JP2014234489A - Method for producing polishing slurry - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing polishing slurry excellent in redispersibility.SOLUTION: Polishing slurry where polishing abrasive grains comprising cerium oxide are dispersed in water is produced by performing a dispersion step and an adding and mixing step. In the dispersion step, an abrasive grain dispersion is obtained by adding polishing abrasive grains to water and agitating it. In the adding and mixing step, a dispersant for dispersing the polishing abrasive grains in water is added to the abrasive grain dispersion and the obtained mixture is agitated. In such a manner, polishing slurry is obtained. In the dispersion step, the agitation is preferably performed for 5 minutes or longer after adding the polishing abrasive grains to the water.

Description

  The present invention relates to a method for producing a polishing slurry in which abrasive grains are dispersed in water.

Glass products are widely used for lenses, optical members, photomasks (synthetic quartz), hard disks and the like. In recent years, glass flat panel displays (FPDs) have also been used in liquid crystal televisions, STNs, mobile phones, touch panels and the like.
These glass products are produced by polishing the surface for the purpose of reducing the roughness of the surface, reducing the weight, removing scratches, removing foreign substances, and the like.

  For polishing the surface of the glass product, a polishing slurry in which abrasive grains made of cerium oxide are dispersed in water is used. In such a polishing slurry, it is desirable that the abrasive grains are uniformly dispersed in order to improve the polishing rate and the quality of the polished surface. However, in the polishing slurry, the abrasive grains easily settle due to their own weight. Therefore, in order to suppress the settling of the abrasive grains and improve the dispersibility of the abrasive grains, polishing slurries to which various dispersants are added have been developed (see Patent Documents 1 to 6).

JP2009-227893A Japanese Patent No. 4420391 International Publication No. WO2002 / 031079 Pamphlet

  However, even in a polishing slurry containing a dispersing agent, if the polishing slurry is allowed to stand for a long time, the abrasive grains made of cerium oxide may aggregate and settle, and a hard precipitate may be generated over time. . Since this hard sediment is difficult to break even when a physical impact is applied, it becomes difficult to redisperse the abrasive grains in water. Therefore, there is a problem that a polishing slurry containing abrasive grains made of cerium oxide cannot be used repeatedly for a long time.

  The present invention has been made in view of such a background, and an object of the present invention is to provide a method for producing a polishing slurry having excellent redispersibility.

One aspect of the present invention is a method for producing a polishing slurry in which abrasive grains made of cerium oxide are dispersed in water.
A dispersion step of obtaining an abrasive dispersion by adding the abrasive grains to water and stirring, and
A method for producing a polishing slurry, comprising: adding a dispersing agent for dispersing the abrasive grains in water to the abrasive dispersion and stirring to obtain the polishing slurry. is there.

  In the production of the polishing slurry, the dispersing step and the additive mixing step are performed. Specifically, by adding abrasive grains made of cerium oxide to water and stirring, an abrasive dispersion is prepared, and then by adding a dispersant to the abrasive dispersion and stirring, The polishing slurry is prepared. That is, after polishing abrasive grains are dispersed in water in advance, a polishing slurry is prepared by adding a dispersant. The polishing slurry thus obtained hardly forms a hard sediment even when left for a long time. Therefore, it is possible to easily disperse the abrasive grains by easily destroying the sediment even after standing. That is, the polishing slurry obtained by the above production method is excellent in redispersibility. On the other hand, a polishing slurry obtained by adding abrasives to water in advance and then adding abrasive grains is likely to form a hard sediment when left standing for a long time.

By performing the dispersion step and the additive mixing step, the effect of improving the redispersibility can be obtained for various dispersants. Therefore, the choice of a dispersing agent can be expanded. For example, it is possible to select a dispersant based on not only dispersibility but also cost and the like.
Moreover, the polishing slurry excellent in redispersibility can be easily manufactured by performing the said dispersion | distribution process and the said addition mixing process.

