JPS59148123A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which is suitable for vertical magnetic recording at a high density, has excellent mechanical strength and chemical stability and has a large SN ratio by forming a magnetic layer of a continuous magnetic layer consisting essentially of an iron oxide having a prescribed characteristic. CONSTITUTION:A magnetic field perpendicular to the surface of targets T1, T2 in a vacuum vessel 1 of a sputtering device is formed to form plasma of a high density between the targets T1 and T2, thus forming a continuous magnetic layer 10 on a substrate 6. Fe (contg. 1 atom% Co) is used for the target material and Ar+O2 for the gas to be introduced to form a magnetic layer 10 having >=0.5% the ratio of the residual magnetization in the direction perpendicular to the plane of the layer 10 with respect to the residual magnetization in the direction within the plane of said layer and 0.2mum<R<=2mum surface roughness R. The magnetic layer which is suitable for vertical magnetic recording at a high density, has excellent mechanical strength and chemical stability, etc. and has good running property and a large SN ratio is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Industrial Application Field The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks.

26 Prior Art Conventionally, this type of magnetic recording medium has been used for video, audio,
It is widely used for recording various electrical signals such as digital ones. These have been developed as a system that uses magnetization in the in-plane longitudinal direction of a magnetic layer (magnetic recording layer) formed on a substrate. However, in recent years, with the increase in the density of magnetic recording, recording methods that use magnetization in the longitudinal direction of the plane,
As the recording signal becomes shorter in wavelength, the demagnetizing field within the medium increases, causing attenuation and rotation of the residual magnetization, resulting in a significant reduction in the reproduction output. For this reason, it is extremely difficult to reduce the recording wavelength to submicron or less.

On the other hand, a perpendicular magnetization recording method that uses magnetization in the thickness direction of the magnetic layer of a magnetic recording medium (so-called perpendicular magnetization) has recently been proposed (for example, [Nikkei Electronics J
August 7, 1978 issue No.

192). According to this recording method, as the recording wavelength becomes shorter, the demagnetizing field that acts on the residual magnetization in the medium decreases, so it has favorable characteristics for increasing density, and is essentially suitable for high-density recording. This is considered to be a method.

By the way, in order to perform this kind of perpendicular recording efficiently,
The recording layer of the magnetic recording medium is perpendicular (thickness direction of the magnetic layer)
It must have an axis of easy magnetization. Such a magnetic recording medium is a coated type in which a magnetic coating mainly composed of magnetic powder and a binder is coated on a substrate (support), and the axis of easy magnetization is oriented in the perpendicular direction of the magnetic layer. medium is known. This coated media includes Co, F
e30s, γ-Fe20kco added Fe5011. C
o-added γ-Fe2e5, hexagonal ferrite (e.g. barium ferrite), MnB+, etc. are used as magnetic powders (JP-A-51-46803, JP-A-53-6).
No. 7406, No. 52-78403, No. 55-8610
No. 3, No. 52-78403, No. 54-87202). However, in these coated media, there is a limit to increasing the packing density of magnetic powder due to the presence of a non-magnetic binder in the magnetic layer, and therefore S/
The N ratio cannot be made high enough. Moreover, the magnitude of the recorded signal is limited by the size of the magnetic particles, and thus a medium having a magnetic layer made of a magnetic coating is unsuitable for perpendicular magnetization recording.

Therefore, continuous thin film magnetic recording media, in which a perpendicularly magnetized magnetic layer is formed by continuously depositing a magnetic material on a support without using a binder, are attracting attention as suitable for high-density recording. ing.

