Recording device and control method

Abstract

Recording device and control method. The recording device includes a liquid ejector head and a detection unit. The liquid ejector head includes a heating element, a first protective layer, a second protective layer, a second electrode, an ejector outlet, and a temperature detection element. The first protective layer blocks contact between the heating element and the liquid. The second protective layer covers at least the portion of the first protective layer to be heated by the heating element and serves as the first electrode. The second electrode is electrically connected to the first electrode through the liquid. The ejector outlet ejects liquid. The temperature detection element corresponds to the heating element. The detection unit is configured to detect feature points in a temperature curve representing the relationship between time and temperature. The combination of the potential set for the first electrode and the potential set for the second electrode differs when printing is performed compared to when the detection unit detects feature points.

Description

Technical Field

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

[0002] In a recording head included in an inkjet recording apparatus, ejection failure may occur in some or all nozzles due to clogging of the nozzles by foreign matter, mixing of bubbles into an ink supply path, change in wettability of the nozzle surface, etc. Therefore, in the recording head, it is necessary to identify the nozzles in which the ejection failure has occurred and reflect the identified nozzles in the image compensation and restoration work of the recording head.

[0003] Japanese Patent Laid-Open No. 2007-290361 proposes a method in which a temperature detection element formed of a thin film resistor is provided on each recording element including a heating element via an insulating film in a recording element board, the temperature of each nozzle is detected, and a nozzle with ejection failure is determined based on temperature changes.

[0004] In addition, Japanese Patent Laid-Open Nos. 2007-331193 and 2008-000914 propose the following inspection method: determine whether the temperature drop process of the temperature curve includes an inflection point indicating that a sharp temperature drop change has occurred, and in the case of the presence of the inflection point, determine that the ejection is normal. Note that it is assumed that the inflection point occurs when the rear end of the ejected droplet contacts the recording element and cools the recording element. Summary of the invention

[0005] However, the methods disclosed in Japanese Patent Laid-Open Nos. 2007-331193 and 2008-000914 have the following problems: in a condition where the contact between the rear end of the ejected droplet and the recording element is unstable, the temperature reduction of the recording element occurs unstably, and thus the detection accuracy is reduced. For example, in a nozzle size where the contact between the rear end of the ejected droplet tends to be unstable, the temperature reduction of the recording element becomes unstable, and a condition where the detection accuracy is reduced tends to occur. In addition, since the contact between the rear end of the ejected droplet is also unstable in a place with low air pressure such as a plateau, the temperature reduction of the recording element becomes unstable, and a condition where the detection accuracy is reduced tends to occur.

[0006] Thus, in view of the foregoing problems, an object of the present disclosure is to provide a technique for grasping the ejection state in a recording element and accurately performing determination of the occurrence of an ejection failure.

[0007] According to an aspect of the present invention, a recording device includes a liquid ejection head, which includes a heating element, a first protective layer, a second protective layer, a second electrode, a ejection port and a temperature detection element, wherein the heating element generates heat energy required to eject the liquid, the first protective layer blocks contact between the heating element and the liquid, the second protective layer covers at least a portion of the first protective layer to be heated by the heating element and serves as a first electrode, the second electrode is electrically connected to the first electrode via the liquid, the ejection port ejects the liquid, and the temperature detection element corresponds to the heating element; and a detection unit, which is configured to detect a characteristic point in a temperature curve obtained by the temperature detection element and represents the relationship between time and temperature, wherein a combination of a potential set for the first electrode and a potential set for the second electrode is different when printing is performed and when the detection unit detects the characteristic point.

[0008] Further features of the present invention 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 showing a schematic configuration of a recording apparatus 1000 according to the first embodiment;

[0010] Figure 2A and Figure 2B is a diagram showing a circulation path in the recording device 1000;

[0011] Figure 3A and Figure 3B is a perspective view of a liquid ejection head 3 according to the first embodiment;

[0012] Figure 4 is an exploded perspective view of the liquid ejection head 3 according to the first embodiment;

[0013] Figure 5A and Figure 5B 2 is a diagram showing the connection relationship of the flow paths in the flow path member 210;

[0014] Fig. 6A and Figure 6B is a diagram showing a spray module 200;

[0015] 7A to 7C is a diagram showing the structure of the recording element board 10;

[0016] Figure 8 is a diagram showing the recording element board 10 along Fig. 7A A three-dimensional cross-sectional view of the structure along the section line VIII-VIII in FIG.

[0017] Fig. 9is a plan view showing the adjacent portion of the recording element board 10 in a partially enlarged manner;

[0018] Fig.10 is a diagram showing a schematic configuration of a recording apparatus 1000 according to a second embodiment;

[0019] Fig.11A and Fig. 11B is a perspective view of a liquid ejection head 3 according to a second embodiment;

[0020] Fig.12 is an exploded perspective view of a liquid ejection head 3 according to a second embodiment;

[0021] FIG. 13A to FIG. 13E is a diagram showing the configuration of a flow path member 210 included in the liquid ejection head 3 according to the second embodiment;

[0022] Fig.14A and Fig. 14B is a diagram for explaining the connection relationship between the recording element board 10 and the flow path in the flow path member 210;

[0023] Fig.15A and Fig. 15B is a diagram showing a spray module 200;

[0024] FIG. 16A to FIG. 16C is a diagram showing the structure of the recording element board 10;

[0025] Fig.17A and Fig. 17B is a diagram showing the structure of a recording element board 10 according to a first example;

[0026] 18A to 18D is a diagram for explaining a curve detected by the temperature detection element 905;

[0027] Fig.19A and Fig.19B 1 is a diagram showing the structure of a heat action portion in the recording element board 10;

[0028] Fig. 20A and Fig. 20B is a diagram showing the relationship between the detection time and Vinv;

[0029] Fig.21A and Fig.21B is a diagram showing the relationship between Vinv and the elapsed time after the potential control is switched; and

[0030] Fig. 22 This is a table that holds the values ​​of various condition examples. DETAILED DESCRIPTION

[0031] As an example of an embodiment according to the present disclosure, a recording device using an inkjet recording method is described below. The recording device may be, for example, a single-function printer having only a recording function, or may be a multi-function printer having multiple functions such as a recording function, a fax machine function, and a scanner function. In addition, the present disclosure may be applicable to a manufacturing device for manufacturing a color filter, an electronic device, an optical device, a microstructure, etc. by using a predetermined recording method.

[0032] Note that in the following description, "recording" does not refer only to the case where meaningful information such as text and graphics are formed, but the product to be recorded may be meaningful or meaningless. In addition, "recording" generally refers to the case where an image, design, pattern, structure, etc. is formed on a recording medium, or the case where the medium is processed, regardless of whether the recorded product is obvious enough to be visually seen by humans.

[0033] In addition, the "recording medium" refers not only to ordinary paper used in a recording apparatus but also to a medium capable of receiving ink, such as cloth, plastic film, metal plate, glass, ceramic, resin, wood, and leather.

[0034] In addition, "ink" should be interpreted broadly like the definition of "recording" mentioned above. Therefore, "ink" refers to a liquid that can be used to form an image, design, pattern, etc., by being applied to a recording medium, for processing the recording medium, or for treating the ink (for example, solidifying or insolubilizing the colorant in the ink applied to the recording medium).

[0035] In addition, unless otherwise specified, a "recording element" (also referred to as a "nozzle" in some cases) refers to an ink ejection outlet, a liquid passage communicating therewith, and an element that generates energy for ejecting ink.

[0036] [First embodiment]

[0037] Although the present embodiment relates to an inkjet recording apparatus of a mode in which a liquid such as ink is circulated between a tank and a liquid ejection head, the mode of the inkjet recording apparatus may be different. For example, instead of circulating the ink, the mode may be to provide two tanks upstream and downstream of the liquid ejection head and to flow the ink from one tank to the other tank to flow the ink in the pressure chamber.

[0038] In addition, although the liquid ejection head according to the present embodiment is a liquid ejection head of a line head having a length corresponding to the width of the recording medium, for example, the present embodiment can also be applied to a so-called serial liquid ejection head that performs recording while scanning the recording medium. Although a configuration in which one recording element board for black ink and one recording element board for color ink are mounted can be given as an example of the configuration of the serial liquid ejection head, the configuration is not limited thereto. Specifically, the mode can be as follows: a short line head having a width smaller than the recording medium and a plurality of recording element boards arranged in such a manner that the ejection nozzle columns overlap each other in the ejection nozzle column direction is prepared, and the short line head is made to scan the recording medium.

[0039] <Inkjet Recording Apparatus>

[0040] Figure 1 The schematic structure of a liquid ejection device according to the present embodiment is shown, 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 line-type liquid ejection head 3 that is configured to be approximately orthogonal to the conveying direction of the recording medium, and is a line-type 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 performing 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 path for supplying ink to the liquid ejection head as described later are fluidly connected to each other (see Figure 2A and Figure 2B ). In addition, an electric 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 electric signal path in the liquid ejection head 3 are described later.

[0041] <First Circulation Path>

[0042] Figure 2A 1 is a schematic diagram showing a first circulation path as one mode of a circulation path suitable for the recording apparatus according to the present embodiment. Figure 2A As shown, the liquid ejection head 3 is fluidly connected to the first circulation pump (high pressure side) 1001, the first circulation pump (low pressure side) 1002, the buffer tank 1003, etc. Although for the sake of simplicity, Figure 2A Only a path through which one of the CMYK inks flows is shown in FIG. 1 , but actually circulation paths for four colors are provided in the liquid ejection head 3 and the recording apparatus main body.

