Printing device and printing method

Abstract

The printing device (1) includes a conveying member (31) capable of conveying a printing medium (M), an ink unit (421) that applies a pigment-containing ink to the printing medium (M) on the conveying member (31), a treatment liquid unit (422) that applies a treatment liquid containing a component that can aggregate the pigment to form an aggregate (A) to the printing medium (M) on the conveying member (31), a liquid tank unit (5) having a transfer member (52) that sends the aggregate (A) present on the conveying member (31) to a liquid tank (51), a settling tank (6) that accumulates the liquid transferred from the liquid tank (51), and a membrane module (7) that performs cross-flow filtration using a membrane (72) on the liquid introduced from the settling tank (6) into a container (71).

Description

[Technical Field]

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

[0002] Printing devices equipped with a transport member for transporting a print medium to be printed are known. In this type of printing device, ink and other printing materials that pass through the print medium may adhere to the surface of the transport member. Therefore, it is necessary to remove and recover the ink and other deposits from the transport member. For example, Patent Document 1 discloses a printing device equipped with a cleaning brush, a flocculation tank, and a filter as a structure for removing and recovering deposits from the transport member. The cleaning brush removes deposits from the transport member by cleaning the transport member using a liquid stored in a storage tank. The flocculation tank stores the cleaned liquid with a flocculant added. The filter separates the flocs from the liquid stored in the flocculation tank and recovers the flocs, including the deposits, from the transport member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-83155 Summary of the Invention

[0004] A printing device according to one aspect of the present disclosure includes a transport member capable of transporting a print medium, an ink unit capable of applying a pigment-containing ink to the print medium on the transport member, a treatment liquid unit capable of applying a treatment liquid containing a component capable of agglomerating the pigment to form an aggregate to the print medium on the transport member, a liquid tank unit having a liquid tank capable of storing a liquid and a transfer member capable of sending the aggregate present on the transport member to the liquid tank, a settling 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 settling tank and the liquid tank and a membrane contained in the container, capable of performing cross-flow filtration using the membrane on the liquid introduced into the container from the settling tank.

[0005] A printing method according 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 a pigment-containing ink to the printing medium on the transport member; a treatment liquid application step of applying a treatment liquid containing a component capable of agglomerating the pigment to form an aggregate to the printing medium on the transport member; a transfer step of sending the aggregate present on the transport member to a liquid tank in which a liquid is stored; a precipitation step of storing the liquid transferred from the liquid tank in a precipitation tank; and a filtration step of performing cross-flow filtration of the liquid introduced from the precipitation tank into the container using a membrane module comprising a membrane housed in a container. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a cross-sectional view of a printing device according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a front view of the printing device according to the first embodiment. [Figure 3] FIG. 3 is a flowchart showing the processing flow of a printing method using the printing device according to the first embodiment. [Figure 4] FIG. 4 is a front view of a printing device according to a second embodiment of the present disclosure. [Figure 5] FIG. 5 is a flowchart showing the processing flow of a printing method using a printing device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] In the prior art printing device disclosed in Patent Document 1, as mentioned above, when liquid circulates through the storage tank and the flocculation tank, the flocculant applied to the flocculation tank may be transferred from the flocculation tank to the storage tank. In this case, the flocculant may change the properties of the liquid in the storage tank, which may reduce the effectiveness of the liquid in the storage tank in removing deposits from the transport members. Furthermore, in prior art printing devices, for example, when printing high-density images on a print medium that is easily permeable to ink, the amount of deposits on the transport members increases, resulting in a large amount of flocs in the flocculation tank. In this case, the filter that separates the flocs from the liquid in the flocculation tank becomes clogged relatively quickly. When the filter becomes clogged, printing must be temporarily stopped to replace the filter, which limits continuous printing for long periods of time.

[0008] Therefore, there is a demand for a printing apparatus and a printing method that can prevent a decrease in the effectiveness of removing deposits from the conveying member and that can perform continuous printing for a long period of time.

[0009] A printing apparatus and a printing method according to an embodiment of the present disclosure will be described below with reference to the drawings. Note that directional relationships will be described below using XY Cartesian coordinates that are orthogonal to each other on a horizontal plane. The vertical direction that is orthogonal to the X and Y directions is defined as the Z direction.

[0010] (First embodiment) FIG. 1 is a cross-sectional view of a printing apparatus 1 according to a first embodiment of the present disclosure. FIG. 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 inking unit capable of applying ink to a medium M, which is a wide and long print medium. The printing apparatus 1 prints an image by applying ink to the medium M using the inking unit. Examples of the printing apparatus 1 include a screen printing apparatus and an inkjet apparatus. If the printing apparatus 1 is a screen printing apparatus, the inking unit includes a screen plate having multiple openings and a squeegee. In this case, the inking unit moves the ink along the screen plate in accordance with the movement of the squeegee, thereby applying the ink to the medium M through the openings in the screen plate. On the other hand, if the printing apparatus 1 is an inkjet apparatus, the inking unit ejects ink onto the medium M, thereby applying the ink to the medium M. The following describes in detail the case where the printing apparatus 1 is an inkjet apparatus.

[0011] The inkjet printing device 1 is suitable for digital textile printing, which prints images such as letters and patterns on a medium M, which is a fabric member made of fabric such as woven fabric or knitted fabric. Of course, the printing device 1 can also be used to print various images on printing media such as paper sheets and resin sheets.

[0012] The printing apparatus 1 includes an apparatus frame 2, a transport unit 3, a printing unit 4, a liquid tank unit 5, a settling 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 settling 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 medium M in the Y direction. The transport unit 3 has 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 that has a width in the X direction and extends in the Y direction. The transport member 31, which is an endless belt, has a transport surface 311 that can support and transport media M in an upward-facing area on the surface of the transport member 31, and is capable of circular movement. The transport member 31 forms a transport path 3R for the 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 moving circularly along the Y direction, the transport member 31 can transport media M in contact with the upward-facing transport surface 311 on the surface of the transport member 31, along the transport path 3R in a transport direction H1, which is a linear direction from one side of the Y direction to the other. An adhesive layer made of an adhesive that adheres the 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 conveying member 31 is wound at the most downstream position of the conveying path 3R. The first conveyor roller 32 is rotated in response to the circular movement of the conveying member 31. The second conveyor roller 33 is a cylindrical roller extending in the X direction, around which the conveying member 31 is wound at the most upstream position of the conveying path 3R. The second conveyor roller 33 is rotated by a drive motor (not shown), thereby moving the conveying member 31 in a circular movement. The conveying member 31 is stretched between the first conveyor roller 32 and the second conveyor roller 33 so that a conveying surface 311 formed by an upward-facing region and a non-conveying surface 312 formed by a downward-facing region on the surface of the conveying member 31 extend horizontally in the X and Y directions between the first conveyor roller 32 and the second conveyor roller 33. The transport member 31 moves in a circular motion in response to the rotational drive of the second transport roller 33, thereby transporting the medium M in the transport direction H1 along the transport path 3R.

