Method for cleaning inkjet head and apparatus for cleaning inkjet head

Abstract

Provided are a method for cleaning an inkjet head and an apparatus for cleaning an inkjet head, the inkjet head having a liquid repellent film in at least a nozzle region of a nozzle surface, the nozzle region being provided with a plurality of nozzles for ejecting ink. The method comprises a cleaning liquid application step for applying a cleaning liquid to the nozzle region. During the cleaning liquid application step or after the cleaning liquid application step, the inkjet head is supported in an inclined posture in which the inclination angle of the nozzle surface with respect to a horizontal plane is greater than or equal to a sliding angle of the cleaning liquid on the liquid repellent film.

Description

Method and apparatus for cleaning inkjet heads

[0001] This disclosure relates to a method and apparatus for cleaning inkjet print heads.

[0002] An inkjet printing apparatus equipped with an inkjet head that ejects ink is known. The inkjet head has a nozzle surface equipped with nozzles that eject ink. In an inkjet head, if the nozzles become clogged with ink or the nozzle surface becomes dirty, ejection abnormalities occur, leading to a decrease in image quality. In an inkjet printing apparatus, the inkjet head is cleaned periodically to prevent the occurrence of ejection abnormalities and to quickly recover from them (see, for example, Japanese Patent Application Publication No. 2014-151585). When cleaning the inkjet head, a cleaning solution is applied to the nozzle surface or the nozzle surface is wiped with a cleaning member such as a blade or web.

[0003] As described in Japanese Patent Publication No. 2014-151585, the inkjet head comprises a nozzle region consisting of a nozzle plate on which nozzles for ejecting ink are provided on the nozzle surface, and a wing region consisting of a support member that supports the nozzle plate. A liquid-repellent film is formed on the nozzle region to prevent ink from adhering to it.

[0004] As a liquid-repellent coating, fluorine-based liquid-repellent coatings are known for their high liquid-repellent properties and durability. However, the use of "fluorine-based liquid-repellent coatings" in inkjet heads is becoming unusable due to PFAS (Per- and Poly FluoroAlkyl Substances) regulations. As a result, inkjet heads equipped with liquid-repellent coatings that are not subject to PFAS regulations, such as "non-fluorine-based liquid-repellent coatings," are being replaced.

[0005] Generally, non-fluorinated liquid-repellent films are known to have lower liquid-repellent properties and durability than fluorinated liquid-repellent films. Therefore, there is a concern that cleaning solution may remain on the nozzle surface equipped with a non-fluorinated liquid-repellent film. In addition, the liquid-repellent properties of a nozzle surface equipped with a non-fluorinated liquid-repellent film deteriorate more quickly than those of a fluorinated liquid-repellent film due to repeated wiping with a cleaning agent.

[0006] This disclosure has been made in view of the above circumstances and aims to provide an inkjet head cleaning method and cleaning apparatus that can suppress the deterioration of the ejection performance of an inkjet head having a liquid-repellent film and improve ejection stability.

[0007] The present disclosure is a method for cleaning an inkjet head, wherein at least the nozzle area of ​​the nozzle surface, which includes a nozzle area on which a plurality of nozzles for ejecting ink are provided, is provided with a liquid-repellent film, and the method includes a step of applying a cleaning solution to the nozzle area, and during or after the cleaning solution application step, the inkjet head is supported in an inclined position such that the inclination angle of the nozzle surface with respect to the horizontal plane is greater than or equal to the sliding angle of the cleaning solution in the liquid-repellent film.

[0008] After the cleaning solution application step, a wiping step may be performed to wipe off at least a portion of the nozzle surface.

[0009] During the cleaning solution application process, the inkjet head may be supported in an inclined position, and the wiping process may be performed while maintaining the inclined position of the inkjet head.

[0010] During the cleaning solution application process, the inkjet head may be supported in a position where the inclination angle of the nozzle surface is smaller than the sliding angle. After the cleaning solution application process, the inkjet head may be tilted to an inclined position, and the wiping process may be performed with the inkjet head supported in this inclined position.

[0011] In the wiping process, at least a portion of the nozzle surface may be wiped, specifically the portion of the nozzle surface that is at the lowest vertical point when the inkjet head is supported in an inclined position.

[0012] The inkjet head may be an inkjet head that ejects ink containing carbon black pigment or titanium dioxide pigment as the ink.

[0013] The inkjet head may have either a fluorine-based liquid-repellent film or a non-fluorine-based liquid-repellent film on the nozzle surface as a liquid-repellent coating.

[0014] The inkjet head cleaning apparatus of the present disclosure is an inkjet head cleaning apparatus having a liquid-repellent film on at least the nozzle region of a nozzle surface including a nozzle region on which a plurality of nozzles for ejecting ink are provided, comprising: a cleaning liquid application unit for applying cleaning liquid to the nozzle surface; and a support unit for supporting the inkjet head, the support unit being configured to support the inkjet head in an inclined position such that the inclination angle of the nozzle surface with respect to the horizontal plane is greater than or equal to the sliding angle of the cleaning liquid in the liquid-repellent film.

[0015] The support unit may include a tilt adjustment mechanism that switches between a first state in which the inkjet head is supported in a position where the tilt angle of the nozzle surface is smaller than the sliding angle, and a second state in which it is supported in an inclined position.

[0016] The device may further include a wiping member for wiping at least a portion of the inkjet head.

[0017] The inkjet head may be an inkjet head that ejects ink containing carbon black pigment or titanium dioxide pigment as the ink.

[0018] The inkjet head may have either a fluorine-based liquid-repellent film or a non-fluorine-based liquid-repellent film on the nozzle surface as a liquid-repellent coating.

[0019] According to the technology disclosed herein, it is possible to suppress the deterioration of the ejection performance of an inkjet head having a liquid-repellent film and improve ejection stability.

[0020] These are a side view (A) and a top view (B) showing the schematic configuration of an inkjet printing apparatus according to one embodiment. This is a perspective view showing the schematic configuration of the print bar. This is a front view of the inkjet head as seen from the nozzle surface side. This is an explanatory diagram of the static contact angle θS. Figures 5A and 5B are explanatory diagrams of the inclination angle of the nozzle surface, respectively. Figures 6A and 6B are explanatory diagrams of the sliding angle, respectively. This is a flowchart of the processing steps of the cleaning method of the first embodiment. This is an explanatory diagram of the cleaning method of the first embodiment. This is a flowchart of the processing steps of the cleaning method of the second embodiment. This is a diagram showing how liquid residue is generated at the end of the inkjet head. Figure 11A is a diagram explaining the wiping process, and Figure 11B is a diagram showing a modified example of the wiping process. This is a flowchart of the processing steps of the cleaning method of the third embodiment. This is an explanatory diagram of the tilt adjustment mechanism. This is a flowchart of the processing steps of the cleaning method of the fourth embodiment. This is a flowchart of the processing steps of the cleaning method of the fifth embodiment. This is a diagram showing a modified example of the cleaning liquid application unit. This is an explanatory diagram of the inclination direction of the nozzle surface. This is an explanatory diagram of the head frame. This is a diagram showing a cleaning device arranged between the image recording position and the retracted position.

