EP0047449A2 - Process for the production of colour-photographic images - Google Patents

Abstract

Colored images with metal-complexed azomethine dyes are produced by chromogenic development of color coupler-containing photographic recording materials, using color developer compounds which contain a group capable of chelating adjacent to a primary amino group and converting the generated azomethine dyes into the corresponding azomethine-metal complexes. The complex formation causes a shift in the color tone and an improvement in the light stability.

Description

The invention relates to a method for producing color photographic images, in which azomethine dyes produced by chromogenic development are stabilized by complexation with metal salts. For this purpose, color developer compounds are used which contain a group capable of chelating adjacent to a primary amino group, and the azomethine dyes produced in the chromogenic development are converted into corresponding azomethine dye-metal complexes.

Chromogenic development is usually used to produce color images, in which silver halide emulsion layers exposed to image are developed in the presence of suitable color couplers by means of suitable color-forming developer substances - so-called color developers. Here, the oxidation product of the developer substances which arises in accordance with the silver image reacts with the color coupler to form a dye image.

Aromatic compounds containing at least one primary amino group, in particular those of the p-phenylenediamine type, which give azomethine dyes with the color couplers are usually used as color developers.

• Bei der Entwicklung müssen die Kuppler so schnell wie möglich mit dem Oxidationsprodukt der Farbentwicklerverbindung unter Bildung eines Farbstoffs reagieren. In anderen Worten, die Kuppler müssen eine möglichst hohe Farbkupplungsgeschwindigkeit aufweisen. Weiterhin müssen die bei einer solchen Kupplungsreaktion gebildeten Farbstoffe eine gute Farbtönung sowie eine gute Licht-, Hitze- und Feuchtigkeitsstabilität aufweisen. Weiterhin dürfen die Kuppler die fotografischen Eigenschaften des lichtempfindlichen Aufzeichnungsmaterials nicht durch Wechselwirkung mit dem darin enthaltenen Silberhalogenid und sonstigen fotografischen Zusätzen, z.B. Sensibilisierungsfarbstoffen, beeinträchtigen. Ferner müssen die Kuppler eine gute Lagerungsstabilität aufweisen und sich preisgünstig herstellen lassen.

The color couplers used in color photographic recording materials are usually selected according to the following criteria:

• During development, the couplers must react as quickly as possible with the oxidation product of the color developer compound to form a dye. In other words, the couplers must have the highest possible color coupling speed. Furthermore, the dyes formed in such a coupling reaction must have good color tint and good light, heat and moisture stability. Furthermore, the couplers must not impair the photographic properties of the light-sensitive material by interaction with the silver halide contained therein and other photographic additives, for example sensitizing dyes. Furthermore, the couplers must have good storage stability and be inexpensive to manufacture.

Experience has shown that the azomethine dyes formed have a lower stability to environmental influences than dyes of other dye classes such as light, heat, moisture and oxygen, so that in the past there has been no lack of attempts to use other classes of dyes.

Another possibility is to subsequently stabilize the class of the azomethine dyes that is easily accessible by oxidative coupling by complex formation. Corresponding experiments have already been described in the literature, e.g. were introduced into yellow and purple couplers Imidazo [4,5-h] quinoline residues in order to stabilize them with regard to diffusion resistance and light fastness. [Z. Chem. 15, (1975) Issue 3, p. 113; J. Signal Recording Materials 4, (1976) pp. 125-130; J. Prakt. Chemie 317, 853 (1975)]%. The influence of the absorption by the complexation and the stability of the complexed azomethine dyes was only slight, presumably because the coordination point of the complex formation is relatively far away from the actual chromophore; In addition, the work on the synthesis of such compounds is preparative very expensive.

The object of the invention is to improve the stability of image dyes obtained by chromogenic development.

It has been found that the stability, in particular the lightfastness, of azomethine dyes can be improved by complexing with metals if an additional coordination point and thus the prerequisite for an increased tendency to form complexes is created in the azomethine dye, in particular in the vicinity of the azomethine group formed by chromogenic development, by means of suitable substituents . This can be achieved by using color developers which contain a group capable of chelating adjacent to the primary amino group. When treated with metal salts, the azomethine dyes obtained with such color developers are converted into the corresponding azomethine dye-metal complexes.

