Liquid ejection head

Abstract

To provide a liquid discharge head capable of suppressing deformation of a flow channel member in a recording medium conveyance direction.SOLUTION: A liquid discharge head 3 includes: an element substrate 10 having a plurality of discharge ports 13 for discharging a liquid to a recording medium 2 and a heating element 5 for heating the liquid; and flow channel members 60 having supply flow channels 211 for supplying the liquid to the element substrate 10 and collection flow channels 212 for collecting the liquid from the element substrate 10. When viewed from the side where the discharge port 13 is opened, the supply flow channels 211 and the collection flow channels 212 are formed in a longitudinal direction of the flow channel member 60, and at least a part of the supply flow channels 211 and at least a part of the collection flow channels 212 overlap each other.SELECTED DRAWING: Figure 7

Description

[Technical field]

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

[0002] An example of a liquid ejection device that ejects liquid onto a recording medium such as paper is an inkjet printer. An inkjet printer includes a liquid ejection head that ejects liquid. The liquid ejection head includes an ejection port for ejecting liquid, a pressure generating element that generates pressure for ejecting liquid from the ejection port, and a pressure chamber to which the pressure generated by the pressure generating element acts.

[0003] When performing an operation of discharging liquid from a discharge port, it is desirable that the viscosity of the liquid is within a desired range, and if the viscosity of the liquid is outside the desired range, there is a risk of the discharge performance being reduced. Patent Document 1 discloses a liquid discharge head in which a heating element for heating the liquid and controlling the viscosity of the liquid is provided near a pressure chamber. This adjusts the temperature of the liquid and controls the viscosity by driving the heating element to a degree that does not cause bubbles. Furthermore, the liquid discharge head described in Patent Document 1 has a recovery flow path for recovering the liquid from the pressure chamber in order to suppress an increase in the viscosity of the liquid caused by evaporation of the liquid from the discharge port, and has a flow path configuration that allows the liquid to circulate between the upstream and downstream of the pressure chamber. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-213871 A Summary of the Invention [Problem to be solved by the invention]

[0005] As described in Patent Document 1, when a heating element for controlling the viscosity of the liquid is provided near the pressure chamber, the liquid heated by the heating element flows in the recovery flow path, which is a flow path downstream of the pressure chamber. Therefore, the temperature of the liquid flowing in the recovery flow path is higher than the temperature of the liquid flowing in the supply flow path, which is a flow path upstream of the pressure chamber, for supplying the liquid to the pressure chamber. As a result, in a flow path member having a recovery flow path and a supply flow path, the temperature around the recovery flow path is higher than the temperature around the supply flow path, and a temperature bias (temperature gradient) occurs in the flow path member. Note that such a temperature gradient occurs in the same way when a heating element for film boiling the liquid is provided as a pressure generating element in the pressure chamber, even if a heating element for controlling the viscosity of the liquid is not provided. Therefore, when the recovery flow path and the supply flow path are arranged side by side in the transport direction of the recording medium, the flow path member may be deformed in the transport direction of the recording medium due to the temperature gradient in the flow path member, which may affect the recording quality.

[0006] In view of the above-mentioned problems, an object of the present invention is to provide a liquid ejection head capable of suppressing deformation of a flow path member in the transport direction of a recording medium. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a liquid ejection head comprising: Disposed at each of the discharge ports and discharged Heating the liquid Multiple an element substrate including a heating element; The element substrate and each of the plurality of heating elements is joined to Supplying liquid Multiple individual A supply channel and a common supply flow path communicating with the plurality of individual supply flow paths; , Through each of the plurality of heating elements Recovering liquids Multiple individual Recovery channel and a common recovery flow path communicating with the plurality of individual recovery flow paths; and a flow path member comprising: common Supply channel and The above common The recovery flow path is formed along the longitudinal direction of the flow path member, common At least a part of the supply flow path and the commonAt least a portion of the recovery channels overlap each other. The common supply flow path and the common recovery flow path are arranged in this order from the element substrate side. It is characterized by: Effect of the Invention

[0008] According to the present invention, it is possible to provide a liquid ejection head capable of suppressing deformation of a flow path member in the transport direction of a recording medium. [Brief description of the drawings]

