JP2018153971A - Inspection method for liquid ejection head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection method for a liquid ejection head, by which a driving condition appropriate for an individual element substrate can be set without increasing the number of man hours and load on a step.SOLUTION: An inspection method for a liquid ejection head executes: a measurement step in which a first measurement result is obtained by measuring current flowing in a heating resistance element when a predetermined voltage is applied to the heating resistance element, and a second measurement result is obtained by measuring electrostatic capacitance between the heating resistance element and a second protective layer via a first protective layer; and an estimation step in which an estimated value of minimum ejection limit energy required to eject liquid from an ejection port is obtained from the first measurement result and the second measurement result. An initial value for driving voltage or pulse width is obtained based on the estimated value, the driving voltage or pulse width is varied from this initial value, and a test pattern is recorded.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a liquid ejection head inspection method.

A liquid ejection apparatus that performs recording by ejecting a liquid such as a recording liquid onto a recording medium or the like includes a liquid ejection head. There are various ejection principles in a liquid ejection head, but a liquid ejection head that includes a heating resistor element and ejects a liquid such as a recording liquid from an ejection port using thermal energy generated by the heating resistor element is a semiconductor device. In general, it is manufactured through the same process. Therefore, such a liquid discharge head includes a substrate forming step in which a heating resistor element and a wiring layer are formed on a substrate to form an element substrate, and a discharge port forming step in which a liquid flow path and discharge ports are formed on the element substrate. It is manufactured through a final assembly process. In the assembly process, the drive element is mounted on the element substrate and other parts are assembled. A circuit for driving each heating resistor element is also provided in the liquid discharge head. In order to confirm the recording quality and discharge performance of the completed liquid discharge head, and to obtain parameters set for each liquid discharge head in order to use the liquid discharge head under the optimal recording conditions, a recording inspection is performed. A process is performed.
In the liquid ejection head, when recording is performed by ejecting liquid, a voltage is applied to the selected heating resistance element in a pulsed manner to drive the heating resistance element. Therefore, in the recording inspection process, a predetermined pattern is recorded by discharging the liquid from the liquid discharge head while changing the drive voltage or pulse width applied to each heating resistance element when driving the liquid discharge head. Next, from the recorded pattern image, the recording state by each heating resistance element is observed, and the limit value of the drive voltage or pulse width at which ejection can be performed is obtained. Then, a margin value obtained separately by experiment is added to the obtained limit value, and the drive voltage value or pulse width obtained in this way is set as the optimum drive condition for the liquid discharge head in the drive circuit of the liquid discharge head. Set.

It is known that the optimum driving conditions, that is, the optimum driving voltage and pulse width, are affected by various variations between different liquid ejection heads (strictly, between element substrates), and there are individual differences between element substrates. ing. In the recording inspection process, in order to derive the optimum driving conditions, a plurality of patterns are recorded while changing the driving conditions stepwise within a range that can be a limit value, that is, within a range of variations in the element substrate after manufacture. It is necessary to confirm the recording state with respect to the driving conditions. However, since the range of driving conditions that can be the limit value is sufficiently wide, the number of patterns to be recorded increases, and a great amount of man-hours and time are spent for the recording inspection process. Since the man-hours and time are enormous, the measurement of the drive voltage or pulse width within the required range may not be practical.
Although there are individual differences for each element substrate, the optimum driving conditions and limit values are used to protect the electrical resistance value (hereinafter simply referred to as resistance value) of the heating resistor element formed on the element substrate and the element substrate. It is also known that the influence of the thickness of the protective film is large. Therefore, it is possible to preliminarily measure the resistance value of the heating resistor element for each element substrate, and to estimate a suitable driving condition to some extent from the obtained resistance value. However, when an appropriate driving condition is estimated only from the resistance value measured for each element substrate, a deviation due to variations in the protective film occurs between the estimated optimum driving condition and the actual optimum driving condition. There are things to do. In this case, when the liquid discharge head is actually used, it cannot be used under optimum driving conditions.
In Patent Document 1, in the recording inspection process of the liquid discharge head, an optimum driving condition is set based on the data on the resistance value of the heating resistor element obtained during the manufacturing process and the data on the film thickness of the protective film. Thus, a method of omitting measurement of the driving voltage and pulse width is disclosed.

