Tdk Corporation

Konica Corporation

Pioneer Electronic Corporation

Tkd Corporation

Akihiko Seki

Takayoshi Kuwajima

Akira Saitoh

Naoto Yajima

Hiroyuki Yamada

Kenichi Kitamura

Kaoru Kawasaki

Shigeo Kurose

Ryosuke Isobe

Katsuhiko Yamazaki

Satoru Tsuchida

Kazuyuki Shimazaki

Takahiro Mori

Takafumi Yanagita

Hideaki Wakamatsu

Eizo Tsunoda

Toru Yokoo

Hisato Kato

Takashi Kobane

Yoshikazu Kawakami

The present invention provides a magnetic recording medium comprising a magnetic layer with excellent surface smoothness, which comprises a thin film magnetic layer of thickness in a range from 0.03 to 0.30 &#x3bc;m that is ideal for short wavelength recording, and displays superior electromagnetic conversion characteristics. The magnetic recording medium comprises a magnetic layer containing at least a ferromagnetic powder and a binder resin on one surface of a non-magnetic support, wherein the thickness of the magnetic layer is within a range from 0.03 to 0.30 &#x3bc;m, and the number of concavities with a depth of 30 nm or greater in the surface of the magnetic layer is 5 per 1 cmof surface area or less. Preferably, the value of the average depth Rv6 of the surface of the magnetic layer, as measured by a contact type surface roughness meter, is 12 nm or less.

Magnetic recording medium

The present invention provides a magnetic recording medium comprising a thin film magnetic layer of thickness in a range from 0.03 to 0.30 &#x3bc;m, and having excellent surface smoothness and superior electromagnetic conversion characteristics. The magnetic recording medium comprises a lower non-magnetic layer containing at least a non-magnetic powder and a binder resin on one surface of a non-magnetic support, an upper magnetic layer containing at least a ferromagnetic powder and a binder resin on the lower non-magnetic layer, and a back coat layer on the other surface of the non-magnetic support, wherein the thickness of the upper magnetic layer is within the range from 0.03 to 0.30 &#x3bc;m, the AFM surface roughness Ra of the upper magnetic layer is 6 nm or less, and the number of concavities with a depth of 30 nm or greater in the surface of the upper magnetic layer is 5 per 1 cmof surface area or less.

A magnetic recording medium is prepared by coating a dispersion of non-magnetic powder and ferromagnetic powder in a binder and a dispersion of ferromagnetic powder in a binder to a non-magnetic substrate by a wet-on-wet coating technique to form subordinate and magnetic layers on the substrate, and subjecting the layers to magnetic field orientation. The subordinate layer has a Br of 80 to 400 gauss, and the magnetic layer has a thickness of 0.1 to 0.4 &#x3bc;m. The medium has surface smoothness and good electromagnetic characteristics and lends itself to recording and reproducing signals having a minimum wavelength of 0.2 to 0.7 &#x3bc;m.

Magnetic recording medium and process for producing the same

The present invention provides a magnetic recording medium having a thinned magnetic layer, excellent electromagnetic conversion characteristics and an excellent durability, and a process for producing the same. A magnetic recording medium comprising a lower non-magnetic layer containing at least a carbon black and a radiation curing type binder resin on a non-magnetic support and an upper magnetic layer having a thickness of 0.30 &mgr;m or less on the lower non-magnetic layer, wherein the upper magnetic layer contains at least a ferromagnetic powder, a binder resin and an abrasive having a Mohs hardness of 6 or higher and a smaller average particle size than the thickness of the upper magnetic layer. The thickness of the upper magnetic layer is, for example, 0.05 to 0.30 &mgr;m. The average particle size of the abrasive is, for example, 0.01 to 0.2 &mgr;m.

Process for producing a magnetic recording medium

A magnetic recording medium comprising a non-magnetic base having on at least one side a non-magnetic layer (undercoat) containing electron beam-curable resins which in turn is over-laid with a magnetic layer (topcoat) containing an iron (Fe) based magnetic powder, said magnetic layer having a glass transition temperature (Tg) of at least 65.degree. C. and said non-magnetic layer being an electron beam cured coating that is formed by coating the non-magnetic base with a non-magnetic coating mix containing electron beam curable resins, the yet to be cured coating having a glass transition temperature (Tg) of 30-53.degree. C. and said electron beam curable resins comprising an electron beam curable vinyl chloride based resin having a sulfur-containing polar group and an electron beam curable urethane resin having a phosphorus-containing polar group. Also disclosed is a process for producing the magnetic recording medium, which has good electromagnetic conversion characteristics in a high-frequency range and which can be manufactured at high production rate.

