Liquid ejection device and control method

Abstract

The present disclosure provides a liquid ejection device and a control method. One aspect of the present disclosure is a liquid ejection device comprising: a liquid ejection head, the liquid ejection head comprising: a conversion element that generates energy required to eject liquid; a first protective layer that prevents contact between the conversion element and the liquid; a second protective layer that partially covers the first protective layer and serves as a first electrode; a second electrode that is electrically connected to the first electrode via the liquid; and an ejection port that ejects the liquid; and a control unit configured to control a potential difference between the first electrode and the second electrode during printing to a predetermined value by changing at least one of the potential of the first electrode and the potential of the second electrode. The control unit sets the potential difference based on at least one of the conditions and configuration of the liquid ejection head.

Description

Technical Field

[0001] The present disclosure relates to a liquid ejecting apparatus including a liquid ejecting head that ejects liquid such as ink. Background Art

[0002] Inkjet recording methods employ an electrothermal conversion element (hereinafter referred to as a "heater"), including a heating resistor, to heat the ink and generate bubbles. Recording heads using these heaters carry the risk of the ejection speed differing from the designer's intended speed, depending on nozzle conditions such as temperature and ink buildup. Therefore, a method for adjusting the ejection speed based on the state of the recording head is needed.

[0003] To address this issue, Japanese Patent Laid-Open No. 2000-246899 proposes a method in which the heating pulse applied to the heater is divided into a first drive pulse and a second drive pulse, thereby increasing the ejection speed compared to using a single pulse. In this method, a superheated liquid layer is formed using the first drive pulse. After ensuring a sufficient thickness of the superheated liquid layer, a second drive pulse is used for rapid heating. This method increases the energy required for bubble generation while ensuring stable bubble generation.

[0004] In addition, Japanese Patent Laid-Open No. 2019-38127 discloses a technology in which, in the recording head of a recording device, an upper protective layer covering the heating portion of a heater is used as an electrode and an opposing electrode connected to this electrode through a liquid is provided. The recording device includes a potential control unit that forms an electric field between the upper protective layer electrode and the opposing electrode, and during normal printing, printing is performed when the potential of the opposing electrode is set to be higher than the potential of the upper protective layer electrode. This prevents the ink color material and resin that cause scaling and are negatively charged from being attracted to the surroundings of the heater and makes scaling less likely to occur. Therefore, unevenness can be suppressed. Summary of the Invention

[0005] However, further improvements in image quality according to the technology described in the aforementioned patent document face the problem of increased control load. This is due to the following: As finer ink droplets are ejected when forming high-definition images, the number of ink droplets required increases, and the number of heat pulses used for driving per unit time also increases. Therefore, when using multiple drive pulses, as in Japanese Patent Laid-Open No. 2000-246899, the control load increases because each drive pulse needs to be optimally modulated.

[0006] Therefore, in view of the above-mentioned problems, an object of the present disclosure is to provide a technology for suppressing unevenness using a lower control load than the conventional technology.

[0007] One aspect of the present disclosure is a liquid ejection device, comprising: a liquid ejection head, the liquid ejection head comprising: a conversion element, the conversion element generating energy required to eject liquid; a first protective layer, the first protective layer preventing contact between the conversion element and the liquid; a second protective layer, the second protective layer partially covering the first protective layer and serving as a first electrode; a second electrode, the second electrode being electrically connected to the first electrode through the liquid; and an ejection port, the ejection port ejecting the liquid; and a control unit, which is configured to control the potential difference between the first electrode and the second electrode during printing to a predetermined value by changing at least one of the potential of the first electrode and the potential of the second electrode, wherein the control unit sets the potential difference based on at least one of the conditions and configuration of the liquid ejection head.

[0008] Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a diagram illustrating a schematic configuration of a recording device;

[0010] Figure 2 is a schematic diagram illustrating a first circulation path;

[0011] Figure 3 is a schematic diagram illustrating a second circulation path;

[0012] Figure 4A and Figure 4B is a perspective view of a liquid ejecting head;

[0013] Figure 5 is an exploded perspective view of a liquid ejecting head;

[0014] Figure 6 is a diagram illustrating a flow channel component;

[0015] Figure 7 is a diagram illustrating a connection relationship between flow channels in a flow channel member;

[0016] Figure 8 It is along Figure 7 A cross-sectional view taken along section line VIII-VIII in FIG.

[0017] Figure 9A and Figure 9B is a diagram illustrating an injection module;

[0018] Figures 10A to 10C is a diagram illustrating the structure of a recording element board;

[0019] Figure 11 The diagram is along Figure 10A A perspective view of the structure of the recording element board and the cover member taken along the section line XI-XI in FIG.

[0020] Figure 12 is a plan view showing an adjacent portion of a recording element board, partially enlarged;

[0021] Figure 13 is a modeling communication diagram between the liquid ejection head and the main body;

[0022] Figure 14 is a graph illustrating the injection speed in the case where the total heating period is divided into two periods and the divided period is changed in various ways;

[0023] Figure 15A and Figure 15B is a diagram illustrating the structure of a heat application portion in a recording element board;

[0024] 16A to 16C is a diagram for explaining electric field control;

[0025] Figure 17 is a graph illustrating the relationship between ΔV and injection speed;

[0026] Figure 18 is a graph illustrating the relationship between the number of ejected droplets and the ejection velocity when ΔV is constant or varied;

[0027] Figure 19A and Figure 19B It is a sequential diagram of a series of processes related to point counting and ΔV adjustment;

[0028] Figure 20A and Figure 20B is a diagram illustrating wiring in a recording element board;

[0029] Figure 21 is a graph illustrating the relationship between temperature and injection velocity;

[0030] Figure 22 is a diagram illustrating a ΔV variation table;

[0031] Figure 23 It is a sequential diagram of a series of processes related to ΔV adjustment based on temperature and point counting;

[0032] Figure 24 is a diagram illustrating a ΔV variation table;

[0033] Figure 25 It is a sequential diagram of a series of processes related to ΔV adjustment based on temperature, duty cycle and point count;

[0034] Figure 26is a graph illustrating the relationship between the elapsed time and the ejection speed in a case where continuous ink ejection is paused;

[0035] Figure 27 is a diagram illustrating a ΔV variation table; and

[0036] Figure 28 : is a graph illustrating the relationship between ΔV and the injection speed. DETAILED DESCRIPTION

[0037] As an example of the present disclosure, a recording device employing an inkjet recording method will be described below. The recording device may be, for example, a single-function printer having only a recording function, or a multifunction printer having multiple functions such as recording, fax, and scanner functions. Furthermore, the present disclosure may be applied to manufacturing devices for manufacturing color filters, electronic devices, optical devices, fine structures, and the like using a predetermined recording method.

[0038] Note that in the following description, "recording" is not limited to cases where meaningful information such as letters and graphics are formed, and the product to be recorded may or may not be meaningful. In addition, "recording" also generally refers to cases where an image, design, pattern, structure, etc. is formed on a recording medium, or when the medium is processed, regardless of whether the recorded product can be clearly seen by people.

[0039] Furthermore, the “recording medium” refers not only to general paper used in recording devices but also to media capable of receiving ink such as cloth, plastic film, metal plate, glass, ceramic, resin, wood, leather, and the like.

[0040] Furthermore, "ink" should be understood broadly, as in the definition of "recording" described above. Thus, "ink" refers to a liquid that can be used to form an image, design, pattern, etc. by applying it to a recording medium, process the recording medium, or process the ink (for example, to solidify or insolubilize a colorant in the ink applied to the recording medium).

[0041] Furthermore, unless otherwise specified, a "recording element" (also referred to as a "nozzle" in some cases) is a general term for an ink ejection port, a liquid channel communicating therewith, and an element that generates energy for ejecting ink.

[0042] [First embodiment]

[0043] While this embodiment relates to an inkjet recording apparatus in a mode in which a liquid such as ink is circulated between a tank and a liquid ejecting head, the inkjet recording apparatus may operate in a different mode. For example, the mode may be such that, instead of circulating the ink, two tanks are provided upstream and downstream of the liquid ejecting head, and the ink flows from one tank to the other, thereby causing the ink in the pressure chamber to flow.

[0044] Furthermore, while the liquid ejection head according to this embodiment is a so-called line head having a length corresponding to the width of the recording medium, this embodiment can also be applied to a so-called serial liquid ejection head that records while scanning the recording medium. While a configuration in which one recording element board for black ink and one recording element board for color ink are installed can be given as an example of a serial liquid ejection head configuration, the configuration is not limited to this. Specifically, a configuration can be as follows: a short line head having a width smaller than the recording medium and in which multiple recording element boards are arranged such that the ejection nozzle rows overlap one another in the ejection nozzle row direction is produced, and this short line head is caused to scan the recording medium.

