JPH1064061A - Production of magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reproducing output with short wavelengths in a magnetic recording layer by introducing water vapor into a vacuum vapor deposition atmosphere and causing the reaction of metal vapor with water vapor to form a metal magnetic thin film. SOLUTION: A Co metal is used as a vapor deposition source in a hearth 7, the atmosphere is maintained 10<-3> Pa order vacuum degree and a cooling can 2 is maintained at -20 deg.C. A nonmagnetic supporting body comprising a PET film is released from a supply roll 1. The position and angle of a shielding plate 8 are patrolled so that the oblique vapor deposition angle ranges 90 to 45 deg. to the longitudinal direction of the nonmagnetic supporting body. The output of an electron gun 4 is controlled to obtain 20nm thickness of a metal magnetic thin film. After vapor deposition, the nonmagnetic supporting body after vapor deposition and wound on a take-up roll 3 is taken out from the vacuum chamber 9, and a back coating layer is applied on the opposite surface of the supporting body to the surface where the magnetic thin film is formed. Then the film is subjected to rust preventing treatment and application of a lubricant, and the film is cut into proper width and assembled in a cassette to obtain a magnetic recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium in which a metal-based magnetic thin film is formed on a non-magnetic support, and more particularly, to improved magnetostatic properties and electromagnetic conversion properties at short wavelengths. And a method of manufacturing a thin-film magnetic recording medium.

[0002]

2. Description of the Related Art In the field of information recording by magnetic recording, the amount of information to be recorded is increased, the size of a magnetic recording device is reduced,
Alternatively, high-density recording has been demanded in view of trends such as a reduction in the relative speed between the magnetic recording medium and the magnetic head. Along with this, instead of a coating type magnetic recording medium in which magnetic particles are dispersed in an organic binder also in a magnetic recording medium, a metal-based magnetic thin film is formed by plating or a vacuum thin film forming technique, that is, vacuum evaporation, sputtering or ion plating. Thin-film magnetic recording media for film formation are becoming mainstream. Among them, a thin-film magnetic recording medium employing a metal-based magnetic thin film is known to be excellent in various magnetostatic characteristics such as coercive force, squareness ratio, and residual magnetic flux density. Further, since it is not necessary to mix a non-magnetic organic binder in the magnetic layer as in the case of the coating type magnetic recording medium, it is possible to reduce the thickness of the magnetic layer for obtaining the required amount of magnetic flux. Is small, so that it also has excellent electromagnetic conversion characteristics in the short wavelength region from this aspect.

In a thin-film magnetic recording medium used for a helical scan video tape recorder (VTR), a digital audio tape recorder (DAT), or the like,
In order to increase the magnetic anisotropy in the longitudinal direction of the tape and achieve higher output at shorter wavelengths, a thin film type magnetic recording medium by oblique deposition has been proposed and put to practical use. In the oblique deposition, a magnetic layer is formed on a non-magnetic support made of a polymer material such as polyester that moves and travels by electron beam deposition or the like oblique to the traveling direction. In a thin film type magnetic recording medium formed by oblique evaporation, magnetic particles are obliquely oriented with respect to the surface of the nonmagnetic support in the fine structure. Therefore, high-density recording is possible as compared with a conventional magnetic tape in which magnetic particles are uniaxially oriented in the longitudinal direction of the plane of the nonmagnetic support. The axis of easy magnetization of a thin-film magnetic recording medium formed by oblique vapor deposition that is currently in practical use is generally inclined at about 20 ° with respect to the surface of the nonmagnetic support.

In a thin film type magnetic recording medium formed by oblique evaporation, Co or Co- is generally used as a metal-based magnetic thin film material.
Ni alloy system is adopted. To form these metal-based magnetic thin films on a non-magnetic support, a moving non-magnetic support is used while introducing a small and fixed amount of oxygen gas into a vapor deposition apparatus using Co or a Co-Ni alloy as an evaporation source. A manufacturing method in which oblique deposition is performed on a body is common. By this oblique deposition process, the metal-based magnetic thin film is formed by combining α-Co (or Co-Ni) magnetic particles with Co-O (or Co-
-Ni-O). The reason for introducing oxygen into the metal-based magnetic thin film is to reduce the medium noise by reducing the size of the magnetic particles, and to increase the oblique shape anisotropy by forming the metal-based magnetic thin film into a columnar structure. It is. In addition to the oblique deposition, Co or Co-Ni
There is a method of forming a metal-based magnetic thin film by a sputtering method using an alloy as a target.