[0043] The buffer tank 1003, which is connected to the main tank 1006 and serves as a sub-tank, has an atmosphere communication port (not shown) that communicates the inside and outside of the tank with each other, and bubbles in the ink can be discharged to the outside. The buffer tank 1003 is also connected to the replenishing pump 1005. In the case where the ink is consumed in the liquid ejection head 3, the replenishing pump 1005 transfers the ink equivalent to the consumed amount from the main tank 1006 to the buffer tank 1003. For example, in the case where the ink is ejected (discharged) from the ejection port of the liquid ejection head in operations such as recording and suction recovery performed by ejecting the ink, the ink is consumed in the liquid ejection head 3.

[0044] The two first circulation pumps 1001 and 1002 have the function of pumping ink out of the liquid connection 111 of the liquid ejection head 3 and making the ink flow to the buffer tank 1003. The first circulation pumps are preferably volumetric pumps with quantitative liquid delivery capability. Specifically, as examples, tube pumps, gear pumps, diaphragm pumps, injection pumps, etc. can be given. For example, a mode of ensuring a constant flow rate by configuring a conventional constant flow valve or a pressure reducing valve at the pump outlet can also be used. In the drive of the liquid ejection head 3, the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 make the ink flow in a constant amount in each of the common supply flow path 211 and the common recovery flow path 212. The flow rate is preferably set to be equal to or higher than the following flow rate: the temperature difference between the recording element plates 10 in the liquid ejection 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 boards 10 becomes excessively large due to the pressure drop in the flow path of the liquid ejection unit 300, and image density non-uniformity occurs. Therefore, it is preferable to set the flow rate in consideration of the temperature difference and negative pressure difference between the recording element boards 10.

[0045] A negative pressure control unit 230 is provided in the middle of the path connecting the second circulation pump 1004 and the liquid ejection unit 300. Therefore, the negative pressure control unit 230 has the function of performing the following operations: even when the flow in the circulation system fluctuates due to the recorded duty cycle difference, the pressure downstream of the negative pressure control unit 230 (i.e., the side where the liquid ejection unit 300 is located) is maintained at a preset constant pressure. Any mechanism can be used as the two pressure regulating mechanisms forming the negative pressure control unit 230, as long as they can control the downstream pressure 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 the so-called "pressure reducing regulator" can be used. In the case of using a pressure reducing regulator, such as Figure 2AAs 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 ejection head 3, the layout freedom of the buffer tank 1003 in the recording device 1000 can be improved. The second circulation pump 1004 only needs to be a pump with a head pressure above a certain pressure within the range of the ink circulation flow used in the drive of the liquid ejection 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, instead of the second circulation pump 1004, a head tank configured to have a certain head difference relative to the negative pressure control unit 230 can be applied.

[0046] like Figure 2A As shown, the negative pressure control unit 230 includes two pressure regulating mechanisms for respectively setting different control pressures. The pressure regulating mechanism located at the high pressure setting side of the two negative pressure regulating mechanisms (in Figure 2A The pressure regulating mechanism (indicated by H in FIG. 1 ) is connected to the common supply flow path 211 in the liquid ejection unit 300 via the interior of the liquid supply unit 220. On the other hand, the pressure regulating mechanism (indicated by H in FIG. 1 ) located on the low pressure setting side Figure 2A The liquid supply unit 220 (indicated by L) is connected to the common recovery flow path 212 via the inside of the liquid supply unit 220.

[0047] The liquid ejection unit 300 is provided with a common supply flow path 211, a common recovery flow path 212, and a separate supply flow path 213 and a separate recovery flow path 214 that are connected to the recording element board 10. Since the separate supply flow path 213 and the separate recovery flow path 214 are connected to the common supply flow path 211 and the common recovery flow path 212, a flow (ie, a flow in which a portion of ink flows from the common supply flow path 211 to the common recovery flow path 212 while passing through the internal flow path of the recording element board 10) is generated. Figure 2A The reason is that since the pressure regulating mechanism H is connected to the common supply flow path 211 and the pressure regulating mechanism L is connected to the common recovery flow path 212, a pressure difference is generated between the two common flow paths.

[0048] As described above, in the liquid ejection unit 300, when the ink flows through the inside of the common supply flow path 211 and the common recovery flow path 212, a flow of a part of the ink passing through the inside of the recording element board 10 is generated. Therefore, the flow passing through the common supply flow path 211 and the common recovery flow path 212 allows the heat generated in the recording element board 10 to be discharged to the outside of the recording element board 10. In addition, since this configuration generates a flow of ink in the ejection port and the pressure chamber where recording is not performed when the liquid ejection head 3 performs recording, it is possible to suppress the increase in viscosity of the ink in this part. In addition, the ink with increased viscosity and foreign matter in the ink can be discharged to the common recovery flow path 212. Therefore, the liquid ejection head 3 of the present embodiment can perform high-quality recording at a high speed.

[0049] <Second Circulation Route>

[0050] Figure 2B 1 is a schematic diagram showing a second circulation path different from the first circulation path described above among the circulation paths applicable to the recording apparatus according to the present embodiment. The main differences from the first circulation path are as follows.

[0051] First, the two pressure regulating mechanisms forming the negative pressure control unit 230 each have a mechanism for controlling the upstream pressure of the negative pressure control unit 230 so that the pressure fluctuates within a certain range centered on the desired set pressure (a mechanism component with the same function as the so-called "back pressure regulator"). In addition, the second circulation pump 1004 is used 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.

[0052] The negative pressure control unit 230 in the second circulation path operates as follows: even if the flow rate fluctuates due to the change of the recording duty cycle when the liquid ejection head 3 performs recording, the pressure upstream of the negative pressure control unit 230 (i.e., the side where the liquid ejection unit 300 is located) fluctuates within a certain range. The pressure fluctuates within a certain range centered on a preset pressure, for example. Figure 2B 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 water head pressure of the buffer tank 1003 on the liquid ejection head 3, it is possible to improve the layout freedom of the buffer tank 1003 in the recording device 1000. For example, instead of the second circulation pump 1004, a water head tank configured to have a certain water head difference relative to the negative pressure control unit 230 can be applied.

[0053] As with the first cycle path, Figure 2B The negative pressure control unit 230 shown includes two pressure regulating mechanisms for respectively setting different control pressures. The pressure regulating mechanism located at the high pressure setting side (in Figure 2B The pressure regulating mechanism (indicated by H in FIG. 1 ) is connected to the common supply flow path 211 in the liquid ejection unit 300 via the interior of the liquid supply unit 220. On the other hand, the pressure regulating mechanism (indicated by H in FIG. 1 ) located on the low pressure setting side Figure 2B The liquid supply unit 220 (indicated by L) is connected to the common recovery flow path 212 via the inside of the liquid supply unit 220.

[0054] The two pressure regulating mechanisms make the pressure in the common supply flow path 211 higher than the pressure in the common recovery flow path 212. This configuration produces the following ink flow: ink flows from the common supply flow path 211 to the common recovery flow path 212 via the individual flow paths 213 and the internal flow paths of the recording element board 10 ( Figure 2B ). 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 ejection unit 300. On the other hand, the second circulation path has two advantages different from those of the first circulation path.

[0055] 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 head is low. The second advantage is as follows: the maximum value of the flow rate necessary for supplying from the buffer tank 1003 to the liquid ejection head 3 in the second circulation path is smaller than the maximum value in the first circulation path. The reason is as follows. The total flow rate in the common supply flow path 211 and the common recovery flow path 212 in the case where the ink circulates during recording standby is called A. The value of A is defined as the minimum flow rate necessary to make the temperature difference in the liquid ejection unit 300 fall within the desired range when adjusting the temperature of the liquid ejection head 3 during recording standby. In addition, the ejection flow rate in the case where ink is ejected from all ejection ports in the liquid ejection unit 300 (full ejection) is defined as F. Thus, in the first circulation path ( Figure 2A ), 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 value of the liquid supply amount required to the liquid ejection head 3 during full ejection is A+F.

[0056] On the other hand, in the second circulation path ( Figure 2B), the amount of liquid supplied to the liquid ejection head 3 during the recording standby period is flow rate A. The amount of liquid supplied to the liquid ejection head 3 during full ejection is flow rate F. Thus, 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 necessary supply flow rate is the larger value of A and F. Therefore, assuming that the liquid ejection unit 300 with the same structure is used, the maximum value of the necessary supply flow rate in the second circulation path (A or F) must be smaller than the maximum value of the necessary supply flow rate in the first circulation path (A+F). In the case of the second circulation path, the degree of freedom of the applicable circulation pump is thus improved. Therefore, for example, a low-cost circulation pump with a simple structure can be used, or the load of a cooler (not shown) installed in the path located 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 line head with a relatively large value of A or F, and among the line heads, a line head with a large length in the length direction benefits more.

