Liquid discharge apparatus and control method of liquid discharge apparatus

Abstract

To provide a liquid discharge apparatus capable of suppressing the deterioration of color development when using coagulant in addition to white ink and color ink of substrate.SOLUTION: A liquid discharge apparatus includes a movement mechanism which reciprocates a liquid discharge unit in a first direction and in a second direction that is opposite to the first direction, and the liquid discharge unit includes a first nozzle array which discharges white first ink, a second nozzle array which discharges white second ink, a third nozzle array which is provided between the first nozzle array and the second nozzle array in a first direction and discharges third ink of color different from the first ink and the second ink, a fourth nozzle array which is provided between the first nozzle array and the third nozzle array in the first direction, and discharges process liquid containing coagulant for coagulating an ink composition included at least in the third ink, and a fifth nozzle array which is provided between the second nozzle array and the third nozzle array and discharges the process liquid, on the nozzle surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection apparatus and a method for controlling the liquid ejection apparatus. [Background technology]

[0002] Conventionally, among liquid ejection devices that eject ink onto a medium, there is known one that uses a reactive liquid that hardens the ink (see, for example, Patent Document 1).Also, among liquid ejection devices that perform color printing using four color inks of cyan, magenta, yellow, and black, or three colors excluding black, there is known one that performs base printing using white ink (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-136538 [Patent Document 2] Japanese Patent Publication No. 2020-69676 Summary of the Invention [Problem to be solved by the invention]

[0004] When performing base printing using white ink in an apparatus that uses a reactive liquid to cure ink, it is necessary to consider the interactions between the color inks, the white ink, and the reactive liquid. For example, if white ink and color inks are ejected onto the reactive liquid, the color inks may harden due to the action of the reactive liquid before the white ink hardens, which could result in a decrease in the color development properties of the color inks. [Means for solving the problem]

[0005] One aspect of the present disclosure is a liquid ejection device comprising: a liquid ejection unit capable of ejecting liquid onto a medium being transported; and a movement mechanism that moves the liquid ejection unit back and forth in a first direction and a second direction opposite to the first direction, wherein the liquid ejection unit has, on a nozzle surface thereof: a first nozzle row that ejects a white first ink; a second nozzle row that ejects a white second ink; a third nozzle row that is disposed between the first nozzle row and the second nozzle row in the first direction and ejects a third ink of a color different from the first ink and the second ink; a fourth nozzle row that is disposed between the first nozzle row and the third nozzle row in the first direction and ejects a treatment liquid containing an aggregating agent that aggregates at least an ink composition contained in the third ink; and a fifth nozzle row that is disposed between the second nozzle row and the third nozzle row in the first direction and ejects the treatment liquid.

[0006] One aspect of the present disclosure is an ejection method for a liquid ejection device comprising: a liquid ejection unit capable of ejecting onto a transported medium a first white ink, a third ink of a different color than the first ink, and a treatment liquid containing an aggregating agent that aggregates at least a composition contained in the third ink; and a movement mechanism that moves the liquid ejection unit back and forth in a first direction and a second direction opposite to the first direction, the ejection method for a liquid ejection device including, during a period in which the liquid ejection unit moves in the first direction, a first step of ejecting the first ink onto the medium; a second step of ejecting the treatment liquid onto an area onto which the first ink was ejected in the first step; a third step of ejecting the third ink onto an area onto which the treatment liquid was ejected in the second step; and a fourth step of ejecting the treatment liquid onto an area onto which the third ink was ejected in the third step. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a perspective view showing a configuration of a liquid ejection apparatus according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a bottom view of a main part including a liquid ejection unit and a carriage. [Figure 3] FIG. 3 is an explanatory diagram showing the arrangement of heads in a liquid ejection unit. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] FIG. 4 is a diagram showing an example of a color arrangement on a head. [Figure 7] FIG. 4 is a diagram showing an example of a color arrangement on a head. [Figure 8] FIG. 4 is a diagram showing an example of a color arrangement on a head. [Figure 9] FIG. 4 is a diagram showing an example of a color arrangement on a head. [Figure 10] FIG. 4 is a diagram showing an example of a color arrangement on a head. [Figure 11] FIG. 4 is a diagram showing an example of a color arrangement on a head. [Figure 12] FIG. 4 is a diagram showing an example of a color arrangement on a head. [Figure 13] FIG. 4 is a diagram showing an example of a color arrangement on a head. DETAILED DESCRIPTION OF THE INVENTION

[0008] [1. Configuration of liquid ejection device] A liquid ejection device 11 according to the present disclosure will be described below with reference to the drawings. In each figure, the same components are given the same reference numerals, and redundant explanations will be omitted. Furthermore, in each figure, X, Y, and Z represent three spatial axes that are orthogonal to one another. In the following explanation, the directions along the X, Y, and Z axes will be referred to as the X-axis direction, Y-axis direction, and Z-axis direction, respectively. When specifying a direction, the positive direction will be indicated by "+" and the negative direction by "-", and both positive and negative signs will be used to indicate the direction, with the direction of the arrow in each figure being referred to as the + direction and the direction opposite the arrow being referred to as the - direction.

[0009] The Z-axis direction indicates the direction of gravity, the +Z direction indicates the vertically downward direction, and the -Z direction indicates the vertically upward direction. Furthermore, the three spatial axes X, Y, and Z, which are not limited to positive and negative directions, will be described as the X-axis, Y-axis, and Z-axis. In the following description, the direction along the X-axis will also be referred to as the width direction X, the direction along the Y-axis as the depth direction Y, and the direction along the Z-axis as the gravity direction Z.

[0010] FIG. 1 is a perspective view showing the configuration of a liquid ejection device 11 according to an embodiment of the present disclosure. The liquid ejection device 11 is, for example, an inkjet printer that prints by ejecting ink, which is an example of a liquid, onto a medium M such as paper.

[0011] The medium M can be a sheet containing natural or synthetic fibers, or a film or sheet made of synthetic resin. For example, the medium M can be paper, cloth, nonwoven fabric, or film. In this embodiment, the configuration of the liquid ejection device 11 that uses a long piece of cloth wound into a roll as the medium M is exemplified, but other sheets can also be used as the medium M. The present disclosure can also be applied to devices that use a sheet cut to a predetermined size as the medium M.

[0012] The liquid ejection device 11 of this embodiment ejects ink, a pretreatment liquid, and a posttreatment liquid onto the medium M. The pretreatment liquid can also be called a reaction liquid. The reaction liquid contains a component that increases the viscosity of the ink when it comes into contact with the ink and hardens the ink. When the reaction liquid mixes with the ink, the viscosity of the mixture of the ink and the reaction liquid becomes higher than the viscosity of the ink, and the mixture hardens. The posttreatment liquid is a material that coats the surface of the medium M when at least one of the pretreatment liquid and the ink is attached to the medium M, and is ejected, for example, on top of the pretreatment liquid and the ink.

[0013] The ink used by the liquid ejection device 11 is white, black, or other color ink, and may be a liquid containing a color pigment or a liquid in which a dye is dissolved. In this embodiment, the case where ink of each color, white, black, cyan, magenta, yellow, red, green, and orange, is used is exemplified, but this is just one example, and there is no limitation on the color of ink used in the liquid ejection device 11, and light color inks such as light cyan and light magenta or intermediate color inks may also be used.

[0014] The ink of this embodiment is a so-called pigment ink that uses water as a solvent and contains a pigment as a coloring component. The white ink of this embodiment is an ink that contains a white pigment. Examples of the pigment include white inorganic pigments. Specific examples include alkaline earth metal sulfates such as barium sulfate, alkaline earth metal carbonates such as calcium carbonate, silicas such as finely powdered silicic acid and synthetic silicates, calcium silicate, alumina, alumina hydrate, metal compounds such as titanium oxide and zinc oxide, talc, and clay. In particular, this embodiment describes an example in which a white ink containing titanium oxide is used as the inorganic pigment. Titanium oxide pigments are known as hard particles, with a Mohs hardness of, for example, 5.5 to 7.5.

[0015] The black ink of this embodiment is an ink containing a black pigment, and includes a black inorganic pigment. Specifically, the black ink includes carbon black. The carbon black pigment has a lower hardness than the titanium oxide pigment, but a higher hardness than the organic pigments contained in inks of other colors. Specifically, the Mohs hardness of carbon black is 1.0 to 2.0.

[0016] In this embodiment, the inks used by the liquid ejection device 11, other than white ink and black ink, contain organic pigments as color components and either do not contain inorganic pigments or contain less inorganic pigment than organic pigments. Therefore, the cyan ink, magenta ink, yellow ink, red-cyan ink, green ink, and orange ink of this embodiment do not contain a substance with a hardness equal to or higher than that of the carbon black contained in the black ink. The same applies when the liquid ejection device 11 uses inks of other colors. White ink corresponds to an example of the first ink and second ink. The pretreatment liquid corresponds to an example of the treatment liquid.

