Recording head

Abstract

This suppresses the possibility of the heater disconnecting when detecting the ejection status of the recording head. [Solution] The recording head includes multiple nozzles for ejecting ink, multiple recording elements corresponding to each of the multiple nozzles, a drive control unit that drives the selected recording element to eject ink, an ejection inspection unit that inspects the ejection state from the nozzles corresponding to the driven recording elements, and a determination unit that determines whether each of the multiple nozzles is a nozzle not subject to inspection, and the drive control unit does not drive the recording elements corresponding to the nozzles not subject to inspection.

Description

Technical Field

[0001] The present invention relates to a recording head.

Background Art

[0002] A recording apparatus such as an inkjet printer is equipped with an inkjet recording head (hereinafter referred to as "recording head") that discharges ink onto a recording medium. As methods for the recording head to discharge ink, various methods such as a thermal method and an ultrasonic method are known. Among them, a thermal recording head that utilizes heat from a heating resistor element (hereinafter referred to as "heater") can relatively easily achieve high-density multi-nozzle formation and enables high-speed recording with high resolution and high image quality.

[0003] In such a recording head, a voltage may be applied using a common wiring for a plurality of heaters. In that case, the degree of voltage drop in the wiring during recording varies depending on the number of heaters driven simultaneously. As a result, it is known that the energy supplied to the heaters fluctuates according to the number of heaters driven simultaneously, and the discharge stability deteriorates. To solve this problem, the recording head described in Patent Document 1 uses a common wiring in which the wiring layer connected to the heaters is thickened and the width is made as wide as possible for the purpose of reducing the resistance of the wiring that causes the voltage drop.

[0004] Also, in this recording head, ink ejection failure may occur in all or some of the nozzles of the recording head due to causes such as clogging of the nozzles by foreign substances or ink with increased viscosity, air bubbles mixed in the ink supply path or the nozzles, changes in the wettability of the nozzle surface, or electrical abnormalities of the heaters. In order to avoid deterioration of the image quality that occurs when such ejection failure occurs, it is preferable to promptly execute a recovery operation to recover the ink ejection state or a complementary operation using other nozzles or the like. In order to promptly perform these operations, it is extremely important to accurately and timely determine the ink ejection state and the occurrence of such ejection failure. Therefore, various ink ejection state determination methods and complementary recording methods have been proposed.

[0005] Patent Document 2 discloses a method for detecting ink ejection failures from a recording head by detecting the temperature drop that occurs during normal ejection. According to Patent Document 2, during normal ejection, a point (feature point) appears where the rate of temperature decrease changes a certain time after the time the detected temperature reaches the highest temperature, but this point does not appear during ejection failures. Therefore, by detecting the presence or absence of this feature point, the ink ejection state can be determined. As a result, ejection failures due to various nozzle conditions, including ejection failures due to electrical abnormalities in the heater, can be detected. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2016-137705 [Patent Document 2] Patent No. 7133956 [Overview of the project] [Problems that the invention aims to solve]

[0007] In recording heads, abnormal electrical resistance of the heater or the generation of abnormal pulses such as noise can cause overcurrent to flow through the heater, or the heater to overheat, leading to unexpected disconnections of the heater on the element board. Since the area around the heater on the element board is exposed to ink, when a heater disconnects, the wiring connected to the heater is also exposed to ink. However, voltage must continue to be supplied to the common wiring in order to drive the other normal heaters. As a result, electrolytic corrosion of the wiring may occur starting from the point where the heater disconnected. If this condition persists, the electrolytic corrosion may spread to the disconnected heater. The damage could extend to the wiring of other heaters adjacent to the affected heater, potentially causing a collectively disrupted heater function starting from the broken heater.

[0008] According to the detection method described in Patent Document 2, a discharge failure due to an abnormality in the electrical resistance of the heater can be detected, and discharge from the detected nozzle can be stopped. However, in order to detect the discharge failure, it is necessary to drive the heater, and this driving may cause the heater to break.

[0009] This invention was made to solve the above problems and aims to suppress the possibility of heater disconnection when detecting the ejection state of the recording head. [Means for solving the problem]

[0010] This invention employs the following configuration: Multiple nozzles that eject ink, A plurality of recording elements provided corresponding to each of the plurality of nozzles, A drive control unit that drives a recording element selected from the plurality of recording elements to eject ink, An ejection inspection unit that inspects the ejection state of ink from the nozzle corresponding to the driven recording element, A determination unit for each of the aforementioned plurality of nozzles determines whether or not it is an exempt nozzle that is not subject to inspection by the discharge inspection unit, A recording head equipped with, The drive control unit does not perform any driving on the recording element corresponding to the nozzle that is not subject to inspection. This is a recording head characterized by the following features. [Effects of the Invention]

[0011] According to the present invention, the possibility of heater disconnection when detecting the ejection state of the recording head can be suppressed. [Brief explanation of the drawing]

[0012] [Figure 1] A schematic diagram showing the general configuration of the recording device. [Figure 2] Block diagram showing the outline of the control system for the recording device. [Figure 3](a)(b) are diagrams showing the structure of the element substrate [Figure 4] Diagram showing the equivalent circuit of a drive circuit for driving one heater [Figure 5] Cross-sectional view showing the multilayer structure of the element substrate [Figure 6] Top view showing the wiring of two heaters [Figure 7] Diagram showing the multilayer structure near the temperature sensing element [Figure 8] Block diagram showing the control configuration of temperature sensing using the element substrate [Figure 9] (a)(b) are diagrams showing the temperature waveforms when drive pulses are applied to the heater [Figure 10] Cross-sectional view of the element substrate with a multilayer structure schematically showing the state where the heater is disconnected [Figure 11] Top view schematically showing the state of the VH common wiring where dissolution has progressed [Figure 12] Flowchart showing the ejection inspection according to Embodiment 1 [Figure 13] (a)(b) are diagrams explaining the stored information according to Embodiment 1 [Figure 14] Flowchart showing the ejection inspection according to Embodiment 2 [Figure 15] Diagram explaining the stored information stored in the non-volatile memory according to Embodiment 2

Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the following embodiments are to be appropriately changed according to the configuration of the device to which the present invention is applied and various conditions. Therefore, unless otherwise specifically described, it is not intended to limit the scope of the present invention. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential to the invention, and the plurality of features may be arbitrarily combined

[0014] In this specification, "record" (sometimes referred to as "print") refers not only to cases where meaningful information such as text and figures is formed, but also to cases where images, patterns, etc. are formed on a recording medium, or where the medium is processed, regardless of whether it is meaningful or not.

[0015] Furthermore, the term "recording medium" refers not only to paper, which is commonly used in recording devices, but also to a wide range of materials that can accept ink, such as cloth, plastic film, metal plates, glass, ceramics, wood, and leather.

[0016] Furthermore, "ink" (sometimes referred to as "liquid") should be interpreted broadly, similar to the definition of "record (print)" above. Therefore, it refers to a liquid that, when applied to a recording medium, can be used to form images, patterns, designs, etc., or to process the recording medium, or to process the ink (for example, to solidify or insolubilize the colorants in the ink applied to the recording medium).

[0017] Furthermore, a "nozzle" is a discharge port or a flow path connected to it, where a recording element that generates the energy used for ink ejection is located. For example, the recording element may be located opposite the discharge port.

[0018] The term "element substrate (head substrate) for recording heads" used below does not refer to a simple substrate made of silicon semiconductor, but rather to a configuration on which various elements and wiring are provided.

[0019] Furthermore, "on the substrate" refers not only to the element substrate itself, but also to the surface of the element substrate and the interior of the element substrate near the surface. Also, in this invention, "built-in" does not simply refer to the separate placement of each element on the substrate surface, but rather to the integral formation and manufacturing of each element on the element board through semiconductor circuit manufacturing processes, etc.

[0020] Furthermore, the terms "upper," "lower," "upper side," "lower side," "upper layer," and "lower layer" used in this disclosure are for convenience when explaining the relative positional relationships between components while referring to the drawings. Therefore, they do not limit the positional relationships in the actual arrangement of the device.

[0021] <Description of the recording device configuration> Figure 1 is a schematic diagram showing the general configuration of an inkjet recording device (hereinafter referred to as "recording device") 100. The recording device 100 is a sheet-fed recording device that forms an ink image on a recording medium 101 using two types of liquids, a processing liquid and ink. The recording medium 101 after image formation becomes the recorded material. In this embodiment, the X direction corresponds to the width direction (overall length direction) of the recording device 100, the Y direction corresponds to the depth direction of the recording device 100, and the Z direction corresponds to the height direction (gravity direction) of the recording device 100. In addition, in this embodiment, since the recording medium 101 is transported in the X direction, the X direction also corresponds to the transport direction of the recording medium, and the Y direction also corresponds to the width direction of the recording medium.

[0022] As shown in Figure 1, the recording device 100 includes a transport unit 107 for transporting the recording medium 101, a paper feeding unit 106 for feeding the recording medium 101 to the transport unit 107, and the transport unit The recording device 100 includes a transport unit 107 and a paper discharge unit 108 that collects the printed recording medium 101. The recording device 100 also includes a first recording head that applies a processing liquid that reacts with ink onto the recording medium 101, and a second recording head that applies ink onto the recording medium 101 to which the processing liquid has been applied, and forms an ink image. The first recording head and the second recording head are collectively referred to simply as the recording head 102. Between the transport unit 107 and the paper discharge unit 108, units (not shown) having functions such as drying, fixing, cooling, and paper inversion may be added at any position depending on the system.

[0023] This description assumes a configuration in which the recording medium 101 is transported while the recording head 102 is fixed. This embodiment is not limited to this configuration and can also be applied to a serial scan type recording device 100 in which the recording head 102 reciprocates to record data on the recording medium 101.

[0024] <Description of the control configuration of the recording device> Figure 2 is a block diagram showing the configuration of the control circuit of the recording device 100. As shown in Figure 2, the recording device 100 mainly consists of a print engine unit 217 that oversees the recording section, a scanner engine unit 211 that oversees the scanner section, and a controller unit 210 that oversees the entire recording device 100.

[0025] The print controller 219, which incorporates an MPU and non-volatile memory (such as EEPROM), controls various mechanisms of the print engine unit 217 according to instructions from the main controller 201 of the controller unit 210. The various mechanisms of the scanner engine unit 211 are controlled by the main controller 201 of the controller unit 210.

[0026] The details of the control configuration are described below. In each control configuration, I / F stands for Interface. In the controller unit 210, the main controller 201, which is composed of a CPU, controls the entire recording device 100 using the RAM 206 as a working area, according to the program and various parameters stored in the ROM 207. For example, when a print job is input from the host device 200 via the host I / F 202 or wireless I / F 203, the image processing unit 208 performs predetermined image processing on the received image data according to the instructions of the main controller 201. Then, the main controller 201 transmits the processed image data to the print engine unit 217 via the print engine I / F 205.

