JP3019612B2 - Manufacturing method of magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium, and more particularly to a method for forming a protective layer on a magnetic recording medium.

[0002]

2. Description of the Related Art A magnetic recording disk as a typical magnetic recording medium generally has a substrate for a magnetic recording medium in which a base metal layer such as a Ni-P plating layer is formed on a non-magnetic substrate, and a magnetic recording disk formed on the surface side thereof. The surface state of the outermost layer largely governs the recording density and reliability of the magnetic recording disk. In particular, C
In an SS (contact start / stop) type magnetic recording disk, the magnetic head floats slightly from the surface of the magnetic recording disk during operation to read or write information. When the surface of the magnetic recording disk is mirror-finished, the friction coefficient between the magnetic head and the surface of the magnetic recording disk is large, and the magnetic head may be attracted to the surface of the magnetic recording disk. Further, at the time of starting, when the magnetic head slides on the surface of the magnetic recording disk, the magnetic head may wear the magnetic layer.

Therefore, measures have been taken to form fine irregularities on the surface layer of the magnetic recording disk to reduce the contact area between the magnetic head and the surface of the magnetic recording disk and reduce the friction coefficient. The typical concavo-convex forming process slides a polishing tape or the like on the surface of the underlying metal layer of the rotating substrate, and as shown in FIG. 12, the underlying metal layer 43 laminated on the substrate 42 has fine concentric circles. This is a texture processing in which the unevenness 43a is formed and the unevenness is reflected on the surface of the magnetic layer 44. Reference numeral 45 denotes a lubricant layer formed of a fluorine-based oil formed on the surface of the magnetic layer 44, and serves to reduce the coefficient of friction between the surface of the magnetic recording disk and the magnetic head.

[0004]

However, the irregularities 43a formed by texture processing are formed concentrically and are in the same direction as the relative movement direction between the surface of the rotating magnetic recording disk and the magnetic head. However, there is a problem that the effect of reducing the frictional force between the surface of the magnetic recording disk and the magnetic head is small. For this reason, a method of reducing the frictional force between the surface of the magnetic recording disk and the magnetic head by further roughening the unevenness due to the texture processing has been adopted. In the unevenness formed by such texture processing, the center line roughness Ra of the magnetic recording disk surface is set to 800 ° (0.080 μm) in order to set the coefficient of friction between the magnetic recording disk surface and the magnetic head to a predetermined value.
m), the maximum height Rmax of the surface roughness is 1200 °
(0.12 μm) processing is required, and the flying height of the magnetic head from the surface of the magnetic recording disk becomes large, which causes a problem of lowering the recording density.

In order to solve such a problem, it is ideal to form a protective layer having fine irregularities 5a having no directivity as shown in FIG. 2 instead of texture processing. In other words, by eliminating the directionality of the irregularities, the effect of reducing the contact area between the rotating magnetic recording disk and the magnetic head is efficiently exhibited, the surface roughness is kept small, and the frictional force between them is reduced. By maintaining the reliability and recording density of the magnetic recording disk,
It is to improve. As a method of forming such irregularities, a method in which oxide particles are mixed with a solvent together with tetrahydroxysilane, applied to the disk surface, and then subjected to a heat treatment to fix the oxide particles to the polysilicate film can be considered. . According to this method, as shown in FIG. 13, the oxide particles 52 are fixed by the polysilicate film 51, and irregularities corresponding to the particle size of the oxide particles 52 can be formed on the surface of the polysilicate film 51. Not only in the circumferential direction of the disk, but also unevenness can be uniformly distributed in a non-directional state, so that all of the sliding characteristics such as abrasion resistance and suction characteristics of the magnetic head and the recording characteristics are improved. be able to. However, in the magnetic recording disk formed by this method, since the oxide particles 52 themselves protrude from the surface of the polysilicate film 51, when the magnetic head slides on the surface of the magnetic recording disk, the oxide particles 52 Has a problem in that it is easily dropped from the polysilicate film 51 due to a large force, and the sliding characteristics are greatly deteriorated with time.

[0006] In view of the above problems, an object of the present invention is to provide:
Uneven irregularities are distributed on the surface and silicon oxide inside
A protective layer of polysilicic acid film particles are dispersed, the improvement of wear characteristics and absorption resistance adhesive properties, as well as the production of a magnetic recording medium which can improve a recording density by low flying height of the magnetic head
It is to provide a method .

[0007]

SUMMARY OF THE INVENTION First, according to the present invention,
In the method of manufacturing a recording medium, a protective layer having irregularities distributed on the surface is laminated on the surface side of the magnetic layer laminated on the surface side of the non-magnetic substrate, and silicon oxide particles are dispersed inside the protective layer. Recording medium formed of a polysilicate film
Is to get

In order to manufacture a magnetic recording medium having such a configuration, the method for manufacturing a magnetic recording medium according to the present invention comprises the steps of: A coating process in which a coating solution containing hydroxysilane is applied in an atmosphere having a relative humidity of 50% or more by a spin coating method or the like; and a heating process is applied to the coating solution applied on the surface side of the magnetic layer, and A heating step of converting tetrahydroxysilane into a polysilicate film in a state where the silicon oxide particles are dispersed to form a protective layer. Note that the atmosphere in which the coating liquid is applied needs to have a relative humidity of 50% or more, but is preferably a condition that does not cause condensation.

Here, in order to easily control the distribution of irregularities on the surface of the protective layer, the amount of silicon oxide particles in the coating solution is set to be less than the amount of tetrahydroxysilane.
1 wt% to 50 in terms of O ₂ (silicon dioxide)
It is preferably in the range up to wt%.

The average particle diameter of the silicon oxide particles is preferably in the range of 5 nm to 30 nm so that the thickness of the silicon oxide particles can be adapted to the thickness of the ordinary protective film.

Also, a method of manufacturing a magnetic recording medium according to the present invention
In the method , a magnetic layer is formed on the surface side of the magnetic recording medium substrate made of a non-magnetic material, and the magnetic layer is formed on the surface side of the magnetic layer.
It has a protective layer in which unevenness is distributed over the entire surface and a lubricant layer held on the surface of the protective layer, and the protective layer is made of a polysilicate film in which a Si compound such as tetrahydroxysilane is converted by heating. To obtain a magnetic recording medium
You .

[0012]

In a manufacturing method for forming a magnetic recording medium having such a structure, a Si compound which can be converted into polysilicic acid by heat treatment is mixed in an organic solvent, and is insoluble in the Si compound and An organic solvent is easily soluble, and a coating liquid containing a concavo-convex forming component having a high evaporating property at a conversion temperature of a Si compound to polysilicic acid is defined on a surface of a magnetic layer at a predetermined relative humidity. A coating step of applying in an atmosphere and a heating treatment of the coating liquid applied on the surface of the magnetic layer at a temperature higher than the conversion temperature of the Si compound, thereby converting the Si compound into a polysilicate film to form a protective layer. And a heating step.

Here, the material used for the coating solution is, for example, tetrahydroxysilane as the Si compound, isopropyl alcohol as the main component in the organic solvent, or an aliphatic hydrocarbon having at least 13 carbon atoms as the concavo-convex forming component. Etc. can be used. In this case, the mixing ratio of the tetrahydroxysilane and the aliphatic hydrocarbon in the coating solution is in the range of 1: 1 to 1: 0.05 in terms of the weight ratio when the tetrahydroxysilane is converted to SiO _2. Is preferred.

[0015]

[0016]

[0017]

[0018]

In the magnetic recording medium obtained by such a method, irregularities having no directivity are formed only on the surface of the protective layer. The coefficient of friction can be reduced, and a magnetic recording medium with good sliding characteristics can be realized. Therefore, the flying height of the magnetic head can be reduced, and a high recording density can be realized.

Further, since the unevenness is formed not by mechanical processing such as texture processing but by a chemical or physical manufacturing method as described below, the thickness of the protective layer can be reduced. is there. Therefore, the distance between the magnetic layer and the magnetic head can be shortened, so that high-density recording can be realized.

