SILVER MICRO-PARTICLE AND METHOD OF PRODUCING THE SAME

To provide silver micro-particles that are less varied in particle size, have a sharp particle-size distribution and are capable of preferably maintaining the dispersibility in a lipophilic solvent.SOLUTION: Silver micro-particles comprise aliphatic amine, e.g. octyl amine, having 6 or more C on a particle surface, with an average particle size in terms of equivalent circle diameter of 70 nm or greater and 150 nm or smaller and a variation coefficient in particle size of 20% or smaller. The silver micro-particles are to be synthesized by a reduction process including the steps of: first reduction to add silver at an addition rate of 0.4 mmol/s per 1 kg of solution or lower into a solution having a reducer concentration of 0.8 molar equivalent/kg or lower and second reduction to add silver at an addition rate of 0.4 mmol/s per 1 kg of solution or lower after a reducer is newly added to a reaction liquid thereof.SELECTED DRAWING: Figure 6 【課題】粒子径のバラツキが少なくシャープな粒度分布を有し、かつ親油性溶媒中での分散性を良好に維持することが可能な銀微粒子を提供する。【解決手段】炭素数６以上の脂肪族アミン、例えばオクチルアミンを粒子表面に有し、円相当径での平均粒子径が７０ｎｍ以上１５０ｎｍ以下であり、粒子径の変動係数が２０％以下である銀微粒子。この銀微粒子は、還元剤の濃度が０.８モル当量／ｋｇ以下である溶液中に、銀を溶液１ｋｇ当たり０.４ｍｍｏｌ／ｓ以下の添加速度で添加する第１還元工程と、その反応液に還元剤を新たに追加したのち、銀を溶液１ｋｇ当たり０.４ｍｍｏｌ／ｓ以下の添加速度で添加する第２還元工程と、を含む還元過程によって合成することができる。【選択図】図６