JP5062354B2 - Inkjet head manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing an ink-jet head, and more particularly to a method for manufacturing an ink-jet head that can easily equalize the ink velocity distribution in each channel even in an ink-jet head having a harmonica type head chip.

  In recent years, inkjet heads that record images by ejecting ink from nozzles have been increasing in number of channels for the purpose of improving recording speed and image quality. In such a multi-channel inkjet head, the uniformity of the velocity distribution of the ink ejected from the nozzles is an important performance. Since the speed of the ink ejected from the nozzle is also related to the volume of the ink droplet and the diameter of the ink droplet, it is necessary to make the channel characteristics including these uniform.

  Inkjet heads include a type that records images by moving the inkjet head relative to the recording paper, and a type that records images by moving the recording paper with the inkjet head fixed. The non-uniformity of the channel characteristics causes variations in ink landing accuracy due to non-uniformity of the velocity distribution of the ejected ink, and degrades the quality of the obtained image. An actual ink jet head usually has a certain speed distribution due to variations in performance of PZT as a material, non-uniform manufacturing processes, and the like.

  In order to make the velocity distribution uniform, there is a method of optimizing the drive voltage for each channel. However, it is necessary to prepare a drive circuit for each channel, and there is a problem that costs increase. Normally, since a driving voltage is applied to each channel from a single power source, each driving voltage is common, and it is difficult to avoid variations in the speed of ink ejected from each nozzle.

  Conventionally, as a technique for making such a velocity distribution uniform, a technique in which a head is configured using a piezoelectric vibrator in which a part of an electrode has been deleted in advance so as to obtain desired electromechanical characteristics (Patent Document 1), After assembling the head, check the ink ejection characteristics with a characteristic measurement device, trimming the electrode surface of the piezo element so that there is no characteristic variation among the nozzles (Patent Document 2), and measuring the ink speed from each nozzle However, there is a technique (Patent Document 3) that adjusts the ink speed by providing a notch on the common electrode on the surface of the piezoelectric element of the piezoelectric element that deforms in the unimorph mode when there is variation between nozzles. However, it is necessary to obtain the velocity distribution by actual driving and make adjustments such as trimming the electrode based on the result of the velocity distribution in order to make the velocity distribution uniform. It is preferred.

  By the way, in an inkjet head, a channel is ground on a piezoelectric element that has been subjected to polarization treatment, a drive electrode is formed on a drive wall that partitions the channel, and a voltage is applied to the drive electrode so that the drive wall is shaped like a dogleg. 2. Description of the Related Art There is known a shear mode inkjet head in which ink in a channel is ejected from a nozzle by being subjected to shear deformation.

  Among them, an actuator for discharging ink is a so-called harmonica type head chip in which drive walls made of piezoelectric elements and channels are alternately arranged in parallel, and outlets and inlets of the channels are arranged on the front and rear surfaces, respectively. The inkjet head (for example, Patent Documents 4 and 5) configured by the above method is extremely productive because a large number of head chips can be formed from one substrate at a time, and the channel is straight from the inlet to the outlet. Therefore, it has many advantages such as good bubble removal, high power efficiency, low heat generation, and excellent high-speed response.Each inkjet head having such a harmonica type head chip also has various advantages. It is desirable to make it possible to record higher quality images by making the velocity distribution between nozzles uniform. To have.

  In such a harmonica type head chip, it is difficult to connect a wiring for applying a driving voltage to the driving electrode. Usually, the electrode electrically connected to each driving electrode is drawn to the outer surface of the head chip, and the head chip Wiring is connected to the outer surface of the wire.

  For example, in the technique described in Patent Document 4, the head chip is sandwiched between two substrates, and electrodes that are electrically connected to the respective drive electrodes are formed on the substrate, whereby the drive voltage from the drive circuit is passed through the substrate. Applied to each drive electrode. At this time, an ink supply chamber is formed by providing a wall portion between the two substrates on the rear surface (channel inlet side) of the head chip.

  In the technique described in Patent Document 5, an ink supply chamber is provided by sandwiching a head chip between two substrates and providing a wall portion between the two substrates on the rear surface (channel inlet side) of the head chip. In addition, the wall portion protrudes further rearward than the substrate, and an electrode that is electrically connected to each drive electrode is formed on the substrate and the protruding portion. Is applied to each drive electrode.

JP-A-57-181874 Japanese Patent Laid-Open No. 61-118261 JP 2000-127384 A JP 2004-209796 A JP-A-2004-35851

  However, in an inkjet head having a harmonica type head chip, as disclosed in Patent Documents 4 and 5, the drive electrode is completely enclosed in the channel, and each of the drive electrodes is disposed on the rear side of the head chip. Since there is a substrate for drawing out an electrode for applying a driving voltage to the driving electrode, this substrate becomes an obstacle, and it is difficult to adjust the driving electrode by trimming after forming the ink jet head.

  If each substrate is made of a flexible material such as FPC, it is possible to largely fold the substrate when trimming each drive electrode, but it is necessary to maintain the bent state of the substrate during work. Moreover, it is not preferable because there is a risk of breakage, peeling, and disconnection of the substrate.

