JP2013159036A - Method for manufacturing liquid ejection head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a liquid ejection head by which a defective piezoelectric element can be detected with higher accuracy at an earlier stage.SOLUTION: A method for manufacturing a liquid ejection head includes: a step of forming a piezoelectric element 18 on a substrate; a step of measuring a hysteresis characteristic of polarization-electric field with respect to the piezoelectric element; and a step of determining a passing status of the piezoelectric element by determining whether or not a polarization amount corresponding to a drive voltage is a value within an allowable polarization amount range on the basis of the measured hysteresis characteristic. The step of determining the passing status of the piezoelectric element is carried out before a step of forming a liquid flow channel on the substrate.

Description

  The present invention relates to a method for manufacturing a liquid jet head such as an ink jet recording head, and more particularly to a method for manufacturing a liquid jet head including a piezoelectric element formed by stacking a first electrode, a piezoelectric body, and a second electrode. It is.

  The liquid ejecting apparatus is an apparatus that includes a liquid ejecting head capable of ejecting liquid as droplets from a nozzle and ejects various liquids from the liquid ejecting head. A typical example of the liquid ejecting apparatus is an ink jet recording that includes an ink jet recording head (hereinafter referred to as a recording head) and performs recording by ejecting liquid ink as ink droplets from the nozzle of the recording head. An image recording apparatus such as an apparatus (printer) can be given. In addition, liquid ejecting apparatuses for ejecting various types of liquids such as color materials used for color filters such as liquid crystal displays, organic materials used for organic EL (Electro Luminescence) displays, electrode materials used for electrode formation, etc. Is used. The recording head for the image recording apparatus ejects liquid ink, and the color material ejecting head for the display manufacturing apparatus ejects solutions of R (Red), G (Green), and B (Blue) color materials. The electrode material ejecting head for the electrode forming apparatus ejects a liquid electrode material, and the bioorganic matter ejecting head for the chip manufacturing apparatus ejects a bioorganic solution.

  A piezoelectric element used as a driving source for ejecting a liquid in a liquid ejecting head, that is, a pressure generating means for causing a pressure fluctuation in a liquid in a head flow path, sandwiches a piezoelectric film made of a piezoelectric material between electrodes. It consists of A so-called flexure mode piezoelectric element is formed by laminating a lower electrode film, a piezoelectric body made of lead zirconate titanate (PZT), and the like, and an upper electrode film by a film forming technique and firing by heat treatment, and by patterning by lithography and etching. It is configured by cutting into each pressure chamber. Then, a pressure fluctuation is generated in the liquid in the pressure chamber by displacing or deforming an operating surface (that is, a driving target) such as an elastic film or a diaphragm constituting a part of the pressure chamber by a piezoelectric element. Is used to eject liquid from the nozzles of the liquid ejecting head.

  In a liquid ejecting head having the above piezoelectric element as a pressure generating means, it is required that liquid is ejected normally from a nozzle when a driving voltage is applied to drive the piezoelectric element. Has been done. As a method for inspecting an initial defect of a piezoelectric element of a general liquid ejecting head, a method of measuring the capacitance of the piezoelectric element (for example, see Patent Document 1) or a method of measuring a resonance frequency characteristic of the piezoelectric element (for example, a patent) Document 2) is known.

JP 2008-062388 A JP 2004009501 A

  However, these methods cannot detect, for example, the degree of displacement (electrostriction) of the piezoelectric element when a predetermined drive voltage is applied and the degree of liquid ejection corresponding to the amount. . The conventional method is generally performed in a state where the liquid jet head is completed. Therefore, when a defect is detected in the piezoelectric element in this state, the components other than the piezoelectric element and the process of manufacturing them are wasted, which has been a problem in terms of yield.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a method of manufacturing a liquid jet head capable of detecting a defect of a piezoelectric element more accurately at an earlier stage. is there.

A method of manufacturing a liquid jet head according to the present invention has been proposed to achieve the above object, and includes a piezoelectric element formed of a piezoelectric body sandwiched between a first electrode and a second electrode, and a nozzle. A flow path substrate having a liquid flow path including a communicating pressure chamber, and driving the piezoelectric element by applying a driving voltage to cause a pressure fluctuation in the pressure chamber, and using the pressure fluctuation A method of manufacturing a liquid ejecting head that ejects liquid from a nozzle,
Forming the piezoelectric element on the flow path substrate;
Measuring the polarization-electric field hysteresis characteristics of the piezoelectric element;
Determining pass / fail of the piezoelectric element by determining whether the polarization amount corresponding to the drive voltage is a value within the allowable polarization amount range based on the measured hysteresis characteristics;
Including
The step of determining whether or not the piezoelectric element is acceptable is performed before the step of forming the liquid channel with respect to the channel substrate.

