JP7384726B2 - Abrasive composition - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to an abrasive composition. More specifically, the present invention relates to an abrasive composition used in precision polishing of lithium tantalate single crystal materials and lithium niobate single crystal materials, which are oxide single crystals, as objects to be polished.

Conventionally, surface acoustic wave devices that utilize surface acoustic waves (SAW) generated by the piezoelectric effect in piezoelectric materials have been widely used as electronic components such as intermediate frequency filters and resonators for televisions. Various piezoelectric materials such as piezoelectric ceramics and piezoelectric thin films are being considered as materials for the piezoelectric elements constituting such surface acoustic wave devices. In particular, in recent years, since hard and brittle materials have excellent properties, lithium tantalate single crystal materials and lithium niobate single crystal materials (hereinafter referred to as "oxide single crystal materials") have been widely used. It has been adopted.

The surfaces of various surface acoustic wave devices are usually polished to obtain a mirror surface. Here, it is known that the oxide single crystal material has high hardness and is chemically extremely stable, resulting in a slow polishing rate. Therefore, in conventional polishing of oxide single crystal materials, a circulating supply system in which the polishing liquid is repeatedly supplied and recovered is generally adopted industrially. However, polishing to a desired thickness may require polishing time of, for example, nearly 10 hours, which may pose a problem in terms of product productivity and production efficiency.

Furthermore, it is known that when the above-mentioned oxide single crystal material is polished as an object to be polished, it is likely to cause minute vibrations called "carrier squeal" that generate a unique frictional sound such as "squeak". The phenomenon of generating such minute vibrations is thought to be caused by the properties of the oxide single crystal material as a piezoelectric material. As a result of such minute vibrations, problems such as movement of the object to be polished from a specified polishing position or cracking may occur. Therefore, suppression of minute vibrations during polishing has become an important issue.

Polishing agents containing colloidal silica as a main component used for polishing silicon wafers are also used for polishing oxide crystal materials such as lithium tantalate single crystal materials. An abrasive containing such a colloidal silica component has an excellent feature of being able to achieve a high degree of precision on the polished surface without causing defects on the surface or inner surface. However, on the other hand, depending on the polishing conditions and the like, micro vibrations of the object to be polished, called the above-mentioned carrier noise, may occur.

On the other hand, for the purpose of improving the polishing rate of oxide single crystal materials, a precision abrasive for hard and brittle materials with a BET specific surface area of 10 to 60 m ² /g and an average particle diameter of secondary particles of 0.5 to 5 μm is used. An aqueous slurry dispersion containing only precipitated particulate silica as a solid component has been proposed (for example, see Patent Document 1). Furthermore, as abrasives for hard and brittle materials, abrasives have already been proposed that improve the polishing speed by adding additives such as sodium gluconate, with the aim of improving the dispersion stability of colloidal silica (for example, , see Patent Document 2).

In addition, there are also substrate polishing agents for substrates made of lithium tantalate single crystal materials or lithium niobate single crystal materials (for example, see Patent Document 3), and polishing agents for polishing lithium tantalate single crystal materials. In addition, it has already been proposed to add a polymer or copolymer containing a structural unit derived from an unsaturated amide to an abrasive for the purpose of suppressing carrier squeal (see, for example, Patent Document 4).

Japanese Patent Application Publication No. 5-1279 Japanese Patent Application Publication No. 2006-150482 Japanese Patent Application Publication No. 2002-184726 Japanese Patent Application Publication No. 2017-218514

However, the abrasives shown in Patent Document 1 and Patent Document 2 described above do not disclose or suggest anything about suppressing minute vibrations called carrier noise in polishing piezoelectric materials.

On the other hand, in the case of the polishing agent for substrates made of a hard and brittle material disclosed in Patent Document 3, the main purpose is to have a high polishing rate and to polish the appearance of the polished surface etc. well. Therefore, it contains γ-alumina and silica as components, as well as a large amount of lubricant and dispersion aid. Here, it is known that if an alumina component such as γ-alumina and a silica component are included, sedimentation tends to occur, making it unsuitable for polishing using the above-mentioned circulating supply method.

Furthermore, when a large amount of lubricant and dispersion aid is contained, the viscosity of the abrasive itself becomes high, which tends to cause various problems. Further, Patent Document 3 neither discloses nor suggests carrier squeal.

On the other hand, Patent Document 4 discloses that a polymer or copolymer containing a structural unit derived from an unsaturated amide is used for the purpose of suppressing carrier noise in polishing oxide single crystal materials such as lithium tantalate single crystal materials. has been proposed to be added to the abrasive. However, it is known that it is insufficient in terms of improving the polishing rate, and it is recognized that further improvements and improvements are needed.

Therefore, when polishing a lithium tantalate single-crystal material or a lithium niobate single-crystal oxide single-crystal material as a polishing workpiece, we aim to improve the polishing speed, and at the same time, carriers generated as the polishing speed increases. There is a need for something that suppresses noise (fine vibrations) and performs stable polishing without causing defects such as shifting of the polishing position or cracks.

In view of the above circumstances, the present invention aims to suppress carrier noise during polishing, improve the flatness of the polished surface after polishing, and improve the polishing rate when polishing an oxide single crystal material (substrate). The object of the present invention is to provide a polishing agent composition that can be used.