[0016] The printing unit 4 is a unit for printing an image on the medium 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 disposed so as to face from above the transport surface 311, which faces upward on the surface of the transport member 31 made of an endless belt. As shown in FIG. 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 portion of the transport surface 311 in the transport direction H1. Note that the upstream end of the printing unit 4 may be located above the central portion of the transport surface 311.

[0017] The printing device 1 is a so-called serial printer that performs printing processing on a medium M using a serial printing method. In a serial printing device 1, a discharge operation in which various types of droplets are discharged from an inkjet head 42 while a carriage 41 is moved back and forth in an X direction that is orthogonal on a horizontal plane to the Y direction, which is a transport direction H1 of the medium M, and a transport operation of the medium M by a transport member 31 are repeatedly performed. In a serial printing device 1, the transport member 31 transports the medium M intermittently 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 with respect to the medium 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 attached to the device frame 2 at a position above the conveying member 31. The carriage 41 is fixed to a timing belt 212 attached to the carriage guide 21 so as to be able to rotate relative to the carriage guide 21. The timing belt 212 is an endless belt, and is driven to rotate in the X direction while attached to the carriage guide 21. As the timing belt 212 rotates in the X direction, the carriage 41 is able to move back and forth in the X direction along the carriage guide 21 while being guided by the guide rail 211.

[0019] Each of the ink head 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 that ejects ink containing a pigment as a coloring material, thereby depositing the ink onto the medium M on the transport member 31. 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 the 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 aligned 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. In another embodiment, a configuration in which only one ink head 421 is mounted on the carriage 41 is exemplified.

[0021] The ink ejected from the ink head 421 contains an aqueous medium, a pigment, and a binder resin. The aqueous medium is a medium whose main component is water. Specific examples of aqueous media include water and a mixture of water and a polar solvent. Examples of polar solvents contained in aqueous media include methanol, ethanol, isopropyl alcohol, butanol, and methyl ethyl ketone. The binder resin exists in a state where it is dispersed in the aqueous medium as resin particles. The resin particles of the binder resin function as a binder that binds the media M and the pigment. The volume median diameter of the resin particles of the binder resin is, for example, 50 nm or more and 150 nm or less. 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. The pigment can be a dispersible pigment that exists dispersed in the aqueous medium as pigment particles. To obtain an ink with excellent image density, hue, and color stability, the volume median diameter of the pigment is, for example, 50 nm or more and 150 nm or less. The pigment may be an anionic pigment. Examples of anionic pigments include pigments having anionic groups such as a carboxyl group, a sulfonic acid group, a phosphate group, a phosphonic acid group, a phenylsulfonic acid group, and a phenylcarboxyl group. The anionic pigment undergoes electrical reaction and aggregation on the medium M with a cationic resin, which serves as an aggregate-forming component contained in the pretreatment liquid ejected from the pretreatment liquid head 422. This can prevent the binder resin contained in the ink from penetrating into the medium M. This can reduce the binder resin's penetration into gaps between fibers and bonding the fibers together when the medium M is a fabric material. This can improve the texture, such as the feel of the fabric material.

[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 medium M by the transport member 31. The pretreatment liquid head 422 is a treatment liquid unit that can eject a pretreatment liquid to deposit the pretreatment liquid onto the medium M on the transport member 31 before the ink. The pretreatment liquid head 422 includes a number of nozzles that eject the pretreatment liquid using an ejection 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 the nozzles, and a wiring board for controlling the ejection operation of the pretreatment liquid. The pretreatment liquid is a treatment liquid that comes into contact with the ink when it is not dried on the medium M and is a non-coloring treatment liquid that does not develop color even when it is attached to the medium M. Note that the treatment liquid unit that deposits the pretreatment liquid onto the medium M on the transport member 31 is not limited to a head structure such as the pretreatment liquid head 422, and may have a spray-type structure that sprays the pretreatment liquid.

[0023] The pretreatment liquid ejected from the pretreatment liquid head 422 contains water or an aqueous solvent composed of water and an organic solvent, and an aggregate-forming component capable of aggregating 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 the aggregate-forming component include ionic resins with different ionicity 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 polymers, polyvinylimidazole, polyvinylbenzylphosphonium, polyalkylallylammonium, polyamidine, and polyamine sulfone. In the pretreatment liquid, the aggregate-forming component reacts with the pigment contained in the ink to aggregate, thereby ensuring excellent color development.

[0024] The posttreatment 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 medium M by the transport member 31. The posttreatment liquid head 423 is a treatment liquid unit that can eject posttreatment liquid to adhere the posttreatment liquid to the medium M on the transport member 31 after the ink. The posttreatment liquid head 423 includes a number of nozzles that eject the posttreatment liquid using an ejection method such as a piezo method using a piezo element or a thermal method using a heating element, a posttreatment liquid flow path that guides the posttreatment liquid to the nozzles, and a wiring board for controlling the ejection operation of the posttreatment liquid. The posttreatment liquid is a treatment liquid that comes into contact with the ink in a non-dried state on the medium M and is a non-color-forming treatment liquid that does not develop color even when attached to the medium M. The posttreatment liquid has the function of improving the fixation of the ink on the medium M. An example of such a posttreatment liquid is a treatment liquid containing silicone oil. Specifically, the posttreatment liquid may contain, for example, emulsified particles containing silicone oil, a surfactant, and an aqueous medium. In other words, the post-treatment liquid is an emulsion in which emulsified particles are dispersed in an aqueous medium, and more specifically, an oil-in-water (O / W) emulsion. The silicone oil may contain unmodified silicone oil. Examples of unmodified silicone oil include dimethylpolysiloxane, methylphenylsilicone oil, and methylhydrogensilicone oil. The silicone oil is stably dispersed in the post-treatment liquid. Note that the treatment liquid unit that applies the post-treatment liquid to the medium M on the conveying member 31 is not limited to a head structure such as the post-treatment liquid head 423, and may have a spray-type structure that sprays the post-treatment liquid.

