JPS63183609A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled recording medium which as a small deterioration rate and has long still time by forming at least >=1 layers of thin ferromagnetic film layers contg. spinel ferrite on a substrate and providing protective film layers consisting of carbon on the thin ferromagnetic film layers. CONSTITUTION:An Al disk 1 subjected to an alumite treatment on the surface by using a sputtering treatment device is set on the rear face of a substrate 3 provided in the upper part in a treatment vessel 2. Fe 5 of 99.9atom% purity is set as a target on a stainless steel electrode 4 provided in the lower part of the vessel 2. Sputtering is then executed in an Ar atmosphere to form the thin ferromagnetic film layers contg. signal ferrite to 1,500Angstrom thickness. Graphite is set as a target on the electrode 4 and is sputtered to form the protective film layers consisting of the carbon to 200Angstrom thickness, by which the ferromagnetic film layers 9 and the protective film layers 10 are successively laminated on the Al disk 1 and the magnetic disk is thus prepd. The magnetic disk having the small deterioration rate, the long still time and the improved durability and corrosion resistance is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium having a ferromagnetic thin film layer containing spinel ferrite as a magnetic recording layer, and more specifically relates to a magnetic recording medium having excellent durability and corrosion resistance. Regarding the medium.

[Conventional technology]

A magnetic recording medium whose magnetic recording layer is a ferromagnetic metal thin film layer is
It is usually made by depositing metals or their alloys on a base film by vacuum deposition, sputtering, etc., and has a thin ferromagnetic metal layer mainly composed of CO, which has excellent magnetic recording properties. widely known. However, a ferromagnetic metal thin film layer mainly composed of Co,
Although it has characteristics suitable for high-density recording, C
There was a problem in that corrosion resistance was lacking because O was unstable.

[Problem that the invention seeks to solve]

Therefore, as a result of various studies on the materials constituting the ferromagnetic metal thin film layer, we found that forming a ferromagnetic thin film layer containing spinel ferrite such as Fe3O4, CoO/Fe2O3, etc., provides magnetic recording that is extremely stable in an acidic atmosphere and has excellent corrosion resistance. Although it was found that a medium could be obtained, it was also found that these ferromagnetic thin film layers containing spinel ferrite had poor abrasion resistance with the magnetic head.

[Means to solve the problem]

In view of the current situation, this invention was made as a result of various studies on providing a protective film layer that is resistant to corrosion and has excellent wear resistance on a ferromagnetic thin film layer. By providing a protective film layer made of carbon on top, durability and corrosion resistance are sufficiently improved.

In this invention, the protective film layer made of carbon formed on the ferromagnetic thin film layer containing spinel ferrite is formed by a so-called paper deposition method such as a sputtering method, a plasma CVD method, or an ion beam evaporation method.

In the case of sputtering, a target mainly composed of carbon such as graphite is set in a processing tank, and this is sputtered with high frequency in the presence of an inert gas such as argon gas or helium gas to form a target on a ferromagnetic thin film layer. It is formed by precipitation. At this time, the gas pressure such as argon gas and high frequency power are set at 0.001 to 0.1 torr to prevent the formed protective film layer made of carbon from becoming brittle and softened. 0.
It is preferably within the range of 1 to 2 W/cd.

In addition, when forming by plasma CVD method, ferromagnetic It is formed by depositing on a thin film layer. At this time, in order to prevent embrittlement and softening, it is preferable that the gas pressure of the hydrocarbon gas be 0.001 to 0.1 Torr and the high frequency power be in the range of 0.5 to 3 W/c+J.

A protective film layer made of carbon is formed in this way, and when electrons are irradiated to the area where the carbon protective film layer is deposited, thermal and chemical effects are applied to the particles forming the carbon protective film layer. The cross-linking reaction is promoted by imparting physical energy, and by negatively charging the surface potential of the ferromagnetic thin film layer, active cations are attracted to the surface of the ferromagnetic thin film layer, resulting in a strong and highly cross-linked film. A carbon protective film layer is formed, the strength of the carbon protective film layer is significantly increased, and the durability and corrosion resistance are further improved.

