Patent Publication Number: US-11034168-B2

Title: Printing within defined zones

Description:
BACKGROUND 
     A print apparatus may be used to deliver print agent, such as ink, in a pattern onto a substrate, such as a sheet of paper. 
     A print apparatus may be used to print anywhere on the substrate, including up to the edges of the substrate. It may be intended that print agent is delivered up to, but not beyond an edge of the substrate. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Examples will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a series of schematics showing an example of eight stages of a print job; 
         FIG. 2  is a flowchart of an example of a method of printing within a defined zone; 
         FIG. 3  is a flowchart of a further example of a method of printing within a defined zone; 
         FIG. 4  is a flowchart of a further example of a method of printing within a defined zone; 
         FIG. 5  is a flowchart of a further example of a method of printing within a defined zone; 
         FIG. 6  is a schematic of an example of a print apparatus; 
         FIG. 7  is a schematic of a further example of a print apparatus; 
         FIG. 8  is a schematic of a further example of a print apparatus; and 
         FIG. 9  is a schematic of an example machine-readable medium with a processor to perform a method of printing within a defined zone. 
     
    
    
     DETAILED DESCRIPTION 
     A printing apparatus may be used to deliver print agent, such as ink, onto a substrate, such as a sheet of paper as the substrate is moved over a platen. Print agent may be contained in a reservoir. For example, print agent may be held in tanks or cartridges. Print agent may be delivered by a nozzle of a print agent distributor, or print head. For example, print heads fluidly connected to ink tanks may deliver ink from the ink tanks to the print head and deposit ink via nozzles of the print heads onto the substrate in a pattern according to print job data processed, for example by processing apparatus. 
     A print job may, in some examples, involve the delivery of print agent within a defined zone adjacent to an edge of the substrate and, in some example, up to (or substantially to) the edge of the substrate. Printing in this way may be referred to as borderless printing or full bleed printing. When printing at full bleed, the print head may, intentionally or otherwise, deliver print agent to area just beyond the edge of the substrate onto a surface supporting the substrate, for example the platen. Print agent delivered onto the platen may transfer onto the substrate as the substrate is moved over the platen, thereby damaging the substrate. The platen may, therefore, be provided or supplemented with a portion, for example a print agent-absorbent portion, onto which print agent may be delivered without the risk (or with a lower risk) that the print agent is then transferred back onto the substrate inadvertently. 
       FIG. 1  is a schematic showing an example of eight stages of a print job using a print apparatus. In  FIGS. 1 a  to 1 h   , a portion of a print apparatus is shown. 
     A print apparatus may be used to print (e.g. deliver print agent) onto a substrate  100 . The substrate  100  may be any type of printable medium (also called a print medium), and may be a sheet of material, such as paper, capable of receiving print agent. In other examples, the substrate  100  may be a sheet of cardboard, wood, glass, metal or plastics material. The substrate  100  may be any shape. In the example described herein the substrate  100  is substantially rectangular having a leading edge  102 , a trailing edge  104 , a first side edge  106  and a second side edge  108 . In some examples, the substrate  100  may take the form of individual sheets while, in other examples, the substrate may include a roll of material, such as a web substrate, to be printed and cut to a desired length. 
     The print apparatus includes a print bed which may include a platen  110 , which may be a flat surface to support the substrate  100  during the printing process. The substrate  100  may be moved, or advanced, over the platen  110  using a substrate advancer, or advancing system (not shown in  FIG. 1 ), which may include a roller and/or a wheel. In the example shown in  FIG. 1 , the direction of movement of the substrate  100  over the platen  110  is shown by arrow A. The platen  110  may, in some examples, include a rib  112  extending at least partially over the platen in the direction of movement of the substrate  100 , shown by the arrow A. In some examples, the platen  110  may include multiple ribs  112 . In the example shown in  FIG. 1 , the platen  110  includes four ribs  112 , but in other examples, more or fewer ribs may be provided. The ribs  112  may extend proud of the platen  110  (that is to say, the ribs may extend slightly upwards from the platen) such that the form a series of ridges. The ribs  112  are provided to support the substrate  100  as the substrate advances over the platen  110 . 