[0025] In the printing unit 4, a discharge operation is performed in which a pretreatment liquid is discharged from the pretreatment liquid head 422, ink is discharged from the ink head 421, and, if necessary, posttreatment liquid is discharged from the posttreatment liquid head 423 onto the medium M on the transport surface 311 of the transport member 31. This causes an image to be printed on the medium M. That is, after the pretreatment liquid discharged from the pretreatment liquid head 422 adheres to the medium M on the transport surface 311 of the transport member 31, the ink discharged from the ink head 421 adheres thereto, and then, if necessary, the posttreatment liquid discharged from the posttreatment liquid head 423 adheres thereto.

[0026] In the printing device 1, if the medium M is, for example, a cloth member made of a thin fabric or a cloth member made of a fabric with a coarse weave or knit, at least the ink, pre-treatment liquid, and post-treatment liquid that have permeated the medium M during the ejection operation onto the medium M by the printing unit 4, as well as fibers that have fallen off the cloth member, may adhere to the conveying member 31. In addition to the ink, the adhered matter present on the conveying member 31 includes aggregates A. Aggregates A are generated when the ink and pre-treatment liquid come into contact on the conveying 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 contact between the ink used to form an image on the medium M and the pre-treatment liquid, even without the addition of an aggregating agent or the like.

[0027] When forming a high-density image on the medium M in the printing device 1, the ink, pre-treatment liquid, and post-treatment liquid may pass through the medium M at a rate of approximately 1.5 to 2.0 liters per unit time during the ejection operation onto the medium M by the printing unit 4. In this case, as the ink and other liquids pass through the medium M, approximately 150 to 300 g of solid content such as aggregates A adhere to the conveying member 31 per unit time. The aggregates A and other solid content present on the conveying member 31 can stain the medium M and can also reduce the adhesiveness of the medium M due to the adhesive layer formed on the surface of the conveying member 31, thereby reducing the print quality of the medium M. For this reason, it is necessary to remove the aggregates A and other solid content present on the conveying member 31 and collect the aggregates A and other solid content.

[0028] The printing device 1 is equipped with a liquid tank unit 5 as a unit for removing agglomerates A and the like present on the conveying member 31, and is equipped with a sedimentation tank 6 and a membrane module 7 as units for recovering agglomerates A and the like removed from the conveying member 31.

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

[0030] A pair of guide rails 22 extending in the Y direction along the conveying path 3R are attached to the device frame 2 below the conveying member 31. The pair of guide rails 22 are spaced a predetermined distance apart 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. This allows the liquid tank unit 5 to move along the conveying path 3R along the conveying surface 311 below the conveying member 31. Specifically, the liquid tank unit 5 is movable between a first position below the conveying member 31 and a second position below the conveying member 31 and downstream of the conveying member 31 in the conveying direction H1 of the conveying path 3R along the conveying surface 311. When the liquid tank unit 5 is positioned at the first position below the conveying member 31, the liquid tank unit 5 can remove aggregates A and the like present on the conveying member 31. On the other hand, when the liquid tank unit 5 is positioned at the second position downstream of the conveying member 31 along the conveying path 3R, the liquid tank unit 5 is positioned outside the device frame 2. In this case, the worker can easily perform maintenance work on the liquid tank unit 5. Maintenance work on the liquid tank unit 5 is work to maintain the effect of the liquid tank unit 5 in removing aggregates A and the like from the conveying 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 storing the liquid L. The liquid L is, for example, water. The liquid L may also contain a surfactant. The surfactant has the function of enhancing the effect of removing deposits such as the aggregate A on the conveying member 31, particularly the silicone oil in the post-treatment liquid. Such surfactants can be appropriately selected from anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc., with nonionic surfactants being particularly preferred. Examples of nonionic surfactants include polyoxyalkylene alkyl ethers and polyoxyethylene alkyl ethers.

[0033] The liquid tank 51 is located below the conveying member 31, downstream of the upstream end of the printing unit 4 in the conveying direction H1 along the conveying surface 311. In this case, the liquid tank 51 is located below the conveying member 31, downstream of the center of the conveying surface 311 of the conveying member 31 in the conveying direction H1. The liquid tank 51 is located within the installation area of ​​the conveying member 31 when viewed from above. In this embodiment, the entire liquid tank 51 is located within the installation area of ​​the conveying member 31 when 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 periphery of the bottom wall 511. The liquid tank 51 is a box-shaped tank that is open at the top so that the bottom wall 511 faces the conveying member 31. The width of the liquid tank 51 along the X direction is approximately the same as the width of the conveying member 31 along the X direction.

[0034] A float sensor 54 is provided in the liquid tank 51. The float sensor 54 is a sensor for detecting the height position of the liquid surface of the liquid L stored in the liquid tank 51 from the bottom wall 511. The liquid tank 51 is capable of storing the liquid L so that the liquid surface of the liquid L is located in a range between a preset upper limit height position and a preset lower limit 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 that connects the liquid tank 51 to a settling tank 6 (described later) is connected to the first flow path joint 5111. A third flow path member 82 that connects the liquid tank 51 to a vessel 71 of a membrane module 7 (described later) is connected to the second flow path joint 5112. As shown in FIG. 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 of the liquid L stored in the liquid tank 51 from the bottom wall 511. As described above, the liquid tank unit 5 is movably supported on a pair of guide rails 22 assembled to the equipment frame 2. As a result, the liquid tank unit 5 can move along the conveying path 3R that runs along the conveying surface 311 below the conveying member 31, with the first flow path member 80 connecting the liquid tank 51 and the settling 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 member capable of removing the aggregate A and the like from the conveying member 31 by sending the aggregate A and the like present on the conveying member 31 to the liquid tank 51. The transfer member 52 is located within the liquid tank 51 and is capable of sending the aggregate A and the like present on the conveying member 31 to the liquid tank 51 using the liquid L stored in the liquid tank 51. By being located within the liquid tank 51, the transfer member 52 is located within the installation area of ​​the conveying member 31 when viewed from above. In the example shown in FIG. 1 , two transfer members 52 are attached to the liquid tank 51. The transfer member 52 has a cylindrical shaft portion 521 extending in the X direction and brush portions 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 abuts against the downward-facing non-transport surface 312 on the surface of the transport member 31. In this state, the brush portion 522 rotates around the shaft portion 521 in response to the rotation of the shaft portion 521, thereby being able to transport the aggregate A and other substances present on the transport member 31 to the liquid tank 51 while using the liquid L stored in the liquid tank 51. The transfer member 52 is able to remove the aggregate A and other substances present on the transport member 31 from the transport member 31 by sending them to the liquid tank 51, thereby cleaning the transport member 31.

