JP2017041294A - Manufacturing method of glass substrate for magnetic disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a glass substrate for a magnetic disk capable of reducing surface roughness and obtaining more accurate polished surface in precision polishing of a glass substrate for a magnetic disk.SOLUTION: A manufacturing method of a glass substrate for a magnetic disk has a polishing step which includes a colloidal silica slurry 100 pts.mass comprising colloidal silica 1 to 30 mass% and water 70 to 99 mass% after polishing a main surface of a glass substrate and polymer containing a cationic amino group 0.0001 to 0.1 pt.mass where weight average molecular weight ranges from 300 to 3000 and the number of amino groups contained in one molecule ranges from 7 to 70 on average and performs polishing with polishing liquid whose pH is 2 to 7.SELECTED DRAWING: None

Description

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

  High precision smoothness is required for glass substrates (glass substrates for magnetic disks) used in the manufacture of magnetic disks mounted on information processing equipment such as hard disk drives. A glass substrate for a magnetic disk is manufactured by polishing a main surface of a glass substrate to obtain a flat and smooth surface, and then performing precision polishing for polishing the main surface more precisely. In this precision polishing, a polishing liquid (colloidal silica slurry) containing colloidal silica is used. In recent years, there has been an increasing demand for higher recording density on magnetic disks. To meet these demands, various additions to polishing liquids containing colloidal silica have been used as a method for polishing the main surface of glass substrates with high accuracy. There has been proposed a method of carrying out precision polishing by containing an agent.

  For example, in Patent Document 1, a main surface of a glass substrate is formed using a polishing liquid in which a water-soluble organic polymer compound having an amino group such as oxypropylenediamine is added as an additive to a polishing liquid containing colloidal silica. A polishing method has been proposed. In Patent Document 2, a polishing liquid containing colloidal silica and a polishing liquid having a pH of 8 or more obtained by adding an acid to sodium nitrate or a water-soluble polyether polyamine or a water-soluble polyalkylene as a zeta potential adjusting component are used. There has been proposed a method of polishing the main surface.

JP 2008-47271 A International Publication No. 2010/038706

  However, in the polishing method using the polishing liquid described in Patent Documents 1 and 2, there is a problem that the surface roughness of the main surface (hereinafter also referred to as “polishing surface”) after precision polishing of the glass substrate cannot be sufficiently reduced. was there.

  The present invention has been made to solve the above-described problems, and in polishing a glass substrate for a magnetic disk, the surface roughness of the main surface of the glass substrate is reduced to obtain a more precise polished surface. An object of the present invention is to provide a method for manufacturing a glass substrate for a magnetic disk.

  The method for producing a glass substrate for a magnetic disk according to the present invention includes a polishing step for polishing the main surface of the glass substrate and then polishing the polished main surface with a polishing liquid containing colloidal silica. In a manufacturing method, the said polishing liquid is 100 mass parts of colloidal silica slurries which consist of 1-30 mass% of colloidal silica, and 70-99 mass% of water, and a weight average molecular weight is 300-3000, and is contained in 1 molecule. And 0.0001 to 0.1 part by mass of a cationic amino group-containing polymer having an average number of amino groups of 7 to 70 and a pH of 2 to 7.

  In the method for producing a glass substrate for a magnetic disk of the present invention, the cationic amino group-containing polymer is preferably at least one selected from a polyalkylene polyamine compound group and a polyalkylene polyimine compound group.

  In the method for producing a glass substrate for a magnetic disk of the present invention, the polyalkylene polyamine compound group and the polyalkylene polyimine compound group may be one or more selected from a compound represented by the following formula (1) and a salt thereof. preferable.

（式中、−［（Ｏ）_ｍ−Ｙ］−のｍ及びＹは、１分子中の繰り返し単位毎に異なっていてもよく、
ｎは５以上の整数であり、
ｍは０又は１であり、
Ｒ^１及びＲ^２は、それぞれ同一であっても異なっていてもよく、アミノ基を有していてもよい炭素数１〜８の直鎖状若しくは分岐を有するアルキル基、水素原子又はアミノ基であり（但し、Ｒ^１に直結する−［（Ｏ）_ｍ−Ｙ］−のｍが１のときは、Ｒ^１は水素原子ではなく、かつアミノ基ではない。）、
Ｙは、第１級アミノ基、第２級アミノ基及び第３級アミノ基からなる群から選ばれる基を１個以上有する直鎖状又は分岐した炭素鎖１〜８のアルキレン基である。）

(In the formula, m and Y in-[(O) _m -Y]-may be different for each repeating unit in one molecule;
n is an integer greater than or equal to 5,
m is 0 or 1,
R ¹ and R ² may be the same or different from each other, and may be a linear or branched alkyl group, a hydrogen atom or an amino group having 1 to 8 carbon atoms which may have an amino group. Yes, (however, directly linked to _{^{R 1 - - [(O)}} m -Y] when m is 1, ^{R 1} is not hydrogen atom, and not the amino group.)
Y is a linear or branched alkylene group having 1 to 8 carbon chains having at least one group selected from the group consisting of a primary amino group, a secondary amino group and a tertiary amino group. )

In the method for producing a glass substrate for a magnetic disk of the present invention, the polyalkylene polyamine compound group and the polyalkylene polyimine compound group are represented by the formula (1), wherein n is an integer of 7 or more, and R ¹ and R ² are Each may be the same or different and is a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms (provided that-[(O) _m -Y] directly connected to R ¹ ). -When m of 1 is 1, R ¹ is not a hydrogen atom)
Y is preferably at least one selected from a compound represented by the following formula (2) and a salt thereof.

（上記式（２）中、
Ｒ^３、Ｒ^４は及びＲ^５は、それぞれ、単結合又は炭素数１〜８の直鎖状若しくは分岐を有するアルキレン基であり（但し、Ｒ^３及びＲ^４がいずれも単結合である場合を除く。）、それぞれ同一であっても異なっていてもよく、
Ｒ^６は、水素原子又は炭素数１〜８の直鎖状若しくは分岐を有するアルキル基であり、Ｒ^５とＲ^６との炭素原子数の合計は０〜８である。）

(In the above formula (2),
R ³ , R ⁴ and R ⁵ are each a single bond or a linear or branched alkylene group having 1 to 8 carbon atoms (provided that R ³ and R ⁴ are both single bonds) Excluding), each may be the same or different,
R ⁶ is a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms, and the total number of carbon atoms of R ⁵ and R ⁶ is 0 to 8. )

In the method for producing a glass substrate for a magnetic disk of the present invention, the polyalkylene polyimine compound group is preferably at least one selected from a compound represented by the following formula (3) and a salt thereof.
_{^{H 2 N-R 7 - [}} (O) m2 -NR 8 -R 9] n2 -NH 2 (3)
(In the formula (3), R ⁷ and R ⁹ may be the same or different, and each is a single bond or a linear or branched alkylene group having 1 to 8 carbon atoms. When m2 directly connected to R ⁷ is 1, R ⁷ is not a single bond),
R ⁸ is a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms,
n2 is an integer of 5 or more,
m2 is 0 or 1,
In one molecule, m @ 2, ^{R 8} and ^{R 9} may be different for each repeating unit. )

The method for producing a glass substrate for a magnetic disk according to the present invention is a urethane foam having a Shore A hardness of 5 to 80, a compressibility of 1 to 60% and a density of 0.05 to 0.9 g / cm ³ in the polishing step. It is preferable to perform polishing with a polishing pressure of 0.5 to 30 kPa using a polishing pad made of resin.