  Accordingly, the present invention provides an inkjet head manufacturing method that can easily equalize channel characteristics by adjusting the shear deformation function of the drive wall after the head chip is formed in the inkjet head having a harmonica type head chip. It is an issue to provide.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

1. Drive heads and channels made of piezoelectric elements are alternately arranged side by side, and outlets and inlets of the channels are arranged on the front and rear surfaces, respectively, and a drive chip is formed on the drive wall, In the method of manufacturing an inkjet head, the drive wall is shear-deformed by applying a voltage to the drive electrode, and the ink in the channel is ejected from the nozzle.
After forming the head chip, forming a connection electrode electrically connected to the drive electrode on the rear surface of the head chip;
A wiring electrode corresponding to the connection electrode is formed, and an opening is provided in a region corresponding to the channel row of the head chip, and has a size that protrudes in a direction perpendicular to the channel row direction from the head chip. Bonding the wiring board so that the connection electrode and one end of the wiring electrode are electrically connected and all the channels of the head chip are exposed from the opening;
After bonding the wiring substrate, closing all channels from the front surface of the head chip;
After closing all the channels, each channel is filled with a liquid, a voltage is applied to the drive electrode via the wiring electrode and the connection electrode to shear the drive wall, and the behavior of the liquid at that time Measuring each channel characteristic by measuring with a laser Doppler measuring instrument through the opening of the wiring board;
Based on the measured channel characteristics, at least one of the drive electrode and the drive wall is formed by a laser from the rear surface side of the head chip through the opening of the wiring board so that the channel characteristics are uniform. The driving electrode or the driving wall is mechanically removed, or a part of the driving wall is heated by a laser. a method of manufacturing an ink jet head, characterized by chromatic and adjusting the shear deformation function of the wall, the.
2. Drive heads and channels made of piezoelectric elements are alternately arranged side by side, and outlets and inlets of the channels are arranged on the front and rear surfaces, respectively, and a drive chip is formed on the drive wall, In the method of manufacturing an inkjet head, the drive wall is shear-deformed by applying a voltage to the drive electrode, and the ink in the channel is ejected from the nozzle.
After forming the head chip, forming a connection electrode electrically connected to the drive electrode on the rear surface of the head chip;
One end of the wiring substrate on which the wiring electrode corresponding to the connection electrode is formed is electrically connected to the one end of the wiring electrode and the head electrode so that all the channels of the head chip are exposed. Bonding to the connection electrode formation region on the rear surface of the chip;
After bonding the wiring substrate, closing all channels from the front surface of the head chip;
After closing all the channels, each channel is filled with a liquid, a voltage is applied to the drive electrode via the wiring electrode and the connection electrode to shear the drive wall, and the behavior of the liquid at that time , From the rear side where all the channels of the head chip are exposed, measuring each channel characteristic by measuring with a laser Doppler measuring instrument,
Based on the measured channel characteristics, a laser removes at least one part of the drive electrode and the drive wall from the rear side where all the channels of the head chip are exposed so that the channel characteristics are uniform. Shearing the drive wall by either mechanically removing at least one part of the drive electrode and the drive wall or heating a part of the drive wall with a laser. And a step of adjusting the deformation function .

According to the first aspect of the present invention, the characteristics of each channel are measured by the laser Doppler measuring device from the rear surface side of the harmonica type head chip after the production , and the opening portion of the wiring board is based on the measurement result. Through, removing at least part of the drive electrode and drive wall with a laser, mechanically removing at least one part of the drive electrode and drive wall, or heating part of the drive wall with laser By adjusting the shear deformation function of the drive wall by any of the above methods, it is possible to make each channel characteristic uniform and provide a method for manufacturing an inkjet head capable of high-quality image recording it can.
According to the invention described in claim 2 , by measuring the characteristics of each channel by the laser Doppler measuring device from the rear surface side of the harmonica type head chip after the production , all the channels of the head chip are determined based on the measurement result. From the exposed rear surface, a part of at least one of the drive electrode and the drive wall is removed with a laser, at least a part of at least one of the drive electrode and the drive wall is mechanically removed, or the drive wall is removed with a laser. By adjusting the shear deformation function of the drive wall by any method of heating a part, it is possible to make the characteristics of each channel uniform and to produce an inkjet head capable of high-quality image recording Can be provided.

1 is an exploded perspective view showing an example of an inkjet head according to the present invention. Sectional drawing which shows an example of the inkjet head which concerns on this invention (A)-(d) is a figure explaining the method of producing a head chip. A diagram explaining another method of creating a head chip The figure explaining the method of creating a head chip from one head substrate (A) (b) is a figure explaining the formation method of a connection electrode. Rear view showing the state where the wiring board is bonded to the head chip Cross-sectional view of a state in which processing to reduce the shear deformation function of the drive wall is performed (A)-(d) is sectional drawing which follows the (ix)-(ix) line | wire of FIG. Sectional view along the direction of the channel row showing how to reduce the shear deformation function of the independent channel type drive wall Sectional drawing explaining an example of the method of measuring a channel characteristic, without discharging ink A perspective view illustrating another example of a method of measuring channel characteristics without ejecting ink The perspective view seen from the back side which shows another mode of a wiring board

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an exploded perspective view showing an example of an ink jet head according to the present invention, and FIG. 2 is a cross-sectional view, where H is an ink jet head, 1 is a head chip, and 2 is joined to the front surface of the head chip 1. The nozzle plate 3 is a wiring substrate bonded to the rear surface of the head chip 1, 4 is an FPC bonded to the wiring substrate 3, and 5 is an ink manifold bonded to the rear surface of the wiring substrate 3.

  In this specification, the surface on the side where ink is ejected from the head chip 1 is referred to as “front surface”, and the opposite surface is referred to as “rear surface”. Further, when the head chip 1 is viewed from the front surface or the rear surface, the outer surfaces positioned above and below the channels arranged side by side are referred to as “upper surface” and “lower surface”, respectively.

  In the head chip 1, drive walls 13 and channels 14 made of piezoelectric elements are alternately arranged in parallel. The shape of the channel 14 is such that both side walls rise substantially perpendicular to the upper and lower surfaces and are parallel to each other. As shown in FIG. 2, an outlet 142 and an inlet 141 of each channel 14 are disposed on the front surface and the rear surface of the head chip 1, respectively, and each channel 14 is sized and shaped in the length direction from the inlet 141 to the outlet 142. Is a straight type with almost no change.

  In the head chip 1, each channel 14 has two channel rows in the upper and lower directions in the drawing. Each channel row is composed of six channels 14, but the number of channels 14 constituting the channel row in the head chip 1 is not limited at all.

  3 and 4 show an example of a method for producing such a head chip 1.

