Hitachi, Ltd.

Hitachi Chemical Company, Ltd.

Mina Ishida

Yutaka Ito

Hiroyuki Matsumoto

Takayuki Nakakawaji

Hiroshi Tani

Takao Miwa

Heigo Ishihara

Yoshiaki Okabe

Hiroshi Sasaki

Akio Takahashi

Takumi Ueno

Shunichi Numata

Yasunari Maekawa

Mitsuyoshi Shouji

Tomoe Takamura

Geraldine Rames-Langlade

A magnetic disk drive having a magnetic disk, a spindle motor for rotating the magnetic disk, a magnetic head slider for recording or reproducing data onto or from the magnetic disk and a housing. A control circuit system is provided for controlling the head slider so that the head slider is positioned on the magnetic disk plane when the magnetic disk is rotating, and the head slider is saved to outside the magnetic disk plane when rotation of the magnetic disk is stopped. A lubricant supplier is provided for supplying lubricant to the surface of the magnetic disk. The lubricant supplier contains at least a perfluoropolyether compound having any one of an alcohol group, a cyclic ether group, and an alkyl-ester group at its terminal position as a lubricant, and the lubricant contains the perfluoropolyether compound having a molecular weight sufficient to enable lubrication and no greater than 4000.

Magnetic disk drive

A lubricant which does not splash easily and has an improved property of slidableness, and a magnetic disk using the lubricant are provided. A magnetic disk apparatus featuring a prolonged service life of a stable operation and an excellent record reproduction property is provided by installing the above magnetic disk. The lubricant of the invention contains perfluoropolyether expressed by the following general formula, in which a component of its molecular weights less than 1000 is smaller than 10 wt. %, a component of its molecular weights not less than 7000 is smaller than 15 wt. %, a ratio between a weight average molecular weight and a numeric average molecular weight is 1.5 or less, and a substitution ratio of its terminal functional group is not less than 90%:R&#x2014;CFO&#x2014;[&#x2014;(CFCFO)&#x2014;&#x2014;(CFO)&#x2014;&#x2014;]&#x2014;CF&#x2014;R&#x2003;&#x2003;(1),where R1 and R2 are univalent organic groups, m and n are positive integers. Further for the magnetic disk which rotates at a speed of 10000 rpm or more, a lubricant containing a perfluoropolyether expressed by the following general formula is used, in which its numeric average molecular weight is not less than 5500, a component of molecular weights less than 3000 is 15 wt. % or less, a ratio between its weight average molecular weight and its numeric average molecular weight is 1.5 or less, and a substitution ratio of its terminal functional group is not less than 90%:HOCH&#x2014;CFO&#x2014;[&#x2014;CFCFO]&#x2014;&#x2014;[CFO]&#x2014;&#x2014;CF&#x2014;CHOH&#x2003;&#x2003;(2),where m and n are positive integers.

Lubricant, magnetic disk and magnetic disk apparatus

A magnetic disk drive having a small decrease in lubricant film thickness on the surface of the magnetic disk and a superior sliding reliability between the magnetic head and the magnetic disk surface. Perfluoropolyether is supplied as the lubricant onto the surface of the magnetic disk using heat and air flow by applying perfluoropolyether onto the surface of a suspension, or impregnating perfluoropolyether into a filter. The lubricant contains perfluoropolyether having a molecular weight sufficient to enable lubrication and smaller than 4000 by at least 40%.

Magnetic disk drive with supply of perfluoropolyether as lubricant

The present invention is a fluorine-containing compound having i) a perfluoropolyoxyalkyl or -alkylene chain having an average molecular weight of 800 or more and ii) a cyclic or non-cyclic polyether atomic group. Its use as a low-scattering lubricant or surface modifier (water repellent) brings about an improvement in sliding durability of magnetic recording media.

Fluorocompound, lubricant, surface modifier, lubricating film, magnetic recording medium, and magnetic recording device

A highly reliable positive type photosensitive resin composition composed of diamine having a carboxyl group as a structural unit, which can be developed with an alkaline aqueous solution, comprising polyamic acid ester having hydrophobic group, o-quinonediazidesulfonyl amide compound, and/or o-quinonediazidesulfonyl amide sulfonic ester compound, and electronic devices using the same. A polyamide film having preferable positive type relief patterns, of which the unexposed portion is not corroded, can be obtained.

Positive photosensitive resin composition and electronic apparatus using

A photosensitive resin composition comprising (a) a polymer having carboxyl groups (b) a photoacid generator which generates an acid when irradiated with light, and (c) an aliphatic amine is capable of development with ease by use of a wide variety of aqueous solvents.

Photosensitive resin composition containing a carboxylic acid polymer,

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Hitachi, Japan

Mina Ishida