  The method for producing a glass substrate for a magnetic disk of the present invention preferably includes a cleaning step of cleaning the polished surface of the glass substrate with a cleaning liquid containing an oxygen-based oxidant after the polishing step. In this case, the pH of the cleaning liquid is preferably 6-12.

  In the method for producing a glass substrate for a magnetic disk of the present invention, after polishing the main surface of the glass substrate and before the precision polishing step, polishing containing colloidal silica and water and not containing a cationic amino group-containing polymer It is preferable to have a preliminary polishing step of polishing the main surface of the glass substrate with a liquid.

  According to the method for producing a glass substrate for a magnetic disk of the present invention, in polishing, the surface roughness of the main surface of the glass substrate can be reduced to obtain a more precise polished surface.

  Hereinafter, embodiments of the present invention will be described in detail.

  A glass substrate for a magnetic disk (hereinafter also simply referred to as “glass substrate”) is usually produced through the following steps. That is, a circular hole is formed in the center of a circular glass plate, and chamfering, main surface lapping, and outer and inner end faces are sequentially polished. Next, the main surface of the circular glass plate is polished to a flat and smooth surface, and after polishing the main surface, a precision polishing step using a colloidal silica slurry is performed to manufacture a glass substrate for a magnetic disk. In addition, the process before the precision polishing process described above is replaced with the order of some processes, some processes are replaced with other processes, and other processes such as strengthening, etching and surface treatment are added. You can also.

  The method for producing a glass substrate for a magnetic disk according to the present invention uses a polishing liquid having a predetermined pH and containing colloidal silica as abrasive grains and a cationic amino group-containing polymer in a predetermined amount in the precision polishing step. Then, the main surface of the glass substrate polished to a flat and smooth surface is polished. Hereinafter, embodiments of the polishing liquid used in the present invention and the method for producing a glass substrate for a magnetic disk of the present invention will be described.

About the glass used for the glass substrate for magnetic discs of this invention, the glass for normal glass substrates for magnetic discs can be used. A typical glass is aluminosilicate glass. Specifically, the following glass is illustrated.
In mol% notation, the SiO ₂ 55 to 75%, the _{Al 2 O 3 5~25%, B} 2 O 3 0 to 15%, the MgO 0-15%, 0-15% of CaO, the SrO 0 10%, 0-10% of BaO, 0 to 10% of Na ₂ O, 0-10% of _{K 2} O, 0 to 15% of Li ₂ O, the TiO ₂ 0 to 5%, a ZrO ₂ 0 5% or more, containing at least one of RO (total amount of MgO + CaO + SrO + BaO) and R ₂ O (total amount of Na ₂ O + K ₂ O + Li ₂ O), and the total content of the 12 components is 97% This is the aluminosilicate glass.

(Polishing liquid)
First, the polishing liquid used in this embodiment will be described. The colloidal silica slurry used in the present embodiment is based on water and colloidal silica, and 100 parts by mass of the colloidal silica slurry is composed of 70 to 99% by mass of water and 1 to 30% by mass of colloidal silica. The polishing liquid used in this embodiment comprises the colloidal silica slurry and a cationic amino group-containing polymer having a weight average molecular weight of 300 to 3000 and an average number of amino groups in one molecule of 7 to 70. Including. In the polishing liquid used in the present embodiment, the content of the cationic amino group-containing polymer is 0.0001 to 0.1 parts by mass with respect to 100 parts by mass of the colloidal silica slurry, and the pH of the polishing liquid is 2. ~ 7.

  In this specification, the weight average molecular weight is a value measured by gel permeation chromatography using tetrahydrofuran (THF) as a developing solvent and polystyrene as an internal standard. Further, the average number of amino groups contained in one molecule in the cationic amino group-containing polymer is a value obtained by dividing the weight average molecular weight by the molecular weight of the basic structure.

  In the polishing liquid used in the present embodiment, the cationic amino group-containing polymer has a weight average molecular weight of 300 to 3000, and the average number of amino groups contained in one molecule is 7 to 70. The cationic amino group-containing polymer is a component that reduces the surface roughness (Ra) of the main surface (polished surface) after polishing in the precision polishing step. The cationic amino group-containing polymer has an amino group that easily adheres to the silicate glass, and adheres to the main surface of the glass substrate via this amino group, thereby relaxing the contact between the colloidal silica and the glass substrate. To do. As a result, when the main plane of the glass substrate is polished using a polishing liquid containing a cationic amino group-containing polymer and colloidal silica, the convex portions existing on the main plane are easily selectively scraped, and the surface of the polished surface It is considered that the roughness (Ra) becomes small. In the present specification, unless otherwise specified, the surface roughness is expressed by arithmetic surface roughness (Ra).

  The cationic amino group-containing polymer is a water-soluble organic compound having a structure in which two or more polymerizable monomers having an amino group are polymerized. The “water-soluble” referred to in the present specification may be any degree as long as it is completely dissolved in the polishing liquid at the concentration used as the polishing liquid. Usually, it is a substance that dissolves in pure water at 1% by mass or more, preferably 5% by mass or more, more preferably 30% by mass or more. As the cationic amino group-containing polymer, one type may be used alone, or two or more types may be used in combination.

  The weight average molecular weight of the cationic amino group-containing polymer is 300 to 3000. When the weight average molecular weight is in the range of 300 to 3000, the surface roughness (Ra) of the polished surface can be sufficiently reduced when the main surface of the glass substrate is polished as described below.

  When the weight average molecular weight is less than 300, the cationic amino group-containing polymer adheres to the glass substrate, but the effect of relaxing the contact between the colloidal silica and the glass substrate is considered to be low. As a result, there is a tendency that the surface roughness (Ra) of the polished surface of the glass substrate cannot be sufficiently reduced.

