Patent Publication Number: US-8991983-B2

Title: Provide heat to end regions of a printhead die

Description:
BACKGROUND 
     Printhead dies may include fluid ejectors corresponding to ejection chambers to selectively eject printing fluid through respective ejection nozzles of corresponding fluid passages. The ejection nozzles may be arranged on a nozzle surface region of the printhead die. A plurality of printhead dies may be used to form a printhead assembly having an extended length to increase a size of a print zone and/or print speed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting examples are described in the following description, read with reference to the figures attached hereto and do not limit the scope of the claims. Dimensions of components 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 die according to an example. 
         FIG. 2  is a bottom view illustrating a printhead die according to an example. 
         FIG. 3A  is a schematic view illustrating the printhead die of  FIG. 2  according to example. 
         FIG. 3B  is a cross-sectional view along line  3 B- 3 B of the printhead die of  FIG. 3A  according to example. 
         FIG. 4A  is a schematic view illustrating the printhead die of  FIG. 2  according to another example. 
         FIG. 4B  is a cross-sectional view along line  4 B- 4 B of the printhead die of  FIG. 4A  according to another example. 
         FIG. 5  is a block diagram illustrating a printhead assembly according to an example. 
         FIG. 6  is a bottom view illustrating the printhead assembly of  FIG. 5  according to an example. 
     
    
    
     DETAILED DESCRIPTION 
     A printhead die such as an inkjet printhead die may include an internal region and an exterior region. The internal region may include fluid ejectors, ejection chambers, and fluid passages having ejection nozzles. The ejection chambers may be in fluid communication with a printing fluid supply, for example, through a feed channel. The fluid ejectors may correspond to the ejection chambers to selectively eject the printing fluid through the respective ejection nozzles of the corresponding fluid passages. The exterior region may include end regions and a nozzle surface region disposed there between. The nozzle surface region may include the ejection nozzles arranged in columns. 
     Temperature variations may exist along the columns of the exterior region. For example, the end regions may become cooler than the nozzle surface region resulting in an end of die banding defect. At times, ejection chambers near ends of the printing die may produce weaker fluid drops than ejection chambers in the middle of the printing die due to thermal variations. That is, thermal variation may cause differences in nucleation and drop ejection. Consequently, drops ejected from the ejection nozzles toward the ends of the printing die may be smaller than the drops ejected from the ejection nozzles toward the middle of the printhead die. Accordingly, a printed media may exhibit a banding signature correlating to the thermal signature. 
     In examples, a printhead die includes end regions, a nozzle surface region, fluid passages, ejection chambers, fluid ejectors, non-ejection chambers, and heating resistors. The nozzle surface region is disposed between the end regions. The fluid passages include corresponding ejection nozzles. The ejection nozzles are disposed on the nozzle surface region. The fluid ejectors correspond to the ejection chambers. Each one of the fluid ejectors selectively ejects printing fluid through a corresponding ejection nozzle. The heating resistors correspond to the non-ejection chambers such that the heating resistors selectively provide heat to the end regions while not ejecting printing fluid through the ejection nozzles. Thus, the heating resistors provide heat to the corresponding end regions to reduce thermal variation along the ejection nozzle columns without causing printing fluid ejection. Consequently, a printed media may exhibit a reduced or non-existent banding signature. 
       FIG. 1  is a block diagram illustrating a printhead die according to an example. Referring to  FIG. 1 , in some examples, a printhead die  100  includes a plurality of end regions  10   a , a nozzle surface region  10   b , a plurality of fluid passages  11 , a plurality of ejection chambers  12 , a plurality of fluid ejectors  13 , a plurality of non-ejection chambers  14 , and a plurality of heating resistors  15 . The nozzle surface region  10   b  is disposed between the end regions  10   a . The plurality of fluid passages  11  includes corresponding ejection nozzles  16 . For example, one end of a respective fluid passage  11  may be disposed at the respective ejection chamber  12  and another end of the fluid passage  11  may be in a form of an ejection nozzle  16  at the nozzle surface region  10   b . The ejection nozzles  16  are disposed on the nozzle surface region  10   b . In some examples, the ejection nozzles  16  may be arranged in columns on the nozzle surface region  10   b.    
     Referring to  FIG. 1 , in some examples, the ejection chambers  12  are in fluid communication with the corresponding fluid passages  11 . The fluid ejectors  13  correspond to the ejection chambers  12 . In some examples, the fluid ejectors  13  may be disposed in the ejection chambers  12 . Alternatively, the fluid ejectors  13  may be proximate to the corresponding ejection chamber  12  such as below or above a surface of the ejection chamber  12 . The fluid ejectors  13  may include resistors, piezoelectric members, and the like. Each one of the fluid ejectors  13  selectively ejects printing fluid through a corresponding ejection nozzle  16 . For example, the printing fluid may be ejected in the form of fluid drops from the respective nozzles  16  of the corresponding fluid passages  11  associated with the respective fluid ejectors  13 . 
