Printing device and printing method

Abstract

A printing device (1) comprises: a conveyance member (31) capable of conveying a printing medium (M); an ink unit (421) that causes an ink containing a pigment to adhere to the printing medium (M) on the conveyance member (31); a treatment liquid unit (422) that causes a treatment liquid containing a component capable of aggregating the pigment to form an aggregate (A) to adhere to the printing medium (M) on the conveyance member (31); a liquid tank unit (5) including a transfer member (52) that sends the aggregate (A) present on the conveyance member (31) to a liquid tank (51); a sedimentation tank (6) that collects a liquid transferred from the liquid tank (51); and a membrane module (7) that performs cross-flow filtration by a membrane (72) on the liquid introduced from the sedimentation tank (6) into a container (71).

Description

Printing Device and Printing Method

[0001] The present disclosure relates to a printing device and a printing method.

[0002] As a printing device, a device including a transport member for transporting a printing medium to be printed is known. In this type of printing device, printing ink or the like that has passed through the printing medium may adhere to the surface of the transport member. Therefore, it is necessary to remove and recover deposits such as ink adhering to the transport member. For example, Patent Document 1 discloses a printing device including a cleaning brush, a coagulation tank, and a filter as a structure for removing and recovering deposits on the transport member. The cleaning brush removes deposits from the transport member by cleaning the transport member using the liquid stored in the storage tank. The coagulation tank stores the liquid after cleaning in a state where a coagulant is added. The filter separates the aggregates from the liquid stored in the coagulation tank to recover the aggregates containing the deposits on the transport member.

[0003] Japanese Unexamined Patent Application Publication No. 2022 - 83155

[0004] A printing device according to one aspect of the present disclosure includes a transport member capable of transporting a printing medium, an ink unit capable of attaching ink containing a pigment to the printing medium on the transport member, a treatment liquid unit capable of attaching a treatment liquid containing a component capable of aggregating the pigment to form aggregates to the printing medium on the transport member, a liquid tank capable of storing a liquid, a transfer member capable of sending the aggregates present on the transport member to the liquid tank, a liquid tank unit having the above, a precipitation tank connected to the liquid tank and capable of storing the liquid transferred from the liquid tank, a container connected to the precipitation tank and the liquid tank, and a membrane housed in the container, and includes a membrane module capable of performing cross - flow filtration on the liquid introduced from the precipitation tank into the container by the membrane.

[0005] A printing method relating to another aspect of the present disclosure includes: a transport step of transporting a printing medium by a transport member; an ink application step of applying an ink containing a pigment to the printing medium on the transport member; a processing liquid application step of applying a processing liquid containing a component capable of agglomerating the pigment to form aggregates to the printing medium on the transport member; a transfer step of sending the aggregates present on the transport member to a liquid tank containing liquid; a sedimentation step of storing the liquid transferred from the liquid tank in a sedimentation tank; and a filtration step of performing cross-flow filtration by a membrane module, in which a membrane is housed in a container, on the liquid introduced from the sedimentation tank into the container.

[0006] Figure 1 is a cross-sectional view of a printing apparatus according to the first embodiment of this disclosure. Figure 2 is a front view of the printing apparatus according to the first embodiment. Figure 3 is a flowchart showing the processing flow of a printing method using the printing apparatus according to the first embodiment. Figure 4 is a front view of a printing apparatus according to the second embodiment of this disclosure. Figure 5 is a flowchart showing the processing flow of a printing method using the printing apparatus according to the second embodiment.

[0007] In the conventional printing apparatus disclosed in Patent Document 1 as described above, when the liquid circulates through the storage tank and the coagulation tank, the coagulant applied to the coagulation tank may be transferred from the coagulation tank to the storage tank. In this case, the properties of the liquid may change due to the coagulant in the storage tank, which may reduce the effectiveness of the liquid in the storage tank in removing deposits on the transport member. Furthermore, in the conventional printing apparatus, for example, when printing a high-density image on a printing medium that is easily permeable to ink, the amount of deposits on the transport member increases, which in turn increases the amount of coagulated material in the coagulation tank. In this case, the filter that separates the coagulated material from the liquid in the coagulation tank becomes clogged in a relatively short time. When the filter becomes clogged, it is necessary to temporarily stop printing in order to replace the filter, which presents a problem in that continuous printing for long periods of time cannot be performed.

[0008] Therefore, there is a need for a printing apparatus and printing method that can suppress a decrease in the effectiveness of removing deposits on the transport member and that can perform continuous printing for a long period of time.

[0009] The printing apparatus and printing method according to the embodiments of this disclosure will be described below with reference to the drawings. In the following, directional relationships will be described using mutually orthogonal XY Cartesian coordinates on the horizontal plane. The vertical direction perpendicular to the X and Y directions will be defined as the Z direction.

[0010] (First Embodiment) Figure 1 is a cross-sectional view of a printing apparatus 1 according to the first embodiment of the present disclosure. Figure 2 is a front view of the printing apparatus 1 according to the first embodiment. The printing apparatus 1 is an apparatus equipped with an ink unit capable of adhering ink to a wide and long printing medium M. The printing apparatus 1 prints an image by adhering ink to the medium M with the ink unit. The printing apparatus 1 can be a screen printing apparatus or an inkjet apparatus. When the printing apparatus 1 is a screen printing apparatus, the ink unit includes a screen plate having a plurality of openings and a squeegee. In this case, the ink unit moves ink along the screen plate in accordance with the movement of the squeegee, thereby adhering the ink to the medium M through the openings of the screen plate. On the other hand, when the printing apparatus 1 is an inkjet apparatus, the ink unit adheres ink to the medium M by ejecting ink onto the medium M. The case where the printing apparatus 1 is an inkjet apparatus will be described in detail below.

[0011] The inkjet printing apparatus 1 is suitable for digital textile printing, which prints images such as characters and patterns onto media M, which is a fabric material made of woven or knitted fabrics. Of course, the printing apparatus 1 can also be used for printing various images onto printing media such as paper sheets and resin sheets.

[0012] The printing apparatus 1 comprises an apparatus frame 2, a transport unit 3, a printing unit 4, a liquid tank unit 5, a sedimentation tank 6, and a membrane module 7. The apparatus frame 2 forms the framework of the printing apparatus 1. In the printing apparatus 1, the transport unit 3, the printing unit 4, the liquid tank unit 5, the sedimentation tank 6, and the membrane module 7 are assembled to the apparatus frame 2.

[0013] The transport unit 3 is a unit for transporting the media M in the Y direction. The transport unit 3 includes a transport member 31, a first transport roller 32, and a second transport roller 33.

[0014] The transport member 31 is a member capable of transporting media M. In this embodiment, the transport member 31 is an endless belt having a width in the X direction and extending in the Y direction. The transport member 31, which is an endless belt, has a transport surface 311 on its surface that supports and transports media M in an upward-facing region, and is capable of circumferential movement. The transport member 31 forms a transport path 3R for media M along the transport surface 311. The transport path 3R has a width in the X direction and extends linearly in the Y direction. By circumferential movement along the Y direction, the transport member 31 can transport media M, which is in contact with the upward-facing transport surface 311 on its surface, along the transport path 3R in a transport direction H1 which is a linear direction from one side to the other in the Y direction. An adhesive layer made of an adhesive that adheres media M is formed on the surface of the transport member 31.

[0015] The first conveyor roller 32 is a cylindrical roller extending in the X direction, around which the conveyor member 31 is wound at the downstream position of the conveyor path 3R. The first conveyor roller 32 rotates in response to the circumferential movement of the conveyor member 31. The second conveyor roller 33 is a cylindrical roller extending in the X direction, around which the conveyor member 31 is wound at the upstream position of the conveyor path 3R. The second conveyor roller 33 is rotationally driven by a drive motor (not shown) to cause the conveyor member 31 to circumferentially move. The conveyor member 31 is stretched by the first conveyor roller 32 and the second conveyor roller 33 such that the conveying surface 311, formed by the upward-facing region and the non-conveying surface 312, formed by the downward-facing region between the first conveyor roller 32 and the second conveyor roller 33 on its surface, are horizontal and extend in the X and Y directions. The conveying member 31 moves in a circular motion in response to the rotational drive of the second conveying roller 33, thereby enabling it to convey the media M along the conveying path 3R in the conveying direction H1.