     As noted above, in some examples, the platen  110  may include a portion  114  formed from a print agent-absorbent (e.g. ink-absorbent) material, such as foam. The absorbent portion  114  may have a width equal to a width of the platen  110 , such that the absorbent material extends over the width of the platen as shown in the example of  FIG. 1 . In other examples, the absorbent portion  114  may have a width less than the width of the platen, but the width of the absorbent portion may be greater than a width of the substrate  100  to be printed. In some examples, the absorbent portion  114  may form a part of the platen  110  while, in other examples, the platen may comprise two separate portions separated by the absorbent portion. As can be seen, in the example of  FIG. 1 , the ribs  112  extend over the platen  110  but not over the absorbent portion  114 . In other examples, however, the ribs  112  may extend at least partially over the absorbent portion  114 . 
     The print apparatus further includes a print agent distributor, or print head  116 , having a plurality of nozzles (not shown) via which print agent may be delivered onto the substrate. As used herein, “delivering” print agent includes firing, ejecting or otherwise depositing print agent or print fluid. The selection of the nozzles via which print agent is to be delivered is made by a control unit, or processing apparatus (not shown), and is made based on the pattern to be printed. In some examples, a printing mask may be used to define which nozzles are to print and which are not to print. The nozzles are, in some examples, arranged in an array, and may be arranged in rows (i.e. parallel to the leading edge  102  of the substrate  100  in  FIG. 1 ) and columns (i.e. parallel to the side edges  106 ,  108  in  FIG. 1 ). During printing, the print head  116  moves over the platen  110  and the substrate  100  in a direction perpendicular to the direction of movement of the substrate, in a printing pass, in the direction of arrow B in  FIG. 1 . 
     The array of nozzles in the print head  116  may be arranged in subgroups. For example, the nozzles of the print head  116  may be arranged in five subgroups or bands, as shown in  FIG. 1 . In the example shown in  FIG. 1 , a first band  118   a  of nozzles is located at a first position in the print head, a second band  118   b  of nozzles is located at a second position in the print head, a third band  118   c  of nozzles is located at a third position in the print head, a fourth band  118   d  of nozzles is located at a fourth position in the print head and a fifth band  118   e  of nozzles is located at a fifth position in the print head. Each band of nozzles may be controlled to deliver print agent independently of the others, or two or more of the bands of nozzles may be controlled to deliver print agent simultaneously. In some examples, some nozzles within a particular band of nozzles may deliver print agent while other nozzles in the particular band of nozzles may be prevented from delivering print agent. 
     The maximum area (for example on a substrate) that can be printed by the print head  116  in a single pass may be called a swath. In this context, the number of rows (which may be measured in rows of nozzles or rows of a resulting pattern/image, for example pixel rows) that may be printed may be referred to as a “swath height”. The expressions “pass” or “print pass” are intended to mean a movement of the print head  116  over the substrate during which print agent is deposited. In some examples, print agent may be delivered when the print head  116  moves in the direction B (i.e. from left to right in  FIG. 1 ). After the pass, the print head  116  may return to its starting position (i.e. its position in  FIG. 1 ) before performing a second pass. In other examples, print agent may also be deposited while the print head  116  moves in the direction opposite to the arrow B (i.e. from right to left in  FIG. 1 ). In such an example, each time the print head travels completely over the substrate may be a print pass. 
     In some examples, the print head  116  may be such that the area to be printed by all of the nozzles, or by all of the bands of nozzles, is completed after multiple passes of the print head. In other words, the swath is completed after multiple passes of the print head  116  over the substrate  100 . By using such a so-called “multi-pass” print mode, the resulting print quality may be higher than can be achieved using a single-pass print mode, as a greater amount of print agent may be delivered to the substrate  100 . Further, the print agent may be able to dry between each pass of the print head  116 , meaning the interaction between fresh print agent delivered during each pass pf the print head with print agent already delivered to the substrate is different to the interaction between print agent and the substrate if the print agent is delivered during a single pass. 
       FIGS. 1 a  to 1 h    show various stages of a multi-pass print job as the substrate  100  is advanced over the platen  110  according to an example. Print agent may, in some examples, be delivered onto the substrate by a different band of nozzles during each pass. In the example shown, print agent is to be delivered (printed) onto the substrate  100  up to the leading edge  102 . In this example, a defined zone  120  is defined adjacent to the leading edge  102  of the substrate  100 , the defined zone defining an area within which print agent is not to be delivered while the leading edge of the substrate  100  is over the platen  110 , as s discussed below. The defined zone  120  may be a zone of any shape. In some examples described herein, the defined zone includes an edge of the substrate. The defined zone  120 , in some examples, may be considered to be a margin. The margin  120  serves as a boundary beyond which print agent may be printed onto the substrate  100  if the leading edge  102  is over a defined area (such as the absorbent portion  114 ) of the platen  110 . 