That is, in the method for manufacturing a magnetic recording medium according to the present invention, a coating solution containing silicon oxide particles and tetrahydroxysilane is spin-coated on the surface side of the magnetic layer laminated on the surface side of the non-magnetic substrate. When applying by a coating method or the like, the relative humidity of the atmosphere is set to a condition of 50% or more, and the coating liquid applied to the surface of the magnetic layer is subjected to a heat treatment. Formed on the surface of the protective layer. Here, the irregularities on the surface of the protective layer are not formed by the silicon oxide particles dispersed inside the polysilicate film protruding from the surface, but the coating liquid is locally aggregated, and the aggregation phenomenon is caused. It is assumed that irregularities are formed. That is, the solvent component evaporates from the coating liquid applied to the surface of the magnetic layer even during the application, and the evaporation of the solvent causes a bias in the component distribution of the coating liquid. This bias is defined by the evaporation rate of the solvent and the presence of silicon oxide particles. Of these, it is assumed that the relative humidity in the atmosphere affects the evaporation rate of the solvent, and provides sufficient time for the components to be biased, that is, sufficient time for the coating liquid to aggregate. Therefore, a heat treatment is performed on the coating liquid that has been aggregated in a predetermined state,
When tetrahydroxysilane is converted into a polysilicate film,
Irregularities are formed corresponding to the aggregation state. In addition to the influence of the relative humidity of the atmosphere on the evaporation rate of the solvent, the water itself affects the silicon oxide, causing a repulsive or attractive force between the silicon oxide particles and causing the aggregation of the coating liquid layer. It is also assumed that they are awake.

In addition, Si such as tetrahydroxysilane
When applying a coating liquid containing a compound and an unevenness forming component such as an aliphatic hydrocarbon in an organic solvent to the surface of the magnetic layer, the coating liquid is converted to a polysilicate film to regulate the relative humidity in the atmosphere. As a result, the uneven shape after forming the protective layer is made uniform. In addition, since the thickness of the polysilicate film does not vary, the thickness of the protective layer does not need to be set unnecessarily large, and there is no need to form SiO ₂ or the like as a base layer. Therefore, since the relative distance between the magnetic layer and the magnetic head can be reduced, the density of recording tracks on the magnetic recording medium can be increased. In addition, the frictional force between the surface of the magnetic recording medium and the magnetic head is reduced by the unevenness of the protective layer, and the lubricant layer is reliably held by the unevenness of the protective layer. The wear characteristics and the adsorption resistance can be improved both initially and over time.

The relationship between the relative humidity and the formation mechanism of the polysilicate film has not been elucidated in detail at present, but is assumed as follows. That is, in the unevenness forming process in the present means, each solvent component of the coating liquid evaporates, and due to the evaporation, the distribution of the unevenness forming components, for example, the distribution of the aliphatic hydrocarbons is biased,
In response to this deviation, the fact that unevenness as a trace after evaporation is formed on the surface of the polysilicate film is utilized. Here, when the surface of the coating liquid during or after coating absorbs moisture in the atmosphere, the absorbed moisture also affects the bias of the component distribution of the coating liquid as the third component of the coating liquid. Since the relative humidity is in a state where the relative humidity is specified, it is assumed that the polysilicate film is formed with uniform unevenness and a stable film thickness without any variation in the influence. In addition, on the surface of a coating liquid in which a hydrophobic component such as an aliphatic hydrocarbon is blended in a hydrophilic component such as isopropyl alcohol, there is water that is not compatible with the aliphatic hydrocarbon. Thereby, it is considered that the distribution of the aliphatic hydrocarbons is made uniform, so that the distribution of the concave portions and the convex portions is made uniform. Furthermore, it can be estimated that the water absorbed on the surface of the coating layer also has the effect of suppressing the evaporation of the solvent component during the coating process and of suppressing the change in the composition of the coating solution until the process proceeds to the heating process.

[0023]

[0024]

Next, embodiments of the present invention will be described.

[0025]

FIG. 1 is a schematic sectional view showing a magnetic recording disk with a part thereof cut away.

Referring to FIG. 1, reference numeral 1 denotes a 3.5-inch magnetic recording disk, and Ni metal as a base metal layer is provided on both sides of an aluminum alloy substrate (non-magnetic substrate) 2 for a metal thin-film magnetic recording disk as a base. -P plating layer 3 and a Co-Cr-Ni magnetic layer 4 (cobalt-
Chromium-nickel magnetic thin film layer). Here, the surface of the Ni—P plating layer 3 was mirror-finished using alumina free abrasive grains and a polishing tape, and the surface roughness was measured using a stylus-type roughness meter with a 2 μm R needle. The center line average roughness Ra is 25 to 30 ° (0.0025).
０．００0.0030 μm), and its maximum height Rmax is 40
0 ° (0.0400 μm) or less. Note that an upper metal layer may be laminated on the upper side of the magnetic layer depending on the material of the magnetic layer and the like.

With respect to the magnetic recording disk 1 having such a configuration,
Each embodiment according to the present means for forming a protective layer 5 in which fine irregularities having no directionality are uniformly distributed on the surface side of the Co-Cr-Ni magnetic layer 3 will be described below.

[Embodiment 1] A magnetic recording disk according to Embodiment 1 has a Co—Cr—Ni magnetic layer 4 as shown in FIG.
A protective layer 5 is formed on the surface side of FIG. 2. The surface of the protective layer 5 is schematically shown in FIG. 2 and a schematic view of the surface state when observed with an electron microscope (magnification: 7500 times). As shown in FIG. 3, fine irregularities having no directionality, that is, irregularities 5a are uniformly formed. Here, the protective layer 5 is composed of a polysilicate film in which silicon oxide particles having an average particle diameter of 12 nm are dispersed.

In this magnetic recording disk 1, since the unevenness formed on the surface of the protective layer 5 has no directionality, the efficiency of reducing the frictional force between the surface of the rotating magnetic recording disk 1 and the magnetic head is reduced. As described later, based on the evaluation result, the surface roughness is small and good sliding characteristics are exhibited. The fluorine-based oil layer 6 is formed on the surface side of the protective layer 5, and the sliding property of the surface of the magnetic recording disk 1 with respect to the magnetic head is further enhanced due to its high lubricity.

A method for manufacturing the magnetic recording disk 1 will be described.

First, after the Ni-P plating layer 3 is formed on both sides of the aluminum alloy substrate 2 by electroless plating, the surface thereof is mirror-finished to secure the flatness of the magnetic recording disk. Further, a Co—Cr—Ni magnetic layer 4 is laminated on the surface side by a sputtering method.

Next, a coating solution in which silicon oxide particles and tetrahydroxysilane are mixed is applied on the surface of the Co—Cr—Ni magnetic layer 4 by spin coating. This spin coating is performed by setting the number of revolutions of the magnetic recording disk to about 1500 rpm. In the present example, as the tetrahydroxysilane, a trade name, Atron NSi-310 (trade name, manufactured by Nippon Soda Co., Ltd.) (a solution of tetrahydroxysilane in ethyl acetate having a content of 5.9 wt% in terms of SiO ₂ content) 559 g, as colloidal silica (silicon oxide particles), Oscar 1432 (trade name, manufactured by Catalyst Chemical Industry Co., Ltd .;
nm, SiO ₂ content is 30 w
0.3 g of t% colloidal silica in isopropyl alcohol) was added to isopropyl alcohol in a total weight of 1 g.
And the mixture ratio of tetrahydroxysilane and colloidal silica was 7: 3 in terms of the amount of SiO ₂ (when tetrahydroxysilane and colloidal silica were converted to SiO ₂ , 0.3% SiO ₂ ) was used.

In the coating step by the spin coating method, the atmosphere is set at a temperature of about 20 ° C. and a relative humidity of about 60% (coating step).

Next, the magnetic recording disk coated on the surface of the Co—Cr—Ni magnetic layer 4 is subjected to a heat treatment for about 4 hours in an atmosphere at a temperature of about 150 ° C. Is performed on tetrahydroxysilane. By this baking treatment, the tetrahydroxysilane becomes a polysilicate film and silicon oxide particles are dispersed therein. The protective layer 5 is a polysilicate film in which such silicon oxide particles are dispersed, and fine irregularities are formed on the surface of the protective layer 5 in a non-directional distribution state as shown in FIGS. (Heating step).

