EP0019178A2 - Process for the preparation of matting layers - Google Patents

Abstract

To produce matt outer layers of photographic silver halide recording materials, particles of a suspension copolymer of maleic anhydride and a C2-C8 monoolefin are dispersed in the aqueous solution of a hydrophilic colloid. The dispersion is applied to one or both surfaces of the photographic material and dried.

Description

The invention relates to a method for producing matt outer layers of photographic recording materials which counteract the tendency of such materials to stick.

The surface layer of conventional photographic silver halide recording materials contains a hydrophilic colloid, for example gelatin, as a binder. The stickiness of such recording materials therefore increases at high atmospheric humidity, especially at higher temperatures, so that such recording materials, for example after packaging in a stack, easily stick to one another. This tendency to stick between different parts of the recording material or between the recording material and other materials, contact with it presents numerous difficulties in the camera, in the production, processing, projection or storage of the recording material.

To overcome these difficulties, it is known to matt the surface layer of the recording material by incorporating finely powdered inorganic compounds, such as silicon dioxide, magnesium oxide, titanium dioxide or calcium carbonate, or organic compounds, such as polymethyl methacrylate or cellulose acetate propionate, in order to reduce their stickiness. However, this "matting" has several disadvantages. For example, do not make the surface layer homogeneous, since the fine powder components mentioned aggregate easily in the coating solution. In addition, recording materials with a surface layer containing the fine powdery materials are more easily damaged and are more difficult to transport in a camera or a projector because their surface is not very slippery. The presence of the fine powdery materials in the surface layer further reduces the transparency of the recording material after processing and increases the graininess of the image.

From DE-OS 2 758 767 a photographic light-sensitive material is known which has an outer light-sensitive gelatin layer, the colloidal Contains silica particles with a size of 7 to 120 m _/ u and a polymer latex, the particles of which are 30 to 80 m µ in size. This gelatin layer gives the photographic material increased fracture and dimensional stability.

A disadvantage of such a photographic material, however, is that the additives reduce the transparency of the layers and, especially at higher humidities (> 85% RH) and temperatures around 35 to 40 ° C., it is not possible to avoid contact marks which are disadvantageously sensitometric when the materials are rolled up.

Various processes are known for producing fine-grained materials with a matting effect. Thus, emulsion polymerization can produce polymer particles having a particle diameter of from about 5 to about 0.01 micron if the amount of the emulsifier (surfactant), the polymerization temperature and the stirring conditions are suitably controlled. The procedure is described, for example, by H. Reinhard, Dispersions of Synthetic High Polymers, Part II, page 3 ff., Springer Verlag or by F. Hölscher in the corresponding Part I, page 31 ff. In this way, however, it is not easily possible to produce particles of uniform size of more than 2 microns. By mechanical pulverization, which is followed by a classification according to particle sizes, polymer particles are also obtained a broad particle size distribution, the shape of which is not spherical but completely irregular.

Spherical polymer particles can be prepared by dissolving a polymer in a water-immiscible organic solvent and spraying the solution from a fine nozzle into an aqueous medium under high pressure. The one there
however, particle size achieved is far from uniform and a large volume device is required. So far, there is generally no viable, economical method for producing polymer particles with a particle size within the range of 1 to 10 microns.

Fine-particle polymer particles can also be produced by dispersing. To this end, one or more polymers are dissolved in a solvent which is insoluble or essentially immiscible in water and has a lower boiling point than water or forms an azeotropic mixture with water having a lower boiling point than water. The polymer solution is dispersed in an aqueous medium as an oil phase in the form of droplets, the viscosity and surface tension being adjusted in a suitable manner and the solvent removed from the droplets of the oil phase to form fine polymer particles. These particles can be separated off by subsequent centrifuge separation and by drying in the form of a powder (DE-OS 2 522 692).

A disadvantage of this process, however, is that the particles have to be generated during the stirring process, so they do not have to be preformed. The particle size depends on the concentration of the polymer solution, the ratio between the polymer solution and the aqueous medium, the type and amount of the hydrophilic colloid, the temperature, stirring speed and the pH of the aqueous medium. In addition, the low-boiling solvent must be carefully distilled off so as not to destroy the particles.

