JPH101327A - Glass substrate for recording medium, magnetic recording medium using the same and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heat resistance, flatness and strength by using oxynitride glass as a substrate material. SOLUTION: A mixture of SiO2 with an oxide such as Na2 O, CaO, Nd2 O3 or Al2 O3 and other metal oxide or metal oxynitride is melted by heating at 1,400-1,900 deg.C for 3-10hr in an inert gaseous atmosphere and the resultant oxynitride glass is molded in a plate shape to obtain a substrate material. This substrate material is lapped and polished to obtain the objective glass substrate 2 for a magnetic recording medium having 3-8Å surface roughness Ra. A ruggedness controlling layer 3 of a metal or alloy having 50-300Å surface roughness Rmax, an underlayer 4, a magnetic layer 5 and a protective layer 6 are successively formed on the glass substrate 2, heat treatment is carried out at a temp. (300-1,000 deg.C) below the glass transition temp. and a lubricative layer 7 is formed by coating with a liq. lubricant to obtain the objective magnetic recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass substrate for a recording medium having excellent heat resistance, flatness and strength, a magnetic recording medium using the glass substrate, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a glass substrate for a magnetic recording medium having a high mechanical strength, a chemically strengthened glass substrate in which the substrate surface is reinforced by ion exchange and a crystallized glass substrate in which the substrate surface is subjected to a crystallization treatment are known. Have been.

For example, as a chemically strengthened glass substrate, Japanese Patent Application Laid-Open No. 1-239036 discloses that, by weight, 60-70% of SiO ₂ , 0.5-14% of Al ₂ O ₃ , and R ₂ O (where R is an alkali metal) 10 to 32%, ZnO 1 to
15%, a glass substrate for a magnetic recording medium having enhanced by a glass containing B ₂ O ₃ 1.1~14% ion exchange is disclosed.

As a crystallized glass substrate, Japanese Patent Application Laid-Open No.
Japanese Patent Publication No. 187711 discloses that SiO ₂ is 50% by weight.
65%, the CaO 18 to 25%, a Na ₂ O 6 to 11
% 6-12% of K ₂ O, the Al ₂ O ₃ 0~2.5%, F
And a glass substrate for a magnetic recording medium containing 5 to 9% by mass and containing kasanite as a main crystal.

However, in recent years, as the size of disks has been reduced and the density of magnetic recording has increased, the flying height of the magnetic head has been reduced and the rotation speed of the disks has been increased. Therefore, the strength of the disks and the surface accuracy of the disk surface have been reduced. The demands have been stricter, and in the future this demand will be stricter.

[0006]

Under such circumstances, the above-mentioned prior art has the following problems.

First, the conventional chemically strengthened glass disclosed in Japanese Patent Application Laid-Open No. 1-239036 has insufficient strength and may not be able to meet the demand for improvement in disk strength in the future.

In the production of a magnetic recording medium, after a magnetic layer is provided on a glass substrate, a predetermined heat treatment may be performed in order to improve characteristics such as coercive force of the magnetic layer. For chemically strengthened glass, the glass transition point is 5
There is a problem that high coercive force cannot be obtained due to poor heat resistance of about 00 ° C.

Further, the conventional crystallized glass as disclosed in Japanese Patent Application Laid-Open No. 7-187711 is superior in strength and heat resistance to the above-mentioned chemically strengthened glass substrate, but has a surface accuracy of Ra. At most, it is about 10 angstroms, and the flatness is poor, and there is a limit to the low flying height of the magnetic head.

Another magnetic recording medium using a carbon substrate as disclosed in Japanese Patent Application Laid-Open No. 3-273525 is known. Carbon substrates are superior to glass substrates in terms of heat resistance, and although high density recording can be expected, they are inferior to glass materials in terms of mechanical strength. There is a problem in doing.

The present invention has been made in view of the above circumstances, and has as its first object to provide a glass substrate for a magnetic recording medium having excellent heat resistance, flatness, and high strength.

A magnetic recording medium and a magnetic recording medium capable of maximizing the improvement of the characteristics of the magnetic layer, achieving low flying of the magnetic head, that is, achieving high-density recording, and achieving thinner and smaller discs. A second object is to provide a manufacturing method.

