JPWO2015129776A1 - Method for producing composite metal oxide polishing material and composite metal oxide polishing material - Google Patents

Abstract

A polishing material having a good polishing rate in a cerium-free polishing material and a simple method for producing the polishing material are provided. A method for producing a composite metal oxide polishing material, comprising: a mixing step of mixing a strontium compound and zirconium oxide; and a baking step of baking the mixture obtained by the mixing step.

Description

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 JP2013-82050A

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.

Further, 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 that it is not suitable for mass production, and rare metals such as nickel and cobalt are used. 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 the spray pyrolysis method and is not suitable for mass production.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a polishing material having a good polishing rate in a cerium-free polishing material and a simple method for producing the polishing material. .

In order to solve the above problems, the present inventors have conducted intensive studies and found that a composite metal oxide polishing material obtained by mixing and baking a strontium compound and zirconium oxide exhibits a good polishing rate. The present invention has been completed.

That is, the manufacturing method of the composite metal oxide polishing material of the present invention (also referred to as “the manufacturing method of the present invention”) includes a mixing step of mixing a strontium compound and zirconium oxide, and firing the mixture obtained by the mixing step. And a firing step.

In the manufacturing method of this invention, the mixing process which mixes a strontium compound and a zirconium oxide as a raw material, and the baking process which bakes the mixture obtained by the said mixing process are included.
In this manufacturing method, by using zirconium oxide as the Zr raw material, the obtained composite metal oxide polishing material forms a composite of ZrO ₂ and SrZrO _3, and a high polishing rate can be realized. Note that the complex of ZrO ₂ and SrZrO _3, refers to secondary particles each of the primary particles of ZrO ₂ and SrZrO ₃ are formed by partially sintering. 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.
By using such a method, it is possible to produce a polishing material having a good polishing rate in a cerium-free polishing material.
As can be seen from the above raw materials, the production method of the present invention is carried out by a solid phase reaction method.

In the production method of the present invention, the strontium compound in the mixing step is preferably at least one selected from the group consisting of strontium carbonate and strontium hydroxide. Strontium carbonate and strontium hydroxide easily react with zirconium oxide to easily produce strontium zirconate (SrZrO ₃ ).

In the production method of the present invention, the half-value width of the maximum peak at 2θ = 27.0 to 31.00 ° in X-ray diffraction of the zirconium oxide in the mixing step using CuKα ray as a radiation source is 0.1 to 3 °. 3.0 ° is desirable, 0.1 to 1.0 ° is more desirable, 0.1 to 0.7 ° is still more desirable, and 0.1 to 0.4 ° is desirable. It is particularly desirable. When the half width exceeds 3.0 °, the crystallinity of ZrO ₂ contained in the obtained composite metal oxide polishing material is low, and the mechanical polishing action derived from ZrO ₂ may not be sufficiently obtained. Further, if the half width is less than 0.1 °, the crystallinity of ZrO _{2 as} a raw material is high, and the reaction with the strontium compound hardly occurs, so that a composite metal oxide polishing material having a good polishing rate can be obtained. There may not be.

The composite metal oxide polishing material of the present invention includes a crystal phase of ZrO _{2 and} a crystal phase of SrZrO ₃ , and (040) of orthorhombic SrZrO ₃ in X-ray diffraction using CuKα rays as a radiation source. The half width of the peak derived from the surface is 0.1 to 3.0 °.
The half width is preferably 0.1 to 1.0 °, more preferably 0.1 to 0.7 °, and still more preferably 0.1 to 0.4 °.
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 good polishing rate can be exhibited.
Furthermore, since ZrO ₂ and SrZrO ₃ form a composite, the mechanical polishing action by the crystal phase of ZrO _{2 and} the chemical polishing action by the crystal phase of SrZrO ₃ are effectively exhibited.
Furthermore, when the half width is 0.1 to 3.0 °, the crystallinity of SrZrO ₃ that effectively exhibits the chemical polishing action is moderate, and the chemical polishing action can be sufficiently exhibited.
When the half width is more than 3.0 °, low crystalline SrZrO _3, there is a chemical polishing action derived from SrZrO ₃ can not be obtained sufficiently. If the half width is less than 0.1 °, the crystallinity of SrZrO ₃ is too high, and the chemical polishing action derived from SrZrO ₃ may not be sufficiently obtained.

