JPH02289920A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve overall durability of a recording medium by successively forming a magnetic recording layer and a thin film protective layer essentially comprising silicon oxide on at least one surface of a substrate and specifying the electric resistivity of the protective layer to >=10<12>OMEGA.cm. CONSTITUTION:On at least one surface of the substrate 1, a ferromagnetic thin film 2 as the magnetic recording layer is formed and then a thin film 3 essentially comprising silicon oxide is formed thereon as the protective layer. The magnetic recording layer 2 consists of ferromagnetic alloy films, ferromag netic oxide films, ferromagnetic nitride films, etc., which essentially comprise Fe, Co and Ni. The protective layer 3 is a thin film essentially comprising silicon oxide with electric resistivity >=10<12>, and more preferably 1 X 10<13> - 1 X 10<15>OMEGA.cm, and further preferably, 3.3 X 10<13> - 3.4 X 10<14>OMEGA.cm. Thereby, wear resistance and durability of the medium can be improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to magnetic recording media, and particularly relates to magnetic recording media that have various properties that are practically required, such as wear resistance, running stability, durability, and environmental resistance. The present invention relates to a ferromagnetic metal thin film type magnetic recording medium.

[Prior art] In recent years, with the increase in the amount of information in the information processing technology field and the improvement in the quality of video and images in the video processing technology field, there has been a demand for magnetic recording media capable of high-density recording. It's increasing.

Therefore, research and development are actively being carried out to meet this demand.

Among them, as a magnetic recording layer (:o-Ni.Co-
Metal thin film magnetic recording media, in which a ferromagnetic metal thin film such as ferromagnetic metal film is formed by sputtering or vapor deposition, are seen as more promising as media suitable for high-density recording than the coating-type magnetic recording media currently in general use. ing.

In metal thin film magnetic recording media, unlike coated media, the entire thin film contributes to magnetic recording and has high planarity, making it possible to minimize spacing loss.

If such advantages of metal thin film type magnetic recording media can be utilized, a magnetic recording medium can be obtained which far exceeds coating type magnetic recording media in both output and CAN ratio.

In addition, by adopting narrower tracks and shorter wavelengths as a recording method, it becomes possible to perform high-density recording at least several times as much as in coating-type magnetic recording media.

However, at present, various problems still remain in the practical application of metal thin film magnetic recording media.

For example, in flexible media such as video tapes, video floppy disks, data recording tapes, and floppy disks, recording and reproduction are performed by the magnetic recording medium traveling while partially in contact with a magnetic head. Therefore, in order to realize high-density recording, it is necessary to further reduce the spacing loss, which tends to increase the probability of contact between the head and the medium. Furthermore, in a rigid magnetic recording medium whose base is made of a nonmagnetic metal or the like, the medium and the magnetic head are generally in contact with each other when the medium is stationary.

However, the magnetic recording layer, which is made of a thin metal film, is easily damaged by contact with the magnetic head, and if it is damaged, the running performance may deteriorate, resulting in a decrease in output, or in extreme cases, the drive may become impossible. There is.

This problem has been the biggest problem preventing the practical use of metal thin film magnetic recording media.

Other problems in the practical application of metal thin film magnetic recording media are:
Depending on the type of metal used, the magnetic H layer, which is a thin metal film, may corrode if it comes into contact with air for a long time.

For example, a Co--Ni metal thin film corrodes in a short period of time under high temperatures or environments containing salt in the air.

Coating type magnetic recording media, which have been commonly used in bidet discs, video floppy disks, data recording floppy disks, etc., are made by mixing magnetic powder with a binder and coating it on a pace film. Because it is finely roughened, frictional resistance is low. Furthermore, by adding substances with excellent wear resistance and lubricity to the binder, problems related to sliding with the magnetic head have been solved and overall reliability has been improved.

In contrast, in metal thin film magnetic recording media, a protective layer is formed on the surface of the metal magnetic layer by the method listed below. Attempts have been made to add such information to recording media.

■Provides wear resistance. An inorganic protective layer made of a hard material is formed on the metal thin film magnetic recording layer.

For example, SiO. SiOa. SiN. A.I.J. Ti
Vacuum deposition of thin films such as O+diamond-like carbon,
It is formed by sputtering, plasma CVD, or the like.

■Providing lubricity: i) A protective layer made of a lubricating material is placed on the metal thin film magnetic recording layer,
Alternatively, it is formed on the inorganic protective layer.

For example, MOS2. WS2. A thin film of an inorganic material such as diamond-like carbon or amorphous carbon is formed by vacuum evaporation, sputtering, plasma CVD, or the like. Alternatively, a layer of an organic material such as a fluororesin, a silicone oil surfactant/solvent, a saturated fatty acid, or an ester oligomer is formed by a liquid coating method, vacuum evaporation, sputtering method, or the like.

ii) Forming fine irregularities on the surface of the magnetic recording medium to reduce the number of real contact points and lower the coefficient of friction.

■Environmental resistance: Forms a corrosion-resistant protective layer.

For example, AI. (A layer of a simple element such as r.Ti.V.si, a layer of an oxide, nitride, carbide, or boride of the above element, or a composite layer of these layers, or a layer of a polyethylene, polyimide, nylon, etc.) A layer of polymeric material is formed by vacuum evaporation, sputtering, plasma CVD, coating liquid coating method, or the like.

Looking at the durability standards for floppy disks, which require high reliability, we find that floppy disks for data recording can withstand more than 3 million passes at room temperature and at high temperatures (approximately 500
℃) and low temperature (approximately 10℃), for video floppy disks, as a guideline for practical use,
Normal temperature, high temperature and high humidity (40°C, 85% RH). Low temperature (-5
Both are required to have continuous running durability of 48 hours (approximately 10 million buses) or more at temperatures (°C).

[Problems to be Solved by the Invention] However, with conventional metal thin film magnetic recording media, scratches and deposits occur on the media surface and the head surface when the bus is run at most tens of thousands to hundreds of thousands of times, making playback difficult. The output has decreased significantly, and it cannot be said that it has reached a practical level. In addition, conventional rigid metal thin film magnetic recording media have been subjected to several to several thousand CSS (Contact.
Start Stop caused scratches and deposits (aggregation of fine powder) to occur on the media surface and head surface, resulting in a significant drop in playback output.

This is because the conventional protective layer does not have sufficient hardness, so the protective layer itself is damaged by sliding with the magnetic head, and this damage also extends to the magnetic recording layer, causing the fine powder generated at this time to be damaged. When the magnetic head gets stuck, it can cause head clogging, which can sometimes cause a significant drop in playback output (for example, dropouts, etc.), or in the worst case, cause damage such as scratches to the media or head surface. , the durability of the media and head is impaired.

