JPS6236285B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing a magnetic recording medium suitable for high-density recording. Recently, with the aim of dramatically increasing recording density, magnetic recording tapes in which a ferromagnetic metal thin film is provided as a magnetic recording layer on a non-magnetic base material without using a resin binder have been developed using wet plating, vacuum evaporation, and sputtering methods. Research and development has been carried out vigorously using thin film formation methods such as the ion plating method and the ion plating method, and some of them have been put into 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. In addition, thin film magnetic recording media formed by sputtering method or ion plating method are
Although the adhesion strength between the magnetic layer and the base material is improved,
Since this method uses direct current glow discharge or high-frequency plasma in a low vacuum with a pressure of 10 ^-3 Torr or more to form a thin film, the ferromagnetic thin film layer may be damaged due to the incorporation of residual gas or the incorporation of impurities. It had drawbacks in magnetic properties, such as a negative effect on crystallinity and a decrease in squareness 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 inventors of the present invention have conducted intensive research to eliminate the drawbacks of thin film magnetic recording media obtained by the conventional thin film forming method and have found a magnetic recording medium with better magnetic performance. It has a structure in which an oxide layer of the ferromagnetic material is interposed between two ferromagnetic thin films whose magnetic easy axes are different from each other and are formed by vapor deposition in a high vacuum of 10 ^-4 Torr or less. The present invention was made possible by discovering that a magnetic recording medium having a magnetic layer has excellent magnetic performance, and the purpose of the present invention is to achieve excellent magnetic properties suitable for high-density recording. It is an object of the present invention to provide a method for manufacturing a magnetic recording medium which has improved recording and reproducing characteristics and can withstand repeated use so that the magnetic layer is not peeled off, abraded or damaged even when running in contact with a magnetic head. That is, the gist of the present invention is that 8×10 ^-4 to 1×
In a vacuum chamber maintained at a high vacuum level of 10 ^-10 Torr, the ferromagnetic material in the crucible is heated and vaporized, and the electrons generated from the electron generator are accelerated by an electric field and subjected to impact. The ionized ferromagnetic particles are accelerated in an electric field and made to collide with a base material made of a non-magnetic material obliquely to the surface of the base material, thereby forming a ferromagnetic thin film layer on the base material. The first step is to form 8×10 ^-4 to 1×
Ferromagnetic gas is vaporized by introducing oxygen-containing gas into the vacuum chamber, which is kept at a high vacuum level of 10 ^-10 Torr, so that the partial pressure of oxygen is kept below 8 x 10 ^-4 Torr. The body particles and oxygen molecules are ionized by being bombarded with electrons generated from an electron generator by accelerating them in an electric field, and the particles and oxygen molecules are accelerated by the electric field and bombarded perpendicularly to the ferromagnetic thin film layer on the base material made of a non-magnetic material. A second step of forming an oxide layer of the ferromagnetic material on the ferromagnetic thin film layer by A ferromagnetic thin film layer is formed by obliquely bombarding the ferromagnetic oxide layer formed in the second step on the base material, but in a step where the bombardment angle is different from that in the first step. A method of manufacturing a magnetic recording medium is characterized by comprising three steps. 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, polyide,
Polymer materials such as polyether sulfon and polyvalabanic 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 is as follows:
It may be determined as appropriate depending on the use of the magnetic recording medium, and is used in the form of a tape, film, disk, drum, etc., for example. Further, in the present invention, the ferromagnetic material used for vapor deposition on the above-mentioned substrate includes iron, cobalt, and nickel, and alloys containing one or more of these metals and one or more of these metals and other elements can be used. A mixture with can also be used. However, alloys of iron include iron, cobalt, nickel, manganese, chromium, copper, gold, titanium, etc.; alloys of cobalt include cobalt and phosphorus, chromium, copper, nickel, manganese, gold, titanium, etc. Yztrium,
Examples of alloys with samarium, bismuth, etc. and alloys of nickel include alloys of nickel with copper, zinc, manganese, etc. 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. The magnetic recording medium manufactured by the present invention and the method for manufacturing the magnetic recording medium of the present invention will be explained below 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 the figure, 1 is a base material made of a non-magnetic material, 2 and 2' are a deposited layer of ferromagnetic metal, and 3 is a ferromagnetic oxide layer.
