WO2016136447A1 - Negatively charged substrate polishing method and manufacturing method of negatively charged substrate with high surface smoothness - Google Patents

Abstract

A polishing method is provided which yields a negatively charged substrate with excellent surface smoothness with good productivity while achieving high polishing speeds. Also provided is a method for achieving a negatively charged substrate with high surface smoothness. In this method of manufacturing a negatively charged substrate using a polishing slurry, the polishing slurry contains an oxide represented by compositional expression ABO₃ (A represents at least one element selected from the group consisting of Sr and Ca. B represents at least one element selected from the group consisting of Ti, Zr and Hf.) and zirconium oxide, and the polishing method involves carrying out, at least once each, a polishing step a for polishing a negatively charged substrate under conditions in which the zeta potential of the polishing slurry becomes positive, and a polishing step b for polishing the negatively charged substrate under conditions in which the zeta potential of the polishing slurry becomes negative.

Description

Method for polishing negatively chargeable substrate and method for producing negatively chargeable substrate having high surface smoothness

The present invention relates to a method for polishing a negatively chargeable substrate and a method for producing a negatively chargeable substrate having high surface smoothness.

A typical example of the negatively chargeable substrate is a glass substrate. The glass substrate can be polished with an abrasive to give a precise optical glass product that requires high transparency and accuracy such as a lens and a prism.

Conventionally, in the polishing of a glass substrate, first, a step of roughly polishing the glass substrate using a cerium oxide-based abrasive, and then a step of precision polishing using colloidal silica in order to increase the smoothness of the glass substrate surface It was common to go through. Recently, a polishing method using cerium oxide in a plurality of polishing steps has also been developed (see Patent Document 1).

JP 2014-83598 A

As described above, in a conventional glass substrate, it is common to perform a precision polishing process using colloidal silica after a rough polishing process using a cerium oxide-based abrasive. However, in this method, since the abrasive is switched from cerium oxide-based abrasive to colloidal silica, switching work and glass substrate cleaning work are required, and the cerium oxide-based abrasive is brown. In the case of using a cerium oxide-based abrasive to clean the polishing machine / equipment or to prevent coloring to other materials, a dedicated grinder / equipment may be required. was there. Also, the polishing process using colloidal silica has a problem in this respect because the polishing rate is very slow.

Further, cerium oxide-based abrasives are produced by firing and pulverizing minerals rich in so-called rare earths (rare earths), but the demand for rare earths has increased and supply has become unstable. Therefore, development of a technique for reducing the amount of cerium oxide used and a technique using an alternative material is desired. However, such a request is required in a polishing method (for example, the method of Patent Document 1) that essentially uses cerium oxide. Can not respond to.

An object of the present invention is to provide a polishing method capable of providing a negatively chargeable substrate excellent in surface smoothness with high productivity while realizing a high polishing rate. Another object of the present invention is to provide a manufacturing method for realizing a negatively charged substrate having high surface smoothness.

The present inventor variously studied a method for polishing a negatively chargeable substrate typified by a glass substrate, and a step of polishing under a condition in which the zeta potential of an abrasive slurry containing a predetermined oxide and zirconium oxide is positive. a negatively chargeable substrate that is excellent in surface smoothness while realizing a high polishing rate by performing a and a step b in which polishing is performed under a condition in which the zeta potential of the abrasive slurry is negative at least once. The present invention has been completed by conceiving that the above problems can be solved brilliantly.

That is, the present invention is a method of polishing a negatively charged substrate using an abrasive slurry,
The abrasive slurry has a composition formula: ABO ₃ (A represents at least one element selected from the group consisting of Sr and Ca. B represents at least one selected from the group consisting of Ti, Zr and Hf. An oxide represented by the following formula:
The polishing method includes a polishing step a in which a negatively chargeable substrate is polished under a condition that the zeta potential of the abrasive slurry is positive, and a negatively chargeable substrate is polished under a condition in which the zeta potential of the abrasive slurry is negative. This is a method for polishing a negatively chargeable substrate, wherein the polishing step b is performed at least once each.

The oxide is preferably SrZrO ₃ and / or CaZrO ₃ . When the abrasive slurry contains strontium zirconate (SrZrO ₃ ) and / or calcium zirconate (CaZrO ₃ ) and zirconium oxide (ZrO ₂ ), a higher polishing rate can be realized. Most preferably, the oxide is SrZrO ₃ .

The polishing step a is preferably performed under conditions where the pH of the abrasive slurry is greater than the isoelectric point of the negatively chargeable substrate and less than the isoelectric point of the abrasive slurry. As a result, the burden on the polishing apparatus / apparatus is reduced, so that the manufacturing method is more advantageous in terms of work and it is possible to sufficiently prevent the abrasive from dissolving under strong acid. Further, the polishing rate can be further increased.

