DE2308711C2 - Process for the production of a polyolefin-coated photographic writing support with a crystalline layer - Google Patents

Description

Magnesium hexafluorosilicate

MgSiF ₆ · _{6H 2} O

Calcium Magnesium Carbonate

(2—20 μΤβΠοΙιβηαυκΙιίτ ^ ΒεΓ)

Silica, colloidal

(2—30 πιμ particle diameter)

Polystyrene sulfonic acid Na salt

(Mole weight approx. 2000)

Non-foaming surfactants

Substance 0.1%

Rest water

1.6% 5.0% 5.0% 1.2%

consists

25th

30th

35

4. The method according to claim 1 and 2, characterized in that on the activated polyolefin surface of the photographic carrier material aqueous suspension is painted on, the out

Calcium hexafluorosilicate 1.10% 45 4.00% CaSiF ₆ · 2 H ₂ O Calcium silicate like 3.00% (50-500 πτμ particle size) 140% Silica, colloidal 0.05% 50 (2-30 Γημ particle size) 4.00% K salts of polyacrylic acid 2.00% Ociylphenoxyethanol (wetting agent) Butanol Methanol Rest water

consists.

55

5. The method according to claim 3 and 4, characterized in that the calcium silicate contained or calcium magnesium carbonate acts as a matting agent and thus mixed precipitation products te, in which part of the calcium is replaced by aluminum or magnesium and one Particle size between 0.1 and 20 μ has.

6. The method according to claim 5, characterized in that in the matting agent used some of the calcium is present as oxide, hydroxide or in the form of another alkaline compound.

7. The method according to claim. 5 and 6, "characterized in that dasyjai the suspension as Basic calcium silicate containing matting agents is replaced by calcium carbide or by mixed compounds, besides ^ calcium, magnesium and aluminum: contained and in the Suspension by double reaction between a water-soluble salt of calcium, optionally with the addition of magnesium and aluminum salts with sodium or potassium sulfate or -Carbonate can be precipitated.

8. The method according to claim 1 to 7, characterized in that the suspension 0.1 to 0.2 % By weight of commercially available wetting agents can be added.

The invention relates to a method for producing a photographic writing carrier with a crystalline one layer

It has long been known to use photographic carrier material, for example photographic base paper, or to be coated on both sides with a polyolefin. Such a coated photographic carrier material forms an excellent substrate for light-sensitive photographic emulsions for black and white or color photography, because the base paper through the Coating with polyolefins to prevent the penetration of photographic processing solutions, for example when developing photographic images, is protected

Closed films made of polyethylene or polypropylene have proven to be particularly effective in this regard proven.

A disadvantage of this polyolefin-coated carrier is however, the fact that the polyolefin coating material has a hydrophobic character. That means that many coating materials and other solutions to be applied to these hydrophobic surfaces or emulsions of a hydrophilic type do not adhere. It is therefore not possible to use water-soluble adhesives directly on the hydrophobic surface of the polyolefin layer to apply or write on with ballpoint pen, ink or printing inks. Also the application of the hydrophilic photosensitive photographic emulsions is without any special surface treatment the polyolefin coating is not possible.

Another disadvantage of this polyolefin coating is its behavior as a dielectric and the resulting properties conditional tendency to be electrostatically charged. Such electrostatic charges often lead to Faults or errors in the further processing of the base papers or in the development process of the emulsified photographic carrier.

Finally, another disadvantage is the great surface smoothness of polyolefins So-called self-lubricating effect occurs and which is undesirable for various reasons, namely bothers you very often the mechanical advance and transport of photographic recording material into the Processing and developing machines, especially of course when the photographic carrier material is also coated on its back with a polyolefin layer, which is used to seal the paper surface against the action of water or photographic chemicals in solution is essential.

