JP2007220181A - Manufacturing method of glass substrate for magnetic disk and magnetic disk - Google Patents

Abstract

An object of the present invention is to increase the thickness of a coating film formed on an inner peripheral end surface of a glass substrate for a magnetic disk that has been subjected to an etching process.
An inner peripheral end face of a disk-shaped glass plate having a circular hole in the center is etched, and a liquid containing an organic polysilazane compound is applied to the inner peripheral end face and baked. It has a structural unit —Si (R ¹ ) (R ² ) — (NH) — and a structural unit —Si (R ³ ) (R ⁴ ) —O—, and R ¹ , R ² , R ³ and R ⁴ are any Is a group selected from the group consisting of an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkylamino group, an alkylsilyl group and an alkoxy group, or any one of R ¹ and R ² And any one or more of R ³ and R ⁴ is a method for producing a glass substrate for a magnetic disk, which is a group selected from the above group.
[Selection figure] None

Description

  The present invention relates to a method of manufacturing a glass substrate used for a magnetic disk and a magnetic disk.

A glass substrate is used as a substrate of a magnetic disk used in a magnetic disk storage device or the like.
This glass substrate has a disk shape with a circular hole in the center, and its main surface has extremely high flatness and smoothness. On the other hand, the inner peripheral end surface and the outer peripheral end surface, particularly the inner peripheral end surface, are also required to be smooth from the viewpoint of improving the mechanical strength of the glass substrate, but are sufficient for the curved surface unlike the flat main surface. There was a problem that it was difficult to polish so as to obtain smoothness.

  As a method for solving this problem, the inner peripheral end face is etched to remove deep scratches that govern the mechanical strength of the glass substrate, and then a liquid containing polysilazane is applied to the etched inner peripheral end face. And the method of baking and forming the silica layer on the surface is proposed (refer patent document 1).

Japanese Patent Laid-Open No. 11-328665

In Example 1 of the example of Patent Document 1, R is an alkyl group, which is mainly composed of a structural unit represented by the general formula of —Si (R) H—NH—, and in addition to —Si (H) H—NH—. It is described that the organic type polysilazane (trade name: L710) manufactured by Tonen which also has a structural unit represented by the general formula is used as polysilazane, and a film having a thickness of 2 to 3 μm is formed on the inner peripheral end face and the outer peripheral end face. .
However, it is considered that the film obtained in this manner has a problem that cracks are likely to occur when the thickness is 2 to 3 μm.
An object of the present invention is to provide a method of manufacturing a glass substrate for a magnetic disk and a magnetic disk that can solve such problems.

  The present invention includes a step of etching an inner peripheral end face of a disk-shaped glass plate having a circular hole in the center, applying a liquid containing an organic polysilazane compound to the etched inner peripheral end face, and firing it. A method of manufacturing a glass substrate for a disk, wherein the organic polysilazane compound has a structural unit A represented by the following general formula (A) and a structural unit B represented by the following general formula (B) Provided is a method for manufacturing a glass substrate.

In general formulas (A) and (B), R ¹ , R ² , R ³ and R ⁴ are all alkyl groups, alkenyl groups, cycloalkyl groups, aryl groups, aralkyl groups, alkylamino groups, alkylsilyl groups. A group selected from the group consisting of a group and an alkoxy group or hydrogen, and one or more of R ¹ and R ² and one or more of R ³ and R ⁴ are a group selected from the above group.

  A magnetic disk in which a plurality of layers including a magnetic layer to be a recording layer are laminated on a glass substrate, and the glass substrate is a glass substrate for a magnetic disk manufactured by the manufacturing method. provide.

  The present inventor found that the film formed on the inner peripheral end face using the polysilazane has a problem as described above that the thickness is 2 to 3 μm, that is, a problem that the film is likely to be cracked. For this reason, the possibility that the mechanical strength of the glass substrate is reduced is increased, and a polysilazane compound that can increase the thickness of the coating without easily causing cracks in the coating is searched for, and the present invention is applied. It came. That is, in Japanese Patent Application Laid-Open No. 2005-36089 in which an invention related to a polysilazane composition is described, a polysilazane composition capable of forming a high heat-resistant film having a thickness of, for example, 10 μm on a high strain point glass substrate manufactured by Asahi Glass Co., Ltd. is described. JP-A-2004-77874, which describes an invention relating to a photosensitive composition for an interlayer insulating film, describes a modified polysilsesquiazane that can increase the film thickness limit of the interlayer insulating film. As a result, they have reached the present invention.