It is also possible to obtain small particles based on a suspension polymer. In general, suspension polymers with a particle diameter of 10-1000 _/ u are obtained in water. However, it is not possible to obtain particles with the desired diameter of 1 to 10 _/ u in as homogeneous a distribution as possible.

The invention is based on the object of developing a process for the production of surface layers which reduce the stickiness of a photographic material and whose matting, in particular with regard to the impression of the graininess of the photographic material, does not adhere to the disadvantages of the known matting layers.

The invention relates to a process for producing matt outer layers of photographic Silver halide recording materials which contain polymer particles dispersed in a binder as matting agents, the process being characterized in that, in the aqueous solution of a hydrophilic colloid, spherical particles of an essentially alternating and equimolecularly structured suspension copolymer of maleic anhydride and a 1-olefin with 2 -8 C atoms with a particle size of 1 to 10 _/ u, preferably 1.5 to 5 _/ u, in an amount of 1 to 15 wt .-%, preferably 5 to 10 wt .-%, based on the weight of the Dispersion, dispersed, the dispersion is applied to one or both surfaces of the photographic material so that the applied layer contains 10 to 500 mg / m ^{2 of} the particles and the layer is dried.

Suspension copolymers suitable according to the invention are, for example, copolymers as maleic anhydride and 1-olefins or vinylaromatics, which are obtainable in the presence of macromolecular dispersants in the form of fine powders with a uniform particle size. Details on this, in particular with regard to the production process, can be found in DE-OS 2 501 123. In addition, reference is made to G.Sackmann and G. Kolb, Angewandte Makromolekulare Chemie 1978, pages 141 to 156.

The following copolymers are mentioned as examples of particularly suitable particles:

The copolymers used according to the invention are essentially alternating and Suspension copolymers of equimolecular structure composed of maleic anhydride and 1-olefins having 2 to 8 carbon atoms or vinyl aromatics, which in the presence of a radical generator at temperatures from 30 to 200 ° C. and pressures of 1 to 200 bar in an organic dispersion medium made from 1-olefin or from 1-olefin and a solvent which is inert towards the monomers and which dissolves the 1-quinfin and the vinylaromatics, but not the maleic anhydride, in the presence of 0.5 to 50% by weight, based on the maleic anhydride used, of a dispersant which is soluble in the dispersing medium will. As dispersants are reaction products of alternating copolymers of maleic anhydride and 1-olefins having 2 to 8 carbon atoms, of maleic anhydride and vinyl esters, of maleic anhydride and vinyl ethers, of maleic anhydride and vinyl aromatics with at least one primary, aliphatic, saturated or monoolefinically or unsaturated, linear branched monohydric alcohol with 6 to 22 carbon atoms or with at least one primary or secondary, aliphatic, saturated, linear or branched monoamine with 6 to 22 carbon atoms or mixtures thereof.

Possible 1-olefins which can be used to prepare the alternating copolymers with maleic anhydride are: ethylene, propylene, butylene, isobutylene, hexene-1, diisobutylene (2,4,4-trimethylpentene-1). The following may be mentioned as vinyl aromatics: styrene and α-methylstyrene.

However, mixtures of the 1-olefins with one another and mixtures of 1-olefins and vinylaromatics can also be used.

This copolymerization process gives copolymer powders which are readily filterable and essentially consist of discrete spheres with particle diameters between 1 and 10 _. to exist, and which have a very narrow particle size distribution. The size of the particles formed and their size distribution can be controlled both by the type and by the amount of the dispersant used, the amount being particularly suitable as a control agent. The average particle diameter of the copolymer particles decreases with increasing amount of dispersant, while the uniformity increases at the same time. For example, the average particle diameter of a Suspensionscopolymerisats of maleic anhydride and diisobutylene with 3 wt .-% - based on the sum of the molar ratio 1: 1 copolymerized monomers - dispersant was prepared, approximately 10 _/ um while the use of 10 wt. -% dispersant particle sizes of about 3 microns and when using 20 wt .-% particle diameter of about 2 _/ um can be obtained. In parallel with the increasing amount of dispersant, the uniformity of the particle size distribution increases: with 3% by weight dispersant there are relatively non-uniform particle sizes, with 10% by weight largely uniform particle sizes with slight differences and with 20% by weight completely uniform particle sizes. The uniformity of the particle sizes can also be influenced by additional technical measures in the preparation of the copolymer, such as the shape of the stirrer used or the stirring speed

