JPH10226539A - Production of glass substrate for information recording medium and production of information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a glass substrate free from defects under a film by immersing a glass substrate in a heated chemical tempering soln., chemically tempering it by ion exchange and bringing the substrate in a heated state into contact with a solvent so that the ionic bonds of salt crystals sticking on the substrate are diminished or separated by utilizing the polarity and heat energy of the solvent to remove the salt crystals. SOLUTION: A glass substrate such as an aluminosilicate glass substrate for a magnetic disk is immersed in a chemical tempering soln. (e.g. a potassium nitrate-sodium nitrate mixed soln.) heated, e.g. to 250-650 deg.C and it is chemically tempered by exchanging ions in the surface layer of the substrate for ions in the soln. The substrate in a heated state is then washed by contact with a solvent that is warm water in the temp. range from the heating temp. of the soln. to room temp., preferably at 30-100 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic, optical, magneto-optical and other information recording medium and a method of manufacturing a glass substrate thereof.

[0002]

2. Description of the Related Art A magnetic disk is a typical information recording medium of this type. Aluminum substrates were widely used as substrates for magnetic disks,
With the demand for smaller and thinner magnetic disks and lower flying height of magnetic heads, it is easier to reduce the size, thinner and flatness of aluminum substrates compared to aluminum substrates. The ratio of using a substrate is increasing.

As described above, when a glass substrate is used as a substrate for a magnetic disk, the surface of the glass substrate is used for the purpose of improving shock resistance and vibration resistance and preventing the substrate from being damaged by shock or vibration. In general, the substrate is reinforced by performing a chemical strengthening treatment by a low-temperature ion exchange method and used.

When the chemical strengthening process is performed as described above, the glass substrate after the chemical strengthening process is subjected to a cleaning process because salt crystals adhere to the glass substrate. Conventionally, cleaning of a glass substrate for a magnetic disk after a chemical strengthening treatment is described in, for example, JP-A-2-28.
As described in Japanese Patent No. 5508, the cleaning is performed using an alkaline cleaning agent, pure water, an organic solvent and the like.

[0005]

As the recording density of the magnetic disk increases, the distance (spacing) between the magnetic disk and the magnetic head is required to be smaller. Therefore, there is an urgent need to completely remove foreign matter on the glass substrate that causes protrusions on the surface of the magnetic disk.

In particular, recently, with the increase in recording density, the magnetic head has also been changed from a thin film head to a magnetoresistive head. The magnetoresistive head is required to have a glass substrate and a flatness of the magnetic disk which are higher than those of the thin film head. This is because, when there is a minute foreign matter on the glass substrate, this is reflected on the surface of the magnetic disk, and the thermal asperity (a problem of the magnetic head due to the protrusion on the surface of the magnetic disk, This is because a phenomenon in which the resistance value fluctuates and the electromagnetic conversion malfunctions) occurs, and a malfunction occurs in the electromagnetic conversion and normal recording and reproduction cannot be performed. Therefore, today, as the ratio of the magneto-resistive head is increasing, the demand for the flatness of the glass substrate is increasing more than ever.

It has been found that such a new problem of the projection on the glass substrate is a problem that cannot be solved even by polishing with high precision polishing. As a result of the inventors' earnest investigation, it has been found that the real technical problem to be solved is "management of the cleanliness of the glass substrate surface". In other words, it is obvious that the precision polishing of the surface of the glass substrate is necessary, but the reason is that the surface that has been precisely polished is not kept clean until a thin film is formed.

[0008] One of the major factors hindering the cleanliness of the glass substrate is a salt crystal attached to the glass substrate when chemically strengthened. Certainly, as described above, cleaning is conventionally performed after chemical strengthening. However, in the conventional cleaning treatment, although a certain cleaning effect can be obtained, complete removal of salt crystals remaining on the glass substrate, that is, the cleanliness of the substrate surface at a modern level (submicron to several microns) Particles have a size of 0.0
02 or less). The crystals of the salt cause sub-film defects such as peeling of the thin film laminated on the glass substrate, and form projections on the surface of the thin film, which hinder the lowering of the flying height. As described above, the crystal of the salt is a problem by itself, but other than that, for example,
It functions as a binder for adhering minute particles such as iron scattered in the atmosphere to the glass substrate, and makes the above-mentioned problem remarkable.

The present invention has been made in view of the above problems, and has been made for an information recording medium capable of effectively removing salt crystals and particles bonded to the salt crystals without damaging the glass substrate. An object is to provide a method for manufacturing a glass substrate and a method for manufacturing an information recording medium. Another object is to manufacture an information recording medium with a high yield by using an information recording glass substrate having no sub-film defects.

