JPS62146431A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To realize a recording medium which has excellent durability, wear resistance, etc., and obviates an attraction by successively laminating a carbon protective film, and a top coat layer consisting of a prescribed material as a lubricating agent on a magnetic metallic layer on a substrate. CONSTITUTION:An underlying layer 3 and an intermediate layer 4 consisting of a nonmagnetic metal is provided on the nonmagnetic substrate 2 consisting of aluminum, etc., and the thin magnetic metallic film layer 5 and a protective film 6 consisting of a nonmagnetic metal are formed thereon. The carbon protective film 7 and the top coat layer 8 contg. perfluoropolyether as the lubricating agent are successively laminated thereon. The top coating is executed by spin coating, etc., to 50-150Angstrom thickness. Since the carbon protective film 7 and the top coat layer 8 are provided in the above-mentioned manner, the recording medium which has the excellent durability, wear resistance, weatherability and corrosion resistance and obviates the generation of the head attraction is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Background Technical Field of the Invention The present invention relates to magnetic recording media, and more particularly to improvements in protective films for magnetic layers of so-called hard-type magnetic disks, magnetic drums, and the like.

Prior art and its problems Magnetic recording media used in magnetic disk devices are generally called magnetic disks or disk media, and their basic structure includes a donut-shaped substrate and magnetic layers usually placed on both sides of the substrate. ing.

There are two types of substrate materials for such recording media: hard materials such as aluminum alloy, and plastic materials such as Mylar, which are the same as magnetic tape media.The former is generally called a hard type magnetic disk, and the latter is called a flexible disk. I'm here.

By the way, magnetic recording media in magnetic disk devices and magnetic drum devices, especially heart-type magnetic disks,
There are problems in terms of durability against mechanical contact with a magnetic head, wear resistance, etc. Therefore, these magnetic recording media are usually coated with a protective film. As a protective film for such a medium, it is conventionally known to provide an inorganic protective film or a lubricating film such as a solid lubricant.

Inorganic protection II! As for 2, Rh, Cr (Special Public Interest Publication No. 52-
18001) Ni-P (Special Publication No. 18001)
(No. Publication), as well as Re, Os, Ru, Ag, Au,
Cu, Pt, Pd (Special Publication No. 57-6177), N
1-Cr (Japanese Patent Publication No. 57-17292) etc. are used, and on the other hand, as solid lubricants, inorganic or organic lubricants such as silicon compounds such as 5i02, Sin,
Si3 N4 etc. (Japanese Patent Publication No. 54-33726), polysilicic acid or silane coupling agents such as tetrahydroxysilane, polyaminosilane etc. (Japanese Patent Publication No. 59-3
9809) and carbon.

However, the materials and structures of these conventional protective films provided on the magnetic layer do not improve the durability, abrasion resistance, or
No material has been developed that has sufficiently high weather resistance, corrosion resistance, etc., and does not cause the so-called adhesion phenomenon in which the head sticks to the surface of the medium.

(2) Purpose of the Invention The purpose of the present invention is to provide a magnetic recording medium which has excellent durability, abrasion resistance, weather resistance, corrosion resistance, etc., has no head attraction, and has extremely high reliability in practical use.

■Disclosure of invention Such objects are achieved by the invention described below.

That is, the present invention includes a metal thin film magnetic layer on a nonmagnetic substrate, a carbon protective film on this magnetic layer, and a top coat layer containing perfluoropolyether as a lubricant on this protective film layer. A magnetic recording medium characterized by having:

■Specific structure of the invention The specific structure of the present invention will be explained in detail below.
FIG. 1 shows an embodiment of the magnetic recording medium of the present invention.

The magnetic recording medium 1 of the present invention generally has a base layer 3 on a non-magnetic substrate 2, a non-magnetic metal intermediate layer 4 on the base layer 3, and a metal thin film magnetic layer on this base layer 3. Generally, a non-magnetic metal protective film 6 is provided on the magnetic layer 5, and a carbon protective film 7 and a top coat layer 8 are sequentially laminated.

In the present invention, the top coat layer 8 provided on the surface of the medium contains perfluoropolyether as a lubricant.