The polishing step b is preferably carried out under conditions where the pH of the abrasive slurry is greater than the isoelectric point of the abrasive slurry and is 13 or less. As a result, the burden on the polishing apparatus / apparatus is reduced, so that the manufacturing method is more advantageous in terms of work and the abrasive can be sufficiently prevented from dissolving under a strong base. Moreover, the surface smoothness of the obtained substrate can be further enhanced.

The negatively chargeable substrate is preferably a glass substrate. Thereby, it becomes possible to fully exhibit the effect by this invention.

The present invention is also a method for producing a negatively charged substrate having a high surface smoothness using the above polishing method.

The negatively chargeable substrate polishing method of the present invention produces a negatively chargeable substrate having excellent surface smoothness while realizing a high polishing rate only by using at least one kind of abrasive that does not contain cerium oxide as a main component. It can be given well. Therefore, the polishing method of the present invention is necessary for a conventional polishing method (a method of performing a precise polishing step using colloidal silica after a rough polishing step using a cerium oxide-based abrasive). Therefore, it can be said that it is an industrially extremely advantageous technology because it eliminates the need for switching work, cleaning work, dedicated equipment, etc., and can sufficiently cope with the recent shortage of rare earth supplies. In addition, since the negatively chargeable substrate polishing method of the present invention can provide a high surface smoothness negatively chargeable substrate with good productivity, the high surface smoothness negative chargeability using such a polishing method can be provided. The substrate manufacturing method can be said to be an industrially extremely advantageous method.

FIG. 1 is an X-ray diffraction pattern of zirconium oxide which is a Zr raw material used in Production Example 1. FIG. 2 is an X-ray diffraction pattern of the abrasive obtained in Production Example 1. FIG. 3 is an SEM image of the abrasive obtained in Production Example 1. FIG. 4 is a graph showing the relationship of the zeta potential to the pH of each abrasive slurry used in the examples or comparative examples. When the polishing step a of the glass is performed under the condition that the pH of the polishing slurry A is 5.5 ((a)), and for the glass roughly polished in the polishing step (a), the polishing slurry A It is a figure which shows the conceptual diagram when the glass grinding | polishing process b is performed on the conditions from which pH of 10 becomes ((b)). It is the graph which showed notionally the relationship between the processing time (polishing time) and the surface roughness of the grinding | polishing object in the conventional grinding | polishing method and the preferable form of the grinding | polishing method of this invention.

Hereinafter, an example of the present invention will be described in detail. However, the present invention is not limited to the following description, and can be applied as appropriate without departing from the scope of the present invention.

[Polishing method of negatively charged substrate]
A method for polishing a negatively chargeable substrate, which is a first aspect of the present invention, will be described.
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 polishing method of the present invention, a polishing step a for polishing a negatively chargeable substrate under conditions where the zeta potential of the abrasive slurry is positive, and a negatively chargeable substrate under conditions where the zeta potential of the abrasive slurry is negative. Each of the polishing steps b to be polished 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 present invention, 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, so that these synergistic effects result in a high polishing rate and negative chargeability after polishing. It is presumed that excellent surface smoothness in the 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. Accordingly, if the object to be polished is a negatively chargeable substrate, the same working mechanism is obtained. Therefore, the polishing method of the present invention can be applied not only to a glass substrate but also to various negatively chargeable substrates.

Here, although the mechanism of the preferable form of the grinding | polishing method of this invention is demonstrated using FIG. 5, the grinding | polishing method of this invention is not limited only to the method shown in this figure.
In FIG. 5, the abrasive slurry A obtained in Example 1 (including a composite of SrZrO ₃ and ZrO ₂ as an abrasive. Isoelectric point: 6.4) has a pH of 5 in the abrasive slurry A. When the glass polishing step is performed under the condition of 0.5 (FIG. (A)) and when the glass polishing step is performed under the condition that the pH of the abrasive slurry A is 10 (FIG. (B)). ) Is a conceptual diagram.
First, when the polishing process of the glass (reference numeral 2) is performed while supplying the abrasive slurry A onto the polishing pad (reference numeral 3), the abrasive A (reference numeral 1) is positive under the condition of pH = 5.5. Therefore, the abrasive A is adsorbed to the negatively charged glass and can penetrate deeply into the fine irregularities on the glass surface. That is, this process is a rough polishing process, and the polishing rate is extremely high.
On the other hand, when the polishing step is performed under the condition of pH = 10 after the polishing step, the abrasive A (reference numeral 1) is negatively charged, so the abrasive repels from the negatively charged glass, and the abrasive The convex part of the glass surface is selectively polished. That is, this process can be said to be a precision polishing process, and although the polishing rate is low, the surface smoothness of the object to be polished (glass in FIG. 5) is remarkably enhanced.

