JPH09314458A - Precision grinding method for crystalline glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To grind crystalline glass so as to provide a smooth surface irrespective of a crystal size by using grinding liquid containing grinding abrasive grains and organic solvent as a dispersion medium. SOLUTION: Crystalline glass is precisely ground by using grinding liquid containing grinding abrasive grains and organic solvent as a dispersion medium. This organic solvent is water-soluble and its boiling point is 60 deg.C or higher. Crystalline glass of a dispersion medium containing water of 40wt.% or lower is crystalline glass used for magnetic disk substrate, little limits is placed by the composition of a glass composition or crystallization conditions, a smooth surface is obtained even from crystalline glass having a large crystal size and a substrate for dealing with the high recording density of a magnetic disk is obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for precisely polishing crystallized glass. More specifically, the present invention can stably impart excellent surface smoothness regardless of the crystal size of the crystallized glass, and is particularly suitable for polishing crystallized glass for magnetic disk substrates. The present invention relates to a precision polishing method for glass.

[0002]

2. Description of the Related Art Magnetic disks are mainly used for computer hard disks. In recent years, with the trend toward miniaturization, thinning and high recording density of magnetic disks, there is an increasing demand for high flatness and high smoothness of the magnetic disk surface. Particularly, regarding the smoothness, in a glass disk substrate after polishing, JIS B 0601-1994
The arithmetic mean roughness (R _a ) of the surface obtained according to
In particular, it is required to be 10 Å or less. R
_By setting a within this range, it is possible to reduce the flying height of the magnetic head and to cope with higher recording density. A conventional method for polishing crystallized glass for a magnetic disk substrate is disclosed in, for example, JP-A-61-48123 or JP-A-61-48123.
In JP-A-132576, SiO ₂ , MgO, CeO ₂ , and Al ₂ O ₃ having a particle size of 0.1 μm or less in pure water.
A polishing liquid in which abrasive grains such as the above are suspended is used. A method for polishing crystallized glass for a magnetic head substrate is disclosed in, for example, Japanese Examined Patent Publication No. 63-31343, and the grain size is 3
A method has been proposed in which a spherical anhydrous alumina powder having a particle size of 20 Å or less is suspended in pure water to use a polishing liquid having a pH of 4 to 5. However, when pure water is used as the dispersion medium of the polishing liquid, not only physical polishing but also chemical polishing proceeds at the same time, which causes a difference in polishing rate between the crystal part in the crystallized glass and the matrix glass part. This causes a phenomenon that the surface roughness of the disk substrate surface becomes large. Therefore, in order to reduce the surface roughness and obtain a magnetic disk substrate having excellent surface smoothness, it is necessary to precipitate crystals with a small crystal size in the crystallized glass. It was constrained by the conditions.

[0003]

DISCLOSURE OF THE INVENTION The present invention relates to a crystallized glass, particularly a crystallized glass for a magnetic disk substrate, which is less restricted by the composition of the glass composition and the crystallization conditions and has a large crystal size. The object of the present invention is to provide a precision polishing method for crystallized glass, which has a surface having excellent smoothness even from glass and can obtain a substrate which can cope with high recording density of magnetic disks. .

