Liquid spraying device

Abstract

To improve printing accuracy.SOLUTION: A liquid jet device 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 10 in a first posture in which the jet surface F1 inclines with respect to a horizontal plane F0. Dynamic surface tension of the first ink is higher than dynamic surface tension of the second ink. The first nozzle array NLA is positioned above the second nozzle array NLB in a gravity direction G1 in the first posture.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection apparatus and a liquid ejection head. [Background technology]

[0002] In a recording head that ejects a plurality of types of ink, the ejection surface that ejects the ink may be inclined relative to the horizontal plane (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-34170 Summary of the Invention [Problem to be solved by the invention]

[0004] The dynamic surface tension of ink may differ depending on the type of ink. Conventional techniques do not take into consideration the relationship between the combined effect of the different dynamic surface tensions of multiple inks and the effect of an inclined ejection surface. [Means for solving the problem]

[0005] A liquid ejection device according to one aspect of the present invention includes 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, and is capable of holding the liquid ejection head in a first position in which the ejection surface is inclined with respect to a horizontal plane. The dynamic surface tension of the first ink is greater than the dynamic surface tension of the second ink. In the first position, the first nozzle row is positioned higher than the second nozzle row in the direction of gravity.

[0006] A liquid ejection device according to one aspect of the present invention includes a first liquid ejection head having a first ejection surface including first nozzles for ejecting a first ink, and a second liquid ejection head having a second ejection surface including second nozzles for ejecting a second ink. The dynamic surface tension of the first ink is greater than the dynamic surface tension of the second ink. The first ejection surface is disposed so that the ejection direction of the first ink ejected from the first nozzles forms a first angle with the direction of gravity, and the second ejection surface is disposed so that the ejection direction of the second ink ejected from the second nozzles forms a second angle that is greater than the first angle.

[0007] A liquid jet head according to one aspect of the present invention includes a first nozzle row that ejects a first ink, a second nozzle row that ejects a second ink, and a third nozzle row that ejects a third ink. The dynamic surface tension of the third ink is smaller than the dynamic surface tension of the first ink and larger than the dynamic surface tension of the second ink. The third nozzle row is located between the first nozzle row and the second nozzle row in the direction of gravity. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram illustrating a liquid ejecting apparatus according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing an ink flow path. [Figure 3] FIG. 2 is a bottom view showing a nozzle plate in which a nozzle row is formed. [Figure 4] 1A and 1B are schematic diagrams illustrating a liquid ejecting head in an inclined position where an ejection surface is inclined with respect to a horizontal plane, and are diagrams illustrating a head difference in a nozzle row. [Figure 5] FIG. 10 is a cross-sectional view showing a nozzle plate according to Comparative Example 1, illustrating a state in which ink droplets are overflowing from the nozzles. [Figure 6] FIG. 10 is a cross-sectional view showing a nozzle plate according to Comparative Example 1, illustrating a state in which ink droplets spilling out of the nozzles hang down along the ejection surface. [Figure 7] FIG. 2 is a cross-sectional view showing the nozzle plate according to the first embodiment, illustrating a state in which ink droplets are overflowing from the nozzles. [Figure 8] 10 is a schematic diagram illustrating a liquid jet head according to a second embodiment, showing an inclined posture in which the jet surface faces obliquely upward. FIG. [Figure 9] 10 is a schematic diagram illustrating a liquid jet head according to a third embodiment, showing an orientation in which the jet surface is perpendicular to a horizontal plane. FIG. [Figure 10] FIG. 10 is a schematic diagram illustrating a liquid ejecting apparatus according to a fourth embodiment. [Figure 11] FIG. 10 is a schematic diagram illustrating a liquid ejecting apparatus according to a fifth embodiment. [Figure 12] FIG. 10 is a schematic diagram illustrating a liquid ejecting apparatus according to a sixth embodiment. [Figure 13] 1 is a table showing components of ink according to an example. [Figure 14] 10 is a bottom view illustrating an ejection surface of a liquid jet head according to a first modified example. FIG. [Figure 15] 10 is a bottom view illustrating an ejection surface of a liquid jet head according to a second modification. FIG. [Figure 16] 11 is a bottom view illustrating an ejection surface of a liquid jet head according to a third modification. FIG. [Figure 17] 10 is a bottom view illustrating an ejection surface of a liquid jet head according to a fourth modification. FIG. [Figure 18] FIG. 10 is a schematic diagram illustrating a liquid ejecting apparatus according to a second embodiment. [Figure 19] FIG. 2 is a schematic diagram illustrating the arrangement of a liquid jet head. [Figure 20] FIG. 2 is a schematic diagram illustrating the arrangement of a liquid jet head. [Figure 21] FIG. 2 is a schematic diagram illustrating the arrangement of a liquid jet head. [Figure 22] FIG. 2 is a schematic diagram illustrating the arrangement of a liquid jet head. [Figure 23] FIG. 2 is a schematic diagram illustrating the arrangement of a liquid jet head. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, in each drawing, the dimensions and scale of each part may differ appropriately from those in reality. Furthermore, the embodiments described below are preferred specific examples of the present invention, and therefore various technically preferable limitations are applied, but the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description to the effect that the present invention is limited.

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

[0011] In addition, the downward direction of the gravity direction will be referred to as the gravity direction G1, and the direction perpendicular to both the gravity direction G1 and the X-axis direction will be referred to as the K-axis direction. Furthermore, the direction opposite to the gravity direction G1 will be referred to as the upward direction G2. The K-axis direction includes the K1 direction and the K2 direction, which are opposite to each other. The K-axis direction is an example of a third direction. The K-axis direction is an example of a horizontal direction. The horizontal direction is a direction perpendicular to the gravity direction G1. The third direction is a direction perpendicular to both the first direction and the gravity direction G1.

[0012] FIG. 1 is a schematic diagram showing a liquid ejection device 1 according to a first embodiment. FIG. 2 is a block diagram showing an ink flow path. The liquid ejection device 1 is an inkjet printing device that ejects ink, an example of a "liquid," as ink droplets onto a medium PA. The liquid ejection device 1 is a so-called line-type printing device in which multiple nozzles that eject ink are distributed across 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 made of any material, such as a resin film or fabric.

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

[0014] The control unit 3 controls the operation of each element of the liquid ejection device 1. The control unit 3 includes, for example, a processing circuit such as a CPU or FPGA, and a storage circuit such as a semiconductor memory. Various programs and data are stored in the storage circuit. The processing circuit executes the programs and uses the data as appropriate to realize various controls. CPU is an abbreviation for Central Processing Unit. FPGA is an abbreviation for Field Programmable Gate Array.

[0015] The medium transport mechanism 4 is controlled by the control unit 3 and transports the medium PA in a transport direction DM. The transport direction DM is the transport direction of the medium PA at a position facing the ejection surface F1, and is parallel or approximately parallel to the Y-axis direction. The medium transport mechanism 4 includes a transport roller that is long along the width direction of the medium PA and a motor that rotates the transport roller. Note that the medium transport mechanism 4 is not limited to a configuration that uses a transport roller, and may be configured, for example, to use a drum or endless belt that transports the medium PA while adsorbed to its outer peripheral surface by electrostatic force or the like.

[0016] The liquid ejecting device 1 is formed with a medium transport path 4a for transporting the medium PA. The medium transport path 4a is a path that leads from the paper feed unit 4b to the paper discharge unit 4c. The medium transport mechanism 4 transports the medium PA along the medium transport path 4a. The paper feed unit 4b and the paper discharge unit 4c include trays that can store the medium PA.

[0017] The liquid container 2 stores ink. Specific examples of the liquid container 2 include a cartridge that is detachable from the liquid ejecting device 1, a bag-shaped ink pack made of flexible film, and an ink tank that can be refilled with ink. 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 liquid container 2A stores a first ink. The liquid container 2B stores a second ink. The liquid container 2C stores a third ink. The liquid container 2D stores a fourth ink. For example, the first ink, second ink, third ink, and fourth ink are inks of different colors. The first ink, second ink, third ink, and fourth ink each have a different dynamic surface tension. The dynamic surface tension of the first ink is greater than that of the second ink. The dynamic surface tension of the third ink is less than that of the first ink and greater than that of the second ink. The dynamic surface tension of the fourth ink is less than that of the third ink and greater than that of the second ink. The components of each type of ink and the measurement of dynamic surface tension will be described later.

[0019] The difference between the dynamic surface tension of the first ink and the dynamic surface tension of the second ink is 1.0 mN / m or more. In the measurement of dynamic surface tension described below, when the lifetime is set to 10 msec, the dynamic surface tension of the first ink is greater than that of the second ink. When the lifetime is set to 10 msec, the dynamic surface tensions of the first to fourth inks are greatest in the following order: first ink, third ink, fourth ink, and second ink.

[0020] The ink supply unit 5 has ink flow paths 6 and 7 that supply ink from the liquid container 2 to the liquid jet head 10, and a pressure adjustment unit 8 that adjusts the pressure of the ink inside the liquid jet 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 jet head 10. The ink flow path 7 includes a flow path formed inside the liquid jet head 10. The ink flow paths 6 and 7 include, for example, flow path members in which grooves, recesses, through-holes, etc. are formed, as well as pipes, 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 nozzle N. The pressure adjustment unit 8 is, for example, a negative pressure generation unit including a pressure adjustment valve. This negative pressure generation unit may have, for example, a pressure adjustment valve that opens and closes the ink flow path, and a flexible member that bends based on the pressure difference between the pressure in the ink flow path downstream of the pressure adjustment valve and atmospheric pressure, and may be configured to control the opening and closing of the pressure adjustment valve by moving the pressure adjustment valve due to the bending of this flexible member, so that a predetermined range of negative pressure acts on the nozzle N.

[0022] Furthermore, the pressure adjustment unit 8 may adjust the pressure of the ink supplied to the liquid jet head 10 by using a sub-tank that temporarily stores ink. Specifically, the pressure adjustment unit 8 may have a sub-tank and any sensor that can detect the amount of ink stored in the sub-tank, and when the amount of ink stored in the sub-tank detected by the sensor falls below a threshold, the pressure adjustment unit 8 may keep the amount of ink stored in the sub-tank approximately constant by refilling the sub-tank with ink from the liquid container 2, that is, by keeping the liquid level of the ink stored in the sub-tank approximately constant, thereby adjusting the pressure of the ink in the liquid jet head 10 by the head difference between the liquid level in the sub-tank and the liquid jet head 10. Furthermore, the pressure in the sub-tank may be adjusted to a predetermined pressure by a compressor, thereby adjusting the pressure of the ink supplied to the liquid jet head 10.

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

[0024] 3 is a bottom view showing a nozzle plate 11 in which a nozzle row NL is formed. The liquid ejection head 10 includes the nozzle plate 11 having a plurality of nozzle rows NL. The nozzle row NL includes a plurality of nozzles N that eject ink. Of the surfaces of the nozzle plate 11, the surface that faces the medium PA is the ejection surface F1 that ejects ink. A plurality of nozzles N are formed in the ejection surface F1. The ejection surface F1 is disposed at a distance from the medium PA.