In this way, the acceleration voltage and electron current of electrons irradiated during the formation of the carbon protective film layer should be within the range of 0.5 to 50 KV and 1 to 500 mA, respectively, and further within the range of 1 to 20 KV and 10 to 200 mA. More preferably, if the voltage is higher than 50 KV and 500 mA, the ferromagnetic thin film layer will be damaged, and if it is lower than 0.5 KV and 1 mA, the desired effect cannot be obtained. Further, as a method for irradiating electrons, both a method of diffusing an electron current and irradiating the entire surface of the ferromagnetic thin film layer, and a method of scanning the surface of the ferromagnetic thin film layer by using the electron current as a beam are preferably used. Note that when relatively high pressure is required, such as in a plasma CVD method, differential pumping of the electron gun portion is required to prevent damage to the filament of the electron gun.

The protective film layer made of carbon formed in this way has excellent wear resistance and does not change itself in an acidic atmosphere. When formed on a magnetic thin film layer, durability and corrosion resistance are sufficiently improved. Note that the protective film layer made of such carbon may be either diamond-like carbon or amorphous carbon, or may be a mixture of these. The thickness of the protective film layer made of carbon is 3.
The range is preferably from 0 to 500. If it is thinner than 30, the durability and corrosion resistance effects of this carbon protective film layer will not be sufficiently exhibited, and if it is thicker than 500, spacing loss will increase. If it is too much, it will adversely affect the electromagnetic conversion characteristics.

As a ferromagnetic thin film layer containing spinel ferrite, F1
3304, Coo-Fe203, r-Fe2o3, or Co −, T s % Ni % 03
It is preferable that the ferromagnetic single layer containing spinel ferrite is added by such means as vacuum evaporation, ion blasting, sputtering, plating, etc. It is deposited and formed on the substrate.

In addition, as magnetic recording media, polyester film,
It includes various forms such as magnetic tapes based on synthetic resins such as polyethylene films and polyimide films, magnetic disks and magnetic drums based on disks and drums made of synthetic resin films, aluminum plates, glass plates, etc.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 Using the sputter processing apparatus shown in FIG. Fe5 having a purity of 99.9 atom % was set as a target on the electrode 4 made of stainless steel disposed in the electrode 4 . Next, the inside of the processing tank 2 is evacuated to 5×10-' torr with the exhaust system 6, and the gas introduction pipe 7 attached to the processing tank 2 is
Oxygen gas was introduced at a flow rate of 20 m1/min and argon gas was introduced at a flow rate of 20 m1/min.
A ferromagnetic thin film layer containing spinel ferrite with a thickness of 1500 nm was formed by sputtering for 2 minutes at a high frequency power density of 4 W/- for electrode 4 in an atmosphere of was formed. Next, graphite is set as a target on the electrode 4 made of stainless steel disposed at the bottom of the processing tank 2, and the electrode 4
Sputtering was performed for 1 minute at a high-frequency power density of 0.5 W/cJ to form a protective film layer of carbon with a thickness of 200 nm, and the ferromagnetic thin films N9 and A magnetic disk A was produced in which protective films N10 were sequentially laminated. The ferromagnetic thin film layer 9 of the obtained magnetic disk was examined by transmission electron beam diffraction, and as a result, Fe (b, c, c) and Fe50° were detected. Note that 8 in the figure is a high frequency power source for applying high frequency to the electrode 4.

Example 2 In the formation of the ferromagnetic groove H\1 layer in Example 1, instead of iron with a purity of 99.9 atomic %, Fe-Co alloy (atomic ratio 70:30) was targeted on the electrode 4 made of stainless steel. A magnetic disk A was produced by forming a ferromagnetic thin film layer and further forming a protective film layer in the same manner as in Example 1, except that the magnetic disk A was set as follows. As a result of examining the ferromagnetic thin film layer 9 of the obtained magnetic disk by transmission electron beam diffraction, it was found that Fa (C
o) (b, c.

