DE2203462C2 - Process for preparing a silver halide photographic emulsion - Google Patents

Description

1.5 G 25th G 6th G 40 G 1 G up to 1000 ml

p-monomethylaminophenol sulfate Sodium sulfite (anhydrous)

Hydroquinone

Sodium carbonate (anhydrous) KBr

water

is developed with a development time of 4 minutes and a development ^{temperature of 20 0} C, result in a fog density of at most 0.2.

2. The method according to claim 1, characterized in that the reducing treatment is carried out during the precipitation of the silver halide.

50

The invention relates to a process for the preparation of a silver halide photographic emulsion by Precipitation of the silver halide in the presence of a protective colloid, reducing treatment before the Silver halide grains have reached their final size and may have undergone chemical ripening.

It is known that light-sensitive silver halide crystals immediately after their formation and even after physical ripening, so-called Ostwald ripening, has a relatively low sensitivity in the emulsion exhibit.

During chemical ripening, centers of sensitivity are formed on the surface of these crystals and thereby markedly improves the photosensitivity and in some cases the gradation.

Depending on the location of the centers of sensitivity that develop during chemical ripening latent image nuclei developable on exposure at or in the vicinity of these sensitivity centers. If the sensitivity scenarios are located inside the silver halide grain, the Exposure of latent image nuclei Essentially only in the interior of the grain, are the sensitivity centers. The latent nuclei arise on the grain surface Image nuclei essentially only on the surface of the silver halide grain. The relative location of the centers of sensitivity and thus the relative position of the latent image nuclei arising during development the type of material used for developing the exposed material required developer. With so-called indoor

kornblldem developers are required who have a Solvents for the silver halide contain, so-called internal developers, in emulsions that are superficial which contain latent image nuclei, developers of conventional compositions can be used will.

By means of chemical ripening, at the sensitivity centers from - according to current knowledge, silver sulfide or noble metal atoms, in particular Gold atoms, silver halide emulsions of high photosensitivity can be produced. Since the practice more and more light-sensitive silver halide demulstones demands, there was still a need for methods, even more highly sensitive silver halide emulsions to manufacture.

From US-PS 32 06 313 it is already known in the production of core / Hullen-Emuls-'Xien the To chemically sensitize the cores before wrapping. In addition to other methods, reduction sensitization is used here called, about the extent of which it is said at one point that the silver halide is not "noticeably" should be veiled, while in column 10, line 43 ff., it is stated that the core can be "completely" to be veiled. In this respect, there is no clarity as to the extent of the obfuscation. Only reducing agents are specified as means for reductive concealment.

The invention is based on the object of producing a highly sensitive silver halide emulsion.

This object is achieved in that the reducing treatment is carried out for production by setting a high silver ion concentration with pAg values between 7 and 0 to a degree that only so few spontaneously developable image nuclei arise that these, if the reducing treatment occurs immediately obtained "emulsion corresponding to an amount of 3 g silver nitrate / m ² applied to a layer support and with a surface developer of the following composition:

20th

25th

30th

35

p-monomethylaminophenol sulfate 1.5 g

Sodium sulfite (anhydrous) 25 g

Hydroquinone 6 g

Sodium carbonate (anhydrous) 40 g

KBr 1 g

Water up to 1000 ml

at the development time of 4 Mk.-uten and one Development temperature of 20 ° C developed spontaneously, resulting in a fog density of at most 0.2.

This means that the test with the surface developer immediately after the generation of the called latent image nuclei has to take place before the 55 'silver halide grains reach their final size to have.

In the process according to the invention, extremely sensitive silver halide emulsions are obtained which are at latent image nuclei form on the surface after exposure and those with conventional surface developers are processable. In this respect, the emulsions obtained by the process according to the invention surprisingly have Properties than the previous rules on the topographical association of the Sensitivity centers with the latent image nuclei for this emulsion do not apply. In the exposure of these emulsions latent particles form on the surface and not on the inside of the grain

centers of sensitivity generated by the reduction.

The essence of the inventive method is that the silver halide grains before their have reached their final size, are produced under reducing • conditions.

The silver halide grains of the emulsion of the present invention are at a certain depth or in different, stepwise varying depths due to the reduction, probably due to the formation of Centers of reductolytically formed silver changed, whereby these centers are not usual centers of sensitivity act because they do not prevent the formation of latent image nuclei in the grain interior during exposure favor.

In addition to the improved photosensitivity, those produced by the process according to the invention have Silver halide emulsions have a lower gradation than a corresponding silver halide emulsion similar grain size distribution, but without the reductive cell treatment was established.

The type and timing of the reducing treatment in the case of precipitation or physical Maturation determine whether an increase in sensitivity or a decrease in gamma predominates.