[0013]

In order to achieve the above object, a glass substrate for a magnetic recording medium according to the present invention has a structure using oxynitride glass as a substrate material.

Further, the glass substrate for a magnetic recording medium of the present invention is the above glass substrate for a magnetic recording medium, wherein the oxynitride glass is a Mg-Al-Si-ON-based glass,
a-Al-Si-ON system, Y-Al-Si-ON
System, Mg-Si-ON system, Ca-Si-ON system, C
It is configured to have a composition selected from e-Al-Si-ON-based compositions or a composition in which two or more of these composition systems are mixed.

Further, the magnetic recording medium of the present invention has a configuration in which at least a magnetic layer is formed on the main surface of the glass substrate for a magnetic recording medium of the present invention.

Further, the magnetic recording medium of the present invention is characterized in that, in the above magnetic recording medium, the magnetic head and the magnetic recording medium are provided as a layer located between the glass substrate and the magnetic layer or as a layer located above the magnetic layer. And a structure in which an unevenness control layer for preventing the adsorption of undulation is provided, or the surface roughness Rmax of the unevenness control layer is 50 to 300 Å.

Further, in the method of manufacturing a magnetic recording medium according to the present invention, at least a magnetic layer is formed on a main surface of an oxynitride glass substrate, and at least the magnetic layer is heated at a temperature lower than a glass transition point. There is.

Further, a method of manufacturing a magnetic recording medium according to the present invention has a configuration in which the heat treatment temperature is 300 to 1000 ° C. in the above-described method of manufacturing a magnetic recording medium.

Further, the glass substrate for a recording medium of the present invention has a configuration using oxynitride glass as a substrate material.

According to the present invention, since oxynitride glass is used as the glass substrate material, a glass substrate for a magnetic recording medium having excellent heat resistance and flatness and high strength can be obtained.

Also, because of its excellent heat resistance, heat treatment necessary for improving the characteristics of the magnetic layer can be performed without deformation of the substrate, and because of its excellent flatness, low flying of the magnetic head, that is, high density recording can be achieved. And high strength, so that the disk can be made thinner and smaller, and the disk can be prevented from being damaged.

Hereinafter, the present invention will be described in detail.

First, the glass substrate for a magnetic recording medium of the present invention will be described.

In the present invention, oxynitride glass is used as a glass substrate material.

The oxynitride glass is a glass containing a nitride in an oxide glass, and is an oxynitride glass.
e) Also called glass, nitrogen is incorporated into its structure.

Oxynitride glass (nitrogen-containing glass) has a structure in which part of divalent oxygen ions in oxide glass is replaced by trivalent nitrogen ions. For this reason, more chemical bonds are formed than in the oxide glass, and the glass network is strengthened. Therefore, it has excellent physical properties such as high hardness and high strength, and has excellent properties as a substrate for a magnetic recording medium.

The type and components of oxynitride glass,
The composition is not particularly limited. Oxynitride glass can change its chemical composition continuously, and depending on the amount of addition, 90 kinds of elements of the periodic table enter into the glass structure.

The nitrogen content in the oxynitride glass is not particularly limited. This is because, depending on the composition system, the physical properties may be dramatically improved with a slight nitrogen content, and conversely, the physical properties may be dramatically improved by increasing the nitrogen content or setting it to the optimum amount. Because there is.

Examples of the oxynitride glass include, for example, Ca—Si—Al—ON, Na—Ca—Si—
ON-based, La-Si-Al-ON-based, Li-Na-
KB-Si-ON system, Ce-Si-ON system, Ce
-Al-Si-ON system, Na-B-Si-ON system,
Li-Si-Al-O-N system, Be-Si-Al-O-
N-based, Mg-Si-Al-ON-based, Si-Al-O-
N system, Li-Mg-Si-Al-ON system, Ce-Mg
-Si-Al-ON-based, Mg-Ba-Si-Al-O
-N system, Y-Si-Al-ON system, Mn-Si-Al
-ON-based, Nd-Si-Al-ON-based, Na-B-
Al-P-O-N system, K-Si-ON system, Si-M-
O-N (M is an alkaline earth metal), Si-ON,
Na-Si-ON system, Mg-Si-ON system, La-
Si-ON-based, Li-Si-ON-based, Ca-Si-
Silicates such as Al-O-N and Na-B-O-N
Borate, Li-PON-based, Na-P-
ON-based, K-P-ON-based, Na-Ba-Al-P-
Those having a composition such as a phosphate type such as an ON-N type are exemplified.

