KR20220148919A - Cerium-based abrasive slurry stock solution and manufacturing method thereof, and polishing solution - Google Patents

Abstract

Disclosed are a cerium-based abrasive slurry stock solution, a method for producing the same, and a polishing solution having good polishing performance for glass materials and excellent productivity. The cerium-based abrasive slurry stock solution of the present invention is a cerium-based abrasive slurry stock solution containing mixed rare earth oxide particles and water. The cerium-based abrasive slurry stock solution includes an anionic water-soluble polymer and a phosphoric acid compound, and the total rare earth element oxide content (TREO) is 10.0-40.0 mass %, the oxide-converted content of cerium in the TREO is 50.0 mass % or more, the content of the anionic water-soluble polymer is 1.5 to 10.0 parts by mass with respect to 100 parts by mass of the TREO, the slurry particles The particle diameter (D ₅₀ ) at 50% of the cumulative volume in the particle size distribution by the laser diffraction scattering method is 0.10 to 0.35 μm.

Description

Cerium-based abrasive slurry stock solution and manufacturing method thereof, and polishing solution

The present invention relates to a cerium-based abrasive slurry stock solution, a method for producing the same, and a polishing liquid used for polishing glass materials such as glass substrates used for liquid crystal panels, hard disks, filters for specific frequency cut, and the like, and glass substrates for optical lenses.

Glass materials are used for various purposes, and surface polishing may be required depending on the use. In particular, glass materials such as glass substrates used for liquid crystal panels, hard disks, filters for specific frequency cut, and the like, glass substrates for optical lenses, etc., are required to be surface polished with high smoothness and high efficiency.

In the surface polishing of glass materials requiring such excellent polishing performance, for example, cerium-based abrasives as described in Patent Literature 1 and Patent Literature 2 are widely used.

In addition, as the demand for higher precision of the polished surface of the glass material progresses, the demand for a cerium-based abrasive slurry (polishing liquid) having fine particles is increasing in order to reduce the surface roughness of the glass material and to further smooth it.

International Publication No. 2019/049932 Japanese Patent Laid-Open No. 2019-208029

However, in the case of a cerium-based abrasive slurry, when the particles in the slurry become finer, it becomes difficult to maintain a polishing rate or a smoothing polishing force, and the polishing performance of the glass material is sometimes deteriorated. In addition, the productivity of the cerium-based abrasive slurry stock solution is lowered, and there has also been a problem that the manufacturing cost of the slurry stock solution is increased.

Therefore, there is a demand for a cerium-based abrasive slurry stock solution capable of maintaining a high level of polishing rate and smoothing power of the glass material, and suppressing manufacturing cost and excellent productivity.

The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a cerium-based abrasive slurry stock solution, a method for producing the same, and a polishing solution having good polishing performance for glass materials and excellent productivity.

According to the present invention, in a cerium-based abrasive slurry using mixed rare earth oxide particles as abrasive grains, good polishing performance is obtained and good polishing performance is obtained by using a predetermined amount of an anionic water-soluble polymer and a phosphoric acid compound in combination. It is based on the discovery that the stock solution of (polishing liquid) can be manufactured with high productivity.

That is, the present invention provides the following [1] to [8].

[1] A cerium-based abrasive slurry stock solution containing mixed rare earth oxide particles and water, wherein the cerium-based abrasive slurry stock solution includes an anionic water-soluble polymer and a phosphoric acid compound, and the total rare earth element oxide equivalent content (TREO) is 10.0 to 40.0 mass %, the oxide equivalent content of cerium in the TREO is 50.0 mass % or more, the content of the anionic water-soluble polymer is 1.5 to 10.0 parts by mass with respect to 100 parts by mass of the TREO, and the laser diffraction scattering method of the slurry particles A cerium-based abrasive slurry stock solution having a particle diameter (D ₅₀ ) of 0.10 to 0.35 μm at 50% of the cumulative volume in the particle size distribution.

[2] The cerium-based abrasive slurry stock solution according to the above [1], wherein the fluorine atom content is 0.1% by mass or less.

[3] The cerium-based abrasive slurry stock solution according to the above [1] or [2], wherein the anionic water-soluble polymer is a polycarboxylic acid-based polymer.

[4] A cerium-based abrasive slurry stock solution, wherein the polycarboxylic acid-based polymer is at least one selected from acrylic acid, a copolymer of acrylic acid and maleic acid, and alkali metal salts thereof.

