JPS6116013A - Magnetic recording medium and its production - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium having a ferromagnetic metal thin film layer as a magnetic recording layer, and a method for manufacturing the same.

[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 substrate by vacuum evaporation, etc. For perpendicular magnetic recording, ferromagnetic materials and a cobalt-chromium alloy are used. The C axis of the ferromagnetic metal thin film layer is oriented in a direction perpendicular to the surface of the ferromagnetic metal thin film layer. [Ryuji Sugita, 4 others, Proceedings of the 28th Applied Physics Association Conference, P470 (1981), Yasushi Maeda, Shigeru Hirono, No. 28
Proceedings of the Joint Conference on Applied Physics, P471 [Problems to be Solved by the Invention] However, in this type of magnetic recording medium for vertical magnetic recording, the C-axis of the cobalt-chromium alloy is connected to a ferromagnetic metal thin film. In order to align the cobalt-chromium alloy in a direction perpendicular to the layer surface, the temperature of the substrate is heated to 100°C to 500°C during the formation of the ferromagnetic metal thin film layer, and the C axis of the cobalt-chromium alloy is aligned perpendicular to the ferromagnetic metal thin film layer surface. For this reason, the substrate for this type of magnetic recording medium must have excellent heat resistance.Generally, commonly used substrates such as polyethylene telecrate do not have high heat resistance. Since this is not so good, it is difficult to sufficiently heat the substrate to orient the C axis of the cobalt-chromium alloy in a direction perpendicular to the surface of the ferromagnetic metal thin film layer. Furthermore, the ferromagnetic metal thin film layer using a cobalt-chromium alloy as the ferromagnetic material contains weakly brittle chromium, is brittle, easily cracks, and has weak adhesion. .

[Means for solving problems]

This invention has been made as a result of various studies in view of the current situation, and is made by plasma polymerizing a monomer gas of a hydrocarbon compound or a monomer gas of a silicon-based organic compound on at least the surface of a substrate to form a hydrocarbon compound. Alternatively, a plasma polymerized film layer made of a silicon-based organic compound is formed on at least the surface of the substrate, and then a ferromagnetic metal thin film layer is formed on the plasma polymerized film layer on the surface of the substrate.
By interposing a plasma polymerized film layer between the substrate and the ferromagnetic metal thin film layer, which has good I properties and excellent adhesion to the substrate and the ferromagnetic metal thin film layer, the heat resistance of the substrate can be improved. Even when using conventionally commonly used substrates such as polyethylene terecrate with low magnetic flux, the C-axis of the cobalt-chromium alloy can be well oriented in the direction perpendicular to the plane of the ferromagnetic metal thin film layer by heating the substrate sufficiently. At the same time, the adhesion between the substrate and the ferromagnetic metal thin film layer is improved.Furthermore, by sufficiently heating the substrate and improving the adhesion of the ferromagnetic metal thin film layer to the substrate, the ferromagnetic metal containing weakly brittle chromium is This improves the brittleness of the thin film layer and effectively suppresses cracks in the ferromagnetic metal thin film layer.

In this invention, the plasma polymerized film layer on the front and back surfaces of the substrate is formed by plasma polymerizing monomer gas of a hydrocarbon compound or monomer gas of a silicon-based organic compound using high frequency in a processing tank, and depositing it on at least the surface of the substrate. It is done by forming.

Examples of monomer gases used to form such a plasma polymerized film layer include monomer gases of hydrocarbon compounds such as acetonitrile, propionitrile, propane, ethylene, and propylene, and tetramethylsilane and octamethylcyclo. Monomer gases of silicon-based organic compounds such as tetrasiloxane and hexamethyldisilazane are preferably used. Radicals of these organic compound monomer gases are generated by high frequency, and the generated radicals react and polymerize. It becomes a film. This radical is more likely to be generated when these organic compounds have double bonds or triple bonds, are metal salt compounds with a metal element at the end, or have functional groups such as 011 groups. , those having these unsaturated bonds, metal elements, functional groups, etc. are more preferably used. In addition, when plasma polymerizing these monomer gases, if a carrier gas such as argon gas or helium gas is coexisting, the polymerization rate will be 3 times higher than when monomer gases are plasma polymerized alone.
Since precipitation is performed at ~5 times the rate, it is preferable to carry out the process in the presence of these carrier gases. When coexisting with these carrier gases, it is preferable that the volume ratio of the carrier gas to the monomer gas of the organic compound be within the range of 1:1 to 20:1, and if the carrier gas is too small, The deposition rate decreases, and if the amount is too high, the amount of monomer gas decreases, causing trouble in the plasma polymerization reaction.

