JPH05101370A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To allow uniform and high-density recording and reproducing by using magnetic powder which is specified in the relative ratio of the respective coercive forces in the longitudinal, thickness and transverse directions of a magnetic layer and the SFD(L) in the longitudinal direction to respectively specific values and is composed mainly of a hexagonal magnetic powder. CONSTITUTION:The longitudinal direction of the coercive force of the magnetic layer provided on a base is designated as Hc (L), the thickness direction as Hc (P) and the transverse direction as Hc (T). The Ha (P)/Hc (L) of the respective relations is specified to >=0.65, Hc (T)/Hc (L) to >=0.80 and the SFD (L) in the longitudinal direction to >=0.3. The hexagonal magnetic powder having the uniaxial anisotropy of the axis of easy magnetization perpendicular to the planar face of the particles is used for the magnetic layer. The fluctuations in output are decreased between adjacent tracks in this way and the excellent recording and reproducing characteristics are obtd. for the uniform and high- density recording at respective points.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium coated with a magnetic layer, and more particularly to a magnetic recording medium such as a long magnetic recording tape.

[0002]

2. Description of the Related Art There are various types of magnetic recording tapes for audio, video, data, etc., but these magnetic recording tapes are required to have an improved recording density. As a method of improving the recording density of the magnetic recording tape, there are a method of improving the linear recording density and a method of improving the areal recording density.

As a method for improving the linear recording density, a perpendicular magnetic recording method using remanent magnetization in the vertical direction, which is less affected by recording demagnetization, has been attracting attention and is extremely excellent as a method for improving the linear recording density. It is a thing. As a method of improving the areal recording density, a method of narrowing the track width is effective.

[0004]

By the way, considering the actual recording / reproducing of the magnetic recording tape, since the recording / reproducing is generally performed by the helical scan method, the recording / reproducing is performed in the longitudinal direction of the magnetic recording tape. As shown in 1, a recording track is formed at a predetermined angle θ1.
For example, with DAT tape, this angle θ1 is 6.6 °, 8
Recording tracks are formed with an inclination of 5 ° on the mm tape and 6 ° on the S-VHS tape.

Further, in the magnetic recording tape, the azimuth recording system is adopted because recording / reproduction is performed with the track interval set to 0. This is because a predetermined angle, that is, the azimuth angle θ2 shown in FIG. 1 is set so that the directions of magnetization are different between the adjacent tracks in order to eliminate the reproduction of other information from the adjacent tracks due to the side surface reproduction of the magnetic head. It is a technology for recording / reproducing provided and is an essential technology for high-density recording. The DAT tape is provided with an azimuth angle θ2 of ± 20 ° between adjacent tracks, the 8 mm tape is ± 10 °, and the S-VHS tape is ± 6 °. Therefore, for example, with DAT tape, a maximum of 26
Recording and playback will be performed at an angle.

From the above, in order to eliminate the undesired influence on the recording / reproduction between the adjacent tracks, it is preferable to further increase the azimuth angle θ2, and gradually the azimuth angle θ2 between the adjacent tracks is gradually increased. The difference between the two is increasing, and it is expected to increase even more in the future.

When the difference in azimuth angle θ2 between adjacent tracks becomes large, the conventional magnetic recording medium may have different reproduction outputs between adjacent tracks. The present invention has been made to address such a problem, and an object of the present invention is to provide a magnetic recording medium that enables uniform and high-density recording / reproducing at various places.

[0008]

The magnetic recording medium of the present invention is a magnetic recording medium having a magnetic layer on a substrate, wherein the coercive force in the longitudinal direction of the magnetic layer is Hc (L), and the thickness of the magnetic layer is When the coercive force in the depth direction is Hc (P) and the coercive force in the width direction of the magnetic layer is Hc (T), Hc (P) / Hc (L) is 0.65 or more, and Hc (T) / Hc ( L)
It is characterized by being 0.80 or more.

And, in particular, SFD (L) in the longitudinal direction of the magnetic layer is
It is characterized in that it is 0.3 or less, and that the magnetic powder is mainly composed of a hexagonal magnetic substance.

[0010]

The feature of the present invention is that the coercive force (Hc (T)) in the width direction of the magnetic layer in the magnetic recording medium is particularly noted.

Then, particularly by setting the coercive force in the width direction (Hc (T)) / the coercive force in the longitudinal direction (Hc (L)) to be 0.80 or more,
Even in a magnetic recording medium for high-density recording having a large azimuth angle θ2, excellent electromagnetic conversion characteristics with no difference in reproduction output between adjacent tracks can be obtained.