Examples of such compounds include those represented by the following formula (I).

Formula (I) Rf(-Rf'0-)-Rf'' In the above formula (I), Rf represents a fluorine atom or a perfluoroalkyl group.

Rf' represents a perfluoroalkylene group.

Rf'' represents a perfluoroalkyl group.

When Rf represents a perfluoroalkyl group, Rf and R
They may be the same or different from f''. n represents a positive integer, and when n is 2 or more, Rf' may be the same or different.

Examples of the perfluoroalkyl group represented by Rf include 10F3 and -C2F5.

Preferred examples of Rf include -F, -CF3.

Preferred examples of Rf'' include -CF2- and the like.

Examples of "Rf" include -CF3 and -C2F5.

n is 10 to 100, particularly preferably 10 to 50.

Among the compounds represented by formula (I), the following formula (I-
1) and (I-2) are preferred.

Formula (I-1) (:F3-[(-0-CF2-CF2)N-(0-
CFz ),]-0(:F 3 Formula (I-2) In the above formulas (I-1) and (I-2), the sum of N and M is about 10 to 100.

N is 5 to 50, preferably 5 to 30. Further, M is 5 to 50, preferably 5 to 3.
It is 0.

Moreover, those represented by the following formula (I-3) are also preferable.

Formula (I-3) In the above formula (I-3), n has the same meaning as in formula (I).

n is 10-100, preferably 30-70.

Such compounds have an average molecular weight of 311,000 to 1,000
0, kinematic viscosity 40-3000cST (20℃), pour point -
It has a temperature of 80 to -10°C.

These compounds can be synthesized according to known methods.

Alternatively, commercially available products may be used.

Specifically, the product name is FOM made by Montefluos.
BLIN YO4, YO6゜Y25. Y45. YR:
FOMBLINY-L-VACO616, Y-L-VA
C14/6°Y-L-VAC16/6. Y-L-VAC
25/6:FOMBLIN Y-H-VAC1B/8
, Y-H-VAC25/9. Y-H-VAC40/11
．． Y-H-VAC140/13 ;FOMBLIN
Z; DuPont KRYTOX143CZ, 143AZ
, 143AA, 143AY, 143AB, 143AC,
143AD; KRYTOX1502.1504.150
6.1509.1514.1516.1525゜161
8.1625.1645.1680.1614, etc.

Among these, KRYTOX143CZ has the formula (I-3)
These are the compounds represented by n-11 to n-49.

Also, FOMBLIN Y is the formula (1-2), FOMB
LIN Zf is expressed by the formula (I-1).

Two or more such compounds may be used in combination.

The total amount of such compounds is 50 to 100% of the total weight of the top coat layer 8,
Preferably it is 70-100%.

If it is less than 50% by weight, a sufficient lubricating effect cannot be obtained.

Moreover, a top coat layer 8 containing such a compound
The thickness of the board is 20 to 300 people, preferably 50 to 150 people.

This is because if there are fewer than 20 people, the sufficient effect of the present invention cannot be obtained and the durability is especially poor, and if more than 300 people are involved, adhesion occurs and so-called head crash occurs.

Furthermore, the top coat layer 8 may also contain fatty acids, fatty acid esters, epoxy resins, phenol resins, and the like.

To form such a top coat layer 8, usually,
The above compound is added to a fluorine-based solvent such as chlorofluorocarbon at a concentration of 0.01 to 1.
0% by weight, more preferably 0.05 to 0.1% by weight, and the solution is applied using a coating method such as spin cording, dipping, or spray coating.

When using a spin code, the number of rotations is 500 to 300
0 rpm, rotation time is about 5 to 20 seconds, and in the case of dipping, for example, first immerse it in a solvent such as Freon for about 15 to 30 seconds to clean it, then soak it in a lubricant solution for 10 to 30 seconds. It may be done by pulling up at a speed of ~20 mad/sec.

Such a top coat layer 8 is provided on a carbon protective film 7, which will be described later.

The carbon protective film 7 is composed of C alone, but may contain less than 5 wL% of other elements.