  First, two piezoelectric element substrates 13a and 13b are bonded onto one base substrate 11 using an epoxy adhesive (FIG. 3A). As a piezoelectric material used for each of the piezoelectric element substrates 13a and 13b, a known piezoelectric material that is deformed by applying a voltage can be used, and lead zirconate titanate (PZT) is particularly preferable. The two piezoelectric element substrates 13a and 13b are laminated with their polarization directions (indicated by arrows) opposite to each other, and are bonded to the substrate 11 using an adhesive.

  Next, a plurality of parallel grooves are ground using a dicing saw or the like over the two piezoelectric element substrates 13a and 13b. Thereby, the drive wall 13 made of a piezoelectric element whose polarization direction is opposite in the height direction is arranged on the base substrate 11 side by side. Each groove is ground at substantially the same constant depth from one end to the other end of the piezoelectric element substrates 13a and 13b, thereby forming a straight channel 14 whose size and shape are not substantially changed in the length direction. (FIG. 3B).

  Although not shown, instead of using the base substrate 11, the piezoelectric element substrate 13b is thick, and a plurality of parallel grooves extending from the thin piezoelectric element substrate 13a side to the middle of the thick piezoelectric element substrate 13b are ground. By doing so, the portion of the base substrate 11 may be integrally formed by the piezoelectric element substrate 13b simultaneously with the formation of the drive wall 13 whose polarization direction is opposite in the height direction.

  Next, the drive electrode 15 is formed on the inner surface of each channel 14 thus formed. The metal that forms the drive electrode 15 includes Ni, Co, Cu, Al, and the like. Al and Cu are preferably used from the viewpoint of electrical resistance, but Ni is preferably used from the viewpoint of corrosion, strength, and cost. Alternatively, a laminated structure in which Au is further laminated on Al may be employed.

  Examples of the formation of the drive electrode 15 include a method of forming a metal film by a method using a vacuum apparatus such as a vapor deposition method, a sputtering method, a plating method, or a CVD (chemical vapor reaction method). It is particularly preferable to form by electroless plating. By electroless plating, a uniform and pinhole-free metal coating can be formed. The thickness of the plating film is preferably in the range of 0.5 to 5 μm.

  Since the drive electrode 15 needs to be independent for each channel 14, a metal film is not formed on the upper end surface of the drive wall 13. For this reason, for example, by sticking a dry film on the upper end surface of each drive wall 13 in advance or forming a resist and forming a metal film, the side walls of each drive wall 13 and each channel 14 are removed. The drive electrode 15 may be selectively formed on the bottom surface (FIG. 3C).

  After the drive electrode 15 is formed in this way, the cover substrate 12 is bonded to the upper end surface of the drive wall 13 using an epoxy adhesive to produce the head substrate 10 having one channel row (FIG. 3 ( d)). For the base substrate 11 and the cover substrate 12, if the same substrate material as the piezoelectric material constituting the drive wall 13 is depolarized and used, the difference in thermal expansion coefficient due to the effect of heating or driving heat at the time of bonding the substrates is caused. Variations in the speed distribution and drive characteristics due to this can be reduced.

  In addition, such a head substrate is not limited to the one produced as shown in FIG. 3D, and as shown in FIG. 4, instead of using the base substrate 11, the piezoelectric element substrate is made thick. Two sets (upper substrate 10a and lower substrate 10b) are prepared by grinding parallel grooves and alternately arranging drive walls 13 and channels 14 and forming drive electrodes 15 on the inner surface of each channel 14. By adhering this so that the drive walls 13 face each other, a head substrate 10A similar to that shown in FIG. In this case, it is not necessary to bond the thin piezoelectric element substrate 13a onto the piezoelectric element substrate 13b as shown in FIG. However, in the following, a case where the head substrate 10 shown in FIG.

  By using two head substrates 10 created as shown in FIG. 3 (d), overlaying the cover substrates 12 on each other as shown in FIG. After forming the laminated head substrate 100 having two channel rows, the laminated head substrate 100 is cut along a plurality of cut lines C1, C2,... Along the direction orthogonal to the length direction of the channel 14. As a result, a plurality of harmonica type head chips 1, 1,...

  The head chips 1, 1... Thus produced have drive walls 13 and channels 14 made of piezoelectric elements alternately arranged in each channel row. The shape of the channel 14 is such that both side walls rise substantially vertically from the base substrate 11 of the head chip 1 and are parallel to each other. An outlet 142 and an inlet 141 of each channel 14 are disposed on the front surface and the rear surface of the head chip 1, respectively. Each channel 14 is a straight type whose size and shape are not substantially changed in the length direction from the inlet to the outlet.

  In such a harmonica type head chip 1, each drive electrode 15 is connected to the drive electrode 15 in each channel 14 in order to connect a wiring such as an FPC for applying a drive voltage from the drive circuit from the outside. It is necessary to pull out to the outer surface of the head chip 1. Therefore, next, on the rear surface of the head chip 1, the connection electrode 16 extends from the portion of the drive electrode 15 formed on the bottom surface of the channel 14 (the surface of the base substrate 11 facing the channel 14) to the rear end surface of the base substrate 11. Pull out to form.

  FIGS. 6A and 6B are explanatory views for explaining an example of a method for leading and forming the connection electrodes 16 electrically connected to the drive electrodes 15 on the outer surface of the head chip 1.

  As shown in FIG. 6A, the connection electrode 16 includes at least a portion of the drive electrode 15 formed on the surface of the base substrate 11 facing the channel 14 on the rear surface of the head chip 1. Formed by attaching a photosensitive dry film 200 having an opening 201 opened on the upper surface side and the lower surface side, depositing a metal for electrode formation such as Al, and forming a metal film in the opening 201 can do.

  In order to smoothly connect the drive electrode 15 and the connection electrode 16 in the channel 14, it is desirable that the deposition is performed at a predetermined angle, rather than making the rear surface of the head chip 1 perpendicular to the deposition direction. Specifically, it is desirable that the vapor deposition direction (the direction in which the metal particles fly) is not perpendicular to the paper surface of FIG. 6A, but is inclined about 30 to 60 degrees from the vertical to the upper side and the lower side.

