Liquid ejection apparatus and control method

Abstract

One embodiment of the present application relates to a liquid ejecting apparatus having: a liquid ejecting head including a heating element, a first protective layer that prevents contact between the heating element and a liquid, a second protective layer that partially covers the first protective layer and functions as a first electrode, a second electrode that is electrically connected to the first electrode via a liquid, and an ejection port that ejects the liquid; and a control unit configured to perform control that sets a potential difference between the first electrode and the second electrode to a predetermined value in each of an aging process and a printing process by changing at least one of a potential of the first electrode and a potential of the second electrode, wherein in a case where the potential difference in the aging process is represented by AVa and the potential difference in the printing process is represented by AVp, AVa ≠ AVp is satisfied. The present application also relates to a control method of a liquid ejecting apparatus.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a liquid ejection apparatus including a liquid ejection head that ejects a liquid such as ink. BACKGROUND

[0002] Since an inkjet recording method among recording methods employed in a recording apparatus such as a multifunction printer is a non-impact recording method and is capable of achieving high-density and high-speed recording with low noise, the method is widely employed. An inkjet recording apparatus includes a mechanism that drives a carriage on which an inkjet head is mounted, a conveyance mechanism that conveys a recording medium such as recording paper, and a control configuration that controls these mechanisms. Note that, in the present specification, an inkjet head is simply referred to as a “(recording) head”. Furthermore, a head that ejects a liquid such as ink is referred to as a “liquid ejection head”.

[0003] Methods of generating energy for ejecting ink from a ejection port of a recording head include a method of applying pressure to ink by using an electromechanical conversion element such as a piezoelectric element, and a method of causing bubbling by using heat generated by irradiation of electromagnetic waves such as laser light and using pressure of a bubble. Furthermore, there is a method of heating ink by using a electrothermal conversion element (hereinafter, referred to as a “heater”) including a heating resistor element to cause bubbling.

[0004] In a recording head using the heater, scale of ink is formed on a surface of the heater due to heating of the heater to the ink, and in some cases, variation in ejection speed is large. Many inks used in such a recording head are inks containing dye-based colorants and pigment-based colorants, and many of these colorants are not soluble in water or are almost not soluble in water. It is said that the substances that are not soluble or almost not soluble thus form scale on the above-described heater, whereby ejection characteristics tend to change.

[0005] It is known that, in a case where ink that can form the above-described scale is ejected in a state where there is almost no scale on a surface layer of a heater at the time of attaching the head, variation in ejection characteristics in an initial stage is large (for example, ejection speed drops) due to formation of scale on the heater. Such variation in ejection characteristics in the initial stage can cause image defects, and defects such as thin lines, deterioration in character quality, and hue variation due to landing position deviation, for example.

[0006] To address this problem, Japanese Patent Publication No. 2014-131867 proposes a technology in which preliminary ink ejection processing that does not contribute to recording on a paper surface (hereinafter, referred to as aging) is performed in advance before recording on a paper surface. By aging, a certain degree of clogging of ink is formed on a heater surface, clogging on the heater surface is made uniform (adhesion and detachment of clogging are in a substantially balanced state), and the heater surface is stabilized to suppress changes in ejection characteristics in the initial stage.

[0007] Further, Japanese Patent Publication No. 2008-105364 proposes a head that includes an upper protective layer in a region of a heat application portion including a heater, the upper protective layer being arranged to be electrically connectable to serve as an electrode for causing an electrochemical reaction with ink.

[0008] Further, Japanese Patent Publication No. 2019-38127 proposes a liquid ejection head that includes an upper protective layer covering a portion of a heater to be heated and serving as one electrode and an opposite electrode connected to the one electrode via a liquid. The liquid ejection head of Japanese Patent Publication No. 2019-38127 includes a potential control unit that generates an electric field between the upper protective layer electrode and the opposite electrode, and the potential of the opposite electrode is set to be higher than the potential of the upper protective layer electrode in a normal printing process, so that clogging is less likely to adhere to the upper protective layer. SUMMARY

[0009] However, the aforementioned patent documents have the following problems. Specifically, in a case where a pulse having a higher voltage value than a voltage pulse normally applied in recording or the like is applied or the time at which a pulse is applied to a recording element is longer than the time at which a pulse is normally applied in order to accelerate aging, a problem occurs. In this case, since excessive energy is applied to the heater material to be powered, there is a risk of damaging the heater material and shortening the life.

[0010] Further, a head provided with an opposite electrode and performing potential control so that clogging is less likely to adhere to a heater surface layer has a problem that, in a state where there is almost no clogging on the heater surface layer, ejection characteristics are less likely to change and aging takes time. An increase in the aging time leads to an increase in downtime and an increase in waste ink.

[0011] Therefore, in view of the above problems, an object of the present disclosure is to complete aging quickly while suppressing damage to a heater material.

[0012] One embodiment of the present invention relates to a liquid jetting device, comprising: a liquid jetting head including a heating element for generating energy required to jettison liquid, a first protective layer preventing contact between the heating element and the liquid, a second protective layer partially covering the first protective layer and acting as a first electrode, a second electrode electrically connected to the first electrode via the liquid, and a jetting port for jetting liquid; and a control unit configured to perform control in each of an aging process and a printing process by changing at least one of the potentials of the first electrode and the second electrode to set a predetermined value, wherein ΔVa≠ΔVp is satisfied when: the potential of the first electrode during the aging process is represented by Vah, the potential of the second electrode during the aging process is represented by Vac, and the potential difference between the potentials of the first electrode Vah and the second electrode Vac is represented by ΔVa (=Vac-Vah); and the potential of the first electrode during the printing process is represented by Vph, the potential of the second electrode during the printing process is represented by Vpc, and the potential difference between the potentials of the first electrode Vph and the second electrode Vpc is represented by ΔVp (=Vpc-Vph).

[0013] Further features of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0014] Figure 1 A view illustrating the schematic construction of the recording device;

[0015] Figure 2 A schematic diagram illustrating the first loop path;

[0016] Figure 3 A schematic diagram illustrating the second loop path;

[0017] Figure 4A and 4B This is a three-dimensional view of the liquid injection head;

[0018] Figure 5 An exploded 3D view of the liquid injection head;

[0019] Figure 6 A view showing the flow channel components;

[0020] Figure 7 A view showing the connection relationship of the flow channels in the flow channel component;

[0021] Figure 8 For along Figure 7 A sectional view of section lines VIII-VIII in the diagram;

[0022] Figure 9A and 9BTo show a view of the injection module;

[0023] Figures 10A to 10C A view showing the structure of the recording component board;

[0024] Figure 11 For along Figure 10A Section line XI-XI shows a perspective view of the structure of the recording element plate and cover component;

[0025] Figure 12 This is a plan view showing adjacent portions of the recording element board in a magnified manner.

[0026] Figure 13A and 13B A view showing the structure of the heat application section in the recording element board;

[0027] Figures 14A to 14D This diagram illustrates a scale inhibition treatment when negatively charged particles are the primary cause of scaling.

[0028] Figures 15A to 15C This diagram illustrates a scaling inhibition treatment when positively charged particles are the primary cause of scaling.

[0029] Figure 16A and 16B This relates the number of sprayed droplets to the spray velocity.

[0030] Figure 17 This represents the relationship between ΔV and the amount of scale buildup on the protective layer of the heater in the first embodiment.

[0031] Figure 18 This represents the relationship between ΔV and the amount of scaling on the protective layer above the heater in the second embodiment.

[0032] Figure 19 This represents the relationship between ΔV and the amount of scaling on the protective layer above the heater in the third embodiment.

[0033] Figure 20 A communication model diagram between the liquid injection head and the main body; and

[0034] Figure 21 This is a flowchart of the process in the first embodiment. Detailed Implementation

[0035] Embodiments of the present disclosure are described below using the accompanying drawings. However, the following description is not intended to unnecessarily limit the scope of the present disclosure. In the following description, as an example, a liquid jetting device including a so-called linear head having a length corresponding to the width of the recording medium is described; however, the ideas of the present disclosure can also be applied to a so-called tandem liquid jetting device that performs recording while scanning the recording medium. As a construction example of a tandem liquid jetting device, a configuration in which a recording element plate for black ink and a recording element plate for color ink are mounted can be given. However, the present disclosure is not limited to this mode and can be applied to a mode in which a short linear head is manufactured and the short linear head scans the recording medium, the short linear head having a width smaller than the recording medium and several recording element plates are arranged such that the jet nozzles overlap each other in the jet nozzle row direction. Furthermore, although the recording device of this embodiment is, for example, a circulating inkjet recording device in which the liquid ink circulates between the tank and the liquid jetting device, the mode of the recording device can be a non-circulating mode.