[0017] The liquid ejection device 11 includes a pair of legs 12 and a housing 13 mounted on the legs 12. The liquid ejection device 11 includes a payout unit 15 that unwinds and pays out the medium M that has been wound up in a roll, a guide unit 16 that guides the medium M that is discharged from the housing 13, and a recovery unit 17 that winds up and recovers the medium M. The liquid ejection device 11 includes a tension applying mechanism 18 that applies tension to the medium M that is recovered in the recovery unit 17.

[0018] The liquid ejection device 11 includes a liquid ejection unit 20 capable of ejecting liquid, a carriage 21 that moves the liquid ejection unit 20, and a maintenance unit 22 that performs maintenance on the liquid ejection unit 20. The liquid ejection device 11 also includes a liquid supply unit 23 that supplies liquid to the liquid ejection unit 20, and an operation panel 24 that is operated by a user. The carriage 21 moves the liquid ejection unit 20 back and forth along the X axis. The liquid ejection unit 20 ejects liquid supplied through the liquid supply unit 23 while moving, and prints on the medium M. The liquid ejection unit 20 is a so-called print head. The liquid ejection unit 20 corresponds to an example of a ejection unit.

[0019] The liquid supply device 23 includes a mounting portion 26 to which a plurality of liquid containers 25 for containing liquid are removably mounted, and a supply flow path 27 that supplies liquid from the liquid containers 25 mounted to the mounting portion 26 to the liquid ejection portion 20.

[0020] The liquid ejection device 11 includes a control unit 29 that controls the operation of the liquid ejection device 11. The control unit 29 includes a processor, such as a CPU (Central Processing Unit), and a memory. The control unit 29 controls the liquid ejection unit 20, the liquid supply device 23, the maintenance unit 22, etc. by the processor executing a program stored in the memory.

[0021] FIG. 2 is a bottom view of the main part including the liquid discharge unit 20 and the carriage 21. As shown in FIG. As shown in FIG. 2, the liquid ejection device 11 includes a guide shaft 47 that supports the carriage 21, and a carriage motor 48 that moves the carriage 21. The guide shaft 47 extends in the width direction X. The control unit 29 controls the driving of the carriage motor 48 to move the carriage 21 and the liquid ejection unit 20 back and forth along the guide shaft 47. The carriage motor 48 corresponds to an example of a movement mechanism. The movement mechanism may include the carriage 21 and the guide shaft 47.

[0022] The liquid ejection unit 20 has a configuration in which a plurality of heads 30 are arranged on a main body made of metal such as stainless steel. The heads 30 are supported by the main body of the liquid ejection unit 20 and arranged in a line along the X-axis and Y-axis. Nozzles of the heads 30 open on a nozzle surface 40 corresponding to the bottom surface of the liquid ejection unit 20.

[0023] The nozzle surface 40 is covered with a liquid-repellent film that repels liquids such as ink. The liquid-repellent film preferably has a thickness of, for example, 1 nm or more and 30 nm or less, more preferably 1 nm or more and 20 nm or less, and even more preferably 1 nm or more and 15 nm or less.

[0024] The nozzles are openings of a tube through which liquid supplied from the liquid supply device 23 via the supply flow path 27 passes, and eject the liquid toward the medium M. In the head 30, a large number of nozzle openings that eject the liquid are arranged at regular intervals in a row in the depth direction Y. These rows of nozzles constitute nozzle groups 36. One head 30 has four nozzle groups 36.

[0025] 3 is an explanatory diagram showing the arrangement of the heads 30 in the liquid ejection unit 20, illustrating the bottom surface of the liquid ejection unit 20. Within the circle in FIG. 3, the configuration of one head 30 is shown in detail. Eighteen heads 30 are arranged in the liquid discharge section 20. These 18 heads 30 are divided into two rows in the depth direction Y, and nine heads 30 are arranged side by side in the width direction X.

[0026] 3, the head 30 has four nozzle groups 36, which are arranged in two rows in the width direction X and two rows in the depth direction Y. In the depth direction Y, the four nozzle groups 36 are arranged with their positions shifted from one another, and two adjacent nozzle groups 36 partially overlap in the depth direction Y. Therefore, as will be described later, when the liquid ejection unit 20 moves in the width direction X together with the carriage 21, the four nozzle groups 36 can eject liquid without any gaps in the depth direction Y.

[0027] In one head 30, two nozzle groups 36 aligned in the depth direction Y are collectively referred to as an ejection array. The head 30 has a first ejection array 31 located on the -X side in the width direction X, and a second ejection array 32 located on the +X side. The liquid ejected by the first ejection array 31 and the liquid ejected by the second ejection array 32 can be selected and changed individually, and can be different liquids or the same liquid.

[0028] The 18 heads 30 possessed by the liquid ejection unit 20 are referred to as heads 30A to 30R, and when there is no need to distinguish between them, they will be referred to as heads 30. Nine heads 30A to 30I are aligned in the width direction X on the -Y side of the liquid ejection unit 20, and nine heads 30J to 30R are aligned in the width direction X on the +Y side of the liquid ejection unit 20. Of the 18 heads 30 possessed by the liquid ejection unit 20, a group of nine heads 30A to 30I located on the -Y side is referred to as a first head group 33. Furthermore, a group of nine heads 30J to 30R located on the +Y side is referred to as a second head group 34. The heads 30 belonging to the first head group 33 and the heads 30 belonging to the second head group 34 are located at the same position in the width direction X. For example, the heads 30A and 30J are located at the same position in the width direction X.

[0029] Each head 30 has a first ejection array 31 and a second ejection array 32. The heads 30A to 30I aligned on the -Y side have first ejection arrays 31A to 31I and second ejection arrays 32A to 32I. Similarly, the heads 30J to 30R aligned on the +Y side have first ejection arrays 31J to 31R and second ejection arrays 32J to 32R.

[0030] Returning to FIG. 2 , the liquid discharger 20 is connected to a liquid flow mechanism 28. The liquid flow mechanism 28 is a device that sends the liquid supplied from the liquid supply device 23 through the supply flow path 27 to the head 30 of the liquid discharger 20. The liquid flow mechanism 28 includes, for example, a pump, a pressure adjustment mechanism, an on-off valve, etc. The liquid flow mechanism 28 is connected to each head 30 via a supply flow path 42, and pressure-feeds the liquid sent from the liquid supply device 23 to the head 30.

[0031] The carriage 21 moves back and forth along a guide shaft 47 by the power of a carriage motor 48. The movement direction of the medium M relative to the liquid discharger 20, i.e., the transport direction F, is parallel to the Y axis, specifically the +Y direction, as shown in FIG. 2. The liquid discharger 20 discharges liquid while moving together with the carriage 21 in the width direction X relative to the medium M.

[0032] [2. Maintenance unit configuration] A maintenance unit 22 is provided at one end of the movement range of the carriage 21 in the width direction X. Here, the maintenance unit 22 will be described.

[0033] Fig. 4 is a plan view of the maintenance unit 22. Fig. 5 is a side view of the liquid collection device 43. As shown in FIG. 4, the maintenance unit 22 has a liquid collecting device 43, a suction device 44, and a capping device 45, which are arranged side by side in the width direction X.

[0034] Above the capping device 45 is the home position HP of the liquid discharger 20. The home position HP is the starting point of movement of the liquid discharger 20. Also, above the liquid collection device 43 is called the cleaning position CP of the liquid discharger 20. In Figure 4, the liquid discharger 20 positioned at the cleaning position CP is shown by a two-dot chain line.

[0035] The suction device 44 includes a suction cap 51, a suction holder 52, a suction motor 53 that moves the suction holder 52 back and forth along the Z axis, and a decompression mechanism 54 that reduces the pressure inside the suction cap 51.

[0036] Four suction caps 51 are arranged on the suction holder 52, corresponding to two heads 30. That is, two suction caps 51 arranged in the depth direction Y surround the first ejection row 31 of the two heads 30 or the second ejection row 32 of the two heads 30.

[0037] The suction motor 53 moves the suction cap 51 between a capping position and a retracted position. The capping position is a position where the suction cap 51 comes into contact with the liquid discharger 20 and surrounds the nozzles. The retracted position is a position where the suction cap 51 is separated from the liquid discharger 20.

[0038] The liquid discharger 11 performs suction cleaning by positioning the liquid discharger 20 above the suction device 44, and positioning the suction cap 51 at the capping position to surround the first discharge row 31 and the second discharge row 32 of the two heads 30, and reducing the pressure inside the suction cap 51 to discharge the liquid from the nozzles. That is, the suction device 44 receives the liquid discharged by the suction cleaning.

[0039] The capping device 45 has a standby cap 56, a standby cap holder 57, and a standby cap motor 58 that moves the standby cap holder 57 back and forth along the Z axis. The standby cap motor 58 is driven to move the standby cap holder 57 and the standby cap 56 upward or downward. The standby cap 56 moves from a separated position, which is a lower position in the +Z direction, to a capping position, which is an upper position, and comes into contact with the liquid discharger 20 that is stopped at the home position HP.

