Liquid ejection method

Abstract

By flowing the liquid through the flow path of the liquid ejection head, it is possible to suppress the increase in viscosity of the ink due to evaporation of the liquid from the ejection port, and reduce color unevenness in the image. [Solution] A liquid ejection head includes an ejection port for ejecting liquid, a flow path in which an energy generating element that generates energy used to eject the liquid is disposed, an ejection port section that communicates the ejection port with the flow path, a supply flow path for introducing liquid into the flow path from the outside, and an outflow flow path for discharging liquid from the flow path to the outside. When the height of the flow path at the communication part between the flow path and the ejection port section is H μm, the length of the ejection port section in the direction in which the liquid is ejected from the ejection port is P μm, and the length of the ejection port section in the direction in which the liquid flows in the flow path is W μm, then H -0.34 ×P -0.66 ×W>1.7.

Description

[Technical Field]

[0001] The present invention ,liquid body Discharge In particular, the method is directed to a liquid ejection head that performs an ejection operation while flowing liquid through a flow path between a liquid ejection port and an element that generates ejection energy. Liquid discharge method It is related to. [Background technology]

[0002] Patent Document 1 describes a liquid ejection head of this type in which ink is circulated through a flow path between the ejection orifices of the liquid ejection head and a heating resistor that generates ejection energy, thereby ejecting ink. With this configuration, the heat generated during the ejection operation causes the water content of the ink to evaporate, allowing the ink to be expelled and new ink to be replenished, thereby preventing clogging of the ejection orifices due to increased ink viscosity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-355973 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a configuration in which liquid flows through a flow path between the ejection orifices and the energy generating elements as described in Patent Document 1, depending on the shape of the flow path and the ejection orifices, variations in the quality of the liquid near the ejection orifices may occur even though the liquid is flowing. For example, in a liquid ejection head that ejects ink, the ink may thicken or the colorant concentration may change, resulting in poor ink ejection or uneven density in the printed image.

[0005] The present invention solves the above-mentioned problems, and in a configuration in which liquid flows through a flow path between an ejection port and an energy generating element, it is possible to suppress changes in the quality of the liquid near the ejection port. Liquid body Discharge The present invention aims to provide a method. [Means for solving the problem]

[0006] Therefore, the liquid ejection method of the present invention is a liquid ejection method using a liquid ejection head comprising: an ejection port section having an ejection port at an end thereof for ejecting liquid; an energy generating element that generates energy used to eject liquid from the ejection port; a flow path in which the energy generating element is arranged and which communicates with the ejection port section; a supply flow path for causing liquid to flow into the flow path from the outside; and an outlet flow path for causing liquid to flow out from the flow path to the outside, wherein a flow of liquid is generated in the liquid ejection head, and the liquid flow (1) flows into the flow path from the outside via the supply flow path, (2) flows from the flow path into the ejection port section, (3) reaches the meniscus position of the liquid formed in the ejection port within the ejection port section, and then returns to the flow path, and (4) flows out from the flow path to the outside via the outlet flow path, In the ejection port portion, the flow of the liquid is maintained to reach the meniscus position of the liquid formed in the ejection port. In this state, the energy generating element is driven to eject the liquid from the ejection port. [Effects of the Invention]

[0007] With the above configuration, it is possible to suppress changes in the quality of the liquid near the ejection ports by flowing the liquid through the flow paths of the liquid ejection head, which in turn makes it possible to suppress thickening of the ink due to evaporation of the liquid from the ejection ports and reduce color unevenness in images. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a perspective view showing a schematic configuration of an inkjet recording apparatus according to an embodiment of a liquid ejection apparatus for ejecting liquid of the present invention. [Figure 2]FIG. 2 is a schematic diagram showing a first circulation mode of a circulation path applied to a recording apparatus according to an embodiment. [Figure 3] FIG. 10 is a schematic diagram showing a second circulation mode of the circulation path applied to the recording apparatus of the embodiment. [Figure 4] 10(a) to 10(f) are diagrams illustrating the difference in the amount of ink that flows into the liquid ejection head 3 between the first circulation mode and the second circulation mode. [Figure 5] 1A and 1B are perspective views showing a liquid ejection head according to an embodiment. [Figure 6] FIG. 2 is an exploded perspective view showing each component or unit that constitutes the liquid ejection head. [Figure 7] 1(a) to 1(f) are diagrams showing the front and back surfaces of the first, second, and third flow path members. [Figure 8] FIG. 7(b) is a perspective view showing a part of FIG. 7(a) and showing an enlarged view of a flow path in a flow path member formed by joining first to third flow path members. [Figure 9] FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 8. [Figure 10] 1(a) and 1(b) are a perspective view and an exploded perspective view showing one discharge module. [Figure 11] 1A, 1B, and 1C are a plan view of the surface of the recording element substrate on which ejection ports are formed, a partially enlarged view, and a plan view of the back side of the surface. [Figure 12] FIG. 12 is a perspective view showing a cross section taken along line XII-XII in FIG. [Figure 13] FIG. 2 is a partially enlarged plan view showing adjacent portions of recording element substrates in two adjacent ejection modules. [Figure 14] 10(a) and 10(b) are perspective views showing a liquid ejection head according to another example of the embodiment. [Figure 15] FIG. 10 is an exploded perspective view showing a liquid ejection head according to another example of the embodiment. [Figure 16] 10(a) to 10(e) are diagrams showing flow path members constituting a liquid ejection head according to another example of an embodiment. [Figure 17] FIG. 10 is a perspective view showing the liquid connection relationship between a recording element substrate and a flow path member in a liquid ejection head according to another example of an embodiment. [Figure 18] FIG. 18 is a cross-sectional view taken along line XVIII-XVIII in FIG. [Figure 19] 10(a) and 10(b) are a perspective view and an exploded view showing a discharge module in a liquid discharge head according to another example of the embodiment. [Figure 20] (a) is a schematic diagram showing the surface of the recording element substrate on which the ejection ports are arranged, (b) is the surface of the recording element substrate when the cover plate provided on the back side of the recording element substrate is removed, and (c) is a schematic diagram showing the back side of the surface on which the ejection ports are arranged. [Figure 21] FIG. 10 is a diagram illustrating a second application example of the inkjet recording apparatus according to the embodiment. [Figure 22] 1(a) to 1(c) are diagrams illustrating the structure of an ejection port and an ink flow path in the vicinity thereof in a liquid ejection head according to a first embodiment of the present invention. [Figure 23] 10A and 10B are diagrams illustrating the state of ink flow in a liquid ejection head according to a second embodiment. [Figure 24] 10A and 10B are diagrams showing the state of the colorant concentration of ink inside the ejection port portion according to the second embodiment and a comparative example. [Figure 25] 10A and 10B are diagrams illustrating a comparison of the colorant concentrations of inks ejected from the liquid ejection heads of the second embodiment and the comparative example. [Figure 26] 10A and 10B are diagrams showing the relationship between a liquid ejection head that generates a flow mode according to the second embodiment and a liquid ejection head that generates a flow mode according to a comparative example. [Figure 27] 27(a) to 27(d) are diagrams illustrating the state of ink flow near the ejection port in the liquid ejection head in the regions above and below the threshold line shown in FIG. 26. [Figure 28] 10A and 10B are diagrams for explaining whether the flow occurs in flow mode A or flow mode B for liquid ejection heads of various shapes. [Figure 29]10(a) to 10(c) are diagrams showing the relationship between the number of ejections (number of ejections) and the ejection speed at that time after a certain period of rest following ejection from a liquid ejection head in each flow mode. [Figure 30] 10A and 10B are diagrams illustrating the state of ink flow in a liquid ejection head according to a third embodiment of the present invention. [Figure 31] 10A and 10B are diagrams showing the state of ink flow in a liquid ejection head according to a fourth embodiment of the present invention. [Figure 32] 10A and 10B are diagrams showing the state of ink flow in a liquid ejection head according to a fifth embodiment of the present invention. [Figure 33] 10A and 10B are diagrams showing the state of ink flow in a liquid ejection head according to a sixth embodiment of the present invention. [Figure 34] 13A and 13B are diagrams showing the state of ink flow in a liquid ejection head according to a seventh embodiment of the present invention. [Figure 35] 13(a) and 13(b) are diagrams showing the shape of the ejection ports of a liquid ejection head according to an eighth embodiment of the present invention. [Figure 36] 13(a) and 13(b) are diagrams showing the state of ink flowing in each flow mode within a liquid ejection head according to a ninth embodiment of the present invention. [Figure 37] 13(a) and 13(b) are diagrams showing the state of the colorant concentration of ink inside the ejection port portion according to the ninth embodiment. [Figure 38] FIG. 13 is a diagram showing the relationship between the evaporation rate and the circulation flow rate for each flow mode in the ninth embodiment. [Figure 39] 13(a) to 13(c) are diagrams showing flow modes of three flow channel shapes according to a tenth embodiment of the present invention. [Figure 40] FIG. 20 is a contour map showing flow mode judgment values ​​when the discharge port diameter is changed according to the tenth embodiment. [Figure 41] 13(a) to 13(c) are diagrams showing the results of observing the discharged droplets from the discharge ports for each flow path shape according to the tenth embodiment. [Figure 42]FIG. 20 is a contour map showing the time it takes for a bubble to communicate with the atmosphere when the diameter of the discharge port is changed according to the tenth embodiment. [Figure 43] 3A and 3B are diagrams illustrating the state of ink flow in the liquid ejection head according to the first embodiment. [Figure 44] FIG. 13 is a diagram showing a liquid ejection head according to an eighth embodiment. [Figure 45] FIG. 13 is a diagram showing a liquid ejection head according to an eighth embodiment. [Figure 46] FIG. 1 is a diagram illustrating a recording device according to a first application example. [Figure 47] FIG. 10 is a diagram showing a third circulation mode. [Figure 48] 10A and 10B are diagrams illustrating modified examples of the liquid ejection head according to the first application example. [Figure 49] 10A and 10B are diagrams illustrating modified examples of the liquid ejection head according to the first application example. [Figure 50] 10A and 10B are diagrams illustrating modified examples of the liquid ejection head according to the first application example. [Figure 51] FIG. 10 is a diagram illustrating a recording device according to a third application example. [Figure 52] FIG. 10 is a diagram showing a fourth circulation mode. [Figure 53] FIG. 10 is a diagram showing a liquid ejection head according to a third application example. [Figure 54] FIG. 10 is a diagram showing a liquid ejection head according to a third application example. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes various application examples and embodiments to which the present invention can be applied, with reference to the drawings. The liquid ejection head of the present invention, which ejects liquid such as ink, and the liquid ejection device equipped with the liquid ejection head, can be used in devices such as printers, copiers, facsimiles with communication systems, and word processors with printer units. They can also be used in industrial recording devices in combination with various processing devices. For example, they can be used for biochip production, electronic circuit printing, and semiconductor substrate production. The application examples and embodiments described below are appropriate specific examples of the present invention, and therefore are subject to various technically desirable limitations. However, as long as they are in line with the concept of the present invention, the application examples and embodiments are not limited to the application examples, embodiments, or other specific methods described in this specification.

[0010] (First application example) <Inkjet recording device> FIG. 1 is a diagram showing the schematic configuration of a liquid ejection device of the present invention, specifically an inkjet recording device (hereinafter also referred to as a recording device) 1000 that ejects ink to perform recording. The recording device 1000 is a line-type recording device that includes a transport unit 1 that transports a recording medium 2 and a line-type liquid ejection head 3 arranged approximately perpendicular to the transport direction of the recording medium 2. The recording device 1000 is a line-type recording device that performs continuous recording in one pass while continuously or intermittently transporting multiple recording media 2. The recording media 2 are not limited to cut paper, but may also be continuous roll media. The liquid ejection head 3 includes a negative pressure control unit 230 that controls the pressure (negative pressure) within the circulation path, a liquid supply unit 220 fluidly connected to the negative pressure control unit 230, a liquid connection unit 111 that serves as an ink supply and discharge port for the liquid supply unit 220, and a housing 80. The liquid ejection head 3 of this embodiment includes arrays of ejection ports that eject cyan (C), magenta (M), yellow (Y), and black (K) inks, respectively, enabling full-color recording. As will be described later in FIG. 2, the liquid ejection head 3 is fluidly connected to a liquid supply mechanism, which is a supply path that supplies liquid to the liquid ejection head 3, a main tank, and a buffer tank (see FIG. 2, which will be described later). Four negative pressure control units 230 and liquid supply units 220 are provided corresponding to the four colors of ink. An electrical control unit that transmits power and ejection control signals to the liquid ejection head 3 is also electrically connected to the liquid ejection head 3. The liquid paths and electrical signal paths within the liquid ejection head 3 will be described later.

[0011] The recording device 1000 is an inkjet recording device configured to circulate a liquid such as ink between a tank (described later) and a liquid ejection head 3. The inkjet recording device of this application example can apply various circulation modes (configurations), such as the first and second circulation modes described below. The first circulation mode is a mode in which circulation is performed by operating two circulation pumps (one for high pressure and one for low pressure) downstream of the liquid ejection head 3, while the second circulation mode is a mode in which circulation is performed by operating two circulation pumps (one for high pressure and one for low pressure) upstream of the liquid ejection head 3. The first and second circulation modes will be described below.

[0012] <Explanation of the first circulation type> 2 is a schematic diagram showing a first circulation form of the circulation path applied to the recording apparatus 1000 of this application example. The liquid ejection head 3 is fluidly connected to a first circulation pump (high pressure side) 1001, a first circulation pump (low pressure side) 1002, a buffer tank 1003, etc. Note that for the sake of simplicity, FIG. 2 shows only the path through which ink of one color flows out of cyan C, magenta M, yellow Y, and black K, but in reality, circulation paths for all four colors are provided in the liquid ejection head 3 and the recording apparatus main body.

[0013] In the first circulation mode, ink in the main tank 1006 is supplied to the buffer tank 1003 by the refill pump 1005, and then supplied to the liquid supply unit 220 of the liquid ejection head 3 via the liquid connection part 111 by the second circulation pump 1004. The ink is then adjusted to two different negative pressures (high pressure and low pressure) by the negative pressure control unit 230 connected to the liquid supply unit 220, and circulates through two flow paths, one on the high-pressure side and one on the low-pressure side. The ink in the liquid ejection head 3 is circulated within the head by the action of the first circulation pump (high-pressure side) 1001 and the first circulation pump (low-pressure side) 1002, which are located downstream of the liquid ejection head 3, and is then discharged from the head 3 via the liquid connection part 111 and returned to the buffer tank 1003.

[0014] The buffer tank 1003, which is a sub-tank, is connected to the main tank 1006 and has an atmosphere communication port (not shown) that connects the inside of the tank with the outside, making it possible to discharge air bubbles in the ink to the outside. A refill pump 1005 is provided between the buffer tank 1003 and the main tank 1006. The refill pump 1005 transfers ink consumed by discharging (discharging) ink from the discharge ports of the liquid discharge head 3 for recording by discharging ink, suction recovery, etc., from the main tank 1006 to the buffer tank 1003.

