Magnetic disk and magnetic recording/reproduction apparatus

A lubricating film is provided for a magnetic disk having a data region and a CSS region formed on its surface. The lubricating film ensures low stiction and good resistance to contact sliding in the data region and also ensures good CSS durability in the CSS region. Therefore, it is possible to provide a magnetic disk and a magnetic recording/reproducing device which do not cause problems with sliding between the magnetic head and the magnetic disk while the apparatus is running normally and even when the apparatus stops accidentally. The lubricating film formed in the data region of the magnetic disk is firmly fixed to the surface of the magnetic disk and is hardly liable to stiction. In addition, it is thick enough to ensure good durability even in the case of contact sliding. The lubricating film formed in the CSS region is composed of a lubricant which is firmly fixed to the surface of the magnetic disk and another lubricant which is weakly fixed to the surface of the magnetic disk; therefore, it is superior in CSS durability. This contributes to the highly reliable magnetic disk and magnetic recording/reproducing device.

TECHNICAL FIELD
 The present invention relates to a magnetic disk and a magnetic
 recording/reproducing device and, more particularly, to a magnetic disk
 and a magnetic recording/reproducing device characterized by a high
 recording density.
 BACKGROUND OF THE INVENTION
 The continuing development of the magnetic recording/reproducing device of
 the hard disk type is following the trend toward reduction in the diameter
 of the magnetic disk, reduction in the size and weight of the apparatus,
 and an increase in recording density. The higher the recording density of
 the magnetic disk becomes, the smaller is the distance (or flying height)
 between the magnetic disk and the magnetic head. It is expected in the
 near future that recording and reproducing will be accomplished in such a
 manner that the magnetic head is in complete contact with the magnetic
 disk. Then, the magnetic disk will be subject to a much severe sliding
 condition. On the other hand, an increase in recording density needs a
 smaller flying height and a smoother magnetic disk surface (for stable
 flying). The consequence is that the head slider (supporting the magnetic
 head) slides on (keeping in contact with) the magnetic disk for a longer
 period of time than before (sliding in this manner is referred to as
 contact sliding hereinafter), the disk is subject to more dynamic friction
 and wear than before during its start-up, and there occurs a limiting
 static friction (referred to as stiction hereinafter) between the head and
 the disk. The result of an increase in the dynamic friction and wear due
 to contact sliding is an occasional disk crash and head wear which tends
 to disable recording and reproducing operations. Moreover, strong stiction
 disables the start-up of the disk and damages the disk head.
 In order to address the above-mentioned problems, there has been developed
 a magnetic disk of a new type which has two separate regions: one in which
 the head slider stands by when the magnetic disk is at rest and
 experiences contact start and contact stop when the disk starts and stops,
 and the other in which the head performs recording and reproducing while
 the disk is running. The former region is referred to as CSS region and
 the latter as a data region. The CSS region is usually formed in an inner
 section of the magnetic disk and it has its surface roughened so as to
 prevent stiction. By contrast, the data region has its surface smoothed so
 as to ensure a stable head floating. The magnetic disk having a CSS region
 and data region needs a special lubricating film and lubricating
 technologies. For example, Japanese Patent Laid-open No. 36277/1994
 discloses a method of preventing stiction by forming a protuberance (about
 5 nm high) on the rail surface of the slider in the CSS region. Also,
 Japanese Patent Laid-open No. 111292/1994 discloses the use of a liquid
 lubricant in the CSS region and a solid lubricant in the data region.
 These prior art technologies are directed to the lubricating film to be
 applied to the magnetic disk in which are formed the CSS region and data
 region, and the lubricating film realizes to some extent the sliding
 characteristics required of the CSS region and data region. There is a
 distinct difference in requirements between the lubricating film for the
 CSS region and the lubricating film for the data region because the
 head-disk sliding state differs in these two regions. In the CSS region,
 it is possible to somewhat reduce stiction by roughening the surface of
 the magnetic disk, but there is a need for a lubricating film with good
 durability because contact sliding takes place when the disk starts up and
 stops. In the data region, however, it is necessary that the disk have a
 small surface roughness and the lubricating film have a low stiction. The
 reason for this is that the head slider could come into contact with the
 data region (causing strong stiction) when the disk stops suddenly (due to
 some anomaly) while the head slider lies in the data region. Therefore,
 the lubricating film in the CSS region should differ in lubricating
 performance from that in the data region.
 The lubricant now in use for magnetic disks is a perfluoropolyether
 compound having functional groups for adsorption to the disk surface. This
 lubricant gives rise to a lubricating film which is composed of a layer
 firmly adsorbed to the disk surface and a layer which is adsorbed weakly
 or not adsorbed to the disk surface. The firmly adsorbed lubricating layer
 does not separate from the disk surface when the disk is washed with a
 perfluorocarbon solvent. On the other hand, the weakly adsorbed
 lubricating layer is easily separated from the disk surface by washing.
 This weakly adsorbed lubricating layer, however, plays an important role
 in the CSS region which needs good durability, because it is necessary
 that the lubricant partly moves to the slide surface of the head slider at
 the time of sliding so that a stable frictional state is established.
 Without this weakly adsorbed layer in the CSS region, it is impossible to
 maintain satisfactory reliability. By contrast, the data region needs low
 stiction, because cohesion of the lubricant in the gap between the head
 and the disk should be avoided when the head comes into contact with the
 data region at the time of an anomalous sudden stop and the excessive
 scraping up of the lubricant by the head during seeking should be avoided.
 Thus, the weakly adsorbed layer, which is easily mobile on the disk
 surface, has an adverse effect on stiction contrary to durability. For
 this reason, the weakly adsorbed layer should be as little as possible. If
 a conventional lubricant of the adsorption type is applied to the entire
 surface of the disk and the data region alone is washed to remove the
 weakly adsorbed layer, it necessarily follows that the lubricating film in
 the data region decreases in thickness. At the present time, there is by
 far a smaller chance of contact sliding in the data region than in the CSS
 region; however, in the future magnetic disk apparatus in which the flying
 height of the head will decrease further, there will be a stronger chance
 of contact sliding between the head and disk even in the data region.
 Thus, there will be, in a near future, a demand for the data region to
 have good durability. This implies that the lubricating film in the data
 region should be thick enough to endure occasional contact sliding.
 These technical problems are not solved completely by the above-mentioned
 prior art technologies. The technology disclosed in Japanese Patent
 Laid-open No. 111292/1994 provides the respective regions with the desired
 lubricating characteristics by coating the CSS region with a liquid
 lubricant and the data region with a solid lubricant. This technology
 suffers the disadvantage of requiring a complex process to form the
 lubricant films. The technology disclosed in Japanese Patent Laid-open No.
 53027/1992 ensures low stiction in the data region and good durability in
 the CSS region by forming the lubricating films such that the lubricating
 film in the data region is thinner than the lubricating film in the CSS
 region. This technology, however, is not satisfactory because it is
 necessary to maintain a certain thickness for the lubricating film in the
 data region in order to ensure good durability. At the present time, there
 is no effective means to ensure satisfactory slide reliability for a disk
 having a CSS region and data region formed thereon.
 The present invention was completed to address the above-mentioned problems
 involved in the prior art technology. It is an object of the present
 invention to provide an effective means to ensure satisfactory slide
 reliability for a disk having a CSS region and data region formed thereon.
 It is another object of the present invention to provide a
 high-performance magnetic disk and magnetic recording/reproducing device
 that employ such means.
 SUMMARY OF THE INVENTION
 The magnetic disk according to the present invention is characterized by
 the provision of lubricating layers formed thereon in a unique manner as
 mentioned below. In the data region in the magnetic disk, the weakly
 adsorbed lubricating layer is as small as possible to so as to ensure low
 stiction, but the lubricating film is thick enough to endure contact
 sliding (between the magnetic head and the magnetic disk) that might
 occasionally occur. This object is achieved by using a lubricant that
 strongly adsorbs to the surface of the magnetic disk or by treating the
 applied lubricant afterward. In the CSS region in the magnetic disk, a
 weakly adsorbed lubricating layer less liable to stiction is formed, so as
 to ensure satisfactory durability and take into consideration the fact
 that the lubricant easily moves to the head slider. The present invention
 discloses the magnetic disk, the process for production thereof, and the
 magnetic recording/reproducing device mentioned below.
