Recording element substrate and recording head

Abstract

To improve sensitivity when detecting temperature changes in ink using a temperature sensor in an ink jet recording type recording apparatus.SOLUTION: There is provided a recording element substrate in which a liquid chamber is formed between a substrate and a flow path forming member, and a discharge port for discharging liquid in the liquid chamber is provided. The substrate includes at least a first layer and a second layer that is located farther from the liquid chamber than the first layer. The first layer is provided with a first heater that heats and discharges the liquid when a drive pulse is applied, and a temperature sensor that is disposed such that at least a portion thereof overlaps with the liquid chamber in a plan view. The second layer is provided with a second heater that is disposed such that at least a portion thereof overlaps with the temperature sensor in a plan view.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a recording element substrate and a recording head. [Background technology]

[0002] There are recording devices that use the inkjet recording method, which ejects ink from a nozzle and deposits it on a recording medium such as paper. Among these, a method in which ink is ejected from a nozzle using thermal energy generated by a heater is called a thermal inkjet recording method. In an inkjet recording device that uses this method, a structure has been proposed in which a conductive plug is provided at the terminal of a temperature sensor made of a thin-film resistor located directly under the heater, and the terminal is connected to the underlying wiring layer (Patent Publication No. 7112287).

[0003] In the inkjet recording device described in Patent Document 1, when detecting the temperature signal output from the temperature sensor, a constant current is applied to the temperature sensor through the underlying wiring layer and conductive plug, while the potential difference between both terminals of the temperature sensor is monitored. By adopting such a structure, it is no longer necessary to provide a wiring layer directly above the temperature sensor, so the temperature sensor can be moved closer to the heater by the thickness of the wiring layer, making the interlayer insulating film between the heater and the temperature sensor thinner. This reduces the thermal resistance between the heater and the temperature sensor, improving the sensitivity of the temperature sensor.

[0004] However, in Patent Document 1, the temperature sensor is located directly under the heater to begin with. Therefore, even if the temperature sensor is placed close to the heater, it must capture the temperature change caused by the ink via the interlayer insulating film directly above and the heater, which limits the improvement of sensitivity.

[0005] To address this issue, a method has been proposed in which the heater itself is used as a temperature sensor (JP Patent Publication No. 2018-535848). However, with this method, it was only possible to detect changes in the ink temperature while the heater was energized. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7112287 [Patent Document 2] Special Publication No. 2018-535848 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, in a printing apparatus using a thermal ink jet printing method in which ink is heated by a heater, it is required to further improve the sensitivity of the temperature sensor to changes in ink temperature.

[0008] The present invention has been made in view of the above problems, and has an object to improve the sensitivity when detecting a temperature change of ink by a temperature sensor in a printing apparatus using an ink jet printing method. [Means for solving the problem]

[0009] The present invention employs the following configuration. A recording element substrate including a substrate and a flow path forming member, a liquid chamber for accommodating a liquid is formed between the substrate and the flow path forming member; The flow passage forming member is provided with a discharge port through which the liquid contained in the liquid chamber is discharged. And, the substrate includes at least a first layer and a second layer that is farther from a surface in which the liquid chamber is formed than the first layer; the first layer is provided with a first heater that generates heat by application of a drive pulse to heat the liquid and eject it from the ejection port, and a temperature sensor that is disposed so that at least a portion of the temperature sensor overlaps with the liquid chamber in a plan view; The second layer is provided with a second heater arranged so that at least a portion of the second heater overlaps with the temperature sensor in a plan view. The recording element substrate is characterized in that Effect of the Invention

[0010] According to the present invention, in a printing apparatus using an ink jet printing method, it is possible to improve the sensitivity when detecting a change in ink temperature using a temperature sensor. [Brief description of the drawings]

[0011] [Figure 1] Plan view of one of the nozzles viewed from the substrate side in the direction of ink ejection. [Figure 2A] Cross section of the nozzle shown in Figure 1 along line AA [Figure 2B] Cross section of the nozzle in Figure 1 [Diagram 3] Block diagram of the heater driver and temperature sensor output processing circuit [Figure 4] Timing chart showing control in the logic circuit section [Figure 5A] Schematic cross-sectional view of a nozzle showing the tail of ejected ink during normal ejection [Figure 5B] Schematic cross-section of a nozzle showing the tailing of ejected ink when ejecting in a skewed manner [Figure 6A] 1 is a timing chart showing the output waveforms of the determination circuit during normal discharge. [Figure 6B] A timing chart showing the output waveforms of the determination circuit when the discharge is in a skewed state. [Figure 7] Block diagram of a heater drive circuit and a temperature sensor output processing circuit according to the second embodiment [Figure 8] 1 is a timing chart showing control in a logic circuit section according to a second embodiment of the present invention; [Figure 9] FIG. 11 is a plan view of one of the nozzles of the third embodiment, viewed from the substrate side in the ink ejection direction. [Figure 10] Section AA of the nozzle in Figure 9 [Figure 11] FIG. 11 is a plan view of one of the nozzles of the fourth embodiment, viewed from the substrate side in the ink ejection direction. [Figure 12A] Section AA of the nozzle in Figure 11 [Figure 12B] Cross section of the nozzle in Figure 11 [Figure 13]Block diagram of a heater drive circuit and a temperature sensor output processing circuit according to the fourth embodiment [Figure 14] Block diagram showing the control configuration of the ejection deviation inspection device DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A preferred embodiment of the present invention will be described in detail below with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described in the embodiment are not intended to limit the scope of the present invention to those alone. Furthermore, the materials, shapes, etc. of the members once described in the following description are the same as those described initially, unless otherwise specified. Well-known or publicly known technologies in the relevant technical field can be applied to configurations and processes not particularly shown or described. Furthermore, duplicated descriptions may be omitted.

[0013] [Example 1] (Inspection equipment configuration) FIG. 14 is a block diagram showing a control configuration of a deviation in ejection inspection device 2 for inspecting deviation in ejection of ink, in which ink liquid lands in a direction deviated from the axis of the nozzle.

[0014] Upon receiving an instruction from the control unit 4, the signal generating unit 3 outputs a clock signal (CLK), a latch signal (LT), a block signal (BLE), a heater selection signal (DATA ), a heat enable signal (HE), and a sub-heat enable signal (SHE). The voltage VH applied to the selected heater is supplied to the recording element substrate 1 from a constant voltage source 302. The signal generating unit 3 further outputs a sensor selection signal (SDATA), a constant current signal (Diref), a threshold signal 1 (Dth1), and a threshold signal 2 (Dth2) related to the selection of the two temperature sensors provided for each nozzle, the amount of current, and the processing of the output signal.

[0015] The constant current generating circuit provided on the recording element substrate 1 is supplied with power by a constant voltage source 303 .

[0016] On the other hand, the judgment result extraction unit 5 receives a judgment result signal (RSLT) output from the recording element substrate 1 based on temperature information detected by the temperature sensor, and extracts the judgment result for each latch period in synchronization with the falling edge of the latch signal LT. Then, when the judgment result is a deviation in ejection, the block signal BLE and the sensor selection signal SDATA corresponding to the judgment result are recorded in the memory 6.

[0017] The control unit 4 receives the block signal BLE and the sensor selection signal SDATA of the twisted ejection nozzle recorded in the memory 6, and if the heater to be driven includes a twisted ejection nozzle, it deletes the twisted ejection nozzle from the heater selection signal DATA of the corresponding block. Then, it adds a nozzle for compensating for twist to the heater selection signal DATA of the corresponding block instead, and outputs it to the signal generation unit 3.

