JP2001052334A - Substrate material for magnetic disk and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a substrate with a high-level smoothness by specifying ratio of an average composition and a crystal part of a crystallized glass, a quantity of a β-spodumene solid solution, and a crystal particle size of each of a β-eucryptite solid solution and the β-spodumene solid solution. SOLUTION: A crystallized glass has an average composition of SiO2 by 50-65 wt.%, Al2O3 by 18-30 wt.%, Li2O3 by 3-8 wt.%, TiO2+ZrO2 by 3-5 wt.%, P2O5 and/or B2O3 by 8 wt.% or smaller in total, RO (R is a metallic atom selected from a group of magnesium, calcium, etc.), by 0.3-7.0 wt.%, R2O (R is a potassium atom or sodium atom) by 3.0 wt.% or smaller, and F by 0.1-0.5 wt.%. A ratio of a crystal part to the entire crystallized glass is set to be 70-85 wt.%, and a quantity of a β-sprodumene solid solution is set to be 60 wt.% or smaller than a total quantity of the β-spodumene solid solution and a β-eucryptite solid solution. A particle size of each crystal particle of the solid solutions is set to be 0.1-0.5 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk substrate material made of crystallized glass and a method of manufacturing the same.

[0002]

2. Description of the Related Art As a substrate of a magnetic disk (so-called hard disk) which is one of storage devices of a computer, a substrate made of aluminum alloy, tempered glass, crystallized glass, or the like is used. As the densification and the speed increase progress, crystallized glass having excellent properties in terms of surface properties and physical properties has attracted attention as a substrate material.

[0003] Crystallized glass is obtained by heat-treating special glass to form a structure in which fine crystal particles are uniformly dispersed in a vitreous matrix. The crystallized glass depends on the type of crystal to be formed, the size and amount of crystal particles, and the like. However, it is excellent as a material for a high-density information substrate, such as having better heat resistance and higher hardness and Young's modulus than a substrate made of tempered glass, hardly being scratched, and being less deformed during high-speed rotation.

[0004] Crystallized glass produced by subjecting glass to a heat treatment for crystallization is not completely crystalline.
The glass has a structure in which glass which has not been partially crystallized and remains as a continuous phase and crystal particles are scattered therein. For this reason, the surface of the magnetic disk substrate manufactured using crystallized glass has a rough surface in which crystal grains that are harder than the glass phase and are less polished form small projections (Japanese Patent Laid-Open No. 2-187922). No.). Such a feature is advantageously used to prevent the magnetic head from sticking to the magnetic disk. However, when the recording density is to be increased by adopting the perpendicular magnetic recording method for the magnetic disk, a particularly high degree of smoothness is required for the substrate, so that the surface roughness Ra (the center line average roughness of JIS B0601) is a few. nm ~
A conventional crystallized glass substrate of about 100 nm cannot be used.

[0005]

As described above, since the surface roughness of a magnetic disk substrate made of crystallized glass is governed by the crystal grain size, it is necessary to reduce the surface roughness beyond the conventional limit. It is necessary to use a crystallized glass having a uniform crystal particle diameter smaller than that of a conventional crystallized glass for manufacturing a substrate.

An object of the present invention is to obtain a polished surface having a Ra of about 0.6 nm or less, and therefore, a high smoothness which can be used for a magnetic disk of a high-density perpendicular magnetic recording system which is a future target. It is an object of the present invention to provide a crystallized vitreous substrate material having a small crystal particle diameter and capable of producing a substrate having a property, and a method for producing the same.

Another object of the present invention is to provide a magnetic disk substrate material which not only has a small crystal grain size but also has excellent properties in terms of physical properties such as surface hardness, Young's modulus and thermal expansion coefficient as a magnetic disk substrate. It is to provide a manufacturing method thereof.

[0008]

The substrate material for a magnetic disk provided by the present invention comprises a β-eucryptite solid solution (Li ₂ O—Al ₂ O ₃ -2SiO ₂ ) crystal particles and a β-spodumene solid solution ( Li _{2 O-Al} 2 _{O 3}
-4 SiO ₂ ) consisting of crystallized glass in which glass particles are scattered in a vitreous matrix. The crystallized glass has an average composition of 50 to 65% by weight of SiO ₂ and Al ₂ O ₃ 18
30 _wt%, Li 2 _O3~8 wt%, _TiO 2 + Zr
O ₂ 3 to 5 _wt%, P 2 _{O 5} and _(or) B 2 _{O 3}
In a total amount of 8% by weight or less, RO (where R represents a metal atom selected from the group consisting of magnesium, calcium, zinc, lead, and vanadium) 0.3 to 7.0% by weight, R ₂ O ( Wherein R represents a potassium atom or a sodium atom) 3.0% by weight or less, F is 0.1 to 0.5% by weight, the ratio of the crystal part to the whole crystallized glass is 70 to 85% by weight, and β- The amount of the solid solution of spodumene is not more than 60% by weight of the total amount of the solid solution of β-eucryptite and the solid solution of β-spodumene, and the particle size of each crystal particle of the β-eucryptite solid solution and the β-spodumene solid solution is 0.1%. ０．５0.5 μm.

