Liquid ejection device

Abstract

To improve printing accuracy.SOLUTION: A liquid jet device 1 includes a liquid jet head 10 which has a jet surface F1 having a first nozzle array NLA for jetting first ink, and a second nozzle array NLB for jetting second ink, and can hold the liquid jet head in an inclined posture in which the jet surface inclines with respect to a horizontal plane F0. Viscosity of the first ink is lower than viscosity of the second ink. The first nozzle array NLA is positioned above the second nozzle array NLB in a gravity direction G1 in the inclined posture.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a liquid injection device and a liquid injection head.

Background Art

[0002] In a recording head that injects a plurality of types of ink, the injection surface for injecting the ink may be inclined with respect to the horizontal plane (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The viscosity of the ink may vary depending on the type of ink. In the prior art, the relationship between the effects when the viscosities of a plurality of inks are different and the effects when the injection surface is inclined has not been considered.

Means for Solving the Problems

[0005] A liquid injection device according to an aspect of the present invention includes a liquid injection head having an injection surface including a first nozzle row for injecting a first ink and a second nozzle row for injecting a second ink, and the liquid injection head can be held in an inclined posture in which the injection surface is inclined with respect to the horizontal plane. The viscosity of the first ink is lower than the viscosity of the second ink. In the inclined posture, the first nozzle row is located above the second nozzle row with respect to the direction of gravity.

[0006] A liquid ejecting apparatus according to one aspect of the present invention includes a first liquid ejecting head having a first ejection surface including a first nozzle for ejecting a first ink, and a second liquid ejecting head having a second ejection surface including a second nozzle for ejecting a second ink. The viscosity of the first ink is lower than the viscosity of the second ink. The first liquid ejecting head is arranged such that an angle formed between a direction in which the first ink is ejected from the first nozzle and the direction of gravity is a first angle. The second liquid ejecting head is arranged such that an angle formed between a direction in which the second ink is ejected from the second nozzle and the direction of gravity is a second angle greater than the first angle.

[0007] A liquid ejecting head according to one aspect of the present invention includes a first nozzle row for ejecting a first ink, a second nozzle row for ejecting a second ink, and a third nozzle row for ejecting a third ink. The viscosity of the third ink is higher than the viscosity of the first ink and lower than the viscosity of the second ink. The third ink row is located between the first nozzle row and the second nozzle row with respect to the direction of gravity.

Brief Description of the Drawings

[0008]

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Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, in each figure, the dimensions and scales of each part may be appropriately different from the actual ones. Further, since the embodiments described below are preferred specific examples of the present invention, various technically preferable limitations are imposed. However, the scope of the present invention is not limited to these embodiments unless otherwise specifically stated in the following description to limit the present invention.

[0010] In the following description, there may be cases where three mutually intersecting directions are described as the X-axis direction, the Y-axis direction, and the Z-axis direction. The X-axis direction includes the X1 direction and the X2 direction which are opposite directions to each other. The X-axis direction is an example of the first direction. The Y-axis direction includes the Y1 direction and the Y2 direction which are opposite directions to each other. The Y-axis direction is an example of the second direction. The Z-axis direction includes the Z1 direction and the Z2 direction which are opposite directions to each other. The X-axis direction, the Y-axis direction, and the Z-axis direction are orthogonal to each other. Note that the X-axis direction, the Y-axis direction, and the Z-axis direction are directions based on the injection surface F1 described later.

[0011] Also, the downward direction of the gravitational direction is defined as the gravitational direction G1, and the direction orthogonal to both the gravitational direction G1 and the X-axis direction is described as the K-axis direction. Also, the direction opposite to the gravitational direction G1 is defined as the upward direction G2. The K-axis direction includes the K1 direction and the K2 direction which are opposite directions to each other. The K-axis direction is an example of the third direction. The K-axis direction is an example of the horizontal direction. The horizontal direction is a direction orthogonal to the gravitational direction G1. The third direction is a direction orthogonal to both the first direction and the gravitational direction G1.

[0012] FIG. 1 is a schematic diagram showing a liquid injection device 1 according to the first embodiment. FIG. 2 is a block diagram showing an ink flow path. The liquid injection device 1 is an inkjet printing device that injects ink, which is an example of "liquid", as droplets onto a medium PA. The liquid injection device 1 is a so-called line-type printing device in which a plurality of nozzles for injecting ink are distributed over the entire range in the width direction of the medium PA. The medium PA is typically printing paper. Note that the medium PA is not limited to printing paper, and may be a printing target of any material such as a resin film or a fabric.

[0013] The liquid ejection device 1 includes a liquid ejection head 10 having an ejection surface F1 that is inclined with respect to the horizontal plane F0. The liquid ejection device 1 includes a plurality of liquid containers 2, a control unit 3, a medium conveyance mechanism 4, an ink supply unit 5, and the liquid ejection head 10. The liquid ejection device 1 may include one liquid ejection head 10 or may include a plurality of liquid ejection heads 10. The liquid ejection device 1 of the present embodiment includes one liquid ejection head 10. When a plurality of liquid ejection heads 10 are provided, the plurality of liquid ejection heads 10 are arranged in the X-axis direction to form a line head.

[0014] The control unit 3 controls the operations of the respective elements of the liquid ejection device 1. The control unit 3 includes, for example, a processing circuit such as a CPU or an FPGA, and a storage circuit such as a semiconductor memory. Various programs and various data are stored in the storage circuit. The processing circuit realizes various controls by executing the programs and appropriately using the data. CPU is an abbreviation for Central Processing Unit. FPGA is an abbreviation for Field Programmable Gate Array.

[0015] The medium conveyance mechanism 4 is controlled by the control unit 3 and conveys the medium PA in the conveyance direction DM. The conveyance direction DM is the conveyance direction of the medium PA at a position facing the ejection surface F1 and is parallel or substantially parallel to the Y-axis direction. The medium PA is illustrated in FIGS. 3 and 4. The medium conveyance mechanism 4 includes a long conveyance roller along the width direction of the medium PA and a motor that rotates the conveyance roller. Note that the medium conveyance mechanism 4 is not limited to a configuration using a conveyance roller, and for example, a configuration using a drum or an endless belt that conveys the medium PA in a state where it is adsorbed to the outer peripheral surface by an electrostatic force or the like may also be used.

[0016] The liquid ejecting apparatus 1 is formed with a medium conveyance path 4a for conveying a medium PA. The medium conveyance path 4a is a path from a paper feeding section 4b to a paper discharging section 4c. The medium conveyance mechanism 4 conveys the medium PA along the medium conveyance path 4a. The paper feeding section 4b and the paper discharging section 4c include trays capable of storing the medium PA.

[0017] FIG. 2 is a block diagram showing an ink flow path. The liquid container 2 stores ink. Specific examples of the liquid container 2 include, for example, a cartridge detachable from the liquid ejecting apparatus 1, a bag-shaped ink pack formed of a flexible film, and an ink tank capable of being refilled with ink. Note that the type of ink stored in the liquid container 2 is arbitrary.

[0018] The liquid container 2 includes liquid containers 2A, 2B, 2C, and 2D. The first ink is stored in the liquid container 2A. The second ink is stored in the liquid container 2B. The third ink is stored in the liquid container 2C. The fourth ink is stored in the liquid container 2D. For example, the first ink, the second ink, the third ink, and the fourth ink are inks of different colors. These first ink, second ink, third ink, and fourth ink have different viscosities. The viscosity of the first ink is lower than the viscosity of the second ink. The viscosity of the third ink is higher than the viscosity of the first ink and lower than the viscosity of the second ink. The viscosity of the fourth ink is higher than the viscosity of the third ink and lower than the viscosity of the second ink. The components for each type of ink will be described later.

[0019] The difference between the viscosity of the first ink and the viscosity of the second ink is 0.5 mPa·S or more. At 25°C, the viscosity of the first ink is lower than the viscosity of the second ink. At 25°C, the viscosities of the first to fourth inks are in the order of the first ink, the third ink, the fourth ink, and the second ink. Note that the temperature at which the viscosities of the inks are compared may be higher than 25°C, may be lower than 25°C, and it is preferable to compare at the temperature of the ink in the actually used liquid ejection head 10.

[0020] The ink supply unit 5 has ink flow paths 6 and 7 that supply ink from the liquid container 2 to the liquid ejection head 10, and a pressure adjustment unit 8 that adjusts the pressure of the ink in the liquid ejection head 10. The ink flow path 6 includes a flow path from the liquid container 2 to the pressure adjustment unit 8. The ink flow path 7 includes a flow path from the pressure adjustment unit 8 to the liquid ejection head 10. The ink flow path 7 includes a flow path formed in the liquid ejection head 10. The ink flow paths 6 and 7 are formed by, for example, piping or tubes. The ink flow paths 6 and 7 include, for example, a flow path member in which grooves, recesses, through holes, etc. are formed, piping, tubes, etc.

[0021] The pressure adjustment unit 8 adjusts the pressure of the ink supplied to the liquid ejection head 10 so that a predetermined pressure acts on the nozzles N. The pressure adjustment unit 8 is, for example, a negative pressure generation unit including a pressure adjustment valve. This negative pressure generation unit has, for example, a pressure adjustment valve that opens and closes the ink flow path, and a flexible member that deflects based on the differential pressure between the pressure of the ink flow path downstream of the pressure adjustment valve and the atmospheric pressure, and controls the opening and closing of the pressure adjustment valve by moving the pressure adjustment valve by the deflection of this flexible member so that a predetermined range of negative pressure acts on the nozzles N.

