JP2000169184A - Crystallized glass for information recording disk and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a crystallized glass and a crystallized glass substrate having a high Young's modulus, a low melting temperature and a low liquid phase temperature and excellent in surface smoothness and to obtain an information recording disk such as a magnetic disk. SOLUTION: The crystallized glass for an information recording disk contains, by mol, 42-65% SiO2, 0-15% Al2O3, 5-30% MgO, 0.5-8% Y2O3 and >10 to 25% Li2O and has a β-quartz solid solution and/or enstatite as the predominant crystal phase. The crystallized glass substrate for an information recording disk comprises the glass and the surface on which an information recording layer is formed has 0.1-0.9 nm surface roughness Ra. The information recording medium has the glass substrate and a recording layer formed on the glass substrate. The magnetic disk has the glass substrate and a magnetic recording layer formed on the glass substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a crystallized glass suitable for a magnetic disk substrate or a substrate for various electronic components, and a glass substrate using the crystallized glass. More specifically, the present invention provides a crystallized glass having high Young's modulus, excellent mechanical strength, surface flatness and heat resistance, and capable of providing a glass substrate having excellent surface smoothness by polishing, and a crystallized glass. The present invention relates to a glass substrate having excellent surface smoothness using crystallized glass. Further, the present invention relates to an information recording medium and a magnetic disk using the glass substrate.

[0002]

2. Description of the Related Art The main components of a magnetic storage device such as a computer are a magnetic recording medium and a magnetic head for magnetic recording and reproduction. Flexible disks and hard disks are known as magnetic recording media. Among them, aluminum alloys have been mainly used as substrate materials for hard disks. Recently, the flying height of a magnetic head has been remarkably reduced with the miniaturization of hard disk drives for notebook personal computers and the densification of magnetic recording. Accordingly, extremely high accuracy has been required for the surface smoothness of the magnetic disk substrate. But,
In the case of aluminum alloy, since the hardness is low, even if polishing is performed using a high-precision abrasive and a machine tool, the polished surface is plastically deformed, so that a flat surface with a high degree of accuracy is manufactured. It is difficult. Also, with the miniaturization and thinning of hard disk drives, it is required to reduce the thickness of the magnetic disk substrate. However, since aluminum alloy has low strength and rigidity, it is difficult to make the disk thin while maintaining a predetermined strength required by the specifications of the hard disk drive.

Therefore, glass substrates for magnetic disks, which require high strength, high rigidity, high impact resistance and high surface smoothness, have appeared instead of aluminum alloy substrates. Among them, a chemically strengthened glass substrate whose substrate surface is strengthened by an ion exchange method (for example, see Japanese Patent Application Laid-Open No. 1-239036)
Also, a crystallized substrate subjected to a crystallization treatment (for example, see US Pat. No. 5,391,522 and US Pat. No. 5,47,621) is well known. The ion exchange strengthened glass substrate described in Japanese Patent Application Laid-Open No.
_{O 2: 50-65%, Al 2} O 3: 0.5-14%, R 2 O ( wherein R is an alkali metal ion): 10-32, ZnO: 1-
This is a magnetic disk glass substrate formed by forming a compressive stress layer on the surface of a glass substrate containing 15% and B ₂ O ₃ : 1.1 to 14% by an ion exchange method using alkali ions, and strengthening it. Furthermore, the crystallized glass described in U.S. Patent 5391522 publication, in weight _{percentages, SiO 2: 65-83%, Li} 2 O:
_{8-13%, K 2 O: 0-7} %, MgO: 0.5-5.5%,
ZnO: 0-5%, PbO: 0-5% (MgO + ZnO + PbO:
_{0.5-5%) P 2 O 5:} 1-4%, Al 2 O 3: 0-7%, As 2
O ₃ + Sb ₂ O ₃ : containing 0-2%, and fine Li ₂ O ·
This is crystallized glass for magnetic disks containing 2SiO ₂ crystal particles. U.S. Pat. No. 5,476,821 discloses that SiO ₂ : 35-
_{60%, Al 2 O 3:} 20-35%, MgO: 0-25%, ZnO: 0-25%, however, MgO + ZnO> 10%, TiO 2: 0-20%, ZrO 2: 0-10 %, Li ₂ O:
Disclosed is a crystallized glass for a disk containing an oxide component such as 0-2%, NiO: 0-8%, and TiO2 + ZrO2 + NiO> 5%, and containing spinel crystal particles as a main crystal.

