Method for producing microcapsules, microcapsules, recording material, and heat-sensitive recording material

A method for producing a microcapsule containing a core substance, the method comprising:

• adding a wall material solution including a capsule wall material to an aqueous phase medium to form a first mixture;
• forming a first emulsion including a primary dispersed particle by emulsifying the first mixture;
• adding an oil phase solution including the core substance to the first emulsion so as to form a second mixture;
• forming a secondary dispersed particle by emulsifying the second mixture;
• and
• forming a capsule wall at an interface of the secondary dispersed particle.

A method for producing a microcapsule containing a core substance, the method comprising:

• adding an oil phase solution including the core substance to a first aqueous phase medium to form a first mixture;
• forming a first emulsion including a first primary dispersed particle of the core substance by emulsifying the first mixture;
• adding a wall material solution including a capsule wall material to a second aqueous phase medium to form a second mixture;
• forming a second emulsion including a second primary dispersed particle of the capsule wall material by emulsifying the second mixture;
• mixing the first emulsion and the second emulsion to form a third mixture;
• forming a secondary dispersed particle by emulsifying the third mixture;
• and
• forming a capsule wall at an interface of the secondary dispersed particle,
• wherein the core substance includes a diazonium salt represented by the following formula (I) or (II):
• wherein in the formula (I):
• R1 and R2 each independently represent an alkyl group, an alkoxy group, an alkylthio group, an arylthio group or an alkylamino group;
• R3 to R6 each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an aryl group, an aryloxy group, an alkylthio group, an arylthio group, an alkylamino group or a —N2+X− group;
• at least one of R3 to R6 represents a —N2+X− group;
• X− represents a monovalent counter anion;
• and Y1 represents a sulfur atom, an oxygen atom, or a nitrogen atom bound to an alkyl group,
• wherein in the formula (II):
• R7 and R8 each independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, an alkylthio group, an arylthio group or an alkylamino group;
• R7 and R8 may be bound to each other to form a nitrogen-containing ring;
• R9 to R12 each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an aryl group, an aryloxy group, an alkylthio group, an alkylamino group or a —N2+X− group;
• at least one of R9 to R12 represents a —N2+X− group;
• X− represents a monovalent counter anion;
• and Y2 represents a sulfur atom, an oxygen atom, or a nitrogen atom bound to an alkyl group.