[0027] The recording device 100 may acquire image data from the host device 200 via wireless or wired communication, or it may acquire image data from an external storage device (such as a USB memory stick) connected to the recording device 100. The communication method used for wireless or wired communication is not limited. For example, Wi-Fi (Wireless Fidelity) (registered trademark) and Bluetooth (registered trademark) can be used as communication methods for wireless communication. Also, USB (Universal Serial) can be used as a communication method for wired communication. A bus or similar interface can be applied. For example, when a read command is input from the host device 200, the main controller 201 transmits this command to the scanner engine unit 211 via the scanner engine interface 209.

[0028] The control panel 204 is a unit for the user to perform input and output operations to the recording device 100. Through the control panel 204, the user can instruct operations such as copying and scanning, set the recording mode, and recognize information from the recording device 100.

[0029] In the print engine unit 217, the print controller 219, which is composed of a CPU, processes the RAM according to the program and various parameters stored in the ROM 220. 221 is used as the work area to control the various mechanisms provided by the print engine unit 217.

[0030] When various commands and image data are received via the controller I / F 218, the print controller 219 temporarily stores them in the RAM 221. To make the recording head 102 available for recording, the print controller 219 instructs the image processing controller 222 to convert the stored image data into recording data. Once the recording data is generated, the print controller 219 instructs the recording head 102 to perform a recording operation based on the recording data via the head I / F 227. At this time, the print controller 219 drives the transport unit 107 via the transport control unit 226 to transport the recording medium 101. Following the instructions of the print controller 219, the recording operation by the recording head 102 is performed in conjunction with the transport operation of the recording medium 101, and the recording process is carried out.

[0031] The head carriage control unit 225 changes the orientation and position of the recording head 102 according to the operating status of the recording device 100, such as the maintenance status and recording status. The ink supply control unit 224 controls the liquid supply unit (not shown) so that the pressure of the ink supplied to the recording head 102 is within an appropriate range. The maintenance control unit 223 controls the operation of the cap unit and wiping unit in the maintenance unit (not shown) when performing maintenance operations on the recording head 102.

[0032] In the scanner engine unit 211, the main controller 201 controls the hardware resources of the scanner controller 215, using the RAM 206 as a working area, according to the program and various parameters stored in the ROM 207. This controls the various mechanisms comprising the scanner engine unit 211. For example, the main controller 201 controls the hardware resources within the scanner controller 215 via the controller I / F 214, so that the document loaded into the ADF (not shown) by the user is transported via the transport control unit 213 and read by the sensor 216. The scanner controller 215 then stores the read image data in the RAM 212. The print controller 219 converts the acquired image data into recording data, making it possible to have the recording head 102 perform a recording operation based on the image data read by the scanner controller 215.

[0033] <Explanation of the component substrate configuration> Figure 3(a) is a plan view showing the layout configuration of the element substrate 300 mounted on the recording head 102. The element substrate 300 shown in Figure 3(a) has a rectangular shape, and multiple pads 305 are provided along the long side of the rectangular plane of the element substrate 300. Data and drive voltage are supplied from the outside (the main body of the recording device) via these pads. Multiple discharge ports 306 (nozzles), multiple ink supply ports 301, multiple ink recovery ports 303, and multiple switching elements 304 are arranged in the direction of the long side of the element substrate 300. Ink circulates through this configuration. That is, ink is supplied from a common supply channel (not shown), passes through the ink supply ports 301, and is recovered from the ink recovery ports 303 into the common recovery channel (not shown).

[0034] Figure 3(b) is an enlarged view of section X, indicated by the dashed line in Figure 3(a). As shown in Figure 3(b), each heater 302 is provided with an ejection port 306 through which ink droplets are ejected. Also, as shown in Figure 3(a), each ejection port 306 is provided with a switching element 304 that drives each heater 302. By driving the heaters 302, the thermal energy necessary for ink ejection is generated and ink droplets are ejected from the ejection ports 306. In this embodiment, the heater 302 will be used as a recording element for explanation.

[0035] <Heater Wiring Explanation> Figure 4 shows the equivalent circuit of a drive circuit that drives one heater (heat-generating resistance element) 302. As shown in Figure 4, one connection point 404 of the heater 302 is electrically connected to the VH common wiring 401 for supplying voltage. Furthermore, the other connection point 405 of the heater 302 is electrically connected to the GND common wiring 402 via a switching element 403 for switching the heater 302 on and off. In this embodiment, the switching element 403 is a MOSFET, and the heater 302 is driven by switching it on and off by applying an external drive voltage to the gate of the MOSFET.

[0036] <Explanation of the multilayer structure of the element substrate> Figure 5 is a cross-sectional view showing the multilayer structure of the element substrate 300. This cross-sectional view corresponds to the A-A' cross-sectional view shown in Figure 3(b).

[0037] As shown in Figure 5, on the element substrate 300, a Poly-Si layer 500, wiring layers 503a, 503b, 503c, 503d, a heater 302, and a cavitation-resistant layer 506 are deposited on a Si substrate 504. Each wiring layer is insulated from each other by insulating layers 501a, 501b, 501c, 501d, 501e, and 501f. In addition, through-holes are provided that penetrate the insulating layers in order to electrically connect each wiring layer, and metal plugs (connecting members) 502a, 502b, 502c, 502d, and 502e are formed in the through-holes.

[0038] A barrier metal, such as a titanium nitride (TiN) film, is formed on the underside and sides of the through-holes, and the underside and sides of these metal plugs are surrounded by this barrier metal. The four wiring layers 503a to 503d are collectively referred to as wiring layer 503, and the five metal plugs 502a to 502e are collectively referred to as connecting member 502.