[0010]

Means for Solving the Problems As a result of repeated studies by the present inventors to achieve the above object, the first constitution of the present invention is to immerse a glass substrate in a heated chemical strengthening treatment solution, By chemically exchanging ions of the substrate surface layer with ions in the chemical strengthening treatment solution and chemically strengthening the glass substrate, by contacting the glass substrate in a state where heat is applied in the above-mentioned process with a solvent, A salt crystal washing step of washing the salt crystals by reducing or separating the ionic bonds of the salt crystals attached to the glass substrate using the polarity and thermal energy of the solvent. A method for producing a glass substrate for an information recording medium, comprising:

According to a second aspect of the present invention, there is provided the information according to the first aspect, wherein the salt crystal washing step is performed in a temperature range between the heating temperature of the chemical strengthening treatment solution and room temperature. A method for manufacturing a glass substrate for a recording medium. A third configuration of the present invention includes:
The method for producing a glass substrate for an information recording medium according to the first or second configuration, wherein the solvent is warm water at 30 ° C. to 100 ° C.

According to a fourth aspect of the present invention, there is provided a glass substrate for an information recording medium according to the third configuration, wherein the hot water is pure water. According to a fifth aspect of the present invention, there is provided a glass substrate for an information recording medium, wherein the salt crystal washing step in the first to fourth aspects enhances the detergency by applying a physical external force. Production method. According to a sixth aspect of the present invention, there is provided a method of manufacturing a glass substrate for an information recording medium, wherein the physical external force in the fifth aspect is an ultrasonic wave propagating in a solvent or a scrubbing method.

A seventh configuration of the present invention is characterized in that a surface of a glass substrate is subjected to an alkali ion sealing treatment or a de-alkali ion treatment after a chemical strengthening treatment step or a salt washing step. The method for producing a glass substrate for an information recording medium according to any one of the above items.

According to an eighth aspect of the present invention, there is provided a method for manufacturing a glass substrate for an information recording medium according to the seventh aspect, wherein the glass substrate is brought into contact with heated concentrated sulfuric acid as an alkali ion sealing treatment. .

According to a ninth aspect of the present invention, in the method for manufacturing a glass substrate for an information recording medium according to the eighth aspect, the heating temperature of the heated acid is more than 100 ° C. to 300 ° C. .

According to a tenth aspect of the present invention, there is provided the information recording medium according to any one of the first to ninth aspects, wherein the glass substrate for the information recording medium is a glass substrate for a magnetic disk. A method for manufacturing a glass substrate.

An eleventh structure of the present invention is characterized in that the glass substrate for a magnetic disk is a glass substrate used for a magnetic disk which is electromagnetically converted by a magnetoresistive magnetic head. Of manufacturing a glass substrate for an information recording medium.

According to a twelfth aspect of the present invention, at least a recording layer is formed on an information recording medium glass substrate manufactured by the method for manufacturing an information recording medium glass substrate described in any one of the first to eleventh aspects. A method for manufacturing an information recording medium, comprising:

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

In the method of manufacturing a glass substrate for a magnetic disk according to the present invention, first, a glass substrate is immersed in a heated chemical strengthening solution, and ions in the surface layer of the glass substrate are exchanged with ions in the chemical strengthening solution. Chemical strengthening of glass substrates.

Here, as the ion exchange method, a low-temperature type ion exchange method, a high-temperature type ion exchange method, a surface crystallization method, a method of dealkalizing a glass surface, and the like are known. From the viewpoint of), it is preferable to use a low-temperature ion exchange method. In particular, in the case of a magnetic recording medium in which thinning is spurred, a low-temperature ion exchange method that causes little deformation of glass even when thinned is preferable.

In the low-temperature ion exchange method, alkali ions in the glass are replaced with alkali ions having a larger ionic radius in a temperature range below the glass transition temperature (Tg), and the volume of the ion exchange part is increased. In this method, a strong compressive stress is generated in the glass surface layer to strengthen the glass surface.

As the chemical strengthening treatment liquid, salts such as potassium nitrate (KNO ₃ ), sodium nitrate (NaNO ₃ ), potassium carbonate (K ₂ CO ₃ ), and a mixture of these salts (for example, KNO ₃ + NaNO ₃₎ , KNO ₃ + K ₂ CO ₃
), Or these salts with Cu, Ag, R
Salts of a mixture of salts of ions such as b and Cs are exemplified.

The heating temperature varies depending on the glass transition point of the glass to be treated.
The temperature is preferably from 0 ° C to 500 ° C, more preferably from 350 ° C to 450 ° C.

The immersion time is preferably about 1 to 20 hours from the viewpoint of the bending strength and the compressive stress layer.

The thickness of the compressive stress layer formed on the surface layer of the glass substrate is set at 6 from the viewpoint of improving the shock resistance and vibration resistance.
The thickness is preferably about 0 to 300 μm.

Before the glass substrate is immersed in the salt, the glass substrate is protected by two to prevent cracking and cracking of the glass substrate.
It is preferable to preheat to 00 to 450 ° C.

In the chemical strengthening step, it is preferable to carry out the chemical strengthening while holding the glass substrate at the end face. this is,
This is for chemically strengthening the entire surface of the glass substrate.