[0036] [First Embodiment]

[0037] Inkjet recording equipment

[0038] Figure 1 A schematic configuration of a liquid jetting apparatus according to this embodiment, specifically an inkjet recording apparatus 1000 (hereinafter also referred to as a recording apparatus) that performs recording by jetting ink, is shown. The recording apparatus 1000 includes a transport unit 1 for transporting recording media 2 and a linear liquid jetting head 3 arranged substantially orthogonal to the transport direction of the recording media. It is a linear recording apparatus that performs continuous recording in a single operation while continuously or intermittently transporting multiple recording media 2. The recording media 2 is not limited to cut paper and can be a continuous roll of paper. The liquid jetting head 3 is capable of performing full-color printing using cyan, magenta, yellow, and black (CMYK) inks. In the liquid jetting head 3, the main tank, buffer tank, and liquid supply unit as described later are fluidly connected to each other (see [link to documentation]). Figure 2 The liquid supply unit forms a supply channel for supplying ink to the liquid ejector head. Furthermore, an electrical control unit that sends power and ejection control signals to the liquid ejector head 3 is electrically connected to the liquid ejector head 3. The liquid path and electrical signal path in the liquid ejector head 3 will be described later.

[0039] <First Loop Path>

[0040] Figure 2 This is a schematic diagram illustrating a first loop path, which is a pattern of loop paths applied to the recording device according to this embodiment. For example... Figure 2As shown, the liquid injection head 3 is fluidly connected to the first circulation pump (high-pressure side) 1001, the first circulation pump (low-pressure side) 1002, the buffer tank 1003, etc. Although in Figure 2 The diagram only shows one flow path for CMYK ink to simplify the explanation, but there are actually four color circulation paths set in the liquid jet head 3 and the recording device body.

[0041] The buffer tank 1003, connected to the main tank 1006 and acting as a secondary tank, has an atmospheric vent (not shown) that allows communication between the interior and exterior of the tank, and allows air bubbles in the ink to be expelled to the outside. The buffer tank 1003 is also connected to a replenishment pump 1005. When ink is consumed in the liquid ejector head 3, the replenishment pump 1005 delivers an amount of ink from the main tank 1006 to the buffer tank 1003 equivalent to the consumed amount. For example, ink is consumed in the liquid ejector head 3 when ink is ejected (discharged) from the ejection port of the liquid ejector head during operations such as recording and suction recovery performed by ink ejection.

[0042] Two first circulation pumps 1001 and 1002 function to pump ink from the liquid connection portion 111 of the liquid ejector head 3 and to allow the ink to flow to the buffer tank 1003. Preferably, each first circulation pump is a volumetric pump with a metering liquid delivery capacity. Specifically, examples include tubular pumps, gear pumps, diaphragm pumps, syringe pumps, etc. For example, a mode that ensures a constant flow rate by arranging a common constant flow valve or safety valve at the pump outlet can also be used. During the operation of the liquid ejector head 3, the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 cause the ink to flow at a constant flow rate in each of the common supply flow channel 211 and the common collection flow channel 212. The flow rate is preferably set to be equal to or higher than a level that keeps the temperature difference between the recording element plates 10 in the liquid ejector head 3 at a level that does not affect the quality of the recorded image. However, if the flow rate is set too high, the negative pressure difference between the recording element plates 10 becomes too large due to the pressure drop in the flow channels in the liquid ejector unit 300, and uneven image density occurs. Therefore, it is preferable to set the flow rate while taking into account the temperature difference and negative pressure difference between the recording element boards 10.

[0043] The negative pressure control unit 230 is positioned midway through the path connecting the second circulation pump 1004 and the liquid injection unit 300. Therefore, the negative pressure control unit 230 functions to maintain the pressure downstream of the negative pressure control unit 230 (i.e., on the side of the liquid injection unit 300) at a preset constant pressure, even when the flow rate in the circulation system fluctuates due to differences in the recording load. Any mechanism can be used as one of the two pressure regulating mechanisms forming the negative pressure control unit 230, as long as they can control the pressure downstream of the negative pressure control unit 230 so that the pressure fluctuates within a specific range centered on the desired set pressure. For example, a mechanism similar to a so-called "pressure reducer" can be used. In the case of using a pressure reducer, such as... Figure 2 As shown, the second circulation pump 1004 preferably applies pressure upstream of the negative pressure control unit 230 via the liquid supply unit 220. Since this configuration can suppress the influence of the hydraulic head pressure of the buffer tank 1003 on the liquid ejector head 3, the layout freedom of the buffer tank 1003 in the recording device 1000 can be increased. The second circulation pump 1004 only needs to be a pump with a head pressure above a certain pressure within the range of ink circulation flow used in driving the liquid ejector head 3, and a turbine pump, positive displacement pump, etc., can be used. Specifically, a diaphragm pump, etc., can be applied. Furthermore, for example, instead of the second circulation pump 1004, a hydraulic head tank arranged to have a certain hydraulic head difference relative to the negative pressure control unit 230 can be used.

[0044] like Figure 2 As shown, the negative pressure control unit 230 includes two pressure regulating mechanisms, each with a different control pressure. The pressure regulating mechanism located on the higher pressure setting side (in...) Figure 2 (represented by H) is connected via the interior of the liquid supply unit 220 to the common supply flow channel 211 in the liquid injection unit 300. Meanwhile, the pressure regulating mechanism on the lower pressure setting side (in...) Figure 2 (represented by L) is connected to the common collection flow channel 212 via the interior of the liquid supply unit 220.

[0045] The liquid jetting unit 300 is provided with a common supply flow channel 211, a common collection flow channel 212, and various supply flow channels 213 and collection flow channels 214 that communicate with the recording element board 10. Since the various supply flow channels 213 and collection flow channels 214 are connected to the common supply flow channel 211 and the common collection flow channel 212, a portion of the ink flows from the common supply flow channel 211 to the common collection flow channel 212 as it passes through the internal flow channels of the recording element board 10. Figure 2(The arrow in the image). The reason is that since the pressure regulating mechanism H is connected to the common supply flow channel 211 and the pressure regulating mechanism L is connected to the common collection flow channel 212, a pressure difference is generated between the two common flow channels.

[0046] As described above, in the liquid ejection unit 300, while ink flows through the common supply flow channel 211 and the common collection flow channel 212, a portion of ink also flows through the interior of the recording element plate 10. Therefore, the flow through the common supply flow channel 211 and the common collection flow channel 212 allows heat generated in the recording element plate 10 to be dissipated to the outside of the recording element plate 10. Furthermore, since this configuration allows ink flow to occur in the ejection port and pressure chamber where recording is not being performed even when the liquid ejection head 3 is performing recording, an increase in ink viscosity in such portions can be suppressed. Additionally, the ink with increased viscosity and foreign matter in the ink can be discharged into the common collection flow channel 212. Therefore, the liquid ejection head 3 of this embodiment can perform high-quality recording at high speed.

[0047] <Second Loop Path>

[0048] Figure 3 This is a schematic diagram illustrating a second loop path, different from the aforementioned first loop path, applied in the loop path of the recording device according to this embodiment. The main differences from the first loop path are as follows.

[0049] First, both pressure regulating mechanisms forming the negative pressure control unit 230 have a mechanism (a mechanism component with the same function as a so-called "back pressure regulator") that controls the pressure upstream of the negative pressure control unit 230 so that the pressure fluctuates within a specific range centered on a desired set pressure. Furthermore, the second circulation pump 1004 acts as a negative pressure source, reducing the pressure downstream of the negative pressure control unit 230. Additionally, the first circulation pump (high-pressure side) 1001 and the first circulation pump (low-pressure side) 1002 are arranged upstream of the liquid injection head, and the negative pressure control unit 230 is arranged downstream of the liquid injection head.

[0050] The negative pressure control unit 230 in the second circulation path operates such that even when the flow rate fluctuates due to changes in the recording load while the liquid injection head 3 is recording, the pressure upstream of the negative pressure control unit 230 (i.e., on the liquid injection unit 300) fluctuates within a specific range. The pressure fluctuates within, for example, a specific range centered on a preset pressure. Figure 3As shown, the second circulation pump 1004 preferably applies pressure to the downstream side of the negative pressure control unit 230 via the liquid supply unit 220. Since this configuration can suppress the influence of the hydraulic head pressure of the buffer tank 1003 on the liquid injection head 3, the layout freedom of the buffer tank 1003 in the recording device 1000 can be increased. For example, instead of the second circulation pump 1004, a hydraulic head tank arranged with a certain hydraulic head difference relative to the negative pressure control unit 230 can be used.

