This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7 119 from my application entitled BUBBLE-JET TYPE INK-JET PRINT HEAD WITH DOUBLE HEATER filed with the Korean Industrial Property Office on Mar. 15, 2001 and there duly assigned Ser. No. 2001-13452.
1. Field of the Invention
The present invention relates to an ink-jet printhead, and more particularly, to a bubble-jet type ink-jet printhead having an improved heater for forming bubbles.
2. Description of the Related Art
The ink ejection mechanisms of an ink-jet printer are largely categorized into two types: an electro-thermal transducer type (bubble-jet type) in which a heat source is employed to form a bubble in ink causing ink droplets to be ejected, and an electromechanical transducer type in which a piezoelectric crystal bends to change the volume of ink causing ink droplets to be expelled.
Meanwhile, an ink-jet printhead having this bubble-jet type ink ejector needs to meet the following conditions. First, a simplified manufacturing procedure, low manufacturing cost, and high volume production must be allowed. Second, to produce high quality color images, creation of minute satellite droplets that trail ejected main droplets must be prevented. Third, when ink is ejected from one nozzle or ink refills an ink chamber after ink ejection, cross-talk with adjacent nozzles from which no ink is ejected must be prevented. To this end, a back flow of ink in the opposite direction of a nozzle must be avoided during ink ejection. Fourth, for a high speed print, a cycle beginning with ink ejection and ending with ink refill must be as short as possible. Fifth, a nozzle and an ink channel for introducing ink into the nozzle must not be clogged by particles or solidified ink.
However, the above conditions tend to conflict with one another, and furthermore, the performance of an ink-jet printhead is closely associated with structures of an ink chamber, an ink channel, and a heater, the type of formation and expansion of bubbles, and the relative size of each component.
In efforts to overcome problems related to the above requirements, ink-jet print heads having a variety of structures have been proposed. However, ink-jet printheads having the structures proposed may satisfy some of the aforementioned requirements but do not completely provide an improved ink-jet printing approach. Accordingly, it is highly desirable to have a bubble-jet type ink-jet printhead whose fabrication process is simplified without a decrease in the ejection energy of ink.
To solve the above problems, it is an object of the present invention to provide a bubble-jet type ink-jet printhead which improves ejection energy and eliminates the need for a separate ink chamber by connecting a plurality of heaters in parallel to form bubbles at predetermined time intervals.
Accordingly, to achieve the above object, the present invention provides a bubble-jet type ink jet printhead having a substrate, a nozzle plate having a plurality of nozzles, the nozzle plate being separated a predetermined distance from the substrate, walls for closing the space between the substrate and the nozzle plate and then forming a common chamber between the substrate and the nozzle plate a plurality of first resistive layers formed on the substrate within the common chamber corresponding to the plurality of nozzles, each of the plurality of first resistive layers being centered around the central axis passing through the center of each nozzle a plurality of second resistive layers disposed within the plurality of first resistive layers, wherein each second resistive layer is connected in parallel to each first resistive layer to thereby form a bubble on a central axis passing through the center of each nozzle a plurality of pairs of electrically conductive layers formed on the substrate, each pair being connected to the first and second resistive layers and extending to the outside of the common chamber; and a plurality of electrode pads which are disposed at the outside of the common chamber on the substrate and electrically connected to the electrically conductive layers.
Preferably, the second resistive layer has resistance greater than the first resistive layer, and the second resistive layer is longer and narrower than the first resistive layer. Preferably, ink feed grooves are formed at two opposite ends of the common chamber on the substrate for supplying ink to the common chamber or an ink feed groove is formed at the center of the substrate for supplying ink to the common chamber.
Preferably, a boundary barrier is provided for dividing the common chamber into a plurality of regions and allowing ink to flow from one region to another by spatially connecting the plurality of regions disposed within the common chamber, wherein the boundary barrier has a height equal to the gap between the substrate and the nozzle plate.