[0057] Note that the first circulation path also has advantages over the second circulation path. Specifically, in the second circulation path, since the flow rate of the ink flowing in the liquid ejection unit 300 is the largest during the recording standby period, the lower the recording duty cycle, the higher the negative pressure applied to each nozzle. Therefore, especially when the flow path width (the length in the direction orthogonal to the flow direction of the ink) of the common supply flow path 211 and the common recovery flow path 212 is reduced to reduce the head width (the length of the liquid ejection head in the short side direction), in the low duty cycle image where the unevenness tends to be noticeable, the nozzle will be applied with a high negative pressure. The application of such a high negative pressure may increase the influence of satellite droplets. On the other hand, in the first circulation path, since the moment when the nozzle is applied with a high negative pressure is when a high duty cycle image is formed, there is the following advantage: even in the case of generating satellite droplets, the satellite droplets are less likely to be noticed, and their influence on the recorded image is small. A preferred circulation path of the two circulation paths can be selected and adopted according to the specifications (ejection flow rate F, minimum circulation flow rate A, and flow path resistance within the head) of the liquid ejection head and the recording apparatus body.

[0058] <Structure of Liquid Ejection Head>

[0059] The configuration of the liquid ejection head 3 according to the first embodiment will be described. Figure 3A and Figure 3B 2 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 plates 10 capable of ejecting inks of four colors, C, M, Y and K, are arranged in a straight line (arranged in a row). Figure 3AAs shown, the liquid ejection head 3 includes a signal input terminal 91 and a power supply terminal 92 which are 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 power necessary for ejection is supplied to the recording element board 10 via the power supply terminal 92.

[0060] By using the circuit in the electric wiring board 90 to gather the electric wires in one place, the number of the signal input terminals 91 and the power supply terminals 92 can be made smaller than the number of the recording element board 10. Thus, the number of electrical connections that need to be installed when the liquid ejection head 3 is mounted on the recording device 1000 or that need to be removed when the liquid ejection head is replaced can be reduced. Figure 3B As shown, the liquid connection parts 111 provided in both ends of the liquid ejection head 3 are connected to the liquid supply system of the recording device 1000. Thus, the inks of the four colors CMYK are supplied from the supply system of the recording device 1000 to the liquid ejection head 3, and the inks that have passed through the inside of the liquid ejection head 3 are recovered in the supply system of the recording device 1000. Thus, the inks of the respective colors can circulate through the paths of the recording device 1000 and the liquid ejection head 3.

[0061] Figure 4 1 is an exploded perspective view of the 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 mounted on the housing 80. The liquid supply unit 220 is provided with a liquid connection portion 111 ( Figure 2A and Figure 2B ), the liquid supply unit 220 is provided with filters 221 ( Figure 2A and Figure 2B ) to remove foreign matter in the supplied ink. Both liquid supply units 220 are provided with filters 221 for two colors respectively. The ink that has passed through the filters 221 is supplied to the negative pressure control unit 230 corresponding to each color and arranged on the liquid supply unit 220.

[0062] The negative pressure control unit 230 is a unit including pressure regulating valves for each color. The negative pressure control unit 230 greatly attenuates the pressure drop variation 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 by means of the action of the valves, spring components, etc. provided in the negative pressure control unit 230. Therefore, the negative pressure control unit 230 can stabilize the negative pressure variation downstream of the negative pressure control unit (the side where the liquid ejection unit 300 is located) within a certain range. Figure 2AAs shown, two pressure regulating valves for each color are built into the negative pressure control unit 230 of 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 path 211 and the common recovery flow path 212 in the liquid ejection unit 300 via the liquid supply unit 220, respectively.

[0063] The housing 80 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 a portion for supporting 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 has the function of correcting the warping and deformation of the liquid ejection unit 300 and ensuring the positional accuracy of the plurality of 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 preferably has sufficient rigidity, 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 bonding 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 bonding rubber.

[0064] The liquid ejection unit 300 includes a plurality of ejection modules 200 and a flow path member 210, and a cover member 130 is mounted on a surface of the liquid ejection unit 300 on the recording medium side. Figure 4 As shown, the cover member 130 is a member having a frame-shaped surface provided with a long opening 131, and includes the recording element board 10 and the sealing member 110 ( Fig. 6A and Figure 6B ) is exposed through the opening 131. The frame portion located around the opening 131 has a function as a contact surface that contacts the cover member that covers the liquid ejection head 3 during the recording standby period. Therefore, it is preferred that an adhesive, a sealing material, a filler, etc. be applied along the periphery of the opening 131, and it is preferred to fill the concave-convex and the gap on the ejection port surface of the liquid ejection unit 300 to form a closed space in the covered state.

[0065] Next, the configuration of the flow path member 210 included in the liquid ejection unit 300 is described. Figure 4As shown, the flow path member 210 is a member in which the first flow path member 50, the second flow path member 60, and the third flow path member 70 are stacked one on top of the other. The flow path member 210 distributes the ink supplied from the liquid supply unit 220 to the ejection module 200, and returns the ink flowing back from the ejection module 200 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.

[0066] Next, by using Figure 5A and Figure 5B The connection relationship of the flow paths in the flow path member 210 is described. Figure 5A 2 is a perspective view in which the flow path in the flow path member 210 formed by joining the first flow path member to the third flow path member is partially observed in an enlarged manner from the side of the first flow path member 50 where the surface of the ejection module 200 is installed. The flow path member 210 is provided with a common supply flow path 211 (211a, 211b, 211c and 211d) for each color extending in the length direction of the liquid ejection head 3 and a common recovery flow path 212 (212a, 212b, 212c and 212d) for each color. A plurality of individual supply flow paths (213a, 213b, 213c or 213d) formed by individual flow path grooves are connected to the common supply flow path 211 for each color via a communication port 61. A plurality of individual recovery flow paths (214a, 214b, 214c or 214d) formed by individual flow path grooves are connected to the common recovery flow path 212 for each color via a communication port 61. This flow path configuration allows ink to be collected from the common supply flow path 211 to the recording element board 10 located in the center portion of the flow path member via the individual supply flow paths 213. In addition, ink can be recovered from the recording element board 10 to the common recovery flow path 212 via the individual recovery flow paths 214.

[0067] Figure 5B It is shown along Figure 5A The cross section of the VB-VB line in FIG. Figure 5B As shown, the separate recovery flow paths (214a and 214c) are both connected to the ejection module 200 via the communication port 51. Figure 5B Only separate recovery flow paths (214a and 214c) are shown, but Figure 5A As shown in FIG. 1 , in another cross section, a separate supply flow path 213 is connected to the ejection module 200. 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 ( 7A to 7C) supply flow path. In addition, in the support member 30 and the recording element plate 10, a flow path for recovering (refluxing) part or all of the ink supplied to the recording element 15 to the first flow path member 50 is formed. In this example, the common supply flow path 211 for each color is connected to the negative pressure control unit 230 (high pressure side) for the corresponding color via the liquid supply unit 220, and the common recovery flow path 212 is connected to the negative pressure control unit 230 (low pressure side) via the liquid supply unit 220. The negative pressure control unit 230 generates a differential pressure (pressure difference) between the common supply flow path 211 and the common recovery flow path 212. Therefore, in the flow path such as Figure 5A and Figure 5B In the liquid ejection head of this embodiment connected as shown, flows are generated from the common supply flow path 211 to the individual supply flow paths 213 , to the recording element board 10 , to the individual recovery flow paths 214 , and to the common recovery flow path 212 for each color.

[0068] <Ejection module>

[0069] Fig. 6A A perspective view of a spray module 200 is shown. Figure 6B 1 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 pre-set with the liquid communication port 31. Subsequently, the terminal 16 on the recording element board 10 and the terminal 41 on the flexible wiring board 40 are electrically connected to each other by wire bonding, and then the wire-bonded portion (electrical connection portion) is covered with a sealing member 110 for sealing. The terminal 42 of the flexible wiring board 40 located on the side opposite to the recording element board 10 is connected to the connection terminal 93 (see FIG. 1 ) of the electrical wiring board 90. Figure 4 ) 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 fluidically connects the recording element board 10 and the flow path member 210 to each other, a member that has high flatness and can be joined to the recording element board with sufficiently high reliability is preferably used as the support member 30. The material of the support member 30 is preferably, for example, alumina or a resin material.

[0070] <Structure of recording element board>

[0071] The configuration of the recording element board 10 in the present embodiment is described. Fig. 7A A plan view showing a surface of the recording element board 10 on the side where the ejection outlet 13 is formed, Figure 7B Shown by Fig. 7A An enlarged view of the portion represented by VIIb, Figure 7C Shows Fig. 7A The back floor plan. Figure 8is a diagram showing the recording element board 10 and the cover member 20 along the Fig. 7A A perspective view of a cross section along the section line VIII-VIII shown. Fig. 7A As shown, four ejection port arrays corresponding to respective ink colors are formed in the ejection port forming member 12 of the recording element board 10. Note that the extending direction along which the plurality of ejection ports 13 of the ejection port array are arranged is hereinafter referred to as "ejection port array direction".

[0072] like Figure 7B As shown in FIG. 1 , a recording element 15, which is a heating element configured to generate bubbles in the ink by means of thermal energy, is arranged at a position corresponding to each ejection port 13. A pressure chamber 23 including the recording element 15 is partitioned by a partition 22. The recording element 15 is connected to the recording element board 10 via an electrical wiring (not shown) provided in the recording element board 10. Fig. 7A The recording element 15 is electrically connected to the terminal 16 in the circuit board 90 ( Figure 4 ) and the flexible wiring board 40 ( Fig. 6A and 6B ) The pulse signal received from the control circuit of the recording device 1000 generates heat and boils the ink. The force of the bubbles generated by the boiling ejects the ink from the ejection port 13. Figure 7B As shown in the figure, the liquid supply passage 18 extends along one side of each ejection port array, and the liquid recovery passage 19 extends along the other side of the ejection port array. The liquid supply passage 18 and the liquid recovery passage 19 are flow paths provided in the recording element board 10 and extending in the direction of the ejection port array, and are connected to each ejection port 13 via the supply port 17a and the recovery port 17b, respectively.