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that by polishing with a polishing liquid containing polishing abrasive grains and an organic solvent as a dispersion medium. Found that a stable and smooth surface can be obtained regardless of the crystal size of crystallized glass.
Based on this finding, the present invention has been completed. That is, the present invention provides (1) a precision polishing method for crystallized glass, which comprises using a polishing liquid containing polishing abrasive grains and an organic solvent as a dispersion medium, (2) the organic solvent is water-soluble, and The method for precisely polishing crystallized glass according to item (1), which has a boiling point of 60 ° C. or higher, and (3) the organic solvent is an alcohol, glycol, triol, glycol ether, glycol ester, glycol ether ester. Precision polishing of crystallized glass according to item (1) or (2), which comprises at least one of the following: glycerol ester, phosphoric ester, carbonate ester, amide, lactone, and sulfur compound. The method, (4) the precision polishing method for crystallized glass according to any one of (1) to (3), wherein the dispersion medium contains 40% by weight or less of water, and (5) crystallization. The glass has a magnetic Crystallized glass for disc substrates (1)
The present invention provides a method for precisely polishing crystallized glass according to any one of items (4) to (4). Furthermore, as a preferred embodiment of the present invention, (6) the grain size of the abrasive grains is 0.0
The method for precision polishing crystallized glass according to any one of the items (1) to (5), wherein the polishing abrasive has a content of 0.5 to 20. % By weight (1)
Item 8. The method for precisely polishing crystallized glass according to any one of items 1 to 6, and (8) the viscosity of the polishing liquid at 25 ° C. is 2 cp to 10 kcp. The precision polishing method for crystallized glass as recited in any one of the above items.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention can be applied to precision polishing of crystallized glass. As the crystallized glass to which the method of the present invention is applied, for example, the main crystal phase is spodumene, mullite, aluminum borate-based crystal, β-quartz solid solution, α-quartz, cordierite, enstatite, celsian, wollastonite, and anodized. Crystallized glass such as sight, forsterite, lithium metasilicate, lithium disilicate and the like can be mentioned. Of these, the method of the present invention can be particularly suitably applied to precision polishing of crystallized glass for a magnetic disk substrate whose main crystal phase is spodumene, mullite or aluminum borate type crystal. Prior to applying the precision polishing method of the present invention, it is preferable to wrap the crystallized glass. Lapping is performed by bringing the surface of the crystallized glass into contact with the surface of the lapping dish and supplying an aqueous dispersion in which general abrasive grains such as aluminum oxide abrasive grains and silicon carbide abrasive grains are suspended as a lapping agent. This can be done by applying a load to the glass and rotating the lap dish. In the method of the present invention, crystallized glass is polished using a polishing liquid containing polishing abrasive grains and an organic solvent as a dispersion medium. There is no particular limitation on the abrasive grains used, for example, silicon oxide,
Abrasive grains such as silicon carbide, aluminum oxide, zirconium oxide, cerium oxide, synthetic diamond, natural diamond, boron carbide, and c-BN can be used. The particle size of the abrasive grains is preferably 0.01 to 1 μm in order to obtain a desired highly smooth surface, and 0.05
To 1 μm is more preferable, and 0.1 to 0.8 μm
Is more preferable. The content of polishing abrasive grains in the polishing liquid is preferably 0.5 to 20% by weight, and 2
More preferably, it is from about 15% by weight. In the method of the present invention, in polishing the crystallized glass, the surface of the crystallized glass is brought into contact with the surface of the crystallized plate, and a load is applied to the crystallized glass while supplying the polishing liquid to the crystallized glass and the crystallized glass. Can be performed by relatively rotating. The material of the polishing plate is not particularly limited, and for example, polyurethane, ceramics, tin, copper or the like can be used. The polishing liquid can be supplied by dropping on the polishing plate, spraying, or the like.

In the method of the present invention, an organic solvent is used as a dispersion medium for the polishing liquid. By using the organic solvent, a surface having excellent smoothness can be obtained regardless of the crystal size of the crystallized glass. When water is used as the dispersion medium of the polishing liquid, a surface having good smoothness can be obtained from a crystallized glass having a small crystal size of 1 μm or less, but a crystal size exceeding 1 μm. It is not possible to obtain a surface having good smoothness from a crystallized glass having a large size. The reason for this is not clear, but when water is used as the dispersion medium, in addition to mechanical polishing, chemical polishing with water proceeds in parallel, and in general, chemical polishing is performed in the glass portion rather than the crystal portion. It is presumed that the surface of the crystallized glass becomes rough because it rapidly progresses. When an organic solvent is used as the dispersion medium of the polishing liquid, the chemical polishing hardly progresses, only mechanical polishing by polishing grains occurs, and the difference in mechanical polishing speed between the crystal part and the glass part is large. Therefore, it is considered that a surface having excellent smoothness can be obtained. Since the crystal size of the crystallized glass is determined by the composition of the glass composition and the heat treatment conditions for crystallization, it is desirable to obtain a crystallized glass having a small crystal size because of limitations in terms of composition and heat treatment conditions. It has been difficult to freely select a crystallized glass having characteristics. According to the method of the present invention, a surface having excellent smoothness can be obtained irrespective of the crystal size, so that the glass composition and the heat treatment conditions can be freely selected so as to impart the necessary properties to the crystallized glass. .