[0016] The printing unit 4 is a unit for printing an image onto the media M on the transport surface 311 of the transport member 31. The printing unit 4 is a unit in which an inkjet head 42 having an ink head 421, a pre-treatment liquid head 422, and a post-treatment liquid head 423 is mounted on a carriage 41. The printing unit 4 is located above the transport member 31. Specifically, the printing unit 4 is positioned so as to face the transport surface 311, which faces upward on the surface of the transport member 31, which is made of an endless belt, from above. As shown in Figure 1, the upstream end of the printing unit 4 in the transport direction H1 along the transport surface 311 is located upstream of the central part of the transport surface 311 in the transport direction H1. The upstream end of the printing unit 4 may be located above the central part of the transport surface 311.

[0017] The printing device 1 is a so-called serial printer that performs printing on media M using a serial printing method. In the serial printing device 1, the carriage 41 is moved back and forth in the X direction, which is perpendicular to the Y direction, which is the transport direction H1 of the media M, while the inkjet head 42 ejects various droplets, and the transport member 31 transports the media M, and these operations are repeated. In the serial printing device 1, the transport member 31 intermittently transports the media M in the transport direction H1. Another embodiment of the printing device 1 is a so-called line printer in which the position of the inkjet head 42 is fixed relative to the media M transported in the Y direction by the transport member 31.

[0018] A flat carriage guide 21 having a guide rail 211 extending in the X direction is assembled to a position above the conveying member 31 on the device frame 2. The carriage 41 is fixed to a timing belt 212 which is assembled to the carriage guide 21 so as to be able to move around it. The timing belt 212 is an endless belt and, when assembled to the carriage guide 21, is driven to move around it in the X direction. As the timing belt 212 moves around it in the X direction, the carriage 41 is guided by the guide rail 211 and can reciprocate along the carriage guide 21 in the X direction.

[0019] Each of the ink heads 421, pre-treatment liquid head 422, and post-treatment liquid head 423 included in the inkjet head 42 mounted on the carriage 41 can move relative to the media M in the X and Y directions as the media M is transported in the Y direction by the transport member 31 and the carriage 41 moves back and forth in the X direction.

[0020] The carriage 41 is equipped with multiple ink heads 421. Each of the multiple ink heads 421 is an ink unit capable of adhering ink to the media M on the transport member 31 by ejecting ink containing pigment as a colorant. Each of the multiple ink heads 421 includes a number of nozzles that eject ink droplets using an ejection method such as a piezoelectric method using a piezoelectric element or a thermal method using a heating element, an ink flow path that guides the ink to these nozzles, and a wiring board for controlling the ink ejection operation. The multiple ink heads 421 are mounted on the carriage 41 so as to be arranged in two rows in the X direction. Two ink heads 421 that eject ink of the same color are mounted on the carriage 41 so as to be offset from each other in the X and Y directions. Another embodiment is a configuration in which one ink head 421 is mounted on the carriage 41.

[0021] The ink ejected from the ink head 421 is an ink containing an aqueous medium, a pigment, and a binder resin. The aqueous medium is a medium whose main component is water. Specific examples of the aqueous medium include water, or a mixture of water and a polar solvent. Examples of polar solvents contained in the aqueous medium include methanol, ethanol, isopropyl alcohol, butanol, and methyl ethyl ketone. The binder resin exists as resin particles dispersed in the aqueous medium. The resin particles of the binder resin function as a binder that binds the medium M and the pigment. The median diameter of the resin particles of the binder resin is, for example, 50 nm to 150 nm. Examples of binder resins include urethane resin, (meth)acrylic resin, styrene-(meth)acrylic resin, styrene-maleic acid copolymer, vinylnaphthalene-(meth)acrylic acid copolymer, and vinylnaphthalene-maleic acid copolymer. For the pigment, dispersible pigments that exist dispersed in the aqueous medium as pigment particles can be used. From the viewpoint of obtaining an ink with excellent image density, hue, and color stability, the median diameter of the pigment is, for example, 50 nm to 150 nm. The pigment may be an anionic pigment. Examples of anionic pigments include pigments having anionic groups such as carboxyl groups, sulfonic acid groups, phosphoric acid groups, phosphonic acid groups, phenylsulfonic acid groups, and phenylcarboxyl groups. The anionic pigment electrically reacts and aggregates on the media M with the cationic resin, which is an aggregate-forming component contained in the pretreatment liquid discharged from the pretreatment liquid head 422, thereby suppressing the penetration of the binder resin contained in the ink into the media M. As a result, when the media M is a cloth material, it is possible to reduce the penetration of the binder resin into the gaps between fibers and the binding of the fibers together. Therefore, the texture and feel of the cloth material can be improved.

[0022] The pretreatment liquid head 422 is mounted on the carriage 41 so as to be positioned upstream of the ink head 421 in the transport direction H1 of the media M by the transport member 31. The pretreatment liquid head 422 is a processing liquid unit that can adhere the pretreatment liquid to the media M on the transport member 31 before the ink by discharging the pretreatment liquid. The pretreatment liquid head 422 comprises a number of nozzles that discharge the pretreatment liquid using a discharge method such as a piezoelectric method using a piezoelectric element or a thermal method using a heating element, a pretreatment liquid flow path that guides the pretreatment liquid to these nozzles, and a wiring board for controlling the discharge operation of the pretreatment liquid. The pretreatment liquid is a processing liquid that comes into contact with the ink while it is not dry on the media M, and is a non-coloring processing liquid that does not produce color even when it adheres to the media M. Note that the processing liquid unit that adheres the pretreatment liquid to the media M on the transport member 31 is not limited to a head structure like the pretreatment liquid head 422, but may also be a spray type structure that sprays the pretreatment liquid.

[0023] The pretreatment liquid discharged from the pretreatment liquid head 422 is a treatment liquid containing water, or an aqueous solvent consisting of water and an organic solvent, and an aggregate-forming component which is a component capable of agglomerating pigments to form aggregates. Examples of organic solvents that the pretreatment liquid may contain include glycols, alcohols, aliphatic hydrocarbons, aromatic hydrocarbons, ketones, esters, ethers, and vegetable oils. The aggregate-forming component is soluble in the aqueous solvent. Examples of aggregate-forming components include ionic resins with different ionic properties from the pigments contained in the ink. Examples of ionic resins include positively charged cationic resins. Examples of cationic resins include ammonium-containing resins, amine-containing resins, polyallylamine, polyvinylamine, polyimine, polyvinylpyrrolidone, polyethyleneimine, polyvinylpyridine, aminoacetalized polyvinyl alcohol, ionene polymer, polyvinylimidazole, polyvinylbenzylphosphonium, polyalkylallylammonium, polyamidine, and polyamine sulfone. In the pretreatment solution, the aggregate-forming components react and aggregate with the pigments contained in the ink, ensuring excellent color development.