       FIG. 1 a    shows the position of the substrate  100  after completion of a first pass of the print head  116 . Prior to the first pass, the substrate  100  may be moved into position by the substrate advancer or advancing system (not shown). During the first pass, print agent may be delivered via nozzles in the first band  118   a  of nozzles to form a pattern  122   a  on the substrate  110 . Depending on the print job data, the pattern printed may include, amongst other things, text, a drawing, a shape and/or a photograph, and may be in black and white (monochrome) or colour. As is shown in  FIG. 1 a   , even though the substrate  100  is positioned such that all of the nozzles in the first band  118   a  of nozzles pass over the substrate during the first pass of the print head, a nozzle (or in some examples, a row of nozzles) may not deliver print agent during the first pass. Specifically, a nozzle within a region  124  may not be fired, or may be prevented from delivering print agent onto the substrate  100 , as those nozzles are aligned with (i.e. fall within) the margin  120  during the first pass. Thus, during the first pass, nozzles in the first band  118   a  that are not within the region  124  may deliver print agent onto the substrate  100  outside the margin  120 , and nozzles within the region  124  in the first band of nozzles are instructed not to deliver print agent, or are otherwise prevented from delivering print agent onto the substrate within the margin. In this way, in the example shown, the pattern  122   a  formed on the substrate from the first pass of the print head  116  has a smaller width than would be possible if the first band  118   a  of nozzles were to fire during a pass over a portion of the substrate that did not include the margin  120 . 
     The way in which a nozzle, or a rows of nozzles, of the print head may be prevented from delivering print agent may be achieved in various ways. In some examples, each row of nozzles may be independently instructed by the processing apparatus in accordance with the print job data. In other words, a particular row of nozzles may be instructed to print or not print, based on whether the particular row of nozzles is aligned with the margin  120  of the substrate  100 . In other examples, a print mask may be generated and applied to the nozzles of the print head  116 . The print mask may be a virtual mask (e.g. a mask defined in computer code) and may comprise a binary code for each nozzle in the print head. In some examples, the print mask may include, for each nozzle, a ONE ( 1 ) which corresponds to an instruction for a nozzle to deliver print agent, or a ZERO ( 0 ) which corresponds to an instruction for the nozzle not to deliver print agent. As such, the print mask may, in some examples comprise an array of ones and zeroes, each digit defining an instruction for a corresponding nozzle. The print mask may be generated and/or applied by processing apparatus, such as processing apparatus associated with, or within, the print apparatus. The print mask may be based on the size of the margin  120  defined for the substrate  100 . For example, if a margin for a particular substrate is defined as being 1 mm (i.e. a strip along the leading edge  102  of the substrate  100  having a width of 1 mm), then the processing apparatus may determine that forty rows of nozzles would fire within the margin during a printing pass and, therefore, each nozzle in those forty rows (i.e. the rows of nozzles within the region  124 ) are masked and instructed not to fire during the first pass. 
     In the example of  FIG. 1 , the second, third, fourth and fifth bands  118   b ,  118   c ,  118   d ,  118   e  of nozzles of the print head  116  do not pass over the substrate during the first pass and, therefore, nozzles within the second, third, fourth and fifth bands may be instructed not to fire during the first pass. Accordingly, the print mask may include a ‘zero’, or a ‘do not fire’ instruction for each nozzle in the second, third, fourth and fifth bands during the first pass. 
     Once the first pass has been completed, and the pattern  122   a  has been printed, the substrate  100  is advanced by a defined distance. In this example, the substrate  100  is advanced in the direction of the arrow A by a distance defined by the number of bands of nozzles in the print head  116 . For example, in the case shown in  FIG. 1 , the substrate  100  is advanced by a distance equivalent to the length of a band of nozzles (i.e. by a distance equivalent to the number of rows of nozzles in a single band of nozzles). 
