JP2003213250A - Cerium polishing material, cerium polishing material slurry, method for polishing glass substrate and method for producing glass substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a cerium polishing material capable of increasing the polishing rate, slightly causing flaws in a polished surface of a polished material to be polished, having a small surface roughness and good quality, sustaining the high polishing rate over a long period and carrying out polishing with high efficiency. <P>SOLUTION: The cerium polishing material consists essentially of cerium oxide and has a settling bulk density within the range of 0.8-1.0 g/ml when 10 mass% of the polishing material is dispersed in water. The primary particle diameter is within the range of 40-80 nm and the specific surface area is within the range of 2-5 m<SP>2</SP>/g. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cerium-based abrasive used for polishing glass or the like, and more specifically, a glass hard disk substrate, a glass substrate for liquid crystal panel, or a glass having relatively high hardness such as borosilicate glass. A cerium-based abrasive containing cerium oxide as a main component used for finish polishing of a substrate, a cerium-based abrasive slurry, and a method for polishing a glass substrate using the cerium-based abrasive slurry,
And a method for manufacturing a glass substrate using the method for polishing a glass substrate.

[0002]

2. Description of the Related Art In recent years, glass materials have been used for various purposes, and surface polishing is often required. For example, a glass substrate for an optical lens or an optical lens is required to have a surface accuracy such as a mirror surface. In particular, glass substrates for optical disks and magnetic disks, thin film transistors (TF)
Glass substrate for liquid crystal such as T) type LCD and twisted nematic (TN) type LCD, color filter for liquid crystal TV,
Since glass substrates for LSI photomasks and the like are required to have flatness, small surface roughness, and no defects, more accurate surface polishing is required.

The glass substrate for liquid crystal is required to have high heat resistance because the heat treatment temperature in the subsequent step is high, and the glass substrate for liquid crystal is being thinned for weight reduction. Also for glass substrates for magnetic discs, demands have been increasing year by year, such as thinning due to weight reduction, mechanical properties that can withstand undulation of the disc at high rotation, particularly high rigidity.

In order to satisfy these thinness and mechanical properties, the chemical composition and manufacturing method of glass have been improved, and glass substrates containing aluminosilicate as a main component have been used for liquid crystals and magnetic disks. It's coming.
As a glass substrate for a magnetic disk, a crystallized glass substrate containing lithium silicate as a main component or a crystallized glass substrate such as quartz crystal has been developed. These glass substrates have very poor workability, and conventional abrasives have a slow processing speed and poor productivity. In addition, a glass substrate for a magnetic disk is required to have a highly accurate surface polishing performance and a high polishing rate.

[0005]

Abrasives used for polishing the surface of a glass substrate are rare earth oxides because they have a polishing rate several times better than iron oxide, zirconium oxide, or silicon dioxide. In particular, an abrasive containing cerium oxide as a main component is used. These abrasives are generally used by dispersing abrasive grains in a liquid such as water, but with conventional cerium oxide-based abrasives, the polishing rate for a hard glass substrate as described above is high. It had the problem of being slow.

Although the polishing mechanism of the cerium oxide-based abrasive has not been fully clarified, polishing is performed by the combined effect of the chemical effect of cerium oxide on glass and the mechanical effect due to the hardness of the cerium oxide particles themselves. It has been confirmed that the progress of phenomenology is phenomenological. However, since the glass substrate containing aluminosilicate as a main component and the crystallized glass substrate containing lithium silicate as a main component have excellent chemical resistance, the chemical effect of the abrasive cannot be sufficiently exhibited. Further, since these glass substrates (workpieces) are hard, the abrasive particles are easily crushed, the mechanical effect on the glass cannot be sufficiently maintained, and the processing speed is immediately reduced.

In order to maintain the mechanical effect for a long period of time, it is possible to add powder particles having a hardness higher than that of the work piece such as alumina and zirconia to the abrasive composition, but the concentration of cerium oxide particles is relatively high. Therefore, the chemical effect becomes insufficient. In addition, defects such as pits and scratches are generated on the glass surface (workpiece surface) due to the powder particles having high hardness.