Proposals for magnetic recording media using silicon oxide as a protective layer (for example, JP-A-61-115229, JP-A-61-1787)
30 or Japanese Unexamined Patent Publication No. 62-229526, etc.), but the results are still not satisfactory.

Co-Cr M1 floppy disk for data recording
Example I using CO,04, which is also a solid lubricant film, as the protective layer of the magnetic layer and showing still durability of more than 10 million passes.
vi et al., IEICE Technical Report 87-15 (1987), but in experiments conducted by the present inventors, sufficient long-term storage durability and environmental resistance have not been obtained with a thin film layer made of Co304. Conventional metal thin film magnetic recording media have passed environmental durability tests (8
Even under the target specifications of 500 hours or more under 5°C and 85 RH conditions, the metal thin film magnetic recording layer corrodes in about 0.1 to 10 hours at most, and the actual situation is that it has not reached a practical level. be.

The present invention solves the above-mentioned problems and provides a magnetic recording medium that has excellent overall durability such as abrasion resistance, environmental resistance, and long-term storage durability.

[Means for Solving the Problems] The magnetic recording medium of the present invention has a magnetic recording layer and a thin protective layer containing silicon oxide as a main component in this order on at least one surface of a substrate, The electrical resistivity of the layer is 1
It is characterized by having a resistance of 0.012 Ω·cm or more.

By the way, it is generally known that the film quality of the protective layer largely depends on the film formation conditions and also varies depending on the film thickness.

The present inventors basically aim for long-term storage durability, iitfJi
As a result of intensive studies on the film quality and durability of thin films made of silicon oxide with t-boundary properties and several hundred thick, we found that the physical properties (e.g. electrical resistivity and refractive index) of silicon oxide thin films were compared to those of the bulk. When the physical properties are brought close to those of silicon dioxide, the abrasion resistance and durability of the thin film improves, and the running durability (bus durability) increases by 10%.
We have newly discovered that it can be used for more than 1,000,000 buses and CSS tests for more than 20,000 times, and that it has excellent long-term storage durability and environmental resistance, leading to the present invention.

FIG. 1 shows the basic structure of a flexible magnetic recording medium according to the present invention. The substrate 1 may be made of a base film that has conventionally been generally used as a base film for flexible magnetic recording media, but is particularly made of glass. Heat-resistant polymer films having a transition temperature of 200° C. or higher, such as polyimide, polysanolefin, polyamideimide, polyadenoletherketone, aramid, etc., are preferred. The front or back surface of the substrate 1 may have a large number of fine protrusions (surface irregularities) as necessary in order to improve the slipperiness of the film and the running stability of the magnetic recording medium.

When a magnetic layer or a protective layer is formed on the surface of the substrate 1 having surface irregularities, irregularities substantially corresponding to the fine irregularities on the surface of the base film are formed on the outermost surface thereof. That is, the surface roughness of the base 1 becomes approximately equal to the surface roughness of the magnetic recording medium formed thereon.

Considering spacing loss and dropout, the surface roughness is determined by the protrusion height corresponding to the 0.01% from the highest when taking the statistical distribution of protrusion heights in the range of 10,000 μm2 or more. 600 people or less, more preferably 30 people
0 people or less, protrusion density between IX10' and IX
109 pieces/mm2. Furthermore, IX105~Ixl08
pieces/mm2. More preferably 1×IO6 to lxlO?
It is desirable that the range is 1/mm”.

Here, the surface roughness and protrusion density of the substrate and magnetic recording medium are
The measurement is performed by the shadowing method, which is a non-contact measurement method, as disclosed in Japanese Patent Application Laid-Open No. 63-188818.

A ferromagnetic thin film 2 is formed as a magnetic recording layer on at least one surface of a substrate 1, and a thin film 3 containing silicon oxide as a main component is formed thereon as a protective layer.

The magnetic recording layer 2 includes, for example, Fe. Co. A ferromagnetic alloy film containing Ni as a main component, a ferromagnetic oxide film, a ferromagnetic nitride film, or the like can be used. These magnetic recording layers can be formed by a vacuum deposition method, an ion blating method, a physical vapor deposition method such as a sputtering method, a plating method, or the like. In particular, when the magnetic recording layer is formed by vacuum evaporation or sputtering, and the magnetic recording layer is a Co-Cr perpendicularly magnetized film containing 15 to 23% by weight of Cr and 85 to 77% by weight of Co. , the present invention is particularly effective.

Is the protective layer 3 a thin film whose main component is silicon oxide? Become,
Its electrical resistivity is 1012)), more preferably 1
x l O" to 1 x 1 (BsΩ-cm, and its electrical resistivity is in the range of 3.3 X I O" to 3.
Most preferably, it is in the range of 4x l Q l 4Ω·cm.

This value is the value of thermally oxidized SiO film (1.O
+4 to 7.5 x l Q IG Ω·cm ) or close to the bulk value of SiOz (10'' to 1014, quartz glass > i o ''). If the electrical resistivity is less than 1012 Ω・cm, the hardness is insufficient and wear resistance is poor, and if the electrical resistivity exceeds 10” Ω・cm, internal stress increases, causing minute cracks in the film or In some cases, the protective layer may peel off from the underlying layer, resulting in a protective layer with poor durability.

The amount of silicon oxide contained as a main component in the protective layer is
It is preferably 80% by weight or more, more preferably 85% by weight or more, based on the protective layer.

The refractive index of the thin film having the above electrical resistivity is 1.460 to
It falls within the range of 1.500 (as measured by an ellipsometer).

The protective layer 3 can be formed by a vacuum deposition method, an incubation ink method, a physical vapor deposition method such as a sputtering method, or a liquid coating method. When formed by a physical vapor deposition method, it is preferable that Si or Si, Si02 is used as the vapor deposition source, and that the introduced oxygen gas is 15% or less of the total pressure (Ar+introduced gas). When the protective layer 3 is formed by physical vapor deposition, the value of the electrical resistivity of the protective layer 3 can be controlled by adjusting the gas pressure, oxygen partial pressure, substrate temperature, applied power, film thickness, etc. For example, when forming the protective layer 3 using an RF magnetron sputtering device, SiO. Using a target, substrate temperature 200°C or higher, argon pressure 0.6P
a or less, input power 2kW or more, film formation rate 0.05μm/
The protective layer according to the present invention can be formed under the conditions that the film thickness is 300 mm or more and the film thickness is 300 mm or less. Generally, as the introduced oxygen gas pressure decreases, the electrical resistivity tends to decrease. Furthermore, when oxygen gas is not introduced, the electrical resistivity tends to increase as the Ar gas pressure decreases.