[0005]

In the field of VTRs and the like, in which a metal-based magnetic thin film formed by oblique deposition or the like is used as a magnetic recording medium, there is a strong demand for high-band recording and digital recording, and higher density recording is required. For the purpose of recording, it is desired to further reduce the size and weight of the magnetic recording medium while increasing the capacity of the magnetic recording medium. For this purpose, it is necessary to develop a magnetic recording medium capable of recording at a shorter wavelength than the current shortest recording wavelength. However, as the recording wavelength becomes shorter, the recorded magnetization pattern is more likely to self-demagnetize, and the apparent residual magnetization becomes smaller. As a result, a satisfactory reproduction output cannot be obtained.

As one of means for increasing the reproduction output at a short wavelength, the coercive force Hc of the magnetic recording medium and the saturation magnetization Φr
It is effective to increase the energy product represented by the product of By increasing the energy product, a magnetization pattern that can oppose the self-demagnetizing field can be formed in the magnetic recording layer.
However, in the conventional vacuum thin film forming technology by introducing oxygen gas, there is a feeling that the improvement of the energy product has been thoroughly studied, and a dramatic improvement of the energy product for further improvement of the recording density cannot be expected. Therefore, an object of the present invention is to provide a new method of manufacturing a thin-film magnetic recording medium capable of increasing the energy product of a magnetic recording layer, improving the reproduction output at a short wavelength, and enabling higher density recording.

[0007]

SUMMARY OF THE INVENTION A method for manufacturing a magnetic recording medium according to the present invention is proposed to achieve the above-mentioned object, and comprises a metal-based material formed on a non-magnetic support by a vacuum deposition method. A method of manufacturing a magnetic recording medium having a magnetic thin film is characterized in that a metal-based magnetic thin film is formed by introducing water vapor into the vacuum deposition atmosphere and reacting the metal vapor with the water vapor.

Another method of manufacturing a magnetic recording medium according to the present invention is a method of manufacturing a magnetic recording medium having a metal-based magnetic thin film formed on a non-magnetic support by a sputtering method. And reacting the sputtered metal particles with water vapor to form a metal-based magnetic thin film.

In any of the methods for manufacturing a magnetic recording medium, it is preferable to introduce water vapor alone, not as a mixed gas with another carrier gas or oxygen gas.

In any of the methods for manufacturing a magnetic recording medium, the metal-based magnetic thin film is preferably a magnetic thin film mainly composed of cobalt (Co). That is, Co simple metal, Co-Ni-based alloy, Co-Ni Pt-based alloy,
Co-Cr alloy, Co-Cr-Ta alloy, Co-C
Co-based alloys such as r-Pt-based alloys are preferably exemplified.

The non-magnetic support employed in the present invention includes:
In addition to polyester resins such as PET (Polyethyleneterephthalate), organic polymers such as polyolefin resins, vinyl resins, polyimide resins, polyamide resins and polycarbonate resins, aluminum-based metals, glasses and ceramics can be used.

As a prior application similar to the present invention, a method of vacuum-depositing a metal-based magnetic thin film in a mixed gas of water vapor and oxygen is disclosed in JP-A-1-294222, and a mixed gas of water vapor and a rare gas is disclosed. A method of sputtering a metal-based magnetic thin film therein is disclosed in JP-A-3-8120. However, none of these aims to improve the energy product.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. First, an example of a vacuum deposition apparatus employed in the method for manufacturing a magnetic recording medium of the present invention will be described with reference to a schematic sectional view shown in FIG.

The vacuum deposition apparatus shown in FIG. 1 is a reel-to-reel type vacuum deposition apparatus. That is, a supply roll 1 for supplying a non-magnetic support such as a PET film, and a cooling can which rotates in synchronization with the running of the non-magnetic support are provided in a vacuum chamber 9 whose inside is evacuated by a vacuum pump (not shown). 2. A take-up roll 3 for winding a non-magnetic support on which a metal-based magnetic thin film is deposited is provided. On the other hand, the vacuum evaporation means deflects and scans the electron beam 5 generated by the electron gun 4 by a magnet 6, irradiates the electron beam to a ferromagnetic metal such as Co in a hearth 7, and dissolves and evaporates this. It is. In order to regulate the oblique evaporation angle, a shielding plate 8 and the like are provided near the cooling can 2. An automatic supply device (not shown) for supplying pellets and wires of ferromagnetic metal such as Co is provided in the hearth 7, and the liquid level of the molten metal accompanying evaporation can be kept at a constant level.

The features of the vacuum deposition apparatus shown in FIG.
H ₂ O for supplying H ₂ O (water vapor) into the vacuum chamber 9
The nozzle 10. In the example of FIG. 1, the opening of the H ₂ O nozzle 10 is located near the shielding plate 8, that is, near the position where the deposition of the ferromagnetic metal thin film on the nonmagnetic support is completed.
This position is a preferable opening position of the H ₂ O nozzle 10, but may be provided at any position in the vacuum chamber 9 other than this example. The H ₂ O nozzle 10 has an H ₂ O valve 11
The H ₂ O pipe 12 is connected via the. This H ₂ O
FIG. 2 shows an enlarged sectional view of an example of the valve 11.