[0009] [Figure 1] FIG. [Diagram 2] FIG. 4 is a schematic diagram showing a flow path of a liquid in the recording device. [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] FIG. 4 is a schematic view showing an internal structure of a flow path member in a comparative example. [Figure 7] FIG. 4 is a schematic view showing a cross section of a second flow path member. [Figure 8] FIG. 8 is a perspective view of the second flow path member shown in FIG. [Figure 9] FIG. 9 is a schematic view of a second flow path member in a second embodiment. [Figure 10] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The longer the flow path member, the greater the tendency for deformation of the flow path member to be. Therefore, the present invention is particularly suitable for use in so-called page-wide heads that have a flow path member longer than that of a so-called serial type liquid ejection head and that correspond to the recording width of a recording medium such as paper. A page-wide head is a head in which a plurality of ejection ports are arranged from one end to the other end of the recording medium in a direction intersecting the conveying direction of the recording medium. Below, an explanation will be given using a page-wide head as an example.

[0011] (Recording device) The recording device will be described with reference to FIG. 1. FIG. 1 is a schematic diagram showing an example of a recording device 1000 equipped with a liquid ejection head 3. The recording device 1000 shown in FIG. 1 ejects liquid from the liquid ejection head 3 onto an intermediate transfer body (intermediate transfer drum) 1007 to form an image pattern (print pattern) on the intermediate transfer body 1007, and then transfers the image pattern to a recording medium 2. In the recording device 1000, four single-color liquid ejection heads 3 corresponding to at least four types of ink, CMYK, are arranged in an arc shape along the intermediate transfer body 1007. As a result, full-color recording is performed on the intermediate transfer body 1007, and the recorded image pattern is appropriately dried on the intermediate transfer body 1007. Thereafter, the recorded image pattern is transferred from the intermediate transfer body 1007 to the recording medium 2 by a transfer roller 1008. At this time, the transfer is performed while the recording medium 2 is transported by a paper transport roller 1009.

[0012] 1 is a recording apparatus that performs recording using an intermediate transfer body 1007, but the recording apparatus equipped with the liquid ejection head of the present invention is not limited to this. That is, the recording apparatus may perform recording by ejecting liquid directly from the liquid ejection head 3 onto the recording medium 2 without using the intermediate transfer body 1007.

[0013] (liquid flow path) The liquid path will be described with reference to FIG. 2. FIG. 2 is a schematic diagram showing the liquid flow path of the recording device 1000. The two pressure adjustment mechanisms constituting the negative pressure control unit 230 are mechanisms (mechanical components with the same function as a so-called "back pressure regulator") that control the pressure fluctuations on the upstream side of the negative pressure control unit 230 to be within a certain range centered on a desired set pressure. Therefore, even if the flow rate of the liquid fluctuates due to a change in the recording duty when recording with the liquid ejection head 3, the pressure fluctuations on the upstream side (the liquid ejection unit 300 side) of the negative pressure control unit 230 are operated to be stable within a certain range centered on a preset pressure. In addition, the second circulation pump 1004 acts as a negative pressure source that reduces the pressure on the downstream side of the negative pressure control unit 230. The first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 are arranged on the upstream side of the liquid ejection head 3, and the negative pressure control unit 230 is arranged in the liquid ejection head 3.

[0014] It is preferable to use the second circulation pump 1004 to pressurize the downstream side of the negative pressure control unit 230 via the liquid supply unit 220. This can suppress the effect of the head pressure of the buffer tank 1003 on the liquid ejection head 3, thereby expanding the range of 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 with respect to the negative pressure control unit 230 can also be applied.

[0015] The negative pressure control unit 230 includes two pressure adjustment mechanisms, each set to a different control pressure. Of the two negative pressure adjustment mechanisms, the high pressure setting side (denoted as H, FIG. 4(b)) and the low pressure side (denoted as L, FIG. 4(b)) are connected to the common supply flow channel 211 and the common recovery flow channel 212 in the liquid ejection unit 300 via the liquid supply unit 220, respectively. By making the pressure of the common supply flow channel 211 relatively higher than the pressure of the common recovery flow channel 212 by the two negative pressure adjustment mechanisms, an ink flow (arrow) is generated that flows from the common supply flow channel 211 to the common recovery flow channel 212 via the individual supply flow channels 213a and the internal flow channels of each element substrate 10.

