JPH05258281A - Magnetic recording medium and magnetic recorder - Google Patents

Abstract

PURPOSE:To prevent the reflocculation of magnetic powder in a magnetic coating material, to enhance the squareness ratio (Br/Bm) of a magnetic recording medium and to further enhance electromagnetic characteristics such as S-N ratio. CONSTITUTION:When a magnetic coating material is produced, 36g powder of polyvinyl butyral resin, 130g powder of epoxy resin and 500g acicular metal powder are charged into a kneader and kneaded for about 15min, 200g cellosolve acetate is slowly added to the kneaded material and 1.5g organically synthesized functional polymer having polyoxyalkylene glycol and acid anhydride structures in the skeleton and 472g cellosolve acetate are further added. They are kneaded for about 4hr in the kneader.

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 such as a coating type magnetic disk used for a storage device and the like and a large capacity magnetic recording device.

[0002]

2. Description of the Related Art A conventional coating type magnetic disk is manufactured by dispersing magnetic powder in a binder (polymer binder) or a solution thereof using a sand mill, a kneader, a ball mill or the like to prepare a magnetic paint, which is applied on a substrate. It is applied by applying it to, and if necessary, orienting it, thermosetting it, and polishing it. If necessary, a lubricant is applied to the produced coating film. The binder is usually a thermosetting resin, so it is thermoset,
It may be used only by heating. Further, the magnetic paint is usually agitated during storage to prevent reaggregation of the magnetic powder.

In recent years, as the capacity and density of magnetic recording devices have increased, finer magnetic powder has come to be used. A magnetic coating material using such magnetic powder easily re-aggregates, and it is difficult to completely prevent re-aggregation only by stirring. In order to solve such a problem, JP-A-2-239
The technique described in Japanese Patent No. 424 uses a magnetic metal powder having an average major axis length of 0.35 μm or less and an acicular ratio of 6 to 9. Further, in the epoxy-phenol system, a magnetic recording medium produced from a styrene allyl alcohol resin, a blocked acid catalyst and various additives is described in JP-B-2-56728.

[0004]

The prior art disclosed in Japanese Patent Application Laid-Open No. 2-239424 is not sufficiently considered in the production of a high density magnetic disk as an in-plane oriented magnetic recording medium, and is excellent. With electromagnetic characteristics such as S /
There is a problem that it is difficult to provide a high density magnetic recording medium and device having a good N ratio and squareness ratio.
That is, the above-mentioned prior art relates to the production of a magnetic tape having a thick coating film of about 2 μm or more.

The magnetic paint for producing such a coating film has a high viscosity of, for example, about 1000 cp. Therefore, since the coating material in which the magnetic metal powder is highly dispersed does not re-aggregate in a short time, it can be easily oriented by magnetic field orientation immediately after dispersing. On the other hand, the coating film of a magnetic disk having a high density is as thin as 1 μm or less. Therefore, it is necessary to use a magnetic paint having a low viscosity for producing such a coating film. Since a low-viscosity (50 to 500 cp) coating material is likely to re-aggregate, if there is time between various treatments and magnetic field orientation, re-aggregation of the magnetic powder will occur correspondingly even for a short time. Therefore, the manufactured magnetic disk has various electromagnetic characteristics, for example, a squareness ratio (B-H characteristic).
However, there was a problem of deterioration of the quality.

The styrene allyl alcohol resin, the organometallic catalyst stannous octoate, the blocked acid catalyst isopropanol / block P-toluenesulfonic acid, etc. described in Japanese Patent Publication No. 2-56728 are used after the magnetic coating is manufactured. The stability of is difficult. That is, due to the properties of the resin and the reactivity as a catalyst, there are problems in that the S / N ratio deteriorates as electromagnetic characteristics, further defects occur, and the output falls.

An object of the present invention is to provide a high-density in-plane oriented magnetic disk and medium excellent in electromagnetic characteristics, in which at least a magnetic coating material in which magnetic powder is dispersed is used to prevent re-aggregation of the magnetic powder and highly oriented. It is to provide a large-capacity magnetic disk device used.

[0008]

The above-mentioned object is to provide a magnetic coating material in which a functional polymer having a polyoxyalkylene glycol structure and an acid anhydride structure is dispersed in a polymer binder in at least an organically synthesizable skeleton. This can be achieved by manufacturing the magnetic recording film by orienting the magnetic powder while maintaining the undried state of the magnetic recording film obtained by coating on the non-magnetic substrate.

In the present invention, by applying a magnetic field to the functional polymer of the obtained magnetic paint and rotating the magnetic disk, the dispersion orientation of the magnetic powder can be further enhanced. Furthermore, since fine powder can obtain high orientation, the electromagnetic characteristics of the magnetic disk are improved.

The magnetic disk has a film thickness of 1 μm or less, more preferably about 0.55 ± 0.05 μm or less on the inner peripheral portion of the disk, and about 0.65 ± 0. 05μ
After forming a coating film consisting of at least a polymer material and magnetic powder to a film thickness of m or less, the coating film is heat-cured to about 0.35 μm or less at the inner peripheral portion and 0.45 μm or less at the outer peripheral portion. Grind to obtain. Thus, for example, a magnetic disk having a recording density of 30,000 BPI or more can be obtained.

