JP2009066797A - Ink-jet head and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink-jet head which is excellent in the performance of discharging an ink. <P>SOLUTION: The ink-jet head includes a piezoelectric substrate 1 in which two or more grooved parts were formed, and a nozzle plate 2 fixed to the front face of the piezoelectric substrate 1 with an adhesive 3. The piezoelectric substrate 1 includes an electrode 14 formed in the wall surface of the grooved part, and an electrode protective film 5 formed on the surface of the electrode 14 and the front face of the piezoelectric substrate 1. The electrode protective film 5 has a projection 5a which projects from the surface at the front face. The projection 5a is formed so that the height may be the thickness of the adhesive 3 or less. The projection 5a is formed so that the part facing the nozzle plate 2 may be nearly plane-like. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inkjet head and a method for manufacturing an inkjet head.

  An inkjet head is an apparatus that can eject minute droplets of ink at an arbitrary number of droplets. The ink jet head includes a nozzle plate having a plurality of nozzles that are minute holes for discharging droplets, and a head portion having an ink flow path having a cross-sectional area larger than the size of the nozzle. The ink jet head has means for giving energy necessary for discharging from the nozzle to the ink flow path. The nozzle plate is arranged so that the center of the nozzle and the center of the ink flow path substantially coincide.

  Some ink jet heads include a piezoelectric substrate and a lid member. In the piezoelectric substrate, a groove portion that forms an ink flow path is formed. The ink flow path is formed by a space surrounded by the groove and the lid member. Electrodes for driving the wall portion are formed on both side surfaces of the wall portion sandwiched between the ink flow paths. When a voltage is applied to the electrode, the wall portion is deformed to pressurize the ink flow path, and ink is ejected from the nozzle.

  In an inkjet head having such a piezoelectric substrate, an electrode protective film may be formed on the surface of the electrode in order to insulate the electrode formed on the side wall constituting the ink flow path from the ink (for example, JP, 2002-127431, A). In addition to being disposed on the surface of the electrode, the electrode protective film is disposed so as to coat the surface of the head portion to which the nozzle plate is bonded. As the electrode protective film, for example, an organic protective film such as a polyparaxylylene film is used.

  In manufacturing an ink jet head including a piezoelectric substrate in a head portion, a nozzle plate in which nozzles are formed with high positional accuracy in advance and a head portion having an ink flow path are prepared. The nozzle plate is joined to the head portion while adjusting the position so that the center of the ink flow path and the center of the nozzle coincide. An adhesive is used as the joining means.

  FIG. 12 shows a schematic cross-sectional view of a process of joining the nozzle plate to the head part in the manufacturing process of the inkjet head.

  The head portion includes a piezoelectric substrate 1. The head unit has a plurality of ink flow paths 11. When the ink jet head is completed, the ink flows in the direction indicated by the arrow 52. The nozzle plate 2 has nozzles 2a formed at a predetermined interval. The nozzle 2 a is formed so as to penetrate the nozzle plate 2. The nozzle plate 2 is bonded and fixed to the piezoelectric substrate 1 so that the nozzle 2 a is disposed at substantially the center in the width direction of the ink flow path 11.

The nozzle plate 2 is held by a pressure member 43. The pressure member 43 has a suction hole 43a. The suction hole 43a is connected to a vacuum exhaust device (not shown). The nozzle plate 2 is adsorbed on the adsorption surface 43 b of the pressure member 43. An adhesive 3 is disposed on the front surface of the piezoelectric substrate 1. As indicated by an arrow 56, the nozzle plate 2 is bonded to the piezoelectric substrate 1 while performing alignment.
JP 2002-127431 A

  The landing accuracy of ink ejected from the inkjet head directly affects the accuracy of printed images and graphics. For example, high landing accuracy is required for an inkjet head that prints an image, a graphic, or the like on a substrate such as paper, or an inkjet head that is included in a manufacturing apparatus. In a manufacturing apparatus, for example, an inkjet head is disposed in an apparatus that forms a color filter of a liquid crystal display panel or an apparatus that forms wiring on the surface of a substrate, and high landing accuracy is required.

  The reason why the ink landing accuracy deteriorates may be that the surface flatness of the nozzle plate 2 is inferior, but the nozzle plate 2 is formed of a polyimide film or metal whose thickness accuracy is controlled. The flatness of the main surface of the nozzle plate 2 is excellent, and the influence of the flatness of the surface is small.

  Alternatively, the flatness of the front surface of the piezoelectric substrate 1 can be considered as a cause of deterioration in landing accuracy. The flatness of the front surface of the piezoelectric substrate 1 is determined by the flatness when the piezoelectric substrate is cut from the wafer state. The flatness when the piezoelectric substrate is cut from the state of the wafer is determined by the mechanical accuracy of the cutting apparatus, and the variation is small and the degree of influence is considered to be small.

  With respect to these problems, there is a problem that the flatness of the adhesion surface of the electrode protective film to the nozzle plate is not sufficiently flat.

  FIG. 13 shows an enlarged schematic cross-sectional view of the end portion of the ink flow path of the piezoelectric substrate and the nozzle portion of the nozzle plate. An electrode 14 is formed on the side surface of the ink flow path 11 of the piezoelectric substrate 1. An electrode protective film 5 is formed so as to cover the surface of the electrode 14 and the front surface of the piezoelectric substrate 1. The nozzle plate 2 is fixed to the piezoelectric substrate 1 with an adhesive 3 disposed on the surface of the electrode protective film 5.

  The electrode protective film 5 may be formed with convex portions 5f that partially protrude from the surface. The convex part 5f appears when the electrode protective film 5 is formed. For example, when a polyparaxylylene film is used as the electrode protective film, a protrusion having a height of about 10 to 15 μm is generated when a polyparaxylylene film having a thickness of 5 μm is formed. As described above, the surface of the electrode protective film 5 is uneven.

