JP2012131175A - Inkjet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet head that can fully protect an electrode without generating a pinhole even if the thickness of an insulating protective film is reduced for the high density of a channel.SOLUTION: An inkjet head includes a head chip 1 constituted by forming a continuous chip-side electrode from the inside of a channel 14 to the rear surface via the inlet, and a wiring substrate 3 that is connected to the rear surface of the head chip 1, that has an opening 32 for exposing the inlet of the channel 14, and that has a wiring electrode electrically connected to the chip-side electrode exposed to the rear surface on a surface oriented to the head chip 1. In the inkjet head, an angle from a surface 36 of the wiring substrate 3 that is oriented to the head chip 1 to an inner wall surface 34 of the opening 32 is 45° or more to 88° or less. An insulating protective film is continuously formed at least from the inside of the channel 14 of the head chip 1 to the inner wall surface 34 of the opening 32 of the wiring substrate 3 such that exposed portions of the chip-side electrode and the wiring electrode are covered.

Description

  The present invention relates to an ink-jet head, and more particularly to an ink-jet head capable of realizing a high density of nozzles without generating pinholes even when the film thickness of an insulating protective film is reduced and the electrodes are sufficiently protected.

  Conventionally, 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. An ink jet head (Patent Document 1) configured by the above is known.

  In recent years, in order to improve the quality of printed images, it has been required to arrange nozzles side by side with a higher density. In the case of an inkjet head having a harmonica type head chip, the channel width is made narrower. In addition, the channel density is increased to meet the demand for higher nozzle density.

JP 2007-83705 A

  By the way, since the wall surface of the channel and the part serving as the ink supply path is in direct contact with the ink, particularly when water-based ink is used, there is a problem of causing corrosion of the electrode if the electrode is exposed in these parts. is there. For this reason, at least a portion where the electrode is exposed is covered with an insulating protective film to protect it from ink.

  However, it has been found that there is a new problem when trying to increase the density of the nozzle by forming the channel width to be narrower in the ink jet head thus coated with the insulating protective film.

  This will be described below with reference to FIGS.

  FIG. 11A is a view of one channel when the channel density of the harmonica type head chip is 180 dpi, as viewed from the ink ejection direction, and FIG. 11B is the channel density of the harmonica type head chip. This shows a case where the density is increased to 300 dpi.

  In the former case of 180 dpi, the channel width is secured to about 82 μm, whereas in the latter case of 300 dpi, the channel width is reduced to 42 μm. In any of these cases, the diameter of the nozzle 621 disposed at the outlet of the channel must be maintained at a predetermined nozzle diameter in order to maintain a predetermined ink droplet diameter and ink ejection characteristics. Is formed. A drive electrode 615 having a thickness of 3 μm is formed on the inner surface of each channel.

  Here, when the insulating protective film M is formed to protect the drive electrode 615 on the inner surface of the channel, it can be formed with a sufficient thickness (specifically, about 7 μm ± 15%) in the case of the former 180 dpi. It was.

  However, in the latter case of 300 dpi, if the driving electrode 615 is formed with a thickness of 3 μm on the inner surface of the channel having a width of 42 μm, the thickness of the insulating protective film M that can be formed on the inner surface of the channel is limited to 3 μm. turn into. This is because when the thickness of the insulating protective film M exceeds 3 μm, considering that the error of the position of the nozzle 621 is about ± 2 μm when the nozzle plate is adhered, the insulating protective film M is This is because the nozzle 621 may be blocked in the worst case.

  In this way, when the insulating protective film M having a thin film thickness of 3 μm is formed, the protection of the electrode is partially insufficient, and there is a problem that the electrode is corroded. This hindered high density of the nozzles, that is, high quality of the printed image.

  The inventor tried to elucidate the reason why the electrode is not sufficiently protected when the insulating protective film is formed with a thin film thickness of 3 μm in the prior art. As a result, it has been found that a portion where the insulating protective film is insufficiently formed occurs at the joint portion with the wiring substrate joined to the rear surface of the head chip.

  That is, voltage is applied to the rear surface of the harmonica type head chip via an electrode drawn from the inside of each channel to the rear surface of the head chip in order to apply a voltage from the driving circuit to the driving electrode in each channel. A wiring board for connecting an external wiring member (FPC) for bonding is joined.

  FIG. 12 is a cross-sectional view of a head chip to which such a wiring board is bonded. 601 is a harmonica type head chip, 602 is a nozzle plate bonded to the front surface of the head chip 601, and 603 is bonded to the rear surface of the head chip 601. This is a printed wiring board.

  The head chip 601 has a plurality of channels 614 arranged in parallel, and a drive electrode 615 is formed on the inner surface thereof. The channel 614 is provided with an outlet 642 and an inlet 641 of the channel 614 on the front surface and the rear surface of the head chip 621, respectively, and is electrically connected to the driving electrode 615 on the inner surface of the channel 614 on the rear surface of the head chip 601. A connection electrode 616 is formed on the rear surface after passing through. Each connection electrode 616 extends from the inlet 641 of each channel 614 toward the outside of the head chip 601.

