Recording apparatus and control method

Abstract

To provide a technology by which a discharge state of a recording element can be grasped and occurrence of discharge failure can be determined with high accuracy.SOLUTION: A recording device includes: a liquid discharge head having a heating element which emits heat energy necessary to discharge liquid, a first protection layer which blocks contact between the heating element and the liquid, a second protection layer which functions as a first electrode by covering at least a part of the first protection layer heated by the heating element, a second electrode which is electrically connected to the first electrode through the liquid, a discharge port which discharges the liquid, and a temperature detection element corresponding to the heating element; and detection means which detects a feature point on a temperature curve indicating a relationship between time and a temperature and acquired by the temperature detection element. Combination of a potential set to the first electrode and a potential set to the second electrode is, different between when printing and when detecting the feature point by the detection means.SELECTED DRAWING: Figure 22

Description

Technical Field

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

Background Art

[0002] In a recording head of an inkjet recording apparatus, ejection failure occurs in some or all of the nozzles due to clogging of the nozzles by foreign matter, bubbles mixed in the ink supply path, or changes in the wettability of the nozzle surface. Therefore, in such a recording head, it is necessary to identify the nozzles in which ejection failure has occurred and reflect them in image compensation or the recovery operation of the recording head.

[0003] In Patent Document 1, a temperature detection element formed of a thin film resistor through an insulating film is provided for each recording element having a heating element in a recording element substrate, and the temperature of each nozzle is detected to identify a nozzle with ejection failure from the state of temperature change.

[0004] Further, in Patent Documents 2 and 3, a method is proposed in which, in the temperature drop process of a temperature curve, it is determined whether there is an inflection point indicating that a rapid temperature drop change has occurred, and if there is an inflection point, it is regarded as normal ejection. It is considered that this inflection point occurs when the rear end of the ejected droplet contacts the recording element and cools the recording element.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the methods disclosed in Patent Documents 2 and 3 have a problem in that, when the contact of the trailing end of the ejected droplet onto the recording element is unstable, stable temperature cooling of the recording element does not occur, resulting in reduced inspection accuracy. For example, if the nozzle dimensions are such that the contact of the trailing end of the ejected droplet is unstable, the temperature cooling of the recording element becomes unstable, which tends to reduce inspection accuracy. Also, in places with low atmospheric pressure, such as at high altitudes, the contact of the trailing end of the ejected droplet becomes unstable, which also tends to reduce the temperature cooling of the recording element, resulting in reduced inspection accuracy.

[0007] Therefore, in view of the above issues, this disclosure aims to provide a technology for accurately understanding the ejection state of a recording element and determining the occurrence of ejection defects. [Means for solving the problem]

[0008] One embodiment of the present invention is a recording device comprising: a heating element that emits thermal energy necessary for discharging a liquid; a first protective layer that blocks contact between the heating element and the liquid; a second protective layer that covers at least the portion of the first protective layer heated by the heating element and functions as a first electrode; a second electrode electrically connected to the first electrode via the liquid; a discharge port for discharging the liquid; a temperature detection element corresponding to the heating element; and a detection means for detecting characteristic points in a temperature curve showing the relationship between time and temperature, acquired by the temperature detection element, wherein the combination of the potential set for the first electrode and the potential set for the second electrode differs when printing and when the characteristic points are detected by the detection means. [Effects of the Invention]

[0009] This disclosure provides a technology for accurately understanding the ejection state of a recording element and determining the occurrence of ejection defects. [Brief explanation of the drawing]

[0010] [Figure 1] Figure showing the schematic configuration of the recording apparatus 1000 according to the first embodiment [Figure 2] Figure showing the circulation path in the recording apparatus 1000 [Figure 3] Perspective view of the liquid ejection head 3 according to the first embodiment [Figure 4] Exploded perspective view of the liquid ejection head 3 according to the first embodiment [Figure 5] Figure showing the connection relationship of the flow paths in the flow path member 210 [Figure 6] Figure showing the ejection module 200 [Figure 7] Figure showing the structure of the recording element substrate 10 [Figure 8] Perspective cross-sectional view showing the structure of the recording element substrate 10 in the cross-section line VIII-VIII of FIG. 7(a) [Figure 9] Plan view showing a partially enlarged adjacent portion of the recording element substrate 10 [Figure 10] Figure showing the schematic configuration of the recording apparatus 1000 according to the second embodiment [Figure 11] Perspective view of the liquid ejection head 3 according to the second embodiment [Figure 12] Exploded perspective view of the liquid ejection head 3 according to the second embodiment [Figure 13] Figure showing the configuration of the flow path member 210 included in the liquid ejection head 3 according to the second embodiment [Figure 14] Figure for explaining the connection relationship of the flow paths in the recording element substrate 10 and the flow path member 210 [Figure 15] Figure showing the ejection module 200 [Figure 16] Figure showing the structure of the recording element substrate 10 [Figure 17] Figure showing the structure of the recording element substrate 10 according to the first example [Figure 18] Figure for explaining the profile detected by the temperature detection element 905 [Figure 19] Figure showing the structure of the heat acting portion in the recording element substrate 10 [Figure 20] Figure showing the relationship between the detection time and Vinv [Figure 21] Figure showing the relationship between the elapsed time after potential control switching and Vinv [Figure 22] Table in which values of various conditional examples are held MODE FOR CARRYING OUT THE INVENTION

[0011] Hereinafter, as an example of an embodiment of the present disclosure, a recording apparatus adopting an inkjet recording method will be described. The recording apparatus may be, for example, a single function printer having only a recording function, or a multi-function printer having a plurality of functions such as a recording function, a FAX function, and a scanner function. Further, it may be a manufacturing apparatus for manufacturing a color filter, an electronic device, an optical device, a micro-structure, etc. by a predetermined recording method.

[0012] In the following description, "recording" not only means forming significant information such as characters and figures, but also regardless of whether it is significant or not. Further, it also represents a case where an image, a pattern, a pattern, a structure, etc. are formed on a recording medium widely, or a case where the medium is processed, regardless of whether it is made manifest so that a human can perceive it visually.

[0013] Further, the "recording medium" not only represents paper used in a general recording apparatus, but also represents cloth, plastic film, metal plate, glass, ceramics, resin, wood, leather, etc., which can receive ink.

[0014] Furthermore, "ink" should be interpreted widely in the same manner as the definition of "recording" above. Therefore, it represents a liquid that can be used for forming an image, a pattern, a pattern, etc., or processing the recording medium, or processing the ink (for example, coagulation or insolubilization of a colorant in the ink applied to the recording medium) by being applied on the recording medium.

[0015] Furthermore, the "recording element" (sometimes referred to as a "nozzle") generally refers to an ink ejection port, a liquid path communicating therewith, and an element that generates energy used for ink ejection, unless otherwise specified.

[0016] [First Embodiment] This embodiment relates to an inkjet recording device in which a liquid such as ink is circulated between a tank and a liquid ejection head, but other configurations are also possible. For example, instead of circulating the ink, two tanks may be provided upstream and downstream of the liquid ejection head, and the ink in the pressure chamber may be made to flow by flowing ink from one tank to the other.

[0017] Furthermore, the liquid ejection head according to this embodiment is a so-called line-type head, having a length corresponding to the width of the recording medium. However, this embodiment can also be applied to a so-called serial-type liquid ejection head that records while scanning the recording medium. Examples of serial-type liquid ejection heads include, but are not limited to, a configuration in which one recording element substrate for black ink and one recording element substrate for color ink are mounted. Specifically, a short line head shorter than the width of the recording medium may be created by arranging several recording element substrates so that the nozzle rows overlap in the direction of the ejection port rows, and this line head is scanned across the recording medium.

[0018] <Inkjet recording device> Figure 1 shows a schematic configuration of a liquid ejection device according to this embodiment, specifically an inkjet recording device 1000 (hereinafter also referred to as the recording device) that ejects ink for recording. The recording device 1000 has a transport unit 1 that transports a recording medium 2 and a line-type liquid ejection head 3 arranged substantially perpendicular to the transport direction of the recording medium, and is a line-type recording device that performs continuous recording in one pass while transporting multiple recording media 2 continuously or intermittently. The recording media 2 is not limited to cut paper, but may also be continuous roll paper. The liquid ejection head 3 is capable of full-color printing using CMYK (cyan, magenta, yellow, black) inks. In the liquid ejection head 3, a liquid supply means that constitutes a supply path for supplying ink to the liquid ejection head, a main tank, and a buffer tank are fluidically connected (see Figure 2). In addition, an electrical control unit that transmits power and ejection control signals to the liquid ejection head 3 is electrically connected to the liquid ejection head 3. The liquid path and electrical signal path within the liquid ejection head 3 will be described later.

[0019] <First Circulation Path> Figure 2(a) is a schematic diagram showing a first circulation path as one form of the circulation path applied to the recording device according to this embodiment. As shown in Figure 2(a), the liquid discharge head 3 is fluidically connected to the first circulation pump (high pressure side) 1001, the first circulation pump (low pressure side) 1002, and the buffer tank 1003, etc. Note that in Figure 2(a), only the path through which one of the CMYK inks flows is shown for the sake of simplicity, but in reality, circulation paths for four colors are provided in the liquid discharge head 3 and the recording device body.