As shown in FIG. 1, the magnetic recording medium manufactured according to the present invention has a plurality of evaporated layers 2, 2' of ferromagnetic metal deposited on a base material 1 using, for example, ion plating deposition method under high vacuum. The ferromagnetic metal oxide layer 3 is interposed between the ferromagnetic metal vapor deposited layers 2 and 2' to form a multilayer structure, and in FIG. Although the metal vapor deposition layer 2' is provided, an oxide layer may be provided on the metal vapor deposition layer 2' so that the ferromagnetic oxide layer becomes the outermost layer. In the magnetic recording medium manufactured according to the present invention, the ferromagnetic metal deposited layers 2 and 2' have mutually different easy axes of magnetization. In this way, in order to make the easy axis of magnetization different between the metal vapor deposited layers 2 and 2', each metal vapor deposited layer 2 and 2' is formed in the presence of magnetic fields applied in different directions. Although it is possible to form the metal vapor deposition layers 2 and 2', it is preferable that the angles of impact of the ferromagnetic metal particles to be vapor deposited on the substrate surface be oblique and different from each other. This angle of impact is preferably selected from an angle within the range of 40° to 89° with respect to the normal to the surface of the base material. The reason why the ferromagnetic metal vapor deposited layers formed by vapor deposition in diagonal directions with respect to the substrate surface and in mutually different directions have mutually different easy axes of magnetization can be explained in detail. Although it is not clear, as shown in FIG. 2, two ferromagnetic metal vapor deposited layers are formed on the base material 1 with a ferromagnetic metal oxide layer 31 interposed therebetween. The growth directions of the crystal grains 21 and 21' are mutually different based on the difference in the projection angle,
For this reason, it is presumed that the directions of the easy magnetization axes differ between the metal deposited layers. Note that the ferromagnetic metal vapor deposited layer 2 shown in FIG.
The thickness of 2' is 200-3000 angstroms,
The thickness of the oxide layer 3 is preferably 500 to 2000 angstroms, and the thickness of the oxide layer 3 is preferably several tens to 3000 angstroms, particularly 200 to 2000 angstroms. Next, FIG. 3 is a schematic diagram showing an example of the apparatus used in the method of manufacturing a magnetic recording medium of the present invention, in which A shows the first step in the method of the invention, B shows the second step, and FIG. Figure C corresponds to the third step. In FIG. 3, 41, 42, and 43 are vacuum chambers, which are connected to exhaust ports 51, 52, and 53, respectively, and are composed of exhaust system equipment (oil rotary pump, oil diffusion pump, etc., but not shown in the figure). This makes it possible to maintain a high vacuum of up to 1×10 ^-10 Torr. Inside the vacuum chambers 41 and 43 are ion sources 61 and 62 for performing high vacuum ion plating.
are placed respectively. Further, an ion source 63 for performing high vacuum reactive ion plating is arranged in the vacuum chamber 42. The film-like base material 7 made of a non-magnetic material is run by a film-like base material feeding mechanism composed of a supply roll 71, a take-up roll 72, and guide rolls 73, 73. (However, a roll drive device consisting of a motor, gears, etc. is not shown.) Further, in each vacuum chamber, acceleration electrodes 81, 82, 83 are provided facing each ion source via a film-like base material 7.
are arranged, and a negative DC high voltage is applied to these by a power source 84. FIG. 4 shows the structure of the ion sources 61 and 62 shown in FIG. 3 and a power supply circuit arranged outside the vacuum chamber. In the figure, 20 is an electron beam evaporation source,
It consists of a 180° deflection E gun 22, a water-cooled copper hearth 23, and an evaporation source material crucible 24. (However, a power source and the like are not shown.) 25 is a baffle plate for shielding steam, and the steam particles that have advanced as shown in the diagram are ionized in an ionization section 26. The ionization section 26 includes a filament 27 for emitting thermionic electrons, a mesh-shaped electrode 28 for accelerating electrons with an electric field, and a guard 29 for controlling the electric field. A power supply 32 is connected to the filament 27 and the guard 29.
