JPH07240019A - Magnetic recording medium and its production and apparatus for production - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent recording and reproducing characteristics and its production and apparatus for production. CONSTITUTION:The film thickness of the magnetic layers of the thin-film magnetic recording medium consists of the magnetic layers consisting essentially of cobalt and oxygen is 0.05mum to 0.12mum. The magnetic layers consist of the first magnetic layer 101 formed on the substrate and the second magnetic layer 102 formed on the first magnetic layer. The columnar particles forming the first magnetic layer and the second magnetic layer incline approximately in the same direction and the ratio at which the film thickness of the second magnetic layer occupies in the entire part of the film thicknesses of the magnetic layers is specified to 50% to 80%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium excellent in high density recording / reproducing characteristics, a magnetic recording medium manufacturing method and a manufacturing apparatus for manufacturing the same.

[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.
In this regard, a metal thin film type medium made of Co—Ni—O has been put to practical use as a magnetic tape for VTR and is known as an ME tape. From the viewpoint of productivity, the oblique incidence vacuum vapor deposition method is adopted as the method of manufacturing the thin film magnetic layer.

An example of a conventional oblique incident vacuum vapor deposition method will be described below with reference to the drawings. FIG. 3 schematically shows a conventional continuous vacuum vapor deposition apparatus for performing oblique vapor deposition. The polymer film substrate 1 is unwound from a supply roll 3, travels along the circumferential surface of a rotating cylindrical can 2, and is finally wound up by a winding roll 4. Reference numeral 10 is a free roller, and a plurality of free rollers are arranged at appropriate places so that the polymer film substrate 1 can stably run. On the polymer film substrate 1 running along the peripheral surface of the cylindrical can 2, the shielding plate 7
Evaporated atoms from the evaporation source 5 that have passed through the opening between and 8 are deposited to form a magnetic layer. For the evaporation source 5, M
In the case of E-tape, it is filled with Co-Ni alloy. 6 is an electron beam for heating the evaporation source 5. As a heating means of the evaporation source, there are methods such as resistance heating and induction heating, but electron beam heating is suitable for evaporating a refractory metal such as Co at a high evaporation rate. The incident angle of the vaporized atoms with respect to the substrate is defined by the angle formed by the vaporized atoms and the normal of the substrate, and the shield plate 7 controls the initial incident angle φ _i and the shield plate 8 controls the final incident angle φ _f . The magnetic characteristics of the magnetic layer are controlled by the range of the incident angle and the amount of oxygen introduced from the oxygen inlet 9. In the case of ME tape, the initial incident angle is 90 ° and the final incident angle is around 30 °. The structure of the magnetic layer includes a single layer type and a multilayer type, and the film thickness of the magnetic layer is about 0.2 μm in each case.

The magnetic layer manufactured as described above has a columnar structure, and the easy axis of magnetization is inclined with respect to the normal line of the magnetic film. That is, the axis of easy magnetization is not in the film surface or in the direction of the normal to the film surface, but is in the direction oblique to the normal in the normal including the incident direction of the vaporized atoms to the substrate. For example, a commercially available Hi8 VTR
In the ME tape for use, the easy magnetization axis is inclined by about 20 ° from the film surface in the normal plane including the longitudinal direction of the tape. Here, the longitudinal direction of the tape is the longitudinal direction of the tape, and in the manufacturing apparatus shown in FIG. 3, it is the running direction of the polymer film substrate 1. The magnetization recorded by the magnetic head remains in the direction of the easy axis of magnetization that is obliquely inclined, and forms a magnetization mode different from that of conventional longitudinal recording. By forming such an oblique magnetization mode, the high recording density characteristic is remarkably improved as compared with the conventional longitudinal recording medium.

A magnetic tape having a thin film type magnetic layer greatly contributes to the popularization of a camera-integrated home VTR and the like, and can be applied as a magnetic tape corresponding to a next-generation home small digital VTR, particularly a high-definition digital VTR. Is expected.

[0006]

[Problems to be Solved by the Invention] In the future, the magnetic recording / reproducing apparatus will become smaller and larger in capacity. Also in the field of VTR, in order to realize, for example, a high-definition digital VTR with a small magnetic tape cassette, the linear recording density and the track density must be further improved. Therefore, in the magnetic tape, it is required to achieve higher C / N than ever before, especially in the short wavelength region. However, it is hard to say that the magnetic tapes currently in practical use have sufficiently high recording density characteristics to satisfy the above demands. Therefore, realization of a high-performance magnetic tape suitable for digital recording has become a major issue.

[0007]

The present invention provides a magnetic recording medium excellent in high-density recording / reproducing characteristics, a method of manufacturing the same, and an apparatus for manufacturing the same from the above viewpoint. The first invention is Co and O. And a first magnetic layer formed on a substrate, wherein the magnetic layer has a film thickness of 0.05 μm or more and 0.12 μm or less. The second magnetic layer is formed on the first magnetic layer, the columnar particles forming the first magnetic layer and the second magnetic layer are inclined in substantially the same direction, and the film thickness of the second magnetic layer is 50% to 80% of the total magnetic layer thickness
It is characterized by the following.

