Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-12-06
2002-04-02
Tran, Huan (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S082000, C347S100000
Reexamination Certificate
active
06364469
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an ink jet 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 electrophoto-graphic printers; dot matrix impact printers; thermal paper printers; film recorders; thermal wax printers; 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 ink jet 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 application and the only specific fluid used in the example is water.
Another feature of that patent 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 inkjet printing systems, such as the system employing asymmetric heating drop deflection, is the requirement of inks useful in ink jet 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 ink jet printer in which a continuous stream of ink jet ink is emitted from a nozzle that is responsive to digital data signals;
b) loading the printer with an ink jet recording element;
c) loading the printer with an ink jet ink comprising a thermally-responsive polymeric material; 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 in a thermally-steered, continuous ink jet print head which provides a greater difference in deflection angle.
DETAILED DESCRIPTION OF THE INVENTION
In a preferred embodiment of the invention, the thermally-responsive material comprises at least one kind of block copolymer with at least one block comprising poly(ethylene oxide) or PEO. In another preferred embodiment of the invention, the thermally-responsive material comprises a tri-block copolymer of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), or PEO-PPO-PEO dissolved in an aqueous solution. This material is sold commercially under the trademark Pluronic® (BASF Corp.).
In another preferred embodiment of the invention, the ink jet ink contains about 1-40% of the thermally-responsive material and about 0.5-5% of a dye.
The viscosity of the ink increases dramatically when heated from room temperature to about 80° C. In a preferred embodiment of the invention, ink jet ink containing the thermally-responsive material has a viscosity of less than 10 centipoise at 20° C. and a viscosity of more than 100 centipoise upon heating.
For example, a 15% by weight aqueous solution of Pluronic® P85 has a viscosity of about 4 centipoise at 22° C. and a viscosity of about 3000 centipoise at 80° C.
When the ink is heated asymmetrically at the orifice of the nozzle plate, the thermally-responsive material causes the jet of ink to deflect at a greater angle than would otherwise be obtained with ink without any such material. It is believed that this occurs because the localized heating of the material near one side of the orifice causes the thermally-responsive material to temporarily form a plug, which causes the material to flow around it and be deflected in the opposite direction.
The viscosity change of the formulated solutions in response to a temperature change is entirely reversible as the ink solution returns to the original viscosity when cooled down to its initial temperature.
In another preferred embodiment of the invention, the continuous stream of ink has a deflection angle greater than that of ink without any such thermally-responsive material.
As noted above, a continuous ink jet printer system that employs the method of asymmetric heating deflection is disclosed in the above-referred to U.S. Pat. No. 6,079,821. Following is a general description of the process employed. For specific details, please referred to the above-referred to 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 recycled by an ink recycling unit. The ink-recycling unit reconditions the ink and feeds it back to a reservoir. Such ink recycling units are well known in the art. The ink pressure
Hirsh Jeffrey I.
Sharma Ravi
Yang Zhihao
Cole Harold E.
Eastman Kodak Company
Tran Huan
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