It is of course also possible to adjust by this method particle sizes or particle size distributions to be outside of desired for use in photographic recording materials order of 1 to 10 _/. The particles obtained are residue-free and can be used without further grinding and sieving processes.

The copolymers are built-up alternately and equimolar and have degrees of polymerization between 20 and 1000, but preferably between 50 and 300, corresponding to molecular weights of about 4000 to 2 ₀ 0 0 _00, preferably from 10,000 to 60,000 as determined by membrane osmometry. The preferred copolymers have intrinsic viscosities of 0.05 to 0.70 dl / g, measured in dimethylformamide (DMF) at 25 ° _C.

• In einem 2-1-Dreihalskolben, der mit Rührer, Thermometer,_'Rückflußkühler, Tropftrichter sowie einer Vorrichtung zur Einleitung von Stickstoff ausgerüstet ist, wird folgendes Reaktionsgemisch vorgelegt:
  

The experimental preparation of the copolymers according to the invention is described using the example of copolymer 3:

• In a 2-1 three-necked flask equipped with stirrer, thermometer, _'reflux condenser, dropping funnel and a device for introducing nitrogen, a reaction mixture is provided:
  

The mixture is heated to 75 ° C. while passing over a weak stream of nitrogen and stirring (220 rpm). 25% by volume of the following initiator solution (I) are then added:

Now the temperature is raised to 90 ^° C. within one hour and the rest of (I) are added dropwise within a further hour.

After the initiator addition has ended, the mixture is stirred at 90 ° C. for a further six hours. The mixture is then cooled to room temperature, the fine-particle copolymer suspension formed is filtered off with suction, washed with fresh diisobutylene and dried in a vacuum drying cabinet at 70 ° C. to constant weight.

Yield: 654 g (≙ 99.5% of theory).

• Copolymerisat 1: 155,33 g Dispergator
• Copolymerisat 2: 310,65 g Dispergator
• Copolymerisat 4: 150,88 g Dispergator

Copolymers 1, 2 and 4 were prepared in an analogous manner, but with different amounts of dispersant:

• Copolymer 1: 155.33 g of dispersant
• Copolymer 2: 310.65 g of dispersant
• Copolymer 4: 150.88 g of dispersant

To determine the particle size, the copolymer powders are slurried in a water: glycerol mixture (1: 1) and counted and measured with a light microscope with a phase contrast device at 1000 × magnification.

The powders are distributed in a second step in aqueous solutions of hydrophilic colloids with any wetting agents. The following compounds can serve as hydrophilic colloids: proteins, such as gelatin, gelatin derivatives, for example acetylated gelatin, phthaloyl gelatin or succinyl gelatin, albumin, casein, gum arabic, agar agar, alginic acid, cellulose derivatives, for example alkyl esters of carboxymethyl cellulose, preferably the methyl or ethyl ester, hydroxyethyl cellulose, carboxymethyl cellulose and the like. Synthetic polymers, for example polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, salts of polyacrylic acid, salts of polymethacrylic acid, salts of polymaleic acid, salts of polystyrene or sulfonic acid, preferably the sodium and mixed sulfonic acid, and preferably the sodium and mixed sulfonic acid, as well as the sodium and mixed mixed acid, as well as the mixed sodium sulfate polymer contain at least one of the monomers of the abovementioned polymers. Among these hydrophilic colloids, amphoteric polymeric electrolytes, such as gelatin, gelatin derivatives, casein and other protein compounds, have a particularly pronounced effect. They can also be used individually or in combination. Preferred colloids include gelatin, gelatin derivatives, casein and other protein compounds. The colloid is advantageously used in an amount of about 1 to about 15% by weight, preferably in an amount of 5 to 10% by weight, in each case based on the weight of the dispersion.

