CS255602B1 - Process for preparing Lippmann emulsions - Google Patents

Abstract

The method for preparing Lippamann emulsions consists in that the precipitation of silver halides is carried out in the presence of substances containing a heterocycle or a substituted heterocycle or a heterocycle with condensed nuclei, which contains one or more nitrogen atoms, such as imidazole, benzimidazole, naphthoimidazole, pyridine, quinoline, pyrazole, tetrazole, triazole, azaindolizine and is optionally substituted by a straight or branched chain with 1 to 20 carbon atoms, a cyclic alkyl group with 1 to 20 carbon atoms, a monocyclic or bicyclic aryl group, an amino group, a hydroxyl group, an alkoxy group with 1 to 20 carbon atoms, a cyano group, a carboxyl group, an alkoxycarbonyl group with 2 to 20 carbon atoms, a 5- or 6-membered heterocycle containing an oxygen or sulfur atom as a heteroatom, in an amount of 10"4 to 10-1 mole per mole of silver halides.

Description

The invention relates to the field of photochemistry, to the technology for producing photographic emulsions based on silver halides, to the preparation of high dispersion crystals of silver halides of the Lippmann type.

Lippmann emulsions are those which consist of a set of silver halide crystals with a mean crystal size of less than 100 nm. Lippmann emulsions are particularly important for the preparation of high resolution plates or films for use in photomicrography and astrophotography, to record nucleo-physical phenomena, to prepare photomasks for the production of microelectronic integrated circuits, to prepare recording material in holography, etc.

At present, there is an increasing need to prepare photographic plates or films containing a layer of Lippmann emulsion with a mean silver halide crystal size of less than 50 nm. These emulsions are referred to as so-called grain-free emulsions, since they only minimally scatter the light beam passing through the layer of this material. Photographic materials of this type are of great importance for reflective holography where high diffraction efficiency and high signal to noise ratio are required. In the manufacture of microelectronic integrated circuits, the design masks need to be reduced in several steps and reproduced on a material with a high resolution. For this purpose, it is advantageous to use Luppmann plates or Lippmann films.

Several methods for preparing Lippmann emulsions are disclosed in the published literature.

The precipitation of silver halides by rapid mixing of dilute solutions of alkali halides and silver nitrate results in a polydisperse set of crystals with a mean crystal size of about 15 nm. However, the emulsion polydispersity greatly reduces the resolution of the material.

It is known from the literature that monodisperse materials allow to achieve the same resolution as polydisperse crystal materials, and the mean size of the monodisperse crystals can be much larger. The monodisperse emulsion can be prepared by two-stream precipitation according to the well-known method described in the literature.

Methods for preparing Lippmann emulsions can be found in which precipitation is carried out in the presence of compounds that regulate the growth of silver halide crystals and suppress the Gibbs-Thomson effect. According to published procedures, the precipitation of silver halides is carried out in the presence of two groups of substances which regulate crystal growth and stabilize the formed crystals in terms of their thermodynamic equilibrium with the solution. The first group includes heterocyclic compounds that contain sulfur or selenium atoms in the side chain. The second group of silver halide crystal growth regulators includes heterocyclic compounds having one or more nitrogen atoms in the heterocycle, each of which at least two heterocycles are linked by a simple chemical bond or by a chain of atoms listed in U.S. Pat. No. 3,704,130. By varying the choice of silver halide precipitation conditions, however, it is not possible to find conditions under which a growing set of monodisperse silver halide crystals would achieve a thermodynamic equilibrium with a solution at an average crystal size of less than about 60 nm.