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 is an X-ray diffraction pattern of zirconium oxide as a Zr raw material used in Example 1. FIG. 2 is an X-ray diffraction pattern of the composite metal oxide polishing material according to Example 1. FIG. 3 is an SEM image of the composite metal oxide polishing material according to Example 1. FIG. 4 is a graph showing the relationship of the zeta potential with respect to the pH of each abrasive slurry used in the reference example or the 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 includes a mixing step of mixing a strontium compound and zirconium oxide, and a baking step of baking the mixture obtained by the mixing step. Therefore, the composite metal oxide polishing material can achieve a high polishing rate.

First, a strontium compound, one of the raw materials in the production method of the present invention, will be described.
In the production method of the present invention, the strontium compound is desirably at least one selected from the group consisting of strontium carbonate and strontium hydroxide. Strontium carbonate and strontium hydroxide easily react with zirconium oxide to easily produce strontium zirconate (SrZrO ₃ ).

Next, the raw material zirconium oxide will be described.
Zirconium oxide as a raw material has a half-width of the maximum peak at 2θ = 27.0 to 31.00 ° in X-ray diffraction using CuKα ray as a radiation source (hereinafter, simply referred to as a half-width of the maximum peak of ZrO ₂ ). Is preferably 0.1 to 3.0 °, more preferably 0.1 to 1.0 °, still more preferably 0.1 to 0.7 °, It is particularly desirable to be ~ 0.4 °.
When the half width exceeds 3.0 °, the crystallinity of ZrO ₂ contained in the obtained composite metal oxide polishing material is low, and the mechanical polishing action derived from ZrO ₂ may not be sufficiently obtained. Further, if the half width is less than 0.1 °, the crystallinity of ZrO _{2 as} a raw material is high and the reaction with the strontium compound hardly occurs, so that a composite metal oxide polishing material having a good polishing rate cannot be obtained. Sometimes.
In this specification, CuKα rays were used for all X-ray diffraction sources.

It zirconium oxide raw material, it is desirable that a specific surface area of 2.0~200m ² / g, and more desirably 2.0~180m ² / g, a 2.0~160m ² / g Is more desirable. When the specific surface area of zirconium oxide is 2.0 to 200 m ² / g, it becomes easy to efficiently produce a moderately crystalline SrZrO ₃ phase.
When the specific surface area of zirconium oxide is less than 2.0 m ² / g, the reactivity with the strontium compound may be lowered. Further, when the specific surface area of zirconium oxide exceeds 200 m ² / g, the reactivity of zirconium oxide becomes too high, and the reaction control with the strontium compound becomes difficult, and a composite metal oxide polishing material having a good polishing rate is obtained. It may be difficult to get it.

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.

The crystal form of the raw material zirconium oxide is preferably a monoclinic, tetragonal or cubic crystal structure, or a mixed crystal of these crystal structures.

Next, the mixing process will be described.
The production method of the present invention includes a mixing step of mixing zirconium oxide and a strontium compound. It is desirable that the ratio of the raw materials when mixing is 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 the wet mixing is not particularly limited, and water or lower alcohol can be used. However, 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 wet mixing, one or more dispersants may be added. The dispersant is not particularly limited, and cationic, nonionic, anionic, amphoteric and nonionic surfactants can be used. Further, it is desirable to perform a drying step following the wet mixing in order to remove the dispersion medium.

