JP4187776B1 - Ink jet head adhesion failure determination method, ink jet head manufacturing method, and image forming apparatus manufacturing method - Google Patents

Abstract

The present invention determines whether or not there is an adhesion failure of an inkjet head with high accuracy without being affected by the connection state between a measurement terminal and a set of input / output terminals.
A measurement step and a determination step are performed on an inkjet head. In the measurement step, the anti-resonance frequency due to the set of input / output terminals of each adjacent ink chamber is measured for the plurality of sets of input / output terminals. In the determination step, the presence / absence of adhesion failure between the plurality of members is determined based on the variation in the anti-resonance frequency measured in the measurement step.
[Selection] Figure 4

Description

  The present invention relates to a method for determining the presence or absence of adhesion failure of an inkjet head such as a share mode inkjet head, a method for manufacturing an inkjet head, and a method for manufacturing an image forming apparatus.

  An ink jet head using a shear mode deformation of a piezoelectric material (hereinafter referred to as a shear mode ink jet head) includes an ink chamber, and applies pressure to the ink in the ink chamber using the shear mode deformation. The ink chamber is provided with a piezoelectric element wall having drive electrodes on both sides. When drive power is supplied to the drive electrode from the input / output terminal, shear mode deformation occurs in the piezoelectric element wall, the volume of the ink chamber changes, and pressure is applied to the ink.

  By the way, in an inkjet head having a large number of nozzles, it is necessary that the ejection characteristics of each nozzle are as uniform as possible. Here, the ejection characteristics include ejection speed, droplet amount, ejection direction, and the like. For example, if there are nozzles with significantly different droplet amounts, the amount of droplets attached will be significantly different from the others where the droplets ejected from those nozzles land, resulting in image quality in image printing and device production. Device performance will be greatly impaired.

  The piezoelectric element wall of the inkjet head is bonded to another member. When adhesion failure occurs in the bonded portion, the ejection characteristics between the ink chambers also vary. Therefore, the presence or absence of adhesion failure in the inkjet head may be inspected based on the characteristic change in the piezoelectric circuit formed between the input / output terminals of the adjacent ink chambers (see, for example, Patent Documents 1 and 2).

  In the technique of Patent Document 1, a measurement terminal such as an impedance analyzer is connected between input / output terminals provided at both ends of a piezoelectric element, and the impedance of the piezoelectric circuit is measured. Then, the harmonic frequency of the piezoelectric circuit is acquired. In a piezoelectric circuit having a low harmonic frequency, it is determined that an adhesion failure has occurred in the bonded portion.

In the technique of Patent Document 2, the impedance of the piezoelectric circuit with respect to an input signal having a predetermined frequency is acquired. Then, it is determined that electrical and mechanical damage has occurred in the ink chamber having a large variation from the specified impedance.
JP-A-11-64175 JP 2001-138514 A

  When determining the presence or absence of adhesion failure using an impedance analyzer or the like, the measurement terminal of the impedance analyzer is connected to the input / output terminal of the inkjet head. Depending on these connection states, the impedance of the piezoelectric circuit may change.

  The harmonic frequency fluctuates greatly due to this change in the connection state, and when determining the presence or absence of adhesion failure with high accuracy based on the harmonic frequency, the impedance analyzer measurement terminal is connected to the inkjet head input / output terminal. It was necessary to connect without any variation. If there is a slight shift in the connection position between the input / output terminal and the measurement terminal or a small difference in the terminal shape, the harmonic frequency will fluctuate greatly even if the same terminal is used.

  SUMMARY OF THE INVENTION An object of the present invention is to suppress the influence of the connection state between the input / output terminal and the measurement terminal and determine the presence or absence of adhesion failure with high accuracy, and a method for determining the adhesion failure of the inkjet head and a method for manufacturing the inkjet head And an image forming apparatus manufacturing method.

  The ink jet head includes a plurality of piezoelectric element walls, a plurality of adhesive portions, and a plurality of drive electrodes. The plurality of piezoelectric element walls are provided between the top plate and the bottom plate, respectively, and are bonded to other members including at least the top plate member by an adhesive portion to partition the plurality of ink chambers. The plurality of drive electrodes are provided in each of the plurality of ink chambers.