  On the other hand, when the weight average molecular weight exceeds 3000, the contact between the colloidal silica and the glass substrate is excessively relaxed, contrary to the case where the weight average molecular weight is small, the surface roughness (Ra) of the polished surface. There is a tendency that it cannot be reduced sufficiently. Moreover, when a weight average molecular weight exceeds 3000, it becomes easy to promote aggregation of colloidal silica by a molecular chain becoming long. As a result, there is a tendency that the polishing rate is remarkably lowered or the surface roughness (Ra) of the polished surface of the glass substrate cannot be sufficiently reduced.

  When the weight average molecular weight of the cationic amino group-containing polymer is in the range of 300 to 3000, the degree of improvement with respect to the surface roughness (Ra) of the polished surface of the glass substrate is high, and there is no concern about a significant decrease in the polishing rate. The weight average molecular weight of the cationic amino group-containing polymer is preferably 300 to 1800, and more preferably 600 to 1200, from the viewpoint that the effect of improving the surface roughness (Ra) of the polished surface is high.

The average number of amino groups contained in one molecule of the cationic amino group-containing polymer is 7 to 70. The amino group may be any of a primary amino group (—NH ₂ ), a secondary amino group (—NH—), and a tertiary amino group (—N <). Groups are preferred. The number of amino groups contained in one molecule is preferably 7 to 42 and more preferably 14 to 28 in terms of a high effect of improving the surface roughness (Ra) of the polished surface.

  The cationic amino group-containing polymer is preferably one or more compounds selected from a polyalkylene polyamine compound group or a polyalkylene polyimine compound group described below. As the cationic amino group-containing polymer, one compound of the polyalkylene polyamine compound group or the polyalkylene polyimine compound group may be used, or two or more compounds may be used in combination.

  Specific examples of the polyalkylene polyamine compound group or the polyalkylene polyimine compound group include compounds represented by the following formula (1) and salts thereof.

In the above formula (1), R ¹ and R ² may be the same as or different from each other, and may have an amino group and may have a linear or branched alkyl group having 1 to 8 carbon atoms. , A hydrogen atom or an amino group. However, directly connected to _{^{R 1 - [(O) m}} -Y] - When m is 1 the, ^{R 1} is not hydrogen atom, and not the amino group.

In the above formula (1), when both R ¹ and R ² are an amino group or an alkyl group having an amino group, n is 5 to 68. That is, when two amino groups contained in R ¹ and R ² are combined, the amino group in one molecule of the compound represented by the formula (1) becomes 7 to 70. For this reason, when only ^one of R ¹ or R ² is an amino group or an alkyl group having an amino group, n is 6 to 69. When R ¹ and R ² are not both an amino group or an alkyl group having an amino group, n is 7 to 70.

In the above formula (1), R ¹ and R ² are each independently a hydrogen atom, a linear alkyl group having 1 to 8 carbon atoms represented by CH ₃ — to C ₈ H ₁₇ —, an amino group (NH _2- ) or H ₂ N—CH ₂ — to H ₂ N—C ₈ H ₁₆ — is preferably an aminoalkyl group having 1 to 8 carbon atoms.

Y is linear or branched having at least one group selected from the group consisting of a primary amino group (—NH ₂ ), a secondary amino group (—NH—), and a tertiary amino group (—N <). And an alkylene group having 1 to 8 carbon chains. n is an integer of 5 or more, and m is 0 or 1.

-[(O) _m -Y]-may be different for each repeating unit in one molecule. Specifically, in all of the above repeating units contained in one compound, m and Y may be the same or different m and Y may be contained.

  Examples of the salt of the compound of the formula (1) include compounds in which the amino group of the compound of the formula (1) is a salt such as sulfate or hydrochloride.

As the polyalkylene polyamine compounds, in the above formula (1), n is 7 or more, R ¹ and R ² is a linear or branched alkyl group having a hydrogen atom or a C1-8 there, directly linked to _{^{R 1 - [(O) m}} -Y] - when m is 1 the, ^{R 1} is not hydrogen atom, Y is compounds and a group represented by the following formula (2) It is preferably at least one selected from salts.

When Y is represented by the above formula (2), in the above formula (1), R ¹ and R ² are preferably the same, and both are preferably a hydrogen atom or a linear alkyl group. . When R ¹ and R ² are alkyl groups, the number of carbon atoms is preferably 1 to 6, and more preferably 1 or 2.

In the above formula (2), R ³ and R ⁴ are a single bond or a linear or branched alkylene group having 1 to 8 carbon atoms. However, the case where R ³ and R ⁴ are simultaneously a single bond is excluded. R ³ and R ⁴ are preferably a single bond or a linear alkylene group. In the case of an alkylene group, the number of carbon atoms is preferably 1 to 6, and preferably 1 or 2. More preferred.

In the above formula (2), R ⁵ is an alkylene group having a single bond or a linear or branched having from 1 to 8 carbon atoms. R ⁵ is preferably a linear alkylene group, and preferably has 1 to 6 carbon atoms, more preferably 1 or 2. R ³ , R ⁴ and R ⁵ may be the same or different.

In the above formula (2), R ⁶ is an alkyl group having a linear or branched hydrogen atom or a 1 to 8 carbon atoms, the total number of carbon atoms of R ⁵ and R ⁶ is a 0-8 . R ⁶ is preferably a hydrogen atom.

When Y is represented by the above formula (2), m in the formula (1) and R ³ , R ⁴ , R ⁵ and R ⁶ in the formula (2) may be different for each repeating unit in one molecule. . n is 7 to 70, preferably 14 to 53.

A typical preferred compound as a group of polyalkylene polyamine compounds is that in the above formula (1), R ¹ and R ² are both hydrogen atoms, m = 0, Y is the above formula (2), R ³ is a single bond, R ⁴ and ^{R 5} are methylene group, polyallylamine ^{R 6} is a hydrogen atom _{(allylamine: H 2 C = C (H} ) CH 2 NH 2 in the polymer) and the like.

  Moreover, as a polyalkylene polyimine compound group, it is preferable that it is 1 or more types chosen from the compound represented by following formula (3), and its salt.

_{^{H 2 N-R 7 - [}} (O) m2 -NR 8 -R 9] n2 -NH 2 (3)

In the above formula (3), R ⁷ and R ⁹ are a single bond or a linear or branched alkylene group having 1 to 8 carbon atoms. However, when m2 directly connected to R ⁷ is 1, R ⁷ is not a single bond. R ⁷ and R ⁹ may be the same or different.

R ⁸ is a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms, n2 is an integer of 5 or more, and m2 is 0 or 1. Further, in one molecule of the compound represented by the above formula (3), m2, R ⁸ and R ⁹ may be different for each repeating unit.

As a polyalkylene polyimine compound group represented by the above formula (3), R ⁷ is preferably a single bond, R ⁸ is a hydrogen atom, R ⁹ is an ethylene group, and n is preferably 7 to 42.