Particularly, as a glass substrate for a magnetic recording medium, Mg—Al—Si—O— having a relatively low specific gravity, a relatively high elastic modulus and a high heat resistance, and no alkali elution is used.
N-based, Ca-Al-Si-ON-based, Y-Al-Si-
ON-based, Mg-Si-ON-based, Ca-Si-ON
It is preferable to use an oxynitride glass having a composition selected from the group consisting of a Ce-Al-Si-ON system and a composition obtained by mixing two or more of these composition systems.

The method for producing oxynitride glass is as follows:
There is no particular limitation, and various production methods can be used. For example,
There are known a high-temperature melting method, a method of introducing nitrogen gas into a melt by bubbling, a method of treating porous glass with ammonia gas to make it non-porous, a sol-gel method, a CVD method, and the like.

The various physical properties of the oxynitride glass include the nitrogen content, the raw material, the type of the nitrogen source compound to be added as the raw material, the melting temperature, the melting time, the melting atmosphere, the cooling rate of the melt, and the contamination of impurities. It is affected by the presence / absence (including the case of being positively mixed), the type of crucible, the amount of molten glass, and the like. Therefore, it is necessary to appropriately select these conditions for production.

In the method for producing oxynitride glass, for example, SiO ₂ as a raw material and other oxides (eg, Na ₂ O, CaO, Na ₂ O ₃ , Al ₂ O ₃ , Y ₂ O
₃ , MgO, K ₂ O, ZnO, As ₂ O ₃ ), and a mixture of a metal oxide and a metal oxynitride as a nitrogen supply source (high-temperature melting method).

Here, as the metal oxide, SiO ₂ ,
Al ₂ O ₃ , BaO, Sb ₂ O ₃ , SrO, Na ₂ O, Na ₂
O ₃ , CaO, MgO, K ₂ O, La ₂ O ₃ , CeO ₂ , Y ₂
O ₃ , ZrO ₂ , ZnO ₂ , As ₂ O ₃ , TiO ₂ , B ₂ O ₃ ,
Cr ₂ O ₃ , PbO, V ₂ O ₅ , SnO _{2 and the} like can be mentioned. Further, as a metal oxide raw material, a carbonate, a hydroxide, or an oxalate which becomes these metal oxides by thermal decomposition may be blended as a raw material.

As the metal nitride, Si ₃ N ₄ , AlN,
Al ₂ N ₂ , Mg ₂ N ₂ , Li ₃ N and the like can be mentioned.

As the metal oxynitride, Si ₂ N ₂ O, Si
₅ N ₆ O and the like.

These raw materials are sufficiently mixed, heated and melted to obtain oxynitride glass. At this time, for example, the mixture is melted at 1400 to 1900 ° C. for 3 to
Vitrification is preferably performed in an atmosphere of an inert gas such as nitrogen or argon for 100 hours.

The vitrified oxynitride glass is refined, formed into a plate by a known method such as press molding or down-draw molding, and then subjected to processing such as grinding and polishing to obtain a desired size and shape. Of the magnetic recording medium.

In the polishing, lapping (sanding) and polishing (precision polishing) with a polishing powder such as cerium oxide can be performed to adjust the surface accuracy to, for example, Ra in the range of 3 to 8 angstroms.

In the glass substrate of the present invention, as long as the flatness of the substrate is not deteriorated, Ti is added to the glass.
By adding a crystal nucleating agent such as O ₂ or ZrO ₂ , or by performing a heat treatment at a temperature higher than the glass transition point without adding the crystal nucleating agent, a part of the glass is crystallized (phase separation is performed). Included). Further, glass containing a component of nitrogen-based ceramics or glass containing a state similar to sintered nitrogen-based ceramics may be used. Further, the glass substrate of the present invention includes any of transparent, translucent and opaque modes.