According to a second aspect of the present invention, a first magnetic layer containing Co and O as main components and a second magnetic layer are formed on a polymer film substrate running along the peripheral surface of a cylindrical can by an oblique evaporation method.
In a method of manufacturing a magnetic recording medium in which magnetic layers are sequentially formed, when an angle formed by a normal line of a polymer film substrate and an incident direction of vaporized atoms is defined as an incident angle, an incident angle at the initial formation of the first and second magnetic layers is defined. The angle is greater than the angle of incidence at the end of formation,
Further, the incident angle at the final stage of forming the first magnetic layer is larger than the incident angle at the final stage of forming the second magnetic layer, and the value of (oxygen introduction amount) / (film deposition rate) when forming the first magnetic layer is It is a method of manufacturing a magnetic recording medium, which is larger than a value of (oxygen introduction amount) / (film deposition rate) when forming the second magnetic layer.

A third invention is a magnetic recording medium manufacturing apparatus for forming a magnetic layer by a vacuum deposition method on a polymer film substrate running along a cylindrical can.
With respect to one cylindrical can, the first and second evaporation sources are arranged along the running direction of the polymer film substrate on the same side upstream of the running of the polymer film substrate with respect to the vertical line passing through the center of the cylindrical can. A shield plate is provided between the cylindrical can and the first and second evaporation sources to set the first and second openings corresponding to the respective evaporation sources, and a vertical plate passing through the center of the cylindrical can. The distance between the line and the center of the evaporation portion of the first evaporation source is longer than the radius of the cylindrical can, and the distance between the vertical line passing through the center of the cylindrical can and the center of the evaporation portion of the second evaporation source is the cylinder. Shorter than the radius of the can, the first evaporation source is the second
It is characterized in that it is arranged above the horizontal position of the opening.

[0010]

In order to increase the C / N in the short wavelength region suitable for digital recording, it is necessary to enhance the magnetic orientation of the magnetic layer. In other words, the magnetic orientation of the magnetic layer is the magnetic anisotropy of the magnetic layer. The magnetic anisotropy of the magnetic layer is substantially determined by the shape and directionality of the columnar particles constituting the magnetic layer, which is related to the shape magnetic anisotropy, and the crystallinity of the columnar particles, which is related to the crystalline magnetic anisotropy. It In order to obtain a high-performance magnetic layer, the easy axis of magnetization is oriented in a predetermined direction, and high magnetic anisotropy energy is applied to the magnetic layer by the effects of both shape magnetic anisotropy and crystalline magnetic anisotropy. is necessary.

FIG. 1 is a schematic sectional view of a magnetic layer of the magnetic recording medium of the present invention. The first magnetic layer 101 is provided on the polymer film substrate 100, and the second magnetic layer 1 is provided on the first magnetic layer 101.
There is 02. That is, two magnetic layers are laminated to form a magnetic layer of a magnetic recording medium.

The main components of the magnetic material are Co and O. Co
Is a material having both high saturation magnetization and high crystal magnetic anisotropy energy and is most suitable as a material for the thin film type magnetic layer. C
The combination of o and O is optimal in extracting the properties of Co.

In order to increase the energy of the magnetic layer due to the shape magnetic anisotropy, the present invention employs the following two methods. The first point is that the first magnetic layer 101 and the second magnetic layer 1
The columnar particles in No. 02 have the same inclination direction. The second point is to make the columnar particles as close to a straight line as possible.
As can be seen from the manufacturing method described later, it is difficult to make the columnar particles linear by the method using the cylindrical can, and the columnar particles are curved. It is important to reduce this curvature. The degree of bending is preferably within 15 °. Also, considering that a ring-type magnetic head is used for recording and reproduction,
It is preferable that the inclination of the columnar particles be 20 ° or more and 35 ° or less from the substrate surface because the shape magnetic anisotropy of the columnar particles can be utilized.

In order to increase the energy of the magnetic layer due to the crystal magnetic anisotropy, the present invention has a structure in which the first magnetic layer 101 is thin and the second magnetic layer is thick. When the magnetic layer is directly formed on the polymer film substrate 100 as in the present invention, it is difficult to obtain high crystallinity. It is considered that this is because various impurities including gas existing near the surface of the polymer hinder the crystal growth. However, if the film thickness is increased, the crystallinity will increase due to the preferential growth property of the crystal. However, since the crystal grains are also coarsened, noise becomes high.