Thereafter, on the surface side of the protective layer 5, as a fluorinated oil, FOMBL (trade name, manufactured by Montefluos)
IN · Z-DOL was used as a perfluorocarbon solvent with a product name of FOMBLIN · ZS-100 manufactured by the same company as 0.0.
The solution diluted to 75 wt% is spin-coated on the surface of the protective layer 5 with the rotation speed of the magnetic recording disk 1 set to about 1500 rpm, and then heat-treated for about 1 hour in an atmosphere at a temperature of about 150 ° C. Then, the solvent is removed to form the lubricant layer 6.

Thus, the magnetic recording disk 1 is manufactured.

Here, the process of forming irregularities on the surface of the protective layer 5 cannot be understood in detail,
By setting the relative humidity of the atmosphere in the coating step by the spin coating method to about 60%, the evaporation rate of isopropyl alcohol, the presence of colloidal silica, The presence of moisture causes microscopic condensation of the coating solution,
It is assumed that irregularities are formed on the surface of the protective layer 5 when the tetrahydroxysilane heated in this condensed state becomes a polysilicate film. Therefore, it is considered that the irregularities 5a of the protective layer 5 are not formed by reflecting the shape of the silicon oxide particles as they are on the irregularities 5a.

The above assumption is supported by the fact that when the relative humidity is set to 30% in the results of Comparative Example 1 described later, the above-mentioned unevenness 5a is not formed.

[Embodiment 2] The configuration of a magnetic recording disk according to Embodiment 2 is the same as that of Embodiment 1, and corresponding layers are denoted by the same reference numerals. The surface of the protective layer 5 laminated on the surface side of the Co—Cr—Ni magnetic layer 4 of the magnetic recording disk 1 of the present example is a schematic diagram of the surface state when observed with an electron microscope (magnification: 7500 times). As shown in FIG. 4, fine irregularities having no directionality are formed. Again, the protective layer 4 has an average particle size of 12
This is a polysilicate film in which silicon oxide particles of nm are dispersed.

Also in this magnetic recording disk, since the unevenness formed on the surface of the protective layer 5 has no directionality, as described later, the friction coefficient between the surface of the rotating magnetic recording disk 1 and the magnetic head is low. Low and low surface roughness. Further, a fluorine-based oil layer 6 is formed on the surface side of the protective layer 5, and the sliding characteristics of the magnetic recording disk 1 are further enhanced by its high lubricity.

A method for manufacturing the magnetic recording disk 1 having such a configuration will be described.

First, in the same manner as in Example 1, a mirror-finished Ni—P plating layer 3 and a Co—Cr—Ni magnetic layer 4 were laminated on both sides of an aluminum alloy
-A coating solution in which silicon oxide particles and tetrahydroxysilane are mixed is applied on the surface of the Cr-Ni magnetic layer 4 by a spin coating method. This spin coating is performed by setting the number of revolutions of the magnetic recording disk to about 1500 rpm. The conditions of the atmosphere in the application step by the spin coating method were as follows:
C. and relative humidity are set at about 60%.

In this example, a coating liquid having a composition different from that of Example 1 was used. That is, Nippon Soda Co., Ltd. product name Atron NS as tetrahydroxysilane
4.576 g of i-310 (ethyl acetate solution of tetrahydroxysilane having a content of 5.9 wt% in terms of SiO ₂ content) and colloidal silica (silicon oxide particles) manufactured by Catalyst Chemicals, Inc. 0.1 g of brand name Oscar 1432 (an isopropyl alcohol solution of colloidal silica having an average particle diameter of 12 nm and a content of 30 wt% in terms of SiO ₂ content) mixed with isopropyl alcohol so that the total weight becomes 100 g. to the ratio of the amount of the tetrahydroxy silane and colloidal silica, in terms of SiO ₂ 9: 1 coating solution (SiO tetra hydroxy silane and colloidal silica ₂
(Containing 0.3% of SiO ₂ when converted to).

After the coating solution of this composition is applied to the surface of the Co—Cr—Ni magnetic layer 4, a heating treatment is performed for about 4 hours in an atmosphere at a temperature of about 150 ° C. As shown in FIGS. 1 to 3, a baking treatment is performed on the silane, and unevenness 5 a uniformly distributed without directionality is formed on the surface, and the protective layer 5 as a polysilicate film in which silicon oxide particles are dispersed. To form

Here, as for the process of forming irregularities on the surface of the protective layer 5, as in the first embodiment, the relative humidity of the atmosphere in the application step by the spin coating method is set to about 60%. It is assumed that the coating liquid is condensed and that the surface of the protective layer 5 is formed with irregularities corresponding to the condensed state.

Comparative Example 1 Next, a comparative example in which the conditions of Example 1 were changed to form a magnetic recording disk will be described in order to demonstrate the unevenness forming mechanism in Examples 1 and 2.

First, in Comparative Example 1, of the manufacturing method in Example 1, the relative humidity of the atmosphere of the spin coating performed in the coating step was changed to 30%. Other conditions are the same as in the first embodiment.

The surface of the protective layer formed in Comparative Example 1 was observed with an electron microscope (magnification: 7500
As shown in FIG. 5, which is a schematic view of the surface state of (2), the protective layer is a polysilicate film in which silicon oxide particles are dispersed, but fine irregularities were not formed on the surface. That is, the unevenness 5a of the protective layer 5 formed in Example 1 and Example 2 is not simply formed by the projection of the silicon oxide particles in the polysilicate film, but is determined by setting the relative humidity and the like. In other words, the assumption that the particles were formed by the aggregation generated in the coating liquid was supported.

[Comparative Example 2] In Comparative Example 2,
A magnetic recording disk was manufactured using a coating liquid in which the particle diameter of silicon oxide particles was changed to 45 nm. That is, the coating solution used in Comparative Example 2 is calculated as Nippon Soda K.K. Atron NSi-310 (SiO ₂ content as tetrahydroxy silane content of 5.9 wt% of tetrahydroxy silane 3.559 g of an ethyl acetate solution and Oscar 1435 (trade name, manufactured by Catalysts & Chemicals, Inc., having a mean particle size of 45 nm and a SiO ₂ content of 1 wt% as a colloidal silica (silicon oxide particles)) 9.0 g of colloidal silica in isopropyl alcohol) is mixed with isopropyl alcohol so that the total weight becomes 100 g, and the mixing ratio of tetrahydroxysilane and colloidal silica is converted into SiO ₂ by 7: 3 composition (the tetrahydroxy silane and colloidal silica in terms of SiO _2, 0 3% SiO ₂ was used as a contained). Other conditions are the same as in the first embodiment.

The surface of the protective layer formed in Comparative Example 2 was observed with an electron microscope (magnification: 7500
As shown in FIG. 6 which is a schematic diagram of the surface state of (2), the protective layer is a polysilicate film in which silicon oxide particles are dispersed, and a large number of irregularities of about 1 μm are formed on the surface. . Therefore, as described later, although the sliding characteristics are relatively good, there is a problem that silicon oxide particles fall off when the contact of the magnetic head to the surface of the magnetic recording disk is repeated.

[Comparative Example 3] Further, as a conventional method employed for improving the sliding characteristics of a magnetic recording disk, a thickness of about 20 mm was formed on the surface of a Co-Cr-Ni magnetic layer.
An amorphous carbon layer having a thickness of 0 ° (20 nm) is formed as a protective film, and the surface thereof is coated with fluorinated oil as FOMBLIN AM 2001 (trade name, manufactured by Montefluos).
As a perfluorocarbon solvent
The solution diluted to 0.1 wt% with OMBLIN.ZS-100 was rotated at about 2,000 rpm by rotating the magnetic recording disk.
And the lubricant layer 6 was formed.

In this case, no irregularities were formed on the surface of the protective layer as shown in FIG. 7, which is a schematic view of the surface state when observed with an electron microscope (magnification: 7,500 times).

[Comparative Example 4] As another conventional method employed for improving the sliding characteristics of a magnetic recording disk, the surface roughness Ra = 60 to 70 ° (texture processing described above as a conventional technique) was used. 0.0060-0.
0070 μm), Rmax = 800 ° (0.0800 μm)
m) A Co—Cr—Ni magnetic layer is laminated on the surface side of the Ni—P layer on which the irregularities are formed as described below, and an amorphous carbon layer is formed on the surface side by the same process as in Comparative Example 3. Then, a magnetic recording disk provided with a fluorine-based oil layer was formed.