  According to the present invention, after a piezoelectric element is manufactured, a pass / fail inspection of the piezoelectric element is performed based on polarization-electric field hysteresis characteristics before a flow path such as a pressure chamber is formed on the flow path substrate. Thus, it is possible to determine whether the piezoelectric element is good or bad at an earlier stage than before. For this reason, even if a failure of the piezoelectric element occurs, the subsequent process of forming the flow path and the like is not wasted, and it is possible to reduce the labor and cost for that. Moreover, the quality determination of the piezoelectric element can be performed with higher accuracy by determining the quality of the piezoelectric element based on the polarization amount. Therefore, by adopting the piezoelectric element determined to be acceptable as the pressure generating means of the liquid ejecting head, the amount of liquid ejected from the nozzle by driving the piezoelectric element by applying a predetermined driving voltage is within an allowable range. Guaranteed to be.

In the above configuration, a step of setting a setting range of a driving voltage for driving the piezoelectric element;
Determining an allowable polarization range corresponding to a setting range of the drive voltage;
It is desirable to perform in advance before the step of determining the pass / fail of the piezoelectric element.

Further, in the above configuration, in the step of forming the piezoelectric element, an inspection piezoelectric element to be inspected for the hysteresis characteristic is formed,
Forming a first inspection terminal portion conducting to the first electrode of the inspection piezoelectric element and a second inspection terminal portion conducting to the second electrode of the inspection piezoelectric element; desirable.

  According to the above configuration, the first inspection terminal portion that conducts to the first electrode of the inspection piezoelectric element, and the second inspection terminal portion that conducts to the second electrode of the inspection piezoelectric element. By providing, it becomes easy to measure the polarization-electric field hysteresis characteristics.

FIG. 3 is a perspective view illustrating a configuration of a printer. FIG. 3 is a diagram illustrating a configuration of a recording head. 2 is a block diagram illustrating an electrical configuration of a printer. FIG. It is a wave form diagram explaining the structure of an ejection drive pulse. It is a figure explaining the process of forming an elastic film, an insulator film, and a lower electrode on a silicon wafer. It is a schematic diagram explaining the layer structure of the lower electrode before baking. 6 is a graph showing a relationship between a drive voltage of an ejection drive pulse and the weight of ejected ink. It is a graph which shows the polarization-electric field hysteresis characteristic of a piezoelectric element. It is a graph explaining an example of the relationship between the drive voltage and polarization amount based on a hysteresis characteristic.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In the embodiments described below, various limitations are made as preferred specific examples of the present invention. However, the scope of the present invention is not limited to the following description unless otherwise specified. However, the present invention is not limited to these embodiments. In the following description, the piezoelectric element 18 used in the recording head 2 which is a kind of liquid ejecting head will be described as an example of the piezoelectric element of the present invention.

  FIG. 1 is a perspective view showing the configuration of the printer 1. The printer 1 includes a carriage 4 to which a recording head 2 is attached and an ink cartridge 3 which is a kind of liquid supply source is detachably attached, and a platen 5 disposed below the recording head 2 during a recording operation. The carriage 4 is transported in the sub-scanning direction orthogonal to the main scanning direction, and the carriage moving mechanism 7 for reciprocating the carriage 4 in the paper width direction of the recording paper 6 (a kind of landing medium or landing target), that is, the main scanning direction. And a paper feed mechanism 8 that performs the operation.

  The carriage 4 is attached while being supported by a guide rod 9 installed in the main scanning direction, and is configured to move in the main scanning direction along the guide rod 9 by the operation of the carriage moving mechanism 7. ing. The position of the carriage 4 in the main scanning direction is detected by the linear encoder 10, and the detection signal, that is, the encoder pulse is transmitted to a printer controller (not shown). The linear encoder 10 is a kind of position information output means, and outputs an encoder pulse corresponding to the scanning position of the recording head 2 as position information in the main scanning direction. For this reason, the printer controller can recognize the scanning position of the recording head 2 mounted on the carriage 4 based on the received encoder pulse. That is, for example, the position of the carriage 4 can be recognized by counting the received encoder pulses. Thus, the printer controller can control the recording operation by the recording head 2 while recognizing the scanning position of the carriage 4 (recording head 2) based on the encoder pulse from the linear encoder 10.