[0051] As in the first loop path Figure 3 The negative pressure control unit 230 shown includes two pressure regulating mechanisms, each with a different control pressure. The pressure regulating mechanism located on the higher pressure setting side (in...) Figure 3 (represented by H) is connected via the interior of the liquid supply unit 220 to the common supply flow channel 211 in the liquid injection unit 300. Meanwhile, the pressure regulating mechanism on the lower pressure setting side (in...) Figure 3 (represented by L) is connected to the common collection flow channel 212 via the interior of the liquid supply unit 220.

[0052] Two pressure regulating mechanisms ensure that the pressure in the common supply flow channel 211 is higher than the pressure in the common collection flow channel 212. This configuration generates ink flow from the common supply flow channel 211 to the common collection flow channel 212 via the respective flow channels 213 and the internal flow channels of the recording element plate 10. Figure 3 (The arrow in the image). As described above, in the second circulation path, a similar ink flow state is obtained in the liquid jetting unit 300 as in the first circulation path. At the same time, the second circulation path has two advantages that differ from the first circulation path.

[0053] The first advantage is as follows: In the second circulation path, since the negative pressure control unit 230 is arranged downstream of the liquid ejector head 3, the risk of dust and foreign matter generated in the negative pressure control unit 230 flowing into the liquid ejector head is lower. The second advantage is as follows: In the second circulation path, the maximum flow rate required to supply ink from the buffer tank 1003 to the liquid ejector head 3 is less than the maximum value in the first circulation path. The reason is as follows. When ink circulates during recording standby, the total flow rate in the common supply flow channel 211 and the common collection flow channel 212 is called A. The value of A is defined as the minimum flow rate required to bring the temperature difference in the liquid ejection unit 300 within the desired range when adjusting the temperature of the liquid ejector head 3 during recording standby. Furthermore, the ejection flow rate is defined as F when ink is ejected from all ejection ports of the liquid ejection unit 300 (all ejected). Then, in the first circulation path ( Figure 2In the case of [condition], the set flow rates of the first circulation pump (high-pressure side) 1001 and the first circulation pump (low-pressure side) 1002 are A. Therefore, the maximum liquid supply flow rate required to supply the liquid injection head 3 during all injections is A+F.

[0054] Meanwhile, in the second loop path ( Figure 3 In the case of recording standby, the liquid supply flow rate required to supply the liquid jet head 3 is flow rate A. The supply flow rate required to supply the liquid jet head 3 during all jetting is flow rate F. Then, in the case of the second circulation path, the total set flow rate of the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 (i.e., the maximum required supply flow rate) is the larger of A and F. Therefore, if a liquid jetting unit 300 with the same structure is used, the maximum required supply flow rate (A or F) in the second circulation path is necessarily less than the maximum required supply flow rate (A+F) in the first circulation path. In the case of the second circulation path, the degree of freedom of the applicable circulation pump is thus increased. Therefore, for example, a low-cost circulation pump with a simple structure can be used or the load on the cooler (not shown) installed in the path on the main body side can be reduced, and the second circulation path has the advantage of being able to reduce the cost of the main body of the recording device. This advantage is more obvious in linear printheads with relatively large values ​​of A or F, and in linear printheads, linear printheads with a larger length in the longitudinal direction benefit more.

[0055] However, the first circulation path also has advantages over the second circulation path. Specifically, in the second circulation path, since the flow rate of ink flowing in the liquid jetting unit 300 is maximum during recording standby, the lower the recording load, the higher the negative pressure applied to each nozzle. Therefore, especially when the flow channel width (length in the direction orthogonal to the ink flow direction) of the common supply flow channel 211 and the common collection flow channel 212 is reduced to reduce the head width (length of the liquid jetting head in the shorter side direction), a high negative pressure is applied to the nozzles in low-load images where non-uniformity is often noticeable. This application of high negative pressure may increase the effect of dripping. Meanwhile, in the first circulation path, since the high negative pressure is applied to the nozzles during the formation of a high-load image, the advantage is that even if dripping occurs, the dripping is less noticeable and has less impact on the recorded image. The preferred one of the two circulation paths can be selected and adopted according to the specifications of the liquid jetting head and the recording device body (jet flow rate F, minimum circulation flow rate A, and flow channel resistance within the head).

[0056] <Construction of a liquid jet head>

[0057] The construction of the liquid injection head 3 according to the first embodiment is described. Figure 4Aand 4B This is a perspective view of the liquid ejector head 3 according to this embodiment. The liquid ejector head 3 is a linear liquid ejector head, in which 15 recording element boards 10 are arranged in a straight line (row arrangement), and each recording element board 10 is capable of ejecting ink of four colors: C, M, Y, and K. Figure 4A As shown, the liquid injection head 3 includes a signal input terminal 91 and a power supply terminal 92 electrically connected to the recording element board 10 via a flexible wiring board 40 and an electrical wiring board 90. The signal input terminal 91 and the power supply terminal 92 are electrically connected to the control unit of the recording device 1000. The injection drive signal is supplied to the recording element board 10 via the signal input terminal 91, and the power required for injection is supplied to the recording element board 10 via the power supply terminal 92.

[0058] By using the circuitry in the electrical wiring board 90 to group all the wires in one place, the number of signal input terminals 91 and power supply terminals 92 can be reduced to fewer than the number of recording element boards 10. Therefore, the number of electrical connections that need to be attached during the attachment of the liquid jet head 3 to the recording device 1000 or removed during liquid jet head replacement can be reduced. Figure 4B As shown, liquid connection portions 111 located at both ends of the liquid ejector head 3 are connected to the liquid supply system of the recording device 1000. Thus, CMYK inks are supplied from the supply system of the recording device 1000 to the liquid ejector head 3, and ink already inside the liquid ejector head 3 is collected back into the supply system of the recording device 1000. Therefore, inks of various colors can circulate through the paths of the recording device 1000 and the liquid ejector head 3.

[0059] Figure 5 An exploded perspective view of the components or units forming the liquid injection head 3 is shown. The liquid injection unit 300, the liquid supply unit 220, and the electrical wiring board 90 are attached to the housing 80. The liquid supply unit 220 is provided with a liquid connection portion 111. Figure 2 and 3 ), and filters 221 for various colors that communicate with the opening of the liquid connection part 111. Figure 2 and 3 A filter 221 is installed in the liquid supply unit 220 to remove foreign matter from the supplied ink. Both liquid supply units 220 are equipped with filters 221 for each of the two colors. Ink that has passed through the filters 221 is supplied to a negative pressure control unit 230 corresponding to each color and arranged on the liquid supply unit 220.

[0060] The negative pressure control unit 230 is a unit that includes pressure regulating valves for various colors. Each of the negative pressure control units 230 significantly attenuates pressure drop variations in the supply system of the recording device 1000 (the supply system upstream of the liquid jet head 3) by means of valves, spring members, etc., provided in the negative pressure control unit 230, which occur with fluctuations in ink flow. Therefore, the negative pressure control unit 230 can stabilize the negative pressure variations downstream of the negative pressure control unit (on the side of the liquid jet unit 300) within a certain range. Two pressure regulating valves for each color are included in the negative pressure control unit 230 for each color, such as... Figure 2 As shown in the figure, different control pressures are set for each pressure regulating valve, and the valves on the high-pressure side and the low-pressure side are connected to the common supply flow channel 211 and the common collection flow channel 212 in the liquid injection unit 300 via the liquid supply unit 220, respectively.

[0061] The housing 80 is formed by a liquid jet unit support portion 81 and a wiring board support portion 82, supporting the liquid jet unit 300 and the wiring board 90, and ensuring the rigidity of the liquid jet head 3. The wiring board support portion 82 is for supporting the wiring board 90 and is fixed to the liquid jet unit support portion 81 with screws. The liquid jet unit support portion 81 has the function of correcting the warping and deformation of the liquid jet unit 300 and ensuring the positional accuracy of the multiple recording element boards 10 relative to each other, thereby suppressing streaks and unevenness in the recorded product. Therefore, the liquid jet unit support portion 81 preferably has sufficient rigidity, and its material is preferably a metallic material such as SUS or aluminum, or a ceramic material such as alumina. Openings 83 and 84 are provided in the liquid jet unit support portion 81 for inserting the bonding rubber 100. Ink supplied from the liquid supply unit 220 is guided via the bonding rubber to the third flow channel member 70 forming the liquid jet unit 300.