[0018] (Printing element board and nozzle) Fig. 1 is a plan view of one nozzle 100 of the multiple nozzles provided on a recording element substrate 1 in this embodiment, as viewed from the substrate side in the ink ejection direction. Fig. 2 is a cross-sectional view of the nozzle in Fig. 1, with Fig. 2A showing a cross-sectional view taken along line AA, and Fig. 2B showing a cross-sectional view taken along line BB. Below, the structure around the nozzle in this embodiment will be described with reference to Fig. 1, Fig. 2A, and Fig. 2B.

[0019] An ink flow path 118 is formed for each nozzle on the recording element substrate 1, and each ink flow path 118 is separated by a flow path partition wall 202. An ink supply port 119 and an ink discharge port 120 are formed in the recording element substrate 1 in a direction perpendicular to the bottom surface of the ink flow path 118. An orifice plate 203 is provided on the upper surface of the flow path partition wall 202. In the orifice plate 203, one ejection port 117 is formed for each nozzle.

[0020] The space partitioned by the recording element substrate 1, the orifice plate 203, and the flow path partition wall 202 is formed as a liquid chamber in which liquid (ink) is contained. The orifice plate 203 and the flow path partition wall 202 function as flow path forming members that form the flow paths and liquid chambers together with the recording element substrate 1. The recording head of the recording device is constituted by a substrate including the multiple liquid chambers formed by the recording element substrate 1 and the orifice plate 203. The liquid contained in each of the multiple liquid chambers bubbles due to heat generated when a voltage is applied to the heaters 101 arranged corresponding to each liquid chamber, and is discharged from the discharge port 117. For this reason, the liquid chambers are also referred to as bubble chambers.

[0021] A rectangular heater 101 made of a thin film resistor made of a material having high resistivity and thermal stability, such as TaSiN, is provided in the recording element substrate 1 immediately below the ejection ports 117 .

[0022] Furthermore, in the same layer as the heater 101, a pair of temperature sensors 104, 107 are provided adjacent to the center of the long side of the heater 101 in a plan view so as to be approximately symmetrical with respect to the heater 101. In order to increase the sensitivity of the temperature sensors 104, 107, it is desirable to use a material that has a high temperature coefficient of resistance in addition to a high specific resistance. Here, when the pair of temperature sensors are arranged approximately symmetrically, the shape and arrangement do not have to be strictly line symmetric or point symmetric, but it is necessary that they are arranged at least on opposite sides across the heater 101.

[0023] By arranging them as described above, the two temperature sensors 104, 107 can be located closest to the heater 101. However, to prevent short circuits, the temperature sensors 104, 107 cannot be brought closer than a certain distance to the heater 101, and the heater 101 alone cannot sufficiently heat the temperature sensors.

[0024] Therefore, two auxiliary heaters 110, 113 for heating the temperature sensors 104, 107 are provided below the temperature sensors 104, 107 via the insulating member 204. That is, the auxiliary heater 110 is provided for heating the temperature sensor 104, and the auxiliary heater 113 is provided for heating the temperature sensor 107.

[0025] Conventionally, in order to keep the ink warm inside the recording element substrate 1, a sub-heater (not shown) may be provided across multiple nozzles between the ink supply port 119 and the ejection port 117 in a plan view. Unlike this sub-heater, the auxiliary heaters 110 and 113 are provided to increase the sensitivity of the temperature sensors 104 and 107 by generating heat in a short period of time on the order of 0.1 μs.

[0026] A protective film 201 made of an insulator such as SiN is formed on the heater 101 and the temperature sensors 104 and 107. An anti-cavitation film 116 made of, for example, Ta is further formed thereon so as to cover the heater 101 and the temperature sensors 104 and 107 in the plan view of Fig. 1. As a result, the heater 101 and the temperature sensors 104 and 107 are arranged on the same layer (first layer) so as not to overlap each other in plan view.

[0027] 1 and 2A, the temperature sensors 104, 107 are provided at positions overlapping the ink flow path 118 via the protective film 201 and the cavitation-resistant film 116. Furthermore, the auxiliary heaters 110, 113 are provided so as to cover the spaces between the conductive plugs 105, 106, 108, 109 at both ends of the temperature sensor. In FIG. 1, the outlines of the temperature sensors 104, 107 overlapping with the auxiliary heaters 110, 113 are shown by dashed lines. As a result, the layer including the auxiliary heaters 110, 113 (second layer) is disposed away from the surface of the recording element substrate 1 that is closer to the liquid chamber than the first layer.

[0028] The recording element substrate 1 is configured by providing a plurality of wiring layers on an insulating member 204 on a substrate 213. The insulating member 204 is configured by laminating a plurality of interlayer insulating films, and each of the wiring layers is provided between the interlayer insulating films. The substrate 213 is made of a semiconductor material such as silicon, and the insulating member 204 is made of an insulating material such as silicon oxide.

[0029] The heater 101 and the temperature sensors 104 and 107 are electrically connected via the wiring patterns and conductive plugs provided in the multiple wiring layers to form a circuit capable of realizing a recording function. In this embodiment, a total of two wiring layers are provided: a first layer closest to the substrate 213 and a second layer above it.

[0030] One end of the heater 101 on the short side is connected to a wiring pattern 214 of the second layer via a conductive plug 102, and the other end is connected to a pad 215 of the second layer via a conductive plug 103, and is further connected to a wiring pattern 217 of the first layer via a conductive plug 216. The wiring pattern 214 is connected to a constant voltage source, and the wiring pattern 217 is grounded via a switch element 319 (see FIG. 3) described below.

[0031] As shown in FIG. 2B, the temperature sensor 104 is connected to a pad 218 on the second layer via a conductive plug 105 provided at one end thereof, and is further connected to a wiring pattern 220 on the first layer via a conductive plug 219. The other end is connected to a pad 205 on the second layer via a conductive plug 106. , and further connected to a first layer wiring pattern 207 via a conductive plug 206 .

[0032] The wiring pattern 220 is connected to a constant current source 309 via a switch element 327 (see FIG. 3) described later, and the wiring pattern 207 is grounded. The temperature sensor 107 is similarly connected to a predetermined wiring pattern.

[0033] As shown in FIG. 2B, the auxiliary heater 110 is connected at one end to a second layer wiring pattern 221 via a conductive plug 111, and at the other end to a second layer pad 222 via a conductive plug 112, and is further connected to a first layer wiring pattern 224 via a conductive plug.

[0034] The wiring pattern 221 is connected to the same constant voltage source to which the wiring pattern 214 is connected, and the wiring pattern 223 is grounded via a switch element 319 (see FIG. 3) described below. The auxiliary heater 113 is also connected to a predetermined wiring pattern in a similar manner.

[0035] 1, the thick solid lines drawn from the conductive plugs connected to heater 101 and auxiliary heaters 110 and 113 are a schematic plan view of the wiring to each wiring layer described above. In the figure, terminal 121 represents the connection point between wiring patterns 214 and 221 and the constant voltage source. Meanwhile, terminal 122 represents the connection point between wiring pattern 217 and switch element 319 (see FIG. 3). Also, terminal 123 represents the connection point between wiring pattern 224 and switch element 319 (see FIG. 3).

[0036] Further, below the heater 101, a heat dissipation pattern 209 is disposed on the second layer. The heat dissipation pattern 209 is connected to a heat dissipation pattern 211 on the first layer via a plug 210. The heat dissipation pattern 211 is connected to a substrate 213 via a plug 212. With this configuration, when the heater 101 is driven to generate heat and then the driving is suppressed, the heat is quickly dissipated to the substrate 213.