[0024] The post-treatment liquid head 423 is mounted on the carriage 41 so as to be positioned downstream of the ink head 421 in the transport direction H1 of the media M by the transport member 31. The post-treatment liquid head 423 is a processing liquid unit capable of adhering post-treatment liquid to the media M on the transport member 31 after the ink by discharging post-treatment liquid. The post-treatment liquid head 423 comprises a number of nozzles that discharge post-treatment liquid using a discharge method such as a piezoelectric method using a piezoelectric element or a thermal method using a heating element, a post-treatment liquid flow path that guides the post-treatment liquid to these nozzles, and a wiring board for controlling the discharge operation of the post-treatment liquid. The post-treatment liquid is a processing liquid that comes into contact with the ink on the media M while it is not yet dry, and is a non-coloring processing liquid that does not develop color even when it adheres to the media M. The post-treatment liquid has the function of improving the fixation of the ink on the media M. As such a post-treatment liquid, a processing liquid containing silicone oil can be used. Specifically, the post-treatment liquid may contain, for example, emulsion particles containing silicone oil, a surfactant, and an aqueous medium. In other words, the post-treatment liquid is an emulsion in which emulsion particles are dispersed in an aqueous medium, and more specifically, it is an oil-in-water (O / W) type emulsion. The silicone oil may include unmodified silicone oil. Examples of unmodified silicone oils include dimethylpolysiloxane, methylphenyl silicone oil, and methylhydrogen silicone oil. The silicone oil is stably dispersed in the post-treatment liquid. The treatment liquid unit that applies the post-treatment liquid to the media M on the transport member 31 is not limited to a head structure such as the post-treatment liquid head 423, but may also be a spray type structure that sprays the post-treatment liquid.

[0025] In the printing unit 4, a dispensing operation is performed on the media M on the transport surface 311 of the transport member 31. This involves dispensing pre-treatment liquid from the pre-treatment liquid head 422, ink from the ink head 421, and, if necessary, post-treatment liquid from the post-treatment liquid head 423. This prints an image onto the media M. Specifically, on the media M on the transport surface 311 of the transport member 31, the pre-treatment liquid dispensed from the pre-treatment liquid head 422 adheres first, then the ink dispensed from the ink head 421 adheres, and then, if necessary, the post-treatment liquid dispensed from the post-treatment liquid head 423 adheres.

[0026] In the printing apparatus 1, if the media M is, for example, a cloth material made of a thin fabric, or a cloth material made of a fabric finished with a coarse weave and knit, at least ink, pre-treatment liquid and post-treatment liquid that has permeated the media M, and fibers that have fallen off the cloth material may adhere to the transport member 31 during the ejection operation of the printing unit 4 to the media M. The deposits present on the transport member 31 include not only ink, but also aggregates A. Aggregates A are generated when the ink and pre-treatment liquid come into contact on the transport member 31, causing a reaction and aggregation between the pigment contained in the ink and the aggregate-forming components contained in the pre-treatment liquid. Aggregates A are generated by the contact between the ink used for image formation on the media M and the pre-treatment liquid, even without the addition of a coagulant.

[0027] When a high-density image is formed on media M in the printing apparatus 1, ink, pre-treatment liquid, and post-treatment liquid may permeate the media M at a rate of approximately 1.5 to 2.0 liters per unit time during the ejection operation of the printing unit 4 onto media M. In this case, as the ink and other substances permeate the media M, solid matter such as aggregates A, amounting to approximately 150 to 300 g per unit time, adheres to the transport member 31. The aggregates A present on the transport member 31 can cause contamination of the media M and reduce the tackiness of the media M due to the adhesive layer formed on the surface of the transport member 31, thereby degrading the print quality of the media M. For this reason, it is necessary to remove the aggregates A present on the transport member 31 and to recover the aggregates A.

[0028] The printing apparatus 1 includes a liquid tank unit 5 as a unit for removing aggregates A and the like present on the transport member 31, and a sedimentation tank 6 and a membrane module 7 as units for recovering the aggregates A and the like removed from the transport member 31.

[0029] The liquid tank unit 5 is located below the conveying member 31. Specifically, the liquid tank unit 5 is positioned so as to face from below the downward-facing non-conveying surface 312 on the surface of the conveying member 31, which is made of an endless belt. The liquid tank unit 5 is located below the conveying member 31, downstream of the upstream end of the conveying direction H1 along the conveying surface 311 of the printing unit 4. In this case, the liquid tank unit 5 is located below the conveying member 31, downstream of the central part of the conveying surface 311 of the conveying member 31 in the conveying direction H1. Because the liquid tank unit 5 is located below the conveying member 31, aggregates A and other materials present on the conveying member 31 can be efficiently removed.

[0030] A pair of guide rails 22 extending in the Y direction along the transport path 3R are assembled to a position below the transport member 31 on the device frame 2. Each of the pair of guide rails 22 is positioned at a predetermined distance in the X direction. The liquid tank unit 5 is supported by the pair of guide rails 22 so as to be movable in the Y direction. As a result, the liquid tank unit 5 is movable below the transport member 31 along the transport path 3R that is aligned with the transport surface 311. Specifically, the liquid tank unit 5 is movable between a first position below the transport member 31 and a second position below the transport member 31 and downstream of the transport path 3R in the transport direction H1, which is aligned with the transport surface 311 than the transport member 31. When the liquid tank unit 5 is positioned at the first position below the transport member 31, the liquid tank unit 5 is capable of removing aggregates A and the like that present on the transport member 31. On the other hand, when the liquid tank unit 5 is positioned at the second position downstream of the transport path 3R from the transport member 31, the liquid tank unit 5 is located outside the device frame 2. In this case, the operator can easily perform maintenance work on the liquid tank unit 5. Maintenance work on the liquid tank unit 5 is work to maintain the effectiveness of the liquid tank unit 5 in removing aggregates A and other substances on the transport member 31, and includes work such as cleaning the liquid tank unit 5. Note that maintenance work on the liquid tank unit 5 is performed when printing of images on the media M in the printing device 1 is stopped.

[0031] The liquid tank unit 5 includes a liquid tank 51, a transfer member 52, and a blade 53.

[0032] The liquid tank 51 is located below the conveying member 31 and is a tank capable of holding liquid L. Liquid L is, for example, water. Liquid L may also contain a surfactant. The surfactant has the function of enhancing the removal effect of deposits such as aggregates A on the conveying member 31, particularly silicone oil in the post-treatment liquid. Such surfactants can be appropriately selected from anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc., but nonionic surfactants can be particularly preferably selected. Examples of nonionic surfactants include polyoxyalkylene alkyl ethers and polyoxyethylene alkyl ethers.

[0033] The liquid tank 51 is located below the transport member 31, downstream of the upstream end of the transport direction H1 along the transport surface 311 of the printing unit 4. In this case, the liquid tank 51 is located below the transport member 31, downstream of the central portion of the transport surface 311 of the transport member 31 in the transport direction H1. The liquid tank 51 is located within the installation area of ​​the transport member 31 when the transport member 31 is viewed from above. In this embodiment, the entire liquid tank 51 is located within the installation area of ​​the transport member 31 when the transport member 31 is viewed from above. The liquid tank 51 has a flat bottom wall 511 that extends in the X and Y directions, and a peripheral wall 512 that extends upward from the outer edge of the bottom wall 511. The liquid tank 51 is a box-shaped tank with its top open so that the bottom wall 511 faces the transport member 31. The width dimension of the liquid tank 51 along the X direction is approximately the same as the width dimension of the conveying member 31 along the X direction.

[0034] A float sensor 54 is provided inside the liquid tank 51. The float sensor 54 is a sensor for detecting the height position of the liquid surface L stored in the liquid tank 51 from the bottom wall 511. The liquid tank 51 is capable of storing liquid L such that the liquid surface L is located within a range between a preset upper height position and a preset lower height position.

[0035] A first flow path joint 5111 and a second flow path joint 5112 are connected to the bottom wall 511 of the liquid tank 51. A first flow path member 80, which connects the liquid tank 51 to the sedimentation tank 6 described later, is connected to the first flow path joint 5111. A third flow path member 82, which connects the liquid tank 51 to the container 71 of the membrane module 7 described later, is connected to the second flow path joint 5112. As shown in Figure 1, the upper end of the first flow path joint 5111 connected to the bottom wall 511 is located on the inner surface of the bottom wall 511. The upper end of the second flow path joint 5112 connected to the bottom wall 511 is located above the upper limit height position of the liquid surface L stored in the liquid tank 51 from the bottom wall 511. As previously described, the liquid tank unit 5 is movably supported by a pair of guide rails 22 assembled to the apparatus frame 2. As a result, the liquid tank unit 5 is movable along the transport path 3R that runs along the transport surface 311 below the transport member 31, with the first flow path member 80 connecting the liquid tank 51 and the sedimentation tank 6, and the third flow path member 82 connecting the liquid tank 51 and the membrane module 7.

