Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
1999-09-30
2001-05-01
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031620, C106S031650, C106S031670
Reexamination Certificate
active
06224661
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a printing ink, and specifically a pigmented ink for marking porous media.
Ink-jet printing systems have been developed to provide high speed and high quality printing. These printing systems can provide precise printed images quietly, accurately, and at low cost. Drop on-demand systems (or pressure pulse systems) and thermal ink-jet systems are two ink-jet systems that use different methods to eject ink. In these ink-jet printing systems, liquid inks and solid, “hot melt” inks have been developed. “Hot melt” inks are inks which are typically in a solid form at room temperature, but which change to a liquid at an elevated temperature above the room temperature. Hot melt ink technology can be used to print images on many different types of media. The liquid inks are fluid at room temperature. Water-based inks employ water as a primary solvent and oil-based inks employ an organic solvent as a main solvent.
Because the liquid inks are fluid at room temperature, printed images from the inks tend to feather when printed on a porous medium, such as a corrugated container or Kraft paper, limiting the print density and clarity that can be achieved. Hot melt oil-based ink-jet ink compositions, which are solid at room temperature and melt upon heating, can produce smaller dot sizes and reduced smearing because the ink hardens rapidly. If the ink is not hard enough, smear may remain. It is important to maintain both the speed and the quality of printing by adjusting the properties of the printing ink. Dot size and edge definition can be adversely affected when printing on porous media, due in part to bleeding and smearing of the printed image.
SUMMARY OF THE INVENTION
The invention features an ink composition that is semi-solid. The ink composition can provide large dot size, low smear, fast drying, and sharp edge definition images when printed on a porous medium. The semi-solid ink composition has the combined properties of both liquid and solid inks.
In one aspect, the invention features an ink composition including a pigment, a mineral oil, a fatty acid, a low melting point wax, and a resin. The ink composition is semi-solid at room temperature. The semi-solid ink has the consistency of a slurry or paste. The pigment can include carbon black.
In another aspect, the invention features an ink composition, which is semi-solid at room temperature, including less than 10 weight percent of a pigment, at least 10 weight percent of a mineral oil, between about 30 and 70 weight percent of a fatty acid, between about 5 and 30 weight percent of a low melting point wax, less than 10 weight percent of a dispersing agent, and between about 1 and 15 weight percent of a resin.
In yet another aspect, the invention features a method of printing on a porous medium. The method includes delivering an ink composition including a pigment, a mineral oil, a fatty acid, a low melting point wax, and a resin, to a porous medium to form a mark. The mark has a sharp edge and being substantially free of smear.
The ink composition can be used to print a mark on a porous medium, such as a bar code printed on a corrugated container. Errors in reading a bar code can be encountered when the mark lacks density or edge definition. Density and edge definition errors can be encountered when the bar code is printed on a porous medium due to, for example, spreading and wicking of the ink on the substrate. Liquid oil-based inks typically have large dot size due to longer drying time which enables ink to spread on the substrate. In addition, because of spreading, edge definition of such inks is not very clear. The semi-solid ink according to the invention can produce bar codes on porous media with a large dot size that dry quickly and do not smear as readily as liquid inks before they dry. The improved sharpness of the bar code can lead to decreased reading failure errors.
REFERENCES:
patent: 4808227 (1989-02-01), Yuasa et al.
patent: 5350446 (1994-09-01), Lin et al.
patent: 6099631 (2000-08-01), Tregub et al.
Jolly Augusta
Tregub Inna
Faison Veronica F.
Hitachi Koki Imaging Solutions, Inc.
Klemanski Helene
Pillsbury & Winthrop LLP
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