[0037] (Circuit block configuration) 3 is a block diagram of a heater drive circuit and a processing circuit for an output signal of a temperature sensor mounted on the recording element substrate 1 in this embodiment. For ease of explanation, the recording element substrate 1 is assumed to have four heaters 101a to 101d and eight temperature sensors 104a to 104d, 107a to 107d in each nozzle row 301, and is arranged in the order shown in FIG.

[0038] The recording element substrate 1 includes a constant current source 304 for supplying power to the temperature sensors 104a to 104d and 107a to 107d, and an input / output section (pad or terminal) for inputting / outputting signals and information to / from the outside.

[0039] A constant voltage source 302 for driving the heaters 101a-d and the auxiliary heaters 322a-d is connected between the VH pad and the GNDH pad. A constant voltage source 303 for supplying power to a constant current source 304 is connected between the VHTA pad and the VSS pad, and a VHTA of, for example, 5V is applied to the high voltage side of the constant current source 304, and the low voltage side is grounded to VSS as GND.

[0040] The constant current source 304 is composed of two systems of constant current sources 309 and 310, and the current Iref is mirrored to the constant current sources 309 and 310 at the same amplification factor by a mirroring circuit 308 using the same current-type DAC 307 as a reference current source.

[0041] The driving circuit 316a supplies a constant voltage source 30 to the heater 101a and the auxiliary heater 322a. 2. The auxiliary heater 322a is constituted as a circuit for controlling the application of the voltage VH of the auxiliary heater 322a. Here, the auxiliary heater 322a is represented as one auxiliary heater in which the auxiliary heaters 110 and 113 are electrically connected in parallel.

[0042] When the outputs of the gate circuits 317a and 318a both become High and the switch element 319a turns on, a VH of, for example, 24 V is applied to the high voltage side of the heater 101a, and the source terminal of the switch element 319a is grounded to GNDH. The voltage application to the auxiliary heater 322a is also controlled by a similar switching operation. The other three heaters 101b to 101d and the three auxiliary heaters 322b to 322d are also controlled by similar switch elements.

[0043] The temperature sensors 104a and 107a, together with the switch elements 327a to 330a, constitute one temperature acquisition circuit 326a. The switch element 327a controls the supply of current from the constant current source 309 to the temperature sensor 104a. Furthermore, the switch element 328a controls the output of the voltage generated in the temperature sensor 104a to the voltage follower 331. Similarly, the switch element 329a controls the supply of current from the constant current source 310 to the temperature sensor 107a. Furthermore, the switch element 330a controls the output of the voltage generated in the temperature sensor 107a to the voltage follower 332.

[0044] The switch elements 327a to 330a are simultaneously turned on, and at this time the temperature sensors 104a and 107a output temperature signals for inspecting the state of distortion of ink droplets ejected from the nozzle corresponding to the heater 101a to the voltage followers 331 and 332. The other six temperature sensors 104b to 104d and 107b to 107d are also controlled by similar switch elements.

[0045] 3 includes four drive circuits 316a-316d and four temperature acquisition circuits 326a-326d. The four drive circuits 316a-316d and the four temperature acquisition circuits 326a-326d are divided into two groups, G1 and G2. Each group is made up of two drive circuits and two temperature acquisition circuits.

[0046] (Control Timing) 4 is a timing chart showing the timing of control in the logic circuit section of the recording element substrate 1. Hereinafter, the operation of the logic circuit section of the recording element substrate 1 of this embodiment will be described with reference to FIGS.

[0047] The recording element substrate 1 receives a clock signal (CLK), a latch signal (LT), a block signal (BLE), and a heater selection signal (DATA), which is 2-bit serial data, a heat enable signal (HE), and a sub-heat enable signal (SHE), all of which are transferred from the misaligned ejection inspection device 2. Note that the block signal (BLE) is usually multi-bit serial data, but in this embodiment it is 1-bit data.

[0048] The recording element substrate 1 also receives a sensor selection signal (SDATA) which is 2-bit serial data. All signals except the clock signal (CLK) are received at intervals of a block period tb. That is, the four drive circuits 316a-316d and the four temperature acquisition circuits 323a-323d are controlled in a time-division manner over two block periods, and this is repeated twice to complete acquisition of the temperature signals from the eight temperature sensors 104b-104d, 107b-107d.

[0049] The block signals BL1 to BL4 are transferred to the shift register 311 in synchronization with a clock signal (CLK), latched by the latch circuit 312 at timings t0 to t3, respectively, decoded by the decoder 313, and output to the wires B1 and B2. In this embodiment, the shift register 311 is a 1-bit register. The signals on the wires B1 and B2 are held for a period of tb until the next latch timing, during which time the next block signal is transferred to the shift register 311. will be transferred.

[0050] The signals on the wires B1 and B2 are used to select the heaters to be driven simultaneously, with only one of the two signals being valid. In FIG. 3, the wire B1 is connected to the gate circuits 317a and 317c. Therefore, when the signal on the wire B1 is valid (high active), the heaters 101a and 101c can be driven simultaneously. Similarly, when the signal on the wire B2 is valid, the heaters 101b and 101d can be driven simultaneously.

[0051] As shown in FIG. 4, this embodiment deals with a case where driving is performed in a time-division manner such that B1 is effective between t0 and t1 and between t2 and t3, and B2 is effective between t1 and t2 and between t3 and t4.

[0052] The heater selection signals DT1 to DT4 are transferred to the shift registers 314a and 314b in synchronization with a clock signal (CLK), latched by the latch circuits 315a and 315b at timings t0 to t3, respectively, and output to the wires D1 and D2. The signals on the wires D1 and D2 are held for a period tb until the next latch timing, during which time the next heater selection signal is transferred to the shift registers 314a and 314b.

[0053] The signals on the wires D1 and D2 are used to select the heater groups G1 and G2. In Fig. 3, the wire D1 is connected to the gate circuits 317a and 317b. Therefore, when the signal on the wire D1 becomes valid (high active), the heaters 101a and 101b and the auxiliary heaters 322a and 322b of the group G1 can be selected. Similarly, when the signal on the wire D2 becomes valid, the heaters 101c and 101d and the auxiliary heaters 322c and 322d of the group G2 can be selected.

[0054] In this embodiment, the heaters and auxiliary heaters of group G1 are selected in the first two block periods, and the heaters and auxiliary heaters of group G2 are selected in the last two block periods. In other words, the driving of all four heaters and auxiliary heaters is completed in four block periods.

[0055] The signal on the wiring B1 is input to the gate circuit 317a together with the signal on the wiring D1. The output signal of the gate circuit 317a is further input to the gate circuits 318a and 320a together with a heat enable signal (HE) or a sub-heat enable signal (SHE). The gate circuits 318a and 320a output pulse signals 401 and 405 to the wirings H1 and H5, respectively. The wirings H1 and H5 are connected to the switch elements 319a and 321a, respectively, and the heater 101a and the auxiliary heater 322a are driven by the pulse signals 401 and 405, respectively.

[0056] Similarly, pulse signals 402, 403, and 404 are output to wirings H2, H3, and H4 by gate circuits 318b, 318c, and 318d, respectively. Also, pulse signals 406, 407, and 408 are output to wirings H6, H7, and H8 by gate circuits 320b, 320c, and 320d, respectively.