Therefore, in the present invention, crystallographically, the first magnetic layer 101 is regarded as an underlayer of the second magnetic layer 102 to be formed next, and the thickness of the first magnetic layer is kept small. However, although the first magnetic layer 101 has a small contribution as a magnetic layer from the viewpoint of crystal magnetic anisotropy, it naturally has a shape magnetic anisotropy and therefore functions as a magnetic layer. Further, the crystal grains forming the first magnetic layer inhibit crystal growth due to various impurities including gas existing near the surface of the polymer, so that the crystal grains become small and noise can be suppressed low. Since the second magnetic layer 102 is formed on the first magnetic layer 101 as the underlayer, relatively high crystallinity can be obtained from the initial stage of film formation. The second magnetic layer 102 becomes an excellent magnetic layer having both high crystal magnetic anisotropy energy and high shape magnetic anisotropy. However, when the crystal magnetic anisotropy is strong, the direction of easy magnetization may not coincide with the direction of the columnar particles. In the case of the present invention, the incident angle and the amount of oxygen introduced when forming the two magnetic layers within the allowable range so that they substantially match, that is, the magnetic anisotropy energy of the magnetic layers becomes high. I am adjusting. At this time, considering that a ring type magnetic head is used for recording and reproduction,
It is desirable to adjust the direction of easy magnetization of the magnetic layer to be in the range of 10 ° or more and 25 ° or less from the substrate surface. The direction of easy magnetization referred to here includes the shape anisotropy of the thin film. The so-called intrinsic easy magnetization direction from which the influence of the thin film shape is removed is a direction further raised from the substrate surface than the easy magnetization direction here. When the direction of easy magnetization of the magnetic layer is smaller than 10 ° from the substrate surface, noise that is considered to be caused by the zigzag domain wall due to the abutment of magnetization increases. Further, when the direction of easy magnetization of the magnetic layer is larger than 25 ° from the substrate surface, the perpendicular component of the recording magnetic field of the ring type magnetic head is small, so that the recording efficiency is lowered and the reproduction output is lowered, and the spacing loss factor is reduced. To increase.

The film thickness of the magnetic layer will be described. In order for the first magnetic layer 101 to function as a base of the second magnetic layer 102, about 0.01 μm or more is necessary. If it is about 0.6 μm or more, the grain size increases and the noise increases as the film thickness increases. . Therefore, the thickness of the first magnetic layer 101 is 0.01 μm.
Above 0.6 μm is suitable. In addition, the first magnetic layer 1
The preferable range of the total film thickness of the magnetic layer including 01 and the second magnetic layer 102 is 0.05 μm or more and 0.12 μm or less. When the total thickness of the magnetic layer is about 0.05 μm or less, the reproduction output in the super wavelength region is drastically reduced as well as the reproduction output in the short wavelength region, and tracking adjustment becomes difficult.
If it is more than μm, noise tends to be high and C / N tends to be low. The optimum values of the film thickness ratio and the total film thickness of the magnetic layer differ depending on the head used. This is because the writing ability of the head is related to the coercive force of the magnetic layer. In the thickness range of the magnetic layer of the present invention, the coercive force of the first magnetic layer tends to increase as the film thickness increases, and the coercive force of the second magnetic layer tends to increase as the film thickness decreases. is there. Therefore, for example, in the case of a ferrite ring head with a small saturation magnetization and a wide gap length, the total film thickness of the magnetic layer is increased and the film thickness ratio of the second magnetic layer is increased to set the coercive force of the entire magnetic layer low. In the case of a metal ring head having a large saturation magnetization and a narrow gap length, the total film thickness of the magnetic layer is reduced and the film thickness ratio of the second magnetic layer is decreased to increase the coercive force of the entire magnetic layer. It is preferable to set it.

Next, a method of manufacturing the magnetic recording medium of the present invention will be described with reference to FIG. Since FIG. 3 is used in the description of the conventional example, the description of each element in the drawing is omitted here.

In order to obtain the high magnetic anisotropy energy as described above, the structure of the magnetic layer is important, but the manufacturing method is also important. Above all, the incident angle of vaporized atoms to the substrate and the amount of introduced oxygen are important. The magnetic layer of the present invention can be obtained by setting the conditions of each magnetic layer using the apparatus of FIG. 3 and repeating vapor deposition. However, after forming the first magnetic layer, it is necessary to rewind the wound roll once to form the second magnetic layer.

The incident angle will be described. The incident angle is defined by the angle formed by the normal line of the polymer film substrate and the incident direction of vaporized atoms.

When forming the first magnetic layer and the second magnetic layer, it is necessary to make the initial incident angle φ _i larger than the final incident angle φ _f in any case. There are two reasons for this. The first point is the mechanical strength of the film. If the final incident angles φ _f are made larger than the initial incident angle φ _i , the density of the film surface, that is, the magnetic layer surface becomes low. If the incident angle is large, the self-shading effect becomes large and the density becomes low. The lower the density, the weaker the mechanical strength. If the mechanical strength is low, the surface of the magnetic layer is easily damaged, which is inconvenient. The second point is from the viewpoint of crystal growth. C, which is the direction of easy magnetization of Co
The axis originally grows perpendicularly to the substrate, and the crystal that grows later has the property of growing so that the crystal axes are aligned. When trying to tilt the c-axis, it is necessary to increase the incident angle. However, the larger the incident angle, the larger the dispersion of the c-axis. Then, although the resulting c-axis tilt has a large dispersion, it is succeeded even if the incident angle changes thereafter.
Therefore, the direction of easy magnetization cannot be tilted unless the initial incident angle is increased.