• a) Oxidation einer in gleichförmiger Verteilung vorliegenden, mindestens eine primäre Aminogruppe aufweisenden Farbentwicklerverbindung durch bildmäßig belichtetes Silberhalogenid und
• b) Kupplung der oxidierten Farbentwicklerverbindung mit einem in gleichförmiger Verteilung vorliegenden Farbkuppler unter Erzeugung eines aus einem Azomethinfarbstoff bestehenden Farbbildes,
  dadurch gekennzeichnet, daß durch Verwendung einer Farbentwicklerverbindung die benachbart zur primären Aminogruppe eine zur Chelatbildung befähigte Gruppe enthält, die Voraussetzung für eine Metallkomplexierung des chromogen entwickelten Azomethinfarbstoffes geschaffen wird und daß der chromogen entwickelte Azomethinfarbstoff in Gegenwart von Metallsalzen in einen Azomethinfarbstoff-Metall-Komplex umgewandelt wird.

The invention accordingly relates to a method for producing color photographic images by chromogenic development of an imagewise exposed recording material with at least one silver halide emulsion layer, comprising the steps

• a) oxidation of a color developer compound present in uniform distribution and having at least one primary amino group by imagewise exposed silver halide and
• b) coupling the oxidized color developer compound with a color coupler present in a uniform distribution to produce a color image consisting of an azomethine dye,
  characterized in that the use of a color developer compound which contains a group capable of chelating adjacent to the primary amino group creates the conditions for metal complexation of the chromogenically developed azomethine dye and that the chromogenically developed azomethine dye is converted into an azomethine dye-metal complex in the presence of metal salts .

An important characteristic of the invention is therefore the use of special color developer compounds. According to the invention, these have, next to a primary amino group, a group capable of chelating, e.g. in the form of a nitrogen atom or a carbon atom to which a substituent capable of chelating is bound. During chromogenic development, this group capable of chelating comes into the vicinity of the azomething group formed from the primary amino group, which apparently results in a favorable prerequisite for subsequent complex formation with metal ions. The observed intensive color shift speaks for the participation of the chromophoric azomething group in the complex formation.

worin bedeuten

• X einen Rest, der zusammen mit C und Z einen 5- oder 6-gliedrigen, carbocyclischen oder heterocyclischen aromatischen Ring bildet;
• Y einen Substituenten, der zusammen mit NH₂ dem durch C, X und Z gebildeten Ring die Eigenschaften einer Farbentwicklerverbindung verleiht,
• Z ein Kohlenstoffatom, an das eine zur Chelatbildung befähigte Gruppe gebunden ist, oder ein Stickstoffatom.

Color developer compounds according to the invention can thus be described by the following formula I:

in what mean

• X is a radical which together with C and Z forms a 5- or 6-membered, carbocyclic or heterocyclic aromatic ring;
• Y is a substituent which together with NH ₂ imparts the properties of a color developer compound to the ring formed by C, X and Z,
• Z is a carbon atom to which a group capable of chelating is attached, or a nitrogen atom.

In the color developer compounds used in accordance with the invention, the primary amino group is therefore bound to a carbon atom of a 5- or 6-membered carbocyclic or heterocyclic aromatic ring, as in the previously known color developer compounds. The carbocyclic or heterocyclic ring completed by X in formula I is otherwise so procured and substituted by Y and optionally further substituents in a suitable manner, so that a color developer compound results. The best known examples of such color developer compounds are those of the p-phenylenediamine type, which result from formula I when the ring completed by X is a benzene ring and the substituent Y is a disubstituted amino group in the p-position to the primary amino group. In addition, of course, according to the invention, a group capable of chelating adjacent to the primary amino group must also be present. Such color developer compounds are also known from the literature / for example J. Amer. Chem. Soc. 73, 3100 ff (1971), compounds 20 and 27 /, have so far only been investigated with regard to the influence of substituents on the half-level potential. So far nothing has been known about the complex formation behavior of such developers. Compounds of the formula I in which X completes a heterocyclic ring, for example a pyrazolone or isoxazolone ring are described, inter alia, in DE-PS 1 002 627. These color developer compounds already contain, in the form of a group capable of chelating, adjacent to the primary amino group (enolic) hydroxyl group and are therefore directly usable for the process of the present invention. Other examples of color developer compounds of the present invention having an X completed heterocyclic ring include color developer bonds derived from 1,3-diazine.

worin bedeuten

• x¹,x² ein Stickstoffatom oder eine Methingruppe
• Z ' eine zur Chelatbildung befähigte Gruppe _z._B. -OH, -NH-SO₂-CH₃,
  
  
• R¹,R² Alkyl, insbesondere mit 1 bis 4 C-Atomen, z.B. Methyl, Ethyl, n-Propyl, Isopropyl, n-Butyl oder substituierte Alkylreste wie Hydroxyethyl, ω-Hydroxybutyl, ω-Sulfobutyl oder N-Methansulfonylaminoethyl, oder R¹ und R² zusammen den zur Vervollständigung einer cyclischen Aminogruppe (z.B. Pyrrolidino, Piperidino, Morpholino) erforderlichen Rest.