On the other hand, when the protective layer 3 is formed by a liquid coating method, the specific resistance of the protective layer can be controlled by adjusting the concentration, curing temperature, curing time, film thickness, etc.

By the way, depending on the environmental conditions, a film containing silicon oxide as a main component may be exposed to high temperatures (e.g., 40°C, 85%
There is a problem in that the internal stress of the film tends to change greatly in environments such as RH) or low temperature (for example, -5° C.). Generally, internal stress changes from compressive stress to tensile stress as the temperature rises. If the internal stress change in the film is large, the flatness of the magnetic recording medium may change, cracks may occur in the film, or the film may peel off.

Further, when the value of the thermal expansion coefficient of the protective layer is extremely small compared to the ferromagnetic metal thin film constituting the magnetic recording layer,
Curling is likely to occur in the formed magnetic recording medium.

If there is a possibility that the above two problems may occur, B. C. N. P. S. Al. Ti. V. Cr.
Zn. Ge. Zr. Nb. Mo. Ta. Mg. Hf.
Au. At least one element selected from the group consisting of Pt or a compound containing one or more of these elements
It is desirable to contain more than one species. Among them, B.
．． Al20a. TiOz. BJ3. B20. ．． ．． MgO
etc. are preferred. The amount added is determined by the protective function of the protective layer (
Abrasion characteristics) are not reduced, i.e., l for the protective layer 3.
0 to 20% by weight is preferred.

The thickness of the polymer film base 1 is, for example, 75 μm or less, 6
μm or more, and small diameter floppy disks such as 2
For a video floppy disk with an inch diameter, the thickness is preferably 40 μm or less and 7 μm or more, more preferably 30 μm or less and 7 μm or more.

On the other hand, the thickness of the magnetic recording layer 2 is not particularly limited, although it is sufficient to have a thickness of about 0.1 to 1.0 μm. The thickness of the protective layer 3 is desirably 300 or less, preferably 250 or less. The lower limit of the protective layer 3 may be such that the function of the protective layer 3 is not impaired, for example, 50 or more people, preferably 100 or more people.

By using a protective layer with the thickness described above,
An l7 magnetic recording medium with sufficiently reduced spacing loss can be obtained.

Furthermore, by forming an organic lubricant layer 4 on the protective layer 3 as necessary, wear resistance and durability under harsher environmental conditions such as high temperatures or low temperatures can be improved.

As the material for the organic lubricant layer 4, fluororesins, silicone oils, surfactants, saturated fatty acids, ester oligomers, etc. can be used, and liquid coating methods such as dipping and subin coating, and physical vapor deposition methods such as vacuum evaporation and sputtering can be used. can be formed by

The thickness of the organic lubricant layer 4 is preferably 100 or less, more preferably 30 or less.

Although the presence of the organic lubricant layer 4 can cause spacing loss as with the protective layer 3, the spacing loss can be sufficiently reduced by setting the layer thickness as described above.

A back coat layer 5 is coated on the back surface of the polymer film base 1 as necessary for the purpose of lubrication.

l 8 The back coat layer 5 contains inorganic fine particles such as carbon black, graphite, CaCO3, polyester resin,
It is possible to use a commonly used composite material that can be formed by dispersing it in a binder such as polyurethane resin or urethane resin and applying it.

As shown in FIG. 2, the magnetic recording medium of the present invention has a magnetic recording layer 2.2'', a protective layer 3.3'', and an organic lubricant layer 4.4'' on both sides of a polymeric film base l. Alternatively, as shown in FIG. 3, a back coat layer 5 may be added to the protective layer 3. Incidentally, in the magnetic recording medium having the configuration as shown in FIG. 2, magnetic recording layers on both sides can be used as the magnetic recording layers.

In Figure 2, the layer thicknesses of magnetic recording layers 2 and 2' may be the same if they are formed at the same time, but if one of the layers is formed first, forming the same thickness will result in a medium Curls may not be properly corrected.

This is because when forming a magnetic recording layer on one side of the substrate,
Because the thermophysical properties of the base film change, the conditions for subsequently forming a magnetic recording layer on the other side of the base are substantially different from those when forming the first magnetic recording layer. it is conceivable that.

Therefore, if curl control is required, either the magnetic recording layer 2 or 2' may be made thinner as appropriate.

Similarly, the thickness of the silicon dioxide thin film 3.3 mm may be the same, or one may be made thinner as appropriate.

Further, the magnetic recording layer 2 may be a single layer or a multilayer. Further, below the magnetic recording layer 2, there are
As shown in Fig. 6, A
l. Ge. Cr. A thin film of Ti, SiO+, etc. or a high magnetic permeability layer such as a FeNi film, a Co--Zr film, etc. may be provided as the intermediate layer 6.6 as a backing layer of the perpendicularly magnetized film.

The rigid magnetic recording medium is the magnetic recording medium described in FIGS. 1 to 6, and has a rigid base material such as a nonmagnetic metal.

FIG. 7 shows a typical example of a rigid magnetic recording medium. In FIG. 7, the intermediate layer 6, magnetic recording layer 2, protective layer 3, and lubricant layer 4 are the same as those of the flexible magnetic recording medium explained in FIGS. 1 to 6, and therefore their explanations will be omitted. . Further, the back coat layer is also the same as the back coat layer 5 in FIG. 1, so a description thereof will be omitted. However, in the case of a rigid magnetic recording medium, the thickness of the protective layer 3 is preferably 500 or less, most preferably 300 or less. The lower limit of the thickness of the protective layer 3 may be such that the function of the protective layer 3 is not impaired.
For example, the number is 50 or more, preferably 100 or more.

It is preferable to use a non-magnetic metal as the base body 21, for example, it is preferable to use an aluminum alloy. In addition, resins such as polysulfur resin and polyimide, glass, etc. can also be used as the substrate 21.

It is preferable that a surface treatment layer 22 is provided on the base body 21 as necessary. As the surface treatment layer 22, for example, a Ni-P alloy or an anodized layer (alumite layer) is preferable. The surface of the surface treatment layer 22 is mirror-polished and then formed to have a desired surface roughness, if necessary. The thickness of the base body 21 is 0.5 to 3
A range of mm is preferred.

The surface roughness of the rigid magnetic recording medium is preferably in the same range as the surface roughness of the flexible magnetic recording medium.

The present invention will be specifically described below with reference to Examples.

Example 1 A medium having the configuration shown in FIG. 3 was created.

