EP0620480A1 - Light-sensitive silver halide recording material having reduced pressure sensitivity - Google Patents

Abstract

The occurrence of pressure marks can be reduced by protective coatings containing suitable additives. However, this adversely affects other properties of the recording materials, such as sensitivity, contrast and clarity. Recording materials having protective coatings containing polyolefin oxidates are substantially insensitive to pressure marks and have low haze, high sensitivity and high contrast. The novel recording materials can be used in all areas of photographic and radiographic image production, in particular in the reproduction of colour images in the print precursor and in the recording of X-ray images in medical diagnostics.

Description

The invention relates to a light-sensitive recording material according to the preamble of the main claim.

In the manufacture, storage and processing, photosensitive silver halide recording materials are moved while they are in contact with the surfaces e.g. B. of other films, guide rollers and plates of imagesetters, cassettes and processing machines are in contact. In practice, such surfaces show roughness or peaks due to the deposition of dirt, dust, scratches or matting agents. At the contact points with such tips, considerable pressure is exerted on the film surface, which is transferred to the silver halide grains and can lead to pressure sensitization. During development, the material is blackened at these points even if no exposure has taken place, so that gray or black printed marks are produced. This happens in particular without mechanically damaging the outer layer. Typically, such print marks are in the form of black lines that affect the recorded image. Such black print marks are particularly disadvantageous in photoset films and in films which have been processed with infectious development.

The problem of pressure sensitivity has increased in importance due to the more recent development of faster and largely automatic handling of the materials, for example during exposure. Because of the simultaneously required suitability for rapid processing, it cannot be solved by simply increasing the proportion of binder in the emulsion or the thickness of the protective layer.

Patent application EP 02 09 010-A2 describes recording materials with ultra-partial contrast and reduced pressure sensitivity, which contain polyhydroxybenzenes, for example hydroquinone. With these materials, however, the sensitivity to pressure only decreases after longer storage and at the same time the sensitivity decreases.

In application EP 04 90 302-A2 it is proposed to add colloidal silica to the emulsion layer and to limit the dynamic coefficient of friction by incorporating a lubricant into the protective layer.

It is also known to reduce pressure sensitivity by incorporating soft polymer latices into the emulsion or overmold layer (see, e.g., Research Disclosure 308 119, December 1989).

The known methods lead to a certain reduction in pressure sensitivity, but in many cases this is not sufficient. In addition, lubricants or latices incorporated into the layers cause a number of other disadvantages, in particular in larger amounts, such as tendency to stick, reduced wet scratch resistance and haze. The processing time required is also extended. Colloidal silica affects the flatness of the materials and undesirably increases the viscosity of the casting solutions.

The invention has for its object to provide a rapidly processable light-sensitive silver halide recording material which is largely insensitive to the appearance of print marks and has a low haze and optimal sensitometric properties.

This object is achieved by a light-sensitive silver halide recording material with a layer support and at least one layer arrangement composed of at least one Silver halide emulsion layer and an outer protective layer containing a hydrophilic colloid on the side of the layer arrangement facing away from the carrier, which is characterized in that the protective layer contains a polyolefin oxidate.

Polyolefin oxydates are products whose molecules consist of a polyolefin chain with oxidatively generated functional groups, essentially carboxyl and hydroxyl groups. Production and properties are described, for example, in Kunststoff-Handbuch, Volume IV, page 161 ff. (Carl Hanser Verlag, Munich 1969) and in Ullmann's Encyclopedia of Technical Chemistry, 4th edition, Volume 24, page 42 f. (Verlag Chemie, Weinheim 1983). Suitable products are commercially available both in pure form and as an aqueous dispersion.

The use of oxidized polyethylene as a closed layer on soot-containing antihalation backing layers to improve the tendency to stick, scratch sensitivity, abrasion and behavior in alkaline development baths is described in the patent specification DD 02 12 339. After that, however, it was not to be expected for the person skilled in the art that polyolefin oxidates as a component of protective layers over the light-sensitive emulsion prevent the formation of printed marks.

The hydrophilic colloid in the protective layer is preferably gelatin. However, other macromolecular hydrophilic substances can also be used, for example polyacrylamide, polyvinyl alcohol and copolymers of the corresponding monomers, if appropriate also with acrylic acid.

The polyolefin oxidate contained in the protective layer of the recording materials according to the invention is preferably a polyethylene oxidate.

