JP2970219B2 - Magnetic recording medium and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thin-film magnetic recording medium and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the progress of the information society, the capacity and density of information recording carriers have been increased. In the field of magnetic tapes as well, research and development aimed at increasing the density of recording media have been actively pursued, and several thin-film media have been proposed to meet this requirement. Co-Cr and the like have been widely studied as ultra-high density magnetic recording materials, and Co-Cr thin films (or Co-Cr thin films) have been studied.
Research and development using Ni-Cr thin films) have been conducted.
Also, a Co—O / Co— layer obtained by laminating a magnetic Co—O (or Co—Ni—O thin film) on a Co—Cr thin film.
Studies have been made to achieve both recording density characteristics and practical durability by using a Cr magnetic recording medium. As a method for manufacturing a thin film magnetic recording medium, a continuous winding vacuum evaporation method is superior to other methods, particularly in terms of productivity, and is very effective as a practical mass production method. That is, as shown in FIG. 7, the magnetic recording medium can be mass-produced by evaporating the magnetic layer while the long polymer substrate is running along the peripheral surface of the cylindrical can. As the magnetic material, Co, Ni, Fe, a combination thereof, and an oxide obtained by vapor deposition in an oxygen atmosphere are mainly used.

[0003]

SUMMARY OF THE INVENTION Co-O / Co-Cr
Media parameters for realizing excellent recording / reproducing characteristics in a system-based magnetic recording medium have not been sufficiently clarified. Further, when the medium is formed by a vacuum evaporation method, it is necessary to increase the substrate temperature from the viewpoint of securing recording and reproduction characteristics and preventing the occurrence of cracks, and a polyamide or polyimide polymer substrate having high heat resistance is required. A polyethylene naphthalate (PEN) substrate or a polyethylene terephthalate (PET) substrate could not be used.

[0004]

In order to solve this problem, the present invention provides a method for forming C on a substrate directly or sequentially through an underlayer.
In a magnetic recording medium on which a layer containing o and Cr or Co, Ni and Cr as a main component, and a layer containing Co and O or Co, Ni and O as a main component, Co and Cr or Co, Ni and Cr are used. The layer containing as a main component has a saturation magnetization of less than 0.002 emu per 1 cm ² , and is manufactured by forming Co and Cr or Co on a substrate either directly or through an underlayer. N
In a method for manufacturing a magnetic recording medium for forming a layer containing i and Cr as main components and a layer containing Co and O or Co, Ni and O as main components, it is preferable that Co and Cr or Co, Ni and C
The substrate temperature when forming a layer containing r as a main component is:
The temperature is lower than the substrate temperature when a layer containing Co and O or Co, Ni and O as main components is formed.

[0005]

By setting the saturation magnetization of a layer containing Co and Cr or Co, Ni and Cr as main components to 0.002 emu or less, high output is ensured, noise is reduced, and recording / reproducing characteristics are improved. be able to. Also, P
Since a substrate such as ET or PEN can be used, the cost can be reduced.

[0006]

Embodiments of the present invention will be described below.

FIG. 1 is a schematic view of a high-output, low-noise medium according to an embodiment of the present invention. This medium was formed by an apparatus as shown in FIG. In the figure, a rotation direction 12 is taken from an unwind roll 3 in a vacuum chamber 2 evacuated by an exhaust system 1.
The long polymer substrate 4 unwound along the periphery of the magnetic layer forming can 5 is irradiated with the electron beam 6 while traveling along the peripheral surface of the can 5 for opening the shielding plate 9 from the electron beam evaporation source 7. After being subjected to the deposition of a Co—Cr layer in, the film is taken up by a take-up roll 10. The lamination of the Co-O layer on the Co-Cr layer is performed by changing the evaporation source from Co-Cr to Co-O after the formation of the Co-Cr layer and repeating the same steps.

[0008] When forming the Co-O layer, oxygen gas is introduced from the oxygen introducing nozzle 8, and an oxide magnetic layer is formed by reactive vapor deposition.

The angle of incidence of the vapor stream on the substrate is limited by the shielding plate 9 so as to be in the range of 60 to 30 degrees with respect to the normal to the substrate. The thickness of the Co—O layer is set to 100 nm to 200 nm.
And the saturation magnetization of the Co—O layer is set to 500 emu /
cc, the film thickness d of the Co—Cr layer and the saturation magnetization M
changed s. The thickness d of the Co—Cr layer was changed according to the film transport speed. The evaluation of d was performed by SEM using a film formed at a relatively low transport speed. When the transport speed of the film was high, d was calculated as being inversely proportional to the speed. The saturation magnetization Ms was measured by changing the Cr concentration of the evaporation source, and the saturation magnetization measured by a vibrating sample magnetometer using a 1 cm ² sample piece was used as an index for evaluating Ms · d. The can temperature at the time of forming the Co—O layer is 20 ° C.
And 10 ° C., and the can temperature when forming the Co—Cr layer is 2
The temperature was changed in the range of 0 ° C to 250 ° C. The recording / reproducing characteristics of the produced medium were measured using Sendust MIG using a drum tester.
The evaluation was performed at a recording wavelength of 0.5 μm using a head. FIG. 2 shows that the Co-Cr layer has a thickness of 10 nm or more.
Co-O / Co when changing the thickness and saturation magnetization of the Cr layer
-Shows the measurement results of the recording and reproducing characteristics of the Cr medium. The horizontal axis is C
The saturation magnetization was determined per 1 cm ^{2 of the} o-Cr layer. The recording wavelength is 0.5 μm. As can be seen from FIG.
As the saturation magnetization per cm ^{2 of the} r layer increases, the reproduction output decreases when the can temperature is low. Also,
Regardless of the can temperature, noise increases as the saturation magnetization per cm ² increases. When the thickness of the Co—O layer is 100 nm or 200 nm,
The saturation magnetization per cm ^{2 of the} Cr layer is 0.002 em
High output and low noise can be obtained at u or less. This tendency was common when the saturation magnetization was changed by either the film thickness or the saturation magnetization.

[0010] The saturation magnetization of the Co-Cr layer may be 0, that is, non-magnetic. FIG. 3 shows that the average saturation magnetization is 500 emu / c when the thickness of the Co—Cr layer is 100 nm.
FIG. 9 is a diagram showing the measurement results of the film thickness d of the Co—Cr layer and the recording / reproducing characteristics when the film transport speed is changed under the evaporation condition of c. The recording wavelength is 0.5 μm. From the results shown in FIG. 3, when the thickness of Co—Cr becomes 5 nm or less, the reproduction output sharply decreases. Therefore, Co-Cr running 5n
m or more. Although the reason for this is not clear, it is thought to be related to the coverage of the substrate surface, the crystal orientation of the Co—Cr layer surface, and the like. Co-C
When the thickness of the r layer is 100 nm or less, the substrate temperature is 20 ° C.
No cracks were generated on the film surface.

FIG. 4 shows a Co-Cr layer having a thickness of 40 nm and a thickness of 1 cm.
A square magnetization ratio of the in-plane direction magnetization curve of the entire medium and a recording wavelength of 0.5 μm when the saturation magnetization amount per ² was formed at 0.0012 nm and the Co—Cr layer was formed at different deposition temperatures and incident angles. FIG. 6 is a diagram showing a relationship between reproduction outputs in the case of FIG. FIG.
As can be seen from FIG.
A range from degrees to 0.9 is desirable.

FIG. 5 shows a Co-Cr layer having a thickness of 40 nm and 1 cm.
^When the saturation magnetization per ² was formed at 0.0012 nm, and the Co-Cr layer was formed by changing the deposition temperature and the incident angle, the direction of easy magnetization of the entire medium and the recording wavelength of 0.5 μm
FIG. 6 is a diagram showing a relationship between reproduction outputs in the case of FIG.

As can be seen from FIG. 5, the easy magnetization direction is desirably in the range of 15 to 35 degrees from the plane of the film. Also, when the recording wavelength was 0.3 μm, the same results as in FIGS. 5 and 6 were obtained.

Until now, high substrate temperature has been indispensable for the deposition of the Co—Cr layer.
It was found that the substrate temperature at the time of forming the Co—Cr layer can be lowered by reducing the saturation magnetization per unit area of the r layer. This means that there is no need to use expensive polyamide or polyimide substrates, which are extremely high in heat resistance, which was conventionally required when depositing a Co-Cr layer, and polyethylene naphthalate substrates and polyethylene are inexpensive compared to these substrates. This indicates that a terephthalate substrate can be used, and has great industrial significance. further,
Forming the Co—Cr layer at a low temperature also has an advantage in terms of performance. This is described below.

In a thin-film magnetic recording medium, it is general that the shape of the fine particles is preliminarily applied to the surface of the substrate by depositing fine particles on the surface of the substrate, and the shape of the fine particles is stored and reflected on the surface of the medium by vapor deposition. This lowers the coefficient of friction between the magnetic head and the recording medium to ensure the practical durability of the medium. Therefore, the number of protrusions and the shape of the protrusions due to the fine particles are factors to be strictly controlled, and if the protrusion density is too small or too large, the durability is adversely affected. Also, the projection height causes spacing loss during recording and playback,
The height of the projection is designed to be as low as possible within a range where durability can be ensured. However, when the deposition temperature is high in the deposition including the oblique incident component, the deposited film itself generates a prominent projection shape due to the self-shading effect. The projections formed by the self-shading effect during oblique deposition have a higher projection density than the optimum projection density which has been conventionally studied by applying fine particles, and the projection height is particularly high in the case of high-temperature deposition. Therefore, from the viewpoint of protrusions on the medium surface, it is desirable that the deposition temperature be as low as possible in order to ensure practical durability and high-density recording / reproducing characteristics. Co-O layer there is a limit to reduction in the substrate temperature since the static magnetic properties and the recording reproducing characteristics vary by the substrate temperature, but as shown in the embodiment of the present invention, Co-Cr layer per 1 cm ² When the saturation magnetization is 0.0
If it is equal to or less than 02 emu, the recording / reproducing characteristics do not deteriorate even if the substrate temperature is lowered. Therefore, making the substrate temperature at the time of forming the Co-Cr layer lower than the substrate temperature at the time of forming the Co-O layer also as a manufacturing condition of the medium for suppressing the generation of the extra projection due to the self-shading effect, This is important as a condition that does not become the main factor of the protrusion. In other words, by setting the saturation magnetization per cm ^{2 of the} layer containing Co and Cr or Co, Ni and Cr as the main components under the substrate temperature condition to 0.002 emu or less, the recording and reproducing characteristics can be secured, and The shape given to the substrate can be fully utilized.

It is preferable that the initial incident angle of the vapor flow at the time of forming the Co—Cr layer is not 90 degrees (tangential direction). When the 90-degree component is added, the adhesion strength of the film is reduced, and the recording / reproducing characteristics are slightly deteriorated. Regarding the Co-O layer, the recording / reproducing characteristics are clearly deteriorated both when the incident angle component of 90 degrees (tangential direction) is included and when the incident angle component is 0 degrees (normal incidence). In particular, when the 0-degree component is added, it is considered that the output changes very sensitively to the change in the height of the protrusion and the thickness of the surface protective layer, and the spacing loss factor is increased. The optimum range of the incident angle in the range from 90 degrees to 0 degrees differs depending on the substrate temperature and the characteristics of the magnetic head used.

In the embodiment, the first layer is made of Co-
Although only the case where Cr is used has been described, Co-N
Similar effects were obtained when i-Cr was used. Similarly, in the embodiment, only the case where Co-O was used as the second layer was described, but the same effect was obtained when Co-Ni-O was used. Although the measurement results of the recording / reproducing characteristics of the embodiments have been described only for the tape-shaped thin film magnetic recording medium, the present invention is not limited to this, and it goes without saying that the present invention is effective for thin film magnetic recording media in general.

[0018]

As described above, according to the magnetic recording medium and the method of manufacturing the same of the present invention, a Co-O / Co-Cr film having excellent recording / reproducing characteristics using a polyethylene naphthalate substrate or a polyethylene terephthalate substrate. System magnetic recording medium can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of the configuration of a magnetic recording medium according to the present invention.

FIG. 2 is a characteristic diagram showing measurement results of recording / reproducing characteristics of a Co—O / Co—Cr medium when a saturation magnetization amount per 1 cm ^{2 of a} Co—Cr layer is changed.

FIG. 3 is a characteristic diagram showing measurement results of recording / reproducing characteristics when a film thickness d of a Co—Cr layer is changed.

FIG. 4 is a characteristic diagram showing the relationship between the squareness ratio of the in-plane direction magnetization curve of the entire medium and the reproduction output.

FIG. 5 is a characteristic diagram showing the relationship between the direction of easy magnetization of the entire medium and the reproduction output.

FIG. 6 is a schematic view showing an example of a method for manufacturing a magnetic recording medium by a continuous vapor deposition method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust system 2 Vacuum tank 3 Unwind roll 4 Polymer substrate 5 Can for magnetic layer formation 6 Electron beam 7 Electron beam evaporation source 8 Oxygen introduction nozzle 9 Shielding plate 10 Take-up roll 11 Guide roll 12 Rotation direction

Continuation of front page (56) References JP-A-5-334646 (JP, A) JP-A-53-62198 (JP, A) JP-A-3-86914 (JP, A) JP-A-5-159269 (JP, A) , A) (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 5/66 G11B 5/85

Claims (7)

(57) [Claims] 1. A layer forming comprising a layer containing Co and Cr, or Co, Ni and Cr in order directly or via an underlying layer on the substrate as a main component, and Co and O or Co, Ni and O as main components In one of the layers containing Co and Cr or Co, Ni and Cr as main components,
A magnetic recording medium having a saturation magnetization per cm ² of 0.002 emu or less. 2. The magnetic recording medium according to claim 1, wherein the thickness of the layer containing Co and Cr or Co, Ni and Cr as main components is 5 nm or more. 3. The magnetic recording medium according to claim 1, wherein the squareness ratio in the in-plane direction is 0.6 or more and 0.9 or less. 4. An angle between the easy magnetization direction and the in-plane direction of the film is 1.
The angle is not less than 5 degrees and not more than 35 degrees,
The magnetic recording medium according to claim 2 or claim 3. Vacuum a layer containing 5. A layer comprising in sequence directly or via an undercoat layer on a substrate as main components Co and Cr, or Co, Ni and Cr, and Co and O or Co, Ni and O as main components In the method for manufacturing a magnetic recording medium formed by a vapor deposition method, the Co and Cr or Co, Ni and C
The layer containing r as a main component has a saturation magnetization of not more than 0.002 emu per 1 cm ² , and the substrate temperature when forming the layer containing Co and Cr or Co, Ni and Cr as a main component is Co A method for producing a magnetic recording medium, wherein the temperature is equal to or lower than the substrate temperature when a layer containing Co and Ni and O as main components is formed. 6. Co and Cr or Co, Ni and C on a substrate.
6. The method for producing a magnetic recording medium according to claim 5, wherein the range of the vapor incident direction when forming the layer containing r as a main component does not include the tangential direction. 7. A method of forming a layer containing Co and O or Co, Ni and O as main components on a substrate, wherein a range of a vapor incidence direction does not include both a normal incidence and a tangential incidence. The method for manufacturing a magnetic recording medium according to claim 5 or 6, wherein