As a typical preferable compound as the polyalkylene polyimine compound group of the formula (3), polyethylene represented by the formula (3), wherein R ⁷ and R ⁹ are ethylene groups, R ⁸ is a hydrogen atom, and m2 = 0. And imine (polymer of ethyleneimine: (C ₂ H ₅ N)).

  In addition, as a salt of the compound of Formula (3), the compound whose amino group of the compound of Formula (3) is salts, such as a sulfate and hydrochloride, for example is mentioned.

  The pH of the polishing liquid used in this embodiment is 2-7. This is due to the following reason. The lower the pH of the polishing liquid, the higher the polishing rate because the glass component is more eluted from the glass substrate during polishing. On the other hand, if the pH is too low, the surface roughness (Ra) of the polished surface of the glass substrate tends to deteriorate. Further, since the colloidal silica tends to aggregate when the pH is in the range of more than 7 and 8 or less, the stability of the polishing liquid becomes low, and when the pH exceeds 8, the stability is improved again. Thus, the stability of colloidal silica changes with changes in pH.

  In relation to the surface roughness (Ra) of the polished surface, the surface roughness (Ra) can be improved if the pH is in the range of 2-10. The polishing pad is also polished in the same manner as glass, and pad scraps are generated. In the alkaline region where the pH of the polishing liquid is 8 or more, the hydroxyl group on the pad scrap surface and the hydroxyl group on the glass surface tend to adhere firmly due to the dehydration condensation reaction, which is not preferable because it is difficult to remove by washing. When a polishing pad made of urethane resin is used, the polishing pad may be damaged, and the damaged polishing pad piece may adhere to the glass surface and become a residue.

  When the pH of the polishing liquid used in the present embodiment is 2 or more, colloidal silica has high stability, and an effect of improving the surface roughness (Ra) of the polishing surface can be obtained. In addition, when the pH is 7 or less, a sufficiently high polishing rate can be obtained, and there is no risk of residue remaining on the polishing surface due to damage to the polishing pad.

  A pH adjusting agent may be added to the polishing liquid used in this embodiment in order to adjust the pH to the above-described preferable range. The pH adjuster may be either acid or base. Acids include nitric acid, sulfuric acid, sulfurous acid, persulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid, phosphonic acid, phosphinic acid, methoxyacetic acid, maleic acid, ascorbic acid, succinic acid, citric acid, oxalic acid, acetic acid, glycolic acid , Cyanacetic acid, malonic acid, methylmalonic acid, malic acid, fumaric acid, benzoic acid, ascorbic acid, phthalic acid, aspartic acid, lactic acid, tartaric acid, gluconic acid, glutaric acid, adipic acid, glutamic acid, iminodiacetic acid, pimelic acid Etc. Moreover, you may further add the above-mentioned inorganic acid or organic acid salt as a pH adjuster. Examples of the base include ammonia compounds, hydroxides, carbonates, bicarbonates, etc., specifically ammonia, lithium hydroxide, sodium hydroxide, potassium hydroxide, potassium hydroxide, calcium hydroxide, strontium hydroxide, Barium hydroxide, ammonium carbonate, lithium carbonate, sodium carbonate, potassium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, calcium hydrogen carbonate and the like can be used. As a pH adjuster, 1 type may be used independently and 2 or more types may be used together.

  In addition, when using the acid or base of an organic compound as a pH adjuster, the one where these molecular weights are smaller is preferable. When an organic compound having a large molecular weight, such as a polymer or a polymer compound, is used, the cationic amino group-containing polymer contained in the polishing liquid and the polymer organic compound form an ionic association, and the surface roughness of the polished surface is increased. There is a possibility that the improvement effect of (Ra) may be reduced. Therefore, it is preferable to use a low molecular weight compound or an inorganic compound as the pH adjuster, and among them, it is preferable to use citric acid, acetic acid as the acid, and ammonia, sodium hydroxide, or potassium hydroxide as the base.

In the polishing liquid used in the present embodiment, colloidal silica is silicon oxide (SiO ₂ ) fine particles and is used as polishing abrasive grains. The kind of colloidal silica is not particularly limited, and those produced by various known methods can be used. As a kind of colloidal silica, colloidal silica produced by ion-exchange of sodium silicate and then particle growth (water glass method) is generally used. In addition, although colloidal silica is normally supplied as a colloidal silica slurry in which colloidal silica is dispersed in water in advance, the pH is preferably 8 to 11, and more preferably 9 to 10.

  The average particle size of the colloidal silica is preferably 5 nm or more and 100 nm or less. If the thickness is less than 5 nm, the colloidal silica may aggregate. If the thickness exceeds 100 nm, the production cost of the colloidal silica increases, which is economically disadvantageous. In addition, the average particle diameter of colloidal silica is shown by the average primary particle diameter obtained by measuring with a transmission electron microscope, for example.

  The amount of colloidal silica in the colloidal silica slurry of the polishing liquid is 1 to 30% by mass, preferably 5 to 30% by mass, and more preferably 5 to 15% by mass. The amount of water is 70 to 99% by mass, preferably 70 to 95%. If the colloidal silica content is less than 1% by mass relative to the total mass of the colloidal silica slurry, a sufficient polishing rate may not be obtained, and if it is 5% by mass or more, a high polishing rate is obtained. When the colloidal silica content exceeds 30% by mass with respect to the total mass of the colloidal silica slurry, no improvement in the polishing rate commensurate with the increase in the abrasive concentration is observed, and the viscosity of the polishing liquid is too high. There is.

  In the polishing liquid used in the present embodiment, water disperses the colloidal silica that is the abrasive grains, dissolves the cationic amino group-containing polymer and the pH adjuster, and is optionally added as necessary. It is a medium for dispersing and dissolving components. Although there is no restriction | limiting in particular about water, Pure water or deionized water is preferable from the influence with respect to another compounding component, the mixing of an impurity, pH, etc. Since water has a function of controlling the fluidity of the polishing liquid, the content thereof can be appropriately set according to the target polishing characteristics such as the polishing rate and the flattening characteristics.

  When the water content is less than 70% by mass with respect to the colloidal silica slurry, the viscosity of the polishing liquid may be increased and the fluidity may be impaired. When the water content exceeds 99% by mass, the concentration of colloidal silica that is an abrasive grain. And the polishing rate may be greatly reduced. As for the water content of the colloidal silica slurry used in the present embodiment, the colloidal silica slurry containing a smaller amount of water than the above water content range is added to an aqueous solution of a cationic amino group-containing polymer or other When an aqueous solution of an additive or the like is added, it may be 70 to 99% by mass with respect to the total of water and colloidal silica contained in the finally prepared polishing liquid.

