JP2000311336A - Manufacture of substrate for magnetic disk, substrate for magnetic disk resulted by this method and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for manufacturing a substrate for a magnetic disk which is capable of stably forming micro-ruggedness free of asperity, manufacturing the substrate with good reproducibility and improving the yield in producing the magnetic disk, the substrate for the magnetic disk obtained by this process and a magnetic recording medium. SOLUTION: The substrate for the magnetic disk is produced by subjecting a substrate consisting of inorganic material, such as glass, to plural times of an immersion treatment or scrubbing treatment under different treatment conditions using an acidic solution. Further, the substrate is subjected to the treatment using a neutral solution or alkaline solution after during the treatment by the acidic solution or after the treatment by the acidic solution. The substrate for the magnetic disk manufactured by these treatments has minute irregularities which is 0.4 to 3.0 nm in the average surface height Ra on its surface and <=14 in the ratio of the ten point average surface height (Rz) of the substrate surface to the average surface high (Ra) of the substrate surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an information recording device,
In particular, the present invention relates to a method for manufacturing a magnetic disk substrate used for a magnetic recording medium such as a hard disk, and a magnetic disk substrate and a magnetic recording medium obtained by the method. More specifically, a method of manufacturing a magnetic disk substrate used for a hard disk device having various heads, disks, interfaces, and the like such as a so-called CSS system, a ramp load system, and a contact system, a magnetic disk substrate obtained by the method, The present invention relates to a magnetic recording medium.

[0002]

2. Description of the Related Art In a hard disk of a type in which a magnetic head floats during driving, such as a CSS system or a ramp load system, or in a hard disk called a contact system in which the magnetic head is always in contact with the surface of the magnetic disk during driving and stopping. In order to increase the density of magnetic recording while preventing the occurrence of sticking between the magnetic head and the magnetic disk, finer irregularities (with a surface roughness Ra of 0.4 to 3)
(about nm) on the surface of a magnetic disk.

[0003] Forming such finer irregularities on the surface of a magnetic disk can be achieved by various methods for forming irregularities on the surface of a magnetic disk that are currently in practical use on a commercial basis.
For example, it is difficult to use a film texture method for forming irregularities on a glass substrate or a mechanical texture method for forming irregularities on an aluminum substrate.

On the other hand, several techniques for forming irregularities on the surface of a substrate made of an inorganic material such as glass by etching have been studied in the past. For example, Japanese Patent Application Laid-Open No. 5-31445
Japanese Patent Application Laid-Open No. 6-64294 discloses a technique for forming irregularities by etching a glass substrate with a mixed solution of hydrofluoric acid and potassium fluoride.

[0005]

However, according to these prior arts, the average unevenness formed is considerably larger than the average minute unevenness targeted by the present inventors. Then, the present inventors re-examined the etching conditions, and examined the target minute unevenness under the etching conditions other than the above-mentioned conventional technology.

[0006] However, when the present inventors have formed fine irregularities on the surface of a glass substrate by etching, the convexities which are higher or higher than the average convexities called asperities are discretely or partially formed. Occurred in some cases. When a magnetic disk is manufactured using a glass substrate having fine asperities having such asperities formed on the surface, there is a problem that a head crash is caused or a yield in manufacturing the magnetic disk is reduced.

Further, even when a glass substrate having the same composition is etched under the same conditions, the roughness and the shape of the fine irregularities may not be formed with good reproducibility. Such inconsistency in the roughness and reproducibility of the shape of the minute unevenness makes it difficult to stably mass-produce a glass substrate with the uniformity of the roughness and shape of the minute unevenness.

In recent years, in addition to the CSS method, a method of storing the head when the hard disk device is stopped between the head and the disk, such as a ramp load method and a contact method, and a method of contacting the head and the disk when the hard disk device is driven, other than the CSS method. The configuration of heads, disks, and interfaces, such as the presence or absence, heads having various slider shapes, and flying and running characteristics, has been diversified.

[0009] This is because each head, depending on the manufacturer who assembles the hard disk using the magnetic disk,
It is considered that this suggests that the required surface roughness of the magnetic disk is slightly different depending on the manufacturer of each hard disk because the design of the disk and the interface are different. Therefore, it is desirable that the fine irregularities formed on the substrate surface can control the roughness finely and accurately.

The present invention has been made by focusing on the problems existing in the prior art as described above. The purpose is to make it possible to stably form minute asperities without asperities, to produce a substrate with good reproducibility, and to improve the yield when manufacturing a magnetic disk. An object of the present invention is to provide a method of manufacturing a substrate for a magnetic disk, a magnetic disk substrate and a magnetic recording medium obtained by the method.

