JP2628460B2 - Magnetic disk substrate and method of manufacturing the same - Google Patents

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 made of crystallized glass having a crystal structure with improved surface characteristics after polishing, a magnetic disk formed by subjecting the magnetic disk substrate to a film forming process, and The present invention relates to a method for manufacturing a magnetic disk substrate.

[0002]

2. Description of the Related Art The demand for magnetic disks as external storage media for large computers, personal computers and the like has been increasing in recent years, and their development has been progressing rapidly. Generally, the following characteristics are required for the magnetic disk substrate material. That is, (1) In the start / stop (CSS) characteristics of the magnetic disk, if the disk has a smooth surface having a surface roughness (Ra) of 15 ° or less, the head and the disk are accompanied by an increase in contact resistance caused by high-speed rotation. Since adsorption occurs, the surface roughness (R
a) is 15 ° or more, and the surface roughness (Ra)
However, a rough surface having a surface roughness of 50 ° or more causes damage to the head and destruction of the medium. Therefore, the surface roughness (Ra) must have a controlled surface characteristic of 50 ° or less.

(2) In order to improve the recording density of the magnetic disk, the flying height of the head is decreasing to 0.1 μm to 0.05 μm, and the disk surface is flat and smooth enough to allow the flying height of the head. That.

(3) The substrate material for a magnetic disk must have a fine, homogeneous and fine structure without crystal anisotropy and defects.

(4) It has mechanical strength and hardness enough to withstand high-speed rotation and head contact.

[0006] (5) Since the material Na ion when containing Na ₂ O component in diffuses into the film forming process, the characteristics of the film are deteriorated, essentially contains no Na ₂ O component.

(6) It has chemical durability enough to withstand cleaning and etching by various chemicals.

Conventionally, an aluminum alloy has been used for a magnetic disk substrate material. However, in the case of an aluminum alloy substrate, due to the influence of various material defects, projections or spot-like irregularities on the substrate surface in the polishing step occur, and the flatness is reduced. ,
The surface roughness is not sufficient, and it is not possible to cope with high-density recording due to a further increase in the amount of information today.

Further, as a material for solving the problem of the aluminum alloy plate, various glass substrates for magnetic disks such as chemically strengthened glass are known. In this case, (1) polishing is performed after chemical strengthening, and the disk is thinned. The instability factor of the strengthening layer in the formation is high.

(2) Mechanical or mechanical texture for improving start / stop (CSS) characteristics or
There is a disadvantage that it is necessary to carry out chemical chemical texture and it is difficult to mass-produce the product at low cost.

(3) Since the glass contains a Na ₂ O component as an essential component, the film-forming characteristics are deteriorated, and a surface coating treatment or the like is required. In addition, a technique for roughening the surface in a polishing process has recently been used as a means for solving the problem of texture processing for improving start / stop (CSS) characteristics in chemically strengthened glass and crystallized glass. It is not enough for stable mass production.

Therefore, a large number of crystallized glasses satisfying some of the above-mentioned requirements for aluminum alloy substrates and chemically strengthened glass substrates are known. For example, JP
The publication No. 0-229234 SiO ₂ -Al ₂ O ₃ -
Li ₂ O-based crystallized glass is a β-quartz solid solution or β-quartz
A spodumene solid solution is precipitated and the crystal grain size is about 0.1 ~
1.0 μm in granular form.
SiO ₂ -Li ₂ O system crystallized glass 2547 JP primarily crystalline as to precipitate the lithium disilicate and metasilicate lithium, respectively grain size lithium disilicate about 0.3~1.5μm plate The shape and lithium metasilicate are granular with a size of 0.3 to 0.5 μm. Also, US Pat. No. 3,231,456 discloses SiO ₂ —Li ₂
O-P ₂ O ₅ CuO in -MgO based glass, is contained SnO component has lithium disilicate as main crystalline phase, crystallized glass as the sub crystalline α- quartz may be deposited is disclosed. However, the crystallization temperature of these glasses is
Because a high temperature heat treatment of 850 to 1050 ° C. is required,
As described later in detail, the present invention does not have a spherical structure of α-quartz aggregated particles. The discussion of the crystal phase and crystal structure in the above-mentioned US Pat. No. 3,231,456 merely teaches a good ceramic material as an adhesive material.

