JPS5830570B2 - Sensitization method for silver halide photographic emulsions - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for chemically sensitizing silver halide photographic emulsions by incorporating sulfur compounds.

Many chemical sensitization methods are known in the production of silver halide photographic emulsions to increase their photographic sensitivity.

For example, compounds containing unstable sulfur atoms in their molecules, such as sodium thiosulfate and thiourea, are known as sulfur sensitizers, and reducing agents, such as stannous chloride and hydrogen, are known as reduction sensitizers. ing.

Further, the inclusion of certain gold compounds such as gold ammonium thiocyanide and gold chloride in the emulsion also has a chemical sensitizing effect, which is known as gold sensitization.

In practice, these compounds may be added at any stage for preparing the photographic emulsion, for example, as a ripening additive before the second ripening, or after the second ripening.

A disadvantage of these chemical sensitizers is that the increase in sensitivity they provide tends to cause uniform fogging on the emulsion during development.

In other words, the fog associated with the addition of a chemical sensitizer limits the amount of the sensitizer used, or the increase in sensitivity caused by it is insufficient, so that the practical requirements are not fully met. I can't say that it is.

The present invention provides a novel method for sensitizing silver halide photographic emulsions using a sulfur sensitizer, which does not have the above-mentioned disadvantages.

The present inventors investigated the sensitizing effects of various sulfur-containing compounds and found that the general formula [where R is an alkyl group having 1 to 6 carbon atoms, a benzenesulfonyl group, or a substituted R1 is an alkyl group having a hydrogen atom and 1 to 6 carbon atoms, or a phenyl group.

Further, R and R1, together with the nitrogen atom to which they are bonded, may form a heterocycle which may contain an oxygen atom.

It has been found that all emulsions to which the disulfide compound represented by the following formula is added as a sensitizer exhibit a good sensitizing effect and have very little fog.

Furthermore, it has been found that the emulsion to which the disulfide compound used in the present invention is added exhibits less decrease in sensitivity and increase in fog during storage than emulsions using conventional sensitizers.

Representative examples of disulfide compounds used in the present invention are shown below.

The amount of the disulfide compound used in the present invention varies depending on the type of silver halide or the desired effect, but it is usually 0.3772 @ per mole of silver halide.
It is preferable to use the range from 307729 to 307729.

The compound can be dissolved in a photographically acceptable organic solvent such as methanol, ethanol, etc. and added to the photographic emulsion.

The disulfide compound used in the present invention is preferably added to the photographic emulsion at the start of the second ripening.

In addition to the above, conventional gold sensitizers, sulfur sensitizers, etc. can also be added before, during, or after the second ripening.

There are no particular limitations on the type of silver halide emulsion that can be sensitized by the present invention.

For example, silver chloride, silver bromide, silver chlorobromide, or silver iodide emulsion can be used.

In addition to gelatin, these emulsions may contain a suitable hydrophilic binder depending on the purpose.

Suitable binders include polyvinyl compounds, cellulose derivatives, polyacrylamide, other water-soluble synthetic polymers, and water-insoluble synthetic polymers.

The end use of the emulsion coating is also not limited, such as black and white photography, color photography, microfilm,
It can be used for line detection and also as an emulsion for diffusion transfer method.

The photographic emulsion according to the present invention may also contain various additives used in ordinary photographic emulsions, such as stabilizers, hardeners, ultraviolet absorbers,
It can contain color toning agents, antioxidants, couplers, sensitizing dyes, surfactants, thickeners, development rate regulators, and the like.

The silver halide photographic emulsion according to the present invention prepared as described above has excellent photographic performance with less occurrence of fog and is effectively sensitized.

Examples will be described below, but the present invention is not limited thereto.

Example-1 The average particle diameter produced by the normal double jet method is 0.
．． 4μ silver bromide emulsion at 40℃, pH 6.0, PA,! 7
It was adjusted to 6.3 and divided into 5 parts.

The first part contains a disulfide compound (1
) is 1.4■, and the second part is a disulfide compound (3).
1.4772@, disulfide compound 5 in the third part
) and 3.4 m9 of disulfide compound 7) dissolved in methanol were added to the fourth part, and no disulfide compound was added to the fifth part.

These were designated as emulsions 1, 2, 3, 4, and 5, respectively.

After aging the above five emulsions at 50°C for 60 minutes, 40°C
The PA was adjusted to 98.0, a conventional surfactant and a hardening agent were added, and the mixture was coated on a polyester film.

Table 1 shows the photographic properties after heating at 50° C. and 50% relative humidity for 24 hours.

As is clear from the results, it can be seen that emulsions 1 to 4 according to the present invention have much higher sensitivity than comparative emulsion 5 without increasing fog.

Example 2 A silver bromide emulsion prepared in the same manner as in Example 1 was adjusted to pH 6.0 and PAJ 6.3 at 40° C. and divided into three.

Sodium thiosulfate 27% per mole of silver bromide
7729, disulfide compound (1) 5m in the second part
@, After adding 13■ of disulfide compound (5) dissolved in water or methanol to the third part, 1% of each
Added 2.7 rul of AuCt3 aqueous solution and added emulsion 6 to each
, 7.8.

After aging the above three emulsions at 50°C for 60 minutes,
The mixture was adjusted to PAJ 8.0 at ℃ and coated on a polyester film with the addition of a conventional surfactant and a hardening agent.

Table 2 shows the photographic properties after heating at 50°C and relative humidity of 50°C for 24 hours.

As is clear from this result, emulsions 7 and 8 according to the present invention
It can be seen that compared to emulsion 6, emulsion 6 has higher sensitivity with almost no increase in fog.

Example-3 A silver bromide emulsion prepared in the same manner as in Example-1 was heated at 40°C.
It was adjusted to pF (6.0, PAJ 6.3) and divided into two.

To the first part, 1 mole t of silver bromide and 17 m2 of sodium thiosulfate were added as an aqueous solution, and to the second part, 7 m9 of disulfide compound (5) was added as a methanol solution to form emulsions 9 and 10, respectively.

This is aged at 50℃ for up to 5 hours, during which the emulsion is taken at appropriate intervals, adjusted to PAJ 8.0 at 40℃, and the usual surfactants and hardeners are added and applied to a polyester film. did.

Table 3 shows the photographic properties after heating at 50°C and relative humidity of 50φ for 24 hours.

The density in Table 3 is the density obtained after development under constant light, and as the ripening was extended, the comparative emulsion 9
Although the density rapidly decreased after reaching the maximum value, emulsion 10 according to the present invention showed less decrease in density, less fog, and good stability.

Claims (1)

[Scope of Claims] 1. A method for sensitizing a silver halide photographic emulsion, which comprises incorporating a disulfide compound represented by the following general formula. [Here, R is an alkyl group having 1 to 6 carbon atoms, a benzenesulfonyl group, or an optionally substituted aryl group, and R1 is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a phenyl group. It is. Further, R and R1, together with the nitrogen atom to which they are bonded, may form a heterocycle which may contain an oxygen atom. ]