 The first aspect of the present invention resides in a magnetic disk having
 a seed layer, a magnetic layer, and a protective layer sequentially
 laminated on a non-magnetic substrate, characterized in that the disk has
 a CSS region and a data region, the CSS region having a protective layer
 with a surface roughness greater than or equal to Ra 10 nm at the place
 where the magnetic head slider is positioned when the magnetic disk starts
 and stops rotating, the data region having a protective layer with a
 surface roughness smaller than or equal to Ra 3 rm at the place where the
 magnetic head slider is positioned while the magnetic disk is rotating,
 the protective layer being coated with a lubricating film which contains
 at least one member selected from perfluoropolyether compounds expressed
 by the formulas (I) to (III) below,
EQU R.sub.1 --X--(CF.sub.2 CF.sub.2 O).sub.m --(CF.sub.2 O).sub.n --X--R.sub.2
 (I)
EQU F(CF.sub.2 CF.sub.2 CF.sub.2 --O).sub.n --C.sub.2 F.sub.4 --X--R.sub.3
 (II)
EQU F--(CF(CF.sub.3)--CF.sub.2 --O).sub.n --CF(CF.sub.3)--X--R.sub.4 (III)
 (where m and n are integers; R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are
 hydrocarbon chains; and X is a divalent binding group) the lubricating
 film is composed of a lubricant which is firmly fixed to the surface of
 said protective film and another lubricant which is weakly fixed to the
 surface of said protective film, the lubricating film formed in the CSS
 region containing a lubricant which is weakly fixed in an amount not less
 than 10% of the total amount of the lubricant in the CSS region, the
 lubricating film formed in the data region containing a lubricant which is
 weakly fixed in an amount less than 10% of the total amount of the
 lubricant in the data region.
 The second aspect of the present invention resides in a magnetic disk as
 defined in the first aspect, the magnetic disk being characterized in that
 the lubricating film is composed of a lubricant which is firmly fixed to
 the surface of the protective layer such that it is not washed out by a
 perfluorocarbon solvent, and another lubricant which is weakly fixed to
 the surface of the protective layer such that it is washed out by a
 perfluorocarbon solvent.
 The third aspect of the present invention resides in a magnetic disk having
 a seed layer, a magnetic layer, and a protective layer sequentially
 laminated on a non-magnetic substrate, characterized in that the disk has
 a CSS region and a data region, the CSS region having a protective layer
 with a surface roughness greater than or equal to Ra 10 nm at the place
 where the magnetic head slider is positioned when the magnetic disk starts
 and stops rotating, the data region having a protective layer with a
 surface roughness smaller than or equal to Ra 3 nm at the place where the
 magnetic head slider is positioned while the magnetic disk is rotating,
 the protective layer being coated with a lubricant which contains at least
 one member selected from perfluoropolyether compounds expressed by the
 formulas (I) to (III) above, the lubricant being applied to the entire
 surface of the magnetic disk, the entire surface of the magnetic disk
 being heated above 80.degree. C. or the entire surface or the data region
 being irradiated with ultraviolet rays, the CSS region being subsequently
 washed with a per fluorocarbon solvent, such that the lubricating film
 formed in the CSS region has a thickness greater than equal to 1.5 nm and
 the lubricating film formed in the data region has a thickness greater
 than or equal to 1 nm.
 The fourth aspect of the present invention resides in a magnetic disk
 having a seed layer, a magnetic layer, and a protective layer sequentially
 laminated on a non-magnetic substrate, characterized in that the disk has
 a CSS region and a data region, the CSS region having a protective layer
 with a surface roughness greater than or equal to Ra 10 nm at the place
 where the magnetic head slider is positioned when the magnetic disk starts
 and stops rotating, the data region having a protective layer with a
 surface roughness smaller than or equal to Ra 3 nm at the place where the
 magnetic head slider is positioned while said magnetic disk is rotating,
 the protective layer being coated with a lubricant which contains at least
 one member selected from perfluoropolyether compounds expressed by the
 formulas (I) to (III) above, the lubricant being applied to the entire
 surface of the magnetic disk, the entire surface of the magnetic disk
 being heated above 80.degree. C. or the entire surface or the data region
 being irradiated with ultraviolet rays, the entire surface of the magnetic
 disk being washed with a perfluorocarbon solvent, subsequently the CSS
 region being coated with a perfluorocarbon compound having adsorptive
 functional groups selected from perfluoropolyether compounds expressed by
 the formulas (I) to (III) above, such that the lubricating film formed in
 the CSS region has a thickness greater than or equal to 1.5 nm and the
 lubricating film formed in the data region has a thickness greater than or
 equal to 1 nm.
 The fifth aspect of the present invention resides in a magnetic disk having
 a seed layer, a magnetic layer, and a protective layer sequentially
 laminated on a non-magnetic substrate, characterized in that the disk has
 a CSS region and a data region, the CSS region having a protective layer
 with a surface roughness greater than or equal to Ra 10 nm at the place
 where the magnetic head slider is positioned when the magnetic disk starts
 and stops rotating, the data region having a protective layer with a
 surface roughness smaller than or equal to Ra 3 nm at the place where the
 magnetic head slider is positioned while said magnetic disk is rotating,
 the protective layer being coated with a lubricant which contains at least
 one member selected from perfluoropolyether compounds expressed by the
 formulas (I) to (III) above, the lubricant being applied to the entire
 surface of the magnetic disk, the entire surface of the magnetic disk
 being heated above 80.degree. C. or the entire surface or the data region
 being irradiated with ultraviolet rays, the entire surface of the magnetic
 disk being washed with a perfluorocarbon solvent, subsequently the data
 region being coated with a perfluorocarbon compound having functional
 groups chemically reactive with the surface of said protective film
 selected from perfluoropolyether compounds expressed by the formulas (I)
 to (III) above, such that the lubricating film formed in the CSS region
 has a thickness greater than or equal to 1.5 nm and the lubricating film
 formed in the data region has a thickness greater than or equal to 1 nm.
 The sixth aspect of the present invention resides in a magnetic disk having
 a seed layer, a magnetic layer, and a protective layer sequentially
 laminated on a non-magnetic substrate, characterized in that the disk has
 a CSS region and a data region, the CSS region having a protective layer
 with a surface roughness greater than or equal to Ra 10 nm at the place
 where the magnetic head slider is positioned when the magnetic disk starts
 and stops rotating, the data region having a protective layer with a
 surface roughness smaller than or equal to Ra 3 nm at the place where the
 magnetic head slider is positioned while the magnetic disk is rotating,
 the protective layer being coated with a lubricant which contains at least
 one member selected from perfluoropolyether compounds having functional
 groups chemically reactive with the surface of said protective film
 expressed by the formulas (I) to (III) above, the lubricant being applied
 to the entire surface of the magnetic disk, the entire surface of the
 magnetic disk being heated above 80.degree. C. or the entire surface or
 the data region being irradiated with ultraviolet rays, the entire surface
 of the magnetic disk being washed with a perfluorocarbon solvent,
 subsequently the data region being coated with a perfluorocarbon compound
 having functional groups chemically reactive with the surface of said
 protective film selected from perfluoropolyether compounds expressed by
 the formulas (I) to (III) above, such that the lubricating film formed in
 the CSS region has a thickness greater than or equal to 1.5 nm and the
 lubricating film formed in the data region has a thickness greater than or
 equal to 1 nm.
