Silica particle and method for producing the same

1. Silica particles, comprising:

the silica particles containing a quaternary ammonium salt,

wherein the following expressions are satisfied,

0.90≤ F BEFORE /F AFTER ≤1.10, and

5≤ F SINTERING /F BEFORE ≤20,

wherein

F BEFORE represents a maximum frequency value of a pore diameter of 2 nm or less in the silica particles before washing, which is obtained from a pore distribution curve in a nitrogen gas adsorption method;

F AFTER represents a maximum frequency value of a pore diameter of 2 nm or less in the silica particles after washing, which is obtained from a pore distribution curve in the nitrogen gas adsorption method; and

F SINTERING represents a maximum frequency value of a pore diameter of 2 nm or less in the silica particles before washing and after sintering at 600° C., which is obtained from a pore distribution curve in the nitrogen gas adsorption method.

2. The silica particles according to claim 1 ,

wherein the quaternary ammonium salt contains a compound represented by a general formula (AM),

wherein, in the general formula (AM),

R 1 , R 2 , R 3 and R 4 each independently represents an optionally substituted alkyl group, aralkyl group or aryl group,

X − represents an anion, and

two or more of R 1 , R 2 , R 3 and R 4 may be linked to each other to form a ring.

3. The silica particles according to claim 2 ,

wherein, in the general formula (AM), R 1 , R 2 , R 3 and R 4 each independently represents an optionally substituted alkyl group having 1 or more and 16 or less carbon atoms, or an optionally substituted aralkyl group having 7 or more and 10 or less carbon atoms.

4. The silica particles according to claim 1 ,

wherein a number average particle diameter of the silica particles is 5 nm or more and 300 nm or less.

5. The silica particles according to claim 1 ,

wherein a number average particle diameter of the silica particles is 5 nm or more and 100 nm or less.

6. The silica particles according to claim 1 ,

wherein the silica particles satisfy the following expression:

0.01≤ N /(silica particle)×100≤1.00,

wherein

N represents an abundance of a nitrogen element derived from the quaternary ammonium salt detected by an oxygen and nitrogen analysis, and

(silica particle) represents a total weight of the silica particles.

7. The silica particles according to claim 1 ,

wherein an average pore diameter of the silica particle is 0.55 nm or more and 2.00 nm or less.

8. The silica particles according to claim 1 ,

wherein the silica particles are is hydrophobically treated silica.

9. The silica particles according to claim 1 ,

wherein the silica particles contain aluminum.

10. The silica particles according to claim 9 ,

wherein a ratio Si/Al of an abundance Si of a silicon element detected by an X-ray photoelectron spectroscopy to an abundance Al of an aluminum element detected by the X-ray photoelectron spectroscopy is 0.01 or more and 0.30 or less.

11. A method for producing the silica particles according to claim 1 , comprising:

preparing a silica particles-containing suspension; and then

mixing the silica particles-containing suspension with the quaternary ammonium salt to obtain a powder in which the silica particles are surface-treated with the quaternary ammonium salt using a supercritical fluid.

12. The method for producing the silica particles according to claim 11 , further comprising:

surface-treating the powder with an organosilicon compound in the supercritical fluid after the mixing.