Japanese Patent Laid-Open No. 06-320729

As described in Patent Document 1, when measuring the resistance value of the heating resistor element and the film thickness of the protective film of the element substrate, a man-hour and a measurement mechanism for measuring the film thickness are required, and rather, the process load is increased. It gets bigger.
An object of the present invention is to provide a liquid ejection head inspection method capable of setting appropriate driving conditions for individual element substrates without increasing the number of man-hours and the process load.

  The inspection method for a liquid ejection head according to the present invention includes a heating resistance element provided on a first surface of a substrate, a first protective layer formed of a dielectric formed on the first surface so as to cover the heating resistance element, and A second protective layer made of metal and formed on the first protective layer at least at a position where the heating resistor element is formed, and applying a voltage pulse to the heating resistor element to cause thermal energy to act on the liquid This is a method for inspecting a liquid discharge head that discharges liquid from a discharge port provided corresponding to a heating resistance element, and measures a current flowing through the heating resistance element when a predetermined voltage is applied to the heating resistance element. Measuring a first measurement result, measuring a capacitance between the heating resistance element and the second protective layer via the first protective layer, and obtaining a second measurement result; From the measurement result of 1 and the second measurement result, A prediction step for obtaining a predicted value of the minimum discharge limit energy necessary for discharging the liquid, and at least one of a driving voltage and a pulse width of a voltage pulse applied to the heating resistance element as a driving variable is used as a predicted value. A recording process that repeats recording the test pattern on the recording medium by determining the initial value of the driving variable based on the driving variable and driving the heating resistance element while discharging the liquid from the discharge port while changing the driving variable from the initial value. It is characterized by having.

  According to the present invention, it becomes possible to perform an inspection that makes it possible to set an appropriate driving condition for each element substrate without increasing the number of man-hours and the process load.

FIG. 3 is a perspective view conceptually showing a liquid discharge head. It is a perspective view which shows a liquid discharge head unit typically. It is a conceptual diagram which shows the heat generating part vicinity of the element substrate used with a liquid discharge head. It is a flowchart which shows the procedure of a recording test process. It is an equivalent circuit diagram which shows the measuring method in one Embodiment of invention. It is a figure which shows typically the image used for a measurement.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 conceptually shows an example of a liquid discharge head to be inspected by the method according to the present invention. The liquid discharge head 1 is provided in a liquid discharge device that causes thermal energy to act on the liquid and discharges the liquid as droplets from a fine discharge port by the pressure of bubbles generated at that time. If the liquid discharged from the discharge port is a recording liquid such as ink, the liquid discharge head is an ink jet recording head, and the liquid discharge device is an ink jet recording apparatus. The illustrated liquid discharge head 1 is formed by adhering a discharge port forming member 120 to an element substrate 100 formed of a semiconductor substrate such as silicon. In the element substrate 100, a supply port 130 for supplying a liquid from the second surface side to the first surface side is formed as a through hole. The first surface of the element substrate 100 is formed with a plurality of heat acting portions 117 that act on the liquid, and each of the heat acting portions 117 is provided with a heating resistance element 308 as will be described later. ing. In the discharge port forming member 120, a discharge port 121 for discharging a liquid is formed at a position facing the heat application unit 117 for each heat application unit 117, and the formation of the heat application unit 117 from the supply port 130. A channel 116 communicating with the discharge port 121 through the position is formed. In particular, a portion of the flow path 116 from the position in contact with the heat acting portion 117 to the discharge port 121 is formed as a liquid chamber 131 (see FIG. 3B) that can temporarily store the liquid to be discharged. Has been. Therefore, the heat acting part 117 is formed for each liquid chamber 131 communicating with the discharge port 121. A plurality of external electrodes (terminals) 311 that are electrically connected to the outside are provided at the outer peripheral end of the element substrate 100 in order to supply power to the heat acting unit 117.

