Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-08-23
2002-10-22
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06467884
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to a substrate unit for a liquid discharging head which discharges liquid, method for producing the same, liquid discharging head incorporating the substrate unit, cartridge which monolithically combines the liquid discharging head and liquid tank holding a liquid to be sent to the liquid discharging head, and image forming apparatus which forms an image on a printing medium. They are applicable to general printing apparatuses, copiers, facsimiles having a communication system, word processors or the like having a printing section, industrial recording apparatuses combined with one or more varying processing units, and various devices, such as those for textile printing and etching.
“Printing” or “recording” used in this specification includes forming information of meaning, e.g., letters or patterns, and also forming a variety of images, patterns or the like on a printing medium, whether or not they have a meaning or recognizable by visual sense of a human. It also includes etching and other processing methods.
The “printing medium” used in this specification is not limited to paper or the like to be printed by general printers, but includes fabrics, plastic films, metallic plates, glass sheets, ceramics, lumbers, leathers or the like which can receive an ink. Its shape is not limited, but includes three-dimensional objects, e.g., spheres and cylinders, in addition to sheet-shaped objects.
The “liquid” used in this specification should be interpreted broadly, as is the case of definition of the above-described “printing or recording,” and includes those for forming images, patterns or the like on a printing medium, etching of a printing medium, and processing of ink, e.g., solidification or insolubilization of a colorant in a ink attached to a printing medium.
RELATED BACKGROUND ART
Of the various printing methods known so far, liquid jet printing method (hereinafter referred to as ink jet printing method) is a very useful method for various reasons, e.g., nonimpact type printing which produces little noise while being in service, highspeed printing, and capacity of printing a common paper without needing a special fixation treatment.
This ink jet printing method flies droplets of an ink or a treatment solution for adjusting printability of an ink on a printing medium (hereinafter referred to generically as ink) by a varying working principle onto a printing medium, e.g., paper, for printing. The basic principle, as described by Japanese Patent Application Laid-Open No. 54-59936, is outlined below. In the ink jet printing method, thermal pulses are given as the information signal to an ink in an ink chamber capable of holding an ink, thereby discharging and flying the ink in the form of droplets by the force generated as a result of vaporization/expansion of the ink through a discharge port connected to the ink chamber onto a printing medium for printing.
This method has various advantages. It is suitable for high-speed prints and color prints, when a high-density, multi-array structure is used. The printer structure therefor can be simpler than the conventional one, making the printing head, i.e., ink jet head, compacter as a whole. Such heads are suitable for mass production, and may be elongated by fully utilizing IC and microwave processing techniques, which have been greatly advanced in level and reliability for the semiconductor industry. As such, it is applicable to wide areas.
A characteristic ink jet head of the ink jet printer for the ink jet printing method is provided with thermal energy generating means for forming flying droplets of ink discharged from the discharge port. It is considered that the thermal energy generating means is preferably designed to come into direct contact with the ink, for efficiently acting the energy on the ink and enhancing response of the ink jet head to the ON-OFF thermal actions.
The thermal energy generating means for an ink jet head is basically comprises a heat generating resist (electrothermal transducer) layer and a pair of electrode circuits for supplying electricity to the layer. Such a design may cause various problems, when the resist layer directly comes into contact with the ink, e.g., the ink may pass electricity, depending on its electrical resistance, to possibly cause electrolysis of the ink itself, or the energized resist layer may react with the ink on supplying electricity to the heat generating resist layer, to possibly cause corrosion of the resist layer to change its resist and eventual failure or breakdowns.
Therefore, various methods have been proposed to solve the above problems and thereby to improve reliability and durability of the resist layer for repeated used. For example, the resist layer is made of an inorganic material of relatively good characteristics for heat generating resist layer, e.g., alloy such as Ni or Cr, or metal boride such as ZrB
2
or HfB
2
. The resist layer may be coated with a protective layer of an oxidation-resistant compound, e.g., SiO
2
, to positively prevent it from directly coming into contact with the ink.
It is a normal practice, when thermal energy generating means for an ink jet head is produced, to coat a heat generating resist layer, formed on a given substrate, with electrode circuits and a protective layer in this order. The protective layer is required to uniformly cover the resist layer to fully satisfy the requirements, i.e., prevention of failure of the resist layer and short-circuit between the resist layer and electrode wiring. In addition, it should be free of defects, e.g., pinholes.
Normally, the protective layer is further coated with a second, relatively thin protective layer, in order to securely cut off the protective layer from the ink. The thin second layer is normally of a metal, e.g., Ta, formed by sputtering. This second protective layer prevents inflow of ink, even when the first protective layer of SiO
2
, SiN or the like is cracked by repeated exposure to heat, generated in the heat generating resist layer. It also protects the resist layer from cavitation, resulting from foaming and defoaming cycles, to improve durability of the layer for repeated use.
However, the second protective layer may cause cracking of the first protective layer below, because of stresses therein being different from each other. Therefore, the second protective layer is normally removed by etching in the region free of the ink on the substrate surface.
When a resin is used for forming the discharge port, it is little adhesive to the second protective layer of Ta or the like, causing the discharge port to easily come off the second protective layer. One of the proposals to solve the above problem is use of an adhesive layer of polyether amide or the like between the substrate coated with the second protective layer of Ta or the like and material that forms the discharge port, in order to improve adhesion between them, as disclosed by Japanese Patent Application Laid-Open No. 11-348290.
The ink jet head generally comprises an electric wiring on the heat generating resist layer, as described earlier, and one or more steps tend to be formed between the electric wiring and the heat generating resist layer. Thickness of the layer tends to be uneven around such a step, and the layer must be formed in such a way to sufficiently cover the step and prevent exposure of the wiring or resist layer it protects. When coverage of the step (hereinafter referred to as “step coverage”) is insufficient, the exposed portion of the heat generating resist layer may directly come into contact with the ink, to possibly cause problems, e.g., electrolysis of the ink, and reactions between the ink and a material which constitutes the heat generating resist layer to eventually destroy the resist layer. Such a step tends to cause uneven layer thickness, which, in turn, may cause partial concentration of thermal stresses produced in the protective layer as it is repeatedly exposed to heat, and eventually cracking of the protecti
Fujita Kei
Hayakawa Yukihiro
Murooka Fumio
Terui Makoto
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Gordon Raquel Yvette
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