Color developer compounds preferably used according to the invention correspond to the following formula II:

in what mean

• x ¹ , x ^{2 is} a nitrogen atom or a methine group
• Z 'a group capable of chelating _z . _B. -OH, -NH-SO ₂ -CH ₃ ,
  
  
• R ¹ , R ² alkyl, in particular with 1 to 4 carbon atoms, for example methyl, ethyl, n-propyl, isopropyl, n-butyl or substituted alkyl radicals such as hydroxyethyl, ω-hydroxybutyl, ω-sulfobutyl or N-methanesulfonylaminoethyl, or R. ¹ and R ² together the residue necessary to complete a cyclic amino group (eg pyrrolidino, piperidino, morpholino).

Examples of color developers which can be used according to the invention are given below:

As already stated, the color developer compounds used according to the invention have a primary amino group. However, this does not rule out the fact that the primary amino group is initially only latent is there. This means that the primary amino group is in a capped form. from which it is released during the actual chromogenic development, possibly under the influence of alkali, and which is available for the oxidative coupling with the color coupler. Color developer precursor compounds with a latent primary amino group are known, for example, from GB 783 887, US 3,342,599 or DE-AS 1 007 171. Such compounds are particularly suitable for incorporation into color photographic recording materials. To improve the diffusion resistance, the color developer compounds can be equipped with diffusion-proofing radicals which are either in the actual color developer radical (for example in the form of a longer alkyl radical having up to 18 carbon atoms for R ¹ in formula II) or in the radical capping the primary amino group can.

Practically all known color couplers which can be chromogenically developed with known color developer substances can be used as color couplers in the process according to the invention. Color couplers of various types come into question here (4-equivalent coupler, 2-equivalent coupler, DIR coupler, Mask coupler). The prerequisite is that a chromophore azomething group is formed in the chromogenic development.

Examples of yellow couplers are given below:

Yellow couplers give yellow to yellow-orange dyes in the oxidative coupling with the color developers according to the invention having the structure D-1 to D-8.

Suitable purple couplers, for example, have the structure:

Purple couplers generally give red to purple hues with the developers of structure D-1 to D-9; M-11 gives gray and M-12 gives yellow dyes.

Typical examples of cyan couplers are:

Phenolic cyan couplers couple with the color developers D-1 to D-8 according to the invention blue to cyan; naphtholic, on the other hand brown, orange or red. For example, C-5 couples brown-red, C-7 orange and C-8 blue-green.

The color couplers described as examples have in common that they have groups which make them diffusion-resistant in hydrophilic binder layers. Such couplers are generally embedded in a layer of a photographic recording material in a diffusion-resistant manner. The incorporation methods used depend on whether the couplers are hydrophilic couplers or hydrophobic couplers. The corresponding methods are known and do not need to be explained here. The incorporation in the photographic layer, be it a light-sensitive silver halide emulsion layer or a hydrophilic binder layer adjacent to it, ensures a uniform distribution of the Color coupler is produced, from which an image-like distribution of azomethine dyes is formed during the chromogenic development of the light-sensitive material in the presence of the color developer substances according to the invention. According to the method of the present invention, soluble color couplers can be used in the same way, but also according to the so-called development process, which, in contrast to the previously mentioned color couplers, are not incorporated into the layer but are contained in solution in the color developer bath. This method also requires no further explanation at this point. Since the developer bath penetrates uniformly into the imagewise exposed silver halide emulsion layer, a uniform distribution of the color coupler in the layer initially arises here, which results in an imagewise distribution of azomethine dye in the layer during development with oxidative coupling with the color developer substance. The processing is accordingly carried out in the customary manner in that the imagewise exposed recording material is chromogenically developed in the presence of a color coupler. This is followed by the normal process steps, such as bleaching, fixing and watering, which are customary in a photographic processing process, the bleaching and fixing process optionally being able to be combined into a single process step or - for example in the case of very small silver orders - can also be omitted entirely, and depending on the color coupler and color developer used, a colored image is obtained.