[0009] The present invention also relates to an oxide composition comprising SiO ₂ 50
65 _{wt%, Al} 2 O 3 _18~30 wt%, _Li 2 O
3-8 _wt%, TiO 2 + _ZrO 2 _3~5 wt%, _{P 2}
O ₅ and _(or) B 2 _{O 3} 8% by weight in a total amount below, RO (wherein R represents magnesium, calcium, zinc, lead, and the metal atoms selected from the group consisting of vanadium) 0.3 7.0% by weight, R ₂ O (R
Represents a potassium atom or a sodium atom) 3.0% by weight or less, and 0.1 to 0.5% by weight of glass formed into a shape required for a magnetic disk substrate material by crystallization treatment. Β having a crystal particle diameter of 0.1 to 0.5 μm
A method for producing a magnetic disk substrate, wherein crystallized glass in which crystal particles of a eucryptite solid solution and crystal particles of a β-spodumene solid solution are dispersed in a vitreous matrix.

In a particularly preferred embodiment of the above-mentioned production method, the amount of β-spodumene solid solution is 6 times the total amount of β-eucryptite solid solution and β-spodumene solid solution.
The crystallization treatment is performed so as not to exceed 0% by weight.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail while explaining a method of manufacturing a substrate material for a magnetic disk in the order of steps.

First, 50 to 65% by weight of SiO ₂ , Al ₂
O ₃ 18 to 30% by weight, Li ₂ O _{3 to} 8% by weight, TiO
₂ + _ZrO 2 3 to 5 _wt%, P 2 _{O 5} and (or)
B ₂ O ₃ in a total amount of 8% by weight or less, RO (where R represents a metal atom selected from the group consisting of magnesium, calcium, zinc, lead, and vanadium).
0% by weight, R ₂ O (R represents a potassium atom or a sodium atom) 3.0% by weight or less, F 0.1 to 0.
Raw minerals necessary for obtaining a glass having a composition of 5% by weight are prepared.

[0013] If the content of SiO ₂ is less than 50%, the glass tends to be devitrified during molding, and if it exceeds 65%, melting becomes difficult.
If the content of Al ₂ O ₃ is less than 17%, the thermal expansion coefficient becomes large and the thermal shock resistance becomes poor, and if it exceeds 30%, melting becomes difficult. Li ₂ O is difficult to melt at less than 3%,
%, The coefficient of thermal expansion becomes too large.

TiO ₂ and ZrO ₂ are components that are blended as a crystal nucleating agent. These are preferably used in combination, but one of them may be used alone. If the total amount of the two components is less than 3%, it takes too much time for crystallization, but if it exceeds 5%, the glass is liable to be devitrified, and melting becomes difficult.

[0015] P ₂ O ₅ and B ₂ O ₃ have the effect of improving the melting property of the glass and making the properties of the vitreous portion after the crystallization treatment favorable. Slows crystallization in the process and gives crystallized glass with a high glass phase.

RO and R ₂ O are effective components for lowering the melting temperature and improving the moldability. However, if they are too much, undesired results such as devitrification and deformation of the glass molding are produced.

F also lowers the melting temperature of glass and facilitates the production of glass from raw materials of the above oxide composition. Furthermore, when F is blended, a β-eucryptite crystallized glass having a high degree of crystallinity can be easily obtained, and is an important component for achieving the object of the present invention. Where F
Also has the effect of lowering the viscosity of glass at medium and high temperatures, and the resulting decrease in glass viscosity acts to increase the size of the precipitated crystal particles. Therefore, it is necessary to prevent the crystal grains from becoming coarse, and it is desirable not to exceed 0.5% by weight.

The above-mentioned raw materials are pulverized and mixed according to a conventional method of glass production, and further heated to be mixed in a molten state, thereby vitrifying the raw materials.

The obtained glass is pressed, rolled,
It is formed into a shape required for manufacturing a magnetic disk substrate, such as a disk or a column, by any method such as a casting method.