  According to the present invention, it is possible to increase the thickness of a coating film obtained by applying a liquid containing a polysilazane compound to an inner peripheral end face and baking it, and as a result, a magnetic disk glass substrate and a magnetic disk machine. It is possible to increase the mechanical strength.

  In the method for producing a glass substrate for magnetic disk of the present invention (hereinafter referred to as the production method of the present invention), the glass substrate for magnetic disk is usually produced through the following steps. That is, a circular hole is formed in the center of the disk-shaped glass plate, and end face polishing, chamfering, main surface lapping, and outer peripheral end face mirror polishing are sequentially performed. After that, a disk-shaped glass plate is laminated and the inner peripheral end face is etched. An organic polysilazane compound-containing liquid is applied to the etched inner peripheral end face by a spray method or the like, and baked to form a coating on the inner peripheral end face. To do. Next, the main surface of the disk-shaped glass plate having the coating film formed on the inner peripheral end surface is polished to obtain a flat and smooth surface, thereby obtaining a magnetic disk glass substrate.

  The outer diameter, inner diameter (circular hole diameter), and thickness of the magnetic disk glass substrate (hereinafter referred to as the glass substrate of the present invention) produced by the production method of the present invention are not particularly limited, but those having an outer diameter of 95 mm If the diameter is 25 mm, the thickness is 1.0 mm or 0.8 mm, and the outer diameter is 84 mm, the inner diameter is 25 mm. If the thickness is 1.0 mm or 0.63 mm, the outer diameter is 65 mm, the inner diameter is 20 mm, and the thickness is 0. If the diameter is 635 mm and the outer diameter is 48 mm, the inner diameter is 12 mm and the thickness is 0.55 mm. If the outer diameter is 27.1 mm, the inner diameter is 7 mm and the thickness is 0.38 mm.

The glass of the glass substrate of the present invention is not particularly limited, but when it is desired to have high weather resistance, it is preferable that the glass meets the following criteria for water resistance, acid resistance, and alkali resistance.
Water resistance: When the glass is immersed in water at 80 ° C. for 24 hours, the weight loss (elution amount) of the glass accompanying elution of the components from the glass is 0.02 mg / cm ² or less.
Acid resistance: When the glass is immersed in an aqueous 0.1 N hydrochloric acid solution at 80 ° C. for 24 hours, the weight loss (elution amount) of the glass accompanying elution of the components from the glass is 0.06 mg / cm ² or less.
Alkali resistance: When the glass is immersed in an aqueous 0.1 N sodium hydroxide solution at 80 ° C. for 24 hours, the weight loss (elution amount) of the glass accompanying elution of the components from the glass is 1 mg / cm ² or less, more preferably 0.8. 18 mg / cm ² or less.

Moreover, in the manufacturing method of this invention, since a chemical strengthening process is not essential, there is no restriction | limiting that content of alkali metals, such as Na and Li, must be made into a certain value or more.
As glass of the glass substrate of the present invention, glass containing 1-20% by mass of alkali metal oxide such as soda lime silica glass, alumina silicate glass (including those containing 1-20% by mass of alkali metal oxide), Non-alkali glass and crystallized glass are exemplified.

As an alkali-free glass, the following oxide-based mass percentage display composition is SiO ₂ 56.0%, B ₂ O ₃ 6.0%, Al ₂ O ₃ 11.0%, Fe ₂ O ₃ 0.05%, _{Na 2 O 0.1%, MgO 2} %, CaO 3%, BaO 15.0%, the glass a is illustrated which is 6.5% SrO. The elution amounts (unit: mg / cm ² ) in the water resistance, acid resistance, and alkali resistance tests of this glass are 0.01, 0.03, and 0.67, respectively.

The surface of the circular hole of the disk-shaped glass plate having a circular hole in the center, that is, the inner peripheral end surface is polished with abrasive grains of about # 200 to # 1000 mesh, for example, diamond abrasive grains of # 500 mesh under, before etching. It is preferable to keep it.
The difference between the center of the disk-shaped glass plate whose inner peripheral end face is polished and the center of the circular hole is preferably 25 μm or less, and the roundness of the circular hole is preferably 25 μm or less.
Further, the polished inner peripheral end surface is usually chamfered, and then the chamfered surface is mirror-polished using an abrasive such as cerium oxide.

