Metal working – Method of mechanical manufacture – Fluid pattern dispersing device making – e.g. – ink jet
Reexamination Certificate
2000-03-17
2002-06-04
Vo, Peter (Department: 3729)
Metal working
Method of mechanical manufacture
Fluid pattern dispersing device making, e.g., ink jet
C029S852000, C029S846000, C029SDIG001, C216S027000, C216S032000, C216S056000, C430S320000
Reexamination Certificate
active
06397467
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an ink jet print head with mutually parallel ducts formed inside a substrate and separated by partition walls. The ducts are provided with a cover plate and one outlet opening on each of their ends. One thermal or piezoelectric element is associated with each duct. Upon excitation and with ink fluid disposed inside the duct, the element effects an expulsion of a drop of ink from the outlet opening. The invention further relates to a method of producing such an ink jet print head.
2. Description of the Related Art
Ink jet print heads are widely used in ink jet printers. The ink jet print head usually operates by the known drop on demand or DOD method, described for instance in German Patent DE 30 12 698 C2. There, to create a dot on a medium to be imprinted, such as paper, a drop of ink is expelled from a duct of the ink jet print head as soon as a thermal or piezoelectric element associated with the duct is triggered with a suitable current pulse from a driver circuit. The excitation occurs as the result of a current pulse 2 &mgr;s to 10 &mgr;s in duration, for instance, thus releasing thermal energy of approximately 15 to 50 microjoules. This heating leads to local evaporation of the ink fluid (bubble formation). The column of fluid is positively displaced from the corresponding duct outlet opening but without initially tearing. Once the current pulse ends, the bubble collapses above the thermal element. As a consequence, some of the fluid column is drawn back in. A drop of ink separates from the column outside the duct outlet openings and moves onward due to the conservation of momentum. These drops of ink create a black printed dot, in the case of black ink, on the paper. The typical emission frequency is approximately 5 kHz.
To create a character, such as a letter, the thermal or piezoelectric elements of the parallel ducts must be suitably supplied with current pulses by the driver circuit in such a way that the dots required for these letters become visible on the paper as a result of the impact of corresponding drops of ink.
Because of the very small duct diameter and close matrix spacings between the ducts (or jets), processing methods known from semiconductor technology are employed to create ink jet print heads. Examples of such processing methods are described in European Patent Disclosures EP 0 359 417 A2 and EP 0 434 946 A2, and in IEEE Transactions on Electron Devices, Vol. 26, 1979, p. 1918. In contrast to the production of integrated semiconductor circuits, which are formed on a single substrate, the prior art methods for producing ink jet print heads require at least two different substrates. On one substrate, partitions between ducts are formed, and these are closed by a separately produced cover plate made of a second substrate.
In the prior art methods, heating resistors can be disposed on or in the duct for thermal excitation. Often the ducts are formed by orientation-dependent etching in a silicon substrate. The heating resistors can be secured to the ducts by bonding. A glass plate, for instance, may be used as the cover plate. The glass plate is mounted on the duct plate, and hence in the first substrate, by anodic bonding.
As disclosed by the European document EP 0 443 722 A2, the ducts of the ink jet print head can also be formed by adjusting a cover plate, provided with partitions, onto a first substrate that is provided with heating resistors. Instead of the cover plate provided with partitions, a flat cover plate can also be glued to the first substrate, if the aforementioned ducts have already been machined into the first substrate, in the form of duct bottoms and two duct side walls each. The glued-on cover plate then forms the top of the duct for these ducts.
A problem associated with these prior art methods for producing integratable ink jet print heads is the absolute necessity of two substrates that must be joined to one another. This requires complicated adjustment, and the fine conduits must be protected against contamination while the two substrates are being glued together, which means additional effort and expense.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a TITLE, which overcomes the above-mentioned disadvantages of the prior art devices and methods of this general type and which renders unnecessary complicated adjustment and gluing and bonding of two separately produced substrates.
With the foregoing and other objects in view there is provided, in accordance with the invention, an ink jet print head, comprising:
a substrate formed with a plurality of mutually parallel ducts each having an outlet opening and partition walls separating the ducts;
an ink ejection element, selected from the group consisting of thermal elements and piezoelectric elements, operatively associated with each of the ducts for selectively ejecting ink fluid from the ink duct and ejecting ink droplets through the respective outlet openings upon an excitation of the ink ejection element; and
a cover plate disposed on the ducts, the cover plate including a first layer disposed directly on the ducts, the first layer being a deposition layer formed with a plurality of openings, and including a second layer disposed directly on the first layer and covering the openings, the second layer being a deposition layer formed by depositing a material selected from the group consisting of boron phosphorus silicate glass and Si
3
N
4
.
In other words, the above-noted objects are satisfied in that the cover plate comprises at least two layers, the cover layer is disposed directly on the duct with its first layer, the first layer is formed with a plurality of openings located above the ducts, and a second layer closing the openings is formed directly on the first layer (on its surface remote from the duct.
In accordance with an added feature of the invention, an electronic trigger circuit integrated inside the substrate.
In accordance with an additional feature of the invention, the thermal element—a heating resistor formed by a polysilicon layer—is disposed on the bottom of the duct. One or more protective layer may be disposed between the duct bottom and the polysilicon layer.
In accordance with another feature of the invention, the ink ejection elements are disposed inside the duct and suspended peripherally from the side walls of the ducts. In that case, the ink ejection elements are formed of erosion-proof material.
When the ink ejection elements are chemical elements, the invention provides for a heat-storing layer disposed below the chemical element distally from the duct bottom. The preferred heat-storing layer is a layer of silicon oxide with a thickness greater than 1.0 &mgr;m.
In accordance with a further feature of the invention, at least one protective layer is disposed between the duct bottom and the ink ejection elements when they are formed of thermal elements. The protective layer is formed with a plasma oxide layer and a plasma nitride layer. Preferably, the plasma oxide layer has a thickness of substantially 300 nm and the plasma nitride layer has a thickness of substantially 600 nm.
In accordance with again an added feature of the invention, a second protective layer is formed on the first above-mentioned protective layer. That second layer is preferably a sputtered tantalum layer.
In accordance with again an additional feature of the invention, the ducts have side walls with a height between substantially 5 &mgr;m and substantially 50 &mgr;m. The side walls may be formed of plasma oxide, polysiloxanes, or polyimide. The first layer of the cover plate may be a layer of structured plasma nitride and structured polysilicon, and the second layer may be formed of boron phosphorus silicate glass or Si
3
N
4
.
With the above and other objects in view there is also provided, in accordance with the invention, a method of producing an ink jet print head, the method which comprises:
providing a substrate and placing ink ejection elements at locations of
Werner Wolfgang
Zettler Thomas
Infineon - Technologies AG
Mayback Gregory L.
Tugbang A. Dexter
Vo Peter
LandOfFree
Ink jet print head and method of producing the ink print head does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ink jet print head and method of producing the ink print head, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ink jet print head and method of producing the ink print head will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2904470