[0036] The transfer member 52 is a component capable of removing aggregates A and the like that present on the transport member 31 from the transport member 31 by sending them to the liquid tank 51. The transfer member 52 is located inside the liquid tank 51 and can send aggregates A and the like that present on the transport member 31 to the liquid tank 51 using the liquid L stored in the liquid tank 51. Because the transfer member 52 is located inside the liquid tank 51, it is located within the installation area of ​​the transport member 31 when viewed from above. In the example shown in Figure 1, two transfer members 52 are installed inside the liquid tank 51. The transfer member 52 has a cylindrical shaft portion 521 extending in the X direction and a brush portion 522 extending radially from the outer circumferential surface of the shaft portion 521. The shaft portion 521 is rotatably supported on the peripheral wall 512 of the liquid tank 51. In the transfer member 52, the brush portion 522 is partially immersed in the liquid L stored in the liquid tank 51 and contacts the downward-facing non-transporting surface 312 on the surface of the transport member 31. In this state, the brush portion 522 rotates around the shaft portion 521 in accordance with the rotation of the shaft portion 521, thereby enabling it to transport aggregates A and other materials present on the transport member 31 to the liquid tank 51 using the liquid L stored in the liquid tank 51. The transfer member 52 can remove aggregates A and other materials present on the transport member 31 by transporting them to the liquid tank 51, thereby cleaning the transport member 31.

[0037] The blade 53 is a plate-shaped rubber member extending in the X direction, attached to the peripheral wall 512 of the liquid tank 51 so as to contact the non-conveying surface 312 facing downward on the surface of the conveying member 31. In this embodiment, two blades 53 are attached to the peripheral wall 512. The blade 53 is capable of removing the liquid L remaining on the conveying member 31 after cleaning of the conveying member 31 by the transfer member 52, in accordance with the circumferential movement of the conveying member 31.

[0038] In the printing apparatus 1, aggregates A on the transport member 31 are sent to the liquid tank 51 by the transfer member 52. In this case, the liquid L stored in the liquid tank 51 contains aggregates A. Aggregates A are generated in the liquid tank 51 by contact between the ink and the pretreatment liquid on the transport member 31, even if no flocculant is added to the liquid L.

[0039] If the transfer member 52, which is immersed in the liquid L containing aggregates A, etc., in the liquid tank 51, comes into contact with the transport member 31, there is a risk that the aggregates A, etc. in the liquid L will reattach to the transport member 31, making it impossible to accurately remove the aggregates A, etc. from the transport member 31. Therefore, the printing apparatus 1 is equipped with a sedimentation tank 6 and a membrane module 7. In the printing apparatus 1, the liquid tank 51, the sedimentation tank 6, and the membrane module 7 are connected to each other, forming a flow path through which the liquid L in the liquid tank 51 circulates. As the liquid L circulates through the liquid tank 51, the sedimentation tank 6, and the membrane module 7, the aggregates A, etc. contained in the liquid L are recovered by the sedimentation tank 6 and the membrane module 7.

[0040] The sedimentation tank 6 is connected to the liquid tank 51, and the container 71 of the membrane module 7 is also connected to it. The sedimentation tank 6 is capable of storing the liquid L transferred from the liquid tank 51, and is a tank to which aggregates A and other substances contained in the liquid L settle.

[0041] The sedimentation tank 6 has an inlet 6A1 connected to the liquid tank 51 through which liquid L can flow in, and an outlet 6C1 connected to the container 71 of the membrane module 7 through which liquid L can flow out. In the sedimentation tank 6, the inlet 6A1 is connected to the first flow joint 5111 of the liquid tank 51 via a first flow channel member 80. The first flow channel member 80 is made of a flexible tube and connects the liquid tank 51 and the sedimentation tank 6. The liquid L stored in the liquid tank 51 flows through the first flow channel member 80 and flows into the sedimentation tank 6 through the inlet 6A1. Since the first flow channel member 80 is connected to the first flow joint 5111 of the bottom wall 511 of the liquid tank 51, liquid L including aggregates A that settle on the bottom wall 511 flows into the sedimentation tank 6. In the sedimentation tank 6, the outlet 6C1 is connected to the container 71 of the membrane module 7 via a second flow channel member 81. The liquid L that flows out of the sedimentation tank 6 through the outlet 6C1 flows through the second flow channel member 81 and is introduced into the container 71 of the membrane module 7.

[0042] The precipitation tank 6 is located below the liquid tank 51 and has a flat bottom wall 61 that extends in the X and Y directions, and a peripheral wall 62 that extends upward from the outer peripheral edge of the bottom wall 61. The precipitation tank 6 is a box-shaped tank that is open at the top such that the bottom wall 61 faces the liquid tank 51. The dimension of the precipitation tank 6 in the width direction along the X direction is smaller than the dimension of the liquid tank 51 in the width direction along the X direction. In the precipitation tank 6, the inlet 6A1 is provided at one end in the X direction of the peripheral wall 62, and the outlet 6C1 is provided at the other end opposite to the one end in the X direction of the peripheral wall 62.

[0043] The precipitation tank 6 is located downstream of the upstream end in the conveyance direction H1 along the conveyance surface 311 of the printing unit 4 below the liquid tank 51. In this case, the precipitation tank 6 is located downstream of the central portion in the conveyance direction H1 of the conveyance surface 311 of the conveyance member 31 below the liquid tank 51. The precipitation tank 6 is located within the installation region of the liquid tank 51 when viewed from above the liquid tank 51. In the present embodiment, the entire precipitation tank 6 is located within the installation region of the liquid tank 51 when viewed from above the liquid tank 51.

[0044] The precipitation tank 6 can store the liquid L such that the liquid level of the liquid L transferred from the liquid tank 51 through the first flow path member 80 is at a position below the central position in the height direction (Z direction) with respect to the bottom wall 61. In the state where the liquid L is stored in the precipitation tank 6, aggregates A and the like contained in the liquid L precipitate on the bottom wall 61. The aggregates A are generated by the contact between the ink and the pretreatment liquid on the conveyance member 31 even without adding a flocculant or the like to the liquid L in the precipitation tank 6.

[0045] The membrane module 7 is located at a position adjacent to the precipitation tank 6 in the X direction below the liquid tank 51. In this case, the membrane module 7 is located downstream of the central portion in the conveyance direction H1 of the conveyance surface 311 of the conveyance member 31 below the liquid tank 51. The membrane module 7 is located within the installation region of the liquid tank 51 when viewed from above the liquid tank 51. In the present embodiment, the entire membrane module 7 is located within the installation region of the liquid tank 51 when viewed from above the liquid tank 51.

[0046] The membrane module 7 includes a container 71 connected to the sedimentation tank 6 and the liquid tank 51, and at least one hollow fiber membrane 72 as a membrane housed in the container 71. The membrane housed in the container 71 is not limited to a hollow fiber membrane 72, but may be, for example, a flat membrane. The membrane module 7 is configured to perform cross-flow filtration using the hollow fiber membrane 72 on the liquid L introduced into the container 71 from the sedimentation tank 6. Cross-flow filtration is a method in which a flow of liquid L parallel to the membrane surface of the hollow fiber membrane 72 is applied within the container 71, and the liquid L from which aggregates A have been filtered out by permeating the hollow fiber membrane 72 is taken out as a filtrate, while the liquid L that has flowed along the membrane surface without permeating the hollow fiber membrane 72 is taken out as a concentrate. Examples of cross-flow filtration methods include internal pressure type and external pressure type. In internal pressure cross-flow filtration, liquid L is introduced to the inner surface side of the hollow fiber membrane 72 within the container 71, and the filtrate is extracted from the outer surface side while the concentrated liquid is extracted from the inner surface side. In external pressure cross-flow filtration, liquid L is introduced to the outer surface side of the hollow fiber membrane 72, and the filtrate is extracted from the inner surface side while the concentrated liquid is extracted from the outer surface side. In this embodiment, the membrane module 7 performs internal pressure cross-flow filtration. In cross-flow filtration, the flow of liquid L parallel to the membrane surface of the hollow fiber membrane 72 within the container 71 suppresses the accumulation of aggregates A and other substances on the membrane surface, thereby suppressing clogging of the hollow fiber membrane 72.

