JP2002334423A - Information recording medium, its manufacturing method, and information recording device equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive information recording medium, and an information recording device in which the medium can be loaded by easily and accurately positioning the medium. SOLUTION: Only on one side of a hard disk 10, a magnetic recording film 12 and a protective film 14 are formed. In a magnetic recording device 30, the hard disk 10 is loaded inside a easing 31 having a cover 32. A rotor 33 is provided with a small diameter part 33a around which the through-hole 15 of the hard disk 10 is fitted, and a step 34 for fixing the hard disk 10 to the rotor 33. Of both surfaces of the hard disk 10, a surface having a magnetic recording film 12 is abutted on the step 34 to be fixed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an information recording medium, an information recording device provided with the information recording medium, and a method for manufacturing the information recording medium.

[0002]

2. Description of the Related Art Conventionally, magnetic recording media have been used in personal computers and the like as information recording media. Among magnetic recording media, hard disks are particularly widespread. recent years,
The recording density of this hard disk has been significantly improved.
Therefore, the number of hard disks mounted on the hard disk device tends to decrease. Along with this trend, hard disk drives having only one hard disk have been widely used.

FIG. 7 shows a hard disk mounted on such a hard disk device. FIG. 7 is a schematic diagram showing a hard disk mounted on a conventional hard disk device.

As is well known, the hard disk 1 has a disk-shaped substrate 2 on both front and back sides of which a magnetic recording layer 3 and the like are formed, and a protective film 4 covering the magnetic recording layer 3 is formed. A lubricant (not shown) is applied on the top.
In the center of the substrate 2, a through-hole 5 for attaching to a hard disk device is formed.

[0005] Such a hard disk 1 originally uses both front and rear surfaces as a recording surface for reading and writing information.

[0006]

However, some low-end type personal computers and home electric appliances whose selling point is lower price than performance do not necessarily require a hard disk having a large storage capacity. Many of such products are sufficient if they have a storage capacity for one side of one hard disk. 2. Description of the Related Art A hard disk drive using both sides of a hard disk is provided with a head used for reading, writing, and erasing information on each side. That is, two heads are provided. Therefore, when only one side of the hard disk is used, the head is 1
Only one is needed. If the number of heads is reduced from two to one, the manufacturing cost of the hard disk drive will be reduced accordingly. However, if a hard disk manufactured for double-sided recording was originally used, the cost of manufacturing could not be reduced in proportion to the halving of the storage capacity due to the needless processing of processing the unused surface. There is.

Therefore, when manufacturing a hard disk having a magnetic recording layer only on one side, it is conceivable to omit the processing of the surface on the side opposite to the magnetic recording layer from the processing of the hard disk substrate in order to reduce the manufacturing cost. . For example, it is conceivable to omit a polishing step for keeping the thickness of the hard disk substrate within a predetermined range. in this case,
Since the precision of the thickness of the substrate for a hard disk is coarse, when a magnetic recording medium prepared using the substrate is mounted on a hard disk device, the distance between the magnetic recording surface and the head greatly differs depending on the hard disk device. Such variation in the distance between the magnetic recording surface and the head causes a significant decrease in magnetic recording density when the distance is too large, and causes a head crash when the distance is too narrow.
Therefore, there arises a problem that a new positioning technique for positioning the hard disk with respect to the head needs to be developed.

In order to obtain the plate thickness accuracy required for the glass substrate for double-sided recording, the relative positional relationship between the two head positions and the positions of the recording surfaces on both surfaces of the glass substrate must be accurately set. It is necessary to increase the accuracy of the thickness of the glass substrate by grinding and polishing, and the amount of polishing (Lap) removal must be increased. Therefore, it is difficult to significantly reduce costs.

It is an object of the present invention to provide an inexpensive information recording medium and an information recording apparatus capable of easily and accurately positioning and mounting the information recording medium.

[0010]

According to another aspect of the present invention, there is provided an information recording medium comprising a substrate and an information recording layer formed on the substrate. The recording layer is formed only on one surface of the substrate.

According to the information recording medium of the first aspect, since the information recording layer is formed only on one surface of the substrate,
The manufacturing cost is lower than that in which the information recording layer is formed on both the one surface and the other surface of the substrate, so that the information recording medium can be provided at low cost.

