WO2016136314A1

WO2016136314A1 - Production method of composite metal oxide polishing material, and composite metal oxide polishing material

Info

Publication number: WO2016136314A1
Application number: PCT/JP2016/050881
Authority: WO
Inventors: 寿夫小泉; 啓治小野; 高橋　直人; 大樹橋本; 加藤　良一; 務山本; 勝見上; 瑞穂和田
Original assignee: 堺化学工業株式会社
Priority date: 2015-02-26
Filing date: 2016-01-13
Publication date: 2016-09-01
Also published as: JP2016155986A; TW201638047A; JP6458554B2; TWI678352B

Abstract

A cerium-free polishing material is provided which has an excellent polishing speed, and which can cut production costs and has improved production efficiency; also provided is a production method for conveniently obtaining said polishing material. This production method of the composite metal oxide polishing material involves a mixing step for mixing a strontium compound and a zirconium compound and a firing step for firing the mixture obtained in the mixing step, wherein said zirconium compound contains less than or equal to 2.0 parts by weight of a sulfur compound in terms of SO₃ per 100 parts by weight of said zirconium compound in terms of ZrO₂.

Description

Method for producing composite metal oxide polishing material and composite metal oxide polishing material

The present invention relates to a method for producing a composite metal oxide polishing material and a composite metal oxide polishing material.

Cerium oxide-based abrasives are used for polishing precision optical glass products that require high transparency and accuracy, such as lenses and prisms. This abrasive is produced by firing and pulverizing minerals rich in so-called rare earths (rare earths).

However, since the demand for rare earth has increased and the supply has become unstable, the development of technology and alternative materials that reduce the amount of cerium used is desired. As such an alternative abrasive, Patent Literature 1 discloses that a perovskite oxide is suitable as an abrasive, Patent Literature 2 discloses an iron-based perovskite-type abrasive, and Patent Literature 3 discloses. A zirconium-based perovskite-type abrasive is disclosed.

JP 2001-107028 A JP 2012-124202 A JP 2013-82050 A

However, when glass polishing is performed using the abrasive disclosed in Patent Document 1, the polished glass has a problem that the polishing rate is low although a smooth surface can be obtained.

In addition, the abrasive described in Patent Document 2 is manufactured by spray pyrolysis, and requires special equipment and a great deal of time for manufacturing, so it is not suitable for mass production and uses rare metals such as nickel and cobalt. Therefore, there are problems such as concern about supply insecurity similar to cerium oxide. The abrasive described in Patent Document 3 is also manufactured by spray pyrolysis, and is not suitable for mass production.

Therefore, the inventor of the present invention is a method for producing a cerium-free polishing material at a low cost without introducing a special equipment with a simple manufacturing process, and polishing by mixing and baking a strontium compound and a zirconium compound. A method for obtaining a material has been found, and among the polishing materials obtained by this method, those using zirconium oxide as a raw material zirconium compound have already been found to be remarkably excellent in polishing rate. However, since zirconium oxide is usually produced by firing and pulverizing zirconium hydroxide, there is room for improvement to further reduce production costs and improve production efficiency by omitting this firing and pulverization step. was there.

In view of the above-described situation, the present invention provides a polishing material that has a good polishing rate in a cerium-free polishing material and that can realize reduction in manufacturing cost and improvement in manufacturing efficiency, and the polishing material in a simple manner. An object of the present invention is to provide a production method for obtaining the above.

The present inventor has been diligently studying in order to solve the above-mentioned problems. Among the polishing materials obtained by mixing and baking a strontium compound and a zirconium compound, polishing using a zirconium compound other than zirconium oxide as a raw material. Focusing on the fact that the polishing rate of the material is not good, we have newly found that this factor is the content of the sulfur compound contained in the raw zirconium compound. In general, zirconium compounds such as zirconium hydroxide and zirconium carbonate often use substances containing sulfate ions such as sulfuric acid, ammonium sulfate, sodium sulfate, and potassium sulfate at the time of synthesis. In the neutralization precipitation method using zirconium oxychloride, which is a general method for synthesizing zirconium compounds, basic zirconium sulfate (Zr (OH) _(4-2x) (4) is added by adding a substance containing sulfate ions. SO ₄ ) _x · nH ₂ O (where 0 <x <2)) is produced, and then the basic zirconium sulfate is neutralized to obtain zirconium compounds such as zirconium hydroxide and zirconium carbonate. This is because when the sulfur compound is added, the moisture content of the resulting cake is reduced, and the handling properties and filterability are improved. When no sulfur compound is added, it takes a very long time to filter the resulting zirconium hydroxide, and the productivity is remarkably lowered, which is not industrially suitable. Therefore, although the zirconium compound obtained by the usual synthesis method contains a sulfur compound, the present inventor has found that the content of this sulfur compound affects the polishing rate of the polishing material after mixing and firing with the strontium compound. I found a new thing. Although the cause is not certain, for example, it is estimated as one of the causes that the crystallinity of the obtained zirconium compound varies depending on the amount of sulfur compound added when the zirconium compound is produced. Therefore, it has been found that if the content of the sulfur compound in the zirconium compound is set within a predetermined range, and this and the strontium compound are mixed and fired, a polishing material having a high level of polishing speed can be easily obtained. As a result, the present invention was completed.

That is, the present invention is a method for producing a composite metal oxide polishing material comprising a mixing step of mixing a strontium compound and a zirconium compound, and a firing step of firing the mixture obtained by the mixing step,
The SO ₃ equivalent of the sulfur compound contained in the zirconium compound is 2.0 parts by weight or less with respect to 100 parts by weight of the zirconium compound in terms of ZrO ₂ .

The strontium compound in the mixing step is preferably at least one selected from the group consisting of strontium carbonate and strontium hydroxide. Since strontium carbonate and strontium hydroxide easily react with the zirconium compound to easily produce strontium zirconate (SrZrO ₃ ), productivity is further improved.

The zirconium compound in the mixing step is preferably at least one selected from the group consisting of zirconium carbonate and zirconium hydroxide. Since zirconium carbonate and zirconium hydroxide have high reactivity with the strontium compound, a polishing material with better polishing characteristics can be provided. Moreover, if these are used, reduction of manufacturing cost and improvement of manufacturing efficiency can be realized more.

The firing temperature in the firing step is preferably more than 800 ° C. and 1500 ° C. or less. When the firing temperature is within this range, a polishing material with better polishing characteristics can be provided.

The present invention also provides a composite metal oxide polishing material comprising:
The SO ₃ equivalent of the sulfur compound contained in the composite metal oxide polishing material is 1.2 parts by weight or less with respect to 100 parts by weight of the zirconium compound equivalent to ZrO ₂ contained in the composite metal oxide polishing material. It is also a composite metal oxide polishing material.