[0025] The multiple nozzle arrays NL include nozzle arrays NLA, NLB, NLC, and NLD. The nozzle array NLA includes multiple nozzles N that eject a first ink. The nozzle array NLB includes multiple nozzles N that eject a second ink. The nozzle array NLC includes multiple nozzles N that eject a third ink. The nozzle array NLD includes multiple nozzles N that eject a fourth ink. Note that when there is no need to distinguish between the nozzle arrays NLA, NLB, NLC, and NLD, they may be referred to as the nozzle array NL.

[0026] The nozzle row NL includes a plurality of nozzles N lined up in the X-axis direction. The nozzles N are through-holes that penetrate the nozzle plate 11 in the thickness direction. The 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 from each other in the Y-axis direction.

[0027] The nozzle arrays NLA, NLC, NLD, and NLB are arranged in this order in the Y1 direction. The nozzle arrays NLA, NLC, NLD, and NLB are spaced apart from one another in the Y-axis direction. The nozzle array NLC is arranged between the nozzle arrays NLA and NLB in the Y-axis direction. The nozzle array NLD is arranged between the nozzle arrays NLC and NLB in the Y-axis direction.

[0028] When viewed in the Y-axis direction, the nozzle arrays NLA, NLC, NLD, and NLB at least partially overlap. In this embodiment, when viewed in the Y-axis direction, the nozzle arrays NLA, NLC, NLD, and NLB completely overlap.

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

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

[0031] 4, the multiple nozzle arrays NL are arranged at different heights in the direction of gravity G1. The nozzle array NLA is arranged at a height position HA, and the nozzle array NLB is arranged at a height position HB. The height position HA is located higher than the height position HB. In other words, the nozzle array NLA, which ejects the first ink having a higher dynamic surface tension, is located higher than the nozzle array NLB, which ejects the second ink having a lower dynamic surface tension.

[0032] The nozzle row NLC is disposed at a height position HC. The height position HC is lower than the height position HA and higher than the height position HB. When the liquid ejecting head 10 is in an inclined position, the nozzle row NLC is located lower than the nozzle row NLA and higher than the nozzle row NLB. In other words, the nozzle row NLC, which ejects the third ink, which has the second highest dynamic surface tension among the first ink, second ink, and third ink, is disposed between the nozzle row NLA and the nozzle row NLB in the direction of gravity G1.

[0033] The nozzle row NLD is disposed at a height position HD. The height position HD is lower than the height position HC and higher than the height position HB. When the liquid ejecting head 10 is in an inclined position, the nozzle row NLD is located lower than the nozzle row NLC and higher than the nozzle row NLB. In other words, the nozzle row NLD, which ejects the fourth ink, which has the second highest dynamic surface tension among the second ink, the third ink, and the fourth ink, is disposed between the nozzle row NLC and the nozzle row NLB in the direction of gravity G1.

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

[0035] When a plurality of nozzle rows NL are compared, the nozzle row NL that ejects ink with a larger dynamic surface tension is positioned above the nozzle row NL that ejects ink with a smaller dynamic surface tension.

[0036] Next, with reference to FIGS. 5 to 7 , a case will be described in which ink droplets 101, 102 drip along the ejection surface F1 due to positive pressure at the meniscus of the nozzle N caused by factors such as an abnormality in the pressure adjustment unit 8 or circulation cleaning, which circulates ink in a flow path within the liquid ejection head 10 using a circulation mechanism (not shown). Here, nozzle plates 11, 111 that eject two types of ink with different dynamic surface tensions will be described as examples. FIGS. 5 and 6 illustrate the nozzle plate 111 according to Comparative Example 1, and FIG. 7 illustrates the nozzle plate 11 according to Example 1. In the nozzle plate 111 according to Comparative Example 1, the nozzle row NLB that ejects the second ink, which has a smaller dynamic surface tension, is positioned above the nozzle row NLA that ejects the first ink, which has a larger dynamic surface tension. In the nozzle plate 11 according to Example 1, the nozzle row NLA that ejects the first ink is positioned above the nozzle row NLB that ejects the second ink, which is the opposite of Comparative Example 1.

[0037] Fig. 5 is a cross-sectional view showing a state in which ink droplets 101 and 102 are overflowing from nozzles NA and NB of a nozzle plate 111 according to Comparative Example 1. In the state shown in Fig. 5, ink droplets 102, which are the second ink, are overflowing from the upper nozzle row NLB, and ink droplets 101, which are the first ink, are overflowing from the lower nozzle row NLA.

[0038] FIG. 6 is a cross-sectional view of a nozzle plate 111 according to Comparative Example 1, illustrating a state in which an ink droplet 101 spilling out of a nozzle NA drips along the ejection surface F1. In the state shown in FIG. 6, the ink droplet 102 is moving in the Y1 direction along the ejection surface F1. The ink droplet 101 spilling out of the lower nozzle row NLA is in front of the nozzle NA. The front of the nozzle NA is outside the nozzle NA, located in the Z1 direction of the nozzle NA. The ink droplet 102 with a smaller dynamic surface tension is more likely to drip downward due to gravity than the ink droplet 101 with a larger dynamic surface tension. The ink droplet 102 moves in the Y1 direction and approaches the ink droplet 101 below. Over time, the ink droplet 102 moves in the Y1 direction and comes into contact with the ink droplet 101, causing the ink droplets 102 and 101 to mix together.

[0039] In this state, when the first ink is ejected from the nozzle array NLA, the first ink mixed with the second ink lands on the medium PA, which may result in a decrease in printing accuracy.

[0040] FIG. 7 is a cross-sectional view of the nozzle plate 11 according to the first embodiment, showing a state in which ink droplets 101 and 102 are overflowing from the nozzles NA and NB. In the state shown in FIG. 7, the ink droplet 102 is moving in the Y1 direction along the ejection surface F1. In this case, the ink droplet 101 overflowing from the upper nozzle array NLA remains in front of the nozzle NA. The upper ink droplet 101 does not approach the lower nozzle array NLB. The ink droplet 102 overflowing from the lower nozzle array NLB moves downward due to gravity, but the ink droplet 102 does not approach the ink droplet 101. The ink droplets 101 and 102 do not mix. In this way, the nozzle array NLA, which ejects the first ink having a greater dynamic surface tension, is positioned above the nozzle array NLB in the gravity direction G1, so that color mixing between the first ink and the second ink can be suppressed in the first embodiment.

[0041] 4, the nozzle arrays NLA, NLB, NLC, and NLD are arranged according to the dynamic surface tension of the ink. The nozzle array NLA, which ejects the first ink, which has the highest dynamic surface tension, is arranged at a higher position in the direction of gravity G1 than the other nozzle arrays NLB, NLC, and NLD. In this way, because the nozzle array NLA, which ejects the first ink, which is least likely to drip, is arranged at a higher position, the first ink is prevented from mixing with the other inks, the second ink, the third ink, and the fourth ink.

[0042] In the liquid ejection head 10, the nozzle row NLB that ejects the second ink, which has the smallest dynamic surface tension, is disposed at a lower position in the direction of gravity G1 than the other nozzle rows NLA, NLC, and NLD. In this way, because the nozzle row NLB that ejects the second ink, which is most likely to drip, is disposed at a lower position, the second ink is prevented from mixing with the other first ink, third ink, and fourth ink.

[0043] In the liquid ejection head 10, the nozzle row NLA that ejects the first ink, which has a higher dynamic surface tension, is positioned higher in the direction of gravity G1 than the nozzle row NLB that ejects the second ink, which has a lower dynamic surface tension, thereby preventing the inks from mixing together. As a result, it is possible to improve the printing accuracy of the liquid ejection device 1. Compared to the configuration of Comparative Example 1, in which the nozzle row NLB that ejects the second ink, which has a lower dynamic surface tension, is positioned higher than the nozzle row NLA that ejects the first ink, which has a higher dynamic surface tension, the liquid ejection head 10 has a lower possibility of the inks mixing together.

[0044] Next, the head differences H1 to H4 in the nozzle row NL will be described with reference to FIG. 4. FIG. 4 illustrates the height position H0 of the pressure adjustment unit 8 with respect to the gravity direction G1. The height position H0 is located higher than the height positions HA, HB, HC, and HD of the nozzle rows NLA, NLB, NLC, and NLD. As described above, the positions HA, HC, HD, and HB are higher in this order. The height position H0 of the pressure adjustment unit 8 is not limited to being higher than the height positions of the nozzle rows NLA, NLB, NLC, and NLD. The height position H0 of the pressure adjustment unit 8 may be lower than the height positions of the nozzle rows NLA, NLB, NLC, and NLD. Furthermore, the height position H0 of the pressure adjustment unit 8 may be a height position between the nozzle row NLA and the nozzle row NLB. Furthermore, the height positions of the multiple pressure adjustment units 8A, 8B, 8C, and 8D are all height position H0.

[0045] The head difference H2 between the pressure adjustment unit 8 and the nozzle row NLB is greater 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 greater 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 greater than the head difference H1 between the pressure adjustment unit 8 and the nozzle row NLA.

[0046] 4, the head differences H1, H2, H3, and H4 acting on the nozzle row NL differ depending on the height position. When the head difference is large, ink is more easily supplied to the nozzle row NL than when the head difference is small. When comparing the nozzle row NLA and the nozzle row NLB, ink is more difficult to be supplied to the nozzle row NLA, which has a smaller head difference H1, than to the nozzle row NLB, which has a larger head difference H2.

[0047] Furthermore, for example, when multiple types of ink have different dynamic surface tensions, the capillary force and meniscus withstand pressure acting on the ink in the nozzle N will be different. The capillary force acting on the first ink, which has a higher dynamic surface tension, is greater than the capillary force acting on the second ink, which has a lower dynamic surface tension. The meniscus withstand pressure of the first ink, which has a higher dynamic surface tension, is greater than the meniscus withstand pressure of the second ink, which has a lower dynamic surface tension. Furthermore, the first ink, which has a higher dynamic surface tension, is easier to supply to the nozzle row NL than the second ink, which has a lower dynamic surface tension.

[0048] In other words, because differences in the dynamic surface tension of the ink affect variations in the ease of ink supply to the nozzle rows NL, by allocating inks with different dynamic surface tensions according to the height of the nozzle rows NL in order to mitigate variations in the ease of ink supply to the nozzle rows NL caused by variations in the head difference, it is possible to reduce variations in the ease of ink supply to the nozzle rows NL and, as a result, reduce variations in the ejection characteristics, such as the weight Iw and velocity Vm of the ejected droplets.

[0049] The liquid ejection device 1 according to the prior art did not take into consideration the combined effect of the influence of differences in dynamic surface tension and the influence of the inclination of the ejection surface F1 of the liquid ejection head 10. If the difference in dynamic surface tension between inks and the inclination of the ejection surface F1 are not taken into consideration, a problem occurs in that the difference in the ejection characteristics of the ink between the nozzle rows NL becomes large.