US Pat. No. 3,977,857 discloses a SiO ₂ —Li ₂ O—MgO—P ₂ O suitable for directly bonding to a metal member as a crystallized glass for metal bonding.
_{A 5-} (Na ₂ O + K ₂ O) -based crystallized glass is disclosed. The main crystalline phase of the crystallized glass obtained in this US patent publication is described to be a Li ₂ O · 2SiO _2, spherical consisting aggregated particles as α- quartz grain structure as in the present invention There is no description of the granular structure.

JP-A-63-210039 discloses a SiO ₂ —Li ₂ O—MgO suitable as a substrate for a magnetic head.
-P ₂ O ₅ based crystallized glass is disclosed. According to this publication, the main crystal phase of the crystallized glass obtained is Li ₂ O · 2
It describes that it is SiO ₂ and α-cristobalite, and there is no description about a spherical granular structure composed of aggregated particles as a granular structure of α-quartz as in the present invention. The nucleation temperature is 550 ° C. to 8
The temperature was 00 ° C., and the MgO component was added to suppress the change in the coefficient of thermal expansion due to the coexistence with the P ₂ O ₅ component.

[0015]

The above conventional Li ₂ O—
SiO ₂ -based crystallized glass (JP-A-62-72547, US Pat. No. 3,231,456, US Pat. No. 3,977,857 and JP-A-63-2100)
No. 39), the precipitated crystal phases are Li ₂ O.2SiO ₂ as a main crystal phase and a small amount of SiO ₂ (α-cristobalite or α-quartz) as a sub-crystal phase.
It is. The main function of these conventional crystallized glasses is the Li ₂ O.2SiO ₂ crystal phase, which is the main crystal phase, and not the α-quartz or α-cristobalite crystal phase. These conventional crystallized glasses have a surface characteristic inherent to the crystallized glass after polishing, which is required for the start / stop (CSS) characteristics of the magnetic disk by 15 °.
Cannot provide surface roughness of ~ 50 °. For this reason, the start / stop (CS
S) In order to improve the characteristics, it is indispensable to perform some texture processing step for roughening the surface of the crystallized glass after the polishing process. Therefore, a magnetic disk having the above-mentioned necessary characteristics can be produced at low cost. Prevent mass production.

An object of the present invention is to solve the above-mentioned drawbacks in the prior art, and to control the crystal structure and crystal grains of the precipitated crystal to make the magnetic disk substrate made of crystallized glass more excellent in surface characteristics by polishing. It is to provide a manufacturing method thereof.

Another object of the present invention is to provide a magnetic disk having a magnetic medium film formed on the magnetic disk substrate.

[0018]

Means for Solving the Problems The inventor of the present invention has conducted intensive tests and researches in order to achieve the above object, and has found that SiO _2-
The crystallized glass obtained in a Li ₂ O—P ₂ O ₅ system containing MgO as an essential component and in a strictly limited heat treatment temperature range has a crystal phase of lithium disilicate (Li ₂ Si).
The phases were uniformly precipitated in ₂ O ₅₎ alpha-quartz (alpha-Si
O ₂ ) takes a microstructure in which agglomerated spherical particles are randomly precipitated, and this microstructure is composed of a mechanically and chemically unstable lithium disilicate (Li ₂ Si ₂ O ₅ ) phase and a mechanical and chemical Of α-quartz (α-SiO ₂ ) aggregated spherical particles that are stable to the surface, and have been found to produce surface irregularities in response to mechanical and chemical actions caused by polishing.
The present inventors have found that a magnetic disk substrate having excellent surface characteristics can be obtained by controlling the size of agglomerated spherical particles of quartz (α-SiO ₂ ).

That is, in the magnetic disk substrate for achieving the above object of the present invention, the crystallized glass has a crystal phase of lithium disilicate (Li ₂ O.2SiO ₂ ) and α-quartz (α).
—SiO ₂ ), which has a spherical particle structure composed of a plurality of particles in which the α-quartz grown crystal particles are aggregated, and the spherical particles have a diameter in the range of 0.3 μm to 3.0 μm. And the roughness (Ra) of the polished surface of the magnetic disk substrate is from 15 ° to 50 °.
It is characterized by being within the range of Å.

In one aspect of the present invention, the magnetic disk substrate comprises 65-83% of SiO ₂ ,
_{2 O 8~13%, K 2 O} 0~7%, MgO 0.5
0 to 5.5%, ZnO 0 to 5%, PbO 0 to 5%, but MgO + ZnO + PbO 0.5 to 5.5%, P ₂ O
_{5 1~4%, Al 2 O 3} 0~7%, As 2 O 3 + S
obtained by heat-treating a glass containing b ₂ O ₃ 0~2%.