The incident angle of the first magnetic layer is larger than that of the second magnetic layer. In particular, the final incident angle φ _f is increased.
This is because the incident angle is not important when the first magnetic layer is considered as a pure underlayer, but it is necessary to increase the incident angle and sufficiently induce the shape magnetic anisotropy when considered as the magnetic layer. Further, since the first magnetic layer does not appear on the surface of the medium, it does not need to be mechanically sufficiently strong. The initial incident angle φ _i of the two magnetic layers should be about the same or the initial incident angle of the first magnetic layer should be large, but in any case, it is preferably 85 ° or less. This is because the dispersion of the c-axis extremely increases at 85 ° or more. The region where the incident angle is 85 ° or more is a region where the trajectory of the vaporized atoms is a tangent to the circumferential surface of the cylindrical can 2 when the vaporized atoms are assumed to go straight, and the region where the attachment efficiency approaches 0%. is there. If the vaporized atoms proceed with the residual gas or while colliding with each other, the deposition form of the vaporized atoms on the substrate is considered to be unstable. In the present invention, an incident angle of 85 ° or more is not used in order to obtain a magnetic layer having good controllability and high performance. The final incident angle φ _f is
In order to make the inclination of the columnar particles 35 ° or less from the substrate surface, it is necessary to set 50 ° or more.

The amount of oxygen introduced at the time of forming the magnetic layer determines the saturation magnetization of the magnetic layer, and is one of the important factors in forming the magnetic layer. Generally, the larger the saturation magnetization, the higher the reproduction output, but it is meaningless only if the reproduction output is high. Since the saturation magnetization is one factor that determines the easy magnetization direction of the magnetic layer, it has an optimum value. If the saturation magnetization is large, the direction of easy magnetization approaches the in-plane direction of the magnetic layer, so if the saturation magnetization is too large, noise increases. On the other hand, if the saturation magnetization is too small, the anisotropy energy of the magnetic layer becomes small, which is inconvenient for the magnetic layer. It is important to set the range of inclination of the columnar grains constituting the magnetic layer to 20 ° to 35 ° depending on the incident angle, and the range of easy magnetization direction to 10 ° to 25 ° by adjusting the oxygen introduction amount. is there.
The optimum oxygen introduction amount differs depending on the device configuration, the device scale, the residual gas pressure in the device, and the exhaust capacity, so it is difficult to unambiguously express it with a specific numerical value. It is necessary to determine the optimum amount of oxygen introduced according to the device.

When manufacturing the magnetic recording medium of the present invention,
The value of (oxygen introduction amount) / (film deposition rate) when forming the first magnetic layer is (oxygen introduction amount) when forming the second magnetic layer.
It should be larger than the value of / (film deposition rate). In terms of saturation magnetization, the saturation magnetization of the first magnetic layer needs to be smaller than that of the second magnetic layer. The first magnetic layer has a function as a base of the second magnetic layer and a function as an original magnetic layer. The oxygen introduction amount is not a big problem when the first magnetic layer is regarded as a base, but the oxygen introduction amount is important when regarded as the magnetic layer. As described above, the first magnetic layer has the meaning of a magnetic layer due to the shape magnetic anisotropy of the columnar particles. Therefore, it is necessary to form the first magnetic layer at a high incident angle having a large self-shading effect and to promote the magnetic separation between the columnar particles by introducing oxygen. Therefore, it is necessary to make the value of (oxygen introduction amount) / (film deposition rate) larger than that of the second magnetic layer, and the saturation magnetization also becomes smaller. On the other hand, the second magnetic layer is
In addition to the shape magnetic anisotropy of the columnar particles, the crystal magnetic anisotropy also greatly contributes. In general, the introduction of gas reduces the crystallinity. Therefore, when forming the second magnetic layer,
It is necessary to minimize the decrease in crystallinity, and to minimize the amount of oxygen introduced so as to ensure the minimum required magnetic separation between columnar particles. That is, it is necessary to make the value of (oxygen introduction amount) / (film deposition rate) as small as possible. The absolute amount of oxygen introduced during the actual formation of the magnetic layer depends on conditions such as the power of the electron beam input to the evaporation source and the range of the incident angle, when the second magnetic layer is formed rather than the first magnetic layer. There may be a large amount, and vice versa.

Next, the manufacturing apparatus of the magnetic recording medium of the present invention will be described with reference to FIG. According to the apparatus shown in FIG. 2, the magnetic recording medium of the present invention can be obtained by running the polymer film substrate once, and the productivity is greatly improved.

