JP2000200414A - Glass base board for information recording medium and its manufacture; magnetic recording medium using such base board and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable high-density recording and reproduction while maintaining stable and excellent characteristic by setting roughness on the main surface of a glass base board at a specific value or less. SOLUTION: The roughness on the main surface of a glass base board is set at Rmax<=15 nm, Ra<=1 nm, and Rq<=1.5 nm. Rq is a root-mean-square root(RMS). The glass base board made of alumino-silicate glass cut out in a shape of a disk is ground with a diamond stone, and is further ground by brushing so that the surface roughness on the end face is approximately 1 μm at Rmax and 0.3 μm at Ra. After sandblast, lapping with alumina abrasive grain, and No.1 to No.3 grinding with abrasive powder, chemical strengthening is performed and then the glass base board 1 is obtained. Formed successively on the base board 1 are the first substrate 2, second substrate 3, ruggedness formed layer 4, third substrate 5, magnetic layer 6, protective layer 7 and a lubricant layer 8. The intrasurface distribution in the magnetic recording medium and the variance of the magnetic recording medium within a pallet are suppressed, and the stability is thereby improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium capable of high-density recording and reproduction, a method of manufacturing the same, a glass substrate for an information recording medium used for the magnetic recording medium, and a method of manufacturing the same. When manufacturing a magnetic recording medium by sputtering, the present invention relates to a magnetic recording medium capable of performing high-density recording / reproduction by suppressing variations in the magnetic characteristics of each magnetic recording medium in a pallet or variations in the in-plane magnetic characteristics of each magnetic recording medium.

[0002]

2. Description of the Related Art In recent years, there has been a demand for a magnetic disk capable of coping with higher density recording. In order to achieve high-density recording on a magnetic disk, it is important to reduce the flying height of the magnetic head relative to the surface of the magnetic recording medium. Recently, it has been required that the flying height be 0.2 to 0.1 μm or less. Therefore, magnetic disks such as those disclosed in JP-A-5-303735 and JP-A-8-293177 have been developed as magnetic disks capable of responding to this demand for high-density recording.

The magnetic disk disclosed in JP-A-5-303735 has an annular substrate (glass substrate) having a surface roughness Ra of 1n.
m and a flatness of 1 μm or less,
The flying height of the magnetic head with respect to the magnetic disk is reduced to enable high-density recording. In this publication, a polishing technique for making the surface roughness of an annular substrate (glass substrate) extremely smooth, and a surface having a surface roughness of 0.3 nm or less for Ra and 5 nm or less for Rmax were super-smooth finished. A glass substrate is disclosed.

Japanese Patent Application Laid-Open No. 8-293177 discloses a CSS in which a head rests on a medium when a magnetic disk is started and stopped.
A magnetic disk mounted on a dynamic head loading type magnetic disk drive in which the head separates from the disk when stopped, instead of the drive, is disclosed. This magnetic disk has a magnetic layer having a super smooth finished magnetic surface and a super smooth finished protective surface formed on a super smooth finished substrate as an example, thereby reducing the magnetic space between the head and the medium. Thus, high-density recording is enabled. Further, this publication also discloses a technique for reducing the distance (effective flying height) between the head of the magnetic layer and the head by reducing the thickness of the protective layer.

[0005]

By the way, in the above-mentioned conventional magnetic recording medium, by setting each of Rmax and Ra to a predetermined value or less, the magnetic distance between the head and the medium can be made sufficiently small. became.
However, according to the study of the present inventors, coercive force and S
It has been found that magnetic characteristics such as / N and recording / reproducing characteristics do not always sufficiently satisfy recent severe requirements. That is, it was found that even if the conditions such as the surface roughness of the glass substrate and the magnetic layer formed thereon were made uniform, it was not always possible to obtain a magnetic disk having good magnetic properties. As a result of the present inventors' earnest research on this cause, the cause is caused by the variation in the surface roughness of the glass substrate, and this variation disturbs the crystal growth of the thin film formed thereon, thereby deteriorating the magnetic characteristics and recording / reproducing. It was concluded that the properties would be degraded. That is, the state of the surface of the glass substrate (surface roughness and variations in surface roughness) is closely related to the crystal grains of the underlying layer and the magnetic layer formed thereon, and has good magnetic properties and high density recording / reproducing. It has been clarified that in order to obtain a possible magnetic recording medium, it is necessary to suppress the variation in the surface roughness of the glass substrate and to make the crystal grains of the thin film formed thereon uniform. On the other hand, in the above-described conventional magnetic recording medium, since the relationship between Rmax and Ra was not taken into account, even when a very smooth substrate was used, a plurality of magnetic recording media were manufactured. It was found that there was variation in each magnetic characteristic. That is,
It has been found that even if the conditions such as the surface roughness of the glass substrate and the magnetic layer formed thereon are made uniform, a magnetic disk having always stable and good magnetic properties cannot be obtained. In particular, the variation in the magnetic characteristics was remarkable when a magnetic disk was manufactured by an in-line continuous sputtering method.

The present inventors have conducted intensive studies on the cause, and found that the cause is the surface roughness Rmax of each glass substrate.
(Rmax / Ra) has not been determined, and it has been concluded that variations in the magnetic characteristics of each magnetic disk will occur with the fluctuation of this relationship (Rmax / Ra).

The present invention has been made based on the results of this elucidation, and includes a glass substrate used for an information recording medium such as a magnetic disk and an optical disk, and a method of manufacturing the same.
It is another object of the present invention to provide a magnetic recording medium capable of high-density recording and reproduction while maintaining stable and good magnetic characteristics, and a manufacturing method capable of stably manufacturing the magnetic recording medium.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention essentially provides a glass substrate having a surface roughness and a variation thereof within a predetermined range, an underlayer formed on the glass substrate, By making the grains of the layer uniform,
A magnetic recording medium having good magnetic properties and capable of high-density recording and reproduction is obtained, and the surface roughness (Rmax, Ra) of a glass substrate and the relationship between the Rmax and Ra (Rmax / Ra), etc. By controlling the magnetic recording medium to a stable and good magnetic property and a high-density recording / reproducing magnetic recording medium,
Specifically, it has the following configuration.

The first means is that the glass substrate main surface has a surface roughness of Rmax ≦ 15 nm, Ra ≦ 1 nm, Rq ≦ 1.5 nm.
nm (where Rq is root-mean-square roughness (= RMS)).

A second means is that the surface roughness of the main surface of the glass substrate is Rmax ≦ 10 nm, Ra ≦ 0.5 nm, Rq
The glass substrate for an information recording medium according to claim 1, wherein ≤ 0.7 nm.