By the method for producing a composite metal oxide polishing material of the present invention, a polishing material having a good polishing rate in a cerium-free polishing material can be efficiently produced. Since the production method of the present invention is performed by a solid phase reaction method, the production process is simpler than that of the spray pyrolysis method, and the production can be performed at a low cost without introducing special equipment. In addition, the composite metal oxide polishing material of the present invention can exhibit a good polishing rate, and can sufficiently cope with the recent shortage of rare earth supply, and thus can be said to be an extremely advantageous material industrially.

FIG. 1-1 is a graph showing the results of differential heat measurement for each zirconium compound used in Example 1 and Comparative Example 1. 1-2 is a graph showing the results of thermogravimetric measurement for each zirconium compound used in Example 1 and Comparative Example 1. FIG. FIG. 2-1 is a graph showing the results of differential heat measurement for each mixed powder (dried product of the mixture) according to Example 1 and Comparative Example 1. FIG. 2-2 is a graph showing the results of thermogravimetric measurements on the mixed powders (dried mixture) according to Example 1 and Comparative Example 1. FIG. 3 is a graph showing the relationship of zeta potential to pH for each abrasive slurry used in the Reference Example or Comparative Reference Example.

[Method for producing composite metal oxide polishing material]
The method for producing a composite metal oxide polishing material of the present invention (also referred to as “the production method of the present invention”) includes a mixing step of mixing a strontium compound and a zirconium compound, and a baking for baking the mixture obtained by the mixing step. Process. Therefore, the composite metal oxide polishing material can achieve a high polishing rate.
As can be seen from the raw materials used, the production method of the present invention is performed by a solid phase reaction method. Therefore, the manufacturing process is simpler than that of the spray pyrolysis method, and manufacturing at a low cost is possible without introducing special equipment.

-material-
First, a strontium compound, one of the raw materials in the production method of the present invention, will be described.
The strontium compound is not particularly limited as long as it is a compound containing a strontium atom, but among them, at least one selected from the group consisting of strontium carbonate and strontium hydroxide is preferable. Strontium carbonate and strontium hydroxide easily react with the zirconium compound to easily produce strontium zirconate (SrZrO ₃ ).

Next, another zirconium compound as a raw material will be described.
In the production method of the present invention, as the zirconium compound, SO ₃ equivalent amount of sulfur compounds contained in this respect in terms of ZrO ₂ per 100 parts by weight of said zirconium compound, using 2.0 or less part by weight compound. When the content of the sulfur compound in the raw material zirconium compound is within this range, a polishing material having a very good polishing rate can be obtained. The sulfur compound content (SO ₃ equivalent) is preferably 1.5 parts by weight or less, more preferably 1.1 parts by weight or less, and even more preferably 0.5 parts by weight or less.

The zirconium compound is not particularly limited as long as it is a compound containing a zirconium atom, but among them, zirconium oxide, zirconium carbonate, and zirconium hydroxide are preferable. These can provide a polishing material having high reactivity with a strontium compound and better polishing characteristics. Among them, it is preferable to use a zirconium compound other than zirconium oxide, whereby the firing and pulverization steps during the synthesis of zirconium oxide can be omitted, and the manufacturing cost can be reduced and the manufacturing efficiency can be improved. That is, it is preferably at least one selected from the group consisting of zirconium carbonate and zirconium hydroxide.

The zirconium compound preferably has a specific surface area of 0.1 to 250 m ² / g. When the specific surface area is within this range, a moderately crystalline SrZrO ₃ phase is easily generated efficiently. For example, when the specific surface area of the zirconium compound is 0.1 m ² / g or more, the reactivity with the strontium compound is further increased, and when it is 250 m ² / g or less, the reaction control with the strontium compound becomes easy. Therefore, in any case, a composite metal oxide polishing material having a good polishing rate is easily obtained. More preferably, it is 0.3 to 240 m ² / g, and still more preferably 0.5 to 230 m ² / g.

In the present specification, the specific surface area (also referred to as SSA) means the BET specific surface area.
The BET specific surface area refers to a specific surface area obtained by the BET method, which is one method for measuring the specific surface area. The specific surface area refers to the surface area per unit mass of a certain object.
The BET method is a gas adsorption method in which gas particles such as nitrogen are adsorbed on solid particles and the specific surface area is measured from the amount adsorbed. Specifically, the specific surface area is determined by obtaining the monomolecular adsorption amount VM by the BET equation from the relationship between the pressure P and the adsorption amount V.

-Mixing process-
Next, the mixing process will be described.
The production method of the present invention includes a mixing step of mixing a strontium compound and a zirconium compound. The mixing ratio of the raw materials is preferably SrO: ZrO ₂ = 10: 90 to 43:57 in terms of weight ratio in terms of oxide. The mixing method is not particularly limited, and may be wet mixing or dry mixing, but wet mixing is desirable from the viewpoint of mixing properties. The dispersion medium used for wet mixing is not particularly limited, and water or lower alcohol can be used, but water is preferable from the viewpoint of production cost, and ion-exchanged water is more preferable. In the case of wet mixing, a ball mill, a paint conditioner, or a sand grinder may be used. In order to remove the dispersion medium, it is preferable to perform a drying step following the wet mixing.
The zirconium compound can be used for the mixing step in the form of a cake obtained by synthesis.

-Drying process-
After the mixing step, a drying step may be performed as necessary.
In the drying step, the dispersion medium is removed from the slurry obtained in the mixing step and dried. The method for drying the slurry is not particularly limited as long as the solvent used at the time of mixing can be removed, and examples thereof include drying under reduced pressure and drying by heating. Further, the slurry may be dried as it is, or may be dried after being filtered.
Note that the dry product of the mixture may be dry-pulverized.

-Baking process-
Then, a baking process is demonstrated.
In the firing step, the raw material mixture obtained in the mixing step (may be a dried product obtained through a further drying step) is fired. Thereby, a composite metal oxide polishing material can be obtained. In the firing step, the raw material mixture may be fired as it is, or may be fired after being molded into a predetermined shape (for example, a pellet shape). The firing atmosphere is not particularly limited. The firing step may be performed only once or twice or more.

The firing temperature in the firing step may be a temperature sufficient for the reaction between the strontium compound and the zirconium compound, but is preferably more than 800 ° C. and 1500 ° C. or less. When the firing temperature exceeds 800 ° C., the reaction proceeds more sufficiently, and the zirconium compound is easily crystallized as zirconium oxide. When the firing temperature is 1500 ° C. or less, the generated strontium zirconate may be vigorously sintered. Since it is sufficiently suppressed, the polishing rate can be further increased in any case. The lower limit of the firing temperature is more preferably 850 ° C. or higher. Thereby, it becomes possible to fully exhibit the effect of this invention. More preferably, it is 900 degreeC or more, Most preferably, it is 930 degreeC or more. Further, the upper limit is more preferably 1300 ° C. or less, and still more preferably 1200 ° C. or less.
In the present specification, the firing temperature in the firing step means the highest temperature reached in the firing step.