The proportion of the polyolefin oxidate in the protective layer can be about 2 to 85 percent by weight, preferably between 5 and 70 Percent by weight. A particularly preferred range is between 20 and 60 percent by weight.

Parameters for polyolefin oxydates are determined according to the DGF standard methods, Department M: Waxes and Wax Products, Stuttgart 1975, the German Society for Fat Science.

Polyolefin oxidates preferred according to the invention have a ball pressure hardness according to DGF-M-III 9a between 150 and 1100 bar. The range from 250 to 1100 bar is particularly preferred.

The molecular weight of the polyolefin oxydates according to the invention is preferably between 3000 and 8000 g / mol.

The acid number of the polyolefin oxidates according to the invention is between 10 and 35 mg KOH per g. The range from 15 to 25 mg KOH per g is preferred.

Polyolefin oxidates with a melting point of 90 to 140 ° C., determined according to DIN 53736, are preferred.

The polyolefin oxidates are expediently processed into an aqueous dispersion for incorporation into the coating solutions. This can be done in a known manner by heating a mixture with water above the melting point and stirring, if appropriate under increased pressure and preferably in the presence of an alkali metal hydroxide. The particle size of the dispersion should be below 200 nm, preferably between 50 and 100 nm.

In contrast to other polymer dispersions, the polyolefin oxidates surprisingly do not significantly hinder the access of the processing solutions to the light-sensitive emulsion layer, even with a high proportion in the protective layer. The suitability of the materials for rapid processing is therefore not reduced.

The thickness of the protective layer of the recording materials according to the invention can be selected within wide limits depending on the intended use and the desired properties will. A preferred range is characterized by an application weight of the dried layer between 0.1 and 1.5 g / m². The range between 0.5 and 1.2 g / m 2 is particularly preferred.

The light-sensitive silver halides of the recording materials used according to the invention consist of silver chloride, silver bromide, silver chlorobromide, silver bromoiodide or silver chlorobromoiodide. They can be monodisperse or polydisperse, but have a uniform composition, but also have grains with a core-shell structure and also mixtures of grains of different composition and grain size distribution. The shape of the grains can be predominantly spherical, polyhedral or also tabular. The silver halides are produced using a hydrophilic colloidal binder, preferably gelatin. Methods for producing suitable light-sensitive silver halide emulsions are known to the person skilled in the art and are summarized, for example, in Research Disclosure 308 119 (December 1989).

The grain size of the silver halide grains in the emulsions depends on the sensitivity required and can be, for example, between 0.1 and 1 μm. Precious metal salts, especially salts of rhodium or iridium, can be present in the usual amounts in the emulsion preparation in order to improve the photographic properties.

The emulsions are preferably chemically sensitized. Suitable methods are sulfur, reduction and noble metal sensitization, which can also be used in combination. For the latter, for example, gold or iridium compounds can be used.

The emulsions can be spectrally sensitized with conventional sensitizing dyes.

The emulsions can also contain conventional antifoggants. Tetrazaindenes, optionally substituted, are preferred Benzotriazole, 5-nitroindazole and mercury chloride. These agents can be added at any time during the preparation of the emulsion or can be contained in an auxiliary layer of the photographic material. To improve the photographic properties, an iodide can be added to the emulsion in an amount of about 1 mmol per mole of silver before or after chemical ripening.

The photographic material can contain other additives which are known and customary for the production of certain properties. Such agents are listed, for example, in Research Disclosure 308 119 in chapters V (brightener), XI (coating aids), XII (plasticizers and lubricants) and XVI (matting agents).

The gelatin content of the emulsions is generally between 50 and 200 g per mole of silver; the range between 70 and 150 g per mole of silver is preferred.

The recording materials according to the invention preferably contain a contrast-enhancing hydrazine compound. This hydrazine compound can be incorporated in a manner known per se either into the silver halide emulsion layer or into an auxiliary layer which is reactive with it. Here, "reactive relationship" means that the hydrazine compound or its reaction products can pass into the emulsion layer at least during the action of an aqueous alkaline developer solution. Suitable compounds and incorporation methods are described, for example, in Research Disclosure 235 010 (November 1983), DE-27 25 743-A1, EP-00 32 456-B, EP-01 26 000-A2, EP-01 38 200-A2, EP -02 03 521-A2, EP-02 17 310-A2, EP-02 53 665-A2, EP-03 24 391-A2, EP-03 24 426-A2, EP-03 26 443-A2, EP-03 56 898-A2, EP-04 73 342-A1, EP-05 01 546-A1.

