Patent Publication Number: US-8991974-B2

Title: Ink jetting

Description:
This application claims the benefit of U.S. Provisional Application No. 61/076,788, filed Jun. 30, 2008, and incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This description relates to ink jetting. 
     BACKGROUND 
     Ink jetting can be done using an ink jet printhead that includes jetting assemblies. Ink is introduced into the ink jet printhead and when activated, the jetting assemblies jet ink to form images on a substrate. 
     SUMMARY 
     In an aspect, for jetting ink, a first set of orifices of an apparatus are arranged to print at a first maximum resolution, the first maximum resolution being along a direction different from a process direction. A second set of orifices is coupled to the first set of orifices. The second set of orifices is arranged to print at a second maximum resolution lower than the first maximum resolution, the second maximum resolution being along a direction different from the process direction. 
     Implementations may include one or more of the following features. The first set of orifices belongs to a first printhead and the second set of orifices belongs to a second printhead. The position of the first printhead relative to the second printhead is adjustable. The orientation of the first printhead relative to the process direction is adjustable. The first printhead is in front of the second printhead in the process direction. The first printhead is behind the second printhead in the process direction. The first printhead is in front of the second printhead in a direction perpendicular to the process direction. The first printhead is behind the second printhead in a direction perpendicular to the process direction. The first and second printheads each comprises a jetting assembly having more than 100 jets. The angle between the process direction and a length of the jetting assembly in the first printhead is between about 30° to about 85°. The second printhead is arranged to print at between about 100 dpi and 400 dpi. The first printhead is arranged to print at greater than 800 dpi. The first printhead is arranged to print at greater than 1000 dpi. The first printhead is arranged to print at about 1200 dpi. The different direction is perpendicular to the process direction. More than one printhead is arranged to print at a higher maximum resolution than the second printhead. The first and second printheads are incorporated in a single-pass ink jet printer and the substrate transports along the process direction. The first and second printheads are incorporated in a step-and-repeat ink jet printer and the substrate transports along a direction perpendicular to the process direction. The first printhead is arranged to print a portion of an image along a direction perpendicular to the process direction. During the relative motion, the substrate is moving along the process direction and the apparatus is stationary. During the relative motion, the substrate is stationary and the apparatus is moving along the process direction. The first set of orifices is in a first set of parallel arrays and the second set of orifices is in a second set of parallel arrays having an angle ranging from about 30° to about 85° with respect to the first set of parallel arrays. 
     In an aspect, during a relative motion in a process direction between an ink jetting apparatus and a substrate, a first portion of the ink jetting apparatus is caused to print on the substrate at a first maximum resolution. A second portion of the ink jetting apparatus is caused to print on the substrate at a second maximum resolution lower than the first resolution in a direction different from the process direction. 
     Implementations may include one or more of the following features. The location of the first portion of the ink jetting apparatus is adjusted relative to the second portion of the ink jetting apparatus prior to the relative motion. The causing comprises causing the first portion of the ink jetting apparatus to print in an area of the substrate before the second portion of the ink jetting apparatus prints in the area. The causing comprises causing the first portion of the ink jetting apparatus to print in an area of the substrate after the second portion of the ink jetting apparatus prints in the area. The causing comprises moving the ink jetting apparatus in the process direction perpendicular to a direction the substrate transports and printing on the substrate. The causing comprises transporting the substrate in a direction parallel to the process direction and printing on the substrate. 
     These and other aspects and features can be expressed as methods, apparatus, systems, means for performing a function, and in other ways. 
     Other features and advantages will be apparent from the following detailed description, and from the claims. 
    
    
     
       DESCRIPTION 
         FIGS. 1A and 1B  are exploded perspective views of an ink jet printhead and an ink jetting assembly. 
         FIG. 1C  is a schematic bottom view of an ink jet printhead. 
         FIGS. 2 and 3  are schematic top views of ink jet printers. 
         FIGS. 3A-3C  are schematic top views of a portion of a step-and-repeat ink jet printer. 