Polyimide film substrate 1 (manufactured by Ube Industries, Ubilex S type, coefficient of thermal expansion 1.2 XIO-5cm/
cm/℃, tensile modulus of elasticity 1020 kg/mm2, surface roughness, protrusion height corresponding to 0.01% from the highest protrusion is 300 people, protrusion density 5X]06 pieces/l Tlm2)
A Co--Cr perpendicularly magnetized film of 2.2 DEG thick was formed on both sides of the substrate using a facing target sputtering device, and then a silicon oxide thin film of 3.3 DEG thick was formed using an RF magnetron sputtering device.

FIG. 8 shows a schematic diagram of the facing target type sputtering apparatus used in this example. A long polyimide film substrate 1 having a thickness of 20 μm and a width of 80 mm was subjected to heat treatment in a vacuum prior to forming a magnetic layer.

Specifically, the rotating drum 1 was heated to 190°C in a vacuum.
1 (diameter 30 mm) long polyimide film substrate 1
were conveyed in contact with each other, and the heat treatment was performed while maintaining the ultimate pressure of 2×10 Pa or less. The tension of the polyimide film base 1 at that time was 1.2 kg. The conveyance speed was 6 cm/min.

After the heat treatment, the vacuum was evacuated to an ultimate degree of vacuum of 5×10−′Pa or less, and then a Co—Cr perpendicular magnetization film was formed. The dimensions of target 13 are 4 inches x 6 inches x 6 mm, and the distance from the center between targets to the rotating drum surface is 120 m.
m, the composition of the target was 80% by weight of Co-20% by weight of Cr. The film forming conditions were an argon pressure of 0.2 Pa. Input power: 2.5kW. Film forming rate: 1000 people/min. The temperature of the rotating drum l1 is 190°C, the tension of the polyimide film base 1 is 1.2 kg, and the formed Co-Cr
The thickness of the 6B layer was 0.4 um. After forming the magnetic layer 2 on one side in this way, Co-
A 2° Cr magnetic layer was formed.

Note that the roller 7 is a feed roller roller 8 for the base l.
and 10 are conveying rollers, and roller 9 is a winding roller for the substrate l. Further, l2 is a shielding plate.

Furthermore, a silicon oxide thin film of 3.3 DEG was formed as a protective layer on the 2.2 DEG of this Co--Cr magnetic layer using an RF magnetron scattering device.

FIG. 9 shows a schematic diagram of the RF magnetron sputtering apparatus used in this example. A 4-inch φ Si02 target 14 was used, the temperature of the rotating drum 31 was 200°C, the argon pressure was 0.3 Pa, the input power was 2 kW, and the film formation rate was 0.0.
The film thickness was 200 at a speed of 5 μm/min. The electrical resistivity of the silicon oxide thin film formed at this time was measured by the method described below (in the present invention, electrical resistivity is measured by the following method)7. L x l Q l 3Ω
・It was cm.

Method for measuring electrical specific resistance: A silicon oxide thin film was formed on the Si wafer under the same conditions as when forming the protective layer of the silicon oxide thin film, and then a silicon oxide thin film was formed on top of the silicon oxide thin film as shown in plan view in FIG. A1 electrode in shape 16.1
7 was formed by vapor deposition to a thickness of 0.2 μm. The distance W between the electrodes is 0.
25mm, the length of the part where a pair of electrodes are facing each other! (The length from point A to point B of electrode 17 in Figure 10) is 50
It was mm. D between these electrodes. C. Apply voltage and
The resistance value was calculated from the leakage current value.

In addition, when the refractive index of the formed silicon oxide thin film 3.3' was measured with an ellipsometer, it was found to be 1.462.
and 1.463.

Furthermore, the via hole density of this silicon oxide thin film 3,3゜ was determined by the copper decoration method (using electrochemical reaction in an organic solvent.r Shiono, Yashiro: Applied Physics .Volume 45, No. 1O (
1976) Learn more about 952. ) was measured,
The average number was 3.1 pieces/CII+2.

Following the formation of the protective layer 3.3°, a 20-layer thick layer of ester-based ligoma (manufactured by Asahi Glass Co., Ltd., trade name ST-117) was formed as a lubricating layer 4 on the protective layer 3.

Next, a back coating liquid (manufactured by Toyo Ink Mfg. Co., Ltd., trade name: T
PII-3091 black) was coated, and a back coat layer 5 was coated to a thickness of 0.5 μm.

The magnetic recording medium produced as described above was punched out into a disk shape with a diameter of 47 mm to obtain a video floppy disk.

The obtained video floppy disk was connected to a commercially available video floppy disk drive deck (manufactured by Fuji Photo Film Co., Ltd., trade name: FUJIX P-3), and its RF output was measured and durability tests were performed. The results are shown in Table 1.

The RF output of the magnetic recording medium of this example is as follows, assuming that the RF output level (hereinafter referred to as MPL) of a commercially available coating type medium (product name: Canon Video Floppy Disk VF-50, hereinafter referred to as MP) is OdB. It was +3.8dB.

In the durability test, after recording a 7 MHz signal, only playback was performed, the fluctuation of the playback output was observed, and the time when the playback output attenuated to the initial value -3 dB was defined as the durability time.
Evaluation was made based on the durability time.

In a still durability test at room temperature (25°C), after 48 hours (approximately 10 million buses), the playback output decreased by -0. It was 6dB.

Since the specification was for 48 hours or more, the durability test was stopped at 50 hours, but it was estimated that the product had sufficient durability even after that time.

On the other hand, in a still durability test at high temperatures (40°C, 85% RH), the durability was 16 hours (approximately 3.5 million passes).
Met.

From the above results, it is clear that the floppy disk obtained in this example sufficiently satisfies the durability standards for data recording in terms of the number of buses.

Furthermore, compared to MP, the floppy disk obtained in this example had a much higher reproduction output, and its durability was found to be at a practical level according to data recording durability standards.

The floppy disk obtained in this example was left in a natural environment for one year and then evaluated in the same manner as above, and the same results were obtained.

This shows that the magnetic recording medium of the present invention has excellent storage durability.

Example 2 A magnetic recording medium (video floppy disk) was produced in the same manner as in Example I, except that the argon pressure was 0.4 Pa for the formation of the 3.3° silicon oxide thin film serving as the protective layer.

The electrical resistivity of the silicon oxide thin film formed at this time was 3
．． It was 3X10'3Ω・CII1.

In addition, when the refractive index of the formed silicon oxide thin film 3.3° was measured with an ellipsometer, it was 1.465.
Met.

The RF output measurement and durability test of the obtained video floppy disk were conducted in the same manner as in Example 1. The obtained results are the first
Shown in the table.

That is, the RF output was M P L +3.5 dB.