 The seventh aspect of the present invention resides in a process for
 producing a magnetic disk having a seed layer, a magnetic layer, a
 protective layer, and a lubricating layer sequentially laminated on a
 non-magnetic substrate, the process comprising forming the CSS region
 having a protective layer with a surface roughness greater than or equal
 to Ra 10 nm at the place where the magnetic head slider is positioned when
 the magnetic disk starts and stops rotating, forming the data region
 having a protective layer with a surface roughness smaller than equal to
 Ra 3 nm at the place where the magnetic head slider is positioned while
 the magnetic disk is rotating, coating the surface of said protective
 layer all over the magnetic disk with a lubricant which contains at least
 one member selected from perfluoropolyether compounds expressed by the
 formulas (I) to (III) above, heating the entire surface of the magnetic
 disk above 80.degree. C. or irradiating the entire surface of the magnetic
 disk or the data region with ultraviolet rays, and washing the CSS region
 with a perfluorocarbon solvent, such that the lubricating film formed in
 the CSS region has a thickness greater than or equal to 1.5 nm and the
 lubricating film formed in the data region has a thickness greater than or
 equal to 1 nm.
 The eighth aspect of the present invention resides in a process for
 producing a magnetic disk as defined in the seventh aspect, which further
 comprises, after washing the entire surface of the magnetic disk with a
 perfluorocarbon solvent, coating the CSS region with a perfluoropolyether
 compound having adsorptive functional groups selected from the
 perfluoropolyether compounds expressed by the formulas (I) to (III) above,
 such that the lubricating film formed in the CSS region has a thickness
 greater than or equal to 1.5 nm and the lubricating film formed in the
 data region has a thickness greater than or equal to 1 nm.
 The ninth aspect of the present invention resides in a process for
 producing a magnetic disk as defined in the seventh aspect, which further
 comprises, after washing the entire surface of the magnetic disk with a
 perfluorocarbon solvent, applying a perfluoropolyether compound having
 functional groups chemically reactive with the surface of the protective
 film which is selected from the perfluoropolyether compounds expressed by
 the formulas (I) to (III) above, such that the lubricating film formed in
 the CSS region has a thickness greater than or equal to 1.5 nm and the
 lubricating film formed in the data region has a thickness greater than or
 equal to 1 nm.
 The tenth aspect of the present invention resides in a process for
 producing a magnetic disk as defined in the seventh aspect, which further
 comprises, after heating the entire surface of the magnetic disk above
 80.degree. C. or irradiating it with ultraviolet rays, applying to the
 entire surface of the magnetic disk a perfluoropolyether compound-having
 adsorptive functional groups which is selected from the perfluoropolyether
 compounds expressed by the formulas (I) to (III) above, and, after washing
 the data region with a perfluorocarbon solvent, applying a
 perfluoropolyether compound having chemically reactive functional groups
 which is selected from perfluoropolyether compounds expressed by the
 formulas (I) to (III) above, such that the lubricating film formed in the
 CSS region has a thickness greater than or equal to 1.5 nm and the
 lubricating film formed in the data region has a thickness greater than or
 equal to 1 nm.
 The eleventh aspect of the present invention resides in a magnetic
 recording/reproducing device composed of a magnetic head, a magnetic head
 slider carrying the magnetic head, and a magnetic disk having a seed
 layer, a magnetic layer, and a protective layer sequentially laminated on
 a non-magnetic substrate, characterized in that the disk has a CSS region
 and a data region, the CSS region having a protective layer with a surface
 roughness greater than or equal to Ra 10 rim at the place where the
 magnetic head slider is positioned when the magnetic disk starts and stops
 rotating, the data region having a protective layer with a surface
 roughness smaller than or equal to Ra 3 nm at the place where the magnetic
 head slider is positioned while the magnetic disk is rotating, the
 protective layer being coated with a lubricating film which contains at
 least one member selected from perfluoropolyether compounds expressed by
 the formulas (I) to (III) above, the lubricating film is composed of a
 lubricant which is firmly fixed to the surface of said protective film and
 another lubricant which is weakly fixed to the surface of said protective
 film, the lubricating film formed in the CSS region containing a lubricant
 which is weakly fixed in an amount not less than 10% of the total amount
 of the lubricant in the CSS region, the lubricating film formed in the
 data region containing a lubricant which is weakly fixed in an amount less
 than 10% of the total amount of the lubricant in the data region, such
 that the limiting static friction, and dynamic friction that occur in the
 data region between the magnetic head slider and the magnetic disk are
 smaller than or equal to 1.5 and 1.0, respectively, and the limiting
 static friction and dynamic friction that occur in the CSS region between
 the magnetic head slider and the magnetic disk are smaller than or equal
 to 1.0 and 0.5, respectively.
 The twelfth aspect of the present invention resides in a magnetic
 recording/reproducing device composed of a magnetic head, a magnetic head
 slider carrying the magnetic head, and a magnetic disk having a seed
 layer, a magnetic layer, and a protective layer sequentially laminated on
 a non-magnetic substrate, characterized in that the disk has a CSS region
 and a data region, the CSS region having a protective layer with a surface
 roughness greater than or equal to Ra 10 nm at the place where the
 magnetic head slider is positioned when the magnetic disk starts and stops
 rotating, the data region having a protective layer with a surface
 roughness smaller than or equal to Ra 3 nm at the place where the magnetic
 head slider is positioned while the magnetic disk is rotating, the
 protective layer being coated with a lubricating film which contains at
 least one member selected from perfluoropolyether compounds expressed by
 the formulas (I) to (III) above, the lubricant being applied to the entire
 surface of the magnetic disk, the entire surface of the, magnetic disk
 being heated above 80.degree. C. or the entire surface or the data region
 being irradiated with ultraviolet rays, the CSS region being subsequently
 washed with a perfluorocarbon solvent, such that the lubricating film
 formed in the CSS region has a thickness greater than or equal to 1.5 nm
 and the lubricating film formed in the data region has a thickness greater
 than or equal to 1 nm, and the limiting static friction and dynamic
 friction that occur in the data region between the magnetic head slider
 and the magnetic disk are smaller than or equal to 1.5 and 1.0,
 respectively, and the limiting static friction and dynamic friction that
 occur in the CSS region between the magnetic head slider and the magnetic
 disk are smaller than or equal to 1.0 and 0.5, respectively.
 The thirteenth aspect of the present invention resides in a magnetic
 recording/reproducing device as the twelfth aspect, which is characterized
 in that the magnetic disk has the data region which is coated, after
 washing with a fluorocarbon solvent, with a perfluoropolyether compound
 having adsorptive functional groups which is selected from the
 perfluoropolyether compounds expressed by the formulas (I) to (III) above,
 such that the lubricating film formed in the CSS region has a thickness
 greater than or equal to 1.5 nm and the lubricating film formed in the
 data region has a thickness greater than or equal to 1 nm.
 The fourteenth aspect of the present invention resides in a magnetic
 recording/reproducing device as defined in the twelfth aspect, which is
 characterized in that the entire surface of the magnetic disk is coated,
 after the washing of the data region with a fluorocarbon solvent, with a
 perfluoropolyether compound having functional groups chemically reactive
 with the protective film which is selected from the perfluoropolyether
 compounds expressed by the formulas (I) to (III) above, such that the
 lubricating film formed in the CSS region has a thickness greater than or
 equal to 1.5 nm and the lubricating film formed in the data region has a
 thickness greater than or equal to 1 nm.
 The fifteenth aspect of the present invention resides in a magnetic
 recording/reproducing device composed of a magnetic head, a magnetic head
 slider carrying the magnetic head, and a magnetic disk having a seed
 layer, a magnetic layer, and a protective layer sequentially laminated on
 a non-magnetic substrate, characterized in that the disk has a CSS region
 and a data region, the CSS region having a protective layer with a surface
 roughness greater than or equal to Ra 10 nm at the place where the
 magnetic head slider is positioned when the magnetic disk starts and stops
 rotating, the data region having a protective layer with a surface
 roughness smaller than or equal to Ra 3 nm at the place where the magnetic
 head slider is positioned while the magnetic disk is rotating, after
 coating the surface of the protective film all over the magnetic disk with
 at least one perfluoropolyether compound expressed by the formulas (I) to
 (III) above, heating the entire surface of the magnetic disk above
 80.degree. C. or irradiating the entire surface of the magnetic disk or
 the data region with ultraviolet rays, coating the entire surface of the
 magnetic disk with a perfluoropolyether compound having adsorptive
 functional groups which is selected from the perfluoropolyether compounds
 expressed by the formulas (I) to (III) above, and, after washing the data
 region with a perfluorocarbon solvent, applying a perfluoropolyether
 compound having chemically reactive functional groups which is selected
 from the perfluoropolyether compounds expressed by the formulas (I) to
 (III) above, such that the lubricating film formed in the CSS region has a
 thickness greater than or equal to 1.5 nm and the lubricating film formed
 in the data region has a thickness greater than 1 nm, and the limiting
 static friction and dynamic friction that occur in the data region between
 the magnetic head slider and the magnetic disk are smaller than or equal
 to 1.5 and 1.0, respectively, and the limiting static friction and dynamic
 friction that occur in the CSS region between the magnetic head slider and
 the magnetic disk are smaller than or equal to 1.0 and 0.5, respectively.