[0037] The blades 53 are plate-shaped rubber members extending in the X direction and attached to the peripheral wall 512 of the liquid tank 51 so as to abut against the downward-facing non-conveying surface 312 on the surface of the conveying member 31. In this embodiment, two blades 53 are attached to the peripheral wall 512. The blades 53 can remove the liquid L remaining on the conveying member 31 after the transfer member 52 cleans the conveying member 31, in accordance with the circular movement of the conveying member 31.

[0038] In the printing device 1, the aggregate A and the like 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 the aggregate A and the like. The aggregate A is generated by contact between the ink and the pretreatment liquid on the transport member 31, even if a flocculant or the like is not added to the liquid L in the liquid tank 51.

[0039] When the transfer member 52 immersed in the liquid L containing the coagulate A and the like in the liquid tank 51 comes into contact with the conveying member 31, the coagulate A and the like in the liquid L may re-adhere to the conveying member 31, making it difficult to accurately remove the coagulate A and the like from the conveying member 31. To address this, the printing apparatus 1 is provided with a settling tank 6 and a membrane module 7. In the printing apparatus 1, the liquid tank 51, the settling 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. While the liquid L circulates through the liquid tank 51, the settling tank 6, and the membrane module 7, the coagulate A and the like contained in the liquid L are collected by the settling tank 6 and the membrane module 7.

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

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

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

[0043] The settling tank 6 is located below the liquid tank 51, downstream of the upstream end of the printing unit 4 in the conveying direction H1 along the conveying surface 311. In this case, the settling tank 6 is located below the liquid tank 51, downstream of the center of the conveying surface 311 of the conveying member 31 in the conveying direction H1. The settling tank 6 is located within the installation area of ​​the liquid tank 51 when viewed from above. In this embodiment, the entire settling tank 6 is located within the installation area of ​​the liquid tank 51 when viewed from above.

[0044] The settling tank 6 is capable of storing the liquid L so 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 equal to or lower than the center position in the height direction (Z direction) relative to the bottom wall 61. When the settling tank 6 stores the liquid L, aggregates A and the like contained in the liquid L settle on the bottom wall 61. The aggregates A are generated by contact between the ink and the pretreatment liquid on the conveying member 31, even if a coagulant or the like is not added to the liquid L in the settling tank 6.

[0045] The membrane module 7 is located below the liquid tank 51 and adjacent to the settling tank 6 in the X direction. In this case, the membrane module 7 is located below the liquid tank 51, downstream of the center of the conveying direction H1 of the conveying surface 311 of the conveying member 31. The membrane module 7 is located within the installation area of ​​the liquid tank 51 when viewed from above. In this embodiment, the entire membrane module 7 is located within the installation area of ​​the liquid tank 51 when viewed from above.

[0046] The membrane module 7 includes a container 71 connected to the settling tank 6 and the liquid tank 51, and at least one hollow fiber membrane 72 housed within the container 71. The membrane housed within the container 71 is not limited to the hollow fiber membrane 72 and may be, for example, a flat membrane. The membrane module 7 is configured to perform crossflow filtration using the hollow fiber membrane 72 on the liquid L introduced into the container 71 from the settling tank 6. Crossflow filtration is a method in which the liquid L is caused to flow parallel to the membrane surface of the hollow fiber membrane 72 within the container 71, and the liquid L that has permeated the hollow fiber membrane 72 and filtered out the aggregates A is extracted as a filtrate, while the liquid L that flows along the membrane surface without permeating the hollow fiber membrane 72 is extracted as a concentrate. Filtration methods for crossflow filtration include internal pressure and external pressure. In internal pressure crossflow filtration, liquid L is introduced to the inner surface side of the hollow fiber membrane 72 in the container 71, and filtrate is removed from the outer surface side while a concentrated liquid is removed from the inner surface side. In external pressure crossflow filtration, liquid L is introduced to the outer surface side of the hollow fiber membrane 72, and filtrate is removed from the inner surface side while a concentrated liquid is removed from the outer surface side. In this embodiment, the membrane module 7 performs internal pressure crossflow filtration. In crossflow filtration, the flow of liquid L parallel to the membrane surface of the hollow fiber membrane 72 in the container 71 prevents deposition of aggregates A and the like on the membrane surface, thereby preventing clogging of the hollow fiber membrane 72.

[0047] The hollow fiber membrane 72 may be made of various materials, without any particular limitation. Examples include polyethylene and polyvinylidene fluoride. The pore size of the membrane surface of the hollow fiber membrane 72 is appropriately set depending on 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 reactive aggregation between the pigment in the ink and the aggregate-forming components in the pretreatment liquid, and is, for example, 6 μm or more and 20 μm or less. 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, 0.05 μm or more and 1.00 μm or less.

[0048] The membrane module 7 is configured so that, with regard to the filtrate and concentrate obtained in response to crossflow filtration of the liquid L introduced into the container 71 from the settling tank 6, the filtrate can be discharged from the container 71 toward the liquid tank 51, and the concentrate can be discharged from the container 71 toward the settling tank 6. Specifically, the container 71 has a liquid inlet 711 through which the liquid L from the settling tank 6 can be introduced, a filtrate outlet 712 through which the filtrate can be discharged, and a concentrate outlet 713 through which the concentrate can be discharged.