[0020] The buffer tank 1003, which is connected to the main tank 1006 and functions as a sub-tank, has an air vent (not shown) that connects the inside and outside of the tank, allowing air bubbles in the ink to be discharged to the outside. The buffer tank 1003 is also connected to the replenishment pump 1005. When ink is consumed by the liquid ejection head 3, the replenishment pump 1005 transfers the consumed ink from the main tank 1006 to the buffer tank 1003. Ink is consumed by the liquid ejection head 3 when ink is ejected (discharged) from the ejection port of the liquid ejection head, for example, when recording by ejecting ink or when suction recovery occurs.

[0021] The two first circulation pumps 1001 and 1002 are responsible for drawing ink from the liquid connection part 111 of the liquid ejection head 3 and flowing it to the buffer tank 1003. A positive displacement pump with a quantitative liquid delivery capacity is preferred as the first circulation pump. Specifically, this could be a tube pump, gear pump, diaphragm pump, syringe pump, etc., but it can also be used in a configuration where a constant flow rate is ensured by placing a general constant flow valve or relief valve at the pump outlet. When the liquid ejection head 3 is driven, a certain amount of ink flows through the common supply channel 211 and the common recovery channel 212, respectively, by the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002. It is preferable to set this flow rate to a level that does not affect the recording image quality due to the temperature difference between each recording element substrate 10 within the liquid ejection head 3. However, if the flow rate is set too high, the negative pressure difference between each recording element substrate 10 becomes too large due to the pressure loss in the flow path within the liquid ejection unit 300, resulting in uneven image density. Therefore, it is preferable to set the flow rate while taking into account the temperature difference and negative pressure difference between each recording element substrate 10.

[0022] The negative pressure control unit 230 is located in the middle of the path connecting the second circulation pump 1004 and the liquid discharge unit 300. Therefore, the negative pressure control unit 230 has the function of maintaining the pressure downstream of the negative pressure control unit 230 (i.e., on the liquid discharge unit 300 side) at a preset constant pressure, even when the flow rate of the circulation system fluctuates due to differences in the recording duty cycle. Any mechanism can be used as the two pressure adjustment mechanisms that constitute the negative pressure control unit 230, as long as it can control the pressure downstream of itself within a certain range of fluctuations around a desired set pressure. For example, a mechanism similar to a so-called "pressure reducing regulator" can be adopted. When a pressure reducing regulator is used, it is preferable to pressurize the upstream side of the negative pressure control unit 230 via the liquid supply unit 220 using the second circulation pump 1004, as shown in Figure 2(a). This suppresses the effect of hydrostatic pressure on the liquid discharge head 3 of the buffer tank 1003, thereby increasing the flexibility of the layout of the buffer tank 1003 in the recording device 1000. The second circulation pump 1004 can be any pump that has a head pressure above a certain level within the range of ink circulation flow rate used when driving the liquid discharge head 3, and can be a turbo pump or a positive displacement pump, for example. Specifically, a diaphragm pump is applicable. Alternatively, instead of the second circulation pump 1004, a head tank positioned with a certain head difference relative to the negative pressure control unit 230 can also be used.

[0023] As shown in Figure 2(a), the negative pressure control unit 230 is equipped with two pressure adjustment mechanisms, each with a different control pressure setting. Of the two negative pressure adjustment mechanisms, the one with the relatively higher pressure setting (labeled H in Figure 2(a)) is connected to the common supply channel 211 in the liquid discharge unit 300 via the liquid supply unit 220. The one with the relatively lower pressure setting (labeled L in Figure 2(a)) is connected to the common recovery channel 212 via the liquid supply unit 220.

[0024] The liquid discharge unit 300 is provided with a common supply channel 211, a common recovery channel 212, and individual supply channels 213a and individual recovery channels 213b that communicate with each recording element substrate 10. Since the individual supply channels 213a and 213b communicate with the common supply channel 211 and the common recovery channel 212, a flow occurs in which some of the ink flows from the common supply channel 211 through the internal channels of the recording element substrate 10 to the common recovery channel 212 (arrow in Figure 2(a)). This is because a pressure adjustment mechanism H is connected to the common supply channel 211 and a pressure adjustment mechanism L is connected to the common recovery channel 212, resulting in a pressure difference between the two common channels.

[0025] In this way, the liquid ejection unit 300 flows ink through the common supply channel 211 and the common recovery channel 212, respectively, while generating a flow that allows some of the ink to pass through each recording element substrate 10. As a result, the heat generated in each recording element substrate 10 can be discharged to the outside of the recording element substrate 10 by the flow in the common supply channel 211 and the common recovery channel 212. Furthermore, with this configuration, ink flow can be generated even in the ejection port and pressure chamber that are not recording when the liquid ejection head 3 is performing recording, thereby suppressing ink viscosity in those areas. In addition, the viscous ink and foreign matter in the ink can be discharged into the common recovery channel 212. As a result, the liquid ejection head 3 of this embodiment enables high-speed, high-quality recording.

[0026] <Second Circulation Pathway> Figure 2(b) is a schematic diagram showing a second circulation path, which is different from the first circulation path described above, among the circulation paths applied to the recording device according to this embodiment. The main differences from the first circulation path are as follows.

[0027] First, the two pressure adjustment mechanisms constituting the negative pressure control unit 230 both have a mechanism (a mechanism component that functions similarly to a so-called "back pressure regulator") that controls the pressure upstream of the negative pressure control unit 230 within a certain range of fluctuations centered on a desired set pressure. In addition, the second circulation pump 1004 acts as a negative pressure source that reduces the pressure downstream of the negative pressure control unit 230. Furthermore, the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 are located upstream of the liquid discharge head, and the negative pressure control unit 230 is located downstream of the liquid discharge head.

[0028] The negative pressure control unit 230 in the second circulation path operates in such a way that even if the flow rate fluctuates due to changes in the recording duty cycle when recording is performed by the liquid discharge head 3, the pressure fluctuation on its upstream side (i.e., the liquid discharge unit 300 side) remains within a certain range. The pressure fluctuation is kept within a certain range, for example, centered around a preset pressure. As shown in Figure 2(b), it is preferable to pressurize the downstream side of the negative pressure control unit 230 via the liquid supply unit 220 using the second circulation pump 1004. This suppresses the influence of the buffer tank 1003's hydrostatic pressure on the liquid discharge head 3, thereby increasing the flexibility of the layout of the buffer tank 1003 in the recording device 1000. Alternatively, instead of the second circulation pump 1004, a hydrostatic tank positioned with a predetermined hydrostatic head difference relative to the negative pressure control unit 230 may be used.

[0029] Similar to the first circulation path, the negative pressure control unit 230 shown in Figure 2(b) is equipped with two pressure adjustment mechanisms, each with a different control pressure set. Of the two negative pressure adjustment mechanisms, the one with the relatively higher pressure setting (labeled H in Figure 2(b)) is connected to the common supply channel 211 in the liquid discharge unit 300 via the liquid supply unit 220. The one with the relatively lower pressure setting (labeled L in Figure 2(b)) is connected to the common recovery channel 212 via the liquid supply unit 220.

[0030] Two negative pressure adjustment mechanisms ensure that the pressure in the common supply channel 211 is relatively higher than the pressure in the common recovery channel 212. This configuration generates an ink flow from the common supply channel 211 through the individual channels 213 and the internal channels of each recording element substrate 10 to the common recovery channel 212 (arrows in Figure 2(b)). Thus, the second circulation path provides the same ink flow conditions within the liquid ejection unit 300 as the first circulation path, but with two advantages that differ from the first circulation path.

[0031] The first advantage is that in the second circulation path, the negative pressure control unit 230 is located downstream of the liquid ejection head 3, so there is less concern about dust and foreign matter generated from the negative pressure control unit 230 flowing into the head. The second advantage is that in the second circulation path, the maximum required flow rate from the buffer tank 1003 to the liquid ejection head 3 is less than in the first circulation path. The reason for this is as follows: Let A be the sum of the flow rates in the common supply channel 211 and the common recovery channel 212 when circulation is in operation during recording standby. The value of A is defined as the minimum flow rate required to bring the temperature difference within the liquid ejection unit 300 within the desired range when adjusting the temperature of the liquid ejection head 3 during recording standby. Also, let F be defined as the ejection flow rate when ink is ejected from all ejection ports of the liquid ejection unit 300 (full ejection). In the case of the first circulation path (Figure 2(a)), the set flow rates of the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002 are A, so the maximum amount of liquid supplied to the liquid discharge head 3 required when the entire volume is discharged is A + F.

