EP0275234A2 - Layers for photographic materials - Google Patents

Abstract

Schichten für photographische Materialien, die ein Polysaccharid enthalten.

Description

The present invention relates to layers for photographic materials.

Photographic materials usually contain one or more gelatin-containing layers on a support, at least one of these layers being photosensitive. Silver halide emulsions are present in the light-sensitive layers, each of which can be sensitized to light of a specific wavelength. In addition to silver halide, these layers may have other components, such as e.g. Color couplers, image dyes or filter dyes.

The light-sensitive layers can be arranged in the vicinity of light-insensitive gelatin layers, so-called auxiliary layers.

Auxiliary layers in photographic materials are free of photosensitive components. They usually contain only gelatin and can perform a wide variety of functions in the material in this form or with suitable additives, such as filter dyes. Depending on the arrangement of the auxiliary layers in the material, they are referred to as lower, intermediate or protective layers.

Auxiliary layers are necessary in photographic materials for various reasons, e.g. for the spatial separation of neighboring light-sensitive layers, for preventing undesired interactions, for promoting adhesion with the layer support or as protective layers against mechanical injuries.

Auxiliary layers, in particular sublayers, can also be used to eliminate a phenomenon called "mottle", which is particularly disturbing in the form of density fluctuations in the form of density fluctuations. In this regard, it should be noted that polyethylene-coated papers which are used as supports are generally not completely flat, but have a surface structure. This surface structure is almost compensated for by the application of photographic casting solutions and in this way causes local differences in the application weight, which are expressed as "mottle" in the processed material. This effect can be suppressed if the support is first applied to the support using the method described in Research Disclosure, November 1984, 24844, which is only poured with the solutions of the upper layers of the layered ensemble in the solidified but not yet dried state.

Auxiliary layers, however, increase the total layer thickness of the photographic material, which reduces the processing and drying speed. It is therefore advantageous if the thickness of the auxiliary layers can be kept to a minimum. For the same reasons, efforts are also being made to keep the thickness of the light-sensitive layers as small as possible.

For reasons of casting technology, however, it is extremely difficult to produce such thin layers, since the corresponding casting solutions have a very low viscosity. Multi-layer casting processes such as cascade or curtain casting, however, require a coordinated viscosity of the different casting solutions to be applied simultaneously, since otherwise the layers will mix or other casting problems will occur.

Thin gelatin layers, which are to be poured on further in the solidified state according to the method described above, melt easily again, for example, which naturally impairs their function.

Another problem arises from the low gelatin concentration of such casting solutions: the rate of solidification of gelatin-containing casting solutions decreases very rapidly as the gelatin concentration decreases, and below a critical concentration they no longer solidify. As a result, layers that have been produced with such very low-viscosity casting solutions are blown off by the air circulating in the dryer in the drying step that takes place on the coating and therefore have an intolerable casting quality.

It is therefore an object of the present invention to propose thin layers for photographic materials which, in spite of their low gelatin content, do not differ from conventional gelatin-rich layers with regard to the length of the setting time and the strength of the gel formed during the setting, and which are also easy and inexpensive can be produced without casting problems.

An alternative to the mottle suppression method mentioned at the outset is to use extremely highly viscous casting solutions for the image-determining layers. As a result, the compensation process leading to the smoothing of the carrier surface can be suppressed to such an extent that it does not interfere with the image, but problems that are difficult to solve, for example relating to the degassing of the casting solutions, have to be accepted. It would therefore be much more advantageous to use low- to medium-viscosity casting solutions that solidify so quickly that local differences in the application weight cannot form on the surface of structured supports.

A further object of the present invention is therefore to propose photographic layers which gel within a very short time when they come into contact with the support.

It has now surprisingly been found that the objects mentioned can be achieved if specific polysaccharides are used to produce the layers.

The present invention thus relates to layers for photographic materials, characterized in that they contain a polysaccharide which is formed extracellularly by bacterial fermentation of glucose, maltose, sucrose or xylose, optionally in the presence of yeast, or yeast or casein hydrolyzate, and with gives mono-, bi- and / or trivalent metal ions gels whose solidification temperature is between 24 and 45 ° C.

Further objects of the invention are the use of these polysaccharides in layers, in particular in auxiliary layers of photographic materials, photographic materials containing these layers, and also a method for increasing the rate of solidification of gelatin-containing photographic layers.

The polysaccharides which can be used according to the invention can be obtained from the carbohydrates mentioned, if appropriate in the presence of the nitrogen sources also mentioned. They form both with mono- and / or with di- and / or trivalent metal ions, preferably alkali and alkaline earth metal ions such as Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ but also B³⁺ and Al³⁺ and transition metal ions such as Zn²⁺, Cu²⁺ and Ni²⁺ gels, the mechanical strength (gel strength) of which can be changed within wide limits by the respective composition of the corresponding casting solution. This also applies to the solidification temperature of the casting solution, which according to the invention is between 30 and 45 ° C., that is to say significantly higher than is typical for gelatin solutions (12 to 25 ° C.). After falling below the solidification temperature one finds - with sufficiently large metal ion concentration - already after gel times of up to about 5 seconds gel strengths, which can only be achieved with gelatin solutions, if at all, after considerably longer times (more than 10 seconds).

