JP2014093099A - Glass hard disk substrate polishing liquid composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass hard disk substrate polishing liquid composition that can attain both of a high polishing rate and low surface roughness, and can maintain the high polishing rate for a long time in a recycle polishing.SOLUTION: The glass hard disk substrate polishing liquid composition contains a silica grain that satisfies conditions 1 to 3 described below: 1) an average first-order grain diameter measured by a transmission type electron microscope is 10.0 nm or more and 20.0 nm or less; 2) an average degree of association of second-order aggregation measured by the transmission type electron microscope is 2.5 or more and 5.0 or less; 3) second-order aggregation in which a degree of constriction (envelope failure rate) expressed by a below-described expression (I) is 5.0% or more and 10.0% or less occupies 30% or more of grains as a whole, the degree of constriction=(envelope area-projection area)/envelope area×100 (I), where the projection area denotes an actual area of a transmission image of the grain captured by the transmission type electron microscope, and the envelope area denotes an area of a protrusion closure connecting a protrusion part so as to surround the grain photographed by the transmission type electron microscope.

Description

  The present invention relates to a polishing liquid composition for a glass hard disk substrate, a method for polishing a glass hard disk substrate, and a method for producing a glass hard disk substrate.

  A hard disk mounted on a memory hard disk drive has high power consumption because it rotates at a high speed. In recent years, it has become a big problem from the environmental consideration, and low power consumption is required. In order to reduce power consumption, there is a method of increasing the recording capacity per hard disk, reducing the number of hard disks installed in the drive, and reducing the weight. In order to reduce the weight of one substrate, it is necessary to reduce the thickness of the substrate. From this point of view, the demand for a glass substrate having a higher mechanical strength than that of an aluminum substrate has increased, and the recent growth has been remarkable. . In order to improve the recording capacity per substrate, it is necessary to reduce the unit recording area. However, when the recording area is reduced, the magnetic signal becomes weak. Therefore, in order to improve the detection sensitivity of the magnetic signal, technological development for lowering the flying height of the magnetic head has been advanced. In polishing a glass hard disk substrate, in order to cope with the low flying height of the magnetic head, there are strict requirements for reducing the surface roughness and residues.

  In response to such a request, for example, Patent Document 1 discloses silica having an average primary particle diameter of 5 to 50 nm and an acrylic acid / sulfonic acid copolymer having a weight average molecular weight of 1,000 to 5,000. A polishing composition for glass substrates having a pH of 0.5 to 5 containing

  In Patent Document 2, irregular colloidal silica particles having an average particle diameter of 10 to 50 nm and having protrusions on the surface are connected, and the median diameter (D1) by the dynamic light scattering method is 30 to 150 nm. By using a glass substrate polishing liquid in which colloidal silica particle aggregates having a ratio (D1 / D2) to an average particle diameter (D2) measured by a scanning electron microscope of 2 to 5 are dispersed in water. It is disclosed that both the polishing and the high flatness of the substrate surface can be satisfied.

  Many other methods for producing such secondary agglomerates (linked bodies) composed of primary particles of colloidal silica have been proposed. For example, Patent Document 3 discloses a water glass method using an active silicic acid aqueous solution as a silica source, tetraethylammonium hydroxide used as an alkali agent, and a conventional alkali metal hydroxide used in the colloidal particle growth process. The ratio of major axis / minor axis of silica particles is 1.5 to 15, the alkali metal content per silica is 50 ppm or less, and the silica concentration is characterized in that tetraethylammonium hydroxide is used. Discloses a method for producing a deformed particle group of non-spherical colloidal silica having a content of 10 to 60% by mass.

  Also, in order to reduce the cost of manufacturing the substrate, in the final polishing process of the glass hard disk substrate, the used polishing liquid is put into the polishing machine again, and the polishing liquid is continuously circulated and reused. A technique is known (see Patent Document 4).

JP 2007-191696 A JP 2010-250915 A JP 2008-266080 A JP 2007-245265 A

  However, with the compositions disclosed in Patent Documents 1 and 2, the surface roughness can be reduced, but on the other hand, the polishing rate is lowered and the productivity is remarkably lowered. Further, even if the polishing method of Patent Document 4 is used, the improvement in polishing rate and productivity is insufficient. With the increase in capacity of magnetic disk drives, the required characteristics for substrate surface quality are becoming stricter, and the glass substrate manufacturing method can further reduce the surface roughness of the substrate after polishing while maintaining high productivity. Development is required.

  Further, the colloidal silica secondary aggregates described in Patent Documents 2 and 3 are based on the conventional method, and when the primary particle diameter is the short diameter and the secondary particle diameter is the long diameter, the long diameter / short diameter ratio is the degree of association. Although these appropriate ranges that can achieve both a polishing rate and a surface roughness are specified, a sufficient polishing rate and surface roughness can be obtained even for particles that are actually included in the ranges described in the examples of the patent literature. There is no problem.

  Furthermore, in the method using the conventional polishing liquid as proposed in Patent Document 4, the polishing durability of the glass hard disk substrate in which the polishing liquid is circulated and used (recycled) is low. There are few things that can be done and there is a problem with productivity.

  Therefore, the present invention can achieve both a low surface roughness and a high polishing rate defined by using a different method for defining colloidal silica secondary agglomerates, and polishing while maintaining a polishing rate for a long time in cyclic polishing. A polishing composition for a glass hard disk substrate that can be used, a method for producing a glass hard disk substrate using the polishing composition, and a method for polishing a glass hard disk substrate are provided.

In one aspect, the present invention relates to a polishing liquid composition for glass hard disk substrates containing silica particles, wherein the silica particles satisfy the following conditions 1 to 3.
1) The average primary particle diameter measured by a transmission electron microscope is 10.0 nm or more and 20.0 nm or less.
2) The average degree of association of secondary aggregates measured with a transmission electron microscope is 2.50 or more and 5.00 or less.
3) A secondary aggregate having a squeezing degree (envelope area defect rate) represented by the following formula (I) of 5.0% or more and 10.0% or less of the entire silica particles contained in the polishing composition. It occupies 30% or more.
Necking degree = (envelope area−projected area) / envelope area × 100 (I)
[In the formula (I), the projected area indicates the actual area of the transmission image of the particles photographed by the transmission electron microscope, and the envelope area is the convex hull formed by connecting the convex portions so as to surround the particles photographed by the transmission electron microscope. Indicates area. ]

In one aspect, the present invention provides a polishing liquid composition containing silica particles to a surface to be polished of a glass hard disk substrate to be polished containing silica particles, and a polishing pad is brought into contact with the surface to be polished. And / or a method for polishing a glass hard disk substrate comprising moving and polishing the substrate to be polished, wherein the silica particles satisfy the following conditions 1 to 3.
1) The average primary particle diameter measured by a transmission electron microscope is 10.0 nm or more and 20.0 nm or less.
2) The average degree of association of secondary aggregates measured with a transmission electron microscope is 2.50 or more and 5.00 or less.
3) Secondary aggregates having a squeezing degree (envelope area defect rate) represented by the above formula (I) of 5.0% or more and 10.0% or less occupy 30% or more of the whole particles.

  According to the present invention, a polishing liquid composition for a glass hard disk substrate capable of achieving both a higher polishing rate and a lower surface roughness than conventional ones and maintaining a high polishing rate in cyclic polishing, The manufacturing method of the used glass hard disk substrate and the polishing method of the glass hard disk substrate can be provided.

