JPWO2016017819A1 - Polishing slurry preparation method, polishing abrasive grains, polishing slurry, and glass substrate manufacturing method - Google Patents

Abstract

Provided are a polishing slurry preparation method, polishing abrasive grains, and polishing slurry capable of improving the polishing rate and suppressing the generation of scratches on a glass substrate. Moreover, the manufacturing method of the glass substrate using such polishing slurry and abrasive grain is provided. The method for producing a polishing slurry of the present invention is a method for producing a polishing slurry containing abrasive grains for use in a polishing treatment of a glass substrate, and comprises a raw material slurry containing raw abrasive grains that are raw materials for the abrasive grains An addition process for adding a binder to the substrate, a drying process for drying the raw material slurry containing the binder to produce a lump of raw material abrasive grains containing the binder, and firing the lump of the raw material abrasive grains, And a firing process for producing an aggregate of raw material abrasive grains containing the material.

Description

  The present invention relates to a method for producing a polishing slurry, a polishing abrasive grain, a polishing slurry, and a method for producing a glass substrate.

Glass substrates used for magnetic disks, photomasks, or mask blanks that are substrates thereof are generally polished using abrasive grains (hereinafter referred to as cerium-based abrasives) mainly composed of cerium oxide (ceria). Then, finish polishing is performed using colloidal silica. Among these, cerium-based abrasives contain expensive rare earth element oxides, and are therefore collected and reused after use.
The recycling method for reusing the cerium-based abrasive is, for example, removing foreign substances from the used polishing slurry, followed by solid-liquid separation, and drying, firing, crushing, and filtering the solid content. Is done. As a conventional method of reclaiming abrasives, in order to bring the decreased used abrasive polishing rate close to the unused abrasive polishing rate, for example, before solid-liquid separation of used abrasive slurry, acid It is known to perform processing (for example, Patent Document 1).

JP 2007-276055 A

  The cerium-based abrasive is bonded at the grain boundary by firing, and the particle size acting as particles during actual polishing is increased, whereby the polishing rate is improved. However, even if the polishing material is recovered by the method of Patent Document 1 and the polishing rate is recovered to a level close to that of an unused polishing material, the bonding force at the grain boundary is not sufficient, so that it can be reused. As a result, it was found that the material could be crushed and reduced in diameter and the polishing rate could be lowered. Also, if the abrasive is crushed during use and many decomposed particles are generated, the abrasive particle size distribution becomes non-uniform, and the load applied to the abrasive having a large particle size increases, so that the load on the glass substrate is locally increased. It was found that polishing scratches were easily generated on the glass substrate.

  An object of the present invention is to provide a polishing slurry preparation method, polishing abrasive grains, and polishing slurry that can improve the polishing rate and suppress the generation of scratches on a glass substrate. Moreover, an object of this invention is to provide the manufacturing method of the glass substrate using such polishing slurry and polishing abrasive grain.

A first aspect of the present invention is a method for producing a polishing slurry containing abrasive grains for use in polishing a glass substrate,
An addition treatment for adding a binder to a raw material slurry containing raw material abrasive grains as raw materials for the abrasive grains;
Drying the raw material slurry containing the binder to produce a lump of raw material abrasive grains containing the binder; and
A method for producing a polishing slurry, comprising: firing a lump of the raw material abrasive grains to produce an aggregate of raw material abrasive grains containing the binder.

  The binder preferably contains silica particles.

  The average particle size of the binder is preferably 3 to 20 nm.

  The average grain size of the raw material abrasive grains is preferably 0.3-2 μm.

Furthermore, a crushing process for crushing the aggregate of raw material abrasive grains to produce the abrasive grains,
The average particle size of the abrasive grains produced by the crushing treatment is preferably 0.5 to 10 μm.

In the addition treatment, a binder aggregation inhibitor for suppressing aggregation between the binders is further added,
In the drying treatment, it is preferable that the binder is dispersed and disposed in the lump of the raw material abrasive grains via the binder aggregation inhibitor.

  In the baking treatment, it is preferable to burn at least a part of the binder aggregation inhibitor by baking the lump of the raw material abrasive grains.

  The binder aggregation inhibitor is preferably a polysaccharide, and more preferably a polysaccharide that dissolves in water or gels by heating.

  The firing is preferably performed at a temperature of 800 ° C. or lower.

  In the drying process, it is preferable to dry the raw material slurry containing the binder by spray drying.

  The raw slurry preferably contains ceria particles used for the polishing treatment of the glass substrate.

Another aspect of the first aspect is a polishing abrasive grain,
A polishing abrasive used for polishing a glass substrate, wherein silica particles are present as a binder between ceria or zirconia particles in the polishing abrasive.

  The abrasive grains preferably have an average crushing strength measured in accordance with JIS R1639-5 of 0.1 to 20 MPa.

Another aspect of the first aspect is a polishing slurry,
The polishing abrasive grain according to the another aspect is included.

Another aspect of the first aspect is a method of manufacturing a glass substrate,
The surface of the glass substrate is polished using the polishing slurry prepared by the polishing slurry preparation method, the polishing abrasive grains, or the polishing slurry.

A second aspect of the present invention is a method for producing a polishing slurry containing abrasive grains for use in polishing a glass substrate,
An addition treatment for adding a pore-forming agent to a raw material slurry containing raw material abrasive grains used as raw materials for the abrasive grains;
Drying the raw material slurry containing the pore former to produce a lump of raw material abrasive grains containing the pore former; and
Firing a mass of the raw abrasive grains to eliminate at least a part of the pore former, thereby forming a void in the portion of the raw abrasive grain mass where the pore former is located. It is characterized by that.

  The pore-forming agent is preferably a polysaccharide, more preferably a polysaccharide that dissolves in water or gels when heated.

  The average particle size of the pore former in the lump of raw material abrasive grains is preferably 3 to 20 μm.

  The average grain size of the raw material abrasive grains is preferably 0.3-2 μm.

Furthermore, a crushing process for crushing the aggregate of raw material abrasive grains to produce the abrasive grains,
The average particle size of the abrasive grains produced by the crushing treatment is preferably 0.5 to 10 μm.

  In the drying treatment, it is preferable to dry the raw material slurry containing the pore-forming agent by spray drying.

  The raw slurry preferably contains ceria particles used for the polishing treatment of the glass substrate.

In the addition treatment, further, a binder disposed on the surface of the raw material abrasive grains is added,
In the drying treatment, it is preferable that the binder is dispersed and arranged in the lump of the raw material abrasive grains through the pore-forming agent.

  The abrasive grains preferably have an average crushing strength measured in accordance with JIS R1639-5 of 0.1 to 20 MPa.

Another aspect of the second aspect is a method of manufacturing a glass substrate,
The surface of the glass substrate is polished using the polishing slurry prepared by the polishing slurry preparation method.

According to the method for producing a polishing slurry of the present invention, since the raw abrasive grains of the aggregate of raw abrasive grains are bonded together through a binder and the strength of the grain boundary is increased, this aggregate of raw abrasive grains The abrasive grains produced from the above are difficult to break during use. For this reason, it can suppress that a damage | wound generate | occur | produces on a glass substrate with the decomposition | disassembly particle | grains produced | generated by breaking. In addition, the polishing abrasive is produced from a material whose abrasive grains are bonded with a binder to have a large diameter, so that the polishing rate is improved and the high polishing rate can be maintained by being hard to break.
The abrasive grains and polishing slurry of the present invention contain ceria or zirconia particles with a binder on the surface, and the abrasive grains are less likely to break than abrasive grains that do not have a binder, resulting in a decrease in the polishing rate. It can be suppressed.
According to the method for producing a glass substrate of the present invention, a glass substrate can be polished at a high polishing rate and a glass substrate with few scratches can be obtained.

FIG. 1A is a diagram showing a lump of raw material abrasive grains according to the first and second embodiments. FIG.1 (b) is a figure which shows the aggregate | assembly of the raw material abrasive grain of 1st and 2nd embodiment. It is a figure which shows notionally the abrasive grain produced by the production method of the polishing slurry of 1st and 2nd embodiment.

  Hereinafter, a method for producing a polishing slurry, a polishing abrasive, a polishing slurry, and a method for producing a glass substrate of the present invention will be described in detail.

<First Embodiment>
(Preparation method of polishing slurry)
A first embodiment of the present invention will be described.
The method for producing a polishing slurry according to the first embodiment is a method for producing a polishing slurry containing abrasive grains for use in a glass substrate polishing process, and includes an addition process, a drying process, and a firing process. . In the addition process, a binder is added to the raw material slurry containing the raw material abrasive grains used as the raw material of the abrasive grains. In the drying process, the raw material slurry containing the binder is dried to produce a lump of raw material abrasive grains containing the binder. In the firing treatment, a lump of raw material abrasive grains is fired to produce an aggregate of raw material abrasive grains containing a binder.
The raw material slurry is obtained by dispersing raw material abrasive grains using water as a dispersion medium.
The lump of raw material abrasive grains refers to a lump formed by collecting a plurality of raw material abrasive grains, and the lump of raw material abrasive grains comprises raw material abrasive grains, a binder, and a binder aggregation inhibitor that is optionally blended. Have. The lump of the raw material abrasive grains has, for example, a form in which a large number of raw material abrasive grains adhere to the binder aggregation inhibitor containing moisture so as to cover the surface, and the binder is dispersed and arranged between the raw material abrasive grains. Have.
The aggregate of raw material abrasive grains refers to a raw material abrasive grain mass in which raw abrasive grains are joined together by at least a part of the binder (for example, the binder melts and hardens). The aggregate of raw material abrasive grains has raw material abrasive grains and a binder. The aggregate of raw material abrasive grains preferably has holes (voids) formed by the disappearance of at least a part of the binder aggregation inhibitor contained in the bulk of the raw material abrasive grains.
The state after the drying treatment and before the firing treatment is called a lump of raw material abrasive grains, and the state after the firing treatment and before the crushing treatment can be called an aggregate of raw material abrasive grains.

