Block copolymeric dispersant for pigment particle in aqueous system, and ink composition comprising the same

1. A dispersant comprising a block copolymer having both a hydrophilic moiety and a hydrophobic moiety and a hydrophobic substituent attached to a terminal end of said hydrophobic moiety,

wherein said hydrophilic moiety comprises a repeating unit represented by Formula I below:

wherein,

R 1 is H or a C 1 -C 6 alkyl group;

X is H, a substituted or unsubstituted C 1 -C 20 alkyl group, a C 1 -C 20 alkenyl group, a C 1 -C 20 alkynyl group, a C 1 -C 20 alkoxy group, a substituted or unsubstituted C 6 -C 20 aryl group, a substituted or unsubstituted C 2 -C 20 heteroaryl group or a substituted or unsubstituted C 7 -C 20 arylalkyl group;

Y is —OA, —COOA, —SO 2 A, —SO 2 NH 2 , —SO 2 NHCOT 1 , —T 2 SO 3 A, —SO 3 A, —PO 3 NH 2 , —PO 3 A 2 , —NH 2 or —N(T 1 ) 2 , wherein A is a hydrogen atom, an alkali metal, or N(Q 1 )(Q 2 )(Q 3 )(Q 4 ) in which Q 1 , Q 2 , Q 3 or Q 4 each independently represents a hydrogen atom, a C 1 -C 20 alkyl group or a C 6 -C 20 aryl group; T 1 is a C 1 -C 20 alkyl group, a C 6 -C 20 aryl group or a C 2 -C 20 heteroaryl group; T 2 is a C 1 -C 20 alkylene group, a C 6 -C 20 arylene group or a C 2 -C 20 heteroarylene group; and

m is an integer of 2 to 150,

wherein said hydrophobic moiety comprises a repeating unit represented by Formula II below:

wherein

R 2 is H or a C 1 -C 6 alkyl group;

R 3 is a substituted or unsubstituted C 1 -C 20 alkyl group, a C 1 -C 20 alkenyl group, a C 1 -C 20 alkynyl group, a C 1 -C 20 alkoxy group, a substituted or unsubstituted C 6 -C 20 aryl group, a substituted or unsubstituted C 2 -C 20 heteroaryl group or a substituted or unsubstituted C 7 -C 20 arylalkyl group;

Z is H, a substituted or unsubstituted C 1 -C 20 alkyl group, a C 1 -C 20 alkenyl group, a C 1 -C 20 alkynyl group, a C 1 -C 20 alkoxy group, a substituted or unsubstituted C 6 -C 20 aryl group, a substituted or unsubstituted C 2 -C 20 heteroaryl group or a substituted or unsubstituted C 7 -C 20 arylalkyl group; and

n is an integer of 2 to 150,

wherein the hydrophobic substituent is a substituted or unsubstituted C 1 -C 20 alkyl group, a substituted or unsubstituted C 6 -C 20 aryl group, a substituted or unsubstituted C 2 -C 20 heteroaryl group, or a substituted or unsubstituted C 7 -C 20 arylalkyl group,

wherein said hydrophobic substituent is included in an amount of 0.05 to 90 parts by weight based on total weight of said dispersant.

2. The dispersant of claim 1 , wherein said hydrophilic moiety comprises a repeating unit derived from at least one monomer selected from the group consisting of acrylic acid, an acrylate, maleic acid anhydride and sodium styrene sulfonate and derivatives thereof.

3. The dispersant of claim 1 , wherein said hydrophobic moiety comprises a repeating unit derived from at least one monomer selected from the group consisting of methyl methacrylate, butyl metharylate, lauryl methacrylate, ethyl acrylate, butyl acrylate, acrylonitrile, methacrylonitrile, 2-ethylhexyl methacrylate, 3,3-dimethoxypropyl acrylate, 3-methacryloxypropyl acrylate, 2-acetoxyethyl methacrylate, p-tolyl methacrylate, 2,2,3,3,4,4,4-heptafluorobutyl acrylate, ethyl 2-cyanoacrylate, N,N-dimethylacrylamide, 4-fluorophenyl acrylate, 2-methacryloxyethyl acrylate, propyl vinyl ketone, ethyl 2-chloroacrylate, glycidyl methacrylate, 3-methoxypropyl methacrylate, phenyl acrylate, 2-(trimethylsiloxy)ethyl methacrylate, 2-(methylsiloxy)ethyl methacrylate, allyl acrylate and methacrylate, ethyleneglycol diacrylate, diethyleneglycol diacrylate, glycerol diacrylate, glyceryl triacrylate, ethyleneglycol dimethacrylate, and hexamethylene diol diacrylate.