The third means is that the surface roughness of the main surface of the glass substrate is Rmax ≦ 5 nm, Ra ≦ 0.3 nm, Rq ≦
The glass substrate for an information recording medium according to claim 1, wherein the glass substrate has a thickness of 0.4 nm.

4. The information recording medium according to claim 1, wherein a ratio (Rmax / Ra) of a surface roughness of the main surface of the glass substrate is 30 or less. It is a glass substrate.

According to a fifth aspect, in a magnetic recording medium having a thin film including at least a magnetic layer on a glass substrate, the glass substrate for an information recording medium according to claim 1 is used as the glass substrate. This is a magnetic recording medium.

A sixth means is that the thin film is composed of substantially uniform crystal grains by controlling the surface roughness of the glass substrate, and the average crystal grain size of the crystal grains is 5 to 5.
The magnetic recording medium according to claim 5, wherein the thickness is 30 nm.

According to a seventh means, in a magnetic recording medium having a thin film including at least a magnetic layer on a glass substrate, the glass substrate has a main surface having a surface roughness Rmax ≦ 15 nm,
a ≦ 1 nm, the surface roughness ratio (Rmax / Ra) is 30 or less, and the thin film is composed of substantially uniform crystal grains by controlling the surface roughness of the glass substrate. Has a mean crystal grain size of 5 to 30 nm.

According to an eighth means, the surface roughness of the main surface of the glass substrate is Rmax ≦ 10 nm, Ra ≦ 0.5 nm, and the ratio of surface roughness (Rmax / Ra) is 30 or less. Item 8. A magnetic recording medium according to Item 7.

The ninth means is characterized in that the surface roughness of the main surface of the glass substrate is Rmax ≦ 5 nm, Ra ≦ 0.3 nm, and the ratio of surface roughness (Rmax / Ra) is 30 or less. Item 8. A magnetic recording medium according to Item 7.

The tenth means is that the crystal grains of the thin film are
6. A half-width at a point where the crystal grain size of the thin film is most distributed is 20 nm or less, when a crystal grain size distribution existing in a micron square is measured.
10. A magnetic recording medium according to any one of claims 1 to 9.

11. The magnetic recording medium according to claim 5, wherein the thin film has an underlayer formed between the glass substrate and the magnetic layer. It is.

The twelfth means is characterized in that an unevenness forming layer made of a low melting point metal is formed between the glass substrate and the magnetic layer. It is a magnetic recording medium.

A thirteenth means is the magnetic recording medium according to claim 12, wherein the surface roughness ratio Rq / Ra of the unevenness forming layer is 1.5 or less.

The fourteenth means is the magnetic recording medium according to claim 12 or 13, wherein the surface roughness of the unevenness forming layer is 10 to 50 nm in Rmax.

A fifteenth means is a step of lapping a disc-shaped glass substrate, and after the step, the surface roughness of the glass substrate is Rmax ≦ 15 nm, Ra ≦ 1 nm, Rq ≦ 1.
5 nm (where Rq is root mean square roughness (= RM
(S)) a step of mirror-polishing using a polishing liquid containing polishing abrasive grains having a particle diameter selected in advance so as to satisfy (S)).

According to a sixteenth aspect, a thin film including at least a magnetic layer is formed on a glass substrate manufactured by the method for manufacturing a glass substrate for an information recording medium according to the fifteenth aspect of the present invention. Composed of crystal grains,
A method for manufacturing a magnetic recording medium, comprising a thin film forming step of forming a film so that the average crystal grain size of the crystal grains is 5 to 30 nm.

The seventeenth means is that the surface roughness of the glass substrate on which the thin film including at least the magnetic layer is formed is Rmax.
≦ 15 nm, Ra ≦ 1 nm, Rq ≦ 1.5 nm, and a glass substrate surface treatment step, wherein the crystal grains constituting the thin film are composed of substantially uniform crystal grains on the main surface of the glass substrate. The average crystal grain size of the crystal grains is 5
And forming a thin film to a thickness of 30 nm.

The eighteenth means is that the surface roughness of the glass substrate on which the thin film including at least the magnetic layer is formed is Rmax.
≦ 15 nm, Ra ≦ 1 nm, surface roughness ratio (Rmax /
A glass substrate surface treatment step of making Ra) 30 or less; and crystal grains constituting the thin film on the main surface of the glass substrate are formed of substantially uniform crystal grains, and the average crystal grains of the crystal grains are formed. And forming a thin film having a diameter of 5 to 30 nm.

The nineteenth means is that the surface roughness of the main surface of the glass substrate is Rmax ≦ 15 nm, Ra ≦ 1.3 nm, Rmax
A glass substrate for an information recording medium, wherein x / Ra ≧ 10.

A twentieth means is that the surface roughness of the glass substrate main surface is Rmax ≦ 10 nm, Ra ≦ 0.8 nm,
22. The glass substrate for an information recording medium according to claim 21, wherein max / Ra ≧ 10.5.

A twenty-first means is a magnetic recording medium having a thin film including at least a magnetic layer on a glass substrate, wherein the glass substrate for an information recording medium according to claim 21 or 22 is used as the glass substrate. This is a magnetic recording medium.

[0030] The twenty-second means may be defined by claim 19 or claim 2.
Preparing a glass substrate for an information recording medium according to 0,
Forming a thin film including at least a magnetic layer on the glass substrate.

A twenty-third means is the method of manufacturing a magnetic recording medium according to claim 22, wherein the thin film is formed by an in-line continuous sputtering method.

[0032]

[Embodiment] Example 1 FIG. 1 is a partial sectional view showing a configuration of a magnetic recording medium according to Example 1 of the present invention. Hereinafter, a magnetic recording medium according to the present invention and a method of manufacturing the same will be described with reference to FIG.

In FIG. 1, this magnetic recording medium comprises a first underlayer 2, a second underlayer 3,
This is a magnetic disk on which a third underlayer 5 composed of a texture layer 4, a Cr layer 5a and a CrMo layer 5b, a magnetic layer 6, a protective layer 7, and a lubricating layer 8 are formed. Less than,
The method of manufacturing the magnetic disk will be described in the order of the steps, and the detailed configuration will be described.

(1) Roughing Step First, a glass substrate made of aluminosilicate glass having a diameter of 96 mmφ and a thickness of 3 mm cut out from a sheet glass formed by a downdraw method with a grinding wheel is used.
Grinding with a relatively rough diamond wheel
It was molded to a diameter of 15 mm and a thickness of 15 mm.