The organic solvent used in the method of the present invention is preferably water-soluble. In the present invention, the water-soluble organic solvent refers to an organic solvent having a solubility in water at 25 ° C. of 20% by weight or more. If the organic solvent is water-soluble, the crystallized glass after polishing can be washed with water to easily wash away the attached polishing liquid and the like. If the organic solvent remains attached to the polished crystallized glass, peeling of the magnetic film layer may occur or the magnetic film characteristics may deteriorate when the magnetic film layer is formed on the surface later. Using a non-water-soluble organic solvent as a dispersion medium of the polishing liquid, after polishing is washed with a second organic solvent having a solubility in both the organic solvent and water, further, using a second organic solvent using water. It is possible to wash it off,
The number of washing steps is increased. The organic solvent used in the method of the present invention preferably has a solubility in water at 25 ° C. of 40% by weight or more, and more preferably 50% by weight or more. The organic solvent used in the method of the present invention preferably has a boiling point of 60 ° C or higher. During the polishing operation, heat is generated due to friction between the crystallized glass and the polishing plate. Therefore, if the boiling point of the organic solvent is less than 60 ° C., the organic solvent may evaporate and the concentration of the polishing liquid may fluctuate. When the concentration of the polishing liquid changes, it becomes difficult to maintain the properties of the polishing liquid constant, and the polishing rate and the like change, which may make it difficult to control the surface properties of the crystallized glass. In the method of the present invention, the boiling point of the organic solvent is 80.
C. or higher is more preferable, and 100.degree. C. or higher is still more preferable. The organic solvent used in the method of the present invention preferably has low toxicity, high flash point, and excellent safety.

The organic solvent used in the method of the present invention includes:
For example, alcohols, glycols, triols,
Examples thereof include glycol ethers, glycol esters, glycol ether esters, glycerin esters, phosphoric acid esters, carbonic acid esters, amides, lactones, and sulfur compounds. Examples of alcohols include propanol, tert-butyl alcohol, and 3-buten-2-ol. Examples of glycols include ethylene glycol, propanediol, butanediol, pentanediol, and 2-butene-1,4. -Diol, 2-methyl-2,4-pentanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, low molecular weight polyethylene glycol, dipropylene glycol, low molecular weight polypropylene glycol, and the like. Examples of triols include glycerin. Examples of glycol ethers such as 1,2,6-hexanetriol include diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether. Glycol, triethylene glycol monomethyl ether, diethylene glycol diethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monobutyl ether, 2- (methoxymethoxy) ethanol, etc. Is, for example, ethylene glycol monoacetate and the like, as glycol ether esters, for example, diethylene glycol monoethyl ether acetate, ethylene glycol monomethyl ether acetate and the like, and as glycerin esters, for example, monoacetin, diacetin and the like. As the phosphoric acid esters, for example, triethyl phosphate and the like can be used as carbonic acid esters. For example, propylene carbonate and the like, amides such as formamide, N-methylformamide, N-methyl-2-pyrrolidone and the like, lactones such as γ-butyrolactone and the like, sulfur compounds Examples thereof include dimethyl sulfoxide and sulfolane. From the viewpoint of safety and economy, among these, propanol, tert-butyl alcohol, ethylene glycol, propanediol, 2-methyl-2,4-pentanediol, diethylene glycol, triethylene glycol, low-molecular-weight polyethylene glycol, Dipropylene glycol, glycerin, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, formamide and dimethyl sulfoxide can be used particularly preferably.

