JPH0318253B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic recording medium having a multilayered ferromagnetic layer deposited by ion plating under high vacuum.

Conventionally, magnetic recording media have been widely used in which acicular magnetic powder such as iron oxide or chromium oxide or ultrafine powder of ferromagnetic metal is dispersed in a resin binder and coated on a non-magnetic base material. has been used.

However, in recent years, there has been a strong demand for high-density recording of information in magnetic recording media, and various improvements have been made to this end. The particle size of the magnetic powder has a limit as the smallest unit of the recording element, and it is theoretically impossible to increase the recording density beyond this limit. It was difficult to answer.

For this reason, recently, with the aim of dramatically increasing recording density, magnetic layers that do not use resin binders have been developed.
Thin-film (vapor-deposited) magnetic recording media made of 100% ferromagnetic material have been actively researched and developed using thin-film formation methods such as wet plating, vacuum evaporation, sputtering, and ion plating. is 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, in thin-film magnetic recording media formed by wet plating or vacuum deposition, the adhesion strength between the magnetic layer and the base material is extremely low, so during recording and reproduction,
The disadvantage is that the magnetic layer is susceptible to peeling, wear, damage, etc. due to mechanical friction caused by contact scanning with a magnetic head.

Furthermore, thin film magnetic recording media formed by the sputtering method and the conventionally proposed ion plating method improve the adhesion strength between the magnetic layer and the base material, but the adhesion strength is as low as 10 ^-3 Torr or more. Since this method uses direct current glow discharge or high-frequency plasma in a vacuum to form a thin film, the incorporation of residual gas and contamination of impurities may adversely affect the crystallinity of the ferromagnetic thin film layer, resulting in a square shape. There were drawbacks to the magnetic properties, such as a small ratio. Furthermore, it has drawbacks such as variations and non-uniformity in film quality and magnetic properties due to non-uniformity of the discharge state, and these problems still need to be solved as a magnetic recording medium for high-performance, high-density recording. I left a lot of.

The present invention was developed with the aim of solving the drawbacks of thin-film magnetic recording media obtained by the above-mentioned thin-film forming method. A magnetic recording medium having excellent magnetic properties can be obtained by forming a layer and interposing an oxide layer of the ferromagnetic material between a plurality of the ferromagnetic layers to form a multilayer structure. This was done by finding out that
The gist is that ferromagnetic particles are heated and vaporized in a crucible in a vacuum chamber maintained at a high vacuum level of 8 x 10 ^-4 to 1 x 10 ^-8 Torr. Electrons generated from an electron generator are accelerated by an electric field and bombarded to ionize them, and the ionized ferromagnetic particles are accelerated by an electric field and made to collide with a base material made of a non-magnetic material, so that they are ionized onto the base material. A thin film layer of a magnetic non-oxide is formed, and then an oxygen-containing gas is introduced into a vacuum chamber so that the oxygen partial pressure is maintained in the range of 8×10 ^-4 to 1×10 ^-5 Torr, and steam is generated. The ferromagnetic particles and oxygen molecules are ionized by accelerating and impacting electrons generated from an electron generator with an electric field, and the ionized ferromagnetic particles and oxygen molecules are accelerated with an electric field to form the ferromagnetic material. forming an oxide layer of the ferromagnetic material on the non-oxide layer of the ferromagnetic material by bombarding the non-oxide thin film layer of the ferromagnetic material; The formation of the oxide layer is alternately performed to form a deposited layer on the base material with a multilayer structure in which a ferromagnetic oxide layer is interposed between a plurality of ferromagnetic non-oxide thin film layers. A method of manufacturing a magnetic recording medium is provided.

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 sulfone and polyparabanic 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 determined as appropriate depending on the usage method of the magnetic recording medium.
Used in the form of disks, drums, etc.

In addition, in the present invention, iron, cobalt, and nickel can be mentioned as the ferromagnetic material used for vapor deposition on the above-mentioned substrate by the ion plating vapor deposition method, and alloys containing one or more of these may be used. Mixtures of one or more metals with other elements can also be used. However, iron alloys include iron, cobalt, nickel, manganese, chromium,
Alloys with copper, gold, titanium, etc. Cobalt alloys include cobalt and phosphorus, chromium, copper, nickel, manganese, yttrium, samarium, bismuth, etc. Alloys of nickel include nickel and copper, zinc, manganese, etc. Examples include alloys with

In addition, as a mixture of iron, cobalt or nickel and other elements, the other elements may be phosphorus, chromium,
Examples include copper, zinc, gold, titanium, yttrium, samarium, bismuth, etc., and one or more of these other elements may be selectively used.

Hereinafter, a method for manufacturing a magnetic recording medium according to the present invention will be explained with reference to the drawings.

