TWI867165B - Abrasive composition - Google Patents

Abstract

The invention provides an abrasive composition which can suppress the bracket noise generated during the polishing process of a single crystal oxide substrate, improve the flatness of the polished surface after polishing, and increase the polishing speed. The abrasive composition for grinding lithium tantalum single crystal material or lithium niobate single crystal material comprises: silicon dioxide particles, water-soluble polymer compound, and water; wherein the silicon dioxide particles comprise small-sized silicon dioxide particles with an average particle size of 10-60 nm and large-sized silicon dioxide particles with an average particle size of 70-200 nm, and the mass ratio of the small-sized silicon dioxide particles to the total mass of the small-sized silicon dioxide particles and the large-sized silicon dioxide particles is 50-95% by mass; wherein the water-soluble polymer compound is composed of a polymer or copolymer containing unsaturated amide as a structural unit.

Description

Abrasive composition

The present invention relates to an abrasive composition. More specifically, it relates to an abrasive composition for precision grinding, and the object to be ground is a single crystal oxide, namely, lithium tantalum single crystal material or lithium niobate single crystal material.

Traditionally, surface elastic wave devices that utilize surface elastic waves (SAW) generated by the piezoelectric effect in piezoelectrics have been widely used as electronic components, such as medium-frequency filters and resonators for televisions. As materials for piezoelectric components constituting such surface elastic wave devices, the use of various piezoelectric materials such as piezoelectric ceramics and piezoelectric films is being examined. In particular, in recent years, lithium tantalum single crystal materials and lithium niobate single crystal materials (hereinafter referred to as "single crystal oxide materials") have been widely used due to the excellent properties of hard and brittle materials.

In order to obtain a mirror effect on the surface of various surface elastic wave devices, polishing and grinding are usually performed. Here, it is known that single-crystal oxide materials are a kind of material with high hardness and extremely stable chemically, but it will slow down the grinding speed. Therefore, the traditional single-crystal oxide material grinding generally adopts a circulating supply method of continuous supply and recycling of grinding fluid in the industry. However, if you want to grind to the required thickness, the grinding time may take about 10 hours, for example, which causes problems in terms of product capacity and production efficiency.

Furthermore, when the above-mentioned single crystal oxide material is used as the object to be polished, it is known that a unique "squeaking" friction sound is easily generated, which is generally referred to as "carrier noise". This phenomenon of fine vibration is believed to be caused by the characteristics of single crystal oxide materials as piezoelectric materials. In addition, such fine vibrations may cause the object to be polished to move from the specified polishing position or even crack. Therefore, how to suppress fine vibrations during polishing has become an important issue.

The polishing of oxide crystal materials such as lithium tantalum single crystal materials also uses abrasives containing colloidal silicon oxide used for polishing silicon wafers as the main component. Abrasives containing such colloidal silicon oxide components have the following excellent characteristics: no defects are generated on the surface and back, and a high degree of precision of the polished surface can be achieved. However, on the other hand, depending on factors such as polishing conditions, the above-mentioned fine vibration of the object being polished, which is called bracket noise, may be generated.

On the other hand, for the purpose of improving the polishing rate of single-crystal oxide materials, an aqueous slurry dispersion containing only precipitated silica particles with a BET specific surface area of 10 to 60 m ² /g and an average secondary particle size of 0.5 to 5 μm as a solid component has been proposed as a precision abrasive for hard and brittle materials (see patent document 1). Furthermore, as an abrasive for hard and brittle materials, in order to improve the dispersion stability of colloidal silica, it has been proposed to prepare an abrasive for the purpose of improving the polishing rate by adding additives such as sodium gluconate (see patent document 2).

In addition, a substrate polishing agent specifically for substrates made of lithium tantalum single crystal material or lithium niobate single crystal material has been proposed (see patent document 3), and a method of "adding a polymer or copolymer containing unsaturated amide as a structural unit to the polishing agent" to suppress bracket noise when polishing materials such as lithium tantalum single crystal (see patent document 4).

【Previous technical literature】

【Patent Literature】

[Patent document 1] Japanese Patent Publication No. 5-1279

[Patent document 2] Japanese Patent Publication No. 2006-150482

[Patent document 3] Japanese Patent Publication No. 2002-184726

[Patent Document 4] Japanese Patent Publication No. 2017-218514

However, the abrasives shown in the above-mentioned Patent Documents 1 and 2 do not disclose or teach how to suppress the minute vibrations known as "bracket noise" during the piezoelectric material grinding process.

On the other hand, as disclosed in Patent Document 3, in the case of abrasives for substrates made of hard and brittle materials, the main purpose is to make the polishing speed during the polishing process fast and maintain a good appearance of the polished surface. Therefore, the ingredients contain γ-alumina and silica, and contain a large amount of lubricants and dispersing aids. It is known that once aluminum oxide components such as γ-alumina and silica components are contained, precipitation is easy to occur, which is not conducive to the polishing of the above-mentioned circulation supply method.

Furthermore, once a large amount of lubricant and dispersant is contained, the viscosity of the abrasive itself will increase, which can easily lead to various problems. In addition, Patent Document 3 does not disclose or teach anything about bracket noise.