This continuous thin film type perpendicular magnetization recording medium has a magnetic recording layer made of an alloy film of cobalt and chromium, as disclosed in Japanese Patent Publication No. 57-17282, and has a particularly high chromium content. states that a Co--Cr alloy film containing 5 to 25% by weight is superior. Further, a magnetic recording medium having a magnetic layer formed by adding 30% by weight or less of rhodium to a Co-Cr alloy film is disclosed in JP-A-55-111110, and furthermore, a cobalt-vanadium alloy film (for example, Institute of Electrical and Electronics Communication Engineers: Abbreviation T
transaction on Magnetism″1
982 Vol. 18 No. 6.1116) and cobalt.
Ruthenium alloy film (for example, No. Xa held in March 1982)
) Magnetic recording media using the 18th Tohoku University Research Institute Symposium ``Perpendicular Magnetic Recording'' are known.

Among these, the Co--Cr alloy film has been shown to be promising for perpendicular magnetization, but it has been found that it has the following drawbacks.

(1) In order to orient the axis of easy magnetization perpendicular to the surface of the magnetic layer, it is necessary to create the magnetic layer in a high vacuum of 10 Torr or more, and it is necessary to use advanced cleaning treatments for the substrate, low sputtering speed, etc. Such conditions are required, and the control factors for vertical alignment become extremely complicated.

(2) During signal recording and reproduction, since the magnetic recording medium and the perpendicular recording/reproducing head slide relative to each other, the interface between the head and the medium is poor and scratches occur on the medium. This can easily cause damage to the head.

(3) Since the magnetic layer is hard, cracks are likely to occur when the magnetic layer is provided on a flexible substrate.

(4) The corrosion resistance as a magnetic recording medium is not sufficient, so it is necessary to provide a protective film on the surface.

(5) Cobalt, a raw material, is difficult to obtain stably and is expensive.

3. Purpose of the Invention In view of the above-mentioned circumstances, the present inventors have made extensive studies and found that S We succeeded in obtaining a magnetic recording medium having a uniform magnetic layer with a high /N ratio.

4. Structure of the invention and its effects, that is, the present invention provides a magnetic recording medium in which a magnetic layer is provided on a substrate, wherein the magnetic layer is (a) a continuous magnetic layer containing iron oxide as a main component. Something.

(b), the ratio of the residual magnetization (MH) in the in-plane direction of the magnetic layer to the residual magnetization (Mv) in the perpendicular direction to the plane of the magnetic layer (
Mv /MH) is 0.5 or more.

and the surface roughness R) is 0.2.
The present invention relates to a magnetic recording medium characterized in that it is provided on the substrate with μm<R528m.

According to the present invention, since the magnetic layer has iron oxide as its main component, excellent properties unique to oxides (i.e. mechanical strength, chemical stability, etc.) can be obtained, which are necessary for conventional alloy thin films. The surface protective film that was previously used is no longer necessary. As a result, the distance between the magnetic head and the medium can be reduced, making it possible to perform high-density recording, and also to reduce costs in terms of materials.

Furthermore, since the residual magnetization ratio (MV/MH) between the in-plane direction and the perpendicular direction of the magnetic layer whose main component is iron oxide is set to 0.5 or more, the magnetic moment of the iron oxide magnetic material is in the in-plane direction. On the other hand, it rises in the vertical direction by more than 30 degrees, and has a structure that can sufficiently realize perpendicular magnetization. The magnetization amounts Mv and MH can be measured, for example, with a sample vibrating magnetometer (manufactured by Toei Kogyo Co., Ltd.). That is, if MV/MH is less than 0.5, it is difficult to obtain a magnetic moment suitable for perpendicular magnetization.