Further, the glass may contain an inclusion containing Si as a main component.

Further, fibers such as ceramic fibers such as SiC and alumina fibers, carbon fibers, boron fibers, glass fibers, aramid fibers, inorganic fibers, and fibers such as various whiskers or reinforcing materials are put into glass, and a high temperature region is added. May be imparted with high mechanical properties.

In the present invention, if necessary, the main surface of the glass substrate may be subjected to texturing by forming irregularities by means of etching, film formation, or laser light irradiation.

Specifically, the surface of the glass substrate can be wet-etched with an etching solution composed of a mixed solution of hydrofluoric acid and nitric acid to form irregularities on the glass surface and to perform texturing. Also, on the surface of the glass substrate,
By providing a concavo-convex film of aluminum or the like, the glass surface can be subjected to texturing.

The above-mentioned glass substrate for a magnetic recording medium of the present invention is excellent in heat resistance, flatness, chemical durability, optical properties and strength (mechanical properties). It can be suitably used as a glass substrate, a glass substrate for electro-optics such as an optical disk, a heat-resistant glass substrate for a low-temperature polycrystalline silicon liquid crystal display expected as a next-generation LCD, or a glass substrate for electric / electronic parts.

Next, the magnetic recording medium of the present invention and a method for manufacturing the same will be described.

The magnetic recording medium of the present invention is obtained by forming at least a magnetic layer on the main surface of the above-mentioned glass substrate for a magnetic recording medium of the present invention.

Here, the main surface refers to the surface on which the magnetic layer is formed, of the two surfaces of the glass substrate for a magnetic recording medium, and refers to one surface or both surfaces.

The layers other than the magnetic layer include an underlayer, a protective layer, a lubricating layer, a concavo-convex control layer, and the like in terms of function, and are formed as necessary. Various thin film forming techniques are used to form these layers.

The material of the magnetic layer is not particularly limited. Examples of the magnetic layer include, in addition to Co-based, ferrite-based and iron-rare-earth-based. The magnetic layer may be any of horizontal magnetic recording and perpendicular magnetic recording.

As the magnetic layer, specifically, for example, C
CoPt, CoCr, CoNi, Co mainly containing o
NiCr, CoCrTa, CoPtCr, CoNiC
rPt, CoNiCrTa, CoCrPtTa, CoC
A magnetic thin film such as rPtSiO may be used. Further, the magnetic layer may be divided by a non-magnetic film to have a multilayer structure in which noise is reduced.

The underlayer in the magnetic recording medium is selected according to the magnetic layer. As the underlayer, for example, Cr, M
Examples include at least one or more materials selected from nonmagnetic metals such as o, Ta, Ti, W, V, B, and Al, and an underlying layer made of an oxide, nitride, carbide, or the like of these metals. In the case of a magnetic layer containing Co as a main component, it is preferable to use Cr alone or a Cr alloy from the viewpoint of improving magnetic properties. The underlayer is not limited to a single layer, and may have a multilayer structure in which the same or different layers are stacked. For example, Al
/ Cr / CrMo, Al / Cr / Cr, etc.

In the present invention, an unevenness control layer may be provided between the glass substrate and the magnetic layer or above the magnetic layer to prevent the magnetic head and the magnetic recording medium from adsorbing. By providing this unevenness control layer, the surface roughness of the magnetic recording medium is appropriately adjusted, so that the magnetic head and the magnetic recording medium do not stick to each other, and a highly reliable magnetic recording medium can be obtained.

There are various known materials and methods for forming the unevenness control layer, and there is no particular limitation. For example, Al, Ag, Ti, Nb, Ta, Bi, S
i, Zr, Cr, Cu, Au, Sn, Pd, Sb, G
e, at least one or more metals selected from Mg, etc.
Or an alloy thereof, or an underlayer made of an oxide, nitride, carbide, or the like thereof.

From the viewpoint that the formation is easy and effective, it is desirable that the material of the unevenness control layer is a metal mainly composed of Al, such as Al alone, an Al alloy, Al oxide, or Al nitride.