  When the convex portion 5f appears on the surface of the electrode protective film, the nozzle plate 2 may bend at that portion. When the nozzle plate 2 bends, the center line 2c of the nozzle 2a faces sideways, and the direction in which ink is ejected deviates from the design. As a result, there is a problem that the accuracy of the ink landing position deteriorates.

  Alternatively, when the convex portion 5f appears, a part of the adhesion surface of the nozzle plate 2 and a part of the electrode protection film 5 disposed on the front surface of the piezoelectric substrate 1 are not in contact with each other. There are cases where air bubbles are caught in the part. When bubbles are generated in the vicinity of the nozzle 2a, there is a problem in that the ink enters the bubble portion when the ink is discharged and the discharge characteristics of the droplets deteriorate.

  Alternatively, a gap may be formed between the electrode protective film and the nozzle plate, and the ink flow paths adjacent to each other may communicate with each other. When the ink flow paths communicate with each other, there is a problem in that the droplet discharge characteristics deteriorate.

  Alternatively, referring to FIG. 12, bonding is performed in a state where the main surface of nozzle plate 2 and the front surface of piezoelectric substrate 1 are not substantially parallel as a result of the formation of a plurality of convex portions on the surface of the electrode protective film. May be. In such a case, there is a problem that the ejection direction of the ink ejected from the ink jet head is changed and the landing accuracy is deteriorated.

An object of the present invention is to provide an ink jet head excellent in ink ejection performance and a method for manufacturing the same.

  An ink jet head according to the present invention includes a substrate on which a plurality of grooves are formed, and a nozzle plate fixed to the front surface of the substrate with an adhesive. The substrate includes at least an electrode formed on the wall surface of the groove, and an electrode protective film formed on the surface of the electrode and the front surface of the substrate. The electrode protective film has a protrusion protruding from the surface on the front surface. The convex portion is formed so that the height is equal to or less than the thickness of the adhesive. The convex part is formed in a substantially flat portion toward the nozzle plate.

Preferably, in the above invention, the convex portion has a substantially trapezoidal cross-sectional shape.
Preferably, in the above invention, the convex portion is formed so as to have a height of 2 μm or less in a cross-sectional shape.

In the above invention, preferably, the electrode protective film includes a polyparaxylylene film.
In the above invention, preferably, the electrode protective film includes a polymonochloroparaxylylene film and a polyparaxylylene film.

  An inkjet head manufacturing method according to the present invention includes a step of forming a plurality of grooves on a substrate, a step of forming an electrode on at least a wall surface of the groove, and an electrode protective film on the surface of the electrode and the front surface of the substrate. The process of carrying out is included. A flattening step of flattening a convex portion formed on the surface of the electrode protection film on the front surface of the substrate; A step of disposing an adhesive on the surface of the electrode protection film on the front surface of the substrate; and a step of adhering a nozzle plate to the electrode protection film on the front surface of the substrate.

  In the above invention, preferably, the flattening step includes a step of plastically deforming the convex portion so that a cross-sectional shape is substantially trapezoidal.

  Preferably, in the above invention, the flattening step includes a step of deforming the convex portion so that the height is 2 μm or less.

  Preferably, the above invention includes a step of disposing a polyparaxylylene film as the electrode protective film.

  Preferably, the above invention includes a step of laminating a polymonochloroparaxylylene film and a polyparaxylylene film as the electrode protective film.

  Preferably, in the above invention, the flattening step includes a step of deforming the convex portion by pressing the convex portion using a pressing member.

In the present invention preferably the planarization step, force pressing the convex portion, 8N / mm ² or more 10 N / mm ² is performed so that the following.

  Preferably, in the above invention, the flattening step includes a step of pressing with the pressing member while interposing an elastic body.

  Preferably, in the above invention, the planarization step is performed while heating at least one of the pressing member and the electrode protective film.

  In the above invention, a polyparaxylylene film is preferably used as the electrode protective film. The one heating is performed so that the temperature of the polyparaxylylene film is equal to or higher than the glass transition point.

  Preferably, in the above invention, the method includes a step of forming the substrate from a piezoelectric substrate, and the one heating is performed to be equal to or lower than a Curie point of the piezoelectric substrate.

  Preferably, in the above invention, the flattening step is performed while using ultrasonic waves together when pressing the convex portion.

  According to the present invention, it is possible to provide an ink jet head excellent in ink ejection performance and a manufacturing method thereof.

(Embodiment 1)
With reference to FIGS. 1 to 11, an ink jet head and a method of manufacturing the ink jet head according to the first embodiment of the present invention will be described.

  FIG. 1 is a schematic perspective view of the ink jet head in the present embodiment. FIG. 1 is a schematic perspective view when the nozzle plate is separated from the inkjet head.

  The ink jet head includes a head unit 6. The head unit 6 includes a piezoelectric substrate 1 as a substrate. The piezoelectric substrate 1 is made of a piezoelectric material. The piezoelectric substrate 1 has a plurality of grooves 1a. Each groove part 1a is formed so that the extending directions may be parallel to each other. Each groove part 1a is formed so that a mutual space | interval may become substantially equal intervals.

  The head unit 6 includes a lid member 4. The lid member 4 is bonded to the upper surface of the piezoelectric substrate 1. By joining the lid member 4 to the piezoelectric substrate 1, an ink flow path 11 that is an ink flow path is formed.

  The piezoelectric substrate 1 has a wall portion 1b formed between the groove portions 1a. An electrode 14 is formed on the side surface of the groove portion 1a of the piezoelectric substrate 1, that is, on the wall surface of the wall portion 1b. The electrode 14 is formed in a film shape so as to cover the wall surface. One wall portion 1 b is sandwiched between two electrodes 14. The electrode 14 in the present embodiment is made of metal.

