EP0254151B1 - Colour photographic material containing couplers - Google Patents

Description

The invention relates to a color photographic material with an emulsified phenolic cyan couplers with a phenylureido structure.

It is known to produce color photographic images by chromogenic development, i. H. by developing imagewise exposed silver halide emulsion layers in the presence of suitable color couplers using suitable color images of the developer substances - so-called color developers - the oxidation product of the developer substances resulting in accordance with the silver image reacting with the color coupler to form a dye image. Aromatic compounds containing primary amino groups, in particular those of the p-phenylenediamine type, are usually used as color couplers.

Naphtholic or phenolic cyan couplers are usually used to produce the cyan partial image. In color photographic recording materials, the former has so far been preferred because of the more favorable absorption (at approx. 700 nm) of the image dyes produced from them in the chromogenic development. In contrast, the phenolic cyan couplers generally provide dyes with an absorption maximum at shorter wavelengths.

Although the naphtholic cyan couplers are ideal from a spectral point of view, particularly when used in color negative films, there is a serious disadvantage in the inadequate stability properties of the dyes, in particular in the poor stability to moisture and heat. In this regard, the phenolic ones are preferable to the naphtholic teal couplers; However, as already mentioned, the dyes produced from them absorb too short-wave and therefore have an undesirable secondary density in the green spectral range which is too high. This leads to desaturated color reproduction in the copying material, unless the excessively high secondary density in the green spectral range in the color negative film is compensated for by additional measures, for example the use of increased amounts of mask coupler.

EP-A-O 028 099 and EP-A-0 067 689 describe phenolic cyan couplers which contain a phenylureido group substituted in the benzene ring in the 2-position of the phenol ring. During color development, these couplers provide dyes with good stability and a comparatively long-wave absorption maximum; however, the absorption maximum for these dyes is generally well below 700 nm, so that in this respect they cannot be compared with the dyes obtained from naphtholic cyan couplers. Rather, these dyes still have too high a secondary absorption in the green spectral range. EP-A-0 184 057 also describes cyan couplers of the 2-phenylureidophenol type which contain a fluorosulfonyl group in the phenylureido group. Although these color couplers represent an optimum with regard to the long-wave absorption of the dyes made from them, there is a disadvantage that the fluorosulfonyl group can apparently react under certain climatic conditions with uncrosslinked amino groups of the gelatin, which can result in a flattening of the gradation.

The invention is based on the object of specifying a color photographic recording material which contains color couplers which, in the chromogenic development, provide a stable blue-green partial color image with an absorption maximum at approximately 700 nm and a low secondary density.

worin bedeuten

• R¹ eine Ballastgruppe
• X H oder eine von Wasserstoff verschiedene, bei Farbkupplung freisetzbare Gruppe
• R², R³ H, R, Cl, -CN, -CF₃ oder -SO₂-R⁴, worin R⁴ für F, Alkyl oder Alkylamino steht, wobei aber R² und R³ nicht beide gleichzeitig H oder -CN sind,

und wobei die Kuppler der Formeln I und II in Mengenverhältnissen zwischen 1:4 und 4:1 eingesetzt werden.The invention relates to a color photographic recording material with at least one silver halide emulsion layer sensitized to the red spectral range, to which a cyan coupler of the 2-phenylureidophenol type is assigned, characterized in that the silver halide emulsion layer sensitized to the red spectral range has at least one cyan coupler of the formula and at least one cyan coupler Formula 11 are assigned

in what mean

• R ^{1 is} a ballast group
• XH or a group other than hydrogen that can be released on color coupling
• R ² , R ³ H, R, Cl, -CN, -CF ₃ or -SO ₂ -R ⁴ , wherein R ^{4 is} F, alkyl or alkylamino, but R ² and R ^{3 are} not both H or -CN at the same time are,

and wherein the couplers of the formulas I and II are used in proportions between 1: 4 and 4: 1.

A releasable group represented by X is, for example, a halogen atom such as F, CI or Br, or an organic group linked via an oxygen atom, a sulfur atom or a nitrogen atom.