FIG. 6 is a graph conceptually showing the relationship between the processing time (polishing time) and the surface roughness of the object to be polished in the conventional polishing method (i) and the preferred embodiment (ii) of the polishing method of the present invention. As shown, the polishing method of the present invention is not limited to the method (ii) shown in this graph.
In the conventional polishing method (i), as in Comparative Example 1 to be described later, first, rough polishing is performed with a cerium oxide-based abrasive until reference numeral 4, and then the abrasive is switched (reference 4), and then colloidal silica. The target surface roughness (symbol 6) is achieved by carrying out precision polishing.
On the other hand, in the preferred embodiment (ii) of the polishing method of the present invention, first, after rough polishing by the polishing step a until the point of reference numeral 7, the zeta potential of the abrasive slurry (preferably the pH of the abrasive slurry) is switched ( The target surface roughness (symbol 6) is achieved by performing precise polishing in the polishing step b). The achievement time (symbol 8) is sufficiently shorter than the achievement time (symbol 5) in the conventional polishing method.

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 any case, a slurry containing an oxide represented by the composition formula: ABO ₃ and zirconium oxide may be used as the abrasive slurry. As described above, in the present invention, the abrasive slurry can be continuously used (reused), and even when switching, it is not necessary to prepare abrasive slurry of greatly different types. No cleaning work or dedicated equipment is required. Moreover, since a high polishing rate and excellent surface smoothness can be realized without using cerium oxide, the polishing method of the present invention can be said to be a very advantageous method compared to conventional polishing methods.

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, in the present invention, the negatively chargeable substrate is polished under the condition that the zeta potential of the abrasive slurry is positive in the polishing step a and under the condition that the zeta potential of the abrasive slurry is negative in the polishing step b. However, it is preferable to perform each polishing step under the condition that the absolute value of the zeta potential of the abrasive slurry is 5 mV or more. Thereby, it becomes possible to fully exhibit the effect of this invention. 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. 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 to sufficiently increase the polishing rate. 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 an oxide represented by the composition formula: ABO ₃ and zirconium oxide, the zeta potential is positive when the pH of the abrasive slurry is adjusted to less than the isoelectric point of the abrasive slurry. On the other hand, when the pH of the abrasive 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 abrasives used in 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 polishing method of the present invention, the polishing step a may be performed under the condition that the pH of the abrasive slurry is greater than the isoelectric point of the negatively chargeable substrate and less than the isoelectric point of the abrasive slurry. preferable. 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. Thereby, it is sufficiently suppressed that the abrasive is dissolved by the strong base, and the polishing action by the abrasive is more exhibited. In addition, the burden on the polishing machine / device can be reduced. The upper limit of the pH of the abrasive slurry in the polishing step b is more preferably 12 or less. More preferably, it is 11 or less.

In the present specification, the isoelectric point of the abrasive slurry (and abrasive) is the point where the algebraic sum of the charge on the abrasive grains (abrasive) in the abrasive slurry is zero, that is, the abrasive grains. The point at which the positive charge and the negative charge are equal is said, and can be represented by the pH of the abrasive slurry at that point. For reference, for example, the isoelectric point of an abrasive comprising a composite of CaZrO ₃ and ZrO ₂ (Ca content: 27% by weight in terms of CaO) is 6.1, and the composite of CaTiO ₃ and ZrO ₂ The isoelectric point of the abrasive comprising the body (Ca content: 30% by weight in terms of CaO) is 5.9, and from the composite of SrTiO ₃ and ZrO ₂ (Sr content: 40% by weight in terms of SrO) The isoelectric point of the resulting abrasive is 5.7.

<Abrasive slurry>
Next, the abrasive slurry used in the polishing method of the present invention will be described.
The abrasive slurry has a composition formula: ABO ₃ (A represents at least one element selected from the group consisting of Sr and Ca. B represents at least one type selected from the group consisting of Ti, Zr and Hf. And an oxide represented by (2) and zirconium oxide.
In this specification, the oxide represented by the composition formula: ABO ₃ is also referred to as “ABO ₃ oxide”, and the oxide composed of ABO ₃ oxide and zirconium oxide is also referred to as “abrasive”.

The abrasive content (total amount of ABO ₃ oxide and zirconium oxide) in the abrasive slurry is preferably, for example, 0.001 to 90% by weight in 100% by weight of the abrasive slurry. More preferably, it is 0.01 to 30% by weight.

It is preferable that the abrasive slurry further contains a dispersion medium.
Although it does not specifically limit as a dispersion medium, For example, water, an organic solvent, or these mixtures 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 above-mentioned abrasive slurry may also contain one or more additives as long as it does not interfere with the effects of the present invention. The additive is not particularly limited, and examples thereof include pH adjusters (acids, alkalis, etc.), chelating agents, antifoaming agents, dispersants, viscosity modifiers, aggregation inhibitors, lubricants, reducing agents, rust inhibitors, A well-known polishing material etc. are mentioned.
In addition, from the viewpoint of enhancing the effect of the polishing method of the present invention, the content of additives other than the pH adjuster is preferably as small as possible. 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 abrasive, the dispersion medium and the pH adjuster are preferably 90% by weight or more, more preferably 95% by weight or more, and further preferably 99% by weight or more. .

