JP2000222720A - Substrate for information recording medium and information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate for an information recording medium having excellent mechanical properties (elasticity, strength, hardness or the like) which can be easily produced, and to provide an information recording medium (such as a magnetic disk, optical disk and magneto-optical disk) having an information recording layer on the substrate and having excellent mechanical properties and recording characteristics. SOLUTION: This substrate for an information recording medium is a nonmagnetic rigid substrate on which coatings of an information recording medium are formed on the surface facing to a recording head. The substrate is produced by forming a Ni-P layer 2 having <=20 nm surface roughness Rmax on a rigid substrate 1 consisting of an oxynitride glass having >=90 GPa Young's modulus and >=0.5 wt.% nitrogen content. Then a laminated body of a base layer 3, a magnetic layer 4, a protective layer 5 and a lubricant layer 6 is formed on the substrate 1, 2 for a magnetic recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate for an information recording medium and an information recording medium having an information recording layer provided on the substrate (for example, a magnetic disk, an optical disk, a magneto-optical disk, etc.). .

[0002]

2. Description of the Related Art In recent years, a substrate for a magnetic recording medium used as a substrate for a magnetic disk (magnetic recording medium), which is an example of a so-called information recording medium, has recently been required to have a higher density of information recording capacity. The smoothness has been improved. In a magnetic disk device, as a typical external recording device of a personal computer, the capacity, size, and cost have been remarkably increased.

The progress of such magnetic disk devices is largely due to the high performance and high accuracy of magnetic disks and magnetic heads for recording and reproducing information. It is brought about by sophistication. Above all, the improvement in the magnetic disk density (especially the improvement in linear recording density) is largely due to the improvement in the magnetic film and the reduction in the flying height of the magnetic head. Recent magnetic disk devices have a low flying height of about 35 to 50 nm. The quantity is about to be realized.

[0004] In order to realize such low flying height, the surface of the magnetic disk is required to be flat and smooth. In other words, in recent years, a substrate for a magnetic recording medium has been required to have improved surface flatness and smoothness in accordance with a demand for a higher density of information recording capacity. The substrate for a magnetic recording medium is generally required to have the following characteristics. 1) Good surface accuracy 2) High strength and high rigidity 3) Good shape and dimensional accuracy 4) High surface hardness 5) Excellent chemical stability 6) Low specific gravity 7) No magnetism 8) Low cost Among the substrates for magnetic recording media, the substrates for high recording density
The surface accuracy is important, and in order to realize a low flying height, it is required that the surface is flat and smooth, and that there is no abnormal protrusion or sudden change in waviness that causes head crash.

At present, aluminum alloy substrates, aluminosilicate glass substrates, crystallized glass substrates, and the like are actually used as substrates for magnetic recording media. Particularly recently, aluminosilicate glass substrates capable of obtaining a smoother surface have attracted attention. FIG. 4 shows a configuration of a magnetic recording disk using a conventionally used magnetic recording medium substrate (aluminosilicate glass substrate). Actually, on the lower surface of the substrate shown in the figure, a film having the same configuration as the upper surface is provided from the substrate 8 side as a base film (layer) 3, a magnetic film (layer) 4, a protective film (layer).
5, a lubricating film (layer) 6 is formed in this order.

In recent years, in response to the increase in density of magnetic disk devices, the speed of rotation of magnetic disks has been remarkably increased.
Some devices have a disk rotation speed of 10,000 rpm.

[0007]

The aluminosilicate glass substrate often used for magnetic disks has been subjected to a low-temperature ion exchange treatment.
a, Poisson's ratio 0.23, a Knoop hardness 660 kgf / mm ² approximately, has excellent elasticity, strength and hardness. However, as described above, the speed of rotation of the magnetic disk has been remarkably increased in response to the increase in the density of the magnetic disk device, and devices having a disk rotation speed of 10,000 rpm or more will appear in the future.

Under this high-speed rotation, it is required that the magnetic disk (substrate) be less deformed due to the high-speed rotation. This is because suppressing the deformation of the substrate at a high speed is important for keeping the flying height of the head constant. However, the aluminosilicate glass substrate subjected to the low-temperature ion exchange treatment has not been able to sufficiently satisfy the above requirements.

Accordingly, oxynitride glass has been proposed as a material for a substrate for a magnetic recording medium (magnetic disk) having further excellent mechanical properties such as elasticity, strength and hardness.
That is, by using an oxynitride glass obtained by incorporating a large amount of nitrogen into a glass structure for a substrate for a magnetic recording medium, it is possible to obtain a magnetic disk having more excellent mechanical strength than conventional ones.

