Patent Publication Number: US-7909438-B2

Title: Piezo-electric type inkjet printhead

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 10-2006-0120979, filed on Dec. 1, 2006, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present general inventive concept relates to an inkjet printhead, and more particularly, to a piezoelectric type inkjet printhead. 
     2. Description of the Related Art 
     Generally, inkjet printheads are devices for printing a color image on a printing medium by ejecting droplets of ink onto a desired region of the printing medium. Depending on an ink ejecting method, the inkjet printheads can be classified into two types: electro-thermal transducers (bubble jet type inkjet printheads) and electro-mechanical transducers (piezoelectric type inkjet printheads). The electro-thermal transducers generate bubbles in the ink that is to be ejected by using heat, and eject the ink utilizing the expansion of the bubbles, and the electro-mechanical transducers eject ink by using pressure generated by deforming a piezoelectric material. 
       FIG. 1  is a cross-sectional view illustrating a normal ink ejection of a conventional piezoelectric type inkjet printhead.  FIG. 2  is a cross-sectional view illustrating an abnormal ink ejection of the conventional piezoelectric type inkjet printhead illustrated in  FIG. 1 . 
     Referring to  FIG. 1 , a lower substrate  10  and an intermediate substrate  20  are attached to each other. A damper  21  is formed in the intermediate substrate  20  as a path through which ink flows. A nozzle  11  is formed in the lower substrate  10 . The nozzle  11  includes an ink ejecting hole  12  formed on a lower portion of the lower substrate  10 , and an ink leading unit  13  formed on an upper portion of the lower substrate  10 . Ink is ejected through the ink ejecting hole  12 . The ink leading unit  13  connects the damper  21  to the ink ejecting hole  12 , and pressurizes and leads ink from the damper  21  into the ink ejecting hole  12 . 
     A bottom surface of the lower substrate  10  is coated with a hydrophobic layer  30 , so that the lower substrate  10  is hydrophobic, thereby preventing the ink injecting hole  12  from being wetted by the ejected ink, and stably ejecting an ink drop  15  from the ink injecting hole  12 . 
     The conventional piezoelectric type inkjet printhead finishes ejecting ink, and then performs maintenance for which ink stained around the nozzle  11  is wiped using a wiper  40  that wipes the lower substrate  10  while moving in an arrow direction. 
     However, as illustrated in  FIG. 2 , when the wiper  40  wipes and contacts the hydrophobic layer  30  coated around the ink ejecting hole  12 , the hydrophobic layer  30  may be removed from the lower substrate  10 . 
     As a result, the possibility of wetting the ink ejecting hole  12  with the ink drop  15  is increased while the hydrophobic layer  30  around the ink ejecting hole  12  is gradually removed by the wiper  40 , and thus, the ink drop  15  may be abnormally ejected from the ink ejecting hole  12 . In this manner, since an appropriate amount ink can not be ejected on a desired location on a printing medium when the ink drop  15  is abnormally ejected as described-above, the reliability of the conventional piezoelectric type inkjet printhead may be reduced. 
     SUMMARY OF THE INVENTION 
     The present general inventive concept provides a piezoelectric type inkjet printhead including a nozzle formed so that a hydrophobic layer formed around the nozzle may be stably maintained even when maintenance is continually performed using a wiper. 
     Additional aspects and utilities of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept. 
     The foregoing and/or other aspects and utilities of the present general inventive concept may be achieved by providing a piezoelectric type inkjet printhead including an upper substrate including a pressure chamber that is formed in the upper substrate and filled with ink that is to be ejected, a reservoir to store ink that flows in from an ink container, a restrictor to connect the reservoir to one end of the pressure chamber, an intermediate substrate comprising a damper formed in the intermediate substrate on a portion of the intermediate substrate, which corresponds to other end of the pressure chamber, a lower substrate comprising a nozzle to eject ink and formed in a portion of the lower substrate, which corresponds to the damper, a hydrophobic layer formed on a bottom of the lower substrate, and a piezoelectric actuator formed on the upper substrate to supply driving power to eject ink to the pressure chamber, wherein the nozzle is formed in lower substrate at a predetermined depth from a bottom surface of the lower substrate. 