     
    
    
     Referring to  FIG. 1A , ink jetting can be done using an ink jet printhead  2  that includes at least one jetting assembly  4  assembled into a collar element  10 . The collar element  10  is attached to a manifold plate  12  which is attached to a plate  14  having orifices  16 . When in use, the printhead  2  and a substrate  18  move relative to each other along a process direction perpendicular to a length  6  of the jetting assembly  4  (see also  FIG. 1B ) and during the relative motion, ink is loaded into the jetting assembly  4  through the collar element  10  and jetted through orifices  16  to form an image  8  on a substrate  18 . In particular, when the ink jet printhead  2  is assembled into what is called a single-pass ink jet printer, the printhead  2  jets ink drops on the substrate  18  that is moving in a transporting direction y. When the ink jet printhead  2  is assembled into what is called a step-and-repeat ink jet printer, the printhead  2  moves along they direction and jets ink drops on the substrate  18  that moves in a transporting direction x. 
     Referring to  FIG. 1B , the ink jetting assembly  4  has a body  20  that includes one or more ink passages  24  and an ink fill passage  26 . A cavity plate and a stiffener plate (not shown) are attached on the opposite surfaces of the body  20  to form an array of wells  22  (not all shown) on each surface. Each well  22  can be elongated and the body  20  can include ceramic, sintered carbon, or silicon. Each ink passage  24  receives ink from an ink reservoir (not shown) and delivers ink to the ink fill passage  26 . When the opposite surfaces are covered by polymer films  32  and  32 ′, pumping chambers, for example, elongated pumping chambers, are formed by the wells  22 . Each pumping chamber includes an ink inlet  28  to receive ink from the ink fill passage  26  and an ink outlet end  30  to direct ink back into the body  20  through an ink jetting passage (not shown), from where ink is jetted at one of a row of openings (not shown) at the bottom of the body  20 . In some embodiments, the orifice plate  14  ( FIG. 1A ) is attached directly to the bottom of the body  20 . Each orifice  16  on the orifice plate  14  corresponds to one opening and ink is jetted through the orifices  16  onto the substrate  18  ( FIG. 1A ). In some embodiments, when two or more jetting assemblies  4  are assembled in the printhead  2  as shown in  FIG. 1A , the manifold plate  12  is arranged between bottoms of the bodies  20  and the orifice plate  12  and manifolds multiple rows of openings, each at the bottom of one body  20 , into a single row of openings from which ink passes. 
     Generally, each pumping chamber, together with its corresponding ink jetting passage, the opening and the orifice can be referred to as a jet of the jetting assembly. Information about the jetting assembly  4  is also provided in U.S. Ser. No. 12/125,648, filed May 22, 2008, which is incorporated here by reference. 
     The jetting assembly  4  also includes electronic components  29  to trigger the pumping chambers formed from the wells  22  to jet ink. For example, the electronic components  29  include two sets of electrodes  33  and  33 ′ on the polymer films  32  and  32 ′, which are connected by leads (not shown) to respective flexible printed circuits  31 ,  31 ′ and integrated circuits  34  and  34 ′. Piezoelectric elements  36  and  36 ′ are attached to the outer side of each of the polymer films  32  and  32 ′, respectively, and each includes a set of electrodes  35  and  35 ′ that contacts the polymer films  32  and  32 ′. Each electrode in the electrode sets  35  and  35 ′ covers a pumping chamber. In use, electrode sets  35  and  35 ′ receives pulse voltages sent from the integrated circuits  34  and  34 ′ and activates the corresponding portion of the piezoelectric elements  36  and  36 ′ to change their shapes to apply pressures to corresponding pumping chambers. Information about the ink jetting assembly is also provided in U.S. Pat. No. 6,755,511, and incorporated here by reference. 
     Production of a high resolution image (expressed as a number of dots or pixels per inch (dpi) of substrate), for example, along a direction different from, e.g., perpendicular to the process direction, requires a relatively smaller pitch between adjacent pumping chambers or wells  22  ( FIG. 1B ). The size of the pitch may reach a mechanical limit that limits the density of the pumping chambers or wells  22  in a jetting assembly. In some embodiments, more than one jetting assembly covering a given width of the substrate is used to achieve a higher resolution. 
