JP2964428B2 - Flexible magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a magnetic recording medium provided with a protective layer on the surface of a magnetic layer.

[0002]

2. Description of the Related Art Usually, a flexible magnetic recording medium has a magnetic layer on the surface which comes into intense sliding contact with a magnetic head during recording and reproduction.
With the recent demand for higher density magnetic recording, magnetic recording media are required to have even higher wear resistance. Therefore, as one method for improving the wear resistance of the magnetic layer, an attempt has been made to provide a protective layer on the surface of the magnetic layer. For example, it has been proposed that a protective layer such as tetrafluoroethylene telomer is provided on a magnetic layer, and the friction coefficient of the magnetic layer is reduced by the excellent lubricating effect of the fluororesin to improve wear resistance. Since this kind of tetrafluoroethylene telomer has low molecular weight, it is rich in flexibility and excellent in lubricity, it is widely used as a protective layer of magnetic recording media, not only in flexible media but also in rigid magnetic disks. It is used for

[0003]

However, although the wear resistance is certainly improved by this protective layer, it is still not sufficient, and the protective layer is relatively easily lost by repeated sliding with the magnetic head. It has the drawback that it cannot withstand long-term use and that the protective layer is transferred to the magnetic head and causes spacing loss. A technical object of the present invention is to provide a magnetic recording medium having a protective layer having excellent lubricity and excellent wear resistance in view of the above-mentioned drawbacks.

[0004]

That is, according to the present invention, a tetrafluoroethylene telomer is provided on a magnetic layer by using tetrafluoroethylene-perfluoro (2,2-dimethyl-1,3- By fixing to the surface of the magnetic layer with a binder composed of (dioxyol) copolymer,
This is a flexible magnetic recording medium having a protective layer in which separation of the protective layer is suppressed and transfer of the protective layer to the magnetic head is suppressed.

[0005]

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In the present invention, the tetrafluoroethylene telomer used together with the binder in the protective layer usually has a particle size of 0.3 to 10 (μm), and preferably has a low molecular weight of 10,000 or less, Specific examples include Vidax AR and Vidax 5100 manufactured by DuPont and Lubron LD- manufactured by Daikin Industries, Ltd.
For example, tetrafluorotelomers having an average particle diameter of 5 (μm) and a molecular weight of about 4000, such as 1 and the like, are usually used in the form of a suspension dispersed in trichlorotrifluoroethane or the like. The addition amount of the protective layer of the magnetic recording medium is
The amount is preferably in the range of 0.01 to 0.1% by weight based on the total amount of trichlorotrifluoroethane and the binder. If the amount is too small, the lubricating effect is not sufficient. Tends to have poor film properties. The tetrafluoroethylene-perfluoro (2,2-dimethyl-1,3-dioxyol) copolymer used as a binder in the present invention has a maximum use temperature of 285.
It is an amorphous fluororesin that maintains excellent dimensional stability up to (degree). This resin is characterized in that it is soluble only in a specific solvent, and usually is dissolved to about 3% by weight with respect to a fluorine-based inert liquid. Specific examples of the fluorine-based inert liquid include, for example, FC-72 and FC-7 manufactured by 3M.
7 and the like. The formation of the protective layer of the magnetic recording medium in the present invention, when using this amorphous fluororesin as a binder, a solution obtained by dissolving the amorphous fluororesin in this fluorine-based inert liquid as a binder This was performed by mixing and dispersing a suspension in which a tetrafluoroethylene telomer was dispersed in trichlorotrifluoroethane or the like, applying a protective layer paint on the magnetic paint, and drying. The amount of the tetrafluoroethylene-perfluoro (2,2-dimethyl-1,3-dioxyol) copolymer used as a binder in the present invention is in the range of 5 to 50% by weight based on the tetrafluoroethylene telomer. When the content is less than 5% by weight, the bonding strength between the tetrafluoroethylene telomer and the magnetic layer is not sufficient, and when the content is more than 50% by weight, the binder is aggregated, and the film property of the binder is unfavorably deteriorated.