The carbon protective film 7 can be formed by various vapor phase film forming methods such as sputtering, ion blasting, vapor deposition, and CVD, but sputtering is particularly preferred.
In this case, the formed film becomes extremely dense and has excellent durability and weather resistance.

The thickness of the carbon protective film 7 formed in this way is 100 mm.
-800 people, especially 300-500 people is preferred.

Furthermore, it is preferable that the surface of the carbon protective film 7 be subjected to plasma treatment. By doing so, the surface of the carbon protective film can be chemically activated, and the above-mentioned top coat layer 8 can be formed with good adhesion. Therefore, adhesive strength is improved.

Plasma treatment may be performed by a known method, such as Ar,
Using one or more processing gases such as Ne, He, N2, N2, etc., the frequency of the power supply is 50 [1z ~ 13.56].
Approximately MHz, applied current, processing time, etc. may be set to normal conditions.

Examples of the nonmagnetic substrate 2 used in the present invention include metals such as aluminum and aluminum alloys, glass, ceramics, and engineering plastics.

Among these, it is preferable to use aluminum, aluminum alloy, etc., which have good mechanical rigidity, workability, etc., and can easily form a base layer, which will be described later.

The thickness of such a nonmagnetic substrate 2 is about 1.2 to 1.9 mm, and its shape is usually not particularly limited, such as a disk shape or a drum shape.

In particular, when a metal substrate such as AfL is used as the material of the non-magnetic substrate 2, it is preferable to provide the underlayer 3 on this substrate. This base layer 3 is made of N i-P,
N1-Cu-P, N1-W-P, N1-B
It is formed by containing any of the following compositions. This film is preferably formed by a liquid phase plating method, particularly an electroless plating method. According to the electroless plating method, an extremely dense film can be formed, and mechanical rigidity, hardness, and workability can be improved.

In addition, the composition ratio (wt) of the base layer consisting of the above composition is:
It is as follows.

That is, (NixCuy)8P B, (NixWy
) PB In these cases, x+y=100:O~10:90, A:B=97:3~85:15.

In the case of N i xBy, x:y=97:3~
The ratio is 90:3.

To briefly describe an example of the process of this electroless plating method, first, after alkaline degreasing and acid degreasing, zincate treatment is repeated several times, and the surface is further adjusted with sodium bicarbonate, etc., and then p84. Plating may be carried out in a nickel plating solution of ~6.0° C. at about 80 DEG -95 DEG C. for about 0.5 to 3 hours.

These plating treatments are, for example,
No. 50-1438, Japanese Patent Publication No. 50-1438, etc.

The thickness of such upper layer 3 is 3 to 50 μm, especially 5 to 2 μm.
0 μm is preferable.

Furthermore, it is preferable to provide the surface of the base layer 3 with an uneven portion.

To create the uneven portion, for example, while rotating the disc-shaped substrate 2 on which the base layer 3 is provided, an abrasive or the like is applied to form concentric irregular grooves on the surface of the base layer 3.

Note that the uneven portions may be provided randomly on the base layer 3.

By providing such uneven portions, the adsorption characteristics and durability are improved.

In addition, when the base layer 3 is not provided on the base body 2, the above-mentioned unevenness may be provided directly on the base body 2.

Further, on a substrate that may have such an underlayer 3, a metal thin film magnetic layer 5 whose main components are Co or CO and one or more of Ni, Cr, and P is provided.

Specific examples of the composition of this material include Co-Ni, Co-
Ni-Cr, Co-Cr, Co-N1-P, Co-Zn
-P, Co-Ni-Mn-Re-P, etc. Among these, Co-Ni, Co-Ni-Cr, Co-C
r, Co-N1-P, etc. are preferable, and the preferred composition ratio of these alloys is Co:N1=1:1 to 9:1 by weight, and x:y= in (CoN1)Cre.
IyA: 1-9:l, A:B=99.9:0.
1~75:25, Co:Cr=7:3~9:1°(Co
N1y), in PB, x:y=1:O~1:9, A:B=99.9:0
．． 1 to 85: L5. Outside these ranges, recording characteristics deteriorate.