The present invention has been made to solve the problems of the prior art as described above, and an object of the present invention is to improve the polishing rate at the beginning of polishing for glass that is hard and difficult to obtain a high polishing rate. Can be maintained for a long time, and
A cerium-based abrasive that does not cause surface defects such as pits and scratches on a workpiece such as glass and has excellent surface quality after polishing, a cerium-based abrasive slurry containing this cerium-based abrasive, and this cerium-based abrasive slurry The present invention provides a method for polishing a glass substrate using, and a method for manufacturing a glass substrate using the method for polishing a glass substrate.

[0009]

The present invention is as follows. (1) A cerium-based abrasive containing cerium oxide as a main component, and the sedimentation bulk density when 10% by mass of the abrasive is dispersed in water is within a range of 0.8 g / ml to 1.0 g / ml. A cerium-based abrasive characterized by being (2) The cerium-based abrasive as described in (1) above, wherein the primary particle diameter is in the range of 40 nm to 80 nm. (3) the specific surface area being in the range of ^{2m 2 / g~5m 2 / g (} 1) or cerium based polishing material according to (2). (4) The cerium-based abrasive according to any one of (1) to (3) above, which contains 35% by mass or more of cerium in terms of oxide. (5) A cerium-based abrasive slurry in which the cerium-based abrasive according to any one of (1) to (4) above is dispersed in a dispersion medium at a concentration of 5% by mass to 30% by mass. . (6) The cerium-based abrasive slurry according to (5) above, wherein the dispersion medium is water. (7) The cerium-based abrasive slurry according to (5) above, wherein the dispersion medium is an organic solvent. (8) Organic solvents are alcohols, polyhydric alcohols,
The cerium-based abrasive slurry according to (7) above, which contains any one selected from the group consisting of acetones and tetrahydrofurans. (9) The cerium-based abrasive slurry according to any one of (5) to (8) above, wherein the cerium-based abrasive slurry contains a surfactant. (10) The surfactant is at least one selected from the group consisting of anionic surfactants and nonionic surfactants.
The cerium-based abrasive slurry according to (9) above, which is a seed. (11) The anionic surfactant is at least one selected from the group consisting of a low molecular weight compound such as a carboxylate salt, a sulfonate salt, a sulfuric acid ester salt and a phosphoric acid ester salt, and a high molecular compound. The cerium-based abrasive slurry according to (10) above. (12) The nonionic surfactant is at least one selected from the group consisting of polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl ethers, and polyoxyethylene fatty acid esters. (10) Cerium-based abrasive slurry. (13) A method for polishing a glass substrate, which comprises using the cerium-based abrasive slurry according to any one of (5) to (12) above. (14) A method for manufacturing a glass substrate, which comprises using the method for polishing a glass substrate according to (13) above.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The cerium-based abrasive of the present invention contains cerium oxide as a main component and has a sedimentation bulk density of 0.8 g / ml to 1.0 g / ml when 10% by mass of the abrasive is dispersed in water. It is characterized by being inside.

The cerium-based abrasive is an abrasive containing cerium oxide as a main component, and is a substance other than cerium oxide, such as lanthanum (La), niobium (Nd), praseodymium (Pr), or an oxide thereof. You may include things etc.

The sedimented bulk density in the present invention is the density of the abrasive which is settled in the liquid after the abrasive containing no additive such as a dispersant is dispersed in a liquid and the dispersion is allowed to stand.
Perform the measurement according to the following procedure.