The pronounced ability of the casting solutions according to the invention for rapid gel formation at a temperature which is significantly higher than that of gelatin solutions is surprisingly retained even if the polysaccharide is mixed with comparatively large amounts of gelatin or other casting solution components such as silver halide emulsions, image dyes, color couplers, UV absorbers, hardeners, etc. .

Gellan gum has proven to be a particularly advantageous polysaccharide for use in the layers according to the invention. Gellan Gum is a polysaccharide known from the literature, which is obtained by aerobic biodegradation of a suitable fermentation medium using Pseudomonas elodea. The production and characterization of gellan gum and its use in the food industry are described, for example, in US 4,326,052, US 4,326,053, US 4,503,084, Carbohydrate Research, 124 (1983), pages 135 to 139, Food Technology, Vol. 37, April 1983, pages 63 to 70 or Gum and Stabilizers for the Food Industry, 2 (1984), pages 201 to 210. There are no references to photographic use in these publications.

Only the deacetylated form of the Gellan gum is of importance for the present invention, which e.g. is marketed as GELRITE or K3A 123 by Merck & Co., Inc., Kelco Division, USA. The clarified deacetylated form is preferably used by Gellan Gum.

Another suitable polysaccharide is the fermentation product referred to as XM-6 in US-A-4,638,059. The preparation and properties of this polysaccharide are mentioned in this patent. However, there are no indications of a photographic application.

Pouring solutions containing Gellan Gum, depending on the concentration of this polysaccharide, have a pronounced solidification hysteresis relative to other components in the casting solutions, i.e. the melting or remelting temperature of the gel, which is usually above 70 ° C, is significantly higher than the solidification temperature. In contrast, casting solutions that contain XM-6 are thermoreversible.

To produce the layers according to the invention, the polysaccharide is preferably used in the form of aqueous solutions. The concentrations of these solutions are preferably 0.05 to 2.0, in particular 0.1 to 1.0 percent by weight. Solidification rate, solidification temperature and remelting temperature are caused by ions of mono-, di- and / or trivalent metals such as Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Ba²⁺, Sr²⁺, B³⁺, Al³⁺, Zn²⁺, Cu²⁺ and Ni²⁺ controllable in a wide range. In general, 2 to 40 mmol of monovalent metal salts or 0.05 to 5 mmol of divalent or 0.02 to 0.2 mmol of trivalent metal salts can be added per 100 g of aqueous solution.

Instead of the polysaccharide alone, its mixtures with gelatin can optionally also be used in the production of photographic layers. Polysaccharide and gelatin are then preferably present in a weight ratio of 2: 1 to 1: 150, in particular 2: 1 to 1:70 and especially 1: 2 to 1:50. The solidification and remelting temperature of such solutions depend on the concentration of gelatin, polysaccharide and the concentration and type of metal ions added.

The additives known from the prior art, such as, for example, the wetting agents known from Research Disclosure, December 1978, 17643, XI, can also be added to the casting solutions.

The layers that can be produced with these casting solutions can have a very small dry layer thickness. Layers with dry layer thicknesses of 0.05 to 2, especially 0.05 to 1.00 µm are of great importance in many cases. Such layers are particularly suitable as underlayers in photographic materials, preferably silver color bleaching materials. Gellan Gum has proven particularly useful for use in the underlayers of silver color bleaching materials.

Casting solutions with a gelatin concentration of 0 to 1.5 percent by weight are suitable for the production of layers with very low dry layer thicknesses. As can be seen from example 4, they form gels with remarkably high strength very quickly, whereas corresponding solutions without polysaccharide do not gel even after a very long waiting time and are therefore unusable.

The polysaccharides which can be used according to the invention also enable the production of casting solutions which solidify immediately after contact with an uncoated or already coated support. For this purpose, the mixing temperature that is currently set when the warm casting solution is applied to the cold carrier must be below the solidification temperature of the casting solution. Furthermore, the casting solution must have the ability to solidify very quickly. The mixing temperature is determined by the initial temperature and heat capacity of the optionally precoated film carrier as well as the initial temperature, application amount and specific heat of the casting solution. If, for example, one chooses 20 to 25 ° C for the initial temperature of the film carrier and 40 ° C for that of the casting solution, the mixing temperatures under the conditions of multiple cascade casting, for example, are between 27 and 35 ° C. The solidification temperature of the casting solution should therefore be brought in the range of 28 to 38 ° C, for example by metal ions. By cooling the layer support in front of the first casting point, the application quantity can be increased without increasing the mixing temperature. Corresponding casting solutions preferably contain mixtures of polysaccharide and gelatin.

Layers of polysaccharide and mixtures of polysaccharide and gelatin adhere well to the supports customary in photography, as described, for example, in Research Disclosure, December 1978, 17643, XVII. They also show good compatibility with gelatin layers.

The swelling factor, which is about 8 to 10 without curing, can be reduced to values of 2 to 4 by reaction with the hardening agents customary in photography, which are summarized, for example, in Research Disclosure, December 1978, 17643, X. On the other hand, the layers according to the invention in an uncured or partially cured state can also contribute to increasing the swelling volume of the material.