To make the hydrophobic surface of polyolefin coatings of this type writable and coat them with hydrophilic paints, solutions or suspensions, it is known to first apply the polyolefin surface by activation processes, for example by a corona discharge using high-voltage alternating current, high frequency or using an alternating current with superimposed direct current to activate, the photographic carrier material provided with the or with the polyolefin layers passed through a gap-bin- * wint the one side of the earthed guide roller for the web-shaped «; Material is formed while extending on the other side of the electrode via the web ": · at DIE the ¹⁵ high voltage is applied.

A water-soluble film-forming agent, for example, is then deposited on the basis of cellulose derivatives or polyvinyl alcohol alone or in conjunction with therein ^x kdjleiidaler dispersed silicic acid on a thus prepared activated polyolefin surface. Such a layer can then be written on with aqueous paints or inks after it has dried.

To eliminate the electrostatic charge on the polyolefin-coated carrier material, it is known to incorporate antistatic agents into the polyolefins or to apply them in the form of a thin layer to the polyolefin surface, this layer with the antistatic agent often being a hydrophilic layer, whose adhesion to the hydrophobic layer, as already mentioned ^J0 mentioned above, with the interposition of an activation of the hydrophobic layer, for example by corona discharge.

It is also known that activation of the polyolefin surface to Haftbarmachung hydrophilic Schich- ^J5 th thereby effect that instead of the activation means of corona discharge, an acidic, aqueous mixture of an aqueous silica sol, an acid-resistant organic film-forming material and an acid at a pH between 2 and 7 and then dried at elevated or room temperature, whereupon this film is heated to elevated temperatures after drying. This film then has absorbent properties.

Finally, it is known that the activity brought about by corona discharge, dung is inherently inactive Surface of the polyolefin coating material for hydrophilic substances subsides again over time and you must carry out a renewed activation if between the activation and the subsequent '" After the coating of the carrier material, for example with the photographic emulsion, a longer period of time The time in which this activation decays depends on various factors Factors such as the relative humidity and other environmental influences. One can As is known, preserve such activated surface or use it for its intended purpose, if an adhesive coat is applied to the surface activated in this way, which has a hydrophilic character and which then the necessary further coats, for example photographic emulsions, are applied.

All these additional layers to be applied to bring about an adhesion between hydrophilic substances and a surface which is hydrophobic in itself are used, but have a considerable effect Disadvantage, since it is always a film former, for example a polyethylene emulsion or a cellulose derivative and one therein dispersed agent or pigment containing the actual hydrophilic properties, for example the silica sol. So there is a layer in which the silica particles are distributed in the film former uhddürch 'this both with the surface of the Polyolefins as, 'are also interconnected. Each particle is practically without a firm bond to the neighboring particle; As a result, the mechanical cohesion is naturally low, and due to the embedding of the silica particles in the film-forming material, the thickness of this layer is relatively large and practical immutable. - ;; .- \

The object of the present invention is therefore to provide a Procedure for; Coating of surfaces. from To propose polyolefin layers on photographic supports that its polyolefin layer can be written on made the applied layer good adhesive strength and the electrostatic charge of the Reduced recording material.

This is achieved according to the invention in that a crystalline surface is placed on an acuved polyolefin surface Layer is applied, which consists of an aqueous suspension of a silica in sol form of an alkaline reactive matting agent; a soluble salt of calcium, magnesium, zinc and / or lead hexafluorosilicate and a polymeric organic polyelectrolyte had been produced.

Such a layer on the surface of the polyolefin lamination of the photographic carrier material is one that has grown together through crystallization Layer which in this form also stands in connection with the activated polyolefin surface because of the crystalline intergrowth, excellent mechanical strength, which is particularly important when writing or printing and it creates the possibility of the crystal structure or the crystal costume by controlling the crystallization conditions before and after application design so that it can be optimally adapted to the most varied of purposes.

The crystal layer arises from the fact that a self-binding one in the aqueous solution or suspension Silicic acid sol and a salt of hexafluorosilicic acid are included, for example the calcium or Magnesium salt, as well as a matting agent based on calcium silicate or calcium carbonate

In addition to the antistatic agent, the dispersion can optionally also contain further additives.