[0021] Embodiments of the technology of this disclosure will be described below with reference to the drawings. In each drawing, the same elements are denoted by the same reference numerals.

[0022] The cleaning method and cleaning apparatus of this disclosure are used, for example, to clean an inkjet head provided in an inkjet printing apparatus 1. First, the inkjet printing apparatus 1 will be described.

[0023] "Configuration of Inkjet Printing Apparatus" In Figure 1, (A) is a side view showing the schematic configuration of an inkjet printing apparatus 1 according to one embodiment, and (B) is a top view.

[0024] The inkjet printing apparatus 1 is an inkjet-type color digital printing apparatus that forms a desired image on a sheet of paper P. The inkjet printing apparatus 1 is a single-sided printing apparatus that forms an image on only one side of the paper P. However, the technology of this disclosure is also applicable to a double-sided printing apparatus that forms an image on both sides of the paper P. Paper P is an example of a recording medium. The material and shape of the recording medium are not particularly limited, and various sheets can be used regardless of material or shape, such as sticker paper, resin sheets, films, cloth, nonwoven fabrics, etc. The recording medium is not limited to a sheet-fed medium, but may also be a continuous medium such as continuous paper, continuous form paper, or flexible packaging film. Here, an inkjet printing apparatus 1 that records an image on a sheet of paper using a single-pass method will be described.

[0025] As shown in Figure 1(A), the inkjet printing apparatus 1 comprises a transport mechanism 10, a paper feed device 20, an image forming unit 40, and an accumulation device 80. Furthermore, as shown in Figure 1(B), it also has a linear movement mechanism 90 for moving the image forming unit 40 between an image recording position and a retracted position, and a cleaning device 100 positioned between the image recording position and the retracted position. Here, the vertical direction is represented as the Z direction, and the horizontal directions are represented as the X and Y directions. Here, the longitudinal direction of the inkjet head 45, which will be described later, is defined as the X direction, and the direction perpendicular to the X direction is defined as the Y direction.

[0026] The transport mechanism 10 transports the paper P with its recording surface (i.e., paper surface) Pa facing the print bar of the image forming unit 40, which will be described later. In Figure 1, the transport path 12 through which the paper P is transported is shown by a dashed line.

[0027] The transport mechanism 10 includes a plurality of transport members along the transport path 12. The plurality of transport members include a plurality of transport roller pairs 14, a paper feed drum 16 and an discharge drum 18, and a drawing drum 41, which will be described later. Each transport roller pair 14 includes a drive roller 14a and a pinch roller 14b arranged opposite each other. The transport roller pair 14 grips the paper P between the drive roller 14a and the pinch roller 14b and rotates to feed out the paper P. The transport members may also include a transport drum, a belt conveyor, a chain gripper and a transport guide. The transport mechanism 10 also includes a drive unit such as a motor (not shown) and a motor drive circuit (not shown) as a power source. The paper P is transported along the transport path 12 by these elements constituting the transport mechanism 10. Note that in Figure 1(B), components of the transport mechanism 10 other than the transport path 12 are omitted.

[0028] The paper feeder 20 is an example of a paper feed section that houses the paper P to be transported toward the image forming unit 40. The paper feeder 20 is equipped with a paper feed tray on which a stack of multiple sheets of paper P is placed. The type of paper P is not particularly limited, but for example, cellulose-based printing paper such as fine paper, coated paper, and art paper can be used. The maximum paper size that can be used in the inkjet printer 1 is, for example, A0 size (841 mm x 1189 mm).

[0029] The paper feeder 20 takes out the stack of paper P set inside, one sheet at a time from the top, and supplies it to the transport path 12.

[0030] The image forming unit 40 performs image formation by ejecting droplets onto the recording surface Pa of the paper P. The image forming unit 40 includes a drawing drum 41 and a head unit 42. The drawing drum 41 receives the paper P from the paper feed drum 16, subjects the received paper P to image formation by the head unit 42, and discharges the paper P from the discharge drum 18. The drawing drum 41 is equipped with a gripper (not shown) on its circumferential surface, and by gripping the leading edge of the paper P with the gripper and rotating it, the paper P is wrapped around the circumferential surface of the drum and transported. The drawing drum 41 is also equipped with a suction mechanism (not shown), which suctions the paper P wrapped around the circumferential surface of the drum and transports it. Negative pressure is used for suction. The drawing drum 41 is equipped with numerous suction holes on its circumferential surface, and by suction from inside the drawing drum 41 through these suction holes, the paper P is suctioned to the circumferential surface of the drawing drum 41.

[0031] The head unit 42 includes print bars 43C, 43M, 43Y, and 43K. Print bar 43C is equipped with an inkjet head 45C that ejects droplets of cyan ink. Print bar 43M is equipped with an inkjet head 45M that ejects droplets of magenta ink. Print bar 43Y is equipped with an inkjet head 45Y that ejects droplets of yellow ink. Print bar 43K is equipped with an inkjet head 45K that ejects droplets of black ink. In the following, print bars 43C, 43M, 43Y, and 43K have the same configuration and will be referred to as print bar 43 when there is no need to distinguish between them. Similarly, when there is no need to distinguish between inkjet heads 45C, 45M, 45Y, and 45K, they will be referred to as inkjet head 45.

[0032] As shown in Figure 2, the print bar 43 comprises a rectangular prism-shaped housing 44, and an inkjet head 45, a circuit board 46, and a flexible cable 47, each housed within the housing 44. Therefore, in this example, the inkjet head 45 is housed within the print bar 43 and moves integrally with the print bar 43. In the following, when we refer to moving the inkjet head 45 or tilting the nozzle surface 49 of the inkjet head 45, we are actually referring to moving or tilting the inkjet head 45 together with the print bar 43. Also, the nozzle surface of the print bar 43 is synonymous with the nozzle surface 49 of the inkjet head 45.

[0033] Figure 3 is a front view of the inkjet head 45 as seen from the nozzle surface 49 side. The inkjet head 45 is a line head composed of multiple (in this case, n) head modules 48-i (i = 1, 2, ..., n) connected together. The inkjet head 45 consists of multiple head modules 48-i (i = 1, 2, ..., n) arranged along the longitudinal direction X. Each head module 48-i (i = 1, 2, ..., n) has multiple nozzles 50 for ejecting liquid.