[0050] For example, if the pressure adjustment units 8 corresponding to each of the multiple nozzle rows NL have a common configuration, and the distances (water head differences) in the direction of gravity between each nozzle row NL and each pressure adjustment unit 8 corresponding to each nozzle row NL are equal, the pressure (negative pressure) acting on each nozzle row NL will be the same. However, if the liquid ejection head 10 is tilted, the multiple nozzle rows NL will be disposed at different positions relative to the direction of gravity, which will cause variations in the water head differences and, further, differences in the dynamic surface tension of each ink, which may cause variations in the pressure acting on each nozzle row NL.

[0051] If the first ink, which is easy to supply, is supplied to the nozzle row NLB, which is easy to supply, and the second ink, which is difficult to supply, is supplied to the nozzle row NLA, a large difference will occur between the ejection characteristics of the nozzle row NLA and the ejection characteristics of the nozzle row NLB. In this case, there is also a risk that a relatively large negative pressure will act on the meniscus of the nozzle row NLA, drawing in air bubbles from the nozzles N, or that a relatively large positive pressure will act on the meniscus of the nozzle row NLB, causing ink to overflow from the nozzles N and destroying the meniscus.

[0052] In the liquid jet head 10 of this embodiment, the nozzle arrays NLA, NLB, NLC, and NLD are arranged according to the dynamic surface tension of the ink. The nozzle array NLA, which ejects the first ink having the highest dynamic surface tension, is arranged at a higher position in the direction of gravity G1 than the other nozzle arrays NLB, NLC, and NLD. The first ink, which is easier to supply, is supplied to the nozzle array NLA, which has the smallest head difference H1.

[0053] In the liquid ejection head 10, the nozzle row NLB that ejects the second ink, which has the smallest dynamic surface tension, is positioned lower in the direction of gravity G1 than the other nozzle rows NLA, NLC, and NLD. The second ink, which is more difficult to supply, is supplied to the nozzle row NLB, which has a larger head difference H2.

[0054] In the liquid ejection head 10, the nozzle row that ejects the first ink, which has a higher dynamic surface tension, is positioned higher in the direction of gravity G1 than the nozzle row that ejects the second ink, which has a lower dynamic surface tension, so that the variation in ease of ink supply can be reduced, thereby suppressing the variation in ink ejection characteristics among the multiple nozzle rows. As a result, the printing accuracy of the liquid ejection device 1 can be improved.

[0055] Furthermore, in the liquid ejection device 1, the multiple pressure adjustment units 8 are arranged at the same height position H0 in the direction of gravity G1, which makes it possible to reduce the size of the liquid ejection device 1 and simplify the structure of the liquid ejection device 1 compared to when the multiple pressure adjustment units 8 are arranged at different height positions. By aligning the height positions H0 of the multiple pressure adjustment units 8, it is possible to simplify the ink flow path.

[0056] Next, the inclined posture of the liquid jet head 10 according to Example 2 will be described with reference to Fig. 8. Fig. 8 is a schematic diagram showing the liquid jet head 10 according to Example 2, illustrating an inclined posture in which the ejection surface F1 faces obliquely upward. The liquid jet head 10 of Example 2 shown in Fig. 8 differs from the liquid jet head 10 of the first embodiment shown in Fig. 4 in that the inclination angle θ2 of the ejection surface F1 is different from the inclination angle θ1.

[0057] The tilt angle θ2 is an obtuse angle greater than 90 degrees relative to the horizontal plane F0. The tilt angle θ2 is a rotation angle in the counterclockwise direction in the figure, centered on a rotation axis along the X-axis direction. In FIG. 8, the ejection surface F1 is tilted so that it faces diagonally upward. The liquid jet head 10 according to Example 2 has the same effects as the liquid jet head 10 according to the first embodiment, and can suppress variations in the ink ejection characteristics among the multiple nozzle rows.

[0058] Next, with reference to FIG. 9, the inclined posture of the liquid jet head 10 according to Example 3 will be described. FIG. 9 is a schematic diagram showing the liquid jet head 10 according to Example 3, illustrating a posture in which the ejection surface F1 is perpendicular to the horizontal plane F0. The liquid jet head 10 according to Example 3 shown in FIG. 9 differs from the liquid jet head 10 according to the first embodiment shown in FIG. 4 in that the angle θ3 of the ejection surface F1 is different from the inclination angle θ1. The inclined posture of the liquid jet head 10 may also include a posture perpendicular to the horizontal plane F0. In this embodiment, the case in which the ejection surface F1 is perpendicular to the horizontal plane F0 may be referred to as being inclined. The angle θ3 is 90 degrees, or a right angle, with respect to the horizontal plane F0. The liquid jet head 10 according to Example 3 has the same effects as the liquid jet head 10 according to the first embodiment, and can reduce variations in the ease of ink supply and suppress variations in the ink ejection characteristics among multiple nozzle rows.

[0059] Next, a description will be given of a change in posture of the liquid jet head 10 according to the fourth embodiment with reference to Fig. 10. Fig. 10 is a schematic diagram showing the liquid jet head 10 according to the fourth embodiment. In Fig. 10, the liquid jet head 10 in a 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 jet head 10 in a second posture P2 in which the ejection surface F1 is disposed along the horizontal plane F0 is shown by a dashed line. The liquid jet head 10 can rotate about a rotation axis S1 extending in the X-axis direction.

[0060] The attitude of the liquid jet head 10 is changeable to a plurality of attitudes including a first attitude P1 and a second attitude P2. The liquid jet device 1 according to the fourth embodiment has an attitude change mechanism 13 that changes the attitude of the liquid jet head 10. The attitude change mechanism 13 includes a bearing 14 that holds a rotation shaft S1 that extends 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.

[0061] In Figure 10, the imaginary lines L1 and L2 are shown as two-dot chain lines. The imaginary line L1 is an imaginary straight line that passes through the center C1 between the nozzle row NLA and the nozzle row NLB and extends in a direction perpendicular to the ejection surface F1 in the first posture P1. The imaginary line L1 extends in the Z-axis direction when viewed in the X-axis direction. When the liquid jet head 10 is in the first posture P1, the rotation axis S1 is located closer to the nozzle row NLB than the imaginary line L1 is. In other words, when the liquid jet head 10 is in the first posture P1, the rotation axis S1 is located closer to the nozzle row NLB in the Y-axis direction than the imaginary line L1.

[0062] The imaginary line L2 is an imaginary straight line that passes through the center C1 between the nozzle row NLA and the nozzle row NLB and extends in a direction perpendicular to the ejection surface F1 in the second attitude P2. The imaginary line L2 extends in the Z-axis direction when viewed in the X-axis direction. In FIG. 10, arrows indicating the X-axis, Y-axis, and Z-axis directions in the second attitude P2 are indicated by dashed lines. The first attitude P1 and the second attitude P2 are shifted by an angle θ1 when viewed in the X-axis direction. When the liquid jet head 10 is in the second attitude P2, the rotation axis S1 is positioned closer to the nozzle row NLB when viewed from the second imaginary line L2. In other words, when the liquid jet head 10 is in the second attitude P2, the rotation axis S1 is positioned closer to the nozzle row NLB in the Y-axis direction than the imaginary line L2.

[0063] In addition, in the first posture P1 and the second posture P2, the rotation axis S1 may be located at the same position or at different positions. When the posture of the liquid jet head 10 changes from the first posture P1 to the second posture P2, the liquid jet head 10 may move linearly. The liquid jet device 1 can linearly move the bearing 14 that holds the rotation axis S1. For example, linear movement can be achieved by a rack and pinion. The liquid jet head 10 can also be linearly moved by using other mechanisms such as a ball screw, a guide groove, an actuator, or a belt mechanism.

[0064] Next, the centrifugal force acting on the meniscus when the liquid jet head 10 is rotated will be described. When the liquid jet head 10 is rotated about the rotation axis S1, a centrifugal force acts on the meniscus in the multiple nozzle arrays NL. The radius of rotation RA from the rotation axis S1 to the nozzle array NLA is larger than the radius of rotation RB from the rotation axis S1 to the nozzle array NLB. When the liquid jet head 10 is rotated, the magnitude of the centrifugal force acting on the meniscus of the nozzle array NLA is different from the magnitude of the centrifugal force acting on the meniscus of the nozzle array NLB. When the liquid jet head 10 is rotated, the magnitude of the centrifugal force acting on the meniscus of the nozzle array NLA is larger than the magnitude of the centrifugal force acting on the meniscus of the nozzle array NLB.

[0065] The centrifugal force acting immediately after the start of rotational movement of the liquid ejection head 10 acts to move the meniscus inside the nozzle N toward the outside of the nozzle. In other words, this centrifugal force acts to move the meniscus in a direction away from the rotation axis S1. Furthermore, an inertial force due to this centrifugal force acts on the meniscus inside the nozzle N that has been moved toward the outside of the nozzle by this centrifugal force. This inertial force due to the centrifugal force is a force that moves the meniscus into the nozzle N. In other words, the inertial force due to the centrifugal force is a force that acts on the meniscus in a direction approaching the rotation axis S1. Such centrifugal force and the inertial force due to the centrifugal force may cause the meniscus to fly out of the nozzle N or the meniscus to recess, drawing air bubbles into the nozzle N.

[0066] When the dynamic surface tensions of the inks are the same, the nozzle row NLA, which experiences a greater centrifugal force, is more likely to cause a meniscus to collapse than the nozzle row NLB, which experiences a less centrifugal force. In the liquid ejection head 10, a first ink, which experiences a greater dynamic surface tension, is supplied to the nozzle row NLA, and a second ink, which experiences a less dynamic surface tension, is supplied to the nozzle row NLB. The first ink is supplied to the nozzle row NLA, which experiences a greater centrifugal force, and the second ink is supplied to the nozzle row NLB, which experiences a less centrifugal force. As a result, the first ink, which experiences a greater dynamic surface tension, is supplied to the nozzles which experience a greater centrifugal force, thereby preventing the meniscus from collapsing.

[0067] In the liquid ejection head 10, of the multiple types of ink, the ink with the higher dynamic surface tension is supplied to the nozzle row NL with the higher centrifugal force, and the ink with the lower dynamic surface tension is supplied to the nozzle row NL with the lower centrifugal force, thereby suppressing the collapse of the ink meniscus in the nozzle N.

[0068] In the liquid ejecting head 10, by suppressing the collapse of the meniscus, it is possible to suppress the intrusion of air bubbles into the nozzles N of the nozzle array NLA, or to suppress the leakage of ink from the nozzles N of the nozzle array NLA.

[0069] Note that the liquid jet head 10 according to the fourth embodiment includes a plurality of nozzle rows NL each extending in the X-axis direction, but may also include a nozzle row NL extending in a direction intersecting the X-axis when the ejection surface F1 is viewed in a plan view toward the Z-axis direction. In this case, the rotation radius from the rotation axis S1 to the nozzle row NL may be the distance between the rotation axis S1 and the nozzle N that is farthest from the rotation axis S1 among the plurality of nozzles N that constitute the nozzle row NL when viewed in the X-axis direction.