[0004]

However, with the recent miniaturization, thinning, and high-density recording of hard disks, low flying height of magnetic heads and high speed of disk rotation have rapidly progressed. There are increasing demands on the strength, Young's modulus, surface smoothness and the like of the substrate material. In particular, due to the recent increase in the density of 3.5-inch hard disk information recording for personal computers and servers, the surface smoothness and surface flatness of substrate materials are strictly required. Therefore, the requirements for the rigidity of the substrate material have become more severe, and the limitations of the conventional aluminum substrate have already become clear. In the future, as long as the demand for high capacity and high speed rotation of hard disks is inevitable, high Young's modulus, high strength, excellent surface flatness, impact resistance, etc. are being strongly demanded as substrate materials for magnetic recording media. No doubt.

For this reason, it is clear that the chemically strengthened glass disclosed in Japanese Patent Application Laid-Open No. 1-239036 cannot meet the severe requirements of hard disks in the future when the Young's modulus is about 80 GPa. In addition, since glass that has been chemically strengthened by ion exchange contains a large amount of alkali components, if it is used for a long time in a high-temperature, high-humidity environment, the thin portion of the magnetic film, such as the pinhole portion of the magnetic film or the periphery of the magnetic film, or It has been found that alkali ions are precipitated from a portion where the glass is exposed, and this causes a trigger to corrode or deteriorate the magnetic film. In addition, the conventional ion exchange strengthened substrate glass introduces a large amount of alkali ions into the glass for ion exchange, and therefore, most of the tempered glass has a low Young's modulus (100 GPa) and low rigidity, so that 3.5 inch There is a drawback that it cannot be applied to a high-end disk substrate or a thin disk substrate. Further, in the process of manufacturing a magnetic recording medium, after a magnetic layer is provided on a glass substrate, a predetermined heat treatment may be performed to improve characteristics such as a coercive force of the magnetic layer. In the tempered glass, the transition temperature of the glass is at most about 500 ° C. and the heat resistance is poor, so that there is a problem that a high coercive force cannot be obtained.

The conventional crystallized glass disclosed in US Pat. No. 5,391,522 is slightly superior to the above-mentioned chemically strengthened glass substrate in Young's modulus and heat resistance. However, since the surface roughness is greater than 10 angstroms and the surface smoothness is poor, there is a limit to the low flying height of the magnetic head, and there is a problem that it is impossible to cope with high density of magnetic recording. Furthermore, Young's modulus is at most 90-100Gpa
There is also a drawback that it cannot be used for a 3.5-inch high-end disk substrate or a thin disk substrate.
The crystallized glass for a magnetic disk disclosed in U.S. Pat. No. 5,447,821 has a high Young's modulus of about 140 Gpa, but has a high melting temperature and a high liquidus temperature because spinel is a main crystal, and a high hardness spinel crystal. Has a disadvantage that the hardness difference between the base glass and the base glass is too large to be polished. It is difficult to produce such a high Young's modulus crystallized glass at low cost, and the profitability is poor, so that it is not suitable for mass production.

Accordingly, an object of the present invention is to provide a crystallized glass having a high Young's modulus which can be used for an information recording disk such as a magnetic disk, has excellent surface smoothness, and has a low melting temperature and a low liquidus temperature. It is to provide a crystallized glass. Further, an object of the present invention is to use a crystallized glass having a high Young's modulus, a low melting temperature or a low liquidus temperature, and excellent surface smoothness, and can be used for an information recording disk such as a magnetic disk. It is to provide a glass substrate. Another object of the present invention is to provide an information recording medium and a magnetic disk using the crystallized glass substrate.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method for producing SiO ₂ : 42-65.
Mol%, Al ₂ O _3: 0-15 mol%, MgO: 5-30 mol%, Y
₂ O ₃ : 0.5-8 mol%, Li ₂ O: more than 10 mol%, 25 mol%
The present invention relates to a crystallized glass for an information recording disk, comprising: a main crystal phase of which is β-quartz solid solution and / or enstatite. Further, the present invention relates to an information recording disk substrate made of the above crystallized glass, and an information recording medium and a magnetic disk using the substrate.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The composition of the crystallized glass of the present invention is as follows.
It is indicated on an oxide basis as in the original glass. The reason why the composition range of the raw glass is limited as described above will be described below. In this specification, “%” means “mol” unless otherwise specified.
% ”SiO ₂ is a formation of a glass network structure, and is also a component of β-quartz solid solution and enstatite, which are the main precipitated crystals. Although not a main crystal, it is also a component of β-spodumene solid solution. If the content of SiO ₂ is less than 42%, the melted glass is unstable, so that high-temperature molding tends to be impossible, and the above crystals are difficult to precipitate as main crystals. When the content of SiO ₂ is less than 42%, the chemical durability of the remaining glass matrix phase tends to deteriorate, and the heat resistance tends to deteriorate. On the other hand, when the content of SiO ₂ exceeds 65%, the Young's modulus of the glass tends to rapidly decrease. As described above, the content of SiO ₂ is in the range of 42 to 65% in consideration of the precipitated crystal seed and the amount of the precipitated crystal, Young's modulus, chemical durability, heat resistance, and molding / productivity, and the lower limit is preferable. It is at least 45%, more preferably at least 48%, and the upper limit is preferably at most 62%, more preferably at most 60%.

