Ink, and ink-jet recording method and instrument using the same

Claim 1

An ink comprising at least a coloring material and a liquid medium dissolving or dispersing the coloring material therein, wherein the viscosity of the ink reaches a maximum peak in a pH range of from 4 to 10, said ink further comprises a compound whose solubility reaches a minimum peak in a pH range of from 4 to 10 represented by the general formula ##STR8## wherein R 1 denotes an alkyl group having 1 to 48 carbon atoms, or a hydrogen atom, R 2 denotes (CH 2 ) a --X 1 or a hydrogen atom, in which a is an integer of 1 to 4, R 3 denotes (CH 2 ) b --X 2 , R 4 --Y or a hydrogen atom, in which b is an integer of 1 to 4, R 4 denotes an alkyl group having 1 to 48 carbon atoms, or a hydrogen atom, Z denotes (NR 5 C l H 2l ) c (NHC n H 2n ) d , in which l is an integer of 2 to 4, n is an integer of 2 to 4, and c+d is an integer of 0 to 50, Y denotes (NR 6 C m H2 m ) e (NHC p H 2p ) f , in which m is an integer of 2 to 4, p is an integer of 2 to 4, and e+f is an integer of 0 to 50, R 5 denotes (CH 2 ) g --X 3 , in which g is an integer of 1 to 4, R 6 denotes (CH 2 ) h --X 4 , in which h is an integer of 1 to 4, and X 1 , X 2 , X 3 and X 4 independently denote groups selected from the group consisting of a carboxyl group, a salt of the carboxyl group, a sulfonic group, a salt of the sulfonic group and a hydrogen atom, with a proviso that R 2 and R 3 , and c and e are not a hydrogen atom and 0 respectively at the same time, and X 1 , X 2 , X 3 and X 4 are not a hydrogen atom at the same time.