[0070] Next, a liquid jet head 10 according to a fifth embodiment will be described with reference to FIG. 11. FIG. 11 is a schematic diagram showing the liquid jet head 10 of the liquid jet device 1 according to the fifth embodiment and a cap 22 that covers the ejection surface F1 of the liquid jet head 10. The liquid jet device 1 is capable of performing a maintenance operation. The liquid jet device 1 performs the maintenance operation when the liquid jet head 10 is in the second position P2. The liquid jet device 1 performs a printing operation (recording operation) when the liquid jet head 10 is in the first position P1 shown in FIG. 10, and performs the maintenance operation when the liquid jet device 1 is in the second position P2 shown in FIG. 11. In other words, the first position P1 is an example of a "recording position," and the second position P2 is an example of a "maintenance position." The printing operation is an example of a recording operation. The "recording operation" refers to ejecting ink from the nozzles N and depositing the ink on a medium to record characters, images, etc.

[0071] The liquid ejecting device 1 includes a cap 22, a pipe 23, and a pump 24 that are used for maintenance operations. The cap 22 covers the ejection surface F1 of the liquid ejecting head 10. The cap 22 is arranged to cover the openings of the nozzles N of the multiple nozzle rows NL. The cap 22 is formed with a space 22a that receives ink ejected from the nozzles N.

[0072] A pipe 23 is connected to the cap 22. The pipe 23 is a pipe that discharges 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 inside the cap 22 can be sucked and discharged outside the cap 22.

[0073] Maintenance operations for the liquid ejection device 1 include flushing, suction cleaning, and pressure cleaning. These maintenance operations are performed when the liquid ejection head 10 is in the second attitude P2. In the flushing, an actuator of the liquid ejection head 10 is used to apply pressure fluctuations to pressure chambers communicating with the nozzles N, thereby ejecting ink that does not contribute to the recording operation from the nozzles N. In the suction cleaning, for example, a pump 24 is used to suction ink from the nozzles N. In addition, in the pressure cleaning, a pump (not shown) or the like may be used to pressurize the ink flow paths in the liquid ejection head 10 from upstream of the pressure chambers, thereby discharging ink from the nozzles N.

[0074] In this manner, in the liquid ejection device 1, unnecessary ink in the nozzles N can be discharged to the outside of the liquid ejection head 10 by performing a maintenance process. When the liquid ejection head 10 is in the second attitude P2, the ejection surface F1 is parallel to the horizontal plane F0. In the liquid ejection device 1, a maintenance operation can be performed in this second attitude P2, so the amount of ink remaining in the cap 22 can be reduced during idle suction, in which the pump 24 is driven while the space inside the cap 22 is in communication with the atmosphere. For example, when the liquid ejection head 10 is in the first attitude P1, the cap 22 is tilted, so ink remains in the corners 22c of the cap 22. On the other hand, in this embodiment, the maintenance operation is performed with the bottom surface 22b of the cap 22 positioned along the horizontal plane F0, so the amount of ink remaining in the cap 22 can be reduced. Performing a maintenance operation in an inclined attitude carries the risk of ink leakage from a sealed portion during capping. The sealed portion during capping includes the portion where the cap 22 and the ejection surface F1 come into contact.

[0075] In the liquid ejection device 1, the attitude of the liquid ejection head 10 can be changed from a first attitude P1 to a second attitude P2. As described above, when the liquid ejection head 10 rotates around the rotation axis S1, centrifugal force and the inertial force caused by this centrifugal force act on the meniscus of the ink in the nozzle array NL, which may cause the meniscus to collapse. In the liquid ejection device 1, the first ink, which has the greatest dynamic surface tension among the multiple types of ink, is supplied to the nozzle array NLA, where the centrifugal force and the inertial force caused by this centrifugal force are greatest, thereby reducing the possibility of the meniscus collapsing. By preventing the meniscus from collapsing, the intrusion of air bubbles into the nozzles N of the liquid ejection head 10 is prevented, or the leakage of ink from the nozzles N of the nozzle array NLA is prevented.

[0076] Next, a liquid ejection device 1 according to a sixth embodiment will be described with reference to FIG. 12. In the sixth embodiment, the influence of centrifugal force acting on the nozzle row NL of the liquid ejection head 10 when the liquid ejection device 1 is placed on a floor surface 26 will be described. The liquid ejection head 10 of the liquid ejection device 1 is disposed at an angle with respect to a horizontal plane F0. The liquid ejection device 1 includes a housing 1a that accommodates the liquid ejection head 10. The liquid ejection head 10 is held relative to the housing 1a. Legs 1c and 1d are provided on the bottom of the housing 1a. The legs 1c and 1d are disposed on the floor surface 26. The floor surface 26 is, for example, along the horizontal plane F0.

[0077] In FIG. 12, the K-axis direction, which is perpendicular to the direction of gravity G1 when viewed in the X-axis direction, is indicated by an arrow. The K-axis direction is along the left-right direction in FIG. 12. The legs 1c and 1d are spaced apart in the K-axis direction. For example, the K-axis direction is along the longitudinal direction of the housing 1a when the liquid ejecting device 1 is viewed in the direction of gravity G1. Note that the legs 1c and 1d may also be spaced apart in other directions.

[0078] Leg 1c includes contact Q1, and leg 1d includes contact Q2. Contact Q1 is an example of a first contact, and contact Q2 is an example of a second contact. Contacts Q1 and Q2 are portions that come into contact with floor surface 26 when housing 1a is placed on floor surface 26. Contact Q1 is located closer to one end 1e of housing 1a in the K-axis direction. Contact Q2 is located closer to the other end 1f of housing 1a in the K-axis direction. One end 1e of housing 1a is the end of housing 1a in the K1 direction. The other end 1f of housing 1a is the end of housing 1a in the K2 direction.

[0079] The center of gravity G of the liquid ejection device 1 is located between the tangent point Q1 and the tangent point Q2 in the K-axis direction, closer to the tangent point Q1 than the tangent point Q2. When viewed in the X-axis direction, the distance UR between the tangent point Q1 and the nozzle row NLA is greater than the distance DR between the tangent point Q1 and the nozzle row NLB. When viewed in the X-axis direction, the distance UL between the tangent point Q2 and the nozzle row NLA is greater than the distance DL between the tangent point Q2 and the nozzle row NLB. The position of the nozzle row NL is, for example, the center position of the opening of the nozzle N on the ejection surface F1.

[0080] 12, the distance UR is greater than the distance DL. In the first posture of the liquid jet head 10, the distance UL is greater than the distance DR.

[0081] For example, when moving the liquid ejection device 1, it is assumed that multiple workers carry the liquid ejection device 1 and eventually place the liquid ejection device 1 on the floor surface 26. For example, two workers spaced apart in the K-axis direction can hold the liquid ejection device 1 from both sides. When placing the liquid ejection device 1 on the floor surface 26, one worker closer to the one end 1e first touches the leg 1c to the floor surface 26, and then the other worker closer to the other end 1f touches the leg 1d to the floor surface 26. When the leg 1c first touches the floor surface 26, the liquid ejection device 1 rotates counterclockwise R1 as viewed in the X-axis direction, with the contact point Q1 as the fulcrum. In this case, because the distance UR is longer than the distance DR, a greater centrifugal force acts on the nozzle row NLA than on the nozzle row NLB.

[0082] Thus, when the liquid ejection device 1 is placed on the floor surface 26, centrifugal forces and inertial forces due to these centrifugal forces of different magnitudes are generated in the nozzle arrays NLA and NLB depending on the distances UR and DR from the contact point Q1. In the liquid ejection device 1, the first ink is supplied to the nozzle array NLA, and the second ink is supplied to the nozzle array NLB. The first ink, which has a higher dynamic surface tension, is supplied to the nozzle array NLA, which has a higher centrifugal force and inertial force, and the second ink, which has a lower dynamic surface tension, is supplied to the nozzle array NLB, which has a lower centrifugal force and inertial force. This reduces the risk of the meniscus of the first ink in the nozzle array NLA collapsing in the liquid ejection head 10. In other words, the risk of the meniscus collapsing is lower when the first ink is supplied to the nozzle array NLA than when the second ink is supplied to the nozzle array NLA.

[0083] In the case of the liquid ejecting device 1, the center of gravity G of the liquid ejecting device 1 is located closer to leg 1c than to leg 1d in the K-axis direction, so there is a high possibility that the worker will bring leg 1c into contact with the floor surface 26 before leg 1d. In the liquid ejecting device 1, as described above, the first ink is supplied to the nozzle array NLA, so the risk of the meniscus in the nozzle N of the nozzle array NLA collapsing is reduced.

[0084] Next, a case will be described in which the liquid ejection device 1 is positioned so that the leg 1d contacts the floor surface 26 before the leg 1c. When the leg 1d contacts the floor surface 26 first, the liquid ejection device 1 rotates clockwise R2 as viewed in the X-axis direction, with the contact point Q2 as the fulcrum. In this case, since the distance UL is longer than the distance DL, a greater centrifugal force and inertial force due to this centrifugal force act on the nozzle array NLA than on the nozzle array NLB. In this way, when the liquid ejection device 1 is placed on the floor surface 26, different magnitudes of centrifugal force and inertial force due to this centrifugal force are generated in the nozzle arrays NLA and NLB depending on the distances UL and DL from the contact point Q2. In the liquid ejection head 10, the first ink, which has a greater dynamic surface tension, is supplied to the nozzle array NLA, which is subjected to a greater centrifugal force and inertial force due to this centrifugal force, and the second ink, which has a smaller dynamic surface tension, is supplied to the nozzle array NLB, which is subjected to a smaller centrifugal force and inertial force due to this centrifugal force. This reduces the risk of the meniscus of the first ink in the nozzle array NLA collapsing in the liquid ejection head 10. In other words, there is less risk of the meniscus collapsing when the first ink is supplied to the nozzle array NLA than when the second ink is supplied to the nozzle array NLA.

[0085] For example, in a plan view of the liquid ejection device 1 seen in the direction of gravity G1, the length along the K-axis direction is longer than the length along the X-axis direction. When moving such a liquid ejection device 1, it is easier for multiple workers to balance the liquid ejection device 1 by holding it apart in the K-axis direction rather than holding it apart in the X-axis direction. In the liquid ejection head 10, the first ink is assigned to the nozzle array NLA, and therefore collapse of the meniscus can be suppressed compared to when the second ink is assigned to the nozzle array NLA. In the liquid ejection device 1, either the leg 1c or the leg 1d may be lowered first.

