Tdk Electronics Company, Limited

Tdk Corporation

Hitoshi Azegami

Eiji Horigome

Hiroshi Ota

Hiroshi Kawahara

Kuniichi Yoda

Fujio Shibata

Takehisa Ohkawa

Kazuhiro Kuroda

Yuji Ishihara

Hiroshi Ohta

Kazushi Tanaka

Toshihiko Ishida

Yasufumi Takasugi

Norifumi Kajimoto

Kazunori Tamazaki

Yoshio Kawakami

Kenji Hirabayashi

Shigeru Takamatsu

Naoyuki Nagashima

Hideo Dobashi

Polyoxymethylene articles having a surface printable with an ultraviolet-curing ink are obtained by molding a polyoxymethylene and treating the molded article by ultraviolet irradiation, corona discharge, or electron-beam radiation until the surface has an X-ray photoelectron spectrum in which the ratio of the �C--O!.sub.n bond peak at 302 eV to the C--C bond peak at 305 eV, i.e., the �C--O!.sub.n bond peak/C--C bond peak ratio, is at least 2.5.

Polyoxymethylene articles having printable surface method of imparting

A magnetic recording medium whose magnetic layer formed on a base comprises a magnetic powder and a binder which contains a tertiary amine and uses 1,4-cyclohexanedimethanol as a chain extender. The magnetic powder is preferably of CrO.sub.2. The medium is made by mixing and dispersing the magnetic powder in a binder which consists of a reaction product of (A) a polyester which is a reaction product of a diol selected from among ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentadiol, and 1,6-hexanediol, and adipic acid, (B) a chain extender consisting of 1,4-cyclohexanedimethanol, (C) an aliphatic or aromatic diisocyanate in an amount substantially equal to the combined molar amount of the polyester and the chain extender, and (D) a tertiary amine, and applying the resulting magnetic coating material to a base.

Magnetic recording medium

A magnetic recording medium comprising a plastic base and a magnetic layer formed thereon by applying a dispersion of a ferromagnetic powder in a resin binder, the magnetic layer containing the ferromagnetic powder which has a BET specific surface area of at least 35 m.sup.2 /g and .alpha.-Al2O3 particles having a particle size not exceeding one half the mean particle diameter of the ferromagnetic powder and less than 0.1 .mu.m in diameter, the .alpha.-Al2O3 particles being added in an amount greater than 5% but less than 15% by weight on the basis of the weight of the ferromagnetic powder. The magnetic powder is a metallic magnetic powder containing iron as the major constituent. The .alpha.-Al2O3 particles are cube-shaped.

A magnetic recording medium, comprising a plastic base coated with a magnetic layer of a ferromagnetic powder dispersed in a resin binder, contains in the magnetic layer .alpha.-Al.sub.2 O.sub.3 particles with an average particle size of 0.1 to 0.3 .mu.m as determined by electron microscopy in an amount of more than 0.5% but less than 15% by weight on the basis of the ferromagnetic powder weight. The .alpha.-Al.sub.2 O.sub.3 particles have an .alpha.-transformation rate of at least 50%. The powder is produced by an organic alumina process.

In a magnetic recording medium having a magnetic recording coat formed on one side of a base and a back coat on the other side, the back coat consists of a dispersion in a binder of an inorgainc pigment powder having an average particle diameter of 0.2 to 0.5 .mu.m and a Mohs hardness of not greater than 6. The binder consists of a specific copolymer, a rubber-like binder, and a polyisocyanate ingredient. The copolymer consists of vinyl chloride, a vinyl alkyl carboxylate, a monomer copolymerizable with vinyl chloride, and a saponified vinyl alkyl carboxylate and has an OH/CH absorption ratio as determined from its infrared absorption spectrum in the range of 0.2 to 0.7.