In the method of the present invention, the non-volatile substance is dissolved in an organic solvent having a boiling point of less than 60 ° C. in place of the organic solvent having a boiling point of 60 ° C. or more, and the boiling point is raised to 60 ° C. or more by the boiling point raising effect. Different solvents can be used.
As the non-volatile substance that dissolves in the organic solvent, it is preferable to select a non-volatile substance that does not react with the organic solvent. Further, in the method of the present invention, a commercially available water-soluble cutting oil can be used instead of the organic solvent. In the method of the present invention, 40% by weight or less, preferably 20% by weight or less, and more preferably 10% by weight or less of the organic solvent as the dispersion medium can be replaced with water. By including water in the polishing liquid, the effect of chemical polishing by water appears and the surface smoothness is slightly lowered, but the polishing rate is increased and the productivity is improved. The water content of the polishing liquid can be appropriately selected in consideration of both the required surface smoothness of the crystallized glass and the productivity. Furthermore, the surface roughness of the crystallized glass can be controlled by adjusting the water content of the polishing liquid. The viscosity of the organic solvent used in the method of the present invention is 2
It is preferably 2 cp to 10 kcp at 5 ° C. and 3 c
More preferably, it is p to 1.5 kcp. If the viscosity of the organic solvent is less than 2 cp at 25 ° C., the abrasive grains may settle and aggregate during storage of the polishing liquid. When the viscosity of the organic solvent exceeds 10 kcp at 25 ° C., handling becomes difficult and workability may be deteriorated. If necessary, other known additives can be added to the polishing liquid used in the method of the present invention. Examples of such additives include a dispersant, a viscosity modifier, and a chemical polishing control agent. By finishing polishing the crystallized glass for a magnetic disk substrate using the method of the present invention, even the crystallized glass containing a portion having low chemical durability can be polished without extremely damaging the surface. Even if a highly smooth surface is required, a satisfactory smooth surface can be obtained.