When the coercive force in the width direction (Hc (T)) / the coercive force in the longitudinal direction (Hc (L)) is smaller than 0.80, when the head gap in the longitudinal direction of the magnetic recording medium is different by 10 ° or more,
Since there is a difference in reproduction output between adjacent tracks, good recording / reproduction cannot be performed.

A further characteristic of the present invention is that the vertical coercive force (Hc (P)) / longitudinal coercive force (Hc (L)) is set to 0.65 or more. As a result, the magnetic charge component in the vertical direction can be effectively used to achieve high-density recording / reproducing. Vertical coercive force (Hc (P)) / longitudinal coercive force (Hc (L)) is 0.6
If it is less than 5, it becomes difficult to sufficiently increase the linear recording density due to the effect of recording demagnetization. Therefore, according to the magnetic recording medium having the above-described configuration, uniform and high-density recording / reproducing can be achieved at various places.

The SFD (L) in the longitudinal direction of the magnetic layer is
As shown in FIG. 2, it is particularly preferable that it is smaller than 0.3 in order to obtain a high reproduction output. In FIG. 2, a magnetic recording medium having a magnetic layer mainly composed of Ba-ferrite powder is used as the magnetic recording medium, the vertical axis represents the reproduction output, and the horizontal axis represents the SFD (L) in the longitudinal direction of the magnetic layer. From this figure, it can be understood that the reproduction output can be further improved if the SFD (L) in the longitudinal direction is smaller than 0.3.

In the magnetic recording medium according to the present invention, hexagonal magnetic powder is particularly preferable as the magnetic powder used in the construction of the magnetic layer, and the easy axis of magnetization is uniaxially different from the grain plate surface. Has a coercive force, for example, a coercive force of 200 Oe
~ 2000 Oe M-type or W-type Ba ferrite, Sr
Examples thereof include ferrite, Ca ferrite, Pb ferrite, a solid solution thereof, or an ultrafine particle powder of ferrite such as an ion-substituted body represented by the following general formula. The hexagonal magnetic powder is plate-shaped in nature, and has a property of being easily oriented in the vertical direction due to its peculiar shape, and is therefore a particularly preferable magnetic powder for the present invention.

General formula: AO.n (Fe _1-m M _m ) ₂ O ₃
(In the formula, A is any one element of Ba, Sr, Ca, and Pb, and M is Zn, Co, Ti, Ni, Mn, In, and C.
At least one element selected from u, Ge, Nb, Sn, Zr, Hf, Al, etc., m is 0 to 2, and n is 5.4.
Each represents a number of ˜6.0. However, when M is a divalent or tetravalent or higher valent element, M is a combination of two or more elements having an average valence of 3. )

These hexagonal magnetic powders have a hexagonal plate-like crystal structure and have an average particle size in the range of 0.03 μm to 0.1 μm when the particle size is the length of the diagonal line of the plate surface. It is suitable for recording and reproducing in the short wavelength range.

The ratio of the length of the diagonal line of the hexagonal plate surface to the thickness, that is, the plate ratio, is preferably in the range of 2 to 7.
The magnetic layer of the present invention can be obtained relatively easily by using a plate having a relatively large plate ratio.

Further, as the binder component constituting the magnetic layer of the present invention, various conventionally known binder components can be used, for example, polyurethane resin, polyester resin, polycarbonate resin,
Examples thereof include polyacrylic resins, epoxy resins, phenol resins, vinyl chloride resins, vinyl acetate resins, and mixtures or copolymers thereof. Examples of the lubricant include lauric acid, palmitic acid and stearic acid, and examples of the dispersant include lecithin and various surfactants.

The abrasive added to the magnetic layer is, for example, TiO ₂ , Cr ₂ O ₃ , Al ₂ O ₃ or Si.
C, ZrO ₂ etc. Mohs hardness 5 or more, average particle size 0.1 μ
It is advisable to add about 0.5 to 10 parts by weight of an inorganic powder of about m to 2.0 μm to 100 parts by weight of the magnetic powder.

The method for obtaining the magnetic recording medium of the present invention varies greatly depending on the material composition, but can be obtained relatively easily by properly selecting the drying conditions, the orientation method, the calendering method and the like. ..