[0039] The connection point 404 of the heater 302 is connected to the VH common wiring 401 formed by the wiring layer 503c via a metal plug 502e, a wiring layer 503d, and another metal plug 502d. The VH common wiring 401 is electrically connected to a portion of the pad 305 of the element substrate 300 and is supplied with voltage from an external source. The other connection point 405 of the heater 302 is connected to one side of the switching element 403 via a metal plug 502e, a wiring layer 503d, a metal plug 502d, a wiring layer 503c, a metal plug 502c, a wiring layer 503b, a metal plug 502b, and a metal plug 502a.

[0040] Furthermore, the other end of the switching element 403 is connected to the common GND wiring 402 formed by the wiring layer 503d via the metal plug 502a, wiring layer 503a, metal plug 502b, wiring layer 503b, metal plug 502c, wiring layer 503c, and metal plug 502d.

[0041] Therefore, in order to connect the VH common wiring 401 shown in Figure 4 to one end of the heater 302, and further connect the other end of the heater 302 to the switching element 403, and then connect the switching element 403 to the GND common wiring 402, each element between different layers is connected via a metal plug.

[0042] In addition, in the element substrate 300, multiple heaters 302 are formed in the same layer, and the layer on which multiple heaters 302 are formed is sometimes called the heater layer. Similarly, multiple switching elements 403 are formed in the same layer, separate from the heater layer, and the layer on which multiple switching elements are formed is sometimes called the switching layer.

[0043] An ink chamber 507 is provided above the heater 302. When the switching element 403 is turned on by data supplied from the outside, current flows to the heater 302, and as the heater 302 heats up, the ink in the ink chamber 507 foams up. The ink then flows to the element substrate 300. It is discharged from the discharge port 306 formed by the top plate 508. A temperature sensing element 509 is also provided at the bottom of the heater 302.

[0044] Figure 6 is a top view showing the wiring of two heaters 302. As shown in Figure 6, the VH common wiring 401 is electrically connected to all of the heaters 302 via metal plugs and wiring. The multiple metal plugs are arranged in a row. The GND common wiring 402 is connected to all of the switching elements 403 that are individually connected to each heater 302. Figure 6 shows the position of the metal plug 502e that is in contact with the bottom surface of the heater.

[0045] <Explanation of the multilayer structure near the temperature sensing element> Figure 7 shows an enlarged view of the multilayer structure near the temperature sensing element 509, specifically portion A in Figures 5 and 6. Figure 7(a) is a top view showing the temperature sensing element 509 placed on a sheet with an insulating layer 501f below the heater 302. Figure 7(b) is a cross-sectional view along the dashed line x-x' in the top view shown in Figure 7(a), and Figure 7(c) is a cross-sectional view along the dashed line y-y' shown in Figure 7(a).

[0046] In the x-x' cross-sectional view shown in Figure 7(b) and the y-y' cross-sectional view shown in Figure 7(c), a wiring layer 503d made of aluminum or the like is formed on the insulating layer 501d, and an insulating layer 501e is further formed on the wiring layer 503d. The wiring layer 503d and a temperature sensing element 509 made of a thin-film resistor such as a titanium and titanium nitride laminate are electrically connected via a metal plug 701 made of tungsten or the like embedded in the insulating layer 501e.

[0047] As shown in Figure 7, a multilayer structure is formed in which an intermediate layer of independent temperature sensing elements 509 is provided between the wiring layer 503d and the heater layer 302. This makes it possible to obtain temperature information for each heater 302 of the element substrate 300 using the temperature sensing elements 509 provided in conjunction with each heater 302.

[0048] Then, based on the temperature information detected by the temperature sensing element 509 and the temperature change, a logic circuit (inspection unit) provided inside the element substrate 300 can obtain a judgment result signal RSLT indicating the ink ejection state from the corresponding heater 302. The judgment result signal RSLT is a 1-bit signal, where "1" indicates normal ejection and "0" indicates a ejection failure.

[0049] <Explanation of the temperature detection control configuration> Figure 8 is a block diagram showing the control configuration for temperature detection using the element substrate 300 shown in Figure 7. As shown in Figure 8, the print engine unit 217 includes a print controller 219 with a built-in MPU, a head I / F 227 connected to the recording head 102, and RAM 221 in order to detect the temperature of the heater 302 mounted on the element substrate 300. The head I / F 227 also includes a signal generation unit 801 that generates various signals to be transmitted to the element substrate 300, and a determination result extraction unit 802 that receives the determination result signal RSLT output from the element substrate 300 based on the temperature information detected by the temperature detection element 509.

[0050] To detect temperature, the print controller 219 issues an instruction to the signal generation unit 801, which then outputs a clock signal CLK, a latch signal LT, a block signal BLE, a recorded data signal DATA, and a heat enable signal HE to the element substrate 300. The signal generation unit 801 further outputs a sensor selection signal SDATA, a constant current signal Diref, and an ejection inspection threshold signal Ddth.

[0051] The sensor selection signal SDATA includes selection information for selecting a temperature sensing element 509 to detect temperature information, information specifying the amount of current supplied to the selected temperature sensing element 509, and information related to the output instruction of the judgment result signal RSLT. For example, the element substrate 300 is a heater array consisting of multiple heaters 302. In a configuration where four columns are implemented, the selection information included in the sensor selection signal SDATA includes column selection information that specifies the column and heater selection information that specifies the heater 302 for that column. Meanwhile, the element substrate 300 outputs a 1-bit determination result signal RSLT based on temperature information detected by the temperature sensing element 509 corresponding to one of the heaters 302 in the column specified by the sensor selection signal SDATA.