[0016] Since the negative pressure control unit 230 is disposed downstream of the liquid ejection head 3, there is little concern that dust or foreign matter generated from the negative pressure control unit 230 will flow into the head. In addition, the maximum flow rate required to supply liquid from the buffer tank 1003 to the liquid ejection head 3 can be reduced. The reason is as follows. 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 A. The value of A is defined as the minimum flow rate required to keep the temperature difference in the liquid ejection unit 300 within a desired range when adjusting the temperature of the liquid ejection head 3 during standby for recording. In addition, the ejection flow rate when ink is ejected from all ejection ports (not shown) of the liquid ejection unit 300 (during full ejection) is defined as F. Then, the amount of liquid supplied to the liquid ejection head 3 required during standby for recording is the flow rate A. And the amount of liquid supplied to the liquid ejection head 3 required during full ejection is the flow rate F. Then, the total value of the set flow rates of the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002, i.e., the maximum value of the required supply flow rate, is the larger value of A or F. Therefore, as long as the liquid ejection unit 300 of the same configuration is used, the maximum value of the required supply amount (A or F) becomes smaller. Therefore, the degree of freedom of the applicable circulation pump increases, 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 main body. This advantage becomes greater as the value of A or F becomes relatively larger in the line head, and is more beneficial for line heads with a longer longitudinal length among line heads.

[0017] The first function can prevent excessive or insufficient pressure from being applied to the flow path downstream of the first circulating pumps 1001 and 1002 or upstream of the second circulating pump 1004. For example, if a malfunction of the first circulating pumps 1001 and 1002 occurs, an 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 breakage at each joint within the liquid ejection head 3. However, if a bypass valve is added to the first circulating pumps 1001 and 1002, even if excessive pressure occurs, the bypass valve 1010 opens to open the liquid path to the upstream side of each circulating pump, thereby preventing the above-mentioned trouble.

[0018] In addition, due to the second function, when the circulation drive is stopped, after the first circulation pumps 1001, 1002 and the second circulation pump 1004 are stopped, all the bypass valves 1010 are quickly opened based on a control signal from the main body side. This allows the high negative pressure (for example, several to several tens of kPa) in the downstream part of the liquid discharge head 3 (between the negative pressure control unit 230 and the second circulation pump 1004) to be released in a short time. When a volumetric 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 in the downstream part of the liquid discharge head 3 can be released from the downstream buffer tank 1003 side as well. Although the pressure in the downstream part of the liquid discharge head 3 can be released only from the upstream side, there is a pressure loss in the upstream flow path of the liquid discharge head and the flow path inside the liquid discharge head. Therefore, it takes time to release the pressure, and the pressure in the common flow path in the liquid discharge head 3 drops too much transiently, which may destroy the meniscus of the discharge 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.

[0019] 2 shows a recording apparatus in which liquid such as ink is circulated between the main tank 1006 and the liquid ejection head 3, but the present invention is not limited to this. For example, instead of circulating the ink, tanks may be provided on the upstream and downstream sides of the liquid ejection head, and the ink may flow from one tank to the other tank to cause the ink to flow.

[0020] (Liquid ejection head) The liquid ejection head 3 will be described with reference to Figs. 3 to 5. Fig. 3(a) is a perspective view of the liquid ejection head 3. Fig. 3(b) is an exploded perspective view of the liquid ejection head 3 (shield plate 132 is not shown). Fig. 4(a) is a side view of the liquid ejection head. Fig. 4(b) is a schematic diagram showing the flow of liquid inside the liquid ejection head 3. The circulation flow of liquid shown in Fig. 4(b) is the same as the circulation path shown in Fig. 2 in terms of circuitry, but Fig. 4(b) shows the actual flow of liquid within each component of the liquid ejection head 3. Note that some of the configuration has been simplified to facilitate understanding.

[0021] The liquid ejection head 3 has an element substrate 10 that ejects liquid from the ejection ports 13, and a flow path member 210 that has a flow path that supplies and recovers liquid to the element substrate 10. The liquid ejection head 3 is a so-called page-wide type head that has 36 element substrates 10 that are arranged linearly (in-line) in the longitudinal direction of the liquid ejection head 3. The element substrate 10 is formed with a pressure generating element 5 (FIG. 5) that generates pressure for ejecting liquid from the ejection ports 13 and a heating element 15 that heats the liquid to adjust the temperature of the liquid in the pressure chamber 7. The liquid in the pressure chamber 7 is heated by the heating element 15, and adjusted to a viscosity appropriate for ejection. The liquid ejection head 3 has a signal input terminal 91 for receiving a signal from the outside of the liquid ejection head 3, a power supply terminal 92 for receiving power, a shield plate 132 for protecting the side surface of the liquid ejection head 3, and the like.

