Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-12-20
2001-07-17
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S067000, C347S093000
Reexamination Certificate
active
06260957
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to printheads of ink cartridges for ink jet printing and, more particularly, to a filter for an ink jet cartridge printhead.
2. Description of the Related Art
There are several types of electronic printers currently in wide-spread use. One type is known as the laser printer while another type is known as the ink jet printer.
The laser printer utilizes toner from a toner cartridge deposited onto the print medium to produce printing. The ink jet printer utilizes ink from an ink cartridge assembly to deposit or jet ink onto a print medium such as paper in a predetermined pattern from a plurality of ink emitting orifices or nozzles.
Generally, ink jet printers are thermal, drop on demand systems that utilize thermal energy pulses to produce vapor bubbles in ink-filled channels, each channel in communication with an orifice or nozzle. The vapor bubbles produced in the ink-filled chambers which are connected to channels cause the ink to be expelled from the orifices. The channels are in communication with an ink reservoir. Thermal energy generators, usually resistors, are located in the chambers near the nozzle. The resistors are individually addressed with a current pulse to momentarily vaporize the ink and form a bubble that expels an ink droplet toward the print medium. The printhead includes the plurality of nozzles in a predetermined pattern.
The printhead includes a heater chip and nozzle plate. The heater chip is conventionally formed with active semiconductor devices in silicon. The heater chip includes arrays of resistive and active elements oriented both horizontally and vertically which when mated with a nozzle plate forms a path for thermal ejection of ink drops. Depending upon the physical orientation of the nozzle plate relative to the print receiving medium, the diameter of the nozzles and the spacing between nozzles determines the vertical size of the print swath, and the horizontal width and spacing determine the packing density and firing rate of the printhead. As printing speeds and resolution density increase, larger and larger arrays of smaller elements and smaller diameter nozzles are utilized.
Ink jet printers currently on the market generally have a resolution of 300 to 360 dpi (dots per inch). Ink jet printers with higher resolutions currently may reach 720 dpi or higher. As can be appreciated, printing at 720 dpi has approximately four times the resolution as 360 dpi. In other words, at 720 dpi a one inch square printing area contains 720×720 or 518,400 dots. A resolution of 360 dpi, on the other hand, has a 360×360 or 129,600 dots per one inch square printing area. The resolution depends at least in part on the configuration of the printhead. Because the number of nozzles must increase for higher dpi printing resolutions, the size or diameter of each nozzle must necessarily decrease in order to maintain the same size printhead.
Since the nozzle diameters are relatively small, mechanical filters are used to remove particles from the ink in ink jet print cartridges that if not filtered would tend to cause clogs in the nozzles. These mechanical filters are generally screen mesh filters disposed over what is known as a standpipe. The standpipe provides fluid communication between the ink supply and the printhead.
It is now conceivable for ink jet printers to have resolutions of 1200 dpi. Because of the small diameter nozzles necessary to achieve 1200 dpi, it will become essential to filter smaller particles from the ink with a smaller pressure drop. If filtration is inadequate, the resulting clogged nozzles will eventually lead to a failed printhead. Also, inadequate filtration leads to bad or unsightly printing.
What is thus needed is an ink filter for ink jet printers that will provide filtration of minute particles with a small pressure drop.
SUMMARY OF THE INVENTION
The present invention is directed to an ink filter for an inkjet printhead heater chip and method of manufacture.
The invention comprises, in one form thereof, an ink filter for a thermal inkjet printhead that is formed integral with the heater chip. The heater chip includes a substrate defining a first surface and a second surface, with the first and second surfaces being opposed, substantially parallel surfaces. A via in the substrate extends from the second surface a depth towards the first surface, the via formed by micromachining and defining a filter entrance. A plurality of holes are formed in the substrate by laser drilling, the plurality of holes extending from the first surface to the via and defining a filter exit. A heater element is disposed on the first surface adjacent the plurality of holes and is adapted to be electrically coupled to actuating circuitry.
The via may be rectangular with a first width at the second surface that is greater than a second width at the depth or at the point of intersection of the plurality of holes.
The invention comprises, in another form thereof, a method for forming a heater chip of an ink jet printhead with an ink filter. The heater chip is formed by providing a substrate having a first surface and a second surface, the first and second surfaces being substantially opposed, parallel surfaces. A first protective layer is formed on the first surface while a second protective layer is formed on the second surface. An ink filter via is micromachined in the substrate extending from the second protective layer towards the first surface a given depth while a plurality of holes are laser drilled through the first protective layer into the via. Thereafter, a heater element is provided on the first protective layer adjacent the plurality of holes.
Preferably, the step of micromachining includes patterning the second protective layer with an opening for the via by use of a photo sensitive material, transferring the pattern on the second protective layer into the substrate, and etching the pattern into the substrate.
The step of laser drilling a plurality of holes is preferably accomplished utilizing a YAG, excimer, carbon dioxide or diode pumped laser.
An advantage of the present invention is that an ink filter may be produced to trap minute particles in the ink with a small pressure drop in a heater chip for a thermal inkjet printhead.
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Corley, Jr. Richard Earl
Spivey Paul Timothy
Sullivan Carl Edmond
Barlow John
Lexmark International Inc.
Stephens Juanita
Taylor & Aust P.C.
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