| 摘要 |
PROBLEM TO BE SOLVED: To provide a superior electromagnetic conversion characteristic and run durability by setting the protrusion frequency originating from inactive particles on a polyester layer surface and the particle aggregation ratio of the inactive particles on the polyester layer surface respectively within specified ranges. SOLUTION: The protrusion frequency originating from inactive particles on a polyester layer surface is set to 5000-50000 protrusions/mm2, and the particle aggregation ratio of the inactive particles on the polyester layer surface is set to 4-20%. The inactive particle in the polyester layer uses particles composed of heat-resistive org. macromolecules such as cross-linked silicone resin, cross-linked polystyrene, cross-linked styrene-divinylbenzene copolymer, polymethylmetacrylate, etc., or org. compd. such as silica, alumina, titanium dioxide, etc. The main grain size of the particle is 30-120 nm, pref. 35-110 nm, and the volume shape coefficient f=V/R3 is 0.1-π/6, pref. 0.3-π/6 where (f) is the volume shape coefficient, V is the vol. of particle, and R is the mean grain size of particles.
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