Furthermore, what is important in the present invention is that the magnetic layer is provided on a substrate with a surface roughness R) of 0.2 μm<9528 m. In the conventional magnetized film, a magnetized film containing iron oxide as a main component and having a residual magnetization ratio (Mv/Ms) suitable for perpendicular magnetization as in the present invention is not expected at all, and such a magnetized film is provided. The reality is that no consideration has been given to the surface roughness of the substrate in relation to good reproduction characteristics. As a result of intensive studies by the present inventor, the surface of the substrate on which the magnetic layer is to be provided must have an appropriate roughness, and the roughness range is set to 0.2 μm < 95
It was discovered for the first time that the distance should be 28 m. In other words, when R≦0.2 μm, the surface is too smooth and the surface of the magnetic layer provided thereon is also excessively smooth, resulting in poor slipperiness and poor running properties, resulting in so-called "" This is because "squealing" may occur. Also,
When R > 2 μm, the surfaces are too similar, making it difficult to form a uniform magnetic layer, and the noise level is high, making S
/N ratio becomes small. In this case, the substrate surface is too rough and the thickness of the magnetic layer becomes uneven, resulting in poor magnetic properties.
In particular, since variations occur in the coercive force (He) and the above-mentioned (7) remanent magnetization ratio (MV/M)l), it is extremely unsuitable for perpendicular magnetization.

Therefore, the surface roughness R) of the substrate is 0.2 μm < 95
It is essential to set the distance to 28 m, and only by setting it within this range can the running performance and magnetic properties be sufficiently satisfied.

In addition, the above-mentioned "surface roughness" in the present invention is JTSO6
The magnetic layer according to the present invention is fundamentally different from conventional coated magnetic layers in that it is made of iron oxide (e.g. Fe30Il, r Fe2O3 (or a belt-ride compound consisting of a non-stoichiometric composition intermediate between these) itself consists of a continuous thin film.In this magnetic layer, the sum of both elements iron and oxygen is magnetic. The content of the layer is preferably 50% by weight or more, and more preferably 70% by weight or more.The ratio of iron to oxygen is preferably 1 to 3 (number of oxygen atoms/number of iron atoms). Well, 4/3 ~
2 is even better, and the iron oxides exemplified above are suitable. However, metals other than iron and oxygen (8) or their oxides, nonmetals, semimetals, or compounds thereof are added to the magnetic layer, thereby changing the magnetic properties of the magnetic layer (
For example, it is possible to improve coercive force, saturation magnetization, residual magnetization), crystallinity, and orientation of crystals in a specific axial direction. Such additive elements or compounds include /l, C
oXCo-Mn.

Zn, Co-Zn, , Li, , CrXTi, , Li −
cr, , Mg, Mg-NisMn-ZnXNt, Ni.

N1-Aj! ,Ni-Zn,,Cu%Cu
-Mn, Cu-Zn, V, etc., but other elements and compounds may be used.

Further, base materials that can be used in the magnetic recording medium of the present invention include:
Magnetic material can be deposited and the thickness is 0.2μm〈9528m
Various materials can be used as long as they have a surface roughness of . For example, preferred substrates include substrates made of plastics such as polyethylene terephthalate, polyvinyl chloride, cellulose triacetate, polycarbonate, polyimide, polyamide, and polymethyl methacrylate, and ceramics such as glass.

Alternatively, metal substrates may also be used. The shape of the substrate may be a sheet, a card, a disk, a drum, or a long tape. In order to bring the surface of the substrate into a roughness range according to the present invention, the surface of the substrate material may be treated with a rotating roll with a sand film or the like.

To produce this magnetic recording medium, the substrate can be closely supported on a fixed plate, or the magnetic material can be applied while the substrate is running. For this purpose, a sputtering method is used in which a magnetic material target is sputtered in a processing chamber connected to an evacuation system such as a vacuum pump, or the material is evaporated from a magnetic material evaporation source and deposited on the substrate. Vapor deposition method etc. can be applied.

In either case, the elements constituting the magnetic layer are made to fly,
A continuous thin film is formed on the substrate. Note that, before forming this continuous thin film, the surface of the substrate is preferably cleaned by ion bombardment (Ar + bombardment is possible in the sputtering device described later), or subjected to baking treatment, or treated by applying high frequency.

(11) 5. Examples The magnetic recording medium of the present invention will be explained in more detail below with reference to the drawings.