The use of the glass substrate is not particularly limited. For example, it is a panel for various display devices such as a liquid crystal display device; a photomask or a mask blank that is a substrate thereof; and a magnetic disk for an HDD device. The glass substrate polishing process is performed, for example, using a double-side polishing apparatus in a glass substrate manufacturing method described later.
The abrasive grains are not particularly limited, but are cerium-based abrasives or zirconia-based abrasives mainly composed of zirconium oxide (zirconia) in that they can polish glass substrates by chemical action in addition to mechanical action. Is preferably used. The polishing slurry is obtained by dispersing polishing abrasive grains using water as a dispersion medium, and the polishing abrasive grains are used as free abrasive grains in the polishing process. The polishing slurry may contain other components such as, for example, a phosphoric acid dispersant, in addition to the abrasive grains and water. The concentration of the abrasive grains in the polishing slurry is not particularly limited, but is, for example, 1 to 30% by mass, preferably 3 to 20% by mass.

(A) Addition treatment The raw material abrasive is a raw material of the polishing abrasive contained in the polishing slurry produced by the method of the first embodiment, and the polishing abrasive contained in the used polishing slurry described later as the raw abrasive Is used, it means the used abrasive grains. The average grain size of the raw material abrasive grains is preferably 0.3 to 2 μm. By using the raw material abrasive grains having such an average particle diameter, abrasive grains having a size suitable for polishing a glass substrate can be produced. Raw material abrasive grains having a relatively small average particle diameter (for example, less than 0.3 to 0.5 μm) among the raw material abrasive grains in the range of 0.3 to 2.0 μm are difficult to be recovered by solid-liquid separation. Moreover, even if it was able to be recovered, it was found that those regenerated by the conventional method are reduced in diameter in the polishing process to lower the polishing rate or cause scratches on the glass substrate. According to the production method of the first embodiment, as will be described later, since abrasive grains having an appropriate hardness (crushing strength) are produced, a polishing slurry having a relatively small average particle diameter as raw material grains is used. It is suitable for manufacturing. The raw material abrasive grains are secondary particles obtained by agglomerating several to several tens of primary particles, and the average particle diameter of the raw material abrasive grains means the average particle diameter of the secondary particles. Note that secondary particles act as particles of one abrasive grain during actual polishing. Moreover, in this specification, an average particle diameter means a median diameter (d50). d50 is a particle diameter corresponding to a cumulative particle diameter of 50% from the fine particle side, for example, by a laser diffraction / scattering particle size distribution measurement method.
The raw material slurry may be unused or a used polishing slurry. In this specification, “used” means that the glass substrate has been used at least once for polishing the glass substrate. When the polishing slurry is prepared using the used polishing slurry, the used polishing abrasive grains can be recycled, and the cost of the polishing slurry can be suppressed. In the present specification, when the used polishing slurry is used as the raw material slurry, the method for preparing the polishing slurry of this embodiment can be referred to as a used polishing slurry regeneration method, and the polishing slurry mainly contains ceria particles. When a cerium-based abrasive as a component is included, it can be said that the used ceria slurry is regenerated.
Moreover, the used polishing slurry used as the raw material abrasive may be regenerated by a method for regenerating the used polishing slurry. In this case, the cost of the polishing slurry can be further reduced by repeatedly regenerating and using the used polishing slurry.

A binder melt | dissolves in the case of a baking process, and can increase the intensity | strength of a grain boundary by joining raw material abrasive grains. In addition, a grain boundary means the boundary between adjacent raw material abrasive grains. This increases the secondary particle diameter of the abrasive grains (the particle diameter of particles that act as one abrasive grain during polishing), thereby improving the polishing rate of the abrasive grains and polishing treatment. It is difficult to crush and can maintain a high polishing rate. On the other hand, when the raw material abrasive grains are bonded to each other through the binder, the strength of the grain boundary is not too strong compared to the case where the raw material abrasive grains are directly bonded to each other. Can be suppressed.
Further, if the particles are easily crushed during the polishing process, the proportion of small particles increases, and a large polishing load is applied to the relatively small particles, so that polishing scratches are likely to occur. Therefore, it is possible to suppress the occurrence of polishing scratches by bonding the abrasive grains with the binder.
On the other hand, aggregates of raw material abrasive grains containing a binder can be easily crushed by ultrasonic irradiation, etc., because the grain boundary strength is not too strong, and the particle size distribution with an appropriate size for the polishing process Can obtain uniform abrasive grains. For this reason, it is not necessary to crush by costly pulverization or the like, and it is not necessary to classify, so that abrasive grains can be easily produced at low cost.

  Specifically, a binder that does not disappear in the firing process is used. In this respect, the binder decomposition temperature is preferably a temperature that exceeds the firing temperature in the firing step. Therefore, it is preferably not organic. This is because the organic binder disappears in the firing step. The binder is preferably particles made of an inorganic compound. Among them, oxides such as silicon dioxide (silica) and titanium oxide (titania), and hydrates thereof are preferable because of excellent dispersibility in the raw material slurry. Particles made of glass such as aluminosilicate, and hydroxides such as cerium hydroxide, silicon hydroxide, and zirconia hydroxide are preferable. Among them, since silica melts at a relatively low temperature (for example, 800 ° C. or less) and joins the raw material abrasive grains, even if the firing temperature during the firing process is such a low temperature, the grain boundaries of the raw material abrasive grains Strength can be increased. Silica exists as a hydrate in the slurry, and it is considered that the raw material abrasive grains are bonded together by being dehydrated during the baking treatment to become silica anhydrous. In addition, a grain boundary means the boundary between adjacent raw material abrasive grains. Examples of the silica include colloidal silica and fumed silica, and colloidal silica is preferably used in terms of more excellent dispersibility. In addition, when silica and glass melt | dissolve and it joins raw material abrasive grains, it is also considered that one part forms the vitrified bond.

  The average particle size of the binder is preferably 3 to 20 nm. The binder having such an average particle size is sufficiently small with respect to the raw material abrasive grains, and is easily dispersed and arranged between the raw material abrasive grains in the drying process and firing process, and is a good binder for joining the raw abrasive grains. To work. When the average particle size of the binder is less than 3 nm, the bonding between the raw material abrasive grains may be insufficient. When the average particle size is greater than 20 nm, the binder is bonded to become coarse particles, which may cause polishing scratches. The average particle size of the binder can be measured using a laser diffraction particle size distribution measuring device.

The binder is preferably used abrasive grains used in the second polishing process of the glass substrate manufacturing method described later. For example, colloidal silica is usually discarded after use as used abrasive grains. By using this as a binder, raw material costs are not required, and a polishing slurry can be produced at low cost. Further, since the recovered used polishing slurry can be added to the raw material slurry as it is, the workability is excellent.
The addition amount of the binder is preferably 1 to 10 parts by mass, and more preferably 1 to 5 parts by mass with respect to 100 parts by mass of the raw material abrasive grains. If the amount is less than 1 part by mass, the effect of the binder cannot be obtained sufficiently, and the abrasive grains can be easily broken, and the polishing rate may decrease. On the other hand, when the amount is more than 10 parts by mass, coarse particles that cause the binder to aggregate and cause scratches on the glass substrate may be generated. On the other hand, when the amount is more than 10 parts by mass, an excessive amount of binder adheres to the surface of the ceria polishing abrasive grains, so that the polishing function by the abrasive grain surface is lowered and the polishing rate may be lowered. In particular, when the polishing abrasive is a cerium-based abrasive, it is said that the glass substrate exhibits a chemical action and has a high polishing rate, so if the surface is excessively covered with a substance other than ceria, The contact area becomes smaller and the polishing rate decreases.

  In the addition treatment, it is preferable to further add a binder aggregation inhibitor for suppressing aggregation between the binders. When the binder aggregation inhibitor is present in the raw material slurry, the aggregation between the binders is suppressed, and the binder is easily dispersed and disposed between the raw material abrasive grains. In particular, silica is likely to agglomerate in water as the particle size becomes smaller, and may become coarse silica particles that cause scratches on the glass substrate. Can be suppressed. In particular, when the average particle size of silica is 3 to 20 nm, it is preferable to add a binder aggregation inhibitor.

  The binder aggregation inhibitor is preferably one having a high affinity with the binder, and examples of such a substance include those having a hydroxyl group on the surface. Specific examples include polysaccharides. More preferably, it is a polysaccharide that dissolves in water or gels by heating (hereinafter also referred to as the polysaccharide in the present embodiment). Since such a polysaccharide is in a state where the binder easily adheres in the process of being dried in the drying process, the binder is dispersed and arranged between the raw material abrasive grains while suppressing the aggregation of the binders. Has a function to help. This function is considered to be performed by positioning the binder with respect to the raw material abrasive grains by capturing the binder with the water-containing polysaccharide.

  The temperature at which the polysaccharide is dissolved in water or gelled is not particularly limited. For example, at the drying temperature in the drying process, the polysaccharide is preferably dissolved in water or gelled. Since the polysaccharide contains water in the drying treatment, the raw material abrasive grains easily adhere to the surface. Moreover, the polysaccharide can be easily eliminated by baking at a relatively low temperature. In this respect, the decomposition temperature of the binder aggregation inhibitor is preferably 600 ° C. or lower, more preferably 500 ° C. or lower. In addition, since at least a part of the polysaccharide disappears in the baking treatment, the portion that was present in the lump of raw material abrasive grains becomes pores (voids) in the aggregate of raw material abrasive grains. The assembly can be made porous. In this respect, the binder aggregation inhibitor can be referred to as a pore-forming agent.

  Specifically, starch, glycogen, agarose, pectin, or a combination thereof is preferably used as the polysaccharide. Examples of the starch include corn starch, wheat flour, starch, rice starch and the like, and the raw materials thereof are not particularly limited, and cereals such as corn, wheat, rice, potato, and sweet potato are used.

The addition amount of the binder aggregation inhibitor is preferably 10 to 100 parts by mass, and more preferably 10 to 50 parts by mass with respect to 100 parts by mass of the raw material abrasive grains. If it is less than 10 parts by mass, there are cases where pores are not sufficiently formed in the aggregate of raw material abrasive grains and it is difficult to disintegrate. On the other hand, when the amount is more than 100 parts by mass, the effect of the binder is hindered and the polishing abrasive grains (raw material abrasive grains) are not sufficiently increased, and the effect of improving the polishing rate by granulation may not be obtained.
The binder aggregation inhibitor is added to the raw material slurry in a state of being dispersed in a solvent such as water.