  The ink jet head in the present embodiment is formed such that a voltage is applied to the electrode 14 and an electric field is generated inside the wall 1b, whereby the wall 1b is deformed and the ink flow path 11 is pressurized. Yes. When the ink flow path 11 is pressurized, ink is ejected from the nozzle 2a.

  The nozzle plate 2 is joined to the front surface of the head portion 6 as indicated by an arrow 51. The nozzle plate 2 has a plurality of nozzles 2a. The nozzles 2 a are formed so as to correspond to the positions of the respective ink flow paths 11 of the head unit 6. The nozzles 2a are formed at a predetermined interval. The nozzles 2a are arranged in a straight line. The nozzle plate 2 is formed so that the nozzle 2 a is disposed at substantially the center in the width direction of the ink flow path 11 when the nozzle plate 2 is joined to the head portion 6. In addition, the nozzle 2 a is formed at the approximate center in the height direction of the ink flow path 11.

  FIG. 2 shows an enlarged schematic cross-sectional view of the ink flow path portion and the nozzle portion of the nozzle plate. The ink flows in the direction indicated by the arrow 52 by being pressurized. That is, ink flows along the extending direction of the groove 1a. A nozzle plate 2 is bonded to the front surface of the piezoelectric substrate 1 via an electrode protective film 5. The nozzles 2a formed on the nozzle plate 2 are formed so that the opening area gradually decreases along the direction in which the ink flows.

  The electrode 14 is electrically connected to an external electric circuit (not shown). An electrode protective film 5 is formed on the surface of the electrode 14 and the front surface of the piezoelectric substrate 1. The electrode protective film 5 is formed so as to cover the entire surface of the electrode 14. In the present embodiment, a polyparaxylene film that is an organic protective film is formed as the electrode protective film 5. The nozzle plate 2 is bonded and fixed to the surface of the electrode protective film 5 with an adhesive 3.

  The center line 2b of the nozzle 2a is substantially parallel to the direction in which the groove 1a extends. That is, the center line 2 b is substantially perpendicular to the front surface of the piezoelectric substrate 1. In the present embodiment, a convex portion 5 a is formed on a part of the front surface of the electrode protective film 5.

  FIG. 3 shows an enlarged schematic cross-sectional view of the convex portion formed on the electrode protective film. FIG. 3 is an enlarged schematic cross-sectional view of a portion A in FIG. The convex portion 5 a is formed so that the height h 1 is smaller than the thickness of the adhesive 3. The convex part 5a is formed so that the cross-sectional shape is a trapezoid. The convex part 5a is formed in a substantially flat shape at the part toward the nozzle plate 2.

  In FIG. 2 and FIG. 3, one convex portion 5 a is shown, but a plurality of convex portions are formed on the surface of the electrode protective film 5. In the present embodiment, a plurality of convex portions 5a having the highest height are formed. These convex portions 5a have substantially the same height h1. Among the plurality of convex portions, the highest convex portion 5a is formed so that the portion facing the nozzle plate is formed in a substantially flat shape, and the flat portion facing the nozzle plate is included in one plane. Has been.

  As described above, in the ink jet head according to the present embodiment, the electrode protective film has the convex portion, and the convex portion is formed so that the portion facing the nozzle plate is substantially planar. The convex part is formed so that the height is lower than the thickness of the adhesive. With this configuration, it is possible to avoid the convex portion from coming into contact with the nozzle plate, and it is possible to prevent the nozzle plate from being bent or the nozzle plate from being inclined and bonded. Alternatively, the center line of the nozzle of the nozzle plate and the direction in which the ink flow path extends can be made substantially parallel. That is, it can suppress that a nozzle inclines. As a result, ink landing accuracy can be improved.

  Further, it is possible to prevent air bubbles from being caught between the substrate and the nozzle plate. Alternatively, the ink flow paths can be prevented from communicating with each other. As a result, ink landing accuracy is improved and ink ejection stability is improved. Thus, the ejection performance of the inkjet head is improved.

  In the present embodiment, the convex portion 5a and the nozzle plate 2 are separated from each other. However, the present invention is not limited to this configuration, and at least some of the convex portions 5a and the thickness of the adhesive are substantially the same among the plurality of convex portions. It may be formed so as to be. At least a part of the convex portions 5a and the nozzle plate 2 may be in contact with each other. By adopting this configuration, the convex portion 5a can be used as a spacer, and the undulation and inclination of the nozzle plate can be prevented in the same manner as described above, and the ejection performance of the inkjet head is improved.

  When at least a part of the convex portion 5a is in contact with the nozzle plate 2, the planar portion of the convex portion facing the nozzle plate is formed so as to be substantially parallel to the front surface of the piezoelectric substrate 1. preferable. That is, it is preferable that the cross-sectional shape of the convex portion is formed in a substantially trapezoidal shape. By adopting this configuration, the nozzle plate and the convex portion are in surface contact with each other, the area for supporting the nozzle plate is increased, and an adhesive having a uniform thickness can be formed. Therefore, it is possible to prevent air bubbles from being caught between the substrate and the nozzle plate and the ink flow paths from communicating with each other. In addition, it is possible to prevent the nozzle plate from swelling and tilting, and it is possible to more reliably prevent the nozzle from tilting. As a result, the ejection performance of the inkjet head is improved.

  With reference to FIG. 3, the convex part 5a in this Embodiment is formed so that the maximum of height h1 may be 2 micrometers or less. If the thickness of the adhesive 3 when the nozzle plate 2 is bonded and fixed is too thin, air bubbles may be caught or the adhesive strength may be insufficient. On the other hand, when the thickness of the adhesive agent 3 is too thick, the adhesive agent wraps around the nozzle and the nozzle is clogged. For this reason, for example, the thickness of the adhesive is preferably about 2 μm. By using the convex portion as a spacer, the thickness of the adhesive can be made uniform, and the thickness of the adhesive can be reduced to 2 μm or less in a state where the biting of bubbles and lack of adhesive strength are suppressed. .