FIG. 1 is a cross-sectional view showing an example of a magnetic recording medium manufactured according to the present invention, in which 1 is a base material made of a non-magnetic material, 2 is a thin film layer of a ferromagnetic non-oxide, and 3 is a sectional view showing an example of a magnetic recording medium manufactured according to the present invention. is a ferromagnetic oxide layer. Although the ferromagnetic oxide layer 3 is provided as the outermost layer in FIG. 1, the non-oxide thin film layer 2 may be the outermost layer.

The thickness of the non-oxide thin film layer 2 is usually
Preferably, the thickness is between 200 and 600 angstroms.
Further, the thickness of the ferromagnetic oxide layer 3 is several tens to
Preferably, the thickness is 300 angstroms.

FIG. 2 is a model diagram showing an example of an apparatus used to manufacture magnetic recording media. It is possible to maintain a high vacuum of up to 1×10 ^-8 Torr by using a diffusion pump (not shown).

Inside the vacuum chamber 5, there are a vapor deposition ion source 7, a film-like base material 8, a supply roll 81, and a take-up roll 82.
(However, a roll drive device is not shown) and an ion accelerating electrode 9 are installed.

The vapor deposition source 7 includes a vapor generating section 10 and a vapor ionizing section 11.

The steam generation section 10 includes an open crucible 101,
It consists of a filament 102 for thermionic emission and a guard 103 for electric field control.

The steam ionization unit 11 includes a filament 111 for emitting thermionic electrons, a mesh electrode 112 for accelerating emitted electrons with an electric field, and a guard 113 for controlling the electric field.
It is composed of. Further, 12 is a device for supplying oxygen into the vacuum chamber 5.

Furthermore, in FIG. 2, power supplies 21 to 25 installed outside the vacuum chamber 4 and their circuits for operating the apparatus are shown.

Next, a second method of manufacturing a magnetic recording medium according to the present invention will be described.
This will be explained with reference to the figures.

First, as shown in FIG. 2, a supply roll 81 on which a non-magnetic base material 8 such as a polyethylene terephthalate film is wound is installed, and the base material 8 is arranged so as to be wound around a take-up roll 82. A ferromagnetic material is supplied into the crucible 101 of the steam generating section 10, and the vapor deposition ion source 7 is configured as shown in FIG.

Next, the vacuum chamber 5 is evacuated to a high vacuum of 8×10 ^-4 to 10 ^-8 Torr (usually 10 ^-5 to 10 ^-6 Torr) from the exhaust port 6 by the exhaust system device, but at this time,
It is preferable to perform unwinding in order to deaerate the adsorbed material present on the surface of the film-like base material 8 and the air drawn into the supply roll 81. When the degree of vacuum is lower than 8 x 10 ^-4 Torr, DC glow discharge occurs due to accelerated electrons, which makes vapor deposition difficult, and residual gas is taken in, which becomes an impurity in the ferromagnetic non-oxide thin film. If mixed into the layer, the crystallinity of the ferromagnetic material decreases, the squareness ratio decreases, and other magnetic properties deteriorate, and conversely, it is almost impossible to increase the degree of vacuum above 10 ^-8 Torr, so 8×10 ^{- Four} ~
Limited to 10 ^-8 tolls.

When the degree of vacuum in the vacuum chamber 5 becomes constant, the power supplies 21 to 25 are turned on.

To heat the crucible 101, the filament 102 is energized and heated by the power source 22 to emit thermoelectrons, and the filament 102 and the guard 102 are heated.
By applying a negative DC voltage to the crucible 101 from the power supply 21 and grounding the crucible 101, the emitted electrons are accelerated by an electric field and the crucible is bombarded and heated.

The evaporation source material in the heated crucible 101 is evaporated at a vapor pressure depending on the heating temperature, and the evaporated particles reach the vapor ionization section 11.

In order to ionize the evaporated particles in the steam ionization section 11, the filament 111 is electrically heated by the power supply 23 to emit thermoelectrons, and a negative DC voltage is applied to the filament 111 and the guard 113 by the power supply 24. By grounding the mesh electrode 112, the emitted thermionic electrons are accelerated by an electric field and collide with the evaporated particles to ionize them. Since the ionized evaporation particle ions are in a positively charged state,
By applying a negative DC voltage to the crucible 101 grounded to the ion accelerating electrode 9 by the power source 25, the ionized evaporated particles are accelerated and given high kinetic energy.

Thus, the evaporated particle ions accelerated by the electric field are
It impinges on the surface of the substrate 8, thereby forming a thin layer of ferromagnetic non-oxide on the substrate.