  A home position serving as a base point for scanning of the carriage is set in an end area outside the recording area within the movement range of the carriage 4. In the home position in the present embodiment, a capping member 11 for sealing the nozzle formation surface (nozzle formation substrate 15: see FIG. 2) of the recording head 2 and a wiper member 12 for wiping the nozzle formation surface are disposed. ing. The printer 1 is bi-directional between when the carriage 4 moves from the home position toward the opposite end and when the carriage 4 returns from the opposite end to the home position. So-called bidirectional recording in which characters, images, etc. are recorded on the recording paper 6 is possible.

  2A and 2B are diagrams illustrating a configuration of the recording head 2 according to the present embodiment, in which FIG. 2A is a plan view of the recording head 2, FIG. 2B is a cross-sectional view taken along the line AA ′ in FIG. It is BB 'sectional view taken on the line in (a). In addition, illustration of the protective substrate 19 is abbreviate | omitted in FIG.2 (c). Moreover, although the structure for four nozzles is illustrated in FIG. 2, the structure corresponding to the remaining other nozzles is also the same. The recording head 2 in this embodiment is configured by laminating a pressure chamber substrate 14, a nozzle forming substrate 15, an elastic film 16, an insulator film 17, a piezoelectric element 18, a protective substrate 19, and the like.

  The pressure chamber substrate 14 (a kind of narrow channel substrate in the present invention) is, for example, a plate material made of a silicon single crystal substrate. In the pressure chamber substrate 14, a plurality of pressure chambers 20 are arranged in parallel in the width direction (nozzle row direction) with a partition wall therebetween. A communication portion 21 is formed in a region outside the pressure chamber 20 in the longitudinal direction (direction orthogonal to the nozzle row direction) of the pressure chamber substrate 14, and the communication portion 21 and each pressure chamber 20 are provided for each pressure chamber 20. Are communicated with each other through an ink supply path 22. The communication portion 21 constitutes a part of a reservoir 30 that communicates with a reservoir portion 29 of the protective substrate 19 described later and serves as a common ink chamber for the pressure chambers 20. The ink supply path 22 is formed with a width narrower than that of the pressure chamber 20, and imparts flow path resistance to the ink flowing into the pressure chamber 20 from the communication portion 21. Channels such as the pressure chamber 20 and the ink supply channel 22 in the pressure chamber substrate 14 are formed by anisotropic etching.

On the lower surface of the pressure chamber substrate 14, a nozzle forming substrate 15 in which a plurality of nozzles 23 corresponding to each pressure chamber 20 are arranged in a line is joined. As a result, the opening on the lower surface side of the pressure chamber 20 is sealed by the nozzle forming substrate 15 and the bottom of the pressure chamber 20 is defined. An elastic film 16 made of, for example, silicon dioxide (SiO ₂ ) is formed on the upper surface of the pressure chamber substrate 14. An insulator film 17 made of zirconium oxide (ZrO ₂ ) is formed on the elastic film 16. The portion of the elastic film 16 and the insulator film 17 that seals the opening of the pressure chamber 20 functions as an operating surface. On the insulator film 17, a lower electrode 24 (corresponding to the first electrode in the present invention), a piezoelectric body 25, and an upper electrode 26 (corresponding to the second electrode in the present invention) are formed. These constitute the piezoelectric element 18 in a laminated state.

  In general, one electrode of the piezoelectric element 18 is used as a common electrode, and the other electrode (positive electrode or individual electrode) and the piezoelectric body 25 are patterned for each pressure chamber 20. A portion that is constituted by any one of the patterned electrodes and the piezoelectric body 25 and in which piezoelectric distortion is generated by applying a voltage to both electrodes is referred to as a piezoelectric active portion. In this embodiment, the lower electrode 24 is a common electrode for the piezoelectric element 18 and the upper electrode 26 is an individual electrode for the piezoelectric element 18. Therefore, it is possible to adopt a configuration in which these are entirely reversed. In any case, a piezoelectric active part is formed for each pressure chamber 20. Further, a lead electrode 27 made of, for example, gold (Au) or the like is connected to the upper electrode 26 of each piezoelectric element 18.

