Technique for printing ink quantity control for depositing fluid within precise tolerance

Abstract

To provide a technique for printing ink quantity control for depositing a fluid within a precise tolerance.SOLUTION: An ink printing process adopts droplet quantity measurement and processing software per nozzle for planning a combination of droplets so as to reach specific total ink filling per target region and granting minimum and maximum ink filling compliance that is set in accordance with a specification. In various embodiments, different droplet combinations are generated through different print heads / substrate scan offsets, offsets between print heads, use of different nozzle drive waveforms and / or the other technique. A pattern of filling variation can be optionally introduced so as to reduce line effects observable in a completed display device. The disclosed technique has a number of other possible applications.SELECTED DRAWING: Figure 3A

Description

[Technical field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to each of the following patent applications: U.S. Provisional Patent Application No. 61 / 746,545, filed December 27, 2012, entitled "Smart Mixing," inventor Conor Francis Madigan, et al.; U.S. Provisional Patent Application No. 61 / 822,855, filed May 13, 2013, entitled "Systems and Methods Providing Uniform Printing of OLED Panels," inventor Nahid Harjee, et al.; U.S. Provisional Patent Application No. 61 / 842,351, filed July 2, 2013, entitled "Systems and Methods Providing Uniform Printing of OLED Panels," inventor Nahid Harjee, et al.; U.S. Provisional Patent Application No. 61 / 857,298, filed July 23, 2013, entitled "Systems and Methods Providing Uniform Printing of OLED Panels," inventor Nahid Harjee, et al. No. 61 / 898,769, filed Nov. 1, 2013, entitled "Systems and Methods Providing Uniform Printing of OLED Panels," inventors Nahid Harjee et al.; and U.S. Provisional Patent Application No. 61 / 920,715, filed Dec. 24, 2013, entitled "Techniques for Print Ink Volume Control To Deposit Fluids Within Precise Tolerances," inventors Nahid Harjee et al., each of which is incorporated herein by reference.

[0002] The present disclosure relates to the use of printing processes to transfer fluids to target areas of a substrate. In one non-limiting application, the techniques provided by the present disclosure can be applied to manufacturing processes for large scale displays. [Background technology]

[0003] In a printing process where a printhead has multiple nozzles, not all nozzles respond in the same way to a standard drive waveform. That is, each nozzle may produce slightly different volume droplets. In situations where the nozzles are relied upon to deposit fluid droplets into their respective fluid deposition areas ("target areas"), the lack of consistency can lead to problems.

[0004] FIG. 1A is used to introduce this nozzle-droplet inconsistency problem with an exemplary schematic diagram generally referenced using the numeral 101. In FIG. 1, a printhead 103 can be seen to have five ink nozzles, each depicted using a small triangle at the base of the printhead, numbered (1)-(5), respectively. In an exemplary application, it is desired to deposit 50 picoliters (50.00 pL) of fluid into each of five specific target regions of an array of such regions, and further, each of the five nozzles of the printhead is assumed to eject 10 picoliters (10.00 pl) of fluid into each of the various target regions with each relative movement ("pass" or "scan") between the printhead and the substrate. The target regions can be any surface region of the substrate, including adjacent unseparated regions (e.g., such that the deposited fluid ink partially diffuses and mixes together between the regions), or respective fluidically separated regions. These regions are generally represented in FIG. 1 using ovals 104-108, respectively. It can therefore be assumed that to fill each of the five specific target regions, exactly five passes of the printhead are required as depicted. However, printhead nozzles will, in practice, have some minor variations in structure or operation, such that a given drive waveform applied to each nozzle transducer will result in slightly different droplet volumes for each nozzle. For example, as depicted in FIG. 1A, firing nozzle (1) produces a droplet volume of 9.80 picoliters (pL) on each pass, with five 9.80 pL droplets depicted within oval 104. Note that although each of the droplets is represented in the diagram by a different location within target region 104, in practice the locations of each of the droplets may be identical or may overlap. Meanwhile, nozzles (2)-(5) produce slightly different respective drop volumes of 10.01 pL, 9.89 pL, 9.96 pL, and 10.03 pL. With five passes between the printhead and the substrate, with each nozzle mutually exclusively depositing fluid into target areas 104-108, this deposition would result in a total deposited ink volume variation of 1.15 pL across the five target areas, which may be unacceptable for many applications.For example, in some applications, a difference of just one percent (or even less) in the deposited fluid can cause problems.

[0005] One exemplary application where this problem arises is in the manufacturing processes applied to the fabrication of displays such as organic light emitting diode ("OLED") displays. When a printing process is used to deposit the ink carrying the light generating material of such displays, volume differences across a row or column of fluid reservoirs or "wells" (e.g., with three such reservoirs per pixel) can lead to color or lighting defects visible in the displayed image. As used herein, "ink" refers to any fluid applied to a substrate by a nozzle of a print head, regardless of color characteristics; note that in the described manufacturing application, the ink is typically deposited in place and then processed or cured to directly form a permanent material layer. Thus, television and display manufacturers will effectively specify precise volume ranges that must be observed with a high degree of accuracy, e.g., 50.00 pL ± 0.25 pL, for the resulting product to be considered acceptable. Note that in this application, the specified tolerance must be within 0.5 percent of the 50.00 pL target. In an application where each nozzle represented by FIG. 1 was to deposit into pixels within each horizontal line of a high definition television ("HDTV") screen, the depicted variation of 49.02 pL to 50.17 pL could therefore result in unacceptable quality. Although display technology is cited as an example, the nozzle It should be appreciated that the droplet inconsistency problem may occur in other situations as well.

[0006] In FIG. 1A, the nozzles are specifically aligned with the target regions (e.g., wells) such that a particular nozzle prints into a particular target region. In FIG. 1B, an alternative case 151 is shown in which the nozzles are not specifically aligned, but the nozzle density is high relative to the target region density, in which case any nozzles that happen to cross certain target regions during a scan or pass are used to print into those target regions, potentially with several nozzles crossing each target region on each pass. In the example shown, the print head 153 is seen to have five ink nozzles, and the substrate is seen to have two target regions 154-155, each positioned such that nozzles (1) and (2) cross target region 154, nozzles (4) and (5) cross target region 155, and nozzle (3) does not cross any target region. As shown, on each pass, one or two droplets are deposited into each well as depicted. Again, droplets can be deposited in an overlapping manner or at individual points within each target area; note that the particular illustration of FIG. 1B is merely illustrative; similar to the example presented in FIG. 1A, it is again assumed that it is desired to deposit 50 picoliters (50.00 pL) of fluid into each of target areas 154-155, with each nozzle having a nominal droplet volume of approximately 10.00 pL. Utilizing the same droplet volume variation per nozzle as observed in connection with the example of FIG. 1A, and assuming that each nozzle that overlaps a target area in a given pass will deliver droplets into that target area until a total of five droplets have been delivered, it is observed that the target area is filled in three passes, with a total deposited ink volume variation of 0.58 pL from a target of 50.00 pL across the two target areas, which again may be unacceptable for many applications.

[0007] Techniques have been proposed to address the problem of inconsistency, but generally speaking, these techniques either still do not reliably provide a fill volume that remains within the desired tolerance range or they significantly increase manufacturing time and cost, i.e., they are inconsistent with the goal of having high quality along with a low consumer price point, which may be important for applications involving commodity products such as HDTVs.

[0008] Therefore, what is needed is a technique useful in depositing fluid into target areas of a substrate using a printhead with a nozzle. More specifically, what is needed is a technique for precisely controlling the amount of fluid deposited at each target area of ​​a substrate, taking into account variations in nozzle and droplet ejection volumes, ideally on a cost-effective basis that enables high speed fluid deposition operations, thus improving the speed of device fabrication. The techniques described below meet these needs and provide further related advantages. Summary of the Invention [Means for solving the problem]

[0009] The present disclosure relates to the use of a printing process to transfer layer material to a substrate. The nozzle consistency problem introduced above is addressed by measuring the drop volume per nozzle (or the drop volume variation across nozzles) of a printhead for a given nozzle firing waveform. This allows planning of printhead firing patterns and / or motions to deposit a precise total loading of ink in each target area. With an understanding of how the drop volume varies across nozzles, the printhead / substrate position offset and / or drop firing pattern can be planned in a manner that accommodates the drop volume differences but still simultaneously deposits drops in adjacent target areas with each pass or scan. From a different perspective, rather than normalizing or averaging the nozzle-to-nozzle variation in drop volume, the specific drop volume characteristics of each nozzle are measured and used in a planned manner to simultaneously achieve a specific range total volume for multiple target areas of the substrate. In many embodiments, this task is This is done using an optimization process that reduces the number of scans or printhead passes based on one or more optimization criteria.

[0010] In one optional embodiment, the printhead and / or substrate are variably "staged" to change the nozzles used for each target area in various passes as appropriate, to emit a specifically desired drop volume. Multiple passes are planned so that each target area receives a specific total fill. That is, each target area (e.g., each well in a row of wells that will form a pixelated component of a display) receives a planned combination of one or more drop volumes to achieve a total volume within a specified tolerance range using different geometric steps of the printhead relative to the substrate. In a more detailed feature of this embodiment, given the positional relationship of the nozzles relative to each other, a Pareto optimal solution can be calculated and applied, allowing for a tolerance of volume variation in each target area within specifications, while at the same time planning the printhead / substrate movement to maximize the average simultaneous use of nozzles for each target deposition area. In one optional refinement, features are applied to reduce and even minimize the number of passes of the printhead / substrate required for printing. To briefly consider these various functions, the printing of layers of material on a substrate can be accomplished quickly and efficiently, thereby significantly reducing production costs.

[0011] Note that in a typical application, the target area to receive ink may be aligned or laid out in rows or columns, and the swath represented by the relative printhead / substrate motion will deposit ink in a manner that is within some of all of the rows (of the target area of ​​the array), but covers all of the columns of the array in one pass. Also, the number of rows, columns, and printhead nozzles may be quite large, e.g., involving hundreds or thousands of rows, columns, and / or printhead nozzles.

[0012] A second optional embodiment addresses the nozzle consistency issue in a slightly different manner. A set of multiple pre-arranged alternative nozzle firing waveforms with known (and different) drop volume characteristics are made available to each nozzle; for example, a set of four, eight, or another number of alternative waveforms can be hardwired or otherwise predefined to provide a corresponding set of selectable slightly different drop volumes. The volume data (or difference data) per nozzle is then used to plan the simultaneous deposition of multiple target areas by determining a set of nozzle-waveform combinations for each target area of ​​the substrate. Again, the specific volume characteristics of each nozzle (in this case, each nozzle-waveform combination) are relied upon to achieve a specific fill volume; that is, rather than trying to compensate for the volume variation per nozzle, that variation is specifically used in combination to obtain a specific fill volume. Note that there will typically be a large number of alternative combinations that can be used to deposit droplets to reach a desired range in each target area of ​​the substrate. In a more detailed embodiment, a "common set" of nozzle waveforms can be shared across several (or even all) nozzles of a printhead, with the drop volumes per nozzle stored and available to mix and match different drop volumes to achieve a particular fill. As a further option, a calibration stage can be used to select the different waveforms in an offline process, with a set of specific nozzle firing waveforms being selected based on the calibration to achieve the specifically desired volume characteristics of each of the set. Again, in a more detailed embodiment, optimization can be performed to plan the printing in a way that improves print time, for example, by minimizing the number of scans or passes of the printhead, by maximizing simultaneous nozzle usage, or by optimizing some other criteria.

[0013] An optional third embodiment relies on the use of multiple printheads, each with nozzles that can be offset with respect to one another (or equivalently, a printing structure with multiple rows of nozzles that can be offset with respect to one another). Using offsets, the volume variations per nozzle can be intelligently combined on each pass or scan across the printhead (or row of nozzles). Again, there are typically many alternative combinations that can be used to deposit droplets to reach the desired coverage in each target area of ​​the substrate, and in particular embodiments, optimization is performed to plan the use of offsets in a way that improves print time, for example, by minimizing the number of scans or printhead passes, or by maximizing simultaneous nozzle usage, etc.

[0014] It should be noted that one benefit of the techniques described above is that by accepting droplet volume variations but combining them to achieve a particular predetermined target area fill volume, one can achieve a high degree of control over the precise volume and intentionally controlled (or injected) variation of such volume as well as the ability to meet desired fill tolerance ranges. For example, in one exemplary application of the described techniques, namely, the fabrication of display devices, the techniques described above facilitate controlled and intentional variation of fill volume from pixel to pixel that will obscure any display artifacts in the finished display (i.e., reduce the "line effect" that would otherwise be visible to the human eye in the finished electronically operable display). That is, even slight differences in the display at low spatial frequencies can be visible to the human eye and thus introduce undesirable, unintentional artifacts. Thus, in some embodiments, it is desired to intentionally vary the fill volume of each target area while still being within specifications. Using an exemplary tolerance of 49.75 pL to 50.25 pL, rather than simply arbitrarily ensuring that all target area fills are at a common precise value within this tolerance range, it may be desirable for such applications to intentionally introduce random variation within this range such that any patterns of variation or difference are not observable to the human eye as patterns in a finished, working display. When applied to color displays, one exemplary embodiment intentionally adds such fill volume variation in a statistically independent manner in at least one of: (a) the x dimension (e.g., along the direction of the rows of the target areas), (b) the y dimension (e.g., along the direction of the columns of the target areas), and / or (c) across one or more color dimensions (e.g., independently for red vs. blue, blue vs. green, red vs. green target areas). In one embodiment, the variation is statistically independent across each of these dimensions. It is believed that such variation renders any fill volume variation imperceptible to the human eye, and thus contributes to the high image quality of such displays. The present invention further provides, for example, the following: (Item 1) 1. A method of generating control data for causing nozzles of a print head to deposit a total volume of ink at at least one target area of ​​a substrate, the total volume being within a predetermined volume tolerance range, each of the nozzles producing at least one respective drop volume, the method comprising: receiving information representative of the droplet volume; calculating combinations of droplets whose corresponding droplet volumes sum to a value constrained to be within said predetermined tolerance range; generating the control data in accordance with the combination; Including, the control data is sufficient to direct relative motion between the print head and substrate to bring each of the nozzles associated with the combination into proximity with a first one of the at least one target area, and is sufficient to direct firing of each of the nozzles associated with the combination to deposit respective drop volumes associated with the combination at the first target area. (Item 2) The predetermined tolerance range comprises a range centered around a target amount, the range being encompassed by the target amount plus or minus a range represented by one percent of the target amount, and generating the control data. 2. The method of claim 1, wherein generating the control data in a manner adapted to use a combination of droplets from at least two of the nozzles to generate a total target volume for a target area of ​​the at least one target area. (Item 3) Item 3. The method of item 2, wherein the method is embodied as a method of controlling an inkjet printing mechanism, the method further comprising controlling the inkjet printing mechanism to effect relative movement and firing of the nozzles associated with the combination in dependence on the control data. (Item 4) 4. The method of claim 3, wherein the inkjet printing mechanism includes a drop measurement device, and receiving the information includes engaging the drop measurement device to empirically determine each of the drop volumes, and receiving the information includes receiving the information from the drop measurement device. (Item 5) The substrate comprises a row of wells, each well representing a respective pixel of a display device and a respective target area of ​​the at least one target area, and the method comprises: performing said calculations in a manner sufficient to calculate said droplet volume combinations for corresponding wells for each of said rows; 2. The method of claim 1, wherein generating includes generating control data sufficient to direct relative motion between the print head and substrate to bring nozzles associated with each of the combinations into proximity with the corresponding wells for each of the rows, and sufficient to direct firing of the nozzles associated with each of the combinations to simultaneously deposit droplets in the corresponding wells. (Item 6) a method for generating control data for causing nozzles of a print head to deposit a total amount of the ink within the predetermined tolerance range at each target area of ​​the substrate; said calculation of combinations is performed for each of said respective target regions; 2. The method of claim 1, wherein the generating of control data is performed to generate the control data in a manner associated with each combination, the control data being sufficient to direct relative motion between the print head and the substrate to simultaneously bring at least one nozzle associated with each combination into proximity with the respective target area, and sufficient to direct firing of the at least one nozzle associated with each combination to simultaneously deposit the drop volumes at the respective target areas. (Item 7) The method further includes identifying a set of predefined nozzle control waveforms, each predefined nozzle control waveform generating a respective ink drop volume when applied to a nozzle; 2. The method of claim 1, wherein the combinations for each of the respective target regions are associated with an integer number of droplets and are adapted to include at least two different ones of the nozzles and at least two different ones of the predetermined nozzle control waveforms. (Item 8) the at least one target area includes a plurality of target areas, each of the target areas achieving the predetermined dose tolerance range, the target areas being offset from one another in a direction of a first axis, the relative motion including at least two scans, each of the scans being substantially perpendicular to the first axis, the at least two scans being offset from one another according to a series of at least one geometric step, and each of the nozzles having a positional relationship to one another; The method includes, for each one of the target areas, determining at least one combination of droplets whose corresponding droplet volumes add up to a value constrained to be within the predetermined tolerance range. calculating a combination of generating the control data in a manner associated with a particular combination of droplets for each one of the target areas; 2. The method of claim 1, further comprising selecting each geometric step in a manner associated with the particular combination. (Item 9) the nozzles have a fixed positional relationship to one another, the nozzles collectively spanning a distance along a direction of the first axis, the at least two scans comprising two scan paths offset by a geometric step of the series of geometric steps, each scan path representing a substantially continuous motion between the print head and the substrate; 9. The method of claim 8, wherein generating the control data is performed such that the geometric step of the series of geometric steps is associated with the particular combination for each target area of ​​target areas, and the geometric step of the series of geometric steps is free to represent a non-integer multiple of the distance. (Item 10) 9. The method of claim 8, wherein generating the control data includes selecting the particular combination for each of the target areas in a manner that minimizes the number of geometric steps required to deposit an amount of ink for all of the target areas. (Item 11) 9. The method of claim 8, wherein calculating at least one combination of droplets includes calculating, for each target area of ​​the target areas, each possible combination of droplets from the nozzles whose corresponding droplet volumes add up to a value constrained to be within the predetermined tolerance range. (Item 12) the print head has 128 or more of the print nozzles; The method is further embodied as a method of controlling a split axis inkjet printing mechanism including a printhead, a printhead motion control mechanism, and a substrate motion control mechanism, comprising: 2. The method of claim 1, wherein generating the control data further comprises having a machine control the inkjet printing mechanism to provide relative motion between the print head and the substrate such that the substrate motion control mechanism is for moving the substrate relative to the print head in a first direction and the print head motion control mechanism is for moving the print head relative to the substrate in a second direction independent of the first direction. (Item 13) 2. The method of claim 1, wherein the at least one target area comprises target areas arranged in an array, and the relative motion comprises a series of scan paths, the scan paths being offset from one another according to a series of variable-sized geometric steps. (Item 14) Item 10. The method of item 1 embodied as a method for forming an organic light-emitting layer for an electronic device, wherein the ink comprises at least one of a solvent-borne organic material, an organic monomer, or an organic polymer. (Item 15) 2. The method of claim 1, wherein the at least one target area includes a first target area for receiving a first ink, the predetermined amount tolerance range is a first tolerance range, the first target areas are arranged as a first array on the substrate comprising rows and columns of the first target areas, each first target area for receiving the first ink within the first tolerance range. (Item 16) Calculating the combinations includes calculating a specific combination for each of the first target regions. 16. The method of claim 15, further comprising causing a machine to select the particular combination of droplets for each of the first target areas in a manner that results in a variation in total ink volume across the first target area within the first tolerance range along at least one of the rows or columns. (Item 17) the first target area is defined by a first well, and the first ink produces a first light color of a display device; the substrate also has second target areas formed as second wells arranged as a second array on the substrate overlapping the first array, the second array comprising rows and columns of the second wells, each second well receiving a second ink with a total ink volume within a second tolerance range, the second ink producing a second light color of the display device; the substrate also has third target areas formed as third wells arranged as a third array on the substrate overlapping each of the first array and the second array, the third array comprising rows and columns of the third wells, each third well receiving a third ink with a total ink volume within a third tolerance range, the third ink producing a third light color of the display device; Item 17. The method according to item 16. (Item 18) Item 18. The method of item 17, wherein each of the first ink, the second ink, and the third ink is for forming a light generating layer of the display. (Item 19) Item 2. The method of item 1, wherein at least two of the nozzles are for ejecting ink mutually exclusively into wells of the substrate. (Item 20) In an inkjet printing process for controlling the ejection of ink into target areas of a substrate, the ink including a material that will form a permanent layer of a device, the inkjet printing process using printheads having nozzles each ejecting a respective droplet amount of ink, each target area receiving a target amount of ink using multiple droplets from the printhead, the improvement comprising: receiving data representative of a volume measurement for each of the nozzles, the data representing the respective drop volumes of ink; calculating a combination of droplets for each target area that sums to a fill value that is constrained to fall within a tolerance range that is within ±1 percent of the value; scheduling multiple scans of the print head relative to the substrate; Including, The improvement, wherein each scan is scheduled in a manner associated with the combination such that nozzles of the print head are used to deposit droplets of the ink at respective ones of the target areas. (Item 21) 21. The improvement of claim 20, further comprising planning the multiple scans of the print head in a manner that deposits the fill value in the respective target areas across the substrate using a minimum number of the multiple scans relative to other scan permutations. (Item 22) 21. The improvement of claim 20, further comprising planning the multiple scans of the print head in a manner that deposits the fill value in the respective target areas across the substrate in a minimum amount of time relative to other scan permutations. (Item 23) 1. A printer comprising: a printhead having nozzles for printing ink onto an array of target areas of a substrate; at least one motion mechanism providing relative motion between the print head and the substrate, the relative motion comprising a substantially continuous scanning motion between the print head and the substrate; a memory device storing data identifying a drop volume for each of said nozzles; instructions stored on a non-transitory machine-readable medium; Equipped with The instructions, when executed, receiving an electronic file defining a desired amount of fill for each of the target areas, the desired amount of fill for each of the target areas being achieved within an associated amount tolerance range; controlling the motion mechanism and the print head to print combinations of droplets from one or more of the nozzles for each target area based on the data identifying drop volumes for each of the nozzles and the file defining the fill volumes for each of the target areas, the combinations of droplets having corresponding drop volumes that sum to a fill value within the associated volume tolerance range; causing the printer to perform a printer, the instructions being for controlling the motion mechanism and the print head to deposit the fill value for each target area to fill all of the target areas using a number of scans that is less than each of the number of rows of the target area in the array and the number of columns of the target area in the array. (Item 24) 24. The printer of claim 23, wherein the instructions, when executed, are for controlling the motion mechanism and the print head to deposit droplets in multiple rows of the target area using each nozzle simultaneously. (Item 25) 24. The printer of claim 23, wherein the instructions, when executed, are for controlling the motion mechanism and the print head to deposit the fill value for each of the target areas such that the number of scans is the minimum number for different combinations of drop volumes from the nozzles at which the fill value for each of the target areas is achieved within the associated volume tolerance range. (Item 26) 24. The printer of claim 23, further comprising a gas enclosure for containing the print head and the substrate, and an atmosphere control system for injecting a controlled atmosphere into the gas enclosure during printing. (Item 27) 24. The printer of claim 23, wherein the substrate is for forming a display device and has three arrays of target areas on the substrate, the target areas of each array representing a respective color component of the pixels of the array, and the printer comprises at least three printheads, at least one for each color component, for printing respective inks onto the target areas of corresponding ones of the three arrays. (Item 28) 28. The printer of item 27, wherein the display device is an organic light emitting diode (OLED) panel, and each of the respective inks includes an organic material carried as a fluid, and each of the respective inks is for generating light corresponding to one of the respective color components, forming a light generating layer of the OLED panel. (Item 29) a drop measurement device, the instructions, when executed, further causing the printer to use the drop measurement device to measure the drop volume for each of the nozzles in situ, the data identifying the drop volume being associated with each of the nozzles in situ. 24. The printer of claim 23, wherein the droplet volume is obtained from measurements of the droplet volume by the droplet measuring device for each of the droplets. (Item 30) 30. The printer of claim 29, wherein the instructions, when executed, further cause the printer to use the drop measurement device intermittently to update the drop volumes for each of the nozzles in situ. [Brief description of the drawings]