[0057] Wires H2, H3, and H4 are connected to switch elements 319b, 319c, and 319d, respectively, and heaters 101b, 101c, and 101d are driven by pulse signals 402, 403, and 404. Wires H6, H7, and H8 are connected to switch elements 321b, 321c, and 321d, respectively, and auxiliary heaters 322b, 322c, and 322d are driven by pulse signals 406, 407, and 408, respectively.

[0058] The sensor selection signals SDT1 to SDT4 are shifted in sync with the clock signal (CLK). The signals are transferred to the shift registers 323a and 323b, latched by the latch circuits 324a and 324b at timings t0 to t3, and output to the wirings SD1 and SD2. The signals on the wirings SD1 and SD2 are held for a period of time tb until the next latch timing, during which time the next sensor selection signal is transferred to the shift registers 323a and 323b.

[0059] The signals on the wires SD1 and SD2 are used to select one of the groups G1 and G2 that includes the temperature sensors corresponding to the heater to be driven and the auxiliary heater. In FIG. 3, the wire SD1 is connected to the gate circuits 325a and 325b. Therefore, when the signal on the wire SD1 becomes valid (high active), the temperature sensors 104a, 104b, 107a, and 107b of the group G1 can be selected as the temperature sensors corresponding to the heater to be driven and the auxiliary heater. Similarly, when the signal on the wire SD2 becomes valid, the temperature sensors 104c, 104d, 107c, and 107d of G2 can be selected as the temperature sensors corresponding to the heater to be driven and the auxiliary heater.

[0060] 4, in this embodiment, the signal on the line SD1 is enabled in the first and second block periods out of the four block periods to select the temperature sensor in group G1, and the signal on the line SD2 is enabled in the third and fourth block periods to select the temperature sensor in group G2.

[0061] The signals on the wirings B1 and B2 are used as block signals for selecting the temperature sensor. That is, the signals on the wirings B1 and B2 are input to the gate circuits 325a and 325b together with the signal on the wiring SD1. Similarly, the signals on the wirings B1 and B2 are input to the gate circuits 325c and 325d together with the signal on the wiring SD2.

[0062] The set value Diref of the constant current Iref is determined as a 5-bit digital value that can be set in 32 steps, and is transferred to a shift register 305 in synchronization with a clock signal CLK. Then, it is latched by a latch circuit 306 in synchronization with a latch signal LT, and is output to a current output type digital-to-analog converter (DAC) 307.

[0063] That is, the DAC 307 outputs an output current Irefin based on the set value Diref. The output signal of the latch circuit 306 is held until the next latch timing, during which the next set value Diref is transferred to the shift register 305. The output current Irefin of the DAC 307 is mirrored to the constant current sources 309 and 310, amplified by, for example, 12 times, and output as the constant current Iref.

[0064] As a result, in the first block period, the gate circuit 325a outputs a pulse signal 409 that is valid between t0 and t1 to the wiring S1. The wiring S1 is connected to the switch elements 327a and 328a, and the pulse signal 409 supplies a constant current Iref from the constant current source 309 to the temperature sensor 104a between t0 and t1.

[0065] The resistance Rs1 of the temperature sensor 104a at temperature T1 is expressed by the following equation (1), where T0 is the room temperature, Rs0 is the resistance at that time, and TCR is the temperature coefficient of resistance of the temperature sensor 104a.

number

[0066] A temperature signal Vs1 generated at the constant current supply side terminal of the temperature sensor 104a is expressed by the following equation (2).

number

[0067] The temperature signal Vs1 expressed by the above equation (2) is output to the voltage follower 331 through the line V1.

[0068] The wiring S1 is also connected to switch elements 329a and 330a, and a pulse signal 409 causes a constant current Iref to be supplied from a constant current source 310 to the temperature sensor 107a during the period from t0 to t1.

[0069] The resistance Rs2 of the temperature sensor 107a at the temperature T2 is expressed by the following equation (3).

number

[0070] A temperature signal Vs2 generated at the constant current supply side terminal of the temperature sensor 107a is expressed by the following equation (4).

number

[0071] The temperature signal Vs2 expressed by the above equation (4) is output to the voltage follower 332 through the line V2.

[0072] In this embodiment, the temperature sensors 104a and 107a are configured to have the same room temperature resistance Rs0, but the room temperature resistances may be different. In this case, the constant current values ​​supplied to the temperature sensors 104a and 107a are adjusted by the constant current sources 309 and 310 so that the temperature signals Vs1 and Vs2 at room temperature T0 are equal.

[0073] In the second block period, similarly to the first block period, from t1 to t2, temperature signals Vs1 and Vs2 generated at the constant current supply side terminals of temperature sensors 104b and 107b are output to voltage followers 331 and 332 through wirings V1 and V2, respectively.

[0074] In the third block period, similarly to the first and second block periods, from t2 to t3, temperature signals Vs1 and Vs2 generated at the constant current supply side terminals of temperature sensors 104c and 107c are output to voltage followers 331 and 332 through wirings V1 and V2, respectively.

[0075] In the fourth block period, similarly to the first to third block periods, from t3 to t4, temperature signals Vs1 and Vs2 generated at the constant current supply side terminals of temperature sensors 104d and 107d are output to voltage followers 331 and 332 through wirings V1 and V2, respectively.

[0076] If the temperature signals Vs1, Vs2 are directly input to the differential amplifier 333, the resistance of the switch element affects the input impedance of the differential amplifier 333, causing a voltage drop in the temperature signals Vs1, Vs2 before they are input to the differential amplifier 330. For this reason, the temperature signals Vs1, Vs2 are first received by voltage followers 331, 332 provided in the nozzle row 301 and then input to the differential amplifier 333.

[0077] In each of the first to fourth block periods, the differential amplifier 333 amplifies the signal obtained by subtracting the temperature signal Vs1 expressed by equation (2) from the temperature signal Vs2 expressed by equation (4) with the amplification factor Gdif of the differential amplifier, and outputs a signal Vdif expressed by the following equation (5) offset by a voltage Vofs.

number

[0078] This differential amplifier 333 cancels out two types of noise. One is noise that is superimposed on the temperature signals Vs1 and Vs2 in proportion to the constant current Iref shown in equations (2) and (4) due to current fluctuations in the reference current source 307. The other is crosstalk noise caused by voltage fluctuations in wiring that intersects with the wirings V1 and V2 via parasitic capacitance. Any other noise remaining in the signal Vdif is suppressed by the low-pass filter 334 and output as the signal VF.

[0079] The signal VF is compared with threshold voltages Vdth1 and Vdth2 based on two threshold signals Dth1 and Dth2 to determine whether the ejection is distorted. That is, the signal VF is input to the positive terminal of the comparator 338, and compared with the threshold voltage Vdth1 input to the negative terminal. Then, if VF>Vdth1, a signal that is high level (distorted ejection) and if VF≦Vdth1, a signal that is low level (normal ejection) is output to the wiring CMP1.

[0080] On the other hand, the signal VF is input to the negative terminal of the comparator 342, and compared with the threshold voltage Vdth2 input to the positive terminal. If Vdth2>VF, a signal that is high level (distorted discharge) is output to the wiring CMP2, and if Vdth2≦VF, a signal that is low level (normal discharge) is output.

[0081] The threshold voltages Vdth1, Vdth2 can be set in 256 ranks from 0.5V to 2.54V in increments of 8mV, for example. The set values ​​Dth1, Dth2 of the threshold voltages Vdth1, Vdth2 are determined as 8-bit digital values ​​that can be set in 256 ranks, for example, and are transferred from the signal generating unit 3 to shift registers 335, 339, respectively, in synchronization with a clock signal CLK. The threshold signal Dth1 is latched in a latch circuit 336 in synchronization with a latch signal LT, and is output to a voltage output type DAC 337.