In the simplest case, photographic material according to the present invention contains at least one light-sensitive layer which has one of the polysaccharides mentioned on a support. Other light-sensitive layers and also auxiliary layers can also contain a polysaccharide. Materials which contain said polysaccharide only in auxiliary layers are also photographic materials according to the present invention. In this context, photographic material can be understood to mean all customary photographic materials, e.g. Chromogen materials, color diffusion transfer materials and especially silver color bleaching materials.

Preferred photographic material according to the present invention is silver color bleaching material which contains on a support at least one light-sensitive layer, at least one layer containing a bleachable image dye and at least one layer according to the invention as an auxiliary layer or at least one light-sensitive layer containing a bleachable image dye and at least one layer according to the invention as an auxiliary layer . In such materials, the auxiliary layer is preferably an underlayer.

• Figur 1: Messapparatur zur Bestimmung der Erstarrungsgeschwindigkeit und Gelfestigkeit
• Figur 2: Erstarrungstemperatur eines Gemisches aus Gellan Gum und Gelatine in Abhängigkeit von der Konzentration an Kalium­ionen
• Figur 3: Abhängigkeit der Gelfestigkeit von der Abkühlzeit für Unterkühlung um 4,5, 9,5 und 27°C für eine Gelatinelösung, die 0,15 g Gellan Gum/100 g Lösung enthält.
• Figur 4: Abhängigkeit der Gelfestigkeit von der Abkühlzeit für Unterkühlung um 4,1, 8,6 und 30°C für eine Gelatinelösung, die 0,30 g Gellan Gum/100 g Lösung enthält.

The solidification properties of the casting solutions used to produce the layers according to the invention are described in the following examples. The figures belonging to these examples relate to:

• Figure 1: Measuring apparatus for determining the solidification rate and gel strength
• Figure 2: Solidification temperature of a mixture of gellan gum and gelatin depending on the concentration of potassium ions
• Figure 3: Dependence of the gel strength on the cooling time for subcooling at 4.5, 9.5 and 27 ° C for a gelatin solution containing 0.15 g of Gellan Gum / 100 g of solution.
• Figure 4: Dependence of the gel strength on the cooling time for subcooling by 4.1, 8.6 and 30 ° C for a gelatin solution containing 0.30 g of Gellan Gum / 100 g of solution.

To determine the rate of solidification and gel strength, 500 µl of the solution to be tested are placed in the measuring cuvette (2) of 2 x 2 cm², which is made of brass and can be tempered by means of PELTIER cooling or heating (1). The temperature of the 1250 µm thick solution layer is measured with a calibrated thermocouple. At time t = 0, the target temperature is lowered from its initial value (40 or 45 ° C) to the desired final value (usually 7.5 ° C). After a - systematically varied - waiting time t, a test specimen made of iron (base area 0.5 cm², mass 2.7 g) (4) held by a magnetic coil (3) in its rest position d₀ = 1450 µm is then left on (4) the underside is thermally insulated by a layer of polyacrylic glass onto which the gel forms. The resulting position d above the cell bottom is recorded with the help of an inductive distance sensor (5) and by a Double recorder (6) - together with the actual temperature - registered. The higher the end position above the cell base, the greater the gel strength: d is therefore a direct measure of the gel strength.

If you bring the solution temperature back to the initial value, you can see immediately whether and if so at what temperature the gel can be melted again. On the other hand, if the cooling time is kept at a fixed value of about 10 seconds, the limit temperature at which the position d begins to deviate from zero, at which the gelling process begins, can be determined by systematically changing the respectively set temperature.

The following examples illustrate the invention without restricting it.

Example 1: Production of a sub-layer made of Gellan gum with a dry layer thickness of 0.12 µm

enthält,
eine Gelatinezwischenschicht aus 1,5 g/m² Gelatine,
eine grünempfindliche Schicht, die pro m² 2,00 g Gelatine, 0,27 g Silber als Silberbromojodidemulsion mit 2,6 Mol % Jodid und 162 mg des Magentafarbstoffs der Formel

enthält,
eine Filtergelbschicht aus 0,04 g/m² Kolloidsilber und 0,054 g/m² des Gelbfarbstoffs der Formel

eine blauempfindliche Schicht, die pro m² 0,90 g Gelatine, 0,22 g Silber als Silberbromojodidemulsion mit 2,6 Mol% Jodid und 80 mg des Farbstoffs der Formel (102) enthält, und
eine Gelatineschutzschicht aus 0,8 g/m² Gelatine.To produce a photographic material for the silver color bleaching process, the following layers are applied to a polyethylene-coated paper support:
an underlayer containing 0.12 g GELRITE and 30 mg magnesium sulfate per m²,
a red-sensitive layer containing 1.20 g gelatin and 0.30 g silver per m² as a silver bromoiodide emulsion with 2.6 mol% iodide and 140 mg of the cyan dye of the formula

contains
an intermediate gelatin layer of 1.5 g / m² gelatin,
a green-sensitive layer containing 2.00 g of gelatin, 0.27 g of silver as a silver bromoiodide emulsion with 2.6 mol% of iodide and 162 mg of the magenta dye of the formula per m²

contains
a filter yellow layer of 0.04 g / m² of colloidal silver and 0.054 g / m² of the yellow dye of the formula

a blue-sensitive layer which contains 0.90 g of gelatin, 0.22 g of silver as silver bromoiodide emulsion with 2.6 mol% of iodide and 80 mg of the dye of the formula (102) per m², and
a protective gelatin layer made of 0.8 g / m² gelatin.

