JP3048416B2 - Magnetic recording media - Google Patents

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 having a magnetic layer formed by coating.

[0002]

2. Description of the Related Art A magnetic recording medium is roughly classified into a magnetic recording medium having a magnetic layer formed on a support by a vacuum technique such as sputtering or vapor deposition, and a magnetic layer formed on a support by applying a magnetic paint. Some are composed of In particular, magnetic recording media formed by coating are inexpensive and excellent in mass productivity, and are currently most frequently used.

Incidentally, in the above-mentioned coating type magnetic recording medium, it is conceivable that the surface of the magnetic layer is mirror-finished in order to reduce the spacing between the magnetic head and the surface of the magnetic layer for the purpose of improving the output. However, when the surface of the magnetic layer is mirror-finished in this way, sliding friction between the magnetic layer and the magnetic head,
Alternatively, the strength of the magnetic layer itself becomes a problem, causing problems such as dropping of the magnetic layer due to contact with the head, adhesion of the magnetic layer to the head, and clogging of the head.

To solve such problems, for example, Japanese Patent Laid-Open Publication No. Sho 61-57036 discloses that an abrasive having a Mohs hardness of 6 or more is contained in an amount of 3 to 15 wt% based on the magnetic powder. . With such a configuration, the durability of the magnetic recording medium and the running property of the magnetic head are improved.

[0005]

In recent years, there has been an increasing demand for large capacity magnetic recording media. For example, magnetic disks such as floppy disks have been researched and developed one after another. As the capacity increases, the point is how to access a large amount of recorded information at high speed.

Therefore, high-speed data access can be achieved by increasing the relative speed between the medium and the magnetic head. However, it is necessary to further improve the durability of the magnetic recording medium and the running property of the magnetic head as compared with the prior art. Come up.

Although it is possible to improve the durability of the magnetic recording medium and the running property of the magnetic head by increasing the amount of abrasive in the magnetic layer, components other than magnetic powder, ie, abrasive, are added to the magnetic layer. And the like are mixed in a large amount, which causes a decrease in reproduction output and an increase in noise.

[0008] Figure 2, the vertical axis to the durability and the reproduced output, an illustration take the amount of the abrasive on the horizontal axis, figure curve (a) The addition amount of the abrasive and durability of the magnetic recording medium In the figure, (b) shows the reproduction output of the magnetic recording medium and polishing.
The relationship with the amount of material added is shown. From this figure, it is increasing the amount of the abrasive, as described above, although improving the durability of the magnetic recording medium, it can be seen that lowering the reproduction output.

Further, such a solution using only the added amount causes a new problem such as abrasion of the magnetic head and detachment of abrasive particles from the surface of the magnetic layer, and is not at all preferable.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a magnetic recording medium capable of improving the durability of the magnetic recording medium without causing wear of the magnetic head. It was done.

[0011]

The magnetic recording medium of the present invention According to an aspect of a magnetic recording comprising magnetic powder and abrasive material in the binder resin is provided on at least one principal surface of the substrate a magnetic layer formed by dispersing In the medium, the amount of the abrasive added was as follows.
3.0 to 8.0 parts by weight with respect to 00 parts by weight, and
The magnetic layer is formed together with the binder resin and the magnetic powder.
It is obtained from a dispersion of the abrasive, and
Wherein the average particle diameter D1 of the abrasive projecting magnetic layer on the surface, if a protrusion average size of the abrasive was D2, D2 / D1 is 0.5 or more and 0.85 or less in Things.

[0012]

The present inventors have focused on the surface properties of a magnetic layer particularly suitable for a large-capacity magnetic recording medium and have conducted various studies.
It has been found that the presence of the abrasive greatly affects the wear of the magnetic head and the durability of the magnetic recording medium.

That is, as described above, when the average particle diameter of the abrasive is D1 and the average diameter of the protruding portion of the abrasive projecting onto the magnetic layer is D2, D2 / D1 is particularly 0.5 or more. , 0.85 or less.