[0082] The output signal of the latch circuit 336 is held until the next latch timing, during which the next threshold signal Dth1 is transferred to the shift register 335. Similarly, the threshold signal Dth2 is latched by the latch circuit 340 in synchronization with the latch signal LT, and is output to a voltage output type DAC 341. The output signal of the latch circuit 340 is held until the next latch timing, during which the next threshold signal Dth2 is transferred to the shift register 339.

[0083] The signals CMP1 and CMP2 are input to an OR gate circuit 343 and output to a wiring CMP. By inputting the signal CMP to a set input terminal of an RS latch circuit 344, the pulse signal of the signal CMP is held at a high level and output to a wiring HCMP. By latching this signal HCMP in a flip-flop circuit 345 using the latch signal LT as a trigger, a determination result signal RSLT that becomes a high level in the next latch period when a twisted ejection occurs is obtained. The signal HCMP is reset at the falling edge of the latch signal LT by inputting an inverted signal of the latch signal LT to a reset input terminal of the RS latch circuit 344.

[0084] The decision result signal RSLT is extracted by the decision result extractor 5 shown in FIG. 14 in synchronization with the falling edge of the latch signal LT, together with the block signal BLE and the sensor selection signal SDATA delayed by the latch period.

[0085] In this embodiment, the determination circuit section from the differential amplifier 333 to the flip-flop circuit 345 is configured to be provided inside the recording element substrate 1 outside the nozzle row 301, but it may be provided in a control chip provided in the recording head outside the recording element substrate 1. Also, the determination circuit section may be provided in a control chip provided in the recording device outside the recording head.

[0086] (Nozzle cross section and output waveform during discharge) FIG. 5 is a schematic cross-sectional view of a nozzle showing a state when an ink droplet 501 is ejected from an ejection port 117 and a tail 502 falls onto an anti-cavitation film 116, FIG. 5A showing normal ejection and FIG. 5B showing distorted ejection.

[0087] Fig. 6 is a timing chart showing the output waveforms of the determination circuit of the recording element substrate 1 during the first block period shown in Fig. 4, with Fig. 6A showing normal ejection and Fig. 6B showing misaligned ejection. The other block periods have similar timing charts, so they are omitted in this embodiment.

[0088] Hereinafter, the difference in operation of the determination circuit unit during normal ejection and during deviation ejection during the first block period of this embodiment will be described with reference to FIG. 5 and FIG.

[0089] 5A is a schematic cross-sectional view of the nozzle during normal ejection, in which an ink droplet 501 is ejected perpendicular to the surface of the orifice plate 203. The negative pressure inside the foamed air bubble 141 acts symmetrically on the tail 502, and the air communication of the air bubble 141 due to the bursting of the meniscus also occurs simultaneously around the entire circumference of the ejection port 117, causing the tail 502 to crash into the center of the heater 101 in a plan view.

[0090] Therefore, the fallen tail 502 spreads symmetrically with respect to the heater 101 in a plan view, and the temperature sensors 104 and 107 arranged symmetrically with respect to the heater 101 are uniformly cooled by the tail 502. Therefore, as shown in FIG. 6A, the output signals Vs1 and Vs2 of the temperature sensors 104 and 107 appear to overlap as waveforms 601.

[0091] The waveform 601 rises gradually from the initial voltage Vini due to heating from the heater 101 to which the drive pulse 401 is applied. Then, the waveform 601 rises suddenly due to heating from directly below the temperature sensor by the auxiliary heaters 110 and 113 to which the drive pulse 405 is applied, and the temperature starts to drop rapidly from the characteristic point 602 due to cooling caused by the fall of the tail 502.

[0092] If heating by the auxiliary heaters 110 and 113 were not performed, the temperature would rise gradually due to heating from the heater 101 as shown in waveform 603, and then would drop gradually due to cooling caused by the fall of the tail 502. Therefore, heating by the auxiliary heaters 110 and 113 would provide the temperature sensors 104 and 107 with higher sensitivity to the fall of the tail.

[0093] Since the output signals Vs1 and Vs2 are the same (T1=T2), the output signals Vs1 and Vs2, including the current fluctuation noise and crosstalk noise, are cancelled out according to equation (5), and the output signal Vdif of the differential amplifier 330 becomes a constant voltage Vofs. Therefore, the output signal VF of the low-pass filter 334 also becomes a waveform 604 of a constant voltage Vofs, as shown in FIG.

[0094] The threshold voltages Vdth1 and Vdth2 are set so that they are equal above and below Vofs. In FIG. 6A, Vdth2≦VF≦Vdth1, so the signal CMP1 , CMP2 are both at a low level (normal discharge), and the output signal CMP of the OR gate circuit 343 is also at a low level, so that no pulse is generated (605). Therefore, the signal HCMP (606) and the judgment result signal RSLT (607) are also at a low level (normal discharge) and are output to the judgment result extraction unit 5.

[0095] 5B is a schematic cross-sectional view of the nozzle during deviated ejection, showing the state in which the ink droplet 501 is ejected deviating to the left on the paper surface from the ejection direction in FIG. 5A. The negative pressure inside the foamed air bubble 141 acts asymmetrically on the tail 502, and the air communication of the air bubble 141 also occurs asymmetrically from the point where the meniscus has become thin, resulting in the tail 502 being deviated to the left from the center of the heater 101 and crashing down.

[0096] 5A. Therefore, the fallen tail 502 is closer to the temperature sensor 107 and farther from the temperature sensor 104 in plan view than in FIG. 5A. Therefore, the temperature sensor 107 is cooled more strongly by the tail 502 than the temperature sensor 104.

[0097] 6(B), the timing of appearance of feature point 610 in waveform 608 of output signal Vs1 of temperature sensor 104 is later than that of feature point 611 in waveform 609 of output signal Vs2 of temperature sensor 107. In addition, the temperature drop rate after feature point 610 is slower than the temperature drop rate after feature point 611, and the slope of the waveform becomes gentler.

[0098] However, the appearance time difference between feature point 611 and feature point 610 is slight, and in order to extract the appearance timing of feature points 610 and 611, a separate circuit such as a differential filter is required, and the accuracy is low, so that the appearance time difference cannot be detected with good accuracy.

[0099] On the other hand, after the characteristic point 611, the waveform 609 of the output signal Vs2 stably falls below the waveform 608 of the output signal Vs1, and the signal Vdif obtained by taking the differential between the output signals of the waveforms 608 and 609 and amplifying it can be detected stably with good accuracy. Therefore, the deviation ejection state is determined based on the signal Vdif.

[0100] From equation (5), the output signal Vdif of the differential amplifier 333 drops from the constant voltage Vofs after the characteristic point 611. Therefore, the output signal VF of the low-pass filter 334 also has a waveform 612 that drops from the constant voltage Vofs after the characteristic point 611, as shown in FIG.

[0101] 6B, in the section where Vdth2>VF, the signal CMP1 goes low and the signal CMP2 goes high (distortion discharge), and the output signal CMP of the OR gate circuit 343 goes high (distortion discharge) to generate a pulse 614. Therefore, a pulse 615 that holds the pulse 614 is generated in the signal HCMP, and the judgment result signal RSLT (616) goes high (distortion discharge) and is output to the judgment result extraction unit 5.

[0102] When the ejection direction of the ink droplet 501 is distorted to the right, which is the opposite direction to the direction shown in FIG. 5B, the waveforms 608 and 609 in FIG. 6B are switched, and the signal VF becomes a waveform 613 that is a reflection of the waveform 612 with respect to the constant voltage Vofs.