The earlier the reducing treatment occurs during the formation of the silver halide grain; H. the deeper the sensitivity centers are generated inside, the more the gradation is lowered. Will the reducing treatment is carried out towards the end of the growth of the silver halide cone, so the Increase in sensitivity before, the gradation is then not or only slightly reduced. the reducing treatment affects neither the grain size nor the grain size distribution.

It is necessary that the reducing treatment is not so severe that the reductolytic ones formed Silver nuclei can be developed by light as with copy-out materials. Of course, it should be reducing Treatment according to the present invention not together with compounds that reduce the copy-out effect favor, such as sulfur compounds for copy materials, z. B. according to US-PS 16 23 499 used will.

For setting the reducing treatment required in the method according to the invention The conditions that are used in the so-called »Silver Digestionw technology are already sufficient. Such methods are described in the publication by H. W. Wood, H. phot. May be. 1, (1953), p. 163. The "Silver Digestion" technique is used at slightly increased temperatures of around 50 ° C and possibly worked with increased pH bets between 7 and 10. The silver ion concentration is increased; H. a relatively low pAg value between 7 and 0, preferably 3, is used.

The precipitation of the silver halide takes place in a known manner Catfish by introducing one of the precipitation components and adding the other or by simultaneous Addition of both precipitation components to a solution of the protective colioid.

In the first method, an aqueous solution of a soluble silver salt, e.g. B. silver nitrate, with stirring in an aqueous alkali halide solution containing the protective colloid, preferably gelatin, and optionally contains other additives, added. With simultaneous enema, an aqueous solution becomes one soluble silver salt and a solution of a water-soluble Alkali halide is added simultaneously with stirring into the solution of the protective colioid.

According to a particular embodiment of the present invention, the precipitation is carried out by double inlet interrupted at a certain grain size. The silver halide grains already formed become then subjected to the reducing treatment in the emulsion to the extent that the formation of Veil germs that can develop spontaneously are still reported.:.

The short-term intermediate reduction treatment can be carried out analogously if a precipitation component is presented. In this method, an aqueous silver nitrate solution is converted into a stoichiometric excess, Introduced existing aqueous alkali halide solution containing the protective colloid. If the If the desired grain size is achieved, the excess of the alkali metal halide is removed by washing removed. The treatment is then reduced as described above, and the crystal growth is carried out Continuation of the precipitation or by simple physical ripening after adding a further amount of Alkali halides ^ whereby microcrystals are dissolved and larger crystals grow stronger, continued.

In the various embodiments of the present invention, it is not absolutely necessary that the reducing treatment is done all at once and in a very short time, but it can be optional interrupted or continued continuously over the entire time of the precipitation of the silver halide will.

The method according to the invention is suitable for the preparation of any type of silver halide emulsion, e.g. B. coarse-grained or fine-grained, suitable. With the method according to the invention, for. B. fine-grain silver halide emulsions with relatively flat gradation and a narrow grain size distribution can be produced. Such emulsions contain silver halide grains whose diameter is less than 0.6 μm, preferably 0.05 to 0.3 μm. A narrow grain size distribution means that at least 95 Ge ^- * .- 96 and / or at least 95% of the number of silver halide grains have a diameter which deviates from the mean grain diameter by at most 40%, preferably only by 30%. The grain diameter and the average grain diameter can be measured, for example, according to "Methods of Particle Size Analysis" by RP Loveland, ASTM Symposium on Light Microscupy, 1952, STP 143, 94.

Such fine-grain silver halide kenide emulsions are preferably prepared by the double-jet process produced, whereby certain pH and pAg values are observed. The precipitation temperature is usually 30 to 60 ° C. at pH values up to 9, preferably up to 6, and pAg values up to 9.8. Reference is made to the publication "Properties of Photographic Emulsion Grains," by E. Klein and E. Moisar, J. Phot. Science, 12 (1964), pp. 242-251.

The process of the present invention can be used for the formation of any type of silver halide emulsion be applied, e.g. B. silver chloride emulsions, silver bromide emulsions, silver chloride world bromide emulsions, Silver bromide iodide and silver chloride bromide iodide emulsions with a low content of silver iodide of up to 10 mol-5d. A particularly beneficial effect will be with photographic material with a silver bromide or silver bromide iodide emulsion achieved.

The inventive method can also be used for

if if '. ¹

the preparation of high speed direct positive silver halide emulsions can be used with a flatter gradation. These direct positive emulsions are produced by the surface fogging of the silver halide grains with a reducing agent or by light, e.g. B. manufactured according to GB-PS 11 55 404.

The inventive method can also be used for the preparation of emulsions with layered Grain structure are applied. The core of the Siberha iogenide grain can be chemically sensitized and the Shell may be obscured by conventional methods to obtain a direct positive type emulsion. Reference is made to GB-PS 10 27 146 or US-PS 33 76 778. If the invention is used The method of producing such emulsion is with a layered grain structure, especially in the If the shell falls on the core, direct positive emissions with a relatively flat gradation are obtained. Then it is further processed in the usual way.