An alkyl group contained in R2 or R3 can be straight-chain or branched and contain, for example, 1-18 C atoms.

worin bedeuten:

• Z O oder S;
• R5 eine Methylengruppe oder eine Alkylidengruppe mit 2 bis 20 C-Atomen der Formel
  
• H oder Alkyl bedeutet und wobei Alkyl geradkettig oder verzweigt sein kann;
• R⁶ Halogen, Hydroxy, Carboxy, Alkyl, Cycloalkyl, Aryl, Aralkyl, Alkoxy, Aryloxy, Alkylsulfamoyl, Arylsulfamoyl, Alkylsulfonamido, Arylsulfonamide, Alkylsulfonyl, Arylsulfonyl, Alkoxycarbonyl oder Acyloxy, worin Alkyl 1 bis 20 C-Atome enthält, worin Aryl vorzugsweise eine gegebebenenfalls substituierte Phenylgruppe ist und worin Alkyl, Aryl und Aralkyl auch beliebig mit Alkyl, Hydroxy, Carboxy, Alkoxycarbonyl oder Acyloxy substituiert sein können; und
• m1 -3.
• R¹ kann auch ein Segment aus dem Gerüst eines Polymers sein, das entstanden ist durch Polymerisation eines monomeren Kupplers einer der Formeln I und II, worin R1 für einen Rest steht, der eine polymerisierbare Gruppe enthält. R¹ muß nicht notwendigerweise in beiden Blaugrünkupplern einer bestimmten Kombination von Blaugrünkupplern der Formel I und II identisch sein.

The ballast group represented by R ¹ preferably corresponds to formula III

in which mean:

• ZO or S;
• R5 is a methylene group or an alkylidene group with 2 to 20 C atoms of the formula
  
• Is H or alkyl and where alkyl can be straight-chain or branched;
• R ⁶ halogen, hydroxy, carboxy, alkyl, cycloalkyl, aryl, aralkyl, alkoxy, aryloxy, alkylsulfamoyl, arylsulfamoyl, alkylsulfonamido, arylsulfonamides, alkylsulfonyl, arylsulfonyl, alkoxycarbonyl or acyloxy, in which alkyl contains 1 to 20 carbon atoms, in which aryl preferably one is optionally substituted phenyl group and wherein alkyl, aryl and aralkyl can also be substituted as desired with alkyl, hydroxy, carboxy, alkoxycarbonyl or acyloxy; and
• m1 -3.
• R ¹ can also be a segment from the backbone of a polymer which is formed by polymerizing a monomeric coupler of one of the formulas I and II, in which R1 is a radical which contains a polymerizable group. R ¹ does not necessarily have to be identical in both cyan couplers of a certain combination of cyan couplers of the formula I and II.

Examples of cyan couplers of the general formulas I and II, from which combinations according to the invention can be put together, are listed below.

Couplers of the general formula can be prepared by methods which are known in principle, e.g. B. by reacting 3,4-dicyanophenyl isocyanate or phenyl-3,4-dicyanophenyl carbamate with a suitable 2-aminophenol; Such methods are described, for example, in EP-A-0 028 099, EP-A-0 067 689, EP-A-0 175 573 and EP-A-0 184 057. The 3,4-dicyanophenyl isocyanate required as an intermediate can, for example, be like are produced as follows:

A solution of 143 g (1 mol) of 3,4-dicyanoaniline in 800 ml of acetonitrile is dropped into a template from 150 g of phosgene in 750 ml of toluene while cooling at 0-5 _° C. With further introduction of phosgene and a successive increase in temperature up to 95 _° C. while simultaneously distilling off the acetonitrile, the 3,4-dicyanophenylcarbamide chloride initially formed is converted into the 3,4-dicyanophenyl isocyanate with elimination of hydrogen chloride. When the evolution of hydrogen chloride has ended, the toluene is distilled off in vacuo and replaced by 750 ml of anhydrous ethyl acetate.

The yield, determined by volumetric NCO determination, is 93-94% of theory.

Couplers of the general formula 11 are described, for example, in EP-A-0 028 099, EP-A-0 067 689, EP-A-O 175 573 and EP-A-0 184 057.

Usable results are obtained if the couplers of the general formulas I and 11 are used in a combined ratio of between 1: 4 and 4: 1.