The abrasive slurry is not particularly limited as long as it contains zirconium oxide as ABO ₃ oxide preferably contains a zirconium oxide and ABO ₃ oxide as a composite thereof. That abrasive material composed of ABO ₃ oxide and zirconium oxide is preferably a composite of the zirconium oxide and the ABO ₃ oxide. In other words, the abrasive slurry in the present invention has a composition formula: ABO ₃ (A represents at least one element selected from the group consisting of Sr and Ca. B represents a group consisting of Ti, Zr and Hf. It is preferable to include a composite of an oxide represented by (2) representing at least one selected element and zirconium oxide as an abrasive. Thereby, a high polishing rate can be realized more in the cerium-free abrasive. Note that the complex with the zirconium oxide and the ABO ₃ oxide refers to secondary particles each of the primary particles of the zirconium oxide and the ABO ₃ oxide is formed by partially sintered. For example, if elemental mapping is performed on the composite by energy dispersive X-ray spectroscopy (EDS), primary particles from which elements contained in A and B are detected and primary particles from which only Zr is detected are obtained. A state of forming secondary particles is observed.

More preferably, the abrasive contains an ABO ₃ oxide crystal phase and a zirconium oxide (ZrO ₂ ) crystal phase. Since the crystal phase of ABO ₃ oxide contained in the abrasive material is responsible for the chemical polishing action and the crystal phase of ZrO ₂ is responsible for the mechanical polishing action, a better polishing rate can be exhibited. Furthermore, when the ABO ₃ oxide and ZrO ₂ form a composite, the chemical polishing action by the ABO ₃ oxide and the mechanical polishing action by the crystal phase of ZrO ₂ are more effectively exhibited.

The crystal phase of the ABO ₃ oxide is particularly preferably a crystal phase of SrZrO ₃ and / or CaZrO ₃ , and most preferably a crystal phase of SrZrO ₃ . In this case, the half-value width of the peak derived from the (040) plane of orthorhombic SrZrO ₃ and / or the peak derived from the (121) plane of CaZrO ₃ in X-ray diffraction using CuKα rays as a radiation source is 0. It is preferably 1 to 3.0 °. When the half width is in this range, the crystallinity of SrZrO ₃ and / or CaZrO ₃ that effectively exhibits the chemical polishing action is improved, so that the chemical polishing action can be sufficiently exhibited. 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 abrasive 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 is in the range of 1.5 to 50, the variation in the particle diameter becomes appropriate, and the polishing material and the substrate to be polished can be sufficiently brought into contact with each other, thereby realizing a better polishing rate. be able to. More preferably, it is 1.5 to 45, and still more preferably 1.5 to 40.
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 abrasive preferably has a specific surface area of 1.0 to 50 m ² / g. When the specific surface area is 1.0 m ² / g or more, it is possible to sufficiently contact the substrate to be polished, and thus it is possible to polish more suitably. Further, at 50 m ² / g or less, since the size of the abrasive grains constituting the abrasive becomes appropriate, the mechanical polishing action is further enhanced. More preferably, it is 1.0 to 45 m ² / g, and still more preferably 1.0 to 40 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.

The abrasive preferably contains 10 to 43% by weight of the element A in the ABO ₃ oxide in terms of oxide. For example, it is preferable to contain 10 to 43% by weight of Sr in terms of SrO. In this range, since the chemical polishing action and the mechanical polishing action are more exhibited, the polishing efficiency can be further increased. More preferably, it is 11 to 43% by weight, and still more preferably 12 to 43% by weight.

First, the ABO ₃ oxide will be described below.
The ABO ₃ oxide has a composition formula: ABO ₃ (A represents at least one element selected from the group consisting of Sr and Ca. B represents at least one selected from the group consisting of Ti, Zr and Hf. Represents a seed element).
In the formula, A represents at least one element selected from the group consisting of strontium (Sr) and calcium (Ca), among which Sr is preferable. B represents at least one element selected from the group consisting of titanium (Ti), zirconium (Zr), and hafnium (Hf). Among them, Ti and / or Zr are preferable, and Zr is more preferable. is there.

The ABO ₃ oxide is, for example, at least one selected from the group consisting of strontium carbonate, strontium hydroxide, calcium carbonate and calcium hydroxide, and titanium oxide, titanium hydroxide, zirconium oxide, zirconium hydroxide, zirconium carbonate. And those obtained by reacting at least one selected from the group consisting of hafnium oxide. Since this reaction proceeds easily, ABO ₃ oxide can be easily obtained.

Of the oxides that are the raw materials for producing the ABO ₃ oxide, the production method, shape, crystal type, particle size, etc. of titanium oxide (TiO ₂ ) are not particularly limited. For example, a chlorine method may be used as a method for producing titanium oxide, or a sulfuric acid method may be used. The crystal type may be a rutile type, an anatase type, a brookite type, or a mixture thereof. The production method, shape, crystal type, particle diameter, etc. of hafnium oxide (HfO ₂ ) are not particularly limited. Zirconium oxide (ZrO ₂ ) is not particularly limited, but is preferably in the same form as zirconium oxide described later.