It is explanatory drawing which shows the structure of a typical organic acid, Comprising: (a) which shows the structure of a citric acid, (b) which shows the structure of tartaric acid, Explanation which shows the structure of 2, 6- pyridinedicarboxylic acid FIG. 4C is an explanatory diagram showing the structure of ethylenediaminetetraacetic acid (d), and an explanatory diagram showing the structure of phytic acid (e). It is explanatory drawing which shows the structure of typical organic acid, Comprising: (a) explanatory drawing which shows the structure of 1-hydroxy ethylidene-1, 1- diphosphonic acid, explanatory drawing (b) which shows the structure of nitrilotrismethylene phosphonic acid Explanatory drawing (c) which shows the structure of malic acid, Explanatory drawing (d) which shows the structure of diethylenetriaminepentaacetic acid. It is explanatory drawing which shows the structure of typical organic acid, Comprising: (a) explanatory drawing which shows the structure of glycolic acid, explanatory drawing (b) which shows the structure of malonic acid, explanatory drawing (c) which shows the structure of oxalic acid , Explanatory diagram showing the structure of lactic acid (d), explanatory diagram showing the structure of maleic acid (e), explanatory diagram showing the structure of succinic acid (f), explanatory diagram showing the structure of fumaric acid (g), glutaric acid Explanatory drawing (h) which shows the structure of this. It is explanatory drawing which shows the structure of typical polyphosphoric acid, Comprising: (a) explanatory drawing which shows the structure of potassium diphosphate, explanatory drawing (b) which shows the structure of sodium hexametaphosphate.

Next, a preferred embodiment of the method for producing the polishing slurry will be described.
In the dispersion step, the abrasive dispersion is obtained by adding the abrasive grains to water and stirring. The amount of the abrasive grains dispersed in water can be appropriately determined as long as the abrasive grains are dispersed in water. For example, at the stage of distribution to the market, a polishing slurry having a relatively high polishing abrasive concentration can be prepared, and the user of the polishing slurry can use the polishing slurry by diluting it appropriately. The abrasive grains are made of cerium oxide, but may contain other components as long as cerium oxide is the main component. Specifically, commercially available cerium oxide-based abrasive grains can be used.

  In the dispersion step, it is preferable to stir for 5 minutes or more after adding abrasive grains to water. In this case, the redispersibility of the polishing slurry can be further improved. The stirring in the dispersion step is more preferably 10 minutes or more, and further preferably 30 minutes or more. In addition, from the viewpoint that productivity decreases when the stirring time becomes too long, the stirring time in the dispersion step is preferably 24 hours or less, more preferably 12 hours or less, and even more preferably 6 hours or less.

  Moreover, in the said addition mixing process, a polishing slurry is obtained by adding and stirring the dispersing agent for disperse | distributing polishing abrasives in water to an abrasive dispersion. In the addition and mixing step, it is preferable to stir for 1 minute or more after adding the dispersant to the abrasive dispersion. In this case, the redispersibility of the polishing slurry can be further improved. In addition, from the viewpoint of reducing productivity when the stirring time becomes too long, the stirring time in the addition and mixing step is preferably 24 hours or less, more preferably 12 hours or less, and even more preferably 5 hours or less.

Moreover, it is possible to control the average particle diameter (median diameter) of the abrasive grains in the polishing slurry by adjusting the length of the stirring time in the dispersion process and the additive mixing process. Specifically, when the stirring time in the dispersion step of mixing the abrasive grains and water is lengthened, the abrasive grains made of cerium oxide tend to aggregate to increase the median diameter of the abrasive grains. On the other hand, if the stirring time in the addition and mixing step of adding and mixing the dispersant is increased, the dispersion of the abrasive grains by the dispersant proceeds and the median diameter of the abrasive grains tends to be reduced. The median diameter of the abrasive grains in the polishing slurry can be adjusted to 0.5 to 10 μm, for example. In the present specification, the median diameter of the abrasive grains refers to the particle diameter (d ₅₀ ) at an integrated value of 50% in the particle size distribution determined by the laser diffraction / scattering method.

（但し、上記一般式（１）において、Ｘ₁、Ｘ₂は、それぞれ独立してＰＯ₄、ＰＯ(ＯＨ)₂、ＣＯＯＨ、ＳＯ₂(ＯＨ)、ＰＨＯ(ＯＨ)から選ばれる少なくとも１種であり、Ａは、Ｘ₁とＸ₂との間に存在する炭素数１〜４の直鎖状有機鎖である。該直鎖状有機鎖は少なくともＣを一つ含有し、炭素数が１の場合には、上記直鎖状有機鎖を構成するＣにＯ、Ｎ、Ｓのいずれかの原子が結合しており、炭素数２〜４の場合には上記直鎖状有機鎖を構成するＣの一部がＯ、Ｎ、及びＳから選ばれる少なくとも１つの原子によって置換されていてもよい。また、上記直鎖状有機鎖はｓｐ³原子及び／又はｓｐ²原子からなり、ｓｐ²原子を少なくとも１つ含有する場合には、上記直鎖状有機鎖の炭素数は３又は４である。） As said dispersing agent, the salt of an organic acid and an alkali and an organic acid and an alkali can be used.
The organic acid preferably has at least partially a structure represented by the following general formula (1) in the molecule, and the first dissociation constant pKa1 of the organic acid is preferably 0.1 to 3.5. In this case, the dispersibility of the abrasive grains can be further improved, and the redispersibility of the polishing slurry can be further improved.