In order to solve the above-mentioned problems, the present inventors conducted intensive studies and found that the present invention contains two types of silica particles with different average particle diameters, a water-soluble polymer compound, and water, and the water-soluble polymer compound is unsaturated. By using an abrasive composition characterized by being a polymer or copolymer containing a structural unit derived from amide, the oxide single crystal of lithium tantalate single crystal material or lithium niobate single crystal material can be removed. When polishing a substrate, we have discovered that it is possible to suppress minute vibrations called carrier noise of the polished object, improve the polishing rate, and improve the flatness of the substrate after polishing, and have completed the present invention. That is, according to the present invention, the polishing composition shown below is provided.

[1] Contains silica particles, a water-soluble polymer compound, and water, and the silica particles include small silica particles with an average particle diameter of 10 to 60 nm and large silica particles with an average particle diameter of 70 to 200 nm. The ratio of the mass of the small particle size silica particles to the total mass of the small particle size silica particles and the large particle size silica particles is 50 to 95% by mass, and the water-soluble polymer compound is An abrasive composition for polishing lithium tantalate single crystal material or lithium niobate single crystal material, which is composed of a polymer or copolymer containing a structural unit derived from a saturated amide.

[2] The polishing agent according to [1] above, wherein the water-soluble polymer compound is a polymer or copolymer containing a structural unit derived from (meth)acrylamide and/or N-substituted (meth)acrylamide. Composition.

[3] The water-soluble polymer compound is a copolymer having a structural unit derived from (meth)acrylamide and/or N-substituted (meth)acrylamide and a structural unit derived from a carboxyl group-containing vinyl monomer. The polishing composition according to [1] or [2] above.

[4] The polishing composition according to any one of [1] to [3] above, further containing at least one of an inorganic acid and/or a salt thereof, an organic acid and/or a salt thereof, and a basic compound. .

[5] The polishing composition according to [4] above, wherein the organic acid and/or its salt is a chelating compound.

A polymer or copolymer containing two types of silica particles with different average particle diameters, a water-soluble polymer compound, and water, where the water-soluble polymer compound contains a structural unit derived from an unsaturated amide. By polishing a lithium tantalate single crystal material or a lithium niobate single crystal material using an abrasive composition characterized by Can be done.

Embodiments of the present invention will be described below. The present invention is not limited to the following embodiments, and changes, modifications, and improvements may be made without departing from the scope of the invention.

1. Abrasive Composition The abrasive composition of one embodiment of the present invention contains silica particles, a water-soluble polymer compound, and water, and the silica particles include small silica particles and large silica particles having different average particle sizes. The water-soluble polymer compound is a polymer or copolymer containing a structural unit derived from an unsaturated amide, and contains silica particles having a specified diameter. This is for polishing crystalline materials.

1.1 Silica Particles Examples of the silica particles used in the polishing composition of this embodiment include colloidal silica, wet process silica (precipitated process silica, gel process silica, etc.), fumed silica, etc. Preference is given to using colloidal silica. Colloidal silica can be produced by the water glass method, which is produced by reacting an alkali metal silicate such as sodium silicate with an inorganic acid, by the method in which alkoxysilane such as tetraethoxysilane is hydrolyzed with acid or alkali, or by the method in which metallic silicon and water are produced. There is a method of reacting in the presence of an alkali catalyst. Among these, the water glass method can be preferably used in terms of manufacturing cost.

The silica particles include small silica particles with an average particle size of 10 to 60 nm and large silica particles with an average particle size of 70 to 200 nm, and the sum of the small silica particles and the large silica particles. The ratio of small-sized silica particles to the mass (=mass of small-sized silica particles/(mass of small-sized silica particles + mass of large-sized silica particles) x 100) is in the range of 50 to 95% by mass. . The proportion of such small-sized silica particles is preferably in the range of 55 to 90% by mass, more preferably in the range of 60 to 85% by mass.

Furthermore, the average particle size of the small size silica particles is preferably in the range of 15 to 55 nm, while the average particle size of the large size silica particles is preferably in the range of 75 to 150 nm.

Further, the average particle diameter of all silica particles including small-sized silica particles, large-sized silica particles, and other silica particles can be in the range of 10 to 150 nm. Preferably, it can be in the range of 20 to 120 nm. Here, by setting the average particle diameter of all silica particles to 10 nm or more, an effect of suppressing the occurrence of "carrier noise" during polishing is expected.

Furthermore, by setting the average particle diameter of all silica particles to 150 nm or less, it is possible to expect an improvement in the "polishing rate" during polishing. Here, the average particle diameter of each silica particle mentioned above was calculated by analyzing based on observation results using a transmission electron microscope (TEM). In addition, the ratio of the total mass of small particle size silica particles and large particle size silica particles to the total mass of all silica particles can be 80% by mass or more, more preferably 90% by mass or more.

Further, the concentration of all silica particles in the polishing composition is preferably in the range of 5 to 50% by mass, more preferably in the range of 10 to 40% by mass. By setting the concentration of all silica particles to 5% by mass or more, the polishing effect of the silica particles and particularly excellent surface quality can be obtained. On the other hand, by setting the content to 50% by mass or less, it is advantageous in terms of economy, and problems such as agglomeration and gelation due to blending of abrasives and other compounding agents other than silica particles are less likely to occur.