In the preparation of the color photographic light-sensitive material, the combination of the diffusion-resistant cyan couplers of the present invention can be incorporated in the casting solution of the silver halide emulsion layers or other colloid layers in a known manner. For example, the preferably oil-soluble or hydrophobic couplers can be added to a hydrophilic colloid solution from a solution in a suitable coupler solvent (oil former), if appropriate in the presence of a wetting or dispersing agent. The hydrophilic casting solution can of course contain other conventional additives in addition to the binder. The solution of the couplers need not be directly dispersed in the casting solution for the silver halide emulsion layer or other water permeable layer; Rather, it can also be advantageously first dispersed in an aqueous, non-photosensitive solution of a hydrophilic colloid, whereupon the mixture obtained, after removal of the low-boiling organic solvents used, may be mixed with the coating solution for the photosensitive silver halide emulsion layer or another water-permeable layer before application.

Suitable light-sensitive silver halide emulsions are emulsions of silver chloride, silver bromide or mixtures thereof, possibly with a low silver iodide content of up to 10 mol% in one of the commonly used hydrophilic binders. Gelatin is preferably used as a binder for the photographic layers. However, this can be replaced in whole or in part by other natural or synthetic binders.

The emulsions can be chemically and spectrally sensitized in the usual way, and the emulsion layers as well as other non-light-sensitive layers can be hardened in the usual way with known hardening agents.

Color photographic recording materials usually contain at least one silver halide emulsion layer for recording light from the three spectral ranges red, green and blue. For this purpose, the light-sensitive layers are spectrally sensitized in a known manner by means of suitable sensitizing dyes. Blue-sensitive silver halide emulsion layers do not necessarily have to contain a spectral sensitizer, since in many cases the intrinsic sensitivity of the silver halide is sufficient for the recording of blue light.

Each of the light-sensitive layers mentioned can consist of a single layer or, in a known manner, for example in the case of the so-called double-layer arrangement, also comprise two or more silver halide emulsion partial layers (DE-C-1 121 470). Usually, red-sensitive silver halide emulsion layers are arranged closer to the layer support than green-sensitive silver halide emulsion layers and these are in turn closer than blue-sensitive layers, a yellow filter layer which is not sensitive to light generally being located between green-sensitive layers and blue-sensitive layers. However, other arrangements are also conceivable. A layer which is not sensitive to light is generally arranged between layers of different spectral sensitivity and can contain means for preventing the incorrect diffusion of developer oxidation products. If several silver halide emulsion layers with the same spectral sensitivity are present, can these are directly adjacent to one another or be arranged such that a light-sensitive layer with a different spectral sensitivity is located between them (DE-A-1 958 709, DE-A-2 530 645, DE-A-2 622 922).

Color photographic recording materials for producing multicolored images usually contain, in spatial and spectral assignment to the silver halide emulsion layers of different spectral sensitivity, coloring compounds, here in particular color couplers, for producing the different partial color images cyan, purple and yellow.

Spatial assignment is understood to mean that the color coupler is in such a spatial relationship with the silver halide emulsion layer that an interaction between them is possible which allows an image-wise match between the silver image formed during development and the color image generated from the color coupler. This is usually achieved by the fact that the color coupler is contained in the silver halide emulsion layer itself or in a possibly non-light-sensitive binder layer adjacent to it.

Spectral assignment is understood to mean that the spectral sensitivity of each of the light-sensitive silver halide emulsion layers and the color of the partial color image generated from the spatially assigned color coupler are in a specific relationship to one another, with each of the spectral sensitivities (red, green, blue) having a different color of the relevant partial color image (e.g. teal, purple, yellow) is assigned.

One or more color couplers can be assigned to each of the differently spectrally sensitized silver halide emulsion layers. If there are several silver halide emulsion layers of the same spectral sensitivity, each of them can contain a color coupler, which color couplers need not necessarily be identical. They should only result in at least approximately the same color during color development, normally a color that is complementary to the color of the light, for which the silver halide emulsion layers in question are predominantly sensitive.

In preferred embodiments, red-sensitive silver halide emulsion layers are therefore assigned at least one non-diffusing color coupler for producing the blue-green partial color image, in the present case at least one coupler of the formulas I and 11. Green-sensitive silver halide emulsion layers are assigned at least one non-diffusing color coupler for producing the purple partial color image, usually color couplers of the type 5-pyrazolone, indazolone or pyrazoloazole can be used. Finally, blue-sensitive silver halide emulsion layers are assigned at least one non-diffusing color coupler for producing the yellow partial color image, usually a color coupler with an open-chain ketomethylene grouping. Color couplers of this type are known in large numbers and are described in a large number of patents. Examples include the publications "Farbkuppler" by W. PELZ in "Mitteilungen aus der Forschungslaboratorien der Agfa, Leverkusen / München", volume 111, page 111 (1961) and by K. VENKATARAMAN in "The Chemistry of Synthetic Dyes", Vol 4, 341 to 387, Academic Press (1971).