Between the three components of this suspension, namely the silica sol, the salt of hexafluorosilicic acid and the matting agent based on basic calcium silicate or basic Calcium carbonate undergoes chemical conversion and crystallization. Here, the hexafluorosilicate with the alkaline calcium compounds settles on the Surface of the pigment particles to form calcium fluoride and silica, both very are difficult to dissolve.

Instead of the calcium salt of hexafluorosilicic acid, the magnesium salt can of course also be used will.

The reaction of hexafluorosilicic acid salts with alkaline calcium compounds, for example calcium hydroxide, results in silicic acid, which is known to crystallize in chains, ribbons and networks, so that an intimate crystal interlocking in the Layer occurs.

The calcium fluoride and / or magnesium fluprid and the silica forms on the pigment particles well adhering weakness; When applying and When the dispenser dries, the silicic acid reacts shell of the Pigine'ntteUchea with the silica, which in Solform was added, whereby a bond between the silica particles takes place. The enveloped As a result, pigment particles are firmly embedded in the silica film

This silica film with the firmly embedded n> Pigment particles impart to the polyolefin surface or surfaces the desired hydrophilic character and the necessary matting. For antistatic equipment the layer will be one as mentioned earlier known Äntistatifcum, z. B. an alkali or Ammont <5 salt of a polycarboxylic acid, for example the Polyacrylic or polymethacrylic acid or a polysulfonic acid used To prepare the aqueous, spreadable suspension, the generally used usual additives, and for the special purpose of coating the polyolefin surface is the additive a network init is required.

The invention will now be based on two examples explained in more detail, the percentages given therein being percentages by weight and the size and Quantities are given in the metric system.

example 1

On the surface of a photographic base paper coated with polyethylene on one or both sides an aqueous suspension is applied which has the following composition:

approx. 2000 serves as an antistatic means to prevent it the electrostatic charge. The corona irradiated to activate the polyethylene surface; he follows at an alternating voltage of 50,000 V and 45 kHz.

Example 2

A photographic raw paper with a weight of about 200 gfm ² , which is coated on both sides with a polyethylene layer by extrusion and which has a weight of about 35 g / m ² , is according to Example 1 initially by corona irradiation for the application of an aqueous suspension of the the following composition has been made adhesive:

Magnesium hexafluorosilicate

(MgSiF ₆ · 6 H ₂ O) 1.6%

Calcium Magnesium Carbonate

2–20 μ particle diameter 5.0%

Silica, colloidal

2—30 πιμ particle diameter 5.0%

Polystyrene sulfonic acid Na salt,

Mol weight approx. 2000 1.2%

Non-foaming surfactants

Substance 0.1%

Rest water

35

40

45

Before coating with the aqueous dispersion, the polyethylene surface of the photographic carrier material is exposed to corona radiation for activation in order to achieve good adhesion of the coating to the polyethylene surface. The coating itself takes place in a manner known per se with an air knife, a roller squeegee or another known application device and is then dried. The weight of the dry layer is about 1 g / m ² . As already mentioned at the beginning, the crystal structure can be changed within limits by choosing the drying conditions, for example temperature.

In this embodiment, the basic agent that forms the basis of this reaction is ^b0 calcium magnesium carbonate, in which the calcium and magnesium ions are loosely bound and react with the fluorine ions to form fluorspar and magnesium chloride, while at the same time further magnesium ^{b <from the magnesium hexafluorosilicate i} fluoride is formed.