1.2 Water-soluble polymer compound As the water-soluble polymer compound in the polishing composition of the present embodiment, a polymer or copolymer containing a structural unit derived from an unsaturated amide is used.

That is, a polymer or copolymer containing a structural unit derived from (meth)acrylamide and/or N-substituted (meth)acrylamide can be suitably used. Furthermore, a polymer containing a structural unit derived from (meth)acrylamide and/or N-substituted (meth)acrylamide, a structural unit derived from (meth)acrylamide and/or N-substituted (meth)acrylamide, and a carboxyl group. A copolymer containing a structural unit derived from a vinyl monomer contained therein can be suitably used. In the above, "(meth)acrylamide" is defined herein to mean acrylamide and/or methacrylamide (the same applies hereinafter).

In addition, N-substituted (meth)acrylamide is
General formula (1): CH ₂ =C(R ¹ )-CONR ² (R ³ )
(R ¹ is a hydrogen atom or a methyl group, R ² is a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms, and R ³ is a linear or branched alkyl group having 1 to 4 carbon atoms. (Indicates an alkyl group.)
It is a compound represented by

In addition, examples of the linear or branched alkyl group having 1 to 4 carbon atoms represented by R ² or R ³ in the above general formula (1) include methyl group, ethyl group, n-propyl group, i -propyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group, etc. On the other hand, specific examples of N-substituted (meth)acrylamides include N,N-dimethyl (meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, and Nn-propyl (meth)acrylamide. , Ni-propyl (meth)acrylamide, N-n-butyl (meth)acrylamide, Ni-butyl (meth)acrylamide, N-s-butyl (meth)acrylamide, and Nt-butyl (meth)acrylamide. Mention may be made of acrylamide.

When the water-soluble polymer compound is a copolymer, the ratio of (meth)acrylamide and/or N-substituted (meth)acrylamide to the total number of moles of vinyl monomers constituting the copolymer is 5 to 5. A preferable range is 99 mol%. Furthermore, in this case, it is more preferable that the proportion of (meth)acrylamide and/or N-substituted (meth)acrylamide used is in the range of 10 to 98 mol%.

On the other hand, carboxyl group-containing vinyl monomers include monocarboxylic acids such as (meth)acrylic acid, crotonic acid, and (meth)allylcarboxylic acid, dicarboxylic acids such as itaconic acid, maleic acid, and fumaric acid, or sodium chloride of these various organic acids. Examples include salts, alkali metal salts such as potassium salts, ammonium salts, and the like. Particularly preferred is the use of (meth)acrylic acid or itaconic acid. Here, in the above, (meth)acrylic acid is defined herein to indicate acrylic acid and/methacrylic acid (the same applies hereinafter).

The proportion of the carboxyl group-containing vinyl monomer used is preferably in the range of 1 to 95 mol % based on the total number of moles of the vinyl monomer. Furthermore, in this case, it is more preferable that the proportion of the carboxyl group-containing vinyl monomer used is in the range of 2 to 90 mol%.

As vinyl monomers constituting the copolymer other than (meth)acrylamide, N-substituted (meth)acrylamide, and carboxyl group-containing vinyl monomers, various conventionally known compounds can be exemplified. For example, as the anionic vinyl monomer, organic sulfonic acids such as vinyl sulfonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, alkali metal salts such as sodium salts and potassium salts of these various organic acids, ammonium Examples include salt.

On the other hand, examples of cationic vinyl monomers include vinyl monomers having a tertiary amino group such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, and diethylaminopropyl (meth)acrylamide. or their salts of inorganic or organic acids such as hydrochloric acid, sulfuric acid, acetic acid, etc., or by reacting the tertiary amino group-containing vinyl monomer with a quaternizing agent such as methyl chloride, benzyl chloride, dimethyl sulfate, or epichlorohydrin. Examples include vinyl monomers containing quaternary ammonium salts.

In addition, nonionic vinyl monomers include carboxyl group-containing vinyl monomers or alkyl esters of anionic vinyl monomers (alkyl groups having 1 to 8 carbon atoms), acrylonitrile, styrene, divinylbenzene, vinyl acetate, methyl vinyl ether, N-vinyl Examples include pyrrolidone.

Note that the method for producing carboxyl group-containing polyacrylamide by copolymerizing (meth)acrylamide and/or N-substituted (meth)acrylamide, a carboxyl group-containing vinyl monomer, and further, if necessary, a vinyl monomer other than the above, is conventional. It can be manufactured using a well-known method. For example, the various monomers and water mentioned above are put into a predetermined reaction container, a radical polymerization initiator is added, and the desired carboxyl group-containing polyamide is produced by heating while stirring at a predetermined rotation speed. It is possible to obtain acrylamide.

As a radical polymerization initiator, a normal radical polymerization initiator is used, such as a persulfate such as potassium persulfate or ammonium persulfate, or a redox polymerization initiator in the form of a combination of these and a reducing agent such as sodium bisulfite. be able to. Furthermore, an azo initiator may be used as the radical polymerization initiator. The amount of such a radical polymerization initiator used can be about 0.05 to 2% by weight based on the total weight of vinyl monomers.

