JP2948178B2 - Substrate for magnetic disk - 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, which is less likely to cause sticking of a magnetic head, has high sliding reliability, and has high reliability.
The present invention relates to a magnetic disk substrate having excellent head flying characteristics and suitable for manufacturing a low-cost magnetic disk.

[0002]

2. Description of the Related Art Conventionally, a substrate surface for a thin-film magnetic disk has been required to have an appropriate roughness rather than a mirror surface in order to prevent adhesion of a head. For example, JP 62
As described in JP-A-248133, a method of machining a concentric groove called a texture on the Ni-P surface, or as described in JP-A-60-38720, the unevenness of the material of the alumina-TiC ceramics substrate is reduced. There have been devised a method of using such a method, or a method of dispersing fine particles in a base plating film as disclosed in JP-A-61-123016, and attempts have been made to achieve the above object.

[0003]

However, none of the substrates according to the prior art achieves all the necessary characteristics from the viewpoint of disk performance, cost and mass productivity. I couldn't get it. This is described below.

[0004] The base C is applied to the mirror-polished surface of the Ni-P substrate.
In a magnetic disk on which an r film, a magnetic medium, a protective film, and a lubricating oil film are formed, when the head is stopped, lubricating oil and moisture collect on the contact surface between the disk and the head, causing a head sticking phenomenon. As a result, the rotation of the disk becomes impossible, and the head holding mechanism parts are broken or deformed, which is a problem.

[0005] For this reason, it is currently widely practiced to perform what is called texture processing for processing concentric grooves on the Ni-P polished surface to roughen the disk surface and prevent sticking. However, texture processing has the following essential problems. Texture processing is a mechanism that cuts the Ni-P surface with fine abrasive grains, so burrs due to the plastic flow of the material during processing and bumps that collide with the head due to reattachment of cutting chips are generated. Cheap. For this reason, it is difficult to form a surface for floating the head over the entire surface of the disk with, for example, a spacing of about 0.2 μm.

In order to increase the recording density of a disk in the future, it is necessary to gradually reduce the spacing distance. At that time, however, there are many problems in the current texture processing.

Another problem with the Ni-P texture substrate is cost. Starting from the Al material, the machining of the Al material surface, the Ni-P plating process, the polishing process of the Ni-P surface, and the texturing process of the polished surface are completed. Not cheap. This is partly because the disk substrate is Al
This is because it is a composite composed of a multilayer film of two materials different from each other and Ni-P. On the other hand, in the case of a substrate made of a single material such as ceramics or glass, the number of steps is reduced and the cost can be reduced.

[0008] As described above, texturing the Ni-P layer has essential problems in terms of head levitation and cost. The present invention can solve these problems as described later.

Next, a conventional ceramic substrate will be described. This is, as quoted above, Al ₂ O ₃ −
A composite ceramic substrate such as TiC is used, and once a flat surface is polished, a step is formed by chemical or physical etching utilizing the difference in material properties between the composite materials.

In this method, the height of the projections on the final surface and the dimension between the projections are determined by the dispersion state of the two materials of Al ₂ O ₃ and TiC, so that a very advanced dispersion technique is required. .

When this Al ₂ O ₃ —TiC substrate was evaluated, there were two problems as follows. The first is heavy, and the other is the presence of voids. As for the weight, the specific gravity of Al ₂ O ₃ (alumina) is about 4, which is about 1.5 times that of metallic Al. This is an undesirable characteristic from the mechanism of a magnetic disk rotating at high speed. However, as the strength of the ceramics is large, there is still a method of reducing the thickness of the plate to take measures.

However, voids, which is another problem, is an essential problem determined by materials and processes. That is, in forming the ceramic substrate, since the ceramic powder is formed by sintering, the voids between the powder particles cannot be completely eliminated. For this reason, a high-pressure hot press method or the like is being studied, but voids cannot be eliminated. Processing oil and moisture tend to permeate and remain in the voids, causing defects in the film formed on the upper side and reducing the adhesion between the films.

A substrate using a composite ceramic having the above two points has a problem in actual use. In contrast, as described below, the present invention does not have these problems and provides an essentially excellent substrate material.

The method of dispersing fine particles in a plating film, which is the third method of the prior art, is specifically described in a Ni—P chemical plating solution of the order of several μm such as Al ₂ O ₃ or SiC.
Alternatively, fine particles on the order of submicrons are mixed to incorporate fine particles into the plating film. This allows
A film in which hard fine particles are scattered is formed in the Ni-P matrix.