[0103] In this case, in the section where VF>Vdth1, the signal CMP1 becomes high level (discharge of distortion) and the signal CMP2 becomes low level, the output signal CMP of the OR gate circuit 343 becomes high level (discharge of distortion), and a pulse 614 is generated as in the case of distortion to the left. Therefore, a pulse 615 that holds the pulse 614 is generated in the signal HCMP, and the judgment result signal RSLT (616) becomes high level (discharge of distortion) and is output to the judgment result extraction unit 5.

[0104] When heating the temperature sensor with an auxiliary heater, the cavitation-resistant film 11 directly above the auxiliary heater must be removed. It is necessary to adjust the amount of heat generated so as not to cause the ink to bubble on the interface of 6.

[0105] Now, the heater 101 has a heating length Lm, a sheet resistance Rshm, and a heating density Qm. Similarly, the auxiliary heaters 110 and 113 have heating lengths Ls, sheet resistance Rshs, and heating density Qs. Then, the heating length ratio r, the sheet resistance ratio γ, and the heating density ratio κ2 of the heater can be expressed by the following formulas (6) to (8).

number

[0106] In this case, the relationship expressed by the following formula (9) is established among the heating length ratio r, the sheet resistance ratio γ, and the heating density ratio κ2 of the heater.

number

[0107] Now, assuming that Ls is 60% of Lm, the auxiliary heater film is made of the same material and has the same thickness as the heater film, and γ = 1, the heat generation density ratio κ2 is 0.36 from equation (9). Since the auxiliary heaters 110 and 113 are farther away from the ink interface than the heater 101, if the amount of heat generated per unit area of ​​the auxiliary heater is the same as that of the heater 101, no bubbles will be generated at the ink interface directly above the auxiliary heater. Then, since κ2 = 0.36, if the pulse width of the drive pulse 405 is set to 0.36 times the pulse width of the drive pulse 401, the amount of heat generated per unit area of ​​the auxiliary heater will be the same as that of the heater 101, and it will be possible to adjust the amount of heat generated so that bubbles do not occur at the ink interface directly above the auxiliary heater.

[0108] As described above, in this embodiment, two temperature sensors are arranged symmetrically in plan view in the same layer as the heater provided in the nozzle, and two auxiliary heaters for heating the two temperature sensors are provided below the temperature sensors. The heater and auxiliary heater can be driven independently by separate drive pulses.

[0109] Therefore, by driving the auxiliary heater after driving the heater and before the tail falls, the sensitivity of the temperature sensor to the tail falls can be increased without affecting the ejection of ink droplets, and the degree of ink droplet misalignment can be detected with high accuracy. Also, the heat generation amount of the auxiliary heater can be adjusted simply by adjusting the pulse width of the drive pulse applied to the auxiliary heater.

[0110] [Example 2] A second embodiment of the present invention will be described below. Fig. 7 is a block diagram of a heater drive circuit mounted on the recording element substrate 1 in this embodiment, and a processing circuit for an output signal of a temperature sensor. Fig. 8 is a timing chart showing the control timing in the logic circuit section of the recording element substrate 1 in this embodiment.

[0111] In the first embodiment, as shown in the block diagram of FIG. 3, the heater 101 and the auxiliary heater 322 were driven individually by switch element 319 and switch element 321. In contrast, in this embodiment, as shown in Fig. 7, they are driven collectively by switch element 701. With this configuration, the heater drive signals required for the two, HE and SHE, can be reduced to one, HE, and further the two switch elements required per nozzle can be reduced to one, simplifying the drive circuit and enabling shrinking of the recording element substrate 1.

[0112] 8 are applied to the heater 101 and the auxiliary heater 322 at the same time. The heat generated by the auxiliary heater 322 by the drive pulses 801-804 does not contribute to the ejection of ink droplets, but has the effect of preheating the temperature sensors 104 and 107.

[0113] Due to the above preheating effect, the driving pulses 805 to 808 for heating the temperature sensor can provide sufficient heating with shorter pulses than the driving pulses 405 to 408. However, the total amount of heat generated by the auxiliary heaters due to the driving pulses 801 to 804 and the driving pulses 805 to 808 exceeds the amount of heat generated by the auxiliary heaters due to the driving pulses 405 to 408.

[0114] On the other hand, although the heat generated by the heater 101 by the driving pulses 805 to 808 contributes slightly to the heating of the auxiliary heater 322 , the fallen tail 502 is heated before it reaches the upper surfaces of the temperature sensors 104 and 107 .

[0115] Therefore, when the tail 502 reaches the upper surface of the temperature sensor 104, 107, the temperature difference between the tail 502 and the temperature sensor 104, 107 is smaller than that in the first embodiment, and the cooling effect of the tail 502 on the temperature sensor 104, 107 is slightly weakened. Therefore, the sensitivity of the temperature sensor 104, 107 to the tail 502 is slightly weakened than in the first embodiment.

[0116] Now, if the amount of heat generated per unit area of ​​the auxiliary heater by the driving pulses 801 to 804 is the same as that of the heater 101, and no bubbles are generated at the ink interface directly above the auxiliary heater, the heat density ratio κ2 is 1. If the heat length ratio r of the heater is 1 / 0.6, the same as in Example 1, the sheet resistance ratio γ is 0.36 from formula (9).

[0117] If the heater film and the auxiliary heater film are made of the same material, the thickness of the auxiliary heater should be 0.36 times that of the heater film to obtain a sheet resistance ratio γ of 0.36. Alternatively, if the thicknesses are the same, it is necessary to select a material such that the resistivity of the auxiliary heater film is 1 / 0.36 = 2.78 times that of the heater film.

[0118] [Example 3] A third embodiment of the present invention will be described below. Fig. 9 is a plan view of one of the nozzles provided on the recording element substrate 1 in this embodiment, as viewed from the substrate side in the ink ejection direction. Fig. 10 shows a cross-sectional view of the nozzle taken along line AA in Fig. 9. The driving circuit for the heater 101 and the auxiliary heaters 110 and 113 in this embodiment uses the driving circuit shown in Fig. 7, as in the second embodiment. The differences from the second embodiment will be described below with reference to Figs. 9 and 10.

[0119] In the second embodiment, the heater 101 and the auxiliary heaters 110 and 113 are electrically connected in parallel as shown in FIG. 1, and the voltage VH of the constant voltage source 302 is applied by turning on the switch element 701.

[0120] At this time, as described in Example 2, in order to suppress bubbles at the ink interface directly above the auxiliary heater, if the heater film and the auxiliary heater film are made of the same material, the film thickness of the auxiliary heater is set to be equal to or larger than that of the heater film. It was necessary to thin it to 0.36 times its thickness.

[0121] However, when the thickness of the auxiliary heater is reduced to 0.36 times that of the heater, the auxiliary heater is deposited in a shorter time than the heater, resulting in a problem that the variation in the resistance value due to the variation in the thickness becomes large.

[0122] Therefore, in this embodiment, as shown in FIGS. 9 and 10, the auxiliary heaters 110 and 113 are electrically connected in series via a conductive plug 111, a wiring pattern 1002 of the second layer, and a conductive plug 114.

[0123] By connecting the auxiliary heaters 110 and 113 in series, the heating length of the auxiliary heater is doubled. which is 1.2 times the heating length of the heater 101. Therefore, the heating length ratio r of the heater is 1 / 1.2, and if the heating density ratio κ2 is 1, then the sheet resistance ratio γ becomes 1.44 from formula (9).