  A measurement step and a determination step are performed on the ink jet head to determine whether there is a connection failure between the constituent members. In the measurement step, the anti-resonance frequency of the piezoelectric circuit formed by each piezoelectric element wall and the drive electrode opposed via the piezoelectric element wall is measured for each set of drive electrodes in the adjacent ink chamber. In the determination step, the presence / absence of adhesion failure in each adhesion portion is determined based on the variation in the anti-resonance frequency measured in the measurement step.

  The inkjet head is manufactured through an adhesion process and an adhesion failure determination process. In the bonding step, each of the plurality of piezoelectric element walls is bonded to another member including at least the top plate member by an adhesive portion. In the mounting failure determination process, a measurement step and a determination step are performed.

  The image forming apparatus is manufactured through an adhesion process, an adhesion failure determination process, and a mounting process. In the mounting step, the ink jet head that has been determined to have been satisfactorily bonded to the plurality of mounting portions in the adhesion failure determination step is mounted on the ink jet mounting portion of the image forming apparatus.

  In the determination step, the variation in the anti-resonance frequency may be calculated based on the average value, the maximum value, and the minimum value of the anti-resonance frequency measured in the measurement step.

  In the determination step, when the anti-resonance frequency of each piezoelectric circuit is within a predetermined range including the average value of the anti-resonance frequencies measured in the measurement step, it may be determined that the adhesion of the bonding portion is good.

  In the measurement step, a measurement signal may be input to each piezoelectric circuit while sweeping the frequency, and an impedance change may be grasped from a response signal to the measurement signal to measure the anti-resonance frequency.

  According to the present invention, it is possible to determine the presence or absence of adhesion failure of the inkjet head with high accuracy without being affected by the connection state between the input / output terminal and the measurement terminal.

  A configuration example of the ink jet head will be described below. This ink-jet head is a share mode ink-jet head that can be easily multi-channeled and can easily produce a high-density ink-jet head.

FIG. 1 is a perspective view showing each stage in the manufacturing process of a shear mode type ink jet head. First, as shown in FIG. 1A, an upper piezoelectric element plate 12 is bonded on a lower piezoelectric element plate 11 with an adhesive. Adhere using. Each of the lower piezoelectric element plate 11 and the upper piezoelectric element plate 12 is made of PZT (lead zirconate titanate), which is a general piezoelectric material, and is vertically polarized in the groove depth direction. The lower piezoelectric element plate 11 is polarized so that the downward direction in the thickness direction is positive and the upward direction is negative. The upper piezoelectric element plate 12 is positive in the upward direction in the thickness direction and negative in the downward direction. It is polarized to become. In this way, by bonding the lower piezoelectric element plate 11 and the upper piezoelectric element plate 12 with the polarization directions being reversed, one piezoelectric element 10 having a different polarization direction with respect to the bonding surface is obtained.

  Next, as shown in FIG. 2B, dicing is performed from the front surface to the back surface of the piezoelectric element 10 to a depth extending from the upper surface side to the lower piezoelectric element plate 11. This dicing is performed a plurality of times in parallel to form a plurality of grooves. Each groove forms an ink chamber 21.

  Next, as shown in FIG. 3C, a metal film is formed inside the plurality of ink chambers 21 by a sputtering method, whereby independent drive electrodes 31 are formed for each ink chamber 21. Although not shown, the rear end side of the ink chamber 21 is partially filled with an adhesive, and the drive electrode 31 on the rear end side of the adhesive is used as an input / output terminal.

  Next, as shown in FIG. 4D, dicing is performed at a depth extending from the upper surface side to the lower piezoelectric element plate 11 between both side surfaces of the piezoelectric element 10. By dicing the front end side of the ink chamber 21 from the position filled with the adhesive, a common ink chamber 22 communicating with the plurality of ink chambers 21 is formed.

  Next, as shown in FIG. 5E, the top plate 13 is bonded to the upper surface of the piezoelectric element 10 using an adhesive.