In addition, when using a used polishing slurry as a raw material abrasive grain, it is preferable to perform filtering, solid-liquid separation, and crushing with respect to a used polishing slurry beforehand before an addition process. In the filtering, a coarse particle (for example, 15 μm or more) is removed. In the solid-liquid separation, glass components such as glass sludge contained in the collected used polishing slurry are removed. In crushing, for example, the solid content generated by solid-liquid separation is crushed by ultrasonic irradiation using a homogenizer. In order to facilitate this crushing, a hard cake inhibitor (for example, a water-insoluble polysaccharide) that prevents the solid content from becoming too hard is added to the used polishing slurry before solid-liquid separation. It may be left.
Further, after solid-liquid separation, the residual liquid which is a supernatant liquid is further subjected to solid-liquid separation, and a solid obtained by pulverization may be used as a raw material slurry. Thereby, used abrasive grains having a small average particle diameter (for example, 0.3 to 2 μm) that were not collected by the first solid-liquid separation are collected and used as raw abrasive grains to regenerate the abrasive grains. Can do. When the solid-liquid separation is performed a plurality of times as described above, the recovery rate of expensive abrasive grains such as a cerium-based abrasive can be increased, and the cost reduction effect of the polishing slurry is increased. In this case, the solid content having a large average particle size (for example, 0.5 to 5 μm) obtained by the first solid-liquid separation is separately crushed after water injection, and further filtered, and then the glass substrate. During the polishing process, it may be circulated for use, stored in a tank for storing the polishing slurry, or may be regenerated using the polishing slurry preparation method of this embodiment.

(B) Drying treatment In the drying treatment, it is preferable to dry the raw material slurry containing the binder by spray drying. By performing spray drying, the size of the lump of the raw material abrasive grains can be controlled. The spray drying method is preferable because the average particle size can be reduced as compared with other methods, and the variation in particle size can be reduced. Specifically, the spray drying can be performed by spraying using a known spraying means such as a rotating disk type, a two-fluid nozzle type, a pressure nozzle type, etc., and supplying and drying the spray dryer. . Conditions such as the type of spraying means, the nozzle hole diameter, and the supply pressure of the raw slurry are appropriately set according to the target size of the raw material abrasive grains. The size (average particle size) of the raw material abrasive grains obtained by spray drying is preferably about 5 to 10 μm, for example. If it is larger than 10 μm, coarse particles may remain after crushing and cause polishing scratches. On the other hand, if it is less than 5 μm, the proportion of small particles increases and the polishing rate may be lowered. Here, the average particle diameter is a value obtained by determining the long diameter of each lump of the above-mentioned raw material abrasive grains selected at random in SEM observation and averaging them.
Moreover, when adding a pore making material to the raw material slurry before spray drying, it is preferable that the size of the pore forming agent (average particle diameter of the pore forming agent) is 3 to 20 μm. When the pore-forming agent is in such a size range, the size of the crushed abrasive grains is set to an appropriate size by setting the size of the pores in the aggregate of the raw material abrasive grains after firing. (For example, an average particle diameter of 0.5 to 10 μm). As for drying temperature (atmosphere temperature in a drying chamber), the inlet temperature of a drying chamber is 150-250 degreeC, for example. Note that the drying process may be performed without heating.
Here, FIG. 1A shows a lump of raw material abrasive grains produced by a drying process. Here, a spherical lump of raw material abrasive grains produced by drying a raw material slurry containing a binder aggregation inhibitor is shown as an example. The lump 10 of raw material abrasive grains is formed by adhering a large number of raw material abrasive grains 3 so as to cover the surface of the binder aggregation inhibitor 7 containing moisture, and a binder (not shown) is interposed between the raw material abrasive grains 3. Distributed. The lump of raw material abrasive grains 10 includes a large number of raw material abrasive grains 3, but in FIG. 1A, the boundaries of the large number of raw material abrasive grains 3 are not shown for convenience. .

(C) Firing process Although the apparatus which performs a baking process is not restrict | limited in particular, For example, a muffle furnace is mentioned. The firing temperature in the firing treatment is preferably 800 ° C. or lower. The firing temperature is the atmospheric temperature in the space where firing is performed. By setting the firing temperature to 800 ° C. or less, the energy cost for producing the polishing slurry can be reduced. When the firing temperature exceeds 800 ° C., bonding at the grain boundaries between the raw abrasive grains proceeds, and the grain boundary strength of the abrasive grains may become too high. In addition, the binders may be combined to form coarse particles. In these cases, the glass substrate is easily damaged. On the other hand, when the firing temperature exceeds 800 ° C., the composition of the raw material abrasive grains changes, the hardness increases, and the glass substrate may be damaged. Moreover, the firing temperature in the firing treatment is preferably 500 ° C. or higher, more preferably 600 ° C. or higher. When the temperature is lower than 500 ° C., the bonding between the raw material abrasive grains may be insufficient.

In the firing treatment, when a binder aggregation inhibitor is added to the raw slurry, it is preferable to eliminate at least a part of the binder aggregation inhibitor by firing. As a result, the portion where the binder aggregation inhibitor is disposed in the lump of raw material abrasive grains becomes pores, and a porous aggregate of raw material abrasive grains is produced.
Here, FIG. 1B shows an aggregate of raw material abrasive grains produced by a firing process. Here, an aggregate of raw material abrasive grains produced by drying and firing a raw material slurry containing a binder aggregation inhibitor is shown as an example. The aggregate 20 of raw material abrasive grains has pores 9 formed by eliminating the binder aggregation inhibitor. The aggregate of the raw material abrasive grains is the raw material abrasive grains formed by the disappearance of the binder aggregation inhibitor disposed between the raw material abrasive grains surrounding the holes 9 in addition to the illustrated holes 9. It is porous by having a large number of minute voids between them. The size (average particle diameter) of the aggregate 20 of raw material abrasive grains is preferably about 5 to 10 μm, for example. If it is larger than 10 μm, coarse particles may remain after crushing and cause polishing scratches. On the other hand, if it is less than 5 μm, the proportion of small particles increases and the polishing rate may be lowered. Here, the average particle diameter is a value obtained by determining the long diameter of each lump of the above-mentioned raw material abrasive grains selected at random in SEM observation and averaging them. In the aggregate 20 of raw material abrasive grains, a binder (not shown) is melted in the firing process, and then the raw material abrasive grains 3 are joined together when they are solidified, so that the strength of the grain boundaries of the raw material abrasive grains 3 is moderate (for example, The average value of the crushing strength described later is 0.1 to 20 MPa). The aggregate 20 of raw material abrasive grains includes a large number of raw material abrasive grains 3, but in FIG. 1B, the boundaries of the large number of raw material abrasive grains 3 are not shown for convenience. Yes. The presence of a binder between the raw material abrasive grains 3 can be confirmed by element mapping using, for example, EDX (Energy Dispersive X-ray microanalyzer).

(D) Crushing treatment It is preferable that the method for producing a polishing slurry of the first embodiment further includes a crushing treatment for crushing an aggregate of raw material abrasive grains to produce abrasive grains. Thereby, polishing abrasive grains having a size suitable for the polishing process can be obtained. When pores are formed in the aggregate of raw material abrasive grains, it is easier to crush.
The crushing is performed by irradiating the aggregate of raw material abrasive grains with ultrasonic waves using, for example, a homogenizer. The frequency of the ultrasonic wave is preferably 16 to 120 kHz. The crushing may be performed using means other than the homogenizer. The crushing time is not particularly limited, but is, for example, 1 to 20 minutes.
The pulverization is preferably performed so that the average particle size of the abrasive grains is 0.5 to 10 μm. More preferably, they are 0.5-5 micrometers and 0.7-3 micrometers. When the polishing treatment is performed using such abrasive grains having an average particle diameter, polishing can be performed at a high polishing rate, and generation of scratches on the surface of the glass substrate can be suppressed.
The crushing treatment may be performed by a milling method in which physical destruction is performed using a ball mill or the like, but the ultrasonic method described above is more convenient.

  A grinding | polishing slurry can be produced by disperse | distributing grinding | polishing abrasive grain in water after a crushing process. At this time, it is preferable to remove particles of coarse size (for example, 15 μm or more) by filtering before water injection. The coarse-sized particles here are a part of an aggregate of raw material abrasive grains that have not been crushed to a predetermined size by the pulverization treatment.

According to the method for producing a polishing slurry of the first embodiment, an aggregate of raw material abrasive grains containing a binder can be produced by adding a binder to the raw material slurry, and drying and firing it. This aggregate of raw material abrasive grains has a portion where the raw material abrasive grains are joined with a binder interposed therebetween, so that the strength of the grain boundary is too strong compared to the case where the raw abrasive grains are joined directly. There is no. For this reason, it can be easily crushed by ultrasonic irradiation or the like, and abrasive grains having a size suitable for polishing treatment and a uniform particle size distribution can be obtained. As described above, according to the method of the first embodiment, it is not necessary to perform costly pulverization or the like, and it is not necessary to classify, so that abrasive grains can be easily produced at low cost. The polishing rate is improved because the raw abrasive grains have a larger diameter. Moreover, since the abrasive grains produced by the method of the first embodiment are bonded to each other through the binder, the grain boundaries are not too strong, so that the glass substrate is damaged. Can be suppressed. On the other hand, the polishing abrasive produced by the method of the first embodiment is improved in the polishing rate because the raw material abrasive grains are bonded to each other through a binder and the secondary particle diameter is increased. In addition, since the strength of the grain boundary is increased, it is difficult to break in the polishing process, and a high polishing rate can be maintained.
In addition, the polishing abrasives produced by the method of the first embodiment are improved in the polishing rate because the raw material abrasives are bonded to each other via a binder to increase the diameter, and appropriate grain boundaries are formed. Since it has strength, it is difficult to break during use, and a high polishing rate is maintained.