Here, as a raw material zirconium compound, when a compound having a sulfur compound content exceeding the range set in the present invention is used, even if the firing step is performed at the same firing temperature as in the case of using the zirconium compound of the present invention. Since the resulting polishing material does not have sufficient crystallinity, a good polishing rate cannot be obtained. Further, even if the calcination temperature is further increased so that the crystallinity of the polishing material is approximately the same, a sufficient polishing rate cannot be obtained.

The holding time at the firing temperature may be a time sufficient for the reaction between the strontium compound and the zirconium compound. For example, it is preferably 5 minutes to 24 hours. When the holding time is within this range, the reaction proceeds more sufficiently, and when the holding time is 24 hours or less, the generated fired product (strontium zirconate) is sufficiently suppressed from being vigorously sintered. The polishing rate can be further increased. More preferably, it is 7 minutes to 22 hours, and further preferably 10 minutes to 20 hours.

In the firing step, it is preferable that the rate of temperature rise during the temperature rise until reaching the maximum temperature (firing temperature) is 0.2 to 15 ° C./min. If the rate of temperature increase is 0.2 ° C./min or more, the time required for temperature increase does not become too long, so that waste of energy and time can be sufficiently suppressed, and if it is 15 ° C./min or less. The temperature of the furnace contents can sufficiently follow the set temperature, and firing unevenness is more sufficiently suppressed. More preferably, it is 0.5 to 12 ° C./min, and further preferably 1.0 to 10 ° C./min.

-Crushing process-
After the firing step, a pulverization step may be performed as necessary.
In the pulverization step, the fired product obtained in the firing step is pulverized. The pulverization method and pulverization conditions are not particularly limited, and for example, a ball mill, a reiki machine, a hammer mill, a jet mill, or the like may be used.

[Composite metal oxide polishing material]
Next, the composite metal oxide polishing material of the present invention will be described.
The composite metal oxide polishing material of the present invention (hereinafter also simply referred to as “polishing material”) includes a sulfur compound contained in the polishing material (more specifically, a sulfur compound incorporated in the crystal of the polishing material). ) In terms of SO ₃ is 1.2 parts by weight or less with respect to 100 parts by weight in terms of ZrO _{2 of the} zirconium compound contained in the composite metal oxide polishing material. When the content of the sulfur compound is within this range, the polishing material has a very good polishing rate. The content of the sulfur compound is preferably 1.0 part by weight or less, more preferably 0.8 part by weight or less, and still more preferably 0.6 part by weight or less.
The abrasive material is preferably obtained by the production method of the present invention described above.

The polishing material preferably includes a crystal phase of ZrO _{2 and} a crystal phase of SrZrO ₃ . Since the crystal phase of ZrO ₂ contained in the polishing material is responsible for the mechanical polishing action and the crystal phase of SrZrO ₃ is responsible for the chemical polishing action, a better polishing rate can be exhibited. The polishing material of the present invention is preferably a composite of ZrO ₂ and SrZrO ₃ , but this can increase the polishing rate. The composite of SrZrO ₃ and ZrO ₂ refers to secondary particles formed by partially sintering the primary particles of SrZrO ₃ and zirconium oxide. For example, when element mapping is performed on the composite by energy dispersive X-ray spectroscopy (EDS), primary particles from which Sr and Zr are detected and primary particles from which only Zr is detected form secondary particles. The situation is observed.

The polishing material preferably has a half width of a peak derived from the (040) plane of orthorhombic SrZrO ₃ in X-ray diffraction using CuKα rays as a radiation source in a range of 0.1 to 3.0 °. When the half width is in this range, the crystallinity of SrZrO ₃ that effectively exhibits the chemical polishing action is improved, and thus the chemical polishing action can be sufficiently exhibited. When the half width exceeds 3.0 °, the crystallinity of SrZrO ₃ is not sufficient, and when the half width is less than 0.1 °, the crystallinity of SrZrO ₃ becomes too high. In some cases, the chemical polishing action derived from SrZrO ₃ may not be sufficiently obtained. The angle is more preferably 0.1 to 1.0 °, further preferably 0.1 to 0.7 °, and particularly preferably 0.1 to 0.4 °.

The polishing material is preferably ratio _{D 10} of _{D 90} indicative of sharpness of volume-based particle size distribution _{_(D} 90 _/ D ₁₀₎ is 1.5 to 50. FIG. When D ₉₀ / D ₁₀ exceeds 50, the particle size variation is too large, so that sufficient contact between the polishing material and the object to be polished cannot be obtained, and the polishing rate may not be sufficient. When D ₉₀ / D ₁₀ is less than 1.5, the variation in particle diameter is too small, so that contact between the polishing material and the object to be polished cannot be obtained sufficiently, and the polishing rate may not be sufficient. .
Incidentally, as D _{90 /} D ₁₀ is large, it means that the particle size distribution is broad, smaller value means that the particle size distribution is sharp.
D ₁₀ and D ₉₀ are values obtained by measuring the particle size distribution, respectively. It means 10% cumulative particle diameter on a volume basis and D _10, and D ₉₀ refers to the 90% cumulative particle diameter on a volume basis.

The polishing material preferably contains 10 to 43% by weight of Sr in terms of SrO. When the Sr content is less than 10% by weight in terms of SrO, the content of SrZrO ₃ is lowered and the chemical polishing action may not be sufficiently obtained. Also, if the Sr content exceeds 43 wt% in terms of SrO, ZrO ₂ content is relatively reduced, mechanical polishing action may not be obtained sufficiently. More preferably, it is 11 to 43% by weight, and still more preferably 12 to 43% by weight.

The polishing material preferably has a specific surface area of 1.0 to 50 m ² / g. When the specific surface area is less than 1.0 m ² / g, the specific surface area of the polishing material is too small to sufficiently contact the object to be polished, and may not be sufficiently polished. On the other hand, if the specific surface area exceeds 50 m ² / g, the abrasive grains constituting the polishing material may be too small to obtain a sufficient mechanical polishing action. More preferably, it is 1.0 to 45 m ² / g, and still more preferably 1.0 to 40 m ² / g.

The polishing material of the present invention can be applied to various polishing objects. For example, the present invention can be applied to a polishing object in which cerium oxide, chromium oxide, bengara (Fe ₂ O ₃ ), or the like has been conventionally used as a polishing material. The object to be polished is not particularly limited, and examples thereof include a glass substrate, a metal plate, a stone, sapphire, silicon nitride, silicon carbide, silicon oxide, gallium nitride, gallium arsenide, indium arsenide, and indium phosphide.

The polishing material may be used by appropriately mixing with other components depending on the application. For example, the polishing material of the present invention may be mixed with a dispersion medium, may be mixed with an additive, or the dispersion medium and the additive may be mixed simultaneously. The form at the time of mixing with a dispersion medium and / or an additive is not specifically limited, For example, it can use in forms, such as a powder form, a paste form, and a slurry form.