The sodium salt of polystyrene sulfonic acid mentioned in the example with the molecular weight of Calcium hexafluorosilicate

(CaSiF ₆ -2 H ₂ O) 1.10%

Calcium silicate precipitated,

50-500 ΐημ particle diameter 4.00%

Silica, colloidal,

2—30 πιμ particle diameter 3.00%

Potassium polyacrylate 1.50%

Octylphenoxyethanol 0.05%

Butanol 4.00%

Methanol 2.00%

Rest water

Octylphenoxyethanol is preferably used as a 5% aqueous solution and is a wetting agent. Butanol and methanol are present as foam suppressors in the above approach.

To produce such a coated photographic support material with a one or two-sided coating of a polyolefin, the procedure is that the chemical compounds mentioned in Examples 1 and 2 are dissolved or dispersed in water in the specified amount and particle size and the dispersion obtained applies, brushes or prints onto the selected previously activated polyolefin surface using devices known per se and the web of the photographic carrier material provided with the layer applied is passed through a drying device in which the layer is dried, the above-mentioned crystallization process taking place during the drying time. The drying is carried out in such a way that the carrier material is not adversely affected by the action of heat, but the water contained in the suspension and any alcohols that may also be present, such as butanol and methanol, are evaporated. Drying temperatures in the range from 50 to 200 ^° C. are suitable for this
It has been shown that the disadvantages described at the outset can be eliminated with the aqueous suspension solution according to the invention. The addition of an antistatic avoids electrostatic charging, and the applied dry layer is easy to write on and print on with water-based inks and dyes. It provides the necessary static friction and thus avoids the self-lubricating effect of polyolefin surfaces on transport rollers and rollers, which, as stated at the beginning, can lead to malfunctions in, for example, developing machines, and it is even suitable as an adhesion-promoting layer for photographic emulsions. Due to its mechanical strength, it can also withstand mechanical stresses, for example the multiple overrun of guide and transport rollers, with no abrasion. The layer is resistant to

Water and the usual chemical baths used for Development of black and white and color photographs can be used.

With regard to the coefficient of friction, the sliding angle was determined, which is under the effect of the applied layer according to the invention of tga = 0.4 on the uncoated polyolefin surface increased to tg a = 0.6.

The antistatic properties were significantly improved when the layer according to the invention was used. A reduction in the surface resistance of the polyolefin layer of the untreated surface from 10 ¹³ to 10 ^M ohm / cm to 10 to 10 ohm / cm compared to the surface treated according to the invention was achieved (measurement according to DIN 53 482). These are excellent values that guarantee trouble-free processing of such a material.

In Examples 1 and 2, calcium magnesium carbonate precipitated or calcium silicate precipitated is mentioned in the second line. These compounds form a matting agent which the polyolefin surfaces coated with the agent according to the invention give a matte appearance. This matting agent can also consist of precipitated calcium carbonate or mixtures of the two precipitation products. t: eri, namely calcium silicate or calcium carbonate, exist. Some of the calcium can also be replaced by aluminum or magnesium, and the Particle size should preferably be between 0.1 and

to 20 μ. It is important that the calcium or

Magnesium partly as oxide, hydroxide or in the form

another alkaline reacting calcium resp.

Magnesium compound is present. Similarly, instead of that in the examples

Listed salts of hexafluorosilicic acids also the zinc and lead salts or mixtures are used from such salts.

In any case, it is important that it is easy soluble salts of hexafluorosilicic acid are involved, d. H.

easily soluble in water.

Claims (3)

Patent claims: 1. A process for the production of a polyolefin-coated photographic writing medium with a crystalline layer, characterized in that an activated polyolefin surface a crystalline layer is applied, which consists of an aqueous suspension of a silica in Solform, an alkaline reacting matting agent, a soluble salt made from calcium, magnesium, zinc and / or lead hexafluorosilicate and a polymeric organic polyelectrolyte. 2. The method according to claim 1, characterized in that the aqueous suspension contains an antstatic which consists of an alkali or ammonium salt of a polycarbonate or polysulfonic acid 3. The method according to claim 1 and 2, characterized in that on the activated polyolefin surface of the photographic carrier material aqueous suspension is painted on, the out