In this case, in place of the down-draw method, a sheet glass formed by a float method and cut out into a disk shape in the same manner as described above, or a molten glass is formed by using an upper mold,
A disk-shaped glass body may be obtained by direct pressing using a lower mold and a body mold.

As the aluminosilicate glass, 57% to 74% of SiO 2, ZnO 2
0 to 2.8%, Al2O3 3 to 15%, LiO2 7 to 16%, and Na2O 4 to 14% as a main component.
O2: 67.0%, ZnO2: 1.0%, Al2O3:
9.0%, LiO2: 12.0%, Na2O: 10.0
%) As a main component.

Next, both surfaces of the glass substrate were ground one by one with a diamond grindstone having a finer grain size than the grindstone. The load at this time was about 100 kg. As a result, the surface roughness of both surfaces of the glass substrate is set to 10 μm in Rmax.
m.

Next, a hole is made in the center of the glass substrate using a cylindrical grindstone, and the outer peripheral end surface is also ground to a diameter of 95 mmφ. Then, the outer peripheral end surface and the inner peripheral surface are subjected to predetermined chamfering. did. At this time, the end surface of the glass substrate (the side surface and the surface roughness of the chamfered portion 9 were about 4 μm in Rmax).

(2) Mirror Processing of End Surface Next, the surface roughness of the end surface portion (angular portion, side surface, and chamfered portion) of the glass substrate is 1 μm in Rmax and Ra in brush polishing while rotating the glass substrate. 0.3μ
m. This end-face mirror finishing step is effective for preventing sub-film defects caused by the generation of dust from the glass substrate end face generated during the transfer of the glass substrate, the cleaning step, and the like, which adhere to the main surface of the glass substrate.

The surface of the glass substrate which had been subjected to the above-mentioned mirror polishing was washed with water. Note that this end face mirror processing step may be performed before any of the first, second, and third polishing steps described later, and the end face mirror processing step may not be provided.

(3) Sanding (Lapping) Step Next, the glass substrate was sanded. This sanding step aims at improving dimensional accuracy and shape accuracy.
The sanding step was performed using a lapping apparatus, and was performed twice while changing the abrasive grain size to # 400 and # 1000.

More specifically, first, a load L was set to about 100 kg using alumina abrasive grains having a grain size of # 400.
By rotating the internal rotation gear and the external rotation gear, both sides of the glass substrate housed in the carrier are surface-accurate 0-1 μm,
Lapping was performed to a surface roughness (Rmax) of about 6 μm.

Next, the particle size of the alumina abrasive grains was reduced to # 1000.
Perform lapping instead of surface roughness (Rmax) 2μ
m.

The glass substrate that had been subjected to the sanding process was washed by sequentially immersing it in a washing tank of a neutral detergent and water.

(4) First Polishing Step Next, a first polishing step was performed. This first polishing step is intended to remove scratches and distortion remaining in the above sanding step, and was performed using a polishing apparatus.

More specifically, the first polishing step was carried out under the following polishing conditions using a hard polisher (cerium pad MHC15: manufactured by Speed Fam) as a polisher (polishing powder).

Polishing liquid: cerium oxide (particle diameter: about 1 μm) + water Load: 150 to 300 g / cm 2 (L = 238 kg) Polishing time: 15 to 30 minutes Removal amount: 25 to 45 μm Lower platen rotation speed: 40 rpm Upper platen Rotation speed: 35 rpm Inner gear rotation speed: 14 rpm Outer gear rotation speed: 29 rpm The glass substrate after the first polishing step was washed with a neutral detergent, pure water, pure water, IPA (isopropyl alcohol), IPA.
(Steam drying) and sequentially immersed in each washing tank to wash.
This cleaning step can be omitted when the polishing liquid in the next second polishing step is used together.

(5) Second Polishing Step Next, using the polishing apparatus used in the first polishing step, the polisher was changed from a hard polisher to a soft polisher (Polyak: manufactured by Speed Fam: particle size of about 0.8 μpm). Thus, a second polishing step was performed. Polishing conditions are 25 to 15 loads.
0g / cm2, polishing time 5-20 minutes, removal amount 2.5-10μm
Other than the above, it was the same as the first polishing step.

After the second polishing step, the glass substrate is
Washing was performed by sequentially immersing in a washing tank of a neutral detergent, a neutral detergent, pure water, pure water, IPA (isopropyl alcohol), and IPA (steam drying). In addition, ultrasonic waves were applied to each cleaning tank.

(6) Third Polishing Step Next, using the polishing apparatus used in the second polishing step, a third polishing step was performed in place of the ultra-soft polisher (polishing powder: 0.5 μm or less). The polishing conditions were as follows: the polishing liquid was changed to colloidal silica (particle diameter 0.2 μm or less) + water, and the load was 25 to
100g / cm2, polishing time 5-20 minutes, removal amount 1-5μ
Except having changed to m, it was the same as that of the 2nd grinding process.

The glass substrate after the ultra-precision polishing step is sequentially immersed in each of washing tanks of a neutral detergent, a neutral detergent, pure water, pure water, IPA (isopropyl alcohol), and IPA (steam drying). Washed. In this case, ultrasonic waves were applied to each cleaning tank.

The abrasive (abrasive) used in the third polishing step preferably has a small particle size, and preferably has a small particle size.
It is preferably 15 μm or less, more preferably 0.1 μm or less.

Further, the hard polisher and the soft polisher listed in the above description are not limited to those described above. Examples of the hard polisher include hard velor, urethane foam,
Pitch impregnated suede and the like, and soft polishers include, for example, those made of suede and velor. Further, examples of the abrasive (abrasive) include cerium oxide, alumina, wax, chromium oxide, zirconium oxide, titanium oxide, and colloidal silica.

Here, the particle size of the abrasive (abrasive particles) of the polishing liquid used in the above-mentioned first to third polishing steps is not limited to the one used above, but in the first polishing step, the particle size is 1 to 3 μm. In the second polishing step, the particle size is 0.5 to 2 μm, and in the third polishing step,
The adjustment is appropriately performed within the range of μm or less. By using an abrasive (abrasive grains) in the above range, a substrate that is smooth and has no variation in roughness can be efficiently planarized.

(7) Chemical Strengthening Step Next, the glass substrate after the grinding and polishing steps was chemically strengthened.

For the chemical strengthening, a chemical strengthening solution prepared by mixing cerium nitrate (60%) and sodium nitrate (40%) is prepared, and this chemical strengthening solution is heated to 400 ° C., and is washed at 300 ° C. The glass substrate was immersed for about 3 hours. In this immersion, in order to chemically strengthen the entire surface of the glass substrate, the immersion was performed in a state where a plurality of glass substrates were housed in a holder so as to be held at end faces.