In consideration of head stiction, it is desirable that the surface roughness of the unevenness control layer is Rmax = 50 to 300 Å. A more preferred range is Rmax = 100-200 Å.

If Rmax is less than 50 angstroms, the surface of the magnetic recording medium is almost flat, so that the magnetic head and the magnetic recording medium are attracted, and the magnetic head and the magnetic recording medium are damaged, or a head crash occurs due to the attracting. Not preferred. When Rmax exceeds 300 angstroms, glide height (glide height)
And the recording density decreases, which is not preferable.

Examples of the protective layer include a Cr film, a Cr alloy film, a carbon film, a zirconia film, and a silica film. These protective films can be continuously formed with an underlayer, a magnetic layer, and the like by an in-line type sputtering apparatus. Further, these protective films may have a single-layer structure or a multi-layer structure composed of the same or different films.

Another protective layer may be formed on the protective layer or in place of the protective layer. For example, colloidal silica fine particles may be dispersed and applied to the above-mentioned protective layer while diluting tetraalkoxylan with an alcohol-based solvent, and then fired to form a silicon oxide (SiO ₂ ) film. In this case, it functions as both the protective layer and the unevenness control layer.

Although various proposals have been made for a lubricating layer, generally, a liquid lubricant, perfluoropolyether (PFPE), is diluted with a solvent such as a Freon-based solvent and dipped on a medium surface by a dipping method. It is formed by applying by a spin coating method or a spraying method and performing a heat treatment as needed.

In the present invention, at the time of producing a magnetic recording medium, at least a magnetic layer is formed on the main surface of the oxynitride glass substrate, and then at least the magnetic layer is heat-treated at a temperature lower than the glass transition point. Is preferred.

This is because, depending on the type of the magnetic layer, the magnetic properties can be improved by performing the heat treatment. Since the oxynitride glass substrate used in the present invention has higher heat resistance than a conventional glass substrate, it can be heat-treated at a higher optimum temperature, and the magnetic properties can be maximized.

This heat treatment can be performed at any stage when forming the magnetic layer or after forming the magnetic layer and at any temperature that does not affect the properties of the protective layer and the lubricating layer. Good.

The heat treatment temperature required to improve the magnetic properties differs depending on the magnetic layer and is appropriately selected. For example, in the case of a Co-based magnetic layer, in order to obtain a high coercive force,
It is preferable to heat-treat the magnetic layer at 300 to 1000C.

When the heat treatment temperature is lower than 300 ° C., the non-magnetic material constituting the underlayer has less heat diffusion to the crystal grain boundaries of the ferromagnetic material constituting the magnetic layer, so that the ferromagnetic substance A strong magnetic interaction cannot be broken, and a magnetic recording medium having a high coercive force cannot be obtained. The heat treatment temperature is controlled not to exceed 1000 ° C. because the glass transition point of the oxynitride glass is 950 to 1000 ° C.
This is for avoiding deformation and the like of the glass substrate.

[0065]

EXAMPLES The present invention will be described below more specifically based on examples.

Production of glass substrate for magnetic recording medium

Examples 1 to 3

A glass substrate for a magnetic recording medium made of oxynitride glass having the composition shown in Table 1 was manufactured.

In each of the embodiments, raw materials such as oxides, nitrides, carbonates, and nitrates were mixed,
The raw glass sample is melted in the range of 0 to 1650 ° C., defoamed, homogenized by stirring, clarified, formed into a plate shape, cooled, and cut into a disk shape. A glass substrate for a magnetic recording medium was obtained by polishing with cerium oxide.

Table 1 shows the measurement results of the glass transition point, Young's modulus, specific gravity, specific elastic modulus, bending strength, Knoop hardness, and surface roughness (Ra) after polishing of the obtained glass substrate for a magnetic recording medium. Shown in

Comparative Examples 1 and 2

For comparison, a chemically strengthened glass substrate described in Japanese Patent Application Laid-Open No. 1-239036 (Comparative Example 1) and a crystallized glass substrate described in Japanese Patent Application Laid-Open No. 7-197711 (Comparative Example) Table 1 shows the composition and characteristics of 2).