[0011]

According to a first aspect of the present invention, there is provided a method for manufacturing a magnetic disk substrate comprising an inorganic material such as glass, crystallized glass, ceramics, and aluminum. An immersion process or a scrub process is performed a plurality of times under different processing conditions using an acidic solution on the substrate or a substrate on which an alloy film such as nickel-phosphorus (NiP) is formed in advance, and the average surface of the substrate surface is obtained. The roughness Ra is 0.4 to 3.0 nm, and the 10-point average surface roughness (R) of the substrate surface with respect to the average surface roughness (Ra) of the substrate surface.
It is characterized in that minute irregularities having a ratio of z) of 14 or less are formed.

According to a second aspect of the present invention, in the method for manufacturing a magnetic disk substrate according to the first aspect of the present invention, neutralization is performed during or after the treatment using the acidic solution. A treatment using a solution or an alkaline solution is performed.

According to a third aspect of the present invention, in the method of manufacturing a magnetic disk substrate according to the first or second aspect of the present invention, the inorganic material is added to a 0.1% by weight aqueous hydrofluoric acid solution at 50 ° C. The glass substrate has an etching depth of 50 to 10,000 nm when immersion treatment is performed for 2.5 minutes.

According to a fourth aspect of the present invention, in the method of manufacturing a magnetic disk substrate according to the third aspect, the glass substrate has a calcium oxide (CaO) content of 1%.
The glass is 0% by weight or less and the content of magnesium oxide (MgO) is 15% by weight or less.

According to a fifth aspect of the present invention, in the method of manufacturing a magnetic disk substrate according to any one of the first to fourth aspects, the method further comprises: New irregularities are formed by applying processing means such as laser light irradiation.

A magnetic disk substrate according to a sixth aspect of the present invention is manufactured by the manufacturing method according to the fifth aspect. According to a seventh aspect of the present invention, there is provided a magnetic recording medium wherein a layer for a recording medium such as an underlayer, a magnetic layer, and a protective layer is formed on the surface of the magnetic disk substrate according to the sixth aspect.

[0017]

Embodiments of the present invention will be described below in detail. The magnetic disk substrate is made of glass,
A substrate made of an inorganic material such as crystallized glass, ceramics, aluminum or the like, or nickel-phosphorus (Ni
It is manufactured by performing a plurality of immersion treatments or scrubbing treatments under different treatment conditions on a substrate on which an alloy film such as P) is previously formed by using an acidic solution. The manufactured magnetic disk substrate has an average surface roughness Ra of 0.4 to 3.
It has fine irregularities of 0 nm and the ratio of the 10-point average surface roughness (Rz) of the substrate surface to the average surface roughness (Ra) of the substrate surface is 14 or less.

The material forming the substrate is an inorganic material,
Glass, crystallized glass other than glass, ceramics, and metals such as aluminum are used. Examples of the acidic solution used for the surface treatment of the substrate include aqueous solutions of hydrofluoric acid, sulfuric acid, nitric acid, phosphoric acid, hydrochloric acid, and the like. The treatment with the acidic solution is a dipping treatment or a scrub treatment. The immersion treatment is a method of immersing a substrate in an acidic solution under predetermined conditions. Scrub processing (or scrub etching) is a method of etching while rubbing the surface of a substrate material with a pad having a hardness lower than that of the substrate material.

On the solid surface (including the surface of a thin film), the composition, structure, and the like of the outermost layer and the bulk layer deeper than the outermost layer are chemically, physically, or mechanically different. It has been known. Generally, the outermost surface layer has a non-uniform composition and structure in the depth direction and the plane direction, whereas the bulk layer often has a uniform composition and structure.

Therefore, when the solid surface is etched, when the etching depth is changed using the same chemical,
Even if etching is performed under the same conditions using the same chemical solution, some difference occurs in the unevenness of the newly generated etched surface when there is some subtle variation in the etching conditions and the state of the solid surface to be etched. .

The occurrence of asperities and the instability of reproducibility of roughness due to the etching of the glass substrate as described above are remarkable when the etching depth is small. In that case, asperities are generated when forming minute irregularities on the glass substrate surface, and the cause of the instability of the roughness reproducibility is due to the non-uniformity of the composition and structure near the top surface layer of the glass substrate. Conceivable. The thickness of the outermost surface layer, which is considered to have a non-uniform composition and structure in the glass substrate, is considered to have a thickness of at least about 50 nm.

Therefore, when the solid surface is etched and the etching depth is changed using the same chemical,
Even if the same chemical solution is used for etching under the same conditions, there are some subtle variations in the etching conditions and the state of the solid surface to be etched. For this reason, there is a possibility that the unevenness of the newly generated etching surface may vary or asperity may occur.

On the other hand, even on a solid surface having a uniform composition and structure chemically and physically or mechanically in the depth direction, such as a bulk layer on the solid surface, a treating agent for etching is used. If the type of the material is different or the concentration and temperature of the same treating agent are different, the etching mechanism and the etching rate on the solid surface may be different. Further, many inorganic materials often have some two-phase or multi-phase structure.