Such a metal thin film magnetic layer 5 can be formed by a plating method in a gas phase or a liquid phase.
A seed sputtering method is preferred. By using the sputtering method, a magnetic layer with good magnetic properties can be obtained.

Sputtering methods can be further divided into two types, plasma methods and ion beam methods, depending on the area to be worked on.

In the plasma sputtering method, an abnormal glow discharge is generated in an atmosphere of an inert gas such as Ar, and a target (vapor deposition material) is sputtered using Ar ions, and is deposited on, for example, an adherend.

Either direct current sputtering, in which a direct current voltage of several volts is applied to the target, or high frequency sputtering, in which high frequency power of several hundred to several kilowatts is applied, may be used.

In addition, we have changed the number of poles from 2fil to 3-pole and 4-pole sputtering equipment, and added an orthogonal electromagnetic field to give electrons in the plasma a cycloidal motion similar to a magnetron to create high-density plasma.We also lowered the applied voltage to reduce sputtering. Highly efficient magnetron sputtering may also be used.

In the ion beam method, Ar or the like is ionized using an appropriate ion source, extracted, and extracted as an ion beam to the high vacuum side using a negative high voltage applied to an electrode.The ion beam is then irradiated onto the target surface to sputter the sputtered target material. Vapor-deposit onto the target body.

Further, the kinetic energy of the deposited particles in the sputtering method is approximately several eV to 100 eV, which is extremely large compared to, for example, that in the vapor deposition method (approximately 0.1 eV to feV).

In the present invention, as the material of the target, an alloy or the like corresponding to the composition of the intended thin metal wire magnetic layer 5 may be used.

By the way, the composition of the metal thin film magnetic layer 5 is set to CoP or Co.
In the case of using N i P, the layer may be formed by a liquid phase plating method, particularly an electroless plating method.

The magnetic layer exhibits good magnetic properties similar to the sputtering method described above.

Various known plating bath compositions, plating conditions, etc. used in electroless plating can be applied, such as those disclosed in Japanese Patent Publication No. 54-9136 and Japanese Patent Publication No. 55-14865.
Any of those described in the No. 1 publication, etc. can be used.

The thickness of the metal thin film magnetic layer 5 as described above is 200~
5000 people, especially 500-1000 people, even 500-
Preferably 600 people.

When such a metal thin film magnetic layer 5 is deposited by the sputtering method as described above, C is deposited between the base layer 3 and the magnetic layer 5.
It is preferable to provide a nonmagnetic metal intermediate layer 4 containing r.

By providing this nonmagnetic metal intermediate layer 4, the magnetic properties of the medium are improved, and the reliability of the recording properties can also be improved.

The nonmagnetic metal intermediate layer 4 is usually most preferably formed from Cr, but the Cr content may be 99wL% or more.

This intermediate layer 4 can be formed by various known vapor phase deposition methods, but it is usually preferable to deposit it by sputtering as in the case of the metal thin film magnetic layer 5 described above. The thickness of such a non-magnetic metal intermediate layer 4 should be appropriately determined depending on the type of metal thin film magnetic layer 5 used, but is usually 500 to 300 mm.
It is about 000λ.

In the magnetic recording medium 1 of the present invention, it is preferable that a nonmagnetic metal protective film 6 such as Or is provided between the metal thin film magnetic layer 5 and the carbon protective film 7 described above.

The method for forming the protective film 6 may be the same as that for the nonmagnetic metal intermediate layer 4 described above.

The thickness of such a non-magnetic metal protective film 6 is preferably 30 to 300, particularly preferably 100 to 200.

The magnetic recording medium 1 as described above may be a single-sided recording medium as shown in FIG. 1, but it may also be a so-called double-sided recording medium in which magnetic layers and the like are provided on both sides of the base 2 in the same manner as shown in FIG. It may also be used as a medium.

■Specific effects of the invention According to the present invention, a thin metallic thin layer is provided with a protective film on the upper layer, and a top coat layer containing a predetermined lubricant is provided on this protective film layer. The media has excellent durability, abrasion resistance, weather resistance, corrosion resistance, etc., and has less head adsorption.
It has extremely high reliability in practical use.

(2) Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown and the present invention will be explained in more detail.