In the present invention, it is preferable that after the above-mentioned chemical strengthening, the glass substrate is pulled up from the chemical strengthening treatment liquid and gradually cooled to a predetermined temperature so as to suppress the occurrence of thermal distortion. By slow cooling in this way, damage due to thermal distortion can be avoided.

The rate at which the glass substrate is gradually cooled is 2 ° C./min.
100 ° C./min, especially 5 ° C./min to 60 ° C./min, and even 1
It is preferably from 0 ° C / min to 50 ° C / min.

In the salt crystal washing step of the present invention, when the ionic bonds of the salt crystals attached to the surface of the glass substrate are reduced or separated by utilizing the polarity of the solvent, the heat energy held by the solvent is used. This promotes reduction or separation. Examples of this type of solvent include warm water. The action and effect of the present invention in hot water can be realized by combining temperature and time so as to reduce the ionic bond of salt crystals. Temperature is 50 ° C-10
The temperature is preferably 0 ° C. (up to about 180 ° C. if pressurized), and the time is preferably about 2 to 6 hours. The warm water may be ordinary water, but pure water is preferable in order to suppress adhesion of particles. Incidentally, the crystal of the salt is a nitrate which is a precipitated molten salt,
Chloride.

In order to effectively remove salt crystals, not only the glass substrate is brought into contact with the solvent but also a cleaning method in which ultrasonic waves are transmitted to the solvent or a physical external force such as a scrub method is applied. May be. Further, since the solvent is used for the purpose of washing, not only salt crystals but also dirt such as other particles may be removed together. In this case, in addition to the solvent used for cleaning the salt crystals, a different cleaning agent for removing dirt such as particles may be mixed to collectively wash different foreign substances.

As described above, the salt crystal washing step of the present invention utilizes the heat energy of a solvent to separate salt crystals. However, since the glass substrate is already heated to, for example, 250 ° C. to 650 ° C. in the chemical strengthening process, the heat stored in the chemical strengthening process is almost completely stored, or a part of the heat is reduced. When the salt washing step is performed in this state, the amount of heat accumulated in the glass substrate in the chemical strengthening treatment step can also be used for reducing and separating ionic bonds of salt crystals. Therefore, it is preferable to carry out the salt crystal washing step using the heat accumulated in the chemical strengthening treatment step. When there is a temperature difference between the solvent temperature in the salt crystal washing step and the chemical strengthening treatment liquid, the salt washing step can also serve as a heat shock. Further, in order to reduce the temperature difference between the two, a temperature difference mitigation step may be provided.

Alternatively, a heat shock step may be separately provided after the salt crystal washing step of the present invention. In the heat shock step, micro cracks in the glass substrate are grown using thermal strain caused by a temperature difference, and defective products are removed at this stage. Therefore, so that such a thermal strain occurs, if a refrigerant having a lower temperature than the solvent in the salt crystal washing step is prepared, and the glass substrate is brought into contact with this refrigerant,
Heat shock can be applied to the present invention.

In the present invention, the glass substrate may be subjected to alkali ion sealing treatment or alkali removal treatment after the chemical strengthening treatment or after the salt crystal washing step. These processes cause film defects when alkali ions on the glass substrate surface move to the thin film formed on the substrate,
This is a process for preventing movement of alkali ions. By the way,
The alkali ions are not eluted by contact with warm water in the salt crystal washing step, but the amount is extremely small.
Therefore, the contact between the glass substrate and the hot water does not satisfy the standard of the alkali ion elution amount required at present, and there is almost no effect of removing alkali ions. Therefore, in order to prevent the movement of the alkali ions to the thin film, it is necessary to take measures to prevent the movement of the alkali ions to the glass substrate other than the salt crystal washing step.

As measures against such alkali ions, there are a dealkalization treatment for sufficiently eluting alkali ions near the glass substrate surface in advance, and an alkali ion sealing treatment by surface treatment of the glass substrate. Comparing the two, the alkali ion sealing treatment is more effective because the effect of preventing ion migration is remarkable. As the sealing treatment of the alkali ions, there is a method of treating the surface of the glass substrate with a heated acid to prevent elution of the alkali ions from the surface of the glass substrate. As described above, when an acid is used, an effect of washing the salt crystal by the acid can be obtained. As another alkali ion sealing treatment, there is a method in which a water-soluble organic solvent such as glycerin or polyethylene glycol is heated to 80 ° C. to 240 ° C. and brought into contact with the organic solvent for 1 minute to 1 hour.

When an acid is used, by controlling the type, temperature, concentration, etc. of the heated acid, salt crystals attached to the glass substrate can be removed, and at the same time, chemical alteration of the glass surface can be reduced to a high level. To a surface state that can be prevented.