FIG. 2 shows a liquid discharge head unit configured using the liquid discharge head. The liquid discharge head unit 210 is formed of the liquid discharge head 1 as shown in FIG. 1 and a tank 204 that stores the liquid for discharge and supplies it to the liquid discharge head 1, and is a cartridge that can be attached to the liquid discharge apparatus. It has the form. A tape-like electric wiring member 202 having a terminal connected to the element substrate 100 by TAB (Tape Automated Bonding) for supplying electric power to the liquid discharge head 1 is connected to the liquid discharge head 1. The electrical wiring member 202 extends from the liquid ejection head 1 along the tank 204, and a terminal 203 used for electrical connection with the main body of the liquid ejection device is formed at the tip of the electrical wiring member 202. From the main body of the liquid ejection device, electric power is selectively supplied to the heating resistor elements 308 (see FIG. 3) corresponding to the thermal action unit 117 via the terminal 203 and the electric wiring member 202, respectively.
In addition, the liquid discharge head based on this invention is not limited to the thing integrated with the tank of the liquid for discharge as FIG. 2 shows. For example, a tank is detachably mounted, and when there is no remaining liquid in the tank, the tank is removed and a new tank filled with liquid is mounted. Good. Alternatively, the liquid discharge head and the tank may be provided separately, and the discharge liquid may be supplied from the tank to the liquid discharge head via a tube or a pipe. Further, the liquid discharge head is a range corresponding to the full width of the recording medium, as applied to a line printer, even if it is applied to a serial recording type liquid discharge apparatus that performs recording while scanning by the recording head. A discharge port may be provided over the entire area.

  3A and 3B are diagrams showing the vicinity of the heat acting portion in the element substrate 100. FIG. 3A is a schematic plan view of the element substrate 100, and FIG. 3B is a diagram of B in FIG. It is a schematic cross section which shows the state which cut | disconnected the element substrate 100 along the -B line. The element substrate 100 has a structure in which a heat storage layer 302, a heating resistor layer 304, and an electrode wiring layer 305 as a wiring are stacked in this order on the first surface of the substrate 301. The heat storage layer 302 is made of a silicon thermal oxide film, a SiO film, a SiN film, or the like, and the electrode wiring layer 305 is made of a metal material such as Al, or an alloy material such as Al—Si or Al—Cu. The heat generation resistance layer 304 is made of a material having an appropriate volume resistivity that is sufficiently higher than the electrode wiring layer 305 so as to have a desired electrical resistance and generate heat when energized. In the laminated structure of the heat generation resistance layer 304 and the electrode wiring layer 305, a part of the electrode wiring layer 305 is removed to form a gap, and the heat generation resistance layer 304 in that part is exposed to form the heat generation resistance element 308. The electrode wiring layer 305 is connected to a driving element circuit (not shown) and a selection circuit (not shown) provided on the element substrate 100 and is also connected to the external electrode 311 and can receive power from the outside. It is like that. In the example shown here, the electrode wiring layer 305 is disposed on the heating resistor layer 304. However, the electrode wiring layer 305 is formed on the substrate 301 or the heat storage layer 302, and a part thereof is partially formed. The heating resistor layer 304 may be disposed after removing the gap to form a gap.

