Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2002-09-06
2004-09-07
Bell, Mark L. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031280, C106S476000
Reexamination Certificate
active
06786958
ABSTRACT:
TECHNICAL FIELD
1. Field of the Invention
The present invention relates to an oil based ink for a ball-point pen, specifically to an oil based ink for a ball-point pen in which an alcohol-soluble dye is used in combination with carbon black as a coloring material and which is excellent in stability with the passage of time.
2. Background Art
An oil based ink for a ball-point pen in which an oil-soluble dye is used in combination with carbon black is disclosed in Japanese Patent Application Laid-Open No. Hei 11-293174.
However, carbon black is no more than being described in the examples in this official gazette, and it is understood as if carbon blacks of all grades can be used. In many cases, however, when carbon blacks are used for an oil based ink for a ball-point pen, caused are the problems in that the ink is short of stability with the passage of time and that when the ball-point pen is used for a long time, the ink discharge amount is reduced to a large extent or on the contrary, it grows large in a certain case.
On the other hand, the advantage that an alcohol-soluble dye is used in combination with carbon black resides in the point that problems which are difficult to overrcome by themselves alone can be solved by making best use of the merits thereof each other. For example, if only an alcohol-soluble dye is used, drawn lines are a little inferior in fastness such that the lines drawn on paper are eluted or decolored by alcohol base solvents (alcohol resistance) or oxidation-reduction agents (chemical resistance) or that when exposed to sunlight, they are faded or decolored in a short time (light fastness). Accordingly, in order to obtain good drawn line fastness, particularly good light resistance, a metal-containing dye containing chromium, which is a heavy metal, in a dye skeleton has to be used in a large amount, so that likely to be caused is an environmental problem such as leaking of chromium, though a trace amount, into the environment due to incineration treatment.
Further, a Nigrosine base dye is available as a black dye having very high fastness, but this dye has a peculiar odor, and therefore there is a problem in that it is unpleasantly felt for some users in writing.
In contrast with this, when only carbon black is added to an ink in an amount sufficient for obtaining a practically satisfactory drawn line density, it is difficult in practice to industrially produce a carbon black dispersion having a high concentration. The ink is inferior in stability with the passage of time and falls into an unwritable state in a very short period of time, and it has a problem in cost. Further, when priority is put on stability with the passage of time, a sufficiently large amount of carbon black can not be contained in an ink, so that the drawn lines are light and the ink does not stand practical use.
In light of the problems described above, the present invention is intended for solving them, and an object thereof is to provide an oil based ink for a ball-point pen which is excellent in stability with the passage of time in a combined use system of an alcohol-soluble dye and carbon black and which has less change in a discharge amount when a ball-point pen is used for a long time.
DISCLOSURE OF THE INVENTION
Intensive researches repeated by the present inventors in order to solve the problems described above have resulted in finding that an ink is excellent in stability with the passage of time when carbon black used has a DBP oil absorption of 80 cc/100 g or less and that a change in the discharge amount in using a ball-point pen for a long time is smaller when it has a particle diameter of 30 m&mgr; or less, and thus the present invention has come to be completed. Further, it has been found that if carbon black contained in the ink has a content of 1 to 15 mass %, the sufficiently high fastness is obtained and the stability with the passage of time is much more improved and that a change in the discharge amount caused when the ball-point pen is used for a long time is less.
That is, the present invention comprises:
(1) an oil based ink for a ball-point pen comprising at least an alcohol-soluble dye, carbon black, a resin and an organic solvent, wherein the carbon black described above has a DBP oil absorption of 80 cc/100 g or less,
(2) the oil based ink for a ball-point pen as described in the above item (1), wherein the carbon black has a particle diameter of 30 m&mgr; or less, and
(3) the oil based ink for a ball-point pen as described in the above item (1) or (2), wherein the carbon black has a content of 1 to 15 mass % based on the total amount of the ink.
The oil based ink for a ball-point pen according to the present invention can provide an oil based ink composition for a ball-point pen which is excellent in stability with the passage of time and which has less change in a discharge amount in use of a ball-point pen by regulating the characteristics of carbon black used.
BEST MODE FOR CARRYING OUT THE INVENTION
The embodiment of the present invention shall be explained below in details.
The DBP oil absorption of carbon black described in the present invention means a volume (cc) of dibutyl phthalate (DBP) which is adsorbed on 100 g of carbon black, and it shows primarily a structure (three-dimensional state of an aggregate of primary particles) of carbon black.
The particle diameter of carbon black means an average value of diameters of primary particles of carbon black which is measured by magnifying under an electron microscope.
In the present invention, it is not sure why the excellent stability with the passage of time is obtained when carbon black having a DBP oil absorption of 80 cc/100 g or less, preferably 80 cc/100 g to 40 cc/100 g is used unlike other carbon blacks. However, carbon black having a DBP oil absorption exceeding 80 cc/100 g exhibits a higher viscosity when dispersed because of a larger structure thereof, and a required amount of a binder grows larger as well. This is considered to be a factor for deteriorating the stability with the passage of time.
It is not certain either why when carbon black having a particle diameter of 30 m&mgr; or less is used, a change in the discharge amount caused when a ball-point pen is used for a long time is small. However, when hard particles such as carbon black are present in an ink, they work as if they are abrasive particles in a tip in writing, whereby the tip is abraded in an inside thereof, and the respective parts cause a dimensional change to a large extent as compared with the original. This causes a change such as a reduction or an increase in the discharge amount in a certain case, and it is considered that when carbon black has a particle diameter of 30 m&mgr; or less, it is sufficiently small as an abrasive particle and therefore provides less abrasion, so that a large dimensional change is not caused. As a result, it is considered that a large change in the discharge amount is not observed even when the ball-point pen is used for a long time. Further, selection of carbon black having a BET specific surface area of 100 m
2
/g or less among these carbon blacks makes it possible to readily control a viscosity of the ink.
The alcohol-soluble dye used in the present invention includes Aizen Spilon Yellow C-2GH, Aizen Spilon Yellow C-GNH, Aizen Spilon Red C-GH, Aizen Spilon Red C-BH, Aizen Spilon Violet C-RH, Aizen Spilon Blue C-RH, Aizen S.B.N. Blue 701, S. B. N. Yellow 530, S. B. N. Violet 510, Valifast Yellow 1110, Valifast Yellow 3150, Valifast Violet 1701, Valifast Violet 1702 and Valifast Red 1360.
These alcohol-soluble dyes each may be used alone or in a mixture of two or more kinds thereof. These alcohol-soluble dyes are added preferably in a range of 5 to 50 mass %, preferably 15 to 40 mass % based on the total mass of the ink composition. If the blending amount is less than 5 mass %, the drawn line density becomes light. On the other hand, if it exceeds 50 mass %, an adverse effect is exerted on the other blended components.
Carbon black used for the ink composition of the present i
Kobayashi Kyoko
Morita Masaaki
Suzuki Susumu
Takayanagi Toshiaki
Bell Mark L.
Burns Doane Swecker & Mathis L.L.P.
Faison Veronica F.
Mitsubishi Pencil Kabushiki Kaisha
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