[0045] <Inkjet Recording Device>

[0046] Figure 1 The diagram illustrates a schematic configuration of a liquid ejection device according to the present embodiment, specifically, an inkjet recording device 1000 (hereinafter also referred to as a recording device) that performs recording by ejecting ink. The recording device 1000 includes a conveying unit 1 that conveys a recording medium 2 and a linear liquid ejection head 3 that is arranged approximately orthogonally to the conveying direction of the recording medium, and is a linear recording device that performs continuous recording in one pass while continuously or intermittently conveying a plurality of recording media 2. The recording medium 2 is not limited to cut paper and may be a continuous roll of paper. The liquid ejection head 3 is capable of full-color printing by using cyan, magenta, yellow, and black (CMYK) inks. In the liquid ejection head 3, a main tank, a buffer tank, and a liquid supply unit that forms a supply channel for supplying ink to the liquid ejection head, which are described later, are fluidly connected to each other (see Figure 2 ). In addition, an electrical control unit that sends power and an ejection control signal to the liquid ejection head 3 is electrically connected to the liquid ejection head 3. The liquid path and the electrical signal path in the liquid ejection head 3 will be described later.

[0047] <First Circulation Path>

[0048] Figure 2 1 is a schematic diagram illustrating a first circulation path as one mode of a circulation path applied to the recording apparatus according to the present embodiment. Figure 2 As shown, the liquid ejecting head 3 is fluidically connected to a first circulation pump (high pressure side) 1001, a first circulation pump (low pressure side) 1002, a buffer tank 1003, etc. Figure 2 , only one of the CMYK inks flows through a path, but actually, circulation paths for four colors are provided in the liquid ejecting head 3 and the recording apparatus main body.

[0049] The buffer tank 1003, which is connected to the main tank 1006 and serves as a sub-tank, has an atmospheric communication port (not shown) that allows the inside and outside of the tank to communicate with each other, and can discharge bubbles in the ink to the outside. The buffer tank 1003 is also connected to the replenishment pump 1005. When ink is consumed in the liquid ejecting head 3, the replenishment pump 1005 transfers the consumed amount of ink from the main tank 1006 to the buffer tank 1003. For example, when ink is ejected (discharged) from the ejection port of the liquid ejecting head during operations such as recording by ejecting ink and recovery by suction, the ink is consumed in the liquid ejecting head 3.

[0050] The two first circulation pumps 1001 and 1002 have the function of pumping out ink from the liquid connection portion 111 of the liquid ejecting head 3 and causing the ink to flow to the buffer tank 1003. Each of the first circulation pumps is preferably a displacement pump with a quantitative liquid delivery capability. Specifically, a tube pump, a gear pump, a diaphragm pump, a syringe pump, etc. can be given as examples. For example, a mode in which a constant flow rate is ensured by arranging a universal constant flow valve or a safety valve at the pump outlet can also be used. In the process of driving the liquid ejecting 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 speed in each of the common supply flow channel 211 and the common collection flow channel 212. The flow rate is preferably set to a flow rate equal to or higher than the flow rate at which the temperature difference between the recording element plates 10 in the liquid ejecting head 3 is at a level that does not affect the quality of the recorded image. However, when an excessively high flow rate is set, the negative pressure difference between the recording element plates 10 becomes too large due to the pressure drop in the flow channel in the liquid ejecting unit 300, and uneven image density occurs. Therefore, it is preferable to take the temperature difference and the negative pressure difference between the recording element boards 10 into consideration when setting the flow rate.

[0051] The negative pressure control unit 230 is provided in the middle of the path connecting the second circulation pump 1004 and the liquid injection unit 300. Therefore, the negative pressure control unit 230 has the following function: to operate so that even when the flow in the circulation system fluctuates due to the difference in the recording duty cycle, the pressure downstream of the negative pressure control unit 230 (i.e., on the liquid injection unit 300 side) can still be maintained at a preset constant pressure. Any mechanism can be used as the two pressure adjustment 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 certain range centered on the desired set pressure. For example, a mechanism similar to a so-called "decompression regulator" can be used. In the case of using a decompression regulator, such as Figure 2As shown, the second circulation pump 1004 preferably applies pressure to the upstream side of the negative pressure control unit 230 via the liquid supply unit 220. Since this structure can suppress the influence of the head pressure of the buffer tank 1003 on the liquid ejecting head 3, the freedom of layout 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 certain pressure or a lifting range pressure higher than the certain pressure within the range of the ink circulation flow rate used in the driving process of the liquid ejecting head 3, and a turbine pump, a volumetric pump, etc. can be used. Specifically, a diaphragm pump, etc. can be applied. In addition, for example, a head tank arranged to have a certain head difference with respect to the negative pressure control unit 230 can be used instead of the second circulation pump 1004.

[0052] like Figure 2 As shown, the negative pressure control unit 230 includes two pressure adjustment mechanisms that are respectively set to different control pressures. The pressure adjustment mechanism on the higher pressure setting side of the two negative pressure adjustment mechanisms ( Figure 2 The common supply flow path 211 of the liquid ejecting unit 300 is connected to the liquid supply unit 220 via the interior of the liquid supply unit 220. At the same time, the pressure adjustment mechanism ( Figure 2 The liquid supply unit 220 (denoted by L) is connected to the common collection channel 212 via the interior of the liquid supply unit 220.

[0053] The liquid ejecting unit 300 is provided with a common supply flow channel 211, a common collection flow channel 212, and individual supply flow channels 213 and individual collection flow channels 214 that communicate with the recording element board 10. Since the individual supply flow channels 213 and the individual collection flow channels 214 communicate with the common supply flow channel 211 and the common collection flow channel 212, a flow ( Figure 2 This is because, 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 differential pressure is generated between the two common flow channels.

[0054] As described above, in the liquid ejection unit 300, while the ink flows through the interior of the common supply flow channel 211 and the common collection flow channel 212, a flow of ink is generated that partially passes through the interior of the recording element board 10. Therefore, the flow through the common supply flow channel 211 and the common collection flow channel 212 allows the heat generated in the recording element board 10 to be discharged to the exterior of the recording element board 10. Furthermore, since this configuration enables the generation of ink flows in the ejection ports and pressure chambers where recording is not being performed while the liquid ejection head 3 is recording, it is possible to suppress increases in ink viscosity in these areas. Furthermore, ink with increased viscosity and foreign matter in the ink can be discharged to the common collection flow channel 212. Therefore, the liquid ejection head 3 of this embodiment can perform high-quality recording at high speed.

[0055] <Second Circulation Route>

[0056] Figure 3 1 is a schematic diagram illustrating a second circulating path different from the first circulating path described above, among the circulating paths applied to the recording apparatus according to the present embodiment. The main differences from the first circulating path are as follows.

[0057] First, the two pressure adjustment mechanisms forming the negative pressure control unit 230 each have a mechanism for controlling the pressure upstream of the negative pressure control unit 230 so that the pressure fluctuates within a certain range centered on the desired set pressure (a mechanism having the same function as a so-called "back pressure regulator"). In addition, the second circulation pump 1004 serves as a negative pressure source for reducing the pressure on the downstream side of the negative pressure control unit 230. In addition, the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 are arranged upstream of the liquid ejection head, and the negative pressure control unit 230 is arranged downstream of the liquid ejection head.

[0058] The negative pressure control unit 230 in the second circulation path operates so that when the liquid ejecting head 3 is recording, even if the flow rate fluctuates due to changes in the recording duty cycle, the pressure upstream of the negative pressure control unit 230 (i.e., on the liquid ejecting unit 300) will fluctuate within a certain range. For example, the pressure fluctuates within a certain range centered on a preset pressure. Figure 3 As 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 head pressure of the buffer tank 1003 on the liquid ejecting head 3, the degree of freedom in the layout of the buffer tank 1003 in the recording apparatus 1000 can be increased. For example, a head tank arranged to have a certain head difference with respect to the negative pressure control unit 230 can be used instead of the second circulation pump 1004.

[0059] As in the first loop path, Figure 3The negative pressure control unit 230 shown includes two pressure adjustment mechanisms that are respectively set to different control pressures. The pressure adjustment mechanism on the higher pressure setting side of the two pressure adjustment mechanisms ( Figure 3 The pressure regulating mechanism (indicated by H in FIG) is connected to the common supply flow channel 211 in the liquid ejecting unit 300 via the interior of the liquid supply unit 220. Figure 3 The liquid supply unit 220 (denoted by L) is connected to the common collection channel 212 via the interior of the liquid supply unit 220.