[0052] The values ​​of "1" indicating normal ejection and "0" indicating ejection failure, output from the judgment result signal RSLT, are obtained by comparing the temperature information output from the temperature sensing element 509 with the ejection inspection threshold voltage (TH) indicated by the ejection inspection threshold signal Ddth within the element substrate 300. This comparison will be described in detail later.

[0053] As can be seen in Figure 8, the latch signal LT, block signal BLE, and sensor selection signal SDATA are fed back to the judgment result extraction unit 802. Meanwhile, the judgment result extraction unit 802 receives the judgment result signal RSLT output from the element substrate 300 based on the temperature information detected by the temperature sensing element 509, and extracts the judgment result in each latch period in synchronization with the falling edge of the latch signal LT. If the judgment result is a discharge failure, the block signal BLE and sensor selection signal SDATA corresponding to the judgment result are stored in the RAM 221.

[0054] The print controller 219 then erases the signal for the defective nozzle from the recorded data signal DATA of the corresponding block, based on the block signal BLE and sensor selection signal SDATA used to drive the defective nozzle stored in the RAM 221. In its place, it adds the nozzle for non-discharge compensation to the recorded data signal DATA of the corresponding block and outputs it to the signal generation unit 801.

[0055] <Explanation of output waveform from temperature sensing element> Figure 9(a) is a graph showing the temperature waveform (sensor temperature: T) output from the temperature sensing element 509 when a drive pulse is applied to the heater 302. Figure 9(b) is a graph showing the temperature change signal (dT / dt) of that temperature waveform.

[0056] Note that in Figure 9(a), the temperature waveform (sensor temperature: T) is shown in degrees Celsius (°C), but in reality, a constant current is supplied to the temperature sensing element 509, and the terminal voltage (V) of the temperature sensing element 509 is detected. Since this detected voltage is temperature-dependent, in Figure 5, the detected voltage is converted to temperature and shown as temperature. Also, the temperature change signal (dT / dt) in Figure 9(b) is shown as the time change of the detected voltage (mV / sec).

[0057] As shown in Figure 9(a), when the drive pulse 901 is applied to the heater 302 and the ink is ejected normally (normal ejection), the output waveform of the temperature sensing element 509 will be as shown by the solid line waveform 902.

[0058] When the temperature decrease process detected by the temperature sensing element 509 is as shown in waveform 902, a feature point 903 appears in the waveform. This is because, during normal ejection, the trail of ink droplets ejected to the interface of the heater 302 falls, cooling the interface. Then, from feature point 903 onward, the rate of temperature decrease in waveform 902 increases sharply.

[0059] In contrast, in the case of a dispensing malfunction, the output waveform of the temperature sensing element 509 will be as shown by the dotted line waveform 904. In this case, characteristic points 903, such as the waveform 902 during normal dispensing, do not appear, and the cooling rate gradually decreases during the cooling process.

[0060] Figure 9(b) shows the temperature change signal (dT / dt), and waveforms 905 and 904 are the waveforms after processing the output waveforms 902 and 904 of the temperature sensing element 509 into a temperature change signal (dT / dt). Let it be 07. The method of converting to the temperature change signal at this time is appropriately selected according to the system. The temperature change signal (dT / dt) in this embodiment is a waveform output after passing the temperature waveform through a filter circuit (first derivative in this configuration) and an inverting amplifier.

[0061] Now, in the waveform 905 shown by the solid line, a peak 906 appears due to the maximum cooling rate after the feature point 903 of the waveform 902. The waveform (dT / dt) 905 is compared with a preset ejection inspection threshold voltage (TH) of a comparator mounted on the element substrate 300. This comparison result is the determination signal (CMP) at the upper part of FIG. 9(a). Regarding the waveform 905, a section (dT / dt≧TH) exceeding the ejection inspection threshold voltage (TH) is detected and appears in the determination signal (CMP) 908. This determination signal becomes a pulse indicating normal ejection.

[0062] On the other hand, since the feature point 903 does not appear in the waveform 904, the cooling rate is low. Therefore, the peak appearing in the waveform 907 shown by the dotted line is lower than the ejection inspection threshold voltage (TH). The waveform (dT / dt) 907 is also compared with the ejection inspection threshold voltage (TH) preset in the comparator mounted on the element substrate 300. And in the section (dT / dt<TH) below the ejection inspection threshold voltage (TH), no pulse appears in the determination signal (CMP) (909).

[0063] Therefore, by obtaining this determination signal (CMP), it becomes possible to grasp the ejection state of each nozzle. This determination signal (CMP) becomes the determination result signal RSLT described above.

[0064] <Explanation of problems caused by driving of inspection pulses> The problems that this embodiment aims to solve will be described in detail below. Unexpected disconnections of the heater 302 may occur in the element substrate 300. One of the causes of disconnections is an abnormality in the heater resistance. As an example of an abnormality in heater resistance, we will describe the case where the heater resistance is smaller than that of other nozzles. As explained in Figures 4 to 6, a common voltage is supplied to each of the multiple nozzles by the VH common wiring 401. The current flowing through the heater 302 is given by I = V / R, where V is the supplied voltage, R is the resistance value, and I is the current value. In other words, the smaller the resistance value R, the larger the current that flows.

[0065] Next, let's consider the amount of heat generated in heater 302. If we denote the amount of heat as Q, it is expressed as Q = I^2 / R × t (time). In other words, when the resistance value R is small, the current I increases and the amount of heat generated Q increases. Therefore, when the resistance value R is small and shows an abnormal value, the amount of heat generated will be large compared to other nozzles, and if it continues to operate, overheating abnormalities may occur and lead to wire breakage.

