Liquid ejection head, liquid ejection device, and cleaning method

Abstract

To provide a technique that can appropriately sense a timing for replacing a liquid discharge head.SOLUTION: A liquid discharge head comprises: a discharge port through which liquid stored in a liquid chamber is discharged; an electric heat converting element that discharges the liquid through the discharge port by producing heat; a first electrode that protects the electric heat converting element and can be eluted to the liquid by electrochemical reaction with the liquid; and a second electrode provided to be electrically connected to the first electrode through the liquid, and makes the first electrode elute to the liquid, by making the second electrode enable the first electrode to cause electrochemical reaction with the liquid while applying voltages thereto, which is configured to be able to apply voltages while reversing a polarity between the first electrode and the second electrode and to be able to measure wiring resistance in a circuit having the plurality of second electrodes as a potion of wiring.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection head that can be widely used as, for example, a recording head that can eject ink by an inkjet method, a liquid ejection apparatus that includes the liquid ejection head, and a method for cleaning the liquid ejection head. [Background technology]

[0002] In liquid ejection heads that apply a voltage to a heating resistor element to induce film boiling in the liquid and eject the liquid using the energy generated by bubble growth, kogation can be a problem when ejecting liquids such as ink containing colorants. Kogation is a phenomenon in which the heat generated by the heating resistor element causes thermally soluble ink components to decompose or denature, resulting in kogation on the heating resistor element or the coating covering the surface of the heating resistor element. Kogation reduces the thermal conductivity from the heating resistor element to the liquid, causing bubbling and ultimately unstable ejection.

[0003] Patent Document 1 discloses a technology for removing kogation by forming the surface of the upper protective layer of a heating resistor element from a material that can be dissolved into a liquid through an electrochemical reaction, and applying a positive potential to the material to cause the material to dissolve into the liquid. In order to maintain this kogation removal function, the amount of material eluted by the material layer made of the above material needs to be controlled so that the liquid ejection head can be replaced when the remaining amount of the material layer falls below a specified value as the material dissolves into the liquid.

[0004] Patent Document 2 discloses a technology that can grasp the amount of elution of the material layer by measuring the conductivity of the liquid before cleaning and determining the cleaning conditions, even if there is variation in the conductivity of the liquid, particularly the ink, during cleaning. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-105364 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-221498 Summary of the Invention [Problem to be solved by the invention]

[0006] The technology disclosed in Patent Document 2 can manage the amount of elution of the material constituting the material layer, but cannot directly manage the material layer, such as by measuring the film thickness of the material layer. Meanwhile, during the manufacturing process of a liquid ejection head, process variations occur, such as film thickness distribution during film formation within a wafer or between wafers and film reduction distribution in post-processing. As a result, the initial film thickness of the material layer varies in the manufactured liquid ejection head. Therefore, with the technology disclosed in Patent Document 2, the number of cleanings, which serves as an indicator of when to replace the liquid ejection head, is determined based on the minimum film thickness of the material layer due to process variations.

[0007] Specifically, the manufacturing tolerance of the material layer is, for example, 10 nm or more, and the amount of film loss due to one cleaning process is, for example, several nm. In this case, with a liquid ejection head configured with an average film thickness, once the number of cleanings determined in consideration of process variations was reached, the liquid ejection head had to be replaced even though several more cleaning processes were possible.

[0008] The present invention has been made in view of the above-mentioned problems, and has an object to provide a technique that can appropriately detect the timing for replacing a liquid ejection head. [Means for solving the problem]

[0009] In order to achieve the above object, one embodiment of the present invention is a liquid ejection head comprising: an ejection port for ejecting liquid stored in a liquid chamber; an electrothermal conversion element for ejecting the liquid from the ejection port by generating heat; a first electrode for protecting the electrothermal conversion element and capable of being dissolved into the liquid by an electrochemical reaction with the liquid; and a second electrode provided so as to be electrically connectable to the first electrode via the liquid, wherein a voltage is applied to the first electrode to cause an electrochemical reaction with the second electrode, thereby dissolving the first electrode into the liquid; and wherein a voltage can be applied with polarity reversed between the first electrode and the second electrode, and the head is configured so as to be able to measure wiring resistance in a circuit in which a plurality of the second electrodes are part of wiring. The plurality of second electrodes are connected in series by wiring in the circuit. It is characterized by the fact that [Effects of the Invention]

[0010] According to the present invention, it is possible to appropriately detect the timing for replacing the liquid ejection head. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram illustrating the configuration of a recording apparatus as a liquid ejection apparatus. [Figure 2] FIG. 2 is a perspective view of the head unit. [Figure 3] FIG. 2 is a block diagram of a control system of the recording apparatus. [Figure 4] FIG. 2 is a schematic diagram of a recording head. [Figure 5] FIG. 2 is a diagram illustrating the detailed configuration of a recording head. [Figure 6] FIG. 2 is a cross-sectional view of the vicinity of a heat generating resistor element in a recording head. [Figure 7] FIG. 2 is a diagram illustrating a circuit for suppressing and removing kogation. [Figure 8] FIG. 10 is a diagram illustrating a circuit capable of detecting disappearance of an upper electrode and a counter electrode. [Figure 9] 10 is a flowchart showing detailed processing contents of a recording process. [Figure 10] 10A and 10B are diagrams showing modified examples of common wiring for each electrode. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, with reference to the accompanying drawings, an example of an embodiment of a liquid ejection head, a liquid ejection device, and a cleaning method will be described in detail. Note that the following embodiment does not limit the present invention, and not all of the combinations of features described in the embodiment are necessarily essential to the solution of the present invention. Furthermore, unless otherwise specified, the relative positions, shapes, and the like of the components described in the embodiment are merely examples, and are not intended to limit the scope of the present invention to only those.

[0013] (Configuration of recording device) First, the configuration of a liquid ejection device equipped with a liquid ejection head according to this embodiment will be described. In this specification, an inkjet recording device (hereinafter referred to as "recording device") that ejects ink onto a recording medium to record will be described as an example of the liquid ejection device. Therefore, in this recording device, the recording head that ejects ink to record corresponds to the liquid ejection head that ejects liquid. FIG. 1 is a schematic diagram showing the configuration of a recording device equipped with a recording head according to this embodiment, with a portion cut away. FIG. 2 is a perspective configuration diagram of a head unit. FIG. 3 is a block diagram showing the configuration of a control system of the recording device.

[0014] The recording device 10 includes a carriage 14 to which the head unit 12 can be detachably attached. The carriage 14 is attached to a belt 20 that is endlessly stretched between a drive pulley 16 and a driven pulley 18. The carriage 14 is also slidably mounted on a guide shaft 22 that is arranged parallel to the extension direction of the belt 20. When the drive pulley 16, which is driven by a carriage motor 24, rotates, the belt 20 rotates, and the carriage 14 moves in the direction of arrow X while being supported by the guide shaft 22. Therefore, the carriage 14 is configured to be able to move back and forth in the direction of arrow X depending on the rotation direction of the drive pulley 16.

[0015] The recording device 10 is equipped with an encoder sensor 26. The encoder sensor 26 detects slits in a linear scale 28 extending in the X direction. A control unit 52 (described later) of the recording device 10 detects the position of the carriage 14 in the X direction based on the detection result of the linear scale 28 by the encoder sensor 26.

[0016] The recording device 10 includes a pair of transport rollers 30 and 32. The pair of transport rollers 30 and 32 are rotated by a transport motor 70 (see FIG. 3) and transport the recording medium P in the direction of the arrow Y. The pair of transport rollers 30 is located upstream in the Y direction, which is the transport direction of the recording medium P, and the pair of transport rollers 32 is located downstream in the Y direction. The pair of transport rollers 30 and 32 are located in the Y direction so as to sandwich an area onto which ink is ejected by the head unit 12. The pair of transport rollers 30 and 32 nip and transport the recording medium P, thereby maintaining smoothness of the recording medium P at a position facing a recording head 42 (described later) of the head unit 12.