[0040] The capping device 45 has 36 standby caps 56. The standby caps 56 positioned at the capping position surround the nozzle openings of the first ejection row 31 and the second ejection row 32 of the 18 heads 30. This maintenance in which the standby caps 56 surround the nozzle openings is called standby capping. Standby capping is a type of capping. Standby capping prevents liquid from evaporating from the nozzles.

[0041] The liquid collection device 43 includes a belt-shaped member 60 capable of absorbing liquid. The belt-shaped member 60 is an example of a sheet-shaped absorbent member. The liquid collection device 43 includes a case 61 that houses the belt-shaped member 60, a pair of rails 62 that extend along the Y axis, a wiping motor 63, a winding motor 64, and a power transmission mechanism 65 that transmits the power of the winding motor 64. The case 61 has an exposure opening 67 that exposes the belt-shaped member 60.

[0042] When the wiping motor 63 is driven in the forward direction, the case 61 moves in a first wiping direction W1 parallel to the Y axis, and when the wiping motor 63 is driven in the reverse direction, the case 61 moves in a second wiping direction W2 opposite to the first wiping direction W1.

[0043] The case 61 moves back and forth on the rail 62 along the Y axis by the power of the wiping motor 63, and performs wiping by wiping the nozzle surface 40 with the strip-shaped member 60. When wiping is not being performed, the case 61 is located outside the movement range of the carriage 21. The liquid ejection device 11 positions the liquid ejection unit 20 at the cleaning position CP, moves the case 61 to a position facing the liquid ejection unit 20, and performs wiping. The case 61 and the strip-shaped member 60 are an example of a wiping unit, and the wiping unit may include each part of the maintenance unit 22.

[0044] The liquid ejection device 11 wipes the liquid ejection part 20 during at least one of the process of moving the case 61 in the first wiping direction W1 and the process of moving it in the second wiping direction W2. Wiping is a maintenance process in which the belt-shaped member 60 wipes the nozzle surface 40. In other words, the liquid collection device 43 is provided so as to be able to wipe the nozzle surface 40. The liquid collection device 43 is an example of a wiping part.

[0045] In this embodiment, the liquid discharger 11 performs wiping while moving the belt-shaped member 60 in the second wiping direction W2 relative to the liquid discharger 20. That is, during wiping, the contact position 60a where the belt-shaped member 60 comes into contact with the liquid discharger 20 moves in the second wiping direction W2.

[0046] The liquid ejection device 11 also flushes the liquid collection device 43 from the liquid ejection unit 20. The liquid collection device 43 receives the liquid ejected from the liquid ejection unit 20 by flushing. Flushing is a maintenance procedure in which liquid is ejected from the liquid ejection unit 20 as waste liquid in order to either prevent or eliminate clogging of the nozzles, or to expel foreign matter that has entered the nozzles. Note that foreign matter also includes liquids other than the liquid ejected from the nozzles.

[0047] The liquid ejection device 11 may also perform pressure cleaning, in which the liquid ejection unit 20 applies pressure to the liquid collection device 43 to cause the pressurized liquid to be discharged from the nozzles. In this case, the liquid collection device 43 receives the liquid discharged by the pressure cleaning. Pressure cleaning is an example of cleaning in which the liquid is discharged as waste liquid with the aim of maintaining a normal liquid state in any of the liquid ejection unit 20, the supply flow path 27, and the supply flow path 42. Pressure cleaning is maintenance in which the pressurized liquid is forcibly discharged from the nozzles by driving and controlling the liquid flow mechanism 28 of the liquid supply device 23. The liquid flow mechanism 28 is an example of a cleaning unit.

[0048] As shown in FIG. 5, the liquid collecting device 43 includes an unwinding section 70 having an unwinding shaft 69 and a winding section 72 having a winding shaft 71. The unwinding section 70 holds the strip-shaped member 60 in a rolled state. The strip-shaped member 60 unwound and fed from the unwinding section 70 is transported along a transport path to the winding section 72. The liquid collecting device 43 includes an upstream roller 74, a tension roller 75, a pressing section 76, and a downstream roller 79, which are arranged in this order from upstream to downstream along the transport path of the strip-shaped member 60. The case 61 supports the unwinding shaft 69, the upstream roller 74, the tension roller 75, the pressing section 76, the downstream roller 79, and the winding shaft 71 rotatably about the X-axis.

[0049] The winding shaft 71 rotates when driven by the winding motor 64. The winding unit 72 winds the strip-shaped member 60 in a roll onto the winding shaft 71. By winding the strip-shaped member 60, the winding unit 72 moves the portion of the strip-shaped member 60 that has been unwound from the unwinding unit 70 in direction D. The direction D is a direction along the transport path of the strip-shaped member 60, and is the direction of movement from the upstream unwinding unit 70 toward the downstream winding unit 72.

[0050] Power transmission mechanism 65 transmits the driving force of winding motor 64 to winding shaft 71. Power transmission mechanism 65 may connect winding motor 64 and winding shaft 71 when case 61 is located at the standby position, and may disconnect winding motor 64 and winding shaft 71 when case 61 moves away from the standby position.

[0051] The tension roller 75 is disposed upstream in the D direction and in the +Z direction from the pressing portion 76. The tension roller 75 applies tension to the belt-shaped member 60 by pressing the belt-shaped member 60 downward.

[0052] The pressing portion 76 in this embodiment is a roller around which the belt-shaped member 60 is wound. The pressing portion 76 presses the belt-shaped member 60 unwound from the unwinding portion 70 from below upward, causing the belt-shaped member 60 to protrude from the exposure opening 67.

[0053] The contact area A2 is an area that comes into contact with the liquid discharger 20 during wiping. The pressing unit 76 presses the contact area A2 located at the contact position 60a of the belt-shaped member 60, and can bring the contact area A2 into contact with the liquid discharger 20. In other words, the liquid collection device 43 wipes the liquid discharger 20 by moving the case 61 with the contact area A2 in contact with the liquid discharger 20.

[0054] 5, when the liquid ejector 20 is located at the cleaning position CP, the belt-shaped member 60 located in the receiving area A1 faces the area BW of the nozzle surface 40. In this state, the liquid ejector 11 performs either flushing or pressurized cleaning. In this case, the liquid collection device 43 receives in the receiving area A1 the liquid discharged by either flushing or pressurized cleaning.

[0055] [3. Color arrangement in the liquid ejection section] The liquid ejected by each of the multiple heads 30 of the liquid ejection unit 20 can be individually assigned to each head 30, and different liquids can be assigned to the first ejection array 31 and the second ejection array 32 of one head 30. The liquids ejected by the heads 30 include pre-treatment liquid, post-treatment liquid, white ink, and various colored inks including black ink. In the following description, white ink, black ink, and other colored inks are collectively referred to as ink. Inks other than white ink are referred to as colored inks, and inks further excluding black ink are referred to as colored inks. As an example, the colored inks are cyan, magenta, yellow, red, green, and orange inks. The colored inks correspond to an example of a third ink.

[0056] The liquid ejected by each head 30 of the liquid ejection unit 20 is selected from ink, pre-treatment liquid, and post-treatment liquid. The selection and determination of the liquid ejected by each first ejection array 31 and second ejection array 32, that is, the result of the allocation of the liquid ejected by each head 30, will be referred to below as the color arrangement. The color arrangement refers to the allocation of pre-treatment liquid, post-treatment liquid, and ink in the liquid ejection unit 20, and does not refer to an arrangement limited to color inks.

[0057] The white ink is used as a base for applying color ink to the medium M. In other words, by applying the white ink to the medium M and then applying the color ink on top of that, the color ink can be made to develop a good color regardless of the background color of the medium M. Therefore, when using white ink, it is necessary to deposit the white ink on the medium M and then eject the color inks onto the medium M during the printing process while the liquid ejection unit 20 moves over the medium M. This order can be achieved by a color arrangement that takes into account the position of the head 30 in the width direction X. Specifically, a specific ejection order of the white ink and the color inks can be achieved by assigning the white ink to the head 30 that arrives at the printing position on the medium M first in the width direction X, and assigning the color inks to the heads 30 that arrive at the printing position later.

[0058] Furthermore, when using white ink, it is preferable to apply the pretreatment liquid to the medium M between the white ink and the color ink. This is because if the white ink and the color ink are ejected on top of the pretreatment liquid, the color ink may harden before the white ink, which could result in a decrease in color development. For this reason, it is preferable to eject the white ink, pretreatment liquid, and color ink in this order onto the medium M. Therefore, the color arrangement is determined taking into account the order of the white ink, pretreatment liquid, and color ink.