In addition, in a still durability test at room temperature (25°C), 4
After 8 hours (approximately 10 million buses), the playback output decreased by -1. It was 1 dB. The durability test was stopped at 50 hours because the specification was for 48 hours or more, but it was estimated that the product had sufficient durability even after that.

On the other hand, in a still durability test at high temperatures (40° C., 85% RF {), the durability time was 15 hours (approximately 3.2 million buses).

From the above results, it is clear that the floppy disk obtained in this example sufficiently satisfies the durability standards for data recording in terms of the number of buses.

Furthermore, it was found that the floppy disk obtained in this example had a significantly higher reproduction output than the MP, and its durability met the data recording durability standards and was at a practical level.

Example 3 A magnetic recording medium (video floppy disk) was prepared in the same manner as in Example 1, except that the argon pressure was changed to 0.5 Pa for the formation conditions of the silicon oxide thin film 3.3 as the protective layer. The electrical resistivity of the silicon oxide thin film formed at this time was 2.
It was IX10"Ω'Cm.

In addition, when the refractive index of the formed silicon oxide thin film of 3.3° was measured with an ellipsometer, it was 1.466.
and 1.464.

The RF output measurement and durability test of the obtained video floppy disk were conducted in the same manner as in Example 1. The obtained results are the first
Shown in the table.

The RF output was M P L +3.3 dB.

In addition, in a still durability test at room temperature (25°C), 4
After 8 hours (approximately 10 million buses), the reproduction output decreased by -1.5 dB from the initial value. Since the specification was for 48 hours or more, the durability test was stopped at 50 hours, but it was estimated that the product had sufficient durability even after that time.

On the other hand, in a still durability test at high temperature (40° C., 85% R H ), the durability time was 9 hours (approximately 1.9 million passes).

From the above results, it is clear that the floppy disk obtained in this example sufficiently satisfies the durability standards for data recording in terms of the number of passes.

Furthermore, compared to MP, the floppy disk obtained in this example had a much higher reproduction output, and its durability was found to be at a practical level according to data recording durability standards.

Example 4 A magnetic recording medium (video floppy disk) was produced in the same manner as in Example 1, except that the argon pressure was 0.6 Pa for the formation of the 3.3° silicon oxide thin film serving as the protective layer.

The electrical resistivity of the silicon oxide thin film formed at this time was 1
It was 0×10”Ω·cm.

In addition, when the refractive index of the formed silicon oxide thin film 3.3゛ was measured with an ellipsometer, it was found to be 1.495.
and 1. It was 494.

3l The RF output measurement and durability test of the obtained video floppy disk were conducted in the same manner as in Example 1. The obtained results are the first
Shown in the table.

The RF output was M P L + 3.0 dB.

In addition, in a still durability test at room temperature (25°C), 4
After 8 hours (approximately 10 million passes), the reproduction output decreased by -1.9 dB with respect to the initial value. Since the specification was for 48 hours or more, the durability test was stopped at 50 hours, but it was estimated that the product had sufficient durability even after that time.

On the other hand, in a still durability test at high temperature and high humidity (40° C., 85% RH), the durability time was 5 hours (approximately 1.1 million passes).

From the above results, it is clear that the floppy disk obtained in this example sufficiently satisfies the durability standards for data recording in terms of the number of buses.

Furthermore, compared to MP, the floppy disk obtained in this example had a much higher reproduction output and was found to have a practical level of durability according to data recording durability standards.

Comparative Example 1 A magnetic recording medium (video floppy disk) was produced in the same manner as in Example 1, except that the argon pressure was 0.7 Pa for the formation of the 3.3° silicon oxide thin film serving as the protective layer.

The electrical resistivity of the silicon oxide thin film formed at this time was 5
．． It was 5×10”Ω·cm.

Furthermore, when the refractive index of the formed silicon oxide thin film of 3.3゛ was measured with an ellipsometer, it was found to be 1. 50
It was 3.

The RF output measurement and durability test of the obtained video floppy disk were conducted in the same manner as in Example 1. The obtained results are the first
Shown in the table.

RF output was on par with MP. The still durability test results are
2 hours at room temperature (approximately 400,000 baths), high temperature (40℃, 8
5% RH) for 0.5 hours (approximately 10,000 passes), and the durability is extremely poor. After the durability test, scratches were generated on the media, and powder was found around the scratches, and scratches and adhesion of lubricant and powder were observed on the surface of the head.

Example 5 A magnetic recording medium (video floppy disk) was produced in the same manner as in Example 1 except that the lubricant layer 4 was not formed.

What is the electrical resistivity of the protective layer formed at this time? ．． OX1
Furthermore, when the refractive index of the formed silicon oxide thin film of 3.3'' was measured with an ellipsometer, it was 1.462 Ω'cm.
and 1. It was 463.

The RF output measurement and durability test of the obtained video floppy disk were conducted in the same manner as in Example 1. The obtained results are the first
Shown in the table.

The RF output is M P L + 3.9 dB, and the still durability is more than 48 hours (approximately 10 million passes) at room temperature, which is about the same as Example 1, but at high temperature and high humidity (40 ° C, 8
Still durability time is 10 hours (approximately 22
0 passes). By forming a lubricating layer, it was possible to further improve the still durability under high temperature and high humidity conditions.

Example 6 The polyimide film substrate 1 was Ubilex S type (Ube Industries) with a thermal expansion coefficient of 1.2×10-5cr.
y/cmfc, tensile modulus of elasticity 1050 kg/mm2, and surface roughness Rffl. ．． A magnetic recording medium (video floppy disk) was produced in the same manner as in Example 1, except that 50 people or less used one in which no fine irregularities were formed.

The electrical resistivity of the protective layer formed at this time was 7. OXI
The OI was 3Ω'cm.

In addition, when the refractive index of the formed silicon oxide thin film of 3.3° was measured with an ellipsometer, the results were as follows. 462
Met.

The RF output measurement and durability test of the obtained video floppy disk were conducted in the same manner as in Example 1.

RF output is MPL+7. odtl, and the still durability was 14 hours (approximately 3 million passes) at room temperature and approximately 5 hours (approximately 1.1 million passes) at Takataki high temperature (40° C., 85% RH). Fine irregularities on the media surface? If not formed,
Although the reproduction output can be improved by reducing the spacing loss, the durability is slightly lowered. However, the durability was within the practical level.

Example 7 When forming a protective layer, TiO2 pellets were welded onto a 4 inch φ SiO2 target so that the area ratio was about 15% and used as a target for forming the protective layer. Other conditions were the same as in Example 1.
A floppy disk was created.

The electrical resistivity of the Si-Ti-0 thin film formed at this time was 2.8×IO13Ω-cm.

In addition, when the refractive index of the formed silicon oxide thin film of 3.3゛ was measured with an ellipsometer, it was found to be 1.464.
Met.