[5] The cerium-based abrasive slurry stock solution according to any one of [1] to [4], wherein the phosphoric acid compound is at least one selected from tripolyphosphoric acid, pyrophosphoric acid and hexametaphosphoric acid, and alkali metal salts thereof.

[6] The cerium-based abrasive slurry stock solution according to any one of [1] to [5], wherein the content of the phosphoric acid compound is 0.5 to 10.0 parts by mass based on 100 parts by mass of TREO.

[7] The method for producing the cerium-based abrasive slurry stock solution according to any one of [1] to [6], wherein a mixed raw material comprising the mixed rare earth oxide particles, water and the anionic water-soluble polymer is wet-pulverized to obtain a grinding slurry A cerium-based abrasive slurry comprising: a step of obtaining a classification slurry by wet classifying the grinding slurry to obtain a classification slurry; and a step of adding and mixing water and the phosphoric acid compound to the classification slurry to obtain the cerium-based abrasive slurry stock solution Method for preparing the stock solution.

[8] The cerium-based abrasive slurry stock solution according to any one of [1] to [6] is a polishing solution diluted with water, and the TREO is 0.1 to 10.0 mass%.

The cerium-based abrasive slurry stock solution of the present invention can provide a polishing solution having excellent productivity and good polishing performance for glass materials.

In addition, according to the manufacturing method of the present invention, the cerium-based abrasive slurry stock solution can be suitably prepared.

Therefore, the polishing liquid obtained by using the cerium-based abrasive slurry stock solution of the present invention can suppress the manufacturing cost while maintaining good polishing performance for the glass material.

Hereinafter, embodiments of the cerium-based abrasive slurry stock solution of the present invention, a method for producing the same, and a polishing solution obtained using the cerium-based abrasive slurry stock solution will be described in detail.

[Cerium-based abrasive slurry stock solution]

The cerium-based abrasive slurry stock solution of the present embodiment is a slurry containing mixed rare-earth oxide particles and water, and contains an anionic water-soluble polymer and a phosphoric acid compound. The total rare earth element oxide content (TREO; abbreviation for Total Rare Earth Oxides) of the cerium-based abrasive slurry stock solution is 10.0 to 40.0 mass %, and the cerium oxide (CeO ₂ ) equivalent content in the TREO (hereinafter, “Ce amount”) is ') is 50.0 mass% or more. Content of the said anionic water-soluble polymer in the said slurry is 1.5-10.0 mass parts with respect to 100 mass parts of said TREO. The cerium-based abrasive slurry stock solution is characterized in that the particle diameter (D ₅₀ ) at 50% of the cumulative volume in the particle size distribution of the slurry particles by the laser diffraction scattering method is 0.10 to 0.35 μm.

In addition, the "cerium-based abrasive" in the present invention refers to an abrasive having an oxide-converted content of cerium with respect to TREO in the abrasive of 50.0% by mass or more.

(Mixed rare earth particles)

In the present embodiment, "mixing" of mixed rare earth oxide with mixed rare earth particles means that a plurality of types of rare earth elements are contained. The mixed rare earth oxide may contain rare earth elements other than Ce. Examples of the rare earth element include La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and the like.

TREO in the mixed rare earth particles is preferably 80.0 mass % or more, more preferably 85.0 mass % or more, further preferably 90.0 mass % or more, from the viewpoint of improving the productivity of a cerium-based abrasive slurry stock solution suitable for surface polishing of glass materials. -100 mass %.

From the same viewpoint, the mixed rare earth particles contain Ce as a main component among all the rare earth elements contained, and the amount of Ce in TREO (Ce amount/TREO) is preferably 50.0 mass % or more, more preferably 60.0 mass % or more, further Preferably it is 65.0-100 mass %.

In addition, TREO can be measured by oxalate precipitation, calcination, and a gravimetric method, and can be measured by the method specifically described in the Example mentioned later.

Incidentally, the content of each rare earth element such as Ce can be measured by instrumental analysis such as high-frequency inductively coupled plasma (ICP) analysis and fluorescence X-ray analysis, and in this embodiment, ICP emission spectroscopy (ICP-AES) ), a value obtained by converting each rare earth element into an oxide is taken as the oxide conversion amount.