(Example 1) A NiP base layer with a thickness of 20 μm was provided by electroless plating on a disc-shaped A2 substrate with a diameter of 13 cm, a thickness of 1′, and a 9 mm. Note that the electroless plating method was performed under the following process and manufacturing conditions.

(NiP electroless plating) Process Manufacturing Conditions, Alkaline Albretsubu 204 (Fino Pharmaceutical Co., Ltd. Degreasing
250 ml/l, 65°C, 5 minutes 2, acidic degreasing Albretsubu 230 (manufactured by Jitsukei Pharmaceutical Co., Ltd.) 15011
/42.65℃, 5 minutes 3゜Zincate Arp 302 (manufactured by Jitsukei Pharmaceutical Co., Ltd.) 250
! IJl/ffi, 25°C, 30 seconds 4, zincate 6
2 vol 1% concentrated nitric acid, peeling 800 ml /
l, 25℃, 30 seconds 5, Zincate Arp 302 (
Jitskei Pharmaceutical Co., Ltd.) 25011171.25℃, 20 seconds 6, surface conditioning Sodium bicarbonate 30g/iL, 20
℃, 30 seconds 7, nickel metal knife clad 719A (manufactured by Jitsukei Pharmaceutical Tsuki Co., Ltd.) 80 Td/il.

Knife Lad 719B (manufactured by Jitsukei Pharmaceutical Co., Ltd.) 150 J/l1 pH 4, 5, 90°C, 2 hours The composition of the base layer is Ni:P = 85 + 15 (weight ratio)
, the thickness is 20μ.

In addition to the Af1 substrate with such a NiP underlayer,
Substrates made of various materials such as AM, glass (manufactured by Corning), and plastic (polyetherimide resin) as shown in Table 1 were also used.

Next, the surfaces of the various substrates described above (for those having an underlayer on the surface of the substrate, the surface of the underlayer) were polished under the following conditions.

Surface polishing treatment> Using a lapping machine 9B-5P manufactured by Speed Fam ■, while rotating the above-mentioned substrate, a polishing liquid of Fujimi Polishing and Mediball No. was applied.

8 (50% diluted solution), polishing was performed for 10 minutes while applying a load of 100 g.

Thereafter, it was cleaned using a disk substrate cleaning device (manufactured by Speed Fam Clean System ■). The process is as shown below.

Cleaning process> 1. Neutral detergent solution, immersion, ultrasound 2, ultrapure water, scrub 3, ultrapure water, scrub 4, ultrapure water, immersion, ultrasonic 5, ultrapure water, immersion 6, Freon/ Ethanol mixture, immersion, ultrasonic wave 7, Freon/ethanol mixture, immersion 8.70 l/ethanol, steam (→drying) After such a cleaning process, the substrate surface (if there is a base layer on the substrate surface, An uneven portion was provided on the surface of the base layer as follows (hereinafter referred to as texturing step). That is, concentric irregular grooves were formed on the surface of the substrate while rotating the substrate using a tape bodging machine (manufactured by Tomoe Techno Corporation). The process conditions were: polishing tape number #4000, contact pressure 1.2, g/crn',
The oscillator was set at 5250 times/min and the work rotation speed was set at 150 times/min.

Thereafter, the same cleaning as above was performed, and then a non-magnetic magnetic metal intermediate layer made of C was formed by sputtering to a thickness of 2,000 yen.

The layer construction conditions were A: pressure 2.OPa, DC 8KW.

Note that before forming this intermediate layer, Ar gas pressure is 0.2 Pa, R
Etching treatment was performed under the condition of F400W.

Thereafter, various metal thin film magnetic layers as shown below were successively deposited thereon. Note that when forming a magnetic layer by electroless plating, the above etching process is not performed.
Moreover, no nonmagnetic metal intermediate layer such as Cr was provided.

Formation of Metal Thin Film Magnetic Layer> A CoNi magnetic layer was formed using a sputtering method. The film forming conditions were Ar gas pressure 2. OPa, DC8KW.
The CoN i composition weight ratio is Co/N i = 80/
20. The film thickness was 600 people.