[0060] The two pressure adjustment mechanisms make the pressure in the common supply flow channel 211 higher than the pressure in the common recovery flow channel 212. This configuration generates an ink flow ( Figure 3 As described above, in the second circulation path, an ink flow state similar to that in the first circulation path is obtained in the liquid ejecting unit 300. At the same time, the second circulation path has two advantages different from the first circulation path.

[0061] The first advantage is as follows: in the second circulation path, since the negative pressure control unit 230 is arranged downstream of the liquid ejection head 3, the risk of dust and foreign matter generated in the negative pressure control unit 230 flowing into the ejection head is low. The second advantage is as follows: the maximum value of the flow rate required to supply the liquid ejection head 3 from the buffer tank 1003 in the second circulation path is smaller than the maximum value of the flow rate required to supply the liquid ejection head 3 from the buffer tank 1003 in the first circulation path. The reason is as follows. The total flow rate in the common supply flow channel 211 and the common collection flow channel 212 in the case where ink circulates during recording standby is referred to as A. The value of A is defined as the minimum flow rate required to make the temperature difference in the liquid ejection unit 300 fall within the desired range when the temperature of the liquid ejection head 3 is adjusted during recording standby. In addition, the ejection flow rate in the case of ejecting ink from all ejection ports in the liquid ejection unit 300 (total ejection) is defined as F. Then, in the first circulation path ( Figure 2 ), 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 amount of liquid supplied to the liquid ejecting head 3 required for all ejections is A+F.

[0062] At the same time, in the second loop path ( Figure 3), the amount of liquid supplied to the liquid ejection head 3 required during the recording standby period is flow rate A. The amount of liquid supplied to the liquid ejection head 3 required for all injections is flow rate F. Then, in the case of the second circulation path, the total value of the set flow rates of the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002, that is, the maximum value of the flow rate required to be supplied is the larger value of A and F. Therefore, if a liquid ejection unit 300 with the same structure is used, the maximum value of the supply amount required in the second circulation path (A or F) must be less than the maximum value of the supply flow required in the first path (A+F). Therefore, in the case of the second circulation path, the degree of freedom of the applicable circulation pump is increased. Therefore, for example, a low-cost circulation pump with a simple structure can be used, or the load of the cooler (not shown) in the path installed 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 recording device body. This advantage is greater in a linear head with a relatively large value of A or F, and among linear heads, a linear head with a larger length in the longitudinal direction has more benefits.

[0063] 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 through the liquid ejecting unit 300 is greatest during the recording standby period, the lower the recording duty cycle, the higher the negative pressure applied to each nozzle. Therefore, especially when the channel width (the length in a direction perpendicular to the ink flow direction) of the common supply channel 211 and the common collection channel 212 is reduced to reduce the head width (the length of the liquid ejecting head along its shorter side), high negative pressure is applied to the nozzles in low-duty cycle images, where unevenness tends to be noticeable. This application of high negative pressure may increase the impact of satellite droplets. At the same time, in the first circulation path, since high negative pressure is applied to the nozzles at the time of high-duty cycle image formation, there is the advantage that even if satellite droplets are generated, they are less noticeable and their impact on the recorded image is minimal. The preferred one of the two circulation paths can be selected and adopted based on the specifications of the liquid ejecting head and the recording device body (ejection flow rate F, minimum circulation flow rate A, and flow channel resistance in the head).

[0064] <Structure of Liquid Jet Head>

[0065] Next, the configuration of the liquid ejecting head 3 according to the first embodiment will be described. Figure 4A and Figure 4B : is a perspective view of the liquid ejection head 3 according to the present embodiment. The liquid ejection head 3 is a line type liquid ejection head in which 15 recording element boards 10 are aligned along a straight line (arranged along a line), and each recording element board 10 is capable of ejecting four colors of ink, C, M, Y, and K. Figure 4AAs shown, the liquid ejection head 3 includes a signal input terminal 91 and a power supply terminal 92 electrically connected to the recording element board 10 via the flexible wiring board 40 and the 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, and an ejection drive signal is supplied to the recording element board 10 via the signal input terminal 91, and electric power required for ejection is supplied to the recording element board 10 via the power supply terminal 92.

[0066] By concentrating the wires in one place using the circuit in the electrical wiring board 90, the number of signal input terminals 91 and power supply terminals 92 can be made smaller than that of the recording element board 10. Thus, the number of electrical connection parts that need to be attached when attaching the liquid ejecting head 3 to the recording device 1000 or the number of electrical connection parts that need to be removed when detaching the liquid ejecting head can be reduced. Figure 4B As shown, the liquid connection portions 111 provided at both ends of the liquid ejecting head 3 are connected to the liquid supply system of the recording apparatus 1000. Thus, inks of the four colors CMYK are supplied from the supply system of the recording apparatus 1000 to the liquid ejecting head 3, and ink that has passed through the interior of the liquid ejecting head 3 is collected in the supply system of the recording apparatus 1000. Thus, inks of various colors can be circulated through the paths of the recording apparatus 1000 and the paths of the liquid ejecting head 3.

[0067] Figure 5 1 is an exploded perspective view of components or units forming the liquid ejection head 3. The liquid ejection 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 connecting portion 111 ( Figure 2 and Figure 3 ), and filters 221 of various colors communicating with the opening of the liquid connecting portion 111 ( Figure 2 and Figure 3 ) are provided in the liquid supply unit 220 to remove foreign matter from the supplied ink. Each of the two liquid supply units 220 is provided with a filter 221 for each color. The ink that has passed through the filter 221 is supplied to a negative pressure control unit 230 corresponding to each color and arranged on the liquid supply unit 220.

[0068] The negative pressure control unit 230 is a unit that includes pressure regulating valves for various colors. Each negative pressure control unit 230 significantly reduces the pressure droplet changes that occur in the supply system of the recording device 1000 (the supply system upstream of the liquid ejection head 3) due to the fluctuation of the ink flow rate through the action of the valves, spring components, etc. set in the negative pressure control unit 230. Therefore, the negative pressure control unit 230 can stabilize the negative pressure changes downstream of the negative pressure control unit (on the side of the liquid ejection unit 300) within a certain range. Figure 2As shown, two pressure regulating valves for each color are incorporated into the negative pressure control unit 230 for each color. Different control pressures are set for each pressure regulating valve, and the valve on the high-pressure side and the valve on the low-pressure side are connected to the common supply flow channel 211 and the supply collection flow channel 212 in the liquid ejecting unit 300 via the liquid supply unit 220, respectively.

[0069] The housing 80, which is formed by a liquid ejection unit support portion 81 and an electrical wiring board support portion 82, supports the liquid ejection unit 300 and the electrical wiring board 90 and ensures the rigidity of the liquid ejection head 3. The electrical wiring board support portion 82 is used to support the electrical wiring board 90 and is fixed to the liquid ejection unit support portion 81 by screws. The liquid ejection unit support portion 81 corrects warping and deformation of the liquid ejection unit 300 and ensures 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 ejection unit support portion 81 is preferably sufficiently rigid, and its material is preferably a metal material such as SUS or aluminum, or a ceramic such as alumina. Openings 83 and 84 for inserting the joint rubber 100 are provided in the liquid ejection unit support portion 81. The ink supplied from the liquid supply unit 220 is guided to the third flow path member 70 forming the liquid ejection unit 300 via the joint rubber.

[0070] The liquid ejecting unit 300 includes a plurality of ejecting modules 200 and a flow path member 210, and the cover member 130 is attached to the surface of the liquid ejecting unit 300 on the recording medium side. Figure 5 As shown, the cover member 130 is a member having a frame-shaped surface provided with a long opening 131, and the recording element board 10 and the sealing member 110 ( Figure 9A ) is exposed through the opening 131. The frame portion around the opening 131 has the function of covering the contact surface of the cover member of the liquid ejecting head 3 during the recording standby period. Therefore, it is preferable to apply an adhesive, a sealing material, a filler, or the like along the periphery of the opening 131 and fill unevenness and gaps on the ejection port surface of the liquid ejecting unit 300, thereby forming a closed space in the covered state.

[0071] Next, the configuration of the flow path member 210 included in the liquid ejecting unit 300 will be described. Figure 5 As shown, the flow path member 210 is a member formed by stacking the first flow path member 50, the second flow path member 60, and the third flow path member 70. The flow path member 210 distributes ink supplied from the liquid supply unit 220 to the ejection module 200 and allows the ink to flow from the ejection module 200 back to the liquid supply unit 220. The flow path member 210 is fixed to the liquid ejection unit support portion 81 with screws, which suppresses warping and deformation of the flow path member 210.