[0073]

[Table 1]

As is clear from Table 1, Examples 1 to 3 are shown.
Since the glass substrate has a high glass transition point, it can be seen that the glass substrate has sufficient heat resistance to cope with a desired heat treatment. Also, the values of Young's modulus, specific elastic modulus, bending strength, Knoop hardness and the like are large, and it is understood that the strength is high. Especially,
Since the specific elastic modulus is large, it can be understood that, when used as a glass substrate for a magnetic recording medium, even if the glass substrate rotates at a high speed, the substrate is hardly warped or blurred, and the substrate can be made thinner. Further, the surface roughness (R
a) can be about 4 angstroms and is excellent in flatness, so that high-density recording can be achieved.
It is useful as a glass substrate for a magnetic recording medium.

On the other hand, the chemically strengthened glass substrate of Comparative Example 1 is excellent in flatness, but is significantly inferior to the glass substrate of the present invention in heat resistance and strength. Therefore, when manufacturing a magnetic recording medium, the heat treatment on the magnetic layer for obtaining a high coercive force cannot be performed sufficiently, and a magnetic recording medium having a high coercive force cannot be obtained.

The crystallized glass substrate of Comparative Example 2 is significantly inferior to the glass substrate of the present invention in specific elastic modulus and flatness. In particular, since flatness is impaired, high-density recording cannot be achieved.

From the above, it can be seen that, for use as a substrate for a magnetic recording medium, the above-mentioned physical properties and mechanical properties are desirably excellent, and oxynitride glass is useful.

Manufacturing of magnetic recording medium

Embodiment 4 FIG. 1 is a schematic sectional view showing the structure of a magnetic recording medium according to an embodiment of the present invention.

As shown in FIG. 1, a magnetic recording medium 1 according to the present invention comprises an oxynitride glass substrate 2 in which an unevenness control layer 3, an underlayer 4, a magnetic layer 5, a protective layer 6, a lubricating layer 7
Is formed.

More specifically, each oxynitride glass substrate is formed into a disk having an outer diameter of 65 mmφ, a hole diameter at the center of 20 mmφ, and a thickness of 0.381 mm. Was precisely polished so that the surface roughness was Ra = 4 Å and Rmax = 40 Å.

The unevenness control layer is an AlN thin film having an average thickness of 50 angstroms, a surface roughness Rmax of 150 angstroms, and a nitrogen content of 5 to 35%.

The underlayer is a thin film of CrV having a thickness of about 600 Å, and has a composition ratio of Cr: 83 at% (atomic%) and V: 17 at%.

The magnetic layer is a thin film of CoPtCr having a thickness of about 300 Å, and has a composition ratio of Co: 76 at%,
Pt: 6.6 at%, Cr: 17.4 at%.

The protective layer is a carbon thin film having a thickness of about 100 Å.

The lubricating layer is formed by applying a lubricant made of perfluoropolyether onto the carbon protective layer by spin coating to a thickness of 8 Å.

Next, a method for manufacturing a magnetic recording medium according to one embodiment of the present invention will be described.

First, an oxynitride glass was prepared with an outer diameter of 65 mmφ, a hole diameter of 20 mmφ at the center, and a thickness of 0.381.
Then, the two main surfaces are precisely polished so that the surface roughness is Ra = 4 angstroms and Rmax = 40 angstroms to obtain a glass substrate for a magnetic recording medium.

Next, after setting the above glass substrate in the substrate holder, the glass substrate is fed into the charging chamber of the in-line sputtering apparatus. Subsequently, the holder on which the glass substrate is set is sent to the first chamber in which the Al target is installed, and the pressure is 4 mtorr, the substrate temperature is 350 ° C., and Ar + N
Sputtering is performed in a ₂ gas (N ₂ = 4%) atmosphere. As a result, an AlN thin film (irregularity control layer) having a surface roughness Rmax = 150 Å and a film thickness of 50 Å was obtained on the glass substrate.