[0059] Furthermore, it is preferable that the color arrangement in the liquid ejection section 20 be determined taking into consideration wear of the head 30 due to wiping. As described above, the maintenance unit 22 wipes the nozzle surface 40 with the strip-shaped member 60. During this process, the strip-shaped member 60, to which the ink ejected by the head 30 is attached, moves while rubbing against the nozzle surface 40. For this reason, in each head 30, the strip-shaped member 60 impregnated with the liquid ejected by the head 30 rubs against the nozzle surface 40.

[0060] Furthermore, as shown in FIG. 3, the liquid ejection unit 20 has two rows of heads 30 aligned along the depth direction Y, and the heads 30 positioned on the +Y side are wiped by the strip-shaped member 60 before the heads 30 positioned on the -Y side. Therefore, the heads 30 positioned on the -Y side are wiped by the strip-shaped member 60 to which the liquid has just been attached. In the example of FIG. 3, the heads 30A and 30J are aligned along the Y axis, and during wiping, the head 30A is wiped after the head 30J. Therefore, the nozzle surface 40 of the head 30A is rubbed by the strip-shaped member 60 to which the liquid ejected by the head 30J is attached.

[0061] Of the liquids ejected by the head 30, the white ink and black ink contain pigments with particularly high hardness. When the strip-shaped member 60 with these pigments attached wipes the nozzle surface 40, this can cause wear on the nozzle surface 40. For this reason, when determining which head 30 to allocate the white ink and black ink to, it is preferable to take into consideration the position of the head 30 in the depth direction Y.

[0062] From the above various viewpoints, examples of allocating liquids to the heads 30 of the liquid ejection unit 20 will be described with reference to Figures 6 to 13. Figures 6 to 13 respectively show examples of the correspondence between the positions of the first ejection array 31 and the second ejection array 32 of the head 30 and the ejected liquid. Figures 6 to 13 are schematic plan views of the liquid ejection unit 20 viewed from above, with the home position HP being on the right side of the figures.

[0063] 6 to 13, the pre-processing liquid is referred to as Pre (Pre-processing solution), and the post-processing liquid is referred to as Pos (Post-processing solution). Furthermore, white ink is referred to as WH, black ink as K, cyan ink as CY, magenta ink as M, yellow ink as Y, red ink as R, green ink as G, and orange ink as O.

[0064] 6 to 13, the movement direction of the medium M relative to the liquid discharger 20, i.e., the transport direction, is indicated by the symbol F. Also, paths P1 and P2 are shown as the movement directions of the liquid discharger 20 during printing. Path P1 is the movement of discharging liquid onto the medium M in the process of moving the liquid discharger 20 toward the -X side during the printing operation of the liquid discharger 11. Path P2 is the movement of discharging liquid onto the medium M in the process of moving the liquid discharger 20 toward the +X side. One path P1 and one path P2 correspond to one reciprocating movement of the liquid discharger 20.

[0065] 6 to 13 indicates the center position of the head 30 arranged in the liquid ejection section 20. The center position C refers to the center in the order of the first ejection row 31 and the second ejection row 32 aligned in the width direction X. The center position C is not necessarily the exact center of the size of the liquid ejection section 20 in the width direction X.

[0066] [3-1. First color layout example] FIG. 6 is a diagram showing an example of a color arrangement in the head 30, and shows a first example of a color arrangement. In the first head group 33, post-treatment liquid and white ink are assigned to the head 30A. Pre-treatment liquid is assigned to the first ejection array 31B and the second ejection array 32B, cyan ink is assigned to the first ejection array 31C, and red ink is assigned to the second ejection array 32C. Yellow ink is assigned to the first ejection array 31D, magenta ink is assigned to the second ejection array 32D, and black ink is assigned to the first ejection array 31E. In addition, ink, pre-treatment liquid, and post-treatment liquid are assigned to the first head group 33 symmetrically with respect to the center position C. That is, liquids are assigned to the second ejection array 32E to the second ejection array 32I symmetrically with respect to the first ejection array 31A to the first ejection array 31E.

[0067] In the second head group 34, post-treatment liquid is assigned to the head 30J. Pre-treatment liquid is assigned to the first ejection array 31K and the second ejection array 32K, cyan ink is assigned to the first ejection array 31L, and red ink is assigned to the second ejection array 32L. Yellow ink is assigned to the first ejection array 31M, black ink is assigned to the second ejection array 32M, and magenta ink is assigned to the first ejection array 31N. In the second head group 34, ink, pre-treatment liquid, and post-treatment liquid are assigned symmetrically with respect to the center position C. That is, liquids are assigned to the second ejection arrays 32N to 32R symmetrically with respect to the first ejection arrays 31J to 31N.

[0068] At a predetermined printing position in the transport direction F of the medium M, the first head group 33 ejects liquid first, and then the second head group 34 ejects liquid. The first color layout example has the following first to third advantages.

[0069] A first advantage is that the liquid ejection unit 20 can eject the white ink, pre-treatment liquid, color ink, and post-treatment liquid onto the medium M in this order in both the path P1 and the path P2.

[0070] When this ejection order is adopted, after the white ink adheres to the surface of the medium M, the white ink is cured by the pretreatment liquid, and the color inks ejected onto the pretreatment liquid are mixed with the pretreatment liquid and cured. This makes it possible to suppress or prevent the color inks from curing before the white ink is cured, thereby suppressing a decrease in color development.

[0071] More specifically, when the first head group 33 ejects liquid in pass P1, the liquid ejection device 11 first ejects white ink using the second ejection array 32A, and then ejects pretreatment liquid using the first ejection array 31B and the second ejection array 32B. After that, the liquid ejection device 11 ejects color ink using some or all of the first ejection array 31C to second ejection array 32G. After that, the liquid ejection device 11 ejects posttreatment liquid using the second ejection array 32I.

[0072] When the first head group 33 ejects liquid in path P2, the liquid ejection device 11 first ejects white ink using the first ejection array 31I, and then ejects pretreatment liquid using the second ejection array 32H and the first ejection array 31H. After that, the liquid ejection device 11 ejects color ink using some or all of the second ejection array 32G to first ejection array 31C. After that, the liquid ejection device 11 ejects posttreatment liquid using the first ejection array 31A.

[0073] Furthermore, in the first color arrangement example, the second head group 34 does not include white ink. When the second head group 34 ejects liquid in pass P1, the liquid ejection device 11 first ejects pre-treatment liquid using the first ejection array 31K and the second ejection array 32K, ejects color inks using some or all of the first ejection arrays 31L to 32P, and ejects post-treatment liquid using the first ejection array 31R and the second ejection array 32R. When the second head group 34 ejects liquid in pass P2, the liquid ejection device 11 ejects pre-treatment liquid using the second ejection array 32Q and the first ejection array 31Q, ejects color inks using some or all of the second ejection arrays 32P to 31L, and then ejects post-treatment liquid using the second ejection array 32J and the first ejection array 31J.

[0074] A second advantage is that the liquid ejection unit 20 has few combinations in which both of the two first ejection rows 31 or both of the two second ejection rows 32 aligned in the depth direction Y contain hard pigments. In other words, wear on the head 30 when the strip-shaped member 60 wipes the nozzle surface 40 can be suppressed.

[0075] Specifically, the post-treatment liquid is assigned to the second ejection array 32J aligned with the second ejection array 32A that ejects white ink. The same applies to the relationship between the first ejection array 31I and the first ejection array 31R. Furthermore, the magenta ink is assigned to the second ejection array 32D aligned with the second ejection array 32M that ejects black ink. The same applies to the relationship between the first ejection array 31O and the first ejection array 31F. Furthermore, the magenta ink is assigned to the first ejection array 31N aligned with the first ejection array 31E that ejects black ink, and the second ejection array 32N aligned with the second ejection array 32E that ejects black ink. Therefore, not all of the multiple heads 30 aligned in the depth direction Y are configured to eject hard pigments, which is expected to have the effect of suppressing wear on the heads 30.

[0076] A third advantage is that, because the color inks are arranged symmetrically with respect to the central position C, color reproducibility on the medium M is high. That is, the order in which the color inks are ejected onto the medium M is the same when the liquid ejection unit 20 prints in pass P1 and when it prints in pass P2. This makes it possible to avoid a situation in which the color hues differ between pass P1 and pass P2, thereby improving color reproducibility.

[0077] [3-2. Second color layout example] FIG. 7 is a diagram showing an example of a color arrangement in the head 30, and shows a second example of the color arrangement. 7, the color arrangement of the first head group 33 is the same as in the first color arrangement example. In the second head group 34, black ink is arranged in the first ejection array 31L and the second ejection array 32P. Furthermore, cyan ink is arranged in the second ejection array 32J and the first ejection array 31R. Furthermore, in the second head group 34, the number of first ejection arrays 31 and second ejection arrays 32 that eject post-treatment liquid is fewer than in the first color arrangement example. The other color arrangements of the second head group 34 are the same as in the first color arrangement example.