FIG. 1 is an example illustrating a projected area (dotted line) and an envelope area (solid line) of a secondary aggregate. FIG. 2 is an example of an electron microscope (TEM) observation photograph of silica particles AJ. Black dots in the photograph show an example of a transmission image (projected area) of silica particles.

  The polishing composition of the present invention contains silica particles as an abrasive. The silica particles contain secondary aggregates of colloidal silica monomers. In this specification, the secondary aggregate means a connected state in which particles are cross-linked by silicic acid.

  Colloidal silica secondary aggregates used as abrasives in conventional polishing liquid compositions have a primary particle diameter (hereinafter also referred to as “short diameter”) and a secondary particle diameter (hereinafter also referred to as “long diameter”). , And the degree of association (= major axis / minor axis). However, in actuality, unreacted colloidal silica monomer is contained as an impurity, and distribution occurs in the shape and size of the secondary aggregate. In one aspect, the present invention is based on the knowledge that the definition of only the above three parameters cannot completely define an appropriate range of a colloidal silica secondary aggregate that achieves both a high polishing rate and a low surface roughness. . In addition, in one aspect, the present invention has been conventionally supplied in the industrial field by using a parameter called a degree of constriction (envelope area defect rate) in addition to an average primary particle diameter (short diameter) and an average degree of association. By using a silica particle dispersion having a secondary agglomeration form that is distinguished from the silica particle dispersion, it is possible to achieve both higher polishing speed and lower surface roughness than before, and a higher polishing speed in cyclic polishing. This is based on the knowledge that it is possible to define a polishing composition that can be maintained, that is, can improve durability in cyclic polishing. In addition, as a usage form of the said silica particle, it is preferable that it is a slurry form.

That is, the present invention is a polishing composition for a glass hard disk substrate (hereinafter also referred to as “the polishing composition of the present invention”), and in one aspect, a polishing composition for a glass hard disk substrate containing silica particles. And the said silica particle is related with the polishing liquid composition for glass hard disk substrates which satisfy | fills the following conditions 1-3.
1) The average primary particle diameter measured by a transmission electron microscope is 10.0 nm or more and 20.0 nm.
2) The average degree of association of secondary aggregates measured with a transmission electron microscope is 2.50 or more and 5.00 or less.
3) A secondary aggregate having a squeezing degree (envelope area defect rate) represented by the following formula (I) of 5.0% or more and 10.0% or less of the entire silica particles contained in the polishing composition. It occupies 30% or more.
Necking degree = (envelope area−projected area) / envelope area × 100 (I)
According to the polishing liquid composition of the present invention, low surface roughness of the substrate surface after polishing can be realized, polishing can be performed at a high polishing rate, and the polishing rate can be maintained in cyclic polishing.

  The reason why the surface roughness of the glass substrate can be reduced while maintaining a high polishing rate by the polishing composition of the present invention is estimated as follows. The substrate surface roughness after polishing is considered to depend on the number of contact points of silica particles that are in contact with the glass substrate surface. At the time of polishing the glass substrate, it is considered that the portion where the glass substrate and the silica particles, which are abrasive grains, are in contact with each other at a minimal portion close to a point. In the case of the conventionally known spherical silica particles, the smaller the silica particles are used, the shorter the distance between the contact points of the silica particles on the glass surface and the closer the parts to be polished. The larger the spherical silica particles with a larger particle size, the longer the distance between the contact points of the silica particles to the glass surface, the more the portion to be polished is separated, and the more uneven polishing occurs, and the substrate surface roughness cannot be sufficiently reduced. . On the other hand, it is considered that when each silica particle pressed against the glass substrate by the polishing pad moves longer on the substrate, the polishing progresses more efficiently and the polishing rate is improved. During the movement of the glass substrate such as rotation of the glass substrate by the polishing machine, the silica particles are polished while moving toward or away from the substrate surface. When the silica particles are small, the movement of the silica particles is frequent, and the movement of each silica particle on the substrate is short and the speed is not sufficiently increased. When the silica particles are large, the movement of the silica particles is slow, and the movement of each silica particle on the substrate is considered to be long and increase in speed.

  The polishing composition of the present invention is a silica secondary having a structure portion in which agglomerated silica particles are arranged in a plane satisfying the average primary particle size, the average degree of association, and the degree of constriction disclosed in the above conditions 1 to 3. Contains aggregates. The average primary particle size determines the size of the secondary particles after associating and determines the residence time on the glass substrate surface as described above. The primary particle size and the average aggregation of secondary aggregates defined in the present invention are determined. The size of the secondary aggregate determined by the degree is the size with the best polishing efficiency, and within the range of the average degree of association and the degree of constriction of the present invention, several primary particles serving as contacts to the glass plane are planar. It becomes a structure lined up. That is, the colloidal silica secondary aggregate satisfying the average primary particle size, the average degree of association, and the degree of constriction disclosed in the above conditions 1 to 3 should be formed with a plurality of contacts with the glass surface at very close intervals. Therefore, polishing unevenness hardly occurs and the substrate surface roughness is improved. In addition, since the colloidal silica secondary aggregate satisfying the average primary particle diameter, average association degree and squeezing degree disclosed in the above conditions 1 to 3 has a larger particle size due to secondary aggregation, It is possible to stay for a long time, which is considered to improve the polishing rate.

  Conventionally, as agglomerated silica particles and irregular-shaped silica particles, for example, a confetti shape or a bead shape is known, but it is not in the range of the average primary particle size, the average degree of association and the degree of constriction disclosed in the above conditions 1 to 3. In the case of a confetti shape, the particle size is increased and the polishing rate is improved, but the contact with the glass substrate is generally one and the substrate surface roughness cannot be improved. In addition, in the case of beaded irregular shaped silica particles, a plurality of contacts with the glass surface can be made, but since there is anisotropy, the residence time on the glass substrate surface becomes non-uniform and the polishing rate Is not sufficient and may cause scratches. As described above, the colloidal silica secondary aggregate satisfying the average primary particle diameter, the average degree of association and the degree of constriction disclosed in the above conditions 1 to 3 is provided with a plurality of adjacent contacts between the glass substrate to be polished. It is presumed that the aggregated particles that can be held in the substrate can improve the polishing rate and reduce the surface roughness of the substrate. However, the present invention is not construed as being limited to these estimations.

[Silica particles]
The polishing liquid composition of the present invention contains a colloidal silica secondary aggregate that satisfies the average primary particle size, the average degree of association and the degree of constriction disclosed in the above conditions 1 to 3. Hereinafter, the colloidal silica secondary aggregate satisfying the average primary particle diameter, the average degree of association, and the degree of constriction disclosed in the above conditions 1 to 3 is also referred to as “secondary aggregate according to the present invention”. In one or a plurality of embodiments, the polishing liquid composition of the present invention satisfies the above conditions 1 to 3 with the colloidal silica monomer that forms the secondary aggregate in addition to the secondary aggregate according to the present invention. You may contain in the range. In one or a plurality of embodiments, the polishing composition of the present invention is an aqueous dispersion of secondary aggregates according to the present invention.

[Method for producing silica particles]
The colloidal silica monomer can be obtained by a water glass method in which particles are grown by a condensation reaction in an aqueous solution using an alkali metal silicate such as sodium silicate as a raw material. Alternatively, it can be obtained by an alkoxysilane method in which an alkoxysilane such as tetraethoxysilane is used as a raw material and grown by condensation reaction in water containing a water-soluble organic solvent such as alcohol. Colloidal silica particles obtained by the alkoxysilane method are excellent in that the content of metal impurities is low, and are therefore mainly used as abrasives for polishing semiconductors. However, the high cost of silica raw materials is a problem. Therefore, from the viewpoint of reducing the cost at the time of manufacturing the substrate, colloidal silica particles that can be obtained by the water glass method are preferable in polishing a glass hard disk substrate because they are inexpensive and can suppress raw material costs. Examples of the water glass method include a build-up method using an alkali silicate aqueous solution as a starting material.