The mixed rare earth oxide can be obtained by, for example, calcining a mixed hard rare earth compound such as mixed rare earth carbonate, mixed monooxy carbonate rare earth, mixed oxalate rare earth, mixed rare earth hydroxide, or the like. In addition, "mixing" here is synonymous with "mixing" of the mixed rare earth oxide mentioned above.

The mixed light rare earth compound preferably has a reduced content of impurities of non-rare earth components such as alkali metals, alkaline earth metals and radioactive substances, and heavy rare earths, and has Ce as the main component. more preferably. As the mixed rare earth compound, for example, mixed rare earth carbonate having a TREO content of 45 to 55 mass% and a Ce content (Ce content/TREO) in the TREO of about 65 mass% is preferably used.

Incidentally, in this specification, the heavy rare earth refers to a rare earth element having an atomic number greater than that of Pm, and rare earth elements other than the heavy rare earth are referred to as light rare earth.

The method for producing the mixed hard rare earth compound is not particularly limited. The mixed light rare earth compound is obtained, for example, by separating and reducing the content of impurities other than rare earth elements and heavy rare earth from ore containing rare earth elements by chemical treatment.

As the ores containing rare earth elements, for example, rare earth concentrates obtained from raw ores such as natural monazite and bastnaesite containing a large amount of Ce are preferably used.

As a chemical treatment method for reducing the content of impurity components in the preparation of a mixed light rare earth compound, sulfuric acid roasting is a common method. Sulfuric acid roasting is a method in which the pulverized raw ore is roasted with sulfuric acid to produce sulfate (rare earth sulfate), the sulfate is dissolved in water to make a sulfuric acid rare earth solution, and insoluble impurity components are removed by filtration or the like. The content of the impurity component in the mixed light rare earth compound is preferably reduced to 1.0 mass% or less.

In addition, as a chemical treatment method for reducing the content of heavy rare earth, for example, carbonate is added to the sulfuric acid rare earth solution after roasting the sulfuric acid to obtain a crude carbonate rare earth, then hydrochloric acid is added thereto to obtain a mixed chloride rare earth solution. , by solvent extraction using an organic solvent. In solvent extraction, each content of Ce and other hard rare earth can be adjusted as needed using well-known methods, such as adjustment of the extraction degree and use of an additive. The content of the heavy rare earth in the mixed light rare earth compound is preferably reduced to 1.0% by mass or less.

Mixed rare earth compounds include mixed rare earth carbonates made into carbonates using sodium carbonate or ammonium bicarbonate, and/or mixed rare earth oxalates made into oxalates using oxalic acid or the like after treatment to reduce the content of impurity components. may be doing

The calcination temperature when calcining the mixed hard rare earth compound to obtain the mixed rare earth compound is appropriately adjusted depending on the composition of the mixed hard rare earth compound, but is preferably 600 to 1200°C, more preferably 700 to 1150°C, still more preferably is 800 to 1100 °C. The calcination time is preferably 0.5 to 48 hours, more preferably 1 to 40 hours, still more preferably 1.5 to 30 hours. It is preferable that the firing atmosphere is in an atmospheric atmosphere.

The mixed rare earth oxide obtained by firing preferably has a D ₅₀ measured by laser diffraction scattering method of 20 µm or less, more preferably 3 to 18 µm, and still more preferably 5 to 15 µm. Moreover, after calcination, it may pulverize by a mechanical method, and you may adjust to the particle|grains of the same particle size as the above.

In addition, mixed rare-earth particles are commercially available, and a commercially available product may be used as a raw material. In some commercially available mixed rare earth oxide particles, mixed rare earth carbonate, mixed monooxy rare earth carbonate, mixed oxalate rare earth, and the like, which are raw materials for production, remain.

The cerium-based abrasive slurry stock solution of this embodiment preferably has a fluorine atom content of 0.1% by mass or less, more preferably 0.05% by mass or less, still more preferably 0.01% by mass or less from the viewpoint of reducing the load on the environment. . When the fluorine atom content is 0.1 mass % or less, it is said that the cerium-based abrasive slurry stock solution contains substantially no fluorine atoms.