  The convex portion in the present embodiment has a trapezoidal cross-sectional shape. However, the convex portion is not particularly limited to this shape, and the convex portion may be formed so that the portion facing the nozzle plate is substantially planar.

  FIG. 4 shows an enlarged schematic cross-sectional view of another convex portion in the present embodiment. FIG. 5 shows an enlarged schematic cross-sectional view of still another convex portion in the present embodiment.

  Referring to FIG. 4, convex portions 5 b as other convex portions are formed on electrode protection film 5. The convex part 5b is formed so that the cross-sectional shape is a quadrangle. As for the convex part 5b, the surface which goes to the nozzle plate 2 is formed in substantially planar shape. The surface of the convex portion 5b facing the nozzle plate 2 and the surface of the nozzle plate 2 are not parallel. The convex portion 5 b is formed so that the maximum height is lower than the thickness of the adhesive 3.

  Referring to FIG. 5, convex portion 5 c as another convex portion is formed on electrode protection film 5. The convex part 5c is formed in a substantially planar shape at the part toward the nozzle plate 2. The cross-sectional shape of the planar portion facing the nozzle plate 2 is slightly curved. The surface toward the nozzle plate 2 is formed so that the center is recessed. The convex portion 5 c is formed so that the maximum height is lower than the thickness of the adhesive 3.

  As shown in FIG. 4 and FIG. 5, the portion of the convex portion that faces the nozzle plate may be formed so as to be substantially flat rather than a complete flat surface.

  The electrode protective film in the present embodiment is formed of a polyparaxylylene film. With this configuration, an electrode protective film that is chemically stable and has high chemical resistance and insulation can be formed. Some water-based inks and inks containing metal particles have slightly conductivity. In such ink, when driving the wall portion of the piezoelectric substrate, a leakage current flows in each ink flow path (channel), and the deformation of the regular wall portion in the shear mode cannot be achieved, and the ejection is performed. Problems that cause defects may arise. Alternatively, there may be a problem that the ink jet head is damaged due to electric field corrosion of the electrode material. By adopting a polyparaxylylene film as the electrode protective film, such a problem can be suppressed.

  In addition, in an ink containing an organic solvent as a main component, there is a possibility that a member constituting the ink jet head, an adhesive, or the like may be dissolved, and it is necessary to isolate such a member having a high possibility of solubility from the ink. By employing a polyparaxylylene film as the electrode protective film, each member can be protected from the ink even when highly soluble ink is used.

  In addition, polyparaxylylene films can be formed by vapor phase growth at room temperature, so thermal damage to members whose characteristics deteriorate due to heat or whose surface shape is complicated when forming an electrode protection film A substantially uniform electrode protective film can be formed without giving any.

Next, a method for manufacturing the ink jet head in the present embodiment will be described.
FIG. 6 is a flowchart of the manufacturing process of the ink jet head in the present embodiment. The manufacturing method of the inkjet head in the present embodiment includes steps 1 to 3.

  Step 1 is a manufacturing process of the head part, and Step 2 is a manufacturing process of the nozzle plate. Step 3 is a process of joining the head portion and the nozzle plate.

  With reference to FIGS. 1, 2, and 6, in Step 1, the head portion is manufactured. In step 1-1, a groove serving as an ink flow path is formed in the piezoelectric substrate. In the present embodiment, a piezoelectric substrate 1 made of a piezoelectric ceramic material such as zirconate titanate (PZT) or lead titanate (PT) subjected to polarization treatment is formed as the piezoelectric substrate 1. A plurality of groove portions 1 a having a depth of about 300 μm and a width of about 70 μm are formed on the piezoelectric substrate 1 using a dicing apparatus equipped with a diamond blade. This groove 1a will later constitute an ink flow path.

Next, an electrode is formed in step 1-2. Using a deposition apparatus such as a vapor deposition apparatus, a sputtering apparatus, or a plasma CVD (Chemical Vapor Deposition) apparatus, the groove 1
The electrode 14 is formed on the wall surface of a. Alternatively, the electrode 14 is formed by plating or the like. As the electrode, a metal film such as Cu, Al, Ni, Au is formed. In the present embodiment, the electrode 14 is formed on the wall surface of the groove 1a while adjusting the film formation time so that the thickness is about 0.5 μm or more and 1 μm or less. The electrode 14 is a piezoelectric drive electrode that drives the wall 1b. The electrode is not limited to a metal film, and a conductive film may be formed.

  Next, in step 1-3, the lid member is bonded to the piezoelectric substrate to form an ink flow path. Of the surface of the piezoelectric substrate 1, the unnecessary adhesive film formed on the adhesive surface is removed by polishing the adhesive surface with the lid member 4. Also, the adhesive surface is flattened by polishing. The lid member 4 formed in a flat plate shape is bonded and fixed to the piezoelectric substrate 1. The ink flow path 11 is formed by bonding the piezoelectric substrate 1 and the lid member 4 together.

  Next, in step 1-4, an electrode protective film is formed. In the present embodiment, a polyparaxylylene film is formed as the electrode protective film 5. In the present embodiment, the electrode protective film 5 is formed by vapor phase growth at room temperature. In the present embodiment, a polyparaxylylene film is formed in the ink flow path 11, on the front surface of the piezoelectric substrate 1 and on the front surface of the lid member 4 so as to have a film thickness of 5 μm.

