JPS6037531B2 - Method for manufacturing magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a magnetic recording medium that has excellent short wavelength recording characteristics because the residual magnetization is oriented in the normal direction of the surface of the medium.

FIG. 1 is a diagram illustrating a conventional general magnetic recording and reproducing system.

Reference numeral 1 denotes a magnetic recording medium, which is composed of a non-magnetic substrate 2 and a magnetic layer 3 formed on the non-magnetic substrate 2 and having an axis of easy magnetization in the horizontal direction (in the direction of the arrow in the figure).

4 is a ring-shaped head for recording (reproduction), and excitation winding 5
When a signal current flows through the magnetic layer 3, the magnetic layer 3 is magnetized in a direction parallel to the film surface as shown by the arrow in the figure, and a signal is recorded.

In this method, the direction of residual magnetization is horizontal to the film surface, so when the signal has a short wavelength, the demagnetizing field within the medium increases and the reproduction output decreases significantly. On the other hand, according to a recording/reproducing method in which the residual magnetization is oriented perpendicularly to the film surface of the medium (hereinafter referred to as a perpendicular recording method), short wavelength recording characteristics are significantly improved.

As shown in FIG. 2, this is a magnetic recording medium 6 in which a magnetic thin film 7 (hereinafter referred to as a perpendicular magnetization film) having an axis of easy magnetization in the vertical direction (in the direction of the arrow in the figure) is formed on a non-magnetic substrate 2. A signal is recorded on a perpendicular recording medium (hereinafter referred to as a perpendicular recording medium) by a perpendicular head 9 made of a ferromagnetic thin film 8 having an excitation winding 5. In this method, the residual magnetization of the medium on which the signal is recorded is in the direction perpendicular to the film surface of the medium, so that the shorter the wavelength of the signal, the smaller the demagnetizing field within the medium, and excellent reproduction output can be obtained. The perpendicular magnetization film 7 of the perpendicular recording medium 6 currently in use is a metal thin film made by sputtering and mainly containing Co and Cr.

A sputter film mainly composed of Co and Cr has a base of about 3 Cr.
In the range of 0% by weight or less, the crystal system is a steel-tight structure,
Since the C axis can be oriented perpendicularly to the film surface and the saturation magnetization can be lowered until the perpendicular anisotropic magnetic field becomes larger than the demagnetizing field, a perpendicularly magnetized film can be realized. According to experiments, the amount of Cr required for a Co-Cr thin film to become a perpendicularly magnetized film is approximately 10 to 25% by weight.
is within the range of However, since the sputtering method has a slow rate of forming a magnetic thin film, it is difficult to produce perpendicular magnetization at high speed and at low cost.

The present invention provides a manufacturing method in which the formation speed of a magnetic thin film is fast and a vertical rudder film can be formed without significantly increasing the substrate temperature.

The basic configuration of the vacuum evaporation system is shown in Figure 3.

2 is a recording medium substrate, 1 is an evaporation source, 11 is a thin film material, 1
2 is a heating device, and 13 is a vacuum container.

In order for a thin film mainly composed of Co and Cr to be a perpendicularly magnetized film, the crystal system of the thin film must have a dense 60,000 structure and the C axis must be oriented perpendicular to the film surface. The Co-Cr thin film made by vacuum evaporation equipment having the above structure is Cr
When the amount of C is less than 3% by weight, the crystal system has a steel-tight hexagonal structure, but when the substrate temperature during vapor deposition is less than 40,000, C
There is almost no orientation of the axis, and in the case of 40,000 or more, orientation of the C axis is observed, although not completely.

C actually created at a substrate temperature of 2000 and 50000
The X-ray diffraction patterns of the o-Cr deposited film are shown in FIGS. 4 and 5, respectively. 14, 15, and 16 are reflections from the 101,002, and 100 planes of the steel-tight hexagonal structure crystal, respectively.

