JPH10255255A - Magnetic storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the friction with a magnetic head and to improve durability without sacrificing electromagnetic conversion characteristics by forming the surface performance property of a guard band part being located at both sides of a magnetic recording part where a magnetic truck is formed so that it is coarser than that of the magnetic recording part. SOLUTION: A magnetic powder such as an Fe powder is dispersed in a binder resin such as a polyester polyurethane resin and a solvent such as toluene, it applied to a support made of a 7μm thick polyethylene terephthalate film by a gravure coating method, and is dried, thus forming a 5μm thick magnetic layer. A 0.5μm backcoat layer is formed on the rear surface of the support by carbon black. When the surface of the magnetic layer is subjected to a calendar treatment, for example, the surface roughness of a roller, a pressure, and the number of treatments are changed between a magnetic recording part 1 where a magnetic truck 1a is formed and a guard band part 2, thus setting the surface property of the magnetic recording part 1 to 1-15nm and that of the guard band part 2 to 20-50nm by SRa.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording medium having a guard band portion on both sides of a magnetic recording portion.

[0002]

2. Description of the Related Art In recent years, the performance of magnetic recording media has been remarkably improved, and application fields such as digital video recorders and other high-quality video recorders requiring high electromagnetic conversion characteristics and digital tape recorders are being widely used. Expected to be wide.

[0003] As such a magnetic recording medium, a magnetic layer in which a magnetic powder in which a magnetic powder is dispersed in an organic binder is applied to a non-magnetic support such as a polyethylene terephthalate film and dried is formed. A coating type magnetic recording medium having a structure in which a back coat layer is formed on the back surface of a support is generally used.

In order to improve the electromagnetic conversion characteristics of such a magnetic recording medium, various attempts have been made to improve the magnetic material itself. However, the surface properties of the magnetic recording medium are improved and the surface is made smooth. As a result, a great effect is obtained.

[0005]

However, since the surface properties and durability of the magnetic recording medium are contradictory,
When the smoothness is improved by improving the surface properties, the frictional force between the magnetic recording medium and the magnetic head increases, and in some cases, sticking occurs. Further, there is also a problem that a force for scraping foreign substances such as magnetic powder or the like adhered to the magnetic head (hereinafter referred to as a cleaning effect) is reduced, thereby causing clogging. For this reason, conventionally, in order to secure a practical level of durability, the electromagnetic conversion characteristics have to be sacrificed to some extent.

An object of the present invention is to solve the above-mentioned problems of the prior art and reduce the friction between a magnetic recording medium and a magnetic head without sacrificing the electromagnetic conversion characteristics.
It is an object of the present invention to stabilize the running properties of a magnetic recording medium, further prevent head clogging, and improve durability as a result.

[0007]

As shown in FIG. 1, the present inventor provides a cleaning effect to a guard band 2 which is a non-magnetically recorded area on both sides of a magnetic recording section 1 of a magnetic recording medium. It has been found that it is possible to realize high electromagnetic conversion characteristics and durability in a magnetic recording medium, and to achieve that, it is more effective to roughen the surface properties of the guard band portion than the surface properties of the magnetic recording medium, The present invention has been completed.

That is, according to the present invention, in a magnetic recording medium having a magnetic recording portion and a guard band portion, the surface property of the guard band portion is higher than that of the magnetic recording portion so that the guard band portion has a cleaning effect. A magnetic recording medium characterized by being coarse.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The magnetic recording medium of the present invention has a structure in which a magnetic layer is formed on a support, and the magnetic layer is, as shown in FIG.
And a guard band 2. Here, the guard band section 2 may be arranged on one side of the magnetic recording section, but is preferably arranged on both sides as shown in FIG. Further, a back coat layer may be provided on the back surface of the support for stabilization of running property and the like. Further, a lubrication layer, a rust prevention layer, and the like may be formed on the surface of the magnetic layer.

Incidentally, the electromagnetic conversion characteristics of the magnetic recording medium largely depend on the surface properties of the magnetic recording section 1. Therefore,
In order to improve or maintain the electromagnetic conversion characteristics of the magnetic recording medium, it is effective to improve the surface properties of the magnetic recording unit 1. However, if the surface properties of the magnetic recording section 1 are improved, the durability is expected to decrease.