In addition, the fluorine atoms that can be contained in the cerium-based abrasive slurry stock solution of the present embodiment are considered only derived from the mixed rare-earth particles, and the fluorine atoms derived from the anionic water-soluble polymer, the phosphoric acid compound and water are 0% by mass. considered to be Accordingly, the fluorine atom content in the cerium-based abrasive slurry stock solution is estimated from the measured value of the fluorine atom content in the mixed rare-earth oxide particles used to prepare the slurry.

The content of fluorine atoms in the mixed rare-earth particles can be measured by the ion electrode method by melting the mixed rare-earth particles with an alkali to form an aqueous solution.

(TREO)

The TREO in the cerium-based abrasive slurry stock solution of the present embodiment is derived from mixed rare-earth particles, and from the viewpoint of productivity and polishing performance, etc., in the cerium-based abrasive slurry stock solution, TREO is 10.0 to 40.0 mass%, preferably It is 15.0-35.0 mass %, More preferably, it is 20.0-30.0 mass %.

(water)

The cerium-based abrasive slurry stock solution is a slurry containing water, and water is used as a dispersion medium. In addition, it is preferable to use soft water or pure water as water from a viewpoint of the dispersibility of a slurry particle, etc.

As the dispersion medium, an aqueous dispersion medium other than water (for example, a water-soluble organic solvent such as alcohol, acetone, tetrahydrofuran, etc.) may be included in the range that does not impair the effects of the present invention, but usually only water desirable.

The content of water in the cerium-based abrasive slurry stock solution is such that the TREO is 40.0% by mass or less, and is appropriately adjusted according to the desired polishing processing of the glass material. From the viewpoint of uniform dispersibility and viscosity of components other than water in the cerium-based abrasive slurry stock solution, the water content in the cerium-based abrasive slurry stock solution is preferably 60% by mass or more, more preferably 65.0 to 90.0% by mass, More preferably, it is 70.0-85.0 mass %.

(anionic water-soluble polymer)

The anionic water-soluble polymer of the present embodiment refers to a polymer that dissociates in ion-exchanged water to form an ionic atmosphere of negative charge, and dissolves 10 g or more per 100 g of water at 25°C.

The cerium-based abrasive slurry stock solution contains 1.5 to 10.0 parts by mass of the anionic water-soluble polymer based on 100 parts by mass of TREO, more preferably 2.0 to 8.0 parts by mass, and still more preferably 2.2 to 5.0 parts by mass.

When the content of the anionic water-soluble polymer in the cerium-based abrasive slurry stock solution is 1.5 parts by mass or more with respect to 100 parts by mass of TREO, it is easy to prepare a homogeneous slurry, and the productivity of the cerium-based abrasive slurry stock solution is improved. In addition, when the content is 10.0 parts by mass or less, the homogeneity of the slurry is easily maintained and a cerium-based abrasive slurry stock solution having excellent productivity is easily obtained.

Examples of the anionic water-soluble polymer include polycarboxylic acid-based polymers and polysulfonic acid-based polymers from the viewpoint of dispersing the mixed rare-earth oxide particles in water to easily obtain a homogeneous slurry. A carboxylic acid-based polymer is preferred. Among these, it may be used individually by 1 type, or may use 2 or more types together. In addition, the polycarboxylic acid-type polymer in this embodiment means the polymer whose monomer derived from an unsaturated carboxylic acid is 60 mol% or more in 100 mol% of structural monomer units.

Examples of the polycarboxylic acid-based polymer include (meth)acrylic acid copolymers such as poly(meth)acrylic acid, polyhydroxy(meth)acrylic acid, (meth)acrylic acid and maleic acid copolymers, and olefin and maleic acid copolymers. polymers, copolymers of alkylene oxide adducts such as ethylene oxide and propylene oxide of maleic acid and allyl alcohol, copolymers of allylsulfonic acid and maleic acid, and alkali metal salts such as sodium salts and potassium salts thereof. Among these, polyacrylic acid, a copolymer of acrylic acid and maleic acid, or an alkali metal salt thereof is preferable, and a copolymer of acrylic acid and maleic acid or an alkali metal salt thereof is more preferable.

(phosphoric acid compound)

The cerium-based abrasive slurry stock solution contains a phosphoric acid compound together with the anionic water-soluble polymer. By using the phosphoric acid compound in combination with the anionic water-soluble polymer, it is possible to maintain good polishing performance on the free material of the polishing liquid obtained by diluting the cerium-based abrasive slurry stock solution.