[0022] The rigidity of the liquid ejection head 3 is ensured by the second flow path member 60 constituting the flow path member 210. The liquid ejection unit support part 81 is connected to both ends of the second flow path member 60, and this liquid ejection unit 300 is mechanically coupled to a carriage of the recording apparatus 1000 to position the liquid ejection head 3. The liquid supply unit 220 including the negative pressure control unit 230 and the electric wiring board 90 are coupled to the liquid ejection unit support part 81. A filter (not shown) is built into each of the two liquid supply units 220. The two negative pressure control units 230 are set to control pressure at different, relatively high and low negative pressures.

[0023] Next, the flow path member 210 of the liquid discharge unit 300 will be described in detail. The flow path member 210 is a laminate of a first flow path member 50 and a second flow path member 60, and distributes the liquid supplied from the liquid supply unit 220 to each discharge module 200. The flow path member 210 also functions as a flow path member for returning the liquid circulating from the discharge module 200 to the liquid supply unit 220. The second flow path member 60 of the flow path member 210 is a flow path member in which a common supply flow path 211 and a common recovery flow path 212 are formed, and has a function of mainly providing the rigidity of the liquid discharge head 3. For this reason, the material of the second flow path member 60 is preferably one having sufficient corrosion resistance against liquid and high mechanical strength. Specifically, stainless steel (SUS), Ti, alumina, etc. can be preferably used.

[0024] The first flow path member 50 is configured by arranging a plurality of members corresponding to the respective element substrates 10 adjacent to each other. With such a configuration, a plurality of element substrates 10 can be arranged on the first flow path member 50, and the length of the liquid ejection head 3 can be made to correspond to the width of the recording medium. For example, this is particularly suitable for use in a relatively long-scale liquid ejection head corresponding to a length of B2 size or larger. The individual supply flow paths 213a and the individual recovery flow paths 213b of the first flow path member 50 are fluidly connected to the element substrate 10.

[0025] In the element substrate 10, flow paths communicating with each ejection port 13 are formed, so that a part or all of the supplied liquid can circulate through the ejection ports 13 that are not ejecting. In addition, 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) via the liquid supply unit 220. Therefore, due to the pressure difference, ink flows from the common supply flow path 211 through the ejection ports 13 of the element substrate 10 to the common recovery flow path 212.

[0026] A set 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 in the long second flow path member 60. The flow direction of the liquid flowing in the common supply flow path 211 and the flow direction of the liquid flowing in the common recovery flow path 212 are opposite to each other, and a filter 221 is provided on the upstream side of each flow path to collect foreign matter entering from the liquid connection part 111, etc. In this way, by flowing the liquid in the common supply flow path 211 and the common recovery flow path 212 in the opposite directions to each other, heat exchange between the common supply flow path 211 and the common recovery flow path 212 is promoted, which is preferable in that the temperature gradient in the longitudinal direction in the liquid ejection head 3 is reduced. Note that in FIG. 2, the flow direction of the common supply flow path 211 and the common recovery flow path 212 are shown in the same direction to simplify the explanation.

[0027] A negative pressure control unit 230 is connected to the downstream side of each of the common supply flow path 211 and the common recovery flow path 212. In addition, the common supply flow path 211 has a branching portion into a plurality of individual supply flow paths 213a, and the common recovery flow path 212 has a branching portion into a plurality of individual recovery flow paths 213b. The individual supply flow paths 213a and the individual recovery flow paths 213b are formed in a plurality of first flow path members 50.

[0028] The negative pressure control units 230 indicated by H and L in FIG. 4(b) are units of the high pressure side (H) and the 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 with relatively high (H) and low (L) negative pressures. The common supply flow path 211 is connected to the negative pressure control unit 230(H), and the common recovery flow path 212 is connected to the negative pressure control unit 230(L), so that a pressure difference occurs between the common supply flow path 211 and the common recovery flow path 212. Due to the pressure difference, the liquid flows from the common supply flow path 211 through the individual supply flow paths 213a, the element substrate 10, and the individual recovery flow paths 213b in this order to the common recovery flow path 212. The liquid in the element substrate 10 flows as indicated by the arrow 8 in FIG. 5.