[0022] Alternatively, the pressure adjustment unit 8 may adjust the pressure of the ink supplied to the liquid ejection head 10 by a sub-tank that temporarily stores the ink. Specifically, the pressure adjustment unit 8 has a sub-tank and an arbitrary sensor capable of detecting the storage amount of the ink in the sub-tank. When the storage amount of the ink in the sub-tank detected by the sensor decreases below a threshold value, the ink is replenished from the liquid container 2 to keep the storage amount of the ink in the sub-tank substantially constant, that is, to keep the liquid level of the ink stored in the sub-tank substantially constant, thereby adjusting the pressure of the ink in the liquid ejection head 10. Also, the pressure in the sub-tank may be set to a predetermined pressure by a compressor to adjust the pressure of the ink supplied to the liquid ejection head 10.

[0023] The pressure adjustment unit 8 includes pressure adjustment units 8A, 8B, 8C, and 8D. The pressure adjustment unit 8A communicates with the liquid container 2A and adjusts the pressure of the first ink. The pressure adjustment unit 8B communicates with the liquid container 2B and adjusts the pressure of the second ink. The pressure adjustment unit 8C communicates with the liquid container 2C and adjusts the pressure of the third ink. The pressure adjustment unit 8D communicates with the liquid container 2D and adjusts the pressure of the fourth ink.

[0024] FIG. 3 is a bottom view showing the nozzle plate 11 on which the nozzle rows NL are formed. The liquid ejection head 10 includes a nozzle plate 11 having a plurality of nozzle rows NL. The nozzle row NL includes a plurality of nozzles N for ejecting ink. Among the surfaces of the nozzle plate 11, the surface facing the medium PA is the ejection surface F1 for ejecting ink. A plurality of nozzles N are formed on the ejection surface F1. The ejection surface F1 is arranged at a distance from the medium PA.

[0025] The plurality of nozzle rows NL include nozzle rows NLA, NLB, NLC, and NLD. The nozzle row NLA includes a plurality of nozzles N for ejecting the first ink. The nozzle row NLB includes a plurality of nozzles N for ejecting the second ink. The nozzle row NLC includes a plurality of nozzles N for ejecting the third ink. The nozzle row NLD includes a plurality of nozzles N for ejecting the fourth ink. When the nozzle rows NLA, NLB, NLC, and NLD are not distinguished, they may be described as the nozzle row NL.

[0026] The nozzle row NL includes a plurality of nozzles N arranged in the X-axis direction. The nozzle N is a through hole that penetrates in the plate thickness direction of the nozzle plate 11. The plate thickness direction of the nozzle plate 11 is along the Z-axis direction. The nozzle rows NLA, NLB, NLC, and NLD are arranged at different positions in the Y-axis direction.

[0027] In the direction of Y1, the nozzle rows NLA, NLC, NLD, and NLB are arranged in this order. The nozzle rows NLA, NLC, NLD, and NLB are spaced apart from each other in the Y-axis direction. The nozzle row NLC is arranged between the nozzle row NLA and the nozzle row NLB in the Y-axis direction. The nozzle row NLD is arranged between the nozzle row NLC and the nozzle row NLB in the Y-axis direction.

[0028] When viewed in the Y-axis direction, at least a part of the nozzle rows NLA, NLC, NLD, and NLB overlap. In this embodiment, when viewed in the Y-axis direction, the nozzle rows NLA, NLC, NLD, and NLB all overlap.

[0029] As shown in FIG. 1, the liquid ejection head 10 is held in an inclined posture with respect to the housing 1a of the liquid ejection device 1, for example. Note that "the liquid ejection head 10 is held with respect to the housing 1a of the liquid ejection device 1" includes both the case where the liquid ejection head 10 is directly fixed and held with respect to the housing 1a, and the case where the liquid ejection head 10 is indirectly held with respect to the housing 1a via a member different from the housing 1a. The liquid ejection device 1 can hold the liquid ejection head 10 in an inclined posture in which the ejection surface F1 is inclined with respect to the horizontal plane F0.

[0030] FIG. 4 is a schematic view showing the liquid ejection head 10 in an inclined posture in which the ejection surface F1 is inclined with respect to the horizontal plane F0, and is a view showing the head differences H1 to H4 in the nozzle row NL. As shown in FIG. 4, the ejection surface F1 of the liquid ejection head 10 is inclined at an inclination angle θ1 with respect to the horizontal plane F0. The inclination angle θ1 is, for example, an acute angle less than 90 degrees. The inclination angle θ1 may be an obtuse angle exceeding 90 degrees. The inclination angle θ1 may be 90 degrees. The inclination here includes 90 degrees. The inclined posture of the liquid ejection head 10 in which the ejection surface F1 is inclined at the inclination angle θ1 with respect to the horizontal plane F0 is an example of the inclined posture.

[0031] In the inclined posture of the liquid ejection head 10 shown in FIG. 4, the plurality of nozzle rows NL are arranged at different heights with respect to the gravitational direction G1. The nozzle row NLA is arranged at the height position HA, and the nozzle row NLB is arranged at the height position HB. The height position HA is located above the height position HB. That is, the nozzle row NLA that ejects the first ink with a lower viscosity is located above the nozzle row NLB that ejects the second ink with a higher viscosity.

[0032] The nozzle row NLC is arranged at the height position HC. The height position HC is below the height position HA and above the height position HB. In the inclined posture of the liquid ejection head 10, the nozzle row NLC is located below the nozzle row NLA and above the nozzle row NLB. That is, among the first ink, the second ink, and the third ink, the nozzle row NLC that ejects the third ink with the second lowest viscosity is arranged between the nozzle row NLA and the nozzle row NLB with respect to the gravitational direction G1.

[0033] The nozzle row NLD is arranged at the height position HD. The height position HD is below the height position HC and above the height position HB. In the inclined posture of the liquid ejection head 10, the nozzle row NLD is located below the nozzle row NLC and above the nozzle row NLB. That is, among the second ink, the third ink, and the fourth ink, the nozzle row NLD that ejects the fourth ink with the second lowest viscosity is arranged between the nozzle row NLC and the nozzle row NLB with respect to the gravitational direction G1.

[0034] As shown in FIG. 4, when viewed in the X-axis direction, the nozzle rows NLA, NLC, NLD, and NLB are arranged at intervals from each other.

[0035] When comparing the plurality of nozzle rows NL, the nozzle row NL that ejects the ink with a lower viscosity is located above the nozzle row NL that ejects the ink with a higher viscosity.

[0036] Next, with reference to FIGS. 5 to 7, the behavior of the droplets 101 and 102 ejected from the nozzle N and the satellite droplets 101a separated from the droplet 101 will be described. Here, the nozzle plates 11 and 111 of a liquid ejection head that ejects two types of inks having different viscosities will be exemplified and described. In FIGS. 5 and 6, the nozzle plate 111 according to Comparative Example 1 is illustrated, and in FIG. 7, the nozzle plate 11 according to Example 1 is illustrated. In the nozzle plate 111 according to Comparative Example 1, the nozzle row NLB that ejects the second ink having a higher viscosity is located above the nozzle row NLA that ejects the first ink having a lower viscosity. In the nozzle plate 11 according to Example 1, contrary to the case of Comparative Example 1, the nozzle row NLA that ejects the first ink is located above the nozzle row NLB that ejects the second ink.

[0037] FIG. 5 is a cross-sectional view showing the nozzle plate 111 according to Comparative Example 1 and shows a state in which droplets are ejected from the nozzle. The droplet 102, which is the second ink, is ejected from the nozzle NB. The droplet 101, which is the first ink, is ejected from the nozzle NA. The viscosity of the first ink is lower than that of the second ink, and satellite droplets 101a are more likely to be generated compared to the second ink. The volume of the satellite droplet 101a is smaller than the volume of the droplet 101. The mass of the satellite droplet 101a is smaller than the mass of the droplet 101. According to the study by the present inventors, it was found that the satellite droplet 101a rises in the upward direction G2 after being ejected from the nozzle N.

[0038] FIG. 6 is a cross-sectional view showing the nozzle plate 111 according to Comparative Example 1, and is a view showing a state in which satellite droplets separated from the droplet 101 are rising. As shown in FIG. 6, when the satellite droplet 101a rises, it may adhere to the nozzle NB on the ejection surface F1. And when the satellite droplet 101a adheres to the nozzle NB, there is a possibility that the second ink in the nozzle NB and the first ink which is the satellite droplet 101a are mixed and the print quality is deteriorated. Further, when the satellite droplet 101a rises, it adheres to a portion around the nozzle NB on the ejection surface F1, which may cause an abnormality in the meniscus of the second ink formed in the nozzle NB and cause ejection failure.

[0039] FIG. 7 is a cross-sectional view showing the nozzle plate 11 according to Example 1, and is a view showing a state in which droplets 101 and 102 are ejected from the nozzles NA and NB. In the state shown in FIG. 7, the satellite droplet 101a separated from the droplet 101 is located above the droplet 101. Above the satellite droplet 101a, the nozzle NB and the droplet 102 do not exist. Therefore, there is no possibility that the satellite droplet 101a adheres to the droplet 102. Thus, since the nozzle row NLA for ejecting the first ink having a lower viscosity is located above the nozzle row NLB with respect to the gravitational direction G1, in Example 1, the possibility of color mixing between the first ink and the second ink and an abnormality occurring in the meniscus of the first ink in the nozzle N of the nozzle row NLA is reduced.

[0040] In the liquid ejection head 10 according to the first embodiment shown in FIG. 4, the nozzle rows NLA, NLB, NLC, and NLD are arranged according to the viscosity of the ink. The nozzle row NLA for ejecting the first ink having the lowest viscosity is arranged at a higher position with respect to the gravitational direction G1 than the other nozzle rows NLB, NLC, and NLD. Thus, since the nozzle row NLA for ejecting the first ink which is most likely to generate satellite droplets is arranged at a high position, it is possible to prevent the first ink from being mixed with the other second ink, third ink, and fourth ink and causing an abnormality in the meniscus of the second ink, third ink, and fourth ink in the nozzles N of the nozzle rows NLB, NLC, and NLD.

