US3320068A - Silver halide emulsions with increased sensitivity - Google Patents

Description

United States Patent 3,320,068 SILVER HALIDE EMULSFONS WITH INCREASED SENSITIVITY Wolfgang Miiller-Bardorlf, Cologne, and Wilhelm Saleck, Schildgen, Bergisch-Gladbach, Germany, assignors to Agfa Aktiengesellschaft, Leverknsen, Germany, a corporation of Germany No Drawing. Filed Mar. 31, 1964, Ser. No. 356,075 Claims priority, application Germany, Apr. 24, 1963, A 42,947 5 Claims. (Cl. 96-107) The invention relates to a method of increasing the sensitivity of photographic silver halide emulsions.

Numerous compounds are known which can be used as additives to the emulsion or developer to increase the sensitivity of a photographic layer. Many different terms are used for substances that have this effect, e.g., chemical sensi-tizers or activators. The best known class of substances in this field are polyalkylene oxides, in particular polyethylene oxides and water-soluble onium compounds such as quaternary ammonium-, phosphoniumand sulphonium salts or combinations thereof or derivatives of thiourea, for example, thiouronium salts.

The maximum sensitivities obtained in silver halide emulsions by the addition of the above mentioned compounds presupposes that the silver halide emulsions have been activated by treatment with noble metal salts, especially gold salts.

The most commonly used combination for gold sensitization consists of gold-(III)-salts and thiocyanate or thiosulphate, although the solutions of thiocyanate are not very stable and those of thiosulphate are diflicult to pre pare. Reaction kinetic investigations, e.g., by Protass, Bjirrum and Kirschner (Z. Wiss. Angew. Phot. Kine l, 455 (1956)) on gold complexes with thiocyanate ions admit of the assumption that sensitization is caused by a controlled, slow decomposition of the Au-(I)-complexes in which the thiocyanate ions participate. The mecha nism of this sensitization process is not certain since many reaction components are involved, such as metallic gold, Au-(I)-, Au-(IID- and thiocyanate ions, dithiocyanogen and additional sulphur degradation products including thiosulphate and gelatine.

Moreover, a considerable excess of thiocyanate ions is required to stabilise the gold-(I) complex and obtain maximum sensitivity of the silver halide emulsions.

This method thus has numerous disadvantages. A considerable amount of the gold-(III) salts are bound by the gelatin, partly by absorption and partly by complex formation; another amount is reduced to metallic gold and lost for chemical sensitization. In addition the large excess of thiocyanate impairs the stability of the latent image after exposure.

It has now been found that a combined noble metal ripening and reduction ripening of silver halide emulsions is obtained if the chemical ripening is performed with salts of noble metals of group VIII of the periodic system of the elements having an atomic Weight greater than 100 and of gold, particularly platinum, palladium, iridium and more preferably gold-(III) salts in the effective presence of o-hydroxybenzylamine compounds of the following general formula In this formula, R represents a hydrogen atom or an alkyl group preferably lower alkyl up to 5 carbon atoms, which may be substituted, for example, with hydroxyl, halogen such as C1 or Br, carboxyl, or an aryl group preferably phenyl which may be substituted, for example with alkyl, preferably lower alkoxy, halogen preferably C1 or Br, carboxyl, amine, hydroxyl, x represents a hydrogen atom, a hydroxyl group or a halogen atom preferably chlorine and bromine; and n is an integer between 1 and 5. The phenolic benzene ring in the above general formula can in addition be substituted, especially in the o-position or p-position to the hydroxy group, with lower alkyl radicals preferably those having up to 3 carbon atoms which may be substituted if desired, or with halogen atoms preferably chlorine and bromine, hydroxy or lower alkoxy groups preferably those having up to 3 carbon atoms.

The following compounds exhibit particular utility: (I) (|)H @CHz-NHCH;OHOH

Galena-anteater (III) c H H3OOOHPNH-CH2-CHPOH IV on Br--CHrNHOHz-CH2OH CFOCHy-NH-OHT-CHPOH Br ort2NH cH2-om-Br l Br our on OHIOOHNHCHz-CE-C1 vrn on:

CHz-OHr-OH CHrN CH2OOOH CHz-COOH uch compounds are already known. They can be easily reduced by reacting the appropriate substituted salicylldehyde with the appropriate amine. The resulting chiffs bases are hydrogenated in aqueous solution with 1e aid of a Raney nickel catalyst. The substituent R can 1en be introduced with the aid of active chlorine comounds in an aqueous alkaline medium. In the case of re bromobenzyl compounds, the bromine can be subseuently introduced.

