Liquid jetting apparatus and method for switchably driving heaters

#The present invention relates to liquid jetting technologies for jetting liquid droplets toward recording medium, by utilizing the phenomenon that as thermal energy is given to a body of liquid in a liquid chamber (bubble generation chamber), bubbles are generated in the body of liquid.

#Typical liquid jetting methods (ink jet recording methods) may be roughly classified into two categories: a category in which an electrothermal transducer element, such as a heater, is used, and a category in which a piezoelectric element is used. From the standpoint of reducing the size of a recording head, an ink jetting method which uses an electrothermal transducer element is superior to an ink jetting method which uses a piezoelectric element, because an electrothermal transducer element takes up less space, making it easier to place a large number of liquid jetting nozzles in an extremely small space, than a piezoelectric element. On the other hand, a liquid ejecting method which uses an electrothermal transducer element has a problem which is peculiar to this method, more specifically, the adverse effects which the cavitation, which occurs when a bubble collapses, has on an electrothermal transducer element, the adhesion of baked or scorched ink residues to the outer surface of the heater protection film, etc. These problems are likely to lead to the formation of an inferior image; they are liable to reduce the performance of an ink jet recording head in terms of print quality.

#As the countermeasure for the adverse effects of the cavitation which occurs when a bubble collapses, and/or in order to protect a heater from the body of ink which will have been heated to an extremely high temperature, a heater is provided with cavitation-resistant film for protecting the heater. As the material for the cavitation-resistant film, a metallic substance such as Ta (tantalum) has been used. From the standpoint of making a heater more durable, however, ordinary metals (which include precious metals), and alloys thereof, which are greater in mechanical strength than Ta have been studied as the material for the cavitation-resistant film (U.S. Patent Application Publication No. 2005/0140732).

#FIGS. 1(a) and 1(b) are perspective and top views, respectively, of the liquid jetting head in accordance with the present invention, in one of the preferred embodiments of the present invention.

#FIGS. 2(a) and 2(b) are enlarged sectional and plan views, respectively, of one of the ink delivery passages, and its adjacencies, of the liquid jetting head shown in FIG. 1.

#FIG. 3 is an enlarged sectional view of one of the heaters, and its adjacencies, of the liquid jetting head shown in FIG. 1, showing the details thereof.

#Hereinafter, one of the preferred embodiments of the present invention will be described in detail with reference to the appended drawings.

#[Structure of Liquid Jetting Head]

#FIG. 1 shows one of the liquid jetting heads (ink jet recording heads) in accordance with the present invention. FIG. 1(a) is a perspective view of the liquid jetting head, and FIG. 1(b) is a top view of the liquid jetting head.