JPS6063724A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the durability of a magnetic recording medium, by forming a compact and hard plasma polymerized protective film layer of an organic compound by moving a base body on which a ferromagnetic metallic thin layer is formed along the peripheral side face of a cylindrical can and, at the same time, performing plasma processing by introducing a monomer gas of the organic compound to a space between a trough-like shielding frame and the cylindrical can from a side from which the base body is introduced. CONSTITUTION:Since plasma processing is performed by introducing a monomer gas of an organic compound to a space 10 formed between a trough-like shielding frame 11 and cylindrical can 4 from a side from which a base body 1 is introduced, plasma polymerization successively proceeds as the base body 1 moves and, because of the gas pressure being high at first, a plasma polymerized material of the organic compound having a relatively low molecular weight and a good adhesion is adhered to the surface of the ferromagnetic metallic thin layer on the base body 1 with a good adhesiveness. Then, as the gas pressure becomes lower, a hard and compact plasma polymerized material having a relatively high molecular weight is adhered and as approaching to the surface a more compact and harder plasma polymerized protective layer is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a magnetic recording medium having a ferromagnetic metal thin film layer as a magnetic recording layer, and more particularly to a method of manufacturing the above-mentioned magnetic recording medium having excellent durability.

A magnetic recording medium whose magnetic recording layer is a ferromagnetic metal thin film layer is
It is usually made by bonding metals or their alloys onto a base film by vacuum deposition, etc., and has characteristics suitable for high-density recording, but on the other hand, it has a high coefficient of friction with the magnetic head and is susceptible to wear and damage. It has the disadvantage that it is easy to use and sufficient durability cannot be obtained.

For this reason, durability has been conventionally improved by providing various protective film layers on the ferromagnetic metal thin film layer. Then, the polyester film 1 with a ferromagnetic metal thin film layer formed on the surface is moved from the raw roll 3 of the vacuum chamber 2 along the circumferential side of the cylindrical can 4 and wound onto the take-up roll 5. -L, 1-1 gas system 6 inside the vacuum chamber 2
At the same time, a predetermined degree of vacuum is maintained, and an organic compound gas is introduced from the gas inlet tube 7 attached to the vacuum chamber 2, and a high frequency is applied to the electrode 9 using the AC power source 8. A plasma polymerized protective film layer of an organic compound is provided on the surface of the IIA layer.

However, in this method, the monomer gas of the organic compound must be uniformly present in the vacuum chamber, so the flow rate of the monomer gas of the organic compound introduced into the vacuum chamber is large, and the plasma polymerization formed by this method Since the protective film layer can only have a uniform composition and the surface of the protective film layer is not sufficiently dense and hard, it has not yet been possible to obtain a protective film layer with sufficiently good durability.

In view of the current situation, the inventors conducted various studies and found that a thin ferromagnetic metal made of metal or an alloy thereof is formed on a substrate! ! After that, the substrate on which the ferromagnetic metal thin film layer was formed was placed in a cylindrical can in a vacuum chamber and a gutter-shaped shield frame in which a gap was provided at the lower periphery of the cylindrical can. and a plasma generation electrode disposed within the shield frame, and move the base body along the circumferential side of the cylindrical can, and remove the cylindrical can formed by the gutter-shaped shield frame. A monomer gas of an organic compound is introduced from the side where the substrate is introduced into the gap with the shaped can, and is made to flow in the direction of the substrate, and plasma treatment is performed using the plasma generation electrode in the shield frame to form a ferromagnetic metal thin film layer. Forming a plasma-polymerized protective film layer of an organic compound on the surface reduces the amount of organic compound monomer gas introduced, and also forms a plasma-polymerized protective film layer of an organic compound that is denser and harder toward the surface on the ferromagnetic metal thin film layer. It was discovered that a magnetic recording medium with sufficiently improved durability can be obtained by forming a magnetic recording medium, and the present invention was completed based on this discovery.

The present invention will be described below with reference to the drawings.