[0017] Then, in the recording device 10, the control unit 52 drives the carriage motor 24, while the recording head 42 of the head unit 12 performs a recording operation in which ink is ejected onto the recording medium P in accordance with the recording data based on the detection result of the encoder sensor 26. As a result, one band of image is recorded on the recording medium P. Thereafter, the control unit 52 drives the transport motor 70 to perform a transport operation in which the recording medium P is transported in the direction of arrow Y by a distance equivalent to one band. In this way, the recording device 10 forms a recorded image on the recording medium P by repeatedly alternately performing the recording operation and the transport operation.

[0018] The recording device 10 also has a recovery unit 34 at a home position located at one end in the X direction for performing maintenance on the recording head 42 of the head unit 12. The recovery unit 34 includes a cap member 36 for protecting the recording head 42, and a pump 38 for suctioning to generate negative pressure within the cap member 36.

[0019] Four head units 12 are arranged on the carriage 14, and each head unit 12 is configured to be able to eject cyan, magenta, yellow, and black ink. Each head unit 12 has a tank 40 that stores ink therein, and a recording head 42 for ejecting the ink stored in the tank (see FIG. 2). The head unit 12 also has a wiring tape 44 for supplying recording data, power, and the like to the recording head 42. This wiring tape 44 has contact points 46 formed on it for electrically connecting the head unit 12 to the main body of the recording device 10 when the head unit 12 is attached to the carriage 14.

[0020] In this embodiment, the recording device 10 uses a head unit 12 in which the tank 40 and the recording head 42 are integrated, but this is not limited to this. That is, the tank 40 and the recording head 42 may be separate. Specifically, a recording head is provided on the carriage 14, and ink is supplied to the recording head via a tube or the like from a tank detachably provided inside the recording device 10. In this case, a recording head may be provided for each color, or only one recording head capable of ejecting four inks may be provided. The number of inks used in the recording device 10 and the types of liquid ejected are not limited to those described above. That is, the number of inks may be only one color, or may be two, three, or five or more colors. Furthermore, the type of liquid may be a processing liquid other than ink that performs a predetermined process on the recording medium P or the like.

[0021] Next, the configuration of the control system of the recording device 10 will be described with reference to FIG. 3. The recording device 10 is connected to a separately provided host device 50 via an interface (I / F) 48. The recording device 10 transmits and receives various information to and from the host device 50 via this I / F 48. Specifically, the recording device 10 receives recording commands and image data from the host device 50 and transmits status information about the recording device 10 to the host device 50 via the I / F 48. The host device 50 can be a general-purpose personal computer or any known device such as a digital camera, scanner, or mobile terminal. When a recording command is issued by the host device 50, the recording command is input to the recording device 10 via the I / F 48 along with the image data.

[0022] The overall operation of the recording device 10 is controlled by a control unit 52. The control unit 52 includes an MPU 54, a ROM 56, a DRAM 58, an EEPROM 60, and a gate array (GA) 62. The EEPROM 60 is a memory for recording various information required for the recording device 10 when the power is turned on again, even if the power is turned off. The GA 62 also controls data transfer between the I / F 48 under the direction of the MPU 54.

[0023] The MPU 54 performs various processes using the DRAM 58 as a work area in accordance with the programs and parameters stored in the ROM 56. For example, the MPU 54 drives the carriage motor 24 via a CR motor driver 64 connected to the control unit 52 to move the carriage 14 in the X direction. During the recording operation, recording data is transferred from the DRAM 58 to the recording head 42 via a head driver 66 connected to the control unit 52, and one band of image is recorded by the recording head 42.

[0024] Furthermore, each time one band of image is recorded, the MPU 54 drives the conveying motor 70 via the LF motor driver 68 connected to the control unit 52, and conveys the recording medium P a predetermined distance in the Y direction using the pair of conveying rollers 30, 32. The image data received from the host device 50 is recorded on the recording medium P by alternately repeating the recording operation controlled by the carriage motor 24 and recording head 42 of the MPU 54 and the conveying operation controlled by the pair of conveying rollers 30, 32.

[0025] Furthermore, the MPU 54 drives a recovery motor 74 via a recovery motor driver 72 connected to the control unit 52, for example, after recording of one page of images has been completed, and executes suction recovery processing on the recording head 42. That is, the recovery motor 74 includes a motor that drives the pump 38 and a motor that, for example, raises and lowers the cap member 36.

[0026] Furthermore, the MPU 54 adjusts the potentials of the upper electrode 506 and the counter electrode 508 provided in the recording head 42 via the electric field regulator 76 connected to the control unit 52. Furthermore, the measurement unit 82 (measurement units 82-1 and 82-2 described below) measures the resistance value of a circuit in the head unit 12 (recording head 42) in which the plurality of upper electrodes 506 or the plurality of counter electrodes 508 form part of the wiring, and outputs the measurement result to the control unit 52. The upper electrode 506 and the counter electrode 508 will be described later.

[0027] The ROM 56 stores various parameters used by the MPU 54 to perform various controls, such as the shape of the voltage pulse applied to the heat generating resistor elements of the print head 42, the current value and timing applied to the upper electrode 506 and the opposing electrode 508, the transport speed of the print medium P, and the movement speed of the carriage 14.

[0028] (Recording head configuration) Next, the configuration of the printhead will be described. Fig. 4 is a schematic perspective view of the printhead according to this embodiment. Fig. 5(a) is a plan view schematically showing the configuration of the substrate. Fig. 5(b) is an enlarged view of frame Vb in Fig. 5(a). Fig. 10 shows modified circuit configurations of the frame Vb portion of Fig. 5(a), where (a) is a modified common wiring 514 and (b) is a modified common wiring 526.

[0029] The print head 42 includes a print head substrate (hereinafter also simply referred to as "substrate") 406 on which are formed ink supply paths 402 that supply ink to pressure chambers 418 (described later) and ink recovery paths 404 that recover ink from the pressure chambers 418. On one surface of this substrate 406, there is provided a flow path forming member 408 on which is formed an ejection port array with a plurality of ejection ports 412 for ejecting ink. In addition, on the other surface of the substrate 406 opposite to the one surface, there is formed a cover plate 410.

[0030] The ink supply path 402 and the ink recovery path 404 extend in the direction in which the ejection port array in the flow path forming member 408 extends. Furthermore, on one surface of the substrate 406, a plurality of supply ports 414 communicating with the ink supply path 402 are arranged in the direction in which the ejection port array extends. Furthermore, on one surface of the substrate 406, a plurality of recovery ports 416 communicating with the ink recovery path 404 are arranged in the direction in which the ejection port array extends.

[0031] On one surface of the substrate 406, a thermal application section 415 for causing bubbles in the ink with thermal energy is formed at a position corresponding to the ejection port 412. This thermal application section 415 includes a printing element (hereinafter also referred to as a "heating resistance element" or "electrothermal conversion element") 610 (see FIG. 6) for ejecting ink to perform printing, and an upper electrode 506 (described later) for protecting the heating resistance element 610. The thermal application section 415 is located inside a pressure chamber 418 formed in the flow path forming member 408.

[0032] Furthermore, on one surface of the substrate 406, terminals 420 are formed which are electrically connected to the heating resistor element 610 by electrical wiring (not shown) provided on the substrate 406. Therefore, the heating resistor element 610 generates heat based on a pulse signal input via an external wiring substrate (not shown), causing the ink in the pressure chamber 418 to boil. The bubbling force caused by this boiling causes the ink to be ejected from the ejection port 412.

[0033] The cover plate 410 is provided with an opening 422 that communicates with the ink supply path 402 and an opening (not shown) that communicates with the ink recovery path 404. Ink is supplied to the recording head 42 from this opening 422, and is recovered from the recording head 42 via an opening that communicates with the ink recovery path 404. Therefore, in the recording head 42, ink is supplied to the pressure chamber 418 through the opening 422, the ink supply path 402, and the supply port 414. In addition, the ink supplied to the pressure chamber 418 is recovered through the recovery port 416, the ink recovery path 404, and an opening that communicates with the ink recovery path 404.

