Techniques for measuring printing ink droplets and controlling fluid deposition within precise tolerances.

Abstract

To provide a suitable technique for printing ink droplet measurement and control of fluid deposition within tight tolerances.SOLUTION: An ink printing process plans droplet combinations to reach a specific total ink fill per target area and adopts droplet volume per nozzle measurement and processing software that ensures compliance with minimum and maximum ink fills set by specifications. In various embodiments, different droplet combinations are generated through different printhead / substrate scan offsets, offsets between print heads, use of different nozzle drive waveforms, and / or other techniques. These combinations can be based on repeated high-speed drop measurements that develop an understanding of each nozzle of expected drop volume, velocity, trajectory averaging and diffusion, along with the planned drop combinations based on these statistical parameters. Optionally, random fill variations may be introduced to reduce the uneven effect in a completed display device. The disclosed technique has many possible uses.SELECTED DRAWING: Figure 8A

Description

[Technical Field]

[0001] (Cross-reference to related applications) This application claims priority to U.S. Provisional Patent Application No. 61 / 950,820, titled "Techniques For Print Ink Droplet Volume Measurement And Control Over Deposited Fluids Within Precise Tolerances," filed on 10 March 2014 by the first inventor, Nahid Harjee. This application is also a continuation of U.S. Patent Application No. 14 / 162525, titled "Techniques for Print Ink Volume Control To Deposit Fluids Within Precise Tolerances," filed on 23 January 2014 by the first inventor, Nahid Harjee. U.S. Patent Application No. 14 / 162525 claims priority over Taiwan Patent Application No. 102148330 (first inventor Nahid Harjee), filed on December 26, 2013, entitled "Techniques for Print Ink Volume Control To Deposit Fluids Within Precise Tolerances," and is a continuation of PCT Patent Application No. PCT / US2013 / 077720 (first inventor Nahid Harjee), filed on December 24, 2013, entitled "Techniques for Print Ink Volume Control To Deposit Fluids Within Precise Tolerances."PCT patent application PCT / US2013 / 077720 is a compilation of the following: U.S. Provisional Patent Application No. 61 / 746,545 titled "Smart Mixing" filed on December 27, 2012 (first inventor: Conor Francis Madigan); U.S. Provisional Patent Application No. 61 / 822855 titled "Systems and Methods Providing Uniform Printing of OLED Panels" filed on May 13, 2013 (first inventor: Nahid Harjee); U.S. Provisional Patent Application No. 61 / 842351 titled "Systems and Methods Providing Uniform Printing of OLED Panels" filed on July 2, 2013 (first inventor: Nahid Harjee); and "Systems and Methods Providing Uniform Printing of OLED" filed on July 23, 2013. U.S. Provisional Patent Application No. 61 / 857298 titled "Panels" (first inventor Nahid Harjee), U.S. Provisional Patent Application No. 61 / 898769 titled "Systems and Methods Providing Uniform Printing of OLED Panels" (first inventor Nahid Harjee), filed on November 1, 2013, and "Techniques for Print Ink Volume Control," filed on December 24, 2013. Priority is claimed to each of U.S. Provisional Patent Application No. 61 / 920,715, entitled "rol To Deposit Fluids Within Precise Tolerances" (first inventor Nahid Harjee). This application also claims the benefit of U.S. Provisional Patent Application No. 61 / 816,696, entitled "OLED Printing Systems and Methods Using Laser Light Scattering for Measuring Ink Drop Size, Velocity and Trajectory" (first inventor Alexander Sou-Kang Ko), filed on April 26, 2014, and U.S. Provisional Patent Application No. 61 / 866,031, entitled "OLED Printing Systems and Methods Using Laser Light Scattering for Measuring Ink Drop Size, Velocity and Trajectory" (first inventor Alexander Sou-Kang Ko), filed on August 14, 2013. Each of the above patent documents is incorporated herein by reference.

[0002] The present disclosure relates to techniques for measuring inkjet droplet volumes used in organic light emitting diode ("OLED") device fabrication with high statistical accuracy, the use of printing processes for transferring droplets of fluid ink to target areas of a substrate in precise total quantities, and related methods, devices, improvements, and systems. In one non-limiting application, the techniques provided by the present disclosure can be applied to manufacturing processes for OLED display panels.

Background Art

[0003] (Background) In printing processes where a printhead has multiple nozzles, not all nozzles respond to a standard drive waveform in the same way; that is, each nozzle may produce slightly different amounts of droplets. In situations where nozzles are relied upon to deposit fluid droplets into their respective fluid deposition areas ("target areas"), this lack of consistency can lead to problems. This is particularly true in manufacturing applications where ink transports material that will form permanent thin-film structures within electronic devices. One exemplary application where this problem arises is in manufacturing processes applied to the fabrication of displays such as organic light-emitting diode ("OLED") displays used in small and large electronic devices (e.g., portable devices, large-scale high-resolution television panels, and other devices). When a printing process is used to deposit ink carrying the light-emitting material of such displays, differences in amounts across rows or columns of pixels contribute to visible illumination or color defects in the displayed image. As used herein, “ink” refers to any fluid applied to a substrate by the nozzle of a print head, regardless of its color characteristics. For example, in the OLED display processing application described, the ink is typically deposited in place and then processed, dried, or cured to directly form a permanent material layer. It should be noted that this process may be repeated with the same or different inks to form several such layers.

[0004] Figure 1A is used to illustrate this nozzle-droplet inconsistency problem using an illustrative schematic, generally referred to by the number 101. In Figure 1A, it can be seen that the printhead 103 has five ink nozzles, each depicted using small triangles at the bottom of the printhead, numbered (1)-(5). Note that in a typical manufacturing application, there may be more than five nozzles, e.g., 24-10,000 nozzles, depending on the application, and in the case of Figure 1A, five nozzles are simply referred to for ease of understanding. In the illustrative application, it is desired to deposit 50 picoliters (50.00 pL) of fluid into each of five specific target areas of an array of such areas, and it is assumed that each of the five nozzles of the printhead releases 10 picoliters (10.00 pL) of fluid into each of the various target areas 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., where deposited fluid ink partially diffuses and mixes together between regions) or each fluidly isolated region. These regions are generally represented in Figure 1A using ovals 104-108, respectively. Thus, it can be assumed that exactly five passages of the printhead are required to fill each of the five specific target regions, as depicted. However, in practice, the printhead nozzles will have some minor variations in structure or operation, as a given drive waveform applied to each nozzle transducer will produce slightly different droplet amounts for each nozzle. For example, as depicted in Figure 1A, the ejection of nozzle (1) produces a droplet amount of 9.80 picoliters (pL) in each pass, and five 9.80 pL droplets are depicted within the oval 104. While each droplet is represented in the figure by its specific location within the target region 104, it should be noted that in practice, the locations of each droplet may be identical or overlapping. Nozzles (2)-(5), in contrast, produce slightly different droplet volumes of 10.01 pL, 9.89 pL, 9.96 pL, and 10.03 pL.Each nozzle deposits fluid into the target areas 104-108 mutually, and the five pass-throughs between the printhead and the substrate result in a total ink deposition variation of 1.15 pL across the five target areas. This may be unacceptable for many applications. For example, in some applications, a difference of just 1 percent (or even less) in deposited fluid can cause problems. In the case of OLED display processing, such variation could potentially lead to observable image artifacts in the finished display.

[0005] Therefore, manufacturers of televisions and other forms of displays would effectively specify a precise quantitative range 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 exemplary case, the specified tolerance must be within 0.5 percent of the 50.00 pL target. In an application where each nozzle represented by Figure 1A was depositing into pixels within each horizontal line of a high-resolution television ("HDTV") screen, the depicted variation of 49.02 pL to 50.17 pL would therefore represent approximately ±1.2% (instead of the desired maximum tolerance of, for example, ±0.5% variation), thus resulting in unacceptable quality. While display technology is cited as an example, it should be understood that nozzle-droplet inconsistency issues can occur in other situations as well.

[0006] In Figure 1A, the nozzles are specifically aligned with target areas (e.g., wells) so that a particular nozzle prints into a specific target area. Figure 1B shows an alternative example 151 where the nozzles are not specifically aligned, but the nozzle density is high relative to the target area density, in which case any nozzle that happens to traverse a particular target area during scanning or passing is used to print into these target areas, and potentially several nozzles traverse each target area in each pass. In the embodiment shown, it is found that the printhead 153 has five ink nozzles, and the substrate has two target areas 154-155, where nozzles (1) and (2) traverse target area 154, nozzles (4) and (5) traverse target area 155, and nozzle (3) is positioned so as not to traverse any target area. As shown, in each pass, one or two droplets are deposited into each well to be depicted. Again, droplets can be deposited in an overlapping manner or at discrete points within each target region, and it should be noted that the specific diagram in Figure 1B is illustrative only, and as with the embodiment presented in Figure 1A, it is desired to deposit 50 picoliters (50.00 pL) of fluid into each of the target regions 154-155, with each nozzle assumed to have a nominal droplet volume of approximately 10.00 pL. Using the same droplet volume variation per nozzle as observed in relation to the embodiment in Figure 1A, and assuming that each nozzle overlapping the target region in a given pass will deliver droplets into that target region until a total of 5 droplets are delivered, the target region is filled in 3 passes, and a total deposited ink volume variation of 0.58 pL from 50.00 pL across the two target regions, as well as differences outside of specific tolerances, is observed, which again may be unacceptable for many applications.

[0007] In relation to the above embodiments, it should be noted that the droplet inconsistency problem is further exacerbated by the fact that the droplet volume can statistically vary even with respect to a given nozzle and a given drive waveform. Therefore, in the embodiments discussed above, while the printhead nozzle (1) from Figures 1A and 1B would produce a droplet volume of 9.80 pL in response to a given drive waveform, it is assumed that in real-world practice, the droplet volume may vary slightly depending on various factors, such as process, voltage, temperature, printhead age, and many other factors, so that the actual droplet volume may not be accurately known.

[0008] While techniques have been proposed to address the problem of droplet inconsistency, generally speaking, these techniques either still fail to reliably provide a fill volume that remains within the desired tolerance range, or they significantly increase manufacturing time and cost. In other words, they contradict the goal of having high quality along with a low consumer price point, and such quality and a low price point may be important for applications involving commodity products such as HDTVs.

[0009] Therefore, what is needed is a technique useful in depositing fluid into a target area of ​​a substrate using a print head with a nozzle. More specifically, what is needed is a technique for precisely controlling the amount of fluid deposited in each target area of ​​the substrate, despite variations in nozzle droplet discharge, on a cost-effective basis, ideally enabling high-speed fluid deposition operation and thus improving the speed of device fabrication. The technique described below satisfies these needs and offers further relevant advantages. [Overview of the project] [Means for solving the problem]

[0010] This disclosure relates to a printing process for transferring layer material to a substrate, a technique for droplet measurement with high precision, and the use of related methods, improvements, devices, and systems.

[0011] The nozzle consistency problem described above can be addressed by measuring the droplet volume per nozzle of the printhead (or the variation in droplet volume across nozzles) for a given nozzle emission waveform. This allows for the planning of the printhead emission pattern and / or motion to deposit a precise total amount of ink in each target area. Understanding how droplet volume varies across nozzles allows for the planning of the printhead / substrate position offset and / or droplet emission pattern in a manner that adapts to the differences in droplet volume but optimizes simultaneous printing in adjacent target areas with each pass or scan. From a different perspective, rather than normalizing or averaging the inter-nozzle variation in droplet volume, the specific droplet volume characteristics of each nozzle are measured and used in a planned manner to simultaneously achieve a specific range total amount for each of multiple target areas on the substrate. In many embodiments, this planning is done using a process that reduces the number of scans or printhead passes, depending on one or more optimization criteria.

[0012] Several different embodiments that contribute to achieving these results will be presented below. Each embodiment can be used in isolation, and it is explicitly considered that features of any embodiment can be mixed and matched with features of different embodiments as desired.

[0013] One embodiment presents a system and technique for providing individualized droplet measurement over very large printhead assemblies (e.g., having hundreds, thousands, or more nozzles). Using a sub-deposition measurement technique (i.e., by redirecting light away from the vicinity of the printhead, beyond the relative distance where the substrate would normally be positioned for deposition), large printhead assemblies (e.g., in a limited space) can be housed at will (e.g., in a printer service station), and the logistical difficulties associated with the positioning of the optical unit are resolved by using an optical assembly that can articulate up to three dimensions so that the droplet measurement device can be precisely articulated relative to the large printhead assembly. The precise positioning of the sub-deposition optical assembly allows for droplet volume measurement of the filling nozzle array at the required distance from the nozzle plate, despite the limited space (the printhead assembly typically operates about 1 millimeter from the substrate surface). In one optional embodiment, the optical system employs shadowgraphy and repeated measurements of droplets (and optionally, various nozzle drive waveforms) originating from a specific nozzle to increase the statistical confidence of the expected droplet volume. In another optional embodiment, the optical system employs interferometry and repeated measurements of droplets (and optionally, various nozzle drive waveforms) originating from a specific nozzle to increase the statistical confidence of the expected droplet volume.

[0014] It should be noted that in production lines, typically, it is desirable to have as little downtime as possible in production in order to maximize productivity and minimize manufacturing costs. In another discretionary embodiment, droplet measurement time is therefore "hidden" or "stacked" behind other line processes. For example, in a discretionary flat panel display processing production line, as each new substrate is loaded or otherwise handled, processed, or transported, droplet measurement is used to analyze the printer printhead assembly to facilitate an accurate statistical understanding of the amount of droplets per nozzle (and / or per nozzle, per drive waveform). For printhead assemblies with tens of thousands of nozzles, repeated droplet measurement (e.g., dozens of droplet measurements per nozzle, and per drive waveform if multiple drive waveforms are used) can be very time-consuming. Therefore, discretionary system control processes and associated software can perform droplet measurement at discretion, on a dynamic incremental basis. For example, if a virtual load / unload process requires, say, 30 seconds, and each print takes 90 seconds, the printhead assembly can be measured during the load / unload process in 2-minute cycles, and the droplet measurements can be updated to obtain the average droplet amount and confidence interval per nozzle using a sliding window of nozzles / droplets analyzed during the load / unload process associated with each 2-minute cycle. It should be noted that many other processes are possible, and a continuous dynamic process is not required for all embodiments. However, in practice, the droplet amount for a given nozzle and drive waveform will not only vary for other nozzles and drive waveforms, but also, due to subtle variations in ink properties, nozzle age and degradation, and other factors, the typical value will change over time. Therefore, a process that periodically updates the measurements, for example, every few hours to every few days, can, advantageously, further improve reliability.

[0015] In yet another optional embodiment, the droplet measurement system uses interferometry and non-imaging techniques to obtain very fast droplet measurements, for example, measuring per droplet in microseconds and performing repeated droplet measurements across a printhead assembly with thousands of nozzles in less than 30 minutes. In contrast to imaging techniques (which use a camera and captured image pixel processing techniques to derive the quantity measurement), interferometry can provide accurate droplet quantity measurements by using multiple optical sensors to detect interference pattern intervals representing droplet shape and correlating these intervals with droplet quantity. In one implementation, a laser source and / or associated optics and / or sensors are mechanically mounted for sub-deposition measurement and effective articulation over large printhead assemblies. Due to the very fast measurements obtainable with such a system, interferometry is particularly useful in embodiments that perform such dynamic incremental measurements, allowing repeated droplet measurements (e.g., 30 droplet measurements per nozzle) to be performed on tens to hundreds of nozzles in each print cycle to achieve high statistical confidence around each expected droplet quantity.

[0016] In yet another optional embodiment, numerous droplet measurements are performed per nozzle and (for embodiments using diverse nozzle drive waveforms) per nozzle drive waveform. As the number of measurements increases, the mean and standard deviation for each nozzle-waveform combination become more robust (assuming a normally random distribution). Using mathematical processes implemented by the software, a statistical model of each droplet can be created and precisely combined to generate a statistical model of the composite ink filling per target area. To provide an example, numerous measurements are performed for each nozzle for each drive waveform. If a given single measurement of droplet volume is expected to be accurate with a 2 percent standard deviation, then by performing numerous measurements, a statistically accurate mean is obtained with reduced variance or standard deviation; that is, again, assuming a normally random distribution, the standard deviation is reduced by the number of measurements n according to σ / (n)¹ / ², such that four measurements of droplet volume reduce the standard deviation by half. Thus, in one embodiment, the software is used to achieve a much higher confidence interval around the expected droplet volume through specifically planned repeated measurements, which helps to substantially reduce measurement errors. While many different statistical measures can be used, for example, in embodiments where composite filling is expected to fall within ±x% (e.g., ±0.5% of the target filling), droplet measurements can then be performed for each nozzle and for each different drive waveform, ensuring that a 3σ (99.73%) confidence interval is obtained around the expected droplet volume within the same range (e.g., ±0.5%) of the average droplet volume. Perhaps to put it another way, known techniques can be used to plan droplet combinations based on a mathematical combination of relevant statistical models to produce a higher degree of accuracy around the total ink filling per target area (despite droplet volume variations between nozzles and waveforms) using precise statistical models constructed for each different droplet. Note that while a normal random distribution is used in the selected embodiment, any statistical model can be used (e.g., Poisson, Student's T, etc.) whose individual distributions can be combined (e.g., by software) to obtain an aggregate distribution representing different droplet combinations.Furthermore, it should be noted that while a 3σ (99.73%) scale is used in some embodiments, other types of statistical scales, such as 4σ, 5σ, or 6σ, or scales not specifically associated with a random distribution, may be used in other embodiments considered.

[0017] It should be noted that similar techniques can be applied to generate models of droplet velocity and flight trajectory for each nozzle-waveform combination. These variables can further be applied in other optional embodiments.

[0018] Any permutation or subset of the techniques and embodiments described above can be applied to precisely plan the total ink filling in a target area, that is, to plan a specific composite amount based on variations in droplet volume per nozzle. In other words, rather than attempting to average the differences in volume across nozzles, these differences are understood and specifically used in the print control process to combine different droplets (e.g., from different nozzles or using different drive waveforms) to obtain highly precise ink filling.

[0019] In one optional embodiment, the print head and / or substrate are "stepwise" in a variable amount to change one or more nozzles used for each target region in various passes to release a specifically desired amount of droplets. For example, the print head to the substrate By selectively offsetting the head or printhead assembly, droplets from one nozzle (e.g., with an average droplet volume of 9.95 pL) can be combined with droplets from a second nozzle (e.g., with an average droplet volume of 10.05 pL to obtain a total composite volume of 20.00 pL). Multiple passes are planned so that each target area accepts a specific total fill that matches the desired target fill. That is, each target area (e.g., each well in a row of wells that will form the pixelated components of a display) accepts one or more planned combinations of droplet volumes to achieve a total volume within a specific tolerance range using different geometric steps of the printhead relative to the substrate. In a further detailed feature of this embodiment, considering the relative positional relationships of the nozzles, a tolerance for volume variation in each target area is allowed within the specification, while at the same time, a Pareto optimal solution can be calculated and applied so that the printhead / substrate movement is planned to maximize the average simultaneous use of the nozzles for each target deposition area. The statistical techniques discussed above can be used to ensure that the statistical model of composite (i.e., multiple droplet) ink filling falls within any desired tolerance range. One optional refinement can be applied to reduce and further minimize the number of printhead / substrate passes required for printing to achieve these objectives. A brief consideration of these various features reveals that the printing of layers of material on the substrate can be done quickly and efficiently, resulting in a significant reduction in processing costs.

[0020] In typical applications, the target areas that receive ink can be aligned, or laid out, within rows or columns, and it should be noted that the strip-like locations represented by the relative printhead / substrate motion will be within all parts of the rows (of the array's target areas), but will deposit ink in a manner that covers all columns of the array in a single pass. Also, the number of rows, columns, and printhead nozzles can be extremely large, for example, involving hundreds or thousands of rows, columns, and / or printhead nozzles.

[0021] Another optional embodiment addresses the nozzle consistency problem in a slightly different manner. A set of multiple pre-arranged alternative nozzle emission waveforms, each with known (and different) droplet volume characteristics, is made available to each nozzle. For example, four, eight, or another number of alternative waveform sets can be wired together or otherwise predefined to provide a corresponding set of slightly different droplet volumes to which can be selected. Per-nozzle quantity data (or difference data) and any relevant statistical models are then used to plan simultaneous deposition of multiple target areas by determining a set of nozzle-waveform combinations for each target area of ​​the substrate. Again, specific quantity characteristics, confidence intervals, etc., of each nozzle (in this case, each nozzle-waveform combination) and the relevant distribution are relied upon to achieve a specific filling amount with high confidence; that is, the variation is used specifically in combinations to obtain a specific filling amount within a well-understood statistical range, rather than attempting to compensate for the per-nozzle quantity variation. Typically, it should be noted that there will be a number of alternative combinations that can be used to deposit droplets to reach a desired range in each target area of ​​the substrate to satisfy these purposes. In more detailed embodiments, a "general set" of nozzle waveforms can be shared across some (or even all) nozzles of the printhead, storing droplet amounts per nozzle and available for mixing and matching different droplet amounts to achieve a specific fill. As a further option, a calibration step can be used to select different waveforms in an offline process (e.g., the dynamic incremental measurement process described above), and the set of nozzle emission waveforms is selected based on calibration so that each achieves a set of specifically desired quantity characteristics. Again, in more detailed embodiments, optimizations can be made to plan printing in a way that improves print time, for example, by minimizing the number of scans or printhead passes, by maximizing simultaneous nozzle use, or by optimizing some other criteria.

[0022] Yet another embodiment relies on the use of multiple printheads (or, equivalently, a printing structure having multiple rows of nozzles, each of which can be offset relative to one another) within a printhead assembly, where each printhead and its nozzles can be offset relative to one another. Using such intentional offsets, the amount variation per nozzle can be intelligently combined with each pass or scan across the printhead (or row of nozzles). Again, a number of alternative combinations arise that can typically be used to deposit droplets to reach a desired range in each target area of ​​the substrate, and in detailed embodiments, optimizations are made to plan the use of offsets in a way that improves printing time, for example, by minimizing the number of scans or printhead passes, or by maximizing simultaneous nozzle use.

[0023] It should be noted that one advantage of the techniques described above is that, while accepting droplet volume variations, by combining them to achieve a specific, predetermined target area filling volume, they can achieve not only the ability to meet a desired filling tolerance range, but also a high degree of control over precise volumes and intentionally controlled (or injected) variations of such volumes. The presence of geometric patterns from the deposition process, which may result in unevenness or observable patterns, can be mitigated through several techniques presented herein. That is, even slight differences in target filling volumes at low spatial frequencies can be visible to the human eye and thus introduce undesirable, unintentional geometric artifacts. Therefore, in some embodiments, it is desirable, still within the specifications, to intentionally, but randomly, vary the composite filling volume or specific combination of droplets used to achieve composite filling for each target area. Rather than simply using an exemplary tolerance of 49.75 pL to 50.25 pL to arbitrarily ensure that all target area fillings are within this tolerance range, such applications may desire to introduce intentional variation within this range, for example, so that any pattern of variation or difference is not observable to the human eye as a pattern in a finished, working display. When applied to a color display, one exemplary embodiment intentionally adds such filling variation in a manner that is statistically independent of at least one of (a) the x-dimension (e.g., along the row direction of the target area), (b) the y-dimension (e.g., along the column direction of the target area), and / or (c) one or more color dimensions (e.g., independently for red-to-blue, blue-to-green, and red-to-green target areas). In one embodiment, the variation is statistically independent across each of these dimensions. Such variation is considered to make any filling variation imperceptible to the human eye and thus contribute to the high image quality of such a display.For embodiments that use planned combinations of droplets from different nozzles, generated through a repeatable set of "geometric steps" or offsets in the scan path, it should be noted that the use of subtle but intentional droplet volume variations for each nozzle (i.e., generated through the use of multiple alternative firing waveforms for each nozzle) provides a powerful technique for suppressing the possibility of unevenness without the need to vary the scan path. In one considered embodiment, for example, each nozzle is assigned a set of alternative waveforms, each producing its average volume within ±10.0% of the ideal volume. Then, combinations of droplets from different nozzles can be planned according to a precise average (i.e., to achieve precise intended filling), with unevenness suppressed through the use of injected variations in the droplet pattern (either through planned combinations of droplet volumes from different nozzle-waveform pairings, or through waveform variations injected after the selection / planning of nozzle-droplet combinations to achieve a particular filling). In other embodiments, different composite droplet quantities can be intentionally pre-arranged for each target region to generate total filling, or different nozzle-droplet combinations can be applied along the scan path, or a nonlinear scan path can be used, all for the same reason. Other modifications are also possible.

[0024] Furthermore, conventional droplet measurement techniques take several hours or even longer, and therefore, long measurement times While potential variations in droplet characteristics within the cycle can lead to errors in the printing process, the use of high-speed techniques such as interference techniques and related structures (as described above) provides a more up-to-date understanding of inter-nozzle and inter-droplet volume variations, thus promoting a more accurate dynamic understanding and enabling the use of planned combinations as previously described with high reliability. For example, while conventional droplet measurement techniques can take hours to perform, the use of non-imaging techniques (such as interference) allows for continuous updating of droplet measurements, thus enabling accurate tracking of the process, voltage and temperature (PVT variations), printhead nozzle degradation, ink replacement, and other dynamic processes that may affect the accuracy of the measurement. For example, by using a rolling measurement process that masks incremental droplet measurements during substrate loading and unloading times as described above, droplet measurements can be updated almost continuously (e.g., every 3-4 hours for each nozzle), thus enabling the presentation of an accurate model that allows for composite filling plans as previously described. In one embodiment, droplets generated by all nozzles or nozzle-waveform pairs are remeasured periodically, for example, once every 2-24 hour period, preferably at shorter time intervals such as 2 hours (e.g., from the beginning). Note that the rolling process is not required in all embodiments; i.e., in one embodiment, measurements can be taken (or taken again) for all nozzles during a dedicated calibration process in which printing is interrupted. To provide one example, in one possible embodiment, a printhead assembly having 6,000 nozzles and 24,000 nozzle-waveform pairs can be measured over 15 seconds during the substrate loading and unloading phases for each 90-second print cycle, as a continuous process, where different rolling subsets of 24,000 nozzle-waveform pairs are examined in each iteration until all nozzle-waveform combinations have been processed, and then the process is repeated on a cyclic basis.As an alternative, in an embodiment where a dedicated calibration process is used (e.g., every 3 hours), such a print head assembly can be parked for a period of time (e.g., 30 minutes) to generate a statistical model for all nozzle / waveform combinations before returning to active printing.

[0025] Again, note that each of the optional techniques and embodiments introduced above are considered optional with respect to each other, and conversely, in various embodiments, it is contemplated that such techniques can be optionally combined in any possible permutation or combination. As an example, measurements of droplet velocity and / or flight angle per nozzle / drive waveform can be used to deem "errant" droplets for a given nozzle / waveform combination as unacceptable, based on the determination that a particular nozzle / waveform combination results in an abnormal droplet "average" or based on the determination that a particular nozzle / waveform combination results in a statistical spread of droplets that exceeds a threshold. To provide another non-limiting example, interferometry or other non-imaging techniques can be used to dynamically update the velocity and / or flight angle behavior by making such measurements incrementally and dynamically at various windows of nozzle / waveform combinations, i.e., when the print head assembly is "parked" during substrate loading and / or unloading at intermittent intervals. Clearly, many combinations and permutations are possible based on the permutations introduced above.