FIG. 2 shows an example of a plasma processing apparatus used in the present invention. This plasma processing apparatus consists of a vacuum chamber 2 containing an original fabric roll 3, a cylindrical can 4, and a take-up roll 5.
It is the first in that the exhaust system 6 is installed in the vacuum chamber 2.
Although it is the same as the conventional plasma processing apparatus shown in the figure, a gutter-shaped shield frame 11 is fitted with a predetermined gap IO provided at the lower periphery of the cylindrical can 4, and plasma is generated within this shield frame II. An electrode 12 is provided and connected to an AC power source 13. In addition, the gutter-shaped shield frame 11 is connected to the cylindrical can 4.
The tip of the gas introduction pipe 14 attached to the vacuum chamber 2 is inserted into the side of the gap 10 formed by fitting the substrate 1 to the lower peripheral edge of the vacuum chamber 2, and the monomer gas of the organic compound is introduced into the gap 10. The monomer gas of the organic compound is supplied into the gap 10 and flows along the traveling direction of the substrate 1, so that it is discharged from the side from which the substrate 1 is led out. However, according to this plasma processing apparatus, when performing plasma processing by introducing monomer gas of an organic compound from the gas introduction pipe 14, sufficient plasma processing can be performed even if the flow rate of the monomer gas of the organic compound is small. Furthermore, the gap 1 formed between the gutter-shaped shield frame 11 and the cylindrical can 4
Since the plasma treatment is carried out by supplying a 7-mer gas of an organic compound from the side where the substrate 1 is introduced, plasma polymerization proceeds sequentially as the substrate 1' moves, and the gas pressure is high at first. On the surface of the ferromagnetic metal thin film layer on the base 1,
Plasma polymerized organic compounds with relatively low molecular weight and adhesive properties adhere with good adhesion. Then, the gas pressure is gradually lowered, and a relatively high molecular weight, hard and dense plasma polymer is deposited, and a dense and hard plasma polymerized protective film layer is formed as it approaches the surface. Therefore, a plasma-polymerized protective film layer with good adhesion and a dense and hard surface is formed on the ferromagnetic metal thin film layer on the substrate 1, and the 1iif abrasion resistance is sufficiently improved, resulting in even more durable magnetic recording. A medium is obtained.

The gap 1o formed by the cylindrical can 4 and the plasma generating pole 12 in the shield frame 11 fitted to the lower periphery of the cylindrical can 4 is set so as to facilitate discharge. It is preferably within the range of 1 cm to 10 cm.

Examples of the organic compound monomer gas introduced from the gas introduction pipe 14 into the gap 10 formed by the cylindrical can 4 and the gutter-shaped shield frame 11 include C2F, fluorine-based organic compound monomer gas, and ethylene. , monomer gas of hydrocarbon compounds such as propylene, and tetramethylsilane, octamethylcyclotetrasiloxane,
Monomer gases of silicon-based organic compounds such as hexamethyldisilazane are preferably used, and these organic compound monomer gases generate radicals when plasma treatment is performed by applying high frequency to the plasma generation electrode 12. The generated radicals react and polymerize to form a film. At this time, monomer gas of the organic compound is supplied into the gap 10 from the side where the substrate 1 is introduced, and plasma polymerization proceeds sequentially, so the gas pressure is initially high and the substrate 1
On the surface of the upper ferromagnetic metal thin film layer, a plasma polymer of a relatively low-molecular-weight, sticky organic compound adheres with good adhesion, and then the gas pressure gradually decreases (as it becomes relatively high-molecular-weight, hard, and dense). The plasma polymer is deposited and a dense and hard plasma polymerized protective film layer is formed as it approaches the surface.Radicals during such plasma treatment are caused by the fact that these organic compounds have double or triple bonds. It is a metal salt compound with a metal element at the end, or O
The more functional groups such as H groups are present, the less the formation occurs, so those having these unsaturated bonds, metal elements, functional groups, etc. are more preferably used. In addition, when plasma polymerizing these 7-mer gases, if a carrier gas such as argon gas, helium gas, or oxygen gas is coexisting, the monomer gas will be deposited at a rate 3 to 5 times faster than when monomer gas is plasma polymerized alone. Therefore, it is preferable to use these carrier gases together. When coexisting with these carrier gases, it is preferable that the composition ratio is 4:1 in terms of the ratio of the carrier gas to the monomer gas of the organic compound; if the carrier gas is too small, the precipitation rate will decrease; If it is too much, the amount of 7-mer gas will decrease, which will interfere with the plasma polymerization reaction. Note that when using a 7-mer gas of a hydrocarbon compound, it is not preferable to use oxygen gas as a carrier gas because an oxidation reaction will occur if oxygen gas is used as a carrier gas.

In this way, the gas pressure and high frequency output when plasma polymerization is performed by introducing monomer gas of an organic compound from the gas introduction pipe 14 into the gap IO formed by the cylindrical can 4 and the gutter-shaped shield frame 11 The higher the gas pressure, the faster the deposition rate, but the monomer gas has a relatively low molecular weight and is plasma-polymerized, making it impossible to obtain a hard protective film layer.The lower the gas pressure and the higher the high-frequency output, the slower the deposition rate. On the other hand, a relatively hard polymerized protective film layer can be obtained, but if the gas pressure is low and the high frequency output is too high, the monomer gas will turn into powder and a plasma polymerized protective film layer will not be formed. Preferably, the pressure is in the range of 0.03 to 3 torr and the high frequency output is in the range of 0.03 to 0.5 W/-, the gas pressure is in the range of 0.1 to 1 torr, and the high frequency output is in the range of 0. More preferably, it is within the range of .05 to 0.3 W/CIl+.