[0073] like Figure 7C and Figure 8 As shown in FIG. 1 , a sheet-like cover member 20 is stacked on the back side of the surface of the recording element board 10 on which the ejection port 13 is formed, and a plurality of openings 21 which are described later and communicate with the liquid supply passage 18 and the liquid recovery passage 19 are provided in the cover member 20. In the present embodiment, three openings 21 are provided for one liquid supply passage 18, and two openings 21 are provided for one liquid recovery passage 19. Figure 7B As shown, the openings 21 in the cover member 20 are respectively Figure 5A The plurality of communication ports 51 shown in the figure are connected. Figure 8As shown, the cover member 20 has a function of a cover that forms a part of the wall of the liquid supply passage 18 and the liquid recovery passage 19, which are formed in the substrate 11 of the recording element board 10. The cover member 20 is preferably an object having sufficient corrosion resistance to ink, and from the viewpoint of preventing color mixing, the opening shape and opening position of the opening 21 are required to have high accuracy. Therefore, it is preferable to use a photosensitive resin material and a silicon plate as the material of the cover member 20, and to set the opening 21 by a photolithography process. As described above, the cover member is a member that changes the pitch of the flow path by using the opening 21, preferably has a small thickness in consideration of the pressure drop, and is desirably formed of a film-like member.

[0074] Next, the flow of ink in the recording element board 10 is described. Figure 8 is a diagram showing the recording element board 10 and the cover member 20 along the Fig. 7A In the recording element board 10, a substrate 11 made of Si and a nozzle forming member 12 made of a photosensitive resin are stacked one on top of the other, and a cover member 20 is bonded to the back surface of the substrate 11. The recording element 15 is formed on one surface ( 7A to 7C ), and grooves forming a liquid supply passage 18 and a liquid recovery passage 19 extending along each ejection port array are formed on the back side of the substrate 11. The liquid supply passage 18 and the liquid recovery passage 19 formed by the substrate 11 and the cover member 20 are respectively connected to the common supply flow path 211 and the common recovery flow path 212 in the flow path member 210, thereby generating a differential pressure between the liquid supply passage 18 and the liquid recovery passage 19. When ink is ejected from the plurality of ejection ports 13 of the liquid ejection head 3 to perform recording, in the ejection ports that do not perform ejection operation, the flow of ink in the liquid supply passage 18 provided in the substrate 11 is caused by the differential pressure. Figure 8 Specifically, the ink flows to the liquid recovery passage 19 via the supply port 17a, the pressure chamber 23, and the recovery port 17b. In the ejection port 13 and the pressure chamber 23 where recording is paused, this flow allows bubbles, foreign matter, ink with increased viscosity due to evaporation from the ejection port 13, and the like to be recovered into the liquid recovery passage 19. In addition, the increase in the viscosity of the ink in the ejection port 13 and the pressure chamber 23 can be suppressed. The ink recovered into the liquid recovery passage 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 6B ), and is sequentially recovered to the communication port 51 in the flow path member 210, the individual recovery flow path 214, and the common recovery flow path 212. The ink is finally recovered to the supply path of the recording apparatus 1000.

[0075] Specifically, the ink supplied from the recording device body to the liquid ejection head 3 flows in the following order to be supplied and recovered. First, the ink flows from the liquid connection portion 111 of the liquid supply unit 220 into the interior of the liquid ejection head 3. Then, the ink is sequentially supplied to the joint rubber 100, to the communication port and the common flow path groove provided in the third flow path member, to the common flow path groove and the communication port 61 provided in the second flow path member, and to the individual flow path groove and the communication port 51 provided in the first flow path member. Then, the ink is sequentially supplied to each pressure chamber 23 via the liquid communication port 31 provided in the support member 30, the opening 21 provided in the cover member, the liquid supply passage 18 provided in the substrate 11, and the supply port 17a. The ink supplied to the pressure chamber 23 but not ejected from the ejection port 13 sequentially flows through the recovery port 17b and the liquid recovery passage 19 provided in the substrate 11, the opening 21 provided in the cover member, and the liquid communication port 31 provided in the support member 30. Then, the ink flows sequentially through the communication port 51 and the individual flow path grooves provided in the first flow path member, the communication port 61 and the common flow path groove provided in the second flow path member, the common flow path groove and the communication port provided in the third flow path 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 ejection head 3. Figure 2A In the first circulation path mode shown in FIG. 1 , the ink flowing in from the liquid connection portion 111 passes through the negative pressure control unit 230 and is then supplied to the bonding rubber 100. Figure 2B In the illustrated second circulation path mode, the ink recovered 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.

[0076] In addition, if Figure 2A and Figure 2B As shown, not all the ink flowing in from one end of the common supply flow path 211 of the liquid ejection unit 300 is supplied to the pressure chamber 23 via the individual supply flow path 213a. Some of the ink flows from the other end of the common supply flow path 211 to the liquid supply unit 220 without flowing into the individual supply flow path 213a. By providing a path for the ink to flow without passing through the recording element board 10 as described above, even in the case where the recording element board 10 including a fine flow path with large flow resistance is provided as in the present embodiment, the backflow of the ink circulation flow can be suppressed. As described above, since the liquid ejection head of the present embodiment can suppress the increase in the viscosity of the ink located in the pressure chamber and the ejection port, it is possible to suppress non-ejection and the deviation of the ejection direction from the normal direction, and as a result, high-quality recording can be performed.

[0077] <Positional Relationship Between Adjacent Recording Element Boards>

[0078] Fig. 9FIG. 1 is a plan view showing adjacent portions of recording element boards in two adjacent ejection modules in a partially enlarged manner. Fig. 7A As shown in FIG. 1 and FIG. 2 , in this embodiment, a recording element board having a substantially parallelogram shape is used. Fig. 9 As shown, in each recording element board 10, the ejection port array (14a to 14d) in which the ejection ports 13 are arranged is arranged to be inclined at a certain angle relative to the conveying direction of the recording medium. In the ejection port arrays in adjacent parts of each recording element board 10, at least two ejection ports overlap each other in the conveying direction of the recording medium. Fig. 9 In the embodiment, two ejection ports on each D line are in an overlapping relationship. This configuration makes it possible to make black stripes and blank areas in the recorded image less noticeable by performing drive control on the overlapping ejection ports even when the position of the recording element board 10 deviates from the predetermined position to a certain extent. This configuration can also be achieved when a plurality of recording element boards 10 are arranged in a straight line (in a row) instead of a zigzag pattern. Fig. 9 This can provide a countermeasure against black streaks and blank areas in the overlapping portion of the recording element board 10 while suppressing an increase in the length of the liquid ejection head in the conveying direction of the recording medium. Although the main plane of each recording element board has a parallelogram shape in this example, the present embodiment is not limited thereto, and the construction of the present embodiment can also be preferably applied to the case of using a recording element board having, for example, a rectangular shape, a trapezoidal shape, or other arbitrary shapes.

[0079] [Second embodiment]

[0080] The configurations of an inkjet recording apparatus 1000 and a liquid ejection head 3 according to the second embodiment are described below. Note that in the following description, portions different from the first embodiment are mainly described, and description of portions identical to the first embodiment is appropriately omitted.

[0081] <Inkjet Recording Apparatus>

[0082] Fig.10 Schematic diagram of the inkjet recording apparatus 1000 according to the present embodiment is shown. Fig.10 As shown, the recording apparatus 1000 of the present embodiment is different from the first embodiment in that four monochrome liquid ejection heads 3 corresponding to the respective inks of CMYK are arranged in parallel with each other to perform full-color recording on the recording medium 2. In the first embodiment, the number of ejection port arrays available for one color is one. On the other hand, in the present embodiment, the number of ejection port arrays available for one color is 20 (see FIG. FIG. 16A to FIG. 16C). Therefore, performing recording while appropriately allocating recording data to a plurality of nozzle columns enables recording at a very high speed. In addition, even in the case where there is a nozzle that does not eject ink, nozzles in another column located at a position corresponding to the nozzle that does not eject ink in the conveying direction of the recording medium complementarily perform ejection, which improves reliability. Therefore, this structure is preferably used for commercial printing, etc. In the recording device 1000 according to the present embodiment, as in the first embodiment, the supply system, buffer tank 1003 and main tank 1006 of the recording device 1000 are fluidly connected to each liquid ejection head 3 (see Figure 2A and Figure 2B ). In addition, an electric control unit that sends power and an ejection control signal to each liquid ejection head 3 is electrically connected to the liquid ejection head 3.

[0083] <Circular Path>

[0084] As in the first embodiment, the first circulation path ( Figure 2A ) or the second loop path ( Figure 2B ) can be used as a liquid circulation path that connects each liquid ejection head 3 and the recording apparatus 1000 according to the present embodiment to each other.