On the other hand, in Patent Document 4, in order to suppress the bracket noise during the polishing process of single crystal oxide materials such as lithium tantalum single crystal materials, a method of adding a polymer or copolymer containing unsaturated amide as a structural unit to the polishing agent is proposed. However, as is well known, from the perspective of increasing the polishing speed, this method is still insufficient and is generally considered to require further improvement or modification.

Here, in the grinding process of single crystal oxide materials such as lithium tantalum single crystal materials or lithium niobate single crystal materials as the grinding object, it is desired to have a grinding agent that can improve the grinding speed while suppressing the bracket noise (fine vibration) generated as the grinding speed increases, and does not cause grinding position deviation or cracking of the grinding object, so as to achieve stable grinding.

In view of the above facts, the subject of the present invention is to provide an abrasive composition that can suppress the bracket noise generated during the polishing process of a single crystal oxide material (substrate), improve the flatness of the polished surface after polishing, and increase the polishing speed.

In order to solve the above problems, the inventors of the present invention have found through intensive research that an abrasive composition can be used, which is characterized by: containing two kinds of silicon dioxide particles with different average particle sizes, a water-soluble polymer compound and water, wherein the water-soluble polymer compound is a polymer or copolymer containing unsaturated amide as a structural unit. During the polishing process of a single crystal oxide substrate of a lithium tantalum single crystal material or a lithium niobate single crystal material, the abrasive composition can suppress a kind of fine vibration of the polished object called "bracket noise", and increase the polishing speed, and improve the flatness of the substrate after polishing, thereby completing the present invention. That is, by using the present invention, an abrasive composition as shown below can be provided.

[1] An abrasive composition for grinding lithium tantalum single crystal material or lithium niobate single crystal material, comprising: silica particles, a water-soluble polymer compound, and water. The silica particles include small-sized silica particles with an average particle size of 10-60 nm and large-sized silica particles with an average particle size of 70-200 nm; the mass ratio of the small-sized silica particles to the total mass of the small-sized silica particles and the large-sized silica particles is 50-95 mass%. The water-soluble polymer compound is composed of a polymer or copolymer containing unsaturated amide as a structural unit.

[2] The abrasive composition as described in item [1] above, wherein the water-soluble polymer compound is a polymer or copolymer containing structural units derived from (meth)acrylamide and/or N-substituted (meth)acrylamide.

[3] The abrasive composition as described in item [1] or [2] above, wherein the water-soluble polymer compound is a copolymer having structural units derived from (meth)acrylamide and/or N-substituted (meth)acrylamide and structural units derived from carboxyl-containing vinyl monomers.

[4] The abrasive composition as described in any one of items [1] to [3] above further contains at least one of an inorganic acid and/or its salt, an organic acid and/or its salt, and an alkaline compound.

[5] The abrasive composition as described in item [4] above, wherein the organic acid and/or its salt is a chelate.

An abrasive composition is characterized by comprising two kinds of silicon dioxide particles with different average particle sizes, a water-soluble polymer compound, and water; wherein the water-soluble polymer compound is a polymer or copolymer containing unsaturated amide as a structural unit. When polishing lithium tantalum single crystal material or lithium niobate single crystal material, the use of the abrasive composition can achieve the effects of improving flatness, improving polishing speed, and suppressing bracket noise.

The following describes the implementation of the present invention, but the present invention is not limited to the following implementation, and can be changed, modified and improved without departing from the scope of the present invention.

1. Abrasive composition

An abrasive composition of one embodiment of the present invention is used for grinding lithium tantalum single crystal material or lithium niobate single crystal material, and comprises: silicon dioxide particles, a water-soluble polymer compound, and water; wherein the silicon dioxide particles comprise small-sized silicon dioxide particles and large-sized silicon dioxide particles with different average particle sizes according to respective prescribed ratios; wherein the water-soluble polymer compound is a polymer or copolymer containing unsaturated amide as a structural unit.

1.1 Silica particles

The silica particles used in the abrasive composition of the present embodiment can be listed as colloidal silica, wet silica (precipitated silica, gel silica, etc.), high temperature molded silica (fumed silica), etc., and colloidal silica is particularly preferred. There are several methods for preparing colloidal silica, including: a water glass method in which alkaline metal silicates such as sodium silicate react with inorganic acids, or a method in which alkoxysilanes such as tetraethylsiloxane are decomposed by acid or alkali hydrolysis, or a method in which metal silicon and water are reacted in an alkaline catalyst environment. Among them, the water glass method is preferably used in consideration of preparation cost.

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

Furthermore, the average particle size of small-sized silica particles is preferably in the range of 15 to 55 nm; on the other hand, the average particle size of large-sized silica particles is preferably in the range of 75 to 150 nm.

Furthermore, the average particle size of the total silica particles including small-sized silica particles, large-sized silica particles, and other silica particles may be in the range of 10 to 150 nm. Preferably, it is in the range of 20 to 120 nm. Here, by making the average particle size of the total silica particles greater than 10 nm, it is expected to have the effect of suppressing the "bracket noise" generated during the grinding process.

Furthermore, by making the average particle size of the total silica particles less than 150nm, it is expected that the "polishing speed" during the polishing process will be improved. Here, the average particle size of each silica particle mentioned above is analyzed and calculated based on the observation results of a transmission electron microscope (TEM). In addition, the total mass of small-sized silica particles and large-sized silica particles can account for more than 80% by mass of the total mass of the total silica particles, preferably more than 90% by mass.

