JPS63121124A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve running durability and corrosion resistance by projecting the ionized active particles or hydrogen atom ions or hydrogen molecule ions of an org. compd. simultaneously at the time of forming a plasma-polymerized protective film layer consisting of the org. compd. on the surface of a thin ferromagnetic metallic film layer. CONSTITUTION:A polyester film 1 on which the thin ferromagnetic metallic film layer 12 is formed is moved from a stock roll 2 along the peripheral side face of a cylindrical can roll 3. Gaseous monomer of tetrafluoroethylene is introduced from a gas introducing pipe 6 mounted to a treatment vessel 5 into said vessel and a high frequency is impressed thereto by an electrode 7 to effect plasma polymn. The gaseous methane is simultaneously introduced through a gas introducing port 9 into a Kaufmann type ion gun 8 to ionize the monomer gas and to project the ionized active particles to the region of the film 1 where the plasma polymn. progresses. The plasma-polymerized protective film layer 13 is thus formed. The crosslinking degree of the plasma-polymerized protective film is thereby increased and the durability and corrosion resistance of the film are improved to a greater extent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a magnetic recording medium having a magnetic recording layer made of a ferromagnetic metal thin film. More specifically, the present invention relates to a method for manufacturing a magnetic recording medium with excellent running durability and corrosion resistance.

[Prior Art] A magnetic recording medium having a magnetic recording layer made of a ferromagnetic metal thin film is usually manufactured by depositing metals or alloys thereof on a substrate by a method such as vacuum deposition or sputtering. Such magnetic recording media have characteristics suitable for high-density recording, but on the other hand, they have a high coefficient of friction with the magnetic head (which makes them susceptible to wear and damage, and they also gradually corrode due to oxygen and moisture in the air). However, there are drawbacks such as deterioration of magnetic properties such as maximum magnetic flux density.

For this reason, attempts have been made to improve durability and corrosion resistance by providing various protective film layers on the ferromagnetic metal thin film layer. In recent years, for example, a monomer gas of a fluorine-based organic compound is plasma-polymerized to provide a plasma-polymerized protective film layer of a fluorine-based organic compound on the ferromagnetic metal thin film layer 1- (JP-A-58-88828, JP-A No. 1980-10
No. 2330), or by plasma polymerizing a monomer gas of a silicon-based compound to provide a plasma-polymerized protective film layer of a silicon-based organic compound on the ferromagnetic metal thin film layer 1 (
JP-A-57-82229), JP-A-58-604';
, ts;-> has been proposed.

[Problems to be Solved by the Invention] However, the plasma-polymerized protective film layer of an organic compound obtained by this conventional method has an uneven crosslinking density, so that sufficient improvements in durability and corrosion resistance cannot be obtained. . In particular, if the deposition speed is increased by increasing the gas pressure during plasma polymerization, the crosslinking density of the plasma polymerization decreases, and a hard protective film layer is not formed, making it difficult to obtain good wear resistance. was there. If the protective film is soft, the magnetic layer is also easily affected by oxygen and moisture.

[Object of the Invention] Accordingly, an object of the present invention is to provide a method for manufacturing a magnetic recording medium having a plasma polymerized protective film having excellent durability and corrosion resistance.

[Means for Solving the Problems] In order to solve the problems of the prior art described above and achieve the purpose of the present invention, the present inventor has continued extensive trial production and research for many years, and as a result, a ferromagnetic metal thin film has been developed. When forming a plasma-polymerized protective film layer of an organic compound on the surface of the layer, at the same time the surface of the ferromagnetic metal thin film layer is irradiated with ionized active particles of the organic compound, hydrogen atom ions, or hydrogen molecular ions. It has been discovered that the degree of crosslinking can be dramatically increased, and as a result, a magnetic recording medium with excellent running durability and corrosion resistance can be obtained.

In this invention, the plasma polymerized protective film layer is formed on the ferromagnetic metal thin film layer in a treatment tank using a hydrocarbon compound,
It is formed by subjecting a monomer gas such as a fluorine-based organic compound and a silicon-based organic compound to plasma polymerization using high frequency waves and depositing it on a ferromagnetic metal thin film layer.

Examples of the monomer gas used to form this plasma polymerization retention film layer include monomer gas of hydrocarbon compounds such as propane, ethylene, and propylene, and C2
Monomer gases of fluorine-based organic compounds such as F//, C3F6, and monomer gases of silicon-based organic compounds such as tetramethylsilane, octamethylcyclotetrasiloxane, and hexamethyldisilazane are preferably used.

When a high frequency is applied to the monomer gas of these organic compounds, radicals are generated, and the generated radicals undergo a polymerization reaction to form a film having a crosslinked structure.