[0032] On the other hand, in the case of the second circulation path (Figure 2(b)), the amount of liquid supplied to the liquid discharge head 3 required when recording is in standby mode is flow rate A. The amount of liquid supplied to the liquid discharge head 3 required when full discharge is achieved is flow rate F. In this case, in the case of the second circulation path, the sum of the set flow rates of the first circulation pump (high pressure side) 1001 and the first circulation pump (low pressure side) 1002, i.e., the maximum required supply flow rate, is the larger of A or F. Therefore, as long as the same liquid discharge unit 300 configuration is used, the maximum required supply amount (A or F) in the second circulation path will always be smaller than the maximum required supply flow rate (A + F) in the first circulation path. Consequently, in the case of the second circulation path, the degree of freedom in the applicable circulation pump increases. For example, it is possible to use a simple and low-cost circulation pump, or reduce the load on the cooler (not shown) installed in the main unit-side path, which has the advantage of reducing the cost of the recording device itself. This advantage becomes greater for line heads where the value of A or F is relatively large, and is more beneficial for line heads with a longer longitudinal length.

[0033] Furthermore, the first circulation path has advantages over the second circulation path. Specifically, in the second circulation path, the flow rate within the liquid ejection unit 300 is maximum when recording is in standby mode. Therefore, the lower the recording duty cycle, the higher the negative pressure applied to each nozzle. For this reason, especially when the flow path width (length in the direction perpendicular to the ink flow direction) of the common supply flow path 211 and the common recovery flow path 212 is reduced, and the head width (length in the short side direction of the liquid ejection head) is reduced, high negative pressure is applied to the nozzles in low-duty images where unevenness is easily visible. Due to this high negative pressure application, there is a risk that the effect of satellite droplets will be greater. On the other hand, in the case of the first circulation path, the timing of high negative pressure being applied to the nozzles is when high-duty images are formed. Therefore, even if satellite droplets occur, they are less likely to be visible, and the impact on the recorded image is small. The two circulation paths can be preferred in light of the specifications of the liquid ejection head and the recording device body (ejection flow rate F, minimum circulation flow rate A, and flow resistance inside the head).

[0034] <Configuration of the liquid dispensing head> The configuration of the liquid ejection head 3 according to the first embodiment will now be described. Figures 3(a) and 3(b) are perspective views of the liquid ejection head 3 according to this embodiment. The liquid ejection head 3 is a line-type liquid ejection head in which 15 recording element substrates 10 capable of ejecting four colors of ink (C / M / Y / K) from a single recording element substrate 10 are arranged in a straight line (inline). As shown in Figure 3(a), the liquid ejection head 3 has a signal input terminal 91 and a power supply terminal 92 that are electrically connected to each recording element substrate 10 via a flexible wiring board 40 and an electrical wiring board 90. The signal input terminal 91 and the power supply terminal 92 are electrically connected to the control unit of the recording device 1000, and an ejection drive signal is supplied to the recording element substrate 10 via the signal input terminal 91, and the power required for ejection is supplied to the recording element substrate 10 via the power supply terminal 92.

[0035] By consolidating the wiring using the electrical circuits within the electrical wiring board 90, the number of signal output terminals 91 and power supply terminals 92 can be reduced compared to the number of recording element boards 10. This reduces the number of electrical connections that need to be removed when assembling the liquid ejection head 3 to the recording device 1000 or when replacing the liquid ejection head. As shown in Figure 3(b), the liquid connection parts 111 provided at both ends of the liquid ejection head 3 are connected to the liquid supply system of the recording device 1000. As a result, CMYK four-color inks are supplied from the supply system of the recording device 1000 to the liquid ejection head 3, and the ink that has passed through the liquid ejection head 3 is recovered to the supply system of the recording device 1000. In this way, the ink of each color can be circulated via the path of the recording device 1000 and the path of the liquid ejection head 3.

[0036] Figure 4 shows an exploded perspective view of each component or unit constituting the liquid discharge head 3. The liquid discharge 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 part 111 (Figure 2), and inside the liquid supply unit 220, there are color-specific filters 221 (Figure 2) that communicate with each opening of the liquid connection part 111 in order to remove foreign matter from the supplied ink. Each of the two liquid supply units 220 is provided with filters 221 for two colors. The ink that has passed through the filters 221 is supplied to a negative pressure control unit 230 located on the supply unit 220, corresponding to each color.

[0037] The negative pressure control unit 230 is a unit consisting of pressure regulating valves for each color. Through the action of valves and spring members provided inside each unit, the negative pressure control unit 230 significantly reduces pressure loss changes in the supply system of the recording device 1000 (the supply system upstream of the liquid ejection head 3) that occur due to fluctuations in ink flow rate. As a result, the negative pressure control unit 230 can stabilize negative pressure changes downstream of the pressure control unit (on the liquid ejection unit 300 side) within a certain range. Each negative pressure control unit 230 for each color has two pressure regulating valves built in, as described in Figure 2(a). These pressure regulating valves are set to different control pressures, and the high-pressure side is connected to the common supply passage 211 in the liquid ejection unit 300, and the low-pressure side is connected to the common recovery passage 212, via the liquid supply unit 220.

[0038] The housing 80 consists of a liquid ejection unit support section 81 and an electrical wiring board support section 82, supporting the liquid ejection unit 300 and the electrical wiring board 90, and ensuring the rigidity of the liquid ejection head 3. The electrical wiring board support section 82 is for supporting the electrical wiring board 90 and is fixed to the liquid ejection unit support section 81 by screws. The liquid ejection unit support section 81 corrects warping and deformation of the liquid ejection unit 300 and ensures the relative positional accuracy of the multiple recording element substrates 10, thereby suppressing streaks and unevenness in the recorded material. For this reason, the liquid ejection unit support section 81 preferably has sufficient rigidity, and suitable materials include metal materials such as SUS or aluminum, or ceramics such as alumina. The liquid ejection unit support section 81 is provided with openings 83 and 84 into which the joint rubber 100 is inserted. The ink supplied from the liquid supply unit 220 is guided through the joint rubber to the third flow path member 70 that constitutes the liquid ejection unit 300.

[0039] The liquid ejection unit 300 has a plurality of ejection modules 200 and a flow path member 210, and a cover member 130 is attached to the side of the liquid ejection unit 300 that is on the recording medium side. Here, as shown in Figure 4, the cover member 130 is a member having a frame-like surface with a long opening 131, and the recording element substrate 10 and sealing material 110 (Figure 6) included in the ejection module 200 are exposed through the opening 131. The frame portion around the opening 131 functions as a contact surface for a cap member that caps the liquid ejection head 3 when it is in standby mode for recording. For this reason, it is preferable to apply an adhesive, sealing material, filler, etc. along the perimeter of the opening 131 to fill in any irregularities or gaps on the ejection port surface of the liquid ejection unit 300 so that a closed space is formed when the cap is applied.

[0040] Next, the configuration of the flow channel member 210 included in the liquid discharge unit 300 will be described. As shown in Figure 4, the flow channel member 210 is made up of a stack of a first flow channel member 50, a second flow channel member 60, and a third flow channel member 70. The flow channel member 210 distributes the ink supplied from the liquid supply unit 220 to each discharge module 200, and returns the ink circulating from the discharge module 200 back to the liquid supply unit 220. The flow channel member 210 is fixed to the liquid discharge unit support 81 with screws, thereby suppressing warping and deformation of the flow channel member 210.

[0041] Next, the connection relationships of each flow path within the flow path member 210 will be explained using Figure 5. Figure 5(a) is a perspective view of the flow paths within the flow path member 210, which is formed by joining the first to third flow path members, with a portion enlarged from the side of the first flow path member 50 on which the discharge module 200 is mounted. The flow path member 210 is provided with common supply flow paths 211 (211a, 211b, 211c, 211d) and common recovery flow paths 212 (212a, 212b, 212c, 212d) that extend in the longitudinal direction of the liquid discharge head 3 for each color. Multiple individual supply flow paths (213a, 213b, 213c, 213d) formed by individual flow path grooves are connected to the common supply flow path 211 for each color via a communication port 61. In addition, multiple individual recovery flow paths (214a, 214b, 214c, 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 concentrated from each common supply flow path 211 through individual supply flow paths 213 to the recording element substrate 10 located in the center of the flow path member. Furthermore, ink can be recovered from the recording element substrate 10 through individual recovery flow paths 214 to each common recovery flow path 212.

[0042] Figure 5(b) is a cross-section along the line Vb-Vb in Figure 5(a). As shown in this figure, each individual recovery channel (214a, 214c) communicates with the discharge module 200 via the communication port 51. Although only the individual recovery channels (214a, 214c) are shown in Figure 5(b), in another cross-section, the individual supply channel 213 and the discharge module 200 are in communication, as shown in Figure 5(a). The support member 30 and the recording element substrate 10 included in each discharge module 200 have channels formed therein for supplying ink from the first channel member 50 to the recording element 15 (Figure 7) provided on the recording element substrate 10. The support member 30 and the recording element substrate 10 also have channels formed therein for recovering (recirculating) some or all of the ink supplied to the recording element 15 back to the first channel member 50. Here, the common supply channel 211 for each color is connected to the corresponding color's negative pressure control unit 230 (high pressure side) and liquid supply unit 220, and the common recovery channel 212 is connected to the negative pressure control unit 230 (low pressure side) and liquid supply unit 220. The negative pressure control unit 230 creates a differential pressure (pressure difference) between the common supply channel 211 and the common recovery channel 212. As a result, in the liquid discharge head of this embodiment, where each channel is connected as shown in Figure 5, a flow occurs for each color in the following order: common supply channel 211 ~ individual supply channel 213a ~ recording element substrate 10 ~ individual recovery channel 213b ~ common recovery channel 212.