 The sixteenth aspect of the present invention resides in a magnetic disk
 having a seed layer, a magnetic layer, and a protective layer sequentially
 laminated on a non-magnetic substrate, characterized in that the disk has
 a CSS region and a data region, the CSS region having a protective layer
 with a surface roughness greater than or equal to Ra 10 nm at the place
 where the magnetic head slider is positioned when the magnetic disk starts
 and stops rotating, the data region having a protective layer with a
 surface roughness smaller than or equal to Ra 3 nm at the place where the
 magnetic head slider is positioned while the magnetic disk is rotating,
 the protective layer being coated with a lubricant which contains at least
 one member selected from perfluoropolyether compounds expressed by the
 formulas (IV) to (XIII) below,
EQU F(CF.sub.2 CF.sub.2 CF.sub.2 O).sub.n --C.sub.2 F.sub.4 --CONH--C.sub.3
 H.sub.6 --Si(OC.sub.2 H.sub.5).sub.3 (IV)
EQU F(CF(CF.sub.3)--CF.sub.2 O).sub.n --CF(CF.sub.3)--CONH--C.sub.3 H.sub.6
 --Si(OC.sub.2 H.sub.5).sub.3 (V)
EQU (C.sub.2 H.sub.5 O).sub.3 Si--C.sub.3 H.sub.6 --NHCO--(CF.sub.2 CF.sub.2
 O).sub.m --(CF.sub.2 O).sub.n --CONH--C.sub.3 H.sub.6 --Si(OC.sub.2
 H.sub.5).sub.3 (VI)
EQU C.sub.6 H.sub.5 --O--C.sub.6 H.sub.4 --H.sub.3 N+--OCO--(CF.sub.2 CF.sub.2
 O).sub.m --(CF.sub.2 O).sub.n --COO--+NH.sub.3 --C.sub.6 H.sub.4
 --O--C.sub.6 H.sub.5 (VII)
EQU F(CF.sub.2 CF.sub.2 CF.sub.2 --O).sub.n --C.sub.2 F.sub.4 --CH.sub.2 OH
 (VIII)
EQU HO--CH.sub.2 --(CF.sub.2 CF.sub.2 O).sub.m --(CF.sub.2 O).sub.n --CH.sub.2
 OH (IX)
EQU HO--(CH.sub.2 CH.sub.2 --O).sub.p --CH.sub.2 CF.sub.2 --(CF.sub.2 CF.sub.2
 O).sub.m --(CF.sub.2 O).sub.n --OCF.sub.2 CH.sub.2 (O--CH.sub.2
 CH.sub.2).sub.q --OH (X)
EQU F(CF.sub.2 CF.sub.2 CF.sub.2 O).sub.n --C.sub.2 F.sub.4 --COO--+NH.sub.3
 --C.sub.6 H.sub.4 --O--C.sub.6 H.sub.5 (XI)
EQU F(CF(CF.sub.3)--CF.sub.2 O).sub.n --CF(CF.sub.3)--COO--+NH.sub.3 --C.sub.6
 H.sub.4 --O--C.sub.6 H.sub.5 (XII)
 ##STR1##
 (where m, n, p, and q are integers) all over the surface of the magnetic
 disk, the entire surface of the magnetic disk being heated above
 80.degree. C. or the data region being irradiated with ultraviolet rays,
 the CSS region being subsequently washed with a perfluorocarbon solvent,
 such that the lubricating film formed in the CSS region has a thickness
 greater than or equal to 1.5 nm and the lubricating film formed in the
 data region has a thickness greater than or equal to 1 nm.
 The seventeenth aspect of the present invention resides in a magnetic disk
 having a seed layer, a magnetic layer, and a protective layer sequentially
 laminated on a non-magnetic substrate, characterized in that the disk has
 a CSS region and a data region, the CSS region having a protective layer
 with a surface roughness greater than or equal to Ra 10 nm at the place
 where the magnetic head slider is positioned when the magnetic disk starts
 and stops rotating, the data region having a protective layer with a
 surface roughness smaller than or equal to Ra 3 nm at the place where the
 magnetic head slider is positioned while the magnetic disk is rotating,
 the protective layer being coated with a lubricant which contains at least
 one member selected from perfluoropolyether compounds expressed by the
 formulas (IV) to (XIII) above, all over the surface of the magnetic disk,
 the entire surface of the magnetic disk being heated above 80.degree. C.
 or the data region being irradiated with ultraviolet rays, the entire
 surface of the magnetic disk being washed with a perfluorocarbon solvent
 and the CSS region being coated with a perfluoropolyether compound having
 adsorptive functional groups which is selected from the perfluoropolyether
 compounds expressed by the formulas (VII) to (XIII) above, such that the
 lubricating film formed in the CSS region has a thickness greater than or
 equal to 1.5 nm and the lubricating film formed in the data region has a
 thickness greater than 1 nm.
 The eighteenth aspect of the present invention resides in a magnetic disk
 having a seed layer, a magnetic layer, and a protective layer sequentially
 laminated on a non-magnetic substrate, characterized in that the disk has
 a CSS region and a data region, the CSS region having a protective layer
 with a surface roughness greater than or equal to Ra 10 nm at the place
 where the magnetic head slider is positioned when the magnetic disk starts
 and stops rotating, the data region having a protective layer with a
 surface roughness smaller than or equal to Ra 3 nm at the place where the
 magnetic head slider is positioned while the magnetic disk is rotating,
 the protective layer being coated with a lubricant which contains at least
 one member selected from perfluoropolyether compounds expressed by the
 formulas (IV) to (XIII) above, the lubricant being applied to the entire
 surface of the magnetic disk, the entire surface of the magnetic disk
 being heated above 80.degree. C. or the entire surface of the magnetic
 disk or the data region being irradiated with ultraviolet rays, the data
 region being subsequently washed with a perfluorocarbon solvent, and
 coating the data region with a perfluoropolyether compound having
 functional groups reactive with the surface of the protective film which
 is selected from the perfluoropolyether compounds expressed by the
 formulas (IV) to (VI) above, such that the lubricating film formed in the
 CSS region has a thickness greater than or equal to 1.5 nm and the
 lubricating film formed in the data region has a thickness greater than or
 equal to 1 nm.
 The nineteenth aspect of the present invention resides in a magnetic disk
 having a seed layer, a magnetic layer,-and a protective layer sequentially
 laminated on a non-magnetic substrate, characterized in that the disk has
 a CSS region and a data region, the CSS region having a protective layer
 with a surface roughness greater than equal to Ra 10 nm at the place where
 the magnetic head slider is positioned when the magnetic disk starts and
 stops rotating, the data region having a protective layer with a surface
 roughness smaller than or equal to Ra 3 nm at the place where the magnetic
 head slider is positioned while said magnetic disk is rotating, the
 protective layer being coated with a lubricant which contains at least one
 member selected from perfluoropolyether compounds expressed by the
 formulas (IV) to (VI) above, the lubricant being applied to the entire
 surface of the magnetic disk, the entire surface of the magnetic disk
 being heated above 80.degree. C. or the entire surface of the magnetic
 disk or the data region being irradiated with ultraviolet rays, the
 surface of said protective film being coated all over the magnetic disk
 with a perfluoropolyether compound having adsorptive functional groups
 which is selected from the perfluoropolyether compounds expressed by the
 formulas (VII) to (XIII) above, the data region being subsequently washed
 with a perfluorocarbon solvent, and coating the data region with a
 perfluoropolyether compound having functional groups chemically reactive
 with the surface of the protective film which is selected from the
 perfluoropolyether compounds expressed by the formulas (IV) to (VI) above,
 such that the lubricating film formed in the CSS region has a thickness
 greater than equal to 1.5 nm and the lubricating film formed in the data
 region has a thickness greater than or equal to 1 nm.