There are various differences in the composition and structure of such a plurality of phases and the scale of the phase size. For example, in glass, phase separation by spinodal decomposition, in crystallized glass, a crystal phase and a glass phase, or in polycrystal, In the case of ceramics, there are crystal grains and grain boundaries surrounding them, and in the case of metals such as alloys, the presence of a polycrystalline phase composed of two or more phases is exemplified. Therefore, when the solid material is composed of two or more phases whose etching rate is significantly different from a certain acid treatment condition, if the solid surface is treated under the aforementioned acid treatment condition, the etching rate becomes lower. Since the solid surface is unevenly etched by the difference, unevenness is formed.

Therefore, if a difference between the treatment agent and the etching mechanism and the etching rate of the solid surface and the two-phase or multi-phase structure of the solid material itself are used, uneven surfaces having different roughnesses and shapes can be formed.

Taking glass as an example, when a glass having a multi-component composition is treated with an acidic solution, generally, the acid-sensitive components in the glass tend to preferentially dissolve. Utilizing this property, if the reactivity between glass and acid is selected so that the difference in dissolution rate between the acid-strong part and the acid-sensitive part of the glass becomes large, the glass surface dissolves unevenly,
Irregularities can be formed and grown on the glass substrate surface. On the other hand, by taking advantage of this property in reverse, if the reactivity between the glass and the acid is selected so that the difference in the dissolution rate between the acid-resistant part and the acid-sensitive part of the glass becomes small, the glass surface becomes uniform and uniform. Therefore, flat or very small minute unevenness can be formed on the surface of the glass substrate.

As described above, if a different etching mechanism is selected depending on the difference in reactivity between the solid surface and the acid, it is possible to form an uneven surface having a different roughness or shape.

Here, there are two purposes for carrying out the acid treatment at least twice or more as described above. A first object is to etch and remove a layer having an uneven composition and structure on the outermost surface of a substrate, which causes asperity and instability of reproducibility of unevenness roughness, by etching substantially uniformly and uniformly. Another object of the present invention is to form an altered layer on a substrate surface by an acid treatment in order to facilitate formation and control of unevenness in a second acid treatment step to be described later, or to perform both at the same time. In order to satisfy such a first purpose, the composition,
Acid treatment conditions such as concentration and temperature are set.

The acid treatment conditions are as follows: when a substrate having a Ra of 1 nm or less is polished smoothly and etched to a range of X to X + Y nm (where X> 0, 50 <Y <10,000). Average surface roughness Ra value is 0.1 to 2.6 n
It is desirable that the condition be such that it converges to a specific value within the range of m. This is because it is possible to easily control the shape and roughness of the minute unevenness in the second object described below.

A second object is to etch the substrate surface unevenly in order to control the roughness of the unevenness to a desired roughness. In order to satisfy such a second object, acid treatment conditions such as composition, concentration, and temperature are set.

The acid treatment conditions are as follows: a substrate having a Ra value of 1 nm or less, which is polished once, or a substrate having an etching surface converged to a specific Ra value by an acid treatment satisfying the first object, is etched by 5 nm or more. It is desirable that the Ra value at an arbitrary etching depth at this time be equal to or more than the Ra value before the second target etching +0.4 nm. This is because Ra targeted by the present invention is 0.4 to 3 Ra.
This is because minute irregularities having a desired roughness can be formed in the range of nm.

The type, concentration and temperature of the acid used for the acid treatment satisfying the first and second objects are determined by the acid resistance of the substrate and the acid treatment for the first object or the acid for the second object. It is necessary to select appropriate conditions depending on the processing.

In the acid treatment having the first and second objects, after the acid treatment having the first object is performed at least once,
It is most desirable to perform the acid treatment having the second purpose in order to control the shape and roughness of the minute unevenness to be formed. However, the acid treatment having the reverse order or the first and second purposes is performed. The processes may be alternately combined and performed plural times.

In the case of using hydrofluoric acid which has a remarkable etching effect on a glass substrate, its concentration is preferably in the range of 0.001 to 1% by weight. In this case, the concentration is preferably in the range of 0.01 to 1% by weight during the acid treatment for the first purpose, and 0.001 to 0.5% by weight in the case of the acid treatment for the second purpose. % Is desirable. In particular, when the aluminosilicate glass is etched with hydrofluoric acid, when the acid treatment for the first purpose is performed,
The concentration is preferably in the range of 0.02 to 1% by weight.
In the case of acid treatment for the purpose of the above, the range of 0.005 to 0.1% by weight is desirable. When using sulfuric acid, nitric acid, phosphoric acid, etc., which have a smaller etching action than hydrofluoric acid,
Since the etching action is not so remarkable as hydrofluoric acid, the acid concentration is set in the range of 0.01 to 5% by weight.