Next, the holder on which the glass substrate on which AlN was formed was set was placed on a CrV (Cr: 83 at%,
V: 17 at%) a second chamber in which a target was installed, CoPtCr (Co: 76 at%, Pt: 6.6 a)
(t%, Cr: 17.4 at%) The wafer is continuously and sequentially fed into a third chamber in which a target is installed, and a film is formed on a substrate. These films have a pressure of 2 mtorr and a substrate temperature of 35
Sputtering in an Ar atmosphere at 0 ° C.
An Angstrom CrV underlayer and a CoPtCr magnetic layer having a thickness of about 300 Å are obtained.

Next, the laminate on which the unevenness control layer, the underlayer, and the magnetic layer are formed is sent to a fourth chamber provided with a heater for performing a heat treatment. At this time, a heat treatment is performed at 850 ° C. in an atmosphere of Ar gas (pressure 2 mtorr) in the fourth chamber.

The substrate was fed into a fifth chamber in which a carbon target was installed, and Ar + H ₂ gas (H ₂ = 6)
%) Under the same film forming conditions as the CrV underlayer and the CoPtCr magnetic layer except that the film was formed in an atmosphere, a film thickness of about 100
Angstrom carbon protective layer is obtained.

Finally, the substrate after the formation of the carbon protective layer was taken out of the in-line sputtering apparatus, and the surface of the carbon protective layer was coated with a perfluoropolyether by dipping to form a lubricating layer having a thickness of 8 angstroms. Was formed to obtain a magnetic recording medium.

Evaluation The coercive force of the magnetic recording medium obtained above was 3000 Oe, and a magnetic recording medium having a high recording density was obtained. In relation to the head, the dynamic friction coefficient is 0.2,
The coefficient of static friction is 0.25, and CSS (contact start /
stop) Endurance test (100,000 times), but no problem,
Since the glide height at that time was also 0.015 μm or less, a highly reliable magnetic recording medium having a high recording density was obtained.

When a grind test was performed on the obtained magnetic disk, a hit (the head touches a protrusion on the surface of the magnetic disk) and a crash (the head hit the protrusion on the surface of the magnetic disk) were found. Did not.

Examples 5 to 10 and Comparative Examples 3 to 4 The sputtering conditions (substrate temperature, film thickness, nitrogen content) of the concavo-convex control layer were appropriately selected to obtain the surface roughness Rma of the concavo-convex control layer.
A magnetic recording medium was obtained in the same manner as in Example 4 except that x was changed.

With respect to the magnetic recording medium obtained above, the durability of the magnetic recording medium when the surface roughness Rmax of the unevenness control layer was changed was examined. Table 2 shows the results.

[0098]

[Table 2]

As is clear from Table 2, when the surface roughness Rmax of the unevenness control layer is 50 to 300 Å,
Since the medium surface roughness Rmax is 60 to 300 angstroms, adsorption between the magnetic head and the magnetic recording medium can be prevented, and the glide height can be suppressed to 0.03 [mu] m or less. A medium is obtained.

On the other hand, the surface roughness Rmax of the unevenness control layer
Is 45 angstroms, the Rmax of the medium surface formed due to it is almost flat at 50 angstroms, so that the coefficient of dynamic friction and the coefficient of static friction increase, and C
In the SS durability test, the magnetic head and the magnetic recording medium were adsorbed 2000 times (Comparative Example 3). Also, when the surface roughness Rmax of the unevenness control layer is 350 Å, the AlN crystal grows abnormally (the growth of each crystal varies), so that the adhesion between the magnetic head and the magnetic recording medium can be prevented. The height is undesirably increased to 0.04 μm, which hinders an increase in recording density (Comparative Example 4).

Examples 11 to 15 and Comparative Example 5 Magnetic recording media were obtained in the same manner as in Example 4 except that the heat treatment temperature after the formation of the magnetic layer was changed.

With respect to the magnetic recording medium obtained above, the change in coercive force when the heat treatment temperature of the magnetic layer was changed was examined. Table 3 shows the results.