[0034] Multiple head modules 48-i (i=1, 2, ..., n) are mounted and integrated on a common frame 51. In the following, when it is not necessary to distinguish between head modules 48-i (i=1, 2, ..., n), they will be referred to simply as head module 48. Also, in the following, when referring to head module 48-i, (i=1, 2, ..., n) may be omitted. The number of head modules 48 and their arrangement are not limited to the illustrated example. By combining two or more appropriate numbers of head modules, an inkjet head 45 with a desired recordable width can be constructed. Note that a head module 48 may also be used as an inkjet head on its own.

[0035] The head modules 48-i (i=1, 2, ... n) each have a nozzle region 52-i (i=1, 2, ... n) where nozzles 50 are provided on the nozzle surface 49-i (i=1, 2, ... n), and a wing region 54-i (i=1, 2, ... n) where no nozzles 50 are provided. The wing regions 54-i (i=1, 2, ... n) are provided on both sides of the nozzle region 52-i (i=1, 2, ... n), sandwiching the nozzle region 52-i (i=1, 2, ... n). The nozzle region 52-i (i=1, 2, ... n) is one surface of the nozzle plate on which the nozzles 50 are formed, and the wing region 54-i (i=1, 2, ... n) is one surface of a support member that supports the nozzle plate from both widthwise sides. A liquid-repellent film 55 is provided in the nozzle region 52-i (i=1, 2, ... n). In FIG. 3, the number of nozzles is drawn reduced for convenience of illustration, but for example, 32×64 nozzles 50 are two-dimensionally arranged on the nozzle surface 49-i of one head module 48-i. The nozzle density in the longitudinal direction of the nozzle surface 49-i is, for example, 1200 dpi (dot per inch).

[0036] As described above, the nozzle surface 49 of the inkjet head 45 includes a plurality of nozzle surfaces 49-i (i=1, 2, ... n). The nozzle surface 49 of the inkjet head 45 includes a nozzle region 52 and a wing region 54. The nozzle region 52 includes a plurality of nozzle regions 52-i (i=1, 2, ... n). The wing region 54 includes a plurality of wing regions 54-i (i=1, 2, ... n). At least the nozzle region 52 of the nozzle surface 49 is provided with a liquid-repellent film 55. The liquid-repellent film 55 will be described later.

[0037] The print bar 43 is arranged in a posture where the nozzle surface 49 faces the recording surface Pa. In the image forming unit 40, the print bar 43 is arranged such that the longitudinal direction X intersects the conveyance direction Y of the paper P (in this example, perpendicular to each other). Further, as shown in FIG. 1, the plurality of print bars 43C, 43M, 43Y, 43K are arranged in sequence along the conveyance direction Y.

[0038] Further, in the respective inkjet heads 45C, 45M, 45Y, and 45K of the print bars 43C, 43M, 43Y, and 43K, the corresponding inks are supplied by an ink supply mechanism not shown in FIG. 1. Various inks such as water-based ink, oil-based ink, or solvent-based ink can be used as drawing ink in the inkjet printing apparatus.

[0039] The head module 48 includes flow paths communicating with the respective nozzles 50, and individual pressure chambers in part of the flow paths, and ejection energy generating elements that generate ejection energy required for ejecting liquid droplets. As the ejection energy generating element, for example, a piezoelectric element is provided. The piezoelectric element is disposed on a vibration plate that constitutes one surface of the pressure chamber. When the piezoelectric element displaces the vibration plate, ink droplets are ejected from the nozzles 50 due to the displacement of the vibration plate.

[0040] In the image forming unit 40, ink droplets are ejected toward the paper P conveyed by the drawing drum 41, and the ejected droplets adhere to the paper P, whereby an image is formed on the paper P.

[0041] Note that in this example, a configuration using four colors of CMYK inks is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and print bars for light ink, dark ink, special color ink and the like may be added as necessary. Also, the arrangement order of the print bars for respective colors is not particularly limited.

[0042] The stacking device 80 stacks the paper P on which an image has been formed. The stacking device 80 receives the paper P discharged from the conveyance path 12, and stacks the paper P in a bundle on a stacking tray (not shown).

[0043] In the inkjet printing apparatus 1 of this configuration, the paper P is conveyed along the conveyance path 12 from the paper feeding device 20 by the conveyance mechanism 10, image formation (printing) is performed by the image forming unit 40, and the paper P on which the image is formed is discharged to the stacking device 80.

[0044] Here, we will describe the liquid-repellent film 55 provided on the nozzle surface 49 of the inkjet head 45. The liquid-repellent film 55 is provided in the nozzle region 52 where the nozzle 50 is formed. The wing region 54 may or may not have the liquid-repellent film 55.

[0045] The liquid-repellent film 55 may be a fluorine-based liquid-repellent film or a non-fluorine-based liquid-repellent film. Preferably, the material of the liquid-repellent film 55 is a material that is not subject to PFAS regulations. The contact angle of the liquid-repellent film 55 with respect to the ink is preferably 60 degrees or more, more preferably 70 degrees or more, and even more preferably 80 degrees or more. By forming the liquid-repellent film 55 in the nozzle region 52, the wipe resistance of the nozzle region 52 can be improved, and the recovery of ink that overflows from the nozzle 50 during ink discharge into the nozzle can be easily facilitated. The contact angle referred to here is the static contact angle θS.

[0046] The static contact angle θS is represented by the angle between the tangent to the edge of the liquid surface of an ink droplet at rest on the surface of the liquid-repellent film and the surface of the liquid-repellent film, as shown in Figure 4. A relatively larger static contact angle θS indicates relatively better liquid repellency. Static contact angle measurement is performed, for example, in accordance with ISO 19403-5.

[0047] A non-fluorine-based material preferred as the material for the liquid-repellent film 55 has a substructure represented by the following formula 1: (L-Y) ｋ Si-(O-*) ４－ｋ Formula 1

[0048] In formula 1, L is a hydrocarbon group, Y is a single bond or a divalent linking group that does not contain a fluorine atom, k is an integer between 1 and 3, and * indicates the bond position with other structures.

[0049] The hydrocarbon group represented by L in Formula 1 may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. The hydrocarbon group is preferably an aliphatic hydrocarbon group, and more preferably an alkyl group. The alkyl group may be a linear alkyl group, a branched alkyl group, or a cyclic alkyl group.

[0050] The number of carbon atoms in the hydrocarbon group is preferably 1 to 30, more preferably 1 to 20. The hydrocarbon group may have a substituent. The substituent preferably does not contain a fluorine atom.

[0051] Examples of the divalent linking group containing no fluorine atom represented by Y in Formula 1 include a combination of at least one selected from the group consisting of -O-, -C(=O)-, and NR-, and a hydrocarbon group. R represents a hydrogen atom or a hydrocarbon group. However, the linking portion of Y to L is not a hydrocarbon group.