  Furthermore, in the element substrate 100, a protective layer 306 made of a dielectric material such as a SiO film or a SiN film and functioning also as an insulating layer is provided as an upper layer of the heating resistor element 308 and the electrode wiring layer 305. Further, an upper protective layer 307 is formed as an upper layer of the protective layer 306. The protective layer 306 is a first protective layer, and the upper protective layer 307 is a second protective layer. The upper protective layer 307 is a layer that protects the heat generating resistive element 308 from chemical and physical impact caused by heat generation of the heat generating resistive element 308, and is formed of, for example, a metal such as Ta or Ir having high chemical resistance. The upper protective layer 307 is a common part that connects between a part that is individually formed on the protective layer 306 corresponding to the position at which each heating resistor element 308 is formed and a part that is formed individually. And is composed of. Here, the protective layer 306 formed on the heating resistance element 308 is an insulating dielectric film, and the upper protective layer 307 which is a metal film is formed thereon. Therefore, a parallel plate conductor type capacitance element is formed in which the heating resistor element 308 is one electrode, the protective layer 306 is a dielectric, and the upper protective layer 307 is the other electrode. The upper protective layer 307 is electrically connected to the electrode wiring layer 305 through a through hole 310 formed through the protective layer 306. The electrode wiring layer 305 extends to the end of the element substrate 100, and the tip of the electrode wiring layer 305 constitutes an external electrode 311 for electrical connection with the outside. Although not shown separately in FIGS. 1 and 3, the external electrode 311 includes an external electrode 311 a for supplying power to each heating resistor element 308 in common, an external electrode 311 b for grounding (GND), and an upper part. And an external electrode 311c electrically connected to the protective layer 307. As will be described later, the conduction is controlled by the switching transistor 401, but the external electrodes 311a and 311b are respectively a first external electrode and a second external electrode that are electrically connected to both ends of the heating resistor element 308. Configure. The external electrode 311c constitutes a third external electrode. The external electrode 311 includes an external electrode connected to a selection circuit (not shown) for individually driving each heating resistor element 308.

  Next, the recording inspection process of the liquid ejection head in this embodiment will be described. FIG. 4 is a flowchart for explaining the recording inspection process. As described above, in the recording inspection process, regarding the completed liquid ejection head 1, the recording quality and ejection performance are confirmed, and parameters to be set for each liquid ejection head 1 for recording under optimum recording conditions are set. It is a process to obtain. In the recording inspection process, first, in step 601, the resistance value R or current value I of the heating resistor element 308 of the liquid ejection head 1 and the static layer sandwiching the protective layer 306 between the heating resistor element 308 and the upper protective layer 307 are sandwiched. A measurement process for measuring the capacitance C is performed. The resistance value R or the current value I measured here is the first measurement result, and the capacitance C is the second measurement result.

First, the measurement process will be described. FIG. 5A is an equivalent circuit diagram for explaining the measurement of the resistance value R or the current value I of the heating resistor element 308 in the measurement process, and FIG. 5B is a diagram of the heating resistor element 308 and the upper protective layer 307. It is an equivalent circuit diagram explaining the measurement of the electrostatic capacitance C between. In the element substrate 100, one end of each heating resistor element 308 is connected in common to the external electrode 311 a for supplying power, and the other end is connected to the drain of the switching transistor 401 for each heating resistor element 308. The source of each switching transistor 401 is connected in common to the external electrode 311b serving as ground (GND), and the gate is connected to a selection circuit (not shown). In the liquid ejection head 1 of this embodiment, the heating resistor element 308 is provided for each ejection port 121, but any heating resistor element 308 can be selected and driven by the selection circuit.
In a normal operation as the liquid ejection head 1, the heating resistor element 308 is driven by a voltage pulse, but when measuring the resistance value R and the current value I, a voltage is applied to the heating resistor element 308 for a long time. Therefore, in the measurement of the resistance value R or the current value I, a power source 320 having a predetermined voltage V that does not damage the heating resistance element 308 even when applied for a long time is connected between the external electrodes 311a and 311b via the ammeter 321. Apply to. For example, a voltage of 5.0 V or less is used as the predetermined voltage V. Then, the switching transistor 401 corresponding to the heating resistor element 308 to be measured is selectively driven by a selection circuit (not shown), and at this time, the current value I flowing from the power source is measured by the ammeter 321. At this time, the resistance value R is
R ≒ V / I
When the voltage V of the power source 320 is fixed, the current value I has a correlation with the resistance value R of the heating resistor element 308. In the measurement, it is common to set the predetermined voltage V to a constant value, and it is considered that the deviation from Ohm's law due to the influence of heat generation or the like is very small. Therefore, in the subsequent steps, the resistance value R and the current value I Any of these may be used.