[0021] In another aspect of the present invention, the magnetic disk substrate has a SiO ₂ content of 70-82% by weight.
_{Li 2 O 8~12%, K 2} O 1~6%, MgO 1
~ 5%, ZnO 0.2 ~ 5%, but MgO + Zn
O 1.5-5.5%, P ₂ O ₅ 1-3%, Al ₂ O
₃ 1-6%, obtained by heat-treating a glass containing _{As 2 O 3 + Sb 2 O} 3 0~2%.

A magnetic disk for achieving the above object of the present invention is a magnetic disk having a magnetic medium film formed on a substrate, wherein the crystal phase of the crystallized glass is lithium disilicate (Li ₂ O.2SiO ₂ ) and α-quartz (α-SiO ₂ ), each having a spherical particle structure composed of a plurality of particles in which the grown crystal particles of α-quartz are aggregated. 0.3 μm to 3.0 μm
Wherein the surface roughness of the polished surface of the substrate (Ra) is in the range of 15 ° to 50 °.

In one aspect of the present invention, the substrate of the magnetic disk comprises 65 to 83% of SiO ₂ ,
_{2 O 8~13%, K 2 O} 0~7%, MgO 0.5
0 to 5.5%, ZnO 0 to 5%, PbO 0 to 5%, but MgO + ZnO + PbO 0.5 to 5.5%, P ₂ O
_{5 1~4%, Al 2 O 3} 0~7%, As 2 O 3 + S
obtained by heat-treating a glass containing b ₂ O ₃ 0~2%.

In another aspect of the present invention, the substrate of the magnetic disk comprises 70 to 82% by weight of SiO ₂ ,
_{Li 2 O 8~12%, K 2} O 1~6%, MgO 1
~ 5%, ZnO 0.2 ~ 5%, but MgO + Zn
O 1.5-5.5%, P ₂ O ₅ 1-3%, Al ₂ O
₃ 1-6%, obtained by heat-treating a glass containing _{As 2 O 3 + Sb 2 O} 3 0~2%.

The method for manufacturing a magnetic disk substrate achieving the above object of the present invention, in% by weight, SiO ₂ sixty-five to eight
_{3%, Li 2 O 8~13%} , K 2 O 0~7%, Mg
O 0.5-5.5%, ZnO 0-5%, PbO 0
5%, but MgO + ZnO + PbO 0.5 to 5.5
_{%, P 2 O 5 1~4%} , Al 2 O 3 0~7%, As
A glass containing 0 to 2% of ₂ O ₃ + Sb ₂ O ₃ is melted, molded, heated and heated to a nucleation heat treatment in the range of 450 ° C. to 540 ° C. After the crystallization heat treatment, the surface is polished to a surface roughness in the range of 15 ° to 50 °.

As the raw glass for producing the magnetic disk substrate of the present invention, those having various compositions can be used. One preferred example will be described below.

The composition of the crystallized glass constituting the magnetic disk substrate of the present invention can be expressed on an oxide basis, similarly to the original glass. The reason why the composition of the raw glass is limited to a specific range in the above preferred example will be described below.

The SiO ₂ component is a very important component that generates α-quartz (α-SiO ₂ ) and lithium disilicate (Li ₂ O · 2SiO ₂ ) as a crystal phase by heat treatment of the raw glass. If the amount is less than 65%,
Precipitated crystals of the crystallized glass obtained are unstable and the structure is liable to be coarsened. If it exceeds 83%, melting of the raw glass becomes difficult. As a result of the experiment, a particularly preferable range is 70 to 8
It turned out to be 2%.

The Li ₂ O component is converted to lithium disilicate (Li ₂ O · 2SiO ₂ ) as a crystal phase by heat treatment of the glass.
When the amount is less than 8%, it becomes difficult to precipitate the above crystals, and at the same time, it becomes difficult to melt the original glass. When the amount exceeds 13%, the obtained crystallized glass precipitates. The crystals are unstable and the structure is likely to be coarse, and the chemical durability and hardness deteriorate. A particularly preferred range is from 8 to 11%.

The K ₂ O component is a component for improving the melting property of glass, and can be contained up to 7%. A particularly preferred range is 1 to 6%.