[0012] The information recording medium according to the second aspect is the first aspect.
In the information recording medium described above, a protective film is formed on the other surface of the substrate.

According to the information recording medium of the present invention, since the protective film is also formed on the other surface opposite to the surface on which the information recording layer is formed, the film stress on one surface of the substrate is reduced. And the film stress on the other surface can be balanced, thereby preventing the information recording medium from being warped. Further, the occurrence of corrosion due to the substrate can be prevented.

According to a third aspect of the present invention, there is provided an information recording medium.
The information recording medium according to any one of the preceding claims, further comprising a dummy layer formed on the other surface of the substrate for suppressing warpage of the substrate caused by the information recording layer.

According to the information recording medium of the present invention, since the information recording medium has a dummy layer formed on the other surface of the substrate for suppressing the warpage of the substrate caused by the information recording layer,
The substrate is less likely to warp.

The information recording medium according to the fourth aspect is the first aspect.
The information recording medium according to any one of claims 1 to 3,
The substrate is made of an inorganic material.

The information recording medium according to the fifth aspect is the fourth aspect of the present invention.
In the information recording medium described above, the inorganic material is made of one of glass and crystallized glass.

[0018] The information recording medium according to the sixth aspect is the fifth aspect.
In the information recording medium described above, the substrate is glass formed in a plate shape by a float method, and the information recording layer is formed on a top surface of both surfaces of the substrate.

According to the information recording medium of the present invention, since the glass substrate is formed in a plate shape by the float method, the surface flatness of the substrate is good, so that the information recording medium and the information recording apparatus of the present invention are provided. This eliminates the need for a processing step, a processing device, and the like for increasing the thickness of the substrate to a predetermined accuracy that causes an increase in processing cost required conventionally.

[0020] The information recording medium according to claim 7 is claim 1.
7. The information recording medium according to any one of claims 1 to 6,
The thickness of the substrate is 0.1 mm to 3.0 mm.

According to the information recording medium of the present invention, since the board thickness of the board is 0.1 mm to 3.0 mm, the rigidity of the board is maintained and the weight is light.
The miniaturization is promoted with the power saving of the information recording device.

According to another aspect of the present invention, there is provided an information recording apparatus, comprising: a rotating body having a step portion concentrically; and a rotating member having the step portion concentrically fixed to the step portion.
An information recording device comprising the information recording medium described in the paragraph, wherein the one side of the information recording medium is in contact with the step portion.

According to the information recording apparatus of the present invention, the surface of the information recording medium having the information recording layer is fixed in contact with the stepped portion, so that the information recording layer is independent of the thickness of the information recording medium. The positioning of the side surface on which is formed only requires the positioning of the step portion, so that the information recording medium can be easily and accurately positioned.

The information recording apparatus according to the ninth aspect of the present invention provides the information recording apparatus according to the eighth aspect.
In the above information recording apparatus, the number of the information recording medium is one.

In order to achieve the above object, a method for manufacturing an information recording medium according to claim 10 is a method for manufacturing an information recording medium comprising a substrate and an information recording layer formed on the substrate. An information recording layer forming step of forming the information recording layer only on one surface of the substrate.

According to the tenth aspect of the present invention, since the information recording layer is formed only on one side of the substrate, the information recording layer is formed on both one side and the other side of the substrate. An information recording medium can be manufactured at a lower manufacturing cost than that of the information recording medium.

[0027] According to a eleventh aspect of the present invention, in the manufacturing method of the tenth aspect, a precise polishing step of precisely polishing one surface of the substrate before executing the information recording layer forming step. It is characterized by having.

According to a twelfth aspect of the present invention, in the manufacturing method of the eleventh aspect, in the manufacturing method of the eleventh aspect, the precision polishing step is polished using abrasive grains having a hardness smaller than a material of the substrate. I do.

According to a thirteenth aspect of the present invention, in the method for manufacturing an information recording medium according to the twelfth aspect, a protective layer is formed on a non-polished surface opposite to a surface on which the information recording layer is formed. A method for manufacturing an information recording medium, comprising the steps of:

According to the method for manufacturing an information recording medium according to the thirteenth aspect, since the protective layer is formed on the non-polished surface opposite to the surface on which the information recording layer is formed, the film on the surface on which the information recording layer is formed is formed. The balance between the stress and the film stress on the non-polished surface on which the protective layer is formed can be balanced, so that it is possible to manufacture an information recording medium that is less likely to warp and that prevents chemical deterioration of the glass surface.

