Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
1998-08-06
2001-06-26
Wu, David W. (Department: 1713)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031430, C106S031270, C106S031280, C106S031860, C528S212000, C528S271000
Reexamination Certificate
active
06251175
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink jet ink composition in general, and to an ink jet ink composition suitable for printing images on non-porous substrates with improved adhesion.
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, e.g., electronically, 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. Patents: 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. In addition, the jet ink composition should provide printed images that adhere well to the substrates, particularly non-porous substrates. Those of ordinary skill in the art know of challenges that non-porous substrates pose in achieving image adhesion.
Ink jet ink compositions have been disclosed. They generally contain an ink carrier, a binder resin, a colorant, and other optional additives. The carrier can be an aqueous or non-aqueous solvent. For jet printing on non-porous substrates such as glass, ceramics, metal or plastics, ink jet ink compositions have been prepared mostly using non-aqueous solvents.
Thus, ink jet inks for non-porous substrates are generally based on methanol and methyl ethyl ketone (MEK). These solvents offer fast drying jet inks and have the ability to dissolve or disperse binder resins and colorants. Additionally, these solvents have the ability to ionize conducting agents and thus provide good conductivity, especially for continuous ink jet printing operation. Thus, for example, U.S. Pat. No. 4,834,799 discloses a jet ink composition suitable for jet printing onto vinyl substrates which contain vinyl polymers and plasticizers. The composition is formulated to include a resin component having a pendant amino group such as a copolymer of methyl methacrylate and dimethylaminoethyl methacrylate, a dye, and a carrier. The carrier typically comprises a mixture of a lower alcohol such as methanol and a lower ketone such as MEK.
However, in view of the increasing public awareness and governmental regulations concerning the safety of MEK and methanol, it has become important to develop jet inks that do not contain a significant amount of MEK or methanol. To achieve this goal, ethanol based jet inks have been proposed. For example, UK Patent Application GB 2 286 402 discloses a jet ink for continuous ink jet printers containing ethanol as the liquid vehicle and a polyamide resin as the binder resin. Although ethanol based jet inks have served with some success, certain ethanol based inks do not dry fast enough for many ink jet applications due to the slow evaporation of ethanol.
Thus, there exists a need for a jet ink composition suitable for printing on non-porous substrates such as glass, plastic, metal, or ceramics, images with improved adhesion. There also exists a need for a jet ink composition that is substantially free of methanol and MEK. There further exists a need for a jet ink composition that dries fast enough for use in continuous jet ink printers. There further exists a need for an ethanol based jet ink composition that provides short drying times.
These and other objects of the present invention will be apparent from the detailed description of certain embodiments of the invention set forth below.
SUMMARY OF THE INVENTION
The foregoing needs have been fulfilled to a great extent by the present invention which provides a jet ink composition comprising an organic solvent, a colorant, and a hydroxyaromatic resin with its hydroxyaromatic units being linked to one another by linkages other than alkylene ether linkages. The images printed on non-porous substrates using the jet ink composition of the present invention have improved adhesion, e.g., improved rub resistance and tape peel resistance.
The present invention further provides a method of forming printed images on porous and non-porous surfaces using the ink composition of the present invention. In one aspect of the present the invention, the method comprises projecting a stream of droplets of the ink composition onto a surface and controlling the direction of the stream, e.g., electronically, so that the ink droplets form the desired printed image on the surface.
While the invention has been described and disclosed below in connection with certain 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 EMBODIMENTS
The present invention provides a jet ink composition comprising an ink carrier, a colorant, and a hydroxyaromatic resin. Preferably, the resin is free or substantially free of alkylene ether linkages. Thus, the hydroxyaromatic resin has hydroxyaromatic repeat units which are linked to one another, by linkages other than alkylene ether linkages. The jet ink composition of the present invention are free or substantially free of MEK and methanol and are suitable for printing images with improved adhesion on non-porous substrates such as glass, metals, ceramics, and plastics.
General Properties
In general, the jet ink composition of the present invention exhibits the following characteristics for use in ink jet printing systems: (1) a viscosity of from about 1.6 to about 7.0 centipoises (cps) at 25° C.; (2) an electrical resistivity of from about 50 to about 2000 ohm-cm; and (3) a sonic velocity of from about 1100 to about 1700 meters/second.
A detailed discussion of the ingredients and the characteristics of the inventive jet ink composition are set forth below.
Ink Carrier
Any suitable organic solvent can be used as the ink carrier. Suitable organic solvents include alcohols, esters, ketones, amides, ethers, and halides. Alcohols other than methanol and MEK are preferred solvents. Particular examples of preferred solvents include ethanol and acetone. Typically the carrier is present in an amount of from about 40% by weight to about 90% by weight, and preferably from about 60% by weight to about 85% by weight of the jet ink composition. A mixture of solvents can also be used. For example, a mixture of acetone and ethanol can be used. Preferably, the amount of acetone in the mixture is less than that of ethanol. Thus, acetone can be used in an amount of up to about 30% by weight and ethanol up to about 70% by weight, and preferably acetone can be used in an amount of up to about 25% by weight and ethanol up to about 75% of the solvent mixture. Small quantities of water can also be used in the carrier to provide the necessary electrical conductivity when using non-aqueous solvents as the jet ink carrier.
Colorant
The jet ink composition of the present invention comprises one or more colorants that impart the desired color to the printed message. Any dye, pigment, lake, or combinations thereof, that may be dissolved or dispersed in the ink composition can be used. Dyes are particular
Siddiqui Mohammed
Zhu Linfang
Choi Ling-Siu
Leydig , Voit & Mayer, Ltd.
Marconi Data Systems Inc.
Wu David W.
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