[0011]

By including a functional polymer such as polyoxyalkylene glycol in the magnetic paint, the binding of the magnetic powder is weakened and the magnetic powder in the coating film is dispersed and oriented. The method of dispersing and orienting the magnetic powder is, for example, using an aluminum disc having a diameter of 5.25 inches and a thickness of 2 mm, and the magnetic poles of the magnet are N (or S) poles and N (or S) poles, a gap of 5 mm, and the same. It is achieved by applying a normal repulsive magnetic field with the poles aligned (about 3500 Oe). Further, the disk rotation speed during re-dispersion / orientation was more effective in the range of 20 to 60 RPM. When the thickness of the coating film is 1 μm or less, the gradient is high and the squareness ratio is 0.
It was over 85.

When the magnetic powder is a fine powder, for example, the average particle size is 0.4 μm or less, more preferably 0.2 μm or less, the magnetic powder moves and rotates in the coating film. Due to the low resistance, more effectiveness was obtained. In addition,
As the functional polymer material, a polymer material having a polyoxyalkylene glycol structure and an anhydrous structure is effective for enhancing dispersibility. This medium can provide a large-capacity device.

[0013]

【Example】

<Example 1> Polyvinyl butyral resin powder 36 g,
130 g of epoxy resin powder and acicular metal powder (average particle size: 0.17 x 0.02 μm, coercive force Hc: 1300 O
e, residual magnetic flux density δs: 120 emu / g, specific surface area B
ET: 54 m ² / g) 500 g was put into a kneader kneader,
Knead for about 15 minutes. Next, 200 g of cellosolve acetate
Is gradually added, and 1.5 g of a functional polymer having a polyoxyalkylene glycol structure and an acid anhydride structure in the organically synthesized skeleton and 472 g of cellosolve acetate are added, and kneading is performed for about 4 hours.

887 g of this kneaded material was taken and alumina 3
g and cellosolve 700g together in a 31 ball mill pot and kneaded with a ball mill for 7 days to obtain a magnetic powder,
Disperses the alumina well. Next is phenol resin 8
6 g and butyl cellosolve 500 g are added and mixed to prepare a magnetic paint. Next, this paint was applied to a disk whose surface had been cleaned in advance, and had disk diameters of 1 ", 1.5", 2.5 ", 3.5", 5.2.
5 ″, 8.8 ″, and 10.5 ″ aluminum discs were spin-coated, immediately subjected to in-plane magnetic field orientation with a conventional magnetic disk orientation apparatus, and cured at 210 ° C. in nitrogen. The relation with the BH curve (square ratio: Br / Bm) of (cut to 7 mm square) is as shown by the curve a in Fig. 1. Conventional method (without functional polymer) Is the curve b in the figure, and the one without magnetic field orientation (unoriented) is as shown by the curve C in the figure.

The squareness ratio (Br / Bm) here is 0.85.
(A: present invention), 0.55 (b: conventional), 0.52 (c:
(Unoriented). Moreover, the coercive force is 1410 Oe (a: the present invention), 1310 Oe (b: conventional), 1260 Oe.
(C: unoriented). In all cases, the products of the present invention showed a great improvement in characteristics.

The recording / reproducing characteristics of the magnetic disk having the inner peripheral portion of the magnetic recording film thus obtained of 0.27 μm were measured by a metal-in-gap type head having a gap length of 0.3 μm. However, the S / N ratio was improved by 32%.

Example 2 70 g of polyvinyl butyral powder and acicular γ-Fe ₂ O ₃ magnetic powder (average particle size: 0.35)
× 0.06 μm, coercive force Hc: 330 Oe, specific surface area B
ET: 22 m ² / g) 700 g is put into a kneader kneader and kneading is performed for about 15 minutes. Next, cellosolve acetate 25
0 g is gradually added and kneading is performed for about 4 hours. Taking 480 g of this kneaded material, 3 g of alumina, 1.5 g of a functional polymer having a polyoxyalkylene glycol structure and an acid anhydride structure in the organically synthesized skeleton, and 70 cellosolve acetate.
Both 0 g are put in a ball mill pot 31 and kneaded by a ball mill for 7 days to satisfactorily disperse the magnetic powder and alumina. Next, 120 g of phenolic resin, 300 g of butyl cellosolve solution of 40% epoxy resin, and 500 g of butyl cellosolve are added and mixed to prepare a magnetic paint. Next, apply this paint to a disk whose surface has been cleaned in advance.
It was spin-coated on a 5 ″ aluminum disk, subjected to in-plane magnetic field orientation with a normal magnetic disk orientation apparatus, and cured at 210 ° C. The relation to the squareness ratio (Br / Bm) of the obtained magnetic recording film is shown in Table 1. It is as shown in (2) of.

[0018]

[Table 1]

The recording / reproducing characteristics of the magnetic disk having an inner peripheral portion of the magnetic recording film thus obtained of 0.32 μm were measured by an MnZn ferrite head having a gap length of 0.5 μm. On the other hand,
The S / N ratio was improved by 7%.

