Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2000-01-18
2001-12-04
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031690, C106S031860, C106S031650, C106S031700
Reexamination Certificate
active
06325845
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an aqueous ink for ball point pens and more particularly to an aqueous ink for ball point pens that prevents a separation of pigment particles in a high viscosity liquid of polysaccharide for a long period.
PRIOR ART
Conventionally, various aqueous ink compositions for ball point pens comprising a colorant, a polysaccharide and water are disclosed (Japan Unexamined Patent Publication No.59-74175, No.2-279777, No.4-214782, No.6-88050, No.8-151547, No.11-29734, No.11-80629, No.11-130998). These aqueous ink compositions maintain their high viscosity at rest, however once applied to writing, they exhibit low viscosity and a good writing characteristic thanks to a shear force generated by the rotation of a ball.
However, these conventional aqueous inks do not have sufficient stability for a long-term storage. Specifically, when used for a long time, an aqueous ink for ball point pens containing a coloring pigment as a coloring agent often separates to in a low viscosity component including coloring pigment and the other high viscosity component inside an ink container. As a result, when a ball point pen containing such an ink is allowed to stand with its pen tip oriented downward, the low viscosity components precipitate to the pen tip and leak from the pen tip. When such a ball point pen is applied to writing, a writing characteristic deteriorates because of an excess ink flow and the writing portion dries too slowly. Further, the low viscosity components include an excess amount of the coloring pigment and hence, the writing portion will exhibit an excess change in its tint and will have a concentrated dark color.
It generally has been considered that the above-mentioned inconvenience is caused by the coagulation of pigment particles whose uniform dispersion is destroyed. For example, Japan Unexamined Patent Publication No.6-8805 tried to improve stability in long-term storage of an ink composition by adding succinoglucan as a polysaccharide in order to prevent the coagulation of the pigment particles (the enlargement of the particle diameter) and maintain the uniform dispersion of pigment particles. However, such an ink, actually, separation of the low viscosity components including an excess amount of the coloring pigment tends to occur inside of an ink container and further segregation of color causes different shades in a writing portion as mentioned above. In an extreme case, when the pen is used for a long period, a concentrated pigment solution flows out from a pen tip.
Particularly, with an aqueous ink composition for ball point pens comprising a polysaccharide such as rhamzan gum, weran gum, xanthan gum and succinoglucan, a water-soluble organic solvent and water, and further including an aluminum powder pigment together with a coloring pigment as a coloring agent, the coloring pigment tends to separate even from the metallic powder pigment with time, besides the above-mentioned separation. Then, it develops to the segregation of color. In an extreme case, when the pen is used for a long time, the high viscosity components including an aluminum powder pigment and the low viscosity component including a coloring pigment could develop to an upper liquid layer and a lower liquid layer respectively. With these separations, the precipitation of the coloring pigment is visible even when the pen is laid for on its side storage and the outward appearance deteriorates remarkably. When the ink with such separation which has been stored with its pen tip oriented downward for a long time, is applied to writing, an expected metallic tone cannot be obtained in its writing potion because the concentrated coloring pigment solution without aluminum metallic powder pigment flows out from the pen tip at first.
Accordingly, one of the objects of the present invention is to provide an aqueous ink for ball point pens with excellent stability against long-term storage which prevents separation of the coloring pigment, restrains segregation providing the writing portion of uniform color without any different shades and prevents leakage or excess flow of the ink.
Another object of the present invention is to provide an aqueous ink for ball point pens with excellent stability to long-term storage, which prevents separation of the coloring pigment from the other components and the metallic powder pigment even after being used for a long period and restrains segregation so that its writing portion has a metallic tone and uniform color without any different shades and further prevents leakage or excess flow of the ink.
SUMMARY OF THE INVENTION
As a result of intensive study to achieve the above-mentioned objects, the present inventor found that an aqueous ink comprising a coloring pigment, a water-soluble organic solvent, water and a polysaccharide, in which pigment particles of said coloring pigment gather to form a spotted agglomerate phase, does not cause separation between the bulk phase of the coloring pigment and the other components.
The present invention relates to an aqueous ink for ball point pens comprising a coloring pigment, a water-soluble organic solvent, water and a polysaccharide wherein pigment particles of a coloring pigment gather and form a spotted agglomerate phase.
Accordingly, even after being used for a long time, the separated liquid of the concentrated coloring pigments does not appear in the ink remaining inside of an ink container of a ball point pen.
When an ink is prepared by mixing a phase containing a conventional coloring pigment dispersed beforehand together with a vehicle phase containing a solution of a polysaccharide (the phase other than that containing the coloring pigment), both phases seem to be mixed uniformly just after the preparation. However, the phase containing the coloring pigment is not compatible with the polysaccharide and both phases would separate with time.
In the present invention, the agglomerate phase of the coloring pigment is formed beforehand and that makes a contact area between the phase containing the coloring pigment (hereinafter, called a pigment phase) and the vehicle phase (the phase containing components other than coloring pigment) smaller. Therefore their compatibility is improved and the separation between the both phases can be prevented.
Further, the inventor found that an aqueous ink for ball point pens comprising a coloring pigment, a metallic powder pigment, a water-soluble organic solvent, water and a polysaccharide, wherein pigment particles of both said coloring pigment and said metallic powder pigment gather to the same pigment phase and form a complex agglomerate phase, different shade of color or disappearance of color in a writing portion can be prevented.
That is, a further embodiment of the present invention is an aqueous ink for ball point pens comprising a coloring pigment, a metallic powder pigment, a water-soluble organic solvent, water and a polysaccharide wherein pigment particles of both said coloring pigment and said metallic powder pigment gather to the same pigment phase to form the spotted complex agglomerate phase. With such an ink, the liquid separation between the coloring pigment and the metallic powder pigment does not occur even after the ball point pen is used for a long time. Further, pigment particles of both the coloring pigment and the metallic powder pigment gather to the same pigment phase and form the complex agglomerate phase as mentioned above, and the metallic writing portion with the color of the coloring pigment can be obtained.
The preferable binding medium for the gathering of the pigment particles that forms the mentioned agglomerate phase or complex agglomerate phase is a water-soluble polymer. The agglomerate phase or the complex agglomerate phase of the pigment particles in the present invention indicates an agglomeration wherein the pigment particles gather with the effect of the i.e. water-soluble polymer as a binding medium between the particles, and not a coagulation wherein the pigment particles coagulate directly.
In
Inoue Hiroshi
Kurihara Norimasa
Faison Veronica F.
Klemanski Helene
Merchant & Gould P.C.
Sakura Color Products Corporation
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