In wet mixing, it is desirable to perform mixing using media such as beads. By mixing using the media, the zirconium oxide and the strontium compound are sufficiently mixed, so that the risk of remaining unreacted strontium compound in the obtained composite metal oxide polishing material can be sufficiently reduced. The medium used for the wet mixing is not particularly limited, and zirconia beads, zircon beads, titania beads, alumina beads, glass beads, and nylon balls can be used, but zirconia beads are preferable from the viewpoint of suppressing contamination.

In the wet mixing, the concentration of the mixed powder of zirconium oxide and strontium compound (this concentration is also referred to as “mixed slurry concentration”) varies depending on the amount of dispersant added and the like, and is not particularly limited. L is desirable, 100 to 450 g / L is more desirable, and 150 to 400 g / L is even more desirable. More desirably, it is 200 to 400 g / L, particularly desirably 250 to 400 g / L, and most desirably 270 to 400 g / L. When the mixed slurry concentration is 50 to 500 g / L, it becomes easy to efficiently generate a moderately crystalline SrZrO ₃ phase.
When the above mixed slurry concentration is less than 50 g / L, the dispersion medium may be wasted and productivity may not be improved, and the pulverization of each of the zirconium oxide and the strontium compound proceeds so that the reaction control is performed more appropriately. It may be difficult to obtain a composite metal oxide polishing material having a good polishing rate. Also, when the mixed slurry concentration exceeds 500 g / L, the viscosity of the slurry becomes too high and handling properties may not be good, and the resulting composite metal is not sufficiently mixed with zirconium oxide and strontium compound. An unreacted strontium compound may remain in the oxide polishing material.

In the mixing step, the mixing time of the zirconium oxide and the strontium compound varies depending on the concentration of the mixed slurry and is not particularly limited. For example, the mixing time is preferably more than 0 minutes and within 100 minutes. By setting the mixing time within this range, the zirconium oxide and the strontium compound are sufficiently mixed and the pulverization does not proceed excessively, so that the polishing rate of the obtained composite metal oxide polishing material can be further improved. it can. More preferably, it is 5 minutes or more, More preferably, it is 15 minutes or more, Especially preferably, it is 20 minutes or more, More preferably, it is 80 minutes or less, More preferably, it is 60 minutes or less, Especially preferably, it is 40 minutes or less.

Then, a drying process is demonstrated.
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.
In addition, a drying process should just be performed as needed and the dry thing of a mixture may be dry-pulverized.

Then, a baking process is demonstrated.
In the firing step, a composite metal oxide polishing material is obtained by firing a mixture of zirconium oxide and a strontium compound. The firing atmosphere is not particularly limited.

In the firing step, the raw material mixture obtained in the mixing step and the dried product obtained in the drying step may be fired as they are, or may be fired after being molded into a predetermined shape (for example, a pellet shape). .

The firing temperature in the firing step means the highest temperature reached in the firing step. The firing temperature may be a temperature sufficient for the reaction between the strontium compound and zirconium oxide, preferably 700 to 1300 ° C, more preferably 730 to 1270 ° C, and more preferably 750 to 1250 ° C. Is more desirable. When the firing temperature is lower than 700 ° C., the reaction between the strontium compound and zirconium oxide may not sufficiently proceed. Further, when the firing temperature exceeds 1300 ° C., the produced strontium zirconate may be vigorously sintered and the polishing rate may be reduced.

The holding time at the calcination temperature may be a time sufficient for the reaction between the strontium compound and zirconium oxide, preferably 5 minutes to 24 hours, more preferably 7 minutes to 22 hours. More desirably, it is from minutes to 20 hours. When the holding time is less than 5 minutes, the strontium compound and zirconium oxide may not sufficiently react. Moreover, when holding time exceeds 24 hours, the produced | generated strontium zirconate sinters violently and a polishing rate may fall.