Magnetic recording medium and a process for producing the same

A magnetic recording medium includes a flexible substrate, an undercoating layer formed on the substrate, and a magnetic layer formed on the undercoating layer. The undercoating layer contains a binder and nonmagnetic particles having an average particle size in the range of 0.01 to 0.20 .mu.m. The content of the nonmagnetic particles in the undercoating layer is in the range of 40 to 85% by weight. The magnetic layer contains ferromagnetic powder, a binder and an abrasive having an average particle size in the range of 0.10 to 0.40 .mu.m. The magnetic layer has a thickness in the range of 0.10 to 0.30 .mu.m and contains the abrasive in the range of 1 to 5 parts by weight relative to 100 parts by weight of the ferromagnetic powder. With this arrangement, the magnetic recording medium is capable of high density recording and excellent in electromagnetic transducer property and durability.

Disclosed is a magnetic recording medium which comprises a non-magnetic support and a magnetic layer formed thereon and containing at least ferromagnetic metallic powder, and the medium contains an aliphatic acid, wherein average existence ratios of elements in terms of the number of atoms forming the surface of the ferromagnetic metallic powder which is being subjected to orientation treatment in the magnetic layer, are less than 1 of sodium (Na), 40 or less of alkaline earth elements, and 1 to 50 of rare earth elements based on the number of iron (Fe) atom as 100, and the number of carbon atoms of the aliphatic acid being 12 to 24.

Magnetic recording medium comprising a magnetic layer containing

This invention concerns a method for producing a magnetic recording medium by passing a magnetic coating material comprising a ferromagnetic powder and a binder resin through an ultrasonic treating device under the operating conditions of 10 to 200 kHz of frequency of oscillation and 10 to 100 .mu.m of amplitude of ultrasonic wave thereby effecting ultrasonic treatment of the magnetic coating material and coating the treated magnetic coating material on a substrate either directly or through an undercoating layer, characterized in that the ultrasonic treating device comprises an ultrasonic treating tank adapted to effect ultrasonic wave treatment of the magnetic coating material by passing the material therethrough, an ultrasonic wave horn inserted into the ultrasonic treating tank and provided with an operating end surface capable of exerting an ultrasonic oscillation on the magnetic coating material, and an ultrasonic wave oscillator connected to a basal part side of the ultrasonic wave horn, an operating depth H defined by the distance from the operating end surface of the ultrasonic wave horn to a bottom wall surface of the ultrasonic treating tank opposed to the operating end surface is set at a magnitude in the range of 2 to 40 mm, and the magnetic coating material to be coated on the substrate is subjected to tile ultrasonic treatment.

Method for production of magnetic recording medium

Disclosed is a magnetic recording medium which comprises a non-magnetic support and a layer containing .alpha.-iron oxide powder as a lower layer and a layer containing ferromagnetic powder as an upper layer which are provided on the non-magnetic support in this order from a side of the non-magnetic support, wherein weight ratios of elements in the whole composition of the .alpha.-iron oxide powder are 0.05 to 5 parts by weight of aluminum (Al) atom and 0.05 to 5 parts by weight of silicon (Si) atom based on 100 parts by weight of iron (Fe) atom, and average existence ratios of elements in terms of the number of atoms forming the surface of the .alpha.-iron oxide powder are 40 or less of Al atom and 1 to 60 of Si atom based on the number of Fe atom as 100.

Magnetic recording medium comprising an underlayer containing

A mixture containing a magnetic powder, a binder, and an organic solvent is kneaded by passing it through a twin-shaft continuous kneader while the shearing force applied to the mixture is varied by changing the set angle of paddles used. The temperature of the mixture is controlled to be higher than Tg and lower than the boiling point of the organic solvent when it passes through the maximum shearing force zone, and to be lower than the temperature of the mixture upon its passage through the maximum shearing force zone, preferably lower than Tg when it passes through zones other than the maximum shearing force zone. There is obtained a magnetic recording medium which has improved dispersion of magnetic powder and excellent electromagnetic properties as well as a low coefficient of friction and improved transport stability.

Method for preparing magnetic recording medium

A rear projection screen comprises, in combination, a Fresnel lens having concentric annular ridges arranged at a radial pitch of P1, and a lenticular lens having parallel lenticulars arranged at a pitch P2. The pitch ratio P1/P2 between the pitches P1 and P2 is determined in the range of 0.1505 to 0.1545 or in the range of 0.176 to 0.181. The rear projection screen meeting such a condition suppresses effectively the moire effect of the concentric annular ridges of the Fresnel lens and the parallel lenticulars of the lenticular lens disposed adjacent to the Fresnel lens.

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Tokyo, Japan

Akihiko Seki