[0015] Two first circulation pumps 1001 and 1002 draw liquid from the liquid connection 111 of the liquid ejection head 3 and send it to the buffer tank 1003. The first circulation pump is preferably a positive displacement pump with a constant liquid delivery capacity. Specific examples include a tube pump, gear pump, diaphragm pump, and syringe pump. Alternatively, a constant flow rate may be ensured by providing a general constant flow valve or relief valve at the pump outlet. When the liquid ejection head 3 is driven, the first circulation pump (high-pressure side) 1001 and the first circulation pump (low-pressure side) 1002 are operated to cause ink to flow at a predetermined flow rate through the common supply path 211 and the common recovery path 212, respectively. By flowing ink in this manner, the temperature of the liquid ejection head 3 is maintained at an optimal temperature during recording. The predetermined flow rate when the liquid ejection head 3 is driven is preferably set to a flow rate that can be maintained at a level that does not affect the image quality of the recording due to temperature differences between the recording element substrates 10 in the liquid ejection head 3. However, if the flow rate is set too high, the negative pressure difference between the recording element substrates 10 will increase due to the influence of pressure loss in the flow paths within the liquid ejection unit 300, resulting in uneven density in the image. For this reason, it is preferable to set the flow rate while taking into consideration the temperature difference and negative pressure difference between the recording element substrates 10.

[0016] The negative pressure control unit 230 is provided in the path between the second circulation pump 1004 and the liquid ejection unit 300. This negative pressure control unit 230 operates to maintain the pressure downstream of the negative pressure control unit 230 (i.e., the liquid ejection unit 300 side) at a preset constant pressure even when the ink flow rate in the circulation system fluctuates due to differences in the ejection amount per unit area, etc. The two pressure adjustment mechanisms, high-pressure side (H) and low-pressure side (L), that make up the negative pressure control unit 230 may be any mechanism that can control the pressure downstream of the negative pressure control unit 230 within a certain range centered on a desired set pressure. As an example, a mechanism similar to a so-called "pressure reduction regulator" may be employed. In the circulation flow path in this application example, the second circulation pump 1004 pressurizes the upstream side of the negative pressure control unit 230 via the liquid supply unit 220. By doing so, the influence of the head pressure of the buffer tank 1003 on the liquid ejection head 3 can be suppressed, and the degree of freedom in the layout of the buffer tank 1003 in the recording apparatus 1000 can be increased.

[0017] The second circulation pump 1004 may be any pump having a head pressure equal to or greater than a certain pressure within the range of the ink circulation flow rate used when driving the liquid ejection head 3, and may be a turbo pump, a positive displacement pump, or the like. Specifically, a diaphragm pump or the like may be used. Also, instead of the second circulation pump 1004, for example, a head tank disposed with a certain head difference relative to the negative pressure control unit 230 may be used.

[0018] As shown in Fig. 2, the negative pressure control unit 230 is equipped with two pressure adjustment mechanisms H and L, each set to a different control pressure. Of the two negative pressure adjustment mechanisms, the relatively high pressure setting side (denoted as H in Fig. 2) and the relatively low pressure setting side (denoted as L in Fig. 2) are connected to a common supply path 211 and a common recovery channel 212 in the liquid ejection unit 300, respectively, via the liquid supply unit 220. The liquid ejection unit 300 is provided with the common supply path 211, the common recovery channel 212, and individual channels 215 (individual supply channels 213, individual recovery channels 214) that communicate with each recording element substrate. The pressure adjustment mechanism H is connected to the common supply channel 211, and the pressure adjustment mechanism L is connected to the common recovery channel 212, respectively, thereby generating a pressure difference between the two common channels. Since the individual flow paths 215 are connected to the common supply path 211 and the common recovery path 212, a flow (arrow in FIG. 2) occurs in which a portion of the liquid flows from the common supply path 211 through the internal flow path of the recording element substrate 10 to the common recovery path 212. The two negative pressure adjustment mechanisms H and L are each connected to a path from the liquid connection part 111 via a filter 221.

[0019] In this way, in the liquid ejection unit 300, a flow is generated in which liquid flows through the common supply flow path 211 and the common recovery flow path 212, while a portion of the liquid passes through each recording element substrate 10. As a result, heat generated in each recording element substrate 10 can be discharged to the outside of the recording element substrate 10 by the ink flowing through the common supply flow path 211 and the common recovery flow path 212. Furthermore, with this configuration, while recording is being performed using the liquid ejection head 3, ink flows can also be generated in ejection ports and pressure chambers that are not ejecting. This reduces the viscosity of ink that has increased in the ejection ports, thereby suppressing the increase in ink viscosity. Furthermore, the thickened ink and foreign matter in the ink can be discharged to the common recovery flow path 212. As a result, the liquid ejection head 3 of this application example is capable of high-speed, high-quality recording.

[0020] <Explanation of the second circulation type> 3 is a schematic diagram showing a second circulation mode, which is a circulation mode different from the first circulation mode described above, among the circulation paths applied to the recording apparatus of this application example. The main difference from the first circulation mode described above is that both of the two pressure adjustment mechanisms constituting the negative pressure control unit 230 control the pressure upstream of the negative pressure control unit 230 to fluctuate within a certain range centered on a desired set pressure. Another difference from the first circulation mode is that a second circulation pump 1004 acts as a negative pressure source that reduces the pressure downstream of the negative pressure control unit 230. Another difference is that a first circulation pump (high-pressure side) 1001 and a first circulation pump (low-pressure side) 1002 are arranged upstream of the liquid ejection head 3, and the negative pressure control unit 230 is arranged downstream of the liquid ejection head 3.

[0021] In the second circulation mode, as shown in FIG. 3 , ink in the main tank 1006 is supplied to the buffer tank 1003 by the refill pump 1005. The ink is then divided into two flow paths and circulated through two flow paths, one high-pressure side and one low-pressure side, by the operation of the negative pressure control unit 230 provided in the liquid ejection head 3. The ink divided into the two flow paths, the high-pressure side and the low-pressure side, is supplied to the liquid ejection head 3 via the liquid connection part 111 of the liquid ejection head 3 by the operation of the first circulation pump (high-pressure side) 1001 and the first circulation pump (low-pressure side) 1002. The ink circulated within the liquid ejection unit 300 by the operation of the first circulation pump (high-pressure side) 1001 and the first circulation pump (low-pressure side) 1002 is then passed through the negative pressure control unit 230 and discharged from the liquid ejection head 3 via the liquid connection part 111. The discharged ink is returned to the buffer tank 1003 by the second circulation pump 1004.

[0022] The negative pressure control unit 230 in the second circulation configuration stabilizes pressure fluctuations upstream of the negative pressure control unit 230 (i.e., the liquid ejection unit 300 side) within a certain range centered on a preset pressure, even if there are fluctuations in flow rate caused by changes in the ejection amount per unit area. In the circulation flow path of this application example, the second circulation pump 1004 pressurizes the downstream side of the negative pressure control unit 230 via the liquid supply unit 220. This configuration suppresses the effect of the head pressure of the buffer tank 1003 on the liquid ejection head 3, thereby broadening the options for the layout of the buffer tank 1003 in the recording apparatus 1000. Instead of the second circulation pump 1004, for example, a head tank arranged with a predetermined head difference relative to the negative pressure control unit 230 can also be applied. In the second circulation configuration, as in the first circulation configuration described above, the negative pressure control unit 230 includes two pressure adjustment mechanisms H and L, each set to a different control pressure. Of the two negative pressure adjustment mechanisms H and L, the high pressure setting side (denoted as H in FIG. 3) and the low pressure setting side (denoted as L in FIG. 3) are respectively connected to the common supply path 211 and the common recovery flow path 212 in the liquid ejection unit 300 via the inside of the liquid supply unit 220. By using the two negative pressure adjustment mechanisms to make the pressure in the common supply flow path 211 relatively higher than the pressure in the common recovery flow path 212, an ink flow is generated that flows from the common supply flow path 211 to the common recovery flow path 212 via the individual flow paths 213 and the internal flow paths of each recording element substrate 10.

[0023] In this second circulation mode, the same ink flow state as in the first circulation mode is obtained within the liquid ejection unit 300, but there are two advantages that differ from the first circulation mode. First, in the second circulation mode, because the negative pressure control unit 230 is disposed downstream of the liquid ejection head 3, there is less concern that dust or foreign matter generated from the negative pressure control unit 230 will flow into the liquid ejection head 3. Second, in the second circulation mode, the maximum flow rate required to supply liquid from the buffer tank 1003 to the liquid ejection head 3 can be smaller than in the first circulation mode. The reasons for this are as follows.

[0024] The total flow rate in the common supply flow path 211 and the common recovery flow path 212 when circulating during standby for recording is defined as flow rate A. The value of flow rate A is defined as the minimum flow rate required to keep the temperature difference within the liquid ejection unit 300 within a desired range when adjusting the temperature of the liquid ejection head 3 during standby for recording, for example. Furthermore, the ejection flow rate when ink is ejected from all the ejection ports of the liquid ejection unit 300 (during full ejection) is defined as flow rate F (ejection amount per ejection port × ejection frequency per unit time × number of ejection ports).

[0025] Figure 4 is a diagram illustrating the difference in the amount of ink flowing into the liquid ejection head 3 between the first circulation mode and the second circulation mode. Figure 4(a) shows the first circulation mode during standby, and Figure 4(b) shows the first circulation mode during full ejection. Figures 4(c) to 4(f) show the flow rates in the case of the second circulation flow path, with Figures 4(c) and (d) showing the case where flow rate F<flow rate A, and Figures 4(e) and (f) showing the case where flow rate F>flow rate A, and showing the flow rates during standby and full ejection, respectively.

[0026] The first circulation configuration (FIGS. 4(a) and 4(b)) will be described, in which a first circulation pump (high-pressure side) 1001 and a first circulation pump (low-pressure side) 1002, each with a constant liquid delivery capacity, are disposed downstream of the liquid ejection head 3. In this case, the total set flow rate of the first circulation pump 1001 and the first circulation pump 1002 is flow rate A (FIG. 4(a)). This flow rate A enables temperature control within the liquid ejection unit 300 during standby. When full ejection is performed by the liquid ejection head 3, the total set flow rate of the first circulation pump 1001 and the first circulation pump 1002 remains at flow rate A, but negative pressure generated by ejection from the liquid ejection head 3 acts. As a result, the maximum flow rate supplied to the liquid ejection head 3 is the total set flow rate A plus the amount consumed by full ejection (flow rate F). Therefore, the maximum amount of liquid supplied to the liquid ejection head 3 is flow rate A + flow rate F, since flow rate F is added to flow rate A (FIG. 4(b)).

[0027] On the other hand, in the case of the second circulation configuration in which the first circulation pumps 1001 and 1002 are disposed upstream of the liquid ejection head 3 (FIGS. 4(c) to 4(f)), the amount of liquid supplied to the liquid ejection head 3 during standby for printing is flow rate A, as in the first circulation configuration. Therefore, in the second circulation configuration in which the first circulation pumps 1001 and 1002 are disposed upstream of the liquid ejection head 3, when flow rate A is greater than flow rate F (FIGS. 4(c) and 4(d)), the amount of liquid supplied to the liquid ejection head 3 is sufficient even during full ejection. In this case, the discharge flow rate from the liquid ejection head 3 is flow rate A minus flow rate F (FIG. 4(d)). However, when flow rate F is greater than flow rate A (FIGS. 4(e) and 4(f)), if the supply flow rate to the liquid ejection head 3 is flow rate A, the amount of liquid supplied to the liquid ejection head 3 during full ejection will be insufficient. Therefore, when flow rate F is greater than flow rate A, the amount of liquid supplied to the liquid ejection head 3 must be flow rate F. At that time, if full ejection is performed, the flow rate F is consumed in the liquid ejection head 3, and the discharge flow rate from the liquid ejection head 3 becomes a state in which almost no liquid is discharged (FIG. 4(f)). Note that if the flow rate F is greater than the flow rate A and ejection is performed but not full ejection, the amount discharged from the liquid ejection head 3 is the flow rate F minus the amount consumed in ejection.

[0028] Thus, in the second circulation mode, the total value of the set flow rates of the first circulation pump 1001 and the first circulation pump 1002, i.e., the maximum required supply flow rate, is the larger of the flow rate A and the flow rate F. Therefore, as long as the liquid discharge unit 300 having the same configuration is used, the maximum required supply flow rate in the second circulation mode (flow rate A or flow rate F) will be smaller than the maximum required supply flow rate in the first circulation mode (flow rate A + flow rate F).

[0029] Therefore, in the case of the second circulation mode, there is a greater degree of freedom in the applicable circulation pump, and for example, it is possible to use a low-cost circulation pump with a simple configuration, and to reduce the load on a cooler (not shown) installed in the main body side path, which has the advantage of reducing the cost of the recording device. This advantage becomes greater as the value of flow rate A or flow rate F becomes relatively large in a line head, and is more beneficial for line heads with a longer longitudinal length.

[0030] However, the first circulation mode has some advantages over the second circulation mode. Specifically, in the second circulation mode, the flow rate through the liquid ejection unit 300 is at its maximum during standby for printing. Therefore, the lower the ejection volume per unit area (hereinafter referred to as a low-duty image), the higher the negative pressure applied to each ejection port. Therefore, when the flow path width is narrow and the negative pressure is high, a high negative pressure is applied to the ejection port in a low-duty image, which tends to show unevenness. This can result in the generation of many so-called satellite droplets ejected along with the main ink droplets, potentially resulting in a decrease in print quality. On the other hand, in the first circulation mode, a high negative pressure is applied to the ejection port only when an image with a high ejection volume per unit area (hereinafter referred to as a high-duty image) is being formed. Therefore, even if satellite droplets are generated, they are less visible, and their impact on the image is minimal. The selection between these two circulation modes can be made based on the specifications of the liquid ejection head and the printing apparatus itself (ejection flow rate F, minimum circulation flow rate A, and flow path resistance within the head).

[0031] <Explanation of the third circulation type> 47 is a schematic diagram showing a third circulation path, which is one form of the circulation path applied to the recording device of this application example. Explanation of the same functions and configurations as the first and second circulation paths will be omitted, and the differences will be mainly explained.

[0032] In this circulation path, liquid is supplied into the liquid ejection head 3 from a total of three locations: two locations in the center of the liquid ejection head 3 and one end side of the liquid ejection head 3. The liquid flows from the common supply path 211 through each pressure chamber 23, then is recovered into the common recovery path 212, and is recovered to the outside through a recovery opening at the other end of the liquid ejection head 3. The individual paths 213 communicate with the common supply path 211 and the common recovery path 212, and the recording element substrate 10 and the pressure chambers 23 disposed within the recording element substrate are provided along the path of each individual path 213. Therefore, a portion of the liquid flowed by the first circulation pump 1002 flows from the common supply path 211 through the pressure chambers 23 of the recording element substrate 10 and into the common recovery path 212 (arrows in FIG. 47). This is because a pressure difference is created between the pressure adjustment mechanism H connected to the common supply path 211 and the pressure adjustment mechanism L connected to the common recovery path 212, and the first circulation pump 1002 is connected only to the common recovery path 212.

[0033] In this way, in the liquid ejection unit 300, a flow of liquid that passes through the common recovery channel 212 and a flow that passes from the common supply channel 211 through the pressure chambers 23 in each recording element substrate 10 to the common recovery channel 212 are generated. Therefore, while suppressing an increase in pressure loss, heat generated in each recording element substrate 10 can be discharged to the outside of the recording element substrate 10 by flowing from the common supply channel 211 to the common recovery channel 212. Furthermore, this circulation path makes it possible to reduce the number of pumps that are liquid transport means compared to the first and second circulation paths.