Next, the glass compact is placed in a heating furnace and subjected to a two-stage heat treatment for crystallization. The first heat treatment is a crystal nucleation step, in which the glass molded body is heated to about 600-700.
C. for about 1-3 hours. As a result, crystal nuclei are generated in the glass molded body having the above composition, and microcrystals of the β-eucryptite solid solution start to precipitate around the crystal nuclei.

Thereafter, the temperature is raised to about 650-850 ° C., preferably 700-800 ° C.
When held for several minutes to several hours, crystals of a β-eucryptite solid solution grow with the above-mentioned microcrystals as nuclei, and a part of the crystals is converted into a β-spodumene solid solution, and crystallization proceeds.
Approximately 70-85% of the glass crystallizes in 3 hours. The resulting crystals are in the form of fine particles with a diameter of about 0.1-0.5 μm,
It is dispersed in the glass phase. By setting the crystallization temperature lower, a crystallized glass having a higher β-eucryptite solid solution ratio can be produced.The higher the crystallization temperature, the higher the β-spodumene solid solution ratio and the higher the crystallization temperature. The particle size increases. Therefore, in relation to the object of the present invention that a high smooth surface can be obtained when polished, a β-spodumene solid solution is desirably used so that a high ratio of β-eucryptite solid solution is obtained as much as possible. It is desirable to select the conditions for the crystallization treatment so that the amount does not exceed 60% by weight of the total amount of the β-eucryptite solid solution and β-spodumene solid solution.

The crystallized glass obtained after the crystallization treatment is usually composed of slightly coarse crystal grains in a portion from the surface to about 1.2 μm, and contains fine crystal grains under the crystal grains. There are many thin layers, which cover a uniform crystallized glass consisting of a β-eucryptite solid solution, a β-spodumene solid solution and a glass phase as described above. Since only the core layer can be used as the material of the magnetic disk substrate, when the crystallized glass molded body is a disk-shaped one for manufacturing one substrate, It is necessary to completely remove the heterogeneous layer on the surface in the first stage of the polishing process.

In the case where the crystallized glass molded article has a columnar shape for producing a plurality of substrates, it is sliced into a disk having a thickness necessary for producing one substrate. Then, the surface is polished.

Polishing for obtaining a smooth surface can be carried out in the same manner as in the case of manufacturing this type of magnetic disk substrate. A surface having a smoothness can be obtained.

[0025]

EXAMPLES Example 1 57.4% of SiO ₂ , 22.8% of Al ₂ O ₃ , Li ₂ O
_{5.2%, TiO 2 2.6%,} ZrO 2 1.7%, P 2
O ₅ 1.9%, B ₂ O ₃ 2.7%, ZnO 1.7%, M
_{gO2.2%, K 2 O + Na} 2 O1.5%, F0.4%
The raw materials were prepared so as to have the composition described above, heated to 1450 ° C. and melted, and the obtained glass was formed into a disk shape by press molding.

Next, the glass compact is kept at 600 ° C. for 2 hours to form crystal nuclei, and then heated to 700 ° C.
The temperature was maintained for one hour to grow crystals.

The molded body that was transparent before the heat treatment was translucent due to crystallization. According to X-ray diffraction analysis, the crystallinity was about 70%, the main crystal was a β-eucryptite solid solution and a small amount of a β-spodumene solid solution was formed, and the β-eucryptite solid solution and β-spodumene solid solution were formed. The ratio of the β-eucryptite solid solution to the total amount with the solid solution was about 70%. The average crystal grain size is 0.15 μm, the coefficient of thermal expansion is 4 × 10 ⁻⁷ / k, the Young's modulus is 8.7 × 10 ⁵ kg / cm ² , and the Vickers hardness is 6
57.

The surface of the crystallized glass is wrapped by a conventional method and then polished to a thickness of about 1 mm.
The surface roughness Ra of the polished surface of the disk was 0.25 nm.

Example 2 A disk-shaped glass compact prepared in the same manner as in Example 1 was kept at 660 ° C. for 2 hours to form crystal nuclei, and then heated to 740 ° C. The crystals were grown by holding for a time.

The molded body that was transparent before the heat treatment became milky white due to crystallization, and when examined by X-ray diffraction, a β-eucryptite solid solution and a β-spodumene solid solution were mixed. They accounted for about 55% of the total amount of both. The average crystal grain size is about 0.2 μm, the coefficient of thermal expansion is 15 × 10 ⁻⁷ / k, and the Young's modulus is 8.7 × 10 ^5.
kg / cm ² and Vickers hardness was 616.

When the surface of the crystallized glass was wrapped and polished by a conventional method, the surface roughness was Ra.
Of 0.41 nm was obtained.