  The colloidal silica secondary aggregate can be prepared by connecting colloidal silica monomers via silicic acid and aggregating them. The heating temperature is preferably 95 ° C. or higher, more preferably 130 ° C. or higher, and even more preferably 150 ° C. or higher from the viewpoint that the colloidal silica monomers are easily cross-linked and linked. In addition, the heating temperature is preferably 250 ° C. or less, more preferably 230 ° C. or less from the viewpoint of reducing gelation at the time of temperature increase. Although heating can be performed under reflux conditions, a microwave heating apparatus or an autoclave apparatus may be used. The latter is more preferable because the heating time can be shortened.

[Average primary particle diameter / average minor diameter]
The average primary particle size of the silica particles contained in the polishing liquid composition of the present invention is preferably 10.0 nm or more, more preferably 12.0 nm or more, from the viewpoint of improving the polishing rate and improving the durability in cyclic polishing. From the viewpoint of reducing the surface roughness, it is preferably 20.0 nm or less, more preferably 18.0 nm or less. Therefore, 10.0-20.0 nm is preferable, More preferably, it is 12.0-18.0 nm. In this specification, the average primary particle diameter of the silica particles refers to the average value of the primary particle diameter of the colloidal silica monomer and the short diameter of the secondary aggregate. In this specification, the minor axis of the secondary aggregate is a value measured using an electron microscope, and the average primary particle diameter obtained from one secondary aggregate photographed with an electron microscope is 10.0. The number of primary particles corresponding to the range of ˜20.0 nm or 12.0 to 18.0 nm is arbitrarily estimated, and the secondary aggregates are cut off at the concave portions of the secondary aggregates that are assumed to be the connection sites of the primary particles. This is the equivalent circle diameter of the circumscribed circle, which is the smallest circle that contains the projection surface of the primary particles that can be produced.

[Average major axis]
The average major axis of the colloidal silica secondary aggregate is preferably 20.0 nm or more, more preferably 30.0 nm or more from the viewpoint of improving the polishing rate and improving the durability in the circular polishing, and also reduces the surface roughness. From the viewpoint, it is preferably 100.0 nm or less, more preferably 80.0 nm or less. In this specification, the major axis of the secondary aggregate is a value measured using an electron microscope, and refers to the equivalent circle diameter of a circumscribed circle that is the smallest circle including the projection surface of the secondary aggregate inside. . Whether colloidal silica is a secondary aggregate or a primary particle can be easily determined by observation with an electron microscope.

  The primary particle diameter or short diameter, and the secondary particle diameter or long particle diameter in the abrasive are all the transmission electron microscope (TEM) trade name “JEM-2000FX” (80 kV, 1 to 50,000 times, JEOL According to the instructions attached by the manufacturer, the TEM image is photographed, the photograph is taken into a personal computer as image data with a scanner, and analysis software “WinROOF ver. 3.6” (sales source) : The equivalent circle diameter of each silica particle is determined using Mitani Corporation), and the average particle diameter is calculated by calculating the average value after obtaining the particle diameter of 1000 or more and 2000 or less silica particles. Can do.

[Average degree of meeting]
The average degree of association of the secondary agglomerates according to the present invention indicates a value obtained by dividing the average major axis by the average primary particle size or the average minor axis. From the viewpoint of improving the polishing rate, reducing the surface roughness, and improving the durability in cyclic polishing. Therefore, 2.50 or more is preferable, 2.70 or more is more preferable, 2.80 or more is more preferable, and 5.00 or less is preferable, 4.00 or less is more preferable, and 3.50 or less is preferable from the same viewpoint. Further preferred.

[Necking degree]
In the present specification, the degree of squeezing of silica particles refers to an envelope area defect rate (%) represented by the following formula (I).
Necking degree = (envelope area−projected area) / envelope area × 100 (I)

  In formula (I), the projected area refers to the actual area of a transmission image of particles taken with a transmission electron microscope. The envelope area refers to the area of a convex hull in which convex portions are connected so as to surround particles photographed by a transmission electron microscope. The degree of squeezing can be measured using a transmission electron microscope, and specifically can be measured by the method described in Examples.

  In the silica particles in the polishing liquid composition of the present invention, colloidal silica secondary aggregates having a squeezing degree of 5.0% or more and 10.0% or less are improved in polishing rate, reduced in surface roughness, and durable in cyclic polishing. From the viewpoint of improving the properties, it is present at a number ratio of 30% or more of the entire silica particles, preferably at a number ratio of 33% or more, and from the same viewpoint, it is preferably present at a number ratio of 60% or less. However, it is more preferable that it is present at a number ratio of 50% or less.

[Colloidal silica secondary aggregate]
The secondary aggregate according to the present invention preferably has an average squeezing degree of 5.00% or more from the viewpoint of greater contribution to the polishing rate than the colloidal silica monomer. The secondary aggregate according to the present invention preferably has an average squeezing degree of 10.00% or less from the viewpoint of reducing the surface roughness.

[Content of silica particles]
The content of the silica particles in the polishing composition is preferably 1% by mass or more, more preferably 2% by mass or more, still more preferably 4% by mass or more, from the viewpoint of improving the polishing rate and reducing the surface roughness. More preferably, it is 6% by mass or more, and from the same viewpoint, it is preferably 20% by mass or less, more preferably 18% by mass or less, still more preferably 16% by mass or less, and even more preferably 10% by mass or less. .

[acid]
The polishing composition of the present invention preferably contains an acid. In the present invention, the acid may be in the form of a salt. Examples of the acid used in the polishing liquid composition of the present invention include nitric acid, sulfuric acid, sulfurous acid, persulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, tripolyphosphoric acid, and amidosulfuric acid. Acids; sulfur-containing organic acids such as methanedisulfonic acid, ethanedisulfonic acid, phenoldisulfonic acid, naphthalenedisulfonic acid; 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), Ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid), ethane-1,1, -diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic Acid, ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydride Organic phosphonic acids such as xyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, α-methylphosphonosuccinic acid; malonic acid, oxalic acid, succinic acid, glutar Acid, adipic acid, maleic acid, fumaric acid, itaconic acid, malic acid, tartaric acid, citric acid, isocitric acid, phthalic acid, nitrotriacetic acid, nitroacetic acid, ethylenediaminetetraacetic acid, oxaloacetic acid and other polyvalent carboxylic acids; acetic acid, propion Monovalent carboxylic acids such as acid, benzoic acid, lactic acid and glycolic acid; and aminocarboxylic acids such as glutamic acid, picolinic acid and aspartic acid. These compounds may be used alone or in combination. Among these, sulfur-containing organic acids, polyvalent carboxylic acids, monovalent carboxylic acids, and organic phosphones from the viewpoint of improving durability in cyclic polishing, as well as improving polishing speed, reducing surface roughness, and reducing contamination of polishing waste liquid. Acids and phosphorus-containing inorganic acids are preferred. Among these, an acid selected from the group consisting of a polyvalent carboxylic acid, a monovalent carboxylic acid, an organic phosphonic acid, and a phosphorus-containing inorganic acid is preferable, more preferably a polyvalent carboxylic acid, 1 An acid selected from the group consisting of monovalent carboxylic acids and phosphorus-containing inorganic acids, even more preferably an acid selected from the group consisting of polyvalent carboxylic acids and monovalent carboxylic acids, and even more preferably Acid, malic acid, tartaric acid, citric acid, glycolic acid, phosphorus-containing inorganic acid, citric acid, phosphoric acid, glycolic acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, tripolyphosphoric acid are more preferred, citric acid, glycolic acid Is even more preferred.