(Polishing abrasive grains and polishing slurry)
FIG. 2 conceptually shows the polishing abrasive grain 1 of the first embodiment.
The polishing abrasive grain 1 includes a raw material abrasive grain 3 containing ceria or zirconia particles and a binder 5 disposed on the surface of the raw abrasive grain 3, which are used for a polishing process of a glass substrate. More specifically, the abrasive grains 1 are abrasive grains used for polishing a glass substrate, and silica particles are present as a binder 5 between ceria or zirconia particles.
As shown in FIG. 1, a large number of raw material abrasive grains 3 are included in each of raw material abrasive grain lump 10 and raw material abrasive grain aggregate 20.
The raw material abrasive 3 is the same as the cerium-based abrasive or zirconia-based abrasive among the above-described raw material abrasive. In addition to ceria, cerium-based abrasives are oxides of other rare earth elements such as lanthanum, praseodymium, neodymium, and their fluorides in order to suppress the occurrence of scratches on the glass substrate while achieving a high polishing rate. It is preferable that it is a mixture containing at least one of the above. The zirconia-based abrasive may be a mixture containing silicon dioxide in addition to zirconia.
The average particle diameter of the raw material abrasive grains 3 is, for example, 0.3 to 2 μm, and for example, particles having a primary particle diameter of about 80 to 150 nm are aggregated.
The binder 5 is the same as the binder described above. In FIG. 2, the binder 5 is disposed on the surface of the raw material abrasive grain 3 that is a secondary particle, but may be disposed on the surface of the primary particle constituting the raw material abrasive grain 3. The binder 5 preferably covers less than 50% of the surface area of the surface of the raw abrasive 3. If it is 50% or more, the contact surface between the surface of the abrasive grains and the substrate to be polished becomes small, and the polishing rate tends to decrease.

As for abrasive grain 1, it is preferred that the average value of crushing strength measured according to JIS R1639-5 is 0.1-20 MPa. When the average value of the crushing strength is 0.1 MPa or more, it is possible to prevent the abrasive grains from being easily broken and reduced in diameter in the polishing process, thereby suppressing a decrease in the polishing rate. In addition, since the crushing strength varies widely, it is preferable to measure 20 points or more. From the viewpoint of more reliably suppressing the decrease in the polishing rate, the average value of the crushing strength is more preferably 3 MPa or more. Moreover, it can suppress generating a damage | wound on the glass substrate surface in a grinding | polishing process because the average value of crushing strength is 20 Mpa or less.
The average particle diameter of the abrasive grains 1 is, for example, 0.5 to 10 μm. The number of the raw material abrasive grains 3 included in the abrasive grains 1 is not particularly limited, and is, for example, several to a dozen.

The polishing slurry of the first embodiment includes the polishing abrasive grain 1 and a dispersion medium such as water in which the polishing abrasive grain 1 is dispersed.
The abrasive grains and the polishing slurry of the first embodiment are produced, for example, by the above-described method for producing an abrasive slurry.

<Second Embodiment>
(Preparation method of polishing slurry)
Next, a second embodiment of the present invention will be described.
The method for producing a polishing slurry according to the second embodiment is a method for producing a polishing slurry containing abrasive grains for use in a glass substrate polishing process, and includes an addition process, a drying process, and a firing process. . In the addition treatment, a pore forming agent is added to the raw material slurry containing the raw material abrasive grains that are the raw materials of the abrasive grains. In the drying process, the raw material slurry containing the pore forming agent is dried to produce a lump of raw material abrasive grains containing the pore forming agent. In the firing treatment, the abrasive lump is fired to eliminate at least a part of the pore-forming agent, thereby forming a hole in the raw material abrasive particle portion where the pore-forming agent is located.
The raw material slurry is obtained by dispersing raw material abrasive grains using water as a dispersion medium.
The lump of raw material abrasive grains refers to a lump formed by collecting a plurality of raw material abrasive grains, and the lump of raw material abrasive grains has raw material abrasive grains, a pore former, and a binder that is optionally blended. doing. The lump of raw material abrasive grains has, for example, a form in which a large number of raw material abrasive grains adhere to a pore-forming agent containing moisture so as to cover the surface thereof. It is preferable that a binder is dispersed and disposed between the raw material abrasive grains.
The aggregate of raw material abrasive grains refers to a material in which pores (voids) are formed by eliminating at least a part of the pore forming agent in the lump of raw material abrasive grains. The aggregate of raw material abrasive grains has raw material abrasive grains and an arbitrarily blended binder. In the aggregate of raw material abrasive grains, it is preferable that the raw material abrasive grains are bonded to each other by a binder (for example, the binder melts and hardens).
The state after the drying treatment and before the firing treatment is called a lump of raw material abrasive grains, and the state after the firing treatment and before the crushing treatment can be called an aggregate of raw material abrasive grains.

The cerium-based abrasive is bonded at the grain boundary by firing, and the particle size acting as particles during actual polishing is increased, whereby the polishing rate is improved. However, the abrasive that has been enlarged by firing is generally pulverized in order to adjust the size to a size suitable for the polishing process. However, grinding the abrasive is costly and labor intensive. Moreover, since the particle size distribution of the abrasive tends to be non-uniform when pulverized, it is necessary to classify after pulverization, which also requires cost and labor. For this reason, the second embodiment aims to provide a method for producing a polishing slurry with an improved polishing rate at low cost and with ease. Moreover, 2nd Embodiment aims at providing the manufacturing method of the glass substrate using such polishing slurry.
According to the method for producing a polishing slurry of the second embodiment, by using a pore-forming agent, an aggregate of raw abrasive grains in which holes (voids) are formed and which is easily crushed is produced. For this reason, the aggregate of raw material abrasive grains can be crushed by a simple method, and a polishing slurry can be easily produced at low cost. Moreover, since the abrasive grains are those obtained by increasing the diameter of the raw abrasive grains through drying and firing, the polishing rate is improved. Moreover, according to the method for producing a glass substrate of the second embodiment, the glass substrate can be polished at a high polishing rate.

The use of the glass substrate is not particularly limited. For example, it is a panel for various display devices such as a liquid crystal display device; a photomask or a mask blank that is a substrate thereof; and a magnetic disk for an HDD device. The glass substrate polishing process is performed, for example, using a double-side polishing apparatus in a glass substrate manufacturing method described later.
The abrasive grains are not particularly limited, but are cerium-based abrasives or zirconia-based abrasives mainly composed of zirconium oxide (zirconia) in that they can polish glass substrates by chemical action in addition to mechanical action. Is preferably used. The polishing slurry is obtained by dispersing polishing abrasive grains using water as a dispersion medium, and the polishing abrasive grains are used as free abrasive grains in the polishing process. The polishing slurry may contain other components such as, for example, a phosphoric acid dispersant, in addition to the abrasive grains and water. The concentration of the abrasive grains in the polishing slurry is not particularly limited, but is, for example, 1 to 30% by mass, preferably 3 to 20% by mass.

(A) Addition treatment The raw material abrasive is a raw material of the polishing abrasive contained in the polishing slurry produced by the method of the second embodiment, and when a used polishing slurry described later is used as the raw abrasive, The used abrasive grain is meant. The average grain size of the raw material abrasive grains is preferably 0.3 to 2 μm. By using the raw material abrasive grains having such an average particle diameter, abrasive grains having a size suitable for polishing a glass substrate can be produced. Raw material abrasive grains having a relatively small average particle diameter (for example, less than 0.3 to 0.5 μm) among the raw material abrasive grains in the range of 0.3 to 2.0 μm are difficult to be recovered by solid-liquid separation. Moreover, even if it was able to be recovered, it was found that those regenerated by the conventional method are reduced in diameter in the polishing process to lower the polishing rate or cause scratches on the glass substrate. According to the production method of the second embodiment, as will be described later, abrasive grains having an appropriate hardness (crushing strength) are produced. It is suitable for manufacturing. The raw material abrasive grains are secondary particles obtained by agglomerating several to several tens of primary particles, and the average particle diameter of the raw material abrasive grains means the average particle diameter of the secondary particles. Note that secondary particles act as particles of one abrasive grain during actual polishing. Moreover, in this specification, an average particle diameter means a median diameter (d50). d50 is a particle diameter corresponding to a cumulative particle diameter of 50% from the fine particle side, for example, by a laser diffraction / scattering particle size distribution measurement method.
The raw abrasive grains may be unused or used polishing slurry. In this specification, “used” means that the glass substrate has been used at least once for polishing the glass substrate. When the polishing slurry is prepared using the used polishing slurry, the used polishing abrasive grains can be recycled, and the cost of the polishing slurry can be suppressed. In the present specification, when the used polishing slurry is used as the raw material slurry, the method for preparing the polishing slurry of this embodiment can be referred to as a used polishing slurry regeneration method, and the polishing slurry mainly contains ceria particles. When a cerium-based abrasive as a component is included, it can be said that the used ceria slurry is regenerated.
Moreover, the used polishing slurry used as the raw material abrasive may be regenerated by a method for regenerating the used polishing slurry. In this case, the cost of the polishing slurry can be further reduced by repeatedly regenerating and using the used polishing slurry.

The pore-forming agent is preferably an organic compound having a hydroxyl group on the surface. As such a substance, for example, a polysaccharide can be mentioned, and preferably a polysaccharide (hereinafter referred to as a polysaccharide) that dissolves in water or gels by heating. In the present embodiment, it is also referred to as the above polysaccharide). In the above-mentioned polysaccharide, the raw material abrasive grains can adhere to the surface in a state of containing water in the drying treatment, and at least a part of the raw material abrasive particles disappears by firing in the firing treatment. Since the portion which has been positioned becomes a void in the aggregate of raw material abrasive grains, a porous aggregate of raw material abrasive grains can be produced. The temperature at which the polysaccharide is dissolved in water or gelled is not particularly limited. For example, at the drying temperature in the drying process, the polysaccharide is preferably dissolved in water or gelled. The decomposition temperature of the pore-forming agent is preferably 600 ° C. or less, more preferably 500 ° C. or less, because it can be easily eliminated by firing at a relatively low temperature.
In addition, when the binder described later is added to the raw material slurry, the polysaccharide is in a state where the binder easily adheres in the process of being dried in the drying process. It has a function of helping to disperse and arrange the raw material abrasive grains. This function is considered to be performed by positioning the binder with respect to the raw material abrasive grains by capturing the binder with the water-containing polysaccharide. In this respect, the pore-forming agent can be referred to as a binder aggregation inhibitor.

  Specifically, starch, glycogen, agarose, pectin, or a combination thereof is preferably used as the polysaccharide. Examples of the starch include corn starch, wheat flour, starch, rice starch and the like, and the raw materials thereof are not particularly limited, and cereals such as corn, wheat, rice, potato, and sweet potato are used.

The amount of pore-forming agent added is preferably 10 to 100 parts by mass and more preferably 10 to 50 parts by mass with respect to 100 parts by mass of the raw material abrasive grains. If it is less than 10 parts by mass, there are cases where pores are not sufficiently formed in the aggregate of raw material abrasive grains and it is difficult to disintegrate. On the other hand, when the amount is more than 100 parts by mass, the effect of the binder is hindered and the polishing abrasive grains (raw material abrasive grains) are not sufficiently increased, and the effect of improving the polishing rate by granulation may not be obtained.
For example, the pore-forming agent is added to the raw material slurry in a state of being dispersed in a solvent such as water.