These o-hydroxybenzylamin-compounds are good comlexing agents for heavy and noble metal ions. For exmple, with gold-(III)-chloride, gold-(III)-cornplexes are ormed, which are often deep in color. Due to the weakly :ducing effect of the compounds of the above general ormula, such Au-(III) complexes are reduced to Au-(I) omplexes. To ensure the formation of the Au-(l)-comlexes in every case, it is advisable to additionally add 168k reducing agents.

The process of the invention is capable of being used Ilih all photographic silver halide emulsions. The silver alide can consist of silver chloride, silver bromide, silver )dide or mixtures thereof.

An additional advantage of the process of the invention that the emulsions can be further sensitized with, for xample, sulphur compounds, polyalkylene oxides, wateroluble onium compounds or combinations of polyethylne oxides and onium compounds. In addition, they can e optically sensitized by, e.g., cyanine or merocyanine lyestuffs and the like.

Basic stabilizers can be included in the emulsions, for xample, organic mercapto compounds, quaternary benzhiazoles, triazoles, tetrazaindolizines and the like. Antther advantage of the process according to the invention 5 that the sensitized emulsions can be used for black- .nd-white photographic material or color photographic naterial, it being possible in the latter case to incorporate lydrophobic or hydrophilic color couplers into the emulion layer.

As compared with a gold ripening using thiocyanate, ome of the compounds according to the invention proluce the same sensitivity with half the quantity of gold, usually with less fogging.

The mode of addition of the o-hydroxybenzylamin- :om pounds of the invention to the emulsions is not critical. Fhe compounds may be added in dissolved or in solid orrn, and before, during or after the addition of the noble netal salt. Alternatively, the noble metal salt, for exlmple, gold-(IID-chloride, may be first mixed with a .olution of the o hydroxybenzylamin-compounds and then ldded to the emulsions. Generally speaking, this addiion is made before the chemical ripening of the emul- .ion. The chemical ripening is also called after-ripening. lhe compounds are used in concentrations of 0.1 g. to i g. per kg. of emulsion (preferably 0.25-0.35 g./kg.). [he optimum quantity to be added depends on the reiucing power of the o-hydroxybenzylamin-compound and he nature of the emulsion. It can easily be determined Jy a few tests.

According to one preferred form of the present inven- ;ion, the o-hydroxybenzylamin-compounds are used in :ombination with weak reducing agents. Suitable for this purpose are, for example, the polyhydroxycarboxylic acids, in particular those of the following general formula:

wherein n is 0 or an integer between 1 and 8, advantageously l5, e.g., hydroxyacetic acid, d-gluco-ot-hexonic acid, d-gluco-a-heptonic acid, etc.

Suitable are also aldo sugars, such as glucose, dimethylformamide, nitrilotriacetic acid and similar compounds. Generally suitable for the present purpose are those reducing agents which are able to reduce trivalent gold to monovalent gold, but have too small a reduction potential to precipitate metallic gold from the complexes of the monovalent gold.

The process can be varied in many ways even when using the o-hydroxybenzyl-amin-compounds in combination with the previously described weak reducing agents. The compounds can be added, in dissolved or in solid form, before, during or after the addition of the noble metal salt. Alternatively the noble metal salt, for example, gold-(IlD-chloride, can first of all have added thereto a solution of the compounds according to the invention, be thereafter reduced with'the reducing agent and then the gold-(I)-complex solution can be added to the emulsions. The addition compounds are generally added prior to the chemical or after-ripening of the emulsion. The compounds are used in concentrations from 0.1 g. to 5 g. preferably 0.25-0.35 g. per kg. of emulsion with addition of 0.1 to 5 g. preferably 0.l50.3 g. of the reducing agent. The optimum quantity of the reducing agent depends on the reducing power of the compounds and the nature of the emulsion, and can easily be determined by a few tests. The reducing agents should generally be used in a concentration which is smaller than or at most equal to that of the o-hydroxy-benzylarnine derivatives. The amount to be used can be between 0.1 g./kg. of emulsion and the amount of the o-hydroxybenzylamine complexing agent.

The process according to the invention is illustrated by reference to the following examples, without limiting the invention in any way.

Example 1 A highly sensitive gelatino-silver bromiodide emulsion with a 4 mol percent of silver iodide, which contains 50 g. of silver per liter, has 35-40 mg./ liter of KBr and sulphurcompounds, etc. added thereto for the chemical ripening in the usual way and is divided before the ripening into three samples A, B and C.