According to a fourteenth aspect of the present invention, in the method for manufacturing an information recording medium according to the twelfth aspect, the information recording medium is provided on a non-polished surface opposite to a surface on which the information recording layer is formed. A dummy layer forming step of forming a dummy layer for suppressing the warpage of the substrate caused by the layer.

According to the method for manufacturing an information recording medium of the present invention, a dummy for suppressing the warpage of the substrate caused by the information recording layer is provided on the non-polished surface opposite to the surface on which the information recording layer is formed. Since the layer is formed, it is possible to manufacture an information recording medium in which the substrate is less likely to warp.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An information recording medium according to an embodiment of the present invention, an information recording apparatus provided with the information recording medium, and a method for manufacturing the information recording medium will be described in detail below with reference to the drawings.

FIG. 1 is a side view showing a schematic configuration of an information recording medium according to the first embodiment of the present invention.

In FIG. 1, a hard disk 10 as an information recording medium is mounted on a hard disk device attached to a personal computer or the like. The hard disk 10 includes a disk-shaped substrate 11 and a magnetic recording film 12. A through hole 15 is formed in the center of the hard disk 10. The through-hole 15 is externally fitted to a rotating part of the hard disk drive of FIG. 3 described later. Note that the thickness of the magnetic recording film 12 is greatly exaggerated relative to the thickness of the substrate 11 for ease of explanation.

The substrate 11 is made of glass and has two surfaces 11
a, 11b (on the paper surface, upper surface 11a and lower surface 11b), the magnetic recording film 12 described later only on the upper surface 11a (one surface).
Are formed. A precision polished surface 13 is formed on the upper surface 11a. In the present invention, as described later, the hard disk 10 does not need to consider the accuracy of the thickness,
Polishing may be performed with abrasive grains having a hardness smaller than the material of the substrate 11. The abrasive used for grinding is diamond or alumina abrasive, and the abrasive used for subsequent polishing is cerium oxide, zirconium oxide, manganese oxide, silicon dioxide abrasive, or the like. Among them, cerium oxide having a large polishing ability is preferable. Alternatively, only polishing may be performed without grinding. The thickness of the substrate 11 is 0.1 mm to 3.0 mm.
It is preferable that If the thickness is 0.1 mm or more, insufficient rigidity is resolved, so that occurrence of fluttering due to insufficient rigidity can be prevented. If the thickness is 3.0 mm or less, the weight of the hard disk itself does not hinder the miniaturization and power saving of the hard disk device, and it is easy to cope with the miniaturization and power saving of the hard disk device. In particular, in a mobile hard disk device, the weight of the hard disk itself has a large effect, but if the thickness of the substrate 11 is in the range of 0.1 mm to 3.0 mm, it can be dealt with without inconvenience.

A magnetic recording film 12 is formed on the precision polished surface 13, and a protective film 14 is formed on the magnetic recording film 12 so as to cover it. The magnetic recording film 12 is composed of multiple layers, and the seed layer 12
a, an underlayer 12b, and a magnetic recording layer 12c (information recording layer). In each of these layers, for example, the seed layer 12a is made of titanium or the like, and the underlayer 1
2b is made of chromium or the like, and the recording layer 12c is made of a Co-based alloy or the like. Further, protective film 14 is made of carbon, hydrogenated carbon, silicon carbide, or the like. An organic lubricant 16 such as perfluoroalkyl polyether is applied on the protective film 14.

FIG. 2 is a side view showing a schematic configuration of an information recording medium according to a second embodiment of the present invention.

In FIG. 2, portions common to FIG. 1 are denoted by the same reference numerals.

Hard disk 20 as information recording medium
The magnetic recording film 12 and the protective film 14 are formed on the upper surface 11a of the hard disk 10 according to the first embodiment. On the other hand, an underlayer 22 is formed on the lower surface 11b, and a protective film 24 is formed so as to cover the underlayer 22.

The hard disk 20 is manufactured as follows.

