DE1253004B - Process for the galvanic production of layer magnetogram carriers - Google Patents

Description

GERMAN # l # PATENT OFFICE

EDITORIAL

DeutscheKI .: 48 a -5/58

Number: 1253 004

File number: B 68943 VI b / 48 a

1 253 004 filing date: September 20, 1962

Opening day: October 26, 1967

It is known to produce layered magnetogram carriers, which consist of a carrier film and a magnetizable layer of a ferromagnetic metal applied thereon, by placing a layer of a ferromagnetic material on a carrier film made of plastic, for example by vapor deposition in a high vacuum at pressures of IO ^-3 to IO ^-6 Torr. It is also known to provide the carrier films with a magnetizable layer by homogeneously distributing the finely powdered metals in an organic binder and applying these metal dispersions to the carrier film, for example by dipping, pouring, spraying or applying with rollers.

It is also known to produce magnetogram carriers by using a metallic magnetic Layer by galvanic means on a carrier, z. B. non-magnetic tapes and wires or paper, fabric or other flexible material, applied beforehand through a thin Coating made of metal or another suitable material has been made electrically conductive. Finally, it is also known to galvanically apply a magnetic carrier to a metallic carrier to apply metallic layer made of cobalt or nickel or alloys of these metals.

It has been found that layered magnetogram carriers can be obtained by applying an electrically conductive layer to a plastic carrier film and coating this layer with a further layer containing a ferromagnetic metal in an electroplating bath at currents of 0.01 to 20 A / dm ² with improved magnetic properties Properties obtained when using electrolytes which, in addition to the compounds of subgroup VIII of the Periodic Table, compounds of the metals of the V., VT. and VII. subgroup of the periodic system. These compounds can be in the form of their salts, e.g. B. chlorides and sulfates, but also as complex salts can be added. Even in amounts of 0.1 to 5 percent by weight, they result in a significant increase in the magnetic properties of the electroplated layer.

The electrically conductive layer can be applied in a known manner by vapor deposition of metals with or without metal oxides in a high vacuum. It is also possible to apply such layers to the carrier film by immersing the film in a solution of a copper or silver salt and then using a process for galvanic production
of layer magnetogram carriers

Applicant:

Aniline & Soda Factory in Baden
Aktiengesellschaft, Ludwigshafen / Rhein

Named as inventor:

Dr. Adolf Diebold,

Dipl.-Ing. Dr. Georg Boehm,

Franz Kühnel, Ludwigshafen / Rhine

Treated reducing agent. However, the layers applied to a film in this way show only a low bond strength. Better adhesive strength can be achieved if the finely powdered metals are distributed in a binder and the resulting dispersion applies in a known manner to the carrier film. As binders, for. B. acetyl and nitrocelluloses, chlorinated polyvinyl chlorides, polyvinyl acetals, polystyrenes and polyvinyl ethers, polyacrylic acid esters, Polyester and epoxy resins are suitable, which can be used together with in organic solvents Wetting and dispersing agents, metal powders and / or metal alloys e.g. B. in vibrating mills with each other mixed. You can also work with aqueous plastic emulsions as binders, which together with metal powder finely distributed therein, applied to the foils and dried to form a film will. But you can also use an adhesive in the form of an aqueous emulsion on plastic films Or apply dissolved in organic solvents and apply the finely powdered metals to the still Spray on a damp layer.

As an electrically conductive material, for. B. graphite, copper, bronze, aluminum or silver powder can be used. Ferromagnetic metals, e.g. B. Use iron, nickel or cobalt, or mixtures of these metals and their alloys. Carrier foils coated with such metals represent useful magnetogram carriers However, their magnetic properties are enhanced by the subsequent electroplating still vastly improved.

709 679/455

Claims (2)