(However, in the general formula (1), X ₁ and X ₂ are each independently at least one selected from PO ₄ , PO (OH) ₂ , COOH, SO ₂ (OH), and PHO (OH)). A is a linear organic chain having 1 to 4 carbon atoms that exists between X ₁ and X _{2. The} linear organic chain contains at least one C and has 1 carbon. In some cases, any one of O, N, and S is bonded to C constituting the linear organic chain, and in the case of 2 to 4 carbon atoms, C constituting the linear organic chain. May be substituted by at least one atom selected from O, N, and S. The linear organic chain is composed of sp ³ atoms and / or sp ² atoms, and the sp ² atoms are In the case of containing at least one, the linear organic chain has 3 or 4 carbon atoms.)

General formula (1) shows the partial structure of an organic acid. In the addition and mixing step, an organic acid having at least a part of the structure represented by the general formula (1) can be employed. Hereinafter, the structure represented by the general formula (1) will be described.
In the general formula (1), X ₁ and X ₂ are each independently at least one selected from PO ₄ , PO (OH) ₂ , COOH, SO ₂ (OH), and PHO (OH). X ₁ and X ₂ may be the same or different. From the viewpoint of easy availability, X ₁ and X ₂ are preferably the same organic acid.

Further, A is a linear organic chain of 1 to 4 carbon atoms present between the X ₁ and X _2. In other words, an organic acid having a structure in which the linear organic chain present between X ₁ and X ₂ in the organic acid is A and the organic chain has 1 to 4 carbon atoms is employed. be able to. The organic acid may have an organic chain branched from the linear organic chain, but such a branched chain does not correspond to A and does not count into the carbon number of A.
The structure of a typical example of an organic acid having at least the structure represented by the general formula (1) is shown in FIGS. In FIGS. 1 and 2, the portions corresponding to X ₁ and X ₂ in the general formula (1) are surrounded by dotted lines, and the portions corresponding to A are surrounded by solid lines. For example, as shown in FIG. 2 (a), 1-hydroxyethylidene-1,1-diphosphonic acid, none as X ₁ and X ₂ have the PO (OH) _2, between the X ₁ and X ₂ The linear organic chain present in 1 has 1 carbon. 1-hydroxyethylidene-1,1-diphosphonic acid has an organic chain (carbon number 1) branched from a linear organic chain (carbon number 1) existing between X ₁ and X ₂ . such branched chain is present between X ₁ and X _2, for X ₁ and X ₂ and not a linear organic chain which binds to, does not correspond to the a. Accordingly, 1-hydroxyethylidene-1,1-diphosphonic acid is an organic acid having PO (OH) ₂ as X ₁ and X ₂ and a linear organic chain having 1 carbon atom.
In General formula (1), carbon number of a linear organic chain becomes like this. Preferably it is 1-3, More preferably, 1-2 is good.

In the general formula (1), a functional group such as OH may be bonded to the linear organic chain. For example malic acid shown in tartaric and FIG 2 (c) shown in FIG. 1 (b), both having a COOH as X ₁ and X _2, exist between X ₁ and X _2, bind to these The organic acid having 2 carbon atoms in the linear organic chain. And in tartaric acid (refer FIG.1 (b)), the hydroxyl group has couple | bonded with both of two carbon which comprises a linear organic acid, and in malic acid (refer FIG.2 (c)), linear A hydroxyl group is bonded to one of the two carbons constituting the organic acid. These correspond to the organic acid having the structure represented by the general formula (1).

Moreover, the linear organic chain of A in General formula (1) has at least one carbon atom (C). When the carbon number of the linear organic chain is 1, any atom of O, N, and S is bonded to C constituting the linear organic chain. O and N are preferable, and O is more preferable.
For example, the above-mentioned 1-hydroxyethylidene-1,1-diphosphonic acid (see FIG. 2A) has an organic chain having 1 carbon as a linear organic chain corresponding to A in the general formula (1). , O (OH) is bonded to the organic chain. Therefore, 1-hydroxyethylidene-1,1-diphosphonic acid corresponds to an organic acid having a structure represented by the general formula (1).
On the other hand, malonic acid (see FIG. 3B) has COOH as X ₁ and X ₂ , and is similar to 1-hydroxyethylidene-1,1-diphosphonic acid between X ₁ and X _2. Is an organic acid having 1 carbon atom in the linear organic chain. However, in malonic acid, none of O, N, and S atoms are bonded to the organic chain having 1 carbon atom. Therefore, malonic acid does not correspond to the organic acid having the structure represented by the general formula (1).