The material also contains 100 mg / m² of the gelatin hardener 2,4-dichloro-6-hydroxytriazine.

The material is exposed in the usual way behind a step wedge and processed as follows:
Development 1.5 minutes
Soak 0.5 minutes
Silver and color bleaching for 1.5 minutes
Soak 0.5 minutes
Fixation for 1.5 minutes
Soak 3.0 minutes
Drying
The temperature of the corresponding baths is 30 ° C.

The developer bath contains the following components per liter of solution:
Sodium sulfite 3.0 g
Potassium sulfite 19.9 g
Lithium sulfite 0.6 g
1-phenyl-3-pyrazolidinone 1.0 g
Hydroquinone 12.0 g potassium carbonate 29.1 g
Potassium bromide 1.5 g
Benzotriazole 0.5 g
Ethylenediaminetetraacetic acid (sodium salt) 4.0 g

The color bleaching bath has the following composition per liter of solution:
concentrated sulfuric acid 56.3 g
m-nitrobenzenesulfonic acid (sodium salt) 6.0 g
Potassium iodide 8.0 g
Hydroxyethylpyridinium chloride 2.4 g
2,3-dimethylquinoxaline 2.5 g
4-mercaptobutyric acid 1.8 g

The fixer contains per liter of solution:
Ammonium thiosulfate 200 g
Ammonium bisulfite 12 g
Ammonium sulfite 39 g

A positive image of the exposed gray wedge with a good contrast balance is obtained. There is very good adhesion between the support and the photographic element.

Example 2: Production of an underlayer from a mixture of Gellan gum and gelatin with a dry layer thickness of 1.00 µm.

A photographic element according to Example 1 is produced, but which contains an underlayer of 0.88 g / m² gelatin, 0.12 g / m² GELRITE and 30 mg / m² magnesium sulfate.

The material is exposed and processed as indicated in Example 1. Images similar to those in Example 1 are obtained.

Example 3: Solidification properties of additive-free gelatin solutions (comparative example ).

The setting time, the setting temperature and the maximum gel strength of aqueous solutions of a commercially available bone gelatin are measured at pH 5.7 and concentrations between 1 and 6% using the apparatus described in FIG. 1. The results are summarized in Table 1.

It can be seen from Table 1 that with increasing gelatin concentration the setting time decreases, the setting temperature as well as the max. However, gel strength increases. Gelatin solutions with a concentration of less than 1.5% gelatin no longer solidify under the given conditions.

The gels formed during cooling melt very easily again: the shorter the setting time t _E , the lower the remelting temperature T _rem . Typical values for T _rem are between 8 and 23 ° C.

Example 4: Casting solutions according to the invention for producing thin sublayers, the casting solutions containing gellan gum.

0.5% of an aqueous solution of gellan gum are mixed with various concentrations of metal salts and, as in Example 3 with respect to their solidification temperature (T _E) and max. Gel strength (d) examined: The type and concentration of the metal salt and the corresponding measurement results are shown in Table 2.

The values in Table 2 show that all solutions achieve a gel strength that can only be obtained in Example 3 at higher gelatin concentrations. The solidification temperatures are between 30 and 40 ° C depending on the salt and concentration of this salt. In spite of the low concentration of gellan gum, the setting times are less than three, sometimes even less than one second.

The gels formed from the above solutions no longer melt below 45 ° C.

Similar results are obtained if appropriate aqueous solutions of the polysaccharide XM-6 are used in combination with the metal salts mentioned. However, the gels obtained in this way are thermoreversible.

EXAMPLE 5 Pouring Solutions According to the Invention for the Production of Thin Bottom Layers, The Pouring Solutions Containing a Mixture of Gellan Gum and Gelatin.

The procedure is as described in Example 4, but aqueous solutions are used which contain 1% of a bone gelatin and 0.5% of gellan gum with different metal salt additives. The results are summarized in Table 3.

The values in Table 3 show that all solutions achieve a gel strength that is only obtained in Example 3 at gelatin concentrations of over 3.5%. The solidification temperatures are between 30 and 40 ° C depending on the salt and concentration of this salt. In spite of the low concentration of gellan gum, the setting times are less than three, sometimes even less than one second.

The gels formed from the above solutions no longer melt below 45 ° C.

Similar results are obtained if appropriate aqueous solutions of the polysaccharide XM-6 are used in combination with the metal salt mentioned. However, the gels obtained in this way are thermoreversible.

Example 6: Reduction of the mottle effect.