     Referring to  FIG. 1C , an ink jet printhead  52  includes jetting assemblies  40  and  42 , each as described in  FIG. 1B , assembled adjacent to each other into a collar element  38  (orifice plate and manifold plate not shown). The ink jet printhead  52  also includes opening arrays  41  and  43  at the bottom of the body  44  and  46  of the jetting assemblies  40  and  42 , respectively. The pitch distance in each jetting assemblies can be, for example, the same. The two jetting assemblies are so arranged that each opening in the array  41  and a corresponding opening in the array  43  offsets by, for example, half the distance  45  between the neighboring opening distances along the direction perpendicular to the process direction y. A manifold plate (not shown) can be attached to the bottom of the bodies  44  and  46  and manifolds the two arrays of openings into one array, which matches the array of orifices in an orifice plate. The density of the orifices along the length of the jetting assemblies  40  and  42  is effectively doubled along the combined length of the two jetting assemblies and a higher resolution image can be printed. 
     The combined width W 1C  of the jetting assemblies  40  and  42  in the process direction y is increased relative to a width of a single jetting assembly. Printing at a high resolution along the process direction y requires a high precision relative motion between the substrate and the printhead along the process direction y. Printing at a high precision along a direction different from, for example, perpendicular to, the process direction y, requires careful control of the side to side motion of the substrate along the x direction when the substrate is moving along the process direction y. Even higher resolution printheads can be made using more than two jetting assemblies each offset relative to the others in a similar way described above, the use of which calls for increasingly high precision control of the substrate motion. Information about ink jet printhead  52  having more than one jetting assembly is also provided in U.S. Pat. No. 6,592,204, U.S. Pat. No. 6,575,558, and U.S. Pat. No. 5,771,052, all of which being incorporated here by reference. 
     Referring to  FIG. 2 , during relative motion  61  between an ink jet printer  54  and a substrate  60  along the y direction (the process direction and the substrate transporting direction), the single-pass ink jet printer  54  is stationary and the substrate  60  moves along they direction. The ink jet printer  54  includes a high resolution printhead module  58  that prints a high resolution feature, for example, feature  64  of an image  62 , across the substrate  60  and a low resolution printhead module  56  to print low resolution features, for example, features  66  of the image  62  across the substrate  60 . The ink jet printer  54  also includes a controller  63  connected to the printhead modules  56  and  58  and a detector  65  in communication with the substrate  60 . Based on the information for the image  62  obtained before printing and the instant information about the substrate motion sent from the detector  65  during printing, the controller  63  sends signals to the electronic components  29  ( FIG. 1B ) of each jetting assembly in each printhead of printhead modules  56  and  58  to activate the jets to jet ink at proper location of the substrate  60 . Repeated copies of the image  62  can be produced along the process direction y as the substrate  60  moves. 
     The printhead module  56  in this example includes one or more printheads  68  each having the features of the printhead  2  of  FIG. 1A  and having aligned its length parallel to the width W 2  of the substrate  60  to cover the total width of an image desired to be printed the substrate  60 . In the example shown in the figure, each printhead  68  contains at least one array of orifices and is capable of printing at the same maximum resolution. The printheads  68  are staggered across the substrate  60 , each partially overlapping with its neighboring printhead in regions  70 , in which each orifice of the printhead  68  aligns with a corresponding orifice of its overlapping printhead along the y direction. The at least one array of the orifices in one of the printheads  68  is parallel to the arrays of orifices in other printheads  68 . 
     Each printhead  68  has a length L of about 2 to 4 inches and a width D of about 1 inch, and the total width W 2  the printhead  56  can print can range from about 2 cm to more than 2 meters. The printhead module  56  can print at a maximum resolution, along the process direction y, for example, of at least about 100, 200, 300, or 360 dpi, and/or up to about 400, 600, 720, 1000, or 1200 dpi, depending on the resolution at which each printhead  68  included in the module  56  can print. In some embodiments, when the low resolution features  66  require a resolution higher than 400 dpi, each printhead  68  can include the features of printhead  52  described in  FIG. 1C  to print at a higher maximum resolution. 
     The printhead module  58  includes one or more printhead  72  each having the features of printhead  2  of  FIG. 1A  or of printhead  52  of  FIG. 1C . The printheads  72  can be arranged relative to each other similarly as the printheads  68  in the printhead module  56  to increase the span S of the printhead module  58 . 
     In some embodiments, the printhead module  58  is arranged so that the length  1  of each printhead  72  forms an angle θ with the process direction y. When the printhead module  58  includes more than one jetting assembly, the corresponding pumping chambers and orifices of the jetting assemblies in the overlapping regions are aligned along the process direction y. The maximum resolution in the direction perpendicular to process direction, at which the printhead  58  is capable of printing, is 1/sin θ times the maximum resolution at which each printhead  72  is capable to print when its length  1  is perpendicular to the process direction y. The angle θ, and thus the orientation of the printhead module relative to the process direction, can be adjustable for different resolution requirements. For example, the angle θ is about 30 degrees to about 85 degrees, e.g., about 60 degrees to about 80 degrees, about 70.53 degrees, or about 75.5 degrees and the printhead module  58  is capable of printing at a maximum resolution, for example, of at least about 400 dpi, 600 dpi, or 800 dpi, and/or up to, for example, 1000 dpi, 1200 dpi, 1600 dpi, 2000 dpi, 4000 dpi, or 6000 dpi. 
     Generally, the span S of the printhead module  58 , and therefore the total number of printheads  72 , is selected so that the projected width I p  along the direction perpendicular to the process direction y covers the width of the high resolution feature  64  and can be smaller than the total width W 2  of the substrate  50 . 
     In the process direction y, the printhead module  58  can be either ahead of ( FIG. 2 ) or behind (not shown) the printhead module  56  relative to the process direction y, depending on, for example, properties, such as visual effect and quality requirement of the image  62 , properties of ink used to print the different features of the image  62 , and properties of the substrate  60 . In the direction perpendicular to the process direction y, the printhead module  58  can be adjusted to a location that matches the location of the high resolution feature  64 . 
     In some embodiments, the image  62  includes more than one high resolution feature  64  in the direction perpendicular to the process direction y. In such embodiments, additional one or more printhead modules  58  can be installed at other locations across the substrate in the ink jet printer  54 , each arranged to print one or more high resolution features  64 . In some embodiments, one printhead module  58  is capable of printing at a different high resolution from other printhead modules  58 . 
     Referring to  FIG. 3 , in contrast to  FIG. 2  where the image  62  is printed on the substrate  60  during the motion of the substrate  60 , a step-and repeat ink jet printer  76  that includes printhead modules  78  and  80  mounted on a rail  82  prints the image  62  on a substrate  74  when the substrate  74  is stationary and the print modules  78  and  80  scans across the substrate  74 . In particular, during printing, the substrate  74  moves along the transporting direction x for a step width of Δx and stops, the printhead modules  78  and  80  then move along the rail  82  back and forth between two ends  84  and  86  in a direction parallel to y and print part of or all of the image  62  on the substrate  74 . The substrate and the printhead modules then repeat the motions to complete printing image  62 . Each movement of the printhead modules  78  and  80  from one of the two ends  84  and  86  to the other end of the two ends  84  and  86  in either the +y direction or the −y direction, is called a pass. The ink jet printer  76  also includes a controller  73  and a detector  75  that work similarly to the controller  63  and the detector  65  of  FIG. 2 . 
     In some embodiments, the printhead modules  78  and  80  print only during one of each two sequential passes and the substrate  74  moves Δx once every two passes. In some embodiments, the printhead modules  78  and  80  print bi-directionally in multiple  25  passes, i.e., the printhead modules print during each pass and the substrate  74  moves along the transporting direction x after each pass. Δx can be about one pixel to about a length L s  of the printhead module  78  when the image can be printed, for example, in one pass. 
     The printhead modules  78  and  80  have similar features, for example, resolutions, to the printhead modules  56  and  58 , respectively. In particular, the printhead module  80  forms an angle α that is similar to the angle θ described above with respect to the y direction. However, unlike the single-pass ink jet printer  54 , a total width L s  that the printhead module  78  prints during one pass can be smaller than the width W 3  of the substrate, and therefore, fewer printheads are needed for the printhead module  78 . Generally, the total width L s  is at least one, for example, two, three, four, or more times Δx. In some embodiments, printhead module  78  includes at least one, for example, many printheads as described in  FIG. 1A  or  FIG. 1C  and the total length L s  can range from about 2 cm to more than 2 meters. 
     Referring to  FIGS. 3 ,  3 A,  3 B, and  3 C, the printhead module  80  can have various positions relative to the printhead module  78 . In the examples shown in the  FIGS. 3 and 3A , the printhead module  80  is in front of and behind the printhead module  78  in the transporting direction x, respectively. In the examples shown in the  FIGS. 3B and 3C , the printhead module  80  is in front of and behind the printhead module  78  in the y direction, respectively. The selection of the arrangement between the printhead modules  78  and  80  depends, for example, on the factors discussed with respect to the printhead modules  56  and  58 . The arrangement shown in  FIGS. 3 and 3A  can allow the features printed by the first printhead in the transporting direction x to dry before the second printhead prints the other features (dry printing), and the arrangement shown in  FIGS. 3B and 3C  can allow the features later printed to be formed when the features earlier printed are still wet (wet printing). 
     In the examples shown in  FIGS. 3 and 3A , the distance t between the printhead modules  78  and  80  along the process direction x is also adjustable. To print the high resolution features, for example, the feature  64  of the image  62 , at a precise location relative to the rest of the image, the distance t is carefully adjusted before printing based on the dimensions of the image  62 , the total width L s  of the printhead module  78 , and the step width Δx of the substrate motion. 
     The inclusion of two or more printhead modules arranged to print at different resolutions in the single-pass ink jet printer  54  or the step-and-repeat ink jet printer  76  separates the process of printing of high resolution features, for example, 800 dpi to 1200 dpi, from the process of printing of relatively low resolution features, for example, 100 dpi to 400 dpi, of an image. This separation allows the printhead module that prints at a relatively low resolution to include fewer printheads. Fewer printheads are required to be arranged as described in  FIG. 1C , which in turn allows the relative motion in the process direction between the substrate and the printhead modules to have a relatively lower precision than, for example, a printhead module that includes printheads arranged as shown in  FIG. 1C  to realize high resolution printing. For images that contains a substantial amount of low resolution features, using a low-resolution printhead module to print these features can reduce the cost of printing, for example, the cost of the printer, and be done at a higher printing speed. 
     Other embodiments are also within the scope of the following claims. 
     For example, printheads other than that described in  FIG. 1A  can be used, for example, printheads that are made of silicon and described in U.S. Pat. No. 5,265,315 and printheads described in U.S. Ser. No. 12/125,648, filed May 22, 2008, both of which are incorporated here by reference. The printhead modules in each ink jet printer can have different relative locations than the ones exemplified in  FIGS. 2 ,  3 , and  3 A- 3 C. 
     For example, the jetting assembly  4  can include the body  20  having wells machined on surfaces of the body  20 . Pumping chambers can be formed without the use of the cavity plate and by sealing the machined wells in the body  20  using polymer films. The pumping chambers can be activated by piezoelectric elements attached to an outer surface of the polymer films that is opposite to an inner surface that contacts the body  20 . In some implementations, the piezoelectric elements can directly seal the wells to form pumping chambers without the polymer films between the wells and the piezoelectric elements. Activation of the pumping chambers can be done using elements, e.g., electrodes and integrate circuits, similar to those discussed with regard to  FIGS. 1A-1B . Features of the ink droplets and images, for example, sizes of the ink droplets and resolution of the images, printed by such jetting assemblies are similar to those printed by the jetting assemblies of  FIGS. 1A-1B . 
     Information about jetting assemblies and ink jetting devices is also provided, for example, in U.S. Pat. No. 6,755,511 and U.S. Ser. No. 09/749,893, filed Dec. 29, 2000, and incorporated here by reference.