[0062] The liquid jetting unit 300 includes a flow channel member 210 and a plurality of jetting modules 200, and a cover member 130 is attached to the surface of the liquid jetting unit 300 on the recording medium side. In this example, as Figure 5 As shown, the cover member 130 is a member having a frame-shaped surface with an elongated opening 131, and includes the recording element plate 10 and the sealing member 110 in the injection module 200. Figure 9A The liquid jetting unit 300 is exposed through opening 131. The frame portion at the outer periphery of opening 131 has a contact surface that contacts the cover member that covers the liquid jetting head 3 during recording standby. Therefore, it is preferable to apply adhesive, sealing material, filler, etc. along the outer periphery of opening 131 and fill the unevenness and gaps on the jetting nozzle surface of liquid jetting unit 300 to form a closed space in the covered state.

[0063] Next, the structure of the flow channel member 210 included in the liquid injection unit 300 will be described. For example... Figure 5 As shown, the flow channel member 210 is a member in which the first flow channel member 50, the second flow channel member 60, and the third flow channel member 70 are stacked on top of each other. The flow channel member 210 dispenses ink supplied from the liquid supply unit 220 to the jetting module 200 and returns ink flowing back from the jetting module 200 to the liquid supply unit 220. The flow channel member 210 is fixed to the liquid jetting unit support portion 81 with screws, which prevents warping and deformation of the flow channel member 210.

[0064] Figure 6 Reference numerals (a) to (f) in the figures are views showing the front and back sides of the first to third flow channel components. Figure 6 In the accompanying drawings, reference numeral (a) indicates the surface of the first flow channel member 50 on the side where the injection module 200 is installed. Figure 6 Reference numeral (f) in the figures indicates the surface of the third flow channel member 70 that contacts the liquid injection unit support portion 81. The first flow channel member 50 and the second flow channel member 60 are joined together such that... Figure 6 The surface indicated by reference numeral (b) in the attached drawing and in Figure 6 The surfaces indicated by reference numeral (c) in the accompanying drawings (which serve as the contact surfaces of the respective flow channel members) face each other. The second and third flow channel members engage with each other such that... Figure 6 The surface indicated by reference numeral (d) in the attached drawing and in Figure 6 The surfaces indicated by reference numeral (e) in the accompanying drawings (which serve as the contact surfaces of the respective flow channel members) face each other. The engagement of the second flow channel member 60 and the third flow channel member 70 results in a set of common flow channel grooves 62 and a set of common flow channel grooves 71 formed in the respective flow channel members, creating eight common flow channels extending along the longitudinal direction of the flow channel members. Figure 7 As shown, a common supply flow channel 211 and a common collection flow channel 212 are formed for each color in the flow channel member 210. The communication port 72 of the third flow channel member 70 communicates with a corresponding hole in the engaging rubber 100 and is in fluid communication with the liquid supply unit 220. A plurality of communication ports 61 are formed on the bottom surface of the common flow channel groove 62 of the second flow channel member 60 and communicate with one end portion of each flow channel groove 52 of the first flow channel member 50. Communication ports 51 are formed in the other end portions of each flow channel groove 52 of the first flow channel member 50, and each flow channel groove 52 is in fluid communication with a plurality of injection modules 200 via the communication ports 51. Each flow channel groove 52 allows flow channels to converge at the center side of the flow channel member.

[0065] The first to third flow channel components are preferably made of a material resistant to liquid corrosion and having a low linear coefficient of thermal expansion. For example, a composite material (resin material) using alumina, liquid crystal polymer (LCP), polyphenylene sulfide (PPS), or polysulfone (PSF) as the base material and adding inorganic fillers (such as fine silica particles and fibers) is preferred. As a method of forming the flow channel component 210, the three flow channel components can be stacked and bonded to each other. Furthermore, when a composite resin material is selected as the material, a bonding method by welding can be employed.

[0066] Next, use Figure 7 Describe the connection relationship of the flow channels in the flow channel component 210. Figure 7 This is a transparent view, showing, in magnified view, the flow channels in the flow channel member 210 formed by joining the first to third flow channel members, partially viewed from the side of the first flow channel member 50 where the injection module 200 is mounted. The flow channel member 210 is provided with common supply flow channels 211 (211a, 211b, 211c, and 211d) for various colors and common collection flow channels 212 (212a, 212b, 212c, and 212d) for various colors, extending along the longitudinal direction of the liquid injection head 3. Multiple individual supply flow channels (213a, 213b, 213c, or 213d) formed by the various flow channel slots 52 are connected to the common supply flow channel 211 for each color via a connection port 61. Multiple individual collection flow channels (214a, 214b, 214c, or 214d) formed by the various flow channel slots 52 are connected to the common collection flow channel 212 for each color via a connection port 61. This flow channel configuration allows ink to be collected from the common supply flow channel 211 to the recording element plate 10 located at the center of the flow channel component via a separate supply flow channel 213. In addition, ink can be collected from the recording element plate 10 to the common collection flow channel 212 via a separate collection flow channel 214.

[0067] Figure 8 It shows along Figure 7 A view of the cross-section along line VIII-VIII. (See also:) Figure 8 As shown, each of the various collection flow channels (214a and 214c) is connected to the injection module 200 via a connection port 51. Although in Figure 8 Only the individual collection flow channels 214a and 214c are shown, but as Figure 7As shown, each supply flow channel 213 communicates with the jetting module 200 in another cross-section. In the support member 30 and recording element plate 10 included in each jetting module 200, a mechanism is formed for supplying ink from the first flow channel member 50 to the recording element 15 disposed in the recording element plate 10. Figures 10A to 10C The ink supplied to the recording element 15 has a flow channel. Furthermore, in the support member 30 and the recording element plate 10, a flow channel is formed for partially or completely collecting (returning) the ink supplied to the recording element 15 to the first flow channel member 50. In this example, a common supply flow channel 211 for each color is connected via a liquid supply unit 220 to a negative pressure control unit 230 (high-pressure side) for the corresponding color, and a common collection flow channel 212 is connected via a liquid supply unit 220 to the negative pressure control unit 230 (low-pressure side). The negative pressure control unit 230 generates a pressure difference between the common supply flow channel 211 and the common collection flow channel 212. Therefore, in this embodiment, the flow channel is as follows... Figure 7 and 8 In the liquid jet head connected as shown, for each color, a flow is generated from the common supply flow channel 211 to each supply flow channel 213, to the recording element plate 10, to each collection flow channel 214, and to the common collection flow channel 212.

[0068] <Injection Module>

[0069] Figure 9A A perspective view of a spray module 200 is shown. Figure 9B An exploded view of the jetting module 200 is shown. As a method of manufacturing the jetting module 200, firstly, the recording element board 10 and the flexible wiring board 40 are pre-attached to the support member 30, which is provided with a liquid communication port 31. Subsequently, the terminals 16 on the recording element board 10 and the terminals 41 on the flexible wiring board 40 are electrically connected to each other via lead wires, and then the lead wire connection portion (electrical connection portion) is covered by a sealing member 110 to be sealed. The terminal 42 of the flexible wiring board 40 on the opposite side of the recording element board 10 is electrically connected to the connection terminal 93 of the electrical wiring board 90 (see...). Figure 5 Since the support member 30 is a support for the recording element plate 10 and also a flow channel member that enables fluid communication between the recording element plate 10 and the flow channel member 210, it is preferred to use a member with high flatness and capable of being joined to the recording element plate with sufficiently high reliability as the support member 30. The material of the support member 30 is preferably, for example, alumina or resin.

[0070] <Structure of the Recording Component Board>

[0071] The structure of the recording element board 10 in this embodiment is described. Figure 10AA plan view of the recording element board 10 on the side where the injection port 13 is formed is shown. Figure 10B It shows Figure 10A An enlarged view of the portion represented by XB in the image. Figure 10C It shows Figure 10A A plan view of the back side. Figure 11 To illustrate the recording element plate 10 and cover member 20 along... Figure 10A A perspective view of the cross-section along section line XI-XI shown. (See also...) Figure 10A As shown, four rows of nozzles corresponding to the respective ink colors are formed in the nozzle forming member 12 of the recording element board 10. Note that the extending direction of the nozzle rows in which a plurality of nozzles 13 are arranged is referred to below as the "nozzle row direction".