[0034] The flow path forming member 408, together with the substrate 406, forms a liquid chamber 502 (see FIG. 5(b)), which includes a pressure chamber 418 and is a space for storing ink. Within this liquid chamber (inside the liquid chamber 502), an upper electrode 506 is provided in the heat application section 415 so as to cover the heating resistor element 610. The upper electrode 506 is formed of a material that can be dissolved into ink by an electrochemical reaction. In this manner, the upper electrode 506 is provided above the heating resistor element on the side of the substrate 406 that comes into contact with the ink. Furthermore, a counter electrode 508 (second electrode) is provided in the liquid chamber 502 in correspondence with the upper electrode 506 (first electrode). Note that this counter electrode 508 is an electrode that causes an electrochemical reaction between the upper electrode 506 and the ink, thereby dissolving the upper electrode 506 into the ink. Note that the counter electrode 508 is formed, for example, using the same material as the upper electrode 506.

[0035] Although details will be described later, the upper electrode 506 is connected to a terminal 516 (see FIG. 8) via a common wiring 514 for the upper electrode, and an external potential is applied via the terminal 516. In addition, the counter electrode 508 is connected to a terminal 528 (see FIG. 8) via a common wiring 526 for the counter electrode, and an external potential is applied via the terminal 528. This allows a voltage to be applied to the upper electrode 506 and the counter electrode 508 via the ink in the liquid chamber 502.

[0036] The upper electrode 506 and the counter electrode 508 are made of a conductive material. As will be described in detail later, the layer of the protective layer 616 (see FIG. 6) that protects the heating resistor element 610 and that is exposed to the ink functions as the upper electrode 506. The upper electrode 506 and the counter electrode 508 may have the same area in contact with the ink, or the counter electrode 508 may have a smaller area. The upper electrodes 506 and the counter electrodes 508 may be provided in the same number, or the counter electrodes 508 may have a smaller number. In recent years, with the trend toward higher image quality in printing, the area of ​​the liquid chamber 502 has become smaller, and the space available for arranging the counter electrode 508 has also become smaller. For this reason, the area of ​​the counter electrode 508 tends to become smaller.

[0037] Furthermore, as will be described in detail later, the common wiring 514 connecting the upper electrodes 506 forms a circuit 802 (described later) together with a terminal 516, the plurality of upper electrodes 506, and a terminal 520. In the circuit 802 (see FIG. 8), the terminal 520 is disposed on the opposite side of the common wiring 514 to which the upper electrodes 506 are connected from the terminal 516, that is, disposed on the common wiring 514 so as to sandwich the plurality of upper electrodes 506 between the terminal 516 and the common wiring 514. Furthermore, on the substrate 406, the common wiring 514 is connected to the individual wirings 512 connected to the two upper electrodes 506 via fuse portions 513, as shown in FIG. 5(b), for example. The circuit 802 is capable of measuring wiring resistance (see FIG. 8). Specifically, the circuit 802 is provided with a measuring unit 82-1 capable of measuring wiring resistance (see FIG. 8). 5(b), the circuit 802 includes a terminal 516, a terminal 520, a common wiring 514, a fuse portion 513, individual wiring 512, a plurality of upper electrodes 506, and a measuring portion 82-1. Note that the connection between the common wiring 514 and the upper electrode 506 is not limited to the form shown in FIG. 5(b). Specifically, as shown in FIG. 10(a), the common wiring 514 may be configured to connect a plurality of upper electrodes 506 in series.

[0038] Furthermore, the common wiring 526 connecting the counter electrodes 508 forms a circuit 806 (described later) together with the terminal 528, the terminal 532, and the plurality of counter electrodes 508. In FIG. 806 (see FIG. 8), the terminal 532 is disposed on the opposite side of the common wiring 526 from the terminal 528, i.e., the common wiring 526 is disposed so as to sandwich the plurality of counter electrodes 508 between itself and the terminal 528. On the substrate 406, the common wiring 526 connects the plurality of counter electrodes 508 in series, as shown in FIG. 5(b), for example. The circuit 806 is also configured to be capable of measuring wiring resistance. Specifically, the circuit 806 includes a measuring unit 82-2 capable of measuring wiring resistance (see FIG. 8). Therefore, in FIG. 5(b), the circuit 806 includes the terminal 538, the terminal 532, the common wiring 526, the plurality of counter electrodes 508, and the measuring unit 82-2. The connection between the common wiring 526 and the counter electrodes 508 is not limited to the form shown in Fig. 5(b). Specifically, as shown in Fig. 10(b), each counter electrode 508 may be connected to the common wiring 526 via an individual wiring 524.

[0039] <Configuration of upper electrode and counter electrode> Next, the laminated structure of the heat-generating resistor element, upper electrode, and counter electrode on the substrate will be described. Figure 6 is a cross-sectional view of a recording head on which a flow path-forming member is formed, taken at a position corresponding to line VI-VI in Figure 5(a). For ease of understanding, wiring is omitted, but the heat-generating resistor element, upper electrode, and counter electrode provided on the substrate are each electrically connected to wiring for obtaining the power required for heating, kogation suppression, and cleaning processes for kogation removal.

[0040] The substrate 406, on which the driving elements (not shown) and the wiring (not shown) for driving the driving elements are formed, has an insulating layer 604 made of SiO provided on the upper surface of a silicon base material (hereinafter also simply referred to as "base material") 602. Also, a first wiring pattern 606 made of an alloy of aluminum and copper is provided on the upper surface of the insulating layer 604. This first wiring pattern 606 is wiring for supplying voltage to the heating resistor elements 610.

[0041] The first wiring pattern 606 is covered with an insulating layer 608 made of SiO or the like. This insulating layer 608 is provided with plugs 612 for connecting the first wiring pattern 606 and the heating resistor elements 610. The plugs 612 may be made of tungsten or the like. The upper surface of the insulating layer 608 is planarized using a method such as CMP (Chemical Mechanical Polishing).

[0042] A heating resistor element 610 is provided on the upper surface of the insulating layer 608. The heating resistor element 610 includes a heating resistor layer made of TaSiN or the like. A plug 612 is connected to this heating resistor layer. The portion of the heating resistor layer through which current flows via the plug 612 functions as the heating resistor element 610. A second wiring pattern (not shown) made of an aluminum-copper alloy or the like is provided on the upper surface of the insulating layer 608. The second wiring pattern can be used to supply voltage to the upper electrode 506 and the counter electrode 508.

[0043] The heating resistor element 610 and the second wiring pattern are covered with a 20-nm-thick insulating layer 614 made of, for example, SiN. A protective layer 616 is provided on the upper surface of the insulating layer 614. The protective layer 616 has a two-layer structure, for example, formed by stacking a 30-nm iridium (Ir) layer (the open layer in the figure) and a 60-nm tantalum (Ta) layer (the hatched layer in the figure) in this order from the insulating layer 614 side. In the portion of the protective layer 616 covering the region where the heating resistor element 610 is located, the upper tantalum layer is removed, exposing the iridium layer within the pressure chamber 418. This exposed iridium layer functions as the upper electrode 506. The heating resistor element 610 and the protective layer 616 are electrically insulated by the insulating layer 614.

[0044] Furthermore, individual wiring 512 and common wiring 514 are provided on the upper surface of insulating layer 614. Individual wiring 512 and common wiring 514 may be formed in the same layer using the same material as protective layer 616. In this embodiment, fuse portion 513 is provided between individual wiring 512 and common wiring 514, but this configuration is not necessarily required. In this embodiment, fuse portion 513 is formed in the same layer using the same material as individual wiring 512 and common wiring 514.

[0045] Furthermore, a counter electrode 508 is provided on the upper surface of the insulating layer 614 at a distance from the upper electrode 506 in a direction intersecting the arrangement direction of the upper electrodes 506. The counter electrode 508 is formed by laminating a 30-nm iridium layer and a 60-nm tantalum layer, similar to the upper electrode 506, and is formed by removing a portion of the upper tantalum layer to expose the iridium layer inside the pressure chamber 418. In this embodiment, the counter electrode 508 is formed in the same layer as the upper electrode 506. Although not shown in FIG. 6 , the common wiring 526 is also formed in the same layer as the upper electrode 506, the individual wiring 512, and the common wiring 514. The common wiring 514 and the common wiring 526 have the same configuration as the protective layer 616. However, by opening the insulating layer 614 and connecting it to a second wiring pattern, the common wiring 514 and the common wiring 526 can also be routed using the second wiring pattern.