The H ₂ O valve 11 shown in FIG. 2 is a needle valve. For example, the flow rate of distilled water or pure water supplied through an H ₂ O pipe 12 made of a metal such as stainless steel having an inner diameter of 3.0 mm. Is arbitrarily controlled. Distilled water or pure water is supplied to the H ₂ O pipe 12 at a pressure of, for example, 2 kg / cm ² . The H ₂ O pipe 12 and the H ₂ O valve 11 have a heating mechanism such as a coil heater or a ribbon heater (not shown) in order to prevent dew condensation or icing due to latent heat of vaporization of distilled water or pure water. The means for supplying H ₂ O (steam) is not limited to this example, but may be a general heating bubbling method, a method of directly supplying by steam piping, or the like.
Any method may be selected.

Hereinafter, a preferred example of manufacturing the magnetic recording medium of the present invention using the vacuum deposition apparatus shown in FIG. 1 will be described. Example 1 In this example, a magnetic recording medium was manufactured under the condition that H ₂ O was introduced at a rate of 10 g per minute. Pure Co metal is used for the evaporation source in the hearth 7, and the degree of vacuum at the time of evaporation is 10 ^-3.
The temperature was maintained at −20 ° C. on the Pa basis. The feed speed of the non-magnetic support made of, for example, a 30 cm wide PET film from the supply roll 1 is 25 m / min, and the oblique deposition angle is 90 to the longitudinal direction of the non-magnetic support.
The position and angle of the shielding plate 8 were set so as to be in the range of 45 ° to 45 °. At this time, the thickness of the metal-based magnetic thin film is 20
The output of the electron gun 4 was controlled to be 0 nm.

After the deposition of the metal-based magnetic thin film is completed, the deposited non-magnetic support wound around the take-up roll 3 is taken out of the vacuum chamber 9 and a back coat layer comprising a known antistatic agent and a binder is removed. It is applied to the opposite side of the metal-based magnetic thin film formation surface. Next, this is also subjected to a known rust prevention treatment and lubricant application, slit into, for example, 8 mm width, and then assembled into a cassette to complete the magnetic recording medium of Example 1. FIG. 3 shows this series of flows.

[0019] Examples 2 to 5 the previous Example 1 is an example of producing a magnetic recording medium according to the conditions every minute 10g introducing H ₂ O, the H ₂ O introduced amount per minute 20 g, 40 g , 60 g and 80 g, and the magnetic recording media of Examples 2 to 5 were manufactured under the same deposition conditions as in Example 1.

The magnetic characteristics and electromagnetic conversion characteristics of the magnetic recording media of the examples manufactured as described above were measured.
The magnetic properties were determined by measuring the coercive force Hc and the residual magnetic flux Φr from the magnetic properties in the longitudinal direction of the surface of the magnetic recording medium using a sample vibration type magnetometer, and calculating the energy product Hc × Φr. The electromagnetic conversion characteristics are based on Sony high-band 8mm VTR (EV-
Using a modified measurement VTR (S900), a sine wave having a recording frequency of 7.0 MHz was recorded at a relative speed of 3.8 m / sec between the magnetic recording medium and the magnetic head, and the reproduction output was measured. The recording current was set to a value at which the highest reproduction output was obtained for each magnetic recording medium.

The measurement results of the magnetic recording media of Examples 1 to 5 are summarized in Table 1 below.

[0022]

[Table 1]

FIG. 4 is a graph showing the relationship between the amount of H ₂ O introduced and the energy product of each of the magnetic recording media of Examples 1 to 5. From Table 1 and FIG. 4, the amount of H ₂ O introduced was 40 g.
/ Min maximum energy product at 7.3 kA / m · nWb
It can be seen that the reproduction output also shows the maximum value.

Comparative Examples 1 to 5 The same as in Example 1 except that oxygen was introduced instead of steam.
In the same manner as in the above, magnetic recording media of Comparative Examples 1 to 5 were manufactured. The amount of oxygen introduced was from 0.4 l / min to 0.8 l / min for each comparative example. The magnetic characteristics and the electromagnetic conversion characteristics of the magnetic recording media of Comparative Examples 1 to 5 were measured under the same conditions as in the previous example. The measurement results are shown in [Table 2].