[0072] like Figure 10B As shown, a recording element 15, configured as a heating element to generate bubbles in the ink using thermal energy, is positioned corresponding to a corresponding ejection port 13. This includes a pressure chamber 23 of the recording element 15 separated by a partition 22. The recording element 15 is electrically connected to the recording element plate 10 via electrical wiring (not shown). Figure 10A Terminal 16 in the middle. Recording element 15 is based on the electrical distribution board 90 ( Figure 5 ) and flexible wiring board 40 ( Figure 9B The pulse signal received from the control circuit of the recording device 1000 generates heat and causes the ink to boil. The force of the bubbles generated by this boiling propels the ink out of the ejection nozzle 13. Figure 10B As shown, a liquid supply channel 18 extends along each nozzle row on one side, and a liquid collection channel 19 extends along the nozzle row on the other side. The liquid supply channel 18 and the liquid collection channel 19 are flow channels disposed in the recording element plate 10 and extending along the nozzle row direction, and are connected to each nozzle 13 via a supply port 17a and a collection port 17b, respectively.

[0073] like Figure 10C and 11 As shown, a sheet-like cover member 20 is stacked on the back side of the recording element board 10 where the injection port 13 is formed, and the cover member 20 has a plurality of openings 21, which will be described later, and communicate with the liquid supply channel 18 and the liquid collection channel 19. In this embodiment, the cover member 20 has three openings 21 for one liquid supply channel 18 and two openings 21 for one liquid collection channel 19. Figure 10B As shown, the openings 21 in the cover member 20 are respectively with Figure 7 The multiple connection ports 51 shown in the figure are connected. Figure 11As shown, the cover member 20 functions as a cover that forms part of the wall of the liquid supply channel 18 and the liquid collection channel 19 formed in the substrate 11 of the recording element board 10. The cover member 20 is preferably an object with sufficient resistance to ink corrosion, and from the viewpoint of preventing color mixing, the shape and position of the opening 21 need to be highly accurate. Therefore, it is preferable to use a photosensitive resin material and a silicon substrate as the materials for the cover member 20, and to provide the opening 21 through a photolithography process. As described above, the cover member is a component that, by using the opening 21, changes the spacing of the flow channels, ideally has a small thickness considering the pressure drop, and is ideally formed of a film-like component.

[0074] Next, the ink flow in the recording component board 10 will be described. Figure 11 It shows the recording element plate 10 and the cover member 20 along... Figure 10A A perspective view of the cross-section along section line XI-XI. In the recording element board 10, a substrate 11 made of Si and an ejector forming member 12 made of photosensitive resin are stacked on top of each other, and a cover member 20 is attached to the back side of the substrate 11. A recording element 15 is formed on one side of the substrate 11. Figure 10B A groove is formed on the back side of the substrate 11, forming a liquid supply channel 18 and a liquid collection channel 19 extending along each ejection port. The liquid supply channel 18 and the liquid collection channel 19 formed by the substrate 11 and the cover member 20 are respectively connected to the common supply flow channel 211 and the common collection flow channel 212 in the flow channel member 210, and a pressure difference is generated between the liquid supply channel 18 and the liquid collection channel 19. In the ejection ports where no ejection operation is performed when ink is ejected from the plurality of ejection ports 13 of the liquid ejection head 3 to perform recording, the ink flow in the liquid supply channel 18 provided in the substrate 11 is affected by this pressure difference. Figure 11 The flow is indicated by arrow C. Specifically, ink flows through supply port 17a, pressure chamber 23, and collection port 17b to liquid collection channel 19. This flow allows air bubbles, foreign matter, and ink with increased viscosity due to evaporation from the injection port 13 in the suspended spray port 13 and pressure chamber 23 to be collected in liquid collection channel 19. Furthermore, it can suppress the increase in ink viscosity in the injection port 13 and pressure chamber 23. The ink collected in liquid collection channel 19 passes through opening 21 of cover member 20 and liquid communication port 31 of support member 30 (see...). Figure 9B The ink is collected sequentially into the connection port 51 in the flow channel component 210, each collection flow channel 214, and the common collection flow channel 212. The ink is finally collected into the supply path of the recording device 1000.

[0075] Specifically, the ink supplied from the main body of the recording device to the liquid ejector head 3 flows in the following order for supply and collection. The ink first flows from the liquid connection portion 111 of the liquid supply unit 220 into the interior of the liquid ejector head 3. Then, the ink is sequentially supplied to the bonding rubber 100, the communication port 72 and common flow channel groove 71 provided in the third flow channel member, the common flow channel groove 62 and communication port 61 provided in the second flow channel member, and each flow channel groove 52 and communication port 51 provided in the first flow channel member. Then, the ink is sequentially supplied to each pressure chamber 23 via the liquid communication port 31 provided in the support member 30, the opening 21 provided in the cover member, the liquid supply channel 18 provided in the substrate 11, and the supply port 17a. Ink supplied to the pressure chamber 23 but not ejected from the ejector port 13 flows sequentially through the collection port 17b and liquid collection channel 19 provided in the substrate 11, the opening 21 provided in the cover member, and the liquid communication port 31 provided in the support member 30. Then, the ink flows sequentially through the connecting port 51 and each flow channel groove 52 provided in the first flow channel member, the connecting port 61 and the common flow channel groove 62 provided in the second flow channel member, the common flow channel groove 71 and the connecting port 72 provided in the third flow channel member 70, and the bonding rubber 100. Furthermore, the ink flows from the liquid connection portion 111 provided in the liquid supply unit to the outside of the liquid injection head 3. Figure 2 In the first circulation path pattern shown, ink flowing in from the liquid connection portion 111 passes through the negative pressure control unit 230 and is then supplied to the bonding rubber 100. Figure 3 In the second circulation path pattern shown, the ink collected from the pressure chamber 23 passes through the engagement rubber 100, then through the negative pressure control unit 230, and flows from the liquid connection portion 111 to the outside of the liquid jet head.

[0076] In addition, such as Figure 2 and 3 As shown, not all ink flowing in from one end of the common supply flow channel 211 of the liquid jet unit 300 is supplied to the pressure chamber 23 via the individual supply flow channels 213a. A portion of the ink flows from the other end of the common supply flow channel 211 to the liquid supply unit 220 without flowing into the individual supply flow channels 213a. Even when the recording element plate 10, as in this embodiment, includes narrow flow channels with high flow resistance, backflow of the ink circulation flow can be suppressed by setting a path for the ink to flow without passing through the recording element plate 10. As described above, since the liquid jet head of this embodiment can suppress the increase in ink viscosity in the pressure chamber and the area near the jet nozzle, it can suppress non-jetting and deviation of the jetting direction from the normal direction, resulting in high-quality recording.

[0077] <Positional relationships between the recording element boards>

[0078] Figure 12 This is a magnified plan view showing adjacent portions of the recording element boards in two adjacent injection modules. For example... Figure 10A As shown in the figures, this embodiment uses a recording element board with a generally parallelogram shape. Figure 12 As shown, in each recording element plate 10, rows of ejector nozzles (14a to 14d) with ejector nozzles 13 arranged are tilted at an angle relative to the transport direction of the recording medium. In adjacent portions of each recording element plate 10, at least two ejector nozzles in the rows of nozzles thus overlap each other in the transport direction of the recording medium. Figure 12 In this arrangement, the two nozzles on each D-line overlap. Even if the position of the recording element board 10 deviates from the predetermined position to a certain extent, this arrangement can make the black stripes and blank areas in the recorded image less noticeable by performing drive control on the overlapping nozzles. This can also be achieved when multiple recording element boards 10 are arranged in a straight line (row) rather than in a zigzag pattern. Figure 12 The construction in this embodiment provides measures for black stripes and blank areas in the overlapping portions of the recording element board 10, while suppressing the increase in length of the liquid jet head in the transport direction of the recording medium. Although the main flat surface of each recording element board in this example has a parallelogram shape, this embodiment is not limited to this, and the construction of this embodiment can also be preferably applied to cases using recording element boards having, for example, a rectangular shape, a trapezoidal shape, or any other shape.

[0079] <Structure of the heat application section in the recording component board>

[0080] The following uses Figure 13A and 13B The structure of the heat application portion in the recording element board according to this embodiment is described. Figure 13A This is a schematic plan view of the area surrounding the heat application portion of the recording element board 10, shown in an enlarged manner. Furthermore, Figure 13B It is along Figure 13A A cross-sectional view of the single-dotted dashed line XIIIB-XIIIB in the diagram.