A magnetic recording medium comprises a magnetic coating material, or a dispersion of magnetic particles in a resinous binder, and a base to which the coating material is solidly applied, the resinous binder comprising as its ingredients a copolymer composed of vinyl chloride, vinylidene chloride, a vinyl alkylcarboxylate, another monomer copolymerizable with vinyl chloride, and a saponified vinyl alkylcarboxylate and having an OH/CH absorption ratio according to the infrared absorption spectrum of at least 0.2, a polyurethane resin having in its molecule a --SO.sub.3 M group wherein M represents an alkali metal atom, and a polyisocyanate.

A magnetic recording medium comprising a resinous component in which magnetic particles are dispersed and a base to which the dispersion is solidly applied, the resinous component consisting of a copolymer having an OH/CH absorption ratio according to the infrared absorption spectrum of 0.2 or more and made from (A) vinyl chloride, (B) vinylidene chloride, (C) a vinyl alkylcarboxylate, (D) an other monomer copolymerizable with vinyl chloride, and (E) a saponified vinyl alkylcarboxylate, and a rubbery binder. Alternatively, a polyisocyanate is added to the above copolymer.

A magnetic recording medium which has dynamic range (I) of 70 dB or more and dynamic range (II) of 45 dB or more in control of a thickness of a magnetic layer and magnetic characteristics wherein said dynamic range (I) is given as a difference between an output at 3% input level of third harmonic wave output at a wavelength of 237.5 .mu.m in the optimum bias recording by a head having a recorded width of 1 to 1.1 mm based on an output of the original signal and a reproduced output calibrated by auditory sense calibration at non-signal recording in the bias and said dynamic range (II) is given as a difference between a saturated output at a wavelength of 4.75 .mu.m under the same condition and the reproduced output calibrated by the A-curve calibration at non-signal recording in the bias.

A magnetic recording medium, comprising a magnetic layer and a non-magnetic substrate therefor, which magnetic layer is formed by dispersing magnetic powder in a vehicle formed of a copolymer containing vinyl chloride, another monomer copolymerizable with said vinyl chloride, a vinyl ester of an alkanoic acid and a saponification product thereof and having an OH/CH absorption ratio of 0.2 to 0.7 in the infrared absorption spectrum, and a rubbery binder.

A magnetic recording medium having a magnetic layer comprising a magnetic powder and a resin binder, which is characterized by that the magnetic layer contains an ethylene trifluoride chloride polymer of a low degree of polymerization and a fatty acid ester.

A magnetic recording medium having two coated magnetic layers of a first magnetic layer and a second magnetic layer on a non-magnetic substrate. The first magnetic layer has a coercive force of 400 to 590 Oe and a thickness of 2.1 to 2.8.mu. and said second magnetic layer has a coercive force of 590 to 800 Oe and a thickness of at least 2.1.mu..

A magnetic recording medium which comprises a substrate coated with a magnetic paint which has a magnetic powder dispersed in a binder comprising a vinyl chloride - vinyl acetate copolymer containing at least 10% of polyvinyl alcohol, a urethane resin and a polyester resin.

A magnetic recording medium comprises a lower magnetic layer containing a magnetic powder having a coercive force of 700 Oe or higher dispersed in an organic binder which is coated on a non-magnetic substrate and an upper magnetic layer containing a magnetic powder having a coercive force higher than the coercive force of said lower magnetic la

A magnetic recording medium comprises a substrate coated with a magnetic layer comprising a magnetic powder and a binder comprising an urethane resin and a vinyl chloride-vinyl acetate-maleic acid copolymer having a content of maleic acid component of at least 1.5%.

A magnetic recording medium including a substrate having a magnetic coating layer thereon, said magnetic coating layer comprising ferromagnetic particles dispersed in a binder vehicle, characterized in that the magnetic coating layer contains one or more ketones selected from the compounds expressed by the general formula ##STR1## wherein R.sub.1 and R.sub.2 represent saturated or unsaturated chain aliphatic radicals, both or either of which have 11 to 22 carbon atoms and may contain hydroxyl, carboxyl or amino groups.

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Tobu, Japan

Hitoshi Azegami