4. The dispersant of claim 1 , wherein at least one hydrogen atom of a C 1 -C 20 alkyl group of said hydrophobic substituent, is substituted with at least one substituent selected from the group consisting of a hydroxy group, a halogen atom, a cyano, a nitro, an amino, an imino, an imidino, a hydrazine, a hydrazole, an amide group, a sulfonamide group, a carboxyl group or its salt, a phosphoric acid group or its salt, a sulfuric acid or its salt, a thiol group, a C 1 -C 20 alkyl group, a C 1 -C 20 alkenyl group, a C 1 -C 20 alkynyl group, a C 1 -C 20 alkoxy group, a C 1 -C 20 heteroalkyl group, a C 6 -C 20 aryl group, a C 6 -C 20 arylalkyl group, a C 2 -C 20 heteroaryl group, and a C 2 -C 20 heteroarylalkyl group.

5. The dispersant of claim 1 , wherein said C 6 -C 20 aryl group of said hydrophobic substituent includes at least one substituent selected from the group consisting of a haloalkylene, an alkyl, an aryl, a nitro, a halogen, a cyano, a hydroxy, a thiol, an amino, an imino, an amidino and an alkoxy group.

6. The dispersant of claim 1 , wherein said C 2 -C 20 heteroaryl group of said hydrophobic substituent, is a monocyclic, bicyclic or polycyclic aromatic organic compound including a 6- to 20-membered ring, which comprises at least one heteroatom selected from the group consisting of N, O, P or S, and C.

7. The dispersant of claim 1 , wherein said block copolymer comprises 10 to 90% by mole of said hydrophilic moiety and 90 to 10% by mole of said hydrophobic moiety.

8. The dispersant of claim 1 , wherein the number average molecular weight of the block copolymer is 300 to 120,000.

9. An ink composition comprising pigment particles, a dispersant and an aqueous medium, wherein said dispersant is of a block copolymer having both a hydrophilic moiety and a hydrophobic moiety and a hydrophobic substituent attached to a terminal end of said hydrophobic moiety,

wherein said hydrophilic moiety comprises a repeating unit represented by Formula I below:

wherein,

R 1 is H or a C 1 -C 6 alkyl group;

X is H, a substituted or unsubstituted C 1 -C 20 alkyl group, a C 1 -C 20 alkenyl group, a C 1 -C 20 alkynyl group, a C 1 -C 20 alkoxy group, a substituted or unsubstituted C 6 -C 20 aryl group, a substituted or unsubstituted C 2 -C 20 heteroaryl group or a substituted or unsubstituted C 7 -C 20 arylalkyl group;

Y is —OA, —COOA, —SO 2 A, —SO 2 NH 2 , —SO 2 NHCOT 1 , —T 2 SO 3 A, —SO 3 A, —PO 3 NH 2 , —PO 3 A 2 , —NH 2 or —N(T 1 ) 2 , wherein A is a hydrogen atom, an alkali metal, or N(Q 1 )(Q 2 )(Q 3 )(Q 4 ) in which Q 1 , Q 2 ,Q 3 or Q 4 each independently represents a hydrogen atom, a C 1 -C 20 alkyl group or a C 6 -C 20 aryl group; T 1 is a C 1 -C 20 alkyl group, a C 6 -C 20 aryl group or a C 2 -C 20 heteroaryl group; T 2 is a C 1 -C 20 alkylene group, a C 6 -C 20 arylene group or a C 2 -C 20 heteroarylene group; and

m is an integer of 2 to 150,

wherein said hydrophobic moiety comprises a repeating unit represented by Formula II below:

wherein

R 2 is H or a C 1 -C 6 alkyl group;

R 3 is a substituted or unsubstituted C 1 -C 20 alkyl group, a C 1 -C 20 alkenyl group, a C 1 -C 20 alkynyl group, a C 1 -C 20 alkoxy group, a substituted or unsubstituted C 6 -C 20 aryl group, a substituted or unsubstituted C 2 -C 20 heteroaryl group or a substituted or unsubstituted C 7 -C 20 arylalkyl group;

Z is H, a substituted or unsubstituted C 1 -C 20 alkyl group, a C 1 -C 20 alkenyl group, a C 1 -C 20 alkynyl group, a C 1 -C 20 alkoxy group, a substituted or unsubstituted C 6 -C 20 aryl group, a substituted or unsubstituted C 2 -C 20 heteroaryl group or a substituted or unsubstituted C 7 -C 20 arylalkyl group; and

n is an integer of 2 to 150,

wherein the hydrophobic substituent is a substituted or unsubstituted C 1 -C 20 alkyl group, a substituted or unsubstituted C 6 -C 20 aryl group, a substituted or unsubstituted C 2 -C 20 heteroaryl group, or a substituted or unsubstituted C 7 -C 20 arylalkyl group,

wherein said hydrophobic substituent is included in an amount of 0.05 to 90 parts by weight based on total weight of said dispersant.

10. The ink composition of claim 9 , wherein said pigment particles and said dispersant form a particle/dispersant composite having diameters less than 250 nm.

11. The ink composition of claim 9 , wherein said pigment particles are organic or inorganic pigment particles.