The relationship between gas pressure and high frequency power when performing plasma polymerization is that the higher the gas pressure, the faster the deposition rate (on the other hand, the monomer gas has a relatively low crosslinking density and is plasma polymerized and remains hard, resulting in a hard film layer). In addition, lowering the gas pressure (and increasing the high-frequency power) will slow down the deposition rate, but will yield a protective film layer with relatively high crosslinking density. However, if the gas pressure is low and the high-frequency power is too high, , the plasma-polymerized protective film layer cannot be formed because the 7-mer gas turns into powder.

Therefore, as a general guideline when carrying out the method of the present invention, it is preferable that the gas pressure be within the range of 0.001 to 5 Torr, and the high frequency power be within the range of 0.03 to 5 W/cs2; More preferably, the pressure is 0.003 to 1 Torr, and the high frequency power is within the range of 0.05 to 3 W/cm2.

When performing this plasma polymerization, the ferromagnetic metal thin film layer is simultaneously formed! ! (The ionizing activity of an organic compound or hydrogen atom ion or hydrogen molecular ion that is irradiated is the H+ produced by the decomposition and ionization of an organic compound or hydrogen molecule
, C+ and other atomic ions and H2+, CH", CH2
", refers to a group of particles consisting of a mixture of molecular ions such as C2Hs, and is produced by a hot filament method, a plasma method, etc. using an organic compound or hydrogen gas alone or in combination as a raw material gas.

The irradiation amount of ionized active particles, hydrogen atom ions, or hydrogen molecule ions to be irradiated is not particularly limited, but as a general indicator, the ion current is 0.05 to 1 Om.
It is preferable to use it within the range of A/c■2.

Irradiation can be performed using an ion gun or the like. Other irradiation means can also be used.

When these ionized active particles are extracted by an electric field and irradiated onto the surface of a ferromagnetic metal thin film where plasma polymerization is progressing, the kinetic energy of the ions activates the ablation motion on the surface of the plasma polymerized film that is being formed. Compared to ordinary plasma polymerized membranes, the degree of crosslinking is higher, a tougher and denser membrane can be obtained, and wear resistance and corrosion resistance are further improved.

Irradiation of ionized active particles or hydrogen atomic or hydrogen molecule ions must be simultaneous with plasma polymerization. When irradiated after plasma polymerization, only the surface portion of the formed polymer film can be cured. When irradiated simultaneously with plasma polymerization, it seems to act synergistically to increase the degree of crosslinking of the entire produced film.

In particular, when a hydrocarbon such as methane, ethylene, or benzene is used as a monomer gas for plasma polymerization, and a hydrocarbon such as methane or ethane is used as an organophilic compound when generating ionized active particles, a plasma polymerized film is formed. forms a diamond-like carbon film, which significantly improves wear resistance.

The thickness of the plasma polymerized y1 film layer of such an organic compound is preferably within the range of 20 to 1000 layers.

If the film thickness is too thin, this problem will occur! The durability and corrosion resistance effects of the IIM layer are not exhibited within 1 minute, and if it is too thick, the svening loss becomes too large, which adversely affects the electromagnetic conversion characteristics.

As a material for forming the ferromagnetic metal thin film layer, C01F es
NilCo Ni alloy, Co-Cr alloy, Go
Ferromagnetic materials such as -P alloy and Co-N1-P alloy are used, and the ferromagnetic metal thin film layer made of these ferromagnetic materials is
The material is deposited on the substrate by means such as N-vacuum deposition, ion blasting, sputtering, and plating.

In addition, as magnetic recording media, polyester film,
Various types of structures that come into sliding contact with magnetic heads, such as magnetic tapes based on synthetic resin films such as polyimide films, magnetic disks and magnetic drums based on disks and drums made of synthetic resin films, aluminum plates, glass plates, etc. includes.

[Example] Hereinafter, an example of the method of the present invention will be described in more detail with reference to the drawings.

1. Load a polyester film with a thickness of 10 μm into a vacuum evaporation device, and heat and evaporate the cobalt under 1X10-5 Torr to make a polyester film with a thickness of 100 μm.
A ferromagnetic metal thin film layer consisting of zero cobalt was formed.

Next, using the plasma polymerization apparatus shown in FIG. 1, the polyester film l on which the ferromagnetic metal thin film layer was formed was moved from the raw roll 2 along the circumferential side of the cylindrical can roll 3, and wound around the take-up roll 4. I set it to take it.

Next, while running the polyester film 1 at a running speed of 2 m/min, 50% of tetrafluoroethylene monomer gas was supplied from the gas introduction pipe 6 attached to the processing tank 5.
A high frequency of 13.58 MH2 was introduced at electrode 7 at a flow rate of 0.5 W/c at a gas pressure of 0.05 Torr.
Plasma polymerization was performed by applying a power density of m2.