Although it does not specifically limit as a dispersion medium, For example, water, an organic solvent, a mixture thereof, etc. are mentioned, 1 type (s) or 2 or more types can be used. Examples of the organic solvent include alcohol, acetone, dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, dioxane and the like. Examples of the alcohol include monovalent water-soluble alcohols such as methanol, ethanol and propanol; bivalent or more such as ethylene glycol and glycerin. Of water-soluble alcohols. The dispersion medium is preferably water, and more preferably ion-exchanged water.

The additive is not particularly limited, and examples thereof include acids, alkalis, pH adjusters, chelating agents, antifoaming agents, dispersants, viscosity modifiers, aggregation inhibitors, lubricants, reducing agents, rust inhibitors, and publicly known. An abrasive material etc. are mentioned. These may be used alone or in combination of two or more, as long as the effects of the present invention are not impaired.

[Polishing method]
Next, an example of a polishing method using the composite metal oxide polishing material of the present invention will be described.
As described above, the composite metal oxide polishing material of the present invention can be applied to various types of polishing targets. When a negatively chargeable substrate is to be polished, it is preferable to apply the polishing method described below. . The polishing method using the composite metal oxide polishing material of the present invention is not limited only to the following polishing method.
That is, a polishing step a for polishing a negatively-charged substrate under a condition in which a zeta potential of a slurry containing the composite metal oxide polishing material of the present invention (hereinafter also referred to as an abrasive slurry) is positive, and the abrasive slurry This is a polishing method in which the polishing step b for polishing the negatively chargeable substrate under a condition where the zeta potential is negative is performed at least once each.

In the present specification, the negatively chargeable substrate is preferably a substrate that is always negatively charged in an aqueous solution having a pH higher than 4, for example, a glass substrate (isoelectric point of glass = about 2.0). Is mentioned. In addition, a silicon carbide substrate (isoelectric point of silicon carbide = about 4.0) is also included.
In addition, as a glass substrate, transparent or semi-transparent things, such as soda-lime glass, an alkali free glass, borosilicate glass, quartz glass, are mentioned, for example.

In the above polishing method, the polishing step a for polishing the negatively chargeable substrate under a condition where the zeta potential of the abrasive slurry is positive, and the negatively chargeable substrate is polished under a condition where the zeta potential of the abrasive slurry is negative. Each of the polishing steps b is performed at least once. The order of these polishing steps is not particularly limited, and the polishing step b may be performed after the polishing step a, or the polishing step a may be performed after the polishing step b. Among them, in order to obtain a negatively chargeable substrate having better surface smoothness, it is particularly preferable to perform the polishing step a at least once and then perform the polishing step b at least once. In addition, each polishing step may be performed a plurality of times, or the polishing step a and the polishing step b may be performed alternately. When the polishing step a is performed a plurality of times, as long as the zeta potential of the abrasive slurry is positive, the zeta potential may be changed or may be changed. The same applies when the polishing step b is performed a plurality of times, and as long as the zeta potential of the abrasive slurry is negative, the zeta potential may be changed or may be changed.
In the present specification, “the zeta potential of the abrasive slurry” is a value obtained under the measurement conditions described in the examples described later.

In the above polishing method, the action due to electrostatic attraction is exhibited in the polishing step a, and the action due to electrostatic repulsion is exhibited in the polishing step b. Thus, a high polishing rate and a negative charge after polishing due to these synergistic effects. It is estimated that excellent surface smoothness in the conductive substrate will be realized. Usually, the surface of the negatively chargeable substrate before polishing has a recess made of fine scratches or holes. In the polishing step a, the substrate to be polished is negatively charged, whereas the abrasive slurry is positively charged, so that the abrasive penetrates deep into the recesses by electrostatic attraction and promotes polishing. Therefore, it is considered that the polishing rate is increased. On the other hand, in the polishing step b, since the substrate to be polished and the abrasive slurry are both negatively charged, the abrasive does not penetrate deep into the recess due to electrostatic repulsion, but is applied between the polishing pad and the substrate. It is considered that a large amount of abrasive is present on the convex portion of the substrate surface due to the pressure, thereby smoothing the substrate surface. Therefore, if the object to be polished is a negatively chargeable substrate, the same working mechanism is obtained. Therefore, the above polishing method can be applied not only to a glass substrate but also to various negatively chargeable substrates.

In both the polishing step a and the polishing step b, polishing is performed in the presence of an abrasive slurry. In the polishing step a and the polishing step b, the same abrasive slurry may be used, that is, continuously used (reused) to control only the zeta potential of the slurry, and the zeta potential may be positive or negative. It is also possible to prepare each abrasive slurry separately and switch the abrasive slurry in each polishing step. In either case, a slurry containing the composite metal oxide polishing material of the present invention may be used as the abrasive slurry. Thus, in the above polishing method, the abrasive slurry can be used continuously (reused), and even when switching, it is not necessary to prepare abrasive slurry of greatly different types. This eliminates the need for cleaning work and dedicated equipment. In addition, since the high polishing rate and the excellent surface smoothness can be realized without using cerium oxide, the above polishing method can be said to be a very advantageous method compared to the conventional polishing method.

The polishing step a is a step of polishing the negatively chargeable substrate using the abrasive slurry under conditions where the zeta potential of the abrasive slurry is positive. In this polishing process, it is possible to achieve a high polishing rate almost equal to that when using a conventional cerium oxide-based abrasive, and the surface of the negatively charged substrate is higher than when using a cerium oxide-based abrasive. Smoothness can also be improved.

The polishing step b is a step of polishing a negatively chargeable substrate using the abrasive slurry under conditions where the zeta potential of the abrasive slurry is negative. In this polishing process, while achieving a significantly higher polishing speed than the precision polishing process using conventional colloidal silica, it is possible to carry out precise polishing that is almost the same as the precision polishing process using colloidal silica. High surface smoothness can be realized in the conductive substrate.

As described above, the negatively chargeable substrate is polished under the condition where the zeta potential of the abrasive slurry is positive in the polishing step a and under the condition where the zeta potential of the abrasive slurry is negative in the polishing step b. However, it is preferable to perform each polishing step under conditions where the absolute value of the zeta potential of the abrasive slurry is 5 mV or more. Each is more preferably 10 mV or more, further preferably 15 mV or more, and particularly preferably 20 mV or more. Although the upper limit of the absolute value in each step is not particularly limited, for example, ease of control (for example, if the zeta potential is excessively large in the polishing step a, the abrasive may adhere to the glass substrate surface, For example, if the zeta potential is too low in the polishing step b, the electrostatic repulsion between the negatively chargeable substrate and the abrasive slurry may be too strong and the polishing rate may not be sufficiently increased. Therefore, from the viewpoint of preventing this, it is preferable that the voltage is 100 mV or less.