  FIG. 7 shows an enlarged schematic cross-sectional view of a convex portion that appears on the surface when an electrode protective film is formed. In FIG. 7, convex portions 5 d and 5 e are developed in the electrode protective film 5. The convex parts 5d and 5e have a shape of a knob. The cause of the protrusions protruding from the surface of the electrode protection film is not clear, but impurities floating inside the chamber for forming the electrode protection film are mixed during film formation, and the impurities become nuclei. Since polyparaxylylene and the like are deposited, it is considered that a convex portion is formed. Alternatively, when minute dust, cutting waste, or the like attached to the film-forming surface of the electrode protection film 5 is present, it is considered that the deposit forms a projection as a nucleus when the electrode protection film 5 is formed. It is done.

  A plurality of convex portions appear on the surface of the electrode protective film. In the present embodiment, a convex portion having a height h2 from the surface of the electrode protective film of approximately 10 μm to 15 μm appears with respect to the electrode protective film having a thickness of approximately 5 μm. For example, approximately several tens of such convex portions appear on the front surface of the head portion having dimensions of about 3 mm in length and about 15 mm in width. Even when the thickness of the electrode protective film is changed, it has been confirmed that a convex portion having a height of about 2 to 3 times that of the electrode protective film to be formed appears.

  Next, in step 1-5, a flattening process is performed for flattening the convex portions that have developed on the surface of the electrode protective film. In the present embodiment, by pressing the convex portion with a pressing member, the top portion of the convex portion is plastically deformed and flattened.

  FIG. 8 shows a schematic perspective view of the planarization step in the present embodiment. The pressing member 31 is brought into contact with the front surface of the head unit 6. In the present embodiment, a flat pressure plate is used as the pressing member 31. The contact surface of the pressing member 31 is formed such that the surface unevenness is 1 μm or less. That is, a pressing member having a contact surface with a flatness of 1 μm or less is used.

  The main surface of the pressing member 31 and the front surface of the head unit 6 are brought into contact with each other. As indicated by an arrow 53, the pressure is applied by a pressure device (not shown). As a pressurizing device in the present embodiment, pressurization is performed using a joining device for joining the nozzle plate to the head portion in a later step.

  In the present embodiment, an elastic member 32 is disposed between the pressing member 31 and the pressure device. The elastic member 32 is formed in a plate shape and is formed so as to cover the entire main surface opposite to the contact surface of the pressing member 31. The pressing member 31 is pressed against the front surface of the head portion 6 while maintaining the main surface of the pressing member 31 and the front surface of the head portion 6 substantially parallel to each other.

  FIG. 9 shows an enlarged schematic cross-sectional view when the convex portion is pressed by the pressing member in the flattening step. As indicated by an arrow 53, the pressing member 31 and the elastic member 32 are pressurized by a pressurizing device. The pressing member 31 selectively contacts the convex portions 5 d and 5 e of the electrode protective film 5.

  The convex portions 5d and 5e are pressed and plastically deformed from the top. In the present embodiment, the convex portions 5d and 5e have a substantially trapezoidal cross-sectional shape. In the present embodiment, the pressing is performed so that the height of the protrusions 5d and 5e from the main surface of the electrode protective film 5 is 2 μm or less.

Pressure in our definitive pressing member in this embodiment is about 8N / mm ² or more to about 10 N / mm ² or less. By this method, the height of the convex portions 5d and 5e can be made 2 μm or less. In the case of a pressing force smaller than this range, the height of the convex portion could not be made sufficiently low. Further, in the case of a pressing force larger than this range, peeling of the electrode protective film from the head part was confirmed.

  In the flattening step, the height of the convex portion needs to be the same as the thickness of the adhesive for bonding the nozzle plate or lower than the thickness of the adhesive. In the present embodiment, the design value of the thickness of the adhesive is 2 μm. In the flattening step, flattening is performed so that the height of the convex portion is 2 μm or less.

  In the flattening process, by making the height of the convex portion substantially the same as the thickness of the adhesive, the convex portion can be used as a spacer for defining the thickness of the adhesive. Can be made uniform.

  By pressing the pressing member in the flattening step, several tens of convex portions formed on the front surface of the head portion could be made to have a substantially uniform height. At this time, the variation in flattening depending on the variation in the number density of the convex portions was hardly observed. Moreover, even when the film thickness of the electrode protective film was changed, the convex portions could be flattened uniformly by changing the pressing force of the pressing member.

  For the step of forming the electrode protective film, after performing the planarization step, for example, a surface treatment may be performed with oxygen-containing plasma or the like to improve the adhesion with the adhesive.

  Next, referring to FIG. 6, a nozzle plate is manufactured in Step 2. In the present embodiment, the nozzle plate is manufactured using a metal material as a base material. A nozzle plate is formed by forming a nozzle on a base material such as a stainless steel base or Ni base by electroforming or punching. Alternatively, the nozzle plate is formed by performing excimer laser processing or the like on a synthetic resin base material such as polyimide.

  Referring to FIG. 2, in forming the nozzle 2a, the nozzle fixed on the piezoelectric substrate 1 is tapered such that the diameter of the nozzle is larger than the diameter of the outer nozzle. The nozzle 2a is formed so as to conform to the voltage necessary for ejecting ink and the size of the ink droplet. For example, when the thickness of the nozzle plate 2 is about 50 μm, in the cross-sectional shape of the nozzle 2a, the diameter on the piezoelectric substrate 1 side is about 40 μm, the outer diameter is about 20 μm, and the taper angle is about 10 °. To form.

  It is preferable that the outer surface of the nozzle plate 2 has high liquid repellency with respect to the ink used. By increasing the liquid repellency of the outer surface of the nozzle plate 2, it is possible to improve the stability when ejecting ink. In the present embodiment, a material having high liquid repellency is applied to the outer surface of the nozzle plate 2.