[0047] Various materials can be used as the material for the hollow fiber membrane 72, and are not particularly limited. Examples include polyethylene and polyvinylidene fluoride. The pore size of the membrane surface of the hollow fiber membrane 72 is appropriately set according to the particle size of the aggregates A contained in the liquid L. The volume median diameter of the aggregates A is larger than the volume median diameter of the pigment particles in the ink. The volume median diameter of the aggregates A has a wide distribution depending on the degree of reaction and aggregation between the pigment in the ink and the aggregate-forming components in the pretreatment liquid, for example, between 6 μm and 20 μm. The pore size of the membrane surface of the hollow fiber membrane 72 is sufficiently smaller than the volume median diameter of the aggregates A, for example, between 0.05 μm and 1.00 μm.

[0048] The membrane module 7 is configured such that, in the filtrate and the concentrated liquid obtained by cross-flow filtration of the liquid L introduced into the container 71 from the sedimentation tank 6, the filtrate is led out from the container 71 toward the liquid tank 51, and the concentrated liquid can be led out from the container 71 toward the sedimentation tank 6. Specifically, the container 71 has a liquid inlet 711 through which the liquid L from the sedimentation tank 6 can be introduced, a filtrate outlet 712 through which the filtrate can be led out, and a concentrated liquid outlet 713 through which the concentrated liquid can be led out.

[0049] In the container 71, the liquid inlet 711 is connected to the outlet 6C1 of the sedimentation tank 6 through the second flow path member 81. The second flow path member 81 is constituted by a flexible tube and connects the sedimentation tank 6 and the container 71. The second flow path member 81 is provided with a liquid introduction valve 811 which is an on-off valve for switching the flow and interruption of the liquid L. Further, a filtration pump 73 is connected to the second flow path member 81. By driving the filtration pump 73, the liquid L stored in the liquid tank 51 is transferred to the sedimentation tank 6, flows into the sedimentation tank 6 through the inlet 6A1, and flows out from the sedimentation tank 6 through the outlet 6C1. The liquid L flowing out from the outlet 6C1 of the sedimentation tank 6 according to the driving of the filtration pump 73 flows through the second flow path member 81 and is introduced into the inner surface side of the hollow fiber membrane 72 in the container 71 through the liquid inlet 711 with the liquid introduction valve 811 opened. The liquid L introduced into the inner surface side of the hollow fiber membrane 72 is taken out as a filtrate from the outer surface side and taken out as a concentrated liquid from the inner surface side by internal pressure type cross-flow filtration by the hollow fiber membrane 72. The filtration pump 73 is driven such that the flow velocity of the liquid L flowing through the inner surface side of the hollow fiber membrane 72 is 1 m / s or more without load.

[0050] Furthermore, a strainer 9 may be connected to the second flow channel member 81. A flow channel for liquid L is formed inside the strainer 9. The strainer 9 is capable of filtering and separating fibers derived from the media M contained in the liquid L flowing through the second flow channel member 81. The filtration accuracy of the strainer 9 is, for example, about 180 μm. Therefore, although the strainer 9 is capable of filtering and separating fibers in the liquid L, it is not capable of separating aggregates A, which have a volume median diameter smaller than the filtration accuracy. Aggregates A in the liquid L are filtered and separated by cross-flow filtration of the hollow fiber membrane 72.

[0051] In the container 71, the filtrate outlet 712 is connected to the second flow joint 5112 of the liquid tank 51 via a third flow channel member 82. The third flow channel member 82 is made of a flexible tube and connects the liquid tank 51 and the container 71. The third flow channel member 82 is provided with a filtrate outlet valve 821, which is an on / off valve that switches between the flow and blockage of the filtrate. The filtrate obtained by cross-flow filtration of the hollow fiber membrane 72 into the liquid L introduced into the container 71 in response to the drive of the filtration pump 73 is discharged from the container 71 through the filtrate outlet 712 when the filtrate outlet valve 821 is open, flows through the third flow channel member 82, and flows into the liquid tank 51 through the second flow joint 5112.

[0052] In the container 71, the concentrate outlet 713 is connected to the inlet 6A1 of the sedimentation tank 6 via a fourth flow channel member 83. The fourth flow channel member 83 is made of a flexible tube and connects the sedimentation tank 6 and the container 71. The fourth flow channel member 83 is provided with a concentrate outlet valve 831, which is an on / off valve that switches between the flow and blockage of the concentrate. The concentrate obtained by cross-flow filtration of the liquid L introduced into the container 71 in response to the drive of the filtration pump 73 is discharged from the container 71 through the concentrate outlet 713 with the concentrate outlet valve 831 open, flows through the fourth flow channel member 83, and flows into the sedimentation tank 6 through the inlet 6A1.

[0053] In Figure 2, the first flow channel member 80 and the fourth flow channel member 83 are connected and then connected to the sedimentation tank 6, but they may be connected to the sedimentation tank 6 separately. By connecting the first flow channel member 80 and the fourth flow channel member 83 separately to the sedimentation tank 6, the flow of liquid L from the liquid tank 51 to the sedimentation tank 6 can be stabilized. If the first flow channel member 80 and the fourth flow channel member 83 are connected, when the flow rate of the concentrated liquid increases, the amount of liquid L flowing from the liquid tank 51 to the sedimentation tank 6 may decrease drastically, or in an even more extreme case, the concentrated liquid may flow into the liquid tank 51. By connecting them separately, such problems can be prevented.

[0054] By connecting to the sedimentation tank 6 at a single point, the flow of the stored liquid L when it flows into the sedimentation tank 6 becomes less complex, making it easier to understand or control the behavior of the aggregates A in the sedimentation tank 6. Furthermore, the structure of the sedimentation tank 6 can be simplified. In addition, to stabilize the amount of liquid L flowing from the liquid tank 51 to the sedimentation tank 6, the length of the flow path of the first flow path member 80 before connecting to the fourth flow path member 83 may be made longer than the length of the flow path after the connection between the fourth flow path member 83 and the first flow path member 80. Alternatively, the flow resistance of the former may be made greater than the flow resistance of the latter to stabilize the amount of liquid L flowing from the liquid tank 51 to the sedimentation tank 6. Furthermore, the drive of the filtration pump 73 may be controlled so that the flow rate of the concentrated liquid is below a predetermined value to stabilize the amount of liquid L flowing from the liquid tank 51 to the sedimentation tank 6.

[0055] In the printing apparatus 1, the liquid tank 51, the sedimentation tank 6, and the container 71 of the membrane module 7 are connected to each other, forming a flow path through which the liquid L in the liquid tank 51 circulates. The liquid L transferred from the liquid tank 51 to the sedimentation tank 6 in response to the operation of the filtration pump 73 is stored in the sedimentation tank 6. In the sedimentation tank 6, aggregates A and other substances contained in the liquid L settle on the bottom wall 61. Aggregates A are generated in the sedimentation tank 6 by contact between the ink and the pretreatment liquid on the transport member 31, even if no flocculant is added to the liquid L. In this case, the mixing of flocculant into the liquid L circulating between the liquid tank 51, the sedimentation tank 6, and the membrane module 7 is suppressed, and thus the change in the properties of the liquid L due to the flocculant is suppressed. This prevents a decrease in the removal effect of aggregates A and other substances on the transport member 31 by the liquid L stored in the liquid tank 51.