On the other hand, under the acid treatment conditions as described above,
Glass suitable for forming uneven surfaces having various roughnesses needs to be easy to selectively dissolve specific components by acid treatment. As a glass satisfying such a condition, an etching depth when immersing in a 0.1% by weight hydrofluoric acid aqueous solution at 50 ° C. for 2.5 minutes, which is an index of acid resistance, is 50 nm or more and 10,000 nm or less. Desirably. When the etching depth is less than 50 nm, the acid treatment makes it difficult to selectively dissolve the specific component that is weak to the acid in the glass. Therefore, even if the acid treatment having the second object is performed, it is difficult to form and grow irregularities within the range of the roughness intended by the present invention. Meanwhile, 10,
By the acid treatment exceeding 000 nm, the selective dissolution of the specific component which is weak to the acid in the glass becomes very easy to occur. Therefore, even if the acid treatment having the first object is performed,
Even if a flat surface or a minute uneven surface aimed at by the present invention cannot be obtained, even if an acid treatment having the second object is performed, irregularities are formed within the range of the roughness intended by the present invention, It becomes difficult to control.

The etching rate as described above is 50 nm.
The chemical components of the above general glass include SiO ₂ and R ₂ O (R = Li, N
a, K) and MO (M = a divalent metal ion such as Mg, Ca, Sr) are expressed in terms of weight fraction and SiO ₂ is 40 to 7
5 wt%, R ₂ O (R = Li, Na, K) is 5 to 25 wt%, and MO (M = divalent metal ion such as Mg, Ca, Sr) is 0 to 35 wt%. Desirably, other components other than the above-mentioned main components may be contained as necessary.

In the case of using hydrofluoric acid or an acidic solution composed of multiple components including hydrofluoric acid when forming fine irregularities on the surface of the glass substrate having the above-mentioned components, hardly soluble or insoluble foreign substances may be contained in the above solution. It may precipitate and contaminate the surface of the glass substrate. The generation of such foreign matter is not desirable because it causes a glide error and the like. Therefore, it is preferable that there are few components in the glass, such as CaO and MgO, which easily form a fluoride having extremely low solubility when reacted with hydrofluoric acid. Therefore, when it is assumed that the glass having the above-described components is treated with an acid containing hydrofluoric acid, Ca
It is preferable that O is 10% by weight or less and MgO is 15% by weight or less.

Further, when aluminosilicate glass is used, the following composition (% by weight) is preferable. The aluminosilicate glass having this composition is hereinafter referred to as aluminosilicate glass (1).

Silicon dioxide (SiO ₂ ) 58-70%, aluminum oxide (Al ₂ O ₃ ) 9-22%, lithium oxide (Li ₂ O) 2-10%, sodium oxide (Na ₂ O) 4-13% , potassium oxide _{(K 2 O) 0~ 5%} , magnesium oxide (MgO) 0~ 4%, calcium oxide (CaO) 0~ 7%, strontium oxide (SrO) 0~ 2%, barium oxide (BaO) 0 to 2% of titanium dioxide (TiO ₂₎ 0 to 2%, cerium oxide (CeO ₂₎ 0 to 2%, iron oxide _{(Fe 2 O 3) 0~ 2} %, manganese dioxide (MnO) 0 to 1% zirconium dioxide (ZrO ₂ ) 0-7% Such an aluminosilicate glass is produced by, for example, a float method. This float method is a method of manufacturing a plate-like glass by flowing molten glass from one end into a high-temperature bath in which molten tin is contained and the upper space has a reducing atmosphere, and the glass is stretched from the other end. Glass obtained by the float method has a low melting temperature, good water resistance and weather resistance after chemical strengthening treatment, and has an expansion coefficient that can be used in combination with metal products.

The glass substrate and the aluminosilicate glass substrate having the above-mentioned composition are chemically strengthened by generating a compressive stress on the surface by performing ion exchange in a molten salt containing potassium, sodium or both. It may be processed. By performing the chemical strengthening treatment, the durability of minute unevenness formed on the substrate surface can be improved. Further, such a chemical strengthening treatment may not be performed. Further, the substrate which has not been subjected to the chemical strengthening treatment may be subjected to the chemical strengthening treatment after forming the fine irregularities by the above-described method.

Regardless of the material constituting the substrate, the substrate immediately before being subjected to the acid treatment is preferably polished smoothly so that Ra is 1 nm or less. It is desirable because the unevenness history of the substrate surface before processing is less likely to be affected, and the roughness and shape of the minute unevenness to be formed can be easily controlled. However, the R of the substrate before the acid treatment
Even if a is 1 nm or more, if the etching depth is increased, the unevenness history of the substrate surface before the acid treatment can be reduced, so that the substrate surface before the acid treatment has a rough surface with a Ra of 1 nm or more. It may be.