The biggest problem of this method is that Al ₂ O ₃ or Si
Fine particles such as C cannot be uniformly dispersed in the plating film, and the density varies depending on the location of the particle density. Therefore, it is unsuitable for a magnetic disk substrate that requires uniform surface roughness and surface shape over the entire surface. Further, Ni-P also has a problem that it becomes ferromagnetic when heated at about 250 ° C.

On the other hand, it is known to use tempered glass as a magnetic disk substrate. In this method, sodium ions on a normal glass surface are subjected to ion exchange treatment with potassium ions having a larger ionic radius and the like, and a strengthened layer having a compressive stress is provided on the surface to form a glass substrate that is hard to break.

When a magnetic disk is formed by actually using this tempered glass substrate, it is necessary to use the same surface as that of the Ni-P plating film and appropriately roughen the surface by performing the same texture processing. However, when texturing a glass surface with a strong compressive stress, chipping or the like is likely to occur, and it is quite difficult to form a textured surface with no defect and a uniform surface shape.

An object of the present invention is to solve the problems of the prior art and to provide a magnetic disk substrate having excellent disk characteristics.

In other words, the appropriate surface roughness and surface suitable for preventing head adhesion, especially related to sliding reliability, including non-magnetic, lightweight, mechanical strength and defect-free properties required for a magnetic disk substrate. shape and productivity required when actually manufacturing the magnetic disk, heat resistance, in all the above overall characteristics such as low cost of the present invention to provide a novel board which is superior than the conventional substrate The purpose of.

[0020]

SUMMARY OF THE INVENTION The object of the present invention is to provide an amorphous material.
Glass as the continuous phase, and the crystal phase is dispersed in the glass phase.
Using a crystallized glass that is a complex
A magnetic disk substrate having a crystal phase projection formed thereon.
Surface density of the crystal grains of KitotsuOkoshi is 10 ² to 10 ⁶ months / mm ²
Range, and the crystal phase per unit area of the substrate is
Even if the sum of the areas exposed on the surface
Achieved by a magnetic disk substrate that is 30% .

That is, crystallized glass, which is a kind of composite material in which an amorphous glass is used as a continuous phase and a crystal phase is isolated and dispersed in the glass phase, is used as a substrate material. Utilizing and forming a large number of fine protrusions on the surface, a substrate suitable for the above-mentioned purpose is formed.

How the crystallized glass works to solve the above-mentioned problem will be roughly described in terms of a crystallized portion existing as dispersed particles in the crystallized glass and a glass layer which is a continuous matrix layer.

Before that, the materials of the crystallized glass and the manufacturing process will be outlined. Crystallized glass refers to alkali metal oxides (Li ₂ O, Na ₂ O, K ₂ O), alkaline earth oxides (MgO, CaO, BaO, SrO), Al ₂ O ₃ , Si
It is made of a material selected and combined from O _{2 and the} like. The production method is to form a glass plate after melting the raw material, and then to partially form, for example, L in the amorphous glass by a heat treatment for crystallization.
It precipitates crystals such as i ₂ O and 2SiO ₂ .

The size of the crystallized portion is set to 100
The preferred range is about Å to 3.0 μm, and the dimensions and density are as follows:
It can be controlled by heat treatment conditions. The composition of this crystallized part is
_{Li 2 O · 2SiO 2, Li} 2 O · SiO 2, LiO 2 · A
l ₂ O ₃ · 2SiO ₂ , Li ₂ O · Al ₂ O ₃ · 4SiO ₂ ,
It is such as SiO ₂ or _{2MgO · 2Al 2 O 3 · 5SiO} 2. The crystallized portion is generally harder and more chemically stable than the matrix layer. Therefore, by appropriately selecting the processing method and conditions, the crystallized portion becomes a small protrusion uniformly distributed on the substrate surface. Since the minute projections serve as point-like contact points of the magnetic head, they have an effect of preventing the sticking phenomenon with the head due to lubricating oil or moisture. In addition, it serves to prevent damage to the magnetic film due to collision with a magnetic head that comes into contact intermittently when the disk rotates at high speed. Further, the minute protrusion has an effect of cleaning dirt deposited on the slider surface of the magnetic head. For this reason, it also has the effect of preventing the head from falling or colliding, and dramatically increasing the reliability life of the disk device.

In other words, the characteristics and effects of the textured surface, which have been widely used in the past, are obtained.
There are minute projections on the crystallized glass surface.