The conductivity of the foils must be so good that the electroplating can be carried out with a voltage of 2 to 10 volts and a current density of 0.1 to 5 A / dm2. The subsequent electroplating S has a favorable effect if the electrically conductive layer is applied under the action of a magnetic field. This gives the applied particles a preferred direction of magnetization. Of the elements of subgroup VIII of the Periodic Table, nickel or cobalt in particular are used. Particularly smooth surfaces are achieved if the elements mentioned are used in the form of complex salts. Tartrate, nitrilotriacetate, ethylenediaminetetraacetate, etc. are suitable as ligands. Mixtures of complex salts of nickel or cobalt with normal salts of the elements mentioned, e.g. B. the sulfates, chlorides, sulfamines can be used. The metal ion concentration should be about 5 to 50 g per liter. The thickness of the galvanically applied layer can be up to 30 μ without impairing the adhesive strength. In order to meet the practical requirements, however, thicknesses of about 3 to 5 μ are sufficient. The magnetic values of the magnetogram carrier produced according to the invention can be increased further if the electroplating is carried out under the influence of a magnetic field, in such a way that the particles, for. B. be aligned in the running direction of the tape. The magnets can be arranged inside a closed roller rotating in the electroplating bath or attached directly in the bath if they are covered with water and acid-resistant plastic resins. The temperature of the electroplating bath can be varied within the range from 10 to 50 ° C. For economic reasons it is expedient to work at room temperature, i. H. at temperatures of around 15 to 25 ° C. To achieve constant magnetic values, it is necessary to continuously control the pH value of the bath and keep it constant within a range of 2 to 8. The pH is preferably between 4 and 7. Example 1 A polyester tape approximately 15 μm thick is coated with a 20% strength solution of polyvinyl butyrate in a mixture of toluene and tertiary butanol. After drying, an approximately 5 μ thick layer is obtained. The strip prepared in this way is then coated with a dispersion made in a vibrating mill from 50 parts of silver bronze, 1 part of a copolymer of arylamide and methacrylamide (1: 1), 5 parts of polyvinyl butyrate and 44 parts of a solvent mixture of toluene and butanol (in a ratio of 1: 1 ) coated. It is dried at about 100 ° C. and a very conductive, adhesive and glossy coating is obtained in a layer thickness of about 3 μ. This film is then provided with an adhesive, magnetizable coating in an electroplating bath containing 150 g of nickel citrate, 30 g of ethylenediamine disodium cobalt tetraacetate, 20 g of cobalt chloride and 2 g of manganese sulfate per liter. One works in a pH range from 5 to 7, with a current density of 0.5 to 1 A / dm2 at a voltage of 2 to 4 volts at room temperature. The magnetogram carrier obtained shows a coercive force of 500 Oerstedt, a remanence of 785 Gauss and a saturation remanence of 1450 Gauss. Example 2 A polyester film vapor-deposited with copper in a high vacuum and loaded with 0.1 mg copper per square centimeter is galvanically reinforced with copper to achieve a completely closed metal surface, so that a copper loading of about 0.25 mg / cm 2 surface is obtained. This film is in a bath containing 70 g of nickel citrate, 24 g of cobalt chloride, 5 g of chrome alum and 10 g of ammonium chloride per liter, the pH of which is adjusted to 5 by adding sodium hydroxide solution and then adding triethanolamine to a pH value of 6 electroplated at a current density of 0.5 A / dm2 and a voltage of 2.5 volts for about 10 minutes. In this way, firmly adhering magnetizable coatings are obtained whose static magnetic values at 1000 Oerstedt premagnetization are: 170 Oerstedt for the coercion force, 4900 Gauss for the remanent magnetization and 6300 Gauss for the saturation induction, the remanence being 78% of the saturation induction. When the same copper-coated foil is electroplated in a bath which, however, does not contain any chrome alum, but under otherwise identical conditions, only remanence values of 61.8% of the saturation induction are achieved. Example 3 As described in Example 2, an electrically conductive copper layer is produced on a polyester film and this is treated in a bath containing 18 g of nickel as citrate, 6 g of cobalt as chloride and 2 g of vanadium as vanadium oxide sulfate per liter. Electroplating is carried out at a current density of 1 A / dm2 and a voltage of 3 volts, the electrolyte having a pH of 5.5 to 6.0. Adhesive, glossy coatings are obtained, the remanent magnetization of which is 4060 Gauss and about 85% of the saturation induction which is 4760 Gauss. Patent claims: 1. A process for the galvanic production of layered magnetogram carriers by applying an electrically conductive layer to a plastic carrier film and coating this layer with another layer containing a ferromagnetic metal at current densities of 0.01 to 20 A / dm ² , characterized in that electrolytes are used are, in addition to the compounds of subgroup VIII of the Periodic Table of compounds of metals of V., VI. and VII. subgroup of the periodic system. 2. The method according to claim 1, characterized in that the electrolyte is the compounds the metals of the V., VI. and VII. subgroup of the periodic system in a quantity from 0.1 to 5 percent by weight can be added.