Next, the measurement of the capacitance C with the protective layer 306 between the heating resistor element 308 and the upper protective layer 307 in the measurement process will be described. In order to measure the capacitance C, a capacitance meter 322 is connected between the external electrode 311 a for supplying power and the external electrode 311 c connected to the upper protective layer 307. At this time, the switching transistor 401 connected to each heating resistance element 308 is in a cut-off state. As described above, the upper protective layer 307 is configured by a portion formed individually for each heating resistance element 308 and a common portion connecting the portions formed individually. The electrostatic capacity of the entire element substrate 100 is measured.
The capacitance of the parallel plate conductor is generally “interlayer dielectric constant ε” × “area S” / “interlayer distance (film thickness) d”. In this case, since the area S and the dielectric constant ε of the protective layer 306 that is an interlayer film are not different for each element substrate 100 and are constant, the measured capacitance C is eventually the film of the upper protective layer 307. There is a correlation with the thickness d. In step 601, the resistance value R of the heating resistance element 308 or a value correlated therewith that greatly affects the optimum driving conditions and limit values of the liquid discharge head 1, and the thickness of the protective layer 306 for protecting the element substrate 100. Thus, a value having a correlation is required.

As described above, when the resistance value R of each heating resistor element 308 and the entire capacitance C of the element substrate 100 are obtained by the measurement process in step 601, next, in step 601, the discharge limit is determined based on these measurement values. The energy E _th is predicted. The limit discharge energy E _th is the minimum energy required for discharging the liquid from the discharge port. Similarly, the minimum drive voltage and pulse width necessary for discharging liquid are referred to as a limit drive voltage and a limit pulse width, respectively. Since the resistance value R of the heating resistor element 308 has already been obtained, the minimum driving voltage (limit driving voltage) required for ejection under the condition of constant pulse width from the ejection limit energy E _th or constant driving voltage. The minimum pulse width (limit pulse width) under the above conditions can be obtained. When the predicted value of the limit discharge energy E _th is obtained, in step 603, an appropriate margin α is added to the predicted limit discharge energy E _th to set the recording energy _Er . Next, in step 604, each heating resistance element 308 is driven using a drive voltage or pulse width that satisfies the recording energy _Er, and a test pattern is recorded on the test recording medium by ejecting a liquid. In the following description, the driving voltage or the pulse width is changed as the driving condition. At this time, both the driving voltage and the pulse width may be changed, or one of the driving voltage and the pulse width is changed and the other is fixed. The value may be left as it is. Changing one of the drive voltage and pulse width is easier to control and requires fewer changes to the drive conditions. However, changing both the drive voltage and drive pulse more accurately limits the critical discharge energy and The limit drive voltage and limit pulse width can be obtained. Therefore, a change in drive voltage and pulse width is also referred to as a drive variable.

In this embodiment, a test pattern is recorded a plurality of times under different driving conditions relating to the driving voltage or pulse width, the recorded test pattern or image is evaluated for quality, and the actual ejection limit energy value of the liquid ejection head is determined. judge. If the test pattern is recorded in step 604, it is next determined in step 605 whether the number of times of recording has reached the designated number. If the specified number of times has not been reached, the recording energy _Er is reset by subtracting a predetermined step size β from the current recording energy _Er in step 606, and the process returns to step 604. When step 604 is executed with the reset recording energy _Er , at least one of the drive voltage and the pulse width changes as compared with the previous time as described above. As a result, the recording of the test pattern with the recording energy _Er reduced by the step width β is repeated, and the recording is performed the designated number of times. In Steps 603 to 606, a recording process for repeatedly recording a test pattern by driving the heating resistor element 308 using each of a plurality of driving voltages or pulse widths obtained by gradually increasing or decreasing the driving voltage or pulse width was performed. It will be.
If the number of times of recording specified in step 605 has been reached, the recorded test pattern is confirmed in step 607, and the actual discharge limit energy value is determined in step 608 based on the confirmation result. Steps 607 and 608 constitute a determination process for determining the actual limit driving voltage or limit pulse width of the liquid ejection head. When step 608 is executed, the recording inspection process in this embodiment is completed. Thereafter, if necessary, an optimum driving condition for the liquid ejection head is obtained, and the obtained optimum driving condition or the like may be written in a nonvolatile memory (not shown) in the liquid ejection head.