• Giessstelle 1: eine Unterschicht in den Varianten a, b oder c (siehe unten)
• Giessstelle 2: eine rotempfindliche Schicht, eine Gelatinezwischen­schicht, eine grünempfindliche Schicht, eine Filter­gelbschicht, eine blauempfindliche Schicht sowie eine Gelatineschutzschicht

To produce a photographic material for the silver color bleaching process, the following layers are applied to a polyethylene-coated paper support at two pouring points 1 and 2 separated by a solidification zone:

• Casting point 1: a lower layer in variants a, b or c (see below)
• Casting point 2: a red-sensitive layer, an intermediate gelatin layer, a green-sensitive layer, a filter yellow layer, a blue-sensitive layer and a protective gelatin layer

• Unterschicht, Variante a: enthält pro m² 0,54 g Gellan Gum (K3A 123) sowie 60 mg Bariumnitrat
• Unterschicht, Variante b: enthält pro m² 0,48 g Gellan Gum, 1,2 g Gelatine sowie 60 mg Bariumnitrat
• Unterschicht, Variante c: enthält pro m² 0,54 g Gellan Gum sowie 21 mg Nickelsulfat

These layers have the following composition:

• Lower layer, variant a: contains 0.54 g gellan gum (K3A 123) and 60 mg barium nitrate per m²
• Lower layer, variant b: contains 0.48 g gellan gum, 1.2 g gelatin and 60 mg barium nitrate per m²
• Lower layer, variant c: contains 0.54 g gellan gum and 21 mg nickel sulfate per m²

In a fourth material variant d, the lower layer is completely omitted.

The red-sensitive layer contains 1.20 g gelatin and 0.30 g silver per m² as a silver bromoiodide emulsion with 2.6 mol% iodide and 153 mg of the cyan dye of the formula

The intermediate gelatin layer consists of 1.5 g / m² gelatin,

The green-sensitive layer contains 2.00 g of gelatin, 0.27 g of silver as a silver bromoiodide emulsion with 2.6 mol% iodide and 186 mg of the magenta dye of the formula per m²

The filter yellow layer contains 0.04 g / m² of colloidal silver and 0.059 g / m² of the yellow dye of the formula

The blue-sensitive layer contains 0.90 g of gelatin, 0.22 g of silver as a silver bromoiodide emulsion with 2.6 mol% of iodide and 87 mg of the dye of the formula (105) per m².

The protective gelatin layer consists of 0.8 g / m² gelatin.

The material also contains in the lower layer 19 (variants a and c) or 29 mg / m² (variant b), in the remaining layers a total of 100 mg / m² of the gelatin hardener 2,4-dichloro-6-hydroxytriazine (potassium salt). The pH of the solution is consistently 6.5.

The casting solutions poured at 45 ° C have a viscosity of 5.6 (variants a and c) and 7.4 mPa · s (variant b) at 40 ° C; the solidification temperature for variants a and b is 34.5 ° C, for variant c 31.5 ° C. By preheating the uncoated carrier to about 30 ° C and by a sufficient distance between the first casting point and the subsequent solidification zone mentioned above, it is achieved that the temperature of the cast web remains above 39 ° C over a period of 1.5 to 2 seconds , the poured underlayer solution therefore maintains a low viscosity before the solidification process begins by cooling to 7 ° C.

Large-area samples of the finished material are subjected to a homogeneous gray exposure to characterize their mottle effect and processed as described in Example 1.

The strength of the mottle effect resulting after processing is assessed visually with grades from 1 to 6. Grade 1 corresponds to a completely homogeneous image impression and Grade 6 corresponds to a strongly inhomogeneous image impression. Grade 6 would indicate completely unusable results, while grades between 2 and 4 correspond to perfectly acceptable results.

Variants a to c give mottle marks between 2.5 and 3.5 (weak mottle), reference sample d a mottle note of 5.5 (very strong mottle), see Table 4.

Example 7: Use of Gellan Gum in combination with a gelatin hardener.

• Schicht a besteht aus 1 g Gellan Gum pro m².
• Schicht b besteht aus 1 g Gellan Gum und 2 mg des Härtungsmittels 2,4-Dichlor-6-hydroxytriazin-Kaliumsalz pro m².
• Schicht c besteht aus 1 g Gellan Gum und 4 mg 2,4-Dichlor-6-hydroxy­triazin-Kaliumsalz pro m².

Three layers are produced on a transparent support:

• Layer a consists of 1 g gellan gum per m².
• Layer b consists of 1 g of Gellan gum and 2 mg of the curing agent 2,4-dichloro-6-hydroxytriazine potassium salt per m².
• Layer c consists of 1 g of Gellan gum and 4 mg of 2,4-dichloro-6-hydroxytriazine potassium salt per m².

The thickness of the dry layer and then the layer thickness of the layer swollen with water are first measured on microscopic thin layers. The resulting swelling factors are given in Table 5. The swelling reduced by the hardening agent is clearly visible.

Example 8: Highly concentrated casting solutions with modified solidification properties suitable for auxiliary layers.