[0066] Figure 10 is a cross-sectional view of a multilayer element substrate 300 schematically showing a state in which the heater 302 is disconnected. The element substrate 300 shown in Figure 10 is the same as the element substrate 300 shown in Figure 5. Therefore, the reference numerals shown in Figure 10 are the same as those shown in Figure 5, and their explanations are omitted.

[0067] If the wire breaks, a portion of the ink-resistant cavitation-resistant layer 506 in the heater 302 will be lost, and the tungsten metal plug 502 will be exposed to the ink. Tungsten will dissolve due to the ink even when no potential is applied. Furthermore, since the connection part 404 is actually connected to a high potential (VH), there is a risk that the dissolution of tungsten will progress even further.

[0068] A barrier metal, such as a titanium nitride (TiN) film, is formed on the underside and sides of the through-hole, and the underside and sides of the metal plug 502 are surrounded by this barrier metal. Here, since the barrier metal layer is less soluble in ink than tungsten, the progression of dissolution is normally suppressed by the barrier layer. However, through-hole When the aspect ratio of the through-hole (through-hole height / through-hole diameter) increases, it becomes more difficult for the film-forming material constituting the barrier metal layer to reach the corners of the through-hole. As a result, the film thickness of the barrier metal layer tends to be thinner at the corners of the through-hole, and in some cases, the film thickness of the barrier metal layer may not be sufficient, leading to dissolution by the ink. The arrows in the figure indicate the progression of dissolution, and a dissolved region 811 is formed where dissolution has progressed.

[0069] Figure 11 schematically shows the state of the VH common wiring 401 as melting progresses. As shown in Figure 11, as melting progresses in a heater 302 (302a), the melted region 811 of the VH common wiring 401, which is made of aluminum, may eventually reach the wiring portion of the adjacent heater 302 (302b).

[0070] As a result, a break in one heater 302 can cause adjacent heaters 302 to stop functioning, further melting of the aluminum VH common wiring 401, and eventually the heaters 302 may collectively fail to function.

[0071] As shown by waveform 902 in Figure 9(a), when ink is ejected normally, a trail of ink droplet falls onto the heater, cooling the interface and causing feature point 903 to appear. On the other hand, as shown by waveform 904 in Figure 9(a), if the ink is not ejected normally, feature point 903 does not appear. The same is true if the heater resistance is abnormal. If the heater resistance is abnormal and heat is not properly transferred to the heater 302, resulting in ejection failure, the trail of ink droplet does not fall. Therefore, feature point 903 does not appear in the temperature waveform, and it can be detected as an ejection failure. Such ejection failure can be detected by determining the judgment signal 908 as shown in Figure 9(b).

[0072] The ejection state detection method described above can detect ejection failures caused by various factors, such as nozzle clogging due to foreign matter or ink with increased viscosity, air bubbles mixed into the ink supply path or inside the nozzle, changes in the wettability of the nozzle surface, or electrical abnormalities in the heater. Therefore, conventionally, inspections were performed on all nozzles to detect ejection failures. However, if the heater 302 was continuously driven to inspect the nozzle condition of a nozzle with a risk of wire breakage, such as abnormal resistance values, wire breakage could occur, potentially affecting not only the nozzle being inspected but also surrounding nozzles.

[0073] <Embodiment 1> The inspection method in this embodiment will be explained using Figures 12 and 13(a) and 13(b). This embodiment provides a method that does not perform discharge inspection on nozzles that are at risk of wire breakage. Figure 12 is a flowchart of the discharge inspection performed in this embodiment. Figures 13(a) and 13(b) show the nozzle state stored in the non-volatile memory provided in the recording head 102 or the like. The storage area can be any memory unit that can store the nozzle state and can be accessed by the control unit.

[0074] The information stored in storage area 1 in Figure 13(a) is explained below. Storage area 1 stores information indicating the presence or absence of a wire breakage risk as the nozzle status for each nozzle number (seg). In this storage area 1, nozzles with a wire breakage risk, such as those with abnormal electrical resistance values ​​as described above, are stored as "1" as electrical resistance abnormal nozzles. Nozzles other than those with a wire breakage risk, i.e., nozzles without a wire breakage risk, are stored as "0" as discharge nozzles. In storage area 1, nozzles with a wire breakage risk are those with electrical resistance abnormalities discovered during the electrical inspection process when the recording head is shipped. In other words, the nozzle status detected during the shipping inspection is written to the storage area.

[0075] The information stored in storage area 2 in Figure 13(b) will be explained. The information stored is the discharge status determined by the discharge test. Therefore, in the state where no test has been performed, "0" is written for all nozzles. When a discharge test is performed and a nozzle is determined to be discharging poorly, "1" is written to the storage area 2 as a discharging poorly nozzle. When a discharge test is performed and a nozzle is determined to be discharging properly, "0" is written to the storage area 2 as a discharging nozzle.

[0076] When the ejection inspection is initiated, the flow shown in Figure 12 begins. This process can be thought of as being executed by the controller unit 210, scanner engine unit 211, and print engine unit 217 working together as a control unit. In that case, each step of the flow is executed by the control unit. Alternatively, the print engine unit 217, which mainly oversees the recording unit, can be considered the control unit. For example, if the print controller 219 controls the application of voltage for driving the recording elements, performs ejection inspection, and determines whether the nozzle is subject to inspection or not, then the print controller 219 can be said to function as a drive control unit, ejection inspection unit, and judgment unit. However, this is just one example. It does not matter which block corresponds to the control unit; it is sufficient that any information processing device included in the recording device 100 or recording head 102 can perform the processing of each step of the flow.

[0077] In step S101 shown in Figure 12, the control unit reads the information in storage area 1 in Figure 13(a) and sets the nozzles that are written as electrical resistance abnormal nozzles as nozzles not to be inspected.