[0015] [Figure 1A] FIG. 1A is a schematic diagram presenting a hypothetical problem of depositing ink in target areas of a substrate in which a printhead with five nozzles is used to deposit a target fill of 50.00 pL in each of five specific target areas. [Figure 1B] FIG. 1B is another schematic diagram presenting a hypothetical problem of depositing ink in target areas of a substrate in which a printhead with five nozzles is used to deposit a target fill of 50.00 pL in each of two specific target areas. [Figure 2A] FIG. 2A is an exemplary schematic diagram showing a hypothetical arrangement of a printer and substrates in an application where the substrates will ultimately form a display panel having pixels. [Figure 2B] FIG. 2B is a cross-sectional close-up view of the printhead and substrate of FIG. 2A taken from the perspective of line AA from FIG. 2A. [Figure 3A] 3A is a schematic diagram similar to FIG. 1A, but illustrating the use of a combination of drop volumes to reliably generate ink fill for each target area within a predetermined tolerance range. In one optional embodiment, the combination of different drop volumes is generated from a set of predetermined nozzle firing waveforms, and in another optional embodiment, the combination of different drop volumes is generated from each nozzle of the printhead using relative motion (305) between the printhead and the substrate. [Figure 3B] FIG. 3B is a schematic diagram used to illustrate relative printhead / substrate motion and the ejection of combinations of different drop volumes into each target area of ​​the substrate. [Figure 3C] 3C is a schematic diagram similar to FIG. 1B, but illustrating the use of a combination of drop volumes to reliably generate ink fill for each target area within a predetermined tolerance range. In one optional embodiment, the combination of different drop volumes is generated from a set of predetermined nozzle firing waveforms, and in another optional embodiment, the combination of different drop volumes is generated from each nozzle of the printhead using relative motion (372) between the printhead and the substrate. [Figure 4] FIG. 4 provides an illustrative diagram showing a series of optional tiers, products, or services that can each independently embody the techniques previously introduced. [Diagram 5] FIG. 5 provides a block diagram illustrating a method for planning droplet combinations for each target area of ​​a substrate, which can be applied to either of the optional methods introduced by FIG. 3A. [Figure 6A] FIG. 6A provides a block diagram for selecting a particular set of acceptable droplet combinations for each target area of ​​a substrate, which can be used, for example, with any of the previously introduced embodiments. [Figure 6B] FIG. 6B provides a block diagram for iteratively planning printhead / substrate motion and nozzle usage based on drop combinations for each print area. [Figure 6C] FIG. 6C specifically provides a block diagram illustrating further optimization of print head / substrate motion and nozzle usage to sequence scans in a manner that allows printing to occur as efficiently as possible. [Figure 6D] 6D is a virtual plan view of a substrate that will ultimately produce multiple flat panel display devices, such as 683. As represented by region 687, the print head / substrate motion can be optimized for a specific region of a single flat panel display device, and the optimization is repeated or cyclically used across each display device (four depicted flat panel display devices). [Figure 7]FIG. 7 provides a block diagram for intentionally varying the fill amount within acceptable tolerances to reduce visual artifacts in a display device. [Figure 8A] FIG. 8A provides a graph showing the variation in target area fill volume without adjustment for nozzle-to-nozzle drop volume variation of the printhead. [Figure 8B] FIG. 8B provides a graph illustrating the variation in target area fill volume where different nozzles are randomly used to statistically compensate for nozzle-to-nozzle drop volume variation in the printhead. [Figure 8C] FIG. 8C provides a graph illustrating variation in target area fill, where one or more droplets of different volumes are used to achieve target area fill within precise tolerances on a planned basis. [Figure 9A] FIG. 9A provides a graph showing the variation in target area fill volume without adjustment for nozzle-to-nozzle drop volume variation of the printhead. [Figure 9B] FIG. 9B provides a graph showing the variation in target area fill volume where different nozzles are randomly used to statistically compensate for nozzle-to-nozzle drop volume variation in the printhead. [Figure 9C] FIG. 9C provides a graph illustrating variation in target area fill, where one or more droplets of different volumes are used to achieve target area fill within precise tolerances on a planned basis. [Figure 10] Figure 10 shows a top view of a printer used as part of a fabrication apparatus. The printer may be within a gas enclosure, allowing printing to occur in a controlled atmosphere. [Figure 11] 11 provides a block diagram of a printer. Such a printer can optionally be employed in, for example, the production apparatus depicted in FIG. [Figure 12A] FIG. 12A shows an embodiment in which multiple printheads (each with a nozzle) are used to deposit ink on a substrate. [Figure 12B] FIG. 12B illustrates rotation of multiple printheads to better align the nozzles of each printhead with the substrate. [Figure 12C] FIG. 12C illustrates offsetting of individual printheads of a plurality of printheads in conjunction with intelligent scanning to purposefully produce specific drop volume combinations. [Figure 12D] FIG. 12D shows a cross-sectional view of a substrate including layers that can be used in an organic light emitting diode (OLED) display. [Figure 13A] FIG. 13A illustrates several different ways to customize or vary the nozzle firing waveform. [Figure 13B] FIG. 13B illustrates a method for defining a waveform according to individual waveform sections. [Figure 14A] FIG. 14A illustrates an embodiment in which different combinations of predetermined nozzle firing waveforms can be used to achieve different drop volume combinations. [Figure 14B] Figure 14B shows the circuitry associated with generating and applying programmed waveforms to the nozzles of a print head at programmed times (or locations), providing, for example, one possible implementation of each of circuits 1423 / 1431, 1424 / 1432, and 1425 / 1433 from Figure 14A. [Figure 14C] FIG. 14C illustrates a flow diagram of an embodiment using a different nozzle firing waveform. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The subject matter defined by the recited claims may be better understood by reference to the following detailed description, which should be read in conjunction with the accompanying drawings. The present description of one or more specific embodiments, which are provided below to enable one to build and use various implementations of the technology described by the claims, is not intended to limit the recited claims, but to illustrate their applications. Without limiting the foregoing, the present disclosure provides a method for scheduling printhead movement to maintain the amount of ink deposited within a predetermined tolerance, while reducing the number of printhead passes (and thus the number of times a deposited layer is completed). This paper provides several different examples of techniques used to fabricate layers of material by not excessively increasing the time required to deposit a layer of material onto a substrate (e.g., the time required to deposit a layer of material onto a substrate). These techniques may be embodied as software for performing these techniques, in the form of a computer, printer, or other device that executes such software, in the form of control data (e.g., a print image) for forming layers of material, as a deposition mechanism, or in the form of an electronic or other device (e.g., a flat panel device or other consumer end product) that is fabricated as a result of these techniques. Although specific examples are presented, the principles described herein may be applied to other methods, devices, and systems.

[0017] The examples will help introduce some concepts regarding intelligent planning of fill volume per target area. The per-nozzle volume data (or differential data) for a given nozzle firing waveform can be used to plan the simultaneous deposition of multiple target areas by determining a set of possible nozzle-droplet volumes for each target area. Typically, there will be many possible combinations of nozzles that can deposit ink droplets in multiple passes to fill each target area to the desired fill volume within a narrow tolerance range that meets the specifications. Returning briefly to the hypothesis introduced using FIG. 1A, if an acceptable fill volume according to specification is between 49.75 pL and 50.25 pL (i.e., within 0.5% of the target), then, without limitation, (a) five passes through nozzle 2 (10.01 pL) for a total of 50.05 pL, (b) one pass through nozzle 1 (9.80 pL) and four passes through nozzle 5 (10.03 pL) for a total of 49.92 pL, (c) one pass through nozzle 3 (9.89 pL) and four passes through nozzle 4 (10.03 pL) for a total of 50.01 pL, and (d) one pass through nozzle 5 (10.03 pL) for a total of 49.92 pL. Acceptable fill volumes can also be achieved using many different sets of nozzles / passes, including (d) four passes through nozzle 5 (10.03 pL), (e) one pass through nozzle 2 (10.01 pL), two passes through nozzle 4 (9.96 pL), and two passes through nozzle 5 (10.03 pL) for a total of 49.99 pL. Other combinations are clearly possible as well. Thus, even if only one choice of nozzle drive waveforms is available for each nozzle (or all nozzles), the first embodiment introduced above can be used to apply as many nozzles as possible during each scan to deposit drops (e.g., in different target areas), but offset the print head relative to the substrate in a series of planned offsets or "geometric steps" that combine the deposited drops for each target area in a specifically intended manner.That is, many combinations of nozzles and droplet volumes in this assumption can be used to achieve the desired fill volume, and certain embodiments effectively select a particular one of the acceptable droplet combinations for each target area (i.e., a particular set for each area) through its selection of scanning motion and / or nozzle driving waveforms to facilitate simultaneous filling of different rows and / or columns of the target area using each nozzle. By selecting a pattern of relative printhead / substrate motion in a manner that minimizes the time over which printing occurs, this first embodiment provides substantially enhanced manufacturing throughput. Note that this enhancement can be optionally embodied in a form that minimizes the number of printhead / substrate scans or "passes," in a manner that minimizes the raw distance of relative printhead / substrate movement, or in a manner that otherwise minimizes overall printing time. That is, print head / substrate movement (e.g., scanning) can be planned in advance and used to fill a target area in a manner that meets predefined criteria, such as minimum print head / substrate passes or scans, minimum print head and / or substrate movement in one or more defined dimensions, printing in a minimum amount of time, or other criteria.

[0018] All of the same approaches apply equally to the assumption of FIG. 1B, where the nozzles are not specifically aligned with their respective target areas. Again, without limitation, if an acceptable fill volume according to specification is between 49.75 pL and 50.25 pL (i.e., within 0.5% on either side of the target). However, acceptable fill volumes can also be achieved with many different sets of nozzles / passes, including all of the embodiments described above for Figure 1A, as well as additional embodiments specific to the hypothetical Figure 1B in which two adjacent nozzles are used in one pass to fill a particular target area, e.g., two passes through nozzle (4) (9.96 pL) and nozzle (5) (10.03 pL) for a total of 49.99 pL, and one pass through nozzle (2) (10.01 pL). Other combinations are clearly possible as well.

[0019] These same principles also apply to the second embodiment introduced above. For example, in the hypothetical scenario presented by FIG. 1A, each of the nozzles can be driven by five different firing waveforms, identified as firing waveforms AE, where the resulting volume characteristics of the different nozzles for the different firing waveforms are illustrated by Table 1A below. Considering only the target area 104, and only nozzle (1), for example, it would be possible to deposit a 50.00 pL target in five passes, with a first printhead pass using predefined firing waveform D (to generate 9.96 pL drops from nozzle (1)) and four subsequent passes using predefined firing waveform E (to generate 10.01 pL drops from nozzle (1)), all without any offset of the scan path. Similarly, different combinations of firing waveforms can be used simultaneously in each pass for each nozzle to generate a volume close to the target value within each of the target areas, without any offset of the scan path. Thus, using multiple passes in this manner may be advantageous for embodiments in which it is desired to simultaneously deposit droplets in different target areas (i.e., within different rows of pixels, for example).

[0020] [Table 1A]

[0021] All of these same principles apply equally to the hypothetical of Figure 1B. For example, considering only target area 104 and nozzles (1) and (2) (i.e., the two nozzles that overlap target area 154 during the scan), it is possible to achieve 50.00 pL in three passes, for example, with a first printhead pass using nozzle (1) and predefined waveform B (for a drop volume of 9.70 pL) and nozzle (2) and predefined waveform C (for a drop volume of 10.10), a second printhead pass using nozzle (1) and predefined waveform E (for a drop volume of 10.01 pL) and nozzle (2) and predefined waveform D (for a drop volume of 10.18 pL), and a third printhead pass using nozzle (1) and predefined waveform E (for a drop volume of 10.01 pL).

[0022] It should be noted that perhaps both the assumptions of Figure 1A and Figure 1B could be used to deposit each fill of each target volume in a single row of the target area in a single pass in this example. For example, the print head could be rotated 90 degrees to deposit, for example, a waveform (E) on nozzle (1), a waveform (A) on nozzles (2), (4), and (5), and a waveform (C) on nozzle (3). (C) Using (10.01 pL + 10.01 pL + 9.99 pL + 9.96 pL + 10.03 pL = 50.00 pL), it would be possible to deposit exactly 50.00 pL with a single drop from each nozzle onto each target area in a row.

[0023] These same principles also apply to the third embodiment introduced above. For example, for the hypothetical presented by FIG. 1A, the volume characteristics can reflect the nozzles for a first printhead (e.g., “printhead A”) that is integrated with four additional printheads (e.g., printheads “B”-“E”), each driven by a single firing waveform and with their own drop volume characteristics per nozzle. As the printheads perform a scan pass, each of the nozzles identified as nozzles (1) for the printhead is aligned to print into a target area (e.g., target area 104 from FIG. 1A), each of the nozzles identified as nozzles (2) from the various printheads is aligned to print into a second target area (e.g., target area 105 from FIG. 1A), and so on, with the volume characteristics of the different nozzles for the different printheads being collectively organized as described by Table 1B below. Optionally, the respective printheads can be offset from one another, for example, using a motor to adjust the spacing between scans. Considering only the target area 104 and only the nozzles (1) on each printhead, it would be possible to deposit 50.00 pL in four passes, for example, with a first printhead pass in which both printhead D and printhead E fire droplets into the target area, and three subsequent passes in which only printhead E fires droplets into the target area. Other combinations are possible using fewer passes that can still produce amounts in the target area approaching the 50.00 pL target, for example, in the range of 49.75 pL to 50.25 pL. Again, considering only the target area 104 and only the nozzles (1) on each printhead, it would be possible to deposit 49.83 pL in two passes, for example, with a first printhead pass in which printheads C, D, and E all fire droplets into the target area, and a second printhead pass in which printheads D and E both fire droplets into the target area.Similarly, different combinations of nozzles from different printheads can be used simultaneously in each pass to produce amounts in each of the target regions that are close to the target values ​​without any offset in the scan path. Thus, using multiple passes in this manner may be advantageous for embodiments in which it is desired to simultaneously deposit droplets in different target regions (i.e., for example, at different rows of pixels).

[0024] [Table 1B]

[0025] All of the same approaches apply equally well to the hypothetical case of FIG. 1B. Again, considering only target area 154 and only nozzles (1) and (2) on each printhead (i.e., the nozzles that overlap target area 154 during the scan), for example, in a first scan in which printheads C and E fire nozzle (1) and printheads B and C fire nozzle (2), It is possible to deposit 50.00 pL in two passes using a printhead pass and a second printhead pass where printhead C fires nozzle (2). It is also possible to deposit 49.99 pL in one pass (specifically within the target range of 49.75 pL to 50.25 pL) using, for example, a printhead pass where printheads C, D, and E fire nozzle (1) and printheads B and E fire nozzle (2).

[0026] It should also be apparent that the use of alternative nozzle firing waveforms, optionally combined with scan path offsets, significantly increases the number of drop volume combinations that can be achieved for a given printhead, and these options are further increased with multiple printheads (or equivalently multiple rows of nozzles) as described above. For example, in the hypothetical example conveyed by the discussion of FIG. 1 above, the combination of five nozzles with their respective unique ejection characteristics (e.g., drop volumes) and eight alternative waveforms could provide literally thousands of different sets of possible drop volume combinations. Optimizing the set of nozzle-waveform combinations and selecting a particular set of nozzle-waveform combinations for each target area (or for each row of print wells in the array) allows further optimization of printing according to desired criteria. In embodiments using multiple printheads (or rows of printhead nozzles), the ability to selectively offset these printheads / rows also further enhances the number of combinations that can be applied per printhead / substrate scan. Again, for these embodiments, while multiple sets (one or more) of nozzle waveform combinations could alternatively be used to achieve a particular fill volume, this second embodiment selects a particular set of the "allowable" sets for each target area, and this selection of that particular set across the target area generally corresponds to the simultaneous printing of multiple target areas using multiple nozzles. That is, by varying parameters to minimize the time over which printing occurs, each of these embodiments promotes manufacturing throughput, minimizing the number of printhead / substrate scans or "passes" required, the raw distance of relative printhead / substrate movement along a particular dimension, overall printing time, or anything else that helps meet some predetermined criteria.

[0027] It should be noted that these techniques are optional with respect to each other; that is, for example, it is possible to use multiple nozzle firing waveforms to achieve a desired drop combination without varying the position step of the printhead / substrate scan and without offsetting multiple printhead / nozzle rows, and it is possible to use printhead / nozzle row offsets without varying the position step or varying the nozzle firing waveforms.

[0028] These various techniques can also be optionally combined with each other or with other techniques in any desired manner, for example, the nozzle drive waveform can be "tuned" for each nozzle (e.g., shaping the drive pulse by changing the drive voltage, rise or fall slope, pulse width, decay time, number of pulses used per drop and their respective levels, etc.) to reduce variation in drop volume per nozzle.

[0029] Although certain applications discussed herein refer to fill volumes in individual fluid reservoirs or "wells," it is also possible to use the described techniques to deposit "blanket coatings" having large topographies onto other structures on a substrate (e.g., onto transistors, vias, diodes, and other electronic components, etc.). In such situations, the fluid ink carrying the layer material (which may, for example, be cured, dried, or hardened in situ to form a permanent device layer) will spread to some extent but will still retain certain properties relative to other target deposition areas of the substrate (taking into account ink viscosity and other factors). In this situation, for example, specific localization of the ink fill volume for each target area may be achieved. The techniques herein can be used to deposit blanket layers, such as encapsulation layers or other layers, with control. The techniques discussed herein are not limited by the specifically presented applications or embodiments.

[0030] Other variations, advantages, and applications from the techniques introduced above will be readily apparent to those skilled in the art. That is, these techniques can be applied in many different fields and are not limited to the fabrication of display devices or pixelated devices. As used herein, a printing "well" refers to any container in a substrate that is intended to receive deposited ink and thus has chemical or structural properties adapted to inhibit the flow of that ink. As exemplified for OLED printing below, this can include situations where each fluid container is intended to receive a respective amount of ink and / or a respective type of ink, e.g., in a display application where the described techniques are used to deposit light-emitting materials of different colors, a successive printing process can be performed for each color using a respective print head and a respective ink, where each process can deposit "every other well" in an array (e.g., for all "blue" color components), or equivalently, all wells in every other array (interspersing wells with overlapping arrays for other color components). Other variations are possible. Also, note that "row" and "column" are used in this disclosure without implying any absolute direction. For example, a "row" of printing wells can extend the length or width of a substrate, or in another manner (linear or nonlinear), and generally speaking, "row" and "column" will be used herein to refer to directions each representing at least one independent dimension, although this need not be true in all embodiments. Also, note that since modern printers can use relative substrate / printhead motion with multiple dimensions, the relative movement need not be linear in path or velocity, i.e., the printhead / substrate relative motion need not follow a straight or even continuous path, or a constant velocity. Thus, a "pass" or "scan" of a printhead relative to a substrate simply refers to the repeated deposition of droplets using multiple nozzles over multiple target areas, with relative printhead / substrate motion.However, in many embodiments described below for the OLED printing process, each pass or scan may be a substantially continuous linear motion, ensuring that each subsequent pass or scan is parallel to the next pass or scan and offset by a geometric step relative to each other. This offset or geometric step may be a difference in the pass or scan start position, average position, end position, or some other type of position offset, and does not necessarily imply parallel scan paths. It should also be noted that various embodiments discussed herein talk about the "simultaneous" use of different nozzles to deposit in different target areas (e.g., different rows of target areas), and that this term "simultaneous" does not require simultaneous drop emission, but rather merely refers to the concept that different nozzles or groups of nozzles may be used to fire ink into respective target areas in a mutually exclusive manner during any scan or pass. For example, a first group of one or more nozzles can be fired during a given scan to deposit a first droplet into a first row of fluid wells, while a second group of one or more nozzles can be fired during that same scan to deposit a second droplet into a second row of fluid wells.

[0031] With the major components of several different embodiments laid out in this manner, the present disclosure will be organized roughly as follows: Figures 2A-3C will be used to introduce some general principles related to the problem of nozzle consistency, OLED printing / fabrication, and how embodiments address the problem of nozzle consistency. These figures will also be used to introduce concepts related to planning printhead / substrate motion, for example, where offset variation is used to change which printhead nozzles are used to deposit droplets within each row of an array of target areas of a substrate. Figures 4-7 will be used to illustrate a software process that can be used to plan the drop combinations for each target area of ​​the substrate. Figures 8A-9C will be used to present some empirical data that demonstrates the effectiveness of the described techniques in improving well-fill consistency. Figures 10-11 will be used to discuss an example application to OLED panel fabrication and associated printing and control mechanisms. Figures 12A-12C will be used to discuss printhead offsets that can be used to vary the drop combinations that can be deposited in each scan. Finally, Figures 13A-14C will be used to further discuss different alternative nozzle firing waveforms that can be applied to provide different drop volumes.

[0032] As represented by FIG. 2A, in certain applications, a printing process can be used to deposit one or more layers of material onto a substrate. The techniques discussed above can be used to generate printer control instructions (e.g., electronic control files that can be transferred to a printer) for later use in fabricating a device. In certain applications, these instructions can be adapted for an inkjet printing process useful in printing layers of low-cost, scalable organic light-emitting diode ("OLED") displays. More specifically, the described techniques can be applied to deposit one or more emissive or other layers of such OLED devices, such as the "red," "green," and "blue" (or other) pixelated color components or other emissive layers or components of such devices. This exemplary application is non-limiting, and the described techniques can be applied to the fabrication of many other types of layers and / or devices, whether or not these layers emit light, and whether or not the device is a display device. In this exemplary application, various conventional design constraints of inkjet printheads provide challenges to process efficiency and film coating uniformity of various layers of an OLED stack that can be printed using various inkjet printing systems. These challenges may be addressed through the teachings herein.

[0033] More specifically, FIG. 2A is a plan view of one embodiment of a printer 201. The printer includes a printhead 203 that is used to deposit fluid ink onto a substrate 205. Unlike printer applications that print text and graphics, the printer 201 in this example is used in a manufacturing process to deposit fluid ink that will have a desired thickness. That is, in a typical manufacturing application, the ink carries a material that will be used to form a permanent layer of a finished device, with the layer having a specific desired thickness that depends on the amount of ink applied. The ink typically features one or more materials that will form part of the finished layer, formed as a monomer, polymer, or material carried by a solvent or other transport medium. In one embodiment, these materials are organic. Following deposition of the ink, the ink is dried, cured, or hardened to form a permanent layer; for example, some applications use an ultraviolet (UV) curing process to convert the monomer or polymer into a hardened material, while other processes dry the ink to remove the solvent and leave the transported material in a permanent location. Other processes are possible. It should be noted that there are many other variations that distinguish the depicted printing process from traditional graphics and text applications, for example, in some embodiments, deposition of the desired material layer occurs in an environment that is controlled to either condition the surrounding atmosphere to be other than air or otherwise exclude unwanted particulate matter. For example, as described further below, one envisioned application uses a fabrication mechanism that encloses the printer 201 in a gas chamber so that printing can occur in the presence of a controlled atmosphere, such as an inert environment, including, but not limited to, nitrogen, any of the noble gases, and any combination thereof.

[0034] As further seen in FIG. 2A, printhead 203 includes several nozzles, such as nozzle 207. Note that in FIG. 2A, for ease of illustration, printhead 203 and nozzles are depicted as opening out from the top of the page, but in reality, these nozzles and printhead face downward toward the substrate and are hidden from view from the perspective of FIG. 2A (i.e., FIG. 2A actually shows what is a cutaway view of printhead 203). It can be seen that the nozzles are arranged in rows and columns (such as exemplary row 208 and column 209), but this is not required for all embodiments, i.e., some implementations use only one row of nozzles (such as row 208). Additionally, rows of nozzles can be arranged on each printhead, and each printhead can (optionally) be individually offset with respect to one another as introduced above. In applications where a printer is used to fabricate parts of a display device, for example materials for each of the respective red, green, and blue components of the display device, the printer typically uses dedicated printhead components for each different ink or material, and the techniques discussed herein can be applied separately to each corresponding printhead.

[0035] FIG. 2A illustrates one print head 203. The printer 201 includes two different motion mechanisms that can be used to position the print head 203 relative to the substrate 205 in this example. First, a traveler or carriage 211 can be used to mount the print head 203 and enable relative motion as represented by arrow 213. Second, however, a substrate transport mechanism can be used to move the substrate relative to the traveler along one or more dimensions. For example, as represented by arrow 215, the substrate transport mechanism can enable motion in each of two orthogonal dimensions, such as according to x and y Cartesian dimensions (217), and can optionally assist with substrate rotation. In one embodiment, the substrate transport mechanism includes a gas floating table that is used to selectively fix and enable substrate movement on gas bearings. Additionally, it is noted that the printer optionally enables rotation of the print head 203 relative to the traveler 211, as represented by rotation graphic 218. Such rotation allows the apparent spacing and relative configuration of the nozzles 207 to be changed with respect to the substrate, for example, if each target area of ​​the substrate is defined to be of a particular area or has a spacing relative to another target area, then rotating the print head and / or substrate can change the relative separation of the nozzles along or perpendicular to the scan direction. In an embodiment, the elevation of the print head 203 with respect to the substrate 205 can also be changed, for example along the z Cartesian dimension, which is in or out of the orientation of the diagram in FIG. 2A.

[0036] The two scan paths are illustrated by directional arrows 219 and 220, respectively, in FIG. 2A. Briefly, the substrate motion mechanism moves the substrate back and forth in the direction of arrows 219 and 220, while the print head moves in a geometric step or offset in the direction of arrow 213. Using a combination of these movements, the nozzles of the print head can reach any desired area of ​​the substrate for depositing ink. As previously referenced, ink is deposited into discrete target areas of the substrate on a controlled basis. These target areas can optionally be aligned, i.e., arranged, in rows and columns, such as along the depicted y and x dimensions, respectively. Note that the rows of nozzles (such as row 208) are viewed in this illustration perpendicular to the rows and columns of target areas, i.e., such that a row of nozzles sweeps along the direction of the rows of target areas and traverses each of the columns of target areas of the substrate (e.g., along direction 219) for each scan. This need not be true for all embodiments. For efficiency of motion, a subsequent scan or pass then reverses the direction of this motion and hits the rows of the target area in reverse order, ie, along direction 220.

[0037] The arrangement of target areas in this example is depicted by highlighted area 221, seen in enlarged view on the right side of the figure. That is, two rows of pixels, each having red, green, and blue color components, are each represented by numeral 223, while columns of pixels perpendicular to the scan direction (219 / 220) are each represented by numeral 225. In the top left most pixel, it can be seen that the red, green, and blue color components occupy different target areas 227, 229, and 231 as part of respective overlapping arrays of areas. Each color component within each pixel can also have associated electronics, as represented by numeral 233, for example. If the device being fabricated is a backlit display (e.g., as part of a conventional LCD television), these electronics can control the selective generation of light filtered by the red, green, and blue color regions. If the device being fabricated is a newer type of display, where the red, green, and blue regions directly produce unique colors with corresponding color characteristics, then these electronics 233 can include patterned electrodes and other material layers that contribute to the desired light generation and light characteristics.

[0038] FIG. 2B provides a close-up cross-sectional view of the print head 203 and substrate 205 taken from the perspective of line AA in FIG. 2A. In FIG. 2B, the numerals already introduced with reference to FIG. 2A represent the same features. More specifically, numeral 201 generally represents the printer, while numeral 208 represents a row of print nozzles 207. Each nozzle is designated using a bracketed numeral, e.g., (1), (2), (3), etc. A typical print head typically has a number of such nozzles, e.g., 64, 128, or another number, and in one embodiment there may be 1,000 or more nozzles arranged in one or more rows. As previously mentioned, the print head in this embodiment is moved relative to the substrate in a direction referenced by arrow 213 to achieve a geometric step or offset during the scan. Depending on the substrate motion mechanism, the substrate can also be moved perpendicular to this direction (e.g., into and out of the page relative to the view of FIG. 2B) and, in some embodiments, in the direction represented by arrow 213. Note that FIG. 2B also shows a row 225 of target areas 253 of each of the substrate, arranged in this case as "wells," which will receive the deposited ink and hold the deposited ink within the structural areas of each well. For purposes of FIG. 2B, it will be assumed that only one ink is represented (e.g., each depicted well 253 represents only one color of the display, such as a red component, with other color components and associated wells not shown). Note that the drawing is not to scale, e.g., the nozzles can be seen to be numbered from (1) to (16), while the wells are seen to be lettered from (A) to (ZZ), representing 702 wells. In some embodiments, the nozzles will be aligned with their respective wells such that the depicted printhead with 16 nozzles uses scanning relative printhead / substrate motion into and out of the page from the perspective of FIG. 2B to deposit ink in as many as 16 wells simultaneously in the direction of the arrow 255.In other embodiments as described (e.g., with reference to FIG. 1B), the nozzle density is even greater than the target area density, and in any scan or pass, a portion of the nozzles (e.g., a group of one to many nozzles, depending on which nozzles traverse each target area) will be used for deposition. For example, again using the illustrative example of 16 nozzles, nozzles (1)-(3) could be used to deposit ink at a first target area, and nozzles (7)-(10) could be used simultaneously to deposit ink in a second target area, mutually exclusive for a given pass.

[0039] Conventionally, a printer might be operated to use 16 nozzles to simultaneously deposit ink in as many as 16 rows of wells, moving back and forth as necessary in successive scans until five droplets have been deposited in each well, with the printhead advanced as necessary using fixed steps that are an integer multiple of the width of the swath traversed by the scan. However, the techniques provided by this disclosure require that a printer be able to simultaneously deposit ink in as many as 16 rows of wells, moving back and forth as necessary in successive scans until five droplets have been deposited in each well. The present invention takes advantage of the inherent variation in the drop volumes produced by different nozzles in combinations calculated to produce a particular fill volume for each well. Different embodiments rely on different techniques to achieve these combinations. In one embodiment, the geometric step is varied to achieve different combinations and can be free to be other than an integer multiple of the width represented by the printhead swath. For example, if appropriate for depositing a selected set of drop combinations in each well 253 of FIG. 2A, the geometric step may actually be 1 / 160th of the printhead swath, which in this example represents a relative displacement between the printhead and the substrate for a spacing of one-tenth of a row of wells. The next offset or geometric step may be appropriately different for the particular combination of drops desired in each well, for example a virtual offset of 5 / 16th of the printhead swath, corresponding to an integer spacing of wells. This variation may continue with both positive and negative steps as necessary to deposit ink to obtain the desired fill volume. It should be noted that many different types or sizes of offsets are possible, and the step size does not have to be fixed between scans or a specific percentage of the well spacing. However, in many manufacturing applications, it is desirable to minimize print time in order to maximize production rate and minimize manufacturing cost per unit as much as possible. To achieve this goal, in certain embodiments, printhead motion is planned and sequenced in a manner that minimizes the total number of scans, the total number of geometric steps, the size of the offset or geometric step, and the cumulative distance traversed by the geometric steps. These or other measures can be used individually, together, or in any desired combination to minimize the total print time.In embodiments where rows of independently offsettable nozzles (e.g., multiple printheads) are used, the geometric step can be represented in part by an offset between printheads or nozzle rows, and such offset combined with an overall offset of the printhead components (e.g., a fixed step of the printhead assembly) can be used to achieve geometric steps of variable size and thus deposit a combination of droplets into each well. In embodiments where variation of nozzle driving waveforms is used alone, a conventional fixed step can be used and droplet volume variation is achieved using multiple printheads and / or multiple printhead passes. As described below, in one embodiment, the nozzle driving waveform can be programmed for each nozzle between droplets, thus enabling each nozzle to generate and provide a respective droplet volume per well within a row of wells.

[0040] 3A, 3B, and 3C are used to provide additional detail regarding the reliance on specific drop volumes in achieving a desired loading volume.

[0041] 3A presents an illustrative diagram 301 of a printhead 303 and two associated schematics seen below the printhead 303. The printhead is optionally used in embodiments that provide for non-fixed geometric stepping of the printhead relative to the substrate, and numeral 305 is used to represent offsets that align particular printhead nozzles (e.g., 16 nozzles total with nozzles (1)-(5) depicted in the figure) with different target areas (five in this example: 307, 308, 309, 310, and 311). Recalling the example of FIG. 1A, if nozzles (1)-(16) produce fluid ink drop volumes of 9.80, 10.01, 9.89, 9.96, 10.03, 9.99, 10.08, 10.00, 10.09, 10.07, 9.99, 9.92, 9.97, 9.81, 10.04, and 9.95 pL, respectively, and if it is desired to deposit 50.00 pL per target area (±0.5 percent of this value), the print head would be used to deposit the drops in five passes or scans using geometric steps of 0, −1, −1, −2, and −4, respectively, resulting in total fill values ​​of 49.82, 49.92, 49.95, 49.90, and 50.16 pL per area, as depicted in the figure. This is clearly within the desired tolerance range of 49.75 pL to 50.25 pL for each of the delineated target areas. All steps in this example are expressed incrementally relative to the previous position, although other scales may be used. Thus, as shown, a combination of droplets in a deliberate manner depending on the respective droplet volume and desired filling for each target area can be used to achieve precisely regulated filling with a high degree of reliability.

[0042] Note that this same diagram can be used to represent nozzle drive waveform variations and / or the use of multiple printheads. For example, if nozzle references (1)-(16) refer to the drop volume for a single nozzle generated by 16 different drive waveforms (i.e., using waveforms 1-16), one can obtain a theoretical per-area fill volume simply by using different drive waveforms, e.g., waveform numbers 1, 3, 4, 5, and 9, in the target area 307. In practice, since process variations may result in different per-nozzle characteristics, the system would measure the drop volume for each nozzle for each waveform and intelligently plan the drop combinations on this basis. In embodiments where nozzle references (1)-(15) refer to multiple printheads (e.g., references (1)-(5) refer to a first printhead, references (6)-(10) refer to a second printhead, and references (11)-(15) refer to a third printhead), an offset between the printheads can be used to reduce the number of passes or scans. For example, the right-most target area 311 can have three droplets deposited in one pass, including drop volumes of 10.03, 10.09, and 9.97 pL (print head (1), 0 offset; print head (2), +1 offset; and print head (3), +2 offset). It should be apparent that the combination of these various techniques facilitates many possible combinations of droplets of specific volumes to achieve a specific fill volume within the tolerance range. Note in FIG. 3A that the variance in total ink fill volume between the target areas is small and within tolerance, i.e., within the range of 49.82 pL to 50.16 pL.