As a rule, 0.1 to 1% by weight of surface-active agents, based on the weight of the water, are used as dispersants. Examples of suitable surfactants include saponin and other compounds of natural origin, nonionic surfactants such as alkylene oxide, glycerin compounds such as monoglycerides, glycidol compounds and the like, anionic surfactants with or several acid groups, such as one or more carboxylic acid, sulfonic acid, phosphoric acid, sulfonic acid ester or phosphoric acid ester groups and the like. Particularly suitable surfactants are described in U.S. Patents 2,271,623, 2,240,472, 2,288,226, 2,676 122, 2 676 924, 2 676 975, 2 691 566, 2 721 860, 2 730 498, 2 742 379, 2 739 891, 3 068 101, 3 158 484, 3 201 253, 3 210 191, 3 294 540, 3 415 649, 3 441 413, 3 442 654, 3 475 174 and 3 545 974, in German Offenlegungsschrift 1 942 665 and in British Patents 1 077 317 and 1 198 450 and in "Kaimen Kassi Zai no Gosei to Sono Ohyo "(Synthesis and Application of Surface Active Agent) by Ryohei Oda et al (published by Maki Publishing Co, 1964)," Surface Active Agents "by JW Perry and AM Schwartz (published by Interscience Publications Inc., 1958)," Encyclopedia of Surface Active Agents ", Volume 2, by JP, Sisley (published by Chemical Publishing Co., 1964)" Kaimen Kassi Zai Binran (Surfactants En cyclopedia) ", 6th edition (published by Sangyo Tosho Co., Dec. 20, 1966) and the like. Fluorine-containing wetting agents as described, for example, in DE-OS 1 961 638 can also be used.

These surface-active agents can also be used alone or in the form of combinations, and particularly suitable compounds are those with an SO ₃ M group, such as, for example, sulfonate esters of ordinary types Alcohols of the general formula RO-S0 ₃ M or R- (OCH ₂ CH ₂ ) _n CS0 ₃ M (in which R is an alkyl group with 8 to 30 carbon atoms, M is an alkali metal or ammonium ion and n is a positive integer of up to 20 ) and alkylbenzenesulfonic acid compounds with the general formula

Where R 'is hydrogen or an alkyl group having 1 to 18 carbon atoms, R "is an alkyl group having 1 to 18 carbon atoms, M is an alkali metal or ammonium ion, m is a positive integer from 0 to 20 and n is 3 or 4.

The dispersions of copolymers obtained with the particle size 1-10μ, preferably 1.5-5μ, are obtained in each case to 70-80% in the same size or as particles with the same grain diameter. Only 20-30% of the particles have a larger or smaller particle diameter.

The dispersions can either be added directly to the photographic coating solutions for the top protective layer or the particles can be isolated in the form of pastes as a solid residue by centrifugation. In this way, so-called "Instant matting agents", ie matting agents which can be stirred into any photographic coating solution without dispersing agents. The compounds are photographically inert and do not change the granularity of the recording material if they are used in the appropriate amount of approximately 500-100 mg / m ² surface.

The advantageous matting effect achieved by the process of the invention can be further improved by adding colloidal silica in the form of a hydrosol to the matting dispersion before it is applied to the surface of the photographic material. Good results are obtained with commercially available hydrosols with a particle size of 1 to 150 nm, which are added to the matting dispersion in amounts of 0.5 to 2 parts by weight, based on 1 part by weight of the hydrophilic colloid. The silica particles introduced with the hydrosol differ by orders of magnitude from the copolymer particles of the invention and are therefore not involved in their specific action. The proportion of the silica particles in the overall effect is merely that they further suppress the already slight tendency of the surface layers produced by the process of the invention to form gloss spots or color spots.