Although it is not completely clear why the deterioration (burn etc.) of the glass surface can be prevented at a high level by the treatment with the heated acid, generally, the vicinity of the glass surface is reduced to the Si—O—Na From the non-crosslinked state,
Na ⁺ is ion-exchanged with hydronium ions or H ⁺ to form a hydrated state, and thereafter, a silanol group is formed by heat dehydration, and the silanol group is dehydrated to form a cross-linking of Si—O—Si on the glass surface. It is considered that this is done.

The heating temperature of the heated acid may be any temperature at which the elution of alkali ions near the surface of the glass substrate can be suppressed. The heating temperature of the heated acid is preferably from about 40 ° C. to about the glass transition point, more preferably from about 80 ° C. to about 300 ° C., and even more preferably from over 100 ° C. to about 300 ° C.

When the heating temperature of the heated acid is low, the glass surface is liable to be degraded because Si—O—Si is not crosslinked on the glass surface. On the other hand, if the temperature exceeds 300 ° C., K ions in the glass substrate move into the substrate, so that the strength of the glass substrate decreases.

The heating temperature of the heated acid is 100 ° C.
If it exceeds, the ability to prevent chemical alteration of the glass substrate surface is dramatically improved.

The treatment time with the heated acid is 1 minute to 2 minutes.
Time is preferred. 1 minute to 1 when using hot concentrated sulfuric acid
Time is preferred.

The treatment with a heated acid includes, for example, hot concentrated sulfuric acid (for example, concentrated sulfuric acid having a concentration of 96% or more), heated sulfuric acid, phosphoric acid, nitric acid, hydrofluoric acid, hydrochloric acid, and the like; The glass substrate is immersed in a mixed acid or a treatment solution obtained by adding salts of these acids (such as ammonium fluoride and potassium nitrate) to these acids. In this case, the processing may be performed while applying ultrasonic waves.

Among these acids, hot concentrated sulfuric acid (for example, a hot concentrated sulfuric acid having a concentration of 96% or more at a temperature exceeding 100 ° C.) or a hot concentrated sulfuric acid in terms of removing salt crystals and preventing deterioration of the glass surface. Acids containing sulfuric acid and / or phosphoric acid are preferred. In this case, it is preferable to perform the treatment by adding hydrogen peroxide to an acid containing sulfuric acid and / or phosphoric acid and generating heat by the reaction, since the treatment effect is improved.

The treatment with the heated acid may be performed by providing a plurality of treatment layers of the same or different acids and sequentially dipping the glass substrate. In this case, the temperature and concentration of the acid may be different.

The concentration of the acid is determined in consideration of removal of salt crystals and prevention of deterioration of the glass surface. Although the optimum concentration varies depending on the acid used, for example, when sulfuric acid is used, the concentration is preferably at least 50 wt%, more preferably at least 95 wt%.

After the treatment with the heated acid described above,
Known washing treatments such as washing with a commercially available detergent (neutral detergent, surfactant, alkaline detergent, etc.), scrub washing, pure water washing, solvent washing, solvent vapor drying, centrifugal drying and the like may be performed. In each cleaning, heating or ultrasonic wave application may be performed.

The ultrasonic wave may be either a multi-frequency type that oscillates in a certain frequency range or a fixed-frequency type that oscillates at a constant frequency. The lower the frequency, the higher the cleaning effect, but the greater the damage to the glass substrate. Therefore, the frequency is determined in consideration of these factors.

In steam drying, since the drying speed is high, stains due to drying are hardly generated. Examples of the solvent used for steam drying include isopropyl alcohol, chlorofluorocarbon, acetone, methanol, and ethanol.

The glass substrate is not particularly limited as long as it is an ion-exchangeable glass substrate. Further, the size, thickness, and the like of the glass substrate are not particularly limited.

Examples of the material of the glass substrate include aluminosilicate glass, soda lime glass, sodaaluminosilicate glass, aluminoborosilicate glass,
Examples include borosilicate glass, quartz glass, chain silicate glass, and crystallized glass. Aluminosilicate glass is particularly preferable because it has excellent shock resistance and vibration resistance.

As the aluminosilicate glass, Si
O ₂ : 62 to 75% by weight, Al ₂ O ₃ : 5 to 15% by weight,
Li ₂ O: 4 to 10% by weight, Na ₂ O: 4 to 12% by weight,
ZrO _2: 5.5 to 15 with containing by weight% as the main component, the weight ratio of Na ₂ O / ZrO ₂ is 0.5 to 2.
0, glass for chemical strengthening with a weight ratio of Al ₂ O ₃ / ZrO ₂ of 0.4 to 2.5, or SiO ₂ : 62 to 75
% By weight, Al ₂ O ₃ : 5 to 15% by weight, B ₂ O ₃ : 0.5 to
5 wt%, Li ₂ O: 4~10 wt%, Na ₂ O: 4~1
2% by weight, MgO: 0.5 to 5% by weight, CaO: 0.5
Glass for chemical strengthening and the like containing, as main components, 5 to 5% by weight and Sb ₂ O ₃ : 0.01 to 1.0% by weight are preferable.