[0034] <Description of Liquid Ejection Head Configuration> The configuration of a liquid ejection head 3 according to a first application example will be described. FIGS. 5A and 5B are perspective views showing the liquid ejection head 3 according to this application example. The liquid ejection head 3 is a line-type (page-wide) liquid ejection head in which 15 recording element substrates 10, each capable of ejecting four colors of ink (cyan C, magenta M, yellow Y, and black K), are arranged in a straight line (arranged inline). As shown in FIG. 5A, the liquid ejection head 3 includes a signal input terminal 91 and a power supply terminal 92 electrically connected to each recording element substrate 10 via a flexible wiring substrate 40 and an electrical wiring substrate 90. The signal input terminal 91 and the power supply terminal 92 are electrically connected to a control unit of the recording apparatus 1000 and supply an ejection drive signal and power required for ejection to the recording element substrate 10, respectively. By consolidating the wiring using an electrical circuit within the electrical wiring substrate 90, the number of signal output terminals 91 and power supply terminals 92 can be reduced compared to the number of recording element substrates 10. This reduces the number of electrical connections that need to be removed when assembling the liquid ejection head 3 to the recording apparatus 1000 or when replacing the liquid ejection head. As shown in FIG. 5(b), the liquid connections 111 provided on both ends of the liquid ejection head 3 are connected to the liquid supply system of the recording apparatus 1000 described above with reference to FIGS. 2 and 3. This allows four colors of ink, cyan C, magenta M, yellow Y, and black K, to be supplied from the supply system of the recording apparatus 1000 to the liquid ejection head 3, and the ink that has passed through the liquid ejection head 3 is collected by the supply system of the recording apparatus 1000. In this way, the inks of each color can circulate via the paths of the recording apparatus 1000 and the paths of the liquid ejection head 3.

[0035] FIG. 6 is an exploded perspective view showing each component or unit constituting the liquid ejection head 3. The liquid ejection unit 300, liquid supply unit 220, and electrical wiring board 90 are attached to a housing 80. The liquid supply unit 220 is provided with a liquid connection portion 111 (see FIG. 3), and the liquid supply unit 220 is provided with color-specific filters 221 (see FIGS. 2 and 3) that communicate with the openings of the liquid connection portion 111 to remove foreign matter from the ink being supplied. Each of the two liquid supply units 220 is provided with filters 221 for two colors. The liquid that passes through the filters 221 is supplied to negative pressure control units 230, which are disposed on the liquid supply unit 220 corresponding to each color. The negative pressure control units 230 are units comprising pressure adjustment valves for each color, and the valves and spring members provided therein significantly attenuate pressure loss changes in the supply system of the recording apparatus 1000 (the supply system upstream of the liquid ejection head 3) that occur due to fluctuations in the liquid flow rate. This enables the negative pressure control unit 230 to stabilize negative pressure changes downstream of the pressure control unit (on the liquid ejection unit 300 side) within a certain range. Two pressure adjustment valves are built into the negative pressure control unit 230 for each color, as described in Figure 2. The two pressure adjustment valves are set to different control pressures, and their high-pressure sides communicate with the common supply flow path 211 (see Figure 2) in the liquid ejection unit 300, and their low-pressure sides communicate with the common recovery flow path 212 (see Figure 2) via the liquid supply unit 220.

[0036] The housing 80 is composed of a liquid ejection unit support portion 81 and an electric wiring board support portion 82. It supports the liquid ejection unit 300 and the electric wiring board 90 while ensuring the rigidity of the liquid ejection head 3. The electric wiring board support portion 82 supports the electric wiring board 90 and is fixed to the liquid ejection unit support portion 81 with screws. The liquid ejection unit support portion 81 corrects warping and deformation of the liquid ejection unit 300 to ensure the relative positional accuracy of the multiple recording element substrates 10, thereby suppressing streaks and unevenness in printed materials. Therefore, the liquid ejection unit support portion 81 preferably has sufficient rigidity and is preferably made of a metal material such as stainless steel or aluminum, or a ceramic such as alumina. The liquid ejection unit support portion 81 has openings 83 and 84 through which the joint rubber 100 is inserted. Liquid supplied from the liquid supply unit 220 is guided via the joint rubber to the third flow path member 70 constituting the liquid ejection unit 300.

[0037] The liquid ejection unit 300 is composed of a plurality of ejection modules 200 and a flow path member 210, and a cover member 130 is attached to the recording medium side surface of the liquid ejection unit 300. Here, the cover member 130 is a member having a frame-shaped surface with a long opening 131 provided therein, as shown in FIG. 6, and the recording element substrate 10 and the sealant portion 110 (see FIG. 10 described later) included in the ejection module 200 are exposed through the opening 131. The frame portion around the opening 131 functions as an abutment surface for a capping member that caps the liquid ejection head 3 when the liquid ejection unit 300 is on standby for recording. For this reason, it is preferable to apply an adhesive, sealant, filler, or the like around the periphery of the opening 131 to fill in any irregularities or gaps on the ejection port surface of the liquid ejection unit 300, thereby forming a closed space when the liquid ejection unit 300 is capped.

[0038] Next, the configuration of the flow path member 210 included in the liquid discharge unit 300 will be described. As shown in Fig. 6, the flow path member 210 is formed by laminating a first flow path member 50, a second flow path member 60, and a third flow path member 70, and distributes the liquid supplied from the liquid supply unit 220 to each discharge module 200. The flow path member 210 is also a flow path member for returning the liquid circulating from the discharge module 200 to the liquid supply unit 220. The flow path member 210 is fixed to the liquid discharge unit support part 81 with screws, which prevents the flow path member 210 from warping or deforming.

[0039] 7(a) to 7(f) are diagrams showing the front and back surfaces of each of the first to third flow path members. Fig. 7(a) shows the surface of the first flow path member 50 on which the discharge module 200 is mounted, and Fig. 7(f) shows the surface of the third flow path member 70 that abuts against the liquid discharge unit support part 81. The first flow path member 50 and the second flow path member 60 are joined so that the abutting surfaces of the respective flow path members shown in Figs. 7(b) and 7(c) face each other, and the second flow path member and the third flow path member are joined so that the abutting surfaces of the respective flow path members shown in Figs. 7(d) and 7(e) face each other. By joining the second flow path member 60 and the third flow path member 70, eight common flow paths (211a, 211b, 211c, 211d, 212a, 212b, 212c, 212d) extending in the longitudinal direction of the flow path member are formed from the common flow path grooves 62 and 71 formed in each flow path member. As a result, a set of a common supply flow path 211 and a common recovery flow path 212 is formed for each color in the flow path member 210. Ink is supplied from the common supply flow path 211 to the liquid ejection head 3, and the ink supplied to the liquid ejection head 3 is recovered by the common recovery flow path 212. The communication ports 72 (see FIG. 7(f)) of the third flow path member 70 communicate with each hole of the joint rubber 100, and are in fluid communication with the liquid supply unit 220 (see FIG. 6). A plurality of communication ports 61 (communication port 61-1 communicating with the common supply flow path 211, and communication port 61-2 communicating with the common recovery flow path 212) are formed on the bottom surface of the common flow path groove 62 of the second flow path member 60, and these communication ports 61 are in communication with one end of the individual flow path groove 52 of the first flow path member 50. A communication port 51 is formed on the other end of the individual flow path groove 52 of the first flow path member 50, and these individual flow path grooves 52 are in fluid communication with a plurality of discharge modules 200 via the communication port 51. These individual flow path grooves 52 make it possible to aggregate the flow paths toward the center of the flow path member.

[0040] The first to third flow path members are preferably made of a material that is resistant to corrosion by liquids and has a low linear expansion coefficient. Suitable materials include alumina, LCP (liquid crystal polymer), PPS (polyphenyl sulfide), PSF (polysulfone), and modified PPE (polyphenylene ether) as a base material, and a composite material (resin material) to which inorganic fillers such as silica particles and fibers are added. The flow path member 210 may be formed by laminating three flow path members and bonding them together, or, when a resin composite resin material is selected as the material, a welding bonding method may be used.

[0041] 7(a) shows the α portion, and is a partially enlarged perspective view of the flow paths within a flow path member 210 formed by joining the first to third flow path members, viewed from the side of the first flow path member 50 on which the discharge module 200 is mounted. The common supply flow paths 211 and the common recovery flow paths 212 are alternately arranged from the flow paths at both ends. Here, the connection relationship of the respective flow paths within the flow path member 210 will be described.

[0042] The flow path member 210 is provided with common supply flow paths 211 (211a, 211b, 211c, 211d) and common recovery flow paths 212 (212a, 212b, 212c, 212d) that extend in the longitudinal direction of the liquid ejection head 3 for each color. A plurality of individual supply flow paths (213a, 213b, 213c, 213d) formed by the individual flow path grooves 52 are connected to the common supply flow path 211 for each color via communication ports 61. Furthermore, a plurality of individual recovery flow paths (214a, 214b, 214c, 214d) formed by the individual flow path grooves 52 are connected to the common recovery flow path 212 for each color via communication ports 61. With this flow path configuration, ink can be collected from each common supply flow path 211 via the individual supply flow paths 213 to the recording element substrate 10 located at the center of the flow path member. Furthermore, ink can be recovered from the recording element substrate 10 to each common recovery flow path 212 via the individual recovery flow paths 214 .

[0043] 9 is a cross-sectional view taken along line IX-IX in FIG. 8. Each of the individual recovery channels (214a, 214c) communicates with the ejection module 200 via a communication port 51. While only the individual recovery channels (214a, 214c) are shown in FIG. 9, in another cross-section, the individual supply channels 213 communicate with the ejection module 200 as shown in FIG. 8. A channel is formed in the support member 30 and the recording element substrate 10 included in each ejection module 200 to supply ink from the first channel member 50 to the recording elements 15 provided on the recording element substrate 10. Furthermore, a channel is formed in the support member 30 and the recording element substrate 10 to recover (return) a part or all of the liquid supplied to the recording elements 15 to the first channel member 50.

[0044] Here, the common supply flow path 211 for each color is connected to the negative pressure control unit 230 (high pressure side) of the corresponding color via the liquid supply unit 220, and the common recovery flow path 212 is connected to the negative pressure control unit 230 (low pressure side) via the liquid supply unit 220. This negative pressure control unit 230 generates a differential pressure (pressure difference) between the common supply flow path 211 and the common recovery flow path 212. For this reason, as shown in Figures 8 and 9, within the liquid ejection head of this application example in which the flow paths are connected, an ink flow occurs in the order of the common supply flow path 211 -> individual supply flow path 213 -> recording element substrate 10 -> individual recovery flow path 214 -> common recovery flow path 212 for each ink color.

[0045] <Explanation of the dispensing module> FIG. 10(a) is a perspective view of one ejection module 200, and FIG. 10(b) is an exploded view thereof. The manufacturing method of the ejection module 200 involves first adhering the recording element substrate 10 and the flexible wiring substrate 40 to a support member 30, which is provided with a liquid communication port 31. Then, the terminals 16 on the recording element substrate 10 are electrically connected to the terminals 41 on the flexible wiring substrate 40 by wire bonding, and then the wire-bonded portions (electrical connection portions) are covered and sealed with a sealant 110. The terminals 42 on the flexible wiring substrate 40 on the side opposite the recording element substrate 10 are electrically connected to the connection terminals 93 (see FIG. 6) on the electrical wiring substrate 90. The support member 30 is a support that supports the recording element substrate 10 and also serves as a flow path member that fluidly connects the recording element substrate 10 and the flow path member 210. Therefore, it is preferable that the support member 30 has high flatness and can be bonded to the recording element substrate with sufficiently high reliability. Examples of the material for the support member 30 include alumina and resin.

[0046] <Explanation of the structure of the recording element substrate> FIG. 11(a) shows a plan view of the surface of the recording element substrate 10 on which the ejection ports 13 are formed, FIG. 11(b) shows an enlarged view of the portion indicated by A in FIG. 11(a), and FIG. 11(c) shows a plan view of the back surface of FIG. 11(a). The configuration of the recording element substrate 10 in this application example will now be described. As shown in FIG. 11(a), four ejection port arrays corresponding to each ink color are formed in the ejection port forming member 12 of the recording element substrate 10. Hereinafter, the direction in which the ejection port arrays in which the multiple ejection ports 13 are arranged will be referred to as the "ejection port array direction." As shown in FIG. 11(b), recording elements 15, which are heat-generating elements for foaming liquid with thermal energy, are arranged at positions corresponding to the ejection ports 13. Partition walls 22 define pressure chambers 23 each containing the recording elements 15. The recording elements 15 are electrically connected to terminals 16 via electrical wiring (not shown) provided on the recording element substrate 10. The recording elements 15 generate heat based on pulse signals input from the control circuit of the recording device 1000 via the electric wiring board 90 (see FIG. 6) and the flexible wiring board 40 (see FIG. 10), causing the liquid to boil. The bubbling caused by this boiling causes the liquid to be ejected from the ejection ports 13. As shown in FIG. 11(b), a liquid supply path 18 extends on one side along each ejection port row, and a liquid recovery path 19 extends on the other side. The liquid supply path 18 and the liquid recovery path 19 are flow paths provided in the recording element substrate 10, extending in the ejection port row direction, and are connected to the ejection ports 13 via the supply ports 17a and the recovery ports 17b, respectively.

[0047] As shown in FIG. 11(c), a sheet-like cover plate 20 is laminated on the back surface of the recording element substrate 10 opposite the surface on which the ejection ports 13 are formed. The cover plate 20 has a plurality of openings 21 that communicate with the liquid supply channels 18 and the liquid recovery channels 19 (described later). In this application example, the cover plate 20 has three openings 21 for each liquid supply channel 18 and two openings 21 for each liquid recovery channel 19. As shown in FIG. 11(b), each opening 21 in the cover plate 20 communicates with the plurality of communication ports 51 shown in FIG. 7(a). The cover plate 20 preferably has sufficient corrosion resistance against liquids. Furthermore, high precision is required for the shape and position of the openings 21 to prevent color mixing. For this reason, it is preferable to use a photosensitive resin material or a silicon plate as the material for the cover plate 20, and to form the openings 21 using a photolithography process. As such, the cover plate 20 changes the flow path pitch using the openings 21. Considering pressure loss, it is desirable for the cover plate 20 to be thin and made of a film-like material.

[0048] FIG. 12 is a perspective view showing a cross section of the recording element substrate 10 and the cover plate 20 taken along line XII-XII in FIG. 11(a). Here, the flow of liquid within the recording element substrate 10 will be described. The cover plate 20 functions as a lid that forms part of the walls of the liquid supply path 18 and the liquid recovery path 19 formed in the substrate 11 of the recording element substrate 10. The recording element substrate 10 is formed by laminating the substrate 11 made of Si and the ejection port forming member 12 made of photosensitive resin, and the cover plate 20 is bonded to the back surface of the substrate 11. Recording elements 15 are formed on one surface of the substrate 11 (see FIG. 11), and grooves that form the liquid supply path 18 and the liquid recovery path 19 that extend along the ejection port array are formed on the back surface. The liquid supply path 18 and the liquid recovery path 19 formed by the substrate 11 and the cover plate 20 are connected to a common supply path 211 and a common recovery path 212 in a flow path member 210, respectively, and a pressure difference is generated between the liquid supply path 18 and the liquid recovery path 19. When liquid is being ejected from the ejection ports 13 to perform printing, this pressure difference causes the liquid in the liquid supply path 18 provided in the substrate 11 to flow to the liquid recovery path 19 via the supply port 17a, the pressure chamber 23, and the recovery port 17b at ejection ports that are not ejecting (arrow C in FIG. 12). This flow allows thickened ink, bubbles, foreign matter, and the like that are generated by evaporation from the ejection ports 13 at ejection ports 13 and pressure chambers 23 that are not ejecting to be recovered into the liquid recovery path 19. It is also possible to prevent the ink in the ejection ports 13 and pressure chambers 23 from becoming thicker or the concentration of the colorant from increasing. The liquid recovered to the liquid recovery channel 19 passes through the opening 21 in the cover plate 20 and the liquid communication port 31 (see FIG. 10b) in the support member 30, and is then recovered in the order of the communication port 51 in the flow path member 210, the individual recovery flow path 214, and the common recovery flow path 212. The liquid is then recovered from the liquid ejection head 3 to the supply path of the recording device 1000. In other words, the liquid supplied from the recording device main body to the liquid ejection head 3 flows, is supplied, and is recovered in the following order.