These disadvantages are overcome by the process of preparing Lippmann emulsions according to the invention, which comprises precipitation of silver halides, for example silver bromide, silver chloride, silver chloride bromide, silver bromide iodide, silver chloride iodide or silver chioridobromide iodide, in the presence of hydrophilic colloid compounds. contain a heterocycle or a substituted heterocycle or a fused-ring heterocycle containing at least one nitrogen atom, such as imidazole, benzimidazole, naphthoimidazole, pyridine, quinoline, pyrazole, tetrazole, triazole, azaindolizine. The substituents are hydrogen atoms, straight chains, branched or cyclic alkyl groups having 1 to 20 carbons, monocyclic or bicyclic aryl groups, amino groups, hydroxyl groups, alkoxy groups having 1 to 20 carbons, cyano groups, carboxyl groups, alkoxycarbonyl groups having a number carbon atoms of 2 to 20, 5-membered or 6-membered heterocycles containing an oxygen or sulfur atom as a heteroatom, alkylthio groups of 1 to 6 carbon atoms, carbamoyl groups which may be substituted by an aliphatic or aromatic group and halogens.

These compounds have long been known in photographic chemistry and are used as stabilizing ingredients in photographic emulsions, but in the literature published so far, the fines are applied only in the chemical maturation phase or during other operations prior to coating.

However, the proposed process uses these compounds for the first time to control the growth of silver halide crystals and stabilize them. By using the compounds of the present invention during the precipitation of silver halides, homodisperse Lippmann emulsions with an average crystal size much smaller than in the absence of these can be prepared. The materials prepared in this way achieve a high resolution. It is particularly preferred to carry out the precipitation in the presence of compounds of the formulas I and II wherein R 1 to R 2 are the same or different substituents, wherein the substituents are as defined above or R, R and R may together form the aforementioned 5-membered group. or 6-membered ring.

These substances are added to the aqueous hydrophilic protective colloid, especially the aqueous gelatin solution, before the precipitation of the silver halides. They are used in amounts Io ^- Io ^ to ^"1 mole per 1 mole of silver halide. By using the substances in the precipitation phase, the same resolution of the Lippmann emulsions as in the known methods of higher light sensitivity is obtained.

Weight the ratio of hydrophilic protective colloid to silver halides in the form of highly dispersed crystals is preferably in the range of 0.1 to 8.0: 1. As conventional hydrophilic protective colloid, any conventional hydrophilic colloid used in photographic light sensitive emulsions may be used, for example gelatin, albumin, casein, cellulose derivatives such as carboxymethylcellulose, synthetic protective colloids such as polyvinyl alcohol, poly-N-vinylpyrrolidone, etc. also use mixtures of two or more colloids.

The silver halide crystals may consist of silver bromide, silver chloride or mixed silver halide crystals such as silver chloride bromide, silver bromide iodide, silver chloride bromide. Emulsions which contain silver bromide or silver chloride or a mixture of silver chloride and silver bromide with a silver iodide content of up to 8 mol% have advantageous properties.

After exposing the high dispersion silver halide crystals according to the method of preparing the Lippmann emulsions of the invention, the emulsion is allowed to solidify, bored, then washed to remove the water-soluble salts. The degree of washing can be controlled by conductometry.

The emulsions of the invention may be spectrally sensitized by any known optical sensitizer such as a dye of the cyanines, merocyanines, etc. Chemical maturation may be performed in the presence of compounds containing a certain amount of sulfur, for example arylthiocyanates, arylthiourea, sodium thiosulfate etc. The emulsion may be chemically sensitized using reducing agents such as imino-aminomethanesulfinic acid derivatives, cadmium salts, stannous salts, zinc salts, small amounts of noble metal compounds such as gold, platinum, palladium, iridium, ruthenium, rhodium.

Compounds that accelerate development can be added to these emulsions, thereby increasing the sensitivity of the emulsions. These compounds include polyoxyalkylene compounds, quaternary ammonium compounds, quaternary phosphonium and tertiary sulfonium compounds, etc.

The substances used to control the growth of silver halide crystals act as stabilizers in the emulsion. Thus, the stabilizing effect of these substances may be utilized, or other stabilizing additives such as heterocyclic compounds such as nitrogen atoms: benzothizoline-2-thione and 1-phenyl-2-tetrazoline-5-thione, hydroxytriazolopyrimidone-type compounds, mercury compounds, etc. may be added to the emulsion.