[0052] When Y is a divalent linking group, examples of Y include * １ -O-C(=O)-(hydrocarbon group)-C(=O)-O-(hydrocarbon group)-* ２ * １ -O-(hydrocarbon group)-O-(hydrocarbon group)-* ２ * １ -C(=O)-NH-(hydrocarbon group)-* ２ * １ -NH-C(=O)-NH-(hydrocarbon group)-* ２ * １ -O-C(=O)-NH-(hydrocarbon group)-* ２ and the like are mentioned.

[0053] * １ means the bonding position to L, and * ２ means the bonding position to Si.

[0054] The hydrocarbon group contained in the fluorine-free divalent linking group represented by Y in Formula 1 may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. The aforementioned hydrocarbon group is preferably an aliphatic hydrocarbon group, more preferably an alkylene group. The alkylene group may be any of a linear alkylene group, a branched alkylene group, and a cyclic alkylene group. The alkylene group is preferably a linear alkylene group.

[0055] From the viewpoint of improving the durability of the non-fluorine liquid-repellent film by further aggregating the hydrocarbon groups with each other, Y is preferably a single bond. Also, from the viewpoint of ejection reliability, k is preferably 3 or more.

[0056] The substructure represented by formula 1 above is preferably formed using a compound represented by formula 11 or formula 12 below. L-Y-SiX ３ Formula 11 LY-SiNR １１ NSi-Y-L Formula 12

[0057] In formula 11, L is a hydrocarbon group, Y is a single bond or a divalent linking group that does not contain a fluorine atom, and X is independently a hydrolyzable group. Compounds represented using formula 11 and compounds represented using formula 12 may be used in combination, and compounds other than those represented using formula 11 and formula 12 that do not contain a fluorine atom may be used in combination, to the extent that the effects resulting from the use of the above compounds are not impaired.

[0058] In formula 12, L is independently a hydrocarbon group, Y is independently a single bond or a divalent linking group that does not contain a fluorine atom, and R １１ This is either a hydrogen atom or a methyl group.

[0059] The preferred embodiment of the hydrocarbon group represented by L in formulas 11 and 12 is the same as the hydrocarbon group represented by L in formula 1. The preferred embodiment of the fluorine-free divalent linking group represented by Y in formulas 11 and 12 is the same as the fluorine-free divalent linking group represented by Y in formula 1. In formulas 11 and 12, Y is preferably a single bond.

[0060] Examples of hydrolyzable groups represented by X in formula 11 include halogen atoms, alkoxy groups, and acyloxy groups. Hydrolyzable groups are preferably halogen atoms or alkoxy groups, and more preferably alkoxy groups.

[0061] Examples of halogen atoms include chlorine, bromine, and iodine atoms. Chlorine atoms are preferred as the halogen atom. The alkoxy group is preferably an alkoxy group having 1 to 6 carbon atoms, and more preferably an alkoxy group having 1 to 3 carbon atoms. When the hydrolyzable group is an alkoxy group, the density of the liquid-repellent film is relatively improved, and alkali resistance is also relatively improved.

[0062] A liquid-repellent film having a substructure represented by formula 1 can be obtained using a compound represented by formula 11 or formula 12. The liquid-repellent film may contain hydrolysates of the compound represented by formula 11 or formula 12. The hydrolysates of the compound represented by formula 11 or formula 12 have Si-O-Si bonds, which can relatively improve the durability of the non-fluorine-based liquid-repellent film.

[0063] The thickness of the liquid-repellent film 55 is preferably 50 nm (nanometers) or less, and more preferably 0.5 nm to 40 nm. When the thickness of the liquid-repellent film 55 is 50 nm or less, deviation in the direction of droplet discharge is suppressed, and the straightness of discharge is improved.

[0064] "Cleaning Method" Hereinafter, an embodiment of the inkjet head cleaning method of the present disclosure will be described. The inkjet head cleaning method of the present disclosure is applicable to cleaning an inkjet head 45 which has, for example, a nozzle surface 49 including a nozzle region 52 on which a plurality of nozzles 50 for ejecting ink are provided, and which has a liquid-repellent film 55 on at least the nozzle region 52. The inkjet head cleaning method of the present disclosure includes a cleaning solution application step of applying a cleaning solution to the nozzle region 52. During or after the cleaning solution application step, the inkjet head 45 is supported in an inclined position such that the inclination angle α of the nozzle surface with respect to the horizontal plane is equal to or greater than the sliding angle θm of the cleaning solution in the liquid-repellent film 55.

[0065] The inclination angle α of the nozzle surface 49 refers to the angle of inclination of the nozzle surface 49 with respect to the horizontal plane. As in the embodiment shown in Figure 1, when the inkjet head 45 is positioned vertically above the paper P, the inclination angle α of the nozzle surface is the angle between the horizontal plane below the nozzle surface and the nozzle surface, as shown in Figure 5A. On the other hand, when the inkjet head is positioned vertically below the paper, the inclination angle α of the nozzle surface is the angle between the horizontal plane above the nozzle surface and the nozzle surface, as shown in Figure 5B. Hereinafter, the inclination angle α of the nozzle surface 49 may be referred to as the inclination angle α of the inkjet head 45.

[0066] The sliding angle θm of the cleaning solution on the liquid-repellent film 55 refers to the angle of inclination at which the cleaning solution droplets on the surface begin to move downward along the slope when the cleaning solution S is applied to the nozzle surface 49 coated with the liquid-repellent film 55 while the nozzle surface 49 is held horizontally and the nozzle surface 49 is gradually tilted. In the embodiment shown in Figure 1, when the inkjet head 45 is positioned vertically above the paper P, first, as shown in Figure 6A, the nozzle surface of the inkjet head is supported horizontally and vertically downward. Then, the cleaning solution is applied to the liquid-repellent film provided on the nozzle surface. After that, the nozzle surface is tilted so that the inclination with respect to the horizontal plane gradually increases. In this case, the angle between the liquid-repellent film surface and the horizontal plane when the cleaning solution droplets begin to move is the sliding angle θm of the cleaning solution with respect to the liquid-repellent film when the nozzle surface is vertically downward. On the other hand, when the inkjet head is positioned vertically below the paper, first, as shown in Figure 6B, the nozzle surface of the inkjet head equipped with the liquid-repellent film is supported horizontally and vertically upward. Next, the cleaning solution is applied to the liquid-repellent film on the nozzle surface. Then, the nozzle surface is tilted so that the inclination gradually increases with respect to the horizontal plane. In this case, the angle between the liquid-repellent film surface and the horizontal plane when the cleaning solution begins to move is the sliding angle θm of the cleaning solution relative to the liquid-repellent film when the nozzle surface is vertically upward. For measuring the sliding angle, for example, a contact angle meter DMs-401 (manufactured by Kyowa Interface Science Co., Ltd.) can be used.