The weight average molecular weight of the water-soluble polymer compound is usually about 1,000 to 10,000,000, preferably 5,000 to 5,000,000, and more preferably 10,000 to 3,000. ,000. Here, in this specification, the weight average molecular weight is a value measured in terms of standard polystyrene using GPC (gel permeation chromatography).

The content of the water-soluble polymer compound is preferably in the range of 0.0001 to 1.0% by mass, more preferably in the range of 0.01 to 0.8% by mass. By setting the content of the water-soluble polymer compound to 0.0001% by mass or more, suppression of carrier noise during polishing is expected. On the other hand, by setting the content to 1.0% by mass or less, a decrease in fluidity due to increased viscosity can be suppressed, and workability can be improved.

1.3 Other additives The polishing composition of the present embodiment further contains at least one of an inorganic acid and/or a salt thereof, an organic acid and/or a salt thereof, and a basic compound for pH adjustment. It can contain. Further, as the organic acid and/or its salt, it is preferable to use a chelating compound.

More specifically, examples of inorganic acids include nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, and tripolyphosphoric acid, and salts of these can also be used. It is. For example, as the salt, it is preferable to use sodium salt, potassium salt, ammonium salt, and the like.

Examples of organic acids include monocarboxylic acids such as formic acid, acetic acid, and propionic acid; dicarboxylic acids such as malic acid, malonic acid, maleic acid, and tartaric acid; tricarboxylic acids such as citric acid; aminocarboxylic acids such as glycine; Examples include polyaminocarboxylic acid compounds such as acetic acid, and salts thereof can also be used. For example, as the salt, it is preferable to use sodium salt, potassium salt, ammonium salt, and the like.

Examples of basic compounds include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide, aqueous ammonia, and organic amines. can.

Furthermore, the content of the inorganic acid and/or its salt, the organic acid and/or its salt, and the basic compound in the polishing composition of the present embodiment is preferably in the range of 0.05 to 4% by mass, It is more preferably in the range of 0.1 to 3% by weight, and still more preferably in the range of 0.2 to 2% by weight.

As the organic acid and/or its salt, it is preferable to use a chelating compound as described above, and examples include dicarboxylic acid, tricarboxylic acid, aminocarboxylic acid, and polyaminocarboxylic acid compounds. Furthermore, specific examples of polyaminocarboxylic acid compounds include ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, nitrilotriacetic acid, and ammonium salts, amine salts, sodium salts, and potassium salts thereof. Can be mentioned.

When a chelating compound is used as the organic acid and/or its salt, the polishing rate can be further improved and has the effect of suppressing carrier noise during polishing.

In the polishing composition of the present embodiment, it is preferable that the pH value (25° C.) is adjusted to a range of 7 to 11. It is known that when the pH value (25° C.) is adjusted to a range of 7 to 11, the charge of silica particles tends to become more negative. Therefore, the electric repulsive force acting between the silica particles becomes large, and the abrasive particles are evenly dispersed by effectively acting on each silica particle.

On the other hand, if the pH value (at 25° C.) is less than 7, particularly around 5 to 6, the charge balance between silica particles will be disrupted, and aggregation and gelation of silica particles will likely occur. Further, if the pH value (25° C.) exceeds 11, the surface of the silica particles will gradually dissolve, and there is a possibility that the polishing composition will not be able to exert its effects.

2. Polishing Method When polishing a substrate made of lithium tantalate single crystal material or lithium niobate single crystal material using the polishing composition of the present embodiment, various conventionally known polishing methods can be used. It can be selected as appropriate. For example, a predetermined amount of the polishing agent composition is put into a supply container provided in a polishing machine. Thereafter, the abrasive composition is dripped from the supply container through the nozzle or tube onto the polishing pad attached to the surface plate of the polisher, while the object to be polished (lithium tantalate single crystal material etc.) is pressed against the surface of the polishing pad and the surface plate is rotated at a predetermined rotational speed to polish the surface of the object to be polished.

Here, as the polishing pad, one made of conventionally well-known nonwoven fabric, foamed polyurethane, porous resin, non-porous resin, etc. can be appropriately selected and used. Furthermore, in order to facilitate the supply of the abrasive composition to the polishing pad or to ensure that a certain amount of the abrasive composition remains on the polishing pad, the surface of the polishing pad may have a lattice, concentric, spiral, etc. It may also be provided with grooves.

Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited to these Examples. Furthermore, in addition to the following embodiments, various changes and improvements can be made to the present invention based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

(Synthesis of water-soluble polymer compound)
The water-soluble polymer compounds (Synthesis Examples 1 to 4) used in each Example and Comparative Example were synthesized by the method shown below. In the synthesis examples below, "parts" and "%" indicate "parts by mass" or "% by mass" unless otherwise specified.