 The twentieth aspect of the present invention resides in a magnetic disk
 having a seed layer, a magnetic layer, a protective layer, and a
 lubricating layer sequentially laminated on a non-magnetic substrate,
 characterized in that the disk has a CSS region and a data region, the CSS
 region having a protective layer with a surface roughness greater than or
 equal to Ra 10 nm at the place where the magnetic head slider is
 positioned when the magnetic disk starts and stops rotating, the data
 region having a protective layer with a surface roughness smaller than or
 equal to Ra 3 nm at the place where the magnetic head slider is positioned
 while the magnetic disk is rotating, the protective layer being coated
 with a lubricant which contains at least one member selected from
 perfluoropolyether compounds expressed by the formulas (IV) to (XIII)
 above, the lubricant being applied to the entire surface of the magnetic
 disk, the entire surface of the magnetic disk being heated above
 80.degree. C. or the entire surface of the magnetic disk or the data
 region being irradiated with ultraviolet rays, the CSS region being
 subsequently washed with a perfluorocarbon solvent, such that the
 lubricating film formed in the CSS region has thickness greater than or
 equal to 1.5 nm and the lubricating film formed in the data region has a
 thickness greater than or equal to 1 nm.
 The twenty-first aspect of the present invention resides in a process for
 producing a magnetic disk having a seed layer, a magnetic layer, a
 protective layer, and a lubricating layer sequentially laminated on a
 non-magnetic substrate, said process comprising forming a CSS region
 having a protective layer with a surface roughness greater than or equal
 to Ra 10 nm at the place where the magnetic head slider is positioned when
 the magnetic disk starts and stops rotating, forming a data region having
 a protective layer with a surface roughness smaller than or equal to Ra 3
 nm at the place where the magnetic head slider is positioned while the
 magnetic disk is rotating, coating the surface of the protective layer all
 over the magnetic disk with a lubricant which contains at least one member
 selected from perfluoropolyether compounds expressed by the formulas (IV)
 to (XIII) above, heating the entire surf ace of the magnetic disk above
 80.degree. C. or irradiating the entire surface of the magnetic disk or
 the data region with ultraviolet rays, and washing the entire surface of
 the magnetic disk with a perfluorocarbon solvent, and coating the CSS
 region with a perfluoropolyether compound having adsorptive functional
 groups which is selected from the perfluoropolyether compounds expressed
 by the formulas (VII) to (XIII) above, such that the lubricating film
 formed in the CSS region has a thickness greater than or equal to 1.5 nm
 and the lubricating film formed in the data region has a thickness greater
 than or equal to 1 nm.
 The twenty-second aspect of the present invention resides in a process for
 producing a magnetic disk having a seed layer, a magnetic layer, a
 protective layer, and a lubricating layer sequentially laminated on a
 non-magnetic substrate, said process comprising forming a CSS region
 having a protective layer with a surface roughness greater than or equal
 to Ra 10 nm at the place where the magnetic head slider is positioned when
 the magnetic disk starts and stops rotating, forming a data region having
 a protective layer with a surface roughness smaller than or equal to Ra 3
 nm at the place where the magnetic head slider is positioned while the
 magnetic disk is rotating, coating the surface of the protective layer all
 over the magnetic disk with a lubricant which contains at least one member
 selected from perfluoropolyether compounds expressed by the formulas (IV)
 to (XIII) above, heating the entire surface of the magnetic disk above
 80.degree. C. or irradiating the entire surface of the magnetic disk or
 the data region with ultraviolet rays, and washing the entire surface of
 the magnetic disk with a perfluorocarbon solvent, and coating the data
 region with a perfluoropolyether compound having functional groups
 chemically reactive with the surface of the protective layer which is
 selected from the perfluoropolyether compounds expressed by the formulas
 (IV) to (VI) above, such that the lubricating film formed in the CSS
 region has a thickness greater than or equal to 1.5 nm and the lubricating
 film formed in the data region has a thickness greater than or equal to 1
 nm.
 The twenty-third aspect of the present invention resides in a process for
 producing a magnetic disk having a seed layer, a magnetic layer, a
 protective layer, and a lubricating layer sequentially laminated on a
 non-magnetic substrate, said process comprising forming a CSS region
 having a protective layer with a surface roughness greater than or equal
 to Ra 10 nm at the place where the magnetic head slider is positioned when
 the magnetic disk starts and stops rotating, forming a data region having
 a protective layer with a surface roughness smaller than or equal to Ra 3
 nm at the place where the magnetic head slider is positioned while the
 magnetic disk is rotating, coating the surface of the protective layer all
 over the magnetic disk with a lubricant which contains at least one member
 selected from perfluoropolyether compounds having functional groups
 chemically reactive with the surface of the protective film expressed by
 the formulas (IV) to (VI) above, heating the entire surface of the
 magnetic disk above 80.degree. C. or irradiating the entire surface of the
 magnetic disk with ultraviolet rays, coating the entire surface of the
 magnetic disk wit h a perfluoropolyether compound having adsorptive
 functional groups which is selected from perfluoropolyether compounds
 expressed by the formulas (VII) to (XIII), and washing the data region
 with a perfluorocarbon solvent, and coating with a perfluoropolyether
 compound having functional groups chemically reactive with the surface of
 the protective layer which is selected from the perfluoropolyether
 compounds expressed by the formulas (IV) to (VI) above, such that the
 lubricating film formed in the CSS region has a thickness greater than or
 equal to 1.5 nm and the lubricating film formed in the data region has a
 thickness greater than or equal to 1 nm.
 The twenty-fourth aspect of the present invention resides in a magnetic
 recording/reproducing device comprising a magnetic head, a magnetic head
 slider carrying the magnetic head, and a magnetic disk having a seed
 layer, a magnetic layer, and a protective layer sequentially laminated on
 a non-magnetic substrate, characterized in that the disk has a CSS region
 and a data region, the CSS region having a protective layer with a surface
 roughness greater than or equal to Ra 10 nm at the place where the
 magnetic head slider is positioned when the magnetic disk starts and stops
 rotating, the data region having a protective layer with a surface
 roughness smaller than or equal to Ra 3 nm at the place where the magnetic
 head slider is positioned while the magnetic disk is rotating, the
 protective layer being coated with a lubricating film which contains at
 least one member selected from perfluoropolyether compounds expressed by
 the formulas (IV) to (XIII) above, subsequently the entire surface of the
 magnetic disk is heated above 80.degree. C. or the entire surface of the
 magnetic disk or the data region is irradiated with ultraviolet rays, and
 the data region is washed with a perfluorocarbon solvent, such that the
 lubricating film formed in the CSS region has a thickness greater than or
 equal to 1.5 nm and the lubricating film formed in the data region has a
 thickness greater than or equal to 1 nm, and the limiting static friction
 and dynamic friction that occur in the data region between the magnetic
 head slider and the magnetic disk are smaller than or equal to 1.5 and
 1.0, respectively, and the limiting static friction and dynamic friction
 that occur in the CSS region between the magnetic head slider and the
 magnetic disk are smaller than or equal to 1.0 and 0.5, respectively.