The content of the phosphoric acid compound in the cerium-based abrasive slurry stock solution is preferably 0.5 to 10.0 parts by mass, more preferably 0.5 to 10.0 parts by mass, based on 100 parts by mass of the TREO from the viewpoint of maintaining good polishing performance of the polishing liquid with respect to the glass material. Preferably it is 0.8-8.0 mass parts, More preferably, it is 1.0-5.0 mass parts.

As said phosphoric acid compound, For example, inorganic phosphoric acid of tripolyphosphoric acid, pyrophosphoric acid, tetrametaphosphoric acid, hexametaphosphoric acid, orthophosphoric acid, and phosphorous acid; organic phosphonic acids such as aminotrimethylenephosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, ethylenediaminetetramethylenephosphonic acid, and diethylenetriaminepentamethylenephosphonic acid; or alkali metal salts such as sodium salts and potassium salts thereof. These may be used individually by 1 type, and may use 2 or more types together. Among these, tripolyphosphoric acid, pyrophosphoric acid, hexametaphosphoric acid, or alkali metal salts thereof are preferable.

In addition, the said cerium-based abrasive slurry stock solution may contain additives such as a pH adjuster, an antifoaming agent, and a rust preventive agent, if necessary, within a range that does not interfere with the polishing performance of the polishing solution prepared using the cerium-based abrasive slurry stock solution.

(D ₅₀ )

The particle _diameter of the slurry particles in the cerium-based abrasive slurry stock solution is 0.10 to 0.35 µm, preferably 0.15 to 0.30 µm, more preferably 0.17 to 0.28 µm.

The above D ₅₀ is obtained from a particle size distribution measured by a laser diffraction scattering method, and specifically, a value measured by a Microtrac particle size distribution meter described in the following examples.

When the D ₅₀ is 0.10 µm or more, the cerium-based abrasive slurry stock solution can be prepared with good productivity. Further, when the D ₅₀ is 0.35 µm or less, the polishing surface can be favorably smoothed using the polishing liquid prepared using the cerium-based abrasive slurry stock solution, and excellent polishing performance is easily obtained.

[Method for preparing cerium-based abrasive slurry stock solution]

The cerium-based abrasive slurry stock solution of the present embodiment is prepared by wet grinding a mixed raw material containing mixed rare earth oxide particles, water, and the anionic water-soluble polymer to obtain a grinding slurry (1); by the manufacturing method of this embodiment, comprising the step (2) of obtaining a classification slurry, and the step (3) of adding and mixing water and the phosphoric acid compound to the classification slurry to obtain a cerium-based abrasive slurry stock solution, can be appropriately prepared.

Hereinafter, each process is demonstrated in order.

(Process (1))

In step (1), a mixed raw material containing mixed rare-earth oxide particles, water, and the anionic water-soluble polymer is wet-pulverized to obtain a pulverized slurry.

By performing wet grinding using water as a dispersion medium for the mixed raw material, a homogeneous grinding slurry can be efficiently produced in a state in which the thickening of the slurry is suppressed.

It is preferable to perform the said wet grinding by media mills, such as a ball mill and a bead mill, from a viewpoint of obtaining a homogeneous grinding|pulverization slurry. As a dispersion medium, you may mix and use water-soluble organic solvents, such as alcohol, other than water from a viewpoint of a dispersibility improvement.

In wet grinding using, for example, a bead mill, the mixed raw material can be pulverized without disturbing safe and stable pulverization due to increases in internal pressure and temperature of the mill even if the mixed rare earth oxide particle concentration is 50 mass % or higher. It is said that a slurry can be manufactured and it is excellent in productivity.

The said wet grinding is a post-process (2) _WHEREIN : From a viewpoint of raising the yield of the classified slurry whose D50 of the slurry particle is 0.10-.35 micrometer, for example, when using a bead mill, zirconia beads (beads) It is preferable to obtain a grinding slurry by using a diameter of 0.1 to 0.5 mm) and grinding at a mill peripheral speed of 5 to 10 m/s.

(Process (2))

In a process (2), the grinding|pulverization slurry obtained in the said process (1) is wet-classified, and a classification slurry is obtained.