  When these acid salts are used, there is no particular limitation, and specific examples include salts with metals, ammonium, alkylammonium and the like. Specific examples of the metal include metals belonging to the periodic table (long-period type) 1A, 1B, 2A, 2B, 3A, 3B, 4A, 6A, 7A, or Group 8. Among these, a salt with a metal belonging to Group 1A or ammonium is preferable from the viewpoint of improving the polishing rate and reducing the roughness.

  The content of the acid in the polishing composition of the present invention is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, from the viewpoint of improving the polishing rate and from the viewpoint of improving durability in cyclic polishing. More preferably, it is 0.15 mass% or more. Further, the content of the acid is preferably 10% by mass or less, more preferably 7.5% by mass or less, and further preferably 5% by mass or less from the viewpoint of suppressing corrosion of the polishing apparatus. In addition, content of the above-mentioned acid shows the sum total of content of each acid, when there are two or more types of acids in polishing liquid composition.

[water]
The water in the polishing composition is used as a medium, and distilled water, ion exchange water, pure water, ultrapure water, or the like can be used. The water content in the polishing liquid composition of the present invention is preferably 55% by mass or more, more preferably 70% by mass or more, and still more preferably 80% by mass or more because the handling of the polishing liquid composition becomes easier. Especially preferably, it is 85 mass% or more. In addition, the water content is preferably 99% by mass or less, more preferably 98% by mass or less, and still more preferably 97% by mass or less, from the viewpoint of improving the polishing rate.

[PH of polishing composition]
The pH of the polishing composition of the present invention can be adjusted as appropriate by adjusting the acid content. The pH of the polishing composition of the present invention is preferably 0.5 or more, more preferably 1.0 or more, still more preferably 1.5 or more, from the viewpoint of preventing corrosion of the polishing machine and improving worker safety. Even more preferably, it is 2.0 or more. Moreover, 4.0 or less is preferable from a viewpoint of a polishing rate improvement, More preferably, it is 3.5 or less.

[Amine compound]
The polishing liquid composition of the present invention may further contain an amine compound from the viewpoint of reducing the surface roughness and improving the durability in cyclic polishing. The amine compound is an amine compound selected from the group consisting of amino alcohol and piperazine and derivatives thereof from the viewpoint of reducing surface roughness and improving durability in cyclic polishing, and contains 2 or 2 nitrogen atoms in the molecule. Those having three are preferred. The nitrogen atom may be in any state of primary amine, secondary amine and tertiary amine, but at least one of them is primary amine or from the viewpoint of reducing surface roughness and improving durability in cyclic polishing. A secondary amine is preferred. In the present invention, the amine compound may be one kind or two or more kinds. In the present invention, the amine compound may be in the form of a salt, and examples thereof include salts with inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid, and organic acids.

  It is considered that the amine compound is adsorbed on the glass hard disk substrate and the surface roughness can be reduced because the protective film effect is exhibited. However, the molecular weight of the amine is preferably such that a protective film layer that does not cause a decrease in the polishing rate is formed. That is, in order to achieve both reduction in surface roughness and improvement in polishing rate, it is necessary to add a compound containing an optimal number of amines. Furthermore, the presence of the amine compound can suppress changes in pH due to the elution of alkali metal ions (especially sodium ions) from the glass hard disk substrate during polishing, maintaining the polishing rate in cyclic polishing, that is, polishing. The durability of the liquid composition in cyclic polishing can be improved. However, these assumptions do not limit the present invention.

  Examples of the amine compound used in the present invention include 2-[(2-aminoethyl) amino] ethanol, 2,2 '-(ethylenebisimino) bisethanol, N- (2-hydroxyethyl) -N'. -(2-aminoethyl) ethylenediamine, 2,2 '-(2-aminoethylimino) diethanol, N1, N4-bis (hydroxyethyl) diethylenetriamine, N1, N7-bis (hydroxyethyl) diethylenetriamine, 1,3-diamino Amino alcohols such as -2-propanol; piperazine, 1-methylpiperazine, 3- (1-piperazinyl) -1-propanamine, 1- (2-aminoethyl) piperazine, 4-methylpiperazine-1-amine, 1- Piperazine methanamine, 4-ethyl-1-piperazineamine, 1-methyl-4- 2-aminoethyl) piperazine, piperazine derivatives such as 1- (2-hydroxyethyl) piperazine, and the like. From the viewpoint of coexistence of reduction of polishing speed and surface roughness, and improvement of durability in cyclic polishing, 1- (2-hydroxyethyl) piperazine, 1- (2-aminoethyl) piperazine, 2-[(2-aminoethyl) amino] ethanol, piperazine, more preferably 1- (2-aminoethyl) piperazine, 2 -[(2-aminoethyl) amino] ethanol, more preferably 1- (2-aminoethyl) piperazine, 2-[(2-aminoethyl) amino] ethanol.

  In addition, the amine compound preferably has a vapor pressure at 25 ° C. of 0.2 mmHg or less, more preferably 0.1 mmHg or less, from the viewpoint of preventing off-flavor generation due to amine volatilization and the like and improving worker safety. is there. As such an amine compound, for example, 2-[(2-aminoethyl) amino] ethanol, 1- (2-hydroxyethyl) piperazine, and 1- (2-aminoethyl) piperazine are preferable. Here, the vapor pressure at 25 ° C. refers to the pressure of the vapor phase in equilibrium with the liquid phase or the solid phase at a constant temperature, and specifically, the Handbook of Chemical Compound Data Process Safety (Author: Carl L Yaws, published by Gulf Publishing Company), or CRC Handbook of Chemistry and Physics 88th Edition (Author: Lide, DR, (ed)).

  The content of the amine compound in the polishing composition is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, from the viewpoint of improving the cleanliness and improving the durability in circulating polishing. More preferable is 0.05% by mass or more. From the viewpoint of improving the polishing rate, it is preferably 5% by mass or less, more preferably 4% by mass or less, further preferably 3% by mass or less, still more preferably 0.5% by mass or less, and further more preferably 0.2% by mass or less. More preferred. In addition, content of the above-mentioned amine compound shows content of each amine compound, when the amine compound in polishing liquid composition has multiple types.

[Other ingredients]
The polishing composition of the present invention may further contain a bactericidal agent, an antibacterial agent, a thickener, a dispersant, a rust inhibitor, and the like. The content of these components in the polishing liquid composition is preferably 5% by mass or less, more preferably 3% by mass or less, and still more preferably 1% by mass or less from the viewpoint of polishing characteristics.

[Method for preparing polishing liquid composition]
The polishing liquid composition of this invention can be prepared by mixing each component by a well-known method. The polishing composition is usually produced as a concentrated solution from the viewpoint of economy, and it is often diluted at the time of use. The polishing composition may be used as it is, or diluted if it is a concentrated solution. When diluting the concentrate, the dilution factor is not particularly limited, and can be appropriately determined according to the concentration of each component (silica particle content and the like) in the concentrate and the polishing conditions.