In addition, the total silica particle concentration in the abrasive composition is preferably in the range of 5-50 mass %, and more preferably in the range of 10-40 mass %. By making the total silica particle concentration above 5 mass %, the polishing effect of the silica particles, especially the excellent surface texture, can be obtained. On the other hand, by making the total silica particle concentration below 50 mass %, in addition to being cost-effective, it can also be used with abrasive materials other than silica particles or other composite agents to prevent problems such as agglomeration or gelation.

1.2 Water-soluble polymer compounds

The water-soluble polymer compound in the abrasive composition of this embodiment is a polymer or copolymer containing unsaturated amide as a structural unit.

That is, it is preferred to use a polymer or copolymer containing a structural unit derived from (meth)acrylamide and/or N-substituted (meth)acrylamide. Furthermore, it is preferred to use a polymer containing a structural unit derived from (meth)acrylamide and/or N-substituted (meth)acrylamide, and a copolymer containing 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. Among the above, "(meth)acrylamide" is defined in this specification to mean acrylamide and/or methacrylamide (the same applies hereinafter).

In addition, N-substituted (meth)acrylamide is a compound represented by the following

General formula (1): CH ₂ =C(R ¹ )-CONR ² (R ³ )

( ^R1 represents a hydrogen atom or a methyl group, ^R2 represents a hydrogen atom or a linear or branched chain alkyl group having 1 to 4 carbon atoms, and ^R3 represents a linear or branched chain alkyl group having 1 to 4 carbon atoms.)

In the above general formula (1), examples of the linear or branched alkyl group having 1 to 4 carbon atoms represented by ^R2 or ^R3 include methyl, ethyl, N-propyl, i-propyl, N-butyl, i-butyl, s-butyl, t-butyl, etc. On the other hand, examples of N-substituted (meth)acrylamide include N,N-dimethyl (meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, NN-propyl (meth)acrylamide, Ni-propyl (meth)acrylamide, NN-butyl (meth)acrylamide, Ni-butyl (meth)acrylamide, Ns-butyl (meth)acrylamide, and Nt-butyl (meth)acrylamide.

If the water-soluble polymer compound is a copolymer, the usage ratio of (meth)acrylamide and/or N-substituted (meth)acrylamide is preferably in the range of 5 to 99 mol% relative to the total molar number of vinyl monomers constituting the copolymer. Furthermore, in this case, it is particularly preferred to make the usage ratio of (meth)acrylamide and/or N-substituted (meth)acrylamide in the range of 10 to 98 mol%.

On the other hand, examples of carboxyl-containing vinyl monomers include: monocarboxylic acids such as (meth)acrylic acid, crotonic acid, and (meth)allyl carboxylic acid; dicarboxylic acids such as itaconic acid, succinic acid, and fumaric acid; or alkaline metal salts such as sodium salts and potassium salts of these various organic acids, ammonium salts, etc. It is particularly preferred to use (meth)acrylic acid or itaconic acid. Here, in the above, (meth)acrylic acid is defined in this specification as acrylic acid and/or methacrylic acid (the same applies hereinafter).

The usage ratio of the carboxyl group-containing vinyl monomer is preferably in the range of 1 to 95 mol% relative to the total molar number of the vinyl monomer. Furthermore, in this case, the usage ratio of the carboxyl group-containing vinyl monomer is more preferably in the range of 2 to 90 mol%.

The vinyl monomers constituting the copolymers other than (meth)acrylamide, N-substituted (meth)acrylamide and carboxyl-containing vinyl monomers include various conventionally known compounds. For example, examples of anionic vinyl monomers include organic sulfonic acids such as ethylene sulfonic acid, styrene sulfonic acid, and 2-acrylamide-2-methylpropanesulfonic acid; or alkaline metal salts such as sodium salts and potassium salts of these organic acids, ammonium salts, etc.

On the other hand, examples of cationic vinyl monomers include: vinyl monomers containing tertiary amines such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, diethylaminopropyl (meth)acrylamide, or salts of inorganic or organic acids such as hydrochloric acid, sulfuric acid, and acetic acid, or vinyl monomers containing quaternary ammonium salts obtained by reacting vinyl monomers containing the tertiary amines with quaternary reagents such as methyl chloride, chlorotoluene, dimethyl sulfide, and epichlorohydrin, etc.

In addition, examples of anionic vinyl monomers include: carboxyl-containing vinyl monomers or alkyl esters of anionic vinyl monomers (alkyl carbon number is 1 to 8), acrylonitrile, styrene, divinylbenzene, vinyl acetate, methyl vinyl ether, N-vinylpyrrolidone, etc.

In addition, the method of preparing carboxyl-containing polyacrylamide by copolymerizing (meth)acrylamide and/or N-substituted (meth)acrylamide, vinyl monomers containing carboxyl groups, and further copolymerizing vinyl monomers other than the above-mentioned monomers as needed, can be prepared by conventional well-known methods. For example, the above-mentioned monomers and water are put into a specified reaction container, a free radical polymerization initiator is added, and the mixture is stirred and heated at a specified speed, so that the desired carboxyl-containing polyacrylamide can be obtained.

