Ink jet recording ink, ink jet image-forming method and ink jet recording apparatus

An ink jet image-forming method for forming an image by applying each of at least 4 color inks of black, cyan, magenta, and yellow in a fixed amount of from 0.5 pl or more to 6.0 pl or less for each ink to plain paper, wherein:

• each of the 4 color inks (1) comprise (a) a self-dispersion pigment, to the surface of which an anionic functional group represented by the following general formula (I) has been bonded directly or through another atomic group, (b) water, (c) a water-soluble substance having a coefficient of hydrophilicity-hydrophobicity of 0.37 or more as defined by the following equation (A), (d) a water-soluble substance having a coefficient of hydrophilicity-hydrophobicity of 0.25 or less as defined by the equation (A), and (e) an ethylene oxide adduct of acetylene glycol having a HLB value of 10 or more, and (2) has a surface tension of 34 mN/m or less, wherein the water-soluble substance having a coefficient of hydrophilicity-hydrophobicity of 0.37 or more is a water-soluble compound having a glycol structure of a hydrocarbon having 4 to 7 carbon atoms, the proportion (A)/(B) of the content of the water-soluble compound (A) to the content of the water-soluble compound (B) in the ink is 1/5 or more and 5/1 or less, and the ethylene oxide adduct of acetylene glycol is contained in the ink in an amount of 0.2% by mass or more and 5% by mass or less, and
• the application of the inks is divided into plural times when an image having a portion where the inks are applied in a duty of 80% or more and in an amount of 5.0 μl/cm2 or less in total is formed in a basic matrix for forming the image, and the amount of the inks applied at each of the times divided is 0.7 μl/cm2 or less:
• wherein M1 and M2 are, independently of each other, a hydrogen atom, alkali metal, ammonium, or organic ammonium;
• Coefficient of hydrophilicity-hydrophobicity=[(Water activity value of a 20% aqueous solution)×(Molar fraction of water in the 20% aqueous solution)]/[1−(Molar fraction of water in the 20% aqueous solution)]. Equation (A)

An ink jet recording apparatus equipped with a recording head for forming an image by applying each of at least 4 color inks of black, cyan, magenta, and yellow in a fixed amount of from 0.5 pl or more to 6.0 pl or less for each ink to plain paper, wherein:

• the apparatus comprises a control mechanism, by which the application of the inks is divided into plural times when an image having a portion where the inks are applied in a duty of 80% or more and in an amount of 5.0 pl/cm2 or less in total is formed in a basic matrix for forming the image, and the amount of the inks applied at each of the times divided is controlled to 0.7 μl/cm2 or less, and
• each of the inks (1) comprises (a) a self-dispersion pigment, to the surface of which an anionic functional group represented by the following general formula (I) has been bonded directly or through another atomic group, (b) water, (c) a water-soluble substance having a coefficient of hydrophilicity-hydrophobicity of 0.37 or more as defined by the following equation (A), (d) a water-soluble substance having a coefficient of hydrophilicity-hydrophobicity of 0.25 or less as defined by the equation (A), and (e) an ethylene oxide adduct of acetylene glycol having a HLB value of 10 or more, and (2) has a surface tension of 34 mN/m or less, wherein the water-soluble substance having a coefficient of hydrophilicity-hydrophobicity of 0.37 or more is a water-soluble compound having a glycol structure of a hydrocarbon having 4 to 7 carbon atoms, the proportion (A)/(B) of the content of the water-soluble compound (A) to the content of the water-soluble compound (B) in the ink is 1/5 or more and 5/1 or less, and the ethylene oxide adduct of acetylene glycol is contained in the ink in an amount of 0.2% by mass or more and 5% by mass or less:
• wherein M1 and M2 are, independently of each other, a hydrogen atom, alkali metal, ammonium, or organic ammonium;
• Coefficient of hydrophilicity-hydrophobicity=[(Water activity value of a 20% aqueous solution)×(Molar fraction of water in the 20% aqueous solution)]/[1−(Molar fraction of water in the 20% aqueous solution)]. Equation (A)