As described above, by performing the immersion treatment in the chemical strengthening solution, the lithium ions and the sodium ions on the surface layer of the glass substrate become the sodium ions and the sodium ions in the chemical strengthening solution.
The glass substrate is strengthened by being respectively substituted by potassium ions.

The thickness of the compressive stress layer formed on the surface of the glass substrate was about 100 to 200 μm.

The glass substrate which has been chemically strengthened is
It was immersed in a water bath at a temperature of 10 ° C. and rapidly cooled and maintained for about 10 minutes.

The quenched glass substrate is heated to about 40 ° C.
The substrate was immersed in heated sulfuric acid and washed while applying ultrasonic waves to obtain a glass substrate whose main surface was ultra-precisely polished.

Under the above conditions, the polishing step is performed in several steps, and the abrasive grains used in each step are finer than those in the normal case. Can be obtained, and the production efficiency can be significantly improved.

When the surface roughness of the main surface of the glass substrate at this time was measured, Rmax was 2.6 nm and Ra was 0.2 nm.
The surface roughness ratio (Rmax / Ra) was 3 nm. The surface roughness was measured with an atomic force microscope (AFM).

In the above example, the case where the third polishing step is performed before the chemical strengthening step has been described. However, the third polishing step is performed in order to prevent a sub-film defect due to the generation of a precipitated salt on the glass substrate due to the chemical strengthening. The step may be performed after the chemical strengthening step.

(8) Magnetic Disk Manufacturing Process Next, the above glass substrate is subjected to a heat treatment of the glass substrate,
The steps of forming the first underlayer, forming the second underlayer, forming the concavo-convex forming layer, forming the third underlayer, forming the magnetic layer, and forming the protective layer are performed by in-line sputtering. It is performed continuously using an apparatus.

This in-line type sputtering apparatus comprises:
Although not shown, a first chamber provided with a substrate heating heater, an Al target, a C
r target, a second chamber in which an Al target is installed, a third chamber in which a heater is installed, a Cr target, a CrMo target (Cr: 94
at%, Mo: 6 at%) and CoCrPtTa target (Co: 78 at%, Cr: 13 at%, Pt: 6)
(at%, Ta: 3 at%) are sequentially provided, and a fifth chamber in which a carbon target is provided is provided.

When 50 of the above glass substrates are mounted on a pallet made of titanium or the like and introduced into the first chamber via the load lock chamber, these glass substrates are transferred to each of the chambers by a predetermined transfer device. The film is conveyed one after another at a predetermined constant speed, during which film formation and processing are performed under the following conditions and the like.

That is, in the first chamber, the substrate is
A process of heating at 50 ° C. for 2 minutes is performed. In the second chamber, an Al film having an average film thickness of 5 nm as the first underlayer 2 is formed.
Film, a Cr film having a thickness of 20 nm as the second underlayer 3, an average film thickness of 5 nm as the unevenness forming layer 4, and a surface roughness (Rmax) of 24 n
A continuous texture film made of m Al is formed. In the third chamber, heat treatment is performed at 350 ° C. for one minute. In the fourth chamber, a Cr film 5a having an average film thickness of 50 nm as the third underlayer 5 and an average film thickness of 30 n
An mCrMo film 5b and a CoCrPtTa film having an average film thickness of 24 nm as the magnetic layer 6 are sequentially formed. In the fifth chamber, a carbon film having an average film thickness of 15 nm which forms the protective layer 7 is sequentially formed.

The sputtering conditions in the second, fourth, and fifth chambers are such that the sputtering pressure is 5 mTorr in the second chamber and 3 mTorr in the fourth chamber.
Torr, 5 mTorr in the fifth chamber, the sputtering atmosphere of the second and fourth chambers is an inert gas of argon, and the sputtering atmosphere of the fifth chamber is an inert gas of argon or 1 to 25% of argon.
A mixed gas in which hydrogen and / or nitrogen is mixed, or a mixed gas in which argon is mixed with a hydrocarbon gas (methane or the like) of 1 to 25% is used. Further, each sputtering power is 200 W in the third chamber and 2 W in the fifth chamber.
00 W, and 100 W in the sixth chamber.

Next, the substrate having been subjected to the steps up to the formation of the protective layer is taken out of the above-mentioned in-line type sputtering apparatus, and the surface of the protective layer is coated with perfluoropolyether by an immersion method. A layer was formed to obtain a magnetic recording medium according to Example 1.

Further, at each of the obtained magnetic recording media, at a radius of 22 mm, 0 °, 90 °, 180 °,
When the magnetic characteristics and the recording / reproducing characteristics of 270 ° (the center of the sputter mark formed by mounting the pallet is 0 °) were measured, the coercive force of each point and each magnetic recording medium was in the range of 1900 to 2000 Oe. And the S / N ratio was in the range of 24.2 to 25.8 dB. Process capability index Cp (= {(upper limit specification) − (lower limit specification)} / 6σ; indicating the stability of the manufacturing process; {(average value) − (lower limit specification)} / 3σ; ), The coercive force (Hc) is 1950 ± 100 Oe
Is 2.4 with respect to both-side standards and 5.3 with respect to the lower limit standard of 19 dB or more, and variations in the in-plane distribution of each magnetic recording medium and the magnetic characteristics of the magnetic recording medium in the pallet are suppressed. In addition, not only a magnetic recording medium having good magnetic properties was obtained, but also the stability of the manufacturing process was improved. Also, in a 100,000 times CSS durability test using a 70% head slider with a load of 3 g, no adsorption phenomenon occurs between the magnetic recording medium and the magnetic head, no head crash occurs, and a high CSS durability test is performed. Thus, a magnetic recording medium having properties was obtained.

The coercive force (Hc) was measured by cutting a sample of 8 mmφ from the manufactured magnetic recording medium, applying a magnetic field in the direction of the film surface, and using a vibrating sample magnetometer with a maximum externally applied magnetic field of 10 kOe.

The recording / reproducing characteristics (S / N ratio) were measured as follows. That is, using the obtained magnetic disk, an MR (magnetoresistive) head having a magnetic head flying height of 0.055 μm, a relative speed between the MR head and the magnetic disk of 9.6 m / s, and a linear recording density of 120 kfc
The recording / reproducing output at 1 (linear recording density of 120,000 bits per inch) was measured. In addition, medium noise during signal recording and reproduction was measured by a spectrum analyzer with a carrier frequency of 23 MHz and a measurement band of 26 MHz, and the S / N ratio was calculated. MR used for this measurement
The head has a track width of 3 on the write / read side.
1 / 2.4 μm, magnetic head gap length 0.35 / 0.
28 μm. The measurement of the surface roughness, the crystal grain size, the coercive force, and the S / N ratio in the following examples and comparative examples were performed by the above-described methods.