  Next, as shown in FIG. 2F, the nozzle plate 14 is bonded to the front surface of the piezoelectric element 10 with an adhesive. A plurality of nozzle holes 23 communicating with the respective ink chambers 21 are formed in the nozzle plate 14.

  FIG. 2A is a perspective view of the share mode type ink jet head. In the figure, a part of the nozzle plate 14 is omitted for explanation. FIG. 2B shows a cross-sectional view of this share mode type ink jet head.

  The inkjet head 100 includes a piezoelectric element 10, a top plate 13, and a nozzle plate 14. The piezoelectric element 10 includes a bottom plate portion 15 and a plurality of piezoelectric element wall portions 16. The bottom plate portion 15 is a rectangular flat plate portion. The plurality of piezoelectric element wall portions 16 are portions that extend in parallel from the front surface to the back surface of the inkjet head 100 and stand on the upper surface of the bottom plate portion 15. The top plate 13 is a rectangular flat plate-like member and is bonded to the upper surface of each of the plurality of piezoelectric element wall portions 16. The nozzle plate 14 is bonded to the front side surfaces of the piezoelectric element 10 and the top plate 13. The piezoelectric element wall portion 16 constitutes the piezoelectric element wall of the present invention. A drive electrode 31 is formed in the ink chamber 21. The rear end side of the ink chamber 21 is partially filled with an adhesive 33, and the input / output terminal 32 of the present invention is configured by an electrode on the rear end side of the adhesive 33.

  The ink jet head 100 is an image forming apparatus (not shown) when it is determined that the nozzle plate 14 is bonded well after the bonding failure determination apparatus determines the bonding failure between the members after the nozzle plate 14 is bonded. It will be mounted on the inkjet head mounting section.

  After mounting on the inkjet head mounting portion, the drive electrode 31 is connected to the drive circuit of the image forming apparatus via the input / output terminal 32, and an individual drive signal is applied from the drive circuit. The common ink chamber 22 is connected to an ink tank of an image forming apparatus (not shown) via a supply tube, and receives ink from the ink tank.

  FIG. 3 is a diagram for explaining the deformation of the ink chamber by the drive signal. FIG. 4A shows a static state where no drive signal is applied, FIG. 5B shows a state where a positive drive signal is applied, and FIG. 4C shows a negative potential. A state in which a drive signal is applied is shown.

  The arrows shown in the figure indicate the polarization direction of the piezoelectric element wall. That is, the upper side (upper piezoelectric element plate) of the piezoelectric element walls 16A and 16B is positive in the upper direction and negative in the lower direction, and the lower side (lower piezoelectric element plate) is negative in the upper direction and positive in the lower direction. Is polarized.

  At the time of stabilization shown in FIG. 4A, the drive electrodes 31A to 31C of the ink chambers 21A to 21C are grounded, and the piezoelectric element wall portion 16A and the piezoelectric element wall portion 16B are not deformed.

  In the state shown in FIG. 5B, a positive potential is applied as a drive signal to the drive electrode 31B of the ink chamber 21B, and the drive electrodes 31A and 31C of the ink chambers 21A and 21C on both sides thereof are grounded. In this state, an electric field is applied to the piezoelectric element wall portion 16A and the piezoelectric element wall portion 16B, and each of them undergoes shear mode deformation, thereby expanding the volume of the ink chamber 21B. As a result, ink flows from the common ink chamber 22 into the ink chamber 21B.

  In the state shown in FIG. 5C, a negative potential is applied as a drive signal to the drive electrode 31B of the ink chamber 21B, and the drive electrodes 31A and 31C of the ink chambers 21A and 21C on both sides thereof are grounded. In this state, an electric field in the opposite direction to that shown in FIG. 5B is applied to the piezoelectric element wall portion 16A and the piezoelectric element wall portion 16B, and each of them undergoes shear mode deformation in the opposite direction, and the volume of the ink chamber 21B contracts. The pressure applied to the ink is increased by the volume change of the ink chamber 21, and ink droplets are ejected from the nozzle hole 23 of the ink chamber 21B.