It is important that the MgO component is found in the present invention to randomly precipitate crystals of α-quartz (α-SiO ₂ ) as a main crystal phase throughout the glass as spherical crystals of aggregated particles. If the amount is less than 0.5%, the above effects cannot be obtained, and 5.5%
If it exceeds 300, it is difficult to deposit desired crystals. A particularly preferred range is 1 to 5%.

Also, ZnO and PbO components can be added because they have the same effect as MgO. However, if their amounts exceed 5%, desired crystals hardly precipitate. A particularly preferred range for ZnO is 0.2-5%.

However, the total amount of the MgO, ZnO and PbO components should be 0.5 to 5.5% for the same reason.

In the present invention, the P ₂ O ₅ component is indispensable as a crystal nucleating agent for glass. If the amount is less than 1%, desired crystals cannot be formed, and 4%
If it exceeds 300, the precipitated crystals of the crystallized glass obtained are unstable and easily coarsened, and the devitrification of the original glass deteriorates. A particularly preferred range is 1-3%.

The Al ₂ O ₃ component is an effective component for improving the chemical durability of the crystallized glass.
%, The meltability deteriorates, and the amount of α-quartz (α-SiO ₂ ) crystal precipitation as the main crystal decreases. A particularly preferred range is 1 to 6%.

The As ₂ O ₃ and / or Sb ₂ O ₃ components can be added as a fining agent in melting the glass, but a total amount of one or two of these components of 2% or less is sufficient.

In the present invention, a small amount of B ₂ O ₃ , CaO, SrO, BaO, TiO ₂ , SnO is added to the glass to be used in addition to the above components, as long as desired properties are not impaired.
₂ and ZrO ₂ can be contained.

In order to manufacture a magnetic disk substrate from the raw glass having the above composition range, the glass having the above composition is melted, and then hot-formed and / or cold-formed, and then 450 ° C.
Heat treatment at a temperature in the range of 〜540 ° C. for about 1 to 5 hours to form crystal nuclei, followed by crystallization by heat treatment in a temperature of 700 to 840 ° C. for about 1 to 5 hours.

When the nucleation temperature is lower than 450 ° C., nucleation caused by phase separation by P ₂ O ₅ is insufficient,
On the other hand, if the nucleation temperature exceeds 540 ° C., the fine crystals of Li ₂ O.SiO _{2 which} are deposited as crystal nuclei are not uniformly deposited, and at the same time become coarse crystal nuclei.
-Disperse the aggregated particles of quartz to make α-quartz a single particle.

The crystallization temperature is an important temperature for controlling the spherical structure of particles obtained by aggregating α-quartz (α-SiO ₂ ) crystals in combination with the effect of the MgO component. If the temperature is lower than ℃, α-quartz (α-SiO ₂ )
It is difficult for crystals to sufficiently precipitate, and when the temperature exceeds 840 ° C., α
-The spherical structure of the aggregated particles of quartz (α-SiO ₂ ) cannot be maintained, and the above effects cannot be obtained.

Next, the heat-crystallized glass is lapped by a conventional method and then polished to obtain a magnetic disk substrate having a surface roughness (Ra) in the range of 15 ° to 50 °.

[0042]

Next, preferred embodiments according to the present invention will be described. Tables 1 to 5 show practical composition examples (No. 1 to No. 13) of the magnetic disk substrate of the present invention and a conventional SiO ₂ —Li ₂ O—Al ₂ O ₃ —P ₂ O ₅ system as a comparative composition example. Crystallized glass (JP-A-62-72547, Comparative Example 1), SiO ₂ —Li ₂ O—MgO—P ₂ O ₅ -based crystallized glass (US Pat. No. 3,231,456, Comparative Example 2) ) And SiO ₂ —Li ₂ O—MgO—P ₂ O ₅ -based crystallized glass (JP-A-63-210039, Comparative Example 3) were subjected to heat treatment temperature, heat treatment time, α-
These are shown together with the measurement results of the crystal grain size, crystal phase, and surface roughness (Ra) after polishing of the crystal grains grown from quartz. In the table, α-Q is α-quartz (SiO ₂ ), α-C
ri represents α-cristobalite (SiO ₂ ).

