JP2729544B2 - Magnetic recording medium and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a so-called ferromagnetic metal thin film type magnetic recording medium in which a ferromagnetic metal thin film is formed as a magnetic layer on a non-magnetic substrate by a vacuum deposition method, and more particularly to a high-vision application. And a ferromagnetic metal thin film type magnetic recording medium suitable for wideband signal recording and high density recording.

[0002]

2. Description of the Related Art In a magnetic recording medium, high-density recording has been strongly oriented. In order to achieve high-density recording, it is necessary to increase reproduction output, reduce noise, or achieve both to increase the so-called C / N (ratio of reproduction output C to noise). .

The magnetic material used in a coating type magnetic recording medium, which has been widely used in the past, is changed from iron oxide powder to ferromagnetic metal powder, and the material itself is changed. The magnetic recording / reproducing characteristics of high density and high S / N have been achieved by improving the magnetic field and improving the particle size.

However, despite these efforts, the limits of high-density recording have begun to be seen in coating-type recording media, and the development of metal thin-film media as a new material for achieving the next high-density recording has been promoted. ing. As a method for forming a metal magnetic thin film, there are a vacuum film forming method of forming a thin film in a vacuum such as a sputtering method, an ion plating method, and an electron beam evaporation method on a ferromagnetic metal on a substrate such as a polymer film; A so-called plating method for forming a thin film on a substrate is known.

[0005] Among them, a part of magnetic tape media obtained by the electron beam evaporation method has begun to be put into practical use as a magnetic tape for an 8 mm video system, so-called "Hi-8ME". However, in recent years, the demand for achieving a higher recording density has been extremely strong, and for example, the demand for large-capacity recording, such as a demand as a recording medium for a high-vision system, has been increasing. In order to respond to such demands, studies have been made on improving the characteristics of ferromagnetic metal thin-film magnetic recording media.

As a method of improving the characteristics of a metal thin film type recording medium, an electron beam evaporation method employing Co-Ni has been proposed to improve the magnetic film particle structure, for example, a coercive force by introducing oxygen during vacuum evaporation. Technology for increasing noise, reducing noise, and improving corrosion resistance (for example, Japanese Patent Publication No. 57-2)
3931 and JP-A-58-32234. ), A method of improving magnetic properties by oblique incidence vapor deposition in which a ferromagnetic metal vapor stream is obliquely introduced onto a non-magnetic substrate to form a film (for example, Japanese Patent Publication No. 41812/1972)
And Japanese Patent Publication No. 56-52377. A method of reducing noise by forming a multilayer structure of a plurality of deposited films and improving recording / reproducing characteristics by improving magnetic characteristics of a magnetic film (including providing a non-magnetic intermediate layer) (for example, Japanese Patent Publication No. No. 3133). A technique for eliminating the direction dependency of the recording / reproducing characteristics by controlling the growth direction of magnetic particles by forming a film by oblique incidence vapor deposition into a multilayer structure (for example, 54-141608 and JP-A-57-3223).

[0007] Among these attempts, the method of introducing oxygen into a ferromagnetic thin film and the oblique incidence evaporation method are particularly noted as techniques for producing a magnetic recording medium for high-density recording with improved magnetic characteristics and excellent electromagnetic conversion characteristics. Have been.

However, these techniques are not sufficient to improve the reproduction output and C / N over a wide frequency band of a recording signal, and the recording wavelength is 0.4 μm or less as in a high-vision system. It is necessary for recording a high-density recording signal of 1 μm ² / bit or less and a digital signal of a high transfer rate with a track width of 5 μm or less at a high density.
It has not been sufficient to obtain a magnetic recording medium capable of obtaining a high reproduction output over a wide frequency range, that is, a wide recording wavelength range.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional situation, and an object of the present invention is to provide a high reproduction output and a high C / C over a wide recording frequency range.
An object of the present invention is to provide a ferromagnetic metal thin film type magnetic recording medium capable of achieving an improvement in reproduction output and C / N ratio particularly in a high frequency region, that is, in a short wavelength, in order to obtain an N ratio.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a non-magnetic thin film formed on a non -magnetic substrate by a vacuum film forming method and the non-magnetic thin film.
A ferromagnetic thin film on the magnetic thin film, the ferromagnetic thin film having a thickness
At 1000 to 2000 °, the product of the residual magnetic flux density (Br (Gauss)) and the coercive force (Hc (Oersted)) (Br ×
Hc) is 6.5 × 10 ⁶ (Gauss Oersted) or more of the high magnetic energy layer, and prior to the ferromagnetic thin film
Average oxygen concentration at 100 ° near the interface with the non-magnetic thin film
Degree of 12-16 atomic%, near the surface of the ferromagnetic thin film
The average oxygen concentration at 100 ° is 10 to 50 atomic%.
At an angle of 100 ° near the interface with the non-magnetic thin film.
The average oxygen concentration is 100 ° near the surface of the ferromagnetic thin film.
After forming a non-magnetic thin film on a non-magnetic substrate by a vacuum film forming method on a magnetic recording medium characterized by being smaller than the average oxygen concentration in the non-magnetic thin film, The maximum angle of incidence (θmax
) To the minimum incident angle (θmin), and the minimum incident angle (θ
min), a high magnetic energy layer is formed by an oblique incidence vapor deposition method in which an oxidizing gas is introduced into the ferromagnetic metal gas stream so that the amount of oxygen to be introduced becomes larger near the min .
This can be achieved by the above-described method for manufacturing a magnetic recording medium.