[0010] Al ₂ O ₃ is an intermediate oxide of glass and also a component of β-quartz solid solution which is a main crystal seed. Al ₂ O
The introduction of ₃ promotes the precipitation of metastable β-quartz solid solution crystals,
Contributes to improvement of glass surface hardness. However, when the content of Al ₂ O ₃ exceeds 15%, the melting temperature and the liquidus temperature increase, so that the glass is hardly melted and the glass is hardly formed.
Therefore, the content of Al ₂ O ₃ is set to 15% or less. Soluble glass, high temperature moldability, considering that such precipitated crystals species, the content of Al ₂ O ₃ is in the range from 0 to 15% lower limit is preferably 1% or more, more preferably 2% or more The upper limit is preferably 10% or less, more preferably 7% or less. Further, the content of SiO ₂ + Al ₂ O ₃ is preferably at least 50%, more preferably at least 55%, from the viewpoint of giving the glass a high-temperature viscosity capable of being formed.

MgO forms β-quartz solid solution and enstatite crystal by heat treatment of raw glass together with SiO ₂ component,
It is a very important component that has the effect of maintaining transparency while improving hardness and heat resistance. However, if the content of MgO is less than 5%, the above effects cannot be obtained. Further, when the content of MgO decreases, the tendency of devitrification of the glass and the melting temperature also increase, so the content of MgO is set to 5% or more. On the other hand, when the content of MgO exceeds 30 mol%, the liquidus temperature of the glass rapidly increases, and the productivity and workability also deteriorate. Therefore, the content of MgO is set to 30% or less. The content of MgO is in the range of 5 to 30% in consideration of productivity, melting property and mechanical strength of the glass, and the lower limit is preferably 7% or more, more preferably 10% or more, and the upper limit. Is preferably 25% or less, more preferably 20% or less.

The above crystallized glass contains Y ₂ O ₃ .
By introducing at least 0.5% of Y ₂ O ₃ , the Young's modulus of the crystallized glass is increased by about 5 GPa, and the liquidus temperature is increased by 5 GPa.
It can be reduced by about 0 ° C. In addition, at least 0.5
By introducing% Y ₂ O ₃ , the thermal stability of the glass can also be improved. Thus, by introducing a small amount of Y ₂ O ₃ , the properties and productivity of the glass can be remarkably improved. However, since Y ₂ O ₃ also has the function of suppressing the nucleation of the above glass main crystal, if the introduction amount of Y ₂ O ₃ becomes too large, the glass undergoes surface crystallization during heat treatment, and the target There is a tendency that it is difficult to obtain crystallized glass having surface smoothness. Therefore, the content of Y ₂ O ₃ is reduced to 8%.
The following is assumed. The lower limit of the content of Y ₂ O ₃ is preferably 0.5%, more preferably 1%. The upper limit of the content of Y ₂ O ₃ is preferably 5%, more preferably 3%.

Li ₂ O is a component that produces a crystal such as β-quartz solid solution or β-spodumene solid solution by heat treatment of the raw glass together with SiO ₂ , and has the effect of lowering the liquidus temperature and crystallization temperature of the glass. If the content of Li ₂ O is 10% or less, the above effects cannot be obtained. Furthermore, the content of Li ₂ O
If it is less than 10%, the melting temperature of the glass will be high, and the working temperature range for forming the glass disc will be narrow. Therefore,
Suitably, the content of Li ₂ O exceeds 10%. On the other hand, L
When the content of i ₂ O exceeds 25%, the glass becomes extremely unstable, and the Young's modulus of the obtained crystallized glass tends to be greatly reduced. Therefore, the content of Li ₂ O is set to 25% or less. In consideration of productivity, chemical durability and mechanical properties of glass, the lower limit of the content of Li ₂ O is preferably 10.5% or more, more preferably 11% or more. Further, the upper limit of the content of Li ₂ O is preferably 22% or less, more preferably 20% or less.

