JPS61246915A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled medium provided with a protective film having a low friction coefficient and excellent wear resistance and lubricity by forming 1-9 odd built-up films of the monomolecular layers of trialkylphosphine oxide on a ferromagnetic metallic thin film. CONSTITUTION:A ferromagnetic metallic thin film is formed on a nonmagnetic carrier in a magnetic recording medium and 1-9 odd built-up films of the monomolecular layers of trialkyphosphine oxide is formed on the ferromagnetic metallic thin film. The trialkylphosphine oxide is shown by the formula and has a P=0 group showing excellent affinity for the ferromagnetic metallic thin film and an alkyl group exhibiting an excellent lubricating effect. When a soln. obtained by dissolving the compd. in a volatile solvent, for example, with the Langmuir-Blodgett's technique is added dropwise into the underlying liq. such as water 2 and left standing under an appropriate surface, molecules are easily arranged to form a monomolecular layer. Consequently, the monomolecular layers 3 are built-up on the surface of the ferromagnetic metallic thin film 4, the molecules are densely arranged and a lubricating film having uniform thickness is formed as the protective layer.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A. Field of industrial application B. Overview of the invention C. Prior art D. Problem to be solved by the invention E. Means for solving the problem F. Effect G Example G-■ Example 1゜G-■ Comparative example 1゜G-■ Example 2゜G-■ Comparative example 2゜G-■ Example 3゜G-■ Comparative example 3゜G-■ Example 4゜G-■ Comparative example 4゜G-■ Example 5゜G-[Phase] Comparative Example 5゜G-■ Comparative Example 6゜H Effects of the Invention A Industrial Field of Application The present invention is directed to magnetic recording in which a ferromagnetic metal thin film is formed as a magnetic layer on a non-magnetic support. The present invention relates to media, and specifically relates to improvements in protective films for protecting ferromagnetic metal thin films.

B. Summary of the Invention The present invention provides a magnetic recording medium in which a ferromagnetic metal thin film is formed as a magnetic layer on a non-magnetic support, in which a monomolecular layer cumulative film of trialkylphosphine oxide is formed on the surface of the ferromagnetic metal thin film. An odd number of layers are formed to reduce the coefficient of friction and improve wear resistance, rust prevention, etc.

C. Conventional technology Traditionally, magnetic recording media have been made using r-
T-Fe20 containing Fezes, FexO4, Go
7-F exoa containing ff+ Co, r
-Bertolide compound of FeZo3 and Fe5Oa.

Powder magnetic materials such as ferromagnetic oxide powders such as CO-containing bertolide compounds and Cr0z, or alloy magnetic powders containing Fe, Co, Ni, etc. as main components are combined with vinyl chloride-vinyl acetate copolymers, polyester resins, etc. Applying magnetic paint dispersed in an organic binder such as polyurethane resin.
Coated magnetic recording media obtained by drying are widely used.

In response, with the increasing demand for high-density magnetic recording, ferromagnetic metal materials such as metals such as iron, cobalt, nickel, and alloys such as Co-Ni have been developed using vacuum deposition methods, sputtering methods, ion blating methods, etc. A so-called ferromagnetic metal thin film type magnetic recording medium, which is directly deposited on a nonmagnetic support such as a polyester film or a polyimide film, using vacuum thin film formation technology has been proposed and is attracting attention. This ferromagnetic metal thin film type magnetic recording medium not only has a large coercive force Hc and a large residual magnetic flux density Br, but also allows the thickness of the magnetic layer to be extremely thin. It has many advantages in terms of magnetic properties, such as extremely small thickness loss during demagnetization and reproduction, and the ability to increase the packing density of the magnetic material because there is no need to mix an organic binder, which is a non-magnetic material, into the magnetic layer. It has the following advantages.

However, in the above-mentioned ferromagnetic metal thin film type magnetic recording medium, the surface smoothness of the magnetic layer is extremely good, so the substantial contact area becomes large, and adhesion phenomena (so-called sticking) tend to occur. It has many drawbacks in terms of durability, running performance, etc., such as a large coefficient of friction, and improving these issues is a major issue.