As described above, microcrystals are essentially generated by a natural phenomenon in which an amorphous material is transformed into a stable crystal, and the protrusion is caused by a difference in material properties such as hardness between a glass portion and a crystallized portion. It is formed by using. The process is essentially a natural process. Therefore, there is no problem of burrs, chipping, and reattachment of chips, which are problems in the conventional texture processing. Furthermore, by optimizing the density of the size of the crystal fine particles, the height of the protrusion can be controlled, and as a result, a surface with extremely excellent head floating characteristics can be formed over the entire surface of the substrate.

The crystallized portion serves as an end point of microcracks generated in the continuous glass layer, and thus has an effect of suppressing the growth and expansion of cracks. For this reason, the mechanical strength and hardness of the crystallized glass are increased, so that the glass is less likely to be broken, and has the effect of realizing sufficient mechanical strength as a magnetic disk substrate.

Next, the operation and effect of the glass layer as a continuous layer will be described below. (1) The material composition is non-magnetic, and there is no fear of being magnetized by heating or the like. (2) It is essentially inexpensive because it is a raw material composed of elements (Al, Si, Na, O, etc.) which are abundant on the earth. (3) Since the material is a single substrate material, the number of steps is small and the manufacturing cost can be reduced. (4) Since it is formed by vitrification through a melting process, there are no voids and voids, which are problems with sintered materials.

In addition, since crystallized glass utilizes a natural phenomenon called crystallization, precipitated microcrystalline particles have a property of being substantially uniformly dispersed.

As described above, in the crystallized glass, the precipitated crystal layer and the matrix glass layer have advantages of each other, and have excellent physical properties due to their interaction. Therefore, it is a composite material suitable as a high-performance substrate for a magnetic disk.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) An embodiment of the present invention will be described below. The process of manufacturing a magnetic disk substrate using crystallized glass starts with material adjustment, and then continues in the order of heat melting, glass plate formation, disk shape processing, nucleation heat treatment, nucleus growth heat treatment, and surface polishing. It is basically to do.

The manufacturing process is not limited to the above. For example, sputter etching or chemical etching may be performed instead of surface polishing, or high-speed flat smoothness of the disk surface can be realized after the disk shape processing. The heat treatment may be performed after performing the machining for the purpose. The heat treatment can be completed in one step.

Changing the order of the steps and the contents of the steps in accordance with the technical contents and material characteristics does not depart from the gist of the present invention.

Examples will be described below in accordance with the above-described typical process procedures. In this embodiment, a Li ₂ O—SiO ₂ —P ₂ O ₅ system was used as a material. That is,
Li ₂ O component 19.4 wt%, SiO ₂ component 77.9
The raw material powders Li ₂ CO ₃ , SiO ₂ , and H ₃ PO ₄ are weighed so that the wt% and the P ₂ O ₅ component become 2.7 wt%.
Mix in the usual way.

Next, after heating and melting the material at 1400 ° C.,
2.0 m thick using float method using liquid metal tin
m on a glass plate. 130 diameter from this glass plate
-A glass disk was cut out by machining to an inner diameter of 40.

Next, the glass disk is placed in a heat treatment furnace and placed at 10 ° C.
/ Min. After heating to 550 ° C. at a heating rate of 1 minute, the temperature was maintained for 1 minute, and then 10 ° C./min. The temperature was raised to 600 ° C. at the temperature rising rate, and the temperature was maintained for 1 minute, followed by cooling. Cooling was performed at 5 ° C./min. At a speed of

The above-mentioned heat treatment at 550 ° C. is a treatment for generating crystal nuclei in the glass, and the subsequent heat treatment at 600 ° C. is a treatment for growing the crystal nuclei to a predetermined size. For crystallized glass substrates for magnetic disks,
The density and size of the crystal nuclei precipitated in the glass are particularly important because they relate to the characteristics and density of the magnetic disk.

The temperature and time of the heat treatment determine the density and size of the crystal nucleus. Therefore, other than the conditions described in this embodiment, the heat treatment temperature and time may be changed as needed. Generally, the nucleation temperature is preferably slightly higher than the glass transition temperature, and the nucleus growth temperature is preferably higher than the nucleation processing temperature and lower than the softening temperature.

Next, the glass substrate after the heat treatment and cooling is processed by a polishing machine. The polishing machine is provided with two polishing plates on the upper and lower sides. The glass substrate to be processed is sandwiched between jigs using a jig, and the polishing is performed by rotating the platen.