For the etching process of the inner peripheral end face, a wet etching method using an etching solution, which is a general glass etching method, a dry etching method using an etching gas, or the like can be used. Among them, a wet etching method using an etching solution such as a hydrofluoric acid solution, a hydrofluoric acid solution, a hydrofluoric acid solution, or hydrofluoric acid can be preferably used, but a method using a hydrofluoric acid solution or a hydrofluoric acid is particularly preferable. .
This etching process is generally performed by immersing a disk-shaped glass plate in an etching solution, but can also be performed by a spray method or other methods. This etching process is preferably such that high protrusions are not formed on the inner peripheral end face.

  The etching depth, which is the etching amount of the inner peripheral end face, that is, the removal thickness of the inner peripheral end face glass by the etching process, is preferably 8 to 40 μm. If it is less than 8 μm, the removal of deep scratches existing on the inner peripheral end face becomes insufficient, and the mechanical strength may be lowered. If it exceeds 40 μm, a high protrusion may be formed on the inner peripheral end face.

  The inner peripheral end face etching process of a disk-shaped glass plate made of the glass A and having an outer diameter of 65 mm, an inner diameter of 20 mm, and a thickness of 0.9 mm is, for example, in a sulfuric acid solution containing 5% by mass of hydrofluoric acid and sulfuric acid What is necessary is just to immerse for 10 minutes, and the etching depth at that time is about 20 micrometers.

The liquid containing the organic polysilazane compound (hereinafter referred to as the coating liquid) is applied to the etched inner peripheral end face by, for example, any one of the following methods (1) to (4). The coating liquid may protrude from the inner peripheral end surface and reach the main surface.
(1) A brush coating method using a brush.
(2) The coating liquid is supplied to the porous surface of the roller brush made of foamed plastic or the like, and the roller brush roll is rotated at 10 to 60 rpm while contacting the inner peripheral end surface of the disk-shaped glass plate to apply the coating liquid. Roller coating method to transfer and apply. In this case, it is preferable that the disk-shaped glass plate is also held by vacuum suction and rotated at 30 to 50 rpm.
(3) A direct coating method in which a disk-shaped glass plate is held by vacuum suction and is rotated at 10 to 200 rpm, and a coating liquid is supplied to the inner peripheral end surface by a dispenser and applied.
(4) A spray coating method in which a disk-shaped glass plate is laminated, and a coating liquid is sprayed from a spray nozzle onto the inner peripheral end face of the laminated body while rotating the laminated body at 5 to 50 rpm.

Next, the organic polysilazane compound (hereinafter, this organic polysilazane compound may be simply referred to as an organic polysilazane compound) contained in the coating liquid in the present invention will be described.
The organic polysilazane compound has structural units A and B. In the organic polysilazane compound, each structural unit generally exists in the form of _Am or _Bn , where m and n are positive integers. The same applies to the structural units described below.

N _Si—O / (N _Si—N where N _Si—O is the number of Si—O bonds and N _Si—N is the number of Si—N bonds in the copolymer formed by the reaction of the polymerizable component of the coating liquid. + N _{Si—O 2} ) is preferably 0.50 to 0.99, particularly preferably 0.80 to 0.95. If N _Si-O / (N _Si-N + N _Si-O ) is less than 0.50, the elastic modulus tends to increase and become brittle, and if it exceeds 0.99, the number of crosslinking points in the polymer decreases and the polymer The hardness may be insufficient.

The organic polysilazane compound may have a structural unit C represented by the following formula (C).
In the following general formula (C), R ⁵ , R ⁶ , R ⁸ and R ⁹ are all alkyl groups, alkenyl groups, cycloalkyl groups, aryl groups, aralkyl groups, alkylamino groups, alkylsilyl groups and alkoxy groups. A group selected from the group consisting of groups or hydrogen, wherein at least one of R ⁵ , R ⁶ , R ⁸ and R ⁹ is a group selected from the above group, and R ⁷ is a divalent aromatic group. .

  The organic polysilazane compound is selected from the group consisting of a structural unit D represented by the following general formula (D), a structural unit E represented by the following general formula (E), and a structural unit F represented by the following general formula (F). It may have one or more structural units.