In this case, as shown in FIG. 8, which is a schematic view of the surface state when observed with an electron microscope (magnification: 7,500), the concentric unevenness described with reference to FIG. Are observed, and no irregularities having no direction are formed.

[Evaluation Results of Characteristics of Magnetic Recording Disk] Table 1 shows the results of investigating the characteristics of the magnetic recording disks A to F according to Examples 1 and 2 and Comparative Examples 1 to 4.

The investigation items here are center line average roughness R
a, 2000 cycles of C in addition to the maximum height Rmax
The SS test, that is, the dynamic friction coefficient μ _D of each magnetic recording disk at a relative speed of 2 mm / sec after the start and stop of the disk device was repeated 2000 cycles, and the magnetic recording disk was left in an atmosphere of about 33 ° C. for about 240 hours. the static friction coefficient mu _S was measured. Here, the dynamic friction coefficient mu _D is indicative of the wear characteristics, the coefficient of static friction mu _S is an index of the of difficulty adsorbed, either it is preferably less, be regarded is a bad thing exceeding 1 it can.

[0058]

[Table 1]

As shown in Table 1, Example 1 according to the present invention
And a magnetic recording disk A, B according to the second embodiment, both the surface roughness (Ra, Rmax) is small, and none of the dynamic friction coefficient mu _D and static friction coefficient mu _S is small. Accordingly, it was confirmed that the abrasion resistance and the adsorption resistance can be improved while the flying height of the magnetic head is kept small and the recording density is kept high.

On the other hand, the magnetic disks C and E according to Comparative Examples 1 and 3 each had a surface roughness (Ra, R
max) Although small, none of the dynamic friction coefficient mu _D and static friction coefficient mu _S is large and was not possible to obtain sufficient anti-wear properties and absorption resistance adhesive properties. The magnetic recording disk D according to Comparative Example 2, although the surface roughness (Ra, Rmax) is small, can not be dynamic friction coefficient mu _D is increased to obtain a sufficient wear properties.

The magnetic recording disk F according to Comparative Example 4
It is to reduce any of the dynamic friction coefficient mu _D and static friction coefficient mu _S, since the wear characteristics and absorption resistance adhesive properties is textured to have a good level, the surface roughness (Ra, Rmax) is large In order to prevent damage to the magnetic head, it is necessary to increase the flying height of the magnetic head, thereby sacrificing the recording density.

[0062] As described above {Effect of Examples 1 and 2}, a magnetic recording disk according to Example 1 and Example 2 Silicon oxide particles and tetrahydroxy-silane was applied to the surface side of the ,, magnetic layer is mixed Since the unevenness is formed by utilizing the aggregation phenomenon of the applied coating solution, a protective layer in which unevenness without directivity is uniformly distributed can be formed without sacrificing surface roughness. Therefore, in the magnetic recording disks according to any of the embodiments, the wear resistance and the adsorption resistance can be improved.

The compounding amount of the silicon oxide particles in the coating solution is based on the compounding amount of tetrahydroxysilane.
It has been confirmed that the unevenness can be surely formed in the range of 1 wt% to 50 wt% in terms of SiO ₂ , but when it is out of this range, it is difficult to control the formation density of the unevenness. . Further, the silicon oxide particles can sufficiently cope with the thickness of the normally formed protective film as long as the average particle size is in the range of 5 nm to 30 nm. Furthermore, as a result of variously evaluating the relative humidity of the atmosphere at the time of applying the coating liquid, the desired unevenness was obtained stably in an atmosphere of 50% or more. It was confirmed that variations occurred. Although the relative humidity may be higher than 50%, it has been confirmed that the state of dew condensation is not preferable.

Next, before describing the third and fourth embodiments, the configuration of the magnetic recording disk used in each embodiment will be described.

FIG. 9 is a schematic sectional view showing a part of the magnetic recording disk cut away.

In the drawing, reference numeral 11 denotes a 3.5-inch magnetic recording disk, and Ni--Ni as a base metal layer is provided on both sides of an aluminum alloy substrate (non-magnetic substrate) 12 for a metal thin-film magnetic disk as a base. The P plating layer 13 is formed to form the magnetic recording disk substrate 11a. On the front side of the magnetic recording disk substrate 11a,
A Co-Cr-Ta magnetic layer 14 (cobalt-chromium-tantalum magnetic thin film layer) is formed by sputtering. here,
The surface of the Ni-P plating layer 13 was mirror-finished using alumina free abrasive grains and a polishing tape, and the surface roughness was measured using a stylus-type roughness meter with a 2 μm R needle.
The center line average roughness Ra is 15 to 20 mm (0.0015 to
0.0020 μm) and the maximum height Rmax is 300
Å (0.0300 μm) or less. Note that, depending on the material of the magnetic layer, a metal layer may be laminated on the upper or lower side of the magnetic layer.

On the surface of the Co—Cr—Ta magnetic layer 14, a surface protective layer 15 in which fine irregularities are uniformly distributed on the surface side of the magnetic recording disk substrate 11a having such a structure is implemented. An example is described below.

[Embodiment 3] As shown in FIG. 9, a magnetic recording disk according to Embodiment 3 has a Co—Cr—Ta magnetic layer 1.
4, a protective layer 15 is formed on the surface side, and fine crater-shaped convex portions 15a and concave portions 15b are uniformly formed on the surface of the protective layer 15, as schematically shown. . Here, the protective layer 15 is made of a polysilicate film formed by converting tetrahydroxysilane, and has a maximum thickness of about 10 nm to about 20 nm. Further, on the surface of the protective layer 15, a lubricating layer 16 made of fluorine-based oil is held by the convex portions 15a and the concave portions 15b.

In the magnetic recording disk 11, since the convex portions 15a and the concave portions 15b formed on the surface of the protective layer 15 do not have any directionality, the magnetic recording disk 11 is in a position between the surface of the rotating magnetic recording disk 11 and the magnetic head. High efficiency in reducing frictional force. Therefore, although the evaluation results will be described later,
Despite its small surface roughness, it has excellent adsorption resistance to the magnetic head. On the surface side of the protective layer 15, the lubricant layer 16 is particularly strongly held in the concave portion 15b, so that the lubricating property of course ensures that the initial lubricating property of the surface of the magnetic recording disk 11 is high. In addition, its wear resistance over time has been improved. Further, in the magnetic recording disk 11 of the present embodiment, the flying distance of the magnetic head can be reduced, and since the protective layer 15 itself is thin, the relative distance between the Co—Cr—Ta magnetic layer 14 and the magnetic head is short. The recording tracks on the recording disk 11 can be made denser.

A method for manufacturing the magnetic recording disk 11 having such a configuration will be described.

First, the C of the magnetic recording disk substrate 11a
On the surface of the o-Cr-Ta magnetic layer 14, a coating solution containing tetrahydroxysilane is applied by spin coating. This spin coating is performed by setting the number of revolutions of the magnetic recording disk to about 2500 rpm. In this example, as the tetrahydroxysilane, a trade name of Atron NSi-310 (trade name, manufactured by Nippon Soda Co., Ltd.) (ethyl acetate solution of tetrahydroxysilane having a content of 5.9 wt% in terms of SiO ₂ content) 5. 085g and n-
A mixture of 0.3 g of hexadecane and isopropyl alcohol so that the total weight was 100 g was used as a coating solution (the blending amount of tetrahydroxysilane was about 0.3 g in terms of SiO ₂ ). Here, the mixing ratio of tetrahydroxysilane and n-hexadecane in the coating solution is approximately 1: 1 in terms of weight ratio when tetrahydroxysilane is converted to SiO ₂ .

In the spin coating method, the atmosphere is set at a temperature of about 20 ° C. and a relative humidity of about 60 ° C.
% (Coating step).

Next, the coating solution on the surface of the Co—Cr—Ta magnetic layer 14 is subjected to a heat treatment for about 4 hours in an atmosphere at a temperature of about 150 ° C., and a baking treatment for tetrahydroxysilane is performed. Do. By this baking treatment, the tetrahydroxysilane becomes a polysilicate film. This polysilicic acid film is the protective layer 15, and on the surface thereof, as shown in FIG. 9, fine convex portions 15a and concave portions 15b are distributed without directivity. (Heating step).