  Further, the connection electrode 16 may have a laminated structure by a method such as vapor deposition of Au on a metal film of Al. Further, the connection electrode 16 may be formed by sputtering instead of vapor deposition.

  In particular, when the head chip 1 is cut using the head substrate 10A prepared as shown in FIG. 4, there is an adhesive between the drive electrode 15 of the upper substrate 10a and the drive electrode 15 of the lower substrate 10b. Not electrically connected. For this reason, when forming a metal film in the opening part 201 of the photosensitive dry film 200, it is necessary to connect these two drive electrodes 15 and 15. FIG. When electrode formation is performed by vapor deposition, this can be realized by performing the vapor deposition direction a plurality of times in a predetermined direction or changing the direction of the substrate during vapor deposition. When forming electrodes by sputtering, metal particles fly from various directions, so that the two drive electrodes 15 and 15 can be connected without changing the direction of the substrate.

  Note that the opening 201 is desirably opened over the entire surface of the channel 14 in consideration of workability in the development process and the water washing process of the photosensitive dry film 200. Opening on the entire surface facilitates removal of the developer and washing water in the channel 14.

  Thereafter, when the photosensitive dry film 200 is removed, as shown in FIG. 6B, the connection electrodes 16 that are electrically connected to the drive electrodes 15 from the channels 14 are provided on the rear surface of the head chip 1 for each channel 14. Pulled independently.

  The nozzle plate 2 is provided with nozzles 21 at positions corresponding to the respective channels 14 of the head chip 1, and is bonded to the front surface of the head chip 1 on which the connection electrodes 16 are formed using an epoxy adhesive.

  The wiring board 3 is a plate-like member for connecting a wiring for applying a driving voltage from a driving circuit (not shown) to each driving electrode 15 of the head chip 1. The substrate used for the wiring substrate 3 is a substrate made of a ceramic material such as non-polarized PZT, AlN-BN, or AlN, a substrate made of low thermal expansion plastic or glass, or a piezoelectric element used in the head chip 1. A substrate obtained by depolarizing the same substrate material as the substrate material can be used. Preferably, the material is selected so that the difference in thermal expansion coefficient from the head chip 1 is within ± 1 ppm in order to suppress the occurrence of distortion or the like of the head chip 1 due to the difference in thermal expansion coefficient.

  The substrate constituting the wiring substrate 3 is not limited to a single plate, and a plurality of thin plate materials may be laminated to form a desired thickness.

  The wiring substrate 3 has the same width as the width direction of the head chip 1 and extends in a direction (vertical direction in FIGS. 1 and 2) orthogonal to the alignment direction (channel row direction) of the channels 14 of the head chip 1. The head chip 1 protrudes greatly from the upper surface and the lower surface, and the protruding ends serve as wiring connection portions 31 and 31 for connecting the FPCs 4 and 4 respectively.

  In addition, an opening 32 is formed through substantially at the center of the wiring board 3. The opening 32 is formed to a size that can expose the inlet 141 side of all the channels 14 of the head chip 1. Therefore, as shown in FIG. 7, in a state where the wiring substrate 3 is bonded to the rear surface of the head chip 1, the entire driving wall 13, all the channels 14, and all the driving electrodes 15 of the head chip 1 are viewed through the opening 32. Can be done.

  As a method for forming the opening 32, a method of processing with a dicing saw, a method of processing with an ultrasonic processing machine, a method of molding and firing ceramics before sintering, or the like can be employed depending on the substrate material.

  Wiring electrodes 33 are formed at the same number and the same pitch as the connection electrodes 16 formed on the rear surface of the head chip 1 on the surface of the wiring substrate 3 on the bonding surface side with the head chip 1. It extends to. The wiring electrode 33 is electrically connected to each wiring 41 formed on the FPC 4 when the FPC 4 is bonded, and the driving voltage supplied from the driving circuit via the wiring 41 of the FPC 4 is supplied to the connecting electrode 16. It functions as an electrode to be applied to the drive electrode 15 in the channel 14 via.

  The wiring electrode 33 is formed by coating the surface of the wiring substrate 3 with a positive resist by a spin coating method, and then exposing and developing the positive resist using a stripe-shaped mask to develop a stripe-shaped positive resist. It can be performed by exposing the surface of the wiring substrate 3 at the same number and pitch as the connection electrodes 16 and forming a metal film on the surface with a metal for electrode formation by vapor deposition or sputtering. As the metal for forming the electrode, the same metal as the connection electrode 16 can be used.

  The wiring board 3 is aligned so that each wiring electrode 33 is electrically connected to each connection electrode 16 of the head chip 1 and the openings 32 expose the inlets 141 side of all the channels 14 of the head chip 1. It is joined to the rear surface of the head chip 1 by an anisotropic conductive film or the like. As other electrical connection methods, anisotropic conductive paste containing conductive particles, pressure welding bonded with a nonconductive adhesive, solder is used for at least one of the wiring electrode 33 and the connection electrode 16, and heating is performed. A method used in a normal mounting technique such as a method of melting and connecting can also be used.

  By bonding the wiring board 3 to the rear surface of the head chip 1 in this way, electrodes (connection electrodes 16) for applying a drive voltage from the drive circuit to the drive electrodes 15 in the channels 14 of the head chip 1 are obtained. And the wiring electrode 33) are drawn out in a direction orthogonal to the channel row. Among these, the wiring electrode 33 is drawn out to the wiring connecting portions 31 and 31 that are greatly extended from the head chip 1, and therefore, the electrical connection with the FPCs 4 and 4 is easy. The FPCs 4 and 4 do not exist on the rear side of the head chip 1, and the space on the rear side of the head chip 1 can be largely opened.

  The ink manifold 5 stores ink to be supplied to each channel 14 of the head chip 1 through the opening 32 of the wiring board 3. The ink manifold 5 is formed in a box shape, and the opening 51 is joined so as to cover the opening 32 formed in the wiring board 3.