[0072] Figure 6 It is a diagram illustrating the front and back surfaces of the first to third flow path members. Figure 6 Reference numeral (a) in FIG. 5 denotes a surface of the first flow path member 50 on the side where the ejection module 200 is mounted, and reference numeral (f) denotes a surface of the third flow path member 70 on the side in contact with the liquid ejection unit support portion 81. The first flow path member 50 and the second flow path member 60 are joined to each other so that the contact surfaces of the respective flow path members are Figure 6 The surface indicated by reference numeral (b) and the surface indicated by reference numeral (c) face each other. The second flow path member and the third flow path member are joined to each other so that the contact surfaces of the respective flow path members Figure 6 The surface indicated by reference numeral (d) and the surface indicated by reference numeral (e) face each other. The second flow channel member 60 is joined to the third flow channel member 70 so that a set of common flow channel grooves 62 and a set of common flow channel grooves 71 formed in each flow channel member form eight common flow channels extending in the longitudinal direction of the flow channel member. Figure 7 As shown, in the flow channel member 210, a set of common supply flow channels 211 and common collection flow channels 212 are formed for each color. The communication port 72 of the third flow channel member 70 communicates with the respective holes of the joint 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 of each flow channel groove 52 of the first flow channel member 50. Communication ports 51 are formed in the other end of each flow channel groove 52 of the first flow channel member 50, and each flow channel 52 is in fluid communication with the plurality of injection modules 200 via the communication ports 51. Each flow channel groove 52 concentrates the flow channels on the central side of the flow channel member.

[0073] The first to third flow channel members are preferably made of a material that is resistant to liquid corrosion and has a low linear thermal expansion coefficient. For example, a composite material (resin material) using aluminum oxide, liquid crystal polymer (LCP), polyphenylene sulfide (PPS) or polysulfone (PSF) as a base material and added with inorganic fillers such as silica particles and fibers can be preferably used as the material. As a method of forming the flow channel member 210, the three flow channel members can be superimposed on each other and combined. In addition, when a composite resin material is selected as the material, a bonding method by welding can be adopted.

[0074] Next, we will use Figure 7 The connection relationship of the flow channels in the flow channel member 210 will be described. Figure 7This is a perspective view of the flow channels in the flow channel member 210 formed by joining the first flow channel member to the third flow channel member, partially enlarged and viewed from the side of the surface of the first flow channel member 50 on which the ejection module 200 is mounted. The flow channel member 210 is provided with common supply channels 211 (211a, 211b, 211c, and 211d) for each color and common collection channels 212 (212a, 212b, 212c, and 212d) for each color, extending in the longitudinal direction of the liquid ejection head 3. A plurality of individual supply channels (213a, 213b, 213c, or 213d) formed by the individual flow channel grooves 52 are connected to the common supply channel 211 for each color via the communication port 61. A plurality of individual collection channels (214a, 214b, 214c, or 214d) formed by the individual flow channel grooves 52 are connected to the common collection channel 212 for each color via the communication port 61. Such a flow channel configuration allows ink to be collected from the common supply flow channel 211 to the recording element board 10 located at the center portion of the flow channel member via the individual supply flow channels 213. Ink can also be collected from the recording element board 10 into the common collection flow channel 212 via the individual collection flow channels 214.

[0075] Figure 8 The diagram is along Figure 7 The cross section of the diagram is taken along the line VIII-VIII. Figure 8 As shown, each of the separate collecting flow channels (214a and 214c) is communicated with the injection module 200 via the communication port 51. Figure 8 Only separate collection channels (214a and 214c) are shown in FIG, but Figure 7 As shown, the individual supply flow path 213 is communicated with the ejection module 200 in another cross section. In the support member 30 and the recording element board 10 included in each ejection module 200, a channel for supplying ink from the first flow path member 50 to the recording element 15 ( Figure 10B ) flow channel. In addition, in the support member 30 and the recording element plate 10, a flow channel for collecting (returning) part or all of the ink supplied to the recording element 15 to the first flow channel member 50 is formed. In this example, the common supply flow channel 211 of each color is connected to the negative pressure control unit 230 (high pressure side) of the corresponding color via the liquid supply unit 220, and the common collection flow channel 212 is connected to the negative pressure control unit 230 (low pressure side) via the liquid supply unit 220. The negative pressure control unit 230 generates a differential pressure (pressure difference) between the common supply flow channel 211 and the common collection flow channel 212. Therefore, in the flow channel such as Figure 7 and Figure 8In the liquid ejection head of this embodiment connected as shown, flows are generated from the common supply flow channel 211 to the individual supply flow channels 213 , to the recording element board 10 , to the individual collecting flow channels 214 , and to the common collecting flow channel 212 for each color.

[0076] <Injection Module>

[0077] Figure 9A A perspective view of a jetting module 200 is shown, and Figure 9B The figure shows an exploded view of the ejection module 200. As a method for manufacturing the ejection module 200, first, the recording element board 10 and the flexible wiring board 40 are bonded to the support member 30 provided with the liquid communication port 31. Thereafter, 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 by wire bonding, and then the wire bonding portion (electrical connection portion) is covered with a sealing member 110 to seal it. The terminals 42 of the flexible wiring board 40 on the opposite side of the recording element board 10 are connected to the connection terminals 93 of the electrical wiring board 90 (see FIG. 1 ). Figure 5 ) is electrically connected. Since the support member 30 is a support body that supports the recording element board 10 and is also a flow path member that connects the recording element board 10 and the flow path member 210 to each other, it is preferable to use a member that has high flatness and can be bonded to the recording element board with sufficiently high reliability as the support member 30. The material of the support member 30 is preferably, for example, alumina or a resin material.

[0078] <Structure of Recording Element Board>

[0079] Next, the configuration of the recording element board 10 in this embodiment will be described. Figure 10A 1 is a plan view of the face of the recording element board 10 on the side where the ejection ports 13 are formed, Figure 10B Pictured Figure 10A The enlarged view of the portion indicated by XB in FIG. Figure 10C Pictured Figure 10A Back floor plan. Figure 11 The diagram is along Figure 10A 1 is a perspective view of a section of the recording element board 10 and the cover member 20 taken along the section line XI-XI. Figure 10A As shown, four ejection opening rows corresponding to respective ink colors are formed in the ejection opening forming member 12 of the recording element board 10. Note that the ejection opening row extending direction along which the plurality of ejection openings 13 are aligned is hereinafter referred to as an "ejection opening row direction."

[0080] like Figure 10BAs shown, recording elements 15 are arranged at positions corresponding to the respective ejection ports 13. The recording elements 15 are heating elements configured to generate bubbles in the ink by thermal energy. The pressure chamber 23 including the recording elements 15 is separated by a partition 22. The recording elements 15 are connected to the recording element board 10 via wires (not shown) provided in the recording element board 10. Figure 10A The recording element 15 is based on the terminal 16 in the recording element 15 via the electrical wiring board 90 ( Figure 5 ) and the flexible wiring board 40 ( Figure 9B ) receives a pulse signal from the control circuit of the recording device 1000, generates heat and boils the ink. The bubble force generated by the boiling ejects the ink from the ejection port 13. Figure 10B As shown, a liquid supply channel 18 extends along each ejection port row on one side thereof, and a liquid collection channel 19 extends along the ejection port row on the other side thereof. The liquid supply channel 18 and the liquid collection channel 19 are flow channels provided in the recording element board 10 and extending in the ejection port row direction, and are communicated with each ejection port 13 via the supply port 17a and the collection port 17b, respectively.

[0081] like Figure 10C and Figure 11 As shown, a sheet-like cover member 20 is superimposed on the back side of the surface of the recording element board 10 on which the ejection ports 13 are formed, and a plurality of openings 21 communicating with the liquid supply channel 18 and the liquid collection channel 19, which will be described later, are provided in the cover member 20. In this embodiment, in the cover member 20, three openings 21 are provided for one liquid supply channel 18 and two openings 21 are provided for one liquid collection channel 19. Figure 10B As shown, the openings 21 in the cover member 20 are respectively Figure 7 The multiple communication ports 51 shown are connected. Figure 11 As shown, the cover member 20 functions as a cover for a portion 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 made of an object having sufficient corrosion resistance to ink, and from the perspective of preventing color mixing, the opening 21 is required to have high precision in both shape and position. Therefore, a photosensitive resin material or a silicon plate is preferably used as the material for the cover member 20, and the opening 21 is provided by a photolithographic process. As described above, the cover member is a member that converts the flow channel pitch using the opening 21, and in view of pressure droplets, it is desirably formed of a film-like member with a small thickness.