  A wiring electrode 633 for applying a voltage from the drive circuit to the drive electrode 615 via the connection electrode 616 is formed on the surface to be bonded to the head chip 601 on the wiring substrate 603, and is formed on the rear surface of the head chip 601. By being joined, electrical connection between the wiring electrode 633 and the connection electrode 616 is achieved.

  In the wiring substrate 603, an opening 632 is formed on the rear surface of the head chip 601 so that the inlets 641 of all the channels 614 are exposed. The opening 632 is usually formed by sand blasting. However, sand blasting has a property that machining efficiency decreases as cutting progresses from the surface to the inside. In order to perform cutting processing, sandblasting is performed from both sides.

  This sandblasting process has the property that the machining range becomes narrower as cutting proceeds from the surface to the inside. Therefore, as shown in FIG. 13 which is a partially enlarged view of the region A in FIG. 12, when the opening 632 is formed by sandblasting from both sides, the inner wall surface 634 of the opening 632 has a “<” shape as shown in the figure. It becomes the shape which protrudes.

  In the shape protruding in a “<” shape, the peripheral portion 635 of the opening 632 on the side of the surface 636 that is oriented to the head chip 601, the surface 636 of the wiring substrate 603 from the surface 636 that is oriented to the head chip 601. Since the angle α formed over the inner wall surface 634 is an obtuse angle of 90 ° or more, the portion where the insulating protective film M is to be formed has a convoluted shape, and the coating component of the insulating protective film M does not spread, so that the insulating protection is achieved. The formation of the film M became unstable and pinholes were easily generated.

  If pinholes are formed in the insulating protective film M, there is also a problem that ink penetrates into the adhesive and the adhesive strength is lowered by long-term use.

  Based on this knowledge, the present inventor conducted an earnest study paying attention to the relationship between the angle α and the film formation state of the insulating protective film M, and by making the angle α an acute angle within a predetermined range, It has been found that even when such a thin insulating protective film M is formed, sufficient film formation is possible without generating pinholes, and the present invention has been achieved.

  Accordingly, an object of the present invention is to provide an ink jet head that can sufficiently protect an electrode without causing a pinhole even if the film thickness of an insulating protective film is reduced to increase the density of a channel. It is in.

  The other subject of this invention becomes clear by the following description.

  The above problems are solved by the following inventions.

The invention according to claim 1 has a plurality of channels arranged side by side, and an outlet and an inlet of the channel are arranged on the front surface and the rear surface, respectively, and continue from the inside of the channel through the inlet of the channel to the rear surface. A head chip on which a chip-side electrode is formed;
It is bonded to the rear surface of the head chip, and has an opening that exposes the inlet of the channel for supplying ink of the head chip, and is exposed to the rear surface of the head chip on the surface oriented to the head chip. In an inkjet head having a wiring substrate having a wiring electrode electrically connected to the chip side electrode,
The angle formed from the surface oriented to the head chip in the wiring board to the inner wall surface of the opening is in the range of 45 ° to 88 °,
An insulating protective film is continuously formed so as to cover at least the chip side electrode and the exposed portion of the wiring electrode from within the channel of the head chip to the inner wall surface of the opening of the wiring board. This is an inkjet head.

  The invention according to claim 2 is the ink jet head according to claim 1, wherein the opening is one opening exposing the entrances of all the channels.

  A third aspect of the present invention is the ink jet head according to the first aspect, wherein a plurality of the openings are provided so as to expose the inlets of the channels independently.

According to a fourth aspect of the present invention, the head chip has a plurality of channel rows,
The inkjet head according to claim 1, wherein the opening is provided for each channel row.

In the invention according to claim 5, in the plurality of channels arranged in parallel, an ink channel that ejects ink and a dummy channel that does not eject ink are alternately arranged in parallel.
2. The ink jet head according to claim 1, wherein the opening is provided so as to expose an inlet of the ink channel and not to expose an inlet of the dummy channel.

  A sixth aspect of the present invention is the ink jet head according to any one of the first to fifth aspects, wherein the insulating protective film has a thickness in the range of 1 μm to 3 μm.

  The invention according to claim 7 is the ink jet head according to any one of claims 1 to 6, wherein the insulating protective film is a film made of polyparaxylylene or a derivative thereof.

  The invention according to claim 8 is the ink jet head according to any one of claims 1 to 7, wherein the wiring board has a thickness in a range of 300 μm to 700 μm.

  The invention according to claim 9 is the ink jet head according to any one of claims 1 to 8, wherein the wiring board is made of glass, ceramics or alumina.

  According to the present invention, it is possible to provide an ink jet head capable of sufficiently protecting an electrode without generating a pinhole even if the thickness of the insulating protective film is reduced to increase the density of the channel. .