Next, between each of the plurality of acid treatment steps and after the final acid treatment step, a step of immersion cleaning or scrub cleaning with a neutral or alkaline solution may be included a plurality of times. . This is the removal of reaction products and other dirt and foreign substances deposited on the substrate surface in the acid treatment step, the removal of the altered layer different from the bulk layer formed on the outermost surface layer of the substrate in the acid treatment step, or the a-time The acid solution that has adhered to the substrate surface in the acid treatment step is brought into the (a + 1) th acid treatment step having a different composition and concentration from the a-th acid solution, and
This is to prevent the first acid solution from being contaminated with the a-th acid solution (where a is an integer of 1 or more).

When the substrate material is glass or crystallized glass, at least one substrate is provided after the final acid treatment step.
It is desirable to perform immersion cleaning or scrub cleaning with an alkaline solution more than once.

The purpose of this alkali treatment is to reach a leaching layer (a glass skeleton component in the glass while retaining the glass skeleton component) remaining on the surface of the glass substrate or the crystallized glass substrate by the acid treatment.
(A layer in which components easily soluble in acid are selectively eluted). Such alkali treatment can prevent the acid-treated substrate and the magnetic disk manufactured using the substrate from deteriorating the weather resistance. That is, with the lapse of time, the prevention of deposition of foreign substances composed of alkali metal salts on the surface of a glass substrate or a crystallized glass substrate or the surface of a magnetic disk, or in a multilayer film formed on a glass substrate or a crystallized glass substrate Alkali metal diffusion can be suppressed. By performing such a treatment, the surface of a glass substrate or a crystallized glass substrate on which fine irregularities are formed and a magnetic disk manufactured using the glass substrate or the crystallized glass substrate may be alkali metal causing a glide error or the like. It is possible to suppress the generation of asperities made of carbonate or the like and foreign substances.

The neutral or alkaline solution as described above is not particularly limited, but can be selected from, for example, commercially available neutral detergents and alkaline detergents. When such a detergent is alkaline, an aqueous solution mainly containing an alkali component, a surfactant and a chelating agent is used, and when the detergent is neutral, an aqueous solution mainly containing a surfactant and a chelating agent is used.

Examples of the alkaline component include sodium hydroxide (caustic soda), potassium hydroxide (caustic potash),
Tetramethylammonium hydroxide, sodium carbonate, potassium carbonate and the like are used.

Examples of the surfactant include nonionic surfactants such as polyoxyethylene derivatives in addition to polyoxyethylene alkyl ethers, and quaternary ammonium salts such as lauryltrimethylammonium chloride.
Higher amine halides such as hardened tallow amine, cationic surfactants such as dodecylpyridium chloride, anionic surfactants such as sodium alkyl sulfates, sodium fatty acids, and alkyl aryl sulfonates, laurylaminopropionic acid An amphoteric surfactant such as an amino acid salt such as sodium is used.

As the chelating agent, for example, dimethylglyoxime, dithizone, oxine, acetylacetone, glycine, ethylenediaminetetraacetic acid, nitrilotriacetic acid and the like are used.

The concentrations of the alkali component, the surfactant and the chelating agent are not particularly limited.
001 to 5% by weight, 0.001 to 1% by weight of a surfactant and 0.001 to 1% by weight of a chelating agent.

[0050] New irregularities can be formed by further performing processing means such as laser light irradiation on a specific region of the substrate on which fine irregularities without asperities are formed on the surface as described above. YA as laser light
G laser at the same wavelength, or half or quarter
A wavelength obtained by converting the wavelength to the above wavelength is desirable because a large output can be easily obtained and the device is relatively inexpensive.

As the glass constituting the substrate, a glass having a laser light absorption coefficient of 266 nm at a wavelength of 266 nm in the range of 20 to 2000 mm ^-1 is preferable because new irregularities can be formed with high accuracy. The projections formed by the irradiation of the laser beam are of a plane circular shape and are arranged almost regularly. This projection has, for example, a height of 5
１００100 nm, diameter 1-20 μm, spacing 1-100
It is in the range of μm.

Next, an underlayer, a magnetic layer, a protective layer, and the like are sequentially formed on the surface of the glass substrate or the like obtained as described above, for example, by sputtering, to produce a magnetic recording medium. Specifically, chromium (C
r) -molybdenum (Mo) layer, the magnetic layer may be a cobalt (Co) -platinum (Pt) -chromium (Cr) -tantalum (Ta) layer, and the protective layer may be a carbon (C) layer. . Further, a lubricating layer of a perfluoropolyether-based lubricant may be formed thereon.

