JPH07282431A - Magnetic recording medium and apparatus and process for producing magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium which is high in reproduced output and low in noise by executing suppression of dispersion of axes of easy magnetization and regulation of the anisotropic magnetic fields in an easy magnetization direction. CONSTITUTION:This magnetic recording medium consists of a high-polymer film substrate 101 and a magnetic thin film 102 formed on the substrate 101. The magnetic particles having magnetization vector within + or -10 deg. from the easy magnetization direction including the shape anisotropy of the medium in a residual magnetization state are 70 to 90% of all the magnetic particles. The ferromagnetic thin film which is inclined in the easy magnetization direction including the shape anisotropy of the medium by 65 to 80 deg. from a normal direction and has the anisotropy magnetic field of 1000 to l200kA/m in the easy magnetization direction including the shape anisotropy of the medium is formed as a recording layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film magnetic recording medium used in a digital VTR or the like and a method for manufacturing the thin film magnetic recording medium.

[0002]

2. Description of the Related Art At present, magnetic recording / reproducing devices tend to be smaller and have higher densities, and metal thin film type media have been attracting attention as exceeding the limit of high density of conventional coating type media.
Perpendicular recording and in-plane recording are available as recording methods for the metal thin film type medium, and the oblique evaporation method is known as a suitable manufacturing method of the in-plane recording medium that is currently put into practical use.

An example of a conventional manufacturing method will be described below with reference to the drawings. FIG. 5 shows a schematic diagram of a conventional continuous vacuum vapor deposition apparatus for performing oblique vapor deposition. In FIG. 5, 1 is a polymer film substrate, 2 is a cylindrical can, 3 is a shield plate that defines the initial incident angle, 4 is a shield plate that defines the final incident angle, 5 is a gas introduction nozzle, 6 is a vapor deposition material, Reference numeral 7 is a crucible for charging the vapor deposition material 6, and 8 and 9 are rollers. Polymer film substrate 1 traveling along a cylindrical can 2
Vaporized atoms that have passed through the opening between the shields 3 and 4 are deposited on top. The incident angle is defined by the angle formed by the incident direction of the vaporized atomic flow and the normal line of the polymer film substrate 1. The shield plate 3 can control the initial incident angle φi and the shield plate 4 can control the final incident angle φf. The magnetic characteristics of the magnetic layer are controlled by the range of the incident angle and the introduction of gas from the nozzle 5. In addition, in order to prevent the polymer film substrate 1 from losing heat due to radiant heat from the evaporation source, the cylindrical can 2 may be cooled by a coolant before use.

[0004]

By the way, the saturation magnetization is an important parameter for designing a magnetic recording medium.
Although coercive force, squareness ratio, etc. can be considered, control of magnetic anisotropy, particularly easy magnetization direction, is indispensable in a magnetic recording medium in a magnetic recording system using a current ring type magnetic head.

The average easy magnetization direction of the magnetic layer can be controlled by the incident angle during vapor deposition. However, the incident angle has a certain spread due to the problem of productivity. Therefore, the easy axis of magnetization in each grain is
It does not match the average easy magnetization direction of the magnetic layer. When the axes of easy magnetization are dispersed, the effective magnetic flux sensed by the magnetic head decreases, and the magnetic flux from the magnetic layer does not contribute effectively to the reproduction output. Moreover, the dispersion of the easy magnetization axis is also considered to cause noise. At this time, it is possible to increase the saturation magnetization of the magnetic layer or increase the film thickness in order to increase the reproduction output, but there are material limitations in the former, and in the latter, the particle size increases as the film thickness increases. It becomes large and causes noise.

Therefore, it is necessary to suppress the dispersion of the easy magnetization axis, but for that purpose, the angle between the initial incident angle and the final incident angle must be limited in the above-mentioned conventional method. However, narrowing the opening between the shielding plates that regulates the incident angle causes a problem in productivity.

If a cooling can is used, the temperature of the substrate is lowered to suppress the diffusion of vapor-deposited atoms on the substrate, and the incident direction of vapor-deposited atoms is made to coincide with the crystal growth direction on the substrate to regulate the incident angle. It is possible to suppress dispersion of the easy axis of magnetization of the magnetic particles without narrowing the opening between the shielding plates. However, when the can is cooled, outgas (mainly water) emitted from each member of the apparatus during vapor deposition is easily adsorbed on the polymer film substrate, which adversely affects the characteristics of the magnetic layer. There is.