However, because of its high hardness, oxynitride glass requires a longer polishing time in the step of precisely polishing the surface compared to aluminosilicate glass, and the life of the polishing pad used in the polishing step is high. Is also short, which is a major disadvantage in producing a disk substrate. In addition to oxynitride glass, crystallized glass has been proposed as a material for a magnetic disk substrate having excellent mechanical properties such as elasticity, strength, and hardness.

However, the magnetic disk substrate made of crystallized glass has a high possibility that crystal grains in the material will be removed during the polishing of the substrate surface (therefore, dents are likely to occur on the substrate surface). It is difficult and difficult to obtain a suitable substrate surface. In addition, there is a problem that a concave portion formed on the substrate surface becomes a defect when a magnetic recording layer (magnetic layer) is formed thereon, which adversely affects magnetic recording characteristics.

Further, since a magnetic disk substrate made of crystallized glass contains an alkali component in the material, a step of forming a magnetic recording layer (magnetic layer) on the substrate (for example, a sputtering step) By the substrate heating in the above, the alkali component diffuses into the magnetic recording layer (magnetic layer),
There is a problem that the magnetic recording characteristics may be adversely affected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a substrate for an information recording medium which has excellent mechanical properties (elasticity, strength, hardness, etc.) and is easy to manufacture, It is an object of the present invention to provide an information recording medium (for example, a magnetic disk, an optical disk, a magneto-optical disk, etc.) having excellent information on mechanical properties and recording characteristics, provided with an information recording layer.

[0014]

Therefore, the present invention firstly provides a non-magnetic rigid substrate having a coating of an information recording medium formed on a surface facing a recording head,
On a rigid substrate composed of oxynitride glass with a Young's modulus of 90 GPa or more and a nitrogen content of 0.5 wt% or more,
An information recording medium substrate (Claim 1) having a Ni-P layer having a surface roughness Rmax of 20 nm or less is provided.

[0015] The present invention also provides a non-magnetic rigid substrate having a coating of an information recording medium formed on a surface facing a recording head and having a Young's modulus of 90 GPa or more. An information recording medium substrate (Claim 2) comprising a Ni-P layer having a surface roughness Rmax of 20 nm or less formed on a rigid substrate made of glass. Also,
Thirdly, the present invention provides "a substrate for an information recording medium according to claim 1 or 2, wherein the rigid substrate has a Young's modulus of 160 GPa or less".

Further, the present invention fourthly provides "Information according to any one of claims 1 to 3, wherein the Knoop hardness of the rigid substrate is 800 kg / mm ² or more and 1000 kg / mm ² or less. A recording medium substrate (claim 4) "is provided. Further, the present invention provides a fifth non-magnetic rigid substrate having a coating of a magnetic recording medium formed on a surface facing a magnetic head, having a Young's modulus of 90 GPa or more and a nitrogen content of 0.5 wt% or more. The present invention provides a magnetic recording medium substrate (Claim 5) in which a Ni-P layer having a surface roughness Rmax of 20 nm or less is formed on a rigid substrate made of oxynitride glass.

A sixth aspect of the present invention relates to a non-magnetic rigid substrate having a coating of a magnetic recording medium formed on a surface facing a magnetic head and having a Young's modulus of 90 GPa or more. A magnetic recording medium substrate (Claim 6) comprising a Ni-P layer having a surface roughness Rmax of 20 nm or less formed on a rigid substrate made of glass. Also,
The present invention seventhly provides "a substrate for a magnetic recording medium according to claim 5 or 6, wherein the rigid substrate has a Young's modulus of 160 GPa or less (claim 7)."

The present invention also provides an eighth aspect of the present invention, wherein the rigid substrate has a Knoop hardness of 800 kg / mm ² or more and 1000 kg / mm ² or less. A recording medium substrate (claim 8) "is provided. The present invention ninthly provides an "information recording medium comprising at least an information recording layer provided on the substrate according to any one of claims 1 to 4 (claim 9)".

The present invention tenthly provides a "magnetic recording medium comprising at least a magnetic layer provided on the substrate according to any one of claims 5 to 8 (claim 10)". Further, the present invention provides an eleventh aspect, "a magnetic recording medium according to claim 10, wherein an underlayer, a magnetic layer, a protective layer, and a lubricating layer are provided on the substrate (claim 11)." I do.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An information recording medium substrate (for example, a magnetic recording medium substrate) according to the present invention (claims 1 to 8) comprises:
A non-magnetic rigid substrate having a coating of an information recording medium (for example, a magnetic recording medium) formed on a surface facing a recording head, and having a Young's modulus of 90 GPa or more and a nitrogen content of 0.5 wt% or more. It is made of nitride glass or crystallized glass having a Young's modulus of 90 GPa or more.

Oxynitride glass is a glass in which nitrogen is incorporated in a glass structure in a large amount and has excellent mechanical properties. As the type of the oxynitride glass according to the present invention, for example, Si-ON, Mg-Si-ON, La-Si
-ON, Al-Si-ON, Y-Al-Si-ON, Ca-Al-Si-ON, Mg-Al-
Si-ON, Na-Si-ON, Na-Ca-Si-ON and the like can be mentioned.