Example 3 Needle-like Co-γ-Fe ₂ O ₃ magnetic powder (average particle size: 0.40 × 0.07 μm, coercive force Hc: 6)
The same treatment as in Example 2 was performed except that 50 Oe and specific surface area BET: 22.5 m ² / g) were used. The results are shown in Table 1.
It is as shown in (3) of. Moreover, the S / N ratio was improved by 9% as compared with the conventional one.

<Example 4> Needle-like fine powder Co-γ-Fe ₂ O ₃
Magnetic powder (average particle size: 0.2 × 0.02 μm, coercive force Hc:
770 Oe, specific surface area BET: 50 m ² / g) was used, and the same treatment as in Example 2 was performed. The results are shown in Table 1.
It is as shown in (4). Further, the S / N ratio was improved by 12% as compared with the conventional one.

Example 5 25 parts by weight of powdery epoxy resin and plate-like hexagonal barium ferrite magnetic powder (diameter about 0.1 μm, coercive force Hc: 655 Oe, specific surface area BE)
T: 30 m ² / g) 100 parts by weight, 1 g of a functional polymer having a polyoxyalkylene glycol structure and an acid anhydride structure in an organically synthesized skeleton and 5 parts by weight of single crystal alumina are thoroughly mixed, and then 10 parts by weight of cyclohexanone Parts were added and further mixed in a kneader kneader. afterwards,
Further, 5 parts by weight of cyclohexanone was added and kneading was continued for about 4 hours.

This kneaded product was put in a ball mill pot, 140 parts by weight of a mixed solvent of cyclohexanone and isaphorone was added, and ball mill kneading was carried out for 3 days to disperse the magnetic powder. Next, a magnetic coating material was prepared by adding a solution prepared by dissolving 25 parts by weight of a phenol resin and 6 parts by weight of a vinyl resin in 490 parts by weight of a mixed solvent of cyclohexanone / isophorone / dioxane. Next, the surface was cleaned in advance 5.25
Spin coating this paint on an inch aluminum substrate,
Alignment was performed with a normal aligner.

Further, the coating film was cured at 210 ° C. and surface-treated to make a magnetic recording film having a thickness of 0.3 μm, and a fluorine-based liquid lubricant was applied to obtain a magnetic disk. The electrical characteristics of this magnetic disk were measured using a thin film magnetic head with a gap length of 0.3 μm. In contrast to that of a conventional oriented magnetic disk ((5) in Table 1), a functional polymer was added, The oriented material had an improved S / N ratio of 10%.

<Embodiment 6> By combining the magnetic disks of Embodiments 1 to 5 with a thin film head having a gap length of 0.4 μm to form a magnetic disk device, the magnetic disk device can be made 1.
We achieved a 2-1.5 times larger capacity.

<Embodiment 7> By combining the magnetic disk of Embodiments 1 to 5 with the recording / reproducing separated magnetic head having a gap length of 0.35 μm to form a magnetic disk device, the magnetic disk device is 2-3 times as large as the conventional device. It was possible to realize a large capacity device.

[0027]

The magnetic disk and manufacturing method of the present invention are
(EN) A magnetic disk and a magnetic recording device which prevent re-aggregation of magnetic powder in a magnetic paint, improve the squareness ratio (Br / Bm) of a magnetic recording medium, and have excellent electromagnetic characteristics such as S / N ratio. it can.

[Brief description of drawings]

FIG. 1 is a characteristic diagram of a BH curve showing the squareness ratio (Br / Bm) of a magnetic film of the present invention.

[Explanation of symbols]

a ... Relation with BH curve of magnetic recording film, b ... Conventional method, c
… Those without magnetic field orientation.

Claims (6)

[Claims] 1. A coating characterized in that a film thickness of a magnetic layer containing a plurality of kinds of polymer materials and magnetic powder is 1 μm or less, and a squareness ratio in a magnetic head traveling direction is 0.85 or more. Type magnetic recording medium. 2. The size of magnetic powder according to claim 1, which is 0.4.
A magnetic recording medium having a size of μm or less. 3. The magnetic recording medium according to claim 1, wherein the size of the magnetic powder is 0.2 μm or less. 4. A magnetic recording medium according to claim 1, wherein the polymer material contains polyoxyalkylene glycol as a functional polymer material. 5. A magnetic coating material comprising a functional binder having a polyoxyalkylene glycol structure and an acid anhydride structure in a polymer binder in which at least an organically synthesizable skeleton has a magnetic component dispersed on a non-magnetic substrate. A magnetic disk, wherein the magnetic powder is orientated to produce the magnetic recording film while maintaining the undried state of the magnetic recording film obtained by coating. 6. A main component polymer is finely pulverized, at least polyvinyl butyral powder resin and epoxy powder resin are mixed with magnetic powder, and a kneader is kneaded by kneading with a solvent and, if necessary, additives. A method for producing a magnetic paint for a magnetic disk, characterized in that the composition ratio of the above is maintained.