[0085] <Structure of Liquid Ejection Head>

[0086] Next, the configuration of each liquid ejection head 3 according to the present embodiment will be described. Fig.11A and Fig. 11B FIG. 2 is a perspective view of the liquid ejection head 3 according to the present embodiment. Fig.11A As shown, the liquid ejection head 3 includes 16 recording element plates 10 arranged in a straight line along the length direction of the liquid ejection head 3, and is a line-type inkjet recording head capable of performing recording by using one color of ink. Fig.11A and Fig. 11B As shown in the figure, the liquid ejection head 3 includes a liquid connection portion 111, a signal input terminal 91, and a power supply terminal 92, as in the first embodiment. However, since the liquid ejection head 3 of this embodiment has more ejection port arrays than the first embodiment, the signal input terminal 91 and the power supply terminal 92 are arranged on both sides of the liquid ejection head 3. This is to reduce the voltage drop and signal transmission delay that occur in the wiring unit provided in the recording element board 10.

[0087] Fig.12: is an exploded perspective view of the liquid ejection head 3 according to the present embodiment, and shows the components and units forming the liquid ejection head 3 in a manner divided according to their functions. Although the functions of the various units and components and the order of liquid flow in the liquid ejection head are basically the same as those in the first embodiment, the function of ensuring the rigidity of the liquid ejection head is different from that in the first embodiment. Specifically, in the first embodiment, the liquid ejection unit support portion 81 mainly ensures the rigidity of the liquid ejection head, while in the liquid ejection head of the present embodiment, the second flow path member 60 included in the liquid ejection unit 300 ensures the rigidity of the liquid ejection head. The liquid ejection unit support portion 81 according to the present embodiment is connected to both ends of the second flow path member 60, and the liquid ejection unit 300 is mechanically connected to the carriage of the recording device 1000 to align the liquid ejection head 3. The electrical wiring board 90 and the liquid supply unit 220 including the negative pressure control unit 230 are connected to the liquid ejection unit support portion 81. Filters (not shown) are built in both liquid supply units 220. The two negative pressure control units 230 are configured to control the pressure to be different from each other, respectively, to be a relatively high negative pressure and a relatively low negative pressure. Fig.12 As shown, in the case where the high-pressure side negative pressure control unit 230 is arranged in one end of the liquid ejection head 3 and the low-pressure side negative pressure control unit 230 is arranged in the other end, the ink flow in the common supply flow path 211 extending in the length direction of the liquid ejection head 3 and the ink flow in the common recovery flow path 212 extending in the length direction of the liquid ejection head 3 are in an opposite relationship. This promotes heat exchange between the common supply flow path 211 and the common recovery flow path 212, and reduces the temperature difference in the two common flow paths. Therefore, the temperature difference between the plurality of recording element boards 10 arranged along the common flow path is unlikely to occur, and there is an advantage that recording unevenness due to the temperature difference is unlikely to occur.

[0088] Next, the details of the flow path member 210 included in the liquid ejection unit 300 are described. Fig.12 As shown, the flow path member 210 is a member in which the first flow path member 50 and the second flow path member 60 are stacked one on top of the other, and distributes the ink supplied from the liquid supply unit 220 to the ejection module 200. In addition, the flow path member 210 serves as a flow path member for returning the ink flowing back from the ejection module 200 to the liquid supply unit 220. The second flow path member 60 is a flow path member formed with a common supply flow path 211 and a common recovery flow path 212 and having a function of mainly ensuring the rigidity of the liquid ejection head 3. Therefore, the material of the second flow path member 60 is preferably a material with high mechanical strength and sufficient corrosion resistance to ink. Specifically, SUS, Ti, aluminum oxide, etc. can be preferably used.

[0089] Fig.13AThe surface of the first flow path member 50 on the side where the ejection module 200 is mounted is shown. Fig. 13B Shown as Fig.13A The surface is located on the back side of the surface and is located on the side in contact with the second flow path member 60. Unlike the first embodiment, the first flow path member 50 according to this embodiment is a member in which a plurality of members corresponding to each ejection module 200 are arranged adjacent to each other. Since the split structure as described above can cope with liquid ejection heads of any length by configuring a plurality of modules, this structure can be preferably applied to relatively long specifications of liquid ejection heads such as B2 size or larger. Fig.13A As shown, the communication port 51 of the first flow path member 50 is in fluid communication with the ejection module 200, and as shown in FIG. Fig. 13B As shown, the individual communication port 53 of the first flow path member 50 is in fluid communication with the communication port 61 of the second flow path member 60 . Fig. 13C The surface of the second flow path member 60 that is in contact with the first flow path member 50 is shown. Fig.13D : shows a cross section of the center portion of the second flow path member 60 in the thickness direction, Fig.13E 2 is a diagram showing the surface of the second flow path member 60 on the side in contact with the liquid supply unit 220. The functions of the flow path and the communication port of the second flow path member 60 are the same as those of the ink supply system for one color in the first embodiment. One of the common flow path grooves 71 of the second flow path member 60 is Fig.14A and Fig. 14B The common supply flow path 211 shown is a common flow path groove 71, and the other common flow path groove 71 is a common recovery flow path 212. Ink is supplied to each common flow path groove 71 from one end side to the other end side along the longitudinal direction of the liquid ejection head 3.

[0090] Fig.14A 1 is a perspective view showing the connection relationship between the ink flow path in the recording element board 10 and the flow path member 210. Fig.14A As shown, a group of common supply flow paths 211 and common recovery flow paths 212 extending in the length direction of the liquid ejection head 3 are provided in the flow path member 210. The communication port 61 of the second flow path member 60 is aligned with and connected to the individual communication port 53 of the first flow path member 50, and a liquid supply path is formed that extends from the communication port 72 of the second flow path member 60 to the communication port 51 of the first flow path member 50 via the common supply flow path 211. Similarly, a liquid recovery path is also formed that extends from the communication port of the second flow path member 60 to the communication port 51 of the first flow path member 50 via the common recovery flow path 212.

[0091] Fig. 14B It is shown along Fig.14A Figure 1 shows a cross section of the XIVB-XIVB line in FIG. Fig. 14BAs shown, the common supply flow path is connected to the ejection module 200 via the communication port 61, the individual communication port 53, and the communication port 51. Fig. 14B Not shown, but refer to Fig.14A , it is obvious that a separate recovery flow path is connected to the ejection module 200 in a similar path on another cross section. As in the first embodiment, a flow path connected to each ejection port 13 is formed in each ejection module 200 and each recording element board 10, and the supplied ink can flow back partially or completely while passing through the ejection port 13 (pressure chamber 23) where the ejection operation is suspended. In addition, as in the first embodiment, the common supply flow path 211 and the common recovery flow path 212 are connected to the negative pressure control unit 230 (high pressure side) and the negative pressure control unit 230 (low pressure side) via the liquid supply unit 220, respectively. Therefore, the differential pressure generates a flow that flows from the common supply flow path 211 to the common recovery flow path 212 while passing through the ejection port 13 (pressure chamber 23) of the recording element board 10.

[0092] <Ejection module>

[0093] Fig.15A is a three-dimensional diagram of a spray module 200. Fig. 15B An exploded view of the ejection module 200 is shown. The difference between this embodiment and the first embodiment is that the outer end portion (long side portion of the recording element board 10) of the recording element board 10 in the direction along which the plurality of ejection port columns are arranged is provided with a plurality of terminals 16. In addition, as another difference, two flexible wiring boards 40 electrically connected to the terminals 16 are provided for one recording element board 10. This is because the number of ejection port columns provided in the recording element board 10 is 20, which is much larger than the 8 in the first embodiment. Specifically, the purpose of this construction is to suppress the maximum distance from the terminal 16 to the recording element 15 provided to correspond to the ejection port column to a short distance, and to reduce the voltage drop and signal transmission delay occurring in the wiring unit within the recording element board 10. In addition, the liquid communication port 31 of the support member 30 is provided in the recording element board 10, and is opened in a manner extending across all ejection port columns. Other aspects are the same as those in the first embodiment.

[0094] <Structure of recording element board>

[0095] Fig.16A 1 is a schematic diagram showing a surface of the recording element board 10 on the side where the ejection outlet 13 is arranged. Fig. 16C It is shown Fig.16A Schematic diagram of the back side of the surface. Fig. 16B It is shown in Fig. 16C FIG. 2 is a schematic diagram of the surface of the recording element board 10 with the cover member 20 provided on the back side of the recording element board 10 removed. Fig. 16BAs shown, the liquid supply passage 18 and the liquid recovery passage 19 are alternately arranged on the back side of the recording element board 10 along the direction of the ejection port array. Although the number of ejection port arrays is much larger than that in the first embodiment, the substantial difference between the present embodiment and the first embodiment is that, as described above, the terminals 16 are arranged on both sides of the recording element board extending along the direction of the ejection port array. The basic structure such as the following is the same as that in the first embodiment: a set of liquid supply passages 18 and liquid recovery passages 19 are provided for each ejection port array and the cover member 20 is provided with an opening 21 that communicates with the liquid communication port 31 of the support member 30.

[0096] Examples of the liquid ejection head 3 of the present disclosure have been described above by using the first and second embodiments. The recording element board 10 included in the liquid ejection head 3 described herein may have specific configurations of the recording element board 10 described in the following examples.