[0124] From the above, when the heater film and the auxiliary heater film are made of the same material, the thickness of the auxiliary heater only needs to be 1.44 times that of the heater, and it is possible to form an auxiliary heater film with a smaller variation in resistance value than that of the heater.

[0125] [Example 4] A fourth embodiment of the present invention will be described below. Fig. 11 is a plan view of one of the nozzles provided on the recording element substrate 1 in this embodiment, as viewed from the substrate side in the ink ejection direction. Fig. 12 is a cross-sectional view of the nozzle in Fig. 1, with Fig. 12A showing the AA cross-sectional view and Fig. 12B showing the BB cross-sectional view. The structure around the nozzle in this embodiment will be described below with reference to Figs. 11 and 12.

[0126] In this embodiment, the temperature sensor 1107 is placed in the center of the nozzle when viewed in-plane in order to maximize the sensitivity to the tail 502 that has crashed onto the anti-cavitation film 116. Heaters 1101 and 1104 are provided in the same layer as the temperature sensor 1107, so as to be symmetrical with respect to the temperature sensor 1107.

[0127] Although the temperature sensor 1107 is heated to a certain extent by driving the heaters 1101 and 1104, this is not sufficient, so an auxiliary heater 1110 for heating the temperature sensor is provided below the temperature sensor 1107 via an insulating member 204. The auxiliary heater 1110 is also driven to supplement the driving of the heaters 1101 and 1104, which is accompanied by the ejection of ink droplets.

[0128] As shown in FIG. 12A, heaters 1101, 1104 and auxiliary heater 1110 are connected at one end of the short sides to a common wiring pattern 1201 on the second layer via conductive plugs 1102, 1105 and 1111, respectively.

[0129] As shown in FIG. 12B, the auxiliary heater 1110 is connected at the other end to a pad 1202 on the second layer via a conductive plug 1112 , and is further connected to a wiring pattern 1204 on the first layer via a conductive plug 1203 .

[0130] The wiring pattern 1201 is connected to a constant voltage source 302, and the wiring pattern 1204 is grounded via a switch element 701 (see FIG. 13) which will be described later.

[0131] The temperature sensor 1107 is connected to a pad 1205 of the second layer via a conductive plug 1108 provided at one end, and is further connected to a wiring pattern 1207 of the first layer via a conductive plug 1206. The other end is connected to a pad 1208 of the second layer via a conductive plug 1109, and is further connected to a wiring pattern 1210 of the first layer via a conductive plug 1209. The wiring pattern 1207 is connected to a constant current source 309 via a switch element 327 (see FIG. 13) which will be described later, and the wiring pattern 1210 is grounded.

[0132] In FIG. 11, the thick solid lines extending from the conductive plugs connected to the heaters 1101 and 1104 and the auxiliary heater 1110 are schematic plan views of the wiring to each of the wiring layers described above.

[0133] In the figure, terminal 121 represents a connection point between wiring pattern 1201 and constant voltage source 302. Meanwhile, terminal 122 represents a connection point between the wiring pattern connecting conductive plugs 1103 and 1106 and switch element 701 (see FIG. 13). Furthermore, terminal 123 represents a connection point between wiring pattern 1204 and switch element 701 (see FIG. 13).

[0134] FIG. 13 is a block diagram of a driving circuit for the heater mounted on the recording element substrate 1 in this embodiment, and a processing circuit for the output signal of the temperature sensor.

[0135] The drive circuit 316a is configured as a circuit that controls the application of the voltage VH from the constant voltage source 302 to the heater 1301a and the auxiliary heater 1110a.

[0136] Here, the heater 1301a is represented as a single heater consisting of heaters 1101 and 1104 electrically connected in parallel. The auxiliary heater 1110a is also driven to supplement the driving of the heater 1301a, which involves the ejection of ink droplets, so the heater 1301a and the auxiliary heater 1110a are configured to be driven collectively by a switch element 701a, similar to the drive circuit shown in Fig. 7. The other three heaters 1301b to 1301d and the three auxiliary heaters 1110b to 1110d are also controlled by similar switch elements.

[0137] The temperature sensor 1107a, together with switch elements 327a and 328a, constitute one temperature acquisition circuit 326a. The switch element 327a controls the supply of current from the constant current source 309 to the temperature sensor 1107a. In addition, the switch element 328a controls the output of the voltage generated in the temperature sensor 1107a to the voltage follower 331.

[0138] The switch elements 327a and 328a are simultaneously turned on, and at this time the temperature sensor 1107a outputs a temperature signal for inspecting the ejection state of ink droplets ejected from the nozzle corresponding to the heater 1301a to the voltage follower 331. The ground side terminal voltage VSS of the temperature sensor 1107a is output to the voltage follower 332. The other three temperature sensors 1107b to 1107d are also controlled by similar switch elements.

[0139] The output signal Vs 2 of the voltage follower 332 and the output signal Vs 1 of the voltage follower 331 are differentially amplified by the differential amplifier 333 and output to the band pass filter 501 as a signal Vdif representing the voltage across the temperature sensor 1107 .

[0140] The bandpass filter 1302 removes high frequency noise from the signal Vdif and cuts low frequency components by differentiation processing to output the signal VF. The inverting amplifier inverts and amplifies the filter output signal VF and outputs it as the signal Vinv. If the ink droplet ejection state is normal, a positive peak appears in the signal Vinv. Therefore, the comparator 1307 compares the signal Vinv with a threshold voltage Vdth, and outputs a signal CMP that goes high when a positive peak appears in the inverted signal VF.

[0141] The signal processing in the RS latch circuit 344 and the flip-flop circuit 345 is the same as that in the block diagram shown in FIG. 3 in the first embodiment, and therefore the description thereof will be omitted in this embodiment. Since the auxiliary heater is provided below the temperature sensor, the distance between the auxiliary heater and the ink interface is greater than the distance between the heater and the ink interface. Therefore, in order to simultaneously generate bubbles at the ink interfaces directly above the heaters 1101 and 1104 and the auxiliary heater 1110 by driving the heaters to eject ink droplets, the heat generation density of the auxiliary heater 1110 needs to be higher than the heat generation density of the heaters 1101 and 1104.

[0142] Now, if the heat density Qs of the auxiliary heater is 1.2 times the heat density Qm of the heater, and if bubbles form simultaneously at the ink interface, the heat density ratio κ2 is 1 / 1.2 from equation (8). The heat length ratio r is 1 as shown in Figure 11, so the sheet resistance ratio γ is 1.2 from equation (9). If the heater film and auxiliary heater film are made of the same material, the film thickness of the auxiliary heater needs to be 1.2 times that of the heater film in order for the sheet resistance ratio γ to be 1.2. Alternatively, if the film thicknesses are the same, it is necessary to select a material such that the specific resistance of the auxiliary heater film is 1 / 1.2 = 0.83 times that of the heater.

[0143] (Other Examples) Although the first to fourth embodiments have been described above, the present invention is not limited to the above values ​​and forms. For example, the temperature sensor and the auxiliary heater adjacent to the heater may be provided on one side each. In addition, the positions at which the two temperature sensors and the two auxiliary heaters are provided may be different. The nozzles may be arranged on the short side of the heater instead of on the long side. The number of nozzles per nozzle row is not limited to four but may be, for example, 512, and the nozzle row itself may be multiple rows instead of one.