In the firing step, the rate of temperature rise during the temperature rise until reaching the maximum temperature (firing temperature) is preferably 0.2 to 15 ° C./min, and preferably 0.5 to 12 ° C./min. More desirably, it is further desirably 1.0 to 10 ° C./min. When the rate of temperature increase is less than 0.2 ° C./min, the time required for temperature increase becomes too long, and energy and time are wasted. Moreover, when it exceeds 15 degreeC / min, the temperature of the furnace content cannot follow preset temperature, temperature unevenness generate | occur | produces inside a furnace, and it may become a cause of baking unevenness.

Next, the grinding process will be described.
In the pulverization step, the fired product obtained in the calcination step is pulverized, but 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.
In addition, what is necessary is just to perform a grinding | pulverization process as needed.

In the production method of the present invention, the firing step may be performed only once or twice or more.

As described above, the solid phase reaction method is used in the production method of the present invention. By using the solid-phase reaction method, the manufacturing process becomes simpler than that of the spray pyrolysis method, and it is possible to manufacture at a low cost without introducing special equipment.
Further, the composite metal oxide polishing material produced by the above method includes a crystal phase of ZrO _{2 and} a crystal phase of SrZrO ₃ , and an orthorhombic SrZrO in X-ray diffraction using CuKα rays as a radiation source. ₃ of the peak derived from the (040) plane (hereinafter, also simply referred to as SrZrO ₃ (040) half width) is 0.1 to 3.0 °.

[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 includes a crystal phase of ZrO _{2 and} a crystal phase of SrZrO ₃ , and (040) of orthorhombic SrZrO ₃ in X-ray diffraction using CuKα rays as a radiation source. The half width of the peak derived from the surface is 0.1 to 3.0 °.
The half width is preferably 0.1 to 1.0 °, more preferably 0.1 to 0.7 °, and still more preferably 0.1 to 0.4 °.
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 good polishing rate can be exhibited.
Furthermore, when the half width is 0.1 to 3.0 °, the crystallinity of SrZrO ₃ that effectively exhibits the chemical polishing action is moderate, and the chemical polishing action can be sufficiently exhibited.
When the half width is more than 3.0 °, low crystalline SrZrO _3, there is a chemical polishing action derived from SrZrO ₃ can not be obtained sufficiently. If the half width is less than 0.1 °, the crystallinity of SrZrO ₃ is too high, and the chemical polishing action derived from SrZrO ₃ may not be sufficiently obtained.

Composite metal oxide abrasive of the present invention, it is desirable ratio _{D 10} of _{D 90} indicative of sharpness of volume-based particle size distribution _(D 90 _/ D ₁₀₎ is 1.5 to 50, 1. It is more desirably 5 to 45, and further desirably 1.5 to 40. A larger value (D ₉₀ / D ₁₀ ) means that the particle size distribution is broader, and a smaller value means that the particle size distribution is sharper. 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 decrease. When D ₉₀ / D ₁₀ is less than 1.5, the variation in particle diameter is too small, so that sufficient contact between the polishing material and the object to be polished cannot be obtained, and the polishing rate may decrease.
D ₁₀ and D ₉₀ are values obtained by measuring the particle size distribution. 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 composite metal oxide polishing material of the present invention preferably contains 10 to 43% by weight of Sr in terms of SrO, more preferably 11 to 43% by weight, and still more preferably 12 to 43% by weight. . When the Sr content is less than 10% by weight in terms of SrO, the content of SrZrO ₃ may be reduced and the chemical polishing action may be reduced. Also, if the Sr content exceeds 43 wt% in terms of SrO, ZrO ₂ content is relatively reduced, mechanical polishing action may be decreased.

Composite metal oxide abrasive of the present invention is desirably a specific surface area of 1.0~50m ² / g, and more desirably 1.0~45m ² / g, 1.0~40m ² / More desirably, it is g. When the specific surface area is less than 1.0 m ² / g, the specific surface area of the polishing material may be too small to sufficiently contact the object to be polished, and may not be polished. Moreover, when a specific surface area exceeds 50 m < ² > / g, the abrasive grain which comprises polishing material is too small, and a mechanical polishing effect | action may fall.