• a) Gelatine      :8,5 g auf 100 g Lösung
  Gellan Gum      : 0 bzw. 0,3 g pro 100 g Lösung
  Kaliumnitrat: Gehalt variiert zwischen 1 und 3 mmol auf 100 g Lösung
• b) Gelatine      : 5,0 g auf 100 g Lösung
  Bariumnitrat: 0,23 mmol auf 100 g Lösung
  Gellan Gum      : 0,15 bzw. 0,30 g auf 100 g Lösung
• c) wie b; anstelle von Gellan Gum wird hingegen XM-6 in Mengen zwischen 0,1 und 0,3 g auf 100 g Lösung eingestzt
• d) wie b; anstelle von Gellan Gum wird jedoch Dextransulfat ver­wendet, und zwar 0,5 g auf 100 g Lösung. (Dextransulfat ist eine aus US 3,762,924 bekannte, die Erstarrungstemperatur von wäss­rigen Gelatinelösungen erhöhende Verbindung.)
• e) wie b; die Giesslösung enthält jedoch zusätzlich noch eine UV-Absorber-Emulsion nach RD 27 832, und zwar 1,0 g auf 100 g Lösung
• f) Gelatine:      8,5 g auf 100 g Lösung
  Bariumnitrat:      0,75 mMol auf 100 g Lösung
  Gellan Gum:      0,085 g auf 100 g Lösung

und untersucht sie auf die eingangs beschriebene Weise auf ihre Erstarrungscharakteristik.Aqueous solutions of pH 6.5 adjusted to the following composition are prepared:

• a) Gelatin: 8.5 g per 100 g of solution
  Gellan Gum: 0 or 0.3 g per 100 g solution
  Potassium nitrate: content varies between 1 and 3 mmol per 100 g solution
• b) Gelatin: 5.0 g per 100 g solution
  Barium nitrate: 0.23 mmol per 100 g solution
  Gellan Gum: 0.15 or 0.30 g per 100 g solution
• c) as b; instead of Gellan Gum, however, XM-6 is used in amounts between 0.1 and 0.3 g per 100 g of solution
• d) as b; Instead of gellan gum, however, dextran sulfate is used, namely 0.5 g per 100 g of solution. (Dextran sulfate is a compound known from US Pat. No. 3,762,924, which increases the solidification temperature of aqueous gelatin solutions.)
• e) as b; however, the casting solution also contains a UV absorber emulsion according to RD 27 832, namely 1.0 g per 100 g solution
• f) Gelatin: 8.5 g per 100 g solution
  Barium nitrate: 0.75 mmol per 100 g solution
  Gellan Gum: 0.085 g per 100 g solution

and examines them for their solidification characteristics in the manner described at the beginning.

The solidification temperature T _E can, as shown in FIG. 2 using the example of Gellan Gum, be shifted between 23 and 45 ° C. in the solutions according to the invention by appropriately selecting the cation concentration (variants a and b). When the solution cools below its solidification temperature, the solutions solidify quickly, with sufficient polysaccharide and salt contents within one second. This also applies if the hypothermia only reaches 4 ° C, i.e. the final temperature remains well above the range typical for pure gelatin solutions (10-24 ° C). 3 and 4, the dependence of the gel strength d on the cooling time t for different temperatures of supercooling is shown, where t₀ is the time required to cool the sample to the solidification temperature T _E. The gel strength achieved with only slight hypothermia remains well below the max. achievable value. However, it still corresponds to the gel strength of a 3% gelatin solution kept at 7 ° C. for 30 seconds.

If Gellan Gum is replaced by XM-6 (variant c), similar results are obtained. However, if you use e.g. dextran sulfate (variant d) described in US Pat. No. 3,762,924, the viscosity rises to extremely high values (950 mPa · s at 40 ° C. Usual viscosities for multiple casting are below 100 mPA · s), while the solidification temperature changes only slightly - increased from 18 to 25 ° C. On the other hand, it does not matter whether the gelatin solution is free of special layer additives or additives typical for auxiliary layers such as e.g. UV absorber emulsions contain: Solution e does not differ in its solidification behavior from solution b.

If the layers produced from the casting solutions according to the invention are heated again, there are characteristic differences from pure gelatin gels: pure gelatin solutions melt completely again at relatively low remelting temperatures; they are therefore very sensitive to the air circulating in the dryer. The layers according to the invention, however, retain their original at temperatures of 25 to 30 ° C Strength almost completely. Layers of this type can thus be dried at relatively high temperatures without the formation of melting strips.

This applies even if the amount of polysaccharide is reduced to one hundredth of the amount of gelatin (variant f). In this case, too, a marked increase in the setting temperature up to 39 ° C, a short setting time (approx. 1 sec) and a remarkable resistance of the gel layers formed to re-melting can be demonstrated: after heating to 40 ° C their gel strength remains with a d -Value of 300 µm still at a level that corresponds to the maximum strength of a three percent gelatin gel (see Table 1 from Example 3) at low temperature (5 ° C).

Example 9: Emulsion-containing casting solutions with modified solidification properties.

The casting solutions described below are prepared.