The crystallized glass of the present invention contains one or both of β-quartz solid solution and enstatite as a main crystal phase. The crystal phase of β-quartz solid solution is 2MgO ・ 2Al ₂ O ₃・ 5S
Although in metastable quartz (quartz solid solution) having one or more compositions selected from _{iO 2, MgO · Al 2 O} 3 · 3SiO 2, and the group consisting of _{MgO · Al 2 O 3 · 4SiO} 2 . In addition, the crystal phase of enstatite can be, for example, a clinoenstatite crystal phase having a composition of Mg ₂ Si ₂ O ₆ . Further, the crystallized glass of the present invention may contain other crystals such as β-spodumene solid solution as a crystal phase in addition to the above-mentioned crystals.

Further, the crystal grain size of the crystal contained in the crystallized glass of the present invention is such that the crystallized glass of the present invention can form a polished surface so that the surface roughness Ra is in the range of 0.1 to 0.9 nm. It is more preferable that the crystal grain size of the crystal phase is such that the polished surface can be formed such that the surface roughness Ra is in the range of 0.1 to 0.5 nm. When the crystal grain size of the crystal phase contained in the crystallized glass is within the above range, an information recording disk having excellent surface smoothness can be provided.

Further, in the crystallized glass of the present invention,
The composition of the glass is preferably selected so that the liquidus temperature of the raw glass is 1200 ° C. or lower. More preferably, it is selected such that the liquidus temperature of the raw glass is 1150 ° C. or lower. The low liquidus temperature of the raw glass facilitates the production of a crystallized glass substrate. That is, in the steps of melting the raw materials performed when manufacturing the glass substrate, forming and the like,
Since it is not necessary to use a remarkably high temperature, there is an advantage that manufacturing is easy, for example, the range of adoption of the material of the melting furnace and the forming die is widened.

TiO ₂ , ZrO ₂ , and P ₂ O ₅ all act as crystal nucleus generating agents and promote the precipitation of fine crystal particles such as β-quartz solid solution and enstatite. Also, when the content of SiO ₂ is relatively small, it is a component that gives the glass thermal stability. Therefore, the crystallized glass of the present invention preferably contains at least one of TiO ₂ , ZrO ₂ , and P ₂ O ₅ . In that case, the total content of TiO ₂ + ZrO + P ₂ O ₅ is 5
If it is less than%, the effect of the main crystal as a nucleating agent cannot be sufficiently obtained, and the glass is crystallized on the surface, which tends to make it difficult to produce a homogeneous crystallized glass. Therefore, TiO ₂ , ZrO ₂ ,
And the total content of P ₂ O ₅ is preferably 5% or more. On the other hand, if the total content of TiO ₂ , ZrO ₂ , and P ₂ O ₅ exceeds 18%, the high-temperature viscosity of the glass becomes too low, causing phase separation or devitrification. There is a tendency to be extremely deteriorated. Therefore, the total content of TiO ₂ + ZrO + P ₂ O ₅ is preferably 18% or less. Glass productivity, chemical durability, high temperature viscosity, considering that such crystal nucleation, total content of _{TiO 2 + ZrO + P 2 O} 5 is in the range 5 to 18%, as described above Is preferred. TiO ₂ + ZrO + P ₂ O ₅
Is preferably 6% or more, more preferably 7% or more, and the upper limit is preferably 15% or less, more preferably 13% or less.

Alkali and alkaline earth metal oxide components such as Na ₂ O, K ₂ O, CaO, SrO, BaO, ZnO and NiO mainly adjust the high temperature viscosity of glass, suppress the tendency of devitrification, Is a component that can be homogenized. By adding at least one of these components to the glass, the Young's modulus of the glass is slightly reduced, but the productivity of the glass is improved, and other properties of the glass, such as the size of crystallized particles are homogenized. Can be improved. Considering properties such as Young's modulus of glass, productivity, surface smoothness and strength of crystallized glass
Na ₂ O content ranges from 0 to 10%, K ₂ O content from 0 to 10%
And the content of Na ₂ O + K ₂ O is preferably 10% or less. The contents of Na ₂ O, K ₂ O and Na ₂ O + K ₂ O are:
Both are preferably at most 8%. Similarly, CaO
Is in the range of 0-10%, SrO is in the range of 0-10%, BaO is in the range of 0-10%, and ZnO is in the range of 0-10%.
%, The content of NiO is in the range of 0-10%, and
The content of O + SrO + BaO + ZnO + NiO is preferably at most 10 mol%. Furthermore, CaO, SrO, BaO, ZnO, NiO and CaO
The content of + SrO + BaO + ZnO + NiO is preferably at most 8%.