[0010]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Further, in Examples and Comparative Examples, the crystal phase, the crystal size, and the arithmetic average roughness of surface ( _Ra )
The ten-point average roughness (R _z ) was measured by the following method. (1) Crystal phase The obtained polished compact was measured using an X-ray diffractometer. (2) Crystal Size The obtained polished compact was immersed in 5% by weight of hydrofluoric acid for 5 seconds, and the surface of the sample was observed with a scanning electron microscope. In this 10,000-fold visual field, 10 points of crystals were randomly selected, and the average major axis was taken as the crystal size. (3) Arithmetic Average Roughness (R _a ) and Ten-Point Average Roughness (R _z ) The obtained abrasive compact was subjected to atomic force microscopy (Digital).
1 Instruments (manufactured by Instruments). Randomly select 5 locations on the sample surface
4 randomly in a 10 μm × 10 μm field of view
A line was drawn and the respective R _a and R _z were calculated. The average of these 20 points in total was taken as R _a and R _z . Example 1 Glass composition: SiO ₂ : 70.0% by weight, Al ₂ O ₃ :
6.0 wt%, Li ₂ O: 8.0 wt%, TiO _2: 2.5
Wt%, ZrO _2: 4.0 wt%, P ₂ O _5: 1.8 wt%, Sb ₂ O _3: 0.2 wt%, B ₂ O _3: 2.0 wt%, C
aO: 2.0% by weight, BaO: 1.5% by weight and ZnO:
Each component raw material was weighed and mixed so as to be 2.0% by weight.
The mixed raw materials are put into a platinum crucible in an electric furnace, melted at 1,450 ° C. for 5 hours, stirred to be homogeneous, then molded into a plate of 50 × 50 × 5 mm, strain-removed and cooled. Then, a glass molded body was obtained. This glass molded body is heated at 600 ° C. for 3 hours and then 720
Heat treatment was performed at 2 ° C. for 2 hours to precipitate crystals in the glass.
The crystal phase of this crystallized glass was spodumene, lithium disilicate and α-quartz. The crystallinity was 17% by volume for spodumene, 15% by volume for lithium disilicate, and 10% by volume for α-quartz. The crystal size was 0.4 μm. An iron-based surface plate having a diameter of 200 mm was used as a polishing plate for this crystallized glass, and the surface to be polished of the crystallized glass was brought into contact with the surface of the polishing plate to disperse 10% by weight of silicon carbide abrasive grains having D ₅₀ of 25 μm in water. While spraying the polishing liquid at a rate of 9 ml / min, both were relatively rotated at a rotation speed of 60 rpm and a load of 300 g / cm ² , and surface grinding was performed for 30 minutes. Then, under the same conditions, water has a D ₅₀ of 10
Lapping was performed for 30 minutes using a polishing liquid in which 10% by weight of silicon carbide abrasive grains having a diameter of 3 μm was dispersed, and 30 minutes was further used for 30 minutes in which a polishing liquid in which 5% by weight of silicon carbide abrasive grains having a D ₅₀ of 3 μm was dispersed in water was used. The diameter of the crystallized glass after lapping is 2
Using a 00 mm polyurethane polishing plate, the surface of the polishing plate is brought into contact with the surface to be polished of crystallized glass, and a polishing liquid in which 5 wt% of cerium oxide having a particle size of 0.8 μm is dispersed in ethylene glycol is added at a rate of 1 ml / min. Rotation speed 60 while dripping
Rotate both at a rpm of 150 g / cm ² and rotate them to 3
Polished for 0 minutes. The arithmetic average roughness (R _a ) of the crystallized glass surface after polishing is 7Å, and the ten-point average roughness (R _z ) is 26.
It was 3Å. Comparative Example 1 The same lapped crystallized glass as in Example 1 was used as a polishing plate made of polyurethane having a diameter of 200 mm, and the surface of the crystallized glass to be polished was brought into contact with the surface of the polishing plate.
1 ml of polishing liquid in which 5 μ% of 8 μm cerium oxide is dispersed
Rotation speed 60 rpm, load 1 while dropping at a rate of / min
Both were relatively rotated at 50 g / cm ² and polished for 30 minutes. The arithmetic average roughness (R _a ) of the crystallized glass surface after polishing is 1
It was 2Å, and the ten-point average roughness (R _z ) was 337Å. Example 2 The same glass molded body as in Example 1 was heat-treated at 680 ° C. for 3 hours and then at 850 ° C. for 3 hours to precipitate crystals in the glass. The crystal phase of this crystallized glass was spodumene, lithium disilicate and α-quartz. The crystallinity was 23% by volume for spodumene, 13% by volume for lithium disilicate, and 7% by volume for α-quartz. The crystal size was 2.0 μm. This crystallized glass was lapped with silicon carbide abrasive grains in the same manner as in Example 1, and then polished with a polishing liquid in which cerium oxide was dispersed in ethylene glycol. The arithmetic average roughness ( _Ra ) of the crystallized glass surface after polishing was 9Å, and the ten-point average roughness ( _Rz ) was 272Å. The surface state of the crystallized glass after polishing, which was observed by an atomic force microscope, is shown in FIG. Comparative Example 2 The crystallized glass subjected to the same lapping as in Example 2 was polished in the same manner as in Comparative Example 1 using a polishing liquid in which cerium oxide was dispersed in water. The arithmetic average roughness ( _Ra ) of the crystallized glass surface after polishing is 26Å, and the ten-point average roughness ( _Rz ).
Was 458Å. The surface state of the crystallized glass after polishing, which is observed by an atomic force microscope, is shown in FIG. Example 3 The glass composition was SiO ₂ : 78.0 wt%, Al ₂ O ₃ :
8.0% by weight, Li ₂ O: 3.5% by weight, TiO ₂ : 0.5
Wt%, ZrO _2: 4.0 wt%, P ₂ O _5: 2.3 wt%, Sb ₂ O _3: 0.2 wt%, B ₂ O _3: 1.0 wt%, M
gO: 1.0 wt%, ZnO: 1.0 wt% and PbO:
Raw materials for each component were weighed and mixed so as to be 0.5% by weight.
The mixed raw materials are put into a platinum crucible in an electric furnace, melted at 1,500 ° C. for 5 hours, stirred to be homogeneous, then molded into a plate of 50 × 50 × 5 mm, strain-relieved and cooled. Then, a glass molded body was obtained. This glass molded body is heated at 700 ° C. for 3 hours and then 900 times.
Heat treatment was performed at 2 ° C. for 2 hours to precipitate crystals in the glass.
The crystal phase of this crystallized glass is spodumene and α-
It was quartz. Crystallinity is 25 for Spodumene
% By volume and 15% by volume of α-quartz. The crystal size was 0.8 μm. This crystallized glass was lapped with silicon carbide abrasive grains in the same manner as in Example 1, and then a ceramic polishing plate having a diameter of 200 mm was used, and the polishing plate surface was brought into contact with the surface to be polished of the crystallized glass. Then, 1 ml of a polishing liquid in which 5% by weight of aluminum oxide having a particle diameter of 0.3 μm is dispersed in glycerin containing 0.5% by weight of an ester nonionic activator [San Nopco Ltd., SN Dispersant 9228] as a dispersant. Both were relatively rotated at a rotation speed of 60 rpm and a load of 150 g / cm ² while dripping at a rate of 30 minutes, and polishing was performed for 30 minutes. The arithmetic average roughness (R _a ) of the crystallized glass surface after polishing was 7Å and the ten-point average roughness (R _z ) was 292Å. Examples 1-3
The results of Comparative Examples 1 and 2 are shown in Table 1.