Further, in order to eliminate projections on the glass substrate surface caused by undissolved ZrO ₂ , 57% to 74% of SiO ₂ , 0% to 2.8% of ZnO ₂ ,
The Al ₂ O ₃ 3~15%, the LiO ₂ 7~16%, Na ₂ O
It is preferable to use glass for chemical strengthening containing 4 to 14%.

The aluminosilicate glass having such a composition can control the three factors of compressive stress, tensile stress, and depth of the compressive stress layer in a well-balanced manner by being chemically strengthened, and has excellent bending strength and heat resistance. In addition, even under a high temperature environment, there is almost no precipitation of Na and the like, flatness is maintained, and Knoop hardness is excellent.

The method for manufacturing a glass substrate for an information recording medium according to the present invention includes a method for manufacturing a glass substrate for a magnetic disk, a method for manufacturing a glass substrate for a magneto-optical disk, and a method for manufacturing a glass substrate for abnormal projections, fine scratches and glass. It can also be used as a method for treating a disk substrate for electro-optics such as an optical memory disk that does not want to be deteriorated, and as a surface modification treatment method.

Next, a method for manufacturing the information recording medium of the present invention will be described.

The method for producing an information recording medium of the present invention is characterized in that at least a recording layer is formed on a glass substrate for an information recording medium obtained by using the above-mentioned method for producing a glass substrate for an information recording medium. I do.

In the present invention, since a glass substrate having no sub-film defects on its surface is used, the quality of the information recording medium is high. In other words, by using a glass substrate having a much better surface condition than in the past, when an information recording medium is used, head crashes due to foreign matter due to sub-film defects and film peeling do not occur, and the recording layer, etc. There is no possibility that defects due to burns or the like occur in the film and cause errors.

In the magnetic disk, a low flying height can be realized without causing a head crash caused by a salt crystal. Further, since a magnetic disk which is electromagnetically converted by a magnetoresistive head does not have a protrusion on the disk surface formed by reflecting a protrusion on a substrate, the occurrence of thermal asperity can be prevented. Further, since a magnetic disk glass substrate capable of preventing deterioration of the glass surface at a high level is used, a magnetic disk having excellent weather resistance and long life and high reliability can be manufactured with a high yield.

The magnetic recording medium is usually provided on a glass substrate for a magnetic disk, with an underlayer, a magnetic layer, a concavo-convex forming layer, a protective layer,
It is manufactured by sequentially laminating a lubricating layer and the like as necessary.

The underlayer in the magnetic recording medium is appropriately selected according to the magnetic layer. As the underlayer, for example, C
An underlayer made of at least one material selected from non-magnetic metals such as r, Mo, Ta, Ti, W, V, B, and Al is exemplified. In the case of a magnetic layer containing Co as a main component, it is preferable to use Cr alone or a Cr alloy from the viewpoint of improving magnetic properties. The underlayer is not limited to a single layer, and may have a multilayer structure in which the same or different layers are stacked. For example, Cr / Cr, Cr / CrMo, Cr
/ CrV, CrV / CrV, Al / Cr / CrMo, A
A multi-layer underlayer such as 1 / Cr / Cr is exemplified.

The material of the magnetic layer is not particularly limited.

As the magnetic layer, specifically, for example, C
CoPt, CoCr, CoNi, Co mainly containing o
NiCr, CoCrTa, CoPtCr, CoNiP
t, CoNiCrPt, CoNiCrTa, CoCrP
Magnetic thin films such as tTa and CoCrPtSiO may be used. Further, the magnetic layer is formed of a non-magnetic film (for example, Cr, CrM).
o, CrV, etc.) to reduce noise (for example, CoPtCr / CrMo / CoPtC)
r, CoCrTaPt / CrMo / CoCrTaPt).

The magnetic layer may be made of, for example, ferrite, iron-rare earth, SiO 2
₂ , Fe, Co, CoF in a non-magnetic film such as BN
e, granular having a structure in which magnetic particles such as CoNiPt are dispersed. The magnetic layer may be either an inner surface type or a vertical type.

The unevenness forming layer is provided for the purpose of controlling the unevenness of the medium surface. There is no particular limitation on the method of forming the unevenness forming layer, the material, and the like. Further, the formation position of the unevenness forming layer is not particularly limited.

In the case of a magnetic recording medium for a non-contact type recording type magnetic disk device, the unevenness forming layer forms unevenness due to the unevenness of the unevenness forming layer on the medium surface. It is formed for the purpose of preventing attraction between the magnetic recording medium and the magnetic recording medium and improving CSS durability.

In the case of a magnetic recording medium for a contact-type recording type magnetic disk drive, the surface of the medium is preferably as flat as possible to avoid damage to the magnetic head and the magnetic recording medium. No need.

The surface roughness of the unevenness forming layer is Ra = 10 to 5
Preferably, it is 0 Å. A more preferred range is Ra = 10 to 30 angstroms.