The purpose of this polishing process is to form fine projections on the surface of the crystallized glass. That is, since the glass portion in the crystallized glass has a lower hardness than the crystallized portion, it is polished relatively promptly, and as a result, a fine projection can be formed on the surface. In this case, the crystallized portion becomes convex. In addition, it is preferable that if there is an abnormally high protrusion on the surface, the platen pressure is concentrated at that point, and such a high protrusion is promptly removed.

Therefore, by using this processing method, it is possible to obtain a processed surface in which the heights of the protrusions are uniform in the plane of the substrate. Therefore, it is possible to obtain a surface having no abnormally high protrusions colliding with the magnetic head and having fine and uniform protrusions necessary and sufficient for preventing sliding reliability and adhesion.

The polishing platen pressure, rotation speed,
The time and the polishing material are important in controlling the fine convex shape of the processed surface.

Next, the surface of the substrate was washed with an organic solvent and pure water using brushing or ultrasonic waves.

Thereafter, in a vacuum sputtering apparatus at 300 ° C.
Then, a chromium base film, a Co—Ni magnetic film, and a carbon protective film are sequentially formed. Finally, a lubricating oil composed of fluorine-type hydrocarbon is applied to the surface in the atmosphere to complete a magnetic disk. The Cr underlayer may not be provided in some cases.

When the performance of the magnetic disk according to the present embodiment was tested, the recording density was 65,000 bits / inch.
And the minimum flying height of the head at this time is 0.08 μm.
m. In addition, CSS resistance (C
As a result of evaluation of the contact start stop, no head crash occurred and no adhesion of dirt or the like was observed on the magnetic head slider surface after the test even when the test was performed up to 50,000 times.

The adhesive strength also showed a low value equal to or lower than that of the conventional coated disk, and it was confirmed that there was no practical problem.

Example 2 In Example 1, a Li ₂ O—SiO ₂ —P ₂ O ₅ system was used as a material, but the crystallized glass material is not limited to this, and the following material systems are also used. A crystallized glass substrate for a disk is provided. Li ₂ O—SiO ₂ system Li ₂ O—Al ₂ O ₃ —SiO ₂ system Li ₂ O—MgO—Al ₂ O ₃ —SiO ₂ system MgO—Al ₂ O ₃ —SiO ₂ system Na ₂ O—Al ₂ O _3- SiO ₂ system BaO-Al ₂ O ₃ -SiO ₂ system In addition, as a precipitated crystal phase obtained from the above-mentioned material system,
There are the following: _{Li 2 O · SiO 2 Li 2} O · 2SiO 2 LiO 2 · Al 2 O 3 · 2SiO 2 Li 2 O · Al 2 O 3 · 4SiO 2 SiO 2 2MgO · 2Al 2 O 3 · 5SiO 2 these precipitation phases starting It is determined by the material, the heat treatment conditions, the nucleation accelerator described below, and the like, and is precipitated in various combinations, and is not uniquely determined.

In general, a nucleating agent is often added to produce crystallized glass. For example, there is a method using metal colligo produced by a combination of gold, silver, copper and cerium. In addition, oxides such as TiO ₂ , ZrO ₂ , and P ₂ O ₅ can also be used as nucleation promoters, and Nb, Ta, Mo, W elements, etc. may be used.
On the other hand, some types of glass materials do not require the addition of a nucleating agent.

(Example 3) In the case of Example 1, the precipitated crystal phase produced by the two-step heat treatment step had an average density of 5 × 10
⁴ particles / mm ² , and the average particle size was 0.05 μm.

When the starting material of the precipitated crystal phase is the same, the average density and the average particle size are determined by the two-stage heat treatment temperature and time. What is important here is not the heat treatment condition but the density and size of the obtained precipitated crystal phase. From the results of a large number of substrate samples and the results of an experiment evaluating the performance of the disk using the substrate, the average particle size of the precipitated crystal phase was 0.01 to 3.0 μm, and the average density was 10 ^2. in the range of 10 ⁶ months / mm ² has revealed that the preferred range of properties as a substrate for a disk.

If the particle diameter is less than 100 °, the minute projections formed on the substrate will be too small, causing a problem of sticking to the magnetic head. On the other hand, the particle size is 3.0 μm.
When it is more than m, the protrusion on the surface becomes too large, and a large number of protrusions are generated which may cause the magnetic head to fly, which is a problem. Also, bit errors increase.

From the above results, the preferred average particle size of the precipitated crystal phase is in the range of 0.01 to 3.0 μm.