       FIG. 1 b    shows the position of the substrate  100  after the substrate has been advanced (following the first pass) and after a second pass of the print head  116 . After the substrate has advanced, the pattern  122   a  may be aligned with the second band  118   b  of nozzles in the print head  116 , and the first band  118   a  of nozzles may be aligned with a portion of the substrate adjacent to the pattern  122   a . During the second pass of the print head  116  over the substrate  100 , all of the nozzles in the first band  118   a  may be instructed or allowed to fire as none of the rows of nozzles in the first band are aligned with the margin  120  after the substrate has advanced. However, after the substrate has advanced following the first pass, the margin  120  of the substrate  100  is aligned with a nozzle (or a row of nozzles) in the second band  118   b . Therefore, a processing apparatus associated with the print apparatus and/or the print head may generate and/or apply a print mask in which nozzles (e.g. a row of nozzles) within the region  124  (see  FIG. 1 a   ) are instructed or allowed to fire during the second print pass, but nozzles (e.g. a row of nozzles), which are within a region  126 , and therefore are aligned with the margin  120 , are not fired or are instructed not to fire during the second print pass. The print mask generated for the second print pass may allow those nozzles or rows of nozzles in the second band  118   b  which are not within the region  126  to fire during the second print pass, along with the nozzles within the first band  118   a . As in the first print pass, the nozzles within third, fourth and fifth bands  118   c ,  118   d ,  118   e  may be prevented from firing/Instructed not to fire during the second print pass as those nozzles do not pass over the substrate during the second pass. 
     During the second pass, those nozzles in the second band  118   b  that are enabled to print (e.g. are not masked by the print mask) may deliver print agent onto the substrate  100  in the same location as the pattern  122   a . The nozzles in the first band  118   a  may deliver print agent onto the substrate  100  in a pattern  122   b.    
     Following the second pass of the print head  116 , the substrate  100  may be advanced by a defined distance (which may be the same distance by which the substrate is defined following the first print pass) by the substrate advancer or other advancing system. 
       FIG. 1 c    shows the position of the substrate  100  after the substrate has been advanced (following the second pass) and after a third pass of the print head  116 . During the third print pass, nozzles in the third band  118   c  of nozzles deliver print agent onto the substrate  100  in the pattern  122   a , and those nozzles of the third band within a region  128 , which are aligned with the margin  120 , are masked so that they do not deliver print agent during the third pass. During the third pass, nozzles in the first band  118   a  may deliver print agent onto the substrate  100  in a pattern  122   c.    
       FIG. 1 d    shows the position of the substrate  100  after the substrate has been advanced (following the third pass) and after a fourth pass of the print head  116 . Nozzles in the fourth band  118   d  of nozzles deliver print agent onto the substrate  100  in the pattern  122   a , and those nozzles of the fourth band within a region  130 , which are aligned with the margin  120 , are masked so that they do not deliver print agent during the fourth pass. During the fourth pass, nozzles in the first band  118   a  may deliver print agent onto the substrate  100  in a pattern  122   d.    
     By the fourth pass of the print head  116 , the substrate  100  has been advanced by such a distance that the leading edge  102  of the substrate is over the absorbent portion  114  of the platen  110 . Thus, the margin  120  may be printed without the risk that print agent may be inadvertently delivered onto the platen  110 .  FIG. 1 e    shows the position of the substrate  100  after the substrate has been advanced (following the fourth pass) and after a fifth pass of the print head  116 . Once the leading edge  102  of the substrate is over the absorbent portion  114 , print agent may be delivered onto the substrate in the margin  120  by a subset of nozzles of the print head which have not delivered print agent during the first, second, third or fourth passes. In this example, a subset  132  of nozzles may be used to deliver print agent within the defined zone  120  (i.e. within the margin). In some examples, when a borderless print job is to be performed, the subset  132  of nozzles may be used just for printing within the margin  120 , and not used for printing outside the margin. In some examples, if a print job is to be performed in which print agent is not to be delivered to within a margin (i.e. if the print job is not a borderless print job), then nozzles in the subset  132  may be used to deliver print agent to other areas of the substrate. 
     In the example shown in  FIG. 1 , the subset  132  of nozzles form part of the fifth band  118   e  of nozzles. It will be apparent also that, in some example, not all of the nozzles in the subset  132  of nozzles are to deliver print agent onto the substrate within the defined zone. The number of nozzles (or rows of nozzles) to be used to print within the margin may depend on the size of the margin to be printed and/or the number of print passes to be performed when printing the margin. 
     During the fifth pass of the print head  116 , nozzles within the subset  132  of nozzles may deliver print agent into part of the margin  120 . In the example shown in  FIG. 1 e   , half of the margin  120  is printed during the fifth pass. Thus, nozzles in a region  134  within the subset  132  may be used to print a pattern  122   e  on the substrate. The pattern  122   e  is a strip which is, in this example, thinner than the pattern  122   a  printed during previous passes. Thus, the distance by which the substrate is advanced prior to the fifth pass may be shorter than the distance by which the substrate is advanced between the first, second, third and fourth passes. 