First, if necessary, the upper surface 11a of the substrate 11 is ground with abrasive grains such as alumina or diamond and polished precisely to form a precision polished surface 13 having a surface roughness (Ra) of 1 nm or less. A precision polishing process is performed. At this time, abrasive grains used for precision polishing have a hardness smaller than the material of the substrate 11. Next, a seed layer forming step of forming the seed layer 12a on the precision polished surface 13 by sputtering is performed. Subsequently, an underlayer 12b is formed on the seed layer 12a, and
An underlayer forming step of forming an underlayer 22 of the same material is also performed on 1b. The underlayers 12b and 22 are also formed by sputtering.

A recording layer forming step of forming a magnetic recording layer 12c on the underlayer 12b on the upper surface 11a by sputtering is performed. Further, a protective film 14 is formed on the magnetic recording layer 12c by the CVD method or the like so as to cover the magnetic recording layer 12c, and a protective film 24 is also formed on the underlayer 22 on the lower surface 11b so as to cover the underlayer 22. A protective film forming step is performed. Further, an organic lubricant 26 is applied to the surfaces of the protective films 14 and 24 by dipping the substrate. Hard disk 2 as described above
0 is manufactured.

Although the substrate 11 has been described as being made of glass, other materials such as crystallized glass, ceramics, and metals may be used. Further, an organic resin substrate may be used. As the organic resin, for example, a polyolefin resin is preferably used. When such a resin material is used as the substrate, it is preferable to cover the resin surface with a silicon dioxide film in order to suppress the deposition of impurity gas in the recording film forming step by sputtering.

When the substrate 11 is glass or crystallized glass, the substrate material may be formed into a molten material of the substrate material and then cut or polished, or may be formed by a float method, a fusion down draw method, or the like. What melt | dissolved the board | substrate material in the plate shape by the method, slot down draw method, etc. may be used. When the substrate is formed by a float method using, for example, tin as the molten metal, the magnetic recording film 12 is formed on a surface (top surface) of the substrate that does not contact the molten tin.

When the edge of the glass or crystallized glass substrate is polished, it is preferable that the edge is polished in a single wafer system. As a method of edge polishing, for example, there are a wet method of polishing with a brush using a grindstone or an abrasive and a dry method of melting with a laser.

A hard disk drive having the above-described hard disk 10 will be described with reference to FIGS.

FIG. 3 is an exploded perspective view showing a schematic configuration of the information recording apparatus according to the embodiment of the present invention. FIG. 4 is a partial cross-sectional view taken along line IV-IV in FIG.

The hard disk device 30 as an information recording device includes a housing 31, a hard disk 10 mounted inside the housing 31, and a cover 32 attached to the housing 31.

The housing 31 has a spindle motor (not shown).
Is attached, and the rotating body 33 of the spindle motor
A small-diameter portion 33 a into which the through-hole 15 of the hard disk 10 fits outside, and a step portion 34 for fixing the hard disk 10 to the rotating body 33 are formed. The small diameter portion 33a is slightly smaller than the diameter of the through hole 15. On the other hand, the outer diameter of the step portion 34 is larger than the diameter of the through hole 15 of the hard disk 10. Therefore, the hard disk 10 can be fixed to the rotating body 33 concentrically. As shown in FIG. 4, the hard disk 10 is disposed such that a surface having the magnetic recording film 12 (hereinafter, referred to as a magnetic recording surface) faces a bottom surface 31 a of the housing 31. That is, the magnetic recording surface is in contact with and fixed to the step 34.

A support shaft 35 is fixed to the bottom surface 31a. An arm 36 is attached to a lower portion of the support shaft 35 so as to be rotatable about the support shaft. From the free end 36a of the arm 36, a suspension 37 extends below the hard disk 10. A head 38 is mounted on a tip 37 a of the suspension 37. The head 38 is disposed so as to contact the magnetic recording surface. The head 38 writes information on the magnetic recording film 12 while moving according to the rotation of the arm 36.
The information written on the magnetic recording film 12 is read or erased.