     The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an inkjet head usable with a piezoelectric type inkjet printhead, including a substrate having one or more surfaces to define a pressure chamber to be filled with ink, a damper to receive the ink from the pressure chamber, and a nozzle having a center axis as an ink ejecting direction to receive the ink from the damper and to eject the ink to an outside of a bottom surface of the substrate in the ink ejecting direction, an inclination portion having a surface formed between the surface of the nozzle and the bottom surface of the substrate and inclined with respect to the ink ejecting direction, and a hydrophobic layer formed on the bottom surface of the substrate and the inclination portion. 
     The nozzle may be spaced-apart from the bottom surface of the substrate by a distance, and the inclination portion may have a length corresponding to the distance in the ink ejecting direction. 
     The nozzle may have a nozzle area in a direction perpendicular to the ink ejecting direction, and the inclination portion may have an area larger than the nozzle area. 
     The hydrophobic layer may include an end portion formed on the inclination portion as a part of the surface of the nozzle to eject the ink. 
     The hydrophobic layer may include an end portion formed on the inclination portion and being parallel to the surface of the nozzle. 
     The hydrophobic layer may include a first portion formed on the bottom surface of the substrate and having a first thickness and a second portion formed on the inclination portion and having a second thickness. 
     The first thickness in a direction perpendicular to the bottom surface may be thicker than the second thickness in a direction perpendicular to the surface of the inclination portion. 
     The first thickness and the second thickness may be a same in the ink ejecting direction. 
     The nozzle may include an ink leading unit to receive the ink from the damper, and an ink ejecting hole to eject the received ink, the ink leading unit may have a cross-sectional area variable according to a distance from the bottom surface of the substrate, the ink ejecting hole may have a cross-sectional area constant along the ink ejecting direction, and the inclination portion may have a cross-sectional area variable according to a distance from the bottom surface of the substrate. 
     The surface of the nozzle may include a first surface to define an ink leading unit to receive the ink from the damper, and a second surface to define an ink ejecting hole to eject the received ink, and the inclination portion may include an inside circumference corresponding to the second surface of the ink ejecting hole and an outside circumference corresponding to the bottom surface of the substrate. 
     The inside circumference may have a first shape, and the outside circumference may have a second shape different from the first shape. 
     The inside circumference may have a circular shape, and the outside circumference may have a non-circular shape. 
     The inclination portion may include an inside circumference corresponding to the surface of the nozzle and having a first dimension, and an outside circumference corresponding to the bottom surface of the substrate and having a second dimension. 
     The surface of the inclination portion may be connected between the inside circumference and the outside circumference. 
     The surface of the inclination portion may include one of a flat surface, a curved surface, and an inclined surface. 
     The surface of the inclination portion may include a combination of a flat surface, a curved surface, and an inclined surface. 
     The surface of the inclination portion may be different from the surface of the nozzle in the ink ejecting direction. 
     The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an inkjet head usable with a piezoelectric type inkjet printhead, including a substrate having surfaces to define a pressure chamber to be filled with ink, a damper to receive the ink from the pressure chamber, and a nozzle disposed along an ink ejecting direction to receive the ink from the damper and eject the ink to an outside of a bottom surface of the substrate, an inclination portion disposed between the nozzle and the bottom surface of the substrate to have an angle with the ink ejecting direction, and a hydrophobic layer formed on the bottom surface of the substrate and the inclination portion. 
     The foregoing and/or other aspects and utilities of the present general inventive concept may be achieved by providing an inkjet head usable with a piezoelectric type inkjet printhead, including a substrate having surfaces to define a pressure chamber to be filled with ink, a damper to receive the ink from the pressure chamber, and a nozzle disposed along an ink ejecting direction to receive the ink from the damper and eject the ink to an outside of a bottom surface of the substrate, an inclination portion connected between the nozzle and the bottom surface of the substrate and having an ink ejecting area increasing in the ink ejecting direction, and a hydrophobic layer formed on the bottom surface of the substrate and the inclination portion. 