  Further, the inner surface of the nozzle plate 2 is preferably highly lyophilic, contrary to the outer surface. By increasing the lyophilicity of the inner surface of the nozzle plate, the flow of ink can be made smooth, and the stability when ejecting ink can be improved. For example, in the case where the nozzle plate is formed of a synthetic resin material such as polyimide, the surface of the inner surface of the nozzle plate and the inner surface of the nozzle are subjected to surface treatment using plasma containing oxygen, The lyophilicity with the ink can be increased.

  Next, referring to FIG. 6, in step 3, a joining process for joining the head portion and the nozzle plate is performed.

  FIG. 10 is a schematic perspective view when the nozzle plate is joined to the head portion. An adhesive is disposed on the front surface of the head unit 6. For example, the adhesive is placed on the surface of the polyimide film by a coating device such as a bar coater device. An adhesive is uniformly applied on the surface of the polyimide film so as to have a thickness of 4 μm. In the present embodiment, an epoxy adhesive is used as the adhesive. Next, the polyimide film to which the adhesive is applied is pressed against the front surface of the head unit 6 to perform stamp transfer, whereby an adhesive having a uniform thickness that is about half the amount of the adhesive transferred to the polyimide film. Can be arranged.

  Next, the nozzle plate 2 is bonded and fixed to the head portion 6. In the present embodiment, a nozzle plate joining apparatus is used. The nozzle plate joining apparatus in the present embodiment includes a pressing member 43 made of an elastic body and an alignment camera 41.

  FIG. 11 shows a schematic cross-sectional view when the nozzle plate is bonded to the head portion. The piezoelectric substrate 1 has a plurality of grooves 1a. The direction in which the ink flows is the direction indicated by the arrow 52. In bonding and fixing the nozzle plate 2, the nozzle plate 2 is translated toward the head portion 6 as indicated by an arrow 55. Adhesion is performed so that the nozzle 2a of the nozzle plate 2 is disposed at substantially the center of the ink flow path 11.

  The pressure member 43 made of an elastic body has a suction hole 43a. The suction hole 43a is connected to a vacuum exhaust device (not shown). The nozzle plate 2 is held on the suction surface 43b by suction.

  Referring to FIGS. 10 and 11, in joining nozzle plate 2, first, alignment position of nozzle plate 2 is adjusted using alignment camera 41. Using the alignment camera 41, the position of the head unit 6 is adjusted.

  While confirming the relative position using the alignment camera 41, the nozzle plate 2 is brought into contact with the head unit 6. When the nozzle plate 2 comes into contact with the adhesive, the nozzle plate 2 is pressurized using the pressure member 43 as indicated by an arrow 54. By this pressing step, the adhesive is reduced to a thickness of about 2 μm or less. Thereafter, the nozzle plate 2 is fixed to the head portion 6 by curing the adhesive.

  In the present embodiment, an epoxy-based adhesive is used as an adhesive, but the present invention is not limited to this, and any adhesive can be used. By using a high viscosity adhesive, it is possible to suppress the adhesive from entering the nozzle. Further, by using an adhesive having a low viscosity, it is possible to suppress the entrapment of bubbles due to the unevenness of the surface of the electrode protective film.

  In the prior art, while using a high-viscosity adhesive, it was necessary to increase the pressure applied to extrude the generated bubbles. However, since this pressure is high, the nozzle plate may be bent or the nozzle plate may be inclined due to the unevenness caused by the convex portions formed on the surface of the electrode protective film.

  In the present embodiment, since the height of the convex portions on the surface of the electrode protective film is as low as 2 μm or less (because the surface irregularities are small), it is not necessary to consider that bubbles are generated. Therefore, it is only necessary to consider that the adhesive enters the nozzle. For example, even if an adhesive having a high viscosity is used, adhesion can be performed while preventing the entrapment of bubbles.

  In the present embodiment, adhesion was performed with the above pressing force using an adhesive having a viscosity of 3000 cp. As a result, it is possible to fix the nozzle plate to the head portion while suppressing the nozzle from being clogged with the adhesive and the entrapment of bubbles. Further, the nozzle plate can be bonded while preventing the nozzle plate from being bent (wavy) or inclined.

  The ink jet manufacturing method according to the present embodiment includes a step of forming an electrode protective film on the surface of the electrode and the front surface of the substrate, and a flattening step of flattening the convex portions generated on the surface of the electrode protective film. By adopting this method, the height of the convex portion generated in the electrode protective film can be made equal to or less than the thickness of the adhesive, and the nozzle plate can be prevented from being inclined or bent. That is, a convex part can be arrange | positioned inside an adhesive layer and it can avoid that a convex part affects a nozzle plate. As a result, an ink jet head having excellent ink ejection characteristics can be manufactured.

  Further, the flattening step in the present embodiment includes a step of plastically deforming the convex portion. By this method, the shape of the convex portion when the flattening step is performed can be maintained, and the height of the convex portion can be easily adjusted.

  In the planarization step in the present embodiment, the planarization is performed so that the cross-sectional shape of the convex portion is substantially trapezoidal. By this method, the maximum height of the plurality of convex portions can be easily adjusted at a time. Moreover, when using a convex part as a spacer when adhering a nozzle plate, a convex part can be surface-contacted with respect to a nozzle plate. As a result, the center of the nozzle and the center of the ink flow path can be arranged on a straight line. Moreover, it can suppress that a nozzle inclines in another direction.

  Moreover, the planarization process in this Embodiment has pressed the convex part using the press member. By adopting this method, the convex portion can be easily flattened. In the present embodiment, a flat plate is used as the pressing member. By adopting this method, at least a part of the plurality of convex portions can be flattened to a uniform height.

  The planarization process in this Embodiment includes the process of pressing a convex part with a pressing member, interposing an elastic body. By adopting this method, it is not necessary to strictly manage the parallelism between the pressing member and the front surface of the head portion, and the pressing member can be easily pressed uniformly. That is, the convex part of the electrode protective film can be pressed uniformly. As a result, it is possible to suppress the occurrence of cracks or chipping in the piezoelectric substrate.