1 is an exploded perspective view showing an example of an inkjet head according to the present invention. Sectional view taken along line ii-ii in FIG. Partial enlarged view of region A in FIG. The figure explaining an example of the formation method of angle (alpha) in the opening edge of a wiring board Sectional drawing explaining the other aspect of a wiring board Sectional drawing explaining the other aspect of a wiring board The rear view which shows the other aspect of the inkjet head which concerns on this invention Viii-viii cross-sectional view in FIG. The rear view which shows the further another aspect of the inkjet head which concerns on this invention Rear view showing still another embodiment of the inkjet head according to the present invention. Diagram explaining the relationship between channel density and channel width Sectional drawing of the principal part showing an example of an inkjet head according to the prior art Partial enlarged view of region A in FIG.

  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 inkjet head according to the present invention.

  The inkjet head includes a head chip 1, a nozzle plate 2 bonded to the front surface of the head chip 1, a wiring substrate 3 bonded to the rear surface of the head chip 1, and a flexible printed circuit board (external wiring substrate bonded to the wiring substrate 3). FPC) 4 and an ink manifold 5 joined to the rear surface of the wiring board 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. In this embodiment, all the channels 14 are ink channels that eject ink, and ink is supplied to all the channels 14 from the ink manifold 5.

  In this head chip 1, each channel 14 has two upper and lower channel rows in FIG. 1, and each channel row consists of six channels 14, but the channel row in the head chip 1 The number of channels 14 and the number of channels 14 constituting each channel row are not limited at all.

  FIG. 2 is a cross-sectional view taken along the line ii-ii in FIG. 1 and shows an enlarged view of the nozzle plate 2, the head chip 1, and the wiring substrate 3.

  As shown in FIG. 2, the shape of the channel 14 is a straight type in which each channel 14 has almost the same size and shape in the length direction from the inlet 141 to the outlet 142. That is, both side walls rise substantially perpendicular to the upper and lower surfaces, and the channels 14, 14,... Are parallel to each other.

  Further, 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.

  Driving electrodes 15 are formed on the inner surface of the head chip 1 so as to be in close contact with at least the driving wall 13, and the rear surface of the head chip 1 is connected to the inner surface of each channel 14 through the inlet 141 and the head chip 1. A connection electrode 16 that is electrically connected to each drive electrode 15 is formed on the rear surface. These drive electrode 15 and connection electrode 16 are chip side electrodes in the present invention.

  In the nozzle plate 2 attached to the front surface of the head chip 1, the nozzles 21 are opened so as to correspond to the outlets 142 of the respective channels 14.

  The wiring substrate 3 bonded to the rear surface of the head chip 1 has a voltage from the drive circuit applied to each drive electrode 15 via a connection electrode 16 exposed on the rear surface of the head chip 1 on the surface bonded to the head chip 1. A wiring electrode 33 for applying the voltage is formed. In addition, an opening 32 having a rectangular shape in plan view passes through the front and back so that the inlets 141 of all the channels 14 opened on the rear surface of the head chip 1 are exposed in a region corresponding to the channel row of the head chip 1. Is formed. In FIG. 2, one opening 32 having a size including all of these is formed for two channel rows. However, the opening 32 may be formed for each channel row.

  The wiring substrate 3 forms a connecting portion between the head chip 1 and the ink manifold 5 and at the same time provides a connection portion with the FPC 4. Therefore, the wiring substrate 3 needs to have a certain strength, and preferably has a thickness of 300 μm to 700 μm. It is formed in the range. Preferred examples of the material of the wiring board 3 include glass, ceramics, and alumina. In particular, glass (heat-resistant glass) is preferable because it is inexpensive and easy to process.

  The size (area) of the wiring substrate 3 is sufficiently larger than the area of the rear surface of the head chip 1, and thereby, a region on the side of contact with the FPC 4 that largely protrudes to the side (upper surface side and lower surface side) of the head chip 1. Is secured. On the other hand, the size (opening area) of the opening 32 is smaller than the area of the rear surface of the head chip 1 so that a bonding margin with the head chip 1 is formed, but slightly in the bonding position with respect to the rear surface of the head chip 1. Considering that the substrate portion of the wiring substrate 3 does not block the inlet 141 of the head chip 14 even if the deviation occurs, it is slightly larger than the region including the inlets 141 of all the channels 14. Is formed.

  Thus, when the wiring substrate 3 is bonded to the rear surface of the head chip 1, the opening peripheral edge 35 on the side of the opening 32 that is oriented to the head chip 1 is the peripheral edge of the inlet 141 of the channel 14 on the rear surface of the head chip 1. It is located outside 143, and a separation distance D of about 300 μm is formed between them (see FIG. 3). Therefore, when viewed from the rear surface side of the head chip 1, the inlet 141 of the channel 14 and the rear surface portion of the surrounding head chip 1 are exposed in the opening 32 so as to surround the entire inlet 141. Yes.