In FIG. 2, two evaporation sources 51 and 52 are arranged for one cylindrical can 2 along the traveling direction of the polymer film substrate 1. The first evaporation source 51 is for the first magnetic layer, and the second evaporation source 52 is for the second magnetic layer. Between the first and second evaporation sources 51 and 52 and the cylindrical can 2, there are shield plates 71, 81 and 72 and 82 for setting the first and second openings 111 and 112 corresponding to the respective evaporation sources. It is arranged. First for first magnetic layer
In the opening 111, the shield plate 71 defines the initial incident angle φ _i1 of the first magnetic layer, and the shield plate 81 similarly defines the final incident angle φ _f1 of the first magnetic layer. Second opening 11 for the second magnetic layer
2, the shield plate 72 has an initial incident angle φ _i2 of the second magnetic layer.
The shield plate 82 also defines the final incident angle φ _f2 of the second magnetic layer. Also, the first and second evaporation sources 51 and 5
2 is arranged on the same side of the upstream of the polymer film substrate 1 with respect to the vertical line passing through the center of the cylindrical can 2, and the vertical line passing through the center of the cylindrical can 2 and the evaporation portion of the first evaporation source 51. The distance from the center of is longer than the radius of the cylindrical can 2,
The distance between the vertical line passing through the center of the cylindrical can 2 and the center of the evaporation portion of the second evaporation source 52 is shorter than the radius of the cylindrical can 2, and the first evaporation source 51 is located at the horizontal position of the second opening 112. It is located above.

According to the apparatus configuration of the present invention, all parameters other than the traveling speed of the polymer film substrate 1 can be independently controlled in the step of simultaneously forming the two magnetic layers. Further, it is also a great feature of the apparatus configuration of the present invention that the residual gas pressure in the vicinity of the vapor deposition section, which is important in the vacuum vapor deposition method, can be lowered. For example, the first evaporation source 5
When 1 is lower than the horizontal position of the second opening 112, the first evaporation source 51 hinders exhausting the residual gas in the vicinity of the second opening 112, and the evaporation atoms from the first evaporation source 51 If a shielding plate is separately provided so that the gas does not reach the second opening, this shielding plate also hinders exhausting the residual gas in the vicinity of the second opening 112.

Electron beam heating using a pierce type electron gun as an electron beam source is suitable for mass production, but installing a plurality of electron beam guns increases the scale of the apparatus and the inertness introduced for electron beam focusing. The influence of gas also becomes large, and the residual gas pressure near the opening is increased. Therefore, when the reduction of the residual gas pressure and the reduction of the apparatus scale are taken into consideration, it is desirable to deflect the electron beam from one electron beam source and direct it to two evaporation sources. On this occasion,
By controlling the distribution ratio of the electron beam,
It is possible to control the input power of the electron beam to each evaporation source.

The two evaporation sources are electron beams 61 and 62.
When heating at 1, the electron beams for each evaporation source are prevented from intersecting the vaporized atomic flow from the other evaporation source toward the opening. For example, in FIG. 2, assuming that the first evaporation source is arranged at a position apart from the cylindrical can 2 and beyond the electron beam 62, the electron beam 62 is emitted from the first evaporation source 5.
Although it intersects with the vaporized atomic flow from 1 toward the first opening 111, such an arrangement is not very convenient because it lowers the productivity and requires an additional shielding plate.

It is convenient to make the first evaporation source 51 smaller than the second evaporation source 52. By making the first evaporation source 51 small and making it close to the cylindrical can 2,
The evaporation source 52 can be irradiated at a more acute angle, resulting in high productivity and controllability. This device configuration is concerned with the fact that the first magnetic layer is thin and the second magnetic layer is thick, which is a structural feature of the magnetic layer of the magnetic recording medium of the present invention. The evaporation source 51 for the first magnetic layer is located outside the lower portion of the cylindrical can 2 and has a structure in which the portion having the highest vapor density cannot be used for film formation, but is arranged close to the cylindrical can 2. Therefore, the deposition rate of the film is so high that there is no practical problem. Therefore, the second
It may be smaller than the evaporation source for the magnetic layer and may have a low electron beam input power. Although it is equipped with two evaporation sources, it can be a very compact device.

A pair of openings is provided for each of the two evaporation sources, and an oxygen inlet is provided for each opening. Shielding plate 81 for the first magnetic layer
Oxygen inlet 9 arranged between the cylindrical can 2 and the cylindrical can 2.
Oxygen is introduced from 1 and the shield plate 82 for the second magnetic layer is formed.
Oxygen inlet 9 arranged between the cylindrical can 2 and the cylindrical can 2.
Oxygen is introduced from 2. It is important to suppress the oxygen introduced from the oxygen inlet 91 for the first magnetic layer from flowing into the second opening 112, and it is necessary to devise a key-shaped end portion of the shielding plate 81. is there.

[0031]

EXAMPLES Examples of the present invention will be described below.

A Co—O film was formed as a magnetic layer using the magnetic recording medium manufacturing apparatus shown in FIG. A polyethylene terephthalate film having a thickness of 7 μm was used as the polymer film substrate 1. The diameter of the cylindrical can 2 is 1.5
m.