[0043] FIG. 3B shows another illustrative diagram 351, in which each scan is represented by a different rectangle or bar as referenced by numerals 353-360. In relation to this diagram, it should be assumed that the printhead / substrate relative motion is advanced in a series of variable-sized geometric steps. Again, note that typically each step will designate a scan that sweeps multiple columns of target areas (e.g., pixels) beyond one column of five regions represented on the plane of the drawing page (and represented by numerals 362-366). The scans are shown in a top-to-bottom order, including a first scan 353, in which the printhead is seen displaced to the right relative to the substrate such that only nozzles (1) and (2) are aligned with target areas 365 and 366, respectively. Within each print scan depiction (such as box 353), a circle represents each nozzle either solid black to represent that the nozzle is to be fired when the nozzle covers the specifically depicted target area during the scan, or "hollow" or filled white to represent that the nozzle is not to be fired at the relevant time (but may be fired for other target areas encountered in the scan). Note that in this embodiment, each nozzle is fired on a binary basis, i.e., each nozzle is either fired or not fired according to any adjustable parameters, e.g., to deposit a predetermined drop volume for each target area encountered during the scan. This "binary" firing scheme may be optionally employed in any of the embodiments described herein (i.e., in embodiments in which multiple firing waveforms are used, where waveform parameters are adjusted between drops, for example). It can be seen that in the first pass 353, nozzle (1) is fired to deposit a 9.80 pL drop into the second rightmost target area, while nozzle (2) is fired to deposit a 10.01 pL drop into the rightmost target area 366. The scan continues to sweep other columns of target areas (e.g., other rows of pixel wells), depositing ink drops as appropriate. When the first pass 353 is complete, After the first scan is completed, the print head is advanced a geometric step of −3, which moves the print head left relative to the substrate such that nozzle (1) traverses target area 362 during a second scan 354, in the opposite direction to the first scan. During this second scan 354, nozzles (2), (3), (4), and (5) will also traverse areas 363, 364, 365, and 366, respectively. It can be seen by the solid circles that nozzles (1), (2), (3), and (5) will be fired at the appropriate time to deposit drop volumes of 9.80 pL, 10.01 pL, 9.89 pL, and 10.03 pL, corresponding to the unique characteristics of nozzles (1), (2), (3), and (5), respectively. Also, in any one pass, the nozzles in a row of nozzles used to deposit ink will deposit into their respective target areas mutually exclusively. It should also be noted, for example, that for pass 354, nozzle (1) is used to deposit ink into target area 362 (and not into any of target areas 363-366), nozzle (2) is used to deposit ink into target area 363 (and not into any of areas 362 or 364-366), nozzle (3) is used to deposit ink into target area 364 (and not into any of areas 362-363 or 365-366), and nozzle (5) is used to deposit ink into target area 366 (and not into any of areas 362-365). The third scan, represented using the numeral 355, effectively advances the printhead by one row of the target area (-1 geometric step) such that nozzles (2), (3), (4), (5), and (6) traverse areas 362, 363, 364, 365, and 366, respectively, during the scan, and the filled-in nozzle graphic represents that during this pass, each of nozzles (2)-(6) will be actuated to fire droplets to produce volumes of 10.01, 9.89, 9.96, 10.03, and 9.99 pL, respectively.

[0044] If the printing process were stopped at this point, region 362 would have a fill of 19.81 pL (9.80 pL + 10.01 pL), corresponding to two drops, while region 366 would have a fill of 30.03 pL (10.01 pL + 10.03 pL + 9.96 pL), corresponding to three drops, for example. Note that the scan pattern, in one embodiment, follows the back and forth pattern represented by arrows 219 and 220 in Figure 2A. Subsequent passes 356, 357, 358, 359, 360, and 361 of these target regions (or scans of multiple rows of multiple such regions) result in (a) 10.01 pL, 0.00 pL, 0.00 pL, 10.08 pL, and 10.09 pL droplets in region 362, corresponding to passes by nozzles (2), (3), (4), (7), and (9), respectively, in successive scans; (b) 0.00 pL, 0.00 pL, 10.03 pL, 10.00 pL, and 10.07 pL droplets in region 363, corresponding to passes by nozzles (3), (4), (5), (8), and (10), respectively, in successive scans; (c) 0.00 pL, 0.00 pL, 10.03 pL, 10.00 pL, and 10.07 pL droplets in region 364, corresponding to passes by nozzles (4), (5), (8), and (10), respectively, in successive scans; (d) 0.00 pL, 9.99 pL, 10.08 pL, 10.07 pL, and 0.00 pL droplets in region 365 corresponding to passes by nozzles (5), (6), (7), (10), and (12) in successive scans; and (e) 9.99 pL, 0.00 pL, 10.00 pL, 0.00 pL, and 0.00 pL droplets in region 366 corresponding to passes by nozzles (6), (7), (8), (11), and (13) in successive scans. Again, note that the nozzles in this embodiment are used on a binary basis and with only a single firing waveform (i.e., so that their droplet volume characteristics do not change with scan), so that, for example, in the fifth scan 357, nozzle (7) is not fired and produces no droplets (0.00 pL) for region 366, while in the next scan it is fired and produces a 10.08 pL droplet for region 365.

[0045] As seen in the graph at the bottom of the page, this virtual scan process easily produces total fills of 49.99 pL, 50.00 pL, 49.96 pL, 49.99 pL, and 50.02 pL, within the desired range of the target value (50.00 pL) ±0.5 percent (49.75 pL to 50.25 pL). In this example, the nozzles were used to deposit ink into multiple target areas substantially simultaneously for each scan, and specific combinations of drop volumes for each delineated area (i.e., as graphically identified by numbers 362, 363, 364, 365, and 366) were planned to allow multiple passes to deposit multiple drops in each target area. Although the eight depicted passes are associated with a particular set of drop volumes (or particular combinations) that together produce a fill volume within a specified tolerance range (e.g., for region 362, a combination of drops from nozzles (1), (2), (2), (7), and (9)), other sets of possible drops could conceivably have been used. For example, for region 362, it would have been possible to alternatively use five drops from nozzle (2) (5×10.01 pL=50.05 pL). However, this alternative would have been inefficient because nozzle (3) (9.89 pL) could not have been used extensively at the same time during this time (i.e., the result from five drops from this nozzle would have been 5×9.89=49.45 pL, outside the desired tolerance range), which would have required an additional scan. In the example conveyed by Figure 3B, the particular scans and their order were selected to use less printing time, fewer passes, smaller geometric steps, and potentially smaller total geometric step distance, or according to some other criteria. Note that the depicted example is for narrative discussion only, and it may be possible to further reduce the number of scans using the presented drop volumes to fewer than eight scans to obtain the target fill.In some embodiments, the scanning process is planned in a manner that avoids worst-case scenarios with the number of scans required (e.g., one scan per row of target area with the printhead rotated 90 degrees). In other embodiments, this optimization is applied to an extent based on one or more maximum or minimum values, for example, planning the scans in a manner that results in the fewest possible scans, considering all possible drop combinations for each target area for a given ink.

[0046] 3C presents an illustrative view 301 of a printhead 303, similar to FIG. 3A, but now with nozzles not specifically aligned with particular wells, and two associated schematic views seen below the printhead 303. Because the printhead is used in an embodiment that optionally provides for non-fixed geometric stepping of the printhead relative to the substrate, the numeral 305 is used to represent an offset that aligns a particular printhead nozzle (e.g., 16 nozzles total, with nozzles (1)-(5) depicted in the figure) with a different target area (in this example, two, 374 and 375). Again following the example of FIG. 3A , if nozzles (1)-(16) produce fluid ink drop volumes of 9.80, 10.01, 9.89, 9.96, 10.03, 9.99, 10.08, 10.00, 10.09, 10.07, 9.99, 9.92, 9.97, 9.81, 10.04, and 9.95 pL, respectively, and if it is desired to deposit 50.00 pL per target area (±0.5 percent of this value), the print head can be used to deposit the drops in three passes or scans, using geometric steps of 0, −1, and −3, respectively, and firing one or two drops into each target area per scan. This would again result in a total fill value of 49.93 or 50.10 per region as depicted in the figure, clearly within the desired tolerance range of 49.75 pL to 50.25 pL for each of the depicted target regions. Thus, as shown, the same approach can be equally applied in the case of nozzles not aligned to the wells, using a combination of droplets in a deliberate manner depending on the respective droplet volume and desired fill for each target region to achieve a precisely regulated fill. Furthermore, in FIG. As explained above for the hypothesis, this same diagram can be used to represent nozzle drive waveform variations and / or the use of multiple printheads. For example, if the nozzle references (1)-(16) refer to the drop volume for a single nozzle generated by 16 different drive waveforms (i.e., using waveforms 1-16), one can obtain the theoretical fill volume per area simply by using different drive waveforms. Those skilled in the art can appreciate that the same approach as described above with reference to FIG. 3B also applies equally to the case of nozzles that are not specifically aligned with the wells, i.e., a group of one or more nozzles is used for simultaneous drop deposition into each well. Finally, it should be noted that FIGS. 3A, 3B, and 3C also represent a relatively simple example, and in a typical application there may be hundreds to thousands of nozzles and millions of target areas. For example, in an application where the disclosed techniques are applied in the fabrication of each pixel color component of a current resolution high resolution television screen (e.g., where each pixel has a red, green, and blue well, and the pixels are arranged with 1080 horizontal lines of vertical resolution and 1920 vertical lines of horizontal resolution), there are approximately 6 million wells (i.e., three overlapping arrays of 2 million wells each) that can receive ink. Next generation televisions are expected to increase this resolution by more than four times. In such a process, to improve printing speed, the print head may use thousands of nozzles for printing, and there will typically be an overwhelming number of possible printing process permutations, for example. The simplified example presented above is used to introduce the concept, but it should be noted that the permutations represented by real-world television applications are extremely complex, given the overwhelming number presented in typical combinations, and printing optimizations are typically applied by software and use complex mathematical operations. Figures 4-7 are used to provide a non-limiting example of how these operations can be applied.

[0047] It should be noted that the techniques introduced in this disclosure can be manifested in several different ways. For example, FIG. 4 depicts several different implementation layers, collectively designated by reference numeral 401, each of which represents a possible individual implementation of the techniques introduced above. First, the techniques introduced above can be embodied as instructions (e.g., software for controlling a computer or printer) stored on a non-transitory machine-readable medium, as represented by graphic 403. Second, by computer icon 405, the techniques can be implemented as part of a computer or network, for example, within a company that designs or manufactures components for sale or use in other products. For example, the techniques introduced above can be implemented as design software by a company that consults with or designs for manufacturers of high definition televisions (DTVs), or alternatively, the techniques can be used directly by such manufacturers to create televisions (or display screens). Third, as previously introduced and illustrated using storage medium graphic 407, the techniques previously introduced can take the form of printer instructions, e.g., as stored instructions or data that, when acted upon, will cause a printer to fabricate one or more layers of a component that depend on the use of a planned drop coalescence technique, per the above discussion. Fourth, as represented by fabrication device icon 409, the techniques introduced above can be implemented as part of a fabrication apparatus or machine, or in the form of a printer within such an apparatus or machine. For example, fabrication machines can be sold or customized in a manner in which droplet measurements and translation of externally supplied "layer data" are automatically converted by the machine (e.g., through the use of software) into printer instructions that will print using the techniques described herein to transparently optimize / accelerate the printing process. Such data can also be calculated offline and then reapplied on a repeatable basis in a scalable pipeline manufacturing process that produces many units.It is noted that the particular depiction of production device icon 409 represents one exemplary printer device, which will be discussed below (eg, with reference to FIGS. 8-9). can also be embodied as an assembly, such as an array 411 of multiple components that will be sold separately. In FIG. 4, for example, several such components are depicted in the form of an array of semi-finished flat panel devices that will later be sold separately for incorporation into a final consumer product. The depicted device may have one or more layers (e.g., color component layers, semiconductor layers, encapsulation layers, or other materials) deposited depending on the methods introduced above. The techniques introduced above can also be embodied in the form of final consumer products as referenced, for example, in the form of a display screen for a portable digital device 413 (e.g., an electronic pad or smartphone, etc.), as a television display screen 415 (e.g., HDTV) or other types of devices. For example, FIG. 4 uses a solar panel graphic 417 to represent that the processes introduced above can be applied to other forms of electronic devices, for example to deposit structures (such as one or more layers of individual cells that make up an aggregate device) or blanket layers (e.g., encapsulation layers for televisions or solar panels) per target area. Clearly, many implementations are possible.

[0048] The techniques introduced above can be applied to any of the layers or components illustrated in FIG. 4, without limitation. For example, one embodiment of the techniques disclosed herein is an end consumer device, and a second embodiment of the techniques disclosed herein is an apparatus equipped with data to control the fabrication of layers using a combination of specific nozzle volumes to obtain a fill per specific target area. The nozzle volumes can be predetermined or measured and applied in situ. Yet another embodiment is a deposition machine, for example, using a printer to print one or more inks using the techniques introduced above. These techniques can be implemented in one machine or more than one machine, for example, a network of machines or a series of machines, where different steps are applied in different machines. All such embodiments and others independently utilize the techniques introduced by this disclosure.

[0049] An exemplary process for planning printing is introduced by Figure 5. This process and related methods and devices are generally referred to using the numeral 501.

[0050] More specifically, the drop volume for each nozzle (and for each nozzle for each waveform if multiple drive waveforms are applied) is specifically determined (503). Such measurements can be made using a variety of techniques including, for example, but not limited to, optical or laser imaging devices built into the printer (or factory-resident machine) that image the drops in flight (e.g., during a calibration print operation or a live print operation) and calculate the volume with precision based on the drop shape, velocity, trajectory, and / or other factors. Other techniques can also be used, including printing the ink and then using post-print imaging or other techniques to calculate individual drop volumes based on pattern recognition. Alternatively, the identification can be based on data provided by the printer or printhead manufacturer, e.g., based on measurements taken at the factory well in advance of the fabrication process and provided to the machine (or online). In some applications, the drop volume characteristics may change over time, for example, depending on ink viscosity or type, temperature, nozzle clogging, or other degradation, or due to other factors. Thus, in one embodiment, drop volume measurements can be made dynamically in situ with each new print of a substrate, for example, upon power up (or upon other types of power cycle events), upon expiration of a predetermined time, or on another calendar or non-calendar basis. As represented by numeral 504, this (measured or provided) data is stored for use in the optimization process.

[0051] In addition to the drop volume data per nozzle (and optionally per drive waveform), information regarding the desired fill volume for each target area (505) is also received. This data may be a single target fill value applied to all target areas, or a desired fill volume for an individual target area, a row of target areas, or a column of target areas. The data may be the respective target fill values ​​applied, or values ​​resolved in some other manner. For example, when applied to fabricating a single "blanket" layer of a large material for an individual electronic device structure (such as a transistor or via), such data may consist of a single thickness to be applied to the entire layer (e.g., software then converts it to a desired ink fill volume per target area based on predefined conversion data specific to the associated ink). In such a case, the data may be converted to a common value for each "printing cell" (which in this case may be equivalent to each target area or may consist of multiple target areas). In another example, the data may represent a specific value (e.g., 50.00 pL) for one or more wells, with range data either provided or understood based on the context. As should be understood from these examples, the desired fill may be specified in many different forms, including, but not limited to, thickness data or volume data. Additional filtering or processing criteria may also optionally be provided to or implemented by the receiving device. For example, as previously referenced, random variations in fill volume can be injected by the receiving device into one or more provided thickness or volume parameters to make line effects invisible to the human eye in the finished display. Such variations can be made in advance (provided as fill per each target area that varies by area) or can be derived independently and transparently from the receiving device (e.g., by a downstream computer or printer).

[0052] Based on the target fill volume for each region and the individual drop volume measurements (i.e., per print head nozzle and driving waveforms per nozzle), the process then continues to calculate various drop combinations that optionally sum to a fill volume within a desired tolerance range (i.e., by process block 506). As described, this range can be provided with the target fill data or can be "figured out" based on the situation. In one embodiment, the range is understood to be ±1 percent of the provided fill value. In another embodiment, the range is understood to be ±0.5 percent of the provided fill value. Clearly, many other possibilities exist for the tolerance range, whether larger or smaller than these exemplary ranges.

[0053] At this point, an example will help convey one possible method for calculating a set of possible droplet combinations. Returning to the simplified example previously described, it is assumed that there are five nozzles, each with respective hypothetical droplet volumes of 9.80 pL, 10.01 pL, 9.89 pL, 9.96 pL, and 10.03 pL, and that it is desired to deposit a target volume of 50.00 pL ±0.5 percent (49.75 pL to 50.25 pL) in the five wells. The method begins by determining the number of droplets that can be combined to reach but not exceed a tolerance range, and for each nozzle, determining the minimum and maximum number of droplets from that nozzle that can be used in any acceptable permutation. For example, in this hypothesis, given the minimum and maximum droplet volumes of the nozzles under consideration, no more than one droplet from nozzle (1), no more than two droplets from nozzle (3), and no more than four droplets from nozzle (4) can be used in any combination. This step limits the number of combinations that need to be considered. With such constraints on the set consideration, the method then takes each nozzle in turn and considers combinations for the required number of droplets (five in this example). For example, the method first starts with nozzle (1), understanding that the only acceptable combinations involving nozzle (1) feature no more than one droplet from this nozzle. Having considered combinations involving a single droplet from this nozzle, the method then considers the minimum and maximum droplet volumes of the other nozzle-waveform combinations under consideration. For example, considering that nozzle (1) is determined to produce a droplet volume of 9.80 pL for a given drive waveform, it may be determined that no more than one droplet from nozzle (3), or no more than two droplets from nozzle (4), can be combined with a droplet from nozzle (1) to reach the desired tolerance range. The method then considers combinations of droplets from nozzle (1) with combinations of four droplets from other nozzles (e.g., four droplets from nozzles (2) or (5), three droplets from nozzle (2) and one droplet from nozzle (4), etc.) To simplify the discussion, considering combinations involving only nozzle (1), any of the following different combinations involving the first nozzle could potentially be used within the tolerance range: {1(1),4(2)}, {1(1),3(2),1(4)}, {1(1),3(2),1(5)}, {1(1),2(2),1(4),1(5)}, {1(1),1(2),1(3),2(5)}, {1(1),1(2),1(4),2(5)}, {1(1),1(2),3(5)}, {1(1),1(3),3(5)}, {1(1),2(4),2(5)}, {1(1),1(4),3(5)}, and {1(1),4(5)} In the formulas described above, the use of square brackets represents a set of five drops, representing a combination of drop volumes from one or more nozzles, with each parenthesis within these square brackets identifying a particular nozzle. For example, the formula {1(1),4(2)} represents one drop from nozzle (1) and four drops from nozzle (2), i.e., 9.80 pL + (4 x 10.01 pL) = 49.84 pL, which is within the specified tolerance range. In practice, the method in this example considers the largest number of drops from nozzle (1) that can be used to produce the desired tolerance, evaluates the combination with this largest number, reduces the number by one, and repeats the process of consideration. In one embodiment, this process is repeated to determine all possible sets of non-redundant drop combinations that can be used. When the combinations with nozzle (1) have been fully explored, the method tests each possible nozzle combination to determine whether the desired tolerance range can be achieved, moving on to combinations with nozzle (2) but not nozzle (1), repeating the process, and so on. For example, in this embodiment, since the method has determined that a combination of two or more droplets from nozzle (1) cannot be used, it begins by considering combinations involving one droplet from nozzle (1) and four droplets from the other nozzles in various combinations. The method evaluates whether it can in fact use four droplets from nozzle (2), determining that it could be {1(1), 4(2)}, then reduces this number by one (three droplets from nozzle 2) and determines that this number can be used in combination with a single droplet from nozzle (4) or (5), resulting in an acceptable set of {1(1), 3(2), 1(4)}, {1(1), 3(2), 1(5)}, etc. The method then further reduces the number of acceptable droplets from nozzle (2), evaluating combinations of {1(1), 2(2)...}, then {1(1), 1(2)...}, etc.Once combinations involving nozzle (2) have been considered in combination with droplets from nozzle (1), the method then brings in the next nozzle, i.e., nozzle (3), and considers combinations of nozzle (1) with this nozzle but not nozzle (2), determining that the only acceptable combination is given by {1(1),1(3),3(5)}. Once all combinations involving droplets from nozzle (1) have been considered, the method then considers five droplet combinations involving droplets from nozzle (2) but not nozzle (1), such as {5(2)}, {4(2),1(3)}, {4(2),1(4)}, {4(2),1(5)}, {3(2),2(3)}, {3(2),1(3),1(4)}, etc.

[0054] It should also be noted that the same approach applies equally in cases where a nozzle can be driven by multiple firing waveforms (each producing a different drop volume). These additional nozzle-waveform combinations simply provide additional drop volumes for use in selecting a set of drop combinations that are within the tolerance of the target volume. The use of multiple firing waveforms can also improve the efficiency of the printing process by making available a larger number of acceptable drop combinations, thereby increasing the likelihood of simultaneously firing drops from a majority of the nozzles on each pass. In cases where a nozzle has multiple driving waveforms and geometric steps are also used, the selection of a set of drop combinations can be determined by the number of drive waveforms used for a given scan. This will incorporate both the geometric offset that will be used in the design and the nozzle waveform that will be used for each nozzle.

[0055] It should be noted that for illustrative purposes, a brute force approach has been described, and that where the number of nozzles and target regions is large (e.g., greater than 128 each), an overwhelming number of possible combinations would typically be presented in practice. However, such calculations are well within the capabilities of a fast processor with appropriate software. It should also be noted that there are various mathematical shortcuts that can be applied to reduce the calculations. For example, in a given embodiment, the method can eliminate from consideration any combination that would correspond to the use of less than half of the available nozzles in any one pass (or alternatively, can limit consideration to combinations that minimize the volume variance across the target region (TR) in any one pass). In one embodiment, the method determines only a certain set of drop combinations that would produce an acceptable total fill value, and in a second embodiment, the method exhaustively calculates all possible sets of drop combinations that would produce an acceptable total fill value. It is also possible to use an iterative approach, in which multiple iterations of print scans are performed and the volume of ink that has not yet been deposited to reach the desired tolerance range is considered for the purpose of optimizing the next subsequent scan. Other approaches are possible.

[0056] Also note that if, as an initial operation, the same fill values ​​(and tolerances) are applied to each target area, it is sufficient to calculate the combinations once (e.g., for one target area) and store these possible droplet combinations for initial use with each target area. This is not necessarily true for all set calculation methods and all applications (e.g., in some embodiments, the acceptable fill range may vary for all target areas).

[0057] In yet another embodiment, the method uses mathematical shortcuts, such as approximations, matrix mathematics, random selection, or other techniques, to determine a set of acceptable droplet combinations for each target region.

[0058] Once an acceptable combination of sets is determined for each target area, as represented by process block 507, the method then effectively calculates scans in a manner associated with a particular set (or drop combination) for each target area. This particular set selection is done in a manner in which the particular set (one for each target area) represents process savings through the use of at least one scan to simultaneously deposit drop volumes in multiple target areas. That is, in the ideal case, the method selects one particular set for each target area, which particular set represents a particular drop volume combination in a manner that the printhead can print simultaneously into multiple rows of the target area at one time. The selection of particular drops in the selected combination represents a printing process that meets predetermined criteria, such as minimum printing time, minimum number of scans, minimum size of geometric steps, minimum total geometric step distance, or other criteria. These criteria are represented by numeral 508 in FIG. 5. In one embodiment, the optimization is Pareto optimal, where the particular set is selected in a manner that minimizes each of the number of scans, total geometric step distance, and geometric step size, in that order. Again, the selection of this particular set can be done in any desired manner, some non-limiting examples of which are discussed further below.

[0059] In one embodiment, the method selects a droplet from each set for each target region that corresponds to a particular geometric step or waveform that is applied to all regions under consideration, and then subtracts this droplet from the available set to determine a residual. For example, the selection of the available set may initially be {1(1),4(2)}, {1(1),3(2), 1(4)}, {1(1),3(2),1(5)}, {1(1),2(2),1(4),1(5)}, {1(1),1(2),1(3),2(5)}, {1(1),1(2),1(4),2(5)}, {1(1),1(2),3(5)}, {1(1),1(3),3(5)}, {1(1),2(4),2(5)}, {1(1),1(4),3(5)}, and {1(1), 4(5)}, the embodiment would subtract one drop (1) from this first set to obtain a specific residual for a first of the five target regions, one drop (2) from the first set to obtain a specific residual for a second of the five target regions, one drop (3) from the first set to obtain a specific residual for a third of the target regions, and so on. This evaluation would represent a geometric step of "0". The method would then evaluate the residual and repeat the process for other possible geometric steps. For example, if a geometric step of "-1" was applied, the method would then evaluate the residual by subtracting one drop (2) from the first set for the first of the five target regions, one drop (3) from the first set for the second of the target regions, and so on.

[0060] In selecting a particular geometric step (and nozzle firing) as part of the printing plan, the method analyzes the various residuals according to a scoring and priority function and selects the geometric step with the best score. In one embodiment, the scoring is applied to weight more heavily the step that (a) maximizes the number of nozzles used simultaneously and (b) maximizes the minimum number of remaining combinations for the affected target area. For example, a scan that used drops from four nozzles during the scan would be favored more than one that used drops from only two nozzles. Similarly, if the subtraction process discussed above in considering the different steps resulted in a remaining combination of 1, 2, 2, 4, and 5 for each target area for one possible step, and a remaining combination of 2, 2, 2, 3, and 4 for each target area for a second possible step, the method would weight more heavily the latter (i.e., the maximum minimum number is "2"). In practice, suitable weighting factors can be generated empirically. Clearly, other algorithms can be applied, and other forms of analysis or algorithmic shortcuts can be applied. For example, matrix mathematics can be used (e.g., using eigenvector analysis) to determine particular droplet combinations and associated scan parameters that meet predetermined criteria. In another variation, other formulas can be used that take into account, for example, the use of planned random packing variations to mitigate line effects.

[0061] Once a particular set and / or scan path has been selected by numeral 507, the printer actions are sequenced by numeral 509. It is noted that, for example, if total fill volume was the only consideration, a set of droplets could typically be deposited in an arbitrary order. If printing is planned to minimize the number of scans or passes, the order of geometric steps can also be selected to minimize printhead / substrate motion. For example, if acceptable scans in the hypothetical example involve the geometric steps {0, +3, -2, +6, and -4}, these scans can be reordered to minimize printhead / substrate motion and thus further improve printing speed, e.g., by ordering the scans as a series of steps {0, +1, +1, +2, and +4}. Compared to the first series of geometric steps {0, +3, -2, +6, and -4} with a total step increment distance of 15, the second series of geometric steps {0, +1, +1, +2, and +4} with a total step increment distance of 8, promoting faster printer response.

[0062] For applications involving multiple rows of target areas receiving the same target fill, as represented by numeral 510, a particular solution may then be represented as a repeatable pattern that is replicated across a sub-area of ​​the substrate. With 128 nozzles aligned, and a target area of ​​1024 rows, it is expected that an optimal scan pattern can be determined for sub-areas of the target area with 255 rows or less, and thus, in this example, the same print pattern can be applied to four or more sub-areas of the substrate. Thus, some embodiments utilize repeatable patterns as represented by optional process block 510.

[0063] Note the use of non-transitory machine-readable medium icon 511. This icon represents that the methods described above are optionally implemented as instructions for controlling one or more machines (e.g., software or firmware for controlling one or more processors). The non-transitory medium can include any machine-readable physical medium, such as a flash drive, floppy disk, tape, server storage or mass storage, dynamic random access memory (DRAM), compact disk (CD), or other local or remote storage device. This storage device can be embodied as part of a larger machine (e.g., resident memory in a desktop computer or printer) or on a separate basis (e.g., a flash drive or a stand-alone storage device that will later transfer files to another computer or printer). Each of the functions described with reference to FIG. 5 can be implemented as part of a composite program or as stand-alone modules stored either together on a single media representation (e.g., a single floppy disk) or on multiple separate storage devices.

[0064] Upon completion of the planning process, as represented by numeral 513 in FIG. 5, data will be generated that effectively represents a set of printer instructions comprising nozzle firing data for the printhead and instructions for relative movement between the printhead and the substrate to support the firing pattern. This data, effectively representing the scan path, scan order, and other data, is an electronic file (513) that can either be stored for later use (e.g., as depicted by non-transient machine-readable medium icon 515) or immediately applied to control a printer (517) to deposit ink representing a selected combination (a particular set of nozzles per target area). For example, the method can be applied on a stand-alone computer and the instruction data stored in RAM for later use or for downloading to another machine. Alternatively, the method can be implemented and applied dynamically by the printer to "incoming" data to automatically plan the scan depending on the printer parameters (nozzle, drop volume data, etc.). Many other alternatives are possible.

[0065] 6A-6C generally provide a flow chart for the nozzle selection and scan planning process. Again, note that the scan does not have to be continuous or linear in direction or speed of movement, and does not have to proceed from one side of the substrate to another.

[0066] The first block diagram is represented by numeral 601 in FIG. 6A. This diagram represents many of the exemplary processes discussed in the preceding narrative. The method begins by first retrieving from memory, by numeral 603, a set of acceptable drop volume combinations for each target area. These sets could be calculated dynamically or could have been pre-calculated, for example, using software on a different machine. Note the use of a database icon 605, which represents either a locally stored database (e.g., stored in local RAM) or a remote database. The method then effectively selects (607) a particular set of acceptable sets for each target area. This selection is indirect in many embodiments, meaning that the method processes the acceptable combinations to select a particular scan (e.g., using the techniques referenced above) and actually selects a particular set of acceptable drop volume combinations. It is these scans that define the sets. Nevertheless, by planning the scans, the method selects a particular set combination for each target region. This data is then used to sequence the scans and summarize the motion and firing patterns (609), as referenced above.

[0067] The center and right of FIG. 6A illustrate several process options for planning scan paths and nozzle firing patterns and, in effect, selecting specific drop combinations for each target area in a manner that represents print optimization. As represented by numeral 608, the illustrated technique represents only one possible methodology for performing this task. Per numeral 611, the analysis can involve determining the minimum and maximum usage of each nozzle (or nozzle-waveform combination, in those cases where a nozzle is driven by more than one firing waveform) in an acceptable combination. If a particular nozzle is poor (e.g., does not fire or fires with an unacceptable trajectory), that nozzle can be removed from use (and from consideration). Second, if a nozzle has either very low or very high drop volume, this can limit the number of drops that can be used from that nozzle in an acceptable combination. Numeral 611 represents a pre-processing that reduces the number of combinations that will be considered. As represented by numeral 612, a process / shortcut can be used to limit the number of sets of drop combinations that will be evaluated. For example, instead of considering "all" possible drop combinations for each nozzle, the method can be optionally configured to exclude combinations that involve fewer than half the nozzles (or another quantity of nozzles, such as 1 / 4), combinations in which more than half the drops come from any particular nozzle waveform, or combinations that represent a high variance in drop volume or a large variance in the simultaneous drop volumes applied across the target area. Other metrics can also be used.

[0068] Subject to any limitations on the number of sets calculated / considered, the method then proceeds to calculate and consider acceptable drop combinations, per numeral 613. Various processes can be used to plan scans and / or otherwise effectively select a particular set of drop volumes per target region (TR), as referenced by numerals 614 and 615. For example, as introduced above, one method assumes a scan path (e.g., a particular geometric step selection) and then considers the maximum of the fewest remaining set selections across all TRs being considered. The method can favorably weight those scan paths (alternative geometric steps) that maximize the ability of the next scan to cover multiple target regions at once. Alternatively, or in addition, the method can favorably weight those geometric steps that maximize the number of nozzles used at once. Returning to the simplified five nozzle discussion above, a scan that would apply five nozzles to a target region can be favorably weighted over a scan or pass that would fire only three nozzles in one pass. Thus, in one embodiment, the following algorithm can be applied by the software:

[0069]

number

[0070] In this exemplary equation, "i" represents a particular choice of geometric step or scan path, w1 represents one empirically determined weighting, w2 represents a second empirically determined weighting, #RemCombsTR,i represents the number of remaining combinations per target region given scan path i, and #Simult.Nozzlesi represents a measure of the number of nozzles used for scan path i. This latter value need not be an integer, and may be any number, for example, where the fill value per TR is a measure of the number of nozzles (e.g., potentially visible on a display device). It should be noted that if the number of nozzles used per row of target area is varied (to hide typical artifacts), then a given scan path may feature a varying number of nozzles used per row of target area, e.g., an average or some other measure may be used. It should also be noted that these coefficients and weightings are merely illustrative, i.e., it is possible to use different weightings and / or considerations, to use only one variable but not the other, or to use a completely different algorithm.

[0071] 6A also shows some further options. For example, the consideration of the droplet set in one implementation is done according to an equation / algorithm by numeral 617. To select a particular step or offset, the comparison metric can be expressed as a score that can be calculated for each possible alternative geometric step. For example, another possible algorithmic approach involves an equation with three terms as shown below:

[0072]

number

[0073] where the terms based on Sv, Se, and Sd are scores calculated for the variance of deposited drop volume, efficiency (maximum nozzles used per pass), and geometric step variation, respectively. In one formulation, the "(Sv,min / Sv)" term attempts to minimize the variation of the loading volume from a target value per pass in a manner that depends on the total number of drops.

[0074] Number 619 in FIG. 6A represents that in one embodiment, the selection of droplet combinations can be performed using matrix mathematics, for example through the use of mathematical techniques that consider all droplet volume combinations simultaneously and use a form of eigenvector analysis to select scan paths.

[0075] As represented by numeral 621, an iterative process can be applied to reduce the number of droplet combinations considered. That is, for example, the geometric steps can be calculated one at a time, as represented by the previous description of one possible processing technique. Each time a particular scan path is planned, the method determines the incremental amount still required in each target area under consideration, and then continues to determine the scan or geometric offset that is most suitable to produce a total amount or fill amount per target area that is within the desired tolerance. This process can then be repeated for each iteration until all scan paths and nozzle firing patterns have been planned.

[0076] Numeral 622 also allows for the use of hybrid processes. For example, in one embodiment, a first set of one or more scans or geometric steps may be selected for use, for example, based on minimized variation in drop volume per nozzle and maximum efficiency (e.g., nozzles used per scan). Once a certain number of scans, e.g., 1, 2, 3 or more scans, are applied, a different algorithm may be invoked that, for example, maximizes nozzles used per scan (e.g., regardless of the variation in drop volume applied). Any of the specific equations or techniques discussed above (or other techniques) may optionally be one of the applied algorithms in such a hybrid process, and other variations will no doubt occur to those skilled in the art.

[0077] It should be noted that, as previously referenced, in the exemplary display manufacturing process, the amount of fill per target area can have a planned randomization (623) that is intentionally injected to mitigate line effects. In one embodiment, optionally, the target fill amount can be intentionally varied (and / or randomized) in a manner to achieve this planned randomization or other effect. A generator function (625) is applied such that σ makes the total volume generated for the droplet combination for each target area asymmetric. As mentioned above, in different embodiments, it is also possible to apply an algorithmic approach as previously shown such that such variations are included in the target fill volume and tolerances and to meet, for example, fill requirements per target area, i.e., even before the droplet combinations are analyzed.

[0078] FIG. 6B and numeral 631 refer to a more detailed block diagram relating to the iterative solution method referenced above. As indicated by numerals 633 and 635, again possible droplet combinations are first identified, stored, and retrieved for evaluation by the software as appropriate. For each possible scan path (or geometric step), by numeral 637, the method stores the footprint identifying the scan path and the nozzle applied (639), subtracts the firings per nozzle from the set per target area (641), and determines the remaining combinations for each target area (643). These are also stored. Then, by numeral 645, the method evaluates the stored data according to predefined criteria. For example, as indicated by optional (dashed) block 647, a method that seeks to maximize the minimum number of droplet combinations over all relevant target areas can assign a score indicating whether the just stored combination is better or worse than previously considered alternatives. If the identified criteria are met (645), a particular scan or geometric step may be selected and the remaining combinations may be stored or otherwise flagged for use in consideration of another printhead / substrate scan or pass, as represented by numerals 649 and 651. If the criteria are not met (or consideration is incomplete), another step may be considered and / or the method may adjust consideration of the geometric step under consideration (or a previously selected step), per numeral 653. Again, many variations are possible.

[0079] It was previously noted that the order in which the scans are performed or the order in which the droplets are deposited is not critical to the final fill value of the target area. While this is true, to maximize printing speed and throughput, the scans are preferably ordered to result in the fastest or most efficient printing possible. Thus, if not previously included in the geometric step analysis, then reordering and / or ordering of the scans or steps can be performed. This process is represented by FIG. 6C.

[0080] Specifically, numeral 661 is used to generally designate the method of FIG. 6C. For example, software running on a suitable machine causes a processor to retrieve (663) a selected geometric step, a particular set, or other data identifying a selected scan path (and optionally a nozzle firing pattern, which in those embodiments where a nozzle may be driven by more than one firing waveform, may further include data identifying which of a plurality of firing waveforms is to be used for each droplet). These steps or scans are then reordered or ordered in a manner that minimizes the incremental step distance. For example, again referring to the hypothetical example introduced earlier, if the selected steps / scan paths were {0, +3, -2, +6, and -4}, these may be reordered maximally to minimize each incremental step and to minimize the overall (total) distance traversed by the motion system during the scan. For example, without reordering, the incremental distances between these offsets would be equivalent to 3, 2, 6, and 4 (the total distance traversed would be "15" in this example). If the scans (e.g., scans "a", "b", "c", "d", and "e") were reordered in the manner described (e.g., in the order "a", "c", "b", "e", and "d"), the incremental distances would be +1, +1, +2, and +4 (for a total distance traversed of "8"). As represented by numeral 667, at this point the method can assign motion to the print head motion system and / or the substrate motion system, and reorder the nozzle firings. The order can be reversed (e.g., when alternating back and forth scan path directions are used, per numerals 219 and 220 in FIG. 2A). As previously described and represented by optional process block 669, in some embodiments, planning and / or optimization can be performed for a portion of the target area, and the solution is then applied on a spatially iterative basis across a larger substrate.

[0081] This iteration is represented in part by FIG. 6D. As suggested by FIG. 6D, for this description, it should be assumed that it is desired to fabricate an array of flat panel devices. A common substrate is represented by numeral 681, and a set of dashed boxes, such as box 683, represent the geometry of each flat panel device. Preferably, fiducials 685 with two-dimensional characteristics are formed on the substrate and used to position and align the various fabrication processes. Following final completion of these processes, each panel 683 will be separated from the common substrate using a cutting or similar process. If the array of panels represents respective OLED displays, the common substrate 681 will typically be glass, and the structure will be deposited on the glass, followed by one or more encapsulation layers. Each panel will then be flipped over so that the glass substrate forms the light-emitting surface of the display. For some applications, other substrate materials can be used, e.g., transparent or opaque flexible materials. As described, many other types of devices can be manufactured according to the described techniques. For a particular portion 687 of the flat panel 683, a solution can be calculated. This solution can then be repeated for other similarly sized portions 689 of the flat panel 683, and then the entire solution set can be repeated for each panel formed from a given substrate.

[0082] Considering the various techniques and considerations introduced above, manufacturing processes can be made to mass-produce products quickly and at low per-unit cost. When applied to display device manufacturing, e.g., flat panel displays, these techniques enable a high-speed per-panel printing process where multiple panels are produced from a common substrate. By providing high-speed repeatable printing techniques (e.g., using common inks and printheads from panel to panel), it is believed that printing can be substantially improved, e.g., reducing printing time per layer to a small fraction of the time that would otherwise be required while ensuring that the fill amount per target area is within specifications. Returning again to the example of a large HD television display, it is believed that each color component layer can be accurately and reliably printed for a large substrate (e.g., a 8.5 generation substrate that is approximately 220 cm x 250 cm) in 180 seconds or less, or even 90 seconds or less, which represents a significant process improvement. Improving the efficiency and quality of printing paves the way for a significant reduction in the cost of producing large HD television displays, and therefore a lower end-consumer cost. As mentioned above, display manufacturing (specifically OLED manufacturing) is one application of the techniques introduced herein, however, these techniques can be applied to a wide variety of processes, computers, printers, software, manufacturing equipment, and end devices and are not limited to display panels.

[0083] One benefit of the ability to deposit precise target area volumes (e.g., well volumes) within tolerance is the ability to inject intentional variations within the tolerance, as described. These techniques facilitate significant quality improvements in displays because they provide the ability to hide the pixelation artifacts of the display and make such "line effects" imperceptible to the human eye. FIG. 7 provides a block diagram 701 associated with one method for injecting this variation. As with the various methods and block diagrams discussed above, block diagram 701 and associated methods can optionally be implemented as software, either on a stand-alone medium or as part of a larger machine.

[0084] The variation can be made dependent on a particular frequency criterion, as represented by numeral 703. For example, it is generally understood that the sensitivity of the human eye to contrast variations is a function of luminance, expected viewing distance, display resolution, color, and other factors. Taking into account the typical human eye sensitivity to spatial variations in contrast between colors at different luminance levels as part of the frequency criterion, a measure is used to ensure that such variations will be smoothed in a manner that is not perceptible to the human eye, and will be varied in a manner that does not provide a human-observable pattern, for example (a) in one or more arbitrary directions, or (b) between color components given the expected viewing conditions. This can optionally be achieved using a planned randomization function, as previously referenced. Once the minimum criterion is identified, the target fill amount for each color component and each pixel can be purposefully varied in a manner calculated to hide any visual artifacts from the human eye, as represented by numeral 705. Note that the right side of FIG. 7 represents various process options, for example, where the variations can be made independent across color components (707), with tests for perceptible patterns applied on an algorithmic basis to ensure that the fill variations do not result in perceptible patterns. As described by numeral 707, for any given color component (e.g., any given ink), the variations can also be made independent in each of multiple spatial dimensions, e.g., in the x and y dimensions (709). Again, in one embodiment, not only is the variation smoothed for each dimension / color component so as to be not perceptible, but any patterns of differences between each of these dimensions are also suppressed from being seen. Per numeral 711, one or more generator functions can be applied to ensure that these criteria are met, for example, by optionally assigning minor target fill variations to the fill of each target area prior to drop volume analysis, using any desired criteria. As represented by numeral 713, in one embodiment, the variations can be made to be random, optionally.

[0085] The selection of a particular drop combination for each target area is thus weighted in favor of the selected variation criterion, per numeral 715. This can be done via target fill variation or at drop (e.g., scan path, nozzle-waveform combination, or both) selection time, as described. There are other ways to impart this variation as well. For example, in one contemplated implementation, per numeral 717, the scan path is varied non-linearly, effectively varying the drop volume across the average scan path direction. Per numeral 719, the nozzle firing pattern can also be varied, for example, by adjusting the firing pulse rise time, fall time, voltage, pulse width, or by using multiple signal levels per pulse (or other forms of pulse shaping techniques) to provide minor drop volume variations. In one embodiment, these variations can be pre-calculated, and in a different embodiment, only waveform variations that produce very minor volume variations are used, with other measures employed to ensure that the total fill remains within a specified tolerance range. In one embodiment, for each target area, multiple droplet combinations that fall within a specified tolerance range are calculated, and for each target area, the selection of which droplet combinations are used for that target area is varied (e.g., randomly or based on a mathematical function), thereby effectively varying the droplet volume across the target area to mitigate line effects. Such variation can be implemented along the scan path direction, across a row of target areas, across a column of target areas, or both.

[0086] 8A-9C are used to provide simulation data for the techniques discussed herein. While FIGS. 8A-8C represent fill volumes based on five droplets, FIGS. 9A-9C represent fill volumes based on ten droplets. For each of these figures, the letter designation "A" (e.g., FIGS. 8A and 9A) represents a situation in which a nozzle is used to deposit droplets without any consideration for volumetric differences. In contrast, the letter designation "B" (e.g., FIGS. 8B and 9B) represents a situation in which a nozzle is used to deposit droplets (either five or ten droplets) so as to "average out" the expected volumetric differences between nozzles. ) represents a situation where a random combination of droplets is selected. Finally, the letter designation "C" (e.g., Figures 8C and 9C) represents a situation where scanning and nozzle firing rely on a particular total ink volume per target area that attempts to minimize the total fill variance across the target area. In these various figures, the variation per nozzle is assumed to match the variation observed in an actual device, with each vertical axis representing the total fill volume in pL and each horizontal axis representing the number of target areas, e.g., pixel wells or pixel color components. Note that the emphasis in these figures is to show the variation in the total fill volume assuming randomly distributed droplet variation about an assumed average. For Figures 8A-8C, the average volume per nozzle is assumed to be slightly below 10.00 pL per nozzle, and for Figures 9A-9C, the average drop volume per nozzle is assumed to be slightly above 10.00 pL per nozzle.

[0087] The first graph 801 depicted in FIG. 8A shows the volume variations per well assuming nozzle drop volume differences without attempting to mitigate these differences. Note that these variations can be extreme (e.g., by peak 803), with a range of total fill volume of approximately ±2.61%. As noted, the average of the five drops is just under 50.00 pL, and FIG. 8A shows two sets of sample tolerance ranges around this average, including a first range 805 representing a ±1.00% range around this value, and a second range 807 representing a ±0.50% range around this value. As seen by the numerical peaks and troughs (e.g., peak 803) that fall outside either range, such a printing process would result in a large number of wells that would fail to meet specifications (e.g., either one or the other of these ranges).

[0088] A second graph 811 depicted in FIG. 8B shows volume variation per well using a randomized set of five nozzles per well in an attempt to statistically average out the effects of droplet volume variation. Note also that such techniques do not allow for precise production of a specific volume of ink in any particular well, nor does such a process guarantee a total volume within range. For example, while the percentage of fill volumes that fall outside of specification represents a much better case than depicted by FIG. 8A, there are still situations where individual wells (as identified by trough 813) fall outside of specification, e.g., the ±1.00% and ±0.50% variations represented by numbers 805 and 807, respectively. In such cases, the min / max error is ±1.01%, reflecting an improvement using random mixing over the data depicted in FIG. 8A.

[0089] FIG. 8C represents a third case using a specific combination of droplets per nozzle according to the techniques described above. Specifically, graph 821 shows that the variation is entirely within the ±1.00% range, and very close to meeting the ±0.50% range for all represented target areas. Again, these ranges are represented by numbers 805 and 807, respectively. In this example, five specifically selected droplet volumes are used to fill the wells in each scan line, with printhead / substrate shifts as appropriate, for each pass or scan. The min / max error is ±0.595%, reflecting further improvement with this form of "smart mixing." Note that the improvement and data observations will be consistent for any form of intelligent droplet volume combination to achieve a specific fill or tolerance range (e.g., where offsets between nozzle rows (or multiple printheads) are used, or where multiple preselected drive waveforms are used to enable specifically selected droplet volume combinations).

[0090] As described, Figures 9A-9C present similar data, but assume a combination of 10 droplets per well with an average droplet volume of approximately 10.30 pL per nozzle. Specifically, graph 901 in Figure 9A represents a case where no attention was paid to mitigating droplet volume differences, while graph 911 in Figure 9B shows a case where droplets were randomized in an attempt to statistically "average out" the volume differences. 9A represents a case where the solution is applied to achieve the average fill volume of FIG. 9A / 9B, i.e., about 103.10 pL, and graph 921 of FIG. 9C represents a case of planned mixing of particular droplets (to achieve the average fill volume of FIG. 9A / 9B, i.e., about 103.10 pL). These various figures show a tolerance range of ±1.00% and ±0.50% variation about this average, represented using arrows 905 and 907, respectively. Each of the figures further shows a respective peak 903, 913, and 923, represented by the variation. However, it is noted that FIG. 9A represents a variation of ±2.27% about the target, FIG. 9B represents a variation of ±0.707% about the target, and FIG. 9C represents a variation of ±0.447% about the target. It can be seen that by averaging a larger number of droplets, the "random droplet" solution of FIG. 9B achieves a ±1.00% tolerance range about the average, rather than a ±0.50% range. In contrast, the solution depicted by FIG. 9C was found to meet both tolerance ranges, demonstrating that it is possible to constrain the variation to be within specification while still allowing for variation in droplet combinations between wells.

[0091] One optional embodiment of the technique described in this disclosure is described precisely in these terms. That is, for a printing process in which a nozzle with a maximum drop volume variation of x% is used to deposit a total fill volume with a maximum expected volume variation of y%, traditionally there is little means to guarantee that the total fill volume will vary by less than x%. For applications where x% is greater than y%, this presents a potential problem. Droplet averaging techniques (e.g., as represented by the data seen in Figures 8B and 9B) statistically reduce the volume variation across a target area to an expected variance of x% / (n)1 / 2, where n is the average number of drops required per target area to achieve the desired fill volume. Note that even with such a statistical approach, there is no mechanism for reliably ensuring that the actual target area fill volume will be within a tolerance of y%. The techniques discussed herein provide a mechanism for providing such confidence. Thus, one optional embodiment provides a method for generating control data or for controlling a printer, and related devices, systems, software, and improvements, in which the statistical volume variance across the target area is better than x% / (n)1 / 2 (e.g., significantly better than x% / (n)1 / 2). In a specific implementation, this condition is met in a situation where print head nozzles are used simultaneously to deposit droplets in each row (e.g., each pixel well) of the target area in each scan. Perhaps stated differently, in such a specific implementation, nozzles that represent a drop variation of ±x% of the target drop volume combine their drops to achieve a target area fill in which the total target area fill has a statistical variance of less than x% / (n)1 / 2, featuring simultaneous use of different nozzles for each different row of the target area for each print head / substrate scan.

[0092] With the above described set of basic techniques for combining droplets such that their sum is specifically selected to meet a particular target, reference is now made to a more detailed description of specific devices and applications that can benefit from these principles. This discussion is intended to be non-limiting, i.e., to describe a small number of specifically contemplated implementations for practicing the methods introduced above.

[0093] As seen in FIG. 10, the multi-chamber fabrication apparatus 1001 includes several general modules or subsystems, including a transfer module 1003, a printing module 1005, and a processing module 1007. Each module maintains a controlled environment, such that, for example, printing can be performed by the printing module 1005 in a first controlled atmosphere, and other processing, e.g., another deposition process such as an inorganic encapsulation layer deposition or a curing process (e.g., for the printed material), can be performed in a second controlled atmosphere. The apparatus 1001 uses one or more mechanical handlers to move substrates between modules without exposing the substrates to an uncontrolled atmosphere. Within any given module, other substrate handling devices adapted for the processing to be performed for that module may be used. It is possible to use handling systems and / or specific devices and control systems.

[0094] Various embodiments of the transfer module 1003 can include an input load lock 1009 (i.e., a chamber that provides buffering between different environments while maintaining a controlled atmosphere), a transfer chamber 1011 (also having a handler for transporting the substrate), and an atmospheric buffer chamber 1013. Other substrate handling mechanisms can be used within the print module 1005, such as a floating table for stable support of the substrate during the printing process. In addition, an xyz motion system, such as a split axis or gantry motion system, can be used to precisely position at least one print head relative to the substrate, as well as provide a y-axis transport system for transport of the substrate through the print module 1005. Furthermore, it is also possible to use multiple inks for printing within the print chamber, for example, using respective print head assemblies, so that, for example, two different types of deposition processes can be performed within the print module in a controlled atmosphere. The printing module 1005 can include a gas enclosure 1015 that houses the inkjet printing system along with means for introducing an inert atmosphere (e.g., nitrogen, a noble gas, another similar gas, or a combination thereof) and otherwise controlling the atmosphere for environmental conditioning (e.g., temperature and pressure), gas constituents, and the presence of particulate matter.

[0095] The processing module 1007 can include, for example, a transfer chamber 1016, which also has a handler for transporting the substrate. In addition, the processing module can also include an output load lock 1017, a nitrogen stack buffer 1019, and a curing chamber 1021. In some applications, the curing chamber can be used to cure the monomer film into a uniform polymer film, for example, using a thermal or ultraviolet radiation curing process.

[0096] In one application, the apparatus 1001 is adapted for the mass production of integrated liquid crystal or OLED display screens, for example, fabrication of an array of eight screens at a time on a single large substrate. These screens can be used as display screens for televisions and other forms of electronic devices. In a second application, the apparatus can be used in a more similar manner for the mass production of solar panels.

[0097] When applied to the drop volume combination technique described above, the printing module 1005 can be advantageously used in display panel manufacturing to deposit one or more layers, such as light filtering layers, emissive layers, barrier layers, conductive layers, organic or inorganic layers, encapsulation layers, and other types of materials. For example, the depicted apparatus 1001 can be loaded with a substrate and controlled to move the substrate back and forth between various chambers to deposit and / or cure or harden one or more printed layers, all in an uninterrupted manner with intervening exposure to an uncontrolled atmosphere. The substrate can be loaded via an input load lock 1009. A handler positioned in the transfer module 1003 can move the substrate from the input load lock 1009 to the printing module 1005 and, following completion of the printing process, to the processing module 1007 for curing. By repeated deposition of subsequent layers, controlled volumes per target area, each of the cohesive layer properties can be built up to suit any desired application. Again, it should be noted that the techniques described above are not limited to display panel manufacturing processes, and many different types of tools can be used. For example, the configuration of device 1001 can be varied to arrange the various modules 1003, 1005, and 1007 in different juxtapositions, and further, additional or fewer modules can also be used.

[0098] While Figure 10 provides one example of a set of linked chambers or fabrication components, clearly many other possibilities exist. The ink droplet deposition techniques introduced above can be used to control a fabrication process performed with the device depicted in Figure 10, or indeed with any other type of deposition equipment.

[0099] FIG. 11 provides a block diagram showing various subsystems of one apparatus that can be used to fabricate a device having one or more layers as specified herein. Coordination across the various subsystems is provided by a processor 1103, acting under instructions provided by software (not shown in FIG. 11). During the fabrication process, the processor provides data to the print head 1105 to cause the print head to eject various amounts of ink in response to firing instructions provided, for example, by a halftone print image. The print head 1105 typically has a number of inkjet nozzles arranged in a row (or rows of an array) and associated reservoirs that allow the ejection of ink in response to activation of a piezoelectric or other transducer per nozzle, such transducer causing the nozzle to eject a controlled amount of ink in an amount governed by an electronic nozzle drive waveform signal applied to the corresponding piezoelectric transducer. Other firing mechanisms can also be used. The print head applies ink to the substrate 1107 at various xy locations that correspond to grid coordinates within various print cells as represented by the halftone print image. The change in position is accomplished by both the print head motion system 1109 and the substrate handling system 1111 (e.g., causing printing of one or more swaths across the substrate). In one embodiment, the print head motion system 1109 moves the print head back and forth along a traveler while the substrate handling system provides "y" dimension transport of the substrate to enable stable substrate support and "split-axis" printing of any portion of the substrate. The substrate handling system provides a relatively fast y dimension transport while the print head motion system 1009 provides a relatively slow x dimension transport. In another embodiment, the substrate handling system 1111 can provide both x and y dimension transport. In yet another embodiment, the primary transport can be provided entirely by the substrate handling system 1111. An image capture device 1113 can be used to locate any fiducials, assist with alignment and / or error detection.

[0100] The apparatus also includes an ink delivery system 1115 and a printhead maintenance system 1117 that supports printing operations. The printheads may be periodically calibrated or undergo a maintenance process, and to this end, during a maintenance sequence, the printhead maintenance system 1117 is used to perform appropriate priming, ink or gas purging, testing and calibration, and other operations as appropriate for the particular process.

[0101] As previously introduced, the printing process can be performed in a controlled environment, i.e., in a manner that offers reduced risk of contaminants that can degrade the effectiveness of the deposited layer. To this effect, the apparatus includes a chamber control subsystem 1119 that controls the atmosphere within the chamber as represented by functional block 1121. An optional process variation, as described, can include performing the ejection of deposition material in the presence of an ambient nitrogen gas atmosphere.

[0102] As previously mentioned, in the embodiments disclosed herein, individual drop volumes are combined to achieve a specific fill volume per target area, which is selected depending on the target fill volume. A specific fill volume can be planned for each target area, with the fill value varying about the target value within an acceptable tolerance range. For such embodiments, the drop volume is specifically measured in a manner that depends on the ink, nozzle, drive waveform, and other factors. To this end, reference numeral 1123 indicates that the drop volume 1125 is determined for each nozzle and for each drive waveform. 1127 represents an optional drop volume measurement system in which droplets are measured for shape and then stored in memory 1127. Such a drop measurement system can be an optional strobe camera or laser scanning device (or other volume measurement tool) that is incorporated into commercially available printing devices, as described above. In one embodiment, such a device operates in real time (or near real time) to measure individual drop volumes, deposition trajectories, drop velocities, and similar data. This data is provided to processor 1103 either during printing, or during one-time intermittent calibration operations, or during periodic calibration operations. A pre-arranged set of firing waveforms, as indicated by numeral 1129, can also be optionally associated with each nozzle for later use in generating a combination of droplets per specific target area. If such a set of waveforms is used in an embodiment, drop volume measurements are advantageously calculated during calibration for each waveform using drop measurement system 1127 for each nozzle. Providing a real-time or near real-time droplet volume measurement system greatly enhances reliability in providing target area volume filling within desired tolerances, since measurements can be taken as needed and processed (e.g., averaged) to minimize statistical volume measurement error.