  In the polishing liquid used in the present embodiment, in addition to colloidal silica that is an essential component, water, a cationic amino group-containing polymer, and a pH adjuster that is an optional component, within the range that does not impair the effects of the present invention. You may contain the other arbitrary components which the abrasive | polishing agent for grinding | polishing contains.

(Method for producing glass substrate for magnetic disk)
Next, the manufacturing method of the glass substrate for magnetic disks of this embodiment is demonstrated. As described above, the magnetic disk glass substrate is manufactured through the following steps. That is, a circular hole is formed in the center of a circular glass plate, and chamfering, main surface lapping, outer peripheral and inner peripheral end face polishing are sequentially performed. The main surface lapping step may be divided into a rough lapping step and a fine lapping step, and a shape processing step (drilling at the center of the circular glass plate, chamfering, end face polishing) may be provided between them. In addition, when manufacturing the glass substrate for magnetic discs which does not have a circular hole in the center, it cannot be overemphasized that the drilling of the center of a circular glass plate is unnecessary.

  In the lapping process, both main surfaces of the glass substrate are ground. Specifically, a double-side grinding apparatus that simultaneously grinds both main surfaces of the glass substrate is used. This double-side grinding apparatus simultaneously grinds both main surfaces of a glass substrate using loose abrasive grains such as aluminum oxide, silicon carbide, zirconium oxide, boron carbide, diamond, or fixed abrasive grains. A part of the lapping process may be performed before the base plate processing process or before the chamfering process.

  In the end surface polishing step, the two inclined surfaces and the vertical surface of the end surface are respectively polished to remove the work-affected layer on the two inclined surfaces and the vertical surface. The end surface polishing method is, for example, brush polishing, sponge polishing, viscous fluid polishing, magnetic fluid polishing, or the like.

  Next, the main surface of the circular glass plate is polished to a flat and smooth surface (main surface polishing step). In the main surface polishing step, for example, polishing is performed using a slurry containing cerium oxide having an average particle diameter of 0.5 to 2.0 μm and a urethane polishing pad. Next, polishing is performed using a slurry containing a cerium oxide having an average particle diameter smaller than that described above, for example, a slurry containing cerium oxide having an average particle diameter of 0.15 to 0.5 μm and a urethane pad. Further, a chemical strengthening step may be provided after the main surface polishing step.

  Then, after the main surface polishing step, a precision polishing step using the above polishing liquid is performed to manufacture a magnetic disk glass substrate. In the precision polishing step, the main surface polished as described above is further polished under conditions of a polishing pressure of 0.5 kPa to 30 kPa, preferably 4 kPa to 20 kPa. When the polishing pressure is 4 kPa or more, the stability of the glass substrate during polishing is reduced, and it is possible to suppress the fluttering easily. Therefore, it is possible to suppress the waviness of the main surface from increasing. The polishing time can be appropriately set depending on the hardness of the polishing pad, the polishing pressure, and the like, and is, for example, about 5 to 30 minutes.

As a polishing pad used in the precision polishing step, a foamed urethane resin having a Shore D hardness of 45 to 75, a compressibility of 0.1 to 10%, and a density of 0.5 to 1.5 g / cm ³ , Shore A A typical material is a foamed urethane resin having a hardness of 5 to 80, a compressibility of 1 to 60%, and a density of 0.05 to 0.9 g / cm ³ . Note that the Shore A hardness of the polishing pad is preferably 20 or more. If it is less than 20, the polishing rate may decrease.

  The Shore A hardness and the Shore D hardness are measured by the methods of measuring the durometer A hardness and D hardness of plastic specified in JIS K7215, respectively. The compression rate (unit:%) is measured as follows. That is, for a measurement sample cut out to an appropriate size from the polishing pad, a material thickness t0 when a stress of 10 kPa is applied for 30 seconds from a no-load state using a shopper type thickness measuring device is obtained, Next, the material thickness t1 when a stress load of 110 kPa is immediately pressed for 5 minutes from the state where the thickness is t0 is calculated, and (t0−t1) × 100 / t0 is calculated from the values of t0 and t1, The compression rate.

  In this way, for example, the surface roughness (Ra) of the polished surface is polished to 0.2 nm or less by the precision polishing step.

  In order to increase the polishing amount (depth) after the main surface polishing step and before the precision polishing step with the polishing liquid containing the cationic amino group-containing polymer, the same colloidal as the precision polishing step is used as abrasive grains. You may perform the preliminary polishing process grind | polished using the polishing liquid which contains a silica and does not contain a cationic amino group containing polymer, and a urethane polishing pad. This pre-polishing step is also included in the general precision polishing from the viewpoint of polishing accuracy, but in this specification, after the main surface polishing step, a step of polishing with a polishing liquid containing a cationic amino group-containing polymer. Is called a “precise polishing step”, and a step of polishing with a polishing liquid not containing a cationic amino group-containing polymer before the precise polishing step is called a “preliminary polishing step”, which is shown separately for convenience. In this preliminary polishing step, for example, the surface roughness (Ra) of the main surface of the glass substrate is set to 0.1 to 0.2 nm.

  By performing the preliminary polishing step, the polishing rate after the main surface polishing step, that is, the polishing rate through the preliminary polishing step and the precision polishing step can be improved. From the viewpoint of improving the polishing rate, the polishing time in the preliminary polishing step is preferably 3 to 60 minutes. Further, it is preferable that the time of the preliminary polishing step is as long as possible with respect to the polishing time through the preliminary polishing step and the precision polishing step. In the preliminary polishing step, the scratches in the previous polishing step may be substantially eliminated, and polishing may be performed so that the surface roughness (Ra) is 0.2 nm or less. When the preliminary polishing step is provided, the precision polishing step is preferably 2 to 10 minutes. Even if the precision polishing step is performed for more than 10 minutes, there is almost no improvement in the surface roughness (Ra), and the polishing time becomes long, so that the productivity tends to decrease. Therefore, the precision polishing step is more preferably 5 minutes or less, particularly preferably 3 minutes or less. For example, when the polishing time through the preliminary polishing process and the precision polishing process is 15 minutes, the precision polishing process has a sufficient effect of reducing the surface roughness in about 3 minutes, and the preliminary polishing process time becomes longer, The effect of improving the polishing rate can be obtained. The reduction amount (polishing amount) of the plate thickness in this preliminary polishing step is typically 0.1 to 3 μm.

  Moreover, you may perform the washing | cleaning process which removes the polishing liquid adhering to the main surface after grinding | polishing after a precision grinding | polishing process. In the cleaning step, the polished surface after the precision polishing is cleaned with a cleaning liquid. Then, rinse with pure water as necessary. At this time, cleaning or pure water rinsing may be performed while applying ultrasonic waves with an ultrasonic cleaner. After rinsing with pure water, the glass substrate may be dried by spraying compressed nitrogen, dry air, or the like, or by IPA vapor drying or spin drying using isopropyl alcohol (IPA).