C) and 000.Fe3O4 were detected.

Example 3 A polyester film 11 with a thickness of 10 μm was placed in a processing tank 12 using a vacuum evaporation/sputter processing apparatus shown in FIG.
The ferromagnetic material is moved from the supply roll 13 along the circumferential side of the cylindrical can 14 and set to be wound up on the take-up roll 15, and the ferromagnetic material evaporation source 16 disposed at the bottom of the processing tank 12 is supplied with purity. was set at 99.9 atom % Fe17.

Next, the inside of the processing tank 2 is evacuated to 2×10"5 Torr using the exhaust system 18, and 500 ml of oxygen gas is introduced from the gas introduction pipe 20 arranged between the cylindrical can 14 and the anti-adhesion plate 19.
Fe17 was introduced at a flow rate of min., heated to evaporate Fe17 at a gas pressure of 5 x 10'''4 Torr, and obliquely deposited at a minimum incidence angle of 50 degrees and a deposition rate of 1000 people/sec to a thickness of 1500 mm.
A ferromagnetic thin film layer containing human spinel ferrite was formed. Next, using a sputtering device 21 disposed adjacent to the cylindrical can 14, sputtering is performed with a power of 500 W using graphite as a target, and a protective film layer made of carbon with a thickness of 100 mm is coated with a ferromagnetic material containing spinel ferrite. Formed on a thin film layer. Thereafter, it was cut to a predetermined width to produce a magnetic tape B in which a ferromagnetic thin film layer 22 and a protective film layer 23 were sequentially laminated on a polyester film 11, as shown in FIG. As a result of examining the ferromagnetic thin film layer 22 of the obtained magnetic tape by transmission electron beam diffraction, it was found that F
e(b, c, c) and Fe3O4 were detected.

Example 4 In the formation of the ferromagnetic thin film layer in Example 3, Fe-Co alloy (atomic ratio 7
Magnetic tape B was produced by forming a ferromagnetic thin film layer and further forming a protective film layer in the same manner as in Example 3, except that a magnetic tape (0:30) was set in the ferromagnetic material evaporation source 16. The ferromagnetic thin film layer 22 of the obtained magnetic tape was examined by transmission electron beam diffraction, and as a result, Fe (Go) (b, c, c) and Coo-Fe3O4 were detected.

Example 5 A film with a thickness of 10 μm was prepared in the same manner as in Example 3, except that sputtering in the sputter processing equipment was omitted.
A ferromagnetic i-film layer containing spinel ferrite with a thickness of 1500 mm was formed on a polyester film 11 of 150 mm thick. Next, using the plasma processing apparatus shown in FIG.
It was moved from the inner fabric roll 25 along the circumferential side of the cylindrical can 26 and set to be wound up on the winding roll 27. Next, while running the polyester film 11 along the circumferential side of the cylindrical can 26 at a running speed of 2 m/min, the gas introduction pipe 2 attached to the processing tank 24 is moved.
8, methane monomer gas is introduced at a flow rate of 50 scc-, and the gas pressure is set to 0000 Torr to the electrode 29 at 13.
A high frequency of 56 MHz is applied at a power density of 0.6 w/cd, and at the same time an accelerating voltage of 2 K is applied by the electron gun 31 in the differential pumping tank 30 disposed adjacent to the lower end of the processing tank 24.
V, an electron current of 50 mA, electrons are scanned and irradiated to the area where the carbon film is being formed on the polyester film 11 to form a protective film layer made of carbon with a thickness of 180 mA.
It was formed on a ferromagnetic thin film layer containing spinel ferrite.

Thereafter, it was cut to a predetermined width to produce magnetic tape B shown in FIG. In FIG. 5, 32 is a high frequency power source for applying high frequency to the electrode 29, and 33 and 34 are exhaust systems for evacuating the processing tank 24 and the differential exhaust tank 30, respectively.