[0049] In the vessel 71, the liquid inlet 711 is connected to the outlet 6C1 of the settling tank 6 via the second flow path member 81. The second flow path member 81 is made of a flexible tube and connects the settling tank 6 and the vessel 71. The second flow path member 81 is provided with a liquid inlet valve 811, which is an on-off valve that switches between allowing and blocking the flow of the liquid L. The second flow path member 81 is also connected to the filtration pump 73. When the filtration pump 73 is driven, the liquid L stored in the liquid tank 51 is transferred to the settling tank 6, flows into the settling tank 6 through the inlet 6A1, and flows out of the settling tank 6 through the outlet 6C1. The liquid L that flows out of the outlet 6C1 of the settling tank 6 in response to the driving of the filtration pump 73 flows through the second flow path member 81 and, with the liquid inlet valve 811 open, is introduced into the vessel 71 through the liquid inlet 711 to the inner surface side of the hollow fiber membrane 72. The liquid L introduced to the inner surface side of the hollow fiber membrane 72 is extracted as a filtrate from the outer surface side and as a concentrated liquid from the inner surface side by internal pressure cross-flow filtration using the hollow fiber membrane 72. The filtration pump 73 is driven so that the flow rate of the liquid L flowing on the inner surface side of the hollow fiber membrane 72 is 1 m / s or more under no load.

[0050] A strainer 9 may also be connected to the second flow path member 81. A flow path through which the liquid L flows is formed inside the strainer 9. The strainer 9 is capable of filtering out and separating fibers derived from the media M contained in the liquid L flowing through the second flow path member 81. The filtration accuracy of the strainer 9 is, for example, approximately 180 μm. Therefore, although the strainer 9 is capable of filtering out and separating fibers in the liquid L, it is unable to separate aggregates A having a volume median diameter smaller than the filtration accuracy. The aggregates A in the liquid L are filtered out and separated by cross-flow filtration of the hollow fiber membranes 72.

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

[0052] In the vessel 71, the concentrated liquid outlet 713 is connected to the inlet 6A1 of the settling tank 6 via a fourth flow path member 83. The fourth flow path member 83 is formed of a flexible tube and connects the settling tank 6 and the vessel 71. The fourth flow path member 83 is provided with a concentrated liquid outlet valve 831, which is an on-off valve that switches between allowing and blocking the flow of the concentrated liquid. The concentrated liquid obtained by cross-flow filtration of the hollow fiber membranes 72 on the liquid L introduced into the vessel 71 in response to the operation of the filtration pump 73 is discharged from the vessel 71 through the concentrated liquid outlet 713 with the concentrated liquid outlet valve 831 open, flows through the fourth flow path member 83, and flows into the settling tank 6 through the inlet 6A1.

[0053] In FIG. 2, the first flow path member 80 and the fourth flow path member 83 are connected and then connected to the settling tank 6, but they may also be connected separately to the settling tank 6. If the first flow path member 80 and the fourth flow path member 83 are connected separately to the settling tank 6, the flow of the liquid L from the liquid tank 51 to the settling tank 6 can be stabilized. If the first flow path member 80 and the fourth flow path member 83 were connected, an increase in the flow rate of the concentrated liquid could drastically reduce the amount of liquid L flowing from the liquid tank 51 to the settling tank 6, or in more extreme cases, the concentrated liquid could flow into the liquid tank 51. Connecting them separately can prevent this from happening.

[0054] If the connection to the settling tank 6 is at a single point, the flow of the accumulated liquid L when it flows into the settling tank 6 is less likely to become complicated, making it easier to understand and control the behavior of the flocculant A in the settling tank 6. Furthermore, the structure of the settling tank 6 can be simplified. Furthermore, in order to stabilize the amount of liquid L flowing from the liquid tank 51 to the settling tank 6, the length of the flow path of the first flow path member 80 up to the connection with the fourth flow path member 83 may be longer than the length of the flow path after the fourth flow path member 83 and the first flow path member 80 are connected. Alternatively, the flow path resistance of the former may be made greater than the flow path resistance of the latter, thereby stabilizing the amount of liquid L flowing from the liquid tank 51 to the settling tank 6. Furthermore, the amount of liquid L flowing from the liquid tank 51 to the settling tank 6 may be stabilized by controlling the operation of the filtration pump 73 so that the flow rate of the concentrated liquid is equal to or less than a predetermined value.

[0055] In the printing apparatus 1, the liquid tank 51, the settling tank 6, and the container 71 of the membrane module 7 are connected to one another to form 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 settling tank 6 in response to the operation of the filtration pump 73 is stored in the settling tank 6. In the settling tank 6, aggregates A and other substances contained in the liquid L settle on the bottom wall 61. The aggregates A are generated by contact between the ink and the pretreatment liquid on the conveying member 31, even if a coagulant or other agent is not added to the liquid L in the settling tank 6. In this case, the incorporation of the coagulant into the liquid L circulating between the liquid tank 51, the settling tank 6, and the membrane module 7 is suppressed, thereby suppressing changes in the properties of the liquid L due to the coagulant. This suppresses a decrease in the effectiveness of the liquid L stored in the liquid tank 51 in removing aggregates A and other substances from the conveying member 31.

[0056] Furthermore, as described above, when forming a high-density image on the medium M in the printing device 1, the ink, pretreatment liquid, and the like permeate the medium M at a rate of approximately 1.5 to 2.0 liters per unit time, which can result in a large amount of solid matter, such as aggregates A, adhering to the conveying member 31 at a rate of approximately 150 to 300 g per unit time. In this case, the liquid L stored in the liquid tank 51 also contains a large amount of aggregates A. In this case, if the aggregates A are filtered and separated using a conventional bobbin-wound filter, the filter will clog in a relatively short time. When the filter clogs, printing must be temporarily stopped to replace the filter, which may prevent continuous printing for long periods of time.

[0057] Therefore, in the printing apparatus 1 according to this embodiment, the liquid L introduced from the settling tank 6 into the container 71 of the membrane module 7 in response to the operation of the filtration pump 73 is subjected to cross-flow filtration using the hollow fiber membrane 72. In cross-flow filtration, the flow of the liquid L parallel to the membrane surface of the hollow fiber membrane 72 in the container 71 can suppress the deposition of aggregates A and the like on the membrane surface, thereby making it possible to suppress clogging of the hollow fiber membrane 72. This makes it possible to reduce the frequency with which printing has to be temporarily stopped due to clogging of the hollow fiber membrane 72, thereby enabling continuous printing for long periods of time.

