JPH0520672A - Coating-type magnetic medium - Google Patents

Abstract

PURPOSE:To provide a coating-type magnetic medium for magnetic recording excellent in traveling durability with little dropout of abrasive particles. CONSTITUTION:The coating-type magnetic medium for magnetic recording it produced bye applying a mixture of a magnetic powder 4, binder 7, and abrasive, etc., on a nonmagnetic supporting body 6. This medium features in containing acicula titanium oxide 3 having <=3 acicula ratio as the abrasive. Thus, the obtd. coating-tape magnetic medium has improved traveling durability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated magnetic medium having excellent running durability.

[0002]

2. Description of the Related Art Conventionally, a coating type magnetic medium used in a magnetic recording apparatus is prepared by coating a mixture of a magnetic powder 4, a binder 7 and an abrasive on a non-magnetic support 6 as shown in FIG. can get. It is important that such a coating type magnetic medium has good electromagnetic conversion characteristics and excellent durability.

Particularly, in a coating type magnetic medium such as a magnetic tape or a magnetic disk, since it travels while directly contacting a recording / reproducing and erasing head, it is apt to be worn as compared with other magnetic media in which the head and the medium do not contact each other. , Driving durability is an important requirement.

Conventionally, generally spherical abrasive particles 2 such as Al ₂ O ₃ and SiC have been often used in order to secure the running durability of the coating type magnetic medium. This type of abrasive generally has a Mohs hardness of 5 or more and a spherical shape, and a part thereof is exposed on the surface in the medium layer 5 as shown in FIG.
When the head actually contacts the medium, the abrasive particles 2 on the surface of the medium support the head to suppress wear and ensure running durability.

[0005]

However, when the spherical abrasive is used, the abrasive particles are fixed at a shallow portion in the medium layer, and therefore the abrasive particles on the surface of the coating film are contacted by contact between the head and the medium. It is known that there is a phenomenon of lack of powder, that is, powder removal occurs, and the abrasive generated by powder removal enters between the head and the medium and causes new wear, which causes a problem of deterioration of running durability. It was. For this reason, a coupling agent or the like is being used to strengthen the bond between the binder and the abrasive particles, but no sufficient effect has been obtained.

The present invention has been made in view of the present circumstances. That is, an object of the present invention is to prevent the powder of abrasive particles from falling off, and further to provide a coating type magnetic medium having excellent running durability.

[0007]

The present invention relates to a coating type magnetic medium for magnetic recording, which comprises mixing magnetic powder, a binder, an abrasive and the like and coating the mixture on a non-magnetic support. The coating type magnetic medium is characterized by containing acicular titanium oxide having a ratio (particle length / particle diameter) of 3 or more.

[0008]

[Function] When acicular titanium oxide is used as an abrasive,
Since the abrasive particles have a needle-like shape, the abrasive particles of the magnetic powder 4 and the acicular titanium oxide 3 are present in the binder 7 intricately entangled with each other as shown in FIG. Therefore, even if the head travels on the medium, the abrasive particles of the acicular titanium oxide 3 on the surface of the coating film are less likely to be lost, and powder falling can be reduced.

Furthermore, the Mohs hardness of titanium oxide is 6.0.
Since the acicular titanium oxide particles support the traveling head, the wear resistance of the medium is improved and, as a result, the traveling durability can be improved.