In the addition treatment, it is preferable to further add a binder disposed on the surface of the raw material abrasive grains. A binder melt | dissolves in the case of a baking process, and can increase the intensity | strength of a grain boundary by joining raw material abrasive grains. In addition, a grain boundary means the boundary between adjacent raw material abrasive grains. This increases the secondary particle diameter of the abrasive grains (the particle diameter of particles that act as one abrasive grain during polishing), thereby improving the polishing rate of the abrasive grains and polishing treatment. It is difficult to crush and can maintain a high polishing rate. On the other hand, when the raw material abrasive grains are bonded to each other through the binder, the strength of the grain boundary is not too strong compared to the case where the raw material abrasive grains are directly bonded to each other. Can be suppressed.
Further, if the particles are easily crushed during the polishing process, the proportion of small particles increases, and a large polishing load is applied to the relatively small particles, so that polishing scratches are likely to occur. Therefore, it is possible to suppress the occurrence of polishing scratches by bonding the abrasive grains with the binder.
On the other hand, aggregates of raw material abrasive grains containing a binder can be easily crushed by ultrasonic irradiation, etc., because the grain boundary strength is not too strong, and the particle size distribution with an appropriate size for the polishing process Can obtain uniform abrasive grains. For this reason, it is not necessary to crush by costly pulverization or the like, and it is not necessary to classify, so that abrasive grains can be easily produced at low cost.

  Specifically, a binder that does not disappear in the firing process is used. In this respect, the binder decomposition temperature is preferably a temperature that exceeds the firing temperature in the firing step. Therefore, it is preferably not organic. This is because the organic binder disappears in the firing step. The binder is preferably particles made of an inorganic compound. Among them, oxides such as silicon dioxide (silica) and titanium oxide (titania), and hydrates thereof are preferable because of excellent dispersibility in the raw material slurry. Particles made of glass such as aluminosilicate, and hydroxides such as cerium hydroxide, silicon hydroxide, and zirconia hydroxide are preferable. Among them, since silica melts at a relatively low temperature (for example, 800 ° C. or less) and joins the raw material abrasive grains, even if the firing temperature during the firing process is such a low temperature, the grain boundaries of the raw material abrasive grains Strength can be increased. Silica exists as a hydrate in the slurry, and it is considered that the raw material abrasive grains are bonded together by being dehydrated during the baking treatment to become silica anhydrous. Examples of the silica include colloidal silica and fumed silica, and colloidal silica is preferably used in terms of more excellent dispersibility. In addition, when silica and glass melt | dissolve and it joins raw material abrasive grains, it is also considered that one part forms the vitrified bond.

  The binder has a property of easily agglomerating. However, the presence of the pore forming agent in the raw material slurry suppresses the aggregation of the binders, and the binder is easily distributed and distributed between the raw material abrasive grains. In particular, silica is prone to agglomerate in water and may result in coarse silica particles that cause scratches on the glass substrate. However, the addition of a pore-forming agent can suppress such agglomeration of silica particles. it can.

  The average particle size of the binder is preferably 3 to 20 nm. The binder having such an average particle size is sufficiently small with respect to the raw material abrasive grains, and is easily dispersed and arranged between the raw material abrasive grains in the drying process and firing process, and is a good binder for joining the raw abrasive grains. To work. When the average particle size of the binder is less than 3 nm, the bonding between the raw material abrasive grains may be insufficient. When the average particle size is greater than 20 nm, the binder is bonded to become coarse particles, which may cause polishing scratches. The average particle size of the binder can be measured using a laser diffraction particle size distribution measuring device.

The binder is preferably used abrasive grains used in the second polishing process of the glass substrate manufacturing method described later. For example, colloidal silica is usually discarded after use as used abrasive grains. By using this as a binder, raw material costs are not required, and a polishing slurry can be produced at low cost. Further, since the recovered used polishing slurry can be added to the raw material slurry as it is, the workability is excellent.
The addition amount of the binder is preferably 1 to 10 parts by mass, and more preferably 1 to 5 parts by mass with respect to 100 parts by mass of the raw material abrasive grains. If the amount is less than 1 part by mass, the effect of the binder cannot be obtained sufficiently, and the abrasive grains can be easily broken, and the polishing rate may decrease. On the other hand, when the amount is more than 10 parts by mass, coarse particles that cause the binder to aggregate and cause scratches on the glass substrate may be generated. On the other hand, when the amount is more than 10 parts by mass, an excessive amount of binder adheres to the surface of the ceria polishing abrasive grains, so that the polishing function by the abrasive grain surface is lowered and the polishing rate may be lowered. In particular, when the polishing abrasive is a cerium-based abrasive, it is said that the glass substrate exhibits a chemical action and has a high polishing rate, so if the surface is excessively covered with a substance other than ceria, The contact area becomes smaller and the polishing rate decreases.

In addition, when using a used polishing slurry as a raw material abrasive grain, it is preferable to perform filtering, solid-liquid separation, and crushing with respect to a used polishing slurry beforehand before an addition process. In the filtering, a coarse particle (for example, 15 μm or more) is removed. In the solid-liquid separation, glass components such as glass sludge contained in the collected used polishing slurry are removed. In crushing, for example, the solid content generated by solid-liquid separation is crushed by ultrasonic irradiation using a homogenizer. In order to facilitate this crushing, a hard cake inhibitor (for example, a water-insoluble polysaccharide) that prevents the solid content from becoming too hard is added to the used polishing slurry before solid-liquid separation. It may be left.
Further, after solid-liquid separation, the residual liquid which is a supernatant liquid is further subjected to solid-liquid separation, and a solid obtained by pulverization may be used as a raw material slurry. Thereby, used abrasive grains having a small average particle size (for example, 0.3 to 2 μm) that have not been collected by the first solid-liquid separation can be collected and used as raw material abrasive grains to be regenerated. When the solid-liquid separation is performed a plurality of times as described above, the recovery rate of expensive abrasive grains such as a cerium-based abrasive can be increased, and the cost reduction effect of the polishing slurry is increased. In this case, the solid content having a large average particle size (for example, 0.5 to 5 μm) obtained by the first solid-liquid separation is separately crushed after water injection, and further filtered, and then the glass substrate. During the polishing process, it may be circulated for use, stored in a tank for storing the polishing slurry, or may be regenerated using the polishing slurry preparation method of this embodiment.

(B) Drying treatment In the drying treatment, it is preferable to dry the raw material slurry containing the pore-forming agent by a spray drying method. By performing spray drying, the size of the lump of the raw material abrasive grains can be controlled. The spray drying method is preferable because the average particle size can be reduced as compared with other methods, and the variation in particle size can be reduced. Specifically, the spray drying can be performed by spraying using a known spraying means such as a rotating disk type, a two-fluid nozzle type, a pressure nozzle type, etc., and supplying and drying the spray dryer. . Conditions such as the type of spraying means, the nozzle hole diameter, and the supply pressure of the raw slurry are appropriately set according to the target size of the raw material abrasive grains. The size (average particle size) of the raw material abrasive grains obtained by spray drying is preferably about 5 to 10 μm, for example. If it is larger than 10 μm, coarse particles may remain after crushing and cause polishing scratches. On the other hand, if it is less than 5 μm, the proportion of small particles increases and the polishing rate may be lowered. Here, the average particle diameter is a value obtained by determining the long diameter of each lump of the above-mentioned raw material abrasive grains selected at random in SEM observation and averaging them.
Moreover, when adding a pore making material to the raw material slurry before spray drying, it is preferable that the size of the pore forming agent (average particle diameter of the pore forming agent) is 3 to 20 μm. When the pore-forming agent is in such a size range, the size of the crushed abrasive grains is set to an appropriate size by setting the size of the pores in the aggregate of the raw material abrasive grains after firing. (For example, an average particle diameter of 0.5 to 10 μm). As for drying temperature (atmosphere temperature in a drying chamber), the inlet temperature of a drying chamber is 150-250 degreeC, for example. Note that the drying process may be performed without heating.
Here, FIG. 1A shows a lump of raw material abrasive grains produced by a drying process. Here, a spherical lump of raw material abrasive grains produced by drying a raw material slurry containing a binder is shown as an example. The lump 10 of raw material abrasive grains is formed by adhering a large number of raw material abrasive grains 3 so as to cover the surface of the pore forming agent 7 containing moisture, and a binder (not shown) is dispersed between the raw material abrasive grains 3. It is arranged. The lump of raw material abrasive grains 10 includes a large number of raw material abrasive grains 3, but in FIG. 1A, the boundaries of the large number of raw material abrasive grains 3 are not shown for convenience. .

(C) Firing process Although the apparatus which performs a baking process is not restrict | limited in particular, For example, a muffle furnace is mentioned. The firing temperature in the firing treatment is preferably 800 ° C. or lower. The firing temperature is the atmospheric temperature in the space where firing is performed. By setting the firing temperature to 800 ° C. or less, the energy cost for producing the polishing slurry can be reduced. When the firing temperature exceeds 800 ° C., bonding at the grain boundaries between the raw abrasive grains proceeds, and the grain boundary strength of the abrasive grains may become too high. In addition, the binders may be combined to form coarse particles. In these cases, the glass substrate is easily damaged. On the other hand, when the firing temperature exceeds 800 ° C., the composition of the raw material abrasive grains changes, the hardness increases, and the glass substrate may be damaged. Moreover, the firing temperature in the firing treatment is preferably 500 ° C. or higher, more preferably 600 ° C. or higher. When the temperature is lower than 500 ° C., the bonding between the raw material abrasive grains may be insufficient.

