Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-09-08
2001-04-10
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06213590
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink-on-demand ink jet recording apparatus, and to a manufacturing method for an ink jet head therefor.
2. Description of the Related Art
Ink jet printers offer numerous desirable features, including extremely quiet operation when printing, especially at high speed, a high degree of freedom in the choice of ink, and the ability to use low-cost plain paper. So-called “ink-on-demand” printer heads in which ink is ejected only when required during recording have become the mainstream because it is not necessary to recover ink ejected unnecessarily during recording.
The ink jet head disclosed in JP-B-8316/1987 is one type of ink-on-demand ink jet head according to the prior art. In this type of head, a filter disposed in the ink supply path of the ink jet head is formed simultaneously with the ink passage by a photo-etching process, resulting in an ink jet head comprising an internal filter enabling ink to be ejected stably. The filter prevents foreign particulate from partially or fully blocking the flow of ink in the ink jet head and various passages therein.
The cross-sectional area of the filter opening preventing penetration of foreign particulate into the ink jet head must be smaller than the cross-sectional area of the any other ink passages consisting of nozzles, ejection chambers, ink supply cavity, and orifices communicating with the ejection chambers and ink supply cavity. In the above-described ink jet head, however, the filter is formed simultaneously with the other ink passages by an isotropic etching method, and the depth of the filter is therefore substantially the same as the depth of the nozzles and the orifices. As a result, the size of foreign particulate passing through the filter may be the same size as the nozzle and orifices. The probability of a nozzle or orifices becoming clogged is therefore high, and it is not possible to completely prevent clogging of all nozzles and orifices. This characteristic has a tendency to reduce the print quality and ink jet head reliability.
Further, the following problems are presented by simply forming the filter inside the head as in the above ink jet head, and achieving such a head is difficult.
The ink supply cavity distributes or supplies the ink to the ejection chamber through the orifices, and simultaneously buffers or reduces the pressure caused by the back flow of ink from the ink ejection chambers when the ink is ejected from the nozzle.
When the inertance of the filter is high, the pressure caused by ink back flow from the ink ejection chambers when ink is ejected from the nozzle cannot be sufficiently absorbed or reduced. This characteristic has a tendency to cause a pressure increase in the ink supply cavity, introducing pressure interference between the other ink ejection chambers and causing ink to be ejected from the other nozzles for which the pressure generating means has not been operated (i.e., ink is ejected from non-driven nozzles). If the flow resistance of the filter channel is high, ink cannot be sufficiently supplied from the filter to the ink supply cavity. The ejected ink volume therefore drops, air is taken in from the nozzle, and consistent ink ejection cannot be assured. Additionally, when the ink volume of the ink supply cavity is low, pressure cannot be sufficiently absorbed or reduced. Pressure interference between the ink ejection chambers therefore occurs, as when the filter inertance is high, and ink is ejected from nozzles of which the pressure generating means has not been operated.
In each of these cases, print reliability drops because of missing, incompletely formed or extra pixels in the printed image, contributing to indefinite images, reading errors and reduced print quality.
When the filter is formed using glass or another isotropic material, the etching ratio is not stable, and it is difficult to manufacture an ink jet head in which the filter is formed easily and with good precision.
OBJECTS OF THE INVENTION
Accordingly, it is an object of the present invention to provide an ink jet recording head which overcomes the aforementioned problems.
It is another object of the present invention to provide an ink jet recording apparatus whereby clogging of the ink supply path by the inflow of foreign particulate is prevented, thereby eliminating dropped dots and improving reliability, and to provide a manufacturing method for an ink jet head therefor.
It is another object of the invention to provide an ink jet head and an ink jet recording apparatus whereby there is no pressure interference between ink supply paths. Ink supply deficiencies are thus eliminated to assure consistent ink ejection and good print quality.
It is an additional object of the invention to provide an ink jet head and an ink jet recording apparatus which are simple to manufacture, are low cost, and provide high dimensional precision and quality.
SUMMARY OF THE INVENTION
To achieve the aforementioned object, an ink jet recording apparatus according to the present invention comprises an ink jet head having a plurality of nozzle openings and a plurality of independent ejection chambers respectively communicating to each of said nozzle openings from which ink droplets are ejected according to the change in pressure generated by each ejection chamber. The apparatus further includes an ink cavity for storing ink, ink supplying paths which supply ink to each of the ejection chambers from the ink cavity and a filter formed in or attached to the ink cavity. The ejection chambers, the ink supplying paths, the ink cavity and the filter are formed together on an anisotropic crystalline substrate, such as a silicon substrate, and the filter has a plurality of channels, which are shallower than any of the other channels of the nozzles and ink supplying paths.
The filter is provided for preventing the introduction of foreign particulate to the ink chamber and to the nozzles. The filter also functions as inlet ports for supplying ink from an external source to the ink cavity.
The preferred shape of the filter is a cross-sectional area of the filter opening that is smaller than the cross-sectional area of the ink supply paths and the nozzles. In addition, the inertance of the filter is preferably a maximum one-fifth the inertance of the ink passage consisting of the ejection chambers and the ink supplying paths plus the corresponding nozzles; and the flow resistance of the filter is preferably a maximum one-fourth the flow resistance consisting of the ejection chambers and the ink supplying paths plus the corresponding nozzles. At least one wall of the ink cavity is also preferably flexible.
A method for producing an ink jet head according to the present invention comprises the step of at least anisotropic etching an anisotropic crystalline substrate on the first surface thereof to form at least a plurality of communicating channels delineating a plurality of independent ejection chambers, an ink cavity, ink paths, each of which connects with each of the ejection chambers and the ink cavity, and a filter connecting with the ink cavity. Next, by means of anisotropic etching, a group of adjacently disposed grooves with said filter is formed, each of which is shallower than the channels delineating the ejection chambers, the ink cavity and the ink paths, and nozzle openings each of which connects with each of the ejection chambers. Forming, by means of anisotropic etching, a plurality of diaphragms with each of the bottom walls of said ejection chambers and bonding a cover substrate to the first surface of the anisotropic crystalline substrate sealing the rims of ejection chambers, the ink cavity, the ink paths and the filter to enclose the same while maintaining the communication therebetween.
To form the actuator for driving the diaphragm, this manufacturing method further comprises a process for forming electrodes in the first surface of an insulating substrate, and bonding the insulating substrate to the second surface of the anisotropic crys
Fujii Masahiro
Hagata Tadaaki
Maruyama Hiroyuki
Miyashita Ikuhiro
Mukaiyama Keiichi
Barlow John
Gordon Raquel Yvette
Seiko Epson Corporation
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