The RF output measurement and durability test of the obtained video floppy disk were conducted in the same manner as in Example 1. The obtained results are the first
Shown in the table.

RF output is MPL + 3.8 dB, and Sujiru durability is over 48 hours (approximately 10 million passes) at room temperature, and approximately 35 hours (approximately 760
10,000 passes). The still durability under high temperature and high humidity conditions could be improved by forming a protective layer containing silicon oxide as a main component by adding Ti as an additive element to Si-0.

Example 8 A medium having the configuration shown in FIG. 1 was created.

7.5 μm thick polyimide film substrate 1 (manufactured by Ube Industries, Ubilex copolymer type, coefficient of thermal expansion 1
．． 5 X 1 0-5cm/cm/℃, tensile modulus 5
80 kg 7 mm", the surface roughness is 320, the protrusion density is 5XIO' pieces/mm2), and the surface roughness is 320 people, the protrusion density is 5XIO' pieces/mm2). A magnetized film 2 was formed.

FIG. 11 shows a schematic diagram of the EB device used in this example.

No preheat treatment of the polyimide film substrate 1 was performed.

The temperature of the rotating drum 4I is 200℃, Co80 heavy plate%-C
Is electricity applied to the alloy vapor deposition source 15 containing 20% by weight of r? Continuous vapor deposition using a beam. The film formation rate was 0.5 μm/min.
The film thickness was 0.35 μm.

Next, a silicon oxide thin film 3 was formed as a protective layer on the Co-(:r perpendicularly magnetized film 2) by sputtering.

A 4-inch φ SiO2 target was used, the rotating drum temperature was 200°C, and the argon pressure was 0.3 Pa. O■ partial pressure 6%, input power 2kW, film formation rate 0. 05 μm/m
fn, and the film thickness was 100. The electrical resistivity of the silicon oxide thin film protective layer formed at this time was 8. O XIO
It was 13Ω·cm.

Further, the refractive index of the formed silicon oxide thin film 3 was measured with an ellipsometer and was found to be 1.462.

Next, FEP (manufactured by DuPont) was coated on the protective layer 3 as a lubricating layer 4 to a thickness of about 20 coats.

Furthermore, a back coat layer 5 was coated on the back surface of the polyimide film substrate 1. The material is a urethane binder containing fine particles of carbon black and TiO (manufactured by Toyo Ink Manufacturing Co., Ltd., product name TB-501).
4 black), and the film thickness was 0.5 μm.

The magnetic recording medium produced as described above was cut into a width of 8 mm to obtain a magnetic tape.

Using the obtained magnetic data, recording and playback was performed on a commercially available 8 mm video deck (EV-A80, manufactured by SONY).
Table 2 shows the results of evaluation of RF reproduction output, pass durability, and still durability.

In this pass durability test, after recording an RF signal, the bus is run only for reproduction, and fluctuations in the reproduction output are observed. The evaluation was performed by defining the time required for the reproduction output to attenuate to the initial value -3 dB as the path durability time.

The still durability test is a test in which, after recording an RF signal, only playback is performed by still running, and fluctuations in the playback output are observed. The time for the reproduction output to attenuate to the initial value -3 dB was defined as the still durability time and evaluated.

The RF playback output is the RF playback output (hereinafter referred to as MPL) of a commercially available coated tape (product name: Canon 8mm bidet tape P6).
4.0d[3 higher, pass durability,
Both still durability was at a practical level.

Example 9 The conditions for forming the silicon oxide thin film 3, which is the protective layer, were as follows: argon pressure 0.3 Pa. A magnetic tape was produced in the same manner as in Example 8 except that the oxygen partial pressure was 10%.

The electrical resistivity of the silicon oxide thin film formed at this time was 3.
It was 4×10 Ω·cm.

Further, the refractive index of the formed silicon oxide thin film 3 was measured with an ellipsometer and found to be 1.461.

The obtained magnetic tape was evaluated in the same manner as in Example 8, and the results are shown in Table 2.

RF output is MP L' +3.7dB. pass durability,
Both still durability was at a practical level.

Example 10 The conditions for forming the silicon oxide thin film 3, which is the protective layer, were as follows: argon pressure 0.3 Pa. A magnetic tape was produced in the same manner as in Example 8 except that the oxygen partial pressure was 14%.

What is the electrical resistivity of the silicon oxide thin film formed at this time? ．．
It was 5XIO”Ω·cm.

Furthermore, when the refractive index of the formed silicon oxide thin film 3 was measured using an ellipsometer, it was found to be 1. It was 460.

The obtained magnetic tape was evaluated in the same manner as in Example 8, and the results are shown in Table 2.

The RF output is MPL' +3.3dB. Both pass durability and still durability were at a practical level.

Example 11 The conditions for forming the silicon oxide thin film 3, which is the protective layer, were as follows: argon pressure [+. 3Pa. Example 8 except that the oxygen partial pressure was 16%
A magnetic tape was produced in the same manner.

The electrical resistivity of the silicon oxide thin film formed at this time was 1.
It was O x 10'2 Ω·cm.

Furthermore, when the refractive index of the formed silicon oxide thin film 3 was measured using an ellipsometer, it was found to be 1. It was 460.

The obtained magnetic tape was evaluated in the same manner as in Example 8, and the results are shown in Table 2.

RF output is MP L' +3.1dB. Both pass durability and still durability were at a practical level.

Example 12 The film forming conditions for the silicon oxide thin film 3.3° serving as the protective layer were as follows: argon pressure 0.3 Pa. A video floppy disk was produced in the same manner as in Example 1 except that the oxygen partial pressure was 18%.

The electrical resistivity of the silicon oxide thin film formed at this time was 5.
OXI015Ω·Cm.

In addition, when the refractive index of the formed silicon oxide thin film of 3.3° was measured with an ellipsometer, it was 1.460.
and 1.461.

The obtained video floppy disk was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

The RF output is M P L + ]. ．． 2dB. Still durability is 30 hours (approximately 6.5 million baths) at room temperature, high temperature and high humidity (
The test time was 40° C. and 85% RF{) for 5 hours (approximately 1.1 million passes).

From the above results, it is clear that the floppy disk obtained in this example sufficiently satisfies the durability standards for data recording in terms of the number of passes.

Furthermore, compared to MP, the floppy disk obtained in this example had a much higher reproduction output, and its durability was found to be at a practical level according to data recording durability standards.

Table 1 *l The output level of a commercially available coated magnetic recording medium (liver) is OdB.