Next, an oxygen-containing gas, that is, oxygen or a gas containing oxygen, is introduced into the vacuum chamber 5 from the oxygen supply device 12 so that the oxygen partial pressure is maintained in the range of 8×10 ^-4 to 1×10 ^-5 Torr. . In this case, the degree of vacuum within the vacuum chamber 5 is 8×10 ⁻⁴ to 1×10 ⁻⁵ Torr. For example, the pressure inside the vacuum chamber 5 is reduced to 1×10 ^-6 Torr, and oxygen is
When 10 ^-4 Torr is introduced, the degree of vacuum in vacuum chamber 5 is
Since the pressure is 8.01×10 ^-4 Torr, if the initial vacuum level is increased, the oxygen partial pressure and the vacuum level in the vacuum chamber 5 will be virtually the same. Furthermore, when the oxygen partial pressure is lower than 8×10 ^-4 Torr, DC glow discharge occurs due to accelerated electrons, which makes vapor deposition difficult, and residual gas is taken in, which is mixed into the ferromagnetic oxide layer as an impurity. However, the crystallinity of the ferromagnetic material decreases, and the magnetic properties such as the squareness ratio decreases. Conversely, if the temperature exceeds 10 ^-5 Torr, the ferromagnetic material becomes difficult to oxidize, so the oxygen partial pressure is 8× Limited to 10 ^-4 to 1×10 ^-5 torr.

Maintaining the oxygen partial pressure in the vacuum chamber 5 within the above range,
In the same manner as above, the ferromagnetic material is evaporated, the evaporated particles are ionized, accelerated by an electric field, and projected onto the base material 8 on which the non-oxide thin film layer is formed. A ferromagnetic oxide layer is formed on the non-oxide thin film layer.

In the present invention, the formation of the non-oxide thin film layer and the ferromagnetic oxide layer are alternately performed, so that the ferromagnetic oxide layer is interposed between the plurality of non-oxide thin film layers. A vapor-deposited layer having a multilayer structure is formed on the base material 8.

Further, in the above manufacturing method, it is preferable that the electron current for ionizing the evaporated particles is 30 mA or more, from the viewpoint of making the obtained magnetic recording medium more excellent in mechanical properties and magnetic properties. The ion current density due to ionized evaporation particles is 1μA/
For the same reason, it is preferable to set it to cm ² or more. Furthermore, if the accelerated evaporated particle ions are incident obliquely on the substrate, especially at an incident angle of 30° or more with respect to the normal to the substrate, the ferromagnetic thin film that is formed will be , magnetic anisotropy occurs in a specific direction, giving favorable results in terms of magnetic properties.

The manufacturing method of the magnetic recording medium of the present invention is as described above, and since the ferromagnetic non-oxide thin film layer provided on the base material is formed by the ion plating vapor deposition method, the base material of rapidly accelerated ions is Ferromagnetism is formed by ion implantation, which includes sputtering and etching of materials on the surface of the substrate during the collision process, and physical embedding with evaporated particles when sputtered substrate materials re-deposit. The adhesion strength between the non-oxide thin film layer of the body and the base material is increased, and the magnetic recording medium has excellent abrasion resistance and head crush resistance.

Furthermore, since the deposition is carried out in a high vacuum,
Intake of residual gas and contamination of impurities arise from the fact that the DC glow discharge, high-frequency plasma, etc. used for ionization in conventional ion plating must be performed in a low vacuum of less than 10 ^-4 Torr. A uniform magnetic recording medium with improved magnetic properties, especially squareness ratio, can be obtained by eliminating defects in crystallinity and the like.

Furthermore, since the magnetic recording medium obtained in the present invention has a multilayer structure in which a ferromagnetic oxide layer is interposed between a plurality of ferromagnetic non-oxide thin film layers, Among its magnetic properties, it has particularly excellent coercive force and squareness.

Examples of the present invention will be described below.

Example 10 g of high-purity cobalt metal ingot was inserted into a crucible, and two layers of cobalt ferromagnetism were formed on a polyethylene terephthalate base material with a thickness of 15 μm under the following conditions using the high-vacuum ion plating evaporation apparatus shown in Figure 2. A magnetic recording medium having a cobalt oxide layer and two cobalt oxide layers was prepared.

Vacuum conditions Initial vacuum: 2×10 ^-6 Torr Oxygen gas introduction conditions Oxygen gas partial pressure: 1×10 ^-4 Torr Crucible conditions Crucible temperature: 1800°C Crucible material: High purity carbon Cobalt and oxygen molecule ionization conditions Thermionic acceleration Voltage: 300V Ionization current: 50mA Cobalt ion and oxygen ion acceleration conditions Acceleration voltage: -1200V Ion current: 150μA Thin film layer thickness Cobalt layer: approx. 700Å Cobalt oxide layer: approx. 100Å Direct current due to the magnetic properties of the obtained magnetic recording medium When measured with a magnetization measuring device, the coercive force Hc = 6200e (Oersted), the residual magnetic flux density Br = 9500 Gauss, and the squareness ratio γ = 0.95.