As described above, since the magnetic recording surface of both surfaces of the hard disk 10 abuts on and is fixed to the step 34, the positioning accuracy of the magnetic recording film 12 in the vertical direction from the bottom surface 31a is It depends only on the accuracy of the position, and is not affected at all by the accuracy of the thickness of the hard disk 10. Therefore, the hard disk 10 can be easily and accurately positioned and mounted on the hard disk device 30 without precisely controlling or adjusting the thickness.
The surface having the magnetic recording film 12 is the bottom surface 31 of the housing 31.
a, the hard disk drive 3
Dust and foreign matter falling in an atmosphere of an assembly environment of 0 hardly adhere to the magnetic recording surface. Therefore, the assembly yield of the hard disk device 30 does not decrease due to dust or the like attached to the magnetic recording surface, and the assembly yield improves. Further, the reliability of the hard disk device 30 is also improved.

FIG. 5 is a partial sectional view showing a schematic configuration of a modification of the hard disk device 30 of FIG.

In FIG. 5, among the components of the hard disk device 40, those common to the hard disk device 30 of FIG. 3 are denoted by the same reference numerals (the same applies to FIG. 6 described later). The difference between the hard disk device 40 and the hard disk device 30 is that the magnetic recording surface of the hard disk 10 is mounted in a direction facing the cover 32 opposite to the bottom surface 31 a of the housing 31.
This is the point that the shape of the rotating body 43 for fixing 0 is different.

The hard disk 1 is located at the upper end of the rotating body 43.
Step portion 44 having an outer shape larger than the diameter of through hole 15 of zero
Is formed, and a portion below the step portion 44 is formed in the through hole 1.
A small diameter portion 43a smaller than the diameter of No. 5 is formed. The magnetic recording surface side of both surfaces of the hard disk 10
Abuts and is fixed. Since the magnetic recording surface is attached so as to face the cover 32, the head 37 is disposed so as to contact the magnetic recording surface from above the hard disk 10. Therefore, also in this modified example, the positioning accuracy of the magnetic recording surface depends only on the positioning accuracy of the step 34, and is not affected by the thickness accuracy of the hard disk 10 at all. That is, it is possible to accurately and easily mount the hard disk drive 30 on the hard disk drive 30 without precisely controlling or adjusting the thickness of the substrate 11 over the thickness of the hard disk 10.

In FIG. 5, the hard disk 1
0 is brought into contact with the step portion 43, and then the small-diameter portion 43a is
a.

FIG. 6 is a partial sectional view showing a schematic configuration of still another modification of the hard disk device 30 of FIG.

In FIG. 6, the hard disk device 50 is different from the hard disk device 30 in that the hard disk device 50 includes two hard disks 10, the shape of the rotating body 53 is different, and that each hard disk 10 has one head 38. A point, that is, a point having two heads 38.

The rotating body 53 has a disk-shaped large-diameter portion 54 having a diameter larger than the diameter of the through hole 15 of the hard disk 10 at a position lower than the upper end. This large diameter portion 54
Of the two steps 54a and 54b formed by
The magnetic recording surface of the hard disk 10 is in contact with the step 54a facing the bottom surface 51a of the housing 51 of the hard disk device. The magnetic recording surface of another hard disk 10 is in contact with the other step 54b.

The two heads 38, 38 are arranged in a gap between the two hard disks 10, 10. Also in this modification, since the magnetic recording surface of both surfaces of the hard disk 10 abuts and is fixed to the step portions 54a and 54b, the positioning accuracy of the magnetic recording surface is reduced by the step portions 54a and 54b.
And the thickness accuracy of the hard disk 10 is not affected at all.

[0061]

Next, embodiments of the present invention will be described specifically.

(Glass substrate for hard disk) Thickness 0.64 mm ± 0.05 mm formed by float method
The plate-shaped aluminosilicate glass is cut by a known method, processed into a disk, and has an outer diameter of 65 mmφ and an inner diameter of 26 mm.
Shaped as a glass substrate for φ hard disk.

The glass substrate was chamfered on both inner and outer peripheral edges with a sheet-type chamfering device, and washed to remove foreign substances and dirt attached after the chamfering.

Next, only one side was precisely polished by a known method using an abrasive mainly composed of cerium oxide, and the surface was mirror-finished. Thereafter, cleaning was performed a plurality of times by a known method using pure water or a chemical solution to clean the surface, and in order to further increase mechanical strength, chemical strengthening was performed by an ion exchange method according to a known method.

