Aqueous ink, aqueous ink set, ink cartridge, ink-jet recording apparatus, ink-jet recording method, and image-forming method

Abstract

An aqueous ink comprises water, a water-insoluble coloring material, and plurality of water-soluble organic solvents and the plurality of water-soluble organic solvents including a good medium or good mediums for the water-insoluble coloring material and a poor medium or poor mediums for the water-insoluble coloring material. The ratio of the content of the poor medium and the content of the good medium is in a specific range. A water-soluble organic solvent showing the maximum Ka value out of respective Ka values of the plurality of water-soluble organic solvents is the poor medium. When the aqueous ink is in contact with a specific reaction liquid, the dissolution state or dispersed state of the water-insoluble coloring material in the ink is made unstable. As a result, an image which has a sufficiently large area factor even with a small amount of ink droplets and is excellent in image density, bleeding resistance, and fixability can be obtained. In addition, the aqueous ink is excellent in storage stability.

1 . An aqueous ink to be used for an image-forming method including the step of applying a reaction liquid capable of making the state of dissolution or dispersion of a water-insoluble coloring material in an aqueous ink unstable on contact with the aqueous ink, 
 wherein the aqueous ink comprises at least water; a water-insoluble coloring material; and plurality of water-soluble organic solvents, and    wherein the plurality of the water-soluble organic solvents includes a good medium or good mediums for the water-insoluble coloring material and a poor medium or poor mediums for the water-insoluble coloring material,    wherein the ratio B/A is 0.5 or more and 3 or less, where A denotes the total content (mass %) of the good medium based on the total mass of the aqueous ink and B denotes the total content (mass %) of the poor medium based on the total mass of the aqueous ink, and    wherein a water-soluble organic solvent showing a maximum Ka value out of respective Ka values of the plurality of water-soluble organic solvents as each determined by the Bristow method is the poor medium.    
   
   
       2 . An aqueous ink according to  claim 1 , wherein the total content (mass %) of the poor medium is 4 mass % or more based on the total mass of the ink.  
   
   
       3 . An aqueous ink set to be used for an image-forming method that may include as required the step of applying a reaction liquid capable of making the state of dissolution or dispersion of a water-insoluble coloring material in an aqueous ink unstable on contact with the aqueous ink, and the aqueous ink set comprising: 
 at least two kinds of aqueous inks having the same hue, and the at least two kinds of aqueous inks including at least a first aqueous ink and a second aqueous ink, and    wherein the first aqueous ink is used in combination with a reaction liquid only when the step of applying the reaction liquid is performed; and    wherein the first aqueous ink comprises water, a water-insoluble coloring material, and plurality of water-soluble organic solvents, and the plurality of the water-insoluble organic solvents including a good medium or good mediums for the water-insoluble coloring material and a poor medium and poor mediums for the water-insoluble coloring material; and    wherein the ratio B/A in the first aqueous ink is more than the ratio B/A in the second aqueous ink, where A denotes the total content (mass %) of good medium based on the total mass of the aqueous ink and B denotes the total content (mass %) of poor medium based on the total mass of the aqueous ink.    
   
   
       4 . An aqueous ink set according to  claim 3 , wherein the first aqueous ink comprises the aqueous ink according to  claim 1 .  
   
   
       5 . An aqueous ink set according to  claim 3 , wherein the ratio B/A in the second aqueous ink is less than 0.5.  
   
   
       6 . An aqueous ink set according to  claim 3 , wherein the content (mass %) of the water-insoluble coloring material in the first water based ink is more than the content (mass %) of the water-insoluble coloring material in the second aqueous ink.  
   
   
       7 . An aqueous ink set according to  claim 3 , wherein, in the first aqueous ink, the water-insoluble coloring material comprises a self-dispersion organic pigment or self-dispersion carbon black having at least one kind of hydrophilic group bonded to a surface of a water-insoluble coloring material particle directly or via another atomic group.  
   
   
       8 . An aqueous ink set according  claim 3 , wherein, in the second aqueous ink, the water-insoluble coloring material comprises a resin-dispersed pigment.  
   
   
       9 . An ink cartridge comprising an ink holding member containing an ink therein, wherein the ink comprises the aqueous ink according to  claim 1  or  3 .  
   
   
       10 . An ink-jet recording method comprising the step of ejecting an ink by means of an ink-jet method, wherein the ink comprises the aqueous ink according to  claim 1  or  2 .  
   
   
       11 . An ink-jet recording method comprising the step of ejecting ink by means of an ink-jet method, 
 wherein the ink comprises the aqueous ink according to  claim 1  or  2 ; and    the ink-jet recording method may further comprise the step of applying a reaction liquid to a recording medium in accordance with a recording condition.    
   
   
       12 . An image-forming method comprising the steps of: 
 (i) applying an aqueous ink comprising a water-insoluble coloring material to a recording medium; and    (ii) applying a reaction liquid capable of making the state of dissolution or dispersion of a water-insoluble coloring material in an aqueous ink unstable on contact with the aqueous ink,    wherein the aqueous ink comprises the aqueous ink according to  claim 1  or  3 ; and    the step (i) is performed after fixation of the reaction liquid to the recording medium in the step (ii) has been completed.    
   
   
       13 . An image-forming method comprising the steps of: 
 performing recording on a recording medium by means of a black ink and at least one color ink by an ink-jet recording method; and    applying, as required, a reaction liquid capable of making the state of dissolution or dispersion of a water-insoluble coloring material in an aqueous ink unstable on contact with an ink comprising a water-insoluble coloring material, and    wherein the aqueous ink according to  claim 1  or  3  is used as the black ink; and    wherein in forming an image composed of an image formed by the black ink and an image formed by the color ink are adjacent to each other, performing scanning for applying the black ink to form the image and thereafter performing scanning for applying the color ink to the area where the image has been formed by the precedent scanning.    
   
   
       14 . An image-forming method according to  claim 13 , wherein the color ink is applied by scanning with delay of at least one scanning after application of the black ink by scanning.  
   
   
       15 . An image-forming method according to  claim 13 , wherein the inks are applied by means of a recording head in which an ejection orifice line for ejecting a black ink therefrom and an ejection orifice line for ejecting color inks therefrom are placed to be shifted from each other in a secondary scanning direction.  
   
   
       16 . An aqueous ink set to be used for an image-forming method that may include as required the step of applying a reaction liquid capable of making the state of dissolution or dispersion of a water-insoluble coloring material in an aqueous ink unstable on contact with an aqueous ink comprising a water-insoluble coloring material, the aqueous ink set comprising: 
 at least two kinds of aqueous inks having the same hue, and the at least two kinds of aqueous inks including a first aqueous ink and a second aqueous ink, and    wherein the first aqueous ink is used in combination with a reaction liquid only when the step of applying the reaction liquid is performed; and    wherein the second aqueous ink is used at least when the step of applying the reaction liquid is not performed;    wherein the first aqueous ink comprises water, a water-insoluble coloring material, and plurality of water-soluble organic solvents, and the plurality of water-soluble organic solvents including a good medium or good mediums for the water-insoluble coloring material and a poor medium and poor mediums for the water-insoluble coloring material; and    wherein a water-soluble organic solvent showing a maximum Ka value out of respective Ka values of the plurality of water-soluble organic solvents as each determined by the Bristow method is the poor medium; and    wherein the poor medium permeates into a recording medium ahead of the good medium and the poor medium promotes flocculation of the water-insoluble coloring material in the good medium on a surface side of the recording medium.