(Example 1) The first magnetic layer has an incident angle range of 8
It was formed at 0 ° to 60 °. Co is charged in the evaporation source 5
It was melted by an electron beam of 0 kW. 0.9 liter of oxygen was introduced from the gas introduction nozzle 5 per minute. The film thickness was changed to 0.005 by changing the running speed of the polymer film substrate 1.
A film having a thickness of μm to 0.2 μm was formed. After forming the first magnetic layer, the wound roll was rewound once, and the second magnetic layer was formed thereon with an incident angle range of 70 ° to 50 °. Co was charged in the evaporation source 5 and melted by an electron beam of 60 kW. From the gas introduction nozzle 5, 1.0 liter of oxygen was introduced per minute. The running speed of the polymer film substrate 1 was adjusted to form a film having a thickness of 0.06 μm.

The resulting sample is slit into a tape,
The recording / reproducing characteristics were examined. The recording / reproducing characteristics were measured by using a ring type magnetic head made of sendust and having a gap length of 0.15 μm. The reproduction output is a value at a recording wavelength of 0.4 μm, and the noise is noise at a frequency 1 MHz lower than the frequency of the recording signal when a signal having a recording wavelength of 0.4 μm is recorded. The results are shown in Fig. 4.

FIG. 4 shows the dependence of reproduction output and noise on the thickness of the first magnetic layer. The reproduction output increases and saturates as the thickness of the first magnetic layer increases. It is considered that this is because the function of the first magnetic layer as a base increases with the film thickness. It is considered that the function is sufficiently exhibited when the film thickness is 0.01 μm or more. Further, noise also increases with an increase in the film thickness of the first magnetic layer. It is considered that when the film thickness is 0.06 μm or more, the noise is sharply increased, and the influence of the coarsening of the columnar particles is remarkable. This tendency does not change even if the second magnetic layer is selected to have another thickness. However, the absolute noise value increases as the film thickness of the second magnetic layer increases. Figure 4
From this, the optimum range of the thickness of the first magnetic layer is known.

(Example 2) A magnetic layer was formed in the same manner as in Example 1. However, as the first magnetic layer, the traveling speed of the polymer film substrate 1 is adjusted to form a film having a film thickness of 0.02 μm, and as the second magnetic layer, the polymer film substrate 1 is formed.
The film thickness was changed from 0.02μm to 0.2 by changing the running speed of
A μm film was formed. A sample produced in the same manner as in Example 1 was slit into a tape shape, and the recording / reproducing characteristics were examined. Results are shown in FIG.

FIG. 5 shows the dependence of the reproduction output and noise on the thickness of the second magnetic layer. The reproduction output increases and saturates as the film thickness of the second magnetic layer increases. This indicates that the total thickness of the magnetic layer needs to be 0.05 μm or more. Further, noise also increases with an increase in the thickness of the second magnetic layer. When the film thickness is 0.1 μm or more, noise is considerably high, and it is considered that the influence of coarsening of columnar particles appears. This tendency does not change even if the first magnetic layer is selected to have another thickness. However, the absolute noise value increases with an increase in the film thickness of the first magnetic layer, and the film thickness of the second magnetic layer at which the noise starts to increase sharply shifts to a smaller thickness. It is considered that this is because the particle size of the columnar particles of the second magnetic layer inherits the particle size of the columnar particles of the first magnetic layer to some extent. That is, in order to suppress noise to a low level, it is necessary to make the second magnetic layer thin when the first magnetic layer is thick, and even if the second magnetic layer is made thick to some extent when the first magnetic layer is thin. This means that noise can be kept low.

Since the systematic examination as in Example 1 and Example 2 is conducted, the preferable range of the total thickness of the magnetic layer is
It is 0.05 μm to 0.12 μm, and it can be judged that the ratio of the second magnetic layer to the total thickness of the magnetic layer is preferably 50% or more and 80% or less. In addition, playback output and C /
Judging from the viewpoint of N, the range of the total film thickness of the magnetic layer is 0.
It is more preferable that the thickness is from 06 μm to 0.1 μm, and the ratio of the second magnetic layer to the entire thickness is 60% or more and 75% or less.

Example 3 A magnetic layer was formed in the same manner as in Example 1. However, the running speed of the polymer film substrate 1 is adjusted as the first magnetic layer to form a film having a thickness of 0.03 μm, and the second magnetic layer is used as the polymer film substrate 1.
The traveling speed of was adjusted to form a film having a thickness of 0.07 μm. Further, the amount of oxygen introduced was changed when the second magnetic layer was formed. A sample produced in the same manner as in Example 1 was slit into a tape shape, and the recording / reproducing characteristics were examined. Results are shown in FIG.

FIG. 6 shows the dependence of reproduction output and noise on the amount of oxygen introduced during the formation of the second magnetic layer. It can be seen that the amount of introduced oxygen has an optimum value with respect to the reproduction output. Further, when the oxygen introduction amount is equal to or more than the optimum value, the reproduction output sharply decreases. It is considered that this is because the crystallinity of the columnar particles is significantly reduced by the excess oxygen. On the other hand, the noise monotonously decreases as the amount of introduced oxygen increases. It is considered that this is because the saturation magnetization is reduced and the magnetic separation between the columnar particles is promoted as the amount of introduced oxygen increases. The amount of oxygen introduced in FIG. 6 is 0.6 liter /
The direction of easy magnetization of the sample between min and 1.2 l / min was within the range of 10 ° to 25 ° from the substrate surface.
On the other hand, the 0.4 liter / min sample is 7 °,
The 0.14 liter / min sample was 32 °. From this, it is understood that the control of the easy magnetization direction by the amount of introduced oxygen is important. Also, from FIG. 6, high C / N
It can be seen that the range of the optimum amount of introduced oxygen for obtaining the above is narrow and the amount of introduced oxygen must be strictly controlled.

Next, a Co—O film was formed as a magnetic layer using the magnetic recording medium manufacturing apparatus of the present invention shown in FIG. A polyethylene terephthalate film having a thickness of 7 μm was used as the polymer film substrate 1. The diameter of the cylindrical can 2 is 1.5 m.

(Embodiment 4) A shielding plate is provided so that the incident angle range of the first magnetic layer is 85 ° to 75 ° and the incident angle range of the second magnetic layer is 80 ° to 55 °. It was set. Co was charged in the evaporation sources 51 and 52. The amount of Co charged into the evaporation source 51 was ⅓ of the evaporation source 52.
The input power of the electron beam is 20k for the first evaporation source.
W and 60 kW for the second evaporation source. 0.4 l / min of oxygen was introduced from the gas introduction nozzle 91, and 1.0 l / min of oxygen was introduced from the gas introduction nozzle 92. The running speed of the polymer film substrate 1 was adjusted to form a film having a total magnetic layer thickness of 0.9 μm.

The resulting sample was slit into a tape,
The recording / reproducing characteristics were examined in the same manner as in Example 1, and a commercially available ME
Compared to tape. As a result, the tape of this example has a reproduction output of +7 dB or more and C / N as compared with the commercially available ME tape.
Was +6 dB or more.

The excellent recording / reproducing characteristics of the tape of this example are considered to be due to the high magnetic anisotropy energy of the magnetic layer. Therefore, the magnetic anisotropy energies K _{u of} both were investigated. As a result, the commercially available ME tape _Ku
Of about 1.4 × 10 ⁶ erg / cc, whereas the K _u of the tape of this example was about 2.7 × 10 ⁶ erg / cc. It can be said that the tape of this example exhibits excellent performance because of its high energy as described above although the tape thickness is thin.

Comparative Example 1 A magnetic layer was formed by the same method as in Example 4. However, if the incident angle range of the first magnetic layer is 9
The angle was 0 ° to 75 °. The resulting sample was slit into a tape and the recording / reproducing characteristics were examined, but the surface of the tape was easily scratched and the measurement was difficult. This has an incident angle of 90
It is considered that this is because the crystal grains grow abnormally due to the expansion up to a degree and the crystal grains that grow abnormally are easily broken by sliding with the head. Also, the anisotropic energy K _u is about 2.1.
It was as low as × 10 ⁶ erg / cc.

(Comparative Example 2) A magnetic layer was formed in the same manner as in Example 4. However, the key-like portion at the rear end portion of the shielding plate 81 was removed to widen the gap with the cylindrical can 2. The produced sample was slit into a tape shape and the recording / reproducing characteristics were examined.
Both were 3 to 4 dB lower. Also, the anisotropic energy K
_u was also low at about 1.7 × 10 ⁶ erg / cc. this is,
It is considered that oxygen introduced for the first magnetic layer penetrated into the initial incidence side of the second magnetic layer and significantly lowered the crystallinity of the second magnetic layer. From this result, it is understood that the control of introduced oxygen is very important. Considering the behavior of excess oxygen, it is necessary to have a structure that can be quickly exhausted. It is also understood that it is necessary to introduce oxygen from the final stage of film formation without introducing oxygen from the initial stage of film formation.

In the above embodiment, the diameter of the cylindrical can 2 is set to 1.5 m, but other sizes may be used. Further, the polymer film substrate 1 may be a film made of a polymer material other than polyethylene terephthalate. The conditions such as the incident angle and the film thickness may be within the ranges specified in the present invention.

[0048]

As described above, according to the magnetic recording medium of the present invention and the method of manufacturing the same, the magnetic anisotropy energy of the magnetic layer can be increased, so that a high C / N ratio can be achieved and the digital device can be used. It is possible to obtain a magnetic recording medium having excellent recording and reproducing characteristics that can be dealt with.

Furthermore, by using the manufacturing apparatus of the present invention, it is possible to obtain the above magnetic recording medium with high productivity.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of a magnetic recording medium of the present invention.

