JPS61188727A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the durability of the title medium and a head while maintaining sufficient recording and reproducing characteristics at >=40kbpi recording density by providing a specified surface lubricating and protective film material in less than specified thickness on the surface of magnetic layer. CONSTITUTION:A surface lubricating and protective film material contg. a polyurethane elastomer having an OH group, a system obtained by mixing a silica compd. shown by formula 1 into one of saturated polyester resins or their mixture and a di- or polyisocyanate compd. is provided in <=0.08mum thick ness on the surface of a magnetic layer to obtain a magnetic medium. Conse quently, <=0.2muK value and <=0.02DELTAmuk value can be attained, the traveling of a head is smoothed and the spacing loss is simultaneously reduced. Accordingly, the output of the recording and reproducing head is sufficiently increased and the durability of the medium and the head is remarkably improved.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a magnetic recording medium such as a flexible disk (hereinafter abbreviated as FD) or tape that can be used in information-related equipment, audio equipment, video equipment, etc. It is.

Conventional technology In recent years, audio and video equipment has become smaller and more diverse.

With the spread and diversification of information-related equipment such as office computers and personal computers, there has been a demand for magnetic recording media (disks or tapes) used as external memory that can increase recording density and increase storage capacity. .

Currently, applied magnetic recording media are mainly coated horizontal magnetic recording media that have a magnetic layer made of a resin-based binder mixed and dispersed with magnetic powder. With this medium and the horizontal magnetic recording method, for example, in digital recording, the recording density is 1 kilobit per inch (hereinafter abbreviated as kbpi) and the recording capacity of a mini FD is 0.6 to 1.6 megabytes (hereinafter abbreviated as MB). Things are simply being commercialized.

Although there have been announcements of a recording density of 40 kbpi in this technology, it has been pointed out that there is a limit to achieving even higher recording densities with horizontal magnetic recording.

Therefore, in order to achieve high-density recording of 40 kbpi or more in digital recording and meet the market demand for larger storage capacity, a magnetic recording medium whose magnetic layer is a thin metal film, especially a medium compatible with perpendicular magnetic recording, has been proposed. and research is being actively conducted.

A perpendicular magnetic recording medium is a non-magnetic support, such as a polyethylene terephthalate (hereinafter abbreviated as PET) film or a polyimide film, on which a horizontally magnetized film mainly composed of Fe-N1 is deposited on one or both sides by vapor deposition or sputtering. A device with a perpendicular magnetization film mainly made of Go-Cr has been proposed, in which the traveling medium is sandwiched between a main magnetic pole head and an auxiliary magnetic pole head, or a main magnetic pole head or a ring head and a pad are used. Recording and reproduction are performed by sandwiching the magnetic layer between the magnetic layers and magnetizing it in the perpendicular direction, achieving high-abundance recording.

Problems to be Solved by the Invention Perpendicular magnetic recording technology uses permalloy or Co-Zr-Nb permalloy or Co-Zr-Nb perpendicular magnetic recording media having a CO/Cr thin film layer formed by electron beam evaporation or sputtering.
Recording is performed by sandwiching the main magnetic pole head, which has a main magnetic pole film made of amorphous or the like and combines a highly hard support material such as ceramics or glassy carbon, with the auxiliary magnetic pole head, which is made of ferrite, other metal compounds, ceramics, etc. Playing is in progress. In this case, in order to obtain sufficient output with high recording density, the contact level between the medium and the head must be increased, so the head pressure is 1o? It is desirable that the spacing loss is 1 μm or less. In particular, the compatibility between the metal thin film magnetic layer and the head is
The sliding property is poor and the coefficient of dynamic friction (μk) is 4 or more, and the fluctuation value Δμ of μ during one revolution of the medium in contact with the head
, is generally known to increase, which increases the physical load on the medium and head surface. For this reason, when the medium is run for recording and playback, scratches occur on the medium after about 10 passes, and scratches also occur on the head surface, causing dropouts and a reduction in head output. However, this had the problem that it could not be put to practical use because the overall durability life of the head was drastically reduced.

The present invention is intended to solve this problem, and aims to ensure sufficient recording and reproducing characteristics at a recording density of 40 kbpi or higher, while at the same time improving the durability of the medium and head.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides O2 on the surface of a metal thin film magnetic layer provided on one or both sides of a non-magnetic support.
A surface lubricating protective film material containing a polyurethane di-stomer having an H group, a saturated polyester resin alone or in combination, a silicon compound represented by the following formula, and a di- or polyisocyanate compound is coated with a thickness of o. ,08
A medium by making it a magnetic recording medium provided with a thickness of μm or less.