In the oxynitride glass, N is Si-O-Si
Is substituted to form a structure of Si-N (-Si) -Si. On glass
The inclusion of N increases the microhardness at room temperature. La-Si-O
In -N system, which is obtained as the Knoop hardness 1220kg / mm ^2, the Ca-Al-Si-ON system, Knoop hardness by the addition of about 5.5 wt% of N becomes 900 kg / mm ^2.

As described above, when nitrogen is incorporated into the glass structure, the hardness increases, but the Young's modulus also increases.
This change in Young's modulus is particularly remarkable among the changes in properties due to the N content. For example, in the Ca-Al-Si-ON system,
The Young's modulus was about 105 GPa when N was not included, but becomes about 135 GPa by adding about 5.5 wt% N. This value is the Young's modulus of SiO ₂ glass 73 GPa, high modulus without N
Considerably larger than the _{SiO 2- Y 2 O 3 -Al 2} O 3 glass Young's modulus 115 GPa.

The substrate for an information recording medium (for example, a substrate for a magnetic recording medium) according to the present invention using oxynitride glass in which nitrogen is incorporated in a glass structure as described above or using crystallized glass, It has better mechanical properties (elasticity, strength, hardness, etc.) than before. That is, the information recording medium substrate (eg, magnetic recording medium substrate) according to the present invention has a Young's modulus of 90 GPa or more, or further has a high Knoop strength (corresponding to a nitrogen content of 0.5 wt% or more). Therefore, when the speed of rotation of the information recording medium (for example, a magnetic disk) is taken into consideration, deformation such as deflection of the substrate due to the high speed rotation does not pose a problem.

Further, the information recording medium substrate (for example, a magnetic recording medium substrate) according to the present invention (claims 1 to 8)
On the rigid substrate having a Young's modulus of 90 GPa or more,
A Ni-P layer having a surface roughness Rmax of 20 nm or less is further formed. Ni-P layer according to the present invention (in particular, electroless Ni-P plating layer)
Is superior in precision workability compared to oxynitride glass or crystallized glass, so if a Ni-P layer is provided on the rigid substrate and processed, a precise substrate with a surface roughness Rmax of 20 nm or less can be obtained. The surface can be easily obtained in a relatively short time (claims 1 to 8).

For example, an electroless Ni-P plating layer is formed on an oxynitride glass substrate or a crystallized glass substrate finished to a surface roughness Rmax of about 30 nm, and then a planar precision polishing process is performed to adjust the surface condition. By applying
A smooth surface (with a surface roughness Rmax of 20 nm or less) can be easily obtained in a relatively short time. At this time, the electroless Ni-P plating layer may be formed to have a thickness of, for example, about 10 μm, and the surface thereof is shaved by 1 to 2 μm by finish polishing. Finally, the surface roughness of the electroless Ni-P layer subjected to the plane precision polishing step becomes Rmax 20 nm or less.

The electroless plating method for forming such an electroless plating layer employs metals, glasses, ceramics,
It has been established as a practical coating method for materials such as plastic. The surface roughness (Rmax 20 nm or less) of the information recording medium substrate according to the present invention (claims 1 to 8) is 10 Gbit.
/ in ² is a value corresponding to the flying height of the head corresponding to the surface recording density of 50 nm or less, the surface roughness Rmax 20 nm
By obtaining the following precise substrate surface, the possibility of contact between the head and the substrate can be minimized. If the surface recording density is further improved, the required surface roughness will be at a level of Rmax 10 nm or less.

In the present invention, when the electroless Ni-P plating layer is formed on the crystallized glass substrate, for example, the surface of the crystallized glass substrate finished to have a surface roughness Rmax of about 30 nm may be used. Since the surface of the electroless Ni-P plating layer is finally polished afterwards, there is no danger that crystals in the raw material will be removed during the polishing of the substrate surface during the final polishing process. Polished surface roughness Rmax 2
A substrate surface coated with an electroless Ni-P plating layer of 0 nm or less can be easily obtained.

Further, the Ni-P plating layer (particularly, the electroless Ni-P plating layer) according to the present invention has excellent heat resistance and non-magnetic properties, and is suitable for increasing the temperature during the formation of the magnetic recording layer (magnetic layer). Also non-magnetic. Further, the Ni-P plating layer according to the present invention (particularly, the electroless Ni-P plating layer) can be formed into a film when a material containing an alkali component such as crystallized glass is selected as a substrate material. It can serve as a protective layer (barrier) for preventing the alkaline component in the substrate material from being eluted into the information recording layer due to the temperature rise.