(Synthesis example 1)
100 parts by mass of acrylamide (95 mol% based on the total molar sum of vinyl monomers, the same applies hereinafter) and 5.3 parts by mass (5 mol%) of acrylic acid in a four-necked flask equipped with a thermometer, a reflux condenser, and a nitrogen introduction tube. , 5.3 parts by mass of isopropyl alcohol, and 400 parts by mass of ion-exchanged water were added, and nitrogen gas was introduced to remove oxygen from the reaction system. Thereafter, the temperature in the reaction system was adjusted to 40° C., and while stirring was continued, 0.3 parts by mass of ammonium persulfate and 0.2 parts by mass of sodium sulfite were added as polymerization initiators. The start of the polymerization reaction was confirmed by heat generation in the reaction system, and after the temperature of the liquid in the reaction system reached 90°C, it was kept at that temperature for 2 hours. After the completion of the polymerization reaction, 5.5 parts by mass of a 48% aqueous sodium hydroxide solution and 11 parts by mass of ion-exchanged water were introduced into the reaction system, and the pH value (at 25°C) was 7.5, and the polymer concentration was 20% carboxyl groups. The water-soluble polymer compound of Synthesis Example 1, which is an aqueous solution containing polyacrylamide, was obtained. The composition of the resulting water-soluble polymer compound of Synthesis Example 1 was acrylamide/acrylic acid = 95/5 (mol %), and the weight average molecular weight was 900,000.

(Synthesis example 2)
In a four-necked flask equipped with a thermometer, reflux condenser, and nitrogen inlet tube, 100 parts by mass of acrylamide (95 mol% based on the total mole of vinyl monomers), 6.3 parts by mass (5 mol%) of methacrylic acid, and propyl alcohol. 5.3 parts by mass and 400 parts by mass of ion-exchanged water were added, and nitrogen gas was introduced to remove oxygen from the reaction system. Thereafter, the temperature in the reaction system was adjusted to 40° C., and while stirring was continued, 0.3 parts by mass of ammonium persulfate and 0.2 parts by mass of sodium bisulfite were added as polymerization initiators. The start of the polymerization reaction was confirmed by heat generation within the reaction system, and after the temperature of the liquid in the reaction area reached 90°C, it was kept at that temperature for 2 hours. After the completion of the polymerization reaction, 5.5 parts by mass of a 48% aqueous sodium hydroxide solution and 11 parts by mass of ion-exchanged water were added to produce carboxyl group-containing polyacrylamide with a pH value (25°C) of 7.5 and a polymer concentration of 20%. The water-soluble polymer compound of Synthesis Example 2 in the form of an aqueous solution was obtained. The composition of the resulting water-soluble polymer compound of Synthesis Example 2 was acrylamide/methacrylic acid=95/5 (mol %), and the weight average molecular weight was 1,400,000.

(Synthesis example 3)
In the above Synthesis Example 1, the acrylamide was changed to t-butylacrylamide, and the monomer ratio was adjusted to t-butylacrylamide/acrylic acid = 14/86 (mol%) to perform synthesis, resulting in a carboxyl group-containing polyacrylamide aqueous solution. A water-soluble polymer compound of Synthesis Example 3 was obtained. The composition of the resulting water-soluble polymer compound of Synthesis Example 3 was t-butylacrylamide/acrylic acid=14/86 (mol %), and the weight average molecular weight was 13,000.

(Synthesis example 4)
In Synthesis Example 1, acrylamide was replaced with acrylic acid, and acrylic acid was homopolymerized to obtain a water-soluble polymer compound of Synthesis Example 4. The obtained water-soluble polymer compound of Synthesis Example 4 was an acrylic acid homopolymer and had a weight average molecular weight of 12,000.

Examples 1 to 21 and Comparative Examples 1 to 8 were prepared using the synthesized water-soluble polymer compounds of Synthesis Examples 1 to 4, respectively, in the following manner so that the blending ratios are as shown in Table 1 or Table 2 below. A polishing composition was prepared. Note that Comparative Examples 1 and 4 are abrasive compositions that do not contain the water-soluble polymer compounds of Synthesis Examples 1 to 4.

(Example 1)
Commercially available alkaline colloidal silica A (average particle diameter 20 nm, solid content concentration 50% by mass) and alkaline colloidal silica B (average particle diameter 100 nm, solid content concentration 50% by mass) at a mass ratio of 7:3, 300 g as solid content. To this was added 2 g of the water-soluble polymer compound synthesized in Synthesis Example 1 above. Further, 400 g of an acidic aqueous solution containing the necessary amount of phosphoric acid to adjust the pH value (25° C.) of the polishing composition to 8.5 was added and stirred to obtain 1 kg of the polishing composition of Example 1. I got it.

(Example 2)
In the above Example 1, 1 kg of the polishing composition of Example 2 was obtained by changing phosphoric acid to malonic acid.

(Example 3)
In the above Example 1, 1 kg of the polishing composition of Example 3 was obtained by changing phosphoric acid to citric acid.

(Example 4)
In Example 1 above, 1 kg of the abrasive composition of Example 4 was obtained by changing the water-soluble polymer compound synthesized in Synthesis Example 1 and using the water-soluble polymer compound synthesized in Synthesis Example 2. Ta.

(Example 5)
In Example 4, 1 kg of the polishing composition of Example 5 was obtained by changing phosphoric acid to malonic acid.

(Example 6)
In Example 4, 1 kg of the polishing composition of Example 6 was obtained by changing phosphoric acid to citric acid.