Brief Description of the Drawings

[0026] [Figure 1A] FIG. 1A is a schematic view presenting a virtual problem of depositing ink in a target area of a substrate, where a print head with five nozzles is used to deposit a target fill of 50.00 pL in each of five specific target areas. [Figure 1B]Figure 1B is another schematic view presenting a virtual problem of depositing ink in the target areas of a substrate, where a print head with five nozzles is used to deposit 50.00 pL of target fill in each of two specific target areas. [Figure 2A] Figure 2A is an illustrative schematic view showing a droplet measurement system capable of measuring the droplet volume for each nozzle of a large print head assembly. [Figure 2B] Figure 2B is a schematic view of a method showing various processes and options associated with the measurement of the droplet volume for each nozzle. [Figure 2C] Figure 2C is a schematic view of a method showing various process options associated with the measurement of the droplet volume for each nozzle to achieve a highly reliable understanding of the expected droplet volume. [Figure 2D] Figure 2D is a schematic view showing the layout of various components used in one embodiment for performing droplet measurement. [Figure 2E] Figure 2E is a schematic view showing the layout of various components used in another embodiment for performing droplet measurement. [Figure 3A] Figure 3A provides an illustrative diagram showing a series of optional steps, products, or services that can each independently embody previously introduced techniques. [Figure 3B] Figure 3B is an exemplary schematic view showing a virtual arrangement of a printer and a substrate in an application where the substrate ultimately forms a display panel having pixels. [Figure 3C] Figure 3C is a cross-sectional close-up view of the print head and the substrate of Figure 3B obtained from the perspective of line C-C in Figure 3B. [Figure 4A]Figure 4A is a schematic diagram similar to Figure 1A, but illustrates the use of droplet volume combinations to ensure that the amount of ink filling for each target area is generated within a predetermined tolerance range. In one optional embodiment, different droplet volume combinations are generated from a predetermined set of nozzle emission waveforms, and in another optional embodiment, different droplet volume combinations are generated from each nozzle of the print head using the relative motion (405) between the print head and the substrate. [Figure 4B] Figure 4B is a schematic diagram used to illustrate the relative printhead / substrate motion and the release of different droplet volume combinations into each target area of ​​the substrate. [Figure 4C] Figure 4C is a schematic diagram used to illustrate the use of different nozzle drive waveforms at each nozzle to generate different droplet volume combinations within each target region of the substrate. [Figure 4D] Figure 4D is a schematic diagram similar to Figure 1B, illustrating the use of droplet volume combinations to ensure that the ink filling amount for each target area is generated within a predetermined tolerance range. In one optional embodiment, different droplet volume combinations are generated from a predetermined set of nozzle emission waveforms, and in another optional embodiment, different droplet volume combinations are generated from each nozzle of the print head using the relative motion (472) between the print head and the substrate. [Figure 5] Figure 5 provides a block diagram illustrating a method for planning droplet combinations for each target region of a substrate, and this method can be applied to any of the optional embodiments shown in Figures 4A-D. [Figure 6A] Figure 6A provides a block diagram for selecting a specific set of acceptable droplet combinations for each target region of the substrate, which can be used, for example, with any of the embodiments previously described. [Figure 6B] Figure 6B provides a block diagram for iteratively planning printhead / substrate motion and using nozzles based on droplet combinations for each printing area. [Figure 6C]Figure 6C provides a block diagram illustrating further optimization of printhead / substrate motion and nozzle usage to sequence scans in a manner that allows printing to be performed as efficiently as possible. [Figure 6D] Figure 6D is a hypothetical plan view of the substrate on which multiple flat panel display devices (e.g., 683) will ultimately be produced. 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 can be used repeatably or periodically across each display device (e.g., the four flat panel display devices depicted). [Figure 7] Figure 7 provides a block diagram for intentionally varying the fill amount within tolerances to reduce visual artifacts in display devices. [Figure 8A] Figure 8A provides a block diagram showing how droplet measurement can be used to adapt to statistical variations in droplet volume per nozzle and per drive waveform, and furthermore, to enable precise total ink filling within a given target area. [Figure 8B] Figure 8B provides a block diagram showing how droplet measurements can be planned to adapt to statistical variations in droplet volume per nozzle and per drive waveform, and to enable precise total ink filling within a given target region. [Figure 9A] Figure 9A provides a graph showing the variation in the amount of liquid filling in the target area without adjusting the variation in droplet volume between the printhead nozzles. [Figure 9B] Figure 9B provides a graph showing the variation in target area fill volume when different nozzles are used randomly to statistically compensate for variations in droplet volume between printhead nozzles. [Figure 9C] Figure 9C provides a graph showing the variation in target area fill volume, where one or more droplets of different amounts are used to achieve a target area fill volume within precise tolerances according to the planned criteria. [Figure 10A]Figure 10A provides a graph showing the variation in the target area filling amount without adjustment of the droplet volume variation between printhead nozzles. [Figure 10B] Figure 10B provides a graph showing the variation in target area filling amount, where different nozzles are used randomly to statistically compensate for variations in droplet volume between printhead nozzles. [Figure 10C] Figure 10C provides a graph showing the variation in target area filling amount, where one or more droplets of different amounts are used to achieve a target area filling amount within a precise tolerance according to the planned standard. [Figure 11] Figure 11 shows a plan view of a printer used as part of a processing apparatus. The printer may be housed in a gas enclosure, which allows printing to occur in a controlled atmosphere. [Figure 12] Figure 12 provides a block diagram of a printer. Such a printer can optionally be used in, for example, the processing apparatus depicted in Figure 11. [Figure 13A] Figure 13A shows an embodiment in which multiple print heads (each with a nozzle) are used to deposit ink on a substrate. [Figure 13B] Figure 13B shows the rotation of multiple print heads to better align the nozzles of each print head with the substrate. [Figure 13C] Figure 13C shows the offset of individual printheads among multiple printheads associated with intelligent scanning to intentionally generate specific droplet volume combinations. [Figure 13D] Figure 13D shows a cross-sectional view of the substrate, including a layer that can be used in an organic light-emitting diode (OLED) display. [Figure 14A] Figure 14A shows several different ways to customize or vary the nozzle firing waveform. [Figure 14B] Figure 14B shows how to define a waveform according to discrete waveform sections. [Figure 15A]Figure 15A shows an embodiment in which different combinations of droplet volumes can be achieved by using different combinations of predetermined nozzle emission waveforms. [Figure 15B] Figure 15B shows a circuit associated with generating a programmed waveform and applying it to the printhead nozzles at a programmed time (or position). This circuit provides, for example, one possible implementation of circuits 1523 / 1531, 1524 / 1532, and 1525 / 1533 from Figure 15A. [Figure 15C] Figure 15C shows a flowchart of one embodiment using different nozzle firing waveforms. [Figure 15D] Figure 15D shows a flow chart associated with nozzle or nozzle waveform qualification. [Figure 16] Figure 16 shows a perspective view of an industrial printer. [Figure 17] Figure 17 shows another perspective view of an industrial printer. [Figure 18A] Figure 18A presents a schematic diagram showing the layout of components in an embodiment of a shadowgraphy-based droplet measurement system. [Figure 18B] Figure 18B presents a schematic diagram showing the layout of components in an embodiment of an interferometry-based droplet measurement system. [Figure 19] Figure 19 shows a flowchart associated with one exemplary process for integrating a droplet measurement system with an industrial printer, which can be optionally used in OLED device processing. [Modes for carrying out the invention]

[0027] The subject matter defined by the enumerated claims should be read in conjunction with the accompanying drawings and may be better understood by referring to the embodiments for carrying out the invention described below. This description of one or more specific embodiments, which are constructed below to enable the construction and use of various implementations of the techniques described by the claims, is not intended to limit the enumerated claims but to illustrate their applications. Without limiting the foregoing, this disclosure provides several different embodiments of techniques used to process material layers by planning printhead movements to maintain an amount of deposited ink within a predetermined tolerance, while not excessively increasing the number of printhead passes (and thus the time required to complete the deposited layer). In connection with these techniques, precise droplet measurements can be performed to precisely plan composite ink filling in any target area, and the measurements are highly integrated with production printing. Various techniques can be embodied as software for performing these techniques, in the form of a computer, printer, or other device running such software, in the form of control data (e.g., print image) for forming the material layer, 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) processed as a result of these techniques. While specific embodiments are presented, the principles described herein may also be applicable to other methods, devices, and systems.

[0028] (Detailed explanation) The examples will help introduce some concepts relating to intelligent planning of fill volume per target area. By determining the possible nozzle-droplet volume sets for each target area on the substrate, data (or difference data) of the amount per nozzle for a given nozzle firing waveform can be used to plan simultaneous deposition on multiple target areas. Typically, there will be numerous possible combinations of nozzles and / or drive waveforms that allow ink droplets to be deposited in multiple passes to fill each target area to a desired fill volume within a narrow tolerance range that meets the specifications. Returning briefly to the hypothesis presented using Figure 1A, if the allowable fill volume according to the specifications is 49.75 pL to 50.25 pL (i.e., within 0.5% of the target), then, though not limited, (a) five passes of nozzle 2 (10.01 pL) for a total of 50.05 pL, (b) one pass of nozzle 1 (9.80 pL) and four passes of nozzle 5 (10.03 pL) for a total of 49.92 pL, (c) one pass of nozzle 3 (9.89 pL) and five passes of nozzle 5 for a total of 50.01 pL. The acceptable fill volume can also be achieved using many different sets of nozzles / passes, including (d) four passes of nozzle 3 (10.03 pL), one pass of nozzle 3 (9.89 pL), three passes of nozzle 4 (9.96 pL), and one pass of nozzle 5 (10.03 pL) for a total of 49.80 pL, and (e) one pass of nozzle 2 (10.01 pL), two passes of nozzle 4 (9.96 pL), and two passes of nozzle 5 (10.03 pL) for a total of 49.99 pL. Other combinations are also clearly possible. The droplet measurement techniques described above can be used to obtain these expected (e.g., average) droplet volumes despite the relatively large statistical tolerances (e.g., ±2% of the volume) associated with single droplet measurements. Therefore, even if only one nozzle drive waveform selection is available for each nozzle (or all nozzles), a series of planned offsets or "geometric" combinations of deposited droplets for each target region are applied during each scan to deposit droplets (e.g., in different target regions), but in a specifically intended manner. The first embodiment described above can be used to offset the printhead relative to the substrate in a certain "technical step." That is, many combinations of nozzle droplet amounts under this assumption can be used to achieve the desired fill amount within a well-understood range of statistical variance that matches the specification tolerance, and the specific embodiment effectively selects one particular of the allowable droplet combinations for each target area (i.e., a specific set for each area) through its selection of scan motion and / or nozzle drive waveform to facilitate the 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 way that minimizes the time over which printing occurs, this first embodiment provides substantially increased manufacturing throughput. It should be noted that this increase can be embodied, at will, in a way that minimizes the number of printhead / substrate scans or "passes," in a way that minimizes the raw distance of relative printhead / substrate movement, or in a way that minimizes the overall printing time. In other words, printhead / board movement (e.g., scanning) can be pre-planned and used to fill a target area in a manner that satisfies predefined criteria such as minimal printhead / board pass-through or scanning, minimal printhead and / or board movement in one or more defined dimensions, printing in a minimum amount of time, or other criteria.

[0029] All identical approaches apply equally to the hypothesis in Figure 1B, where the nozzles are not specifically aligned with their respective target areas. Again, if the allowable fill volume according to the specifications is 49.75 pL to 50.25 pL (i.e., within 0.5% of both sides of the target), then, without limitation, the allowable fill volume can also be achieved with many different sets of nozzles / passes, including all the examples described above for Figure 1A, as well as additional examples specific to the hypothesis in Figure 1B, where two adjacent nozzles are used in a single pass to fill a particular target area, e.g., two passes of nozzle (4) (9.96 pL) and nozzle (5) (10.03 pL) for a total of 49.99 pL, and one pass of nozzle (2) (10.01 pL). Again, each such volume can be considered equivalent to a statistical average based on many droplet measurements. For example, if nozzles (4), (5), and (2) in this embodiment are associated with a statistical model featuring a 3σ value of the stated average and less than or equal to 0.5% of the stated average, then the total filling will also generally have a 3σ value equal to or less than ±0.5% of 49.99 pL, satisfying the specified tolerance with a high degree of statistical precision. For high-resolution OLED displays (i.e., with millions of pixels), a 3σ (99.73%) value that closely matches the filling tolerance may be insufficient, for example, this statistically indicates that potentially thousands of pixels may still be outside the desired tolerance. For this reason, it should be noted that in many embodiments, a larger diffusion scale (e.g., 6σ) is used to match the composite filling tolerance, effectively ensuring that virtually every pixel of the high-resolution display conforms to the manufacturer's specifications.

[0030] These same principles also apply to embodiments of multiple drive waveforms per nozzle. For example, in the hypothesis presented by Figure 1A, each nozzle can be driven by five different firing waveforms, identified as firing waveform AE, as described by Table 1A below, which describe the resulting quantitative characteristics of different nozzles for different firing waveforms. Considering a single target region 104 and a single nozzle (1), it would be possible to deposit a 50.00 pL target in five passes, for example, using a first printhead pass with a predefined firing waveform D (to produce a 9.96 pL droplet from nozzle (1)) and four subsequent passes with a predefined firing waveform E (to produce a 10.01 pL droplet from nozzle (1)), all without any offset in the scan path. Similarly, different combinations of firing waveforms can be used simultaneously in each pass so that each nozzle produces an amount close to the target value within each of the target regions, all without any offset in the scan path. [Table 1A]

[0031] All of these identical principles apply equally to the hypothesis in Figure 1B. For example, considering only one target area 154 and nozzles (1) and (2) (i.e., two nozzles overlapping the target area 154 during scanning), it is possible to achieve 50.00 pL in three passthroughs, for example, using nozzle (1) and a predefined waveform B (for a droplet volume of 9.70 pL) and nozzle (2) and a predefined waveform C (for a droplet volume of 10.10 pL), a second printhead pass using nozzle (1) and a predefined waveform E (for a droplet volume of 10.01 pL) and nozzle (2) and a predefined waveform D (for a droplet volume of 10.18 pL), and a third printhead pass using nozzle (1) and a predefined waveform E (for a droplet volume of 10.01 pL).

[0032] Note that in both the hypothesis in Figure 1A and the hypothesis in Figure 1B, it is possible to deposit each target amount within a single row of the target region in a single pass. For example, by rotating the print head 90 degrees, it would be possible to deposit exactly 50.00 pL for each target region in a single row using a single droplet from each nozzle, for example, using waveform (E) on nozzle (1), waveform (A) on nozzles (2), (4), and (5), and waveform (C) on nozzle (3) (10.01 pL + 10.01 pL + 9.99 pL + 9.96 pL + 10.03 pL = 50.00 pL). It may also be possible to deposit all the droplets necessary to achieve the target amount in a single pass without rotating the print head. For example, nozzle (1) may be able to dispense one droplet using waveform D and four droplets from waveform E into region 104 in a single pass.

[0033] These same principles also apply to the printhead offset embodiments described above. For example, for the hypothesis presented by Figure 1A, the quantitative characteristics can reflect the nozzles for a first printhead (e.g., "printhead A"), which is integrated with four additional printheads (e.g., printheads "B" - "E"), each driven by a single firing waveform and having droplet volume characteristics per nozzle. When the printheads perform a scan pass, each nozzle identified as nozzle (1) for the printhead is aligned to print into a target area (e.g., target area 104 from Figure 1A), and each nozzle identified as nozzle (2) from the various printheads is aligned to print into a second target area (e.g., target area 105 from Figure 1A), and so on, with the quantitative characteristics of different nozzles for different printheads being collectively organized as described in Table 1B below. Optionally, each printhead can be offset from one another, for example, using motors to adjust the interval between scans. Considering a single target area 104 and nozzles (1) on each printhead, it would be possible to deposit 50.00 pL in four passes, for example, using a first printhead pass in which both printheads D and E eject droplets into the target area, and three subsequent passes in which only printhead E ejects droplets into the target area. For example, within the range of 49.75 pL to 50.25 pL, close to a 50.00 pL target. Other combinations are possible using even fewer passes, still able to generate a certain amount in the target area. Again, considering only one target area 104 and nozzles (1) on each printhead, for example, it would be possible to deposit 49.83 pL in two passes, using a first printhead pass in which printheads C, D, and E all eject droplets into the target area, and a second printhead pass in which printheads D and E both eject droplets into the target area. Similarly, different combinations of nozzles from different printheads can be used simultaneously in each pass to generate an amount close to the target value in each of the target areas without any offset in the scan path. Thus, using multiple passes would be advantageous for embodiments where it is desired to deposit droplets simultaneously in different target areas (i.e., in different rows of pixels, for example). Again, statistical accuracy can be ensured by planning droplet measurements in a manner that is calculated to obtain desired statistical characteristics associated with the amount of droplets per nozzle and / or per drive waveform, as well as the associated average. [Table 1B]

[0034] All of the same approaches are equally applicable to the hypothesis in Figure 1B. Again, considering a single target area 154 and nozzles (1) and (2) on each printhead (i.e., nozzles that overlap with the target area 154 during scanning), it is possible to deposit 50.00 pL in two passes, for example, using a first printhead pass in which printheads C and E fire nozzle (1) and printheads B and C fire nozzle (2), and a second printhead pass in which printhead C fires nozzle (2). It is also possible to deposit 49.99 pL in a single pass (specifically, within the exemplary target range of 49.75 pL to 50.25 pL with high statistical accuracy) using a printhead pass in which printheads C, D, and E fire nozzle (1) and printheads B and E fire nozzle (2).

[0035] Furthermore, the optional use of alternative nozzle emission waveforms, combined with scan path offset, significantly increases the number of droplet volume combinations that can be achieved for a given printhead, and it should be evident that these options can be further increased by multiple printheads (or equivalently multiple rows of nozzles), as described above. For example, in the hypothetical embodiment conveyed by the discussion in Figure 1 above, the combination of five nozzles with their respective intrinsic emission characteristics (e.g., droplet volume) and eight alternative waveforms can provide literally thousands of different sets of possible droplet volume combinations. Optimizing the set of nozzle-waveform combinations and selecting a specific set of nozzle-waveform combinations for each target area (or for each row of print wells in the array) allows for 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 increases the number of combinations that can be applied to the printhead / substrate scan. Again, considering that, for these embodiments, to achieve a specific filling volume, multiple sets of nozzle-waveform combinations (one or more) can be used as alternatives, this embodiment selects a specific set from among the "acceptable" sets for each target region, and this selection of a specific set across the target region is generally multiple It supports simultaneous printing of multiple target areas using the nozzles. In other words, by varying parameters to minimize the time that printing takes place, each of these embodiments helps to increase manufacturing throughput and minimize the number of printhead / board scans or "passes" required, the raw distance of relative printhead / board movement along a particular dimension, or any other criterion that helps to be met.

[0036] Many other processes can be used in conjunction with or combined with the various techniques described above. For example, the nozzle drive waveform can be "adjusted" on a per-nozzle basis to reduce variations in droplet volume per nozzle (e.g., shaping the drive pulse by changing the drive voltage, rising or falling slope, pulse width, decay time, the number of pulses used per droplet, and the level of each pulse).

[0037] While some applications discussed herein refer to the amount of filling in discrete fluid containers or "wells," the described techniques can also be used to deposit "blanket coatings" with larger topography relative to other structures on a substrate (e.g., transistors, paths, diodes, and other electronic components). In such situations, the fluid ink supporting the layer material (which would be cured, dried, or hardened in situ to form a permanent device layer, for example) would diffuse to some extent, but would still retain specific properties relative to other target deposition areas on the substrate (considering ink viscosity and other factors). In this situation, the techniques described herein can be used, for example, to deposit blanket layers such as encapsulation or other layers using specific local control of the amount of ink filling for each target area. The techniques discussed herein are not limited to the applications or embodiments specifically presented.

[0038] Other variations, advantages, and applications of the techniques described above will be readily apparent to those skilled in the art. That is, these techniques can be applied to many different fields and are not limited to the processing of display devices or pixelated devices. As used herein, a printing “well” refers to any container on the substrate that receives the deposited ink and therefore has chemical or structural properties adapted to contain the flow of that ink. This can include situations where, as illustrated in the OLED printing below, each fluid container receives a respective amount of ink and / or ink of each type, for example, in a display application where the techniques described for depositing different colored light-emitting materials are used, a continuous printing process can be carried out for each color using a separate printhead and respective ink, in which case each process can deposit “every other well” in an array (for, for example, all “blue” color components), or equivalently all wells in a third array (with wells scattered with overlapping arrays for other color components). Each printing well is an embodiment of one possible type of target area. Other variations are also possible. Furthermore, note that the terms “row” and “column” are used in this disclosure without implying any absolute direction. For example, a “row” of a print well may extend along the length or width of the substrate, or in another manner (linear or nonlinear), and generally speaking, “row” and “column” will be used herein to refer to directions representing at least one independent dimension, respectively, although this is not required in all embodiments. Also note that modern printers can use relative substrate / printhead motion with multiple dimensions, so the relative motion does not need to have a linear path or velocity; i.e., the printhead / substrate relative motion does not need to follow a straight or continuous path, or even a constant velocity. Thus, “passing” or “scanning” of the printhead over the 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 of the OLED printing process described below, each pass or scan may be a substantially continuous linear motion, and each subsequent pass or scan is offset by a geometric step relative to each other and parallel to the next pass or scan. This offset or geometric step may be a difference in the start position, average position, end position, or some other kind of positional offset, and does not necessarily imply a parallel scanning path. It should also be noted that the various embodiments discussed herein speak of the “simultaneous” use of different nozzles for deposition in different target areas (e.g., different rows of a target area), and the term “simultaneous” does not require simultaneous droplet emission, but rather refers to the concept that different nozzles or groups of nozzles can be used to mutually exclusively eject ink into their respective target areas during any scan or pass. For example, one or more nozzles in a first group may be fired during a given scan to deposit a first droplet in a first row of a fluid well, while one or more nozzles in a second group may be fired during this same scan to deposit a second droplet in a second row of a fluid well. The term "printhead" refers to a single or modular device having one or more nozzles used to print (eject) ink toward a substrate. "Printhead assembly," in contrast, refers to an assembly or modular element that supports one or more printheads as a group for general positioning toward the substrate. Thus, a printhead assembly may, in some embodiments, contain only a single printhead, while in other embodiments, such an assembly may contain six or more printheads. In some implementations, individual printheads can be offset from one another within such an assembly.In typical embodiments used in large-scale manufacturing processes (e.g., flat-panel displays for televisions), printhead assemblies can be extremely large, encompassing thousands of print nozzles, and depending on the implementation, such assemblies can be large. It should be noted that the droplet measurement mechanism discussed herein is designed to articulate around such an assembly to obtain measurements per droplet. For example, with a printhead assembly having six printheads and approximately 10,000 or more print nozzles, the printhead assembly can be housed in an off-axis service station within the printer for various support operations, including droplet measurement.

[0039] With the key components of several different embodiments laid out in this manner, the disclosure will be organized approximately as follows. Figures 2A-2E will be used to illustrate a droplet measurement configuration for imaging a large printhead assembly. These configurations can optionally be integrated with a printer, e.g., a flat panel display processing device that prints ink material that will form a permanent thin film layer on a flat panel device substrate. In optional implementations, these configurations can utilize some or all of the three-dimensional articulation of the optics associated with droplet measurement to articulate around a printhead assembly with multiple printheads and thousands of inkjet nozzles, for example, housed in a printer service station. Figures 3A-4D will be used to illustrate some general principles regarding nozzle consistency issues, OLED printing / processing, and how embodiments address nozzle consistency issues. These techniques can optionally be used in conjunction with the described droplet measurement configurations. Figures 5-7 will be used to illustrate a software process that can be used to plan droplet combinations for each target region of a substrate. Figures 8A-B illustrate the principles associated with constructing statistical models of droplet volume for each nozzle / waveform combination and the use of these models to generate statistical models of total ink filling for each target area. These principles can optionally be used in conjunction with droplet measurement (i.e., through the use of planned droplet combinations) to ensure the production of composite ink fillings that meet specific tolerance ranges with quantifiable certainty (e.g., 99% or better confidence per target area) despite nozzle consistency issues. Figures 9A-10C are used to present some empirical data demonstrating the effectiveness of the planned droplet combination technique described above in improving the consistency of target area filling. Figures 11-12 will be used to discuss exemplary applications to OLED panel processing, as well as related printing and control mechanisms.Figures 13A–13C are used to discuss printhead offsets, which can be used to vary the combination of droplets that can be deposited in each scan. Figures 14A–15D are used to further discuss different alternative nozzle firing waveforms that can be applied to provide different droplet volumes or combinations. Figures 16–17 will provide additional details about the structure and configuration of an industrial printer, including a droplet measurement device. Figures 18A and 18B will be used to discuss a detailed embodiment of a droplet measurement system, for example, integrated with such an industrial printer. Finally, Figure 19 will be used to discuss techniques for concealing droplet measurement time behind other system processes in order to maximize production time.

[0040] Figures 2A-2E are generally used to illustrate techniques for measuring droplet size per nozzle.

[0041] More specifically, Figure 2A provides an illustrative diagram depicting an optical system 201 and a relatively large printhead assembly 203, the printhead assembly having multiple printheads (205A / 205B), each with a large number of individual nozzles (e.g., 207) with hundreds to thousands of nozzles. An ink supply unit (not shown) is fluidically connected to each nozzle (e.g., nozzle 207), and a piezoelectric transducer (also not shown) is used to eject droplets of ink under the control of an electronic control signal per nozzle. The nozzle design maintains a slight negative pressure of ink at each nozzle (e.g., nozzle 207) to avoid flooding of the nozzle plate, and an electronic signal to a given nozzle is used to activate the corresponding piezoelectric transducer, pressurizing the ink for the given nozzle, thereby ejecting droplets from the given nozzle. In one embodiment, the control signal to each nozzle is typically 0 volts, and a positive pulse or signal level at a given voltage is used to cause a particular nozzle to eject droplets (one per pulse) from that nozzle. In another embodiment, different regulated pulses (or other more complex waveforms) can be used per nozzle. However, in relation to the embodiment provided by Figure 2A, it is desirable to measure the amount of droplet produced by a particular nozzle (e.g., nozzle 207) that is ejected downward from the printhead (i.e., in direction "h", representing the z-axis height relative to the three-dimensional coordinate system 208) so that the droplet is collected by the ejection jar 209. Note that in a typical application, the dimension of "h" is typically about 1 millimeter or less, and there are thousands of nozzles (e.g., 10,000 nozzles) in a working printer, each of which is measured individually in this way. Therefore, in order to optically measure each droplet precisely (i.e., a droplet from a particular nozzle among thousands of nozzles in a large printhead assembly environment within a measuring window of about 1 millimeter as described), a technique is used in the disclosed embodiment to precisely position the optical assembly 201, the printhead assembly 203, or elements of both relative to each other for optical measurement.

[0042] In one embodiment, these techniques utilize a combination of (a) xy motion control (211A) of at least a portion of the optical system (e.g., in a dimensional plane 213) for precisely positioning the measurement area 215 directly adjacent to any nozzle that generates droplets for optical calibration / measurement (e.g., thereby enabling easy positioning of the measurement area adjacent to any nozzle despite the large printhead surface area). Thus, in an exemplary embodiment having about 10,000 or more print nozzles, this motion system is used for each nozzle of the printhead assembly It is possible to position at least a portion of the optical system at approximately 10,000 discrete positions close to the discharge path. Two considered optical measurement techniques, as discussed below, include shadowgraphy and interferometry. Using each, the optical unit is typically tuned to a fixed position so that a precise focus is maintained on the measurement area to capture a droplet in flight (for example, to effectively image the shadow of the droplet in the case of shadowgraphy). It should be noted that, since a typical droplet can have a diameter of about a few microns, the optical arrangement is typically extremely precise and presents challenges regarding the relative positioning of the printhead assembly and the measuring optical unit / measurement area. In some embodiments, to assist this positioning, the optical unit (mirror, prism, etc.) is used to orient a light capture path for sensing below the dimensional plane 213 arising from the measurement area 215, so that the measuring optical unit can be positioned close to the measurement area without interfering with the relative positioning of the optical system and the printhead. This allows for effective positional control in a manner not limited by the millimeter-order deposition height h in which the droplet is imaged internally, or by the large x and y widths occupied by the monitored printhead. Using interferometry-based droplet measurement techniques, separate light rays incident on the droplet from different angles create interference patterns detectable from a viewpoint approximately perpendicular to the optical path, and thus the optics in such a system also capture light in a manner utilizing subplane optical recovery to measure droplet parameters, although at an angle approximately 90 degrees off the path of the light source beam. Other optical measurement techniques can also be used. In yet another variation of these systems, the motion system 211A is fabricated to be an xyz motion system that allows for selective engagement and disengagement of the droplet measurement system at will and, advantageously, without moving the printhead assembly during droplet measurement.In short, in industrial processing devices having one or more large printhead assemblies, it is considered that, in order to maximize manufacturing uptime, each printhead assembly may sometimes be "resident" at a service station to perform one or more maintenance functions, and given the sheer size of the printhead and the number of nozzles, it may be desirable to perform multiple maintenance functions on different parts of the printhead simultaneously. In this regard, in such embodiments, it may be advantageous to move the measurement / calibration device around the printhead rather than the other way around. [This then also allows for the engagement of other non-optical maintenance processes, for example, on another nozzle, if desired.] To facilitate these operations, the printhead assembly may optionally be "resident" using a system that identifies a specific nozzle or set of nozzles to be optically calibrated. Once the printhead assembly or a given printhead is stationary, the motion system 211A is engaged to move at least a portion of the optical system relative to the "stationed" printhead assembly to precisely position the measurement area 215 in a suitable location for detecting droplets ejected from a particular nozzle. The use of the z-axis of the movement allows for selective engagement of the photorecovery optics from well below the surface of the printhead, facilitating other maintenance operations in place of or in addition to optical calibration. Perhaps to put it another way, the use of the xyz motion system allows for selective engagement of the droplet measurement system, independent of other tests or test devices used in a service station environment. It should be noted that this structure is not required in all embodiments, and for example, in relation to Figures 16-17 below, a mechanism will be described that allows for the movement of both the measurement assembly and the printhead assembly, e.g., z-axis movement of the printhead assembly relative to the measurement assembly having xy motion for the purpose of droplet measurement. Other alternatives are also possible, where only the printhead assembly moves and the measurement assembly is stationary, or where stationary of the printhead assembly is not required.

[0043] Generally speaking, the optical unit used for droplet measurement would include a light source 217, an optional set of light delivery optics 219 (which directs light from the light source 217 to the measurement area 215 as needed), one or more light sensors 221, and a set of recovery optics 223 which directs light used for measuring droplets from the measurement area 215 to one or more light sensors 221. The stem 211A optionally moves one or more of these elements together with the discharge jar 209, while also providing a container (e.g., discharge jar 209) to collect the ejected ink, thereby enabling the directing of light after droplet measurement from the measurement area 215 around the discharge jar 209 to a subsurface location. In one embodiment, the light delivery optics 219 and / or the light recovery optics 223 use a mirror that directs light to and from the measurement area 215 along a vertical dimension parallel to the droplet's movement, and the motion system moves each of the elements 217, 219, 221, 223, and the discharge jar 209 as an integrated unit during droplet measurement. This setup offers the advantage that the focus does not need to be recalibrated relative to the measurement area 215. As described by figure 211C, the light-delivering optics unit is also optionally used to supply light from a location below the dimensional plane 213 of the measurement area, along with both the light source 217 and the light sensor 221, which direct light on both sides of the ejection cistern 209 for measurement purposes, for example, as generally illustrated. As described by figures 225 and 227, the optical system may optionally include lenses for focusing purposes, as well as photodetectors (for example, for non-imaging techniques that do not rely on the processing of multi-pixel "photographs"). Again, it should be noted that the optional use of z-motion control for the optical assembly and the ejection cistern allows for the optional engagement and disengagement of the optical system, as well as precise movement of the measurement area 215 in proximity to any nozzle at any point while the printhead assembly is "resident". Such residenting of the printhead assembly 203 and xyz motion of the optical system 201 are not required in all embodiments. For example, in one embodiment, laser interferometry is used to measure droplet characteristics, and the printhead assembly (and / or optical system) is moved either within or parallel to the deposition plane (e.g., within or parallel to plane 213) to image droplets from various nozzles. Other combinations and permutations are also possible.

[0044] Figure 2B provides a process flow associated with droplet measurement for several embodiments. This process flow is generally specified using the figure 231 in Figure 2B. More specifically, as used by reference figure 233, in this particular process, the printhead assembly is first stationed, for example, at a service station (not shown) of the printer or deposition device. Then, the droplet measuring device is engaged together with the printhead assembly by selective engagement of part or all of the optical system, for example, through movement from below the deposition surface to a position where the optical system can measure individual droplets (235). As shown by figure 237, this relative motion of one or more components of the optical system with respect to the stationed printhead can be performed arbitrarily in the x, y, and z dimensions.

[0045] As previously suggested, even a single nozzle and associated nozzle ejection drive waveform (i.e., the pulse or signal level used to eject droplets) can generate droplet volume, trajectory, and velocity that vary slightly from droplet to droplet. According to the teachings herein, in one embodiment, a droplet measurement system, such as the one shown by figure 239, obtains n measurements of a parameter per droplet to derive a statistical confidence in the expected properties of the parameter of choice. In one implementation, the measured parameter may be a quantity, while in another implementation, the measured parameter may be flight velocity, flight trajectory, or another parameter, or a combination of several such parameters. In one implementation, “n” may differ for each nozzle, while in another implementation, “n” may be a fixed number of measurements performed on each nozzle (e.g., “24”), and yet another implementation, “n” refers to a minimum number of measurements so that additional measurements can be taken to dynamically adjust the measured statistical properties of the parameter or to refine the confidence. Clearly, many modifications are possible. In the embodiment provided by Figure 2B, it is assumed that the droplet volume is measured to obtain an accurate average representing the expected droplet volume and a tight confidence interval from a given nozzle. This allows for the arbitrary planning of droplet combinations (using multiple nozzles and / or drive waveforms) while ensuring that the distribution of composite ink filling is maintained in the target area around the expected target (i.e., with respect to the composite volume of the droplet average). Ideally, an optical measurement process, such as interferometry or shadowgraphy, is considered, which allows for instantaneous or near-instantaneous measurement and calculation of the volume (or other desired parameter), as described by the arbitrary process boxes 241 and 243. Using such high-speed measurements, it becomes possible to frequently and dynamically update the volume measurements to address changes over time in, for example, ink properties (including viscosity and constituent materials), temperature, power supply fluctuations, and other factors.Based on this, while shadowgraphy typically features the capture of droplet images using, for example, a high-resolution CCD camera as a photosensor mechanism, and can accurately image droplets at multiple locations within a single image capture frame (e.g., using a strobe light source), image processing software typically involves a finite amount of time to calculate droplet volume, as imaging a sufficient population of droplets from a large printhead assembly (e.g., with thousands of nozzles) can take several hours. Interferometry, which relies on multiple binary photodetectors and the detection of interference pattern intervals based on the outputs of such detectors, is a non-imaging technique (i.e., does not require image analysis) and therefore generates droplet volume measurements many times faster (e.g., 50 times faster) than shadowgraphy or other techniques. For example, with a 10,000-nozzle printhead assembly, a large measurement population for each of thousands of nozzles can be obtained in minutes, which is expected to make frequent and dynamic droplet measurements feasible. As described above, in one discretionary embodiment, droplet measurement (or measurement of other parameters such as trajectory and / or velocity) can be performed as a periodic intermittent process using a droplet measurement system that is engaged according to a schedule or stacked between substrates (e.g., when substrates are loaded or unloaded) or against other assemblies and / or other printhead maintenance processes. In embodiments that allow alternative nozzle drive waveforms to be used in a manner specific to each nozzle, it should be noted that a high-speed measurement system (e.g., an interferometer system) facilitates the generation of statistical swarms for each nozzle and for each alternative drive waveform for that nozzle, thereby facilitating planned droplet combinations of droplets generated by various nozzle-waveform pairings, as previously suggested. The digits 245 and 247 allow for highly precise droplet planning per target deposition area by measuring the expected droplet volume for each nozzle (and / or per nozzle-waveform pair) with an accuracy of better than 0.01 pL. Compound filling can also be planned with a resolution of 0.01 pL, keeping the target volume within 0.5% or better of the target volume within a specific error (e.g., tolerance).As indicated by the figure 247, a measurement set for each nozzle or each nozzle-waveform pair is planned, in one embodiment, to generate a confidence distribution model for each such nozzle or nozzle-waveform pair, i.e., with a 3σ confidence level (or other statistical measures such as 4σ, 5σ, 6σ) smaller than the specified maximum filling error. Once sufficient measurements have been made for various droplets, these can be used to evaluate filling with combinations of these droplets and to plan printing (248) in the most efficient manner possible. As indicated by the separation line 249, droplet measurements can be performed by intermittently switching back and forth between the active printing process and the measurement and calibration process.

[0046] Figure 2C illustrates a flow chart of one possible process 251, associated with planning droplet measurements per nozzle (per nozzle-waveform pair) and / or initializing statistical data to model the behavior of each nozzle using them. As indicated by figure 253, in this process, data specifying a desired tolerance range, which can be established, for example, according to the manufacturer's specifications, is first received. In one embodiment, for example, this tolerance or allowable range can be specified as ±5.0% of a given target, and in another embodiment, a different range such as ±2.5%, ±2.0%, ±1.0%, ±0.6%, or ±0.5% of the desired target droplet size can be used. It is also possible to specify a range or set of allowable values ​​in an alternative manner, depending on the desired tolerance and droplet system measurement error. Regardless of the specification method, the number of measurement thresholds is then identified (255). As shown above, it should be noted that this number can be selected to achieve several purposes, namely, (a) to obtain a sufficiently large set of droplet measurements to provide a reliable measure of expected droplet parameters (e.g., average volume, velocity, or trajectory), (b) to obtain a sufficiently large set of droplet measurements to model variations in droplet parameters (e.g., standard deviation or σ for a given parameter), and / or (c) to obtain sufficient data to identify nozzles or nozzle-waveform pairs with larger-than-expected errors for the purpose of considering the use of certain nozzles / nozzle-waveform pairs unsuitable during the printing process. With any planned number of droplet measurements, or with any desired metric or associated minimum value thus defined, measurements are then performed using the droplet measurement system 259 (e.g., using optical techniques as discussed herein) (257). The process determination block 261 then performs measurements for each nozzle (or nozzle-waveform) until a specific criterion is met. If the number of measurements meets the planned criteria, the method terminates with process block 269. If additional measurements are required, the measurement process loops until sufficient measurements are obtained, as shown in Figure 2C.

[0047] Figure 2C shows several exemplary process variations. Firstly, as indicated by the number 263, this measurement process is optionally applied to all nozzles (and / or all possible nozzle / waveform combinations) of the printhead assembly. This does not have to apply to all embodiments. For example, in one embodiment (see the discussion of Figures 14A-15C below), a potentially infinite number of variations of the drive waveform can be used to affect the parameters of ejected droplets for a given nozzle. Instead of exclusively testing each possible waveform, the droplet measurement process can be experimented with a given set of waveforms representing a broad distribution of possible waveforms, using an iterative interpolation search process, which is used to select a small number of waveforms (which are likely to produce an average droplet volume that extends over a range of ±10% of the desired droplet size). In another embodiment, if, based on the initial measurements, a given nozzle is considered defective (e.g., droplet volume with a distribution exceeding 20% ​​from the desired average), that nozzle (or nozzle-waveform pair) can be optionally excluded from further consideration. In yet another embodiment, if in practice a print scan is planned that does not use a certain nozzle, it may be advantageous to perform dynamic, additional droplet measurements only on the nozzles actively used in the planned scan until at least some kind of error or dispersion criterion is reached. Again, many possibilities exist, and functional block 263 simply indicates that the applied process does not need to involve all nozzles (or nozzle-waveform pairs). Secondly, figure 265 indicates that in one embodiment, the minimum criterion may be a minimum threshold which may differ for each nozzle or nozzle-waveform pair. To cite some embodiments of this function, in one embodiment droplet measurements are performed on a given nozzle or nozzle-waveform pair, a distribution-diffusion measure (e.g., variance, standard deviation, or another measure) is calculated, and measurements are performed above a raw threshold until the diffusion measure meets a predetermined criterion.As should be understood, if the minimum is, for example, 10 droplet measurements per nozzle, and 10 droplet measurements for a particular nozzle result in greater dispersion than expected, additional measurements can be uniquely performed on a given nozzle until the desired diffusion is achieved (e.g., 3σ ≤ 1.0% of the average amount) or until a certain maximum number of measurements are performed. Such embodiments can result in a different number of measurements per nozzle, i.e., measurement iterations are planned to achieve a certain minimum criterion (e.g., a minimum number of measurements and a diffusion measure below a threshold) in this embodiment. Thirdly, as indicated by figure 267, it is also possible to use dead reckoning in the droplet measurement plan, e.g., to obtain "exactly 24" droplet measurements per nozzle (or nozzle waveform), or to obtain x measurements per hour, etc. Finally, regardless of the measurement control technique, it is possible to apply the measurements to determine whether a given nozzle or nozzle waveform combination is eligible (pass) or ineligible. To reiterate, regarding possible implementation options, following the measurement of a threshold number, a nozzle or nozzle waveform can be considered eligible or ineligible based on the measurement data, according to the number 270. For example, if the ideal droplet volume is 10.00 pL for a given application, a nozzle / nozzle waveform pair that does not produce an average droplet volume of 9.90 pL to 10.10 pL can be immediately considered ineligible. The same approach can be taken for statistical diffusion; for example, following a minimum number of measurements, any nozzle / nozzle waveform pair that produces droplet diffusion (e.g., dispersion, standard deviation, etc.) greater than 0.5% can be immediately considered ineligible. Again, many implementation examples exist.

[0048] Figure 2D is a schematic diagram of one implementation of a droplet measurement system predicted by optical technique, generally referred to by the figure 271. More specifically, the printhead 273 is shown in cross-section as having five enumerated printing nozzles arranged as a row of nozzles that will eject fluid ink downward in the z direction (as shown by reference legend 274). The light source 275A is positioned on the side of the printhead to illuminate a measurement area 278 through which droplets will pass for measurement. In Figure 2D, this measurement area (and part or all of the optical system) is positioned to measure droplets originating from the nozzles (3) of the printhead. The light source 275A is depicted outside one side of the printhead 273 to generate an optical path 277 that will direct light into the optical measurement area (i.e., within a height of millimeter order, represented by the variable h) to illuminate one of the multiple nozzles without interfering with the printhead 273. As represented by the figure 275B, in one embodiment, the light source may also be favorably mounted below the deposition surface 289 (and above the periphery of the discharge bin 286) to provide relatively easy fixed-distance positioning of the optics relative to the droplet path from any nozzle. Again, five nozzles are depicted in Figure 2D, but in one embodiment, there may be hundreds, thousands, or even more nozzles. Under-deposition light generation, using the optics used to direct illumination into the droplet measurement area 278, facilitates easy positioning of the optics system relative to any nozzle of the depicted printhead 273, and for selective engagement and disengagement of the droplet measurement system (e.g., relative to an optional service station as previously described). In the depicted embodiment, a mirror 285A is used to redirect light from the light source 275B to incident on droplets in the measurement area 278 traveling from the printhead 273 toward the discharge bin 286. In non-limiting embodiments, other means of positioning the optical path relative to the light source 275B may also be used, such as prisms or fiber optic cables. For implementations where imaging measurement techniques are used (e.g., shadowgraphy), the light source 275A / 275B may be a strobe thermal light source or a monochromatic light source.Figure 2D also shows light from a third source position directed along path 275C, which directs light into or out of the drawing page with or without the help of the optical path designation optics unit (e.g., along the y-dimension as depicted by Reference Legend 274), even when the light source is outside the drawing page. Note that such a positioning framework can be used when interferometry is relied upon, for example, with the detection of interference patterns arising from directions perpendicular to (or at another angle to) the illumination path. Note that regardless of the relative arrangement of the illumination sources, light is directed along optical path 277 and illumination surface 290, which are intermediate with respect to the positions of the print head 273 and deposition surface 290, and the measured light (i.e., from the measured droplet) is routed by the optical path designation optics unit 285B from the imaging surface to a photodetector mounted below the deposition surface 289. Again, this allows for narrow directing and focusing of light despite the large print head size and relatively small height h. Furthermore, similar to the optical path designation optics unit 285A, mirrors, prisms, optical fibers, or other optical redirection devices and techniques can be used to achieve sub-deposit surface path designation for this optical recovery. As seen in Figure 2D, the measurement light is directed to the focusing optics unit 279 (e.g., a lens) and onto the photodetector 280. The distance of the optical path between the focusing optics unit and the measurement area is identified by a distance f, which represents the focal length of the optical system. As previously suggested, droplet measurement (depending on the optical technique) provides the precise focusing required to properly image droplets, and in this regard, for the system represented by Figure 2D, it is desirable that the optical path designation optics unit 285B, the focusing optics unit 279, the droplet measurement area 278, and the ejection urn 286 lens all move as an integrated unit to measure droplets from different nozzles, as represented by the depicted connections to the common chassis 283. The light sources 275A / 275B and the light source directional optics unit can also be optionally connected to this chassis, depending on the embodiment.

[0049] Similarly, in the interferometry-based system schematically represented by Figure 2D, it should be noted that the light source 275A / 275B (or generating optical path 275C) may be a laser, the beam of which is split at some point along the optical path into two or more different components used to generate the interference pattern. Additional details regarding these optical components and the use of multiple beams to create the interference pattern will be discussed further below in relation to Figure 18B. For the time being, assume that the laser source (including the light source for interferometry) is encompassed by references 275A / 275B / 275C.

[0050] Figure 2E illustrates another schematic diagram of an implementation of a droplet measurement system predicted by optical techniques, generally referred to by the digit 291. More specifically, the implementation seen in Figure 2E relies on interferometry to measure droplet parameters (such as volume). As previously, this configuration relies on a print head 273, a measurement area 278, a chassis 283, and an ejection jar 286. However, in this embodiment, a laser is specifically used as the light source 292 to generate a beam of light directed to the measurement area via an irradiation path 293. Typically, it should be noted that two or more beams are directed in this manner, as will be further described below. An interference pattern is generated in the droplet in the measurement area 278, and this interference pattern is observed from a direction substantially perpendicular to the irradiation path 293, as represented by the digit 297. This same relationship (measurement from a direction not parallel to the irradiation path) was also represented by Figure 2D (e.g., using path 275C), but in Figure 2E, the divergent measurement angle is such that the measurement light is naturally directed downward below the plane of the measurement area 278. The photodetector 295 is non-imaging in the sense that it does not require the use of a camera (although typically multiple photodetectors are used) and does not require the use of image processing to identify droplet contours in a pixelated image, substantially improving the speed of detection and measurement, namely, the interference approach simply measures the change in the interference pattern as the droplet passes through the region of the simultaneous rays, and the droplet volume can be derived from the resulting value. The use of two or more rays (or an increased number of detectors) facilitates the measurement of droplet trajectory and velocity as well as other parameters. As before, the light source 292, the discharge jar 286, and the photodetector 295 can be moved as one unit (i.e., using the common chassis 283), facilitating the preservation of precise optical path parameters. In one implementation, the optical system's motion is again performed three-dimensionally relative to a "stationed" printhead assembly, so as to selectively engage and disengage the droplet measuring device while the printhead assembly is in the service station, and so as to easily and precisely position the droplet measuring device to measure any of the thousands of nozzles of a large printhead.

[0051] As described above, using a suitable configuration of droplet measurement device or system, industrial printers (e.g., those used in OLED device processing) can be repeatedly calibrated for nozzles and the resulting droplets, enabling highly precise planning of droplet combinations within any target area. In other words, the measurement device can be used to quickly generate accurate, tightly grouped statistical distributions of quantities for each nozzle and each waveform used for each nozzle, enabling precise planning of droplet combinations used to achieve composite filling. In other embodiments, these same techniques are used to construct models for droplet velocity and flight angle so that models for these parameters can be applied to the printing process.

[0052] It should be noted that any of these various techniques (and any of the printing or composite filling techniques described herein) may be manifested in different products and / or at different manufacturing stages. For example, Figure 3A represents several different implementation stages, collectively designated by reference numeral 301, each of which represents a possible discrete implementation of the techniques described above. Firstly, the techniques described above can be embodied as instructions stored on a non-transient machine-readable medium, as represented by graphic 303 (e.g., software for controlling a computer or printer). Secondly, as indicated by computer icon 305, these techniques can be implemented as part of a computer or network within a company that designs or manufactures components for sale or use in other products, for example. For example, the techniques described above can be implemented as design software by a company that advises or designs for manufacturers of high-definition televisions (HDTVs). Alternatively, these techniques can be used directly by such manufacturers to produce televisions (or display screens). Thirdly, as previously introduced and illustrated using the storage medium graphic 307, the techniques described above can take the form of printer instructions, for example, as stored instructions or data that, when applied, will cause a printer to process one or more layers of components that, according to the above discussion, depend on the use of the planned droplet aggregation technique. Fourthly, as represented by the processing device icon 309, the techniques described above can be implemented as part of a processing apparatus or machine, or in the form of a printer within such an apparatus or machine. For example, a processing machine can be sold or customized in such a way that droplet measurement and conversion 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 reproducibly reapplied in a scalable pipeline manufacturing process that produces many units. Note that the particular depiction of the processed device icon 309 represents one exemplary printer device, which will be discussed below (see, for example, Figures 11-12). The techniques introduced above can also be embodied as assemblies such as arrays 311 of multiple components that will be sold separately, for example, in Figure 3, some such components are depicted in the form of an array of semi-finished flat panel devices, which will be separated and sold later for incorporation into end consumer products. The depicted devices may have one or more layers (e.g., a color component layer, a semiconductor layer, an encapsulation layer, or other material) that are deposited, for example, depending on the method introduced above. The techniques introduced above can also be embodied in the form of end consumer products such as the referenced, for example, in the form of a display screen for a portable digital device 313 (e.g., an electronic pad or smartphone), a television display screen 315 (e.g., an HDTV), or other types of devices. For example, Figure 3A uses a solar panel graphic 317 to illustrate that the process described above can be applied to other forms of electronic devices, such as depositing a structure per target region (e.g., one or more layers of individual cells constituting an aggregate device) or a blanket layer (e.g., an encapsulation layer for a television or solar panel). Clearly, many embodiments are possible.

[0053] The techniques described above can be applied to any of the steps or components illustrated in Figure 3A, but are not limited to these. 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 that includes data to control the processing of layers using a specific combination of nozzle amounts to obtain filling per specific target area. The nozzle amounts can be determined in advance or measured in situ and applied. Yet another embodiment is, for example, a deposition machine that uses a printer to print one or more inks using the techniques described above. These techniques can be applied to one machine or more machines, for example, different steps in different machines. The technology can be applied to a machine, or implemented on a network or set of machines. All such embodiments and other embodiments can utilize the techniques introduced herein, independently or collectively.

[0054] As shown in Figure 3B, 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 when processing the device. In certain applications, these instructions can be linked to an inkjet printing process useful when printing layers of a low-cost, scalable organic light-emitting diode ("OLED") display. More specifically, the described techniques can be applied to deposit one or more light-emitting or other layers of such an OLED device, e.g., the "red," "green," and "blue" (or other) pixelating color components or other light-emitting layers or components of such a device. This exemplary application is non-limiting, and the described techniques can be applied to the processing of many other types of layers and / or devices, regardless of whether these layers are light-emitting and whether the device is a display device. In this exemplary application, various conventional design constraints of inkjet printheads present challenges to the process efficiency and film coating uniformity of the various layers of an OLED stack that can be printed using various inkjet printing systems. These challenges can be addressed through the teachings herein.

[0055] More specifically, Figure 3B is a plan view of one embodiment of the printer 321. The printer includes a printhead assembly 323 used to deposit fluid ink onto a substrate 325. Unlike printer applications for printing text and graphics, the printer 321 in this embodiment 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 the finished device, and that layer has a specifically desired thickness. The thickness of the layer produced by the deposition of fluid ink 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 monomers, polymers, or materials carried by a solvent or other transport medium. In one embodiment, these materials are organic. Following ink deposition, 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 liquid monomer into a solid polymer, while other processes dry the ink to remove the solvent and leave the material transported to a permanent location. Other processes are also possible. It should be noted that there are many other variations that distinguish the described printing process from conventional graphics and text applications. For example, in some embodiments, the deposition of the desired material layer is carried out in an environment that is controlled to either modify the ambient atmosphere to be non-air or otherwise exclude unwanted particulate matter. For example, as will be further described below, one considered application uses a processing mechanism that encapsulates the printer 321 in a gas chamber so that printing can be carried out in the presence of a controlled atmosphere, such as an inert environment, which includes, but is not limited to, nitrogen, any of the noble gases, and any combination thereof.

[0056] As can be seen further in Figure 3B, the printhead assembly 323 includes several nozzles, such as nozzle 327. Note that in Figure 3B, for the sake of illustration, the printhead assembly 323 and nozzles are depicted as opening outwards from the top of the page; however, in reality, these nozzles face downward toward the substrate and are hidden from view in Figure 3B (i.e., Figure 3B actually shows what is a cross-section of the printhead assembly 323). The nozzles are arranged in rows and columns (example row 3). It can be seen that the nozzles are arranged in rows 28 and 329, etc., but this is not required in all embodiments; that is, some implementations use only one row of nozzles (row 328, etc.). In addition, rows of nozzles can be positioned on each printhead, and each printhead can be (optionally) individually offset from one another as described above. In applications where the printer is used to process materials for each of the red, green, and blue components of a 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 or printhead assembly.

[0057] Figure 3B illustrates the printhead assembly 323 (i.e., one or more individual printheads are not depicted separately). The printer 321 includes two different motion mechanisms that can be used to position the printhead assembly 323 relative to the substrate 325 in this embodiment. Firstly, a traveler or carriage 331 can be used to mount the printhead assembly 323 and to enable relative motion as represented by arrow 333. This motion mechanism can also optionally transport the printhead assembly 323 to a service station, if present, such a service station, represented by the number 334 in Figure 3B. Secondly, 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 335, the substrate transport mechanism can enable movement in each of two orthogonal directions, such as x and y according to the Cartesian dimensions (337), and optionally can assist in substrate rotation. In one embodiment, the substrate transport mechanism comprises a gas-floating table used to selectively ensure and enable the movement of the substrate on a gas bearing. Furthermore, it should be noted that the printer optionally allows rotation of the printhead assembly 323 relative to the traveler 331, as represented by the rotation graphic 338. Such rotation allows the apparent spacing and relative configuration of the nozzles 327 to be changed with respect to the substrate, for example, if each target area of ​​the substrate is defined as a specific area, or to have spacing to another target area, the rotation of the printhead assembly and / or the substrate can change the relative separation of the nozzles along or perpendicular to the scanning direction. In embodiments, for example, the elevation of the printhead assembly 323 relative to the substrate 325 can also be changed along the z-Cartes dimension, in and out of the diagram direction in Figure 3B.

[0058] The two scan paths are illustrated by directional arrows 339 and 340 in Figure 3B, respectively. Briefly, the substrate motion mechanism moves the substrate back and forth in the directions of arrows 339 and 340 as the print head moves in geometric steps or offsets in the direction of arrow 333. Using a combination of these movements, the nozzles of the print head assembly can reach any desired area on the substrate to deposit ink. As previously referenced, the ink is deposited into discrete target areas on the substrate according to a controlled standard. These target areas can optionally be aligned, i.e., arranged, in rows and columns, equal to, along the depicted y and x dimensions, respectively. Note that in this figure, a row of nozzles (e.g., row 328) is viewed perpendicular to the rows and columns of the target areas, i.e., one row of nozzles sweeps along the direction of the row of target areas with each scan and traverses each of the columns of target areas on the substrate (e.g., along direction 339). This does not necessarily apply to all embodiments. For the efficiency of the motion, subsequent scans or passes then reverse the direction of this motion and address the column of target regions in the reverse order, i.e., along direction 340.