[0086] When moving the liquid ejection device 1, multiple workers may hold the liquid ejection device 1 at intervals in the X-axis direction. Because the nozzle array NLA is located higher than the nozzle array NLB in the direction of gravity G1, the distance between the nozzle array NLA and the point of contact between the housing 1a and the floor surface 26 that is closest to the X1 direction is longer than the distance between that point of contact and the nozzle array NLB. Similarly, the distance between the nozzle array NLA and the point of contact between the housing 1a and the floor surface 26 that is closest to the X2 direction is longer than the distance between that point of contact and the nozzle array NLB. Therefore, whether the end of the housing 1a in the X1 direction or the end of the housing 1a in the X2 direction is lowered first, collapse of the meniscus can be suppressed because the first ink is assigned to the nozzle array NLA.

[0087] Note that the liquid jet head 10 according to the sixth embodiment includes a plurality of nozzle rows NL each extending in the X-axis direction, but may also include a nozzle row NL extending in a direction intersecting the X-axis when the ejection surface F1 is viewed in a plan view in the Z-axis direction. In this case, the distance from the tangent point to the nozzle row NL may be the distance between the tangent point and the nozzle N farthest from the tangent point among the plurality of nozzles N constituting the nozzle row NL when viewed in the X-axis direction.

[0088] Next, a method for measuring the dynamic surface tension of ink and the properties of the ink will be described. The dynamic surface tension of ink can be determined, for example, by the maximum bubble pressure method. Other methods for measuring dynamic surface tension may also be used, such as the hanging drop method, the Wihelmy method, and the ring method. In the maximum bubble pressure method, the tip of a capillary tube is immersed in ink, and the maximum pressure required to release bubbles from the capillary tube is measured. In this maximum bubble pressure method, bubbles are continuously generated at the tip of the capillary tube, and the maximum pressure is measured.

[0089] In this maximum bubble pressure method, the lifetime is the time from when a new bubble appears at the tip of the capillary tube during measurement of the maximum pressure until the maximum bubble pressure is reached. The maximum bubble pressure is reached when the radius of curvature of the bubble is equal to the radius of the capillary tube. The dynamic surface tension of the ink is the surface tension of the ink when the ink is in motion. The dynamic surface tension of the ink can be adjusted, for example, by changing the type and content of surfactants, water-soluble organic solvents, resins, etc. contained in the ink.

[0090] The properties of the ink will be explained below, but unless otherwise specified, the amounts of components are expressed as "parts" and "%" by weight. Figure 13 is a table showing the ink components.

[0091] Pigment Dispersion 1 will be described. A solution of 5.0 g of concentrated hydrochloric acid dissolved in 5.5 g of water was cooled to 5°C, and 1.6 g of 4-aminophthalic acid was added to this solution. The container containing this solution was placed in an ice bath and stirred to maintain the solution temperature below 10°C. A solution of 1.8 g of sodium nitrite dissolved in 9.0 g of ion-exchanged water at 5°C was added. After stirring for 15 minutes, 6.0 g of pigment was added under stirring and stirred for another 15 minutes to obtain a slurry. The pigment added under stirring was carbon black with a specific surface area of ​​220 m2 / g and a DBP oil absorption of 105 mL / 100 g. The resulting slurry was filtered through filter paper, the particles thoroughly washed with water, and dried in an oven at 110°C. The filter paper used was Advantec's "Standard Filter Paper No. 2." The counter ions were replaced from sodium ions to potassium ions by ion exchange, and then an appropriate amount of ion-exchanged water was added to adjust the pigment content, yielding Pigment Dispersion 1 with a pigment content of 20.0%. Pigment Dispersion 1 was used to prepare a first ink with a black hue.

[0092] Pigment Dispersion Liquid 2 will now be described. A styrene-ethyl acrylate-acrylic acid copolymer (resin dispersant) with an acid value of 150 mgKOH / g and a weight-average molecular weight of 8,000 was prepared. The prepared resin dispersant was neutralized with potassium hydroxide in an amount equimolar to its acid value and then dissolved in ion-exchange water to prepare an aqueous solution of resin dispersant with a resin (solids) content of 20.0%. A mixture was obtained by mixing 20.0 parts of pigment (CI Pigment Blue 15:3), 30.0 parts of the aqueous solution of resin dispersant, and 50.0 parts of ion-exchange water.

[0093] The resulting mixture and 200 parts of 0.3 mm diameter zirconia beads were placed in a batch-type vertical sand mill (manufactured by Imex) and dispersed for 5 hours while cooling with water, after which the mixture was centrifuged to remove coarse particles. The mixture was pressure filtered through a 3.0 μm pore size microfilter (manufactured by Fujifilm), and an appropriate amount of ion-exchanged water was added to obtain Pigment Dispersion 2. The resulting Pigment Dispersion 2 had a pigment content of 20.0% and a resin dispersant content of 6.0%. Pigment Dispersion 2 was used to prepare a second ink with a cyan hue.

[0094] Pigment Dispersion 3 will now be described. Pigment Dispersion 3 with a pigment content of 20.0% and a resin dispersant content of 6.0% was obtained using the same procedure as for Pigment Dispersion 2 described above, except that the pigment was changed to CI Pigment Yellow 74. Pigment Dispersion 3 was used to prepare a third ink with a yellow hue.

[0095] Pigment Dispersion Liquid 4 will now be described. Pigment Dispersion Liquid 4, with a pigment content of 20.0% and a resin dispersant content of 4.0%, was obtained using the same procedure as for Pigment Dispersion Liquid 2 described above, except that the ingredients were changed to 20.0 parts of pigment (CI Pigment Magenta 122), 20.0 parts of an aqueous solution of resin dispersant, and 60.0 parts of ion-exchanged water. Pigment Dispersion Liquid 4 was used to prepare a fourth ink with a magenta hue.

[0096] The ink preparation will now be described. The components (unit: %) shown in Table 1 were mixed, thoroughly stirred, and then pressure-filtered through a 0.8 μm pore size cellulose acetate filter (manufactured by Advantec) to prepare each ink. In Table 1, "Acetylenol E100" and "Acetylenol E60" are the trade names of surfactants manufactured by Kawaken Fine Chemicals. The bottom row of Table 1 shows the dynamic surface tension γ at a lifetime of 10 milliseconds. The dynamic surface tension γ was measured using a dynamic surface tensiometer using the maximum bubble pressure method at 25°C. The dynamic surface tensiometer used was a "Bubble Pressure Tensiometer BP-2" manufactured by Kruss.

[0097] Next, the arrangement of the nozzle arrays NL of the liquid jet head 10B according to Modification 1 will be described with reference to FIG. 14. FIG. 14 is a bottom view showing the ejection surface 11B of the liquid jet head 10B according to Modification 1. The liquid jet head 10B has a plurality of nozzle arrays NL. The nozzle arrays NL include nozzle arrays NLA1, NLA2, and NLA3 that eject a first ink, nozzle arrays NLB1, NLB2, and NLB3 that eject a second ink, nozzle arrays NLC1, NLC2, and NLC3 that eject a third ink, and nozzle arrays NLD1, NLD2, and NLD3 that eject a fourth ink. Note that when there is no need to distinguish between the nozzle arrays NLA1, NLA2, NLA3, NLB1, NLB2, NLB3, NLC1, NLC2, NLC3, NLD1, NLD2, and NLD3, they may be referred to as the nozzle array NL. In the liquid ejection head 10B, the nozzle row NLA is an example of a first nozzle row, the nozzle row NLB is an example of a second nozzle row, the nozzle row NLC is an example of a third nozzle row, and the nozzle row NLD is an example of a fourth nozzle row.

[0098] The liquid jet head 10B has a plurality of head chips 12. The head chip 12 is provided with a nozzle plate in which nozzles N are formed. The head chip 12 is provided with a nozzle row NL that ejects one type of ink. The head chip 12 has a pressure chamber and an actuator (not shown). The actuator increases the pressure of the ink in the pressure chamber, causing the ink to be ejected from the nozzle N.

[0099] The nozzle rows NLA1, NLA2, and NLA3 are arranged at different positions in the X-axis direction. The nozzle rows NLA1, NLA2 and the nozzle row NLA3 are arranged at different positions in the Y-axis direction. The nozzle row NLA2 is positioned higher in the Y2 direction than the nozzle rows NLA1 and NLA3. In the first attitude P1 of the liquid jet head 10B, the nozzle row NLA2 is positioned higher in the gravity direction G1 than the nozzle rows NLA1 and NLA3. In the first attitude P1, the ejection surface F2 is inclined with respect to the horizontal plane.

[0100] The nozzle rows NLB1, NLB2, and NLB3 are arranged in the same manner as the nozzle rows NLA1, NLA2, and NLA3. The nozzle rows NLB1, NLB2, and NLB3 and the nozzle rows NLA1, NLA2, and NLA3 are spaced apart from each other in the Y-axis direction.

[0101] The nozzle arrays NLC1, NLC2, and NLC3 are arranged in the same manner as the nozzle arrays NLA1, NLA2, and NLA3. The nozzle arrays NLC1, NLC2, and NLC3 are located between the nozzle arrays NLA1, NLA2, and NLA3 and the nozzle arrays NLB1, NLB2, and NLB3 in the Y-axis direction.

[0102] The nozzle arrays NLD1, NLD2, and NLD3 are arranged in the same manner as the nozzle arrays NLA1, NLA2, and NLA3. The nozzle arrays NLD1, NLD2, and NLD3 are located between the nozzle arrays NLC1, NLC2, and NLC3 and the nozzle arrays NLB1, NLB2, and NLB3 in the Y-axis direction.

[0103] The liquid jet device 1 may include a liquid jet head 10B instead of the liquid jet head 10. The liquid jet device 1 including the liquid jet head 10B achieves the same effects as the liquid jet device 1 including the liquid jet head 10 described above.

[0104] Next, the arrangement of the nozzle rows NL of the liquid jet head 10C according to Modification 2 will be described with reference to FIG. 15. FIG. 15 is a bottom view showing the ejection surface F3 of the liquid jet head 10C according to Modification 2. The liquid jet head 10C has a plurality of nozzle rows NL. The nozzle rows NL include a nozzle row NLA that ejects a first ink, a nozzle row NLB that ejects a second ink, a nozzle row NLC that ejects a third ink, and a nozzle row NLD that ejects a fourth ink. Note that when there is no need to distinguish between the nozzle rows NLA, NLB, NLC, and NLD, they may be referred to as the nozzle row NL.

[0105] The liquid jet head 10C has a plurality of head chips 12C. The head chip 12C is provided with a nozzle plate 11C in which nozzles N are formed. The head chip 12C is provided with nozzle rows NLA, NLB, NLC, and NLD.

[0106] Figure 15 shows the V-axis direction and the W-axis direction, which are perpendicular to each other. The V-axis direction and the W-axis direction are perpendicular 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 the V1 direction and the V2 direction. The W-axis direction includes the W1 direction and the W2 direction. The V-axis direction intersects with the X-axis direction at an inclination angle α.