The ABO ₃ oxide is particularly preferably strontium zirconate (SrZrO ₃ ) and / or calcium zirconate (CaZrO ₃ ), and most preferably strontium zirconate (SrZrO ₃ ). Thereby, an even higher polishing rate can be realized.
The strontium zirconate is obtained by, for example, reacting at least one selected from the group consisting of strontium carbonate and strontium hydroxide with at least one selected from the group consisting of zirconium oxide, zirconium hydroxide and zirconium carbonate. It is preferred to obtain. Since this reaction proceeds easily, strontium zirconate is likely to be generated.
In addition, the calcium zirconate is obtained, for example, by a reaction between at least one selected from the group consisting of calcium carbonate and calcium hydroxide and at least one selected from the group consisting of zirconium oxide, zirconium hydroxide and zirconium carbonate. It is preferred to obtain. Since this reaction proceeds easily, calcium zirconate is likely to be generated.

Next, zirconium oxide (ZrO ₂ ) will be described.
The crystal form of zirconium oxide is preferably a monoclinic, tetragonal or cubic crystal structure, or a mixed crystal of these crystal structures.

The zirconium oxide is not particularly limited. For example, the half-value width of the maximum peak at 2θ = 27.00 to 31.00 ° in X-ray diffraction using CuKα ray as a radiation source (hereinafter simply referred to as “ZrO ₂ maximum”). The peak half-width ") is preferably from 0.1 to 3.0 °. When the half width is 3.0 ° or less, the crystallinity of ZrO ₂ contained in the abrasive slurry is increased, and a mechanical polishing action derived from ZrO ₂ can be sufficiently obtained. In addition, when the half width is 0.1 ° or more, an abrasive slurry that is superior in polishing rate can be 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 °.
In this specification, CuKα rays are used for all X-ray diffraction sources.

Particularly preferably, the abrasive slurry used in the present invention includes an abrasive comprising strontium zirconate (SrZrO ₃ ) and / or calcium zirconate (CaZrO ₃ ) and zirconium oxide (ZrO ₂ ), and more Preferably, it contains a complex of strontium zirconate and / or calcium zirconate and zirconium oxide, and most preferably contains a complex of strontium zirconate and zirconium oxide. This abrasive (complex of strontium zirconate and zirconium oxide) includes, for example, a mixing step of mixing a strontium compound and a zirconium compound and a baking step of baking the mixture obtained by the mixing step Is preferably obtained. Since this manufacturing method is performed by a solid-phase reaction method, the manufacturing process is simpler than that of the spray pyrolysis method, and it is possible to manufacture at a low cost without introducing special equipment. A complex of calcium zirconate and zirconium oxide is also preferably obtained by a production method almost the same as that (however, a calcium compound such as calcium carbonate or calcium hydroxide is used in place of the strontium compound).
Hereinafter, each step will be further described.

-Mixing process-
In the mixing step, the strontium compound and the zirconium compound are mixed. 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 preferable 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 and ion-exchanged water is more preferable from the viewpoint of production cost. 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 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 ).

The zirconium compound is not particularly limited as long as it is a compound containing a zirconium atom, but among these, at least one selected from the group consisting of zirconium oxide, zirconium carbonate and zirconium hydroxide is preferable. These have high reactivity with the strontium compound, and can provide an abrasive having better polishing characteristics.
Note that when a zirconium compound other than zirconium oxide (for example, zirconium carbonate and / or zirconium hydroxide) is used, the firing and pulverizing steps during the synthesis of zirconium oxide can be omitted.
The said zirconium compound can also be used for a mixing process with the cake form obtained by the synthesis | combination.

The specific surface area of the zirconium oxide is preferably 2.0 to 200 m ² / g. Thereby, it is possible to obtain an abrasive slurry superior in polishing rate. More preferably, it is 2.0 to 180 m ² / g, and still more preferably 2.0 to 160 m ² / g.

The specific surface area of the zirconium compound other than the zirconium oxide is preferably 0.1 to 250 m ² / g. Thereby, it is possible to obtain an abrasive slurry superior in polishing rate. More preferably, it is 0.3 to 240 m ² / g, and still more preferably 0.5 to 230 m ² / g.

When a compound other than zirconium oxide is used as the zirconium compound, the SO ₃ equivalent amount 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 equivalent to ZrO _2. Preferably there is. Thereby, an abrasive with an even better polishing rate can be obtained. The sulfur compound content (SO ₃ equivalent) is more preferably 1.5 parts by weight or less, still more preferably 1.1 parts by weight or less, and particularly preferably 0.5 parts by weight or less.

