JPS5841439A - Magnetic recording medium and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a ferromagnetic metallic thin film type magnetic recording medium with enhanced corrosion and wear resistances by oxidizing the surface of a vapor-deposited magnetic layer made of a substance contg. Co. CONSTITUTION:A material 2 to be evaporated in a container 3 is vapor-deposited on a substrate 1 transferred from a feeding shaft 7 to a coiling shaft 8 along a rotating can 9 through a shielding plate 11 in a vacuum vessel 4, and while introducing oxygen or a gaseous mixture contg. oxygen from a nozzle 10 attached to one end of the side of the plate 11 facing to the can 9, glow discharge treatment 15 is carried out to oxidize the surface of the vapor-deposited ferromagnetic layer. Thus, a protective film contg. CoO and Co3O4 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium whose magnetic recording layer is a ferromagnetic layer deposited on a polymer molded substrate, and a method for manufacturing the same.

The present invention provides a medium having an oxide layer that effectively protects the surface of a deposited layer made of a substance containing cobalt (Cψ), and a method for producing the medium.

In magnetic recording, the usefulness of using a ferromagnetic metal thin film as a magnetic recording layer for short wavelength recording is well known.

However, the biggest problem when using such media on a practical level is the resistance of the ferromagnetic layer to corrosion and wear.

Conventionally, this kind of problem has been common to ferromagnetic films obtained by either wet plating or vapor deposition, and efforts have been made in various fields to solve this problem.

Most of the methods taken for this purpose were to provide another protective layer on the ferromagnetic layer (Japanese Patent Application Laid-Open No. 51-43110).

N1-B alloy (Japanese Unexamined Patent Publication No. 52-2405), N1 alloy layer hardened by heat treatment (Japanese Unexamined Patent Publication No. 51-1
02605), Ni-Cr alloy (JP-A-5
3-73108), oxides, carbides (JP-A-50-104602), α-Fe20. system thin film as a protective layer (Japanese Unexamined Patent Publication No. 51-59606), 5
i-8i oxide (JP-A-52-127203),
5i-8ja with Cr interposed between it and the magnetic layer? compound (Japanese Unexamined Patent Publication No. 52-127204), silicon nitride compound (
JP-A-56-73931), La boride layer (JP-A-56-11626) as a protective layer, organic material as a protective layer, for example, a monomolecular layer of saturated fatty acid (JP-A-56-11626). JP-A No. 61-20805) and one containing an antioxidant in the lubricating liquid layer (JP-A No. 61-20805) have been proposed.

A problem common to these disclosed techniques arises from the fact that these protective layers are required to be made extremely thin due to the limitations of spacing loss in short wavelength recording. In other words, if the thickness is about 50 mm, it is difficult to improve both corrosion resistance and abrasion resistance. However, it is becoming more serious.

The ferromagnetic layer and the protective layer are made of different materials, and
The fact that the protective film is formed in a process independent of the formation of the ferromagnetic layer involves a problem that should be improved.

That is, the media when stored for a long time in a natural environment.

Even if no change is observed in visual observation (including observation with increased magnification using an optical microscope), as mentioned above, the protective layer may peel off when it comes into contact with a high-speed rotating head. This fact often indicates destruction of the interface between different amounts of substances, and improvements are desired.

The present invention has been made in view of this point, and achieves the object by using an oxide layer of Co itself, which constitutes the magnetic material. In this case, as mentioned above, since no additional substances are used, it clearly has the advantages in terms of stability and reliability, which will be described later.

Note that the term "vapor deposition" as used in the present invention includes vacuum deposition, sputtering, ion blasting, and the like.

The present invention provides a magnetic recording medium in which a ferromagnetic layer containing CO deposited on a polymer molded substrate has a coating layer containing at least Coo, 0o504, and a method for obtaining such a medium at high speed. It is something.