  As the cleaning liquid used in the cleaning process, a cleaning liquid containing an oxygen-based oxidizing agent is used. An oxygen-based oxidizing agent is a peracid having a structure in which a hydroxy group (—OH) of an oxo acid is replaced with a hydroperoxy group (—O—OH), or a salt thereof. To remove. As the oxygen-based oxidizing agent, one type may be used alone, or two or more types may be used in combination.

  The oxygen-based oxidizing agent may be either an inorganic compound peracid or an organic compound peracid. As a peracid of an inorganic compound, persulfuric acid, percarbonate, perphosphoric acid, hypoperchlorous acid, or a salt of these peracids can be used. Examples of persulfuric acid include peroxomonosulfuric acid and peroxodisulfuric acid. As the peracid of the organic compound, percarboxylic acids such as peracetic acid and perbenzoic acid, or salts of these peracids can be used. When each of the above-mentioned peracid salts is used as the oxygen-based oxidizing agent, the counter ion is not particularly limited, but sodium salts, potassium salts, ammonium salts and the like are preferably used.

  Among the above-mentioned oxygen-based oxidants, those containing no phosphorus, halogen, etc. are preferable from the viewpoint of maintaining the cleanliness of the glass substrate after washing, and inorganic compounds are more preferable than organic compounds. As the oxygen-based oxidizing agent, it is preferable to use percarbonate, persulfuric acid, peracetic acid or a salt thereof, and hydrogen peroxide or persulfate is more preferable. As persulfuric acid, both peroxomonosulfuric acid and peroxodisulfuric acid are preferably used.

  The pH of the cleaning liquid containing the oxygen-based oxidizing agent is preferably 6 or more from the viewpoints of oxidizing power and stability. On the other hand, when the pH of the cleaning liquid increases and the alkalinity increases, the surface roughness (Ra) of the glass substrate may be deteriorated. Therefore, the pH of the cleaning liquid is preferably 12 or less. In order to adjust the pH of the cleaning liquid to the above preferred range, the cleaning liquid may contain a pH adjuster. The pH adjuster is not particularly limited as long as the pH can be adjusted, and carbonates, bicarbonates, ammonia, alkali metal hydroxides, and the like can be used. Specifically, ammonia, lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, ammonium carbonate, lithium carbonate, sodium carbonate, potassium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate , Potassium hydrogen carbonate, calcium hydrogen carbonate and the like. Of these, hydrogen carbonate and carbonate, such as sodium hydrogen carbonate and sodium carbonate, are preferably used because they have a buffering action because they are weakly alkaline.

  The concentration of the oxygen-based oxidant in the cleaning liquid containing the oxygen-based oxidant is preferably 1% by mass or more based on the total amount of the cleaning liquid from the viewpoint of obtaining a sufficient cleaning effect.

  The cationic amino group-containing polymer contained in the polishing liquid used in the above-described precision polishing step adheres to the main surface of the glass substrate via the amino group as described above, and relaxes the contact between the colloidal silica and the glass substrate. Therefore, it is considered that the effect of improving the surface roughness (Ra) of the polished surface is excellent. However, on the other hand, since the cationic amino group-containing polymer adheres to the main surface of the glass substrate, the polished surface may not be sufficiently cleaned when washed with a commonly used cleaning agent. In order to clean the polished surface, the surface roughness (Ra) of the polished surface may deteriorate if the pH is increased and the substrate is washed with a strongly alkaline cleaning agent.

  On the other hand, the cationic amino group polymer adhering to the polishing surface can be effectively removed while the pH of the cleaning liquid is suppressed to about 12 or less by performing the cleaning process using the above-described cleaning liquid. Thereby, it is possible to sufficiently clean the polished surface while suppressing deterioration of the surface roughness (Ra) of the polished surface.

  As mentioned above, according to the manufacturing method of the glass substrate for magnetic disks of this embodiment, in precision grinding | polishing of the glass substrate for magnetic disks, surface roughness can be reduced and a more precise grinding | polishing surface can be obtained. Furthermore, by performing the cleaning step, it is possible to sufficiently clean the polished surface while suppressing deterioration of the surface roughness (Ra) of the polished surface.

  Next, examples will be described. The present invention is not limited to the following examples. Examples 2, 4 to 8, Examples 10 to 13, Examples 18 to 23, and Example 25 are examples of the present invention, and Examples 1, 3, and 9, Examples 14 to 17 and Example 24 are comparative examples.

(Production of glass substrate)
In Examples 1 to 23, a silicate glass plate formed by the float process (mol% display content is SiO ₂ : 65%, Al ₂ O ₃ : 12%, LiO ₂ : 13%, Na ₂ O: 5%, In Examples 24 and 25, silicate glass plates formed by the float process (mol% display content: SiO ₂ : 67%, Al ₂ O ₃ : K ₂ O: 3%, ZrO ₂ : 2%) 13%, B ₂ O ₃ : 1%, MgO: 9%, CaO: 5.5%, SrO: 4.5%), a glass substrate having an outer diameter of 65 mm, an inner diameter of 20 mm, and a plate thickness of 0.635 mm is obtained. Such a donut-shaped circular glass plate (circular glass plate having a circular hole in the center) was processed. In addition, the grinding process of the inner peripheral surface and the outer peripheral surface was performed using a diamond grindstone, and lapping of the upper and lower surfaces of the glass plate was performed using a fixed abrasive pad.

  Next, chamfering of the inner and outer peripheral end faces was performed. After the inner and outer peripheral processing, a cerium oxide slurry was used as the polishing liquid, a brush was used as the polishing tool, and the end surface was mirror-finished by brush polishing.

  Thereafter, the upper and lower main surfaces were polished by a double-side polishing apparatus using a cerium oxide slurry as a polishing liquid and a urethane pad as a polishing tool.

  Next, precision polishing with a polishing liquid containing a cationic amino group-containing polymer was performed on the main surface of the circular glass plate produced above. The compounds used as cationic amino group-containing polymers in the following examples are as follows. Table 1 summarizes the weight average molecular weight of the following compounds and the average number of amino groups in one molecule.