     Following the fifth print pass, the substrate may be advanced, in this example, by a distance equal to the advance made following the fourth print pass, such that the substrate is in the position shown in  FIG. 1 f   . In some examples, the advance distance may be different to preceding advance distances. Figure if shows the substrate  100  after the substrate has been advanced (following the fifth pass) and after a sixth pass of the print head  116 . During the sixth pass, print agent may be delivered onto the substrate within the whole of the margin  120 , using nozzles within the subset  132  of nozzles. In this example, nozzles (or rows of nozzles) within a region  136  are used for printing in the margin  120 . The nozzles within the region  136 , which includes the region  134  shown in  FIG. 1 e   , deliver print agent in the pattern  122   e  printed during the fifth print pass, and also into a pattern  122   f.    
     Following the sixth print pass, the substrate, in some examples, may again be advanced by a distance equal to the advance made following the fifth print pass. In some examples, the substrate may not be advanced following the sixth print pass, as the margin  120  is over the absorbent portion  114 , and nozzles in the subset  132  are able to print within the margin.  FIG. 1 g    shows the substrate  100  after a seventh pass of the print head  116 . During the seventh pass, print agent is delivered onto the substrate using nozzles within a region  138  of the subset  132  of nozzles. The nozzles within the region  138  are, in this example, the same nozzles that are in the region  134  (see  FIG. 1 e   ). The print agent delivered during the seventh print pass completes the delivery of print agent within the margin. Thus, in this example, the margin  120  is printed during three print passes, with two strips (e.g. patterns  122   e ,  122   f ) each receiving two deposits of print agent. In this example, during each print pass to print the margin, print agent may be delivered with 50% of the final intended density, such that the total intended amount of print agent is to be delivered into each strip on the substrate in the margin after two passes. During the print passes in which the margin  120  is printed, nozzles in the bands  118   a - d  are prevented from firing, for example using a print mask. 
     After the margin has been printed (i.e. after the seventh print pass in this example), nozzles within the subset  132  of nozzles may not be used to deliver print agent again until it is intended to print within another margin of another substrate. Thus, a print mask may applied to prevent nozzles within the subset  132  from delivering print agent, but which allows print agent to be delivered by other nozzles in the print head, such as nozzles within the bands  118   a - d . Following the seventh print pass, the substrate  100  may be advanced by a distance to bring the patterns  122   b, c, d  into alignment with the bands of nozzles  118   d, c, b  respectively. Thus, the substrate  100  may be advanced by a distance that is shorter than the advance made following the first, second and third print passes. In other words, the substrate advance made following the completion of the printing of the margin  120 , in this example, is the same as the advance made following the first, second and third print passes, minus the distance by which the substrate is advanced while printing the margin (i.e. during the fifth, sixth and seventh print passes). Printing of the substrate outside the margin  120  may then continue, with print agent being delivered by nozzles in the bands  118   a - d.    
       FIG. 1 h    shows the substrate  100  after the substrate has been advanced (following the seventh pass) and after an eighth pass of the print head  116 . During the eighth print pass, nozzles in the bands  118   d, c  and  b  deliver print agent onto the substrate  100  in the patterns  122   b, c  and  d  respectively. In this example, following the eighth pass, printing on the substrate in the patterns  122   a  and  122   b  is complete. Printing using the nozzles in the bands  118   a - d  may continue until the intended pattern or image to be printed on the substrate  110  is complete. However, the nozzles within the subset  132  are not used to print outside the margin  120 . 
     As noted above, the example described above with reference to  FIG. 1  relates to a print operation which involves four print passes to print a swath outside the margin  120 , and three passes to print the region within the margin (i.e. the defined zone)  120 . In other examples, however, print operations may involve a smaller or greater number of print passes to complete a swath outside the defined zone and/or within the defined zone and, in some examples, the distance by which the substrate  100  is advanced after each print pass may be relatively smaller than in the example described above. In some examples, the edge  102  of the substrate may be positioned over the absorbent portion  114  for more than three print passes. In such scenarios, print agent may be delivered onto the substrate  100  within the margin  120  during a larger number of print passes, which may result in a relatively higher quality print, as the print agent intended to print in the margin may be divided between additional passes. In some examples, the print agent to be delivered within the margin may be divided evenly between the multiple print passes while, in other examples, the proportion of print agent to be delivered during a print pass of the multiple print passes when printing the margin may be more or less than the proportion of print agent to be delivered during other print passes when printing the margin. 