  The size of the opening 51 of the ink manifold 5 includes the opening 32 of the wiring board 3 and is large enough to reach the overhanging portions 31, 31. The opening 51 is larger than the area of the rear surface of the head chip 1. have. As described above, even when the ink manifold 5 is joined, by using the overhang portions 31, 31 of the wiring substrate 3, it is possible to store a large amount of ink as compared with the size of the head chip 1. Ink is supplied from the ink supply port 52 into the ink manifold 5.

  When the wiring board 3 has a sufficient thickness, instead of providing the ink manifold 5, the opening 32 of the wiring board 3 is closed with the ink supply port remaining, so that the inside of the opening 32 is closed. Can be used as an ink common chamber for supplying ink to all the channels 14 in common.

  Next, a method for adjusting the shear deformation function of the drive wall in order to make the channel characteristics uniform from the rear surface side of the head chip 1 in the inkjet head H will be described.

  Here, the channel characteristics are not particularly limited as long as they can be measured with characteristics related to the velocity distribution of the ink ejected from the inkjet head H, but ink is actually ejected from each nozzle 21. It is preferable that the channel characteristics can be measured with higher accuracy. For example, as described below, it is preferable to measure the speed of the ink droplet, the volume of the ink droplet, and the diameter of the ink droplet.

  First, a method of measuring the velocity distribution of ink droplets ejected from each nozzle 21 and adjusting the shear deformation function of the drive wall 13 so that the velocity distribution is uniform will be described.

  In the manufacturing process of the inkjet head H, the nozzle plate 2, the wiring board 3, and the FPCs 4, 4 are bonded to the manufactured head chip 1, so that the driving electrodes 15 are driven from the driving circuit (not shown) via the FPCs 4, 4. After creating the state shown in FIG. 8 that can be driven by applying a voltage, ink is supplied to each channel 14 through the opening 32 of the wiring board 3.

  As a method for supplying this ink, a temporary ink supply member or ink manifold 5 having a size enough to cover the opening 32 is pressed against the wiring board 3 so as not to leak ink, or an adhesive that can be peeled off. The method of temporarily fixing using etc. is mentioned.

  After the ink can be supplied to each channel 14 of the head chip 1 in this way, a common drive voltage is actually applied to the drive electrode 15 of each channel 14, whereby the drive wall 13 is shear-deformed and each nozzle 21. Ink is ejected from each of the nozzles, the ejection speed of the ink droplets at that time is measured, and the speed distribution of all the nozzles 21 is obtained.

  The method for measuring the ink ejection speed is not particularly limited. For example, the ink ejected from the nozzle 21 is imaged, the speed is calculated by recognizing the image from the ink imaging position, and the ink flying path is detected. Examples include a method of arranging the optical axis of the sensor, detecting a change in the light amount of the light receiving sensor when the ink passes through the optical axis, and calculating the speed from the ink ejection timing and the detection timing.

  After the velocity distribution is measured, when the temporary ink supply member or the ink manifold 5 is removed and the ink ejection speed varies between the channels 14, the ink ejection of the channel 14 that ejects the fast ink is performed. Processing to reduce the shear deformation function of the drive wall 13 is performed from the rear surface side of the head chip 1 so as to reduce the speed. On the rear surface of the head chip 1, all the driving walls 13, all the channels 14 and all the driving electrodes 15 are exposed through the openings 32 of the wiring board 3, and the space on the rear side of the head chip 1 is largely open. Therefore, the processing work is extremely easy. Further, even if the temporary ink supply member or the ink manifold 5 is removed, the temporary ink supply member or the ink manifold 5 is not an electrical connection component, so there is no concern that disconnection or the like may occur.

  Next, a method for measuring the volume distribution of ink droplets ejected from each nozzle 21 and adjusting the shear deformation function of the drive wall 13 so that the volume distribution is uniform will be described.

  In this case as well, the ink is supplied to each channel 14 through the opening 32 of the wiring board 3 after the state shown in FIG.

  After the ink can be supplied to each channel 14 of the head chip 1, the drive wall 13 is shear-deformed by actually applying a common drive voltage to the drive electrode 15 of each channel 14, so that the ink is supplied from each nozzle 21. Each of the ink droplets is ejected, and the volume of each ink droplet is measured, and the volume distribution of all the nozzles 21 is obtained.

  If the volume of the ink droplet is V0, the nozzle radius is r, the ejection speed is V, and the driving frequency is ω, then V0 = πr × r × V / (2ω). Since the accuracy of nozzle processing is sufficiently high and the nozzle radius may be considered to be constant in any channel, the distribution of the ejection speed can be found by measuring the volume V0 of the ink droplet.

  The method for measuring the volume of the ink droplet is not particularly limited, but the ink droplet is measured by discharging a predetermined number (a predetermined time) of ink from the same nozzle and measuring the weight of all the discharged ink. be able to. For example, when the average ink droplet amount is 10 ng and the driving frequency is 10 kHz, the discharge time is 10 seconds, and 10 ng × 10 kHz × 10 = 1 mg. By measuring this weight using a balance, the volume of ink droplets can be determined.

  After measuring the volume distribution of the ink droplets in this way, in the same manner as described above, if the volume of the ink droplets varies among the channels 14, Processing for reducing the shear deformation function of the drive wall 13 is performed on the discharge channel 14 from the rear surface side of the head chip 1 so as to reduce the volume.

  Further, a method of measuring the diameter distribution of the ink droplets ejected from each nozzle 21 and adjusting the shear deformation function of the drive wall 13 so that the diameter distribution is uniform will be described.

  In this case as well, the ink is supplied to each channel 14 through the opening 32 of the wiring board 3 after the state shown in FIG.

  After the ink can be supplied to each channel 14 of the head chip 1, the drive wall 13 is shear-deformed by actually applying a common drive voltage to the drive electrode 15 of each channel 14, so that the ink is supplied from each nozzle 21. Each of the ink droplets is ejected and the diameter of each ink droplet is measured to obtain the diameter distribution of all the nozzles 21.