[0043] <Discharge Module> Figure 6(a) shows a perspective view of one discharge module 200, and Figure 6(b) shows an exploded view thereof. As for the manufacturing method of the discharge module 200, first, the recording element substrate 10 and the flexible wiring board 40 are bonded to a support member 30 which is pre-equipped with a liquid communication port 31. Then, the terminals 16 on the recording element substrate 10 and the terminals 41 on the flexible wiring board 40 are electrically connected by wire bonding, and then the wire bonding portion (electrical connection portion) is covered and sealed with a sealing material 110. The terminal 42 on the side of the flexible wiring board 40 opposite to the recording element substrate 10 is electrically connected to the connection terminal 93 (see Figure 4) of the electrical wiring board 90. The support member 30 is a support body that supports the recording element substrate 10 and a flow channel member that fluidly communicates the recording element substrate 10 and the flow channel member 210, so it is preferable that it has high flatness and can be bonded to the recording element substrate with sufficiently high reliability. As for the material, alumina or resin material is preferred.

[0044] <Structure of recording element substrate> The configuration of the recording element substrate 10 in this embodiment will now be described. Figure 7(a) is a plan view of the side of the recording element substrate 10 on which the ejection ports 13 are formed, Figure 7(b) is an enlarged view of the portion indicated by VIIb in Figure 7(a), and Figure 7(c) is a plan view of the back surface of Figure 7(a). Figure 8 is a perspective view showing the cross-section of the recording element substrate 10 and the lid member 20 along the cross-sectional line VIII-VIII shown in Figure 7(a). As shown in Figure 7(a), four rows of ejection ports corresponding to each ink color are formed on the ejection port forming member 12 of the recording element substrate 10. Hereafter, the direction in which the rows of ejection ports in which the multiple ejection ports 13 are arranged extend will be referred to as the "ejection port row direction."

[0045] As shown in Figure 7(b), recording elements 15, which are heating elements for foaming the ink using thermal energy, are positioned at locations corresponding to each discharge port 13. A partition wall 22 separates a pressure chamber 23 containing the recording elements 15. The recording elements 15 are electrically connected to the terminals 16 in Figure 7(a) by electrical wiring (not shown) provided on the recording element substrate 10. The recording elements 15 generate heat and boil the ink based on pulse signals input from the control circuit of the recording device 1000 via the electrical wiring board 90 (Figure 4) and the flexible wiring board 40 (Figure 6). The force of foaming caused by this boiling ejects the ink from the discharge port 13. As shown in Figure 7(b), a liquid supply path 18 extends along one side of each row of discharge ports, and a liquid recovery path 19 extends along the other side. The liquid supply path 18 and the liquid recovery path 19 are flow paths extending in the direction of the discharge port row provided on the recording element substrate 10, and are in communication with the discharge port 13 via the supply path 17a and the recovery path 17b, respectively.

[0046] As shown in Figures 7(c) and 8, a sheet-like lid member 20 is laminated on the back surface of the recording element substrate 10 where the ejection port 13 is formed. The lid member 20 is provided with multiple openings 21 that communicate with the liquid supply passage 18 and liquid recovery passage 19, which will be described later. In this embodiment, three openings 21 are provided in the lid member 20 for each liquid supply passage 18, and two openings 21 are provided for each liquid recovery passage 19. As shown in Figure 7(b), each opening 21 of the lid member 20 communicates with a plurality of communication ports 51 shown in Figure 5(a), etc. As shown in Figure 8, the lid member 20 functions as a lid that forms part of the walls of the liquid supply passage 18 and liquid recovery passage 19 formed in the substrate 11 of the recording element substrate 10. The lid member 20 is preferably made of a material that has sufficient corrosion resistance to ink, and from the viewpoint of preventing color mixing, high precision is required in the shape and position of the openings 21. Therefore, it is preferable to use a photosensitive resin material or a silicon plate as the material for the lid member 20 and to create the opening 21 by a photolithography process. In this way, the lid member changes the pitch of the flow path by the opening 21, and considering the pressure loss, it is desirable that the thickness be thin, and it is preferable that it be composed of a film-like material.

[0047] Next, the flow of ink within the recording element substrate 10 will be described. Figure 8 is a perspective view showing a cross-section of the recording element substrate 10 and the lid member 20 along the cross-sectional line VIII-VIII in Figure 7(a). The recording element substrate 10 is formed by laminating a substrate 11 made of Si and an ejection port forming member 12 made of photosensitive resin, with the lid member 20 bonded to the back surface of the substrate 11. A recording element 15 is formed on one side of the substrate 11 (Figure 7), and grooves constituting a liquid supply passage 18 and a liquid recovery passage 19 extending along the row of ejection ports are formed on the back surface. The liquid supply passage 18 and the liquid recovery passage 19 formed by the substrate 11 and the lid member 20 are connected to a common supply passage 211 and a common recovery passage 212 in the flow path member 210, respectively, and a differential pressure is generated between the liquid supply passage 18 and the liquid recovery passage 19. When ink is being ejected and recorded from multiple ejection ports 13 of the liquid ejection head 3, the differential pressure at the ejection ports that are not currently ejecting causes the ink flow in the liquid supply passage 18 provided in the substrate 11 to follow the flow shown by arrow C in Figure 8. In other words, the ink flows to the liquid recovery passage 19 via the supply port 17a, pressure chamber 23, and recovery port 17b. This flow allows thickened ink, foam, and foreign matter generated by evaporation from the ejection ports 13 and pressure chamber 23 to be recovered into the liquid recovery passage 19. It also suppresses the thickening of the ink in the ejection ports 13 and pressure chamber 23. The ink recovered into the liquid recovery passage 19 is then recovered in the following order: through the opening 21 of the lid member 20 and the liquid communication port 31 of the support member 30 (see Figure 6(b)), to the communication port 51 in the flow path member 210, the individual recovery passage 214, and the common recovery passage 212. This ink is ultimately recovered into the supply path of the recording device 1000.

[0048] In other words, the ink supplied from the recording device body to the liquid ejection head 3 flows, is supplied, and is recovered in the following order. First, the ink flows into the liquid ejection head 3 from the liquid connection part 111 of the liquid supply unit 220. The ink is then supplied in the following order: through the joint rubber 100, the communication port and common flow channel groove provided in the third flow channel member, the common flow channel groove and communication port 61 provided in the second flow channel member, and the individual flow channel groove and communication port 51 provided in the first flow channel member. After that, it is supplied to the pressure chamber 23 in the following order: through the liquid communication port 31 provided in the support member 30, the opening 21 provided in the lid member, and the liquid supply path 18 and supply port 17a provided in the substrate 11. Of the ink supplied to the pressure chamber 23, the ink that is not ejected from the ejection port 13 flows in the following order: through the recovery port 17b and liquid recovery path 19 provided in the substrate 11, the opening 21 provided in the lid member, and the liquid communication port 31 provided in the support member 30. Subsequently, the ink flows sequentially through the communication port 51 and individual flow channel grooves provided in the first flow channel member, the communication port 61 and common flow channel groove provided in the second flow channel member, the common flow channel groove and communication port provided in the third flow channel member 70, and the joint rubber 100. Furthermore, ink flows from the liquid connection part 111 provided in the liquid supply unit to the outside of the liquid discharge head 3. In the configuration of the first circulation path shown in Figure 2(a), the ink flowing in from the liquid connection part 111 is supplied to the joint rubber 100 after passing through the negative pressure control unit 230. In the configuration of the second circulation path shown in Figure 2(b), the ink recovered from the pressure chamber 23 passes through the joint rubber 100 and then flows from the liquid connection part 111 to the outside of the liquid discharge head via the negative pressure control unit 230.

[0049] Furthermore, as shown in Figures 2(a) and 2(b), not all ink flowing in from one end of the common supply channel 211 of the liquid ejection unit 300 is supplied to the pressure chamber 23 via the individual supply channel 213a. Some ink flows from the other end of the common supply channel 211 to the liquid supply unit 220 without flowing into the individual supply channel 213a. By providing a path through which the ink flows without passing through the recording element substrate 10, even when the recording element substrate 10 has fine channels with high flow resistance, as in this embodiment, backflow of the circulating ink can be suppressed. In this way, the liquid ejection head of this embodiment can suppress the viscosity of the ink in the pressure chamber and near the ejection port, thereby suppressing deviations from the normal direction of ejection and failure to eject, and as a result, high-quality recording can be achieved.