[0082] Next, the flow of ink in the recording element board 10 will be described. Figure 11 The diagram is along Figure 10AXI-XI in FIG. 1 is a perspective view of a section of the recording element board 10 and the cover member 20. In the recording element board 10, a substrate 11 made of Si and an ejection port forming member 12 made of a photosensitive resin are superimposed on each other, and the cover member 20 is bonded to the back surface of the substrate 11. The recording element 15 is formed on one surface ( Figure 10B ), and grooves forming a liquid supply channel 18 and a liquid collection channel 19 extending along each ejection port row are formed on the back surface of the substrate 11. The liquid supply channel 18 and the liquid collection channel 19 formed by the substrate 11 and the cover member 20 are connected to the common supply flow channel 211 and the common collection flow channel 212 in the flow channel member 210, respectively, and a differential pressure is generated between the liquid supply channel 18 and the liquid collection channel 19. In the ejection port that does not perform the ejection operation when ink is ejected from the plurality of ejection ports 13 of the liquid ejection head 3 for recording, the flow of ink in the liquid supply channel 18 provided in the substrate 11 is as follows due to this differential pressure. Figure 11 Specifically, the ink flows toward the liquid collection channel 19 via the supply port 17a, the pressure chamber 23, and the collection port 17b. In the ejection port 13 and the pressure chamber 23 where recording is suspended, this flow allows bubbles, foreign matter, ink with increased viscosity generated by evaporation from the ejection port 13, and the like to be collected in the liquid collection channel 19. In addition, it is possible to suppress the increase in viscosity of the ink in the ejection port 13 and the pressure chamber 23. The ink collected in the liquid collection channel 19 passes through the opening 21 of the cover member 20 and the liquid communication port 31 of the support member 30 (see FIG. 2 ). Figure 9B ), and is collected in order into the communication port 51 of the flow path member 210, the individual collecting flow path 214, and the common collecting flow path 212. The ink is finally collected into the supply path of the recording apparatus 1000.

[0083] Specifically, ink supplied from the recording device body to the liquid ejecting head 3 flows for supply and recovery in the following order. First, ink flows from the liquid connection portion 111 of the liquid supply unit 220 into the interior of the liquid ejecting head 3. The ink is then supplied sequentially to the joint rubber 100, the communication port 72 and the common flow channel groove 71 provided in the third flow channel member, the common flow channel groove 62 and the communication port 61 provided in the second flow channel member, and the individual flow channel groove 52 and the communication port 51 provided in the first flow channel member. The ink is then supplied sequentially 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 ejection port 13 flows sequentially through the collection port 17b and the 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 in order through the communication port 51 and the individual flow channel groove 52 provided in the first flow channel member, the communication port 61 and the common flow channel groove 62 provided in the second flow channel member, the common flow channel groove 71 and the communication port 72 provided in the third flow channel member 70, and the joint rubber 100. In addition, the ink flows from the liquid connection portion 111 provided in the liquid supply unit to the outside of the liquid ejecting head 3. Figure 2 In the first circulation path mode shown, the ink flowing from the liquid connection portion 111 passes through the negative pressure control unit 230 and is then supplied to the joint rubber 100. Figure 3 In the illustrated second circulation path mode, the ink collected from the pressure chamber 23 passes through the joint rubber 100 , then passes through the negative pressure control unit 230 , and flows from the liquid connection portion 111 to the outside of the liquid ejection head.

[0084] In addition, if Figure 2 and Figure 3 As shown, not all of the ink flowing in from one end of the common supply channel 211 of the liquid ejecting unit 300 is supplied to the pressure chamber 23 via the individual supply channel 213a. Some of the ink flows from the other end of the common supply channel 211 to the liquid supply unit 220 without flowing into the individual supply channel 213a. Even in the case of a recording element board 10 including a thin channel with large flow resistance as in this embodiment, providing a path through which the ink flows but does not pass through the recording element board 10 as described above can suppress the reverse flow of the ink circulation flow. As described above, since the liquid ejecting head of this embodiment can suppress the increase in ink viscosity in the pressure chamber and the portion near the ejection port, it can suppress non-ejection and deviation of the ejection direction from the normal direction, thereby enabling high-quality recording.

[0085] <Positional Relationship Between Recording Component Boards>

[0086] Figure 12 FIG. 1 is a plan view showing adjacent portions of recording element boards in two adjacent ejection modules in a partially enlarged manner. Figure 10A As shown in FIG. 1 , a substantially parallelogram-shaped recording element board is used in this embodiment. Figure 12 As shown, in each recording element board 10, the ejection port rows (14a to 14d) in which the ejection ports 13 are aligned are arranged to be inclined at a certain angle relative to the conveying direction of the recording medium. Thus, in the ejection port rows in adjacent portions of each recording element board 10, at least two ejection ports are superimposed on each other in the conveying direction of the recording medium. Figure 12 In the example, the two ejection ports on each D line are in a superimposed relationship. Even if the position of the recording element board 10 deviates to a certain extent from the predetermined position, this arrangement can make the black stripes and blank areas in the recorded image less noticeable by controlling the drive of the superimposed ejection ports. This can also be achieved when multiple recording element boards 10 are arranged in a straight line (inline) instead of a zigzag pattern. Figure 12 The configuration shown. This provides a countermeasure against black stripes and blank areas in the superimposed portion of the recording element boards 10 while suppressing an increase in the length of the liquid ejection head in the conveying direction of the recording medium. Although the principal plane of each recording element board has a parallelogram shape in this example, the present embodiment is not limited thereto, and the configuration of this embodiment can also be preferably applied to a case where a recording element board having a rectangular, trapezoidal, or any other shape is used, for example.

[0087] <Communication Control Between Liquid Ejection Head and Main Body>

[0088] The following will use Figure 13 Communication control between the liquid ejecting head and the main body according to the present embodiment will be described. Figure 13 This is a diagram modeling the communication between the liquid ejection head and the main body. The main body board incorporated into the main body of the recording device 1000 includes a CPU, ROM, RAM, and the like. This main body board receives information about the temperature of each recording element board 10 from the liquid ejection head 3 and, based on the received information, transmits control signals for driving the recording element board 10 to the electrical wiring board 90 of the liquid ejection head 3.

[0089] In addition to various types of information such as temperature information, the control signal also includes information about the pulses applied to each heating element (referred to as pulse information). For example, in Japanese Patent Laid-Open No. 2000-246899, the transmission timing T1 and pulse width Pw1 of the first pulse signal, and the transmission timing T2 and pulse width Pw2 of the second pulse signal are transmitted as pulse information. Meanwhile, in this embodiment, even when voltage information is additionally added to the control information, only the transmission timing T1 and pulse width Pw1 of the first pulse signal need to be transmitted as pulse information, and the amount of data to be processed is also small. Therefore, the processing load can be reduced.

[0090] <Pulse Signal Pulse Width and Ink Droplet Ejection Speed>

[0091] In this embodiment, when the heating element generates bubbles in the ink for ejection from the ejection port, a greater effect can be expected when the total heating period is 0.5 microseconds or less. The shorter the heating period for bubble generation in the ink, that is, the greater the heat flux, the more stable the bubble generation and the smaller the variation in the ejection velocity. Ink containing a large amount of solids is particularly susceptible to bubble generation, so pulse signals with shorter pulse widths are preferred for such inks. However, the greater the heat flux and the shorter the heating period, the lower the ejection velocity.

[0092] Figure 14 This graph shows the injection speed when the total heating period is divided into two periods and the divided periods are varied in various ways, as described in Japanese Patent Laid-Open No. 2000-246899. In this graph, the data for a total heating period of 0.2 microseconds is illustrated by black dots, while the data for a total heating period of 0.3 microseconds is illustrated by white dots. When the data for 0.2 microseconds is compared with the data for 0.3 microseconds, the injection speed modulation width is smaller in the case of a total heating period of 0.2 microseconds, and the injection speed modulation may be insufficient.

[0093] In this embodiment, as described below, while shortening the total heating time, a recording element driving process is performed that involves adjusting the potential difference ΔV based on the conditions and configuration of the liquid ejection head (recording element board), thereby enabling correction of ejection speed while suppressing fluctuations in ejection. In this specification, the conditions of the liquid ejection head include the amount of fouling in the recording element board, the temperature of the element board, the adsorption state of ink components, and the like, as described later, and the configuration of the liquid ejection head includes the size of the ejection orifices of the recording element board, as described later.

[0094] <Structure of Heat Application Portion in Recording Element Board>

[0095] The following will use Figure 15A and Figure 15BThe structure of a heat application portion in the recording element board according to the present embodiment is described. Figure 15A 1 is a plan view schematically illustrating an area around a heat application portion in the recording element board 10 in an enlarged manner. Figure 15B It is along Figure 15A A cross-sectional view taken along the dashed line XVB-XVB in FIG.