According to the above embodiment, the following effects can be obtained. The average surface roughness Ra of the substrate surface is 0.4 to 3.0 nm and the average surface roughness of the substrate surface is obtained by performing the immersion treatment or the scrub treatment plural times under different treatment conditions using an acidic solution. When the ratio of the 10-point average surface roughness (Rz) of the substrate surface to (Ra) is 14 or less, fine irregularities without asperity can be stably formed. Moreover, such a substrate can be manufactured with high reproducibility.

Further, if a magnetic disk is manufactured using a substrate obtained by performing a treatment using an acidic solution as described above, a glide error can be eliminated and the yield can be improved.

Further, since the roughness of the fine unevenness of the substrate can be finely and accurately controlled, it has fine unevenness of various roughness according to the difference in the design specification of the head disk interface which has been diversified in recent years. A magnetic disk or a substrate for a magnetic disk can be manufactured.

The removal of reaction products and other dirt and foreign matter deposited on the surface of the substrate in the acid treatment step by the combined use of the treatment using a neutral solution or an alkaline solution, and the formation on the outermost surface layer of the substrate It is possible to remove the altered layer different from the deposited bulk layer or prevent the substrate surface from being contaminated with the acid solution.

0.1% by weight at 50 ° C. as an inorganic material
By using a glass substrate having an etching depth of 50 nm or more and 10,000 nm or less when immersing in a hydrofluoric acid aqueous solution for 2.5 minutes, various roughnesses can be obtained based on the acid treatment. It is possible to form an uneven surface having.

Calcium oxide (C) as a glass substrate
If a glass having an aO) content of 10% by weight or less and a magnesium oxide (MgO) content of 15% by weight or less is used, deposition of hardly soluble or insoluble foreign substances is suppressed, and contamination of the glass substrate surface is prevented. Thus, occurrence of a glide error or the like can be avoided.

The specific area of the surface of the substrate having the fine irregularities is subjected to processing means such as laser light irradiation to form new irregularities, whereby the range of the roughness of the fine irregularities is not limited. Larger irregularities can be formed.

A magnetic disk substrate having desired irregularities on the surface can be manufactured by the manufacturing method described above, and layers for a recording medium such as an underlayer, a magnetic layer, and a protective layer are formed on the surface. Thereby, a magnetic recording medium useful as a hard disk or the like can be obtained.

[0061]

EXAMPLES Hereinafter, the embodiment will be described more specifically with reference to examples and comparative examples. It should be noted that the present invention is not limited to these embodiments. (Example 1) <Process A> A 2.5-inch glass substrate obtained by chemically strengthening the above-mentioned substrate made of aluminosilicate glass (1) was used. Then, the surface of the glass substrate was precisely polished, and Ra of the surface was set to 0.3 to 0.6 nm, and then scrub-cleaned using pure water. <Process B> Next, the glass substrate was immersed in a 0.1% by weight aqueous solution of hydrofluoric acid (HF) at 50 ° C. for 2.5 minutes while rocking, and then rinsed with warm pure water to remove the chemical solution. <Process C> Subsequently, the glass substrate was immersed in a hydrofluoric acid aqueous solution at 50 ° C. at 0.03% by weight for 20 minutes while rocking, and then rinsed with warm pure water to remove the chemical solution. <Process D> Thereafter, immersion cleaning was performed for 30 seconds in an aqueous potassium hydroxide solution adjusted to pH 11 while irradiating ultrasonic waves, followed by scrub cleaning. Then, again at pH
The substrate was immersed and washed in a potassium hydroxide aqueous solution adjusted to 11 while irradiating with ultrasonic waves for 160 seconds. Next, the operation of immersing in a pure water bath and rinsing was repeated several times, and then the glass substrate was immersed and washed while irradiating the bath of isopropyl alcohol with ultrasonic waves, and finally dried for 1 minute in isopropyl alcohol vapor. One sample was used. (Example 2) Processes A and B were performed in the same manner as in Example 1. Next, the glass substrate was immersed in a hydrofluoric acid aqueous solution of 0.03% by weight at 50 ° C. for 40 minutes while rocking, and then rinsed with warm pure water to remove the chemical solution. Thereafter, Process D was performed in the same manner as in Example 1. This test was repeated three times (# 1, # 2, # 3), and the average value and standard deviation were determined.
This was used as a sample of Example 2. (Example 3) Processes A and B were performed in the same manner as in Example 1. Next, the substrate was immersed in a hydrofluoric acid aqueous solution of 0.01% by weight at 50 ° C. for 30 minutes, and then rinsed with warm pure water to remove the chemical solution.