Similarly, the particle density has a lower limit and an upper limit. When the particle density is 10 ² particles / mm ² or less, the magnetic head tends to stick. Conversely, the particle density is 10 ⁶ /
If it exceeds mm ² , problems such as an increase in wear of the slider surface of the magnetic head and an increase in signal noise occur.

From the above results, the preferred density of the precipitated crystal phase is 10 ² to 10 ⁶ / mm ² .

It is also important that the total area of the crystal grains present on the surface in the form of protrusions occupy a unit area of the substrate. If the ratio exceeds 30%, a problem occurs in the flying characteristics of the head. Therefore, 30% or less is a preferable range and is sufficient.

(Example 4) In Example 1 above, a projection was formed on the surface by polishing after two-step heat treatment. As a quantitative expression of the protrusion on the surface,
The height of the protrusion is used. This refers to the average height from the center position of the surface roughness of the glass phase, which is a continuous phase, to a reference line and from there to the top of the protrusion made of the crystal phase.

The average height of protrusions after polishing in Example 1 was 0.02 μm. The height of this average protrusion is
It is an amount that can be controlled by the size, density, and polishing conditions of the precipitated crystal phase. However, as a result of various studies, it is clear that the height of the protrusion is preferably in the range of 0.005 to 0.20 μm. I made it.

That is, when the height of the protrusion exceeds 0.20 μm and becomes higher, the surface roughness increases, and the magnetic head does not stably fly or the S / N deteriorates. Conversely, if the height is less than 0.005 μm, the surface characteristics approach those of a mirror surface, causing problems such as generation of adhesion to the head.

From the above results, it is understood that the average height of the fine protrusions is preferably in the range of 0.005 to 0.20 μm.

(Example 5) In Example 1 described above, polishing was performed after heat treatment for crystal nucleus growth, and surface protrusions were formed using the difference in hardness between the crystal phase and the glass phase. . This polishing is one application example, and in addition, it can be replaced by a so-called ion milling or sputter etching method in which a glass substrate is set in a vacuum and bombarded with Ar ⁺ ions at a high speed to perform etching.

Similarly, a method called so-called sand blasting, in which fine particles of Al ₂ O ₃ or SiC are blown together with air for processing, is also possible.

Further, as a chemical method, a method in which a crystal phase is formed as a protrusion by utilizing a difference between an etching rate of a crystal phase and a glass phase with respect to a hydrofluoric acid-based processing solution is also possible. In this case, there is an advantage that a relatively inexpensive process of immersing the crystallized glass substrate in the treatment liquid for a certain time can be obtained.

[0063]

According to the present invention, it is possible to form a magnetic disk substrate utilizing the excellent properties of crystallized glass, so that the following practical effects can be obtained.

1. Improvement of Head Flying Characteristics and Head Adhesion Characteristics The crystallized glass substrate according to the present invention can realize stable low flying characteristics of the head while preventing the adhesion phenomenon of the magnetic head. Quantitatively, if the value of the head adhesive force is assumed to be 1.0 for a coated disk having a proven track record, that of a conventional Ni-P texture substrate is 1.2 to 1.3, but that of the present invention is The value is between 0.9 and 1.0.

Regarding the flying characteristics of the magnetic head, a comparison is made between the minimum limit flying height when there is no protrusion that collides with the head in the state of the substrate. The flying height of the present invention is 0.08 μm, while that of the conventional Ni—P texture substrate is 0.15 μm.
It is.

It is important that the flying height of the head can be reduced to 0.08 μm while keeping the adhesive strength of the head low.

This is because the projections on the surface of the disk substrate according to the present invention are formed essentially by utilizing the phase change from amorphous to crystalline, so that the reproducibility and controllability are uniform. To be rich.

Further, since the formed irregularities on the surface are isotropically distributed both in the circumferential direction and in the radial direction within the disk surface, the adhesive force of the magnetic head in the circumferential direction and in the radial direction is obtained. Becomes isotropic. This is essentially different from the fact that the texturing is asymmetrical in one direction only in the circumferential direction.

2. Improvement of head-disk sliding reliability The thin-film magnetic disk manufactured using the disk substrate according to the present invention has a CSS resistance count of 50,000 or more,
There is no inferiority to the coated disk that has been used in the past. As a comparison, textured Ni-
A thin-film magnetic disk manufactured using a P substrate has a CS
When S was 32,000 times, a head crash occurred.

The use of the crystallized glass substrate improves the sliding reliability for the following reasons.