If desired, the casting compositions used to produce the surface layers can contain further additives which have no effect on the matting effect according to the invention. Examples include: very fine-grained (Ø <0.1 µ) latices of hard polymers such as polystyrene, polymethyl methacrylate. Further very fine-grained (particle diameter <0.1 / u) latices of soft homo- and copolymers such as polyethylacrylate, polyacrylate butyl ester-ethyl acrylate or latices of polyether or polyester-polyurethanes, as described in the journal Research dischlosure, Dec. 1978, Industrial Opportunities Ltd. Hampshire, UK, page 27 (XII A). Also conductivity-increasing compounds as described in "Research Disclosure", Dec. 1978, page 27 (XIII A). Finally, curing agents such as are given in "Research Disclosure", December 1978, page 26 as (X) and Begießhilfsmit ^tel as described in "Research Disclosure", December 1978, page 26 as (XI).

The compounds used according to the invention can advantageously be used in the protective or surface layers of black-and-white photographic materials, in color materials and in the so-called non-curling layers of roll and 35 mm films or flat films.

The following examples serve to illustrate the invention.

example

in 120 ml Ethanol und behandelte die Mischung in einem Hochdruck-Homogenisator. Die Dispersion wurde unter geringem Druck durch ein Gazefilter abgesaugt. Die Dispersion kann nun entweder direkt der Schutzschichtgießlösung zugesetzt werden oder durch Zentrifugieren in eine Paste mit 50-60 % Wassergehalt überführt werden. Die Dispersion enthielt ca. 5 Gew.-% Gelatine und 1 Gew.-% Copolymerisat.1900 ml of water were placed in a 3 liter beaker. 100 g of gelatin (alkaline ash) were added with stirring. The gelatin is then swelled 30 ', after which it was melted at 40 ^° C. with stirring. To this was added a slurry of 20 g of matting material in a solution of 0.2 g of the wetting agent

in 120 ml of ethanol and treated the mixture in a high pressure homogenizer. The dispersion was sucked off through a gauze filter under low pressure. The dispersion can now either be added directly to the protective layer casting solution or can be converted into a paste with 50-60% water content by centrifugation. The dispersion contained about 5% by weight of gelatin and 1% by weight of copolymer.

• Gießlösung:
• 400 g wäßrige Gelatinelösung 15 %ig
• 2800 g Wasser (entsalzt)
• 80 g Netzmittel der Formel
  
  4 %ig in Wasser
• 4 g polymeres Mattierungsmittel wie unten angegeben 2000 g einer 10 Gew.-%igen wäßrigen Lösung des Härtungsmittels der Formel
  
• Naßauftrag: 50 g/m²; pH 6,5-7,0

The dispersions were added to samples of a coating solution for a protective layer for a color negative film. The casting solutions had the following composition:

• Pouring solution:
• 400 g 15% aqueous gelatin solution
• 2800 g water (desalinated)
• 80 g wetting agent of the formula
  
  4% in water
• 4 g of polymeric matting agent as indicated below 2000 g of a 10% by weight aqueous solution of the curing agent of the formula
  
• Wet application: 50 g / m ² ; pH 6.5-7.0

The following casting solutions were prepared in accordance with the above recipe:

Casting solutions with the following known matting agents not according to the invention were also prepared as comparative samples:

The coating solutions were coated with a molding machine on an uncured color negative film as the uppermost protective layer coated (wet coating 50 g solution per m ²⁾ and the layer at 25 ⁰ C and 60% rel. Humidity dried. The protective layers formed a dry layer of 0.6-0.7 g / m ² .

The color negative film used had a conventional structure. A red-sensitized silver halide layer with emulsified cyan color component, an intermediate layer, a green-sensitized silver halide layer with a magenta component, a yellow filter layer and a blue-sensitized yellow component-containing silver halide layer were applied in succession to a cellulose triacet substrate.

The intermediate layers consisted of gelatin and a pouring aid, the yellow filter layer also contained yellow colloidal silver. The layer thicknesses of the layers containing halogen silver were between 5- and 6 _/ u, those of the intermediate layer at 1-2µ. The film was cast without curing agent and cured by overlaying the top protective layer solution.