A CoN i Cr magnetic layer was formed using a sputtering method. The film forming conditions were Ar gas pressure 2. OPa, DC8KW.

The CoNiCr composition weight ratio was 62.5:30, and the film thickness was 600.

A CoCrwL layer was formed using a sputtering method. The film forming conditions were Ar gas pressure 2. OPa, DC8KW.

The composition weight ratio of CoCr is Co/Cr = 87/
13. The film thickness was 1000 people.

Mother Masashikan-Dokukooka A CoN1P magnetic layer was formed using an electroless plating method.

The composition weight ratio of CoN i P is Co=Ni:P=6:
4:1. The film thickness was 1000 people.

The electroless plating process and manufacturing conditions were as follows.

Process Manufacturing Conditions Sodium hypophosphite 0.25 mol/2 0 Tsel salt 1.00 mol/2 Ammonium sulfate 0.40 mol/U 3 minutes On the various metal thin film magnetic layers deposited in this way C
A nonmagnetic metal protective film made of r was formed. Film formation is performed by sputtering, and the conditions are Ar gas pressure 2. OPa,D
C8 was set to W, and the film thickness was set to 200.

Further, on this protective film, a carbon protective film with a thickness of 400 mm was formed by sputtering as shown in Table 1. The sputtering conditions are Ar gas pressure 0.2 Pa, DC 8 KW.
And so.

However, the magnetic layer No. mentioned above as the metal thin film magnetic layer 5,
Among 1 to 4, only when the material of magnetic layer N014 is used, etching treatment is performed on the surface of the metal thin film magnetic layer on the surface where the non-magnetic metal/metal layer is to be formed under the conditions of Ar gas pressure of 0.2 Pa and RF of 400 W. did.

Note that the film thickness is as shown in Table 1.

The surface of this carbon protective film was subjected to plasma treatment as shown in Table 1, if necessary. The plasma conditions were processing gas N2, pressure 5 Pa, power supply 13,56 Mt (z
The high frequency was set at 3 kW, and the input power was set at 3 kW. A top coat layer containing various lubricants as shown below was formed thereon by a spin cord method. The spin code conditions were a rotation speed of 1000 rpm and a duration of 10 seconds. The film thickness was as shown in Table 1.

As a lubricant, Finprin Y25 (manufactured by Monte Fluos, molecular weight 13000) was mixed in the solvent of Freon 113 (manufactured by Daikin Industries, Ltd., Daiflon 5-3) to provide lubrication. The concentration of the agent-containing coating solution was adjusted to 0.05% by weight.

As a lubricant, 7onpurin Y45 (manufactured by Monte Fluos, molecular weight 4100) was mixed in the solvent of Freon 113 (manufactured by Daikin Industries, Ltd., Daiflon 5-3), and the concentration of the lubricant-containing coating solution was adjusted. was adjusted to 0.1% by weight.

1 (L → "") As a lubricant, Klytox 143AZ (manufactured by DuPont, molecular weight 2000) having the structural formula shown below was used as a lubricant, and Freon 113 (manufactured by Daikin Industries, Ltd., Daiflon 5-3) was used as a lubricant.
) in a solvent, and the concentration of the lubricant-containing coating solution was 0.05.
Adjusted to % by weight.

As a lubricant, Krytox 143AC (manufactured by DuPont, molecular 15500) was mixed in the solvent of Freon 113 (manufactured by Daikin Industries, Ltd., Daiflon 5-3) to form a lubricant-containing coating. The concentration of the part solution was adjusted to 0.05% by weight.

As a lubricant, a fluorine oil having the structural formula shown below (Daifloil #50, molecular weight 700, manufactured by Daikin Industries, Ltd.) was mixed into the solvent used in the composition 1, and the lubricant-containing The concentration of the coating liquid was adjusted to 0.05 wt%.

(Toshiba Silicone TSF45) Use lubricant with silicone oil (Toshiba Silicone TSF45)
1. The composition was the same as the above composition 5 except that the viscosity was changed to 1000 CPS).

In this way, various magnetic disk samples shown in Table 1 below were produced, and the characteristics shown below were measured.