Example 3 SiO ₂ 60%, Al ₂ O ₃ 21%, Li ₂ O 5.5
%, TiO ₂ + ZrO ₂ 4%, P ₂ O ₅ + B ₂ O ₃ 7.
_{5%, ZnO + MgO4%,} K 2 O + Na 2 O1.5
% And a composition of 0.9% F, and 143
It was heated to 0 ° C. and melted, and the obtained glass was formed into a disk shape by press molding.

Next, the glass molded body was kept at 600 ° C. for 1 hour, heated to 750 ° C., kept at this temperature for 1 hour, and cooled.

The molded product that was transparent before the heat treatment turned into a translucent milky white due to crystallization. From the X-ray diffraction pattern, the main crystal was β-spodumene solid solution, which accounted for about 85% of the total amount of β-eucryptite solid solution and β-spodumene solid solution. The average grain size is about 0.4μ
m, coefficient of thermal expansion is 14 × 10 ⁻⁷ / k, Young's modulus is 8.
7 × 10 ⁵ kg / cm ² and Vickers hardness was 610.

When the surface of the crystallized glass was wrapped and polished by a conventional method, the surface roughness Ra was changed.
Of 0.8 nm was obtained.

[0036]

The substrate material for a magnetic disk according to the present invention can form a highly smooth surface having a surface roughness of about 0.2 to 0.6 nm and is used as a substrate for a next-generation magnetic disk having a high recording density. It is suitable. In addition, it is an excellent material having all the properties required for a magnetic disk substrate in terms of physical properties.

Continued on the front page (72) Inventor Hiroshi Yuko 380 Juyo, Kashiwa-shi, Chiba Prefecture F-term in Okamoto Glass Co., Ltd. 4G062 AA11 BB01 CC09 DA06 DB04 DC01 DC02 DC03 DD01 DD02 DD03 DE01 DE02 DE03 DF01 DF02 DF03 EA03 EB01 EB02 EB03 EC01 EC02 EC03 ED02 ED03 EE02 EE03 EF01 EG01 FA01 FB03 FC03 FD01 FE01 FF02 FF03 FG01 FH01 FJ01 FK01 FL01 GA01 GA10 GB01 GC01 GD01 GE01 HH01 HH03 HH05 HH07 KK03 HH09 HH11 KK QQ10 QQ11 5D112 AA02 BA03 BA09

Claims (3)

[Claims] 1. A β- eucryptite solid solution crystal grains and β- Supojuumen solid solution crystal grains of consists crystallized glass interspersed in glassy matrix, the crystallized glass is average composition SiO ₂ 50 to 65 _{wt%, Al} 2 O 3 18 to 30 _wt%, Li 2 _{O3~8 wt%,} TiO 2 + _ZrO 2 _{3~5 wt%,} 8 wt in P 2 _{O 5} and _(or) the total amount of B 2 _{O 3} %, RO (where R represents a metal atom selected from the group consisting of magnesium, calcium, zinc, lead, and vanadium).
3 to 7.0% by weight, R ₂ O (R represents a potassium atom or a sodium atom) 3.0% by weight or less, F0.
1 to 0.5% by weight, the ratio of the crystal part to the whole crystallized glass is 70 to 85% by weight, and the amount of the β-spodumene solid solution is β-eucryptite solid solution and β-eucryptite solid solution.
A magnetic disk comprising not more than 60% by weight of the total amount of the solid solution of spodumene and the crystal grains of the solid solution of β-eucryptite and the solid solution of β-spodumene having a particle size of 0.1 to 0.5 μm; Substrate material. _2. 50 to 65% by weight of SiO ₂ , Al ₂ O ₃
18-30 _wt%, Li 2 _O3~8 wt%, _TiO 2 +
ZrO ₂ 3 to 5 _wt%, P 2 _{O 5} and (or) _{B 2}
O ₃ 8% by weight in a total amount below, RO (wherein R represents magnesium, calcium, zinc, lead, and a metal atom selected from the group consisting of vanadium) from 0.3 to 7.0 wt%, _{R 2} O (where R represents a potassium atom or a sodium atom) 3.0% by weight or less and F-0.1 to 0.5% by weight of glass formed into a required shape as a substrate material for a magnetic disk. Forming a crystallized glass in which crystal particles of a β-eucryptite solid solution and crystal particles of a β-spodumene solid solution having a crystal particle diameter of 0.1 to 0.5 μm are scattered in a vitreous matrix. Manufacturing method of a magnetic disk substrate material. 3. The amount of the β-spodumene solid solution produced by the crystallization treatment is between β-eucryptite solid solution and β-eucryptite solid solution.
The production method according to claim 2, wherein the crystallization treatment is performed so as not to exceed 60% by weight of the total amount with the solid solution of spodumene.