[0049] The liquid first flows into the liquid ejection head 3 from the liquid connection portion 111 of the liquid supply unit 220. The liquid is then supplied, in this order, through the joint rubber 100, the communication port 72 and common flow path groove 71 provided in the third flow path member, the common flow path groove 62 and communication port 61 provided in the second flow path member, and the individual flow path grooves 52 and communication port 51 provided in the first flow path member. The liquid is then supplied to the pressure chamber 23 via the liquid communication port 31 provided in the support member 30, the opening 21 provided in the cover plate 20, and the liquid supply path 18 and supply port 17a provided in the substrate 11. Of the liquid supplied to the pressure chamber 23, the liquid that is not ejected from the ejection port 13 flows, in this order, through the recovery port 17b and liquid recovery path 19 provided in the substrate 11, the opening 21 provided in the cover plate 20, and the liquid communication port 31 provided in the support member 30. The liquid then flows in this order through the communication port 51 and individual flow channel grooves 52 provided in the first flow channel member, the communication port 61 and common flow channel groove 62 provided in the second flow channel member, the common flow channel groove 71 and communication port 72 provided in the third flow channel member 70, and the joint rubber 100. The liquid then flows from the liquid connection part 111 provided in the liquid supply unit 220 to the outside of the liquid ejection head 3.

[0050] In the first circulation mode shown in FIG. 2, the liquid flowing in from the liquid connection part 111 passes through the negative pressure control unit 230 and is then supplied to the joint rubber 100. In the second circulation mode shown in FIG. 3, the liquid collected from the pressure chamber 23 passes through the joint rubber 100 and then flows from the liquid connection part 111 to the outside of the liquid ejection head via the negative pressure control unit 230. Not all of the liquid flowing in from one end of the common supply flow path 211 of the liquid ejection unit 300 is supplied to the pressure chamber 23 via the individual supply flow paths 213a. In other words, some of the liquid flowing in from one end of the common supply flow path 211 flows from the other end of the common supply flow path 211 to the liquid supply unit 220 without flowing into the individual supply flow paths 213a. By providing a flow path that does not pass through the recording element substrate 10, it is possible to prevent backflow of the circulating flow of the liquid, even when using a recording element substrate 10 that has fine flow paths with relatively high flow resistance, as in this application example. In this way, the liquid ejection head 3 of this application example can suppress thickening of the liquid in the pressure chamber 23 and in the vicinity of the ejection port, thereby suppressing distorted ejection and non-ejection, and as a result, high-quality recording can be performed.

[0051] <Explanation of the positional relationship between the recording element substrates> FIG. 13 is a partially enlarged plan view showing adjacent portions of the recording element substrates in two adjacent ejection modules 200. In this application example, a recording element substrate having a shape of a substantial parallelogram is used. Each of the ejection port arrays (14a to 14d) in which the ejection ports 13 of each recording element substrate 10 are arranged is inclined at a certain angle with respect to the conveyance direction of the recording medium. The ejection port arrays in the adjacent portions of the recording element substrates 10 are arranged so that at least one ejection port overlaps with the conveyance direction of the recording medium. In FIG. 13, two ejection ports on line D overlap with each other. With this arrangement, even if the position of the recording element substrate 10 is slightly shifted from the predetermined position, black stripes and white spots in the recorded image can be made less noticeable by controlling the drive of the overlapping ejection ports. Even when multiple recording element substrates 10 are arranged in a straight line (inline) rather than in a staggered arrangement, black stripes and white spots at the joints can be prevented. 13, it is possible to prevent black streaks and white spots at the joints between the recording element substrates 10 while suppressing an increase in the length of the liquid ejection head 3 in the recording medium transport direction. Note that in this application example, the main plane of the recording element substrate is a parallelogram, but this is not limited to this, and the configuration of the present invention can also be preferably applied when a recording element substrate having a rectangular, trapezoidal, or other shape is used.

[0052] <Description of Modified Examples of Liquid Ejection Head Configuration> A modified example of the liquid ejection head configuration described above is explained with reference to FIGS. 46, 48 to 50. Descriptions of configurations and functions similar to those of the above-described example will be omitted, and differences will be mainly explained. In this modified example, as shown in FIGS. 46 and 48, multiple liquid connection portions 111, which connect the liquid ejection head 3 to the outside, are concentrated at one end of the liquid ejection head in the longitudinal direction. Multiple negative pressure control units 230 are concentrated at the other end of the liquid ejection head 3 (FIG. 49). The liquid supply unit 220 included in the liquid ejection head 3 is configured as an elongated unit corresponding to the length of the liquid ejection head 3, and is equipped with flow paths and filters 221 corresponding to the four colors of liquid to be supplied. As shown in FIG. 49, the positions of openings 83 to 86 provided in the liquid ejection unit support portion 81 are also different from those of the liquid ejection head 3 described above.

[0053] FIG. 50 shows the stacked state of the flow path members 50, 60, and 70. A plurality of recording element substrates 10 are linearly arranged on the upper surface of the flow path member 50, which is the uppermost layer of the plurality of flow path members 50, 60, and 70. The flow paths communicating with the openings 21 (FIG. 19) formed on the back surface of each recording element substrate 10 include two individual supply flow paths 213 and one individual recovery flow path 214 for each liquid color. Correspondingly, the openings 21 formed in the cover plate 20 provided on the back surface of the recording element substrate 10 also include two supply openings 21 and one recovery opening 21 for each liquid color. As shown in FIG. 50, common supply flow paths 211 and common recovery flow paths 212 extending along the longitudinal direction of the liquid ejection head 3 are alternately arranged in parallel.

[0054] (Second application example) <Inkjet recording device> Next, the configuration of an inkjet recording apparatus 2000 and a liquid ejection head 2003 according to a second application example, which differs from the inkjet recording apparatus according to the first application example described above, will be described. In the following explanation, mainly only the parts that differ from the recording apparatus according to the first application example will be described, and explanations of the parts that are the same as those of the apparatus according to the first application example will be omitted.

[0055] FIG. 21 illustrates an inkjet recording apparatus 2000 according to a second application example. The recording apparatus 2000 of this application example differs from the first application example in that it performs full-color recording on a recording medium by arranging four single-color liquid ejection heads 2003, each corresponding to one ink (cyan C, magenta M, yellow Y, and black K), in parallel. While the first application example only allows one nozzle row per color, the present application example allows 20 nozzle rows per color. This allows for extremely high-speed recording by appropriately allocating print data to multiple nozzle rows. Furthermore, even if a nozzle row fails to eject ink, ink can be compensated for by ejecting ink from another nozzle row located in the direction of conveyance of the recording medium, improving reliability and making the apparatus suitable for commercial recording. As in the first application example, each liquid ejection head 2003 is fluidly connected to the supply system of the recording apparatus 2000, the buffer tank 1003 (see FIGS. 2 and 3), and the main tank 1006 (see FIGS. 2 and 3). Furthermore, each liquid ejection head 2003 is electrically connected to an electrical control unit that transmits power and ejection control signals to the liquid ejection head 2003 .

[0056] <Explanation of the circulation route> As in the first application example, the first to third circulation forms shown in FIGS. 2, 3, and 47 can be used as the liquid circulation path between the recording device 2000 and the liquid ejection head 2003.

[0057] <Explanation of liquid ejection head structure> 14(a) and 14(b) are perspective views showing a liquid ejection head 2003 according to this application example. The liquid ejection head 2003 is a line-type print head that includes 16 recording element substrates 2010 arranged in a straight line in the longitudinal direction of the liquid ejection head 2003 and ejects ink of one color. Like the first application example, the liquid ejection head 2003 includes a liquid connection portion 111, a signal input terminal 91, and a power supply terminal 92. However, since the liquid ejection head 2003 of this embodiment has more ejection port rows than the head of the first application example, the signal output terminals 91 and the power supply terminals 92 are arranged on both sides of the liquid ejection head 2003. This makes it possible to reduce voltage drops and signal transmission delays that occur in the wiring provided on the recording element substrate 2010.

[0058] FIG. 15 is an exploded perspective view of a liquid ejection head 2003, showing each component or unit constituting the liquid ejection head 2003, broken down by function. The role of each unit and member and the order of liquid flow within the liquid ejection head are essentially the same as in the first application example, but the function for ensuring the rigidity of the liquid ejection head differs. While the rigidity of the liquid ejection head in the first application example was primarily ensured by the liquid ejection unit support part 81, the rigidity of the liquid ejection head 2003 in the second application example is ensured by the second flow path member 2060 included in the liquid ejection unit 2300. The liquid ejection unit support part 81 in this application example is connected to both ends of the second flow path member 2060, and the liquid ejection unit 2300 is mechanically coupled to the carriage of the recording apparatus 2000 to position the liquid ejection head 2003. A liquid supply unit 2220 including a negative pressure control unit 2230 and an electrical wiring board 90 are coupled to the liquid ejection unit support part 81. Each of the two liquid supply units 2220 has a built-in filter (not shown).

[0059] The two negative pressure control units 2230 are set to control pressure at different, relatively high and low negative pressures. Furthermore, as shown in FIG. 14, when high-pressure and low-pressure negative pressure control units 2230 are installed at both ends of the liquid ejection head 2003, the liquid flows in the common supply flow path and the common recovery flow path extending in the longitudinal direction of the liquid ejection head 2003, opposing each other. This configuration promotes heat exchange between the common supply flow path and the common recovery flow path, reducing the temperature difference within the two common flow paths. This reduces the temperature difference among the multiple recording element substrates 2010 provided along the common flow path, offering the advantage of reducing the likelihood of recording irregularities due to temperature differences.

[0060] Next, the flow path member 2210 of the liquid discharge unit 2300 will be described in detail. As shown in FIG. 15, the flow path member 2210 is formed by laminating a first flow path member 2050 and a second flow path member 2060, and distributes the liquid supplied from the liquid supply unit 2220 to each discharge module 2200. The flow path member 2210 also functions as a flow path member for returning the liquid circulating from the discharge module 2200 to the liquid supply unit 2220. The second flow path member 2060 of the flow path member 2210 is a flow path member in which a common supply flow path and a common recovery flow path are formed, and also has the function of mainly providing rigidity for the liquid discharge head 2003. For this reason, the material of the second flow path member 2060 is preferably one that has sufficient corrosion resistance against liquid and high mechanical strength. Specifically, SUS, Ti, alumina, etc. can be used.

[0061] FIG. 16(a) shows the surface of the first flow path member 2050 on which the ejection module 2200 is mounted, and FIG. 16(b) shows the back surface, which is a surface that abuts against the second flow path member 2060. Unlike the first application example, the first flow path member 2050 in this embodiment is formed by arranging multiple components corresponding to each ejection module 2200 adjacent to one another. This divided structure allows multiple modules to be arranged to accommodate the length of the liquid ejection head 2003, making this structure particularly suitable for relatively long-scale liquid ejection heads, such as those corresponding to B2 size or larger. As shown in FIG. 16(a), the communication port 51 of the first flow path member 2050 is fluidly connected to the ejection module 2200. As shown in FIG. 16(b), the individual communication port 53 of the first flow path member 2050 is fluidly connected to the communication port 61 of the second flow path member 2060. FIG. 16(c) shows the surface of the second flow path member 60 that contacts the first flow path member 2050, FIG. 16(d) shows a cross section of the second flow path member 60 at the center in the thickness direction, and FIG. 16(e) shows the surface of the second flow path member 2060 that contacts the liquid supply unit 2220. The functions of the flow paths and communication ports of the second flow path member 2060 are the same as those of one color in the first application example. The common flow path grooves 71 of the second flow path member 2060 are a common supply flow path 2211 and a common recovery flow path 2212, respectively, which are provided along the longitudinal direction of the liquid ejection head 2003 and supply liquid from one end to the other end, as shown in FIG. 17 (described later). In this embodiment, unlike the first application example, the liquid flows in the common supply flow path 2211 and the common recovery flow path 2212 in opposite directions.

[0062] 17 is a perspective view showing the liquid connection relationship between the recording element substrate 2010 and the flow path member 2210. A set of a common supply flow path 2211 and a common recovery flow path 2212 extending in the longitudinal direction of the liquid ejection head 2003 is provided within the flow path member 2210. The communication ports 61 of the second flow path member 2060 are aligned and connected to the individual communication ports 53 of each of the first flow path members 50. In addition, a liquid supply path is formed that communicates from the communication port 72 of the second flow path member 2060 to the communication port 51 of the first flow path member 2050 via the common supply flow path 2211. Similarly, a liquid supply path is also formed that communicates from the communication port 72 of the second flow path member 2060 to the communication port 51 of the first flow path member 2050 via the common recovery flow path 2212.

[0063] FIG. 18 is a cross-sectional view taken along line XVIII-XVIII in FIG. 17. The common supply channel 2211 is connected to the discharge module 2200 via the communication port 61, the individual communication port 53, and the communication port 51. Although not shown in FIG. 18, it is clear from FIG. 17 that the common recovery channel 2212 is connected to the discharge module 2200 via a similar route in another cross-section. As in the first application example, each discharge module 2200 and the recording element substrate 2010 has a channel communicating with each discharge port, allowing some or all of the supplied liquid to circulate through discharge ports that are not discharging. Also, as in the first application example, the common supply channel 2211 is connected to the negative pressure control unit 2230 (high-pressure side), and the common recovery channel 2212 is connected to the negative pressure control unit 2230 (low-pressure side), both via the liquid supply unit 2220. Therefore, due to the pressure difference, a flow is generated that flows from the common supply flow path 2211 to the common recovery flow path 2212 through the ejection ports of the recording element substrate 2010 .

[0064] <Explanation of the dispensing module> FIG. 19(a) is a perspective view showing one discharge module 2200, and FIG. 19(b) is an exploded view thereof. The difference from the first application example is that a plurality of terminals 16 are arranged on both sides (each long side of the recording element substrate 2010) of the recording element substrate 2010 along the direction of the plurality of discharge port arrays. Accordingly, two flexible wiring substrates 40 electrically connected to the recording element substrate 2010 are also arranged for one recording element substrate 2010. This is because the recording element substrate 2010 has 20 discharge port arrays, which is significantly more than the eight arrays in the first application example, and is intended to shorten the maximum distance from the terminals 16 to the recording elements and reduce voltage drops and signal delays that occur in the wiring section within the recording element substrate 2010. Furthermore, the liquid communication port 31 of the support member 2030 is arranged in the recording element substrate 2010 and opens so as to straddle all of the discharge port arrays. Other points are the same as those of the first application example.