[0011] Namely, the present invention is a non-magnetic thin film on a nonmagnetic substrate
On provided by a vacuum deposition method, towards the oxygen concentration of oxygen distribution in the thickness direction at the surface side is controlled to be higher specific weight than the oxygen concentration in the non-magnetic base side similarly by the vacuum deposition method A ferromagnetic thin film is provided, and the product of Br and Hc of the ferromagnetic thin film is 6.5 × 10 ⁶ (Gauss Oersted) or more.

In other words, the magnetic recording medium of the present invention
Since it has a high magnetic energy layer with a large Br × Hc,
High output can be maintained even in a magnetic recording system that supports wideband signal recording and has a small recording wavelength, for example, about 0.4 μm or less. This is based on the principle of magnetic recording.

Although the details of the mechanism for forming such a high magnetic energy layer are unknown, it is considered as follows. When a ferromagnetic thin film is formed directly on a non-magnetic substrate, the ferromagnetic crystal particles are formed by gas components such as low molecular weight components and moisture generated from the surface of a polymer film such as polyethylene phthalate by exposing the surface to a high temperature. Inducing some fluctuations to the initial growth and disturbing this growth, but if a ferromagnetic thin film or non-magnetic thin film is provided below the high magnetic energy layer as in the present invention, it can be prevented, It is considered that by defining the oxygen distribution of the high magnetic energy layer as described above, the disturbance of the initial growth of the ferromagnetic crystal grains can be minimized as described above.

The specific method for producing such a magnetic recording medium having a high magnetic energy layer is not particularly limited, but the high magnetic energy layer is formed at a later stage of film formation (at the time of forming the surface of the high magnetic energy layer). Can be produced by increasing the amount of oxygen introduced. Specifically, as described above, the incident angle of the ferromagnetic metal vapor forming the high magnetic energy layer with respect to the non-magnetic substrate continuously changes from the maximum incident angle (θmax) to the minimum incident angle (θmin), and Manufactured by oblique incidence vapor deposition in which an oxidizing gas is introduced into the ferromagnetic metal gas stream so that the amount of oxygen introduced is greater near the minimum incident angle (θmin) than near the maximum incident angle (θmax). it can. Here, in the oblique incidence evaporation method of the present invention, high magnetic
The energy layer is provided on the non-magnetic thin film.
Any magnetic and / or non-magnetic material between the non-magnetic thin film and the non-magnetic substrate
A magnetic thin film layer may be provided.

In the process leading to the present invention, the present applicant has made various proposals such as a single magnetic layer, an underlayer + a magnetic layer, a lower magnetic layer + a nonmagnetic intermediate layer + an upper magnetic layer on the same nonmagnetic substrate. Producing many ferromagnetic metal thin film type magnetic recording media with layer structure,
The relationship between Br × Hc of the ferromagnetic thin film layer A farthest from the substrate and the distribution of oxygen in the film and C / N in the short wavelength region was examined. As described above, the present invention has a ferromagnetic thin film layer A, that is, a high magnetic energy layer and a nonmagnetic thin film, and the product Br × of the residual magnetic flux density Br (Gauss) and the coercive force Hc (Oersted) of the high magnetic energy layer. Hc is 6.5 × 10 ⁶ (Gauss ·
Oersted) or higher and identification of high magnetic energy layer
Characteristics of the interface between the oxygen concentration on the surface
Oxygen concentration in the vicinity of the constant range is within a specific range, and the former is the latter.
Higher than who has been found to be important for obtaining a high C / N at short wavelength region.