In this specification, the SO ₃ equivalent amount of the sulfur compound contained in the zirconium compound is measured on the measurement sample stage using an EZ scan which is a contained element scanning function of an X-ray fluorescence analyzer (manufactured by Rigaku Corporation: model number ZSX Primus II). It can be obtained by setting the pressed sample and selecting the following conditions (measurement range: FU, measurement diameter: 30 mm, sample form: oxide, measurement time: long, atmosphere: vacuum).

-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 particularly suitable as an abrasive can be preferably 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. For example, the temperature is preferably 700 to 1500 ° C. When the firing temperature is within this range, the reaction proceeds more sufficiently, and when the firing temperature is 1500 ° C. or less, the polishing rate of the resulting abrasive is further increased. The lower limit value is more preferably 730 ° C. or more, still more preferably 750 ° C. or more, and the upper limit value is more preferably 1300 ° C. or less, still more preferably 1270 ° C. or less, and particularly preferably 1250 ° C. or less. In particular, when a compound other than zirconium oxide is used as the zirconium compound, it is particularly preferable to increase the firing temperature, for example, preferably 800 ° C. or higher, more preferably 850 ° C. or higher, still more preferably 900 ° C. or higher, even more preferably. Is 930 ° C. or higher.
In the present specification, the firing temperature in the firing step means the highest temperature reached in the firing step.

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.

[Method of manufacturing negatively charged substrate with high surface smoothness]
A method for producing a negatively charged substrate having high surface smoothness, which is a second aspect of the present invention, will be described.
The method for producing a high surface smoothness negatively charged substrate of the present invention uses the above-described method for polishing a negatively charged substrate of the present invention. That is, the manufacturing method includes a polishing step a in which a negatively chargeable substrate is polished under the condition that the zeta potential of the abrasive slurry is positive in the presence of the abrasive slurry, and the abrasive slurry in the presence of the abrasive slurry. And a polishing step b for polishing the negatively chargeable substrate under a condition that the zeta potential of the substrate is negative at least once, and the abrasive slurry is composed of a composition formula: ABO ₃ (A is composed of Sr and Ca). And B represents at least one element selected from the group consisting of Ti, Zr, and Hf.) And zirconium oxide. That's it. By using such a manufacturing method, a high polishing rate and excellent surface smoothness can be realized, so that a negatively chargeable substrate having high surface smoothness can be provided with high productivity.

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

Production Example 1 (Production of Abrasive Material A)
(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 placed in an alumina crucible having an outer diameter of 55 mm and a capacity of 60 mL, and baked using an electric muffle furnace (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) Mixing step 26.1 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 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 above (4) 10 g of the obtained baked product by baking step, an automatic mortar (crusher) (Nitto Kagaku Co., Ltd.: ANM-0.99) to feed, by grinding for 10 minutes, SrZrO ₃ An abrasive comprising a composite of ZrO ₂ was obtained. This is also referred to as “Abrasive A”.

<Performance evaluation of abrasive and Zr raw material used>
Various physical properties of the abrasive material obtained in Production Example 1 and the Zr raw material (zirconium oxide) used in Production Example 1 were evaluated according to the methods described in (i) to (vi) below.

(I) Measurement of powder X-ray diffraction For each of the Zr raw material (zirconium oxide) and the abrasive, 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
Orthorhombic CaZrO ₃ : JCPDS card 00-035-0645

An X-ray diffraction pattern of the Zr raw material used in Production Example 1 is shown in FIG. 1, and an X-ray diffraction pattern of the obtained abrasive is shown in FIG.
The X-ray diffraction pattern of the abrasive 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 abrasive obtained in Production Example 1 had a crystal phase of SrZrO _{3 and} a crystal phase of ZrO ₂ .

(Ii) Measurement of full width at half maximum From the diffraction pattern obtained by X-ray diffraction measurement of the Zr raw material, the full width at half maximum of ZrO ₂ at 2θ = 27.00 to 31.00 ° was measured. The orthorhombic SrZrO ₃ (040) half width was measured from the diffraction pattern obtained by the X-ray diffraction measurement. The results are shown in Table 1.
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 °. , a peak derived from the (040) plane of orthorhombic SrZrO ₃ is near 2 [Theta] = 44.04 °, peak derived from the (121) plane of orthorhombic CaZrO ₃ is in the vicinity of 2 [Theta] = 31.5 ° .
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 the Zr raw material (zirconium oxide) used in Production Example 1, and 2θ = 27.00− The half-width of the maximum peak at 31.00 ° 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 abrasive obtained in Production Example 1, and the half width was 0.33 °. It was.

(Iii) Measurement of specific surface area The specific surface area of each of the Zr raw material and the abrasive was measured under the following conditions. The results are shown in Table 1.
Used machine: Macsorb Model HM-1220, manufactured by Mountec
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) Measurement of Electron Microscope Image With respect to the abrasive, a SEM image was taken with a scanning electron microscope (SEM) (manufactured by JEOL Ltd .: model number JSM-6510A). An SEM image of the abrasive material obtained in Production Example 1 is shown in FIG.
As shown in FIG. 3, the abrasive obtained in Production Example 1 forms irregular secondary particles in which a plurality of primary particles are randomly gathered.