In general formulas (D), (E), and (F), R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , and R ¹⁴ are all alkyl groups, alkenyl groups, cycloalkyl groups, aryl groups, and aralkyl groups. , A group selected from the group consisting of an alkylamino group, an alkylsilyl group and an alkoxy group.

  The organic polysilazane compound is selected from the group consisting of the structural unit G represented by the following general formula (G), the structural unit H represented by the following general formula (H), and the structural unit I represented by the following general formula (I). It may have one or more structural units.

In general formulas (G), (H) and (I), R ¹⁵ , R ¹⁷ , R ¹⁸ and R ²⁰ are all alkyl groups, alkenyl groups, cycloalkyl groups, aryl groups, aralkyl groups, alkylamino groups. A group selected from the group consisting of a group, an alkylsilyl group and an alkoxy group, and R ¹⁶ , R ¹⁹ and R ²¹ are all divalent aromatic groups.

  In the present invention, the alkyl group is a C1-C3 alkyl group, the alkenyl group is a C1-C2 alkenyl group, the cycloalkyl group is a C6-C8 cycloalkyl group, the aryl group is a C6-C8 aryl group, and the aralkyl group is a C1-C3 aralkyl group. The alkylamino group is preferably a C1-C3 alkylamino group, the alkylsilyl group is preferably a C1-C3 alkylsilyl group, and the alkoxy group is preferably a C1-C3 alkoxy group.

  In the present invention, the divalent aromatic group is preferably an aralkylene group or an arylene group, and particularly preferably a phenylene group, a tolylene group, a xylylene group, a benzylidene group, a phenethylidene group, an α-methylbenzylidene group, a cinnamylidene group, or a naphthylene. It is a group.

Other preferred embodiments of R ¹⁶ , R ¹⁹ and R ²¹ which are divalent aromatic groups include groups represented by the following general formula.

In the above general formula, (R22) a is a halogen atom or a lower alkyl group, preferably a C1-C3 alkyl group.
A is an integer of 0 to 4, and Z is a direct bond or a group represented by the following general formula.
R23 in the following general formula is a halogen atom or a lower alkyl group, preferably a C1-C3 alkyl group. b is an integer of 0 to 4, Y is a direct bond or a divalent group, and preferably Y is a direct bond, —O—, —S—, —CH ₂ —. Or —CH ₂ CH ₂ —.

R ¹⁶ , R ¹⁹ and R ²¹ are all preferably groups selected from the group consisting of a phenylene group, a tolylene group, a xylylene group, a benzylidene group, a phenethylidene group, an α-methylbenzylidene group, a cinnamylidene group and a naphthylene group. .

  The organic polysilazane compound can be synthesized by a known method according to JP-A No. 2005-36089, JP-A No. 2004-77874, or the like.

For example, after replacing a reaction vessel installed in a thermostat with dry nitrogen, 47 g (0.222 mol) of phenyltrichlorosilane (PhSiCl ₃ ) and 56 g (0.222) of diphenyldichlorosilane (Ph ₂ SiCl ₂ ) are added to 1000 ml of xylene. Mol), 3.8 g (0.033 mol) of methyldichlorosilane (MeSiHCl ₂ ), and 50 g (0.19 mol) of 1,4-bis (dimethylchlorosilyl) benzene are charged into the reaction vessel. To do.

  Next, the temperature in the reaction vessel is set to −5 ° C., and a solution prepared by dissolving 13.0 g (0.7222 mol) of water in 1000 ml of pyridine is poured into the reaction vessel at a rate of about 30 ml / min. At this time, the reaction between halosilane and water occurs with the injection, and the temperature in the container rises to -2 ° C. Stirring is continued for 1 hour after the injection of the water and pyridine mixed solution is completed. Thereafter, ammonia is injected at a rate of 2 mol / min for 10 minutes and stirred for the purpose of completely reacting unreacted chlorosilane. After completion of the reaction, dry nitrogen is blown to remove unreacted ammonia, followed by pressure filtration under a nitrogen atmosphere to obtain about 2300 ml of filtrate. The filtrate is subjected to solvent substitution under reduced pressure to obtain 100 g of an organic polysilazane compound a1, which is a colorless and transparent viscous resin.

