| 摘要 |
PURPOSE:To improve storage property and to prevent increase of dropout by making the surface free energy of the magnetic layer larger than that of a back coating layer by a specified value and specifying the gloss of both layers to specific values. CONSTITUTION:The magnetic layer contains ferromagnetic powder, binder, carbon black, abrasive material and lubricant and is formed on a nonmagnetic supporting body, the other side of which is covered with the back layer containing a binder and carbon black. The surface free energy (SFE) of the magnetic layer is 40 to 55dyn/cm, while the SFE of the back layer is 45 to 55dyn/cm and made larger than that of the magnetic layer by more than 1dyn/ cm. These states of SFE can be realized by using binders having different values of critical surface tension for each layer. The gloss value of the magnetic layer is >150, while the gloss value of the back layer is 2 to 7. This can be realized by subjecting the medium after coating to supercalendering to satisfy the specification. |