[0067] In the case of the liquid-repellent film 55 made of the non-fluorine-based material described above, our studies showed that the sliding angle of the cleaning solution was approximately 10 to 40 degrees. Depending on the combination of cleaning solution and liquid-repellent film, the sliding angle tends to be smaller when the liquid repellency is good and larger when the liquid repellency is poor. Generally, liquid-repellent films that comply with PFAS regulations tend to have lower liquid repellency and a larger sliding angle compared to conventional fluorine-based liquid-repellent films.

[0068] A more detailed explanation of the cleaning method will be provided, along with the configuration of the cleaning device 100.

[0069] "First Embodiment of Cleaning Method" In an inkjet printing apparatus 1, the case in which the inkjet head 45 is supported at an inclination angle α of the nozzle surface 49 with respect to the horizontal plane that is greater than or equal to the sliding angle θm of the cleaning solution with respect to the liquid-repellent film 55 provided on the nozzle surface 49 is described. For example, the case in which the inclination angle α of the inkjet head 45 is 24 degrees and the sliding angle θm is 20 degrees.

[0070] As shown in Figure 7, the cleaning process includes a cleaning solution application step (S11) in which cleaning solution S is simply applied to the nozzle surface 49 without changing the tilt angle α of the inkjet head 45. In the cleaning solution application step S11, cleaning solution S is applied to the nozzle surface 49 to clean the nozzle surface 49.

[0071] The cleaning device 100 includes, for example, a support section 70 for supporting the inkjet head 45 and a cleaning liquid application section 60. As shown in Figure 8, the inkjet head 45 is supported by the support section 70 in an inclined position such that the inclination angle α is greater than or equal to the sliding angle θm of the cleaning liquid S in the liquid-repellent film 55 while the cleaning liquid S is applied to the nozzle surface 49 by the cleaning liquid application section 60, i.e., during the cleaning liquid application process. The support section 70 includes, for example, a head frame 71 that supports the inkjet head 45 in an inclined position. The cleaning liquid application section 60 includes, for example, a spray nozzle 61 that sprays the cleaning liquid S toward the nozzle surface 49. The cleaning liquid application section 60 may also include a moving mechanism that moves the spray nozzle 61 relative to the nozzle surface 49.

[0072] The cleaning liquid S applied to the nozzle surface 49 flows downward along the nozzle surface 49 due to gravity (in the direction indicated by the arrow in Figure 8) and is removed from the nozzle surface 49. By making the inclination angle α greater than or equal to the sliding angle θm, the cleaning liquid S slides off more easily, and its residue on the liquid-repellent film 55 can be suppressed.

[0073] "Second form of cleaning method" The cleaning method preferably includes a wiping step (S12) to wipe off at least a portion of the nozzle surface 49 after the cleaning solution application step (S11), as shown in Figure 9. After the cleaning solution application step, the cleaning solution S flows downward along the nozzle surface 49 due to gravity, but as shown in Figure 10, it may remain at the bottom vertical end of the inclined inkjet head 45.

[0074] Therefore, it is preferable to wipe away any remaining liquid at the edges in the wiping step S12. In this case, as shown in Figure 11A, the cleaning device 100 includes a wiping member 62 in addition to the cleaning liquid application unit 60. As shown in Figure 11A, it is preferable to use the wiping member 62 to wipe away any remaining liquid at the bottom vertical end of the inkjet head 45 while maintaining the inclined position of the inkjet head 45. The edges of the inkjet head 45 include at least a portion of the nozzle surface 49. Note that in the wiping step S12, not only may at least a portion of the nozzle surface 49 be wiped away, but the entire surface of the nozzle surface 49 may also be wiped away with the wiping member 62, as shown in Figure 11B.

[0075] Furthermore, since it is desirable to avoid wiping the nozzle area 52 (see Figure 3), the method of wiping away the remaining liquid at the edges, as shown in Figure 11A, is more preferable. In the cleaning liquid application step, the cleaning liquid S is applied to the nozzle surface 49 under the condition that the inclination angle α ≥ the sliding angle θm, so ink mist and other particles that were attached to the nozzle surface 49 before the application of the cleaning liquid S are largely removed along with the cleaning liquid S. Therefore, even when the entire surface of the nozzle surface 49 is wiped as shown in Figure 11B, wiping damage caused by pigments and other particles contained in the ink is suppressed.

[0076] This cleaning method is particularly effective for inkjet heads that eject inks containing hard pigments, such as black ink using black carbon black pigment and white ink using white titanium dioxide pigment. Since the hard pigment is removed from the nozzle surface 49 before wiping, damage to the nozzle surface 49 during wiping can be suppressed.

[0077] The wiping member 62 can be a blade or a nonwoven fabric. Using a nonwoven fabric is more effective in reducing damage to the nozzle surface.

[0078] "Third form of cleaning method" In an inkjet printing apparatus 1, the case in which the inkjet head 45 is supported such that the inclination angle α of the nozzle surface 49 with respect to the horizontal plane is less than the sliding angle θm of the cleaning solution with respect to the liquid-repellent film 55 provided on the nozzle surface 49 (α < θm) is described. For example, the case in which the inclination angle α is 8 degrees and the sliding angle θm is 20 degrees.

[0079] As shown in Figure 12, the third cleaning method includes a step (S20) of tilting the inkjet head 45 so that its tilt angle α is greater than or equal to the sliding angle θm. For example, the tilt angle α is tilted from an initial angle of 8 degrees to 24 degrees, which exceeds the sliding angle θm. Then, a cleaning solution S is applied to the nozzle surface 49 (S21), and after the cleaning solution application step, the tilt angle α of the inkjet head 45 is returned to its original position (S23). For example, the tilt angle α, which was tilted to 24 degrees, is returned to its initial angle of 8 degrees. In this case, as shown in Figure 13, the cleaning device 100 only needs to be equipped with a tilt adjustment mechanism 72 that tilts the inkjet head 45 together with the head frame 71, in addition to the head frame 71, as a support part 70. The tilt adjustment mechanism 72 is configured to switch between, for example, a first state in which the inkjet head 45 is supported in a position in which the tilt angle (tilt angle α) of the nozzle surface 49 is smaller than the sliding angle θm, and a second state in which the inkjet head 45 is supported in a tilted position in which the tilt angle α is greater than or equal to the sliding angle θm. The tilt adjustment mechanism 72 can be configured, for example, with a motor-driven hinge, a cam mechanism including a rotating cam, etc. Preferably, the tilt adjustment mechanism 72 is configured to allow the tilt angle α to be freely adjusted.