When performing such plasma polymerization, the gas pressure and high frequency output are such that the higher the gas pressure, the faster the deposition rate of the plasma polymerized film layer, but on the other hand, the monomer gas has a relatively low molecular weight and is plasma polymerized, resulting in a hard plasma polymerized film layer. In addition, lowering the gas pressure and increasing the high-frequency output (this will slow down the deposition rate, but will yield a relatively hard plasma polymerized film layer, but lowering the gas pressure and increasing the high-frequency output) If the pressure is too high, the monomer gas will turn into powder and plasma polymerization HER will not be formed, so the gas pressure should be set at 0.001.
~5 Torr, and the high frequency output is 0.03~5 Torr.
It is preferably within the range of W/cJ, the gas pressure is 0.003 to 1 Torr, and the high frequency output is 0.05 to 3 Torr.
More preferably, it is within the range of W/ca.

The plasma polymerized film layer deposited and formed by plasma polymerization in this manner has very good surface flatness, excellent heat resistance, and excellent adhesion to the substrate and the ferromagnetic metal thin film layer. Therefore, this type of plasma polymerization IW
When Ii is formed, the heat resistance of the substrate such as polyethylene terephthalate is improved and the adhesion with the ferromagnetic metal thin film layer is improved without impairing the very good smoothness of the substrate. During layer forming, the substrate can be sufficiently heated to properly orient the C-axis of the cobalt-chromium alloy in a direction perpendicular to the ferromagnetic metal thin film layer surface, and the substrate can be heated sufficiently and the ferromagnetic metal thin film layer can be formed on the substrate. By improving the adhesion to the ferromagnetic metal thin film layer, the brittleness of the ferromagnetic metal thin film layer containing chromium, which is weakly brittle, can be sufficiently improved, and cracking of the ferromagnetic metal thin film layer can be effectively suppressed. The thickness of such a plasma polymerized film layer is preferably within the range of 20 to 100.000. If the film thickness is too thin, the heat resistance of the substrate cannot be sufficiently improved, and if it is too thick, When a plasma polymerized film layer is formed, deformations such as curling tend to occur.

The material for forming the ferromagnetic metal thin film layer is C01Fe,
Ferromagnetic materials such as Ni, Go-Ni alloy, C0-Cr alloy, Co-P alloy, Co-N1-P alloy are used, and ferromagnetic metal thin film layers made of these ferromagnetic materials can be formed by vacuum deposition,
It is deposited on the substrate by means such as ion blasting, sputtering, and plating.

Further, as the substrate, any commonly used plastic film such as polyimide film, polyester film, polyamide film, polypropylene film, polycarbonate film, polyethylene film, etc., can be suitably used.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 Using the plasma processing apparatus shown in FIG. and set it so that it would be wound onto a winding roll 7 via a guide roll 6. Next, monomer gas of hexamethyldisilazane was introduced at a flow rate of 50 seconds from the gas introduction pipe 8 attached to the processing tank 2, and the gas pressure was set to 0.051-rel. Plasma polymerization was performed while the feed speed of the film 1 was sequentially changed from 0.05 m/min to 2 m/min to form a plasma polymerized film layer on the surface of the polyethylene terephthalate film 1. After taking it out of the plasma processing apparatus, it is set again in the same processing apparatus so that the back side of the polyethylene terephthalate film 1 faces the electrode 9 and moves along the circumferential side of the cylindrical can 5. Plasma polymerization was carried out using □ to form the same plasma polymerized film layer on the back surface of the polyethylene terephthalate film 1 as on the front surface. In the figure, 10 is an exhaust system for reducing the pressure inside the processing tank 2, and 11 is a high frequency power source for applying high frequency to the electrode 9.