The zeta potential of the abrasive slurry can be controlled by adjusting the pH of the abrasive slurry. If the abrasive slurry contains the composite metal oxide abrasive of the present invention, adjusting the pH of the abrasive slurry to less than the isoelectric point of the abrasive slurry, while its zeta potential becomes positive, When the pH of the material slurry is adjusted to a range exceeding the isoelectric point of the abrasive slurry, the zeta potential becomes negative. In the past, the abrasives emphasized increasing the polishing rate or increasing the surface smoothness, but the composite metal oxide polishing material of the present invention can easily control the abrasiveness only by pH. In this respect, a unique effect that cannot be conceived from the prior art can be exhibited.

The pH may be adjusted by adding a pH adjusting agent to the abrasive slurry, or the pH of the abrasive slurry may be adjusted using a pH buffer solution.
In addition, when the pH of the abrasive slurry is already in a region preferable for polishing, pH adjustment may not be performed.

An acid or an alkali can be used as the pH adjuster. If an acid is used, the pH of the abrasive slurry can be adjusted to the acidic side, and if an alkali is used, the pH of the abrasive slurry can be adjusted to the alkali side. The acid is preferably, for example, an inorganic acid such as nitric acid, sulfuric acid, hydrochloric acid, perchloric acid or phosphoric acid; an organic acid such as oxalic acid or citric acid; and the alkali is, for example, an aqueous sodium hydroxide solution or potassium hydroxide. Alkaline aqueous solutions, such as aqueous solution, calcium hydroxide aqueous solution, sodium carbonate aqueous solution, ammonia water, sodium hydrogen carbonate aqueous solution, are preferable.

In the above polishing method, it is preferable that the polishing step a is performed under the condition that the pH of the abrasive slurry is larger than the isoelectric point of the negatively chargeable substrate and less than the isoelectric point of the abrasive slurry. As a result, it is sufficiently suppressed that the composite metal oxide polishing material of the present invention is dissolved by the strong acid, and the polishing action by the polishing material is further exhibited, and the burden on the polishing machine / device can be reduced. it can. Specifically, the lower limit of the pH of the abrasive slurry in the polishing step a is preferably 2 or more. More preferably, it is 3 or more, More preferably, it is 4 or more.

Moreover, it is preferable to implement the grinding | polishing process b on the conditions from which pH of an abrasive slurry is larger than the isoelectric point of this abrasive slurry, and is 13 or less. As a result, dissolution of the composite metal oxide polishing material of the present invention by the strong base is sufficiently suppressed, and the polishing action by the polishing material is further exhibited, and the burden on the polishing machine / device is reduced. You can also. The upper limit of the pH of the abrasive slurry in the polishing step b is preferably 12 or less. More preferably, it is 11 or less.

The isoelectric point of the abrasive slurry (and the composite metal oxide polishing material of the present invention) means that the algebraic sum of the charge on the abrasive grains (the composite metal oxide polishing material of the present invention) in the abrasive slurry is zero. A certain point, that is, a point at which the positive charge and negative charge on the abrasive grains become equal, can be expressed by the pH of the abrasive slurry at that point.

The content of the composite metal oxide polishing material of the present invention in the abrasive slurry is preferably 0.001 to 90% by weight in 100% by weight of the abrasive slurry, for example. More preferably, it is 0.01 to 30% by weight. The abrasive slurry preferably further contains a dispersion medium. The dispersion medium is as described above.

In order to describe the present invention in detail, examples will be given below, but the present invention is not limited to these examples.

Example 1
(1) Zr raw material preparation step Zirconium oxychloride octahydrate (made by Showa Chemical Co., Ltd.) (3.0 kg) was dissolved in 6.7 L of ion-exchanged water with stirring. The solution was adjusted to 25 ° C. with stirring, and while maintaining this temperature, 180 g / L of an aqueous sodium hydroxide solution was added over 1 hour with stirring until pH 9.5, and the mixture was further stirred for 1 hour. . The slurry was washed with filtered water, and washed with water until the electric conductivity of the washing became 100 μS / cm or less to obtain a zirconium hydroxide cake.

(2) Mixing Step Sr material as strontium carbonate (manufactured by Sakai Chemical Industry Co., Ltd.: SW-P-N) 26.1g and, as Zr raw material (1) Zr raw material preparation step ZrO ₂ The resulting zirconium hydroxide cake by It measured to a 300 mL mayonnaise bottle so that it might become 31.3g in conversion, 172 mL of ion-exchange water and 415 g of 1 mm diameter zirconia beads were added, and it mixed for 30 minutes using the paint conditioner (Red Devil company type: 5110 type | mold).

(3) Drying step The slurry obtained in the above (2) mixing step is passed through a sieve of 400 mesh (aperture 38 μm) to remove zirconia beads and subsequently filtered to obtain a cake of the mixture at a temperature of 120 ° C. And dried sufficiently to obtain a dry product of the mixture.

(4) Firing step 30 g of the dried product of the mixture obtained in the above (3) drying step is placed in an alumina crucible having an outer diameter of 55 mm and a capacity of 60 mL, and an electric muffle furnace (ADVANTEC, KM-420). Was fired to obtain a fired product. As firing conditions, the temperature was raised from room temperature to 950 ° C. over 285 minutes, held at 950 ° C. for 180 minutes, and then the heater was turned off and cooled to room temperature. The firing was performed in the air.

(5) Grinding step 10 g of the fired product obtained in the above (4) firing step is charged into an automatic mortar (Laikai machine) (manufactured by Nichito Kagaku Co., Ltd .: ANM-150), and ground for 10 minutes to obtain composite metal An oxide polishing material was obtained.

Examples 2 and 3
(4) A composite metal oxide polishing material was obtained in the same manner as in Example 1 except that the firing temperature in the firing step was changed to the temperature shown in Table 1.

Example 4
(1) Zr raw material preparation process Zirconium oxychloride octahydrate (made by Showa Chemical Co., Ltd.) 3.0 kg and ammonium sulfate (made by Toagosei Co., Ltd.) 0.35 kg are dissolved in 6.7 L of ion-exchanged water while stirring. I let you. The solution was adjusted to 25 ° C. with stirring, and while maintaining this temperature, 180 g / L of an aqueous sodium hydroxide solution was added over 1 hour with stirring until pH 9.5, and the mixture was further stirred for 1 hour. . The slurry was washed with filtered water, and washed with water until the electric conductivity of the washing became 100 μS / cm or less to obtain a zirconium hydroxide cake.
(2) Drying step to (5) Grinding step were performed in the same manner as in Example 1 to obtain a composite metal oxide polishing material.

Example 5
(2) A composite metal oxide polishing material was obtained in the same manner as in Example 1 except that 109 g of zirconium carbonate (manufactured by Sakai Kogyo Co., Ltd.) was used as the Zr raw material in the mixing step.

Example 6
(2) A composite metal oxide polishing material was obtained in the same manner as in Example 1 except that 69 g of zirconium carbonate (manufactured by Sakai Kogyo Co., Ltd.) was used as the Zr raw material in the mixing step.