[0011]

[Table 1]

From the results shown in Table 1, when a polishing liquid containing ethylene glycol as a dispersion medium was used with respect to crystallized glass containing spodumene as a main crystal phase, the crystal size was small even in Example 1. Example 2 with large size
Also in the above, the value of the surface roughness is small and good surface smoothness is obtained. On the other hand, when the conventional polishing liquid containing water as the dispersion medium was used, the crystal size was small in Comparative Example 1
In Comparative Example 2 in which the crystal size is large, the surface roughness value is large, and the polishing liquid containing water as the dispersion medium exhibits good surface smoothness. You can see that you cannot get it. Example 4 The glass composition was SiO ₂ : 23% by weight, Al ₂ O ₃ : 40
% By weight, B ₂ O ₃ : 20% by weight, MgO: 10% by weight, C
aO: 2% by weight, BaO: 2% by weight, ZnO: 2% by weight
And Li ₂ O: Weigh each component raw material so that it becomes 1% by weight,
Mixed. The mixed raw materials are put into a platinum crucible in an electric furnace, melted at 1,500 ° C. for 5 hours, stirred to be homogeneous, then molded into a plate of 50 × 50 × 5 mm, strain-relieved and cooled. Then, a glass molded body was obtained. The glass molded body was heated at 700 ° C. for 2 hours and then 870.
Heat treatment was performed at 2 ° C. for 2 hours to precipitate crystals in the glass.
The crystal phase of this crystallized glass was mullite and aluminum borate-based crystals, and the crystallinity was 25 vol% for mullite and 18 vol% for aluminum borate-based crystals. The crystal size was 1.4 μm. This crystallized glass was lapped with silicon carbide abrasive grains in the same manner as in Example 1, and then a polishing plate made of polyurethane having a diameter of 200 mm was used to bring the polishing plate surface into contact with the surface to be polished of the crystallized glass. Then, diethylene glycol has a particle size of 0.1.
While polishing liquid containing 8% by weight of zirconium oxide of 5 μm added dropwise at a rate of 1 ml / min, both were relatively rotated at a rotation speed of 60 rpm and a load of 150 g / cm ² , and polishing was performed for 30 minutes. The arithmetic average roughness (R _a ) of the crystallized glass surface after polishing is 6Å, and the ten-point average roughness (R _z ) is 201Å.
Met. Example 5 The same lapped crystallized glass as in Example 4 was used as a polishing plate made of polyurethane having a diameter of 200 mm. The polishing plate surface was brought into contact with the surface to be polished of the crystallized glass, and 90% by weight of diethylene glycol and 10% by weight of water were used. % Of a zirconium oxide having a particle diameter of 0.5 μm dispersed in a mixed solvent of 1% / min at a rate of 1 ml / min, while rotating both at a rotation speed of 60 rpm and a load of 150 g / cm ^2. And polished for 30 minutes. The arithmetic average roughness (R _a ) of the crystallized glass surface after polishing is 9Å, and the ten-point average roughness (R _z )
Was 243Å. Comparative Example 3 The crystallized glass which was lapped in the same manner as in Example 4 was used as a polishing plate made of polyurethane having a diameter of 200 mm, and the surface of the crystallized glass to be polished was brought into contact with the surface of the polishing plate.
While polishing liquid containing 8% by weight of zirconium oxide of 5 μm added dropwise at a rate of 1 ml / min, both were relatively rotated at a rotation speed of 60 rpm and a load of 150 g / cm ² , and polishing was performed for 30 minutes. The arithmetic average roughness (R _a ) of the crystallized glass surface after polishing is 22Å, and the ten-point average roughness (R _z ) is 358.
Was Å. The results of Examples 4 to 5 and Comparative Example 3 were
It is shown in the table.