  In the present embodiment, among a plurality of piezoelectric elements 18 arranged in parallel corresponding to each nozzle 23, the piezoelectric element 18 positioned at one end (the piezoelectric element 18 positioned at the upper end in FIG. 2A) will be described later. It is formed as an inspection piezoelectric element 18 ′ to be inspected in the quality inspection. Regarding the inspection piezoelectric element 18 ′, the configuration of the lower electrode 24, the piezoelectric body 25, and the upper electrode 26 is the same as that of the other piezoelectric elements 18, but the first inspection terminal portion that is electrically connected to the lower electrode 24. 46 and a second inspection terminal portion 47 that is electrically connected to the upper electrode 26 via the lead electrode 27 is different from the other piezoelectric elements 18. Thus, by providing the first inspection terminal portion 46 and the second inspection terminal portion 47 of the inspection piezoelectric element 18 ′, the polarization-electric field hysteresis characteristics can be easily measured. The quality inspection for the inspection piezoelectric element 18 'will be described later.

  On the surface of the pressure chamber substrate 14 on the piezoelectric element 18 side, a protective substrate 19 having a piezoelectric element holding portion 28 that is a space having a size that does not hinder the displacement is bonded to a region facing the piezoelectric element 18. Yes. Further, the protective substrate 19 is provided with a reservoir portion 29 in a region corresponding to the communication portion 21 of the pressure chamber substrate 14. The reservoir portion 29 is formed in the protective substrate 19 as a through hole having a rectangular opening shape elongated along the direction in which the pressure chambers 20 are juxtaposed. As described above, the reservoir portion 29 is connected to the communication portion 21 of the pressure chamber substrate 14. The reservoir 30 is defined in communication. The reservoir 30 is provided for each type of ink (for each color), and common ink is stored in the plurality of pressure chambers 20.

  A through hole 31 that penetrates the protective substrate 19 in the thickness direction is provided in a region between the piezoelectric element holding portion 28 and the reservoir portion 29 of the protective substrate 19. A part and the tip of the lead electrode 27 are exposed. Further, the second inspection terminal portion 47 of the inspection piezoelectric element 18 ′ is exposed in the through hole 31. Further, in the protective substrate 19, an inspection opening 48 that exposes the inspection terminal portion 46 is formed at a position facing the first inspection terminal portion 46 of the inspection piezoelectric element 18 ′. It is formed so as to penetrate in the direction. During the pass / fail inspection, an inspection probe or the like is conducted to the first inspection terminal portion 46 and the second inspection terminal portion 47 through the through hole 31 and the inspection opening 48, respectively.

  A compliance substrate 34 including a sealing film 32 and a fixing plate 33 is bonded on the protective substrate 19. The sealing film 32 is made of a flexible material (for example, polyphenylene sulfide film), and one surface of the reservoir portion 29 is sealed by the sealing film 32. The fixing plate 33 is made of a hard material such as metal (for example, stainless steel). A region of the fixing plate 33 facing the reservoir 30 is an opening 35 that penetrates the thickness direction. For this reason, one surface of the reservoir 30 is sealed only by the flexible sealing film 32.

  In the recording head 2 configured as described above, ink is taken in from an ink supply means such as an ink cartridge and is filled with ink from the reservoir 30 to the nozzle 23. Then, by supplying a drive signal from the printer main body side, an electric field corresponding to the potential difference between the two electrodes is applied between the lower electrode 24 and the upper electrode 26 corresponding to the pressure chamber 20, and the piezoelectric element 18 and the operation surface. When the (elastic film 16) is bent and deformed, a pressure fluctuation occurs in the pressure chamber 20. By controlling the pressure fluctuation, ink is ejected from the nozzle 23, or the meniscus in the nozzle 23 is vibrated slightly to the extent that ink is not ejected.

Next, the electrical configuration of the printer 1 will be described.
FIG. 3 is a block diagram illustrating the electrical configuration of the printer 1. The external device 38 is an electronic device that handles images, such as a computer or a digital camera. The external device 38 is communicably connected to the printer 1 and transmits print data corresponding to the image or the like to the printer 1 so that the printer 1 prints an image or text on a recording medium such as recording paper.

  The printer 1 in this embodiment includes a paper feed mechanism 8, a carriage moving mechanism 7, a linear encoder 10, a recording head 2, and a printer controller 39. The printer controller 39 is a type of control means in the present invention, and is a control unit that controls each part of the printer. The printer controller 39 includes an interface (I / F) unit 40, a CPU 41, a storage unit 42, and a drive signal generation unit 43. The interface unit 40 transmits and receives printer status data such as sending print data and a print command from the external device 38 to the printer 1 and receiving the status information of the printer 1 from the external device 38. The CPU 41 is an arithmetic processing device for controlling the entire printer. The memory | storage part 42 is an element which memorize | stores the data used for the program and various control of CPU41, and contains ROM, RAM, and NVRAM (nonvolatile memory element). The CPU 41 controls each unit according to a program stored in the storage unit 42.