[0144] As described above, in a configuration in which a nozzle provided on a recording element substrate has a temperature sensor below the heater, a configuration in which the sensor is located below the heater has been conventionally known. In such a configuration, even if the temperature sensor is brought closer to the heater by using a conductive plug structure, the distance between the sensor and the ink is far to begin with, and there is a limit to how much the sensor can improve its sensitivity to temperature changes.

[0145] Therefore, in the present invention, the temperature sensor is made of a film in the same layer as the heater, which allows the temperature sensor to be closer to the ink interface than in the conventional configuration. Furthermore, the temperature sensor is electrically separated from the heater and placed outside the heater, and an auxiliary heater for heating the temperature sensor is placed below the temperature sensor, so that the temperature sensor is heated sufficiently. Therefore, it is possible to detect temperature changes accompanying changes in the state of the ink after the heater is driven, such as tailing, defoaming, and refilling, with higher sensitivity.

[0146] [Configuration 1] A recording element substrate including a substrate and a flow path forming member, a liquid chamber for accommodating a liquid is formed between the substrate and the flow path forming member; the flow passage forming member is provided with a discharge port through which the liquid contained in the liquid chamber is discharged, the substrate includes at least a first layer and a second layer that is farther from a surface in which the liquid chamber is formed than the first layer; the first layer is provided with a first heater that generates heat by application of a drive pulse to heat the liquid and eject it from the ejection port, and a temperature sensor that is disposed so that at least a portion of the temperature sensor overlaps with the liquid chamber in a plan view; The second layer is provided with a second heater arranged so that at least a portion of the second heater overlaps with the temperature sensor in a plan view. A recording element substrate comprising: [Configuration 2] The first heater and the temperature sensor provided in the first layer are arranged so as not to overlap each other in a plan view. 2. The recording element substrate according to configuration 1. [Configuration 3] The first layer is a layer formed by providing a protective film of an insulating material on the first heater and the temperature sensor. 3. The recording element substrate according to configuration 2. [Configuration 4] The liquid chamber includes a plurality of liquid chambers, and a plurality of the first heaters are provided for each of the plurality of liquid chambers. 4. The recording element substrate according to any one of configurations 1 to 3. [Configuration 5] A plurality of the temperature sensors are provided for each of the liquid chambers. 5. The recording element substrate according to any one of configurations 1 to 4. [Configuration 6] In a plan view, a pair of temperature sensors are disposed approximately symmetrically with respect to the first heater. 6. The recording element substrate according to configuration 5. [Configuration 7] a plurality of the second heaters corresponding to the plurality of temperature sensors, The plurality of second heaters are electrically connected in parallel or in series. 7. The recording element substrate according to configuration 5 or 6. [Configuration 8] A plurality of the first heaters are provided for each of the liquid chambers, The plurality of first heaters are electrically connected in series or in parallel. 8. The recording element substrate according to any one of configurations 1 to 7. [Configuration 9] The second heater is provided to heat the temperature sensor, and a drive pulse that is electrically independent of a drive pulse applied to the first heater is applied to the second heater. 9. The recording element substrate according to any one of configurations 1 to 8. [Configuration 10] The recording element substrate according to configuration 9, characterized in that for each of the liquid chambers, at least one switch element for driving the first heater and at least one switch element for driving the second heater are provided. [Configuration 11] The recording element substrate described in any one of configurations 1 to 8, characterized in that the second heater is provided to heat the temperature sensor, and a drive pulse is applied to the second heater in synchronization with a drive pulse applied to the first heater. [Configuration 12] A switch element is provided for each of the liquid chambers to drive a configuration in which at least one of the first heaters and at least one of the second heaters are electrically connected in parallel. 12. The recording element substrate according to claim 11, [Configuration 13] The second heater does not cause the liquid contained in the liquid chamber to bubble. 13. The recording element substrate according to any one of configurations 1 to 12. [Configuration 14] a plurality of the first heaters are provided for each of the liquid chambers so as to be substantially symmetrical with respect to the ejection port; The temperature sensor is disposed between the first heaters. 8. The recording element substrate according to any one of configurations 1 to 7. [Configuration 15] A recording element substrate according to any one of configurations 1 to 14, A control unit for controlling the driving of the recording element substrate; A recording head comprising: [Explanation of symbols]

[0147] 1: printing element substrate, 101: heater, 104, 107: temperature sensor, 110, 113: auxiliary heater

Claims

1. A recording element substrate including a substrate and a flow path forming member, a liquid chamber for accommodating a liquid is formed between the substrate and the flow path forming member; the flow passage forming member is provided with a discharge port through which the liquid contained in the liquid chamber is discharged, the substrate includes at least a first layer and a second layer that is farther from a surface in which the liquid chamber is formed than the first layer; the first layer is provided with a first heater that generates heat by application of a drive pulse to heat the liquid and eject it from the ejection port, and a temperature sensor that is disposed so that at least a portion of the temperature sensor overlaps with the liquid chamber in a plan view; The second layer is provided with a second heater disposed so as to overlap at least a portion of the second heater with the temperature sensor in a plan view. A recording element substrate comprising:

2. The first heater and the temperature sensor provided in the first layer are arranged so as not to overlap each other in a plan view.

2. The recording element substrate according to claim 1.

3. The first layer is a layer formed by providing a protective film of an insulating material on the first heater and the temperature sensor.

3. The recording element substrate according to claim 2.

4. The liquid chamber includes a plurality of liquid chambers, and a plurality of the first heaters are provided for each of the plurality of liquid chambers.

4. The recording element substrate according to claim 1, wherein the recording element substrate is a substrate having a first surface and a second surface.

5. A plurality of the temperature sensors are provided for each of the liquid chambers.

4. The recording element substrate according to claim 1, wherein the recording element substrate is a substrate having a first surface and a second surface.

6. A pair of temperature sensors are disposed approximately symmetrically across the first heater in a plan view.

6. The recording element substrate according to claim 5.

7. a plurality of the second heaters corresponding to the plurality of temperature sensors, The plurality of second heaters are electrically connected in parallel or in series.

6. The recording element substrate according to claim 5.

8. A plurality of the first heaters are provided for each of the liquid chambers, The plurality of first heaters are electrically connected in series or in parallel.

4. The recording element substrate according to claim 1, wherein the recording element substrate is a substrate having a first surface and a second surface.

9. The second heater is provided to heat the temperature sensor, and a drive pulse that is electrically independent of a drive pulse applied to the first heater is applied to the second heater.

4. The recording element substrate according to claim 1, wherein the recording element substrate is a substrate having a first surface and a second surface.

10. 10. The recording element substrate according to claim 9, wherein at least one switch element for driving the first heater and at least one switch element for driving the second heater are provided for each of the liquid chambers.

11. 4. A recording element substrate according to claim 1, wherein the second heater is provided to heat the temperature sensor, and a drive pulse is applied to the second heater in synchronization with a drive pulse applied to the first heater.

12. A switch element is provided for each of the liquid chambers to drive a configuration in which at least one of the first heaters and at least one of the second heaters are electrically connected in parallel.

12. The recording element substrate according to claim 11.

13. The second heater does not cause the liquid contained in the liquid chamber to bubble.

4. The recording element substrate according to claim 1, wherein the recording element substrate is a substrate having a first surface and a second surface.

14. a plurality of the first heaters are provided for each of the liquid chambers so as to be substantially symmetrical with respect to the ejection port; The temperature sensor is disposed between the first heaters.

4. The recording element substrate according to claim 1, wherein the recording element substrate is a substrate having a first surface and a second surface.

15. A recording element substrate according to claim 1 , A control unit for controlling the driving of the recording element substrate; A recording head comprising:

Images