[0029] FIG. 5(a) is a top view of the element substrate 10. FIG. 5(b) is an enlarged view of part B shown in FIG. 5(a). The liquid is supplied to the ejection port 13 through the individual supply flow path 213a. A heating element (hereinafter referred to as the main heater 5) is formed as a pressure generating element 5 directly below the ejection port 13. The main heater 5 is driven to cause film boiling of the liquid, and pressure is obtained for ejecting the liquid from the ejection port 13. A heating element 15 (hereinafter referred to as the sub-heater) that heats the liquid in order to control the viscosity of the liquid is formed in the vicinity of the ejection port 13 along the arrangement direction of the ejection port. The liquid is heated by driving the sub-heater 15, and the viscosity of the liquid can be controlled.

[0030] (First embodiment) The first embodiment of the present invention will be described with reference to Figs. 6 to 8. Fig. 6(a) is a schematic diagram showing the internal structure of a flow path member in a comparative example of this embodiment, and is a cross-sectional view of line GG in Fig. 4(a). Fig. 6(b) is a top view of the second flow path member 60 shown in Fig. 6(a) when viewed from the +Z direction, and illustrates the internal structure so that the internal flow path can be seen. Fig. 7 is a schematic diagram showing a cross section of the second flow path member 60 of this embodiment. Fig. 8 is a perspective view of the second flow path member 60 shown in Fig. 7(a). Figs. 6 to 8 are simplified for the purpose of explanation.

[0031] As described above, in the liquid ejection head 3 of this embodiment, the common supply flow path 211 and the common recovery flow path 212 extend in the longitudinal direction in the second flow path member 60. In other words, the common recovery flow path 211 and the common recovery flow path 212 are formed along the longitudinal direction of the flow path member. Liquid heated to a predetermined temperature by a heating element flows into the common recovery flow path 212 via the individual recovery flow paths 213b. As a result, the liquid temperature in the common recovery flow path 212 becomes higher than the liquid temperature in the common supply flow path 211, and the common recovery flow path side of the second flow path member 60 becomes relatively hot and the common supply flow path side becomes relatively cold. Due to this temperature gradient, as shown in FIG. 6(b), the common recovery flow path 212 side thermally expands more than the common supply flow path 211 side, so that the second flow path member 60 bends so as to protrude toward the common recovery flow path side in the recording medium transport direction. At this time, the higher the heating temperature of the liquid or the greater the flow rate of the liquid flowing into the common recovery channel 212, the higher the temperature of the common recovery channel 212 and the greater the amount of bending. Note that such bending increases as the length of the second flow channel member 60 increases, so there is a risk that bending will become more pronounced in a so-called page-wide type liquid ejection head having a length corresponding to the width of the recording medium 2.

[0032] Therefore, in the present invention, in order to suppress the bending of the second flow path member 60 in the recording medium conveying direction, the flow path is configured as shown in FIG. 7. Specifically, the common supply flow path 211 and the common recovery flow path 212 are arranged so that at least a part of the common supply flow path 211 and at least a part of the common recovery flow path 212 overlap each other when viewed from the side where the ejection port opens. With this configuration, the bending of the second flow path member 60 in the recording medium conveying direction is suppressed. Note that the view from the side where the ejection port opens refers to the view through the internal structure of the head, such as the common supply flow path 211 and the common recovery flow path 212 of the second flow path member. When the common supply flow path 211 and the common recovery flow path 212 are arranged so that at least a part of the common supply flow path 211 and at least a part of the common recovery flow path 212 overlap each other, the above-mentioned temperature gradient occurs in a direction intersecting the recording medium conveying direction. This makes it possible to suppress the occurrence of a temperature gradient in the recording medium conveying direction, and therefore to suppress the bending of the second flow path member 60 in the recording medium conveying direction.

[0033] More preferably, as shown in FIG. 7(g), (h), (l), and (m), the flow paths 211 and 212 are arranged so that the position of the center of gravity B of the cross section of the common supply flow path 211 coincides with the position of the center of gravity B' of the cross section of the common recovery flow path 212 when viewed from the side where the ejection port is opened. This can significantly reduce the temperature distribution in the recording medium transport direction, and can further suppress the deformation of the second flow path member 60 in the recording medium transport direction. Note that the center of gravity of the cross section refers to the position of the center of gravity of the flow path in the cross section shown in FIG. 7 in the recording medium transport direction. In other words, the center of gravity coincides with the position of the center of gravity of one flow path in the recording medium transport direction and the position of the center of gravity of the other flow path in the recording medium transport direction. In addition, the position of the center of gravity coincides with the position of the center of gravity does not only mean a strict (complete) coincidence, but also means including an error to the extent that is permissible in terms of product performance and an error that may occur during product manufacturing. Although it is sufficient that the positions of the centers of gravity of at least one cross section coincide, it is more preferable that the average values ​​of the centers of gravity of the cross sections at 10 randomly selected points coincide, since this means that the temperature distribution of the entire flow path approaches uniformity. Furthermore, as shown in Figures 7(g) and 7(h), it is preferable that the common supply flow path 211 and the common recovery flow path 212 all overlap each other when viewed from the side where the ejection port 13 opens. With this configuration, the temperature distribution in the recording medium transport direction can be further suppressed, and the bending of the second flow path member 60 can be further suppressed.