In the firing treatment, when a pore forming agent is added to the raw material slurry, it is preferable to eliminate at least a part of the pore forming agent by firing. As a result, the portion where the pore-forming agent is arranged in the lump of the raw material abrasive grains becomes pores, and an aggregate of porous raw material abrasive grains is produced.
Here, FIG. 1B shows an aggregate of raw material abrasive grains produced by a firing process. Here, an aggregate of raw material abrasive grains produced by drying and firing a raw material slurry containing a binder is shown as an example. The aggregate 20 of raw material abrasive grains has holes 9 formed by eliminating the pore-forming agent. The aggregate of the raw material abrasive grains is the raw material abrasive grains formed by the disappearance of the binder aggregation inhibitor disposed between the raw material abrasive grains surrounding the holes 9 in addition to the illustrated holes 9. It is porous by having a large number of minute voids between them. The size (average particle diameter) of the aggregate 20 of raw material abrasive grains is preferably about 5 to 10 μm, for example. If it is larger than 10 μm, coarse particles may remain after crushing and cause polishing scratches. On the other hand, if it is less than 5 μm, the proportion of small particles increases and the polishing rate may be lowered. Here, the average particle diameter is a value obtained by determining the long diameter of each lump of the above-mentioned raw material abrasive grains selected at random in SEM observation and averaging them. In the aggregate 20 of raw material abrasive grains, a binder (not shown) is melted in the firing process, and then the raw material abrasive grains 3 are joined together when they are solidified, so that the strength of the grain boundaries of the raw material abrasive grains 3 is moderate (for example, The average value of the crushing strength described later is 0.1 to 20 MPa). The aggregate 20 of raw material abrasive grains includes a large number of raw material abrasive grains 3, but in FIG. 1B, the boundaries of the large number of raw material abrasive grains 3 are not shown for convenience. Yes. The presence of a binder between the raw material abrasive grains 3 can be confirmed by element mapping using, for example, EDX (Energy Dispersive X-ray microanalyzer).

(D) Crushing treatment The method for producing a polishing slurry of the present embodiment preferably further comprises a crushing treatment for crushing an aggregate of raw material abrasive grains to produce abrasive grains. Thereby, polishing abrasive grains having a size suitable for the polishing process can be obtained. When pores are formed in the aggregate of raw material abrasive grains, it is easier to crush.
The crushing is performed by irradiating the aggregate of raw material abrasive grains with ultrasonic waves using, for example, a homogenizer. The frequency of the ultrasonic wave is preferably 16 to 120 kHz. The crushing may be performed using means other than the homogenizer. The crushing time is not particularly limited, but is, for example, 1 to 20 minutes.
The pulverization is preferably performed so that the average particle size of the abrasive grains is 0.5 to 10 μm. More preferably, they are 0.5-5 micrometers and 0.7-3 micrometers. When the polishing treatment is performed using such abrasive grains having an average particle diameter, polishing can be performed at a high polishing rate, and generation of scratches on the surface of the glass substrate can be suppressed.
The crushing treatment may be performed by a milling method in which physical destruction is performed using a ball mill or the like, but the ultrasonic method described above is more convenient.

  A grinding | polishing slurry can be produced by disperse | distributing grinding | polishing abrasive grain in water after a crushing process. At this time, it is preferable to remove particles of coarse size (for example, 15 μm or more) by filtering before water injection. The coarse-sized particles here are a part of an aggregate of raw material abrasive grains that have not been crushed to a predetermined size by the pulverization treatment.

  According to the method for producing a polishing slurry of this embodiment, an aggregate of porous raw material abrasive grains in which holes are formed can be produced by adding a pore-forming agent to the raw material slurry, and drying and firing it. . Such an aggregate of raw material abrasive grains can be easily crushed by ultrasonic irradiation or the like, and abrasive grains having a size suitable for polishing treatment and a uniform particle size distribution can be obtained. Thus, according to the method of this embodiment, it is not necessary to perform costly pulverization or the like, and it is not necessary to classify, so that abrasive grains can be easily produced at low cost. The polishing rate is improved because the raw abrasive grains have a larger diameter.

(Polishing abrasive grains and polishing slurry)
FIG. 2 conceptually shows the polishing abrasive grain 1 produced by the above method.
Here, a case where the raw abrasive 3 is a cerium-based abrasive or a zirconia-based abrasive will be described as an example.
The polishing abrasive grain 1 includes a raw material abrasive grain 3 containing ceria or zirconia particles and a binder 5 disposed on the surface of the raw abrasive grain 3, which are used for a polishing process of a glass substrate. More specifically, the abrasive grains 1 are abrasive grains used for polishing a glass substrate, and silica particles are present as a binder 5 between ceria or zirconia particles.
As shown in FIG. 1, a large number of raw material abrasive grains 3 are included in each of raw material abrasive grain lump 10 and raw material abrasive grain aggregate 20.
In addition to ceria, the cerium-based abrasive used for the raw material abrasive grain 3 is made of other rare earth elements such as lanthanum, praseodymium, neodymium, etc. in order to suppress the generation of scratches on the glass substrate while achieving a high polishing rate. A mixture containing at least one of oxides and fluorides thereof is preferable. The zirconia-based abrasive may be a mixture containing silicon dioxide in addition to zirconia.
The average particle diameter of the raw material abrasive grains 3 is, for example, 0.3 to 2 μm, and for example, particles having a primary particle diameter of about 80 to 150 nm are aggregated.
In FIG. 2, the binder 5 is disposed on the surface of the raw material abrasive grains 3 that are secondary particles, but may be disposed on the surface of the primary particles constituting the raw material abrasive grains 3. The binder 5 preferably covers less than 50% of the surface area of the surface of the raw abrasive 3. If it is 50% or more, the contact surface between the surface of the abrasive grains and the substrate to be polished becomes small, and the polishing rate tends to decrease.

As for abrasive grain 1, it is preferred that the average value of crushing strength measured according to JIS R1639-5 is 0.1-20 MPa. When the crushing strength is 0.1 MPa or more, it is possible to suppress the abrasive grains from being easily broken and reduced in diameter in the polishing process, thereby suppressing a decrease in the polishing rate. In addition, since the crushing strength varies widely, it is preferable to measure 20 points or more. From the viewpoint of more reliably suppressing the decrease in the polishing rate, the average value of the crushing strength is more preferably 3 MPa or more. Moreover, it can suppress generating a damage | wound on the glass substrate surface in a grinding | polishing process because the average value of crushing strength is 20 Mpa or less.
The average particle diameter of the abrasive grains 1 is, for example, 0.5 to 10 μm. The number of the raw material abrasive grains 3 included in the abrasive grains 1 is not particularly limited, and is, for example, several to a dozen.

  The polishing slurry includes the polishing abrasive grains 1 and a dispersion medium such as water in which the polishing abrasive grains 1 are dispersed.

(Glass substrate manufacturing method)
Next, the manufacturing method of the glass substrate of this embodiment is demonstrated.
Here, a case where a glass substrate used for a magnetic disk is manufactured will be described as an example.
The manufacturing method of this embodiment is characterized by polishing the surface of a glass substrate using the polishing slurry described in the first and second embodiments. That is, the manufacturing method of the present embodiment is a method in which the polishing slurry described in the first and second embodiments can be used in common.

  If the outline of the manufacturing method of this embodiment is demonstrated, the shaping | molding process which forms the plate-shaped glass blank which has a pair of main surface first will be performed. The glass blank is a material for a glass substrate for a magnetic disk. Next, this glass blank is subjected to a rough grinding process. Thereafter, the glass blank is subjected to shape processing to form a glass substrate, and further subjected to end face polishing. Thereafter, the glass substrate is subjected to a precision grinding process using fixed abrasive grains. Thereafter, a first polishing process and a second polishing process are performed on the glass substrate. In the present embodiment, the flow is performed according to the above flow, but the flow and the type of processing are not limited, and the above processing can be appropriately omitted as necessary. Hereinafter, each process described above will be described.

(A) Molding process of glass blank In a molding process, it shape | molds, for example using the press molding method. A disk-shaped glass blank can be obtained by the press molding method. Instead of the pressing method, a glass blank may be manufactured using a known forming method such as a downdraw method, a redraw method, or a fusion method. A disk-shaped glass substrate that is a base of the magnetic disk glass substrate can be obtained by appropriately performing the shape processing described later on the plate-shaped glass blank made by these methods.

(B) Rough grinding process Next, a rough grinding process is performed. In the rough grinding process, the main surfaces on both sides of the glass blank are ground while the glass blank is held on a carrier (not shown) of a well-known double-side grinding apparatus. Specifically, the glass blank is held in a holding hole provided in the carrier, and is sandwiched between an upper surface plate and a lower surface plate, and an upper surface plate or a lower surface plate is supplied while supplying a grinding liquid containing an abrasive. By moving either one or both, the glass substrate and each surface plate are relatively moved, and both main surfaces of the glass substrate are ground. For example, loose abrasive grains are used as the abrasive. In the rough grinding process, the glass blank is ground so as to approximate the target plate thickness dimension and the flatness of the main surface. The rough grinding process is performed according to the dimensional accuracy or surface roughness of the molded glass blank, but can be omitted as appropriate.

(C) Shape processing processing Next, shape processing processing is performed. In the shape processing, by forming a circular hole in a glass blank using a known processing method, a disk-shaped glass substrate having a circular hole is obtained. Thereafter, the end surface of the glass substrate is chamfered. Chamfering is performed on both the inner and outer end faces of the glass substrate. By performing chamfering, a side wall surface orthogonal to the main surface and a chamfered surface (intervening surface) connecting the side wall surface and the main surface are formed on the end surface of the glass substrate.

(D) End surface polishing process Next, the end surface polishing process of a glass substrate is performed. In the end surface polishing treatment, a polishing liquid containing free abrasive grains is supplied between the polishing brush and the end surface of the glass substrate, and polishing is performed by relatively moving the polishing brush and the glass substrate in the thickness direction of the glass substrate. Do. By the end surface polishing treatment, the end surfaces on the inner peripheral side and the outer peripheral side of the glass substrate are polished into a mirror state.

(E) Fine grinding process Next, a fine grinding process is performed on the main surface of the glass substrate. In the fine grinding process, the main surface of the glass substrate is ground using a double-side grinding apparatus in which fixed abrasive grains are attached to a surface plate. Specifically, both main surfaces of the glass substrate are ground in substantially the same manner as the rough grinding process, except that the fixed abrasive is used instead of the loose abrasive.