[0097] [First example]

[0098] The first example is described below. Fig.17A and Fig. 17B is a diagram showing the structure of a recording element board 10 according to this example. Specifically, Fig.17A 1 shows a cross-sectional configuration of a heating member (heating element) 15 and a temperature detection element 905 forming a recording element in a recording element board 10, Fig. 17B The planar configuration of the heating element 15 and the temperature detection element 905 is shown. Note that Fig.17A It is along Fig. 17B The cross-sectional view along the XVIIA-XVIIA line in FIG. Fig. 17B This is a perspective view from the Si substrate 901 side, and is used to show the positional relationship of the temperature detection element 905. For the convenience of description, the nozzle portion of the ejection port 13 and some films are omitted from illustration.

[0099] like Fig.17A As shown, in the recording element board 10, a plurality of layers are formed on a Si substrate 901. Specifically, an insulating film PSG 903 is formed on the Si substrate 901 via a field oxide film 902 of SiO2 or the like. A temperature detection element 905 formed of a thin film resistor of Al, Pt, Ti, Ta or the like is provided on the insulating film PSG 903, and an AL1 wiring 904 for connecting and wiring the temperature detection element 905 is provided.

[0100] In addition, as an upper layer, an interlayer insulating film 906 of SiO or the like is provided, and a heating element 15 of TaSiN or the like that performs electrothermal conversion and an AL2 wiring 908 that connects the heating element 15 and a driving circuit formed on the Si substrate 901 are provided on the interlayer insulating film 906. In addition, a passivation film 909 of SiO2 or the like and an anti-cavitation film 910 of Ta, Ir or the like that improves cavitation resistance on the heating element 15 are provided.

[0101] like Fig. 17B As shown, on the plane of the recording element board 10, there are an area 911 of the heater 15, an area 912 of the AL2 wiring connected to the driving circuit of the heater 15, and an area 914 of the AL1 wiring used as a separate wiring for the temperature detection element 905.

[0102] The recording element board 10 according to the present embodiment is prepared by a semiconductor manufacturing process. Specifically, the temperature detection element 905 is placed on the AL1 layer, and film formation and patterning are performed to prepare the recording element board 10. As described above, the recording element board 10 according to the present example can be prepared without changing the basic structure of the conventional recording element board.

[0103] Despite Fig. 17B , the temperature detection element 905 is shown as having a meandering sawtooth shape, but the shape of the temperature detection element is not limited thereto and may be, for example, a rectangular shape. Fig. 17B The sawtooth shape shown has the following advantages: the larger the resistance value of the temperature detection element 905 is, the larger the detection signal is; therefore, the temperature change can be accurately detected.

[0104] Next, refer to 18A to 18D A description is given of a curve detected by the temperature detection element 905 in the case where a driving voltage for ink ejection is applied to the heater 15 . Fig.18A is a circuit diagram for showing an outline of a temperature detection process according to the present example, Fig.18B The temperature curves of normal ejection and non-ejection respectively are shown when a driving voltage is applied to the heating element 15 .

[0105] like Fig.18A As shown, the heating element 15 is driven by a constant voltage source. When the heating element driving signal HE becomes ON (high level active), the switch element is closed, thereby applying a constant voltage VH to the heating element 15. On the other hand, when the heating element driving signal HE becomes OFF (low), the switch element is opened, thereby cutting off the constant voltage VH applied to the heating element 15. As described above, the constant voltage VH is applied to the heating element 15 in a square pulse shape according to the ON and OFF of the heating element driving signal HE.

[0106] On the one hand, the temperature detection element 905 is a thin film resistor, and the constant current source applies current to the temperature detection element 905. When the sensor selection signal SE becomes ON (high level is effective), the switch element is closed, thereby applying a constant current Iref to the temperature detection element 905. At the same time, the voltage signal at both ends of the temperature detection element 905 is input to the differential amplifier. On the other hand, when the sensor selection signal SE becomes OFF (low), the switch element is opened, thereby cutting off the constant current Iref applied to the temperature detection element 905, and also cutting off the input of the voltage signal at both ends of the temperature detection element 905 to the differential amplifier.

[0107] For example, the constant current Iref can be set to any one of 32 levels from 0.6 mA to 3.7 mA in increments of 0.1 mA. In the following description, a setting width of one level is referred to as one grade.

[0108] In the case of a range of 32 levels, the set value Diref of the constant current Iref is defined as a 5-bit digital value and is transmitted to the shift register in synchronization with a clock signal not shown. Then, the set value Diref is latched in the latch circuit at the moment of a latch signal not shown and output to a current output digital-to-analog converter (DAC).

[0109] The output signal of the latch circuit is held until the next latching time and the next set value Diref is transmitted to the shift register. The output current Irefin of the digital-to-analog converter (DAC) is input to the constant current source and amplified, for example, 12 times, to be output as the constant current Iref.

[0110] When T0 represents normal temperature, Rs0 represents resistance at this temperature, and TCR represents the temperature coefficient of resistance of the temperature detection element 905, the resistance Rs of the temperature detection element 905 at temperature T is expressed by the following formula (1).

[0111] [Mathematical formula 1]

[0112] Rs=Rs0{1+TCR(T-T0)}...Formula (1)

[0113] When a constant current Iref is applied to the temperature detection element 905, a differential voltage VS between both ends is expressed by the following equation (2).

[0114] [Mathematical formula 2]

[0115] VS=Iref·Rs=Iref·Rs0{1+TCR(T-T0)}...Equation (2)

[0116] The differential voltage VS is inverted and input to the differential amplifier 950. However, the output Vdif is a negative voltage lower than the ground potential GND as it is, and what is actually fed back to the negative terminal of the operational amplifier in the differential amplifier 950 is Vdif=0V. Therefore, an undesired signal is outputted in the end. To avoid this, the constant voltage source applies an offset voltage Vref to the differential amplifier 950, and the offset voltage Vref is high enough to make the output Vdif equal to or higher than the ground potential GND.

[0117] Fig.18C Shown in Fig.18B The temperature curves shown are respectively the Vdif curves when the nozzle is in normal spraying and when it is not spraying. Fig.18B and Fig.18C As shown in FIG. 1 , the waveform of the Vdif curve is upside down relative to the waveform of the temperature curve. Therefore, when the slope of the waveform of the Vdif curve is negative, it indicates a temperature rise process, and when the slope is positive, it indicates a temperature drop process.

[0118] like Fig.18B and Fig.18C As shown in FIG. 1 , during normal ejection, the following characteristic point appears: at this characteristic point, a part of the ejected droplets falls onto the heating element 15 due to the contraction of the bubble after the bubble is generated, and the temperature of the heating element 15 drops sharply due to the fall. On the other hand, during non-ejection, there is no such droplet fall. Therefore, the temperature changes smoothly and no characteristic point appears. Note that in this example, the CPU of the recording device 1000, for example, executes the operation shown in FIG. Fig.18B The CPU of the recording device 1000 thus obtains information about the characteristic point, such as the presence or absence of the characteristic point (presence or absence) and the time and temperature at which the characteristic point appears. Then, the CPU of the recording device 1000 can determine that ejection is normal when the CPU can detect the characteristic point, and can determine that ejection is not performed when the CPU cannot detect the characteristic point.

[0119] Then, the output Vdif of the differential amplifier 950 as described above is input to the filter circuit. The filter circuit is a circuit for converting the maximum gradient of the temperature drop in the ejection state expressed by Vdif into a peak value, and is formed by a band pass filter (BPF) in which a second-order low pass filter and a first-order high pass filter are connected in cascade. The low pass filter attenuates high-frequency noise in a range higher than the cutoff frequency fcL, and the high pass filter extracts the gradient of the temperature drop by performing a first-order differential in a range lower than the cutoff frequency fcH to remove the DC component.

[0120] The aforementioned signal processing by the filter circuit causes the filter circuit to output a signal VF used when determining normal ejection or non-ejection.

[0121] Note that since the signal VF may also take a negative voltage lower than the ground potential GND in this case, the constant voltage source applies an offset voltage Vofs to the positive terminal as described above, and the offset voltage Vofs is high enough to make the signal VF equal to or higher than the ground potential GND.

[0122] Since the high-pass filter attenuates the low-range signal and the output voltage decreases, the output signal VF of the filter circuit is amplified in the inverting amplifier (INV) at a later stage.

[0123] Since the input signal VF of a positive voltage is inverted in the inverting amplifier (INV) and becomes a negative voltage, an offset voltage is applied to boost the signal as in a high-pass filter.

[0124] In this case, the output of the constant voltage source that applies the offset voltage Vofs to the high-pass filter is branched, and the same offset voltage Vofs is also applied to the inverting amplifier (INV).

[0125] As a result, when Ginv represents the amplification factor of the inverting amplifier (INV), the output signal Vinv of the inverting amplifier (INV) is expressed by the following equation (3).

[0126] [Mathematical formula 3]

[0127] Vinv=Vofs+Ginv(Vofs-VF)...Formula (3)

[0128] Fig.18D The Vinv curves for normal ejection and non-ejection are shown. In normal ejection, a peak value Vp appears due to the maximum temperature drop rate after the characteristic point. In non-ejection, no characteristic point appears, so the temperature drop rate is low. The peak value that appears in the waveform when non-ejection is smaller than the peak value in the waveform when normal ejection occurs.

[0129] The output signal Vinv of the inverting amplifier (INV) is input to the positive terminal of the comparator 951 and compared with the threshold voltage Dth input to the negative terminal. When Vinv>Dth, a valid signal CMP is output.