Comparative Example 1 10g of high-purity cobalt metal ingot was inserted into a crucible, and cobalt ferromagnetism was deposited on a 10μ-thick polyethylene terephthalate base material under the following conditions using the high-vacuum ion plating vapor deposition apparatus shown in Figure 2. A magnetic recording medium having layers was created.

Vacuum degree conditions Initial vacuum degree: 2 × 10 ^-6 Torr Crucible temperature: 1800℃ Crucible material: High purity carbon Cobalt ionization conditions Thermal electron acceleration voltage: 300V Ionization current: 50mA Cobalt ion acceleration conditions Acceleration voltage: -1200V Ion current : 150 μA The thickness of the cobalt ferromagnetic thin film layer of the obtained magnetic recording medium was repeatedly measured using a reflection interferometry type film thickness measuring device and found to be 1500 Å. Next, the magnetic properties of the magnetic recording medium were measured using a DC magnetization measuring device, and found that the coercive force Hc = 4100e (Oersted), the residual magnetic flux density Br = 7300 Gauss, and the squareness ratio γ = 0.65.

Comparative Example 2 10 g of high-purity cobalt metal ingot was inserted into a crucible, and an initial vacuum condition of 9 x 10 A magnetic recording medium having a cobalt ferromagnetic layer and a cobalt oxide layer was produced in the same manner as in the example except that ^-4 torr was used. Note that the introduction of oxygen gas was carried out after the pressure inside the vacuum chamber was reduced to 1×10 ⁻⁶ Torr.

During the process of forming the cobalt ferromagnetic layer and the cobalt oxide layer, a DC glow discharge occurred near the ion accelerating electrode 9, electrode 112, filament 111, and guard 113 shown in FIG.

The thickness of the cobalt ferromagnetic thin film layer and the cobalt oxide layer of the obtained magnetic recording medium were repeatedly measured using a reflection interferometry type film thickness measuring device.
The cobalt ferromagnetic thin film layer was approximately 1000 Å thick, and the cobalt oxide layer was approximately 100 Å thick. Next, the magnetic properties of the magnetic recording medium were measured using a DC magnetization measuring device, and found that the coercive force Hc = 3000e (Oersted), the residual magnetic flux density Br = 550 Gauss, and the squareness ratio γ = 0.13.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a magnetic recording medium obtained by the manufacturing method of the present invention, and FIG. 2 is a schematic diagram showing an example of an apparatus used in the manufacturing method of the magnetic recording medium of the present invention. 1...Base material, 2...Ferromagnetic non-oxide layer, 3
... Ferromagnetic oxide layer, 4 ... Vacuum chamber, 5 ... Vacuum chamber, 6 ... Exhaust port, 7 ... Vapor deposition ion source, 8 ...
...Film-like base material, 9...Ion accelerating electrode, 10
...Steam generation section, 101 ... Crucible, 102,1
11...Filament for thermionic emission, 103,1
13...guard, 11...steam ionization section, 11
2...Mesh electrode, 12...Oxygen supply device, 21-
25...electrode.

Claims (1)

[Claims] 1 In a vacuum chamber maintained at a high vacuum level of 8×10 ^-4 to 1×10 ^-8 Torr, the ferromagnetic material in the crucible is heated and vaporized to produce an electron generator. The ionized ferromagnetic particles are accelerated by an electric field and bombarded with electrons, and the ionized ferromagnetic particles are accelerated by an electric field and bombarded with a base material made of a non-magnetic material, thereby producing ferromagnetic particles on the base material. A thin film layer of non-oxide is formed, and then the oxygen partial pressure is 8×10 ^-4
Oxygen-containing gas is introduced into the vacuum chamber so as to maintain the pressure within the range of ~1×10 ^-5 Torr, and the vaporized ferromagnetic particles and oxygen molecules are accelerated by electric field accelerating the electrons generated from the electron generator. Ionizes by impact,
By accelerating the ionized ferromagnetic particles and oxygen molecules with an electric field and causing them to collide onto the non-oxide thin film layer of the ferromagnetic material, the ferromagnetic material is deposited on the non-oxide thin film layer of the ferromagnetic material. forming an oxide layer of the ferromagnetic material, and forming the ferromagnetic non-oxide thin film layer and forming the oxide layer alternately to form a layer between the plurality of ferromagnetic non-oxide thin film layers. A method for manufacturing a magnetic recording medium, comprising forming on the base material a deposited layer having a multilayer structure in which a ferromagnetic oxide layer is interposed.