D Problems to be Solved by the Invention Conventionally, a protective layer is formed on the surface of a ferromagnetic metal thin film by applying a lubricant such as a fatty acid or a fatty acid ester or by oxidizing the surface. Attempts have been made to improve running performance.

However, when the protective layer is formed using this method, there is a limit to how thin the protective layer can be made, so the gap between the magnetic head and the ferromagnetic metal thin film that is the magnetic recording layer becomes large. , there is a risk that high-density recording will be impossible due to so-called spacing loss.

Alternatively, as described in Japanese Patent Publication No. 56-30609, for example, as a protective layer of a ferromagnetic metal thin film, carbon number 8
It has also been proposed to form a monomolecular layer of ~28 linear saturated fatty acids or their metal salts by the Langmuir-Prodgett method, but in this case the friction coefficient is not lowered sufficiently, and conventional coating It is difficult to achieve the low-friction, wear-resistant properties achieved with molded magnetic tape.

In view of these circumstances, the present invention has been proposed, and it has a protective film with a low coefficient of friction and excellent wear resistance, lubricity, etc., and the thickness of this protective film can be reduced to several hundred angstroms or less. The purpose of the present invention is to provide a magnetic recording medium that can control spacing loss and suppress spacing loss.

E. Means for Solving the Problems As a result of intensive research, the present inventor discovered that trialkylphosphine oxide has an excellent lubricating effect and is easy to arrange molecules, and that the monomers of this trialkylphosphine oxide can be easily arranged. We have found that excellent frictional properties can be obtained by cumulatively forming an odd number of molecular layers so that the alkyl groups face the surface of the magnetic recording medium.

The present invention was completed based on the above findings, and provides a magnetic recording medium in which a ferromagnetic metal thin film is formed on a non-magnetic support, in which a trialkylphosphine oxide is formed on the ferromagnetic metal thin film. Monolayer cumulative film 1 to 9
It is characterized in that an odd number of layers are formed.

The trialkylphosphine oxide used in the present invention is a compound represented by the general formula % (where m = 12 to 22), and has an excellent affinity for ferromagnetic metal thin films. It has an o group and an alkyl group that exhibits a lubricating effect.

For example, according to the Langmuir-Prodgett method, this trialkylphosphine oxide can be dissolved in a volatile solvent and dropped into a lower layer liquid such as water and left under an appropriate surface pressure.The molecules of this trialkylphosphine oxide are easily arranged into single molecules. By forming a layer and thus accumulating this monolayer on the surface of a thin ferromagnetic metal film, a lubricating film with densely arranged molecules and a uniform thickness is formed as a protective film.

In this case, the cumulative number of monomolecular layers is preferably an odd number of 1 to 9 layers. That is, when the above-mentioned monomolecular layer is liquid-deposited in one layer, the trialkylphosphine oxide is accumulated so that the P=O group, which has excellent affinity for the ferromagnetic metal thin film, faces the ferromagnetic metal thin film, and the trialkylphosphine oxide is deposited on the surface side. towards the alkyl group.

The same applies to the case where an odd number of layers such as 3rd layer, 5th layer, 7th layer, and 9th layer are accumulated. When the alkyl groups are arranged so as to face the surface side, the coefficient of friction is significantly reduced, and the friction characteristics and wear resistance are significantly improved. On the other hand, 2 layers, 41i, and 6 layers.

When an even number of the above monomolecular layers are cumulatively formed, such as eight layers, the alkyl groups with high affinity for the alkyl groups that are arranged toward the surface side in the case of an odd number of layers face each other. A monomolecular layer is accumulated on the surface, with P=O groups facing toward the surface.

If the P=o groups are arranged so as to face the surface side, for example, the P=O groups will be adsorbed to a metal part such as a guide bottle, and the accumulated film will fall off within a short time. etc,
The coefficient of friction cannot be lowered sufficiently, and the surface becomes more susceptible to damage.

Furthermore, when the trialkylphosphine oxide is deposited on the surface of a ferromagnetic metal thin film by means such as dipping, the coefficient of friction and the degree of damage are different when the monomolecular layer is accumulated in an odd number and when an even number is accumulated. It was estimated that the orientation of the trialkylphosphine oxide molecules adhering to the surface was random.