[0078] The second arrangement example has the first to third advantages described for the first arrangement example. For example, cyan ink is assigned to the first ejection array 31C, which is aligned in the depth direction Y with the first ejection array 31L that ejects black ink. The same is true for the second ejection array 32G, which is aligned with the second ejection array 32P. Therefore, because not all of the multiple heads 30 aligned in the depth direction Y contain a configuration that includes a hard pigment, wear on the heads 30 due to wiping can be reduced.

[0079] Furthermore, a fourth advantage of the second color layout example is that it can print clearer black. In the second color layout example, the second head group 34 has four first ejection rows 31 and four second ejection rows 32 that eject black ink, and color inks are ejected between each black ink. Therefore, when printing using black ink and other color inks, the black ink can be printed clearly.

[0080] [3-3. Third color layout example] FIG. 8 is a diagram showing an example of a color arrangement in the head 30, and shows a third example of the color arrangement. The third color arrangement example differs from the first color arrangement example in FIG. 6 in that green ink is arranged in the second head group 34. The color arrangement of the first head group 33 is the same. In the second head group 34, green ink is assigned to the second ejection array 32L and the first ejection array 31P, and red ink is assigned to the first ejection array 31L and the second ejection array 32P. Furthermore, cyan ink is assigned to the second ejection array 32J and the first ejection array 31R. Furthermore, in the second head group 34, the number of first ejection arrays 31 and second ejection arrays 32 that eject post-treatment liquid is fewer than in the first color arrangement example. The other color arrangements of the second head group 34 are the same as in the first color arrangement example.

[0081] The third arrangement example has the first to third advantages described for the first arrangement example. Furthermore, in the third color arrangement example, green ink is ejected in addition to the inks used in the first and second arrangement examples. Therefore, a fifth advantage is that the color reproduction range, or gamut, can be expanded, enabling a wider variety of color expressions.

[0082] [3-4. Fourth color layout example] FIG. 9 is a diagram showing an example of the color arrangement in the head 30, and shows a fourth example of the color arrangement. The fourth color arrangement example is an example in which the color arrangement of the first head group 33 is the same as the first color arrangement example, and further, the color arrangement of the second head group 34 is the same as the color arrangement of the first head group 33.

[0083] According to the fourth color arrangement example, the first and third advantages described above can be obtained. That is, as a first advantage, the liquid ejection unit 20 can eject the white ink, pre-treatment liquid, color ink, and post-treatment liquid onto the medium M in this order in both pass P1 and pass P2. Furthermore, as a third advantage, since the color inks are arranged symmetrically with respect to the central position C, high color reproducibility on the medium M can be achieved.

[0084] Furthermore, in the fourth color layout example, the color layout of the first head group 33 and the second head group 34 is heavy rain. As shown in FIGS. 2 and 3, the nozzle groups 36 of the first head group 33 and the nozzle groups 36 of the second head group 34 overlap in the depth direction Y. Therefore, by driving both the first head group 33 and the second head group 34, printing can be performed without gaps across the entire overlapping area of ​​the first head group 33 and the second head group 34 in a single pass P1 or pass P2. Furthermore, because the color development characteristics of the area printed by the first head group 33 and the area printed by the second head group 34 are approximately equal, printing can be performed at high throughput without degrading print quality. Therefore, the fourth color layout example has a sixth advantage: extremely high throughput.

[0085] [3-5. Fifth color layout example] FIG. 10 is a diagram showing an example of the color arrangement in the head 30, and shows a fifth example of the color arrangement. 10, the color arrangement of the first head group 33 is the same as in the first color arrangement example. In the second head group 34, black ink is arranged in the second ejection array 32J and the first ejection array 31R. Furthermore, in the second head group 34, the number of first ejection arrays 31 and second ejection arrays 32 that eject post-treatment liquid is fewer than in the first color arrangement example. The other color arrangements of the second head group 34 are the same as in the first color arrangement example.

[0086] The fifth arrangement example provides the first and third advantages described above. That is, as a first advantage, the liquid ejection unit 20 can eject the white ink, pre-treatment liquid, color ink, and post-treatment liquid onto the medium M in this order in both pass P1 and pass P2. Furthermore, as a third advantage, since the color inks are arranged symmetrically with respect to the central position C, high color reproducibility on the medium M is achieved.

[0087] Furthermore, the fifth color layout example achieves the fourth advantage of being able to print clearer black. That is, in the second head group 34, there are four first ejection rows 31 and four second ejection rows 32 that eject black ink, and color inks are ejected between each black ink. Therefore, when printing using black ink and other color inks, the black ink can be printed clearly.

[0088] [3-6. Sixth color layout example] FIG. 11 is a diagram showing an example of the color arrangement in the head 30, and shows a sixth example of the color arrangement. 11, the color arrangement of the first head group 33 is the same as in the first color arrangement example. In the second head group 34, black ink is arranged in the second ejection array 32L and the first ejection array 31P. Also, in the second head group 34, there are fewer first ejection arrays 31 and second ejection arrays 32 that eject red ink than in the first color arrangement example. The other color arrangements of the second head group 34 are the same as in the first color arrangement example.

[0089] The sixth arrangement example provides the first, third, and fourth advantages described above. That is, as a first advantage, the liquid ejection unit 20 can eject the white ink, pre-treatment liquid, color ink, and post-treatment liquid onto the medium M in this order in both pass P1 and pass P2. Furthermore, as a third advantage, since the color inks are arranged symmetrically with respect to the central position C, high color reproducibility on the medium M is achieved. Furthermore, the sixth arrangement example provides the advantage of being able to print clearer black.

[0090] [3-7. Seventh color layout example] FIG. 12 is a diagram showing an example of the color arrangement in the head 30, and shows a seventh example of the color arrangement. In the first head group 33, post-treatment liquid is assigned to the first ejection array 31A, and cyan ink is assigned to the second ejection array 32A. Pre-treatment liquid is assigned to the first ejection array 31B and the second ejection array 32B, green ink is assigned to the first ejection array 31C, and yellow ink is assigned to the second ejection array 32C. Magenta ink is assigned to the first ejection array 31D, black ink is assigned to the second ejection array 32D, and pre-treatment liquid is assigned to the first ejection array 31E. In addition, ink, pre-treatment liquid, and post-treatment liquid are assigned to the first head group 33 symmetrically with respect to the center position C. That is, liquids are assigned to the second ejection arrays 32E to 32I symmetrically with respect to the first ejection arrays 31A to 31E.

[0091] In the second head group 34, post-treatment liquid is assigned to the first ejection array 31J, and black ink is assigned to the second ejection array 32J. Cyan ink is assigned to the first ejection array 31K, orange ink to the second ejection array 32K, red ink to the first ejection array 31L, and green ink to the second ejection array 32L. Yellow ink is assigned to the first ejection array 31M, magenta ink to the second ejection array 32M, and pre-treatment liquid to the first ejection array 31N. In the second head group 34, ink, pre-treatment liquid, and post-treatment liquid are assigned symmetrically with respect to the center position C. That is, liquids are assigned to the second ejection arrays 32N to 32R symmetrically with respect to the first ejection arrays 31J to 31N.

[0092] The seventh color arrangement example achieves the second advantage described above. That is, the liquid ejection unit 20 does not have a combination in which both of the two first ejection arrays 31 or both of the two second ejection arrays 32 aligned in the depth direction Y contain hard pigments, thereby achieving the advantage of suppressing wear on the heads 30 when wiping the nozzle surface 40. For example, cyan ink is assigned to the second ejection array 32A aligned with the second ejection array 32J in the depth direction Y. Similarly, magenta ink is assigned to the second ejection array 32M aligned with the second ejection array 32D. The same applies to the combination of the first ejection array 31F and the first ejection array 31O, and the combination of the first ejection array 31R and the first ejection array 31I. Therefore, not all of the multiple heads 30 aligned in the depth direction Y are configured to eject hard pigments, which is expected to suppress wear on the heads 30.

[0093] Moreover, according to the seventh color layout example, the third advantage mentioned above, that is, high color reproducibility on the medium M, can be obtained. Furthermore, in the seventh color layout example, orange ink is ejected in addition to the inks used in the first to sixth layout examples. In other words, the color inks used are cyan, magenta, yellow, green, red, orange, and black. This results in a fifth advantage: the color reproduction range, or gamut, is expanded, making it possible to express a wider variety of colors.

[0094] [3-8. First color layout example] FIG. 13 is a diagram showing an example of the color arrangement in the head 30, showing an eighth example of the color arrangement. 13, the color arrangement of the first head group 33 is the same as in the seventh color arrangement example. In the second head group 34, cyan ink is assigned to the second ejection array 32J, orange ink is assigned to the first ejection array 31K, and red ink is assigned to the second ejection array 32K. Furthermore, green ink is assigned to the first ejection array 31L, and black ink is assigned to the second ejection array 32L. The allocation of liquids to the first ejection arrays 31M to 31N is the same as in the seventh color arrangement example. Furthermore, the color arrangement of the second head group 34 is symmetrical with respect to the center position C. The other color arrangements of the second head group 34 are the same as in the seventh color arrangement example.

