Stock material or miscellaneous articles – Composite – Of polyamidoester
Patent
1986-11-19
1987-11-24
Robinson, Ellis P.
Stock material or miscellaneous articles
Composite
Of polyamidoester
252 6254, 427 44, 427 541, 427128, 428522, 428694, 428900, G11B 5702
Patent
active
047089091
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a magnetic coating material curable upon exposure to radiation and also to a magnetic recording medium obtained by using the coating material.
Presently, varied forms of magnetic recording media, including cassette tapes, open reel tapes, magnetic cards, and magnetic disks, are made by dispersing or dissolving powdered iron oxide or suchlike magnetic substance and a binder in an organic solvent, adding to the solution a plasticizer, dispersant, antistatic agent, and/or other additives which may be desired according to the intended use, mixing and kneading the mixture, and then applying the resulting coating material on a base film of polyester, polyvinyl chloride, polyacetate, or paper.
While various thermoplastic resins are still in use, it is a more customary practice, in order to obtain greater resistance to wear and heat and improve other physical properties of the product, to use a thermosetting resin as the binder and bake (cure) the coating in an oven for many hours (e.g., at 70.degree. C. for 2-20 hours). Besides the complexity of the process, the practice presents problems of blocking of the coating, deformation of the tape due to tightening on winding, loss of smoothness on the magnetic coating surface, and other factors adversely affecting the electrical properties of the product.
Furthermore, the magnetic coating material of the type dispersed or dissolved in an organic solvent requires such a large volume of the solvent that the process poses not only fire hazards but also environmental hygiene problems. For these reasons, the employment of aqueous resin type magnetic coating material instead has been proposed in recent years.
The aqueous resin type precludes the fire and health hazards associated with the use of the organic solvent type. The proposed method frequently uses a thermoplastic resin but more often prefers a thermosetting one and, as is the case with the organic solvent tape, the coating material applied on the substrate is baked (cured) over a long period of time in an oven so that the coating film will be more resistant to wear and heat and possess better physical properties. However, the method again offers problems, in addition to the complexity of the process, such as blocking of the coating, tape deformation due to tightening on winding, loss of smoothness on the coating surface, and other deleterious effects on the electrical properties of the product.
The present invention has been arrived at after intensive investigations made in search of an aqueous magnetic coating material adapted for use in making a magnetic recording medium which presents no such problems of the prior art but is excellent, especially in wear resistance and electrical properties. The magnetic coating material according to this invention will harden at a low temperature within a short time upon irradiation with electron beams or other radioactive rays. The material, which cures continuously as it is applied and dried, makes for improved productivity and causes no blocking due to takeup before curing nor any excessive tightening on winding. Presumably, irradiation with electron beams or the like causes a resin in the material which has at least one unsaturated double bond to produce radicals, which in turn initiate polymerization or cross-linking to form a three-dimensional network structure with good resistance to wear and heat and with other desirable physical properties. Thus, the present invention provides an excellent radiation-curable, magnetic coating material, hazardless and highly desirable from the viewpoint of environmental hygiene and which can be used in manufacturing a magnetic recording medium excellent in dimensional stability, wear resistance, surface smoothness, and other properties, within a short time in a simplified process.
In brief, the invention provides a radiation-curable, magnetic recording medium which comprises as essential components an aqueous vehicle containing of a water-soluble resin, a water-dispersible resin, or mixtures thereof each having at
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Isobe Yukihiro
Kanno Nobumori
Konno Ryozo
Kubota Yuichi
Mihoya Takashi
Robinson Ellis P.
Toyo Ink Mfg. Co. Ltd.
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