[0046] The upper electrode 506 is an electrode that is laminated so as to cover the heating resistor element 610 via an insulating layer 614. The upper electrode 506 functions as a negative electrode during printing, mainly to repel anions in the ink. The upper electrode 506 also functions to protect the heating resistor element 610 from physical and chemical shocks, and has thermal conductivity that instantly transfers heat generated by the heating resistor element 610 to the ink. The upper electrode 506 is made of a material that does not form, or is difficult to form, a strong oxide film when overheated to about 700°C.

[0047] In this embodiment, the upper electrode 506 is set to a state in which the potential is relatively high with respect to the counter electrode 508, thereby dissolving the upper electrode 506 into the ink and removing kogation that originates from the ink and adheres to the upper electrode 506. Whether or not metal is eluted by an electrochemical reaction can generally be determined from the potential-pH diagram of various metals.

[0048] The counter electrode 508 functions as a positive electrode during printing in order to repel anions in the ink away from the upper electrode 506. When performing a cleaning process to remove kogation that has formed on the upper electrode 506, a current is passed from the upper electrode 506 to the counter electrode 508 via the ink, thereby continuing the reaction that dissolves the upper electrode 506 into the ink. For this reason, it is preferable to use a material for the counter electrode 508 that has low conductivity and is unlikely to form an oxide film, in order to maintain a stable current value between the counter electrode 508 and the upper electrode 506. In this specification, unless otherwise specified, the removal of kogation that has formed on the upper electrode 506 is referred to as "cleaning."

[0049] Furthermore, when removing kogation from the upper electrode 506, i.e., during cleaning, the polarities of the upper electrode 506 and the counter electrode 508 are reversed. This makes it possible to release negatively charged particles that have adhered to or been attracted to the upper electrode 506 during kogation removal back into the ink, enabling kogation to be efficiently removed from the upper electrode 506. In this case, there is a concern that the counter electrode 508 itself may dissolve into the ink due to an anodic oxidation reaction, just as with the upper electrode 506. However, even if the film thickness of the counter electrode 508 gradually decreases with repeated cleanings, this does not pose a problem as long as its original function is not impaired.

[0050] <Circuit configuration> Next, we will explain the circuit configuration including the upper electrode 506 and the counter electrode 508. In this embodiment, the print head 42 is equipped with a circuit for suppressing the occurrence of kogation on the upper electrode 506 and for removing kogation that has occurred on the upper electrode 506, and a circuit for detecting the disappearance of the upper electrode 506 and the counter electrode 508.

[0051] = Circuit for removing burnt food = First, a circuit for suppressing the occurrence of kogation on the upper electrode 506 and removing kogation formed on the upper electrode 506 will be described. Fig. 7 is a diagram showing the configuration of a circuit for suppressing the occurrence of kogation on the upper electrode and removing kogation formed on the upper electrode. Note that in Fig. 7, some components of the substrate 406 are omitted for ease of understanding.

[0052] The upper electrode 506 and the counter electrode 508 can be electrically connected by a first circuit 706 that passes through a constant-voltage power supply 702 and a switch 704. In the first circuit 706, a closed circuit electrically connected by the ink in the liquid chamber 502 is formed. The first circuit 706 prevents kogation of the upper electrode 506 during printing. For example, the upper electrode 506, the counter electrode 508, and part of the first circuit 706 are provided in the print head 42, while the remaining first circuit 706, the switch 704, and the constant-voltage power supply 702 are provided outside the print head 42. The switch 704 may be provided in the print head 42.

[0053] In the first circuit 706, when the switch 704 is closed, the upper electrode 506 becomes a cathode and the counter electrode 508 becomes an anode. As a result, the anions and negative colloidal particles in the ink in the liquid chamber 502 move away from the upper electrode 506 and toward the counter electrode 508. With such an electric field formed, even if the heating resistor element 610 suddenly generates heat or even if such heat generation is repeated, ink components are less likely to adhere to the upper electrode 506, thereby suppressing the occurrence of kogation.

[0054] Furthermore, the upper electrode 506 and the counter electrode 508 can be electrically connected by a second circuit 712 that passes through a power source 708 and a switch 710. Note that this second circuit 712 forms a closed circuit electrically connected by the ink in the liquid chamber 502. This second circuit 712 removes kogation that has adhered to the upper electrode 506. For example, the upper electrode 506, the counter electrode 508, and part of the second circuit 712 are provided in the print head 42, while the remaining second circuit 712, switch 710, and power source 708 are provided outside the print head 42. Note that the switch 710 may be provided in the print head 42.

[0055] Specifically, when the switch 710 in the second circuit 712 is closed to side a as shown in FIG. 7, a current flows from the upper electrode 506 to the counter electrode 508 via the ink in the liquid chamber 502. This causes the upper electrode 506 to dissolve into the ink, and kogation adhering to the upper electrode 506 is removed. In this embodiment, when the printhead 42 is performing a printing operation, the control unit 52 closes the switch 704 in the circuit 706 and opens the switch 710 in the circuit 712 as a kogation prevention mode. As a result, even when ink components are heated by the heating resistor element 610, they do not adhere to the upper electrode 506 but are directed toward the counter electrode 508, thereby suppressing the occurrence of kogation. Furthermore, when the printhead 42 ejects ink a predetermined number of times and a film of anions is formed on the counter electrode 508, the control unit 52 determines that cleaning of the upper electrode 506 is necessary. Then, at an appropriate timing when no recording operation is being performed, the control unit 52 performs a cleaning process by opening the switch 704 in the circuit 706 and closing the switch 710 in the circuit 712 to the side a. This causes a current to flow from the upper electrode 506 to the counter electrode 508, and the kogation adhering to the upper electrode 506 is removed.

[0056] During the cleaning process to remove kogation, the control unit 52 may appropriately or periodically switch the switch 710 between side a and side b to reverse or repeatedly reverse the polarities of the upper electrode 506 and the counter electrode 508. This makes it possible to suppress adhesion of negatively charged particles to both the upper electrode 506 and the counter electrode 508.

[0057] When the upper electrode 506 and the counter electrode 508 differ in area or number, the control unit 52 adjusts the pulse width when reversing the polarity. Specifically, the control unit 52 adjusts the pulse width in accordance with the total area ratio between the upper electrode 506 and the counter electrode 508 so that the amounts of iridium layer eluted from the upper electrode 506 and the counter electrode 508 are equal. For example, as shown in FIG. 5( b), when the total area of ​​the counter electrode 508 is smaller than the total area of ​​the upper electrode 506, the control unit 52 adjusts the pulse width so that the remaining amount of iridium layer on the counter electrode 508 matches the remaining amount of iridium layer on the upper electrode 506. This makes it possible to avoid situations where an electric field for kogation suppression is not generated during recording, resulting in insufficient kogation suppression, or where no current flows during kogation removal, leaving kogation behind.

[0058] =Circuit for detecting electrode loss= Next, a circuit configuration for detecting the disappearance of the upper electrode 506 and the counter electrode 508 will be described. Fig. 8 is a diagram showing the configuration of a circuit capable of detecting the disappearance of the upper electrode and the counter electrode. Note that in Fig. 8, for ease of understanding, some components of the substrate 406 are omitted.

[0059] When the upper electrode 506 dissolves and disappears due to cleaning, it becomes impossible to stably generate the electric field necessary for suppressing kogation and cleaning. For this reason, it is necessary to detect the timing of the disappearance of the upper electrode 506. The recording head 42 is provided with a circuit 802 for detecting the timing of the disappearance of the upper electrode 506.