  The head chip 1 and the wiring substrate 3 are joined by interposing a conductive adhesive between the connection electrode 16 and the wiring electrode 33. Although it does not specifically limit as a conductive adhesive, The adhesive agent which disperse | distributed nickel particle can be illustrated preferably.

  The ink manifold 5 is bonded to the surface of the wiring board 3 opposite to the head chip 1. 52 is an ink inlet to the ink manifold 5.

  The insulating protective film M is continuously formed at least from the inside of the channel 14 of the head chip 1 to the inner wall surface 34 of the opening 32 of the wiring substrate 3 after the head chip 1 and the wiring substrate 3 are joined. That is, the insulating protective film M covers the exposed portions of the drive electrode 15, the connection electrode 16, and the wiring electrode 33.

  “The exposed portions of the drive electrode 15, the connection electrode 16, and the wiring electrode 33” means the exposed portion of the drive electrode 15 is the entire inner surface of the channel 14. Further, the exposed portion of the connection electrode 16 is a portion that does not overlap the wiring electrode 33 between the inlet peripheral edge 143 of the channel 14 and the electrical connection portion with the wiring electrode 33, and the exposed portion of the wiring electrode 33 is Between the surface of the electrically connected connection electrode 16 and the surface 36 oriented on the head chip 1 of the wiring substrate 33, the side surface facing the opening 32 (the side surface forming the thickness of the wiring electrode 33). is there.

  The insulative protective film M is continuously formed means that there is no partial discontinuity in a portion that covers the drive electrode 15, the connection electrode 16, and the wiring electrode 33. .

  In the present invention, the insulating protective film M is preferably a film formed by vapor deposition such as chemical vapor deposition (hereinafter sometimes referred to as CVD), and in particular, polyparaxylene. A film made of Len or a derivative thereof is preferable.

  The film thickness of the insulating protective film M is 1 μm or more and 3 μm or less, preferably 2 μm or more and 3 μm or less as the film thickness on the inner surface of the channel 14. If it exceeds 3 μm, it tends to be an obstacle to realizing high density of the channel 14, that is, high quality of the printed image, and if it is less than 1 μm, a sufficient protective function may not be exhibited.

  Here, as shown in FIG. 3 which is a partial enlarged view of FIG. 2, an angle α (hereinafter referred to as an opening edge cross-sectional angle) formed from the surface 36 oriented to the head chip 1 on the wiring substrate 3 to the inner wall surface 34 of the opening 32. is sometimes 45 ° to 88 °, preferably 60 ° to 80 °. As a result, the peripheral portion of the electrical connection portion between the connection electrode 16 and the wiring electrode 33 is widened and opened from the rear surface of the head chip 1 toward the rear of the wiring substrate 3, and is opened from the rear side. When the inside of the part 32 is viewed, it becomes difficult to form a shadow portion.

  For this reason, when forming the insulating protective film M from the gas phase or the like, when the fluid containing the protective film component enters the opening 32 from the rear side of the wiring board 3, the fluid easily flows to the vicinity of the peripheral edge 35 of the opening. Even if a thin film having a thickness of 1 μm or more and 3 μm or less is formed in consideration of the nozzle diameter as the film thickness, the occurrence of pinholes due to the lack of the protective film component in the vicinity of the opening periphery 35 of the opening 32 is prevented. As a result, the drive electrode 15, the connection electrode 16, the wiring electrode 33, and the conductive adhesive can be reliably isolated from the ink by the insulating protective film M, and there are problems of electrode corrosion and adhesive strength reduction. Is solved, and the performance of the inkjet head can be maintained over a long period of time.

  When the angle α is less than 45 °, the wiring board 3 has insufficient strength in the vicinity of the opening peripheral edge 35, and is liable to be damaged particularly during bonding with the head chip 1 (thermocompression bonding, etc.). In the case of exceeding, the protective film component tends to be insufficiently inserted in the vicinity of the opening periphery 35, and the generation of pinholes cannot be effectively prevented.

  As a result, the insulating protective film M can be thinly formed, so that it is possible to increase the density of the nozzles, that is, to improve the image quality of the printed image.

  Next, an example of a method for forming the angle α in the opening peripheral edge 35 of the opening 32 of the wiring board 33 will be described with reference to FIG.

  The method of forming the angle α in the wiring board 3 is not particularly limited, but a method of forming by sandblasting, a method of processing with a dicing saw, a method of processing with an ultrasonic processing machine, and molding of ceramics before sintering And a method of firing. Among them, the method of forming by sand blasting is preferable because it is easy to adjust the angle α. Here, a case where the glass substrate is formed by sandblasting is illustrated.

  First, a single flat glass substrate 300 to be the wiring substrate 3 is prepared (FIG. 4A), and a masking material 301 is formed on one surface of the non-working region other than the region where the opening 32 is to be formed. And set on the stage (FIG. 4B).

