JPH0121539B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic recording medium formed by depositing a ferromagnetic metal onto a substrate surface. Conventionally, magnetic recording media in which oblique magnetic powder or ultrafine powder of iron oxide, chromium oxide, etc. are dispersed in a resin binder and coated on a non-magnetic substrate have been widely used. In these magnetic recording media, the frequency characteristics in the high range can be improved by increasing the coercive force, but if the coercive force is increased too much, the frequency characteristics in the low range tend to deteriorate. In coated magnetic recording media, it has not yet been found that the frequency characteristics can be improved without increasing the coercive force. Recently, thin film deposition type magnetic recording media in which the magnetic layer is made of ferromagnetic material and do not use a resin binder have been actively developed using thin film formation methods such as wet plating, vacuum evaporation, sputtering, and ion plating. Some of these have been researched and developed and are in practical use. However, the magnetic recording media obtained by each of the above-mentioned thin film forming methods have their own drawbacks and have various practical problems. That is, thin-film magnetic recording media formed by wet plating have disadvantages such as variations and non-uniformity in film quality and magnetic properties due to non-uniformity of the solution. In addition, in magnetic recording media formed by wet plating and vacuum evaporation, the adhesion strength between the magnetic layer and the base material is extremely low; It has the disadvantage that the magnetic layer is likely to peel off or be damaged by abrasion, and its frequency characteristics have not been as good as those of conventional coating-type magnetic recording media. Furthermore, although the adhesion strength between the magnetic layer and the base material is improved in thin film magnetic recording media formed by the sputtering method and the conventionally proposed ion plating method, these ^methods
Because thin films are formed using DC glow discharge or high-frequency plasma in a low vacuum of Torr or higher, the crystallinity of the ferromagnetic thin film layer may be adversely affected by the incorporation of residual gas or the incorporation of impurities. It had drawbacks in magnetic properties, such as a small squareness ratio. In addition, it has disadvantages such as non-uniformity in film quality and magnetic properties due to non-uniformity in the discharge state. In view of the above-mentioned drawbacks of conventional magnetic recording media, the present invention has been made with the object of providing a thin film deposition type magnetic recording medium that has good adhesion strength to the substrate surface and also has excellent frequency characteristics. The gist is to bombard the surface of a base material made of non-magnetic material with ionized evaporated particles of ferromagnetic material at an incident angle of 40 to 75 degrees with respect to the normal to the surface under high vacuum. A ferromagnetic thin film is formed by bombarding the ferromagnetic thin film with ionized evaporated particles of ferromagnetic material at an incident angle of 80° or more with respect to the normal. The base material made of non-magnetic material used in the present invention includes polyvinyl chloride, polyvinyl fluoride,
Cellulose acetate, polyethylene terephthalate,
polybutylene terephthalate, polyethylene, polypropylene, polycarbonate, polyimide,
Polymer materials such as polyether sulfon and polyparapanic acid, non-magnetic metal materials such as aluminum, copper, and copper-zinc alloys, and ceramic materials such as sintered bodies, porcelain, earthenware, and glass are used. In the present invention, the shape of the base material made of the non-magnetic material may be appropriately determined depending on the method of using the magnetic recording medium, and is used in the shape of a tape, film, disk, drum, etc., for example. Further, as the ferromagnetic material in the present invention, iron, cobalt, nickel, and alloys or mixtures containing one or more of these metals are used. The magnetic recording medium of the present invention and its manufacturing method will be explained below. FIG. 1 is an explanatory diagram for explaining the incident angle in the present invention, and a direction line 2 indicating the incident direction of ionized evaporated particles of ferromagnetic material incident on the surface of the base material 1.