  A method for measuring the diameter of the ink droplet is not particularly limited, and examples thereof include a method of obtaining an image of the ink droplet ejected from the nozzle 21 and measuring the diameter of the ink droplet on the image.

  After measuring the diameter distribution of the ink droplets in this way, in the same manner as described above, when the diameter of the ink droplet varies between the channels 14, the ink droplet having a large diameter is removed. Processing for reducing the shear deformation function of the drive wall 13 is performed from the rear surface side of the head chip 1 so as to reduce the diameter of the channel 14 to be discharged.

  As a process for reducing the shear deformation function of the drive wall 13, first, as shown in FIG. 9A, a method of removing a part of the drive electrode 15 formed on the surface of the drive wall 13 by laser machining is given. It is done.

  As the laser, an excimer laser, a double frequency using SHG, and a triple frequency laser using THG are preferable. As shown in the figure, the laser beam is irradiated obliquely from the inlet 141 side of the channel 14 to be processed. A part of the drive electrode 15 of the drive wall 13 is removed. The drive wall 13 made of piezoelectric elements undergoes shear deformation due to the potential difference between the voltages applied to the drive electrodes 15 on both sides thereof, so that the sensitivity of the drive wall 13 decreases as a result of the area of the drive electrode 15 being reduced. As a result, the amount of shear deformation of the drive wall 13 decreases, and the ink ejection speed decreases.

  As an example, if the drive electrode 15 is removed from the inlet 141 of the channel 14 to a depth of 25 μm in the head chip 1 whose length (L length) in the ink discharge direction of the channel 14 is 2.5 mm, 1% of the drive electrode 15 Decreases, and the sensitivity decreases accordingly. In practice, the removal amount of the drive electrode 15 and the degree of sensitivity reduction may be measured in advance, and the removal amount of the drive electrode 15 may be determined based on the data.

  The amount of shear deformation of the drive wall 13 is also reduced by removing a part of the drive wall 13 itself. Therefore, as a process for reducing the shear deformation function of the drive wall 13, a method of removing a part of the drive wall 13 by laser machining as shown in FIG. As the laser, the same laser as that used to remove the drive electrode 15 can be used. In this case as well, the removal amount of the drive wall 13 and the degree of sensitivity reduction may be measured in advance, and the removal amount of the drive wall 13 may be determined based on the data.

  Furthermore, depolarization occurs when the piezoelectric element subjected to the polarization treatment is heated. The sensitivity of the depolarized piezoelectric element is lowered, so that the shear deformation function is lowered. Therefore, as a process for reducing the shear deformation function of the drive wall 13, a method of heating the drive wall 13 from the rear surface side of the head chip 1 as shown in FIG. For heating, it is preferable to use a laser because only the driving wall 13 to be processed can be heated in a spot shape. By setting the output of the laser so that the drive wall 13 is not removed, the sensitivity can be lowered by heating the drive wall 13.

  The laser that can be used in this case is not particularly limited, but an infrared semiconductor laser, a YAG laser, or the like is preferable. The decrease in sensitivity of the drive wall 13 is greatest at the laser irradiation site, and the decrease in sensitivity decreases as the distance increases. Therefore, in this case as well, the heating amount (heating temperature, heating time) of the drive wall 13 and the degree of sensitivity reduction are measured in advance, and the heating amount of the drive wall 13 may be determined based on the data. .

  In addition, as a process for reducing the shear deformation function of the drive wall 13, a method of mechanically machining the drive wall 13 itself from the rear surface side of the head chip 1 can be cited. FIG. 9D shows a case where sensitivity is lowered by mechanically removing a part of the drive wall 13 itself. The mechanical processing can be performed by grinding the drive wall 13 from the rear surface side of the head chip 1 using the end mill 300. In this case as well, the processing amount of the drive wall 13 and the degree of sensitivity reduction are measured in advance, and the processing amount of the drive wall 13 may be determined based on the data.

  As described above, when adjusting the shear deformation function of the drive wall 13, there is a possibility that evaporated metal may adhere to the nozzle 21 in laser processing, and there is a possibility that shavings may clog the nozzle 21 in machining. is there. In order to avoid such damage to the nozzle 21, it is preferable to apply a protective agent that can be removed later to the nozzle 21 in advance. As the protective agent that can be removed later, an organic polymer film such as a resist that can be removed with an organic solvent is suitable.

  In the inkjet head in which the drive wall 13 and the channel 14 are alternately arranged, all of the channels 14 are set as ink discharge channels, and the adjacent channels 14 are sequentially driven in three cycles, There is an independent channel type in which ink discharge channels and empty channels are divided and arranged alternately.

  In the case of a three-cycle head, two adjacent channels 14 share one drive wall 13, so if the sensitivity of one drive wall 13 is reduced, ink from the two channels 14 on both sides of the drive wall 13 is reduced. It affects the discharge speed. In general, the cause of non-uniformity in channel characteristics such as velocity distribution is often attributed to the drive wall 13, so that the channel characteristics can be made sufficiently uniform by the method described above. However, there are rare cases where non-uniformity of channel characteristics occurs due to causes other than the drive wall 13, but in this case also, non-uniformity of channel characteristics tends to be improved.

  On the other hand, in the case of the independent channel type, the drive wall 13 is dedicated to the ink ejection channel and is not shared. In this case, since the processing of the drive wall 13 affects only the channel 14 dedicated to it, it is possible to completely adjust the channel characteristics.

  In the case of this independent channel type, it is necessary to prevent ink from flowing into the empty channel. Normally, as shown in FIG. 10, there is a hole 401 for supplying ink in the ink discharge channel on the rear surface of the head chip, but a plate 400 without a hole is provided so that ink does not flow into the empty channel. Realized by pasting.

  When channel characteristics such as velocity distribution are measured after the plate 400 is stretched and processing is performed from the rear surface side of the head chip 1, the ink supply hole 401 of the plate 400 is formed larger than the entrance area of the channel 14. In addition, as shown in FIG. 9A, the driving electrode 15 can be removed by irradiating the laser beam obliquely, or the driving wall 13 can be heated by irradiating the laser beam. The methods of FIGS. 9B and 9D are difficult to apply in this case.