[0050] <Positional relationship between adjacent recording element substrates> Figure 9 is a plan view showing a partially enlarged view of the adjacent portion of the recording element substrate in two adjacent ejection modules. As shown in Figure 7(a), etc., this embodiment uses a substantially parallelogram-shaped recording element substrate. As shown in Figure 9, each ejection port row (14a to 14d) in which the ejection ports 13 of each recording element substrate 10 are arranged is positioned at a certain angle with respect to the transport direction of the recording medium. As a result, at least one ejection port in the ejection port row of adjacent recording element substrates 10 overlaps in the transport direction of the recording medium. In Figure 9, the two ejection ports on line D overlap each other. With this arrangement, even if the position of the recording element substrate 10 is slightly shifted from a predetermined position, the drive control of the overlapping ejection ports can make black streaks and white spots in the recorded image less noticeable. Even when multiple recording element substrates 10 are arranged in a straight line (inline) rather than in a staggered arrangement, the configuration shown in Figure 9 can be achieved. This makes it possible to suppress the increase in the length of the recording medium in the transport direction of the liquid ejection head while preventing black streaks and white gaps at the connections between the recording element substrates 10. In this embodiment, the main plane of the recording element substrate is a parallelogram, but this embodiment is not limited to this, and the configuration of this embodiment can be preferably applied even when a rectangular, trapezoidal, or other shaped recording element substrate is used.

[0051] [Second Embodiment] The configuration of the inkjet recording apparatus 1000 and liquid ejection head 3 according to the second embodiment will be described below. In the following description, we will mainly describe the parts that differ from the first embodiment, and the description of parts that are the same as the first embodiment will be omitted as appropriate.

[0052] <Inkjet recording device> Figure 10 shows a schematic configuration of the inkjet recording device 1000 according to this embodiment. As shown in Figure 10, the recording device 1000 of this embodiment differs from the first embodiment in that it performs full-color recording on the recording medium 2 by arranging four single-color liquid ejection heads 3 corresponding to each CMYK ink in parallel. In the first embodiment, there was one ejection port row that could be used per color, whereas in this embodiment, there are 20 ejection port rows that can be used per color (see Figure 16). Therefore, by appropriately distributing the recording data to multiple ejection port rows for recording, very high-speed recording is possible. Furthermore, even if there is an ejection port that fails to eject, reliability is improved by interpolating ejection from an ejection port in another row that is located in a position corresponding to the transport direction of the recording medium, making it suitable for commercial printing and the like. In the recording device 1000 according to this embodiment, as in the first embodiment, the supply system of the recording device 1000, the buffer tank 1003, and the main tank 1006 are fluidly connected to each liquid ejection head 3 (see Figure 2). Furthermore, each liquid dispensing head 3 is electrically connected to an electrical control unit that transmits power and dispensing control signals to the liquid dispensing head 3.

[0053] <Circulation Route> As in the first embodiment, a first circulation path (Figure 2(a)) or a second circulation path (Figure 2(b)) can be used as the liquid circulation path connecting the recording device 1000 and the liquid discharge head 3.

[0054] <Configuration of the liquid dispensing head> The configuration of the liquid ejection head 3 according to this embodiment will now be described. Figures 11(a) and 11(b) are perspective views of the liquid ejection head 3 according to this embodiment. As shown in Figure 11(a), the liquid ejection head 3 is an inkjet-type line recording head that has 16 recording element substrates 10 arranged in a straight line in the longitudinal direction of the liquid ejection head 3 and is capable of recording with one color of ink. Also, as shown in Figures 11(a) and 11(b), the liquid ejection head 3 has a liquid connection part 111, a signal input terminal 91, and a power supply terminal 92, similar to the first embodiment. However, since the liquid ejection head 3 of this embodiment has more rows of ejection ports than the first embodiment, the signal output terminal 91 and the power supply terminal 92 are arranged on both sides of the liquid ejection head 3. This is to reduce voltage drops and signal transmission delays that occur in the wiring section provided on the recording element substrate 10.

[0055] Figure 12 is an exploded perspective view of the liquid discharge head 3 according to this embodiment, showing each component and unit constituting the liquid discharge head 3 divided according to its function. The roles of each unit and component and the order of liquid flow within the liquid discharge head are basically the same as in the first embodiment, but the function that ensures the rigidity of the liquid discharge head differs from the first embodiment. Specifically, in the first embodiment, the rigidity of the liquid discharge head was mainly ensured by the liquid discharge unit support portion 81, whereas in the liquid discharge head of this embodiment, the rigidity of the liquid discharge head is ensured by the second flow path member 60 included in the liquid discharge unit 300. The liquid discharge unit support portion 81 according to this embodiment is connected to both ends of the second flow path member 60, and the liquid discharge unit 300 is mechanically coupled to the carriage of the recording device 1000 to position the liquid discharge head 3. The liquid supply unit 220 equipped with a negative pressure control unit 230 and the electrical wiring board 90 are coupled to the liquid discharge unit support portion 81. Each of the two liquid supply units 220 has a built-in filter (not shown). The two negative pressure control units 230 are set to control the pressure with different, relatively high and low negative pressures. Furthermore, as shown in Figure 12, when the high-pressure negative pressure control unit 230 is installed at one end of the liquid discharge head 3 and the low-pressure negative pressure control unit 230 is installed at the other end, the ink flow in the common supply channel 211 and the ink flow in the common recovery channel 212, which extend in the longitudinal direction of the liquid discharge head 3, are in a counter-relationship. In this way, heat exchange is promoted between the common supply channel 211 and the common recovery channel 212, and the temperature difference between the two common channels is reduced. As a result, temperature differences are less likely to occur in each of the recording element substrates 10 provided along the common channel, which has the advantage of reducing recording inconsistencies caused by temperature differences.

[0056] Next, the details of the flow path member 210 included in the liquid discharge unit 300 will be described. As shown in Figure 12, the flow path member 210 is made up of a stacked first flow path member 50 and a second flow path member 60, and distributes the ink supplied from the liquid supply unit 220 to each discharge module 200. The flow path member 210 also functions as a flow path member for returning the ink circulating from the discharge module 200 back to the liquid supply unit 220. The second flow path member 60 is a flow path member in which a common supply flow path 211 and a common recovery flow path 212 are formed, and its main function is to provide rigidity to the liquid discharge head 3. For this reason, the material of the second flow path member 60 is preferably one that has sufficient corrosion resistance to ink and high mechanical strength. Specifically, SUS, Ti, alumina, etc. can be preferably used.

[0057] Figure 13(a) shows the side of the first flow channel member 50 on which the discharge module 200 is mounted, and Figure 13(b) shows the back surface of the said side, which is in contact with the second flow channel member 60. Unlike the first embodiment, the first flow channel member 50 in this embodiment has multiple members corresponding to each discharge module 200 arranged adjacent to each other. This divided structure can accommodate the length of the liquid discharge head by arranging multiple modules, and is therefore suitable for relatively long-scale liquid discharge heads, such as those corresponding to B2 size or larger. As shown in Figure 13(a), the communication port 51 of the first flow channel member 50 is in fluidic communication with the discharge module 200, and as shown in Figure 13(b), the individual communication ports 53 of the first flow channel member 50 are in fluidic communication with the communication ports 61 of the second flow channel member 60. Figure 13(c) shows the side of the second flow channel member 60 that is in contact with the first flow channel member 50, Figure 13(d) shows a cross-section of the central part in the thickness direction of the second flow channel member 60, and Figure 13(e) shows the side of the second flow channel member 60 that is in contact with the liquid supply unit 220. The functions of the flow channels and communication ports of the second flow channel member 60 are the same as those of the single-color ink supply system in the first embodiment. One end of the common flow channel groove 71 of the second flow channel member 60 is the common supply channel 211 shown in Figure 14, and the other end is the common recovery channel 212, and ink is supplied from one end to the other along the longitudinal direction of the liquid discharge head 3.

[0058] Figure 14(a) is a perspective view showing the connection relationship of the ink flow path between the recording element substrate 10 and the flow path member 210. As shown in Figure 14(a), a set of common supply flow paths 211 and common recovery flow paths 212 are provided inside the flow path member 210, extending in the longitudinal direction of the liquid discharge head 3. The communication port 61 of the second flow path member 60 is aligned and connected to the individual communication ports 53 of each of the first flow path members 50, forming a liquid supply path that communicates 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 communicates 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.

[0059] Figure 14(b) is a cross-sectional view of the line XIVb-XIVb in Figure 14(a). As shown in Figure 14(b), the common supply channel is connected to the ejection module 200 via the communication port 61, individual communication ports 53, and communication port 51. Although not shown in Figure 14(b), it is clear from Figure 14(a) that in another cross-section, the individual recovery channel is connected to the ejection module 200 via a similar path. Similar to the first embodiment, each ejection module 200 and recording element substrate 10 has a channel formed that communicates with each ejection port 13, so that some or all of the supplied ink can be recirculated by passing through the ejection port 13 (pressure chamber 23) where the ejection operation is suspended. Also, similar to the first embodiment, the common supply channel 211 is connected to the negative pressure control unit 230 (high pressure side), and the common recovery channel 212 is connected to the negative pressure control unit 230 (low pressure side) via the liquid supply unit 220. Therefore, the differential pressure generates a flow that travels from the common supply channel 211 through the discharge port 13 (pressure chamber 23) of the recording element substrate 10 to the common recovery channel 212.