(A1 to A4) polyalkylene polyamine compound group: polyallylamine (allylamine: polymer of H ₂ C═C (H) CH ₂ NH ₂ ))

(B1-B5) Polyalkylene polyimine compound group: polyethyleneimine (polymer of ethyleneimine (C ₂ H ₅ N)))

(C1) polyoxypropylene isopropylidene diamine _{(H 2 N- (CH (CH} 3) -CH 2 -O) k -CH (CH 3) -CH 2 -NH 2)
: Weight average molecular weight: 400, Average number of amino groups in one molecule: 2
(C2) Polyoxyisopropylenediamine (same chemical structure as C1 but only the degree of polymerization)
: Weight average molecular weight: 2000, Average number of amino groups in one molecule: 2
(D1) Triethyltetramine

(Example 1)
Colloidal silica slurry (product name ST50, SiO ₂ particles having an average particle diameter of 20 to 25 nm, SiO ₂ concentration 48 mass% aqueous dispersion) manufactured by Nissan Chemical Industries, Ltd., citric acid as a pH adjuster, and Pure water was added and stirred to prepare a polishing liquid having a SiO ₂ concentration of 9.8% by mass and a pH of 4.11.

And the main surface of said glass substrate is used for the polishing liquid prepared above, IRHD hardness is 55.5 as a polishing tool, Shore A hardness is 53.5, compression rate is 1.9%, and density is 0.00. Using a polishing pad made of urethane foam resin of 24 g / cm ³ , polishing was performed for 20 minutes using a FAM12B manufactured by Speed Fam Co., Ltd. with a polishing pressure of 12 kPa and a platen rotation speed of 40 rpm. Thereafter, the polished glass substrate was washed with pure water while applying ultrasonic waves.

(Measurement of surface roughness)
The main surface of the glass substrate after polishing was observed at 1 μm × 1 μm (256 pixels × 256 pixels) using an atomic force microscope (AFM), and the surface roughness (Ra) was measured.

(Measurement of polishing rate)
Further, the mass of the glass substrate before and after polishing was measured, and the polishing rate was calculated by the following formulas (5-1) and (5-2).
V = Δm / m0 × T0 × 60 / t (5-1)
Δm = m0−m1 (5-2)
(In the formula, Δm (g) is the mass change before and after polishing, m0 (g) is the initial mass of the unpolished substrate, m1 (g) is the mass of the substrate after polishing, V is the polishing rate (μm / hr), and T0 is The substrate thickness (μm) of the unpolished substrate, and t represents the polishing time (min).)

  The surface roughness (Ra) measured in Example 1 was 0.12 nm, and the polishing rate was 0.041 μm / min.

(Example 2)
Colloidal silica slurry (product name ST50, SiO ₂ particles having an average particle diameter of 20 to 25 nm, SiO ₂ concentration 48 mass% aqueous dispersion) manufactured by Nissan Chemical Industries, Ltd. as in Example 1 was added to polyallylamine (A1 ), A citric acid and pure water as a pH adjusting agent are added and stirred, and the SiO ₂ concentration is 9.8% by mass and the cationic amino group-containing polymer is added to 100 parts by mass of the colloidal silica slurry. A polishing liquid containing 0.001 part by mass was prepared. The polishing liquid had a pH of 4.16.

  The main surface of said glass substrate was grind | polished with the apparatus and conditions similar to Example 1 using the obtained polishing liquid.

  The glass substrate after polishing was immersed in pure water, and then washed with a cleaning solution for 2 minutes while applying ultrasonic waves. Thereafter, it was again immersed in pure water for cleaning and air blown. As the cleaning liquid, a hydrogen peroxide aqueous solution having a concentration of 1 mass% and pH 12 to which sodium hydroxide was added as a pH adjuster was used.

  The surface roughness (Ra) and polishing rate of the main surface of the glass substrate after polishing were measured in the same manner as in Example 1. The surface roughness (Ra) measured in Example 2 was 0.073 nm, and the polishing rate was 0.019 μm / min.

  Moreover, when the washing | cleaning property of the main surface of the glass substrate after washing | cleaning in Example 2 was evaluated as follows, the washing | cleaning property in Example 2 was "(circle)".

(Evaluation of detergency)
Detergency was evaluated by observation with an electron microscope (S4800, manufactured by Hitachi High-Technologies Corporation). In the electron microscope observation, five visual fields were observed at 50,000 times, and the number of colloidal silica adhering to each visual field was counted. The average value of the number of particles counted in 5 fields of view is calculated. The average number of adhering particles is 10 (or less) for 10 or less particles, △ (slightly acceptable) for 10 to 100 particles, and × (failed) for 100 or more particles. It was said that.

(Evaluation of surface roughness)
The surface roughness Ra of the main surface of the glass substrate after washing was measured in the same manner as in Example 1.
Using a surface roughness (Ra) of 0.12 nm measured in Example 1 as a reference, a sample having an Ra of 0.10 nm or less was regarded as acceptable.

(Examples 3-17, Examples 24-25)
The same procedure as in Example 2 was conducted except that the type of cationic amino group-containing polymer and the content of the cationic amino group-containing polymer (mass parts relative to 100 parts by mass of SiO ₂ ) were changed as shown in Table 2. Then, precision polishing and cleaning of the main surface of the glass substrate were performed. As the cleaning liquid, the same cleaning liquid as in Example 2 (hydrogen peroxide aqueous solution having a concentration of 1 mass% and pH 12 to which sodium hydroxide was added as a pH adjusting agent) was used. The surface roughness (Ra) of the main surface after polishing was measured. The results are shown in Table 2 together with Examples 1 and 2.

  About Examples 4-8 and Examples 10-13 which are the Examples of this invention, the washability of the main surface of the glass substrate after washing | cleaning was evaluated similarly to the said Example 2. The results were all “◯”.

  From Table 2, a cationic amino group-containing polymer having a weight average molecular weight of 300 to 3,000 and an average number of amino groups contained in one molecule of 7 to 70 is added to the colloidal silica slurry in an amount of 0.000. In Examples (Example 2, Examples 4 to 8, Examples 10 to 13, and Example 25) in which precision polishing was performed using a polishing liquid containing 0001 to 0.1 parts by mass and having a pH of 2 to 7, Ra is 0.10 nm or less, and it can be seen that the effect of improving the surface roughness is excellent.

(Examples 18 to 21)
In Examples 18 to 21, the cleaning performance of the polished surface after cleaning when the type of cleaning liquid was changed was evaluated.
With the same polishing liquid as in Example 5 (the polishing liquid containing 0.001 part by mass of polyallylamine (A2) with respect to 100 parts by mass of the colloidal silica slurry and having a pH of 4.13), and the above glass substrate. Precision polishing was performed with the same apparatus and conditions. Next, the polished surface was cleaned in the same manner as in Example 5 using the cleaning liquids shown in Table 3. As a cleaning solution, Example 18 is a sodium percarbonate solution having a concentration of 1% by mass with addition of sodium hydrogencarbonate as a pH adjusting agent and a pH 8 potassium peroxomonosulfate solution. Example 19 is a sodium percarbonate having a concentration of 1% by mass without adding a pH adjusting agent. An aqueous solution, Example 20, was prepared by using 98 wt% isopropyl alcohol (IPA) having a pH of 7% without adding a pH adjusting agent, and Example 21 using a pH 12 sodium hydroxide aqueous solution in which sodium hydroxide was added to pure water.