[0041] In the liquid ejection head 10, the nozzle row NLB for ejecting the second ink with the highest viscosity is arranged at a position lower than the other nozzle rows NLA, NLC, and NLD in the gravitational direction G1. In this way, since the nozzle row NLB for ejecting the second ink, which is least likely to generate satellite droplets, is arranged at a lower position, it is possible to prevent the second ink from mixing with the other first ink, third ink, and fourth ink, and from causing abnormalities in the menisci of the first ink, third ink, and fourth ink in the nozzles N of the nozzle rows NLA, NLC, and NLD.

[0042] In the liquid ejection head 10, among the plurality of types of inks, the nozzle row for ejecting the first ink with a lower viscosity is located above the nozzle row for ejecting the second ink with a higher viscosity in the gravitational direction G1. Therefore, the mixing of the inks and the occurrence of abnormalities in the menisci in the nozzles N are suppressed. As a result, the printing accuracy in the liquid ejection apparatus 1 can be improved. Compared with the configuration of Comparative Example 1 in which the nozzle row NL for ejecting the second ink with a higher viscosity is arranged at a higher position than the nozzle row NL for ejecting the first ink with a lower viscosity, in the liquid ejection head 10, the possibility of mixing of the plurality of inks and the possibility of causing abnormalities in the menisci of the inks in the nozzles N are low.

[0043] In the liquid ejection head 10, the nozzle row NLC is located between the nozzle row NLA and the nozzle row NLB in the gravitational direction G1. The viscosity of the third ink ejected from the nozzle row NLC is higher than the viscosity of the first ink and lower than the viscosity of the second ink. The satellite droplets separated from the first ink are less likely to adhere to the lower third ink. Since the possibility of generating satellite droplets from the second ink is low, the possibility of the second ink adhering to the third ink and the possibility of causing abnormalities in the meniscus of the third ink in the nozzle N of the nozzle row NLC are low.

[0044] In the liquid ejection head 10, the nozzle row NLD is located between the nozzle row NLC and the nozzle row NLB with respect to the gravitational direction G1. The viscosity of the fourth ink ejected from the nozzle row NLD is higher than that of the third ink and lower than that of the second ink. The satellite droplets separated from the third ink are less likely to adhere to the lower fourth ink. Since there is little possibility of generating satellite droplets from the second ink, the possibility that the second ink adheres to the fourth ink or that the meniscus in the nozzle N of the nozzle row NLD is abnormal is low.

[0045] In the liquid ejection device according to the related art, the combined relationship between the influence of the different viscosities of the plurality of inks and the influence of the inclination of the ejection surface F1 of the liquid ejection head 10 has not been considered. Examples of the influence of the different viscosities of the inks include variations in the ink supply ability due to differences in pressure loss, or variations in the ease of generating satellite droplets as described above. The lower the viscosity of the ink, the smaller the pressure loss of the ink flowing through the ink flow path 7, and the higher the viscosity of the ink, the greater the pressure loss of the ink flowing through the ink flow path 7 tends to be.

[0046] Examples of the influence of the inclination of the ejection surface F1 include differences in the height positions of the plurality of nozzles N that eject different types of inks, and variations in the head difference between the pressure adjustment unit 8 and the nozzle N due to differences in the heights of the plurality of nozzles N that eject different types of inks.

[0047] When there are variations in the head difference, there is a possibility that the ease of supplying ink to the plurality of nozzle rows NL varies. If the differences in viscosity between the inks and the inclination of the ejection surface F1 are not considered, for example, as described above, the satellite droplets of the ink that are likely to generate satellite droplets may adhere to the ink that is less likely to generate satellite droplets, causing color mixing, or may adhere to the meniscus of the nozzle N corresponding to the ink that is less likely to generate satellite droplets, causing an abnormality in the meniscus.

[0048] In addition, when not considering that the viscosity differs for each ink and that the ejection surface F1 is inclined, there also arises a problem that the difference in the ink ejection characteristics for each nozzle row NL becomes large. Examples of the ejection characteristics include, for example, the weight Iw and the velocity Vm of the ejected droplets.

[0049] For example, when each pressure adjusting unit 8 corresponding to each of the plurality of nozzle rows NL has a common configuration, if each distance (head difference) in the gravitational direction between each nozzle row NL and each pressure adjusting unit 8 corresponding to each nozzle row NL is equal, the pressure (negative pressure) acting on each nozzle row NL becomes the same. However, when the liquid ejection head 10 is inclined, the plurality of nozzle rows NL are arranged at different positions with respect to the gravitational direction, resulting in variations in each head difference, and further variations in the pressure loss due to differences in the viscosity of each ink, which may cause variations in the pressure acting on each nozzle row NL.

[0050] Next, with reference to FIG. 4, the head differences H1 to H4 in the nozzle row NL will be described. In FIG. 4, the height position H0 of the pressure adjusting unit 8 is shown with respect to the gravitational direction G1. The height position H0 is located above the height positions HA, HB, HC, and HD of the nozzle rows NLA, NLB, NLC, and NLD. As described above, they are in the order of the positions HA, HC, HD, and HB from high to low. The height position H0 of the pressure adjusting unit 8 is not limited to being above the height positions of the nozzle rows NLA, NLB, NLC, and NLD. The height position H0 of the pressure adjusting unit 8 may also be below the height positions of the nozzle rows NLA, NLB, NLC, and NLD. The height position H0 of the pressure adjusting unit 8 may also be the height position between the nozzle row NLA and the nozzle row NLB. Also, the height positions of the plurality of pressure adjusting units 8A, 8B, 8C, and 8D are all the height position H0.

[0051] The head difference H2 between the pressure adjustment unit 8 and the nozzle row NLB is larger than the head difference H4 between the pressure adjustment unit 8 and the nozzle row NLD. The head difference H4 between the pressure adjustment unit 8 and the nozzle row NLD is larger than the head difference H3 between the pressure adjustment unit 8 and the nozzle row NLC. The head difference H3 between the pressure adjustment unit 8 and the nozzle row NLC is larger than the head difference H1 between the pressure adjustment unit 8 and the nozzle row NLA.

[0052] In the inclined posture of the liquid ejection head 10 shown in FIG. 4, the head differences H1, H2, H3, and H4 acting on the nozzle row NL are different according to the height position.

[0053] Here, paying attention to the two nozzle rows of the nozzle row NLA and the nozzle row NLB, the variation in the ease of ink supply due to the variation in the head difference will be described. Generally, the larger the head difference, the more likely it is to supply ink to the nozzle row. As described above, since the head difference H2 between the pressure adjustment unit 8 and the nozzle row NLB is larger than the head difference H1 between the pressure adjustment unit 8 and the nozzle row NLA, in a configuration where inks having the same viscosity are supplied to the nozzle row NLA and the nozzle row NLB, the nozzle row NLB is more likely to supply ink than the nozzle row NLA. That is, the nozzle row NLB is more likely to supply ink than the nozzle row NLA. Further, since the first ink has a lower viscosity than the second ink, the first ink is an ink that is easier to supply than the second ink.

[0054] Then, when the easily supplyable first ink is supplied to the easily supplyable nozzle row NLB and the difficultly supplyable second ink is supplied to the difficultly supplyable nozzle row NLA, a large difference occurs between the ejection characteristics of the nozzle row NLA and the ejection characteristics of the nozzle row NLB. Further, in this case, there is also a possibility that a relatively large negative pressure acts on the meniscus of the nozzle row NLA to draw air bubbles from the nozzle N, or a relatively large positive pressure acts on the meniscus of the nozzle row NLB to cause the ink to overflow from the nozzle N and the meniscus to be destroyed.

[0055] In the liquid ejection device 1, the viscosity of the first ink supplied to the nozzle row NLA disposed above is lower than the viscosity of the second ink supplied to the nozzle row NLB disposed below. Thereby, variations in the ease of ink supply due to differences in pressure loss for each ink caused by the viscosity difference and variations in the ease of ink supply due to variations in the head difference are alleviated, and variations in the ease of ink supply to the plurality of nozzle rows NL that eject different types of ink can be alleviated. As a result, in the liquid ejection device 1, variations in the ejection characteristics of ink among the plurality of nozzle rows NL are alleviated.

[0056] In the liquid ejection device 1, the viscosity of the third ink supplied to the nozzle row NLC is higher than the viscosity of the first ink supplied to the upper nozzle row NLA and lower than the viscosity of the second ink supplied to the lower nozzle row NLB. Thereby, in the liquid ejection device 1, variations in the ejection characteristics of ink among the plurality of nozzle rows NL are alleviated.

[0057] In the liquid ejection device 1, the viscosity of the fourth ink supplied to the nozzle row NLD is higher than the viscosity of the third ink supplied to the upper nozzle row NLC and lower than the viscosity of the second ink supplied to the lower nozzle row NLB. In the liquid ejection device 1, variations in the ejection characteristics of ink among the plurality of nozzle rows NL are alleviated.

[0058] Next, with reference to FIG. 8, the inclined posture of the liquid ejection head 10 according to the second embodiment will be described. FIG. 8 is a schematic view showing the liquid ejection head 10 according to the second embodiment, and is a view showing an inclined posture in which the ejection surface F1 is inclined so as to face obliquely upward. The difference between the liquid ejection head 10 of the second embodiment shown in FIG. 8 and the liquid ejection head 10 of the first embodiment shown in FIG. 4 is that the inclination angle θ2 of the ejection surface F1 is different from the inclination angle θ1.