Thereafter, FOMBLIN Z-DOL (trade name, manufactured by Montefluos Co., Ltd.) was used as a fluorine-based oil.
Company name FOM as perfluorocarbon solvent
A solution prepared by diluting the solution to 0.075 wt% with BLIN-ZS-100 was applied to the magnetic recording disk 11 at about 250 rpm.
At a setting of 0 rpm, the surface of the protective layer 15 is spin-coated, and then a heat treatment is performed in an atmosphere at a temperature of about 150 ° C. for about 1 hour to form the lubricant layer 16. Thereby, the magnetic recording disk 11 is manufactured.

In the manufacturing method of the present embodiment, when the coating liquid is applied, the relative humidity in the atmosphere is regulated, so that the concavo-convex shape after forming the protective layer 15 by converting to a polysilicate film is used. Be uniformed. Further, since the film thickness variation in the polysilicic acid film is not generated, it is not necessary to set unnecessarily increase the thickness of the protective layer 15, also SiO ₂ as an underlayer
It is not necessary to form such as.

[Fourth Embodiment] The magnetic recording disk according to the fourth embodiment has the same structure as that of the third embodiment, and the corresponding layers are denoted by the same reference numerals. As shown in FIG. 9, the magnetic recording disk 11 of this example also has a protective layer 15.
Fine protrusions 15a and recesses 1 having no directivity on the surface of
5b are distributed. Also in this case, the protective layer 15 is formed of a polysilicate film obtained by converting tetrahydroxysilane, and has a maximum thickness of about 10 nm to about 20 nm. In addition, on the surface of the protective layer 15,
The lubricant layer 16 made of a fluorine-based oil is held by the a and the recess 15b.

Also in this magnetic recording disk 11, similarly to the third embodiment, the protrusions 1 formed on the surface of the protective layer 15 are formed.
Since the 5a and the recess 15b do not have directionality, the evaluation results thereof will be described later. However, despite the small surface roughness, the magnetic head has excellent adsorption resistance. Further, since the lubricant layer 16 is strongly held in the concave portion 15b of the protective layer 15, the initial and temporal wear resistance of the surface of the magnetic recording disk 11 is also improved. Further, the flying distance of the magnetic head can be reduced, and since the protective layer 15 itself is thin, the relative distance between the Co—Cr—Ta magnetic layer 14 and the magnetic head is short.
It is possible to increase the density of one recording track.

A method for manufacturing the magnetic recording disk 11 having such a configuration will be described.

First, as in the third embodiment, Co-Cr-T
On the surface of the a magnetic layer 14, a coating solution containing tetrahydroxysilane is applied by spin coating. Here, a coating liquid having a composition different from that of Example 3 was used.
That is, 5.085 g of a product of Atron NSi-310 (trade name, manufactured by Nippon Soda Co., Ltd. as a tetrahydroxysilane) (a solution of tetrahydroxysilane in ethyl acetate having a content of 5.9 wt% in terms of SiO ₂ content) and n −
A coating solution in which 0.1 g of hexadecane was mixed with isopropyl alcohol so that the total weight was 100 g (the mixing amount of tetrahydroxysilane was about 0.3 g in terms of SiO ₂ ) was used. Here, the spin coating is performed by setting the number of revolutions of the magnetic recording disk to a condition of about 2500 rpm. The conditions of the atmosphere in the application step by the spin coating method are, as in Example 3, a temperature of about 20 ° C. and a relative humidity of about 60% (application step).

Next, the coating liquid on the surface of the Co—Cr—Ta magnetic layer 14 is subjected to a heat treatment for about 4 hours in an atmosphere at a temperature of about 150 ° C. to remove tetrahydroxysilane in the coating liquid. A firing process is performed. As a result, FIG.
As shown, the protection layer 15 is a polysilicate film in which fine projections 15a and depressions 15b are uniformly distributed without any directivity.
Is formed (heating step).

Thereafter, FOMBLIN.Z-DOL (trade name, manufactured by Montefluos) as a fluorine-based oil was used as a perfluorocarbon solvent, and FOMB (trade name, manufactured by the company)
The solution obtained by diluting the solution to 0.075 wt% with LIN-ZS-100 was adjusted to about 2500 revolutions of the magnetic recording disk 11.
At a setting of rpm, the surface of the protective layer 15 is spin-coated, and then heat-treated for about 1 hour in an atmosphere at a temperature of about 150 ° C. to form the lubricant layer 16. Thereby, the magnetic recording disk 11 is manufactured.

In the manufacturing method of this embodiment, as in the case of the third embodiment, when the coating liquid is applied, the protective layer 15 is converted into a polysilicate film in order to regulate the relative humidity in the atmosphere.
The uneven shape after forming is uniformized. Further, since the thickness of the polysilicate film does not vary, the thickness of the protective layer 15 does not need to be set unnecessarily thick, and it is not necessary to form SiO ₂ or the like as a base layer.

Comparative Example 5 Next, a magnetic recording disk as a comparative example used for evaluating the sliding characteristics of the magnetic recording disks according to the third and fourth embodiments will be described.

In the magnetic recording disk according to Comparative Example 5, in the manufacturing method of Example 3, a coating liquid having a composition different from that of Examples 3 and 4 was used as the coating liquid used in the coating step. That is, Nippon Soda Co., Ltd. product name Atron NS as tetrahydroxysilane
A coating solution prepared by blending 5.085 g of i-310 (a solution of tetrahydroxysilane in ethyl acetate having a content of 5.9 wt% in terms of SiO ₂ content) with isopropyl alcohol in a total weight of 100 g was used. Using. That is, n-hexadecane is not blended. The other process conditions are the same as those in the third and fourth embodiments, and thus the description thereof is omitted.

When the surface of the protective layer formed in Comparative Example 5 was observed with an electron microscope, it was confirmed that no fine irregularities were formed on the surface of the protective layer.

[Comparative Example 6] Further, as Comparative Example 6, C
On the surface of the o-Cr-Ta magnetic layer, a thickness of about 20 nm (2
The amorphous carbon layer of (00) is formed as a protective layer instead of the polysilicate film. On the surface, FOMBLIN.AM2001 (trade name, manufactured by Montefluos) as a fluorinated oil, and FOMBLIN (ZS-1, trade name, manufactured by the company) as a perfluorocarbon solvent.
A solution diluted to 0.1 wt% with 00 was applied at a rotation speed of the magnetic recording disk of about 2000 rpm to form a surface lubricant layer. It has been confirmed that no irregularities are formed on the surface of this protective layer.

{Effects of Examples 3 and 4 } [Evaluation Results of Characteristics of Magnetic Recording Disks] The characteristics of the magnetic recording disks G to J according to Examples 3 and 4 and Comparative Examples 5 and 6 are described below. Table 2 shows the results of the evaluation.

The evaluation items here are center line average roughness R
a, In addition to the maximum height Rmax, a 20,000 cycle CSS test, that is, a dynamic friction coefficient μ _{D at} a relative speed of 2 mm / sec of each magnetic recording disk after 20,000 cycles of starting and stopping of the disk device, and a temperature of about 2,000 cycles 33 ° C., was measured static friction coefficient mu _S after the relative humidity was left in 80% atmosphere about 240 hours. Here, the dynamic friction coefficient mu _D is indicative of the wear characteristics, the coefficient of static friction mu _S is an index of the of difficulty adsorbed, either it is preferably less, be regarded is a bad thing exceeding 1 it can. In the table, p-Si represents a polysilicate film, and α-C represents amorphous carbon.

[0089]

[Table 2]

As shown in Table 2, the magnetic recording disks G and H according to Example 3 and Example 4 each have a small surface roughness (Ra, Rmax) and a kinetic friction coefficient μ _D.
And any of static friction coefficient mu _S is small. Therefore,
The wear resistance and the adsorption resistance can be improved while the flying height of the magnetic head is kept small and the recording density is kept high.

[0091] In contrast, a magnetic disk I according to Comparative Example 5, although the surface roughness (Ra, Rmax) is small, both of the dynamic friction coefficient mu _D and static friction coefficient mu _S is large, the abrasion characteristics and It was confirmed that the adsorption resistance was poor. The magnetic recording disk J of Comparative Example 6, the surface roughness (Ra, Rmax) is large, in addition to it is necessary to secure a wide floating distance of the magnetic head, the dynamic friction coefficient mu _D and coefficient of static friction any of the mu _S is large, poor in wear characteristics and absorption resistance adhesive properties was confirmed.