As for the cumulative number of monomolecular layers, it is preferable to suppress the cumulative number to 9N, in addition to using an odd number of layers as described above. The monomolecular layer of the above-mentioned trialkylphosphine oxide is thought to have a thickness of about 25 to 30 layers per layer, and if there are too many layers, there is a possibility that the output will be reduced due to spacing loss, and the friction properties There is also a risk that the characteristics may deteriorate due to damage or damage.

On the other hand, the magnetic recording medium to which the present invention is applied is one in which a ferromagnetic metal thin film is provided as a magnetic layer on a non-magnetic support, and the material of the non-magnetic support is polyester such as polyethylene terephthalate. polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, cellulose diacetate, and cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, polyimide, and polyamideimide, and aluminum. Examples include alloys, light metals such as titanium alloys, and ceramics such as alumina glass. The forms of this non-magnetic support include films, sheets, disks,
It may be a card, a drum, etc.

Further, the ferromagnetic metal thin film that is the magnetic layer is formed as a continuous film by a vacuum thin film forming technique such as a vacuum evaporation method, an ion blating method, or a sputtering method.

In the vacuum evaporation method described above, a ferromagnetic metal material is evaporated by resistance heating, high frequency heating, electron beam heating, etc. under a vacuum of 10-' to 10-'' Torr, and the evaporated metal (
Generally, in order to obtain a high coercive force, an oblique evaporation method is employed in which the ferromagnetic metal material is deposited obliquely to the substrate. or,
It also includes those in which the above-mentioned vapor deposition is performed in an oxygen atmosphere in order to obtain higher coercive force.

The above ion blating method is also a type of vacuum deposition method, in which DC glow discharge and RF glow discharge are caused in an inert gas atmosphere of 10-4 to 10-3 Torr, and the ferromagnetic metal material mentioned above on the disk is evaporated during discharge. It is to let them do so.

The above sputtering method uses 10-3 to 10-' Torr.
A glow discharge is caused in an atmosphere mainly composed of argon gas, and the generated argon gas ions are used to knock out atoms on the target surface. method, or magnetron sputtering method using magnetron discharge.

In the case of this sputtering method, Cr or W is used.

A base film such as V may be formed in advance.

In any of the above methods, Bi, Sb, Pb, Sn, Ga, and In are preliminarily deposited on the substrate.

By pre-depositing a base metal layer such as Cd, Ge, St, 'T''1, etc., and forming the film from a direction perpendicular to the substrate surface, it is possible to form an in-plane method without orientation of magnetic anisotropy. It is possible to form an excellent magnetic layer and is suitable for use in, for example, magnetic disks.

When forming a metal magnetic thin film using such vacuum thin film forming technology, the ferromagnetic metal materials used include Fe,
In addition to metals such as Co and Ni, C.

-Ni alloy, Go-pt alloy + Co NiP alloy, Fe-Co alloy, Fe-Ni alloy, Fe-Co-
Ni alloy, Fe-CO-B alloy, Go-Ni-Fe-B
alloy, co-Cr alloy or these with Cr, Ajl!
Examples include those containing metals such as. In particular, Co
When a -Cr alloy is used, a perpendicularly magnetized film is formed.

The thickness of the magnetic layer formed by such a method is 0.
It is about 0.04 to 1 μm.

F Function A protective film made of a monomolecular layer of trialkylphosphine oxide is a uniform film in which single molecules are densely arranged, and has excellent lubricating properties. In particular, 1 to 9 monomolecular layers of trialkylphosphine oxide are coated on the surface of a ferromagnetic metal thin film.
By cumulatively forming an odd number of layers, the alkyl groups are oriented toward the surface of the magnetic recording medium, and the coefficient of friction is significantly reduced.

G. Examples Specific examples of the present invention will be described below, but the present invention is not limited to these examples.

G-■ Example 1゜CO, on a base film of polyethylene terephthalate having a thickness of 12 μm. Niz. A magnetic alloy consisting of the following was formed to a thickness of 1,500 to 1,600 mm by an oblique vapor deposition method to form a magnetic layer. Furthermore, carbon was applied to the back surface of this base film to a thickness of 1 μm.