*2 Endurance time is the time when the reproduction output attenuates to the initial value -3 dB. The practical level for a floppy disk is over 3 million busses at room temperature (approximately 13 hours for a video floppy), and 1 million busses at high temperature and high humidity.
(approximately 5 hours) or more.

Table 2 *3 The time when the reproduction output attenuated to the initial value -3 dB was defined as the durability time. The practical level is 200 in pass durability.
Pass or above, still endurance of 120 minutes or more.

Example 13 A medium having the configuration shown in FIG. 7 was created.

First, an alumite treatment was performed on an aluminum alloy substrate 21 having a thickness of 1.27 mm by a known method to form a surface treated layer 22.22° of aluminum oxide to a thickness of about 15 μm. Next, after mirror polishing the surface and cleaning thoroughly,
It was installed in a sputtering device and formed as a soft magnetic layer using an in-line method using MoCu-Permalloy (JIS (: 25
31. Composition ratio Ni: 78%, Mo: 4%, other Cu. Cr
with the remainder being Fe) film 6,6°, and Co as the magnetic recording layer.
-Cr perpendicular magnetization films 2 and 2' were sequentially formed by magnetron sputtering, each having a thickness of 0.5 μm.

The substrate temperature was 120°C, and the target size was 8 inches (2
03.2mm) φ, Co-Cr target composition is Co80wt%-Cr20wt%, Argon pressure 0.2P
a. Input power 1kll, film formation speed 400 people? It was a minute.

Next, a silicon oxide thin film of 3.3 degrees was formed as a protective layer on the 2.2 degrees of the Co--Cr magnetic layer using an RF magnetron sputtering device. At this time, an 8-inch φ SiO target was used, the substrate temperature was 200°C, and the argon pressure was 0.3 Pa.
．． The input power was 2 kW, the film formation rate was 0.05 μm/min, and the film thickness was 270.

When the electrical resistivity of the silicon oxide thin film 3.3° formed here was measured, it was found to be 7. It was O x 10”Ω·cm.

In addition, when the refractive index of the formed silicon oxide thin films 3 and 3 was measured with an ellipsometer, both were 1.465.
Met.

Next, a 4.4° lubricant layer was applied on the 3.3° protective layer. K
0.1 of rytoxl43AD (manufactured by Dupont)
A diluted solution with a concentration of 100% was applied to give a dry thickness of 30%.

When the electromagnetic conversion characteristics of the thus obtained magnetic recording medium with a diameter of 3.5 inches were measured, high-density recording of 70 kbpi was possible.

In addition, Sony's 3.5-inch hard disk drive S
Figure 12 shows the results of running the CSS test on the RD2040Z 10 times with different tracks.

The number of CSS operations before scratches occur on the medium is 50,000~
It was 70,000 times. 2 which is a practical level poder line
At the time of 10,000 cycles, no change or damage was observed in the medium.

Further, no change was observed in the medium even when it was left at high temperature and high humidity (85° C., 85% R H ) for 500 hours.

From the above, it can be said that the medium of this example has a much higher reproduction output than the conventional coated magnetic recording medium, and has a practical level of durability, wear resistance, and environmental resistance.

Example 4 A magnetic recording medium was produced in the same manner as in Example 13, except that the argon pressure was 0.4 Pa for the formation of the 3.3° silicon oxide thin film serving as the protective layer.

The electrical resistivity of the silicon oxide thin film 3.3° formed at this time was: l. It was 3×10 13 Ω·cm.

In addition, when the refractive index of the formed silicon oxide thin film of 3.3° was measured with an ellipsometer, it was 1.465.
and 1.46: { was.

When the obtained medium was evaluated in the same manner as in Example 13, as shown in FIG. 12, the number of CSS cycles until scratches occurred on the medium was 30,000 to 60,000 times. At the point of 20,000 cycles, which is a borderline level for practical use, no change or damage was observed in the medium. In addition, this medium is Example 1
No change was observed in the high-temperature environment test shown in 3 for over 500 hours. In addition, the electromagnetic conversion characteristics of this medium are shown in Example 13.
It was about the same level as the medium.

Example 15 The silicon oxide thin film 3.3' which is a protective layer was formed under an argon pressure of 0. A magnetic recording medium was torn in the same manner as in Example 13, except that the pressure was 55 Pa.

The electrical resistivity of the 3.3° silicon oxide thin film formed at this time was l. OXI was 013Ω·cm.

In addition, when the refractive index of the formed silicon oxide thin film of 3.3° was measured with an ellipsometer, it was 1.471.
Met.

When the obtained medium was evaluated in the same manner as in Example 13, as shown in FIG. 12, the number of CSS cycles until scratches occurred on the medium was 25,000 to 40,000. This medium also passed the high temperature and high humidity environment test shown in Example 13.
No changes were observed over time. Further, the electromagnetic conversion characteristics of this medium were comparable to those of the medium of Example 3.

Example 16 A magnetic recording medium was produced in the same manner as in Example 13, except that the argon pressure was 0.6 Pa for the formation of the silicon oxide thin film 3.3° serving as the protective layer.

The electrical resistivity of the silicon oxide thin film 3.3'' formed at this time was 1. It was OX1012Ω·cm.

In addition, when the refractive index of the formed silicon oxide thin film 3.3' was measured with an ellipsometer, it was found to be 1.495.
and 1.496.

When the obtained medium was evaluated in the same manner as in Example 13, as shown in FIG. 12, the number of CSS cycles until scratches occurred on the medium was 20,011 to 30,000 times.

Further, the medium of this example showed no change for more than 500 hours in the high temperature, high humidity environment test shown in Example 13. Further, the electromagnetic conversion characteristics of this medium were comparable to those of the medium of Example 13.

Comparative Example 2 A magnetic recording medium was produced in the same manner as in Example 13, except that the argon pressure was 0-7 Pa for forming the 3.3° silicon oxide thin film serving as the protective layer.

The electrical resistivity of the silicon oxide thin film 3.3" formed at this time was 3.3". OXIO”Ω·cm.

In addition, when the refractive index of the formed silicon oxide thin film of 3.3° was measured with an ellipsometer, it was 1.511.
Met.

When the obtained medium was evaluated in the same manner as in Example 13, as shown in FIG. 12, the number of CSS cycles until scratches occurred on the medium was 1,000 to 5,000 times. Practically speaking, it must be able to withstand 20,000 CSS tests, and the durability of the medium of this comparative example did not reach a practical level in any track.

? When the medium of this comparative example was subjected to the high-temperature, high-humidity environment test shown in Example 13, two to three minute corrosion points were found. The electromagnetic conversion characteristics of the medium of this comparative example were comparable to those of the medium of Example 13.

From the above, although the reproduction output of the medium of this comparative example is much higher,
Durability and abrasion resistance did not reach a practical level. There was also a problem with environmental resistance.