According to the present invention, the media obtained by any of the Examples described below were shown to contain Coo and 00304 by surface analysis, and the media obtained by other specific methods were shown to contain Coo and 00304.
Compared to a medium containing only OO or Co3O4, it has excellent improvement effects in environmental stability and abrasion resistance, which will be described later.

Backscattered electron diffraction and ESCA are used to analyze the surface structure.

Auger electron spectroscopy was used.

These analyzes showed that there was no need for any special limitation on the ratio of Coo and Co3O4, and it was concluded that it was important that it was a composite oxide (although the mechanism was not clear). .

Before describing each embodiment in detail, an apparatus for carrying out the present invention will be described with reference to the drawings.

FIG. 1 shows an example of the device. As shown in the figure, the vacuum chamber 4 is comprised of two chambers: an upper chamber 13 in which a mechanism for winding up the polymer molded substrate is disposed, and a lower chamber 14 in which an evaporation source is disposed. Whether or not to choose a two-chamber configuration may be determined based on the purpose, scale of the device, etc., and does not limit the present invention.

The upper chamber 13 is heated to a pressure of 10' Torr to 10' Torr by an exhaust system 6 mainly composed of an oil diffusion ejector pump, for example.
The vacuum level is maintained at r. The lower chamber 14 has a pressure of 105 TOrr to 10-6 To by an exhaust system 6 mainly composed of an oil diffusion pump.
It is evacuated to a vacuum level of rr.

The substrate 1 is moved from the feed shaft 7 along the rotary can 9 and is rolled up by the winding shaft 8.

Figure 1 shows a model of the simplest winding system, but specifically, the role of the rotating can 9 is to both cool and support the substrate 1, and to improve the deposition efficiency in oblique deposition. For further improvement, for example, it is possible to perform the same role as a rotating can by moving with a stainless steel belt KG that rotates once. 15 is a model showing the glow discharge treatment mechanism. A specific example is shown in FIG.

An evaporation source is provided in the lower chamber 14 in FIG.

The evaporation source is shown as a model with an evaporation source container 3 and an evaporation material 2, but heating is preferably done by an electron beam.1 The highest temperature part of the evaporation source is the evaporation point 6, and the shielding plate 1
The point where the straight line passing through the end M of 1 intersects with the surface of the can is P
Let it be O.

The magnetic layer is formed using a system in which the incident angle and deposition rate dynamically change from a high incidence angle and low deposition rate to a low incidence angle and maximum deposition rate on the substrate 1 moving in the direction of the arrow M. It will be held in

A nozzle 1o, for example a pipe with a plurality of holes, is arranged at the end of the shielding plate 11 on the side where the can is seen, and from here,
Oxygen or a gas mixture containing oxygen is introduced into the system.

This introduction is performed by adjusting the angle and determining the arrangement relationship so that the gas flow ejected from the hole of the nozzle 1Q is directed mainly toward Po or a region close to PO.

This differs depending on the nozzle mechanism, but the important thing is to direct the introduced gas to the maximum deposition rate region.

In this case, directing the introduced gas to the maximum deposition rate region means directing the introduced gas to the portion of the evaporation air flow from the evaporation source that participates in forming the surface portion of the magnetic layer. 12
is a wall that partitions the upper chamber 13 and the lower chamber 14. The glow discharge treatment mechanism shown in FIG. 2 shows elements for inducing a known coaxial magnetron discharge.

As shown in FIG. 2, the surface of the ferromagnetic layer 1 formed on the moving substrate 16 is exposed to the anode 18 (
This is a cylindrical electrode with a permanent magnet or electromagnet Mar-IJ Lux built into it, and as shown in the figure, it is assembled to create a magnetic field that causes electrons to move in a spiral manner and increases the probability of ionization! 1) and cathode 19. cover 2
The treatment is performed using a glow discharge obtained by forcibly introducing oxygen gas or a mixed gas containing oxygen into the space 21 consisting of zero.