[0060] <Discharge Module> Figure 15(a) is a perspective view of one ejection module 200, and Figure 15(b) is an exploded view of this ejection module 200. The difference between this embodiment and the first embodiment is that multiple terminals 16 are arranged at each of the ends (each long side of the recording element substrate 10) along the direction in which the multiple ejection port rows of the recording element substrate 10 are arranged. Furthermore, another difference is that two flexible wiring boards 40, which are electrically connected to the terminals 16, are arranged for one recording element substrate 10. This is because the number of ejection port rows provided on the recording element substrate 10 is 20, which is a significant increase from the 8 rows in the first embodiment. In other words, the purpose is to reduce voltage drops and signal transmission delays that occur in the wiring section within the recording element substrate 10 by shortening the maximum distance from the terminals 16 to the recording elements 15 provided corresponding to the ejection port rows. In addition, the liquid communication port 31 of the support member 30 is provided on the recording element substrate 10 and opens so as to span all the ejection port rows. Other points are the same as in the first embodiment.

[0061] <Structure of recording element substrate> Figure 16(a) is a schematic diagram showing the side of the recording element substrate 10 where the discharge port 13 is located, and Figure 16(c) is a schematic diagram showing the back side of the side shown in Figure 16(a). Figure 16(b) is a schematic diagram showing the side of the recording element substrate 10 when the cover member 20 provided on the back side of the recording element substrate 10 in Figure 16(c) is removed. As shown in Figure 16(b), liquid supply passages 18 and liquid recovery passages 19 are alternately provided on the back side of the recording element substrate 10 along the direction of the discharge port rows. Although the number of discharge port rows has increased significantly compared to the first embodiment, the essential difference between this embodiment and the first embodiment is that, as mentioned above, the terminals 16 are arranged on both sides of the recording element substrate along the direction of the discharge port rows. The basic configuration is the same as in the first embodiment, such as the provision of a pair of liquid supply passages 18 and liquid recovery passages 19 for each discharge port row, and the provision of an opening 21 in the cover member 20 that communicates with the liquid communication port 31 of the support member 30.

[0062] Examples of the liquid ejection head 3 of this disclosure have been described above using the first and second embodiments. The recording element substrate 10 of the liquid ejection head 3 described herein can have the specific configuration of the recording element substrate 10 shown in the following embodiments.

[0063] [First Embodiment] The first embodiment will be described below. Figure 17 shows the structure of the recording element substrate 10 according to this embodiment. Specifically, Figure 17(a) shows the cross-sectional configuration of the heater (heating element) 15 and the temperature detection element 905 that constitute the recording element in the recording element substrate 10, and Figure 17(b) shows the planar configuration of the heater 15 and the temperature detection element 905. Note that Figure 17(a) is a cross-section along the line XVIIa-XVIIa in Figure 17(b), and Figure 17(b) is a perspective view from the Si substrate 901 side to show the positional relationship of the temperature detection element 905. For the sake of explanation, nozzle parts such as the discharge port 13 and some films are omitted from the illustration.

[0064] As shown in Figure 17(a), in the recording element substrate 10, multiple layers are formed on the Si substrate 901. Specifically, an insulating film PSG 903 is formed on the Si substrate 901 via a field oxide film 902 such as SiO2. A temperature detection element 905, formed from a thin-film resistor such as Al, Pt, Ti, or Ta, is provided on the insulating film PSG 903, and AL1 wiring 904 for connecting the temperature detection element 905 is also provided.

[0065] Furthermore, an interlayer insulating film 906 made of SiO or the like is provided as an upper layer, and on the interlayer insulating film 906, a heater 15 that performs electrothermal conversion made of TaSiN or the like, and AL2 wiring 908 that connects the heater 15 to a drive circuit formed on the Si substrate 901 are provided. In addition, a passivation film 909 made of SiO2 or the like, and a cavitation-resistant film 910 made of Ta, Ir or the like that is provided on the heater 15 to improve its resistance to cavitation are also provided.

[0066] As shown in Figure 17(b), the recording element substrate 10 has a region 911 for the heater 15, a region for the AL2 wiring 912 that connects to the drive circuit of the heater 15, and a region for the AL1 wiring 914 that serves as individual wiring for the temperature detection element 905.

[0067] The recording element substrate 10 according to this embodiment is manufactured using a semiconductor manufacturing process. Specifically, it is manufactured by placing the temperature sensing element 905 on an AL1 layer, followed by film deposition and patterning. In this way, the recording element substrate 10 according to this embodiment can be manufactured without changing the basic structure of conventional recording element substrates.

[0068] In Figure 17(b), the temperature sensing element 905 is shown in a zigzag shape, but the shape of the temperature sensing element is not limited to this; for example, it may be rectangular. In the case of a zigzag shape as shown in Figure 17(b), the larger the resistance value of the temperature sensing element 905, the larger the detection signal becomes, which has the advantage of being able to detect temperature changes with high accuracy.

[0069] Next, the profile detected by the temperature detection element 905 when a drive voltage is applied to the heater 15 to eject ink will be explained using Figure 18. Figure 18(a) is a circuit diagram showing an overview of the temperature detection process according to this embodiment, and Figure 18(b) shows the temperature profiles for normal ejection and non-ejection when a drive voltage is applied to the heater 15.

[0070] As shown in Figure 18(a), the heater 15 is driven by a constant voltage source. When the heater drive signal HE is ON (High active), the switch element closes and a constant voltage VH is applied to the heater 15. When the heater drive signal HE is OFF (Low), the switch element opens and the application of the constant voltage VH to the heater 15 is interrupted. In this way, the constant voltage VH is applied to the heater 15 in a rectangular pulse pattern in response to the ON / OFF state of the heater drive signal HE.

[0071] On the other hand, the temperature sensing element 905 is a thin-film resistor to which current is applied by a constant current source. When the sensor selection signal SE is ON (High active), the switch element closes, and a constant current Iref is applied to the temperature sensing element 905. At the same time, the voltage signal across the temperature sensing element 905 is input to the differential amplifier. When the sensor selection signal SE is OFF (Low), the switch element opens, interrupting the application of the constant current Iref to the temperature sensing element 905, and also interrupting the input of the voltage signal across the temperature sensing element 905 to the differential amplifier.

[0072] The constant current Iref can be set in 32 steps, for example, in 0.1mA increments from 0.6mA to 3.7mA. Hereafter, one setting step will be referred to as one rank.

[0073] For a 32-rank range, the constant current Iref setting value Diref is defined as a 5-bit digital value and transferred to a shift register in synchronization with a clock signal (not shown). Then, it is latched into a latch circuit at the timing specified by a latch signal (not shown) and output to a current-output type digital-to-analog converter (DAC).

[0074] The output signal of the latch circuit is held until the next latch timing, and the next setpoint value Diref is transferred to the shift register. The output current Irefin of the digital-to-analog converter (DAC) is input to a constant current source, amplified, for example by 12 times, and output as a constant current Iref.

[0075] The resistance Rs of the temperature sensing element 905 at temperature T is expressed by the following equation (1), where T0 is room temperature, Rs0 is the resistance at that temperature, and TCR is the temperature resistance coefficient of the temperature sensing element 905.

[0076]

number

[0077] When a constant current Iref is applied to the temperature sensing element 905, the differential voltage VS across it is expressed by the following equation (2).

[0078]

number

[0079] The differential voltage VS is inverted and input to the differential amplifier 950. However, if left as is, the output Vdif becomes a negative voltage below ground potential GND, and in reality Vdif = 0V, which is fed back to the negative terminal of the operational amplifier inside the differential amplifier 950, ultimately resulting in the output of an unexpected signal. To avoid this, a sufficient offset voltage Vref to ensure that the output Vdif is above ground potential GND is applied to the differential amplifier 950 by a constant voltage source.

[0080] Figure 18(c) shows the Vdif profiles for normal and non-discharge conditions, given the temperature profile shown in Figure 18(b). As shown in Figures 18(b) and 18(c), the waveform of the Vdif profile is inverted vertically compared to the waveform of the temperature profile. Therefore, a negative slope in the Vdif profile waveform represents a heating process, and a positive slope represents a cooling process.

[0081] As shown in Figures 18(b) and 18(c), during normal dispensing, some of the dispensed droplets fall onto the heater 15 due to the contraction of the foam after foaming, resulting in a characteristic point where the temperature of the heater 15 drops sharply. In contrast, during non-dispensing, there is no such droplet fall. Therefore, the temperature changes smoothly, and no characteristic point appears. In this embodiment, the CPU of the recording device 1000 performs a differential calculation on a temperature curve showing the relationship between elapsed time and temperature, for example, as shown in Figure 18(b). As a result, the CPU of the recording device 1000 obtains information about the characteristic point, such as whether or not the characteristic point exists, and the time and temperature at which the characteristic point appeared. If a characteristic point is detected, it can be determined that normal dispensing occurred; if a characteristic point is not detected, it can be determined that non-dispensing occurred.

[0082] The output Vdif of such a differential amplifier 950 is then input to a filter circuit. The filter circuit is designed to convert the maximum gradient during cooling, which represents the discharge state in Vdif, into a peak, and consists of a bandpass filter (BPF) formed by cascading a second-order low-pass filter and a first-order high-pass filter. The low-pass filter attenuates high-frequency noise above the cutoff frequency fcL, and the high-pass filter extracts the gradient during cooling by first-order differentiation below the cutoff frequency fcH, removing the DC component.