Casting solutions for the silver color bleaching process:

• a) 100 g of a red-sensitive casting solution batch contain 4 g of gelatin, 0.58 g of silver as a sensitized and stabilized silver bromoiodide emulsion with 2.6 mol% of iodide, 306 mg of the cyan dye described in Example 6, 60 mg of barium nitrate and Gellan gum additives between 0 and 0.4 g. The pH is 6.5 in each case.
• b) 100 g of a blue-sensitive solution, also adjusted to pH 6.5, contain 3.8 g of gelatin, 0.89 g of silver as a sensitized and stabilized silver bromoiodide emulsion with 2.6 mol% of iodide, 365 mg of the yellow dye presented in Example 6, 60 mg barium nitrate and Gellan Gum additives between 0 and 0.4 g.
• c) 100 g of a green-sensitive, pH 6.5 solution contain 5.2 g of gelatin, 0.52 g of silver as a sensitized and stabilized silver bromoiodide emulsion with 2.6 mol% of iodide, 402 mg of the magenta dye presented in Example 6, 0 , 15 g of Gellan gum and 108 mg of the potassium salt of 2,4-dichloro-6-hydroxytriazine (potassium salt).
• d) as c; however, the triazine salt is replaced by 0.49, 0.91 or 1.41 mmol potassium ions (partly as hydroxide, partly as nitrate).

Pouring solution with a chromogenic color coupler:

100 g of a blue-sensitive, pH 6.5 solution contain 5.55% gelatin, 0.98 g silver as silver bromide emulsion, 2.3 g yellow coupler, which is introduced as an oil emulsion with the composition described below, 0.30 g gellan gum and 2.7 mmol potassium nitrate.

entfallen dabei 3,0 kg Aethylacetat, 250 g Trikresylphosphat sowie 50 g von Natrium-isopropyl-naphthalinsulfonat.The preparation of the coupler emulsion follows the procedure described in DE 27 16 204, Example 7. For 1 kg of a yellow coupler of the formula

3.0 kg of ethyl acetate, 250 g of tricresyl phosphate and 50 g of sodium isopropyl naphthalenesulfonate are omitted.

Casting solution for a black and white material:

100 g of a solution set to pH 6.0 contain 6.4 g gelatin, 1.87 g silver as chlorobromide emulsion, 0.30 g gellan gum and 60 mg barium nitrate and 100 mg 2,4-dichloro-6-hydroxytriazine (potassium salt) .

The solutions mentioned are examined according to the method described at the beginning with regard to solidification behavior. The polysaccharide additive according to the invention brings about an increase in the solidification temperature in all cases and, in addition, a marked reduction in the solidification time. A comparison of the solidification behavior of the casting solutions a and b according to the invention with that of the corresponding additive-free solutions (not according to the invention) reveals: The solidification temperatures rise, depending on the Gellan-Gum content, from 16 to 17 ° C. to values between 38 and 42 ° C. The cooling times are reduced from around 18 to 2 to 4 seconds. The setting times decrease from 7 (solution a) or 8 seconds (solution b) to less than 1 second.

Similar results are also achieved if the divalent metal salt is replaced by the triazine salt, which acts as a gelatin hardener, or another alkali metal salt (solutions c and d). For solution c there is a solidification temperature of 40.3 ° C, for solutions d temperatures of 35.7, 38.4 and 40.3 ° C, respectively. Similar behavior is also observed with the casting solution for the chromogen process and for the black and white material.

Example 10: Mottle reduction by using rapidly solidifying casting solutions.

• a) 8,5 g Gelatine sowie 50 mg Bariumnitrat in Wasser
• b) wie a, jedoch zusätzlich noch 0,3 g Gellan Gum

100 g Magentagiesslösung enthalten

• a) 6,0 g Gelatine, 0,52 g Silber als stabiliserte, grün sensibi­lisierte Silberbromojodidemulsion mit 2,6 Mol-% Jodid, 402 mg des in Beispiel 6 vorgestellten Magentafarbstoffs sowie 75 mg Bariumnitrat.
• b) wie a, jedoch zusätzlich noch 0,25 g Gellan Gum

100 g Schutzschichtgiesslösung enthalten
8,5 g Gelatine und 590 mg des Kaliumsalzes von 2,4-Dichlor-6-­hydroxytriazin.25.1 g of an underlayer casting solution, 40.0 g of a magenta casting solution and 18.2 g of a protective layer casting solution are applied per square meter to a polyethylene-coated paper carrier. The solutions have the following composition:
Contain 100 g of underlayer casting solution

• a) 8.5 g of gelatin and 50 mg of barium nitrate in water
• b) as a, but additionally 0.3 g of Gellan gum

Contain 100 g of magenta solution

• a) 6.0 g of gelatin, 0.52 g of silver as a stabilized, green-sensitized silver bromoiodide emulsion with 2.6 mol% of iodide, 402 mg of the magenta dye presented in Example 6 and 75 mg of barium nitrate.
• b) as a, but additionally 0.25 g of Gellan Gum

Contain 100 g of protective layer casting solution
8.5 g of gelatin and 590 mg of the potassium salt of 2,4-dichloro-6-hydroxytriazine.