Thereafter, the substrate was immersed and washed in a 0.1 N aqueous potassium hydroxide solution for 2.5 minutes, and then rinsed with warm pure water and pure water. Next, the sample was immersed and washed in isopropyl alcohol while being irradiated with ultrasonic waves, and finally dried for 1 minute in isopropyl alcohol vapor to obtain a sample of Example 3. (Example 4) Aluminosilicate glass (1) described above
A 2.5-inch glass substrate manufactured by KK was used. This glass substrate is not chemically strengthened. Then, the surface of the glass substrate is precisely polished, and Ra of the surface is set to 0.3 to 0.6 n.
Then, scrub cleaning was performed using pure water.

Next, the same acid treatment as in process B of Example 1 was performed. Thereafter, the glass substrate was immersed in a hydrofluoric acid aqueous solution of 0.03% by weight at 50 ° C. for 30 minutes, and rinsed with warm pure water to remove the chemical. The subsequent washing in an aqueous potassium hydroxide solution was carried out in the same manner as in Example 3, and this was designated as Example 4. Comparative Example 1 Processes A and B were performed in the same manner as in Example 1. Thereafter, the process D was performed without performing the process C. Comparative Example 2 Process A was performed in the same manner as in Example 1. Next, the glass substrate was immersed in a 0.01% by weight hydrofluoric acid aqueous solution at 50 ° C. for 0.3 minutes while rocking, and then rinsed with warm pure water to remove the chemical solution. Thereafter, the process D was performed without performing the process C. Comparative Example 3 Process A was performed in the same manner as in Example 1. Next, the glass substrate was immersed in a 50% hydrofluoric acid aqueous solution at 0.01% by weight for 30 minutes, and rinsed with warm pure water to remove the chemical. Subsequent washing in an aqueous potassium hydroxide solution was performed in the same manner as in Example 3, and this was designated as Comparative Example 3. Comparative Example 4 Process A was performed in the same manner as in Example 1. Next, after immersing the glass substrate in a hydrofluoric acid aqueous solution of 0.005% by weight at 50 ° C. for 2.5 minutes while rocking the glass substrate,
The chemical solution was removed by rinsing with warm pure water, followed by scrub cleaning. Thereafter, Process D was performed in the same manner as in Example 1. Repeat this test three times (# 1, # 2, # 3)
Mean and standard deviation were determined. This was designated as Comparative Example 4. (Evaluation of micro unevenness) Examples 1 to 4 and Comparative Example 1
4 to 10 μm × 10 μm by a scanning probe microscope (Nanoscope III, manufactured by Digital Instruments)
Asperity ratio (Rz / Ra), which is a value obtained by dividing the average surface roughness Ra and the 10-point average surface roughness by the average surface roughness, was observed in a field of view of m, and summarized in Tables 1 and 2. In addition, the micro unevenness of all the measured samples had a continuous uneven shape which is isotropic and has no substantially flat portion between the concave portion or the convex portion.

[0064]

[Table 1]

[0065]

[Table 2] As shown in Tables 1 and 2, in each of Examples 1 to 4, asperity ratios (Rz / Ra) were as small as about 10, and glass substrates having various Ra values could be produced.

On the other hand, in Comparative Example 1, the Ra value was small, but the asperity ratio was slightly larger than 14. In Comparative Example 2, the Ra value is small as in Comparative Example 1, but
The asperity ratio was 19.4, which was larger than Comparative Example 1. Also, a bird's eye view of an atomic force microscope (AFM) clearly confirmed that asperities were discretely present. The generation of such asperities is because the etching depth of Comparative Example 2 was smaller than that of Comparative Example 1, and the deteriorated layer having an uneven composition and structure on the outermost surface of the glass substrate could not be sufficiently removed. Conceivable.

In Comparative Example 3, the glass substrate surface was etched non-uniformly, so irregularities grew and the Ra value increased, but the asperity ratio exceeded 15.4 at 15.5.

In Comparative Example 4, the Ra value was 1.5 to 2.2, but the asperity ratio exceeded 14 at about 15 to 18. The above embodiment may be modified as follows.

The treatment with the neutral solution or the alkaline solution may be performed by a scrub treatment. According to this method, the cleaning treatment with the neutral solution or the alkaline solution can be reliably performed.

A plurality of treatments with the acidic solution,
The immersion treatment and the scrub treatment may be performed in combination. Further, a technical idea grasped from the embodiment will be described below.

The substrate is glass, the acidic solution is a solution of hydrofluoric acid, and the concentration of hydrofluoric acid is 0.01 to 1
After performing the immersion treatment or the scrub treatment using the acidic solution of wt%, the concentration of hydrofluoric acid is 0.001 to 0.5 wt%.
The method for producing a magnetic disk substrate according to claim 1, wherein the immersion treatment or the scrub treatment is performed using the acidic solution of (1).

According to this method, the shape and roughness of the fine unevenness formed on the substrate surface can be suitably controlled. The method for manufacturing a magnetic disk substrate according to any one of claims 1 to 5, wherein the average surface roughness (Ra) of the substrate before performing the immersion treatment or the scrub treatment using the acidic solution is 1 nm or less. .