(Example 7)
In Example 1 above, 1 kg of the abrasive composition of Example 7 was obtained by changing the water-soluble polymer compound synthesized in Synthesis Example 1 and using the water-soluble polymer compound synthesized in Synthesis Example 3. Ta.

(Example 8)
In Example 7, 1 kg of the polishing composition of Example 8 was obtained by changing phosphoric acid to malonic acid.

(Example 9)
In Example 7, 1 kg of the polishing composition of Example 9 was obtained by replacing phosphoric acid with citric acid.

(Example 10)
Commercially available alkaline colloidal silica C (average particle diameter 40 nm, solid content concentration 50 mass%) and alkaline colloidal silica B (average particle diameter 100 nm, solid content concentration 50 mass%) at a mass ratio of 8:2, 300 g as solid content. To this was added 2 g of the water-soluble polymer compound synthesized in Synthesis Example 1 above. Further, 400 g of an acidic aqueous solution containing the necessary amount of phosphoric acid to adjust the pH value (25° C.) of the abrasive composition to 8.5 was added and stirred to obtain 1 kg of the abrasive composition of Example 10. I got it.

(Example 11)
Commercially available alkaline colloidal silica D (average particle diameter 30 nm, solid content concentration 50% by mass) and alkaline colloidal silica E (average particle diameter 80 nm, solid content concentration 50% by mass) at a mass ratio of 7:3, 300 g as solid content. To this was added 0.2 g of the water-soluble polymer compound synthesized in Synthesis Example 1 above. Further, 400 g of an acidic aqueous solution containing the necessary amount of phosphoric acid to adjust the pH value (25° C.) of the abrasive composition to 8.5 was added and stirred to obtain 1 kg of the abrasive composition of Example 11. I got it.

(Example 12)
Commercially available alkaline colloidal silica D (average particle diameter 30 nm, solid content concentration 50% by mass) and alkaline colloidal silica E (average particle diameter 80 nm, solid content concentration 50% by mass) at a mass ratio of 9:1, 300 g as solid content. To this was added 0.2 g of the water-soluble polymer compound synthesized in Synthesis Example 1 above. Further, 400 g of an acidic aqueous solution containing the necessary amount of phosphoric acid to adjust the pH value (25° C.) of the polishing composition to 8.5 was added and stirred to obtain 1 kg of the polishing composition of Example 12. I got it.

(Examples 13 to 21)
Example 13 was prepared similar to Example 1, Example 14 was prepared similar to Example 2, Example 15 was prepared similar to Example 3, and Example 16 was prepared similar to Example 4. Example 17 was prepared in the same manner as Example 5, Example 18 was prepared in the same manner as Example 6, Example 19 was prepared in the same manner as Example 7, and Example 20 was prepared in the same manner as Example 8. Example 21 was prepared in the same manner as Example 9, and 1 kg of each abrasive composition was obtained.

(Comparative example 1)
A polishing agent composition of Comparative Example 1 (1 kg) was prepared in the same manner as in Example 1 except that the water-soluble polymer compound synthesized in Synthesis Example 1 was not added.

(Comparative example 2)
In Example 1 above, the water-soluble polymer compound synthesized in Synthesis Example 1 was changed and the water-soluble polymer compound synthesized in Synthesis Example 4 was used. 1 kg of the drug composition was obtained.

(Comparative example 3)
0.2 g of the water-soluble polymer compound synthesized in Synthesis Example 1 was added to 300 g of commercially available alkaline colloidal silica A (average particle diameter 20 nm, solid content concentration 50% by mass) as a solid content. Further, 400 g of an acidic aqueous solution containing the required amount of phosphoric acid to adjust the pH value (25° C.) of the abrasive composition to 8.5 was added and stirred to obtain 1 kg of the abrasive composition of Comparative Example 3. I got it.

(Comparative example 4)
300 g of commercially available alkaline colloidal silica B (average particle diameter 100 nm, solid content concentration 50% by mass) was added as a solid content, and 0.2 g of the water-soluble polymer compound synthesized in Synthesis Example 1 above was added thereto. Further, 400 g of an acidic aqueous solution containing the necessary amount of phosphoric acid to adjust the pH value (25° C.) of the abrasive composition to 8.5 was added and stirred to obtain 1 kg of the abrasive composition of Comparative Example 4. I got it.

(Comparative Examples 5 to 8)
Comparative Example 5 was prepared in the same manner as Comparative Example 1, Comparative Example 6 was prepared in the same manner as Comparative Example 2, Comparative Example 7 was prepared in the same manner as Comparative Example 3, and Comparative Example 8 was prepared in the same manner as Comparative Example 4. 1 kg of each polishing composition was obtained.

(Particle size of colloidal silica)
The particle diameter (Heywood diameter) of colloidal silica was determined by taking a photograph of the field of view at a magnification of 100,000 times using a transmission electron microscope (TEM) (manufactured by JEOL Ltd., transmission electron microscope JEM2000FX (200 kV)). This photograph was analyzed using analysis software (Mac-View Ver. 4.0, manufactured by Mountech Co., Ltd.) to measure the Heywood diameter (diameter equivalent to a circle of projected area). The average particle diameter of colloidal silica can be determined by analyzing the diameters of about 2000 colloidal silica particles using the method described above, and determining the particle diameter at which the cumulative particle size distribution (cumulative volume basis) from the small particle size side is 50% using the above analysis software. This is the average particle diameter (D50) calculated using Mac-View Ver. 4.0 (manufactured by Mountech Co., Ltd.).