10 g of the abrasive was dispersed in ion-exchanged water, and 1
Put in a graduated cylinder of 00 ml and make the liquid level 100 ml. After sufficiently stirring this dispersion, it is allowed to stand for 24 hours and the sedimentation volume of the powder layer is measured. Using this settling volume, the settling bulk density is calculated by the following formula. Sedimentation bulk density (g / ml) = 10 (g) / sedimentation volume (m
l)

In the cerium-based abrasive of the present invention, it is necessary that the sedimented bulk density is within the range of 0.8 g / ml to 1.0 g / ml. If the sedimented bulk density of the cerium-based abrasive is lower than 0.8 g / ml, the polishing rate for hard glass having a low workability will be slow and the object of the present invention cannot be achieved. Also, the sedimented bulk density of the cerium-based abrasive is 1.0
If it is higher than g / ml, scratches and the like are likely to occur on the polished surface, and the object of the present invention cannot be achieved.

Further, in the present invention, if the sedimented bulk density is preferably within the range of 0.85 g / ml to 0.95 g / ml, even higher polishing characteristics can be obtained.

The sedimentation bulk density can be controlled by the firing temperature when, for example, a slurry of a crushed substance of bastnasite is dried, fired and crushed to produce a cerium-based abrasive. If the particle sizes of the pulverized products are almost the same, the higher the calcination temperature, the higher the settling bulk density, and the lower the calcination temperature, the lower the settling bulk density.

The primary particle diameter of the cerium-based abrasive of the present invention is preferably within the range of 40 nm to 80 nm, more preferably within the range of 50 nm to 70 nm.

The primary particle diameter of the cerium-based abrasive of the present invention is measured by the crystallite diameter calculation formula (Scherrer's equation) from the half-value width of the X-ray diffraction peak. That is, ε = 0.9 λ / β _1/2 / cos θ ε: primary particle size λ: measured X-ray wavelength (angstrom) β _1/2 : half-value width (radian) of diffraction line determines the primary particle size To do. In order to determine the primary particle size of the cerium-based abrasive of the present invention, X due to cerium oxide, which appears near 2θ = 28 degrees to 28.4 degrees, is used.
A line diffraction peak is used.

When the primary particle diameter of the cerium-based abrasive of the present invention is smaller than 40 nm, the mechanical polishing force becomes weak and it becomes difficult to obtain a sufficient polishing rate. When the primary particle diameter of the cerium-based abrasive of the present invention is larger than 80 nm, the particles constituting the abrasive become hard and large crystals, so that scratches are easily generated on the polished surface.

The cerium-based abrasive material of the present invention, preferably a specific surface area in the range of 2m ² / g~10m ² / g, more preferably, in the range of 2m ² / g~5m ² / g. When the specific surface area of the abrasive is less than 2 m ² / g, scratches are easily generated on the polished surface, and the specific surface area of the abrasive is 5 m.
^If it is more than ² / g, the polishing rate will decrease. In addition, in measuring the specific surface area of the cerium-based abrasive of the present invention, BET
Preferably, the method is used.

The cerium-based abrasive of the present invention contains cerium oxide as a main component. Here, the main component of cerium oxide is 35 mass% of cerium (Ce) in terms of oxide.
As described above, more preferably 45% by mass or more is contained.
If the amount of Ce converted to oxide is lower than 35% by mass, it becomes difficult to obtain a sufficient polishing rate. The higher the oxide conversion amount of Ce is, the more preferable, but when the oxide conversion amount of Ce is 70% by mass or more, it is difficult to noticeably improve the polishing power. Therefore, in practice, the cerium-based abrasive of the present invention preferably contains Ce in the range of 35% by mass to 70% by mass in terms of oxide.

The cerium-based abrasive of the present invention is usually handled in the form of powder, but when used as an abrasive, it is in the form of a dispersion (slurry) in the form of a glass substrate for optical lenses, a glass for optical disks or magnetic disks. It is preferably used for finish polishing of various glass materials and glass products such as substrates and glass substrates for liquid crystals.

For example, when dispersed in a dispersion medium such as water, the concentration is preferably in the range of 5% by mass to 30% by mass,
More preferably, it is used in the state of a slurry within the range of 10% by mass to 20% by mass. Other than water, the dispersion medium preferably used in the present invention is an organic solvent, particularly preferably a water-soluble organic solvent.