Moreover, the planarization process in this Embodiment is performed so that the force which presses a convex part may be 10 N / mm < ² > or less. By adopting this method, it is possible to prevent peeling of the electrode protective film due to pressurization. Further, the irregularities on the surface of about 15 μm generated when a polyparaxylene film having a thickness of 5 μm is formed as the electrode protective film can be plastically deformed to 2 μm or less. When the pressing force by the pressing member is pressed at less than 8 N / mm ² , the convex portion of the electrode protective film cannot be sufficiently plastically deformed. Therefore, the pressure applied by the pressing member is preferably 8 N / mm ² or more.

  Moreover, the planarization process in this Embodiment can use the joining apparatus which joins the nozzle plate used conventionally to a head part. For this reason, this invention can be implemented with the existing installation, without requiring a new installation.

  In this embodiment, a polyparaxylylene film is formed as the electrode protective film, but the present invention is not limited to this, and an arbitrary electrode protective film can be formed. For example, an electrode protective film including a plurality of layers may be formed as the electrode protective film. For example, a polymonochloroparaxylylene film and a polyparaxylylene film may be formed. In this case, after the polymonochloroparaxylylene film is formed, the polyparaxylylene film is formed.

  By forming a polymonochloroparaxylylene film, it is possible to form a protective film having no pinholes and having excellent insulating properties with respect to the electrode. Furthermore, by forming a polyparaxylylene film, chemical resistance can be improved, and the electrode can be protected against various inks. In this way, an electrode protective film having excellent insulating properties and chemical resistance can be formed.

  Even when an electrode protective film including these two layers is formed, when the electrode protective film has a thickness of 5 μm, a protrusion having a height of about 10 μm to about 15 μm appears on the surface of the polyparaxylylene film. However, the convex portion can be plastically deformed and flattened by pressing the convex portion.

  In the inkjet manufacturing method according to the present embodiment, the respective members are assembled after being separated from each other. Cleaning can be performed each time each member is processed, and the cleanliness of the ink flow path of the completed inkjet head can be increased. Moreover, it becomes possible to process the nozzles of the nozzle plate all at once, thereby improving productivity. Further, it is possible to cope with an increase in the size of the inkjet head, and it is possible to provide an inkjet head that is easy to manufacture and inexpensive.

(Embodiment 2)
A method for manufacturing the ink jet head according to the second embodiment of the present invention will be described. The method of manufacturing the ink jet head in the present embodiment is different from the first embodiment in the flattening process.

  In the first inkjet head manufacturing method in the present embodiment, in the planarization step, heat is used in combination to planarize the convex portions generated in the electrode protective film.

  Referring to FIG. 8, when pressing the convex portion of the electrode protective film, heating at least one of the pressing member 31 and the electrode protective film reduces the film rigidity of the electrode protective film and reduces the applied pressure. However, the convex portion can be easily plastically deformed. The film rigidity of the electrode protective film decreases in proportion to the temperature rise when heating. In particular, the convex portion can be plastically deformed at a lower pressure by setting the temperature of the electrode protective film to the glass transition temperature or higher. In addition, since the planarization process can be performed at a low pressure, it is possible to suppress the occurrence of cracks and chipping in the piezoelectric substrate in the planarization process.

For example, in the first embodiment, when a polyparaxylylene film as an electrode protective film, within a pressure of 8N / mm ² or more 10 N / mm ² or less when performing the flattening, the convex height It was able to plastically deform the 2μm or less is, by the electrode protective film to at least the glass transition temperature, in a 4N / mm ² or more 5N / mm ² or less in a range which is a pressure of half convex The part could be plastically deformed to 2 μm or less.

  In the case of using a polyparaxylylene film as the electrode protective film, the glass transition point of the polyparaxylylene film is 77 ° C. In order to perform heating so that the temperature of the polyparaxylylene film becomes equal to or higher than the glass transition point, for example, heating is performed so that the temperature of the polyparaxylylene film becomes about 80 ° C.

  Furthermore, when the temperature of the polyparaxylylene film reaches approximately 175 ° C. or higher, the film rigidity decreases by one digit or more of room temperature. Therefore, it is more preferable to heat the polyparaxylylene film so that the temperature of the polyparaxylene film becomes 175 ° C. or higher. By this method, the convex portion can be plastically deformed with a smaller pressure.

  In the case where the polymonochloroparaxylylene film and the laminate of the polyparaxylylene film are used as an electrode protective film, the glass transition point of the polymonochloroparaxylylene film is approximately 97 ° C. It is preferable to set the above. By this method, both the polymonochloroparaxylylene film and the polyparaxylylene film have a temperature equal to or higher than the glass transition point, and the convex portions formed on the surface can be easily plastically deformed.

  On the other hand, if the temperature is raised too much in the planarization step, the temperature of the piezoelectric substrate also rises, and the temperature of the piezoelectric substrate may exceed the Curie point. When the piezoelectric substrate exceeds the Curie point, the piezoelectric characteristics change. Therefore, when heating is performed, it is preferable that the temperature of the piezoelectric substrate be lower than the Curie point.

  The Curie point of the piezoelectric substrate varies depending on the type of substrate, but is approximately 210 ° C. or higher and 300 ° C. or lower. For this reason, it is preferable to perform heating temperature at 210 degrees C or less, for example.

  In the second inkjet head manufacturing method according to the present embodiment, in the planarization step, ultrasonic waves are used together to planarize the convex portions generated in the electrode protective film.

  By using ultrasonic waves together when pressing the electrode protective film with the pressing member, it is possible to generate strong frictional heat on the convex portions and to locally plastically deform the convex portions at a high temperature. As a result, the pressing force for pressing the convex portion can be reduced.