After the reductive treatment in the context of the process according to the invention, the silver halide emulsions become Physically matured in the usual way, the emulsion solidifies by cooling or by flaking failed. Thereafter, the excess salts are washed out and the emulsions according to known methods Methods chemically ripened if necessary. The usual additives can then be added to the finished casting solution be added.

The silver halides can be dispersed in the usual hydrophilic binders, for example in carboxymethyl cellulose, polyvinyl alcohol, polyvinylpyrrolidone, alginic acid and their salts, Esters or amides or proteins, preferably gelatin.

The emulsions can also be chemically sensitized, e.g. B. with reducing agents, such as tin-II salts, Polyamines, such as diethylenetriamine, sulfur compounds, as in US-PS 15 74 944 or the book by Meet "Theory of the Photographic Process" (1954), pages 149-161.

For chemical sensitization of the specified emulsions, salts of noble metals such as Ruthenium, rhodium, palladium, iridium, platinum or gold can be applied, as in the article by R. KoslGwsky, Z. Wiss. Phot., 46, pp. 65-72 (1951). Connections are also suitable for this from the Thiomorpholinrelhe, z. B. those described in FR-PS 15 06 230, or polyalkylene oxides, in particular polyethylene oxide and derivatives thereof.

The emulsions can also be spectrally sensitized, e.g. D. with the usual polymethine dyes ^ like Neutrocyanines, basic or acidic carbocyanines ^ mero or rhodacyanines, hemicyanines, styryl dyes and oxonols. Such sensitizers are described in the work by F. M. Hamer "The Cyanine Dyes and Related Comoounds ”(1964).

The emulsions can be hardened in the usual way be, for example, with formaldehyde or halogen-substituted aldehydes that have a carboxyl group contain, such as mucobromic acid, diketones, methanesulfonic acid esters and dialdehydes.

The emulsions produced by the process according to the invention can be used for the most varied of purposes photographic materials can be used, e.g. B. for phototechnical films, for copy or recording materials, preferably for highly sensitive recording materials. They are also useful for X-ray films as well as for color photographic materials what kind, e.g. B. for light-sensitive recording materials containing color couplers or for materials for the silver dye bleaching process, and also for photographic materials used for the silver salt diffusion process or are to be used for other instant photography processes.

example 1

A direct positive type layered grain structure silver halide emulsion was obtained as follows manufactured:

A 3 molar aqueous silver nitrate solution and a 3 molar aqueous potassium bromide solution were simultaneously to a solution of 50 g of gelatin in 1300 ml Added water. The reaction temperature was 60 ° C., during the precipitation ai «pAg-Wret of 0 mV and a pH of 6.5 kept constant. Precipitation took 7 minutes at one addition rate of the silver nitrate solution vck- 19 ml per minute. The average grain size of the grain obtained was 0.13 μm.

Then, this silver halide nuclei were in a conventional manner by adding 3.5 ml of a 10 ~ ² molar aqueous solution of thiourea dioxide to the total amount of the crystals formed long, and 30 minutes heating at 45 ° C matured. Then 1.5 ml of an aqueous 0.08% solution of GoldOID chloride and 1.5 ml of an aqueous 2% solution of ammonium thiocyanate were added. After this addition, the mixture was heated to 45 ° C. for a further 10 minutes. To produce the comparative sample with a conventional structure, the tray was then filled up as follows (2nd precipitation):

A pH of 9.3 was set by adding an aqueous solution of ammonia, and at the same time was an aqueous 3 molar potassium bromide solution and an aqueous 3 molar silver nitrate solution with a Added at a rate of 19 ml per minute over a period of 35 minutes.

The pAg value was set to a value of +20 mV (measured on a silver electrode against a calomel electrode) kept constant.

To produce the emulsion A the 2nd precipitation is carried out as follows.

The "Silver Dlgestion" method was used by setting a pAg value of + 150 mV (silver / saturated calomel electrode) during the second precipitation. The precipitation temperature of the Comparative emulsion and emulsion A was 50 ° C.

Both emulsions were then flocculated after the addition of 84 g of gelatin, washed in the usual way and redisperglerted.

Thereafter wurrfen these two emulsions, the silver halide had a grain structure, for 80 minutes at 45 ° C with 11 ml of a 10- ² molar aqueous solution of thiourea dioxide per kg of emulsion, the hot Sllberbromid contained, treated and characterized was a spontaneously at the grain surface Developable veil formed.

After the masking, the same amount of gelatin was added to each of the samples and the pAg was added by adding an aqueous potassium bromide solution to a value of 23 mV (silver / saturated calomel electrode) set.