That is, when a large amount of oxygen is contained on the substrate side of the ferromagnetic thin film layer A, it is effective to increase Br × Hc by reducing the amount of oxygen introduced during film formation to increase Br × Hc. However, when the amount of introduced oxygen decreases, the size of the particles forming the magnetic layer increases, and the noise level sharply increases accordingly. Even if the output level increases due to the increase in Br, the C / N does not increase. whereas, by controlling the oxygen concentration distribution is not particularly necessary to reduce the oxygen amount introduced如rather surface side of the high magnetic energy layer in the present invention
As a result , Br can be relatively easily increased, and as a result, the output level can be increased without increasing the noise level, and the C / N is increased.

In the measurement of the magnetic properties of the high magnetic energy layer in the magnetic recording medium of the present invention, a nonmagnetic layer is formed on a nonmagnetic substrate by a vacuum film forming method, and a nonmagnetic layer having the same structure as the high magnetic energy layer is formed thereon. The measurement sample with the magnetic layer formed under the same conditions
Created separately. The magnetic properties were measured with a vibrating sample magnetometer (VSM).

In the present invention, the oxygen distribution in the film of the uppermost ferromagnetic thin film layer of the constituent layers (that is, the high magnetic energy layer which is the magnetic layer located farthest from the base) is represented by a nonmagnetic thin film.
The average oxygen concentration at 100 ° near the interface with the film is 12 to
16 atomic%, and 100 ° near the surface of the ferromagnetic thin film.
Has an average oxygen concentration of 10 to 50 atomic%,
Average oxygen concentration at 100 ° near the interface with the non-magnetic thin film
Is the average oxygen at 100 ° near the surface of the ferromagnetic thin film.
What is necessary is just to satisfy that it is smaller than the concentration .

The product (Br × Hc) of the high magnetic energy layer in the magnetic recording medium of the present invention is 6.5 × 10 ⁶ or more, preferably 7.0 × 10 ⁶ or more, and more preferably 8.0 × 10 ^6. More than Oersted Gauss.

The other magnetic properties are not particularly limited, but if Br is too small at 3000 Gauss or less, sufficient output for high-density recording cannot be obtained, and if Hc is too small at 800 Oe or less, high density is obtained. Not enough output for recording. Therefore, Br is preferably 3000 Gauss or more, and particularly preferably 4500 Gauss or more. Hc is preferably 800 Oe or more, and more preferably 1300 Oe or more.

The thickness of the high magnetic energy layer is 1000
２０００2000Å .

[0022] In the thin film from the thickness of 10 Å that is substantially difficult to secure the magnetic properties. The thickness is 20
If it exceeds 00 °, the surface roughness becomes coarse, the output decreases with an increase in spacing loss, and the size of the columnar particles increases to increase the noise during reproduction, which is not practical.

In the present invention, the layer structure having the high magnetic energy layer as the uppermost layer is formed on a non-magnetic substrate by a vacuum film forming method.
, Non-magnetic thin film and structure der lever having a ferromagnetic thin film on a non-magnetic thin film, the number and each layer of the layer to the product <br/> layer between the nonmagnetic substrate and a non-magnetic thin film material There is no limitation on the thickness, the production method, or the like .

FIGS. 1 and 2 show specific examples of the layer structure of the magnetic recording medium according to the present invention. In the example of FIG. 1, after forming a non-magnetic underlayer 2 on a non-magnetic substrate 1,
2 is a structure in which a high magnetic energy layer 3 is formed. In the example of FIG. 2, a lower magnetic layer 4, a nonmagnetic intermediate layer 5, and a high magnetic energy layer 6 are sequentially laminated on a nonmagnetic substrate 1.

As means for forming the ferromagnetic metal thin film, a vapor phase plating method, a sputtering method, a vapor deposition method, an ion plating method, a CVD method and the like are exemplified. In order to more effectively achieve the object of the present invention, an oblique incidence evaporation method is preferable as a means for forming the high magnetic energy layer, and a ferromagnetic metal thin film formed by the oblique columnar particles is preferable.