  FIG. 6 schematically shows test pattern recording on the recording medium in the present embodiment. Here, it is assumed that the discharge ports 121 are arranged in the direction a in the liquid discharge head 1 and the recording medium 501 is conveyed in the direction b in the drawing. While the recording medium 501 is being conveyed, the heating resistor element 308 is driven under a predetermined driving condition so as not to discharge simultaneously from the adjacent discharge ports 121, and discharge is performed continuously for five dots from the same discharge port 121. Next, continuous printing of 5 dots is performed from one of the adjacent ejection ports 121 under the same driving conditions. By repeating this, all the ejection ports 121 are made to perform continuous printing of 5 dots. In the illustrated example, these discharge ports 121 are divided into four groups based on the remainder when the order is given to the arranged discharge ports 121 and the order is divided by four. Then, 5 dots are continuously recorded for each group, and when the recording in one group is completed, the next group is recorded. As a result, as shown in FIG. 6, the long and narrow records 502 are formed by the droplets ejected from the ejection ports 121 and landing on the recording medium 501 so as not to overlap each other.

If the ejection of the liquid by driving the heating resistor element 308 under a certain driving condition is completed for all the ejection ports 121, then the continuous printing of 5 dots is performed at all the ejection ports 121 in the same manner by changing the driving condition. Let it be done. In the figure, E1 to E9 indicate which driving condition is used for recording. In the process shown in FIG. 5, the drive conditions are changed so that the recording energy _Er gradually decreases. Therefore, in the case shown in FIG. 5, the recording 502 corresponding to the driving condition E1 has a high recording density (if the liquid is ink, the color of the image that is the recording 502 is the darkest), and the recording density is the driving condition E2. It slightly decreases, and further decreases under the driving condition E3.
Therefore, by confirming the recording formed by changing the driving conditions as described above and determining the recording density, it is determined to which driving condition the recording was practically performed, that is, the discharge limit energy. The value can be determined. The recording density can be confirmed by visually observing the recording medium 501 after recording. However, the pixel value in the digitized data, or the ratio of the area occupied by the recording pixels, is digitized by imaging with a camera. It may be done by asking.

When measuring the dischargeable drive voltage or pulse width and measuring all the drive voltage or pulse width assumed from the manufacturing process variation of the element substrate 100 having the heating resistor element 308, the test pattern recording and Judgment takes a lot of time. Therefore, in the present embodiment, the current value I or resistance value R flowing through the heating resistor element 308 and the capacitance C between the heating resistor element 308 and the upper protective layer 307 are obtained, and the minimum required drive voltage is obtained from these values. Or predict the pulse width. The drive voltage or pulse width is changed using the predicted drive voltage or pulse width as an initial value. As a result, the change range of the drive voltage or the pulse width is limited to a reasonable range, so that the test pattern can be recorded and determined in a short time. In the example described above, nine types of driving conditions E1 to E9 are used (therefore, the designated number of recordings in step 605 is also nine), and the driving voltage or pulse width is reduced within this range. That is, the drive voltage or pulse width is decreased in nine steps in the direction in which the recording energy _Er decreases from the initial value. However, the number of stages of change in drive voltage or pulse width is not limited to 9, but can be increased or decreased as appropriate. In the example shown here, by changing the drive voltage or pulse width in the direction in which the recording energy _Er decreases from the initial value, the minimum drive voltage or pulse width actually required for ejection can be actually achieved with a small number of repetitions. Can be sought.

In the example shown in FIG. 5, the driving voltage or the pulse width is changed in the direction in which the recording energy _Er decreases from the initial value, but the driving is performed in both the direction in which the recording energy _Er decreases and the direction in which the recording energy _Er decreases. The voltage or pulse width can be changed. When the drive voltage or the pulse width is changed both in the direction in which the recording energy _Er decreases and in the direction in which the recording energy _Er increases, the certainty of measurement is improved.