In the general formula (1), when the straight-chain organic chain of A has 2 to 4 carbon atoms, a part of C constituting the straight-chain organic chain is selected from O, N, and S. It may be substituted by at least one atom. Preferably, the atom substituted for C is O or N.
For example, 2,6-pyridinedicarboxylic acid (see FIG. 1 (c)) has COOH as X ₁ and X ₂ , and has a linear organic chain A existing between X ₁ and X ₂ . Although it is an organic acid having 3 carbon atoms, it has a structure in which a part of C (C located in the middle) is substituted with N. Similarly, in ethylenediaminetetraacetic acid (see FIG. 1 (d)), nitrilotrismethylenephosphonic acid (see FIG. 2 (b)), and diethylenetriaminepentaacetic acid (see FIG. 2 (d)), X ₁ and X ₂ The linear organic chain A existing between them is an organic acid having 3 carbon atoms, but has a structure in which a part of C is substituted with N. These organic acids all correspond to organic acids having a structure represented by the general formula (1).

In the general formula (1), the linear organic chain A is composed of sp ³ atoms and / or sp ² atoms. That is, the linear organic chain A is an organic chain bonded by a single bond and / or a double bond. Further, when it contains at least one sp ² atom, that is, when it contains at least one double bond, the linear organic chain has 3 or 4 carbon atoms. This means that an organic acid having a linear organic chain A having 2 or less carbon atoms and having an sp ² atom does not correspond to the organic acid having the structure represented by the general formula (1).

For example, 2,6-pyridinedicarboxylic acid (see FIG. 1C) has 3 carbon atoms in the linear organic chain A existing between X ₁ and X ₂ and contains sp ² atoms. Organic acid. Therefore, 2,6-pyridinedicarboxylic acid corresponds to an organic acid having a structure represented by the general formula (1).
In contrast, maleic acid (see FIG. 3 (e)) and fumaric acid (see FIG. 3 (g)) contain sp ² atoms in the linear organic chain A, but the carbon of the linear organic chain A The number is two. Therefore, fumaric acid and maleic acid do not correspond to the organic acid having the structure represented by the general formula (1).

  In the organic acids shown in FIGS. 1 to 3, the organic acids shown in (a) to (e) in FIG. 1, (a) to (d) in FIG. 2, and (f) and (h) in FIG. It has a structure represented by the general formula (1). The organic acids (a) to (e) and (g) in FIG. 3 do not have the structure represented by the general formula (1). When the organic acid not having the structure represented by the general formula (1) is used, the dispersibility of the abrasive grains in the polishing slurry may be insufficient, and the effect of improving the redispersibility. May become insufficient. In addition, although the succinic acid shown in FIG. 3 (f) and the glutaric acid shown in FIG. 3 (h) have the structure of the above general formula (1), since the pKa1 described later is too large, it is not suitable for the dispersant. Not.

In the polishing additive, it is preferable to use an organic acid having a first-stage dissociation constant (acid dissociation constant), that is, a first dissociation constant pKa1 of 0.1 to 3.5.
When pKa1 exceeds 3.5, the dispersibility of the abrasive grains may be insufficient. On the other hand, when pKa1 is less than 0.1, the effect of improving the redispersibility of the abrasive grains by performing the dispersion step and the additive mixing step may be insufficient. More preferably, pKa1 is 0.3 to 3.0, and even more preferably, pKa1 is 0.5 to 2.5.

The second-stage dissociation constant (acid dissociation constant) of the organic acid, that is, the second dissociation constant pKa2 is preferably 1.5 to 10.
In this case, the dispersibility and redispersibility of the abrasive grains in the polishing slurry can be further improved. More preferably, pKa2 is 2.0 to 9.0, and even more preferably, pKa2 is 2.5 to 7.0.
The above-described pKa1 and pKa2 can be defined by values in an infinitely diluted aqueous solution at 25 ° C.

  Specific examples of the organic acid include phytic acid, malic acid, citric acid, tartaric acid, ethylenediaminetetraacetic acid, 2,6-pyridinedicarboxylic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, nitrilotris ( Methylenephosphonic acid), N-2-hydroxyethyliminodiacetic acid, N-2-hydroxyethylethylenediaminetriacetic acid, aspartic acid, 3-hydroxy-2,2′-iminodisuccinic acid, ethylenediaminetetra (methylenephosphonic acid), nitrilotri Acetic acid, diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid, dicarboxymethylglutamic acid, (S, S) -ethylenediaminedisuccinic acid, triethylenetetraminehexaacetic acid, 1,3-diamino-2-hydroxypropanetetraacetic acid, hydroxyethylimino Two vinegar , And can be used glycol ethers diaminetetraacetic acid or the like. These acids can be used alone or in combination of two or more.