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

[Table 3]

[0046]

[Table 4]

[0047]

[Table 5]

In the accompanying drawings, FIG. 1 shows the surface roughness (Ra) of the crystallized glass of Example 4 after polishing, and FIG. 2 shows the surface roughness (Ra) of the crystallized glass of Comparative Example 1 after polishing. FIG. 3 is a graph showing the surface roughness (Ra) of the crystallized glass of Comparative Example 2 after polishing. 4 and 5 (enlarged photographs) are HF etching treatments of the crystallized glass of Example 4 above, FIG. 6 is a comparative example 1 above, and FIGS. 5 is a comparison between scanning electron micrographs of the crystal shape obtained by performing the above. FIG. 9 shows that the crystallized glass of Example 5 had an α-
It is a graph showing the relationship between the crystallization temperature range and the surface roughness of the quartz (α-SiO ₂₎ aggregated particles (Ra). further,
FIG. 10 shows that in Example 5, the surface of the substrate having a surface roughness (Ra) of 32 ° after polishing was AFM (Atomic Force).
Particle structure by three-dimensional image of the Microscope)
This is a photograph showing the structure, and shows that a spherical structure of a plurality of agglomerated particles of α-quartz (α-SiO ₂ ) forms fine and smooth protrusions on the entire substrate surface.

The glass of the above embodiment of the present invention is prepared by mixing raw materials such as oxides, carbonates and nitrates, melting them at a temperature of about 1350 to 1500 ° C. using a usual melting apparatus, and stirring. After homogenization, it was molded into a desired shape and cooled to obtain a glass molded body. Then, add this to 450-540
After forming a crystal nucleus by heat treatment for about 1 to 5 hours at
It was kept at each crystallization temperature of 40 ° C. for about 1 to 5 hours to obtain a desired crystallized glass. Next, in order to manufacture a magnetic disk substrate having a surface roughness (Ra) of 15 ° to 50 °, the crystallized glass was subjected to polishing for about 1 hour using abrasive grains having an average particle size of 9 to 12 μm.
Wrap for 0-20 minutes, then average particle size 1-2μ
m of oxidized cerium for about 30 to 40 minutes.

The crystallized glass substrate becomes a magnetic disk for high recording density through a film forming process as a magnetic disk. That is, the crystallized glass substrate is heated in a vacuum state, and thereafter, an intermediate layer of Cr, C
A magnetic disk can be obtained by forming a magnetic layer of an o-alloy and a protective layer of C and applying a lubricant layer thereon.

As shown in Tables 2 and 5, the magnetic disk substrate of Example 4 has a desired surface roughness, whereas those of Comparative Examples 1 to 3 have such a desired surface roughness. I haven't. As is clear from FIGS. 1 to 3, the magnetic disk substrate of Example 4 has a desired surface roughness, but the magnetic disk substrates of Comparative Examples 1 and 2 do not have the desired surface roughness. FIG.
As is clear from the SEM images of Comparative Examples 1 to 6, the magnetic disk substrate of Example 4 had a spherical particle structure composed of a plurality of aggregated particles protruding from the substrate surface, whereas the crystal particles of Comparative Example 1 had needle-like or It shows a rod-like particle structure, indicating that a desired surface roughness cannot be obtained. Similarly, although not shown, the crystal particles of Comparative Example 3 also have a needle-like or rod-like particle structure, and a desired surface roughness cannot be obtained. Further, as shown in FIG. 7 and FIG. 8 (enlarged photograph), the crystal particles of Comparative Example 2 have a monocyte structure in which no aggregation of particles is observed, and a desired surface roughness cannot be obtained with this structure. Further, it is impossible to freely control the particle size as in the present invention. As shown in FIG. 8, according to the present invention, the particle size can be freely adjusted within the range of 0.3 μm to 3 μm by changing the heat treatment conditions. That is, 15Å to 50Å
The desired surface roughness within the range can be freely obtained.

Here, the difference between the spherical particle structure of α-quartz aggregated particles according to the present invention and the non-aggregated monocyte particle structure of α-quartz of Comparative Example 2 and the difference in the structure affect the effect of the present invention. The effect will be described in more detail.

As is clear from the scanning electron micrograph of Example 4 shown in FIG. 5, the α-quartz particles of the present invention are formed by agglomeration of fine particles to form spherical particles.
Further, as shown in FIG. 4, these particles are randomly scattered in fine particles of lithium disilicate (Li ₂ O.2SiO ₂ ) (a flat portion in the photograph). This state has a great effect on the surface roughness control characteristics obtained by polishing. On the other hand, the crystallized glass of Comparative Example 2 shown in the scanning electron micrographs of FIGS. 7 and 8 shows that lithium disilicate (Li ₂ O.2SiO ₂ ) and α-quartz (α-SiO ₂ ) were obtained by X-ray diffraction. ) Has been confirmed, but the distinction between the precipitation states of lithium disilicate (Li ₂ O.2SiO ₂ ) and α-quartz (α-SiO ₂ ) is not clear as in the present invention, and these are not clear. The shape of the crystal grains is irregular.