The information recording medium substrate (for example, a magnetic recording medium substrate) according to the present invention preferably has a Young's modulus of 160 GPa or less (claims 3 and 7). This is because if the Young's modulus of the substrate material exceeds 160 GPa, the substrate material is too hard, and there is a problem that the processing time increases in the processing steps such as lapping and polishing.

Similarly, the Knoop hardness is 800 kg / mm in consideration of not only the hardness but also the processing time in the processing step.
And a ^two or more 1000 kg / mm ² or less (claim 4,8). In addition, it has a Young's modulus of 90 GPa or more or high Knoop hardness (corresponding to a nitrogen content of 0.5 wt% or more)
(Corresponding to excellent mechanical strength), surface roughness Rmax
According to the present invention (claims 1 to 8), having an accurate substrate surface of 20 nm or less and capable of preventing the alkali component in the substrate material from being eluted into the information recording layer (corresponding to excellent recording characteristics). When an information recording layer (for example, a magnetic layer) is provided on an information recording medium substrate (for example, a magnetic recording medium substrate), an information recording medium (for example, a magnetic recording medium) that has better mechanical strength and recording characteristics than before. Can be obtained (claims 9 to 10).
11).

For example, by providing at least a magnetic layer on the substrate according to any one of claims 5 to 8, a magnetic recording medium having more excellent mechanical strength and recording characteristics than before can be obtained. Can be As such a magnetic recording medium, for example, a magnetic recording medium in which an underlayer, a magnetic layer, a protective layer, and a lubricating layer are provided on a substrate (claim 11) can be mentioned.

Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

[0034]

Embodiment 1 A substrate for a magnetic recording medium (substrate for a magnetic disk) according to the present embodiment is a non-magnetic rigid substrate having a coating of a magnetic recording medium formed on a surface facing a magnetic head. , Young's modulus 90 GPa or more, nitrogen content 0.
A surface roughness Rmax 2 is formed on a rigid substrate 1 composed of oxynitride glass of 5 wt% or more and polished precisely.
The Ni-P electroless plating layer 2 having a thickness of 0 nm or less is formed.

Further, the magnetic recording medium (magnetic disk) according to the present embodiment is a laminate of an underlayer 3, a magnetic layer 4, a protective layer 5, and a lubricating layer 6 on the magnetic recording medium substrates 1, 2. The structure is shown in FIG. Although FIG. 1 shows the laminate only on the upper surfaces of the substrates 1 and 2, a laminate having a similar configuration is actually provided on the lower surface of the substrates.

Hereinafter, a method for manufacturing a magnetic recording medium substrate (magnetic disk substrate) and a magnetic recording medium (magnetic disk) according to this embodiment will be described. First, a high-temperature melting method was selected as a method for producing oxynitride glass as a material for a magnetic disk substrate. Here, a nitride was used as a glass material, and the melting atmosphere was nitrogen gas.
Since the nitride has a higher melting point than the corresponding oxide, the melting temperature was set higher.

As the nitride, Si ₃ N ₄ , AlN or the like is used. In this case, Y-Al-Si-ON glass is selected. Y-Al-Si-O
-N glass composition is Al (13.3 at%), Si (13.3 at%)
%), Y (13.3 at%), O (46.7 at%), and N (13.3 at%). The Young's modulus of the obtained oxynitride glass is
157 GPa, Poisson's ratio was 0.315. Also, the Knoop hardness was able to secure 800 kgf / mm ² or more.

As described above, the material of the magnetic disk substrate (oxynitrite) having more excellent mechanical properties such as elasticity, strength and hardness than the aluminosilicate glass magnetic disk substrate subjected to the low-temperature ion exchange treatment. Ride glass). Next, make this material into a plate shape,
The blank was rounded to a desired outer diameter, and a hole for an inner diameter was further formed. Then, after lapping (roughing) the surface of the blank with fine powder of silicon carbide, the inner and outer diameters are set to predetermined dimensions,
Processed into shape.

Next, the blank surface was wrapped again (2
After the next lapping, the abrasive and the dirt attached to the blank were removed by ultrasonic cleaning. After the secondary lapping and cleaning, the surface of the blank was polished with an abrasive (cerium oxide) to obtain a predetermined flatness (3 to 5 μm). Here, polishing was performed using a double-sided processing machine, and the substrate was finished to a surface roughness Rmax of about 30 nm.

Next, a cleaning step was performed to remove abrasives and the like remaining on the substrate surface, and finally, surface defects were inspected to produce a magnetic disk substrate (substrate). In the next electroless Ni-P plating process, as a pretreatment, degreasing to remove oils and fats on the substrate surface with a non-erosive degreasing agent, etching to remove an uneven natural protective film, and substitution reaction are used. A zinc substitution treatment for forming a zinc film on the substrate surface was performed.