       FIG. 2  is a flowchart of an example method  200  of printing on a printable medium. The method of printing may use a print head having a plurality of nozzles. The printable medium may have a leading edge and a defined zone adjacent to the leading edge. The print head may deposit print agent onto the printable medium via the plurality of nozzles during successive printing passes. The method  200  comprises, at block  202 , printing outside, and not within, the defined zone on the printable medium using a first subset of nozzles of the plurality of nozzles. The method further comprises, at block  204 , printing within, and not outside, the defined zone on the printable medium using a second subset of nozzles of the plurality of nozzles. Thus, as in the example described above, nozzles in the first subset of nozzles (e.g. the subset  132  in  FIG. 1 ) may not be used to deliver print agent until the printable medium, or substrate, is in a particular position relative to a print bed of the print apparatus to which the print belongs. When printing a borderless print job on a printable medium (e.g. printing onto a printable medium which is to be printed up to the leading edge, nozzles in the first subset (e.g. the subset  132  of  FIG. 1 ) are used just to print within a defined zone adjacent to the leading edge (e.g. within the margin). Nozzles in a second subset of the print head (e.g. nozzles not within the subset  132  of  FIG. 1 ) may be used to print just outside the defined zone, and may not be used to print within the defined zone. 
     In some examples, the nozzles included within the first subset of nozzles are not included within the second subset of nozzles. In other words, the nozzles of the print head may be divided (e.g. by a mask) into two distinct or discrete sets of nozzles; a first set to print within the margin of a substrate and a second set to print outside the margin. 
     As explained in the example described above with reference to  FIG. 1 , the first subset of nozzles may print outside the defined zone on the printable medium during a first printing pass, and the second subset of nozzles may print within the defined zone on the printable medium during a second printing pass, after the first printing pass. Thus, some printing may be performed on the printable medium outside the margin before the margin is printed. Following the printing of the margin, in some examples, the first subset of nozzles may print outside the defined zone on the printable medium during a third printing pass, after the second printing pass. 
     In some examples, the second subset of nozzles may print within the defined zone on the printable medium when the leading edge of the printable medium is within a defined area. The defined area may, for example, be an area above a print agent-absorbing portion, such as absorbent foam  114 . The second subset of nozzles may be prevented from printing within the defined zone on the printable medium when the leading edge of the printable medium is outside the defined area (e.g. not in an area above the print agent-absorbing portion). In this way, print agent is less likely to be inadvertently deposited onto a platen of the print apparatus. 
       FIG. 3  is a flowchart of an example method  300  of printing on a printable medium. The method  300  may include blocks  202  and  204  discussed above. The method  300  may further comprise, at block  302 , generating a print mask corresponding to the plurality of nozzles, the print mask defining those nozzles which are to print within the defined zone, and those nozzles which are to print outside the defined zone. In some examples, the method  300  may comprise generating multiple print masks, for example a first print mask defining those nozzles which are to print within the defined zone (e.g. a border mask), and a second print mask defining those nozzles which are to print outside the defined zone (e.g. a regular printing mask). The print mask may, in some examples, be a virtual print mask. The print mask may be generated in the form of computer code. In the some examples, the print mask may be generated by a processor, or processing circuitry associated with the print apparatus. At block  304 , the method  300  may comprise applying the print mask to the print head. The print mask may be generated based on print job data defining the print job to be performed. In some examples the print mask may be generated prior to any print agent having been deposited from the print head. 
       FIG. 4  is a flowchart of an example method  400  of printing on a printable medium. The method  400  may include any of blocks  202 ,  204 ,  302  and  304  discussed above. At block  402 , the method  400  may comprise advancing the printable medium between successive printing passes. For example, once a printing pass has been completed, a substrate advancer of the print apparatus may move the printable medium along a path so that subsequent printing passes may be performed. In some examples, between printing passes in which the first subset of nozzles are to print, the printable medium may be advanced by a first defined distance, and between printing passes in which the second subset of nozzles are to print, the printable medium may be advanced by a second defined distance, different from the first defined distance. In other words, the number of nozzles (or rows of nozzles) used to print outside the defined zone on the printable medium during a printing pass may be different to the number of nozzles (or rows of nozzles) used to print within the defined zone during a printing pass. Thus, a different number of printing passes may be used to print a swath that forms the margin than the number of printing passes used to print a swath outside the margin. 
