Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
1999-06-10
2002-09-03
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031580, C106S031720, C106S031860
Reexamination Certificate
active
06444019
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention generally relates to ink jet printing and an ink jet ink composition, and in particular, to ink jet printing with a drop-on-demand (DOD) printer and an ink composition suitable therefor.
BACKGROUND OF THE INVENTION
Ink jet printing is a well-known technique by which printing is accomplished without contact between the printing device and the substrate on which the printed characters are deposited. Briefly described, ink jet printing involves the technique of projecting a stream of ink droplets to a surface and controlling the direction of the stream so that the droplets are caused to form the desired printed image on that surface. This technique of noncontact printing is well suited for application of characters onto a variety of surfaces including porous and non-porous surfaces.
Reviews of various aspects of ink jet printing can be found in these publications: Kuhn et al.,
Scientific American,
April, 1979, 162-178; and Keeling,
Phys. Technol.,
12(5), 196-303 (1981). Various ink jet apparatuses are described in the following U.S. Pat. Nos.: 3,060,429, 3,298,030, 3,373,437, 3,416,153, and 3,673,601.
In general, an ink jet ink composition must meet certain rigid requirements to be useful in ink jet printing operations. These relate to viscosity, resistivity, solubility, compatibility of components, and wettability of the substrate. Further, the ink must be quick-drying and smear resistant, must be capable of passing through the ink jet nozzle without clogging, and must permit rapid cleanup of the machine components with minimum effort.
There are at present two types of ink jet printers, the continuous flow ink jet printers and the DOD ink jet printers. In continuous ink jet printers, ink droplets are continuously emitted from a nozzle without regard as to whether or not a printing operation is performed. The ink droplets are charged in accordance with print information data and are deflected in response to the amount of charge carried thereon as they pass through a constant high-voltage field. The thus deflected ink droplets are deposited onto a recording surface while the unused ink droplets are directed towards a beam gutter for recirculation. Since the ink droplets flow continuously through the nozzle, the risk of ink drying out and clogging the nozzle is minimal.
In DOD ink jet printers, the print head comprises a number of individual ink channels. When a certain character is to be generated on a recording surface, ink droplets are issued from some of these channels. Thus, only those ink droplets that form the character are emitted. Further, the operation of the ink jet printer can be interrupted for varying periods of time, for example, to suit the operator or factory schedule, which can be, e.g., a few hours, overnight, a week end, or longer. Since there is no continuous flow of ink droplets through the nozzles, certain problems arise from the ink drying out in the nozzle orifice during the non-printing intervals due to the ink's exposure to air. The ink drying out results in the precipitation of solids, such as the resins and colorants, at the nozzle orifice and leads to nozzle clogging. A normal or routine maintenance procedure such as purging, e.g., by applying a slight pressure to the ink cartridge to expel a small amount of the ink from the clogged nozzles, is of little or no help as the nozzles can become permanently or irreversibly clogged.
Solutions have been proposed to alleviate this problem although a satisfactory solution is lacking. For example, ink jet ink compositions have been prepared which include large amounts of one or more humectants or high boiling solvents such as glycols to reduce evaporative loss at the nozzle orifice. These inks, however, are not suitable for printing on non-porous substrates as they take excessively long times to dry on such substrates and are thus unsuitable for achieving rapid printing.
U.S. Pat. NO. 4,228,442 discloses a modified printer. Thus, the '442 patent discloses an ink jet print head that includes a chamber that is placed adjacent to the nozzle orifice and containing the liquid ink solvent therein. An absorbent material member is positioned to have one end thereof on the chamber-containing solvent and is directed to an area which is in front of the nozzle to carry fluid or vapor therearound for the purpose of providing a solvent enriched atmosphere at the nozzle orifice to prevent drying of the ink. This approach cannot, of course, be practiced with existing printers without first modifying them.
U.S. Pat. No. 5,781,214 discloses a method of preventing clogging of the nozzles by the use of an ink composition which is made up of (a) a volatile organic solvent, (b) one or more hygroscopic and low volatile components selected from the group consisting of polyhydric alcohols, glycol ethers, ethanolamines, and amides, calcium chloride, and magnesium chloride, and (c) a colorant. The ink composition may also include water and a binder resin as additional ingredients. This method relies for its operation on the moisture present in the surrounding atmosphere. According to the patent, the hygroscopic salt absorbs the atmospheric moisture which, in turn, helps to keep the salt in solution at the nozzle tip and acts to block or hinder further evaporation of the solvent. This method has its limitations. For example, since this method relies on the conditions existing in the surrounding atmosphere, the non-clogging time interval would be dependent upon the atmospheric conditions. Thus, in a dry or hot atmospheric condition, the non-clogging time interval could be significantly diminished.
The foregoing shows that there exists a need for an ink jet ink composition that is suitable for use in DOD printers. There further exists a need for an ink jet ink composition that permits operation of the ink jet printer without nozzle clogging with extended non-printing intervals. There further exists a need for an ink jet ink composition that provides good print quality and short print drying time when printed on non-porous substrates. There further exists a need for a jet ink composition that is suitable for printing on plastics, metal, and glass substrates images that have good adhesion.
These and other advantages of the present invention will be apparent from the detailed description of the preferred embodiments of the invention set forth below.
BRIEF SUMMARY OF THE INVENTION
Many of the foregoing needs have been fulfilled by the present invention which provides a jet ink composition comprising a volatile organic solvent, an oil, one or more binder resins, and a colorant. The present invention further provides a process for jet ink printing onto a substrate comprising projecting a stream of ink droplets of the ink composition of the present invention to the substrate and controlling the direction of the droplets so that the droplets form the desired printed image on the substrate.
The present invention provides a method for reducing nozzle clogging that arises due to the evaporation of the volatile solvent from the ink composition at the nozzle orifice during non-printing intervals. Accordingly, the ink composition of the present invention includes an oil that forms a continuous oil phase or a boundary layer at the nozzle orifice during non-printing intervals. The boundary layer prevents further evaporation of the volatile solvent from the ink composition and reduces formation of solids and the attendant nozzle clogging.
While the invention has been described and disclosed below in connection with certain preferred embodiments and procedures, it is not intended to limit the invention to those specific embodiments. Rather it is intended to cover all such alternative embodiments and modifications as fall within the spirit and scope of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention provides a jet ink composition suitable for use in ink jet printers and having one or more of the following advantages, namely, the ink is fast drying when
Dong Qiao Qiao
Wang Xiaomang
Woodcock Carrie
Xiao Fengfei
Zou Wan Kang
Faison Veronica F.
Klemanski Helene
Leydig , Voit & Mayer, Ltd.
Videojet Technologies Inc.
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