  In the above description, the nozzle plate 2 is bonded to the front surface of the head chip 1 and the ink is actually ejected from the nozzle 21 to measure the channel characteristics such as the velocity distribution. However, the structure of the inkjet head H according to the present invention is described. According to the above, it is possible to measure the channel characteristics without actually ejecting ink.

  FIG. 11 is a cross-sectional view illustrating an example of a method for measuring channel characteristics without ejecting ink.

  Since the head chip 1 can apply a driving voltage to each drive electrode 15 when the wiring substrate 3 and the FPCs 4 and 4 are joined, the wiring substrate 3 and the FPCs 4 and 4 are joined to the head chip 1 on which the connection electrodes 16 are formed. Then, after the nozzle plate is prepared until it is not joined, the front surface of the head chip 1 is closed. Here, the lid member 500 is affixed to the front surface of the head chip 1 using a peelable adhesive or the like. In addition, the outlet 142 side of the channel 14 may be sealed by pressing the front surface of the head chip 1 against an elastic member or the like.

  Thereafter, the liquid W is filled in each channel 14 with the front surface side of the head chip 1 facing down, and the drive wall 13 is shear-deformed by applying a common drive voltage to the drive electrode 15 of each channel 14. The liquid W filled in each channel 14 is preferably a non-volatile liquid, such as oil-based ink.

  When a drive voltage is applied to the drive electrode 15, the drive wall 13 is shear-deformed into a dogleg shape, and the volume in the channel 14 is reduced or expanded, whereby the liquid level of the liquid W filled in the channel 14 is raised and lowered. Move in the direction. By measuring the behavior of the liquid W with the laser Doppler measuring device 600, the characteristics of each channel 14 can be measured, and the velocity distribution of all the channels 14 can be predicted from the channel characteristics. .

  After measuring the channel characteristics of all the channels 14 in this way, the shear deformation function of the drive wall 13 may be adjusted from the rear surface side of the head chip 1. The nozzle plate 2 may be bonded to either before or after processing, but from the viewpoint of protecting the nozzle 21, it is preferable to bond after processing.

  In addition, in the case of the independent channel type in which the ink discharge channels and the empty channels are alternately arranged, when obtaining the characteristics of each channel 14 before applying the nozzle plate 2 by this method, only the ink discharge channel is filled with the liquid W. do it. This can be done by filling only the channel from which the liquid W is discharged with an inkjet head. Also in this case, if the method shown in FIGS. 9B and 9D is applied, it becomes difficult to attach a plate 400 for closing the rear end as shown in FIG. The method of FIG. 9C is desirable.

  Further, when discharging a liquid that corrodes the drive electrode 15 such as water-based ink, it is necessary to form a protective film for protecting each drive electrode 15. For example, a polyparaxylylene film can be used as the protective film.

  If a process for reducing the shear deformation function is performed after the polyparaxylylene film is formed as the protective film, the function of the protective film may be reduced. Further, since the polyparaxylylene film is formed by CVD and adheres to the entire surface of the head chip 1, it is not preferable that the nozzle plate 2 is attached to the head chip 1 when the protective film is formed. Therefore, when forming the protective film, before applying the nozzle plate 2, after measuring the channel characteristics using the laser Doppler measuring device 600 as shown in FIG. 11, processing to adjust the shear deformation function, After that, it is preferable to form a protective film and then affix the nozzle plate 2 thereafter. Alternatively, the nozzle plate 2 is temporarily pasted in order to measure the channel characteristics, the nozzle plate 2 is removed after the measurement, the shear deformation function is adjusted, the nozzle plate is formed after the protective film is formed. It is preferable to perform the main pasting for pasting 2.

  When a high heat resistance film such as a silicon oxide film or a silicon nitride film is used as the protective film, the protective film is formed, the nozzle plate 2 is attached, the channel characteristics are measured, and laser light is irradiated. By heating the drive wall 13, it is possible to perform processing for adjusting the shear deformation function in a method that does not change the appearance.

  When the processing of the drive wall 13 for making the channel characteristics uniform is completed, the ink manifold 5 is joined to the wiring board 3 as necessary to complete the inkjet head H.

  Furthermore, as another example of the method for measuring the channel characteristics without ejecting ink, there is a method for measuring the capacity distribution of the drive wall 13 of each channel 14.

  In order to measure the capacity of the drive wall 13, for example, as shown in FIG. 12, two probers 701 and 701 connected to the LCR meter 700 are brought into contact with the adjacent wiring electrodes 33, whereby the two wirings are connected. The capacity of the drive wall 13 in which the drive electrode 15 electrically connected to the electrode 33 is formed can be measured. For this measurement, by using an automatic stage and computer-controlled, the capacity of all the driving walls 13 can be easily measured, and the speed distribution of all the channels 14 can be predicted from this capacity distribution.

  Thus, after measuring the capacity | capacitance of all the channels 14, what is necessary is just to adjust the shear deformation function of the drive wall 13 from the rear surface side of the head chip 1 based on the capacity | capacitance distribution.

  The measurement of the channel characteristics and the adjustment of the shear deformation function of the drive wall 13 described above are preferably repeated a plurality of times as necessary, thereby further improving the effect of making the channel characteristics uniform.

  FIG. 13 shows another embodiment of the wiring board. 1 and 2 have the same configuration, and thus detailed description thereof is omitted.

  This wiring board is composed of two substrates 6 and 6 that are respectively independent of the two channel rows of the head chip 1. The same substrate as the wiring substrate 3 can be used for forming the wiring substrates 6 and 6.

  Each wiring substrate 6, 6 has a wiring electrode 61 corresponding to the connection electrode 16 of the head chip 1 formed on the joint surface with the head chip 1, and the connection electrode 16 of each channel row on the rear surface of the head chip 1. One end of each of the wiring electrodes 61 and each connection electrode 16 is joined to the formation region, and the other end protrudes in a direction perpendicular to the channel row. The projecting ends are wiring connection portions 62 and 62, and the respective wirings 41 of the FPCs 4 and 4 are joined so as to be electrically connected to the respective wiring electrodes 61.