[0059] The inclination angle θ2 is an angle greater than 90 degrees with respect to the horizontal plane F0 and is an obtuse angle. The inclination angle θ2 is a rotation angle in the counterclockwise direction as shown in the figure about the rotation axis along the X-axis direction. In FIG. 8, the ejection surface F1 is inclined so as to face obliquely upward. The liquid ejection head 10 according to such Example 2 exhibits the same operational effects as the liquid ejection head 10 according to the above-described first embodiment, and can suppress variations in the ejection characteristics of ink in a plurality of nozzle rows.

[0060] Next, with reference to FIG. 9, the inclination posture of the liquid ejection head 10 according to Example 3 will be described. FIG. 9 is a schematic view showing the liquid ejection head 10 according to Example 3, and is a view showing a posture in which the ejection surface F1 is perpendicular to the horizontal plane F0. The difference between the liquid ejection head 10 of Example 3 shown in FIG. 9 and the liquid ejection head 10 of the first embodiment shown in FIG. 4 is that the angle θ3 of the ejection surface F1 is different from the inclination angle θ1. Note that the inclination posture of the liquid ejection head 10 may include a posture perpendicular to the horizontal plane F0. In the present embodiment, there may be a case where the ejection surface F1 is perpendicular to the horizontal plane F0 and is said to be inclined. The angle θ3 forms 90 degrees with respect to the horizontal plane F0 and is a right angle. The liquid ejection head 10 according to such Example 3 exhibits the same operational effects as the liquid ejection head 10 according to the above-described first embodiment, and can suppress variations in the ejection characteristics of ink in a plurality of nozzle rows.

[0061] Next, with reference to FIG. 10, the posture change of the liquid ejection head 10 according to Example 4 will be described. FIG. 10 is a schematic view showing the liquid ejection head 10 according to Example 4. In FIG. 10, the liquid ejection head 10 in the first posture P1 in which the ejection surface F1 is inclined with respect to the horizontal plane F0 is shown by a solid line, and the liquid ejection head 10 in the second posture P2 in which the ejection surface F1 is arranged along the horizontal plane F0 is shown by a broken line. The liquid ejection head 10 can rotate about a rotation axis S1 extending in the X-axis direction. The first posture P1 is an example of an inclined posture.

[0062] The posture of the liquid ejection head 10 can be changed to a plurality of postures including a first posture P1 and a second posture P2. The liquid ejection apparatus 1 according to Example 4 has a posture changing mechanism 13 that changes the posture of the liquid ejection head 10. The posture changing mechanism 13 includes a bearing 14 that holds a rotation shaft S1 extending in the X-axis direction, and a drive mechanism 15 that rotates the rotation shaft S1. The bearing 14 rotatably supports the rotation shaft S1. The drive mechanism 15 includes, for example, a motor.

[0063] Next, with reference to FIG. 11, the liquid ejection head 10 according to Example 5 will be described. FIG. 11 is a schematic diagram showing the liquid ejection head 10 of the liquid ejection apparatus 1 according to Example 5 and a cap 22 that covers the ejection surface F1 of the liquid ejection head 10. The liquid ejection apparatus 1 can perform a maintenance operation. The liquid ejection apparatus 1 performs a maintenance operation in the second posture P2 of the liquid ejection head 10 shown in Example 4. The liquid ejection apparatus 1 performs a printing operation in the first posture P1 shown in FIG. 10 and a maintenance operation in the second posture P2 shown in FIG. 11.

[0064] The liquid ejection apparatus 1 includes a cap 22, a pipe 23, and a pump 24 that are used for a maintenance operation. The cap 22 covers the ejection surface F1 of the liquid ejection head 10. The cap 22 is arranged so as to cover the openings of the nozzles N in the plurality of nozzle rows NL. A space 22a for receiving the ink ejected from the nozzles N is formed in the cap 22.

[0065] A pipe 23 is connected to the cap 22. The pipe 23 is a pipe that discharges the ink present in the space 22a of the cap 22. A pump 24 is connected to the pipe 23. By driving the pump 24, the ink in the cap 22 can be sucked and discharged outside the cap 22.

[0066] As maintenance operations of the liquid ejection device 1, there are flushing processing, suction cleaning, and pressure cleaning processing. These maintenance operations are executed in the second posture P2 of the liquid ejection head 10. In the flushing processing, by applying pressure fluctuations to the pressure chamber communicating with the nozzle N using the actuator of the liquid ejection head 10, ink that does not contribute to the recording operation is ejected from the nozzle N. In the suction cleaning processing, for example, the ink is sucked from the nozzle N using the pump 24. Further, in the pressure cleaning processing, the ink flow path in the liquid ejection head 10 may be pressurized from upstream of the pressure chamber using a pump or the like (not shown) to discharge the ink from the nozzle N. Note that the "recording operation" means discharging ink from the nozzle N, attaching the ink to a medium, and recording characters, images, etc.

[0067] In this way, in the liquid ejection device 1, by performing maintenance processing, unnecessary ink in the nozzle N can be discharged to the outside of the liquid ejection head 10. The second posture P2 of the liquid ejection head 10 is such that the ejection surface F1 is parallel to the horizontal plane F0. In the liquid ejection device 1, in this second posture P2, maintenance operations can be performed, so the remaining amount of ink in the cap 22 during air suction can be reduced. For example, when the liquid ejection head 10 is in the first posture P1, the cap 22 is inclined, so ink remains in the corner portion 22c in the cap 22. On the other hand, in this embodiment, since the maintenance operation is performed with the bottom surface 22b of the cap 22 arranged along the horizontal plane F0, the ink remaining in the cap 22 can be reduced. When performing the maintenance operation in an inclined posture, there is a risk of ink leakage from the seal portion during capping. The seal portion during capping includes the portion where the cap 22 and the ejection surface F1 contact.

[0068] Next, with reference to FIG. 12, the maintenance operation in a state where the liquid ejection head 10 is inclined will be described. As shown in FIG. 12, in the state of the first posture P1 in which the liquid ejection head 10 shown in the fourth embodiment is inclined, the maintenance operation may be performed.

[0069] The liquid ejecting apparatus 1 including a liquid ejecting head 10 executes a cleaning operation of ejecting a first ink from a nozzle row NLA and a second ink from a second nozzle row NLB onto an ejection surface F1 in a state of a first posture P1. The cleaning operation is one of maintenance operations. Ejecting ink onto the ejection surface F1 means, for example, collapsing the meniscus of the ink in the nozzle N to cause the ink to leak from the nozzle N. The ink leaking from the nozzle N flows along the ejection surface F1.

[0070] Here, when ink with a high viscosity is ejected onto the ejection surface F1, the ink tends to stay on the ejection surface F1, and when ink with a low viscosity is ejected onto the ejection surface F1, the ink tends to move on the ejection surface F1. From the nozzle row NLA arranged at the highest position among the plurality of nozzle rows NL, the first ink with a low viscosity leaks out. Thereby, the ink adhering to the ejection surface F1 can be washed away. Since the first ink that most easily flows along the ejection surface F1 is ejected from a high position, the second ink that is ejected from a low position and tends to stay on the ejection surface F1 can be washed away. As a result, the ink remaining on the ejection surface F1 can be reduced. When ink remains on the ejection surface F1, the ink adhering to the ejection surface F1 may flow downward and mix with the ink ejected from the lower nozzles N. However, in the liquid ejecting apparatus 1, since the ink remaining on the ejection surface F1 is reduced, a decrease in print quality is suppressed.

[0071] In this cleaning operation, a pressure cleaning process of ejecting ink from the nozzle N by pressurizing from inside the liquid ejecting head 10 may be executed, or a suction cleaning process of ejecting ink from the nozzle N by suction from outside the liquid ejecting head 10 may be executed.

[0072] Next, the components of the ink will be described with reference to the component table shown in FIG. 13. Hereinafter, unless otherwise specified, those described as "parts" and "%" with respect to the component amounts are based on mass.

[0073] <Adjustment of Pigment Dispersion Liquid> To a solution prepared by dissolving 5.0 g of concentrated hydrochloric acid in 5.5 g of water, 1.6 g of 4-amino-1,2-benzenedicarboxylic acid was added at a temperature of 5 °C. In order to maintain the temperature below 10 °C, while stirring with an ice bath, a solution prepared by dissolving 1.8 g of sodium nitrite in 9.0 g of water was added to the solution obtained above. After stirring for 15 minutes, 6.0 g of carbon black with a specific surface area of 220 m 2 / g and a DBP oil absorption of 105 mL / 100 g was added and then mixed. Further, after stirring for 15 minutes, the resulting slurry was filtered through filter paper, the carbon black was washed thoroughly with water, and dried in an oven at 110 °C. Water was added to the obtained carbon black to obtain a pigment dispersion liquid (pigment content: 15.0%) in a state where a self-dispersing pigment having -C6H3-(COONa)2 groups bonded to the particle surface of the carbon black was dispersed in water. Thereafter, using the ion exchange method, the sodium ions in the pigment dispersion liquid were replaced with potassium ions. The pigment dispersion liquid was used for the preparation of the second ink having a black hue.

[0074] <Adjustment of Liquid Containing Dye> A liquid (dye content: 10.0%) containing Dye 1 (C.I. Direct Blue 199), Dye 2 (C.I. Acid Red 289), and Dye 3 (C.I. Direct Yellow 132) was obtained. The liquid containing Dye 1 was used for the preparation of the first ink having a cyan hue. The liquid containing Dye 2 was used for the preparation of the fourth ink having a magenta hue. The liquid containing Dye 3 was used for the preparation of the third ink having a yellow hue.

[0075] <Adjustment of Ink> The components shown in the table shown in FIG. 13 were mixed and stirred well. Then, pressure filtration was performed using a cellulose acetate filter with a pore size of 1.2 μm (manufactured by Advantec) to prepare the ink. The viscosity η of the ink at 25°C is described in the lower part of the table. The viscosity η of the ink was measured using a rotational viscometer (RE80 type viscometer, manufactured by Toki Sangyo Co., Ltd.). Note that the viscosity of the ink may also be measured with a viscometer (trade name "RE80 type viscometer", manufactured by Toki Sangyo Co., Ltd.). Acetylenol E100 is a nonionic surfactant manufactured by Kawaken Fine Chemicals Co., Ltd.