Comparative Example 1
(1) Zr raw material preparation step Zirconium oxychloride octahydrate (produced by Showa Chemical Co., Ltd.) 3.0 kg and ammonium sulfate (produced by Toagosei Co., Ltd.) 0.70 kg are dissolved in 6.7 L of ion-exchanged water with stirring. I let you. The solution was adjusted to 25 ° C. with stirring, and while maintaining this temperature, 180 g / L of an aqueous sodium hydroxide solution was added over 1 hour with stirring until pH 9.5, and the mixture was further stirred for 1 hour. . The slurry was washed with filtered water, and washed with water until the electric conductivity of the washing became 100 μS / cm or less to obtain a zirconium hydroxide cake.
The (2) drying step to (5) pulverization step were performed in the same manner as in Example 1 to obtain a comparative polishing material.

Comparative Example 2
(1) A comparative polishing material was obtained in the same manner as in Example 1 except that the zirconium hydroxide cake obtained in the Zr raw material preparation step was dried at 130 ° C. for 15 hours.

Comparative Examples 3 and 4
(4) Except having changed the calcination temperature in a baking process into the temperature of Table 1, it carried out similarly to the comparative example 2, and obtained the abrasive material for a comparison.

<Performance evaluation>
The performance of the polishing materials and the raw materials prepared in each Example and Comparative Example was evaluated by the following procedure.

(I) Measurement of full width at half maximum With respect to each of the Zr raw material (zirconium compound) and the polishing material, a powder X-ray diffraction pattern (also simply referred to as an X-ray diffraction pattern) was measured under the following conditions.
Machine used: RINT-UltimaIII, manufactured by Rigaku Corporation
Radiation source: CuKα
Voltage: 40 kV
Current: 40 mA
Sample rotation speed: non-rotating divergent slit: 1.00 mm
Divergence length restriction slit: 10 mm
Scattering slit: Open light receiving slit: Open scanning mode: FT
Counting time: 2.0 seconds Step width: 0.0200 °
Operation axis: 2θ / θ
Scanning range: 10.000 to 70.000 °
Integration count: 1 time Monoclinic ZrO ₂ : JCPDS card 00-037-1484
Tetragonal ZrO ₂ : JCPDS card 00-050-1089
Cubic ZrO ₂ : JCPDS card 00-049-1642
Orthorhombic SrZrO ₃ : JCPDS card 00-044-0161
Thereafter, the orthorhombic SrZrO ₃ (040) half width was measured from the diffraction pattern obtained by the X-ray diffraction measurement of the polishing material obtained in each Example and Comparative Example. The results are shown in Table 2.
In the X-ray diffraction using CuKα ray as the radiation source, the peak derived from the (−111) plane, which is the maximum peak of monoclinic ZrO ₂ , is in the vicinity of 2θ = 28.14 °, and the tetragonal ZrO ₂ The peak derived from the (011) plane which is the maximum peak is in the vicinity of 2θ = 30.15 °, and the peak derived from the (111) plane which is the maximum peak of the cubic ZrO ₂ is in the vicinity of 2θ = 30.12 °. The peak derived from the (040) plane of orthorhombic SrZrO ₃ is in the vicinity of 2θ = 44.04 °.

(Ii) Elemental analysis For each of the Zr raw material (zirconium compound) and the polishing material, elemental analysis was performed by EZ scan which is a contained element scanning function of a fluorescent X-ray analyzer (manufactured by Rigaku Corporation: model number ZSX Primus II).
Specifically, the pressed sample is set on the measurement sample stage, and the following conditions are selected (measurement range: FU, measurement diameter: 30 mm, sample form: oxide, measurement time: long, atmosphere: vacuum) Thus, the SO ₃ content in the Zr raw material, the Sr content (SrO conversion) and the SO ₃ content in the polishing material were measured. The results are shown in Table 2.
Based on the SO ₃ content of Zr in the raw material obtained in this manner was calculated the content of SO ₃ with respect to terms of ZrO ₂ per 100 parts by weight of Zr raw material (parts by weight). This is shown in the column “SO ₃ ^{* 1} (parts by weight)” in Table 2.
Further, based on the SO ₃ content in the polishing material obtained as described above, the SO ₃ content (parts by weight) relative to 100 parts by weight of the zirconium compound equivalent in ZrO ₂ contained in the polishing material was calculated. This is shown in the column “SO ₃ ^{* 2} (parts by weight)” in Table 2.

(Iii) Measurement of specific surface area The specific surface area of each of the Zr raw material (zirconium compound) and the polishing material was measured under the following conditions. The results are shown in Table 2.
Used machine: Macsorb Model HM-1220 manufactured by Mountec Co., Ltd.
Atmosphere: Nitrogen gas (N ₂ )
Degassing condition of external degassing device: 200 ° C-15 minutes Degassing condition of specific surface area measuring device body: 200 ° C-5 minutes

(Iv) Sharpness of particle size distribution (D ₉₀ / D ₁₀ )
The abrasive was subjected to particle size distribution measurement using a laser diffraction / scattering particle size analyzer (manufactured by Nikkiso Co., Ltd .: Model No. Microtrack MT3300EX).
First, 60 mL of ion-exchanged water was added to 0.1 g of the polishing material, and a suspension of the polishing material was prepared by thoroughly stirring at room temperature using a glass rod. In addition, the dispersion | distribution operation using an ultrasonic wave was not performed. Thereafter, 180 mL of ion exchange water is prepared in a sample circulator, and the suspension is dropped so that the transmittance is 0.71 to 0.94, and ultrasonic dispersion is not performed at a flow rate of 50%. The measurement was carried out while circulating.

(V) Differential thermal / thermogravimetric measurement of zirconium compound (zirconium hydroxide) In order to investigate the cause of the decrease in the polishing rate of the abrasive material when the zirconium compound contains a sulfur compound, it was used in Example 1 and Comparative Example 1. Each Zr raw material (zirconium hydroxide) was dried at 130 ° C. for 12 hours, and then subjected to differential thermal and thermogravimetric analysis (TG / DTA).
Specifically, differential heat / thermogravimetry (TG / DTA) was performed under the following conditions. The measurement results are shown in FIGS. 1-1 and 1-2. For the dried product of the mixture obtained in “(3) Drying step” of Example 1 and the dried product of the mixture obtained in “(3) Drying step” of Comparative Example 1, the differential thermal and thermogravimetric measurements were similarly performed. (TG / DTA) was performed. The measurement results are shown in FIGS. 2-1 and 2-2.
Measuring instrument: manufactured by Rigaku Corporation, differential thermal / thermogravimetric measuring device (model number: Thermo plus EVO2 TG8121)
Temperature increase rate: 10 ° C / min Measurement temperature range: 30-1200 ° C
Measurement atmosphere: air 200 mL / min Reference: Al ₂ O ₃
Sample weight: 10.0mg
Sample container: platinum