[0060] The multiple upper electrodes 506 function as part of the wiring, and together with the terminal 516, the terminal 520, and the common wiring 514 (including the individual wiring 512 and the fuse portion 513), form a third circuit 802. A switch 804 is provided in this third circuit 802, and a closed circuit is formed by closing the switch 804 to the d side. In addition, the third circuit 802 is provided, between the terminal 516 and the terminal 520, with the switch 804 and a measuring unit 82-1 capable of measuring the wiring resistance.

[0061] As the number of cleaning operations increases, the amount of elution of the upper electrode 506 increases, and when the upper electrode 506 disappears, the control unit 52 determines from the measurement results of the measurement unit 82-1 that a portion of the third circuit 802 has become disconnected, that is, has become open. That is, the control unit 52 can detect the timing at which the upper electrode 506 disappeared, according to the measurement results of the measurement unit 82-1.

[0062] On the other hand, when the counter electrode 508 dissolves due to the voltage reversal caused by cleaning and disappears, it becomes impossible to stably form the electric field necessary for suppressing kogation and cleaning. Therefore, it is also necessary to detect the timing of the disappearance of the counter electrode 508. The recording head 42 is provided with a circuit 806 for detecting the timing of the disappearance of the counter electrode 508.

[0063] The multiple counter electrodes 508 function as part of the wiring and form a fourth circuit 806 together with a terminal 528, a terminal 532, and a common wiring 526. A switch 808 is provided in this fourth circuit 806, and a closed circuit is formed by closing the switch 808 to the f side. In addition, the fourth circuit 806 is provided with a measuring unit 82-2 between the terminal 528 and the terminal 532, together with the switch 808, that is capable of measuring the wiring resistance.

[0064] As the number of cleaning operations increases, the amount of elution of counter electrode 508 increases, and when counter electrode 508 disappears, control unit 52 determines from the measurement results of measurement unit 82-2 that a portion of fourth circuit 806 has been interrupted, that is, an open state has occurred. That is, control unit 52 can detect the timing at which counter electrode 508 disappeared, according to the measurement results of measurement unit 82-2.

[0065] The voltage application conditions during cleaning are set so that dissolution occurs almost uniformly in the area where the ink and the electrode material come into contact. Therefore, the timing of disappearance within the electrode surface is almost simultaneous, which can be detected as an increase in resistance value. In this way, in this embodiment, the control unit 52 functions as a detection unit that can detect the degree of dissolution of the upper electrode 506 and the counter electrode 508 into the ink based on the results of measurement by the measurement unit.

[0066] The power supply 708 and switch 710 used during the cleaning process are connectable to the upper electrode 506 via a switch 804. The power supply 708 and switch 710 are also connectable to the counter electrode 508 via a switch 80. During the cleaning process, the switch 710 is closed to side a, the switch 804 is closed to side c, and the switch 808 is closed to side e. As described above, the switch 710 is switched between side a and side b as needed or periodically. In this embodiment, the measuring unit 82 (measuring units 82-1 and 82-2) and the switches 804 and 808 serving as measuring means are configured to be external to the printhead 42. However, at least some of these components may be provided inside the printhead 42. That is, in the printhead 42, the circuits 802 and 806 only need to be configured to measure the wiring resistance, and some of the components constituting the circuits 802 and 806 may be provided external to the printhead 42.

[0067] Furthermore, the circuits 802 and 806 may include, for example, all electrodes (upper electrode, counter electrode) connected by a common wiring between two terminals. In this case, the wiring resistance including all electrodes is measured, and if even one electrode disappears, the head replacement is prompted. Note that, for example, if the amount of elution varies greatly depending on the electrode arrangement position, the common wiring may be routed so that any two arbitrary locations on the common wiring to which multiple electrodes are connected in a location where the amount of elution is large can be connected to a terminal. Alternatively, by changing the lead-out position (terminal connection position), that is, by changing the multiple electrodes included in the circuit and routing the wiring so that the wiring resistance can be measured, the location where the electrode disappeared can be identified from the difference in resistance values. In this case, by controlling so that ink is not ejected from the identified location during printing, it is possible to suppress degradation of print quality.

[0068] In the above description, the upper electrode 506 and the counter electrode 508 have a two-layer structure in which an iridium (Ir) layer and a tantalum (Ta) layer are stacked, but this is not limiting. In other words, by forming an adhesion layer (e.g., a tantalum layer) below the iridium layer, the adhesion between the substrate and the iridium layer can be improved. The presence of an adhesion layer is more effective in recording heads designed for high durability, where the iridium layer is thick and tends to be subject to large stresses.

[0069] When an adhesive layer is provided, the tantalum used in the adhesive layer is a conductor, so even if the electrode layer disappears, a current will flow through the tantalum in the adhesive layer, raising the concern that the disappearance of the electrode layer may be overlooked. However, once the electrode layer disappears, the tantalum in the adhesive layer comes into contact with the ink and acts as an anode when a cleaning voltage is applied. Therefore, the oxidation of the tantalum in the adhesive layer progresses rapidly, and it no longer interferes with detecting the disappearance of the electrode layer.

[0070] Furthermore, the control unit 52 may monitor whether elution is occurring as expected during the cleaning process, and may predict when the upper electrode 506 and the counter electrode 508 will disappear. In this case, in order to accurately measure the resistance change due to a decrease in the film thickness of the upper electrode 506 and the counter electrode 508, it is preferable to make the common wiring 514 (including the individual wiring 512 and the fuse portion 513) and the common wiring 526 as low as possible. Specifically, for example, the resistance can be reduced by using the first wiring pattern 606 and the second wiring pattern. This makes it possible to more accurately detect the degree of elution of the upper electrode 506 and the counter electrode 508, such as their disappearance due to elution into the ink, the amount remaining after elution, and the amount of elution.

[0071] In this embodiment, the print head 42 includes a circuit 802 that detects the disappearance of the upper electrode 506 and a circuit 806 that detects the disappearance of the counter electrode 508, but this is not limiting. When either the upper electrode 506 or the counter electrode 508 disappears, the kogation suppression and removal effects are lost. Therefore, the above-described circuit may be formed for either the upper electrode 506 or the counter electrode 508, whichever electrode disappears first. For example, if the total area of ​​the counter electrodes 508 is smaller than the total area of ​​the upper electrodes 506, the counter electrodes 508 will disappear before the upper electrodes 506. In this case, therefore, it is sufficient to provide only the fourth circuit 806 without providing the third circuit 802.

[0072] (Recording Processing) In the recording device 10 described above, when a recording command is input from the host device 50 or the like, a recording process is executed. FIG. 9 is a flowchart showing the detailed processing contents of the recording process. The series of processes shown in the flowchart in FIG. 9 are performed by the control unit 52, in which the MPU 54 loads program code stored in the ROM 56 into the DRAM 58 and executes it. Alternatively, some or all of the functions of the steps in FIG. 9 may be executed by hardware such as an ASIC or an electric circuit. Note that the symbol S in the description of each process indicates a step in the flowchart.

[0073] When the recording process is started, first, the MPU 54 loads image data input from the host device 50 or the like via the I / F 48 into the DRAM 58 via the GA 62, and generates recording data for controlling whether or not to eject ink from the recording head 42 (S902). Next, the MPU 54 applies a voltage for suppressing kogation (S904). That is, in S904, the switch 704 is closed and the switch 710 is opened via the electric field regulator 76, and a voltage is applied from the constant-voltage power supply 702 with the upper electrode 506 as the cathode and the counter electrode 508 as the anode.

[0074] Thereafter, the MPU 54 performs a printing operation (and a transport operation) based on the print data, and starts counting the number of times C ink is ejected from the print head 42 during the printing operation (S906). At a timing such as when a predetermined amount of printing operation is completed, the MPU 54 reads out the cumulative number of ejections S stored in the DRAM 58 (S908). The cumulative number of ejections S is the total number of times ink has been ejected from the print head 42. The cumulative number of ejections S is initialized when the print head 42 is replaced. Then, the cumulative number of ejections S and the number of ejections C counted during the printing operation are added together to obtain the total number of ejections Sn (S910). Note that in S910, the MPU 54 also updates the value of the cumulative number of ejections S stored in the DRAM 58 to the value of the total number of ejections Sn.