     The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an inkjet head usable with a piezoelectric type inkjet printhead, including a substrate having surfaces to define a pressure chamber to be filled with ink, a damper to receive the ink from the pressure chamber, and a nozzle having a first cross-sectional area constant in an ink ejecting direction to receive the ink from the damper and to eject the ink to an outside of a bottom surface of the substrate in the ink ejecting direction, an inclination portion formed between the nozzle and the bottom surface of the substrate and having a second cross-sectional area varying according to a distance from the bottom surface of the substrate, and a hydrophobic layer formed on the bottom surface of the substrate and the inclination portion. 
     The foregoing and/or other aspects and utilities of the present general inventive concept may also be achieved by providing an inkjet head usable with a piezoelectric type inkjet printhead, including a substrate having surfaces to define a pressure chamber to be filled with ink, a damper to receive the ink from the pressure chamber, and a nozzle having a first shape to receive the ink from the damper and eject the ink to an outside of a bottom surface of the substrate, an inclination portion having a surface formed between the nozzle and the bottom surface of the substrate and having a second shape different from the first shape of the nozzle, and a hydrophobic layer formed on the bottom surface of the substrate and the inclination portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects and utilities of the present general inventive concept will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
         FIG. 1  is a cross-sectional view illustrating a normal ink ejection of a conventional piezoelectric type inkjet printhead; 
         FIG. 2  is a cross-sectional view illustrating an abnormal ink ejection of the conventional piezoelectric type inkjet printhead illustrated in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view illustrating a piezoelectric type inkjet printhead including a nozzle, according to an embodiment of the present general inventive concept; 
         FIG. 4  is an enlarged view of a portion A of the piezoelectric type inkjet printhead of  FIG. 3 ; 
         FIG. 5  is a bottom view of the nozzle of  FIG. 3 ; 
         FIG. 6  is an enlarged cross-sectional view illustrating a nozzle, according to an embodiment of the present general inventive concept; 
         FIG. 7  is a bottom view of the nozzle of  FIG. 6 ; 
         FIG. 8  is an enlarged cross-sectional view illustrating a nozzle, according to an embodiment of the present general inventive concept; and 
         FIG. 9  is a bottom view of the nozzle of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures. 
       FIG. 3  is a cross-sectional view illustrating a piezoelectric type inkjet printhead including a nozzle  410 , according to an embodiment of the present general inventive concept.  FIG. 4  is an enlarged view of a portion A of  FIG. 3 , and  FIG. 5  is a bottom view of the nozzle  410  of  FIG. 3 . 
     Referring to  FIG. 3 , the piezoelectric type inkjet printhead is configured by stacking and attaching upper, intermediate, and lower substrates  200 ,  300  and  400 . The elements constituting an ink flow channel are formed in each of the upper, intermediate, and lower substrates  200 ,  300  and  400 . A piezoelectric actuator  100  that generates driving power for to eject ink is disposed on the upper substrate  200 . In particular, since each of the upper, intermediate, and lower substrates  200 ,  300  and  400  is a single crystal silicon wafer, the elements constituting the ink flow channel can be formed to be very minute and be easily formed in each of the upper, intermediate, and lower substrates  200 ,  300  and  400  using micromachining technology such as photolithography and etching. 
     The ink flow channel includes a reservoir  310  in which ink that flows from an ink container (now shown) is stored, a restrictor  250  that provides ink from the reservoir  310  to a pressure chamber  240 , the pressure chamber  240  in which ink that is to be ejected is filled, and which varies in pressure in order to eject ink, and a nozzle  410  through which ink is ejected. A damper  320  is formed as an ink path between the pressure chamber  240  and the nozzle  410 , and the damper  320  concentrates energy generated by the pressure chamber  240  towards the nozzle  410  due to the piezoelectric actuator  100  and buffs remarkable pressure change. The elements constituting the ink flow channel are separated so as to be respectively disposed in the upper, intermediate, and lower  200 ,  300  and  400 , as described above. 