[0058] Furthermore, in the membrane module 7, of the filtrate and concentrated liquid obtained by cross-flow filtration of the liquid L introduced into the container 71 from the settling tank 6, the filtrate is returned from the container 71 to the liquid tank 51, and the concentrated liquid is returned from the container 71 to the settling tank 6. This makes it possible to keep the amount of waste liquid generated during continuous printing on the medium M in the printing device 1 to an extremely small amount of approximately 0.02 liters per kg of the medium M. The waste liquid is liquid L containing a high concentration of aggregates A and the like removed from the conveying member 31 during continuous printing on the medium M, and is accumulated in the settling tank 6.

[0059] As described above, in the printing apparatus 1, the liquid tank unit 5 is located below the conveying member 31, and the settling 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 conveying member 31 when viewed from above, and the settling tank 6 and membrane module 7 are located within the installation area of ​​the liquid tank 51 when viewed from above. In this case, the liquid tank unit 5, the settling tank 6, and the membrane module 7 are each concentrated within the area below the conveying member 31 without moving out of the area below the conveying member 31. This improves the ease of maintenance work performed on the liquid tank unit 5, the settling tank 6, and the membrane module 7. Maintenance work on the settling tank 6 includes, for example, cleaning the settling tank 6 by discharging liquid L containing a high concentration of coagulate A and the like from the settling tank 6 as waste liquid. An example of maintenance work for the membrane module 7 is replacing a membrane module 7 that has become clogged in the hollow fiber membrane 72. Note that maintenance work for the liquid tank unit 5, the settling tank 6, and the membrane module 7 is performed when printing of images on the media M in the printing device 1 is stopped.

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

[0061] 2, the settling 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 settling tank 6 may have only one of the first partition plate 63 and the second partition plate 64. The first chamber 6A has an inlet 6A1 connected to the liquid tank 51 and is defined at one end of the settling tank 6 in the X direction. The second chamber 6B is defined in the settling tank 6 at a position adjacent to the first chamber 6A in the X direction, with the first partition plate 63 standing on the bottom wall 61 between them. The third chamber 6C has an outlet 6C1 connected to the container 71 of the membrane module 7 and is defined at the other end of the settling tank 6 in the X direction, with the second partition plate 64 standing on the bottom wall 61 between them.

[0062] In the first chamber 6A, the inlet 6A1 is located above the liquid level of the liquid L stored in the settling tank 6. In the third chamber 6C, the outlet 6C1 is located below the liquid level of the liquid L stored in the settling 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 the opening facing the side wall of the first chamber 6A. Such a shape can prevent the liquid L flying through the air from hitting the surface of the liquid L stored in the settling tank 6, even when the flow rate of the liquid L flowing out of the inlet 6A1 is high. This prevents the settling aggregates A and other particles from being agitated and resuspended in the stored liquid L. It also prevents the stored liquid L from foaming and overflowing from the first chamber 6A or the settling tank 6. Even when the inlet 6A1 is extended within the first chamber 6A, the opening at the tip of the inlet 6A1 is located below the surface of the liquid L stored in the settling tank 6 and at a predetermined distance above the bottom wall 61.

[0064] The first partition plate 63 is, for example, a plate having a substantially U-shape in a plan view. The first partition plate 63 can control the flow of the 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 portion 63A restricts the flow of the liquid L, while the lower portion 63B has an opening and can allow the flow of the liquid L. In the first partition plate 63, the upper end of the upper portion 63A is located above the liquid level of the liquid L stored in the settling tank 6, the boundary between the upper portion 63A and the lower portion 63B is located below the liquid level, and the lower end of the lower portion 63B abuts against the bottom wall 61. The first chamber 6A and the second chamber 6B, separated by the first partition plate 63, are in communication with each other through the opening in the lower portion 63B of the first partition plate 63.

[0065] The second partition plate 64 is, for example, a plate having a substantially U-shape in a plan view. The second partition plate 64 can control the flow of the 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 portion 64A has an opening to allow the flow of the liquid L, and the lower portion 64B can restrict the flow of the liquid L. In the second partition plate 64, the upper end of the upper portion 64A is located above the liquid level of the liquid L stored in the settling tank 6, the boundary between the upper portion 64A and the lower portion 64B is located below the liquid level, and the lower end of the lower portion 64B abuts the bottom wall 61. The second chamber 6B and the third chamber 6C, while separated by the second partition plate 64, are in communication with each other through the opening in the upper portion 64A of the second partition plate 64.

[0066] In the settling tank 6 having the first chamber 6A, the second chamber 6B, and the third chamber 6C, liquid L flows into the first chamber 6A through the inlet 6A1 in response to the operation of the filtration pump 73. The liquid L is restricted in flow by the upper portion 63A of the first partition plate 63 and flows into the second chamber 6B through the opening in the lower portion 63B. When the liquid L flows from the first chamber 6A to the second chamber 6B through the opening in the lower portion 63B of the first partition plate 63, the liquid L takes with it aggregates A and the like that have settled on the bottom wall 61. For this reason, the amount of aggregates A and the like that have accumulated on the bottom wall 61 of the settling tank 6 tends to be greater in the second chamber 6B than in the first chamber 6A.

[0067] The liquid L that flows into the second chamber 6B through the opening in the lower portion 63B of the first partition plate 63 flows into the third chamber 6C through the opening in the upper portion 64A while its flow is restricted by the lower portion 64B of the second partition plate 64. When the liquid L flows from the second chamber 6B to the third chamber 6C through the opening in the upper portion 64A of the second partition plate 64, the flow of the liquid L is restricted by the lower portion 64B, so that the flocculants A and the like that have settled on the bottom wall 61 are prevented from being taken in by the liquid L. For this reason, the amount of flocculants A and the like that has accumulated on the bottom wall 61 of the settling 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 settling tank 6 flows out of the third chamber 6C through the outlet 6C1 in response to the operation of the filtration pump 73, flows through the second flow path member 81, and is introduced into the container 71 of the membrane module 7. Here, as described above, the amount of deposition of flocculants A and the like in the settling tank 6 is smallest in the third chamber 6C. Furthermore, in the third chamber 6C, the outlet 6C1 is located a predetermined distance above the bottom wall 61 where the flocculants A and the like settle. In this case, even if liquid L containing a high concentration of flocculants A and the like removed from the conveying member 31 during continuous printing on the media M is stored in the settling tank 6, the supernatant of the liquid L stored in the third chamber 6C, where the amount of deposition of flocculants A and the like is smallest, flows out from the outlet 6C1 and is introduced into the container 71 of the membrane module 7. In this case, the membrane module 7 performs crossflow filtration using the hollow fiber membranes 72 on the liquid L containing a relatively low content of flocculants A and the like. This effectively prevents clogging of the hollow fiber membrane 72 due to the accumulation of aggregates A and the like on the membrane surface of the hollow fiber membrane 72. This further reduces the frequency with which printing must be temporarily stopped due to clogging of the hollow fiber membrane 72, making it possible to perform continuous printing for even longer periods of time.