[0076] Next, with reference to FIG. 14, the arrangement of the nozzle rows NL of the liquid ejection head 10B according to Modification 1 will be described. FIG. 14 is a bottom view showing the ejection surface 11B of the liquid ejection head 10B according to Modification 1. The liquid ejection head 10B has a plurality of nozzle rows NL. The nozzle rows NL include nozzle rows NLA1, NLA2, NLA3 for ejecting the first ink, nozzle rows NLB1, NLB2, NLB3 for ejecting the second ink, nozzle rows NLC1, NLC2, NLC3 for ejecting the third ink, and nozzle rows NLD1, NLD2, NLD3 for ejecting the fourth ink. Note that when the nozzle rows NLA1, NLA2, NLA3, NLB1, NLB2, NLB3, NLC1, NLC2, NLC3, NLD1, NLD2, NLD3 are not distinguished, they may be described as the nozzle row NL.

[0077] The liquid ejection head 10B has a plurality of head chips 12. A nozzle plate having nozzles N formed thereon is provided on the head chip 12. A nozzle row NL for ejecting one type of ink is provided on the head chip 12. The head chip 12 has a pressure chamber and an actuator (not shown). The pressure of the ink in the pressure chamber is increased by the actuator to eject the ink from the nozzles N.

[0078] The nozzle arrays NLA1, NLA2, and NLA3 are arranged at different positions from each other in the X-axis direction. The nozzle arrays NLA1, NLA2 and the nozzle array NLA3 are arranged at different positions from each other in the Y-axis direction. The nozzle array NLA2 is positioned in the Y2 direction relative to the nozzle arrays NLA1 and NLA3. In the first posture P1 of the liquid ejection head 10B, the nozzle array NLA2 is positioned above the nozzle arrays NLA1 and NLA3 with respect to the gravitational direction G1. In the first posture P1, the ejection surface F2 is in a state inclined with respect to the horizontal plane.

[0079] The arrangement of the nozzle arrays NLB1, NLB2, and NLB3 is the same as the arrangement of the nozzle arrays NLA1, NLA2, and NLA3. The nozzle arrays NLB1, NLB2, NLB3 and the nozzle arrays NLA1, NLA2, NLA3 are spaced apart from each other in the Y-axis direction.

[0080] The arrangement of the nozzle arrays NLC1, NLC2, and NLC3 is the same as the arrangement of the nozzle arrays NLA1, NLA2, and NLA3. The nozzle arrays NLC1, NLC2, NLC3 are positioned in the Y-axis direction between the nozzle arrays NLA1, NLA2, NLA3 and the nozzle arrays NLB1, NLB2, NLB3.

[0081] The arrangement of the nozzle arrays NLD1, NLD2, and NLD3 is the same as the arrangement of the nozzle arrays NLA1, NLA2, and NLA3. The nozzle arrays NLD1, NLD2, NLD3 are positioned in the Y-axis direction between the nozzle arrays NLC1, NLC2, NLC3 and the nozzle arrays NLB1, NLB2, NLB3.

[0082] The liquid ejection device 1 may include the liquid ejection head 10B instead of the liquid ejection head 10. The liquid ejection device 1 including the liquid ejection head 10B exhibits the same operational effects as the liquid ejection device 1 including the above-described liquid ejection head 10.

[0083] Next, with reference to FIG. 15, the arrangement of the nozzle rows NL of the liquid ejection head 10C according to Modification 2 will be described. FIG. 15 is a bottom view showing the ejection surface F3 of the liquid ejection head 10C according to Modification 2. The liquid ejection head 10C has a plurality of nozzle rows NL. The nozzle rows NL include a nozzle row NLA for ejecting the first ink, a nozzle row NLB for ejecting the second ink, a nozzle row NLC for ejecting the third ink, and a nozzle row NLD for ejecting the fourth ink. Note that when not distinguishing the nozzle rows NLA, NLB, NLC, and NLD, they may be referred to as the nozzle row NL.

[0084] The liquid ejection head 10C has a plurality of head chips 12C. A nozzle plate 11C having nozzles N formed thereon is provided on the head chip 12C. The nozzle rows NLA, NLB, NLC, and NLD are respectively provided on the head chip 12C.

[0085] In FIG. 15, a V-axis direction and a W-axis direction orthogonal to each other are shown. The V-axis direction and the W-axis direction are orthogonal to the Z-axis direction. The V-axis direction and the W-axis direction are directions based on the ejection surface F3. The V-axis direction includes a V1 direction and a V2 direction. The W-axis direction includes a W1 direction and a W2 direction. The V-axis direction intersects the X-axis direction at an inclination angle α.

[0086] The plurality of nozzle rows NL extend along the V-axis direction. The nozzles N included in the nozzle row NL are arranged in the V-axis direction. The nozzle row NLA and the nozzle row NLD are arranged in the V-axis direction. The nozzle row NLA and the nozzle row NLD are separated from each other in the V-axis direction. The nozzle row NLA and the nozzle row NLD are separated from each other in the Y-axis direction. In FIG. 15, virtual lines L3 and L4 are shown as two-dot chain lines. The virtual lines L3 and L4 are straight lines that are separated from each other in the Y-axis direction and extend along the X-axis direction. The virtual line L3 is located in the Y2 direction with respect to the virtual line L4. The nozzle rows NLA and NLC are located in the Y2 direction with respect to the virtual line L3, and the nozzle rows NLB and NLD are located in the Y1 direction with respect to the virtual line L4.

[0087] The nozzle rows NLC and NLB are arranged in the V-axis direction. The nozzle row NLC and the nozzle row NLB are spaced apart in the V-axis direction. The nozzle row NLC and the nozzle row NLB are spaced apart in the Y-axis direction. In the liquid ejection head 10C, the nozzle rows NLA and NLC are an example of the first nozzle row, and the nozzle rows NLD and NLB are an example of the second nozzle row.

[0088] When viewed in the Y-axis direction, at least a part of the nozzle row NLA and the nozzle rows NLD and NLB overlap. For example, of two head chips 12C adjacent to each other in the X-axis direction, the one arranged in the X1 direction is defined as the head chip 12C1, and the one arranged in the X2 direction of the head chip 12C1 is defined as the head chip 12C2. The nozzle row NLA of the head chip 12C1 and the nozzle rows NLD and NLB of the head chip 12C2 overlap at least partially when viewed in the Y-axis direction. Note that the nozzle row NLA and the nozzle rows NLD and NLB within the same head chip 12 may overlap at least partially in the Y-axis direction.

[0089] Similarly, when viewed in the Y-axis direction, at least a part of the nozzle row NLC and the nozzle rows NLD and NLB overlap. The nozzle row NLC of the head chip 12C1 and the nozzle rows NLD and NLB of the head chip 12C2 overlap at least partially when viewed in the Y-axis direction. Note that the nozzle row NLC and the nozzle rows NLD and NLB within the same head chip 12 may overlap at least partially in the Y-axis direction.

[0090] When viewed in the X-axis direction, the nozzle row NLA and the nozzle rows NLD and NLB are arranged with a space therebetween in the Y-axis direction. When viewed in the X-axis direction, the nozzle row NLC and the nozzle rows NLD and NLB are arranged with a space therebetween in the Y-axis direction.

[0091] Regarding the Y-axis direction, the distance between the nozzle row NLA and the nozzle row NLC provided in the same head chip 12C is narrower than the distance between the nozzle row NLC provided in the head chip 12C1 and the nozzle row NLA provided in the head chip 12C2.

[0092] The nozzle NA1 located at the upper end of the nozzle row NLA with respect to the gravity direction G1 is located above the nozzle ND1 located at the upper end of the nozzle row NLD and the nozzle NB1 located at the upper end of the nozzle row NLB with respect to the gravity direction G1.

[0093] The nozzle NC1 located at the upper end of the nozzle row NLC with respect to the gravity direction G1 is located above the nozzle ND1 located at the upper end of the nozzle row NLD and the nozzle NB1 located at the upper end of the nozzle row NLB with respect to the gravity direction G1.

[0094] The liquid ejecting apparatus 1 including such a liquid ejecting head 10C exhibits the same operational effects as the liquid ejecting apparatus 1 including the above-described liquid ejecting head 10.

[0095] In the liquid ejecting head 10C including nozzle rows NL that at least partially overlap each other with respect to the gravity direction G1, when considering the influence of variations in the head difference as described above as an issue, it is desirable to determine the height relationship between the nozzle rows NL that at least partially overlap each other by comparing the positions of the upper-end nozzles N of each nozzle row NL with respect to the gravity direction G1. This is because the nozzle N located at the upper end of the nozzle row NL is the nozzle N that is most difficult to supply ink due to the head difference. Therefore, it is desirable to compare the heights of the nozzles N located at the upper end so that the first ink can be supplied to this nozzle N that is most difficult to supply ink.

[0096] As shown in FIG. 15, the liquid ejection head 10C includes a nozzle row NLA and a nozzle row NLC that at least partially overlap each other with respect to the gravitational direction G1, and a nozzle row NLB and a nozzle row NLD that at least partially overlap each other with respect to the gravitational direction G1. Then, since the nozzle NA1 located at the upper end of the nozzle row NLA is located above the nozzle NC1 located at the upper end of the nozzle row NLC, and the nozzle ND1 located at the upper end of the nozzle row NLD is located above the nozzle NB1 located at the upper end of the nozzle row NLB, the nozzle row NLA may be taken as an example of the first nozzle row, the nozzle row NLB may be taken as an example of the second nozzle row, the nozzle row NLC may be taken as an example of the third nozzle row, and the nozzle row NLD may be taken as an example of the fourth nozzle row.