On the other hand, as shown in Figure 1, 3
x 10-' mol/j2 of BaCJ, and 4 x 10
Distilled water (2) containing -'mol/1 of KHCO (
(temperature: 20°C), and within this water surface barrier (5), trialkylphosphine oxide (CI4H29)3P=
O was added to develop a monomolecular film (3) of trialkylphosphine oxide. The barrier (
5) to reduce the surface pressure within the barrier (5) to 10 dyne.
/cm, and a monomolecular film (3) of trialkylphosphine oxide was formed on the water surface. Then, the magnetic tape (4) on which the magnetic layer was deposited was passed once through the monomolecular film (3) to form one monomolecular layer of trialkylphosphine oxide on the magnetic layer.

When the coefficient of dynamic friction of the obtained sample tape was measured after running the shuttle 100 times, it showed an extremely small value of 0.28. Note that this coefficient of kinetic friction is at a temperature of 25
°C, humidity 60%, tape speed (5mm/see),
The coefficient of friction between the magnetic layer surface and IS stainless steel was determined under the conditions of a stroke of 4 cm and a load of 50 g.

Further, after this friction test, when the surface condition of the sample tape was observed, it was observed that there were almost no scratches on the tape surface, and the surface appeared to be protected.

G-■ Comparative Example 1 Two monomolecular layers of trialkylphosphine oxide were formed on the magnetic layer in the same manner as in Example 1 above.

The coefficient of dynamic friction of the obtained sample tape was measured after running the shuttle 100 times, and it showed a high coefficient of friction of 0.44.

Further, after this friction test, when the surface condition of the sample tape was observed, it was found that there were considerable scratches, and the scratches were found to have reached the magnetic layer, which is the vapor deposited layer.

G-■ Example 2 Three monomolecular layers of trialkylphosphine oxide were formed on the magnetic layer in the same manner as in Example 1 above.

When the coefficient of dynamic friction of the obtained sample tape was measured after running the shuttle 100 times, it showed an extremely small value of 0.25.

Furthermore, when the surface condition of the sample tape was observed after this friction test, it was observed that there were almost no scratches on the tape surface, and the surface appeared to be protected.

G-■ Comparative Example 2 Four monomolecular layers of trialkylphosphine oxide were formed on the magnetic layer in the same manner as in Example 1 above.

The coefficient of dynamic friction of the obtained sample tape after running the shuttle 100 times was measured and showed a high coefficient of friction of 0.43.

Further, after this friction test, when the surface condition of the sample tape was observed, it was found that there were considerable scratches, and the scratches were found to have reached the magnetic layer, which is the vapor deposited layer.

G-■ Example 3 Five monomolecular layers of trialkylphosphine oxide were formed on the magnetic layer in the same manner as in Example 1 above.

When the coefficient of dynamic friction of the obtained sample tape was measured after running the shuttle 100 times, it showed an extremely small value of 0.24.

Furthermore, when the surface condition of the sample tape was observed after this friction test, some scratches on the tape surface were observed, but the extent of the scratches was slight.

G-■ Comparative Example 3 Six monomolecular layers of trialkylphosphine oxide were formed on the magnetic layer in the same manner as in Example 1 above.

The coefficient of dynamic friction of the obtained sample tape after running the shuttle 100 times was measured and showed a high coefficient of friction of 0.39.

Further, after this friction test, when the surface condition of the sample tape was observed, it was found that there were considerable scratches, and the scratches were found to have reached the magnetic layer, which is the vapor deposited layer.

G-■ Example 4 Seven monomolecular layers of trialkylphosphine oxide were formed on the magnetic layer in the same manner as in Example 1 above.

When the coefficient of dynamic friction of the obtained sample tape was measured after running the shuttle 100 times, it showed an extremely small value of 0.26.

Further, after this friction test, when the surface condition of the sample tape was observed, some damage was observed on the tape surface, but the extent of the damage was minor.

G-■ Comparative Example 4 Eight monomolecular layers of trialkylphosphine oxide were formed on the magnetic layer in the same manner as in Example 1 above.

The coefficient of dynamic friction of the obtained sample tape after running 100 times was measured, and it showed a high coefficient of friction of 0.45.

Further, after this friction test, when the surface condition of the sample tape was observed, it was found that there were considerable scratches, and the scratches were found to have reached the magnetic layer, which is the vapor deposited layer.