From this diffraction pattern, when the substrate temperature is 2000, Co-C
It can be seen that the r vapor deposition thickness is almost non-oriented, and at 50,000, the C axis is oriented perpendicularly to the film surface. However, 500
There are only a limited number of substrates that can withstand temperatures of about 0.000 C, and in particular, it is impossible to use substrates made of polymeric materials.
This means that perpendicular recording media, such as current magnetic tapes, cannot be produced using a simple vacuum deposition method. In the present invention, substrates made of polymeric materials can also be used.
It is also a manufacturing method that can form a thin film at a high rate, and this will be explained below.

From the substrate temperature dependence of the C-axis orientation of Co-Cr thin films obtained by vacuum evaporation, it is necessary to increase the mobility of evaporated atoms on the substrate surface in order to promote C-axis orientation. It is expected to be. Also in the sputtering method,
Since sputtered atoms have a kinetic energy that is approximately one order of magnitude larger than that of evaporated atoms, the mobility of sputtered atoms on the substrate surface is considered to be large, promoting C-axis alignment. In order to increase the mobility of evaporated atoms on the substrate surface in a vacuum evaporation method, the evaporated atoms may be brought into a discharge state.

In the present invention, by bringing the evaporated atoms into a discharge state in the vacuum evaporation method, Co
The present invention provides a means for forming a magnetic film containing Cr and Cr as main components. The present invention will be explained below using FIGS. 6 to 12. The basic configuration of the present invention is shown in FIG. Reference numeral 17 is an evaporation source for heating the thin film material 11 from the filtration beam 2, 18 is a steel hearth, 19 is an electron gun for generating an electron beam 20, and the substrate 2 is placed above the evaporation source 17. ing.

The thin film material 11 is heated and evaporated by the two electron beams, but when the power supplied to the electron gun 19 exceeds a suitable value, the evaporated atoms enter a discharge state. To check whether the evaporated atoms are in a discharge state, place the probe 21 between the substrate 2 and the evaporation source 17 as shown in FIG. 7, apply a voltage to it, and measure the flowing current. Bye. Figure 7 22, 23, 2
4 are a variable DC power supply, a DC voltmeter, and a DC ammeter, respectively. In the device used in the experiment, the relationship between the voltage and current applied to the probe 21 is as shown in Figure 8, and when the crab force supplied to the electron gun is W (curve 25) and 10 KW (curve 26), The current that flows is small, but when the power reaches 16 KW (curve 27), the current suddenly increases. A curve 28 in FIG. 9 shows the relationship between the electric power supplied to the electron gun and the current flowing through the probe 21 when the voltage applied to the probe 21 is 5 V. When the electric power exceeds 14 KW, the current increases rapidly. This indicates that the evaporated atoms are in a discharge state. However, the degree of vacuum in the vacuum evaporation system was 5×10-5 Ton, and the electric power supplied to the electron gun had a constant voltage of 10 KV and a variable current. The power required to reach the discharge state varies depending on the degree of vacuum, the structure of the evaporation source, etc. However, in the evaporation source having the structure shown in FIG. 6, although it could enter a discharge state at a power of 14 KW or more, it was unstable. Therefore, when the evaporation source was improved as shown in FIG. 10, a stable discharge state was obtained at a power of more than 10 W (voltage constant 10 KV, current 0.3 A or more). However, 29 in FIG. 10 is a heat-resistant insulator such as magnesia or zirconia, which insulates the thin film material IH in the evaporation source 17 from any other part except when the electron gun 19 is activated. (The electron gun 19 operates and the electron beam
When the beam 20 is being generated, the electron gun 19 and the thin film material 11
is in the inducing state). Next, a description will be given of Co--Cr thin films obtained when the evaporated atoms are in a discharge state (in the present invention) and when they are not.