[0097] In the liquid ejection head 10C including the nozzle rows NL that at least partially overlap each other with respect to the gravitational direction G1, when considering the problem that satellite droplets adhere to the upper nozzles N as described above, by comparing the nozzles N located at the same position on the X-axis, which is the extending direction of the intersection line between the ejection surface F3 in the inclined posture of each nozzle row NL and the horizontal plane F0, it is desirable to determine the height relationship between the nozzle rows NL that at least partially overlap each other. This is because when the intersection line between the ejection surface F3 in the inclined posture and the horizontal plane F0 is along the X-axis, the satellite droplets separated from the ink ejected from the nozzle N rise at the same position as the nozzle N on the X-axis and are likely to adhere to the upper nozzles N.

[0098] Also, the problem of satellite droplets adhering to the nozzle rows is likely to occur within the same head chip 12C. In this modification, within the same head chip 12C, the nozzle row NLA and the nozzle row NLC at least partially overlap each other with respect to the gravitational direction G1, and the nozzle row NLB and the nozzle row NLD at least partially overlap each other with respect to the gravitational direction G1.

[0099] Here, when comparing nozzle NA of nozzle row NLA and nozzle NC of nozzle row NLC, which are located at the same position on the X-axis within the same head chip 12C, since the nozzle NA is located above the nozzle NC, it is preferable to interpret the nozzle row NLA as a nozzle row above the nozzle row NLC. Similarly, when comparing nozzle ND of nozzle row NLD and nozzle NB of nozzle row NLB, which are located at the same position on the X-axis within the same head chip 12C, since the nozzle ND of the nozzle row NLD is located above the nozzle NB of the nozzle row NLB, it is preferable to make the nozzle row NLD a nozzle row above the nozzle row NLB. Thus, the nozzle row NLA may be taken as an example of the first nozzle row, the nozzle row NLB as an example of the second nozzle row, the nozzle row NLC as an example of the third nozzle row, and the nozzle row NLD as an example of the fourth nozzle row.

[0100] Next, with reference to FIG. 16, the arrangement of the nozzle rows NL of the liquid ejection head 10D according to Modification 3 will be described. FIG. 16 is a bottom view showing the ejection surface F4 of the liquid ejection head 10D according to Modification 3. The liquid ejection head 10D has a plurality of nozzle rows NL. The nozzle rows NL include a nozzle row NLA that ejects the first ink and a nozzle row NLB that ejects the second ink. When the nozzle rows NLA and NLB are not distinguished, they may be described as the nozzle row NL.

[0101] The liquid ejection head 10D has a plurality of head chips 12D. A nozzle plate 11D having nozzles N formed thereon is provided on the head chip 12D. The head chip 12D is provided with the nozzle rows NLA and NLB, respectively.

[0102] The plurality of nozzle rows NL extend along the V-axis direction. The nozzles N included in the nozzle row NL are arranged in the V-axis direction. The nozzle rows NLA and NLB are arranged at different positions from each other in the W-axis direction. When viewed in the W-axis direction, at least a part of the nozzle rows NLA and NLB overlaps. When viewed in the Y-axis direction, at least a part of the nozzle row NLA and the nozzle row NLB overlaps. When viewed in the X-axis direction, at least a part of the nozzle row NLA and the nozzle row NLB overlaps.

[0103] When viewed in the X-axis direction, at least a part of the nozzle row NLA and the nozzle row NLB overlap, that is, with respect to the gravity direction G1, at least a part of the nozzle row NLA and the nozzle row NLB overlap. The nozzle NA1 located at the upper end of the nozzle row NLA with respect to the gravity direction G1 is located above the nozzle NB1 located at the upper end of the nozzle row NLB with respect to the gravity direction G1.

[0104] Also, when comparing the nozzle NA of the nozzle row NLA and the nozzle NB of the nozzle row NLB that are located at the same position on the X-axis within the same head chip 12D, the nozzle NA of the nozzle row NLA is located above the nozzle NB of the nozzle row NLB. For this reason, regardless of considering either the problem of the variation in the head difference between the pressure adjustment unit 8 and the nozzle row NL or the problem of satellite droplets separated from the ink droplets adhering to the upper nozzle N, in the liquid ejection head 10D, similar to the above-described Modification 2, the nozzle row NLA may be regarded as an example of the first nozzle row, and the nozzle row NLB may be regarded as an example of the second nozzle row.

[0105] In FIG. 16, the virtual lines L5 and L6 are illustrated by two-dot chain lines. The virtual lines L5 and L6 are straight lines that are spaced apart from each other in the Y-axis direction and extend along the X-axis direction. The virtual line L5 is located in the Y2 direction with respect to the virtual line L6. When viewed in the Z-axis direction, the virtual line L5 overlaps the nozzle NA1, and the virtual line L6 overlaps the nozzle NB1. The nozzle row NLA includes a portion arranged in the Y2 direction with respect to the virtual line L6.

[0106] The liquid ejection apparatus 1 including such a liquid ejection head 10D exhibits the same operational effects as the liquid ejection apparatus 1 including the above-described liquid ejection head 10.

[0107] Next, with reference to FIG. 17, the arrangement of the nozzle rows NL of the liquid ejection heads 10G and 10H according to Modification 4 will be described. FIG. 17 is a bottom view showing the ejection surface of the liquid ejection heads 10G and 10H according to Modification 4. The liquid ejection apparatus 1 shown in FIG. 1 may include a head unit 20 having a plurality of liquid ejection heads 10G and 10H instead of the liquid ejection head 10. The head unit 20 has a plurality of liquid ejection heads 10G and 10H arranged alternately in the X-axis direction. In FIG. 18, a plurality of liquid ejection heads 10G and a liquid ejection head 10H arranged between the plurality of liquid ejection heads 10G are illustrated.

[0108] The liquid ejection head 10G includes, as a plurality of nozzle rows NL, a nozzle row NLA1 for ejecting a first ink, a nozzle row NLB1 for ejecting a second ink, a nozzle row NLC1 for ejecting a third ink, and a nozzle row NLD1 for ejecting a fourth ink.

[0109] The liquid ejection head 10G has a plurality of head chips 12G1, 12G2, 12G3, and 12G4. The nozzle row NLA1 is provided on the head chip 12G1, the nozzle row NLB1 is provided on the head chip 12G2, the nozzle row NLC1 is provided on the head chip 12G3, and the nozzle row NLD1 is provided on the head chip 12G4.

[0110] In the liquid ejection head 10G, the nozzle row NLA1 is an example of a first nozzle row, the nozzle row NLB1 is an example of a second nozzle row, the nozzle row NLC1 is an example of a third nozzle row, and the nozzle row NLD1 is an example of a fourth nozzle row. The plurality of nozzle rows NLA1, NLB1, NLC1, and NLD1 extend in the X-axis direction. In the Y1 direction, the nozzle rows NLA1, NLC1, NLD1, and NLB1 are arranged in this order. In the X-axis direction, the lengths are long in the order of the nozzle row NLB1, the nozzle row NLD1, the nozzle row NLC1, and the nozzle row NLA1. The nozzle row NLB1 is longer than the nozzle row NLA1 in the X-axis direction. In the inclined posture of the head unit 20, the nozzle rows NLA1, NLC1, NLD1, and NLB1 are arranged in this order at higher positions.

[0111] The liquid ejection head 10H includes, as a plurality of nozzle rows NL, a nozzle row NLA2 for ejecting a first ink, a nozzle row NLB2 for ejecting a second ink, a nozzle row NLC2 for ejecting a third ink, and a nozzle row NLD2 for ejecting a fourth ink.

[0112] The liquid ejection head 10H has a plurality of head chips 12H1, 12H2, 12H3, 12H4. The nozzle row NLA2 is provided on the head chip 12H1, the nozzle row NLB2 is provided on the head chip 12H2, the nozzle row NLC2 is provided on the head chip 12H3, and the nozzle row NLD2 is provided on the head chip 12H4.

[0113] In the liquid ejection head 10H, the nozzle row NLA2 is an example of a first nozzle row, the nozzle row NLB2 is an example of a second nozzle row, the nozzle row NLC2 is an example of a third nozzle row, and the nozzle row NLD2 is an example of a fourth nozzle row. The plurality of nozzle rows NLA2, NLB2, NLC2, NLD2 extend in the X-axis direction. In the Y1 direction, the nozzle rows NLA2, NLC2, NLD2, and NLB2 are arranged in this order. The lengths in the X-axis direction are long in the order of the nozzle row NLA2, the nozzle row NLC2, the nozzle row NLD2, and the nozzle row NLB2. The nozzle row NLA2 is longer than the nozzle row NLB2 in the X-axis direction. In the inclined posture of the head unit 20, the nozzle rows NLA2, NLC2, NLD2, and NLB2 are arranged at higher positions in this order.

[0114] The liquid ejection device 1 including such liquid ejection heads 10G and 10H exhibits the same operational effects as the liquid ejection device 1 including the above-described liquid ejection head 10.

[0115] Next, referring to FIG. 18, the liquid ejecting apparatus 1B according to the second embodiment will be described. FIG. 18 is a schematic view showing the liquid ejecting apparatus 1B according to the second embodiment. The liquid ejecting apparatus 1B includes a plurality of liquid ejecting heads 30A to 30E, a drum 35 that conveys the medium PA, and pressure adjusting units 38A to 38E. In the description of the second embodiment, the same description as that of the first embodiment will be omitted. As described above, the X-axis direction, the Y-axis direction, and the Z-axis direction shown in each figure differ according to the postures of the liquid ejecting heads 30A to 30E. Note that the drum 35 may be an intermediate transfer member on which the ink ejected from the liquid ejecting heads 30A to 30E lands.