     The pressure chamber  240  having a predetermined depth is formed in a lower surface of the upper substrate  200 , which is a single crystal silicon wafer that is widely used for manufacturing integrated circuits. In particular, the upper substrate  200  may be a silicon-on-insulator (SOI) wafer having a stack structure including a first silicon substrate  210 , an inter-oxide layer  220  formed on the first silicon substrate  210 , and a second silicon substrate  230  attached to the inter-oxide layer  220 . The first silicon substrate  210  is formed of silicon single crystal, and has a thickness of about several hundreds of μm. The inter-oxide layer  220  is formed by oxidizing a surface of the first silicon substrate  210 , and has a thickness in the range of about 1 to 2 μm. The second silicon substrate  230  is formed of silicon single crystal, and has a thickness of about several tens of μm. Since the SOI wafer is used as the upper substrate  200  as described above, the depth of the pressure chamber  240  can be correctly adjusted. Hence, the inter-oxide layer  220  constituting an intermediate layer of the SOI wafer functions as an etch stop layer. Thus, when the thickness of the first silicon substrate  210  is determined, the depth of the pressure chamber  240  is accordingly determined. In addition, the second silicon substrate  230  constituting an upper wall of the pressure chamber  240  is deformed so as to bend due to the piezoelectric actuator  100 , and thus, the second silicon substrate  230  functions as a diaphragm that changes the volume of the pressure chamber  240 , and the thickness of the diaphragm is determined according to the thickness of the second silicon substrate  230 . 
     The piezoelectric actuator  100  is disposed on the upper substrate  200 . A silicon oxide layer  140  functioning as an insulating layer is formed between the upper substrate  200  and the piezoelectric actuator  100 . The piezoelectric actuator  100  includes a lower electrode  130  functioning as a common electrode, a piezoelectric film  120  that deforms according to an applied voltage, and an upper electrode  110  functioning as a driving electrode to apply the voltage. The piezoelectric film  120  is formed on the lower electrode  130 , and is disposed right above the pressure chamber  240 . The piezoelectric film  120  is deformed due to the applied voltage so as to bend the second silicon substrate  230  of the upper substrate  200 , which constitutes the upper wall of the pressure chamber  240 , that is, the diaphragm. The upper electrode  110  is formed on the piezoelectric film  120 , and functions as the driving electrode applying the voltage to the piezoelectric film  120 . 
     The reservoir  310 , storing ink that flows in from the ink container, is formed in the intermediate substrate  300  to have a predetermined depth. The restrictor  250  is formed in the intermediate substrate  300  to have a depth that is less than that of the reservoir  310 , wherein the restrictor  250  connects the reservoir  310  to one end of the pressure chamber  240 . In addition, the damper  320 , which is vertically formed through the intermediate substrate  300  so as to be perpendicular to the pressure chamber  240 , is formed in a portion of the intermediate substrate  300 , which corresponds to other end of the pressure chamber  240 . The restrictor  250  prevents ink from flowing back into the reservoir  310  from the pressure chamber  240  when ink is ejected, as well as functions as a path to supply ink from the reservoir  310  to the pressure chamber  240 . In order to prevent ink from flowing back into the reservoir  310 , the cross section of the restrictor  250  may be much smaller than each of those of the pressure chamber  240  and the damper  320 . 
     The first silicon substrate  210 , the intermediate substrate  300 , and the lower substrate  400  may be formed in a single monolithic body as a single substrate. The pressure chamber  240  is formed in the first silicon substrate  210 . 
     The nozzle  410  is formed through the lower substrate  400  on a portion of the lower substrate  400 , which corresponds to the damper  320 ., and the nozzle  410  includes an ink ejecting hole  412  formed in a lower portion of the lower substrate  400 , and an ink leading unit  411  formed in an upper portion of the lower substrate  400 . Ink is ejected through the ink ejecting hole  412 . The ink leading unit  411  connects the damper  320  to the ink ejecting hole  412 , and pressurizes and leads ink from the damper  320  into the ink ejecting hole  412 . The ink ejecting hole  412  is a vertical hole having a predetermined diameter. The ink leading unit  411  has a shape of circular cone of which a cross section gradually decreases from the damper  320  towards the ink ejecting hole  412 . That is, the ink leading unit  411  may have a shape of a frustum of a cone. A surface to define the ink leading unit  411  corresponds to a side surface of the frustum of a cone. 