[0083] Through the signal processing performed by the filter circuit described above, the filter circuit outputs a signal VF, which is used to determine whether the output is normal or not.

[0084] Furthermore, since the signal VF may be a negative voltage below the ground potential GND, as mentioned above, a sufficient offset voltage Vofs to be above the ground potential GND is applied to the + terminal by a constant voltage source.

[0085] The output signal VF of the filter circuit is amplified by the subsequent inverting amplifier (INV) because the output voltage decreases due to the attenuation of low-frequency signals by the high-pass filter.

[0086] In an inverting amplifier (INV), the positive input signal VF is inverted to a negative voltage, so, similar to a high-pass filter, an offset voltage is applied to boost the signal.

[0087] At this time, 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).

[0088] As a result, if the amplification factor of the inverting amplifier (INV) is Ginv, then the output signal Vinv of the inverting amplifier (INV) is given by equation (3) below.

[0089]

number

[0090] Figure 18(d) shows the Vinv profiles for normal discharge and non-discharge. During normal discharge, a peak Vp appears due to the maximum cooling rate after the feature point, while during non-discharge, the feature point does not appear, the cooling rate is low, and the peak appearing in the waveform during non-discharge is smaller than that during normal discharge.

[0091] The output signal Vinv of the inverting amplifier (INV) is input to the positive terminal of comparator 951 and compared with the threshold voltage Dth input to the negative terminal. If Vinv > Dth, the valid signal CMP is output.

[0092] The threshold voltage Dth can be set in 256 ranks, for example, in increments of 8mV from 0.5V to 2.54V. Within the 256 rank range, the set value Ddth of the threshold voltage Dth is defined as an 8-bit digital value and transferred to a shift register in synchronization with a clock signal (not shown). Then, at the timing determined by a latch signal (not shown), it is latched into a latch circuit and output to a voltage-output type digital-to-analog converter (DAC). The output signal of the latch circuit is held until the next latch timing, during which time the next set value Ddth is transferred to the shift register.

[0093] The peak voltage Vp of Vinv is detected using the comparator 951 according to the procedure described below. First, during the initial latch period, a constant current Iref0 (e.g., 1.6mA) corresponding to the reference setpoint Diref0 is applied to the temperature sensing element 905, and a drive pulse is applied to the heater 15. At this time, the reference setpoint Ddth0 corresponding to the reference threshold voltage Dth0 is input to the comparator 951 and compared with the peak of Vinv.

[0094] Once the judgment pulse CMP is output, the rank of Dth is increased by one during the next latch period, and a comparison with the peak of Vinv is performed in the same manner.

[0095] This process is repeated until the judgment pulse CMP is no longer output, and the peak voltage Vp is defined as the Dth of the last rank where the judgment pulse CMP was output. For example, if you want to detect the peak voltage Vp of normal discharge as shown in Figure 18(d), you can sequentially increase the Dth from Dth0 to Dth1, Dth2, etc., until the judgment pulse CMP is no longer output at Dth5, so Dth4, where the judgment pulse CMP was last output, will be Vp.

[0096] On the other hand, if no judgment pulse CMP is output during the initial latch period, the rank of Dth is lowered by one during the next latch period, and a comparison with the peak of Vinv is performed in the same manner.

[0097] This process is repeated until a judgment pulse CMP is output, and the peak voltage Vp is defined as the Dth of the rank at which the judgment pulse CMP is output. In the example of normal output in Figure 18(d), as Dth is lowered to 5 and then to 4, the judgment pulse CMP is output at Dth4, so Dth4 becomes Vp.

[0098] The structure of the thermal area in the recording element substrate according to this embodiment will be described below with reference to Figure 19. Figure 19(a) is a schematic, enlarged plan view showing the vicinity of the thermal area in the recording element substrate 10. Figure 19(b) is a cross-sectional view taken along the dashed line XIXb-XIXb in Figure 19(a). Although the substrate lamination configuration in this figure differs from the example described in Figure 17, any lamination configuration of the recording element substrate is applicable.

[0099] The recording element substrate of the liquid ejection head is formed by stacking multiple layers on a silicon substrate. In this embodiment, a heat storage layer formed of a thermal oxide film, SiO film, SiN film, etc. is placed on the substrate. A heat-generating resistor 126 is placed on the heat storage layer, and an electrode wiring layer (not shown) formed of a metallic material such as Al, Al-Si, or Al-Cu is connected to the heat-generating resistor 126 via a tungsten plug 128. As shown in Figure 19(b), an insulating protective layer 127 (first protective layer) is placed on the heat-generating resistor 126, and the insulating protective layer 127 is provided above the heat-generating resistor 126 to cover it and block contact with the liquid. The insulating protective layer 127 is an insulating layer formed of an SiO film, SiN film, etc.

[0100] A protective layer is provided on the insulating protective layer 127. This protective layer on the insulating protective layer 127 includes a lower protective layer 125, an upper protective layer 124 (second protective layer), and an adhesion protective layer 123. In this embodiment, the lower protective layer 125 and the upper protective layer 124 are provided on the heating resistor 126 to protect the surface of the heating resistor 126 from chemical and physical shocks caused by the heating of the heating resistor 126. Therefore, this protective layer covers at least the area directly above the heater 15 that is heated by the heater 15. This area is referred to as the thermal area.

[0101] In this embodiment, the lower protective layer 125 is made of tantalum (Ta), the upper protective layer 124 is made of iridium (Ir), and the adhesion protective layer 123 is made of tantalum (Ta). Furthermore, the protective layers formed from these materials are electrically conductive. On the adhesion protective layer 123, a protective layer 122 is placed to improve adhesion with the discharge port forming member 12 as a liquid-resistant layer. The protective layer 122 is made of SiC.

[0102] When liquid is discharged, the upper part of the upper protective layer 124 is in contact with the liquid, and the liquid temperature rises instantaneously at this upper part, causing foaming, defoaming, and cavitation to occur in a harsh environment. Therefore, in this embodiment, the upper protective layer 124, which is made of a highly corrosion-resistant and reliable iridium material, is formed at a position corresponding to the heat-generating resistor 126 and is in contact with the liquid.

[0103] The recording device 1000 according to this embodiment performs a burn suppression treatment during printing to suppress the accumulation of burnt material on the upper protective layer 124 on the heating resistor 126. More specifically, the upper protective layer 124 is used as one electrode 121 (first electrode), and a counter electrode 129 (second electrode) corresponding to electrode 121 is provided, forming an electric field in the liquid chamber through the liquid. This causes negatively charged particles such as pigments in the liquid to repel from the surface of the upper protective layer 124 on the heating resistor 126. In this way, the presence of negatively charged particles such as pigments near the surface of the upper protective layer 124 is reduced, thereby suppressing the accumulation of burnt material on the upper protective layer 124 on the heating resistor 126 during printing. This burn suppression takes into account that the phenomenon occurs when colorants, additives, etc. contained in the liquid are decomposed at the molecular level by high-temperature heating, changing into poorly soluble substances that are physically adsorbed onto the upper protective layer. When the upper protective layer 124 is heated to a high temperature, reducing the presence of colorants, additives, etc. that cause charring near the surface of the upper protective layer 124 on the heating resistor 126 helps to suppress charring.

[0104] For example, the potential difference between electrode 121 and counter electrode 129 is preferably about 0.2 to 2.5 V. This is because, when the upper protective layer 124 is made of iridium, if the potential difference between the two electrodes exceeds 2.5 V, an electrochemical reaction occurs between electrode 121 and the liquid, causing the surface of electrode 121 to dissolve into the liquid. Therefore, it is preferable to have a potential difference that does not cause electrode 121 to dissolve. In other words, at this time, an electric field is formed between electrode 121 of the upper protective layer and counter electrode 129 via the liquid, but no current is flowing. Since electrode 121 of the upper protective layer is at a negative potential relative to counter electrode 129, negatively charged particles are repelled from the surface of electrode 121 of the upper protective layer, and the abundance of particles near the surface of electrode 121 of the upper protective layer decreases.

[0105] In the following, the mode in which the above-described method for determining whether or not to discharge is used will be referred to as the non-discharge determination mode, and the mode during printing in which this method is not used will be referred to as the printing mode. Furthermore, potential control is performed to adjust the potential difference between the upper protective layer 124 and the counter electrode 129 through the liquid. In addition, in this embodiment, in the non-discharge determination mode, the potential control by forming an electric field through the liquid between the upper protective layer 124 and the counter electrode 129 is performed in a way that does not suppress charring, unlike in the printing mode. Alternatively, in the non-discharge determination mode, the potential difference between the electrode 121 and the counter electrode 129 is set so that the repulsion of particles in the liquid that cause charring from the electrode 121 is suppressed compared to the printing mode.

[0106] The graph in Figure 20(b) is an example of a graph showing the relationship between detection time and Vinv in printing mode as a comparative example. Vinv was acquired while changing 8 heaters approximately every 400 μs, for a total of 256 heaters. In this comparative example, the upper protective layer 124 was set to ground potential, and 1.9V was applied to the counter electrode 129. In printing mode, potential control is performed to suppress scorching, so foaming becomes relatively large, and the amount of ejected droplets that fall onto the heater 15 due to foam contraction becomes relatively small. Therefore, Vinv, which is the output value of the characteristic point where the temperature of the heater 15 drops sharply, is relatively low. If this output value is low, there is a risk that the ejection state cannot be determined with high accuracy.