In addition to the above components, the crystallized glass of the present invention contains B ₂ O ₃ , Nb ₂ O ₅ , and Ta as long as desired properties are not impaired.
Rare earth metal oxide components such as ₂ O ₅ and La ₂ O ₃ can be contained. However, these components significantly reduce the Young's modulus of the glass. Therefore, the content of B ₂ O ₃ is in the range of 0-5%, and the content of R ₂ O ₃ is in the range of 0-5% (where R is a rare earth metal ion (eg, Nd ³⁺ , Pr ³⁺ , Pm ³⁺ , Sm ³⁺ , Eu ³⁺ , G
d ³⁺ , Tb ³⁺ , Dy ³⁺ , Ho ³⁺ , Er ³⁺ , Tm ³⁺ , Yb ³⁺ ),
The content of CeO ₂ is in the range of 0-5%, the content of N ₂ O ₅ is in the range of 0-5% (where N is Nb or Ta), and B ₂ O ₃ + R
It is preferable that ₂ O ₃ + CeO ₂ + N ₂ O ₅ ≦ 5 mol%. Further, considering the productivity of glass, it is more preferable that the content of each of the above components and the total content be 4% or less.

As ₂ O ₃ and Sb ₂ O ₃ are components added as defoaming agents in order to homogenize glass as a raw material of crystallized glass. An appropriate amount of As ₂ O according to the high temperature viscosity of each glass
_By adding one or both of ₃ and Sb ₂ O ₃ to the glass,
A more homogeneous glass is obtained. However, if the amount of the defoaming agent is too large, the specific gravity of the glass tends to increase and the Young's modulus tends to decrease, and the glass may react with the melting platinum crucible and damage the crucible. Therefore, the content of As ₂ O ₃ is in the range of 0 to ₂ %, and the content of Sb ₂ O ₃ is 0%.
It is preferred that the content be in the range of −2% and that As ₂ O ₃ + Sb ₂ O ₃ ≦ 2 mol%. In particular, the content of each of As ₂ O ₃ , Sb ₂ O ₃ and As ₂ O ₃ + Sb ₂ O ₃ is preferably 1.5% or less.

The method for producing crystallized glass of the present invention is not particularly limited, and crystallized glass can be obtained by heat-treating glass obtained by using various glass production methods. For example, a high-temperature melting method, that is, a glass material of a predetermined ratio is melted in the air or an inert gas atmosphere, and the glass is homogenized by bubbling, addition of a defoaming agent, stirring, etc. It is formed into a sheet glass by a method such as molding or down-drawing, and then subjected to processing such as grinding and polishing to obtain a glass molded product having a desired size and shape. The heat treatment method of the obtained glass molded article is not particularly limited, and can be selected according to the content of the crystallization promoter, the glass transition temperature, the crystallization peak temperature, and the like. However, it is preferable to grow the crystal at a higher temperature after first generating a large number of crystal nuclei by heat treatment at a relatively low temperature in order to obtain fine crystals. Heat treatment under appropriate conditions reduces the crystal grain size to 5-
A crystallized glass containing one or both of β-quartz solid solution and enstatite in the range of 500 nm is obtained.

The surface of the molded article after the heat treatment can be polished by a conventional method. There is no particular limitation on the polishing method, synthetic diamond, silicon carbide, aluminum oxide, synthetic abrasive grains such as boron carbide, natural diamond,
Polishing can be performed by a known method using natural abrasive grains such as cerium oxide. For example, by lapping and polishing with cerium oxide by a usual polishing method and apparatus, the surface roughness (Ra) is 0.1-0.9 n.
m.

The crystallized glass of the present invention thus obtained is suitable for use in information recording disks. The magnetic disk substrate using the crystallized glass of the present invention satisfies all of the surface smoothness, flatness, strength, hardness, chemical durability, heat resistance, and the like required for the magnetic disk substrate. Also,
Compared to conventional crystallized glass (Li ₂ O-SiO ₂ crystallized glass), it has a higher Young's modulus, so it can reduce the deflection due to high-speed rotation of the disk, and has a high TPI
It is suitable as a substrate material for realizing a hard disk.

In producing the crystallized glass of the present invention, the size and amount of precipitated crystals can be controlled by appropriately changing the heat treatment schedule and the glass composition, and if necessary, the characteristics of the crystallized glass can be greatly increased. Can be adjusted.

Next, the information recording medium of the present invention will be described. An information recording medium according to the present invention includes the glass substrate for an information recording medium according to the present invention, and a recording layer formed on the glass substrate. Here, the “recording layer formed on the glass substrate” means a recording layer having a single-layer structure or a multi-layer structure formed directly or via a desired layer on the surface of the glass substrate. The material and the layer structure are appropriately selected so as to function as a magnetic recording layer, an optical recording layer, a magneto-optical recording layer, and the like, depending on the type of the intended information recording medium.

