JPH0551967B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a magnetic recording medium using a ferromagnetic metal thin film as a magnetic recording layer, and particularly relates to a method for manufacturing a magnetic recording medium that has high output on the high frequency side and has excellent durability and corrosion resistance. It provides a manufacturing method. BACKGROUND ART Known methods for forming a protective film for improving the durability and corrosion resistance of metal thin film magnetic recording media include the 1-coating method, 2-sputtering method, 3-organic vapor deposition method, and 4-plasma CVD method. Among these, the plasma CVD method is a method of creating a protective film by exciting various gases to an active state in plasma. . In particular, in metal thin film type magnetic recording media, DC
Plasma CVD becomes possible, making it possible to create stronger protective films. Problems to be Solved by the Invention However, if the roller that conducts current to the magnetic recording medium is a metal roller, no defects will occur with a weak current, but if the current is large, heat will be generated due to the concentration of current, and this heat will cause non-performance. The magnetic substrate polyethylene terephthalate (PET) loses heat and can no longer be used as a magnetic recording medium. On the other hand, if the current-carrying roller is made of an insulating material or one that is not grounded to prevent this, no defects will occur because no current will flow between the roller and the medium, but the problem will be that the medium will be charged and abnormal discharge will occur. It was hot. That is, by forming, for example, a diamond-like carbon film as a protective film of a metal thin film type magnetic recording medium by the DC plasma CVD method, the still durability and running durability of this medium can be significantly improved. However, when the flowing current increases, the current locally concentrates on the surface of the magnetic tape in the metal roller, and the resulting heat causes local damage to the PET, resulting in a fatal defect in the magnetic tape. In other words, this causes an increase in dropouts and head clogging. In order to solve this problem, the present invention provides a manufacturing method that does not cause any defects in the medium even when a considerable amount of current is passed through the magnetic layer when a protective film is formed on the magnetic recording medium by the DC plasma CVD method. It is something. Means for Solving the Problems The present invention unwinds a magnetic recording medium onto a current-carrying roller installed in a film forming apparatus so that the magnetic layer of the medium touches the roller, and generates plasma within the apparatus. When forming a protective film on the surface of the magnetic layer by applying an electric current to the surface of the magnetic layer conveyed through the apparatus, the surface of the roller in contact with the surface of the magnetic layer is heated to a surface resistance value of 10 ³ Ω/cm. ² ～
The present invention provides a method for manufacturing a magnetic recording medium in which the current is released through the surface of a roller made of a semiconductor having a diameter of 10 ⁶ Ω/cm ² . Effect: This method provides a magnetic recording medium with excellent characteristics. Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a diamond-like carbon film forming apparatus, and numeral 1 indicates an energized roller having a semiconductor-like surface resistance value, which is the central feature of the present invention. The magnetic recording medium is unwound so that the magnetic layer side touches this current-carrying roller. A voltage is applied in the discharge tube 5 to generate plasma, and a current is applied to the surface of the magnetic layer being transported to form a diamond-like carbon film. The outlet for this current is the semiconductor energizing roller. First, a 500 mm wide polyethylene terephthalate film with a controlled surface roughness and no abnormally large protrusions (for example, a maximum surface roughness of 300 Å
~400 Å, center line average roughness of 50 Å to 150 Å, and density of mountain-like protrusions of ^{10 4 to} 10 ⁸ per mm 2 ), a magnetic layer of Co ₈₀ −Ni ₂₀ was deposited while introducing oxygen by vacuum evaporation. After forming 1800Å, apply vacuum to this magnetic layer.
After forming a plasma polymerized film of perfluorocyclobutane to a thickness of approximately 20 Å using a continuous winding device under the conditions of 0.1 Torr, 13.56 MHz, and high frequency output of 100 W, a surface resistance value of 10 ³ Ω/cm was further applied onto the plasma polymerized film. ² ～
In the range of 10 ⁶ Ω/cm ² For example, the metal thin film magnetic layer 2 is made negative by the current-carrying roller 1 made of alumina-titania, amorphous silicon, or conductive rubber, and the electrode 3 is made positive and DC is applied.
A diamond-like carbon film is formed by plasma CVD. That is, the current flows from the electrode 3 on the surface of the magnetic layer and flows out from the surface of the roller 1. At this time, the gas composition is Ar:CH ₄ =1:6
Introduced from introduction pipe 4 as a vacuum at 0.3 Torr.
Add a thickness of 100Å. Note that the current-carrying roller may be a metal roller coated with a semiconductor material, or a roller formed only of a semiconductor material. 5 is a discharge tube, and 6 is a can. The number of defects per unit area of 1 m ² of the magnetic tape thus produced was counted and the difference was confirmed. Furthermore, a fluorine-containing fatty acid of 30 Å is deposited on this diamond-like carbon film by a coating method or an organic vapor deposition method, and then cut into a width of 8 mm using a slitter.
The number of dropouts of the 8 mm video metal thin film tape thus prepared was examined using a Kodak 8 mm VTR. A dropout counter manufactured by Shibasoku was used to count the dropout counter for 15 μs and −16 dB or more. Thereafter, the still durability was examined under a special environment of 23°C - 10% under an accelerated tension of 20g. The results are shown in Table-1.