  Next, an abrasive is sprayed on the glass substrate 300 from the surface coated with the masking material 301 by the abrasive wiping device 302 toward the glass substrate 300 to scrape off the unmasked portion (FIG. 4C).

  Sandblasting has the property that the processing range becomes narrower as processing proceeds in the depth direction from the surface. Therefore, when the spraying process is performed until the processing site penetrates, the glass substrate 300 is formed with an opening 32 formed of a through hole, and the inner wall surface 34 is formed in a tapered shape that gradually narrows as the depth increases. The angle α of the opening periphery 35 is less than 90 ° (FIG. 4D).

  Since this angle α can be adjusted by the processing strength and processing time of the sandblasting treatment from only one surface, it is adjusted to be in the range of 45 ° or more and 88 ° or less by appropriately adjusting these. Can do.

  Thereafter, by removing the masking material 301, the wiring board 3 having the opening 32 is produced (FIG. 4E).

  The wiring electrode 33 may be performed either before or after the opening 32 is processed. The wiring electrode 33 can be patterned by a known method such as sputtering or vapor deposition.

  In the above embodiment, the wiring substrate 3 is composed of a single plate. However, the wiring substrate 3 may be formed by stacking a plurality of substrates. In this case, in the substrate 3a laminated on the head chip 1 side, the angle α formed from the surface 36 oriented to the head chip to the inner wall surface 34 of the opening 32 is adjusted in the range of 45 ° to 88 °. Thus, the purpose of electrode protection can be achieved.

  Therefore, as shown in FIG. 5, for example, in the case of the wiring board 3 composed of two substrates 3a and 3b, the angle α formed from the surface 36 oriented to the head chip to the inner wall surface 34a of the opening 32 is 45 ° or more 88 If it is within the range of 0 ° or less, the inner wall surface 34b on the substrate 3b side may have a taper of the same angle, and the substrate laminated on the opposite side to the head chip 1 as shown in FIG. 3b may have a taper with a different angle.

  However, it is desirable that the portion of the opening 32 on the substrate 3b side laminated on the side opposite to the head chip 1 is formed so as not to cover the portion of the opening 32 on the substrate 3a side arranged on the head chip 1 side. .

  Further, from the viewpoint of more suitably protecting the adhesive layer that joins the head chip 1 and the wiring substrate 3 with the insulating protective film M, the opening 32 is formed from the surface 36 of the wiring substrate 3 oriented to the head chip 1. The angle α formed over the inner wall surface 34 is preferably set to the above angle over the entire circumference of the opening 32.

  In the embodiment described above, the configuration in which one opening 32 provided in the wiring board 3 exposes the inlets 141 of all the channels 14 included in the head chip 1 has been shown, but the present invention is limited to this configuration. Is not to be done.

  FIG. 7 is a view showing another embodiment of the ink jet head according to the present invention (viewed from the rear surface side of the head chip 1), and the openings 32 expose the inlets 141 of the channels 14 independently. The aspect provided with two or more is shown. In this embodiment, the channel 14 and the opening 32 have a one-to-one correspondence.

  FIG. 8 is a cross-sectional view taken along the line viii-viii in FIG. 7 and shows an enlarged view of the head chip 1 and the wiring board 3 in the inkjet head. Reference numeral 37 denotes an adhesive layer for bonding the head chip 1 and the wiring board 3 together.

  As shown in FIG. 8, also in this embodiment, in each opening portion 32, the angle α formed from the surface 36 oriented to the head chip 1 in the wiring substrate 3 to the inner wall surface 34 of the opening portion 32 is 45 ° or more and 88 ° or less. The range is preferably 60 ° or more and 80 ° or less.

  Then, insulation is performed so as to cover the exposed portions of the chip-side electrode (drive electrode 15 and connection electrode 16) and the wiring electrode 33 from at least the channel 14 of the head chip 1 to the inner wall surface 34 of the opening 32 of the wiring substrate 3. The protective film M is continuously formed.

  As a result, similarly to the embodiment shown in FIGS. 1 to 3, even if the thickness of the insulating protective film M is reduced to increase the density of the channel 14, the electrode (drive electrode 15, connection There is an effect that the electrode 16 and the wiring electrode 33) can be sufficiently protected.

  In this embodiment, in particular, since the periphery of the inlet 141 of each channel 14 is surrounded by the opening 32 of the wiring board 3, the wiring board 3 can be protected from the viewpoint of protecting the adhesive layer 37 with the insulating protective film M. The angle α formed from the surface 36 oriented to the head chip 1 to the inner wall surface 34 of the opening 32 is preferably set to the above angle over the entire circumference of the opening 32.

  FIG. 9 is a view (a view seen from the rear surface side of the head chip 1) showing still another aspect of the ink jet head according to the present invention.