  The CPU 41 functions as a timing pulse generation unit that generates a timing pulse PTS from the encoder pulse EP output from the linear encoder 10. Then, the CPU 41 controls transfer of print data, generation of the drive signal COM by the drive signal generation unit 43, and the like in synchronization with the timing pulse PTS. Further, the CPU 41 generates a timing signal such as a latch signal LAT based on the timing pulse PTS and outputs the timing signal to the head control unit 53 of the recording head 2. The head controller 53 performs application control of the ejection drive pulse DP (see FIG. 4) of the drive signal COM to the piezoelectric element 18 of the recording head 2 based on the head control signal (print data and timing signal) from the printer controller 39. Do.

  The drive signal generation unit 43 functions as drive waveform generation means, and generates an analog voltage signal based on waveform data relating to the waveform of the drive signal. The drive signal generator 43 amplifies the voltage signal to generate the drive signal COM. This drive signal COM is applied to the piezoelectric element 18 which is a pressure generating means of the recording head 2 at the time of printing processing (recording processing or jetting processing) on the recording medium. 4 is a series of signals including at least one injection driving pulse DP shown in FIG. Here, the ejection drive pulse DP is for causing the piezoelectric element 18 to perform a predetermined operation so as to eject ink droplets from the nozzles 23 of the recording head 2.

  FIG. 4 is a waveform diagram showing an example of the configuration of the ejection drive pulse DP included in the drive signal COM. In FIG. 4, the vertical axis represents potential and the horizontal axis represents time. The ejection drive pulse DP has an expansion element p1 that expands the pressure chamber 20 by changing the potential from the reference potential (intermediate potential) Vb to the lowest potential (minimum voltage) Vmin lower than the reference potential Vb. An expansion maintaining element p2 that maintains the minimum potential Vmin for a certain time, and a contraction element that rapidly contracts the pressure chamber 20 by changing the potential from the minimum potential Vmin to the maximum potential (maximum voltage) Vmax that is higher than the reference potential Vb. p3, a contraction maintenance (vibration hold) element p4 for maintaining the maximum potential Vmax for a certain period of time, and a return element p5 for returning the potential from the maximum potential Vmax to the reference potential Vb. The ejection drive pulse DP in the present embodiment has a positive voltage waveform on average, but the minimum potential Vmin is −2 [V] lower than 0 volts. That is, the ejection drive pulse DP has a waveform that partially shows a negative value in relation to the bias voltage applied to the lower electrode 24. Of course, the minimum potential Vmin may be 0 volt or more.

  When the ejection driving pulse DP is applied to the piezoelectric element 18, it operates as follows. First, the expansion element p1 causes the central portion in the width direction of the operating portion of the piezoelectric element 18 and the elastic film 16 to bend toward the outside of the pressure chamber 20 (side away from the nozzle forming substrate 15). Along with this, the pressure chamber 20 expands from the reference volume corresponding to the reference potential Vb to the maximum volume corresponding to the lowest potential Vmin. Thereby, the meniscus exposed to the nozzle 23 is drawn into the pressure chamber side. The expansion state of the pressure chamber 20 is maintained constant throughout the application period of the expansion maintaining element p2. When the contraction element p3 is applied to the piezoelectric element 18 subsequent to the expansion maintaining element p2, the piezoelectric element 18 and the central portion of the operating portion bend to the inside of the pressure chamber 20 (side adjacent to the nozzle forming substrate 15). As a result, the pressure chamber 20 rapidly contracts from the maximum volume to the minimum volume corresponding to the maximum potential Vmax. The ink in the pressure chamber 20 is pressurized by the rapid contraction of the pressure chamber 20, and thereby, from the nozzle 23, dozens of ng to several tens of ng of ink is ejected. The contraction state of the pressure chamber 20 is maintained for a short time over the application period of the contraction maintaining element p4, and then the damping element p5 is applied to the piezoelectric element 18 so that the pressure chamber 20 has a volume corresponding to the minimum potential Vmin. To the reference volume corresponding to the reference potential Vb.