Examples 2 to 4 and Comparative Examples 1 to 4 Next, a magnetic recording medium was manufactured in the same manner as in Example 1 except that the polishing conditions were changed to change the surface roughness of the glass substrate. These are referred to as Examples 2 to 4 and Comparative Examples 1 to 4, and in each case, the surface roughness Ra (nm), Rmax (nm), and Rmax / R of the main surface of the glass substrate.
a, coercive force Hc (Oe), S / N ratio (dB), Cp, C
The results of the SS durability test are summarized in a table and shown in FIG.

As described above, in the embodiment, the coercive force Hc
Is within 1850-2050 (Oe) and the S / N ratio is 19
(DB) or more, Cp also exceeded 1.3, variation in magnetic characteristics was suppressed, and a magnetic recording medium could be stably manufactured. On the other hand, in the comparative example, Rmax
When / Ra is less than 10, adsorption occurs between the magnetic head and the magnetic recording medium, and not only CSS durability is not good, but also coercive force (Oe), S / N due to large Rmax and / or Ra. It can be seen that the dispersion of the magnetic characteristics of each magnetic recording medium having a ratio (dB) becomes large, and a stable magnetic recording medium cannot be manufactured.

Examples 5 to 11 and Comparative Examples 5 to 9 Next, the polishing conditions were changed to change the surface roughness of the glass substrate, and the average thickness of the first underlayer 2 was 1 nm, and the irregularities were formed. Except that the surface roughness (Rmax) of the layer was set to 24 nm, magnetic recording media were prepared in the same manner as in Example 1, and these were referred to as Examples 5 to 11 and Comparative Examples 5 to 9, respectively. Surface roughness Ra (n) of the main surface of the substrate
m), Rmax (nm), Rq (nm), Rmax / R
a, average crystal grain size (nm) of magnetic layer, S / N ratio (d
B), the presence or absence of a head crash and the like are shown in a table in FIG.

When the average crystal grain size of the magnetic layer of the magnetic recording medium of Example 5 was measured by surface observation using a transmission electron microscope (TEM), it was reflected as it was on the underlayer. Was 11 nm, and the distribution of the crystal grain size of the magnetic crystal grains was examined. As a result, it was possible to obtain a magnetic layer having a uniform crystal grain size with a half-width of 20 nm or less from the point of the most distributed grain size. (Note that the distribution of the crystal grain size of the magnetic crystal grains is described in IEEE Tran.
Zaction on Magnetics. VOL.
32, NO. 5 "Microstructure / Ma
geneticProperty Relationship
ips in CoCrPt Magnetic Th
in Films / Mary Doerner ", and the same as the measurement of the magnetic crystal grain size distribution by TEM.
And its Number of Grain
The degree of distribution of the crystal grain size was evaluated based on the half width from the maximum value of s. ). When the magnetic characteristics and recording / reproducing characteristics of the obtained magnetic recording medium were measured, the coercive force was 2300.
A good magnetic recording medium having an Oe and S / N ratio of 24.7 dB was obtained. Also, in a 100,000 CSS durability test using a 70% head slider with a load of 3 g, no adsorption phenomenon occurs between the magnetic recording medium and the magnetic head, and no head crash occurs.
A magnetic recording medium having high CSS durability was obtained.

The coercive force (Hc) was measured by cutting a sample of 8 mmφ from the manufactured magnetic recording medium, applying a magnetic field in the direction of the film surface, and using a vibrating sample magnetometer with a maximum externally applied magnetic field of 10 kOe.

The recording / reproducing characteristics (S / N ratio) were measured as follows. That is, using the obtained magnetic disk, an MR (magnetoresistive) head having a magnetic head flying height of 0.055 μm, a relative speed between the MR head and the magnetic disk of 9.6 m / s, and a linear recording density of 120 kfc
i (Linear recording density of 120,000 bits per inch)
The recording / reproducing output was measured. In addition, medium noise during signal recording and reproduction was measured by a spectrum analyzer with a carrier frequency of 23 MHz and a measurement band of 26 MHz, and the S / N ratio was calculated. The MR head used for this measurement has a track width of 3.1 /
2.4 μm, magnetic head gap length 0.35 / 0.28
μm. The measurement of the surface roughness, the crystal grain size, the coercive force, and the S / N ratio in the following examples and comparative examples were performed by the above-described methods. The coercive force of the magnetic recording media in Examples 6 to 11 and Comparative Examples 5 to 9 was measured.
(Oe) or higher.

In Comparative Examples 5 and 7, the surface roughness Ra of the glass substrate was larger than 1.0 nm and / or Rq
Is larger than 1.5 nm, the crystal grain size of the underlayer formed thereon is irregular and abnormally grown, and the crystal grain size of the magnetic layer is large. It is considered that this occurred and the S / N ratio decreased.

In Comparative Example 6, the surface roughness Rm of the glass substrate
Since ax is larger than 15.0 nm, it is affected by the surface of the magnetic disk, so that low flying traveling of the magnetic head cannot be realized, not only the recording / reproducing characteristics are deteriorated, but also S due to abnormal crystal grain growth. It is not preferable because the / N ratio deteriorates and a head crash occurs.

In Comparative Example 8, the surface roughness Rm of the glass substrate
The fact that the magnetic head does not achieve low flying traveling due to the large ax, and that the crystal grain size of the magnetic layer formed thereon locally abnormally grows due to the large difference between Ra and Rmax As a result, the S / N ratio deteriorates and a head crush accompanying abnormal projections occurs, which is not preferable.

In Comparative Example 9, as in Comparative Examples 5 to 8 described above, the crystal grain size of the magnetic layer increased, the S / N ratio deteriorated due to the variation in crystal grain size, and the magnetic head It is not preferable because low levitation traveling cannot be realized and a head crush occurs.

In Examples 6 to 10, the distribution of the crystal grain size of the magnetic layer crystal grains was measured in the same manner as in Example 5. The results were the same as those in Example 5. A layer had been formed. In addition, the distribution of the crystal grain size of the magnetic layer crystal grains of Comparative Examples 5 to 9 was measured, and the crystal grain size was varied.