The present invention solves the above-mentioned problems of the prior art, and provides a magnetic recording medium having high reproduction output and low noise, and a manufacturing method and a manufacturing apparatus capable of manufacturing the magnetic recording medium with high productivity. The purpose is to provide.

[0009]

In order to achieve the above object, the magnetic recording medium of the present invention has a magnetization vector within ± 10 ° from the easy magnetization direction including the shape anisotropy of the medium in the residual magnetization state. The magnetic particles are 70% or more and 90% or less of the total magnetic particles, and the easy magnetization direction including the shape anisotropy of the medium is inclined 65 ° to 80 ° from the normal direction of the film surface, and the shape of the medium is Anisotropic magnetic field in the easy magnetization direction including anisotropy is 1000 kA / m or more and 1200 kA / m
The following ferromagnetic thin film is used as a magnetic recording layer.

The magnetic recording medium manufacturing apparatus of the present invention is a magnetic recording medium manufacturing apparatus for forming a thin film magnetic recording layer on a polymer film substrate running along a cylindrical can by a continuous vacuum deposition method. An ion gun is provided above the substantially plate-like shielding plate that defines the initial incident angle of the vaporized atoms to the polymer film substrate, and a cooling pipe is installed between the ion gun and the cylindrical can, and The cylindrical can is used as a cooling can.

The method of manufacturing a magnetic recording medium of the present invention is
Using the magnetic recording medium manufacturing apparatus of the present invention, the polymer film substrate is irradiated with ions from the ion gun at an acceleration voltage of 400 V or less, the temperature of the cooling can is 0 ° C. or less, and the temperature of the cooling tube is 0 ° C. or less. It is characterized in that the thin film magnetic recording layer is formed at -100 ° C or less.

[0012]

In the magnetic recording medium of the present invention, the dispersion of the magnetic flux in the vicinity of the surface of the magnetic layer is suppressed by suppressing the dispersion of the easy axis of magnetization of the magnetic particles, and the magnetization due to the high magnetic anisotropy in the optimized easy magnetization direction. Due to vector stabilization, high playback output and low noise can be achieved. When a ring type magnetic head is used as the magnetic head, in order for the magnetic flux from the magnetic layer to effectively act on the magnetic head, the easy magnetization direction including the shape anisotropy of the medium should be the normal to the film surface. 65 ° -80 ° from the direction, more preferably 70 ° -7
It must be tilted 5 °.

The manufacturing apparatus and manufacturing method of the magnetic recording medium of the present invention will be described below. FIG. 3 is a schematic view of a magnetic recording medium manufacturing apparatus of the present invention. In FIG. 3, the polymer film substrate 1 runs in the direction of arrow R along the peripheral surface of the cylindrical can 2. Evaporated atoms are deposited on the polymer film substrate 1 to form a thin film. 5 is a gas introduction nozzle.
Reference numerals 3 and 4 are shield plates that define the incident angle of vaporized atoms. The cylindrical can 2 uses a cooling can cooled by a refrigerant. The above is almost the same as the conventional device of FIG. The magnetic recording medium manufacturing apparatus of the present invention is different from the conventional apparatus in that
An ion gun 10 and a cooling pipe 11 installed above the shield plate 3. The ion gun 10 and the cooling pipe 11 will be described below.

FIG. 4 is an enlarged view for clarifying the positional relationship between the ion gun 10 and the cooling pipe 11 above the shield plate 3.
The ion gun 10 is the same as that used in ion beam sputtering, ion milling, substrate pretreatment, and the like. Accelerated ions 14 such as argon, nitrogen, hydrogen and oxygen come out from the grid 13 of the ion gun 10. In addition, generally argon is used. Cooling pipe 8
A cooled refrigerant is circulated in the pipe. In order to prevent the ions 14 from irradiating the cooling pipe 11, the shield plate 12 is installed between the ion gun 10 and the cooling pipe 11. When the can is cooled, outgas (mainly water) emitted from each member of the apparatus during vapor deposition is easily adsorbed on the polymer film substrate, so that the ion gun is formed before the thin film is formed on the polymer film substrate 1. The gas adsorbed by the impact of the ions 14 from 10 is knocked out. At this time, if the energy of the ions is too high, the substrate is deteriorated. Although not described in the text, the polymer film substrate may be attached to the can using an electron gun in order to prevent heat loss of the polymer film substrate. At this time, if the energy of the ions from the ion gun is too high, the electrons from the electron gun are neutralized, and the crucifixion effect of the electron gun is lost. The purpose of the ion gun here is not to modify the surface of the substrate but to remove the gas physically adsorbed on the surface of the substrate, so it is not necessary to increase the energy of the ions. For these reasons, the ion acceleration voltage is preferably 400 V or less. The blown gas is adsorbed by the cooling pipe cooled to a temperature lower than that of the can, and is prevented from being adsorbed again on the substrate.

As described above, even when the cooling can is used, the thin film can be formed while keeping the substrate clean. Therefore, the effect of suppressing the dispersion of the easy axis of magnetization of the magnetic particles by lowering the substrate temperature is effective. Can be implemented

[0016]

Embodiments of the present invention will be described below with reference to the drawings and experimental results.

FIG. 1 is a schematic sectional view showing a magnetic recording medium according to an embodiment of the present invention. The magnetic recording medium shown in this drawing comprises a polymer film substrate 101 and a magnetic thin film 102 provided thereon. Although the magnetic thin film 102 has a single layer in this embodiment, it may have a multi-layer structure.

A case where a cobalt-oxygen (Co-O) -based thin film is formed as a magnetic layer using the conventional vacuum vapor deposition apparatus shown in FIG. 5 will be described. Cobalt is evaporated from the vapor deposition material 6 heated by an electron gun, and C partially oxidized on the polymer film substrate 1 continuously while introducing oxygen gas from the gas introduction nozzle 5 into the vacuum chamber during vapor deposition.
An OO magnetic film was formed to produce a thin film magnetic recording tape. Here, a polyethylene terephthalate (PET) film was used as the polymer film substrate, and the running speed was adjusted so that the magnetic film thickness was 800 nm. The amount of oxygen introduced from the gas introduction nozzle 5 was set to 1 liter / min for vapor deposition. At this time, the atmospheric pressure in the device is 6.7.
It was × 10 ^-3 Pa. The temperature of the cylindrical can 2 supporting the polymer film substrate 1 was 40 ° C. The initial incident angle φi at the time of vapor deposition was all 80 °, and the final incident angle φf was changed.

The distribution of the residual magnetization vector was measured in order to quantitatively obtain the dispersion of the easy axis of magnetization of the formed magnetic layer.
Usually, the magnetization vector points in the direction of the easy axis of magnetization. However, in the case of a thin film, it is more stable if the magnetization vector is oriented in the plane of the thin film due to its shape anisotropy. Therefore, when the easy axis of magnetization is not in the plane of the thin film, the magnetization vector is stable in the intermediate direction between the easy axis of magnetization and the plane of the thin film (the easy direction of magnetization including the shape anisotropy of the medium). Therefore, more practical information can be obtained by obtaining the distribution of the residual magnetization vector than by obtaining the dispersion of the easy axis of magnetization.

The distribution of the residual magnetization vector was measured using a vibrating sample magnetometer (VSM). The measuring method is as follows.

First, a magnetic field H (0) is applied within the film surface in the same direction as the running direction of the polymer film substrate to saturate the magnetic layer, and then the magnetic field is removed. The distribution of the residual magnetization vector in the film direction at this time is shown in FIG. Further, the residual magnetization in the tape longitudinal direction is Mr (0).

Next, in a plane perpendicular to the tape width direction, a magnetic field H (θ) is applied in a direction deviated from the tape longitudinal direction by a small angle θ, the magnetic field is removed, and the residual magnetization Mr ( θ) is measured. The distribution of the residual magnetization vector at this time is as shown in FIG. At this time, the magnetization vector in A in FIG.
After applying (θ), it is inverted to B in FIG. 2 (b).
It should be noted that there is no change in the residual magnetization vector other than A.
Therefore, the difference between Mr (0) and Mr (θ) is the magnetization vector A
Is equal to the difference between the component in the film surface direction and the component in the magnetization vector B in the film surface direction. This relationship is shown in (Equation 1). In (Equation 1), V is the volume of magnetic particles existing in A, and Ms is saturation magnetization. The volume V of the magnetic particles existing in A can be obtained from (Equation 1).

By repeating this measurement, the volume of the magnetic particles having the magnetization vector in each direction can be obtained, and the distribution of the magnetization vector can be determined. From this distribution curve, the volume ratio f of magnetic particles having a magnetization vector within ± 10 ° from the easy magnetization direction β was determined and used as an index representing the degree of orientation of the easy magnetization axis. When the commercially available ME tape was measured, the volume ratio f was 62%.

[0024]

[Equation 1]

Further, the easy magnetization direction β including the shape anisotropy of the medium of the formed magnetic layer, and the anisotropic magnetic field H _K ^* in the β direction were measured using a magnetic torque meter. The measurement and analysis method is Noda's β + 45 ° torque analysis method (I-E-E-E-
Transaction on Magnetics 27 (1991)
Pp. 4864 to 4866 (IEEE Trans.on Magn 27 (1991) P.
4864-4866)).

The production conditions and the characteristics of each example and comparative example are shown in (Table 1).

[0027]

[Table 1]

Next, the recording / reproducing characteristics of each example and comparative example were evaluated. A commercially available 8 mm VTR was used for evaluation, and the reproduction output and noise at a recording frequency of 7 MHz were evaluated and compared. The evaluation results are shown in (Table 2).

[0029]

[Table 2]

From the above, it can be seen that when the degree of orientation of the easy axis of magnetization is low (Comparative Example 1), the anisotropic magnetic field H _K ^* is low and both the reproduction output and noise deteriorate. On the other hand, in each of the embodiments to which the present invention is applied, high reproduction output and low noise are realized.

Therefore, ± 10 ° from the easy magnetization direction β.
The volume fraction of magnetic particles with a magnetization vector within 70%
It is necessary to be 90% or more and 90% or less, more preferably 80% or more and 90% or less.

In order to stabilize the magnetization vector in the easy magnetization direction β, the anisotropic magnetic field in the easy magnetization direction including the shape anisotropy of the medium should be 1000 kA / m or more and 1200 kA / m or less. preferable.

Next, a case where a cobalt-oxygen (Co-O) -based thin film is formed as a magnetic layer using the magnetic recording medium manufacturing apparatus of the present invention shown in FIG. 3 will be described. Cobalt is evaporated from the vapor deposition material 6 heated by an electron gun, and Co—O partially oxidized on the polymer film substrate 1 continuously while introducing oxygen gas from the gas introduction nozzle 5 into the vacuum chamber during vapor deposition. A system magnetic film was formed to produce a thin film magnetic recording tape. Here, a polyethylene terephthalate (PET) film was used as the polymer film substrate, and the running speed was adjusted so that the magnetic film thickness was 80 nm. The initial incident angle φi during vapor deposition was 80 °, and the final incident angle φf was 60 °. The cylindrical can 2 and the cooling pipe 11 were cooled by a refrigerant to control the temperature. Required amount of oxygen is reduced enough to a cooling can in a low temperature, the introduction amount of oxygen when the can temperature -20 ° C is min 0.6 l, pressure in the device at this time is 5.0 × 10 ^{- 3} Tor
It was r. The gas introduced into the ion gun 10 was argon (flow rate was 10 cc / min). Here, the ion current density is set to 20 mA / cm ² , but it may be appropriately adjusted according to the running speed of the polymer film substrate. The distribution of the residual magnetization vector of the formed magnetic layer was measured by the above-mentioned method to examine the degree of orientation. Also, the recording / reproducing characteristics were evaluated by the above-mentioned method.

The production conditions of each example and comparative example are shown in Table 3 below.
Table 4 shows the evaluation results of the orientation degree and the recording / reproducing characteristics. The reproduction output and noise were set to 0 dB in Example 3 in which the incident angles were the same.