Next, a method for manufacturing the piezoelectric element 18 will be described.
FIG. 5 is a diagram for explaining the steps until the elastic film 16, the insulator film 17, and the lower electrode 24 are formed on the silicon wafer 51 that is the base material of the pressure chamber substrate 14. FIG. 6 is a diagram illustrating a process from patterning to each piezoelectric element 18 until a protective film is formed. In FIG. 6, constituent members (nozzle forming substrate 15, pressure chamber substrate 14, elastic film 16, and insulator film 17) below the lower electrode 24 are used as a substrate 54 (a kind of channel substrate in a broad sense). It is shown.

  First, as shown in FIG. 5A, the silicon wafer 51 is thermally oxidized, and a silicon dioxide film 52 constituting the elastic film 16 is formed on the surface thereof. Subsequently, as shown in FIG. 5B, an insulator film 17 made of zirconium oxide is formed on the elastic film 16. Specifically, first, a zirconium layer is formed on the elastic film 16 by, for example, DC sputtering, and this zirconium layer is thermally oxidized to form an insulator film 17 made of zirconium oxide. Next, as shown in FIG. 5C, a lower electrode precursor that becomes the lower electrode 24 is formed on the insulator film 17.

  Once the lower electrode 24 is formed, next, as shown in FIG. 6A, for example, a piezoelectric body 25 (piezoelectric precursor) made of lead zirconate titanate (PZT) and, for example, iridium After the upper electrode 26 (upper electrode precursor) to be formed is sequentially formed on the lower electrode 24 (lower electrode precursor), patterning is performed in a region facing each pressure chamber 20 as shown in FIG. Thus, the piezoelectric element 18 is formed. In this embodiment, the piezoelectric body 25 is formed by a so-called sol-gel method in which a so-called sol in which a metal organic material is dissolved and dispersed in a solvent is applied and dried to form a metal oxide by baking it at a high temperature. The piezoelectric body 25 is formed using In addition, the formation method of the piezoelectric body 25 is not specifically limited, For example, MOD method, sputtering method, etc. can also be used.

  When the piezoelectric element 18 is formed in this way, a flow path (corresponding to a liquid flow path in the present invention) such as the pressure chamber 20 is formed on the silicon wafer 51 which is the base material of the pressure chamber substrate 14. Before and after the inspection, the piezoelectric element 18 is checked for quality. In this pass / fail inspection, when the piezoelectric element 18 is driven by the ejection drive pulse DP, a specified amount (weight or volume targeted in design or specification) of ink is ejected from the nozzle 23 of the recording head 2. This is an inspection to determine whether or not. The drive voltage of the ejection drive pulse DP in the present embodiment is set to a value within a certain range. For this reason, the amount (weight or volume) of ink ejected from the nozzle 23 when the piezoelectric element 18 is driven by applying the ejection driving pulse DP set to the driving voltage within this range is within the allowable range in the specification. It is desirable that the value be within the above range, more preferably the above-mentioned prescribed amount. If the amount of ink within the allowable range is not ejected, it is necessary to remove it from the production line as a defective product.

  In this embodiment, as a representative of the piezoelectric elements 18 corresponding to one nozzle row, hysteresis of polarization (P) -electric field (E) is measured for the above-described inspection piezoelectric element 18 ', and the amount of polarization is measured. A pass / fail determination is made based on the result. Here, there is a correlation between the amount of polarization of the piezoelectric element 18 and the amount of displacement (the magnitude of electrostriction) of the piezoelectric element 18. That is, the greater the amount of polarization, the greater the displacement when a constant drive voltage is applied, so more ink can be ejected. In other words, as the amount of polarization of the piezoelectric element 18 increases, a certain amount of ink can be ejected with a lower driving voltage. Therefore, based on the polarization amount of the piezoelectric element 18, it is possible to estimate the displacement amount when a certain voltage is applied, that is, the ink ejection amount. Hereinafter, the quality determination of the piezoelectric element 18 will be described more specifically.

  FIG. 7 is a graph showing the relationship between the drive voltage ΔV (from the lowest potential to the highest potential) of the ejection drive pulse DP and the weight of ink ejected from the nozzles 23 when the piezoelectric element 18 is driven by the ejection drive pulse DP. It is. In the figure, the horizontal axis represents the drive voltage ΔV [V], and the vertical axis represents the ink weight Iw [ng]. In the printer 1 according to the present embodiment, the drive voltage ΔV of the ejection drive pulse DP is determined in advance within a certain setting range (Vh1 ≦ ΔV ≦ Vh2). Further, the specified amount of ink targeted for the specification is IwX. The ink ejected when the piezoelectric element 18 is driven using the ejection drive pulse DP having the drive voltage in the above setting range is, for example, a range of ± 3% of the specified amount IwX (IwX (−) ≦ Iw ≦ IwX In the case of (+)), the pass / fail judgment is made so that the pass is accepted, while the pass / fail is judged to be rejected if it falls outside the allowable range. The setting range of the drive voltage of the ejection drive pulse DP and the allowable range of the ink amount can be arbitrarily determined according to the specifications of the printer.