The obtained organic polysilazane compound a1 has a number average molecular weight of 2200, structural units A in which R ¹ and R ² are phenyl groups, and structural units B, R ⁵ , R in which R ³ and R ⁴ are phenyl groups ⁶ , an organic polysilazane compound having a structural unit C in which R ⁸ and R ⁹ are CH ₃ , R ⁷ is a phenyl group, a structural unit D in which R ¹⁰ is CH ₃ , and a structural unit E in which R ¹¹ is a phenyl group .
Doing prayer IR spectra min the organic polysilazane compound a1, absorption based on N-H group at a wave number of 3350 cm ^-1, absorption based on Si-H to 2160 cm ^-1, absorption based on Si-Ph group in 1140 cm ^-1, 1060 absorption based on Si-O in -1100Cm ^-1, absorption based on Si-H and Si-N-Si in 1020-820cm ^-1, 3140cm ^-1, 2980cm ^-1 and 1270 cm ^-1 in based on C-H absorption, Absorption based on C—H of the benzene ring is confirmed at 810 cm ⁻¹ and 780 cm ⁻¹ , respectively.

Further, when the ¹ H-NMR spectrum of the organic polysilazane compound a1 was measured, δ 7.2 ppm (br, C ₆ H ₅ ), δ 4.8 ppm (br, SiH), δ 1.4 ppm (br, NH), δ 0.3 ppm ( br, SiCH ₃ ) absorption is confirmed.

The theoretical value of N _{Si—O 2} / (N _Si—N + N _{Si—O 2} ) of the organic polysilazane compound a1 is 0.928.

When it is desired to increase heat resistance or chemical resistance, the coating liquid is an inorganic polysilazane compound having a structural unit J represented by the following general formula (J) (hereinafter, this inorganic polysilazane compound is simply referred to as an inorganic polysilazane compound). It may be preferred to contain. In the inorganic polysilazane compound, the structural unit J is present in the form of J _{l where} l is a positive integer, and l is generally 10 to 10,000, typically 10 to 200.

  The terminal group of the inorganic polysilazane compound is not particularly limited, but is generally a silyl group, methyl group, amino group, methoxy group, alkoxy group or trimethylsilyl group. Moreover, in order to couple | bond with other components, such as an organic polysilazane compound, the terminal may have a carboxyl group, an amino group, a hydroxyl group, a carbonyl group.

The inorganic polysilazane compound is, for example, perhydropolysilazane.
A method for producing perhydropolysilazane is disclosed in, for example, JP-A-60-145903, D.C. Seyferth et al., Communication of Am. cer. sor. , C-13, January (1982).

For example, a gas blowing tube, a mechanical stirrer, and a dewar condenser are attached to a 4-liter flask having an internal volume of 1 liter, and after the inside of the reactor is replaced with deoxygenated dry nitrogen, 490 ml of dry pyridine is placed in the four-necked flask. This is ice-cooled.
Next, 51.9 g of dichlorosilane is added to form a white solid adduct (SiH ₂ Cl ₂ .2C ₂ H ₅ N). The reaction mixture is ice-cooled, and 51.0 g of purified ammonia is blown through a sodium hydroxide tube (absorption paddle) and activated carbon with stirring, and then heated to 100 ° C.
After completion of the reaction, the reaction mixture is centrifuged, washed with dry pyridine, and further filtered under a dry nitrogen atmosphere to obtain 850 ml of filtrate. The solvent is removed from 5 ml of the filtrate to obtain 0.102 g of resinous solid perhydropolysilazane.

The number average molecular weight of this perhydropolysilazane is 1100 when measured by GPC (polystyrene addition).
Further, when the prayer IR spectrum component, absorption based on N-H at a wavenumber of 3390 cm ^-1 and 1180 cm ^-1, absorption based on Si-H of 2170 cm ^-1, based on Si-N-Si of 1040～800Cm ^-1 Each absorption is confirmed.

The blending ratio in the case of adding the inorganic polysilazane compound can be arbitrarily selected according to the purpose, but the blending ratio of the inorganic polysilazane compound is 90 parts by mass or less with the total of the organic polysilazane compound and the inorganic polysilazane compound being 100 parts by mass. Is preferably 50 parts by mass or less.
By changing the blending ratio, the hardness and the film thickness limit of the protective film to be formed are particularly changed. Therefore, it is preferable to change appropriately depending on the glass substrate to be used.