With this configuration, the durability of the magnetic recording medium can be maintained for a long period of time without the abrasive coming off the surface of the magnetic layer even under severe contact between the magnetic layer and the magnetic head. be able to. Further, with the above configuration, it is not necessary to particularly increase the amount of abrasive, so that the magnetic characteristics of the magnetic recording medium do not deteriorate or the magnetic head does not wear. According to the present invention, the durability can be greatly improved without lowering the magnetic characteristics of the magnetic recording medium.

In the present specification, D1 is a polishing material that protrudes toward the surface of the magnetic layer at random as shown in FIG.
Number extracted, the average particle diameter of the extracted Ken Migakuzai (D1 =
D1,1 + D1,2 + ... + D1,100). D2 is the average value of the longest diameters of the 100 abrasives described above, that is, the average diameter of the projections (D2 = D
2, 1 + D2, 2+... + D2, 100).

If D2 / D1 is smaller than 0.5, the head cleaning effect of sufficiently removing foreign substances such as dust adhering to the surface of the magnetic head is reduced, and the running property of the magnetic head is deteriorated, and the magnetic recording medium is thus not easily read. This causes a decrease in durability. Conversely, if D2 / D1 of the abrasive is greater than 0.85, the abrasive falls off the surface of the magnetic layer and enters between the magnetic head and the medium due to severe contact between the magnetic layer and the magnetic head. This is because the durability of the magnetic recording medium is reduced.

Examples of the abrasive usable in the present invention include α-Al ₂ O ₃ , Cr ₂ O ₃ , and SiC.
Particularly, when the Mohs hardness is 6 or more, good durability can be obtained.

The abrasive has a mean particle size of 0.0
It is preferably between 2 and 0.12 microns. If the average particle size is smaller than 0.02 micron, the head cleaning effect is significantly reduced, and if the average particle size is larger than 0.12 micron, there is a possibility that head wear may occur or a missing pulse may be induced.

The amount of the abrasive added is as follows.
3.0 to 8.0 parts by weight with respect to 00 parts by weight. If the amount is less than 3.0 parts by weight with respect to 100 parts by weight of the magnetic powder, it becomes difficult to secure sufficient durability, and if it is more than 8.0 parts by weight, the output may be reduced.

The magnetic powder usable in the present invention includes, for example, hexagonal magnetic powder such as γ-Fe ₂ O ₃ , cobalt-coated γ-Fe ₂ O ₃ , barium ferrite, Fe—Co, Co
Magnetic materials such as alloy powders of -Ni, Mn-Al and the like.

The binder resin usable in the present invention includes, for example, polyvinyl chloride resin, epoxy resin, polyester resin, polyamide resin, polyurethane resin, cellulose derivative and mixtures thereof. Further, for the magnetic recording medium of the present invention, conventionally used lubricants, conductive members and the like can be appropriately used.

Various methods are conceivable for obtaining the magnetic recording medium of the present invention. The magnetic recording medium can be obtained by calendering the magnetic layer in a state where the concentration of the organic solvent containing cyclohexanone is 50 to 200 ppm. There is also a method of adding abrasive particles in which abrasive particles are dispersed in a binder resin in advance. In either method, the binder
From abrasives dispersed with resin and magnetic powder
A magnetic layer is obtained.

[0023]

The present invention will now be described in detail with reference to specific examples and comparative examples. (Specific example 1) (Magnetic powder) Co-Ti-substituted barium ferrite magnetic powder 100 parts by weight (average particle size 0.08 microns, coercive force 700 Oe) (abrasive) Abrasive composition 4 parts by weight (average particle size 0.1 microns) (Binder resin) Polyurethane resin 12 parts by weight Nitrocellulose 6 parts by weight (dispersant) Lecithin 2.1 parts by weight (lubricant) Stearic acid 1.2 parts by weight n-butyl stearate 2.5 parts by weight (solvent) Methyl ethyl ketone 75 parts by weight Cyclohexanone 75 parts by weight Parts toluene 75 parts by weight

After the various materials except the above-mentioned abrasive composition are dispersed by a sand grinder, the abrasive composition is
3 parts by weight of a curing agent was added to the magnetic coating material after adding and redispersing parts by weight and filtering the contaminants. Then, the magnetic paint was applied on a PET (polyethylene terephthalate) film having a thickness of 75 microns using a reverse coater.
In addition, as the above-mentioned abrasive composition, 4 parts by weight of a composition containing 3 parts by weight of an abrasive component in a resin was used.