     Referring to  FIG. 1 , in some examples, the heating resistors  15  correspond to the non-ejection chambers  14 . In some examples, the heating resistors  15  may be disposed in the non-ejection chambers  14 . Alternatively, the heating resistors  15  may be proximate to the corresponding non-ejection chamber  14  such as below or above a surface of the non-ejection chamber  14 . The heating resistors  15  selectively provide heat to the end regions  10   a  while not ejecting printing fluid through the ejection nozzles  16 . That is, each one of the heating resistors  15  is not associated with ejection nozzles  16  of fluid passages  11 . Thus, activation of each one of the heating resistors  15  emits heat therefrom and does not cause printing fluid proximate thereto to be ejected through ejection nozzles  16 . Heat generated from the heating resistors  15  can be transmitted to the end regions  10   a  of the printhead die  100  through portions thereof and/or by heating printing fluid. That is, the heated printing fluid may move through fluid passages  11  that are directed towards the end regions  10   a  of the printing die  100  and are not associated with an ejection nozzle  16 . 
       FIG. 2  is a bottom view illustrating a printhead die according to an example.  FIG. 3A  is a schematic view illustrating the printhead die of  FIG. 2  according to example.  FIG. 3B  is a cross-sectional view along line  3 B- 3 B of the printhead die of  FIG. 3A  according to example.  FIG. 4A  is a schematic view illustrating the printhead die of  FIG. 2  according to another example.  FIG. 4B  is a cross-sectional view along line  4 B- 4 B of the printhead die of  FIG. 4A  according to another example. Referring to  FIGS. 2-4B , a printhead die  200  may include the plurality of end regions  10   a , the nozzle surface region  10   b , the plurality of fluid passages  11 , the plurality of ejection chambers  12 , the plurality of fluid ejectors  13 , the plurality of non-ejection chambers  14 , and the plurality of heating resistors  15  of the printhead of  FIG. 1 . The printhead die  200  is a micro-electro-mechanical system (MEMS). In some examples, the printhead die  200  may include a silicon chip and multiple layers including fluid passages  11  and ejection nozzles  16 . The printhead die  200 , for example, may be an inkjet printhead die such as a thermal inkjet printhead die, and the like. 
     Referring to  FIGS. 2-4B , in some examples, the ejection chambers  12  may be in fluid communication with a printing fluid supply for example, through a feed channel  38 . The fluid ejectors  13  correspond to the ejection chambers  12 . In some examples, the fluid ejectors  13  may be disposed in the ejection chambers  12 . Alternatively, the fluid ejectors  13  may be proximate to the corresponding ejection chamber  12  such as below or above a surface of the ejection chamber  12 . In some examples, the fluid ejectors  13  may include firing resistors. 
     For example, an electric current may pass through a respective firing resistor resulting in rapid heating thereof. A thin layer of printing fluid proximate to the respective firing resistor may become superheated and vaporize, creating a vapor bubble in the corresponding ejection chamber  12 . The rapidly expanding vapor bubble may force a fluid drop out of the corresponding nozzle  16 . When the firing resistor cools, the vapor bubble may quickly collapse drawing more printing fluid into the ejection chamber  12  in preparation to eject another fluid drop from the ejection nozzle  16 . Accordingly, printing fluid is ejected from the respective ejection chamber  12  through a corresponding ejection nozzle  16 , and the respective ejection chamber  12  is then refilled with printing fluid, for example, from the feed channel  38  in fluid communication with the printing fluid supply. 
     Referring to  FIGS. 2-4B , in some examples, the printhead die  200  may also include a plurality of thermal sensing resistors  27 . The thermal sensing resistors  27  may be disposed along the end regions  10   a  and nozzle surface region  10   b  to detect respective temperatures thereof. In some examples, a respective heating resistor  15  is activated based on temperature differences between the respective temperatures detected by the thermal sensing resistors  27 . For example, the respective temperatures may indicate that the end regions  10   a  may be cooler than the nozzle surface region  10   b  resulting in activation of respective heating resistors  15  to heat the end regions  10   a.    
     Referring to  FIGS. 2-4B , the heating resistors  15  may correspond to the non-ejection chambers  14 . In some examples, the heating resistors  15  may be disposed in the non-ejection chambers  14 . Alternatively, the heating resistors  15  may be proximate to the corresponding ejection chamber  12  such as below or above a surface of the non-ejection chamber  14 . In some examples, a plurality of heating resistors  15  may correspond to each one of the non-ejection chambers  14 . The non-ejection chambers  14  may be isolated from the ejection nozzles  16 . The non-ejection chambers  14  may also be isolated (e.g., not in fluid communication) from a printing fluid supply. Alternatively, the non-ejection chambers  14  may be in fluid communication with the printing fluid supply. The ejection nozzles  16  may be arranged in a plurality of columns on the nozzle surface region  10   b.    
