(19) TZZ__Z_T (11) EP 1 146 094 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention (51) Int Cl.: of the grant of the patent: C09D 11/00 (2006.01) C09B 67/22 (2006.01) 16.11.2011 Bulletin 2011/46 (21) Application number: 01302034.2 (22) Date of filing: 06.03.2001 (54) Water-based pigment dispersion, use thereof and process for the production thereof Pigmentdispersion auf Wasserbasis, ihre Verwendung sowie Verfahren zu deren Herstellung Dispersion pigment à base d’eau, son utilisation et procédé de leur production (84) Designated Contracting States: • Suzuki, Eriko, DE FR GB c/o Toyo Ink MFG Co Ltd., Tokyo (JP) (30) Priority: 06.03.2000 JP 2000059754 • Negishi, Takashi, 21.03.2000 JP 2000077499 c/o Toyo Ink MFG Co Ltd., 09.08.2000 JP 2000241015 Tokyo (JP) 09.08.2000 JP 2000241016 • Aida, Seiji, 11.12.2000 JP 2000375362 c/o Toyo Ink MFG Co Ltd., 11.12.2000 JP 2000375363 Tokyo (JP) 22.01.2001 JP 2001012581 (74) Representative: Woods, Geoffrey Corlett (43) Date of publication of application: J.A. Kemp & Co. 17.10.2001 Bulletin 2001/42 14 South Square Gray’s Inn (73) Proprietor: TOYO INK MANUFACTURING CO., London LTD. WC1R 5JJ (GB) Tokyo (JP) (56) References cited: (72) Inventors: EP-A- 0 603 132 EP-A- 0 636 666 • Uemura, Toshiyuki, EP-A- 0 659 842 EP-A- 0 787 775 c/o Toyo Ink MFG Co Ltd., EP-A- 0 834 537 EP-A- 0 851 005 Tokyo (JP) DE-A- 4 321 693 US-A- 3 386 843 • Kaneda, Jun, US-A- 5 271 759 c/o Toyo Ink MFG Co Ltd., Tokyo (JP) Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 1 146 094 B1 Printed by Jouve, 75001 PARIS (FR) EP 1 146 094 B1 Description Field of the Invention 5 [0001] The present invention relates to a process for preparing a water-based pigment dispersion excellent in dis- persibility in water and dispersion stability with the passage of time. The pigment dispersion may be used in an inkjet recording liquid excellent in light resistance, water resistance and hue after printing and excellent in ejection stability in a nozzle. 10 Prior Art of the Invention [0002] In a water-based ink or a water-based coating composition, conventionally, a pigment is dispersed in water by the use of a surfactant or a dispersing resin. However, the surfactant has a problem of the occurrence of foams. When an anti-foaming agent is used in combination for preventing the occurrence of foams, a problem of a decrease in leveling 15 properties occurs. Further, the dispersing resin is effective for a pigment dispersion having a relatively high viscosity, but the dispersing resin exerts only a limited effect on a pigment dispersion having a low viscosity. [0003] There are known methods of dispersing a pigment in water by the use of a dye soluble in water or a pigment derivative. For example, JP-A-56-155261 and JP-A-56-155262 disclose a water-based pigment dispersion containing a pigment and a dye having the same color tone as the color tone of the above pigment. According to the above method, 20 part of the dye is adsorbed on the surface of the pigment, whereby the dispersion stability of the pigment in water is improved. However, when a coating composition or an ink is prepared therefrom, a problem of a color mixture or bleeding occurs since solubility of the dye in water is too large as compared with the affinity of the particle surfaces of the pigment. [0004] JP-A-10-36741 discloses a water-based pigment dispersion containing a phthalocyanine pigment and a phthalocyanine compound into which a carboxylic acid group is introduced. According to the above method, the problem 25 of bleeding is improved. However, a problem is still present in the dispersion stability of a pigment. JP-A-11-49974 discloses a water-based pigment dispersion comprising a pigment and a pigment derivative into which a sulfonic acid group bonding to an inorganic ion is introduced. According to the above method, the dispersion stability of the pigment is secured due to the electrostatic repulsion of divalent metal ion forming a salt with the sulfonic acid group of the pigment derivative integrated with the pigment. However, it is difficult in view of production technology to 30 control the dispersion dispersibility by a trace quantity of the divalent metal ion which is immixed in a pigment-dispersing step. EP 0 787 775 discloses water-dispersible phthalocyanine pigment formulations which are mixtures of conditioned metal phthalocyanine pigment and a water-insoluble sulfonated phthalocyanine. EP 0 636 666 discloses pigment preparations with at least one organic pigment and at least one perylene derivative. 