[0130] For example, the threshold voltage Dth can be set to any one of 256 levels from 0.5V to 2.54V with an increment of 8mV. In the case of a range of 256 levels, the set value Ddth of the threshold voltage Dth is defined as an 8-bit digital value and is transmitted to the shift register synchronously with a clock signal not shown. Then, the set value Ddth is latched in the latch circuit at the moment of the latch signal not shown, and is output to a voltage output digital-to-analog converter (DAC). The output signal of the latch circuit is maintained until the next latch moment and the next set value Ddth is transmitted to the shift register during this period.

[0131] The detection of the peak voltage Vp of Vinv is performed in the following order by using the comparator 951. First, during the initial latch period, a driving pulse is applied to the heating member 15 with a constant current Iref0 (e.g., 1.6 mA) corresponding to the reference setting value Diref0 applied to the temperature detection element 905. In this case, the reference setting value Ddth0 corresponding to the threshold voltage Dth0 as a reference is input to the comparator 951 and compared with the peak value of Vinv.

[0132] In the case where the determination pulse CMP is output, the level of Dth is increased by 1 in the next latch period, and Dth is compared with the peak value of Vinv in a similar manner.

[0133] This operation is repeated until the determination pulse CMP is not output, and Dth of the last level at which the determination pulse CMP is output is set to the peak voltage Vp. Fig.18D The peak voltage Vp in the normal ejection is shown in FIG. Dth increases from Dth0 to Dth1, and then to Dth2, and so on. Then, the determination pulse CMP is not output at Dth5. Therefore, Dth4 where the determination pulse CMP is output last is set to Vp.

[0134] On the other hand, in the case where the determination pulse CMP is not output in the initial latch period, the level of Dth in the next latch period is reduced by 1, and Dth is compared with the peak value of Vinv in a similar manner.

[0135] This is repeated until the determination pulse CMP is output, and Dth of the level at which the determination pulse CMP is output is set to the peak voltage Vp. Fig.18D In the example of normal ejection of , in the case where Dth decreases to Dth5 and then decreases to Dth4, the determination pulse CMP is output at Dth4. Therefore, Dth4 is set to Vp.

[0136] By using Fig.19A and Fig.19BThe structure of the heat action portion in the recording element board according to the present embodiment is described. Fig.19A 1 is a plan view schematically showing an area of ​​the recording element board 10 located near the heat action portion in an enlarged manner. Fig.19B It is along Fig.19A The cross-sectional view of the dotted line XIXB-XIXB in FIG. Although the stacked structure of the plates in these figures is the same as Fig.17A and Fig. 17B The examples described in are different, but any configuration can be applied as the stacked configuration of the recording element board.

[0137] The recording element board of the liquid ejection head is formed by stacking a plurality of layers one above the other on a substrate made of silicon. In the present embodiment, a heat storage layer made of a thermal oxide film, a SiO film, a SiN film, etc. is arranged on the substrate. In addition, a heating resistor element 126 is arranged on the heat storage layer, and the heating resistor element 126 is connected to an electrode wiring layer (not shown) serving as wiring made of a metal material such as Al, Al-Si, Al-Cu, etc. via a tungsten plug 128. Fig.19B As shown, an insulating protective layer 127 (first protective layer) is disposed on the heating resistor element 126. The insulating protective layer 127 is provided above the heating resistor element 126 so as to block contact between the heating resistor element 126 and the liquid by covering the heating resistor element 126. The insulating protective layer 127 is an insulating layer made of a SiO film, a SiN film, or the like.

[0138] A protective layer is provided on the insulating protective layer 127. The protective layer on the insulating protective layer 127 includes a lower protective layer 125, an upper protective layer 124 (second protective layer), and an adhesive protective layer 123. In the present embodiment, the lower protective layer 125 and the upper protective layer 124 are provided on the heating resistor element 126, and protect the surface of the heating resistor element 126 from chemical and physical impacts that occur with the heating of the heating resistor element 126. Therefore, these protective layers cover at least the portion that is located directly above the heating element 15 and is heated by the heating element 15. This portion is referred to as a heat action portion.

[0139] In this embodiment, the lower protective layer 125 is made of tantalum (Ta), the upper protective layer 124 is made of iridium (Ir), and the adhesive protective layer 123 is made of tantalum (Ta). In addition, the protective layers made of these materials are conductive. A protective layer 122 for improving adhesion with the ejection port forming member 12 is provided on the adhesive protective layer 123 as a liquid-resistant. The protective layer 122 is made of SiC.

[0140] In the case of ejecting liquid, the upper portion of the upper protective layer 124 contacts the liquid and is in a harsh environment where bubbles are generated due to the instantaneous temperature rise of the liquid in the upper portion, and the bubbles disappear in this portion, resulting in cavitation. Therefore, in the present embodiment, the upper protective layer 124 made of an iridium material having high corrosion resistance and high reliability is formed, and the upper protective layer 124 contacts the liquid at a position corresponding to the heating resistor element 126.

[0141] In addition, the recording device 1000 according to the present embodiment performs a scaling suppression process during printing to suppress scaling of the upper protective layer 124 deposited on the heating resistor element 126. Specifically, a portion of the upper protective layer 124 is set as an electrode 121 (first electrode), and a counter electrode 129 (second electrode) corresponding to the electrode 121 is set to form an electric field across the liquid in the liquid chamber. As a result, particles such as pigments with negative potential in the liquid are repelled by the surface of the upper protective layer 124 on the heating resistor element 126. By reducing the presence rate of particles such as pigments with negative potential near the surface of the upper protective layer 124 as described above, scaling of the upper protective layer 124 deposited on the heating resistor element 126 during printing is suppressed. This scaling suppression is performed in consideration of the fact that scaling is a phenomenon that occurs when a coloring material, additive, etc. contained in a liquid is heated to a high temperature to decompose at a molecular level, become a low-solubility substance, and is physically adsorbed on the upper protective layer. Reducing the presence rate of coloring materials, additives, and the like that cause scaling near the surface of the upper protective layer 124 on the heating resistor element 126 at the time of high-temperature heating of the upper protective layer 124 leads to suppression of scaling.

[0142] For example, the potential difference between the electrode 121 and the counter electrode 129 is preferably about 0.2V to 2.5V. This is due to the following reasons: it is assumed that the upper protective layer 124 is made of iridium; in this configuration, in the case where the potential difference between the two electrodes exceeds 2.5V, an electrochemical reaction occurs between the electrode 121 and the liquid, and the surface of the electrode 121 is dissolved in the liquid; therefore, it is preferable to set the potential level to a level at which the electrode 121 does not dissolve. Specifically, the state in this case is such that although an electric field is formed between the electrode 121 in the upper protective layer and the counter electrode 129 via the liquid, no current flows between them. Since the electrode 121 in the upper protective layer has a negative potential relative to the counter electrode 129, particles with a negative potential are repelled by the surface of the electrode 121 in the upper protective layer, thereby reducing the presence rate of particles near the surface of the electrode 121 in the upper protective layer.

[0143] Note that in the following description, a mode using the method of determining ejection or non-ejection as described above is referred to as a non-ejection determination mode, and a mode of printing without using this method is referred to as a printing mode. In addition, potential control is performed in which the potential difference between the upper protective layer 124 and the counter electrode 129 across the liquid is adjusted. Furthermore, in the present example, in the non-ejection determination mode, unlike the printing mode, potential control that does not suppress scaling is performed as a potential control performed by forming an electric field across the liquid in the upper protective layer 124 and the counter electrode 129. Optionally, in the non-ejection determination mode, the potential difference between the electrode 121 and the counter electrode 129 is set so that the degree to which particles in the liquid that cause scaling are repelled by the electrode 121 is reduced relative to the printing mode.

[0144] Fig. 20B ' is an example of a diagram showing the relationship between the detection time and Vinv in the printing mode as a comparative example, and Vinv of a total of 256 heating elements is obtained in the following manner: Vinv of 8 heating elements is obtained each time, and the heating element for obtaining Vinv is changed approximately every 400 μs. In this comparative example, the upper protective layer 124 is set to a ground potential, and 1.9 V is applied to the counter electrode 129. In the printing mode, since potential control for suppressing scaling is performed, the bubbles generated are relatively large, and the amount of the portion of the ejected droplets that falls onto the heating element 15 due to the contraction of the bubbles is relatively small. Therefore, Vinv, which is an output value of a characteristic point (a sharp drop in the temperature of the heating element 15), is relatively low. In the case of a low output value, the determination of the ejection state may not be accurately performed.

[0145] Note that in this comparative example, the distance between the heating element surface and the nozzle surface is about 9.5 μm, and the ejection speed in the printing mode is about 12 m / s. In the case where the distance between the heating element surface and the nozzle surface is less than about 22 μm, the detection rate tends to decrease, and in the case where the distance is less than about 12 μm, this tendency appears more obviously. In addition, in the case where the ejection speed is higher than about 10 m / s, the detection rate tends to decrease, and in the case where the ejection speed is higher than about 12 m / s, this tendency appears more obviously.

[0146] Fig. 20A' is an example of a diagram showing the relationship between the detection time and Vinv when the mode is switched from the print mode to the non-ejection determination mode and the potential control is performed without suppressing scaling. In this example, 1.8V is applied to the upper protective layer 124 and 1.9V is applied to the counter electrode 129. Since scaling is not suppressed (or the degree of suppression is reduced), the bubbles generated are relatively small, and the amount of the portion of the ejected droplets that falls on the heating element 15 due to the contraction of the bubbles is relatively large. Therefore, Vinv, which is the output value of the characteristic point (the temperature of the heating element 15 drops sharply), is relatively high.