The color components and pouring aids are shown in the following table

• Prüfung 1: Glanzstellen

Samples A to M were tested after drying in the following manner:

• Test 1: shiny spots

The samples were cut into 5 cm ² pieces and conditioned for 2 days at 30 ° C and 90% humidity. The samples were then stored under pressure for one day against the back of the layer. Then the samples were torn apart and the size of the bonded surface was estimated (bare spots in the surface).

Test 2: cartridge extract

A film of 35 mm width and 125 cm Länqe was wound into a film cartridge and stored for 7 days at 90% relative humidity and 35 ⁰ C. The pull-out force (p) was then determined and registered when the film was pulled out of the cartridge. The maximum value is shown in the table below. In practice, the pull-out force should not be higher than 300 p.

Test 3: yellow spot test

The film stored according to test 2 was developed photographically and checked for visible defects caused by storage, pressure and moisture. The number and size of the differently sized colored spots was evaluated in% based on the area tested. A film with a suitable protective layer should show less than 5% yellow spots.

Test 4: Graininess

-D-Wertes mit einer 29_/u Lochblende bestimmt wie dies von J.H. Altmann in Appl. Optics, Volum 3, (1964) Seiten 35-38 beschrieben wird. Die Körnigkeit von 1,8 ist ein in der Photographie angestrebter Wert.

The graininess of a photographic image was caused by the color grain developed and by dispersions and matting agents, especially in the top layers. It was determined by the

-D value determined with a 29 _/ u pinhole as described by JH Altmann in Appl. Optics, Volum 3, (1964) pages 35-38. The graininess of 1.8 is a value sought in photography.

The results summarized in the previous table show the overall advantageous properties of the matting particles of the invention. While some of the comparative samples in individual tests achieve results comparable to those of the matting samples of the present invention, the samples of the present invention alone provide consistently favorable results throughout all tests, including, and remarkably, the granularity test.

The proportion of larger particles in dispersions with a large size distribution spectrum is particularly noticeable in test 4. All comparative dispersions show a higher granularity in this investigation. This is extremely disruptive in photographic practice.

Example 2

• a) sauer geäscherte Gelatine (Isoelektrischer Punkt: 9)
• b) Acetylgelatine (durch Umsetzung mit 10 Gew.-% Acetanhydrid erhalten)
• c) Polyvinylpyrrolidon (Molgewicht 50 000)
• d) Cellulosesulfat
• e) Polyacrylamid (Molgewicht 40 000) aufgelöst. Jede der Proben wird mit einer Aufschlämmung von 20 g Copolymerisat ¹ in einer Lösung von 0,2 g des Netzmittels
  
  in 120 ml Ethanol versetzt. Dann wurden die Mischungen wie in Beispiel 1 beschrieben behandelt. Anschließena wurden die Proben durch ein Gazefilter gegossen und zentrifugiert. Man erhielt eine Paste, die bezogen auf 3ie Copolymerisat-Teilchen 50-60 Gew.-% enthielt.

1900 cc of water were placed in 3 1 beakers and 100 g were contained therein

• a) acid-washed gelatin (isoelectric point: 9)
• b) acetyl gelatin (obtained by reaction with 10% by weight acetic anhydride)
• c) polyvinylpyrrolidone (molecular weight 50,000)
• d) cellulose sulfate
• e) polyacrylamide (molecular weight 40,000) dissolved. Each of the samples is mixed with a slurry of 20 g of copolymer ¹ in a solution of 0.2 g of the wetting agent
  
  added in 120 ml of ethanol. The mixtures were then treated as described in Example 1. Then the samples were poured through a gauze filter and centrifuged. A paste was obtained which, based on the 3 copolymer particles, contained 50-60% by weight.

As described in Example 1, the pastes were added to individual protective layer casting solutions and the casting solutions were applied to the layer side of a color negative film.

