Monolithic inkjet printhead and ink composition

Abstract

The present disclosure provides a monolithic inkjet printhead for ejecting a set of ink compositions, the printhead comprising at least one substrate, the substrate comprising a plurality of ejectors, each ejector comprising (i) a nozzle, (ii) a chamber for receiving a set of ink compositions, the chamber being in fluid communication with the nozzle, and (iii) a piezoelectric actuator coupled to the nozzle for selectively ejecting the ink composition from the nozzle, each ejector being configured to eject ink droplets of different ink compositions at corresponding volumes and velocities. The present disclosure further provides a set of ink compositions themselves, a printing apparatus, and a method thereof, in which the viscosity value, density value, and surface tension value are adapted.

Description

Technical Field

[0001] The present invention relates to a monolithic inkjet printhead, a set of different ink compositions suitable for use with said printhead, a printing apparatus comprising said printhead, and methods thereof.

Background Art

[0002] Piezoelectric inkjet (PIJ) printheads are an area of active research and development. To date, most PIJ printheads have piezoelectric actuators incorporated into the walls of the ink chambers. Deformation of the piezoelectric element causes the piezoelectric actuator to flex, creating a pressure change in the ink stored in the chamber, thereby ejecting ink droplets from the nozzles. To achieve the required printing resolution, commercially available PIJ printheads typically use a large number of parallel electrical connections to an external actuator driver to drive the individual piezoelectric actuators within the printhead. The large number of wires not only increases manufacturing complexity but also reduces the reliability of the printing itself. Furthermore, in multicolor printing, different operating inputs (e.g., different actuation waveforms) and / or different nozzles for ejecting different inks may be required, both of which complicate the printhead in terms of operation and configuration.

[0003] Known techniques in this field have one or more of the problems described above.

[0004] US2011 / 0134175A1 describes a method for adjusting the ink ejection characteristics of an inkjet printing apparatus, the method comprising adjusting at least one of the voltage and the application period of a drive signal applied to a plurality of piezoelectric actuators that apply ejection pressure to a plurality of nozzles such that the volumes of a plurality of ink droplets ejected from the plurality of nozzles are uniform, and shifting the application start time of the drive signal applied to the plurality of piezoelectric actuators such that the plurality of ink droplets ejected from the plurality of nozzles reach the printing medium simultaneously.

[0005] US6328395B1 describes drive signal generating means for generating a drive signal including a plurality of drive pulses in one cycle. The print data generating means generates print data for inputting one or a plurality of drive pulses to each pressure generating element in one print cycle. The pressure generating means expands and contracts in response to the drive pulses input thereto, thereby causing ejection of an ink droplet or ejection of a plurality of ink droplets.

[0006] US6364444B1 describes an apparatus for driving an inkjet recording head including a piezoelectric device, a drive waveform generating circuit, and a waveform extraction circuit. The drive waveform generating circuit generates a drive waveform in which n basic waveforms each having a single cycle are connected in series. The waveform extraction circuit extracts m of the n basic waveforms as a print drive waveform based on print data supplied from the outside, and applies the print drive waveform to the piezoelectric device. Thereby, ink is ejected from the nozzle based on the distortion of the piezoelectric device.

[0007] An object of the present invention is to provide an improved inkjet print head and a printing apparatus that can reliably provide high-definition and accurate printing in consideration of the drawbacks of the prior art. An embodiment of the present invention aims to provide an inkjet print head that is easy to manufacture, easy to operate, and compact in configuration. The print head according to the present invention is for ejecting a set of different ink compositions, for example, a set of ink compositions of different colors.

[0008] The present invention also aims to provide a set of different ink compositions having performance characteristics for high-quality printing. The ink compositions are preferably a set of ink compositions of different colors. This set can be used with an improved inkjet printhead with a simple design and easy operation. Ink droplets deposited on a printing medium can achieve high-quality printing by producing corresponding sizes and shapes. It should be noted that this does not exclude the use of ink compositions with (printheads with) complex designs and / or operations to achieve high-quality printing.

[0009] According to the present invention, a set of different ink compositions, whose characteristics are controlled to be ejected by corresponding droplet ejectors, is used. Desirably, during use, the ink compositions are ejected by substantially the same operating waveform, and the resulting droplets on a printing medium (e.g., paper) can have the same size and shape to provide high-quality printing while minimizing the complexity of the wiring.

[0010] The present invention further aims to provide the inkjet printhead, preferably a printing apparatus including the ink composition. In this way, this apparatus can provide all the advantages of the printhead and the ink composition.

[0011] WO2021 / 229040A1 describes a droplet ejector assembly for a printhead comprising a substrate having a plurality of layers on a first surface of a CMOS control circuit and the substrate, a fluid chamber having a droplet ejection orifice, and a piezoelectric actuator element formed by one or more of the layers and including a first electrode and a second electrode in contact with a piezoelectric body.

[0012] US2019 / 0283424A1 describes a droplet ejector for a print head, the droplet ejector comprising a substrate having an attachment surface and an opposite nozzle surface, at least one electronic component integrated with the substrate, a nozzle forming layer formed on at least a part of the nozzle surface, a fluid chamber at least partially defined by the substrate and at least partially defined by the nozzle forming layer, and a piezoelectric actuator formed on at least a part of the nozzle portion. SUMMARY OF THE INVENTION

[0013] In a first aspect of the present invention, a monolithic inkjet print head for ejecting a set of different ink compositions is provided, the print head comprising a substrate, the substrate comprising a plurality of ejectors, each ejector comprising (i) a nozzle, (ii) a chamber for receiving the set of ink compositions, each chamber being in fluid communication with the nozzle, and (iii) a piezoelectric actuator coupled to the nozzle for selectively ejecting the ink composition.

[0014] Typically, each ejector is configured to eject ink droplets of different ink compositions at corresponding volumes and velocities.

[0015] Typically, each ejector is configured to eject an ink composition that meets a plurality of physical property criteria at corresponding volumes and velocities, the physical property criteria including at least corresponding density and viscosity. The physical property criteria typically also include corresponding surface tension. Typically, corresponding compressibility is not required.

[0016] Corresponding viscosity means that the viscosities of the ink compositions of the compositions are the same or similar (e.g., at 25 °C and 1 atmosphere). For example, the viscosity values of the compositions may be such that the difference between any two compositions is 20% or less, preferably 10% or less, more preferably 5% or less, and most preferably 1% or less of the maximum viscosity value of the set.

[0017] The corresponding density means that the density of the ink composition is the same or similar (e.g., at 25°C and 1 atm). For example, the difference in density between any two compositions may be 20% or less, preferably 10% or less, more preferably 5% or less, and most preferably 1% or less of the maximum density value of the set.

[0018] The corresponding surface tension means that the surface tension of the ink composition is the same or similar (e.g., at 25°C and 1 atm). For example, the surface tension value of the composition may be such that the difference between any two compositions is 20% or less, preferably 10% or less, more preferably 5% or less, and most preferably 1% or less of the maximum surface tension value of the set.

[0019] It will be understood that all possible combinations of ranges of viscosity, density, and surface tension, as well as preferred ranges of viscosity, density, and surface tension, are also considered. For example, the difference in viscosity, density, and optionally surface tension between any two compositions is 10% or less of the corresponding maximum value of the set, or the difference in viscosity, density, and optionally surface tension between any two compositions is 5% or less of the corresponding maximum value of the set. Also, the difference in viscosity between any two compositions is 20% or less of the maximum viscosity of the set, the difference in density between any two compositions is 10% or less of the maximum density of the set, and optionally, the difference in surface tension between any two compositions is 10% or less or 5% or less of the maximum surface tension of the set. Also, the difference in viscosity between any two compositions is 10% or less of the maximum viscosity of the set, the difference in density between any two compositions is 5% or 1% or less of the maximum density of the set, and optionally, the difference in surface tension between any two compositions is 5% or less of the maximum surface tension of the set. Also, the difference in viscosity between any two compositions is 1% or less of the maximum viscosity of the set, the difference in density between any two compositions is 1% or less of the maximum density of the set, and optionally, the difference in surface tension between any two compositions is 1% or less of the maximum surface tension of the set.

[0020] Generally, the configuration of the ejector includes the dimensions of the nozzle and chamber of the ejector.

[0021] Typically, the configuration of the ejector includes the operating waveform of the actuator during use. The operating waveform typically includes the time-varying displacement of the ink composition in the chamber and the force applied to the ink composition during operation.

[0022] Typically, all nozzles and actuators have corresponding dimensions and materials such that the ejected ink droplets of the ink composition have corresponding volumes and velocities.

[0023] Typically, the substrate has a first surface and a second surface opposite the first surface, the substrate includes a CMOS control circuit and a plurality of layers on the first surface of the substrate, the piezoelectric actuator is formed by one or more of the said layers, the nozzle includes a hole penetrating one or more of the said layers, whereby the piezoelectric actuator ejects the ink composition by displacing one or more of the said layers and the nozzle during use. Thus, the ejector is typically configured to eject the ink composition in inertial mode. The hole may penetrate the piezoelectric actuator.

[0024] In the context of the present invention, the ejected ink droplets of different compositions generally have corresponding volumes and velocities. The said volumes and velocities can be evaluated by known effective methods such as printed test patterns. Various "printed test patterns" methods are described in the prior art, for example, US2011 / 227988A1, US8322814B2, US10589519B2, and US7855037B2, which are incorporated herein by reference. The printed test pattern can be in the form of a printer test page (for example, a color printer test page, etc.) or any suitable form configured to enable corresponding evaluation. This method can be optionally selected and repeated one or more times (for example, when adjustment is required and it is necessary to re-evaluate the correspondence between volume and velocity). In other words, multiple printed test patterns can be generated. The printed test pattern may include features such as one or more symbols (for example, squares, dots, diamonds), numbers, letters, references, crosshairs, lines, grids, and mixtures thereof. Since the positioning is a function of the volume and velocity of the droplets, the positioning(s) of those features can be evaluated (for example, by the user, machine, software, or other suitable techniques) to determine the corresponding satisfaction level.

[0025] The corresponding volume refers to having the same or similar volume (for example, at 25 °C and 1 atmosphere). Preferably, the ejected ink droplets have corresponding volumes such that the volume difference between any two droplets from different ink compositions is 1 picoliter or less, or 0.5 picoliter or less, or 0.2 picoliter or less, or 0.1 picoliter or less, or 0.05 picoliter or less, or 0.01 picoliter or less, or zero. Additionally or alternatively, the volume difference between any two droplets from different ink compositions is 20% or less, or 10% or less, or 5% or less, or 1% or less, or zero with respect to the larger volume of the two droplets.

[0026] The corresponding speed refers to having the same or similar speed (e.g., at 25 °C and 1 atmosphere). Preferably, the ejected ink droplets have a corresponding speed such that the difference in speed between any two droplets from different ink compositions is 2 m / s or less, or 1 m / s or less, or 0.2 m / s or less, or 0.1 m / s or less, or 0.05 m / s or less, or zero. Additionally or alternatively, the difference in speed between any two droplets from different ink compositions is 20% or less, or 10% or less, or 5% or less, or 1% or less, or zero with respect to the speed of the larger of the two droplets. It will be understood that all possible combinations of sub - ranges of volume and speed are also contemplated herein. For example, as described above, the difference in volume may be 10% or less, and the difference in speed may be 10% or 5% or less. For example, as described above, the difference in volume may be 5% or less, and the difference in speed may be 5% or 1% or less. For example, as described above, the difference in volume may be 0.5 picoliters or less, and the difference in speed may be 1 m / second or 0.2 m / second or less. For example, as described above, the difference in volume may be 0.2 picoliters or less, and the difference in speed may be 0.2 m / second or 0.1 m / second or less.

[0027] In the context of the present invention, a print head is a component used in a printing apparatus. In the present invention, monolithic means that all components of the print head are integrated to form a single unit. This can be achieved by manufacturing a plurality of ejectors on a single substrate (e.g., from a single substrate wafer) on a large scale, or by manufacturing a plurality of ejectors on each of a plurality of substrates and bonding them together.

[0028] The print head may comprise at least 100 ejectors, preferably at least 1000 ejectors. The print head may be for ejecting a single ink composition from a plurality of nozzles.

[0029] Typically, a printhead comprises ejectors in a plurality of groups (typically at least 4 groups), with the ejectors in each group for ejecting an ink composition, and at least two (typically at least 4) ink compositions being different from each other. In this way, an exemplary printhead can be used to eject a plurality (usually at least 4) different ink compositions. The groups are typically known as channels in the art. Usually, the printhead comprises a separate manifold for each group of ejectors to supply an ink composition from each ink store to each ejector of each ejector group.

[0030] It will be understood that each ink chamber is in fluid communication with the supply of each ink composition to its respective nozzle. Thus, the chamber not only receives and stores the ink composition but is also in fluid communication with the nozzle such that the composition is ejected from the nozzle.

[0031] It will be understood that the nozzle comprises an aperture through which the ink composition can be controllably ejected by the operation of a piezoelectric actuator. Typically, the nozzle has a cross-sectional area of less than 3 mm 2 , for example less than 0.3 mm 2 . The piezoelectric actuator typically operates to cause displacement of an elastically deformable membrane that defines at least a portion of the nozzle so as to cause ejection of the ink composition from the nozzle during operation of the actuator.

[0032] According to the present invention, piezoelectric actuators are coupled to respective nozzles. Thus, the deformation of the piezoelectric actuators during use leads to the movement of the nozzles. Usually, a droplet ejector comprises a piezoelectric actuator and an elastically deformable membrane that defines at least a part of (or defines) the nozzle. Thus, the elastically deformable membrane defines at least a part of the chamber (e.g., the wall). Usually, the actuator is arranged adjacent to, for example, around the nozzle. Usually, the operation of the piezoelectric actuator deflects the elastically deformable membrane, thereby defining the nozzle. Thus, the elastically deformable membrane and the nozzle move during use to eject the ink composition from the chamber through the nozzle. Usually, a printhead comprises a nozzle-defining layer formed on a substrate, the nozzle-defining layer comprising a piezoelectric actuator and defining the nozzle. The nozzle-defining layer usually comprises at least one piezoelectric layer and one or more electrodes in electrical contact with the at least one piezoelectric layer.

[0033] This is in contrast to an arrangement where the actuator is on the distal side of the nozzle and / or an arrangement where the nozzle and the actuator are on different walls of the chamber (for example, the nozzle is on one wall of the fluid chamber and the actuator is on the opposite wall of the same chamber such that the actuator is far from the nozzle). In existing PIJ technology where the actuator is not coupled to / away from the nozzle, a large operating force is required to compress substantially the entire ink composition stored in the chamber to eject the ink composition. Thus, this operation is dependent on the compressibility mode. In these arrangements, the compressibility of the ink composition directly affects the printing process. For example, the compressibility of the ink composition can affect the ejection procedure (for example, by affecting the rigidity of the ejector). In this way, the compressibility of the ink is also related to the quality of printing. Further, the mass of the droplet can be affected by not only the ink in the chamber but also the entire ink in the nozzle and, in some configurations, the ink located very far from the chamber. The complexity of the compressibility mode is that the remote ink can be related to the attenuation of the ejection procedure. Therefore, the attenuation is moderate and the ejection procedure can be susceptible to crosstalk problems as described below. In contrast, the arrangement of the present invention avoids disturbing most of the ink in the chamber and requires only a small operating force to move the ink in the nozzle. Thereafter, the ink is ejected from the nozzle mainly by inertial forces (i.e., inertial ejection). In this specification, ejection by inertial forces may also be referred to as inertial ejection or ejection by the inertial mode. In the context of the present invention, since the actuator is coupled to each nozzle, the present invention enables ejection of the ink (from each nozzle) by an inertial mode other than the compressibility mode. Thus, the compressibility of the ink becomes secondary compared to the ejection procedure. The actuator of the present invention is suitably configured to eject the ink composition (from each nozzle) by the inertial mode (i.e., inertial ejection).

[0034] Ejection by the inertial mode (i.e., inertial ejection) has many advantages that are closely related. Since the required actuation force at first is small, it becomes possible to use a low-temperature processable piezoelectric material having a lower piezoelectric constant (i.e., a piezoelectric material processable at less than 450 °C or less than 300 °C). A relatively low fluid pressure is applied so that the small force exerted by a piezoelectric actuator including a low-temperature processable piezoelectric material reduces an acoustic crosstalk problem (i.e., the adjacent actuators and fluid chambers interact with each other through pressure waves in the fluid). Since the level of acoustic crosstalk is lower, adjacent ejectors can be closely integrated to compactly configure a print head. Further, the mass of the droplet may be affected by the ink in the nozzle (e.g., the ink in the nozzle head) rather than the total volume of the ink in the chamber. Therefore, damping is light and crosstalk is reduced as described above.

[0035] To obtain high-quality printing, the ejected ink droplets need to have corresponding volumes and velocities. In this way, the droplets deposited on the printing medium (e.g., paper) can give corresponding shapes and volumes. In the case of inertial ejection, it has been found that satisfactory correspondence can be achieved by adapting the frequency of the actuation waveform transmitted to the actuator to the resonance frequency of each nozzle (e.g., the resonance frequency during use). Thus, the complexity of inertial ejection can be directly related to the number of distinct waveforms required to drive the nozzles, especially the nozzles ejecting different ink compositions. For simplicity, it is common for all nozzles to require the same or similar waveforms (i.e., waveforms of the same or similar frequencies, usually the same frequency) during operation. This can be achieved when all nozzles have the same or similar resonance frequencies (e.g., the same or similar resonance frequencies during use). The difference in the resonance frequencies of any two nozzles (e.g., during use) can be 10 kHz or less, or 1 kHz or less, or 100 Hz or less, or 10 Hz or less, or 1 Hz or less, or zero Hz. The difference in the resonance frequencies of any two nozzles (e.g., during use) can also be 10% or less, or 5% or less, or 1% or less, or 0.1% or less, or 0.01% or less, or zero with respect to the higher resonance frequency of the two nozzles. The waveform frequency may be adapted to the resonance frequency of each nozzle (e.g., during use) such that the difference is 10 kHz or less, or 1 kHz or less, or 100 Hz or less, or 10 Hz or less, or 1 Hz or less, or 0 Hz. The difference may be 10% or less, or 5% or less, or 1% or less, or 0.1% or less, or 0.01% or less, or zero with respect to the resonance frequency of each nozzle (e.g., during use). The resonance frequency of the nozzle (e.g., during use) is typically from 100,000 kHz to 10 kHz, more typically from 10,000 kHz to 20 kHz, still more typically from 5000 kHz to 50 kHz, and most typically from 2000 kHz to 100 kHz.The resonance period of the nozzle (e.g., during use) is typically from 0.01 μs (microseconds) to 100 μs (microseconds), more typically from 0.1 μs to 50 μs, even more typically from 0.2 μs to 20 μs, and most typically from 0.5 μs to 10 μs.

[0036] It will be understood that the resonance frequency of the nozzle can be affected by the dimensions and materials of the nozzle, as well as the dimensions and materials of each actuator. To adjust the resonance frequency as described in the previous paragraph, it is desirable for all nozzles within the print head to have corresponding materials and dimensions, and for all actuators within the print head to have corresponding materials and dimensions. The nozzles may have the same dimensions and materials. The actuators may have the same dimensions and materials. As used herein, dimensions include the geometric shape, size, and / or configuration of the nozzles and actuators. Materials refer to the articles (e.g., substances, mixtures) used to construct the nozzles and actuators.

[0037] Furthermore, it will be understood that the resonance frequency can also be affected by the viscosity and density (as well as surface tension) of the ink composition within the nozzle. Therefore, it is necessary to adjust those parameters of different ink compositions so that the resulting resonance frequencies of the nozzles are the same or similar (as described above). Thus, using a simple actuation force (i.e., the same or similar actuation waveform), ink droplets can be ejected from the nozzles at corresponding volumes and speeds, which leads to high-quality printing. In other words, it is beneficial to adjust the specified ink parameters (i.e., viscosity, density, and surface tension) to achieve high-quality printing with a simple operation. This is especially true for inertial ejection.

[0038] Furthermore, since the present invention (using inertial ejection) is different from existing technologies that rely on either a compressibility mode or a thermal ejection mode (e.g., thermal inkjet printheads), it will be understood that adjustment of ink properties such as compressibility (e.g., acoustic compressibility), and / or volatility, and / or specific heat capacity (Cp), and / or thermal conductivity is not usually necessary. In other words, typically, there is no need to match one or more of the above properties between different ink compositions of a set (e.g., no need to match in the manner described later for the second aspect of the present invention).

[0039] In a second aspect of the present invention, a set of different ink compositions for use in a monolithic inkjet printhead according to the first aspect of the present invention is provided, wherein (i) the viscosity values of the compositions are adapted such that the difference between any two compositions is 20% or less, preferably 10% or less, more preferably 5% or less, and most preferably 1% or less of the maximum viscosity value of the set, (ii) the density values of the compositions are adapted such that the difference between any two compositions is 20% or less, preferably 10% or less, more preferably 5% or less, and most preferably 1% or less of the maximum density value of the set, and (iii) the surface tension values of the compositions are adapted such that the difference between any two compositions is 20% or less, preferably 10% or less, more preferably 5% or less, and most preferably 1% or less of the maximum surface tension value of the set. It is also possible that there is no difference between any two compositions of the set with respect to viscosity value, and / or surface tension value, and / or density value. It will be understood that all possible combinations of ranges of viscosity, density, and surface tension, as well as preferred ranges of viscosity, density, and surface tension, are also contemplated herein. For example, the difference in viscosity, density, and optionally surface tension between any two compositions may be 10% or less of the corresponding maximum value of the set, or the difference in viscosity, density, and optionally surface tension between any two compositions may be 5% or less of the corresponding maximum value of the set. It is also possible that the difference in viscosity between any two compositions is 20% or less of the maximum viscosity of the set, the difference in density between any two compositions is 10% or less of the maximum density of the set, and the difference in surface tension between any two compositions is 10% or 5% or less of the maximum surface tension of the set. The difference in viscosity between any two compositions may be 10% or less of the maximum viscosity of the set, the difference in density between any two compositions may be 5% of the maximum density of the set, and optionally the difference in surface tension between any two compositions may be 5% or 1% or less of the maximum surface tension of the set.

[0040] As described above, a set of ink compositions is formulated such that the selected properties of the compositions (viscosity, density, and surface tension) are particularly well - matched. In this way, the set can achieve high - quality printing (with a simple operation). Particularly in inertial ejection, these compatible inks can be ejected using the same or similar actuation waveforms, providing corresponding volumes and velocities, so that the shape and volume of the ink droplets deposited on the print medium are corresponding.

[0041] As described above, generally it is not necessary to match the compressibility of the ink compositions. In this specification, the compressibility (k) refers to the rate of change of volume per unit increase in pressure, usually measured at 20 °C (and 1 atmosphere). The compressibility (k) is also known as the reciprocal of the bulk modulus (B). For example, for every 1 - atmosphere increase in pressure, the volume of water decreases by 46.4 ppm (i.e., k = 46.4).

[0042] In the context of the present invention, the difference in compressibility (k) between two ink compositions of a set, or between any two ink compositions of a set, may be at least 1% or at least 5%, or at least 10%, or at least 20%, or at least 30%, or at least 40%, or at least 50% of the maximum compressibility value of the set.

[0043] In some embodiments, the difference in viscosity between any two compositions is 1% or less of the maximum viscosity of the set, the difference in density between any two compositions is 1% or less of the maximum density of the set, optionally, the difference in surface tension between any two compositions is 1% of the maximum surface tension of the set, while the difference in compressibility (k) between two ink compositions of the set, or between any two ink compositions of the set, is at least 1%.

[0044] In the context of the present invention, the viscosity values, density values, and surface tension values of a set of different ink compositions may be adapted such that ink droplets ejected from a monolithic inkjet printhead have corresponding volumes and velocities. The "printed test pattern" method described herein can be used to evaluate whether the droplets correspond.

[0045] Depending on the combination of the above two paragraphs, the viscosity, density and surface tension of the set may be adapted. As used herein, "different ink compositions" refers to ink compositions that contain one or more components that are different from each other and / or have one or more weight percentages that are different from each other. The weight percentages can be with respect to the same or different components included in the composition, and all weight percentages referred to are based on the total weight of each ink composition. For example, the set may include a first composition containing 80% aqueous carrier and a second composition containing 80% organic carrier. Alternatively, the compositions may include a first composition containing 80% aqueous carrier and a second composition containing 85% aqueous carrier. At least two compositions of the set are different from each other, and any two compositions of the set may be different from each other.

[0046] In the context of the present invention, the viscosity value of the composition may be adapted such that the difference between any two compositions is 4 mPa·s or less, or 2 mPa·s or less, or 1 mPa·s or less, or 0.2 mPa·s or less, or zero. The density value of the composition may be adapted such that the difference between any two compositions is 200 kg / m 3 or less, or 100 kg / m 3 or less, or 50 kg / m 3 or less, or 10 kg / m 3 or less, or 1 kg / m 3 or less, or zero. The surface tension value of the composition may be adapted such that the difference between any two compositions is 7 mN / m or less, or 5 mN / m or less, or 2 mN / m or less, or 1 mN / m or less, or zero.

[0047] The viscosity value of the composition may be 1.5 mPa·s to 20 mPa·s, or 5 mPa·s to 15 mPa·s, or 7.5 mPa·s to 12.5 mPa·s. The density value of the composition is 650 kg / m 3 ~1750 kg / m 3 or 800 kg / m 3 ~1500 kg / m 3 or 1000 kg / m 3 ~1250 kg / m 3 It may be. The surface tension value of the composition may be 20 mN / m to 75 mN / m, or 25 mN / m to 70 mN / m, or 30 N / m to 65 N / m, or 35 mN / m to 60 mN / m, or 40 mN / m to 55 mN / m. The viscosity values, density values, and surface tension values of different ink compositions are appropriately adapted as described herein (i.e., all possible combinations are also considered), and are optionally selected, and these values may be within the numerical ranges described herein (i.e., all possible combinations are also considered). For example, the difference in viscosity may be 4 mPa·s or less, the difference in density may be 50 kg / m 3 or less, the difference in surface tension may be 5 mN / m or less, and optionally the viscosity value may be 5 mPa·s to 15 mPa·s, the density value may be 800 kg / m 3 ~1500 kg / m 3 It may be, and the surface tension value may be 30 N / m to 65 N / m (for example, 35 mN / m to 60 mN / m, or 40 mN / m to 55 mN / m).

[0048] A suitable test method for viscosity may be based on or derived from ASTM D 4040-99. The viscosity referred to in the present invention is suitably measured at 25 °C / 1 atm by using a rotational viscometer (manufactured by RE-80L, TOKI SANGYO CO., LTD). The geometric shape of a standard cone rotor (1°34’×R24) can be used, and the size of the ink sample is about 1.2 mL. The rotational speed of the geometric shape is 50 revolutions per minute (rpm). The measurement continues for 3 minutes. The viscosity value is recorded at the end of the 3-minute measurement. Usually, 3 repetitions are required for one ink sample, and the reported viscosity value is the average of these 3 measurements.

[0049] A suitable test method for density may be based on or derived from ASTM D1475-98. The density referred to in the present invention is suitably measured at 25 °C / 1 atm by using a clean and dry graduated cylinder (e.g., 100 mL or 250 mL). A balance is used to measure the mass (M) of the cylinder (usually in grams). Next, the cylinder is removed from the balance and filled with the ink sample. The volume (V) of the ink sample is recorded. The filled cylinder is returned to the balance and the new mass is recorded. The density of the ink sample is determined by the following formula. D 密度 =(M シリンダ+インク -M シリンダ ) / V インク

[0050] Usually, 3 repetitions are required for one ink sample, and the reported density value is the average of these 3 measurements.

[0051] An appropriate test method for surface tension may be based on or derived from ASTM D1331-20. Appropriately, the surface tension referred to in the present invention is measured at 25 °C / 1 atm by using a Krüss tensiometer (e.g., Krüss K11, K100). The ring method (i.e., the probe is a ring) can be used. Usually, the tensiometer is calibrated with water before each ink measurement (e.g., surface tension = 72 mN / m). An appropriate amount of ink sample (e.g., 2 mL to 5 mL) is placed in a sample container that is equilibrated at 25 °C. The experimental procedure for obtaining the surface tension value usually follows the steps described in the supplier's manual. These steps typically include lowering the ring to contact the surface of the ink, waiting for equilibrium, lifting the ring from the surface of the ink, and recording the surface tension value measured during the lifting process. Usually, three repetitions are required for one ink sample, and the reported surface tension value is the average of these three measurements.

[0052] In the context of the present invention, a set of different ink compositions can have the following chemical characteristics.

[0053] Colorant A set of different ink compositions may include a plurality of ink compositions each containing a different colorant (i.e., any two compositions of the set containing different colorants from each other). Typically, the colorant is selected from cyan (C), yellow (Y), magenta (M), key (K), red (R), green (G), blue (B), orange, purple, gold, silver, white, and mixtures thereof, more typically selected from CYMK and mixtures thereof, or RGBK and mixtures thereof. A set of different ink compositions may include a first composition containing a cyan (C) or red (R) colorant, a second composition containing a yellow (Y) or green (G) colorant, a third composition containing a magenta (M) or blue (B) colorant, and a fourth composition containing a key (K) colorant. Preferably, the first composition contains a cyan (C) colorant, the second composition contains a yellow (Y) colorant, the third composition contains a magenta (M) colorant, and the fourth composition contains a key (K) colorant.

[0054] In a suitable example, the printhead comprises four groups of ejectors (channels), each of the four groups of ejectors comprises a plurality of nozzles (e.g., 100 or 1000), and each group is operably coupled or coupled to the color ink composition as described above so that the composition can be ejected from the plurality of nozzles. In the same example, each of the four ink compositions may contain a different colorant. Preferably, the four ink compositions contain CMYK or RGBK colorants, more preferably CMYK colorants.

[0055] The colorant can be a pigment, a dye, or a lake (i.e., a dye precipitated from a solvent in solid form), and is typically a pigment or a dye. The pigment may be an inorganic pigment, an organic pigment, a pearl pigment, a metallic pigment, or a mixture thereof. The inorganic pigment can be selected from titanium oxide, zinc oxide, zinc sulfate, iron oxide, calcium oxide, antimony oxide, magnesium oxide, zirconium oxide, CI Pigment White 6, 18, and 21, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, carbon black (e.g., acetylene black, channel black, furnace black, lamp black, thermal black), and mixtures thereof. These pigments can be produced by known effective methods such as the contact method, the furnace method, and the thermal method. The organic pigment can be selected from azo pigments (e.g., insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (e.g., phthalocyanine pigments, diarylide pigments, xanthene pigments, perylene pigments, perinone pigments, anthraquinone pigments, anthrapyridone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments), dye chelates, nitro pigments, nitroso pigments, aniline black, white hollow resins, and mixtures thereof. The pearl pigment can be selected from mica coated with titanium dioxide, fish scale foil, bismuth trichloride, and mixtures thereof. The metallic pigment is usually an elemental metal or a mixed metal selected from aluminum, silver, gold, platinum, nickel, chromium, tin, zinc, indium, titanium, copper, and their alloys. The dye can be selected from acid dyes, direct dyes, reactive dyes, basic dyes, food dyes, and mixtures thereof.Examples of dyes include C.I. Acid Yellow 17, 23, 42, 44, 79 and 142, C.I. Acid Red 52, 80, 82, 249, 254 and 289, Disperse Red 60, C.I. Acid Blue 9, 45 and 249, C.I. Acid Black 1, 2, 24 and 94, C.I. Food Black 1 and 2, C.I. Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, 144 and 173, C.I. Direct Red 1, 4, 9, 80, 81, 225 and 227, C.I. Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199 and 202, C.I. Direct Black 19, 38, 51, 71, 154, 168, 171 and 195, C.I. Reactive Red 14, 32, 55, 79 and 249, and C.I. Reactive Black 3, 4 and 35. The total level of the colorant is suitably 0.01% to 10% by weight of the total ink composition, or 0.1 wt% to 8 wt%, or 0.5 wt% to 5 wt%, or 1 wt% to 3 wt%. Typically, the difference in weight percentage of the total colorant contained in at least two compositions of the set, or any two compositions of the set, is 5 or less, or 2 or less, or 1 or less, or 0.1 or less, or zero. In this specification, it is also possible that the difference in weight percentage of the total colorant contained in at least two compositions of the set, or any two compositions of the set, is at least 0.01, or at least 0.1, or at least 1, or at least 2, or at least 5.

[0056] Typically, a set of different ink compositions includes a first composition containing a cyan (C) or red (R) colorant, a second composition containing a yellow (Y) or green (G) colorant, a third composition containing a magenta (M) or blue (B) colorant, and a fourth composition containing a key (K) colorant, and each said colorant is present at 1 to 10% (e.g., 1% to 5%, or 1% to 3%) of the weight of the respective composition. Optionally, the difference in the weight percentages of at least two compositions, or of these colorants contained in any two compositions, is 2 or less, or 1 or less, or 0.1 or less, or zero. For example, the first composition may contain 2 wt% of the cyan colorant, the second composition may contain 2.5 wt% of the yellow colorant, the third composition may contain 3 wt% of the magenta colorant, and the fourth composition may contain 4 wt% of the key colorant. Optionally, the difference in the weight percentages of at least two compositions of the set, or of these colorants contained in any two compositions of the set, is at least 0.01, or at least 0.1, or at least 0.5, or at least 1, or at least 2. For example, the first composition may contain 1 wt% of the cyan colorant, the second composition may contain 3 wt% of the yellow colorant, the third composition may contain 5 wt% of the magenta colorant, and the fourth composition may contain 7 wt% of the key colorant.

[0057] In the context of the present invention, one or more components (excluding the colorants present) of at least two color ink compositions or of any two color ink compositions may be different. Additionally or alternatively, the weight percentages of one or more components (excluding the colorants present) of at least two color ink compositions or of any two color ink compositions may be different.

[0058] At least one ink composition of the set, or each ink composition of the set, may further comprise one or more components selected from a carrier, a rheology modifier, a surfactant, a dispersant, an antifoaming agent, a corrosion inhibitor, a UV curable resin, a preservative, and a humectant, or selected from a carrier, a rheology modifier, a surfactant, and a humectant, or selected from a carrier, a rheology modifier, and a surfactant, or selected from a rheology modifier. At least one ink composition of the set, or each ink composition of the set, may comprise a carrier and / or a rheology modifier, and / or a surfactant. At least one ink composition, or each ink composition, may comprise a carrier, a rheology modifier, and a surfactant.

[0059] Rheology modifier At least one ink composition of the set, or each ink composition of the set, may contain a rheology modifier. The modifier serves to change (e.g., adjust) the rheological behavior (e.g., viscosity) of the ink composition. In this way, if the viscosity values do not match within the set, the rheology modifier can increase or decrease the viscosity (as needed) to assist in the matching. Although not essential, it is desirable for at least two compositions of the set or all compositions of the set to have the same rheology modifier. It is also possible for at least two compositions of the set, or any two compositions of the set, to have different rheology modifiers. A person skilled in the art can effectively adjust the type and / or level of the modifier contained in the composition. Usually, the total level of the rheology modifier based on the weight of the total ink composition is 0.1 wt% to 25 wt%, or 1 wt% to 20 wt%, or 2 wt% to 15 wt%, or 5 wt% to 10 wt%. Usually, the difference in weight percentage of the total rheology modifier contained in at least two compositions of the set, or any two compositions of the set, is 10 or less, or 5 or less, or 1 or less, or 0.1 or less. For example, the first composition may contain 20 wt% of the modifier(s), the second composition may contain 10 wt% of the modifier(s), and the third composition may contain 15 wt% of the modifier(s). At least two compositions of the set (e.g., all compositions of the set) may contain the same level of rheology modifier. The difference in weight percentage of the total rheology modifier contained in at least two compositions of the set (e.g., any two compositions of the set) can also be at least 0.01, or at least 0.1, or at least 1, or at least 2, or at least 5, or at least 10. For example, the first composition may contain 20 wt% of the modifier(s), the second composition may contain 25 wt% of the modifier(s), and the third composition may contain 15 wt% of the modifier(s).

[0060] Suitable examples of rheology modifiers are polymers. The polymers can be natural or synthetic. Further, if desired, they can be selected from anionic polymers, nonionic polymers, or amphoteric polymers. Usually, the polymers are polyurethanes, polyacrylic acids or polyacrylates, polysaccharides (e.g., cellulose, mannose, fructose, galactose, glucose, mannose, ribose, xylose, arabinose, gums, guar, pectin, starch), polyvinyl alcohol, or ethoxylated polymers. A preferred choice is a homopolymer or copolymer of polyacrylic acid or polyacrylate. Such polymers can be prepared by addition polymerization of a mixture of ethylenically unsaturated monomers. The polyacrylic acid or polyacrylate may be a linear or crosslinked copolymer, and such copolymers can optionally be hydrophobically modified. Usually, the ink composition (e.g., at least one ink composition of the set, or all ink compositions of the set) contains a rheology modifier that is a polymer (e.g., polyacrylic acid or polyacrylate as described herein) at a level of 0.1 - 5%, or 0.2 wt% - 2 wt%, or 0.5 wt% - 1 wt% of the total composition weight.

[0061] Commercially available examples of polymer rheology modifiers include, but are not limited to, ACRYSOL® RM - 5000 and ACRYSOL® RM - 825 (Rohm & Haas, a wholly - owned subsidiary of Dow Chemical Company), BORCHIGEL® L75N, BORCHIGEL® L0625, and BORCHIGEL® L W44 (all available from OMG Borchers GmbH, Langenfeld, Germany), BYK® 428 and BYK® 429 (both available from BYK Chemie GmbH), and DSX® R2000 E, DSX® R3000 E, and DSX® R3075 E (all available from Cognis GmbH, Monheim am Rhein, Germany).

[0062] Another suitable example of a rheology modifier is glycerol. Other polyols may also be used. Glycerol has been found to effectively increase the viscosity of the ink composition and assist in the adaptation of the viscosity value. Typically, the ink composition (e.g., at least one ink composition of the set, or all ink compositions of the set) contains glycerol at 5 - 25% by weight of the total composition, or 7 wt% - 20 wt%, or 10 wt% - 15 wt%. One or more compositions of the set (e.g., all compositions of the set) may contain glycerol, or may contain both glycerol and the polymer rheology modifier(s), and optionally, the glycerol / polymer ratio is 100 / 1 - 1, or 50 / 1 - 2 / 1, or 20 / 1 - 5 / 1, or 15 / 1 - 10 / 1. Also, one or more compositions of the set contain glycerol, and one or more compositions may contain a polymer rheology modifier.

[0063] Carrier One or more ink compositions of the set (e.g., all ink compositions) may contain a carrier. The carrier is usually a liquid at atmospheric pressure and 20°C. As used herein, a carrier refers to a liquid in which the other components of the ink composition can be dispersed or dissolved to form the composition.

[0064] The ink composition can suitably contain one or more carriers. The ink composition can be aqueous or oily. Thus, the carrier can be an aqueous carrier, an organic carrier, or a mixture thereof. It is advantageous for at least two compositions of the set, or all compositions of the set, to contain the same carrier, or at least the same type of carrier (e.g., all compositions contain an aqueous carrier, or an organic carrier, or a mixture of an aqueous carrier and an organic carrier). In this way, the density of the set can be easily adapted. It is also possible for at least two compositions of the set, or any two compositions of the set, to contain different carriers, or different types of carriers (e.g., one of at least two ink compositions contains an aqueous carrier, and the other of at least two ink compositions contains an organic carrier).

[0065] As used herein, an aqueous carrier typically refers to a carrier containing water, typically at least 50%, or at least 70 wt%, or at least 80 wt%, or at least 90 wt%, or at least 95 wt% or 100 wt% of the total weight of the aqueous carrier. The aqueous carrier can be water. Usually, the water is purified water. Examples of purified water include, but are not limited to, deionized water (D.I. water), ultrafiltered water, distilled water, and ion-exchanged water. Using such water can improve the hygiene of the ink to prevent the growth of microorganisms (e.g., fungi, mold) during the storage of the ink.

[0066] The carrier can be oil. As used herein, the term "oil" means a water-insoluble organic substance that is liquid at 20°C. A substance having a solubility of less than 0.1 g / 100Ml at 20°C is considered insoluble. The oil can be selected from hydrocarbons (e.g., aliphatic hydrocarbons, isomerized aliphatic hydrocarbons, branched or straight-chain aliphatic hydrocarbons, aromatic hydrocarbons), silicone oils, vegetable oils, and mixtures thereof. The oil carrier is an organic carrier.

[0067] The carrier may be a water-soluble or water-miscible organic carrier. Suitable examples include, but are not limited to, ethanol, isopropyl alcohol, acetone, diacetone alcohol, polyols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, propane diol, butane diol), glycol ethers (e.g., ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether), amines having a hydroxyl group, and mixtures thereof.

[0068] Other suitable examples of the carrier include, but are not limited to, triethylene glycol monobutyl ether, 2-[2-(2-butoxyethoxy)ethoxy]ethanol, 3-methyl-1,5-pentanediol, poly(oxy-1,2-ethanediyl), α,α’-[1,4-dimethyl-1,4-bis(2-methylpropyl)-2-butyne-1,4-diyl]bis[omega-hydroxy], bis(2-ethoxyethyl) ether, and 1-ethoxy-2-(2-methoxyethoxy)ethane.

[0069] The total level of the carrier in the ink composition is typically 10 to 85%, or 15 to 80%, or 20 to 75%, or 50 to 70% of the weight of the entire composition. When the carrier is an aqueous carrier (e.g., water), the total level in the ink composition is typically 50 wt% to 85 wt%, or 55 wt% to 80 wt%, or 60 wt% to 70 wt%. When the carrier is an organic carrier (e.g., oil, water-soluble organic carrier) or a mixture of organic carriers, the total level is typically 10 wt% to 60 wt%, or 20 wt% to 50 wt%, or 30 wt% to 40 wt%. When the carrier is a mixture of an aqueous carrier and an organic carrier, the weight ratio of the aqueous carrier to the organic carrier may be at least 1 / 1, or greater than 1 / 1. Typically, the difference in the weight percentages of the carrier contained in any two compositions of the set, or at least two compositions of the set, is 10 or less, or 5 or less, or 1 or less, or 0.1 or less. It is also possible for all compositions of the set to contain the same level of the carrier. For example, the set may include five different ink compositions, and each ink composition may contain a total of 80 wt% of the carrier(s). The difference in the weight percentages of the carrier contained in at least two compositions of the set (e.g., any two compositions of the set) may also be at least 0.01, or at least 0.1, or at least 1, or at least 5, or at least 10.

[0070] Surfactant Each at least one ink composition or each ink composition of a set may contain a surfactant. Surfactants are typically used to reduce the surface tension of the ink composition. In this way, surfactants help to adjust the surface tension of the ink composition (if necessary). Surfactants can be selected from anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, and mixtures thereof. Any at least two compositions of the set, or any two compositions of the set, may contain the same surfactant or at least the same type of surfactant (i.e., all compositions contain an anionic surfactant, or a cationic surfactant, or a nonionic surfactant, or an amphoteric surfactant). It is desirable that at least two compositions of the set, or any two compositions of the set, contain different surfactants or different types of surfactants (e.g., one of the at least two ink compositions contains an anionic surfactant and the other of the at least two ink compositions contains a nonionic surfactant).

[0071] Typical examples of surfactants include, but are not limited to, acetylene-based surfactants, phosphate surfactants (e.g., phosphates of aliphatic alcohols or aliphatic alcohol alkoxylates), acetylene glycol-based surfactants, silicone-based surfactants (e.g., polysiloxanes), polyethylene glycol (PEG)-based surfactants (e.g., PEG8000, polysorbate 80, pluronic® F-68, PEG-fatty acids), fluorine-based surfactants (e.g., fluorine-modified polymers), and mixtures thereof.

[0072] The total level of surfactant is usually from 0.01% to 10% by weight of the ink composition, or from 0.02 wt% to 2.5 wt%, or from 0.05 wt% to 2 wt%, or from 0.1 wt% to 1 wt%. Usually, the difference in weight percentage of surfactant contained in at least two compositions of the set, or any two compositions of the set, is 5 or less, or 2 or less, or 1 or less, or 0.1 or less. It is also possible that all compositions of the set contain the same level of surfactant. For example, the set may contain five different ink compositions, and each composition may contain the same total level of surfactant. The difference in weight percentage of surfactant contained in at least two compositions (e.g., any two compositions of the set) may also be at least 0.01, or at least 0.1, or at least 1, or at least 2, or at least 5.

[0073] Humectant At least one ink composition, or each ink composition of the set, may contain a humectant. The humectant is usually a water-soluble or water-miscible organic compound. By containing such a compound, the moisture retention of the ink composition is improved, and as a result, the nozzle is less likely to be clogged even after being left for a long time.

[0074] Usually, the humectant contains a hydrophilic group. The humectant can be selected from alkyl polyols (e.g., ethylene glycol, propylene glycol, glycerol), nitrogen-containing cyclic compounds (e.g., 2-pyrrolidone, N-methyl-2-pyrrolidone), lactones (e.g., γ-butyrolactone), betaines, glycol ethers (e.g., diethylene glycol mono-butyl ether, propylene glycol monoethyl ether), ureas (e.g., ethyl urea, tetramethyl urea, thiourea, 1,3-dimethyl-2-imidazolidinone), amides (e.g., N-methylformamide), amines (e.g., monoethanolamine, triethylamine), and mixtures thereof.

[0075] The total level of the humectant is usually 0.1% to 30% by weight of the total ink composition, or 0.2 wt% to 20 wt%, or 0.5 wt% to 15 wt%, or 1 wt% to 10 wt%, or 2 wt% to 5 wt%. The amount included is effective against clogging and enables a skilled operator to match the set viscosity value, density value and surface tension value.

[0076] Any other optional components Furthermore, at least one ink composition of the set, or each ink composition of the set, may contain a preservative. Examples may include sodium benzoate, sodium pentachlorophenol, phenoxyethanol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-benzisothiazolin-3-one, and 4-chloro-3-methylphenol. The ink composition may contain a UV curable resin (e.g., acrylated epoxy, acrylated polyester, acrylated urethane, acrylated silicone). The ink composition may contain a dispersant. Examples of the dispersant may include an anionic dispersant (e.g., sodium naphthalene sulfonate), a nonionic dispersant, a polymer dispersant (e.g., acrylic resin, styrene resin, urethane resin). The composition may contain an antifoaming agent such as a silicone-based antifoaming agent, a polyether-based antifoaming agent, a fatty acid ester-based antifoaming agent. The composition may contain a corrosion inhibitor such as acid sulfite and sodium thiosulfate. Each of the above optional components may be present in an amount effective to achieve its purpose in the ink composition. Generally, these optional components are individually included in an amount of up to 5% by weight of the total ink composition. At least one ink composition of the set, or each composition of the set, may contain one or more optional components as described herein.

[0077] In a preferred embodiment, at least one composition of the set, or each composition of the set, comprises a colorant (e.g., 0.01 wt% to 10 wt%), a carrier (e.g., 10 wt% to 85 wt%), a surfactant (e.g., 0.01 wt% to 5 wt%), and a rheology modifier (e.g., 0.1 wt% to 25 wt%). The composition may also comprise one or more other components as described herein (e.g., optionally a humectant in an amount of 0.1 wt% to 10 wt%). In a further preferred embodiment, a set of different ink compositions comprises a first composition comprising a cyan (C) or red (R) colorant, a second composition comprising a yellow (Y) or green (G) colorant, a third composition comprising a magenta (M) or blue (B) colorant, and a fourth composition comprising a key (K) colorant (e.g., a black colorant), each said colorant being present at 1 to 10% by weight of the respective composition. In the same or other embodiments, at least one composition of the set, or each composition of the set, may further comprise a carrier (e.g., 10 wt% to 85 wt% or 50 wt% to 80 wt%), a surfactant (e.g., 0.01 wt% to 5 wt% or 0.1 wt% to 2 wt%), and a rheology modifier (e.g., 0.1 wt% to 25 wt% or 0.5 wt% to 20 wt%).

[0078] In the above-described preferred embodiments and other embodiments, the difference in the weight percentage of the colorant contained in at least two compositions, or any two compositions of the set, may be 5 or less, or 2 or less, or 1 or less, or 0.1 or less, and any weight percentage is based on the total weight of each ink composition. The difference in the weight percentage of the total colorant contained in at least two compositions of the set (e.g., any two compositions of the set) may be at least 0.01, or at least 0.1, or at least 1, or at least 2, or at least 5. Alternatively or additionally, the difference in the weight percentage of the rheology modifier, and / or surfactant, and / or carrier contained in at least two compositions or any two compositions may be 20 or less, or 10 or less, or 5 or less, or 1 or less, or 0.1 or less. Alternatively or additionally, at least two compositions of the set, or any two compositions of the set, may contain different rheology modifiers, and / or different surfactants, and / or different carriers, and optionally, the difference in the weight percentage of the rheology modifier, and / or surfactant, and / or carrier contained in at least two compositions of the set (e.g., any two compositions of the set) is at least 0.1, or at least 1, or at least 5, or at least 10.

[0079] Method for manufacturing an ink composition In a further aspect of the present invention, a method for producing a set of different ink compositions described herein is provided. The method includes (i) a step of producing at least two ink compositions, (ii) a step of determining whether the viscosity values, density values, and surface tension values of the at least two ink compositions are adapted by the methods described herein (i.e., whether the set is a set of different ink compositions according to the present invention), and (iii) if not, a step of changing at least one of the at least two ink compositions one or more times until the set of compositions becomes a set according to the present invention. The set of different ink compositions is for use in a printing apparatus described below.

[0080] This method can further include (a) a step of mixing a carrier, a colorant, a rheology modifier, a surfactant, and optionally other components (for example, other components described herein), and optionally (b) a step of filtering to remove impurities from the mixture.

[0081] Steps (a) and / or (b) may be optionally repeated.

[0082] In step (a), the mixing can be carried out in any suitable order. This is typically done by adding the necessary components to a container equipped with a stirrer (for example, a magnetic stirrer, a sand mill, a homogenizer, a ball mill) and mixing until homogeneous. The mixing can also be carried out by using a paint shaker, or an ultrasonic dispersion device, or any suitable high-speed dispersion device.

[0083] The viscosity value, density value, and surface tension value of the ink composition can be determined by any suitable method, for example, the ASTM method or a suitable method described herein. Virtual simulations (for example, computer calculations predicting those values of the ink) are not excluded. If the values are adapted as described herein (that is, the set of ink compositions is a set of different ink compositions according to the present invention), further modification(s) of the ink may not be necessary.

[0084] If the values are adapted as described herein, the viscosity, density, and surface tension can be appropriately changed (for example, adjusted) by adjusting, for example, the type and / or level of the rheology modifier, carrier, and surfactant, respectively. The changed (for example, adjusted) ink composition(s) can be determined for its viscosity, density, and surface tension. Optionally, further modification(s) (for example, adjustment) may be performed to achieve the adaptation as described herein. In other words, steps (ii) and (iii) of the method can be optionally repeated until the adaptation is achieved (that is, until the set of compositions becomes a set according to the present invention).

[0085] The set of different ink compositions obtained can be used for printing. The set of different ink compositions obtained can be used as the specifications of the ink to be manufactured. Thereafter, the corresponding ink can be manufactured.

[0086] Selection of a set of ink compositions In yet another aspect of the present invention, there is provided a method of selecting a set of different ink compositions, comprising: (i) defining at least one property of the ejected ink droplets; (ii) using the at least one defined property to determine target values for the viscosity, density and surface tension of the ink composition; and (iii) selecting at least two ink compositions with reference to the target values described in step (ii), wherein the values of the at least two ink compositions are also adapted by the method described herein (i.e., the set of ink compositions is a set of different ink compositions according to the present invention). The set of different ink compositions is for use in a printing apparatus as described below.

[0087] The at least one defined property can be used to determine target values for the viscosity, density and surface tension of the ink composition in combination with the print head according to the present invention or a simulation thereof.

[0088] At least one defined characteristic of the ejected ink droplets may include the size of the droplets. Further, optionally, in step (i), a value of the dots per inch (DPI) may also be defined. The DPI can be 100 to 2000 dpi, or 300 to 1800 dpi, or 600 to 1600 dpi. The defined characteristics of the ink droplets (optionally using the defined DPI) serve to determine the target physical characteristics of the ink, namely viscosity, density, and surface tension. Further, it will be understood that the characteristics of the ejected droplets and / or the DPI can be defined virtually (e.g., by using a computer-implemented method). The ink compositions are selected with reference to their target physical characteristics. Here, "with reference to" means that the physical characteristics of the selected ink are compatible with the target physical characteristics. Typically, the difference in viscosity is 10% or less, or 5% or less, or 1% or less with respect to the target viscosity. Typically, the difference in concentration is 20% or less, or 10% or less, or 5% or less, or 1% or less with respect to the target concentration. Typically, the difference in surface tension is 10% or less, or 5% or less, or 1% or less with respect to the target surface tension. All possible combinations of sub-ranges are also considered. The selected inks also have physical characteristics that are compatible with each other as described herein (i.e., the set of selected ink compositions is a set of different ink compositions according to the present invention).

[0089] After the target physical properties have been determined (i.e., after step (ii)), a set of candidate ink compositions can first be determined. Usually, the candidate ink compositions already differ from each other (due to differences in color or chemical composition, or reactivity). The viscosity, surface tension, and density of the candidates can be determined (e.g., according to the methods described herein). If the values are compatible with each other (as described herein) and with the target physical properties, the candidate set can be selected (e.g., according to step (iii)). Otherwise, at least one composition of the set can be changed (e.g., one or more times, optionally as described in the methods herein), and the physical properties of the changed set can be determined again. The said changes and determinations can be optionally repeated until the required compatibility is achieved. Then, the set of different inks that have been changed can be selected (e.g., according to step (iii)) for subsequent manufacturing and / or use.

[0090] Printer In yet another aspect of the present invention, a printing apparatus comprising a monolithic printhead according to the first aspect of the present invention is provided. The printing apparatus further comprises a signal generator configured to generate a drive signal having a repetitive waveform, and a control circuit configured to relay the drive signal to an actuator via a switch and control the switch to selectively apply the drive signal to individual actuators, thereby ejecting ink droplets of different ink compositions at corresponding volumes and velocities. Preferably, the printing apparatus is a printer. Preferably, the printing apparatus comprises a set of different ink compositions of the present invention, and the ink compositions are received or receivable within the chambers of the printhead. Preferably, the viscosities, densities, and surface tensions of the set of different ink compositions are adapted such that the difference between any two compositions is 5% or less (or 1% or less) of the corresponding maximum value of the set. Optionally and additionally, the difference in the compressibility of two ink compositions or any two ink compositions is at least 5% (or at least 10%) of the maximum compressibility value of the set.

[0091] The print head and a set of different ink compositions may be included within an ink cartridge, and the compositions are received within the chambers of the print head. The ink cartridge can be a component of a printing apparatus.

[0092] Suitably, a control circuit configured to relay drive signals is included within a monolithic ink jet print head. In other words, the control circuit can be part of the print head. Further, since individual control wiring to each actuator need only be provided from the control circuit on each print head, the complexity of the wiring connections within the print head can be reduced, and control commands for any actuator on the print head can be provided to the print head via a single wiring connection to the control circuit on the print head.

[0093] The control circuit can comprise a CMOS circuit (i.e., complementary metal oxide semiconductor) and a plurality of circuit elements each associated with a print head ejector.

[0094] The control circuit may be formed integrally with the print head nozzles. In other words, the formation of the control circuit, the print head nozzles, and (optionally) the piezoelectric actuators can be carried out simultaneously without the need for the assembly of a plurality of separately assembled components. By providing the control circuit using an integrated circuit and providing the control circuit adjacent to the print head nozzles, the print head can be reliably made compact.

[0095] The control circuit may comprise (a) a digital register. The control circuit may comprise (b) a nozzle trimming calculation circuit and / or register. The control circuit may comprise (c) a temperature measurement circuit. The control circuit may comprise (d) a fluid chamber filling detection circuit.

[0096] The digital register may be, for example, a shift register or a latch register. During operation, data may be stored in or read from a register within the control circuit. During operation, the temperature may be measured using a temperature-sensitive component of the temperature measurement circuit. During operation, the filling level of the fluid chamber may be measured.

[0097] The control circuit may be configured to change a voltage pulse applied to one or more electrodes of one or more piezoelectric actuators in response to data stored by the control circuit or measurements from one or more sensors typically within the print head. During operation, the control circuit may measure a voltage pulse applied to one or more electrodes of one or more piezoelectric actuators in response to data stored by the control circuit or measurements from one or more sensors typically within the print head.

[0098] Changing the voltage pulse may include temporally shifting the voltage pulse. Changing the voltage pulse may include compressing or expanding the voltage pulse. Changing the voltage pulse may include changing the magnitude of the voltage pulse. Changing the voltage pulse may include swapping between multiple (typically repetitive) sequences of received actuator drive pulses having different profiles. The control circuit is typically configured to change a voltage pulse applied to one or more electrodes of one or more individual piezoelectric actuators in response to data regarding the individual piezoelectric actuators stored by the control circuit or measurements from one or more sensors.

[0099] The control circuit includes a plurality of circuit elements each associated with a print head ejector. The circuit element may be an ejection transistor. The ejection transistor is typically in direct electrical communication with an electrode of the piezoelectric actuator (without an intervening switching semiconductor junction). During operation, the ejection transistor may be controlled such that a potential output from the ejection transistor is directly applied to the electrode of the piezoelectric actuator.

[0100] The control circuit may be configured to receive an input control signal from outside the print head and output an actuator control signal to each of a plurality of actuators to control the ejection of ink from a plurality of print head nozzles.

[0101] The print head may further include an electrical input for receiving an actuator drive pulse. During operation, the print head may receive an actuator drive pulse.

[0102] The print head may include a controller for controlling the print head. The controller may communicate with a memory storing program code or may include one or more microcontrollers or microprocessors that are integrated or distributed and include the memory.

[0103] The controller may include a signal generator configured to generate (typically a series of) actuator drive pulses. Each print head typically includes an electrical input connected to a controller that receives the actuator drive pulses. During operation, the print head assembly may generate the actuator drive pulses (e.g., within the controller) and conduct them to the print head through an electrical connection.

[0104] The actuator drive pulses are typically analog signals. The actuator drive pulses typically include a voltage waveform that is periodically repeated.

[0105] The control circuit may be configured to selectively activate the piezoelectric actuator by switching the connection or disconnection of at least one electrode of a plurality of piezoelectric actuators or each of a plurality of piezoelectric actuators to an actuator drive pulse received thereby. During operation, the print head may selectively activate the piezoelectric actuator by switching the connection or disconnection of at least one electrode of a plurality of piezoelectric actuators or each of a plurality of piezoelectric actuators to an actuator drive pulse received thereby.

[0106] The controller comprises one or more pulse generators for generating a plurality of sequences of actuator drive pulses, the electrical input to the print head receives a plurality of sequences of actuator drive pulses (generated by one or more pulse generators) via a plurality of electrical connections to the controller, and the control circuit is configured to switch the connection or disconnection of at least one electrode of a plurality of piezoelectric actuators or each of a plurality of piezoelectric actuators for a received actuator drive pulse selected from a plurality of different received actuator pulse sequences. During operation, the print head generates a plurality of different sequences of actuator drive pulses (e.g., within the controller), conducts them to the print head through separate electrical connections, and can switch the connection or disconnection of at least one electrode of a plurality of piezoelectric actuators or each of a plurality of piezoelectric actuators to one or more received actuator drive pulses received from a variable (and selectable) one of the plurality of different sequences of actuator drive pulses.

[0107] The selection of which received actuator pulse sequence at least one electrode of a piezoelectric actuator is connected to may be in response to stored data specific to each piezoelectric actuator and / or in response to measurement of the operation of each piezoelectric actuator. Thus, the control circuit can typically select whether each piezoelectric actuator ejects a droplet at each of a series of periodic droplet ejection decision points. A decision point refers to the time before the start of an actuator drive pulse at which it is determined whether to transmit the actuator drive pulse to at least one electrode of a particular piezoelectric actuator.

[0108] Typically, the actuator drive pulses are repeated periodically. The actuator drive pulses may be amplified by the controller. The actuator drive pulses may not be amplified by the print head. The print head may not be generating the actuator drive pulses.

[0109] Typically, pulses from a pulse generator are conducted to a plurality of control circuits that can be part of a plurality of print heads. Thus, a single pulse generator circuit can drive a plurality of piezoelectric transducers on the same substrate and / or a plurality of print heads having separate substrates each having a plurality of piezoelectric transducers.

[0110] Digital actuation control signals are typically received from a controller. Digital actuation control signals are typically received through a flexible connector. The digital actuation control signals are received in serial form and are converted to parallel control signals using a shift register within the control circuit.

[0111] The controller may comprise a pulse generator configured to generate actuator drive pulses conducted to the print head and digital control signals conducted to the print head, the digital control signals being processed in the control circuit of the print head to determine which actuator drive pulses are conducted to at least one electrode of a piezoelectric actuator or the piezoelectric actuators of one or more print head modules to eject droplets.

[0112] During operation, the print head assembly generates actuator drive pulses (e.g., by a controller) and digital control signals, conducts both the actuator drive pulses and the digital control signals to the control circuit of the print head, the control circuit processes the digital control signals and, in response, conducts the selected actuator drive pulses to at least one electrode of a piezoelectric actuator or the piezoelectric actuators of one or more print heads to eject droplets.

[0113] Thus, typically, analog actuator drive pulses and digital control signals are input by the control circuit (and typically by the print head module). Typically, the digital control signals are used to selectively transmit them to the piezoelectric actuators by selectively switching the analog actuator drive pulses.

[0114] In some embodiments, the control circuit switches and connects one or more grounds and a single fixed non - zero voltage line, or a plurality of fixed voltage lines of different voltages (one or more of which may be grounded) to one or both electrodes of the piezoelectric actuator to configure it to eject droplets of the printing agent. For example, the control circuit can switch the electrode between connection to ground and connection to a fixed voltage or a plurality of fixed voltage lines of different voltages to eject a droplet and then return it to ground again. Usually, the second print head module is configured to conduct the ground and / or the single fixed non - zero voltage from the first print head module to the third print head module.

[0115] Switching the electrode between connection to ground and connection to a fixed voltage, or between fixed voltage lines, may include operating a latch.

[0116] The control circuit is formed by one or more of the layers on the same substrate and is configured to individually and selectively operate at least three (or at least four) of the piezoelectric actuator elements that define part of different respective fluid chambers (each having a different respective droplet ejection orifice, which may be called a print head nozzle). Optionally, the at least three (or at least four) actuator elements are configured to eject different color ink compositions or as redundant droplet ejection orifices.

[0117] The at least three (or at least four) piezoelectric actuator elements are arranged on the substrate (optionally adjacent to each other and optionally in a row), and the control circuit may be connected to a flexible print head cable having one or more electrical signal conductors. The control circuit is configured to individually and selectively operate the actuator elements among the at least three (or at least four) piezoelectric actuator elements in response to an operation command received via the same signal conductor.

[0118] Accordingly, since a control circuit configured to drive at least three (or at least four) actuator elements is integrated, each signal conductor can transmit a control signal for actuating the individual actuator elements of at least three (or at least four) piezoelectric actuator elements. Usually, the control signal is a digital control signal.

[0119] The at least three (or at least four) piezoelectric actuator elements may include a group of piezoelectric actuator elements, for example, a group of piezoelectric actuator elements configured to eject a group of the same ink composition (e.g., having a chamber in fluid communication with the same ink supply source), or different color ink compositions (e.g., having a chamber in fluid communication with separate ink supply sources), or a group of piezoelectric actuator elements divided into a plurality of (usually at least three or at least four) subgroups, or a group of piezoelectric actuator elements, wherein the piezoelectric actuator elements within each subgroup are configured to eject the same ink composition (e.g., having a fluid chamber in fluid communication with the same fluid supply source), and some or all of the piezoelectric actuator elements of the subgroup are configured to eject different color ink compositions (e.g., in fluid communication with separate ink supply sources). The piezoelectric actuator elements within the same subgroup are arranged in an array, and there may be a plurality of arrays for each subgroup.

[0120] The control circuit may be configured to individually and selectively actuate at least twice as many piezoelectric actuator elements as the number of signal conductors through which the control circuit receives the actuation control signal.

[0121] The control circuit is configured to individually and selectively actuate at least 128 (or at least 256) piezoelectric actuator elements, and the control circuit can receive the actuation control signal via a maximum of 32 (or a maximum of 16) signal conductors.

[0122] The control circuit may comprise a serial-to-parallel conversion circuit configured to convert a digital signal received in serial form via one or more signal conductors into a selection of piezoelectric actuators that are actuated to perform droplet ejection simultaneously (i.e., in parallel). The serial / parallel conversion circuit typically comprises one or more shift registers.

[0123] Manufacture of a printing device and printing method In yet another aspect of the invention, a method of manufacturing a printing device is provided that includes: (i) forming a control circuit within a substrate; (ii) forming a plurality of piezoelectric actuators each in electrical communication with the control circuit; (iii) forming a plurality of nozzles each coupled to a respective one of the plurality of piezoelectric actuators; and (iv) forming a plurality of chambers each in fluid communication with a respective one of the plurality of nozzles. A set of different ink compositions may be received within or may be receivable within the plurality of chambers. The method may also include preparing a set of different ink compositions for use with the printing device. The ink compositions may be prepared as described herein. The method may include receiving a set of different ink compositions in each of the plurality of chambers.

[0124] In yet another aspect of the invention, a printing method is provided that includes: (i) providing a printing device as described in the preceding aspect; and (ii) operating a control circuit to eject at least one, typically at least two, of a set of at least one, typically at least two, ink compositions according to the second aspect from at least one, typically at least two, of a plurality of nozzles of a plurality of printhead ejectors. Typically, ink droplets of at least two ink compositions from at least two of the plurality of nozzles are ejected with corresponding volumes and velocities. The printing device may be as described herein. The ink compositions may be as described herein.

[0125] Any feature of one aspect of the present invention can be utilized in other aspects of the present invention as needed. Any feature of a particular embodiment can be utilized in other embodiments of the present invention as needed. Any optional feature (e.g., a feature described as "preferred" or "typical") should be understood to be particularly preferred when combined with additional optional features. Unless otherwise specified, the features described should not be considered incompatible with other features, unless such combinations are clearly inherently incompatible. Each individual feature disclosed in the present invention should generally be assumed to be combinable with other features in any suitable manner, unless explicitly or clearly incompatible. The term "comprising" is intended to mean "including", but not necessarily "consisting of" or "composed of". In other words, the listed steps or options need not be exhaustive. Throughout the description and claims of this specification, unless the context requires otherwise or indicates otherwise, the singular form includes the plural form and vice versa. In particular, when an indefinite article is used, this specification should be understood to contemplate not only the singular but also the plural, unless the context requires otherwise or indicates otherwise. The examples and embodiments given in the above description are intended to clarify the present invention and are not intended to limit the present invention. All percentages are weight percentages based on the total weight of the relevant materials, unless otherwise indicated. Except for operating examples and embodiments, or unless otherwise explicitly indicated, all numerical values in this specification indicating amounts of materials or reaction conditions, physical properties, or materials and / or uses should be understood to be modified by the word "about". A numerical range expressed in the form "from x to y" is understood to include x and y, unless otherwise specified. It is understood that when multiple arbitrary ranges for a particular feature are described in the form "from x to y", all ranges combining different endpoints are also considered. It will be understood that all possible combinations of the ranges and sub-ranges described in this specification are also considered.For example, it is particularly preferable that a viscosity range of 20% or less of the maximum viscosity value of the set is combined with any one of the preferable ranges of density and any one of the preferable ranges of surface tension. For example, it is understood that it is particularly preferable that any one of the preferable ranges of viscosity is combined with any one of the preferable ranges of density and any one of the preferable ranges of surface tension. For example, it is understood that it is particularly preferable that any one of any ranges of volume is combined with any one of any ranges of velocity.

[0126] Here, exemplary embodiments of the present invention will be described with reference to the following drawings.

Brief Description of the Drawings

[0127]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0128] Here, a monolithic inkjet printhead and its operation for which the present invention is useful will be described with reference to FIGS. 1 to 4. FIG. 1 is a schematic diagram showing the arrangement of an actuator, a printhead nozzle, and a control circuit. The droplet ejector assembly 100 includes a silicon substrate 102, and the silicon substrate 102 includes a control circuit 104 on a first surface 106 of the silicon substrate 102. The control circuit 104 is typically an integrated circuit 104 in the form of a CMOS circuit 104. Those skilled in the art will understand that a CMOS circuit includes both a doped region of the substrate and a metallization layer and interconnects formed on the first surface of the substrate. A plurality of layers, shown generally as 112, are formed on the first surface 106 of the silicon substrate 102. The layer 112 is a CMOS metallization layer and includes metal conductive traces and passivation insulators such as SiO2, SiN, and SiON. The droplet ejector assembly 100 further includes a piezoelectric actuator 118 including a piezoelectric body 120, and the piezoelectric body 120 is formed of AlN or ScAlN in this example, but may be formed of another suitable piezoelectric material that can be processed at a temperature below 450°C. The piezoelectric actuator 118 forms a diaphragm with a layer of a material such as silicon, silicon oxide, silicon nitride, or derivatives thereof, and has a passivation layer 160 (which may also be called a nozzle defining layer 160) that prevents the applied potential from contacting the fluid.

[0129] At least one metallization layer 112 conducts a signal from an external controller through a bond pad 180 to a first portion 105a of the control circuit 104, and conducts from a second portion 105b and a third portion 150c of the control circuit 104 to the piezoelectric actuator through an electrical interconnect 108, and in particular, includes interconnects that conduct to a first electrode 140 and a second electrode 142 arranged to operate the piezoelectric body 120 by applying a potential difference. An opening 120a is defined in the piezoelectric body 120 to allow the electrical interconnect 108 between the second portion 105b of the control circuit 104 and the second electrode 142 to pass through.

[0130] The piezoelectric actuator 118 and the accompanying passivation layer 160 define the wall of a fluid chamber 122 that receives a printing agent such as ink (in the case of an inkjet printer) or another printable fluid (e.g., in the case of a stereolithography printer) via a conduit 124, and communicate with a printhead nozzle 126 for ejecting a liquid. The piezoelectric actuator 118 and the nozzle defining layer 160 further define the wall of the printhead nozzle 126. The conduit 124 forms at least a portion of a print agent manifold that provides a fluid communication path between a print agent inlet (not shown in FIG. 1) and the printhead nozzle 126 (and further printhead nozzles, not shown in FIG. 1) via the chamber 122. The conduit 124 is defined by the silicon substrate 102, the metallization layer 112, and the nozzle defining layer 160. The protective front surface 170 provides the outer surface of the droplet ejector assembly 100, is provided to cover and protect the piezoelectric actuator 118, and abuts the surface 162 of the nozzle defining layer 160. The protective front surface 170 has an aperture that defines the nozzle 126. The piezoelectric actuator 118, the chamber 122, and the nozzle 126 together form a droplet ejector shown generally as 101.

[0131] Generally, a CMOS control circuit comprises patterned regions of doped silicon and metallization layers. The number of metallization layers varies depending on the complexity of the CMOS control circuit, but three layers are sufficient for many applications.

[0132] For clarity, only one printhead nozzle 126 and piezoelectric actuator 118 are shown in FIG. 1, but it will be understood that a plurality of printhead nozzles 126 and corresponding piezoelectric actuators 118 are provided, including actuators that dispense a plurality of different inks. Each piezoelectric actuator 118 is configured to control the ejection of the printing agent from its respective printhead nozzle 126.

[0133] The droplet ejector of FIG. 1 ejects the ink composition through the nozzles. The piezoelectric transducer is within the nozzle-defining layer and moves with the nozzle. Thus, the surface of chamber 122 including the nozzle moves during operation. This is in contrast to devices where the surface including the nozzle does not move and another surface, e.g., the opposite surface, operates. As a result, the operating force required to move the ink within the nozzle is small. Thereafter, the ink is ejected from the nozzle mainly by inertial forces (i.e., inertial ejection). In this specification, ejection by inertial forces may also be referred to as inertial ejection or ejection by the inertial mode. The ejection of the ink is mainly determined by the density and viscosity of the ink and not by compressibility as would be the case if another surface operated to move the ink within the chamber as a whole.

[0134] FIG. 2 shows a diagram of the arrangement shown in FIG. 1 including a plurality of printhead nozzles. Specifically referring to FIG. 2, a printhead 100a having a plurality of droplet ejectors 101 (individual piezoelectric actuators, fluid chambers, and droplet ejection orifices) is shown, and a flexible cable interconnect 138 with a limited number of signal conductors connects an external controller to the printhead 100a via wires, and the printhead 100a comprises a plurality of droplet ejectors shown as 101 for ejecting different printing agents, e.g., inks of different colors. Chambers (122a, b, c, and d) may contain inks of different colors. The piezoelectric actuators 118, control circuits 104, and printhead nozzles 126 forming the plurality of droplet ejectors 101 are typically formed from a single CMOS / actuator substrate, but the print agent manifold of each printhead 100a may be at least partially defined by at least one additional component provided in fluid communication with the printhead nozzles 126. In these examples, similar to the main part of the CMOS control circuit 104, the CMOS control circuit includes separate circuit elements 104' associated with each droplet ejector, which may comprise, for example, latches and ejector transistors for each piezoelectric actuator.

[0135] FIG. 3 is a block diagram of a control circuit of a print head assembly. In this example, actuator control is distributed between a machine controller 220 and a control circuit (e.g., a CMOS circuit) 104 within the print head 100a. They are partially connected by conductors extending through single or multiple flexible cable interconnects 138. A plurality of actuators 120 are controlled by applying potentials to their electrodes 140, 142. The machine controller includes at least a processor 200, such as a microprocessor or a microcontroller, having a memory 202 for storing associated data and program code. A wired or wireless electronic interface 204 receives input data from an external device driver. One skilled in the art will understand that the machine controller can be distributed among a number of individual components or functional modules, such as one component that converts an image into a pixelated pattern for printing, e.g., using dithermatrix, and a separate component that converts the pixelated pattern into a printing pattern for various nozzles.

[0136] The machine controller includes a waveform generator and a voltage amplifier 208 that provides a continuous pattern of actuator control pulses (shown in FIG. 4) to the print head via one or more drive signal conductors 210. The machine controller can generate a plurality of different waveforms, but in the context of the present invention, it is advantageous to generate and use a single waveform for ejecting each type of ink in order to reduce wiring and obtain other advantages as described above.

[0137] A ground conductor 212 also extends from the machine controller to the droplet ejector assembly 100. (For clarity, the ground connection within the print head is not shown). The processor 200 typically generates digital control signals 214 as a serial bus and also transmits a clock signal 216 to the print head that serves to synchronize printing with the movement of the print head. This connector also provides voltage levels related to the operating voltage of the CMOS control electronics.

[0138] Within the print head 100a, the contact pad 136 is connected to the conductor of the flexible connector, and the signal is routed through the patterned metallization layer 112 to the CMOS control circuit 104, and from the CMOS control circuit to the electrodes 140, 142 that actuate the individual piezoelectric bodies 120 within each piezoelectric actuator. The control circuit 104 on the substrate 102 includes an ejection switch circuit 220 that includes an ejection transistor having an output that is directly electrically connected to the electrodes 140, 142 (i.e., without further intervening switching semiconductor junctions). The ejection switch circuit switches the actuator control pulse signal, and if one of the electrodes remains connected to ground, the ejection switch circuit can be simplified to one transistor per actuator, or one transistor per electrode for switching the signal applied to the electrode. The ejection switch circuit may be distributed around the substrate having portions (e.g., transistors or transistors and latches) proximate to each droplet ejector.

[0139] The eject switch circuit does not perform power amplification. Instead, it switches the actuator control pulses and determines for each pulse whether each pulse is relayed to its respective actuator. Voltage amplification is performed by the amplifier 208 within the machine controller.

[0140] The ejection switch circuit is controlled by a latch and shift transistor 222 that receives and stores digital data from the control circuit 224. The control circuit 224 processes the received data, for example, converts the received serial data, stores them in the register 226, and determines which actuator to activate during each activation event of the consecutive actuators using the received data. The control circuit 228 also stores trim data that is used to customize the exact timing of the voltage switching of each actuator. This trim data is usually determined during the calibration step at setup and may store configuration data 230 indicating the physical layout of the nozzles, security information, and / or nozzle operation history information. The control circuit 224 also receives data from the sensors 232, 234, 236, some of which are associated with individual actuators, such as nozzle filling level sensors, and some of which sense parameters related to the overall function of the print head, such as temperature sensors.

[0141] Figures 4(a), 4(b), and 4(c) show three possible drive waveforms generated by the waveform generator or voltage amplifier 206 in an alternative embodiment. The x-axis is time in milliseconds, and the y-axis is the potential per 1 μm of the actuator thickness. In this example, since the piezoelectric is made of a non-ferroelectric material, the pulse may be applied in either direction. In Figure 4(a), the default voltage of the signal is 0, switches to a positive potential at each pulse, and returns to zero after a predetermined time. In Figure 4(b), the default voltage of the signal is 0, first switches to a positive potential (so that the piezoelectric actuator deforms in one direction), then switches to a negative potential (so that the piezoelectric actuator deforms in the opposite direction), and then returns to zero. In Figure 4(c), the default voltage of the signal is 200V, but switches to a voltage of -200V (so that the direction of the electric field in the piezoelectric is reversed), and then returns to 200V.

[0142] During operation, the processor 200 receives print data, such as a bitmap, in digital form via the interface 204, processes this data by known means, and sends a series of print commands to each print head via the serial connection portion 216. These print commands can be as detailed as the commands for each print head regarding whether to eject droplets during the printing cycle and when to eject them. In one embodiment, the waveform generator generates repetitive voltage pulses suitable for applying to the electrodes of individual piezoelectric actuators. These are periodic with time intervals that determine the time between droplet ejection events on the print head. Alternatively, the voltage amplifier 208 can provide and maintain a single voltage level out of a plurality of voltage levels to the print head assembly. The ejection transistors within the print head switch these voltages according to the CMOS control circuit.

[0143] Since the waveform generator is not disposed on the print head and is used to drive a large number of piezoelectric actuators, it may generate a large amount of heat without causing problems. Since there are no substantial substrate space limitations, it may become a relatively complex circuit selected and optionally adapted to carefully control the shape of the waveform at an arbitrarily selected variable throughput rate, and when all the actuators that may operate simultaneously operate together, the power amplifier may be selected to generate the desired voltage up to the maximum possible current requirement.

[0144] The control circuit 224 on each print head substrate receives print commands via the serial connection part 216 and processes them (for example, conversion from serial commands to parallel commands). With reference to the clock signal 214, it is determined whether it is necessary to activate each piezoelectric actuator to eject droplets during each printing cycle, and this data is loaded into the latch 222. At an appropriate point during each printing cycle, the latched data is passed to the ejection switch circuit, thereby switching the received printing waveforms to the electrodes of the respective actuator elements to execute the droplet ejection cycle, or, when both electrodes of each actuator element remain grounded and the droplet ejector does not execute the droplet ejection cycle, the switch circuit does not switch the printing waveforms.

[0145] Sensors 232, 234, 236 are monitored during printing. The exact timing for switching the received printing waveforms to the electrodes of the respective actuator elements can vary according to the measurement of temperature using temperature-sensitive CMOS elements.

[0146] The shift register moves the droplet emission pattern information to the latch register. Therefore, the shift register interfaces with the serial connection part and moves all the print data to the latch register in a predetermined printing cycle. The latch register interfaces with the ejection register to start the print command.

[0147] In some embodiments, instead of the machine controller including a waveform generator and the waveform being conducted to the print head and the CMOS control circuit thereon, the CMOS control circuit actuates the piezoelectric actuator to eject droplets by switching the voltage applied to one or more electrodes of each piezoelectric actuator, for example, between ground and a fixed voltage, or between a plurality of fixed voltage levels where one or more of them can be ground. In this case, the flexible connector 138 includes one or more conductors that carry a fixed voltage from the machine controller to the print head.

[0148] FIG. 5 shows a flowchart 500 illustrating a method of matching a plurality of inks used in the apparatus of FIGS. 1-4. First, the characteristics of the ink droplets (e.g., the size of the ink droplets) are defined at 510. The defined characteristics combined with the droplet ejection waveform 510' are used to determine a set of target physical characteristics of the ink (i.e., viscosity, density, and surface tension) that function as physical property criteria at 520. Next, a candidate set of ink compositions (e.g., a candidate set of different ink compositions) can be determined at 530. The candidate set can be, for example, a set of inks manufactured using appropriate components at appropriate levels already aimed at achieving the target physical characteristics. Alternatively, the candidate set can be a random set of inks. After 530, the physical characteristics (i.e., viscosity, density, and surface tension) of the candidate set are determined at 540. Typically, these characteristics can be determined by using the methods described herein or any suitable and effective method known to those skilled in the art. If the characteristics of the candidate ink set are compatible with each other and with the target physical characteristics at 550, the candidate set is selected at 570. Otherwise, one or more inks (e.g., all inks) of the candidate set are changed at 560 and their physical characteristics are determined again at 540. The change can be appropriately implemented by adjusting the type(s) and / or level(s) of appropriate components (e.g., surfactants, carriers, and rheology modifiers). If the candidate set still does not meet the compatibility requirements even after the change at 550, the set can be changed again at 560. In this way, steps 540, 550, and 560 can be appropriately repeated one or more times until an ink set is selected at 570. The selected set can be used (e.g., placed within the chambers of a printhead as described herein) to produce a corresponding ink set that can be packaged in a cartridge, if appropriate, using the specifications of the ink set. The cartridge can contain each ink within the set.

[0149] Detailed description of the ink set The present invention will be described by the following non-limiting examples.

[0150] The components in Table 1 can be used in the ink composition.

Table 1

[0151] An exemplary set of ink compositions is shown in Table 2.

Table 2

[0152] The above weight percentages are based on the total weight of the ink composition. The target viscosity, density, and surface tension of each ink composition are determined experimentally or theoretically for a target dpi (e.g., 1200). Narrow ranges of viscosity, density, and surface tension (e.g., 1% variation) are measured. These ranges depend greatly on the implementation and can be within a viscosity range of 1.5 mPa·s to 20 mPa·s, a density range of 650 kg / m 3 ~1750 kg / m 3 and a surface tension range of 20 mN / m to 75 mN / m.

[0153] The amount of each component is adjusted so that the viscosity, density, and surface tension of all compositions C1 - C4 are within narrow target ranges. These values are measured according to the methods described herein. Thus, the viscosity values, density values, and surface tension values of compositions C1 - C4 are adapted so that the difference between any two compositions is 1% or less of the corresponding maximum value of the set (i.e., the values are adapted according to the present invention). However, since the compressibility is not important, variations in compressibility between different compositions C1 - C4 within the set are allowed and can be 1% or more. The lack of a strict requirement for the allowable range of compressibility facilitates the optimization of the more important viscosity, density, and surface tension parameters.

Claims

1. A monolithic inkjet printhead for ejecting a set of different ink compositions, said printhead comprising at least one substrate, said substrate comprising a plurality of ejectors, each ejector comprising: (i) a nozzle; (ii) a chamber for said set of ink compositions, said chamber being in fluid communication with said nozzle; and (iii) a piezoelectric actuator coupled to said nozzle for selectively ejecting said ink composition from said nozzle, each ejector being configured to eject ink droplets of said different ink compositions at corresponding volumes and velocities, a monolithic inkjet printhead.

2. Each ejector is configured to eject an ink composition that meets a plurality of physical property criteria at corresponding volumes and velocities, said physical property criteria including at least corresponding density and viscosity, the monolithic inkjet printhead according to claim 1.

3. Said configuration of said ejector includes an operating waveform of said actuator during use, said operating waveform generally including a time-varying displacement of said ink composition within said chamber and a force applied to said ink composition during operation, the monolithic inkjet printhead according to claim 1 or claim 2.

4. Said substrate comprises a CMOS control circuit and a plurality of layers on a first surface of said substrate, said piezoelectric actuator being formed by one or more of said layers, said nozzle comprising a hole penetrating one or more of said layers, whereby said piezoelectric actuator displaces one or more of said layers and said nozzle during use, thereby ejecting said ink composition in an inertial mode, the monolithic inkjet printhead according to any one of claims 1 to 3.

5. The monolithic printhead according to any one of claims 1 to 4, comprising at least 100 ejectors, preferably at least 1000 ejectors.

6. A set of different ink compositions for use in a monolithic inkjet printhead according to any one of claims 1 to 5, wherein (i) the viscosity values of the compositions are adapted such that the difference between any two compositions is 20% or less, preferably 10% or less, more preferably 5% or less, and most preferably 1% or less of the maximum viscosity value of the set; (ii) the density values of the compositions are adapted such that the difference between any two compositions is 20% or less, preferably 10% or less, more preferably 5% or less, and most preferably 1% or less of the maximum density value of the set; (iii) the surface tension values of the compositions are adapted such that the difference between any two compositions is 20% or less, preferably 10% or less, more preferably 5% or less, and most preferably 1% or less of the maximum surface tension value of the set. A set of different ink compositions.

7. The set includes a plurality of compositions each containing a different colorant selected from cyan (C), yellow (Y), magenta (M), key (K), red (R), green (G), blue (B), purple, orange, gold, silver, white, and mixtures thereof, preferably selected from CYMK and mixtures thereof, or RGBK and mixtures thereof, and optionally, the difference in the weight percentage of the colorant contained in at least two compositions of the set or any two compositions of the set is 5 or less, or 2 or less, or 1 or less, or 0.1 or less, and any weight percentage is based on the total weight of each ink composition. A set of different ink compositions according to claim 6.

8. The set includes a first composition containing a colorant of cyan (C) or red (R), a second composition containing a colorant of yellow (Y) or green (G), a third composition containing a colorant of magenta (M) or blue (B), and a fourth composition containing a colorant of key (K). A set of different ink compositions according to claim 7.

9. At least one composition of the set or each composition of the set includes a rheology modifier, and / or a surfactant, and / or a carrier, and optionally, the difference in weight percentage of the rheology modifier, and / or the surfactant, and / or the carrier included in at least two compositions of the set or any two compositions of the set is 20 or less, or 10 or less, or 5 or less, or 1 or less, and any weight percentage is based on the total weight of each ink composition. A set of different ink compositions according to any one of claims 6 to 8.

10. At least two compositions of the set or any two compositions of the set include different rheology modifiers, and / or different surfactants, and / or different carriers, and optionally, the difference in weight percentage of the rheology modifier, and / or the surfactant, and / or the carrier included in at least two compositions of the set or any two compositions of the set is at least 0.1, or at least 1, or at least 5, or at least 10, and any weight percentage is based on the total weight of each ink composition. A set of different ink compositions according to claim 9.

11. A printing apparatus comprising: the monolithic print head according to any one of claims 1 to 5; a signal generator configured to generate a drive signal having a repetitive waveform; relaying the drive signal to the actuator via a switch; and a control circuit configured to control the switch to selectively apply the drive signal to individual actuators, thereby ejecting ink droplets of the different ink compositions at corresponding volumes and speeds.

12. The printing apparatus according to claim 11, further comprising a set of ink compositions according to any one of claims 6 to 10, wherein the compositions are received or receivable within the chamber.

13. A printing method, comprising: (i) providing a printing apparatus according to claim 11 or claim 12; and (ii) operating the control circuit so that at least two of the plurality of ink compositions according to any one of claims 6 to 10 are ejected from at least two of the plurality of nozzles of the plurality of print head ejectors, thereby ejecting ink droplets of the at least two different ink compositions from the at least two of the plurality of nozzles at corresponding volumes and speeds.

14. A method for producing a set of different ink compositions according to any one of claims 6 to 10, comprising: (i) producing at least two ink compositions; (ii) determining whether the viscosity values, density values and surface tension values of the at least two ink compositions are such that the set of the at least two ink compositions is a set of different ink compositions according to any one of claims 6 to 10; and (iii) if not, changing at least one of the at least two ink compositions one or more times until the set is a set of different ink compositions according to any one of claims 6 to 10.

15. A method for selecting a set of different ink compositions according to any one of claims 6 to 10, comprising: (i) defining at least one characteristic of the ejected ink droplets; (ii) using the at least one defined characteristic to determine target values for the viscosity, density and surface tension of the ink composition; and (iii) selecting at least two ink compositions with reference to the target values described in step (ii), wherein the values of the at least two ink compositions are such that the set of the at least two ink compositions is a set of different ink compositions according to any one of claims 6 to 10.

16. (i) The viscosity value of the composition is adapted such that the difference between any two compositions is 10% or less, preferably 5% or less, more preferably 1% or less of the maximum viscosity value of the set; (ii) The density value of the composition is adapted such that the difference between any two compositions is 10% or less, preferably 5% or less, more preferably 1% or less of the maximum density value of the set; (iii) The surface tension value of the composition is adapted such that the difference between any two compositions is 10% or less, preferably 5% or less, more preferably 1% or less of the maximum surface tension value of the set. A set of different ink compositions according to any one of claims 6 to 10.

17. (i) The viscosity value of the composition is adapted such that the difference between any two compositions is 5% or less, preferably 1% or less of the maximum viscosity value of the set; (ii) The density value of the composition is adapted such that the difference between any two compositions is 5% or less, preferably 1% or less of the maximum density value of the set; (iii) The surface tension value of the composition is adapted such that the difference between any two compositions is 5% or less, preferably 1% or less of the maximum surface tension value of the set. A set of different ink compositions according to claim 16.

18. The difference in the compressibility (k) between two ink compositions of the set, or between any two ink compositions of the set, is at least 1%, or at least 5%, or at least 10%, or at least 20%, or at least 30%, or at least 40%, or at least 50% of the maximum compressibility value of the set. A set of different ink compositions according to any one of claims 6 to 10, 16 and 17.

19. The difference in the compressibility (k) between two ink compositions of the set, or between any two ink compositions of the set, is at least 5% or 10% of the maximum compressibility value of the set. A set of different ink compositions according to claim 18.

20. A printing apparatus comprising a monolithic printhead according to any one of claims 1 to 5 and a set of different ink compositions according to any one of claims 6 to 10 and 16 to 19, wherein the composition is received or receivable within the chamber.

21. The set of different ink compositions is an ink composition according to any one of claims 17 to 19. A printing apparatus according to claim 20.

22. A signal generator configured to generate a drive signal having a repetitive waveform, and relay the drive signal to the actuator via a switch, and control the switch so as to selectively apply the drive signal to individual actuators, thereby ejecting ink droplets of the different ink compositions at corresponding volumes and speeds. A printing apparatus according to claim 20 or claim 21, further comprising a control circuit configured to perform the above operations.

23. The printing apparatus according to claim 22, wherein the set of different ink compositions is the ink composition according to any one of claims 17 to 19.

24. A printing method including: providing a printing apparatus according to claim 22 or claim 23; operating a control circuit so as to eject at least two ink compositions out of the set of different ink compositions from at least two of the plurality of nozzles of the plurality of print head ejectors, thereby ejecting ink droplets of the at least two different ink compositions from the at least two of the plurality of nozzles at corresponding volumes and speeds.

25. A method of producing a set of different ink compositions for use in a printing apparatus according to any one of claims 20 to 23, the method comprising: producing at least two ink compositions; determining whether viscosity values, density values, and surface tension values of the at least two ink compositions are such that the at least two ink compositions form the set of different ink compositions; and (iii) if not, changing at least one of the at least two ink compositions one or more times until the at least two ink compositions form the set of different ink compositions.

26. A method of selecting a set of different ink compositions for use in a printing apparatus according to any one of claims 20 to 23, the method comprising: defining at least one characteristic of ejected ink droplets; using the at least one defined characteristic to determine target values for viscosity, density, and surface tension of an ink composition; and selecting at least two ink compositions with reference to the target values, wherein the values of the at least two ink compositions are such that the at least two ink compositions form the set of different ink compositions.

27. A method of manufacturing a printing apparatus according to any one of claims 11, 12, and 20 to 23, the method comprising: forming a control circuit in a substrate; forming a plurality of piezoelectric actuators each electrically communicating with the control circuit; forming a plurality of nozzles each coupled to a respective one of the plurality of piezoelectric actuators; and forming a plurality of chambers each in fluid communication with a respective one of the plurality of nozzles.

28. The method of manufacturing a printing apparatus according to claim 27, further comprising a method of producing a set of different ink compositions according to claim 14 or claim 25.

29. The method according to claim 28, further comprising receiving a set of the different ink compositions in respective ones of the plurality of chambers.

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