Particulate Silver Powder and Method of Manufacturing Same

Abstract

A particulate silver powder has an average particle diameter measured by TEM observation (DTEM) of 200 nm or less, an aspect ratio of less than 2.50, and a {(DTEM)/(Dx)} of 5.0 or less (where (Dx) denotes X-ray crystallite size). The particulate silver powder has a content of each of I − , Cl − , SO 4 2− , NO 3 − and CN − of 100 ppm or less. The particulate silver powder is obtained by subjecting a silver compound other than silver nitrate to reduction in an organic solvent having a boiling point of 85° C. or greater at a temperature of 85° C. or greater and in the presence of an organic protective agent.

1 . A particulate silver powder having an average particle diameter measured by TEM observation (DTEM) of 200 nm or less, an aspect ratio of less than 2.50, and a {(DTEM)/(Dx)} of 5.0 or less (where (Dx) denotes X-ray crystallite size), which particulate silver powder has a content of each of I − , Cl − , SO 4   2− , NO 3   −  and CN −  of 100 ppm or less. 
     
     
         2 . The particulate silver powder according to  claim 1 , whose surface is coated with an organic protective agent having a molecular weight of 100 to 400. 
     
     
         3 . The particulate silver powder according to  claim 2 , wherein the organic protective agent is a fatty acid or an amino compound. 
     
     
         4 . A liquid dispersion of silver particles obtained by dispersing the particulate silver powder of  claim 1  in a dispersion medium, which liquid dispersion of silver particles has an average particle diameter (D50) measured by the dynamic light-scattering method of 200 nm or less, a degree of dispersion {(D50)/(DTEM)} of 5.0 or less, and a content of each of I − , Cl − , SO 4   2− , NO 3   −  and CN −  of 100 ppm or less. 
     
     
         5 . The liquid dispersion of silver particles according to  claim 4 , wherein the dispersion medium is a non-polar or low-polarity organic solvent. 
     
     
         6 . A method of manufacturing a particulate silver powder which comprises:
 subjecting a silver compound other than silver nitrate to reduction in an organic solvent having a boiling point of 85° C. or greater at a temperature of 85° C. or greater and in the presence of an organic protective agent.   
     
     
         7 . A method of manufacturing a particulate silver powder according to  claim 6 , wherein the organic solvent is an alcohol or a polyol. 
     
     
         8 . A method of manufacturing a particulate silver powder according to  claim 6 , wherein the silver compound other than silver nitrate is silver carbonate or silver oxide. 
     
     
         9 . A method of manufacturing a particulate silver powder according to  claim 6 , wherein the organic protective agent is a fatty acid or amino compound having a molecular weight of 100 to 400. 
     
     
         10 . A method of manufacturing a liquid dispersion of silver particles which comprises:
 dispersing the particulate silver powder of  claim 1  in a non-polar or low-polarity organic solvent having a boiling point of 85° C. or greater.   
     
     
         11 . A liquid dispersion of silver particles obtained by dispersing the particulate silver powder of  claim 2  in a dispersion medium, which liquid dispersion of silver particles has an average particle diameter (D50) measured by the dynamic light-scattering method of 200 nm or less, a degree of dispersion {(D50)/(DTEM)} of 5.0 or less, and a content of each of I − , Cl − , SO 4   2− , NO 3   −  and CN −  of 100 ppm or less. 
     
     
         12 . A method of manufacturing a particulate silver powder according to  claim 7 , wherein the silver compound other than silver nitrate is silver carbonate or silver oxide. 
     
     
         13 . A method of manufacturing a particulate silver powder according to  claim 7 , wherein the organic protective agent is a fatty acid or amino compound having a molecular weight of 100 to 400. 
     
     
         14 . A method of manufacturing a particulate silver powder according to  claim 8 , wherein the organic protective agent is a fatty acid or amino compound having a molecular weight of 100 to 400. 
     
     
         15 . A method of manufacturing a liquid dispersion of silver particles which comprises:
 dispersing the particulate silver powder of  claim 2  in a non-polar or low-polarity organic solvent having a boiling point of 85° C. or greater.