When Ra is less than 10 angstroms,
Since the surface of the magnetic recording medium is nearly flat, the magnetic head and the magnetic recording medium are attracted to each other, and the magnetic head and the magnetic recording medium are damaged, or the head crashes due to the attracting, resulting in fatal damage. On the other hand, if Ra exceeds 50 angstroms, the glide height becomes large and the recording density is lowered, which is not preferable.

There are various known materials and methods for forming the concavo-convex forming layer, and there is no particular limitation. As the material of the unevenness forming layer, Al, Ti, Cr, Ag, Nb, Ta, Bi, S
i, Zr, Cu, Ce, Au, Sn, Pd, Sb, G
Metals such as e, Mg, In, W, and Pb and alloys thereof, or oxides, nitrides, and carbides of these metals and alloys can be used. From the viewpoint of easy formation, etc., A
l Simple substance, Al alloy, Al oxide (Al ₂ O ₃ etc.), A nitride
It is desirable to use a metal mainly containing Al, such as 1 (AlN or the like).

The concavo-convex forming layer may be a continuous texture film or may be composed of discretely distributed island-like projections. The height of the island-like projections is preferably 100 to 500 Å, and more preferably 100 to 300 Å.

The surface roughness and the height of the unevenness (projections) of the unevenness forming layer can be controlled by the material and composition of the unevenness forming layer, heat treatment conditions, and the like.

As other methods for forming unevenness, texturing by mechanical polishing, texturing by chemical etching, texturing by energy beam irradiation, and the like can be used, and these methods can be combined.

Examples of the protective layer include a Cr film, a Cr alloy film, a carbon film, a zirconia film, and a silica film. These protective films can be continuously formed with an underlayer, a magnetic layer, and the like by an in-line or stationary facing sputtering apparatus. Further, these protective films may be a single layer, or may be a multilayer structure composed of the same or different films.

Another protective layer may be formed on the above protective layer or in place of the above protective layer. For example, instead of the above-mentioned protective layer, colloidal silica fine particles may be dispersed and applied while diluting tetraalkoxylan with an alcohol-based solvent, and then baked to form a silicon oxide (SiO ₂ ) film. . In this case, it functions as both the protective layer and the unevenness forming layer.

Although various proposals have been made for the lubricating layer, generally, a perfluoropolyether (PF) is generally used.
A liquid lubricant composed of PE) or the like is applied to the surface of the medium by a dipping method (immersion method), a spin coating method, a spray method, or the like, and is formed by performing a heat treatment as needed.

[0077]

EXAMPLES The present invention will be described below more specifically based on examples. Example 1 The method for manufacturing a glass substrate for a magnetic disk in this example is roughly divided into (1) a grinding and polishing step, (2) a chemical strengthening step, (3) a temperature difference reducing step, and (4) a crystal of a salt. It is divided into a washing step, (5) an alkali ion sealing step, (6) an iron contamination dissolving step, and (7) a final washing step.

(1) Grinding and Polishing Steps First, a sheet glass made of aluminosilicate glass is formed by a melt molding method. As the aluminosilicate glass, SiO ₂ is 57 to 74 by mol%.
%, ZnO ₂ from 0 to 2.8%, Al ₂ O ₃ from ₃ to 15%,
LiO ₂ 7 to 16% and a glass for chemical strengthening containing Na ₂ O as 4-14% main component. In the present embodiment, a method of press-molding molten glass into a disk shape by a molding die was employed as a method for molding the sheet glass. Other manufacturing methods include a float method, a fusion method, and the like.

Next, the front and back surfaces are ground by sanding. Then, the center portion of the glass substrate is perforated in a disk shape, and the inner and outer peripheral surfaces perforated with a grindstone are polished to determine the outer and inner diameter dimensions, and the inner and outer peripheral surfaces are chamfered. Then, as the last of the polishing process, the front and back surfaces are subjected to precision polishing to finish. Thus, a disk-shaped glass substrate was obtained. The polished disk-shaped glass substrate is then washed. All processes from this washing process to the packing process of packing the finished product of the magnetic disk glass substrate are always performed by a clean booth using clean air (semiconductor device). Cleanliness equivalent to that of the above manufacturing process). As described above, by increasing the cleanliness of the atmosphere in each step, it is possible to prevent particles such as iron contamination from adhering to the glass substrate.

(2) Chemical Strengthening Step Next, the glass substrate that has been subjected to the above-mentioned grinding, polishing and cleaning steps was subjected to chemical strengthening. Chemical strengthening is performed using potassium nitrate (6
0%) and sodium nitrate (40%) are prepared, and the chemically strengthened solution is heated to 400 ° C., and a cleaned glass substrate preheated to 300 ° C. is heated to about 3 ° C.
It was carried out by soaking for a time. In this immersion, in order to chemically strengthen the entire surface of the glass substrate, the immersion was performed in a state where a plurality of glass substrates were housed in a holder so as to be held at end faces.

