Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2002-07-30
2003-12-30
Brooke, Michael S (Department: 2853)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C347S065000
Reexamination Certificate
active
06669336
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to ink jet printheads that have integral internal ink filters, and, more particularly, to thermal ink jet printheads that have filter structures that are fabricated inside the printheads using polymeric layers generally used for other purposes. More broadly, it applies to the formation of internal filtration structures for micro-fluidic devices, where the filtration occurs at a gap intentionally formed between features on two substrates when those two substrates are bonded together.
Thermal ink jet printing systems use thermal energy pulses generated by the heating elements in an ink jet printhead to produce momentary ink vapor bubbles on the heating elements which eject ink droplets from the printhead nozzles. One type of such a printhead has a plurality of parallel ink channels, each communicating at one end with an ink reservoir and having opposing open ends that serve as nozzles in the droplet emitting face of the printhead. A heating element, usually a resistor, is located in each of the ink channels a predetermined distance upstream from the nozzle openings. The heating elements are individually driven with current pulses to momentarily vaporize the ink and form a bubble that forms a pressure wave which expels a droplet of ink. The channel is then refilled by capillary action, drawing ink from a supply tank. A meniscus is formed at each nozzle under a slight negative pressure to prevent ink from weeping therefrom. Operation of a thermal ink jet printer is described, for example, in U.S. Pat. Nos. 4,849,774 and 4,571,599.
The carriage type ink jet printer typically has one or more printheads containing the ink channels which open into a shared nozzle face. The printheads are connected to an ink supply tank. In one configuration, the printhead and one or more ink tanks are integrally assembled and the entire configuration, sometimes referred to as a cartridge, is disposable when the ink in the ink tanks are depleted. In another configuration, the printhead is an integral part of a replaceable ink tank support and replaceable ink supply tanks are installed on the ink tank support. Each of the ink supply tanks is replaced when the ink contained therein is depleted. The replaceable ink tank support should not need to be replaced until several (e.g., ten) ink supply tanks have been emptied during printing operations. In yet another configuration, ink tanks on the carriage are periodically refilled, when needed, from an off-carriage ink supply.
Whether the carriage type ink jet printer uses replaceable cartridges comprising integral printheads and ink supply tanks, or replaceable ink tank supports with integral printheads and separate replaceable ink tanks, or refillable tanks, the printheads are translated in a printing zone in one direction to print a swath of information on a recording medium, such as paper. The swath height is equal to the length of the column of nozzles in the printhead's nozzle face. The paper is held stationary during the printing and, after the swath is printed, the paper is stepped a distance equal to the height of the printed swath or a portion thereof. This procedure is repeated until the entire page is printed or until all information has been printed, if less than a page. For an example of a typical ink cartridge, refer to U.S. Pat. No. 5,519,425 which discloses disposable ink cartridges having integral printheads and ink supply tanks, and refer to U.S. Pat. No. 5,971,531 for a replaceable ink tank support having integral printheads and separately replaceable ink supply tanks.
In yet a further configuration of a thermal ink jet printer, the printer has printheads configured as a page-width array. In this case, the printheads do not move back and forth to form the printed image, but remain stationary and the recording medium, such as paper, is moved at a constant velocity past the page-width printheads. Whether carriage type or page-width printhead array type printer, one cause of unreliability is clogging of printhead channels with particles.
As is well known, particles in the ink can enter the relatively large printhead inlets and plug one or more channels, so that such channels do not eject ink droplets or eject droplets erratically. In order to print with small droplets that are required for high-resolution printing, ink jet printheads necessarily have small fluidic passageways or channels. The smaller the passageways or channels the more readily they are plugged with particulate contamination usually present in all ink supplies. A variety of printhead filters have been used or proposed to solve the problem of particulate matter in the ink. However, all of them have shortcomings ranging from reduced printhead yield during fabrication to early printhead failure due to contaminants found in the volume between filter and channels.
In many existing thermal ink jet printers, filters have been used to remove particulate matter in the ink. Some printers use filters at the ink exit from ink supply cartridges while others have filters bonded over the printhead inlets. For example, in U.S. Pat. Nos. 4,864,329 and 6,139,674, a wafer-sized filter is laminated to the side of the aligned and bonded silicon wafers containing a plurality of printheads that have the printhead inlets. The individual printheads are obtained by a sectioning operation that cuts through the two bonded wafers and the filter. The filter may be a woven mesh screen or electroformed screen or laser ablated film having a predetermined pore size. Since the filter covers one entire side of the printhead, the relatively large contact area prevents delamination of the filter.
U.S. Pat. No. 4,639,748 discloses an ink jet printhead having an internal filter. The printhead is composed of two parts that are aligned and bonded together. A surface of one part contains a linear array of heating elements and addressing electrodes, and a surface of the other part contains a set of etched recesses. The set of etched recesses include a parallel array of elongated recesses for use as capillary-filled ink channels having droplet emitting nozzles at one end. The other end is interconnected to a common reservoir recess. The reservoir recess has an internal wall defining a central chamber with an inlet. Small passageways are etched in the upper surface of the internal wall to permit the passage of ink from the chamber to the other side of the internal wall that is in communication with the channels. When the parts are mated, the top of the internal wall contacts the surface part having the heating elements, and the small passageways in the internal wall permit ink to flow therethrough. Each passageway has a smaller cross-sectional flow area than the nozzles to filter the ink, while the total cross-sectional flow areas of the passageways is larger than the total cross-sectional area of nozzles.
U.S. Pat. No. 5,716,533 discloses a method of fabricating ink jet printheads from channel plates and heater plates that have a filter in the printhead inlets. The channel plates are obtained from p-type silicon waters, one surface of which has a doped n-type patterned layer in the form of a screen. A first etch resistant material is deposited on both surfaces of the wafer and patterned on the surface opposite the one containing the n-type layer. The patterned first etch resistant material provides a first etch mask with channel and reservoir vias. A second etch resistant material is deposited over the first etch resistant material and patterned on the same wafer surface as the first etch resistant material, in order to provide a second etch mask having reservoir vias smaller than the vias in the first etch mask, but aligned therewith. The wafer with the two patterned etch masks is anisotropically etched with a bias potential between the p-n junction formed by the patterned n-type layer and the p-type wafer. The patterned n-type layer functions as an etch stop when under a bias potential. When the reservoir recesses have been etched through the wafer, the sc
Dietl Steven J.
Kneezel Gary A.
Lockett Darron D.
Yeh Andrew S.
Brooke Michael S
Chittum Robert A.
Xerox Corporation
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