Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2002-06-07
2004-08-10
Meier, Stephen D. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S070000, C347S071000
Reexamination Certificate
active
06773084
ABSTRACT:
The invention is based on a printing chip for a printing head working according to the ink-jet printing principle, in accordance with the preamble of claim
1
.
DE 44 43 254 C1 discloses a printing chip of the generic type. This printing chip has a medium chamber formed by a recess in a glass plate, which is also referred to as a support plate. The recess is made to such a depth in the glass plate that the bottom of the recess serves as a deflectable diaphragm, which thus forms one wall of the medium chamber. A duct for feeding an ink that is to be squirted out opens in the medium chamber. Furthermore, a squirting-out opening is provided, which is connected to the medium chamber. The recesses introduced in the glass plate are closed off by a central plate. The known printing chip is thus formed from two substrate parts lying one on top of the other, at least one substrate part being composed of glass.
This known printing chip has the disadvantage that it is not suitable, for lack of thermal stability, for squirting out very hot media at temperatures above 500° C.
The object of the invention, therefore, is to specify a printing chip of the type mentioned in the introduction which does not have this disadvantage.
This object is achieved by means of a printing chip for a printing head working according to the ink-jet printing principle, the printing chip having the features of claim
1
. It thus has at least one medium chamber formed by a recess in the printing chip. Furthermore, a deflectable diaphragm is provided, which forms one wall of the medium chamber. Moreover, a duct for feeding a liquid medium that is to be squirted out hot opens in the medium chamber. In addition, the printing chip has a squirting-out opening connected to the medium chamber. According to the invention, the printing chip is distinguished by the fact that it is produced exclusively from monocrystalline silicon. The printing chip according to the invention is distinguished by high operational reliability when media at temperatures reaching in excess of 1000° C. are sprayed. The known printing chips comprising glass cannot be used to spray such hot media since the glass softens at these temperatures, so that the diaphragm is damaged and/or can no longer be deflected in a reproducible manner, as a result of which an exact drop volume can no longer be ejected from the squirting-out opening. The printing chip according to the invention is also distinguished by the fact that the monocrystalline silicon can be processed according to known and proven fabrication processes in order to be able to produce the medium chamber and the remaining ducts and/or the squirting-out opening.
One development of the invention provides for the printing chip to be formed from at least two substrate parts lying one on top of the other. This affords the advantage for production that the required recesses for the medium chamber and the ducts and also the squirting-out opening can be introduced from one side on the substrate parts. The recesses are then closed off by the substrate parts being laid one on top of the other. The printing chip comprising two substrate parts lying one on top of the other is thus simple and cost-effective to produce.
According to a particularly preferred exemplary embodiment, the feeding duct, the medium chamber and the squirting-out opening are arranged in the printing chip in such a way that the medium to be squirted out flows alternately through the substrate parts. What is advantageous in this case is that it is possible to produce the recesses at least for the medium chamber, the feeding duct and squirting-out opening in the two substrate parts using different fabrication processes. Thus, by way of example, one of the substrate parts can be processed by anisotropic wet etching and the other substrate part by dry etching or another material-removing process, in order to introduce the recesses. By rotating the (100) silicon crystal plane of one of the substrate parts by 45° relative to the other substrate part, it is possible for all of the recesses to be formed favourably in terms of flow properties in the course of the anisotropic wet etching. Since both substrate parts are produced from silicon, which has very good thermal conductivity, strain nevertheless does not arise in the printing chip on account of thermal expansion.
A preferred exemplary embodiment provides for a medium supply chamber, to which the feeding duct is connected, to be located in the printing chip. It is thus possible to provide a large-scale integrated printing chip which contains all the essential functional units. If appropriate, however, it would also be conceivable to design the medium supply chamber, which can also be referred to as a storage chamber, in a separate structural part which can then be fixed to the printing chip. However, if the medium supply chamber is realized in the printing chip, all functionally essential parts can be realized by recesses that are simple to produce in the substrate parts.
A preferred exemplary embodiment provides for the printing chip surfaces, in particular those which come into contact with the hot medium, to be provided with a coating that is resistant to high temperatures. Thus, the hot liquid medium cannot damage the printing chip substrate even over a long service life of the printing chip.
It is preferably provided that the printing chip surfaces, in particular those which come into contact with the hot medium, are passivated by thermal oxide. The thermal oxide is preferably provided on the channel walls and the wall of the medium chamber. In particular, then, the printing chip surfaces past which the hot medium flows are passivated with thermal oxide.
In a particularly preferred exemplary embodiment, the two substrate parts are connected to one another inseparably by silicon fusion bonding. This connection method, which can only be employed for silicon-silicon, ensures reliable connection of the two substrate parts even at operating temperatures of far in excess of 1000° C. Consequently, by comparison with known printing chips, the printing chip is also distinguished by temperature-resistant connection of the two substrate parts to one another.
According to a preferred exemplary embodiment, the recess for the medium chamber, the feeding duct, the squirting-out opening and the medium supply chamber are produced by an anisotropic wet or dry etching process, in particular anisotropic wet etching using potassium hydroxide (KOH) being preferred. It goes without saying that other basic etching solutions, in particular alkaline metal hydroxide solutions, can be used. Anisotropic etching in monocrystalline silicon with (100) orientation produces the recesses for the ducts and the medium chamber always with four pyramidally inclined side walls on the (111) crystal planes. Their angle with respect to the (100) crystal plane of the substrate surface of the silicon is 54.7° on all sides. The dimensions of the recesses can be produced very accurately in this etching process. This affords the advantage, in particular in the substrate part having the recess for the medium chamber, that the diaphragm area can be produced very accurately, if the said diaphragm area is formed by the bottom of the recess. The diaphragm area is thus merely dependent on the opening width of the etching mask and the depth to be etched for the recess. Since the angle of the side walls always has the same value, the effective diaphragm area can thus be produced particularly accurately in a manner dependent on the opening width of the perforated mask and the depth of the recess. If a plurality of medium chambers each having a deflectable diaphragm are provided, all of the diaphragms have essentially the same area in this production process, so that, given the same deflection excursion of the diaphragm, the same drop size can be ejected from each chamber. In particular, the printing chip is thus distinguished by highly accurate drop volumes that can be squirted out.
In a preferred embodiment, the medium chamber, the feeding
Krause Peter
Wehl Wolfgang
Wild Jörg
Bateman IP Law Group
Dudding Alfred E
EKRA Edward Kraft GmbH
Meier Stephen D.
LandOfFree
Printing chip for a printing head working according to the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Printing chip for a printing head working according to the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Printing chip for a printing head working according to the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3346918