As a free radical polymerization initiator, a general free radical polymerization initiator such as a persulfate such as potassium persulfate or ammonium persulfate, or a redox polymerization initiator formed by combining these with a reducing agent such as sodium bisulfite can be used. In addition, an azo initiator can also be used as a free radical polymerization initiator. The amount of these free radical polymerization initiators can account for about 0.05 to 2% by weight of the total weight of the ethylene monomer.

The weight average molecular weight of a water-soluble polymer compound is generally 1,000 to 10,000,000, preferably 5,000 to 5,000,000, and more preferably 10,000 to 3,000,000. The weight average molecular weight described in this specification is the value measured by GPC (gel permeation chromatography) and converted to standard polyacrylic acid.

The content of the water-soluble polymer compound is preferably in the range of 0.0001 mass % or more and 1.0 mass % or less, and more preferably in the range of 0.01 mass % or more and 0.8 mass % or less. By making the content of the water-soluble polymer compound reach 0.0001 mass % or more, the bracket noise during the grinding process can be suppressed. On the other hand, by making the content of the water-soluble polymer compound less than 1.0 mass %, the high viscosity of the aqueous solution can be avoided to reduce the fluidity and improve the workability.

1.3 Other additives

The abrasive composition of this embodiment may further contain at least one of an inorganic acid and/or its salt, an organic acid and/or its salt, and an alkaline compound to adjust the pH value. In addition, it is preferred to use a chelate as the organic acid and/or its salt.

More specifically, examples of inorganic acids include nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, and trimer acid, and their salts can also be used. For example, as salts, sodium salts, potassium salts, and ammonium salts are preferably used.

Examples of organic acids include monocarboxylic acids such as tartaric acid, acetic acid, and propionic acid; dicarboxylic acids such as tartaric acid, malonic acid, citric acid, and tricarboxylic acids; aminocarboxylic acids such as glycine; polyaminocarboxylic acid compounds such as ethylenediaminetetraacetic acid, etc., and their salts can also be used. For example, as salts, sodium salts, potassium salts, and ammonium salts are preferably used.

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

Furthermore, in the polishing agent composition of the present embodiment, the content of inorganic acid and/or its salt, organic acid and/or its salt, and alkaline compound is preferably in the range of 0.05-4 mass %, more preferably in the range of 0.1-3 mass %, and even more preferably in the range of 0.2-2 mass %.

Organic acids and/or their salts are preferably chelates as mentioned above, for example: dicarboxylic acids, tricarboxylic acids, aminocarboxylic acids, and polyaminocarboxylic acid compounds. Furthermore, specific examples of polyaminocarboxylic acid compounds include: ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraaminehexaacetic acid, nitrilotriacetic acid, and their ammonium salts, amine salts, sodium salts, and potassium salts.

If chelates are used as organic acids and/or their salts, the polishing speed can be further increased and the bracket noise generated during the polishing process can be suppressed.

In the abrasive composition of the present embodiment, it is preferred to adjust the pH value (25°C) to a range between 7 and 11. It is known that once the pH value (25°C) is adjusted to a range between 7 and 11, the charge of the silica particles will tend to increase toward the negative charge. Therefore, the electric repulsion acting on the silica particles increases, and by effectively acting on each silica particle, the abrasive particles are evenly dispersed.

In contrast, when the pH value (25°C) is less than 7, especially when it is around 5-6, the charge imbalance between the silica particles is likely to cause agglomeration or gelation of the silica particles. In addition, once the pH value (25°C) exceeds 11, the surface of the silica particles will slowly dissolve, and it may be difficult to exert the effect of being an abrasive composition.

2. Grinding method

When the abrasive composition of this embodiment is used to perform polishing on a substrate made of lithium tantalum single crystal material or lithium niobate single crystal material, various conventional and well-known polishing methods can be appropriately selected. For example, a specified amount of the abrasive composition is put into a supply container set in a grinder. Afterwards, the abrasive composition is dripped from the supply container through a supply nozzle and a supply pipe onto a polishing pad attached to a plate of the grinder, and the polishing surface of the object to be polished (lithium tantalum single crystal material, etc.) is pushed toward the polishing pad surface, and the plate is rotated at a specified rotation speed to polish the surface of the object to be polished.

Here, as the polishing pad, an appropriate one can be selected from the conventionally known non-woven fabric, foamed polyurethane, porous resin, and non-porous resin polishing pads. Furthermore, in order to increase the amount of the abrasive composition supplied to the polishing pad, or to allow a certain amount of the abrasive composition to remain on the polishing pad, the surface of the polishing pad can also be a polishing pad processed with grid, concentric, or spiral grooves.

[Implementation Example]

The present invention is described in detail below based on the embodiments, but the present invention is not limited to the embodiments. In addition, in addition to the following embodiments, those with general knowledge in the technical field to which the present invention belongs can also implement various changes and improvements without departing from the technical scope of the present invention.

(Synthesis of water-soluble polymer compounds)

The water-soluble polymer compounds used in the examples and comparative examples (Synthesis Example 1 to Synthesis Example 4) were synthesized by the following method. In addition, in the following synthesis examples, unless otherwise specified, "parts" and "%" represent "parts by mass" or "mass %".