[0007]

Next, an embodiment of the present invention will be described in detail. Example 1 Magnetic paint ・ Fe-based alloy powder (Hc: 1600 Oe) 75 parts by weight ・ vinyl chloride-vinyl alcohol-based copolymer resin (number average molecular weight: 16000) 7.5 parts by weight ・ polycarbonate polyurethane resin (number average molecular weight: 36000) 15 parts by weight-Antistatic agent (Conductex SC manufactured by Colombian Carbon Co., Ltd.) 5 parts by weight-Lubricant (i-amyl stearate) 2 parts by weight-Lubricant (hexadecyl stearate) 6 parts by weight-Solvent ( Methyl ethyl ketone) 80 parts by weight Solvent (cyclohexanone) 40 parts by weight Solvent (toluene) 80 parts by weight Protective layer coating material Binder (tetrafluoroethylene-perfluoro (2,2-dimethyl-1,3-dioxyol) 0.05 Parts by weight Fluorine inert liquid (FC-72 manufactured by 3M) 4.95 weight 5 parts by weight of Vidax AR (20% by weight trichlorotrifluoroethane suspension of tetrafluoroethylene telomer manufactured by DuPont). 990 parts by weight of Freon-113 (trichlorotrifluoroethylene manufactured by DuPont). After kneading for 72 hours, 10 parts by weight (including a solid content of 5 parts by weight) of a low molecular weight isocyanate compound (Coronate 3041 manufactured by Nippon Polyurethane Industry Co., Ltd.) was further added and kneaded for 2 hours to obtain a magnetic paint. Was applied onto polyethylene phthalate having a thickness of 62 μm so that the thickness after drying was 2 μm, and calendering was performed under the conditions of a nip pressure of 300 kg / cm and a metal roll surface temperature of 60 ° C. 7 at constant temperature
After curing for 2 hours, a protective layer having the above composition was applied, and dried at 65 ° C. for 1 hour.
The sample was punched into an inch disk. Comparative Example 1 A 3.5-inch disk was formed in the same manner as in Example except that the protective layer was formed except for the binder and the fluorine-based inert liquid. Comparative Example 2 A 3.5-inch disk was formed in the same manner as in Example except that the protective layer was not formed. For each of these samples, the running durability, the disk surface, and the head surface were observed by the method described below. Run durability The sample was assembled in a 3.5-inch flexible disk shell, and this was mounted on a 3.5-inch flexible disk drive (FD-1331 manufactured by NEC Corporation).
After recording a signal with a frequency of 625 kHz on track 0,
An on-track continuous running durability test was performed in an atmosphere of 0 ° C. and 80% RH. Note that the reproduction output is the initial output of 80.
% Is defined as the number of passes of running durability. Observation of disk and head surfaces EPMA on the 00 track surface of the medium before and after the running test
And the peak intensity of fluorine was compared for Examples and Comparative Examples. Further, the surface of the magnetic head after the running test was taken out, the fluorine surface analysis was performed by EPMA, and the protective layers transferred to the heads in Examples and Comparative Examples were quantified and compared.

[0008]

[Table 1]

Table 1 shows the obtained results. In the table, the higher the numerical value is, of course, the better the running durability is, but the higher the value, the more practically there are no more than 20 million passes, and the level is excellent. In addition, the change in the peak intensity of fluorine in EPMA analysis of the track position of the medium before and after the running test, assuming that the intensity before running was 100, the lower the peak after running, the more the protective layer was separated from the magnetic layer. Can be Furthermore, the higher the peak intensity of fluorine in the EPMA analysis of the head after running, the more the protective layer released from the medium adhered to the head. As can be seen from Table 1, with respect to the running durability, the sample provided with the protective layer made of only tetrafluoroethylene of Comparative Example 1 certainly has improved durability compared to Comparative Example 2 provided with no protective layer. However, it can be seen that the practical durability is insufficient. On the other hand, it can be seen that the example has a durability of 20,000,000 passes or more, and that the protection layer is separated very little as compared with the comparative example 1.

[0010]

As described above, a tetrafluoroethylene telomer having an average molecular weight of 1,000 to 6000 and a tetrafluoroethylene-perfluoro (2,2
By providing a protective layer containing a binder composed of (-dimethyl-1,3-dioxyol) copolymer, a magnetic recording medium having very little release of the protective layer and excellent durability was obtained.

Claims (1)

(57) [Claims] 1. The method according to claim 1, wherein the magnetic layer has an average molecular weight of 1,000 to
000 tetrafluoroethylene telomer and tetrafluoroethylene-perfluoro (2,2-dimethyl-
A flexible magnetic recording medium comprising a (1,3-dioxyol) copolymer.