| 摘要 |
PURPOSE:To form an insulating layer without any defects such as pinholes and to improve the recording and reproduction efficiency by forming an insulating layer on a magnetic base body with a polyimide resin having <=2.0X10<-5>/ deg.C thermal expansion coefficient. CONSTITUTION:An SiO2 layer 2 for forming a magnetic gap A is provided on a magnetic substrate 1, and an insulating layer 6 for coating an electrically conductive layer 3 on the SiO2 layer 2 is formed with a polyimide resin having <=2.0X10<-5>/ deg.C thermal expansion coefficient (preferably <=1.0X10<-5>/ deg.C) or concretely the coefficient on the order of 10<-6>(7.0X10<-5>/ deg.C) which is intermediate between the coefficients of the SiO2 layer 2 and an upper core 4 (a 'Aendust(R)' layer). Since the thermal expansion coefficient of the polyimide resin layer 6 is approximate to the coefficients of the substrate SiO2 layer 2 and the upper core 4 (a 'Sendust(R)' layer), so large stress is not generated at the interfaces with the SiO2 layer and the 'Sendust(R)' layer by the heat generated during annealing and glass melt-sticking. Consequently, the films are not stripped off, and by cracks are not generated in the insulating layer 6. Besides, the deterioration of the magnetic characteristic due to the stress is not caused, since so large stress is not generated at the interface with the upper core.
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