This improves the durability and lifespan of the head, increasing the possibility of practical use.

R: Alkyl n: Integer of 1 or more The surface lubricating protective film having the structure of the present invention has high adhesion to the magnetic layer and can withstand rotation of the medium in the FD jacket and head pressure. , the value i is 0.2 or less for μ, which represents the compatibility with the head during rotation of the medium, and the value 'ii0 for Δμ.
．． It can be made as small as 0.02 or less, and the entire head can run smoothly. This indicates that the spacing loss with the surface lubricating protective film is small, and even when combined with the surface lubricating protective film having a thickness of 0.08 μm or less, there is no significant drop in head output, improving the durability and life of the media and head. It gives the effect of

In addition, the thickness of the surface lubricating protective film in the present invention is 0.08
The reason why we limited it to less than μm is that if the thickness exceeds this,
This is because the spacing loss between the magnetic layer and the head becomes too large and the head output during recording and reproduction becomes too small to be practical.

In addition, the surface lubricating protective film in the present invention contains commonly used lubricating aids such as fatty acids, fatty acid esters, paraffin, phosphate esters, lecithin, metal soaps, surfactants, dispersion/compatibility agents, etc. May contain.

Example Examples of the present invention will be described below.

Polyethylene terephthalate (hereinafter referred to as PIT) with a thickness of 60 μm
A permalloy (Fe-Ni alloy containing Cu+) layer is provided on both sides of the film, and Go-O
An r-alloy layer was provided using a known direct current magnetron sputtering device to obtain a magnetic recording medium. Next, this medium
Dipped in a surface lubricant protective film material having the composition shown in the upper part of Table 1, then pulled up, dried and hardened to form a surface lubricant protective film having the thickness shown in the middle row of Table 1 on the surface of the medium,
A prototype perpendicular magnetic recording medium with the cross-sectional configuration shown in FIG. 1 was fabricated.

In Figure 1, 1 is PET film, 2 is 0.6 μm
thick permalloy layer, 3 is Q2μm thick CO/Cr layer, 4
is the surface lubricating protective film layer.

In Table 1, for the polyurethane elastomer having an OH group with the material name (■), a is polyurethane N-3119 manufactured by Nippon Polyurethane Industries Co., Ltd. and has an average molecular weight of 11,300.
0 (40% by weight solvent), and b is polyurethane NR-90 manufactured by Nippon Polyurethane Industries Co., Ltd. with an average molecular weight of 330.
00 (35% by weight solvent).

The saturated polyester having an OH group with the material name ■ has C as Byron 2o○ manufactured by Toyobo Co., Ltd. and an average molecular weight of 15oo.
o~20ooQ1d is Byron 30 manufactured by Toyobo Co., Ltd.
0 indicates an average molecular weight of 20,000 to 25,000.

The silicon compound with the material name ■ is manufactured by Shin-Etsu Chemical Co., Ltd. and has the structure of the following formula, where e is the product name X-22-16.
0AS R: Alkyl n: An integer of 1 or more with an average molecular weight of 1000, f is product name X-22-160A
The average molecular weight is 1800jj-.

The other material with the material name ■ is a surfactant where q is compatible and serves as a lubricating aid, and the product name is LX-1 manufactured by Dai-Kogyo Seiyaku Co., Ltd.
It is 021B. h is Zn octenoate which serves as a compatibilizer. i is liquid paraffin which serves as a lubricating aid.

In the solvent of ■, j is methyl ethyl ketone, k is toluene,
E is cyclohexanone.

The isocyanate compound of (iii) is Coronate 304 manufactured by Nippon Polyurethane Industries Co., Ltd. where m is polyisocyanate.
1 (50% by weight solvent)'fr:, n is a diisocyanate compound and is diphenylmethane diisocyanate (50% by weight solvent).

The medium on which the above-mentioned surface lubricating protective film has been completely formed is
．． After punching into a 25-inch mini FD, the characteristic items listed in the lower part of Table 1 were measured by the following methods.

1 First, firmly press and hold the center of the FD5 (5-mounted F'l) having the configuration shown in FIG. 1 above on the device as shown in FIG. 2 (2L) I (b), that is, the metal disk 6. . Next, a steel ball 8 of 5 skins 6 is brought into contact with the FD surface with a pressure of 20 grams, and the disk 6 is rotated at a speed of 300 rpm.