A further essential feature of the method according to the invention consists in treating the generated colored image with a solution of a metal salt following the chromogenic development, the corresponding azomethine dye-metal complex being formed. Suitable metal salts here are, in particular, salts of metals from main groups I to IV and groups I and II as well as subgroups IV to VIII of the periodic system of the elements, which are known to be suitable as the central atom of organometallic complexes. Salts of the following metal ions are particularly preferred according to the invention: Ag, Ba ²⁺ , Ca ²⁺ , Mg ²⁺ , Co ²⁺ , Co ³⁺ , Cu ²⁺ , Cr ³⁺ , Fe ²⁺ , Fe ^3+, Ni ^{2+ ,} Zn ²⁺ , Cd ²⁺ , Mn ²⁺ , Sr ²⁺ .

When the azomethine dyes formed from the color couplers described and the color developers according to the invention are treated with metal salt solutions, intensive color changes occur as a result of complex formation, for example from yellow to red, from yellow to black, from yellow to blue. The absorption spectra are only slightly increased with regard to their extinction, but are shifted and broadened considerably bathochromically or hypsochromically in the position of the maxima. In spite of this, dyes are created that are sometimes very brilliant. The resulting colorations depend to a large extent on the structure of the coupler and the metal ion used. The strongest color changes can be observed with yellow dyes. According to the invention, the metal salts come in aqueous Solution for use, wherein the concentration of the metal salts can fluctuate within wide limits, for example between 0.001 and 20% by weight, preferably between 0.1 and 1% by weight. The complexation time can. from 0.1 seconds to 30 minutes and preferably from 3 seconds to 3 minutes, at pH values from 2 to 13. However, it should be noted here that certain buffer solutions contain complex-forming anions (eg citrate, phosphate) which are associated with the azomethine dyes can compete the metal ion, so that sometimes secondary Farbumschlä e ^g be observed.

Layers that contain only extremely low dye concentrations can be "visually enhanced" due to the change in the absorption spectra. Due to the shift in the absorption maximum caused by complexation with metal ions. The method according to the invention provides the possibility of shifting the spectrum of a particular dye which is barely perceptible to the eye into a spectral range, in that the eye has a higher intrinsic sensitivity without the extinction being significantly changed. For example, by using the color change from yellow to black or from yellow to blue, a yellow azomethine dye image that is difficult to perceive by the eye can be converted into a much more clearly visible blue azomethine dye-metal complex image. Except for a postponement of the

The absorption spectrum results from the complexation, a significant improvement in the light stability of the chromogenically produced azomethine dyes. The storage stability in the heating and tropical cupboard also shows clearly. improved values.

The possibility of moving from a silver image to a color-intensive dye image on the way via a chromogenic development opens up advantageous applications for the method according to the invention. For example, it is possible to use a monochromatic recording material which provides a metal complex dye image instead of a silver image. The silver used can be completely recovered from the recording material by bleaching and fixing. In addition, in contrast to conventional black and white recording materials, DIR connections can also be used to improve graininess and sharpness. The method according to the invention is therefore suitable for the production of storable documents and for microphotography. The method of the present invention is particularly interesting for X-ray photography, since the possibility of black metal complex dyes with significantly higher stability (compared with the dyes from the so-called color couplers of the m-aminophenol type according to DE-OS 2 818 363 and DE-OS 2 644 194 ) produce a significant silver saving.

Multi-colored images can also be produced by the method according to the invention, e.g. if multi-layer recording materials with different couplers are used, which after complexing with the same metal ion. deliver different complex dyes.

Instead of a treatment with the metal salt following the chromogenic development, under certain circumstances it is also possible to add the metal salt directly to the developer bath or to store it in a suitable form in a layer of the color photographic recording material. It should be noted, however, that some couplers, but especially purple or yellow couplers, are capable of forming metal complexes even before chromogenic development, so that suitable measures to prevent premature complexation of the color coupler are appropriate.