Examples of suitable hydrazine compounds are

Die Schichten der erfindungsgemäßen Aufzeichnungsmaterialien können mit einem bekannten Mittel gehärtet sein. Dieses Härtemittel kann der Emulsionsschicht zugesetzt oder über eine Hilfsschicht, beispielsweise die äußere Schutzschicht, eingebracht werden. Bevorzugte Härtungsmittel sind Hydroxydichlorotriazin, Dihydroxydioxan, Divinylsulfone, Biscarbamoylimidazole.

The layers of the recording materials according to the invention can be hardened with a known agent. This hardening agent can be added to the emulsion layer or introduced via an auxiliary layer, for example the outer protective layer. Preferred curing agents are hydroxydichlorotriazine, dihydroxydioxane, divinyl sulfones, biscarbamoylimidazoles.

The layers of the recording materials according to the invention can also contain known polymer dispersions which, for example, improve the dimensional stability of the photographic material. These are generally latices of hydrophobic polymers in an aqueous matrix. Examples of suitable polymer dispersions are given in Research Disclosure 308 119, Chapter IX B. Polymers or copolymers of various acrylic acid esters with particle sizes below 100 nm are preferred.

In the recording materials according to the invention, all light-sensitive layers can be applied in a layer arrangement on one side of the support, the other side remaining uncoated or light-insensitive auxiliary layers, for example for antihalation and flatness. However, the invention also includes materials in which light-sensitive layer arrangements comprising at least one light-sensitive silver halide emulsion layer and an outer protective layer are present on both sides of the layer support.

In addition to the light-sensitive silver halide emulsion layers and the outer protective layer, the layer arrangements can contain further layers, for example to promote adhesion or the coating process or filter layers.

All known layer supports can be used, in particular flexible ones, such as films made from polyesters such as polyethylene terephthalate or from cellulose esters and paper, preferably with a hydrophobic coating.

The recording materials according to the invention can be formulated so that the proportion of the hydrophilic colloid in the emulsion and protective layers is low. Such materials are particularly suitable for rapid processing.

The recording materials according to the invention can be used in all fields of photographic and radiographic imaging, in particular in the reproduction of color images in the prepress and in the recording of X-ray images in medical diagnostics.

L1

wäßrige Dispersion von Styrol-Methylmethacrylat-Copolymer (30/70), Molmasse etwa 100 000 g/mol, Teilchengröße 100 nm, Feststoffgehalt 40 Gewichtsprozent.

L2

wäßrige Dispersion von Polyethylen, Molmasse 20 000 g/mol, Teilchengröße 200 nm, Feststoffgehalt 20 Gewichtsprozent.

L3

wäßrige Dispersion (Latex) von Polyethylacrylat, Molmasse etwa 100 000 g/mol, Teilchengröße 100 nm, Feststoffgehalt 30 Gewichtsprozent.

L4

wäßrige Dispersion von Ethylen-Vinylacetat-Copolymer (90/10), Molmasse 6 000 g/mol, Teilchengröße 500 nm, Feststoffgehalt 20 Gewichtsprozent.

L5

wäßrige Dispersion von Ethylen-Acrylsäure-Copolymer (92,5/7,5), Molmasse 6 000 g/mol, Teilchengröße 150 nm, Feststoffgehalt 20 Gewichtsprozent.

KK

Kolloidale Kieselsäure in Wasser, Teilchengröße 20 nm, Feststoffgehalt 30 Gewichtsprozent.

PO

wäßrige Dispersion von Polyethylenoxydat, Molmasse 8000 g/mol, Kugeldruckhärte ca. 1000 bar, Säurezahl 22 mg KOH/g, Teilchengröße 100 nm, Feststoffgehalt 35 Gewichtsprozent, Schmelzpunkt 130 °C.

HQ

Hydrochinon (wäßrige Lösung).

The following known or inventive agents for improving pressure sensitivity were used in the exemplary embodiments below:

L1

aqueous dispersion of styrene-methyl methacrylate copolymer (30/70), molecular weight about 100,000 g / mol, particle size 100 nm, solids content 40 percent by weight.

L2

aqueous dispersion of polyethylene, molecular weight 20,000 g / mol, particle size 200 nm, solids content 20 percent by weight.

L3

aqueous dispersion (latex) of polyethylene acrylate, molecular weight about 100,000 g / mol, particle size 100 nm, solids content 30 percent by weight.