(Polishing test)
1 kg of each of the abrasive compositions of Examples 1 to 21 and Comparative Examples 1 to 8 obtained above were placed in a double-sided polisher (manufactured by SPEED FAM: 6B-5P-II, polishing surface plate diameter: 422 mm). After introducing the abrasive into the provided abrasive supply container, use this polisher to polish the surface of a substrate (diameter: 76 mm, thickness 0.3 mm) made of lithium tantalate single crystal material or lithium niobate single crystal material. I did some time polishing.

During polishing, the rotational speed (number of revolutions) of the surface plate was set at 55 rpm, and the polishing pressure was 300 g/cm ² . The abrasive composition is supplied onto the abrasive cloth attached to the surface plate at a supply rate of 200 ml/min using a tube pump, and the overflowing abrasive composition is returned to the container. It was used repeatedly by a so-called circulating supply system.

Then, while polishing the surface of the substrate as described above, the thickness of the substrate was measured using a micrometer (manufactured by Mitutoyo, measurement accuracy: 1 μm) every hour after the polishing time elapsed. The polishing rate (μm/hr) for each hour was determined. Table 1 shows the polishing test results of lithium tantalate single crystal material substrates in Examples 1 to 12 and Comparative Examples 1 to 4. Table 2 shows the polishing test results for lithium niobate single crystal substrates in Examples 13 to 21 and Comparative Examples 5 to 8.

(Determination of carrier squeal)
Immediately after the start of polishing until the end of polishing, the sound generated from the rotating surface plate of the polishing testing machine and around the carrier was evaluated according to the following, and the presence or absence of carrier squeal was determined.
○: Normal sliding sound during polishing is observed.
△: A squeaky fricative sound that is not a sliding sound is observed.
×: A strong fricative sound is observed.

(Substrate flatness evaluation)
The thickness of the substrate at 5 points in total, 4 points at the center and the circumference, is measured using a micrometer, and the average thickness of the substrate is calculated. The average thickness of the substrate and the thickness difference at each point were classified based on the following criteria, and the flatness was evaluated.
Good: The difference between the average thickness of the substrate and the thickness at each point is less than 1%.
Δ: The difference between the average thickness of the substrate and the thickness at each point is in the range of 1 to 1.5%.
×: The difference between the average thickness of the substrate and the thickness at each point is 1.5% or more.

(Evaluation of polishing speed)
When the substrate is a lithium tantalate single crystal substrate, the value of Comparative Example 1, which does not use a water-soluble polymer compound, is used as the standard, and when the substrate is a niobate single crystal substrate, the value of Comparative Example 5, which does not use a water-soluble polymer compound, is the standard. Each value was evaluated as a standard.
○: Polishing rate is higher than Comparative Example 1 (or Comparative Example 5) (=improvement in polishing rate).
Δ: Same polishing rate as Comparative Example 1 (or Comparative Example 5).
×: Polishing rate is lower than Comparative Example 1 (or Comparative Example 5) (=reduction in polishing rate).

(Consideration)
From the results in Table 1, it is clear that the present invention is effective in polishing lithium tantalate single crystal substrates. From the comparison between Examples 1, 4, and 7 and Comparative Examples 1 and 2, the addition of a polymer or copolymer containing a structural unit derived from unsaturated amide improves flatness and suppresses carrier noise. I know it will happen. Specifically, the flatness evaluation of Comparative Example 1 is “△” and the flatness evaluation of Comparative Example 2 is “×”, whereas Examples 1, 4, and 7 are all “○”. The carrier squeal was evaluated as "x" in Comparative Example 1 and "△" in Comparative Example 2, whereas it was "○" in Examples 1, 4, and 7. Furthermore, while the polishing rate of Comparative Example 1 was 28.6 μm/hr, the polishing rates of Examples 1, 4, and 7 were 33.8 μm/hr, 35.1 μm/hr, and 30.2 μm/hr, respectively. , and an improvement in the polishing rate is recognized.

From the comparison between Example 1 and Comparative Examples 3 and 4, the combination of small-sized silica particles and large-sized silica particles resulted in more polishing than when small-sized silica particles were used alone or large-sized silica particles were used alone. It can be seen that the speed is improved, the flatness is improved, and carrier noise is suppressed. Specifically, the polishing rates of Comparative Examples 3 and 4 are 10.5 μm/hr and 17.4 μm/hr, respectively, while the polishing rate of Example 1 is 33.8 μm/hr. Furthermore, the evaluation of flatness of Comparative Example 3 was "x" and the evaluation of carrier squeal was "△", whereas the evaluation of flatness and carrier squeal of Example 1 was "○".