 The twenty-fifth aspect of the present invention resides in a magnetic
 recording/reproducing device composed of a magnetic head, a magnetic head
 slider carrying the magnetic head, and a magnetic disk having a seed
 layer, a magnetic layer, and a protective layer sequentially laminated on
 a non-magnetic substrate, characterized in that the disk has a CSS region
 and a data region, the CSS region having a protective layer with a surface
 roughness greater than or equal to Ra 10 nm at the place where the
 magnetic head slider is positioned when the magnetic disk starts and stops
 rotating, the data region having a protective layer with a surface
 roughness smaller than or equal to Ra 3 nm at the place where the magnetic
 head slider is positioned while the magnetic disk is rotating, the
 protective layer being coated with a lubricating film which contains at
 least one member selected from perfluoropolyether compounds expressed by
 the formulas (IV) to (XIII) above, subsequently the entire surface of the
 magnetic disk is heated above 80.degree. C. or the entire surface of the
 magnetic disk or the data region is irradiated with ultraviolet rays, and
 the entire surface of the magnetic disk is washed with a perfluorocarbon
 solvent, the CSS region is coated with a perfluoropolyether compound
 having adsorptive functional groups which is selected from the
 perfluoropolyether compounds expressed by the formulas (VII) to (XIII)
 above, such that the lubricating film formed in the CSS region has a
 thickness greater than or equal to 1.5 nm and the lubricating film formed
 in the data region has a thickness greater than or equal to 1 nm, and the
 limiting static friction and dynamic friction that occur in the data
 region between the magnetic head slider and the magnetic disk are smaller
 than or equal to 1.5 and 1.0, respectively, and the limiting static
 friction and dynamic friction that occur in the CSS region between the
 magnetic head slider and the magnetic disk are smaller than or equal to
 1.0 and 0.5, respectively.
 The twenty-sixth aspect of the present invention resides in a magnetic
 recording/reproducing device composed of a magnetic head, a magnetic head
 slider carrying the magnetic-head, and a magnetic disk having a seed
 layer, a magnetic layer, and a protective layer sequentially laminated on
 a non-magnetic substrate, characterized in that the disk has a CSS region
 and a data region, the CSS region having a protective layer with a surface
 roughness greater than or equal to Ra 10 nm at the place where the
 magnetic head slider is positioned when the magnetic disk starts and stops
 rotating, the data region having a protective layer with a surface
 roughness smaller than or equal to Ra 3 nm at the place where the magnetic
 head slider is positioned while the magnetic disk rotating, the protective
 layer being coated all over the magnetic disk with at least one member
 selected from perfluoropolyether compounds expressed by the formulas (IV)
 to (XIII) above, subsequently the entire surface of the magnetic disk
 being heated above 80.degree. C. or the entire surface of the magnetic
 disk or the data region being irradiated with ultraviolet rays, and the
 data region being washed with a perfluorocarbon solvent, the data region
 being coated with a perfluoropolyether compound having functional groups
 chemically reactive with the surface of the protective film which is
 selected from the perfluoropolyether compounds expressed by the formulas
 (IV) to (VI) above, such that the lubricating film formed in the CSS
 region has a thickness greater than 1.5 nm and the lubricating film formed
 in the data region has a thickness greater than 1 nm, and the limiting
 static friction and dynamic friction that occur in the data region between
 the magnetic head slider and the magnetic disk are smaller than or equal
 to 1.5 and 1.0, respectively, and the limiting static friction and dynamic
 friction that occur in the CSS region between the magnetic head slider and
 the magnetic disk are smaller than or equal to 1.0 and 0.5, respectively.
 The twenty-seventh aspect of the present invention resides in a magnetic
 recording/reproducing device composed of a magnetic head, a magnetic head
 slider carrying the magnetic head, and a magnetic disk having a seed
 layer, a magnetic layer, a protective layer, and a lubricating layer
 sequentially laminated on a non-magnetic substrate, characterized in that
 the disk has a CSS region and a data region, the CSS region having a
 protective layer with a surface roughness greater than or equal to Ra 10
 nm at the place where the magnetic head slider is positioned when the
 magnetic disk starts and stops rotating, the data region having a
 protective layer with a surface roughness smaller than or equal to Ra 3 nm
 at the place where the magnetic head slider is positioned while the
 magnetic disk is rotating, the protective layer being coated all over the
 magnetic disk with at least one member selected from perfluoropolyether
 compounds having functional groups chemically reactive with the protective
 layer, expressed by the formulas (IV) to (VI) above, subsequently the
 entire surface of the magnetic disk being heated above 80.degree. C. or
 irradiated with ultraviolet rays, the entire surface of the magnetic disk
 being coated with a perfluoropolyether compound having adsorptive
 functional groups selected from the perfluoropolyether expressed by the
 formulas (VII) to (XIII) above, and the data region being washed with a
 perfluorocarbon solvent, the data region being coated with a
 perfluoropolyether compound having functional groups chemically reactive
 with the surface of the protective film which is selected from the
 perfluoropolyether compounds expressed by the formulas (IV) to (VI) above,
 such that the lubricating film formed in the CSS region has a thickness
 greater than or equal to 1.5 nm and the lubricating film formed in the
 data region has a thickness greater than or equal to 1 nm, and the
 limiting static friction and dynamic friction that occur in the data
 region between the magnetic head slider and the magnetic disk are smaller
 than or equal to 1.5 and 1.0, respectively, and the limiting static
 friction and dynamic friction that occur in the CSS region between the
 magnetic head slider and the magnetic disk are smaller than or equal to
 1.0 and 0.5, respectively.
 The twenty-eighth aspect of the present invention resides in the magnetic
 disk as defined in the first aspect which has a diameter smaller than or
 equal to 88.9 mm.
 The twenty-ninth aspect of the present invention resides in the magnetic
 disk as defined in the seventh aspect which has a diameter smaller than or
 equal to 88.9 mm.
 The thirtieth aspect of the present invention resides in the magnetic disk
 as defined in the eleventh aspect which has a diameter smaller than or
 equal to 88.9 mm.
 According to the present invention, the CSS region has a lubricating layer
 which is composed of a firmly fixed lubricant and a weakly fixed lubricant
 so as to ensure good durability, and the data region has a lubricating
 layer composed mainly of a firmly fixed lubricant so as to reduce
 stiction. The lubricating layer (of weakly fixed lubricant) in the data
 region needs to have a certain thickness so that it endures contact
 sliding that might accidentally occur in the data region as a result of
 reduction in the flying height of the head. To this end, it is necessary
 not only to select a lubricant having reactive or adsorptive functional
 groups or to increase the thickness of the layer of the firmly fixed
 lubricant by heating or UV treatment, but also to coat the data region
 twice. Conversely, the CSS region is coated with the lubricant twice if
 the weakly fixed lubricant is small in amount. The lubricating layer
 constructed in this manner permits the data region and the CSS region to
 exhibit satisfactory sliding performance required of a reliable magnetic
 disk and magnetic disk apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION
 The invention will be described in more detail with reference to the
 following examples, which are not intended to restrict the scope of the
 invention.
 Example 1
 A substrate of aluminum alloy (3.5 inches in diameter) with its surface
 mirror-finished was coated by sputtering sequentially with an NiP seed
 layer (10 .mu.m thick), a Cr layer (0.5 .mu.m thick), a Co--Cr-Pt layer
 (60 nm thick), and a carbon protective layer (20 nm thick), to produce a
 magnetic disk. The region (15-20 mm in radius) of this magnetic disk
 underwent electrostatic coating with fluorinated resin particles (0.5
 .mu.m in diameter). The entire surface of the magnetic disk underwent
 etching (10 nm deep) with oxygen. The fluorinated resin particles were
 removed by water washing. In this way there were formed uniformly
 cylindrical protuberances (0.5 .mu.m in diameter) in the region covering
 the radius from 15 to 20 mm. In this region was formed a CSS region having
 a center line average roughness of Ra 15 nm, and in another region was
 formed a smooth data region having a center line average roughness of Ra
 1.2 nm.
 Next, the magnetic disk was dipped (for coating) in a solution (1)
 containing in a fluoride-containing solvent ("PF5052" from Sumitomo 3M
 Limited) 0.01 wt % of perfluoropolyether compound expressed by the formula
 (IV) below.
EQU F(CF.sub.2 CF.sub.2 CF.sub.2 O).sub.n --C.sub.2 F.sub.4 --CONH--C.sub.3
 H.sub.6 --Si(OC.sub.2 H.sub.5).sub.3 (IV)
 The conditions of dip coating are as follows.