The cathode 19 and the cover 20 may be at the same potential, but the cover 20 is at ground potential and the anode 18. The cathode 19 is insulated from the cover 2o and a DC voltage is applied so that the electrode 18 is positive with respect to the cathode 19, or the anode 18. It can be freely selected whether to apply an alternating current or more actively a high frequency voltage between the cathodes 19.

Glow discharge treatment is different from other flat plate magnetron discharge.

It can be understood from the examples described later that any known method such as hot cathode glow discharge may be used.

Next, a specific example will be explained.

In addition, as a common condition in Examples 1 to 4 below, the first
Using the device shown in the figure and using a rotating can of φ500, the evaporation point O is (16o, ○) by coordinate display based on the X and Z coordinate axes written in Figure 1.
With the positional relationship such that the intersection Po is (95, 310),
The center position of the nozzle 1o is set as (RY0, 2Ryo6), the center and axis of the nozzle hole are set to face Po, and the glow discharge treatment mechanism is set so that the center of the anode 18 and the ferromagnetic layer 1
7. The distance to the surface is 1QO, and the diameter of the anode 18 is 60.

[Example 1] Polyethylene terephthalate film (10.5 μm
Cobalt (C) is rolled up at 25”/min.
o) Evaporate 100% by electron beam heating, and introduce oxygen at 0-1s 1/min (pressure 1,5 Kli) to 0.13μ at a vacuum level of 4.5X10Torr.
A magnetic layer was formed to a thickness of m. At that time, the temperature of the rotating can was maintained at 25°C and 1°C by circulating a refrigerant.

FIG. 3 shows the results of examining the elemental distribution in the depth direction of this magnetic layer by Auger electron spectroscopy.

For convenience, the surface oxidized layer was defined by the thickness to from the surface to point B in FIG. Note that in FIG. 3, the sensitivity difference between oxygen (0) and Kobal I-(Go) has been corrected.

In the example of a tobacco with a thickness of W, γ0 μm, and C in the region of thickness to.
Analysis showed a mixture of O5O4 and C00.

This magnetic layer consists of columnar crystal grains, and the oxidation state of the side parts of the columnar crystal grains is currently unknown as there is no means of analysis, but a requirement of the present invention is the provision of a surface oxidation layer, and this is a definition of a region corresponding to to as shown by Auger electron spectroscopy, for example. For this, electron diffraction, Es
It is necessary to fix the oxide with c5, etc., and this is confirmed in all of the following examples.

[Example 2] After forming a magnetic layer under the same conditions as in Example 1, a glow discharge treatment was performed. The conditions are: oxygen partial pressure 3 x 10 Torr, high frequency electric field 2 KVp, 3
I went with an 80W pitcher. As a result, Co3O4, Coo
A slight change was observed in the mixed state. i.e. 00504
The equivalent thickness of the layer was 15 people in Example 1, but it was 20 people in this example, which was slightly thicker. However, the thickness to of the surface oxidation layer was the same.

[Example 3] Polyethylene terephthalate) (14.5 μm thick) was
Co75% Ni25 while rolling with m/Bin
% alloy was evaporated by electron beam heating, and a magnetic layer with a thickness of 0.15 μm was formed at a vacuum degree of 5×10 Torr while introducing oxygen at a pressure of 2.3′%, i, and 0.22 l/min. At that time, the temperature of the rotating can is ℃ power, 6
held at °C.

The magnetic layer finally obtained is also CO at to=90 μm.
It had a composite oxide layer containing a mixture of 3O4 and Coo.

[Example 4] While rolling up a polyimide film (26 μm thick) with 15” Ain, an alloy of 80% Go and Ni2O was evaporated,
Oxygen at a pressure of 2-3 Twc4r O-221/min
+ CO gas at a pressure of 1.5 at a rate of 0.031/min
A magnetic layer having a thickness of 01 μm was formed at a vacuum degree of 6×10 TOrr. The rotary can temperature is 10'C, 1°C.