  In the illustrated embodiment, the openings 32a and 32b are provided independently for each of the channel rows 140a and 140b. In this embodiment, the two openings 32a and 32b are formed so as to expose the inlets 141 of all the channels 14 constituting one channel row 140a or 140b, respectively. Furthermore, in this aspect, the channel rows 140a and 140b and the openings 32a and 32b have a one-to-one correspondence.

  Also in this embodiment, as in the embodiments of FIGS. 7 and 8, in each opening 32, the angle formed from the surface 36 oriented to the head chip 1 in the wiring substrate 3 to the inner wall surface 34 of the opening 32 is 45 °. The range is 88 ° or more and preferably 60 ° or more and 80 ° or less.

  Then, insulation is performed so as to cover the exposed portions of the chip-side electrode (drive electrode 15 and connection electrode 16) and the wiring electrode 33 from at least the channel 14 of the head chip 1 to the inner wall surface 34 of the opening 32 of the wiring substrate 3. The protective film M is continuously formed.

  As a result, similarly to the embodiment shown in FIGS. 1 to 3, even if the thickness of the insulating protective film M is reduced to increase the density of the channel 14, the electrode (drive electrode 15, connection There is an effect that the electrode 16 and the wiring electrode 33) can be sufficiently protected.

  Also in this embodiment, from the viewpoint of protecting the adhesive layer 37 by the insulating protective film M, the angle α formed from the surface 36 oriented to the head chip 1 on the wiring substrate 3 to the inner wall surface 34 of the opening 32. Is preferably the above angle over the entire circumference of the opening 32.

  In the present invention, in order to improve the printing quality and printing speed of the ink jet head, a plurality of channels 14 arranged in parallel in the head chip 1 include an ink channel for ejecting ink and a dummy channel for not ejecting ink. May be arranged alternately.

  FIG. 10 is a view showing still another aspect of the ink jet head according to the present invention (viewed from the rear surface side of the head chip 1). In the head chip 1, an air channel 14B provided as a dummy channel is An embodiment in which the ink channels are alternately formed adjacent to the ink channel 14A is shown.

  As described above, the air channel 14B is interposed between the ink channels 14A, so that ink can be ejected from the desired ink channel 14A without affecting the other ink channels 14A, and further, adjacent to the ink channel 14A. Since the drive performance of the driving wall 13 can be improved, it is possible to improve the printing quality and the printing speed.

  In the inkjet head 1 having the air channel 14B as described above, in order to prevent ink from flowing into the air channel 14B, the inlet of the air channel 14B is closed by the wiring board 3 so as not to be exposed to the ink. The opening 32 is formed so as to expose only the inlet 141 of the ink channel 14A to which the water is supplied.

  In the illustrated embodiment, a plurality of openings 32 are provided so that the inlets 141 of the ink channels 14A are independently exposed. Therefore, in this embodiment, the opening 32 has a one-to-one correspondence with only the ink channel 14A that ejects ink.

  Also in this embodiment, as in the embodiments of FIGS. 7 and 8, in each opening 32, the angle formed from the surface 36 oriented to the head chip 1 in the wiring substrate 3 to the inner wall surface 34 of the opening 32 is 45 °. The range is 88 ° or more and preferably 60 ° or more and 80 ° or less.

  Then, at least from the inside of the ink channel 14 </ b> A of the head chip 1 to the inner wall surface 34 of the opening 32 of the wiring substrate 3, the exposed portions of the chip-side electrode (drive electrode 15 and connection electrode 16) and the wiring electrode 33 are covered. An insulating protective film M is continuously formed.

  As a result, similarly to the embodiment shown in FIGS. 1 to 3, even if the film thickness of the insulating protective film M is reduced to increase the density of the ink channel 14 </ b> A, the electrode (drive electrode 15, The connection electrode 16 and the wiring electrode 33) are sufficiently protected.

  Also in this embodiment, in particular, since the periphery of the inlet 141 of each channel 14 is surrounded by the opening 32 of the wiring board 3, the wiring board 3 is also considered from the viewpoint of protecting the adhesive layer 37 by the insulating protective film M. The angle α formed from the surface 36 oriented to the head chip 1 to the inner wall surface 34 of the opening 32 is preferably set to the above angle over the entire circumference of the opening 32.

  7 to 10 can be manufactured in the same manner as in FIG.

  Examples of the present invention will be described below, but the present invention is not limited to such examples.

Example 1
A 300 dpi harmonica type head chip with a channel width of 42 μm is manufactured, and a drive electrode is formed on the inner surface (drive wall) of the channel so as to have a thickness of 3 μm. A connection electrode was formed.

  A wiring board is produced by forming an opening with an angle α of 45 ° formed from the surface oriented to the head chip to the inner wall surface of the opening on a glass plate having a thickness of 300 μm by sandblasting from only one side thereof, After forming the wiring electrode on one side, the wiring electrode and the connection electrode on the rear surface of the head chip were joined by thermocompression bonding using a conductive adhesive in which nickel was dispersed.