  The wiring boards 6 and 6 are spaced apart from each other with a space 63 therebetween, and all the driving walls 13, all the channels 14 and all the driving electrodes 15 facing the rear surface of the head chip 1 are exposed in the space 63. Yes. Therefore, similarly to the above, after measuring the channel characteristics with or without actually ejecting ink, a process for adjusting the shear deformation function of each drive wall 13 from the rear surface side of the head chip 1 through the space 63 is performed. Is easy.

  According to the wiring boards 6 and 6, it is only necessary to use a board having a simple configuration, and it is not necessary to process the opening 32 like the wiring board 3, so that the cost can be further reduced. Further, since each wiring board 6, 6 can be independently bonded to the head chip 1, the electrical connection between the wiring electrode 61 and the connection electrode 16 of one wiring board 6 is the electrical connection of the other wiring board 6. There is no influence on the connection, and a reliable electrical connection with less risk of short-circuiting can be easily performed.

  The space 63 between the wiring substrates 6 and 6 can also form a common ink common chamber for all the channels 14 of the head chip 1 when the wiring substrates 6 and 6 have a sufficient thickness. . The ink manifold 5 may be further bonded to the wiring boards 6 and 6.

  The open portions 631 and 632 on both sides of the space portion 63 may be closed by members not shown, or may be used as ink supply ports or ink discharge ports. Further, when the space 63 is used as an ink common chamber, ink is circulated in the ink common chamber using one open portion 631 as an ink supply port and the other open portion 632 as an ink discharge port. It may be.

  In the inkjet head H described above, the wiring substrates 3 and 6 are formed by plate-shaped substrates, and the FPC 4 is connected to the wiring connection portions 31 and 62. However, the wiring substrates 3 and 6 themselves are formed by FPC. May be. Thereby, the bonding of the head chip 1 and the wiring substrate and the wiring connection for applying the driving voltage to each driving electrode 15 can be performed at the same time, and man-hours can be reduced.

  The head chip 1 of the inkjet head H described above is a case where there are two channel rows, but the channel row may be only one row, or may be a plurality of rows of three or more rows. .

1: Head chip 10, 10A: Head substrate 11: Base substrate 12: Cover substrate 13: Drive wall 13a, 13b: Piezoelectric element substrate 14: Channel 141: Channel inlet 142: Channel outlet 15: Drive electrode 16: Connection electrode 2: Nozzle plate 21: Nozzle 3: Wiring board 31: Wiring connection part 32: Opening part 33: Wiring electrode 4: FPC
41: Wiring 5: Ink manifold 51: Opening 52: Ink supply port 6: Wiring board 61: Wiring electrode 62: Wiring connection part 63: Space part 631, 632: Opening part 100: Laminated head board 200: Photosensitive dry film 201 : Opening 300: End mill 400: Plate 500: Lid member 600: Laser Doppler measuring instrument 700: LCR meter 701: Prober H: Inkjet head W: Liquid

Claims (2)

Drive heads and channels made of piezoelectric elements are alternately arranged side by side, and outlets and inlets of the channels are arranged on the front and rear surfaces, respectively, and a drive chip is formed on the drive wall, In the method of manufacturing an inkjet head, the drive wall is shear-deformed by applying a voltage to the drive electrode, and the ink in the channel is ejected from the nozzle.
After forming the head chip, forming a connection electrode electrically connected to the drive electrode on the rear surface of the head chip;
A wiring electrode corresponding to the connection electrode is formed, and an opening is provided in a region corresponding to the channel row of the head chip, and has a size that projects in a direction perpendicular to the channel row direction from the head chip. Bonding the wiring board so that the connection electrode and one end of the wiring electrode are electrically connected and all the channels of the head chip are exposed from the opening;
After bonding the wiring substrate, closing all channels from the front surface of the head chip;
After closing all the channels, each channel is filled with a liquid, a voltage is applied to the drive electrode via the wiring electrode and the connection electrode to shear the drive wall, and the behavior of the liquid at that time Measuring each channel characteristic by measuring with a laser Doppler measuring instrument through the opening of the wiring board;
Based on the measured channel characteristics, at least one of the drive electrode and the drive wall is formed by a laser from the rear surface side of the head chip through the opening of the wiring board so that the channel characteristics are uniform. The driving electrode or the driving wall is mechanically removed, or a part of the driving wall is heated by a laser. And a step of adjusting a shear deformation function of the wall . Drive heads and channels made of piezoelectric elements are alternately arranged side by side, and outlets and inlets of the channels are arranged on the front and rear surfaces, respectively, and a drive chip is formed on the drive wall, In the method of manufacturing an inkjet head, the drive wall is shear-deformed by applying a voltage to the drive electrode, and the ink in the channel is ejected from the nozzle.
After forming the head chip, forming a connection electrode electrically connected to the drive electrode on the rear surface of the head chip;
One end of the wiring substrate on which the wiring electrode corresponding to the connection electrode is formed is electrically connected to the one end of the wiring electrode and the head electrode so that all the channels of the head chip are exposed. Bonding to the connection electrode formation region on the rear surface of the chip;
After bonding the wiring substrate, closing all channels from the front surface of the head chip;
After closing all the channels, each channel is filled with a liquid, a voltage is applied to the drive electrode via the wiring electrode and the connection electrode to shear the drive wall, and the behavior of the liquid at that time , From the rear side where all the channels of the head chip are exposed, measuring each channel characteristic by measuring with a laser Doppler measuring instrument,
Based on the measured channel characteristics, a laser removes at least one part of the drive electrode and the drive wall from the rear side where all the channels of the head chip are exposed so that the channel characteristics are uniform. Shearing the drive wall by either mechanically removing at least one part of the drive electrode and the drive wall or heating a part of the drive wall with a laser. And a step of adjusting the deformation function .

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