In Examples 2 and 3, the acid used in Example 1 was changed from an inorganic acid to a chelating organic acid, but the polishing rate was improved compared to Example 1. The same can be said for the comparison between Examples 5 and 6 and Example 4, and the comparison between Examples 8 and 9 and Example 7. Specifically, the polishing rate of Example 1 was 33.8 μm/hr, whereas the polishing rate of Example 2 was 36.5 μm/hr, and the polishing rate of Example 3 was 35.8 μm/hr. , an improvement in polishing speed was observed. Similarly, the polishing rate of Example 4 was 35.1 μm/hr, whereas the polishing rate of Example 5 was 39.2 μm/hr, and the polishing rate of Example 6 was 37.3 μm/hr, and The polishing rate of Example 7 was 30.2 μm/hr, whereas the polishing rate of Example 8 was 32.5 μm/hr, and the polishing rate of Example 9 was 31.3 μm/hr. It is observed that the polishing rate is improved by using an organic acid.

Examples 10 to 12 are results obtained by changing the average particle diameter of small-sized silica particles and large-sized silica particles and the ratio of small-sized silica particles and large-sized silica particles with respect to Example 1. It is. As shown in Table 1, it was confirmed that the abrasive compositions satisfying the requirements specified in the present invention obtained good evaluations in terms of polishing speed, flatness, and carrier noise.

From the results in Table 2, it is clear that the present invention is effective also in polishing lithium niobate single crystal substrates. From the comparison between Examples 13, 16, and 19 and Comparative Examples 5 and 6, the addition of a polymer or copolymer containing a structural unit derived from unsaturated amide improves flatness and suppresses carrier noise. I know it will happen. Specifically, the flatness evaluation of Comparative Example 5 is “△” and the flatness evaluation of Comparative Example 6 is “×”, whereas Examples 13, 16, and 19 are all “○”. The carrier squeal was evaluated as "x" in Comparative Example 5 and "△" in Comparative Example 6, but "○" in Examples 13, 16, and 19. Furthermore, while the polishing rate of Comparative Example 5 was 58.5 μm/hr, the polishing rates of Examples 13, 16, and 19 were 66.5 μm/hr, 69.8 μm/hr, and 59.0 μm/hr, respectively. , and an improvement in the polishing rate is recognized.

From the comparison between Example 13 and Comparative Examples 7 and 8, it was found that the combination of small-sized silica particles and large-sized silica particles resulted in more polishing than when small-sized silica particles were used alone or large-sized silica particles were used alone. It can be seen that the speed is improved, the flatness is improved, and carrier noise is suppressed.
Specifically, while the polishing rates of Comparative Examples 7 and 8 are 17.8 μm/hr and 32.7 μm/hr, respectively, the polishing rate of Example 13 is 66.5 μm/hr. Furthermore, the evaluation of flatness of Comparative Example 7 was "x" and the evaluation of carrier squeal was "△", whereas the evaluation of flatness and carrier squeal of Example 13 was "○".

In Examples 14 and 15, the acid used in Example 13 was changed from an inorganic acid to a chelating organic acid, but the polishing rate was improved compared to Example 13. The same can be said for the comparison between Examples 17 and 18 and Example 16, and the comparison between Examples 20 and 21 and Example 19. Specifically, the polishing rate of Example 13 is 66.5 μm/hr, whereas the polishing rate of Example 14 is 70.0 μm/hr, and the polishing rate of Example 15 is 68.7 μm/hr. , an improvement in polishing speed was observed. Similarly, the polishing rate of Example 16 is 69.8 μm/hr, whereas the polishing rate of Example 17 is 74.2 μm/hr, and the polishing rate of Example 18 is 72.1 μm/hr, and , the polishing rate of Example 19 was 59.0 μm/hr, whereas the polishing rate of Example 20 was 62.1 μm/hr, and the polishing rate of Example 21 was 60.8 μm/hr. Improvement is recognized.

Based on the above, using an abrasive composition containing two types of silica particles with different average particle diameters and a polymer or copolymer containing a structural unit derived from unsaturated amide, a lithium tantalate single crystal substrate It can also be seen that by polishing a lithium niobate single crystal substrate, the flatness of the substrate can be improved, the polishing rate can be improved, and carrier noise can be suppressed.

The polishing composition of the present invention can be used for polishing lithium tantalate single crystal materials and lithium niobate single crystal materials.

Claims (5)

Contains silica particles, a water-soluble polymer compound, and water,
The silica particles are
Small particle size silica particles with an average particle size of 10 to 60 nm,
Large particle size silica particles with an average particle size of 70 to 200 nm,
The ratio of the mass of the small particle size silica particles to the total mass of the small particle size silica particles and the large particle size silica particles is 50 to 95% by mass,
The water-soluble polymer compound is
Consisting of a polymer or copolymer containing structural units derived from unsaturated amide,
An abrasive composition for polishing lithium tantalate single crystal material or lithium niobate single crystal material. The water-soluble polymer compound is
The polishing composition according to claim 1, which is a polymer or copolymer containing a structural unit derived from (meth)acrylamide and/or N-substituted (meth)acrylamide. The water-soluble polymer compound is
The polishing composition according to claim 1 or 2, which is a copolymer having a structural unit derived from (meth)acrylamide and/or N-substituted (meth)acrylamide and a structural unit derived from a carboxyl group-containing vinyl monomer. thing. The polishing composition according to any one of claims 1 to 3, further comprising at least one of an inorganic acid and/or a salt thereof, an organic acid and/or a salt thereof, and a basic compound. The organic acid and/or its salt is
The polishing composition according to claim 4, which is a chelating compound.