The glass substrate after the chemical strengthening was cleaned a plurality of times by a known method using a pure or chemical solution to clean the surface.

The glass substrate thus obtained has a thickness of 0.62 mm ± 0.06 mm, and the thickness accuracy is
It was larger than ± 0.025 mm than the thickness accuracy of the conventional hard disk glass substrate using both surfaces. However, plate thickness variation (parallelism) is 10
A sufficient parallelism was secured for a substrate for a hard disk with a thickness of less than μm. The polished surface had a surface roughness Ra <10 μm measured by AFM (atomic force microscope).
At 1.0 nm and Rmax <10 nm, the surface was smooth enough to be used as a recording surface of a hard disk.

(Preparation of Hard Disk) Using a glass substrate for a hard disk prepared by the above-described method, the surface polished precisely was subjected to a sputtering method of a sheet type (Intev).
ac MDP250B), Ti seed layer, C
After forming an r-based underlayer and a CoCr-based magnetic recording layer by sputtering, a C film was further formed by ion beam deposition.

On the other hand, for the surface not polished,
Seed layer, Cr-based underlayer, CoCr
When the system magnetic recording layer was formed by sputtering, a Cr layer having substantially the same thickness was formed. When a C film was formed by sputtering on the surface on which precision polishing was performed, a C film was also formed by sputtering on a surface on which precision polishing was not performed.

As described above, the film stress on both surfaces of the substrate can be balanced by forming the carbon film laminated film on the Cr-based underlayer as a dummy film on the surface on which precision polishing has not been performed. Can be prevented from occurring.
In addition, elution of alkali ions from the substrate and occurrence of corrosion due to corrosion of the dummy Cr layer can be prevented.

Thereafter, a fluorocarbon-based lubricant is applied to the surface of the hard disk by a dip method, and burnished on the polished surface to remove foreign substances and dirt on the surface. Hard disk.

(Assembly of Hard Disk Drive) A series of components for securely holding and positioning the head such as a head, a suspension and an actuator so that the element of the head for reading and writing information faces upward with respect to the housing base. It was arranged on the housing base by a known method.

Next, the hard disk was mounted on the rotating body such that the recording surface of the hard disk was directed toward the housing base of the hard disk device. The hard disk was mounted such that the hard disk fixing surface of the rotating body and the recording surface side of the hard disk were in contact with each other, and then the hard disk was fixed to the rotating body by a known method.

Other components were arranged by a known method to complete a hard disk drive. The hard disk device manufactured in this way was capable of performing magnetic recording with the same reliability as the conventional hard disk device.

[0074]

As described in detail above, according to the information recording medium of the first aspect, since the information recording layer is formed only on one side of the substrate, one side of the substrate and the other side of the substrate are formed. The manufacturing cost is lower than that in which an information recording layer is formed on both sides, and an information recording medium can be provided at a low cost.

According to the information recording medium of the present invention, since the protective film is also formed on the other surface opposite to the surface on which the information recording layer is formed, the film stress on one surface of the substrate is reduced. And the film stress on the other surface can be balanced, thereby preventing the information recording medium from being warped. Further, the occurrence of corrosion due to the substrate can be prevented.

According to the third aspect of the present invention, since the information recording medium has a dummy layer formed on the other surface of the substrate for suppressing the warpage of the substrate caused by the information recording layer,
The substrate is less likely to warp.

According to the information recording medium of the present invention, since the glass substrate is formed in a plate shape by the float method, the substrate has good surface flatness. This eliminates the need for a processing step, a processing device, and the like for increasing the thickness of the substrate to a predetermined accuracy that causes an increase in processing cost required conventionally.

According to the information recording medium of the present invention, since the thickness of the substrate is 0.1 mm to 3.0 mm, the rigidity of the substrate is maintained and the weight is light.
The miniaturization is promoted with the power saving of the information recording device.

According to the information recording apparatus of the present invention, the surface of the information recording medium having the information recording layer is fixed in contact with the step portion, so that the information recording layer is fixed regardless of the thickness of the information recording medium. The positioning of the side surface on which is formed only requires the positioning of the step portion, so that the information recording medium can be easily and accurately positioned.