  Next, an insulating protective film (polyparaxylylene film) continuous from the inside of the channel to the inner wall surface of the opening of the wiring board was formed by CVD so as to have a film thickness of 3 μm.

  Next, a nozzle plate having a nozzle (diameter 26 μm) is attached to the front surface of the head chip, an ink manifold is joined to the rear surface of the head chip via a wiring board, and an FPC is connected to the end of the wiring board. An ink jet head was obtained.

<Evaluation method>
1. Measurement of Protective Film Leakage Current After heating the ink jet head at 100 ° C. for 1 hour, each channel was filled with a test solution having a conductivity of 10 mS / m, and between the test solution and the electrode (part of the wiring electrode) A potential was applied to measure a leakage current from the insulating protective film.

  If the insulating protective film has pinholes or breaks, a current flows between the test solution and the electrode. By measuring this current, the film formation state of the insulating protective film can be confirmed.

Evaluation was performed according to the following criteria.
○: Leakage current is less than 1 nA / V ×: Leakage current is 1 nA / V or more The results are shown in Table 1.

2. Observation of electrode corrosion The electrode corrosion caused by peeling of the insulating protective film was investigated.

  An ink jet head nozzle filled with ink (magenta) in each channel is left immersed in a container containing ink for one month at 60 ° C., and then a DC voltage of + 10V from the wiring electrode to the drive electrode with respect to the ink. Was applied to examine whether there was a leakage current.

  If there is film peeling on the insulating protective film, corrosion of the electrode proceeds and current leaks to the ink.By measuring this current, the presence or absence of electrode corrosion due to film peeling of the insulating protective film can be determined. Can be confirmed.

Evaluation was performed according to the following criteria.
○: Leakage current is less than 1 nA ×: Leakage current is 1 nA or more The results are shown in Table 1.

3. Observation of Adhesive Layer Dyeing The presence or absence of influence (dyeing) on the adhesive layer due to peeling of the insulating protective film was examined.

  Inkjet head nozzles filled with ink (magenta) in each channel are immersed in a container containing ink and left at 60 ° C. for one month. Then, the ink is discharged, the inkjet head is disassembled, and the wiring board and The presence or absence of coloring of the adhesive between the head chip was observed.

  When the insulating protective film peels off, the adhesive layer comes into contact with the ink and swells and is dyed magenta. Therefore, whether the dye is magenta was observed through the glass of the wiring board.

Evaluation was performed according to the following criteria.
○: Staining is not confirmed ×: Staining is confirmed The results are shown in Table 1.

4). Observation of the strength of the wiring board The strength of the wiring board according to the angle α was examined.

  When the wiring board was thermocompression bonded to the rear surface of the head chip, the presence or absence of breakage was observed at the periphery of the opening of the wiring board.

Evaluation was performed according to the following criteria.
○: No damage ×: Damage occurred Table 1 shows the results.

(Example 2)
An inkjet head was obtained in the same manner as in Example 1 except that the angle α formed from the surface oriented to the head chip of the wiring board to the inner wall surface of the opening was 50 °, and the same evaluation as in Example 1 was performed. It was. The results are shown in Table 1.

(Example 3)
An inkjet head was obtained in the same manner as in Example 1 except that the angle α formed from the surface oriented to the head chip of the wiring board to the inner wall surface of the opening was set to 60 °, and the same evaluation as in Example 1 was performed. It was. The results are shown in Table 1.

Example 4
An inkjet head was obtained in the same manner as in Example 1 except that the angle α formed from the surface oriented to the head chip of the wiring board to the inner wall surface of the opening was set to 70 °, and the same evaluation as in Example 1 was performed. It was. The results are shown in Table 1.

(Example 5)
An ink jet head was obtained in the same manner as in Example 1 except that the angle α formed from the surface oriented to the head chip of the wiring board to the inner wall surface of the opening was 88 °, and the same evaluation as in Example 1 was performed. It was. The results are shown in Table 1.

(Example 6)
An ink jet head was obtained in the same manner as in Example 1 except that the thickness of the insulating protective film was changed to 2 μm, and the same evaluation as in Example 1 was performed. The results are shown in Table 1.

(Example 7)
The inkjet head was formed in the same manner as in Example 1 except that the thickness of the insulating protective film was 2 μm, and the angle α formed from the surface oriented to the head chip of the wiring board to the inner wall surface of the opening was 50 °. The same evaluation as in Example 1 was performed. The results are shown in Table 1.

(Example 8)
The inkjet head was formed in the same manner as in Example 1 except that the thickness of the insulating protective film was 2 μm, and the angle α formed from the surface oriented to the head chip of the wiring board to the inner wall surface of the opening was 60 °. The same evaluation as in Example 1 was performed. The results are shown in Table 1.