A negative DC high voltage is applied to the filament 27, and an AC current is applied to the filament 27 by a power supply 32 for heating the filament. FIG. 5 shows the structure of the ion source 63 shown in FIG. The ion source 63 has the same structure as the ion source shown in FIG. 4, except that a loop-shaped oxygen introduction tube 34 is provided for performing reactive ion plating. In FIG. 5, the loop-shaped oxygen gas introduction pipe 34
The amount introduced is adjusted by a slow leak valve 35 located between the ionization section 20 and the baffle plate 25 and located outside the vacuum layer. Next, the method for manufacturing the magnetic recording medium of the present invention will be explained with reference to FIGS. 3 to 5. First, as shown in FIG. A supply roll 71 is installed, and the base material 7 is arranged so as to be wound up on a take-up roll 72. Next, in FIG. 3A, the vacuum chamber 41 is evacuated to a high vacuum of 8×10 ^-4 to 10 ^-10 Torr (usually 10 ^-5 Torr to 10 ^-6 Torr) from the exhaust port 51 by the exhaust system device. At this time, it is preferable to unwind the film base material 7 in order to degas the adsorbed material present on the surface of the film base material 7 and the air caught in the supply roll 71. When the degree of vacuum in the vacuum chamber 41 becomes constant,
The ion source 61 is operated to generate ferromagnetic particles and ionize the particles, and the accelerating electrode 81
The ionized ferromagnetic particles are accelerated by an electric field by applying a negative DC high voltage to the base material 7, and obliquely collide with the base material 7 to form a ferromagnetic thin film layer. This is the first step in the present invention. It is. Note that the thin film layer may be formed while the base material 7 is stationary, but in order to continuously manufacture a magnetic recording medium,
It is preferable to move the substrate 7 continuously while rotating the supply roll 71 and the take-up roll 72 at a speed sufficient to deposit a thin film layer of a predetermined thickness. Further, in order to operate the ion source 61 to ionize the ferromagnetic metal particles, the evaporation source material crucible 24 in the electron beam evaporation source 20 is heated to vaporize the ferromagnetic material, as shown in FIG. This can be done by heating and emitting the filament 27 in the ionization section 26 and applying a negative DC voltage to the filament 27 and the guard 29 to bombard the hot electrons accelerated by an electric field. Next, in the second step of the present invention, the apparatus shown in FIGS. 3B and 5 is used to form a ferromagnetic metal oxide layer by vapor deposition using a reactive ion plating technique. In the second step, the vacuum chamber 42 is brought to a high degree of vacuum of 8×10 ^-4 to 1×10 ^-10 Torr in the same way as in the first step, and then the oxygen partial pressure is reduced to 8×10 ^-4 or less. Oxygen is introduced through the oxygen introduction pipe 34 so that the pressure is preferably maintained at 8 x 10 ^-4 to 1 x 10 ^-5 Torr. Then, in the same way as the first step, the ferromagnetic metal is vaporized, oxygen and metal vapor are ionized,
The ferromagnetic oxide layer is formed by accelerating with an electric field and perpendicularly bombarding the thin film layer formed in the first step. Next, in the third step, on the ferromagnetic oxide layer formed in the second step,
In the same manner as in the first step, a ferromagnetic thin film layer is formed by accelerating ionized ferromagnetic particles with an electric field and causing them to collide obliquely. Thus, the ferromagnetic thin film layers obtained in the first and third steps have different axes of easy magnetization. In the present invention, the first, second,
The third step may be performed continuously using an apparatus as shown in FIG. 3, or a batch method may be adopted in which the first to third steps are performed sequentially using one vacuum chamber. good. In addition, the angle of oblique impact in the first and third steps is from 40° to 89° with respect to the normal to the base material surface.
It is preferable to adopt an angle in the range of .degree. from the viewpoint of performance of the resulting magnetic recording medium. In addition, in order to make the impact angles different in the first and third steps, the impact angle with respect to the normal line of the base material surface should be varied greatly within the range of 40° to 89°, and the specificity of the base material should be changed. In order to obtain excellent magnetic properties, especially initial magnetization properties, it is preferable that the direction, for example, the direction of impact (beam direction) with respect to the traveling direction, is also different from each other. The magnetic recording medium of the present invention has the above-mentioned structure, and in particular has a multilayer structure in which a ferromagnetic oxide layer is interposed between a plurality of ferromagnetic metal vapor deposited layers. Therefore, it has excellent magnetic properties, especially in terms of coercive force and squareness ratio.Furthermore, since the ferromagnetic metal layers have mutually different axes of easy magnetization, it has excellent magnetic properties, especially initial magnetization properties. Therefore, when used as a recording medium, the bias current can be extremely small without impairing the magnetic properties suitable for high-density recording.
If the sensitivity of recording and playback is also improved, excellent effects can be produced. Furthermore, according to the manufacturing method of the present invention, in addition to being able to manufacture magnetic recording media with the above-mentioned excellent performance with relatively simple operations, the adhesion strength between the formed metal vapor layer and the base material is increased. This has the effect of making it possible to obtain a recording medium with excellent wear resistance and head crushing resistance.Furthermore, since the deposition is performed in a high vacuum, it cannot be ionized using conventional ion plating. The DC glow discharge, high-frequency plasma, etc. used for this process must be performed in a low vacuum of 10 ^-3 Torr or higher, which eliminates the problems such as residual gas incorporation, impurity contamination, and poor crystallinity. Due to magnetic properties,
In particular, a uniform magnetic recording medium with improved squareness ratio can be obtained. Examples of the present invention will be described below. Example 1 Using an apparatus similar to that shown in FIG.
