Master and copy tape system for thermomagnetic copying - contg. magnetic pigment with higher Curie temp. in master tape and limited butyl palmitate concn.

摘要

Magnetic tape (MT) for thermomagnetic copying contains a magnetic pigment (I-M) with Curie temp. TC1 and copy tape (CT) a magnetic pigment (I-C) with Curie temp. TC2, both finely dispersed in polymeric binder. For copying, CT is heated to a temp. above TC2 but below TC1 and then cooled in close contact with MT. MT and/or CT contains fatty acid and/or fatty ester with a butyl palmitate (II) fraction as lubricant. The novelty is that the (II) content of MT and/or CT is max. 0.15 g/100g (I). Pref. (I-M) consists of metal (alloy) powder with a coercivity of min. 100 kA/m and TC1 greater than 300 deg.C; and (I-C) or CrO2 with a coercivity of min. 40 kA/m and TC2 ca. 130 deg.C. USE/ADVANTAGE - The system is useful for video purposes. The tapes are suitable for high speed copying. MT still has satisfactory running properties after several thousand passes and transfers the information to TC without loss or distortion, even after prolonged use.