(1) Measure the number of errors per disk recording surface immediately after creating a magnetic disk sample and after 30,000 C55 (contact start and stop) operations, and calculate the number of errors (missing pulse number) before and after C3S. ) displaying the increase in [unit 2 bits/plane].

The number of errors per disk recording surface was measured using a third-day fire for magnetic disks manufactured by Hitachi Electronic Engineering Co., Ltd., and the setting conditions were a missing pulse slice level of 65%.

(2) Weather resistance Immediately after preparing the sample and after leaving it for one month in an environment of 60° C. and 90% RH, it was expressed as an increase in the number of errors per disk recording surface.

(3) Low temperature friction coefficient The dynamic friction coefficient was measured in an environment of 5° C. and 60% RH.

These results are shown in Table 1.

From the results in Table 1, the effects of the present invention are clear.

In addition to the results in Table 1, the following characteristics were further measured for the samples of the present invention.

(1) Durable friction CSS (contact start and stop)
After 30,000 cycles, the friction coefficient of the surface of the magnetic layer of the magnetic disk sample was measured.

The measurement was performed using an I-# rubbing tester manufactured by Patichik ■.

The sample of the present invention was below 0.17.

2) ΔBm (%) The change in saturation magnetic flux density ΔBm was measured after being left in an environment of 60° C. and 90% RH for one month.

Here, △Bm is ΔBm = [(Bm after being left in an environment of 60°C and 90% RH for one month) - (Bm immediately after creation)
)] / (Bm immediately after creation) xlooo (%).

The saturation magnetic flux density Bm of the sample was measured using a vibrating sample magnetometer (VSM-53 manufactured by Toei Kogyo Co., Ltd.) under conditions of a maximum applied magnetic field of 15 and G. The measurement sample is 8
A piece cut out to a size of mm×8+nm was used.

The sample of the present invention had less than 2%.

(3) Weather Resistance Friction Coefficient The friction coefficient of the surface of a magnetic disk sample was measured after being left in an environment of 60° C. and 90% RH for one month.

The sample of the present invention had a value of 0.15 or less.

(4) Adsorption The Mn-Zn ferrite head was left stationary on the surface of the magnetic disk sample under the conditions of 20° C. and 60% RH for 172 hours, and the initial friction coefficient was measured when the sample was suddenly rotated.

The sample of the present invention had a value of 0.24 or less.

[Brief explanation of drawings]

FIG. 1 shows a cross-sectional view of the magnetic recording medium of the present invention. Brief explanation of symbols 1...Magnetic recording medium, 2...Nonmagnetic substrate, 3...
Base layer, 4... Nonmagnetic metal intermediate layer, 5... Metal thin film magnetic layer, 6... Nonmagnetic metal protective film 57... Carbon protective film, 8... Top coat layer Applicant: TDC FIG Co., Ltd., 1 7/'

Claims (9)

[Claims] (1) Having a metal thin film magnetic layer on a nonmagnetic substrate, further having a carbon protective film on this magnetic layer, and having a top coat layer containing perfluoropolyether as a lubricant on this protective film layer. A magnetic recording medium characterized by: (2) The magnetic recording medium according to claim 1, wherein the metal thin film magnetic layer mainly contains Co or one or more of Co, Ni, Cr, and P. (3) The magnetic recording medium according to claim 1 or 2, wherein the surface of the carbon protective film is plasma-treated. (4) The magnetic recording medium according to any one of claims 1 to 3, which has an underlayer between the substrate and the metal thin film magnetic layer. (5) The magnetic recording medium according to any one of claims 1 to 4, which has a nonmagnetic metal intermediate layer in contact with the magnetic layer on the base side of the metal thin film magnetic layer. (6) The magnetic recording medium according to any one of claims 1 to 5, which has a nonmagnetic metal protective film between the metal thin film magnetic layer and the carbon protective film. (7) Claim 4 in which the surface of the base layer has irregularities
6. The magnetic recording medium according to any one of items 6 to 6. (8) Claim 1 in which the non-magnetic substrate is a rigid substrate
The magnetic recording medium according to any one of Items 7 to 7. (9) The magnetic recording medium according to any one of claims 1 to 8, which has a disk-like shape.