Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-03-05
2003-11-18
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S493000, C106S031650, C106S031870
Reexamination Certificate
active
06648954
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a water-based pigment dispersion excellent in dispersibility in water and dispersion stability with the passage of time, a process for the production thereof, and an inkjet recording liquid excellent in light resistance, water resistance and hue after printing and excellent in ejection stability in a nozzle.
PRIOR ART OF THE INVENTION
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 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.
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, 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.
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 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 control the dispersion dispersibility by a trace quantity of the divalent metal ion which is immixed in a pigment-dispersing step.
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, 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
It is an object of the present invention to provide a 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.
According to the present invention, there is provided a water-based pigment dispersion comprising 100 parts by weight of a pigment, 3 to 30 parts by weight of a sulfonic acid group-containing pigment derivative and water, wherein the sulfonic acid group-containing pigment derivative has only one sulfonic acid group in a molecule of a pigment of which the type is the same as the type of the pigment to be dispersed, the sulfonic acid group forms at least one salt selected from the group consisting of ammonia salt, an organic amine salt and a salt in which at least 15% of the sulfonic acid group is liberated and the rest is a salt with monovalent metal, the content of metal ion having a valence of at least 2 in a solid matter of the above water-based pigment dispersion is 500 ppm or less, and the above pigment is dispersed in water according to electrostatic repulsion due to the sulfonic acid group-containing pigment derivative adsorbed on the particle surface of the pigment.
According to the present invention, there is further provided a water-based pigment dispersion according to the above invention, wherein the sulfonic acid group-containing pigment derivative includes a pigment derivative having only one sulfonic acid group in a molecule in an amount of at least 60% by weight based on the pigment to which a sulfonic acid group is to be introduced and a pigment derivative having at least two sulfonic acid groups in a molecule in an amount of 20% by weight or less.
According to the present invention, there is further provided an inkjet recording liquid containing the above water-based pigment dispersion.
According to the present invention, there is further provided a process for the production of a water-based pigment dispersion, comprising a step of introducing at least one sullonic acid group into a molecule by sufonating a pigment, a step of obtaining a sulfonic acid group-containing pigment derivative having only one sulfonic acid group by removing a pigment derivative having at least two sulfonic acid groups from a reaction product, and a step of dispersing the sulfonic acid group-containing pigment derivative obtained in the above step and a pigment having the same type pigment molecule structure as the structure of the above sulfonic acid group-containing pigment derivative in water.
DETAILED DESCRIPTION OF THE INVENTION
The pigment used in the present invention is selected from fused polycyclic pigments such as phthalocyanine pigments, quinacridone pigments, quinacridoneauinone pigments, isoindolinone pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, perylene pigments, perinone pigments, indigo pigments, thioindigo pigments, dioxadine pigments, anthraquinone pigments, pyranthrone pigments, anthanthrone pigments, flavanthrone pigments, indanthrone pigments and metal complex pigments, and organic pigments such as benzimidazolone pigments, insoluble azo pigments, fused azo pigments and soluble azo pigments.
The pigment of the present invention 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 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.
Specific examples of the pigment used in the present invention will be shown hereinafter according to C.I. pigment numbers.
The phthalocyanine pigments include C.I. pigment blue 15, 15:2, 15:3, 15:4, 15:5, 15:6 and 16 and C.I. pigment green 7 and 36.
The quinacridone pigments include C.I. pigment violet 19 and 42, C.I. pigment red 122, 192, 202, 206, 207 and 209, and C.I. pigment orange 48 and 49.
The isoindolinone pigments include C.I. pigment yellow 109, 110 and 173 and C.I. pigment orange 61.
Isoindoline pigments include C.I. pigment 139 and 185, C.I. pigment orange 66 and 69, C.I. pigment red 260 and C.I. pigment brown 38.
The quinophthalone pigments include C.I. pigmentyellow 138.
The diketopyrrolopyrrole pigments include C.I. pigment red 254, 255, 264 and 272 and C.I. pigment 71 and 73.
The benzimidazolone pigments include C.I. pigment yellow 120, 151, 154, 156, 175, 180, 181 and 194, C.I. pigment orange 36, 60, 62 and 72, C.I. pigment red 171, 175, 176, 185 and 208, C.I. pigment violet
Aida Seiji
Kaneda Jun
Negishi Takashi
Suzuki Eriko
Uemura Toshiyuki
Bell Mark L.
Faison Veronica F.
Toyo Ink Mfg. Co. Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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