Therefore, in the present invention, the magnetic recording unit 1
In order to improve the durability without lowering the surface properties of the guard band, attention is paid to the guard band portion 2 where no magnetic recording is performed, and the surface property of the guard band portion is changed so that the portion has a cleaning effect. The surface is made rougher than the surface of the magnetic recording portion. Preferably, the surface property of the magnetic recording medium is 1 to 15 nm in SRa, and the surface property of the guard band portion is S
Ra is set to 20 to 50 nm. As a result, the friction between the magnetic recording medium and the magnetic head is reduced without deteriorating the electromagnetic conversion characteristics of the magnetic recording medium, the running performance of the magnetic recording medium is stabilized, and the head clog is prevented. Performance can be improved.

The surface property is preferably measured using a laser type non-contact roughness meter capable of measuring with higher sensitivity than a needle contact type surface roughness meter. “SRa” which is an index of evaluation indicates ternary average roughness. That is, in the JIS standard, the average roughness in the X direction and the Y direction in two dimensions is Ra, but SRa is Ra.
, The average roughness in the (X + Y + Z) direction is shown.

In the magnetic recording medium of the present invention, the guard band portion 2 is provided so that the guard band portion 2 has a cleaning effect.
However, except that the surface property of the magnetic recording unit 1 is made rougher than the surface property of the magnetic recording unit 1, it is possible to use the same material as the conventional magnetic recording medium and to configure the same components.

For example, as the non-magnetic support, a known non-magnetic support used in a conventional magnetic recording medium can be used. For example, polyesters such as polyethylene terephthalate and polyolefins such as polyethylene and polypropylene can be used. , Cellulose derivatives such as cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, polyimide, polyamide and polyamide imide,
Paper, metals such as stainless steel, aluminum, copper, and thallium; light alloys such as aluminum alloys and titanium alloys; ceramics; and single crystal silicon. In addition, examples of the form of the support include a film, a tape, a sheet, a disk, a card, a drum, and the like.

As the magnetic layer, a coating type magnetic layer used in a conventional magnetic recording medium can be used. For example, a magnetic layer having a structure in which magnetic powder is dispersed in a binder is used. Can be. As magnetic powder, Fe,
Fe ₂ O ₃ , Co-γ, Co-Ni, Sm-Co, Cr
O ₂ , CoO and the like can be mentioned. As the binder, for example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, Vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate-vinylidene chloride copolymer, methacrylate-styrene copolymer, thermoplastic polyurethane resin, phenoxy resin, polyvinyl fluoride, vinylidene chloride -Acrylonitrile copolymer, butadiene-acrylonitrile copolymer, butadiene-acrylonitrile-methacrylic acid copolymer, polyvinyl butyral, cellulose derivative, styrene-butadiene copolymer, polyester resin, phenol resin,
Epoxy resin, thermosetting polyurethane resin, urea resin,
Melamine resins, alkyd resins, urea-formaldehyde resins or mixtures thereof, and the like. These may be crosslinked with an isocyanate compound to improve the durability, or an appropriate polar group may be introduced.

The magnetic layer may be a single layer film.
It may be a multilayer film. Further, the layer thickness can be appropriately determined as needed.

The back coat layer which may be provided on the back surface of the magnetic recording medium is, in addition to carbon black,
If necessary, hematite, mica, silica gel, magnesium oxide, zinc sulfide, tungsten carbide, boron nitride, starch, zinc sulfide, kaolin, talc, clay, lead sulfate, barium carbonate, calcium carbonate, magnesium carbonate, boehmite (γ _{-Al 2 O 3 · H 2 O} ), alumina, are dispersed tungsten sulfide, titanium oxide, polytetrafluoroethylene powder, polyethylene powder, polyvinyl chloride powder, a metal powder, etc., a binder such as used in the magnetic layer Can be mentioned.

As the lubricant for the lubricating layer on the surface of the magnetic recording medium, a fluorine-based lubricant such as von pudding, a higher alcohol-based lubricant, a paraffin-based lubricant, various ester-based lubricants and the like are used. Can be mentioned. Examples of the rust preventive for the rust preventive layer include naphthalene-based rust preventives such as naphthalene diol.

In the magnetic recording medium of the present invention, after a magnetic layer is formed on a support by a conventional method, a calender treatment is performed on a magnetic recording portion and a guard band portion so that the latter has a rougher surface than the former. It can be manufactured by the following. In the calendering treatment, the number of times of calendering, the pressure, the surface roughness of the roller used, and the like may be appropriately adjusted between the two so that the intended surface property is obtained.