L4

aqueous dispersion of ethylene-vinyl acetate copolymer (90/10), molecular weight 6,000 g / mol, particle size 500 nm, solids content 20 percent by weight.

L5

aqueous dispersion of ethylene-acrylic acid copolymer (92.5 / 7.5), molecular weight 6,000 g / mol, particle size 150 nm, solids content 20 percent by weight.

KK

Colloidal silica in water, particle size 20 nm, solids content 30 percent by weight.

PO

aqueous dispersion of polyethylene oxidate, molecular weight 8000 g / mol, ball pressure hardness approx. 1000 bar, acid number 22 mg KOH / g, particle size 100 nm, solids content 35 percent by weight, melting point 130 ° C.

HQ

Hydroquinone (aqueous solution).

The stated amounts always relate to the solid contained in these dispersions.

example 1

A cubic silver halide emulsion (Cl / Br = 80/20) with an average edge length of the silver halide grains of 0.21 μm was produced by pAg-controlled two-jet inlet. After the soluble salts had been removed by means of the flocculation process, the emulsion was chemically ripened with gold and thiosulfate for optimum short-term sensitivity and an optical sensitizer for the blue-green spectral range, as well as conventional stabilizers, coating aids and latex L3 were added. The emulsion contained 0.5 g gelatin and 0.1 g L3 per g silver.

Aqueous coating solutions for protective layers were prepared from gelatin and the additives listed in Table 1 and applied together with the emulsion to a polyethylene terephthalate layer support provided with an adhesive layer and an antihalation backing layer, and dried. The protective layers also contained 30 mg / m² of precipitated silica (particle size 5 μm) as a matting agent and 60 mg / m² of octylphenol diethoxysulfonic acid (sodium salt) as a coating aid. The application weight of the emulsion layer corresponded to 4.4 g of silver per m², that of the protective layers is given in Table 1.

Samples of the recording materials thus obtained were exposed to white light for 2x10⁻⁵ s through a gradient wedge and using a commercially available developer for the rapid processing of line and raster films (CUFD the Du Pont de Nemours (Germany) GmbH) processed in a roll development machine. The development took 25 s at 36 ° C. No differences between the test materials with regard to sensitivity, contrast, maximum density and fog were observed.

To test the sensitivity to pressure sensitization, a hard metal tip (radius of curvature of the surface 0.5 mm) was drawn at 18 mm / s and with an increasing contact force from 1 to 11 N over the surface of the emulsion side of unexposed samples, which rested on a flat glass plate. The samples were processed as described above. The smallest contact force is used as a measure of the sensitivity to pressure sensitization, which a print mark recognizes with the naked eye on the developed film.

The turbidity of the materials is measured on samples which were fixed and dried without exposure and development, using a device of the type "XL-211 Hazegard® Hazemeter" from Gardener Instruments. The proportion of the scattered light intensity is given in relation to the intensity of the incident light.

The results are shown in Table 1. Table 1 attempt Protective layer Print marks at (N) Turbidity (%) Remarks Gelatin (g / m2) Additive, quantity (g / m2) Order (g / m2) 1 0.7 - 0.8 <1 7.4 2nd 1.5 - 1.6 <1 7.6 3rd 0.7 L1, 0.4 1.2 <1 4th 0.7 L1, 0.8 1.6 <1 5 0.7 L2, 0.4 1.2 2nd 9.6 6 0.7 L2, 0.8 1.6 4th 10.0 dirt 7 0.7 KK, 0.4 1.2 <1 8th 0.7 KK, 0.8 1.6 <1 9 0.7 L3, 0.4 1.2 <1 dirt 10th 0.7 L3, 0.8 1.6 <1 dirt 11 0.7 L4, 0.4 1.2 <1 dirt 12th 0.7 L4, 0.8 1.6 <1 dirt 13 0.7 L5, 0.4 1.2 <1 14 0.4 PO, 0.3 0.8 6 7.4 15 0.7 PO, 0.2 1.0 5 6.9 16 0.7 PO, 0.4 1.2 > 11 7.4 17th 0.4 PO, 0.8 1.3 > 11 7.1

The results show that only the addition of the polyethylene oxidate (Experiments 14-17) provides strong protection against pressure sensitization. The overall application of the pouring layer is of minor importance. The addition of the polymer can therefore be compensated for by omitting gelatin. Experiments 14 and 17 also show that large amounts of polyethylene oxidate can also be added to the layer without the layer becoming cloudy. Comparative experiment 6 also shows considerably better protection against pressure sensitization, but is practically unusable because of the strong clouding of the layer and the dirt absorption during processing.