[0107] Multiple nozzle arrays NL extend along the V-axis direction. The nozzles N included in each nozzle array NL are aligned in the V-axis direction. The nozzle arrays NLA and NLD are aligned in the V-axis direction. The nozzle arrays NLA and NLD are spaced apart in the V-axis direction. The nozzle arrays NLA and NLD are spaced apart in the Y-axis direction. In FIG. 15, imaginary lines L3 and L4 are shown by two-dot chain lines. The imaginary lines L3 and L4 are spaced apart from each other in the Y-axis direction and are straight lines extending along the X-axis direction. The imaginary line L3 is located in the Y2 direction from the imaginary line L4. The nozzle arrays NLA and NLC are located in the Y2 direction from the imaginary line L3, and the nozzle arrays NLB and NLD are located in the Y1 direction from the imaginary line L4.

[0108] The nozzle rows NLC and NLB are aligned in the V-axis direction. The nozzle rows NLC and NLB are spaced apart in the V-axis direction. The nozzle rows NLC and NLB are spaced apart in the Y-axis direction. In the liquid jet head 10C, the nozzle rows NLA and NLC are an example of a first nozzle row, and the nozzle rows NLD and NLB are an example of a second nozzle row.

[0109] When viewed in the Y-axis direction, the nozzle row NLA at least partially overlaps with the nozzle rows NLD and NLB. For example, of two head chips 12C adjacent in the X-axis direction, the one arranged in the X1 direction is head chip 12C1, and the one arranged in the X2 direction from head chip 12C1 is head chip 12C2. When viewed in the Y-axis direction, the nozzle row NLA of head chip 12C1 and the nozzle rows NLD and NLB of head chip 12C2 at least partially overlap. Note that the nozzle row NLA and the nozzle rows NLD and NLB within the same head chip 12 may at least partially overlap in the Y-axis direction.

[0110] Similarly, when viewed in the Y-axis direction, nozzle row NLC at least partially overlaps with nozzle rows NLD and NLB. Nozzle row NLC of head chip 12C1 and nozzle rows NLD and NLB of head chip 12C2 at least partially overlap with each other when viewed in the Y-axis direction. Note that nozzle row NLC and nozzle rows NLD and NLB within the same head chip 12 may at least partially overlap with each other in the Y-axis direction.

[0111] When viewed in the X-axis direction, the nozzle row NLA and the nozzle rows NLD and NLB are arranged at intervals 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 at intervals in the Y-axis direction.

[0112] In the Y-axis direction, the distance between nozzle rows NLA and NLC provided on the same head chip 12C is narrower than the distance between nozzle rows NLC provided on head chip 12C1 and nozzle rows NLA provided on head chip 12C2.

[0113] The nozzle NA1 located at the top end of the nozzle row NLA in the direction of gravity G1 is located higher than the nozzle ND1 located at the top end of the nozzle row NLD and the nozzle NB1 located at the top end of the nozzle row NLB in the direction of gravity G1.

[0114] The nozzle NC1 located at the top end of the nozzle row NLC in the direction of gravity G1 is located higher than the nozzle ND1 located at the top end of the nozzle row NLD and the nozzle NB1 located at the top end of the nozzle row NLB in the direction of gravity G1.

[0115] The liquid ejecting apparatus 1 including such a liquid ejecting head 10C has the same effects as the liquid ejecting apparatus 1 including the liquid ejecting head 10 described above.

[0116] In addition, in the liquid ejection head 10C having nozzle rows NL that at least partially overlap with each other in the direction of gravity G1, when the influence of variations in the head difference as described above is considered as an issue, it is desirable to determine the height relationship between the nozzle rows NL that at least partially overlap with each other by comparing the positions in the direction of gravity G1 of the uppermost nozzles N of each nozzle row NL. This is because the nozzle N located at the top of the nozzle row NL is the nozzle N to which ink is most difficult to supply due to the head difference, and therefore it is desirable to compare the heights of the uppermost nozzles N so that the first ink can be supplied to this nozzle N to which ink is most difficult to supply.

[0117] 15, the liquid jet head 10C includes nozzle arrays NLA and NLC that at least partially overlap with each other in the direction of gravity G1, and nozzle arrays NLB and NLD that at least partially overlap with each other in the direction of gravity G1. Since nozzle NA1 located at the top end of nozzle array NLA is located higher than nozzle NC1 located at the top end of nozzle array NLC, and nozzle ND1 located at the top end of nozzle array NLD is located higher than nozzle NB1 located at the top end of nozzle array NLB, nozzle array NLA may be an example of a first nozzle array, nozzle array NLB may be an example of a second nozzle array, nozzle array NLC may be an example of a third nozzle array, and nozzle array NLD may be an example of a fourth nozzle array.

[0118] In the liquid jet head 10C having nozzle rows NL that at least partially overlap with each other in the direction of gravity G1, when the problem of multiple types of ink droplets overflowing from each nozzle row NL along the ejection surface F3 and mixing of colors as described above is considered to be an issue, it is desirable to determine the height relationship between the nozzle rows NL that at least partially overlap with each other by comparing the nozzles N that are located at the same position on the X-axis, which is the direction along which the intersection line between the ejection surface F3 and the horizontal plane F0 when each nozzle row NL is in an inclined position. This is because, because the intersection line between the ejection surface F3 and the horizontal plane F0 when in an inclined position is along the X-axis, the ink that overflows from the nozzles N tends to drip in the Y1 direction on the ejection surface F3 due to the action of gravity.

[0119] Furthermore, the problem of color mixing due to ink dripping is likely to occur within the same head chip 12C. In this modified example, within the same head chip 12C, the nozzle rows NLA and NLC at least partially overlap with each other in the direction of gravity G1, and the nozzle rows NLB and NLD at least partially overlap with each other in the direction of gravity G1.

[0120] Here, when comparing nozzles NA of nozzle array NLA and nozzles NC of nozzle array NLC, which are located in the same head chip 12C and at the same position on the X-axis, the nozzle NA of nozzle array NLA is located higher than the nozzle NC of nozzle array NLB, so it is preferable to define nozzle array NLA as the nozzle array above nozzle array NLC. Similarly, when comparing nozzles ND of nozzle array NLD and nozzles NB of nozzle array NLB, which are located in the same head chip 12C and at the same position on the X-axis, the nozzle ND of nozzle array NLD is located higher than the nozzle NB of nozzle array NLB, so it is preferable to define nozzle array NLD as the nozzle array above nozzle array NLB. In this way, nozzle array NLA may be an example of a first nozzle array, nozzle array NLB an example of a second nozzle array, nozzle array NLC an example of a third nozzle array, and nozzle array NLD an example of a fourth nozzle array.

[0121] Next, the arrangement of the nozzle rows NL of the liquid jet head 10D according to Modification 3 will be described with reference to FIG. 16. FIG. 16 is a bottom view showing the ejection surface F4 of the liquid jet head 10D according to Modification 3. The liquid jet head 10D has a plurality of nozzle rows NL. The nozzle rows NL include a nozzle row NLA that ejects a first ink and a nozzle row NLB that ejects a second ink. Note that when there is no need to distinguish between the nozzle rows NLA and NLB, they may be referred to as the nozzle row NL.

[0122] The liquid jet head 10D has a plurality of head chips 12D. The head chip 12D is provided with a nozzle plate 11D in which nozzles N are formed. The head chip 12D is provided with nozzle rows NLA and NLB.

[0123] Multiple nozzle arrays NL extend along the V-axis direction. The nozzles N included in each nozzle array NL are aligned in the V-axis direction. The nozzle arrays NLA and NLB are arranged at different positions in the W-axis direction. When viewed in the W-axis direction, the nozzle arrays NLA and NLB at least partially overlap. When viewed in the Y-axis direction, the nozzle arrays NLA and NLB at least partially overlap. When viewed in the X-axis direction, the nozzle arrays NLA and NLB at least partially overlap.

[0124] When viewed in the X-axis direction, the nozzle row NLA and the nozzle row NLB at least partially overlap, that is, the nozzle row NLA and the nozzle row NLB at least partially overlap with respect to the direction of gravity G1. The nozzle NA1 located at the top end of the nozzle row NLA with respect to the direction of gravity G1 is located higher than the nozzle NB1 located at the top end of the nozzle row NLB with respect to the direction of gravity G1.

[0125] Furthermore, when comparing nozzles NA of nozzle array NLA and nozzle NB of nozzle array NLB, which are located at the same position on the X-axis within the same head chip 12D, the nozzle NA of nozzle array NLA is located higher than the nozzle NB of nozzle array NLB. Therefore, regardless of whether the issue of variations in the head head difference between the pressure adjustment unit 8 and the nozzle array NL or the issue of ink overflowing onto the ejection surface F4 and causing color mixing is considered, in the liquid ejection head 10D, as in the above-described second modification, the nozzle array NLA can be considered as an example of a first nozzle array, and the nozzle array NLB can be considered as an example of a second nozzle array.

[0126] In Figure 16, imaginary lines L5 and L6 are shown as two-dot chain lines. The imaginary lines L5 and L6 are spaced apart from each other in the Y-axis direction and are straight lines that run along the X-axis direction. The imaginary line L5 is located in the Y2 direction of the imaginary line L6. When viewed in the Z-axis direction, the imaginary line L5 overlaps with the nozzle NA1, and the imaginary line L6 overlaps with the nozzle NB1. The nozzle array NLA includes a portion that is positioned in the Y2 direction from the imaginary line L6.

[0127] The liquid ejecting apparatus 1 including such a liquid ejecting head 10D has the same effects as the liquid ejecting apparatus 1 including the liquid ejecting head 10 described above.

[0128] Next, the arrangement of the nozzle rows NL of the liquid jet heads 10G, 10H according to Modification 4 will be described with reference to FIG. 17. FIG. 17 is a bottom view showing the ejection surfaces of the liquid jet heads 10G, 10H according to Modification 4. The liquid jet device 1 shown in FIG. 1 may include a head unit 20 having a plurality of liquid jet heads 10G, 10H, instead of the liquid jet head 10. The head unit 20 has a plurality of liquid jet heads 10G, 10H arranged alternately in the X-axis direction. FIG. 17 illustrates a plurality of liquid jet heads 10G and a liquid jet head 10H arranged between the plurality of liquid jet heads 10G.

[0129] The liquid ejection head 10G includes a plurality of nozzle arrays NL, including a nozzle array NLA1 that ejects a first ink, a nozzle array NLB1 that ejects a second ink, a nozzle array NLC1 that ejects a third ink, and a nozzle array NLD1 that ejects a fourth ink.

[0130] The liquid jet head 10G has a plurality of head chips 12G1, 12G2, 12G3, and 12G4. The head chip 12G1 is provided with a nozzle array NLA1, the head chip 12G2 is provided with a nozzle array NLB1, the head chip 12G3 is provided with a nozzle array NLC1, and the head chip 12G4 is provided with a nozzle array NLD1.