[0075] Next, the MPU 54 determines whether the total number of ejections Sn in S910 is equal to or greater than a pre-stored threshold value T (S912). This threshold value T is, for example, the upper limit of the number of ejections at which ink ejection in the print head 42 does not become unstable due to kogation adhering to the upper electrode 506, or a value that is a predetermined value smaller than the upper limit. Such threshold value T is determined experimentally depending on, for example, the type of ink used.

[0076] If it is determined in S912 that the total number of ejections Sn is not equal to or greater than the threshold value T, the process proceeds to S922, which will be described later. If it is determined in S912 that the total number of ejections Sn is equal to or greater than the threshold value T, the MPU 54 executes a suction recovery process (S914). That is, in S914, the MPU 54 drives the carriage motor 24 via the CR motor driver 64 to move the carriage 14 to the home position. Then, the MPU 54 drives the recovery motor 74 via the recovery motor driver 72 to bring the cap member 36 into contact with the print head 42, and reduces the pressure inside the cap member 36 using the pump 38 to forcibly expel ink from the ejection ports 412.

[0077] Furthermore, the MPU 54 performs a cleaning process while the suction recovery process is being performed (S916). That is, in S916, the MPU 54 first opens the switch 704 via the electric field regulator 76, closes the switch 710 to side a, and maintains this state for a predetermined time. As a result, a current flows from the upper electrode 506 to the counter electrode 508 via the ink in the liquid chamber 502. As a result, the upper electrode 506 dissolves into the ink at a constant speed, and kogation that has formed on the upper electrode 506 is removed. Note that in S916, the switch 710 may be switched between side a and side b at regular intervals to invert the polarities of the upper electrode 506 and the counter electrode 508.

[0078] The suction recovery process and cleaning process remove the kogation that has formed on the upper electrode 506. The suction recovery process that is performed during the cleaning process makes it possible to discharge the ink containing the kogation that has been removed from the upper electrode 506, and to supply new ink into the liquid chamber 502. The suction recovery process ends when the cleaning process ends.

[0079] After the cleaning process is completed, the wiring resistances in the third circuit 802 and the fourth circuit 806 are measured (S918). That is, in S918, the MPU 54 closes the switch 804 to the d side in the third circuit 802 via the electric field regulator 76, and the wiring resistance is measured by the measuring unit 82-1. Also, in the fourth circuit 806, the switch 808 is closed to the f side, and the wiring resistance is measured by the measuring unit 82-2.

[0080] Then, it is determined whether the resistance value R obtained in S918 is equal to or less than a threshold value Rt (S920). The threshold value Rt is, for example, the lower limit of the resistance value at which it can be determined that the electrodes (upper electrode 506, counter electrode 508) in the circuit have not disappeared, or a value that is smaller than the lower limit by a predetermined value. Such a threshold value Rt is determined experimentally depending on, for example, the type of ink used. In other words, in S920, it is determined whether or not kogation on the upper electrode 506 can be removed.

[0081] If it is determined in S920 that the resistance value R is equal to or less than the threshold value Rt, it is determined again whether or not to perform recording (S922), and if it is determined that recording is to be performed, the process returns to S902, and if it is determined that recording is not to be performed, the recording process ends. That is, if the resistance value R is equal to or less than the threshold value Rt, the MPU 54 determines that the upper electrode 506 and the counter electrode 508 remain with a film thickness that will not cause them to lose their function, and it becomes possible to perform subsequent recording.

[0082] Furthermore, if it is determined in S920 that the resistance value R is not equal to or less than the threshold value Rt, the MPU 54 issues a notification urging the user to replace the print head 42 (S924) and terminates the recording process. That is, if the resistance value R is not equal to or less than the threshold value Rt, i.e., exceeds the threshold value Rt, the MPU 54 determines that the upper electrode 506 and the counter electrode 508 have been lost to the extent that they have lost their function, i.e., the kogation removal function has been lost, and issues a notification urging the user to replace the print head 42. Thus, in this embodiment, the control unit 52 functions as a notification unit that determines the timing for replacing the print head 42 based on, for example, the degree of electrode elution into the ink detected based on the resistance value measured by the measurement unit 82 (detection result), and issues a notification urging the user to replace the print head 42. The control unit 52 may also determine the timing and urge the user to replace the print head 42 based on the resistance value measured by the measurement unit 82.

[0083] In this embodiment, in S920, the resistance value R1 measured by the measuring unit 82-1 and the resistance value R2 measured by the measuring unit 82-2 are each compared with a threshold value Rt. Then, when it is determined that at least one of the resistance values ​​R1 and R2 is equal to or less than the threshold value Rt, the process proceeds to S924. Note that the notification method in S924 can be various known techniques, such as displaying the result on a display unit (not shown) of the host device 50 or the recording device 10.

[0084] The threshold value Rt may be two different threshold values: a threshold value Rt1 that is compared with the resistance value R1 of the third circuit 802 including the upper electrode 506, and a threshold value Rt2 that is compared with the resistance value R2 of the fourth circuit 806 including the counter electrode 508. Because the print head 42 can be used even if the counter electrode 508 disappears, the threshold value Rt2 on the counter electrode 508 side can be set to a value that causes the counter electrode 508 to open. On the other hand, the upper electrode 506 needs to remain to some extent to protect the heating resistor element 610 from cavitation and ink. For this reason, the threshold value Rt1 on the upper electrode 506 side can be set to a value that can detect the minimum remaining amount necessary to maintain the above function.

[0085] As described above, in this embodiment, the print head 42 is formed with a third circuit 802 that protects the heating resistor elements 610 and includes the upper electrode 506 to which kogation due to ink adheres, making it possible to measure the wiring resistance in the third circuit 802. In addition, a fourth circuit 806 is formed with a counter electrode 508 that suppresses the adhesion of kogation to the upper electrode 506, making it possible to measure the wiring resistance in the fourth circuit 806.

[0086] This makes it possible to detect the timing when the recording head 42 loses its function, such as when the upper electrode 506 or the counter electrode 508 disappears. This makes it possible to properly detect the timing for replacing the recording head, and to replace the recording head 42 at a more appropriate time. This makes it possible to reduce the cost required for replacing the recording head 42.

[0087] (Verification experiment) Next, a description will be given of a verification experiment conducted by the inventors of the present application to confirm the effects of this embodiment. The recording device 10 used in the verification experiment has a configuration in which the tank 40 is detachable in the head unit 12 and the recording head 42 is fixedly mounted on the carriage 14. Furthermore, a pigment cyan ink was used as the ink.

[0088] <Verification example 1> = Recording head configuration = In Verification Example 1, a 30 nm iridium layer was formed as a protective layer 616 on an insulating layer 614 of a substrate 406, followed by patterning. A 60 nm tantalum layer was then formed on the iridium layer and patterned. Using the protective layer 616 thus formed, upper electrodes 506, counter electrodes 508, common wiring 514 connecting all of the upper electrodes 506 in series, and common wiring 526 were formed on the substrate 406, as shown in FIG. 5(c). One end of the common wiring 514 was connected to a terminal 516, and the other end was connected to a terminal 520. The total area of ​​the multiple upper electrodes 506 and the total area of ​​the multiple counter electrodes 508 were set to be approximately equal.

[0089] Then, a flow path forming member 408 was formed on a substrate 406, and other necessary terminals and the like were formed to fabricate a recording head 42. Therefore, in Verification Example 1, both ends of the common wiring 514 were taken out at terminals 516 and 520, and in the third circuit 802 in which all of the upper electrodes 506 are part of the wiring, the wiring resistance can be measured by measuring unit 82-1. In other words, in this Verification Example 1, a fourth circuit 806 was not formed.

[0090] =Cleaning process= First, in order to deposit kogation on the upper electrode 506, a voltage of 1 V is applied between the upper electrode 506 and the counter electrode 508 in the second circuit 712 so that the counter electrode 508 becomes an anode. In this state, a voltage of (1×10 9 ) ejection operations were performed. During the ejection operations, the temperature of the recording head 42 was adjusted to 50°C. After the ejection operations were completed, the ink in the liquid chamber 502 was replaced with clear ink, and the surface condition of the upper electrode 506 was observed. As a result, it was confirmed that kogation had adhered to the upper electrode 506.

