| 摘要 |
PURPOSE:To obtain a recording medium having a low coefft. of friction and high durability and keeping a head clean by adding trifunctional isocyanate to polyurethane resin and a vinyl chloride - vinyl acetate copolymer to prepare a binder and by forming a coated magnetic film using the binder and magnetic powder. CONSTITUTION:Polyurethane resin and a vinyl chloride - vinyl acetate copolymer are used in 90:10-50:50 ratio. When the amount of the latter is increased in excess of the ratio, superior characteristics such as high sensitivity and a high S/N ratio are provided to the resulting recording medium, yet the magnetic layer is made rigid and has low durability. When the amount of the former is increased, the adhesive property is improved, yet the coefft. of friction is increased, and a magnetic head is not kept clean. Trifunctional isocyanate with <=2,000 low mol.wt. is added to said resins to prepare a binder. The isocyanate reacts with the polyurethane resin of this invention with <=20,000 number average mol.wt. and hydroxyl groups in the vinyl chloride - vinyl acetate copolymer, causing cross-linking, so the wear and heat resistances of the magnetic layer are improved. The amount of the isocyanate to be added is usually 3-50wt% of the total amount of the binder. |