[0096] The recording element board of the liquid ejection head is formed by stacking a plurality of layers on a substrate made of silicon. In this embodiment, a heat storage layer made of a thermal oxide film, SiO film, SiN film, etc. is arranged on the substrate. In addition, 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 metal material such as Al, Al-Si, Al-Cu, etc. is connected to the heating resistor element 126 via a tungsten plug 128. Figure 15B As shown, an insulating protective layer 127 (first protective layer) is provided on the heating resistor element 126. The insulating protective layer 127 is an insulating layer provided above the heating resistor element 126 to cover the heating resistor element 126. The insulating protective layer 127 is made of a SiO film, a SiN film, or the like.

[0097] A protective layer for preventing contact with liquid 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 adhesive protective layer 123. In this embodiment, the lower protective layer 125 and the upper protective layer 124 are disposed on the heating resistor element 126 and protect the surface of the heating resistor element 126 from chemical and physical influences that occur when the heating resistor element 126 is heated.

[0098] In this embodiment, lower protective layer 125 is made of tantalum (Ta), upper protective layer 124 is made of iridium (Ir), and adhesion protective layer 123 is made of tantalum (Ta). Furthermore, protective layers made of these materials have electrical conductivity. A protective layer 122 is arranged on adhesion protective layer 123 to improve adhesion with ejection port forming member 12, acting as a liquid repellent. Protective layer 122 is made of SiC.

[0099] When liquid is ejected, the upper portion of upper protective layer 124 comes into contact with the liquid, creating a harsh environment where bubbles are generated and disappear within the upper portion due to a sudden temperature rise of the liquid, leading to cavitation. Therefore, in this embodiment, upper protective layer 124 is formed from iridium, a material with high corrosion resistance and reliability, and comes into contact with the liquid at a position corresponding to heating resistor element 126.

[0100] This embodiment adopts an ink circulation structure in which liquid is supplied from the supply port 17a to the pressure chamber 23 and collected in the collection port 17b. Therefore, on the heating resistor element 126, liquid flows from the supply port 17a on the upstream side toward the collection port 17b on the downstream side during printing.

[0101] Furthermore, in this embodiment, a scale suppression process is performed during printing to suppress the deposition of scale on the upper protective layer 124 on the heating resistor element 126. Specifically, the portion of the upper protective layer 124 directly above the heating resistor element 126 is provided as an electrode 121 (first electrode), and a counter electrode 129 (second electrode) corresponding to electrode 121 is provided to form an electric field through the liquid in the liquid chamber. As a result, particles in the liquid, such as negatively charged pigments, are repelled from the surface of the upper protective layer 124 on the heating resistor element 126. Reducing the abundance of particles, such as negatively charged pigments, near the surface of the upper protective layer 124 as described above suppresses the deposition of scale on the upper protective layer 124 on the heating resistor element 126 during printing. This scale suppression is based on the fact that scale occurs when colorants, additives, etc. contained in the liquid are heated to high temperatures, decomposed at the molecular level, become low-solubility substances, and are physically adsorbed onto the upper protective layer. In high-temperature heating of the upper protective layer 124 , reducing the abundance ratio of the colorant, additive, etc. that causes fouling near the surface of the upper protective layer 124 on the heating resistor element 126 leads to fouling suppression.

[0102] The following will use 16A to 16C The mechanism of electric field control (also called potential control and potential difference control) used in this embodiment is described. Figure 16A In the embodiment, the upper protective layer electrode 121 and the counter electrode 129 are arranged in the bubble chamber and the bubble chamber is filled with liquid. The liquid contains particles 141 such as negatively charged pigments, and the particles 141 are substantially uniformly dispersed in the liquid.

[0103] Figure 16BThe diagram illustrates a state where a voltage is applied such that the voltage of electrode 121 in the upper protective layer is lower than that of counter electrode 129. For example, the potential difference between electrode 121 and counter electrode 129 is approximately 0.2V to 2.5V. This is because, assuming that upper protective layer 124 is made of iridium, in this configuration, if the potential difference between the two electrodes exceeds 2.5V, an electrochemical reaction occurs between electrode 121 and the liquid, and the surface of electrode 121 dissolves in the liquid. Therefore, it is preferable to set the potential level to a level at which electrode 121 does not dissolve. Specifically, in this case, although an electric field 140 is formed between electrode 121 in the upper protective layer and counter electrode 129 through the liquid, no current flows between them. Since electrode 121 in the upper protective layer has a negative potential relative to counter electrode 129, negatively charged particles 141 are repelled from the surface of electrode 121 in the upper protective layer, and the abundance ratio of particles 141 near the surface of electrode 121 in the upper protective layer decreases.

[0104] Figure 16C It will Figure 16B The diagram shows an enlarged schematic diagram of a portion near the upper protective layer 124. Negatively charged particles 141 are repelled by a repulsive force 143 along the lines of force of the electric field 140 formed in the liquid. Specifically, when the potential of the counter electrode is represented by Vc and the potential of the upper protective layer electrode of the heater is represented by Vh, the greater the potential difference ΔV (= Vc - Vh), the more negatively charged particles 141 are repelled. At the same time, the closer the positively charged particles are to the heater, the more negatively charged particles 141 are repelled. In this embodiment, negative charge inhibits bubble generation, and the greater the potential difference ΔV, the higher the bubble generation temperature and the higher the ejection speed.

[0105] Figure 17 The relationship between ΔV and injection speed is shown, specifically, the measurement results of the injection speed measured using ΔV varied in increments of 0.5 V. Note that in this example, the measurement was performed with Vh fixed at 0 V and Vc varied. Figure 17 As shown, changing ΔV can change the ejection velocity v. According to the mechanism described herein, in response to changes in the ejection velocity caused by external factors, the ejection velocity can be corrected and printing unevenness can be suppressed by changing ΔV.

[0106] As described above, in this embodiment, the ejection speed is corrected by changing ΔV, thereby preventing scaling on the heater surface from changing the ejection speed and causing uneven printing. Specifically, assume that multiple chips (recording element boards) are installed in the liquid ejection head as described in this embodiment. In this configuration, if the number of droplets ejected varies between chips, the ejection speed and ejection volume will vary between chips, potentially causing unevenness between chips. In this specification, scaling on the heater surface refers to a substance formed when the high temperature reached by the heater surface during ejection denatures the ink and deposits its components on the heater surface.

[0107] Figure 18 The change in ejection speed according to the mechanism of this embodiment is illustrated. Specifically, the solid line illustrates the relationship between the number of ejected droplets and the ejection speed when ΔV is reset in each (two) operations, while the dotted line illustrates the relationship between the number of ejected droplets and the ejection speed when ΔV is not reset.

[0108] The formation of ink on the heater surface suppresses the generation of bubbles. Therefore, under the condition of constant ΔV, if Figure 18 As shown in Figure 1, the droplet ejection velocity decreases as the number of ejected droplets increases. Consequently, the ejection velocity decreases in chips used for printing, while the ejection velocity does not decrease in chips not used for printing. This results in ejection velocity differences between chips and unevenness.

[0109] Therefore, in this embodiment, the potential difference ΔV (=Vc - Vh) for each chip is adjusted according to the amount of scale. This allows printing while maintaining the ejection speed of all chips within a predetermined range. The potential difference ΔV can be adjusted by changing at least one of the potentials of electrode 121 and counter electrode 129. Note that the amount of scale is preferably managed by counting the number of ejected droplets (so-called dot counting).

[0110] <Adjustment of Potential Difference ΔV Based on Point Count>

[0111] Figure 19A This is a sequence diagram of a series of processes related to adjusting the potential difference ΔV based on dot count according to this embodiment. In this example, the initial potential value of the upper protective layer electrode is 0.0 V, while the initial potential value of the counter electrode is approximately 1.9 V. Each of these initial values ​​varies depending on the type of ink, and the voltage that achieves the highest durability is set from the perspective of durability.

[0112] In step S1901, the recording apparatus 1000 performs printing. Note that in the following description, "step S" is abbreviated as "S".

[0113] In S1902 after printing in S1901 is completed, the CPU of the recording apparatus 1000 counts dots for each chip and obtains the number of ejected droplets in each chip. The CPU then derives the difference in the number of ejected droplets between the chip with the maximum number of ejected droplets and each chip other than the chip with the maximum number of ejected droplets, and determines whether the differences in the number of ejected droplets derived for each chip are all equal to or greater than a predetermined threshold value.

[0114] For chips where the determination result in S1902 is true, the process proceeds to S1903. Meanwhile, for chips where the determination result in S1902 is false, the process returns to S1901 and the next printing is continued with the same settings. Note that the predetermined threshold used in S1902 is referred to as the set number Nd of ejected droplets.

