Black ink composition, ink set, and image forming method

Abstract

A black ink composition includes: carbon black and a water-insoluble resin that covers at least a part of the surface of the carbon black; a cyan pigment and a water-insoluble resin that covers at least a part of the surface of the cyan pigment; a magenta pigment and a water-insoluble resin that covers at least a part of the surface of the magenta pigment; water-insoluble resin particle; and water, wherein a content ratio of the carbon black is from 1.0 to 2.0% by mass with respect to the total mass of the composition, and a total amount of pigments is from 1.8 to 3.5% by mass with respect to the total mass of the composition. The black ink composition can be used in an ink set and an image forming method.

1 . A black ink composition, comprising:
 carbon black and a first water-insoluble resin that covers at least a part of a surface of the carbon black;   a cyan pigment and a second water-insoluble resin that covers at least a part of a surface the cyan pigment;   a magenta pigment and a third water-insoluble resin that covers at least a part of a surface of the magenta pigment;   water-insoluble resin particles; and   water,   wherein a content ratio of the carbon black is from 1.0 to 2.0% by mass with respect to a total mass of the composition, and a total amount of pigments is from 1.8 to 3.5% by mass with respect to the total mass of the composition.   
     
     
         2 . The black ink composition according to  claim 1 , wherein a content of the water-insoluble resin particles is larger than a total amount of pigments, at least a part of surfaces of which are coated with water-insoluble resins, and the water-insoluble resins that cover the at least a part of surfaces of the pigments. 
     
     
         3 . The black ink composition according to  claim 2 , wherein a ratio of the content of the water-insoluble resin particles to the total amount of pigments, at least a part of surfaces of which are coated with water-insoluble resins, and the water-insoluble resins that cover the at least a part of surfaces of the pigments, is more than 1.0 but not more than 4.0. 
     
     
         4 . The black ink composition according to  claim 1 , wherein the water-insoluble resin particles comprise self-dispersing polymer particles. 
     
     
         5 . The black ink composition according to  claim 1 , wherein the water-insoluble resin particles have a Tg of 100° C. or higher. 
     
     
         6 . The black ink composition according to  claim 1 , further comprising a solid humectant. 
     
     
         7 . The black ink composition according to  claim 6 , wherein the humectant is selected from urea, a urea derivative, or a mixture thereof. 
     
     
         8 . The black ink composition according to  claim 1 , further comprising a yellow pigment and a fourth water-insoluble resin that covers at least a part of a surface of the yellow pigment. 
     
     
         9 . An ink set, comprising:
 the black ink composition according to  claim 1 ; and   a treatment liquid comprising an aggregation component which is capable of causing formation of an aggregate when contacting the black ink composition.   
     
     
         10 . An image forming method, comprising:
 applying the black ink composition according to  claim 1  to a recording medium by an inkjet method; and   applying a treatment liquid to the recording medium, the treatment liquid comprising an aggregation component which is capable of causing formation of an aggregate when contacting the black ink composition.   
     
     
         11 . The image forming method according to  claim 10 , wherein the applying of the black ink composition comprises applying the black ink composition by a piezoelectric inkjet method. 
     
     
         12 . The image forming method according to  claim 11 , further comprising heating an image formed through the applying of the black ink composition and the applying of the treatment liquid, to fix the image on the recording medium.