[0131] In the liquid jet 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 multiple nozzle rows NLA1, NLB1, NLC1, and NLD1 extend in the X-axis direction. In the Y1 direction, the nozzle row NLA1, the nozzle row NLC1, the nozzle row NLD1, and the nozzle row NLB1 are arranged in this order. The nozzle rows NLB1, NLD1, NLC1, and NLA1 are longer in length in the X-axis direction than the nozzle row NLB1 in the X-axis direction. When the head unit 20 is in an inclined position, the nozzle rows NLA1, NLC1, NLD1, and NLB1 are arranged in higher positions in this order.

[0132] The liquid ejection head 10H includes a plurality of nozzle arrays NL, including a nozzle array NLA2 that ejects a first ink, a nozzle array NLB2 that ejects a second ink, a nozzle array NLC2 that ejects a third ink, and a nozzle array NLD2 that ejects a fourth ink.

[0133] The liquid jet head 10H has a plurality of head chips 12H1, 12H2, 12H3, and 12H4. The head chip 12H1 is provided with a nozzle array NLA2, the head chip 12H2 is provided with a nozzle array NLB2, the head chip 12H3 is provided with a nozzle array NLC2, and the head chip 12H4 is provided with a nozzle array NLD2.

[0134] In the liquid jet 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 multiple nozzle rows NLA2, NLB2, NLC2, and NLD2 extend in the X-axis direction. In the Y1 direction, the nozzle row NLA2, the nozzle row NLC2, the nozzle row NLD2, and the nozzle row NLB2 are arranged in this order. The nozzle row NLA2 is longer in length in the X-axis direction than the nozzle row NLB2. When the head unit 20 is in an inclined position, the nozzle row NLA2, the nozzle row NLC2, the nozzle row NLD2, and the nozzle row NLB2 are arranged in the highest position in this order.

[0135] The liquid ejecting apparatus 1 including such liquid ejecting heads 10G, 10H has the same effects as the liquid ejecting apparatus 1 including the liquid ejecting head 10 described above.

[0136] Next, a liquid ejecting apparatus 1B according to a second embodiment will be described with reference to FIG. 18. FIG. 18 is a schematic diagram 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 transports a medium PA, and pressure adjusting units 38A to 38E. Note that, in the description of the second embodiment, descriptions that are the same as those of the first embodiment will be omitted. As described above, the X-axis direction, Y-axis direction, and Z-axis direction shown in each drawing differ depending on the posture of the liquid ejecting heads 30A to 30E. Note that the drum 35 may be an intermediate transfer body on which ink ejected from the liquid ejecting heads 30A to 30E lands.

[0137] The drum 35 rotates around a rotation axis 35a extending in the X-axis direction. The medium PA is transported in accordance with the rotation of the drum 35. The medium PA passes through positions corresponding to the liquid jet heads 30A to 30E. Ink is ejected from the liquid jet heads 30A to 30E onto the moving medium PA.

[0138] The liquid jet heads 30A to 30E are arranged at different positions in the circumferential direction of the drum 35. The jet surfaces F31 to F35 of the liquid jet heads 30A to 30E are arranged at different angles. The jet surfaces F31 to F35 are surfaces of nozzle plates.

[0139] 19 is a schematic diagram showing the attitude of the liquid jet head 30A. The liquid jet head 30A has a nozzle array NLA that ejects a first ink. The nozzle array NLA is formed on an ejection surface F31 of the liquid jet head 30A. The multiple nozzles NA included in the nozzle array NLA are aligned in the X-axis direction. The LA direction, which is perpendicular to the ejection surface F31, is aligned with the direction of gravity G1. Ink ejected from the nozzles NA of the liquid jet head 30A flies downward in the direction of gravity G1.

[0140] FIG. 20 is a schematic diagram showing the attitude of the liquid jet head 30B. The liquid jet head 30B has a nozzle row NLB that ejects the second ink. The nozzle row NLB is formed on the ejection surface F32 of the liquid jet head 30B. The multiple nozzles NB included in the nozzle row NLB are aligned in the X-axis direction. The LB direction perpendicular to the ejection surface F32 is aligned with the direction of gravity G1. FIG. 20 also shows an upward direction G2, which is the opposite direction to the direction of gravity G1. Ink ejected from the nozzle NB of the liquid jet head 30B flies in the upward direction G2.

[0141] The liquid jet head 30A is an example of a first liquid jet head, and the liquid jet head 30B is an example of a second liquid jet 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 that ejects the second ink. The dynamic surface tension of the first ink is greater than the dynamic surface tension of the second ink.

[0142] In the liquid jet 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 direction of gravity G1 is 0 degrees. The angle β1 is an example of a first angle. In the liquid jet 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 direction of gravity G1 is 180 degrees. The angle β2 is an example of a second angle. The angle β2 is greater than the angle β1.

[0143] FIG. 21 is a schematic diagram showing the attitude of the liquid jet head 30C. The liquid jet head 30C has a nozzle row NLC that ejects a third ink. The nozzle row NLC is formed on the ejection surface F33 of the liquid jet head 30C. The multiple nozzles NC included in the nozzle row NLC are aligned in the X-axis direction. The LC direction perpendicular to the ejection surface F33 is aligned along the K1 direction, which is perpendicular to the direction of gravity G1. FIG. 21 shows the K1 direction, which is perpendicular to the direction of gravity G1. Ink ejected from the nozzles NC of the liquid jet head 30C flies along the K1 direction, which is perpendicular to the direction of gravity G1.

[0144] The liquid jet head 30C is an example of a third liquid jet head. The jetting surface F33 is an example of a third jetting surface. The nozzle NC is an example of a third nozzle that jets the third ink. The dynamic surface tension of the third ink is smaller than the dynamic surface tension of the first ink and larger than the dynamic surface tension of the second ink.

[0145] The angle β3 formed between the direction K1, which is the ejection direction of the third ink ejected from the nozzle NC, and the direction of gravity 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.

[0146] Figure 22 is a schematic diagram showing the attitude of the liquid jet head 30D. The liquid jet 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 jet head 30D. The multiple nozzles ND included in the nozzle row NLD are aligned in the X-axis direction. The LD direction, which is perpendicular to the ejection surface F34, is aligned along a direction that intersects with the direction of gravity G1 and the K-axis direction. Ink ejected from the nozzle ND of the liquid jet head 30D flies obliquely upward in a direction that intersects with the direction of gravity G1 and the K-axis direction, i.e., along the Z1 direction in Figure 22.

[0147] The liquid jet head 30D is an example of a fourth liquid jet head. The jetting surface F34 is an example of a fourth jetting surface. The nozzle ND is an example of a fourth nozzle that jets a fourth ink. The dynamic surface tension of the fourth ink is smaller than the dynamic surface tension of the third ink and larger than the dynamic surface tension of the second ink.

[0148] The angle β4 formed by the ejection direction of the fourth ink ejected from the nozzle ND, i.e., 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 greater than the angle β3 and smaller than the angle β2.

[0149] Figure 23 is a schematic diagram showing the attitude of the liquid jet head 30E. The liquid jet head 30E has a nozzle array NLE that ejects the fifth ink. The nozzle array NLE is formed on the ejection surface F35 of the liquid jet head 30E. The multiple nozzles NE included in the nozzle array NLE are aligned in the X-axis direction. The LE direction, which is perpendicular to the ejection surface F35, is aligned along a direction that intersects with the direction of gravity G1 and the K-axis direction. Ink ejected from the nozzle NE of the liquid jet head 30E flies diagonally downward in a direction that intersects with the direction of gravity G1 and the K-axis direction, i.e., along the Z1 direction in Figure 23.

[0150] The liquid jet head 30E is an example of a fifth liquid jet head. The jetting surface F35 is an example of a fifth jetting surface. The nozzle NE is an example of a fifth nozzle that jets a fifth ink. The dynamic surface tension of the fifth ink is smaller than the dynamic surface tension of the first ink and larger than the dynamic surface tension of the third ink.

[0151] The angle β5 formed by the ejection direction of the fifth ink ejected from the nozzle NE, i.e., the Z1 direction in FIG. 23 and the gravity direction G1, is 45 degrees. The angle β5 is an example of a fifth angle. The angle β5 is larger than the angle β1 and smaller than the angle β3.

[0152] Next, the head differences H1 to H5 in the nozzle rows NLA to NLE will be described with reference to Figure 18. 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.

[0153] The pressure adjustment units 38A to 38E can have the same configuration as the pressure adjustment unit 8 described in the first embodiment. Also, like the first embodiment, the pressure adjustment units 38A to 38E have a common configuration. 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.

[0154] 18 shows the height position H0 of the pressure adjustment units 38A-38E in the direction of gravity G1. The height position H0 is located higher than the height positions HA, HB, HC, HD, and HE of the nozzle rows NLA, NLB, NLC, NLD, and NLE. The positions HA, HE, HC, HD, and HB are higher in this order.

[0155] The head difference H2 between the pressure adjustment unit 38B and the nozzle row NLB is greater than the head difference H4 between the pressure adjustment unit 38D and the nozzle row NLD. The head difference H4 is greater than the head difference H3 between the pressure adjustment unit 38C and the nozzle row NLC. The head difference H3 is greater than the head difference H5 between the pressure adjustment unit 38E and the nozzle row NLE. The head difference H5 is greater than the head difference H1 between the pressure adjustment unit 38A and the nozzle row NLA. That is, the head differences are greatest in the order of H2, H4, H3, H5, and H1.

[0156] The liquid ejecting device 1B according to the second embodiment also achieves the same effects as the liquid ejecting device 1 according to the first embodiment.

[0157] In the liquid ejection device 1B, the positions of the nozzles NA, NB, NC, ND, and NE of the nozzle arrays NLA, NLB, NLC, NLD, and NLE differ depending on the dynamic surface tension of the ink. The nozzle NA of the nozzle array NLA, which ejects the first ink, which has the highest dynamic surface tension, is positioned higher in the direction of gravity G1 than the nozzles NB, NC, ND, and NE of the other nozzle arrays NLB, NLC, NLD, and NLE. In other words, the first ink, which is easier to supply, is supplied to the nozzle NA of the nozzle array NLA, which has a small head difference H1 and is difficult to supply.

[0158] In the liquid ejection device 1B, the nozzles NB of the nozzle array NLB, which eject the second ink having the smallest dynamic surface tension, are positioned lower in the direction of gravity G1 than the nozzles NA, NC, ND, and NE of the other nozzle arrays NLA, NLC, NLD, and NLE. The second ink, which is difficult to eject and supply, is supplied to the nozzles NB of the nozzle array NLB, which has a large head difference H2 and is easy to supply.

[0159] In the liquid ejection device 1B, the nozzles NA of the nozzle array NLA that ejects the first ink, which has a higher dynamic surface tension, are positioned higher in the direction of gravity G1 than the nozzles NB of the nozzle array NLB that ejects the second ink, which has a lower dynamic surface tension. This reduces the variation in the ink supply characteristics to the multiple nozzle arrays NL that eject different types of ink, thereby suppressing the variation in the ink ejection characteristics of the multiple nozzle arrays NL. As a result, the printing accuracy of the liquid ejection device 1B can be improved.

