JPH02192020A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To increase the penetration margin at the time of recording at a high density by specifying the thickness of the magnetic recording medium to a specific range. CONSTITUTION:The thickness of the disk-shaped magnetic recording medium which is provided with a magnetic layer contg. magnetic powder and binder on a polyester base and is used for recording at >=17.5kbpi max. line recording density is specified to >=50mum and <72mum. An output change with a deviation is small in this way even if the position where the disk is held and the position of a head deviate on the axis perpendicular to the disk plane. The recording medium has the large penetration margin and is usable as the magnetic recording medium of a large capacity and high density.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a flexible disk-shaped magnetic recording medium comprising a magnetic layer containing magnetic powder and a binder provided on a polyester support, and particularly relates to a flexible disk-shaped magnetic recording medium that is suitable for high-density recording. The present invention relates to a magnetic recording medium capable of

[Conventional technology and its problems]

In recent years, as compact computers have become more widespread and their performance has improved, there has been a strong demand for larger capacities in magnetic recording media such as flexible disks, and various high-density recording methods have been proposed. At this time, as the recording density increases, it is required that the recording/reproducing head and the magnetic recording medium be in close contact with each other. Furthermore, one of the characteristics of flexible disks as recording media is their interchangeability, and for this reason, flexible disks must be able to fully demonstrate their characteristics for recording and reproduction in various disk drives.

However, with conventional flexible disks, when recording at a high wax density of 17.5 kbpi or higher, the position where the disk is held and the position of the head become misaligned on the axis perpendicular to the disk surface. In this case, the output fluctuation is large with respect to the deviation, that is, the so-called penetration margin is small, so there is a problem that depending on the type of disk drive, problems occur in recording and reproducing.

[Means to solve the problem]

As a result of intensive studies, the present inventors found that the thickness of a magnetic recording medium formed by providing a magnetic layer containing magnetic powder and a binder on a polyester support is within a specific range. As a result, even if the position where the disk is held and the position of the head are misaligned on an axis perpendicular to the disk surface, the output fluctuation due to the misalignment is small and the hentration margin is large. We have arrived at the present invention, which can be used as a large-capacity, high-density magnetic recording medium.

That is, the gist of the present invention is a disk-shaped magnetic recording medium for recording at a maximum linear recording density of 17.5 kbpi or more, which comprises a polyester support and a magnetic layer containing magnetic powder and a binder. The thickness of the magnetic recording medium is 50 μm
The present invention resides in a magnetic recording medium characterized in that the diameter is greater than or equal to 72 μm.

The present invention will be explained in detail below.

The magnetic recording medium of the present invention has a thickness of 50 μm or more and 72 μm.
It is characterized by having a diameter of less than 60 μm and preferably 60 μm or more and 70 μm or less.

If the thickness of the magnetic recording medium is 72 μm or more, for example 80 μm ± 8 μm (JIS If the position of the magnetic recording medium is misaligned with the position of the head, a force that opposes the pressing pressure of the gimbal that supports the head is generated, resulting in poor adhesion between the head and the magnetic recording medium. This reduces the output and increases the variation (modulation) of the output around the circumference of the disk. If the thickness of the medium is thinner than 50 μm, the rigidity of the magnetic recording medium is low, so if the position where the disk is held and the position of the head are misaligned on the axis perpendicular to the disk surface, the head may Since the medium is rapidly distorted around the head, the medium rubs against the edge of the head, deteriorating its durability during continuous recording and playback. In addition, output fluctuations also increase.

In addition, in the present invention, the thickness of the magnetic layer is usually 0.05 mm on one side.
The thickness of the polyester support is preferably 5 to 3 μm.
0 to 70 μm is preferable.

In the present invention, the magnetic powder constituting the magnetic layer includes:
For example, ferromagnetic iron oxide (γ-FezO+, Fe3O4, C
O-containing -Fe203, COO-containing Fe3O4, barium ferrite, etc.), ferromagnetic chromium dioxide, ferromagnetic alloy powder (iron, cobalt, nickel, or their alloys, etc.), or mixtures thereof, which are used in ordinary magnetic recording media. magnetic powder can be used.

Binders used in the present invention include polyurethane resins, vinyl chloride-vinyl acetate copolymers, epoxy resins, cellulose resins, polyester resins, acrylic resins, rubber resins, isocyanate compounds, etc. Any material that is normally used as a binder component of magnetic powder may be used.

As the polyester support, polyethylene terephthalate or the like is usually used.

Further, additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, and the like may be added to the magnetic layer in the present invention, if necessary.

The magnetic recording medium of the present invention has a maximum linear recording density of 17°5k.
When recording at a high recording density of bpi or higher, the output fluctuation is small and the penetration margin is large, so
It has excellent interchangeability and can fully demonstrate its characteristics for recording and reproduction in various disk drives.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to the examples unless it goes beyond the gist thereof.

Example 1 Magnetic powder (barium ferrite) 100 parts by weight Binder resin 18 parts by weight Phosphoric ester dispersant 4.1 parts by weight α-alumina
6.5 parts by weight Butoxyethyl stearate 1.5 parts by weight Conductive carbon blank 3.
5 parts by weight Methyl ethyl ketone 60 parts by weight Toluene 60 parts by weight Cyclohexanone 60 parts by weight The above composition was mixed and dispersed, and the magnetic layers were uniformly coated on both sides of a 62 μm thick polyethylene terephthalate film so that the thickness of each layer was 2.3 μm. After coating and drying, it was calendered and punched into a donut shape with a diameter of 85° and 8 mm to obtain a magnetic disk.

The obtained magnetic disk was rotated at a rotation speed of 30 rpm, and a recording frequency of 1 was achieved using a head with a head gap of 0.4 μm.
,000,0OOFRPS (linear recording density 20.5-34
．． 8 kbpi) and then reproduced by moving the head up and down to measure the penetration margin. The measurement results are shown in Table 1.

Regarding the recording surface, the side with the hub operation port was designated as side 0, and the other side was designated as side 1.

Penetration margin is defined as the amount by which the playback output of a recorded signal changes the head position when the position where the disc is held and the head position are in the same plane on the axis perpendicular to the disc surface. When the initial value is 9
The amount of head displacement that is within 0% and at the same time satisfies the modulation specified by JIS The larger the penetration margin, the greater the displacement on the axis perpendicular to the disk surface, even if the position where the disk is held and the position of the head are misaligned. output fluctuation is small compared to

Comparative Example 1 A magnetic disk was obtained in the same manner as in Example 1 except that a 75 μm thick polyethylene terephthalate film was used as the support. Table 1 shows the measurement results of penetration margin.

Comparative Example 2 A magnetic disk was obtained in the same manner as in Example 1 except that a 32 μm thick polyethylene terephthalate film was used as the support. Table 1 shows the measurement results of penetration margin.

As is clear from Table 1, when the thickness of the magnetic recording medium is 72 μm or more or thinner than 50 μm, as in Comparative Examples 1 and 2, the penetration margin is small, and it is used at a maximum linear recording density of 17.5 kbpi or more. It can be seen that it is not suitable as a magnetic recording medium.

〔Effect of the invention〕

According to the present invention, it is possible to increase the penetration margin during high-density recording compared to conventional magnetic recording media, and it is possible to obtain a highly practical large-capacity magnetic recording medium.

Claims (1)

[Claims] (1) A magnetic layer containing magnetic powder and a binder is provided on a polyester support, with a maximum linear recording density of 17.5 kbp.
1. A disk-shaped magnetic recording medium for recording at a speed of i or more, characterized in that the thickness of the magnetic recording medium is 50 μm or more and less than 72 μm.