  The pH of the polishing composition may be adjusted to a predetermined pH after mixing the components, or may be adjusted before mixing. The pH can be adjusted with a pH adjusting agent.

[Glass hard disk substrate manufacturing method]
The manufacturing method of the glass hard disk substrate of the present invention (hereinafter also referred to as “the manufacturing method of the present invention”) includes a step of polishing the glass hard disk substrate using the polishing composition of the present invention.

  As a glass hard disk substrate (hereinafter also referred to as a substrate to be polished) which is a polishing target of the polishing liquid composition of the present invention, aluminosilicate glass, borosilicate glass, aluminoborosilicate glass, and sodium are replaced with potassium in the chemical strengthening step. In view of improving the polishing rate, an aluminosilicate glass substrate and an aluminosilicate glass in which sodium is substituted with potassium in the chemical strengthening step are preferable, and an aluminosilicate glass substrate is more preferable. The aluminosilicate glass substrate contains the most Si (silicon) as a constituent element other than O (oxygen), and then contains a large amount of Al. Usually, the Si content is 20% by mass or more and 40% by mass or less, the Al content is 3% by mass or more and 25% by mass or less, and may contain other Na or the like, but it is used for hard disks. In this case, from the viewpoint of improving the polishing rate and maintaining the transparency of the substrate, the content of Al is more preferably 5% by mass or more, further preferably 7% by mass or more, more preferably 20% by mass or less, and 15% by mass. %Less than. In addition, the detail of the measurement conditions of content of Al contained in an aluminosilicate glass substrate is as showing in an Example.

  The glass hard disk substrate is, for example, from a process of obtaining a glass substrate by a mold press of molten glass or a method of cutting out from a sheet glass, a shape processing process, an end surface polishing process, a rough grinding process, a fine grinding process, a rough polishing process, and a finish polishing. It is manufactured through a process and a chemical strengthening process. The chemical strengthening step may be performed before the finish polishing step. In addition, a cleaning process may be included between the processes. And a glass hard disk substrate turns into a magnetic hard disk through a recording part formation process in a manufacturing method. The recording part forming step includes, for example, forming an adhesion layer, a soft magnetic layer, an underlayer, an intermediate layer, a magnetic layer, a protective layer, and a lubricating layer. The production method of the present invention may include these steps.

  In one embodiment, for example, about # 400 alumina abrasive grains in the rough grinding step, cylindrical grindstones in the shape processing step, brushes in the end surface polishing step, and # 1000 alumina in the fine grinding step. Abrasive grains are each used. However, the present invention is not limited to these.

  In the rough polishing process, cerium oxide particles are suitably used as abrasive grains, and in the final polishing process, silica particles are suitably used as abrasive grains. The polishing composition of the present invention is preferably used in a final polishing step and / or a final (finish) polishing step.

  After each step, ultrasonic cleaning is performed in a cleaning tank containing an alkaline cleaning agent, a neutral cleaning agent, an acidic cleaning agent, or ultrapure water in order to remove residues on the surface of the glass hard disk substrate. Thereafter, it may include a step of washing with ultrapure water, IPA (isopropyl alcohol), etc., and drying while pulling up the substrate from ultrapure water or IPA, or drying by spin drying or the like. A scrub treatment may be included during the cleaning process.

  The glass hard disk substrate is required to have a smooth surface that does not cause a read / write error of the magnetic head. That is, it is required that the substrate surface has good flatness (roughness, waviness, etc.) and that there are few defects (convex defects such as residues, concave defects such as scratches and pits) and is polished during the substrate manufacturing process. The process plays a role of improving the flatness of the substrate surface and removing defects. Therefore, the finish polishing step is particularly important in the polishing step.

  In the polishing step, the polishing liquid composition of the present invention is supplied to the surface to be polished of the substrate to be polished, the polishing pad is brought into contact with the surface to be polished, and a predetermined pressure (load) is applied to the polishing pad or the substrate to be polished. This can be done by moving. For a specific polishing method in the polishing step, a glass hard disk substrate polishing method described later can be referred to. In addition, the said grinding | polishing can be performed with a conventionally well-known grinding | polishing apparatus. Examples of the substrate to be polished in the polishing step include a glass hard disk substrate immediately after the fine grinding step. In particular, the production method of the present invention preferably includes a step of circulating and polishing a glass hard disk substrate using the polishing composition of the present invention.

[Circulating polishing]
In the present specification, the cyclic polishing is a method in which, in the polishing process of the glass hard disk substrate, the used polishing liquid is again put into the polishing machine, and the polishing liquid is circulated in the polishing machine and reused. The entire amount of the waste liquid after polishing may be recovered once and then re-entered into the polishing machine, or may be continuously re-introduced into the polishing machine while returning the waste liquid to the recovery tank.

  When the polishing composition is circulated and reused in the polishing machine, the number of times of reuse is not particularly limited, but the polishing composition of the present invention preferably uses a glass hard disk substrate 5 to 30 times, more preferably 20 times. Suitable for use when polishing up to 30 times. One polishing means one batch of polishing. When only a colloidal silica monomer is used as an abrasive, the polishing rate is remarkably reduced for each batch of circulating polishing. The cause of this is not clear, but it is considered that colloidal silica having an active surface is consumed. However, when an abrasive containing colloidal silica secondary aggregates is used, the amount of active colloidal silica consumed in one batch due to the shape of the abrasive can be suppressed. The present inventor estimates that the polishing rate can be prevented from decreasing for each batch. Further, at that time, when the acid and the amine compound are used in combination, the pH buffering ability is increased, the decrease in the polishing rate is further suppressed, and cyclic polishing for a longer time becomes possible. However, the present invention is not construed as being limited to these estimations.

[Grinding method of glass hard disk substrate]
The polishing apparatus used in the method for polishing a glass hard disk substrate using the polishing liquid composition of the present invention (hereinafter also referred to as “the polishing method of the present invention”) is not particularly limited, and a jig for holding the substrate to be polished. A polishing apparatus including a carrier (made of aramid or the like) and a polishing cloth (polishing pad) can be used. Among these, a double-side polishing apparatus is preferably used.

  Examples of the material for the polishing pad include organic polymers, and examples of the organic polymer include polyurethane. The shape of the polishing pad is preferably a nonwoven fabric. For example, a suede-like urethane hard pad is suitably used in the rough polishing process, and a suede-like urethane soft pad is suitably used in the final polishing process.

  As a specific example of the polishing method using the polishing apparatus, the substrate to be polished is held by a carrier and sandwiched between a pair of polishing surface plates attached with a polishing pad, and the polishing liquid composition of the present invention is applied to the polishing pad and the substrate to be polished. And polishing the polishing substrate by bringing the polishing composition of the present invention into contact with the substrate to be polished by moving the polishing platen and / or the substrate to be polished under a predetermined pressure. Is mentioned.

  The polishing method of the present invention preferably includes a step of polishing with a predetermined polishing load by causing the polishing composition to exist between the polishing pad and the substrate to be polished. In the present invention, the “polishing load” means a pressure applied to a surface to be polished of a substrate to be polished from a surface plate that sandwiches the substrate to be polished at the time of polishing. The polishing load can be easily adjusted with a normal polishing apparatus. For example, the polishing load can be adjusted by air pressure or weight load on a surface plate or a substrate to be polished. From the viewpoint of improving the polishing rate, the polishing load is preferably 3 kPa or more, more preferably 4 kPa or more, further preferably 5 kPa or more, and further preferably 6 kPa or more. From the viewpoint that the polishing machine can be stably polished so as not to generate vibration during polishing, it is preferably 40 kPa or less, more preferably 30 kPa or less, further preferably 20 kPa or less, even more preferably 15 kPa or less, and even more preferably 10 kPa or less. . The polishing load can be adjusted by the air pressure on the surface plate or the substrate or the load of the weight.