[0021]

EXAMPLE 100 parts by weight of Fe powder (magnetic powder) having a length of 200 nm (needle ratio: 100) are dispersed in a mixture of 120 parts by weight of a binder resin (polyester polyurethane resin) and 300 parts by weight of a solvent (toluene), 0 in dry thickness.
A magnetic layer was formed by coating a 7 μm-thick polyethylene terephthalate film (support) so as to have a thickness of 5 μm and drying. At this time, the magnetic powder was applied by a gravure coating method so as to be parallel to the support. Further, on the back surface of the support, a back coat layer composed mainly of carbon black was formed with a dry thickness of 0.5 μm.

A plurality of magnetic recording media thus obtained were prepared, and a plurality of different calendering processes were performed on the magnetic recording portion and the guard band portion. That is, a normal calendering process is performed, and then a calender roll having a width of 7.5 mm is set to 0.
It was set at intervals of 5 mm and calendered while appropriately changing the pressing pressure of the roll. Then, it is cut into 8mm width so that the normal calendering section hits the guard band section.
evaluated. Tables 1 and 2 show the surface properties (SRa (nm)) of the magnetic recording portion and the guard band portion of the manufactured magnetic recording medium.

The surface properties were measured using a laser non-contact roughness meter (Hiboss, ER-30 manufactured by Kosaka Seisakusho).

[0024]

[Table 1]

[0025]

[Table 2]

Next, each of the magnetic recording media was assembled in a predetermined cassette case for 120 minutes, and the electromagnetic conversion characteristics and the reproduction durability were tested and evaluated as described below.

A blank tape (commercially available 8 mm video tape) is mounted on a Sony 8 mm video tape recorder and run, and the electromagnetic conversion characteristics (recording wavelength 0.54 m
m, used head TSS, gap length 0.22 mm). The reproduction durability was measured by measuring the reproduction output when the magnetic recording medium was recorded for 120 minutes and reproduced after running the cleaning tape.

The results obtained are shown in FIGS. From these results, it can be seen that when the surface property of the magnetic recording portion is high, the electromagnetic conversion characteristics are improved, and when the surface property of the guard band portion is low, the reproduction durability is improved.

A magnetic recording medium having an output difference of less than 0 dB relative to a blank tape or a magnetic recording medium having a reproduction durability of less than 120 minutes is evaluated as x because it is unsatisfactory as a magnetic recording medium. Is evaluated as ◎,
The result is shown in FIG.

FIG. 7 shows that in order to obtain sufficient characteristics as a magnetic recording medium, the surface properties of the magnetic recording portion are preferably SR
It can be seen that a is 1 to 15 nm for a and that the surface property of the guard band portion is preferably 20 to 50 nm for SRa.

[0031]

According to the magnetic recording medium of the present invention, the electromagnetic conversion characteristics are not sacrificed, the friction between the magnetic recording medium and the magnetic head is reduced, the running property of the magnetic recording medium is stabilized, and the head clog is reduced. Is prevented, resulting in improved durability.

[Brief description of the drawings]

FIG. 1 is a plan view of a magnetic layer of a magnetic recording medium according to the present invention.

FIG. 2 is a diagram showing the influence of the surface property of a guard band portion on a magnetic recording medium in which the surface property of a magnetic recording portion is 0.5 nm in SRa.

FIG. 3 is a diagram showing the influence of the surface property of a guard band portion on a magnetic recording medium in which the surface property of a magnetic recording portion is 1.0 nm in SRa.

FIG. 4 is a diagram showing the influence of the surface property of a guard band portion on a magnetic recording medium in which the surface property of a magnetic recording portion is 10 nm in SRa.

FIG. 5 is a diagram showing the influence of the surface property of a guard band portion on a magnetic recording medium in which the surface property of a magnetic recording portion is 15 nm in SRa.

FIG. 6 is a diagram showing the influence of the surface property of a guard band portion on a magnetic recording medium in which the surface property of a magnetic recording portion is 20 nm in SRa.

FIG. 7 is a diagram illustrating a relationship between the surface property of a magnetic recording portion and the surface property of a guard band portion in a magnetic recording medium.

[Explanation of symbols]

 1 magnetic recording section 2 guard band section

Claims (3)

[Claims] In a magnetic recording medium having a magnetic recording portion and a guard band portion, the surface property of the guard band portion is rougher than that of the magnetic recording portion so that the guard band portion has a cleaning effect. A magnetic recording medium characterized by the above-mentioned. 2. The guard band portion having a surface property of SRa of 20
50 nm, and the surface property of the magnetic recording portion is 1 to SRa.
2. The magnetic recording medium according to claim 1, which has a thickness of 15 nm. 3. The magnetic recording medium according to claim 1, wherein the guard band portions are arranged on both sides of the magnetic recording portion.