example 1

1 g of yellow coupler Y-10 was dissolved in a mixture of 3 g of ethyl acetate, 1 g of dibutyl phthalate (oil former) and 0.1 g of di-n-octyl sulfosuccinate (wetting agent). The solution was poured into 100 ml of a 5% gelatin solution emulsified with 30 g of a silver chlorobromide emulsion were added and coated on a polyethylene terephthalate base paper, so that ² per 1 m an order of 1 g of coupler, and 0.7 g of silver (A _G NO ₃ ) resulted. A layer of an instant hardener was drawn over it. The material was exposed and developed at 23 ° C. for 2 minutes in a developer which was obtained by dissolving 4 g of developer D-2 in 400 ml of water and adjusting to pH 13.2 with 600 ml of 1N NaOH. It was then bleached, fixed and watered in a conventional manner. Various strips of the layer thus obtained with a yellow azomethine dye (max. 460 nm) were immersed in 1% strength aqueous metal salt solutions for 1 minute, the color changes given in Table 1 below being obtained. FIG. 1 shows the absorption spectra of the uncomplexed yellow dye (curve 1) and some of the dye-metal complexes formed.

Example 2

As indicated in Example 1, a series of single layers were made and processed with other couplers. The following color changes are observed after treatment with 1% metal salt solutions (Table 2):

Example 3

A material produced according to Example 1, but containing different silver deposits (AgNO ₃ ), was processed with developer D-1 and then post-complexed in 1% CuS04 solution for 1 minute. The results are summarized in Table 3 below.

Because of the shift in the absorption spectrum into a spectral range in which the eye has a higher intrinsic sensitivity, low yellow dye densities can subsequently be "visually enhanced" by complexation.

Example 4

With the color coupler Y-6 a single layer material was produced, exposed and developed as described in example 1 for the yellow coupler Y-10.

The material thus produced was then bathed in a 1% CuS04 solution for 5 minutes and then washed. This created a deep black layer.

When strips of this material were immersed in buffer solution of pH 2-13, color changes from yellow to appeared orange on. On the other hand, if you immerse in hydrochloric acid or sodium hydroxide solutions with the appropriate pH, no color changes are observed.

This shows that the anions present in the buffer solutions (e.g. citrate) compete with the azomethine dye for the metal ion and that, in the absence of such complexing anions, stable metal complex azomethine dyes are formed over a wide pH range.

Example 5

A material produced and processed in accordance with Example 1 was uncomplexed (yellow) and, after complexing with 1% CoC1 ₂ solution or 1% CuS04 solution, was irradiated with 4.8 · 10 ⁷ lux.h in the Xenotest device, resulting in at density 1.5 the following percentage decrease in density

Example 6

A conventional photographic X-ray recording material which additionally contains 1.8 g / m ^{2 of} the yellow coupler Y-10 was exposed to X-rays in a conventional manner and then in a color developer solution which contained 3.0 g / 1 D-1 at pH 13.2 and 23 ° C for 30 seconds.

After the usual bleaching and fixing, the mixture was treated briefly (10 seconds) with a 3% CoCl ₂ solution. An X-ray image of high contrast and good sharpness was taken.

Claims (5)

1. A method for producing color photographic images by chromogenic development of an imagewise exposed recording material with at least one silver halide emulsion layer, comprising the steps a) oxidation of a color developer compound present in a uniform distribution and having at least one primary amino group by imagewise exposed silver halide and b) Coupling of the oxidized color developer compound with a color coupler present in a uniform distribution to produce a color image consisting of an azomethine dye
characterized in that the use of a color developer compound which contains a group capable of chelating adjacent to the primary amino group creates the prerequisites for metal complexation of the chromogenically developed azomethine dye and that the chromogenically developed azomethine dye in the presence of metal salts with the participation of the azomethine group in an azomethine dye. Metal complex is converted. 2. The method according to claim 1, characterized in that a color developer compound of general formula I is used

in what mean X is a radical which together with C and Z forms a 5- or 6-membered carbocyclic or heterocyclic aromatic ring, Y is a substituent which together with NH ₂ imparts the properties of a color developer compound to the ring formed by C, X and Z, Z is a carbon atom to which a group capable of chelating is attached, or a nitrogen atom. 3. The method according to claim 1, characterized in that a color developer compound of the following general formula II is used

in what mean x ¹ , x ² a nitrogen atom or a methine group, Z 'is a group capable of chelating, _R ¹ , _R ² alkyl or _R ¹ and R ² together the residue necessary to complete a cyclic amino group. 4. The method according to claim 1, characterized in that a color developer compound of the following formula is used:

5. The method according to claim 1, characterized in that the chromogenically developed recording material (steps a) and b)) is treated with an aqueous solution which is a salt of a metal of the I. to IV. Main group or the I., II. Or IV. To VIII. Subgroup of the periodic system of the elements contains.

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