  Now, in the manufacturing process of the inkjet head 100, the adhesion failure determination process which determines the presence or absence of adhesion failure is performed.

  FIG. 4 is a diagram for explaining an adhesion failure determination step.

  In the adhesion failure determination step, an impedance analyzer 101 and an analyzer 102 are used as shown in FIG. A measurement terminal of the impedance analyzer 101 is connected to a piezoelectric circuit formed between the two ink chambers via a set of input / output terminals of two adjacent ink chambers of the inkjet head 100. In this state, the measurement signal is output from the impedance analyzer while sweeping the frequency, and this set of frequency-impedance characteristics is obtained from the response signal to the measurement signal. The sweep frequency range of the measurement signal is a range including the anti-resonance frequency.

  The impedance analyzer 101 outputs frequency-impedance characteristic data of the piezoelectric circuit to the analyzer 102 every time one measurement is completed. Then, the set of input / output terminals that connect the measurement terminals of the impedance analyzer 101 is shifted by one, and the frequency-impedance characteristics of the next set are measured. In this way, the frequency-impedance characteristics of all sets of piezoelectric circuits are obtained. These frequency-impedance characteristic data are analyzed by the analyzer 102.

  An example of frequency-impedance characteristics is shown in FIG. Line No. 1 and line no. 2 is a measurement result with respect to another piezoelectric circuit constituting the same share mode type ink jet head. In this figure, line No. 1 and line no. In any of the two groups, a resonance frequency that is a minimum point of impedance is located in the vicinity of a frequency of 1900 kHz to 2000 kHz. Line No. 1 and line no. In both sets, the anti-resonance frequency which is the maximum point of the impedance is located in the vicinity of the frequency of 2120 kHz.

  The impedance measurement is performed by connecting the measurement terminal of the impedance analyzer 101 to the input / output terminal set of the inkjet head, and the impedance value varies greatly depending on the connection impedance between the measurement terminal and the input / output terminal set. For this reason, even if the measurement is performed on the same set of input / output terminals, the characteristics of the piezoelectric circuit change each time the terminal connection is made again.

  Among the characteristics of the piezoelectric circuit, the resonance frequency varies, but the frequency value of the anti-resonance frequency shows a sharp peak compared to the resonance frequency, and if there is no adhesion failure, it hardly changes and can be clearly grasped. If there is an adhesion failure, some variation is indicated.

  On the other hand, since the frequency value of the resonance frequency shows only a peak where the impedance change is dull, it cannot be clearly determined regardless of the presence or absence of adhesion failure.

  The line No. shown in FIG. 1 and line no. In the frequency-impedance characteristic example 2 and the anti-resonance frequency match, the resonance frequency differs by about 50 kHz. As described above, the anti-resonance frequency hardly varies as long as it is a set of input / output terminals that constitute the same ink jet head and do not have poor adhesion.

  If the anti-resonance frequency is obtained for all the input / output terminal groups, the variation can be obtained. Therefore, the analyzer 102 obtains the variation in the anti-resonance frequency based on all the frequency-impedance characteristic data. In the analysis apparatus 102, it is determined that an inkjet head having a variation in anti-resonance frequency smaller than a predetermined threshold is an object that does not have poor adhesion, and an inkjet head in which the variation in anti-resonance frequency exceeds a predetermined range is determined. It is determined that the bonding failure has occurred. The variation of the anti-resonance frequency may be calculated based on the average value, the maximum value, and the minimum value of the anti-resonance frequency measured in the measurement step. At this time, it is preferable to determine that the adhesion is good when the antiresonance frequencies of each set fall within a certain range of the average value of the antiresonance frequencies.

  Note that this adhesion failure determination step can be automated. For example, the connection between each set of input / output terminals and the impedance analyzer 101 may be automatically switched using a switch for measurement. Further, the variation may be automatically obtained from all the obtained anti-resonance frequencies, and an inkjet head having a small variation in the anti-resonance frequency may be automatically selected and mounted on the image forming apparatus.