Furthermore, at the same time as this plasma polymerization, methane gas is introduced into the Kauffman type ion gun 8 from the gas inlet 9 at a flow rate of 20 sccm, ionized, and ionized active particles are transferred to the plasma absorption area of the polyester film l using an accelerating voltage of lkv. I fired one shot.

A plasma polymerized protective film layer having a thickness of 200 mm was formed by the method described below. Thereafter, it was cut into a predetermined size of 11 to make a magnetic tape as shown in FIG. Note that the reference numeral 10 in FIG. 1 is an exhaust system for reducing the pressure in the processing tank 5, and 11 is a high frequency power source for applying high frequency to the electrode 7. Further, reference numeral 12 in FIG. 2 is a ferromagnetic metal thin film layer, and 13 is a plasma polymerized protective film layer.

2. In Example 1, 30% of tetramethylsilane monomer gas was used instead of tetrafluoroethylene monomer gas.
A magnetic tape was produced in the same manner as in Example 1 except that the gas was introduced at a flow rate of sec- and the gas pressure was changed to 00Q3 Torr. The thickness of the plasma polymerized protective film layer at this time was 250 mm.

L5 1 In Example 1, 5 Q scc of ethylene 7mer gas was used instead of tetrafluoroethylene monomer gas.
Example 1 except that the gas was introduced at a flow rate of +++, the gas pressure was 0.03 Torr, and the high frequency power was changed to 1 w/cm2.
I made magnetic tape in the same way. The thickness of the plasma polymerized protective film layer was 150.

In Example 2, the gas introduced into the ion gun was replaced with methane and hydrogen gas was introduced at a flow rate of 5 Qsccm.
A magnetic tape was made in the same manner as in Example 2. The thickness of the plasma polymerized protective film layer was 220.

A magnetic tape was produced in the same manner as in Example 3, except that the gas introduced into the ion gun was replaced with methane and hydrogen gas was introduced at a flow rate of 5 Qseem. The thickness of the plasma polymerized protective film layer was 130.

Mitsutane Takumi 1 In Example 3, the gas introduced into the ion gun was replaced with methane, and a mixture of methane and hydrogen at a volume ratio of 1:5 was used for 50 se
A magnetic tape was produced in the same manner as in Example 3, except that it was introduced by removing the c-slip. The thickness of the plasma polymerized protective film layer was 140.

A magnetic tape was made in the same manner as in Example 1, except that the irradiation with ionized active particles was omitted. The thickness of the plasma polymerized protective film layer was 180.

Ken Yue 1 In Example 2, a magnetic tape was produced in the same manner as in Example 1 except that irradiation with ionized active particles was omitted. The thickness of the plasma polymerized protective film layer was 220.

Hikaku 1 A magnetic tape was produced in the same manner as in Example 3 except that the irradiation with ionized active particles was omitted. The thickness of the plasma polymerized protective film layer was 130.

Comparison 1 A magnetic tape was produced in the same manner as in Example 1, except that the formation of the plasma polymerized SG layer (including the irradiation with ionized active particles) was omitted.

The running durability and corrosion resistance of the magnetic tapes made in each example and comparative example were evaluated. Running durability was determined by a still test, and the time when the initial output decreased by 8 db was defined as the still life. Corrosion resistance of magnetic tape at 60℃ and 90℃
Evaluation was made based on the deterioration rate of saturation magnetization (Ms) when left for 1fff for 30 days under conditions of %RH. The results are shown in the table below.

In a magnetic recording medium consisting of a magnetic recording layer of a ferromagnetic metal thin film and a plasma polymerized protective film layer of an organic compound, simultaneously irradiating the substrate with ionized active particles of an organic compound or hydrogen when forming the plasma polymerized protective film layer. As a result, crosslinking of the plasma polymerized film progresses and becomes a hard and dense film.
It can be seen that the running durability and corrosion resistance were further improved.

[Effects of the Invention] As explained above, according to the method of the present invention, by increasing the degree of crosslinking of the plasma polymerized protective film, the durability and corrosion resistance of the film can be dramatically improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an example of a plasma polymerization apparatus used in the present invention, and FIG. 2 is a partially enlarged sectional view of a magnetic tape obtained by the present invention. 1... Polyester film, 2... Original fabric roll. 3... Can roll, 4... Winding roll. 5... Processing tank, 6... Gas introduction pipe, 7... Electrode. 8... Ion gun, 9... Gas introduction 0.10... Exhaust system 11... High frequency power supply, 12... Ferromagnetic metal thin layer.

Claims (1)

[Claims] (1) In a magnetic recording medium consisting of a nonmagnetic substrate, a magnetic recording layer made of a ferromagnetic metal thin film, and a plasma polymerized protective film layer of an organic compound, the organic compound is simultaneously ionized during the formation of the plasma polymerized protective film layer. A method for producing a magnetic recording medium, which comprises irradiating a substrate with active particles, hydrogen atom ions, or hydrogen molecular ions.