[0095] Like the seventh arrangement example, the second arrangement example provides the second, third, and fifth advantages. That is, the liquid ejection unit 20 can suppress wear on the head 30 when wiping the nozzle surface 40 with the belt-shaped member 60, and has the advantage of high color reproducibility on the medium M because the color inks are arranged symmetrically with respect to the central position C. In addition, the color reproduction range, or gamut, can be expanded, allowing for a wider variety of color expression.

[0096] [4. Effects, etc.] As described above, the liquid ejection device 11 of the present disclosure includes a liquid ejection unit 20 capable of ejecting liquid onto a transported medium M, and a movement mechanism that reciprocates the liquid ejection unit 20 in a first direction and a second direction opposite to the first direction. The liquid ejection unit 20 includes a first nozzle row, a second nozzle row, a third nozzle row, a fourth nozzle row, and a fifth nozzle row on a nozzle surface 40. The first nozzle row ejects a white first ink. The second nozzle row ejects a white second ink. The third nozzle row is disposed between the first and second nozzle rows in the first direction and ejects a third ink of a color different from the first and second inks. The fourth nozzle row is disposed between the first and third nozzle rows in the first direction and ejects a pretreatment liquid containing an aggregating agent that aggregates at least the ink composition contained in the third ink. The fifth nozzle row is disposed between the second and third nozzle rows in the first direction and ejects a pretreatment liquid. The first direction is the direction in which the liquid ejection section 20 moves during printing, and is the width direction X. More specifically, one of the −X direction and the +X direction corresponds to the first direction, and the other corresponds to the second direction.

[0097] For example, in the first to sixth arrangement examples, the first nozzle row is the second ejection row 32A, and the second nozzle row is the first ejection row 31I. In this case, the third nozzle row is one or more of the first ejection row 31C to second ejection row 32G. The fourth nozzle row is one or more of the first ejection row 31B and second ejection row 32B, and the fifth nozzle row is one or more of the first ejection row 31H and second ejection row 32H.

[0098] According to this configuration, in both cases where the liquid discharger 20 prints in path P1 and where the liquid discharger 20 prints in path P2, the pretreatment liquid is discharged after the white ink is discharged, and then the color inks are discharged. Therefore, as described as the first advantage, on the medium M, the white ink is cured by the pretreatment liquid, and the color inks discharged on top of the pretreatment liquid are mixed with the pretreatment liquid and cured. Therefore, it is possible to suppress or prevent the color inks from curing before the white ink is cured, and therefore it is possible to suppress a decrease in color development.

[0099] The liquid ejection unit 20 has a sixth nozzle row and a seventh nozzle row that eject a post-treatment liquid that does not cause the ink composition of the first ink and the ink composition of the third ink to aggregate. In the liquid ejection unit 20, the first nozzle row or the second nozzle row is located between the sixth nozzle row and the seventh nozzle row in the first direction. For example, in a first arrangement example, either the first ejection row 31A or the second ejection row 32I is the sixth nozzle row, and the other is the seventh nozzle row.

[0100] According to this configuration, by ejecting the post-treatment liquid onto the medium M onto which the white ink, pre-treatment liquid, and color ink have been ejected, it is possible to perform post-treatment such as coating the color ink adhering to the medium M. Therefore, it is possible to further improve the color development.

[0101] The first ink and the second ink are white inks containing titanium oxide. The liquid ejection device 11 includes a wiping unit that moves relative to a nozzle surface 40 of the liquid ejection unit 20 in a third direction perpendicular to the first and second directions to wipe the nozzle surface 40. The liquid ejection unit 20 includes a first head including a first nozzle row, and a second head that is disposed upstream of the first head in the third direction. The second head is a head 30 that does not have either a nozzle row that ejects the first ink or the second ink, or a nozzle row that ejects black ink containing carbon black.

[0102] The third direction is, for example, the depth direction Y. In the first to third and sixth arrangement examples, for example, the first head is head 30A, and the second head is head 30J. According to this configuration, in the liquid ejection unit 20, the heads 30 aligned in the depth direction Y with the head 30 that ejects white ink do not eject white ink or black ink containing hard pigments. Therefore, during wiping, the head 30 that is the first head is wiped by the strip-shaped member 60 to which no hard pigment is attached. This reduces or prevents wear on the nozzle surface 40 that accompanies wiping.

[0103] The first ink and the second ink are white inks containing titanium oxide. The liquid ejection device 11 includes a wiping unit that moves relative to a nozzle surface 40 of the liquid ejection unit 20 in a third direction perpendicular to the first and second directions to wipe the nozzle surface 40. The liquid ejection unit 20 includes a fourth head including a fourth nozzle row that ejects a black fourth ink containing carbon black, and a second head that is disposed upstream of the fourth head in the third direction. The second head is a head that does not have a nozzle row that ejects the first ink or the second ink, nor a nozzle row that ejects the fourth ink.

[0104] In the first to third and fifth arrangement examples, for example, the fourth nozzle row is the first ejection row 31E, the fourth head is the head 30E, and the second head is the head 30N. According to this configuration, in the liquid ejection unit 20, the heads 30 aligned in the depth direction Y with respect to the head 30 that ejects black ink do not eject white ink or black ink, which contain hard pigments. Therefore, during wiping, the head 30, which is the first head, is wiped by the strip-shaped member 60 to which no hard pigment is attached. This reduces or prevents wear on the nozzle surface 40 due to wiping.

[0105] The first ink is a white ink containing titanium oxide. The liquid ejection device 11 includes a wiping unit that moves relative to a nozzle surface 40 of the liquid ejection unit 20 in a third direction perpendicular to the first and second directions to wipe the nozzle surface 40. The liquid ejection unit 20 includes a first head including a first nozzle row, and a fifth head that is disposed upstream of the first head in the third direction. The fifth head has a nozzle row that ejects a post-treatment liquid that does not cause the ink composition contained in the first ink to aggregate.

[0106] In the first to third and sixth arrangement examples, for example, the first nozzle row is the second ejection row 32A, the first head is the head 30A, and the fifth head is the head 30J. According to this configuration, in the liquid ejection unit 20, the heads 30 aligned in the depth direction Y with respect to the head 30 that ejects white ink eject post-treatment liquid, so that during wiping, the head 30 that is the first head is wiped by the strip-shaped member 60 to which the post-treatment liquid has adhered. The post-treatment liquid does not have the effect of aggregating the ink composition, and therefore acts as a lubricant during wiping. This reduces or prevents wear on the nozzle surface 40 that accompanies wiping.

[0107] When the liquid ejector 11 moves the wiping unit in the third direction to perform the wiping operation, the liquid ejector 11 may eject the post-processing liquid from the fifth head before the wiping unit reaches the first head. For example, in the process of moving the case 61 in the second wiping direction W2 to perform wiping with the belt-shaped member 60, the liquid ejector 11 may eject the post-processing liquid from the head 30J before the contact position 60a reaches the head 30A. According to this configuration, the post-treatment liquid ejected by the head 30J adheres to the surface of the belt-shaped member 60 that wipes the head 30A, which is the first head, improving the sliding properties between the nozzle surface 40 of the head 30A and the belt-shaped member 60. This further reduces wear on the nozzle surface 40 caused by wiping.

[0108] The liquid ejection device 11 includes a liquid ejection unit 20 capable of ejecting onto a transported medium M a first white ink, a third ink of a different color than the first ink, and a treatment liquid containing an aggregating agent that aggregates at least the composition contained in the third ink. The liquid ejection device 11 also includes a movement mechanism that reciprocates the liquid ejection unit 20 in a first direction and a second direction opposite to the first direction. The ejection method of the liquid ejection device 11 includes, during the period in which the liquid ejection unit 20 moves in the first direction, a first step of ejecting the first ink onto the medium M, and a second step of ejecting the treatment liquid onto the region onto which the first ink was ejected in the first step. The method also includes a third step of ejecting the third ink onto the region onto which the treatment liquid was ejected in the second step, and a fourth step of ejecting the treatment liquid onto the region onto which the third ink was ejected in the third step.

[0109] For example, in the first to sixth arrangement examples, when pass P1 is performed, the liquid ejector 11 ejects white ink from the second ejection array 32A in the first step, and ejects pretreatment liquid from the first and second ejection arrays 31B and 32B in the second step. Then, in the third step, color ink is ejected from one or more of the first to second ejection arrays 31C to 32G, and in the fourth step, posttreatment liquid is ejected from the second ejection array 32I. When pass P2 is performed, the liquid ejector 11 ejects white ink from the first ejection array 31I in the first step, and ejects pretreatment liquid from the second and first ejection arrays 32H and 31H in the second step. Then, in the third step, color ink is ejected from one or more of the second ejection arrays 32G to 31C, and in the fourth step, posttreatment liquid is ejected from the first ejection array 31A.