Further, the magnetic layer was formed on both sides of a PET film by performing a calendering process at a calendar pressure of 250 kg / cm with 120 ppm of the organic solvent remaining in the magnetic layer to obtain a magnetic recording medium. Hereinafter, Examples 2 to 6 and Comparative Examples 1 to 5 are manufactured under the conditions shown in Table 1, and are otherwise the same as Example 1.

The magnetic recording media of the above-described various examples and comparative examples were punched into a disk having a hole for hub installation in the center, and a metal hub was installed in the hole at the center, and the hub was placed in the jacket. Stored rotatably.

The read output and S / S ratio of the various magnetic disks thus obtained were measured using a ring-type ferrite head having a head gap of 0.4 μm and rotating at 300 rpm.
Table 2 shows the results of evaluating N, cycle durability, and head damage.

[0028]

[Table 1]

Note that the reproduction output and S /
N is a relative value when the magnetic disk of Comparative Example 1 is set to 0 dB, and the cycle durability is 5 ° C., 20% and 5%.
The environment of 5 ° C and 60% is one cycle of 24 hours.
It indicates the durability under a cycle environment that changes every two hours, and indicates the durability by the number of running passes when the reproduction output becomes 70% or less of the initial reproduction output. Also, the change in the reproduction output is 10 times the initial reproduction output at room temperature.
The figure shows the rate of decrease in the reproduction output after running a million passes.

[0030]

[Table 2]

As is evident from Table 2, the magnetic recording media of Comparative Examples in which D2 / D1 is smaller than 0.5 or larger than 0.85 have poor durability and damage to the head. Disadvantages are seen.

On the other hand, D2 / D1 is 0.5 or more,
According to the magnetic recording medium of each embodiment of 0.85 or less, good results were obtained with respect to any of reproduction output, S / N, durability, and damage to the head. That is, any magnetic recording medium in which D2 / D1 is within a predetermined range is particularly suitable for a high-speed rotating large-capacity magnetic disk capable of high-speed data access.

As a method for obtaining such a magnetic recording medium, the following can be understood from the above-described Examples and Comparative Examples. For example, when the abrasive is added as it is from Comparative Example 8, the abrasive is added after being dispersed in the resin.
No surface of the present invention is obtained . As the resin to be particularly dispersing the abrasive, tend to better to use the same as the resin used in the magnetic recording medium becomes large protrusion of the abrasive, also improves the more durable a molecular weight greater Can be understood.

[0034]

As described in detail above, according to the present invention,
Ensuring excellent high durability running properties without cause head wear it is possible to provide a magnetic recording medium capable. Further, since the above-mentioned effect can be achieved without increasing the amount of the abrasive, the reproduction output does not decrease.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a magnetic recording medium for explaining D1 and D2 in the present invention.

FIG. 2 is a graph in which the vertical axis indicates the durability and the reproduction output of the magnetic recording medium, and the horizontal axis indicates the amount of abrasive added.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Minoru Hashimoto 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Horikawa-cho Plant (72) Koichi Irie 72-Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Co., Ltd. Toshiba Horikawacho Plant (56) References JP-A-2-23521 (JP, A) JP-A-1-119916 (JP, A) JP-A-62-243116 (JP, A) JP-A-62-86541 ( JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G11B 5/708

Claims (1)

(57) [Claims] 1. A binder magnetic recording medium in which a magnetic powder and abrasive material in the resin is made provided on at least one principal surface of the substrate a magnetic layer formed by dispersing the added amount of the abrasive, the For 100 parts by weight of magnetic powder
3.0 to 8.0 parts by weight, and the magnetic layer comprises the binder resin and the magnetic powder.
Wherein are those abrasive obtained from those obtained by dispersing, if further the average particle diameter D1 of the abrasive projecting magnetic layer on the surface, a protrusion average diameter of the abrasive is D2 also, A magnetic recording medium, wherein D2 / D1 is 0.5 or more and 0.85 or less.