In both Examples 3 and 4, n-hexadecane was used as an aliphatic hydrocarbon having at least 13 carbon atoms and insoluble in tetrahydroxylane and isopropyl alcohol as a readily soluble aliphatic hydrocarbon. However, the present invention is not limited to this, and it can be estimated that similar effects can be obtained with aliphatic hydrocarbons having 13 or more carbon atoms as long as they satisfy the above conditions.

The mixing ratio of tetrahydroxysilane and n-hexadecane (aliphatic hydrocarbon) to the coating liquid is from 1: 1 to 1: 0.05 in terms of weight ratio when tetrahydroxysilane is converted to SiO _2. Up to
The irregularities can be formed stably, but outside this range, it is difficult to control the density of the irregularities.

As a result of various changes in the relative humidity of the atmosphere when the coating liquid is applied, the relative humidity of 50% or more and non-condensing, especially about 60% of the atmosphere. preferable.

Embodiments 5 to 10 Next, Embodiments 5 to 10 will be described.

Fifth Embodiment FIG. 10 shows a cross section of a magnetic disk according to a fifth embodiment. In the disk of this example, first, the surface of the substrate 21 of the 3.5-inch disk in which the Ni-P plating 32 was applied to the aluminum substrate 31 was coated with alumina free abrasive grains and a polishing tape to obtain a surface roughness Ra.
= 15-20 ° (0.0015-0.0020 μm),
Its maximum height Rmax = 300Å (0.0300 μm)
Mirror finishing is performed as follows (when measured using a stylus-type roughness meter with a 2 μmR needle). And this base 21
A Co—Cr—Ta thin film magnetic layer 22 is formed on the surface of the substrate by using a sputtering method. Further, a protective layer 23 made of a polysilicate film and a lubricating layer (lubricant layer) 24 made of a liquid lubricant are formed on the surface of the magnetic layer 22.

The protective layer 23 of the present example is made of Astron NSi-310 manufactured by Nippon Soda Co., Ltd. as tetrahydroxysilane.
(SiO ₂ content 5.9% ethyl acetate solution) 5.085
To 0.9 g, a coating liquid obtained by adding 0.9 g of naphthalene and diluting and mixing with isopropyl alcohol so that the total weight becomes 100 g is used. The SiO ₂ content of this coating solution is 0.3% by weight. The coating method is room temperature 20 °
C, disk rotation speed 2 in an environment of 60% humidity
Spin coating at 500 rpm was employed. Then, the disk is baked at 150 ° C. for 4 hours to form a polysilicate protective layer 23.

The lubricating layer 24 is formed by spin-coating a solution obtained by diluting a fluorine oil, FOMBLIN.Z-DOL, manufactured by Montefluos Co., Ltd. to 0.075 wt% with a perfluorocarbon solvent, FOMBIN.ZS-100 manufactured by the company, at a disk rotation speed of 2500 rpm. After applying with a coat,
It is formed by performing a heat treatment at 50 ° C. for 1 hour.

The magnetic disk manufactured as described above was measured for the static friction coefficient and the dynamic friction coefficient under the conditions described below. The results are summarized in Table 3.

[Embodiment 6] On a magnetic disk having the same structure as in Embodiment 5, a polysilicate protective layer 23 was formed under the following conditions. Except for the structure of the magnetic disk, the lubricating layer 24, and the like, except for the polysilicate protective film 23, they are the same as in the fifth embodiment, and the description is omitted.

The polysilicic acid protective film 23 of this example is made of Atron NSi manufactured by Nippon Soda Co., Ltd. as tetrahydroxysilane.
-310 (5.9% SiO ₂ solution in ethyl acetate)
A coating liquid obtained by adding 0.3 g of n-hexadecane to 5.085 g and then diluting and mixing with isopropyl alcohol so that the total weight becomes 100 g is used. The SiO ₂ content of this coating solution is 0.3% by weight. The coating method is as follows, under an environment of a room temperature of 20 ° C. and a humidity of 60%.
Spin coating at a disk rotation speed of 2500 rpm was employed. Then, the disk was baked at 150 ° C. for 4 hours to form a polysilicate protective layer 23.

For the magnetic disk of this example, the static friction coefficient and the dynamic friction coefficient were measured under the conditions described later.
The results are summarized in Table 3.

[Embodiment 7] On a magnetic disk having the same structure as in Embodiment 5, a polysilicate protective layer 23 was formed under the following conditions. Except for the structure of the magnetic disk, the lubricating layer 24, and the like, except for the polysilicate protective film 23, they are the same as in the fifth embodiment, and the description is omitted.

The polysilicic acid protective film 23 of this example is made of Nippon Soda Co., Ltd.
-310 (5.9% SiO ₂ solution in ethyl acetate)
3.559 g of Oscar 1432 (average particle size 12 nm, Si
A coating solution prepared by adding 0.3 g of a 30% O ₂ content IPA solution) and then diluting and mixing with isopropyl alcohol so that the total weight becomes 100 g is used. The mixing ratio of tetrahydroxysilane and colloidal silica in this coating solution was 7: 3, and the SiO ₂ content was 0.3 wt%.
The coating method employed was spin coating at a disk rotation speed of 2500 rpm in an environment at a room temperature of 20 ° C. and a humidity of 60%. Then, the disk was baked at 150 ° C. for 4 hours to form a polysilicate protective layer 23.

For the magnetic disk of this example, the static friction coefficient and the dynamic friction coefficient were measured under the conditions described later.
The results are summarized in Table 3.

[Embodiment 8] On a magnetic disk having the same structure as in Embodiment 5, a polysilicate protective layer 23 was formed under the following conditions. Except for the structure of the magnetic disk, the lubricating layer 24, and the like, except for the polysilicate protective film 23, they are the same as in the fifth embodiment, and the description is omitted.

The polysilicic acid protective film 23 of this example is made of Nippon Soda Co., Ltd.
-310 (5.9% SiO ₂ solution in ethyl acetate)
3.559 g of Oscar 1432 (average particle size 12 nm, Si
After addition of O ₂ content of 30% IPA solution) 0.3 g, furthermore, after the addition of naphthalene 0.9 g, total weight in isopropyl alcohol is used a coating solution obtained by diluting mixed so that 100g . The mixing ratio of tetrahydroxysilane and colloidal silica in this coating solution was 7: 3,
The SiO ₂ content is 0.3% by weight. The coating method employed was spin coating at a disk rotation speed of 2500 rpm in an environment at a room temperature of 20 ° C. and a humidity of 60%. Then, the disk was baked at 150 ° C. for 4 hours to form a polysilicate protective layer 23.

For the magnetic disk of this example, the static friction coefficient and the dynamic friction coefficient were measured under the conditions described later.
The results are summarized in Table 3.

[Embodiment 9] In a magnetic disk having the same structure as that of Embodiment 5, a polysilicate protective layer 23 was formed under the following conditions. Except for the structure of the magnetic disk, the lubricating layer 24, and the like, except for the polysilicate protective film 23, they are the same as in the fifth embodiment, and the description is omitted.

The polysilicic acid protective film 23 of this example is made of Nippon Soda's Atron NSi as tetrahydroxysilane.
-310 (5.9% SiO ₂ solution in ethyl acetate)
3.559 g of Oscar 1432 (average particle size 12 nm, Si
After addition of O ₂ content of 30% IPA solution) 0.3 g, furthermore, after the n- hexadecane was added 0.2 g, the coating solution total weight in isopropyl alcohol was diluted mixed at a 100g using ing. The mixing ratio of tetrahydroxysilane and colloidal silica in this coating solution was 7: 3, and the SiO ₂ content was 0.3 wt%. The coating method employed was spin coating at a disk rotation speed of 2500 rpm in an environment at a room temperature of 20 ° C. and a humidity of 60%. Then, the disk was baked at 150 ° C. for 4 hours to form a polysilicate protective layer 23.

For the magnetic disk of this example, the static friction coefficient and the dynamic friction coefficient were measured under the conditions described later.
The results are summarized in Table 3.

[Embodiment 10] On a magnetic disk having the same structure as in Embodiment 5, a polysilicate protective layer 23 was formed under the following conditions. Except for the structure of the magnetic disk, the lubricating layer 24, and the like, except for the polysilicate protective film 23, they are the same as in the fifth embodiment, and the description is omitted.