Sample A serves as standard sample. Before the ripening, the following solution is added to sample B, per lite-r of emulsion:

1 ml. of 0.08% gold-(III)-chloride solution, mixed with 3 ml. of a 10% aqueous solution of Compound I. Before the chemical ripening, there was added to sample C per liter, 2 ml. of a 0.08% gold-(III)-chl0ride solution, which has been mixed with 3 ml. of a 10% aqueous solution of Compound I.

After all three samples have been ripened until the maximum sensitivity is reached, they have a wetting agent and a stabilizer, e.g., of the azaindolizine type, added thereto and are cast onto one of the conventional film supports.

The three samples are exposed and developed in a normal commercial p-methylaminophenol hydroquinone de veloper for 10 minutes at 20 C.

The result is to be seen from Table 1.

TABLE 1 Sensitivity Fogging Gamma increase Example 2 A highly sensitive silver bromoiodide emulsion, as described in Example 1, is pretreated as in this example and divided into three samples A, B and C.

Sample A serves as standard sample.

Sample B has added thereto, per liter of emulsion, a mixture consisting of 3 ml. of a aqueous solution of the Compound III and 1 ml. of 0.08% gold-(III)-chloride solution.

Sample C contains, per liter of emulsion, 3 ml. of a 10% aqueous solution of the Compound III, which has been mixed with 2 ml. of a 0.08% gold-(III)-chloride solution.

The three samples are ripened as in Example 1, then coated as described therein onto a film support, and then the material is exposed and developed as described in Example 1.

The result is shown in Table 2.

Three samples A, B and C of a silver halide emulsion as described in Example 1, are treated as follows:

Sample A serves as standard sample.

Sample B has added thereto, per liter of emulsion, a mixture of 3 ml. of a 10% aqueous solution of Compound II and 1 ml. of a 0.08% gold-(III)-chloride solution.

Sample C contains, per liter of emulsion, 3 ml. of a 10% aqueous solution of Compound II, which has been mixed with 2 ml. of a 0.08% gold-(III)-chloride solution.

The ripening of the three samples, the casting onto a film support, the exposure and the development is performed as indicated in Example 1.

The result is shown in Table 3.

Three samples A, B and C of a silver halide emulsion, as described in Example 1, are treated as follows:

Sample A without additives, serves as standard sample.

Sample B has added thereto, per liter of emulsion, a mixture of 3 ml. of a 10% aqueous solution of the Compound VIII, and 1 ml. of a 0.08% gold-(HD-chloride solution.

Sample C contains, per liter of emulsion, 3 ml. of a 10% aqueous solution of the Compound VIII, which has been mixed with 2 ml. of a 0.08% gold-(IID-chloride solution.

The ripening of the three samples, the casting onto a support and the exposure and development is performed as described in Example 1.

The result is shown in Table 4.

TABLE 4 Sensitivity Fogging Gamma increase Sample A 0 0.19 0.55 +2.5" DIN 0. 26 0.55 +2.5 DIN 0. l9 0. 50

Example 5 A highly sensitive gelatino-silver bromiodide emulsion with 4 mol percent of silver iodide, which contains 50 g. of silver per liter, has 35-40 mg./lit'er of KBr and sulphur compounds etc. for the chemical ripening, is divided before ripening into 3 samples A, B and C.

Sample A serves as comparison sample. Before the ripening of sample B, the latter has added thereto the following solution, per liter of emulsion:

6 ml. of a 10% solution of the Compound I, to which are added 2 ml. of a 0.08% gold-(III)-chloride solution. Thereafter, 1 ml. of a 10% solution of sodium hydroxyacetate is added.

Before the chemical ripening of sample C, the latter has added thereto the following mixture per liter of emulsion:

4 ml. of 0.08% gold-(III)-chloride solution are added to 6 ml. of 10% solution of the compound I, the pH of the mixture is adjusted to 8 and finally 1 ml. of 10% solution of sodium hydroxyacetate is added.

After ripening until the maximum sensitivity is reached, a wetting agent and a stabilizer, e.g., of the azaindolizine type are added to each of the three samples which are then cast onto a support such as paper, a cellulose acetate, a polyester preferably of polyethylene terephthalate or a polycarbonate in particular of bis-hydroxyphenyl alkanes.

The three samples are exposed and developed in a commercial p-methylaminophenyl hydroquinone developer for 10 minutes at 20 C.

The result is shown in Table 5.