The pressure 2o grams is the strain sensor 9 provided on the copper leaf spring 10.
Check with. The dynamic friction coefficient μ between the FDs and the steel ball 8 and the variation Δμk in the dynamic friction coefficient during one rotation of the disk are confirmed by a strain sensor 9' provided on a copper plate spring 10/.

In addition, when the disk 6 is rotated with the steel ball and the FD in contact with a 20-gram load, it is possible to detect large changes in the values of μ and Δμ, or at points where the magnetic layer is scratched (μ and Δμk vary greatly). The number of rotations up to (the magnetic layer always had scratches) was defined as the number of durability passes.

Next, the punched 5.25-inch FDi is inserted into an FD jacket made of a combination of a sheet mainly made of polyvinyl chloride and a liner, and the structure has the FD medium and head structure as shown in Fig. 3. FDD for perpendicular magnetic recording and reproduction (
Using the floppy disk driver (floppy disk driver) T-, the head output during recording and reproduction and the number of buses that the FDD actually ran were measured. FIG. 3 shows a perpendicular magnetic recording medium 5 having a PET film 1, a permalloy layer 2, a Go Or layer 3 as a perpendicular magnetization film, and a surface lubricating protective film layer 4 of the present invention, with an auxiliary magnetic pole 11 made of ferrite. , which is sandwiched between the main magnetic pole head 12. Note that the main magnetic pole head includes coil 13, Go
It is composed of a ZrNb thin film main pole 14, a ferrite material 15, and a nonmagnetic ceramic 16.

The head output during recording and playback is at rotation speed 3 of the FD medium.
This is the head output when the head is set to run at a radius of 37 at 00 rpm, recording is performed with the recording frequency set to have a recording density of 70 kbpi, and the head is reproduced using the same head. In addition, the number of FDD actual machine durability passes is
This is the number of rotation passes (one rotation is one bus) until the head output drops to so% when the head runs in contact with the same track at a rotation speed of 300 rpm.

The measured results are shown in the lower part of Table 1.

In addition to the examples of the present invention, comparative examples are shown on the right side of Table 1. The comparative example is a medium without a surface lubrication protective film. Regarding this, when we conducted the same test as above, we found μ, Δ
Since the μ2 value was high and the magnetic layer and head were damaged after several passes, the head output could not be measured and was not practical.

In addition, Comparative Examples G and H have a surface lubricating protective film with a thickness exceeding the range of the present invention, and show sufficient values for μm, Δμ, and number of durable passes, but the head output is very small and is not practical. It wasn't.

The surface lubricating protective film composition of the present invention has improved durability and practicality of media and heads.

Effects of the Invention As is clear from the examples, the present invention provides a metal thin film magnetic layer on one or both sides of a non-magnetic support, and on the surface of this magnetic layer, a polyurethane elastomer having an OH group,
A surface lubricating protective film containing a saturated polyester resin alone or a mixture thereof, a silicon compound represented by the following formula, and a di- or polyisocyanated R: alkyl n: an integer compound of 1 or more. The thickness of the material is 0.08
We were able to achieve a μm value of 0.2 or less and a Δμ value of 0.02 or less, making the head run smoother and reducing the spacing loss. It not only shows a sufficient value as the reproduction head output, but also has the effect of greatly improving the service life of the medium and the head.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a perpendicular magnetic recording medium with a surface lubricating protective film in an embodiment of the present invention, and Figure 2 (2Ll). FIG. 3 is a schematic diagram and an enlarged view of the main parts showing the configuration of an apparatus for measuring the number of passes of steel ball durability. It is a cross-sectional view of the structure of the medium and head when measuring the recording/reproducing head output in the magnetic recording method and the durability path deposit of FDDICJ. 1... PET film, 2... Permalloy layer. , 3... CO/Cr layer, 4... Surface lubricating protective film layer. Name of agent: Patent attorney Toshio Nakao and 1 other person!・
・PET Fill 1 460 Tables 1 7M Heads” Award Layer 2 Figure 311A

Claims (1)

[Scope of Claims] A metal thin film magnetic layer is provided on one or both sides of a non-magnetic support, and on the surface of this magnetic layer, a polyurethane elastomer having an OH group or a saturated polyester resin alone or in a mixed system is coated with the following formula. 1. A magnetic recording medium comprising a surface lubricating protective film material containing a mixed system of the silicon compound shown below and a di- or polyisocyanate compound with a thickness of 0.08 μm or less. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ R: Alkyl n: An integer of 1 or more