[0147] As described above, it is possible to realize a recording apparatus and a control method of a recording apparatus capable of appropriately and accurately performing determination of the ejection state in each recording element or determination of the occurrence of an ejection failure.

[0148] Although a loop structure is adopted in this example, the technical idea according to this example can be applied to structures other than the loop structure.

[0149] [Second example]

[0150] Fig.21A and Fig.21B is a diagram showing the relationship between Vinv and the time elapsed after the potential control is switched for a plurality of heating elements. Fig.21A and Fig.21B In the example, the potential of the upper protective layer 124 is set to the ground potential, 1.9 V is applied to the counter electrode 129 in the printing mode, and then potential switching by potential control is performed.

[0151] Specifically, in Fig.21A In the case where the potential of the counter electrode 129 is maintained at 1.9 V, the potential of the upper protective layer 124 is switched by applying 0.9 V. It takes 2 ms after the switching for Vinv to increase to a value sufficient for detection. Fig.21B In the embodiment, the potential of the counter electrode 129 is switched by applying 1.0 V while the potential of the upper protective layer 124 is maintained at the ground potential. In this switching, Vinv takes about 500 ms after the switching to increase to a value sufficient for detection. Fig.21A and Fig.21B In the example, the potential difference between the upper protective layer and the counter electrode after switching is 1.0 V, but in the case of switching the potential on the upper protective layer side close to the scale attachment portion, higher responsiveness is achieved. In addition, without switching, it takes a long time for Vinv to increase to a value sufficient for detection. As described above, although the target of potential switching can be the upper protective layer or the counter electrode, it is desirable to switch the potential of the upper protective layer with high responsiveness.

[0152] In addition, switching the potential of one electrode as described above can simplify the device compared to the case of switching the potentials of two electrodes. However, for example, the optimal combination of the potentials of the upper protective layer and the counter electrode in the printing mode and the potentials of the upper protective layer and the counter electrode in the non-ejection determination mode may differ depending on the design balance of the entire recording device, the environment in which the recording device is installed, the type of ink, etc. ( Fig. 22 ). In this case, the potential of the upper protective layer and the potential of the counter electrode can be switched at the same time. However, in the case where one of the potentials needs to be switched first, it is desirable to switch the potential of the upper protective layer first.

[0153] <Conditional example>

[0154] By using Fig. 22 Describe various conditional examples.

[0155] Condition example (1) shows an example in which only the potential of the upper protective layer is changed between the printing mode and the non-ejection determination mode.

[0156] Conditional example (2) shows an example in which the potential of only the upper protective layer changes between different modes and the potential difference between the upper protective layer and the counter electrode in the non-ejection determination mode is greater than the potential difference in conditional example (1). In the upper protective layer and the counter electrode, the smaller the amount of potential change, the shorter the time required for the potential change. Therefore, the smaller the amount of potential change in each electrode, the better, as long as the potential difference between the upper protective layer and the counter electrode is sufficient to obtain the necessary detection rate.

[0157] Conditional examples (3) to (6) are modified examples in which the amount of change in potential between different modes is further reduced than the amount of change in conditional example (2). Assume a situation where the smaller the potential difference between the upper protective layer and the counter electrode, the more the detection rate is improved. In this case, as described above, the larger the amount of potential change in the upper protective layer, the longer the time required for the potential change, but the more the detection rate is improved. Therefore, it is desirable to set the amount of change in the potential of the upper protective layer as small as possible according to the necessary detection rate.

[0158] Condition example (7) shows an example of fixing the potential of the upper protective layer to the ground potential and changing the potential of the counter electrode. When it is desired to fix the potential of the upper protective layer to the ground potential, an appropriate effect can also be obtained by adjusting the amount of change in the potential of the counter electrode.

[0159] Conditional Example (8) shows an example in which the potential change of the counter electrode is greater than the potential change in Conditional Example (7). The detection rate after the potential difference between different modes is changed gradually improves. Although the potential change between different modes in Conditional Example (8) takes a longer time than that in Conditional Example (7), due to the large potential difference between the upper protective layer and the counter electrode, the time required to obtain the effect of improved detection rate after the potential change is shorter.

[0160] Condition example (9) shows an example in which the potential of the upper protective layer and the potential of the counter electrode are switched simultaneously when transition is made between the printing mode and the non-ejection determination mode.

[0161] Conditional example (10) shows an example in which the potential of only the upper protective layer is changed between different modes.

[0162] Condition example (11) shows an example in which the potential difference between the upper protective layer and the counter electrode increases when switching from the printing mode to the non-ejection determination mode. Regarding the optimal potential difference under the condition of not suppressing scale formation, reducing the potential difference is not necessarily good, and sometimes increasing the potential difference is better, depending on the conditions.

[0163] Note that the contents of the first embodiment and the second embodiment may be used in combination as appropriate.

[0164] [Other embodiments]

[0165] 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.

[0166] The present disclosure can provide a technique for grasping the ejection state in a recording element and accurately performing determination of the occurrence of an ejection failure.

[0167] While the present invention 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 scope of the claims is to be accorded the broadest interpretation so as to encompass all such modifications, equivalent structures, and functions.

[0168] This application claims priority from Japanese Patent Application No. 2021-112990 filed on Jul. 7, 2021, which is hereby incorporated by reference in its entirety.

Claims

1. A recording device comprising: A liquid ejection head, comprising a heating element, a first protective layer, a second protective layer, a second electrode, an ejection port, and a temperature detection element, wherein the heating element generates heat energy required to eject a liquid containing a pigment having a negative potential, the first protective layer blocks contact between the heating element and the liquid, the second protective layer covers at least a portion of the first protective layer to be heated by the heating element and serves as a first electrode, the second electrode is electrically connected to the first electrode via the liquid, the ejection port ejects the liquid, and the temperature detection element corresponds to the heating element; a detection unit configured to detect a characteristic point in a temperature curve obtained by the temperature detection element and indicating a relationship between time and temperature, and a determination unit configured to determine whether the liquid is normally ejected from the ejection port based on whether the detection unit has detected a characteristic point in the temperature curve, wherein: the recording apparatus having a non-ejection determination mode using the determination unit and a printing mode in which printing is performed without using the determination unit, In the printing mode, the potential set for the first electrode and the potential set for the second electrode are controlled so that an electric field that reduces the existence rate of the pigment near the surface of the second protective layer is formed between the first electrode and the second electrode, and In the non-ejection determination mode, the potential set for the first electrode and the potential set for the second electrode are different from those under the potential control in the printing mode.

2. The recording device according to claim 1, wherein The detection unit detects the characteristic point by performing a differential operation on the temperature curve.

3. The recording device according to claim 1, wherein The recording apparatus operates in a printing mode in a case where printing is to be performed, and operates in a non-ejection determination mode in a case where the characteristic point is to be detected.

4. The recording device according to claim 3, wherein When switching between the printing mode and the non-ejection determination mode, in the case where both the potential of the first electrode and the potential of the second electrode are to be changed, the potential of the first electrode is changed before the potential of the second electrode is changed.

5. The recording device according to claim 3, wherein When switching between the printing mode and the non-ejection determination mode, the potential of the second electrode is not changed, and only the potential of the first electrode is changed.

6. The recording device according to any one of claims 3 to 5, wherein: A potential difference between a potential set for the first electrode and a potential set for the second electrode is greater in the printing mode than in the non-ejection determination mode.

7. The recording device according to claim 1, wherein The liquid ejection head further comprises a pressure chamber, The pressure chamber is connected to a supply flow path and a recovery flow path, the supply flow path supplies the liquid to the pressure chamber, and the recovery flow path recovers the liquid from the pressure chamber, and The liquid circulates by sequentially flowing through the supply flow path, the pressure chamber, and the recovery flow path.

8. The recording device according to claim 1, wherein The heating element and the temperature detection element are arranged at different positions in the direction along which the liquid is ejected, The temperature sensing element has a meandering shape.

9. A control method for a recording device, the recording device comprising a liquid ejection head, the liquid ejection head comprising a heating element, a first protective layer, a second protective layer, a second electrode, an ejection port and a temperature detection element, the heating element generates heat energy required to eject a liquid containing a pigment with a negative potential, the first protective layer blocks contact between the heating element and the liquid, the second protective layer covers at least a portion of the first protective layer to be heated by the heating element and serves as a first electrode, the second electrode is electrically connected to the first electrode via the liquid, the ejection port ejects the liquid, the temperature detection element corresponds to the heating element, and the control method comprises the following steps: detecting a characteristic point in a temperature curve obtained by the temperature detection element indicating a relationship between time and temperature, and Whether the liquid is ejected normally from the ejection port is determined based on whether a characteristic point in the temperature curve has been detected, wherein The recording apparatus has a non-ejection determination mode using a determination unit and a printing mode in which printing is performed without using the determination unit, In the printing mode, the potential set for the first electrode and the potential set for the second electrode are controlled so that an electric field that reduces the existence rate of the pigment near the surface of the second protective layer is formed between the first electrode and the second electrode, and In the non-ejection determination mode, the potential set for the first electrode and the potential set for the second electrode are different from those under the potential control in the printing mode.

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