Patent Publication Number: US-9849673-B2

Title: Generate non-uniform electric field to maintain pigments in ink vehicle of printing fluid in nozzle region of printhead

Description:
BACKGROUND 
     Printing systems such as inkjet printers include printheads. The printheads include nozzles to eject printing fluid there through onto media. The printing fluid may include color pigments in an ink vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting examples of the present disclosure are described in the following description, read with reference to the figures attached hereto and do not limit the scope of the claims. In the figures, identical and similar structures, elements or parts thereof that appear in more than one figure are generally labeled with the same or similar references in the figures in which they appear. Dimensions of components, layers, substrates and features illustrated in the figures are chosen primarily for convenience and clarity of presentation and are not necessarily to scale. Referring to the attached figures: 
         FIG. 1  is a block diagram illustrating a printhead according to an example. 
         FIG. 2  is a schematic view illustratinga printhead according to an example. 
         FIG. 3  is an exploded view illustrating a portion of the printhead of  FIG. 2  according to an example. 
         FIG. 4  is a schematic view including field generating members of the printhhead of  FIG. 2  according to an example. 
         FIG. 5  is a block diagram illustrating a printhead according to an example. 
         FIG. 6  is a flowchart illustrating a method of operating a printhead according to an example. 
     
    
    
     DETAILED DESCRIPTION 
     Printing systems such as inkjet printers include printheads. The printheads include firing chambers including nozzle regions having printing fluid therein, and fluid ejectors to eject the printing fluid in the nozzle regions onto media. The printing fluid may include color pigments in an ink vehicle. Overtime, the color pigments in the ink vehicle located in the nozzle region may diffuse and move away from the nozzle region resulting in pigment ink vehicle separation. Consequently, ejection of the printing fluid in the nozzle region with a reduced amount of color pigments onto the media results in a reduction of image quality. Additionally, at times, pigment ink vehicle separation may result in solidification of the printing fluid in the nozzle region. Accordingly, the respective nozzle region may prevent the ejection of printing fluid and reduce the lifespan of a corresponding fluid ejector. 
     In examples, a printhead includes a plurality of firing chambers, a plurality of fluid ejectors, and at least one field generating member. Each firing chamber includes a nozzle region to receive printing fluid. The printing fluid includes an ink vehicle having pigments disposed therein. At least one field generating member generates a non-uniform electric field to apply forces to maintain respective pigments in the ink vehicle of the printing fluid in the nozzle region. Thus, the pigments in the ink vehicle located in the nozzle region may remain therein, rather than diffuse and move away from the nozzle region. Accordingly, the printing fluid ejected onto the media includes an appropriate amount of pigments. Thus, a reduction of image quality due to pigment ink vehicle separation and solidification of printing fluid in the nozzle region may be reduced. 
       FIG. 1  is a block diagram illustrating a printhead according to an example. Referring to  FIG. 1 , a printhead  100  includes a plurality of firing chambers  10 , a plurality of fluid ejectors  14 , and at least one field generating member  16 . Each firing chamber  10  includes a chamber inlet  10   a  and a nozzle region  12  to receive printing fluid. The printing fluid includes an ink vehicle having pigments disposed therein. For example, the pigments may be randomly dispersed throughout the ink vehicle. In some examples, the pigments may have a neutral charge. Each nozzle region  12  includes a nozzle inlet  12   a , a nozzle outlet  12   c , and a nozzle channel  12   b  disposed between the nozzle inlet  12   a  and the nozzle outlet  12   c . At least one fluid ejector  14  is disposed in each firing chamber  10  to eject the printing fluid therein through the respective nozzle region  12 . That is, a printing fluid drop may be formed and ejected from a corresponding nozzle outlet  12   c . The fluid ejector  14  may correspond to each nozzle region  12 . In some examples, the fluid ejector  14  may include a thermal ejection member, a piezoelectric ejection member, and the like. 
     Referring to  FIG. 1 , at least one field generating member  16  generates a non-uniform electric field to apply forces to maintain respective pigments in the ink vehicle of the printing fluid in the nozzle region  12 . For example, due to chemical compositions of the printing fluid and/or the atmospheric pressure at the nozzle outlet  12   c , the pigments may have a tendency to diffuse and move away from the ink vehicle in the nozzle region  12 . That is, in some examples, the non-uniform electric field generated by the field generating member  16  may apply forces to act as a barrier  29  to prevent neutrally-charged pigments from moving away from the ink vehicle in the nozzle region  12 . 