The polysilicic acid protective film 23 of this example is manufactured by Nippon Soda Co., Ltd.
-310 (5.9% SiO ₂ solution in ethyl acetate)
3.559 g of Oscar 1432 (average particle size 12 nm, Si
After addition of O ₂ content of 30% IPA solution) 0.3 g, further, the naphthalene and 0.6 g n-hexadecane 0.
After adding 2 g, a coating solution diluted and mixed with isopropyl alcohol so that the total weight becomes 100 g is used. The mixture ratio of tetrahydroxysilane and colloidal silica in this coating solution was 7: 3, and the content of SiO _{2 was} 0.1%.
3 wt%. The coating method is such that the disk rotation speed is 2500 in an environment of a room temperature of 20 ° C. and a humidity of 60%.
Spin coating at rpm was employed. Then, the disk was baked at 150 ° C. for 4 hours to form a polysilicate protective layer 23.

For the magnetic disk of this example, the static friction coefficient and the dynamic friction coefficient were measured under the conditions described later.
The results are summarized in Table 3.

Comparative Example 7 On a magnetic disk having the same configuration as in Example 5, a polysilicate protective layer 23 was formed under the following conditions. Except for the structure of the magnetic disk, the lubricating layer 24, and the like, except for the polysilicate protective film 23, they are the same as in the fifth embodiment, and the description is omitted.

The polysilicic acid protective film 23 of this example is made of Nippon Soda Co., Ltd.
-310 (5.9% SiO ₂ solution in ethyl acetate)
A coating solution obtained by diluting 5.085 g with isopropyl alcohol so that the total weight becomes 100 g is used. The SiO ₂ content of this coating solution is 0.3% by weight.

The coating method is as follows: room temperature 20 ° C., humidity 6
Disk rotation speed 2500rpm under 0% environment
m spin coat was adopted. Then, the disk was baked at 150 ° C. for 4 hours to form a polysilicate protective layer 23.

For the magnetic disk of this example, the static friction coefficient and the dynamic friction coefficient were measured under the conditions described later.
The results are summarized in Table 3.

[Comparative Example 8] As a comparative example, a conventional textured disk shown in FIG. 11 was used. First, the disc of this example is made of an aluminum substrate 7.
The surface of the substrate 61 of the 3.5-inch disk on which the Ni-P plating 72 was applied to the substrate 1 was coated with a surface roughness Ra = 30 ° (0.0030 μm) using alumina free abrasive grains and a polishing tape.
m), its maximum height Rmax = 350 ° (0.0350
μm) or less (when measured using a stylus-type roughness meter with a 2 μm R needle). Then, a Co—Cr—Ta thin film magnetic layer 62 and an amorphous carbon protective layer 63 are sequentially formed on the surface of the base 61 by using a sputtering method. Further, a lubricating layer 64 made of a liquid lubricant is formed. The lubricating layer 64 is made of fluorine oil FOMBLIN AM200 manufactured by Montefluos.
1 is a perfluorocarbon solvent FOMBIN-Z
It is formed by applying a solution diluted to 0.0075 wt% by S-100 by spin coating at a disk rotation speed of 2500 rpm, and then performing a heat treatment at 150 ° C. for 1 hour.

The static friction coefficient and the dynamic friction coefficient of the magnetic disk manufactured as described above were measured under the conditions described below. The results are summarized in Table 3.

[Comparative Example 9] As Comparative Example 8, a disk in which a texture having the same roughness as that of the related art was formed in Comparative Example 8 was employed. In the disk of this example, first, the surface of a substrate 61 of a 3.5-inch disk in which an Ni-P plating 72 was applied to an aluminum substrate 71 was coated with alumina free abrasive grains and a polishing tape to obtain a surface roughness Ra = 60 ~ 70Å (0.0060 ~ 0.0070
μm) and its maximum height Rmax = 800 ° (0.080
0 μm) or less (when measured using a stylus-type roughness meter with a 2 μm R needle). Then, a Co—Cr—Ta thin film magnetic layer 62 and an amorphous carbon protective layer 63 are sequentially formed on the surface of the base 61 by using a sputtering method. Further, a lubricating layer 64 made of a liquid lubricant is formed. The same lubricating layer 64 as that of Comparative Example 8 is employed.

The static friction coefficient and the dynamic friction coefficient of the magnetic disk manufactured as described above were measured under the conditions described below. The results are summarized in Table 3.

[Measurement Results] The surface conditions and wear characteristics of the lubricating layers 24 and 64 of the magnetic disks of the respective Examples 5 to 10 and Comparative Examples 7 to 9 manufactured as described above were measured. is there.

[0124]

[Table 3]

Ra and Rmax in the table indicate the surface roughness of the lubricating layers 24 and 64 formed on the surface of each disk. The measuring device used was ET-30K manufactured by Kosaka Laboratories, the probe was 2 μmR, and the measurement length was 2.50 mm. The protective film thickness indicates the thickness of the polysilicate protective layer. This film thickness is measured by measuring the fluorescent X-ray intensity (Kα) of Si in the polysilicate protective layer and comparing it with a detection line obtained from a sample having a known film thickness. The film thickness of the carbon protective layer is measured by measuring the fluorescent X-ray intensity (Kα) of C and comparing it with a detection line obtained from a sample having a known film thickness.

Μ _D is the coefficient of kinetic friction, and shows the measurement result of the coefficient of kinetic friction between the disk and the magnetic head after 20,000 CSS tests (repeated start / stop tests using a disk device). The magnetic head used was a thin-film magnetic head with a load of 6 g, and the relative speed to the disk was:
2 mm / s. Further, mu _S is the static friction coefficient are shown the results of measurement of the static friction coefficient between room temperature 33 ° C, left for the disk and the magnetic head 240 hours under a humidity of 80% RH. The magnetic head is a thin-film magnetic head with a load of 6 g.

<< Effects of Examples 5 to 10 >> As can be seen from the measurement results shown in Table 3, each of Examples 5 to 10 has
In the discs No. 10 to No. 10, the Ra is 25 ° (0.00
25 μm), Rmax is 300 ° (0.0300 μm)
Yet very roughness smaller surface that extent, has large disk substantially equal to the dynamic friction coefficient of a conventional roughness shown in Comparative Example 9 mu _D, and the static friction mu _S. The dynamic friction coefficient μ _D is an index of wear characteristics, and the static friction μ _S
Is an indicator of the difficulty of adsorption. Therefore, the disks of Examples 5 to 10 have the same abrasion characteristics as the conventional disks in spite of the small surface roughness, and also have the same characteristics in attracting the magnetic head. You can see that Since the disk of this embodiment has a small surface roughness, it is possible to lower the flying height of the magnetic head, and it is possible to reduce the distance between the magnetic head and the magnetic layer and perform high-density recording. I have. Further, since the protective film thickness is small, the distance between the magnetic head and the magnetic layer can be further reduced.

Despite the low surface roughness of the disks of the above Examples, the surface performance was such that the kinetic friction coefficient μ _D and the static friction μ _S were 1 or more as in the disks of Comparative Examples 7 and 8. It is not clear why there is no deterioration. However, considering that the surface condition of the disks of Examples 5 to 10 shown in Table 3 is substantially the same as the surface condition of Comparative Example 7 using only hydroxysilane, it is a mixed sublimable hydrocarbon. Due to naphthalene or n-hexadecane, which is a hydrocarbon having a high boiling point and evaporating in the firing process after forming the protective layer, a phenomenon such as evaporation of hydrocarbons occurs on the surface of the protective layer in the firing process of the protective layer. As a result, it is assumed that countless minute irregularities are formed. The same effect has been obtained by mixing colloidal silica having a small particle size. From now on, by forming numerous infinitesimal irregularities on the surface of the protective layer, even if the surface roughness is small, abrasion will occur. It can be seen that a magnetic disk having good characteristics can be formed. Further, from this example, it is understood that any one of these hydrocarbons and colloidal silica, or two or more thereof may be mixed. On the other hand, as shown in Comparative Example 8,
In a disk in which the surface roughness is reduced by reducing the roughness of the texture processing of No. 1, the same surface state as that of the embodiment can be formed by measurement, but good abrasion characteristics cannot be obtained. Therefore, a low flying height of the magnetic head is realized, and furthermore,
In order to realize a magnetic disk capable of high-density recording by reducing the thickness of the protective layer, instead of surface treatment by mechanical processing such as texture processing, chemical processing such as evaporation described above is required. It is considered effective to employ means or physical means such as mixing fine particles.