While unwinding the film on which the magnetic layer was formed in this way, the magnetic layer was coated with 6m//In1n and an oxygen partial pressure of 0.1To.
AC65Q, 550 glow discharge treatment was performed at rr.

The magnetic layer subjected to such treatment has a surface oxidation layer with a thickness of 6 oi.
It was found that a composite oxide layer in which CO3O4 and Coo are mixed is formed. 3 [Example 5] In the same system as in Example 1, a 2-turn high-frequency electric circuit (diameter 46", inter-turn distance 181) was installed, with the electrode-4m section being Z-1.
It was arranged at a position of 30''11, and was configured so that vapor deposition could be performed in a high frequency glow discharge.

C on polyethylene terephthalate (9.5 μnl)
090% Ni 10% alloy was evaporated by electron beam heating and rolled at 16 m/min.
A magnetic layer with a thickness of 6 μm was formed.

The degree of vacuum was 8.6 x 1 o-'rorr, the amount of oxygen introduced was α11/min (pressure 3 K//, 1), and the high frequency power was 350 W (anode voltage 2.8 KV).

The rotating can temperature was maintained at 5°C, 5°C.

The surface oxidation layer of this magnetic layer has a thickness of 10 OA and a Goc
It turns out that it is a mixture of o4 and Coo, so it is -7.

[Example 6] An alloy of C090%Ni5%Or5% was evaporated on polyethylene terephthalate (14.5 μm thick) by electron beam heating, and ion blasting was performed in the same system as in Example 6.

The amount of oxygen introduced is O-11/win (pressure 2.6 Ky/
c, 4), Ar introduction amount is ○-21/min (pressure 2
．． 6 Niri/C4), the degree of vacuum is 9 x 1 o-'ro
The magnetic layer was formed at a temperature of 0°C to 0.5°C. The magnetic layer formed in this way was heated to 400 nm at an oxygen partial pressure of 0.005 Torr using a flat plate magnetron discharge.
50 Surface treatment under the conditions of 2.2 mm (film movement speed 1
2”/min, glow discharge treatment area length 60crr
L) As a result, the surface oxidation layer is to-13oAO and 0o5
It was found that the layer was a composite oxide layer containing 04 and Coo.

[Example A]

The can diameter is 1 m, and the center O of the evaporation source is (30
0, O), and the intersection PO is (250, 400) and 17,
The center position of the nozzle was set at (240, 360), and the nozzle was arranged so that the central axis of the hole faced directly above.

In this system, the can temperature was maintained at 30 °C, and KC090% on polyethylene terephthalate (11,5 μm, If) was
The N110 alloy is heated with an electron beam and evaporated to 0.
．． A magnetic layer with a thickness of 11 μm was formed. Film winding speed is 40 m/win, oxygen introduction amount is 0.461/wi
n (pressure 1.tsK%4), degree of vacuum is 3×10To
It is rr.

The surface oxidation layer of this magnetic layer is Go504 when to=80 people.
It was found that this was a composite oxide layer containing a mixture of /Coo.

[Example 8] Under the same conditions as in Examples 1 and 7, magnetic material was
A magnetic layer was formed using O95%V5%.

The surface of this magnetic layer is mainly composed of Coo and vo2. v,,
C5 showed a strong peak followed by Co3O
A peak of 4 was also observed, indicating that the sample had a surface oxidation layer of to=110 consisting of a p Go504/Coo composite oxide layer.

[Example 9] Under the same conditions as in Example 6, a GO95% RhS magnetic layer was formed.

As a result of analysis using reflected electron beam diffraction in this magnetic layer, the presence of a Co3O4/Coo mixture was observed in the surface layer.

Furthermore, Go94%W6%, Go80%Ni15%Mo
The same thing was confirmed for the 5% magnetic layer.