[0103] Number 1131 refers to the use of print optimization software running on the processor 1103. More specifically, this software uses this information to plan the print based on the drop volume 1125 (measured in situ or otherwise provided) in a way that appropriately combines drop volumes to obtain a particular fill volume per target area. In one embodiment, the above example allows the total volume to be planned down to a resolution of 0.01 pL or better within a certain error tolerance. Once the print is planned, the processor calculates printing parameters such as the number and sequence of scans, drop diameter, relative drop firing times, and similar information, and builds a print image that is used to determine nozzle firing for each scan. In one embodiment, the print image is a half-toe-in image. In another embodiment, the print head has a plurality of nozzles, as many as 10,000. As described below, each drop can be represented according to a time value and a firing value (e.g., data representing a firing waveform, or data indicating whether the drop will be fired "digitally"). In embodiments where geometric steps and binary nozzle firing decisions are relied upon to vary the droplet volume per well, each droplet may be defined by a bit of data, a step value (or scan number), and a position value indicating where the droplet is to be placed. In implementations where the scan represents continuous motion, a time value may be used as the equivalent of a position value. Whether rooted in time / distance or absolute position, the value represents a position relative to a reference (e.g., a synchronization mark, position, or pulse) that precisely specifies where and when the nozzle should be fired. In some embodiments, multiple values ​​may be used. For example, in one particularly contemplated embodiment, a synchronization pulse is generated for each nozzle in a manner that corresponds to each micron of relative printhead / substrate motion during the scan.For each sync pulse, each nozzle is programmed with: (a) an offset value representing an integer clock cycle delay before the nozzle is fired, (b) a 4-bit waveform select signal representing one of 15 waveform selections preprogrammed into memory dedicated to the particular nozzle driver (i.e., one of 16 possible values ​​specifying the "off" or non-firing state of the nozzle), and (c) a repeat value specifying whether the nozzle should be fired only once, once every sync pulse, or once every n sync pulses. In such cases, the waveform selection and address of each nozzle is associated by the processor 1103 with specific drop volume data stored in memory 1127, and the firing of a particular waveform from a particular nozzle represents a planned determination that a particular corresponding drop volume is to be used to deliver total ink to a particular target area of ​​the substrate.

[0104] 12A-14C will be used to introduce another technique that can be used to combine different drop volumes to obtain precise tolerance fill volumes for each target area. In a first technique, rows of nozzles can be selectively offset relative to one another during printing (e.g., during a scan). This technique is introduced with reference to Figures 12A-12B. In a second technique, nozzle drive waveforms can be used to adjust the piezoelectric transducer firing and therefore the properties of each ejected drop (including volume). Figures 13A-13B are used to discuss some options. Finally, in one embodiment, a set of multiple alternative drop firing waveforms are pre-calculated and made available for use with each print nozzle. This technique and associated circuitry are discussed with reference to Figures 14A-C.

[0105] FIG. 12A provides a plan view 1201 of a print head 1203 traversing a substrate 1205 in a scanning direction indicated by arrow 1207. The substrate can now be seen to consist of a number of pixels 1209, each pixel having wells 1209-R, 1209-G, and 1209-B associated with a respective color component. Again, it should be noted that this depiction is merely an example, i.e., techniques as used herein can be applied to any layer of a display (e.g., not limited to individual color components, and not limited to color-imparting layers), and these techniques can also be used to create other than display devices. In this case, assuming that the print head deposits one ink at a time and that the ink is color component specific, it is intended that a separate printing process would be performed for each well of the display, one for each color component. Thus, if a first process is being used to deposit an ink specific to red light production, then only a first well of each pixel, such as well 1209-R of pixel 1209 and the similar well of pixel 1211, will receive the ink in the first printing process. In a second printing process, only a second well (1209-G) of pixel 1209 and the similar well of pixel 1211 will receive the second ink, etc. The various wells are thus considered to be three different overlapping arrays (in this case fluid containers or wells) of the target area.

[0106] The print head 1203 includes several nozzles, as represented using the numbers 1213, 1215, and 1217. In this case, each of the numbers refers to a separate row of nozzles, where the row extends along the column axis 1218 of the substrate. It can be seen that the nozzles 1213, 1215, and 1217 form a first row of nozzles with respect to the substrate 1205, and the nozzle 1229 represents a second row of nozzles. As depicted by FIG. 12A, the nozzles do not align with the pixels, and as the print head scans across the substrate, some nozzles will pass over the target area while others will not. Furthermore, in the figure, the print nozzles 1213, 1215, and 1217 are precisely aligned to the center of the row of pixels starting with pixel 1209, while the second row of print nozzles 1229 will also pass over the row of pixels starting with pixel 1211, but the alignment is not precise to the center of the pixels. However, in many applications, the precise location where the droplets are deposited within the target area is not important, and such misalignment is acceptable. Note that this figure is merely illustrative, e.g., in practice, in some embodiments the nozzles can be spaced closely enough that more than one nozzle of a single printhead can be used to deposit ink into a given well in any given pass (e.g., as shown in the hypothetical of Figures 1B and 3C). The alignment / misalignment of the column of nozzles with the row of wells is depicted by lines 1225 and 1227, which respectively represent the centers of the print wells that are to receive ink.

[0107] FIG. 12B provides a second view 1231 in which all three rows of nozzles (or individual printheads) can be seen to be rotated approximately 30 degrees relative to axis 1218. This optional capability was previously referenced by numeral 218 in FIG. 2A. More specifically, the rotation changes the spacing of the nozzles along column axis 1218, with each column of nozzles aligning with well centers 1225 and 1227. However, the scanning motion 1207 causes nozzles from each column of nozzles to traverse columns of pixels (e.g., 1209 and 1211) at different relative times, and therefore potentially different position firing data (e.g., when to fire a drop). Note that each nozzle will have different timing for positioning the nozzles (for example, different nozzle alignments for each nozzle) to the target area. In some embodiments, a specifically aligned array is preferred, especially when precise positioning of the droplets deposited within the target area is required. In other embodiments, an array in which the nozzles are not specifically or precisely aligned to the target area is preferred due to reduced system complexity, especially when positioning each droplet at a precise location within the target area is not required.

[0108] As represented by FIG. 12C, in one embodiment, a printhead optionally provided with multiple rows of nozzles can have such rows selectively offset from one another. That is, FIG. 12C provides another plan view in which each of the printheads (or nozzle rows) 1219, 1221, and 1223 are offset relative to one another, as represented by offset arrows 1253 and 1255. These arrows represent the use of optional motion mechanisms, one for each row of nozzles, that allow selective offsetting of the corresponding row relative to the printhead assembly. This provides different combinations of nozzles (and associated specific drop volumes) with each scan (e.g., by numeral 1207), and thus different specific drop combinations. For example, in such an embodiment, as depicted by FIG. 12C, such offsets allow both nozzles 1213 and 1257 to be aligned with centerline 1225 and thus have their respective drop volumes combined in a single pass. It should be noted that this embodiment is considered a particular case of an embodiment that varies the geometric step, e.g., even if the geometric step size between successive scans of the printhead assembly 1203 relative to the substrate 1205 is fixed, such scan motion of each of a given row of nozzles is effectively positioned at a variable offset or step using the motion mechanism relative to the position of the given row in other scans. However, consistent with the principles previously introduced, it should be understood that such an embodiment allows the drop volume per individual nozzle to be tallied with a particular combination (or drop set) for each well, but with a reduced number of scans or passes. For example, in the embodiment depicted in FIG. 12C, three drops can be deposited in each target area (e.g., wells for red color components) in each scan, with the offset allowing for planned variation of the drop volume combination.

[0109] FIG. 12D illustrates a cross-sectional view of the completed display for one well (e.g., well 1209-R from FIG. 12A) taken in the direction of the scan. Specifically, this view shows a substrate 1252 of a flat panel display, specifically an OLED display. The depicted cross-sectional view shows an active area 1253 and conductive terminals 1255 that receive electronic signals that control the display (including the color of each pixel). A small oval region 1261 of the view appears enlarged on the right side of the view to illustrate the layers in the active area above the substrate 1252. These layers include, respectively, an anode layer 1269, a hole injection layer ("HIL") 1271, a hole transport layer ("HTL") 1273, an emissive or light-emitting layer ("EML") 1275, an electron transport layer ("ETL") 1277, and a cathode layer 1278. Additional layers, such as polarizers, barrier layers, primers, and other materials, may also be included. In some cases, an OLED device may include only some of these layers. When the depicted stack is finally operated following fabrication, current causes recombination of electrons and "holes" in the EML, resulting in emission of light. The anode layer 1269 may comprise one or more transparent electrodes common to several color components and / or pixels, for example, the anode may be formed from indium tin oxide (ITO). The anode layer 1269 may also be reflective or opaque, and other materials may be used. The cathode layer 1278 typically consists of a patterned electrode to provide selective control to each color component for each pixel. The cathode layer may comprise a reflective metal layer, such as aluminum. The cathode layer may also comprise an opaque or transparent layer, such as a thin layer of metal combined with a layer of ITO. The cathode and anode together serve to supply and collect electrons and holes that enter and / or pass through the OLED stack. The HIL 1271 typically functions to transport holes from the anode into the HTL. The HTL 1273 typically functions to transport holes from the HIL into the EML while impeding the transport of electrons from the EML into the HTL. The ETL 1277 typically functions to transport electrons from the cathode into the EML while impeding the transport of electrons from the EML into the ETL. Together, these layers thereby serve to provide electrons and holes into the EML 1275 and confine them there so that they can recombine to generate light. Typically, the EML consists of separately controlled active materials for each of the three primary colors, red, green, and blue, for each pixel of the display, represented in this case by the red light generating material as described.

[0110] The layers in this active area can be degraded through exposure to oxygen and / or moisture. It is therefore desirable to enhance OLED lifetime by encapsulating these layers on both the face and sides (1262 / 1263) of the layers opposite the substrate, as well as on the outer edges. The purpose of the encapsulation is to provide an oxygen-resistant and / or moisture barrier. Such encapsulation can be formed in whole or in part through the deposition of one or more thin film layers.

[0111] The techniques discussed herein can be used to deposit any of these layers, as well as combinations of such layers. Thus, in one envisioned application, the techniques discussed herein provide ink volumes for EML layers for each of the three primary colors. In another application, the techniques discussed herein are used to provide ink volumes for HIL layers, and so on. In yet another application, the techniques discussed herein are used to provide ink volumes for one or more OLED encapsulation layers. The printing techniques discussed herein can be used to deposit organic or inorganic layers, as appropriate for the process technology, and layers for other types of display and non-display devices.

[0112] FIG. 13A is used to introduce nozzle drive waveform adjustments and the use of alternative nozzle drive waveforms to provide different ejected drop volumes from each nozzle of a printhead. A first waveform 1303 is seen as a single pulse consisting of a quiet period 1305 (0 volts), an upslope 1313 associated with the decision to fire the nozzle at time t2, a voltage pulse or signal level 1307, and a downslope 1311 at time t3. The effective pulse width, represented by the numeral 1309, is of duration approximately equal to t3-t2, depending on the difference between the upslope and downslope of the pulse. In one embodiment, any of these parameters (e.g., upslope, voltage, downslope, pulse duration) can be varied to potentially change the drop volume ejection characteristics of a given nozzle. A second waveform 1323 is similar to the first waveform 1303, except that it represents a larger drive voltage 1325 relative to the signal level 1307 of the first waveform 1303. With a larger pulse voltage and a finite rising slope 1327, it takes longer to reach this higher voltage, and similarly the falling slope 1329 is typically delayed relative to the analogous slope 1311 from the first waveform. In this case, the third waveform 1333 is also similar to the first waveform 1303, except that a different rising slope 1335 and / or a different falling slope 1337 can be used instead of the slopes 1313 and 1311 (e.g., through adjustment of the nozzle impedance). The different slopes can be made either steeper or shallower (steeper in the depicted case). In contrast, in the fourth waveform 1343, the pulse can be made longer, for example, using a delay circuit (e.g., a voltage-controlled delay line) both to increase the time of the pulse at a given signal level (as represented by numeral 1345) and to delay the falling edge of the pulse as represented by numeral 1347. Finally, the fifth waveform 1353 illustrates the use of multiple discrete signal levels as also providing a means of pulse shaping. For example, this waveform begins at a time at the first described signal level 1307, then a second signal level 1308 applied partway between times t3 and t2. It can be seen that the waveform 1357 includes a rising slope to 355. It can be seen that the falling section of this waveform 1357 is delayed after the falling edge 1311 due to the larger voltage.

[0113] Any of these techniques can be used in combination with any of the embodiments discussed herein. For example, the drive waveform adjustment technique can be used to vary the droplet volume within a small range, optionally after the scanning motion and nozzle firing have already been planned, to mitigate line effects. Designing the waveform variation in such a way that the second tolerance matches the specification promotes the deposition of a high quality layer with planned non-random or planned random variation. For example, returning to the previously introduced assumption that a TV manufacturer specifies a fill volume of 50.00 pL ± 0.50%, the fill volume per area can be calculated within a first range of 50.00 pL ± 0.25% (49.785 pL to 50.125 pL), with the variation statistically providing only ± 0.025 pL of volume variation per droplet (considering the five droplets required to reach the total fill volume). Clearly, there are many variations.

[0114] As mentioned above, multiple signal levels can be used to shape the pulse in one embodiment, represented by the fifth waveform 1353 from Figure 13A. This technique is further discussed with reference to Figure 13B.

[0115] That is, in one embodiment, the waveform may be predefined as a series of discrete signal levels, e.g., defined by digital data, and the drive waveform is generated by a digital-to-analog converter (DAC). Number 1351 in FIG. 13B refers to waveform 1353, having discrete signal levels 1355, 1357, 1359, 1361, 1363, 1365, and 1367. In this embodiment, each nozzle driver includes circuitry for receiving and storing up to 16 different signal waveforms, each waveform defined by a series of up to 16 signal levels, each represented as a multi-bit voltage and duration. That is, in such an embodiment, by defining different durations for one or more signal levels, the pulse width may be effectively varied, and the drive voltage may be waveform-shaped in a manner selected to provide subtle droplet size variation, e.g., droplet volume may be metered to provide specific volume increments, such as in 0.10 pL increments. Thus, in such an embodiment, corrugation provides the ability to adjust the drop volume to be closer to the target drop volume value, and when combined with other specific drop volumes, such as using the techniques illustrated above, these techniques facilitate precise fill volumes per target area. In addition, however, these corrugation techniques also facilitate measures to reduce or eliminate line effects, for example, in one optional embodiment, drops of specific volumes are combined as discussed above, but the final drop (or drops) are selected in a manner that provides variation to the boundaries of a desired tolerance range. In another embodiment, a predefined waveform can be applied, with optional further corrugation applied as appropriate to adjust the volume. In yet another example, the use of nozzle drive waveform alternatives provides a mechanism to plan the volume such that further corrugation is not necessary.

[0116] Typically, the effect of different drive waveforms and the resulting drop volume is measured in advance. For each nozzle, up to 16 different drive waveforms are then stored in 1k synchronous random access memories (SRAMs) per nozzle for later selective use in providing individual volume variations as selected by software. With the different drive waveforms at hand, each nozzle is then instructed on a drop-by-drop basis as to which waveform to apply via programming data that achieves the particular drive waveform.

[0117] 14A illustrates such an embodiment, generally designated by the numeral 1401. Specifically, a processor 1403 is used to receive data defining an intended loading volume per target area. As represented by the numeral 1405, this data may be a layout file or a bitmap file that defines the drop volume per grid point or position address. A series of piezoelectric transducers 1407, 1408, and 1409 generate associated ejected drop volumes 1411, 1412, and 1413, respectively, that depend on many factors, including the nozzle driving waveform and printhead-to-printhead manufacturing variations. During the calibration operation, each of the sets of variables is tested for its effect on drop volume, including nozzle-to-nozzle variations and the use of different driving waveforms, given the particular ink that will be used. If desired, this calibration operation can be made dynamic, for example to respond to changes in temperature, nozzle clogging, or other parameters. This calibration is represented by a drop measurement device 1415, which provides measurement data to the processor 1403 for use in managing the print plan and the next print. In one embodiment, this measurement data is calculated on the fly, taking literally minutes, e.g., 30 minutes or less, and preferably even less (e.g., for thousands of printhead nozzles and a potentially large number of possible nozzle firing waveforms). This data may be stored in memory 1417 for use in processing the layout or bitmap data 1405 as it is received. In one implementation, the processor 1403 is part of a computer that is remote from the actual printer, while in a second implementation, the processor 1403 is integrated with either the production facility for the product (e.g., a system for producing a display) or the printer.

[0118] To effect the ejection of droplets, a set of one or more timing or synchronization signals 1419 are received for use as a reference and these are passed through a clock tree 1421 for distribution to each nozzle driver 1423, 1424, and 1425 to generate drive waveforms for a particular nozzle (1427, 1428, and 1429, respectively). Each nozzle driver has one or more registers 1431, 1432, and 1433, respectively, which receive multi-bit programming data and timing information from the processor 1403. Each nozzle driver and its associated registers receive one or more dedicated write enable signals (wen) for the purpose of programming the registers 1431, 1432, and 1433, respectively. In one embodiment, each of the registers includes a significant amount of memory, including a 1k SRAM that stores a number of predefined waveforms, and programmable registers to select between these waveforms and otherwise control the waveform generation. Although the data and timing information from the processor is depicted as multi-bit information, this information can be provided via either serial or parallel bit connections to each nozzle (as seen in FIG. 14B, discussed below, in one embodiment this connection is serial as opposed to the parallel signal representation seen in FIG. 14A).

[0119] For a given deposit, printhead, or ink, the processor selects a set of 16 drive waveforms for each nozzle that can be selectively applied to generate droplets. Note that this number is arbitrary, e.g., one design may use 4 waveforms while another design may use 4000 waveforms. These waveforms are advantageously selected to provide a desired variation in output drop volume for each nozzle, e.g., to have each nozzle have at least one waveform selection that produces a near-ideal drop volume (e.g., 10.00 pL), and to provide a range of deliberate volume variations from each nozzle. In various embodiments, the same set of 16 drive waveforms is used for all of the nozzles, but in the depicted embodiment, 16 possibly unique waveforms are each separate and predefined for each nozzle, each waveform providing a respective drop volume characteristic.

[0120] During printing, data selecting one of the predefined waveforms is then programmed into each nozzle's respective register 1431, 1432, or 1433 on a nozzle-by-nozzle basis to control the deposition of each droplet. For example, considering a target volume of 10.00 pL, the nozzle driver 1423 can select one of the 16 predefined waveforms through writing data to register 1431. The nozzle driver 1423 may be configured to set one of 16 waveforms, each corresponding to one of the different drop volumes of 16 waveforms. The volume produced by each nozzle is measured by the drop measurement device 1415, and the drop volume per nozzle (and per waveform) will be registered by the processor 1403 and stored in memory to assist in producing the desired target fill. The processor can define whether it wants a particular nozzle driver 1423 to output a processor-selected one of the 16 waveforms by programming the register 1431. In addition, the processor can program the register to have a per-nozzle delay or offset for the firing of the nozzles for a given scan line (e.g., to align each nozzle with the grid traversed by the printhead, to correct errors, and for other purposes), this offset being achieved by a counter that skews a particular nozzle by a programmable number of timing pulses for each scan. In one embodiment, the synchronization signal delivered to all nozzles occurs at a defined time interval (e.g., 1 microsecond), while in another embodiment, the synchronization signal is adjusted to the printer motion and substrate topography, for example, to fire every 1 micron of incremental relative motion between the print head and the substrate. A high-speed clock (φhs) is run thousands of times faster than the synchronization signal, for example, at 100 megahertz, 33 megahertz, etc., and in one embodiment, multiple different clocks or other timing signals (e.g., strobe signals) can be used in combination. The processor also programs a value that defines the grid spacing, and in one implementation, the grid spacing is common to the entire set of available nozzles, although this need not be true for each implementation. For example, in some cases, a regular grid can be defined in which all nozzles fire "every 5 microns." In one contemplated embodiment, a memory is shared across all nozzles that allows the processor to pre-store a number of different grid spacings (e.g., 16) that are shared across all nozzles, and the processor can then select (on demand) a new grid spacing that is read out for all nozzles (e.g., to define an irregular grid).For example, in an implementation where a nozzle fires for all color component wells of an OLED (e.g., to deposit a non-color specific layer), three or more different grid spacings can be applied sequentially in a round robin fashion by the processor. Clearly, many design alternatives are possible. Note that the processor 1403 can also dynamically reprogram the registers of each nozzle during operation, i.e., a sync pulse is applied as a trigger to activate any programmed waveform pulses set in that register, and new data will be applied with the next sync pulse if new data is received asynchronously before the next sync pulse. The processor 1403 also controls the start and speed of the scan (1435), in addition to setting parameters for sync pulse generation (1436). In addition, the processor controls the rotation of the print head (1437) for various purposes described above. In this way, each nozzle can be fired in unison (or simultaneously) using any one of 16 different waveforms for each nozzle at any time (i.e., with any "next" sync pulse), and the selected firing waveform can be dynamically switched between fires during a single scan with any other of the 16 different waveforms.

[0121] FIG. 14B shows additional details of a circuit (1441) used in such an embodiment to generate an output nozzle drive waveform for each nozzle, the output waveform being represented in FIG. 14B as "nzzl-drv.wvfm". More specifically, the circuit 1441 receives inputs of a synchronization signal, a single bit line carrying serial data ("data"), a dedicated write enable signal (we), and a high speed clock (φhs). A register file 1443 provides data for at least three registers that convey, respectively, an initial offset, a grid definition value, and a drive waveform ID. The initial offset is a programmable value that adjusts each nozzle to align with the start of the grid, as described. For example, multiple printheads, multiple rows of nozzles, different printhead rotations, nozzle firing speeds, and Considering implementation variables such as the pattern, as well as other factors, the initial offset can be used to align the droplet pattern of each nozzle with the start of the grid to account for delays and other factors. The grid definition value is a number representing the number of sync pulses to be "counted" before the programmed waveform is triggered, and in the case of an implementation printing a flat panel display (e.g., an OLED panel), the target area to be printed will likely have one or more regular intervals for different print head nozzles, corresponding to a regular (constant interval) or irregular (multiple interval) grid. As mentioned above, in one implementation, the processor keeps its own 16-entry SRAM to define up to 16 different grid intervals, which can be read into a register circuit for all nozzles on demand. Thus, if the grid interval value is set to 2 (e.g., every 2 microns), each nozzle will fire at this interval. The drive waveform ID represents the selection of one of the pre-stored drive waveforms for each nozzle, and can be programmed and stored in many ways, depending on the embodiment. In one embodiment, the drive waveform ID is a 4-bit selection value, and each nozzle has its own dedicated 1k byte SRAM to store up to 16 predefined nozzle drive waveforms, stored as 16x16x4B entries. Briefly, each of the 16 entries for each waveform contains 4 bytes representing a programmable signal level, 2 bytes of resolution voltage level, and 2 bytes of programmable duration, which are used to count the number of pulses of a high speed clock. Thus, each programmable waveform can consist of up to 16 individual (0-1) pulses, each of programmable voltage and duration (e.g., of duration equal to 1-255 pulses of a 33 megahertz clock).

[0122] Numerals 1445, 1446, and 1447 designate one embodiment of a circuit showing how a particular waveform can be generated. A first counter 1445 receives a sync pulse triggered by the start of a new line scan and begins counting down an initial offset. The first counter 1445 counts down in micron increments and when it reaches zero, a trigger signal is output from the first counter 1445 to a second counter 1446. This trigger signal essentially starts the firing process of each nozzle for each scan line. The second counter 1446 then implements a programmable grid spacing in micron increments. While the first counter 1445 is reset in conjunction with a new scan line, the second counter 1446 is reset using the next edge of the high speed clock following its output trigger. The second counter 1446, when triggered, activates a waveform circuit generator 1447 which generates a selected drive waveform shape for a particular nozzle. As represented by dashed boxes 1448-1450, seen under the generator circuit, this latter circuit is based on a high speed digital to analog converter 1448, a counter 1449, and a high voltage amplifier 1450, timed according to a high speed clock (φhs). When a trigger from the second counter 1446 is received, the waveform generator circuit takes the number pair (signal level and duration) represented by the drive waveform ID value and generates a given analog output voltage according to the signal level value, and the counter 1449 is effective to hold a DAC output of the duration according to the counter. The associated output voltage level is then applied to the high voltage amplifier 1450 and output as the nozzle drive waveform. The next number pair is then latched from the register 1443 to define the next signal level value / duration, etc.

[0123] The depicted circuitry provides an effective means of defining any desired waveform in accordance with data provided by the processor 1403. As described, in one embodiment, the processor determines in advance a set of waveforms (e.g., 16 possible waveforms per nozzle) and then writes the definitions of each of these selected waveforms into the SRAM for each nozzle's driver circuitry, and then programmable waveform "fire time" determination is accomplished by writing a 4-bit drive waveform ID into each nozzle register.

[0124] FIG. 14C provides a flow chart 1451 that discusses how to use different waveforms and different configuration options per nozzle. As represented by 1453, the system (e.g., one or more processors acting under instructions from suitable software) selects a set of predefined nozzle driving waveforms. For each waveform, and for each nozzle (1455), the drop volume is specifically measured, for example, using a laser measurement device or a CCD camera. These volumes are stored in a memory accessible to the processor, such as memory 1457. Again, the parameters measured may vary depending on the ink selection and many other factors. Thus, depending on these factors and the planned deposition activity, a calibration is performed. For example, in one embodiment 1461, the calibration is performed at the factory that manufactures the printhead or printer, and this data can be pre-programmed into the sales device (e.g., printer) or made available for download. Alternatively, for printers that possess an optional drop measurement device or system, these volume measurements can be performed on first use, for example, during initial device configuration (1463). In yet another embodiment, measurements are made at each power cycle (1465), for example, each time the printer is turned "on" or powered up from a low power state, or otherwise transitioned to a state ready to print. As previously mentioned, for embodiments in which ejected drop volume is affected by temperature or other dynamic factors, calibrations can be made intermittently or periodically (1467), for example, after expiration of a defined time interval, when an error is detected, at each new substrate operation state (e.g., substrate loading and / or during loading), daily, or on some other basis. Other calibration techniques and schedules can also be used (1469).

[0125] Calibration techniques can optionally be performed in an offline process or during a calibration mode, as represented by process separation line 1470. As described, in one embodiment, such a process is completed in less than 30 minutes for potentially thousands of print nozzles and one or more associated nozzle firing waveforms. During online operation (or during a print mode), as represented below this process separation line 1470, the measured drop volumes, as represented by 1471, are used in selecting a set of drops per target area based on the specific measured drop volumes, such that the drop volumes for each set sum to a specific total volume within a defined tolerance range. The volume per area can be selected based on a layout file, bitmap data, some other representation, as represented by numeral 1472. Based on these drop volumes and the acceptable combinations of drop volumes for each target area, a firing pattern and / or scan path is selected that, in effect, represents a specific combination of drops (i.e., one of the acceptable set combinations) for each target area that will be used for the deposition process, as represented by numeral 1473. As part of this selection or planning process 1473, an optimization function 1474 can be optionally employed to, for example, reduce the number of scans or passes to less than the product of the number of rows (or columns) in the target area and the average number of droplets per target area (e.g., less than what would be required for a row of nozzles rotated 90 degrees, stepping one row at a time, and depositing droplets in multiple passes for each row of the target area so that all nozzles in the row can be used in each scan for each affected target area). For each scan, the printhead can be moved and the nozzles can be programmed with waveform data per nozzle to achieve droplet deposition instructions according to a bitmap or layout file, these functions are variously represented by numerals 1477, 1479, and 1481 in FIG. 14C. After each scan, the process is repeated for the next scan, by numeral 1483.

[0126] Again, note that several different implementations are described above that are optional with respect to one another. First, in one embodiment, the drive waveform is not varied but remains constant for each nozzle. Drop volume combinations can be adjusted to assign different nozzles to different areas of the target area, as needed. The resulting rows are generated by using a variable geometric step that represents the printhead / substrate offset. Using the measured drop volume per nozzle, the process allows for a combination of specific drop volumes to achieve a very specific fill volume per target area (e.g., to 0.01 pL resolution). The process can be planned such that multiple nozzles are used to deposit ink into different rows of the target area on each pass. In one embodiment, the printing solution is optimized to produce as few scans as possible, and as fast a print time as possible. Secondly, in another embodiment, again using the specifically measured drop volume, different drive waveforms can be used for each nozzle. The printing process controls these waveforms such that the specific drop volumes are tallied in specific combinations. Again using the measured drop volume per nozzle, the process allows for a combination of specific drop volumes to achieve a very specific fill volume per target area (e.g., to 0.01 pL resolution). The process can be planned such that multiple nozzles are used to deposit ink into different rows of the target area on each pass. In both of these embodiments, a single row of nozzles can be used, or multiple rows of nozzles arranged as one or more printheads can be used. For example, in one envisioned implementation, 30 printheads can be used, each with a single row of nozzles, with each row having 256 nozzles. The printheads can be further organized into a variety of different groups, for example, the printheads can be organized into groups of five printheads that are mechanically mounted together, and the resulting six groups can be separately mounted into the printing system at the same time to provide simultaneous firing of nozzles from all of the printheads in one scan. In yet another embodiment, a clustered printhead is used, with multiple rows of nozzles that can be further positionally offset from one another. This embodiment is similar to the first embodiment above in that different drop volumes can be combined using variable effective position offsets or geometric steps.Again, using the measured droplet volume per nozzle, this process allows for combinations of specific droplet volumes to achieve very specific fill volumes per target area (e.g., to 0.05 pL, or even 0.01 pL resolution). This does not necessarily imply that the measurements are free of statistical uncertainties such as measurement errors. In one embodiment, such errors are small and are included in the target area fill planning. For example, if the droplet volume measurement error is ±a%, the fill volume variation across the target area can be planned within a tolerance range of the target fill ±(b-an1 / 2)%, where ±(b2)% represents the tolerance range of the specification, and ±(n1 / 2) represents the square root of the average number of droplets per target area or well. Perhaps stated differently, a range less than the specification can be planned such that the resulting total fill volume for the target area can be expected to fall within the tolerance range of the specification when the expected measurement error is included. Of course, the techniques described herein can be optionally combined with other statistical processes.

[0127] Droplet deposition can be optionally planned such that multiple nozzles are used to deposit ink in different rows of the target area on each pass, and the printing solution is optionally optimized to produce the fewest possible scans and the fastest possible print times. As mentioned above, any combination of these techniques with each other and / or with other techniques can also be employed. For example, in one particularly envisioned scenario, a variable geometric step is used with drive waveform variations per nozzle and a quantity measurement per drive waveform per nozzle to achieve a very specific quantity combination planned for the target area. For example, in another specifically considered scenario, a fixed geometric step is used with drive waveform variations per nozzle and a quantity measurement per drive waveform per nozzle to achieve a very specific quantity combination planned for the target area.

[0128] By maximizing the number of nozzles that can be used simultaneously during each scan, By planning combinations of droplet volumes to ensure they meet specifications, these embodiments promise high quality displays. Also, by reducing print times, these embodiments facilitate very low per unit printing costs, thus helping to reduce price points for the end consumer.

[0129] Also, as noted above, the use of precise loading amounts per target area allows the use of advanced techniques to vary the loading amount according to defined criteria (within specifications) to avoid line effects, providing a further quality improvement over conventional methods.

[0130] In the foregoing description and accompanying drawings, specific terms and drawing symbols have been set forth to provide a thorough understanding of the disclosed embodiments. In some cases, the terms and symbols may suggest specific details that are not required to practice these embodiments. The terms "exemplary" and "embodiment" are used to express examples, rather than preferences or requirements.

[0131] As shown, various modifications and changes may be made to the embodiments presented herein without departing from the broader spirit and scope of the present disclosure. For example, any feature or aspect of an embodiment may be applied in combination with any other of the embodiments, or in place of its corresponding feature or aspect, at least where practical. Thus, for example, not all features are shown in each and every drawing, and for example, a feature or technique shown according to an embodiment of one drawing should be assumed to be optionally adoptable as an element of or in combination with a feature of any other drawing or embodiment, even if not specifically declared in this specification. Thus, the present specification and drawings are to be regarded in an illustrative rather than restrictive sense.

Claims

1. A printing device, comprising: a print head having a plurality of nozzles; a substrate floating table for positioning the substrate on a deposition surface at a printing position where printing occurs; a print head transport mechanism that transports the print head in an X-axis direction and a Z-axis direction between a first position and a second position adjacent to the printing position; a droplet measurement system disposed adjacent to the substrate floating table, the droplet measurement system comprising: a light source; a plurality of non-imaging photodetectors; an interference optic; a collector disposed between the light source and at least one photodetector; and an optical path extending from the light source to the plurality of photodetectors, wherein the light source, the plurality of photodetectors, the collector, the interference optic, and the optical path are in a fixed positional relationship with respect to one another, the light source, the plurality of photodetectors, the interference optic, and the collector are mounted below the deposition surface, and the optical path is configured such that a portion of the optical path extends above the deposition surface; a motion system for moving the drop measurement system relative to the printhead in each of three independent axes; a controller configured to control the print head, the print head transport mechanism, the drop measurement system, and the motion system to measure droplets from at least one of the plurality of nozzles by applying two or more waveforms to the at least one of the plurality of nozzles and to exclude a portion of the values ​​of the measurements based on at least one criterion; A printing device comprising:

2. The printing apparatus of claim 1 , wherein the optical path is configured to pass through an illumination area immediately adjacent to a nozzle of the print head.

3. The printing apparatus of claim 1 , wherein the drop measurement system outputs a signal representative of one of a trajectory or a velocity of a drop ejected from the printhead.

4. a first plane is defined by the plurality of nozzles; The drop measurement system further comprises a mirror; the translation system translates the segment of the optical path along a second plane parallel to the first plane; The printing apparatus of claim 1 , wherein the light source and the plurality of light detectors are positioned outside the second plane.

5. The printing apparatus of claim 4 , wherein the second plane is above the deposition surface.

6. The printing apparatus of claim 5 , further comprising at least one processor that calculates a value of the droplet characteristic based on an electronic output of the droplet measurement system.

7. the plurality of nozzles includes at least 1,000 nozzles; 7. The printing apparatus of claim 6, wherein the movement system moves the one section while the print head is in the second position such that the one section intersects a flight path of a droplet of liquid ejected from any one of the at least 1,000 nozzles.

8. The printing apparatus of claim 7 , wherein each of the three independent axial directions includes an axial direction extending between one of the plurality of nozzles and an intersection of the optical path and the flight path.

9. the plurality of nozzles includes at least 1,000 nozzles; the motion system positions the optical path at a location above the deposition surface to intersect a flight path of droplets ejected from any of the at least 1,000 nozzles; The printing device of claim 1 , further comprising a non-transitory storage device that stores measurements of the drop measurement system.

10. The printing apparatus of claim 8 , wherein the interference optics includes an optical fiber.

11. The printing apparatus of claim 1 , further comprising an environmental enclosure, the printhead, the substrate floating table, and the drop measurement system being located within the environmental enclosure.

12. 2. The printing apparatus of claim 1, further comprising an electronic control system that automatically controls the print head transport mechanism, the drop measurement system, and the motion system to automatically measure characteristics of droplets ejected from at least one of the plurality of nozzles between successive substrate processing.

13. The printing apparatus of claim 1 , wherein the printhead transport mechanism includes a bridge extending across the substrate floating table.

14. The printing apparatus of claim 13 , wherein the drop measurement system is disposed adjacent an end of the bridge.

15. A printing device, comprising: a print head having a plurality of nozzles; a substrate floating table for positioning the substrate on a deposition surface at a printing position where printing occurs; a print head transport mechanism that transports the print head in an X-axis direction and a Z-axis direction between a first position and a second position adjacent to the printing position; a droplet measurement system disposed adjacent to the substrate floating table, the droplet measurement system comprising: a light source; a plurality of non-imaging photodetectors; an interference optic; a collector disposed between the light source and at least one photodetector; and an optical path extending from the light source to the plurality of photodetectors, wherein the light source, the plurality of photodetectors, the collector, the interference optic, and the optical path are in a fixed positional relationship with respect to one another, the light source, the plurality of photodetectors, the interference optic, and the collector are mounted below the deposition surface, and the optical path is configured such that a portion of the optical path extends above the deposition surface; a motion system for moving the drop measurement system relative to the printhead in each of three independent axes to position the portion of the optical path in a measurement area adjacent a nozzle of the printhead; a controller configured to control the print head, the print head transport mechanism, the drop measurement system, and the motion system to measure droplets from at least one of the plurality of nozzles by applying two or more waveforms to the at least one of the plurality of nozzles and to generate a statistical display of values ​​of the measurements, the controller configured to exclude a portion of values ​​of the measurements based on at least one criterion; A printing device comprising: The drop measurement system detects the interference pattern and images the drops.

16. 16. The printing apparatus of claim 15, further comprising a processor that determines droplet characteristics from an electronic output of the drop measurement system.

17. The printing apparatus of claim 16, wherein the characteristic is a droplet volume, a trajectory, or a velocity.

18. The printing apparatus of claim 17 , wherein each of the three independent axial directions includes an axial direction extending from an intersection of the optical path and the droplet to one of the plurality of nozzles.

19. 16. The printing apparatus of claim 15, wherein the plurality of nozzles define a first plane, the translation system translates a segment of the light path that interacts with droplets in flight into a second plane above the deposition surface, and the light source and each of the plurality of light detectors are positioned outside of the second plane.

20. A printing device, comprising: a print head having a plurality of nozzles; a substrate floating table for positioning the substrate on a deposition surface at a printing position where printing occurs; a print head transport mechanism that transports the print head in an X-axis direction and a Z-axis direction between a first position and a second position adjacent to the printing position; a droplet measurement system disposed adjacent to the substrate floating table and configured to measure characteristics of in-flight droplets ejected from each of the plurality of nozzles, the droplet measurement system comprising: a light source; a plurality of non-imaging photodetectors; an interference optic; a collector disposed between the light source and at least one photodetector; and an optical path extending from the light source to the plurality of photodetectors, the light source, the plurality of photodetectors, the collector, the interference optic, and the optical path being in a fixed positional relationship with respect to one another, the light source, the plurality of photodetectors, the interference optic, and the collector being mounted below the deposition surface, and the optical path being configured such that a portion of the optical path extends above the deposition surface; a motion system for moving the drop measurement system relative to the printhead in each of three independent axes; a controller configured to control the print head, the print head transport mechanism, the drop measurement system, and the motion system to measure droplets from at least one of the plurality of nozzles by applying two or more waveforms to the at least one of the plurality of nozzles and to exclude a portion of the values ​​of the measurements based on at least one criterion; A printing device comprising:

Images