[0091] Next, the ink in the liquid chamber 502 was replaced with pigment cyan ink, and then a cleaning process was performed while a suction recovery process was performed on the recording head 42. Specifically, the cleaning process involved applying a voltage of 5 V between the upper electrode 506 and the opposing electrode 508 in the second circuit 712 for 60 seconds, with the polarity being reversed every second.

[0092] Thereafter, the switch 804 was closed, and the wiring resistance of the third circuit 802 was measured by the measuring unit 82-1. As a result, it was confirmed that the obtained resistance value R was equal to or less than the threshold value Rt. Furthermore, after the cleaning process, the ink in the liquid chamber 502 was replaced with clear ink, and the surface condition of the upper electrode 506 was observed. As a result, it was confirmed that the kogation that had adhered to the upper electrode 506 had been removed.

[0093] Then, the tank 40 was replaced and a new tank 40 was set, and the above-mentioned discharge operation was used to deposit kogation on the upper electrode 506, followed by the above-mentioned cleaning process accompanied by suction recovery. This series of processes was performed a total of 14 times. After the 14th process, observation confirmed that the kogation had been removed from the surface of the upper electrode 506 after the cleaning process. When the tank 40 was replaced after the 14th process and recording was performed, the recording quality was approximately the same as when recording was performed with the tank 40 initially set. Furthermore, it was confirmed that the resistance value R of the wiring resistance of the third circuit 802 after the 14th process was equal to or less than the threshold value Rt, and it was determined that the wiring was not broken.

[0094] Next, the above process was performed once more, for a total of 15 times. After the 15th process, the wiring resistance of the third circuit 802 was confirmed to have a resistance value R exceeding the threshold value Rt, and it was determined that the wiring was broken. After that, the ink in the liquid chamber 502 was replaced with clear ink, and all of the upper electrodes 506 were observed, and they had disappeared. Specifically, the iridium layer on the upper electrodes 506 had disappeared, exposing the underlying insulating layer 614.

[0095] <Verification example 2> = Recording head configuration = In Verification Example 2, a 30 nm iridium layer was formed as a protective layer 616 on an insulating layer 614 of a substrate 406, followed by patterning. A 60 nm tantalum layer was then formed and patterned on the iridium layer. The thus-formed protective layer 616 formed the upper electrode 506, the counter electrode 508, the common wiring 514, and a common wiring 526 connecting all of the counter electrodes 508 to the substrate 406. One end of the common wiring 526 was connected to a terminal 528, and the other end to a terminal 532. Note that one counter electrode 508 was formed for every two upper electrodes 506. The ratio of the total area of ​​the upper electrodes 506 to the total area of ​​the counter electrodes 508 was set to 2:1.

[0096] Then, a flow path forming member 408 was formed on a substrate 406, and other necessary terminals and the like were formed to fabricate a recording head 42. Therefore, in Verification Example 2, both ends of the common wiring 526 were taken out at terminals 528 and 532, and in a fourth circuit 806 in which all of the opposing electrodes 508 are part of the wiring, the wiring resistance can be measured by measuring unit 82-2. In other words, in this Verification Example 2, a third circuit 802 was not formed.

[0097] =Cleaning process= First, in order to deposit kogation on the upper electrode 506, a voltage of 1 V is applied between the upper electrode 506 and the counter electrode 508 in the second circuit 712 so that the counter electrode 508 becomes an anode. In this state, a voltage of (1×10 9 ) ejection operations were performed. During the ejection operations, the temperature of the recording head 42 was adjusted to 50°C. After the ejection operations were completed, the ink in the liquid chamber 502 was replaced with clear ink, and the surface condition of the upper electrode 506 was observed. As a result, it was confirmed that kogation had adhered to the upper electrode 506.

[0098] Next, the ink in the liquid chamber 502 was replaced with pigment cyan ink, and then a cleaning process was performed while a suction recovery process was performed on the recording head 42. Specifically, the cleaning process involved applying a voltage of 5 V between the upper electrode 506 and the opposing electrode 508 in the second circuit 712 for 60 seconds, with the polarity being reversed every second.

[0099] Thereafter, the switch 808 was closed, and the wiring resistance of the fourth circuit 806 was measured by the measuring unit 82-2. As a result, it was confirmed that the obtained resistance value R was equal to or less than the threshold value Rt. Furthermore, after the cleaning process, the ink in the liquid chamber 502 was replaced with clear ink, and the surface condition of the upper electrode 506 was observed. As a result, it was confirmed that the kogation that had adhered to the upper electrode 506 had been removed.

[0100] Then, the tank 40 was replaced and a new tank 40 was set, and the above-mentioned discharge operation was used to deposit kogation on the upper electrode 506, followed by the above-mentioned cleaning process accompanied by suction recovery. This series of processes was performed a total of seven times. After the seventh process, observation confirmed that the kogation had been removed from the surface of the upper electrode 506 after the cleaning process. When the tank 40 was replaced after the seventh process and recording was performed, the recording quality was approximately the same as when recording was performed with the tank 40 initially set. Furthermore, after the seventh process, it was confirmed that the resistance value R of the wiring resistance of the fourth circuit 806 was below the threshold value Rt, and it was determined that the wiring was not broken.

[0101] Next, the above process was performed once more, for a total of eight times. After the eighth process, the wiring resistance of the fourth circuit 806 was confirmed to have a resistance value R exceeding the threshold value Rt, and it was determined that the wiring was broken. The ink in the liquid chamber 502 was then replaced with clear ink, and all of the counter electrodes 508 were observed, revealing that they had disappeared. Specifically, the iridium layer on the counter electrodes 508 had disappeared, exposing the underlying insulating layer 614.

[0102] In this way, in verification examples 1 and 2, it was confirmed that the timing at which the resistance value R of the wiring resistance exceeds the threshold value Rt and it is determined that the wiring is broken is the same as the timing at which the electrode being monitored disappears.

[0103] <Comparative Example> = Recording head configuration = In the comparative example, a 70 nm iridium layer was formed as a protective layer 616 on an insulating layer 614 of a substrate 406, followed by patterning, and a 60 nm tantalum layer was formed on the iridium layer and patterned. The protective layer 616 thus formed formed the upper electrode 506 and the counter electrode 508. Then, a flow path forming member 408 was formed on the substrate 406, and other necessary terminals and the like were formed to produce a recording head 42.

[0104] The comparative example does not include the third circuit 802 and the fourth circuit 806. In addition, in this recording head 42, the number of cleanings, which is used as an indicator of the timing for replacing the recording head 42, was set to 20, taking into account the in-plane distribution of the formed iridium layer and the film thickness distribution in the post-processing.

[0105] =Cleaning process= Similar to Verification Example 1, a new tank 40 was set, and a series of processes, in which kogation was deposited on the upper electrode 506 by the above-mentioned discharge operation and the above-mentioned cleaning process accompanied by suction recovery process, was performed 20 times in total. After the 20th process, the film thickness of the upper electrode 506 was measured, and the remaining film thickness was found to be approximately 30 nm.

[0106] Thus, in the comparative example, it was confirmed that the upper electrode 506 remained at a film thickness of 30 nm even after reaching the upper limit of the number of cleanings set as an indicator of when to replace the print head 42. In this case, the print head 42 ends up being replaced, even though the cleaning process can still be performed and recording can be performed while maintaining the print quality.

[0107] In contrast, in Verification Examples 1 and 2 according to this embodiment, the timing of replacing the print head 42 is managed based on the measured resistance of the wiring including the electrodes. This eliminates the need to add a margin corresponding to the manufacturing tolerances that occur in the manufacturing process of the print head 42 to the value used to determine the timing of replacing the print head 42. This makes it possible to replace the print head 42 at the appropriate time.

[0108] (Other embodiments) The above-described embodiment may be modified as shown in the following (1) to (4).