  Next, FIG. 4C shows the result of an experiment for determining the presence or absence of actual adhesion failure. In this experiment, the dispersion of the anti-resonance frequency and the resonance frequency of a plurality of share mode ink-jet heads having the same shape and different ejection characteristics of the inkjet head, specifically, the ejection speed and the ejection amount are different. Variation was calculated. For measurement, “4294A Precision Impedance Analyzer” manufactured by Agilent Technologies was used. As a value representing the variation of the resonance frequency, a value obtained by dividing the difference between the maximum value and the minimum value of the resonance frequency by the average value was used. Similarly, as the value representing the variation in the antiresonance frequency, a value obtained by dividing the difference between the maximum value and the minimum value of the antiresonance frequency by the average value was used.

  The share mode type ink jet head A is a representative example of the share mode type ink jet head in which the variations in the discharge speed and the discharge amount are both less than the standard reference value. The share mode inkjet head B is a representative example of the share mode inkjet head in which the variation in the ejection speed (or ejection amount) is greater than the standard reference value and less than the limit reference value. The share mode type ink jet head C is a representative example of the share mode type ink jet head in which the variation in the discharge speed (or discharge amount) is equal to or greater than the standard reference value.

  As shown in FIG. 4C, all the ink jet heads have a large variation in resonance frequency compared to the anti-resonance frequency. Further, in the share mode type inkjet head A, the variation of the anti-resonance frequency was 0.9%. Further, in the share mode type ink jet head B, the variation in anti-resonance frequency was 1.3%. Further, in the share mode type ink jet head C, the variation in anti-resonance frequency was 1.5%.

  In the shear mode type ink jet head having the shape used in this experiment, when the variation in the anti-resonance frequency was less than about 1.0%, the variation in the ejection characteristics was less than the set standard reference value, which was extremely small. . In addition, when the variation in the anti-resonance frequency is less than about 1.4%, the variation in the ejection characteristics is less than the set limit reference value, and falls within a certain range. In addition, when the variation in the anti-resonance frequency is about 1.4% or more, the variation in the ejection characteristics exceeds the set limit reference value, which is inappropriate for mounting on the image forming apparatus. . On the other hand, in the variation of the resonance frequency, although a certain degree of correlation is observed, it is difficult to obtain a clear determination reference value.

  As described above, in the share mode type ink jet head, by using the ink jet head in which the variation in the anti-resonance frequency of the set of input / output terminals is below a certain level, the ejection characteristics for each nozzle are within a certain range, and the variation in the ejection characteristics is small. It turns out that an inkjet head is obtained.

  If the nozzle hole is redundant and can be used as an inkjet head even if the nozzle hole related to the input / output terminal group having a large variation is excluded, the input / output terminal group having a large variation in anti-resonance frequency is used. By setting such nozzle holes not to be used, it is also possible to obtain an ink jet head whose variation is within a certain range within the use range.

  In the present embodiment, the description has been given based on the ink jet head having the configuration in which the groove direction of the ink chamber and the discharge direction of the droplet are the same, but the present invention is not limited thereto. For example, as shown in FIG. 5A, the droplet ejection direction may be perpendicular to the direction of the ink chamber groove.

  Further, in the present embodiment, the description has been made based on the ink jet head having a structure in which the polarization direction of the piezoelectric element wall has two different directions, but the present invention is not limited thereto. For example, the structure shown in FIG. 5B in which the direction of polarization of PZT is unidirectional and the electrode is formed in only approximately half in the groove depth direction may be used. Omitted).

  Alternatively, the piezoelectric element wall has one direction of polarization, and electrodes are formed only on approximately 1/3 from the bottom surface of the groove and approximately 1/3 from the top surface of the groove, as shown in FIG. 5C. (Although part of the nozzle plate is also omitted in the figure). In this case as well, the piezoelectric element wall is deformed by forming a potential difference between the two electrodes sandwiching the piezoelectric element wall, but the direction of the potential is opposite between the bottom electrode and the top electrode of the groove. The potential of the ink chamber is increased or decreased to increase or decrease the volume of the ink chamber.