From the above results, in order to obtain a highly reliable magnetic recording medium having good magnetic characteristics and recording / reproducing characteristics and no head crash, the surface roughness of the glass substrate must be Rmax ≦ 15 nm. Ra ≦ 1 nm, R
It is necessary that q ≦ 1.5 nm. Preferably, the surface roughness of the glass substrate is Rmax ≦ 10 nm, Ra ≦
0.5 nm, Rq ≦ 0.7 nm, more preferably, R
max ≦ 5 nm, Ra ≦ 0.3 nm, Rq ≦ 0.4 nm
Is desirable.

Similarly, in order to obtain a magnetic recording medium having extremely high reliability, the surface roughness of the glass substrate is set to Rmax.
It can be seen that ≦ 15 nm, Ra ≦ 1 nm, Rmax / Ra ≦ 30, and the average crystal grain size of the magnetic layer must be 5-30 nm. Preferably, the surface roughness of the glass substrate is Rmax ≦ 10 nm, Ra ≦ 0.5 nm, more preferably Rmax ≦ 5 nm, Ra ≦ 0.3 nm.

Examples 12 to 15 and Comparative Examples 9 to 13 Next, in order to examine the influence of the surface roughness of the glass substrate on the unevenness forming layer 4, a magnetic recording medium having a different thickness of the unevenness forming layer 4 was manufactured. These were prepared in Examples 12 to 15 and Comparative Examples 9 to
13. That is, the average thickness of the unevenness forming layer was 5 nm (Example 5) using the glass substrate of Example 5 described above,
6.5 nm (Example 12), 6 nm (Example 13),
A magnetic recording medium was manufactured in the same manner as in Example 5, except that the thickness was changed to 4.5 nm (Example 14) and 4 nm (Example 15).

Next, as an example outside the scope of the present invention, the glass substrate of Comparative Example 5 was used, and the average film thickness of the unevenness forming layer 4 was 6.5 nm (Comparative Example 9) and 6 nm (Comparative Example 1).
0), 5 nm (Comparative Example 11), 4.5 nm (Comparative Example 1)
2) Example 1 except that the thickness was changed to 4 nm (Comparative Example 13).
In the same manner as in the above, a magnetic recording medium was produced.

The average thickness (nm) of the unevenness forming layer 4 and the surface roughness (Rm) of the unevenness forming layer 4 of the magnetic recording medium thus obtained.
ax) and the values of (Rq / Ra) of the surface of the concavo-convex formation layer 4 are shown in tables in FIGS. 4 and 5, respectively, and the average film thickness (nm) and the surface roughness of the concavo-convex formation layer 4 for each (Rmax) is shown in graphs in FIGS. 6 and 7. FIG.

As can be seen from these results, in the glass substrate of the example, since the film thickness of the unevenness forming layer and the surface roughness are substantially linear, control of the surface roughness to obtain high CSS durability is performed. A magnetic recording medium that can be easily formed and has high reliability can be obtained. On the other hand, in the case of a glass substrate having a large surface roughness (Comparative Example), the relationship between the film thickness of the unevenness forming layer and the surface roughness is different. It is not only extremely difficult to control the surface roughness of the unevenness forming layer, but also the reliability is poor. In each of the examples and the comparative examples regarding the surface roughness ratio (Rq / Ra) of the unevenness forming layer, abnormal protrusions and unevenness of the unevenness of the unevenness forming layer due to unevenness of the surface roughness of the substrate occur. Since the surface roughness of the substrate is good for the examples, the unevenness forming layer has Rq / Ra ≦ 1.5.
At that time, no head crash has occurred,
For the comparative example, the variation in substrate surface roughness,
Due to the abnormal projection, Rq / Ra> 1.5, which indicates that a head crash has occurred.

Although not shown here, the above-described embodiment 6
As for the glass substrates shown in Comparative Examples 6 to 8, the relationship between the film thickness of the unevenness forming layer, the surface roughness, the variation, and the head crash due to the influence of the surface roughness of the glass substrate was examined in the same manner as described above. The same tendency as that shown in the table of FIG. 4 and the graph of FIG. 6 is seen for Examples 6 to 11, and the comparative examples 6 to 8 are the same as those in the table of FIG. The same tendency as that shown in the graph was observed. Therefore, by using the glass substrate of the present invention, the surface roughness of the unevenness forming layer can be easily and accurately controlled,
In addition, it can be seen that a highly reliable magnetic recording medium can be obtained because variation in surface roughness is suppressed.

Examples 16 to 20, Comparative Examples 14 and 15, and
Comparative Example 16 Next, the surface roughness (Rmax) of the unevenness forming layer was adjusted to 9 nm (Comparative Example 14), 10 nm (Example 16), and 20 nm (Example) by appropriately adjusting the thickness of the unevenness forming layer and sputtering conditions. 17), 30 nm (Example 18), 40 nm (Example 1)
9), 50 nm (Example 20), 55 nm (Comparative Example 1)
Except that it was changed to 5), the glass substrate of Example 5 was used,
A magnetic recording medium was manufactured in the same manner as in Example 5. Also,
A magnetic recording medium was manufactured in the same manner as in Example 5, except that an unevenness forming layer having a surface roughness (Rmax) of 10 nm was formed on the glass substrate of Comparative Example 2 described above. FIG. 8 is a table showing the surface roughness, CSS durability and head crash characteristics of the unevenness forming layer at that time.

As can be seen from the above results, when the surface roughness of the concavo-convex forming layer was smaller than 10 nm, the magnetic head and the magnetic recording medium were attracted, and high CSS durability could not be obtained. Also, as in Comparative Example 16, the surface roughness Rmax
When a glass substrate having a large surface roughness is used, the projections of the surface roughness of the unevenness forming layer increase due to the abnormal projections on the glass substrate surface. Therefore, as shown in the table of FIG.
A head crash due to the abnormal projection occurs, and not only the magnetic head but also the magnetic disk is fatally damaged, which is not preferable. Further, Comparative Example 15 is not suitable for high-density recording / reproduction because the magnetic head cannot achieve low flying running due to the large surface roughness Rmax.

Embodiment 21 and Comparative Example 17 In the above embodiment, a magnetic disk in which the unevenness was formed on the surface of the magnetic disk by forming the unevenness forming layer was described. The extremely high smoothness and flatness of the glass substrate used in (1) are reflected directly on the surface of the magnetic disk, and can be used, for example, as a magnetic disk for a contact-type magnetic disk drive. Hereinafter, the case of using the glass substrate of Example 5 as the glass substrate is described as Example 21, and the case of using the glass substrate of Comparative Example 5 as the glass substrate is described as Comparative Example 17 below.