The coating liquid usually contains a solvent and may contain a catalyst or the like as necessary.
Coated with a xylene solution of organic polysilazane compound a1 (solid content concentration 5 mass%), a solution in which this xylene solution and the xylene solution of perhydropolysilazane (solid content concentration 5 mass%) are mixed at a mass ratio of 1: 1. Illustrated as a liquid.

The coating liquid is applied to the inner peripheral end surface subjected to the etching process by, for example, a spray coating method.
Firing is usually performed using an oven. Typically, drying is performed by holding at 210 to 220 ° C. for 20 to 30 minutes, and then holding at 375 ° C. to cure the coating solution.
The thickness of the film obtained by applying the coating liquid to glass, baking and curing it is typically more than 3 μm and 20 μm or less, for example, 4 to 10 μm.

  A disk-shaped glass plate having a coating formed on the inner peripheral end surface thereof is used as a magnetic disk glass substrate by polishing its main surface with, for example, cerium oxide having an average particle diameter of 2.5 μm. Note that the film protruding from the inner peripheral end face during the polishing is removed.

It can be used to manufacture a glass substrate for a magnetic disk. It can also be used as a magnetic disk.

Claims (6)

A glass substrate for a magnetic disk having a process of etching an inner peripheral end face of a disk-shaped glass plate having a circular hole in the center, applying a liquid containing an organic polysilazane compound to the inner peripheral end face subjected to the etching process, and baking the liquid. The organic polysilazane compound has a structural unit A represented by the following general formula (A) and a structural unit B represented by the following general formula (B). Production method.
In general formulas (A) and (B), R ¹ , R ² , R ³ and R ⁴ are all alkyl groups, alkenyl groups, cycloalkyl groups, aryl groups, aralkyl groups, alkylamino groups, alkylsilyl groups. A group selected from the group consisting of a group and an alkoxy group or hydrogen, and one or more of R ¹ and R ² and one or more of R ³ and R ⁴ are a group selected from the above group.

The method for producing a glass substrate for a magnetic disk according to claim 1, wherein the organic polysilazane compound has a structural unit C represented by the following general formula (C).
In general formula (C), R ⁵ , R ⁶ , R ⁸ and R ⁹ are all alkyl groups, alkenyl groups, cycloalkyl groups, aryl groups, aralkyl groups, alkylamino groups, alkylsilyl groups and alkoxy groups. A group selected from the group consisting of or hydrogen, any one or more of R ⁵ , R ⁶ , R ⁸ and R ⁹ is a group selected from the above group, and R ⁷ is a divalent aromatic group.

The organic polysilazane compound comprises a structural unit D represented by the following general formula (D), a structural unit E represented by the following general formula (E), and a structural unit F represented by the following general formula (F). The method for producing a glass substrate for a magnetic disk according to claim 1, wherein the method comprises one or more structural units selected.
In general formulas (D), (E), and (F), R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , and R ¹⁴ are all alkyl groups, alkenyl groups, cycloalkyl groups, aryl groups, and aralkyl groups. , A group selected from the group consisting of an alkylamino group, an alkylsilyl group and an alkoxy group.

The organic polysilazane compound is selected from the group consisting of a structural unit G represented by the following general formula (G), a structural unit H represented by the following general formula (H), and a structural unit I represented by the following general formula (I). 4. The method for producing a glass substrate for a magnetic disk according to claim 1, wherein the glass substrate has one or more selected structural units.
In general formulas (G), (H) and (I), R ¹⁵ , R ¹⁷ , R ¹⁸ and R ²⁰ are all alkyl groups, alkenyl groups, cycloalkyl groups, aryl groups, aralkyl groups, alkylamino groups. A group selected from the group consisting of a group, an alkylsilyl group and an alkoxy group, and R ¹⁶ , R ¹⁹ and R ²¹ are all divalent aromatic groups.

The manufacturing method of the glass substrate for magnetic discs in any one of Claims 1-4 in which the liquid containing the said organic polysilazane compound contains the inorganic polysilazane compound which has the structural unit J represented by the following general formula (J). .

A magnetic disk glass comprising a plurality of layers including a magnetic layer to be a recording layer laminated on a glass substrate, wherein the glass substrate is produced by the production method according to claim 1. A magnetic disk that is a substrate.