  In this embodiment, PZT is used as the piezoelectric material. However, the present invention is not limited to this, and other piezoelectric materials may be used.

  Finally, the description of the above-described embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

It is a figure which shows the structural example of an inkjet head. It is a figure explaining the manufacturing process of an inkjet head. It is a figure explaining the discharge operation of an inkjet head. It is a figure explaining the determination process of the adhesion state of an inkjet head. It is a figure which shows the other structural example of an inkjet head.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Piezoelectric element 11 ... Lower piezoelectric element 12 ... Upper piezoelectric element 13 ... Top plate 14 ... Nozzle plate 15 ... Bottom plate part 16 ... Piezoelectric element wall part 21 ... Ink chamber 22 ... Common ink chamber 23 ... Nozzle hole 31 ... Drive electrode 32 ... Input / output terminal 33 ... Adhesive 100 ... Inkjet head 101 ... Impedance analyzer 102 ... Analyzer

Claims (6)

A plurality of piezoelectric element walls that stand between the top plate and the bottom plate and are bonded to other members including at least the top plate member by an adhesive portion to partition the plurality of ink chambers, and provided in each of the plurality of ink chambers The anti-resonance frequency of the piezoelectric circuit formed by each piezoelectric element wall and the driving electrode facing through the piezoelectric element wall is determined for each pair of driving electrodes in adjacent ink chambers. A measurement step to measure,
A determination step of determining the presence or absence of adhesion failure in each of the plurality of adhesion portions based on variations in the anti-resonance frequency of each piezoelectric circuit measured in the measurement step;
Ink jet head adhesion failure determination method for performing the steps in this order.   2. The inkjet head adhesion failure determination according to claim 1, wherein the determination step calculates a variation in the anti-resonance frequency based on an average value, a maximum value, and a minimum value of the anti-resonance frequency measured in the measurement step. Method.   In the determination step, when the anti-resonance frequency of each piezoelectric circuit falls within a certain range including the average value of the anti-resonance frequency measured in the measurement step, the step of determining that the adhesion of the bonding portion is good The adhesion failure determination method for an ink jet head according to claim 1 or 2.   The measurement step is a step of inputting a measurement signal to each piezoelectric circuit while sweeping the frequency, grasping an impedance change from a response signal to the measurement signal, and measuring the anti-resonance frequency. Item 4. A method for determining adhesion failure of an inkjet head according to any one of Items 1 to 3. For an inkjet head comprising a plurality of piezoelectric element walls standing between a top plate and a bottom plate and partitioning a plurality of ink chambers, and a plurality of drive electrodes provided in each of the plurality of ink chambers, An adhesion step of adhering each of the plurality of piezoelectric element walls to other members including at least a top plate member by an adhesion portion;
A measurement step for measuring the anti-resonance frequency of the piezoelectric circuit by each piezoelectric element wall and the drive electrode facing through the piezoelectric element wall for each set of drive electrodes in the adjacent ink chamber, and each measurement step A determination step of determining whether or not there is a bonding failure in each of the plurality of bonding portions based on variations in the anti-resonance frequency of the piezoelectric circuit;
A method of manufacturing an ink jet head in which the steps are performed in this order. For an inkjet head comprising a plurality of piezoelectric element walls standing between a top plate and a bottom plate and partitioning a plurality of ink chambers, and a plurality of drive electrodes provided in each of the plurality of ink chambers, Adhering step of adhering each of the plurality of drive electrodes to other members including at least the top plate member with an adhesive portion;
A measurement step for measuring the anti-resonance frequency of the piezoelectric circuit by each piezoelectric element wall and the drive electrode facing through the piezoelectric element wall for each set of drive electrodes in the adjacent ink chamber, and each measurement step A determination step of determining whether or not there is a bonding failure in each of the plurality of bonding portions based on variations in the anti-resonance frequency of the piezoelectric circuit;
A mounting step of mounting the inkjet head that has been determined to be satisfactorily bonded to the plurality of bonding portions in the determination step, to the inkjet mounting portion;
A method of manufacturing an image forming apparatus in which the steps are performed in this order.

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