     Referring to  FIGS. 4 and 5 , the nozzle  410  is formed in the lower substrate  400  to have a predetermined depth from a bottom surface  401  of the lower substrate  400 . An inclination portion  420 , which is inclined inwards at a predetermined angle, is formed at the entrance of the ink ejecting hole  412 , and the inclination portion  420  connects the ink ejecting hole  412  to the bottom surface  401  of the lower substrate  400 . The inclination portion  420  and the bottom surface  401  of the lower substrate  400  are all coated with a hydrophobic layer  500 . 
     As illustrated in  FIG. 5 , the ink ejecting hole  412  has a circular shape, and the inclination portion  420  has an inside surface to correspond to the circular shape of the ink ejecting hole  412 , and an outside surface extended from the inside surface toward an outside of the nozzle  410 , i.e., toward the bottom surface  401  the lower substrate  400  to have a rectangular or circular circumference. However, the present general inventive concept is not limited thereto. A surface of the lower substrate  400  defines the inclination portion  420  and may have a side surface of a frustum of a cone to define the inclination portion  420  and to correspond to the reversed shape of the ink leading unit  411  in different dimension, i.e., size or area. The inclination portion  420  has an area corresponding to the inside surface, and another area corresponding to the outside surface, and the another area of the outside surface is larger than the area of the inside surface in a direction perpendicular to an ink flowing direction of the damper  320 , the ink leading unit  411 , and the ink ejecting hole. The inclination portion  420  may have a first angle with a surface to define the ink ejecting hole  412  and a second angle with the bottom surface  401 . 
     The hydrophobic layer  500  may have a first hydrophobic layer formed on the bottom surface  401 , and a second hydrophobic layer formed on the inclination portion  420 . An end portion of the second hydrophobic layer of the hydrophobic layer  500  may form a part of the ink ejecting hole  412 , as illustrated in  FIG. 4 . 
     The hydrophobic layer may include a first portion formed on the bottom surface of the substrate and having a first thickness and a second portion formed on the inclination portion and having a second thickness. The first thickness in a direction perpendicular to the bottom surface may be thicker than the second thickness in a direction perpendicular to the surface of the inclination portion. The first thickness and the second thickness may be a same in the ink ejecting direction. 
     Accordingly, a wiper (see  FIG. 1 ) may not direct-contact the inclination portion  420  when the wiper wipes ink stained on the bottom surface  401  of the lower substrate  400 , the hydrophobic layer  500  coated on the inclination portion  420  barely comes off, and remaining ink can flow along the inclination portion  420 . Thus, ink drops can be stably ejected through the ink ejecting hole  412  of the nozzle  410 . 
       FIG. 6  is an enlarged view illustrating a nozzle  610 , according to an embodiment of the present general inventive concept.  FIG. 7  is a bottom view of the nozzle  610  of  FIG. 6 . 
     Referring to  FIGS. 6 and 7 , the nozzle  610  is formed in a lower substrate  600  to have a predetermined depth from a bottom surface  601  of the lower substrate  600 . A flat portion  620 , which is perpendicular to an ink flowing direction of the ink ejecting hole  612 , is formed at the entrance of an ink ejecting hole  612 . The flat portion  620  and the bottom surface  601  of the lower substrate  600  are connected by an inclination portion  630  inclined inwards at a predetermined angle. The flat portion  620 , the inclination portion  630  and the bottom surface  601  of the lower substrate  600  are all coated with a hydrophobic layer  700 . The ink flowing direction may be a center line passing through centers of the damper  320 , the ink leading hole  411 , and the ink ejecting hole  412 . 
     As illustrated in  FIGS. 6 and 7 , the ink ejecting hole  612  has a circular shape, and the flat portion has an inside surface extended from the ink ejecting hole  612  and an outside surface connected to an inside surface of the inclination portion  630 . An outside surface of the inclination portion  630  has an area larger than the inside surface of the inclination portion  630  and the inside and outside surfaces of the flat portion  620  in a direction perpendicular to the ink flowing direction. The inside surface of the flat portion  620  corresponds to the circular shape of the ink ejecting hole  412 , and the outside surface of the flat portion  620  is extended from the inside surface thereof toward the inclination portion  630 . The outside surface of the flat portion  620  and the inside and outside surfaces of the inclination portion  630  may be a rectangular shape. However, the present general inventive concept is not limited thereto. 