       FIG. 2  is a schematic view illustrating a printhead according to an example.  FIG. 3  is an exploded view illustrating a portion of the printhead of  FIG. 2  according to an example.  FIG. 4  is a schematic view illustrating field generating members of the printhead of  FIG. 2  according to an example. The printhead  200  may include the firing chambers  10 , the fluid ejectors  14 , and the field generating member  16  as previously discussed with respect to the printhead  100  of  FIG. 1 . Referring to  FIGS. 2-4 , in some examples, the field generating member  16  is disposed in the firing chamber  10 . For example, the field generating member  16  is disposed proximate to the chamber inlet  10   a . In some examples, the field generating member  16  may be positioned at or close to the chamber inlet  10   a . Alternatively, the field generating member  16  may be disposed at or close to the nozzle inlet  12   a . In some examples, printing fluid may be supplied to the chamber inlet  10   a  from a fluid supply and/or fluid supply channel (not illustrated). 
     Referring to  FIGS. 2-4 , in some examples, at least one field generating member  16  may include a plurality of field generating members disposed in the firing chamber  10 . For example, the plurality of field generating members  16  may include two field generating members having different sizes from each other as illustrated in  FIG. 4 . In some examples, the field generating members  16  may have different lengths l 1  and l 2  from each other. The field generating members  16  may include tantalum, silicon nitride, and the like. 
     Referring to  FIGS. 2-4 , in some examples, the non-uniform electric field generated by the at least one field generating member  16  is configured to maintain the respective pigments  21   b  in the ink vehicle  21   a  in the nozzle region  12  prior to ejection of the printing fluid through the respective nozzle outlet  12   c  by a corresponding fluid ejector  14 . That is, in some examples, the non-uniform electric field generated by the field generating member  16  may apply forces f to act as a barrier  29  to prevent pigment ink vehicle separation and/or pigments  21   b  having a neutral charge from moving away from the ink vehicle  21   a  in the nozzle region  12  as illustrated in  FIG. 3 , The pigments  21   b  may include color pigments. 
     Referring to  FIGS. 2-4 , in some examples, the non-uniform electric field may be generated in response to a signal  28  received by the field generating member  16 . For example, the field generating member  16  may receive a voltage signal having an amplitude of about one volt. The fluid ejector  14  is disposed in each firing chamber  10  may eject the printing fluid therein through the respective nozzle region  12 . As printing fluid leaves the printhead by being ejected from the nozzle region  12  by a corresponding fluid ejector  14 , a suction is created to enable additional printing fluid to enter the firing chamber  10  through the chamber inlet  10   a  and replace the ejected printing fluid in the nozzle region  12 . 
       FIG. 5  is a block diagram illustrating a printhead according to an example. The printhead  500  may include a plurality of firing chambers  10  and a plurality of fluid ejectors  14  as previously discussed with respect to the printhead  100  of  FIG. 1 . Referring to  FIG. 5 , the firing chambers  10  include chamber inlets  10   a  and nozzle regions  12  to receive printing fluid. The printing fluid includes an ink vehicle having color pigments disposed therein. Each nozzle region  12  includes a nozzle inlet  12   a , a nozzle outlet  12   c , and a nozzle channel  12   b  disposed between the nozzle inlet  12   a  and the nozzle outlet  12   c.    
     Referring to  FIG. 5 , at least one fluid ejector  14  is disposed in each firing chamber  10  to eject the printing fluid therein through the respective nozzle region  12 . That is, a printing fluid drop may be formed and ejected from a corresponding nozzle outlet  12   c . In some examples, the fluid ejector  14  may include a thermal ejection member, a piezoelectric ejection member, and the like. The field generating members  56  have different sizes and are disposed in each firing chamber  10 . For example, the field generating members  56  may have different lengths from each other. The field generating members  56  generate a non-uniform electric field in response to receiving a signal. The non-uniform electric field maintains respective color pigments in the ink vehicle of the printing fluid in the nozzle region  12  prior to ejection of the printing fluid through the respective nozzle outlet  12   c  by a respective fluid ejector  14 . 