(Vi) Glass plate polishing test 1 First, an abrasive slurry was prepared using each polishing material.
Specifically, the polishing material was added to ion-exchanged water so that the concentration of the polishing material was 5.0% by weight. Furthermore, it was dispersed by stirring at 25 ° C. for 10 minutes to prepare a water-dispersed abrasive slurry.
2. Next, the glass plate was polished using each abrasive slurry under the following conditions.
Glass plate used: Soda lime glass (manufactured by Matsunami Glass Industry Co., Ltd., size 36 × 36 × 1.3 mm, specific gravity 2.5 g / cm ³ )
Polishing machine: Desktop polishing machine (manufactured by MT Corporation, MAT BC-15C, polishing plate diameter 300 mmφ)
Polishing pad: Polyurethane foam pad (Nitta Haas, MHN-15A, no ceria impregnation)
Polishing pressure: 101 g / cm ²
Plate rotation speed: 70rpm
Abrasive composition supply amount: 100 mL / min
Polishing time: 60 min
3. The weight of the glass plate before and after the glass plate polishing test was measured with an electronic balance. From the weight reduction amount, the area of the glass plate, and the specific gravity of the glass plate, the thickness reduction amount of the glass plate was calculated, and the polishing rate (μm / min) was calculated.
Three glass plates were polished at the same time, and after polishing for 60 minutes, the glass plate and the abrasive slurry were exchanged. This operation was performed three times, and a value obtained by averaging the polishing rate of a total of 9 sheets was used as the polishing rate value in each example and comparative example. The results are shown in Table 2.
Very good (◎) when the polishing rate is 0.29 μm / min or more, good (◯) when the polishing rate is 0.22 μm / min or more and less than 0.29 μm / min, and defective (<×). ).

In Table 2, “SO ₃ ^{* 1} (parts by weight)” means the SO ₃ equivalent of the sulfur compound contained in the Zr raw material with respect to 100 parts by weight of the Zr raw material (zirconium compound) in terms of ZrO _2. “SO ₃ ^{* 2} (part by weight)” means the SO ₃ equivalent of the sulfur compound contained in the polishing material with respect to 100 parts by weight of the zirconium compound equivalent to ZrO ₂ contained in the abrasive.

From the above examples and comparative examples, the following was confirmed.
The zirconium compound used in Example 1 and the zirconium compound used in Comparative Example 1 are mainly different in content of sulfur compounds.
Comparison of the results of differential thermal / thermogravimetric measurement under this difference shows that, from FIGS. 1-1 and 1-2, any zirconium compound (zirconium hydroxide) has an exothermic peak with no weight change. It was done. This indicates that amorphous zirconium hydroxide is a main component at a temperature below the exothermic peak, and that zirconium hydroxide crystallizes as zirconium oxide at the exothermic peak temperature. The exothermic peak of zirconium hydroxide was 416 ° C., and the exothermic peak of zirconium hydroxide used in Comparative Example 1 was 506 ° C. Therefore, it was found that the zirconium hydroxide used in Comparative Example 1 had a higher temperature required for crystallization than the zirconium hydroxide used in Example 1, that is, it was difficult to crystallize at the same firing temperature.

FIGS. 2-1 and 2-2 show the dried product (called mixed powder) of a mixture of the zirconium compound (zirconium hydroxide) used in Example 1 or Comparative Example 1 and the strontium compound (strontium carbonate). It is a graph which shows the result of having performed differential heat and thermogravimetry. From FIG. 2, an exothermic peak without any weight change is observed in any of the mixed powders, and the mixed powder of Comparative Example 1 is necessary for crystallization compared to the mixed powder of Example 1 due to the difference in peak temperature. It has been found that crystallization is difficult at higher temperatures, ie, at the same firing temperature.

The reason why the temperatures of the exothermic peaks are different is that the amount of the sulfur compound contained in the zirconium hydroxide used in Comparative Example 1 exceeds the range defined in the present invention. It also affects the crystallinity of the resulting abrasive material. From Table 2, the half width of the peak derived from the (040) plane of orthorhombic SrZrO ₃ of the polishing material according to Comparative Example 1 and SSA increased as compared with the composite metal oxide polishing material according to Example 1. ing. This indicates that the crystallinity of the polishing material when fired at the same 950 ° C. is low. Further, a significant difference in polishing rate was confirmed between Comparative Example 1 and Example 1. Therefore, when the content of the sulfur compound contained in the zirconium compound exceeds the range specified in the present invention, it is considered that the crystallinity of the polishing material is lowered and the polishing rate is lowered.

The polishing materials according to Comparative Examples 3 to 4 have higher crystallinity by increasing the firing temperature compared to Example 1. However, from Table 2, the full width at half maximum of the peak derived from the (040) plane of orthorhombic SrZrO ₃ of the polishing materials according to Comparative Examples 3 and 4 and SSA are those of the composite metal oxide polishing material according to Example 1. However, the polishing rate is low. This is presumably because the particles were sintered too much, although the crystallinity of the polishing material became comparable by increasing the firing temperature. Moreover, the polishing material according to Comparative Example 2 was the same as the polishing material according to Example 1 in that the zirconium compound (zirconium hydroxide) was dried at 130 ° C. and then subjected to a mixing step with a strontium compound (strontium carbonate). However, from Table 2, since the amount of the sulfur compound contained in the zirconium compound also exceeds the range defined in the present invention, the polishing rate did not reach a sufficient level.
From the above, it was found that the production method of the present invention can efficiently provide a polishing material having a good polishing rate in a cerium-free polishing material.

Reference example 1
Using the composite metal oxide polishing material prepared in Example 1, an abrasive slurry A was prepared.
Specifically, 20.0 g of the abrasive was dispersed in 380.0 g of ion exchange water and stirred at 25 ° C. for 10 minutes. In this way, an abrasive slurry A was obtained.
For the abrasive slurry A, the zeta potential was measured under the following conditions. The relationship of the zeta potential with respect to pH of this abrasive slurry is shown in FIG. Moreover, the isoelectric point of the abrasive slurry A was 6.2. Here, the isoelectric point is the point where the algebraic sum of the charge on the abrasive grains (composite metal oxide polishing material) in the abrasive slurry is zero, that is, the positive and negative charges on the abrasive grains. The point which becomes equal is said and can be represented by the pH of the abrasive slurry at that point.

(Zeta potential measurement conditions)
Measuring instrument: Otsuka Electronics Co., Ltd., zeta potential measurement system, model number ELSZ-1
pH titrator: manufactured by Otsuka Electronics Co., Ltd., model number ELS-PT
6 g of the abrasive slurry was diluted 5 times with ion-exchanged water, and dispersed with an ultrasonic cleaner for 1 minute while stirring with a glass rod. 50 cc of ion-exchanged water was added to 10 cc of this slurry, and dispersion treatment was performed for 1 minute using an ultrasonic homogenizer (US-600, manufactured by Nippon Seiki Seisakusho) with the strength set to V-LEVEL3. A zeta potential measuring machine was charged with 30 cc of the abrasive slurry for zeta potential measurement thus obtained.
The abrasive slurry C using colloidal silica, which will be described later, was dispersed for 1 minute using an ultrasonic homogenizer (US-600, manufactured by Nippon Seiki Seisakusho) for 60 cc of the abrasive slurry C and setting the strength to V-LEVEL3. Went. A zeta potential measuring machine was charged with 30 cc of the abrasive slurry for zeta potential measurement thus obtained.