The two emulsion samples contained HOg silver bromide, 80 g gelatine and Ig saponin as wetting agents

per kg of emulsion. Shortly before coating, 500 mg of formaldehyde was added as a hardening agent. The emulsion samples are poured onto a substrate made of polyethylene terephthalate and dried. The Sllberhaolgenidauftrag was 7.8 g silver per m ^J. The dried samples are exposed to an incandescent lamp behind a neutral step cell (0.20 wedge constant) and developed at 20 ° C. with a surface developer of the following composition ("development time 135 seconds).

Sodium sulfite (anhydrous) 30 g Trioxymethylene 7.5 g Potassium metabisulfite 2.5 g Boric acid (crystalline) 7.5 g Hydroquinone 22.5 g Potassium bromide 1.6 g Polyethylene oxide 0.5 g (mean molecular weight 2DOOi water up to 1000 r

The sensitometric results obtained for the two samples are summarized in the following table:

pH 6.5 to 7 with AgNOj solution added until a pAg value of 3 existed. After 10 minutes, double enema of 600 ml each of 3n AgNOi and 3n KBr solution, further AgBr falls on the grains of the homodisperse starting emulsion, the The pAg value, which had a value of 3 at the start of the event, was gradually adjusted to a value of 9 became. After adding 60 g of gelatin, watering was carried out as usual, etc. The emulsion obtained was

ίο also homodisperse (narrow grain size distribution); the AgBr crystals with a cubic shape had a particle size of approx. 0.3 μπ \. The emulsion was made with a gold compound, e.g. B. with Na ₁ [Au (S ^ j) ₂ ] (2 ml 10 ~ ² molar solution per 200 g emulsion) chemically ripened. After optimal ripening, it was poured onto a layer support made of cellulose acetate, exposed and developed. A sensitivity was determined from the blackening curve, which is 0.7 log units above that of an optima! reificr. Vcrg! Cich; crr.ü! - ml 20 sion of the same grain size, in which only the setting to pAg 3 was omitted.

attempt veil y /0.1 E. Comparative sample
A. 0.01
0.01 4.75
4.48 6.00
3.90 1.27
1.26

30th

The value · / is the y-value in the straight part of the blackening curve. The γ 0.1 value is the; ^r value at the threshold of the characteristic curve, measured at a density of 0.1 above the veil. The sensitivity E is expressed in relative logarithmic Ε values (log It). The smaller this value is. the higher the sensitivity of the emulsion obtained.

Example 2

40

_{To prepare the starting emulsion used for the further experiments, 1800 ml of a 3n AgNO}} and a 3n KBr solution were run into a solution of 100 g of inert gelatin in 2000 ml of water at 50 ° C. over the course of 3 hours. The inlet was controlled electrometrically so that the silver ion concentration in the solution phase corresponded to a pAg value of about 8. After the precipitation, a further 80 g of gelatin were added; it is then left to solidify, watered and finally a pAg value of 9 is set with KBr.

400 g of this starting emulsion were at 50 ° C and

⁵⁰

Example 3

To produce a heterodisperse starting emulsion having a relatively broad particle size distribution was added to a solution of 32 g of KBr and 240 g of inert gelatin in 4000 ml Wa ■ ss r in the course of 30 seconds at 68 ° C 1000 ml of a 400 g AgNO .. aqueous solution containing shrink calmly. Without further physical ripening, it is solidified, watered and, after remelting, a further 240 g of gelatine are added; the pAg was adjusted to about 9.

650 g of this starting emulsion were adjusted to a pAg value of 3 with AgNOj solution. After digestion at 50 ° C for 10 minutes, 470 m! a 3n-AgNOj and a 3n-KBr solution were allowed to run in, the initial pAg value of approx. 3 being gradually increased to a value of approx. 10 in the course of the precipitation. After the precipitation, 50 g of gelatin were added and it was allowed to solidify and watered as usual. The emulsion was heterodisperse and contained AgBr twin crystals with an average grain size of about 0.7 μm. She was 2 m! a 10 ~ ² mo! aren solution of Nai [Au (S2Oi); i] per 200 g emulsion optimally ripened, poured onto a layer support made of polyethylene terephthalate, exposed and developed. Compared to a comparative emulsion of the same grain size, in which the setting to a pAg value of 3 with AgNO ₃ was only omitted, the emulsion showed a sensitivity that was 0.3 log units higher.

Claims (1)

Patent claims: 1. A process for the production of a photographic silver halide emulsion by precipitation of the silver halide in the presence of a protective colloid, reducing treatment before the silver halide grains have reached their final size and, if necessary, chemical ripening, characterized in that the reducing treatment by setting a high silver ion concentration with pAg values between 7 and 0 is carried out to such an extent that only so few spontaneously developable latent image nuclei arise that these, if the emulsion immediately obtained by the reducing treatment are applied to a support in ^{an amount of 3 g of silver nitrate / m 2 and with a surface developer} of the following composition: