Method and printing chip for high speed single pass monochrome printing

Abstract

A method of printing an image from a printhead module having a plurality of horizontal rows of nozzles. Each row of nozzles has a main row portion and a corresponding drop row portion vertically offset from the main row portion. The method includes the steps of determining a predetermined delay for the drop row portions based on the offset, a print speed, and a print resolution; assigning dot data for an image row to respective rows of nozzles based on the print speed and the print resolution, sending first dot data for each main row portion and second dot data for each drop row portion to the printhead module; and firing nozzles from the main row portions and the drop row portions in a predetermined order. Each drop row portion is fired independently of its corresponding main row portion and is delayed relative to its corresponding main row portion by the predetermined delay.

Description

Invention Field

[0001] This invention relates to a method for single-pass printing using multiple mating print chips, and print chips designed for such printing. It was primarily developed to achieve a wide range of printing modes in a very high-speed monochrome printhead with multiple rows of nozzles. Background of the Invention

[0003] use Inkjet printers are commercially available for a variety of different printing formats and markets. For example, some color printing technologies (such as the label printer described in US 8,562,104 and the wide-format printer described in US 8,480,221) employ color printheads configured to print CMYK ink from a single printhead. As described in US 7,475,976, such color printheads have multiple print chips attached to a manifold that distributes multiple ink colors to each print chip. Recently, inkjet printers have been used... The technology has developed monochrome printheads, particularly to meet the needs of high-speed digital printing presses (such as those described in US 10,081,204), in which multiple monochrome printheads are aligned along the media feed path. As described in US 9,950,527, such a monochrome printhead has multiple print chips attached to a manifold that delivers a single ink color to each print chip.

[0004] The color and monochrome printheads described above are commonly used. Printed chip 1 ( Figure 1 The printing chip is specially designed so that multiple printing chips can be mated together in a row along the print head. Figure 1 As shown Each nozzle row 3 of the print chip 1 uniquely has a descending row portion 7 at one end of the print chip, which is vertically offset from the corresponding main row portion 5, which contains most of the nozzles of that nozzle row. Typically, the vertically offset descending row portions 7 are arranged in a trapezoidal or generally triangular shape (referred to in the art as "descending nozzle region," "displacement nozzle region," or "descending triangle region"), and enable the print chips to be mated together while effectively maintaining a constant dot pitch across the connection area. Figure 3 The diagram schematically illustrates an A4-page-wide printhead 9 consisting of eleven docking Memjet print chips 1 mounted on a substrate 10. Similarly, an A3 printhead can be constructed using 16 docking print chips.

[0005] The nozzles in a given descending nozzle section 7 of nozzle row 3 are hardwired to ignite at the same position as the nozzles in the corresponding main section 5 of that nozzle row. Because there is a fixed vertical spacing along the media feed direction between the nozzles in the descending nozzle region 11 and the main nozzle region 13, the data sent to the nozzles in the descending nozzle region is delayed by a predetermined number of lines, allowing droplets ignited from the nozzles in the descending nozzle region to seamlessly connect with droplets ignited from the main nozzle region, forming a single-line print. Typically, when printing at 1600 x 1600 dpi (i.e., 1DP = 1 / 1600 inch) at the maximum point-to-point print speed (nominal 12 inches per second), there is a fixed spacing of 10 dot pitches (“DP”) in the media feed direction between each descending nozzle section and its corresponding main nozzle section. Therefore, when printing at 1600 dpi in the media feed direction, seamless printing across connected areas can be achieved by delaying the data sent to each descending nozzle section by 10 lines. A design with a descending nozzle row can be found in US 7,290,852. A more detailed description of the printed chip is incorporated herein by reference.

[0006] In principle, for monochrome printing, printing one ink color using all nozzle rows in a single print chip should allow for higher print speeds. However, problems arise with the drop-down nozzle compensation method described above if printing at different resolutions and / or faster speeds is desired. First, because each ignition chamber takes time to refill ink after droplet ejection, the maximum firing frequency of each nozzle is fixed. Therefore, the cycle time for one firing cycle (i.e., the time allocated to firing all nozzles in a single print chip) is necessarily limited by the maximum firing frequency. Consequently, to print at faster speeds, one cannot simply actuate the inkjet nozzles more frequently; typically, the inkjet nozzles are already operating at their maximum firing frequency (or close to their maximum firing frequency). The inkjet nozzle has a maximum ignition frequency of approximately 15 kHz.

[0007] Secondly, in In the case of printheads, when printing at lower print resolution and / or higher speed, the dot pitch of the print must be changed, while the physical spacing between the descending nozzle area and the main nozzle area remains fixed at the nominal 10 / 1600 inches.

[0008] For example, if you want to print at a vertical print resolution of 1600 dpi at a speed of 5× (nominal 60 inches per second), each nozzle row in the descending nozzle region is offset by 10 print rows below its corresponding main nozzle row (10 / 1600 inches ÷ 1 / 1600 = 10). Since 10 rows correspond to 2 firing cycles at 5× print speed, the nozzles in the descending nozzle region 11 can print dots seamlessly to connect with the dot rows printed by the nozzles in the main nozzle region 13. The nozzles in each main row section 5 and the corresponding descending row section 7 of the same nozzle row 3 always fire simultaneously (or more precisely, within the same row time), but the descending row section loads dot data from both rows after the dot data has been loaded into the main row section. Similarly, at a vertical print resolution of 800 dpi, the nozzles in the descending nozzle area 11 can be seamlessly connected to the nozzles from the main nozzle area 13 because the descending nozzle area is offset by 5 print lines (10 / 1600 inches ÷ 1 / 800 = 5), which corresponds to 1 ignition cycle at 5 × print speed.

[0009] On the other hand, if printing at 5x speed with a vertical print resolution of 400 dpi is desired, perfect compensation by the nozzles in the descending nozzle region 11 is impossible. The descending line portion 7 is now offset by 2.5 print lines (10 / 1600 inch ÷ 1 / 400 = 2.5) from its corresponding main line portion 5. Since this 2.5 print lines are inconsistent with the entire ignition cycle at 5x speed, printing artifacts inevitably occur at the transition between the main nozzle region 13 and the descending nozzle region 11, as the descending line portion cannot print droplets aligned with those printed from its corresponding main line portion. A similar error occurs when printing at 5x speed with a vertical print resolution of 1200 dpi, because the descending line portion is offset by 7.5 print lines (10 / 1600 inch ÷ 1 / 1200 = 7.5) from its corresponding main line portion.

[0010] Figure 4 The diagram illustrates the variation in error caused by the fixed offset of the descending nozzle area relative to the main nozzle area at various print resolutions using the method described above at 5× speed (monochrome). As explained above, the minimum error is achieved at resolutions of 1600 dpi and 800 dpi, while the maximum error occurs when printing at 1200 dpi and 400 dpi. The error is considered acceptable at a nominal dot pitch of 1. Figure 4 It can be seen that there are many printing modes that cannot achieve acceptable print quality. In practice, the tolerance for certain artifacts may differ for different types of image content (e.g., continuous-tone images, line images, text, etc.).

[0011] As will be understood from the above, when using the descending nozzle compensation method described in US 7,290,852 for high-speed monochrome printing, a relatively limited number of print patterns can be achieved. Despite this limitation, the basic design of the print chip incorporating the descending nozzle region described in US 7,290,852 remains a very attractive approach for designing page-width printheads for high-speed printing. The descending nozzle region allows the print chips to be mated together in a row, which narrows the print area and avoids positioning the chips in a relatively wide staggered array. Narrowing the print area advantageously places fewer demands on the media feed mechanism and achieves higher print quality overall compared to other page-width systems with relatively wide print areas.

[0012] Therefore, it is desirable to provide a way to combine a print chip with a descending nozzle row so that it can be used for high-speed monochrome printing in a wider range of print modes. Invention Overview

[0014] In a first aspect, a method is provided for printing an image from a printhead module having multiple horizontal nozzle rows, each nozzle row having a main row portion and a corresponding descending row portion vertically offset from the main row portion, the method comprising the following steps:

[0015] Identify printing speed;

[0016] Identify print resolution;

[0017] The predetermined delay for the falling line portion is determined based on offset, print speed, and print resolution;

[0018] The predetermined delay is stored in the register of the printhead module;

[0019] Based on printing speed and printing resolution, dot data for image lines is allocated to the corresponding nozzle lines, wherein each main line portion and its corresponding descending line portion are allocated dot data for the same image line;

[0020] The dot data is sent to the printhead module, which includes first dot data for each main line section and second dot data for each descending line section.

[0021] The nozzles are ignited from the main section in a predetermined order based on printing speed and printing resolution; and

[0022] The nozzles are ignited from the descending row sections in the predetermined order, wherein each descending row section is ignited independently of its corresponding main row section and is delayed relative to its corresponding main row section by a predetermined delay stored in a register, such that the predetermined delay aligns the droplets ignited from each descending row section with the droplets ignited from its corresponding main row section.

[0023] Preferably, the first data point is transmitted to a first data latch corresponding to the main line section, and the second data point is buffered in a dedicated buffer of the printhead module.

[0024] Preferably, the buffered second point data is transmitted to the second data latch corresponding to the falling row portion based on a predetermined delay.

[0025] Preferably, the first data latch is positioned in a row along one side of the main row portion, and the second data latch is positioned in a row along the opposite side of the descending row portion.

[0026] Preferably, the predetermined delay stored in the register is updated for different print jobs.

[0027] Preferably, the descending row portion has a different length.

[0028] Preferably, the descending sections are arranged together in a trapezoidal or triangular shape.

[0029] Preferably, the printhead module includes multiple ink planes, each ink plane containing one or more rows of nozzles supplied with the same ink.

[0030] Preferably, the printhead module includes multiple redundant ink planes.

[0031] Preferably, the printhead module is a monochrome printhead module in which all nozzle rows are supplied with the same ink.

[0032] Preferably, dot data is sent to the printhead module row by row, and the same amount of dot data is sent for each nozzle row.

[0033] Preferably, the point data includes '1' for enabled ignition nozzles and '0' for disabled non-ignition nozzles.

[0034] In a second aspect, a printing chip is provided, the printing chip comprising:

[0035] An elongated silicon substrate that defines the nominal front and rear longitudinal sides of the printed chip;

[0036] One or more circuit layers are positioned on a silicon substrate; and

[0037] A MEMS layer, positioned on top of the circuit layer, includes multiple parallel rows of nozzles, each row comprising multiple inkjet nozzle devices arranged in a main row portion and a descending row portion offset from the main row portion.

[0038] in:

[0039] The circuit layer includes a data latch, which is configured to provide dot data for the inkjet nozzle assembly;

[0040] The first row data latch is positioned adjacent to the preceding row of the main row; and

[0041] The second row data latch is positioned adjacent to the next row of the descending row portion.

[0042] Preferably, the first set of conductive traces extends from the first row data latch toward the main row portion; and the second set of conductive traces extends from the second row data latch toward the descending row portion in the opposite direction to the first set of conductive traces.

[0043] Preferably, the descending sections are arranged together in a trapezoidal shape.

[0044] Preferably, the trapezoidal shape has a front nozzle row and a parallel rear nozzle row, the rear nozzle row being relatively longer than the front nozzle row.

[0045] Preferably, the first set of conductive traces and the second set of conductive traces are parallel to each other.

[0046] Preferably, during use, the front side of the printing chip is located upstream relative to the media feed direction.

[0047] Preferably, in use, the rear side of the printing chip is located downstream relative to the media feed direction.

[0048] Preferably, the circuit layer further includes a command unit for receiving multi-line dot data for printing the chip.

[0049] Preferably, the command unit is positioned adjacent to the rear nozzle of the main section.

[0050] Preferably, the command unit is configured to divide each row of point data into first point data and second point data.

[0051] Preferably, the circuit layer further includes a buffer, and the command unit is configured to route the first data point directly to the first row data latch and to route the second data point via the buffer to the second row data latch.

[0052] Preferably, the buffer is configured to buffer the second point data for a predetermined delay period before the point data is sent to the second row data latch.

[0053] Preferably, the command unit includes a configurable register for storing a value for a predetermined delay period.

[0054] Preferably, the buffer has a data capacity corresponding to the number of nozzles in the descending nozzle section.

[0055] Preferably, the printing chip further includes a row of solder pads positioned along one side of the printing chip, and wherein the command unit is configured to receive multi-row dot data via the solder pads.

[0056] Preferably, the solder pads are positioned along the rear side of the substrate.

[0057] Preferably, each nozzle row in the descending row section is configured to ignite its inkjet nozzle independently of the corresponding nozzle row in the main row section.

[0058] In a third aspect, a method is provided for printing an image from a printhead module having a plurality of horizontal ink planes M supplied with the same ink, each ink plane having at least one row of nozzles, and the nozzle rows of all ink planes having vertically aligned nozzles, the method comprising the following steps:

[0059] Each row of nozzles defines a continuous set of spans, and each set of spans contains N nozzles;

[0060] The point data for each image row is assigned to a predetermined number P of nozzles in each span group of each nozzle row;

[0061] Dot data is sent to the printhead module, and based on the dot data, the nozzles are sequentially ignited from each of the M ink planes to print image rows, so that all ink planes contribute dots to the printed image rows.

[0062] in:

[0063] Only one nozzle in each span group within the same nozzle row ignites simultaneously;

[0064] N is an integer multiple of M; and

[0065] P is N divided by M.

[0066] Preferably, each ink plane includes a pair of nozzle rows.

[0067] Preferably, the nozzle rows are offset to print both even and odd dots.

[0068] Preferably, the method is repeated for all image rows of the printed image.

[0069] Preferably, the span groups of different nozzle rows have different ignition nozzles.

[0070] Preferably, the ignition nozzles in the span group of the continuous ignition nozzle row are horizontally shifted by S nozzles. Preferably, S is 1.

[0071] Preferably, the first / M image row is printable by each ink plane.

[0072] Preferably, the point data includes '1' for enabled ignition nozzles and '0' for disabled non-ignition nozzles.

[0073] Preferably, all aligned nozzle rows in the M ink planes are ignited based on point data within a line time, and wherein a line time is less than or equal to the time period for igniting all nozzles in the printhead module divided by the number of nozzle rows.

[0074] Preferably, one or more steps of the method are repeated to print all image rows of the image.

[0075] Preferably, during the sequential ignition of nozzles from each of the M ink planes, dot data is assigned to a given nozzle row based on the printing speed and the position of the printing medium.

[0076] Preferably, the corresponding span groups in different nozzle rows are vertically aligned.

[0077] As used herein, the term "ink" refers to any jettable fluid and may include, for example, conventional CMYK inks (e.g., pigment- and dye-based inks), infrared inks, UV-curable inks, fixatives, primers, adhesives, 3D printing fluids, polymers, sensing inks, biofluids, etc. Attached Figure Description

[0078] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:

[0079] Figure 1 A printed chip with a descending nozzle area is shown;

[0080] Figure 2 This is an enlarged view of the descending nozzle area;

[0081] Figure 3 This is a schematic diagram of a printhead with multiple docking printing chips;

[0082] Figure 4 The dot placement error caused by drop nozzle area artifacts is shown in various printing modes;

[0083] Figure 5 The logical distribution of dot data in the printed chip is shown;

[0084] Figure 6 The physical layout of selected features of the printed chip is shown; and

[0085] Figure 7A and Figure 7B This is a simulated test print using the printing method described in this article. Detailed Implementation

[0086] refer to Figure 1The printing method described herein employs a printhead module, typically in the form of a print chip, as described, for example, in US 7,290,852. Accordingly, each print chip includes a horizontal row of nozzles extending parallel to the longitudinal axis of the print chip. Each nozzle row has a main row portion and a corresponding displacement (“descend”) row portion that is vertically offset from its main row portion.

[0087] For convenience, the print chip is defined as having a nominal horizontal axis extending parallel to its length dimension and a nominal vertical axis extending perpendicular to the horizontal axis. As used herein, the terms "horizontal" and "vertical" are not intended to limit the orientation of the print chip or nozzle row in use. Furthermore, the term "descending" (e.g., "descending row portion," "descending nozzle area," etc.) is not intended to limit the orientation of the print chip relative to the media feed direction; "descending row portion" simply means that the row portion is displaced upstream or downstream of the corresponding main row portion relative to the media feed direction.

[0088] The nozzles in the main row section extend along most of the length of the printable chip, while the nozzles in the descending row section are positioned at one end of the printable chip. For all nozzle rows, the total number of nozzles in each main row section and the corresponding descending row section is the same (e.g., 640 nozzles per row). However, the descending row sections each have different lengths, and... Figure 1 and Figure 2 As shown, the descending rows are arranged together in an overall trapezoidal shape in the plan view. The multiple descending rows with a trapezoidal shape are collectively referred to as the "descending nozzle area" of the printed chip.

[0089] Figure 1 and Figure 2 The illustrated print chip comprises five ink planes, each supplied with the same color ink for monochrome printing. Each ink plane contains two nozzle rows (“odd” and “even”), horizontally offset from each other by one dot pitch. Because the nozzles within the same nozzle row are spaced two dot pitches apart, the odd and even nozzle rows within an ink plane can print odd and even dots in a single print line. In the illustrated embodiment, the odd and even nozzle rows within the same ink plane are vertically offset from each other by four dot pitches, while each descending line portion is offset by 10 dot pitches (at a nominal 1600 dpi) from its corresponding main line portion.

[0090] Although this document describes one embodiment with reference to a Memjet printer chip printed at a nominal 1600 dpi (horizontal) x 1600 dpi (vertical), it should be understood that the invention is not limited to the manner of printing resolution or printing speed.

[0091] As in Figure 2In the best-looking configuration, each descending row portion is positioned horizontally aligned with its corresponding main row portion, effectively maintaining a constant dot pitch along the print chip and between adjacent print chips. In this way, the descending row portions can, in principle, compensate for printing in the connection areas between adjacent print chips, where nozzles cannot be fabricated due to a lack of available silicon at the edges of the print chips. However, due to the aforementioned problems, the print chip described in US 7,290,852 is not ideally suited for high-speed monochrome printing at all print resolutions (e.g., at a nominal 5× print speed). For example, as above and referenced... Figure 4 The explanation given is that when printing in monochrome at 1200 dpi and a print speed of 5x, an error of 2.5 dpi occurs between the main nozzle area and the descending nozzle area. This error produces noticeable artifacts on the printed page.

[0092] Independent ignition in the descending nozzle area

[0093] Typically, an inkjet printhead receives its dot data and fires its nozzles row by row to eject droplets. If both the row enable signal and column enable signal are set to 1 when an ignition signal is received, the given nozzle device for that row will ignite. In one ignition cycle of the print chip, all nozzle rows receive ignition signals within the ignition cycle time, causing all enabled nozzle devices on the print chip to ignite. For a given number of nozzle rows, the ignition cycle time is limited by the maximum ejection frequency of each nozzle device, a physical limitation caused by the maximum refill rate of each nozzle device.

[0094] Within each ignition cycle, each nozzle line has an assigned line cycle time, which is the ignition cycle time divided by the number of nozzle lines. For dot-to-dot printing (e.g., CMYKK printing), an ignition cycle must be completed within one line time, i.e., the time it takes for the media to advance one line or one vertical dot pitch (for...). The printing chip has a nominal resolution of 1600 dpi. The print chip has five ink planes and ten nozzle rows (one pair of nozzle rows per ink plane, i.e., an even-numbered nozzle row and an odd-numbered nozzle row). Each nozzle row is allocated 1 / 10 of the line time to fire its nozzles at a predetermined print speed (nominal 12 inches per second). When printing monochrome at 5× print speed (nominal 60 inches per second), the media must advance 5 lines (or 5 vertical dot pitches) during one fire cycle. In other words, only two rows of nozzles can print in the time it takes for the media to advance one dot pitch at a nominal 1600 dpi. For some print modes, such as 400 dpi and 1200 dpi at 5× print speed, this results in droplet placement errors.

[0095] To address the aforementioned problem when printing monochrome at a 5x printing speed, the printing chip according to the present invention is configured to ignite the nozzles in the descending nozzle region independently of the nozzles in the main nozzle region. The ignition of the nozzle rows in the descending nozzle region is disconnected from the ignition of the corresponding nozzle rows in the main nozzle region, ensuring perfect alignment of droplets ignited from the descending nozzle region with droplets ignited from the main nozzle region, regardless of printing speed and resolution.

[0096] To date, known printed chips in the prior art are based on line-by-line ignition of nozzles, igniting all enabled nozzles in the same line within the allocated line time. (In practice, due to power constraints, all enabled nozzles in the same line do not ignite simultaneously within their allocated line time. As described in US7,780,256 (the contents of which are incorporated herein by reference), enabled nozzles ignite in groups of spans separated by predetermined 'spans', and ignition is ordered according to a predetermined 'shift' within each group of spans).

[0097] Therefore, independent ignition of nozzles from the “same” nozzle row presents challenges in both implementation and chip design. In short, the print chip can be processed as having 20 nozzle rows (10 in the main nozzle region and 10 in the descending nozzle region). The dot data and ignition signal can then be sent sequentially to the print chip as 20 separate data pulses. However, this type of implementation is problematic because the data pulses will contain unequal amounts of data. Those data pulses corresponding to the main nozzle region will contain a much larger amount of data than those corresponding to the descending nozzle region. Furthermore, even within the descending and main nozzle regions, each nozzle row has a different number of nozzles, thus requiring different amounts of data. Ideally, however, data transmission should be as smooth as possible, with each data pulse having the same data allocation.

[0098] refer to Figure 5 and Figure 6According to one embodiment of the invention, the printing chip 20 is designed to receive dot data and ignition signals for each of 10 nozzle rows line by line. That is, each data pulse for each nozzle row contains dot data for the main nozzle region and the descending nozzle region, such that the data pulse contains an equal amount of data (e.g., 640 bits corresponding to the 640 nozzles in each nozzle row). However, the second dot data associated with the descending nozzle region 11 is routed separately from the first dot data associated with the main nozzle region 13 by the chip's command unit 22. While the command unit 22 sends the first dot data associated with the main nozzle region 13 directly to the corresponding first data latch 24, the second dot data associated with the descending nozzle region 11 is routed to a dedicated buffer 26. The buffer 26 has a data capacity corresponding to the number of nozzles in the descending nozzle region 11.

[0099] The second dot data stored in buffer 26 is transmitted to the second data latch 28 corresponding to the descending nozzle region 11 only after a predetermined delay is retrieved from the dedicated delay register of command unit 22. The value of the predetermined delay stored in the delay register can be configured based on the print job and can be set by the upstream print controller (not shown) at the start of each print job based on the print speed and print resolution. In this way, dot data for the same print line can be transmitted to print chip 20 simultaneously in a single data pulse, while the ignition of the droplets in descending nozzle region 11 is delayed relative to the ignition of the droplets in main nozzle region 13. Since the delay is determined by the print speed and print resolution, unlike print chip 1 described in US 7,290,852, the nozzle line 3 in descending nozzle region 11 can ignite at a different time than the nozzle line in main nozzle region 13, without having to ignite simultaneously with any other nozzle line in the main nozzle region.

[0100] The order in which nozzle rows 3 are ignited is determined based on the optimal placement and minimum error for a given print resolution and print speed. The row ignition order is determined by the print controller, which communicates with the print chip 20.

[0101] refer to Figure 6 The printed chip 20 has a physical layout and architecture configured to efficiently utilize the available space on the chip. A first data latch 24 and a second data latch 28, corresponding to the main nozzle region 13 and the descending nozzle region 11, are positioned on opposite sides of their respective nozzle arrays. Data and power are received via a row bonding pad 30 positioned along a longitudinal side of the printed chip 20 opposite to the first data latch 24.

[0102] The second data latch 28, which receives the second point data via buffer 26, is positioned along the rear of the descending nozzle region 11 (i.e., the longer side of the trapezoidal descending nozzle region). The first data latch 24, which receives the first point data directly from command unit 22, is positioned along the front of the main nozzle region 13. By positioning the second data latch 28 opposite to the first data latch 24, conductive traces can extend from the second data latch across the print chip 20 toward the nozzle assembly without fanning outward from a single point. Therefore, this arrangement avoids high current concentrations in one region of the chip.

[0103] Figure 7A and Figure 7B This is a simulated test print, demonstrating the effect of independent ignition in the drop nozzle area when printing at 400 dpi and a nominal print speed of 5×. Figure 7A In this case, using the method described in US7,290,852, the connection area between two adjacent printed chips appears as a bulge due to imperfect dot placement in the descending nozzle region. However, as... Figure 7B As shown, in the case of independent ignition in the descending nozzle area, the connecting area is not visible in the same printing mode.

[0104] Zixing Ignition

[0105] Ideally, all nozzles in the main row portion of a given nozzle row should ignite simultaneously; and the same applies to nozzles in the descending row portion. Simultaneous ignition of the nozzles would ensure that all droplets corresponding to the same image row fall simultaneously onto the medium passing through. However, in practice, and as explained in US7,780,256, it is not possible to ignite all enabled nozzles simultaneously due to the inherent power constraints of the print chip.

[0106] For this reason, the nozzles are logically grouped into consecutive span groups, with the number of nozzles in each span group defining the 'span'. Only one nozzle in each span group can fire simultaneously, and once these nozzles are fired, a subsequent nozzle is selected from each span group for firing. For example, with a span of 20, a printable chip with 640 nozzles in each nozzle row contains 32 consecutive span groups (each span group contains 20 nozzles), and every 20 nozzles can fire simultaneously. Therefore, in this example, each nozzle row has 20 firing cycles within its allocated row time.

[0107] Within the same span group, the distance between a subsequently ignited nozzle and a previously ignited nozzle is defined as 'displacement'. Therefore, a displacement of 1 means that an adjacent nozzle in each span group is ignited. US7,780,256 describes standards for setting optimal spans and displacements for ink refill and for minimizing aerodynamic interference from fluid crosstalk between jet droplets.

[0108] As will become clear from the above, the effects of span and displacement inevitably produce printing artifacts due to the continuous movement of the printing media during a single print run. For example, with a displacement of 1, each print line is effectively printed as jagged. At normal printing speeds, the effects of span and displacement are almost imperceptible because, although the media is moving continuously, it is practically stationary on the timescale of each line firing cycle. However, at very high printing speeds, the printing artifacts caused by span and displacement become more pronounced due to the increased movement of the media within a line firing cycle. For example, when printing at 10× printing speed using two aligned monochrome printheads, the media will move 2DP within a line firing cycle. Therefore, the 'height' of each jagged edge will be 2DP, which may be unacceptable for some printing applications.

[0109] In the sub-row ignition scheme, nozzles from each ink plane share the same droplet size for printing each image row. Therefore, for monochrome... The print chip has five ink planes (corresponding to ten even / odd nozzle rows). Rows 0, 2, 4, 6, and 8 can each ignite 20% of the even-numbered droplets, while rows 1, 3, 5, 7, and 9 can each ignite 20% of the odd-numbered droplets for a given image row. In contrast to conventional row-based ignition, where all enabled nozzles in the same nozzle row ignite within a single row time, in the sub-row ignition scheme, all aligned nozzle rows of the print chip (e.g., all even-numbered nozzle rows or all odd-numbered nozzle rows) ignite their enabled nozzles within a single row time based on latched dot data. The row time is less than or equal to the time period allocated for igniting all nozzles in the print chip divided by the number of nozzle rows.

[0110] Advantageously, sub-row firing helps map the data of a given print line to any nozzle line with optimal placement for horizontal alignment of the print line dots. Therefore, instead of the 2DP error in a single line firing cycle as in the example above, this error can be reduced to less than 1DP by properly mapping the dot data across the five available nozzle lines in each line firing cycle. Effectively, sub-row firing makes it possible to reduce the height of the serrated artifacts described above to 1 / 5 of their height.

[0111] For sub-row ignition to be possible, the number of nozzles N in each span must be an integer multiple of the number of ink planes M. For example, for the five ink planes in a Memjet print chip, the spans should be 5, 10, 15, 20, etc. Therefore, the predetermined number P of nozzles for ignition in each individual span is N divided by M.

[0112] In a preferred sub-row ignition scheme, the span is 5 and the shift is 1. Different ink planes are printed sequentially from the shifted nozzles along each span (e.g., line 0 prints the 0th nozzle from each span in the first 20% of a line time, line 2 prints the 1st nozzle from each span in the second 20% of a line time, line 4 prints the 2nd nozzle from each span in the third 20% of a line time, line 6 prints the 3rd nozzle from each span in the fourth 20% of a line time, and line 8 prints the 4th nozzle from each span in the last 20% of a line time). Advantageously, sub-row ignition, when combined with proper mapping of line data to each nozzle line, reduces the effects of span and shift artifacts at very high print speeds. A further advantage is that a shift value of 1 will not produce any problems associated with fluid crosstalk or ink refill because the shifted nozzles are not in the same nozzle line.

[0113] Of course, it should be understood that the invention has been described by way of example only, and modifications to the details may be made within the scope of the invention as defined in the appended claims.

Claims

1. A method for printing an image from a printing chip, the printing chip having a plurality of horizontal nozzle rows extending parallel to a longitudinal axis of the printing chip, each nozzle row having a main row portion and a corresponding descending row portion, the corresponding descending row portion being vertically offset from the main row portion and not overlapping the main row portion, the method comprising the steps of: Determine the printing speed and printing resolution for the image to be printed, wherein the printing speed and printing resolution are variable for different print jobs; The delay of the descending line portion is determined based on the offset, the printing speed, and the printing resolution; The delay is stored in a register of the print chip, and the value of the delay stored in the register is configurable based on the print job; Based on the printing speed and the printing resolution, dot data for image rows are allocated to the corresponding nozzle rows, wherein each main row portion and its corresponding descending row portion are allocated dot data for the same image row; The dot data is sent to the printing chip, the dot data including first dot data for each main row section and second dot data for each descending row section; The main row portion of each nozzle row is ignited in a predetermined row-by-row sequence based on the printing speed and the printing resolution; and Ignite the descending section of each nozzle row in the predetermined row sequence. in: Each descending row section is ignited independently of its corresponding main row section and is delayed relative to its corresponding main row section in the register, such that the delay aligns the droplets ignited from each descending row section with the droplets ignited from its corresponding main row section. The delay stored in the register is updated for different print jobs; The descending section of each nozzle row is horizontally positioned relative to its corresponding main section to maintain a constant horizontal point spacing along the nozzle row; and The printing chip is a monochrome printing chip in which all nozzle rows are supplied with the same ink.

2. The method of claim 1, wherein: The first data point is directly routed to the first data latch corresponding to the main row section, and the second data point is buffered in the dedicated buffer of the print chip; and Based on the delay, the buffered second point data is transmitted to the second data latch corresponding to the descending row portion.

3. The method as described in claim 2, wherein, The first data latch is positioned in a row along one side of the main row portion, and the second data latch is positioned in a row along the opposite side of the descending row portion.

4. The method of claim 1, wherein, The descending line portion has a different length.

5. The method of claim 4, wherein, The descending sections are arranged together in a trapezoidal or triangular shape.

6. The method of claim 1, wherein, The dot data is sent to the printing chip row by row, and the same amount of dot data is sent for each nozzle row.

7. A printing chip configured to perform the method according to any one of the preceding claims, the printing chip comprising: An elongated silicon substrate that defines the nominal front longitudinal side and rear longitudinal side of the printed chip; One or more circuit layers are positioned on the silicon substrate; as well as A MEMS layer, positioned on the circuit layer, includes a plurality of parallel nozzle rows extending parallel to the longitudinal axis of the printed chip. Each nozzle row includes a plurality of inkjet nozzle assemblies arranged in a main row portion and a descending row portion that is vertically offset from the main row portion and does not overlap with the main row portion. in: The circuit layer includes: a command unit for receiving multi-line dot data for the print chip; a buffer for delaying nozzle ignition of the descending line portion; a first line data latch adjacent to and extending parallel to the front main line portion on the front side of the print chip; and a second line data latch adjacent to and extending parallel to the rear descending line portion on the opposite rear side of the print chip. The command unit is configured to route the first data point directly to the first row data latch and to route the second data point via the buffer to the second row data latch; In use, the front side of the printing chip is located upstream relative to the media feeding direction, and the rear side of the printing chip is located downstream relative to the media feeding direction. The descending section of each nozzle row is horizontally positioned relative to its corresponding main section to maintain a constant horizontal point spacing along the nozzle row; and The printing chip is a monochrome printing chip in which all nozzle rows are supplied with the same ink.

8. The printed chip as claimed in claim 7, wherein: The first set of conductive traces extends from the first row data latch toward the main row portion; and The second set of conductive traces extends from the second row data latch toward the descending row portion in the opposite direction to the first set of conductive traces.

9. The printed chip as claimed in claim 8, wherein, The descending rows are arranged together in a trapezoidal shape, the trapezoidal shape having a front nozzle row and a parallel rear nozzle row, the rear nozzle row being relatively longer than the front nozzle row.

10. The printed chip as claimed in claim 9, wherein, The first set of conductive traces and the second set of conductive traces are parallel to each other.

11. The printed chip as claimed in claim 7, wherein, The command unit is positioned adjacent to the rear nozzle of the main section.

12. The printed chip as claimed in claim 7, wherein, The command unit includes a configurable register for storing the value of the delay period.

13. The printed chip of claim 7, further comprising a row of solder pads positioned along the rear side of the printed chip, wherein, The command unit is configured to receive the multi-line point data via the solder pad.

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