     During each printing pass while printing within the defined zone, the second subset of nozzles may, in some example, print with a print quality equivalent to the quality of printing performed by the first subset of nozzles during each printing pass while printing outside the defined zone. Thus, the print quality of the image printed within the defined zone may be the same as (or indistinguishable from) the print quality of the image printed outside the defined zone. To achieve this, a density of print agent deposited within the defined zone may be the same as the density of print agent deposited outside the defined zone, for example. 
       FIG. 5  is a flowchart of an example method  500  of printing on a printable medium. The method  500  may include any of the blocks discussed above with reference to  FIGS. 2 to 4 . The method may comprise, at block  502 , identifying particular nozzles of the first subset of nozzles that are aligned with the defined zone of the printable medium during each printing pass. At block  504 , the method  500  may comprise, during each printing pass while printing outside the defined zone on the printable medium, preventing the particular nozzles of the first subset of nozzles from printing. Thus, even though nozzles within the first subset of nozzles are able to print outside the defined zone, some nozzles within the first subset may be prevented from printing if they are aligned with the leading edge of the printable medium, or with the defined zone. Such nozzles are included in the region  124  of  FIG. 1   a.    
     Preventing the particular nozzles from printing (block  504 ) may, in some examples, comprise applying a print mask to the print head, the print mask defining the particular nozzles of the first subset of nozzles which are not to print. As with the print mask or masks used to define which nozzles fall within the first subset and which nozzles fall within the second subset, the print mask used to define the particular nozzles of the first subset of nozzles which are not to print may be a virtual mask, generated using computer code, for example. 
     The method disclosed above may be performed by an apparatus, such as a print apparatus.  FIG. 6  is a schematic showing an example of a portion of a print apparatus  600  for printing in defined zones. The print apparatus  600  may comprise a print agent distributor  602  having a plurality of nozzles to deposit print agent onto a substrate during successive printing passes. In some examples, the substrate may have a leading edge and a defined zone adjacent to the leading edge. The print apparatus  600  may also comprise processing apparatus  604 . The processing apparatus  604  may be operably coupled to, and/or may control, the print agent distributor  602 . The processing apparatus  604  may enable a first subset of nozzles of the plurality of nozzles to deposit print agent outside, and not within, a defined zone on the substrate. The processing apparatus  604  may enable a second subset of nozzles of the plurality of nozzles to deposit print agent within, and not outside, the defined zone on the substrate. The print apparatus  600  may comprise, or be similar to, the print apparatus discussed with reference to  FIG. 1 . 
       FIG. 7  is a schematic showing an example of a portion of a print apparatus  700  for printing in defined zones. The print apparatus  700  may comprise the print agent distributor  602  and the processing apparatus  604 . The print apparatus  700  may comprise a print bed  702  having a platen to support the substrate, and a print agent-absorbing element, such as the absorbent portion  114 . The processing apparatus  604  may enable the second subset of nozzles to deposit print agent within the defined zone on the substrate when the defined zone is over the print agent-absorbing element. The processing apparatus  604  may, for example, generate a print mask to prevent the second subset of nozzles from depositing print agent within the defined zone unless the defined zone is over (i.e. above) the print agent-absorbing element. 
       FIG. 8  is a schematic showing an example of a portion of a print apparatus  800  for printing in defined zones. The print apparatus  800  comprises the print agent distributor  602 , and may comprise the processing apparatus  604  and/or the print bed  702 . The print apparatus  800  may comprise a substrate advancer  802  to advance the substrate between successive printing passes of the print agent distributor  602 . Between print passes in which the first subset of nozzles are to print, the substrate advancer  802  may advance the substrate by a first defined distance. Between print passes in which the second subset of nozzles are to print, the substrate advancer  802  may advance the substrate by a second defined distance, different from the first defined distance. In some examples, the processing apparatus  604  may be operably coupled to the substrate advancer  802 , and may cause the substrate the substrate advancer to advance (i.e. move) the substrate by a defined distance based on the print job data and/or on the nature of the print head (e.g. the number of nozzles). 
       FIG. 9  shows, schematically, a machine-readable medium  902  associated with a processor  904 . The machine-readable medium  902  comprises instructions which, when executed by the processor  904 , cause the processor  904  to cause a first group of nozzles of a print head to deposit print agent outside, and not within, a defined area on a printable medium. In some examples, the first group of nozzles may be caused to deposit print agent by ‘first group’ firing instructions  906  contained within the machine-readable medium  902 . 