  When using the above-mentioned organic acid and alkali or a salt thereof as a dispersant, in the addition and mixing step, the amount of the organic acid with respect to 100 parts by mass of the abrasive grains is 0.01 to 50 parts by mass. It is preferable to add a dispersant to the abrasive dispersion. If the amount of the organic acid is too small, the effect of improving the dispersibility and redispersibility of the abrasive grains may not be obtained sufficiently. May decrease. More preferably, the amount of the organic acid with respect to 100 parts by mass of the abrasive grains is 0.1 to 20 parts by mass.

Further, as the dispersant, polyphosphoric acid and alkali, or a salt thereof can also be used. As the salt, an alkali metal salt such as sodium salt or potassium salt of polyphosphoric acid is preferable.
When using the above-mentioned polyphosphoric acid and alkali or salts thereof as a dispersant, in the addition and mixing step, the amount of polyphosphoric acid is 0.01 to 50 parts by mass with respect to 100 parts by mass of the abrasive grains. It is preferable to add a dispersant to the abrasive dispersion. The reason is the same as the case where the above-mentioned organic acid and alkali or these salts are used.

The polyphosphoric acid is preferably a substance represented by the general formula (2): H ₂ PO ₄ (HPO ₃ ) _n H ₂ PO ₃ (where n is an integer of 0 to 50). More preferably, the polyphosphoric acid may be at least one selected from pyrophosphoric acid (diphosphoric acid), tripolyphosphoric acid (triphosphoric acid), and hexametaphosphoric acid. Also in this case, the dispersibility of the abrasive grains can be further improved, and the redispersibility of the polishing slurry can be further improved. From the same viewpoint, the salt of polyphosphoric acid and alkali is preferably at least one selected from sodium pyrophosphate, potassium pyrophosphate, sodium tripolyphosphate, and sodium hexametaphosphate.

Moreover, the above-mentioned polyphosphoric acid and its salt may be a mixture of substances having different values of n in the general formula (2). For example, a commercially available hexametaphosphate such as sodium hexametaphosphate is composed of a mixture containing not only n = 6 substance of general formula (2) but also substances other than n = 6.
As a typical example of a salt of polyphosphoric acid and alkali, the structure of potassium diphosphate (potassium pyrophosphate) is shown in FIG. 4 (a), and the structure of sodium hexametaphosphate is shown in FIG. 4 (b).

  Moreover, as said dispersing agent, an acidic polymer and an alkali, or these salts can also be used. As the acidic polymer, for example, one having a molecular weight of 1000 to 10,000 can be used. The salt is preferably an alkali metal salt such as a sodium salt or potassium salt of an acidic polymer.

  Acidic polymers include polyacrylic acid, polymaleic acid, polystyrene sulfonic acid, acrylic acid / maleic acid copolymer, acrylic acid / 2-acrylamido-2-methylpropane sulfonic acid copolymer, acrylic acid / acrylamide copolymer, maleic It is preferably at least one selected from an acid / styrene copolymer, naphthalenesulfonic acid-formalin condensate, melamine sulfonic acid-formalin condensate, and acrylic acid / sulfonic acid / maleic acid copolymer. Also in this case, the dispersibility of the abrasive grains can be further improved, and the redispersibility of the polishing slurry can be further improved.

  When an acidic polymer and an alkali or a salt thereof are used as the dispersant, the amount of the acidic polymer added to 100 parts by mass of the abrasive grains is preferably 0.01 to 50 parts by mass. The reason is the same as the case where the above-mentioned organic acid and alkali or these salts are used.

As described above, as the dispersant, a combination of an acid such as an organic acid, polyphosphoric acid, or an acidic polymer and an alkali, or a salt of these acid and alkali can be used. The organic acid, polyphosphoric acid, acidic polymer, and salts thereof are preferably water-soluble.
Examples of the alkali include alkali metal hydroxides such as potassium hydroxide, sodium hydroxide and lithium hydroxide; alkaline earth metal hydroxides such as calcium hydroxide; ammonia; monoethanolamine, diethanolamine and triethanolamine. Alkanolamines such as trimethylamine, monoethylamine, diethylamine, etc .; primary, secondary, or tertiary amines; alkali metal alkoxides such as sodium methoxide, potassium methoxide; tetramethylammonium hydroxide, tetraethylammonium hydroxide, etc. Quaternary ammonium hydroxide or the like can be used. These alkalis can be used alone or in combination of two or more. Preferably, an alkali metal hydroxide is preferable, and an alkali metal salt is preferable as the salt.