The composite metal oxide 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 composite metal oxide polishing material of the present invention may be used by appropriately mixing with other components depending on the application. For example, the composite metal oxide 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 the composite metal oxide polishing material of the present invention with a dispersion medium and / or an additive is not particularly limited, and for example, it can be used in the form of powder, paste, slurry or the like.

The dispersion medium is not particularly limited, and examples thereof include water, an organic solvent, and a mixture thereof. Examples of the organic solvent include monovalent water-soluble alcohols such as methanol, ethanol, and propanol; divalent or higher water-soluble alcohols such as ethylene glycol and glycerin; acetone, dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, and dioxane. Two or more of these may be used in combination as long as the effects of the invention are not impaired.
Examples of additives include acids, alkalis, chelating agents, antifoaming agents, pH adjusting agents, dispersants, viscosity adjusting agents, anti-aggregating agents, lubricants, reducing agents, rust preventing agents, and known polishing materials. These may be used alone or in combination of two or more in a range not impeding the effects of the present invention.

[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. In addition, the upper limit of the absolute value in each step is not particularly limited, but for example, it is easy to control (for example, if the zeta potential is too large in the polishing step a, there is a possibility that the abrasive remains on the glass substrate surface. Therefore, 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 is too strong and the polishing rate cannot be sufficiently increased. From the viewpoint of preventing this, etc., it is preferably 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. Thereby, the dissolution of the abrasive by the strong acid is sufficiently suppressed, and the polishing action by the abrasive is more exhibited, and the burden on the polishing machine / device can be reduced. 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 the 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 0.01-30 weight%.

It is preferable that the abrasive slurry further contains a dispersion medium. The dispersion medium is as described above. Moreover, although an additive may be included as needed, it is so preferable that content of additives other than a pH adjuster is small from a viewpoint of improving the effect by the said grinding | polishing method. For example, the content of additives other than the pH adjuster is preferably 5% by weight or less with respect to 100% by weight of the total amount of the abrasive slurry. In other words, in the total amount of abrasive slurry of 100% by weight, the composite metal oxide polishing material of the present invention, the dispersion medium and the pH adjuster are preferably 90% by weight or more, more preferably 95% by weight or more, and still more preferably. Is 99% by weight or more.

Examples of the present invention will be described 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.
500 g of this zirconium hydroxide cake was sufficiently dried at a temperature of 120 ° C. Next, 40 g of the obtained dried product was put into an alumina crucible having an outer diameter of 55 mm and a capacity of 60 mL, and baked using an electric muffle furnace (manufactured by ADVANTEC, KM-420) to obtain zirconium oxide. As firing conditions, the temperature was raised from room temperature to 800 ° C. over 240 minutes, held at 800 ° C. for 300 minutes, and then the heater was turned off and cooled to room temperature. The firing was performed in the air.

(2) 21.6 g of strontium carbonate (manufactured by Sakai Chemical Industry Co., Ltd .: SW-PN) as the Sr raw material and 31.3 g of zirconium oxide obtained in the above (1) Zr raw material preparation step as the Zr raw material. Weighed into a 300 mL mayonnaise bottle, added 172 mL of ion exchange water and 415 g of 1 mmφ zirconia beads, and mixed for 30 minutes using a paint conditioner (manufactured by Red Devil: Model 5110).

(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 put 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 in an automatic mortar (Laikai machine) (manufactured by Nichito Kagaku Co., Ltd .: ANM-150), and ground for 10 minutes, thereby composite metal An oxide polishing material was obtained.

(Examples 2 to 27)
The firing temperature in the (1) Zr raw material preparation step, the amount of zirconium oxide used in the (2) mixing step, the mixing time in the (2) mixing step, and / or the firing temperature in the (4) firing step are shown. A composite metal oxide polishing material was obtained in the same procedure as in Example 1 except that the changes were made as shown in FIG.