[Conventional example]

As a conventional example for comparison, a magnetic layer was formed with the same positional relationship as in Example 1 but with varying amounts of oxygen introduced. That is, 0.33 l/w of oxygen was introduced from the gas introduction part G shown in Fig. 1.
Coao%Ni was introduced in a vacuum degree of 5X10 Torr.
After forming a 20% magnetic layer to a thickness of 0.13 μm, the surface was subjected to glow discharge treatment under the same conditions as in Example 6. In this case, the surface portion of the magnetic layer was mainly composed of Coo and NiO, and no Co3O4 was detected.

The position of the gas introduction part G is -4007 with respect to the two coordinate axes.
11111, -600 mW on the X coordinate axis. Regarding the influence of the gas introduction position, it was found that the above results did not change even if the gas was introduced from the upper chamber 13, for example.

In each of Examples 1 to 9 and the conventional example, a magnetic layer was formed on a film having a width soo'' and a length of 10 oorrL as a mark ω.The back surface of the film was coated with running properties. To increase the strength, a resin coating was applied, and the width was made into magnetic tape. Each of 100,771 pieces of this was wound onto an open reel and simultaneously stored in various environments to evaluate environmental resistance.

The evaluation method was to record a rectangular wave with a recording wavelength of 0.8μ onto a magnetic tape, and then place the same magnetic tape at 60°C in a 90% RH atmosphere, in pure water at 60°C, in industrial water at 60°C, and at 60°C.
They were stored for about one week in an environment in which CO gas was flowed at CC/min in an atmosphere of 90% RH, and in an environment in which CO2 gas was similarly flowed in an atmosphere of 60° C., 904 RH, and then taken out and subjected to a regeneration test.

As a result, all of them, except for the conventional example, could be put to practical use for more than three weeks. On the other hand, in the case of the conventional example, in all of the various environmental tests mentioned above, the quality deteriorated to such an extent that it could not be put to practical use within one week.

As described above, the product according to the present invention exhibits excellent durability under various environments.

Here, CO3O4 has been known as an oxide constituting a relatively stable oxide layer, but when we investigated its stability against gases in detail, we found that an oxide layer simply containing Coρ4 is particularly sensitive to CO2 gas. It did not necessarily have an effective protective effect.

In this regard, in the present invention, Co is added to the oxide layer on the surface of the magnetic layer.
It is thought that the mixture of 3O4 and Coo provides a sufficient protective effect against gases such as GO2CO2, and as a result, it exhibits excellent durability even in an environment where Go or CO2 gas is flowed as described above.

As has been made clear from the above description, the present invention provides a magnetic recording medium that exhibits excellent durability under various environments, and its industrial value is extremely high.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of an apparatus for carrying out the present invention;
Fig. 2 is a diagram showing the glow and discharge processing section that constitutes the main part of the above device, and Fig. 3 is a diagram showing the results of Auger electron spectroscopy of the magnetic layer constituting the magnetic recording medium according to the present invention. be. 1.16...Substrate, 2...Evaporation material, 3...
...Container, 4...Vacuum chamber, 5,6...
・Exhaust system, 7... Delivery shaft, 8... Rolling shaft, 9... Rotating can, 1Q... Nozzle, 11... Shielding plate . Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (3)

[Claims] (1) Consisting of a polymer molded substrate, a ferromagnetic layer containing cobalt formed on the substrate, and a protective layer containing at least Coo and CO3O4 formed on the surface of the ferromagnetic layer. A magnetic recording medium characterized by: (2) When forming a ferromagnetic layer on the substrate, a vapor flow of a substance containing cobalt is directed onto the polymer molded substrate in a vacuum layer, and the surface portion of the ferromagnetic layer of the vapor flow is A method for manufacturing a magnetic recording medium, characterized by directing a gas containing oxygen to a portion that participates in formation. (3) The method for manufacturing a magnetic recording medium according to claim 2, wherein after forming the ferromagnetic layer, the surface thereof is exposed to a glow discharge atmosphere containing oxygen.