The color couplers can be either conventional 4-equivalent couplers or 2-equivalent couplers, which require a smaller amount of silver halide to produce the color. As is known, 2-equivalent couplers are derived from the 4-equivalent couplers in that they contain a substituent in the coupling point which is split off during the coupling. The 2-equivalent couplers include both those that are practically colorless and those that have an intense inherent color that disappears when the color is coupled or is replaced by the color of the image dye produced. The latter couplers can also be present in the light-sensitive silver halide emulsion layers and serve there as mask couplers to compensate for the undesired secondary densities of the image dyes. However, the known white couplers are also to be counted among the 2-equivalent couplers, but they do not give any dye on reaction with color developer oxidation products. Among the 2-equivalent couplers are also the known DIR couplers, which are couplers which contain a detachable residue in the coupling point, which is released as a diffusing development inhibitor when reacted with color developer oxidation products. Other photographically active compounds, e.g. Development accelerators or fogging agents can be released from such couplers during development.

In addition to the constituents mentioned, the color photographic recording material of the present invention can contain further additives, for example antioxidants, dye-stabilizing agents and agents for influencing the mechanical and electrostatic properties. In order to reduce or avoid the disadvantageous action of UV light on the color images produced with the color photographic recording material according to the invention, it is advantageous to use UV-absorbing compounds in one or more of the layers contained in the recording material, preferably in one of the upper layers to use. Suitable UV absorbers are described for example in US-A-3 253 921, DE-C-2 036 719 and EP-A-1 057 160.

The usual layer supports can be used for the materials according to the invention, see Research Disclosure No. 17 643, Section XVII.

The usual hydrophilic film-forming agents, for example proteins, in particular gelatin, are suitable as protective colloids or binders for the layers of the recording material. Casting aids and Plasticizers can be used. Reference is made to the compounds indicated in Research Disclosure 17,643 above in Sections IX, XI and XII.

The layers of the photographic material can be hardened in the usual manner, for example with hardeners of the epoxy type, the heterocyclic ethylene imine and the acryloyl type. Furthermore, it is also possible to harden the layers in accordance with the process of German Offenlegungsschrift 2 218 009 in order to obtain color photographic materials which are suitable for high-temperature processing. It is also possible to harden the photographic layers with hardeners of the diazine, triazine or 1,2-dihydroquinoline series or with hardeners of the vinyl sulfone type. Further suitable hardening agents are known from German Offenlegungsschriften 2,439,551, 2,225,230, 2,317,672 and from Research Disclosure 17,643, Section XI, given above.

Further suitable additives are given in Research Disclosure 17 643 and in "Product Licensing Index" from December 1971, pages 107-110.

For the production of color photographic images, the color photographic recording material according to the invention is developed with a color developer compound. All developer compounds which have the ability in the form of their oxidation product to react with color couplers to form azomethine dyes can be used as the color developer compound. Suitable color developer compounds are aromatic compounds of the p-phenylenediamine type containing at least one primary amino group, for example N, N-dialkyl-p-phenylenediamines, such as N, N-diethyl-p-phenylenediamine, 1- (N-ethyl-N-methylsulfonamidoethyl) -3 -methyl-p-phenylenediamine, 1- (N-ethyl-N-hydroxyethyl-3-methyl-p-phenylenediamine and 1- (N-ethyl-N-methoxyethyl) -3-methyl-p-phenylenediamine.

Other useful color developers are described, for example, in J. Amer. Chem. Soc. 73, 3100 (1951) and in G. Haist, Modern Photographic Processing, 1979, John Wiley and Sons, New York, pages 545 ff.