Examples of the water-soluble organic solvent include monohydric alcohols having 1 to 10 carbon atoms such as methanol, ethanol, propanol, isopropanol and butanol, polyhydric alcohols having 3 to 10 carbon atoms such as ethylene glycol and glycerin, and acetone. , Dimethyl sulfoxide (DMS
O), dimethylformamide (DMF), tetrahydrofuran, dioxane and the like. Among these, it is particularly preferable to use alcohols, polyhydric alcohols, acetones, and tetrahydrofurans.

In the present invention, it is preferable to add a surfactant as a dispersant to the cerium-based abrasive slurry. As the surfactant preferably used in the present invention,
Examples include anionic surfactants, cationic surfactants, nonionic surfactants, and zwitterionic surfactants.
These may be used alone or in combination of two or more. Among them, anionic surfactants and nonionic surfactants are preferable in the present invention.

Known anionic surfactants include known carboxylates (soaps, N-acyl amino acid salts, alkyl ether carboxylates, acylated peptides, etc.) and sulfonates (alkanesulfonates (alkylbenzenesulfonates). Also) and alkylnaphthalene sulfonate,
Sulfosuccinate, α-olefin sulfonate, N-
Acyl sulfonate, etc., sulfate ester salt (sulfated oil,
Low molecular weight compounds selected from alkyl sulfates, alkyl ether sulfates, alkyl allyl ether sulfates, alkyl amide sulfates, etc.) and phosphate ester salts (alkyl phosphates, alkyl ether phosphates, alkyl allyl ether phosphates, etc.) And high-molecular compounds are also included. Here, the salt is selected from at least one of Li salt, Na salt, K salt, Rb salt, Cs salt, ammonium salt and H type.

For example, the soap is a fatty acid salt having 12 to 18 carbon atoms, and the fatty acid group generally includes lauric acid, myristic acid, palmitic acid and stearic acid, and the N-acyl amino acid salt is exemplified. , N-acyl-N-methylglycine salts having 12 to 18 carbon atoms and N
-Acyl glutamate. Examples of the alkyl ether carboxylic acid salt include compounds having 6 to 18 carbon atoms, and examples of the acylated peptide include 12 carbon atoms.
To 18 compounds. Examples of the sulfonate include the above compounds having 6 to 18 carbon atoms. For example, in the case of alkane sulfonic acid, lauryl sulfonic acid, dioctyl succin sulfonic acid, benzene sulfonic acid, dodecyl benzene sulfonic acid, myristyl sulfonic acid, and keryl benzene. Examples thereof include sulfonic acid and stearyl sulfonic acid. The sulfate ester salt has 6 to 18 carbon atoms.
Examples of the above compounds include, for example, alkyl sulfates such as lauryl sulfate, dioctyl succinic sulfate, myristyl sulfate and stearyl sulfate, and phosphoric acid ester salts include the above compounds having 8 to 18 carbon atoms. Examples of nonionic surfactants include polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ether, and polyoxyethylene fatty acid ester. Further, in addition to the above-mentioned anionic surfactant and nonionic surfactant, known fluorine-based surfactants can be used.

As the polymer type surfactant, a special polycarboxylic acid type compound (manufactured by Kao Corporation, trade name: Poise 530) is used.
Can also be illustrated.

Further, in the cerium-based abrasive slurry of the present invention, in addition to the above-mentioned surfactant, a polymer dispersant such as tripolyphosphate may be added, if necessary, in order to prevent the slurry from settling or improve the stability. Additives such as phosphates such as hexametaphosphate, cellulose ethers such as methylcellulose and carboxymethylcellulose, and water-soluble polymers such as polyvinyl alcohol can also be added. The addition amount of these additives is 0.
It is generally preferred to be in the range of from 05% by mass to 20% by mass, particularly preferably in the range of from 0.1% by mass to 10% by mass.

