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Magnetic recording medium
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Inventors: Ootani, Tsuyoshi; Nakajima, Junsaku; Abe, Chiaki; Wada, Ikuko;
Assignee: Kao Corporation (Tokyo, JP)
Primary Examiner: Robinson; Ellis P.
Assistant Examiner:
Attorney, Agent or Firm: Birch, Stewart, Kolasch & Birch
Disclosed is a magnetic recording medium having a magnetic layer composed mainly of a magnetic powder and a resin binder, wherein the magnetic layer comprises (a) an ester compound comprising (a-1) an ester compound represented by the following formula (1): ##STR1## wherein R stands for a branched alkyl group having 13 carbon atoms, (a-2) butyl stearate and (a-3) butoxyethyl stearate, and (b) carbon black comprising (b-1) carbon black having an average single particle size of 10 to 50 m.mu. and (b-2) carbon black having an average single particle size of 200 to 1,000 m.mu.. This magnetic recording medium has an excellent durability and is utilized as a floppy disk or the like. |
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The lubricant system of the present invention comprises a restricted combination of ester compounds.
The ester compound represented by the formula (1) is tridecyl stearate, which alkyl chain is derived from a branched-chain alcohol.
The branched alkyl chain of the ester may be partially substituted by an unbranched alkyl chain.
However, it is preferred that the content of the branched tridecyl stearate in the whole tridecyl stearate be at least 60% by weight, especially at least 90% by weight.
As for the mixing ratios of the ester compound (a-1) represented by the formula (1), butyl stearate (a-2) and butoxyethyl stearate (a-3), it is preferred that the amounts of the ester compounds (a-1), (a-2) and (a-3) be 20 to 80 parts by weight, 10 to 40 parts by weight and 20 to 80 parts by weight, respectively, per 100 parts by weight of the sum of the ester compounds (a-1), (a-2) and (a-3).
This lubricant system may be mixed into a magnetic paint or may be dissolved in an appropriate solvent and sprayed on a magnetic coating.
The lubricant system comprising the ester compounds (a-1), (a-2) and (a-3) is generally used in an amount of 1 to 15% by weight based on the magnetic powder.
The carbon black used in the present invention is defined by the average single particle size.
Namely, the carbon black system comprises (b-1) carbon black having a average single particle size of 10 to 50m.
mu.
and (b-2) carbon black having an average single particle size of 200 to 1,000m.
mu.
.
The carbon black relating to the present invention may comprise two or more kinds of carbon blacks, if the average single particle size is within the above-mentioned size range.
It is preferred that the amount of carbon black (b-2) be higher than that of carbon black (b-1).
It also is preferred that the total amount of carbon black (b-1) and (b-2) be 8 to 25% by weight based on the magnetic powder.
In the magnetic recording medium of the present invention, it is considered that the specific ester compounds (a-1), (a-2) and (a-3) and the carbon blacks (b-1) and (b-2) having a specific particle size have some interactions and consequently the durability is highly improved, but the mechanism for the improvement is not clear yet
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Electrical and Wave 