(Synthesis Example 1)

In a four-necked flask equipped with a thermometer, a reflux cooling tube and a nitrogen inlet tube, 100 parts by mass of acrylamide (95 mol% relative to the total molar sum of ethylene monomers, the same applies below), 5.3 parts by mass of acrylic acid (5 mol%), 5.3 parts by mass of isopropanol, and 400 parts by mass of ion exchange water were added, and nitrogen was introduced to remove oxygen in the reaction system. After that, the temperature in the reaction system was adjusted to 40°C, and while stirring continuously, 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 the heat in the reaction system. When the liquid temperature in the reaction system reached 90°C, it was kept at this temperature for 2 hours. After the polymerization reaction is completed, 5.5 parts by mass of 48% sodium hydroxide aqueous solution and 11 parts by mass of ion exchange water are added to the reaction system to obtain a carboxyl-containing polyacrylamide aqueous solution with a pH value (25°C) of 7.5 and a polymer concentration of 20%, which is the water-soluble polymer compound of Synthesis Example 1. The composition of the obtained water-soluble polymer compound of Synthesis Example 1 is acrylamide/acrylic acid = 95/5 (molar %), and the weight average molecular weight is 900,000.

(Synthesis Example 2)

In a four-necked flask equipped with a thermometer, a reflux cooling tube and a nitrogen inlet tube, 100 parts by mass of acrylamide (95 mol% relative to the total molar sum of ethylene monomers), 6.3 parts by mass of methacrylic acid (5 mol%), 5.3 parts by mass of propanol and 400 parts by mass of ion exchange water were added, and nitrogen was introduced to remove the oxygen in the reaction system. After that, the temperature in the reaction system was adjusted to 40°C, and while stirring continuously, 0.3 parts by mass of ammonium persulfate and 0.2 parts by mass of sodium hydrogen sulfite were added as polymerization initiators. The start of the polymerization reaction was confirmed by the heat in the reaction system. When the liquid temperature in the reaction system reached 90°C, it was kept at this temperature for 2 hours. After the polymerization reaction is completed, 5.5 parts by mass of 48% sodium hydroxide aqueous solution and 11 parts by mass of ion exchange water are added to obtain a carboxyl-containing polyacrylamide aqueous solution with a pH value (25°C) of 7.5 and a polymer concentration of 20%, which is the water-soluble polymer compound of Synthesis Example 2. The composition of the obtained water-soluble polymer compound of Synthesis Example 2 is acrylamide/methacrylic acid = 95/5 (molar %), and the weight average molecular weight is 1,400,000.

(Synthesis Example 3)

In the above-mentioned Synthesis Example 1, acrylamide is changed to t-butylacrylamide, and the monomer ratio is adjusted to t-butylacrylamide/acrylic acid = 14/86 (mol%), and then synthesis is performed to obtain a carboxyl-containing polyacrylamide aqueous solution, that is, the water-soluble polymer compound of Synthesis Example 3. The composition of the obtained water-soluble polymer compound of Synthesis Example 3 is t-butylacrylamide/acrylic acid = 14/86 (mol%), and the weight average molecular weight is 13,000.

(Synthesis Example 4)

In the above-mentioned Synthesis Example 1, acrylamide is replaced with acrylic acid, and acrylic acid is polymerized alone to obtain the water-soluble polymer compound of Synthesis Example 4. The water-soluble polymer compound of Synthesis Example 4 obtained is a single polymer of acrylic acid, and its weight average molecular weight is 12,000.

The water-soluble polymer compounds synthesized in the above-mentioned Synthesis Examples 1 to 4 are used respectively, with the mixing ratios in Table 1 or Table 2 below, and the polishing agent compositions of Examples 1 to 21 and Comparative Examples 1 to 8 are prepared in the following manner. In addition, Comparative Examples 1 and 4 are polishing agent compositions that do not contain the water-soluble polymer compounds of Synthesis Examples 1 to 4.

(Implementation Example 1)

Commercially available alkaline colloidal silica A (average particle size 20nm, solid content concentration 50% by mass) and alkaline colloidal silica B (average particle size 100nm, solid content concentration 50% by mass) were mixed at a mass ratio of 7:3 to make a solid content of 300g, and then 2g of the water-soluble polymer compound synthesized in Synthesis Example 1 was added. Then, in order to adjust the pH value (25°C) of the abrasive composition to 8.5, 400g of an acidic aqueous solution to which the required amount of phosphoric acid had been added was added, and then stirred to obtain 1kg of the abrasive composition of Example 1.

(Example 2)

In the above-mentioned Example 1, by changing phosphoric acid to malonic acid, 1 kg of the abrasive composition of Example 2 was obtained.

(Implementation Example 3)

In the above-mentioned Example 1, by changing phosphoric acid to citric acid, 1 kg of the abrasive composition of Example 3 was obtained.

(Implementation Example 4)

In the above-mentioned Example 1, by changing the water-soluble polymer compound synthesized in Synthesis Example 1 to the water-soluble polymer compound synthesized in Synthesis Example 2, 1 kg of the abrasive composition of Example 4 was obtained.

(Example 5)

In the above-mentioned Example 4, by changing phosphoric acid to malonic acid, 1 kg of the abrasive composition of Example 5 was obtained.

(Implementation Example 6)

In the above-mentioned Example 4, by changing phosphoric acid to citric acid, 1 kg of the abrasive composition of Example 6 was obtained.