     Referring to  FIGS. 2-4B , in some examples, each one of the non-ejection chambers  14  may include an island member  49  disposed between the plurality of heating resistors  15  to create a fluid recirculation loop around a perimeter of the island member  49 . For example, a respective non-ejection chamber  14  may include a pair of heating resistors  15  to provide heat and cause printing fluid to recirculate through the fluid recirculation loop. When in contact with printing fluid, the heating resistors  15  can deliver enough energy to create a nucleation event that results in the formation of a drive bubble. The formation of the drive bubble may displace the printing fluid causing the printing fluid to move through defined fluid passages  11  that are absent ejection nozzles  16 . The fluid passages  11  may be directed towards the end regions  10   a  of the printhead die  200  or may be directed back towards a printing fluid supply region. Additionally, heating resistors  15  are sufficiently distant from other ejection nozzles  16  that the motion of the printing fluid does not cause the printing fluid to be ejected through ejection nozzles  16 . 
     Each heating resistor  15  may have different dimensions and/or a shape than the firing resistors. For example, the size of the heating resistor  15  may be adjusted to minimize a number of the heating resistors  15  needed to tune the thermal variation along the ejection nozzle columns and corresponding non-ejection chambers  14 . In some examples, the printhead die  200  may include developer ports (not illustrated) to remove wax in forming heating resistors  15  during the fabrication process and not formed to eject fluid drops therefrom. 
       FIG. 5  is a block diagram illustrating a printhead assembly according to an example.  FIG. 6  is a bottom view illustrating the printhead assembly of  FIG. 5  according to an example. Referring to  FIGS. 5 and 6 , in some examples, a printhead assembly  500  includes a carrier  59  and a plurality of printhead dies  100  coupled to the carrier  59  and arranged in a printhead die array. In some examples, the printhead assembly  500  may include a page-wide, inkjet array assembly, a low-cost inkjet array assembly, and the like. For example, the printing assembly  500  may be stationary and the printing media may move through the print zone to be printed on. 
     Referring to  FIGS. 5 and 6 , in some examples, the carrier  59  may be a rigid, plastic member to receive and align printhead dies  100  with respect to each other. In some examples, the printhead die array may include two columns of printhead dies  100  staggered with respect to each other such that a portion of the respective printhead dies  100  may overlap with each other. Each one of the printhead dies  100  may include a plurality of end regions  10   a , a nozzle surface region  10   b , a plurality of fluid passages  11 , a plurality of ejection chambers  12 , a plurality of non-ejection chambers  14 , and a plurality of heating resistors  15  as previously discussed with respect to  FIG. 1 . The printhead assembly  500  may also include firing resistors  53 . 
     Referring to  FIGS. 5 and 6 , in some examples, the nozzle surface region  10   b  is disposed between the end regions  10   a . The plurality of fluid passages  11  includes corresponding ejection nozzles  16 . The ejection nozzles  16  are disposed on the nozzle surface region  10   b . In some examples, the ejection nozzles  16  may be arranged in columns on the nozzle surface region  10   b . In some examples, the ejection chambers  12  are in fluid communication with the corresponding fluid passages  11 . The firing resistors  53  correspond to the ejection chambers  12 . In some examples, the firing resistors  53  may be disposed in the non-ejection chambers  14 . Alternatively, the firing resistors  53  may be proximate to the corresponding non-ejection chamber  14  such as below or above a surface of the non-ejection chamber  14 . Each one of the firing resistors  53  selectively ejects printing fluid through a corresponding ejection nozzle  16 . For example, the printing fluid may be ejected in the form of fluid drops from the respective nozzles  16  of the corresponding fluid passages  11  associated with the respective firing resistors  53 . 
     Referring to  FIGS. 5 and 6 , in some examples, the heating resistors  15  correspond to the non-ejection chambers  14 . In some examples, a plurality of heating resistors  15  may correspond to each one of the non-ejection chambers  14 . In some examples, each one of the non-ejection chambers  14  may include an island member  49  disposed between the plurality of heating resistors  15  to create a fluid recirculation loop around a perimeter of the island member  49 . The non-ejection chambers  14  may be isolated from the ejection nozzles  16 . The heating resistors  15  selectively provide heat to the end regions  10   a  while not ejecting printing fluid through the ejection nozzles  16 . That is, each one of the heating resistors  15  is not associated with ejection nozzles  16  of fluid passages  11 . Thus, activation of each one of the heating resistors  15  emits heat therefrom and does not cause printing fluid proximate thereto to be ejected through ejection nozzles  16 . Heat generated from the heating resistors  15  can be transmitted to the end regions  10   a  of the printhead die  100  through portions thereof and/or by heating printing fluid. That is, the heated printing fluid may move through fluid passages  11  that are directed towards the end regions  10   a  of the printing die  100  and are not associated with an ejection nozzle  16 . 
     The present disclosure has been described using non-limiting detailed descriptions of examples thereof that are not intended to limit the scope of the general inventive concept. 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 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 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 general inventive concept and which are described for illustrative purposes. 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 general inventive concept is limited only by the elements and limitations as used in the claims.