[0069] 2, the settling tank 6 may have a drain pipe 65 connected to the bottom wall 61. The drain pipe 65 is connected to the partitioned 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 from the second chamber 6B as waste liquid. The drain pipe 65 is provided with a drain valve 651, which is an open / close valve that switches between allowing and blocking the flow of the liquid L. The drain pipe 65 discharges the liquid L from the second chamber 6B when the drain valve 651 is open.

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

[0071] The processing steps of the printing method using the printing device 1 according to the first embodiment will be described in detail with reference to the flowchart of FIG.

[0072] First, we will explain the image forming process performed by the printing device 1. Based on image data of an image to be formed on the medium M, the printing device 1 repeatedly performs a transport step a1 in which the medium M is transported by the transport member 31 of the transport unit 3, and a printing step using the inkjet head 42 on the medium M on the transport member 31. The printing step by the inkjet head 42 includes a pretreatment liquid application step a2 in which pretreatment liquid is applied to the medium M in response to the ejection of pretreatment liquid from the pretreatment liquid head 422, an ink application step a3 in which ink is applied to the medium M in response to the ejection of ink from the ink head 421, and a posttreatment liquid application step a4 in which posttreatment liquid is applied to the medium M in response to the ejection of posttreatment liquid from the posttreatment liquid head 423. An image is formed on the medium M on the transport member 31 by repeatedly performing the transport step a1, the pretreatment liquid application step a2, the ink application step a3, and the posttreatment liquid application step a4.

[0073] In the media M on the transport member 31, a reaction and aggregation occurs between the aggregate-forming component contained in the pretreatment liquid and the pigment contained in the ink, which prevents the binder resin contained in the ink from penetrating into the media M. This reduces the possibility of the binder resin binding fibers together when the media M is a fabric material, thereby improving the texture, such as the feel of the fabric material. Furthermore, adhesion of the posttreatment liquid to the media M on the transport member 31 improves the fixability of the ink on the media M.

[0074] Next, a description will be given of the transport process, precipitation process, and filtration process performed by the printing device 1. The printing device 1 performs the transport process, precipitation process, and filtration process while performing continuous printing on the medium M in the image forming process.

[0075] The printing device 1 performs a supply step b1 of supplying the liquid L to the liquid tank 51 based on the detection result of the float sensor 54. Specifically, the printing device 1 supplies the liquid L to the liquid tank 51 based on the detection result of the float sensor 54 so that the liquid level of the liquid L in the liquid tank 51 is located in a range between an upper limit height position and a lower limit height position. As a result, the liquid L is stored in the liquid tank 51 so that a portion of the brush portion 522 of the transfer member 52 attached 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 step b2 and also performs the precipitation step and filtration step b3. When performing the precipitation step and filtration step b3, the printing apparatus 1 keeps the liquid inlet valve 811, the filtrate outlet valve 821, and the concentrated liquid outlet valve 831 open.

[0077] In the transfer step b2, the printing apparatus 1 rotates the shaft 521 of the transfer member 52, thereby rotating the brush part 522 that is immersed in the liquid tank 51 and in contact with the transport member 31, thereby transferring the aggregate A and other materials on the transport member 31 to the liquid tank 51. Therefore, the liquid L stored in the liquid tank 51 contains the aggregate A and other materials. The aggregate A is 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 component contained in the pretreatment liquid.

[0078] The printing apparatus 1 drives the filtration pump 73 in the precipitation step and filtration step b3. By driving the filtration pump 73, the liquid L stored in the liquid tank 51 is transferred to the precipitation tank 6. The precipitation tank 6 stores the liquid L transferred from the liquid tank 51. With the liquid L stored in the precipitation tank 6, aggregates A and the like contained in the liquid L are precipitated on the bottom wall 61. The aggregates A are generated by contact between the ink and the pretreatment liquid on the conveying member 31, even if a flocculant or the like is not added to the liquid L in the precipitation tank 6.

[0079] In response to the operation of the filtration pump 73, the liquid L flowing out of the settling tank 6 is introduced into the container 71 of the membrane module 7. The membrane module 7 performs cross-flow filtration on the liquid L introduced into the container 71 using the hollow fiber membrane 72, discharging the filtrate from the container 71 toward the liquid tank 51 and discharging the concentrated liquid from the container 71 toward the settling tank 6. In cross-flow filtration, the flow of the liquid L parallel to the membrane surface of the hollow fiber membrane 72 in the container 71 prevents the deposition of aggregates A and the like on the membrane surface, thereby preventing clogging of the hollow fiber membrane 72. This reduces the frequency with which printing has to be temporarily stopped due to clogging of the hollow fiber membrane 72, making it possible to perform continuous printing for long periods of time.

[0080] When printing of images on the medium M in the printing device 1 is stopped, an operator can carry out maintenance work on the liquid tank unit 5, the settling tank 6, and the membrane module 7.

[0081] (Second embodiment) 4 is a front view of a printing apparatus 1 according to a second embodiment of the present disclosure. The printing apparatus 1 according to the second embodiment basically has the same configuration and produces the same effects as the first embodiment, 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 that can store a portion of the filtrate discharged from the filtrate outlet 712 of the container 71 in the membrane module 7. In the membrane module 7, the container 71 has a filtrate inlet 714 that can introduce the filtrate stored in the filtrate tank 74, in addition to the liquid inlet 711, the filtrate outlet 712, and the concentrated liquid outlet 713. The filtrate tank 74 is connected to the filtrate outlet 712 of the container 71 via a branch flow path branched from the third flow path member 82, and is connected to the filtrate inlet 714 of the container 71 via the fifth flow path member 84.