Methods for depositing the magnetic material used in the present invention on the substrate include vacuum evaporation methods (including electric field evaporation and ion blating methods), sputtering methods, etc., in which the atoms constituting the magnetic layer are made to fly. A method using a facing target sputtering device is desirable.

FIG. 1 shows a facing target sputtering apparatus.

In the drawing, 1 is a vacuum chamber, 2 is an exhaust system consisting of a vacuum pump etc. for evacuating the vacuum chamber 1, and 3 is an exhaust system that introduces a predetermined gas into the vacuum chamber 1 and sets the gas pressure to about 10 to 1 O Torr. This is a gas introduction system. The target electrodes are configured as opposed target electrodes in which a pair of targets T1 and T2 are separated from each other by a target holder 4 and arranged to face each other in parallel.

Between these targets is a magnetic field generating means (not shown).
A magnetic field is formed by On the other hand, a substrate 6 with a surface roughness of 0.2 μm<R528m on which a magnetic thin film (12) is to be formed is placed by a substrate holder 5 perpendicularly to the side between the opposing targets.

In the sputtering apparatus configured in this way, a magnetic field is formed in a direction perpendicular to each surface of both targets T1 and T2 that face each other in parallel, and this magnetic field causes a cathode fall area (i.e., a droplet generated between target hairs and T2) to be generated. The γ electrons emitted by the impact of the sputtering gas ions accelerated by the electric field on the target surface in the region between the plasma atmosphere and each target 1 and ox are trapped in the space between the targets, and are directed toward the other opposing target. Move to. The γ electrons that have moved to the other target surface are reflected at the cathode fall section nearby. In this way, the γ electrons repeatedly move back and forth between the targets T1 and T2 while being bound by the magnetic field. During this reciprocating motion, the γ electrons collide with the neutral atmospheric gas to generate ions and electrons of the atmospheric gas, and these products promote the release of γ electrons from the target and the ionization of the atmospheric gas. . Therefore, Targera)'T
A high-density plasma is formed in the space between I and 'Th,
As a result, the target material is sufficiently sputtered and deposited as a magnetic material on the side substrate 6.

Compared to other flying methods, this facing target sputtering device enables film formation at a high deposition rate through high-speed sputtering, and the substrate is not directly exposed to plasma, allowing film formation at low substrate temperatures. This is advantageous for forming a perpendicularly magnetized film. Moreover, since the incident energy of the magnetic film material sputtered onto the substrate by the facing target sputtering device is smaller than that of a normal sputtering device, the material is easily deposited directionally in the desired direction, making it possible to record perpendicular magnetization. It becomes easier to obtain a membrane with a structure suitable for

Next, a specific example of producing a magnetic recording medium using the above sputtering apparatus will be described.

The conditions for this preparation were as follows.

Target material Iron (contains 1 atomic% Co) base
Long polyimide film (moves vertically downward) Distance between opposing targets 1001 Magnetic field in sputtering space 1400e Target shape 100III11 diameter disc (5 mm thick) Distance between substrate and target end 30IIffl Back pressure in vacuum chamber IQTorr Introduced gas Ar+Oz Introduced gas Pressure: 4 x 10 Torr Sputtering power: 420 W In this way, as shown in FIG. 2, a magnetic recording medium having an iron oxide magnetic layer 10 on the base film 6 was obtained. Regarding this medium, the characteristics of the magnetic layer were evaluated by identifying the composition using an X-ray microanalyzer (XMA), the state of iron oxide using an X-ray diffraction method, and the magnetic properties using a sample vibrating magnetic needle. The characteristics of the obtained magnetic recording medium were as follows.

