Magnetic recording medium

a recording medium and magnetic technology, applied in the field of magnetic recording mediums, can solve the problems of loss of thickness, disadvantage of analog signals, and difficulty in satisfying respective characteristics at the same time, and achieve the effect of improving durability and electromagnetic transfer characteristics

Inactive Publication Date: 2008-05-29
SONY CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention relates to a magnetic recording medium that can record both digital and analog signals. The medium has a non-magnetic supporter and two magnetic layers, with the first layer including polyester polyol and polyurethane resin and the second layer including carbon black and an abrasive. The medium also has improved durability and electromagnetic transfer characteristics. The invention provides a technique for improving the productivity of the magnetic recording medium.

Problems solved by technology

However, in the digital signals and the analog audio signals, it is difficult to satisfy respective characteristics at the same time due to the difference in their frequency or depth of record and various investigations have been carried out.
However, this method has a problem of loss of thickness due to a self-demagnetization.
However, since the lower layer is non-magnetic, this method is disadvantageous for the analog signal.
However, when the Mag-on-Mag technique is put into practical use, conditions such as sizes of magnetic members combined together in upper and lower layers, magnetic characteristics and the thickness of each layer or the like are strict due to the above-described problem of self-demagnetization.
Here, there is a problem in producing the magnetic recording medium.
When two kinds of magnetic paints are applied in layers, fine stripes (streaks) may be formed on the surfaces of magnetic layers owing to the difference in viscosity characteristics, or an upper layer may not be possibly adequately formed on a lower layer or a discontinuous miss of application may be possibly produced due to the difference in wet characteristics between the upper layer and the lower layer, which frequently causes a serious problem.
As described above, the combination of the upper layer and the lower layer poor in their compatibility deteriorates a roughness in the surfaces of the magnetic layers to deteriorate an output due to a spacing between a head and the magnetic recording medium.
Accordingly, this combination constitutes a problem in practical use.
According to this method, the generation of stripes is suppressed, however, the generation of a miss of application is not frequently effectively prevented.
However, either of these methods has not a satisfactory effect.
Thus, durability is deteriorated or the output and the C / N of a video is greatly changed due to the roughness of the surface of the magnetic layer of a surface layer.
Therefore, a request for the durability of a magnetic tape increasingly becomes severe.

Method used

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Examples

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example 1

Manufacture of Magnetic Layers

[0100]Each paint forming each magnetic layer was prepared on the basis of a below-described composition.

magnetic metal powder:100parts by weightaverage length of major axis:0.15μmspecific surface area:60m2 / g by BETmethodparticle size of crystal:150Åcoercive force Hc:130(kA / m)saturation magnetization σs:130(Am2 / kg)vinyl chloride copolymer:variable(the detail is described in Tables 2 to 4)polyester polyurethane resin:variable(the detail is described in Table 1)α-Al2O3:5parts by weight(produced by Sumitomo Chemical Co., Ltd.,trade name: HIT-50)carbon black:1parts by weight(produced by Cabot Corporation, tradename: BP-L)citric anhydride:3parts by weightpolyisocyanate:4parts by weight(produced by Nippon Polyurethane IndustryCo., Ltd., trade name: Coronate L, in this case,polyisocyanate was mixed immediatelybefore application.)myristic acid:1parts by weightbutyl stearate:1parts by weightmethyl ethyl ketone:80parts by weightmethyl isobutyl ketone:80parts by we...

example 2

Manufacture of Magnetic Layers

[0169]Each paint forming each magnetic layer was prepared on the basis of a below-described composition.

magnetic metal powder:100parts by weightaverage length of major axis:0.15μmspecific surface area:60m2 / g byBET methodcoercive force Hc:125(kA / m)saturation magnetization σs:120(Am2 / kg)vinyl chloride copolymer:15parts by weight(produced by Nippon Zeon Co., Ltd. tradename: MR-110)polyester polyurethane resin:5parts by weight(isophthalic acid / terephthalic acid / neopentylglycol-MDI polyurethane; molecular weightof 25000, polar group = SO3Na of 0.2 wt %)abrasive:variable(The detail is described in Table 5 shown below.)carbon black having a large particle size:variable(The detail is described in Table 5 shown below.)carbon black:1parts by weight(produced by Cabot Corporation, trade name:BP-L)polyisocyanate:4parts by weight(produced by Nippon Polyurethane industryCo., Ltd., trade name: Coronate L, inthis case, polyisocyanate was mixedimmediately before applicat...

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Abstract

A magnetic recording medium includes a non-magnetic supporter, a first magnetic layer and a second magnetic layer on which magnetic paints made of different ferromagnetic materials are applied in order of the first magnetic layer and the second magnetic layer on the non-magnetic supporter. Both the first magnetic layer and the second magnetic layer include polyester polyol having an alicyclic framework and a polyurethane resin composed of diisocyanate.

Description

[0001]The subject matter of application Ser. No. 10 / 714,021 is incorporated herein by reference. The present application is a divisional of U.S. application Ser. No. 10 / 71,4021, filed Nov. 13, 2003, which claims priority to Japanese Patent Application No. JP20002-367894, filed Dec. 10, 2002 and to Japanese Patent Application No. JP20002-367893, filed Dec. 10, 2002. The present application claims priority to these previously filed applications.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a magnetic recording medium capable of recording both an analog signal and a digital signal.[0004]2. Description of the Related Art[0005]In recent television broadcasting or the like, a digital broadcasting or data broadcasting has been familiar to people. As magnetic recording media for audio and video, goods that meet a digitization have been mainly progressively utilized.[0006]Since an analog record has been currently shifted to a digital record,...

Claims

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Application Information

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Patent Type & AuthorityApplications(United States)
IPC IPC(8): G11B5/73G11B5/702G11B5/716
CPCG11B5/716
InventorKATO, ATSUSHIKAGAWA, JUNJIMURAKAMI, HIROYUKIKOIKE, FUMIKO
OwnerSONY CORP