[0022]

EXAMPLES Examples of the present invention will be described below. (Specific Example 1) [Magnetic paint component] 100 parts by weight of Ba-ferrite powder (Co-Ti substitution) (coercive force of 1150 Oe, average particle size of 0.05 µm, plate ratio of 3) Al ₂ O ₃ powder (average particle size of 0.5) μm) 4〃 lecithin 1.5〃 stearic acid 2〃 sodium sulfonate group-containing polyurethane resin (manufactured by Toyobo Co., Ltd.) 8〃 methyl ethyl ketone 80〃 cyclohexane 80〃 toluene 80〃

First, after thoroughly mixing the above-mentioned coating components, the mixture is further dispersed for 1 hour using a sand grinder,
3 parts by weight of an isocyanate compound was added as a curing agent and kneaded.

After that, the film thickness after drying was adjusted to 2.5 μm using an extrusion coater, and then the thickness was 50 μm.
It was applied onto a polyester film of m, and an alternating magnetic field was applied to randomly align it, followed by drying. Then, the surface was smoothed by sufficiently calendering to obtain a magnetic recording medium. Then, this magnetic recording medium was cut into a width of 8 mm and stored in a tape cassette. (Specific example 2)

In the specific example 1, a plate-like ratio of 3.
A magnetic recording medium was manufactured in the same manner except that the Co-Ti-substituted Ba-ferrite powder of 5 was used, cut into 8 mm width, and stored in a tape cassette. (Comparative Example 1)

As the magnetic powder in Example 1, the average particle size is
A magnetic recording medium was manufactured in the same manner except that Co-γ ferrite powder having a coercive force of 850 Oe of 0.3 μm was used, cut into a width of 8 mm, and stored in a tape cassette. (Comparative example 2)

As the magnetic powder in Example 1, the average particle size is
A magnetic recording medium was manufactured in the same manner except that a metal powder having a coercive force of 1400 Oe and a 0.3 μm was used, and was cut into a width of 8 mm.
Stored in a tape cassette. (Comparative example 3)

As the magnetic powder in Example 1, the average particle size is
A magnetic recording medium was manufactured in the same manner except that metal powder having a coercive force of 1580 Oe and a coercive force of 0.25 μm was used.
Stored in a tape cassette.

[0029]

[Table 1]

The coercive force (Hc) in the thickness direction of each layer of the magnetic tapes of the specific example and the comparative example described above is calculated as follows.
(P)), the coercive force in the longitudinal direction (Hc) is the coercive force in the longitudinal direction (Hc
(L)), the coercive force in the width direction (Hc) is the coercive force in the width direction (Hc (T)
), And the electromagnetic conversion characteristics of each magnetic tape are shown in Table 1.

Regarding the measurement of the electromagnetic conversion characteristics of each magnetic tape, a head gap of 0.21 at an azimuth angle of ± 20 ° on a track having an inclination of 6.6 ° with respect to the longitudinal direction of the magnetic tape.
A 9-MHz signal was recorded and reproduced at a tape speed of 3.8 m / s using a micron ring head, and the magnetic tape of Comparative Example 1 was used as a reference. As can be seen from Table 1, in all the magnetic recording tapes of this specific example, there is no significant difference in reproduction output between adjacent tracks of more than 0.5 (dB). Further, according to the magnetic tape of this specific example, 9 MH
It is difficult to obtain a high reproduction output even in a high range such as z.

[0032]

As described in detail above, according to the magnetic recording medium of the present invention, the fluctuation of the output between adjacent tracks is small,
And, very excellent recording / reproducing characteristics can be obtained for high density recording.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a magnetic recording tape for explaining a magnetic recording medium of the present invention.

FIG. 2 is a graph showing the reproduction output on the vertical axis and the longitudinal direction on the horizontal axis.
SFD (L) is taken to show the SFD (L) dependence of the reproduction output of the magnetic recording medium.

Claims (3)

[Claims] 1. A magnetic recording medium comprising a magnetic layer on a substrate in which magnetic powder is dispersed in a resin, wherein the coercive force in the longitudinal direction of the magnetic layer is Hc (L), and the coercive force in the thickness direction of the magnetic layer. Where Hc (P) is the coercive force of Hc (P) and Hc (T) is the coercive force in the width direction of the magnetic layer, Hc (P) / Hc (L) is 0.65 or more, and Hc (T) / Hc (L )
Is 0.80 or more. 2. A magnetic recording medium characterized in that the SFD (L) in the longitudinal direction of the magnetic layer is 0.3 or less. 3. The magnetic recording medium according to claim 1, wherein the magnetic powder is a magnetic powder mainly composed of a hexagonal magnetic substance.