  If the molar ratio of alkali to acid (organic acid, polyphosphoric acid, acidic polymer) in the dispersant is too small, the dispersibility of the abrasive grains may be reduced. Therefore, the blending ratio of alkali to acid (alkali / acid) in the dispersant is preferably 1 or more, more preferably 1.5 or more, and even more preferably 2 or more in molar ratio. Thus, by increasing the molar ratio of alkali to acid, the dispersibility of the abrasive grains can be increased, and the redispersibility of the polishing slurry can be further increased. Further, from the viewpoint that handling becomes difficult when the dispersant becomes strongly alkaline, the molar ratio of alkali to acid is preferably 10 or less, and more preferably 5 or less.

  In the additive mixing step, a dispersant can be added and mixed in advance with water or the like to prepare a dispersant mixture, and the dispersant mixture can be added to the abrasive dispersion. In the dispersant mixed liquid, the pH of the dispersant mixed liquid is adjusted to, for example, a range of 1.5 to 11 by adjusting the mixing ratio of the acid or alkali of the dispersant or by appropriately adding an acid or alkali separately. It is preferable to adjust. Additives such as fungicides, surfactants, alcohols and the like can be added to the dispersant mixture.

  The polishing slurry can be suitably used for polishing materials to be polished such as glass, quartz, quartz and the like. Specifically, it can be used for polishing glass substrates and semiconductor substrates used for hard disks, photomasks, liquid crystals, and the like. The polishing slurry is used by supplying it to the polishing surface of the material to be polished.

Example 1
Next, an example of a method for producing a polishing slurry will be described.
In this example, a polishing slurry is prepared by performing a dispersion step and an addition mixing step. In the dispersion step, the abrasive dispersion is prepared by adding abrasive grains to water and stirring. Next, in the additive mixing step, a polishing slurry is prepared by adding a dispersant for dispersing abrasive grains in water to the abrasive dispersion and stirring.

  First, a dispersant mixture is prepared. Specifically, first, 2 parts by mass of 1-hydroxyethylidene-1,1-diphosphonic acid (pKa1: 0.5, pKa2: 2.5), 1.33 parts by mass of potassium hydroxide, a fungicide (San-ai Oil) 0.055 parts by mass of “CY-30S” manufactured by Co., Ltd. was added to 96.615 parts by mass of water and mixed to prepare a dispersant mixture. The pH of the dispersant mixture is 7, and the molar ratio of alkali to organic acid is 2.4. The dispersant mixture obtained in this example is designated as sample A. The composition is shown in Table 1 below.

Next, 85 parts by mass of pure water is placed in a 100 ml beaker, and 10 parts by mass of abrasive grains made of cerium oxide (CeO ₂ ) (“SHOROX A-10” manufactured by Showa Denko KK) in the pure water. Was added. Then, it stirred for 60 minutes at the temperature of 25 degreeC with the magnetic stirrer (dispersion process). Thereby, an abrasive dispersion was obtained.
Next, 5 parts by mass of the dispersant mixture (sample A) was added to the abrasive dispersion (95 parts by mass) obtained as described above. Then, it stirred for 60 minutes at the temperature of 25 degreeC with the magnetic stirrer (addition mixing process). In this way, a polishing slurry was obtained. About this polishing slurry, the median diameter of polishing abrasive grains and redispersibility evaluation were performed as follows.

"Median diameter of abrasive grains"
In the above-described addition and mixing step, 30 μl of slurry was collected from the polishing slurry after stirring for 60 minutes with a micropipette. Sampling was performed from around the center of the abrasive slurry after stirring. Next, the collected slurry was sandwiched between preparations, and the median diameter of the abrasive grains was measured using a particle size distribution meter (“SALD-2200” manufactured by Shimadzu Corporation). The results are shown in Table 2 below.