[0034] Furthermore, by adopting the configuration of this embodiment, a temperature gradient occurs in the second flow path member in the liquid ejection direction. This may cause the second flow path member 60 to bend in the liquid ejection direction. However, when the second flow path member 60 bends in the liquid ejection direction, the paper-to-paper distance varies depending on the ejection port, but the position of the ejection port in the conveying direction of the recording medium is prevented from varying, so the effect on the recording quality is reduced.

[0035] 7(n), the cross-sectional area of ​​the common supply flow path 211 and the common recovery flow path 212 may be changed. When changing the cross-sectional area of ​​the flow path, it is particularly preferable to make the cross-sectional area of ​​the common recovery flow path 212 smaller than that of the common supply flow path 211. By making the cross-sectional area of ​​the common recovery flow path 212 smaller than that of the common supply flow path 211, the heat conducted from the liquid flowing through the common recovery flow path 212 is reduced around the common recovery flow path 212 of the second flow path member 60. This makes it possible to reduce the temperature gradient generated in the second flow path member 60 compared to when the cross-sectional area of ​​the common recovery flow path 212 is approximately equal to that of the common supply flow path 211, and therefore it is possible to further suppress the bending of the second flow path member 60. Here, the cross-sectional area of ​​the flow path refers to the average value of the cross-sectional areas at 10 randomly selected points.

[0036] Second embodiment The second embodiment will be described with reference to Fig. 9. Note that the same reference numerals are used for the same parts as those in the first embodiment, and the description thereof will be omitted. Fig. 9 is a schematic diagram showing the configuration of a second flow path member 60 in this embodiment.

[0037] As shown in the first embodiment, when the common supply flow path 211 and the common recovery flow path 212 are arranged in the liquid ejection direction so that the common supply flow path 211 and the common recovery flow path 212 overlap each other, a temperature gradient occurs in the liquid ejection direction. For this reason, there is a possibility that the second flow path member 60 will bend in the liquid ejection direction. Therefore, it is more preferable to arrange the common supply flow path 211 and the common recovery flow path 212 in the liquid ejection direction in the order of the common recovery flow path 212, the common supply flow path 211, and the element substrate 10, as shown in FIG. 9. Since the element substrate 10 has a heating element as described above, the temperature of the element substrate 10 also rises due to the driving of the heating element. Therefore, the temperature of the element substrate 10 becomes higher than the temperature of the second flow path member 60 around the common supply flow path 211. Therefore, the two with higher temperatures among the common supply flow path 211, the common recovery flow path 212, and the element substrate 10 are arranged on one end side and the other end side of the second flow path member 60 in the liquid ejection direction. With this configuration, it is possible to reduce the temperature gradient of the second flow path member 60 in the liquid ejection direction. That is, the temperature gradient occurring in the liquid ejection direction is smaller than when the element substrate 10 is disposed on one end side and the common supply flow path 211 is disposed on the other end side. This makes it possible to suppress bending of the second flow path member 60 in the liquid ejection direction. With the configuration as shown in FIG. 9, it is possible to suppress deformation of the second flow path member 60 in the transport direction of the recording medium, while also suppressing bending of the second flow path member 60 in the liquid ejection direction.

[0038] The positions of the common supply flow channel 211 and the common recovery flow channel 212 are determined by the position of the center of gravity of the cross section of the flow channel. That is, arranging the common recovery flow channel 212 on the other end side of the second flow channel member 60 described above means the following. It means arranging it at a position where the average value of the position of the center of gravity of the cross section of the common recovery flow channel 212 in the liquid ejection direction is closer to the other end side than the average value of the position of the center of gravity of the cross section of the common supply flow channel 211 in the liquid ejection direction. Also, the average value of the position of the center of gravity of the cross section of the common recovery flow channel 212 in the liquid ejection direction is the average value of the positions of the center of gravity of the cross section of the common recovery flow channel 212 in the liquid ejection direction at 10 randomly selected points of the common recovery flow channel 212. Similarly, the average value of the position of the center of gravity of the cross section of the common supply flow channel 211 in the liquid ejection direction is the average value of the positions of the center of gravity of the cross section of the common supply flow channel 211 in the liquid ejection direction at 10 randomly selected points of the common supply flow channel 211.