(V) About the elemental analysis abrasive | polishing material, the 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) and Ca content (CaO conversion) were measured. The results are shown in Table 1.

(Vi) 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 abrasive and a suspension of the abrasive was prepared by stirring well 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.

Production Example 2 (Abrasive B)
Production Example 1 except that 31.3 g of the zirconium hydroxide cake obtained in “(1) Zr raw material preparation step” was used as the Zr raw material in “(2) mixing step” of Production Example 1 in terms of ZrO _2. In the same manner as above, an abrasive B made of a composite of SrZrO ₃ and ZrO ₂ was obtained.
About this abrasive | polishing material B, a half value width, a specific surface area, elemental analysis, and the sharpness of a particle size distribution are measured or evaluated similarly to manufacture example 1, and it manufactures also about the Zr raw material (zirconium hydroxide) used in manufacture example 2. As in Example 1, the specific surface area was measured. The results are shown in Table 1.

Production Example 3 (Abrasive E)
As a Ca raw material in “(2) mixing step” of Production Example 1, 22.5 g of calcium carbonate (manufactured by Sakai Chemical Industry Co., Ltd .: CWS-20) is used, and “(1) Zr raw material of Production Example 1 is used as a Zr raw material. Except that 42.4 g of zirconium oxide obtained in the “preparation step” was used, an abrasive E composed of a composite of CaZrO ₃ and ZrO ₂ was obtained in the same manner as in Production Example 1.
About this abrasive material E, the half value width, the specific surface area, the elemental analysis, and the sharpness of the particle size distribution were measured or evaluated in the same manner as in Production Example 1. The results are shown in Table 1.

Production Example 4 (Abrasive Slurry A)
An abrasive slurry A was produced using the abrasive A produced in Production Example 1.
Specifically, 20.0 g of abrasive A was dispersed in 380.0 g of ion-exchanged 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 electric charge on the abrasive grains (abrasive) in the abrasive slurry is zero, that is, the point where the positive and negative charges on the abrasive grains are equal. It can be represented by the pH of the abrasive slurry at that point.

<Conditions for measuring zeta potential>
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.
In addition, the abrasive slurry D using colloidal silica, which will be described later, was dispersed for 1 minute by using an ultrasonic homogenizer (US-600, manufactured by Nippon Seiki Seisakusho) for the abrasive slurry D60cc 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

Production Example 5 (Abrasive Slurry B)
An abrasive slurry B was produced in the same manner as in Production Example 4 (Abrasive Slurry A) except that the abrasive B produced in Production Example 2 was used.
For this abrasive slurry B, the zeta potential was measured under the above measurement conditions. The relationship of the zeta potential with respect to pH of this abrasive slurry is shown in FIG. In addition, the isoelectric point of the abrasive slurry B was 6.2.

Production Example 6 (Abrasive Slurry C)
Except for using a cerium oxide abrasive for glass polishing (made by Showa Denko KK, SHOROX (R) A-10, cerium oxide content: 60 wt%, isoelectric point: 10.4) as an abrasive, An abrasive slurry C was produced in the same manner as in Production Example 4. The relationship of the zeta potential with respect to pH of this abrasive slurry is shown in FIG.

Production Example 7 (Abrasive Slurry D)
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 used as abrasive slurry D. The relationship of the zeta potential with respect to pH of this abrasive slurry is shown in FIG.

Production Example 8 (Abrasive Slurry E)
An abrasive slurry E was produced in the same manner as in Production Example 4 (Abrasive Slurry A) except that the abrasive E produced in Production Example 3 was used.
For this abrasive slurry E, the zeta potential was measured under the above measurement conditions. The relationship of the zeta potential with respect to pH of this abrasive slurry is shown in FIG. The isoelectric point of the abrasive slurry E was 6.1.

Example 1
(1) First Polishing Step After adjusting the pH of the slurry so that the zeta potential of the abrasive slurry A obtained in Production Example 4 has the value shown in Table 2, the following polishing conditions are satisfied in the presence of this slurry. The glass substrate was polished. Table 2 shows the pH value of the abrasive slurry A in this step. Moreover, the polishing rate in the first polishing step and the surface roughness of the glass substrate after the first polishing step were evaluated according to the following methods. The results are shown in Table 2.
(2) Second polishing step The abrasive slurry A used in the first polishing step is continuously used as it is, and the pH of the slurry is adjusted so that the zeta potential becomes the value shown in Table 2, and then 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 2 shows the pH value of the abrasive slurry A in this step. Moreover, the polishing rate in the second polishing step and the surface roughness of the glass substrate after the second polishing step were evaluated according to the following methods. The results are shown in Table 2.