FIG. 8 is a graph showing an example of polarization-electric field hysteresis characteristics of the piezoelectric element 18. In the figure, the horizontal axis represents the electric field [V / mm], and the vertical axis represents the polarization amount [C / cm ² ]. For the measurement of the hysteresis characteristic, for example, a triangular wave set to a driving voltage having a magnitude that includes at least the value of the setting range of the driving voltage ΔV is used. This triangular wave is applied to the piezoelectric body 25 through the first inspection terminal portion 46 and the second inspection terminal portion 47 of the inspection piezoelectric element 18 ′. For measuring the polarization-electric field hysteresis of the piezoelectric element 18, various existing methods can be used. In addition, the portion indicated by a thick line in the hysteresis curve of FIG. 8 is the use range when ink is ejected by the printer 1.

  Based on the measured hysteresis characteristics, a polarization amount Pmin corresponding to the lowest potential Vmin of the ejection drive pulse DP and a polarization amount Pmax corresponding to the highest potential Vmax are acquired, and a difference ΔP is calculated. Specifically, ΔP1 corresponding to the minimum value Vh1 of the specified range of the drive voltage ΔV and ΔP2 corresponding to the maximum value Vh2 of the specified range of the drive voltage ΔV are respectively obtained. Then, it is determined whether or not these ΔP1 and ΔP2 are values within an allowable range.

FIG. 9 is a graph for explaining an example of the relationship between ΔV and ΔP based on the hysteresis characteristic. In the figure, the horizontal axis is ΔV [V], and the vertical axis is ΔP [C / cm ² ]. Further, ΔP (−) represents the lower limit value of the allowable range of ΔP, and ΔP (+) represents the upper limit value of the allowable range of ΔP. The lower limit value and upper limit value of the allowable range of ΔP are determined in advance from the relationship between the polarization amount, the displacement amount of the piezoelectric element 18 and the ink ejection amount. As shown in the figure, both ΔP1 corresponding to the minimum value Vh1 of the specified range of the drive voltage ΔV and ΔP2 corresponding to the maximum value Vh2 of the specified range of the drive voltage ΔV are values within the allowable range of ΔP. If the piezoelectric element 18 is found, the piezoelectric element 18 is determined to be acceptable. On the other hand, either or both of ΔP1 corresponding to the minimum value Vh1 of the specified range of the drive voltage ΔV and ΔP2 corresponding to the maximum value Vh2 of the specified range of the drive voltage ΔV are values within the allowable range of ΔP. In the case of failure, the piezoelectric element 18 is determined to be unacceptable.

  If the pass / fail inspection of the piezoelectric element 18 is performed as described above, the subsequent steps are performed for the recording head 2 (head unit) having the test piezoelectric element 18 'determined to be acceptable. The protective substrate 19 is bonded onto the substrate 54 on which the piezoelectric element 18 is formed in a state where the piezoelectric element 18 is accommodated in the piezoelectric element holding portion 28. In this state, the pressure chamber 20 is formed by anisotropic etching from the lower surface side of the pressure chamber substrate 14. Next, the nozzle plate 22 is bonded to the lower surface of the pressure chamber substrate 14 with an adhesive. Next, in this state, wiring of a flexible cable (not shown) is performed to the electrode terminal of each piezoelectric element 18 through the through hole 31 of the protective substrate 19. Thereafter, a case (not shown) is joined to the upper surface side of the protective substrate 19 to form a unit. A plurality of these units (head units) are combined to form the recording head 2.