【table】

[Table] As is clear from Table 1, the metal rollers of samples No. 1 and 2 have more defects as the amount of current increases, causing dropouts.
The amount of current for various semiconductor rollers No. 3 to 12 is 1A.
No defects occur even at close range, and dropout is stable. Note that the film formation rate is approximately proportional to the amount of current applied, and the greater the amount of current applied, the higher the productivity.
When the current flow is 300 mA or more, the speed of forming the diamond-like carbon film varies depending on the gas used, but it is possible to form the diamond-like carbon film at approximately 20 m/min to 60 m/min. Furthermore, if a defect occurs, the still durability is extremely degraded as described above, but as long as no defect occurs, it was also observed that the still durability tends to increase as the amount of electricity is increased. In this way, the surface of the metal roller is coated with a semiconductor material to a thickness of 50 μm to 5000 μm, but the roller is made of semiconductor material to increase the surface electrical resistance.
When it is 10 ³ Ω/cm ² to 10 ⁶ Ω/cm ² , a diamond-like carbon film can be formed on the magnetic surface of a metal thin film magnetic recording medium at mass production speed without any inconvenience as a magnetic tape. As a result, it becomes possible to significantly improve the still durability and corrosion resistance of the metal thin film type porcelain recording medium. There is also an example of connecting a metal roller to ground via a resistor (Publication Publication No. 63-279426), which has the effect of reducing the overall energy of abnormal discharge of large currents, but it also causes damage to the film due to local concentration of current. There is no effect on heat loss, and film defects will not be eliminated unless the resistance value of the roller is optimized to avoid current concentration between the roller and the magnetic film as in the present application. As in the present invention, by passing current through a semiconductor roller with a surface resistance value of 10 ³ Ω/cm ² to ^{10 6} Ω/cm ² , the current is distributed and flows from a large number of contact points. The current density per piece is low and the amount of heat generated is small, so the film does not suffer from heat loss. In addition, although Table 1 shows the results when only DC was applied, the present invention solves defects caused by current concentration by optimizing the surface resistance of the current-carrying roller. A similar effect is also observed in the current waveform obtained by superimposing these. Effects of the Invention As described above, according to the manufacturing method of the present invention, a metal thin film type magnetic recording medium with significantly improved still durability and corrosion resistance can be manufactured at mass production speed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a method of manufacturing a magnetic recording medium in an embodiment of the present invention. 1... Current roller, 2... Magnetic recording medium, 3
... Electrode, 4 ... Gas introduction tube, 5 ... Discharge tube, 6
...Kyan.

Claims (1)

[Claims] 1. A magnetic recording medium is unwound onto a current-carrying roller installed in a film forming apparatus so that the magnetic layer of the medium touches the roller, plasma is generated in the apparatus, and the magnetic recording medium is transported through the apparatus. When forming a protective film on the surface of the magnetic layer by passing a current through the surface of the magnetic layer, the surface of the roller in contact with the surface of the magnetic layer is made of a semiconductor having a surface resistance value of 10 ³ Ω/cm ² to 10 ⁶ Ω/cm ² . A method for manufacturing a magnetic recording medium, characterized in that the current is released through the surface of the roller.