As described above, the wet classification is performed so that the D ₅₀ of the slurry particles in the cerium-based abrasive slurry stock solution is 0.10 to 0.35 µm from the viewpoint of obtaining a polishing liquid exhibiting good polishing performance with respect to the glass material. In addition, it can be considered that D _{50 of the slurry particles in the classification slurry is substantially equal to D 50 of} the slurry particles in the prepared cerium-based abrasive slurry stock solution.

In the wet classification, it is preferable to remove at least coarse particles having a particle diameter of more than 5.0 μm.

The method of the said wet classification is not specifically limited, For example, it can perform using a liquid cyclone, a centrifugal settler, a slurry screener, etc.

(Process (3))

In the step (3), water and the phosphoric acid compound are added to the classification slurry obtained in the step (2) and mixed to obtain the cerium-based abrasive slurry stock solution.

In the cerium-based abrasive slurry stock solution of the present embodiment, the anionic water-soluble polymer and the phosphoric acid compound are used in combination, but when the phosphoric acid compound is added simultaneously or first with the addition of the anionic water-soluble polymer, it is mixed to prepare a slurry , it becomes easy to thicken remarkably. For this reason, in this embodiment, the said phosphoric acid compound is added later to the said classification slurry, and the cerium-type abrasive|polishing material slurry stock solution is manufactured.

From a viewpoint of suppressing the thickening accompanying the addition of the said phosphoric acid compound, water is also added and mixed with the said phosphoric acid compound to the said classification slurry. The phosphoric acid compound may be added by dissolving it in water.

The method of the said mixing is not specifically limited, What is necessary is just stirring and mixing to the extent that the said phosphoric acid compound can be dissolved in water. For example, you may mix with stirrers, such as a high-speed shearing machine, and you may mix using media mills, such as a ball mill and a bead mill.

The cerium-based abrasive slurry stock solution obtained as described above is prepared by adding additives such as a pH adjuster, an antifoaming agent, and a rust preventive agent as necessary within a range that does not interfere with the polishing performance of the polishing liquid prepared using the cerium-based abrasive slurry. it may be

[Abrasive Fluid]

The cerium-based abrasive slurry stock solution is prepared as a polishing solution by diluting it with water depending on the polishing apparatus used and the required polishing performance. The preparation liquid is preferably used within the range of 0.1 to 10.0 mass % of TREO from the viewpoint of exhibiting good polishing performance for glass materials and from the viewpoint of cost, more preferably 0.5 to 9.0 mass %, further Preferably it is 1.0-8.0 mass %.

In addition, in consideration of the polishing object and specifications of the polishing apparatus, the polishing liquid is, if necessary, used in the preparation of the polishing liquid within a range that does not interfere with the polishing performance of the polishing liquid, for example, a pH adjuster Additives such as , an antifoaming agent and a rust preventive agent may be added.

The grinding|polishing method using the said grinding|polishing liquid is not specifically limited, The method using a well-known grinding|polishing apparatus etc. is applicable. The said polishing liquid can be used by a well-known method, when finishing grinding|polishing, such as mirror grinding|polishing of a glass material, with a single-sided grinder or a double-sided grinder, for example.

The above-mentioned cerium-based abrasive slurry stock solution is excellent in productivity, and the polishing solution prepared using it has good polishing performance on glass materials, and particularly, glass substrates for magnetic disks, glass substrates for liquid crystal displays, and color It can be conveniently used for finishing polishing of various glass materials, such as the glass substrate for filters and photomasks, and the glass substrate for optical lenses.

Example

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to the following examples.

In addition, TREO in the following Examples and Comparative Examples, the content in terms of oxide of heavy and heavy rare earth, content in terms of oxide of Ce with respect to TREO (Ce amount/TREO), and fluorine atom content were calculated as follows.

[TREO]

Ammonia water was added to the solution in which the measurement sample was dissolved in acid. The resulting precipitate was filtered and washed to remove alkali metals, and then acid-dissolved again. Oxalic acid was added to this solution, and the resulting precipitate was calcined in the air to determine TREO by a gravimetric method.

[Content in terms of oxides of heavy and heavy rare earth]

The measurement sample was acid-dissolved, the amount of each rare earth element was measured by the ICP-AES method, and the values were calculated by summing the values converted as oxides with respect to the heavy and heavy rare earth.

[Ce amount/TREO]

The measurement sample was acid-dissolved, and the amount of Ce measured by the ICP-AES method was calculated|required by calculating the value with respect to TREO of the value converted as oxide.