A glass base material or the like polished by using the cerium-based abrasive or the cerium-based abrasive slurry of the present invention is
It is possible to obtain a polished surface of excellent quality and a sufficient polishing rate without causing surface defects such as pits and scratches. Further, there is also an effect that the polishing rate is maintained for a long time.

The cerium-based abrasive of the present invention can be manufactured by a known manufacturing process using a known manufacturing apparatus, and can be efficiently manufactured by setting the following manufacturing conditions. is there.

That is, a material containing a large amount of cerium oxide such as bastnasite is used as a raw material, and the pulverized particle size of the raw material is 1.6 μm to 2.0 μm as measured by an aperture tube 30 μm using a Coulter Multisizer.
Controlled within the range of m, the firing temperature is 1000 ° C to 1100
It is preferable that the temperature is within the range of ℃, and the firing time is about 2 hours when a rotary kiln is used.

[0034]

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[Example 1] Bastnaesite # 4010 manufactured by Moricorp America Inc. was used as a raw material, and the raw material 1k was used.
g was pulverized with 1 liter of water by a wet ball mill to obtain a slurry containing powder having an average particle diameter (D50) of 1.8 μm.

Bustney site made by Moricorp of America #
The composition of 4010 is as follows. CeO _2: 35 wt% La ₂ O _3: 24 wt% Nd ₂ O _3: 8 wt% Pr ₆ O _11: 3 wt% F: 6 wt% total rare earth oxide: 68 wt% to 73 wt% loss on ignition ( 1000 ° C): 20% by mass

The slurry was dried, calcined in an electric furnace at 1000 ° C. for 2 hours, and then cooled, crushed and classified to obtain a cerium-based abrasive. The oxide conversion content of Ce in the produced cerium-based abrasive was 45% by mass.

The average particle size (D50) is 3 using a Coulter Multisizer (manufactured by Coulter Co.).
It is a particle diameter corresponding to a cumulative value of 50% of volume distribution measured with a 0 μm aperture tube.

Next, the obtained cerium-based abrasive was dispersed in water to obtain an abrasive slurry with a concentration of 10% by mass. Using this abrasive slurry, non-alkali glass for thin film transistor (TFT) panels was polished and the polished state was evaluated. The polishing conditions are as follows.

[Polishing Condition] Polishing machine: 4-way type double-sided polishing machine processed product: 5 cm square, non-alkali glass, area 2
5 cm ² Number of processed pieces: 3 pieces / Batch is performed twice Polishing pad: Polyurethane foam pad (LP-7
(7, manufactured by Rhodes Co.) Lower platen rotation speed: 90 rpm Slurry supply amount: 60 ml / min Processing pressure: 156 g / cm ² Polishing time: 30 minutes

The thickness of each of the 6 pieces of alkali-free glass for TFT panel before and after polishing was measured with a micrometer at 4 points per sheet, and the measured values of 4 points × 6 sheets were averaged to obtain a polishing rate (μm / Minutes). Further, the number of scratches per polished surface was determined by visually observing the glass surface using a halogen lamp of 200,000 lux as a light source. Further, the center line average roughness of the glass surface was measured by a Taristep manufactured by Rank Taylor Hobson.

Further, 10 g of the cerium-based abrasive was dispersed in ion-exchanged water, charged into a 100 ml graduated cylinder to bring the liquid level to 100 ml, and after sufficiently stirring this, the mixture was allowed to stand for 24 hours, and the sediment volume of the powder layer was set. Was measured to determine the sedimentation bulk density.

The obtained results are shown in Table 1 for the physical properties of the abrasive, average particle size (D50), BET specific surface area, polishing rate, and sedimented bulk density, and Table 2 for the polishing characteristics.

Example 2 A cerium-based abrasive was obtained in the same manner as in Example 1 except that the average particle size of the raw material after wet pulverization was set to 1.6 μm.