TABLE 5 Sensitivity Fogging Gamma increase Sample A 0 0. 20 0.55 Sample B +1.5 DIN 0.37 0.50 Sample C +3 DIN 0.15 0. 50

Example 6 Three samples A, B and C of a silver halide emulsion, as described in Example 5, are treated as follows:

Sample A serves as standard sample. Before being chemically ripened, Sample B has the following solution added thereto, per liter of emulsion:

2 ml. of a 0.08% gold-(IID-chloride solution are added to 6 ml. of a 10% solution of compound X, the pH of the mixture is adjusted to 8 and finally 1 ml. of a 10% solution of sodium hydroxyacetate is added.

Sample C has added thereto, per liter of emulsion, a

Three samples A, B and C of a silver halide emulsion, described in Example 5, are treated as follows:

Sample A serves as standard sample. Before being hemically ripened, Sample B has the following solution dded thereto, per liter of emulsion:

2 ml. of 0.08% gold-(III)-chloride solution are added 3 6 ml. of a 10% solution of compound III, the pH of 1e mixture is adjusted to 8 and then 1 ml. of a 10% olution of sodium d-gluco-a-heptonate is added.

Sample C has added thereto, per liter of emulsion, a mixture which has been prepared as follows:

4 ml. of a 0.08% gold-(III)-chloride solution are added a 6 ml. of a 10% solution of compound III, the pH of he mixture is adjusted to 8 and finally 1 ml. of a 10% olution of sodium d-gluco-a-heptonate is added.

The ripening of the three samples, the casting onto a upport, the exposure and development is performed as ndicated in Example 5.

The result is shown in Table 7.

An X-ray emulsion with 2 mol. percent of silver iodide, vhich contains 80 g. of silver per liter, and which furher contains bromide and sulphur compounds for the :hemical ripening, is divided before ripening into two ;amples A and B.

Sample A is a standard sample. Before the after-ripenng of Sample B the following solution is added per liter )f emulsion:

3 ml. of a 10% solution of the compound I are mixed with 1.4 ml. of a 0.08% go1d-(III)-chloride solution. The pH of the solution is adjusted to 8 and 0.15 ml. of 1 10% solution of sodium hydroxyacetate is added.

After these samples have been after-ripened until the maximum sensitivity is obtained, a wetting agent and a stabilizer, e.g., of the azaindolizine type, is added thereto. Thereafter the emulsions are coated onto a usual support. The two samples are exposed and developed for minutes at 20 C. in an X-ray developer which yields silver images with a steep characteristic curve.

The result is shown in Table 8.

The procedure is as indicated in Example 8, but the following solution is used with sample B: 3 ml. of a solution of the compound III are mixed with 1.4 ml. of a 0.08% gold-(III)-chloride solution and the pH is adjusted to 8. There is then added 0.15 ml. of a 10% solution of sodium hydroxyacetate. The result is shown in Table 9:

TABLE 9 Sensitivity Fogging Gamma increase SampleA 0 0.17 2.7 SampleB +l.5 DIN 0.16 2.7

Example 10 A gelatino-silver bromoiodide emulsion of medium sensitivity with 6 mol. percent of silver iodide, which contains g. of silver per liter and which further contains potassium bromide and sulphur compounds, etc, for the chemical ripening is divided before after-ripening into two samples A and B.

Sample A is the standard sample.

Sample B, before the after-ripening, the following solution is added thereto per liter of emulsion:

3 ml. of a 25% solution of compound I are mixed with 1 ml. of a 0.08% gold-(IlD-chloride solution. The pH of the solution is adjusted to 8 and 0.5 ml. of a 25% solution of sodium hydroxyacetate is added.

After having ripened these samples until the maximum sensitivity is obtained, a wetting agent and a stabilizer, e.g., of the azaindolizine type, are added and they are then cast onto a usual support.

The two samples are exposed and developed for 10 minutes at 20 C. in a p-methylaminophenol hydroquinone developer.

The result is shown in Table 10.

A gelatino-silver chlorobromoiodide emulsion with 20 mol percent of silver chloride and 6 mol percent of silver iodide which contains g. of silver per liter and which further contains potassium bromide and sulphur compounds etc. for the chemical ripening is divided before after-ripening into :two samples A and B.

Sample A is the comparison sample.

Sample B, before the after-ripening, the following solution is added thereto, per liter of emulsion:

7 ml. of a 10% solution of compound I are mixed with 3 ml. of a 0.08% gold-(IID-chlon'de solution. The pH of the solution is adjusted to 8 and 0.3 ml. of a 10% solution of sodium hydroxyacetate is added.

After this mixture has been added to the emulsion, the samples are after-ripened up to maximum sensitivity, thereafter a wetting agent and a stabilizer, e.g., of the azaindolizine type, are added and the samples are cast onto a paper support.