  The polishing method of the present invention is more preferably used in the final polishing step. The polishing method of the present invention preferably includes a step of circulating and polishing a glass hard disk substrate using the polishing composition of the present invention.

  The method of supplying the polishing liquid composition is a method of supplying the polishing liquid composition between the polishing pad and the glass hard disk substrate with a pump or the like in a state where the constituents of the polishing liquid composition are sufficiently mixed in advance, in a supply line immediately before polishing, etc. For example, a method in which constituent components are mixed and supplied, a method in which a slurry of silica particles and an aqueous solution containing an amine compound are separately supplied to a polishing apparatus can be used.

The supply rate of the polishing composition is preferably 1.0 mL / min or less per 1 cm ^{2 of the} substrate to be polished, more preferably 0.6 mL / min or less, and even more preferably 0.4 mL / min or less from the viewpoint of cost reduction. is there. Moreover, since the said supply rate can further improve a grinding | polishing rate, 0.01 mL / min or more per 1 cm < ² > of glass hard disk substrates is preferable, More preferably, it is 0.025 mL / min or more, More preferably, it is 0.05 mL / min or more, Even more preferably, it is 0.1 mL / min or more. In addition, since the polishing composition can be reused in the case of cyclic polishing, the supply flow rate may be higher than the flow rate described above.

  The present invention further relates to one or more of the following embodiments.

<1> A polishing liquid composition for glass hard disk substrate containing silica particles, wherein the silica particles satisfy the following conditions 1 to 3.
1) The average primary particle diameter measured by a transmission electron microscope is 10.0 nm or more and 20.0 nm or less.
2) The average degree of association of secondary aggregates measured with a transmission electron microscope is 2.50 or more and 5.00 or less.
3) A secondary aggregate having a squeezing degree (envelope area defect rate) represented by the following formula (I) of 5.0% or more and 10.0% or less of the entire silica particles contained in the polishing composition. It occupies 30% or more.
Necking degree = (envelope area−projected area) / envelope area × 100 (I)
[In the formula (I), the projected area indicates the actual area of the transmission image of the particles photographed by the transmission electron microscope, and the envelope area is the convex hull formed by connecting the convex portions so as to surround the particles photographed by the transmission electron microscope. Indicates area. ]

<2> The polishing liquid composition for a glass hard disk substrate according to <1>, wherein the silica particles are silica particles produced by a build-up method using an alkali silicate aqueous solution as a starting material.
<3> The average primary particle size is 12.0 nm or more and / or 20.0 nm or less, preferably 18.0 nm or less, and / or preferably 12.0 to 18.0 nm. <1> or <2> The polishing liquid composition for glass hard disk substrates as described.
<4> The average major axis of the colloidal silica secondary aggregate in the silica particles is 20.0 nm or more, preferably 30.0 nm or more, and / or 100.0 nm or less, preferably 80.0 nm or less. <1> to <3>, The polishing liquid composition for glass hard disk substrates in any one of.
<5> The average degree of association of the colloidal silica secondary aggregate in the silica particles is 2.70 or more, preferably 2.80 or more, and / or 4.00 or less, preferably 3.50 or less. The polishing composition for a glass hard disk substrate according to any one of <1> to <4>.
<6> The secondary aggregate having a squeezing degree represented by the formula (I) of 5.0% or more and 10.0% or less is divided by the number of silica particles contained in the polishing composition. 33% or more and / or 60% or less, preferably 50% or less, the polishing composition for glass hard disk substrates according to any one of <1> to <5>.
<7> The average necking degree of the colloidal silica secondary aggregate in the silica particles is 5.00% or more and / or 10.00% or less, according to any one of <1> to <6>. Polishing liquid composition for glass hard disk substrate.
<8> The content of silica particles in the polishing liquid composition is 1% by mass or more, preferably 2% by mass or more, more preferably 4% by mass or more, further preferably 6% by mass or more, and / or. 20% by mass or less, preferably 18% by mass or less, more preferably 16% by mass or less, and further preferably 10% by mass or less, and the polishing liquid for glass hard disk substrates according to any one of <1> to <7> Composition.
<9> Furthermore, it contains at least one acid selected from the group consisting of polyvalent carboxylic acids and salts thereof, or organic phosphonic acids and salts thereof, according to any one of <1> to <8>. Polishing liquid composition for glass hard disk substrate.
<10> An acid is contained, and the acid content is 0.05% by mass or more, preferably 0.1% by mass or more, more preferably 0.15% by mass or more, and / or 10% by mass. The polishing composition for glass hard disk substrates according to any one of <1> to <9>, preferably 7.5% by mass or less, more preferably 5% by mass or less.
<11> The pH is 0.5 or more, preferably 1.0 or more, more preferably 1.5 or more, further preferably 2.0 or more, and / or 4.0 or less, preferably 3.5 or less. The polishing liquid composition for a glass hard disk substrate according to any one of <1> to <10>.
<12> Further containing an amine compound, the content of the amine compound is 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and / or <1> to <11> 5% by mass or less, preferably 4% by mass or less, more preferably 3% by mass or less, further preferably 0.5% by mass or less, and still more preferably 0.2% by mass or less. The polishing liquid composition for glass hard disk substrates in any one of these.
<13> The polishing liquid composition for a glass hard disk substrate according to any one of <1> to <12>, wherein the glass hard disk substrate to be polished is an aluminosilicate glass substrate.
<14> The glass hard disk substrate to be polished has an Al content of 3% by mass or more, preferably 5% by mass or more, more preferably 7% by mass or more, and / or 25% by mass or less, preferably 20%. <13> The polishing composition for a glass hard disk substrate according to <13>, wherein the polishing composition is not more than mass%, more preferably not more than 15 mass%, and / or not less than 3 mass% and not more than 25 mass%.
<15> The polishing liquid composition for a glass hard disk substrate according to <13> or <14>, wherein the glass hard disk substrate to be polished has a Si content of 20% by mass to 40% by mass.
<16> A polishing liquid composition containing silica particles is supplied to the surface to be polished of the glass hard disk substrate to be polished, the polishing pad is brought into contact with the surface to be polished, and the polishing pad and / or the substrate to be polished is moved. A method for polishing a glass hard disk substrate, comprising a polishing step, wherein the polishing liquid composition is the polishing liquid composition according to any one of <1> to <15>.
<17> The method for producing a glass hard disk substrate according to <16>, comprising a step of polishing the glass hard disk substrate to be polished using the polishing composition in a circulating manner.
<18> The method for producing a glass hard disk substrate according to <17>, wherein a polishing load in the step of polishing the glass hard disk substrate to be polished using the polishing liquid composition is 3 kPa or more and 20 kPa or less.
<19> The polishing load is 3 kPa or more, preferably 4 kPa or more, more preferably 5 kPa or more, further preferably 6 kPa or more, and / or 40 kPa or less, preferably 30 kPa or less, more preferably 20 kPa or less, and further preferably. Is 15 kPa or less, More preferably, it is 10 kPa or less, The manufacturing method of the glass hard disk substrate as described in <18>.
<20> The polishing liquid composition is supplied at a rate of 1.0 mL / min or less per 1 cm ^{2 of the} substrate to be polished, preferably 0.6 mL / min or less, more preferably 0.4 mL / min or less, and / or From <16> to <0.1 mL / min, preferably 0.025 mL / min or more, more preferably 0.05 mL / min or more, and even more preferably 0.1 mL / min or more per 1 cm ^{2 of the} substrate to be polished. The manufacturing method of the glass hard disk substrate in any one of 19>.
<21> A polishing liquid composition containing silica particles is supplied to the surface to be polished of the glass hard disk substrate to be polished, the polishing pad is brought into contact with the surface to be polished, and the polishing pad and / or the substrate to be polished is moved. A method for polishing a glass hard disk substrate, comprising polishing, wherein the polishing liquid composition is the polishing liquid composition according to any one of <1> to <15>.
<22> The method for polishing a glass hard disk substrate according to <21>, which comprises a step of polishing the glass hard disk substrate to be polished using the polishing composition in a circulating manner.
<23> The polishing load in the step of polishing the glass hard disk substrate to be polished using the polishing liquid composition is 3 kPa or more, preferably 4 kPa or more, more preferably 5 kPa or more, more preferably 6 kPa or more, and The method for polishing a glass hard disk substrate according to <22>, which is / or 40 kPa or less, preferably 30 kPa or less, more preferably 20 kPa or less, still more preferably 15 kPa or less, and even more preferably 10 kPa or less.
<24> The polishing liquid composition is supplied at a rate of 1.0 mL / min or less per 1 cm ^{2 of the} substrate to be polished, preferably 0.6 mL / min or less, more preferably 0.4 mL / min or less, and / or From <21> to <0.1 mL / min per 1 cm ^{2 of the} substrate to be polished, preferably 0.025 mL / min or more, more preferably 0.05 mL / min or more, and even more preferably 0.1 mL / min or more. 23> The method for polishing a glass hard disk substrate according to any one of the above.