[0116] The drum 35 rotates around a rotation shaft 35a extending in the X-axis direction. The medium PA is conveyed as the drum 35 rotates. The medium PA passes through positions corresponding to the liquid ejecting heads 30A to 30E. Ink is ejected from the liquid ejecting heads 30A to 30E onto the moving medium PA.

[0117] The plurality of liquid ejecting heads 30A to 30E are arranged at different positions in the circumferential direction of the drum 35. The ejection surfaces F31 to F35 of the liquid ejecting heads 30A to 30E are arranged at different angles. The ejection surfaces F31 to F35 are the surfaces of the nozzle plate.

[0118] FIG. 19 is a schematic view showing the posture of the liquid ejecting head 30A. The liquid ejecting head 30A has a nozzle row NLA that ejects the first ink. A nozzle row NLA is formed on the ejection surface F31 of the liquid ejecting head 30A. The plurality of nozzles NA included in the nozzle row NLA are arranged in the X-axis direction. The LA direction perpendicular to the ejection surface F31 is along the gravitational direction G1. The ink ejected from the nozzles NA of the liquid ejecting head 30A flies downward along the gravitational direction G1.

[0119] FIG. 20 is a schematic diagram showing the posture of the liquid ejection head 30B. The liquid ejection head 30B has a nozzle row NLB that ejects the second ink. A nozzle row NLB is formed on the ejection surface F32 of the liquid ejection head 30B. A plurality of nozzles NB included in the nozzle row NLB are arranged in the X-axis direction. The LB direction perpendicular to the ejection surface F32 is along the gravitational direction G1. In FIG. 20, an upward direction G2 that is opposite to the gravitational direction G1 is shown. The ink ejected from the nozzles NB of the liquid ejection head 30B flies in the upward direction G2.

[0120] The liquid ejection head 30A is an example of a first liquid ejection head, and the liquid ejection head 30B is an example of a second liquid ejection head. The ejection surface F31 is an example of a first ejection surface, and the ejection surface F32 is an example of a second ejection surface. The nozzle NA is an example of a first nozzle that ejects the first ink, and the nozzle NB is an example of a second nozzle row that ejects the second ink. The viscosity of the first ink is lower than the viscosity of the second ink.

[0121] In the liquid ejection head 30A shown in FIG. 19, the angle β1 formed between the ejection direction of the first ink ejected from the nozzle NA and the gravitational direction G1 is 0 degrees. The angle β1 is an example of a first angle. In the liquid ejection head 30B shown in FIG. 20, the angle β2 formed between the ejection direction of the second ink ejected from the nozzle NB and the gravitational direction G1 is 180 degrees. The angle β2 is an example of a second angle. The angle β2 is an angle larger than the angle β1.

[0122] FIG. 21 is a schematic diagram showing the posture of the liquid ejection head 30C. The liquid ejection head 30C has a nozzle row NLC that ejects the third ink. A nozzle row NLC is formed on the ejection surface F33 of the liquid ejection head 30C. A plurality of nozzles N included in the nozzle NC are arranged in the X-axis direction. The LC direction perpendicular to the ejection surface F33 is along the K1 direction that is orthogonal to the gravitational direction G1. In FIG. 21, the K1 direction that is orthogonal to the gravitational direction G1 is shown. The ink ejected from the nozzles NC of the liquid ejection head 30C flies along the K1 direction that is orthogonal to the gravitational direction G1.

[0123] The liquid ejection head 30C is an example of a third liquid ejection head. The ejection surface F33 is an example of a third ejection surface. The nozzle NC is an example of a third nozzle that ejects a third ink. The viscosity of the third ink is higher than that of the first ink and lower than that of the second ink.

[0124] The angle β3 formed between the K1 direction, which is the ejection direction of the third ink ejected from the nozzle NC, and the gravity direction G1 is 90 degrees. The angle β3 is an example of a third angle. The angle β3 is larger than the angle β1 and smaller than the angle β2.

[0125] FIG. 22 is a schematic diagram showing the posture of the liquid ejection head 30D. The liquid ejection head 30D has a nozzle row NLD that ejects a fourth ink. The nozzle row NLD is formed on the ejection surface F34 of the liquid ejection head 30D. A plurality of nozzles ND included in the nozzle row NLD are arranged in the X-axis direction. The LC direction perpendicular to the ejection surface F34 is along a direction that intersects the gravity direction G1 and the K-axis direction. The ink ejected from the nozzle ND of the liquid ejection head 30D flies obliquely upward along a direction that intersects the gravity direction G1 and the K-axis direction, that is, the Z1 direction in FIG. 22.

[0126] The liquid ejection head 30D is an example of a fourth liquid ejection head. The ejection surface F34 is an example of a fourth ejection surface. The nozzle ND is an example of a fourth nozzle that ejects a fourth ink. The viscosity of the fourth ink is higher than that of the third ink and lower than that of the second ink.

[0127] The angle β4 formed between the ejection direction of the fourth ink ejected from the nozzle ND, that is, the Z1 direction in FIG. 22, and the gravity direction G1 is 135 degrees. The angle β4 is an example of a fourth angle. The angle β4 is larger than the angle β3 and smaller than the angle β2.

[0128] FIG. 23 is a schematic diagram showing the posture of the liquid ejection head 30E. The liquid ejection head 30E has a nozzle row NLE that ejects the fifth ink. A nozzle row NLE is formed on the ejection surface F35 of the liquid ejection head 30E. A plurality of nozzles NE included in the nozzle row NLE are arranged in the X-axis direction. The LE direction perpendicular to the ejection surface F35 is along a direction intersecting the gravitational direction G1 and the K-axis direction. The ink ejected from the nozzles NE of the liquid ejection head 30E flies obliquely downward along a direction intersecting the gravitational direction G1 and the K-axis direction, that is, the Z1 direction in FIG. 23.

[0129] The liquid ejection head 30E is an example of a fifth liquid ejection head. The ejection surface F35 is an example of a fifth ejection surface. The nozzle NE is an example of a fifth nozzle that ejects the fifth ink. The viscosity of the fifth ink is higher than that of the first ink and lower than that of the third ink.

[0130] The ejection direction of the fifth ink ejected from the nozzle row NLE, that is, the angle β5 formed between the Z1 direction in FIG. 23 and the gravitational direction G1 is 45 degrees. The angle β5 is an example of a fifth angle. The angle β5 is an angle larger than the angle β1 and smaller than the angle β3.

[0131] Next, with reference to FIG. 18, the head differences H1 to H5 in the nozzle rows NLA to NLE will be described. The pressure adjustment unit 38A is connected to the nozzle row NLA via the ink flow path 7. The pressure adjustment unit 38B is connected to the nozzle row NLB via the ink flow path 37. The pressure adjustment unit 38C is connected to the nozzle row NLC via the ink flow path 37. The pressure adjustment unit 38D is connected to the nozzle row NLD via the ink flow path 37. The pressure adjustment unit 38E is connected to the nozzle row NLE via the ink flow path 37.

[0132] The pressure adjustment units 38A to 38E can adopt the same configuration as the pressure adjustment unit 8 described in the first embodiment. The pressure adjustment unit 38A adjusts the pressure of the first ink. The pressure adjustment unit 38B adjusts the pressure of the second ink. The pressure adjustment unit 38C adjusts the pressure of the third ink. The pressure adjustment unit 38D adjusts the pressure of the fourth ink. The pressure adjustment unit 38E adjusts the pressure of the fifth ink.

[0133] In FIG. 18, the height positions H0 of the pressure adjustment units 38A to 38E are shown with respect to the gravity direction G1. The height position H0 is located above the height positions HA, HB, HC, HD, and HE of the nozzle arrays NLA, NLB, NLC, NLD, and NLE. They are in the order of the positions HA, HE, HC, HD, and HB being higher.

[0134] The head difference H2 between the pressure adjustment unit 38B and the nozzle array NLB is larger than the head difference H4 between the pressure adjustment unit 38D and the nozzle array NLD. The head difference H4 is larger than the head difference H3 between the pressure adjustment unit 38C and the nozzle array NLC. The head difference H3 is larger than the head difference H5 between the pressure adjustment unit 38E and the nozzle array NLE. The head difference H5 is larger than the head difference H1 between the pressure adjustment unit 38A and the nozzle array NLA. That is, they are in the order of the head differences H2, H4, H3, H5, and H1 being larger.

[0135] Also in such a liquid ejecting apparatus 1B according to the second embodiment, the same operational effects as those of the liquid ejecting apparatus 1 of the first embodiment are obtained.

[0136] In the liquid ejection device 1B, the positions of the nozzles NA, NB, NC, ND, and NE in the nozzle rows NLA, NLB, NLC, NLD, and NLE are different according to the viscosity of the ink. The nozzle NA in the nozzle row NLA that ejects the first ink with the lowest viscosity is arranged at a higher position in the direction of gravity G1 than the nozzles NB, NC, ND, and NE in the other nozzle rows NLB, NLC, NLD, and NLE. The first ink that is easy to supply is supplied to the nozzle NA in the nozzle row NLA, for which the head difference H1 is small and it is difficult to supply compared with the nozzles NB, NC, ND, and NE in the nozzle rows NLB, NLC, NLD, and NLE. Due to the influence of the variation in the head difference, the higher the nozzle N in the nozzle row NL arranged above, the more difficult it is to supply. Therefore, by reducing the viscosity of the first ink corresponding to the nozzle NA in the first nozzle row NLA arranged above, the supply is made easier by reducing the pressure loss. Thereby, the variation in the ejection characteristics can also be alleviated.