Using an evaporation source as shown in Figure 10, an electron gun was used under the conditions that the degree of vacuum was 5 x 10-5 Torr, the substrate was a heat-resistant polymer substrate, the substrate temperature was room temperature, and the distance between the substrate and the evaporation source was about 20 mm. 3. When a Co-Cr thin film is created by discharging the evaporated atoms under a low voltage (voltage of 10 KV, current of 0.3 kW) (with the vacuum evaporation layer used in the experiment, the thin film formation rate is approximately 2000 A/sec). ), the X-ray diffraction pattern and hysteresis curve of the obtained Co-Cr thin film (the amount of Cr was about 1% by weight) were
It looked like Figure 12. The X-ray diffraction pattern in Figure 11 is 0
It can be seen that the reflection from only the 02 plane is shown, and the C axis is oriented perpendicular to the film surface. Furthermore, the hysteresis curve in FIG. 12 shows that the axis of easy magnetization is perpendicular to the film surface, and it can be seen that the Co--Cr thin film obtained by the method of the present invention is a perpendicularly magnetized film. However, 30 is a hysteresis curve when a magnetic field is applied perpendicular to the membrane surface, 31 is a hysteresis curve when a magnetic field is applied within the face, and 30 is a hysteresis curve in which demagnetizing field correction is not performed. On the other hand, the power supplied to the electron gun is 2. Song W (voltage loK
V, current o. A Co--Cr thin film prepared under the same conditions as above except that the evaporated atoms were not in a discharge state was almost unoriented and showed an X-ray diffraction pattern similar to that shown in FIG. 4.

As described above, according to the method of the present invention, a Co-Cr perpendicular magnetization film similar to the sputtering method can be obtained using the vacuum evaporation method, but the difference between the sputtering method and the method of the present invention is the thin film formation speed. Formation rates of several thousand A/sec are possible with the method of the present invention, compared to several A/sec of the battering method.

Furthermore, since the method of the present invention uses a substrate made of a polymer material, it is possible to provide a perpendicular recording medium with extremely high productivity. Evaporating Co and Cr from separate evaporation sources 2
In the case of the original evaporation method, an evaporation source using an electron beam may be used for both, but an electron beam is used only for the Co evaporation source, and a resistance heating or high frequency heating evaporation source is used for the Cr evaporation source. However, if power is supplied to the electron gun of the Co evaporation source at a level that causes the evaporated atoms to be in a discharge state, vertical magnetization can be obtained.

As described above, according to the method of the present invention, a perpendicularly magnetized film having excellent high-density field characteristics can be stably obtained on a substrate made of a polymeric material at a high formation rate of several thousand A/sec. Brief explanation of the drawings Figure 1 is a diagram for explaining the magnetic recording and reproducing method of the secondary column, Figure 2 is a diagram for explaining the perpendicular recording method, and Figure 3 is a diagram for explaining the vacuum evaporation method. , Figure 4 shows a Co-Cr thin film obtained by vacuum evaporation (substrate temperature 20q○).
), FIG. 5 is a diagram showing the X-ray diffraction pattern of a Co-Cr thin film obtained by vacuum evaporation (substrate temperature 500 oo), and FIG. FIG. 7 is a diagram showing an example, and FIG. 7 is a diagram showing a measurement method for detecting the operating state of the same manufacturing equipment, and FIGS.
Figure 10 shows an example of the evaporation source according to the present invention, and Figure 11 shows an X-ray diffraction pattern of a Co-Cr thin film produced according to the present invention. 12 are diagrams showing hysteresis curves of the same Co--Cr thin film.

2... Media substrate, 11... Thin film material,
13... Vacuum container, 17... Evaporation source,
18...Water-cooled steel hearth, 19...Electron gun,
20... Electron beam, 29... Heat resistant insulator.

Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12

Claims (1)

[Claims] 1. When forming a magnetic layer mainly composed of Co and Cr on a substrate by vacuum evaporation, at least one evaporation source that heats a thin film material with an electron beam is used as an evaporation source. death,
A method for manufacturing a magnetic recording medium, characterized in that the electric power supplied to the electron gun that generates the electron beam during the formation of the magnetic layer is of a magnitude that causes the evaporated electrons to be in a discharge state. 2. The magnetic recording according to claim 1, characterized in that an evaporation source is used in which the thin film material in the evaporation source is insulated from any other parts except when the electron gun is activated. Method of manufacturing media.