The angle between this and the normal 3 to the surface of the base material 1 is indicated by θ. FIG. 2 is a cross-sectional view of the magnetic recording medium of the present invention,
A first layer of ferromagnetic material formed by bombarding the surface of the base material 1 with ionized evaporated particles of ferromagnetic material at an incident angle of 40 to 75 degrees with respect to the normal to the surface under high vacuum. A second ferromagnetic thin film formed by bombarding the thin film 4 and the surface of the thin film 4 with ionized evaporated particles of ferromagnetic material at an incident angle of 80° or more with respect to the normal under high vacuum. 5 is provided. FIG. 3 is a schematic diagram showing an example of an apparatus for manufacturing a magnetic recording medium according to the present invention. The inside of the vacuum chamber 6 is evacuated to a high vacuum of 1×10 ^-8 Torr by an exhaust system device (consisting of an oil rotary pump, an oil diffusion pump, etc., not shown) connected to the exhaust port 7. It has been made possible to do so. Inside the vacuum chamber 6 are a vapor deposition ion source 11, a supply roll 8 for the film-like substrate 1, a take-up roll 9,
(However, a roll drive device is not shown) and an ion accelerating electrode 10 are installed. The vapor deposition ion source 11 includes a steam generation section 12 and a steam ionization section 17. The steam generating section 12 includes an open crucible 13, a filament 15 for emitting thermionic electrons, and a guard 16 for controlling the electric field. The steam ionization section 17 is composed of a filament 18 for emitting thermionic electrons, a mesh electrode 19 for accelerating emitted electrons with an electric field, and a guard 20 for controlling the electric field. Furthermore, FIG. 3 shows power supplies 21 to 25 installed outside the vacuum chamber 6 and their circuits for operating the apparatus. Next, the operation of manufacturing the magnetic recording medium of the present invention using the above-mentioned apparatus will be explained. First, as shown in FIG. 3, a supply roll 8 on which a non-magnetic base material 1 such as a polyethylene terephthalate film is wound is installed, and the base material 1 is arranged so as to be wound around a take-up roll 9. A material 14 capable of forming a ferromagnetic thin film is supplied into a crucible 13 of a vapor deposition ion source 11 . Next, the inside of the vacuum chamber 6 is evacuated to a high vacuum of 8 × 10 ^-4 Torr to 10 ^-8 Torr (usually 10 ^-5 Torr to 10 ^-6 Torr) from the exhaust port 7 by an exhaust system device. At this time, it is preferable to wind and unwind the film-like base material 1 in order to degas the adsorbed matter present on the surface of the film-like base material 1 and the air caught in the supply roll 8. When the degree of vacuum in the vacuum chamber becomes constant, the power supplies 21 to 25 are turned on. To heat the crucible 13, the power source 22 is used to heat the crucible 13.
The filament 15 is heated with electricity to emit thermoelectrons, and a negative DC voltage is applied to the filament 15 and the guard 16 by the power source 21, and the crucible 1 is heated.
3 is grounded, the emitted electrons are accelerated by an electric field, and the crucible 13 is pumped and heated. The heated evaporation source material 14 evaporates at a vapor pressure corresponding to its heating temperature, and the evaporated particles reach the vapor ionization section 17. In order to ionize the evaporated particles in the steam ionization section 17, the filament 18 is energized and heated by the power source 23 to emit thermoelectrons, and a negative DC voltage is applied to the filament 18 and the guard 20 by the power source 24. By grounding the mesh electrode 19, the emitted electrons are accelerated by an electric field, collide with the evaporated particles, and ionize a portion of the evaporated particles. Since the ionized evaporated particles are in a positively charged state, they are accelerated by applying a negative DC voltage to the crucible 13 grounded to the ion accelerating electrode 10 by the power source 25, resulting in high kinetic energy. Grant. In this way, the ionized evaporated particles accelerated by the electric field are
It hits the surface of the base material 1 and forms a thin film. Incidentally, the evaporated particles that have not been ionized in the vapor ionization section 17 are not accelerated by the electric field by the ion accelerating electrode 10, but they fly due to the kinetic energy given during evaporation and are irradiated onto the surface of the base material 1. Then, it is deposited together with the ionized evaporated particles to form a thin film. Note that the operating conditions in the vapor ionization section 17 are such that the electron current for ionizing the evaporated particles is preferably 30 mA or more, and the ion current density due to the ionized evaporated particles is 1 μA/cm ² or more. is preferred. Therefore, in the magnetic recording medium of the present invention, the first layer is deposited at an angle of incidence of ionized evaporated particles of 40 to 75 degrees with respect to the normal to the base material 1 during the deposition,
Next, the second layer was deposited at an incident angle of 80° or more with respect to the normal line, and by forming a ferromagnetic thin film at such different incident angles,
This results in excellent magnetic properties as a magnetic recording medium. The thickness of the ferromagnetic thin films of the first layer and the second layer is such that the thickness of the second layer is 1/3 of the thickness of the first layer.