The surface roughness control characteristics of the magnetic disk substrate according to the present invention are physically and chemically controlled by lithium disilicate (Li).
Spherical crystal particles composed of a plurality of agglomerated small particles of α-quartz, which are essentially stronger than ₂ O · 2SiO ₂ )
It is obtained by a specific crystal structure formed by randomly depositing in chemically weak lithium disilicate crystal particles. Due to this crystal structure, in the polishing step, lithium disilicate crystal grains are ground more rapidly than α-quartz crystal grains, and as a result, as the polishing step proceeds,
The α-quartz crystal particles relatively prominently protrude from the surface of the lithium disilicate crystal particles, so
A relatively large surface roughness (Ra) of 0 ° is obtained. From the three-dimensional AFM image of FIG. 10, it can be seen that physically and chemically strong α-quartz aggregated particles randomly project over the entire polished surface.

Another advantage of the crystallized glass constituting the magnetic disk substrate of the present invention obtained from the spherical particle structure composed of agglomerated particles of α-quartz is that the particle diameter of the spherical particles can be reduced by changing the crystallization temperature. Can be controlled,
Thereby, a desired particle size can be arbitrarily obtained. This is because, in the present invention, the precipitation of α-quartz crystal particles largely depends on the degree of aggregation of small crystal particles, and the degree of aggregation depends on the employed crystallization temperature. Even if lithium disilicate and α-quartz are precipitated, such fine control of the particle size cannot be attained in Comparative Example 2 in which α-quartz crystal particles are monocytes and have an unspecified structure.

[0056]

As described above, according to the present invention, the crystal phase of the crystallized glass is lithium disilicate (Li ₂ O · 2S).
iO ₂ ) and α-quartz (α-SiO ₂ ), each having a spherical particle structure composed of a plurality of particles in which the grown crystal particles of α-quartz are aggregated. Start / stop of the magnetic disk due to the fact that the magnetic disk substrate is made of crystallized glass having a diameter within the range of 3.0 to 3.0 μm and the roughness (Ra) of the polished surface of the magnetic disk substrate is within the range of 15 ° to 50 °. A magnetic disk substrate having a required surface roughness can be obtained without performing any mechanical or chemical texturing required for a conventional magnetic disk substrate made of crystallized glass for improving the (CSS) characteristics. Moreover, a desired surface roughness within the above range can be easily obtained only by changing the heat treatment conditions. Therefore, it is possible to stably mass-produce a magnetic disk substrate having characteristics suitable for a magnetic disk for high-density recording at low cost.

According to the method of manufacturing a magnetic disk substrate of the present invention, 65 to 83% of SiO ₂ ,
_{2 O 8~13%, K 2 O} 0~7%, MgO 0.5
0 to 5.5%, ZnO 0 to 5%, PbO 0 to 5%, but MgO + ZnO + PbO 0.5 to 5.5%, P ₂ O
_{5 1~4%, Al 2 O 3} 0~7%, As 2 O 3 + S
b ₂ O ₃ was dissolved glass containing 0 to 2%, the temperature was heated to raise after molding, 450 ° C. to 540 perform nucleation heat treatment in the range of ° C., then crystallization heat treatment in the range of 700 ℃ ~840 ℃ Then, the surface is polished to a surface roughness in the range of 15 ° to 50 ° to obtain the magnetic disk substrate of the present invention.

[Brief description of the drawings]

FIG. 1 is a graph showing the surface roughness of a crystallized glass according to an example of the present invention.

FIG. 2 is a graph showing the surface roughness of a conventional crystallized glass.

FIG. 3 is a graph showing the surface roughness of a conventional crystallized glass.

FIG. 4 is a scanning electron micrograph of crystal grains after HF ₂ etching of the crystallized glass of the example of the present invention.

FIG. 5 is an enlarged electron microscope photograph of the embodiment of FIG.

FIG. 6 is a scanning electron micrograph of crystal particles of a conventional crystallized glass.

FIG. 7 is a scanning electron micrograph of crystal particles of another conventional crystallized glass.

8 is an enlarged electron micrograph of the crystallized glass of FIG.