<Polishing 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 slurry supply rate: 100 mL / min
Polishing time: 60 min

<Measurement of polishing rate>
The weight of the glass substrate before and after each polishing step was measured with an electronic balance. From the weight reduction amount, the area of the glass substrate, and the specific gravity of the glass substrate, the thickness reduction amount of the glass substrate was calculated, and the polishing rate (μm / min) was calculated.
Three glass substrates were polished at the same time, and after polishing for 60 minutes, the glass substrate 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 taken as the value of the polishing rate in each example and comparative example.

<Measurement of surface smoothness of glass substrate>
About the glass substrate 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.

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 2) 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 2 shows the pH of the abrasive slurry, the zeta potential, the polishing rate, and the surface roughness of the glass substrate in each step.

Example 3
The first polishing step and the second polishing step were performed in the same manner as in Example 2 except that the abrasive slurry B was used instead of the abrasive slurry A. Table 2 shows the pH of the abrasive slurry, the zeta potential, the polishing rate, and the surface roughness of the glass substrate in each step.

Example 4
The first polishing step and the second polishing step were performed in the same manner as in Example 2 except that the abrasive slurry E was used instead of the abrasive slurry A. Table 2 shows the pH of the abrasive slurry, the zeta potential, the polishing rate, and the surface roughness of the glass substrate in each step.

Comparative Example 1
(1) First polishing step After adjusting the pH of the slurry so that the zeta potential of the abrasive slurry C obtained in Production Example 6 becomes the value shown in Table 2, the same polishing as in Example 1 in the presence of this slurry The glass substrate was polished under the conditions. The pH value of the abrasive slurry C in this step is shown in Table 2. Further, the polishing rate in the first polishing step and the surface roughness of the glass substrate after the first polishing step were evaluated according to the methods described above. The results are shown in Table 2.
(2) Second polishing step The abrasive slurry C used in the first polishing step was taken out from the polishing machine, and the polishing machine was cleaned. After adjusting the pH so that the zeta potential of the separately prepared abrasive slurry D becomes the value shown in Table 2, in the presence of this abrasive slurry D, the glass substrate is subjected to the same polishing conditions as in the first polishing step. Was polished. Table 2 shows the pH value of the abrasive slurry D 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 according to the methods described above. The results are shown in Table 2.

The following was confirmed from the above Examples and Comparative Examples.
Although the surface roughness of the finally obtained substrates (substrates after the second polishing step) is almost the same in Examples 1 and 2 and Comparative Example 1, in Examples 1 and 2, Compared to Example 1, the polishing rate is significantly improved. This was almost the same as the comparison between Examples 3 and 4 and Comparative Example 1. Therefore, it has been found that the method for polishing a negatively charged substrate of the present invention can realize a high polishing rate and excellent surface smoothness in a cerium-free polishing material. Further, in Comparative Example 1, since the 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, etc. In Examples 1 to 4, since the same type of abrasive slurry is used in the first polishing step and the second polishing step, the cleaning operation of the polishing machine is unnecessary, which is very advantageous in terms of work and equipment. It was.
In the second polishing step of 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 Example 2, the abrasive used in the first polishing step. Although it is the same as the slurry A, Example 1 and Example 2 are different 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.

1: Abrasive A
2: Glass 3: Polishing pad 4: Switching time of abrasive in conventional polishing method (i) 5: Time to reach target surface roughness in conventional polishing method (i) 6: Target surface roughness 7: Time 8 for switching the zeta potential of the abrasive slurry (preferably pH of the abrasive slurry) in the polishing method (ii) of the preferred embodiment of the present invention: the target surface roughness in the polishing method (ii) of the preferred embodiment of the present invention Time to reach

Claims (6)

1. A method of polishing a negatively charged substrate using an abrasive slurry,
   The abrasive slurry has a composition formula: ABO ₃ (A represents at least one element selected from the group consisting of Sr and Ca. B represents at least one selected from the group consisting of Ti, Zr and Hf. An oxide represented by the following formula:
   The polishing method includes a polishing step a in which a negatively chargeable substrate is polished under a condition that the zeta potential of the abrasive slurry is positive, and a negatively chargeable substrate is polished under a condition in which the zeta potential of the abrasive slurry is negative. A method of polishing a negatively chargeable substrate, wherein the polishing step b is performed at least once each.
2. The method for polishing a negatively charged substrate according to claim 1, wherein the oxide is SrZrO ₃ and / or CaZrO ₃ .
3. 2. The polishing step a is performed under a condition that the pH of the abrasive slurry is greater than the isoelectric point of the negatively chargeable substrate and less than the isoelectric point of the abrasive slurry. Or the method of polishing a negatively chargeable substrate according to 2.
4. The polishing step (b) is carried out under conditions where the pH of the abrasive slurry is greater than the isoelectric point of the abrasive slurry and is 13 or less. Polishing method of negatively chargeable substrate.
5. The method for polishing a negatively chargeable substrate according to any one of claims 1 to 4, wherein the negatively chargeable substrate is a glass substrate.
6. A method for producing a negatively charged substrate having a high surface smoothness, wherein the polishing method according to any one of claims 1 to 5 is used.

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