Example 6 In place of the electrode 29 of the plasma processing apparatus used in Example 5, a target holder incorporating an electromagnet and graphite were installed. Next, the polyester film 11 is
m/111i1, methane was introduced for 50 sec to set the gas pressure to 0.01 ) -l, and instead of applying high frequency at a power density of 0.6 w/cd, the polyester film 11 was heated at 0.5 m/min. Argon gas was introduced at a flow rate of 203CCI11 and the gas pressure was set to o,
A protective film layer made of carbon having a thickness of 130 mm was formed in the same manner as in Example 5, except that high frequency was applied at a power density of 4 W/aJ and magnetron sputtering was performed. I made it.

Comparative Example 1 In the formation of the ferromagnetic thin film layer in Example 1, a Co-Ni alloy (atomic ratio 80:20) was set as a target on the electrode 4 made of stainless steel instead of iron with a purity of 99.9 at%. Except for the above, a ferromagnetic thin film layer was formed in the same manner as in Example 1, and a protective film layer was further formed to produce a magnetic disk. As a result of examining the ferromagnetic thin film layer of the obtained magnetic disk by transmission electron diffraction, it was found that the C of the H3P product was
It was a mixture of oNi and NaCl type Co (Ni)0.

Comparative Example 2 In the formation of the ferromagnetic thin film layer in Example 3, Co-Ni alloy (atomic ratio 8
0:20) was used as the ferromagnetic material evaporation source 16.
A ferromagnetic thin film layer was formed in the same manner as in Example 3, and a protective film layer was further formed to produce a magnetic tape. The ferromagnetic thin film layer of the obtained magnetic tape was examined by transmission electron diffraction, and it was found that CoN i of H3P product and Co(N
i) It was a mixture of O.

Comparative Example 3 A magnetic disk was produced in the same manner as in Example 1, except that the formation of the protective film layer made of carbon was omitted.

Comparative Example 4 A magnetic tape was produced in the same manner as in Example 3, except that the formation of the protective film layer made of carbon was omitted.

The magnetic disks and magnetic tapes obtained in each Example and Comparative Example were tested for corrosion resistance and durability. Corrosion resistance tests were conducted on the obtained magnetic disks and magnetic tapes at 35° C. and 75% RH at 302 lppm S.
H2S 0.5ppm, NO2lppm
The sample was left in an atmosphere for 20 hours, the saturation magnetization after being left was measured, and the rate of deterioration from the saturation magnetization before being left was measured and calculated. The durability test was conducted using a VH3 type VTR and measuring the time required for the output to drop by 6 dB from the initial value.

Table 1 below shows the results.

Table 1 [Effects of the Invention] As is clear from Table 1 above, the magnetic disks and magnetic tapes (Examples 1 to 6) obtained by the present invention are as follows:
Compared to the magnetic disks and magnetic tapes obtained in Comparative Examples No. 4 to 4, the deterioration rate is lower and the still time is longer. Therefore, the magnetic recording medium obtained by the present invention has a lower deterioration rate and a longer still time.
It can be seen that the durability and corrosion resistance are further improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of a sputter processing apparatus used in forming a protective film layer in the present invention, and FIG. 2 is a partially enlarged cross-sectional view of a magnetic disk obtained by the present invention.
FIG. 3 is a schematic sectional view showing an example of the vacuum evaporation and sputtering processing apparatus used in the present invention, FIG. 4 is a partially enlarged sectional view of the magnetic tape obtained by the present invention, and FIG. 5 is a protected 15f FIG. 2 is a schematic cross-sectional view showing an example of a plasma processing apparatus used when forming a layer. DESCRIPTION OF SYMBOLS 1... Aluminum disk (substrate), 11... Polyester film (substrate), 9.22... Ferromagnetic thin film layer, 10.23... Protective film layer, A... Magnetic disk (
Magnetic recording medium) B...Magnetic tape (magnetic recording medium) Figure 1 Figure 3

Claims (1)

[Claims] 1. A magnetic recording medium characterized in that at least one ferromagnetic thin film layer containing spinel ferrite is formed on a substrate, and a protective film layer made of carbon is provided on the ferromagnetic thin film layer.