First, the ratio of the residual magnetization in the in-plane direction (MH) to the residual magnetization in the perpendicular direction (Mv) is Mν/MH≧0.5
Met. That is, as illustrated in FIG. 3, a hysteresis curve during magnetization in the in-plane direction shown by the broken line and a hysteresis curve during magnetization in the perpendicular direction shown by the solid line were obtained, but when the applied magnetic field is zero The amounts of magnetization at this time were defined as MH and Mv. According to this, it is clear that the former hysteresis curve is smaller than the latter hysteresis curve and Mν≧0.5 MH, indicating that a magnetic layer suitable for perpendicular magnetization is formed. . This is a surprising fact for iron oxide-based magnetic layers.

In addition, the composition of this magnetic recording medium was analyzed using XMA (X-ray microanalyzer: Hitachi, Ltd. rX-556JKEVEX).
-7000 model), it was found that Fe was the main peak, with a small amount of Co present. Furthermore, in order to investigate the state of iron oxide, measurements were taken using an X-ray diffraction device (rJDX-10RAJ manufactured by JEOL Ltd., using a CuKα tube), and as shown in the table below, it was found that the magnetic layer mainly consisted of iron oxide. It turned out that it was an ingredient. Furthermore, it was observed using an electron microscope that this magnetic (15) layer had an ordered structure in the direction perpendicular to the in-plane direction.

For the magnetic recording medium obtained as described above, polyimide films having various surface roughnesses were used as the substrate, and F for perpendicular magnetization with a thickness of 2000 mm was placed on these substrates.
e50J Aoi (however, the coercive force (He) is 10,000e) was formed.

These magnetic recording media (magnetic tapes) were mounted on a known cassette deck, and recording and reproduction were performed (test conditions were room temperature and 65% RH).

(I6) As a result, the results shown in FIG. 4 were obtained for each magnetic tape. In other words, the rate of occurrence of tape squeal changes depending on the surface roughness of the substrate, but especially when the surface roughness exceeds 0.2 μm, tape squeal decreases rapidly. >0.2 μm. However, the surface roughness cannot be made larger than necessary;
If it exceeds 2 μm, the magnetic layer becomes non-uniform and He and M
It has been confirmed that v/MH varies and defects such as a decrease in the S/N ratio occur, so the upper limit should be set at 2 μm.

In addition, in the above-mentioned surface roughness range according to the present invention, there are moderate irregularities on the surface of the substrate, and the particle layer that is first deposited in each concave portion serves as a base (foundation) on which the next particle is deposited. It is thought that the particles are deposited directionally (preferably in the direction perpendicular to the substrate surface), and a columnar group of small grains suitable for perpendicular magnetization grows.

Moreover, the resulting magnetic layer has a sufficiently uneven surface with substantially uniform film thickness within the above-mentioned surface roughness range.

[Brief explanation of the drawing]

The drawings illustrate the present invention, and FIG. 1 is a schematic sectional view of a facing target sputtering apparatus, FIG. 2 is a sectional view of a magnetic recording medium, FIG. 3 is a hysteresis curve diagram of the magnetic recording medium, and FIG. The figure is a graph showing the occurrence rate of tape squeal when the surface roughness of the substrate is changed. In addition, in the symbols shown in the drawings, ■-・--1--Vacuum chamber 2-------1 Exhaust system 3--Gas introduction system 4.5------- -Holder 6---One base 10---One magnetic layer T1, T2---One target. Agent: Patent attorney Hiroshi Aisaka (19) (19) Kan21 Seki 130- 41 躬面米大igo (μ7TL)

Claims (1)

[Claims] 1. In a magnetic recording medium in which a magnetic layer is provided on a substrate, the magnetic layer: (a) consists of a continuous magnetic layer containing iron oxide as a main component. (b) The ratio (Mv/Mh) of the residual magnetization in the in-plane direction of the magnetic layer (IvL+) to the residual magnetization (Mv) in the direction perpendicular to the plane of the magnetic layer is 0.5 or more. . The structure has a surface roughness R) of 0.
A magnetic recording medium, characterized in that it is provided on the substrate with a diameter of 2 μm<352 μm.