FIG. 9 is a diagram showing the film configuration of Example 21 and Comparative Example 9. As shown in FIG. 9, these magnetic recording media are sequentially provided on a glass substrate 1 with a first underlayer 2 (A
l; average thickness 5 nm), second underlayer 3 (Cr; average thickness 50 nm), third underlayer 50 (CrMo; Cr: 94a)
t%, Mo: 6 at%, average film thickness 30 nm), magnetic layer 6
(CoCrPtTa; Co: 78 at%, Cr: 13a
t%, Pt: 6 at%, Ta: 3 at%, average film thickness 24
nm), a protective layer 7 (carbon; average film thickness 15 nm) and a lubricating layer 8 (perfluoropolyether liquid lubricating layer; average film thickness 1 nm).

In this example and the comparative example, almost the same results as those of the above-described example and comparative example were obtained. That is, in the case of the magnetic disk of Example 21 using the glass substrate of Example 5, the crystal grains constituting the underlayer and the magnetic layer formed on the glass substrate were good, and the coercive force was 2400 Oe, S /
A contact type magnetic disk having an N ratio of 24.5 dB and excellent magnetic characteristics and recording / reproducing characteristics can be obtained. On the other hand, in the case of the magnetic disk of Comparative Example 16 using the glass substrate of Comparative Example 9 having a poor substrate surface condition, variations occur in the grain size of the crystal grains constituting the underlayer and the magnetic layer formed on the glass substrate. In addition, the S / N ratio deteriorated to 21.0 dB due to the increase in particle size, resulting in poor recording / reproducing characteristics.

In the above-described embodiment, an example in which a magnetic disk is manufactured using an in-line type continuous sputtering apparatus has been described. However, similar results can be obtained when a stationary facing type sputtering apparatus is used. Further, in the above-described embodiment, the concavo-convex forming layer is provided on the Al / Cr underlayer, but may be formed directly on the surface of the glass substrate without using the underlayer.
FIG. 10 is a diagram showing an example in which a concavo-convex forming layer is provided directly on the surface of a glass substrate without an intervening underlayer. As shown in FIG. 10, this magnetic recording medium is sequentially placed on a glass substrate 1.
An unevenness forming layer 4, a base layer 51 composed of a Cr layer 51a and a CrMo layer 51b, a magnetic layer 6, a protective layer 7, and a lubricating layer 8 are formed.

The low melting point metal material constituting the unevenness forming layer is as follows:
Al, Ti, Cr, Ag, Nb, Ta, Bi, Si, Z
r, Cu, Ce, Au, Sn, Pd, Sb, Ge, M
It is desirable that the material is selected from metals such as g, In, W, and Pb, alloys thereof, and oxides, nitrides, carbides, and the like of these metals or alloys. Particularly preferred materials include Al alone, Al alloy, Al oxide, and Al nitride.
Al as a main component. Al, nitride A
l is the best.

The shape of the unevenness forming layer may be a continuous texture film or discretely distributed island-like projections.

Further, a so-called zone texture in which the unevenness forming layer is formed only in the landing zone, or the read / write zone is provided with smoothness and the surface roughness of the landing zone is increased. Further, depending on the type of drive to be used, the unevenness forming layer can be omitted.

Examples of the glass substrate used in the present invention include a surface-reinforced glass substrate and a crystallized glass substrate.
Specific examples include aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, quartz glass, soda lime glass, oxynitride glass, and the like. Further, non-metallic substrates such as a ceramic substrate, a glass ceramic substrate, a silicon substrate, and a carbon substrate can be given as those having the same properties as glass.

The glass substrate of the present invention is useful not only for the above-described magnetic disk, but also for an optical disk and an optical disk substrate.

As the first underlayer 2, in addition to Al, G
Those containing e, Ga, Zr, Ti or the like as main components can be used. Further, the second underlayer 3 is not limited to Cr alone, but may be an alloy containing Cr as a main component.

Further, as the third underlayer 5, a Cr layer 5
a, instead of the CrMo layer 5b formed on
Mo, Zr, B, Si, Zn, Ti, W, V, Ta, A
It may be composed of one or more layers containing at least one element selected from 1 as a main component.

It is preferable to use Al for the first underlayer 2 and Cr for the second underlayer 3 in order to control the crystal growth of each layer. According to this, the unevenness of the unevenness forming layer 4 which is a low melting point metal thin film formed thereon can be controlled with high accuracy without variation, and a low head flying height is realized by a synergistic effect with the characteristics of the glass substrate. And the reproduction output can be increased.

As the magnetic layer 6, in addition to CoCrPtTa, CoPt, CoCr, CoNi, CoPtCr, C
oCrTa, CoNiCr, CoNiPt, CoNiC
rTa, CoNiCrPt, CoCrPtTaNb, C
C such as oCrPtTaZr and CoCrPtTaSiO
It may be made of an o-based alloy, a magnetic material such as a ferrite or an iron-rare earth element. Further, the magnetic layer may be divided by a non-magnetic film (for example, Cr, CrMo, CrV, etc.) to form a multilayer film in which noise is reduced. For example, CoCrP
tTa / CrMo / CoCrPtTa, CoPtCr /
A layer structure such as CrMo / CoPtCr (the left side of “/” is a layer close to the substrate) may be used.

Further, in the embodiment, an example is shown in which the protective layer 7 is constituted by a single layer of the carbon protective layer. However, the present invention is not limited to this.
Mo, Ti, TiW, CrMo, Ta, W, Si, Ge
And the like, or alloys, oxides, nitrides, and carbides thereof. Instead of the carbon protective layer, colloidal silica fine particles may be dispersed in tetraalkoxylan diluted with an alcohol-based solvent and applied, followed by firing to form a silicon oxide (SiO2) film. In this case, both functions of the protective layer and the unevenness forming layer can be performed.

As a material of the lubricating layer 8, a fluorocarbon-based liquid lubricant or a lubricant composed of an alkali metal salt of sulfonic acid can be used in addition to perfluoropolyether. The thickness is desirably 0.5 to 2 nm. The reason is that if the thickness is less than 0.5 nm, the abrasion resistance cannot be sufficiently ensured, and if it exceeds 2 nm, not only the abrasion resistance does not improve but also a problem of adsorption occurs. is there. If the protective layer itself has a lubricating effect, the lubricating layer can be omitted.