In this way, a plasma-polymerized protective film layer of an organic compound is formed by supplying the organic compound gas into the gap 10 from the side where the substrate 1 is introduced and sequentially causing plasma polymerization to form on the surface. As it progresses, a denser and harder material is obtained, and therefore, a ferromagnetic metal thin film type magnetic recording medium with improved wear resistance and excellent durability is obtained. The film thickness of such a plasma polymerized protective film layer of an organic compound is 30~
It is preferably within the range of 1,000 people. If the film thickness is too thin, the durability effect of this protective film layer will not be fully exhibited, and if it is too thick, the spelling loss will be too large, which will adversely affect the electromagnetic conversion characteristics. affect

The ferromagnetic metal M on the substrate, the formation of the film layer is C01Fe,
, Ni, , Co-Ni alloy, Co-Cr alloy, Co-P
A ferromagnetic phase such as alloy, Co--N1--P alloy, etc. is deposited on a substrate by means such as vacuum evaporation, ion blasting, sputtering, plating, etc.

Next, embodiments of the invention will be described.

Example 1 A polyester film with a thickness of 10 μm was loaded into a vacuum coating device, and cobalt was heated and evaporated under a residual gas pressure of 5×10−5) to form a ferromagnetic metal thin film layer made of a polyester film. Formed. Next, using the plasma processing apparatus shown in FIG. 2, ferromagnetic metal thin I! ! The layered polyester film 1 is moved from the raw roll 3 in the vacuum chamber 2 along the circumferential side of the cylindrical can 4, and set to be wound onto the take-up roll 5. C2'-F4 gas is supplied from the gas introduction pipe 14 while running at the Hid speed.
Introduced at a flow rate of 0 0 sec. Plasma polymerization was carried out at a high frequency output of 500 W from the sulphate generation electrode 12. After that, it was cut into a predetermined width to make a magnetic tape. .

Example 2 Plasma polymerization was carried out in the same manner as in Example 1, except that the plasma polymerization was carried out for 1 minute while the polyester film l was stopped without running, and the magnetic tape was attached ( The total length of the magnetic tape thus imprinted was 75 cm.

Comparative Example 1 In Example 1, the plasma processing apparatus shown in FIG. 1 was used instead of the plasma processing apparatus shown in FIG. 2, and the flow rate of c2F4 gas introduced from the gas introduction pipe 7 was set to 300 s
A magnetic tape was produced in the same manner as in Example 1 except that the ecm was changed to 650 sec.

The magnetic tape obtained in Example 1, the magnetic tape obtained in Example 2 (↓I) at a position 10 co+ from the C2F4 gas inlet side (sample 1) and 10 co+ from the C2F4 gas outlet side.
Regarding the magnetic tape sample at the cm position (Sample 2) and the magnetic tape obtained in Comparative Example 1, the thickness of the plasma polymerized protective film layer was measured and the durability was tested. The durability test is
The obtained magnetic tape was subjected to a sliding test using a Zaphire needle, and the number of times until the plasma polymerized protective film layer was scratched was measured.

The table below shows the results.

As is clear from the above table, the protective film obtained in Sample 1 of Example 2 has a thick film thickness, and the one obtained in Sample 2 has excellent durability. It can be seen that the plasma polymerization rate is fast on the monomer gas introduction side, and that a 1% protective layer with excellent durability is obtained on the output side. Furthermore, in Example 1 (the magnetic tape shown was the magnetic tape obtained in Comparative Example 1).

Compared to the above, the protective film layer is thicker and has better durability. This shows that the manufacturing method of the present invention can provide a magnetic recording medium with excellent durability.

[Brief explanation of drawings]

Figure 1 shows a schematic cross section of a conventional plasma processing apparatus.
The figure is a schematic front view showing one example of a plasma processing apparatus used in the manufacturing method of the present invention, and No. 31 button 1 is a side sectional view of a main part of the plasma processing apparatus. ■...Base body, 2...Vacuum chamber, 4...Cylindrical can, IO...Gap, 11...Shield frame, 12...
Plasma generation electrode, 14... gas introduction tube, patent applicant Hitachi Maxell, Ltd.

Claims (1)

[Claims] 16 A ferromagnetic metal thin film layer made of metal or an alloy thereof is formed on a substrate, and then the substrate on which this ferromagnetic metal thin film layer is formed is placed in a vacuum chamber with a cylindrical can and the lower peripheral edge of the cylindrical can. The substrate is placed in a plasma processing apparatus equipped with a gutter-shaped shield frame that is fitted with a gap between the sides and a plasma generation electrode placed inside the shield frame, and the base is placed along the circumferential side of the cylindrical can. At the same time, an organic compound monomer gas is introduced from the side where the substrate is introduced into the gap between the cylindrical can formed by the gutter-like shield frame and flows in the direction of movement of the substrate, thereby increasing the plasma inside the shield frame. A method for producing a magnetic recording medium, which comprises performing plasma treatment using a generating electrode to form a plasma polymerized protective film layer of an organic compound on the surface of a ferromagnetic metal thin film layer.