[0065] <Explanation of the structure of the recording element substrate> FIG. 20(a) is a schematic diagram of the surface of the recording element substrate 2010 on which the ejection ports 13 are arranged, and FIG. 20(c) is a schematic diagram showing the backside of the surface of FIG. 20(a). FIG. 20(b) is a schematic diagram showing the surface of the recording element substrate 2010 when a cover plate 2020 provided on the backside of the recording element substrate 2010 in FIG. 20(c) is removed. As shown in FIG. 20(b), liquid supply paths 18 and liquid recovery paths 19 are alternately provided along the ejection port array direction on the backside of the recording element substrate 2010. Although the number of ejection port arrays is significantly greater than in the first application example, the essential difference from the first application example is that the terminals 16 are arranged on both sides of the recording element substrate along the ejection port array direction, as described above. The basic configuration is the same as in the first application example, in that a set of liquid supply path 18 and liquid recovery path 19 is provided for each row of ejection ports, and that openings 21 are provided in the cover plate 2020 that communicate with the liquid communication ports 31 of the support member 2030.

[0066] (Third application example) <Inkjet recording device> The configuration of an inkjet recording apparatus 1000 and a liquid ejection head 3 according to a third application example of the present invention will be described. The liquid ejection head of the third application example is a page-wide type that performs printing on a B2-sized recording medium in one scan. Since the third application example has many similarities with the second application example, the following explanation will mainly focus on the differences from the second application example, and will omit explanations of the similarities between the second application example and the third application example.

[0067] FIG. 51 shows a schematic diagram of an inkjet recording device according to this application example. The recording device 1000 does not directly record on a recording medium from the liquid ejection heads 3. Instead, it first ejects liquid onto an intermediate transfer body (intermediate transfer drum 1007) to form an image, and then transfers the image to the recording medium 2. In the recording device 1000, four single-color liquid ejection heads 3, each corresponding to one of four inks (CMYK), are arranged in an arc along the intermediate transfer drum 1007. This allows full-color recording on the intermediate transfer body. The recorded image is then dried appropriately on the intermediate transfer body and transferred by a transfer unit 1008 to the recording medium 2, which is being transported by a paper transport roller 1009. While the paper transport system in the second application example was primarily designed for horizontal transport for cut paper, this application example can also accommodate continuous paper fed from a main roll (not shown). This drum transport system facilitates transporting paper while applying a constant tension, reducing transport jams even during high-speed recording. This improves the reliability of the device, making it suitable for commercial printing. As in the first and second application examples, the supply system, buffer tank 1003, and main tank 1006 of the recording apparatus 1000 are fluidly connected to each liquid ejection head 3. In addition, each liquid ejection head 3 is electrically connected to an electric control unit that transmits power and ejection control signals to the liquid ejection head 3.

[0068] <Explanation of the fourth circulation form> Although the first to third circulation paths shown in FIGS. 2, 3, and 47 can also be applied as the liquid circulation path in this application example, the circulation path shown in FIG. 52 is more preferably applied. It is similar to the second circulation path in FIG. 3, but the main difference is that a bypass valve 1010 is added that communicates with the flow paths of the first circulation pumps 1001 and 1002 and the second circulation pump 1004. This bypass valve 1010 has a function (first function) of lowering the pressure upstream of the bypass valve 1010 by opening when the pressure exceeds a preset value. It also has a function (second function) of opening and closing the valve at any timing in response to a signal from the control board of the recording apparatus main body.

[0069] The first function can prevent excessive or insufficient pressure from being applied to the flow path downstream of the first circulation pumps 1001, 1002 or upstream of the second circulation pump 1004. For example, if a malfunction occurs in the first circulation pumps 1001, 1002, excessive flow rate or pressure may be applied to the liquid ejection head 3. This may cause liquid to leak from the ejection ports of the liquid ejection head 3 or cause ruptures at the joints within the liquid ejection head 3. However, as in this application example, if bypass valves are added to the first circulation pumps 1001, 1002, even if excessive pressure is generated, the bypass valve 1010 opens to open the liquid path to the upstream side of each circulation pump, thereby preventing the above-mentioned problems.

[0070] Furthermore, due to the second function, when the circulation drive is stopped, after the first circulation pumps 1001 and 1002 and the second circulation pump 1004 have stopped, all bypass valves 1010 are quickly opened based on a control signal from the main body. This allows the high negative pressure (e.g., several to several tens of kPa) downstream of the liquid ejection head 3 (between the negative pressure control unit 230 and the second circulation pump 1004) to be released in a short time. When a positive displacement pump such as a diaphragm pump is used as the circulation pump, a check valve is usually built into the pump. However, by opening the bypass valve, the pressure downstream of the liquid ejection head 3 can be released from the downstream buffer tank 1003 side as well. Although the pressure downstream of the liquid ejection head 3 can be released only from the upstream side, there is a pressure loss between the upstream flow path of the liquid ejection head and the flow path within the liquid ejection head. Therefore, it takes time to release the pressure, and the pressure in the common flow path within the liquid ejection head 3 drops too much temporarily, which may destroy the meniscus at the ejection port. By opening the bypass valve 1010 downstream of the liquid ejection head 3, pressure release downstream of the liquid ejection head is promoted, thereby reducing the risk of meniscus destruction at the ejection port.

[0071] (Explanation of liquid ejection head structure) The structure of a liquid ejection head 3 according to a third application example of the present invention will now be described. Fig. 53(a) is a perspective view of the liquid ejection head 3 according to this application example, and Fig. 53(b) is an exploded perspective view thereof. The liquid ejection head 3 is an inkjet page-wide type recording head that has 36 recording element substrates 10 arranged in a straight line (inline) in the longitudinal direction of the liquid ejection head 3 and performs recording using one color liquid. As with the second application example, the liquid ejection head 3 has a signal input terminal 91 and a power supply terminal 92, and is also provided with a shield plate 132 that protects the longitudinal side surfaces of the head.

[0072] FIG. 53(b) is an exploded perspective view of the liquid ejection head 3, showing each component or unit constituting the liquid ejection head 3 separated by its function (the shield plate 132 is not shown). The role of each unit and member and the order of liquid flow within the liquid ejection head 3 are the same as those in the second application example. The main differences from the second application example are the position of the multiple divided electrical wiring boards 90, the negative pressure control unit 230, and the shape of the first flow path member. In the case of a liquid ejection head 3 having a length corresponding to a B2-size recording medium, for example, as in this application example, eight electrical wiring boards 90 are provided due to the large amount of power consumed by the liquid ejection head 3. Four electrical wiring boards 90 are attached to each side of a long electrical wiring board support portion 82 attached to a liquid ejection unit support portion 81.

[0073] Fig. 54(a) is a side view of a liquid ejection head 3 equipped with a liquid ejection unit 300, a liquid supply unit 220, and a negative pressure control unit 230, Fig. 54(b) is a schematic diagram showing the flow of liquid, and Fig. 54(c) is a perspective view showing a cross section taken along line GG in Fig. 54(a). To facilitate understanding, some components have been simplified.

[0074] The liquid supply unit 220 is provided with a liquid connection part 111 and a filter 221, and a negative pressure control unit 230 is integrally formed below the liquid supply unit 220. This reduces the height distance between the negative pressure control unit 230 and the recording element substrate 10 compared to the second application example. This configuration reduces the number of flow path connections within the liquid supply unit 220, which not only improves reliability against leakage of the recording liquid, but also has the advantage of reducing the number of parts and assembly steps.

[0075] Furthermore, since the head difference between the negative pressure control unit 230 and the surface on which the ejection ports are formed is relatively small, this configuration can be suitably adapted to a recording device in which the tilt angle of the liquid ejection heads 3 differs for each liquid ejection head, as shown in Figure 51. Because the head difference can be reduced, even when multiple liquid ejection heads 3 are used with different tilt angles, the negative pressure difference applied to the ejection ports of each recording element substrate can be reduced. Furthermore, since the distance between the negative pressure control unit 230 and the recording element substrate 10 is reduced, the flow resistance therebetween is reduced, and the pressure loss difference due to changes in the liquid flow rate is also reduced, which is preferable in that more stable negative pressure control can be performed.

[0076] FIG. 54(b) is a schematic diagram showing the flow of recording liquid inside the liquid ejection head 3. While the circuit is the same as the circulation path shown in FIG. 52, FIG. 54(b) shows the actual flow of liquid inside each component of the liquid ejection head 3. A pair of common supply flow path 211 and common recovery flow path 212 extending in the longitudinal direction of the liquid ejection head 3 is provided inside the elongated second flow path member 60. The common supply flow path 211 and the common recovery flow path 212 are configured so that liquid flows in opposite directions, and filters 221 are provided upstream of each flow path to trap foreign matter that enters through the connection portion 111, etc. This opposite flow of liquid in the common supply flow path 211 and the common recovery flow path 212 is preferable in that it reduces the temperature gradient in the longitudinal direction inside the liquid ejection head 3. Note that, in FIG. 52, for simplicity of explanation, the flow in the common supply flow path 211 and the common recovery flow path 212 is shown in the same direction.

[0077] Negative pressure control units 230 are connected to the downstream sides of the common supply flow path 211 and the common recovery flow path 212. The common supply flow path 211 has a branching portion into multiple individual supply flow paths 213a, and the common recovery flow path 212 has a branching portion into multiple individual recovery flow paths 213b. The individual supply flow paths 213a and the individual recovery flow paths 213b are formed in multiple first flow path members 50, and each individual flow path communicates with an opening 21 (see FIG. 19(c)) in a cover plate 20 provided on the back surface of the recording element substrate 10.

[0078] The negative pressure control units 230, indicated by H and L in FIG. 54(b), are units with a high-pressure side (H) and a low-pressure side (L). Each negative pressure control unit 230 is a back-pressure type pressure adjustment mechanism set to control the pressure upstream of the negative pressure control unit 230 at a relatively high (H) or low (L) negative pressure. The common supply flow path 211 is connected to the negative pressure control unit 230 (high-pressure side), and the common recovery flow path 212 is connected to the negative pressure control unit 230 (low-pressure side), which generates a pressure difference between the common supply flow path 211 and the common recovery flow path 212. This pressure difference causes liquid to flow from the common supply flow path 211 through the individual supply flow paths 213a, the ejection ports 13 (pressure chambers 23) in the recording element substrate 10, and the individual recovery flow paths 213b, in that order, to the common recovery flow path 212.

[0079] Figure 54(c) is a perspective view showing a cross section taken along line GG in Figure 54(a). In this application example, each ejection module 200 is composed of a first flow path member 50, a recording element substrate 10, and a flexible wiring substrate 40. In this embodiment, the support member 30 (Figure 18) described in the second application example is not present, and the recording element substrate 10 equipped with a cover plate 20 is directly joined to the first flow path member 50. The common supply flow path 211 provided in the second flow path member is supplied to the individual supply flow paths 213a from a communication port 61 formed in the upper surface thereof via an individual communication port 53 formed in the lower surface of the first flow path member 50. The liquid then passes through the pressure chamber 23, passes through the individual recovery flow path 213b, the individual communication port 53, and the communication port 61 in that order, and is recovered into the common recovery flow path 212.

[0080] 15, the individual communication ports 53 on the lower surface (the surface on the second flow path member 60 side) of the first flow path member 50 are openings that are sufficiently large relative to the communication ports 61 formed on the upper surface of the second flow path member 50. With this configuration, even if the position of the ejection module 200 is misaligned when mounting it on the second flow path member 60, fluid communication is reliably achieved between the first flow path member and the second flow path member, thereby improving the yield during head manufacturing and reducing costs.

[0081] Although the first to third application examples to which the present invention can be applied have been described above, the descriptions of the above application examples do not limit the scope of the present invention. As an example, in these application examples, a thermal method in which bubbles are generated by heating a heat generating element to eject liquid has been described, but the present invention can also be applied to liquid ejection heads that employ a piezo method or various other liquid ejection methods.

[0082] Although this application example has been described as an inkjet recording apparatus (recording apparatus) in a form in which liquid such as ink is circulated between a tank and a liquid ejection head, other forms may also be used. As another form, for example, instead of circulating the ink, two tanks may be provided on the upstream side and downstream side of the liquid ejection head, and the ink may flow from one tank to the other tank to cause the ink to flow within the pressure chamber.

[0083] Furthermore, while this application example has been described using a so-called page-wide type head having a length corresponding to the width of the recording medium, the present invention can also be applied to a so-called serial type liquid ejection head that prints while scanning the recording medium. A serial type liquid ejection head may have, for example, one recording element substrate that ejects black ink and one recording element substrate that ejects color ink, but this is not limited to this. In other words, a short liquid ejection head shorter than the width of the recording medium may be created, in which multiple recording element substrates are arranged so that the ejection openings overlap in the ejection opening array direction, and the liquid ejection head is then scanned across the recording medium.

[0084] Next, each embodiment will be described, which more specifically describes the features of the present invention.

[0085] (First embodiment) Figures 22(a) to 22(c) are diagrams illustrating the structure of an ejection port and an ink flow path in the vicinity thereof in a liquid ejection head according to a first embodiment of the present invention. Figure 22(a) is a plan view of the ink flow path and the like, seen from the side from which ink is ejected, Figure 22(b) is a cross-sectional view taken along line A-A' in Figure 22(a), and Figure 22(c) is a perspective view of the cross-section taken along line A-A' in Figure 22(a).

[0086] As shown in these figures, due to the ink circulation described above in FIG. 12 and the like, an ink flow 17 occurs in the pressure chamber 23 provided with the recording element 15 on the substrate 11 of the liquid ejection head and the flow paths 24 before and after it. That is, due to the differential pressure that causes ink circulation, the ink supplied from the liquid supply path (supply flow path) 18 through the supply port 17 provided in the substrate 11 passes through the flow path 24, the pressure chamber 23, and the flow path 24, and a flow that reaches the liquid recovery path (outflow flow path) 19 through the recovery port 17b occurs.

[0087] Along with the above-described ink flow, when not ejecting, the space from the recording element (energy generating element) 15 to the ejection port 13 above it is filled with ink, and an ink meniscus (ink interface 13a) is formed near the end on the ejection direction side of the ejection port 13. In FIG. 22(b), this ink interface is represented by a straight line (plane), but its shape is determined according to the member forming the wall of the ejection port 13 and the surface tension of the ink, and usually becomes a concave or convex curved line (curved surface). It is represented by a straight line to simplify the illustration. In the state where this meniscus is formed, by driving the electrothermal conversion element (heater), which is the energy generating element 15, the heat generated is used to generate bubbles in the ink and eject the ink from the ejection port 13. In addition, although an example in which a heater is applied as the energy generating element in this embodiment is described, the present invention is not limited to this, and for example, various energy generating elements such as piezoelectric elements can be applied. In this embodiment, the speed of the ink flow flowing through the flow path 24 is, for example, about 0.1 to 100 mm / s, and even when the ejection operation is performed with the ink flowing, the influence on the landing accuracy and the like can be made relatively small.

[0088] <Regarding the relationship between P, W, and H> In the liquid ejection head of this embodiment, the relationship between the height H of its flow path 24, the thickness P of the orifice plate (flow path forming member 12), and the length (diameter) W of the ejection port is determined as described below.

[0089] In FIG. 22(b), H denotes the height of the upstream side of the flow path 24 at the lower end (the portion connecting the ejection port portion and the flow path) of the portion of the orifice plate with thickness P of the ejection port 13 (hereinafter referred to as ejection port portion 13B). P denotes the length of the ejection port portion 13b. W denotes the length of the ejection port portion 13b in the direction of liquid flow in the flow path 24. In the liquid ejection head of this embodiment, H is 3 to 30 μm, P is 3 to 30 μm, and W is 6 to 30 μm. The ink has a non-volatile solvent concentration of 30%, a colorant concentration of 3%, and a viscosity adjusted to 0.002 to 0.01 Pa s.