  Hereinafter, the present disclosure will be described in more detail by way of examples. However, these examples are illustrative, and the present disclosure is not limited to these examples.

[Examples 1-2 and Comparative Examples 1-10]
1. Preparation of glass hard disk substrate to be polished An aluminosilicate glass substrate (outer diameter 65 mm, inner diameter 20 mm, thickness 0.635 mm) coarsely polished in advance with a polishing composition containing ceria abrasive grains was prepared as a polished glass hard disk substrate. The content of Si contained in the substrate was 27.1% by mass, the content of Al was 8.6% by mass, and measurement was carried out using the ESCA (Electron Spectroscopy for Chemical Analysis) method under the following measurement conditions.

[ESCA (Electron Spectroscopy for Chemical Analysis) measurement conditions]
-Sample preparation The aluminosilicate glass substrate was cut into 1 cm x 1 cm and placed on a carbon double-sided tape and fixed. In order to remove dust on the surface, Ar sputtering was performed at an acceleration voltage of 2 kV for 6 minutes, and the constituent elements were measured.
・ Measurement equipment: PHI Quantera SXM manufactured by ULVAC-PHI
X-ray source: Monochromatic AlKα ray, 1486.6 eV, 25 W, 15 kV
Beam diameter: 100 μm
X-ray incident angle: 45 °
Measurement range: 500 × 500 (μm ² )
Pass energy: 280.0 (survey), 140.0 eV (narrow)
Step size: 1.00 (survey), 0.250 eV (narrow)
Measurement elements: C, N, O, Na, Mg, Al, Si, S, K, Ti, Zr, Nb
Charging correction: Neutralizer and Ar ⁺ irradiation

2. Preparation of polishing liquid composition After adding acid (citric acid 0.1 to 3% by mass) to ion-exchanged water, the following colloidal silica particles (AL) are added so that the total weight of the polishing liquid is 8% by mass. And pH was adjusted to 3.0 and the polishing liquid composition of Examples 1-2 and Comparative Examples 1-10 was obtained. The amount of citric acid added was appropriately adjusted so that the pH after blending was 3.0. The colloidal silica particles in the polishing liquid compositions of Examples 1-2 and Comparative Examples 1-10 are as shown in Table 1. Silica particles A and B, C, and H to L are colloidal silica produced by a build-up method using an alkali silicate aqueous solution as a starting material. In particular, silica particles A, B, and I to L have a silica concentration. Concentration of silica prepared by passing an alkali silicate aqueous solution in which 4 to 9 mass% of SiO ₂ / Na ₂ O (molar ratio) is in the range of 1.0 to 6.5 and an aqueous silicate aqueous solution through a cation exchange resin tower Was obtained through a two-stage build-up process and an aging process using an active silicic acid solution in which 0.1 to 10% by mass and SiO ₂ / Na ₂ O (molar ratio) were in the range of 100 to 10,000. At this time, although the reaction temperature in each of the two stages of the build-up process, the addition amount of the active silicic acid solution, the addition time, the aging temperature in the aging process, and the aging time are appropriately selected, silica particles having a desired shape are obtained. The method for producing silica particles containing secondary aggregates is not limited to these. Silica particles D to G are colloidal silica produced by an alkoxysilane method using alkoxysilane as a starting material.

3. Measuring method The short diameter, the long diameter, the degree of association, and the degree of constriction of colloidal silica particles were measured as follows.

[Measuring method of minor diameter, major diameter and degree of association of silica particles]
A sample containing colloidal silica was observed with a transmission electron microscope “JEM-2000FX” (80 kV, 1 to 50,000 times, manufactured by JEOL Ltd.) according to the instructions attached by the manufacturer, and TEM (Transmission Electron Microscope) was observed. ) Photographed the statue. This photograph is taken into a personal computer as image data by a scanner, and using the analysis software “WinROOF ver. 3.6” (distributor: Mitani Corp.), it is equivalent to the circle of each colloidal silica particle monomer and secondary aggregate. The diameter was measured, and the primary particle diameter or the short diameter and the long diameter were determined. Thus, after calculating | requiring the particle diameter of 1000 silica particles, the average value of these was computed, and this average value was made into the short axis and long axis as described in an Example. The degree of association was calculated from the following formula.
Average degree of association = average minor axis (average primary particle diameter) / average major axis (average secondary particle diameter)

[Method of measuring the degree of squeezing of the silica secondary aggregate]
In the same manner as described above, the projection data and the envelope area of the secondary aggregates were measured using the analysis software “WinROOF ver. 3.6” (seller: Mitani Corp.) for the image data of the taken TEM photograph, and the following formula ( The necking degree was calculated using I). Here, the projected area indicates the actual area of the transmission image of the particle photographed by the transmission electron microscope, and the envelope area indicates the area of the convex hull that connects the convex portions so as to surround the particle photographed by the transmission electron microscope ( (See FIG. 1). In FIG. 1, an area surrounded by a solid line indicates an envelope area, and an area surrounded by a dotted line indicates a projected area. An example of an electron microscope (TEM) observation photograph of silica particles A-J and an example of a transmission image (projected area: black portion) of silica particles are shown in FIG. Thus, after calculating | requiring the constriction degree of 1000 colloidal silica secondary aggregates, these average value D50 was computed.
Necking degree = (envelope area−projected area) / envelope area × 100 (I)