"Redispersibility evaluation"
The polishing slurry was transferred to a colorimetric tube with a stopcock having a volume of 100 ml and allowed to stand for 48 hours.
After standing, the colorimetric tube with stopcock was turned upside down and allowed to stand for 10 minutes (Step A). Next, after returning from the inverted state to the original position, it was inverted again and allowed to stand for 10 minutes. That is, the colorimetric tube was rotated once from the inverted state (step A) and then allowed to stand for 10 minutes (step B). Then, Step B was repeated until there were no abrasive grains accumulated at the bottom of the colorimetric tube with a stopcock. The number of rotations (the number of times of rotation) until the sediment of abrasive grains completely disappeared was measured, and this was used as the redispersibility evaluation result. The smaller the number of terminations, the better the redispersibility. In addition, when the abrasive grains did not fall even after being rotated 20 times, the evaluation was completed with the number of end times being “over 20”. The results are shown in Table 2 below.

(Examples 2 to 8)
This example is an example in which a polishing slurry was prepared by changing the type of the dispersant from Example 1.
That is, using the various dispersants shown in Table 1 instead of the dispersant of Example 1, a dispersant mixed solution (Sample B to Sample H) was prepared, and a polishing slurry was prepared using this dispersant mixed solution. . In Examples 2 to 8, polishing slurries were prepared in the same manner as in Example 1 except that Samples B to H adjusted at the blending ratios shown in Table 1 were used as the dispersant mixture. (See Table 1). That is, Examples 2 to 8 are polishing slurries obtained by performing the above-described dispersion step and addition and mixing step. In addition, as a sodium hexametaphosphate in Table 1, those manufactured by Nippon Chemical Industry Co., Ltd. were used. In addition, “Aron A-10SL” manufactured by Toagosei Co., Ltd. is used as the polyacrylic acid in Table 1, and “Aron” manufactured by Toagosei Co., Ltd. is used as the sodium salt of acrylic acid / maleic acid copolymer. A-6410 "was used. For the polishing slurries of Examples 2 to 8, similarly to Example 1, measurement of the median diameter of the abrasive grains and evaluation of redispersibility were performed. The results are shown in Table 2 below.
Example 9
This example is an example in which a polishing slurry was prepared by changing the stirring time in the additive mixing step from that in Example 1. That is, in this example, the polishing slurry was the same as in Example 1 except that the stirring time by the magnetic stirrer after adding the dispersant mixture to the abrasive dispersion was changed to 1 minute. (See Table 1). That is, Example 9 is also a polishing slurry obtained by performing the above-described dispersion step and addition mixing step. For the polishing slurry of Example 9, as in Example 1, measurement of the median diameter of the abrasive grains and evaluation of redispersibility were performed. The results are shown in Table 2 below.

(Comparative Examples 1-8)
In this example, a polishing slurry is prepared by changing the order in which the dispersant (dispersant mixed liquid) and the abrasive grains are added to water from those in Examples 1 to 8 described above. In this example, after adding a dispersing agent to water, abrasive grains are added to prepare a polishing slurry.
That is, in the production of the polishing slurries of Comparative Examples 1 to 8, first, 85 parts by mass of pure water was placed in a 100 ml beaker, and various dispersant mixtures (sample A to sample in Table 1) were added to the pure water. H) 5 parts by mass were added respectively. Then, it stirred for 60 minutes at the temperature of 25 degreeC with the magnetic stirrer. Next, 10 parts by weight of abrasive grains made of cerium oxide (CeO ₂ ) were added to 90 parts by weight of water to which the dispersant mixture was added. Then, it stirred for 60 minutes at the temperature of 25 degreeC with the magnetic stirrer. In this way, polishing slurries of Comparative Examples 1 to 8 were obtained. For the polishing slurries of Comparative Examples 1-8, the median diameter of the abrasive grains and the redispersibility evaluation were performed in the same manner as in Examples 1-8 above. The results are shown in Table 3 below.

As known from Tables 1 to 3, the polishing slurries of Examples 1 to 9 prepared by adding a dispersing agent to water after adding the polishing abrasive to water were added with the abrasive after adding the dispersing agent to water. The redispersibility was improved as compared with Comparative Examples 1 to 8 prepared in the above. This is apparent from comparison between the same dispersants in Examples 1 to 9 and Comparative Examples 1 to 8 (see Tables 2 and 3).
As described above, the polishing slurry (Examples 1 to 9) prepared by previously dispersing abrasive grains in water and then adding a dispersant hardly forms a hard precipitate even when left for a long time. It becomes easy to re-disperse the sediment.