[0081] In a liquid jetting head, a recording element board for jetting liquid is formed by stacking multiple layers overlapping each other on a substrate 121 made of silicon. In this embodiment, a heat storage layer made of thermal oxide film, SiO film, SiN film, etc., is arranged on the substrate 121. Furthermore, a heating resistor element 126 is arranged on the heat storage layer, and an electrode wiring layer (not shown) serving as wiring made of a metallic material such as Al, Al-Si, Al-Cu, etc., is connected to the heating resistor element 126 via a tungsten plug 128. Figure 13B As shown, an insulating protective layer 127 (first protective layer) is disposed on the heating resistor element 126. The insulating protective layer 127 is an insulating layer disposed above the heating resistor element 126 to cover the heating resistor element 126. The insulating protective layer 127 is made of SiO film, SiN film, etc.

[0082] A protective layer for preventing contact with liquids is disposed on the insulating protective layer 127. The protective layer includes a lower protective layer 125, an upper protective layer 124 (second protective layer), and an attachment protective layer 123, and protects the surface of the heating resistor element 126 from the effects of chemical and physical shocks caused by heating of the heating resistor element 126.

[0083] In this embodiment, the lower protective layer 125 is made of tantalum (Ta), the upper protective layer 124 is made of iridium (Ir), and the adhesion protective layer 123 is made of tantalum (Ta). Furthermore, the protective layers made of these materials are conductive. A protective layer 122 for improving adhesion to the injection nozzle forming member 12 and the liquid-resistant body is disposed on the adhesion protective layer 123. The protective layer 122 is made of SiC. The upper protective layer 124 is made of a material comprising a metal dissolved by an electrochemical reaction and which does not form an oxide film that hinders dissolution upon heating.

[0084] When liquid is sprayed, the upper portion of the upper protective layer 124 comes into contact with the liquid and is in a harsh environment in which bubbles are generated at the upper portion due to the instantaneous temperature rise of the liquid, and the bubbles disappear in that portion, causing cavitation. Therefore, in this embodiment, the upper protective layer 124 is formed of an iridium material with high corrosion resistance and high reliability, and the upper protective layer 124 comes into contact with the liquid at the position corresponding to the heating resistor element 126.

[0085] This embodiment employs an ink circulation structure in which liquid is supplied from supply port 17a to pressure chamber 23 and collected in collection port 17b. Therefore, during printing, liquid flows from upstream supply port 17a to downstream collection port 17b on heating resistor element 126.

[0086] Furthermore, in this embodiment, a scaling suppression process is performed during printing to suppress scaling deposited on the upper protective layer 124 on the heating resistor element 126. Specifically, a portion of the upper protective layer 124 located directly above the heating resistor element 126 is designated as an electrode 121 (first electrode), and a corresponding electrode 129 (second electrode) is provided to form an electric field penetrating the liquid in the liquid chamber 132. As a result, particles charged to a negative potential (e.g., pigment) in the liquid are repelled from the surface of the upper protective layer 124 on the heating resistor element 126. Reducing the presence ratio of particles charged to a negative potential (e.g., pigment) near the surface of the upper protective layer 124, as described above, suppresses scaling deposited on the upper protective layer 124 on the heating resistor element 126 during printing. This scaling suppression is performed considering the fact that scaling occurs when colored materials, additives, etc., contained in the liquid are heated to high temperatures, decompose at the molecular level, become poorly soluble substances, and are physically adsorbed onto the upper protective layer. During the high-temperature heating process of the upper protective layer 124, the presence ratio of colored materials, additives, etc. that cause scaling near the surface of the upper protective layer 124 on the heating resistor element 126 is reduced, thereby inhibiting scaling.

[0087] The following uses Figures 14A to 14D Describe the mechanism for electric field control (also known as potential control and potential difference control) used in this embodiment. Figure 14A In the liquid chamber 132, the upper protective layer electrode 121 and the opposite electrode 129 are arranged in the liquid chamber 132, and the liquid chamber 132 is filled with liquid. The liquid includes particles 141 (such as pigments) charged to a negative potential, and the particles 141 are generally uniformly dispersed in the liquid.

[0088] Figure 14B A state is illustrated in which a voltage is applied such that the potential of electrode 121 in the upper protective layer is lower than the potential of the opposite electrode 129, for example, the potential difference between electrode 121 and the opposite electrode 129 is approximately 0.5 to 2.5 V. This is because, assuming the upper protective layer 124 is made of iridium, in this configuration, an electrochemical reaction occurs between electrode 121 and the liquid when the potential difference between the two electrodes exceeds 2.5 V, and the surface of electrode 121 dissolves into the liquid; therefore, it is preferable to set the potential level to a level where electrode 121 does not dissolve. Specifically, in this embodiment, when the potential difference between electrode 121 and the opposite electrode 129 during the printing process is represented by ΔVp and the potential difference between electrode 121 and the opposite electrode 129 during the aging process is represented by ΔVa, the following formula is preferably satisfied.

[0089] |ΔVa|≤2.5V…Formula (1)

[0090] |ΔVp|≤2.5V…Formula (2)

[0091] Specifically, in this state, although an electric field 140 is formed between the electrode 121 and the opposite electrode 129 in the upper protective layer through the liquid, no current flows between them. Since the electrode 121 in the upper protective layer has a negative potential relative to the opposite electrode 129, the particles 141 charged to a negative potential are repelled from the surface of the electrode 121 in the upper protective layer, and the proportion of particles 141 near the surface of the electrode 121 in the upper protective layer is reduced.

[0092] Figure 14D It is magnification Figure 14B The diagram shows a portion near the upper protective layer. Particles 141 charged to a negative potential are repelled by a repulsive force 143 from the surface of the electrode 121 of the upper protective layer 11 along the electric field lines 140 formed in the liquid.

[0093] In this embodiment, the above mechanism achieves the following relationship: when the potential of the relative electrode is represented by Vc and the potential of the upper protective layer electrode of the heater is represented by Vh, the larger the potential difference ΔV (=Vc-Vh), the more particles 141 that are charged to a negative potential and cause scaling are repelled, and the less scaling occurs. In this embodiment, the relationship between ΔV and the amount of scaling is as follows: Figure 17 As shown in the image.

[0094] However, in the head structure described above, if the initial aging stage is performed under conditions where the potential difference between the relative electrode 129 and the electrode 121 of the upper protective layer is unlikely to cause scaling as it would during printing, scaling is unlikely to form on the upper protective layer 124, and the ink ejection characteristics are unlikely to change. Therefore, in this case, due to the increased aging time in the initial stage, problems arise with increased downtime and increased waste ink.

[0095] This embodiment provides a method for solving this problem. Specifically, when the potential difference during the printing process is represented by ΔVp and the potential difference during the aging process is represented by ΔVa, the conditions ΔVp ≥ 0 and ΔVa < ΔVp are satisfied, such as... Figure 14B and 14C As shown in the diagram. Note that ΔVp = the potential Vpc of the relative electrode during the printing process - the potential Vph of the upper protective layer electrode of the heater during the printing process, and ΔVa = the potential Vac of the relative electrode during the aging process - the potential Vah of the upper protective layer electrode of the heater during the aging process. When using ΔVa (less than ΔVp) as the potential difference during the aging process, scale formation on the upper protective layer of the heater is more likely compared to using ΔVp (see [reference]). Figure 17 ).

[0096] According to the method described above, the proportion of particles charged to a negative potential near the surface of the upper protective layer 124 of the heater is higher during the aging process than during the printing process, thus making it more likely for scale to form on the upper protective layer 124. This reduces the number of times the heating resistor element 126 needs to be driven until its resistance value stabilizes, and shortens the aging period (the time required until the jetting speed stabilizes). Note that... Figure 14C This illustrates the case where ΔVa < 0. For example, in... Figure 14C Similarly, during the aging process, ΔVa is set to be less than 0, causing particles charged to a negative potential to be attracted to the surface of the upper protective layer 124. As a result, scaling is more likely to form and the aging period can be further shortened.

[0097] refer to Figure 16A and 16B . Figure 16A This is a graph showing the jetting rate variation in the initial stage when aging is performed using a potential difference ΔVp (note that ΔVp > 0, specifically +0.5V to 2.5V) as the potential difference between the upper protective layer electrode and the opposite electrode of the heater. The jetting rate variation in the initial stage described herein refers to, for example, a decrease in jetting rate of approximately 5% to 10% from the jetting rate before aging, when the number of jets during the aging process is approximately 1 × 10^7. Meanwhile, Figure 16B It is a graph showing the change in jetting speed when a smaller potential difference ΔVa (ΔVa<ΔVp) is used during the aging process than during the printing process, and then ΔVp is used as the potential difference between the potential of the upper protective layer electrode of the heater and the potential of the opposite electrode during the subsequent printing process.