Under the conditions shown in the table, thickness: 15 microns, width: 300 mm
Three vapor deposition layers, a cobalt layer, a cobalt oxide layer, and a cobalt layer, were formed on a polyethylene phthalate film base material. The film was fed at a speed of 100 mm/min.

[Table] Note that the incident angle in the beam incidence conditions means the incident angle with respect to the normal to the surface of the base material, and in the formation of the first magnetic layer, from a direction perpendicular to the film feeding direction, In the formation of the oxide layer, from directly below the film surface, and in the formation of the second magnetic layer, from the direction parallel to the plane perpendicular to the film surface including the line drawn in the film feeding direction, as shown in Table 1. The ion particles were made incident at an angle of incidence of In the magnetic recording medium thus obtained, the directions of the easy magnetization axes of the first magnetic layer and the second magnetic layer are different from each other, and when the magnetization curve of the recording medium was examined, it was shown in FIG. The initial magnetization characteristic (O-A curve) is similar to the initial magnetization curve of a commercially available thin film magnetic tape (having a composite deposited layer of cobalt layer and nickel layer) shown in FIG. It was observed that the linearity was improved compared to the magnetization characteristics (O-B curve), and the slope was also increased.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of a magnetic recording medium manufactured according to the present invention, FIG. 2 is a schematic diagram showing the direction of crystal grains of the ferromagnetic metal deposited layer in the magnetic recording medium of the present invention, and FIG. 4 is a structural diagram showing the structure of the ion sources 61 and 62 in FIGS. 3A and 3C, and FIG. 5 is a diagram showing the structure of the ion sources 61 and 62 in FIGS. 6 shows the magnetization curve of the magnetic recording medium obtained in Example 1, and FIG. 7 shows the magnetic curve of the commercially available thin film magnetic tape. DESCRIPTION OF SYMBOLS 1... Base material, 2, 2'... Vapor deposited layer of ferromagnetic metal, 3, 31... Oxide layer of ferromagnetic metal, 2
1, 21'... Crystal grain in ferromagnetic metal vapor deposited layer, 41, 42, 43... Vacuum chamber, 51, 52,
53... Exhaust port, 61, 62, 63... Ion source, 7... Film-like base material, 81, 82, 83...
...Accelerating electrode, 20...Electron beam evaporation source, 24...
...Evaporation source material crucible, 26...Ionization section, 3
2, 33...Power supply, 34...Oxygen introduction tube.

Claims (1)

[Claims] A ferromagnetic material obtained by heating and vaporizing a ferromagnetic material in a crucible in a vacuum chamber maintained at a high vacuum level of 18×10 ^-4 to 1×10 ^-10 Torr. Particles are ionized by accelerating and impacting electrons generated from an electron generator with an electric field, and the ionized ferromagnetic particles are accelerated with an electric field and applied to a base material made of a non-magnetic material against the surface of the base material. The first step is to form a ferromagnetic thin film layer on the base material by colliding it diagonally, and the partial pressure of oxygen is maintained in a vacuum chamber maintained at a high vacuum level of 8 × 10 ^-4 to 1 × 10 ^-10 Torr. Oxygen-containing gas is introduced into the vacuum chamber so that the pressure is maintained at 8×10 ^-4 Torr or less, and the vaporized ferromagnetic particles and oxygen molecules are accelerated by an electric field, which accelerates the electrons generated from the electron generator. The ferromagnetic thin film layer is ionized by impacting the ferromagnetic thin film layer on the ferromagnetic thin film layer by accelerating it in an electric field and colliding perpendicularly to the ferromagnetic thin film layer on the base material made of a non-magnetic material. A second step of forming
Ferromagnetic particles ionized in the same manner as in the first step are accelerated by an electric field and are obliquely projected onto the ferromagnetic oxide layer formed in the second step on the base material made of non-magnetic material. 1. A method for manufacturing a magnetic recording medium, comprising a third step in which a ferromagnetic thin film layer is formed, but the angle of impact is different from that in the first step. 2. The method for manufacturing a magnetic recording medium according to item 1, wherein the impact angle in the first step and the third step is in the range of 40° to 89° with respect to the normal to the surface of the substrate. 3. The method for manufacturing a magnetic recording medium according to item 1 or 2, wherein the ferromagnetic thin film layer is formed by an ion plating method.