After color development, the material is usually bleached and fixed. Bleaching and fixing can be carried out separately or together. The usual compounds can be used as bleaching agents, for example Fe ^{3 +} salts and Fe ^{3 +} complex salts such as ferricyanides, dichromates, water-soluble cobalt complexes, etc. Particularly preferred are iron III complexes of aminopolycarboxylic acids, in particular, for example, ethylenediaminetetraacetic acid, N-hydroxyethylethylenediamine triacetic acid, alkyliminodicarboxylic acids and of corresponding phosphonic acids. Persulphates are also suitable as bleaching agents.

example 1

0.045 mol of color coupler, as indicated in Table 1, was dispersed with 16 g of dibutyl phthalate in 200 ml of 10% gelatin solution and mixed with 1 kg of a red-sensitized silver bromide iodide emulsion (5 mol% iodide) from 129 g AgNOs and 45 g gelatin. The mixture was then poured onto a cellulose triacetate film with a silver coating (AgNOs / m ^z ) of 3.2 g. After curing with a carbamoylpyridinium salt (CAS Reg.-No. 65411-60-1) over an additional protective layer, the material thus produced was exposed behind a gray wedge and, as in Brit. J. of Photographie, 1974, p. 597. At D = 1.0 (red filter status M), the percentage magenta density (green filter status M) and the wavelength of the absorption maximum were determined (Table 1).

Table 1 shows that not only can the desired absorption maximum of 700 ± 2 nm be set fairly accurately with the combination according to the invention, but also much lower secondary densities are obtained.

Example 2

Layers were produced as in Example 1. Instead of the reference couplers called there, the reference couplers shown in Table 2 were used in comparison to the combination according to the invention. A part of the materials produced in this way was kept at 60 _° C. and 35% RH for 7 days. F. stored. The other part was kept at normal room temperature. The materials were then gradually exposed and processed as usual. It can be seen from Table 2 that the comparison couplers are in the desired absorption range, but that after storage at elevated temperature - as a simulation for long-term storage at room temperature - they show a high loss of maximum density compared to the combinations according to the invention.

Example 3

A color photographic recording material for color negative development was prepared by applying the following layers in the order given to a transparent cellulose triacetate support. The quantities given relate to 1 m ² . For the Silver halide application, the corresponding amounts of AgN0 ₃ are given. All silver halide emulsions per 100 g of AgNO _{3 were} stabilized with 0.5 g of 4-hydroxy-6-methyl-1,3,3a, 7-tetraazaindene.

Layer 1 (antihalo layer)

Black colloidal silver sol with 0.32 g Ag and 2.2 g gelatin.

Layer 2 (intermediate layer)

0.3 g gelatin.

Layer 3 (1st red-sensitized layer)

• 2,4 g AgNO₃,
• 0,9 mmol Blaugrünkuppler (Tabelle 3)
• 0,06 g Rotmaske MR-1
• 0,025 g DIR-Kuppler DC-1
• 1,2 g Gelatine

red-sensitized silver chloride bromide iodide emulsion (5 mol% iodide; 2 mol% chloride; average grain diameter 0.5 µm)

• 2.4 g AgNO ₃ ,
• 0.9 mmol cyan coupler (Table 3)
• 0.06 g MR-1 red mask
• 0.025 g DIR coupler DC-1
• 1.2 g gelatin

Layer 4 (2nd red-sensitized layer)

• 2,9 g AgNO₃,
• 0,25 mmol Blaugrünkuppler
• 0,02 g der Rotmaske MR-1
• 0,04 g der DIR-Verbindung DC-2

red-sensitized silver bromide iodide emulsion (10 mol% iodide; average grain diameter 0.8 µm)

• 2.9 g AgNO ₃ ,
• 0.25 mmol cyan coupler
• 0.02 g of the MR-1 red mask
• 0.04 g of the DIR compound DC-2

Layer 5 (intermediate layer)

0.9 g gelatin

Layer 6 (1st green-sensitized layer)

• 2,2 g AgNOs,
• 0,65 g Purpurkuppler M-1
• 0,04 g DIR-Kuppler DC-3
• 0,02 g Gelbmaske MY-1
• 1,4 g Gelatine

green-sensitized silver bromide iodide emulsion (5 mol% iodide; average grain diameter 0.4 µm)

• 2.2 g AgNOs,
• 0.65 g purple coupler M-1
• 0.04 g DIR coupler DC-3
• 0.02 g yellow mask MY-1
• 1.4 g gelatin

Layer 7 (2nd green-sensitized layer)

• 2,7 g AgNO₃,
• 0,17 g Purpurkuppler M-1
• 0,04 g Gelbmaske MY-1
• 1,6 g Gelatine

green-sensitized silver bromide iodide emulsion (10 mol% iodide; average grain diameter 0.8 µm)