(Implementation Example 7)

In the above-mentioned Example 1, by changing the water-soluble polymer compound synthesized in Synthesis Example 1 to the water-soluble polymer compound synthesized in Synthesis Example 3, 1 kg of the abrasive composition of Example 7 was obtained.

(Implementation Example 8)

In the above-mentioned Example 7, by changing phosphoric acid to malonic acid, 1 kg of the abrasive composition of Example 8 was obtained.

(Implementation Example 9)

In the above-mentioned Example 7, by changing phosphoric acid to citric acid, 1 kg of the abrasive composition of Example 9 was obtained.

(Example 10)

Commercially available alkaline colloidal silica C (average particle size 40nm, solid content concentration 50% by mass) and alkaline colloidal silica B (average particle size 100nm, solid content concentration 50% by mass) were mixed at a mass ratio of 8:2 to make the solid content 300g, and then 2g of the water-soluble polymer compound synthesized in Synthesis Example 1 was added. Then, in order to adjust the pH value (25°C) of the abrasive composition to 8.5, 400g of an acidic aqueous solution to which the required amount of phosphoric acid had been added was added, and then stirred to obtain 1kg of the abrasive composition of Example 10.

(Implementation Example 11)

Commercially available alkaline colloidal silica D (average particle size 30nm, solid content concentration 50% by mass) and alkaline colloidal silica E (average particle size 80nm, solid content concentration 50% by mass) were mixed at a mass ratio of 7:3 to make a solid content of 300g, and then 0.2g of the water-soluble polymer compound synthesized in Synthesis Example 1 was added. Then, in order to adjust the pH value (25°C) of the abrasive composition to 8.5, 400g of an acidic aqueous solution to which the required amount of phosphoric acid had been added was added, and then by stirring, 1kg of the abrasive composition of Example 11 was obtained.

(Example 12)

Commercially available alkaline colloidal silica D (average particle size 30nm, solid content concentration 50% by mass) and alkaline colloidal silica E (average particle size 80nm, solid content concentration 50% by mass) were mixed at a mass ratio of 9:1 to make the solid content 300g, and then 0.2g of the water-soluble polymer compound synthesized in Synthesis Example 1 was added. Then, in order to adjust the pH value (25°C) of the abrasive composition to 8.5, 400g of an acidic aqueous solution to which the required amount of phosphoric acid had been added was added, and then stirred to obtain 1kg of the abrasive composition of Example 12.

(Examples 13 to 21)

The preparation method of Example 13 is the same as that of Example 1, the preparation method of Example 14 is the same as that of Example 2, the preparation method of Example 15 is the same as that of Example 3, the preparation method of Example 16 is the same as that of Example 4, the preparation method of Example 17 is the same as that of Example 5, the preparation method of Example 18 is the same as that of Example 6, the preparation method of Example 19 is the same as that of Example 7, the preparation method of Example 20 is the same as that of Example 8, and the preparation method of Example 21 is the same as that of Example 9, and 1 kg of abrasive composition is obtained respectively.

(Comparison Example 1)

In the above-mentioned Example 1, except that the water-soluble polymer compound synthesized in Synthesis Example 1 is not added, the rest of the preparation method is the same as Example 1, and 1 kg of the abrasive composition of Comparative Example 1 is obtained.

(Comparison Example 2)

In the above-mentioned Example 1, except that the water-soluble polymer compound synthesized in Synthesis Example 1 is changed to the water-soluble polymer compound synthesized in Synthesis Example 4, the rest of the preparation method is the same as that of Example 1, and 1 kg of the abrasive composition of Comparative Example 2 is obtained.

(Comparison 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 size 20 nm, solid content concentration 50% by mass) with a solid content. Then, in order to adjust the pH value (25°C) of the abrasive composition to 8.5, 400 g of an acidic aqueous solution to which the required amount of phosphoric acid had been added was added, and then stirred to obtain 1 kg of the abrasive composition of Comparative Example 3.

(Comparison Example 4)

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 B (average particle size 100 nm, solid content concentration 50% by mass) with a solid content. Then, 400 g of an acidic aqueous solution to which the required amount of phosphoric acid had been added was added to adjust the pH value (25°C) of the abrasive composition to 8.5, and then 1 kg of the abrasive composition of Comparative Example 4 was obtained by stirring.

(Compare Examples 5~8)

The preparation method of Comparative Example 5 is the same as that of Comparative Example 1, the preparation method of Comparative Example 6 is the same as that of Comparative Example 2, the preparation method of Comparative Example 7 is the same as that of Comparative Example 3, and the preparation method of Comparative Example 8 is the same as that of Comparative Example 4, and 1 kg of abrasive composition is obtained respectively.

(Colloidal silica particle size)

The particle size (Heywood diameter) of colloidal silica was measured 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)). The photograph was then analyzed using analysis software (manufactured by Sanji Precision Co., Ltd., Mac-View version 4.0) to measure its Heywood diameter (projected area circle equivalent diameter). The average particle size of colloidal silica is calculated by analyzing the particle sizes of about 2,000 colloidal silica particles using the aforementioned method, and using the above-mentioned analysis software (manufactured by Sanji Precision Co., Ltd., Mac-View version 4.0) to calculate the average particle size (D50) corresponding to the particle size when the cumulative particle size distribution (cumulative volume basis) starting from the smallest particle size is 50%.

(Polishing test) 1 kg of each of the abrasive compositions of Examples 1 to 21 and Comparative Examples 1 to 8 obtained above were introduced into the abrasive supply container installed in a double-sided grinder (6B-5P-II manufactured by SpeedFam Co., Ltd.; polishing plate diameter: 422 mm), and then the surface of a substrate (diameter: 76 mm, thickness 0.3 mm) made of lithium tantalum single crystal material or lithium niobate single crystal material was polished for 5 hours using the grinder.

During polishing, the rotation speed (rotation number) of the plate was set to 55 rpm, and the polishing pressure was 300 g/cm ² . The abrasive composition was supplied to the polishing cloth attached to the plate using a tube pump at a supply rate of 200 ml/min, and the overflowed abrasive composition was returned to the container, and was reused through this circulation supply method.

Therefore, the substrate surface was polished as described above. After each hour of polishing, the substrate thickness was measured with a micrometer (manufactured by Mitutoyo, with a measurement accuracy of 1 μm) to obtain the polishing rate per hour (μm/hr). Table 1 lists the polishing test results of lithium tantalum single crystal substrates in Examples 1 to 12 and Comparative Examples 1 to 4. Table 2 lists the polishing test results of lithium niobate single crystal substrates in Examples 13 to 21 and Comparative Examples 5 to 8.

【Table 1】

【Table 2】

(Determination of bracket noise)

According to the following standards, evaluate the sound from the rotating plate and carrier on the grinding test machine from the beginning to the end of grinding to determine whether the carrier noise occurs.

○: It is judged that there is a sliding sound during normal grinding.

△: It is judged to be not a sliding sound, but a "squeaking" friction sound.

×: There is a strong "clicking" friction sound.

(Evaluation of substrate flatness)

Use a micrometer to measure the thickness of the substrate at the center point and 4 points on the circumference, a total of 5 points, and calculate the average thickness of the substrate. Then classify the thickness difference between the average thickness of the substrate and the thickness of each point according to the following criteria to evaluate the flatness.

○: The difference between the average thickness of the substrate and the thickness at each point is less than 1%.

△: The difference between the average thickness of the substrate and the thickness at each point is in the range of 1~1.5%.

×: The difference between the average thickness of the substrate and the thickness at each point is more than 1.5%.

(Evaluation of grinding speed)

When the substrate is a lithium tantalum single crystal substrate, the value of Comparative Example 1 without using a water-soluble polymer compound is used as a benchmark. When the substrate is a niobium oxide single crystal substrate, the value of Comparative Example 5 without using a water-soluble polymer compound is used as a benchmark. Evaluations are performed separately.

○: The polishing speed is greater than that of Comparative Example 1 (or Comparative Example 5) (= polishing speed is increased).

△: The grinding speed is the same as that of Comparative Example 1 (or Comparative Example 5).

×: The polishing speed is lower than that of Comparative Example 1 (or Comparative Example 5) (= polishing speed decreases).

(Conclusion)

The results in Table 1 clearly show the effect of the present invention in the polishing process of lithium tantalum single crystal substrates. From the comparison between Examples 1, 4, and 7 and Comparative Examples 1 and 2, it can be seen that by adding a polymer or copolymer containing unsaturated amide as a structural unit, the flatness is indeed improved and the bracket noise is suppressed. Specifically, compared with the flatness evaluation of Comparative Example 1 being "△" and the flatness evaluation of Comparative Example 2 being "×", the flatness evaluation of Examples 1, 4, and 7 is all "○"; and in terms of the evaluation of bracket noise, compared with the evaluation of Comparative Example 1 being "×" and Comparative Example 2 being "△", the bracket noise evaluation of Examples 1, 4, and 7 is all "○". In addition, compared with the polishing speed of 28.6μm/hr in Comparative Example 1, the polishing speeds of Examples 1, 4, and 7 were 33.8μm/hr, 35.1μm/hr, and 30.2μm/hr, respectively, and an increase in polishing speed was observed.

From the comparison between Example 1 and Comparative Examples 3 and 4, it can be seen that the combination of small-sized silica particles and large-sized silica particles can improve the polishing speed, improve the flatness, and suppress the bracket noise compared with the case of using small-sized silica particles or large-sized silica particles alone. Specifically, the polishing speed of Example 1 is 33.8μm/hr, compared with the polishing speeds of Comparative Examples 3 and 4, which are 10.5μm/hr and 17.4μm/hr respectively. Then, compared with the flatness evaluation of "×" and the bracket noise evaluation of "△" in Comparative Example 3, the flatness and bracket noise evaluation of Example 1 are "○".

Compared with Example 1, Examples 2 and 3 are the result of changing the acid used from an inorganic acid to an organic acid with chelating properties, and from the results, it can be seen that the polishing rate is also significantly improved compared with Example 1. Similarly, the comparison between Examples 5 and 6 and Example 4, and the comparison between Examples 8 and 9 and Example 7 also have the same trend. Specifically, compared with the polishing rate of Example 1 being 33.8 μm/hr, the polishing rate of Example 2 is 36.5 μm/hr, and the polishing rate of Example 3 is 35.8 μm/hr, and the result of improved polishing rate is observed. Similarly, compared with the polishing speed of 35.1 μm/hr in Example 4, the polishing speed of Example 5 is 39.2 μm/hr, and the polishing speed of Example 6 is 37.3 μm/hr; furthermore, compared with the polishing speed of 30.2 μm/hr in Example 7, the polishing speed of Example 8 is 32.5 μm/hr, and the polishing speed of Example 9 is 31.3 μm/hr. It can be seen that the use of a chelating organic acid can improve the polishing speed.

Examples 10 to 12 are the results of Example 1 in terms of the average particle size of small-sized silica particles and large-sized silica particles, and the ratio of small-sized silica particles to large-sized silica particles. As shown in Table 1, as long as the abrasive composition meets the various necessary conditions specified in the present invention, it will receive good evaluations in terms of polishing speed, flatness, and bracket noise.

The results in Table 2 also clearly show the effect of the present invention in the polishing process of lithium niobate single crystal substrates. From the comparison between Examples 13, 16, and 19 and Comparative Examples 5 and 6, it can be seen that by adding a polymer or copolymer containing unsaturated amide as a structural unit, the flatness is indeed improved and the bracket noise is suppressed. Specifically, compared with the flatness evaluation of Comparative Example 5 being "△" and the flatness evaluation of Comparative Example 6 being "×", Examples 13, 16, and 19 are all "○". It is also observed that in terms of the evaluation of bracket noise, compared with the "×" of Comparative Example 5 and the "△" of Comparative Example 6, Examples 13, 16, and 19 are all "○". In addition, compared with the polishing speed of 58.5μm/hr in Comparative Example 5, the polishing speeds of Examples 13, 16, and 19 were 66.5μm/hr, 69.8μm/hr, and 59.0μm/hr, respectively, and the result of improved polishing speed was observed.

From the comparison between Example 13 and Comparative Examples 7 and 8, it can be seen that the combination of small-sized silica particles and large-sized silica particles improves the polishing speed, improves the flatness, and suppresses the bracket noise compared with the case where small-sized silica particles or large-sized silica particles are used alone. Specifically, the polishing speed of Example 13 is 66.5μm/hr, compared with the polishing speeds of Comparative Examples 7 and 8, which are 17.8μm/hr and 32.7μm/hr, respectively. Then, compared with the flatness evaluation of "×" and the bracket noise evaluation of "△" in Comparative Example 7, the flatness and bracket noise evaluation of Example 13 are "○".

Compared with Example 13, Examples 14 and 15 are the result of changing the acid used from an inorganic acid to an organic acid with chelating properties, and from the results, it can be seen that the polishing rate is also significantly improved compared with Example 13. Similarly, the comparison between Examples 17 and 18 and Example 16, and the comparison between Examples 20 and 21 and Example 19 also have the same trend. Specifically, compared with the polishing rate of 66.5 μm/hr in Example 13, the polishing rate of Example 14 is 70.0 μm/hr, and the polishing rate of Example 15 is 68.7 μm/hr, and the result of improved polishing rate is observed. Similarly, compared with the polishing speed of 69.8 μm/hr in Example 16, the polishing speed of Example 17 is 74.2 μm/hr, and the polishing speed of Example 18 is 72.1 μm/hr; further, compared with the polishing speed of 59.0 μm/hr in Example 19, the polishing speed of Example 20 is 62.1 μm/hr, and the polishing speed of Example 21 is 60.8 μm/hr, and the result of the improvement of the polishing speed is observed.

In summary, when polishing a lithium tantalum single crystal substrate or a lithium niobate single crystal substrate, by using an abrasive composition comprising two types of silicon dioxide particles with different average particle sizes and a polymer or copolymer containing unsaturated amide as a structural unit, the flatness of the substrate can be improved, the polishing speed can be increased, and the bracket noise can be further suppressed.

【Industry Usability】

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

Claims (5)

An abrasive composition for grinding a lithium tantalum single crystal material or a lithium niobate single crystal material belonging to a piezoelectric material, comprising: silicon dioxide particles, a water-soluble polymer compound and water; wherein the silicon dioxide particles comprise: small-sized silicon dioxide particles with an average particle size of 10-60 nm; and large-sized silicon dioxide particles with an average particle size of 70-200 nm; relative to the total mass of the small-sized silicon dioxide particles and the large-sized silicon dioxide particles, the mass ratio of the small-sized silicon dioxide particles is 50-95% by mass; wherein the water-soluble polymer compound is composed of a polymer or copolymer containing unsaturated amide as a structural unit. The abrasive composition as described in claim 1, wherein the water-soluble polymer compound is a polymer or copolymer containing structural units derived from (meth)acrylamide and/or N-substituted (meth)acrylamide. The abrasive composition as described in claim 1 or 2, wherein the water-soluble polymer compound is a copolymer having structural units derived from (meth)acrylamide and/or N-substituted (meth)acrylamide and structural units derived from carboxyl-containing vinyl monomers. The abrasive composition as described in claim 1 or 2 further comprises at least one of an inorganic acid and/or its salt, an organic acid and/or its salt, and an alkaline compound. The abrasive composition as described in claim 4, wherein the organic acid and/or its salt is a chelate.