FIG. 9 is a graph showing the relationship between the crystallization temperature range of α-quartz aggregated particles and the surface roughness of the crystallized glass of the example of the present invention.

FIG. 10 shows that the substrate surface after polishing according to the embodiment of the present invention is AF.
M (AtomicForce Microscope)
3 is a photograph showing a particle structure based on a three-dimensional stereoscopic image.

Claims (7)

(57) [Claims] The crystal phases of the crystallized glass are lithium disilicate (Li ₂ O.2SiO ₂ ) and α-quartz (α-S).
iO ₂ ), which has a spherical particle structure composed of a plurality of particles in which the α-quartz grown crystal particles are aggregated, and the spherical particles have a diameter in the range of 0.3 μm to 3.0 μm. A magnetic disk substrate comprising a crystallized glass having a roughness (Ra) of a polished surface of the magnetic disk substrate in a range of 15 ° to 50 °. 2. SiO ₂ 65-83 in weight percentage.
_{%, Li 2 O 8~13%,} K 2 O 0~7%, MgO
0.5-5.5%, ZnO 0-5%, PbO 0
5%, but MgO + ZnO + PbO 0.5 to 5.5
_{%, P 2 O 5 1~4%} , Al 2 O 3 0~7%, As 2
O ₃ + Sb ₂ O ₃ magnetic disk substrate according to claim 1, wherein a obtained by heat-treating the glass containing 0 to 2%. 3. SiO ₂ 70-82 in weight percentage.
_{%, Li 2 O 8~12%,} K 2 O 1~6%, MgO
1-5%, ZnO 0.2-5%, but MgO +
_{ZnO 1.5~5.5%, P 2 O 5} 1~3%, Al
₂ O ₃ 1 to 6%, As ₂ O ₃ + Sb ₂ O ₃ 0 to 2%
The magnetic disk substrate according to claim 1, wherein the magnetic disk substrate is obtained by heat-treating a glass containing: 4. A magnetic disk in which a magnetic medium film is formed on a substrate, wherein the crystal phase of the crystallized glass is lithium disilicate (Li ₂ O.2SiO ₂ ) and α.
-Quartz (α-SiO ₂ ), which has a spherical particle structure composed of a plurality of particles each of which is obtained by aggregating α-quartz grown crystal particles, wherein the spherical particles have a particle diameter of 0.3 μm to
It is made of crystallized glass having a diameter in the range of 3.0 μm, and the surface roughness (Ra) of the polished surface of the substrate is 15 °.
A magnetic disk characterized by being in the range of up to 50 °. 5. The method according to claim 1, wherein the substrate is made of SiO ₂ 6 by weight percentage.
_{5~83%, Li 2 O 8~13%} , K 2 O 0~7
%, MgO 0.5-5.5%, ZnO 0-5%, P
bO 0-5% where MgO + ZnO + PbO
_{5~5.5%, P 2 O 5 1~4} %, Al 2 O 3 0~
_{7%, As 2 O 3 +} Sb 2 O 3 magnetic disk substrate according to claim 4, characterized in that it is obtained by heat-treating the glass containing 0 to 2%. 6. The substrate according to claim 1, wherein said substrate is SiO ₂ 7
_{0~82%, Li 2 O 8~12%} , K 2 O 1~6
%, MgO 1~5%, ZnO 0.2~5 %, however, MgO + ZnO 1.5~5.5%, P 2 O 5 1
３3%, Al ₂ O ₃ ６6%, As ₂ O ₃ + Sb ₂ O
5. The magnetic disk substrate according to claim 4, wherein the magnetic disk substrate is obtained by heat-treating a glass containing _{30 to} 2%. 7. SiO ₂ 65 to 83 in weight percentage.
_{%, Li 2 O 8~13%,} K 2 O 0~7%, MgO
0.5-5.5%, ZnO 0-5%, PbO 0
5%, but MgO + ZnO + PbO 0.5 to 5.5
_{%, P 2 O 5 1~4%} , Al 2 O 3 0~7%, As 2
A glass containing 0 to 2% of O ₃ + Sb ₂ O ₃ is melted, molded, heated and heated to a nucleation heat treatment in a range of 450 ° C. to 540 ° C., and then a crystal in a range of 700 ° C. to 840 ° C. A method for producing a magnetic disk substrate, comprising: after polishing heat treatment, polishing the surface to a surface roughness in the range of 15 ° to 50 °.