If the Lippmann emulsion is to be used to prepare photomasks, light absorbing dyes can be used to suppress light scattering and reflection. The dye addition to the emulsion was determined such that the optical density of the dry stained layer was 0.05-0.2 per 1 µm of the emulsion layer thickness. The absorption maximum of the dye used is chosen to fall within the wavelength range through which the material is exposed.

The emulsions may be cured, for example, with chromium salts, aluminum salts, formaldehyde, dialdehyde, hydroxyaldehyde, acrolein, glyoxal, halogen-substituted aldehyde acids such as mucochloric acid and the like, diketones, divinyl ketones, etc.

Said emulsions may be poured onto different substrates. Preferred substrates are: cellulose ester film, polyvinyl acetal, polystyrene, polyethylene terephthalate, paper, silica glass, organic glass, etc. To enhance the adhesion of the emulsion to the glass, the glass surface can be prepared with silicon compounds.

The preparation of Lippmann emulsions can be carried out according to the examples.

Example 1

Lippmann emulsions were prepared by a two-stream precipitation method of a well-known methodology. These Lippmann emulsions contained, per liter, 10 g of silver bromide and 0.37 g of silver iodide in the form of mixed homodisperse crystals and 50 g of gelatin. The precipitation conditions were chosen such that the mean crystal size of the Lippmann emulsion was 67 nm in the absence of growth regulators. Further samples of Lippmann emulsions were prepared under the same reaction conditions in the presence of the compounds listed in Table I in an amount of 2.23. 10 mol per 1 mol of silver halide. The table shows the mean crystal size, which was determined turbidimetrically.

Example 2

Samples of Lippmann emulsions were prepared in the same manner as in Example 1. Two substances in a mixture of different molar proportions were used to control the growth of the silver halide crystals. The results of the experiments are shown in Table II.

Table I

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Added substance

The average crystal diameter was 67

Table

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I continued

Mean crystal diameter

Added substance

[ ^nm J

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Mean crystal diameter NM NM J

Molar ratio of substances

1 1 0 26 2 0.75 : 0,25 28 3 0.50 : 0,50 27 Mar: 4 0.25 : 0,75 29 5 0 1 29

SUBJECT OF THE INVENTION

Claims (3)

SUBJECT OF THE INVENTION A method for preparing Lippmann emulsions, characterized in that silver halides, for example silver bromide, silver chloride or silver chloride bromide, silver bromide iodide, silver chloride iodide or silver chloride bromide, are precipitated in the presence of substances containing a heterocycle or substituted heterocycle or condensed ring heterocycle containing at least one nitrogen atom, such as imidazole, benzimidazole, naphthoimidazole, pyridine, quinoline, pyrazole, tetrazole, triazole, azaindolizine, and is optionally substituted by a straight or branched chain of 1 to 20 carbon atoms, a cyclic alkyl group with a carbon number 1-20, a monocyclic or bicyclic aryl group, an amino group, a hydroxyl group, an alkoxy group having a carbon number of 1 to 20, a cyano group, a carboxyl group, an alkoxycarbonyl group having a carbon number of 2 to 20, Component or 6-membered heterocycle containing an oxygen or sulfur atom as a heteroatom, an alkylthio group having 1 to 6 carbon atoms, a carbamoyl group which may be substituted by a v-, -4-in-1 aliphatic or aromatic group and halogens in an amount of 10 to 10 moles per mole silver halides. 2. Method according to claim 1, characterized in that precipitation is carried out in the presence of compounds of formula I and II wherein R _{q, R?} , R ₇ and R ₈ are the same or different substituents having the meanings given above, and optionally the substituents R, R and R may be taken together to form a 5-membered or 2-membered substituent. 6-member circle. 3. The process according to claim 1, wherein the precipitation is carried out in the presence -3 -1 growth regulators at concentrations of 10 to 10 moles per mole of silver halides.