[0115] In S1903, the CPU of the recording apparatus 1000 resets the voltage of the counter electrode for all chips for which the most recent determination in S1902 yielded a true result. Specifically, the CPU sets the voltage to a value obtained by subtracting 0.1V from the current value. The CPU of the recording apparatus 1000 then resets the dot counts for all chips and sets the dot count value (also referred to as the number of ejected droplets) to zero. While the predetermined subtraction amount is set to 0.1V in this example, the predetermined subtraction amount is not limited to 0.1V and any value may be used.

[0116] In this series of processes, the potential difference in chips other than the chip with the largest number of ejected ink droplets is adjusted according to the decrease in ejection speed in the chip with the largest number of ejected ink droplets. This makes the ejection speed uniform among chips and suppresses the degradation of print quality.

[0117] Note that the liquid ejection head in this embodiment is a liquid ejection head that prints by using four colors of CMYK ink, and for all ink colors, each of the initial value of the counter electrode potential and the set number Nd of ejected droplets to be used for the dot count may be the same or may vary depending on the ink color.

[0118] Furthermore, the potential difference ΔV may be set commonly for all ink colors or may be set for each ink color. Figure 20A The diagram shows a board with shared wiring between all rows, setting the same potential difference ΔV for all rows, while Figure 20B The diagram shows the board that provides wiring for each row. Figure 20A In the case of the structure shown in FIG, the chip size can be reduced. Figure 20BWith the configuration shown, it's possible to set a ΔV value appropriate for each ink color by assigning wiring to each ink color. For example, for ink colors prone to smearing, the set number Nd of ejected droplets can be set to a small value, and the speed can be fine-tuned. This improves print quality.

[0119] [Second embodiment]

[0120] In this embodiment, the ejection speed variation caused by the temperature variation in the head is offset by using the same mechanism as in the first embodiment. Note that in the following description of the embodiment, the differences from the previously described embodiment are mainly described, and the description of the same contents as in the previously described embodiment is appropriately omitted.

[0121] In an inkjet recording apparatus that uses thermal energy to eject ink droplets, the higher the temperature, the higher the ejection speed. Figure 21 The diagram illustrates an example of jet velocity changes under actual temperature variations. Since jet velocity can vary due to temperature changes, as described above, printing requires maintaining a constant temperature. However, in high-speed inkjet recording devices, temperature changes occur due to head temperature fluctuations (such as temperature increases due to ink droplet ejection and cooling due to ink supply), as well as various other factors (such as cooling due to the paper feed airflow and increases in the main body temperature due to high-speed evaporation of ink). Therefore, printing requires correcting for jet velocity changes due to temperature changes in the recording head.

[0122] The present embodiment is characterized in that a temperature sensor such as a diode mounted in a head is used to measure temperature, and a potential difference is adjusted based on the measured temperature to perform printing. Figure 22 The diagram shows an example of a table storing potential difference ΔV values ​​(referred to as a ΔV change table). The ΔV change table stores potential difference ΔV values ​​that are updated and used when the temperature obtained as a measurement result of the temperature sensor changes from a reference set temperature (referred to as a reference temperature). Figure 22 The "potential control reference values" described in the table are reference values ​​for the potential difference ΔV set when the first embodiment is applied. In this example, four values ​​(0.5, 1.0, 1.5, and 2.0) are assumed as potential control reference values. Note that the specific values ​​stored in this table vary depending on the ink type.

[0123] For example, assuming that the reference temperature is set to 40° C. and the potential control reference value is set to 1.0 V, a temperature of 42° C. is obtained as a result of measurement using the temperature sensor. In this case, 0.7 V can be set as the correction potential difference ΔV (=Vc-Vh).

[0124] Figure 231 is a sequence diagram of a series of processes related to ΔV adjustment based on temperature and point count according to the present embodiment.

[0125] In this example, the initial value of the potential of the upper protective layer electrode is assumed to be 0.0V, and the initial value of the potential of the counter electrode is assumed to be approximately 0.2V to 0.5V.

[0126] like Figure 23 As shown, in this embodiment, in S2301 before printing, the CPU of the recording apparatus 1000 measures the temperature using a temperature sensor installed in the recording apparatus 1000 and derives the difference between the temperature obtained in the temperature measurement and the reference temperature. Figure 22 The ΔV variation table shown is used to obtain the value of ΔV corresponding to the derived difference and reset the voltage of the counter electrode to the obtained value.

[0127] S1901 to S1903 after S2301 are the same as those in the first embodiment (see Figure 19A ). Although the temperature measurement is performed before printing as an example in this description, the temperature measurement can also be performed during printing.

[0128] As described above, according to this embodiment, the ejection speed can be corrected according to the temperature change.

[0129] [Third embodiment]

[0130] In this embodiment, using a mechanism similar to that of the first or second embodiment, the potential control reference value is corrected based on temperature changes caused by ejection. In an inkjet recording device that ejects ink droplets using thermal energy, the greater the number of ink droplets ejected simultaneously, the greater the temperature increase near the ejection port. Because the temperature changes (increases) rapidly with ink ejection, it is preferable to pre-estimate the temperature change based on the print data and pre-correct the ejection speed.

[0131] The following describes an example of estimating temperature changes based on print data according to this embodiment. This section describes an example of estimating temperature increases based on the number of droplets ejected simultaneously from an ejection port row. Note that when the number of simultaneously ejected droplets is calculated per ejection port row, the potential control reference value is corrected based on the ratio of the number of ejection ports performing ejection within the ejection port row (hereinafter referred to as the duty cycle).

[0132] Figure 24An example of a ΔV variation table according to this embodiment is shown. The ΔV variation table stores the value of the potential difference ΔV corresponding to each duty ratio value (0 to 100%). The potential control reference value as the voltage (potential difference) to be referenced in this example is the voltage value obtained in the first embodiment or the second embodiment, and it is assumed that the potential control reference value is Figure 24 Any of the four values ​​(0.5, 1.0, 1.5, and 2.0).

[0133] A specific example of the method using the ΔV variation table will be described below. For example, in the case where the ejection port row is formed by 100 ejection ports and the number of droplets ejected simultaneously is 80, the duty cycle is 80%. In the case where the potential control reference value is 1V in this case, the ΔV variation table can be used. Figure 24 The table sets ΔV to 0.8V.

[0134] Figure 25 FIG. 1 is a sequence diagram of a series of processes related to ΔV adjustment based on temperature, duty ratio, and point count according to the present embodiment.

[0135] In S2501 , the CPU of the recording apparatus 1000 measures the temperature by using the temperature sensor installed in the recording apparatus 1000 .

[0136] In S2502 , the CPU of the recording apparatus 1000 calculates a duty ratio based on the print data.

[0137] In S2503, the CPU of the recording apparatus 1000 derives the difference between the reference temperature and the temperature obtained in the latest measurement of S2501. Figure 22 The ΔV change table shown in FIG. 1 is used to derive the ΔV value corresponding to the difference (referred to as the first correction value) as described in the second embodiment. Then, the CPU of the recording apparatus 1000 further refers to the ΔV change table shown in FIG. Figure 24 The ΔV change table shown in FIG. 1 is used to derive a ΔV value corresponding to the derived first correction value (referred to as a second correction value). Finally, the CPU of the recording apparatus 1000 resets the voltage of the counter electrode to the second correction value.

[0138] S1901 to S1903 after S2503 are the same as those in the first embodiment (see Figure 19A ).

[0139] As described above, according to this embodiment, the electrode potential is set based on temperature changes near the ejection outlets by varying ΔV based on the duty cycle. This allows for correction of the ejection velocity based on rapid temperature changes near the ejection outlets caused by printing, thereby improving print quality. While the number of simultaneously ejected droplets is calculated for each ejection outlet row in this embodiment, the number of simultaneously ejected droplets can also be calculated for the entire chip or head. Alternatively, the ejection outlet rows can be divided into multiple blocks, and the number of simultaneously ejected droplets is calculated for each block.

[0140] [Fourth embodiment]

[0141] The characteristic of this embodiment is that, in the case of continuous ejection of ink droplets, the potential difference ΔV is set according to the number of ejected droplets. The reason for setting ΔV according to the number of ejected droplets is as follows: Figure 26 As shown in FIG, in the case of continuous ejection of ink droplets, the ejection velocity of the ink droplets is high in the initial stage and gradually decreases, and this decrease needs to be offset. Figure 26 As shown in the figure, although the ejection speed temporarily increases again after a period of cessation, it decreases over time while ejection continues. This is presumably due to the following: when ejection is not in progress, ink components are adsorbed to the interface between the ejection orifice and the upper protective film, causing unstable bubble generation. To address this issue, in this embodiment, the potential difference ΔV is set based on the number of continuously ejected droplets.