[0056] Furthermore, as previously described, when a high-density image is formed on the media M in the printing apparatus 1, ink and pre-treatment liquid permeate the media M at a rate of approximately 1.5 to 2.0 liters per unit time, which can cause a large amount of solid matter, such as aggregates A, of approximately 150 to 300 g per unit time to adhere to the transport member 31. In this case, the liquid L stored in the liquid tank 51 will also contain a large amount of aggregates A. In this case, if the aggregates A are filtered and separated using conventional methods such as a wound filter, the filter will become clogged in a relatively short time. If the filter becomes clogged, it will be necessary to temporarily stop printing in order to replace the filter, which may prevent continuous printing for extended periods.

[0057] Therefore, in the printing apparatus 1 according to this embodiment, cross-flow filtration is performed on the liquid L introduced from the sedimentation tank 6 into the container 71 of the membrane module 7 in response to the drive of the filtration pump 73, using a hollow fiber membrane 72. In cross-flow filtration, the flow of liquid L parallel to the surface of the hollow fiber membrane 72 within the container 71 suppresses the accumulation of aggregates A and other substances on the membrane surface, thereby suppressing clogging of the hollow fiber membrane 72. As a result, the frequency of temporary halts in printing due to clogging of the hollow fiber membrane 72 is reduced, making it possible to perform continuous printing for long periods of time.

[0058] Furthermore, in the membrane module 7, the filtrate and concentrate obtained by cross-flow filtration of the liquid L introduced from the sedimentation tank 6 into the container 71 are returned from the container 71 to the liquid tank 51, and the concentrate is returned from the container 71 to the sedimentation tank 6. This makes it possible to reduce the amount of waste liquid generated when continuously printing on the media M in the printing apparatus 1 to an extremely small amount of about 0.02 liters per 1 kg of media M. The waste liquid is liquid L containing a high concentration of aggregates A and other materials removed from the transport member 31 during continuous printing on the media M, and is stored in the sedimentation tank 6.

[0059] As previously described, in the printing apparatus 1, the liquid tank unit 5 is located below the transport member 31, and the sedimentation tank 6 and membrane module 7 are located below the liquid tank 51 of the liquid tank unit 5. In particular, the liquid tank unit 5 is located within the installation area of ​​the transport member 31 when the transport member 31 is viewed from above, and the sedimentation tank 6 and membrane module 7 are located within the installation area of ​​the liquid tank 51 when the liquid tank 51 is viewed from above. In this case, the liquid tank unit 5, the sedimentation tank 6, and the membrane module 7 are all located within the area below the transport member 31 without straying from it. This makes it possible to improve the workability when performing maintenance work on the liquid tank unit 5, the sedimentation tank 6, and the membrane module 7. Maintenance work on the sedimentation tank 6 includes tasks such as cleaning the sedimentation tank 6 by discharging liquid L containing a high concentration of aggregates A, etc., from the sedimentation tank 6 as waste liquid. Maintenance work on the membrane module 7 includes replacing a membrane module 7 that has become clogged in the hollow fiber membrane 72. Maintenance work on the liquid tank unit 5, sedimentation tank 6, and membrane module 7 is performed when printing images onto the media M in the printing device 1 is stopped.

[0060] Furthermore, the liquid tank unit 5 is located below the transport member 31, downstream of the upstream end of the transport direction H1 of the printing unit 4. The sedimentation tank 6 and membrane module 7 are located below the liquid tank 51, downstream of the upstream end of the transport direction H1 of the printing unit 4. In this case, each of the liquid tank unit 5, sedimentation tank 6, and membrane module 7 is concentrated below the transport member 31, in a region downstream of the central part of the transport direction H1 of the transport member 31. In this case, maintenance work can be performed by accessing the liquid tank unit 5, sedimentation tank 6, and membrane module 7 from a position downstream of the transport path 3R in the transport direction H1 from the transport member 31.

[0061] Furthermore, as shown in Figure 2, the sedimentation tank 6 may have a first chamber 6A, a second chamber 6B, a third chamber 6C, a first partition plate 63, and a second partition plate 64. The sedimentation tank 6 may have only one of the first partition plate 63 or the second partition plate 64. The first chamber 6A has an inlet 6A1 connected to the liquid tank 51 and is partitioned on one end side in the X direction of the sedimentation tank 6. The second chamber 6B is partitioned in the sedimentation tank 6 at a position adjacent to the first chamber 6A in the X direction, separated by the first partition plate 63 which is erected against the bottom wall 61. The third chamber 6C has an outlet 6C1 to which the container 71 of the membrane module 7 is connected, is adjacent to the second chamber 6B separated by the second partition plate 64 which is erected against the bottom wall 61 and is partitioned on the other end side in the X direction of the sedimentation tank 6.

[0062] In the first chamber 6A, the inlet 6A1 is located above the liquid level of the liquid L stored in the sedimentation tank 6. In the third chamber 6C, the outlet 6C1 is located below the liquid level of the liquid L stored in the sedimentation tank 6 and at a predetermined distance above the bottom wall 61.

[0063] The inlet 6A1 may be extended and bent within the first chamber 6A, with its opening facing the side wall of the first chamber 6A. Such a shape makes it less likely for the liquid L flowing out of the inlet 6A1 to hit the surface of the liquid L stored in the sedimentation tank 6, even if the flow velocity of the liquid L is high. This makes it less likely for the settled aggregates A to be stirred and re-suspended in the stored liquid L. It also makes it less likely for the stored liquid L to foam and for the foamed liquid L to overflow from the first chamber 6A or the sedimentation tank 6. Even when the inlet 6A1 is extended within the first chamber 6A, the opening at the tip of the inlet 6A1 is below the surface of the liquid L stored in the sedimentation tank 6 and is located at a predetermined distance above the bottom wall 61.

[0064] The first partition plate 63 is, for example, a plate having a roughly U-shape in plan view. The first partition plate 63 can control the flow of liquid L between the first chamber 6A and the second chamber 6B. Specifically, the first partition plate 63 is configured such that, in the height direction (Z direction) relative to the bottom wall 61, the upper part 63A restricts the flow of liquid L, while the lower part 63B has an opening that allows the flow of liquid L. In the first partition plate 63, the upper end of the upper part 63A is located above the liquid surface of the liquid L stored in the sedimentation tank 6, the boundary between the upper part 63A and the lower part 63B is located below the liquid surface, and the lower end of the lower part 63B abuts against the bottom wall 61. The first chamber 6A and the second chamber 6B are separated by the first partition plate 63, but are in communication through the opening in the lower part 63B of the first partition plate 63.

[0065] The second partition plate 64 is, for example, a plate having a roughly U-shape in plan view. The second partition plate 64 can control the flow of liquid L between the second chamber 6B and the third chamber 6C. Specifically, the second partition plate 64 is configured such that, in the height direction (Z direction) relative to the bottom wall 61, the upper part 64A has an opening to allow the flow of liquid L, while the lower part 64B can restrict the flow of liquid L. In the second partition plate 64, the upper end of the upper part 64A is located above the liquid level of the liquid L stored in the sedimentation tank 6, the boundary between the upper part 64A and the lower part 64B is located below the liquid level, and the lower end of the lower part 64B abuts against the bottom wall 61. The second chamber 6B and the third chamber 6C are separated by the second partition plate 64, but are in communication through the opening in the upper part 64A of the second partition plate 64.

[0066] In the sedimentation tank 6, which has a first chamber 6A, a second chamber 6B, and a third chamber 6C, the liquid L that flows into the first chamber 6A through the inlet 6A1 in response to the operation of the filtration pump 73 flows into the second chamber 6B through the opening in the lower part 63B of the first partition plate 63, while its flow is restricted by the upper part 63A. When the liquid L flows from the first chamber 6A to the second chamber 6B through the opening in the lower part 63B of the first partition plate 63, the liquid L flows while taking in aggregates A and other materials that have settled on the bottom wall 61. For this reason, the amount of aggregates A and other materials that accumulate on the bottom wall 61 of the sedimentation tank 6 tends to be greater in the second chamber 6B than in the first chamber 6A.