[Fluorine atom content]

A measurement sample (mixed rare earth oxide particles) was dissolved in alkali, extracted with hot water, and measured by a fluorine ion meter (manufactured by HORIBA, Ltd.; ion electrode method). In addition, the anionic water-soluble polymer, phosphoric acid compound, and water do not contain fluorine atoms, and the fluorine atom content in the abrasive slurry stock solution is determined from the fluorine atom content in the mixed rare earth particles used for the preparation of the cerium-based abrasive slurry stock solution. estimated

[Preparation of cerium-based abrasive slurry stock solution]

(Example 1)

Rare earth concentrate (ore) containing 47.0 mass % of TREO and 2.0 mass % of heavy rare earth in terms of oxide is treated by sulfuric acid roasting method and solvent extraction method, impurities other than rare earth elements are not more than 1.0 mass %, heavy rare earth is oxide A mixed light rare earth compound was obtained in which the content of the rare earth element was adjusted by reducing it to 1.0 mass % or less in terms of conversion. This mixed rare earth compound is carbonized using ammonium bicarbonate to obtain mixed rare earth carbonate, and then the mixed rare earth carbonate is calcined in an electric furnace at 900° C. in the air for 10 hours, and mixed rare earth oxide particles (D ₅₀ : 10 µm). Among the mixed rare earth particles, the TREO content was 97.0 mass% and the fluorine atom content was 0 mass%.

To 5000 g of the mixed rare-earth particles, 3475 g of soft water and a sodium salt of a copolymer of acrylic acid and maleic acid as an anionic water-soluble polymer (“Poise (registered trademark) 521” manufactured by Kao Corporation, a solid content concentration of 40% by mass aqueous solution (solid content as a polymer component) "AA-MA" in Table 1) was added in an amount of 4.1 parts by mass (in terms of solid content) with respect to 100 parts by mass of TREO in the mixed rare earth oxide particles (mixed rare earth oxide particle concentration of 55.7% by mass) , and a bead mill (beads: manufactured by zirconia, diameter 0.3 mm; mill perimeter speed 8 m/s) for 3 hours and pulverized to obtain a pulverized slurry.

The pulverized slurry was wet-classified to remove coarse particles (more than 5.0 µm in particle size) to obtain a classification slurry. In a state in which a phosphoric acid compound (sodium tripolyphosphate) is dissolved in soft water in the classification slurry, it is added in an amount of 4.1 parts by mass to 100 parts by mass of TREO in the mixed rare earth oxide particles and stirred and mixed, and the TREO content is 23.1% by mass of cerium-based An abrasive slurry stock solution was prepared.

(Examples 2 to 10 and Comparative Examples 1 to 5)

A cerium-based abrasive slurry stock solution was prepared in the same manner as in Example 1 with the raw material mixing composition shown in Table 1 below.

In addition, "AA" of the anionic water-soluble polymer in Table 1 is a sodium salt of polyacrylic acid ("POISE (registered trademark) 530, manufactured by Kao Corporation, a solid content concentration of 40 mass % aqueous solution (a solid content is regarded as a polymer component). ))to be. In addition, the notation with "-" has shown that it is not added.

[Evaluation Measurement]

The cerium-based abrasive slurry stock solutions prepared in Examples and Comparative Examples were evaluated and measured below. In addition, polishing performance was evaluated using the polishing liquid prepared by diluting the said cerium-based abrasive slurry stock solution with pure water.

These evaluation and measurement results are summarized in Table 1 below and shown.

[D ₅₀ ]

With a Microtrac particle size distribution meter "MT3300II" (manufactured by Nikkiso Co., Ltd.), the particle size distribution of the slurry particles was measured by a laser diffraction scattering method to determine the particle size (D ₅₀ ) at 50% of the cumulative volume.

[productivity]

In the production of the cerium-based abrasive slurry stock solution, the work load in preparing the grinding slurry is the largest and the effect on productivity is large, so the following evaluation in the process of obtaining the grinding slurry is regarded as an evaluation of productivity. did.

The upper limit concentration of mixed rare earth particles that can obtain a pulverized slurry without increasing the internal pressure and temperature of the bead mill (internal pressure 0.3 MPa or less, temperature 55 ° C or less) was investigated, and based on the upper limit concentration, the following evaluation criteria were used. evaluation was performed.