(F) First polishing treatment Next, a first polishing treatment is performed on the main surface of the glass substrate. In the first polishing process, the main surface on both sides of the glass substrate is polished by holding the glass substrate on a carrier using a well-known double-side polishing apparatus. In the first polishing treatment, polishing is performed by using the free abrasive grains so that the polishing pad attached to the surface plate is brought into contact with the main surface of the glass substrate. During the first polishing process, a slurry containing loose abrasive grains is supplied between a glass substrate and a polishing pad via a pipe (not shown) from a supply tank (not shown) of a double-side polishing apparatus. It is preferable to circulate and use the slurry. The polishing slurry described in the above embodiment is used for the slurry containing loose abrasive grains. As the loose abrasive, for example, a cerium-based abrasive or a zirconia-based abrasive is used.
The following conditions can be mentioned as preferable conditions for the first polishing treatment.
・ Abrasive grain concentration: 1 to 20% by weight
-Load to glass substrate by upper surface plate and lower surface plate of double-side polishing apparatus: 50 to 200 g / cm ²
Polishing time: 10 to 120 minutes It is preferable that the polishing pad is of a suede type because it can prevent the generation of minute scratches. The hardness of the polishing pad is preferably 60 to 90 in terms of Asker C hardness from the viewpoint of improving the polishing rate and reducing fine scratches.

  In the first polishing process, for example, removal of cracks and distortions remaining on the main surface when grinding with fixed abrasive grains is performed, or minute surface irregularities generated on the main surface by the crystallization process are removed. By appropriately adjusting the machining allowance, it is possible to reduce the surface roughness of the main surface, for example, the arithmetic average roughness Ra, while preventing the shape of the end of the main surface from excessively dropping or protruding. In addition, since the polishing slurry used in the first polishing process has polishing abrasive grains that are difficult to break, it is possible to suppress a decrease in the polishing rate by reducing the diameter. Moreover, since the abrasive grains are not too hard, the generation of scratches on the main surface of the glass substrate is suppressed.

  After the first polishing treatment, the polishing slurry may be recovered and further regenerated by the polishing slurry preparation method of the above embodiment, that is, the used polishing slurry regeneration method. Further, it may be used for polishing another glass substrate.

(G) Second polishing (mirror polishing) process Next, a second polishing process is performed. The second polishing treatment aims at mirror polishing of the main surface. The second polishing process may use a double-side polishing apparatus and a polishing method similar to those used in the first polishing process, but it is preferable to make the size of the abrasive grains smaller than the first polishing process. Thereby, the roughness of the main surface can be reduced while preventing the shape of the end portion of the main surface from excessively dropping or protruding. After the second polishing process, the glass substrate is taken out of the double-side polishing apparatus together with the carrier and cleaned. The loose abrasive used in the second polishing treatment is, for example, colloidal silica. Note that the used polishing slurry used in the second polishing treatment can be recovered and added to the raw material slurry in the addition treatment of the polishing slurry preparation method of the above embodiment.

(Example)
(1) Examples relating to the first embodiment In order to confirm the effects of the first embodiment of the present invention, the following experiment was conducted. Specifically, the used polishing slurry as raw material abrasive grains is regenerated with various conditions as shown in Table 1, the crushing strength of the regenerated abrasive grains (samples 1 to 5) is measured, and The polishing rate when the polishing treatment was performed was measured, and the degree of occurrence of scratches on the glass substrate was evaluated.

  The used polishing slurry was regenerated by sequentially performing the following treatments 1 to 7. As the used polishing slurry, a slurry containing an unused cerium-based abrasive having an average particle diameter D50 of 1.0 μm is used, and the first polishing treatment of the above embodiment is performed once, and the recovered slurry is used. It was. The average particle diameter D50 of the recovered cerium-based abrasive was 0.7 μm. The first polishing process was performed using a double-side polishing apparatus under the same conditions as those for the first polishing process described later.

Process 1: Foreign substance removal process By filtering, foreign substances such as polishing pad scraps, particles mixed with particles dried and coarsened in the polishing process, and glass chips were removed from the used polishing slurry. The size of particles to be removed was set to 15 μm or more.

Process 2: Solid-liquid separation process After the process 1, the used polishing slurry was subjected to solid-liquid separation at 800 G for 20 minutes using a centrifuge, and the supernatant was recovered. Subsequently, the supernatant was subjected to solid-liquid separation at 800 G for 1 hour using a centrifuge, and the solid content was recovered.

Treatment 3: Disintegration treatment Water is added to the solid content obtained by the second solid-liquid separation in treatment 2 so that the solid content concentration is 10 to 30% by weight, and the frequency is 20 kHz using a homogenizer. The solid content was crushed by ultrasonic irradiation. Note that the time for the crushing treatment was not fixed, and the crushing process was performed until it was sufficiently crushed.
Process 4: Granulation / drying process Water is added to the crushed solid content so that the concentration of the solid content is 10 to 30% by weight to prepare a raw material slurry, and the binder and binder aggregation inhibitor are added according to Table 1. Added. The binder was added by adding a used polishing slurry containing used colloidal silica (average particle size of 3 to 20 nm in a used state). Corn starch and wheat flour were used as the binder aggregation inhibitor.
Next, the raw material slurry was granulated by spray drying using a co-current type spray dryer to produce a lump of raw material abrasive grains. The co-current type spray dryer is a device that sprays slurry in a drying chamber and blows hot air in parallel to the slurry to dry the slurry. A rotating disk type was used as the spraying means. The spraying conditions are as follows: the diameter of the rotating disk (atomizer) is 50 mm, the rotating speed of the disk is 20000 rpm, the ejection amount is 30 mL / min, the drying chamber inlet temperature (rotating disk position temperature) is 150 degrees, and the outlet temperature is 50 degrees. did.
Process 5: Firing treatment A lump of raw material abrasive grains was put in a crucible and fired at a temperature shown in Table 1 for 2 hours in a muffle furnace to produce an aggregate of raw material abrasive grains.
Process 6: Crushing treatment Aggregate of raw material abrasive grains fired at 800 ° C. or lower was irradiated with ultrasonic waves at a frequency of 20 kHz using a homogenizer to crush solids, thereby producing abrasive grains. On the other hand, the aggregate of raw material abrasive grains fired at a temperature exceeding 800 ° C. was pulverized for 4 hours using a ball mill.
Process 7: Coarse particle removal process Coarse particles of 15 μm or more mixed in the abrasive grains were removed by filtering.

(Measurement of crushing strength)
Based on JIS R1639-5, the crushing strength of the abrasive grains of each sample obtained by the treatment 7 was measured. The results are shown in Table 1. Table 1 shows the crushing strengths of n (n = 20 or more) samples randomly extracted from each sample as a range of measured values and an average value.

(Evaluation of polishing rate and degree of scratching)
A polishing slurry is prepared by dispersing polishing abrasive grains of each sample in water, and a first polishing process described in JP 2012-133882 A is performed as a double-side polishing apparatus including a planetary gear mechanism using the prepared polishing slurry. The first polishing process of the above embodiment was performed on a glass substrate under the following polishing conditions using the double-side polishing apparatus 400 used for the above. A suede-type polishing pad made of polyurethane foam was used on the surfaces of the upper and lower surface plates. In addition, the slurry discharged from the surface plate after polishing was circulated so that it returned to the polishing apparatus.
・ Abrasive grain concentration: 10% by weight
-Load on glass substrate by upper surface plate and lower surface plate: 100 g / cm ²
Polishing time: 60 minutes A 2.5-inch aluminosilicate glass was used for the glass substrate. The number of glass substrates polished in one polishing process was 100.
After the first polishing treatment, the glass substrate was washed and dried, and the polishing rate was calculated from the difference in weight of the glass substrate before and after polishing. In addition, the number of scratches and pits on both surfaces of the glass substrate surface is counted using a laser type surface inspection device. A is 20 / less than one side, B is 20 or more and less than 100 / B, and B is 100. / The case of one side or more was evaluated as C. If it is A and B, generation | occurrence | production of the damage | wound of glass can be suppressed. The polishing rate was shown as a relative value with Sample 4 as 100%. The results are shown in Table 1.

In Table 1, the blending ratio represents the blending ratio (parts by mass) of the three components of the raw material abrasive grains, the binder, and the binder aggregation inhibitor.

As shown in Table 1, with respect to the abrasive grains of Samples 1 and 2 regenerated without adding a binder, Sample 1 fired at a temperature of 800 ° C. or lower does not cause damage to the glass substrate, but the crushing strength is It was found to be small and the polishing rate was low. Further, it was found that Sample 2 baked at a temperature exceeding 800 ° C. has a high crushing strength and a high polishing rate, but many scratches on the glass substrate are generated.
On the other hand, it was found that the abrasive grains of Samples 3 to 5 that were regenerated by adding a binder had a crushing strength in the range of 0.1 to 20 MPa, a high polishing rate, and the occurrence of scratches on the glass substrate was suppressed. It was. In particular, it was found that the abrasive grains of Samples 4 and 5 to which a binder aggregation inhibitor was added had a crushing strength similar to that of Sample 3, but had a sufficiently high polishing rate and no damage to the glass substrate.
In addition, when the aggregate of the raw material abrasive grains of Samples 4 and 5 to which the binder aggregation inhibitor was added was observed with a microscope, it was confirmed that pores having a size almost equal to the size of the added binder aggregation inhibitor were present. It was done. Moreover, when element mapping by EDX was performed on the surface of the abrasive grains of Samples 3 to 5 to which the binder was added, it was confirmed that the binder was disposed.

(Depending on firing temperature)
Further, in order to investigate the influence of the firing temperature, the used slurry was regenerated under the same conditions as Sample 3 except that the firing temperature was changed to 800 ° C. and 1000 ° C. (Samples 6 and 7). As a result, for sample 6, the average value of the crushing strength was 14 MPa, the relative value of the polishing rate was 112, and the degree of scratches was rank B. On the other hand, Sample 7 had an average value of crushing strength of 53 MPa, a relative value of the polishing rate of 112, and the degree of occurrence of scratches was B rank. However, when the degree of scratch generation was compared in detail, the number of samples 3 was 31 / surface, while that of sample 7 was 87 / surface. In other words, it was found that there was a difference in rank B depending on the firing temperature.

(Continuous polishing test)
Further, using the regenerated slurries of Samples 1 and 3 to 5, the above-described first polishing treatment was continuously performed for 5 batches (for the number of processed substrates: 500 sheets), and then the degree of occurrence of scratches was evaluated. As a result, sample 1 was ranked C, but the other samples were the same ranks as shown in Table 1. This is presumably because the regenerated slurry of Sample 1 had a low crushing strength and was therefore destroyed by the polishing process, resulting in an increase in small particles.