• 2.7 g AgNO ₃ ,
• 0.17 g purple coupler M-1
• 0.04 g yellow mask MY-1
• 1.6 g gelatin

Layer 8 (yellow filter layer)

yellow colloidal silver sol with 0.07 g Ag and 0.32 g gelatin

Layer 9 (1st blue sensitive layer)

• 0,95 g AgNO₃,
• 0,96 g Gelbkuppler Y-1
• 1,4 g Gelatine

Silver bromide iodide emulsion (3 mol% iodide; average grain diameter 0.3 µm)

• 0.95 g AgNO ₃ ,
• 0.96 g yellow coupler Y-1
• 1.4 g gelatin

Layer 10 (2nd blue sensitive layer)

• 1,0 g AgNO₃,
• 0,22 g Gelbkuppler Y-1
• 1,6 g Gelatine

Silver bromide iodide emulsion (8 mol% iodide; average grain diameter 0.8 µm)

• 1.0 g AgNO ₃ ,
• 0.22 g yellow coupler Y-1
• 1.6 g gelatin

Layer 11 (protective layer)

• 1.1 g gelatin and
• 0.8 g of UV absorber UV-1

Layer 12 (protective layer)

• 0.8 g gelatin

Layer 13 (hardening layer)

• 0.3 g gelatin and
• 0.9 g hardening agent [CAS Reg.-No. 65411-60-1]

The formulas of the compounds used in Example 3 are listed below:

Different versions of the recording material of the structure described were produced which differ only in the cyan coupler incorporated in layer 3 and layer 4.

General dispersion instructions for the cyan couplers.

100 g of coupler were dissolved together with 80 g of dibutyl phthalate in 300 ml of ethyl acetate and at 50 ° C. in 1.3 l of 7.5% gelatin, likewise heated to 50 _° C., which was additionally mixed with 10 g of sodium dodecylbenzene sulfonate. emulsified. The low-boiling solvent was then removed in vacuo and the remaining dispersion solidified at 6 _° C.

The color chart described by U. Vielmuth, Fernseh- und Kino-Technik 1/1979, p. 21, was exposed on the various materials. After processing as described in Example 1, the corresponding negatives were copied onto Agfacolor paper type 8 (technical data A 81 from Agfa Gevaert AG). Then the green and magenta reproduction was evaluated colorimetrically according to DIN 6174 in the CJELAB 1976 system. From Table 3 it can clearly be seen that the saturation of green and magenta is significantly higher in the combinations according to the invention than in the comparative examples.

The saturation of the combinations according to the invention is in some cases even higher than in the experiment in which the naphtholic cyan coupler of the formula V-1 with ideal absorption properties but very poor dark stability of the dev. Dye, was used as a comparative coupler.

Claims (2)

1. A colour photographic recording material comprising at least one silver halide emulsion layer sensitized for the red spectral region with which a cyan coupler of the 2-phenylureidophenol type is associated, characterized in that at least one cyan coupler corresponding to formula I and at least one cyan coupler corresponding to formula II

in which

R¹ is a ballast group,

X represents H or a group different from hydrogen which is releasable during the colour coupling reaction,

R², R³ represent H, F, Cl, -CN, -CF₃ or -SO₂-R⁴, where R₄ is F, alkyl or alkylamino, but are not both H or -CN,

are associated with the silver halide emulsion layer sensitized for the red spectral region, the couplers corresponding to formulae I and II being used in quantitative ratios of 1:4 to 4:1.

2. A recording material as claimed in claim 1, characterized in that, in at least one of the cyan couplers corresponding to formula I and II, R¹ is a ballast group corresponding to formula III

in which

Z is 0 or S,

R⁵ is a methylene group or a C_2-20 alkylidene group corresponding to the formula

where R⁷ is H or linear or branched alkyl:

R6 is halogen, hydroxy, carboxy, alkyl, cycloalkyl, aryl, aralkyl, alkoxy, aryloxy, alkylsulfamoyl, arylsulfamoyl, alkylsulfonamido, arylsulfonamido, alkylsulfonyl, arylsulfonyl, alkoxycarbonyl or acyloxy, where alkyl contains 1 to 20 C atoms and alkyl, aryl and aralkyl may also be substituted as required by alkyl, hydroxy, carboxy, alkoxycarbonyl or acyloxy, and

m = 1-3.