[0080] When the inclination angle α < sliding angle θm, the applied cleaning liquid S does not slide off and remains on the nozzle surface 49. However, by setting α ≥ θm, the cleaning liquid S slides off and is removed from the nozzle surface 49. In the example shown in Figure 12, the cleaning liquid S is applied after the inclination angle α is tilted to the sliding angle θm or greater, and the inclined position is maintained during the cleaning liquid application process. However, the inclination angle α may be tilted to the sliding angle θm or greater after the cleaning liquid S has been applied. In other words, steps S20 and S21 in Figure 12 may be in the reverse order. Also, the inclination angle α may be tilted to the sliding angle θm or greater while the cleaning liquid S is being applied to the nozzle surface 49. In any of these embodiments, if the inclination angle α ≥ sliding angle θm is maintained during or after the cleaning liquid application process, the cleaning liquid S can be made to slide off.

[0081] "Fourth Embodiment of Cleaning Method" In addition, even when the step of tilting the inclination angle α (S20) is included, it is preferable to include a wiping step (S22) in which at least a part of the nozzle surface 49 is wiped after the cleaning solution application step (S21), as in the fourth embodiment of cleaning method shown in Figure 14. The cleaning solution application step (S21) and the wiping step (S22) are the same as the cleaning solution application step (S11) and the wiping step (S12) in the second embodiment.

[0082] Note that the wiping step (S22) may be performed after the step (S23) in which the tilt angle α of the inkjet head 45 is returned to its original position. In other words, steps S22 and S23 in Figure 14 may be performed in the reverse order. However, as described above, if the inkjet head 45 is tilted, liquid will accumulate at the edges (see Figure 10), so it is preferable to perform the step (S23) in which the tilt angle α is returned to its original position after the wiping step (S22), since only the edges need to be wiped.

[0083] "Fifth form of cleaning method" In an inkjet printing apparatus 1, if the inkjet head 45 is supported at an inclination angle α of the nozzle surface 49 with respect to the horizontal plane that is greater than or equal to the sliding angle θm of the cleaning solution with respect to the liquid-repellent film 55 provided on the nozzle surface 49, cleaning may be performed by the following procedure.

[0084] As shown in Figure 15, first, the inclination angle α of the inkjet head 45 is set to be less than the sliding angle θm (S30). For example, the inkjet head 45 is positioned such that the inclination angle α is smaller than the sliding angle θm, such as by making the nozzle surface 49 approximately horizontal. Then, the cleaning solution S is applied to the nozzle surface 49, which is supported so that the inclination angle α is less than the sliding angle θm (S31).

[0085] Then, after the cleaning solution application step (S31), the inkjet head 45 is tilted so that the inclination angle α is greater than or equal to the sliding angle θm (S32). After that, at least a portion of the nozzle surface 49 is wiped (S33), and finally, the inclination angle α of the inkjet head 45 is returned to its original position (S34).

[0086] When the cleaning solution S is applied while the nozzle surface 49 is maintained at an inclination angle α less than the sliding angle θm, the time the cleaning solution S is retained in the nozzle region 52 is longer compared to when the cleaning solution S is applied while the nozzle surface is inclined at an inclination angle of θm or more. Therefore, the dissolving effect of the cleaning solution S on the ink solidification components can be enhanced. For example, the effect of redispersing aggregated pigments or aggregated latex in the ink is enhanced, improving the cleaning effect.

[0087] Furthermore, it is preferable to maintain the nozzle surface 49 at a nearly horizontal angle, as a smaller inclination of the nozzle surface 49 allows for a longer time to retain the cleaning solution S in the nozzle area 52. In addition, as in the third and fourth embodiments, in the inkjet printing apparatus 1, if the inkjet head 45 is supported such that the inclination angle α of the nozzle surface 49 with respect to the horizontal plane is less than the sliding angle θm of the cleaning solution with respect to the liquid-repellent film 55 provided on the nozzle surface 49 (α < θm), then if the step of tilting the inclination angle α to be greater than or equal to the sliding angle θm (S20) is performed after the cleaning solution application step (S21), the cleaning solution S can be retained in the nozzle area 52, thereby improving the ink cleaning effect, similar to the fifth embodiment.

[0088] In each of the above cleaning methods, during or after the cleaning solution application step, the inkjet head 45 is supported in an inclined position such that the inclination angle α of the nozzle surface 49 with respect to the horizontal plane is greater than or equal to the sliding angle θm of the cleaning solution in the liquid-repellent film 55. With this configuration, the cleaning solution and ink can be quickly slid off from the nozzle area 52, and the occurrence of liquid residue in the nozzle area 52 can be suppressed. By suppressing liquid residue in the nozzle area 52, the decrease in the ejection performance of the inkjet head 45 can be suppressed, and the ejection stability can be improved.

[0089] Furthermore, by applying the cleaning solution S and cleaning the nozzle surface 49, ink mist remaining on the nozzle surface 49 and solidifying ink can be dissolved by the cleaning solution S and removed from the nozzle surface 49. Since cleaning can be performed without contact with the liquid-repellent film 55, this method is suitable when the liquid-repellent film has low abrasion resistance, such as a non-fluorine-based liquid-repellent film.

[0090] Furthermore, when wiping after cleaning with the cleaning solution S, even if the liquid-repellent film 55 has low abrasion resistance, the ink has been removed by the cleaning solution application step, so damage to the liquid-repellent film 55 during wiping can be suppressed. Also, as shown in Figure 11A, if, during the wiping step, the inkjet head 45 is supported in an inclined position and the water-repellent film 55 is not wiped off by wiping the part of the nozzle surface 49 that is at the bottom in the vertical direction, damage to the liquid-repellent film 55 can be suppressed.

[0091] In the above description, a cleaning fluid application unit 60 for applying cleaning fluid S to the nozzle surface 49 was described, which includes a spray nozzle 61 as shown in Figure 8, and in which the cleaning fluid S is sprayed onto the nozzle surface 49. However, the method of applying the cleaning fluid S is not limited to this. As shown in Figure 16, the cleaning fluid application unit 60 may include a cleaning fluid application head 68 which includes a cleaning fluid holding surface 64 that faces the nozzle surface 49 and is inclined at the same inclination angle α as the nozzle surface 49, and a cleaning fluid supply passage 65 that supplies cleaning fluid to the upper part in the inclination direction of the cleaning fluid holding surface. The cleaning fluid application head 68 cleans the nozzle surface 49 facing the cleaning fluid holding surface 64 with the cleaning fluid S held on the cleaning fluid holding surface 64. A cleaning fluid outlet 67 that communicates with the cleaning fluid supply passage 65 is provided near the upper part in the inclination direction of the cleaning fluid holding surface 64, at a position that faces the wing region 54 where the nozzle 50 of the nozzle surface 49 is not formed when the nozzle surface 49 and the cleaning fluid holding surface 64 face each other.