     Referring to  FIG. 5 , in some examples, the field generating members  16  are disposed proximate to the chamber inlet  10   a . For example, the field generating members  56  may be positioned at or close to the chamber inlet  10   a . Alternatively, the field generating members  56  may be disposed at or close to the nozzle inlet  12   a . The field generating members  56  may include tantalum, silicon nitride, and the like. 
       FIG. 6  is a flowchart illustrating a method of operating a printhead according to an example. In some examples, the modules and/or assemblies implementing the method may be those described in relation to the printheads  100 ,  200 , and  500  of  FIGS. 1-5 . Referring to  FIG. 6 , in block S 610 , printing fluid including an ink vehicle and pigments is received into a firing chamber including a nozzle region. The nozzle region includes a nozzle inlet, a nozzle outlet, and a nozzle channel disposed between the nozzle inlet and the nozzle outlet of the printhead. The pigments may include color pigments such as color pigments having a neutral charge. 
     In block S 612 , a non-uniform electric field is generated by a field generating member disposed in the firing chamber. The field generating member may include tantalum, silicon nitride, and the like. The non-uniform electric field applies forces to maintain respective pigments in the ink vehicle of the printing fluid in the nozzle region in response to receiving a signal. That is, in some examples, the non-uniform electric field generated by the field generating member may apply forces to act as a barrier to prevent pigments having a neutral charge from moving away from the ink vehicle in the nozzle region. 
     For example, the respective pigments may be maintained In the ink vehicle of the printing fluid in the nozzle region prior to ejection of the printing fluid therein through the nozzle outlet by the fluid ejector. That is, the pigments in the ink vehicle located in the nozzle region may remain therein, rather than diffuse and move away from the nozzle region. Thus, the non-uniform barrier may reduce pigment ink vehicle separation in the printing fluid in the nozzle region. Accordingly, the printing fluid ejected onto the media may include an appropriate amount of pigments. Thus, image quality degradation due to pigment ink vehicle separation may be reduced. 
     In some examples, the method may also include ejecting the printing fluid in the nozzle region by a fluid ejector disposed in the firing chamber through the nozzle outlet. That is, a fluid ejector may correspond to each nozzle region. As printing fluid is ejected from the nozzle region by the corresponding fluid ejector and leaves the printhead, a suction is created to enable additional printing fluid to enter the firing chamber through the chamber inlet and replace the ejected printing fluid in the nozzle region. In some examples, the fluid ejector may include a thermal ejection member, a piezoelectric ejection member, and the like. 
     It is to be understood that the flowchart of  FIG. 6  illustrates architecture, functionality, and/or operation of examples of the present disclosure. If embodied in software, each block may represent a module, segment, or portion of code that includes one or more executable instructions to implement the specified logical function(s). If embodied in hardware, each block may represent a circuit or a number of interconnected circuits to implement the specified logical function(s). Although the flowchart of  FIG. 6  illustrates a specific order of execution, the order of execution may differ from that which is depicted. For example. the order of execution of two or more blocks may be rearranged relative to the order illustrated. Also, two or more blocks illustrated in succession in  FIG. 6  may be executed concurrently or with partial concurrence. All such variations are within the scope of the present disclosure. 
     The present disclosure has been described using non-limiting detailed descriptions of examples thereof and is not intended to limit the scope of the present disclosure. It should be understood that features and/or operations described with respect to one example may be used with other examples and that not all examples of the present disclosure have all of the features and/or operations illustrated in a particular figure or described with respect to one of the examples. Variations of examples described will occur to persons of the art. Furthermore, the terms “comprise,” “include” “have” and their conjugates, shall mean, when used in the present disclosure and/or claims, “including but not necessarily limited to.” 
     It is noted that some of the above described examples may include structure, acts or details of structures and acts that may not be essential to the present disclosure and are intended to be exemplary. Structure and acts described herein are replaceable by equivalents, which perform the same function, even if the structure or acts are different, as known in the art. 
     Therefore, the scope of the present disclosure is limited only by the elements and limitations as used in the claims.