As the oblique columnar particles, specifically speaking, the structural features include those in which columnar particles, which are aggregates of microcrystals, are obliquely folded and arranged. Oblique incidence deposition is the process of evaporating atoms of a metal from a vapor source onto a moving substrate while continuously changing the vaporized atoms of the metal from a maximum incident angle (θmax) to a minimum incident angle (θmin). When the substrate is transported along a cylindrical can, the deposited ferromagnetic metal thin film is made of a curved columnar ferromagnetic metal crystal.

In the production method of the present invention, the range of θmax is 60 to 90 degrees, preferably 80 to 90 degrees, and the range of θmin is 20 to 60 degrees, preferably 30 to 50 degrees. Can be

In the magnetic recording medium and the method of manufacturing the same according to the present invention, an oxidizing gas containing oxygen or a mixed gas of an oxidizing gas and an inert gas is introduced into the vacuum chamber during the oblique incidence deposition. A film in the form of columnar particles containing an oxide can be formed.

As the oxidizing gas, in addition to oxygen, ozone,
Hydrogen peroxide or the like can be used. In addition, examples of the inert gas include helium and argon. In particular, by increasing the amount of oxygen introduced into the ferromagnetic metal vapor stream from near the θmin than from the vicinity of the θmax, the distribution of oxygen in the high magnetic energy layer can be made closer to the surface than to the base. This is preferable because it can be increased. The vicinity of θmax and the vicinity of θmin mean that θmax and θmin are included.

Here, the specific amount of oxygen introduced into the ferromagnetic metal vapor flow at θmax and θmin is as follows:
There is no particular limitation, and it is appropriately adjusted depending on the size and scale of the vapor deposition apparatus.

Therefore, the oxidizing gas may be introduced only from the low incident angle side when the high magnetic energy layer is formed by oblique incidence deposition. In particular, the film obtained by introducing these oxidizing gases is excellent in magnetic properties, is excellent in reproduction output and nozzles, and can improve durability when used as a magnetic tape.

On the other hand, the method of forming the ferromagnetic thin film layer or the nonmagnetic layer other than the high magnetic energy layer is not particularly limited as long as it is a vacuum film forming method. For example, a vacuum deposition method, a sputtering method, an ion plating method, a CVD method, and the like can be given.

The layer structure of the film formation on our Keru nonmagnetic substrate in the present invention is preferably carried out continuously in a vacuum chamber, also,
A method capable of forming a film at high speed on a continuous nonmagnetic substrate is desirable. When a nonmagnetic layer between the high magnetic energy layer and the nonmagnetic substrate is formed by a vapor deposition method, a vacuum vapor deposition apparatus for producing a ferromagnetic metal thin film can be basically used. That is, the metal material to be deposited is, for example, Cu, Pt, Ti, A
It can be manufactured by using a non-magnetic metal material such as l, Cr, Bi, or by evaporating these metal materials while introducing an oxygen-containing gas. Alternatively, in the practice of the present invention, the non-magnetic layer may be substantially non-magnetic, and therefore, when a magnetic metal material is used, the non-magnetic layer is formed by introducing an oxygen-containing gas during vapor deposition. Can be made. Preferred metal simple substances include Cu, Ti, Au and Al, and preferred metal oxides include oxides such as Co, Ni, Si and Ti.

FIG. 3 schematically shows an example of a vacuum deposition apparatus that can be used in the production of the present invention. This apparatus is set to a predetermined degree of vacuum, for example, 1 × 10 ⁻⁴ Torr or less by a vacuum pump (not shown). When forming a magnetic film by introducing oxygen gas, the pressure is set to 1 × 10 ⁻³ Torr or less. When the nonmagnetic layer is formed of a metal oxide, the pressure is set to 1 × 10 ⁻³ Torr or more. An evaporation source 9 heated by a heating means such as an electron beam heating device 8 of about 20 KeV, a shielding plate 10 for regulating an incident angle θmin of vapor deposition atoms, a cylindrical can 11 for cooling, A glow discharge treatment chamber 12 used for cleaning the surface of the base and removing static electricity, gas introduction parts 13 and 14 for a gas such as oxygen, an unwind roll 15 and a take-up reel 16 are arranged. While continuously moving the non-magnetic substrate 1 supplied from the unwinding roll 15 along the can 11, the evaporated atoms from the evaporation source 9 are adhered to the substrate, and a continuous film of the evaporated atoms is formed. It is formed as a magnetic layer or a nonmagnetic layer.

Therefore, when the present invention is manufactured using only the above-described vacuum deposition method, a magnetic recording medium having a structure as shown in FIG. 1 or FIG. be able to. In this case, the metal species of the evaporation source 9 may or may not be replaced.

As the material of the ferromagnetic metal thin film used in the present invention, in particular, metals such as Fe, Co, and Ni, or alloys thereof, or alloys obtained by adding Cu, Pt, Cr, etc. to these metals. desirable.

The non-magnetic substrate used in the present invention includes:
Bases such as polyethylene terephthalate film (PET), polyethylene naphthalate film (PEN), polyaramid film, polyimide film and polyamide film are used. Thicknesses of several microns to several tens of microns are mainly used for magnetic tape applications. These materials, their thicknesses, and the like are matters to be selected that are compatible with the magnetic recording medium system, and do not define the present invention. On the surface of these bases, one or more projections such as mountain-like projections and wrinkle-like projections may be provided. By providing these, fine protrusions can be formed on the surface of the magnetic layer, and the durability as a magnetic recording medium can be improved. The mountain-like or granular protrusions can be obtained by internally adding organic particles or inorganic particles at the time of forming a polymer film, or by coating organic or inorganic particles on the film surface. The wrinkle-like projections can be formed, for example, by applying and drying a dilute solution of a resin. The height, distribution, density, etc. may be appropriately selected, but the height of the projection is 30 to 200 ° and the density is 1 ×.
It is preferably about 10 ^{4 to} 3 × 10 ⁷ pieces / mm ² .

Due to the heat generated during vacuum film formation, many components are degassed from the nonmagnetic layer substrate. In the present invention, since other layers are formed on the non-magnetic substrate before forming the high magnetic energy layer, the degassing is not affected in forming the high magnetic energy layer. Therefore, when the coating layer is formed on the non-magnetic substrate as described above, the magnetic recording medium of the present invention is particularly advantageous.

The outermost surface of the high magnetic energy layer of the present invention can be provided with a protective film and / or a lubricant for improving the corrosion resistance and durability of the magnetic film. Examples of the protective film include an oxide thin film, a nitride thin film, and a carbon-based thin film. Various fatty acids,
The ester, perfluoropolyether, etc. are mentioned, Usually, 2-40 mg / m < ² >, Preferably, 3-20.
It is applied as it is in the range of mg / m ² or diluted with an organic solvent or the like.

Although the surface shape of the magnetic layer is not particularly defined,
When the projections have a height of 10 to 500 °, the running performance and durability are particularly excellent.

The shape of the magnetic recording medium can be tape, sheet,
Although any of a card, a disk, and the like may be used, a tape shape and a disk shape are particularly preferable. In order to further increase the running durability of the magnetic recording medium of the present invention, a back layer made of non-magnetic particles and a binder resin can be provided on the surface opposite to the surface on which the magnetic layer is provided.

[0042]

EXAMPLES The present invention will be described more specifically with reference to the following examples. It is easily understood by those skilled in the art that the components, ratios, operation orders, and the like shown here can be changed without departing from the spirit of the present invention.

Therefore, the present invention should not be limited to the following embodiments. An embodiment of a configuration whose sectional view is shown in FIG. 1 will be described using a vapor deposition apparatus whose outline is shown in FIG. The surface on the side on which the ferromagnetic metal thin film is deposited as the nonmagnetic substrate 1 has a height of about 200 ° and a density of 1.2 × 10 ⁷ /
A 10 μm-thick polyethylene terephthalate film provided with microprojections made of mm ² SiO ₂ fine particles was used.

First, in order to form a non-magnetic underlayer , the non-magnetic substrate 1 is passed through a glow discharge treatment chamber 12 using oxygen plasma for removing moisture contained therein and cleaning the substrate surface. Then, the film was passed along a cooling cylindrical can 11 through an electron beam heating device 8, an evaporation source 9, a shielding plate 10, and a film formation unit including gas introduction units 13 and 14. Using Cu as the evaporation source 9 and evaporating it by electron beam heating, a thickness of about 2
A nonmagnetic underlayer of 00 ° was deposited.

Next, in order to form the high magnetic energy layer 3, while transporting the substrate provided with the nonmagnetic underlayer 2 in the same manner as above, an alloy having a composition of 80% Co and 20% Ni was used as an evaporation source. Evaporation was performed by electron beam heating, and a lower magnetic layer was applied to the substrate. At this time, the intensity of the electron beam, the amount of oxygen gas introduced from the two gas introduction portions 13 and 14, the transport speed of the non-magnetic substrate, and the shielding plate 10
The thickness of the high magnetic energy layer can be reduced to about 100 by appropriately selecting the relative positions of
The magnetic properties and oxygen distribution in the film were adjusted at 0 to 2000 °. At this time, the introduced amount of oxygen gas is 500 to 1500 SCC.
M (Standard Cubic Centimeter per Minute)
It described in. The intensity of the electron beam is 20 keV,
The transport speed of the non-magnetic substrate is 0.5 m / sec, and θmax is 90
Degree and θmin were set to 40 degrees.

According to the above procedure, magnetic tape samples # 1 to # 7 having a two-layered magnetic film having a high magnetic energy layer 3 having the same non-magnetic underlayer 2 but different magnetic properties and oxygen distribution in the film were obtained. Produced. # 1, 2, 3, and 4 were produced by introducing oxygen only from the gas introduction part 13 when producing the high magnetic energy layer, and # 5, 6, and 7 were produced by introducing oxygen from the gas introduction parts 13 and 14 when producing the high magnetic energy layer. Was introduced. For comparison, a sample # 8 of a ferromagnetic single-layer film having no non-magnetic underlayer 2 and a thickness of about 2000 ° was produced by introducing oxygen from the gas introduction sections 13 and 14.
# 2, 3, 4 are embodiments of the present invention, and # 1, 5, 6,
7 and 8 are comparative examples.

The characteristics of the high magnetic energy layer of samples # 1 to # 7 or the ferromagnetic single layer film of sample # 8 are as follows.
The thickness, the magnetic characteristics in the longitudinal direction in the plane, the surface near 100 ° and the average oxygen concentration in the vicinity of the interface with the nonmagnetic underlayer 2 (in the case of # 1 to # 7) or the nonmagnetic substrate (in the case of # 8) 100 ° It is shown in Table 1.

For measurement of magnetic properties, a vibrating sample magnetometer (T
OEI VSMP-1) was used. Here, the in-plane longitudinal direction is a direction parallel to the substrate transport direction in the film plane. The average oxygen concentration was measured by Auger electron spectroscopy to determine the concentration distribution of Co, Ni, O, and Cu contained in the prepared film in the depth direction. The average value at 100 ° from the interface with the non-magnetic substrate was calculated. For measurement, a PHI660 type manufactured by ULVAC-PHI was used. The acceleration voltage of primary electrons was 3 kV and the current value was 50 nA. Etching with argon ions was performed at an acceleration voltage of 3.5 kV and a current value of 0.5 μA at 2 mm × 2 mm. Performed by raster scan.

Next, a back layer was applied to the substrate surface opposite to the magnetic layer of Samples # 1 to # 8, and KRYTOX-K157SL manufactured by Maruwa Bussan Co., Ltd. was coated on the surface of the magnetic layer for 20 m.
g / m ² FOMBLIN manufactured by Enimont
It was dissolved in ZS-100 and applied. Next, it was cut into a width of 8 mm and incorporated into an 8 mm video cassette, and the electromagnetic conversion characteristics were measured.

The measurement of the electromagnetic conversion characteristics was performed by modifying a Hi-8 movie M870HR made by Fuji Photo Film Co., Ltd.
A single-wavelength signal of MHz is recorded at an optimum recording current, and the reproduction level at that time and the noise level at 6 MHz are measured by a Hewlett-Packard Spectrum Analyzer 3585A.
And the difference was defined as C / N. Table 1 shows the results obtained by using C / N of sample # 8 as a measurement standard (0 dB).

[0051]

[Table 1]

The results in Table 1 show the Br × Hc and C / N of the magnetic layer.
Note that the larger the Br × Hc, the higher the C / N can be obtained. In particular, Br × Hc is 6.
In the range larger than 5 × 10 ⁶ Oe · G (Oersted Gauss), the embodiment in which the oxygen concentration on the surface side is higher than the oxygen concentration on the interface side, even if the value of Br × Hc is almost the same, A C / N higher by about 2 dB is obtained than the comparative example in which the oxygen concentration on the side is higher than the oxygen concentration on the surface side. This can be explained by the oxygen distribution in the film. That is,
When a large amount of oxygen is contained on the interface side as in the comparative example, Br ×
To increase Hc, reduce the amount of oxygen introduced during deposition,
The method of increasing Br is effective. However, when the amount of introduced oxygen decreases, the size of the particles forming the magnetic layer increases, and the noise level sharply increases.
Although the C / N ratio does not increase even if the output level increases due to the increase in r, when the nonmagnetic underlayer is present and the amount of oxygen contained on the interface side is small as in the embodiment, the introduced oxygen amount is particularly small. Without this, Br can be increased relatively easily, and as a result, the output level can be increased without increasing the noise level, and the C / N becomes larger than in the comparative example.