[0035]

[Table 3]

[0036]

[Table 4]

In Comparative Example 2, since the ion energy was too high, the substrate was deteriorated and damaged, and it was difficult to evaluate the recording / reproducing characteristics. It can be seen that in Comparative Example 3, the temperature as a cooling can is not sufficient, although the orientation degree of Example 3 is almost the same. In Comparative Example 4, since the temperature of the cooling pipe is not sufficiently low, it is considered that the effect of adsorbing the gas knocked out by the ions to the cooling pipe is low. Therefore, the temperature of the cooling pipe is -1
00 ° C or less is desirable. The degree of orientation of Examples 4 and 5 is higher than that of Example 3 having the same vapor deposition incident angle, and is almost equal to that of Example 2. Therefore, if the substrate temperature is lowered by using the cooling can, the dispersion of the easy axis of magnetization can be suppressed even if the vapor deposition incident angle is widened.

The specific embodiment of the present invention has been described above. However, the present invention is not limited to this embodiment, and various modifications can be made without departing from the gist of the present invention. Needless to say.

Although cobalt is used as the material of the evaporation source 6 in this embodiment, a metal such as iron or nickel or an alloy such as cobalt-chromium or cobalt-nickel may be used, and no gas is introduced during vapor deposition. The present invention is also effective in the vapor deposition method.

[0040]

As described above, the magnetic recording medium of the present invention is
High reproduction output and low noise can be realized by suppressing the dispersion of the easy magnetization axis and controlling the anisotropic magnetic field in the easy magnetization direction. Further, the apparatus and method for manufacturing a magnetic recording medium of the present invention can improve productivity by performing vapor deposition using a cooling can and suppressing dispersion of the easy axis of magnetization even if the vapor deposition incident angle is widened. You can

[Brief description of drawings]

FIG. 1 is a configuration diagram of a magnetic recording medium according to an embodiment of the present invention.

FIG. 2A shows a residual magnetization vector distribution after applying a magnetic field in the tape longitudinal direction. FIG. 2B shows a residual magnetization vector distribution after applying a magnetic field in a direction offset by an angle θ from the tape longitudinal direction. Figure

FIG. 3 is a block diagram of an apparatus for manufacturing a magnetic recording medium of the present invention.

FIG. 4 is a diagram showing an example of a positional relationship between an ion gun and a cooling pipe in the magnetic recording medium manufacturing apparatus of the present invention.

FIG. 5 is a block diagram of a conventional magnetic recording medium manufacturing apparatus.

[Explanation of symbols]

 101 polymer film substrate 102 magnetic thin film 1 polymer film substrate 2 cylindrical can 3 shield plate 4 shield plate 5 gas introduction nozzle 6 vapor deposition material 7 crucible 8 roller 9 roller 10 ion gun 11 cooling tube 12 shield plate 13 grid 14 ion

Claims (6)

[Claims] 1. A magnetic particle having a remanent magnetization vector within ± 10 ° from an easy magnetization direction including a shape anisotropy of a medium within a normal surface including a tape running direction is 70% of all magnetic particles.
% To 90% of the ferromagnetic thin film as a magnetic recording layer. 2. The magnetic recording medium according to claim 1, wherein the easy magnetization direction including the shape anisotropy of the medium is inclined by 65 ° to 80 ° from the normal line direction of the film surface. 3. An anisotropic magnetic field in the easy magnetization direction including the shape anisotropy of the medium is 1000 kA / m or more and 1200.
The magnetic recording medium according to claim 2, which has a kA / m or less. 4. A manufacturing apparatus of a magnetic recording medium, wherein a thin film magnetic recording layer is formed on a polymer film substrate running along a cylindrical can by a continuous vacuum deposition method. An ion gun is installed at a position above a substantially plate-like shielding plate that defines an incident angle, a cooling pipe is installed between the ion gun and the cylindrical can, and the cylindrical can is used as a cooling can. An apparatus for manufacturing a magnetic recording medium, comprising: 5. The apparatus for producing a magnetic recording medium according to claim 4, wherein the surface of the polymer film substrate is irradiated with ions from the ion gun at an acceleration voltage of 400 V or less, and the temperature of the cooling pipe is changed to the cooling can. A method of manufacturing a magnetic recording medium, comprising forming a thin film magnetic recording layer at a lower temperature. 6. The temperature of the cooling can is set to 0 ° C. or lower,
6. The method of manufacturing a magnetic recording medium according to claim 5, wherein the temperature of the cooling pipe is set to −100 ° C. or lower.