Ink Composition Containing Magenta Solid Solution Pigment and Ink jet Recording Method Using the Same

Abstract

Disclosed is an ink composition for ink jet recording that can realize excellent printing quality on various recording media, has a high level of color developing properties particularly on plain papers, and can realize excellent gloss for glossy paper and, at the same time, is excellent in ink reliability such as ejection stability, storage stability, and recovery from clogging. The ink composition is characterized by comprising at least a magenta solid solution pigment, a polymer, which can render the pigment dispersible in the ink composition, and water, the polymer having been produced by copolymerizing a monomer composition comprising at least a styrene macromer (A) and a salt forming group-containing monomer (B).

1 . An ink composition comprising at least a magenta solid solution pigment, a dispersant polymer, which can render the pigment dispersible in the ink composition, and water,
 wherein the dispersant polymer is produced by copolymerizing a monomer composition comprising at least a styrene macromer (A) and a salt forming group-containing monomer (B).   
   
   
       2 . The ink composition according to  claim 1 , wherein the dispersant polymer further comprises a polyoxyalkylene group-containing monomer (C). 
   
   
       3 . The ink composition according to  claim 2 , wherein the polyoxyalkylne group-containing monomer (C) comprises one or more monomers selected from the group consisting of monomer C1 represented by formula (I): 
     
       
         
         
             
             
         
       
       wherein R 1  represents a hydrogen atom or a methyl group; R 2  represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms or an alkylphenyl group having 1 to 9 carbon atoms; and m is a number of 1 to 30, 
       monomer C2 represented by formula (II): 
     
     
       
         
         
             
             
         
       
       wherein R 1  and R 2  are as defined in formula (I); and n is a number of 1 to 30, 
       monomer C3 represented by formula (III): 
     
     
       
         
         
             
             
         
       
       wherein R 1 , R 2 , and m are as defined in formula (I); n is as defined in formula (II); and the oxyethylene groups and the oxypropylene groups in [ ] are attached as a block polymer or a random polymer, and 
       monomer C4 represented by formula (IV): 
     
     
       
         
         
             
             
         
       
       wherein R 1 , R 2 , and m are as defined in formula (I); n is as defined in formula (II); and the oxypropylene groups and the oxytetramethylene groups in [ ] are attached as a block polymer or a random polymer. 
     
   
   
       4 . The ink composition according to  claim 2 , wherein the dispersant polymer further comprises a monomer (D) which is copolymerizable with the styrene macromer (A), the salt forming group-containing monomer (B), and the polyoxyalkylene group-containing monomer (C). 
   
   
       5 . The ink composition according to  claim 4 , wherein the copolymerizable monomer (D) comprises at least one monomer selected from the group consisting of aromatic ring-containing monomers and macromers. 
   
   
       6 . The ink composition according to  claim 5 , wherein the aromatic ring-containing monomer is at least one monomer selected from the group consisting of styrene, α-methylstyrene, vinyltoluene, and vinylnaphthalene. 
   
   
       7 . The ink composition according to  claim 1 , which exhibits a UV visible absorption spectrum wherein
 at least one absorption peak is present at a wavelength of 510 nm to 535 nm and at least one absorption peak is present at a wavelength of 550 nm to 570 nm, and   the maximum value A of the absorbance in the wavelength range of 510 to 535 nm and the maximum value B of the absorbance in the wavelength range of 550 nm to 570 nm satisfies a relationship of 0.9<A/B<1.0.   
   
   
       8 . The ink composition according to  claim 1 , wherein the magenta solid solution pigment is a solid solution pigment comprising at least two quinacridone compounds selected from the group consisting of unsubstituted quinacridone, 3,10-dichloroquinacridone, 2,9-dimethyl quinacridone, and 2,9-dichloroquinacridone. 
   
   
       9 . The ink composition according to  claim 1 , which further comprises a vinyl polymer produced by polymerizing a monomer composition comprising
 a polyoxyalkylene group-containing monomer (1)   a salt forming group-containing monomer (2), and   a monomer (3) copolymerizable with the polyoxyalkylene group-containing monomer and the salt forming group-containing monomer.   
   
   
       10 . The ink composition according to  claim 1 , wherein the polyoxyalkylene group-containing monomer (1) comprises at least one monomer selected from the group consisting of
 monomer M1 represented by the following formula:   
     
       
         
         
             
             
         
       
       wherein R 1  represents a hydrogen atom or a methyl group; R 2  represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms or an alkylphenyl group having 1 to 9 carbon atoms; and m is a number of 1 to 30, 
       monomer M2 represented by the following formula: 
     
     
       
         
         
             
             
         
       
       wherein R 1  represents a hydrogen atom or a methyl group; R 2  represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms or an alkylphenyl group having 1 to 9 carbon atoms; and n is a number of 1 to 30, and 
       monomer M3 represented by the following formula: 
     
     
       
         
         
             
             
         
       
       wherein R 1  represents a hydrogen atom or a methyl group; R 2  represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms or an alkylphenyl group having 1 to 9 carbon atoms; m and n are a number of 1 to 30; and the oxyethylene groups and the oxypropylene groups in [ ] are attached as a block polymer or a random polymer. 
     
   
   
       11 . The composition according to  claim 10 , wherein the polyoxyalkylene group-containing monomer (1) is monomer M1. 
   
   
       12 . The ink composition according to  claim 9 , wherein the vinyl polymer has a weight average molecular weight of 150,000 to 500,000. 
   
   
       13 . The ink composition according to  claim 9 , wherein the copolymerizable monomer (3) comprises at least one monomer selected from the group consisting of higher alkyl group-containing monomers, aromatic ring-containing monomers, and macromers. 
   
   
       14 . The ink composition according to  claim 9 , which further comprises a surfactant which comprises both
 a compound represented by formula (a):   
     
       
         
         
             
             
         
       
       and a compound represented by formula (b): 
     
     
       
         
         
             
             
         
       
       wherein m and n satisfy a requirement of m+n=10. 
     
   
   
       15 . The ink composition according to  claim 14 , wherein the two surfactants are contained at a weight ratio of (a):(b)=2:1 to 1:4. 
   
   
       16 . A method for ink jet recording, comprising ejecting droplets of an ink composition and depositing the droplets onto a recording medium to performing printing, wherein the ink composition is one according to  claim 1 .