It is particularly preferable that the thickness is 1/6 to 1/3, and the total thickness is preferably 1000 to 2500 Å. As mentioned above, the magnetic recording medium of the present invention is composed of two layers of ferromagnetic thin film formed by bombarding ionized evaporated particles of ferromagnetic material at specific different incident angles. Therefore, it has excellent frequency characteristics, especially favorable characteristics such as a small difference in output between the low frequency region and the high frequency region. Furthermore, since the ferromagnetic thin film is formed by accelerating ionized evaporated particles under high vacuum and causing them to collide with the base material, it has a high adhesion strength with the base material and is durable as a magnetic recording medium. It has excellent abrasion resistance and head crush resistance, and is resistant to residual gas entrapment and impurities like a thin film formed in a low vacuum at a pressure of 10 ^-3 Torr or more using DC glow discharge, high frequency plasma method, etc. It has no defects due to poor crystallinity due to contamination, etc., and has excellent squareness ratio and uniformity of thin film. The present invention will be explained below based on examples. Example 1 10 g of high-purity cobalt metal ingot (purity 99.99%) was placed in the crucible 13 of the high-vacuum ion plating vapor deposition apparatus shown in FIG. A magnetic recording medium was prepared by depositing a cobalt thin film layer under the following conditions.

【table】

[Table] Curve A in FIG. 4 shows the measurement results regarding the frequency characteristics of the obtained magnetic recording medium. Regarding the magnetic properties, the coercive force Hc = 720Oe, the residual magnetic velocity density Br = 9300G, and the squareness ratio γ = 0.92. Comparative Example 1 The frequency characteristics of a commercially available thin film magnetic tape with a film thickness of about 2000 Å and mainly made of cobalt produced by vacuum evaporation method were as shown by curve B in FIG.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram for explaining the incident angle in the present invention, FIG. 2 is a sectional view showing an example of the magnetic recording medium of the present invention, and FIG. 3 is an example of an apparatus for manufacturing the magnetic recording medium of the present invention. FIG. 4 is a schematic diagram showing frequency characteristic curves measured in Example 1 and Comparative Example 1. 1... Base material, 2... Direction line indicating the incident direction, 3
...Incidence angle with respect to normal line, 4...First layer ferromagnetic thin film, 5... Second layer ferromagnetic thin film, 6...
...Vacuum chamber, 7...Exhaust port, 8...Supply roll, 9
... Winding roll, 10 ... Ion accelerating electrode, 1
1... Vapor deposition ion source, 12... Steam generation section, 13
... Crucible, 17 ... Steam ionization section, 21-2
5...Power supply.

Claims (1)

[Claims] 1. Injecting ionized evaporated particles of ferromagnetic material onto the surface of a base material made of a non-magnetic material at an incident angle of 40 to 75 degrees with respect to the normal to the surface under high vacuum. On the ferromagnetic thin film formed by
A magnetic recording medium in which a ferromagnetic thin film is formed by bombarding ionized evaporated particles of ferromagnetic material at an incident angle of 80° or more. 2 The thickness of the thin film layer formed at an incident angle of 80° or more with respect to the normal is 1/3 or less of the thickness of the thin film layer formed at an incident angle of 40 to 75°. magnetic recording medium.