[0067] Liquid L that flows into the second chamber 6B through the opening in the lower part 63B of the first partition plate 63 flows into the third chamber 6C through the opening in the upper part 64A of the second partition plate 64, with its flow restricted by the lower part 64B. When liquid L flows from the second chamber 6B to the third chamber 6C through the opening in the upper part 64A of the second partition plate 64, the flow of liquid L is restricted by the lower part 64B, so that aggregates A and other material settled on the bottom wall 61 are not incorporated into the liquid L. For this reason, the amount of aggregates A and other material accumulated on the bottom wall 61 of the sedimentation tank 6 tends to be greatest in the second chamber 6B and least in the third chamber 6C.

[0068] The liquid L stored in the third chamber 6C of the sedimentation tank 6 flows out of the third chamber 6C through the outlet 6C1 in response to the drive of the filtration pump 73, flows through the second flow channel member 81, and is introduced into the container 71 of the membrane module 7. As previously described, the amount of aggregates A and the like in the sedimentation tank 6 is smallest in the third chamber 6C. Moreover, in the third chamber 6C, the outlet 6C1 is located at a predetermined distance above the bottom wall 61 where the aggregates A and the like settle. In this case, even if liquid L containing a high concentration of aggregates A and the like removed from the transport member 31 during continuous printing on the media M is stored in the sedimentation tank 6, the supernatant liquid of the liquid L stored in the third chamber 6C, where the amount of aggregates A and the like is smallest, will flow out of the outlet 6C1 and be introduced into the container 71 of the membrane module 7. In this case, the membrane module 7 performs cross-flow filtration using the hollow fiber membrane 72 on the liquid L which has a relatively small amount of aggregates A and the like. This effectively suppresses clogging of the hollow fiber membrane 72 caused by the accumulation of aggregates A and other substances on the membrane surface of the hollow fiber membrane 72. As a result, the frequency of temporary halts in printing due to clogging of the hollow fiber membrane 72 can be further reduced, enabling even longer periods of continuous printing.

[0069] Furthermore, as shown in Figure 2, the sedimentation tank 6 may have a drain pipe 65 connected to the bottom wall 61. The drain pipe 65 is connected to the compartmentalized area of ​​the second chamber 6B in the bottom wall 61. The drain pipe 65 is a pipe for discharging the liquid L stored in the second chamber 6B as waste liquid from the second chamber 6B. The drain pipe 65 is equipped with a drain valve 651, which is an on / off valve that switches between the flow and blockage of liquid L. With the drain valve 651 open, the drain pipe 65 discharges liquid L from the second chamber 6B.

[0070] The sedimentation tank 6 stores liquid L containing a high concentration of aggregates A and other materials removed from the transport member 31 during continuous printing on the media M. In particular, the amount of aggregates A and other materials accumulated in the sedimentation tank 6 is greatest in the second chamber 6B. The drain pipe 65 can discharge the liquid L containing a high concentration of aggregates A and other materials as waste liquid from the second chamber 6B. Note that the maintenance work of discharging liquid L from the second chamber 6B through the drain pipe 65 is performed when printing images on the media M in the printing device 1 is stopped.

[0071] The processing steps of each stage of the printing method using the printing apparatus 1 according to the first embodiment will be described in detail with reference to the flowchart in Figure 3.

[0072] First, the image forming process performed by the printing apparatus 1 will be described. The printing apparatus 1 repeatedly performs a transport step a1, in which the transport member 31 of the transport unit 3 transports the media M based on image data of the image to be formed on the media M, and a printing step of the inkjet head 42 on the media M on the transport member 31. The printing step of the inkjet head 42 includes a pre-treatment liquid application step a2, in which the pre-treatment liquid is applied to the media M in response to the discharge of the pre-treatment liquid from the pre-treatment liquid head 422, an ink application step a3, in which ink is applied to the media M in response to the discharge of ink from the ink head 421, and a post-treatment liquid application step a4, in which post-treatment liquid is applied to the media M in response to the discharge of the post-treatment liquid from the post-treatment liquid head 423. By repeatedly performing the transport step a1, the pre-treatment liquid application step a2, the ink application step a3, and the post-treatment liquid application step a4, an image is formed on the media M on the transport member 31.

[0073] On the media M on the transport member 31, a reaction and aggregation occurs between the aggregate-forming components contained in the pretreatment liquid and the pigments contained in the ink, thereby suppressing the penetration of the binder resin contained in the ink into the media M. As a result, when the media M is a fabric material, the binding of fibers by the binder resin can be reduced, thereby improving the texture and feel of the fabric material. In addition, the adhesion of the posttreatment liquid to the media M on the transport member 31 can improve the ink's fixation on the media M.

[0074] Next, the transfer, sedimentation, and filtration processes performed by the printing apparatus 1 will be described. The printing apparatus 1 performs the transfer, sedimentation, and filtration processes while continuously printing on the media M during the image forming process.

[0075] The printing apparatus 1 performs a supply step b1 in which it supplies liquid L to the liquid tank 51 based on the detection result of the float sensor 54. Specifically, the printing apparatus 1 supplies liquid L to the liquid tank 51 based on the detection result of the float sensor 54 so that the liquid level of liquid L in the liquid tank 51 is located within the range between the upper height position and the lower height position. As a result, liquid L is accumulated in the liquid tank 51 so that a part of the brush portion 522 of the transfer member 52 installed in the liquid tank 51 is immersed in the liquid L.

[0076] With a predetermined amount of liquid L stored in the liquid tank 51, the printing apparatus 1 performs the transfer process b2, as well as the sedimentation process and the filtration process b3. When performing the sedimentation process and the filtration process b3, the printing apparatus 1 keeps the liquid introduction valve 811, the filtered liquid outlet valve 821, and the concentrated liquid outlet valve 831 open.

[0077] In the transfer process b2, the printing apparatus 1 rotates the shaft portion 521 of the transfer member 52, thereby rotating the brush portion 522, which is immersed in the liquid tank 51 and in contact with the transport member 31, and sending aggregates A and the like on the transport member 31 to the liquid tank 51. For this reason, the liquid L stored in the liquid tank 51 contains aggregates A and the like. Aggregates A are generated when the ink and the pretreatment liquid come into contact on the transport member 31 or in the liquid L, causing a reaction and aggregation between the pigment contained in the ink and the aggregate-forming components contained in the pretreatment liquid.

[0078] The printing apparatus 1 drives the filtration pump 73 in the sedimentation process and the filtration process b3. When the filtration pump 73 is driven, the liquid L stored in the liquid tank 51 is transferred to the sedimentation tank 6. The sedimentation tank 6 stores the liquid L transferred from the liquid tank 51. With the liquid L stored in the sedimentation tank 6, aggregates A and other substances contained in the liquid L settle on the bottom wall 61. Aggregates A are generated in the sedimentation tank 6 by contact between the ink and the pretreatment liquid on the transport member 31, even if no flocculant or other substances are added to the liquid L.

[0079] In response to the operation of the filtration pump 73, the liquid L that flows out of the sedimentation tank 6 is introduced into the container 71 of the membrane module 7. The membrane module 7 performs cross-flow filtration of the liquid L introduced into the container 71 using a hollow fiber membrane 72, and discharges the filtrate from the container 71 to the liquid tank 51 and the concentrated liquid from the container 71 to the sedimentation tank 6. In cross-flow filtration, the flow of liquid L parallel to the surface of the hollow fiber membrane 72 within the container 71 suppresses the accumulation of aggregates A and other substances on the membrane surface, thereby suppressing clogging of the hollow fiber membrane 72. As a result, the frequency of temporary halts in printing due to clogging of the hollow fiber membrane 72 can be reduced, making it possible to perform continuous printing for long periods of time.

[0080] When printing images onto media M in the printing device 1 is stopped, the operator can perform maintenance work on the liquid tank unit 5, the sedimentation tank 6, and the membrane module 7.

[0081] (Second Embodiment) Figure 4 is a front view of a printing apparatus 1 according to the second embodiment of the present disclosure. The printing apparatus 1 according to the second embodiment basically has the same configuration as the first embodiment and achieves the same effects, but differs from the first embodiment in that it further includes a filtrate tank 74 and a backwash pump 75.