As described above, by immersion treatment in the chemical strengthening treatment liquid, lithium ions and sodium ions in the surface layer of the glass substrate are replaced by sodium ions and potassium ions in the chemical strengthening treatment liquid, respectively, and the glass substrate is strengthened. . The thickness of the compressive stress layer formed on the surface layer of the glass substrate was about 100 to 200 μm.

(3) Temperature Difference Mitigating Step The glass substrate that has been subjected to the above-described chemical strengthening is gradually cooled in the first and second slow cooling chambers. First, the glass substrate is pulled up from the chemical strengthening treatment liquid, transferred to a first annealing room heated to 300 ° C., and held therein for about 10 minutes to gradually cool the glass substrate to 300 ° C. Next, the glass substrate was transferred from the first annealing room to the second annealing room heated to 200 ° C.
The glass substrate is gradually cooled to 200 ° C. By thus gradually cooling the glass substrate in two stages, the glass substrate can be released from damage due to thermal strain.

(4) Salt Crystal Washing Step Next, the glass substrate was immersed in a washing tank containing warm water of pure water maintained at about 90 ° C. for about 1.5 hours, and adhered in the chemical strengthening treatment step. Salt crystals (chloride, nitrate) were removed. At the time of this washing, ultrasonic waves were applied to the warm water.

(5) Alkali ion sealing treatment step The glass substrate having been subjected to the above-mentioned washing step is immersed in hot concentrated sulfuric acid having a concentration of 96 wt% heated to about 200 ° C. for 5 minutes, and treated with heated concentrated sulfuric acid. Alkali ions such as Na ions were sealed on the glass substrate surface by making the bond of Si—O on the glass surface firm. (6) Dissolution treatment of iron contamination Next, the glass substrate was immersed in a treatment tank containing hydrochloric acid to dissolve and remove particles such as iron contamination that might adhere to the glass substrate. (7) Final Cleaning Step Next, the glass substrate was immersed and washed in a washing tank of a neutral detergent, a neutral detergent, pure water, pure water, IPA (isopropyl alcohol), and IPA (steam drying) sequentially. In addition, ultrasonic waves (frequency 40 kHz) were applied to each cleaning tank. Then, the completed glass substrate was stored in a case.

When the surface of the glass substrate for a magnetic disk manufactured through the above steps was inspected with a microscope, no crystal of salt and no contamination with iron were recognized. In addition, burns due to alkali elution of 5 μm or more were not found. On the other hand, as for the glass substrate on which the salt crystal washing process was not performed, 0.01 particles of several microns of potassium ions or sodium ions were confirmed per substrate by visual inspection. Further, an unchemically strengthened portion due to iron contamination attached to the glass substrate due to the salt crystal was observed. Further, when a high-temperature and high-humidity environment test at a temperature of 85 ° C. and a humidity of 85% was conducted for 120 hours, no deterioration of the glass substrate surface such as burns was observed.

In order to confirm the effect of preventing migration of alkali ions, a glass substrate was manufactured in the same manner as in Example 1 except that only the alkali ion sealing step was not performed.
When the surface of this glass substrate was observed, no salt crystals were found, but ten to several hundreds of burns of 5 μm or more were found per 0.09 mm ² .

(8) Magnetic Disk Manufacturing Process A Cr underlayer, a CrMo underlayer, a CoPtCr magnetic layer, and a C protection layer were formed on both surfaces of the magnetic disk glass substrate obtained through the above-described processes by using an in-line sputtering apparatus. The layers were sequentially formed to obtain a magnetic disk.

When the weather resistance and the life of the obtained magnetic disk were examined, no deterioration or defect of the magnetic film or the like due to the chemical deterioration of the glass substrate surface was found.

Further, when a glide test was performed on the obtained magnetic disk, hits (the head touches the protrusions on the magnetic disk surface) and crashes (the head collides with the protrusions on the magnetic disk surface) were recognized. Did not. It was also confirmed that no defect occurred in the film such as the magnetic layer. Further, a recording / reproducing test was performed using a magnetoresistive head (MR head and GMR head), but no occurrence of thermal asperity due to abnormal projections on the surface of the magnetic disk was found.

[0090] soda-lime glass in place of Examples 2-3 aluminosilicate glass (Example 2), except for using crystallized glass (Example 3) In the same manner as in Example 1, a glass substrate for a magnetic disk And a magnetic disk. As a result, the thickness of the compressive stress layer is different from that of aluminosilicate glass,
There was no practical problem, and the cleanliness of the glass substrate surface as in Example 1 could be confirmed. Also, various magnetic characteristics of the magnetic disk were the same as in the first embodiment.

Next, the washing with warm water in the salt crystal washing step of Example 2 and Example 3 was performed at 60 ° C. for 2.5 hours and at 50 ° C. for 3 hours, respectively. The effect was confirmed.