(2) Example regarding the second embodiment In order to confirm the effect of the second embodiment of the present invention, the following experiment was conducted. Specifically, as shown in Table 2 and Table 3, used polishing slurries as raw material abrasive grains are regenerated, and the regenerated abrasive grains (samples 11 to 13, 12A, 13A) are regenerated. In addition to measuring the time required for crushing Samples 11, 12A, and 13A, the crushing strength was measured for Samples 11 to 13, and the polishing rate was measured when the polishing treatment was performed. Moreover, the grade of the generation | occurrence | production of the damage | wound which arose on the glass substrate regarding samples 11-13 was evaluated.

  The used polishing slurry was regenerated by sequentially performing the following treatments 1 to 7. As the used polishing slurry, a slurry containing an unused cerium-based abrasive having an average particle diameter D50 of 1.0 μm is used, and the first polishing treatment of the above embodiment is performed once, and the recovered slurry is used. It was. The average particle diameter D50 of the recovered cerium-based abrasive was 0.7 μm. The first polishing process was performed using a double-side polishing apparatus under the same conditions as those for the first polishing process described later.

Process 1: Foreign substance removal process By filtering, foreign substances such as polishing pad scraps, particles mixed with particles dried and coarsened in the polishing process, and glass chips were removed from the used polishing slurry. The size of particles to be removed was set to 15 μm or more.

Process 2: Solid-liquid separation process After the process 1, the used polishing slurry was subjected to solid-liquid separation at 800 G for 20 minutes using a centrifuge, and the supernatant was recovered. Subsequently, the supernatant was subjected to solid-liquid separation at 800 G for 1 hour using a centrifuge, and the solid content was recovered.

Treatment 3: Disintegration treatment Water is added to the solid content obtained by the second solid-liquid separation in treatment 2 so that the solid content concentration is 10 to 30% by weight, and the frequency is 20 kHz using a homogenizer. The solid content was crushed by ultrasonic irradiation. Note that the time for the crushing treatment was not fixed, and the crushing process was performed until it was sufficiently crushed.
Treatment 4: Granulation / drying treatment A raw material slurry is prepared by adding water to the crushed solid content so that the solid content becomes 10 to 30% by weight. Binder was added. The binder was added by adding a used polishing slurry containing used colloidal silica (average particle size of 3 to 20 nm in a used state). Corn starch and wheat flour were used for the pore-forming agent.
Next, the raw material slurry was granulated by spray drying using a co-current type spray dryer to produce a lump of raw material abrasive grains. The co-current type spray dryer is a device that sprays slurry in a drying chamber and blows hot air in parallel to the slurry to dry the slurry. A rotating disk type was used as the spraying means. The spraying conditions are as follows: the diameter of the rotating disk (atomizer) is 50 mm, the rotating speed of the disk is 20000 rpm, the ejection amount is 30 mL / min, the drying chamber inlet temperature (rotating disk position temperature) is 150 degrees, and the outlet temperature is 50 degrees. did.
Process 5: Firing treatment A lump of raw material abrasive grains was placed in a crucible and fired in a muffle furnace at 600 degrees for 2 hours to produce an aggregate of raw material abrasive grains.
Process 6: Crushing treatment The aggregate of the raw material abrasive grains was subjected to ultrasonic irradiation at a frequency of 20 kHz using a homogenizer, and the solid content was crushed to produce abrasive grains.
Process 7: Coarse particle removal process Coarse particles of 15 μm or more mixed in the abrasive grains were removed by filtering.

(Measurement of crushing strength)
Based on JIS R1639-5, the crushing strength of the abrasive grains of each sample obtained by the treatment 7 was measured. The results are shown in Table 3. Table 3 shows the crushing strengths of n (n = 20 or more) samples randomly extracted from each sample as a range of measured values and an average value.

(Evaluation of polishing rate and degree of scratching)
A polishing slurry is prepared by dispersing polishing abrasive grains of each sample in water, and a first polishing process described in JP 2012-133882 A is performed as a double-side polishing apparatus including a planetary gear mechanism using the prepared polishing slurry. The first polishing process of the above embodiment was performed on a glass substrate under the following polishing conditions using the double-side polishing apparatus 400 used for the above. A suede-type polishing pad made of polyurethane foam was used on the surfaces of the upper and lower surface plates. In addition, the slurry discharged from the surface plate after polishing was circulated so that it returned to the polishing apparatus.
・ Abrasive grain concentration: 10% by weight
-Load on glass substrate by upper surface plate and lower surface plate: 100 g / cm ²
Polishing time: 60 minutes A 2.5-inch aluminosilicate glass was used for the glass substrate. The number of glass substrates polished in one polishing process was 100.
After the first polishing treatment, the glass substrate was washed and dried, and the polishing rate was calculated from the difference in weight of the glass substrate before and after polishing. In addition, the number of scratches and pits on both surfaces of the glass substrate surface is counted using a laser type surface inspection device. A is 20 / less than one side, B is 20 or more and less than 100 / B, and B is 100. / The case of one side or more was evaluated as C. If it is A and B, generation | occurrence | production of the damage | wound of glass can be suppressed. The polishing rate was shown as a relative value with Sample 12 as 100%. The results are shown in Table 3.
In Tables 2 and 3, the blending ratio represents the blending ratio (parts by mass) of the three components of the raw material abrasive grains, the pore former, and the binder.

  It took 60 minutes for the sample 11 regenerated without adding the pore-forming agent to be sufficiently crushed in the above treatment 6. In this case, it cannot be sufficiently crushed in a relatively short time, and it is not possible to obtain abrasive grains having a size suitable for the polishing process.

(Depending on firing temperature)
Further, in order to investigate the influence of the firing temperature, the firing temperature is set to 500 ° C., 80 ° C.
Except for changing to 0 ° C., the used slurry was regenerated under the same conditions as Samples 11, 12A, and 13A, and the time required for crushing was evaluated in the same manner as described above.

As shown in Table 3, the samples 12 and 13 regenerated by adding the pore former were found to have a crushing strength in the range of 0.1 to 20 MPa and a high polishing rate. In addition, it was found that the samples 12 and 13 were hardly scratched on the glass substrate even though they were regenerated by adding a binder.
In addition, when the aggregate | assembly of the raw material abrasive grain of the samples 12 and 13 was observed with the microscope, it was confirmed that the void | hole of the magnitude | size substantially equivalent to the magnitude | size of the added pore making material exists. Further, when element mapping by EDX was performed on the surfaces of the abrasive grains of Samples 12 and 13 to which the binder was added, it was confirmed that the binder was disposed.

  As mentioned above, although the preparation method of the polishing slurry of this invention, polishing abrasive grain, polishing slurry, and the manufacturing method of a glass substrate were demonstrated in detail, this invention is not limited to the said embodiment, The range which does not deviate from the main point of this invention Of course, various improvements and changes may be made.

1 Abrasive grains 3 Raw material abrasive grains (abrasive grains)
5 Binder 7 Binder aggregation inhibitor (pore forming agent)
9 Hole 10 Agglomerate of raw abrasive 20 Aggregate of raw abrasive

Claims (17)

A method for producing a polishing slurry containing abrasive grains for use in polishing a glass substrate,
An addition treatment for adding a binder to a raw material slurry containing raw material abrasive grains as raw materials for the abrasive grains;
Drying the raw material slurry containing the binder to produce a lump of raw material abrasive grains containing the binder; and
A method for producing a polishing slurry, comprising: firing a lump of the raw material abrasive grains to produce an aggregate of raw material abrasive grains containing the binder.   The method for producing a polishing slurry according to claim 1, wherein the binder contains silica particles.   The method for producing a polishing slurry according to claim 1 or 2, wherein the binder has an average particle size of 3 to 20 nm. Furthermore, a crushing process for crushing the aggregate of raw material abrasive grains to produce the abrasive grains,
The method for producing a polishing slurry according to any one of claims 1 to 3, wherein an average particle diameter of the abrasive grains produced by the crushing treatment is 0.5 to 10 µm. In the addition treatment, a binder aggregation inhibitor for suppressing aggregation between the binders is further added,
In the said drying process, the said binder is disperse | distributed and distribute | arranged in the lump of the said raw material abrasive grain through the said binder aggregation inhibitor, The preparation method of the polishing slurry of any one of Claims 1-4 .   The method for producing a polishing slurry according to claim 5, wherein in the firing treatment, at least a part of the binder aggregation inhibitor is eliminated by firing the lump of the raw material abrasive grains.   The method for producing a polishing slurry according to claim 5 or 6, wherein the binder aggregation inhibitor is a polysaccharide.   The method for producing a polishing slurry according to claim 1, wherein the firing is performed at a temperature of 800 ° C. or less.   The method for producing a polishing slurry according to any one of claims 1 to 8, wherein, in the drying treatment, the raw material slurry containing the binder is dried by spray drying.   The method for producing a polishing slurry according to any one of claims 1 to 9, wherein the raw material slurry includes ceria particles used for polishing the glass substrate.   A polishing abrasive for use in a polishing treatment of a glass substrate, wherein silica particles are present as a binder between ceria or zirconia particles in the polishing abrasive.   A polishing slurry comprising the abrasive grains according to claim 11.   A polishing slurry produced by the method for producing a polishing slurry according to any one of claims 1 to 10, a polishing abrasive according to claim 11, or a polishing slurry according to claim 12, and A method for producing a glass substrate, comprising polishing a surface. A method for producing a polishing slurry containing abrasive grains for use in polishing a glass substrate,
An addition treatment for adding a pore-forming agent to a raw material slurry containing raw material abrasive grains used as raw materials for the abrasive grains;
Drying the raw material slurry containing the pore former to produce a lump of raw material abrasive grains containing the pore former; and
Firing a mass of the raw abrasive grains to eliminate at least a part of the pore former, thereby forming a void in the portion of the raw abrasive grain mass where the pore former is located. A method for producing a polishing slurry.   The method for producing a polishing slurry according to claim 14, wherein an average particle diameter of the pore former in the lump of the raw material abrasive grains is 3 to 20 μm. In the addition treatment, further, a binder disposed on the surface of the raw material abrasive grains is added,
The said slurry is a manufacturing method of the polishing slurry of Claim 14 or 15 disperse | distributed and distribute | arranged in the lump of the said raw material abrasive grain through the said pore making material in the said drying process.   A method for producing a glass substrate, comprising polishing a surface of a glass substrate using the polishing slurry produced by the method for producing a polishing slurry according to any one of claims 14 to 16.

Images