Example 17 The film formation conditions for the silicon oxide tW#i3.3°, which is the protective layer, were as follows: argon pressure 0. A magnetic recording medium was produced in the same manner as in Example 13, except that the partial pressure was 3Pa to 1O%).

The electrical resistivity of the silicon oxide thin film 3.3'' formed at this time was 3.4 x 10'' Ω·cm.

In addition, when the refractive index of the formed silicon oxide thin film of 3.3° was measured with an ellipsometer, it was 1.461.
and 1.462.

The obtained medium was evaluated in the same manner as in Example 13, and 5I? However, as shown in FIG. 12, the number of CSS operations before scratches occurred on the medium was 40,000 to 60,000 times.

This is far higher than the practical-level poder line of 20,000 degrees.

Further, when this medium was subjected to the high-temperature environment test shown in Example 13, there was no change at all for over 500 hours. Further, the electromagnetic conversion characteristics of this medium were comparable to those of the medium of Example 13.

Example 18 The film forming conditions for a 3.3 inch silicon oxide thin film serving as a protective layer were as follows: argon pressure 0. A magnetic recording medium was produced in the same manner as in Example 13, except that the pressure was 3 Pa (0 ■ partial pressure 15%).

The electrical resistivity of the silicon oxide thin film 1113.3' formed at this time was 1. It was O x 1015 Ω·cm.

In addition, when the refractive index of the formed silicon oxide thin film of 3.3° was measured with an ellipsometer, it was found to be 1.460.
Met.

The obtained medium was evaluated in the same manner as in Example 13, and as shown in FIG. The number of CSS operations before the problem occurred was 25,000 to 50,000 times.

Further, when this medium was subjected to the high temperature environment test shown in Example 13, there was no change at all for over 500 hours. Further, the electromagnetic conversion characteristics of this medium were comparable to those of the medium of Example 13.

Example 19 The film forming conditions for the silicon oxide thin films 3 and 3, which are the protective layers, were as follows: argon pressure was 0. A magnetic recording medium was produced in the same manner as in Example 13, except that the pressure was 3 Pa (0 ■ partial pressure 18%).

The electrical resistivity of the 3.3° silicon oxide thin film formed at this time was 5. It was O x 1015 Ω·cm.

In addition, when the refractive index of the formed silicon oxide thin film 3.3' was measured with an ellipsometer, it was found to be 1.460.
and 1. It was '461.

When the obtained medium was evaluated in the same manner as in Example 13, as shown in FIG. 12, the number of CSS cycles until scratches occurred on the medium was 20,000 to 30,000 times.

In addition, this medium also passed the high temperature and high temperature environment test shown in Example 13.
There was no change for more than 00 hours. Further, the electromagnetic conversion characteristics of this medium were comparable to those of the medium of Example 13.

[Effects of the Invention] As explained above, the magnetic recording medium of the present invention has an electric resistivity of 1012 Ω-cm as a protective layer on the magnetic recording layer.
As mentioned above, since it has a thin film mainly composed of silicon oxide, preferably in the range of 10'' to 10'' Ω·Cm, it has excellent abrasion resistance, durability, and long-term storage durability.

[Brief explanation of the drawing]

1 to 7 are partial views showing the basic configuration of the magnetic recording medium of the present invention, FIG. 8 is a schematic diagram of a facing target sputtering device, and FIG. 9 is a schematic diagram of an RF magnetron sputtering device. Figure 10 is a plan view showing the shape of the AI electrode used to measure the electrical resistivity of the protective layer, Figure 1 is a schematic diagram of the EB evaporation equipment, and Figure 12 is the electrical resistance of the silicon oxide protective layer. C8 until scratches occur on specific resistance and magnetic recording media
It is a graph showing the relationship between S times. 1.21...One base 2.2゛...One magnetic recording layer 3.3゜--One protective layer 4, 4゜...Lubricant layer 5...Back coat layer 6,6゜One, one intermediate Layer 7...1 feed roller 8, lO...1 transport roller 9...take-up roller +1. :31.4+-... Rotating drum 12-... Shielding plate 13 14... One-ta ~ get 1 15-... Evaporation source 16.17... Electrode 21-... Surface treatment layer 22.22°.・・Surface treatment layer patent application filed by Canon Inc.

Claims (11)

[Claims] (1) A magnetic recording medium having a magnetic recording layer and a thin film protective layer mainly composed of silicon oxide on at least one surface of a substrate, in which the electrical resistivity of the protective layer is 10.
A magnetic recording medium characterized by having a resistance of ^1^2 Ω·cm or more. (2) The electrical resistivity of the protective layer is 10^1^3 to 10^
The magnetic recording medium according to claim 1, wherein the magnetic recording medium has a resistance of 1^5 Ω·cm. (3) The protective layer is B, C, N, P, S, Al, Ti,
V, Cr, Zn, Ge, Zr, Nb, Mo, Ta, Mg
3. The magnetic recording medium according to claim 1, containing at least one element selected from the group consisting of , Hf, Au, and Pt, or a compound thereof. (4) When the magnetic recording medium has fine protrusions on its surface and the total distribution of the protrusion heights is taken, the protrusion height corresponding to the 0.01% from the highest protrusion is 60
0 Å or less, and the protrusion density is 1 x 10^4 to 1 x 10^
The magnetic recording medium according to claim 1, wherein the number of magnetic recording medium is 9 pieces/mm^2. (5) The protrusion density is 10^5 to 10^8 pieces/mm^2
The magnetic recording medium according to claim 4. (6) The magnetic recording medium according to claim 1, wherein the substrate is flexible and the protective layer has a thickness of 300 Å or less. (7) The magnetic recording medium according to claim 6, wherein the thickness of the base is 6 μm or more and 75 μm or less. (8) The magnetic recording medium according to claim 1, wherein the substrate is rigid, and the protective layer has a thickness of 500 Å or less. (9) The magnetic recording medium according to claim 8, wherein the thickness of the base is 0.5 mm or more and 3 mm or less. (10) A magnetic recording medium having a magnetic recording layer and a thin film protective layer mainly composed of silicon oxide on at least one surface of a substrate, in which the magnetic recording layer comprises Co and Cr.
What is claimed is: 1. A magnetic recording medium comprising a perpendicularly magnetized film containing as a main component, the protective layer having an electrical resistivity of 10^1^2 Ω·cm or more, and further comprising a lubricating layer on the protective layer. (11) The magnetic recording medium according to claim 10, wherein the magnetic recording layer is a Co--Cr perpendicularly magnetized film containing 15 to 23% by weight of Cr and 85 to 77% by weight of Co.