     The hydrophobic layer  700  may have a first hydrophobic layer formed on the bottom surface  601 , a second hydrophobic layer formed on the inclination portion  430 , and a third hydrophobic layer formed on the flat portion  620 . An end portion of the third hydrophobic layer of the hydrophobic layer  500  may form a part of the ink ejecting hole  612 , as illustrated in  FIG. 6   
     Accordingly, since a wiper (see  FIG. 1 ) does not contact the flat portion  620  and the inclination portion  630  when the wiper wipes ink stained on the bottom surface  601  of the lower substrate  600 , the hydrophobic layer  700  coated on the flat portion  620  and the inclination portion  630  barely come off, and remaining ink can flow along the inclination portion  630 . Thus, ink drops can be stably ejected through the ink ejecting hole  612 . 
       FIG. 8  is an enlarged view of a nozzle  810 , according to an embodiment of the present general inventive concept.  FIG. 9  is a bottom view of the nozzle  810  of  FIG. 8 . 
     Referring to  FIGS. 8 and 9 , the nozzle  810  is formed in a lower substrate  800  to have a predetermined depth from a bottom surface  801  of the lower substrate  800 . A circular arc portion  820  having a predetermined concave curvature is formed towards the entrance of an ink ejecting hole  812 , and the circular arc portion  820  connects the ink ejecting hole  812  to the bottom surface  801  of the lower substrate  800 . The circular arc portion  820  and the bottom surface  801  of the lower substrate  800  are all coated with a hydrophobic layer  900 . 
     A surface of the circular arc portion  820  may be a shape of a portion of a side circumferential surface of a sphere in an ink flowing direction of the ink leading unit  811  and the ink ejecting hole  812 , and the circular arc portion  820 . 
     The hydrophobic layer  800  may have a first hydrophobic layer formed on the bottom surface  801 , and a second hydrophobic layer formed on the inclination portion  820 . An end portion of the second hydrophobic layer of the hydrophobic layer  800  may form a part of the ink ejecting hole  812 , as illustrated in  FIG. 8 . 
     Accordingly, since a wiper (see  FIG. 1 ) does not contact the circular arc portion  820  when the wiper wipes ink stained on the bottom surface  801  of the lower substrate  800 , the hydrophobic layer  900  coated on the circular arc portion  820  barely comes off, and remaining ink can flow along the circular arc portion  820 . Thus, ink drops can be stably ejected through the ink ejecting hole  812  of the nozzle  810 . In addition, a process for forming the circular arc portion  820  is simpler than a process for forming the flat portion  620  illustrated in  FIGS. 6 and 7 . 
     An operation of a piezoelectric type inkjet printhead having the above structure will be described by referring to  FIG. 3 . 
     Ink that flows from an ink container (not shown) to the inside of the reservoir  310  is supplied to the inside of the pressure chamber  240  through the restrictor  250 . When the pressure chamber  240  is filled with ink, a voltage is applied to the piezoelectric film  120  through the upper electrode  110  of the piezoelectric actuator  100 , thereby, deforming the piezoelectric film  120 , and accordingly, the second silicon substrate  230  of the upper substrate  200 , which functions as a diaphragm, is bent downwards. The volume of the pressure chamber  240  is reduced due to the bending due to the deformation of the second silicon substrate  230 , and accordingly, the ink filling the pressure chamber  240  passes into the damper  320  and is ejected through the nozzle  410  to the outside due to the rise in pressure. 
     As described above, the piezoelectric type inkjet according to the present general inventive concept prevents physical damages to a hydrophobic layer that is formed around a nozzle in order to maintain durability and stability of the piezoelectric type inkjet. Thus, reliability can be maintained with respect to the ejecting performance of ink. 
     Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.