     The machine-readable medium  902  may comprise instructions which, when executed by the processor  904 , cause the processor  904  to cause a second group of nozzles of the print head to deposit print agent within, and not outside, the defined area on the printable medium. In some examples, the second group of nozzles may be caused to deposit print agent by ‘second group’ firing instructions  908  contained within the machine-readable medium  902 . 
     In some examples, the machine-readable medium  902  may comprise instructions which, when executed by the processor  904 , cause the processor  904  to create a first print mask corresponding to the first group of nozzles, and defining those nozzles which are to print outside the defined zone. The machine-readable medium  902  may, in some examples, comprise instructions which, when executed by the processor  904 , cause the processor  904  to create a second print mask corresponding to the second group of nozzles, and defining those nozzles which are to print within the defined zone. In some examples, the machine-readable medium  902  may include print mask creation instructions (not shown). 
     The machine-readable medium  902  may, in some examples, comprise instructions which, when executed by the processor  904 , cause the processor  904  to identify particular nozzles of the first group of nozzles that are aligned with the defined area of the printable medium. In other words, an identification may be made of those nozzles which are aligned with the defined area of the printable medium (which may include the leading edge of the medium), and which are not to deliver print agent (since the defined area is not above a particular region (e.g. the absorbent portion)). The machine-readable medium  902  may, in some examples, comprise instructions which, when executed by the processor  904 , cause the processor  904  to create a third print mask corresponding to the particular nozzles of the first group of nozzles, the third print mask to prevent the particular nozzles from delivering print agent while the first group of nozzles is caused to deposit print agent. 
     Examples in the present disclosure can be provided as methods, systems or machine readable instructions, such as any combination of computer code, hardware or the like. Such machine readable instructions may be included on a computer readable storage medium (including but is not limited to disc storage, CD-ROM, optical storage, etc.) having computer readable program codes therein or thereon. 
     The present disclosure is described with reference to flow charts and/or block diagrams of the method, devices and systems according to examples of the present disclosure. Although the flow diagrams described above show a specific order of execution, the order of execution may differ from that which is depicted. Blocks described in relation to one flow chart may be combined with those of another flow chart. It shall be understood that each flow and/or block in the flow charts and/or block diagrams, as well as combinations of the flows and/or diagrams in the flow charts and/or block diagrams can be realized by machine readable instructions. 
     The machine readable instructions may, for example, be executed by a general purpose computer, a special purpose computer, an embedded processor or processors of other programmable data processing devices to realize the functions described in the description and diagrams. In particular, a processor or processing apparatus may execute the machine readable instructions. Thus functional modules of the apparatus and devices may be implemented by a processor executing machine readable instructions stored in a memory, or a processor operating in accordance with instructions embedded in logic circuitry. The term ‘processor’ is to be interpreted broadly to include a CPU, processing unit. ASIC, logic unit, or programmable gate array etc. The methods and functional modules may all be performed by a single processor or divided amongst several processors. 
     Such machine readable instructions may also be stored in a computer readable storage that can guide the computer or other programmable data processing devices to operate in a specific mode. 
     Such machine readable instructions may also be loaded onto a computer or other programmable data processing devices, so that the computer or other programmable data processing devices perform a series of operations to produce computer-implemented processing, thus the instructions executed on the computer or other programmable devices realize functions specified by flow(s) in the flow charts and/or block(s) in the block diagrams. 
     Further, the teachings herein may be implemented in the form of a computer programme product, the computer programme product being stored in a storage medium and comprising a plurality of instructions for making a computer device implement the methods recited in the examples of the present disclosure. 
     While the method, apparatus and related aspects have been described with reference to certain examples, various modifications, changes, omissions, and substitutions can be made without departing from the spirit of the present disclosure. It is intended, therefore, that the method, apparatus and related aspects be limited only by the scope of the following claims and their equivalents. It should be noted that the above-mentioned examples illustrate rather than limit what is described herein, and that those skilled in the art will be able to design many alternative implementations without departing from the scope of the appended claims. Features described in relation to one example may be combined with features of another example. 
     The word “comprising” does not exclude the presence of elements other than those listed in a claim, “a” or “an” does not exclude a plurality, and a single processor or other unit may fulfil the functions of several units recited in the claims. 
     The features of any dependent claim may be combined with the features of any of the independent claims or other dependent claims.