Method for producing core-shell structured resin microparticles and core-shell structured toner containing core-shell structured resin microparticles

A method for producing core-shell structured resin particles, comprising the steps of:

• (I) providing a dispersion liquid of hydrophobic resin particles in which the hydrophobic resin particles are dispersed into an aqueous medium containing an anionic surfactant A and an anionic surfactant B;
• (II) providing a dispersion liquid of resin microparticles in which the resin microparticles are dispersed into an aqueous medium;
• (III) mixing the dispersion liquid of hydrophobic resin particles and the dispersion liquid of resin microparticles;
• and
• (IV) adhering the resin microparticles to surfaces of the hydrophobic resin particles by adding a water soluble metal salt to a mixture resulting from the step (III),
• wherein
• the surfactant A and the surfactant B satisfy the following conditions (i) to (iv):
• (i) surface tension of 5 mmol/L aqueous solution of the surfactant A<40 mN/m;
• (ii) surface tension of 5mmol/L aqueous solution of the surfactant A, in which the metal salt is contained in an amount to generate an equivalent amount of cations to an amount of anions derived from the surfactant A<40 mN/m;
• (iii) surface tension of 5 mmol/L aqueous solution of the surfactant B<40 mN/m;
• and
• (iv) surface tension of 5mmol/L aqueous solution of the surfactant B, in which the metal salt is contained in an amount to generate an equivalent amount of cations to an amount of anions derived from the surfactant B>40 mN/m wherein a molar concentration of the surfactant A and the surfactant B in the aqueous medium is:
• the surfactant A:the surfactant B=1:7 to 1:15.