[0092] When applying cleaning fluid to the nozzle surface 49, the cleaning fluid holding surface 64 is positioned opposite the nozzle surface 49, and the cleaning fluid S supplied from the cleaning fluid supply passage 65 is ejected from the cleaning fluid outlet 67. The cleaning fluid S ejected from the cleaning fluid outlet 67 flows down the inclined cleaning fluid holding surface 64. As a result, a layer (film) of cleaning fluid S is formed on the cleaning fluid holding surface 64. By bringing the nozzle surface 49 of the inkjet head 45 into contact with the layer of cleaning fluid S formed on the cleaning fluid holding surface 64, the cleaning fluid S is applied to the nozzle surface 49, and the nozzle surface 49 is cleaned by the applied cleaning fluid S.

[0093] Rather than spraying the cleaning solution S forcefully towards the nozzle surface 49, it is preferable to spray it gently at a level that does not cause dirt adhering to the nozzle surface 49 to scatter. By spraying gently, it is possible to suppress the scattering of dirt adhering to the nozzle surface 49, and also to suppress the risk of air bubbles in the cleaning solution S entering the nozzle. For this reason, it is more preferable to apply the cleaning solution S to the nozzle surface 49 in a manner that brings the nozzle surface 49 into contact with the cleaning solution S flowing down a slope, as shown in Figure 16.

[0094] Figure 17 is a plan view of the nozzle surface 49 of the inkjet head 45 and is an explanatory diagram for explaining the axis of inclination X. When tilting the nozzle surface 49 of the inkjet head 45 for cleaning, it is preferable to tilt it around the rotation axis Ax along the longitudinal direction (X direction) of the inkjet head 45 (see also Figure 13). The nozzle surface 49 of the inkjet head 45 can also be tilted by rotating it around an axis parallel to the short direction. However, as shown in Figures 13 and 17, tilting by rotating it around an axis X parallel to the longitudinal direction results in a shorter overall distance over which the cleaning liquid S and ink slide down, and fewer nozzles on the sliding path, thus reducing residual liquid after sliding down. In addition, tilting by rotating it around an axis X parallel to the longitudinal direction results in a shorter rotation stroke, which prevents interference with other parts when rotated.

[0095] In the explanation of each cleaning method described above, Figures 8, 10, 11, 13, and 16 schematically show the configuration in which the inkjet head 45 is supported by the head frame 71. In the inkjet printing apparatus 1 shown in Figure 1, the inkjet head 45 is located within the print bar 43, so the inkjet head 45 is not directly supported by the head frame 71. Specifically, as shown in Figure 18, each print bar 43C, 43M, 43Y, and 43K is supported by the head frame 71. The head unit 42 is composed of the head frame 71 and the print bars 43C, 43M, 43Y, and 43K supported by the head frame 71. As shown in Figure 1(B), the linear movement mechanism 90 moves the head unit 42 between the image recording position and the retracted position. The linear movement mechanism 90 corresponds to the movement mechanism that realizes the relative movement between the inkjet head 45 and the cleaning liquid application unit 60 and the wiping member 62 in the cleaning apparatus 100.

[0096] As shown in Figure 1(B), the cleaning device 100 is positioned in the path that moves the image forming unit 40 to the retracted position. Figure 19 shows the cleaning device 100 positioned between the image recording position and the retracted position. Here, the retracted position is a position for retracting the image forming unit 40 from the image recording position during maintenance of the image forming unit 40 or the transport path, etc. The cleaning device 100 includes a cleaning fluid application unit 60 and a wiping member 62. Here, the wiping member 62 is positioned closer to the image recording position than the cleaning fluid application unit 60. In this case, when the image forming unit 40 is moved from the retracted position to the image recording position, the cleaning fluid application unit 60 applies cleaning fluid S to the nozzle surface 49, and then the wiping member 62 wipes it.

[0097] The relative positions of the cleaning fluid application unit 60 and the wiping member 62 may be reversed, and the cleaning fluid application unit 60 may be positioned closer to the image recording position than the wiping member 62. In that case, when the image forming unit 40 is moved from the image recording position to the retracted position, the cleaning fluid application unit 60 can apply the cleaning fluid S to the nozzle surface 49, and then the wiping member 62 can wipe it. For more specific configuration examples of the cleaning fluid application unit 60 and the wiping member 62, see, for example, International Publication No. 2020 / 095822.

[0098] As shown in Figure 18, the head frame 71 supports the print bars 43C, 43M, 43Y, and 43K radially arranged at regular intervals on concentric circles centered on the rotation axis of the drawing drum 41. Each nozzle surface 49C, 49M, 49Y, and 49K of each print bar 43C, 43M, 43Y, and 43K has an inclination with respect to the horizontal plane. The cleaning device 100 is equipped with an inclination adjustment function (not shown in Figure 18) that adjusts the inclination of the print bars 43C, 43M, 43Y, and 43K according to the relationship between the nozzle surface 49C, 49M, 49Y, and 49K and the sliding angle θm. For example, it is sufficient to provide an inclination adjustment mechanism 72 that tilts the entire head frame 71 as shown in Figure 13.

[0099] Furthermore, among the print bars 43C, 43M, 43Y, and 43K, if the inclination angle α of print bars 43C and 43K, which have a large inclination of the nozzle surface, is greater than the sliding angle θm, a cleaning method that does not change the inclination angle α may be adopted for these two print bars 43C and 43K. In this case, the inclination angle α of print bars 43M and 43Y is tilted during or after the cleaning process so that it is greater than or equal to the sliding angle θm. For this reason, the head frame 71 may be configured to include an inclination adjustment mechanism at the mounting portion of print bar 43M and the mounting portion of print bar 43Y to adjust the inclination of each print bar 43M and 43Y.

[0100] The embodiments of the technology described above can be modified, added to, or deleted as appropriate, without departing from the spirit of the technology of this disclosure. The present invention is not limited to the embodiments described above, and many modifications are possible within the technical concept of the technology of this disclosure by those with ordinary skill in the art.