As described above, the details of the mechanism by which the magnetic properties change due to the oxygen distribution in the film are still unknown, but the presence of a gas such as oxygen at the interface causes the crystal growth in the initial stage of the formation of the ferromagnetic thin film. On the other hand, it is considered that some fluctuations are induced and the magnetic characteristics are degraded. On the other hand, it is considered that a ferromagnetic thin film formed on a thin film layer such as a Cu underlayer without introducing oxygen near the interface has few such fluctuations and can obtain good magnetic properties.

As described above, the embodiment of the present invention has been described with an example in which Cu is used for the non-magnetic underlayer. However, as the material to be used for the non-magnetic underlayer, any material having characteristics close to non-magnetic can be used. Is possible .

Further, the case where the apparatus shown in FIG. 3 is used as an embodiment of the present invention has been described, but two or three layers can be formed at once using a vapor deposition apparatus having two or three cylindrical cans. By forming the magnetic recording medium, the magnetic recording medium of the present invention can be manufactured.

[0056]

According to the magnetic recording medium of the present invention, the ferromagnetic metal thin film layer furthest away from the nonmagnetic substrate has Br × Hc of 6.5 × 10 ⁶ (Gauss Oersted) or more,
Since the concentration of oxygen contained on the surface side of the thin film layer is higher than the concentration of oxygen contained on the substrate side, high output and low noise can be obtained particularly in a short wavelength region, and C / N The ratio can be dramatically improved. This also makes it possible to manufacture video tapes for high definition use at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an example of a cross section of a magnetic recording medium of the present invention.

FIG. 2 is a diagram schematically illustrating an example of a cross section of the magnetic recording medium of the present invention.

FIG. 3 is a view for explaining a specific example of a vacuum evaporation apparatus used for manufacturing the magnetic recording medium of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nonmagnetic base 2 Nonmagnetic underlayer 3 High magnetic energy layer 4 Lower magnetic layer 5 Nonmagnetic intermediate layer 6 High magnetic energy layer 7 Vacuum tank 8 Electron beam heating device 9 Evaporation source 10 Shielding plate 11 Cylindrical can 12 Glow discharge treatment Chamber 13 Gas inlet 14 Gas inlet 15 Unwind roll 16 Take-up roll

Continuation of the front page (72) Inventor Junichi Nakamikawa 2-2-1-1, Ogimachi, Odawara-shi, Kanagawa Fuji Photo Film Co., Ltd. (56) References JP-A-57-98133 (JP, A)

Claims (2)

(57) [Claims] A non-magnetic thin film formed on a non -magnetic substrate by a vacuum film-forming method, and a ferromagnetic thin film on the non-magnetic thin film;
The ferromagnetic thin film has a thickness of 1000 to 2000 ° and a product (Br × Hc) of the residual magnetic flux density (Br (Gauss)) and the coercive force (Hc (Oersted)) of 6.5 × 10 ⁶ (Gauss ·
Oersted) or higher magnetic energy layer, and
Near the interface between the ferromagnetic thin film and the non-magnetic thin film 100 °
Has an average oxygen concentration of 12 to 16 atomic%,
The average oxygen concentration at 100 ° near the surface of the ferromagnetic thin film is 10
50 atomic%, and near the interface with the non-magnetic thin film.
The average oxygen concentration at the near 100 ° is the above ferromagnetic thin film
A magnetic recording medium characterized by having an average oxygen concentration lower than 100 ° near the surface . 2. After a non-magnetic thin film is formed on a non-magnetic substrate by a vacuum film-forming method, the incident angle of the ferromagnetic metal vapor stream on the non-magnetic substrate is set to the maximum incident angle (θmax).
) To the minimum incident angle (θmin), and the minimum incident angle (θ
min), a high magnetic energy layer is formed by an oblique incidence deposition method in which an oxidizing gas is introduced into the ferromagnetic metal gas stream so that the amount of introduced oxygen is larger in the vicinity .
A method for manufacturing a magnetic recording medium according to claim 1 .