, the silver content of each of the red-sensitive and green-sensitive emulsions being between 300 and 650 mg / m2.