[0083] A filtrate branch valve 822, which is an on-off valve that switches between flow and blocking of the filtrate discharged from the filtrate outlet 712 of the container 71, is provided in the branch flow path branched from the third flow path member 82. The filtrate discharged from the filtrate outlet 712 of the container 71 in response to the operation of the filtration pump 73 flows into and is stored in the filtrate tank 74 with the filtrate branch valve 822 open.

[0084] The fifth flow path member 84 is configured by a flexible tube, and connects the filtrate tank 74 and the container 71. The fifth flow path member 84 is provided with a filtrate introduction valve 841, which is an on-off valve that switches between allowing and blocking the flow of the filtrate introduced into the filtrate inlet 714 of the container 71. In addition, a backwash pump 75 is connected to the fifth flow path member 84.

[0085] The backwash pump 75 is an example of a pressure-feeding unit capable of pressure-feeding 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. With the liquid inlet valve 811, the filtrate outlet valve 821, and the filtrate branch valve 822 closed, crossflow filtration by the hollow fiber membrane 72 in the container 71 is stopped. When the backwash pump 75 is driven in this state where crossflow filtration is stopped, the filtrate is introduced into the container 71 through the filtrate inlet 714. The filtrate introduced into the vessel 71 is pushed from the outer surface side to the inner surface side of the hollow fiber membranes 72 while taking with it aggregates A and the like that have accumulated on the membrane surfaces of the hollow fiber membranes 72, flows along the inner surface side, is discharged from the vessel 71 through the concentrated liquid outlet 713, flows through the fourth flow path member 83 and flows into the settling tank 6. In this manner, backpressure washing of the hollow fiber membranes 72 is performed in response to the operation of the backwash pump 75. By performing backpressure washing of the hollow fiber membranes 72 in response to the operation of the backwash pump 75, it is possible to remove aggregates A and the like that have accumulated on the membrane surfaces of the hollow fiber membranes 72 due to crossflow filtration.

[0086] Back pressure cleaning of the hollow fiber membrane 72 in response to the operation of the backwash pump 75 may be performed alternately with cross-flow filtration when continuous printing is being performed on the medium M in the printing device 1, or may be performed when printing on the medium M is stopped. In this embodiment, back pressure cleaning of the hollow fiber membrane 72 is performed when printing on the medium M is stopped.

[0087] The processing of each step of the printing method using the printing apparatus 1 according to the second embodiment will be described with reference to the flowchart in Fig. 5. Note that the conveying step a1, pre-treatment liquid application step a2, ink application step a3, and post-treatment liquid application step a4 of the image formation process performed by the printing apparatus 1 are the same as those in the first embodiment, and therefore descriptions thereof will be omitted. Also, the supplying step b1, transporting step b2, precipitation step, and filtration step b3 of the transfer process, precipitation process, and filtration process performed by the printing apparatus 1 are the same as those in the first embodiment, and therefore descriptions thereof will be omitted.

[0088] The printing apparatus 1 according to the second embodiment performs a backwashing process in the backwashing step b4. In the backwashing step b4, the printing apparatus 1 closes the liquid inlet valve 811, the filtrate outlet valve 821, and the filtrate branch valve 822, and opens the concentrated liquid outlet valve 831 and the filtrate inlet valve 841. Then, the printing apparatus 1 drives the backwash pump 75 while crossflow filtration in the membrane module 7 is stopped.

[0089] By driving the backwash pump 75, 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 side to the inner surface side of the hollow fiber membranes 72 while taking with it aggregates A and the like that have accumulated on the membrane surfaces of the hollow fiber membranes 72, flows along the inner surface side, is discharged from the container 71 through the concentrated liquid outlet 713, flows through the fourth flow path member 83, and flows into the settling tank 6. By performing backpressure washing of the hollow fiber membranes 72 in response to the driving of the backwash pump 75 in this manner, aggregates A and the like that have accumulated on the membrane surfaces of the hollow fiber membranes 72 due to the crossflow filtration can be removed. [Explanation of symbols]

[0090] 1 Printing device 3 Transport unit 31 Transport 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 Settling tank 61 Bottom wall 63 First partition 64 Second partition 6A Room 1 6B Room 2 6C Room 3 7. Membrane module 71 Container 72 Hollow fiber membrane 73 Filtration Pump 74 Filtrate tank 75 Backwash pump (pressure section)

Claims

1. a conveying member capable of conveying a print medium; an ink unit capable of depositing ink containing a pigment onto the print medium on the transport member; a treatment liquid unit capable of applying a treatment liquid containing a component capable of aggregating the pigment to form an aggregate to the print medium on the transport member; a liquid tank unit including a liquid tank capable of storing a liquid and a transfer member capable of sending the aggregate present on the conveying member to the liquid tank; a settling tank connected to the liquid tank and capable of storing the liquid transferred from the liquid tank; a membrane module having a container connected to the settling tank and the liquid tank, and a membrane housed in the container, capable of performing cross-flow filtration using the membrane on the liquid introduced from the settling tank into the container.

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

3. The settling tank has a bottom wall in which the flocculants contained in the liquid settle, and includes: a first chamber connected to the liquid tank and having an inlet through which the liquid can flow; a second chamber adjacent to the first chamber across a first partition plate erected relative to the bottom wall; and a third chamber adjacent to the second chamber across a second partition plate erected relative to the bottom wall, and having an outlet through which the container is connected and through which the liquid can flow out. the first partition plate is configured such that an upper portion thereof restricts the flow of the liquid and a lower portion thereof allows the flow of the liquid in a height direction relative to the bottom wall, The printing device according to claim 1 , wherein the second partition plate is configured such that an upper portion thereof allows the liquid to flow and a lower portion thereof restricts the flow of the liquid in a height direction relative to the bottom wall.

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

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

6. The printing device according to claim 1 , wherein the printing medium is a fabric member made of fabric.

7. a conveying step of conveying the print medium by a conveying member; an ink applying step of applying ink containing a pigment to the print medium on the transport member; a treatment liquid application step of applying a treatment liquid containing a component capable of aggregating the pigment to form an aggregate to the print medium on the transport member; a transferring step of transferring the aggregate present on the transfer member to a liquid tank in which a liquid is stored; a settling step of storing the liquid transferred from the liquid tank in a settling tank; a filtration step of performing cross-flow filtration of the liquid introduced from the settling tank into the container using a membrane module formed by housing a membrane in a container.

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