Claims (13)

In a method for producing a polishing slurry in which abrasive grains made of cerium oxide are dispersed in water,
A dispersion step of obtaining an abrasive dispersion by adding the abrasive grains to water and stirring, and
A method for producing a polishing slurry, comprising: adding a dispersing agent for dispersing the polishing abrasives in water to the abrasive dispersion and stirring to obtain the polishing slurry.   In the said dispersion | distribution process, after adding the said abrasive grain to water, stirring is performed for 5 minutes or more, The manufacturing method of the polishing slurry of Claim 1 characterized by the above-mentioned.   In the said addition mixing process, after adding the said dispersing agent to the said abrasive dispersion, it agitates for 1 minute or more, The manufacturing method of the polishing slurry of Claim 1 or 2 characterized by the above-mentioned.   The dispersant is at least one selected from an organic acid and an alkali, an organic acid and an alkali salt, a polyphosphoric acid and an alkali, a polyphosphoric acid and an alkali salt, an acidic polymer and an alkali, and an acidic polymer and an alkali salt. The manufacturing method of the polishing slurry of any one of Claims 1-3 characterized by the above-mentioned. The organic acid has at least partially a structure represented by the following general formula (1) in the molecule, and the first dissociation constant pKa1 of the organic acid is 0.1 to 3.5. The method for producing a polishing slurry according to claim 4.

(However, in the general formula (1), X ₁ and X ₂ are each independently at least one selected from PO ₄ , PO (OH) ₂ , COOH, SO ₂ (OH), and PHO (OH)). A is a linear organic chain having 1 to 4 carbon atoms that exists between X ₁ and X _{2. The} linear organic chain contains at least one C and has 1 carbon. In some cases, any one of O, N, and S is bonded to C constituting the linear organic chain, and in the case of 2 to 4 carbon atoms, C constituting the linear organic chain. May be substituted by at least one atom selected from O, N, and S. The linear organic chain is composed of sp ³ atoms and / or sp ² atoms, and the sp ² atoms are In the case of containing at least one, the linear organic chain has 3 or 4 carbon atoms.)   The organic acids are phytic acid, malic acid, citric acid, tartaric acid, ethylenediaminetetraacetic acid, 2,6-pyridinedicarboxylic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, nitrilotris (methylenephosphonic acid), N- 2-hydroxyethyliminodiacetic acid, N-2-hydroxyethylethylenediaminetriacetic acid, aspartic acid, 3-hydroxy-2,2′-iminodisuccinic acid, ethylenediaminetetra (methylenephosphonic acid), nitrilotriacetic acid, diethylenetriaminepentaacetic acid, hydroxy Ethylethylenediaminetriacetic acid, dicarboxymethylglutamic acid, (S, S) -ethylenediaminedisuccinic acid, triethylenetetraminehexaacetic acid, 1,3-diamino-2-hydroxypropanetetraacetic acid, hydroxyethyliminodiacetic acid, and glycolate A method of making an abrasive slurry according to claim 4 or 5, characterized in that at least one selected from the diamine tetraacetic acid.   The method for producing a polishing slurry according to any one of claims 4 to 6, wherein the second dissociation constant pKa2 of the organic acid is 1.5 to 10. The polyphosphoric acid is a substance represented by the general formula (2): H ₂ PO ₄ (HPO ₃ ) _n H ₂ PO ₃ (where n is an integer of 0 to 50). The method for producing a polishing slurry according to any one of claims 4 to 7, wherein the salt is a sodium salt or a potassium salt of polyphosphoric acid represented by the general formula (2).   The method for producing a polishing slurry according to any one of claims 4 to 8, wherein the polyphosphoric acid is at least one selected from pyrophosphoric acid, tripolyphosphoric acid, and hexametaphosphoric acid.   The above acidic polymer includes polyacrylic acid, polymaleic acid, polystyrene sulfonic acid, acrylic acid / maleic acid copolymer, acrylic acid / 2-acrylamido-2-methylpropane sulfonic acid copolymer, acrylic acid / acrylamide copolymer, The maleic acid / styrene copolymer, naphthalenesulfonic acid-formalin condensate, melamine sulfonic acid-formalin condensate, and at least one selected from acrylic acid / sulfonic acid / maleic acid copolymer. The manufacturing method of the polishing slurry of 4-9.   The alkali is selected from alkali metal hydroxide, alkaline earth metal hydroxide, ammonia, alkanolamine, primary amine, secondary amine, tertiary amine, alkali metal alkoxide, and quaternary ammonium hydroxide. It is at least 1 sort (s), The manufacturing method of the polishing slurry of any one of Claims 4-10 characterized by the above-mentioned.   The molar ratio of the alkali to the organic acid, the molar ratio of the alkali to the polyphosphoric acid, and the molar ratio of the alkali to the acidic polymer are 1 or more. A method for producing the polishing slurry according to 1.   The method for producing a polishing slurry according to any one of claims 1 to 12, wherein the polishing slurry is for polishing glass, quartz, or quartz.

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