[0109] (1) In the above embodiment, the common wiring 514 connecting the upper electrodes 506 is provided with the terminals 516 and 520 at the ends in the arrangement direction, but this is not limited to this. That is, the terminals may be provided at any two positions so as to include a predetermined number of upper electrodes 506 that are part of the provided upper electrodes 506. For example, if a region where the elution rate of the upper electrodes 506 is high is known in advance, the terminals may be provided at a position that includes the plurality of upper electrodes 506 located in that region.

[0110] The same applies to the counter electrodes 508, and although the common wiring 526 is provided with terminals 528 and 532 at the ends in the arrangement direction, the present invention is not limited to this. That is, the electrodes may be provided at any two positions so as to include a predetermined number of counter electrodes 508 that are part of the provided counter electrodes 508. For example, if the rate at which the dissolution rate of the counter electrodes 508 increases is known in advance, the electrodes may be provided at a position that includes the plurality of counter electrodes 508 located in that region.

[0111] (2) In the above embodiment, the wiring resistance is measured after the cleaning process in the recording process, but this is not limited to this. That is, the wiring resistance may be measured at a predetermined timing before the recording process is performed. In this case, the film thickness of the upper electrode 506 and the counter electrode 508 at the start of the recording process can be obtained, and the number of times the cleaning process can be performed can be calculated from the obtained film thickness, and this number can be used as an index for determining when to replace the recording head 42. Note that the predetermined timing is, for example, the timing when the recording head 42 is replaced.

[0112] (3) The above embodiment is not limited to a recording device that discharges ink onto a recording medium, but can be widely applied to a liquid discharge device that discharges various liquids from a liquid discharge head. In the above embodiment, the recording device 10 is a so-called serial scan type recording device that discharges ink from a recording head that moves in the X direction onto a recording medium that is transported in the Y direction, but the present invention is not limited to this. For example, the present invention may be a so-called full line type recording device that uses a long recording head that spans the entire width of the recording area on the recording medium.

[0113] (4) The above embodiment and the various configurations shown in (1) to (3) above may be combined as appropriate. [Explanation of symbols]

[0114] 42 Recording head 52 Control section 82 Measuring part 802 3rd circuit 806 4th circuit

Claims

1. a discharge port for discharging the liquid stored in the liquid chamber; an electrothermal conversion element that generates heat to eject the liquid from the ejection port; a first electrode that protects the electrothermal conversion element and is soluble in the liquid by an electrochemical reaction with the liquid; a second electrode provided so as to be electrically connectable to the first electrode via the liquid, wherein a voltage is applied to the first electrode to cause an electrochemical reaction by the second electrode, thereby dissolving the first electrode into the liquid, A voltage can be applied between the first electrode and the second electrode with the polarity reversed, a wiring resistance in a circuit in which the plurality of second electrodes are part of wiring can be measured; The liquid ejection head is characterized in that the plurality of second electrodes are connected in series by wiring in the circuit.

2. 2. The liquid ejection head according to claim 1, wherein the plurality of second electrodes includes all of the second electrodes that are provided.

3. 2. The liquid ejection head according to claim 1, wherein the plurality of second electrodes are a part of the second electrodes provided.

4. 4. The liquid ejection head according to claim 3, wherein the circuit is capable of measuring wiring resistance by changing the plurality of second electrodes.

5. a discharge port for discharging the liquid stored in the liquid chamber; an electrothermal conversion element that generates heat to eject the liquid from the ejection port; a first electrode that protects the electrothermal conversion element and is soluble in the liquid by an electrochemical reaction with the liquid; a second electrode provided so as to be electrically connectable to the first electrode via the liquid, wherein a voltage is applied to the first electrode to cause an electrochemical reaction by the second electrode, thereby dissolving the first electrode into the liquid, a wiring resistance in a circuit in which the plurality of first electrodes are part of wiring can be measured; The liquid ejection head is characterized in that the plurality of first electrodes are connected in series by wiring in the circuit.

6. 6. The liquid ejection head according to claim 5, wherein the plurality of first electrodes includes all of the first electrodes that are provided.

7. 6. The liquid ejection head according to claim 5, wherein the plurality of first electrodes are a part of the first electrodes provided.

8. 8. The liquid ejection head according to claim 7, wherein the circuit is capable of measuring wiring resistance by changing the plurality of first electrodes.

9. a discharge port for discharging the liquid stored in the liquid chamber; an electrothermal conversion element that generates heat to eject the liquid from the ejection port; a first electrode that protects the electrothermal conversion element and is soluble in the liquid by an electrochemical reaction with the liquid; a second electrode provided so as to be electrically connectable to the first electrode via the liquid, wherein a voltage is applied to the first electrode to cause an electrochemical reaction by the second electrode, thereby dissolving the first electrode into the liquid, A voltage can be applied between the first electrode and the second electrode with the polarity reversed, a first circuit including the plurality of first electrodes as a part of wiring is configured to be measurable in terms of wiring resistance; a second circuit including the second electrodes as a part of wiring, the second circuit being configured to be measurable in wiring resistance; the plurality of first electrodes are connected in series by wiring in the first circuit, The liquid ejection head, wherein the plurality of second electrodes are connected in series by wiring in the second circuit.

10. A liquid ejection head according to any one of claims 1 to 4, a measuring means for measuring the wiring resistance in the circuit; a detecting means for detecting the degree of elution of the second electrode based on the measurement result of the measuring means.

11. A liquid ejection head according to any one of claims 5 to 8, a measuring means for measuring the wiring resistance in the circuit; a detecting means for detecting the degree of elution of the first electrode based on the measurement result of the measuring means.

12. 12. The liquid ejection apparatus according to claim 10, further comprising a notification unit that determines the timing of replacing the liquid ejection head based on the detection result of the detection unit and issues a notification urging the user to replace the liquid ejection head.

13. a first electrode that protects an electrothermal conversion element that generates heat to eject a liquid in a liquid chamber from an ejection port, and that allows the liquid to elute by an electrochemical reaction with the liquid; a second electrode that is soluble in the liquid by an electrochemical reaction with the liquid and is provided so as to be electrically connectable to the first electrode via the liquid, the method comprising: applying a voltage to the first electrode to cause an electrochemical reaction with the second electrode, thereby dissolving the first electrode into the liquid, thereby removing kogation that originates from the liquid and that has adhered to the first electrode, measuring a resistance value in at least one of a circuit in which the plurality of first electrodes connected in series are part of a wiring and a circuit in which the plurality of second electrodes connected in series are part of a wiring; A cleaning method comprising determining whether or not kogation can be removed from the first electrode based on the measured resistance value.

14. A discharge port for discharging liquid stored in a liquid chamber; an electrothermal conversion element that generates heat to eject the liquid from the ejection port; a first electrode that protects the electrothermal conversion element and is soluble in the liquid by an electrochemical reaction with the liquid; a second electrode provided so as to be electrically connectable to the first electrode via the liquid, wherein a voltage is applied to the first electrode to cause an electrochemical reaction by the second electrode, thereby dissolving the first electrode into the liquid, A voltage can be applied between the first electrode and the second electrode with the polarity reversed, a wiring resistance in a circuit in which the plurality of second electrodes are part of wiring can be measured; The liquid ejection head, wherein the plurality of second electrodes are a part of the second electrodes provided.

15. A liquid ejection head as described in Claim 14, characterized in that the circuit is capable of measuring wiring resistance by changing the plurality of second electrodes.

16. A discharge port for discharging liquid stored in a liquid chamber; an electrothermal conversion element that generates heat to eject the liquid from the ejection port; a first electrode that protects the electrothermal conversion element and is soluble in the liquid by an electrochemical reaction with the liquid; a second electrode provided so as to be electrically connectable to the first electrode via the liquid, wherein a voltage is applied to the first electrode to cause an electrochemical reaction by the second electrode, thereby dissolving the first electrode into the liquid, a wiring resistance in a circuit in which the plurality of first electrodes are part of wiring can be measured; The liquid ejection head, wherein the plurality of first electrodes are a part of the first electrodes provided.

17. A liquid ejection head as described in Claim 16, characterized in that the circuit is capable of measuring wiring resistance by changing the plurality of first electrodes.

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