• 400 g wäßrige Gelatinelösung 15 Gew.-%
  2600 g Wasser (entsalzt)
  7₀ g 4 gew.-%ige Lösung des Netzmittels C₇F₁₅COO⊖ (NH₄)⊕
  4 g polymeres Mattierungsmittel Copolymerisat 3
  1000 g einer 10 gew.-%igen wäßrigen Lösung eines Umsetzungsproduktes von Taurin mit der Verbindung C(CH₂-SO₂-OH=CH₂)₄ (1:1 Molar) als Vernetzungsmittel.

The protective layer casting solutions had the following composition:

• 400 g aqueous gelatin solution 15% by weight
  2600 g water (desalinated)
  7 ₀ g 4% by weight solution of the wetting agent C ₇ F ₁₅ COO⊖ (NH ₄ ) ⊕
  4 g polymeric matting agent copolymer 3
  1000 g of a 10 wt .-% aqueous solution of a reaction product of taurine with the compound C (CH ₂ -SO ₂ -OH = CH ₂ ) ₄ (1: 1 molar) as a crosslinking agent.

In all cases, protective layers were obtained in which the particles were present free of aggregates. The results were determined by microscopic comparison of the samples.

Testing the samples for effectiveness as a spacer (preventing the smooth contact between the protective layer and the back of a material lying on it in a stack or on the roll) according to the 4 methods given in Example 1 carried out. A layer structure containing a protective layer without copolymer was used as comparative sample F. The dry protective layers were 0.6-0.7 _/ u thick. (about 0.6-0.7 g / m ² application)

Sample f) contains no copolymer 3. The pull-out force (test 2) is therefore very high (strong adhesion). In practice, the value of 300 p must not be exceeded. The sample is therefore unusable.

The results show that the copolymer particles of the invention act as spacers in an outstanding manner and independently of the film formers used as the dispersing medium. The particles prevent the contact of an emulsion side with a rear side of a wound photographic film material, since the matting material according to the invention partly projects beyond the surface of the protective layer.

A comparison of the amounts of particles present in the protective layer per unit area of the photographic material before and after color processing shows that the particles were not dissolved in the alkaline developer, i.e. the effect of the spacer is retained even after the material has been processed.

Example 3

The effect of the copolymers according to the invention as spacers can be increased by adding colloidal silica in the form of SiO ₂ hydrosols to the protective layer composition.

The following protective layer compositions were produced:

The pH of the solutions was 6.5-7; the wet application 5 ₀ g / _m ² .

The hardening agent corresponds to the formula

The protective layer solutions were poured onto an uncured color negative film and dried.

The test was then carried out as indicated in Example 1.

Glossy spots and color stains can be almost completely avoided by combining the copolymers according to the invention with silica sol such as Sample B shows.

Claims (5)

1. A process for producing matt outer layers of photographic silver halide recording materials which contain polymer particles dispersed in a binder as matting agents, characterized in that in the aqueous solution of a hydrophilic colloid spherical particles of a substantially alternating and equimolecularly structured suspension copolymer of maleic anhydride and one 1-olefin having 2 to 8 carbon atoms with a particle size of 1 to 10 _/ u, preferably 1.5 to 5 _/ u, in an amount of 1 to 15% by weight, preferably 5 to 10% by weight, based on the weight of the dispersion, the dispersion is applied to one or both surfaces of the photographic material so that the applied layer contains 10 to 500 mg / m ^{2 of} the particles and the layer is dried. 2. The method according to claim 1, characterized in that 0.1 to 1% by weight, based on the weight of the water contained in the dispersion, of a surface-active substance is added to the dispersion before application. 3. Process according to claims 1 and 2, characterized in that gelatin is used as the hydrophilic colloid. 4. Process according to claims 1 to 3, characterized in that a copolymer of diisobutylene and maleic anhydride (1: 1 mol) is used. 5. Process according to claims 1 to 4, characterized in that the dispersion prior to application colloidal silica in the form of a hydrosol having a particle size of 1 to 15 nm in an amount of 0.5 to 2 parts by weight of colloidal silica particles per 1 part by weight of the hydrophilic colloid be added.