[0160] In the liquid ejection device 1B, the nozzles NC of the nozzle array NLC that eject the third ink are positioned between the nozzles NA of the nozzle array NLA and the nozzles NB of the nozzle array NLB in the direction of gravity G1. The third ink, which has a dynamic surface tension lower than that of the first ink, is supplied to the nozzles NC of the nozzle array NLC that have a head difference H3 larger than the head difference H1. The third ink, which has a dynamic surface tension higher than that of the second ink, is supplied to the nozzles NC of the nozzle array NLC that have a head difference H3 smaller than the head difference H2.

[0161] In the liquid ejection device 1B, the nozzles ND of the nozzle array NLD that eject the fourth ink are positioned between the nozzles NC of the nozzle array NLC and the nozzles NB of the nozzle array NLB in the direction of gravity G1. The fourth ink, which has a dynamic surface tension lower than that of the third ink, is supplied to the nozzles ND of the nozzle array NLD that have a head difference H4 larger than the head difference H3. The fourth ink, which has a dynamic surface tension higher than that of the second ink, is supplied to the nozzles ND of the nozzle array NLD that have a head difference H4 smaller than the head difference H2.

[0162] In the liquid ejection device 1B, the nozzles NE of the nozzle array NLE that eject the fifth ink are positioned between the nozzles NA of the nozzle array NLA and the nozzles NC of the nozzle array NLC in the direction of gravity G1. The fifth ink, which has a dynamic surface tension lower than that of the first ink, is supplied to the nozzles NE of the nozzle array NLE that have a head difference H5 larger than the head difference H1. The fifth ink, which has a dynamic surface tension higher than that of the third ink, is supplied to the nozzles NE of the nozzle array NLE that have a head difference H3 smaller than the head difference H3.

[0163] In this liquid ejection device 1B, the height positions of the nozzles NA to NE vary depending on the dynamic surface tension of the ink, which reduces the variation in ink supply characteristics to the multiple nozzles NA to NE that eject different types of ink, thereby suppressing the variation in ink ejection characteristics of the multiple nozzles NA to NE, thereby improving the printing accuracy of the liquid ejection device 1B.

[0164] In this embodiment, the height position H0 of the pressure adjustment units 38A-38E is located higher than the height positions HA, HB, HC, HD, and HE of the nozzles NA, NB, NC, ND, and NE in the direction of gravity G1, but this is not limiting. The height position H0 may be located between the positions HA and HB in the direction of gravity G1, or may be located lower than the positions HA, HE, HC, HD, and HB.

[0165] It should be noted 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 are possible within the scope that does not deviate from the gist of the present invention.

[0166] In the above embodiment, a plurality of inks of different colors are illustrated, but this is not limiting. For example, the first ink and the second ink may have different dynamic surface tensions and may be the same color.

[0167] In the above-described embodiment, a line-type liquid ejection device 1 equipped with a line head is exemplified, but the present invention may also be applied to a serial-type liquid ejection device in which a carriage carrying a liquid ejection head 10 is moved back and forth in the width direction of the medium PA.

[0168] The liquid ejection device 1 illustrated in the above-described embodiment can be employed in various devices such as facsimile machines and copiers, as well as devices dedicated to printing. However, the use of the liquid ejection device of the present invention is not limited to printing. For example, a liquid ejection device that ejects a solution of a color material is used as a manufacturing device for forming color filters for display devices such as liquid crystal display panels. Furthermore, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wiring and electrodes on a wiring board. Furthermore, a liquid ejection device that ejects a solution of an organic substance related to a living organism is used as a manufacturing device for manufacturing biochips, for example. [Explanation of symbols]

[0169] 1, 1B...liquid ejection device, 1a...housing, 8A...pressure adjustment unit, 8B...pressure adjustment unit, 10, 10B to 10D, 10G, 10H...liquid ejection head, 11...nozzle plate, 30A...liquid ejection head, 30B...liquid ejection head, 30C to 30E...liquid ejection head, 38A...pressure adjustment unit, 38B...pressure adjustment unit, F0...horizontal plane, F1...ejection surface, F31...ejection surface, F32...ejection surface (second ejection surface), G1...direction of gravity, L1...first imaginary 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 the first ink and a second nozzle row that ejects the second ink; a first pressure adjusting unit that adjusts the pressure of the first ink supplied to the first nozzle row; a second pressure adjusting unit that adjusts the pressure of the second ink supplied to the second nozzle row; Equipped with the first pressure adjusting unit and the second pressure adjusting unit are disposed at the same position in the direction of gravity, the liquid ejection head can be held in a first position in which the ejection surface is inclined with respect to a horizontal plane, the dynamic surface tension of the first ink is greater than the dynamic surface tension of the second ink; In the first attitude, the first nozzle row is positioned higher than the second nozzle row in the direction of gravity.

2. 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; the liquid ejection head can be held in a first position in which the ejection surface is inclined with respect to a horizontal plane, an attitude of the liquid ejection head is changeable to a plurality of attitudes including the first attitude and a second attitude different from the first attitude; the liquid ejection head is rotatable about a rotation axis along a first direction, which is an extension direction of a line of intersection between the ejection surface and a horizontal plane in the first attitude; the dynamic surface tension of the first ink is greater than the dynamic surface tension of the second ink; In the first attitude, the first nozzle row is positioned above the second nozzle row in the direction of gravity, when viewed in the first direction, a line that passes through a center between the first nozzle row and the second nozzle row in the first attitude and extends in a direction perpendicular to the ejection surface in the first attitude is defined as a first virtual line, the rotation axis is located on the second nozzle row side as viewed from the first virtual line. Liquid injection device.

3. an attitude of the liquid ejection head is changeable to a plurality of attitudes including the first attitude and a second attitude different from the first attitude; the liquid ejection head is rotatable about a rotation axis along a first direction, which is an extension direction of a line of intersection between the ejection surface and a horizontal plane in the first attitude; 2. The liquid ejection device according to claim 1, wherein when a first virtual line is defined as a line that passes through the center between the first nozzle row and the second nozzle row in the first attitude when viewed in the first direction and extends in a direction perpendicular to the ejection surface in the first attitude, the rotation axis is located on the second nozzle row side when viewed from the first virtual line.

4. the first attitude is a recording attitude in which a recording operation is performed by ejecting the first ink and the second ink onto a medium, The liquid ejecting apparatus according to claim 2 , wherein the second posture is a maintenance posture for performing maintenance on the liquid ejecting head.

5. 5. The liquid ejecting device according to claim 2, wherein in the second attitude, the ejection surface is parallel to a horizontal plane.

6. 6. The liquid ejecting apparatus according to claim 1, wherein the difference between the dynamic surface tension of the first ink and the dynamic surface tension of the second ink is 1.0 mN / m or more.

7. 7. The liquid ejecting apparatus according to claim 1, wherein the dynamic surface tension of the first ink at a lifetime of 10 msec is greater than the dynamic surface tension of the second ink at a lifetime of 10 msec.

8. 8. The liquid ejecting apparatus according to claim 1, wherein the first nozzle row and the second nozzle row are formed in a common nozzle plate.

9. a direction in which an intersection line between the ejection surface and a horizontal plane in the first attitude extends is defined as a first direction; When a direction orthogonal to the first direction in the ejection surface is defined as a second direction, The liquid ejecting apparatus according to claim 8 , wherein the first nozzle row and the second nozzle row at least partially overlap when viewed in the second direction.

10. a direction in which an intersection line between the ejection surface and a horizontal plane in the first attitude extends is defined as a first direction; 10. The liquid ejecting apparatus according to claim 1, wherein the first nozzle row and the second nozzle row are arranged with a gap between them when viewed in the first direction.

11. A liquid ejection device according to any one of claims 1 to 10, wherein the nozzle located at the upper end of the first nozzle row in the direction of gravity is located higher in the direction of gravity than the nozzle located at the upper end of the second nozzle row in the direction of gravity.

12. the ejection surface further includes a third nozzle row that ejects a third ink; the dynamic surface tension of the third ink is smaller than the dynamic surface tension of the first ink and larger than the dynamic surface tension of the second ink; 12. The liquid ejecting apparatus according to claim 1, wherein in the first attitude, the third nozzle row is positioned lower than the first nozzle row in the direction of gravity and higher than the second nozzle row.

13. the ejection surface further includes a fourth nozzle row that ejects a fourth ink; the dynamic surface tension of the fourth ink is greater than the dynamic surface tension of the second ink and less than the dynamic surface tension of the third ink; The liquid ejecting apparatus according to claim 12 , wherein, in the first attitude, the fourth nozzle row is located lower than the third nozzle row and higher than the second nozzle row in the direction of gravity.

14. a first liquid ejection head having a first ejection surface including first nozzles that eject a first ink; a second liquid ejection head having a second ejection surface including second nozzles that eject the second ink; the dynamic surface tension of the first ink is greater than the dynamic surface tension of the second ink; the first ejection surface is disposed so that an ejection direction of the first ink ejected from the first nozzle forms a first angle with a direction of gravity; the second ejection surface is disposed so that an angle formed between an ejection direction of the second ink ejected from the second nozzle and a direction of gravity is a second angle that is larger than the first angle; a first pressure adjusting unit that adjusts the pressure of the first ink supplied to the first nozzle; a second pressure adjusting unit that adjusts the pressure of the second ink supplied to the second nozzles, The liquid ejecting device, wherein the first pressure adjusting unit and the second pressure adjusting unit are disposed at the same position in the direction of gravity.

15. a first liquid ejection head having a first ejection surface including first nozzles that eject a first ink; a second liquid ejection head having a second ejection surface including second nozzles that eject a second ink; a third liquid ejection head having a third ejection surface including third nozzles that eject a third ink, the dynamic surface tension of the third ink is greater than the dynamic surface tension of the second ink and less than the dynamic surface tension of the first ink; the first ejection surface is disposed so that an ejection direction of the first ink ejected from the first nozzle forms a first angle with a direction of gravity; the second ejection surface is disposed so that an angle formed between an ejection direction of the second ink ejected from the second nozzle and a direction of gravity is a second angle that is larger than the first angle; A liquid ejection device, wherein the third ejection surface is positioned so that the angle formed between the ejection direction of the third ink ejected from the third nozzle and the direction of gravity is a third angle that is larger than the first angle and smaller than the second angle.

16. a fourth liquid ejection head having a fourth ejection surface including fourth nozzles that eject a fourth ink; the dynamic surface tension of the fourth ink is greater than the dynamic surface tension of the second ink and less than the dynamic surface tension of the third ink; 16. The liquid ejection device according to claim 15, wherein the fourth ejection surface is disposed so that an angle formed between an ejection direction of the fourth ink ejected from the fourth nozzle and a direction of gravity is a fourth angle that is larger than the third angle and smaller than the second angle.

17. A liquid ejection device according to any one of claims 1 to 13, comprising a medium transport mechanism that transports a medium from the lower side to the upper side in the direction of gravity at a position facing the ejection surface of the liquid ejection head held in the first attitude.

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