Example 9
The ink jet head was formed in the same manner as in Example 1 except that the thickness of the insulating protective film was 2 μm, and the angle α formed from the surface oriented to the head chip of the wiring board to the inner wall surface of the opening was 80 °. The same evaluation as in Example 1 was performed. The results are shown in Table 1.

(Example 10)
The ink jet head was formed in the same manner as in Example 1 except that the thickness of the insulating protective film was 2 μm, and the angle α formed from the surface oriented to the head chip of the wiring board to the inner wall surface of the opening was 88 °. The same evaluation as in Example 1 was performed. The results are shown in Table 1.

(Comparative Example 1)
An inkjet head was obtained in the same manner as in Example 1 except that the angle α formed from the surface oriented to the head chip of the wiring board to the inner wall surface of the opening was 40 °, and the same evaluation as in Example 1 was performed. It was. The results are shown in Table 1.

(Comparative Example 2)
An inkjet head was obtained in the same manner as in Example 1 except that the angle α formed from the surface oriented to the head chip of the wiring board to the inner wall surface of the opening was 90 °, and the same evaluation as in Example 1 was performed. It was. The results are shown in Table 1.

  As described above, in the inkjet heads of Examples 1 to 10 in which the angle α is in the range of 45 ° or more and 88 ° or less, the insulating protective film has a thickness of 2 to 3 μm as the film thickness on the channel inner surface. In the measurement of the leakage current of the protective film and the observation of the occurrence of electrode corrosion, no leakage current was observed, and no staining of the adhesive with the ink was observed in the observation of the adhesive layer. It can be seen that the electrode is reliably protected (isolated from the ink) without any pinholes or breaks. In addition, no damage occurred at the periphery of the opening of the wiring board during bonding with the head chip.

  On the other hand, it can be seen that Comparative Example 1 having an angle α of 40 ° is unsuitable because the wiring board is damaged during bonding with the head chip and the strength is lowered.

  On the other hand, in Comparative Example 2 in which the angle α is 90 °, leakage current was observed in the measurement of the protective film leakage current and the observation of the occurrence of electrode corrosion, and in the observation of the adhesive layer, the adhesive was stained with ink. Thus, it can be seen that pinholes and breaks occur in the insulating protective film, resulting in insufficient electrode protection.

  Further, in Examples 6 to 10 in which the film thickness on the inner surface of the channel of the insulating protective film was further reduced to 2 μm, the dyeing with the conductive adhesive ink was recognized in a part of the ink jet head within a practically no problem range. However, no staining was observed in Examples 6 to 9 in which the angle α was in the range of 45 ° to 80 °. From this, it can be seen that when the angle α is in the range of 45 ° or more and 80 ° or less, the protective function by the insulating protective film is more suitably expressed.

1: Head chip 14: Channel 14A: Ink channel 14B: Air channel 15: Drive electrode 16: Connection electrode 2: Nozzle plate 21: Nozzle 3: Wiring substrate 32: Opening 33: Wiring electrode 34: Inner wall surface 35 of the opening : Periphery of opening 36: Surface oriented to head chip 4: FPC
5: Ink manifold

Claims (9)

A plurality of channels are arranged side by side, and an outlet and an inlet of the channel are arranged on the front surface and the rear surface, respectively, and a continuous chip side electrode is formed from the inside of the channel through the inlet of the channel to the rear surface. A head chip,
It is bonded to the rear surface of the head chip, and has an opening that exposes the inlet of the channel for supplying ink of the head chip, and is exposed to the rear surface of the head chip on the surface oriented to the head chip. In an inkjet head having a wiring substrate having a wiring electrode electrically connected to the chip side electrode,
The angle formed from the surface oriented to the head chip in the wiring board to the inner wall surface of the opening is in the range of 45 ° to 88 °,
An insulating protective film is continuously formed so as to cover at least the chip side electrode and the exposed portion of the wiring electrode from within the channel of the head chip to the inner wall surface of the opening of the wiring board. An inkjet head characterized by that.   The inkjet head according to claim 1, wherein the opening is one opening that exposes the entrances of all the channels.   2. The ink jet head according to claim 1, wherein a plurality of the openings are provided so as to expose the inlets of the channels independently. The head chip has a plurality of channel rows,
The inkjet head according to claim 1, wherein the opening is provided for each channel row. The plurality of channels arranged side by side are alternately arranged with ink channels that eject ink and dummy channels that do not eject ink.
2. The ink jet head according to claim 1, wherein the opening is provided so as to expose an inlet of the ink channel and not to expose an inlet of the dummy channel.   The inkjet head according to claim 1, wherein the insulating protective film has a thickness in a range of 1 μm to 3 μm.   The inkjet head according to claim 1, wherein the insulating protective film is a film made of polyparaxylylene or a derivative thereof.   The inkjet head according to claim 1, wherein the wiring board has a thickness in a range of 300 μm to 700 μm.   The inkjet head according to claim 1, wherein the wiring board is made of glass, ceramics, or alumina.

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