35 US 5 271 759 discloses pigment compositions comprising a) at least one organic pigment; b) 0.05 to 10 % by weight of a modified organic pigment; and c) 0.05 to 10 % by weight of a polymeric ammonium salt of molecular weight 500 to 2,500,000 based on the pigment of a) and which is soluble in water or a lower alkanol. EP 0 851 005 discloses an agglomerated pigment comprising (1) an organic pigment; (2) a sulphonated organic pigment; (3)univalent inorganic counter ions bonded to sulphonic groups of (2); and (4) bivalent or higher inorganic counter ions 40 bonded to sulphonic groups of (2). EP 0 659 842 discloses a pigment composition comprising an organic pigment and a dioxazine pigment derivative represented in the form of a free acid. [0005] Concerning an inkjet recording liquid, the diameter of a printer nozzle decreases with an increase in the resolution of a printer. It is therefore required to decrease the diameter of pigment particles so as to form fine particles. However, 45 when an inkjet recording liquid contains a pigment, it is difficult to satisfy requirements for an inkjet recording liquid such as ejection properties in a nozzle, re-solubility (dispersibility) and color development after printing, at the same time. Summary of the Invention 50 [0006] It is an object of the present invention to provide a process for preparing water-based pigment dispersion excellent in dispersibility in water and stability in storage with the passage of time and a process for the production thereof. It is another object of the present invention to provide a pigment type inkjet recording liquid which is excellent in ejection stability in a nozzle when used as an inkjet recording liquid and has a sufficient color reproduction range when used for printing and which has compatible properties of excellent water resistance and excellent light resistance. 55 [0007] According to the present invention, there is provided a process for preparing an aqueous pigment dispersion comprising 3 to 30 parts by weight of a sulphonic acid-group containing derivative of a pigment and 100 parts by weight of a pigment which is the same pigment type as the derivative, wherein at least part of the pigment derivative is present, in the dispersion, in the form of a sulfonic acid salt selected from an ammonium salt, an organic amine salt and a salt 2 EP 1 146 094 B1 with a monovalent metal, provided that at least 15% of the sulphonic acid groups do not form a salt with the monovalent metal, and wherein the dispersion contains 500 ppm or less of solid metal ions having a valence of at least 2, which process comprises: 5 (I) (a) sulphonating a fused polycyclic pigment to introduce thereon at least one sulfonic acid group and treating the thus obtained reaction product by removing pigment derivatives having at least two sulfonic acid groups from the reaction product; or 10 (b) coupling a base component and a coupling component wherein either the base component or the coupling component has one sulfonic acid group, to produce an azo pigment derivative or a benzimidozolone pigment derivative having one sulfonic acid group in each molecule; 15 (II) dispersing in water (i) the thus obtained pigment derivative and (ii) a pigment of the same type as the pigment derivative in (i). The aqueous pigment dispersion produced by the process of the invention may be used in an inkjet recording liquid. 20 Detailed description of the Invention [0008] The pigment used in the present invention is selected from fused polycyclic pigments such as phthalocyanine pigments, quinacridone pigments, quinacridonequinone pigments, isoindolinone pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, perylene pigments, perinone pigments, indigo pigments, thioindigo pigments, dioxadine 25 pigments, anthraquinone pigments, pyranthrone pigments, anthanthrone pigments, flavanthrone pigments, indanthrone pigments and metal complex pigments, and organic pigments such as benzimidazolone pigments, insoluble azo pig- ments, fused azo pigments and soluble azc pigments. [0009] The pigment includes a compound having a substitute in an unselective substitutable position of a pigment molecule skeleton which forms any one of the above pigments. The above substitute includes lower alkyl groups such 30 as methyl and ethyl, lower alkoxy groups such as methoxy and ethoxy, halogen elements such as chlorine and bromine, a halogen-substituted alkyl group, a carboxylate group, an acetyl group and a hydroxyl group. [0010] Specific examples of the pigment used in the present invention will be shown hereinafter according to C.I. pigment numbers.