[0013]

[Table 2]

From the results shown in Table 2, in Example 4 in which a polishing liquid containing diethylene glycol as a dispersion medium was used with respect to crystallized glass containing mullite and aluminum borate crystals as a main crystal phase, the surface roughness was measured. Value is small, and good surface smoothness is obtained. Further, also in Example 5 using a polishing liquid containing a mixed solvent of diethylene glycol and water as a dispersion medium, good surface smoothness almost equal to that in Example 4 was obtained. On the other hand, in Comparative Example 3 in which the conventional polishing liquid containing water as the dispersion medium was used, the surface roughness was large, and the polishing liquid containing water as the dispersion medium did not provide good surface smoothness. I understand.

[0015]

EFFECTS OF THE INVENTION According to the method of the present invention, a crystallized glass can be polished to obtain a surface having excellent smoothness regardless of the size of the crystal size. It is possible to select a wide range, and it is possible to obtain crystallized glass for a magnetic disk substrate having desirable characteristics as a magnetic disk substrate and excellent surface smoothness.

[Brief description of drawings]

FIG. 1 is a surface state of crystallized glass after polishing of Example 2 observed by an atomic force microscope.

FIG. 2 is a surface state of the crystallized glass after polishing of Comparative Example 2 observed by an atomic force microscope.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hajime Wakabayashi 2-21 Hamamatsubara-cho, Nishinomiya-shi, Hyogo Yamamura Glass Co., Ltd.

Claims (5)

[Claims] 1. A precision polishing method for crystallized glass, which comprises using a polishing liquid containing polishing abrasive grains and an organic solvent as a dispersion medium. 2. The organic solvent is water-soluble and has a boiling point of 60.
The method for precision polishing of crystallized glass according to claim 1, which is at least ℃. 3. An organic solvent comprising alcohols, glycols, triols, glycol ethers, glycol esters, glycol ether esters, glycerin esters, phosphoric acid esters, carbonic acid esters, amides, lactones, At least one of the sulfur compounds
The method for precision polishing crystallized glass according to claim 1 or 2, further comprising a seed. 4. The precision polishing method for crystallized glass according to claim 1, wherein the dispersion medium contains 40% by weight or less of water. 5. The precision polishing method for crystallized glass according to claim 1, wherein the crystallized glass is crystallized glass for a magnetic disk substrate.