  For the polished surface after cleaning, the cleaning performance was evaluated in the same manner as described above. The results of Examples 18 to 21 are shown in Table 3 together with the results of Example 4 together with the cleaning conditions.

  From Table 3, when a polishing liquid containing a cationic amino group-containing polymer is used as the polishing liquid, cleaning with a cleaning liquid containing an oxygen-based oxidant is used to clean the polishing surface with extremely suppressed adhesion of the polishing liquid. It can be seen that a smooth polished surface was obtained.

(Examples 22 and 23)
In Examples 22 and 23, the polishing rate when preliminary polishing was performed before precision polishing was evaluated. In Example 22, first, preliminary polishing was performed with the same polishing liquid (polishing liquid containing no cationic amino group-containing polymer) as in Example 1 for 15 minutes under the same apparatus and conditions as in Example 1. Next, precision polishing was carried out for 5 minutes using the same apparatus and conditions as in Example 1 with the same polishing liquid as in Example 5 (polishing liquid containing 0.001 part by weight of polyallylamine (A2) and having a pH of 4.13). went.

  Thereafter, the polished glass substrate was washed in the same manner as in Example 5.

  In Example 23, preliminary polishing was performed for 17 minutes and precision polishing was performed for 3 minutes in Example 22, and the polished surface was cleaned in the same manner as in Example 22.

  For Examples 22 and 23, the surface roughness (Ra), relative Ra, and polishing rate were evaluated in the same manner as in Example 3. The polishing rate was measured through a preliminary polishing step and a precision polishing step. The results are shown in Table 4 together with the results of Example 4 together with the polishing conditions.

  From Table 4, it can be seen that the polishing rate was improved by performing the preliminary polishing step compared to the case where this was not performed.

  According to the method for producing a glass substrate for a magnetic disk of the present invention, after polishing the main surface of the glass substrate, the surface of the main surface of the glass substrate is polished when the polished main surface is polished using colloidal silica. By reducing the thickness, a more precise polished surface can be obtained. Therefore, it is suitable for manufacturing a glass substrate for a magnetic disk that requires a high recording density.

Claims (9)

In the method for producing a glass substrate for a magnetic disk having a polishing step of polishing the main surface of the glass substrate and then polishing the polished main surface with a polishing liquid containing colloidal silica,
The polishing liquid is 100 parts by mass of colloidal silica slurry composed of 1-30% by mass of colloidal silica and 70-99% by mass of water,
Including 0.0001 to 0.1 parts by mass of a cationic amino group-containing polymer having a weight average molecular weight of 300 to 3,000, an average number of amino groups contained in one molecule of 7 to 70, and a pH of 2 to 7 A method for producing a glass substrate for a magnetic disk, wherein:   The method for producing a glass substrate for a magnetic disk according to claim 1, wherein the cationic amino group-containing polymer is at least one selected from a polyalkylene polyamine compound group and a polyalkylene polyimine compound group. The method for producing a glass substrate for a magnetic disk according to claim 2, wherein the polyalkylene polyamine compound group and the polyalkylene polyimine compound group are at least one selected from the compound represented by the following formula (1) and a salt thereof.

(In the formula, m and Y in-[(O) _m -Y]-may be different for each repeating unit in one molecule;
n is an integer greater than or equal to 5,
m is 0 or 1,
R ¹ and R ² may be the same or different from each other, and may be a linear or branched alkyl group, a hydrogen atom or an amino group having 1 to 8 carbon atoms which may have an amino group. Yes, (however, directly linked to _{^{R 1 - - [(O)}} m -Y] when m is 1, ^{R 1} is not hydrogen atom, and not the amino group.)
Y is a linear or branched alkylene group having 1 to 8 carbon chains having at least one group selected from the group consisting of a primary amino group, a secondary amino group and a tertiary amino group. ) The polyalkylene polyamine compound group and the polyalkylene polyimine compound group are represented by the formula (1):
n is an integer greater than or equal to 7,
R ¹ and R ² each may be the same or different and is an alkyl group having a linear or branched hydrogen atom or a 1 to 8 carbon atoms (which is directly linked to R ¹ - [( O) When _{m in m—} Y] — is 1, R ¹ is not a hydrogen atom)
The method for producing a glass substrate for a magnetic disk according to claim 3, wherein Y is at least one selected from a compound which is a group represented by the following formula (2) and a salt thereof.

(In the above formula (2),
R ³ , R ⁴ and R ⁵ are each a single bond or a linear or branched alkylene group having 1 to 8 carbon atoms (except when R ³ and R ⁴ are all single bonds). ), Each may be the same or different,
R ⁶ is a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms, and the total number of carbon atoms of R ⁵ and R ⁶ is 0 to 8. ) The method for producing a glass substrate for a magnetic disk according to claim 2 or 3, wherein the polyalkylene polyimine compound group is at least one selected from a compound represented by the following formula (3) and a salt thereof.
_{^{H 2 N-R 7 - [}} (O) m2 -NR 8 -R 9] n2 -NH 2 (3)
(In the formula (3), R ⁷ and R ⁹ may be the same or different, and each is a single bond or a linear or branched alkylene group having 1 to 8 carbon atoms. When m2 directly connected to R ⁷ is 1, R ⁷ is not a single bond),
R ⁸ is a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms,
n2 is an integer of 5 or more,
m2 is 0 or 1,
In one molecule, m @ 2, ^{R 8} and ^{R 9} may be different for each repeating unit. ) In the polishing step, a polishing pad made of a urethane foam resin having a Shore A hardness of 5 to 80, a compressibility of 1 to 60%, and a density of 0.05 to 0.9 g / cm ³ is 0.5 to ³⁰ kPa. The method for producing a glass substrate for a magnetic disk according to any one of claims 1 to 5, wherein polishing is performed with a polishing pressure.   The method for manufacturing a glass substrate for a magnetic disk according to any one of claims 1 to 6, further comprising a cleaning step of cleaning the polished surface of the glass substrate using a cleaning liquid containing an oxygen-based oxidant after the polishing step.   The method for producing a glass substrate for a magnetic disk according to claim 7, wherein the pH of the cleaning liquid is 6-12.   After polishing the main surface of the glass substrate, before the polishing step, the main surface of the glass substrate is polished with a polishing liquid containing the colloidal silica and water and not containing the cationic amino group-containing polymer. The method for manufacturing a glass substrate for a magnetic disk according to any one of claims 1 to 8, further comprising a preliminary polishing step.