Next, the magnetic disk of the present invention will be described. A magnetic disk according to the present invention includes the glass substrate according to the present invention and a magnetic recording layer formed on the glass substrate. A magnetic disk (hard disk) in which at least a magnetic layer is formed on the main surface of the above-described glass substrate of the present invention will be described below.
The layers other than the magnetic layer include an underlayer, a protective layer, a lubricating layer, an unevenness control layer, and the like from the functional aspect, 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, CoPt containing Co as a main component, CoC
r, CoNi, CoNiCr, CoCrTa, CoPtCr, CoNiCrPt, CoNiCrT
a, CoCrPtTa, CoCrPtSiO and the like. Further, the magnetic layer may be divided by a non-magnetic layer to have a multilayer structure in which noise is reduced.

The underlayer in the magnetic layer is selected according to the magnetic layer. As the underlayer, for example, Cr, Mo, Ta, T
Examples include at least one or more materials selected from nonmagnetic metals such as i, W, V, B, and Al, and an underlayer made of an oxide, nitride, carbide, or the like of those metals. In the case of a magnetic layer containing Co as a main component, from the viewpoint of improving magnetic properties
Preferably, it is Cr alone or a Cr alloy. 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, a multilayer base layer of Al / Cr / CrMo, Al / Cr / Cr, or the like can be given.

An unevenness control layer for preventing the magnetic head and the magnetic disk from being attracted to each other may be provided on a part or all of the substrate surface between the substrate and the magnetic layer or on the magnetic layer. By providing the unevenness control layer, the surface roughness of the magnetic disk is appropriately adjusted, so that the magnetic head and the magnetic disk do not stick to each other, and a highly reliable magnetic disk can be obtained. There are various known materials and methods for forming the unevenness control layer, and there is no particular limitation. For example,
As the material of the unevenness control layer, Al, Ag, Ti, Nb, Ta, Bi,
At least one or more metals selected from Si, Zr, Cr, Cu, Au, Sn, Pd, Sb, Ge, Mg, etc., or alloys thereof, or oxides, nitrides, carbides thereof, etc. And the like. From the viewpoint of easy formation, it is desirable to use a metal containing Al as a main component, such as Al alone, an Al alloy, Al oxide, or Al nitride.

In consideration of head stiction, the surface roughness of the unevenness forming layer is preferably Rmax = 50 to 300 angstroms. A more preferred range is Rmax = 100-200 Å. Rm
When ax is less than 50 angstroms, the magnetic disk surface is almost flat, so the magnetic head and the magnetic disk are attracted, the magnetic head and the magnetic disk are attracted, and the magnetic head and the magnetic disk are damaged or the head is crashed due to the attracting. It is not preferable because it causes Also, Rmax is 3
If the thickness exceeds 00 angstroms, the glide height (glide height) is increased, and the recording density is undesirably reduced. Note that, without providing the unevenness control layer, the surface of the glass substrate may be subjected to texturing by providing an unevenness by means of etching treatment, laser light irradiation, or the like.

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 or the like. 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 film. For example, colloidal silica fine particles may be dispersed and applied while diluting tetraalkoxylan with an alcohol-based solvent on the protective layer, followed by firing to form a silicon oxide (SiO ₂ ) film. In this case, it functions as both the protective film and the unevenness control layer.

Although various proposals have been made for a lubricating layer, generally, a liquid lubricant, perfluoropolyether, is diluted with a solvent such as Freon, and the surface of the medium is dipped or spin-coated. It is formed by applying a spray method and performing a heat treatment as needed.

[0032]

The crystallized glass of the present invention can be easily formed, has a large Young's modulus of 110 GPa or more and a high heat resistance of about 700 ° C., and has excellent surface smoothness (surface roughness Ra).
In the range of 0.1-0.9 nm). Therefore, it is possible to provide a substrate material and a material for electronic components having high hardness and strength. Also,
The magnetic disk using the crystallized glass of the present invention can be subjected to the heat treatment necessary for improving the characteristics of the magnetic film without deforming the substrate. Further, the magnetic disk using the crystallized glass of the present invention is excellent in flatness, so that low flying of the magnetic head, that is, high-density recording can be achieved, and the Young's modulus and strength are large. High-speed rotation can be achieved, and damage to the magnetic disk can be avoided. Furthermore, the melting conditions of the raw glass can be clarified and homogenized in a temperature range of 1350-1450 ° C in 2-5 hours, so that the glass has good melting properties and is easy to produce on an industrial scale. It can be greatly expected as a substrate glass for recording media. Further, since the information recording medium of the present invention has a high Young's modulus and uses a crystallized glass substrate having excellent surface smoothness, vibration can be reduced even at a high rotation of the substrate, especially for a server or the like. It can be suitably used for high-performance hard disk drives.