  For example, referring to FIG. 8, a signal from an ultrasonic oscillator (not shown) is converted into a mechanical signal by a transducer and transmitted to the pressing member 31, thereby causing friction between the convex portion of the electrode protective film and the pressing member 31. Heat can be generated, and the convex portions can be locally plastically deformed for flattening. Since the pressure when pressing the convex portion can be reduced, it is possible to prevent the piezoelectric substrate from being cracked or chipped.

  In this embodiment mode, heating or application of ultrasonic waves is used in the planarization step. However, the present invention is not limited to this mode, and ultrasonic waves may be applied while heating. By this method, the pressing force of the pressing member can be further reduced.

  Since the manufacturing method of the ink jet head other than the above is the same as that of the first embodiment, description thereof will not be repeated here.

  In the respective drawings described above, the same or corresponding parts are denoted by the same reference numerals.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and includes all modifications within the scope and meaning equivalent to the terms of the claims.

2 is an exploded perspective view of the ink jet head according to Embodiment 1. FIG. 2 is an enlarged schematic cross-sectional view of a nozzle portion of the ink jet head in Embodiment 1. FIG. 3 is an enlarged schematic cross-sectional view of a first convex portion of an electrode protective film in the first embodiment. FIG. 5 is an enlarged schematic cross-sectional view of a second convex portion of the electrode protective film in the first embodiment. FIG. 6 is an enlarged schematic cross-sectional view of a third convex portion of the electrode protective film in the first embodiment. FIG. 5 is a process diagram of the method for manufacturing the ink jet head in Embodiment 1. FIG. 3 is a schematic cross-sectional view of a convex portion generated in the electrode protective film in the first embodiment. FIG. FIG. 5 is a schematic perspective view of a planarization process in the first and second embodiments. FIG. 3 is an enlarged schematic cross-sectional view of a planarization process in the first embodiment. FIG. 3 is a schematic perspective view when a nozzle plate is bonded to the head portion in the first embodiment. FIG. 3 is a schematic cross-sectional view when a nozzle plate is attached to the head portion in the first embodiment. It is a schematic sectional drawing when attaching a nozzle plate to the head part based on the prior art. It is an expansion schematic sectional drawing of the part of the nozzle of the inkjet head based on a prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Piezoelectric substrate, 1a Groove part, 1b Wall part, 2 Nozzle plate, 2a Nozzle, 2b, 2c Center line, 3 Adhesive, 4 Lid member, 5 Electrode protective film, 5a-5f Convex part, 6 Head part, 11 Ink Flow path, 14 electrodes, 31 pressing member, 32 elastic member, 41 alignment camera, 43 pressure member, 43a suction hole, 43b suction surface, 51-56 arrows.

Claims (17)

A substrate on which a plurality of grooves are formed;
A nozzle plate fixed to the front surface of the substrate with an adhesive;
The substrate includes at least an electrode formed on a wall surface of the groove;
An electrode protective film formed on the surface of the electrode and the front surface of the substrate;
The electrode protective film has a protrusion protruding from the surface on the front surface,
The convex portion is formed such that the height is equal to or less than the thickness of the adhesive,
The convex portion is an ink jet head in which a portion toward the nozzle plate is formed in a substantially flat shape.   The inkjet head according to claim 1, wherein the convex portion has a substantially trapezoidal cross-sectional shape.   The inkjet head according to claim 1, wherein the convex portion is formed so that a height in a cross-sectional shape is 2 μm or less.   The inkjet head according to claim 1, wherein the electrode protective film includes a polyparaxylylene film.   The inkjet head according to claim 1, wherein the electrode protective film includes a polymonochloroparaxylylene film and a polyparaxylylene film. Forming a plurality of grooves on the substrate;
Forming an electrode on at least the wall surface of the groove;
Forming an electrode protective film on the surface of the electrode and the front surface of the substrate;
On the front surface of the substrate, a flattening step of flattening a convex portion generated on the surface of the electrode protective film;
Disposing an adhesive on the surface of the electrode protection film on the front surface of the substrate;
Adhering a nozzle plate to the electrode protection film on the front surface of the substrate.   The method of manufacturing an ink jet head according to claim 6, wherein the flattening step includes a step of plastically deforming the convex portion so that a cross-sectional shape is substantially trapezoidal.   The method of manufacturing an ink jet head according to claim 6, wherein the flattening step includes a step of deforming the convex portion so that a height is 2 μm or less.   The manufacturing method of the inkjet head of Claim 6 including the process of arrange | positioning a polyparaxylylene film | membrane as the said electrode protective film.   The method for manufacturing an ink jet head according to claim 6, comprising a step of laminating a polymonochloroparaxylylene film and a polyparaxylylene film as the electrode protective film.   The method of manufacturing an inkjet head according to claim 6, wherein the flattening step includes a step of deforming the convex portion by pressing the convex portion using a pressing member. The planarization process, the force that presses the convex portion, 8N / mm ² or more 10 N / mm ² is performed such that the following method for manufacturing an ink jet head according to claim 11.   The method of manufacturing an ink jet head according to claim 11, wherein the flattening step includes a step of pressing with the pressing member while interposing an elastic body.   The method of manufacturing an ink jet head according to claim 11, wherein the flattening step is performed while heating at least one of the pressing member and the electrode protective film. As the electrode protective film, a polyparaxylylene film is used,
The method of manufacturing an ink jet head according to claim 14, wherein the one heating is performed so that a temperature of the polyparaxylylene film is equal to or higher than a glass transition point. Forming the substrate from a piezoelectric material;
The method of manufacturing an ink jet head according to claim 14, wherein the one heating is performed so that a temperature of the piezoelectric material is equal to or lower than a Curie point.   The method of manufacturing an inkjet head according to claim 11, wherein the flattening step is performed while using ultrasonic waves when pressing the convex portion.