In addition, in order to adjust the pH of the abrasive slurry, the following pH adjusters were used as necessary.
Acid side pH adjustment solution: hydrochloric acid aqueous solution, 0.1 mol / L
Alkaline side pH adjustment solution: sodium hydroxide aqueous solution, 1 mol / L

(1) First Polishing Step The pH of the slurry was adjusted so that the zeta potential of the abrasive slurry A obtained as described above became a value shown in Table 3. In the presence of this slurry, the glass plate was polished under the same polishing conditions as in “(vi) Glass plate polishing test” of Example 1, and the polishing rate was measured. Table 3 shows the polishing rate and the pH value of the abrasive slurry A in this step. Furthermore, the surface roughness of the glass substrate after the first polishing step was evaluated according to the following method. The results are shown in Table 3.
(2) Second polishing step After the first polishing step, the abrasive slurry A is taken out, switched to a new abrasive slurry A, and after adjusting the pH of the slurry so that its zeta potential becomes the value shown in Table 3, In the presence of this slurry, the glass substrate was polished under the same polishing conditions as in the first polishing step, and the polishing rate was measured. Table 3 shows the polishing rate and the pH value of the abrasive slurry A in this step. Furthermore, the surface roughness of the glass substrate after the second polishing step was evaluated according to the following method. The results are shown in Table 3.

(Measurement of surface smoothness of glass substrate)
About the glass plate after each grinding | polishing process, the surface roughness was measured on condition of the following.
Measuring instrument: manufactured by ZYGO Corporation, white interference microscope, model number NewView ^™ 7100
Horizontal resolution: <0.1nm
Objective lens: 50 times filter: None Measurement field size: X = 186 μm, Y = 139 μm
Evaluation method: For the polished glass substrate, Ra was measured at a total of 9 points including the center point and the intersection of a concentric circle having a radius of 6 mm and 12 mm from the center point and the diagonal line of the glass substrate, and the average value was calculated. This operation was performed on a total of nine glass substrates used for the above-described polishing rate measurement, and the surface roughness was evaluated by averaging using the average value of Ra of each glass substrate.

Comparative Reference Example 1
(1) A cerium oxide abrasive for glass polishing as an abrasive for the first polishing process (Showa Denko KK, SHOROX (R) A-10, cerium oxide content: 60% by weight, isoelectric point: 10.4) An abrasive slurry B was prepared in the same manner as in Reference Example 1 except that was used. After adjusting the pH of the slurry so that the zeta potential of this abrasive slurry B becomes the value shown in Table 3, in the presence of this slurry, polishing similar to “(vi) Glass plate polishing test” of Example 1 The glass plate was polished under the conditions, and the polishing rate was measured. Table 3 shows the polishing rate and the pH value of the abrasive slurry B in this step. Furthermore, the surface roughness of the glass substrate after the first polishing step was evaluated in the same manner as in Reference Example 1. The results are shown in Table 3.
(2) Second polishing step The abrasive slurry B used in the first polishing step was taken out from the polishing machine, and the polishing machine was cleaned.
Separately, 52.2 g of colloidal silica (Fuso Chemical Co., Ltd., Quarton (R) PL-7, isoelectric point: 5.8) was dispersed in 347.8 g of ion-exchanged water and stirred at 25 ° C. for 10 minutes. This was prepared as an abrasive slurry C. After adjusting the pH so that the zeta potential of the separately prepared abrasive slurry C becomes the value shown in Table 3, the glass is subjected to the same polishing conditions as in the first polishing step in the presence of the abrasive slurry C. The substrate was polished. Table 3 shows the pH value of the abrasive slurry C in this step. Further, the polishing rate in the second polishing step and the surface roughness of the glass substrate after the second polishing step were evaluated in the same manner as in Reference Example 1. The results are shown in Table 3.
In addition, the relationship of the zeta potential with respect to pH of each of the abrasive slurry B and C is shown in FIG.

From the above Reference Example 1 and Comparative Reference Example 1, the following was confirmed.
In Reference Example 1 and Comparative Reference Example 1, the surface roughness of the finally obtained substrate (the substrate after the second polishing step) is almost equal, but in Reference Example 1, Comparative Reference Example 1 The polishing rate is remarkably improved as compared with FIG. Therefore, the preferred polishing method described above (that is, the polishing step a for polishing the negatively chargeable substrate under the condition that the zeta potential of the slurry containing the composite metal oxide polishing material of the present invention is positive, and the zeta of the abrasive slurry) A polishing method in which the polishing step b for polishing the negatively chargeable substrate under a condition where the potential is negative is performed at least once each in a cerium-free polishing material with a high polishing rate and excellent surface smoothness. It turns out that it can be realized. Further, in Comparative Reference Example 1, since a cerium oxide-based abrasive was used in the first polishing step and colloidal silica was used in the second polishing step, it was necessary to perform a cleaning operation of the polishing machine, In Reference Example 1, since the same type of abrasive slurry A is used in the first polishing step and the second polishing step, the cleaning work of the polishing machine is unnecessary, which is very advantageous in terms of work and equipment. It was.

Although not shown in the table, even when the abrasive slurry A used in the first polishing step is continuously used as it is without switching to the new abrasive slurry A in the second polishing step of Reference Example 1, the polishing rate and the gain are obtained. It has been confirmed that there is almost no influence on the surface smoothness of the substrate.

Claims

A mixing step of mixing a strontium compound and a zirconium compound;
A method for producing a composite metal oxide polishing material comprising a firing step of firing the mixture obtained by the mixing step,
The amount of sulfur compound contained in the zirconium compound in terms of SO 3 is 2.0 parts by weight or less with respect to 100 parts by weight in terms of ZrO 2 of the zirconium compound. Method.
The method for producing a composite metal oxide polishing material according to claim 1, wherein the strontium compound in the mixing step is at least one selected from the group consisting of strontium carbonate and strontium hydroxide.
The method for producing a composite metal oxide polishing material according to claim 1 or 2, wherein the zirconium compound in the mixing step is at least one selected from the group consisting of zirconium carbonate and zirconium hydroxide.
The method for producing a composite metal oxide polishing material according to any one of claims 1 to 3, wherein a firing temperature in the firing step is higher than 800 ° C and not higher than 1500 ° C.
A composite metal oxide polishing material comprising:
The SO 3 equivalent of the sulfur compound contained in the composite metal oxide polishing material is 1.2 parts by weight or less with respect to 100 parts by weight of the zirconium compound equivalent to ZrO 2 contained in the composite metal oxide polishing material. A composite metal oxide polishing material characterized by the above.