 Dip rate in the solution: 10 mm/s
 Residence time in the solution: 180 s
 Raising rate from the solution: 2.5 mm/s After complete drying, the coated
 magnetic disk was heated at 100.degree. C. for 2 hours. This heat
 treatment causes the perfluoropolyether compound (IV) to chemically react
 with the surface of the protective layer and hence to firmly fix to the
 surface of the magnetic disk. Subsequently, the magnetic disk was dipped
 (for coating in the same manner as mentioned above) in a solution (2)
 containing in a fluoride-containing solvent ("PF5052" from Sumitomo 3M
 Limited) 0.001 wt % of perfluoropolyether compound expressed by the
 formula (XI) below.
EQU F(CF.sub.2 CF.sub.2 CF.sub.2 O).sub.n --C.sub.2 F.sub.4 --COO--+NH.sub.3
 --C.sub.6 H.sub.4 --O--C.sub.6 H.sub.5 (XI)
 After complete drying, the data region of the coated magnetic disk was
 washed with the above-mentioned fluoride-containing solvent. This washing
 was accomplished by jetting the solvent (50 ml/min) to the data region
 while turning the disk (1000 rpm) by means of a spinner. (An alternative
 washing method is by turning the disk, with the data region dipped in the
 solvent.)
 The thus obtained magnetic disk has in the CSS region a lubricating layer
 which has chemically reacted with the surface of the disk. This
 lubricating layer is composed of a firmly fixed layer and a weakly fixed
 layer of perfluoropolyether compound (XI). In addition, the magnetic disk
 has in the data region a firmly fixed lubricating layer composed almost
 entirely of perfluoropolyether compound (IV). The lubricating layers in
 the data region and CSS region have a thickness of 2.2 nm and 2.7 nm,
 respectively. FIG. 1(a) shows the external appearance of the magnetic disk
 prepared in this example. FIG. 1(b) is a sectional view showing the
 boundary 3 between the CSS region and the data region.
 The sputtered magnetic disk underwent a contact-start-stop (CSS) test and a
 stiction test under the following conditions using the apparatus shown in
 FIG. 2(a).
 The magnetic disk 7 for measurement is attached (and fixed by the disk
 presser 9) to the spindle 8 which is directly connected to the motor
 placed at the bottom of the apparatus. The head slider 12 is of the
 in-line type (20T made of Al.sub.2 O.sub.3 TiC), with its rail surface
 coming into contact in the disk-rotating direction. The head slider 12 is
 fixed to the arm 13 which is connected to the load cell 10. The load cell
 10 is fixed to the stage 11 which is movable in the radial direction, so
 that evaluation for each track is possible. The load cell 10 measures the
 frictional force that occurs between the head slider 12 and the magnetic
 disk 7 during rotation.
 For CSS evaluation, start and stop operations of the disk were repeated (up
 to 100,000 times) at short intervals. After CSS cycles of 1, 50, 100, 500,
 1000, 5000, 10000, and integral multiples of 10000, the disk was stopped,
 the head was allowed to be in contact with the disk for 2 seconds, and the
 disk was turned at 10 rpm. The maximum dynamic friction at that time was
 measured. Also, the number of CSS for disk crash to occur was counted.
 Disk crash is defined as the state in which the carbon protective layer
 (as the undercoat of the lubricating layer) is completely worn and the
 magnetic layer is exposed. Crash gives a visible wear scar. The experiment
 was suspended when crash occurred. In the case where disk crash occurred
 within 100,000 cycles, the maximum dynamic friction force is expressed by
 the maximum dynamic friction coefficient measured up to the CSS cycles
 before disk crash. The maximum speed of the disk is 5400 rpm and the head
 load is 3.0 g. The disk was run for 20 hours, with the head flying
 (because, the head is usually in the flying state in the data region). In
 anticipation of an accidental disk stop, the disk was stopped at certain
 intervals (4, 8, 12, 16, and 20 hours after the start of experiment). As
 in the case of measurement in the CSS region, the head was brought into
 contact for 2 seconds and then the disk was run at 10 rpm, and the maximum
 dynamic friction force was measured. The disk surface was inspected for a
 wear scar, and the experiment was suspended as soon as a crash occurred.
 Stiction was measured as follows. The head slider was kept in contact with
 the disk for 12 hours, the disk was rotated slowly. The limiting static
 friction that occurred immediately after rotation was measured. For
 measurement, in both the CSS region and data region, the load was 3.0 g
 and the disk speed was 1 rpm. The results of evaluation are shown in Table
 1.
 TABLE 1
 CSS test
 CSS region Data region
 Time up
 Max. Max. to Stiction test
 dynamic CSS dynamic occurence Limiting static
 friction cycles friction of wear friction (gf)
 force up to force scar CSS Data
 (gf) crash (gf) (h) region region
 Example 1 1.86 &gt;100000 2.16 &gt;20 1.86 2.12
 Example 2 1.67 &gt;100000 2.38 &gt;20 1.95 2.36
 Example 3 1.49 &gt;100000 2.01 &gt;20 1.66 2.43
 Comparative 7.86 5000 3.12 &gt;20 1.35 2.31
 Example 1
 Comparative 1.82 &gt;100000 3.51 &gt;20 1.86 27.6
 Example 2
 comparative 1.62 &gt;100000 12.6 8 1.92 2.28
 Example 3
 Comparative 1.51 &gt;100000 2.95 &gt;20 1.69 32.8
 Example 4
 Comparative Example 1 demonstrates the effect of coating the magnetic disk
 with the perfluoropolyether compound (IV) alone. Example 1 indicated a
 data region and CSS region which are satisfactory in the CSS test and
 stiction test, whereas Comparative Example 1 indicated a data region which
 is low in stiction and a CSS region which caused a disk crash in the CSS
 test. Comparative Example 2 demonstrates the effect of not performing
 washing on the data region after coating sequentially with the
 perfluoropolyether compound (IV) and the perfluoropolyether compound (XI).
 In this case, the CSS region was satisfactory, but the data region
 suffered strong stiction.
 Example 2
 Example 1 was repeated to prepare a magnetic disk by sputtering. The
 magnetic disk was dipped in a 0.005 wt % solution of the
 perfluoropolyether compound (VI) expressed by the formula (VI) below in
 the same fluoride-containing solvent as used in Example 1 under the same
 condition as in Example 1. Dipping was followed by heat treatment at
 120.degree. C. for 10 minutes, and the entire surface of the magnetic disk
 was washed with the same fluoride-containing disk as mentioned above. The
 lubricating layer has a thickness of 0.75 nm.
EQU (C.sub.2 H.sub.5 O).sub.3 Si--C.sub.3 H.sub.6 --NHCO--(CF.sub.2 CF.sub.2
 O).sub.m --(CF.sub.2 O).sub.n --CONH--C.sub.3 H.sub.6 --Si(OC.sub.2
 H.sub.5).sub.3 (VI)
 The fluorine-based lubricant (VIII) expressed by the formula (VIII) below
 was dissolved in the above-mentioned fluoride-containing solvent to give a
 0.007 wt % solution.
EQU F(CF.sub.2 CF.sub.2 CF.sub.2 --O).sub.n --C.sub.2 F.sub.4 --CH.sub.2 OH
 (VIII)
 This solution was applied in the same manner as in Example 1, and the data
 region alone was washed with the same fluoride-containing solvent as
 mentioned above. A 0.005 wt % solution of the above-mentioned
 perfluoropolyether compound (VI) was applied to the data region again by
 using the spinner. The thickness of the lubricating layers in the data
 region and CSS region was 1.96 rm and 1.84 nm, respectively.
 The lubricating layer formed in this example was tested for CSS
 characteristics and stiction characteristics in the same manner as in
 Example 1. The results are shown in Table 1. This example is superior in
 both CSS characteristics and stiction characteristics to Comparative
 Example 3 in which the recoating of the perfluoropolyether compound (VI)
 was not performed. By contrast, Comparative Example 3 gave wear scars in
 the data region, although its result in the CSS zone is identical with
 that in this example. A probable reason for this that the head flies in
 the data zone, but the head comes into contact with the disk (because of
 low flying height) while the disk is rotating. The poor-results in
 Comparative Example 3 are due to the fact that the lubricating layer in
 the data region is not thick enough to maintain sufficient durability.