[0082] The filtrate tank 74 is a tank capable of storing a portion of the filtrate discharged from the filtrate outlet 712 of the container 71 in the membrane module 7. In addition to the liquid inlet 711, the filtrate outlet 712, and the concentrated liquid outlet 713, the container 71 in the membrane module 7 has a filtrate inlet 714 into which the filtrate stored in the filtrate tank 74 can be introduced. The filtrate tank 74 is connected to the filtrate outlet 712 of the container 71 via a branched channel branched from the third channel member 82, and is also connected to the filtrate inlet 714 of the container 71 via a fifth channel member 84.

[0083] A filter branch valve 822, which is an on / off valve that switches between the flow and blockage of the filter liquid discharged from the filter liquid outlet 712 of the container 71, is provided in the branch channel branched from the third flow channel member 82. When the filter pump 73 is driven, the filter liquid discharged from the filter liquid outlet 712 of the container 71 flows into the filter tank 74 and is stored with the filter branch valve 822 open.

[0084] The fifth flow channel member 84 is made of a flexible tube and connects the filtrate tank 74 and the container 71. The fifth flow channel member 84 is equipped with a filtrate introduction valve 841, which is an on / off valve that switches between the flow and blockage of the filtrate introduced into the filtrate inlet 714 of the container 71. A backwash pump 75 is also connected to the fifth flow channel member 84.

[0085] The backwash pump 75 is an example of a pumping unit capable of pumping the filtrate from the filtrate tank 74 to the container 71. When the backwash pump 75 is driven, the liquid inlet valve 811, the filtrate outlet valve 821, and the filtrate branch valve 822 are closed, and the concentrated liquid outlet valve 831 and the filtrate inlet valve 841 are opened. When the liquid inlet valve 811, the filtrate outlet valve 821, and the filtrate branch valve 822 are closed, cross-flow filtration by the hollow fiber membrane 72 in the container 71 is stopped. When the backwash pump 75 is driven with cross-flow filtration stopped in this state, the filtrate is introduced into the container 71 through the filtrate inlet 714. The filtrate introduced into container 71 is pushed from the outer surface to the inner surface of the hollow fiber membrane 72, taking in aggregates A and other substances that had accumulated on the membrane surface of the hollow fiber membrane 72. It flows along the inner surface and is discharged from container 71 through the concentrated liquid outlet 713, flows through the fourth flow channel member 83, and flows into the sedimentation tank 6. In this way, the hollow fiber membrane 72 is washed by back pressure in response to the operation of the backwash pump 75. By washing the hollow fiber membrane 72 by back pressure in response to the operation of the backwash pump 75, aggregates A and other substances that had accumulated on the membrane surface of the hollow fiber membrane 72 due to cross-flow filtration can be removed.

[0086] The backwashing of the hollow fiber membrane 72 in response to the drive of the backwash pump 75 may be performed alternately with cross-flow filtration when continuous printing on the media M is being performed in the printing apparatus 1, or it may be performed when printing on the media M is stopped. In this embodiment, the backwashing of the hollow fiber membrane 72 is performed when printing on the media M is stopped.

[0087] The processing steps of each stage of the printing method using the printing apparatus 1 according to the second embodiment will be explained with reference to the flowchart in Figure 5. Note that the transport step a1, pre-treatment liquid application step a2, ink application step a3, and post-treatment liquid application step a4 of the image forming process performed by the printing apparatus 1 are the same as in the first embodiment, so their explanation will be omitted. Similarly, the supply step b1, transport step b2, sedimentation step, and filtration step b3 of the transfer process, sedimentation process, and filtration process performed by the printing apparatus 1 are the same as in the first embodiment, so their explanation will be omitted.

[0088] The printing apparatus 1 according to the second embodiment performs the backwashing process in backwashing step b4. In backwashing step b4, the printing apparatus 1 closes the liquid introduction valve 811, the filtered liquid outlet valve 821, and the filtered liquid branch valve 822, while keeping the concentrated liquid outlet valve 831 and the filtered liquid introduction valve 841 open. Then, with cross-flow filtration in the membrane module 7 stopped, the printing apparatus 1 drives the backwashing pump 75.

[0089] When the backwash pump 75 is driven, the filtrate is introduced into the container 71 through the filtrate inlet 714. The filtrate introduced into the container 71 is pushed from the outer surface to the inner surface of the hollow fiber membrane 72, taking in aggregates A and other substances that have accumulated on the membrane surface of the hollow fiber membrane 72, flows along the inner surface, is discharged from the container 71 through the concentrated liquid outlet 713, flows through the fourth flow channel member 83, and flows into the sedimentation tank 6. This back pressure washing of the hollow fiber membrane 72 in response to the driving of the backwash pump 75 makes it possible to remove aggregates A and other substances that have accumulated on the membrane surface of the hollow fiber membrane 72 as a result of cross-flow filtration.

[0090] 1 Printing device 3 Conveying unit 31 Conveying member 4 Printing unit 421 Ink head (ink unit) 422 Pre-treatment liquid head (treatment liquid unit) 5 Liquid tank unit 51 Liquid tank 52 Transfer member 6 Sedimentation tank 61 Bottom wall 63 First partition plate 64 Second partition plate 6A First chamber 6B Second chamber 6C Third chamber 7 Membrane module 71 Container 72 Hollow fiber membrane 73 Filtration pump 74 Filtrate tank 75 Backwash pump (pressure pumping section)

Claims

1. A printing apparatus comprising: a transport member capable of transporting a printing medium; an ink unit capable of attaching pigment-containing ink to the printing medium on the transport member; a processing liquid unit capable of attaching a processing liquid containing a component capable of agglomerating the pigment and forming aggregates to the printing medium on the transport member; a liquid tank unit having a liquid tank capable of storing liquid and a transfer member capable of sending the aggregates present on the transport member to the liquid tank; a sedimentation tank connected to the liquid tank and capable of storing the liquid transferred from the liquid tank; and a membrane module having a container connected to the sedimentation tank and the liquid tank, and a membrane housed in the container, and capable of performing cross-flow filtration by the membrane on the liquid introduced from the sedimentation tank into the container.

2. The printing apparatus according to claim 1, wherein the membrane is a hollow fiber membrane.

3. The printing apparatus according to claim 1 or 2, wherein the sedimentation tank has a bottom wall into which the aggregates contained in the liquid settle, and comprises a first chamber connected to the liquid tank and having an inlet into which the liquid can flow, a second chamber adjacent to the first chamber separated by a first partition plate erected against the bottom wall, and a third chamber adjacent to the second chamber separated by a second partition plate erected against the bottom wall and having an outlet to which the container is connected and from which the liquid can flow out, wherein the first partition plate is configured such that, in the height direction relative to the bottom wall, the upper part restricts the flow of the liquid and the lower part allows the flow of the liquid, and the second partition plate is configured such that, in the height direction relative to the bottom wall, the upper part allows the flow of the liquid and the lower part restricts the flow of the liquid.

4. The printing apparatus according to claim 3, wherein the sedimentation tank further has a drain pipe connected to the second chamber for discharging the liquid from the second chamber.

5. The printing apparatus according to any one of claims 1 to 4, further comprising: a filtrate tank capable of storing a portion of the filtrate discharged from the container; and a pumping unit capable of pumping the filtrate from the filtrate tank to the container.

6. The printing apparatus according to any one of claims 1 to 5, wherein the printing medium is a cloth member made of cloth fabric.

7. A printing method comprising: a transport step of transporting a printing medium by a transport member; an ink application step of applying an ink containing a pigment to the printing medium on the transport member; a processing liquid application step of applying a processing liquid containing a component capable of agglomerating the pigment to form aggregates to the printing medium on the transport member; a transfer step of sending the aggregates present on the transport member to a liquid tank containing liquid; a sedimentation step of storing the liquid transferred from the liquid tank in a sedimentation tank; and a filtration step of performing cross-flow filtration by a membrane module, in which a membrane is housed in a container, on the liquid introduced from the sedimentation tank into the container.

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