(Comparative Example 1)
(1) Zr raw material preparation step Zirconium oxychloride octahydrate (manufactured by Showa Chemical Co., Ltd.) 3.0 kg and ammonium sulfate (manufactured by Toagosei Co., Ltd.) 0.70 kg are stirred in 6.7 L of ion-exchanged water. Dissolved. 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 As the Sr raw material, 26.1 g of strontium carbonate (manufactured by Sakai Chemical Industry Co., Ltd .: SW-PN), and as the Zr raw material, the zirconium hydroxide cake 73. 4 g (21.9 g in terms of ZrO ₂ ) was weighed into a 300 mL mayonnaise bottle, 124 mL of ion-exchanged water and 415 g of 1 mmφ zirconia beads were added, and mixed for 30 minutes using a paint conditioner (manufactured by Red Devil: Model 5110).
After the (3) drying step, a comparative polishing material was obtained in the same procedure as in Example 1 except that the firing temperature in the (4) firing step was 800 ° C. Table 1 shows the amount of zirconium hydroxide used in the (2) mixing step and the firing temperature in the (4) firing step.

(Comparative Example 2)
A comparative polishing material was obtained in the same procedure as in Example 1 except that the amount of zirconium oxide used in the mixing step (2) of Example 1 was changed as shown in Table 1.

(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.

(Measurement of powder X-ray diffraction)
A powder X-ray diffraction pattern (also simply referred to as an X-ray diffraction pattern) was measured under the following conditions for the Zr raw materials used in each Example and Comparative Example and the polishing materials according to each Example and Comparative Example.
Use machine: RINT-UltimaIII made 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 70.0000 °
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

FIG. 1 shows an X-ray diffraction pattern of zirconium oxide as a Zr raw material used in Example 1.
An X-ray diffraction pattern of the composite metal oxide polishing material according to Example 1 is shown in FIG.
The X-ray diffraction pattern shown in FIG. 2 contained both ZrO ₂ and SrZrO ₃ peaks in a database (JCPDS card) with known peak positions. Therefore, it was found that the composite metal oxide polishing material according to Example 1 had a crystal phase of SrZrO _{3 and} a crystal phase of ZrO ₂ . This was the same in all Examples and Comparative Example 1.
For the polishing material obtained in Comparative Example 2, the X-ray diffraction pattern was measured in the same manner as in Example 1. Although the measurement results are not shown, it was found from the measurement results that the polishing material obtained in Comparative Example 2 had only the crystal phase of SrZrO ₃ and did not have the crystal phase of ZrO ₂ .

(Measurement of half width)
The half-value width of the maximum peak at 2θ = 27.0 to 31.00 ° of ZrO ₂ was measured from the diffraction pattern obtained by the X-ray diffraction measurement of the Zr raw material used in each example and comparative example. The orthorhombic SrZrO ₃ (040) half width was measured from the diffraction patterns obtained by the X-ray diffraction measurement of the polishing materials according to the examples and the comparative examples. 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 °.
As shown in FIG. 1, a peak derived from the (−111) plane of monoclinic ZrO ₂ was confirmed in the X-ray diffraction pattern of zirconium oxide used in Example 1, and 2θ = 27.00 to 31.00 °. The full width at half maximum of the peak was 0.38 °.
As shown in FIG. 2, a peak derived from the (040) plane of orthorhombic SrZrO ₃ was confirmed in the X-ray diffraction pattern of the composite metal oxide polishing material according to Example 1, and the half-value width was 0.33. °.

(Measurement of specific surface area)
With respect to the polishing materials according to the examples and comparative examples, and the Zr raw materials used in the examples and comparative examples, the specific surface area 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 main body: 200 ° C.-5 minutes

(Measurement of electron microscope images)
About the polishing material which concerns on each Example and a comparative example, the SEM image was image | photographed with the scanning electron microscope (SEM) (The JEOL Co., Ltd. make: Model number JSM-6510A). An SEM image of the composite metal oxide polishing material according to Example 1 is shown in FIG.
As shown in FIG. 3, the composite metal oxide polishing material according to Example 1 forms amorphous secondary particles in which a plurality of primary particles are randomly gathered.