[0033]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. Table 1 shows the glass compositions of the examples in mol%. Starting materials for melting these glasses include SiO ₂ ,
Al ₂ O ₃ , Al (OH) ₃ , MgO, CaCO ₃ , Y ₂ O ₃ , TiO ₂ , ZrO ₂ , Li ₂ C
O ₃ by using a 250-30 in a predetermined ratio shown in Table 1
0 g was weighed and mixed well to form a blended batch, which was placed in a platinum crucible and stirred at 1550 ° C. in air for 4 hours.
The glass was melted for -5 hours. After melting, pour the glass melt into a carbon mold of size 180 × 15 × 25 mm,
After allowing to cool to the glass transition point temperature, it was immediately placed in an annealing furnace, annealed for about 1 hour in the glass transition temperature range, and allowed to cool to room temperature in the furnace. The obtained glass did not precipitate crystals that could be observed with a microscope.

A glass of 180 × 15 × 25 mm size is
00 × 10 × 10mm, 10 × 10 × 20mm, 10 × 1 ×
After polishing to 20 mm, it is placed in a heat treatment furnace and heated up to the primary heat treatment temperature (nucleation temperature) shown in Table 1 at a rate of 3 to 10 ° C./min, and at that temperature for about 2 to 15 hours. Keep the temperature and perform the first heat treatment. Immediately after completing the first heat treatment, raise the temperature from the first heat treatment temperature to the second heat treatment temperature (crystallization temperature) shown in Table 1 by 1 to 20 ° C / min. The temperature was raised at a rate, and the temperature was kept for about 1 to 8 hours, and then cooled to room temperature in a furnace to produce crystallized glass.

The obtained crystallized glass was further extended to a length of 95 mm.
The sample was polished to obtain a sample for measuring Young's modulus and specific gravity. The sample used for measuring the Young's modulus was further cut, and 25 mm x 2 m
It was precisely polished to a size of mx 15 mm to obtain a sample for measuring surface roughness. The measurement of the Young's modulus was performed by an ultrasonic method using a sample of 95 × 10 × 10 mm. The data obtained by the measurement are shown in Table 1 together with the composition of the glass.

[0036]

[Table 1]

The surface roughness is measured by an atomic force microscope (AFM)
Was used to observe the surface. Arithmetic average roughness in a visual field of 5 × 5 μm per 3 to 5 places on the sample surface was calculated. Of course, the surface roughness varies depending on the polishing conditions and the heat treatment conditions, but FIG. 1 shows Example 4 in which the heat treatment was performed under the heat treatment conditions shown in Table 1.
After polishing the crystallized glass in the optical glass polishing process
An AFM photograph is shown. The surface roughness of Example 4 is as small as about 0.3 nm, which can sufficiently meet the demand for the surface smoothness of the next-generation magnetic disk. Further, by optimizing the heat treatment conditions and the polishing conditions, it is possible to produce crystallized glass having more excellent surface smoothness.

Incidentally, for comparison, Japanese Patent Application Laid-Open No. 1-29033
No. 6 and the ion exchange glass substrate disclosed in US Pat.
Table 2 shows the composition and characteristics of the glass substrate described in No. 16553 as Comparative Examples 1 and 2, respectively.

[0039]

[Table 2]

As is clear from Table 1, the glass substrates of the present invention (Examples 1 to 8) have a Young's modulus (range of 115 to 150 Gpa).
This indicates that, when used as a substrate for a magnetic recording medium, even if the glass substrate is rotated at a high speed, the substrate is unlikely to be warped or blurred, and the substrate can be made thinner. Furthermore, the surface roughness (Ra) of these crystallized glasses can be polished to 5 ° (0.5 nm) or less, and the flatness is excellent, so that the flying height of the magnetic head can be reduced. It is useful as a glass substrate for a recording medium.

On the other hand, the chemically strengthened glass substrate of Comparative Example 1 shown in Table 2 has excellent surface smoothness and flatness, but has strength characteristics such as heat resistance and Young's modulus which are lower than those of the glass substrate of the present invention. Pretty poor. Therefore, when manufacturing a magnetic recording medium, the heat treatment on the magnetic layer to obtain a high coercive force cannot be performed sufficiently, so that a magnetic recording medium having a high coercive force cannot be obtained. Because of containing alkali, corrosion between the magnetic film and the substrate is likely to occur, which may damage the magnetic film.