[0090] In this embodiment, the following is done to suppress the increase in viscosity of ink due to evaporation of ink from the ejection port 13. Figure 43 is a diagram showing the state of the ink flow 17 in the ejection port 13, ejection port portion 13b, and flow path 24 when the ink flow 17 (see Figure 22) of ink flowing in the flow path 24 and pressure chamber 23 of the liquid ejection head reaches a steady state. Note that in this figure, the length of the arrow does not indicate the magnitude of the ink flow velocity. Figure 43 shows a liquid ejection head in which the height H of the flow path 24 is 14 μm, the length P of the ejection port portion 13b is 10 μm, and the length (diameter) W of the ejection port is 17 μm, and a flow of 1.26 × 10 -4 The figure shows the flow when ink flows in at a flow rate of ml / min.

[0091] In this embodiment, the height H of the flow path 24, the length P of the ejection port portion 13b, and the length W of the ejection port portion 13b in the ink flow direction have a relationship that satisfies the following formula (1). H -0.34 ×P -0.66 ×W>1.5 Formula (1)

[0092] By satisfying this condition, the liquid ejection head of this embodiment allows the ink flow 17 flowing through the flow path 24 to flow into the ejection port 13b, reach a position at least halfway through the orifice plate thickness of the ejection port 13b, and then return to the flow path 24, as shown in FIG. 43 . The ink that has returned to the flow path 24 flows through the liquid recovery path 19 to the common recovery flow path 212. That is, at least a portion of the ink flow 17 reaches a position at least halfway through the ejection port 13b in the direction from the pressure chamber 23 toward the ink interface 13a, and then returns to the flow path 24. This flow can suppress ink viscosity increase in many areas within the ejection port 13b. By generating such an ink flow within the liquid ejection head, not only the ink in the flow path 24 but also the ink in the ejection port 13b can flow out to the flow path 24. As a result, ink viscosity increase and an increase in ink colorant concentration can be suppressed in the ejection port 13 and the ejection port 13b. Ink droplets ejected from the ejection ports are a mixture of ink in the ejection port portion 13b and ink in the pressure chamber 23 (flow path 24). In this embodiment, it is preferable that the proportion of ink in the pressure chamber 23 (flow path 24) is higher among the ejected droplets. For example, it is preferable that air bubbles generated during ejection communicate with the atmosphere. In particular, a liquid ejection head with H of 20 μm or less, P of 20 μm or less, and W of 30 μm or less is preferable, as it enables higher-resolution recording. As described above, this embodiment can suppress fluctuations in the quality of the liquid near the ejection ports, and can, for example, suppress thickening of the ink due to evaporation of the liquid from the ejection ports and reduce color unevenness in images.

[0093] (Second embodiment) Figure 23 is a diagram showing the flow of ink inside a liquid ejection head according to a second embodiment of the present invention, and parts that are the same as those in the first embodiment described above are given the same symbols and will not be described again.

[0094] This embodiment is configured as follows to further reduce the effects of ink viscosity increase due to evaporation of liquid from the ejection orifice. Fig. 23 is a diagram similar to Fig. 43, showing the state of the ink flow 17 in the ejection orifice 13, ejection orifice portion 13b, and flow path 24 when the ink flow 17 of ink flowing inside the liquid ejection head reaches a steady state. Note that in this figure, the length of the arrow does not correspond to the magnitude of the velocity, and is represented as a constant length regardless of the magnitude of the velocity. Fig. 23 shows a liquid ejection head having H of 14 μm, P of 5 μm, and W of 12.4 μm, in which a flow rate of 1.26×10 -4 The flow rate of ink when it flows into the flow path 24 is shown in ml / min.

[0095] In this embodiment, the height H of the flow path 24, the length P of the ejection opening 13b, and the length W of the ejection opening 13b in the ink flow direction satisfy the relationship shown in Equation (2), which will be described later. This further reduces the retention of ink whose colorant concentration has changed or whose viscosity has increased due to evaporation of ink from the ejection openings near the ink interface 13a of the ejection opening 13b compared to the first embodiment. That is, in the liquid ejection head of this embodiment, as shown in FIG. 23 , the ink flow 17 flowing through the flow path 24 flows into the ejection opening 13b, reaches the vicinity of the ink interface 13a (meniscus position), and then passes through the ejection opening 13b again and returns to the flow path 24. The ink that has returned to the flow path 24 flows through the liquid recovery path 19 to the common recovery path 212. This ink flow allows the ink not only within the ejection opening 13b, which is susceptible to evaporation, but also near the ink interface 13a, where the effect of evaporation is particularly pronounced, to flow into the flow path 24 without stagnating within the ejection opening 13b. As a result, ink can flow out without stagnating in areas near the ejection orifice, which are particularly susceptible to evaporation of ink moisture, etc., and it is possible to suppress increases in ink viscosity and ink colorant concentration. Since this embodiment can suppress an increase in viscosity at least in part of the ink interface 13a, it is possible to further reduce the impact on ejection, such as changes in ejection speed, compared to when the viscosity increases over the entire ink interface 13a.

[0096] The ink flow 17 described above in this embodiment has a velocity component (hereinafter referred to as a positive velocity component) in the ink flow direction (from left to right in FIG. 23) in at least the central portion (the center of the ejection port) near the ink interface 13a. In this specification, a flow mode in which the ink flow 17 has a positive velocity component at least in the central portion near the ink interface 13a is referred to as "flow mode A." Furthermore, a flow mode in which the ink flow 17 has a negative velocity component in the opposite direction to the positive velocity component at the central portion of the ink interface 13a, as in the comparative example described below, is referred to as "flow mode B."

[0097] 24(a) and (b) show the state of the colorant concentration of the ink inside the ejection port portion 13b, with FIG. 24(a) showing the state of this embodiment and FIG. 24(b) showing the state of a comparative example. That is, FIG. 24(a) shows the case of flow mode A, and FIG. 24(b) shows the case of flow mode B according to the comparative example, in which the flow near the center of the ink interface 13a inside the ejection port portion 13b has a negative velocity component. The contour lines shown in FIG. 24(a) and (b) indicate the distribution of the colorant concentration of the ink inside the ejection port portion 13b.

[0098] These flow modes A and B are determined by the values ​​of P, W, and H, which indicate the structure of the flow path, etc. Figure 24(a) shows a case where 1.26 × 10 -4 24(b) shows the state of flow mode A when ink flows in at ml / min. On the other hand, FIG. 24(b) shows the state of flow mode A when ink flows in at ml / min from the liquid supply path 18 to the flow path 24 of the liquid ejection head having a shape of H 14 μm, P 11 μm, and W 12.4 μm. -424(b) shows the state of flow mode B when ink flows in at ml / min. In flow mode B shown in FIG. 24(b), the colorant concentration of the ink inside the ejection port portion 13b is higher than in flow mode A shown in FIG. 24(a). That is, in flow mode A shown in FIG. 24(a), the ink inside the ejection port portion 13b can be replaced (flowed out) to the flow path 24 by the ink flow 17 that reaches the vicinity of the ink interface 13a with a positive velocity component. This makes it possible to prevent ink from accumulating inside the ejection port portion 13b, and as a result, it is possible to prevent an increase in the colorant concentration and viscosity.

[0099] FIG. 25 is a diagram illustrating a comparison of the colorant densities of ink ejected from a liquid ejection head (head A) that generates flow mode A and a liquid ejection head (head B) that generates flow mode B. The figure shows data for head A and head B, respectively, when ink is ejected with an ink flow 17 generated in the flow path 24, and when ink is ejected without generating an ink flow 17 and without an ink flow in the flow path. In the figure, the horizontal axis represents the elapsed time after ink is ejected from the ejection port, and the vertical axis represents the colorant density ratio of dots formed on the recording medium by the ejected ink. This density ratio is the ratio of the density of dots formed by ink ejected after each elapsed time, assuming that the density of dots formed by ink ejected at a ejection frequency of 100 Hz is 1.

[0100] As shown in Figure 25, when no ink flow 17 is generated, the concentration ratio reaches 1.3 or higher for both heads A and B after an elapsed time of 1 second or more, indicating a relatively high ink colorant concentration. Furthermore, when ink flow 17 is generated using head B, the concentration ratio reaches approximately 1.3, suppressing the increase in colorant concentration compared to when no ink flow is generated. However, ink with a high colorant concentration (a concentration ratio of up to 1.3) remains at the ejection port. In contrast, when ink flow is generated using head A, the colorant concentration ratio ranges to 1.1 or less. Studies have shown that colorant concentration changes of approximately 1.2 or less are difficult for humans to visually perceive. In other words, head A is preferable to head B because it can suppress changes in colorant concentration that would cause visible color unevenness even after an elapsed time of approximately 1.5 seconds. Note that while Figure 25 illustrates a case in which the colorant concentration increases due to evaporation, the liquid ejection head of this embodiment can also suppress changes in colorant concentration when the colorant concentration decreases due to evaporation.

[0101] Through investigations by the present inventors and others, it has been found that in the liquid ejection head that generates flow mode A in this embodiment, the relationship between the height H of the flow path 24, the thickness P of the orifice plate (flow path forming member 12), and the length (diameter) W of the ejection port satisfies the following formula (2). H -0.34 ×P -0.66 ×W>1.7 Formula (2)

[0102] Hereinafter, the value on the left side of the above formula (2) will be referred to as the judgment value J. Studies by the present inventors have revealed that a liquid ejection head that satisfies formula (2) will exhibit flow mode A as shown in Fig. 23, while a liquid ejection head that generates flow mode B will not satisfy formula (2).

[0103] The formula (2) will be explained below.

[0104] Fig. 26 is a diagram showing the relationship between the liquid ejection head that generates flow mode A of the second embodiment and the liquid ejection head that generates flow mode B of the comparative example. The horizontal axis of Fig. 26 represents the ratio of P to H (P / H), and the vertical axis represents the ratio of W to P (W / P). Threshold line 20 is a line that satisfies the following formula (3). (W / P)=1.7×(P / H) -0.34 Formula (3)

[0105] 26, the relationship between H, P, and W results in flow mode A for liquid ejection heads in the shaded region above threshold line 20, and flow mode B for liquid ejection heads in the region below and including threshold line 20. In other words, flow mode A occurs for liquid ejection heads that satisfy the following formula (4). (W / P)>1.7×(P / H) -0.34 Formula (4)

[0106] Equation (4) can be rearranged to obtain equation (2), so heads in which the relationship between H, P, and W satisfies equation (2) (heads with a judgment value J of 1.7 or more) are in flow mode A.

[0107] The above relationship will be further explained with reference to Figures 27 and 28. Figures 27(a) to 27(d) are diagrams illustrating the state of ink flow 17 near the ejection port portion 13b in liquid ejection heads in the regions above and below the threshold line 20 shown in Figure 26. Figure 28 is a diagram illustrating whether the flow will be in flow mode A or flow mode B for liquid ejection heads of various shapes. In Figure 28, black circles indicate liquid ejection heads in flow mode A, and crosses indicate liquid ejection heads in flow mode B.

[0108] Figure 27(a) shows the ink flow in a liquid ejection head with a shape of H 3 μm, P 9 μm, and W 12 μm, where the judgment value J is 1.93, which is greater than 1.7. In other words, the example shown in Figure 27(a) is flow mode A. This head corresponds to point A in Figure 28.

[0109] Figure 27(b) shows the ink flow in a liquid ejection head with a shape of H 8 μm, P 9 μm, and W 12 μm, where the judgment value is 1.39, which is smaller than 1.7. In other words, this flow is flow mode B. This head corresponds to point B in Figure 28.

[0110] Figure 27(c) shows the ink flow in a liquid ejection head with a shape of H 6 μm, P 6 μm, and W 12 μm, where the judgment value is 2.0, which is greater than 1.7. In other words, this flow is flow mode A. This head corresponds to point C in Figure 28.

[0111] Finally, Figure 27(d) shows the ink flow in a liquid ejection head with a shape of H 6 μm, P 6 μm, and W 6 μm, where the judgment value is 1.0, which is smaller than 1.7. In other words, this flow is flow mode B. This head corresponds to point D in Figure 28.

[0112] As described above, the threshold line 20 in Figure 26 serves as a boundary to distinguish between liquid ejection heads that operate in flow mode A and liquid ejection heads that operate in flow mode B. In other words, liquid ejection heads for which the judgment value J in equation (2) is greater than 1.7 operate in flow mode A, and the ink flow 17 has a positive velocity component at least at the center of the ink interface 13a.

[0113] Next, a comparison of the ejection speeds of ink droplets ejected from a liquid ejection head that generates flow mode A (head A) and a liquid ejection head that generates flow mode B (head B) will be described.

[0114] 29(a) and 29(b) are graphs showing the relationship between the number of ejections (number of ejections) and the ejection speed at that time after a certain period of rest following ejection from the liquid ejection head in each flow mode.

[0115] Figure 29(a) shows the relationship between the number of shots and the ejection speed when using head B to eject a pigment ink containing 20% ​​or more by weight of solids, which has an ink viscosity of approximately 4 cP at the temperature during ejection. As shown in the figure, even with the presence of ink flow 17, the ejection speed decreases until about the 20th shot depending on the pause time. Figure 29(b) shows the relationship between the number of shots and the ejection speed when using head A to eject the same pigment ink as in Figure 29(a), and there is no decrease in the ejection speed from the first shot after the pause. In this experiment, ink containing 20% ​​or more by weight of solids was used, but the concentration is not a limitation of the present invention. Depending on the ease of dispersion of solids in the ink, the effect of mode A is clearly apparent when ejecting ink with a solid content of 8% or more by weight (8 wt%).

[0116] In this way, a head that generates flow mode A can suppress a decrease in the ink droplet ejection speed even when the ink tends to have a lower ejection speed due to increased viscosity caused by evaporation of the ink from the ejection ports.

[0117] As described above, the relationship between P, W, and H, which are related to the shape of the flow path, has a dominant influence on whether the ink flow 17 in the ejection orifice will be in flow mode A or B under normal circumstances. Other factors, such as the flow velocity of the ink flow 17, the ink viscosity, and the width of the ejection orifice 13 perpendicular to the direction of the ink flow 17 (the length of the ejection orifice perpendicular to W), have a much smaller effect than P, W, and H. Therefore, the ink flow velocity and ink viscosity can be appropriately set according to the required specifications of the liquid ejection head (inkjet recording device) and the environmental conditions under which it will be used. For example, the flow velocity of the ink flow 17 in the flow path 24 can be set to 0.1 to 100 mm / s, and the ink viscosity can be set to 30 cP or less at the temperature during ejection. Furthermore, if the amount of ink evaporation from the ejection orifice increases significantly due to environmental changes during use, the flow rate of the ink flow 17 can be increased appropriately to achieve flow mode A. Even if the flow rate is increased significantly for a liquid ejection head with flow mode B, flow mode A will not occur. In other words, whether the mode is Mode A or Flow Mode B is determined not by the ink flow speed or ink viscosity, but by the relationship between H, P, and W related to the shape of the liquid ejection head described above. Furthermore, among the various liquid ejection heads that result in Flow Mode A, liquid ejection heads with H of 20 μm or less, P of 20 μm or less, and W of 30 μm or less are particularly preferred, as they enable higher-resolution recording.

[0118] As described above, a liquid ejection head generating flow mode A can cause ink in the ejection opening 13b, particularly ink near the ink interface, to flow to the flow path 24 by the ink flow 17, which reaches the vicinity of the ink interface 13a with a positive velocity component. This prevents ink from stagnating inside the ejection opening 13b. This also reduces increases in the colorant concentration of ink in the ejection opening, even when ink evaporates from the ejection opening. Furthermore, in this embodiment, as described above, ink is ejected while ink is flowing through the flow path 24. Therefore, ink is ejected while there is a flow of ink that enters the ejection opening 13b from the flow path 24 (pressure chamber 23), reaches the ink interface, and then returns to the ink flow path. As a result, even when the recording operation is paused, increases in the colorant concentration inside the ejection opening 13b are always reduced. This allows for a smooth first ejection after the recording operation is paused, and reduces color unevenness and other issues. However, the present invention is also applicable to a liquid ejection head that ejects ink while the ink flow through the ink flow path 24 is stopped. After the recording operation is stopped, a circulating flow may be generated in the ink flow path to reduce the increase in viscosity of the ink inside the ejection port portion 13b, and then ink may be ejected after the circulating flow is stopped.

[0119] (Third embodiment) FIG. 30 illustrates the ink flow within a liquid ejection head according to a third embodiment of the present invention. The same reference numerals are used to designate the same components as those in the above-described embodiments, and their descriptions are omitted. As shown in FIG. 30, in this embodiment, the height of the flow path 24 near the ejection port 13 (ejection port portion 13b) is lower than the height of the flow path 24 in other portions. Specifically, the height H of the flow path 24 upstream of the connecting portion between the flow path 24 and the ejection port portion 13b in the direction of liquid flow within the flow path is lower than the height of the flow path 24 at the connecting portion between the flow path 24 and the liquid supply channel 18 (see FIG. 22). In this embodiment, by setting H, P, and W to satisfy Equation (1), at least a portion of the ink flow 17 can be returned to the flow path 24 after reaching a position at least halfway from the ejection port portion 13b in the direction from the pressure chamber 23 toward the ink interface 13a. Furthermore, in this embodiment, by setting H, P, and W to satisfy Equation (2), flow mode A can be achieved.

[0120] In this embodiment, the flow path height from the communication portion between the flow path 24 and the liquid supply path 18 to the vicinity of the ejection port, and the flow path height from the vicinity of the ejection port to the liquid recovery path 19, are relatively high, thereby reducing the flow path resistance in those areas. Furthermore, by relatively reducing the flow path height H near the ejection port 13b, a liquid ejection head of flow mode A, as described in the second embodiment, can be achieved. Normally, if the height of the flow path 24 is reduced overall to satisfy equation (2), the flow path resistance from the liquid supply path 18 or the liquid recovery path 19 to the ejection port 13 increases, which may reduce the speed at which ink is replenished (refill speed) due to ejection. Therefore, by lowering the flow path height near the ejection port 13 compared to the flow path height of other portions, as in the configuration of this embodiment, it is possible to ensure the necessary refill speed while satisfying equation (1) or (2). This makes it possible to suppress ink viscosity at the ejection port while achieving high-speed recording (improved throughput).

[0121] (Fourth embodiment) FIG. 31 is a diagram showing the flow of ink flowing through a liquid ejection head according to a fourth embodiment of the present invention. In FIG. 31, a recess 13c is formed around the ejection port 13 on the surface of the orifice plate 12. That is, the ejection port 13 is formed in the recess (the bottom surface of the recess 13c) formed in the orifice plate. In a normal state and in a steady state when a circulating flow is generated, the ink meniscus (ink interface 13a) is formed at the boundary surface between the ejection port 13 and the bottom surface of the recess 13c. In this embodiment, by setting H, P, and W to satisfy Equation (1), at least a portion of the ink flow 17 can be returned to the flow path 24 after reaching a position at least halfway from the ejection port portion 13b in the direction from the pressure chamber 23 toward the ink interface 13a. Furthermore, in the configuration of this embodiment, by setting H, P, and W to satisfy Equation (2), flow mode A is achieved. In this embodiment, P in formulas (1) and (2) is the length of the ejection port portion, that is, the length from the portion where the ink meniscus is formed to the flow path 24, as shown in Fig. 31. That is, the thickness of the orifice plate 12 is thinner near the portion where it contacts the ejection port 13 than at other portions. Specifically, the thickness of the orifice plate 12 near the ejection port 13 is thinner than the thickness of the orifice plate at the connection portion between the flow path 24 and the liquid supply path 18 (see Fig. 22).

[0122] In this embodiment, the thickness P of the orifice plate 12 near the discharge port portion 13b can be reduced while maintaining a certain thickness of the orifice plate 12 as a whole head. Normally, when the length P of the discharge port portion is shortened to satisfy formulas (1) and (2), the thickness of the entire orifice plate becomes thin, and the strength of the orifice plate decreases. However, according to the configuration of this embodiment, in addition to the effects of the first and second embodiments, the strength of the orifice plate 12 as a whole can be ensured.

[0123] (Fifth embodiment) FIG. 32 is a diagram showing the state of ink flow in a liquid ejection head according to a fifth embodiment of the present invention. As shown in FIG. 32, the height of the flow path 24 is lower near the connection with the ejection port 13 than at other locations, and a recess 13c is formed around the ejection port 13 on the surface of the orifice plate 12. Specifically, the height H of the flow path 24 on the upstream side of the communication portion between the flow path 24 and the ejection port portion 13b in terms of the direction of liquid flow in the flow path is lower than the height of the flow path 24 near the communication portion between the flow path 24 and the liquid supply path 18 (see FIG. 22). In the configuration of this embodiment, as in the fourth embodiment, in the normal state and in the steady state when a circulating flow is generated, an ink meniscus (ink interface 13a) is formed at the boundary surface between the ejection port 13 and the bottom surface of the recess 13c.

[0124] In this embodiment, the flow path height H near the discharge port 13b can be reduced while maintaining low flow path resistance from the liquid supply path 18 or the liquid recovery path 19 to the discharge port 13, and further, the length P of the discharge port portion 13b can also be shortened. Normally, if the height of the flow path 24 is made lower near the connection with the discharge port 13 than at other locations, the thickness of the orifice plate 12 near the discharge port 13 increases accordingly, and the length P of the discharge port 13 becomes longer. In contrast, the configuration of this embodiment can ensure the necessary refill speed in addition to the effects of the first and second embodiments.

[0125] (Sixth embodiment) FIG. 33 is a diagram illustrating the flow of ink flowing through a liquid ejection head according to a sixth embodiment of the present invention. As shown in FIG. 33, the liquid ejection head of this embodiment has a step at the communication portion between the flow path 24 and the ejection port 13b. In this embodiment, the ejection port 13b extends from the ejection port 13 to the portion where the step is formed, and the ejection port 13b is connected to the flow path 24 via a portion (part of the flow path) with a larger diameter than the ejection port 13b. Therefore, P, W, and H in this embodiment are defined as shown in the figure. In this liquid ejection head, by setting H, P, and W to satisfy Equation (1), at least a portion of the ink flow 17 can be returned to the flow path 24 after reaching a position at least halfway from the ejection port 13b in the direction from the pressure chamber 23 toward the ink interface 13a. Furthermore, by setting H, P, and W to satisfy Equation (2), flow mode A can be generated.

[0126] In this way, by configuring the portion from the flow path toward the discharge port in a multi-stage configuration, it is possible to relatively reduce the flow resistance in the direction from the energy generating element 15 toward the discharge port 13. In this way, the configuration of this embodiment improves discharge efficiency, and in addition to the effects of the first and second embodiments, it is preferable when discharging small droplets of 5 pL or less, for example.

[0127] (Seventh embodiment) FIG. 34 is a diagram illustrating the flow of ink flowing through a liquid ejection head according to a seventh embodiment of the present invention. As shown in FIG. 34, the ejection port 13b, which connects the ejection port 13 and the flow path 24, is frustoconical. Specifically, the opening diameter of the ejection port 13b on the flow path side is larger than the opening diameter of the ejection port 13b on the ejection port 13 side, and the sidewall is tapered. This configuration can relatively reduce the flow resistance in the direction from the energy generating element 15 to the ejection port 13, thereby improving ejection efficiency. In this embodiment, too, by setting H, P, and W to satisfy Equation (1), at least a portion of the ink flow 17 can return to the flow path 24 after reaching a position more than halfway from the ejection port 13b in the direction from the pressure chamber 23 toward the ink interface 13a. Furthermore, in this embodiment, flow mode A can be generated by setting H, P, and W to satisfy Equation (2). 34, W in formulas (1) and (2) in this embodiment defines the length of the communicating portion between the discharge port portion 13b and the flow path 24. In addition to the effects of the first embodiment, the configuration of this embodiment is preferable when discharging small droplets of, for example, 5 pl or less.

[0128] (Eighth embodiment) 35(a) and 35(b) show two examples of the shape of the ejection port of a liquid ejection head according to an eighth embodiment of the present invention, particularly the shape of the ejection port. These are plan views (schematic diagrams) viewed from the direction in which liquid is ejected from the ejection port 13. The shape of the ejection port 13 in this embodiment has protrusions 13d formed at opposing positions and extending toward the center of the ejection port. These protrusions 13d extend continuously from the outer surface of the ejection port 13 to the interior of the ejection port portion 13b. Even in shapes with these protrusions, by setting H, P, and W to satisfy Equation (1), at least a portion of the ink flow 17 can be returned to the flow path 24 after reaching a position at least halfway through the ejection port portion 13b in the direction from the pressure chamber 23 toward the ink interface 13a. Furthermore, by setting H, P, and W to satisfy the above-mentioned Equation (2), flow mode A can be generated.

[0129] The ejection orifice in the example shown in Figure 35(a) has a protrusion 13d that protrudes in a direction intersecting the flow of liquid in the flow path 24, while the ejection orifice in the example shown in Figure 35(b) has a protrusion 13d that protrudes in the direction of the ink flow. By forming such protrusions on the ejection orifice 13, the meniscus formed between the protrusions 13d can be more easily maintained than the meniscus in other parts of the ejection orifice, and the tail of the ink droplet extending from the ejection orifice can be cut off at an earlier timing. This makes it possible to suppress the generation of mist, which is a small droplet that accompanies the main droplet.

[0130] Figures 44 and 45 are diagrams showing a more specific configuration of the liquid ejection head in Figure 35(B). The specific dimensions of each part in this embodiment are H=16 μm, P=6 μm, W=22 μm, with a judgment value J=2.6 in Figure 44, and H=5 μm, P=5 μm, W=20 μm, with a judgment value J=4.3 in Figure 45.

[0131] (Ninth embodiment) 36 to 38 are diagrams illustrating a liquid ejection head according to a ninth embodiment of the present invention. This embodiment is an improvement over the second to eighth embodiments and is not intended to limit the foregoing embodiments. The relationship between the amount of evaporation of ink moisture and other components from the ink interface 13a formed at the ejection port 13 and the flow rate of the ink flow 17 will be described with reference to FIGS. 36 and 37. When the amount of evaporation from the ink interface 13a is relatively large due to environmental conditions or the like and the ratio of the flow rate of the ink flow 17 to the amount of evaporation is small, as shown in FIG. 36(a), the ink flow within the ejection port portion 13b becomes dominated by the flow toward the ink interface 13a. This state in which the ink flow within the ejection port portion 13b becomes dominated by the flow toward the ink interface 13a is hereinafter referred to as state D. In state D, the colorant concentration within the ejection port portion becomes relatively high due to evaporation, as shown in FIG. 37(a). On the other hand, when the ink flow 17 is sufficient relative to the amount of evaporation, even if the evaporation rate is high, the ink flow within the ejection port 13b becomes dominated by the ink flow 17 relative to the flow toward the ink interface 13a, as shown in FIG. 36(b). This state in which the ink flow 17 becomes dominant relative to the flow toward the ink interface 13a within the ejection port 13b is hereinafter referred to as State C. As a result, the colorant concentration within the ejection port 13b becomes relatively low, as shown in FIG. 37(b). That is, State C can be achieved in a liquid ejection head that satisfies the formulas (1) and (2) described in the first and second embodiments. Even if the evaporation rate from the ink interface 13a increases due to environmental conditions during use of the liquid ejection head, State C can be achieved by sufficiently increasing the flow rate of the ink flow 17. This can further prevent ink with a change in colorant concentration due to ink evaporation from the ejection port from stagnating in the ejection port 13b.

[0132] As a comparative example, we will explain the case of a liquid ejection head that does not satisfy formula (2). In this example, no matter how much the flow rate of the ink flow 17 is increased, flow mode A does not occur. In other words, in order to achieve flow mode A, formula (2) must be satisfied.

[0133] Even in the case of a liquid ejection head that satisfies formula (2), increasing the amount of ink flow 17 increases the pressure loss. Therefore, it is necessary to increase the pressure difference between the common supply path 211 and the common recovery path 212 (see FIGS. 2 and 3). Furthermore, the pressure difference between each ejection port in the liquid ejection head increases, making it difficult to achieve uniform ejection characteristics. Therefore, from these perspectives, it is desirable to minimize the flow rate of ink flow 17.

[0134] Therefore, in a liquid ejection head that is in flow mode A, an example of the flow velocity conditions of the ink flow 17 to bring about state C will be described below.

[0135] In this embodiment, in a liquid ejection head with H of 3 to 6 μm, P of 3 to 6 μm, and W of 17 to 25 μm, the following conditions are set to prevent ink whose colorant concentration has changed due to evaporation from accumulating inside the ejection port portion 13b: That is, the relationship between the average flow velocity V17 of the ink flow 17 and the average evaporation flow velocity V12 from the ink interface 13a is expressed by the following formula (5): V17≧27×V12 Formula (5)

[0136] Studies by the inventors of the present application have shown that a liquid ejection head that satisfies formula (5) will be in state C. A liquid ejection head with H of 3 to 6 μm, P of 3 to 6 μm, and W of 17 μm or greater will satisfy formula (2), and therefore can be put into state C by circulating a sufficient amount of ink relative to the amount of evaporation. The above formula (5) shows the circulation flow rate required to achieve state C. Formula (5) will be explained with reference to FIG. 38.

[0137] Figure 38 shows the relationship between the evaporation rate and circulation flow rate for state C and for state D. The horizontal axis of Figure 38 is the evaporation rate V12, and the vertical axis is the ink flow rate V17 due to circulation. The graph shows data for each flow mode for four liquid ejection head shapes 1 to 4. For liquid ejection head 1, H is 6 μm, P is 6 μm, and W is 17 μm, with a judgment value J of 2.83. For liquid ejection head 2, H is 6 μm, P is 6 μm, and W is 21 μm, with a judgment value J of 3.5. For liquid ejection head 3, H is 5 μm, P is 3 μm, and W is 21 μm, with a judgment value J of 5.88. For liquid ejection head 4, H is 5 μm, P is 3 μm, and W is 25 μm, with a judgment value J of 7.0.

[0138] From Figure 38, it can be seen that for a given liquid ejection head, the circulation flow velocity V17 required to achieve State C rather than State D is proportional to the evaporation flow velocity V12. It can also be seen that the smaller the judgment value J, the greater the circulation flow velocity required to achieve State C. Furthermore, for a liquid ejection head with H between 3 and 6 μm, P between 3 and 6 μm, and W between 17 and 25 μm, and with the smallest judgment value J of 2.83 (Liquid Ejection Head 1), it can be seen that State C is achieved when the circulation flow velocity is 27 times or more the evaporation flow velocity. Therefore, for a liquid ejection head with H between 3 and 6 μm, P between 3 and 6 μm, and W equal to or greater than 17 μm, State C is achieved by satisfying Equation (5), and ink whose colorant concentration has changed due to evaporation can be prevented from accumulating in the ejection port portion 13b. In other words, it is possible to reduce the occurrence of color unevenness in images due to liquid evaporation from the ejection port 13. For example, in an experiment conducted by the inventors of the present invention, the evaporation rate from a circular nozzle with a W of 18 μm was approximately 140 pl / s, and the average evaporation flow rate was approximately 1.35 × 10 -4 In this case, the average circulation flow velocity is required to be about 0.0036 m / s or more. Here, the evaporation amount refers to the amount of evaporation when the ink concentration at the ejection port portion 13b does not change.

[0139] Similarly, for a liquid ejection head with H of 8 μm, P of 8 μm, W of 17 μm, and a judgment value J of 2.13, State C can be achieved by increasing the average flow velocity V17 of the ink flow 17 to 50 times or more the average evaporation flow rate V12 from the ink interface 13a. Therefore, for a liquid ejection head with H of 8 μm or less, P of 8 μm or less, and W of 17 μm or more, State C can be achieved by increasing the average flow velocity V17 of the ink flow 17 to 50 times or more the average evaporation flow rate V12 from the ink interface 13a. This prevents ink that has undergone changes in colorant concentration due to evaporation from the ejection orifice 13 from stagnation. As a result, it is possible to reduce the occurrence of color unevenness in images due to liquid evaporation from the ejection orifice 13. Similarly, when the evaporation rate from a circular ejection orifice with a W of 18 μm is approximately 140 pl / s, an average circulation flow velocity of approximately 0.0067 m / s or more is required.

[0140] Similarly, for a liquid ejection head with H of 15 μm, P of 7 μm, W of 17 μm, and a judgment value J of 1.87, state C can be achieved by making the average flow velocity V17 of the ink flow 17 50 times or more the average evaporation flow rate V12 from the ink interface 13 a. Therefore, for a liquid ejection head with H of 15 μm or less, P of 7 μm or less, and W of 17 μm or more, state C can be achieved by making the average flow velocity V17 of the ink flow 17 100 times or more the average evaporation flow rate V12 from the ink interface 13 a. Similarly to the above, when the evaporation rate from a circular ejection orifice with W of 18 μm is approximately 140 pl / s, an average circulation flow velocity of approximately 0.0135 m / s or more is required.

[0141] Next, we will explain the configuration of a different liquid ejection head. This liquid ejection head is a liquid ejection head in which H is 14 μm or less, P is 12 μm or less, and W is 17 μm or more, and H, P, and W satisfy formula (2). This liquid ejection head satisfies the following formula (6) to prevent ink that has undergone changes in colorant concentration due to evaporation of ink from the ejection orifices from accumulating in the ejection orifice portion 13b. In other words, the average flow velocity V17 of the circulating flow 17 and the average evaporation flow velocity V12 from the ink interface 13a satisfy the following formula (6). V17≧900×V12 Formula (6)

[0142] In a liquid ejection head with H of 12.3 μm, P of 9 μm, and W of 17 μm (determination value J is 1.7), state C can be achieved by increasing the average flow velocity V17 of the ink flow 17 to 900 times the average evaporation flow velocity V12 from the ink interface 13 a. Similarly, in a liquid ejection head with H of 10 μm, P of 10 μm, and W of 17 μm (determination value J is 1.7), state C can be achieved by increasing the average flow velocity V17 of the ink flow 17 to 900 times the average evaporation flow velocity V12 from the ink interface 13 a. Similarly, in a liquid ejection head with H of 8.3 μm, P of 11 μm, and W of 17 μm (determination value J is 1.7), state C can be achieved by increasing the average flow velocity V17 of the circulating flow 17 to 900 times the average evaporation flow velocity V12 from the ink interface 13 a. Similarly, even in a liquid ejection head with H of 7 μm, P of 12 μm, and W of 17 μm (determination value J of 1.7), state C can be achieved by making the average flow velocity V17 of the circulating flow 17 900 times the average evaporation flow velocity V12 from the ink interface 13a.

[0143] Therefore, a liquid ejection head in which H is 14 μm or less, P is 12 μm or less, W is 17 μm or more, and H, P, and W satisfy formula (2) is in state C by satisfying formula (6).

[0144] Regarding the ninth embodiment described above, the conditions for state C can be summarized as follows:

[0145] H is 14 μm or less, P is 12 μm or less, W is 17 μm or more and 30 μm or less, and the flow rate of the liquid in the flow path is 900 times or more the evaporation rate from the discharge port.

[0146] Alternatively, H is 15 μm or less, P is 7 μm or less, W is 17 μm or more and 30 μm or less, and the flow rate of the liquid in the flow path is 100 times or more the evaporation rate from the discharge port.

[0147] Alternatively, H is 8 μm or less, P is 8 μm or less, W is 17 μm or more and 30 μm or less, and the flow rate of the liquid in the flow path is 50 times or more the evaporation rate from the discharge port.

[0148] Alternatively, H is 3 μm or more and 6 μm or less, P is 3 μm or more and 6 μm or less, W is 17 μm or more and 30 μm or less, and the flow rate of the liquid in the flow path is 27 times or more the evaporation rate from the discharge port.

[0149] Here, the above-mentioned liquid flow velocity is a range in which state C is reached even for the shape that is least likely to reach state C within each head shape range, and other shapes within each head shape range may reach state C at a lower flow velocity.

[0150] (Tenth embodiment) 39 to 42 are diagrams illustrating a liquid ejection head according to a tenth embodiment of the present invention, and this embodiment relates to the relationship between the following two types of characteristics and the shape of the flow path including the ejection ports. Characteristic 1) Flow mode of ink flow Characteristic 2) Droplets ejected from the ejection port In particular, the relationship with the above characteristics will be explained using the following three types of ejection port shapes with an ejection volume Vd of 5 pl as examples. Channel shape A) H=14μm, P=11μm, W=16μm (J=1.34) Flow path shape B) H=0.9μm, P=1.1μm, W=1.8μm (J=1.79) Channel shape C) H=14μm, P=06μm, W=18μm (J=2.30) where: H: Height of the flow channel 24 on the upstream side in the direction of flow of the liquid in the flow channel 24 (see FIG. 22) P: length of the outlet portion 13b in the direction in which the liquid is discharged from the outlet 13 (see FIG. 22) W: length of the discharge port portion 13b in the direction of flow of the liquid in the flow path 24 (see FIG. 22) Z: Effective length of the inscribed circle of the outlet 13 However, since the shape of the discharge port 13 is circular (see FIG. 22), the effective diameters Z and W of the inscribed circle of the discharge port 13 are equal.

[0151] The reason why Vd is set to 5 pL is that when the ejection volume is large, multiple main droplets and multiple sub-droplets (hereinafter also referred to as satellites) tend to occur, which leads to deterioration of image quality.

[0152] Figures 39(a) to (c) are diagrams showing the flow modes of three flow path shapes A to C, and Figure 40 is a contour map showing the value of the judgment value J when the outlet diameter is changed so that the discharge volume Vd is approximately 5 pl, with H on the horizontal axis and P on the vertical axis.

[0153] Flow path shape A has a judgment value J = 1.34 and produces flow mode B as shown in Figure 39(a). The sum of H and P (hereinafter also referred to as OH) of flow path shape A is 25 μm. To increase the judgment value J, it is necessary to reduce H or P and lower OH. When OH = 20 μm, flow path shape B, in which only H is reduced, has a judgment value J = 1.79 and produces flow mode A as shown in Figure 39(b). Flow path shape C, in which only P is reduced, has a judgment value J = 2.30 and also produces flow mode A as shown in Figure 39(c). In addition, flow path shape C allows the ink flow to flow more easily into the ejection opening than flow path shape B, and can better suppress ink stagnation inside the ejection opening portion 13b. Therefore, the following shapes can be considered regarding the ink flow mode. Shape characteristic (1) For equal OH, it is preferable to make P smaller (see FIG. 40). Shape characteristic (2) It is preferable to reduce OH (see FIG. 40).

[0154] 41(a) to 41(c) are diagrams showing the results of observing the discharged droplets for each of the three types of flow path shapes A to C. Fig. 42 is a contour map showing the calculated values ​​of the time it takes for the bubbles to communicate with the atmosphere (hereinafter also referred to as Tth) when the discharge port diameter is changed so that the discharge volume Vd is approximately 5 pl, with H on the horizontal axis and P on the vertical axis.

[0155] Figures 41(a) and (c) show cases where two types of ejected droplets, a main droplet and a satellite, are generated. Figure 41(b) shows a case where a main droplet and multiple satellites are generated. Flow path shape A has a Tth of 5.8 us, and flow path shape C has a Tth of 4.5 us. Flow path shape B has a Tth of 3.8 us, which is smaller (see Figure 42). Generally, when the ejection volume Vd is large as in this embodiment, a small Tth leads to the generation of multiple satellites. This is because a small Tth, i.e., when communication with the atmosphere is promoted, tends to generate a thin tail, resulting in the generation of multiple nodes due to tail instability. As a result, the thin tail cannot contract into a single entity, resulting in the generation of multiple satellites, as shown in Figure 41(b). Therefore, the following measures can be taken to suppress satellites. Shape characteristic (3): For equal OH, it is preferable to make P smaller (see Figure 42) Shape characteristic (4) It is preferable to increase OH (see Figure 42)

[0156] From the above, the increase in the judgment value J required to suppress the ink accumulation in the ejection port portion 13b is as follows: Shape characteristics A) OH reduction, Shape characteristic B) For equal OH, P must be smaller than H. In addition, the increase in the threshold Tth required to suppress the main droplet and satellite droplets requires: C) Increasing shape characteristics; Shape characteristic D) For equal OH, P must be smaller than H; Since shape characteristic A) and shape characteristic C) are contradictory, it is desirable to satisfy the following conditions to achieve a compatible solution. The flow mode judgment value J>1.7 and the atmospheric communication time judgment value Tth>4.0 μs.

[0157] Therefore, it is preferable to set the range as shown in Fig. 42. When the judgment value Tth satisfies the above condition, the judgment value Tth in the diagram shown in Fig. 42 is Tth=0.350×H+0.227×P―0.100×Z The above shows that when H or P is small or when Z increases, Tth becomes smaller and multiple satellites are more likely to occur. In particular, since H is about 1.5 times more sensitive than P, for equal OH, reducing P prevents Tth from becoming smaller and can suppress the occurrence of satellites. Therefore, the above condition can be expressed by the following formula. 0.350×H+0.227×P―0.100×Z>4 Formula (7) It can be expressed as:

[0158] By setting the shape characteristics of the ejection port within the above valid range, it becomes possible to achieve the circulation effect (suppression of ink retention in the ejection port portion 13b) and suppression of satellite generation when the ejection volume Vd is 5 ng.

[0159] As described above, the above-described embodiments can suppress fluctuations in the quality of the liquid near the ejection orifices, thereby making it possible to suppress, for example, thickening of the ink due to evaporation of the liquid from the ejection orifices and reduce color unevenness in the image. In particular, by satisfying formula (2) described in the second embodiment, flow mode A can be achieved, and ink retention in the ejection orifice portion 13b can be suppressed, thereby making it possible to reduce increases in colorant concentration, etc. The flow velocity of the ink flowing through the flow path 24 can be set appropriately according to the conditions, environment, etc. in which the liquid ejection head is used, in accordance with the concept described in this embodiment.

[0160] The present invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0161] 13 Outlet 13a Meniscus (ink interface) 13b Discharge port 15 Energy generating element 17 Circulating flow 23 Pressure Chamber 24 flow paths

Claims

1. a discharge port portion having a discharge port for discharging liquid provided at an end portion; an energy generating element that generates energy used to eject liquid from the ejection port; a flow path in which the energy generating element is disposed and which communicates with the discharge port; a supply flow path for allowing a liquid to flow into the flow path from the outside; an outflow flow path for causing the liquid to flow out from the flow path to the outside; A liquid ejection method using a liquid ejection head comprising: A liquid flow is generated in the liquid ejection head, The liquid flow is (1) The liquid flows into the flow path from the outside through the supply flow path, (2) the liquid flows from the flow path into the discharge port portion; (3) In the ejection port portion, the liquid reaches a meniscus position of the liquid formed at the ejection port and then returns to the flow path, (4) A flow that flows out from the flow path to the outside through the outflow flow path, A liquid ejection method characterized by ejecting liquid from the ejection outlet by driving the energy generating element while the flow of liquid is maintained within the ejection outlet portion, reaching the meniscus position of the liquid formed in the ejection outlet.

2. 2. The liquid ejection method according to claim 1, wherein the ejection port portion has a cylindrical shape.

3. the liquid ejection head has a substrate and an orifice plate formed on the substrate; The discharge port is formed in the orifice plate, 3. The liquid ejection method according to claim 1, wherein the supply flow path and the outflow flow path are formed in the substrate and penetrate the substrate.

4. a supply port is formed in the substrate between the flow channel and the supply flow channel, the supply port supplying the liquid from the supply flow channel to the flow channel; The liquid ejection method according to claim 3 , wherein a recovery port is formed in the substrate between the flow path and the outflow path, for causing the liquid to flow out from the flow path to the outflow path.

5. a plurality of the supply ports and the recovery ports are formed on the substrate, the supply flow path is connected to the plurality of supply ports, 5. The liquid ejection method according to claim 4, wherein the outflow channel is connected to the plurality of recovery ports.

6. 6. The liquid ejection method according to claim 1, wherein the liquid returning to the flow path flows into the outflow flow path.

7. the orifice plate is made of resin, 6. The liquid ejection method according to claim 3, wherein the substrate is made of silicon.

8. 8. The liquid ejection method according to claim 1, wherein the viscosity of the liquid flowing through the flow path is 30 cP or less, and the speed of the liquid flow is 0.1 to 100 mm / s.

9. 6. The liquid ejection method according to claim 3, wherein the thickness of the orifice plate in the vicinity of the ejection port is thinner than the thickness of the orifice plate at the communicating portion between the flow path and the supply flow path.

10. 6. A liquid ejection method according to claim 3, wherein a recess is formed in the orifice plate, and the ejection port is formed in the recess.

11. The height of the flow path on the upstream side of the communicating portion between the flow path and the discharge port portion in the flow direction of the liquid in the flow path is H μm, The length of the ejection port portion in the direction in which the liquid is ejected from the ejection port is P μm, The length of the discharge port portion in the direction of flow of the liquid in the flow channel is W μm, In this case, H -0.34 ×P -0.66×W>1.7 11. The liquid ejection method according to claim 1, wherein the following is satisfied:

12. 12. The liquid ejection method according to claim 11, wherein the height H is lower than the height of the flow channel at a communication portion between the flow channel and the supply flow channel.

13. 13. The liquid ejection method according to claim 11, wherein H is 20 μm or less, P is 20 μm or less, and W is 30 μm or less.

14. a supply means for causing a liquid to flow from the outside into the flow path through the supply flow path and for causing a liquid to flow from the flow path to the outside through the outflow flow path; 14. The liquid ejection method according to claim 1, wherein the supplying means circulates the liquid to the liquid ejection head.

15. A liquid ejection method according to any one of claims 1 to 14, characterized in that the flow path includes a pressure chamber having the energy generating element therein, and the liquid in the pressure chamber is circulated between the pressure chamber and the outside via the supply flow path and the outflow flow path.

16. 16. A liquid ejection method according to claim 1, wherein the solid content of the liquid is 8 wt % or more.

17. 17. The liquid ejection method according to claim 1, wherein the energy generating element is a heat generating element, and bubbles generated by heating the energy generating element communicate with the atmosphere through the ejection port.

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