Electrophotographic positively charged toner and manufacturing method thereof

Abstract

An electrophotographic positively charged toner and method for its manufacture. The toner includes a core toner that has a binder resin, a wax, a colorant and a charge control agent as its principal component materials. The core toner is spherified through heat treatment. The toner also includes at least fine silica particles as an external additive. The charge control agent contains a resin having a quaternary ammonium salt group as a functional group and a nigrosine dye. Even if after kneading, pulverization and classification, the toner is made spherical by melting the surfaces of the particles in a hot air current, the charge control agent is not coated and hence the charging ability thereof is not reduced.

1 . An electrophotographic, positively charged toner comprising 
 a core toner, spherified through heat treatment, including a binder resin, a wax, a colorant and a charge control agent as principal component materials, the charge control agent containing 
 a resin having a quaternary ammonium salt group as a functional group, and  
 a nigrosine dye; and  
   at least fine silica particles as an external additive.    
     
     
         2 . The toner according to  claim 1 , wherein the colorant includes per 100 parts by weight of the binder resin, 3 to 6 parts by weight of carbon black exhibiting a pH of at least 8.0.  
     
     
         3 . The toner according to  claim 1 , wherein the charge control agent contains 
 2 to 10 parts by weight of the resin having a quaternary ammonium salt group as a functional group, and    0.5 to 5 parts by weight of the nigrosine dye per 100 parts by weight of the binder resin.    
     
     
         4 . The toner according to  claim 3 , wherein the resin having a quaternary ammonium salt group as a functional group has as a principal component a styrene-acrylic copolymer resin, the styrene-acrylic copolymer resin containing 
 a repeat unit represented by the following formula (1)    [Formula 1],                          and a repeat unit represented by the following formula (2)    [Formula 2],                          where, in the formulae (1) and (2), R 1  and R 2  represent a hydrogen atom or a methyl group, R 3  represents an alkylene group, and R 4 , R 5  and R 6  each represents an alkyl group;    the styrene-acrylic copolymer resin including 65 to 97 wt % of the repeat unit represented by the formula (1) and 35 to 3 wt % of the repeat unit represented by the formula (2), and having a weight average molecular weight in a range of 2,000 to 10,000.    
     
     
         5 . The toner according to  claim 3 , wherein the binder resin has a styrene-acrylic copolymer resin as a principal component.  
     
     
         6 . The toner according to  claim 4 , wherein the colorant includes per 100 parts by weight of the binder resin, 3 to 6 parts by weight of carbon black exhibiting a pH of at least 8.0.  
     
     
         7 . The toner according to  claim 3 , wherein the colorant includes per 100 parts by weight of the binder resin, 3 to 6 parts by weight of carbon black exhibiting a pH of at least 8.0.  
     
     
         8 . The toner according to  claim 1 , wherein the resin having a quaternary ammonium salt group as a functional group has as a principal component a styrene-acrylic copolymer resin, the styrene-acrylic copolymer resin containing 
 a repeat unit represented by the following formula (1):    [Formula 1],                          and a repeat unit represented by the following formula (2):    [Formula 2]                         where, in the formulae (1) and (2), R 1  and R 2  represent a hydrogen atom or a methyl group, R 3  represents an alkylene group, and R 4 , R 5  and R 6  each represents an alkyl group;    the styrene-acrylic copolymer resin including 65 to 97 wt % of the repeat unit represented by the formula (1) and 35 to 3 wt % of the repeat unit represented by the formula (2), and having a weight average molecular weight in a range of 2,000 to 10,000.    
     
     
         9 . The toner according to  claim 8 , wherein the binder resin has a styrene-acrylic copolymer resin as a principal component.  
     
     
         10 . The toner according to  claim 9 , wherein the colorant includes per 100 parts by weight of the binder resin, 3 to 6 parts by weight of carbon black exhibiting a pH of at least 8.0.  
     
     
         11 . The toner according to  claim 8 , wherein the colorant includes per 100 parts by weight of the binder resin, 3 to 6 parts by weight of carbon black exhibiting a pH of at least 8.0.  
     
     
         12 . The toner according to  claim 1 , wherein the binder resin has a styrene-acrylic copolymer resin as a principal component.  
     
     
         13 . The toner according to  claim 12 , wherein the colorant includes per 100 parts by weight of the binder resin, 3 to 6 parts by weight of carbon black exhibiting a pH of at least 8.0.  
     
     
         14 . A method of manufacturing an electrophotographic positively charging toner, the method comprising the steps of: 
 mixing/agitating a binder resin, a wax, a colorant and a charge control agent as principal component materials,    hot melt-kneading and pulverizing the mixed/agitated binder resin, a wax, a colorant and a charge control agent, and classifying the kneaded material obtained to produce a core toner, and    spherifying the core toner through hot air blast treatment, and then mixing in at least silica fine particles as an external additive.    
     
     
         15 . The method of  claim 14 , wherein the charge control agent contains 
 2 to 10 parts by weight of the resin having a quaternary ammonium salt group as a functional group, and    0.5 to 5 parts by weight of the nigrosine dye per 100 parts by weight of the binder resin.    
     
     
         16 . The method of  claim 14 , wherein the resin has a quaternary ammonium salt group as a functional group has as a principal component a styrene-acrylic copolymer resin, the styrene-acrylic copolymer resin containing 
 a repeat unit represented by the following formula (1):    [Formula 1],                          and a repeat unit represented by the following formula (2):    [Formula 2]                         where, in the formulae (1) and (2), R 1  and R 2  represent a hydrogen atom or a methyl group, R 3  represents an alkylene group, and R 4 , R 5  and R 6  each represents an alkyl group;    the styrene-acrylic copolymer resin including 65 to 97 wt % of the repeat unit represented by the formula (1) and 35 to 3 wt % of the repeat unit represented by the formula (2), and having a weight average molecular weight in a range of 2,000 to 10,000.    
     
     
         17 . The method of  claim 14 , wherein the binder resin has a styrene-acrylic copolymer resin as a principal component.  
     
     
         18 . The method of  claim 15 , wherein the binder resin has a styrene-acrylic copolymer resin as a principal component.  
     
     
         19 . The method of  claim 14 , wherein the colorant includes per 100 parts by weight of the binder resin, 3 to 6 parts by weight of carbon black exhibiting a pH of at least 8.0.  
     
     
         20 . The method of  claim 15 , wherein the colorant includes per 100 parts by weight of the binder resin, 3 to 6 parts by weight of carbon black exhibiting a pH of at least 8.0.  
     
     
         21 . The method of  claim 16 , wherein the colorant includes per 100 parts by weight of the binder resin, 3 to 6 parts by weight of carbon black exhibiting a pH of at least 8.0.  
     
     
         22 . The method of  claim 15 , wherein the resin has a quaternary ammonium salt group as a functional group has as a principal component a styrene-acrylic copolymer resin, the styrene-acrylic copolymer resin containing 
 a repeat unit represented by the following formula (1)    [Formula 1],                          and a repeat unit represented by the following formula (2)    [Formula 2],                          wherein, in the formulae (1) and (2), R 1  and R 2  represent a hydrogen atom or a methyl group, R 3  represents an alkylene group, and R 4 , R 5  and R 6  each represents an alkyl group;    the styrene-acrylic copolymer resin including 65 to 97 wt % of the repeat unit represented by the formula (1) and 35 to 3 wt % of the repeat unit represented by the formula (2), and having a weight average molecular weight in a range of 2,000 to 10,000;    the colorant including per 100 parts by weight of the binder resin, 3 to 6 parts by weight of carbon black exhibiting a pH of at least 8.0.