The crystallized glass substrate of Comparative Example 2 is inferior to the glass of the present invention in Young's modulus, specific elastic modulus and smoothness. In particular, since the smoothness of the substrate is impaired by the presence of large crystal grains, it is difficult to achieve high-density recording.

The crystallized glass of the present invention has a high Young's modulus and excellent surface smoothness, indicating that it is very useful as a substrate for an information recording medium such as a magnetic recording medium.

[Brief description of the drawings]

FIG. 1 is changed to a drawing showing a state after heat-treated crystallized glass of Example 4 is polished in an optical glass polishing step.
AFM photo.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 5/84 G11B 5/84 Z F term (Reference) 4G062 AA11 BB01 CC09 CC10 DA05 DA06 DB01 DB02 DB03 DB04 DC01 DC02 DC03 DD01 DD02 DD03 DD04 DE01 DE02 DE03 DF01 EA04 EB01 EC01 ED03 ED04 EE01 EE02 EE03 EF01 EF02 EF03 EG01 EG02 EG03 FA01 FB01 FB02 FB03 FB04 FC01 FC02 FC03 FC04 FD01 FE01 F01 F03 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 F01 GE01 HH01 HH03 HH05 HH07 HH09 HH11 HH12 HH13 HH15 HH17 HH20 JJ01 JJ02 JJ03 JJ04 JJ05 JJ07 JJ10 KK01 KK02 KK03 KK04 KK05 KK06 KK07 KK08 KK10 MM27 NN33 NN40 Q04A07 NN40 Q04A08

Claims (15)

[Claims] 1. SiO ₂ : 42-65 mol%, Al ₂ O ₃ : 0-15 mol%, MgO: 5-30 mol%, Y ₂ O ₃ : 0.5-8 mol%, Li ₂ O: 10
More than 25 mol%, and the main crystal phase is β
A crystallized glass for an information recording disk, which is a quartz solid solution and / or enstatite. 2. The glass according to claim 1, wherein SiO ₂ + Al ₂ O ₃ ≧ 50 mol%. 3. The method according to claim 1, further comprising at least one of ZrO ₂ , TiO ₂ and P ₂ O ₅ , and wherein ZrO ₂ + TiO ₂ + P ₂ O ₅ : 5-18 mol%. The glass described. 4. The method according to claim 1, further comprising 0-10 mol% of Na ₂ O and 0-10 mol% of K ₂ O, and wherein Na ₂ O + K ₂ O ≦ 10 mol%. Or the glass of item 1. 5. CaO: 0-10 mol%, SrO: 0-10 mol%,
5. The composition according to claim 1, further comprising 0-10 mol% of BaO, 0-10 mol% of ZnO and 0-10 mol% of NiO, and wherein CaO + SrO + BaO + ZnO + NiO ≦ 10 mol%. A glass according to any one of the preceding claims. 6. B ₂ O ₃ : 0-5 mol%, R ₂ O ₃ : 0-5 mol%
(Here, R is a rare earth metal ions), CeO _2: 0-5 mol%, N ₂ O _5: 0-5 mol% (where, N represents a is Nb or Ta) further contains, and B ₂ The glass according to claim 1, wherein O ₃ + R ₂ O ₃ + CeO ₂ + N ₂ O ₅ ≦ 5 mol%. 7. The As_TwoO_Three: 0-2 mol%, Sb_TwoO_Three： 0-2mol%
And further contains As _TwoO_Three+ Sb_TwoO_Three≦ 2 mol%
The glass according to any one of claims 1 to 6. 8. The glass according to claim 1, further comprising a β-spodumene solid solution as a crystal phase. 9. The glass according to claim 1, wherein the composition is selected such that the liquidus temperature of the raw glass is 1200 ° C. or lower. 10. The crystal phase of the crystal phase has a surface roughness.
The glass according to any one of claims 1 to 9, wherein the polished surface can be formed so that Ra is in a range of 0.1 to 0.9 nm. 11. The method according to claim 11, wherein the crystal phase of the crystal phase has a surface roughness.
The glass according to any one of claims 1 to 9, wherein a polished surface can be formed so that Ra is in a range of 0.1 to 0.5 nm. 12. A glass material according to claim 1, wherein a surface for forming an information recording layer has a surface roughness Ra in a range of 0.1-0.9 nm. Crystallized glass substrate for information recording disks. 13. The surface for forming an information recording layer has a thickness of 0.1 mm.
13. The glass substrate according to claim 12, having a surface roughness Ra in the range of 1-0.5 nm. 14. An information recording medium comprising: the glass substrate according to claim 12; and a recording layer formed on the glass substrate. 15. A magnetic disk comprising: the glass substrate according to claim 12; and a magnetic recording layer formed on the glass substrate.