[0142] Figure 27 An example of a ΔV variation table according to the present embodiment is shown. The ΔV variation table stores the value of the correction potential difference ΔV corresponding to each value (10 to 500) of the number of continuously ejected droplets. Note that the number of continuously ejected droplets according to the present embodiment refers to the number of ink droplets ejected continuously after a predetermined interruption time (specifically, approximately 0.1 seconds) has passed. In addition, the potential control reference value of the voltage (potential difference) used as a reference in the present embodiment is the voltage value obtained in any one of the first to third embodiments, and Figure 27 In the example of FIG. 1 , it is assumed that the potential control reference value is any one of four values ​​(0.5, 1.0, 1.5, and 1.9).

[0143] A specific example of the method of using the ΔV variation table will be described below. For example, in the case where the number of continuously ejected droplets is 100 and the potential control reference value is 1V, it is possible to use Figure 27 The table sets ΔV to 0.85V.

[0144] In the setting sequence of ΔV according to the present embodiment, as described in the third embodiment, the number of continuously ejected droplets and the interruption time are calculated based on the print data before printing (see Figure 25 ). Then, by using Figure 27 The ΔV variation table shown derives a correction ΔV based on the calculated number of continuously ejected droplets and the interruption time, and sets the voltage of the counter electrode according to the derived correction ΔV.

[0145] As described above, in this embodiment, ΔV varies based on the number of continuously ejected droplets. This enables setting the electrode potential in accordance with the adsorption state of the ink components and improves print quality.

[0146] [Fifth embodiment]

[0147] This embodiment is characterized in that an inter-chip potential difference is provided based on the size of an ink jet nozzle configured to eject ink. The ejection velocity can vary depending on the nozzle size, and this size can vary within manufacturing tolerances. A larger nozzle diameter results in a greater amount of liquid ejected, and thus a lower ejection velocity. Therefore, it is necessary to adjust the ejection velocity based on the nozzle size.

[0148] Correction of the ejection speed according to this embodiment can be performed by directly measuring the ejection size and ejection speed during the factory inspection of the recording device 1000. Alternatively, correction can be performed by printing a predetermined grid pattern and estimating the ejection speed difference between chips based on the output result. Providing a potential difference to correct the ejection speed difference between chips enables printing while correcting for ejection speed variations caused by dimensional nonuniformity between chips.

[0149] [Sixth embodiment]

[0150] This embodiment is suitable for the case where the ejection speed decreases monotonically as the potential difference ΔV (=Vc-Vh) between the potential Vc of the counter electrode in the heater and the potential Vh of the upper protective layer electrode increases. Figure 28 ) mode. As described in the first embodiment, the particles that suppress bubble generation are generally negatively charged particles, but in rare cases, they are positively charged particles. In this case, the more positive the potential of the upper protective layer electrode in the heater is set relative to the counter electrode, the more likely the positively charged particles are attracted to the upper protective layer, thereby reducing the ejection velocity.

[0151] Therefore, in this embodiment, when increasing the injection speed, the potential difference ΔV (=Vc - Vh) between the potential Vc of the counter electrode in the heater and the potential Vh of the upper protective layer electrode is set to a smaller value. Meanwhile, when decreasing the injection speed, the potential difference ΔV is set to a larger value. When making such settings, the voltage can be determined by estimating the amount of fouling using point counting, as described in the first embodiment, or by using temperature, as described in the second embodiment.

[0152] As an example, Figure 19BThe diagram shows a sequence using the same dot count as in the first embodiment. In this example, the potential of the upper protective layer electrode is initially 0.0V, while the potential of the counter electrode is initially -0.2V.

[0153] In S1901, the recording device 1000 performs printing.

[0154] In S1902 after printing in S1901 is completed, the CPU of the recording apparatus 1000 counts dots for each chip and obtains the number of ejected droplets in each chip. The CPU then derives the difference in the number of ejected droplets between the chip with the maximum number of ejected droplets and each chip other than the chip with the maximum number of ejected droplets, and determines whether the differences in the number of ejected droplets derived for each chip are all equal to or greater than a predetermined threshold value.

[0155] For chips where the determination result in S1902 is true, the process proceeds to S1904. Meanwhile, for chips where the determination result in S1902 is false, the process returns to S1901 and the next printing is continued with the same settings. Note that the predetermined threshold used in S1902 is referred to as the set number Nd of ejected droplets.

[0156] In S1904, the CPU of recording apparatus 1000 resets the voltage of the counter electrode for all chips for which the most recent determination in S1902 yielded a true result. Specifically, the CPU sets the voltage to a value obtained by adding 0.1V to the current value. The CPU of recording apparatus 1000 then resets the dot counts for all chips and sets the dot count value to zero. While the predetermined amount of addition is set to 0.1V in this example, the predetermined amount of addition is not limited to 0.1V and any value may be used.

[0157] According to the present embodiment, also in the case of using ink in which bubble suppression occurs due to positively charged particles, the ejection speed can be adjusted based on the dot count as in the first embodiment.

[0158] Note that the contents of the first to sixth embodiments can be used in combination as appropriate.

[0159] [Other embodiments]

[0160] The embodiments of the present invention can also be implemented by the following method, that is, providing software (program) that performs the functions of the above-mentioned embodiments to a system or device through a network or various storage media, and the computer or central processing unit (CPU) or microprocessing unit (MPU) of the system or device reads and executes the program.

[0161] The present disclosure may provide a technology for suppressing unevenness with a lower control load than conventional technologies.

[0162] While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The following claims are to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. A liquid injection device, comprising: A liquid ejection head, the liquid ejection head comprising a plurality of element plates, each element plate comprising: a conversion element that generates energy required to eject liquid; a first protective layer that prevents contact between the conversion element and the liquid; a second protective layer that partially covers the first protective layer and serves as a first electrode; a second electrode that is electrically connected to the first electrode through the liquid; and an ejection port that ejects the liquid; a control unit configured to control a potential difference between the first electrode and the second electrode during printing to a predetermined value by changing at least one of the potential of the first electrode and the potential of the second electrode, and to set the potential difference for each of the element plates; a counting unit configured to count the number of ejected droplets of the liquid for each of the element plates; a deriving unit configured to derive a difference in the number of ejected droplets between an element plate having the largest number of ejected droplets and each of element plates other than the element plate having the largest number of ejected droplets; and a determination unit configured to determine, for each of the element plates except the element plate having the largest number of ejected droplets, whether the difference in the number of ejected droplets is equal to or greater than a predetermined threshold value, The control unit sets the potential of the second electrode to a value obtained by performing a subtraction operation or an addition operation on a current value for the element plate whose determination result provided by the determination unit is true.

2. The liquid ejecting device according to claim 1, wherein The control unit is capable of resetting the potential difference during printing.

3. The liquid ejecting device according to claim 2, wherein: The first electrode is a portion of the second protective layer directly above the conversion element. 4 . The liquid ejecting apparatus according to claim 1 , further comprising a measuring unit configured to measure a temperature of the liquid ejecting head, wherein The control unit sets the potential difference based on a difference between a reference temperature and the temperature obtained by the measuring unit. The liquid ejecting device according to claim 1 , wherein: The control unit sets the potential difference based on a print data duty cycle. The liquid ejecting device according to claim 1 , wherein: The control unit sets the potential difference based on the size of the ejection port.

7. The liquid ejecting device according to claim 1, wherein The first protection layer has insulating properties.

8. The liquid ejecting device according to claim 1, wherein The liquid is ink, and The control unit performs potential difference control for each color of ink.

9. A method for controlling a liquid injection device, the liquid injection device comprising: A liquid ejection head, the liquid ejection head including a plurality of element plates, each element plate including: a conversion element that generates energy required to eject liquid; a first protective layer that prevents contact between the conversion element and the liquid; a second protective layer that partially covers the first protective layer and serves as a first electrode; a second electrode that is electrically connected to the first electrode via the liquid; and an ejection port that ejects the liquid; a control unit configured to control a potential difference between the first electrode and the second electrode during printing to a predetermined value by changing at least one of the potential of the first electrode and the potential of the second electrode, and to set the potential difference for each of the element plates; a counting unit configured to count the number of ejected droplets of the liquid for each of the element plates; a deriving unit configured to derive a difference in the number of ejected droplets between an element plate having the largest number of ejected droplets and each of element plates other than the element plate having the largest number of ejected droplets; and a determination unit configured to determine, for each of the element plates except the element plate having the largest number of ejected droplets, whether the difference in the number of ejected droplets is equal to or greater than a predetermined threshold value, The control method includes: The control unit is caused to set the potential of the second electrode to a value obtained by subtracting or adding a current value for the element plate for which the determination result provided by the determination unit is true.

Images