 Example 3
 Example 1 was repeated to prepare a magnetic disk by sputtering. The
 magnetic disk was dipped in a 0.005 wt % solution of the
 perfluoropolyether compound (XIII) expressed by the formula (XIII) below
 in the same fluoride-containing solvent as used in Example 1 under the
 same condition as in Example 1. Dipping was followed by heat treatment at
 110.degree. C. for 2 hours, and the entire surface of the magnetic disk
 was washed with the same fluoride-containing disk as mentioned above. The
 lubricating layer has a thickness of 0.8 nm.
 ##STR2##
 The perfluoropolyether compound (VII) expressed by the formula (VII) below
 was dissolved in the above-mentioned fluoride-containing solvent to give a
 0.007 wt % solution.
EQU C.sub.6 H.sub.5 --O--C.sub.6 H.sub.4 --H.sub.3 N+--OCO--(CF.sub.2 CF.sub.2
 O).sub.m --(CF.sub.2 O).sub.n --COO--.sup.+ NH.sub.3 --C.sub.6 H.sub.4
 --O--C.sub.6 H.sub.5 (VII)
 This solution was applied in the same manner as in Example 1, and the data
 region alone was heated at 1100C for. 2 hours and then washed with the
 same fluoride-containing solvent as mentioned above. The thickness of the
 layers in the data region and CSS region was 1.85 nm and 2.31 nm,
 respectively. The lubricating layer formed in this example was tested for
 CSS characteristics and stiction characteristics in the same manner as in
 Example 1. The results are shown in Table 1. This example is superior in
 both CSS characteristics and stiction characteristics to comparative
 Example 4 in which the washing of the data region was not performed after
 the application of the perfluoropolyether compound. By contrast, the CSS
 region in Comparative Example 4 is identical with that in this example,
 but strong stiction occurred in the data region.
 Example 4
 The magnetic disk prepared in Example 1 was mounted on a magnetic
 recording/reproducing device (for 3.5 inch disk) as schematically shown in
 FIG. 3. During running, the apparatus was deenergized so as to stop the
 head in the data region, and the apparatus was allowed to stand for 24
 hours. On resumption, the magnetic disk permitted recording and
 reproducing normally. The same experiment as above was carried out with
 the magnetic disk prepared in Comparative Example 5. The apparatus could
 not restart due to strong stiction between the head slider and the disk in
 the data region.
 Comparative Example 1
 Example 1 was repeated to produce a magnetic disk by sputtering. The
 magnetic disk was dipped in a 0.01 wt % solution of the perfluoropolyether
 compound (IV) expressed by the formula (IV) below in a fluoride-containing
 solvent ("PF5052" from Sumitomo 3M Limited) under the same condition as in
 Example 1.
EQU F(CF.sub.2 CF.sub.2 CF.sub.2 O).sub.n --C.sub.2 F.sub.4 --CONH--C.sub.3
 H.sub.6 --Si(OC.sub.2 H.sub.5).sub.3 (IV)
 Dipping was followed by complete drying and heat treatment at 110.degree.
 C. for 2 hours. The thickness of the lubricating layer was 1.3 nm. The
 disk was tested for CSS characteristics and stiction characteristics in
 the same manner as in Example 1. The results are shown in Table 1.
 Comparative Example 2
 Example 1 was repeated to produce a magnetic disk by sputtering. The
 magnetic disk was dipped in a 0.01 wt % solution of the perfluoropolyether
 compound (IV) expressed by the formula (IV) below in a fluoride-containing
 solvent ("PF5052" from Sumitomo 3M Limited) under the same condition as in
 Example 1.
EQU F(CF.sub.2 CF.sub.2 CF.sub.2 O).sub.n --C.sub.2 F.sub.4 --CONH--C.sub.3
 H.sub.6 --Si(OC.sub.2 H.sub.5).sub.3 (IV)
 Dipping was followed by complete drying and heat treatment at 100.degree.
 C. for 2 hours. The magnetic disk was coated (by dipping in the same
 manner as in Example 1) with a 0.001 wt % solution of the
 perfluoropolyether compound (XI) expressed by the formula (XI) below in a
 fluoride-containing solvent ("PF5052" from Sumitomo 3M Limited) under the
 same condition as in
 Example 1.
EQU F(CF.sub.2 CF.sub.2 CF.sub.2 O)--C.sub.2 F.sub.4 --COO--.sup.+ NH.sub.3
 --C.sub.6 H.sub.4 --O--C.sub.6 H.sub.5 (XI)
 The lubricating layers in the data region and CSS region have a thickness
 of 2.7 nm. The disk was tested for CSS characteristics and stiction
 characteristics in the same manner as in Example 1. The results are shown
 in Table 1.
 Comparative Example 3
 Example 1 was repeated to produce a magnetic disk by sputtering. The
 magnetic disk was dipped in a 0.005 wt % solution of the
 perfluoropolyether compound (VI) expressed by the formula (VI) below (the
 same one as used in Example 1) in the same fluoride-containing solvent as
 used in Example 1 under the same condition as in Example 1.
EQU (C.sub.2 H.sub.5 O).sub.3 Si--C.sub.3 H.sub.6 --NHCO--(CF.sub.2 CF.sub.2
 O).sub.m --(CF.sub.2 O).sub.n --CONH--C.sub.3 H.sub.6 --Si(OC.sub.2
 H.sub.5).sub.3 (VI)
 Dipping was followed by heat treatment at 110.degree. C. for 2 hours. The
 entire surface of the magnetic disk was washed with the same
 fluoride-containing solvent as above. Then, the magnetic disk was coated
 (by dipping in the same manner as in Example 1) with a 0.007 wt % solution
 of the perfluoropolyether compound (VII) expressed by the formula (VIII)
 below in the above-mentioned fluoride-containing solvent under the same
 condition as in Example 1.
EQU F(CF.sub.2 CF.sub.2 CF.sub.2 --O).sub.n --C.sub.2 F.sub.4 --CH.sub.2 OH
 (VIII)
 The data region alone was washed with the same fluoride-containing solvent
 as mentioned above. The lubricating layers in the data region and CSS
 region have a thickness of 0.75 nm and 1.84 nm, respectively. The disk was
 tested for CSS characteristics and stiction characteristics in the same
 manner as in Example 1. The results are shown in Table 1.
 Comparative Example 4
 Example 1 was repeated to produce a magnetic disk by sputtering. The
 magnetic disk was dipped in a 0.005 wt % solution of the
 perfluoropolyether compound (XIII) expressed by the formula (XIII) below
 (the same one as used in Example 3) in the same fluoride-containing
 solvent as used in Example 1 under the same condition as in Example 1.
 ##STR3##
 Dipping was followed by heat treatment at 110.degree. C. for 2 hours. The
 entire surface of the magnetic disk was washed with the same
 fluoride-containing solvent as above. Then, the magnetic disk was coated
 (by dipping in the same manner as in Example 3) with a 0.007 wt % solution
 of the perfluoropolyether compound (VII) expressed by the formula (VII)
 below in the above-mentioned fluoride-containing solvent under the same
 condition as in Example 3.
EQU C.sub.6 H.sub.5 --O--C.sub.6 H.sub.4 --H.sub.3 N.sup.+ --OCO--(CF.sub.2
 CF.sub.2 O).sub.m --(CF.sub.2 O).sub.n --COO--.sup.+ NH.sub.3 --C.sub.6
 H.sub.4 --O--C.sub.6 H.sub.5 (VII)
 The lubricating layers in the data region and CSS region have a thickness
 of 2.31 nm. The disk was tested for CSS characteristics and stiction
 characteristics in the same manner as in Example 1. The results are shown
 in Table 1.
 Comparative Example 5
 The magnetic disk prepared in Comparative Example 2 was mounted on the same
 magnetic recording/reproducing device as used in Example 1. The apparatus
 was deenergized during running, and the apparatus was allowed to stand for
 24 hours. The magnetic disk could not restart due to strong stiction
 between the head slider and the disk in the data region where there is a
 large amount of weakly adsorbed lubricant.