The two samples are exposed and developed for 2 .minutes in a developer of the following composition:

Grams p-Methylaminophenol 1 Hydroquinone. 3 Anhydrous sodium sulphite 13 Anhydrous sodium carbonate 26 Potassium bromide 1 Water to make 1000 ml.

It will be clear to those skilled in this art that the practice of the invention lends itself readily to a number of useful modifications in method, material etc. For example, the noble metal salts are not limited to the previously mentioned, because it is possible to use any suitable salt which is soluble in water or lower alcohols. Such compounds are: gold halides, such as auric chloride, or complex gold halides, such as potassium chloroaurate (KAuCh) and sodium .chloroaurate (NaAuCl However, gold compounds, such as auric sulfate, are practically as useful as the gold halides. Aurous, as well as auric compounds can be used. Complex gold salts, such as alkali metal aurous thiosulfates, alkali metal aurous sulfites (e.g., sodium or potassium aurous thiosulfate and sodium or potassium aurous sulfite). Potassium chloroaurite, potassium bromoaurite, potassium iodoaurite, or the corresponding sodium, calcium, strontium, cadmium or gallium salts can also be used. Pyridinotrichloro-gold, ethylenediamine-bistrichloro gold, diethyl-monobromo-gold and diethyl gold acetone and gold complexes with sulfur compounds such as are commonly present in gelatin, e.g., the gold thiosinamine complexes, can also be used.

Suitable salts of noble metals of the VIII group are ammonium or potassium, cbloropalladate, ammonium, sodium and potassium chloroplatinate, ammonium potassium and sodium bromoplatinate, ammonium chlororhodate, ammonium chlororuthenate, ammonium chloroiridate, ammonium, potassium and sodium chloroplatinite, ammonium, potassium and sodium chloropalladite, etc.

The after-ripening of the emulsion with the noble metal salt and the o-hydroxybenzylamine compounds is performed at an appropriate temperature particularly between 30 and 60 C. During after-ripening the pH of the emulsion is advantageously adjusted to the acid side of neutrality preferably between 5 and 7. Maintenance of the emulsion on the acid side of neutrality during coating of the emulsion is also preferred.

The noble metal salts are employed in an amount below that which produces a substantial fog. In practicizing the present invention, a quantity of the noble metal salt is employed, equivalent to between 0.1 and mg. of the noble metal per :mole of silver halide in the emulsion. The noble metal compounds are preferably incorporated in the emulsion in the form of their solutions in a suitable sol-vent such as water, methyl alcohol, ethyl alcohol or the like.

We claim:

1. In a process for producing a sensitized photographic silver halide emulsion, the step which comprises afterripening the emulsion on the acid side of neutrality in the effective presence of at least one water-soluble salt of a Group VIII metal having an atomic weight of greater than or gold and in the effective presence of an o-hydroxybenzylamine compound of the formula wherein R represents a substitutent of the group consisting of hydrogen, al-kyl, and a phenyl, x stands for a member of the group consisting of hydrogen, hydroxy and halogen and n in an integer between 1 and 5.

2. A process as defined in claim 1 wherein the phenyl ring of the benzyl grouping of the o-hydroXy-benzylamine compounds is substituted with a radical of the group consisting of hydroxy, lower alkyl, halogen and lower alkoxy.

3. A process as defined in claim 1 wherein the emulsion is after-ripened in the further active presence of a reducing agent of the group consisting of polyhydroxycarboxylic acids, sugars, alphatic acid amides or nitrilotriacetic acid.

4. A process as defined in claim 1, where the metal is gold.

5. A process as defined in claim 1, wherein the emulsion which is to be after-ripened additionally contains at least one member of the group consisting of sulfur compounds, onium compounds, polyalkylene oxides and a tetraazainclolizine stabilizer.

No references cited.

NORMAN G. TORCHIN, Primary Examiner.

I. H. RAUBITSCHEK, Assistdnt Examiner.

Claims (1)

1. IN A PROCESS FOR PRODUCING A SENSITIZED PHOTOGRAPHIC SILVER HALIDE EMULSION, THE STEP WHICH COMPRISES AFTERRIPENING THE EMULSION ON THE ACID SIDE OF NEUTRALITY IN THE EFFECTIVE PRESENCE OF AT LEAST ONE WATER-SOLUBLE SALT OF A GROUP VIII METAL HAVING AN ATOMIC WEIGHT OF GREATER THAN 100 OR GOLD AND IN THE EFFECTIVE PRESENCE OF AN O-HYDROXYBENZYLAMINE COMPOUND OF THE FORMULA