According to the tenth aspect of the present invention, since the information recording layer is formed only on one surface of the substrate, the information recording layer is formed on both one surface and the other surface of the substrate. An information recording medium can be manufactured at a lower manufacturing cost than that of the information recording medium.

According to the method for manufacturing an information recording medium according to the thirteenth aspect, since the protective layer is formed on the non-polished surface opposite to the surface on which the information recording layer is formed, the film on the surface on which the information recording layer is formed is formed. The balance between the stress and the film stress on the non-polished surface on which the protective layer is formed can be balanced, so that it is possible to manufacture an information recording medium that is less likely to warp and that prevents chemical deterioration of the glass surface.

According to the method of manufacturing an information recording medium of the present invention, a dummy for suppressing the warpage of the substrate caused by the information recording layer is provided on the non-polished surface opposite to the surface on which the information recording layer is formed. Since the layer is formed, it is possible to manufacture an information recording medium in which the substrate is less likely to warp.

[Brief description of the drawings]

FIG. 1 is a side view showing a schematic configuration of an information recording medium according to a first embodiment of the present invention.

FIG. 2 is a side view showing a schematic configuration of an information recording medium according to a second embodiment of the present invention.

FIG. 3 is an exploded perspective view showing a schematic configuration of the information recording apparatus according to the embodiment of the present invention.

FIG. 4 is a partial cross-sectional view taken along line IV-IV of FIG. 3;

FIG. 5 is a partial sectional view showing a schematic configuration of a modified example of the hard disk device 30 of FIG.

FIG. 6 is a partial cross-sectional view showing a schematic configuration of still another modified example of the hard disk device 30 of FIG.

FIG. 7 is a schematic diagram showing a hard disk mounted on a conventional hard disk device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Hard disk 11 Substrate 11a Upper surface 11b Lower surface 12 Magnetic recording film 12a Seed layer 12b, 22 Underlayer 12c Magnetic recording layer 14, 24 Protective film 30, 40 Hard disk device 33, 43, 53 Rotating body 34, 44, 54a, 54b Step portion

Claims (14)

[Claims] 1. An information recording medium comprising a substrate and an information recording layer formed on the substrate, wherein the information recording layer is formed only on one surface of the substrate. Medium. 2. The information recording medium according to claim 1, wherein a protective film is formed on the other surface of said substrate. 3. The information recording medium according to claim 1, further comprising a dummy layer formed on the other surface of the substrate, for suppressing warpage of the substrate caused by the information recording layer. 4. The information recording medium according to claim 1, wherein the substrate is made of an inorganic material. 5. The information recording medium according to claim 4, wherein said inorganic material is made of one of glass and crystallized glass. 6. The substrate according to claim 5, wherein the substrate is glass formed in a plate shape by a float method, and the information recording layer is formed on a top surface of both surfaces of the substrate. Information recording medium. 7. The board thickness of the substrate is 0.1 mm to 3.0 m.
7. The method according to claim 1, wherein m is
Information recording medium according to the item. 8. An information recording apparatus comprising: a rotating body having a step concentrically; and an information recording medium according to claim 1 fixed concentrically to said step. The information recording medium is characterized in that the one surface is in contact with the step. 9. The information recording apparatus according to claim 8, wherein the number of the information recording medium is one. 10. A method of manufacturing an information recording medium comprising a substrate and an information recording layer formed on the substrate, wherein the information recording layer is formed only on one surface of the substrate. A method for manufacturing an information recording medium, comprising: 11. The method of manufacturing an information recording medium according to claim 10, further comprising a precision polishing step of precisely polishing one surface of said substrate before executing said information recording layer forming step. 12. The method for manufacturing an information recording medium according to claim 11, wherein said precision polishing step is performed by using abrasive grains having a hardness smaller than that of a material of the substrate. 13. The method of manufacturing an information recording medium according to claim 12, further comprising a protective layer forming step of forming a protective layer on a non-polished surface opposite to a surface on which the information recording layer is formed. 14. A method for forming a dummy layer on a non-polished surface opposite to a surface on which the information recording layer is formed, the method including forming a dummy layer for suppressing warpage of the substrate caused by the information recording layer. 13. The method for manufacturing an information recording medium according to claim 12, wherein: