Print material supply system

Abstract

An inkjet printer has a print material supply system comprising a print assembly and a first circulation circuit and a second circulation circuit, wherein the first circulation circuit is flexibly coupled between the second circulation circuit and the print assembly.

Description

Technology Field

[0001] This application claims priority to U.S. Provisional Patent Application No. 62 / 782,412 filed December 20, 2018 and U.S. Regular Patent Application No. 16 / 717,756 filed December 17, 2019, the whole contents of which are incorporated herein by reference. The present invention relates to a print material supply system. Background Technology

[0002] Inkjet printing of digital display substrates involves depositing an amount of material onto a substrate at a designated location. The material is dispensed from a dispenser in a controlled amount, travels through a gap between the dispenser and the substrate, and lands on the substrate at the target location. The printing material used may be a complex mixture of reactive chemicals, solvents, and solids. Consistently delivering printing material to various locations on the substrate depends on maintaining a consistent composition of the material delivered to different locations on the substrate. Inkjet printing technology is required for a printer equipped with a material delivery system capable of delivering a controlled amount of printing material to the printer at a specific time while maintaining the printing material in a well-mixed and dispersed state. The problem to be solved

[0003] The present invention provides a print material supply system. means of solving the problem

[0004] An embodiment described herein includes a print assembly; and a print material supply system coupled to the print assembly, wherein the print material supply system includes a first circulation circuit and a second circulation circuit, and the first circulation circuit is flexibly coupled between the second circulation circuit and the print assembly.

[0005] A print material supply system according to another embodiment described herein comprises: a print material supply reservoir; a print material discharge reservoir; at least one print head; a print material supply line flexibly coupled from the print material supply reservoir to the at least one print head; and a print material return line flexibly coupled from the at least one print head to the print material discharge reservoir; a first circulation circuit comprising a circulation supply line coupled to the print material supply reservoir; a circulation return line coupled to the print material discharge reservoir; and a second circulation circuit comprising a pump having a suction flexibly coupled to the circulation return line and a discharge flexibly coupled to the circulation supply line.

[0006] An inkjet printing device having a print material supply system according to another embodiment described in this specification comprises a print assembly; a bulk circulation circuit; an intermediate circulation circuit; and a local circulation circuit, wherein the bulk circulation circuit is configured to draw print material from a supply container to a mixing container and to continuously flow print material around the bulk circulation circuit, the intermediate circulation circuit is configured to draw print material from the bulk circulation circuit, return print material to the bulk circulation circuit, and to flow print material around the intermediate circulation circuit, and the local circulation circuit is configured to draw print material from the intermediate circulation circuit, return print material, and supply print material to the print assembly. Effects of the invention

[0007] An inkjet printing device including a printing material supply system including a circulation circuit as described above maintains a mixed state of printing materials moving through the printing material supply system by stirring or circulating the printing materials. Brief explanation of the drawing

[0008] The aspects of the present disclosure are best understood from the following detailed description when read together with the accompanying drawings. In accordance with standard industry practice, various functions are not extended. In fact, the dimensions of various features may be increased or decreased at will for the sake of clarity of discussion. FIG. 1 is a schematic diagram of a print material supply system of an inkjet printer according to one embodiment. FIG. 2 is an isometric projection of an inkjet printer according to one embodiment. FIGS. 3a-3c are schematic diagrams of other embodiments of a print material storage. FIG. 4 is a schematic diagram of a supply storage facility according to one embodiment. FIG. 5 is a schematic diagram of a discharge storage facility according to another embodiment. Specific details for implementing the invention

[0009] The following disclosure provides many different embodiments or examples for implementing different features of the provided subject matter. Specific examples of components, values, actions, materials, arrangements, etc. are described below for the sake of simplicity of the disclosure. Of course, these are merely examples and are not intended to be limiting. Other components, values, actions, materials, arrangements, etc. are considered. For example, forming a first feature on or above a second feature in the description below may include embodiments in which the first feature and the second feature are in direct contact, such as the first feature and the second feature may not be in direct contact, and embodiments in which an additional feature may be formed between the first feature and the second feature. Additionally, the disclosure may repeat reference numbers and / or letters in various examples. Such repetition is for the purpose of simplicity and clarity and does not itself indicate a relationship between the various embodiments and / or configurations discussed.

[0010] Additionally, spatially relative terms such as "beneath," "below," "lower," "above," and "upper" may be used herein for convenience of describing the relationship between one component or feature(s) and other component(s) or feature(s) as illustrated in the drawings. Spatially relative terms are intended to include other directions of the device in use or operation in addition to the directions depicted in the drawings. The device may be oriented differently (rotated 90 degrees or oriented differently), and spatially relative descriptors used herein may be interpreted similarly accordingly.

[0011] In some inkjet printing applications, print materials are deposited onto a substrate in individual volumes. The volumes are typically deposited as uniformly as possible so that the resulting structure complies with manufacturing parameters. An example of such an application is the inkjet printing of display components onto a substrate. If the display components are printed non-uniformly, the display may not emit light uniformly.

[0012] To deposit a uniform amount of print material on a substrate, parameters of the inkjet printing process are controlled. In some cases, individual amounts of print material have a size as small as 10 μm. The controlled parameters of the inkjet printing process may include the position of the printed substrate, the movement of the printed substrate, the separation distance or printing interval between the print head and the upper surface of the printed substrate, the temperature of the components of the inkjet printing device and the printed substrate, and the composition of the print material deposited on the printed substrate.

[0013] Print materials often comprise a combination of fluids and suspended particles. The fluid may be a mixture of monomers that are ultimately cured by heat or photocuring into a rigid material that adheres to the printed substrate. The fluid may also contain cross-linking monomers that link two or more polymer chains within the cured print material, thereby providing greater structural strength and / or stiffness to the cured material. Solvents may also be used to control the surface tension, density, and / or viscosity of the print material for repeatable droplet formation.

[0014] Print materials can also contain insoluble elements such as scattering particles and quantum dots. Scattering particles are small reflective particles that scatter incident light from a light source when embedded within the cured material. Quantum dots absorb light of one wavelength and consequently emit light of another wavelength, depending on their properties. Maintaining good dispersion of scattering particles and quantum dots within the print material improves the uniformity of light output by displays made using print materials containing these particles and quantum dots. One technique for maintaining dispersed print materials is to agitate or mix the print material before depositing it onto the printed substrate. Another technique is to move the print material between deposition instances.

[0015] FIG. 1 is a schematic diagram of a print material supply system (100) of an inkjet printing device according to some embodiments. The print material supply system (100) includes at least two circulation circuits, including a bulk circulation circuit (103), an intermediate circulation circuit (105), and a local circulation circuit (107). The bulk circulation circuit (103) includes a bulk supply container (102) that supplies print material to a print material reservoir (104). Print material is circulated from the print material reservoir (104) through the bulk circulation circuit (103) via a pump (106), a bulk circulation valve (108), and a check valve (110), and is circulated back to the print material reservoir (104). The check valve (110) is optional. By moving print material around the bulk circulation circuit (103), the print material within the circulation circuit remains in a dispersed state. The print material storage (104) may include a mixing element (e.g., see component (414) in FIG. 3a) to make the print material storage (104) a mixed or stirred container.

[0016] The bulk circulation circuit (103) is connected to the intermediate circulation circuit (105). The bulk circulation circuit (103) includes a bulk return line (101) from the check valve (110) to the print material reservoir. Print material flows from the print material reservoir (104) to the pump (106), the bulk circulation valve (108), and the check valve (110), and then flows back to the print material reservoir through the bulk return line (101) in the flow direction (103A). The intermediate circulation circuit (105) is connected to the bulk circulation circuit (103) from the bulk return line (101). A bulk return valve (152) is placed in the bulk return line (101) to regulate the flow from the intermediate circulation circuit (105) to the bulk circulation circuit (103).

[0017] The connection between the bulk circulation circuit (103) and the intermediate circulation circuit (105) is a bidirectional flow connection. Print material flows to / from the bulk and intermediate circulation circuits (103, 105) through the bidirectional connection line (109). The intermediate circulation circuit (105) includes a transfer valve (112) for controlling the flow of print material between the intermediate circulation circuit (105) and the bulk circulation circuit (103). The intermediate circulation circuit (105) has a flow direction (105A) of print material around the circuit. The intermediate circulation circuit (105) includes an optional intermediate supply container (116) connected to an intermediate supply valve (118) to control the input of material from the intermediate supply container (116) to the intermediate circulation circuit (105). The intermediate circulation valve (120) controls the flow of print material within the intermediate circulation circuit (105). As described below, the print material flows through the intermediate circulation circuit (105) in the flow direction (105A) from the intermediate circulation valve (120) to the phase purification module (121), and then flows from the intermediate circulation circuit (105) to the valve (131) which controls the flow of the print material to the local circulation circuit (107). The print material flows back from the local circulation circuit (107) to the intermediate circulation circuit (105) through the intermediate return line (113) in which the valve (127) is located, and then flows to the intermediate pump (138). The discharge from the intermediate pump (138) flows through the intermediate check valve (140) and returns to the intermediate circulation valve (120) along the flow direction (105A). In some embodiments, the valve (127) and the valve (131) are not part of the intermediate circulation circuit (105) but part of the local circulation circuit (103). The valve of the present disclosure is a digital valve, but analog-operated valves are consistent with the subject matter of the present disclosure.

[0018] In some embodiments, the intermediate supply vessel (116) provides flush material to remove print material from the intermediate and / or bulk and / or local circulation circuits (105, 103, 107) during maintenance or when switching the type of product printed by the inkjet printer. Thus, the intermediate supply vessel (116), the supply valve (118), and the intermediate circulation valve (120) may be part of the flushing module (114) of the intermediate circulation circuit (105). In other cases, the intermediate supply vessel (116) may be a print material supply vessel to supply print material to the intermediate and local circulation circuits (105, 107). In either case, the material may be transferred from the intermediate circulation circuit (105) to the local circulation circuit (107), and conversely, from the intermediate circulation circuit (105) to the bulk circulation circuit (103).

[0019] The phase purification module (121) includes a gas detector (122) and a gas remover (124). In some embodiments, the gas detector (122) is a bubble detector. In other cases, a chemical analyzer may be used to detect high vapor pressure types that do not form bubbles. In some cases, the bubble detector performs optical observation of the print material flowing through the intermediate circulation circuit (105). In other cases, the bubble detector performs volume measurement of the print material to determine the presence of gas pockets or dissolved gas within the print material in the intermediate circulation circuit (105). The gas remover (124) may be a bubble collection unit having a bubble collection volume to collect bubbles in the print material flow into the intermediate space of the print material reservoir and remove them from the print material flow path of the intermediate circulation circuit (105). In some cases, the gas remover (124) is a gas extractor. An example of a gas remover that can be used is the pHasor®II module used by Entegris, Inc. in Billerica, Massachusetts. Another example is the UltiFuzor™ model degasser used by Pall Corp. in Port Washington, New York. The gas remover (124) may include a filter, or a filter (not shown) may be coupled to the outlet of the gas remover (124) if desired.

[0020] The intermediate circulation circuit (103) includes an optional full recirculation line (111) connected between the discharge side and the suction side of the intermediate pump (138). Here, the full recirculation line (111) is connected to one end between the gas remover (124) and the local transfer valve (131), and to the other end between the valve (127) and the intermediate pump (138). The full recirculation line (111) provides the function of recirculating the print material of the intermediate circulation circuit (105) while separating the intermediate circulation circuit (105) from the local circulation circuit (107). To put the intermediate circulation circuit (105) into a full recirculation mode, the optional full recirculation valve (125) may be opened and the local transfer valve (131) may be closed. The full recirculation mode allows gas removal from the print material in the intermediate circulation circuit (105) without the print material flowing into the local circulation circuit (107). An intermediate bypass line (119) is provided between the bulk circulation circuit (103) and the local circulation circuit (107) to bypass the intermediate circulation circuit entirely and move the print material directly from the bulk circulation circuit (103) to the local circulation circuit (107).

[0021] The local circulation circuit (107) supplies print material to the print assembly of the inkjet printing device and receives print material from it. As further described below, the print assembly may include one or more print heads that distribute print material during a print job. When the local transfer valve (131) is opened, print material can flow from the intermediate circulation circuit (105) to the local circulation circuit (107). The local circulation circuit (107) includes a supply reservoir (126) and a discharge reservoir (134). The supply reservoir (126) is connected to the local transfer valve by a local supply line (115) through which the supply reservoir (126) receives print material from the intermediate circulation circuit (105). The supply reservoir (126) supplies print material to the print heads (128, 130, and 132) in the flow direction (107A) through the print manifold (123). Here, three print heads are shown in the local circulation circuit, but multiple print heads may be used. Print material that is not distributed onto the printed circuit board and passes through one of the print heads (128, 130, 132) exits the print head through the print return manifold (129). Print material exiting the print head is collected in the discharge reservoir (134) to be returned to the intermediate circulation circuit (105). Continuous circulation of the print material through the local and intermediate circulation circuits (107 and 105) ensures that the print material is well mixed so that solid components are not misdistributed.

[0022] A gas flow section (133), which may be a gas source or a vacuum source, in this case moves the print material around the local circulation circuit (107), moves the print material out of the discharge reservoir (134) and into the intermediate circulation circuit (105), and / or provides negative pressure to the supply reservoir (126) and / or discharge reservoir (134) to regulate the amount of print material filled in the discharge reservoir (134). An optional bypass line (135) is connected between the supply reservoir (126) and the discharge reservoir (134) to provide a flow path that sends the print material to the discharge reservoir (134) without passing through the print heads (128, 130, 132). A bypass valve (136) is placed in the bypass line (135). When opened, the bypass valve (136) bypasses the print heads (128, 130, and 132) to provide a direct flow path from the supply reservoir (126) to the discharge reservoir (134). The gas flow section (133) is configured to maintain a higher pressure in the supply reservoir than in the discharge reservoir (134) to facilitate the flow of print material from the supply reservoir (126) to the discharge reservoir (134) along the flow direction (107A) or when the bypass valve (136) is opened. The liquid volume of the supply reservoir (126) is monitored by a first level sensor (142) to allow for regulation of the volume of print material in the reservoir and to ensure print supply to the print assembly when necessary, and the liquid volume of the discharge reservoir (134) is monitored by a second level sensor (144). Although the gas flow section (133) is shown herein as a single item, multiple gas sources and / or vacuum sources may be used in any convenient configuration. In one example, the gas flow section (133) includes three separate gas sources.

[0023] If the level sensor indicates that the amount of print material in the supply reservoir (126) is too low, more print material is added to the supply reservoir (126) from the intermediate circulation circuit (105) by opening the local transfer valve (131). If the level sensor indicates that the amount of print material in the discharge reservoir (134) is too low, print material can be transferred from the supply reservoir (126) to the discharge reservoir (134) by opening the bypass valve (136). Alternatively, the flow of print material from the discharge reservoir (134) can be controlled based on the liquid level in the discharge reservoir (134) by adjusting the pumping rate of the intermediate pump (138), for example, the pump speed. According to some embodiments, the level sensor is applied to the outer surface of the container or reservoir and detects the amount of print material inside through a capacitive sensor on the outer surface of the container or reservoir. The capacitive level sensor is not wetted by the liquid in the container. Therefore, the print material reservoir does not need to be optically transparent, but simply has sufficient wall thickness for a capacitive detector positioned above it to interact with the print material inside. Many capacitive level sensors can determine the liquid level with an accuracy of 1 mm.

[0024] The pressure difference maintained by the gas flow section (133) between the supply reservoir (126) and the discharge reservoir (134) ensures that the printing material flows from the supply reservoir (126) to the discharge reservoir (134). The level sensors used here may be analog or digital devices, each having its own advantages and disadvantages. Using analog level sensors allows for very accurate reading of the liquid level and very rapid control of the liquid level, which may be useful in some embodiments. The level sensors may be located inside or outside the container. Using internal level sensors eliminates the influence of the container walls on the readings, whereas using external sensors prevents chemical interactions between the materials of the level sensors with the liquid being monitored and eliminates possible leakage paths. Additionally, maintenance of the level sensors can be performed without opening the container.

[0025] The bulk circulation circuit (103), intermediate circulation circuit (105), and local circulation circuit (107) are configured to maintain the movement of print material through the individual circulation circuits independently. For example, the bulk pump (106) can be operated to periodically or continuously add print material to the local circulation circuit (107) without affecting the movement of print material in the intermediate circulation circuit (105). Similarly, valves (131) and (127) can be operated to isolate the intermediate circulation circuit (105) from the local circulation circuit (107). The bulk transfer valve (112) may be a two-way valve that allows material to pass through the valve in both directions from the bulk circulation circuit (103) to the intermediate circulation circuit (105) and from the intermediate circulation circuit (105) to the bulk circulation circuit (103). Here, the bulk transfer valve (112) is also a three-way valve that can direct flow from the bulk circulation circuit (103) to the local transfer valve (131).

[0026] The control unit (150) is operably coupled to the valves (108, 112, 118, 120, 125, 127, 131, 136) and the gas flow unit (133) to control the overall operation of the supply system (100). The control unit (150) is also operably coupled to the level sensors (142 and 144). The control unit (150) is configured to control the volume of liquid in the supply reservoir (126) by adjusting (increasing) the pump speed while the valve (131) is open when the level sensor (144) indicates that the liquid volume in the supply reservoir (126) is below the lower limit, and by adjusting (decreasing) the pump speed while the valve (131) is open when the liquid volume is above the upper limit. Likewise, the control unit (150) may be configured to control the liquid volume of the discharge reservoir (134) by opening the bypass valve (136) when the level sensor (142) indicates that the liquid volume of the discharge reservoir (134) is below a lower limit, and by closing the bypass valve when the liquid volume exceeds an upper limit. The control unit (150) is also configured to control the gas flow unit (133) to maintain a higher pressure at the outlet of the supply reservoir (126) than at the inlet of the discharge reservoir (134) across the print head manifold. The speed of the print material through the print head assembly is maintained at a constant speed by adjusting the pump speed for the print material in the local circulation circuit (107).

[0027] FIG. 2 is an isometric view of an inkjet printer (200) according to one embodiment. The inkjet printer (200) includes a substrate support (202) on which a substrate is placed for processing. The substrate support (202) generally provides a substantially frictionless support so that the substrate can be easily positioned and moved during processing. In this case, the substrate support (202) provides a gas cushion between the substrate support (202) and the substrate. In some cases, the substrate support (202) is monolithic. Here, the substrate support has a first region (204), a second region (206), and a third region (208), each of which has gas openings to provide a gas cushion. The first region (204) and the third region (208) include a pattern of gas outflow openings in the second region (206) and one or more other patterns of gas outflow openings. The second area (206) defines a print area (215) adjacent to the print assembly (209).

[0028] The print assembly includes a dispenser assembly (201) and a print support assembly (203). The dispenser assembly (201) includes a print head housing (210), a print material reservoir assembly (212), and a carriage (207). The print support assembly includes a rail (214) supported by stands (216) on both sides of a substrate support (202). The carriage (207) supports other components of the dispenser assembly (201) on the rail (214) and moves along the rail (214) to position the dispenser assembly (201) at a target position relative to the print area (215). A print material storage assembly (212) is connected to a print head housing (210) by a circulation circuit (211), and a supply segment (211A) of the circulation circuit (211) provides print material from a storage (not shown) inside the print material storage assembly (212), and a return segment (211B) provides print material from the print head housing (210) to the storage of the print material storage assembly (212). The print housing (210) accommodates one or more print heads having discharge nozzles facing a print area (215). In some embodiments, the return and supply segments of the circulation circuit (211) are contained within the print material storage assembly (212) and / or the print head housing (210). In some embodiments, the return and supply segments of the circulation circuit (211) are exposed outside the print material storage assembly (212) and / or the print head housing (210). By placing the print material storage assembly (212) and the print head housing (210) together in the dispenser assembly (201), the circulation circuits for the print material between the print material storage assembly (212) and the print head housing (210) can be static.A gas source (not shown) for providing pressure to the circulation circuit to supply the print head housing (210) may also be included in the dispenser assembly (201).

[0029] FIG. 3a is a schematic diagram of a print material storage (300) according to one embodiment. The print material storage (300) includes side walls (303A and 303B) configured to contain print material (302) (note that if the storage (300) is cylindrical, the side walls (303A and 303B) will be one continuous cylindrical side wall). The print material storage (300) may be used in a bulk circulation circuit, such as the bulk circulation circuit (103) or intermediate circulation circuit (105) described in relation to FIG. 1. An outlet (304) and an inlet (306) allow the print material (302) to enter the circulation circuit (not shown in FIG. 3A). The outlet (304) is located at the bottom position (310) of the print material storage (300). The inlet (306) is located at the side position (312) of the storage (300). The bottom (303C) of the reservoir (300) may be sloped, and the bottom position (310) is the lowest part of the bottom (303C). A bypass outlet (380) is also provided at the bottom (303C) of the reservoir (300) to bypass the outlet (304), which typically transports print material from the reservoir (300) to the print head (Fig. 1). The flow through the bypass outlet (380) may be controlled by a bypass valve (386), which may be the bypass valve (136) of Fig. 1.

[0030] The print material reservoir (300) further comprises a mixing element (314) that extends into the reservoir and is driven by a mixing shaft (316). In some embodiments, the mixing element (314) is a mixer blade and makes the reservoir (300) a stirring vessel. In some embodiments, the mixing element is a jet mixer that draws material out of the reservoir and returns material to the reservoir at high speed to stir the material in the reservoir. In some embodiments, the mixing element (314) comprises multiple mixing surfaces fixed directly to the mixing shaft (316). In some embodiments, a support piece (not shown) is directly connected to the mixing shaft (316), and one or more mixing surfaces extend away from the support piece to stir the print material within the print material reservoir (300). The reservoir (300) may also include static mixing elements such as wall baffles or vanes.

[0031] FIG. 3b is a schematic diagram of a print material storage (305) according to another embodiment. Structural elements shown in FIG. 3B, which are similar to the structural components of other schematic diagrams of print material storages, are numbered in the same way. In the print material storage (305), the print material (302) is contained within side walls (303A and 303B) (if cylindrical, it may be a single side wall). The outlet (304) is located at the bottom surface (303E), while the inlet (306) is located at a second position (320) on the side wall (303B) or may be located at the top of the container. In some embodiments, the second position (320) is located above the upper surface of the print material (302) within the print material storage (305). In some cases, the second position (320) is located below the upper surface of the print material (302).

[0032] The print material reservoir (305) consists of a magnetic stirrer (324) placed within the reservoir. The magnetic stirrer (324) is positioned adjacent to or on the bottom surface (303E) of the reservoir and is moved by a driving source (322) placed parallel to the bottom surface (303E) of the reservoir. The reservoir (304) and the inlet (306) are positioned on the side walls and / or bottom of the reservoir to further facilitate the mixing of the print material within the reservoir.

[0033] FIG. 3c is a plan view of a print material reservoir (315) according to another embodiment. An outlet (304) is located on a side wall (303) at a first position (330), and an inlet (306) is located on a side wall (303B) at a second position (332). Side walls (303A) and (303B) are separated from each other by a side wall (303D). Here, the print material reservoir (315) has a rectangular outline. A mixing element (336) rotating in a rotation direction (338) is optionally included in some embodiments of the print material reservoir (315). In some embodiments, the flow of print material in the flow direction (308) from the outlet (304) to the inlet (306) is sufficiently large to generate a mixing current within the reservoir. A centerline (307) extends from the middle of side wall (303A) to the middle of side wall (303B). The outlet (304) is at the first distance (334A) from the centerline (307), and the inlet (306) is at the second distance (334B) from the centerline (307). In some examples, the outlet (304) and the inlet (306) are symmetrically located on the side wall of the reservoir opposite the centerline (307). In some embodiments, the outlet (304) and the inlet (306) are asymmetrically located opposite the centerline (307). Whether the outlet (304) and the inlet (306) are symmetrically or asymmetrically located with respect to the centerline (307) depends on the flow rate of the print material through the circulation circuit (not shown), the temperature of the print material, and the viscosity of the print material. In some examples, to reduce eddy currents or "dead spots" at the corner locations of the rectangular print material reservoir, the print material reservoir is round rather than rectangular (as shown). Vortex or "dead point" is related to the volume of low-speed printing material where suspended particles of printing material can settle or be separated from the fluid component of printing material.

[0034] FIG. 4 is a schematic diagram of a supply reservoir (400) that can be used in a circulation circuit according to one embodiment. The supply reservoir (400) can be used as the supply reservoir (126) described in FIG. 1. The supply reservoir (400) has an inlet (402) configured to receive fluid from, for example, the intermediate circulation circuit (105) of FIG. 1. When the supply reservoir (400) is used in a print material circulation circuit, the print material entering the inlet (402) is mixed by circulation through the circulation circuit.

[0035] The charge level (422) of the print material (408) is maintained between the upper charge level (424) and the lower charge level (426) by a level sensor (410). Here, the level sensor is a capacitive sensor, but any level sensor may be used. The amount of print material (408) in the supply reservoir (400) is controlled by a charge regulator (413). The charge regulator (413) is connected to the level sensor (410) and valves (431, 433, 436). The charge regulator (413) determines when valves (431, 433 and 436) are opened and closed to regulate the addition of print material to the supply reservoir (400) through valve (531), the outlet of print material from the supply reservoir (400) to the flow line (420) through opening (418), and the addition of pressurized gas or the application of vacuum to the head space (411) in the upper region of the source reservoir. Pressurized gas enters the supply reservoir (400) through line (404) or exits through a gas flow unit (not shown, but see gas flow unit (133) in FIG. 1) to control the pressure in the head space (411) of the supply reservoir (400). In some examples, compressed air is used when positive pressure is required. In other embodiments, vacuum is applied to negative pressure. In some cases, nitrogen may be used as a pressurizing gas to reduce the oxygen content of the print material before it is deposited from the print head onto the printed substrate. Dissolved oxygen can have an undesirable effect on some print materials. Generally, a pressurizing gas that is incompatible with the print material is used.

[0036] The head space (411) is an internal area of ​​the supply reservoir (400) located above the print material of the supply reservoir (400). The head space (411) includes at least one area within the supply reservoir (400) above the upper fill level monitor (410) and includes a portion of the supply reservoir volume between the upper fill limit (424) and the lower fill limit (426). To move the print material (408) through a local circulation system containing the print head during the inkjet printing process, pressurized gas is added to the head space (411) of the supply reservoir (400). When the valve (436) is in the closed position, as pressurized gas is added to the supply reservoir (400), the fill limit (422) of the print material (408) is reduced by forcing the print material out from the opening (416) into the circulation line (414) in the flow direction (407A). When the valve (436) is in the open position, as pressurized gas is added to the supply reservoir (400), the filling limit (422) of the print material (408) is reduced as the print material is forced out from the opening (418) into the circulation line (420) in the flow direction (407B). The circulation line (414) is a print head supply line. The circulation line (420) is a bypass line that surrounds the print head and supplies directly to the discharge reservoir (not shown, but see discharge reservoir (134) in FIG. 1 above). The discharge reservoir has a discharge line that returns the print material that is not discharged from the discharge reservoir to the intermediate circulation circuit. The discharge reservoir is configured to receive print material from the circulation line (414) connected to the print head and to receive print material from the circulation line (420) that bypasses the print head.

[0037] FIG. 5 is a schematic diagram of a discharge reservoir (500) of a circulation circuit according to some embodiments. The discharge reservoir (500) is connected to a pressurizing source (533) by a pressurizing line (504) that supplies pressurized gas to the head space (511) above the print material (508) of the discharge reservoir (500). The discharge reservoir (500) is configured to receive print material (508) in a flow direction (507B) from a circulation line (520) that bypasses the print head of an inkjet printing device, and is controlled by a valve (536) (similar to the bypass valve (136) of FIG. 1 or the valve (436) of FIG. 4). The flow direction (507B) is the same direction as the flow direction (407B) of FIG. 4. The discharge reservoir (500) is configured to receive print material (508) from one or more print heads (530) in a flow direction (507A) by means of a discharge line (514). The flow direction (507A) is the same flow direction as the flow direction (407A) of FIG. 4. The discharge reservoir (500) is configured to discharge print material through a discharge line (505) coupled to the bottom position of the discharge reservoir (500). A discharge valve (534) may be placed in the discharge line (505) to control the print material flowing out of the discharge reservoir (500).

[0038] The print material charge level (522) is maintained between the upper charge limit (524) and the lower charge limit (526) of the discharge reservoir using charge level monitors (510, 512). Here, the charge level monitors (510 and 512) are pressure sensors to illustrate other embodiments of available level sensors. The same type of level sensor is commonly used in the supply and discharge reservoirs of the supply system (100) of FIG. 1. The charge level monitors (510, 512) are connected to a charge regulator (513) to indicate when the print material exceeds the upper charge limit (524) or falls below the lower charge limit (526). When the print material exceeds the upper charge limit (524) or falls below the lower charge limit (526), ​​the charge regulator (513) triggers a change in the print material flow around the discharge reservoir (500). When the print material level exceeds the upper fill limit (524), the fill regulator (513) may perform any combination of operating the valve (533) to increase the pressure in the head space (511), opening the discharge valve (534) to allow faster outflow of the print material, and closing the bypass valve (536) to allow more print material to flow into the discharge reservoir (500). When the print material level falls below the lower fill limit (526), ​​the fill regulator (513) may perform any combination of operating the valve (533) to lower the pressure in the head space (511), closing the discharge valve (534), and opening the bypass valve (536). The fill regulator (513) may monitor the print material fill level.A charge regulator (513) can monitor the material charge level of both the supply reservoir and the discharge reservoir to provide a sufficient flow rate of the print material through a local circulation circuit including print heads that provides a smooth flow of the print material through the print heads of the inkjet printing device during the printing process and / or ensures that the print material is kept uniform without the separation of liquid and / or suspended particles of the print material.

[0039] An inkjet printing device comprising a print material supply system including a circulating circuit as described above maintains a mixed state of the print material moving through the print material supply system by stirring or circulating the print material. Mixing the print material is a factor involved in depositing the print material onto a printed substrate for the manufacture of displays and screens for electronic devices. Displays printed with a more uniform concentration of print material have more uniform color and luminosity. Examples of print materials for displays and electronic device screens include chemical components for resins, quantum dots that convert light incident from a display light source into emitted light having a wavelength different from the incident light, and scattering particles. Quantum dots absorb incident light and convert the light into emitted light having a new wavelength. Scattering particles improve the efficiency of the quantum dots in absorbing and converting incident light into emitted light by reflecting incident light onto more surfaces of the quantum dots than simply the surface facing the incident light source. Scattering particles redirect incident light to the back and sides of the quantum dots, providing a larger surface area for light absorption and re-emission (relative to the direction of travel of the incident light). A uniform concentration of quantum dots and scattering particles increases the uniformity of light absorption and re-emission. The uniform concentration of quantum dots and scattering particles in pixels and / or pixel sub-regions is a function of the uniformity of the print material circulating through the inkjet printer print head or print material supply system during the inkjet printing process.

[0040] As described above, the inkjet printing device includes a print material supply system and further includes a substrate support for supporting a printed substrate during the inkjet printing process. The inkjet printing device further includes printed substrate level sensors, a printed substrate position sensor, a motive source for moving the printed substrate during the inkjet printing process, and at least one gripper for manipulating the printed substrate during the inkjet printing process.

[0041] The foregoing describes the features of various embodiments to enable those skilled in the art to better understand the aspects of the present disclosure. Those skilled in the art should recognize that the present disclosure can be readily used as a basis for designing or modifying other processes and structures to perform the same purpose and / or achieve the same advantages of the embodiments introduced herein. Those skilled in the art should also recognize that such equivalent configurations do not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and modifications can be made in the present specification without departing from the spirit and scope of the present disclosure.

Claims

Claim 1 delete Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 delete Claim 9 delete Claim 10 delete Claim 11 delete Claim 12 delete Claim 13 delete Claim 14 delete Claim 15 delete Claim 16 delete Claim 17 An inkjet printing device having a print material supply system, comprising: a print assembly; a bulk circulation circuit; an intermediate circulation circuit; and a local circulation circuit, wherein the bulk circulation circuit is configured to draw print material from a supply container to a mixing container and to continuously flow print material around the bulk circulation circuit, the intermediate circulation circuit is configured to draw print material from the bulk circulation circuit, return print material to the bulk circulation circuit, and to flow print material around the intermediate circulation circuit, and the local circulation circuit is configured to draw print material from the intermediate circulation circuit, return print material, and supply print material to the print assembly. Claim 18 An inkjet printing device according to claim 17, further comprising a pressure control system that circulates printing material through a circulation pump to the local circulation circuit, and to each of the bulk circulation circuit and the intermediate circulation circuit. Claim 19 In claim 18, the local circulation circuit comprises a supply reservoir, a discharge reservoir, and a bypass line connecting the supply reservoir to the discharge reservoir, and the pressure control system is configured to maintain a higher pressure in the supply reservoir than in the discharge reservoir, in an inkjet printing device.

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