In the case of such a configuration, the history of unevenness on the substrate surface before processing is hardly affected, and the shape and roughness of minute unevenness can be easily controlled. The method of manufacturing a magnetic disk substrate according to any one of claims 2 to 5, wherein the neutral solution or the alkaline solution is an aqueous solution containing a surfactant and a chelating agent as main components.

With this configuration, it is possible to effectively remove reaction products, foreign substances, and the like deposited on the substrate surface after the treatment with the acidic solution.

[0075]

As described above, the present invention has the following advantages. According to the method of manufacturing a magnetic disk substrate according to the first aspect of the present invention, fine irregularities without asperities can be formed, the substrate can be manufactured with good reproducibility, and when manufacturing a magnetic disk. The yield can be improved.

According to the method of manufacturing a magnetic disk substrate of the present invention, a process using a neutral solution or an alkaline solution is performed. For this reason, in addition to the effect of the invention described in claim 1, the reaction product and other dirt and foreign substances deposited on the substrate surface in the acid treatment step are removed, and further, the bulk layer generated on the outermost surface layer of the substrate is It is possible to remove different deteriorated layers or prevent the substrate surface from being contaminated with the acid solution.

According to the method of manufacturing a magnetic disk substrate according to the third aspect of the present invention, in addition to the effects of the first or second aspect of the present invention, 0.1% by weight of an inorganic material at 50 ° C. By using a glass substrate having an etching depth of 50 to 10,000 nm when immersing in a hydrofluoric acid aqueous solution for 2.5 minutes, unevenness having various roughnesses based on the acid treatment is obtained. A surface can be formed.

According to the method of manufacturing a magnetic disk substrate of the present invention, the glass substrate has a calcium oxide (CaO) content of 10% by weight or less and a magnesium oxide (MgO) content of 15% by weight. % Glass or less is used. For this reason, in addition to the effect of the invention described in claim 3, precipitation of hardly soluble or insoluble foreign matter can be suppressed, contamination of the glass substrate surface can be prevented, and occurrence of a glide error or the like can be avoided. .

According to the method of manufacturing a magnetic disk substrate of the present invention, a specific area on the surface of the substrate having the fine irregularities is further subjected to processing means such as irradiation with a laser beam to thereby obtain new irregularities. Is formed. Therefore, claim 1
In addition to the effects of any one of the inventions according to the fourth aspect, larger irregularities not limited to the range of roughness of the minute irregularities can be formed.

According to the magnetic disk substrate of the invention described in claim 6, a magnetic disk substrate having desired irregularities on the surface can be manufactured by the manufacturing method described in claim 5.

According to the magnetic recording medium of the invention described in claim 7, the surface of the magnetic disk substrate described in claim 6 has
By forming layers for a recording medium such as an underlayer, a magnetic layer, and a protective layer, a magnetic recording medium useful as a hard disk or the like can be obtained.

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Claims (7)

[Claims] 1. Glass, crystallized glass, ceramics,
A substrate made of an inorganic material such as aluminum or a substrate on which an alloy film such as nickel-phosphorus (NiP) is previously formed is subjected to a plurality of immersion treatments or scrubbing treatments under different treatment conditions using an acidic solution. The average surface roughness Ra of the substrate surface is 0.4 to 3.0 nm, and the ratio of the 10-point average surface roughness (Rz) of the substrate surface to the average surface roughness (Ra) of the substrate surface is 14 or less. A method for manufacturing a substrate for a magnetic disk, comprising forming certain minute irregularities. 2. The magnetic disk drive according to claim 1, wherein a treatment using a neutral solution or an alkaline solution is performed during the treatment using the acidic solution or after the treatment using the acidic solution. How to make a substrate. 3. The inorganic material is 0.1% by weight at 50 ° C.
3. The method for manufacturing a magnetic disk substrate according to claim 1, wherein the glass substrate has an etching depth of 50 to 10,000 nm when immersed in a hydrofluoric acid aqueous solution for 2.5 minutes. 4. The method according to claim 1, wherein the glass substrate is made of calcium oxide (C
4. The method for producing a magnetic disk substrate according to claim 3, wherein the glass is a glass having an aO) content of 10% by weight or less and a magnesium oxide (MgO) content of 15% by weight or less. 5. The magnetic device according to claim 1, wherein a specific area on the surface of the substrate having the fine irregularities is further subjected to processing means such as laser light irradiation to form new irregularities. How to make a disk substrate. 6. A magnetic disk substrate manufactured by the manufacturing method according to claim 5. 7. A magnetic recording medium having a recording medium layer such as an underlayer, a magnetic layer, and a protective layer formed on the surface of the magnetic disk substrate according to claim 6.