Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2000-01-28
2002-07-23
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031860, C106S031670, C106S031350
Reexamination Certificate
active
06423127
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a water based ink for a ball point pen, more specifically to an ink for a shear thinning water based ink-filled ball point pen having advantages of a ball point pen using an oil based ink, that is, a pseudo-plastic water based ink for a ball point pen.
BACKGROUND ART
In general, inks for a ball point pen have so far been classified into a low-viscosity, water based ink for a ball point pen which contains a solvent comprising a water based solvent such as water and has an ink viscosity of 10 mPa·s or less and an oil based ink which contains a solvent comprising an oil based solvent such as a mineral oil, a polyhydric alcohol, a fatty acid and cellosolve and has an ink viscosity of 1000 to 20000 mPa·s.
A ball point pen using an oil based ink for a ball point pen has such structure that the ink adhered on a ball through an ink reservoir having a small diameter is transferred onto a paper surface by rotation of the ball and only the transferred portion of the ink is fed again from the reservoir to the ball.
A ball point pen using a water based ink for a ball point pen has such structure that the ink is fed to a ball surface and a paper surface by virtue of capillary action of a feed prepared by binding fine fibers.
While the water based ink for a ball point pen and the oil based ink for a ball point pen described above each have excellent advantages, they have various problems as well. For example, in the water based ink for a ball point pen, capillary action is used in a principle of feeding the ink because of a low viscosity thereof, wherein a simple contact of the tip portion of the ball point pen with paper allows the capillary action to be exerted on the contact point thereof to feed the ink, and fine lines can be written on a paper surface without applying so much writing pressure, so that splitting, starving and blobbing scarcely take place. On the other hand, loading the ink directly into the ink reservoir allows the ink to leak due to vibration, impact and a temperature rise in the open air to make the amount of the ink to be fed to the ball unstable, so that the ball point pen requires complicated structure having a feed prepared by binding fine fibers and has the problem that it is difficult to observe the amount of the ink.
On the other hand, an oil based ink for a ball point pen is characterized by that because of a high viscosity thereof, blobbing of the ink from the pen tip can be prevented and the ink can be stored directly in the ink reservoir having a small diameter, so that the structure of the ball point pen can be simplified and that the amount of the ink can be observed by using a transparent material for the ink reservoir. However, there are involved the problems that since the ink is transferred only on a paper surface contacted with the rotating ball, splitting and starving are liable to be caused if the ball rotates unstably and that since the ink hardly penetrates into a paper surface, blobbing, which causes stain with the untransferred ink, is apt to be caused.
In recent years, in order to solve such problems, found in several cases are water based inks for a ball point pen in which a gelatinizer and a water soluble paste are added to impart a specific viscosity characteristic to the ink (hereinafter referred to as a pseudo-plastic water based ink for a ball point pen).
A ball point pen using this pseudo-plastic water based ink for a ball point pen is reduced in an ink viscosity by shear force which is applied to the ink by rotation of the ball at the tip point when writing and can write as smoothly as a ball point pen using a water based ink and draw fine lines on a paper surface. Further, blobbing of the ink from the pen point can be prevented because the ink has a high viscosity when the pen is not used for writing. In addition, the ink can be stored directly into the ink reservoir, so that the structure of the pen can be simplified, and the use of a transparent material for the ink reservoir makes it possible to observe the amount of the ink. Thus, the use of the pseudo-plastic water based ink for a ball point pen enable to provide a writing instrument having both characteristics of a ball point pen using a water based ink and a ball point pen using an oil based ink.
When producing this pseudo-plastic water base ink for ball point pen, a viscosity-controlling agent has so far had to be blended as an essential component for ink materials. The viscosity-controlling agent is added in order to impart pseudo-plasticity to the ink, and it is proposed to add, for example, polyacrylic acid salts, cross-linking type acrylic acid polymers, salts of a styrene-acrylic acid copolymer, salts of a styrene-maleic acid copolymer, nonionic polymers such as polyvinylpyrrolidone and polyethylene glycol, and polysaccharides such as xanthan gum, guar gum, casein, gum arabic, gelatin, carrageenan, alginic acid, tragacanth gum and locust bean gum.
However, these viscosity-controlling agents (thickeners) have caused the problems that they have scattering in the capability of providing a shear thinning property depending on a lot to exert an influence on the writing property and they are inferior in affinity with some coloring materials to cause a change in the viscosity with heating and aging and deteriorate the performances of the ball point pen and that since various materials such as a surfactant, an organic solvent, a dispersant resin for a pigment in addition to these viscosity-controlling agents are compounded depending on the kinds of inks, they cannot be blended optionally.
Thus, the present invention has been made in order to solve the problems described above, and an object thereof is to provide a pseudo-plastic water based ink for a ball point pen which causes less scattering in a viscosity depending on a production lot and has good stability with the passage of time whatever coloring materials are used and which provides a good writing feeling and is excellent in cap-off resistance.
DISCLOSURE OF THE INVENTION
Intensive researches continued by the present inventors in order to achieve the object described above have resulted in solving the conventional problems described above and coming to complete the present invention.
That is, a pseudo-plastic water based ink for a ball point pen according to the present invention comprises at least a colorant, water and a polyglycerin isostearic acid ester represented by the following Formula (1):
wherein n represents an integer of 1 to 8; R
1
to R
4
each independently and R
5
's, which may be the same or different, represent an isostearoyl group or a hydrogen atom; and the number of the isostearoyl group is 1 to 4.
Further, the ink described above has a viscosity of 100 to 4000 mPa·s at a shearing speed of 3.84 s
−1
.
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the respective components used in the pseudo-plastic water based ink for a ball point pen according to the present invention shall be explained.
In the present invention, the polyglycerin isostearic acid ester added to the pseudo-plastic water based ink for a ball point pen is represented by the Formula (1) described above. In the formula, n is an integer of 1 to 8, preferably 3 to 6 and R
1
to R
4
each represent independently an isostearoyl group or a hydrogen atom, and R
5
's, which may be the same or different, represent an isostearoyl group or a hydrogen atom. Further, the number of the isostearoyl group is 1 to 4, preferably 1 to 2.
The polyglycerin isostearic acid ester used in the present invention is excellent in lubricity, provides a shear thinning property and has a vaporization-inhibiting effect, so that it can be used as a substitutive material for each of polar solvents, lubricants and viscosity-controlling agents out of conventional ink materials. In particular, when it is used as a substitutive material for a viscosity-controlling agent, it does not exert an influence which originates in its having scattering in capability of providing a shear thinning property depending a lot o
Miyamoto Masaru
Miyazaki Shigeru
Takeuchi Yoji
Faison Veronica F.
Klemanski Helene
Mitsubishi Kabushiki Kaisha
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