In the embodiment described above, when the test pattern is repeatedly recorded in the recording process, the initial value of the driving voltage or pulse width is obtained from the measurement result of the current value I (or resistance value R) and the capacitance C. It is determined based on the predicted value of the discharge limit energy E _th . As a result, the actual ejection limit energy E _th , limit drive voltage, and limit pulse width can be obtained only by changing the drive voltage or pulse width in the vicinity of the initial value. In other words, in this embodiment, the change range of the drive voltage or pulse width in the recording process is limited, and the actual discharge limit energy E _{th and the} like can be accurately obtained even if the change range is limited. . As a result, even if the number of test patterns to be recorded is limited, it becomes possible to accurately determine the limit drive voltage and the limit pulse width, so that the process load and consumption time in the recording inspection process can be suppressed as compared with the conventional case. become.

DESCRIPTION OF SYMBOLS 1 Liquid discharge head 100 Element substrate 306 Protective layer 307 Upper protective layer 308 Heating resistance element 311 311a-313c External electrode

Claims (6)

A heating resistance element provided on the first surface of the substrate, a first protective layer formed of a dielectric formed on the first surface so as to cover the heating resistance element, and at least a position where the heating resistance element is formed And a second protective layer made of metal formed on the first protective layer, and applying a voltage pulse to the heating resistor element to cause thermal energy to act on the liquid, thereby generating the heating resistor An inspection method of a liquid discharge head for discharging the liquid from an discharge port provided corresponding to an element,
When a predetermined voltage is applied to the heating resistance element, a current flowing through the heating resistance element is measured to obtain a first measurement result, and the heating resistance element and the second through the first protective layer are obtained. A measurement step of measuring a capacitance between the protective layer and obtaining a second measurement result;
A prediction step for obtaining a predicted value of the minimum discharge limit energy necessary for discharging the liquid from the discharge port from the first measurement result and the second measurement result;
Using at least one of the driving voltage and pulse width of the voltage pulse applied to the heating resistor element as a driving variable, an initial value of the driving variable is determined based on the predicted value, and the driving variable is determined from the initial value. A recording step of repeating the recording of a test pattern on a recording medium by driving the heating resistance element and discharging a liquid from the discharge port while changing,
An inspection method characterized by comprising:   The inspection method according to claim 1, wherein, in the recording step, one of the drive voltage and the pulse width is used as the drive variable, and the other of the drive voltage and the pulse width is a fixed value.   The inspection method according to claim 1, further comprising a determination step of evaluating the recorded test pattern and determining a value of the drive variable that is minimum required for ejection.   4. The test pattern is repeatedly recorded in the recording step by changing the drive variable from the initial value in a direction in which energy applied to the heating resistor element decreases. 5. Inspection method described in 1.   2. The test pattern is repeatedly recorded in the recording step by changing the driving variable from the initial value in both directions of increasing and decreasing energy applied to the heating resistor element. 4. The inspection method according to any one of items 1 to 3. A heating resistance element provided on the first surface of the substrate, a first protective layer formed of a dielectric formed on the first surface so as to cover the heating resistance element, and at least a position where the heating resistance element is formed And a second protective layer made of metal formed on the first protective layer, and applying a voltage pulse to the heating resistor element to cause thermal energy to act on the liquid, thereby generating the heating resistor An inspection method of a liquid discharge head for discharging the liquid from an discharge port provided corresponding to an element,
When a predetermined voltage is applied to the heating resistance element, a current flowing through the heating resistance element is measured to obtain a first measurement result, and the heating resistance element and the second through the first protective layer are obtained. A measurement step of measuring a capacitance between the protective layer and obtaining a second measurement result;
Using at least one of the driving voltage and the pulse width of the voltage pulse applied to the heating resistor element as a driving variable, the heating resistor element is driven to discharge liquid from the discharge port while changing the driving variable. A recording process of repeatedly recording a test pattern on a recording medium; and
And a change range of the drive variable in the recording process is limited based on the first measurement result and the second measurement result.

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