Thereafter, the substrate is immersed in a plating solution, and the surface of the substrate is electroless Ni
A -P plating layer was deposited. At this time, the thickness of the layer is 12 μm.
Finished to about m. The substrate on which the Ni-P plating layer is formed is sandwiched between polyurethane polishing cloths, and the surface of the plating layer is subjected to final polishing while pouring an alumina-based abrasive.
２2 μm.

Then, this substrate having an electroless Ni-P plating layer on the outermost surface was finished to a surface roughness Rmax of 15 nm. here,
Polishing of the substrate was performed using a double-sided processing machine having a mechanism as shown in FIG. In particular, in the final polishing step, Rmax 20n
Although the substrate surface is polished to less than m, the processing time of the polishing process after lapping to obtain a high-precision surface is limited to the case where the conventional electroless Ni-P plating layer is not coated (oxynitride glass substrate 12 in case of polishing itself
Although the time was 0 minutes, in the present embodiment, the total processing time of the polishing step after lapping was reduced to 40 minutes.

After performing the final polishing, the magnetic disk substrate according to the present embodiment, on which the electroless Ni-P plating is applied, is subjected to cleaning for removing the abrasive remaining on the surface of the plating layer. Completed. Further, as described below, a magnetic disk generally called a hard disk was completed by a media process of forming a magnetic layer and the like on the magnetic disk substrate.

That is, in the media process, the underlayer and the underlayer are formed on both surfaces of the magnetic disk substrate by sputtering.
By sequentially forming a magnetic layer and a protective layer, and further forming a lubricating layer on the protective layer using a dipping method,
The magnetic disk was completed. Specifically, first, electroless Ni
A base layer, a magnetic layer, and a protective layer were sequentially formed by a sputtering process on the -P-plated magnetic disk substrate. Here, the underlayer is a Cr film, and the magnetic layer is CoNiCr.
The C film was selected for the film and the protective layer.

In the sputtering step, first,
The magnetic disk substrate was polished and precision washed, and then mounted on a substrate holder of an in-line type sputtering apparatus. Then, the substrate holder on which the substrate was mounted was introduced into a vacuum chamber, and the substrate holder was heated by a heater to raise the substrate temperature to 200 ° C.

Next, the substrate holder on which the substrate was mounted was moved to a Cr film forming chamber in a vacuum, and a Cr film (thickness: 100 nm) as an underlayer was formed on the substrate by DC sputtering. Next, the substrate holder on which the substrate on which the Cr film is formed is moved to a CoNiCr film forming chamber in a vacuum, where the CoNiCr film (thickness: 60 nm), which is a magnetic layer, is subjected to DC.
It was laminated on the Cr film by a sputtering method.

Next, the substrate holder on which the substrate having the laminated body of the Cr film and the CoNiCr film is mounted is moved to a C film forming chamber in a vacuum, and the C film (thickness: 30 n) is used as a protective layer.
m) was formed on the CoNiCr film of the laminate by DC sputtering. After the above series of sputtering steps is completed,
The magnetic recording medium substrate on which the laminate was formed was taken out of the vacuum chamber, and the surface thereof was subjected to tape burnishing with a tape containing an abrasive.

Thereafter, a perfluoropolyether-based lubricant was applied to the surface of the laminated body of the magnetic recording medium substrate by dipping to form a lubricating layer, thereby completing a hard disk (magnetic disk). When the holding force of this magnetic disk was measured with a sample vibration magnetometer,
e or more.

The substrate for a magnetic recording medium (magnetic disk) according to the present embodiment has a Young's modulus of 90 GPa or more and a nitrogen content of 0.5 wt% or more (corresponding to hardness). When this is taken into account, deformation such as deflection of the substrate due to high-speed rotation does not pose a problem. Further, the magnetic disk substrate according to the present embodiment has a surface roughness on the outermost surface.
An electroless Ni-P plating layer with a Rmax of 20 nm or less is formed.This electroless Ni-P plating layer is superior in precision workability compared to oxynitride glass, which is a substrate material. If an electroless Ni-P plating layer is provided and processed, a precise substrate surface having a surface roughness Rmax of 20 nm or less can be easily obtained in a relatively short time.

Further, Young's modulus of 90 GPa or more and 0.5 wt%
The magnetic disk of this example having the above nitrogen content (corresponding to hardness) (corresponding to excellent mechanical strength) and having a precise substrate surface with a surface roughness Rmax of 20 nm or less (corresponding to excellent recording characteristics) The magnetic disk of this embodiment in which the information recording layer (magnetic layer) is provided on the substrate for use has better mechanical strength and recording characteristics than the conventional one.

[0051]

Embodiment 2 A magnetic recording medium substrate (magnetic disk substrate) according to this embodiment is a nonmagnetic rigid substrate having a magnetic recording medium coating formed on a surface facing a magnetic head. , A Ni-P electroless plating layer 2 having a surface roughness Rmax of 20 nm or less on a rigidly polished rigid substrate 7 made of crystallized glass having a Young's modulus of 90 GPa or more.
Is formed.