[0025]

[Table 2]

FIG. 5 is a graph showing the relationship between the amount of oxygen introduced and the energy product of the magnetic recording media of Comparative Examples 1 to 5.
From Table 2 and FIG. 5, it can be seen that the energy product shows 6.1 kA / m · nWb when the oxygen introduction rate is 0.6 l / min, and the reproduction output also shows the maximum value. However, it is clear that none of these maximums is far below the maximum in the example. Examples 1 to 5 and Comparative Examples 1 to 5
FIG. 6 shows the relationship between the energy product of each magnetic recording medium and the reproduction output. FIG. 6 shows that the energy product and the reproduction output have a substantially linear correlation, and that the magnetic recording medium of the embodiment into which water vapor is introduced has a larger energy product and reproduction output than the magnetic recording medium into which oxygen of the comparative example is introduced. It is shown that it is possible to obtain.

[0027] Comparative Example 6 in place of the method introduced alone Comparative Example 10 water vapor, magnetic recording before except that introducing a mixed gas of water vapor and oxygen Example 1 compared in the same manner as in Example 6 to Comparative Example 10 The media was manufactured. In each comparative example, the amount of introduced steam was 5 g / min to 40 g / min, and the amount of introduced oxygen was 0.2 l / min to 0.4 l / min. The magnetic characteristics and the electromagnetic conversion characteristics of the magnetic recording media of Comparative Examples 6 to 10 were measured under the same conditions as in the previous example. The measurement results are shown in [Table 3].

[0028]

[Table 3]

From the results shown in Table 3, the amount of introduced steam was 20%.
It can be seen that the energy product is 6.7 kA / m · nwb when a mixed gas of g / min and an oxygen introduction amount of 0.3 l / min is introduced, and the reproduction output also shows the maximum value. However,
Obviously, none of these maximum values fall below the maximum value of the embodiment.

As described above, the magnetic recording medium of the present invention has been described in detail with reference to five examples and ten comparative examples. However, the present invention can have various embodiments other than these examples. For example, pure Co as a metallic magnetic thin film
Although the case where a metal is vapor-deposited is shown, similar good results can be obtained by using various Co alloys or other ferromagnetic metals as described above. Good results can also be obtained when the present invention is applied to a perpendicular magnetic recording medium utilizing perpendicular magnetic anisotropy such as a Co-Cr alloy.

In the embodiment, a method for manufacturing a magnetic recording medium by vapor deposition has been exemplified, but a sputtering method or an ion plating method may be used. The present invention can also be suitably implemented when a hard disk type high-density magnetic recording medium is manufactured using, for example, an Al-based metal or the like as the nonmagnetic support.

[0032]

As is apparent from the above description, by employing the method for manufacturing a magnetic recording medium of the present invention, the energy product of the magnetic recording layer can be increased as compared with the magnetic recording medium manufactured by the conventional manufacturing method. As a result, the reproduction output in the short wavelength region can be improved, and it is possible to stably provide a next-generation high-density magnetic recording medium directed to a submicron recording wavelength.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a vacuum evaporation apparatus employed in a method for manufacturing a magnetic recording medium according to the present invention.

FIG. 2 is an enlarged sectional view of an example of an H ₂ O valve.

FIG. 3 is a diagram showing a flow of a method for manufacturing a magnetic recording medium.

FIG. 4 is a graph showing the relationship between the amount of H ₂ O introduced and the energy product.

FIG. 5 is a graph showing a relationship between an oxygen introduction amount and an energy product.

FIG. 6 is a graph showing a relationship between an energy product and a reproduction output.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Supply roll, 2 ... Cooling can, 3 ... Take-up roll, 4 ... Electron gun, 5 ... Electron beam, 6 ... Magnet, 7 ... Hearth, 8 ... Shielding plate, 9 ... Vacuum chamber, 10
... H ₂ O nozzle, 11 ... H ₂ O valve, 12 ... H ₂ O piping

Claims (4)

[Claims] 1. A method for producing a magnetic recording medium having a metal-based magnetic thin film formed on a non-magnetic support by a vacuum deposition method, wherein steam is introduced into the vacuum deposition atmosphere, and the metal vapor reacts with the steam. A method of manufacturing a magnetic recording medium, the method comprising forming the metal-based magnetic thin film while forming the magnetic recording medium. 2. A method for manufacturing a magnetic recording medium having a metal-based magnetic thin film formed on a non-magnetic support by a sputtering method, wherein steam is introduced into the sputtering atmosphere, and the sputtered metal particles and steam are removed. A method for manufacturing a magnetic recording medium, wherein the metal-based magnetic thin film is formed while reacting. 3. The method for manufacturing a magnetic recording medium according to claim 1, wherein the introduction of the water vapor is performed by introducing the water vapor alone. 4. The method according to claim 1, wherein the metal-based magnetic thin film is a magnetic thin film mainly composed of cobalt.