Next, using the vacuum evaporation apparatus shown in FIG. 2, the polyethylene terephthalate film 1 with plasma polymerized film layers formed on the front and back surfaces is transferred from the raw roll 13 of the vacuum chamber 12 to the cylindrical can 15 via the guide roll 14. It was moved along the circumferential surface and set so as to be wound onto a winding roll 17 via a guide roll 16. Next, the vacuum chamber 12
Evacuate the inside to 3X10-6) with the exhaust system 18,
The ferromagnetic material evaporation source 2 disposed at the bottom of the vacuum chamber 12 is heated while heating the plasma polymerized film forming part with an infrared heater 19.
Cobalt-chromium alloy (molar ratio 88:12) 21 was heated and evaporated at a deposition rate of 500 people/sec to a thickness of 5000 people/sec on the plasma polymerized film layer on the surface of polyethylene terephthalate film 1. 77
:23) A ferromagnetic metal thin film layer was formed. When forming this ferromagnetic metal thin film layer, the thermocouple 22 fixed to the base
and the digital surface temperature liver 2 connected to this thermocouple 22.
3, the temperature of the substrate was measured and varied from 100 to 300°C. Thereafter, a plasma polymerized film layer 25 and a ferromagnetic metal thin film layer 26 are sequentially laminated on the surface of the polyethylene terephthalate film 1 as shown in FIG. A large number of magnetic tapes A each having a plasma polymerized film N25 formed thereon were made. In addition, 24 in FIG. 2 is an adhesion prevention plate.

Example 2 A plasma polymerized film layer was formed in the same manner as in Example 1 except that the same amount of methane monomer gas was used instead of the hexamethyldisilazane monomer gas in forming the plasma polymerized film layer in Example 1. A large number of magnetic tapes A were made by forming a ferromagnetic metal thin film layer.

Example 3 In the formation of the plasma polymerized film layer in Example 1, a process was performed on the front side of the polyethylene terephthalate film 1 in the same manner as in Example 1, except that the formation of the plasma polymerized film layer on the back side of the polyethylene terephthalate film 1 was omitted. A plasma polymerized film layer 25 and a ferromagnetic metal thin film layer are formed on the surface of the polyethylene terephthalate film 1 as shown in FIG. ! A large number of magnetic tapes B in which layers 26 are sequentially laminated.
I made it.

Comparative Example 1 A magnetic tape was produced by forming a ferromagnetic metal thin film layer in the same manner as in Example 1 except that the formation of plasma polymerized film layers on the front and back surfaces of the polyethylene terephthalate film 1 was omitted.

During the formation of the ferromagnetic metal thin film layers in Examples 1 and 2 and Comparative Example 1, the substrate temperature at which the polyethylene terephthalate film was deformed and melted due to heat was measured using a digital surface thermometer 23. FIG. 5 shows the relationship between the heat resistance temperature of the polyethylene terephthalate film measured in this way and the film thickness of the plasma polymerized film layer, where graph A shows the results of Example 1 and graph B shows the results of Example 1. The results of Comparative Example 1 are shown for the plasma polymerized film containing W-NO.

In addition, the magnetic tapes obtained in Example 1.2 and Comparative Example 1 were observed with an optical microscope to observe the state of cracks.

Figure 6 shows the digital surface thermometer 23 with and without cracks.
The graph shows the relationship between the substrate temperature during the formation of the ferromagnetic metal thin film layer and the film thickness of the plasma polymerized film layer, as measured by the method. Above the solid line is a magnetic tape with no cracks, and below the solid line is a magnetic tape with cracks. It is.