The magnetic recording medium (magnetic disk) according to the present embodiment has a laminated structure of an underlayer 3, a magnetic layer 4, a protective layer 5, and a lubricating layer 6 on the magnetic recording medium substrates 7, 2. The structure is shown in FIG. In FIG. 2, the laminate is described only on the upper surfaces of the substrates 7 and 2. However, a laminate having the same configuration is actually provided on the lower surface of the substrates.

Hereinafter, a method of manufacturing a magnetic recording medium substrate (magnetic disk substrate) and a magnetic recording medium (magnetic disk) according to this embodiment will be described. First, a crystallized glass having a Young's modulus of 90 GPa or more, which is a material for a magnetic disk substrate, was prepared. Next, this material was formed into a plate shape, rounded to a desired outer diameter, and further, a hole for an inner diameter was made to form a blank. Then, after lapping (roughing) the surface of the blank with fine silicon carbide powder, the inner and outer diameters were processed into predetermined dimensions and shapes.

Next, the blank surface was wrapped again (2
After the next lapping, the abrasive and the dirt attached to the blank were removed by ultrasonic cleaning. After the secondary lapping and cleaning, the surface of the blank was polished with an abrasive (cerium oxide) to obtain a predetermined flatness (3 to 5 μm). Here, polishing was performed using a double-sided processing machine, and the substrate was finished to a surface roughness Rmax of about 30 nm.

Next, a cleaning process is performed to remove abrasives and the like remaining on the surface of the substrate, and finally, surface defects are inspected. Was prepared. In the next electroless Ni-P plating process, as a pretreatment, degreasing to remove oils and fats on the substrate surface with a non-erosive degreasing agent, etching to remove an uneven natural protective film, and substitution reaction are used. A zinc substitution treatment for forming a zinc film on the substrate surface was performed.

Thereafter, the substrate is immersed in a plating solution, and a non-electrolytic Ni
A -P plating layer was deposited. At this time, the thickness of the layer is 12 μm.
Finished to about m. The substrate on which the Ni-P plating layer is formed is sandwiched between polyurethane polishing cloths, and the surface of the plating layer is subjected to final polishing while pouring an alumina-based abrasive.
２2 μm.

Then, this substrate having an electroless Ni-P plating layer on the outermost surface was finished to a surface roughness Rmax of 15 nm. here,
Polishing of the substrate was performed using a double-sided processing machine having a mechanism as shown in FIG. After performing the polishing, a cleaning is performed to remove the abrasive remaining on the plating layer surface, and the electroless
The magnetic disk substrate according to the present example on which Ni-P plating was performed was completed.

Further, as described below, a magnetic disk generally called a hard disk was completed by a media process of forming a magnetic layer and the like on the magnetic disk substrate. That is, in the media process, an underlayer, a magnetic layer, and a protective layer are sequentially formed on both surfaces of a magnetic disk substrate by using a sputtering method, and further a lubricating layer is formed on the protective layer by using a dipping method. Completed the magnetic disk.

Specifically, first, an underlayer, a magnetic layer, and a protective layer were sequentially formed on the magnetic disk substrate on which electroless Ni-P plating had been applied by a sputtering process. Here, the underlayer is a Cr film, the magnetic layer is a CoNiCr film, and the protective layer is a
C membrane was selected. In the sputtering step, first, the magnetic disk substrate was polished and precision cleaned, and then mounted on a substrate holder of an in-line type sputtering apparatus.

Then, the substrate holder on which the substrate was mounted was introduced into a vacuum chamber, and the substrate temperature was raised to 200 ° C. by heating the substrate holder with a heater. Next, the substrate holder on which the substrate is mounted is moved to a chamber for forming a Cr film in a vacuum, where the underlying layer is formed.
A Cr film (thickness: 100 nm) was formed on the substrate by DC sputtering.

Next, the substrate holder on which the substrate on which the Cr film was formed was mounted was moved to a CoNiCr film forming chamber in a vacuum, and the CoNiCr film (thickness: 60 nm) as the magnetic layer was deposited on the substrate holder.
It was laminated on the Cr film by the C sputtering method. Next, Cr
The substrate holder on which the substrate having the laminate of the film and the CoNiCr film is mounted is moved to a chamber for forming a C film in a vacuum, and the C film (thickness: 30 nm) as a protective layer is deposited by DC sputtering on the laminate. Formed on the CoNiCr film.

After the above series of sputtering steps is completed,
The magnetic recording medium substrate on which the laminate was formed was taken out of the vacuum chamber, and the surface thereof was subjected to tape burnishing with a tape containing an abrasive. Thereafter, a perfluoropolyether-based lubricant was applied to the surface of the laminated body of the magnetic recording medium substrate by a dipping method to form a lubricating layer, thereby completing a hard disk (magnetic disk).