The shape of the acicular titanium oxide used in the present invention may be such that the acicular ratio is 3 or more, and the size is selected in relation to the size of the magnetic powder to be used, but the same or It is desirable that it is more than that.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. Example 1. Fe-based alloy powder (particle length: 0.5 μm, particle diameter: 0.03 μm, acicular ratio: 16.7) 75 parts by weight. Modified nitrocellulose resin (average degree of polymerization: 50, nitrogen content: 11.9%, [-COOH] = 0.05 mmol / g) 7.5 parts by weight. Modified polycarbonate polyurethane resin (number average molecular weight: 36000, [-COOH] = 0.05 mmol / g) 17.5 parts by weight. 23 parts by weight of acicular titanium oxide fine powder (particle length: 3 to 6 μm, particle diameter: 0.05 to 0.10 μm). Antistatic agent (Columbian Carbon Co., Conductox SC) 5 parts by weight. 2 parts by weight of lubricant (i-amyl stearate). Lubricant (hexadecyl stearate) 6 parts by weight. 80 parts by weight of solvent (methyl ethyl ketone). 40 parts by weight of solvent (cyclohexane). 80 parts by weight of solvent (toluene). The above composition was kneaded in a ball mill for 72 hours, and then 10 parts by weight of a low molecular weight isocyanate compound (Coronate 3041 manufactured by Nippon Polyurethane Industry Co., Ltd., including 5 parts by weight of solid content) was added and kneaded for 2 hours to obtain a magnetic coating material. ..

As shown in FIG. 1, the obtained magnetic paint was applied onto a non-magnetic support 6 of a polyethylene terephthalate film having a thickness of 75 μm so that the thickness after drying would be 2 μm, and the nip pressure was 300 kg / cm. After performing a calendering treatment under the condition of the metal roll surface temperature of 60 ° C., curing was carried out at a constant temperature of 45 ° C. for 72 hours, and this was punched into a disc shape having a diameter of 3.5 inches to obtain a sample.

Example 2. In Example 1, the acicular titanium oxide particles had a particle length of 4 to 12 μm and a particle diameter of 0.
A sample was prepared in the same manner as in Example 1 except that the thickness was changed from 05 to 0.15 μm.

Comparative Example 1. A sample was prepared in the same manner as in Example 1 except that spherical titanium oxide (particle size 0.5 μm) was added instead of the acicular titanium oxide.

Comparative Example 2. A sample was obtained in the same manner as in Example 1 except that fine powder of silicon carbide (particle size 0.5 μm) was added instead of the acicular titanium oxide.

Comparative Example 3. In Example 1, fine powder of aluminum oxide (particle size 0.5
A sample was obtained in the same manner as in Example 1 except that (.mu.m) was added.

A running durability test was conducted on the samples obtained in the above examples and comparative examples. Specifically, the sample was assembled in a 3.5-inch flexible disk jacket, mounted on a 3.5-inch flexible disk drive (406 TPI, 360 rpm), and a signal of frequency 625 kHz was recorded on the 0th surface 00 track. An on-track continuous running durability test was conducted in an atmosphere of 50 ° C.-80% HR. The number of passes of running durability was defined as the time when the reproduction output was 80% or less of the initial output. The results obtained are shown in Table 1.

[0018]

[Table 1]

In Table 1, the running durability is at a level of practically no problem if it is 20 million passes. As can be seen from Table 1, the medium using acicular titanium oxide as the abrasive is 200
It has a running durability of 0,000 passes or more and is improved in durability as compared with the case where a spherical abrasive is used.

Although the metal magnetic powder is used as the magnetic powder in the examples according to the present invention, the same effect is observed when other iron oxide type magnetic powder is used. It is not limited to types.

[0021]

As described above, by using needle-shaped titanium oxide as the abrasive, it is possible to obtain a coating type magnetic medium with reduced powder falling from the coating film and improved running durability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing a cross section of a coating type magnetic medium layer when acicular titanium oxide of one example of the present invention is used as an abrasive.

FIG. 2 is a sectional view schematically showing a section of a coating type magnetic medium layer using a conventional spherical abrasive.

[Explanation of symbols]

 1 Medium Surface 2 Abrasive Particles 3 Needle Titanium Oxide 4 Magnetic Powder 5 Medium Layer 6 Nonmagnetic Support 7 Binder

Claims (1)

Claim: What is claimed is: 1. A coating type magnetic medium for magnetic recording, comprising a magnetic powder, a binder, an abrasive and the like mixed and coated on a non-magnetic support. Particle length / particle diameter)
Is a coating type magnetic medium containing 3 or more of acicular titanium oxide.