Furthermore, the adhesive strength was measured for the (d-air tape) obtained in Example 3 and Comparative Example 1. The tension support 27 is bonded with adhesive epoxy 28, the ferromagnetic metal M film layer 26 is bonded to the other tension support 29 with adhesive epoxy 28, and both tension supports 27 and 29 are pulled in opposite directions. The tensile force required for the plasma polymerized film layer 25 to be destroyed and the ferromagnetic metal thin film layer 26 to be peeled off from the polyethylene terephthalate film 1 was measured and expressed.

Graph A in FIG. 8 shows the relationship between the adhesive strength of the magnetic tape B and the thickness of the plasma polymerized film layer measured in this manner. In the graph, the point where the thickness of the plasma polymerized film layer is 0 indicates the adhesive strength of the magnetic tape obtained in Comparative Example 1.

〔Effect of the invention〕

As is clear from graphs A and B in FIG. 5, plasma polymerization 1! Compared to the heat resistance RI of the polyethylene terephthalate film in Comparative Example 1 with a Jffi film thickness of 0, the heat resistance temperature of the plasma polymerized film layer formed on the polyethylene terephthalate film is higher. It can be seen that the heat resistance of the substrate is improved, and it becomes possible to use commonly used inexpensive substrates such as polyethylene terephthalate film in magnetic recording media for perpendicular magnetic recording.

Furthermore, as is clear from Figure 6, the thicker the plasma polymerized film layer is, the lower the substrate temperature at which cracks occur. It can be seen that there are no cracks within the heat-resistant temperature range of the cylindrical base.

Furthermore, as is clear from graph A in FIG. 8, compared to the magnetic tape obtained in Comparative Example 1 in which the thickness of the plasma polymerized film layer was O, the plasma polymerized film layer was formed on a polyethylene terephthalate film. The obtained magnetic tape of the present invention has a high adhesive force, and therefore, the present invention has a high adhesive strength.
It can be seen that the provided magnetic recording medium also has improved adhesion of the ferromagnetic metal thin film layer to the substrate.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing one example of a plasma processing apparatus used in forming the plasma polymerized film layer of the present invention, and FIG.
The figure is a schematic cross-sectional view showing an example of a vacuum evaporation apparatus used in forming the ferromagnetic metal thin film layer of the present invention, and FIG. 3 is a partially enlarged cross-sectional view showing an example of the magnetic tape obtained by the present invention. , FIG. 4 is a partially enlarged sectional view showing another example of the same magnetic tape, FIG. 5 is a diagram showing the relationship between the allowable temperature limit of the substrate obtained by this invention and the film thickness of the plasma polymerized film layer, and FIG. A relationship diagram showing the presence or absence of cracks depending on the substrate temperature and the thickness of the plasma polymerized film layer during the formation of the ferromagnetic metal 74V film layer according to the present invention, FIG. 7 shows the adhesive force between the base of the magnetic tape and the ferromagnetic metal thin film layer. FIG. 8 is a diagram showing the relationship between the adhesion force of the strong ω metal thin film layer to the substrate and the film thickness of the plasma polymerized film layer of the magnetic tape obtained according to the present invention. DESCRIPTION OF SYMBOLS 1..., 1 mm ethylene terephthalate film (substrate), 25... plasma polymerized film layer, 26... ferromagnetic metal thin film layer, A, B... magnetic tape (magnetic recording medium)
Patent applicant: Hitachi Maxell, Ltd. Figure 1 Figure 2 Figure 5 Thickness of plasma polymerized film layer (A) Figure 7 Figure 8 Thickness of plasma polymerized film layer (A) Film thickness (S)

Claims (1)

[Claims] 1. Forming a plasma polymerized film layer made of a hydrocarbon compound or a silicon-based organic compound on at least the surface of the substrate,
A magnetic recording medium 2 characterized in that a ferromagnetic metal thin film layer is formed on a plasma-polymerized film layer on the surface of a substrate. polymerization to form a plasma-polymerized film layer made of a hydrocarbon-based compound or a silicon-based organic compound on at least the surface of the substrate, and then to form a ferromagnetic metal thin film layer on the plasma-polymerized film layer on the surface of the substrate. Features of manufacturing method for magnetic recording media