From the measurement limit of the surface roughness, the lower limit of the surface roughness is that Ra is about 10 ° (0.010 μm),
It is assumed that Rmax is about 100 ° (0.0100 μm). The lower limit of the thickness of the protective layer is assumed to be approximately 15 mg / m ² (about 50 °) in order to secure the layer structure.

[0130]

As described above, in the method of manufacturing a magnetic recording medium according to the present invention, a coating solution containing silicon oxide particles and tetrahydroxysilane is applied to the surface of the magnetic layer at a relative humidity of 50%. Irregularities with no directivity are formed by application in an atmosphere set as described above, so that the friction coefficient between the magnetic recording medium and the magnetic head can be reduced despite the small surface roughness. Therefore, the flying height of the magnetic head can be reduced, and a high recording density can be realized.

Further, the protective layer formed on the surface of the magnetic layer
An Si compound of tetrahydroxysilane is blended in an organic solvent of isopropyl alcohol.
For example, a coating liquid containing an aliphatic hydrocarbon having 13 or more carbon atoms, such as n-hexadecane, is applied to the surface of the magnetic layer in an atmosphere defined at a predetermined relative humidity, and then subjected to a heat treatment to obtain When forming a protective layer of a silica film,
Since irregularities are distributed without directionality on the surface of the protective layer,
Since the contact area with the magnetic head is reduced, and the lubricant layer is held in the concave portions, the friction characteristics of the magnetic recording medium are improved both initially and over time. In addition, since the relative humidity is regulated, the thickness of the protective layer and the shape of the irregularities are stabilized, and the flying distance of the magnetic head can be reduced. Also, since it is not necessary to sputter-form SiO ₂ or the like as an underlayer of the protective layer or to unnecessarily increase the thickness of the protective layer, for example, the magnetic recording medium can be constituted by a protective layer having a maximum thickness of 10 to 20 nm. . Accordingly, since the distance between the magnetic head and the magnetic layer can be reduced, the recording tracks of the magnetic recording medium can be made denser, and the recording capacity can be improved.

[0132]

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a magnetic recording disk according to a first embodiment or a second embodiment of the present invention with a part cut away.

FIG. 2 is a perspective view schematically showing the surface of a protective layer of a magnetic recording disk according to Example 1 or Example 2 of the present invention.

FIG. 3 shows the surface state of the protective layer of the magnetic recording disk according to the first embodiment of the present invention by an electron microscope at a magnification of 7500.
It is a schematic diagram at the time of observing by magnification.

FIG. 4 shows the surface state of the protective layer of the magnetic recording disk according to the second embodiment of the present invention by an electron microscope at a magnification of 7500.
It is a schematic diagram at the time of observing by magnification.

FIG. 5 shows the surface state of the protective layer of the magnetic recording disk according to Comparative Example 1 of the present invention, which was observed by an electron microscope at a magnification of 7500.
It is a schematic diagram at the time of observing by magnification.

FIG. 6 shows the surface state of the protective layer of the magnetic recording disk according to Comparative Example 2 of the present invention, which was observed at an magnification of 7500 using an electron microscope.
It is a schematic diagram at the time of observing by magnification.

FIG. 7 shows the surface state of the protective layer of the magnetic recording disk according to Comparative Example 3 of the present invention, which was observed at an magnification of 7500 using an electron microscope.
It is a schematic diagram at the time of observing by magnification.

FIG. 8 shows the surface state of the protective layer of the magnetic recording disk according to Comparative Example 4 of the present invention, which was observed at an magnification of 7500 by an electron microscope.
It is a schematic diagram at the time of observing by magnification.

FIG. 9 is a schematic cross-sectional view illustrating a magnetic recording disk according to a third embodiment or a fourth embodiment of the present invention, with a portion cut away.

FIG. 10 is a schematic sectional view showing a configuration of a magnetic recording disk according to Embodiments 5 to 10 of the present invention.

FIG. 11 is a schematic sectional view showing a configuration of a magnetic recording disk according to Comparative Example 8 or 9 of the present invention.

FIG. 12 is a perspective view schematically showing the surface of a protective layer of a conventional magnetic recording disk.

FIG. 13 is a schematic sectional view of a magnetic recording disk according to a reference example of the present invention.

[Explanation of symbols]

 1, 11: Magnetic recording disk 2, 12: Aluminum alloy substrate (non-magnetic substrate) 3, 13: Ni-P plating layer 4: Co-Cr-Ni magnetic layer (magnetic layer) 5 , 15, 23 ... Protective layer 5a ... Unevenness 6, 16, 24 ... Lubricant layer 14 ... Co-Cr-Ta magnetic layer (magnetic layer) 15a ... Convex part 15b ... Concave part 21 ... Base 22 ... Magnetic layer 31 ... Substrate 32 ... Plating layer

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuo Nimura 1-1 1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. No. 1 Fuji Electric Co., Ltd. (56) References JP-A-62-36727 (JP, A) JP-A-61-73227 (JP, A) JP-A-52-20804 (JP, A) JP-A-2- 73518 (JP, A) JP-A-60-5423 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/84 G11B 5/72

Claims (6)

(57) [Claims] 1. A protective layer having irregularities on its surface is laminated on the surface side of a magnetic layer laminated on the surface side of a non-magnetic substrate, and the protective layer is made of a poly-oxide in which silicon oxide particles are dispersed. manufacturing a magnetic recording medium comprising formed by silicate film
The method, wherein the silicon oxide is provided on the surface side of the magnetic layer.
Coating with oxide particles and tetrahydroxysilane
Coating to apply cloth liquid in an atmosphere with relative humidity of 50% or more
And a coating solution applied to the surface side of the magnetic layer.
Heat treatment to disperse the silicon oxide particles inside
In the state in which tetrahydroxysilane is applied to the polysilicate film,
A heating step of forming the protective layer by
A method for manufacturing a magnetic recording medium. Wherein Oite to claim 1, the coating solution, spin
A method for producing a magnetic recording medium, wherein the method is applied to the surface side of the magnetic layer by an uncoating method. 3. The method according to claim 1 , wherein
The blending amount of the silicon oxide particles in the coating solution is
Silicon dioxide to the amount of trahydroxysilane
A method for producing a magnetic recording medium, wherein the amount is in the range of 1 wt% to 50 wt% in terms of amount . 4. The method according to claim 1 , wherein:
In the above, the silicon oxide particles have an average particle size
A method for manufacturing a magnetic recording medium, wherein the thickness is in the range of 5 nm to 30 nm . 5. A magnetic layer on a surface side of a substrate for a magnetic recording medium made of a non-magnetic material, a protective layer formed on the surface side of the magnetic layer, and having irregularities distributed over the entire surface; And a lubricant layer held on the surface of the, the protective layer,
In the method for producing a magnetic recording medium in which a Si compound is a polysilicate film converted by heating, a Si compound that can be converted into the polysilicic acid by heat treatment is mixed in an organic solvent, and the Si compound is insoluble, and The organic solvent is easily soluble, and a coating solution comprising a concavo-convex forming component having a high evaporating property at the conversion temperature of the Si compound to the polysilicic acid is added to the surface of the magnetic layer by 50% or more . A coating step of coating in an atmosphere defined by relative humidity, and a coating liquid applied to the surface of the magnetic layer, a heating treatment is performed at a temperature equal to or higher than the conversion temperature, and the Si compound is applied to the polysilicate film. A heating step of forming the protective layer by inversion, wherein the Si compound is tetrahydroxysilane, a main component of the organic solvent is isopropyl alcohol, Convex forming component at least in formula 1
A method for producing a magnetic recording medium, wherein the method is an aliphatic hydrocarbon having 3 carbon atoms. 6. The coating liquid according to claim 5, wherein
Combination of tetrahydroxysilane and the aliphatic hydrocarbon
The ratio is calculated by converting tetrahydroxysilane to SiO _2.
In Kino weight ratio of 1: 1 to 1: The method of manufacturing a magnetic recording medium characterized <br/> in the range of up to 0.05.