4). Polishing Method Polishing using the polishing composition of Examples 1-2 and Comparative Examples 1-10 was performed under the conditions of the following standard polishing test.
[Polishing conditions]
Polishing tester: "Fast double-sided 9B polishing machine" manufactured by Speedfam
Polishing pad: Suede type (thickness 0.9mm, average hole diameter 30μm)
Polishing liquid composition supply amount: 100 mL / min (supply rate per 1 cm ^{2 of} polishing substrate: about 0.3 mL / min)
Lower platen rotation speed: 32.5 rpm
Polishing load: 8.4 kPa
Carrier: Aramid, thickness 0.45mm
Polishing time: 20 minutes Polished substrate: aluminosilicate glass substrate (outer diameter 65 mm, inner diameter 20 mm, thickness 0.635 mm)
Number of input substrates: 10 rinse conditions: load = 2.0 kPa, time = 2 minutes, ion-exchanged water supply amount = about 2 L / min

The following cyclic polishing test was performed using the polishing composition of Example 2 and Comparative Examples 1 and 2, and the circulating durability of the polishing composition was evaluated [Example 3 and Comparative Examples 11 and 12].
[Circulating polishing conditions]
Polishing liquid amount / batch was fixed at 2L, stored in a tank, put into the polishing machine at a constant flow rate, and then the polishing waste liquid discharged from the polishing machine was recovered again and polished continuously for 20 minutes while returning to the tank. . The initial batch in which the polishing composition was first introduced was called the first cyclic polishing, and this process was repeated 6 times. The first, third and sixth cyclic polishing substrates were washed with water and evaluated.
Polishing tester: "Fast double-sided 9B polishing machine" manufactured by Speedfam
Polishing pad: Suede type (thickness 0.9mm, average hole diameter 30μm)
Polishing liquid composition supply amount: 100 mL / min (supply rate per 1 cm ^{2 of} polishing substrate: about 0.3 mL / min)
Lower platen rotation speed: 32.5 rpm
Polishing load: 8.4 kPa
Carrier: Aramid, thickness 0.45mm
Polishing time: 20 minutes / batch Polished substrate: aluminosilicate glass substrate (outer diameter 65 mm, inner diameter 20 mm, thickness 0.635 mm)
Number of input substrates: 10 rinse conditions: load = 2.0 kPa, time = 2 minutes, ion-exchanged water supply amount = about 2 L / min Circulating polishing number: 6 times polishing liquid amount: 2 L

5. Evaluation Method The polishing rate, surface roughness, and circulation durability were evaluated as follows.

[Measurement method of polishing rate]
The polishing amount per unit time obtained by dividing the weight difference (g) of the substrate before and after polishing by the density of the substrate (2.46 g / cm ³ ), the surface area of the substrate (30.04 cm ² ), and the polishing time (minutes). The polishing rate (μm / min) was calculated. The results are shown in Table 1 below as relative values with Comparative Example 1 taken as 100.

[Measurement method of substrate surface roughness]
After polishing, cleaning and drying the glass substrate to be polished, the surface roughness of the substrate surface was measured by an atomic force microscope (AFM) by the method described below.
Measuring instrument: manufactured by Veeco, DI Nano-Scope III
Mode: non-contact
Scan rate: 1.0 Hz
Scan area: 1 × 1μm
Samples: 512 × 512
Amplitude setpoint, integral gain, proportional gain: optimization evaluation for each measurement: out of the 10 polished substrates described above, 4 were selected at random, and both sides of each substrate were measured using AFM and averaged Was calculated. The results are shown in Table 2 below as relative values with Comparative Example 1 taken as 100.

[Evaluation of circulation durability: Measuring method of polishing rate]
The polishing rate for each substrate of 1,3,6 batches obtained by the above-described cyclic polishing test was calculated. The results are shown in Table 3 below as relative values with the polishing rate of the first batch of Comparative Example 11 as 100. The method for measuring the polishing rate was the same as that described above, and the relative polishing rate 100 was 0.63 mg / min.

  As shown in the said Table 2, the polishing liquid composition of Examples 1-2 showed the grinding | polishing rate and surface roughness which were excellent compared with Comparative Examples 1-10. Moreover, as shown in the said Table 3, the polishing liquid composition of Example 3 suppressed the fall of the grinding | polishing rate compared with the comparative examples 11 and 12, and showed the outstanding circulation durability.

  According to the polishing liquid composition of the present invention, in the polishing process of the glass hard disk substrate, it is possible to realize both higher polishing rate and lower surface roughness than in the past, and to maintain a high polishing rate for a long time in cyclic polishing. For example, a glass substrate with improved substrate quality such as a glass hard disk substrate suitable for increasing the recording density can be efficiently produced. Therefore, the polishing composition of the present invention is useful in the production of a glass hard disk substrate.

Claims (8)

A polishing composition for a glass hard disk substrate containing silica particles, wherein the silica particles satisfy the following conditions 1 to 3.
1) The average primary particle diameter measured by a transmission electron microscope is 10.0 nm or more and 20.0 nm or less.
2) The average degree of association of secondary aggregates measured with a transmission electron microscope is 2.50 or more and 5.00 or less.
3) A secondary aggregate having a squeezing degree (envelope area defect rate) represented by the following formula (I) of 5.0% or more and 10.0% or less of the entire silica particles contained in the polishing composition. It occupies 30% or more.
Necking degree = (envelope area−projected area) / envelope area × 100 (I)
[In the formula (I), the projected area indicates the actual area of the transmission image of the particles photographed by the transmission electron microscope, and the envelope area is the convex hull formed by connecting the convex portions so as to surround the particles photographed by the transmission electron microscope. Indicates area. ] The polishing composition for a glass hard disk substrate according to claim 1, wherein the silica particles are silica particles produced by a build-up method using an alkali silicate aqueous solution as a starting material. The polishing liquid composition for glass hard disk substrates according to claim 1, wherein the glass hard disk substrate to be polished is an aluminosilicate glass substrate. The glass in any one of Claim 1 to 3 in which the said polishing liquid composition contains the acid which is 1 or more types selected from the group which consists of polyhydric carboxylic acid and its salt, or organic phosphonic acid and its salt. Polishing liquid composition for hard disk substrates. A method for producing a glass hard disk substrate, comprising a step of polishing and recycling a glass hard disk substrate to be polished using the polishing composition according to claim 1 in a circulating manner. The method for producing a glass hard disk substrate according to claim 5, wherein a polishing load in the step of polishing the glass hard disk substrate to be polished using the polishing liquid composition is 3 kPa or more and 20 kPa or less. A polishing liquid composition containing silica particles is supplied to the surface to be polished of the glass hard disk substrate to be polished, the polishing pad is brought into contact with the surface to be polished, and the polishing pad and / or the substrate to be polished is moved for polishing. A method for polishing a glass hard disk substrate, comprising: a glass hard disk substrate, wherein the polishing composition satisfies the following conditions 1 to 3.
1) The average primary particle diameter measured by a transmission electron microscope is 10.0 nm or more and 20.0 nm or less.
2) The average degree of association of secondary aggregates measured with a transmission electron microscope is 2.50 or more and 5.00 or less.
3) Secondary aggregates having a squeezing degree (envelope area defect rate) represented by the following formula (I) of 5.0% or more and 10.0% or less occupy 30% or more of the whole particles.
Necking degree = (envelope area−projected area) / envelope area × 100 (I)
[In the formula (I), the projected area indicates the actual area of the transmission image of the particles photographed by the transmission electron microscope, and the envelope area is the convex hull formed by connecting the convex portions so as to surround the particles photographed by the transmission electron microscope. Indicates area. ] The method for polishing a glass hard disk substrate according to claim 7, comprising a step of polishing the glass hard disk substrate to be polished using the polishing composition in a circulating manner.