[0103]

[Table 3]

As is evident from Table 3, when the heat treatment temperature after the formation of the magnetic layer is lower than 300 ° C., the non-magnetic material constituting the underlayer heats up the crystal grain boundaries of the ferromagnetic material constituting the magnetic layer. Since the diffusion is small, strong magnetic interaction between the particles of the ferromagnetic material cannot be broken, and a magnetic recording medium having a high coercive force cannot be obtained (Comparative Example 5). On the other hand, if the heat treatment temperature exceeds 950 ° C., the glass transition point of the oxynitride glass is exceeded, so that the substrate is deformed and the nonmagnetic material of the CrV underlayer is made of the ferromagnetic material of the CoPtCr magnetic layer. Since it is excessively diffused into the grain boundaries, the coercive force is undesirably reduced.

Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the above embodiments.

For example, the heat treatment of the magnetic layer was performed after the formation of the magnetic layer and before the formation of the protective layer. If the protective layer can sufficiently withstand the melting point of the oxynitride glass, A heater for performing heat treatment may be provided in the fifth chamber for forming the protective layer, and the heat treatment may be performed after forming the protective layer.

The atmosphere in the heat treatment was at a pressure of 1 m.
A similar effect can be obtained if the pressure is from torr to atmospheric pressure.

Further, the composition of the oxynitride glass and the material of the magnetic layer are not limited to those of the embodiment.

When glass substrates for low-temperature polycrystalline silicon liquid crystal display devices, which are expected to be next-generation LCDs, were manufactured in various sizes, heat resistance, flatness, chemical durability, optical properties and strength (various physical properties) were obtained.・ Mechanical properties) and other advantages, and it has the merit in terms of cost as compared with an expensive quartz glass substrate, and was confirmed to be sufficiently suitable for practical use.

Further, if necessary, the oxynitride glass substrate of the present invention may be bonded to a substrate of another material, or the oxynitride glass C
What formed the VD thin film can also be used according to a use.

[0111]

As described above, according to the glass substrate for a magnetic recording medium of the present invention, since oxynitride glass is used as the glass substrate material, it has excellent heat resistance, flatness and high strength. A glass substrate for a recording medium is obtained.

Further, according to the method for manufacturing a magnetic recording medium of the present invention, since the substrate has excellent heat resistance, the heat treatment required for improving the characteristics of the magnetic layer can be performed without deforming the substrate. Improvement can be maximized.

Further, according to the magnetic recording medium of the present invention,
Because of the excellent heat resistance of the substrate, it is possible to achieve the maximum improvement in the properties of the magnetic layer, and because of the excellent flatness of the substrate, it is possible to achieve low flying of the magnetic head, that is, high density recording,
Further, since the strength of the substrate is large, breakage of the disk can be avoided and the disk can be made thinner and smaller.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration of a magnetic recording medium according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic recording medium 2 Oxynitride glass substrate 3 Unevenness control layer 4 Underlayer 5 Magnetic layer 6 Protective layer 7 Lubrication layer

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Keiji Moroishi 2-7-5 Nakaochiai, Shinjuku-ku, Tokyo Inside Hoya Corporation

Claims (8)

[Claims] 1. A glass substrate for a magnetic recording medium, wherein oxynitride glass is used as a substrate material. 2. An oxynitride glass comprising Mg-A
1-Si-ON system, Ca-Al-Si-ON system, Y
-Al-Si-ON-based, Mg-Si-ON-based, Ca
2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium comprises a composition selected from the group consisting of -Si-ON-based and Ce-Al-Si-ON-based, or a mixture of two or more of these compositions. For glass substrates. 3. A magnetic recording medium comprising at least a magnetic layer formed on the main surface of the glass substrate according to claim 1. 4. A magnetic head and a magnetic recording medium are prevented from being attracted as a layer located between the glass substrate and the magnetic layer according to claim 1 or as a layer located above the magnetic layer. A magnetic recording medium, comprising: a concavo-convex control layer. 5. The surface roughness Rmax of the unevenness control layer is 50 to 50.
5. The magnetic recording medium according to claim 4, wherein the thickness is 300 angstroms. 6. A method for manufacturing a magnetic recording medium, comprising: forming at least a magnetic layer on a main surface of an oxynitride glass substrate; and heat-treating at least the magnetic layer at a temperature lower than a glass transition point. 7. The method according to claim 6, wherein the heat treatment temperature is 300 to 1000 ° C. 8. A glass substrate for a recording medium, wherein oxynitride glass is used as a substrate material.