When the holding force of the magnetic disk was measured by a sample vibration magnetometer, it was 2,000 Oe or more. The substrate for a magnetic recording medium (magnetic disk) according to the present embodiment is 90
Since it has a Young's modulus equal to or higher than GPa, deformation of the substrate due to high-speed rotation does not pose a problem when considering high-speed rotation of the magnetic disk.

Further, the magnetic disk substrate according to this embodiment has an electroless Ni-P plating layer having a surface roughness Rmax of 20 nm or less formed on the outermost surface.
Since it has better precision workability than crystallized glass as a substrate material, if an electroless Ni-P plating layer is provided on the substrate and processed, a precise substrate surface with a surface roughness Rmax of 20 nm or less can be obtained. It is easily obtained in a relatively short time.

Further, the electroless Ni-P plating layer according to the present embodiment is intended to prevent the alkali component in the crystallized glass substrate from being eluted into the magnetic recording film (magnetic film) due to the temperature rise during the film formation in the media process. It can serve as a protective film (barrier) for prevention. It has a Young's modulus of 90 GPa or more (corresponding to excellent mechanical strength), and has a surface roughness Rmax
It has a precise substrate surface of 20 nm or less and can prevent the alkali component in the substrate material from being eluted into the information recording layer (magnetic layer) (corresponding to excellent recording characteristics). The magnetic disk of the present embodiment, in which an information recording layer (magnetic layer) is provided, has better mechanical strength and recording characteristics than the conventional one.

[0066]

According to the present invention (claims 1 to 8), a substrate for an information recording medium (for example, a substrate for a magnetic recording medium) is
Since it has a Young's modulus of GPa or higher, or further has a high Knoop strength (corresponding to a nitrogen content of 0.5 wt% or more), when considering a high-speed rotation of an information recording medium (for example, a magnetic disk), the substrate by high-speed rotation Deformation such as deflection does not pose a problem.

The Ni-P layer (particularly, the electroless Ni-P plating layer) according to the present invention is superior in precision workability as compared with oxynitride glass or crystallized glass, and thus Ni-P layer is formed on the rigid substrate. If a P layer is provided and processed, the surface roughness Rmax 20n
A precise substrate surface of m or less can be easily obtained in a relatively short time (claims 1 to 8). For example, forming an electroless Ni-P plating layer on an oxynitride glass substrate or crystallized glass substrate finished to a surface roughness Rmax of about 30 nm, and then performing a plane precision polishing process to adjust the surface state Makes it easy and smooth (surface roughness Rmax 2
A surface (less than 0 nm) is obtained.

In the present invention, when an electroless Ni-P plating layer is formed on a crystallized glass substrate, for example, the surface of the crystallized glass substrate finished to have a surface roughness Rmax of about 30 nm can be used. Covered with electrolytic Ni-P plating layer, then electroless
Since the Ni-P plating layer surface is finally polished, there is no danger that crystals in the material will be removed during the polishing of the substrate surface in the final polishing process, and the precisely polished surface roughness
A substrate surface coated with an electroless Ni-P plating layer having a Rmax of 20 nm or less can be easily obtained.

The Ni-P plating layer (particularly, the electroless Ni-P plating layer) according to the present invention is excellent in heat resistance and non-magnetic properties, and is not affected by temperature rise during the formation of the magnetic recording layer. It is magnetic. In addition, the Ni-P plating layer according to the present invention (especially, electroless
When a material containing an alkali component, such as crystallized glass, is selected as the substrate material for the Ni-P plating layer, the alkali component in the substrate material is added to the information recording layer by increasing the temperature during film formation. It can serve as a protective layer (barrier) for preventing elution.

The information recording medium substrate (eg, magnetic recording medium substrate) according to the present invention has a Young's modulus of 90 GPa or more.
When the pressure is 160 GPa or less, there is no problem that the processing time is increased in processing steps such as lapping and polishing because the substrate material is too hard (claims 3 and 7). Further, the information recording medium substrate (for example, a magnetic recording medium substrate) according to the present invention, if the Knoop hardness is 800 kg / mm ² or more and 1000 kg / mm ² or less, the substrate material is too hard, such as lapping or polishing. In the processing step, there is no problem that the processing time increases (claims 4 and 8).

Further, it has a Young's modulus of 90 GPa or more, or further has a high Knoop hardness (corresponding to a nitrogen content of 0.5 wt% or more) (corresponding to excellent mechanical strength), and has a surface roughness
The present invention has a precise substrate surface of Rmax of 20 nm or less, and can prevent the alkali component in the substrate material from being eluted into the information recording layer (corresponding to excellent recording characteristics).
When an information recording layer (for example, a magnetic layer) is provided on the information recording medium substrate (for example, a magnetic recording medium substrate) according to 8), an information recording medium (for example, Magnetic recording medium) can be obtained (claims 9 to 11).

