Fibrous copper microparticles and process for producing same

Abstract

The present invention provides fibrous copper microparticles suppressed in the occurrence of irregularities on the surface thereof and the aggregates of the fibrous copper microparticles having an average crystallite diameter controlled so as to fall within a specific range. In the fibrous copper microparticles of the present invention, the number of fibrous copper microparticles each including one or more irregularities each having a dimensional difference of 0.02 μm or more, in a range of 1 μm in the lengthwise direction of a fibrous body, between the maximum diameter portion of the fibrous body and the minimum diameter portion of the fibrous body falling in a diameter dimension range of 0.01 to 0.5 μm, and each having a length of 1 μm or more is 10 or less per 100 of the fibrous copper microparticles.

1 . Fibrous copper microparticles, wherein a number of fibrous copper microparticles each including one or more irregularities each having a dimensional difference of 0.02 μm or more, in a range of 1 μm in a lengthwise direction of a fibrous body, between a maximum diameter portion of the fibrous body and a minimum diameter portion of the fibrous body falling in a diameter dimension range of 0.01 to 0.5 μm, and each having a length of 1 μm or more is 10 or less per 100 of the fibrous copper microparticles. 
     
     
         2 . The fibrous copper microparticles according to  claim 1 , wherein for each of the fibrous copper microparticles, a fiber diameter is 0.01 to 0.5 μm, and an aspect ratio is 10 or more. 
     
     
         3 . Aggregates of fibrous copper microparticles, formed by allowing the fibrous copper microparticles according to  claim 1  to aggregate, wherein an average crystallite diameter is 0.045 to 0.1 μm and an average fiber diameter is 0.05 to 0.15 μm. 
     
     
         4 . Aggregates of fibrous copper microparticles, formed by allowing the fibrous copper microparticles according to  claim 1  to aggregate,
 wherein the average fiber diameter is 0.05 to 0.15 μm, and an average crystallite diameter is 0.45 or more times the average fiber diameter. 
 
     
     
         5 . Aggregates of fibrous copper microparticles, formed by allowing the fibrous copper microparticles according to  claim 1  to aggregate,
 wherein the average crystallite diameter is 0.015 to 0.03 μm, and the average fiber diameter is 0.03 to 0.1 μm. 
 
     
     
         6 . A process for producing fibrous copper microparticles,
 wherein the production process is a process for producing the fibrous copper microparticles according to  claim 1 ; and   the production process comprises a following step (I) and a following step (II) or (III), in this order:   the step (I) of heating, to 50 to 100° C., an aqueous solution containing copper ion, an alkaline compound, a nitrogen-containing compound capable of forming a stable complex with copper ion and a reducing compound;   the step (II) of maintaining for 20 minutes or more a temperature of the aqueous solution after passing through the step (I), and continuously precipitating the fibrous copper microparticles;   the step (III) of cooling the temperature of the aqueous solution after passing through the step (I) to decrease the temperature thereof by 20° C. over a period of time of 15 minutes or more from immediately after a start of cooling, and continuously precipitating the fibrous copper microparticles.   
     
     
         7 . The process for producing fibrous copper microparticles according to  claim 6 , wherein in the step (II) or (III), the reducing compound is further added to the aqueous solution. 
     
     
         8 . A process for producing aggregates of fibrous copper microparticles,
 wherein the production process is a process for producing the aggregates of the fibrous copper microparticles according to  claim 3 ; and the production process comprises the following step (I) and a following step (IIa), in this order, and continuously precipitates the fibrous copper microparticles or the aggregates of the fibrous copper microparticles:   the step (I) of heating to 50 to 100° C. the aqueous solution containing copper ion, an alkaline compound, a nitrogen-containing compound capable of forming a stable complex with copper ion and a reducing compound;   the step (IIa) of maintaining for 30 minutes or more the temperature of the aqueous solution after passing through the step (I).   
     
     
         9 . A process for producing aggregates of fibrous copper microparticles,
 wherein the production process is a process for producing the aggregates of the fibrous copper microparticles according to  claim 5 ; and the production process comprises a following step (Ia) and a following step (IIIa), in this order, and continuously precipitates the fibrous copper microparticles or the aggregates of the fibrous copper microparticles:   the step (Ia) of heating to 65 to 100° C. the aqueous solution containing copper ion, an alkaline compound, a nitrogen-containing compound capable of forming a stable complex with copper ion and a reducing compound;   the step (IIIa) of decreasing the temperature of the aqueous solution after passing through the step (Ia) by 20° C. over a period of time of 15 minutes or more from immediately after a start of cooling.   
     
     
         10 . The process for producing aggregates of fibrous copper microparticles according to  claim 8 , wherein in the step (IIa), the reducing compound is further added to the aqueous solution. 
     
     
         11 . The process for producing aggregates of fibrous copper microparticles according to  claim 9 , wherein in the step (IIIa), the reducing compound is further added to the aqueous solution. 
     
     
         12 . The process for producing fibrous copper microparticles according to  claim 6 , wherein as the reducing compound, one or more selected from ascorbic acid, erythorbic acid and glucose are used. 
     
     
         13 . The process for producing aggregates of fibrous copper microparticles according to  claim 8 , wherein as the reducing compound, one or more selected from ascorbic acid, erythorbic acid and glucose are used.