  In this way, after the piezoelectric element 18 is manufactured, before the flow path such as the pressure chamber 20 is formed on the silicon wafer 51 which is the base material of the pressure chamber substrate 14, the polarization-electric field hysteresis characteristic is based. As a result, the quality of the piezoelectric element 18 can be determined at an earlier stage than before. For this reason, even if a failure of the piezoelectric element 18 occurs, the subsequent process of forming the flow path and the like is not wasted, and it is possible to reduce the labor and cost for that. In addition, the quality of the piezoelectric element 18 (inspection piezoelectric element 18 ') can be determined with higher accuracy by determining the quality of the piezoelectric element 18 based on the amount of polarization. Therefore, in the recording head 2 manufactured through the above manufacturing process, it is guaranteed that the amount of ink ejected from the nozzle 23 by driving the piezoelectric element 18 by applying the ejection driving pulse DP is within an allowable range. The

  By the way, the present invention is not limited to the above-described embodiment, and various modifications can be made based on the description of the scope of claims.

  For example, in the above embodiment, a setting range is set in advance for the drive voltage ΔV of the ejection drive pulse DP, and the piezoelectric element depends on whether or not the polarization value ΔP corresponding to the upper and lower limit values of the setting range falls within the allowable range. Although the example of performing the pass / fail judgment of 18 has been shown, the present invention is not limited to this. For example, the drive voltage ΔV of the ejection drive pulse DP is predetermined as a specific value, and whether the piezoelectric element 18 is good or not depends on whether the polarization value ΔP corresponding to the specific drive voltage ΔV falls within the allowable range. It is also possible to make a determination. As described above, when the drive voltage ΔV is determined to be a specific value, the quality determination of the piezoelectric element 18 can be performed more easily and quickly.

  Further, for example, an approximate appropriate value (provisional value) of the drive voltage ΔV can be obtained based on the hysteresis characteristic of the piezoelectric element 18 described above. That is, the drive voltage ΔV (lower limit value Vmin and upper limit value Vmax) corresponding to the allowable polarization amount range in which the target ink ejection characteristic is obtained is obtained from the hysteresis characteristic, and the obtained drive voltage ΔV is used as the ejection drive pulse DP. Can be set as a provisional value. Based on this provisional value, the process of determining the appropriate voltage of the ejection drive pulse DP after assembling as the recording head 2 can be performed easily and quickly.

  In each of the above-described embodiments, the piezoelectric element 18 used as the pressure generating unit of the recording head 2 that ejects ink is exemplified as the piezoelectric element in the present invention. However, the present invention is not limited to this. For example, a color material ejection head for a display manufacturing apparatus that ejects a solution of each color material of R (Red), G (Green), and B (Blue), and an electrode material ejection for an electrode forming apparatus that ejects a liquid electrode material The present invention can also be applied to a piezoelectric element used in a head or a bioorganic matter ejecting head for a chip manufacturing apparatus that ejects a solution of a bioorganic matter.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 2 ... Recording head, 16 ... Elastic film, 17 ... Insulator film, 18 ... Piezoelectric element, 18 '... Inspection piezoelectric element, 24 ... Lower electrode, 25 ... Piezoelectric body, 26 ... Lower electrode, 40 ... Substrate , 46 ... 1st inspection terminal part, 47 ... 2nd inspection terminal part

Claims (3)

A piezoelectric element comprising a piezoelectric body sandwiched between a first electrode and a second electrode; and a flow path substrate on which a liquid flow path including a pressure chamber communicating with the nozzle is formed, and applying a drive voltage The piezoelectric element is driven to cause a pressure fluctuation in the pressure chamber, and a liquid ejecting head is produced by ejecting a liquid from the nozzle using the pressure fluctuation,
Forming the piezoelectric element on the flow path substrate;
Measuring the polarization-electric field hysteresis characteristics of the piezoelectric element;
Determining pass / fail of the piezoelectric element by determining whether the polarization amount corresponding to the drive voltage is a value within the allowable polarization amount range based on the measured hysteresis characteristics;
Including
The method of manufacturing a liquid jet head, wherein the step of determining whether or not the piezoelectric element is acceptable is performed before the step of forming the liquid flow path with respect to the flow path substrate. Setting a drive voltage setting range for driving the piezoelectric element;
Determining an allowable polarization range corresponding to a setting range of the drive voltage;
The method of manufacturing a liquid jet head according to claim 1, wherein the step is performed in advance before the step of determining whether the piezoelectric element is acceptable. In the step of forming the piezoelectric element, forming an inspection piezoelectric element to be inspected for the hysteresis characteristic,
Forming a first inspection terminal portion conducting to the first electrode of the inspection piezoelectric element and a second inspection terminal portion conducting to the second electrode of the inspection piezoelectric element; The method of manufacturing a liquid jet head according to claim 1, wherein the liquid jet head is a liquid ejecting head.

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