Experiments 3, 4, 7 and 8 show that dispersions of the "hard" fillers known as an additive to the protective layer and silica and styrene-methyl methacrylate copolymer do not result in any specific improvement in the sensitivity to printing marks.

Example 2

A cubic silver bromide emulsion with grains with an edge length of 0.2 μm was produced by pAg-controlled double jet inlet. This emulsion was flocculated, washed and chemically ripened with 0.3 mmol thiosulfate per mol silver. 5x10 noch³ mol of potassium iodide per mol of silver and a sensitizer for the green spectral range, 1 mmol of the hydrazine compound H-7 per mol of silver and a coating aid were also added. This emulsion was applied together with a protective layer on a polyethylene terephthalate support. The silver coating weight was 3.5 g / m². The protective layer consisted of 0.8 g / m² gelatin and the additives according to Table 2. It also contained 2,4-dichloro-6-hydroxytriazine as hardening agent and the matting agent as in Example 1.

For sensitometric testing, samples of these films were brought into contact with a template with a density gradient wedge and a contact grid underlaid with a density gradient wedge Exposed to white light and then processed in a roll developing machine with a commercially available developer for high-contrast high-speed processing and a hardness fixing bath. The development time was 40 s at 38 ° C. The minimum and maximum density (Dmin and Dmax), the sensitivity S for the halftone value 50%, based on experiment 18 as a comparison, and the mean gradation between density values 2 and 4 were determined on the developed film samples.

The procedure for testing the sensitivity to printing marks was as in Example 1, but the samples were processed under the same conditions as for the sensitometric test. The results of the evaluations are summarized in Table 2.

The results show that a significant improvement in susceptibility to printing marks without other disadvantages is only achieved in experiments 26 and 27 according to the invention. The polyethylene dispersion L2 brings about a certain improvement, but the turbidity increases sharply. The beneficial effects of hydroquinone are associated with a sharp decrease in sensitivity and contrast. Table 2 attempt additive Quantity (g / m²) Dmin Dmax S G Print marks at (N) Turbidity (%) 18th - - 0.04 5.8 1.00 > 25 <1 7.0 19th HQ 0.15 0.04 5.8 0.75 18th 5 8.4 L2 0.20 20th KK 0.40 0.04 5.8 0.92 > 25 <1 7.0 21 KK 0.40 0.04 5.8 0.92 25th 2nd 7.9 L2 0.20 22 L1 0.40 0.04 5.8 0.88 > 25 <1 7.0 23 L1 0.40 0.04 5.8 0.88 25th 3rd 8.2 L2 0.20 24th L2 0.20 0.04 5.8 1.00 > 25 4th 8.6 25th L2 0.40 0.04 5.8 0.96 > 25 9 9.1 26 PO 0.20 0.04 5.8 1.05 > 25 9 6.8 27 PO 0.40 0.04 5.8 1.05 > 25 > 11 7.0

Claims (9)

Photosensitive silver halide recording material with a layer support and at least one layer arrangement composed of at least one silver halide emulsion layer and an outer protective layer containing a hydrophilic colloid on the side of the layer arrangement facing away from the support,
characterized in that
the protective layer contains a polyolefin oxidate. Recording material according to claim 1,
characterized in that
the protective layer contains gelatin as a hydrophilic colloid. Recording material according to claim 1 or 2,
characterized in that
the polyolefin oxidate is a polyethylene oxidate. Recording material according to one of claims 1 to 3,
characterized in that
the proportion of the polyolefin oxidate in the protective layer is 5 to 70 percent by weight, based on the hydrophilic colloid. Recording material according to one of claims 1 to 4,
characterized in that
the polyolefin oxidate has a ball pressure hardness of 150 to 1100 bar. Recording material according to one of claims 1 to 5,
characterized in that
the polyolefin oxidate has an acid number of 10 to 35 mg KOH per g. Recording material according to one of claims 1 to 6,
characterized in that
the polyolefin oxidate has a molecular weight of 3000 to 8000 g / mol. Recording material according to one of claims 1 to 7,
characterized in that
the particle size of the polyolefin oxidate in the protective layer is between 50 and 100 nm. Recording material according to one of claims 1 to 8,
characterized in that
it contains a hydrazine compound in at least one silver halide emulsion layer or in a layer which is reactive with such a layer.