Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-12-21
2002-03-26
Tran, Huan (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S100000
Reexamination Certificate
active
06361156
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an inkjet printing process that utilizes aqueous inks in the method of asymmetric heating drop deflection.
BACKGROUND OF THE INVENTION
Ink jet printers are well known in the printing industry. Ink jet printers are just one of many different types of printing systems that have been developed which include laser electrophotographic printers; LED electrophotographic printers; dot matrix impact printers; thermal paper printers; film recorders; thermal wax printers; and dye diffusion thermal transfer printers. Ink jet printing has become recognized as a prominent contender in the digitally controlled, electronic printing arena because, e.g., of its non-impact, low-noise characteristics, its use of plain paper and its avoidance of toner transfers and fixing. However, there is an ongoing demand for improved digitally controlled printing systems that are able to produce high color images at a high speed and low cost using standard paper.
One such improvement is disclosed in U.S. Pat. No. 6,079,821, the disclosure of which is hereby incorporated by reference. That patent discloses an apparatus for controlling ink in a continuous inkjet printer that includes an ink delivery channel; a source of pressurized ink communicating with the ink delivery channel; a nozzle bore which opens into the ink delivery channel to establish a continuous flow of ink in a stream, the nozzle bore defining a nozzle bore perimeter; and a droplet generator which causes the stream to break up into a plurality of droplets at a position spaced from the ink stream generator. The droplet generator includes a heater having a selectively-actuated section associated with only a portion of the nozzle bore perimeter, whereby actuation of the heater section produces an asymmetric patent of heat to the stream to control the direction of the stream between a print direction and a non-print direction. However, there is no disclosure of any specific inks in this patent and the only specific fluid used in the example was water.
Another feature of that patent is a process for controlling ink in a continuous ink jet printer that includes establishing a continuous flow of ink in a stream which breaks up into a plurality of droplets at a position spaced from the ink stream generator, and asymmetrically applying heat to the stream before the position whereat the stream breaks up into droplets to thereby control the angle at which the ink deflects.
Along with the development of ink jet printing systems, such as the system employing asymmetric heating drop deflection, is the requirement of inks useful in inkjet printing. An ink composition must be capable of meeting very stringent criteria to be useful in ink jet printing. Such properties of major concern of the ink composition are viscosity, surface tension, pH, density, conductivity, adhesive characteristics, wetting characteristics, drying rate and shelf life.
It is an object of this invention to provide an ink jet printing process employing a particular ink useful in a thermally-steered, continuous ink jet print head which provides a greater difference in deflection angle.
SUMMARY OF THE INVENTION
This and other objects are achieved in accordance with the invention which comprises an ink jet printing process comprising the steps of;
a) providing an inkjet printer in which a continuous stream of inkjet ink is emitted from a nozzle that is responsive to digital data signals;
b) loading the printer with an inkjet recording element;
c) loading the printer with an aqueous ink jet ink comprising water, a dye, a humectant, an organic solvent and a deflection-enhancing additive comprising a diethanolamine (DEA) or 1-amino-2-propanol (AP); and
d) ejecting ink from a thermally-steered continuous ink jet print head onto one of the ink jet recording elements in response to the digital data signals.
By use of the process of the invention, ink jet prints are obtained using an ink containing a deflection-enhancing additive in a thermally-steered, continuous ink jet print head, wherein the continuous stream of ink has a deflection angle greater than that of ink without any such deflection-enhancing additive.
DETAILED DESCRIPTION OF THE INVENTION
In addition to the deflection-enhancing material, a humectant is employed in the inkjet compositions used in the invention to help prevent the ink from drying out or crusting in the orifices of the printhead. Examples of humectants which can be used include polyhydric alcohols, such as ethylene glycol, diethylene glycol (DEG), triethylene glycol, propylene glycol, tetraethylene glycol, polyethylene glycol, glycerol, 2-methyl-2,4-pentanediol, 2-ethyl-2-hydroxymethyl-1,3-propanediol (EHMP), 1,5 pentanediol, 1,2-hexanediol, 1,2,6-hexanetriol and thioglycol; lower alkyl mono- or di-ethers derived from alkylene glycols, such as ethylene glycol mono-methyl or mono-ethyl ether, diethylene glycol mono-methyl or mono-ethyl ether, propylene glycol mono-methyl or mono-ethyl ether, triethylene glycol mono-methyl or mono-ethyl ether, diethylene glycol di-methyl or di-ethyl ether, poly(ethylene glycol) monobutyl ether (PEGMBE), and diethylene glycol monobutylether (DEGMBE); nitrogen-containing compounds, such as urea, 2-pyrrolidinone, N-methyl-2-pyrrolidinone, and 1,3-dimethyl-2-imidazolidinone; and sulfur-containing compounds such as dimethyl sulfoxide and tetramethylene sulfone. In a preferred embodiment of the invention, the humectant is diethylene glycol monobutyl ether (DB) or 2-methyl-2,4-pentanediol (MP).
As noted above, the ink jet ink contains an organic solvent. In a preferred embodiment of the invention, the organic solvent is a glycol ether, such as dipropylene glycol monomethyl ether (DPM), tripropylene glycol monomethyl ether, propylene glycol monopropyl ether, propylene glycol monomethyl ether, ethylene glycol monobutyl ether, dipropylene glycol monopropyl ether, or diethylene glycol monomethyl ether.
When the ink is heated asymmetrically at the orifice of the nozzle plate, the deflection-enhancing additive causes the jet of ink to deflect at a greater angle than would otherwise be obtained with ink without any such material.
As noted above, a continuous ink jet printer system that employs the method of asymmetric heating deflection is disclosed in the above-referenced U.S. Pat. No. 6,079,821. Following is a general description of the process employed. For specific details, please referred to the above-referenced U.S. Pat. No. 6,079,821. The system includes an image source such as a scanner or computer which provides raster image data, outline image data in the form of a page description language, or other forms of digital image data. This image data is converted to half-toned bitmap image data by an image-processing unit that also stores the image data in memory. A plurality of heater control circuits read data from the image memory and applies time-varying electrical pulses to a set of nozzle heaters that are part of a print head. These pulses are applied at an appropriate time, and to the appropriate nozzle, so that drops formed from a continuous ink jet stream will form spots on a recording medium in the appropriate position designated by the data in the image memory.
Recording medium is moved relative to a print head by a recording medium transport system, which is electronically controlled by a recording medium transport control system, and which in turn is controlled by a micro-controller. In the case of page width print heads, it is most convenient to move a recording medium past a stationary print head. However, in the case of scanning print systems, it is usually most convenient to move the print head along one axis (the sub-scanning direction) and the recording medium along an orthogonal axis (the main scanning direction) in a relative raster motion.
Ink is contained in an ink reservoir under pressure. In the non-printing state, continuous ink jet drop streams are unable to reach a recording medium due to an ink gutter that blocks the stream and which may allow a portion of the ink to be recyc
Chwalek James M.
Garbacz Gregory J.
Hamilton-Winbush Vincent E.
Penner Thomas L.
Romano, Jr. Charles E.
Cole Harold E.
Tran Huan
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