[0101] Furthermore, the disclosure of Japanese Patent Application No. 2025-066431, filed on April 14, 2025, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

[0102] The following further notes are disclosed regarding the above embodiments. <Note 1> A method for cleaning an inkjet head, comprising a cleaning solution application step of applying a cleaning solution to the nozzle area, wherein the cleaning solution is supported in an inclined position during or after the cleaning solution application step, such that the inclination angle of the nozzle surface with respect to the horizontal plane is greater than or equal to the sliding angle of the cleaning solution in the liquid-repellent film. <Note 2> The method for cleaning an inkjet head according to Note 1, wherein a wiping step of wiping at least a part of the nozzle surface is performed after the cleaning solution application step. <Note 3> The method for cleaning an inkjet head according to Note 2, wherein the cleaning solution is supported in an inclined position during the cleaning solution application step, and the wiping step is performed while maintaining the inclined position of the inkjet head. <Note 4> The method for cleaning an inkjet head as described in Note 2, wherein during the cleaning solution application step, the inkjet head is supported in a position where the inclination angle of the nozzle surface is smaller than the sliding angle, and after the cleaning solution application step, the inkjet head is tilted to an inclined position, and the wiping step is performed with the inkjet head supported in the inclined position. <Note 5> The method for cleaning an inkjet head as described in Note 3 or Note 4, wherein in the wiping step, at least a part of the nozzle surface is wiped, with the inkjet head supported in an inclined position, the part of the nozzle surface that is at the lowest vertical position. <Note 6> The method for cleaning an inkjet head as described in any one of Notes 1 to 5, wherein the inkjet head is an inkjet head that ejects ink containing carbon black pigment or titanium dioxide pigment as ink. <Note 7> The method for cleaning an inkjet head as described in any one of Notes 1 to 6, wherein the inkjet head is an inkjet head having either a fluorine-based liquid-repellent film or a non-fluorine-based liquid-repellent film on the nozzle surface as a liquid-repellent film.<Note 8> An inkjet head cleaning device comprising: a cleaning liquid application unit for applying cleaning liquid to the nozzle surface; and a support unit for supporting the inkjet head, the support unit being configured to support the inkjet head in an inclined position where the inclination angle of the nozzle surface with respect to the horizontal plane is greater than or equal to the sliding angle of the cleaning liquid in the liquid-repellent film. <Note 9> The inkjet head cleaning device according to Note 8, wherein the support unit is equipped with an inclination adjustment mechanism that switches between a first state in which the inkjet head is supported in a position in which the inclination angle of the nozzle surface is less than the sliding angle, and a second state in which it is supported in an inclined position. <Note 10> The inkjet head cleaning device according to Note 8 or Note 9, further comprising: a wiping member for wiping at least a part of the inkjet head. <Note 11> An inkjet head cleaning device according to any one of Notes 8 to 10, wherein the inkjet head is an inkjet head that ejects ink containing carbon black pigment or titanium dioxide pigment as ink. <Note 12> An inkjet head cleaning device according to any one of Notes 8 to 11, wherein the inkjet head is an inkjet head having either a fluorine-based liquid-repellent film or a non-fluorine-based liquid-repellent film on the nozzle surface as a liquid-repellent film.

Claims

1. A method for cleaning an inkjet head, comprising a step of applying a cleaning solution to the nozzle region, the nozzle surface of which a plurality of nozzles for ejecting ink are provided, wherein at least the nozzle region is provided with a liquid-repellent film, the method comprising: a step of applying a cleaning solution to the nozzle region, the method of supporting the inkjet head during or after the cleaning solution application step, in an inclined position such that the inclination angle of the nozzle surface with respect to the horizontal plane is greater than or equal to the sliding angle of the cleaning solution in the liquid-repellent film.

2. The method for cleaning an inkjet head according to claim 1, wherein, after the step of applying the cleaning solution, a wiping step is performed to wipe off at least a portion of the nozzle surface.

3. The method for cleaning an inkjet head according to claim 2, wherein the inkjet head is supported in the tilted position during the cleaning solution application step, and the wiping step is performed while the tilted position of the inkjet head is maintained.

4. The method for cleaning an inkjet head according to claim 2, wherein during the cleaning solution application step, the inkjet head is supported in a position such that the inclination angle of the nozzle surface is smaller than the sliding angle, after the cleaning solution application step, the inkjet head is tilted to the inclined position, and the wiping step is performed with the inkjet head supported in the inclined position.

5. The method for cleaning an inkjet head according to claim 3 or 4, wherein in the wiping step, at least a portion of the nozzle surface is wiped, with the inkjet head supported in the inclined position, the portion of the nozzle surface that is at the lowest vertical position.

6. The method for cleaning an inkjet head according to any one of claims 1 to 4, wherein the inkjet head is an inkjet head that ejects an ink containing carbon black pigment or titanium dioxide pigment as the ink.

7. The method for cleaning an inkjet head according to claim 5, wherein the inkjet head is an inkjet head that ejects an ink containing carbon black pigment or titanium dioxide pigment as the ink.

8. The method for cleaning an inkjet head according to any one of claims 1 to 4, wherein the inkjet head is an inkjet head having either a fluorine-based liquid-repellent film or a non-fluorine-based liquid-repellent film on the nozzle surface as the liquid-repellent film.

9. The method for cleaning an inkjet head according to claim 5, wherein the inkjet head is an inkjet head having either a fluorine-based liquid-repellent film or a non-fluorine-based liquid-repellent film on the nozzle surface as the liquid-repellent film.

10. An inkjet head cleaning device comprising: a nozzle surface including a nozzle region having a plurality of nozzles for ejecting ink, wherein at least the nozzle region is provided with a liquid-repellent film, the device comprising: a cleaning liquid application unit for applying cleaning liquid to the nozzle surface; and a support unit for supporting the inkjet head, the support unit being configured to support the inkjet head in an inclined position such that the inclination angle of the nozzle surface with respect to a horizontal plane is greater than or equal to the sliding angle of the cleaning liquid in the liquid-repellent film.

11. The inkjet head cleaning apparatus according to claim 10, wherein the support portion includes a tilt adjustment mechanism that switches between a first state in which the inkjet head is supported in a position in which the tilt angle of the nozzle surface is smaller than the sliding angle, and a second state in which it is supported in the tilted position.

12. The inkjet head cleaning apparatus according to claim 10 or 11, further comprising a wiping member for wiping at least a portion of the inkjet head.

13. The inkjet head cleaning apparatus according to claim 10 or 11, wherein the inkjet head is an inkjet head that ejects an ink containing carbon black pigment or titanium oxide pigment as the ink.

14. The inkjet head cleaning apparatus according to claim 12, wherein the inkjet head is an inkjet head that ejects an ink containing carbon black pigment or titanium oxide pigment as the ink.

15. The inkjet head cleaning apparatus according to claim 10 or 11, wherein the inkjet head is an inkjet head having either a fluorine-based liquid-repellent film or a non-fluorine-based liquid-repellent film on the nozzle surface as the liquid-repellent film.

16. The inkjet head cleaning apparatus according to claim 12, wherein the inkjet head is an inkjet head having either a fluorine-based liquid-repellent film or a non-fluorine-based liquid-repellent film on the nozzle surface as the liquid-repellent film.

17. The inkjet head cleaning apparatus according to claim 13, wherein the inkjet head is an inkjet head having either a fluorine-based liquid-repellent film or a non-fluorine-based liquid-repellent film on the nozzle surface as the liquid-repellent film.

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