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

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.

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.

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.

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.

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.

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.