Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
1999-12-21
2001-10-09
Green, Anthony J. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S498000, C524S100000, C544S187000, C544S188000
Reexamination Certificate
active
06299676
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
This invention relates to dispersants for organic pigments (hereinafter simply referred to as “pigments”), pigment dispersions and writing or recording pigment inks, and more specifically to pigment dispersants and also to pigment dispersions making use of the pigment dispersants, having excellent fluidity, dispersion stability, storage stability and the like and suited especially for the production of writing or recording pigment inks.
b) Description of the Related Art
Marking inks for use in writing instruments, which make use of bundled fiber tips or felt tips, have conventionally been made of resins, pigments and solvents, and as the pigments, dyes have been employed. As the solvents, ester or aromatic solvents have been used from the standpoint of solubility for the resins and also solubility for the dyes.
It is however desired to avoid use of aromatic solvents, because they give deleterious effects on the health of workers (organic solvent intoxication) and they themselves are air pollutants. Although there is a move toward water-based writing inks, solvent-based maker pens are still employed widely. This can be attributed to the excellent writing performance of solvent-based inks on plastic films such as polyethylene films and also to the superb drying characteristics of the solvent-based inks shortly after written on plastic films.
Ink-jet printing, on the other hand, is a digital printing controlled by a computer. Printing information signals are supplied to a printer directly from the computer, so that no plate-making is needed. Ink-jet printing is therefore suited particularly for the printing of various images in small numbers of copies, and recent advancements in ink-jet printers have made it possible to perform printing of a variety of highly-detailed large images.
Ink-jet printing inks are required to have low viscosity and excellent stability. There are organic-solvent-based inks making use of dyes, but as pigment-type inks, water-based inks are used because ink-jet printing inks making use of pigments involve technical difficulties. However, water-based inks contain, as vehicles, resins at extremely low concentrations so that good color developments are not available. Water-based inks are also accompanied by a problem of adhesion to plastic films. Under these circumstances, there is a strong desire for the development of alcohol-based ink-jet printing inks making use of pigments and assuring good color developments.
Incidentally, as is observed from paints and the like, the conventional technology expects much on the dispersing power of a resin for a pigment upon dispersing the pigment on a resin solution. When the dispersing power of the resin is insufficient for the pigment, a pigment dispersant (pigment treatment) (hereinafter simply referred to as “a pigment dispersant) has been employed. in general paints, sufficient dispersion of pigments is feasible with conventional dispersants.
Compared with paints, however, writing or recording pigment inks are required to have extremely low viscosity and in addition, to have an extremely high degree of dispersion of pigments. Despite these requirements, use of conventional resins and dispersants is unable to achieve sufficient dispersion of pigments or leads to changes in the viscosity of pigment dispersions along the passage of time due to desorption of the dispersant from the pigments and insufficient compatibility between the pigments and the resins, thereby making it extremely difficult to obtain pigment dispersions which meet the property and performance requirements.
If an alcoholic solvent such as ethanol can be used as a solvent in an organic-solvent-based pigment ink, deleterious effects on the health of users of writing instruments and people studying or working in the same environment as the users can be reduced, the problem of air pollution can be lessened owing to the avoidance of an organic solvent, and further, the problems of drying characteristics and wetting to plastic films, said problems being inherent to water-based inks, can also be eliminated. Moverover, alcoholic solvents are resources reproducible in the natural world so that use of such solvents is preferred. Nonetheless, with resins soluble in conventionally-known alcoholic solvents, it is still extremely difficult to obtain pigment inks satisfactory in the requirements for low viscosity, high dispersion and high dispersion stability even if dispersants are used.
SUMMARY OF THE INVENTION
An object of the present invention is therefore to provide a dispersant which is excellent in the dispersibility of pigments and permits production of a pigment dispersion excellent in the stability of viscosity. Another object of the present invention is to provide a pigment dispersion, writing ink or recording ink, which is using a pigment as a coloring matter, contains a resin—which is soluble in an organic solvent, especially an alcoholic solvent—in a sufficient. amount relative to the pigment, has a low viscosity, good pigment dispersibility and excellent viscosity stability, and gives less deleterious effects on the health of a user of a writing instrument or recording apparatus and people studying or working in the same environment as the user.
To achieve the above-described objects, the present invention provides an dispersant for organic pigments, comprising a compound represented by the following formula (I):
wherein X and X′ each independently represent a hydrogen atom, a hydroxyl group, an alkoxy group, a primary, secondary or tertiary amino group, or an acylamino group; Y represents an anthraquinonylamino, phenylamino or phenoxy group having a hydrogen atom, a hydroxyl group, an alkoxy group, a primary, secondary or tertiary amino group, or an acylamino group at the 4-position or 5-position thereof; A and B each independently represent an alkyl group, a cycloalkyl group or an aryl group, and at least one of A and B has at least one substituent group containing a basic nitrogen atom; and Z represents a hydrogen atom, a cyano group, a halogen atom, an alkyl group, an alkoxy group, a nitro group, a benzoylamino group or a 3-benzoyl group, and the 3-benzoyl group may be fused together with X to form an acridone ring; a pigment dispersion comprising an organic pigment, a dispersant, a film-forming resin and an organic solvent, wherein the dispersant is the above-described dispersant; a writing or recording pigment ink comprising the dispersion; and a writing instrument or recording apparatus comprising the ink (the pigment dispersion and the writing ink or recording ink will hereinafter be collectively called “the ink”).
The term “at least one substituent group containing a basic nitrogen atom” as used herein may mean a primary, secondary or tertiary amino group, a quaternary ammonium group or a pyridinium group, with a tertiary amino group being particularly preferred.
The dispersant according to the present invention is useful as a dispersant for a variety of conventionally-known pigments, especially as a dispersant for various pigments used as coloring matters in inks, various paints, various printing inks, various, pigment printing agents and synthetic resins. In particular, use of the dispersant according to the present invention by adding it as a dispersant to red, green yellow and purple inks makes it possible to stably produce low-viscosity inks and eventually to obtain excellent inks.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
The present invention will hereinafter be described in further detail based on certain preferred embodiments. Dispersants according to the present invention are useful as dispersants for a variety of conventionally-known pigments used as coloring matters in various paints, various printing inks, various pigment printing agents and synthetic resins. An especially useful application is an application as dispersants for pigments in inks. Accordingly, the present invention will hereinafter be described by taking inks as representative exam
Abe Yoshio
Fukuda Tetsuo
Nakamura Michiei
Okamoto Hisao
Saikatsu Hiroaki
Dainichiseika Color & Chemicals Mfg. Co. Ltd.
Green Anthony J.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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