[0078] In step S102, the control unit selects an inspection nozzle. In step S103, the control unit determines whether the selected nozzle is an inspection-excluded nozzle as set in step S101, or an inspection-excluded nozzle (i.e., a nozzle other than an inspection-excluded nozzle). If it is an inspection-excluded nozzle, the process proceeds to step S106. In this case, the discharge inspection in step S104 is skipped (i.e., the inspection drive is not performed).

[0079] On the other hand, if the nozzle selected in step S102 is not a nozzle that is not subject to inspection, the control unit performs the ejection inspection in step S104. In step S104, the print controller 219 instructs which nozzle to be inspected, and the signal generation unit 801 selects the nozzle to be inspected using the sensor selection signal SDATA according to this instruction. The ejection inspection threshold voltage (TH) of the selected nozzle is set, and the ejection inspection is performed based on the set ejection inspection threshold voltage (TH). If the judgment result signal RSLT is "1", it is determined to be in an ejection state, and if the judgment result signal RSLT is "0", it is determined to be a defective nozzle state.

[0080] In step S105, the control unit saves the determined discharge state to storage area 2. In step S106, the control unit determines whether all nozzles have been selected. The inspection process is then repeated until all nozzles have been selected.

[0081] As explained above, according to the inspection method of this embodiment, nozzles with abnormal electrical resistance that are at risk of wire breakage and nozzles with discharge defects identified by discharge testing are stored separately in different storage areas. This allows the defective nozzle "1" stored in storage area 2 in Figure 13(b) to be handled separately from nozzles at risk of wire breakage. Therefore, when performing inspections, the discharge testing of nozzles at risk of wire breakage can be skipped.

[0082] Storage area 1 and storage area 2 may be stored in separate storage areas within the non-volatile memory built into the print controller 219 as shown in Figure 2, or the non-volatile memory may be built into the recording head 102, and the non-volatile memory in the print controller 219 and the non-volatile memory in the recording head 102 may be stored separately.

[0083] <Embodiment 2> Next, we will describe Embodiment 2. The following description will focus on the differences from Embodiment 1. In Embodiment 1, the storage area was separated to distinguish nozzles with a risk of disconnection. However, it is also possible to address this by changing the value stored in the non-volatile memory according to the nozzle condition without separating the storage area. The following describes the discharge inspection when the value stored in the non-volatile memory is changed according to the nozzle condition, referring to Figures 14 and 15.

[0084] The information stored in the storage area shown in Figure 15 is explained below. Discharge nozzles are written as "0", nozzles with abnormal electrical resistance that pose a risk of wire breakage are written as "2", and nozzles that are determined to be defective during the discharge inspection are written as "1".

[0085] In step S201 shown in Figure 14, the control unit reads the information from the storage area in Figure 15 and sets the nozzle written as "2" (electrical resistance abnormal nozzle) as a nozzle to be excluded from inspection. Nozzles that are not excluded from inspection become nozzles to be inspected. In step S202, the control unit selects a nozzle to be inspected. In step S203, it determines whether the selected nozzle is an excluded nozzle set in S201. If it is excluded from inspection, the discharge inspection in step S204 is skipped (i.e., no inspection-based drive is performed). On the other hand, if the nozzle set in step S202 is not an excluded nozzle, the control unit performs the discharge inspection in step S204.

[0086] In step S204, the print controller 219 instructs the signal generation unit 801 to select the nozzle to be inspected based on the sensor selection signal SDATA. The ejection inspection threshold voltage (TH) for the selected nozzle is set, and the ejection inspection is performed based on the set ejection inspection threshold voltage (TH). If the judgment result signal RSLT is "1", the nozzle is in an ejection state, and if the judgment result signal RSLT is "0", it is determined to be a defective nozzle. The determined ejection state is saved as "defective nozzle 1" in the storage area in step S205. Then, in step S206, it is determined whether all nozzles have been selected, and the inspection method is repeated until all nozzles have been selected.

[0087] As explained above, in this embodiment, nozzles with a risk of wire breakage that are not subject to inspection and nozzles with discharge defects identified by discharge inspection are stored with different values. This allows each nozzle to be handled separately, and thus the discharge inspection of nozzles with a risk of wire breakage can be skipped.

[0088] As described above, according to the configuration of each embodiment of this disclosure, even in a recording head 102 where there is a heater 302 that is at risk of disconnection when driven to inspect the ejection state, the possibility of the heater 302 disconnecting can be suppressed. Therefore, according to the recording device, recording device control method, recording head, and nozzle inspection method of this disclosure, it is possible to reduce the risk of failure and recording defects.

[0089] In Embodiments 1 and 2, nozzles that are not driven by inspection are designated as nozzles with abnormal electrical resistance, but this is not the only option. For example, if the risk of wire breakage increases with durability, nozzles that have reached a certain number of discharge cycles may be stored in a way that distinguishes them as nozzles with a risk of wire breakage using the method of Embodiment 1 or 2.

[0090] Furthermore, the process of writing a nozzle as an uninspected nozzle is not limited to the electrical inspection process at the time of head shipment. A test equivalent to an electrical inspection may be performed and the data written when the recording head is mounted on the recording device 100, or, as described above, when a certain number of ejections is reached. You may write data at the right moment.

[0091] Furthermore, while the discharge inspection uses a temperature sensor, it is not limited to this method. An optical sensor may be used for inspection, or a recording element may be used as a detection element to detect the nozzle state. This indicates a configuration for inspecting the nozzle's discharge state, and it should be appropriately configured according to the system.