[0059] The target region arrangement in this embodiment is depicted by the highlighted region 341, which can be seen in the enlarged view on the right side of the figure. That is, two rows of pixels, each having red, green, and blue components. Each element is represented by the digit 343, while rows of pixels perpendicular to the scan direction (339 / 340) are represented by the digit 345. In the top-leftmost pixel, the red, green, and blue components occupy specific target regions 347, 349, and 351 as part of their respective overlapping arrays. Each color component within each pixel may also have associated electronics, for example, represented by the digit 353. If the device being fabricated is a backlit display (e.g., as part of a conventional LCD television), these electronics can control the selective masking of light filtered by the red, green, and blue regions. If the device being fabricated is a newer type of display, i.e., where the red, green, and blue regions directly produce their own colors with corresponding color properties, these electronics 353 may include patterned electrodes and other material layers that contribute to the desired photogeneration and optical properties.

[0060] Figure 3C provides a close cross-sectional view of the printhead 373 and substrate 375 obtained from the viewpoint of line CC relative to the printhead assembly in Figure 3B. More specifically, the number 371 generally represents the printer, while the number 378 represents a row of print nozzles 377. Each nozzle is designated using a number in parentheses, e.g., (1), (2), (3), etc. A typical printhead has multiple such nozzles, typically, for example, 64, 128, or another number, and in one embodiment there may be 1,000 to 10,000 or more nozzles arranged in one or more rows. As previously stated, the printhead in this embodiment is moved relative to the substrate to achieve a geometric step or offset between scans in the direction referenced by arrow 385. Depending on the substrate motion mechanism, the substrate can also be moved perpendicular to this direction (e.g., in and out of the page relative to the figure in Figure 3C), and in some embodiments, in the direction represented by arrow 385. Note that Figure 3C also shows a row 383 of each target region 379 on the substrate, arranged as “wells” that will receive the deposited ink and hold the deposited ink within the structural constraints of each well. For the purposes of Figure 3C, it will be assumed that only one ink is represented (for example, each depicted well 379 represents only one color of the display, such as the red component, and other color components and associated wells are not shown). Note that the drawing is not strictly to scale, for example, that the nozzles are numbered from (1) to (16), while the wells are lettered from (A) to (ZZ), representing 702 wells. In some embodiments, the nozzles will align with each well so that a depicted printhead with 16 nozzles deposits ink in as many as 16 wells simultaneously in the direction of arrow 381, using a scan of the relative printhead / substrate motion in and out of the page from the viewpoint of Figure 3C.In other embodiments, such as those previously described (see, for example, Figure 1B), the nozzle density is even greater than the target area density, and with 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 within each target area. For example, again using an illustrative embodiment of 16 nozzles, it may be possible to use nozzles (1)-(3) to deposit ink in a first target area and nozzles (7)-(10) to deposit ink in a second target area, mutually exclusive with respect to a given pass.

[0061] Conventionally, a printer may be operated to use 16 nozzles to deposit ink simultaneously in as many wells as 16 rows, moving back and forth as needed with the next scan until, for example, 5 drops of ink are deposited in each well, and the print head is advanced as needed using fixed steps that are integer multiples of the width of the strip of area traversed by the scan. However, the technique provided by this disclosure generates a specific amount of ink for each well using different nozzles in a combination calculated to produce a specific amount of ink for each well. The inherent variation in the amount of droplets to be deposited is utilized. Different embodiments rely on different techniques to achieve these combinations. In one embodiment, the geometric step can be varied to achieve different combinations and can be free to be anything other than an integer multiple of the width represented by the strip location of the printhead. For example, if appropriate for depositing a set of selected droplet combinations in each well 379 in Figure 3C, the geometric step could actually be 1 / 160th of the strip location of the printhead, representing the relative displacement between the printhead and the substrate at intervals of 1 / 10th of a row of wells in this embodiment. The next offset or geometric step may vary as appropriate for a particular combination of droplets desired in each well, for example, it could be a virtual offset of 5 / 16th of the strip location of the printhead, corresponding to an integer interval of wells. This variation can continue as both positive and negative steps as necessary to deposit the ink and obtain the desired fill amount. Note that many different types or sizes of offsets are possible, and the step size does not need to be fixed between scans or a particular percentage of the well spacing. However, in many manufacturing applications, it is desirable to minimize printing time in order to maximize production speed and minimize manufacturing cost per unit. To achieve this objective, in specific embodiments, the printhead movement 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 step. These or other measures can be used individually, together, or in any desired combination to minimize the total printing time.In embodiments where independently offsettable rows of nozzles (e.g., multiple printheads) are used, the geometric step can be partially represented by offsets between printheads or nozzle rows, combined with an overall offset of printhead components (e.g., a fixed step of the printhead assembly), such offsets can be used to achieve a variable-size geometric step and thus to deposit droplet combinations into each well. In embodiments where variations in nozzle drive waveforms are used alone, a conventional fixed step can be used, and droplet volume variations are achieved using multiple printheads and / or multiple printhead passes. In one embodiment, as described below, a nozzle drive waveform can be programmed for each nozzle between droplets, thus enabling each nozzle to generate and provide its respective droplet volume per well in a row of wells.

[0062] Figures 4A-4D are used to provide additional details regarding the reliance on specific droplet volumes when achieving the desired filling volume.

[0063] Figure 4A presents an illustrative Figure 401 of the printhead 404 and two related schematic diagrams seen below the printhead 401. The printhead is used in embodiments to optionally provide an unfixed geometric step of the printhead relative to the substrate, and the number 405 is used to represent an offset that aligns a particular printhead nozzle (for example, a total of 16 nozzles with nozzles (1)-(5) depicted in the figure) with a different target area (in this embodiment, five: 413, 414, 415, 416, and 417). Recalling the embodiment in Figure 1A, if nozzles (1)-(16) produce droplet amounts of fluid ink (e.g., average droplet amounts) 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 plus ±0.5 percent of this value, the printhead can be used to deposit droplets in five passes or scans using geometric steps of 0, -1, -1, -2, and -4, respectively, resulting in (expected average) 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 depicted target areas. Although all steps in this embodiment are expressed progressively relative to the previous position, other measures can also be used. Depending on the variation per expected droplet volume, it is still possible to virtually guarantee that the filling will conform to the desired tolerance range. For example, by performing many droplet measurements (e.g., 20 to 30 or more droplet measurements per nozzle) as referenced above, the expected variance of each droplet volume can be made extremely small, enabling high confidence in the variance of the expected composite volume. Thus, as shown, to achieve highly reliable and precisely controlled filling, a combination of droplets in an intentional manner can be used, depending on the respective droplet volume for each target area and the desired filling.

[0064] It should be noted 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 droplet volume for a single nozzle generated by 16 different drive waveforms (i.e., using waveforms 1-16), then the theoretical fill volume per area can simply be obtained by using different drive waveforms, e.g., waveform numbers 1, 2, 3, 5, and 9, on the target area 413. In practice, since process variations can result in different per-nozzle characteristics, the system would measure the droplet volume for each nozzle for each waveform and intelligently plan droplet combinations based on this criterion. 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), offsets between printheads can be used to reduce the number of passes or scans. For example, the rightmost target region 417 may have three droplets deposited in a single pass, including droplet amounts of 10.03, 10.09, and 9.97 pL (printhead (1), 0 offset; printhead (2), +1 offset; and printhead (3), +2 offset). It should be evident that combinations of these various techniques facilitate many possible combinations of specific droplet amounts to achieve a particular fill amount within tolerance. Note that in Figure 4A, the dispersion of total ink fill amounts between target regions is small and within tolerance, i.e., within the range of 49.82 pL to 50.16 pL.

[0065] Figure 4B shows an illustrative Figure 421 of a series of printhead scans, where each scan is perpendicular to the direction of arrow 422 and the nozzles are represented by different rectangles or bars, as referenced by the numbers 423-430. In relation to this figure, assume that the printhead / substrate relative motion is advanced in a series of variable-sized geometric steps. Again, note that typically each step would specify a scan that sweeps multiple columns of the target area (e.g., pixels) beyond one column of five areas represented on the plane of the drawing page (and represented by the numbers 413-417). Scans are shown in top-to-bottom order, including the first scan 423, where only nozzles (1) and (2) appear to be displaced to the right relative to the substrate so that they are aligned with target areas 416 and 417, respectively. Within each print scan depiction (e.g., box 423), each nozzle is represented either by being filled in black to indicate that the nozzle is fired when it covers a target area specifically depicted during the scan, or by being "hollow," i.e., filled in white, to indicate that the nozzle is not fired at the relevant time (but may fire 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 an arbitrary adjustable parameter to deposit a predetermined amount of droplets for each target area encountered during the scan. This "binary" firing method may optionally be used in any of the embodiments described herein (i.e., using multiple firing waveforms, for example, where the waveform parameter is adjusted between droplets). This can be employed in the following embodiment. In the first pass 423, nozzle (1) is fired to deposit a 9.80 pL droplet into the second-rightmost target area, while nozzle (2) is fired to deposit a 10.01 pL droplet into the rightmost target area 417. The scan continues to sweep other columns of the target area (e.g., other rows of the pixel well) by depositing ink droplets as appropriate. After the first pass 423 is completed, the print head is advanced by a geometric step of -3, moving the print head to the left relative to the substrate, so that nozzle (1) traverses the target area 413 during the second scan 424 in the opposite direction to the first scan. During this second scan 424, nozzles (2), (3), (4), and (5) will also traverse areas 414, 415, 416, and 417, respectively. The blacked-out circles indicate that nozzles (1), (2), (3), and (5) will fire droplets of 9.80 pL, 10.01 pL, 9.89 pL, and 10.03 pL, respectively, at appropriate times, corresponding to the unique characteristics of each nozzle. Furthermore, it should be noted that in any single pass, the nozzles in a row of nozzles used to deposit ink will mutually deposit ink into their respective target areas. For example, in pass 424, nozzle (1) is used to deposit ink into target area 413 (and not into any of the target areas 414-417), nozzle (2) is used to deposit ink into target area 414 (and not into areas 413 or 415-417), nozzle (3) is used to deposit ink into target area 415 (and not into areas 413-414 or 416-417), and nozzle (5) is used to deposit ink into target area 417 (and not into any of the areas 413-416).The third scan, represented by the number 425, effectively advances the printhead by one row of target areas (-1 geometric step) so that nozzles (2), (3), (4), (5), and (6) traverse areas 413, 414, 415, 416, and 417, respectively, during the scan. The filled nozzle graphic indicates that during this passage, each of nozzles (2)-(6) will be activated to fire a droplet, producing expected droplet volumes of 10.01, 9.89, 9.96, 10.03, and 9.99 pL, respectively.

[0066] If the printing process were stopped at this point, region 417 would have a fill of 30.03 pL (10.01 pL + 10.03 pL + 9.99 pL), corresponding to, for example, three droplets, while region 413 would have a fill of 19.81 pL (9.80 pL + 10.01 pL), corresponding to two droplets. Note that in one embodiment, the scan pattern follows the front-to-back pattern represented by arrows 339 and 340 in Figure 3B. The next pass of these target regions 426-430 (or scan of multiple columns of multiple such regions) respectively will be (a) 10.01 pL, 0.00 pL, 0.00 pL, 10.08 pL, and 10.09 pL droplets in region 413, corresponding to the pass by nozzles (2), (3), (4), (7), and (9) in a continuous scan; (b) 0.00 pL, 0.00 pL, 10.03 pL, 10.00 pL, and 10.07 pL droplets in region 414, corresponding to the pass by nozzles (3), (4), (5), (8), and (10) respectively in a continuous scan; and (c) 4) (5), (6), ( (9) and (11), droplets of 9.89 pL, 9.96 pL, 10.03 pL, 9.99 pL, 10.09 pL, and 0.00 pL are deposited in region 415, corresponding to passage by nozzles (5), (6), (7), (10), and (12) in a continuous scan, droplets of 0.00 pL, 9.99 pL, 10.08 pL, 10.07 pL, and 0.00 pL are deposited in region 416, corresponding to passage by nozzles (5), (6), (7), (10), and (12) in a continuous scan, and droplets of 9.99 pL, 0.00 pL, 10.00 pL, 0.00 pL, and 0.00 pL are deposited in region 417, corresponding to passage by nozzles (6), (7), (8), (11), and (13) in a continuous scan. Again, note that in this embodiment, the nozzles are used with only a single firing waveform on a binary basis (i.e., so that their droplet volume characteristics do not change with each scan). For example, in the fifth scan 427, the nozzle (7) does not fire and does not produce a droplet for region 417 (0.00 pL), while in the next scan, it fires and produces a 10.08 pL droplet for region 416.

[0067] As can be seen in the graph at the bottom of the page, this virtual scanning process easily generates expected 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). Note that in this embodiment, the nozzle is used to deposit ink into multiple target areas almost simultaneously for each scan, and specific combinations of droplet amounts for each drawn area (i.e., as graphically identified by the numbers 413-417) were planned so that multiple droplets could be deposited in each target area through many passes. Each of the eight described passes correlates with a specific set (or combination) of droplet amounts that produce a fill volume within a given tolerance range (e.g., for region 413, a combination of droplets from nozzles (1), (2), (2), (7), and (9)), although other sets of possible droplets could also have been used. For example, for region 413, an alternative could have been 5 droplets from nozzle (2) (5 × 10.01 pL = 50.05 pL). However, this alternative would have been inefficient because it would have required an additional scan, as nozzle (3) (9.89 pL) could not have been used extensively simultaneously during this time (i.e., the result from 5 droplets from this nozzle would have been 5 × 9.89 = 49.45 pL, outside the desired tolerance range). In the embodiment shown in Figure 4B, specific 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 criterion. It should be noted that the depicted embodiment is for descriptive discussion purposes only, and it may be possible to further reduce the number of scans using the presented droplet volume to fewer than eight to achieve target filling.In some embodiments, the scanning process is planned in a manner that avoids worst-case scenarios, along with the number of scans required (e.g., one scan per row of target area using a printhead rotated 90 degrees). In other embodiments, this optimization is applied to a degree based on one or more maximum or minimum values, for example, by planning the scans in a manner that results in the fewest possible scans, taking into account all possible droplet combinations for each target area for a given ink.

[0068] Figure 4C presents a schematic diagram similar to Figure 4B, but corresponding to the use of different nozzle drive waveforms for each nozzle. As should be understood, in an inkjet printhead, ink is typically ejected using a piezoelectric actuator that expands and contracts a fluid reservoir to eject ink from each printing nozzle. The ink is usually kept in the reservoir under a slight negative pressure to avoid flooding of the nozzle plate, accompanied by voltage pulses applied to the actuator to eject droplets with properties that depend on the size and shape of the voltage pulses. Thus, different pulse characteristics can result in different amounts, velocities, and other properties of the ejected droplets. In Figure 4C, it should be assumed that different pre-planned voltage pulse waveforms are determined to produce a range of different droplet amounts (and associated droplet amount probability distributions). Scans are generally referred to by the number 441, with each of scans 443-447 occurring perpendicular to bars 443-447. Within each scan bar (e.g., box 443), the numerical designation represents a specific printhead nozzle, while the letter designation represents a different waveform for that particular nozzle. For example, reference "1-A" represents the first drive waveform "A" used for the actuator for nozzle (1), while reference "1-C" represents the third drive waveform "C" used for the actuator for nozzle (1). Note that during the calibration procedure, any desired number of waveforms can be tested to select the waveform that produces the expected droplet volume (or the volume of multiple droplets) that matches the ideal target droplet volume. In Figure 4C, for example, testing multiple waveforms for nozzle (1) may result in two specific waveforms (e.g., "A" and "C") producing expected droplet volumes close to the desired 10.00 pL average, e.g., 9.94 pL and 10.01 pL averages, respectively. In other words, if the tests cannot produce an expected average that precisely matches the ideal droplet volume (e.g., 10.00 pL), two or more waveforms can be selected that group together the desired ideal volumes, e.g., 9.94 pL / 10.01 pL, 9.99 pL / 10.01 pL, 10.03 pL / 9.95 pL, and 9.95 / 10.04 pL, as described for nozzles (1), (3), (4), and (5).Similar to the embodiments described above, different droplets can then be combined using different nozzle drive waveforms to specifically plan the total filling for each target region that is within the desired tolerance. Note that, in the embodiment of Figure 4C, it is not necessary to offset the printhead assembly between scans to achieve these combinations, but in many embodiments, the use of multiple nozzle waveforms can be combined with a partial band-space width offset to produce many possible droplet combinations that can be used to generate targeted filling using a minimum number of scans (and thus minimum printing time per substrate). In Figure 4C, it can be seen that the depicted process produces very tightly grouped virtual fillings, e.g., expected filling amounts of 49.99 pL to 50.02 pL.

[0069] Figure 4D presents two related schematic diagrams of the printhead 474, similar to Figure 4A but here having nozzles not specifically aligned to particular wells, as seen in illustrative Figure 471 and below the printhead 474. The printhead is used in embodiments to optionally provide an unfixed geometric step of the printhead relative to the substrate, and the number 472 is used to represent an offset that aligns a particular printhead nozzle (e.g., a total of 16 nozzles with nozzles (1)-(5) depicted in the figure) to different target areas (in this embodiment, two, 474 and 475). Again, according to the embodiment in Figure 4A, if nozzles (1)-(16) produce expected droplet volumes of fluid ink 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 plus ±0.5 percent of this value, the print head can be used to deposit droplets in three passes or scans by using geometric steps of 0, -1, and -3, respectively, firing one or two droplets into each target area per scan. This, again, clearly, will result in a total fill value of 49.93 or 50.10 per region, as depicted in the figure, which is 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 is equally applicable to nozzles not aligned to the well, and a combination of droplets in an intentional manner can be used, depending on the respective droplet volume for each target region and the desired fill, in order to achieve precisely controlled fill. Furthermore, as explained above regarding the hypothesis in Figure 4A, this same figure 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 droplet volume for a single nozzle produced by 16 different drive waveforms (i.e., using waveforms 1-16), then the theoretical fill volume per region can simply be obtained by using different drive waveforms.Those skilled in the art will see, with reference to Figures 4B-4C, that the same approach described above also applies equally to nozzles that are not specifically aligned to wells, i.e., groups of one or more nozzles used for simultaneous droplet deposition into each well. Finally, it should be noted that Figures 4A-D also represent a relatively simple embodiment, and in a typical application, there can be hundreds to thousands of nozzles and millions of target areas. For example, in an application where the disclosed technique is applied to the processing of each pixel color component of a current high-resolution television screen (e.g., each pixel has red, green, and blue wells, and the pixels are arranged with 1080 horizontal lines for vertical resolution and 1920 vertical lines for horizontal resolution), there are approximately 6 million wells that can accept ink (i.e., three overlapping arrays of 2 million wells each). Next-generation televisions are expected to increase this resolution fourfold or more. In such processes, to improve printing speed, the printhead may use thousands of nozzles for printing, and typically there would be an overwhelming number of possible printing process permutations, for example. While the simplified examples presented above are used to introduce the concepts, it should be noted that the permutations represented by real-world television applications are extremely complex, given the overwhelming number of typical combinations presented, and print optimization is typically applied by software and involves complex mathematical operations. Figures 5-7 are used to provide non-limiting examples of how these operations can be applied.

[0070] An exemplary process for planning a print job is shown in Figure 5. This process, as well as related methods and devices, are generally referred to by the number 501.

[0071] More specifically, the droplet volume for each nozzle (and for each nozzle for each waveform if multiple drive waveforms are applied) is determined specifically (503). Such measurements can be performed using a variety of techniques, including, but are not limited to, optical or laser imaging or non-imaging devices incorporated into the printer (or factory-resident machine) that measure droplets in flight (e.g., during a calibration print operation or a live print operation) and calculate the volume with accuracy based on droplet shape, velocity, trajectory, and / or other factors. In specific embodiments, each measurement is only approximately accurate, as even the droplet volume from a single nozzle produced using a single drive waveform can vary by droplet, as described. In this regard, droplet measurement techniques can be used to generate statistical models for droplets from each nozzle and for each nozzle-waveform combination, where each particular droplet volume is expressed as the average expected droplet volume from a given nozzle and a given nozzle drive waveform. Other measurement techniques can also be used, including printing ink and then using post-print imaging or other techniques to calculate individual droplet volumes based on pattern recognition. Alternatively, identification can be based on data supplied by the printer or printhead manufacturer, for example, measurements taken in the factory well in advance of the processing process and supplied to the machine (or online). In some applications, droplet volume characteristics may change over time depending on, for example, ink viscosity or type, temperature, nozzle clogging, or other degradation, or due to other factors. Therefore, in one embodiment, droplet volume measurements can be performed dynamically in situ with each new print on the substrate, for example, at power-up (or during other types of power cycle events), at the end of a predetermined time or on a different calendar or non-calendar basis. In one embodiment, such measurements are performed intermittently or continuously, as previously referenced, by taking measurements against the moving window of the print nozzle and nozzle waveform combination each time a new flat panel substrate is loaded or unloaded, in order to obtain dynamic updates. As represented by the number 504, this (measured or provided) data is stored for use in the optimization process.

[0072] In addition to droplet volume data per nozzle (or optionally per drive waveform), information (505) regarding the desired fill amount for each target area is also received. This data may be a single target fill value applied to all target areas, each target fill value applied to individual target areas, rows of target areas, or columns of target areas, or values ​​broken down in some other way. For example, as applied to processing a single “blanket” layer of a large material for individual electronic device structures (such as transistors or paths), such data may consist of a single thickness applied to the entire layer (which the software then converts to a desired ink fill amount per target area based on predetermined conversion data specific to the ink in question). In such a case, the data may consist of each “print cell” (in this case, each target The data can be converted to a common value of a target region (which may be equivalent to or comprise multiple target regions). In another embodiment, the data may represent a specific value (e.g., 50.00 pL) of one or more wells, where range data is either provided or understood on a contextual basis. As should be understood from these embodiments, the desired filling can be specified in many different forms, including, but not limited to, thickness data or volume data. Additional filtering or processing criteria can also be optionally provided to or performed by the receiving device. For example, as previously referenced, random variations in filling volume can be injected by the receiving device into one or more provided thickness or volume parameters to make linear effects invisible to the human eye in the finished display. Such variations can be pre-processed (provided as filling per respective target region, varying by region) or can be transparently derived independently of the receiving device (e.g., by a downstream computer or printer).

[0073] Based on the target fill volume for each region and individual droplet volume measurements (i.e., per printhead nozzle and drive waveform per nozzle), the process then optionally calculates various droplet combinations that sum up to a desired fill volume within a tolerance range (i.e., by process block 506). As described, this range can provide target fill data or, on a contextual basis, "understand". 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 within the tolerance range, whether larger or smaller than these exemplary ranges.

[0074] At this point, the example will help convey one possible method for calculating a set of possible droplet combinations. Returning to the simplified example described earlier, suppose we have five nozzles, each having a hypothetical average droplet volume of 9.80 pL, 10.01 pL, 9.89 pL, 9.96 pL, and 10.03 pL respectively, and it is desired to deposit a target volume of 50.00 pL ± 0.5 percent (49.75 pL to 50.25 pL) in five wells. This method begins by determining the number of droplets that can be combined so as to reach but not exceed the tolerance range, and for each nozzle, the minimum and maximum number of droplets from that nozzle that can be used in any allowed permutation. For example, in this hypothesis, taking into account the minimum and maximum droplet volumes of the nozzles under consideration, it would be expected that just one droplet from nozzle (1), two droplets from nozzle (3), and four droplets from nozzle (4) are available in any combination. This step limits the number of combinations that need to be considered. Equipped with such constraints on the set consideration, the method then takes each nozzle in turn and considers combinations of the required number of droplets (5 droplets in this embodiment). For example, the method first begins with nozzle (1), understanding that only the acceptable combination with this nozzle features one or fewer droplets from this nozzle. Having considered combinations with a single droplet from this nozzle, the method then considers the minimum and maximum droplet amounts for the other nozzle-waveform combinations under consideration. For example, considering that nozzle (1) is determined to produce a droplet amount of 9.80 pL for a given drive waveform, just one droplet from nozzle (3) or two droplets from nozzle (4) can be used in combination with the droplet from nozzle (1) to reach the desired tolerance range. This method then considers combinations of droplets from nozzle (1) and combinations of four droplets from other nozzles, for example, four droplets from nozzle (2) or (5), three droplets from nozzle (2), and one droplet from nozzle (4).Considering combinations involving only nozzle (1), for the sake of simplification of the discussion, any of the following different combinations involving the first nozzle, namely {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)}, can potentially be used within the tolerance range. In the formulas described above, the use of square brackets represents a set of five droplets, each representing a combination of droplet amounts from one or more nozzles, with each parenthetical bracket within these square brackets identifying a specific nozzle. For example, formula {1(1),4(2)} represents 9.80 pL + (4 × 10.01 pL) = 49.84 pL, which is expected to produce a composite filling within a specific tolerance range, consisting of one droplet from nozzle (1) and four droplets from nozzle (2). In practice, the method in this embodiment considers the maximum number of droplets from nozzle (1) that can be used to produce the desired tolerance based on various averages, evaluates the combinations with this maximum number, reduces the number by one, and repeats the consideration process. In one embodiment, this process is repeated to determine all possible sets of non-redundant droplet combinations that can be used. When all combinations involving nozzle (1) have been explored, the method proceeds to combinations involving nozzle (2) instead of nozzle (1), repeats the process, and tests the composite average of each possible nozzle combination to determine whether the desired tolerance range can be achieved. For example, in this embodiment, since the method determines that combinations of two or more droplets from nozzle (1) cannot be used, it begins by considering various combinations involving one droplet from nozzle (1) and four droplets from other nozzles.This method actually evaluates whether four droplets from nozzle (2) can be used and determines that this could be {1(1),4(2)}, then reduces this number by 1 (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 the acceptable sets {1(1),3(2),1(4)} and {1(1),3(2),1(5)}. Next, this method further reduces the number of acceptable droplets from nozzle (2) to {1(1),2(2)...}, and then evaluates combinations such as {1(1),1(2)...}. Once combinations involving nozzle (2) have been considered in combination with droplets from nozzle (1), this method then takes in the next nozzle, namely nozzle (3), and considers combinations of nozzle (1) with this nozzle instead of nozzle (2), and determines that the only acceptable combination is {1(1),1(3),3(5)}. Once all combinations involving droplets from nozzle (1) have been considered, the method then considers combinations of 5 droplets involving droplets from nozzle (2) instead of 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.

[0075] It should also be noted that the same approach applies equally when the nozzle can be driven by multiple firing waveforms (each generating a different droplet volume). These additional nozzle-waveform combinations simply provide an additional droplet volume average for use when selecting a set of droplet combinations that are within the tolerance range of the target volume. The use of multiple firing waveforms can also improve the efficiency of the printing process by making a larger number of acceptable droplet combinations available, thereby increasing the possibility of simultaneously firing droplets from a large portion of the nozzle in each pass. When the nozzle has multiple drive waveforms and geometric steps are also used, the selection of a set of droplet combinations will incorporate both the geometric offset used in a given scan and the nozzle waveforms that will be used for each nozzle.

[0076] For the purpose of this description, a forceful approach is explained, and it should be noted that, for example, an overwhelming number of possible combinations will typically be presented in practice, such as a large number of nozzles and target areas (e.g., more than 128 each). The calculations are well within the capabilities of a high-speed processor with appropriate software. It should also be noted that various mathematical shortcuts exist that can be applied to reduce calculations. For example, in a given embodiment, the method can exclude from consideration any combination that would correspond to the use of less than half of the available nozzles in any single pass (or, alternatively, limit consideration to combinations that minimize quantity variation across the target region (TR) in any single pass). In one embodiment, the method determines only a set of droplet combinations that would produce an acceptable composite fill value, while in a second embodiment, the method thoroughly calculates all possible sets of droplet combinations that would produce an acceptable composite fill value. It is also possible to use an iterative approach in which print scans are performed over multiple iterations, and the amount of ink still not deposited to reach the desired tolerance range is considered for the purpose of optimizing subsequent scans. Other approaches are also possible.

[0077] Furthermore, it should be noted that, as an initial operation, if the same fill value (and tolerance) is applied to each target region, it may suffice to calculate the combinations once (for example, for one target region) and to store these possible droplet combinations for initial use with each target region. This is not necessarily true for all set calculation methods and all applications (for example, in some embodiments, the allowable fill range may vary for all target regions).

[0078] In yet another embodiment, the method uses mathematical shortcuts such as approximation, matrix mathematics, random selection, or other techniques to determine the set of acceptable droplet combinations for each target region.

[0079] As represented by process block 507, once a set of acceptable combinations is determined for each target region, the method then effectively plans scans in a manner correlated with a specific set (or combination of droplets) for each target region. This specific set selection is made such that the specific set (one for each target region) represents process savings through the use of at least one scan to simultaneously deposit droplet amounts in multiple target regions. That is, in the ideal case, the method selects one specific set for each target region, the specific set representing a specific combination of droplet amounts such that the print head can simultaneously print into multiple rows of the target region at once. The selection of specific droplets in the selected combination represents a printing process that meets predetermined criteria such as minimum print time, minimum number of scans, minimum geometric step size, minimum total geometric step distance, or other criteria. These criteria are represented by the number 508 in Figure 5. In one embodiment, the optimization is Pareto optimal, where the specific set is selected in a manner that minimizes the number of scans, the total geometric step distance, and the geometric step size, in that order. Again, the selection of this particular set can be done in any desired manner, with several non-restrictive embodiments being discussed further below.

[0080] In one embodiment, the method selects droplets from each set for each target region corresponding to a specific geometric step or waveform applied to all regions under consideration, then subtracts these droplets from the available sets and determines the remainder. For example, the selection of available sets might 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)} If the order is {1(1),1(4),3(5)} and {1(1),4(5)}, this embodiment would subtract one droplet (1) from the first set to obtain a residue specific to the first of the five target regions, subtract one droplet (2) from the first set to obtain a residue specific to the second of the five target regions, subtract one droplet (3) from the first set to obtain a residue specific to the third of the target regions, and so on. This evaluation would represent a geometric step of "0". The method would then evaluate the residue and repeat the process for other possible geometric steps. For example, if a geometric step of "-1" is then applied, the method would evaluate the residue by subtracting one droplet (2) from the first set for the first of the five target regions, subtracting one droplet (3) from the first set for the second of the target regions, and so on.

[0081] When selecting specific geometric steps (and nozzle firings) as part of a print plan, this method analyzes various residuals according to scoring and preference functions and selects the geometric step with the best score. In one embodiment, scoring is applied to give greater weight to steps that (a) maximize the number of nozzles used simultaneously and (b) maximize the minimum number of combinations remaining for the affected target area. For example, a scan using droplets from four nozzles during scanning would be much preferred over one using droplets from only two nozzles. Similarly, if, when considering different steps, the subtraction process discussed above results in one possible step having 1, 2, 2, 4, and 5 remaining combinations for each target area, and a second possible step having 2, 2, 2, 3, and 4 remaining combinations for each target area, this method would give greater weight to the latter (i.e., the maximum minimum is "2"). In practice, a suitable weighting coefficient can be derived empirically. Clearly, other algorithms can be applied, and other forms of analysis or algorithmic shortcuts can be applied. For example, matrix mathematics (e.g., using eigenvector analysis) can be used to determine a specific combination of droplets and the associated scan parameters that satisfy a given criterion. In another variation, other formulas can be used, for example, to take into account the use of random packing variation designed to mitigate linear effects.

[0082] Once a specific set and / or scan path is selected by the digit 507, the printer operations are ordered by the digit 509. For example, if the total fill amount is the only consideration, it is typically possible to deposit sets of droplets 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 movement. For example, if the allowable scans in a hypothetical embodiment involve relative geometric steps of {0, +3, -2, +6, and -4}, these scans can be rearranged to minimize printhead / substrate movement and thus further improve printing speed, for example, by ordering the scans as a series of steps of {0, +1, +2, 0, and +4}. Compared to the first set of geometric steps {0, +3, -2, +6, and -4} with a total step increment distance of 15, the second set of geometric steps {0, +1, +2, +0, and +4} has a total step increment distance of 7, which facilitates a faster printer response.

[0083] For applications involving multiple rows of target regions that accept the same target filling, as represented by the number 510, a specific solution may also be represented as a repeatable pattern that can be reproduced across subset regions of the substrate. For example, in a given application, if there are 128 nozzles arranged in a single row and 1024 rows of target regions, the optimal scan pattern can be determined for a subset region of 255 rows or fewer of target regions, and therefore, in this embodiment, it is expected that the same print pattern can be applied to four or more subset regions of the substrate. Accordingly, some embodiments utilize repeatable patterns, such as those represented by an arbitrary process block 510.

[0084] Note the use of the non-transient machine-readable medium icon 511. This icon indicates that the methods described above may optionally be implemented as instructions for controlling one or more machines (e.g., software or firmware for controlling one or more processors). The non-transient medium may include any machine-readable physical medium, such as a flash drive, floppy disk, tape, server storage or mass storage device, dynamic random access memory (DRAM), compact disk (CD), or other local or remote storage device. This storage device may be implemented as part of a larger machine (e.g., resident memory in a desktop computer or printer) or on an isolated basis (e.g., a flash drive or standalone storage device that will later transfer files to another computer or printer). Each function described with reference to Figure 5 may be implemented as part of a composite program, stored together on a single media representation (e.g., a single floppy disk), or on multiple separate storage devices, or as a standalone module.

[0085] As represented by the number 513 in Figure 5, once the planning process is complete, 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, which effectively represents the scan path, scan sequence, and other data, is an electronic file (513) that can either be stored for later use (as depicted, for example, by the non-transient machine-readable media icon 515) or applied immediately to control the printer (517) to deposit ink representing a selected combination (a specific set of nozzles per target area). For example, this method can be applied on a standalone computer, where the instruction data is stored in RAM for later use or to be downloaded to another machine. Alternatively, this method can be implemented to automatically plan the scan depending on printer parameters (nozzle droplet volume data, etc.) and applied dynamically by the printer to the "incoming" data. Many other alternatives are possible.

[0086] Figures 6A-6D provide a schematic diagram of the nozzle selection and scan planning process in general. Again, note that the scan does not need to be continuous or linear in direction or speed of movement, nor does it need to move from one side of the substrate to another.

[0087] The first block diagram is represented by the number 601 in Figure 6A. This diagram represents many of the exemplary processes discussed in the preceding description. The method begins by first retrieving a set of combinations of permissible droplet amounts for each target region from memory, represented by the number 603. These sets could be calculated dynamically or could be pre-calculated, for example, using software on different machines. Note the use of the 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 one particular set of permissibles for each target region (607). This selection is indirect in many embodiments, meaning the method processes the permissible combinations to select a particular scan (e.g., using the techniques referenced above), and it is these scans that actually define the particular set. Nevertheless, by planning the scans, the method selects a particular set of combinations for each target region. This data is then used to order the scans and put together motion and firing patterns, as referenced above (609).

[0088] The center and right of Figure 6A illustrate several process options for planning the scan path and nozzle firing pattern, and for selecting a specific droplet combination for each target area in a manner that represents print optimization. As shown by the number 608, The technique represents only one possible methodology for performing this task. As indicated by figure 611, the analysis may involve determining the minimum and maximum use of each nozzle (or, in cases where a nozzle is driven by one or more firing waveforms, the nozzle-waveform combination) in acceptable combinations. If a particular nozzle is faulty (e.g., does not fire or fires in an unacceptable trajectory), it can be optionally excluded for use (and consideration). Secondly, if a nozzle has either a very small or very large expected droplet volume, this may limit the number of droplets that can be used from that nozzle in acceptable combinations. Figure 611 represents a pre-processing step that reduces the number of combinations that will be considered. As indicated by figure 612, processes / shortcuts can be used to limit the number of sets of droplet combinations that will be evaluated. For example, instead of considering "all" possible droplet combinations for each nozzle, the method can optionally be configured to exclude combinations involving fewer than half of the nozzles (or another number of nozzles, such as a quarter), combinations where more than half of the droplets originate from any particular nozzle waveform, or combinations that represent a high dispersion of droplet volume or a large dispersion of simultaneous droplet volume applied across a target area. Other metrics can also be used.

[0089] Subject to any constraints on the number of sets to be calculated / considered, the method then calculates and considers acceptable droplet combinations, as shown by figure 613. Various processes can be used to plan scans and / or otherwise effectively select a particular set of droplet amounts per target region (TR), as referenced by figures 614 and 615. For example, as presented above, one method assumes a scan path (e.g., a specific geometric step selection) and then considers the maximum value of the fewest remaining set selections across all TRs considered. The method can favorably weight these scan paths (alternative geometric steps) to maximize the ability of the next scan to cover multiple target regions at once. Alternatively, or in addition, the method can favorably weight geometric steps to maximize the number of nozzles used at once. Returning to the simplified five-nozzle discussion above, scans that would apply five nozzles to the target region can be significantly weighted more than scans or passes that would fire only three nozzles in a single pass. Thus, in one embodiment, the following algorithm can be applied by software.

number

[0090] Figure 6A also shows several further options. For example, the consideration of droplet sets in one implementation is performed according to equation / algorithm, shown by figure 617. A comparative metric can be represented as a score that can be calculated for each possible alternative geometric step in order to select a step or an offset. For example, another possible algorithmic approach involves an equation with three terms, as shown below.

number

[0091] The number 619 in Figure 6A indicates that, in one embodiment, the selection of droplet combinations can be performed using matrix mathematics, for example, by using mathematical techniques that simultaneously consider all combinations of droplet amounts and use a form of eigenvector analysis to select a scan path.

[0092] As represented by the number 621, an iterative process can be applied to reduce the number of droplet combinations considered. That is, geometric steps can be calculated one at a time, for example, as represented by the previous description of one possible processing technique. Each time a particular scan path is planned, the method determines the increment still required in each target region under consideration, and then subsequently determines the scan or geometric offset best suited to producing the total amount or fill amount per target region that is within the desired tolerance. This process can then be repeated as separate iterations until all scan paths and nozzle firing patterns are planned.

[0093] The figure 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 can be selected and used based on the minimized deviation of droplet volume per nozzle and the maximum efficiency (e.g., the number of nozzles used per scan). Once a certain number of scans, e.g., one, two, three, or more scans, have been applied, a different algorithm can be invoked to maximize the number of nozzles used per scan (e.g., regardless of the deviation of the applied droplet volume). Any of the specific equations or techniques (or other techniques) discussed above may optionally be one of the applied algorithms in such a hybrid process, and other variations will naturally be conceivable to those skilled in the art.

[0094] As previously referenced, it should be noted that in exemplary display manufacturing processes, the fill amount per target area may have planned randomization (623), which is intentionally injected to mitigate linear effects. In one embodiment, a generator function (625) is applied to intentionally vary the target fill amount (or to make the total amount generated for each droplet combination for each target area asymmetrical) in a manner that optionally achieves this planned randomization or other effect. As mentioned above, in different embodiments, it is also possible to apply algorithmic approaches as previously shown, i.e., even before the droplet combinations are analyzed, such variation is included in the target fill amount and tolerance, and to satisfy, for example, the fill requirement per target area. It is also possible to plan droplet measurements (and generation per nozzle, per waveform distribution) that depend on such randomization, treating the randomization as a probability distribution and calculating in a manner that satisfies the composite fill tolerance, as discussed below in relation to Figure 8B. For example, if the randomization of the planned filling typically varies within ±0.2% of the target composite filling, and the specific tolerance is ±0.5% of the target composite filling, then droplet measurements for each nozzle and each nozzle-waveform combination can be planned to produce a 3σ value for each nozzle / nozzle waveform that is within 0.3% of the target (0.2% + 0.3% = 0.5%).

[0095] Figure 6B and the digit 631 refer to a more detailed block diagram relating to the iterative droplet combination selection process referenced above. As shown by the digits 633 and 635, again, possible droplet combinations are first identified, stored, and retrieved as appropriate for evaluation by the software. For each possible scan path (or geometric step), as indicated by the digit 637, the method stores the footprint (639) that identifies the scan path and the nozzles to be applied, and subtracts the number of shots per nozzle from the set per target area (641) to determine the remaining combinations for each target area (643). These are also stored. Then, as indicated by the digit 645, the method evaluates the stored data according to predefined criteria. For example, as shown by the optional (dashed line) block 647, a method attempting to maximize the minimum number of droplet combinations across all relevant target areas can assign a score indicating whether the stored combinations are better or worse than previously considered alternatives. If a specific criterion is met (645), a specific scan or geometric step can be selected, and the remaining combinations are stored or flagged separately for use in consideration of other printhead / board scans or passes, as represented by the digits 649 and 651. If the criterion is not met (or the consideration is incomplete), a different step can be considered, and / or the method can adjust the consideration of the geometric step under consideration (or a previously selected step) by the digit 653. Again, many variations are possible.

[0096] It has been noted previously that the order in which scans are performed or droplets are deposited is not important to the final composite fill value of each target area. While this is true, to maximize printing speed and throughput, scans are preferably ordered to result in the fastest or most efficient printing possible. Therefore, if not previously included in the geometric step analysis, then the reordering and / or ordering of scans or steps can be performed. This process is represented by Figure 6C.

[0097] Specifically, the digit 661 is used to generally specify the method in Figure 6C. For example, software operating on a suitable machine causes a processor to retrieve selected geometric steps, a specific set, or other data that identify the selected scan path (and, as appropriate, the nozzle firing pattern, which in these embodiments may further include data identifying which of the multiple firing waveforms is used for each droplet, so that a certain nozzle can be driven by one or more firing waveforms) (663). These steps or scans are then sorted or ordered in a manner that minimizes the incremental step distance. For example, referring again to the hypothetical embodiment previously presented, if the selected step / scan path was {0, +3, -2, +6, and -4}, these could be sorted to minimize each incremental step and to minimize the total distance traversed by the motion system between scans. For example, without sorting, the incremental distances between these offsets would be equivalent to 3, 2, 6, and 4 (so that the total distance traversed is "15" in this embodiment). If the scans (e.g., scans "a", "b", "c", "d", and "e") are sorted in the manner described (e.g., in the order "a", "c", "b", "e", and "d"), the incremental distances would be +1, +2, 0, and +4 (so that the total distance traversed is "7"). As represented by the digit 667, at this point the method can assign motion to the printhead motion system and / or the substrate motion system, and the order of nozzle firing can be reversed (e.g., as shown by the digits 339 and 340 in Figure 3B, when alternating reciprocating scan path directions are used). In some embodiments, as previously described and represented by the optional process block 669, planning and / or optimization can be performed for a portion of the target region, and then the solution is applied on a criterion of spatial iteration across a large substrate.

[0098] This iteration is partially represented by Figure 6D. As suggested by Figure 6D, for this description, it is assumed that it is desired to fabricate an array of flat panel devices. A common substrate is represented by the number 681, and a set of dashed-line boxes, such as box 683, represents the geometry of each flat panel device. Preferably, a reference 685 with two-dimensional properties is formed on the substrate and used to position and align various fabrication processes. Following the final completion of these processes, each panel 683 will be separated from the common substrate using cutting or a similar process. If the array of panels represents each OLED display, the common substrate 681 will typically be glass, with a structure in which glass is deposited on top, followed by one or more encapsulation layers. Each panel will then be inverted so that the glass substrate forms the light-emitting surface of the display. For some applications, other substrate materials, e.g., transparent or opaque flexible materials, can be used. As described, many other types of devices can be fabricated according to the techniques described. For a particular portion 687 of the flat panel 683, the solution can be calculated. This solution can then be repeated for some other similar-sized flat panels 689 of the flat panel 683, and then the entire set of solutions can be repeated as each panel is formed from a given substrate.

[0099] Considering the various techniques and considerations described above, the manufacturing process can be implemented to enable rapid, low-cost mass production of products. When applied to display device manufacturing, such as flat panel displays, these techniques enable a high-speed per-panel printing process where multiple panels are produced from a common substrate. By providing a high-speed, repeatable printing technique (e.g., using common ink and printheads from panel to panel), printing can be substantially improved, for example, by reducing the printing time per layer to a fraction of the time that would be required without the above techniques, 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 conceivable that each color component layer can be accurately and reliably printed for a large substrate (e.g., an 8.5 generation substrate of approximately 220 cm x 250 cm) in 180 seconds or less, or even 90 seconds or less, representing a significant process improvement. Improving the efficiency and quality of printing opens the way for a significant reduction in the cost of producing large HD television displays, and therefore for lower end consumer costs. As mentioned above, display manufacturing (specifically OLED manufacturing) is one application of the techniques described herein, but 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.

[0100] One benefit of the ability to deposit precise target area quantities (e.g., well quantities) within tolerances is the ability to inject intentional variations within tolerances, as described. These techniques facilitate significant quality improvements in displays, as they provide the ability to mask pixelation artifacts in displays and make such “linear effects” imperceptible to the human eye. Figure 7 provides block diagram 701 associated with one method for injecting these variations. As with the various methods and block diagrams discussed above, block diagram 701 and the associated method can optionally be implemented as software, either on a standalone medium or as part of a larger machine.

[0101] As represented by the number 703, the variation can be made dependent on a specific criterion. Example For example, it is generally understood that the human eye's sensitivity to contrast variations is a function of luminance, expected viewing distance, display resolution, color, and other factors. As part of a specific criterion, considering the typical human eye's sensitivity to spatial variations in contrast between colors at different luminance levels, a scale is used to ensure that such variations are smoothed in a manner imperceptible to the human eye, e.g., (a) in one or more arbitrary directions, or (b) between color components, considering expected viewing conditions, in a manner that does not provide a human-observable pattern. This can optionally be achieved using a planned randomization function, as previously referenced. Once a minimum criterion is identified, the target filling amount for each color component and each pixel can be intentionally varied in a manner calculated to conceal any visual artifacts from the human eye, as represented by the figure 705. Note that the right side of Figure 7 represents various process options, including (707) the ability to isolate variations across color components, along with testing for perceptible patterns applied in the algorithmic criterion to ensure that filling variations do not produce a perceptible pattern. As described by digit 707, for any given color component (e.g., any given ink), the variation can also be made independent in each of several spatial dimensions, e.g., the x and y dimensions (709). Again, in one embodiment, not only is the variation smoothed over each dimension / color component so that it is not perceptible, but any pattern of differences between each of these dimensions is also suppressed so that it is visible. As shown by digit 711, for example, one or more generator functions can be applied, for example, optionally, using any desired criteria, to ensure that these criteria are met by assigning minor target filling variations to the filling of each target area prior to droplet volume analysis. As shown by digit 713, in one embodiment, the variation can be made random optionally.

[0102] By digit 715, the selection of a particular droplet combination for each target region is thus weighted in support of the selected variation criterion. This can be done via target filling variation, as described, or during droplet selection (e.g., scan path, nozzle-waveform combination, or both). Other methods exist for imparting this variation. For example, in one considered implementation, by digit 717, the scan path is varied non-linearly to effectively vary the droplet volume across the average scan path direction. By digit 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 (or other forms of pulse shaping techniques) per pulse to provide minor droplet volume variations. In one embodiment, these variations can be pre-calculated, and in a different embodiment, only waveform variation is used to generate very minor quantity variations, along with other measures employed to ensure that the total filling remains within a specific tolerance range. In one embodiment, for each target region, multiple droplet combinations that fall within a specified tolerance range are calculated, and for each target region, the selection of which droplet combination is used in that target region is varied (e.g., randomly or based on a mathematical function), or a specific waveform (i.e., used to generate a given amount of droplets) is varied for one nozzle contributing to the selected combination, for example, providing slight quantity variation, thereby effectively varying the droplet quantity across the target region but without varying the planned scan path. Such variation can be implemented across a row of target regions, across a column of target regions, or both, along the scan path direction.

[0103] Figures 8A-8B are used to illustrate a method for generating a statistical model used to evaluate droplets produced by each nozzle or nozzle-waveform combination, and optionally, to plan multiple droplet combinations according to a statistical mean determined from the measurements. In the embodiment of Figures 8A-8B, the statistical model is constructed for the amount of droplets that can be expected from a given nozzle-drive waveform pair, and in an alternative embodiment, similar statistics It should be noted that the model can be constructed for droplet velocity, droplet trajectory (for example, relative to normality), or some other parameter.

[0104] The method depicted in Figure 8 is generally designated by the number 801. Function block 803 indicates that the method in this embodiment begins with establishing a specification range, e.g., the maximum and minimum fills for a given target area that will receive ink. In previously presented embodiments, this specification range can be expressed as mean ± specific value (e.g., 50.00 pL ± 0.5%), but almost any range or expression of the tolerance can be used. In one considered implementation, the specific tolerance for the target is ±0.5%, but other values ​​such as 1.0% or 2.0% can also be used, though not limited to them. Consistent with previous embodiments, for this embodiment, it would be assumed that the target is 50.00 pL and the tolerance is ±0.5% (so that the tolerance range is 49.75 pL to 50.25 pL), but almost any range or tolerance standard can be used.

[0105] The digit 805 selects one or more candidate waveforms for each nozzle of the printhead or printhead assembly. In embodiments using only a single drive waveform (e.g., a fixed-voltage square voltage pulse), no selection needs to be made. In embodiments that allow customized waveform definitions (see, for example, the following discussion associated with Figures 14B and 15A-B), it is typically desirable to evaluate several selective waveforms representing a range of values ​​(which can be interpolated between them to ultimately identify multiple acceptable waveforms for each nozzle under consideration). This selection can be made according to a manual design process (807) (i.e., with waveforms selected by the designer and pre-programmed into the system), or, as the digit 809, the selection process can be automated.

[0106] Once one or more waveforms are defined for each nozzle, droplet measurements are planned for different droplet emissions for a given nozzle-waveform pair. For example, in one embodiment, several droplets (e.g., "24") may be required for each nozzle, providing a basis for evaluating the measured statistical distribution for various droplets. A droplet measurement device (e.g., imaging or non-imaging) can be used for this purpose, as discussed herein. The 24 (or other number) measurements can be planned for immediate measurement or to be performed in each or multiple measurement cycles or iterations. Furthermore, in one embodiment, a threshold number of measurements can be planned for initialization, and then the measurement dataset can be increased over time so that the system generates strong confidence in the measured statistical distribution. In an alternative embodiment, each measurement can be planned for a travel time window (e.g., remeasurements can be planned "every 3 hours", or the measurement data can be retained only over a limited time interval used for analysis), and thus, in one embodiment, each measurement is stored with a timestamp to indicate its validity and expiration during evaluation. Regardless of the measurement and / or measurement retention criteria used, for the purpose of statistical analysis, the number of measurements can be planned for each nozzle-waveform pair (811). Advantageously, each measurement for droplets resulting from each nozzle-waveform pair is grouped as a set and planned in a manner that facilitates the generation of known common distribution forms using well-understood rules for mathematical processing (including aggregation). For example, the normal, Student's T, and Poisson distributions all have relevant parameters that can be combined according to known mathematical processes to predict the total or composite distribution of filling amounts that would result from individual droplet combinations (for each nozzle-waveform pair). Thus, measurement plans can be made according to the techniques described herein to generate droplet datasets that enable statistical combinations of droplets associated with potentially different nozzle-waveform pairs, enabling precise filling within a given tolerance with a very high degree of confidence (e.g., typically, confidence above 99% by figure 813). In one implementation, droplet measurements for each nozzle-waveform combination are planned to satisfy a set of parameters representing a type of known probability distribution (e.g., for a normal distribution, the number of measurements or components n, the statistical mean μ, and the standard deviation σ), and the measurement data is stored (once acquired) for all possible nozzles and nozzle-waveform pairs under consideration. In one embodiment, the planning and measurement may be iterative, i.e., repeated until some desired criterion is reached, such as a minimum number of raw measurements (n), a minimum number of measurements that satisfy a certain criterion, minimum statistical spread (e.g., a 3σ value that satisfies a certain criterion or desired confidence interval), or another. Regardless of which planning criterion is applied (e.g., by software), the system, including the droplet measurement device and printhead assembly under consideration, then undergoes droplet measurements applied individually to each nozzle (and each drive waveform for a given nozzle) to generate a statistically significant number of droplet measurements (815). As described by figures 817 and 819, such measurements are performed optionally, in situ (e.g., optionally, under a controlled atmosphere, in a printer or OLED device processing apparatus), and in a manner sufficient to generate statistical confidence. The collected data can then be stored as an aggregate probability distribution (821), and / or optionally, in a manner that retains individual measurement data (including any timestamps used to indicate measurements per nozzle).

[0107] As described above, in one embodiment, droplets from potentially different nozzles and / or nozzle drive waveforms are intelligently combined to obtain precise filling within a high degree of statistical confidence. Once a probability distribution of a common form is constructed for each nozzle, this combination (and associated plan) is achieved by combining statistical parameters for each droplet to obtain precise filling (and a well-understood probability distribution for each filling). This is represented by the digits 823, 825, and 827 in Figure 8A. More specifically, the droplet averages are combined in one embodiment to obtain a predicted total filling for a target region (e.g., corresponding to an associated normal distribution). As an example, given first and second nozzle-waveform pairs, if the average droplet volumes are measured as 9.98 pL and 10.03 pL, respectively, then the average total filling based on one droplet associated with each pair is expected to be 20.01 pL (where a normal distribution is involved, μc = μ1 + μ2). In this same hypothetical embodiment, if the standard deviations are 0.032 pL (σ1) and 0.035 pL (σ2) for each droplet, then the expected standard deviation of the aggregate is 0.0474 pL (i.e., based on σ2c = σ21 + σ22), and the 3σ value of the aggregate would be approximately 0.142 pL (note that 1σ is equal to approximately a 68.27% confidence interval, while 3σ is equal to approximately a 99.73% confidence interval). By treating droplet measurements for each nozzle-waveform pair as independent random variables, similar techniques can be applied to any common distribution form. Thus, the technique employed herein uses droplet measurement techniques to construct a statistical model for each nozzle-waveform pair so as to plan various droplet combinations based on an analysis of the aggregate random variable, as shown in box 825 (in the case of a normal distribution). Almost any type of probability distribution can be used, provided that the type of probability distribution is susceptible to the effects of the random variable aggregate. As shown by functional block 827, considering the desired specification range (e.g., 0.5% for the target), the proposed combination is analyzed (e.g., by software) to ensure that it satisfies the desired range with a high degree of statistical confidence.For example, in one embodiment, as described, a desired confidence criterion (e.g., 3σ representing a 99.73% confidence interval) is tested to ensure that it fits within the desired tolerance range. For example, if the desired tolerance is 49.75–50.25 pL according to the example presented above, and the possible droplet combinations are expressed as an average of 49.89 pL with a 3σ value equal to 0.07 pL, this translates to a 99% confidence that the total filling will be well within the desired tolerance range of 49.82 pL–49.96 pL, and a particular combination would be considered an acceptable combination (by the analytical function of droplet combinations described above). Again, any desired statistical criterion or goodness-of-fit data is used. This can be done. In another embodiment, a 4σ value (99.993666%) or other value is analyzed for a desired tolerance range. Once the acceptable droplet combinations are determined for each print well, a specific combination of droplets for each well (representing simultaneous deposition by multiple nozzles of the print head assembly) can then be planned with the next print (829) according to the pre-planned droplet combinations for each well (see Figure 5-7).

[0108] Figure 8B provides another method 851 for adapting to intentional target area filling variations according to a desired criterion, and optionally for performing a variable number of droplet measurements per nozzle (or per nozzle waveform). More specifically, the method can again be implemented as instructions stored on a non-transient mechanical memory medium, controlling at least one processor to perform a set of functions determined by the instructions. A desired tolerance range is received by the digit 853 as a first operand "x", which can specify, for example, that the filling of a target area (e.g., a pixel well) should be within a given percentage of the target quantity, e.g., 50.00 pL ± 0.5%. This tolerance range can be determined by customer or industry specifications, as indicated by function 855. If it is desired to plan intentional variations in a composite quantity (e.g., random variations within a small range to avoid linear effects or other significant artifacts in the finished display), the range is received by function 857 as a second operand "y". Based on these two operands, the method calculates the effective allowable maximum variation, standard deviation, or other measure by block 859. In one embodiment, y is subtracted from x as depicted in the figure and equals the effective allowable filling variation. For example, if the specification requires filling within ±0.5% by the above embodiment, and an intentional random variation of ±0.1% is injected into the planned composite mean of well filling (e.g., 49.95 pL to 50.05 pL), then the allowable variation (prior to random variation) can be limited to 49.80 pL to 50.20 pL, again using an embodiment with a target of 50.00 pL ± 0.5%. It should be noted that other techniques are also possible, and for example, instead of simply subtracting these measures, a different set of boundary criteria can be used based on mathematics associated with, for example, a statistical combination of standard deviations or variances for independent random variables, and many other criteria can be applied depending on the embodiment.Block 859 then allows us to consider the remaining range (e.g., ±0.4% of the target) as equivalent to the desired confidence interval (e.g., 3σ interval or other statistical measure) and use it to assess whether possible droplet combinations are acceptable or should be excluded from consideration by the embodiments described above.

[0109] Alternatively, as shown by functional blocks 861 and 863, the remaining ranges and associated confidence intervals can be applied as a criterion to control droplet measurements in order to construct a desired statistical model for each droplet. For example, as represented by block 861, once a desired confidence interval is defined (e.g., 3σ <= 0.4% of the target), a desired variance or maximum allowable variance can be identified, effectively defining the number of criterion droplet measurements n that need to be performed for each nozzle-waveform combination in a manner that is calculated to produce a statistical model that satisfies the desired statistical criteria. For example, a desired effective tolerance range can be used to identify the number of measurements (e.g., 24, 50, or another number) that is calculated to produce a statistical distribution that will be tight, regardless of whether the filling is intentionally varied, and thus lead to a large number of possible droplet combinations that can be used in print planning. This calculation can be applied in several ways, for example, (a) identifying the threshold number of measurements to be applied to each nozzle-waveform combination (e.g., 24 droplet measurements for each), or (b) identifying the threshold statistical criteria that must be met for each nozzle-waveform combination (e.g., threshold criteria, e.g., variance, standard deviation, etc., where a potentially variable number of measurements are performed for each nozzle or nozzle waveform). Then, various exemplary combinations represented by this test are described in Function Box 865. The droplet testing function is applied using a droplet measuring device to perform measurements using numbers (863). For example, ni droplets can be measured for each nozzle (or nozzle-waveform pair) "i" as shown in box 865. For each measurement, the software controlling the droplet measuring device can perform an incremental droplet volume measurement (867) and store the data in memory (869). Following each measurement (or after measuring a threshold number), collective measurements for a given nozzle-waveform combination can be aggregated to calculate statistical parameters for a particular nozzle-waveform combination (e.g., mean and standard deviation, μ and σ, in the case of a normal distribution type) (871). These values ​​can then be stored in memory (873). Optionally, these same or different measurement techniques can be applied to store one or more droplet measurements for velocity v, as well as x and y-dimensional trajectories (α and β), using function box 874. As reflected by the digit 875, a decision criterion can then be applied to determine whether sufficient measurements have been taken for a given parameter (e.g., quantity) for a particular nozzle-waveform combination (i), or whether additional measurements are desired. If additional measurements are required, the method loops via flow arrow 877 to obtain such additional measurements, i.e., to construct a statistical model that satisfies the desired robustness criterion for the particular nozzle-waveform combination. If additional measurements are not required, the method can then proceed to the next nozzle 879 and loop as appropriate via flow arrow 881 until all nozzles and / or nozzle-waveform combinations have been processed. Note that this order is not required for all embodiments, and for example, loops 877 and 881 can be reordered. For example, if droplet measurements are taken sequentially for each nozzle, this process can be repeated until sufficiently robust data is obtained, and such a process offers certain advantages for embodiments where droplet measurements are performed incrementally in a manner that builds upon other system processes (see, for example, the discussion in Figure 19 below).Once all nozzles or nozzle-waveform combinations have been sufficiently tested, the method terminates or, if running intermittently, is temporarily stopped by the number 883. For the droplet tests described, the acquired data, including measured data and / or calculated statistical parameters, is stored in machine-readable memory 885 for use, for example, in planning droplet combinations as discussed above. The acquired data can also be used in other ways, as is optional, in place of or in addition to intelligent mixing of different droplet volumes. In one embodiment, as described, the stored data can again represent any desired droplet parameters, including one or more of droplet volume, droplet volume, and / or droplet trajectory, in the form of individual measured and / or statistical parameters.

[0110] Figures 9A–10C are used to provide simulation data for the techniques discussed herein. Figures 9A–9C represent the expected composite fill volume based on 5 droplets, while Figures 10A–10C represent the expected composite fill volume based on 10 droplets. For each of these figures, the letter designation "A" (e.g., Figures 9A and 10A) represents a scenario where the nozzle is used to deposit droplets without considering quantity differences. Conversely, the letter designation "B" (e.g., Figures 9B and 10B) represents a scenario where a random combination of droplets (5 or 10) is selected to "average" the expected quantity differences between nozzles. Finally, the letter designation "C" (e.g., Figures 9C and 10C) represents a scenario where scanning and nozzle firing depend on a specific total ink volume per target area, attempting to minimize the total fill dispersion across the target area. In these various figures, the variation per nozzle is assumed to be consistent with the variation observed in actual devices, with each vertical axis representing the total fill volume in pL units and each horizontal axis representing the target area, e.g., the number of pixel wells or pixel color components. Note that the emphasis in these figures indicates the variation in total fill volume, assuming randomly distributed droplet variation with respect to an assumed mean. For Figures 9A-9C, the average volume per nozzle is assumed to be slightly less than 10.00 pL per nozzle, and for Figures 10A-10C, the average droplet volume per nozzle is assumed to be slightly more than 10.00 pL per nozzle.

[0111] The first graph 901, shown in Figure 9A, shows the volume variation per well, assuming these differences without attempting to mitigate the differences in nozzle droplet volume. Note that these variations can be extreme (e.g., by peak 903), with a total fill volume range of approximately ±2.61%. As described, the average of 5 droplets is slightly below 50.00 pL, and Figure 9A shows two sets of sample tolerance ranges around this average, including a first range 905 representing a range of ±1.00% around this value, and a second range 907 representing a range of ±0.50% around this value. As seen by the numerical peaks and troughs (e.g., peak 903) exceeding either range, such a printing process will result in a large number of wells that will not meet the specifications (e.g., either one or the other of these ranges).

[0112] The second graph 911, shown in Figure 9B, shows the volume variation per well, using a randomized set of five nozzles per well in an attempt to statistically average the effect of droplet volume variation. It should be noted that such a technique does not allow for the precise generation of a specific amount of ink in any given well, nor does such a process guarantee a total volume within a range. For example, the percentage of out-of-spec fill volume represents a much better case than that shown by Figure 9A, but there are still situations where individual wells (such as those identified by trough 913) are out of specification, e.g., ±1.00% and ±0.50% outside the variation, represented by the digits 905 and 907, respectively. In such cases, the minimum / maximum error is ±1.01%, reflecting the improvement using random mixing compared to the data shown in Figure 9A.

[0113] Figure 9C illustrates a third example using a specific combination of droplets per nozzle, following the technique described above. Specifically, Graph 921 shows that the variation is entirely within ±1.00%, very close to meeting a ±0.50% range for all represented target areas. Again, these ranges are represented by the digits 905 and 907, respectively. In this embodiment, five specifically selected droplet amounts are used to fill the wells within each scan line, with appropriate printhead / substrate shifts for each pass or scan. The minimum / maximum error is ±0.595%, reflecting further improvements using this form of "smart mixing." Note that improvements and data observations will be consistent as any form of intelligent droplet amount combination achieves a specific filling or tolerance range, for example, by using offsets between nozzle rows (or multiple printheads), or by using multiple pre-selected drive waveforms to enable specific droplet amount combinations.

[0114] As described, Figures 10A–10C 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 1001 in Figure 10A represents a case where no care has been taken to mitigate droplet volume differences; Graph 1011 in Figure 10B represents a case where droplets are applied randomly in an attempt to statistically "average" the volume differences; and Graph 1021 in Figure 10C represents a case of planned mixing of specific droplets (to achieve the average fill volume of Figures 10A / 10B, i.e., approximately 103.10 pL). These various figures show tolerance ranges of ±1.00% and ±0.50% variation around this mean, respectively, represented using arrows 1005 and 1007. Each of the figures further shows the respective peaks 1003, 1013, and 1023, represented by variation. However, please note that Figure 10A represents a variation of ±2.27% for the target, Figure 10B represents a variation of ±0.707% for the target, and Figure 10C represents a variation of ±0.447% for the target. For averaging a larger number of droplets... From this, we can see that the “random droplet” solution in Figure 10B achieves a tolerance range of ±1.00% on average, rather than a ±0.50% range. In contrast, the solution depicted in Figure 10C is found to satisfy both tolerance ranges, demonstrating that the variation can be constrained to stay within specifications while still allowing variation in droplet combinations between wells.

[0115] One optional embodiment of the technique described herein is as follows: For a printing process in which a nozzle with a droplet volume standard deviation of x% is used to deposit a total fill volume with a maximum variation of ±y%, there are conventional means of ensuring that the total fill volume will vary by ±y%. This presents a potential problem. Droplet averaging techniques (such as those represented by the data seen in Figures 9B and 10B) statistically reduce the standard deviation of the total volume across the target area to x% / (n)¹ / ², where n is the average number of droplets required per target area to achieve the desired fill volume. However, even with such statistical approaches, there is no mechanism to ensure that the actual fill volume of the target area will actually be within the maximum error limit of ±y%, especially when y and n are small. The technique discussed herein provides a mechanism to provide such reliability by guaranteeing a known proportion of the target area and achieving composite fill within ±y%. Therefore, one optional embodiment provides a method for generating control data or controlling a printer, as well as associated devices, systems, software, and improvements, such that the standard deviation of the amount across the target region 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 printhead nozzles are used simultaneously to deposit droplets in each row (e.g., each pixel well) of the target region in each scan.

[0116] Using a set of basic techniques for combining droplets so that the sum of those quantities is specifically selected to satisfy the particular target described in this way, this book refers to a more detailed description of specific devices and applications that can benefit from these principles. This discussion is non-restrictive, meaning it aims to describe a few specifically considered implementations for putting the methods presented above into practice.

[0117] As shown in Figure 11, the multi-chamber processing apparatus 1101 includes several common modules or subsystems, including a transfer module 1103, a printing module 1105, and a processing module 1107. Each module maintains a controlled environment so that, for example, printing can be performed by the printing module 1105 in a first controlled atmosphere, and other processing, such as another deposition process, such as inorganic encapsulation layer deposition, or a curing process (for example, for the printed material), can be performed in a second controlled atmosphere. The apparatus 1101 uses one or more mechanical handlers to move the substrates between modules without exposing the substrates to an uncontrolled atmosphere. Within any given module, it is possible to use other substrate handling systems and / or specific devices and control systems adapted to the processing performed for that module.

[0118] Various embodiments of the transfer module 1103 may include an input load lock 1109 (i.e., a chamber that provides buffering between different environments while maintaining a controlled atmosphere), a transfer chamber 1111 (which also has a handler for transporting substrates), and an atmosphere buffer chamber 1113. Within the printing module 1105, other substrate handling mechanisms such as a floating table can be used for stable support of the substrate during the printing process. In addition, xyz motion systems such as split axis or gantry motion systems can be used for precise positioning of at least one print head relative to the substrate, and a y-axis transport system can be provided for transporting substrates through the printing module 1105. Furthermore, multiple inks can be used for printing within the printing chamber, for example, using separate print head assemblies, so that, for example, two different types of deposition processes can be carried out within the printing module in a controlled atmosphere. The printing module 1105 may also include a gas enclosure 1115 that houses an inkjet printing system, which introduces an inert atmosphere (e.g., nitrogen, a noble gas, another similar gas, or a combination thereof) and, alternatively, means for controlling the atmosphere with respect to environmental adjustments (e.g., temperature and pressure), gas components, and the presence of particulate matter.

[0119] The processing module 1107 may include, for example, a transfer chamber 1116, which also has a handler for transporting the substrate. In addition, the processing module may also include an output load lock 1117, a nitrogen stack buffer 1119, and a curing chamber 1121. In some applications, the curing chamber can be used, for example, to cure a monomer film into a uniform polymer film using a thermal or ultraviolet radiation curing process.

[0120] In one application, the apparatus 1101 is suited for the mass production of liquid crystal or OLED display screens, for example, the processing of an array of eight screens on a single large substrate at once. 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 similar manner for the mass production of solar panels.

[0121] When applied to the droplet volume combination techniques described above, the printing module 1105 can be advantageously used in display panel manufacturing to deposit one or more layers such as light filtering layers, light-emitting layers, barrier layers, conductive layers, organic or inorganic layers, encapsulation layers, and other types of materials. For example, the depicted apparatus 1101 can be loaded with a substrate and controlled to deposit and / or cure or harden one or more printing layers by moving the substrate back and forth between various chambers in a continuous manner by intervening in exposure to an uncontrolled atmosphere. Optionally, ink droplet measurement (when used in connection with the depicted system) can be performed as the substrate moves or is processed in any chamber. For example, a first substrate can be loaded via the input load lock 1109, and during this process, the print head assembly in the printing module 1105 can be engaged with a droplet measurement device to perform droplet measurement on a portion of the printing nozzles. In embodiments with multiple print nozzles, droplet measurement can be performed periodically and intermittently so that, between various print cycles, different nozzles representing a cyclically sequential portion of all nozzles in the print assembly are calibrated and the relevant droplets are measured to generate statistical models for droplet volume, emission angle (relative to the vertical), and velocity, respectively. A handler located in the transfer module 1103 moves the first substrate from the input load lock 1109 to the print module 1105, at which point droplet measurement is disengaged and the printhead assembly is moved to the position for active printing. Following the completion of the printing process, the first substrate can be moved to the processing module 1107 for curing. A new cycle of droplet measurement can be performed again, and optionally, a second substrate (if supported by the system) can be loaded into the input load lock 1109. Many other alternatives and process combinations are possible. By repeatedly depositing subsequent layers, for example by moving the first substrate back and forth for repeated printing and curing cycles, a controlled amount per target area and aggregated layer properties can be constructed to suit any desired application.In alternative embodiments, the output load lock 1117 can be used to transfer the first substrate to the second printer (for example, to pipeline print a new layer, such as a new OLED material layer, or encapsulation or other layers in succession). 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 the apparatus 1101 can be varied to arrange various modules 1103, 1105, and 1107 in different juxtapositions, and additional or fewer modules can also be used. As represented by the figures 1121 and 1123, a computer device (e.g., a processor) running suitable software can be used to control various processes and to perform discretionary droplet measurements as described above in conjunction with other processes, i.e., to minimize the downtime of the apparatus, to keep droplet measurements as up-to-date as possible while maintaining a robust statistical model, and to stack as many droplet measurement processes as possible so as to overlap with other system processes.

[0122] Figure 11 provides one embodiment of a set of connected chambers or processing components, although clearly many other possibilities exist. The ink droplet measurement and deposition techniques described above can be used with the device depicted in Figure 11, or in fact, to control processing processes carried out by any other type of deposition equipment.

[0123] Figure 12 provides a block diagram showing various subsystems of a single apparatus that can be used to process a device having one or more layers as specified herein. Coordination across the various subsystems is provided by a processor 1203 that operates under instructions provided by software (not shown in Figure 12). During the processing process, the processor supplies data to the printhead 1205 to cause the printhead to release varying amounts of ink in response to nozzle ejection commands. The printhead 1205 typically has multiple inkjet nozzles arranged in a row (or rows of an array) and associated reservoirs that enable ink ejection in response to activation of a piezoelectric or other transducer per nozzle, such transducers causing the nozzle to release a controlled amount of ink in an amount controlled by an electronic nozzle drive waveform signal applied to the corresponding piezoelectric transducer. If multiple printheads are present, there may be a processor for each printhead, or one processor may control the entire printhead assembly. Other ejection mechanisms may also be used. Each printhead applies ink to the substrate 1207 at various xy positions corresponding to grid coordinates in various printing cells, as represented by a halftone printed image. Positional variation is achieved by both the printhead motion system 1209 and the substrate handling system 1211 (for example, to cause one or more strip-shaped locations across the substrate to be represented in the print). In one embodiment, the printhead motion system 1209 moves the printhead back and forth along a traveler, while the substrate handling system provides stable substrate support and "y"-dimensional transport of the substrate to enable "split axis" printing of any portion of the substrate. The printhead motion system 1209 provides relatively slow x-dimensional transport, while the substrate handling system provides relatively fast y-dimensional transport. In another embodiment, the substrate handling system 1211 can provide both x and y-dimensional transport. In yet another embodiment, primary transport can be provided entirely by the substrate handling system 1211. An image capture device 1213 can be used to position an arbitrary reference and assist in alignment and / or error detection.

[0124] The apparatus also includes an ink delivery system 1215 and a printhead maintenance system 1217 to assist in printing operations. The printhead can be periodically calibrated or undergo a maintenance process, and to achieve this purpose, during the maintenance sequence, the printhead maintenance system 1217 is used to perform appropriate preparation, ink or gas purging, testing and calibration, and other operations as appropriate for a particular process.

[0125] As previously described, the printing process can be carried out in a controlled environment, that is, in a manner that presents a reduced risk of contaminants that could degrade the effectiveness of the deposited layer. To this end, the apparatus includes a chamber control subsystem 1219 that controls the atmosphere within the chamber, as represented by functional block 1221. Optional process modifications are described below. This may include ejecting the deposited material in the presence of an ambient nitrogen gas atmosphere.

[0126] As described above, in the embodiments disclosed herein, individual droplet amounts are combined to achieve a specific fill amount per target area, which is selected depending on the target fill amount. A specific fill amount can be planned for each target area, and the fill value varies with respect to the target value within an allowable tolerance range. For such embodiments, the droplet amount is measured specifically in a manner that depends on the ink, nozzle, drive waveform, and other factors. To achieve this objective, reference numeral 1223 represents a discretionary droplet amount measurement system in which the droplet amount 1225 is measured for each nozzle and for each drive waveform and then stored in memory 1227. Such a droplet amount measurement system may be an optical stroboscopic camera or laser scanning device (or other quantity measuring tool) incorporated into a commercially available printing device, as described above. In one embodiment, such a device uses non-imaging techniques (e.g., using a simple optical detector instead of image processing software acting on pixels) to achieve real-time or near-real-time measurement of individual droplet amounts, deposition flight angle or trajectory, and droplet velocity. This data is provided to processor 1203 either during printing or during a one-time intermittent or periodic calibration operation. As indicated by the figure 1229, a pre-arranged set of firing waveforms can also be optionally associated with each nozzle for later use in generating a combination of droplets per specific target area. When such a set of waveforms is used in the embodiment, droplet volume measurements are advantageously calculated for each waveform during calibration using a droplet measurement system 1223 for each nozzle. Measurements can be performed as needed and processed (e.g., averaged) to minimize statistical volume measurement errors, thus greatly increasing reliability in providing a real-time or near-real-time droplet volume measurement system that delivers target area volume filling within the desired tolerance range.

[0127] The digit 1231 refers to the use of print optimization software operating on processor 1203. More specifically, this software uses this information to plan the print in a manner that combines droplet amounts as appropriate to obtain a specific fill amount per target area, based on a statistical model of droplet amount 1225 (measured in situ or otherwise provided). In one embodiment, the above embodiment allows the total amount to be planned down to a resolution of 0.01 pL or better within a certain error tolerance, even though the droplet measuring device may have lower accuracy associated with individual droplet measurements; that is, the degree of statistical accuracy can be estimated beyond that represented by the accuracy of the droplet measuring system by using the techniques described herein to construct statistical models of droplet amounts per nozzle and per nozzle / waveform combination. Once the print is planned, the processor calculates print parameters such as the number and order of scans, droplet diameter, relative droplet ejection time, and similar information, and constructs a print image used to determine nozzle ejection for each scan. In one embodiment, the print image is a half-toe-in image. In another embodiment, the printhead has as many as 10,000 nozzles. Each droplet can be represented according to a time value and an ejection value (e.g., data representing the ejection waveform, or data indicating whether the droplet will be ejected "digitally"), as described below. In embodiments where geometric steps and binary nozzle ejection decisions are relied upon to vary the droplet volume per well, each droplet can be defined by a bit of data, a step value (or scan number), and a position value indicating where the droplet will be placed. In implementations where the scan represents continuous motion, the time value can be used as an equivalent of the position value. Whether based on time / distance or absolute position, the value represents the position relative to a reference (e.g., synchronization mark, position, or pulse) that precisely specifies where and when the nozzle should be ejected. In some embodiments, multiple values ​​can be used.For example, in one specifically considered embodiment, a synchronization pulse is generated for each nozzle in a manner corresponding to each micron of relative printhead / substrate motion during scanning. For each synchronization 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 selection signal representing one of 15 waveform selections pre-programmed in memory dedicated to a particular nozzle driver (i.e., one of 16 possible values ​​identifies the nozzle as "off" or non-firing), and (c) a reproducibility value that determines whether the nozzle should be fired only once, once for all synchronization pulses, or once for every n synchronization pulses. In such a case, the waveform selection and the address of each nozzle are associated by the processor 1203 with specific droplet volume data stored in memory 1227, and the firing of a particular waveform from a particular nozzle represents a planned decision that a particular corresponding droplet volume is used to supply total ink to a particular target area of ​​the substrate.

[0128] Figures 13A–15D will be used to introduce other techniques that can be used to combine different droplet volumes to obtain precise in-tolerance filling for each target area. In the first technique, the rows of nozzles can be selectively offset relative to each other within the print assembly during printing (e.g., during scanning). This technique will be introduced with reference to Figures 13A–13B. In the second technique, the nozzle drive waveform can be used to adjust the piezoelectric transducer emission, and therefore the properties of each emitted droplet (including the volume). Figures 14A–14B will be used to discuss several options. Finally, in one embodiment, a set of multiple alternative droplet emission waveforms is pre-calculated and made available for use with each print nozzle. This technique and associated circuitry will be discussed with reference to Figures 15A–B.

[0129] Figure 13A provides a plan view 1301 of the print head 1303 traversing the substrate 1305 in the scanning direction indicated by arrow 1307. The substrate can be seen here as consisting of several pixels 1309, each having wells 1309-R, 1309-G, and 1309-B associated with its respective color component. Again, it should be noted that this depiction is merely an embodiment, i.e., techniques used herein can be applied to any layer of a display (e.g., not limited to individual color components and not limited to color-impregnation layers), and these techniques can also be used to fabricate things other than display devices. In this case, assuming the print head deposits one ink at a time and the inks are color component-specific, it is intended that for each well of the display, a separate printing process would be performed for each color component. Therefore, if the first process is used to deposit an ink specific to red light generation, only the first well of each pixel, such as the well 1309-R of pixel 1309 and the similar well of pixel 1311, will receive the ink in the first printing process. In the second printing process, only the second well (1309-G) of pixel 1309 and the similar well of pixel 1311 will receive the second ink, and so on. Thus, the various wells can be considered as three different overlapping arrays (in this case, fluid containers or wells) of the target region.

[0130] The printhead 1303 includes several nozzles, represented by the numbers 1313, 1315, and 1317. In this case, each number refers to a separate row of nozzles, the row of which extends along the column axis 1318 of the substrate. Nozzles 1313, 1315, and 1317 are found to form the first row of nozzles relative to the substrate 1305, and nozzle 1329 represents the second row of nozzles. As depicted by Figure 13A, the nozzles do not align with pixels, and as the printhead traverses the substrate in a scan, some nozzles will pass over the target area while others will not. Furthermore, in the figure, the print nozzles 1313, 1315, and 1317 align precisely to the center of the row of pixels, starting from pixel 1309, while the print nozzle 1329 will also pass over the row of pixels, starting from pixel 1311, although the alignment of print nozzle 1329 is centered on and around pixel 1311. The alignment of the nozzle rows with the rows of wells is not precise. This alignment / misalignment of the nozzle rows with the rows of wells is illustrated by lines 1325 and 1327, which represent the centers of the printing wells that receive the ink, respectively. In many applications, the precise location where droplets are deposited within the target area is not important, and such misalignment is acceptable (for example, as discussed in relation to Figures 1B and 4D, it may be desirable to roughly align groups of multiple nozzles with each row).

[0131] Figure 13B provides a second Figure 1331, showing that all three rows of nozzles (or individual printheads) are rotated approximately 30 degrees with respect to axis 1318. This discretionary capability was previously referenced by the figure 338 in Figure 3B. More specifically, the rotation changes the spacing of the nozzles along the column axis 1318, with each row of nozzles being adjusted to align with the well centers 1325 and 1327 or to increase the apparent density of nozzles per target printing area during scanning. However, it should be noted that such rotation and scanning motion 1307 will cause the nozzles from each row of nozzles to traverse rows of pixels (e.g., 1309 and 1311) at different relative times and therefore will have potentially different positional firing data (e.g., different timings for firing droplets). Methods for adjusting the firing data of each nozzle will be discussed below in relation to Figures 15A-B.

[0132] As shown in Figure 13C, in one embodiment, a printhead assembly, optionally given multiple rows of printheads or nozzles, can have such rows selectively offset from one another. That is, Figure 13C provides another plan view in which each of the printheads (or nozzle rows) 1319, 1321, and 1323 are offset from one another, as represented by the offset arrows 1353 and 1355. These arrows represent the use of an optional motion mechanism, one for each row of nozzles, that allows for the selective offset of the corresponding row to the printhead assembly. This provides different combinations of nozzles (and associated specific droplet amounts) with each scan (e.g., by the number 1307), and therefore different specific droplet combinations. For example, in such an embodiment, as depicted by Figure 13C, such offsets allow both nozzles 1313 and 1357 to align with the centerline 1325 and therefore have their respective droplet amounts combined in a single pass. This embodiment is considered a specific example of an embodiment in which the geometric step is varied, and it should be noted that, for example, even if the geometric step size is fixed during a series of scans of the printhead assembly 1303 on the substrate 1305, each such scan motion of a given row of nozzles can be effectively positioned with a variable offset or step relative to the position of a given row in other scans using the motion mechanism. Alternatively, such offsets can be made to adjust the effective printing grid to provide a variety of spacings between deposited droplets. Consistent with the previously introduced principle, the use of arbitrary offsets allows the amount of droplets per individual nozzle to be aggregated in specific combinations (or droplet sets) for each well, but with a reduced number of scans or passes. For example, in the embodiment depicted in Figure 13C, three droplets can be deposited in each target area (e.g., the well for the red component) in each scan, and furthermore, the offset allows for planned variation of droplet amounts and / or spatial combinations.