FIG. 2 is a schematic cross-sectional view showing an example of the inside of an apparatus for manufacturing a magnetic recording medium of the present invention.

FIG. 3 is a schematic cross-sectional view showing an example of the inside of a conventional magnetic recording medium manufacturing apparatus.

FIG. 4 is a diagram showing the relationship between the reproduction output and noise with respect to the film thickness of the first magnetic layer.

FIG. 5 is a diagram showing the relationship between the reproduction output and noise with respect to the film thickness of the second magnetic layer.

FIG. 6 is a diagram showing the relationship between the reproduction output and noise with respect to the amount of oxygen introduced when forming the second magnetic layer.

[Explanation of symbols]

 100 polymer film substrate 101 first magnetic layer 102 second magnetic layer 1 polymer film substrate 2 cylindrical can 3 supply roll 4 winding roll 5 evaporation source 51 first evaporation source 52 second evaporation source 6 electron beam 61 electron beam 62 Electron Beam 7 Shield Plate 71 Shield Plate 72 Shield Plate 8 Shield Plate 81 Shield Plate 82 Shield Plate 9 Oxygen Inlet Port 91 Oxygen Inlet Port 92 Oxygen Inlet Port 10 Free Roller 111 First Opening 112 Second Opening 112

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuro Ishida 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (9)

[Claims] 1. A thin film magnetic recording medium comprising a magnetic layer containing cobalt and oxygen as main components, wherein the thickness of the magnetic layer is 0.05 μm or more and 0.12 μm or less, and the magnetic layer is on a substrate. The first magnetic layer formed on the first magnetic layer and the second magnetic layer formed on the first magnetic layer, the columnar particles forming the first magnetic layer and the second magnetic layer are inclined in substantially the same direction. The magnetic recording medium is characterized in that the ratio of the film thickness of the second magnetic layer to the total film thickness of the magnetic layer is 50% or more and 80% or less. 2. The columnar particles forming the magnetic layer are separated from the substrate surface by 2
The magnetic recording medium according to claim 1, wherein the magnetic layer is inclined in the range of 0 ° to 35 ° and the easy magnetization direction of the magnetic layer is in the range of 10 ° to 25 ° from the substrate surface. 3. A first magnetic layer containing cobalt and oxygen as main components and a second magnetic layer are sequentially formed on a polymer film substrate running along the peripheral surface of a cylindrical can by an oblique evaporation method. In the method of manufacturing a magnetic recording medium to be formed, when the angle formed by the normal line of the polymer film substrate and the incident direction of vaporized atoms is defined as the incident angle, the incident angle at the initial stage of formation of the first and second magnetic layers is The incident angle at the final stage of formation is larger than the incident angle at the final stage of formation of the first magnetic layer, and the incident angle at the final stage of formation of the second magnetic layer is larger than the incident angle at the time of forming the first magnetic layer. The value of (introduction amount) / (film deposition rate) is larger than the value of (oxygen introduction amount) / (film deposition rate) when forming the second magnetic layer. Method. 4. The method for producing a magnetic recording medium according to claim 3, wherein the incident angle at the initial stage of forming the magnetic layer is 85 ° or less and the incident angle at the final stage of forming the magnetic layer is 50 ° or more. 5. A magnetic recording medium manufacturing apparatus for forming a magnetic layer by a vacuum deposition method on a polymer film substrate which is traveling along a cylindrical can. 1st along the running direction of polymer film substrate
And a second evaporation source are arranged on the same side of the polymer film substrate traveling upstream side with respect to a vertical line passing through the center of the cylindrical can, and between the cylindrical can and the first and second evaporation sources. A shield plate that sets the first and second openings corresponding to each evaporation source, and the distance between the vertical line passing through the center of the cylindrical can and the center of the evaporation portion of the first evaporation source is A distance between a vertical line passing through the center of the cylindrical can and the center of the evaporation portion of the second evaporation source is shorter than the radius of the cylindrical can, and is shorter than the radius of the cylindrical can; An apparatus for manufacturing a magnetic recording medium, wherein an evaporation source is disposed above a horizontal position of the second opening. 6. An apparatus for manufacturing a magnetic recording medium according to claim 5, wherein an electron beam generated from one electron beam source is distributed to two evaporation sources to heat the two evaporation sources. 7. The heating means for the two evaporation sources is an electron beam irradiation, and the electron beams directed to the respective evaporation sources do not intersect with a vaporized atomic flow from another evaporation source toward the opening. 5. An apparatus for manufacturing a magnetic recording medium according to 5. 8. The apparatus for manufacturing a magnetic recording medium according to claim 5, wherein the first evaporation source is smaller than the second evaporation source. 9. An oxygen introducing port for introducing oxygen toward the upstream side of the running of the polymer film substrate to each of the two openings, sets the running side of the opening of the polymer film substrate of the opening. The magnetic recording medium manufacturing apparatus according to claim 5, which is arranged near the shield plate.