[0092] The principle of ink ejection is not limited to heat generation using the heater 302. If the recording head 102 has one terminal of multiple recording elements connected by a common wiring to which a voltage is applied, there is a possibility that melting may progress from one element to another through the common wiring between elements. Therefore, it is preferable to apply the inspection method of this disclosure to determine whether or not to perform inspection on each element. Examples of ink recording elements other than heaters include piezoelectric elements equipped with an ultrasonic transducer that vibrates and generates sound waves when a voltage is applied, and which eject ink by imparting energy through this vibration.

[0093] [Configuration 1] Multiple nozzles that eject ink, A plurality of recording elements provided corresponding to each of the plurality of nozzles, A drive control unit that drives a recording element selected from the plurality of recording elements to eject ink, An ejection inspection unit that inspects the ejection state of ink from the nozzle corresponding to the driven recording element, A determination unit for each of the aforementioned plurality of nozzles determines whether or not it is an exempt nozzle that is not subject to inspection by the discharge inspection unit, A recording head equipped with, The drive control unit does not perform any driving on the recording element corresponding to the nozzle that is not subject to inspection. A recording head characterized by the following features. [Configuration 2] The system further includes a storage unit that stores the nozzle state for each of the aforementioned plurality of nozzles. The determination unit makes the determination by referring to the storage unit. A recording head according to configuration 1, characterized by the above. [Configuration 3] The nozzle state stored in the memory unit includes at least the state in which the nozzle is not subject to inspection. A recording head according to configuration 2, characterized in that it is a recording head. [Structure 4] The memory unit has multiple storage areas, each of which corresponds to a different nozzle state. A recording head according to configuration 3, characterized by the above. [Composition 5] Whether or not the nozzle is an exempt nozzle is detected during the shipping inspection of the recording head and written to the storage unit. A recording head according to any one of configurations 2 to 4, characterized by the above. [Composition 6] Whether or not the nozzle is an inapplicable nozzle is determined based on the electrical resistance value during the electrical inspection of the recording element corresponding to the nozzle. A recording head according to configuration 5, characterized by the above. [Composition 7] The nozzle state stored in the memory unit further includes the state in which the nozzle is ejecting ink normally. This includes a state in which the nozzle is capable of ejecting ink, and a state in which the nozzle is a defective nozzle that cannot eject ink properly. A recording head according to configuration 3 or 4, characterized by the above. [Structure 8] The nozzle state is recorded based on the inspection performed by the discharge inspection unit. A recording head according to configuration 7, characterized by the above. [Composition 9] The plurality of recording elements are connected to a common wiring, and a voltage is applied to them via the common wiring. A recording head according to configuration 5 or 6, characterized by the above. [Configuration 10] The discharge inspection unit performs inspection using a temperature sensor. A recording head according to any one of configurations 1 to 9, characterized in that it is a recording head. [Composition 11] The discharge inspection unit performs inspection using an optical sensor. A recording head according to any one of configurations 1 to 9, characterized in that it is a recording head. [Composition 12] The recording element generates heat and ejects ink when a voltage is applied to it. A recording head according to any one of configurations 1 to 11, characterized in that it is a recording head. [Composition 13] The recording element vibrates and ejects ink when a voltage is applied. A recording head according to any one of configurations 1 to 11, characterized in that it is a recording head. [Explanation of symbols]

[0094] 102: Recording head, 219: Print controller, 302: Heater, 306: Ejector

Claims

1. Multiple nozzles that eject ink, A plurality of recording elements provided corresponding to each of the plurality of nozzles, A drive control unit that drives a recording element selected from the plurality of recording elements to eject ink, An ejection inspection unit that inspects the ejection state of ink from the nozzle corresponding to the driven recording element, A determination unit for each of the aforementioned plurality of nozzles determines whether or not it is an exempt nozzle that is not subject to inspection by the discharge inspection unit, A recording head equipped with, The drive control unit does not perform any driving on the recording element corresponding to the nozzle that is not subject to inspection. A recording head characterized by the following features.

2. The system further includes a storage unit that stores the nozzle state for each of the aforementioned plurality of nozzles. The determination unit makes the determination by referring to the storage unit. The recording head according to feature 1.

3. The nozzle state stored in the memory unit includes at least the state in which the nozzle is not subject to inspection. The recording head according to feature 2.

4. The memory unit has multiple storage areas, each of which corresponds to a different nozzle state. The recording head according to feature 3.

5. Whether or not the nozzle is an exempt nozzle is detected during the shipping inspection of the recording head and written to the storage unit. A recording head according to any one of claims 2 to 4.

6. Whether or not the nozzle is an inapplicable nozzle is determined based on the electrical resistance value during the electrical inspection of the recording element corresponding to the nozzle. The recording head according to feature 5.

7. The nozzle state stored in the storage unit further includes a state in which the nozzle is a discharge nozzle capable of normally ejecting ink, and a state in which the nozzle is a defective discharge nozzle capable of normally ejecting ink. A recording head according to feature 3 or 4.

8. The nozzle state is recorded based on the inspection performed by the discharge inspection unit. The recording head according to feature 7.

9. The plurality of recording elements are connected to a common wiring, and a voltage is applied to them via the common wiring. The recording head according to feature 5.

10. The discharge inspection unit performs inspection using a temperature sensor. A recording head according to any one of claims 1 to 4.

11. The discharge inspection unit performs inspection using an optical sensor. A recording head according to any one of claims 1 to 4.

12. The recording element generates heat and ejects ink when a voltage is applied to it. A recording head according to any one of claims 1 to 4.

13. The recording element vibrates and ejects ink when a voltage is applied. A recording head according to any one of claims 1 to 4.

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