[0137] In the liquid ejection device 1B, the nozzle NB in the nozzle row NLB that ejects the second ink with the highest viscosity is arranged at a lower position in the direction of gravity G1 than the nozzles NA, NC, ND, and NE in the other nozzle rows NLA, NLC, NLD, and NLE. The second ink that is difficult to supply is supplied to the nozzle NB in the nozzle row NLB, for which the head difference H2 is large and it is easy to supply compared with the nozzles NA, NC, ND, and NE in the nozzle rows NLA, NLC, NLD, and NLE. Due to the influence of the variation in the head difference, the lower the nozzle row NL arranged below, the easier it is to supply. Therefore, by increasing the viscosity of the second ink corresponding to the nozzle NB in the second nozzle row NLB arranged below, the supply is made difficult by increasing the pressure loss. Thereby, the variation in the ejection characteristics can also be alleviated.

[0138] In the liquid ejecting device 1B, since the nozzles NA of the nozzle row NLA that eject the first ink with the lower viscosity are positioned above the nozzles NB of the nozzle row NLB that eject the second ink with the higher viscosity with respect to the gravitational direction G1, among a plurality of types of inks, variations in the ink supply characteristics to the plurality of nozzle rows NL can be reduced, and variations in the ink ejection characteristics in the plurality of nozzle rows NL can be suppressed. As a result, the printing accuracy in the liquid ejecting device 1B can be improved.

[0139] In the liquid ejecting device 1B, the nozzles ND of the nozzle row NLC that eject the third ink are positioned between the nozzles NA of the nozzle row NLA and the nozzles NB of the nozzle row NLB with respect to the gravitational direction G1. The third ink having a higher viscosity than the first ink is supplied to the nozzles NC of the nozzle row NLC where the head difference H3 is larger than the head difference H1. The third ink having a lower viscosity than the second ink is supplied to the nozzles NC of the nozzle row NLC where the head difference H3 is smaller than the head difference H2.

[0140] In the liquid ejecting device 1B, the nozzles ND of the nozzle row NLD that eject the fourth ink are positioned between the nozzles NC of the nozzle row NLC and the nozzles NB of the nozzle row NLB with respect to the gravitational direction G1. The fourth ink having a higher viscosity than the third ink is supplied to the nozzles ND of the nozzle row NLD where the head difference H4 is larger than the head difference H3. The fourth ink having a lower viscosity than the second ink is supplied to the nozzles ND of the nozzle row NLD where the head difference H4 is smaller than the head difference H2.

[0141] In the liquid ejecting device 1B, the nozzles NE of the nozzle row NLE that eject the fifth ink are positioned between the nozzles NA of the nozzle row NLA and the nozzles NC of the nozzle row NLC with respect to the gravitational direction G1. The fifth ink having a higher viscosity than the first ink is supplied to the nozzles NE of the nozzle row NLE where the head difference H5 is larger than the head difference H1. The fifth ink having a lower viscosity than the third ink is supplied to the nozzles NE of the nozzle row NLE where the head difference H5 is smaller than the head difference H3.

[0142] In such a liquid ejecting apparatus 1B, since the height positions of the nozzles NA to NE are different according to the viscosity of the ink, variations in the ink supply characteristics to the plurality of nozzles NA to NE that eject different types of ink can be reduced, and variations in the ink ejection characteristics in the plurality of nozzles NA to NE can be suppressed. As a result, the printing accuracy in the liquid ejecting apparatus 1B can be improved.

[0143] In the present embodiment, the height position H0 of the pressure adjusting units 38A to 38E is located above the height positions HA, HB, HC, HD, HE of the nozzles NA, NB, NC, ND, NE with respect to the gravitational direction G1. However, the present invention is not limited to this. The height position H0 may be located between the position HA and the position HB with respect to the gravitational direction G1, or may be located below the positions HA, HE, HC, HD, HB.

[0144] Note that the above-described embodiment merely shows a typical form of the present invention, and the present invention is not limited to the above-described embodiment, and various modifications and additions can be made without departing from the gist of the present invention.

[0145] In the above-described embodiment, a plurality of inks having different colors are exemplified, but the present invention is not limited to this. For example, the first ink and the second ink may have different viscosities and may be the same color.

[0146] In the above-described embodiment, a line-type liquid ejecting apparatus 1 including a line head is exemplified, but the present invention may also be applied to a serial-type liquid ejecting apparatus that reciprocates a carriage on which the liquid ejecting head 10 is mounted in the width direction of the medium PA.

[0147] The liquid ejecting apparatus 1 exemplified in the foregoing embodiments can be adopted not only in equipment dedicated for printing but also in various equipment such as facsimile machines and copying machines. However, the use of the liquid ejecting apparatus of the present invention is not limited to printing. For example, a liquid ejecting apparatus that ejects a solution of a coloring material is used as a manufacturing apparatus for forming a color filter of a display device such as a liquid crystal display panel. Further, a liquid ejecting apparatus that ejects a solution of a conductive material is used as a manufacturing apparatus for forming wirings and electrodes on a wiring board. Further, a liquid ejecting apparatus that ejects a solution of an organic substance related to a living body is used, for example, as a manufacturing apparatus for manufacturing a biochip.

Explanation of Reference Numerals

[0148] 1, 1B... liquid ejecting apparatus, 1a... housing, 10, 10B to 10D, 10G, 10H... liquid ejecting heads, 11... nozzle plate, 30A... liquid ejecting head, 30B... liquid ejecting head, 30C to 30E... liquid ejecting heads, 38A... pressure adjusting unit, 38B... pressure adjusting unit, F0... horizontal plane, F1... ejection surface, F31... ejection surface, F32... ejection surface, G1... direction of gravity, L1... first virtual line, N... nozzle, NA... nozzle, NB... nozzle, NL... nozzle row, NLA... nozzle row, NLB... nozzle row, NLC... nozzle row, NLD... nozzle row, Q1... first contact point, G2... second contact point, S1... rotation axis, X... X-axis direction, Y... Y-axis direction, Z... Z-axis direction.

Claims

1. A liquid ejection head having an ejection surface including a first nozzle row that ejects a first ink and a second nozzle row that ejects a second ink, a first pressure adjustment unit that adjusts the pressure of the first ink supplied to the first nozzle row, a second pressure adjustment unit that adjusts the pressure of the second ink supplied to the second nozzle row, and is capable of holding the liquid ejection head in an inclined posture in which the ejection surface is inclined with respect to a horizontal plane, wherein the viscosity of the first ink is lower than the viscosity of the second ink, in the inclined posture, the first nozzle row is positioned above the second nozzle row with respect to the direction of gravity, and the first pressure adjustment unit and the second pressure adjustment unit are arranged at the same position with respect to the direction of gravity. Liquid ejection device.

2. The liquid ejection device according to claim 1, wherein the difference between the viscosity of the first ink and the viscosity of the second ink is 0.5 mPa·S or more.

3. The liquid ejection device according to claim 1 or 2, wherein the first nozzle row and the second nozzle row are formed on a common nozzle plate.

4. When the direction in which the intersection line between the ejection surface in the inclined posture and the horizontal plane extends is defined as a first direction, and the direction orthogonal to the first direction in the ejection surface is defined as a second direction, when viewed in the second direction, at least a part of the first nozzle row and the second nozzle row overlap. The liquid ejection device according to claim 3.

5. When the direction in which the intersection line between the ejection surface in the inclined posture and the horizontal plane extends is defined as a first direction, when viewed in the first direction, the first nozzle row and the second nozzle row are arranged at intervals. The liquid ejection device according to any one of claims 1 to 4.

6. The nozzle located at the upper end of the first nozzle row with respect to the direction of gravity is located above the nozzle located at the upper end of the second nozzle row with respect to the direction of gravity. The liquid ejection device according to any one of claims 1 to 5.

7. The ejection surface further includes a third nozzle row that ejects a third ink, the viscosity of the third ink is higher than the viscosity of the first ink and lower than the viscosity of the second ink, in the inclined posture, the third nozzle row is below the first nozzle row with respect to the direction of gravity and above the second nozzle row. The liquid ejection device according to any one of claims 1 to 6.

8. The ejection surface further includes a fourth nozzle row that ejects a fourth ink, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The viscosity of the fourth ink is lower than that of the second ink and higher than that of the third ink. Higher. In the inclined posture, the fourth nozzle row is positioned below the third nozzle row and above the second nozzle row with respect to the direction of gravity. The liquid ejecting apparatus according to claim 7.

9. In the state of the inclined posture, while ejecting the first ink from the first nozzle row onto the ejection surface, a cleaning operation of ejecting the second ink from the second nozzle row onto the ejection surface is executed. The liquid ejecting apparatus according to any one of claims 1 to 8.

10. A first liquid ejecting head having a first ejection surface including a first nozzle for ejecting a first ink, a second liquid ejecting head having a second ejection surface including a second nozzle for ejecting a second ink, a first pressure adjusting unit for adjusting the pressure of the first ink supplied to the first nozzle, a second pressure adjusting unit for adjusting the pressure of the second ink supplied to the second nozzle, and the viscosity of the first ink is lower than that of the second ink, 、 the first liquid ejecting head is arranged such that an angle formed between the direction in which the first ink is ejected from the first nozzle and the direction of gravity is a first angle, the second liquid ejecting head is arranged such that an angle formed between the direction in which the second ink is ejected from the second nozzle and the direction of gravity is a second angle larger than the first angle, the first pressure adjusting unit and the second pressure adjusting unit are arranged at the same position with respect to the direction of gravity. The liquid ejecting apparatus.

11. A third liquid ejecting head having a third ejection surface including a third nozzle for ejecting a third ink is provided. The viscosity of the third ink is lower than that of the second ink and higher than that of the first ink. Higher. The third liquid ejecting head is arranged such that an angle formed between the direction in which the third ink is ejected from the third nozzle and the direction of gravity is a third angle larger than the first angle and smaller than the second angle. 、 The liquid ejecting apparatus according to claim 10. ​ ​ ​ ​

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