[0133] Figure 13D illustrates a cross-sectional view of the finished display for one well (e.g., wells 1309-R from Figure 13A) obtained in the direction of scanning. Specifically, this figure shows the substrate 1352 of a flat panel display, specifically an OLED display. The depicted cross-section shows the active region 1353 and conductive end 1355 that receive electronic signals controlling the display (including the color of each pixel). A small elliptical region 1361 in the figure is on the right side of the figure to illustrate the layer within the active region above the substrate 1352. The image is magnified and visible. These layers each include an anode layer 1369, a hole injection layer ("HIL") 1371, a hole transport layer ("HTL") 1373, an emitting or light-emitting layer ("EML") 1375, an electron transport layer ("ETL") 1377, and a cathode layer 1378. 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 manufacturing, an electric current causes the recombination of electrons and "holes" in the EML, resulting in the emission of light. The anode layer 1369 may have 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 1369 may also be reflective or opaque, and other materials may also be used. The cathode layer 1378 typically consists of patterned electrodes to provide selective control of 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. Together, the cathode and anode serve to supply and collect electrons and holes entering and / or passing through the OLED stack. HIL 1371 typically functions to transport holes from the anode into the HTL. HTL 1373 typically functions to transport holes from the HIL into the EML while interfering with electron transport from the EML into the HTL. ETL 1377 typically functions to transport electrons from the cathode into the EML while interfering with electron transport from the EML into the ETL. Together, these layers serve to supply electrons and holes into the EML1375 and confine these electrons and holes within their layers so that they can recombine and generate light. Typically, the EML consists of separately controlled active materials for each of the three primary colors of the display: red, green, and blue, and is represented in this case by the red light-generating material, as described.

[0134] The layers within this active region can degrade through exposure to oxygen and / or moisture. Therefore, it is desirable to extend the OLED lifetime by encapsulating these layers on both the face and side (1362 / 1363) of these layers opposite the substrate, as well as on the outer edge. The purpose of encapsulation is to provide an oxygen and / or moisture barrier. Such encapsulation can be formed entirely or partially through the deposition of one or more thin film layers.

[0135] The techniques discussed herein can be used to deposit any of these layers, as well as combinations thereof. Thus, in one considered application, the techniques discussed herein provide ink quantities for EML layers for each of the three primary colors. In another application, the techniques discussed herein are used to provide ink quantities for HIL layers, etc. In yet another application, the techniques discussed herein are used to provide ink quantities for one or more OLED encapsulation layers. The printing techniques discussed herein can be used, as appropriate, to deposit organic or inorganic layers, and layers for other types of display and non-display devices, against process technology.

[0136] Figure 14A is used to illustrate nozzle drive waveform adjustment and the use of alternative nozzle drive waveforms to provide different droplet emission amounts from each nozzle of the printhead. The first waveform 1403 is considered a single pulse consisting of a quiescent period 1405 (0 volts), an upward slope 1413 associated with the decision to fire the nozzle at time t2, a voltage pulse or signal level 1407, and a downward slope 1411 at time t3. The effective pulse width, represented by the digit 1409, is a duration approximately equal to t3-t2, depending on the difference between the upward and downward slopes of the pulse. In one embodiment, any of these parameters (e.g., upward slope, voltage, downward slope, pulse duration) is used to determine the droplet emission amount from a given nozzle. The output characteristics can be varied to potentially change them. The second waveform 1423 is similar to the first waveform 1403, except that it represents a higher drive voltage 1425 for the signal level 1407 of the first waveform 1403. The higher pulse voltage and finite rising slope 1427 mean it takes longer to reach this higher voltage, and similarly, the falling slope 1429 is typically delayed compared to the similar slope 1411 from the first waveform. In this case, the third waveform 1433 is also similar to the first waveform 1403, except that different rising slopes 1435 and / or different falling slopes 1437 can be used instead of slopes 1413 and 1411 (e.g., through adjustment of the nozzle firing path impedance). Different slopes can be either steeper or shallower (steeper in the case depicted). In contrast, in the fourth waveform 1443, the pulse is made longer by using a delay circuit (e.g., a voltage-controlled delay line) to increase the pulse duration at a given signal level (as represented by the digit 1445) and to delay the falling edge of the pulse (as represented by the digit 1447). Finally, the fifth waveform 1453 represents the use of multiple discrete signal levels, also providing a means of pulse shaping. For example, this waveform can be seen to include a slope that rises from the time at the initially described signal level 1407 to a second signal level 1455 applied midway between times t3 and t2. Due to the larger voltage, the falling interval of this waveform 1457 can be seen to be delayed after the falling edge 1311.

[0137] Any of these techniques can be used in combination with any of the embodiments discussed herein. For example, the drive waveform adjustment technique can optionally be used to vary the droplet volume within a small range after the scanning motion and nozzle firing have already been planned, in order to mitigate linear effects. Designing the waveform variation in a manner such that a second tolerance conforms to the specification facilitates the deposition of high-quality layers 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 the first range of 50.00 pL ± 0.25% (49.785 pL to 50.125 pL) using a non-random or random technique applied to the waveform variation, where the variation statistically provides a quantity variation of only ± 0.025 pL per droplet (considering the 5 droplets required to reach the total fill volume). Alternatively, or in addition, the drive waveform variation can be used to affect the velocity or trajectory (flight angle) of the emitted droplets. For example, in one process, droplets are required to meet a predetermined set of criteria regarding volume and / or velocity and / or trajectory, and if the droplets fall outside the acceptable norms, the nozzle drive waveform can be adjusted until compliance is achieved. Alternatively, a predetermined set of waveforms can be measured, and some of these waveforms are selected based on conformity to the desired norms. Clearly, many variations exist.

[0138] As described above, in one embodiment, as represented by the fifth waveform 1453 from Figure 14A, multiple signal levels can be used to shape the pulse. This technique is further discussed with reference to Figure 14B.

[0139] In other words, in one embodiment, the waveform can be predefined as a series of discrete signal levels defined, for example, by digital data, and the drive waveform is generated by a digital-to-analog converter (DAC). The digit 1451 in Figure 14B refers to waveform 1453, which has discrete signal levels 1455, 1457, 1459, 1461, 1463, 1465, and 1467. In this embodiment, each nozzle driver includes a circuit that receives and stores up to 16 different signal waveforms, each defined by a series of up to 16 signal levels, each of which is represented as a multi-bit voltage and duration. That is, in such an embodiment, the pulse width can be effectively varied by defining different durations for one or more signal levels, and the drive voltage can be waveform-shaped in a manner selected to provide subtle droplet diameter variations, for example, the droplet volume is measured to provide a specific amount of incremental increments, such as 0.10 pL units. Therefore, in such embodiments, wave shaping provides the ability to adjust the droplet volume to approximate a target droplet volume value, and when combined with other specific droplet volumes, such as using the techniques illustrated above, these techniques facilitate precise filling per target area. However, in addition, these wave shaping techniques also facilitate measures to reduce or eliminate linear effects, for example, in one discretionary embodiment, as discussed above, a specific amount of droplets are combined, but the last droplet (or more droplets) is selected in such a way that it provides variation with respect to the boundary of a desired tolerance range. In another embodiment, a predetermined waveform can be applied, and further discretionary wave shaping or timing is applied as appropriate to adjust the droplet volume, velocity, and / or trajectory. In yet another embodiment, the use of a nozzle-driven wave alternative provides a mechanism for planning the volume such that further wave shaping is not required.

[0140] Typically, the effects of different drive waveforms and the resulting droplet volume are measured in advance. For each nozzle, up to 16 different drive waveforms are then stored in 1k synchronous random access memory (SRAM) per nozzle for selective use later, providing discrete volume variations as selected by software. With the different drive waveforms at hand, each nozzle is then instructed on a per-droplet basis which waveform to apply through programming of data to achieve a specific drive waveform.

[0141] Figure 15A illustrates such an embodiment, generally designated by the digit 1501. Specifically, a processor 1503 is used to receive data defining the intended fill amount per target area for a particular layer of material to be printed. As represented by the digit 1505, this data may be a layout file or bitmap file defining the droplet amount per grid point or position address. A series of piezoelectric transducers 1507, 1508, and 1509 generate associated ejected droplet amounts 1511, 1512, and 1513, respectively, which depend on many factors, including nozzle drive waveforms and inter-printhead manufacturing variations. During the calibration operation, each of the set of variables is tested for its effect on droplet amount, including inter-nozzle variations and the use of different drive waveforms, taking into account the specific 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 droplet measuring device 1515 that provides measurement data to the processor 1503 for use in managing print planning and subsequent prints. In one embodiment, this measurement data is calculated in operation, which takes literally minutes (for, for example, thousands of printhead nozzles and a potentially large number of possible nozzle emission waveforms), for example, just 30 minutes for thousands of nozzles, preferably even less time. In another embodiment, as described, such measurements can be performed iteratively, i.e., to update different parts of the nozzles at different points in time. Non-imaging (e.g., interference) techniques can be used optionally, as previously described, covering tens to hundreds of nozzles per second, potentially resulting in tens of droplet measurements per nozzle. This data and any relevant statistical models (and mean) can be stored in memory 1517 for use when processing layout or bitmap data 1505 when received. In one implementation, the processor 1503 is part of a computer located remotely from the actual printer, while in a second implementation, the processor 1503 is integrated with either a processing mechanism for the product (e.g., a system for processing displays) or the printer.

[0142] To fire droplets, a set of one or more timing or synchronization signals 1519 is received for use as a reference, and these are passed through a clock tree 1521 to be distributed to each nozzle driver 1523, 1524, and 1525 to generate drive waveforms for specific nozzles (1527, 1528, and 1529, respectively). Each nozzle driver has one or more registers 1531, 1532, and 1533 that receive multibit programming data and timing information from the processor 1503. Each nozzle driver and its associated registers receive one or more dedicated write-enabled signals (wen) for the purpose of programming registers 1531, 1532, and 1533, respectively. In one embodiment, each register has a substantial amount of memory, including 1k SRAM for storing a plurality of predetermined waveforms, and a programmable register for selecting between these waveforms and controlling waveform generation in a different manner. Data and timing information from the processor is represented as multi-bit information, which can be provided via either a series or parallel bit connection to each nozzle (in one embodiment, as seen in Figure 15B discussed below, this connection is series, in contrast to the parallel signal representation seen in Figure 15A).

[0143] For a given deposition, printhead, or ink, the processor selects a set of 16 drive waveforms for each nozzle, which can be selectively applied to generate droplets. Note that this number is arbitrary; for example, one design may use four waveforms, while another may use 4000. These waveforms are advantageously selected to provide a desired variation in output droplet volume for each nozzle, for example, by causing each nozzle to make at least one waveform selection that produces a nearly ideal droplet volume (e.g., an average droplet volume of 10.00 pL), and to provide a range of intentional volume variations from each nozzle. In various embodiments, the same set of 16 drive waveforms is used for all nozzles, but in the embodiment described, there are 16 pre-defined, presumably unique waveforms for each nozzle, each giving its own droplet volume characteristics, and each is distinct.

[0144] During printing, data is programmed into each nozzle's respective register 1531, 1532, or 1533, on a per-nozzle basis, to select one of a predefined waveform to control the deposition of each droplet. For example, considering a target droplet volume of 10.00 pL, the nozzle driver 1523 can be configured to set one of 16 waveforms corresponding to one of 16 different droplet volumes by writing data to register 1531. Once the per-nozzle (and per-waveform) droplet volumes and associated distributions are registered by the processor 1503 and stored in memory to assist in generating the desired target filling, the amount produced by each nozzle will be measured by the droplet measuring device 1515. The processor can define whether a particular nozzle driver 1523 should output one of the 16 waveforms selected by the processor by programming register 1531. In addition, the processor can program registers to have a per-nozzle delay or offset to the nozzle firing for a given scan line (e.g., to align each nozzle with the grid traversed by the print head, to compensate for errors including velocity or trajectory errors, and for other purposes), and this offset is achieved by counters that make a particular nozzle (or firing waveform) asymmetric by a programmable number of timing pulses for each scan. To provide embodiments, if the droplet measurement results indicate that one particular droplet tends to have a lower velocity than expected, the corresponding nozzle waveform can be triggered earlier (e.g., advanced in time by reducing the dead time before the active signal level used for piezoelectric operation), and conversely, if the droplet measurement results indicate that one particular droplet has a relatively high velocity, the waveform can be triggered later, and so on. Other embodiments are clearly possible, for example, in some embodiments, slow droplet velocities can be hindered by increasing the drive strength (i.e., the signal level and associated voltage used to drive the piezoelectric actuator of a given nozzle).In one embodiment, a synchronization signal delivered to all nozzles occurs at defined time intervals (e.g., 1 microsecond) for synchronization purposes, while in another embodiment, the synchronization signal is adjusted to the printer motion and substrate terrain, for example, to fire progressive relative motions of 1 micron each between the print head and the substrate. A high-speed clock (φhs), for example, 100 megahertz, 33 megahertz, etc., can be operated thousands of times faster than the synchronization signal, 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, but this does not have to apply to each implementation. For example, in some cases, a regular grid can be defined in which all nozzles fire "every 5 microns". This grid may be specific to the printing system, the substrate, or both. Thus, in one optional embodiment, a grid can be defined for a particular printer using a synchronization frequency or nozzle firing pattern that is used to effectively transform the grid to match a priori unknown substrate terrain. In another considered embodiment, a memory shared across all nozzles is provided, allowing the processor to pre-store several different grid spacings (e.g., 16) shared across all nozzles, so that the processor can then (on demand) select a new grid spacing to be read from all nozzles (e.g., to define an irregular grid). For example, in an implementation where the nozzles emit for all color component wells of the OLED (e.g., to deposit a non-color specific layer), three or more different grid spacings can be applied sequentially by the processor in a round-robin manner. Clearly, many design alternatives are possible. It should be noted that the processor 1503 can also dynamically reprogram the registers of each nozzle during operation, i.e., a synchronization pulse is applied as a trigger to invoke any programmed waveform pulse set in that register, and if new data is received asynchronously before the next synchronization pulse, the new data will be applied with the next synchronization pulse.The processor 1503 also controls the start and speed (1535) of the scan, in addition to setting parameters for synchronous pulse generation (1536). In addition, the processor controls the rotation (1537) of the print head for the various purposes described above. In this way, each nozzle can fire simultaneously (or all at once) at any time (i.e., with any "next" synchronous pulse) using any one of the 16 different waveforms for each nozzle, and the selected firing waveform can be dynamically sandwiched between firings during a single scan with any other of the 16 different waveforms.

[0145] Figure 15B shows additional details of a circuit (1541) used in such an embodiment to generate an output nozzle drive waveform for each nozzle, the output waveform being represented as “nzzl-drv.wvfm” in Figure 15B. More specifically, circuit 1541 receives inputs of a synchronization signal, a single bit line carrying serial data ("data"), a dedicated write enable signal (we), and a fast clock (φhs). Register file 1543 provides data for at least three registers, each conveying an initial offset, a grid definition value, and a drive waveform ID, respectively. The initial offset is a programmable value that adjusts each nozzle to align with the grid start, as described. For example, given implementation variables such as multiple print heads, multiple rows of nozzles, different print head rotations, nozzle firing speeds and patterns, and other factors, the initial offset can be used to align the droplet pattern of each nozzle with the grid start, taking into account delays and other factors. Offsets can be applied in different ways across multiple nozzles, for example, to rotate a grid or halftone pattern relative to the substrate terrain, or to compensate for substrate misalignment. Similarly, as described, offsets can also be used to compensate for abnormal speed or other effects. The grid definition value is a number representing the number of synchronization pulses "counted" before a 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 likely has one or more regular intervals for different printhead nozzles, corresponding to a regular (constant interval) or irregular (multiple interval) grid. As mentioned above, in one implementation, the processor maintains its own 16-entry SRAM to define up to 16 different grid intervals, which can be read into register circuits 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 one selection of pre-stored drive waveforms for each nozzle, and depending on the embodiment, can be programmed and stored in many ways.In one embodiment, the drive waveform ID is a 4-bit select value, and each nozzle has its own dedicated 1k-byte SRAM to store up to 16 predetermined nozzle drive waveforms, stored as 16 × 16 × 4B entries. Briefly, each of the 16 entries for each waveform contains 4 bytes representing the programmable signal level, 2 bytes representing the resolution voltage level and 2 bytes representing the programmable duration, used to count the number of pulses in a fast clock. Thus, each programmable waveform can consist of discrete pulses (0 to 1) up to 16 discrete pulses, each with a programmable voltage and duration (e.g., a duration equivalent to 1 to 255 pulses in a 33 megahertz clock).

[0146] The figures 1545, 1546, and 1547 specify one embodiment of the circuit that demonstrates how a specific waveform can be generated for a given nozzle. A first counter 1545 receives a synchronization pulse to begin counting down an initial offset, triggered by the start of a new line scan. The first counter 1545 counts down in micron increments, and when it reaches zero, a trigger signal is output from the first counter 1545 to the second counter 1546. This trigger signal essentially starts the firing process for each nozzle for each scan line. The second counter 1546 then implements a programmable grid spacing in micron increments. While the first counter 1545 is reset in conjunction with the new scan line, the second counter 1546 is reset using the next edge of the fast clock following its output trigger. The second counter 1546, when triggered, activates a waveform circuit generator 1547 that generates a selected drive waveform shape for a particular nozzle. As seen below the generator circuit and represented by the dashed boxes 1548-1550, this latter circuit is based on a high-speed digital-to-analog converter 1548, a counter 1549, and a high-voltage amplifier 1550, whose timing is determined according to a high-speed clock (φhs). When a trigger is received from the second counter 1546, the waveform generator circuit takes a number of pairs (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 1549 is effective in holding the DAC output for a duration according to the counter. The corresponding output voltage level is then applied to the high-voltage amplifier 1550 and output as a nozzle-drive waveform. The next number of pairs is then latched from register 1543 to define the next signal level value / duration, etc.

[0147] The described circuit provides an effective means of defining any desired waveform according to data provided by processor 1503. If it is necessary to conform to the geometric shape of the grid or to mitigate nozzles with abnormal speeds or flight angles, the duration and / or voltage levels associated with any specific signal level (e.g., a first "0" signal level defining an offset relative to synchronization) can be adjusted. As described, in one embodiment, the processor predetermines a set of waveforms (e.g., 16 possible waveforms per nozzle), then writes the definition of each of these selected waveforms to SRAM for the driver circuit of each nozzle, and then the determination of the programmable waveform "launch time" is achieved by writing a 4-bit driven waveform ID to each nozzle register.

[0148] Figure 15C shows how to use different waveforms and configuration options per nozzle. A flowchart 1551 is provided to discuss this. As shown by 1553, the system (e.g., one or more processors acting under instructions from preferred software) selects a predetermined set of nozzle drive waveforms. For each waveform and for each nozzle (1555), the droplet volume is specifically measured using, for example, a laser measuring device or a CCD camera, and a statistical model is constructed. These quantities are stored in a processor-accessible memory, such as memory 1557. Again, the measured parameters may vary depending on the ink selection and many other factors. Therefore, calibration is performed in accordance with these factors and the planned deposition activity. For example, in one embodiment 1561, calibration is performed at the factory that manufactures the print head or printer, and this data can be pre-programmed into the sales device (e.g., the printer) or made available for download. Alternatively, for printers that have a discretionary droplet measuring device or system, these quantity measurements can be performed at the time of first use (1562), for example, during the initial device configuration. In yet another embodiment, measurements are taken with each power or board cycle (1563), for example, whenever the printer is turned "on," started from a low power state, or otherwise transitioned to a print-ready state. As previously stated, for embodiments in which the amount of droplets released is affected by temperature or other dynamic factors, calibration can be performed intermittently or periodically (1564), for example, after the expiration of a defined time interval, when an error is detected, in the state of each new board operation (e.g., board loading and / or during loading), daily or according to some other standard. Other calibration techniques and schedules may also be used (1565).

[0149] Calibration techniques can optionally be performed in an offline process or during calibration mode, as represented by process separation line 1566. As described, in one embodiment, such a process can potentially be completed in less than 30 minutes for thousands of print nozzles and one or more associated nozzle firing waveforms. Represented below this process separation line 1566, during online operation (or during print mode), 1567, the measured droplet amounts are used to select a set of droplets per target area based on a specific measured droplet amount, so that the droplet amounts for each set sum to a specific total amount within a defined tolerance range. The amount per area can be selected based on a layout file, bitmap data, or some other representation, as represented by the digit 1568. Based on these droplet amounts and the allowable combinations of droplet amounts for each target area, a firing pattern and / or scan path is selected, in practice, representing a specific combination of droplets for each target area (i.e., one of the allowable sets of combinations) that will be used in the deposition process, represented by the digit 1569. As part of this selection or planning process 1569, an optimization function 1570 may be optionally employed to reduce the number of scans or passthroughs to a number less than the product of the number of rows (or columns) in the target area multiplied by the average number of droplets per target area (for example, a number less than what would be required for a single row of nozzles, which are rotated 90 degrees so that all nozzles in a row can be used in each scan for each affected target area, and advance one row at a time to deposit droplets in multiple passthroughs for each row of the target area). For each scan, the print head can be moved, and waveform data per nozzle can be programmed to achieve droplet deposition instructions according to a bitmap or layout file, these functions are variously represented by the numbers 1571, 1573, and 1575 in Figure 15C. After each scan, this process is repeated for the next scan, as indicated by the number 1577.Optionally, these techniques and their implementations can be embodied in printer control file 1579, which is created for subsequent or repeatable use in controlling ink release at specific times.

[0150] Again, please note that several different implementations, which are mutually discretionary, have been described above. Firstly, in one embodiment, the drive waveform is not variable, but each nozzle This remains constant. The droplet volume combinations are generated by using variable geometric steps representing the printhead / substrate offset to align different nozzles with different rows of the target area, as needed. Using the measured droplet volume per nozzle, this process enables specific average droplet volume combinations to achieve a highly specific fill volume per target area (e.g., up to 0.01 pL resolution) with high reliability, allowing any droplet volume variation to be adapted within the desired tolerance. This process can be planned so that multiple nozzles are used to deposit ink in different rows of the target area in each pass. In one embodiment, the printing solution is optimized to produce the fewest scans possible and the fastest possible print time. Secondly, in another embodiment, different drive waveforms can be used for each nozzle, again using the specifically measured droplet volume. The printing process controls these waveforms so that specific droplet volumes are aggregated in specific combinations. Again, using the measured droplet volume per nozzle, this process enables specific average droplet volume combinations to achieve a highly specific fill volume per target area (e.g., up to 0.01 pL resolution). This process can be planned to use multiple nozzles to deposit ink in different rows of the target area in each pass. In both of these embodiments, a single row of nozzles can be used, or multiple rows of nozzles can be used, arranged as one or more printheads in a printhead assembly. For example, in one considered implementation, 30 printheads can be used, each having one row of nozzles, with each row having 256 nozzles. The printheads can further be organized into various different groups; for example, these printheads can be organized into a printhead assembly having five printheads mechanically mounted together, and these resulting six groups can be mounted separately in the printing system. In yet another embodiment, a combined printhead assembly is used, having multiple rows of nozzles that can be further positionally offset from one another.This embodiment is similar to the first embodiment described above in that different droplet volumes can be combined using a variable effective position offset or geometric step. Again, using the measured droplet volume per nozzle, this process allows for specific combinations of average droplet volumes to achieve a highly specific filling volume per target area (e.g., 0.05 pL, or even up to 0.01 pL resolution). This does not necessarily imply that the measurement does not contain statistical uncertainties such as measurement error. In one embodiment, such errors are small and included in the target area filling plan. For example, if the droplet volume measurement error is ±a%, the filling volume variation across the target area can be planned within a tolerance range of ±(b-an¹ / ²)% of target filling, where ±(b)% 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, to put it another way, when expected measurement errors are included, a tolerance range smaller than the specification can be planned so that, for example, as described above in relation to Figures 8A-8B, the resulting total filling amount for the target area can be expected to fall within the specification tolerance range. Naturally, the techniques described herein can be combined with other statistical processes as desired.

[0151] Droplet deposition can optionally be planned to use multiple nozzles to deposit ink in different rows of the target area with each pass, and the printing solution can optionally be optimized to produce the fewest scans and the fastest possible printing time. As previously mentioned, any combination of these techniques with each other and / or other techniques can also be employed. For example, in one specifically considered scenario, variable geometric steps are used with drive waveform variation per nozzle and quantity measurement per drive waveform per nozzle to achieve a very specific combination of quantities planned for the target area. For example, in another specifically considered scenario, fixed geometric steps are used with drive waveform variation per nozzle and quantity measurement per drive waveform per nozzle to achieve a very specific combination of quantities planned for the target area.

[0152] By maximizing the number of nozzles that can be used simultaneously during each scan, and by planning droplet volume combinations so that they always meet specifications, these embodiments promise high-quality displays. Also, by reducing print time, these embodiments contribute to very low print costs per unit, and therefore help lower the price point for the end consumer.

[0153] Figure 15D shows a flow chart relating to nozzle qualification. In one embodiment, droplet measurements are performed to produce statistical models (e.g., distribution and mean) for any and / or each of the droplet volume, velocity, and trajectory for each nozzle and for each waveform applied to any given nozzle. Thus, for example, if there are two selections of waveforms for each of 12 nozzles, there are up to 24 waveform-nozzle combinations or pairs. In one embodiment, measurements of each parameter (e.g., volume) are performed for each nozzle or waveform-nozzle pair sufficient to produce a robust statistical model. Despite the plan, it should be noted that it is conceptually possible that a given nozzle or nozzle-waveform pair may produce an exceptionally wide distribution or a mean that is so abnormal as to warrant special treatment. Such special treatment to be applied is conceptually represented in one embodiment by Figure 15D.

[0154] More specifically, the general method is represented using reference number 1581. The data generated by the droplet measurement device is stored in memory 1585 for later use. During the application of method 1581, this data is retrieved from memory, and the data for each nozzle or nozzle-waveform pair is extracted and processed individually (1583). In one embodiment, as described, a normal random distribution is constructed so that each variable is considered eligible, represented by the mean, standard deviation, and the number of droplets measured (n), or using an equivalent measure. Again, it should be noted that other distribution forms (e.g., Student's T, Poisson, etc.) may be used. The measured parameters are compared to one or more ranges to determine whether the relevant droplets are usable in practice (1587). In one embodiment, at least one range is applied so that droplets are considered ineligible for use (e.g., if the droplets are too many or too few for the desired target, the nozzle or nozzle-waveform pair may be excluded from short-term use). To provide examples, if a 10.00 pL droplet is desired, for example, nozzles or nozzle waveforms associated with a droplet mean that are more than 1.5% away from this target (e.g., <9.85 pL or >10.15 pL) can be excluded from use. Alternatively, range, standard deviation, variance, or another diffusion measure can be used. For example, if it is desired to have a statistical model of droplets with a narrow distribution (e.g., 3σ < 1.005% of the mean), droplets with measurements that do not meet this criterion can be excluded. It is also possible to use an elaborate / complex set of criteria that consider multiple factors. For example, an anomalous mean combined with very narrow diffusion may be accepted, and for example, if the diffusion (e.g., 3σ) away from the measured (e.g., anomalous) mean μ is within 1.005%, then the relevant droplet can be used. For example, if it is desired to use droplets with a 3σ volume of 10.00 pL ± 0.1 pL or less, a nozzle-waveform pair that produces a 9.96 pL average with a 3σ value of ±0.8 pL may be excluded, but a nozzle-waveform pair that produces a 9.93 pL average with a 3σ value of ±0.3 pL may be acceptable.Clearly, many possibilities are possible according to any desired rejection / abnormality criteria (1589). It should be noted that the same type of processing can be applied to the flight angle and velocity per droplet, i.e., the flight angle and velocity per nozzle-waveform pair will exhibit a statistical distribution, and it is expected that some droplets can be excluded depending on the measurement and statistical model derived from the droplet measurement device. For example, droplets with an average velocity or flight trajectory that is outside the normal 5%, or with velocity dispersions outside a particular target, can be hypothetically excluded from use. Different ranges and / or evaluation criteria can be applied to each droplet parameter measured and provided by the storage device 1585.

[0155] It should be noted that droplets (and nozzle-waveform combinations) can be processed and / or treated in different ways depending on rejection / abnormality criteria 1589. For example, certain droplets that do not meet the desired criteria can be rejected, as described (1591). Alternatively, additional measurements can be selectively performed for subsequent measurement iterations of a particular nozzle-waveform pair, and, as an example, additional measurements can be specifically performed on a particular nozzle-waveform pair to improve the tightness of the statistical distribution through additional measurements if the statistical distribution is too broad (e.g., variance and standard deviation depend on the number of data points measured). By figure 1593, it is also possible to adjust the nozzle drive waveform, for example, to use higher or lower voltage levels (e.g., to provide larger or smaller velocities or a more consistent flight angle), or to shape the waveform to produce a tuned nozzle-waveform pair that meets specific criteria. By figure 1594, the timing of the waveform can also be adjusted (e.g., to compensate for an abnormal average velocity associated with a particular nozzle-waveform pair). As an embodiment (previously suggested), slower droplets can be fired earlier than other nozzles, and faster droplets can be fired later to compensate for a faster flight time. Many such alternatives are possible. Finally, by figure 1595, any adjusted parameters (e.g., firing time, waveform voltage level, or shape) can be stored, and the adjusted parameters can be applied to remeasure one or more related droplets as desired. After each nozzle-waveform pair (modified or different) is deemed qualified (passed or rejected), the method then proceeds to the next nozzle-waveform pair by figure 1597.

[0156] As should be understood, the described nozzle drive structure provides flexibility in printing droplets of different sizes. The use of precise fill volume, droplet volume, droplet velocity, and droplet trajectory per target area allows for the use of advanced techniques to vary the fill volume and plan the use of nozzles / waveforms and / or droplets according to defined criteria (in the specifications). This provides further quality improvements over conventional methods.

[0157] Here, we use Figures 16-18B to provide further details about two considered droplet measurement devices (or systems), namely, those predicted by shadowgraphy and interferometry, respectively. Figures 16-17 will be used to illustrate one embodiment of a printer having a droplet measurement system, while Figures 18A and 18B will be used to discuss shadowgraphy and interferometry, respectively.

[0158] As described above, this teaching discloses various embodiments of an industrial inkjet thin-film printing system, including a droplet measuring device incorporated into the printing system. The various embodiments of the inkjet thin-film printing system in this teaching can utilize imaging techniques such as shadowgraphy or non-imaging techniques such as phase Doppler analysis (PDA) (an interferometry-based technique), which can provide significant advantages for high-speed measurement of multiple nozzles of an inkjet printhead. The various embodiments of the printhead assembly used in the thin-film inkjet printing system in this teaching can have multiple printheads. Such high-speed measurements can be performed in situ at any time during the printing process and can provide data that may include the amount, velocity, and trajectory of each droplet from each nozzle of each printhead. Collective data obtained from the droplet measuring device incorporated into the inkjet thin-film printing system can be used to provide uniformity of the amount of ink delivered to each of the millions of pixels on an OLED panel display.

[0159] When depositing film during the manufacturing of OLED panels, the deposited film material Since thickness often affects panel performance, and good display uniformity is a crucial attribute of a good OLED panel, it is often desirable to deposit a film material with a uniform thickness across the panel. When using an inkjet printing method to deposit the film, ink droplets are released from the printing apparatus onto the panel substrate, and the thickness of the deposited film in each area of ​​the panel is typically related to the amount of ink dispensed across that area of ​​the panel, which is further related to the amount and placement of droplets on the panel surface. Therefore, it is often desirable to dispense the amount of ink uniformly with respect to both the amount and location of dispensed droplets across the OLED panel display.

[0160] As mentioned above, an inkjet printing system can typically have at least one printhead having multiple inkjet nozzles, each capable of dispensing droplets of ink onto a panel surface. Typically, there are variations across the multiple nozzles of the printhead with respect to the amount, trajectory, and velocity of the dispensed droplets. Such variations can arise from a variety of sources, including, but not limited to, variations in nozzle operating conditions, variations in the behavior of the nozzle actuators, including the age of the piezoelectric nozzle driver, variations in the ink, and variations in the size and shape of the nozzles. The effects of such variations can lead to non-uniformity of volume loading across the panel. For example, variations in droplet volume can directly lead to variations in the amount deposited, while variations in droplet velocity and trajectory can indirectly lead to variations in the amount of ink deposited by causing variations in the arrangement of droplets on the OLED panel surface. Theoretically, these variations can be avoided by using only a single nozzle when printing, but printing with a single nozzle is too slow to be practical for real-world manufacturing applications. In light of such variations in ink droplets dispensed from different nozzles, and the practical need to use multiple nozzles to obtain a reasonable processing speed when using inkjet printing for manufacturing applications, it is desirable to have a method and related apparatus that provides uniform dispensing of ink across an OLED panel area despite such inter-nozzle droplet variations.

[0161] The measuring device incorporated into the thin-film inkjet printing system according to this teaching can be used to provide actual measurements of the amount, velocity, and trajectory for each nozzle of the inkjet printhead at any time during the execution of the printing process, or intermittently during the execution of the printing process. Such measurements can provide a reduction in inter-nozzle droplet variation to achieve a more uniform deposition of film material using the inkjet method. In some embodiments, such measurements can be used to adjust printhead performance by adapting the drive waveform to each of the individual nozzles to directly reduce inter-nozzle droplet variation. In some embodiments, such measurements can be used as input to a print pattern optimization system, which can reduce inter-nozzle droplet variation by adjusting the nozzle selection for droplet deposition to average out the inter-nozzle droplet variation of the deposited film. Various embodiments of the measuring device incorporated into the thin-film inkjet printing system according to this teaching can utilize various imaging techniques such as shadowgraphy, or non-imaging techniques such as PDA. PDA can specifically offer the significant advantage of rapidly analyzing multiple nozzles of an inkjet printhead, which is particularly useful in systems with many nozzles and / or printheads.

[0162] In this regard, an inkjet thin-film printing system according to various embodiments of this teaching may consist of several devices and apparatus that enable the reliable placement of ink droplets to specific locations on a substrate. These devices and apparatus may, in non-limiting embodiments, include a printhead assembly, an ink delivery system, a motion system, a substrate support device such as a floating table or chuck, a substrate loading and unloading system, a printhead maintenance system, and a printhead measuring device. In addition, the inkjet thin-film printing system may be mounted on a stable support assembly, which may include, for example, a granite or metal base. The printhead assembly may consist of at least one inkjet printhead with at least one orifice capable of ejecting ink droplets at a controlled rate, and such ejected droplets may be further characterized by their volume, velocity, and trajectory.

[0163] Because printing requires relative motion between the printhead assembly and the substrate, the printing system may include a motion system such as a gantry or a split-axis XYZ system. Either the printhead assembly can move over a stationary substrate (gantry type), or both the printhead and the substrate can move, for example, in a split-axis configuration. In another embodiment, the printing station may be fixed, and the substrate can move relative to the printhead on the X and Y axes, with Z-axis motion provided by either the substrate or the printhead. As the printhead moves relative to the substrate, ink droplets are released at the correct time so that they are deposited in the desired locations on the substrate. The substrate is inserted and removed from the printer using a substrate loading and unloading system. Depending on the printer configuration, this can be achieved using a mechanical conveyor, a substrate floating table, or a robot with an end effector. The printhead measurement and maintenance system may consist of several subsystems that enable measurements such as droplet volume verification, droplet volume, velocity, and trajectory measurement, as well as printhead maintenance procedures such as wiping the inkjet nozzle surface and preparing for ink discharge into the waste bin. Considering the various components that can comprise an inkjet thin-film printing system, the various embodiments of the inkjet thin-film printing system according to the various embodiments of this teaching can have various installation areas and shape factors.

[0164] As a non-limiting embodiment, Figure 16 depicts various embodiments of an inkjet thin-film printing system that can be used, for example, to print on substrates such as OLED panels. In Figure 16, the inkjet thin-film printing system 1600 utilizes a split-axis motion system. The inkjet thin-film printing system 1600 can be mounted on a printing system support assembly 1610, which may include a pan 1612 supported by a support frame 1614. A base 1616 is mounted above the pan, and the base may optionally be constructed from granite or metal. The inkjet thin-film printing system may include a motion system 1620, for example, a split-axis motion system as shown.

[0165] The motion system 1620 is found to include a bridge 1622 that supports an X-axis carriage 1624, which in turn mounts a Z-axis mounting plate 1626. The Z-axis mounting plate, in turn, supports a printhead mounting and clamping assembly 1628, which is used to mount a replaceable printhead assembly 1640. For the split-axis motion system 1620, a Y-axis track 1623 can be mounted on the base 1616 to provide support for a Y-axis carriage 1625 that carries a substrate support assembly 1630, and these various components provide Y-axis movement of the substrate mounted on the substrate support assembly 1630. As shown in Figure 16, for various embodiments of the thin-film printing system, the substrate support assembly 1630 may be a chuck. The substrate support assembly may be provided by a floating table, for example, as described in detail in U.S. Patent No. 8,383,202, which is incorporated herein by reference. The inkjet thin-film printing system 1600 can utilize a system assembly that supports one or more modular inkjet printhead assemblies, such as various printhead assemblies shown mounted in the tool carousel 1645. By providing selective replacement of various printhead assemblies, it offers flexibility for efficient continuous printing of various ink formulations on a substrate during the printing process, such as during printing of an OLED panel substrate. This can be provided. It should be noted that this is not required in all embodiments, i.e., other embodiments may feature a single printhead assembly that is not exchanged between different printing processes. For example, one considered embodiment features an assembly line of multiple printers, each performing its own printing process (e.g., using its own ink). The techniques described herein can be applied to each such printer.

[0166] A printhead assembly may include a fluid system having, for example, an ink reservoir that is in fluid communication with at least one inkjet printhead to deliver OLED film-forming material onto a substrate. In this regard, as shown in Figure 16, a printhead assembly 1640 may include at least one printhead 1642. In various embodiments, a printhead assembly may optionally include fluid and electronic connections to each printhead. Each printhead may have a plurality of nozzles and orifices capable of releasing ink droplets at a controlled rate with measurable droplet volume, velocity, and trajectory. Various embodiments of the printhead assembly 1640 may have about 1 to about 30 printheads per printhead assembly. A printhead 1642 may have about 16 to about 2048 nozzles, each capable of releasing droplet volumes of about 0.10 pL to about 200.00 pL.

[0167] Measuring the performance of each nozzle of a given printhead may include checking nozzle firing, as well as measuring droplet volume, velocity, and trajectory. As mentioned above, having such measurement data allows for either adjusting the head before printing to provide more uniform performance for each nozzle, or using the measurement data to provide a printing algorithm that can compensate for differences during printing, or a combination of such approaches. Clearly, having a dataset of reliable and up-to-date measurement data allows for various approaches to using the measurement data to compensate for inter-nozzle droplet volume variations, enabling a planned printing process that combines different amounts of droplets (from the same nozzle using different drive waveforms, or from each nozzle). As mentioned above, the measurement data is collected to generate a set of measurements that represent the distribution of each nozzle, which is advantageous, so that expectations for average droplet volume, trajectory, and velocity are generated, and the expected variations of each such droplet parameter are well understood and can be used in the print plan.

[0168] In this regard, the described inkjet thin-film printing system may include a droplet measurement device or system 1650 that can be mounted on the support 1655. Various embodiments of the droplet measurement system 1650 are considered to be based on imaging or non-imaging techniques, such as shadowgraphy or interferometry-based methods, as described. Embodiments utilizing non-imaging PDA techniques can offer the significant advantage of rapidly analyzing about 16 to about 2048 nozzles of each printhead, such as printhead 1642, (for example, about 50 times faster than typical imaging techniques). Recalling that a printhead assembly may include, for example, 30 printheads (i.e., a printing system using more than 10,000 nozzles), this enables high-speed in-situ dynamic measurement of all nozzles (and all alternative drive waveforms, if applicable to the embodiment) in the printer, with droplet recalibration every 2 to 24 hours, or more frequently. Furthermore, various embodiments of the systems and methods according to this teaching may utilize a gas enclosure assembly capable of housing the printing apparatus and a PDA measurement device incorporated into the system. A system and method utilizing a PDA measuring device integrated into a gas enclosure assembly and system housing a printing apparatus can provide high-speed in-situ measurement of multiple nozzles in a print head. This is particularly useful, for example, to ensure uniform deposition across a large substrate having one or more OLED devices and to reduce any unevenness effects.

[0169] The number 1617 is used to specify the area of ​​the inkjet printer associated with the droplet measurement system 1650. This area is illustrated in detail in an enlarged view in Figure 17.

[0170] As shown in Figure 17, the printhead assembly 1740 can be held during printing by the printhead mounting and clamping assembly 1728, which is itself again supported by the Z-axis mount 1726 of the motion system. In this regard, the motion system is used to position the printhead assembly 1740 for measurement in close proximity to the droplet measurement system 1750, for example, in a service area or service station. As previously mentioned, the droplet measurement system 1750 can be designed for selective engagement and disengagement while the printhead assembly 1740 is in this position. With large printhead assemblies (e.g., with thousands of nozzles), such a structure allows the droplet measurement system to perform tests while the printhead assembly 1740 is "stationed" and other tests are performed simultaneously by other test or calibration equipment or processes (not shown). For example, the use of simultaneous processes, applied to help minimize any downtime of the overall inkjet printing system, allows printhead nozzles to be purged, cleaned, or otherwise managed, which helps maximize manufacturing productivity. As described above (and as explained below with respect to Figure 19), droplet measurements (and other inspections) can be performed while the substrate is being transported, dried, cured, loaded, or unloaded, further minimizing any system downtime by stacking droplet measurements against other unavoidable tasks associated with the printing / manufacturing operation. Each nozzle of the printhead 1742 of the printhead assembly 1740 can be adapted to the measurement area 1756 for measuring droplets emitted from each nozzle using the droplet measurement system 1750. In this embodiment, individual printheads 1742 can be moved relative to other printheads for analysis, but again, it should be noted that this is not required in all embodiments. For example, each printhead can also be statically mounted during measurement, and the droplet measurement system can be advanced to each printhead location and each nozzle location within a given printhead.As mentioned above, this allows for the simultaneous processing or "stacking" of multiple inspection operations while the printhead assembly is stationary. It also makes it possible to use multiple droplet measurement systems, for example, to independently measure different nozzles on different spatially separated printheads.

[0171] For illustrative purposes, assume that the droplet measurement system is a PDA device (i.e., an interferometry-based device) having a light source such as a laser source and a light-transmitting optics unit, a beam splitter, and a transmitting lens. In addition, such a PDA device may also have a receiving optics unit including a light-receiving lens and multiple photodetectors. For example, a first optical side 1752 of the droplet measurement system 1750 can supply one or more rays for measurement and focus the light on the measurement area 1756, as shown by the diagonal lines, while a second optical side 1754 can allow the measurement light, dispersed from the droplet in the measurement area 1756 to the receiving optics unit and one or more photodetectors, to pass through.

[0172] The droplet measurement system 1750 can interface with a computer or computer device (not shown), either directly or remotely. Such a computer device can be configured to receive signals representing the measured droplet volume, velocity, and trajectory of each droplet produced by the nozzle (or nozzle-waveform combination) from each print head 1742 of the print head assembly 1740. Again, multiple measurements of many droplets from each nozzle / nozzle-waveform pair are advantageously performed to generate a statistical population representing various reproducible droplets.

[0173] As previously mentioned in relation to Figures 11 and 12, various embodiments of the printing system can be housed in a gas enclosure that provides an inert, low-particle environment, and droplet measurements preferably occur in such an environment. In one embodiment, droplet measurements are performed, for example, in the same general (enclosed) chamber in the common atmosphere used for printing. In a second embodiment, for example, a separate, fluidly isolated chamber is used for measurements as part of a service station area.

[0174] Figure 18A shows the layout of a droplet measurement system 1801 specifically configured to use the shadowgraphy technique. Specifically, the print head 1803 is seen in the position where the droplet 1805 will be ejected into an ejection chutes (not shown in Figure 18A). During the flight of the droplet 1805, the droplet traverses the measurement area to which the droplet is illuminated by a light source, and in Figure 18A, it can be seen that this consists of, for example, a strobe light 1807 and an optional light source optics unit 1809 employed to direct the light from the strobe light 1807 to the measurement area (for example, from below the measurement surface as previously illustrated in relation to Figures 2A-E or 16-17). The optics unit repeatedly exposes the droplet rapidly and continuously at different positions to capture it in a single image frame, by directing the light to illuminate a relatively wide area represented by a focusing or redirection path 1811. Thus, Figure 18A shows three different positions of the same droplet, each representing a different flash of the strobe, together collectively imaged. Therefore, for example, an image frame being analyzed might show what appears to be multiple droplets at different locations (i.e., multiple instances of the figure 1805), but these are actually the same droplet at different locations along its flight path. A second set of optics in the 1813 provides light collection and focusing so that the captured image clearly depicts both the contour of the droplet and a variable amount of shadow representing the droplet diameter, which is used by image processing software to calculate the droplet volume. As should be understood, by imaging the same droplet during its flight at multiple locations, the droplet measurement system can use one image to calculate the droplet volume, velocity, and trajectory, with the shadow parameter used to calculate the droplet mass, and therefore the volume, and the relative position of the droplet used to calculate both velocity and trajectory. For example, a droplet that increases its apparent diameter at the "lower position" in the captured image frame is moving towards the photoreceiving optics in the 1813, while one that decreases its diameter is moving away from it. The light-receiving optical unit 1813 then transmits the captured light to the camera 1815, for example, a high-resolution CCD camera that images the droplet contour and shadow as depicted by the graphic 1817.The droplet measurement system optionally provides control over the zoom / focus (1819) and / or XY position (1821) of the photodetector, all under the control of a centralized computer system 1823 (and instructions stored on a non-transient mechanical storage medium used by one or more processors of the computer system for such control). In one embodiment, as described, the photodetector and light source are mounted on a common chassis and transported together to provide a fixed-focus path, but this is not required in each embodiment. While the described system captures the movement of each droplet in a few microseconds, image processing application software 1825, executed by the computer system 1823, then calculates droplet parameters. In an example, the computer can provide display and visualization (1827) of the droplet and / or measured parameters, and can calculate the values ​​of various parameters such as volume, velocity, and trajectory (1829, 1831, and 1833), or other parameters. It should be noted that the computer system 1823 may be part of an inkjet printing system, or it may be remote (for example, connected by a local area network "LAN" or wide area network "WAN", e.g., the Internet, to collect data remotely), and similarly, the display and visualization 1827 may also be provided remotely from the computer system 1823 via the LAN or WAN, as indicated by the figure 1835. The data system 1823 compiles the measured parameters to form a statistical ensemble of measurements for a given nozzle that produced droplets (and for a given nozzle-waveform pair if alternative drive waveforms are used by a particular embodiment of the printing system). The computer system 1823 optionally stores the individual measurements themselves and / or statistical summaries (e.g., mean and standard deviation or variance in the case of a normal distribution, and equivalent metrics if other types of distributions are supported) in the database 1837. Once a sufficiently robust ensemble has been measured, the database can then be applied in planning and / or optimizing the printing process as described above, for example, using a specific combination of droplet averages to obtain a composite filling for a target area, and the composite filling may be based on different droplet volumes (e.g., from different nozzles and / or drive waveforms).

[0175] Figure 18B shows the layout of a droplet measurement system 1851 specifically configured to use the PDA (Interferometry) technique. A printhead is illustrated in a fixed position for measurement, as referenced by the figure 1853. The printhead will emit droplets downward into the droplet measurement area from a specific nozzle (e.g., using a specific drive waveform), as indicated by the figure 1855. As in previous embodiments, the droplet measurement system can optionally be designed for three-dimensional transport relative to a stationary printhead so that the droplet measurement area is effectively "carried" to the droplet flight of a specific nozzle. A light source, in this case a laser 1857, generates a ray 1859 that is directed to enter a beam splitter 1861. The beam splitter generates two or more rays 1863 and 1864 (only two are illustrated in Figure 18B), and the optics unit 1865 then redirects the rays in a converging manner, i.e., as represented by the digits 1866 and 1867, so that the rays intersect at a position coinciding with the droplet in flight. Note that the optics unit 1865 optionally provides a laser 1857 mounted below the measurement surface (see the discussion in Figures 2D and 2E above), and optionally redirects optical paths 1859 or 1863 / 1864 to reach the measurement area (e.g., by redirecting one or more optical paths around the discharge tub). Note that the digit 1869 is used to represent the general continuous dimensions of the irradiation optics unit (e.g., optical paths 1866 and 1867, etc.). As described above, using interference-based techniques, the diffraction pattern is captured from a direction angularly offset by this continuous dimension 1869, as represented by angle 1873. This angular deviation is typically 90 degrees, but other capture directions can also be used. Thus, the measurement light 1871 is received from the incident light at this angular deviation by a second set of optics 1875 (labeled "optics 2") and redirected by a non-imaging detector 1877 for sub-deposition measurement.These detectors generate data representing a diffraction pattern, as illustrated by graphic 1879, and the spacing of the lines in the diffraction pattern provides a measure of droplet volume, as should be understood (for example, by comparing this graphic 1879 with graphic 1817 from Figure 18A), and this spacing is processed much faster than the imaging method shown in Figure 18A to measure droplet volume. Note that while Figure 18B illustrates the use of one light source 1857 and two incident rays 1866 and 1867, other embodiments may use one or more light sources and two or more incident rays to capture, for example, droplet velocity, trajectory, and other parameters. Similar to the embodiment in Figure 18A, in Figure 18B, a computer (1881) optionally provides zoom / focus (1883) and XY transport for the measuring optics, runs suitable application software (1887) to calculate various droplet parameters, and provides display and visualization (1889). As before, these various elements can be integrated with a printer or manufacturing device, or distributed across a WAN or LAN controlled by multiple separate processors on each computer or server. As before, the measured parameters may include droplet volume (1891), velocity (1893), and trajectory (1895), along with data representing statistical populations (1897) stored in a database (1899) for the purpose of scan planning. This scan plan can again combine droplet parameters from different nozzles and / or waveforms to perform precise filling of the target area based on multiple different droplet volumes.

[0176] As previously described, droplet parameters can change over time due to ambient conditions or ink characteristics, for example, according to system parameters. Therefore, industrial printing systems can, advantageously, update droplet measurements relatively frequently, not only for individual droplets but also for the statistical population of each droplet (as well as the expected average volume / velocity and trajectory of each droplet). This helps ensure precise droplet data that is always accurate and up-to-date, enabling planned droplet combinations that reliably match the maximum tolerance of composite ink filling. In practice, droplet parameters have been found to change somewhat slowly, for example, with detectable fluctuations every 2-12 hours. The use of in-situ droplet measurement allows for the iterative dynamic measurement and construction of a new statistical population of parameters measured within this time range. While this conventional method can take hours to measure a large printhead or printhead assembly, it should be noted that through the use of high-speed tec...

Claims

1. A printing apparatus, the printing apparatus, A print head having nozzles, A floating substrate table for printing, which places the substrate on the deposition surface of the printing position, A print head transport mechanism for transporting the print head in the X and Z directions, A droplet measurement system comprising a light source, a plurality of photodetectors, an interference optical system, a light condenser positioned between the light source and at least one of the photodetectors, and an optical path extending from the light source to the photodetectors, wherein the light source, the photodetectors, the light condenser, the interference optical system, and the optical path are mounted in a fixed positional relationship with respect to each other, the light source, the photodetectors, the interference optical system, and the light condenser 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 that moves the droplet measurement system in three independent directions relative to the print head, A controller configured to control the print head, the print head transport mechanism, the droplet measurement system, and the motion system to measure droplets from a plurality of nozzles by applying a plurality of waveforms to at least one of the nozzles, and to exclude a portion of the measured values ​​based on at least one criterion, A printing device equipped with the following features.

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

3. The printing apparatus according to claim 2, wherein the three independent directions include directions extending between the intersection of the optical path and the droplet and one of the nozzles.

4. The printing apparatus according to claim 1, wherein the droplet measurement system outputs a signal representing either the trajectory or the velocity of a droplet ejected from the print head.

5. The nozzle defines a first plane, The aforementioned droplet measurement system further includes a mirror, The motion system moves the segment of the optical path along a second plane, the second plane being parallel to the first plane. The printing apparatus according to claim 1, wherein the light source and the photodetector are arranged outside the second plane.

6. The printing apparatus according to claim 5, wherein the second plane is located above the deposition surface.

7. The printing apparatus according to claim 6, further comprising at least one processor that calculates a value of the properties of the droplet based on the electronic output of the droplet measurement system.

8. The nozzle includes at least 1,000 nozzles, The printing apparatus according to claim 7, wherein the motion system moves the segment and causes the segment to intersect with the flight path of a liquid droplet ejected from any one of the at least 1,000 nozzles.

9. The printing apparatus according to claim 8, wherein the three independent directions include the direction between one of the nozzles and the intersection of the optical path and the flight path.

10. The nozzle includes at least 1,000 nozzles, The motion system positions the optical path so as to intersect with the flight path of the droplets ejected from any of the at least 1000 nozzles at a position above the deposition surface. The printing apparatus according to claim 1, further comprising a non-transient storage device for storing measured values ​​of the droplet measurement system.

11. The printing apparatus according to claim 9, wherein the interference optical system includes an optical fiber.

12. The printing apparatus according to claim 1, further comprising a gas enclosure for maintaining a controlled atmosphere, wherein the print head, the substrate floating table, and the droplet measurement system are located within the gas enclosure.

13. The printing apparatus according to claim 1, further comprising an electronic control system that automatically controls the print head transport mechanism, the droplet measurement system, and the motion system to automatically measure the characteristics of droplets ejected from at least one of the nozzles during processing of a series of substrates.

14. The printing apparatus according to claim 1, wherein the print head transport mechanism includes a bridge extending over the substrate floating table.

15. The printing apparatus according to claim 14, wherein the droplet measurement system is positioned adjacent to the end of the bridge.

16. Apparatus, the apparatus, A print head having nozzles, A floating substrate table for printing, which places the substrate on the deposition surface of the printing position, A print head transport mechanism that transports the print head in the X direction and the Z direction between a first position and a second position adjacent to the printing position, A droplet measurement system comprising a light source, a plurality of photodetectors, an interference optical system, a light condenser positioned between the light source and at least one of the photodetectors, and an optical path extending from the light source to the photodetectors, wherein the light source, the photodetectors, the light condenser, the interference optical system, and the optical path are mounted in a fixed positional relationship with respect to each other, the light source, the photodetectors, the interference optical system, and the light condenser 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 droplet measurement system in three independent directions relative to the print head in order to position a portion of the optical path in a measurement area adjacent to one of the nozzles of the print head, A controller is configured to control the print head, the print head transport mechanism, the droplet measurement system, and the motion system, to measure droplets from a plurality of nozzles by applying a plurality of waveforms to at least one of the nozzles, to form a statistical representation of the measured values, and to exclude a portion of the measured values ​​based on at least one criterion. The aforementioned droplet measurement system is a device that detects interference patterns and visualizes droplets.

17. The apparatus according to claim 16, further comprising a processor that determines droplet characteristics from the electronic output of the droplet measurement system.

18. The apparatus according to claim 17, wherein the droplet characteristics are the volume, trajectory, or velocity of the droplet.

19. The apparatus according to claim 18, wherein the three independent directions include directions extending from one of the intersection points of the optical path and the droplet to one of the nozzles.

20. The apparatus according to claim 16, wherein the nozzle defines a first plane, the motion system moves a segment of the optical path interacting with the droplet in flight in a second plane above the deposition plane, and the light source and the photodetector are each positioned outside the second plane.

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