Ink composition and inkjet recording method

1. An ink composition comprising a dispersion medium and a charged particle, wherein the charged particle comprises a colorant, a compound having pKb of 16 or less in water and containing a proton-acceptive neutral functional group, and a charge controlling agent having pKa of 16 or less in water and containing a proton-donative group.

2. The ink composition as claimed in claim 1 , wherein the proton-acceptive neutral functional group is a functional group containing one or more atoms selected from a nitrogen atom, an oxygen atom, a sulfur atom and a phosphorus atom.

3. The ink composition as claimed in claim 1 , wherein the charged particles contain a coating agent.

4. The ink composition as claimed in claim 3 , wherein the compound having pKb of 16 or less in water and containing a proton-acceptive neutral functional group is used as a constituting component of the coating agent.

5. The ink composition as claimed in claim 1 , wherein an amount of the proton-acceptive neutral functional group is from 1 to 40% by weight based on the charged particles.

6. The ink composition as claimed in claim 1 , wherein the charge controlling agent having pKa of 16 or less in water and containing a proton-donative group has a carboxy group, a hydroxy group, a phosphono group, a sulfo group, a thiol group, an imido group or a sulfonamido group.

7. An inkjet recording method comprising a step of flying an ink composition as ink droplets by utilizing an electrostatic field, wherein the ink composition comprises a dispersion medium and a charged particle comprising a colorant, a compound having pKb of 16 or less in water and containing a proton-acceptive neutral functional group, and a charge controlling agent having pKa of 16 or less in water and containing a proton-donative group.