For example, by providing at least a magnetic layer on the substrate according to any one of claims 5 to 8, a magnetic recording medium having better mechanical strength and recording characteristics than before can be obtained. Can be As such a magnetic recording medium, for example, a magnetic recording medium in which an underlayer, a magnetic layer, a protective layer, and a lubricating layer are provided on a substrate (claim 11) can be mentioned.

According to the present invention, electroless Ni-P is applied to a substrate of oxynitride glass or crystallized glass having high rigidity and hardness.
Plating and then electroless to condition the surface
By performing the planar precision polishing process on the Ni-P plating layer, a smooth surface can be obtained in a relatively short time. That is, electroless Ni-P
The plating layer is superior in precision workability compared to oxynitride glass and crystallized glass, and as a result, a substrate for a magnetic disk with high rigidity and hardness having a precise substrate surface with a surface roughness Rmax of 20 nm or less is easy. In a short time. Therefore, according to the present invention, the mechanical strength of the magnetic disk is improved, and the magnetic disk can be mounted on a hard disk drive device having a disk rotation speed of 10,000 rpm or more, and it is possible to cope with a high density magnetic disk device. Further, in the present invention, when an electroless Ni-P plating layer is applied on a crystallized glass substrate, a substrate for a magnetic disk having a smooth substrate surface without concave portions can be obtained by the final polishing step. .

Further, according to the present invention, it is possible to prevent the alkali component contained in the substrate material of the crystallized glass from being eluted into the magnetic recording layer (magnetic layer), and to obtain a magnetic recording layer having good magnetic recording characteristics. A recording medium can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a magnetic disk according to a first embodiment.

FIG. 2 is a schematic configuration diagram illustrating a magnetic disk according to a second embodiment.

FIG. 3 is a conceptual diagram showing a polishing machine used for polishing an information recording medium substrate.

FIG. 4 is a schematic configuration diagram showing a conventional magnetic disk.

[Explanation of symbols]

1. substrate for oxynitride glass magnetic recording medium 2. electroless Ni-P plating layer 3. underlayer 4. magnetic layer 5. protective layer 6. lubrication layer 7. crystallized glass For magnetic recording media made of glass 8. Glass substrate for magnetic recording media 9. Abrasive material 10. Upper surface plate 11. Lower surface plate

Claims (11)

[Claims] An oxynitride having a Young's modulus of 90 GPa or more and a nitrogen content of 0.5 wt% or more, comprising a nonmagnetic rigid substrate having a coating of an information recording medium formed on a surface facing a recording head. An information recording medium substrate in which a Ni-P layer having a surface roughness Rmax of 20 nm or less is formed on a rigid substrate made of glass. 2. A non-magnetic rigid substrate having a coating of an information recording medium formed on a surface facing a recording head, wherein the rigid substrate is made of crystallized glass having a Young's modulus of 90 GPa or more. Surface roughness Rmax 20nm
An information recording medium substrate on which the following Ni-P layer is formed. 3. The information recording medium substrate according to claim 1, wherein the rigid substrate has a Young's modulus of 160 GPa or less. 4. The rigid substrate has a Knoop hardness of 800 kg / mm.
Substrate for an information recording medium according to claim 1, characterized in that ² or more 1000 kg / mm ² or less. 5. A nonmagnetic rigid substrate having a coating of a magnetic recording medium formed on a surface facing a magnetic head, wherein the oxynitride has a Young's modulus of 90 GPa or more and a nitrogen content of 0.5 wt% or more. A magnetic recording medium substrate in which a Ni-P layer having a surface roughness Rmax of 20 nm or less is formed on a rigid substrate made of glass. 6. A non-magnetic rigid substrate having a coating of a magnetic recording medium formed on a surface facing a magnetic head, wherein the rigid substrate is made of crystallized glass having a Young's modulus of 90 GPa or more. Surface roughness Rmax 20nm
A magnetic recording medium substrate on which the following Ni-P layer is formed. 7. The magnetic recording medium substrate according to claim 5, wherein the rigid substrate has a Young's modulus of 160 GPa or less. 8. The rigid substrate has a Knoop hardness of 800 kg / mm.
Substrate for a magnetic recording medium according to any one of claims 5-7, characterized in that ² or more 1000 kg / mm ² or less. 9. An information recording medium comprising at least an information recording layer provided on the substrate according to claim 1. 10. A magnetic recording medium comprising at least a magnetic layer provided on the substrate according to claim 5. 11. The magnetic recording medium according to claim 10, wherein an underlayer, a magnetic layer, a protective layer, and a lubricating layer are provided on the substrate.