Example 4 On both surfaces of the glass substrate for a magnetic disk obtained in Example 1, Al (film thickness 50 Å) / Cr (100
0 Å / CrMo (100 Å), CoPtCr (120 Å) / CrMo (50 Å) / Co
A magnetic layer made of PtCr (120 Å),
A Cr (50 Å) protective layer was formed by an in-line type sputtering apparatus.

The above substrate is immersed in an organic silicon compound solution (a mixed solution of water, IPA and tetraethoxysilane) in which fine silica particles (particle size: 100 Å) are dispersed,
A protective layer made of SiO ₂ is formed by firing, and a dip treatment is performed on the protective layer with a lubricant made of perfluoropolyether to form a lubricating layer.
A magnetic disk for an R head was obtained.

When the weather resistance and the life were examined, no deterioration or defect of the magnetic film or the like due to the deterioration of the glass substrate surface was found.

Further, when a glide test was conducted on the obtained magnetic disk, no hit or crash was recognized. It was also confirmed that no defect occurred in the film such as the magnetic layer. It was also confirmed that no thermal asperity was generated.

Example 5 The underlayer was made of Al / Cr / Cr, and the magnetic layer was made of CoNiCr.
A magnetic disk for a thin film head was obtained in the same manner as in Example 4 except that Ta was used. The same thing as Example 4 was confirmed for the magnetic disk.

[0097]

As described above, according to the method for producing a glass substrate for an information recording medium of the present invention, the crystal of the salt is completely removed, and the crystal of the salt serves as a binder. A glass substrate for an information recording medium from which particles adhered to the substrate have been removed can be obtained. or,
By adding an alkali ion migration prevention step,
Chemical deterioration of the glass substrate surface can also be prevented.

Therefore, when an information recording medium is manufactured using the substrate obtained by the above-described manufacturing method, a high-quality magnetic disk with few film defects can be manufactured with a high yield. Further, it is possible to manufacture an information recording medium which is excellent in weather resistance and life and has high reliability. In particular, when the glass substrate of the present invention is used for a magnetic disk, a low flying height can be realized without causing a head crash. In the case of a magnetic disk that performs electromagnetic conversion by a magnetoresistive head, thermal
Asperity can be prevented.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI G11B 7/26 G11B 7/26 11/10 541 11/10 541D 541E (72) Inventor Jun Ozawa 2-chome Nakaochiai, Shinjuku-ku, Tokyo Inside of No. 7-5 Hoya Co., Ltd. (72) Inventor Kazuhiko Maeda Inside of No. 7-5, Nakaochiai, Shinjuku-ku, Tokyo

Claims (12)

[Claims] A chemical strengthening treatment step of immersing a glass substrate in a heated chemical strengthening treatment liquid and ion-exchanging ions of a surface layer of the glass substrate with ions in the chemical strengthening treatment liquid to chemically strengthen the glass substrate; By bringing the glass substrate in a state where heat is applied into contact with a solvent, the ionic bond of the salt crystal attached to the glass substrate is reduced or separated by using the polarity and the heat energy of the solvent. And a salt crystal washing step of washing the salt crystals by the following method. 2. The method for manufacturing a glass substrate for an information recording medium according to claim 1, wherein the salt crystal washing step is performed in a temperature range between the heating temperature of the chemical strengthening treatment solution and room temperature. . 3. The method for producing a glass substrate for an information recording medium according to claim 1, wherein the solvent is warm water at 30 ° C. to 100 ° C. 4. The method for producing a glass substrate for an information recording medium according to claim 3, wherein the hot water is pure water. 5. The glass substrate for an information recording medium according to claim 1, wherein in the salt crystal washing step, the washing power is increased by applying a physical external force. Manufacturing method. 6. The glass substrate for an information recording medium according to claim 5, wherein the physical external force is an ultrasonic wave propagating in a solvent or a scrubbing method. Manufacturing method. 7. The method according to claim 1, wherein the surface of the glass substrate is subjected to a de-alkali ion treatment or an alkali ion sealing treatment after the chemical strengthening treatment step or the salt washing step.
The method for producing a glass substrate for an information recording medium according to any one of the above. 8. The method for producing a glass substrate for an information recording medium according to claim 7, wherein the glass substrate is brought into contact with heated concentrated sulfuric acid as the alkali ion sealing treatment. 9. The temperature of the heated acid is more than 100.degree.
The method for producing a glass substrate for an information recording medium according to claim 8, wherein the temperature is 00C. 10. The glass substrate for an information recording medium is a glass substrate for a magnetic disk.
The method for producing a glass substrate for an information recording medium according to any one of the above. 11. The magnetic disk glass substrate according to claim 1, wherein the glass substrate is a glass substrate used for a magnetic disk that is electromagnetically converted by a magnetoresistive magnetic head.
0. A method for producing a glass substrate for an information recording medium according to 0. 12. A method for manufacturing a glass substrate for an information recording medium according to any one of claims 1 to 11, wherein at least a recording layer is formed on the glass substrate for an information recording medium. Manufacturing method of the information recording medium.