In the same manner as in Example 1, the obtained cerium-based abrasive was used for polishing, and the polishing state was evaluated. The results are shown in Table 1.

[Comparative Example 1] A cerium-based abrasive was obtained in the same manner as in Example 1 except that the temperature for burning the slurry in the electric furnace was changed to 800 ° C.

In the same manner as in Example 1, the obtained cerium-based abrasive was used for polishing, and the polishing state was evaluated. Table 1 shows the physical properties of the abrasive, and Table 2 shows the polishing results.

[Comparative Example 2] A cerium-based abrasive was obtained in the same manner as in Example 1, except that the firing temperature of the slurry in the electric furnace was 1200 ° C.

In the same manner as in Example 1, the obtained cerium-based abrasive was used for polishing, and the polishing state was evaluated. Table 1 shows the physical properties of the abrasive, and Table 2 shows the polishing results.

[0050]

[Table 1]

[0051]

[Table 2]

As is clear from Table 2, Examples 1 and 2
In, the polishing rate was high, and scratches did not occur on the surface of the non-alkali glass that was the object to be polished, and a cerium oxide-based abrasive having good polishing surface quality could be obtained.

On the other hand, in Comparative Example 1, the polishing rate was slow because the sedimentation bulk density was low.

In Comparative Example 2, since the sedimented bulk density was too large, the effect of improving the polishing rate was low. Also, scratches are generated on the polishing surface, the surface roughness of the polishing surface is large,
The quality of the polished surface was poor.

Further, the cerium-based abrasive slurry of the present invention was found to have the effect that the polishing effect lasted for a long time.

[0056]

As described above, according to the present invention,
The polishing rate could be increased, and the polished object had few scratches on the polished surface, small surface roughness, and good quality. In addition, the high polishing rate was maintained for a long time, enabling highly efficient polishing.

Claims (14)

[Claims] 1. A cerium-based abrasive containing cerium oxide as a main component, wherein the sedimented bulk density when 10% by mass of the abrasive is dispersed in water is 0.8 g / ml to 1.0 g / ml. A cerium-based abrasive characterized by being within the range. 2. The cerium-based abrasive according to claim 1, wherein the primary particle diameter is in the range of 40 nm to 80 nm. 3. The cerium-based abrasive according to claim 1, wherein the specific surface area is in the range of ² m ² / g to 5 m ² / g. 4. The method according to claim 1, wherein cerium is contained in an amount of 35% by mass or more in terms of oxide.
The cerium-based abrasive according to the item. 5. The cerium-based abrasive according to claim 1, which has a concentration of 5% by mass to 30% by mass.
The cerium-based abrasive slurry dispersed in the dispersion medium within the range. 6. The cerium-based abrasive slurry according to claim 5, wherein the dispersion medium is water. 7. The cerium-based abrasive slurry according to claim 5, wherein the dispersion medium is an organic solvent. 8. The cerium-based abrasive according to claim 7, wherein the organic solvent contains any one selected from the group consisting of alcohols, polyhydric alcohols, acetones, and tetrahydrofurans. slurry. 9. The cerium-based abrasive slurry according to any one of claims 5 to 8, wherein the cerium-based abrasive slurry contains a surfactant. 10. The cerium-based abrasive slurry according to claim 9, wherein the surfactant is at least one selected from the group consisting of an anionic surfactant and a nonionic surfactant. 11. The anionic surfactant is at least one selected from the group consisting of low molecular compounds such as carboxylates, sulfonates, sulfates, and phosphates and high-molecular compounds. 11. The method according to claim 10,
The cerium-based abrasive slurry described in. 12. The nonionic surfactant is at least one selected from the group consisting of polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ether, and polyoxyethylene fatty acid ester, according to claim 10. The cerium-based abrasive slurry described. 13. A method of polishing a glass substrate, which comprises using the cerium-based abrasive slurry according to any one of claims 5 to 12. 14. A method of manufacturing a glass substrate, which comprises using the method of polishing a glass substrate according to claim 13.