[0039] Next, a method for forming the second flow path member 60 in the above-mentioned first and second embodiments will be described. Fig. 10 is a cross-sectional view of the second flow path member 60, illustrating the common supply flow path 211, the individual supply flow paths 213a, the common recovery flow path 212, and the individual recovery flow paths 213b. Note that the illustration is simplified for the purpose of explanation.

[0040] The second flow path member 60 is formed by bonding a plurality of members by adhesive, sintering, or the like. The dashed lines in FIG. 10 indicate the minimum necessary division points of the members, and the divided members are laminated by adhesion, sintering, or the like to form the second flow path member. Since the common supply flow path 211 and the common recovery flow path 212 overlap in the liquid ejection direction, the individual supply flow path 213a and the individual recovery flow path 213b are formed by bending as shown in FIG. 10(a). The individual supply flow path 213a may be formed straight as shown in FIG. 10(e) instead of being a bent flow path as shown in FIG. The second flow path member 60 may be formed by either a method of laminating a plurality of members in the liquid ejection direction as shown in FIG. 10(a) or a method of laminating a plurality of members in the conveying direction of the recording medium as shown in FIG. 10(b). [Explanation of symbols]

[0041] 13 Outlet 5, 6 Heating elements 10 Element substrate 60 Flow path member 2 Recording media 211 Supply channel 212 Recovery channel 3 Liquid ejection head

Claims

1. an element substrate including a plurality of ejection ports for ejecting liquid onto a recording medium and a plurality of heating elements disposed at the respective ejection ports for heating the ejected liquid; a flow path member bonded to the element substrate, the flow path member including: a plurality of individual supply flow paths that supply liquid to each of the plurality of heating elements; a common supply flow path that communicates with the plurality of individual supply flow paths; a plurality of individual recovery flow paths that recover liquid that has passed through each of the plurality of heating elements; and a common recovery flow path that communicates with the plurality of individual recovery flow paths; In a liquid ejection head having A liquid ejection head characterized in that, when viewed from the side where the ejection ports are opened, the common supply flow path and the common recovery flow path are formed along the longitudinal direction of the flow path member, at least a portion of the common supply flow path and at least a portion of the common recovery flow path overlap each other, and the common supply flow path and the common recovery flow path are arranged in that order from the element substrate side.

2. 2. The liquid ejection head according to claim 1, wherein the center of gravity of the cross section of the common supply flow path coincides with the center of gravity of the cross section of the common recovery flow path when viewed from the side where the ejection ports are open.

3. 3. The liquid ejection head according to claim 1, wherein the common supply flow path and the common recovery flow path are completely overlapped when viewed from the side where the ejection ports are opened.

4. 3. The liquid ejection head according to claim 1, wherein a cross-sectional area of ​​the common recovery flow path is smaller than a cross-sectional area of ​​the common supply flow path.

5. the individual supply flow paths and the individual recovery flow paths are formed in a first flow path member, the common supply flow path and the common recovery flow path are formed in a second flow path member, The liquid ejection head according to claim 1 , wherein the flow path member is formed by stacking the first flow path member and the second flow path member.

6. 6. The liquid ejection head according to claim 1, wherein the heating element is a pressure generating element that heats liquid and generates pressure for ejecting the liquid from the ejection port.

7. 6. The heating element according to claim 1, wherein the heating element is a sub-heater for heating the liquid, separate from a pressure generating element for heating the liquid and generating pressure for discharging the liquid from the discharge port. Item 5. A liquid ejection head according to item 1.

8. 6. A liquid ejection head according to claim 1, wherein the heating element comprises a pressure generating element that heats liquid to generate pressure for ejecting the liquid from the ejection port, and a sub-heater that heats liquid other than the pressure generating element.

9. 9. The liquid ejection head according to claim 1, which is a page-wide type liquid ejection head in which the plurality of ejection ports are arranged from one end to the other end of the recording medium in a direction intersecting a transport direction of the recording medium.

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