The solidification temperature of the two casting solutions b according to the invention is 39.5 ° C .; all other solutions only solidify at temperatures of 20 to 25 ° C. The uncoated carrier has an initial temperature of 23 ° C and a - calorimetrically determined - heat capacity of 75 cal / m² · ° C. The total amount of casting solution applied via cascade casting is 90 g / m². Its initial temperature is 45 ° C, its heat capacity is 90 cal / m² · ° C. Under these circumstances, a mixed temperature of 35 ° C forms at the sprue: this is 4.5 ° C below the solidification temperature of solutions b and, as can be verified by contactless temperature measurements directly behind the pouring point, is due to the good thermal conductivity of the Casting solutions and the paper carrier practically at the moment. The solutions according to the invention respond to this jump in temperature without delay in comparison to gelatin solutions, ie their gel strength immediately reaches finite values. Therefore, the two solidify in variant b lower casting solutions in the same form as immediately after application, while in variant a they spread freely over the unevenness of the carrier surface due to their low solidification temperature before the web has cooled down to such an extent that the solidification can begin.

The two material variants are exposed homogeneously in the green spectral range and then subjected to the processing process described in Example 6. An average color density of about 0.7 density units is obtained. A strong magenta mottle can be seen in variant a; in variant b this mottle is only weakly pronounced.

Example 11: Photographic behavior of layers according to the invention

The casting solutions a, b and d from Example 9, together with a suitable protective layer casting solution, are poured onto a white opal carrier. 100 g of the protective layer casting solution contain 3.7 g of gelatin and 119 mg of the potassium salt of 2,4-dichloro-6-hydroxytriazine. Their pH is 6.5 and their area coverage is 40 g / m². The application quantities for the dye-containing casting solutions are 50 (cyan), 22 (yellow) and 40 g / m² (magenta).

The materials produced in this way are exposed behind a step wedge in the red (cyan), blue (yellow) or green spectral range (magenta), processed according to Example 6 and then measured sensitometrically. The resulting color density curves show no difference between the comparison layers and the layers according to the invention with added polysaccharide.

Claims (27)

1. Layers for photographic materials, characterized in that they contain a polysaccharide which is formed extracellularly by bacterial fermentation of glucose, maltose, sucrose or xylose, optionally in the presence of yeast or yeast or casein hydrolyzate, and with one, two or and / or trivalent metal ions gives gels whose solidification temperature is between 24 and 45 ° C. 2. Layers according to claim 1, characterized in that they additionally contain ions of mono-, di- and / or trivalent metals. 3. Layers according to claim 1, characterized in that they additionally contain gelatin. 4. Layers according to claim 3, characterized in that the ratio of polysaccharide: gelatin = 2: 1 to 1: 150. 5. Layers according to claim 4, characterized in that the ratio of polysaccharide: gelatin = 2: 1 to 1:70. 6. Layers according to claim 5, characterized in that the ratio of polysaccharide: gelatin = 1: 2 to 1:50. 7. Layers according to claim 1, characterized in that they have a dry layer thickness of 0.05 to 2.00 µm. 8. Layers according to claim 1, characterized in that they have a dry layer thickness of 0.05 to 1.00 µm. 9. Layers according to claim 1, characterized in that they are sub-layers. 10. Layers according to claim 1, characterized in that they are present in silver color bleaching materials. 11. Layers according to claim 1, characterized in that they contain MX-6 as polysaccharide. 12. Layers according to claim 1, characterized in that they contain gellan gum as the polysaccharide. 13. Layers according to claim 11, characterized in that they additionally contain a hardening agent. 14. Layers according to claim 1, characterized in that they contain gellan gum and are present as an underlayer in silver color bleaching materials. 15. A photographic material which contains on a support at least one light-sensitive layer with a polysaccharide as defined in claim 1. 16. A photographic material as claimed in claim 13, which contains at least one light-sensitive layer and at least one auxiliary layer on a support, the auxiliary layer having a polysaccharide as defined in claim 1. 17. The photographic material as claimed in claim 16, which contains at least one light-sensitive layer and at least one auxiliary layer on a support, both the light-sensitive layer and the auxiliary layer having a polysaccharide as defined in claim 1. 18. Photographic material according to claim 15, characterized in that it is silver color bleaching material which on a support at least one photosensitive layer, at least one layer containing a bleachable image dye and at least one auxiliary layer or at least one photosensitive, a bleach layer containing image dye and at least one auxiliary layer, the auxiliary layer in each case having a polysaccharide as defined in claim 1. 19. Photographic material according to claim 18, characterized in that the auxiliary layer is an underlayer. 20. Use of the polysaccharide defined in claim 1 in layers of photographic materials. 21. Use of the polysaccharide according to claim 20 in a mixture with ions of mono-, di- and / or trivalent metals and / or gelatin in layers of photographic materials. 22. Use of the polysaccharide according to claim 20 in layers of silver color bleaching materials. 23. Use of the polysaccharide according to claim 22 in auxiliary layers of silver color bleaching materials. 24. Use of the polysaccharide according to claim 21 in a mixture with ions of mono-, di- and / or trivalent metals and / or gelatin in lower layers of silver color bleaching materials. 25. Use of Gellan Gum or MX-6 according to claim 19 in layers of photographic materials. 26. A method for increasing the rate of solidification of gelatin-containing photographic layers, characterized in that casting solutions are used which contain a polysaccharide as defined in claim 1. 27. The method according to claim 26, characterized in that casting solutions are used which contain MX-6 or Gellan gum.

Images