Non-Spherical Silica Sol, Process for Producing the Same, and Composition for Polishing

• US 20110209413A1
• Filed: 05/28/2009
• Published: 09/01/2011
• Est. Priority Date: 11/30/2007
• Status: Active Grant

• Current Assignee: JGC Catalysts and Chemicals Ltd. (JGC Holdings Corporation)
• Original Assignee: JGC Catalysts and Chemicals Ltd. (JGC Holdings Corporation)
• Inventors: Nakayama, Kazuhiro, Nishida, Hiroyasu
• Granted Patent: US 9,272,916 B2
• Time in Patent Office: Days
• US Class Current: 51/308
• CPC Class Codes: C01B 33/14 Colloidal silica, e.g. dispersions, gels, sols
• CPC Class Codes: C01B 33/143 of aqueous solutions of silicates
• CPC Class Codes: C01B 33/1435 using ion exchangers
• CPC Class Codes: C09K 3/1409 Abrasive particles per se preparation of diamond C01B32/25
• CPC Class Codes: C09K 3/1445 the coating consisting exclusively of metals
• CPC Class Codes: C09K 3/1463 Aqueous liquid suspensions
• CPC Class Codes: H01L 21/31053 involving a dielectric removal step

Abstract

Provided is a non-spherical silica sol containing non-spherical silica fine particles dispersed in a dispersion medium, the non-spherical silica fine particles having an average particle diameter in a range of 3 to 150 nm as measured by dynamic light scattering, a minor-diameter/major-diameter ratio in a range of 0.01 to 0.8, and a specific surface area in a range of 10 to 800 m²/g, and also having a plurality of wart-like projections on the surfaces thereof, and a process for producing the non-spherical silica sol. The non-spherical silica fine particles contained in the non-spherical silica sol have a unique structure different from the structure of ordinary non-spherical silica fine particles.

Claims

1. A non-spherical silica sol characterized by comprising non-spherical silica fine particles dispersed in a dispersion medium, the non-spherical silica fine particles having an average particle diameter in a range of 3 to 200 nm as measured by dynamic light scattering, a minor-diameter/major-diameter ratio in a range of 0.01 to 0.8, and a specific surface area in a range of 10 to 800 m²/g, and also having a plurality of wart-like projections on the surfaces thereof.

2. The non-spherical silica sol according to claim 1, characterized in that when an X-Y curve is drawn, where, in a plane containing a major axis of each of the non-spherical silica fine particles having wart-like projections, the distance from an arbitrary point on an outer edge of the non-spherical silica fine particle to an intersection point B of a line passing through the point on the outer edge and orthogonal to the major axis and the major axis is defined as Y, and the distance from one intersection point A of the outer edge of the non-spherical silica fine particle and the major axis to the intersection point B is defined as X, the X-Y curve has a plurality of local maximum values.

3. The non-spherical silica sol according to claim 1, characterized in that when, in a plane containing a major axis of each of the non-spherical silica fine particles having wart-like projections, the distance from an arbitrary point on an outer edge of the non-spherical silica fine particle to an intersection point B of a line passing through the point on the outer edge and orthogonal to the major axis and the major axis is defined as Y, the distance Y has a coefficient of variation in a range of 5% to 50%.

4. The non-spherical silica sol according to claim 1, characterized in that the number of the non-spherical silica fine particles having wart-like projections is 50% or more of the total number of silica fine particles serving as a dispersoid.

5. The non-spherical silica sol according to claim 1, characterized in that the non-spherical silica fine particles having wart-like projections include a [SiO_4/2] unit.

6. The non-spherical silica sol according to claim 1, characterized in that the non-spherical silica fine particles having wart-like projections are composed of polysiloxane including a [SiO_4/2] unit obtained by hydrolysis of tetraethoxysilane.

7. The non-spherical silica sol according to claim 5, characterized in that the content of sodium contained in the non-spherical silica fine particles having wart-like projections is 100 mass ppm or less.

8. A polishing material comprising the non-spherical silica sol according to claim 1.

9. A composition for polishing, characterized by comprising the non-spherical silica sol according to claim 1.

10. A process for producing the non-spherical silica sol according to claim 1, characterized by comprising adding 50 to 2,500 parts by mass (on a silica basis) of a liquid B to 100 parts by mass (on a silica basis) of a liquid A described below in the presence of an electrolyte composed of a salt of a strong acid (where the number of equivalents of the electrolyte is represented by (EE)) to grow non-spherical seed silica fine particles, wherein the liquid B is added so that an equivalent ratio of an alkali to the electrolyte (EA/EE) is in a range of 0.4 to 8.

Liquid A:

A non-spherical seed silica sol in which non-spherical seed silica fine particles having an average particle diameter in a range of 3 to 200 nm measured by dynamic light scattering and a minor-diameter/major-diameter ratio in a range of 0.01 to 0.8 are dispersed in a dispersion medium

Liquid B;

An aqueous alkali silicate solution (where the number of equivalents of the alkali contained in the liquid B is represented by (EA).)

11. The process for producing the non-spherical silica sol according to claim 10, characterized in that the liquid B and the electrolyte are each added to the liquid A in a temperature range of 40°

C. to 150°

C. over a period of 15 minutes to 10 hours, and aging is performed.

12. A process for producing the non-spherical silica sol according to claim 5, characterized by comprising maintaining the temperature of a mixed solvent containing a water-soluble organic solvent and water in a range of 30°

C. to 150°

C.;

simultaneously and continuously or intermittently adding

     1) a water-soluble organic solvent solution of a tetrafunctional silane compound represented by general formula (1) given below and

     2) an alkali catalyst solution to the mixed solvent; and

after the completion of the addition, maintaining the temperature of the resulting liquid in a range of 30°

C. to 150°

C. so that the tetrafunctional silane compound is hydrolyzed and condensed to produce a non-spherical silica sol, wherein a molar ratio of water to the tetrafunctional silane compound is in a range of 2 to 4.

[Chem. 1]

(RO)₄Si 

 

(1)

(In formula (1), R represents an alkyl group having 2 to 4 carbon atoms.)

13. The process for producing the non-spherical silica sol according to claim 12, characterized in that the tetrafunctional silane compound is tetraethoxysilane.