Hydrophobized spherical polyalkylsilsesquioxane fine particle, external additive for toner, dry toner for electrophotography, and method of manufacturing hydrophobized spherical polyalkylsilsesquioxane fine particle

1. A hydrophobized spherical polyalkylsilsesquioxane fine particle, which has a mass-based median diameter in a centrifugal sedimentation method within a range of from 0.05 μm to 0.3 μm,

wherein the hydrophobized spherical polyalkylsilsesquioxane fine particle has a disintegration strength in a crushing strength measurement method of 0.20 N or less.

2. The hydrophobized spherical polyalkylsilsesquioxane fine particle according to claim 1 , wherein the hydrophobized spherical polyalkylsilsesquioxane fine particle comprises a hydrophobized spherical polymethylsilsesquioxane fine particle.

3. An external additive for toner, comprising hydrophobized spherical polyalkylsilsesquioxane fine particles having a mass-based median diameter in a centrifugal sedimentation method within a range of from 0.05 μm to 0.3 μm,

wherein the hydrophobized spherical polyalkylsilsesquioxane fine particles have a disintegration strength in a crushing strength measurement method of 0.20 N or less.

4. A dry toner for electrophotography, comprising:

toner particles; and

hydrophobized spherical polyalkylsilsesquioxane fine particles having a mass-based median diameter in a centrifugal sedimentation method within a range of from 0.05 μm to 0.3 μm.

5. A method of manufacturing a hydrophobized spherical polyalkylsilsesquioxane fine particle, the hydrophobized spherical polyalkylsilsesquioxane fine particle having a mass-based median diameter in a centrifugal sedimentation method within a range of from 0.05 μm to 0.3 μm,

the method comprising:

mixing a raw material solution containing a fine particle precursor selected from the group consisting of (i) a hydrolysate of an alkyltrialkoxysilane, (ii) a partial condensate of the hydrolysate, and (iii) a mixture of the hydrolysate and the partial condensate, and an organic solvent, with an alkaline aqueous medium containing an organic solvent to subject the fine particle precursor to a polycondensation reaction, to thereby obtain a polycondensation reaction liquid;

mixing the polycondensation reaction liquid with an aqueous solution, to thereby obtain a spherical polyalkylsilsesquioxane fine particle dispersion liquid having dispersed therein a spherical polyalkylsilsesquioxane fine particle; and

blending a hydrophobizing agent in the spherical polyalkylsilsesquioxane fine particle dispersion liquid to subject a surface of the spherical polyalkylsilsesquioxane fine particle to hydrophobizing treatment.

6. The method of manufacturing a hydrophobized spherical polyalkylsilsesquioxane fine particle according to claim 5 , wherein the following expression (1) is satisfied:

100×( OS 1 +OS 2)/( L 1+ L 2)≧50 mass %  Expression (1)

in the expression (1):

OS1 represents a content (g) of the organic solvent contained in the raw material solution used in preparation of the polycondensation reaction liquid;

OS2 represents a content (g) of the organic solvent contained in the alkaline aqueous medium used in preparation of the polycondensation reaction liquid;

L1 represents an amount (g) of the raw material solution used in preparation of the polycondensation reaction liquid; and

L2 represents an amount (g) of the alkaline aqueous medium used in preparation of the polycondensation reaction liquid.

7. The method of manufacturing a hydrophobized spherical polyalkylsilsesquioxane fine particle according to claim 5 , wherein the alkyltrialkoxysilane comprises methyltrimethoxysilane.

8. The method of manufacturing a hydrophobized spherical polyalkylsilsesquioxane fine particle according to claim 5 , wherein the mixing of the polycondensation reaction liquid with the aqueous solution is performed so that a composition of a mixed liquid obtained by mixing the polycondensation reaction liquid with the aqueous solution is always kept constant with respect to a lapse of time.

9. The method of manufacturing a hydrophobized spherical polyalkylsilsesquioxane fine particle according to claim 5 , wherein the mixing of the polycondensation reaction liquid with the aqueous solution is performed by continuously supplying the polycondensation reaction liquid in a constant flow amount from an inlet side of a first flow passage of three flow passages trifurcated from a connecting portion toward a connecting portion side, and continuously supplying the aqueous solution in a constant flow amount from an inlet side of a second flow passage of the three flow passages toward the connecting portion side.

10. The method of manufacturing a hydrophobized spherical polyalkylsilsesquioxane fine particle according to claim 5 , wherein the mixing of the polycondensation reaction liquid with the aqueous solution is performed so that a composition of a mixed liquid obtained by mixing the polycondensation reaction liquid with the aqueous solution changes with a lapse of time.

11. The method of manufacturing a hydrophobized spherical polyalkylsilsesquioxane fine particle according to claim 5 , wherein the mixing of the polycondensation reaction liquid with the aqueous solution is performed by dropping a droplet of the polycondensation reaction liquid to a liquid surface of the aqueous solution placed in a container.

12. A hydrophobized spherical polyalkylsilsesquioxane fine particle, which has a mass-based median diameter in a centrifugal sedimentation method within a range of from 0.05 μm to 0.3 μm,

wherein the hydrophobized spherical polyalkylsilsesquioxane fine particle has a ratio of a mass-based 90% cumulative diameter (D90 diameter) to a mass-based 10% cumulative diameter (D10 diameter) (D90 diameter/D10 diameter) within a range of from 1.5 to 4.0 in a mass-based particle size distribution to be obtained by the centrifugal sedimentation method.

13. The hydrophobized spherical polyalkylsilsesquioxane fine particle according to claim 12 , wherein the hydrophobized spherical polyalkylsilsesquioxane fine particle comprises a hydrophobized spherical polymethylsilsesquioxane fine particle.

14. A hydrophobized spherical polyalkylsilsesquioxane fine particle, which has a mass-based median diameter in a centrifugal sedimentation method within a range of from 0.05 μm to 0.3 μm,

wherein the hydrophobized spherical polyalkylsilsesquioxane fine particle has a degree of hydrophobicity in a methanol titration method of 55 vol % or more, and has a floating ratio in methanol water having a methanol concentration of 50 vol % of 80 mass % or more.

15. The hydrophobized spherical polyalkylsilsesquioxane fine particle according to claim 14 , wherein the hydrophobized spherical polyalkylsilsesquioxane fine particle comprises a hydrophobized spherical polymethylsilsesquioxane fine particle.

16. An external additive for toner, comprising hydrophobized spherical polyalkylsilsesquioxane fine particles having a mass-based median diameter in a centrifugal sedimentation method within a range of from 0.05 μm to 0.3 μm,

wherein the hydrophobized spherical polyalkylsilsesquioxane fine particles have a ratio of a mass-based 90% cumulative diameter (D90 diameter) to a mass-based 10% cumulative diameter (D10 diameter) (D90 diameter/D10 diameter) within a range of from 1.5 to 4.0 in a mass-based particle size distribution to be obtained by the centrifugal sedimentation method.

17. An external additive for toner, comprising hydrophobized spherical polyalkylsilsesquioxane fine particles having a mass-based median diameter in a centrifugal sedimentation method within a range of from 0.05 μm to 0.3 μm,

wherein the hydrophobized spherical polyalkylsilsesquioxane fine particles have a degree of hydrophobicity in a methanol titration method of 55 vol % or more, and have a floating ratio in methanol water having a methanol concentration of 50 vol % of 80 mass % or more.