(Evaluation standard)

A: Concentration 55% by mass or more

B: Concentration of 50% by mass or more and less than 55% by mass

C: Concentration 40% by mass or more and less than 50% by mass

D: Concentration less than 40% by mass

In the case of evaluations A and B, it is said that it is excellent in productivity. On the other hand, in the case of evaluations C and D, it was determined that productivity was inferior.

[Abrasive Performance]

The cerium-based abrasive slurry stock solution was diluted with pure water to prepare a polishing solution having a TREO of 5.0% by mass. Using this polishing liquid, a polishing test was performed with a single-sided polishing machine under the following polishing conditions, and the polishing rate and surface roughness (arithmetic mean roughness Ra) were measured as follows.

The polishing rate was determined as an arithmetic mean by measuring the thickness of the sample before and after polishing with a micrometer at four locations per one sample to be polished.

The surface roughness (Ra) was obtained by measuring the polished surface of the sample after polishing for 120 minutes with a stylus profiler ("P-12", manufactured by KLA-Tencor).

<Grinding conditions>

Grinding target sample: commercially available blue plate glass (50mm×50mm×thickness 1.10mm, polished area 25cm ² )

Polishing Pad: Suede Pad

Lower wheel rotation speed: 260rpm

Grinding pressure: 80 g/cm ²

As can be seen from Table 1, it was confirmed that the cerium-based abrasive slurry stock solutions (Examples 1 to 10) having a predetermined particle size prepared by using a predetermined amount of an anionic water-soluble polymer and a phosphoric acid compound in combination were excellent in productivity. In addition, according to the polishing liquid obtained by diluting the cerium-based abrasive slurry stock solution, the polishing rate does not decrease even when the polishing time has elapsed after 120 minutes, the polishing power is maintained, and polishing at a good surface roughness (Ra) (machining accuracy) It has been confirmed that this can be done.

From this, it is said that the cerium-based abrasive slurry stock solution of the present embodiment can provide a polishing solution that improves productivity and exhibits good polishing performance for glass materials.

Claims (8)

A cerium-based abrasive slurry stock solution comprising mixed rare earth oxide particles and water, comprising:
The cerium-based abrasive slurry stock solution includes an anionic water-soluble polymer and a phosphoric acid compound,
The oxide equivalent content (TREO) of all rare earth elements is 10.0 to 40.0 mass%, and the oxide equivalent content of cerium in the TREO is 50.0 mass% or more,
The content of the anionic water-soluble polymer is 1.5 to 10.0 parts by mass based on 100 parts by mass of the TREO,
A cerium-based abrasive slurry stock solution having a particle size (D ₅₀ ) of 0.10 to 0.35 µm at 50% of the cumulative volume in the particle size distribution by the laser diffraction scattering method of the slurry particles. The method of claim 1,
A cerium-based abrasive slurry stock solution having a fluorine atom content of 0.1% by mass or less. 3. The method according to claim 1 or 2,
The anionic water-soluble polymer is a cerium-based abrasive slurry stock solution that is a polycarboxylic acid-based polymer. 4. The method of claim 3,
The polycarboxylic acid-based polymer is a cerium-based abrasive slurry stock solution of at least one selected from polyacrylic acid, a copolymer of acrylic acid and maleic acid, and alkali metal salts thereof. 5. The method according to any one of claims 1 to 4,
The phosphoric acid compound is tripolyphosphoric acid, pyrophosphoric acid and hexametaphosphoric acid, and at least one cerium-based abrasive slurry stock solution selected from alkali metal salts thereof. 6. The method according to any one of claims 1 to 5,
The content of the phosphoric acid compound is 0.5 to 10.0 parts by mass based on 100 parts by mass of the TREO cerium-based abrasive slurry stock solution. A method for producing the cerium-based abrasive slurry stock solution according to any one of claims 1 to 6, comprising:
obtaining a pulverized slurry by wet pulverizing a mixed raw material comprising the mixed rare earth oxide particles, water, and the anionic water-soluble polymer;
a step of wet classifying the pulverized slurry to obtain a classified slurry;
and adding and mixing water and the phosphoric acid compound to the classification slurry to obtain the cerium-based abrasive slurry stock solution. The cerium-based abrasive slurry stock solution according to any one of claims 1 to 6 is a polishing solution diluted with water, and the TREO is 0.1 to 10.0 mass%.