[0108]

As described in detail above, the present invention is intended to reduce the surface roughness and variation of a glass substrate within a predetermined range, and to make the crystal grains of an underlayer and a magnetic layer formed thereon uniform. Thus, a magnetic recording medium having good magnetic properties and capable of high-density recording and reproduction and a method for manufacturing the same are obtained, and the surface roughness (Rmax, Rmax) of the glass substrate is obtained.
a) and their relationship between Rmax and Ra (Rmax / R
By keeping a) within a predetermined range, stable and
A magnetic recording medium having good magnetic properties, high-density recording and reproduction, and a method for manufacturing the same are obtained.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view illustrating a configuration of a magnetic recording medium according to a first embodiment of the present invention.

FIG. 2 is a table showing characteristics and the like of Examples 1 to 4 and Comparative Examples 1 to 4 of the present invention.

FIG. 3 is a table showing characteristics and the like of Examples 5 to 11 and Comparative Examples 5 to 9 of the present invention.

FIG. 4 is a table showing the characteristics and the like of the concavo-convex formation layers of Example 5 and Examples 12 to 15 of the present invention.

FIG. 5 is a table showing characteristics and the like of unevenness forming layers of Comparative Examples 9 to 13 of the present invention.

FIG. 6 is a graph showing the relationship between the average film thickness of the concavo-convex forming layer and Rmax in Examples 5 and 12 to 15 of the present invention.

FIG. 7 is a graph showing the relationship between the average film thickness of the concavo-convex forming layers and Rmax of Comparative Examples 9 to 13 of the present invention.

FIG. 8 shows Examples 14 to 20 and Comparative Examples 15 to 1 of the present invention.
6 is a diagram showing the characteristics and the like of No. 6 in a table. FIG.

FIG. 9 is a view showing a film configuration of Example 21 and Comparative Example 17 of the present invention.

FIG. 10 is a view showing a film configuration of a modification of the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 2 ... 1st underlayer, 3 ... 2nd underlayer, 4
... Asperity forming layer, 5... Third underlayer, 6... Magnetic layer, 7.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C03C 21/00 101 C03C 21/00 101

Claims (17)

[Claims] 1. The method according to claim 1, wherein the surface roughness of the glass substrate main surface is Rmax.
≦ 15 nm, Ra ≦ 1 nm, Rq ≦ 1.5 nm (however,
Rq is a root-mean-square roughness (= RMS), wherein the glass substrate for an information recording medium is provided. 2. The glass substrate for an information recording medium according to claim 1, wherein a ratio (Rmax / Ra) of a surface roughness of the main surface of the glass substrate is 30 or less. 3. A magnetic recording medium having a thin film including at least a magnetic layer on a glass substrate, wherein the glass substrate for an information recording medium according to claim 1 is used as the glass substrate. Medium. 4. The thin film is made up of substantially uniform crystal grains by controlling the surface roughness of the glass substrate, and the average crystal grain size of the crystal grains is 5 to 30 nm. 4. The magnetic recording medium according to claim 3, wherein: 5. A magnetic recording medium having a thin film including at least a magnetic layer on a glass substrate, wherein the surface roughness of the main surface of the glass substrate is Rmax ≦ 15 nm, Ra ≦ 1 nm,
A ratio of surface roughness (Rmax / Ra) is 30 or less, and the thin film is composed of substantially uniform crystal grains by controlling the surface roughness of the glass substrate, and an average crystal grain of the crystal grains is obtained. A magnetic recording medium having a diameter of 5 to 30 nm. 6. The surface roughness of the main surface of the glass substrate is Rm.
ax ≦ 10 nm, Ra ≦ 0.5 nm, surface roughness ratio (R
6. The magnetic recording medium according to claim 5, wherein (max / Ra) is 30 or less. 7. The glass substrate main surface has a surface roughness Rm.
ax ≦ 5 nm, Ra ≦ 0.3 nm, surface roughness ratio (Rm
The magnetic recording medium according to claim 5, wherein (ax / Ra) is 30 or less. 8. When the crystal grains of the thin film are measured for a crystal grain size distribution existing in a square of 1 micron, the half width at the point where the crystal grain size of the thin film is distributed most is 20n.
8. The magnetic recording medium according to claim 3, wherein m is equal to or less than m. 9. A step of lapping a disc-shaped glass substrate, and after the step, the surface roughness of the glass substrate is Rmax.
≦ 15 nm, Ra ≦ 1 nm, Rq ≦ 1.5 nm (however,
A step of mirror-polishing using a polishing liquid containing polishing abrasive grains having a particle diameter selected in advance so that Rq has a root-mean-square roughness (= RMS). A method for manufacturing a glass substrate. 10. A thin film including at least a magnetic layer on a glass substrate manufactured by the method for manufacturing a glass substrate for an information recording medium according to claim 9, wherein the thin film is formed of substantially uniform crystal grains. And a thin film forming step of forming a film so that the average crystal grain size of the crystal grains is 5 to 30 nm. 11. The surface roughness of a glass substrate on which a thin film including at least a magnetic layer is formed is Rmax ≦ 15 nm,
A glass substrate surface treatment step for satisfying Ra ≦ 1 nm and Rq ≦ 1.5 nm, and wherein the crystal grains constituting the thin film are formed of substantially uniform crystal grains on the main surface of the glass substrate. Forming a thin film so that the average crystal grain size of the grains is 5 to 30 nm. 12. The surface roughness of a glass substrate on the side where a thin film including at least a magnetic layer is formed is Rmax ≦ 15 nm,
Ra ≦ 1 nm, surface roughness ratio (Rmax / Ra) is 30
A glass substrate surface treatment step to be as follows, and the crystal grains constituting the thin film are composed of substantially uniform crystal grains on the glass substrate main surface, and the average crystal grain size of the crystal grains is 5 to 5. Forming a thin film to a thickness of 30 nm. 13. The method according to claim 1, wherein the surface roughness of the main surface of the glass substrate is Rmax.
≦ 15 nm, Ra ≦ 1.3 nm, Rmax / Ra ≧ 10
A glass substrate for an information recording medium, wherein: 14. The glass substrate having a surface roughness Rm
ax ≦ 10 nm, Ra ≦ 0.8 nm, Rmax / Ra ≧
22. The glass substrate for an information recording medium according to claim 21, wherein the glass substrate is 10.5. 15. A magnetic recording medium having a thin film including at least a magnetic layer on a glass substrate, wherein the glass substrate for an information recording medium according to claim 13 or 14 is used as the glass substrate. Medium. 16. A step of preparing a glass substrate for an information recording medium according to claim 13 or 14; and a step of forming a thin film including at least a magnetic layer on said glass substrate.
A method for manufacturing a magnetic recording medium, comprising: 17. The method according to claim 16, wherein the thin film is formed by an in-line continuous sputtering method.