[0107] In this comparative example, the distance between the heater surface and the nozzle surface was approximately 9.5 μm, and the ejection speed in printing mode was approximately 12 m / s. The detection rate tends to decrease when the distance between the heater surface and the nozzle surface is less than approximately 22 μm, but this tendency becomes more pronounced when the distance is less than approximately 12 μm. Furthermore, regarding the ejection speed, the detection rate tends to decrease when it is greater than approximately 10 m / s, but this tendency becomes more pronounced when the ejection speed is greater than approximately 12 m / s.

[0108] The graph in Figure 20(a) is an example of a graph showing the relationship between detection time and Vinv when switching from printing mode to non-discharge detection mode and performing potential control without suppressing charring. In this example, 1.8V was applied to the upper protective layer 124 and 1.9V to the counter electrode 129. Because charring is not suppressed (or the degree of suppression is reduced), foaming is relatively small, and a relatively large amount of the discharged droplet falls onto the heater 15 due to the contraction of the bubbles. As a result, Vinv, which is the output value of the characteristic point where the temperature of the heater 15 drops sharply, is relatively high.

[0109] As described above, it is possible to realize a recording device and a control method for the recording device that can perform the determination of the ejection state or the occurrence of ejection failure in each recording element with high accuracy and in a timely manner.

[0110] Although a cyclic configuration is employed in this embodiment, the technical concept related to this embodiment can also be applied to configurations other than cyclic configurations.

[0111] [Second Example] The graphs in Figures 21(a) and 21(b) show the relationship between the elapsed time after potential control switching and Vinv for multiple heaters. In both Figures 21(a) and 21(b), in printing mode, the potential of the upper protective layer 124 was set to ground potential, 1.9V was applied to the counter electrode 129, and then potential switching was performed by potential control.

[0112] Specifically, in Figure 21(a), the potential of the counter electrode 129 remained at 1.9V, while the potential of the upper protective layer 124 was switched to 0.9V. After 2ms following this switch, Vinv increased to a value sufficient for detection. In contrast, in Figure 21(b), the potential of the upper protective layer 124 remained at ground potential, while the potential of the counter electrode 129 was switched to 1.0V. In this case, it took approximately 500ms after the switch for Vinv to increase to a value sufficient for detection. In both Figure 21(a) and Figure 21(b), the potential difference between the upper protective layer and the counter electrode after the switch is 1.0V, but switching the potential on the upper protective layer side, which is closer to the burnt deposit, results in a higher response rate. Furthermore, if no switch is performed, it takes a very long time for Vinv to increase to a value sufficient for detection. Thus, while either the upper protective layer or the counter electrode can be used to switch the potential, it is preferable to switch the potential of the upper protective layer, which has a higher responsiveness.

[0113] Furthermore, as mentioned above, switching the potential of one electrode rather than switching the potential of both electrodes simplifies the device. However, depending on the overall design balance of the recording device, the installation environment of the recording device, the type of ink, etc., the optimal combination of the potentials of the upper protective layer and the counter electrode in printing mode and the potentials of the upper protective layer and the counter electrode in non-discharge detection mode may differ (Figure 22). In such cases, the potential of the upper protective layer and the potential of the counter electrode may be switched simultaneously, but if it is necessary to switch one of them first, it is preferable to switch the potential of the upper protective layer first.

[0114] <Example Conditions> The following examples of various conditions will be explained using Figure 22.

[0115] Example condition (1) shows a case where only the potential of the upper protective layer is changed between the printing mode and the non-discharge detection mode.

[0116] Example condition (2) shows a case where only the potential of the upper protective layer is changed between different modes, and the potential difference between the upper protective layer and the counter electrode in the non-discharge detection mode is larger than in Example condition (1). In both 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, if the potential difference between the upper protective layer and the counter electrode is sufficient to obtain the required detection rate, it is desirable to minimize the amount of potential change at each electrode.

[0117] Examples of conditions (3) to (6) are variations of example condition (2) that further reduce the amount of potential change between different modes. In cases where the detection rate improves as the potential difference between the upper protective layer and the counter electrode decreases, as mentioned above, a larger amount of potential change in the upper protective layer will increase the time required for the potential change, but the detection rate will also improve. Therefore, it is desirable to minimize the amount of potential change in the upper protective layer as much as possible, depending on the required detection rate.

[0118] Example condition (7) shows a case where the potential of the upper protective layer is fixed at ground potential, and the potential of the counter electrode is changed. If you want to fix the potential of the upper protective layer at ground potential, you can also achieve the appropriate effect by adjusting the amount of change in the potential of the counter electrode.

[0119] Example condition (8) shows a case where the amount of potential change of the counter electrode is larger compared to example condition (7). The detection rate gradually increases after the potential difference change between different modes. Compared to example condition (7), example condition (8) takes more time to change the potential between different modes, but because the potential difference between the upper protective layer and the counter electrode is larger, the time it takes to obtain the effect of improved detection rate after the potential change is shorter.

[0120] Example condition (9) shows a case where the potential of the upper protective layer and the potential of the counter electrode are switched simultaneously when transitioning between the printing mode and the non-discharge detection mode.

[0121] Example condition (10) shows a case where only the potential of the upper protective layer is changed between different modes.

[0122] Example condition (11) shows a case where the potential difference between the upper protective layer and the counter electrode increases when transitioning from printing mode to non-discharge detection mode. Regarding the optimal potential difference for conditions that do not suppress scorching, it is not always the case that a smaller potential difference is better; in some conditions, a larger potential difference may be preferable.

[0123] [Other embodiments] The present invention can also be realized by supplying a program that implements one or more of the functions of the above embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions. The contents of the first to sixth embodiments may be used in combination as appropriate. [Explanation of Symbols]

[0124] 3. Liquid dispensing head 11 electrodes 13 Outlet 15 Heater 127 Insulating protective layer 129 Counter electrode 905 Temperature sensing element 1000 recording devices

Claims

1. a liquid ejection head having a heat generating element that generates thermal energy required for ejecting a liquid, a first protective layer that blocks contact between the heat generating element and the liquid, a second protective layer that covers at least a portion of the first protective layer that is heated by the heat generating element and functions as a first electrode, a second electrode that is electrically connected to the first electrode via the liquid, an ejection port that ejects the liquid, and a temperature detection element that corresponds to the heat generating element; a detection means for detecting a characteristic point in a temperature curve indicating the relationship between time and temperature, the temperature curve being acquired by the temperature detection element; A recording device having: a combination of a potential set for the first electrode and a potential set for the second electrode is different between when printing and when detecting the feature point by the detection means; A recording device characterized by:

2. The liquid ejection device further includes a determination unit that determines whether the liquid is being ejected normally from the ejection port based on whether the characteristic point is detected in the temperature curve by the detection unit.

2. The recording apparatus according to claim 1, wherein the recording apparatus is a recording medium.

3. the detecting means detects the characteristic points by performing a differential operation on the temperature curve.

3. The recording apparatus according to claim 1, wherein the recording medium is a recording medium.

4. 4. The recording apparatus according to claim 1, wherein the recording apparatus operates in a print mode when printing, and operates in a discharge failure determination mode when detecting the characteristic points.

5. when switching between the printing mode and the non-ejection determination mode, if the potential of the first electrode and the potential of the second electrode are switched, the potential of the first electrode is changed before the potential of the second electrode is changed.

5. The recording apparatus according to claim 4.

6. 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.

5. The recording apparatus according to claim 4.

7. a potential difference between the potential set for the first electrode and the potential set for the second electrode in the printing mode is greater than that in the non-ejection determination mode; 7. The recording apparatus according to claim 4, wherein the recording apparatus is a recording medium.

8. the liquid ejection head further includes a pressure chamber; a supply flow path that supplies the liquid to the pressure chamber and a recovery flow path that recovers the liquid from the pressure chamber are connected to the pressure chamber; the liquid flows and circulates through the supply flow path, the pressure chamber, and the recovery flow path in this order; 8. The recording apparatus according to claim 1, wherein the recording apparatus is a recording medium.

9. the heating element and the temperature detection element are provided at different positions in the direction in which the liquid is ejected, The temperature sensing element has a serpentine shape.

9. The recording apparatus according to claim 1, wherein the recording apparatus is a recording medium.

10. A control method for a recording device equipped with a liquid ejection head having a heat generating element that generates thermal energy required to eject a liquid, a first protective layer that blocks contact between the heat generating element and the liquid, a second protective layer that covers at least a portion of the first protective layer that is heated by the heat generating element and functions as a first electrode, a second electrode that is electrically connected to the first electrode via the liquid, an ejection port that ejects the liquid, and a temperature detection element corresponding to the heat generating element, detecting a characteristic point in a temperature curve indicating a relationship between time and temperature, the temperature curve being acquired by the temperature detection element; a combination of a potential set for the first electrode and a potential set for the second electrode is different between when printing and when detecting the feature point; A control method comprising:

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