[0098] like Figure 16A As shown, when the same potential difference is used during the aging process as during the printing process, scaling does not form rapidly on the heater. Therefore, the number of sprays required to stabilize the spray rate increases, and this increases during the aging period. Meanwhile, as... Figure 16BAs shown, by using a smaller potential difference ΔVa (ΔVa < ΔVp) during the aging process compared to the printing process, a rapid change in ejection speed in the initial stage can be achieved. Therefore, the number of ejections required to complete aging and the aging time can be reduced. This reduces downtime and waste ink volume while suppressing the shortening of the lifespan of the heating resistor element 126. Furthermore, since the potential difference is set to ΔVp during printing after aging, the heater returns to a state less prone to scaling during longer printing periods, and the ejection speed remains almost unchanged while suppressing image degradation. Note that the change in ejection speed in the initial stage of the aging process at a potential difference ΔVa, as described herein, refers to, for example, a sharp decrease in ejection speed of approximately 5% to 10% from the ejection speed before aging when the number of ejections during the aging process is approximately 5 × 10^6.

[0099] In this embodiment, as a method for changing the potential difference ΔV between the potential of the upper protective layer electrode and the potential of the opposite electrode, both or either the potential of the upper protective layer electrode and the potential of the opposite electrode can be changed. Note that in a construction where the potential difference ΔV can be changed by altering the potential of one of the electrodes, the circuit structure can be simplified, and therefore this construction is advantageous in terms of cost.

[0100] Furthermore, aging of the upper protective layer of the heater can be performed not only when the recording equipment is new and has no spray history, but also when scale has deposited on the upper protective layer and scale removal is performed after the recording equipment has been used. Scale removal is an operation in which a voltage is applied through the liquid between the electrode 121 and the opposite electrode 129 of the upper protective layer to induce an electrochemical reaction between the electrode 121 and the liquid, causing the material forming the upper protective layer to dissolve into the liquid and remove the scale adhering to the upper protective layer. For example, when iridium is used in the upper protective layer, scale removal can be performed by setting the potential of the upper protective layer to be at least +2.5V higher than the potential of the opposite electrode.

[0101] The aging timing also includes situations where the scaling condition on the upper layer of the heater of the target nozzle is such that the scaling is less than that in the nozzles surrounding the target nozzle. Note that regarding the condition of the recording device, since the state of the recording device being new and without spraying history differs from the state after scaling removal has been performed during use, the amount of scaling on the upper protective layer of the heater typically varies between these states. Therefore, the ΔVa used in the absence of spraying history may differ from the ΔVa used when scaling removal has been performed.

[0102] Furthermore, it is preferable to manage the amount of scale buildup during the aging process by using the number of sprayed droplets (also known as point counting).

[0103] Note that, as a method to determine whether aging is performed appropriately, there are methods such as testing by printing an image with uniform concentration and checking the concentration of the output product. A concentration sensor located in the main body of the recording device can be used as a concentration checking unit, or the concentration can be checked visually.

[0104] <Communication control between liquid injection head and body>

[0105] The following uses Figure 20 This describes the communication control between the liquid injection head and the main body according to this embodiment. Figure 20 This is a communication model diagram between the liquid injection head and the main body. The main board contained in the main body of the recording device 1000 includes a CPU, ROM, RAM, etc. Such a main board receives temperature information about each recording element board 10 from the liquid injection head 3, and sends control signals to the electrical wiring board 90 of the liquid injection head 3 to drive the recording element board 10 based on the received temperature information.

[0106]

[0107] Next, refer to Figure 21 . Figure 21 This is a flowchart illustrating a series of processing examples in this embodiment. In this series of processes, aging is performed on a liquid jet head contained in a recording device that is new and has no jetting history, and printing is performed after aging. Subsequently, when the number of jetted droplets reaches a predetermined threshold, scale removal is performed on the upper protective layer of the heater, and then aging is performed again. Each step is described in detail below.

[0108] When a new liquid jet head with no jetting history is attached to the main body of the recording device, in step S2101, the CPU of the recording device 1000 sets the potential of the upper protective layer electrode of the heater to Vah and the potential of the opposite electrode to Vac to obtain the optimal potential difference ΔVa for the initial stage of aging. Note that in the following description, "step S" will be abbreviated as "S".

[0109] In S2102, the CPU of the recording device 1000 performs aging.

[0110] In S2103, the CPU of the recording device 1000 determines whether scale has appropriately formed on the upper protective layer of the heater. If the determination result in this step is yes, the process proceeds to S2104. Conversely, if the determination result is no, the process returns to S2101. Note that in this step, as described above, the concentration of the output product obtained through test printing is checked to obtain a measured concentration, and the determination is based on whether the measured concentration is within a predetermined range. Specifically, it is considered that scale has appropriately formed if the measured concentration is within the predetermined range.

[0111] In S2104, the CPU of the recording device 1000 sets the potential of the upper protective layer electrode of the heater to Vph and sets the potential of the opposite electrode to Vpc to obtain a potential difference ΔVp suitable for printing.

[0112] In S2105, the CPU of the recording device 1000 performs printing processing.

[0113] In S2106, the CPU of the recording device 1000 determines whether the number of sprayed droplets exceeds a predetermined threshold (represented by Nd). If the determination result in this step is yes, the CPU of the recording device 1000 considers that the amount of scale on the upper protective layer of the heater has exceeded the allowable amount, and proceeds to S2107. Conversely, if the determination result in this step is no, the process returns to S2105 and printing is continuously performed with the same settings.

[0114] In S2107, the CPU of the recording device 1000 performs scale removal.

[0115] After the scale removal is performed in S2107, the scale on the upper protective layer of the heater is removed and the upper protective layer is in a state of almost no scale. Therefore, the process proceeds to S2101 and S2102. Specifically, aging is performed again. Note that, as mentioned above, the value of the potential difference ΔVa between the second aging and subsequent aging can be a different value than the value used in the initial stage of aging performed on a new head without a spray history.

[0116] Note that it is crucial to understand how the potential difference changes from ΔVa during the aging process to ΔVp during the printing process. Specifically, rapid potential changes can lead to a rapid change in the way scale forms on the upper protective layer of the heater (e.g., scale formed during aging suddenly detaches or similar conditions occur). This can cause changes in jetting characteristics and result in defects such as image inhomogeneity. To prevent such defects, it is preferable to gradually bring ΔVa closer to ΔVp as the number of jetted droplets increases during the aging process.

[0117] Furthermore, to further accelerate jet changes through aging, pulses with higher voltage values ​​than those under normal conditions (such as recording) can be applied without damaging the heater material. Additionally, pulses can be applied for a longer period during the aging process compared to the pulse duration under normal conditions.

[0118] Furthermore, the liquid jet head in this embodiment performs printing using four CMYK inks (cyan, magenta, yellow, and black), and aging is not required for colors that are unlikely to form scale. Moreover, since the ink colors include both colors that may and are unlikely to form scale, the values ​​of ΔVa and ΔVp do not need to be uniform across all ink colors, and combinations of values ​​can vary between ink colors.

[0119] [Second Embodiment]

[0120] <Structure of the heat application section in the recording component board>

[0121] The second embodiment is a mode for handling the following situation where the amount of scale on the upper protective layer of the heater has a local minimum in relation to the potential difference ΔV (=Vc-Vh) between the potential Vc of the opposite electrode and the potential Vh of the upper protective layer electrode of the heater, such as... Figure 18 As shown in the figure. Note that in the following description, the differences from the first embodiment are mainly described, and descriptions of content that is the same as in the first embodiment are appropriately omitted.

[0122] As described in the first embodiment, since most of the particles causing scaling are negatively charged, the relationship between potential and scaling should be such that the more negative the potential of the upper protective layer electrode of the heater, the less likely the particles 141 charged to a negative potential are to be attracted to the heater and form scaling. Nevertheless, the amount of scaling on the upper protective layer of the heater has the following characteristics: Figure 18 The local extrema shown are believed to be caused by scale deposits on the opposite electrode side.

[0123] Specifically, the more negative the potential of the upper protective layer electrode of the heater, the more positive the potential of the relative electrode. Therefore, negatively charged particles 141 are more likely to be attracted towards the relative electrode and more likely to form scale on it. As a result, the deposits adhering to the relative electrode insulate the relative electrode and the ink from each other, the electric field gradually approaches zero, and a state is established where no potential control is effective. Therefore, with an increase in ΔV, the amount of scale increases. For this reason, the amount of scale is considered to have a similar effect to... Figure 18 The local minimum is shown in the figure.