G-■ Example 5 Nine monomolecular layers of trialkylphosphine oxide were formed on the magnetic layer in the same manner as in Example 1 above.

When the kinetic friction coefficient of the obtained sample tape was measured after 100 shuttle runs, it showed an extremely small value of 0.29, but compared to the previous Examples 1 to 4, there was an upward trend. Understood.

In addition, when we observed the surface condition of the sample tape after this friction test, we observed some scratches on the tape surface, but the degree of scratches became worse as the cumulative number of monomolecular layers increased. Shown.

G-[Phase] Comparative Example 5 C08°Niz on a 12 μm thick polyethylene terephthalate base film. A magnetic alloy consisting of the following was formed to a thickness of 1,500 to 1,600 mm by an oblique vapor deposition method to form a magnetic layer. Furthermore, carbon was applied to the back surface of this base film to a thickness of 1 μm.

Next, this magnetic tape was mixed with trialkylphosphine oxide (C+4Hzw)+P=O in Freon at 0.02
A trialkylphosphine oxide layer was formed on the surface by dipping the sample in a 4% solution.

The coefficient of dynamic friction of the obtained sample tape after running the shuttle 100 times was measured, and it was found to be 0.37, which is about 0.1 larger than that of each example.

The surface condition after this friction test was found to be intermediate in damage between the cases where an odd number of monomolecular layers were provided and the case where an even number of monomolecular layers were provided.

G-■ Comparative Example 6 COeoN i z was applied on a base film of polyethylene terephthalate having a thickness of 12 μm. A magnetic alloy consisting of the following was formed to a thickness of 1,500 to 1,600 mm by an oblique vapor deposition method to form a magnetic layer. Furthermore, carbon was applied to the back surface of this base film to a thickness of 1 μm.

When we measured the coefficient of dynamic friction of the obtained sample tape, it was 0.42 after 100 shuttle runs. Also, after this friction test, two to three streaks were observed on the surface, indicating that the tape surface was damaged. I found out that

From these Examples and Comparative Examples, when an even number of monomolecular layers of trialkylphosphine oxide are formed, that is, when the P=0 group faces the surface side, it is almost the same as the blank tape (Comparative Example 6). Since the friction coefficients are about the same, it is presumed that the P=O group adheres to the guide pin immediately after the start of the friction test, and at the same time, most of the accumulated film falls off. On the other hand, when an odd number of monomolecular layers of trialkylphosphine oxide are formed, that is, when the alkyl group faces the surface side, the interaction between the alkyl group and the guide pin etc. is not strong. It is thought that the cumulative film does not fall off during the friction test, and the coefficient of friction becomes low. When trialkylphosphine oxide was attached by the dipping method (Comparative Example 5), it was estimated that the orientation of the molecules attached to the tape surface was random, and the friction coefficient and surface scratching property of the odd-numbered layer and the even-numbered layer were It is thought that an intermediate behavior was found.

H Effects of the Invention As is clear from the above explanation, in the present invention, a stack of 1 to 9 odd-numbered monomolecular layers of trialkylphosphine oxide is formed as a protective film for a ferromagnetic metal thin film type magnetic recording medium. Since a film is used, it is possible to form a lubricating film in which the molecules are densely arranged and the alkyl groups face toward the surface, resulting in an excellent lubrication effect with a friction coefficient of about 0.25 and a protection effect against scratches. Therefore, the friction characteristics and wear resistance of the resulting magnetic recording medium can be significantly improved.

In addition, the thickness of the above cumulative film is several hundred Å at the molecular level.
It is possible to uniformly control the spacing to a degree below, and spacing loss can also be suppressed.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of an apparatus for forming a monomolecular layer cumulative film of trialkylphosphine oxide. 2... Distilled water 3... Monomolecular film 4... Magnetic tape season 9F)
■Figure 1

Claims (1)

[Scope of Claims] A magnetic recording medium comprising a ferromagnetic metal thin film formed on a non-magnetic support, wherein an odd number of 1 to 9 monomolecular layers of trialkylphosphine oxide are formed on the ferromagnetic metal thin film. A magnetic recording medium characterized by layer formation.