(Elemental analysis)
About the polishing material which concerns on each Example and a comparative example, elemental analysis was performed by the EZ scan which is a contained element scanning function of a fluorescent X-ray-analysis apparatus (Rigaku Corporation make: model number ZSX PrimusII). Set the pressed sample on the measurement sample stage and select the following conditions (measurement range: FU, measurement diameter: 30 mm, sample form: oxide, measurement time: long, atmosphere: vacuum), and Sr content ( SrO conversion) was measured. The results are shown in Table 2.

(Sharpness of the particle size distribution _{(D 90 /} D 10))
About the polishing material which concerns on each Example and a comparative example, the particle size distribution measurement was performed with the laser diffraction and the scattering type particle size analyzer (the Nikkiso Co., Ltd. make: model number Microtrac 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-exchanged 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. The results are shown in Table 2.

(Preparation of abrasive slurry)
An abrasive slurry was produced using the abrasive material produced in each Example and Comparative Example.
The polishing material was added to ion-exchanged water so that the concentration of the polishing material was 5.0% by weight. Further, the slurry was dispersed using a high-speed mixer to prepare a water-dispersed abrasive slurry.

(Glass plate polishing test)
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 surface 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

(Polishing rate evaluation)
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 (◎) if the polishing rate is 0.29 μm / min or more, good (◯) if the polishing rate is 0.10 μm / min or more and less than 0.29 μm / min, and defective if it is less than 0.10 μm / min (× ).

The composite metal oxide polishing materials according to Examples 1 to 27 have a crystal phase of SrZrO _{3 and} a crystal phase of ZrO ₂ , and an orthorhombic SrZrO ₃ (040) half-value width in X-ray diffraction. Since it was 0.1-3.0 degrees, it turned out that it is excellent in polishing rate. _Further, D 90 _{/ D 10} has a 1.5 to 50, moderately volume based particle size distribution, it was suitable for complex metal oxide abrasive.
The comparative polishing material according to Comparative Example 1 had an orthorhombic SrZrO ₃ (040) half width exceeding 3.0, D ₉₀ / D ₁₀ exceeding 50, and the polishing rate was poor (x). It was.
The comparative polishing material according to Comparative Example 2 had a crystal phase of SrZrO ₃ , but did not have a crystal phase of ZrO ₂ and was not a composite. In this case, the polishing rate was poor (x).
Although not shown in the table, as Comparative Example 3, Example 1 and Example 2 except that the amount of strontium carbonate used in the mixing step (2) was set to 0 g (that is, strontium carbonate was not used). By performing the same procedure, a comparative polishing material having only a ZrO ₂ crystal phase and no SrZrO ₃ crystal phase was obtained. For this comparative polishing material, the polishing rate was evaluated in the same manner as in Example 1. The polishing rate was poor (x).
From the above, it was found that the method for producing a composite metal oxide polishing material of the present invention can provide a polishing material having a good polishing rate in a cerium-free polishing material.