[0110] According to this configuration, in both cases where the liquid discharger 20 prints in path P1 and where the liquid discharger 20 prints in path P2, the pretreatment liquid is discharged after the white ink is discharged, and then the color inks are discharged. Therefore, as described as the first advantage, on the medium M, the white ink is cured by the pretreatment liquid, and the color inks discharged on top of the pretreatment liquid are mixed with the pretreatment liquid and cured. Therefore, it is possible to suppress or prevent the color inks from curing before the white ink is cured, and therefore it is possible to suppress a decrease in color development.

[0111] In the above-described ejection method, the liquid ejection device 11 performs an operation including a first step, a second step, a third step, and a fourth step while the liquid ejection section 20 moves in a first direction. Furthermore, the liquid ejection device 11 performs an operation including a first step, a second step, a third step, and a fourth step while the liquid ejection section 20 moves in a second direction.

[0112] For example, in the first to sixth arrangement examples, the liquid ejection device 11 executes pass P1 as described above, and then executes pass P2. According to this, while the liquid ejection section 20 is moved back and forth in the width direction X, on both the outward and return paths, the color ink can be suppressed or prevented from hardening before the white ink hardens, thereby suppressing a decrease in color development.

[0113] The liquid ejection device 11 has a liquid ejection unit 20 capable of ejecting liquid onto the transported medium M, and a wiping unit that wipes the nozzle surface of the liquid ejection unit 20. The liquid ejection unit 20 has a first head and a second head. The first head includes a nozzle row that ejects white ink containing titanium oxide or black ink containing carbon black. The second head is provided upstream of the first head in the wiping direction of the wiping unit, and does not include a nozzle row that ejects white ink or black ink.

[0114] For example, in the first to third and sixth arrangement examples, the first head is any one of heads 30A, 30E, and 30I. When the first head is head 30A, the second head is head 30J. When the first head is head 30E, the second head is head 30N. When the first head is head 30I, the second head is head 30R.

[0115] According to this configuration, in the liquid ejection unit 20, the second head aligned in the depth direction Y with the first head that ejects ink containing hard pigment does not eject white ink or black ink containing hard pigment. Therefore, during wiping, the first head is wiped by the strip-shaped member 60 to which no hard pigment is attached. This reduces or prevents wear on the nozzle surface 40 due to wiping.

[0116] The second head may have a nozzle row that ejects a post-treatment liquid that prevents the white ink composition and the black ink composition from coagulating. For example, in the first to third and sixth arrangement examples, the second head is head 30J or head 30R. According to this configuration, the post-treatment liquid ejected by the second head adheres to the surface of the belt-shaped member 60 that wipes the first head, improving the slipperiness between the nozzle surface 40 of the first head and the belt-shaped member 60. This makes it possible to further reduce wear on the nozzle surface 40 caused by wiping.

[0117] When the wiping operation is performed by the wiping unit, the liquid ejection device 11 may be configured to eject the post-treatment liquid from the second head before the wiping unit reaches the first head. According to this configuration, the post-treatment liquid ejected by the second head adheres to the surface of the belt-shaped member 60 that wipes the first head, improving the slipperiness between the nozzle surface 40 of the first head and the belt-shaped member 60. This makes it possible to further reduce wear on the nozzle surface 40 caused by wiping.

[0118] 5. Other Embodiments The above-described embodiment merely shows a specific example of application of the present invention. The present invention is not limited to the configuration of the above-described embodiment, and can be embodied in various forms without departing from the spirit and scope of the invention.

[0119] In the above embodiment, the maintenance unit 22 has been described as being configured to wipe the nozzle surface 40 with the belt-shaped member 60 while the case 61 moves in the second wiping direction W2, but this is just one example. For example, the maintenance unit 22 may be configured to wipe while the case 61 moves in the first wiping direction W1.

[0120] In the above embodiment, a configuration in which the liquid ejection unit 20 includes 18 heads 30 has been described, but there is no limit to the number of heads 30 that the liquid ejection unit 20 can include. For example, the present disclosure can also be applied to a configuration in which some of the heads 30 in the second head group 34 are removed.

[0121] Furthermore, there are no limitations on the configurations relating to the maintenance unit 22 and the transport of the medium M described in the above embodiment, and various configurations can be adopted.

[0122] [6. Configurations Described by the Embodiments] The above embodiment describes the following configuration.

[0123] (Configuration 1) A liquid ejection device comprising: a liquid ejection unit capable of ejecting liquid onto a medium being transported; and a movement mechanism that moves the liquid ejection unit back and forth in a first direction and a second direction opposite to the first direction, wherein the liquid ejection unit has a nozzle face comprising: a first nozzle row that ejects a white first ink; a second nozzle row that ejects a white second ink; a third nozzle row that is disposed between the first nozzle row and the second nozzle row in the first direction and ejects a third ink of a color different from the first ink and the second ink; a fourth nozzle row that is disposed between the first nozzle row and the third nozzle row in the first direction and ejects a treatment liquid containing an aggregating agent that aggregates at least an ink composition contained in the third ink; and a fifth nozzle row that is disposed between the second nozzle row and the third nozzle row in the first direction and ejects the treatment liquid. According to this, when the liquid ejection unit performs printing, it ejects white ink, then ejects treatment liquid, and then ejects color inks. As a result, on the medium, the white ink is cured by the treatment liquid, and the color inks ejected on top of the treatment liquid are mixed with the pretreatment liquid and cured. As a result, it is possible to suppress or prevent the color inks from curing before the white ink is cured, and therefore it is possible to suppress a decrease in color development.

[0124] (Configuration 2) The liquid ejection device described in Configuration 1, wherein the liquid ejection unit has a sixth nozzle row and a seventh nozzle row that eject a post-treatment liquid that does not cause the ink composition of the first ink and the ink composition of the third ink to aggregate, and the first nozzle row or the second nozzle row is located between the sixth nozzle row and the seventh nozzle row in the first direction. With this, by ejecting post-treatment liquid onto the medium onto which the white ink, treatment liquid, and color ink have been ejected, post-treatment such as coating of the color ink adhering to the medium can be performed, thereby further improving color development.

[0125] (Configuration 3) A liquid ejection device according to configuration 1 or 2, wherein the first ink and the second ink are white inks containing titanium oxide, and the liquid ejection device comprises a wiping unit that moves relative to the nozzle surface of the liquid ejection unit in a third direction perpendicular to the first direction and the second direction to wipe the nozzle surface, the liquid ejection unit comprises a first head including the first nozzle row and a second head arranged upstream of the first head in the third direction, and the second head is a head that does not have either a nozzle row that ejects the first ink or the second ink or a nozzle row that ejects black ink containing carbon black. According to this, the second head next to the first head that ejects white ink does not eject white ink or black ink containing hard pigments. Therefore, during wiping, the first head is wiped by the wiping part that does not have hard pigments attached. This reduces or prevents wear on the nozzle surface that occurs during wiping.

[0126] (Configuration 4) A liquid ejection device according to configuration 1 or 2, wherein the first ink and the second ink are white inks containing titanium oxide, and the liquid ejection device comprises a wiping unit that moves relative to the nozzle surface of the liquid ejection unit in a third direction perpendicular to the first direction and the second direction to wipe the nozzle surface, the liquid ejection unit comprises a fourth head including a fourth nozzle row that ejects a black fourth ink containing carbon black, and a second head that is arranged upstream of the fourth head in the third direction, and the second head is a head that does not have either a nozzle row that ejects the first ink or the second ink, or a nozzle row that ejects the fourth ink. According to this, the second head next to the fourth head that ejects black ink does not eject white ink or black ink containing hard pigments. Therefore, during wiping, the fourth head is wiped by the wiping section that does not have hard pigments attached. This reduces or prevents wear on the nozzle surface due to wiping.

[0127] (Configuration 5) A liquid ejection device according to Configuration 1 or 2, wherein the first ink is a white ink containing titanium oxide, and the liquid ejection device comprises a wiping unit that moves relative to the nozzle surface of the liquid ejection unit in a third direction perpendicular to the first direction and the second direction to wipe the nozzle surface, the liquid ejection unit comprises a first head including the first nozzle row, and a fifth head that is arranged upstream of the first head in the third direction, and the fifth head has a nozzle row that ejects a post-treatment liquid that does not cause the ink composition contained in the first ink to aggregate. According to this, the fifth head, which is aligned with the first head that ejects white ink, ejects post-treatment liquid, so that during wiping, the first head is wiped by the wiping section to which the post-treatment liquid has adhered. Because the post-treatment liquid does not have the effect of aggregating the ink composition, it acts as a lubricant during wiping. This makes it possible to more effectively reduce or prevent wear on the nozzle surface that accompanies wiping.