[0124] Therefore, the feature of this embodiment is that the potential difference satisfies ΔVp≥0 and ΔVa>ΔVp.

[0125] Specifically, the potential difference ΔVp between the relative electrode potential and the upper protective layer electrode potential of the heater during the printing process is preferably set to a value such that even with prolonged use, scale deposition is minimal; that is, it is set to a value such that scale accumulation reaches a local minimum. Simultaneously, the potential difference ΔVa between the relative electrode potential and the upper protective layer electrode potential of the heater during the aging process is preferably set to a value greater than the value at which scale accumulation reaches a local minimum (ΔVa > ΔVp).

[0126] [Third Embodiment]

[0127] <Structure of the heat application section in the recording component board>

[0128] The third embodiment is a mode for handling the following situation where the amount of scale on the upper protective layer of the heater increases monotonically in relation to the potential difference ΔV (=Vc-Vh) between the potential Vc of the opposite electrode and the potential Vh of the upper protective layer electrode of the heater, such as... Figure 19 As shown in the figure. Note that in the following description, the differences from the first embodiment are mainly described, and descriptions of content that is the same as in the first embodiment are appropriately omitted.

[0129] As described in the first embodiment, the particles causing scaling are negatively charged in most cases, but positively charged in very rare cases. In this case, as... Figure 15A and 15B As shown, the more negative the potential of the upper protective layer electrode of the heater, the greater the likelihood that positively charged particles will be attracted to the upper protective layer of the heater and that scale will form on the upper protective layer of the heater.

[0130] Therefore, the feature of this embodiment is that the potential difference satisfies ΔVp<0 and ΔVa>ΔVp.

[0131] Specifically, the potential difference ΔVp between the relative electrode potential and the upper protective layer electrode potential of the heater during the printing process is preferably set to a value such that even with prolonged use, scale deposition is minimal, i.e., it is set as small as possible so that ΔVp < 0. Simultaneously, the potential difference ΔVa between the relative electrode potential and the upper protective layer electrode potential of the heater during the aging process is preferably set to a value larger than the ΔVp value where scale deposition is unlikely (preferably set such that ΔVa > ΔVp). Although Figure 15C The case where ΔVa is greater than 0 is shown, but ΔVa can be equal to or less than 0.

[0132] [Other embodiments]

[0133] Regarding the potential difference between the upper protective layer electrode of the heater and the potential of the opposite electrode, the foregoing embodiments described a different pattern between the potential difference ΔVa during the aging process and the potential difference ΔVp during the printing process. In this case, the potential of each electrode can be set to any potential. Specifically, the potential of the upper protective layer electrode of the heater can be fixed (Vah = Vph). Alternatively, the potential of the opposite electrode can be fixed (Vac = Vpc).

[0134] In addition, all values ​​of Vac, Vah, Vpc, and Vph can be 0 or higher.

[0135] Note that the contents of the first to third embodiments can be used in combination as appropriate.

[0136] Embodiments of this disclosure can also be implemented by a computer of a system or device that reads and executes computer-executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be more fully referred to as a "non-transitory computer-readable storage medium") to implement the functions of one or more of the above embodiments, and / or the computer includes one or more circuits (e.g., application-specific integrated circuits (ASICs)) for implementing the functions of one or more of the above embodiments. Embodiments of the invention can also be implemented by means of a computer of the system or device through methods such as reading and executing computer-executable instructions from a storage medium to perform the functions of one or more of the above embodiments and / or controlling one or more circuits to perform the functions of one or more of the above embodiments. The computer may include one or more processors (e.g., a central processing unit (CPU), a microprocessor unit (MPU)) and may include a network of individual computers or individual processors to read and execute computer-executable instructions. The computer-executable instructions may be provided to the computer, for example, from a network or storage medium. The storage medium may include, for example, a hard disk, random access memory (RAM), read-only memory (ROM), the memory of a distributed computing system, an optical disk (e.g., an optical disc (CD), a digital versatile disc (DVD), or a Blu-ray disc (BD)). TM One or more of the following: flash memory devices, memory cards, etc.

[0137] Other embodiments

[0138] The embodiments of the present invention can also be implemented by providing software (programs) that perform the functions of the above embodiments to a system or device via a network or various storage media, and the computer or central processing unit (CPU) or microprocessor unit (MPU) of the system or device reads out and executes the program.

[0139] According to this disclosure, aging can be completed quickly while suppressing damage to the heater material.

[0140] Although the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims should be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

Claims

1. A liquid jetting device, comprising: A liquid jet head includes a heating element for generating energy required to jet liquid, a first protective layer preventing contact between the heating element and the liquid, a second protective layer partially covering the first protective layer and acting as a first electrode, a second electrode electrically connected to the first electrode via the liquid, and a jet nozzle for jetting liquid. as well as A control unit is configured to perform control in each of the aging process and the printing process by setting the potential difference between the first electrode and the second electrode to a predetermined value by changing at least one of the potentials of the first electrode and the second electrode, wherein... Formula (1) is satisfied under the following conditions: The potential of the first electrode during the aging process is represented by Vah, and the potential of the second electrode during the aging process is represented by Vac. The potential difference between the potentials of the first electrode (Vah) and the second electrode (Vac) is given by... Va indicates; as well as The potential of the first electrode during the printing process is represented by Vph, and the potential of the second electrode during the printing process is represented by Vpc. The potential difference between the potentials of the first electrode (Vph) and the second electrode (Vpc) is given by... Vp means, Va≠ Vp… formula (1).

2. The liquid jetting device according to claim 1, wherein, It satisfies formula (2). Va< Vp… formula (2).

3. The liquid jetting device according to claim 1 or 2, wherein, It satisfies formula (3). Vp ≥ 0... Formula (3).

4. The liquid jetting device according to claim 1, wherein, It satisfies formula (4). Va> Vp… formula (4).

5. The liquid jetting device according to claim 4, wherein, It satisfies formula (5). Vp ≥ 0… Formula (5).

6. The liquid jetting device according to claim 4, wherein, It satisfies formula (6). Vp<0… Formula (6).

7. The liquid jetting device according to claim 6, wherein, It satisfies formula (7). Va ≤ 0… Formula (7).

8. The liquid jetting device according to claim 6, wherein, It satisfies formula (8). Va>0… Formula (8).

9. The liquid jetting device according to claim 1, wherein, It satisfies formula (9). Vah=Vph… formula (9).

10. The liquid jetting device according to claim 1, wherein, It satisfies formula (10). Vac=Vpc… Formula (10).

11. The liquid jetting device according to claim 1, wherein, The second protective layer is made of a material comprising a metal that dissolves through an electrochemical reaction and does not form an oxide film that hinders dissolution when heated.

12. The liquid jetting device according to claim 1, wherein, It satisfies formulas (11) and (12). | Va|≤2.5 V…Formula (11) | Vp|≤2.5 V…Formula (12).

13. The liquid jetting device according to claim 1, wherein, All values ​​of Vac, Vah, Vpc, and Vph are above 0.

14. The liquid jetting device according to claim 1, wherein, After scaling removal is performed, aging is performed, wherein scaling removal is performed by applying a voltage through the liquid between the first and second electrodes to induce an electrochemical reaction between the first electrode and the liquid, and dissolving the material forming the protective layer into the liquid to remove the scale adhering to the protective layer.

15. The liquid jetting apparatus according to claim 1, further comprising a determining unit for determining whether to perform scale removal after printing based on the number of jetted droplets.

16. A control method for a liquid injection device, comprising: A liquid jet head includes a heating element for generating energy required to jet liquid, a first protective layer preventing contact between the heating element and the liquid, a second protective layer partially covering the first protective layer and acting as a first electrode, a second electrode electrically connected to the first electrode via the liquid, and a jet nozzle for jetting liquid. as well as A control unit configured to perform control in each of the aging process and the printing process by changing the potential of the first electrode and the second electrode to a predetermined value, the control method comprising: Formula (13) is satisfied under the following conditions: The potential of the first electrode during the aging process is represented by Vah, and the potential of the second electrode during the aging process is represented by Vac. The potential difference between the potentials of the first electrode (Vah) and the second electrode (Vac) is given by... Va indicates; as well as The potential of the first electrode during the printing process is represented by Vph, and the potential of the second electrode during the printing process is represented by Vpc. The potential difference between the potentials of the first electrode (Vph) and the second electrode (Vpc) is given by... Vp means, Va≠ Vp… formula (13).

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