Although not shown in the table, in the mixing step of Example 1 (2), the composite metal oxide polishing material was the same as Example 1 except that the mixing was not performed using beads but was mixed under blade stirring. Got. When this polishing material was evaluated for the polishing rate in the same manner as in Example 1, the polishing rate was 0.23 μm / min. For this polishing material, the X-ray diffraction pattern was measured in the same manner as in Example 1. Although the measurement results are not shown, from this measurement result, in addition to the crystal phase of SrZrO _{3 and} the crystal phase of ZrO ₂ , a peak derived from unreacted strontium carbonate was also confirmed in this 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. Further, the isoelectric point of the abrasive slurry A was 6.4. 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: manufactured by 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 using an ultrasonic homogenizer (US-600, manufactured by Nippon Seiki Seisakusho), the strength was set to V-LEVEL 3 and dispersion treatment was performed for 1 minute. A zeta potential measuring machine was charged with 30 cc of the abrasive slurry for zeta potential measurement thus obtained.
In addition, the abrasive slurry C using colloidal silica was subjected to a dispersion treatment for 1 minute using an ultrasonic homogenizer (US-600, manufactured by Nippon Seiki Seisakusho Co., Ltd.) for the abrasive slurry C60cc and setting the strength to V-LEVEL3. It was. 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 the “glass plate polishing test” of Example 1. Table 3 shows the pH value of the abrasive slurry A in this step. Further, similarly to the “polishing rate evaluation” test of Example 1, the polishing rate in the first polishing step was measured. 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 The abrasive slurry A used in the first polishing step is continuously used as it is, and after adjusting the pH of the slurry so that the zeta potential becomes the value shown in Table 3, the presence of this slurry Below, the glass substrate was grind | polished on the same grinding | polishing conditions as a 1st grinding | polishing process. Table 3 shows the pH value of the abrasive slurry A in this step. Further, similarly to the “polishing rate evaluation” in Example 1, the polishing rate in the second polishing step was measured. 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.

(Reference Example 2)
Except that the abrasive slurry A was taken out after the first polishing step and switched to a new abrasive slurry A (however, the pH of the slurry was adjusted to the value shown in Table 3) and the second polishing step was performed. In the same manner as in Example 1, the first polishing step and the second polishing step were performed. Table 3 shows the pH, zeta potential, polishing rate, and surface roughness of the glass substrate of the abrasive slurry in each step.

(Comparative Reference Example 1)
(1) Cerium oxide abrasive for glass polishing as a first polishing process abrasive (Showa Denko KK, SHOROX®-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, under the same polishing conditions as the “glass plate polishing test” of Example 1 The glass plate was polished. Table 3 shows the pH value of the abrasive slurry B in this step. Further, the polishing rate in the first polishing process and the surface roughness of the glass substrate after the first polishing process were 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 examples and comparative reference examples, the following was confirmed.
In Reference Examples 1 and 2 and Comparative Reference Example 1, although the surface roughness of the finally obtained substrate (substrate after the second polishing step) is almost equal, in Reference Examples 1 and 2, The polishing rate is remarkably improved as compared with Comparative Reference Example 1. 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 Examples 1 and 2, since the same type of abrasive slurry A is used in the first polishing step and the second polishing step, no cleaning work for the polishing machine is required, which is extremely advantageous in terms of work and equipment. Met.

In the second polishing step of Reference Example 1, the abrasive slurry A used in the first polishing step was continuously used as it was, whereas in the second polishing step of Reference Example 2, the abrasive used in the first polishing step. Although it is the same as the slurry A, Reference Example 1 is different from Reference Example 2 in that polishing is performed by switching to a new abrasive slurry A. However, this difference has been found to have little effect on the polishing rate and the surface smoothness of the resulting substrate.

Claims (4)

A mixing step of mixing a strontium compound and zirconium oxide;
A method for producing a composite metal oxide polishing material, comprising a firing step of firing the mixture obtained by the mixing step. 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 half-value width of the maximum peak at 2θ = 27.0 to 31.00 ° in X-ray diffraction using CuKα rays as a radiation source of zirconium oxide in the mixing step is 0.1 to 3.0 °. The method for producing a composite metal oxide polishing material according to claim 1 or 2. The half-value width of a peak derived from the (040) plane of orthorhombic SrZrO ₃ in X-ray diffraction including a crystal phase of ZrO _{2 and} a crystal phase of SrZrO ₃ and using CuKα rays as a radiation source is 0. A composite metal oxide polishing material characterized by having an angle of 1 to 3.0 °.