[0128] (Configuration 6) The liquid ejection device according to Configuration 5, wherein, when the wiping unit is moved in the third direction to perform a wiping operation, the post-treatment liquid is ejected from the fifth head before the wiping unit reaches the first head. With this, the post-treatment liquid ejected by the fifth head adheres to the surface of the wiping unit that wipes the first head, improving the slipperiness between the nozzle surface of the first head and the wiping unit, thereby further reducing wear on the nozzle surface due to wiping.

[0129] (Configuration 7) A liquid ejection method for a liquid ejection device comprising: a liquid ejection unit capable of ejecting onto a transported medium a first white ink, a third ink of a different color than the first ink, and a treatment liquid containing an aggregating agent that aggregates at least the composition contained in the third ink; and a movement mechanism that moves the liquid ejection unit back and forth in a first direction and a second direction opposite to the first direction, the method comprising: a first step of ejecting the first ink onto the medium during a period in which the liquid ejection unit moves in the first direction; a second step of ejecting the treatment liquid onto an area onto which the first ink was ejected in the first step; a third step of ejecting the third ink onto an area onto which the treatment liquid was ejected in the second step; and a fourth step of ejecting the treatment liquid onto an area onto which the third ink was ejected in the third step. According to this, when the liquid ejection unit performs printing, it ejects white ink, then ejects treatment liquid, and then ejects color inks. As a result, on the medium, the white ink is cured by the treatment liquid, and the color inks ejected on top of the treatment liquid are mixed with the pretreatment liquid and cured. As a result, it is possible to suppress or prevent the color inks from curing before the white ink is cured, and therefore it is possible to suppress a decrease in color development.

[0130] (Configuration 8) An ejection method for a liquid ejection device according to Configuration 7, wherein an operation including the first step, the second step, the third step, and the fourth step is performed during a period in which the liquid ejection unit moves in the first direction, and an operation including the first step, the second step, the third step, and the fourth step is further performed during a period in which the liquid ejection unit moves in the second direction. This makes it possible to suppress or prevent the color ink from curing before the white ink hardens, both on the outward and return paths while the liquid ejection unit is moved back and forth in the first and second directions, thereby suppressing a decrease in color development.

[0131] (Configuration 9) A liquid ejection device having a liquid ejection unit capable of ejecting liquid onto a medium being transported, and a wiping section that wipes the nozzle surface of the liquid ejection unit, wherein the liquid ejection unit comprises: a first head including a nozzle row that ejects white ink containing titanium oxide or black ink containing carbon black; and a second head that is arranged upstream of the first head in the wiping direction of the wiping section, and does not include a nozzle row that ejects the white ink or the black ink. According to this, the second head, which is aligned with the first head that ejects ink containing hard pigments, does not eject white ink or black ink that also contain hard pigments. Therefore, during wiping, the first head is wiped by the wiping section that does not have hard pigments attached. This reduces or prevents wear on the nozzle surface that occurs during wiping.

[0132] (Configuration 10) The liquid ejection device according to Configuration 9, wherein the second head has a nozzle row that ejects a post-treatment liquid that prevents the white ink composition and the black ink composition from coagulating. With this, the post-treatment liquid ejected by the second head adheres to the surface of the wiping unit that wipes the first head, improving the slipperiness between the nozzle surface of the first head and the wiping unit, thereby further reducing wear on the nozzle surface caused by wiping.

[0133] (Configuration 11) The liquid ejection device according to Configuration 9 or 10, wherein when the wiping operation is performed by the wiping unit, the post-treatment liquid is ejected from the second head before the wiping unit reaches the first head. With this, the post-treatment liquid ejected by the second head adheres to the surface of the wiping unit that wipes the first head, improving the slipperiness between the nozzle surface of the first head and the wiping unit, thereby further reducing wear on the nozzle surface caused by wiping. [Explanation of symbols]

[0134] 11...liquid ejection device, 12...leg portion, 13...casing, 15...feeding portion, 16...guiding portion, 17...recovery portion, 18...tensioning mechanism, 20...liquid ejection portion (liquid ejection unit), 21...carriage (movement mechanism), 22...maintenance unit, 23...liquid supply device, 24...operation panel, 25...liquid container, 26...mounting portion, 27...supply flow path, 28...liquid flow mechanism, 29...control portion, 30, 30A to 30R...heads, 31, 31A to 31R...first ejection row, 32, 32A to 32R...second ejection row, 33...first head group, 34...second head group, 36...nozzle group, 40...nozzle surface, 42...supply flow path, 43...liquid collection device, 44...suction device, 45...capping device, 47...guide shaft, 48...carriage motor (movement mechanism), 51...suction cap, 52...suction holder, 53...suction motor, 54...pressure reduction mechanism, 56...standby cap, 57...standby cap holder, 58...standby cap motor, 60...belt-shaped member (wiping section), 60a...contact position, 61...case, 62...rail, 63...wiping motor, 64...winding motor, 65...power transmission mechanism, 67...exposure opening, 69...unwinding shaft, 70...unwinding section, 71...winding shaft, 72...winding section, 74...upstream roller, 75...tension roller, 76...pressure section, 79...downstream roller, M...medium.

Claims

1. a liquid ejection unit capable of ejecting liquid onto a medium being transported; a moving mechanism that reciprocates the liquid ejection unit in a first direction and a second direction opposite to the first direction, The liquid ejection unit includes: a first nozzle row that ejects a first white ink; a second nozzle row that ejects a second white ink; a third nozzle row provided between the first nozzle row and the second nozzle row in the first direction, the third nozzle row ejecting a third ink having a color different from the first ink and the second ink; a fourth nozzle row that is provided between the first nozzle row and the third nozzle row in the first direction and that ejects a treatment liquid containing an aggregating agent that aggregates at least the ink composition contained in the third ink; a fifth nozzle row disposed between the second nozzle row and the third nozzle row in the first direction and configured to eject the treatment liquid, the fifth nozzle row being disposed on a nozzle surface of the liquid ejection device;

2. the liquid ejection unit has a sixth nozzle row and a seventh nozzle row that eject a post-treatment liquid that does not cause the ink composition of the first ink and the ink composition of the third ink to aggregate, The liquid ejection device according to claim 1 , wherein the first nozzle row or the second nozzle row is located between the sixth nozzle row and the seventh nozzle row in the first direction.

3. the first ink and the second ink are white inks containing titanium oxide, a wiping unit that moves relative to the nozzle surface of the liquid ejection unit in a third direction perpendicular to the first direction and the second direction to wipe the nozzle surface, the liquid ejection unit includes a first head including the first nozzle row, and a second head disposed upstream of the first head in the third direction, 3. The liquid ejection device according to claim 1, wherein the second head is a head that does not have any nozzle row that ejects the first ink or the second ink, and any nozzle row that ejects black ink containing carbon black.

4. the first ink and the second ink are white inks containing titanium oxide, a wiping unit that moves relative to the nozzle surface of the liquid ejection unit in a third direction perpendicular to the first direction and the second direction to wipe the nozzle surface, the liquid ejection unit includes a fourth head including a fourth nozzle row that ejects a fourth black ink containing carbon black, and a second head that is disposed upstream of the fourth head in the third direction; 3. The liquid ejection device according to claim 1, wherein the second head is a head that does not have any of a nozzle row that ejects the first ink or the second ink, and a nozzle row that ejects the fourth ink.

5. the first ink is a white ink containing titanium oxide, a wiping unit that moves relative to the nozzle surface of the liquid ejection unit in a third direction perpendicular to the first direction and the second direction to wipe the nozzle surface, the liquid ejection unit includes a first head including the first nozzle row, and a fifth head disposed upstream of the first head in the third direction, 3. The liquid ejection device according to claim 1, wherein the fifth head has a nozzle row that ejects a post-treatment liquid that prevents the ink composition contained in the first ink from coagulating.

6. The liquid ejection device according to claim 5 , wherein, when the wiping unit is moved in the third direction to perform the wiping operation, the post-treatment liquid is ejected from the fifth head before the wiping unit reaches the first head.

7. A method for discharging a liquid discharge device including: a liquid discharge unit capable of discharging a treatment liquid containing a white first ink, a third ink of a color different from the first ink, and an aggregating agent that aggregates at least a composition contained in the third ink, onto a medium being transported; and a movement mechanism that reciprocates the liquid discharge unit in a first direction and a second direction opposite to the first direction, the method comprising: During a period in which the liquid ejection unit moves in the first direction, a first step of ejecting the first ink onto the medium; a second step of ejecting the treatment liquid onto the region onto which the first ink has been ejected in the first step; a third step of ejecting the third ink onto the region onto which the treatment liquid has been ejected in the second step; a fourth step of ejecting the treatment liquid onto the area onto which the third ink has been ejected in the third step.

8. performing an operation including the first step, the second step, the third step, and the fourth step during a period in which the liquid ejection unit moves in the first direction; The ejection method for the liquid ejection device according to claim 7 , further comprising the step of executing operations including the first step, the second step, the third step, and the fourth step during a period in which the liquid ejection unit moves in the second direction.

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