Highly crystalline silver powder and production method of highly crystalline silver powder

Abstract

Object of the present invention is to provide a production method of a highly crystalline silver powder containing powder particles in fine particle region and having a good particle size distribution as well as the highly crystalline silver powder obtained by the production method. In order to achieve the object, the present invention adopts a production method characterized in that the method comprises preparation of a first aqueous solution in which gelatin, silver nitrate and nitric acid are dissolved in water, preparation of a second aqueous solution in which L-sorbic acid and/or ascorbic acid and a water-soluble organic acid are dissolved, adding of the second aqueous solution slowly to mix with the first aqueous solution, stirring of the mixture to grow the silver particles after finishing the mixing, keeping of the mixture still to settle the silver particles, discarding of the supernatant, filtration and rinsing to obtain the highly crystalline silver powder.

1 . A production method of highly crystalline silver powder from a silver ion containing solution by using L-sorbic acid and/or ascorbic acid as a reducing agent, characterized in that the method comprises preparation of a first aqueous solution in which gelatin, silver nitrate and nitric acid are dissolved in water, preparation of a second aqueous solution in which L-sorbic acid and/or ascorbic acid and a water-soluble organic acid are dissolved, adding of the second aqueous solution slowly to mix with the first aqueous solution, stirring of the mixture to grow the silver particles after finishing the mixing, keeping of the mixture still to settle the silver particles, discarding of the supernatant, filtration and rinsing to obtain highly crystalline silver powder. 
   
   
       2 . The production method of the highly crystalline silver powder according to  claim 1 , wherein the gelatin concentration in the first aqueous solution is 2 g/l to 10 g/l. 
   
   
       3 . The production method of the highly crystalline silver powder according to  claim 1 , wherein the silver nitrate concentration in the first aqueous solution is 50 g/l to 150 g/l as silver. 
   
   
       4 . The production method of the highly crystalline silver powder according to  claim 1 , wherein the free nitric acid concentration in the first aqueous solution is adjusted to 40 g/l to 120 g/l by adding the nitric acid aqueous solution. 
   
   
       5 . The production method of the highly crystalline silver powder according to  claim 1 , wherein the concentration of L sorbic acid and/or ascorbic acid in the second aqueous solution is 45 g/l to 120 g/l. 
   
   
       6 . The production method of the highly crystalline silver powder according to  claim 1 , wherein the concentration of the water-soluble organic acid in the second aqueous solution is 1 g/l to 50 g/l. 
   
   
       7 . The production method of the highly crystalline silver powder according to  claim 6 , wherein the water-soluble organic acid is one or combination of two or more kinds selected from DL-malic acid, citric acid, formic acid, valeric acid, isovaleric acid, succinic acid, propionic acid, lactic acid and adipic acid. 
   
   
       8 . The highly crystalline silver powder characterized by obtained by a production method according to  claim 1 . 
   
   
       9 . The highly crystalline silver powder according to  claim 8  characterized in that the powder has a primary particle diameter of 0.07 μm to 4.5 μm and a crystal diameter of 200 Å or more. 
   
   
       10 . The highly crystalline silver powder according to  claim 8  characterized in that the powder has a volume accumulated average particle diameter D 50  measured by laser diffraction scattering-type particle size distribution measurement method of 0.1 μm to 5.0 μm and a particle size distribution index (D 90 −D 10 )/D 50  of not more than 1.5. 
   
   
       11 . The highly crystalline silver powder according to  claim 8  characterized in that the powder has a volume accumulated maximum particle diameter D max  measured by laser diffraction scattering-type particle size distribution measurement method of 16.0 μm or less. 
   
   
       12 . The highly crystalline silver powder according to  claim 8  characterized in that the powder has a specific surface area of 0.2 m 2 /g or more.