JPS6194232A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To increase the PM output by forming a magnetic layer having about 800-900Oe coercive force in a direction perpendicular to the magnetic surface on a nonmagnetic substrate. CONSTITUTION:A magnetic recording medium having about 800-900Oe coercive force in a direction perpendicular to the magnetic surface is used in a recorder and/or a reproducer using a ringlike magnetic head of 'Sendust(R)' alloy. When a magnetic layer having such magnetic characteristics is formed, platy magnetic powder of barium ferrite, a mixture of the platy magnetic powder with needlelike magnetic powder of gamma-Fe2O3 or Co deposited gamma-Fe2O3 or spindle type magnetic powder may be used as a magnetic material in the magnetic layer. High reproduction output is attained during recording in a short wavelength region by properly dispersing or orienting such magnetic powder in a magnetic coating material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention particularly relates to a coated high-density magnetic recording medium.

[Prior art and its problems]

For example, magnetic tape is coated with Co-Fezej,
It is made by coating a base film with a magnetic paint containing various magnetic powders such as flat barium ferrite or spindle-type magnetic powder.

Due to the demand for high-density recording, research and development of magnetic powder contained in the magnetic layer on the base film has been actively conducted, and a number of magnetic materials suitable for high-density recording have been proposed. However, in the short wavelength region where high-density recording can be performed, magnetic recording media using horizontal magnetic recording have the problem of self-demagnetization, so magnetic recording media using perpendicular magnetic recording are recommended instead. A Co--Cr alloy or barium ferrite magnetic powder has been proposed as a magnetic material for such a perpendicular magnetic recording type magnetic recording medium.

However, the inventors of the present invention stood at the origins of high-density recording and asked what was the key to achieving high-density recording. I realized the basic principle that high-density recording is possible when there is a good relationship between the magnetic field of the magnetic head used for reproduction and the magnetic properties of the magnetic recording medium. In other words, conventional magnetic recording media are not necessarily satisfactory considering the origin of high-density recording.

In addition, apart from acicular particles that are oriented in the in-plane direction, flat barium ferrite magnetic powder or spindle-shaped magnetic powder that can be oriented vertically or randomly has a considerable coercive force Hcm in the vertical direction depending on the orientation treatment conditions. Therefore, even magnetic recording media using highly desirable magnetic materials have drawbacks that make it difficult to say that they are truly suitable for high-density recording.

[Disclosure of the invention]

The present inventor returns to the origin as described above, and from this, for example, a ring-shaped Sendust alloy (with a saturation magnetic flux density of 1
High-density recording is possible on magnetic recording media used in recording and/or reproducing devices using magnetic heads (0,000 Gauss) when the coercive force in the direction perpendicular to the magnetic surface is about 800 to 900 Oe. I discovered that.

As for the magnetic materials contained in the magnetic layer to constitute the magnetic layer having such magnetic properties, for example, tabular barium ferrite magnetic powder, tabular barium ferrite magnetic powder and γ-Fears or CO-coated magnetic materials are used. Arrival −Fe=0−
A mixture with acicular magnetic powder such as acicular magnetic powder, spindle type magnetic powder, etc. can be used, and the above characteristics can be obtained by appropriately dispersing or orienting the magnetic paint containing such magnetic powder. I can do it.

[Example 1] Hexagonal plate-shaped barium ferrite powder (coercive force Hc about 720 Oe, saturation magnetization Ms about 53.5 emu/g.

Plate-like ratio 7, average particle size line 0.2 μm) 100 parts by weight, vinyl chloride-vinyl acetate copolymer 10 parts by weight, polyurethane 10 parts by weight, Atzo-ro powder 10 parts by weight, Omushi-Shun 2
Parts by weight, 7 parts by weight of carbon black, 10 parts by weight of Coronae) L (manufactured by Nippon Polyurethane), methyl ethyl ketone,
Mixed solvent of equal amounts of toluene and methyl isobutyl ketone 3
00 parts by weight were sufficiently mixed and dispersed using a sand mill to make a magnetic paint, and this magnetic paint was applied onto a polyester film with a thickness of 14 μm to a dry thickness of 5 μm.
After drying and surface polishing, the tape was slit to a predetermined width to produce a magnetic tape.

The orientation treatment was performed with the viscosity of the magnetic coating layer in a magnetic field (5ooo()) being approximately 3000 cps.

When the coercive force of this magnetic tape in the direction perpendicular to the magnetic coating surface is measured, it is approximately 810 Oe.

[Example 2] In Example 1, the viscosity of the magnetic coating layer in an orientation magnetic field (8000 G) was adjusted to about 3300 cps and orientation treatment was performed to prepare a magnetic tape.

When the coercive force of this magnetic tape in the direction perpendicular to the magnetic coating surface was measured, it was approximately 860 oersteds.

[Example 3] In Example 1, the viscosity of the magnetic coating layer in an orientation magnetic field (8000 G) was adjusted to about 4000 cps and orientation treatment was performed to prepare a magnetic tape.

The coercive force of this magnetic tape in the direction perpendicular to the magnetic coating surface is approximately 900 oersteds.

[Comparative Example 1] In Example 1, the viscosity of the magnetic coating layer in the alignment magnetic field (8000G) was adjusted to about 2500 cps,
Created magnetic tape.

Similarly, when the coercive force of this magnetic tape in the direction perpendicular to the magnetic coating surface is measured, it is approximately 770 Oe.

[Comparative Example 2] In Example 1, the viscosity of the magnetic coating layer in the alignment magnetic field (8000G) was adjusted to about 4200 cps.
Created magnetic tape.

When the coercive force of this magnetic tape in the direction perpendicular to the magnetic coating surface is measured, it is approximately 920 oersteds.

[Comparative Example 3] In Example 1, the viscosity of the magnetic coating layer was adjusted to about 4,500 cps in an orienting magnetic field (8,000 G) to produce a magnetic tape.

The coercive force of this magnetic tape in the direction perpendicular to the magnetic coating surface is approximately 990 Oe.

〔Characteristic〕

Regarding the magnetic tapes of Examples 1 to 3 and Comparative Examples 1 to 3,
Recording and playback (recording signal 5MHz) is performed using a video deck equipped with a ring-shaped Sendust alloy magnetic head.
Examination of the electromagnetic conversion characteristics shows the same as shown in the drawing.

According to this, the coercive force in the direction perpendicular to the magnetic coating surface is about 85
The maximum FM specific output is around 0 Oe, and a magnetic recording medium with a vertical coercive force in the range of about 800 to 900 Oe has an FM specific output of about 370 mVp-p.
The above is a large one, and the reproduction output in short wavelength recording is large.

〔effect〕

It has a large reproduction output in short wavelength recording.

[Brief explanation of the drawing]

The drawing is a graph showing the characteristics of the magnetic recording medium according to the present invention. 1 Exorcism phantom defense n Ij sword (^)

Claims (1)

[Claims] 1. A magnetic recording medium comprising a magnetic layer having a coercive force of about 800 to 900 oersteds in a direction perpendicular to the magnetic surface, provided on a nonmagnetic substrate.