One is that the protruding tip made of crystallization portions scattered on the substrate surface has an effect of cleaning dirt and the like adhering to the slider surface of the magnetic head.

Secondly, the space between the scattered protrusions serves as a place for trapping minute wear powder generated by sliding of the head disk.

Thirdly, since the head slider is supported by the protruding tip, adhesion is hardly generated, and the protective film and the medium are hardly destructed. Note that, at a certain probability, the protective film and the medium are removed at the tips of the protrusions, and a hard crystal precipitation phase may be exposed, but this does not impair the effects of the present invention.

3. Process Shortening Compared with a substrate having a two-layer structure in which a Ni-P plating film is formed on an Al alloy, which is widely used at present, the crystallized glass substrate of the present invention is a single-layer, single-layer substrate. Therefore, the number of steps can be greatly reduced. In the case of a Ni-P substrate, starting from electrolytic refining of Al, for example, casting, hot pressing, cold pressing, disk press punching, inner / outer diameter processing, surface roughing,
The substrate is finally completed through heat treatment, surface finishing, plating pretreatment, Ni-P plating, and plating surface polishing. The number of steps is as large as twelve. On the other hand, the number of manufacturing steps of the crystallized glass substrate of the present invention is at most six as described in the examples, and can be reduced by half. As a result, manufacturing equipment costs and processing costs can be reduced by about half, and this has a great effect on reducing substrate manufacturing costs.

4. Effect of Material Properties In a substrate in which a Ni—P plating film is formed on an Al alloy that has been widely used in the past, the specific gravity of the Al alloy is 2.63. On the other hand, the specific gravity of the crystallized glass substrate according to the present invention is 2.4 to 2.5, which is slightly lighter than the Al alloy.
Therefore, there is an effect that the load on the rotating mechanism of the disk device can be reduced.

Since the material according to the present invention is essentially a non-magnetic material, even if it is heated at 300 ° C. to 400 ° C.,
There is no worry about magnetization. This is because the Ni-P substrate is about 2
It has a large heat-resisting margin in the process compared to being magnetized at 50 to 280 ° C or higher and becoming unusable as a substrate,
Degassing of the substrate can be sufficiently performed.

Since the magnetic disk substrate according to the present invention is once melted and vitrified after passing through a liquid state, there is essentially no void defect. This is symmetric with the point that the ceramic substrate is made by the powder sintering method and voids are easily generated. A magnetic disk with extremely few bit errors can be manufactured.

The magnetic disk substrate according to the present invention has a material property much higher in strength than ordinary general glass. For example, the bending strength of general sheet glass is about 50
In contrast to 0 kg / cm ² , the crystallized glass according to the invention reaches from 1500 up to 3500 kg / cm ² .

This makes it possible to form a substrate which is hard to crack and has practical strength.

[Brief description of the drawings]

FIG. 1 is a sectional view of a magnetic disk having a crystallized glass substrate according to the present invention.

[Explanation of symbols]

 1. Crystallized glass substrate, 2. Cr underlayer, 3. Co-Ni magnetic film, 4. Carbon protective film (surface lubricating oil applied).

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 5/62 C03B 32/02 C03C 10/04

Claims (3)

(57) [Claims] An amorphous glass is used as a continuous phase, and crystallized glass , which is a composite in which a crystal phase is scattered in the glass phase, is used to form a small crystal phase on the surface. Wherein the areal density of the protruding crystal grains is 1
0 ² to 10 ⁶ / mm ² and the unit surface of the substrate
The crystal phase with respect to the product is convex and is exposed on the surface.
A substrate for a magnetic disk having a total area of at most 30%. (2) The amorphous glass is used as a continuous phase, and the glass
Crystallized glass, which is a complex in which the crystalline phase is scattered in the
A magnetic crystal with a microcrystalline phase bump on the surface.
Wherein the area density of the protruding crystal grains is 10 ^Two ~
10 ⁶ Pcs / mm ^Two And the unit area of the substrate
The area where the above-mentioned crystal phase becomes convex and is exposed on the surface
The total sum of the substrates is at most 30%.
A magnetic disk comprising a protective film and a lubricating oil layer.
H. (3) Crystals that are exposed due to the protruding crystal phase on the surface
When the areal density of particles is 10 ^Two -10 ⁶ Pcs / mm ^Two In the range of
The above crystal phase with respect to the unit area of the veneer becomes convex and exposed
With the total area of the crystal grains to be grown is at most 30%
Fine crystals to form the projections of
A magnetic layer characterized by being deposited in large numbers inside glass
Glass plate for disc.